Nitrogen Doping into Thin and Thick Coatings for Nano-structuring and Nano-texturing by Plasma Immersion Nitriding

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Aizawa, T. Fukuda This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5435418/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 26 Jan, 2026 Read the published version in Journal of Bio- and Tribo-Corrosion → Version 1 posted 9 You are reading this latest preprint version Abstract A thin gold film, a poly-crystalline diamond (PCD) coating and a carbon-supersaturated thick SiC (Silicon Carbide) coating, were nitrogen-doped or N-doped by using the plasma immersion nitriding. The N-doped gold thin film was characterized by lattice straining up to 3–5% and by hardening to 300 HV via the massive nitrogen supersaturation (MNS). The N-doped PCD was nano-textured to have a fine acicular-texture array on the PCD surface via self-organization process. The massively carbon supersaturated (MCSed) SiC thick coating was N-doped and characterized by the enrichment of carbon-rich clusters along the 6H-structured SiC grain boundaries. The masking technique was employed to describe the difference in microstructures and electric resistivity between the N-doped and undoped MCSed SiC coatings. N-doping induced the reduction of SiC grain size as well as the increase of stacking faults in the SiC grains as well as carbon-rich clusters along the SiC grain boundaries. The electric resistivity was reduced to 1/2 to 1/3 by this N-doping. Various functions were accommodated to thin and thick coatings by the nitrogen doping via the plasma immersion nitriding. Plasma immersion nitriding Nitrogen doping Gold film Polycrystalline diamond coating thick SiC coating Nanostructuring Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 1. Introduction Various types of coating have been utilized to prolong the manufacturing tool life [ 1 ], to protect the artificial medical and dental products from wearing and corrosion [ 2 ], to improve the bio-activeness for enhancement of bio-compatibility between metallic parts and cells [ 3 ], and to functionalize by themselves via the specified surface textures [ 4 ]. Furthermore, a post-treatment of these original coatings is effective to modify their surface morphology for further functionalization of coating materials [ 5 ]. In the literature, several studies were reported on the functionalization of thin and thick films by the post-treatment. Thin gold film was modified to be nano-porous to pasteurize its surface [ 6 ]. Polycrystalline diamond (PCD) or nano-diamond coatings on the tools were nano-textured for fine shearing and machining via the femtosecond laser machining [ 7 ] and the FIB (Focused Ion Beam) [ 8 ]. The carbon-controlled thick SiC coating was also modified to have a composite microstructure where 6H-structured SiC grains with lots of stacking faults align themselves with carbon-rich clusters along their grain boundaries [ 9 ]. Among these post-treatments, the nitrogen doping process has a capability to make efficient surface modification of thin and thick coatings [ 10 ]. Three approaches of N-doping process are illustrated in Fig. 1 . When impinging the nitrogen or carbon ions, or, nitrogen – hydrogen or carbon – hydrogen radicals into metallic films, they are supersaturated by nitrogen or carbon solutes with high content. As theoretically studied in [ 11 ], most of these nitrogen or carbon solutes occupy the octahedral vacancy sites in the crystalline lattices of coating materials. Then, each crystal lattice with the supersaturated nitrogen or carbon solutes is strained in anisotropic as depicted in Fig. 1 a. Any deposit such as cells and bacterium onto this thin film, is physically influenced by this lattice straining. As illustrated in Fig. 1 b, a nanotexturing of coating layers is highlighted as the second approach. When the thin and thick inorganic films are intensely irradiated by ion beams via the ion implantation and the intensified plasma bombardment, their structure is modified to have nanotextures and nanoporous as pointed in [ 12 ]. In particular, these convex nanotextures induced by intense ion beam irradiation, works as a new type of sensors [ 13 ]. Nano-composites [ 14 ] are formed by selectively nitrogen ion impinging the dissimilar solute atoms into original granular structure as depicted in Fig. 1 c. In the present paper, three thin and thick coatings are prepared for N-doping to describe their modified surface conditions and to investigate the N-doping effect to each coating. The plasma immersion nitriding system is utilized in common for this N-doping. Thin gold film with the thickness of 200 nm is N-doped to have high nitrogen solute content and hardness. Thick PCD coating on the WC (Co) chip with the thickness of 15 µm is N-doped to have an array of acicular textures via self-organization. Thick carbon-controlled SiC coating with the thickness of 4 mm is also N-doped to reduce the SiC grain size and to increase the stacking faults density in the 6H-structured SiC grains as well as the carbon-rich clusters along the SiC grain boundaries. This crystallographic modification results in the selective reduction of electric resistivity to the unmasked surfaces. 2. Methods and Materials Three types of thin and thick coatings were prepared for nitrogen doping process via the plasma immersion nitriding system. In addition to materials characterization on the N-doped coatings, the micro-Vickers testing was employed to measure the hardness of coatings. Furthermore, the masking technique was used to analyze the N-doping effect on the electric resistivity. 2.1 Preparation of thin and thick coatings for post-treatment Three types of thin and thick coatings were prepared for nitrogen doping experiments as shown in Fig. 2 . Figure 2 a shows a thin gold film with the average thickness of 200 nm onto the AISI304 stainless steel substrate. Figure 2 b depicts a thick polycrystalline diamond (PCD) film with the thickness of 15 µm onto the WC (Co) chips. A thick 6H-structured SiC coating plate with the thickness of 4 mm is also prepared as shown in Fig. 2 c. Thin gold film was deposited onto the substrate by sputtering method. PCD film was synthesized by PE-CVD (Plasma Enhanced Chemical vapor Deposition) method onto the WC (Co) chip before polishing. Thick SiC coating with supersaturated carbon content was once synthesized onto a dummy sintered SiC substrate by thermal CVD method and cut to only SiC coating specimen. After chemical cleansing, all these films were used as a specimen for N-doping. 2.2 Nitrogen doping procedure The RF (Radio-Frequency) – DC (Direct Current) plasma immersion nitriding system with the use of the hollow cathode, was utilized for N-doping experiments to film specimens as schematically illustrated in Fig. 3 a. Owing to the hollow cathode device, the nitrogen ion and NH (Nitrogen – Hydrogen) - radical densities were enhanced in the hollow as studied in [ 15 , 16 ]. After its plasma diagnosis, the ion density reached 4 x 10 18 ions/m 3 under the gas flow ratio of nitrogen gas by 160 mL/min to hydrogen gas flow by 30 mL/min. The RF-DC powers were automatically controlled with prompt response less than 1 ms to the spatial impedance change in plasmas by adjusting the frequency of RF power as well as the DC-bias voltage. Heater was embedded into the supporting plate below the DC-biased plate. In the following experiments, as shown in Fig. 3 b, the chamber was evacuated down to the base pressure of 0.1 Pa after setting the specimen into the hollow. The plasma immersion nitriding conditions were optimized for adaptive N-doping process to each specimen. As listed in Table 1 , five items were main nitriding parameters; the RF-voltage, the DC-bias, the holding temperature, the total gas pressure, and the N-doping duration. Two procedures were employed for N-doping to thin gold film specimens; e.g., G1 and G2 procedures. In the G1-procedure, the specimen was preheat-treated at 673 K for 7.2 ks before N-doping. The RF-voltage, the DC-bias and the duration were varied in G1 and G2 procedures. Higher RF-voltage and DC-bias were employed in the PCD procedure at 473 K. The thermocouples embedded onto the DC-biased plate, was used to monitor the temporal transients of temperature. In the SiC procedure, the processing temperature was increased up to 673 K. After presputtering in the nitrogen atmosphere for 1.8 ks at 673 K, the SiC coating specimen was immersed in the nitrogen – hydrogen plasma at 50 Pa under the specified gas flow ratio by 160 mL for nitrogen to 30 mL for hydrogen gas at 673 K for 14.4 ks. After every N-doping process, the specimen was cooled down in the nitrogen atmosphere. 2.3 Materials and mechanical characterization SEM (Scanning Electron Microscopy; JEOL, Tokyo, Japan) – EDS (Electron Dispersive X-ray Spectroscopy) were respectively used for microstructure observation and element mapping. STEM (Scanning Transmission Electron Microscopy; JEOL, Tokyo, Japan) was also utilized for precise analysis of crystallographic structure including defects. This Cs-corrected STEM attains high spatial resolution in 0.08 nm. In this STEM, the raster-scanned electron beam transmits through the specimen to provide three types of TEM images; LAADF (Low-Angle Annular Dark Field), HAADF (High-Angle Annular Dark Field), and ABF (Annular Bright Field) images. A series of steps were used in preparation for a sample for STEM analysis. The N-doped and undoped specimens were mechanically cut and polished. Then both sides of specimens were argon-ion-milled using the masking belt. Finally, the argon-ion slicer (JEOL, Tokyo, Japan) was used to build up the specimens for STEM analysis. A nano-indenter (Shimazu; Kyoto, Japan) and a micro-Vickers hardness tester (Mitsutoyo, Co., Ltd., Yokohama, Japan) were respectively used for N-doped thin and thick coated specimen. Electric resistivity was measured at the masked and unmasked regions using the insulation resistor (SM-8125; HIOKI, Co., Ltd. Nagano, Japan) to describe the nitrogen doping effect on the electric properties. 3. Results Three film specimens were N-doped at each plasma-immersion nitriding condition to yield the massively nitrogen-supersaturated (MNSed) samples for materials and mechanical characterization. In particular, precise analyses were performed on the MNSed CVD-SiC film with carbon control by using STEM and EDS. 3.1 N-doping into thin gold film Two N-doping procedures were employed to investigate the N-doping effect on the supersaturated nitrogen solute content and the measured hardness. In the G1 procedure at Table 1 , a heating treatment was added as a preliminary step to N-doping process. As depicted in Fig. 4 a, the original gold thin film changed its surface color from gold to red through this heat treatment, as pointed in [ 17 ]. On the other hand, the original gold color turned to be more dark gold after the G2 procedure, as shown in Fig. 4 b. The measured nitrogen content and surface hardness of these G1- and G2-specimens were listed in Table 2 . The N-doped gold film is latticed strained via the massive nitrogen supersaturation (MNS) by 3–5% in tension because of higher supersaturated nitrogen content than 1 mass%. This enrichment of nitrogen solutes significantly hardens the thin gold film up to 300 HV. In particular, the G2 procedure provides an efficient N-doping process with very little damage into a thin gold film. 3.2 N-doping into PCD film on the WC (Co) chip PCD film was N-doped at 473 K by 50 Pa for 10.8 ks. As shown in Fig. 5 a, the PCD surface was modified into two colored regions. The inner region, A, in PCD, was gray-colored while the vicinity to PCD surface, B-region, was colored in black. SEM was used to analyze each region. In both regions, the original PCD surface was shaped into an alignment of acicular micro-textures, as respectively shown in Fig. 5 b and 5 c. In the A-region, the acicular microtextures with lower height, align themselves in high density, as depicted in Fig. 5 b. While, in the B-region, the acicular microtextures with higher aspect ratio, align themselves in low density. This difference of acicular texture array reflects on the color change in Fig. 5 a. Figure 6 shows the energy spectrum of elements in the N-doped PCD into B-region by EDS. Carbon was detected as a main component of PCD together with the impurities of iron and the constituent of WC substrate. Nitrogen was detected together with the impurity of oxygen. Table 3 summarizes the chemical composition detected by this EDS analysis. The nitrogen solute content reaches 10 at%. This reveals that carbon sites in PCD are substituted by nitrogen atoms These acicular microtextures are formed by the physical bombardment with selective substitution of nitrogen atoms to carbon sites in PCD with high nitrogen content. The nitrogen solute supersaturates into the grain boundaries of PCD and substitutes into the carbon sites of tetragonal diamond. Then, as suggested in [ 18 ], the supersaturated and substituted PCD zones with high content nitrogen solutes remain as an acicular microtexture during N-doping. While, less supersaturated and substituted PCD zones are physically etched away during N-doping. Regularity in these acicular textures in Figs. 5 b and 5 c proves that this nitrogen supersaturation and substation advances selectively in the self-organization manner with much dependence on the nitrogen content distribution during N-doping. The difference of aspect ratios in the acicular microtextures between A and B regions, comes from the ion and radical density distribution in the plasma sheath. At the vicinity of PCD chip edges, more nitrogen ions and NH-radicals concentrate to make deeper etching by their physical bombardment. 3.3 N-doping into MCSed thick SiC coating A thick MCSed SiC coating is nitrogen-doped at 673 K for 14.4 ks by plasma immersion nitriding. STEM -EDS was first utilized to describe the nitrogen solute distribution in the inside of MNSed top layer. As shown in Fig. 7 , the nitrogen solutes uniformly distribute in the SiC grains and grain boundaries. This implies that the impinged nitrogen solutes have substitutional interaction with the bound carbon atoms in SiC as well as the carbon-rich clusters, synthesized by CVD deposition process with carbon enrichment [ 19 ]. STEM was further utilized to analyze the microstructure of N-doped, MCSed SiC coating. As shown in Fig. 8 , the stacking faults are induced in the inside of SiC grains from one end of its grain boundary (GB) to the other end of its GB, as indicated by the blue arrow. The carbon-rich clusters are also synthesized mainly along the SiC GBs as pointed by the red arrow. This microstructure resembles to that before N-doping; however, more stacking faults and clusters is induced by N-doping. In particular, many stacking faults are induced in each SiC grain by this N-doping. As shown in the electric diffraction pattern inserted into Fig. 8 , a halo-pattern proves that these carbon clusters are unbound in SiC. A precise analysis on the SiC crystallographic structure and the grain boundary structure was performed using STEM and EDS. As shown in Fig. 9 a, lots of stacking faults are formed into the SiC in a defect band. In fact, Fig. 9 b proves that wide stacking faults band is formed in the 6H-structured SiC granular structure. This reveals that many carbon solute atoms are exiled from the inside of SiC grain to its GBs through this stacking fault bands during the N-doping process. Figure 10 shows the STEM image and carbon mapping along the SiC GBs. Many carbon-rich clusters are also formed especially along the SiC GBs. This proves that lots of bound carbon to SiC grains are exiled from the inside of SiC Grains to their GBs via homogeneous nitrogen substitution to SiC grains, and, that these exiled carbon solutes agglomerate with the pre-existing clusters and grow to a larger carbon-rich cluster. 3.4 Comparison of microstructure between masked and unmasked MCSed-SiC coating The masking technique was employed to analyze the difference in microstructure between the N-doped and undoped SiC coatings. Three STEM images were compared under the same magnification between the undoped and N-doped MCSed SiC coatings in Fig. 11 . The average SiC grain size is reduced by N-doping. Much more carbon rich clusters are induced along the grain boundaries. To be discussed later, more stacking faults are induced by N-doping, and, most of them are formed into the inner grains in bands. Since several stacking faults are formed all together with them, these stacking fault bands turn to be a new SiC GB so that the grain size is reduced. The carbon rich cluster distribution is compared between the undoped and N-doped regions. As shown in Fig. 12 , more carbon rich clusters distribute not only in the inner SiC grains but also along their GBs in both regions. To be noticed, the number of clusters is much increased by N-doping in this image. This increase of carbon rich clusters as well as increase of stacking faults bands reveals that more carbon solutes are exiled by substation of nitrogen solutes to carbon sites in SiC and that these carbon solutes diffuse through the stacking faults and agglomerate themselves along the GBs. The carbon solute transportation from inner SiC grains to their GBs might well be enhanced by N-doping. Each carbon cluster before doping is expected to grow itself during N-doping. Fig, 13 depicts HAADf, ABF and LAADF images analyzed by STEM, respectively. Each carbon rich cluster grew up to have nearly the same size of SiC grains. That is, the SiC grains are partially surrounded by carbon rich clusters. This carbon rich cluster distribution is also compared before and after N-doping. As shown in Fig. 14 ., the grown-up carbon clusters surround each SiC grain boundary. Figures 13 and 14 reveal that most of N-doped SiC grains have GBs including the carbon rich clusters. This coverage of carbon rich clusters onto SiC grains reflects on the functional properties of SiC. 3.5 Comparison of electric resistivity between masked and unmasked MCSed-SiC coatings. Silicon carbide, especially 6H-strcutured SiC, has high resistivity as reviewed in [ 20 ]. Various approaches were developed to reduce or control this electric resistivity by microstructure modification. The electric resistivity was measured and compared between the N-doped and undoped regions in the MCSed SiC specimen in Fig. 2 c. As listed in Table 5 , the electric resistivity is reduced by 1/3 to 1/2 of original resistivity to 6H-structure SiC. This is attributed to the coverage of SiC GBs by carbon-rich clusters, the density of which is increased by N-doping. 4. Discussion N-doping process has been utilized in industries with the use of ion implantation technique [ 21 ]. The accelerated nitrogen ions are impinged into the thin and thick coatings with the specified kinetic energy in 100 keV to MeV order. Even under this intense ion bombardment, the affected layer thickness by nitrogen ion implantation is still limited by 1 to 2 µm [ 22 ]. The present N-doping process via the plasma immersion nitriding builds up a thicker affected layer up to 10 to 100 µm range through the nitrogen solute diffusion with modification of microstructure of original coatings. This modification by N-doping is discussed with reference to three N-doping experiments. A nitrogen doping process into thin and thick coatings is characterized by massive nitrogen supersaturation. The nitrogen content [N] reaches 1 mass% in the N-doped thin gold film while [N] ~ 10 mass% in the N-doped PCD film. As theoretically explained in [ 11 ], this MNS induces an anisotropic lattice expansion into the N-doped films. In case of the N-doped gold thin films, this lattice strain reaches + 3 to + 5% in tension. As stated in [ 23 ], the surface strains of nano-porous gold film induced the polarization into the cells for inactivation. This suggests that N-doped gold thin film works as a bioactive coating to pasteurize the gold-coated parts and tools even in vivo. In parallel to lattice-straining effect, the N-doping process significantly harden the soft metals like pure gold. The hardness of 300 HV in the N-doped gold films via G1 and G2 procedures exceeds the hardness of aluminum alloys. This implies that MNS directly drives to harden the gold crystallographic structure by lattice distortion. Thick SCD (Single Crystal Diamond) and PCD films have been widely utilized not only as a machining chip and tool but also as a semi-conductor working at the elevated temperature. In addition to their intrinsic high hardness, their electric properties are also attractive to industrial applications. In particular, as stated in [ 24 ], various new functionalities and performances were induced into SCD and PCD films by nanostructuring processes. A regularized defect introduced by nitrogen doping induces the nitrogen – vacancy centers for luminescence [ 25 ]. After [ 7 , 8 ], micro- and nano-textures were built on the machining tools and piercing punch. In particular, a fully burnished hole surface with mirror-like surface condition was attained by using the nanotextured punch. The nanotexturing morphology of SCD and PCD by those laser and FIB machining processes is limited to have low aspect ratio. As recently reported in [ 26 ], needle-like monocrystalline diamonds with higher aspect ratio than 14, was synthesized by self-organization with aid of catalysis. This fine control of morphology in the diamond coating suggests that the present nitrogen doping approach is effective to yield the acicular diamond nanotextures with higher aspect ratio onto the SCD and PCD films and deposits. A thick MCSed SiC coating by thermal CVD with carbon control, consists of the 6H-structured SiC grains with a few stacking faults in the SiC grains and a few carbon-rich clusters along the grain boundaries. Under the present N-doping, this composite microstructure is enhanced to have much more stacking faults in the inside SiC grains and more carbon-rich clusters along their grain boundaries. These defects and clusters are induced by nitrogen substitution into carbon sites in SiC binding state and by transportation of exiled carbon solutes to grain boundaries. As summarized in Table 4 , increase of stacking fault density reduces the SiC grain size. This proves that the staking fault bands induced by N-doping form new grain boundaries and result in the reduction of SiC grain size. The carbon rich cluster density and size increase nu N-doping. This implies that SiC grain boundaries are gradually covered by these clusters. Due to this coverage, the electric resistivity is reduced by N-doping. N-doping to thin metallic coating is characterized by lattice straining and solid solution hardening. In case of N-doping to thin gold films, no nitrides are synthesized as a precipitate so that gold film is physically hardened by nitrogen solid solution into gold crystallographic structure. This high strained gold surface is attractive to bio-active coating of medical tools. This hardening prolongs the engineering durability of gold-coated pins and connectors. When the transition or refractory metal coating is N-doped, fine precipitation of nitrides could contribute to hardening of these thin metallic films. The carbon-base coatings such as DLC (Diamond Liker Carbon) and CVD diamond films, might well be N-doped to provide the acicularly textured DLC and diamond films with high aspect ratio. This tremendous surface area extension is attractive to sensing the nanoparticles and to radiate the current into solutions. The surface composite layer of 6H-structured SiC grains and carbon-rich grain boundaries, works as a mold in hot stamping of oxide glasses into optical lens and element due its high wear endurance of SiC grains at the elevated temperature and its electric and thermal conductivity with aid of carbon grain boundary network. 5. Conclusion Thin and thick coating materials were nitrogen doped to describe the microstructure and mechanical change before and after doping. The N-doped thin gold film is lattice-strained by nitrogen supersaturation with the nitrogen solute content up to 1 mass%. It has high hardness of 300 HV. High surface straining and high hardening provides an engineering way to functionalize the gold-coated parts and tools. The N-doped PCD film has an acicular microtexture with high aspect ratio via the self-organization in the nitrogen selective-substitution of carbon sites in PCD. The extraordinary surface extension of PCD film works as a sensitive sensor to nano-particles and bacterium and as a tiny electrode for wet plating. SiC microstructure is significantly modified by N-doping to have lots of stacking fault defects in the inside of grains and carbon rich clusters along the grain boundaries. A CVD-synthesized thick SiC substrate turns to have fine-grained crystallographic composite with carbon-rich grain boundaries. This composite surface layer has mechanical stability and strength original to 6H-structure SiC and conductive grain boundaries. Declarations Author Contribution T.A. wrote the main manuscript text.T.F. checked this text.T.A. ad T.F. prepared the samples and made experiments.All authors reviewed this manusript incuding figures and tables [Acknowledgements] The authors would like to express their gratitude to T. Koyama, M. Saito, H. Yoshida, and Y. Ikuhara (University of Tokyo) for their sincere efforts in STEM analysis., and to Nasu T. (Ebinax, Co., Ltd.) for his help in measurement. [Funding] Authore received no funding to the present research. [Confliction of Interests] All authors declared that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest . References Aurich J. C., Kieren-Ehses S., Mayer T., Bohley M., Kirsch B., An investigation of the influence of the coating on the tool lifetime and surface quality for ultra-small micro end mills with different diameters. CIRP J. Manufact. Sci. Eng. 37 (2022) 92-102. Söderholm K-J. M., Coatings in dentistry—A review of some basic principles. Coatings 2 (4) (2012) 138-159. Kim S-J., Lee D-S., Kim I-G,, Sohn D-W., Park J-Y., Choi B-K., Kim S-W., Evaluation of the biocompatibility of a coating material for an implantable bladder volume sensor. Kaohsiung J. Med. Si. 28 (3) (2012) 123-129. Wu F., Liu N., Ma Y., Zhang X., Han Y., Research on the influence of diamond coating microtexture on graphitization law and friction coefficient. Diamond Related Materials 127 (2022) 109153. Aizawa T., Inohara T., Yoshino T., Suzuki Y., Shiratori T., Laser treatment of CVD diamond coated punch for ultra-fine piercing of metallic sheets. Ch. 4 in Engineering Applications of Diamond, Intech Open, UK, London (2021). Wu P., Yanagi K., Yokota K., Hakamada M., Mabuchi M., Unusual effects of a nanoporous gold substrate on cell adhesion and differentiation because of independent multi-branch signaling of focal adhesions. J Mater. Sci.: Materials in Medicine 34 (2023) 54. Aizawa T., Shiratori T., Kira Y., Inohara T., Simultaneous nano-texturing onto a CVD-diamond coated piercing punch with femtosecond laser trimming. J. Applied Sciences 10, 2674 (2020) 1-12. Tuğrul Özel T., Biermann D., Enomoto T., Mativenga P., Structured and textured cutting tool surfaces for machining applications. CIRP Annal. 70 (6) (2021). Aizawa T., Fukuda T., Nitrogen doping into 6H-structured carbon supersaturated SiC coating via plasma immersion nitriding. Proc. 7 th WCMNM (September 19 th , 2024; Pattaya, Thai) 120-124. Tomastik J., Ctvrtlik R., Ingr T., Manak J., Opletalova A., Effect of nitrogen doping and temperature on mechanical durability of silicon carbide thin films. Sci. Rep. 8 (2018) 10428. Domain C.; Becquart C. S., Foct J., Ab initio study of foreign interstitial atom (C, N) interactions with intrinsic point defects in α-Fe. Physical Review B. 2004; 69: 144122. Civantos A., Mesa-Restrepo A., Torres Y., Shetty A. R., Cheng M. K., Jaramillo-Correa C., Aditya T., Allain J. P., Nanotextured porous titanium scaffolds by argon ion irradiation: Toward conformal nanopatterning and improved implant osseointegration. J. Bio. Mater. Res. 111 (12) (2023) 1850-1865. Teranishi N., Fuse G., Sugitani M., A review of Ion Implantation Technology for Image Sensors. Sensors 18(7) (2018) 2358. Kim D-S., Jeong W. S., Ko H., Lee J-S., Byun D., Pretreatment by selective ion-implantation for epitaxial lateral overgrowth of GaN on patterned sapphire substrate. Thin Solid Films 641 (2017) 2-7. Sharma, M.K.; Saikia, B.K.; Bujarbarua, S. Optical Emission Spectroscopy of DC Pulsed Plasmas Used for Steel Nitriding. Surf. Coat. Technol. 2008, 203, 229–233 Aizawa T., Rsadi I., Yunata E. E., High density RF-DC plasma nitriding under optimized conditions by plasma diagnosis. Appl. Sci. 12, 3706; 2022: 1-12. Łapiński M., Piotr Dróżdż P., Gołębiowski M., Gołębiowski M., Piotr Okoczuk P., Karczewski J., Sobanska M., Pietruczik A., Zytkiewicz A. R., Zdyb R., Sadowski W., Kościelska B., Thermal Instability of gold thin films. Coatings 13(8) (2023) 1306. Nguyen K. G., Huš M., Baragau I-A., Bowen J., Heil T., Nicolaev A., Abramiuc L. E., Sapelkin A., Sajjad M. T., Kellici S., Nitrogen-doped carbon quantum dots: tailoring optical and chemical properties through selection of nitrogen precursors. Nano-Micro-Small (2024) 10587. Aizawa T., Fukuda T., Ito K-I., Carbon controlled CVD of 6H-structured fine polycrystalline SiC coating dies for galling-free micro-forging. Proc. 7 th WCMNM (19 th September, 2024; Pattaya, Thai) 116-119. Anwar M. S., Bukhari S. Z. A., Ha J-H., Lee J., Song I-H., Kim Y-W., Controlling the electrical resistivity of porous silicon carbide ceramics and their applications: A review. Appl. Ceram. Technol. 19 (4) (2022) 1814-1840 Kim I. K., Cha S., Hong S-M., Optimization of nitrogen ion implantation condition for β-Ga 2 O 3 vertical MOSFETs via process and device simulation. IEEE Trans, Electron Device 69 (12) (2022) 6948 – 6955. Xie X., Chen C., Luo J., Xu J., Effect of nitrogen ion implantation energy on the mechanical and chemical properties of AISI M50 steel. Int. J. Chem. Eng. 12 (2021) 4630661. Deguchi S., Hakamada M., Shingu J, Sakakibara S., Sugiyama H., Mabuchi M., Inactivation of HeLa cells on nanoporous gold. Materialia 7 (2021) 100370. Yang N., John S. Foord J. S., Xin Jiang X., Diamond electrochemistry at the nanoscale: A review. Carbon 99 (2016) 90-110. Schirhagl R., Chang K., Loretz M., Degen C. L., Nitrogen-vacancy centers in diamond: nanoscale sensors for physics and biology. Annu. Rev. Phys. Chem. 65(1) (2014) 83-105. Hou S., Hao J., Deng L., Cui X., Mao R., Jiang N., The synthesis of needle-like monocrystalline diamonds with a high aspect ratio up to 14. Nano-Micro-Small (2024) 2405521. Tables Tables 1 to 5 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Tables.docx Cite Share Download PDF Status: Published Journal Publication published 26 Jan, 2026 Read the published version in Journal of Bio- and Tribo-Corrosion → Version 1 posted Editorial decision: Revision requested 10 Dec, 2024 Reviews received at journal 10 Dec, 2024 Reviewers agreed at journal 09 Dec, 2024 Reviews received at journal 08 Dec, 2024 Reviewers agreed at journal 02 Dec, 2024 Reviewers invited by journal 14 Nov, 2024 Editor assigned by journal 13 Nov, 2024 Submission checks completed at journal 12 Nov, 2024 First submitted to journal 11 Nov, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Aizawa","email":"data:image/png;base64,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","orcid":"","institution":"Shibaura Institute of Technology","correspondingAuthor":true,"prefix":"","firstName":"T.","middleName":"","lastName":"Aizawa","suffix":""},{"id":385433894,"identity":"53ba06ec-2912-4209-9201-e406a39abe58","order_by":1,"name":"T. Fukuda","email":"","orcid":"","institution":"Tokai Engineering Service, Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"T.","middleName":"","lastName":"Fukuda","suffix":""}],"badges":[],"createdAt":"2024-11-12 02:23:11","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5435418/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5435418/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s40735-025-00958-1","type":"published","date":"2026-01-26T15:58:12+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":70647394,"identity":"c7e46999-ff4d-42bd-91fc-186ae5eb32a2","added_by":"auto","created_at":"2024-12-05 08:33:17","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":25258,"visible":true,"origin":"","legend":"\u003cp\u003eThree post-treatment effects by the nitrogen doping into the thin and thick coatings. (a) Lattice straining into thin films, (b) nanotexturing into thin and thick films, and (c) Nano-composite formation.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/cbce95891053ae28f18007e2.jpg"},{"id":70648546,"identity":"15940dd9-b103-4102-aa06-88c45c63d0a3","added_by":"auto","created_at":"2024-12-05 08:41:17","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":38961,"visible":true,"origin":"","legend":"\u003cp\u003eThree coating specimens for nitrogen doping experiments. (a) Thin gold coating, (b) polycrystalline diamond coated chip, and (c) carbon-supersaturated thick SiC coating.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/86c8a94a8626314bc070dfbb.jpg"},{"id":70647397,"identity":"ad1ebd8b-59e6-434e-b353-b1b9c0f2753f","added_by":"auto","created_at":"2024-12-05 08:33:17","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":68515,"visible":true,"origin":"","legend":"\u003cp\u003eAn experimental setup for nitrogen doping with the use of plasma immersion nitriding system. (a) Schematic view of nitrogen doping process, and (b) plasma immersion nitriding system.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/55fa7956835d2c113c4a76ef.jpg"},{"id":70648780,"identity":"d7ef9868-8aad-4a1f-8797-4dc3227b662e","added_by":"auto","created_at":"2024-12-05 08:49:18","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":38658,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of the N-doped gold film by controlling the plasma processing conditions. (a) N-doped thin gold film after heat treatment, and (b) N-doped thin gold film without heat treatment.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/88faa2e3f6250cc442e37d9c.jpg"},{"id":70650006,"identity":"e41e2b56-d3bf-4a28-b436-f941d62dc4bc","added_by":"auto","created_at":"2024-12-05 08:57:18","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":51073,"visible":true,"origin":"","legend":"\u003cp\u003eSurface morphology of the N-doped PCD film. (a) Overview on the N-doped PCD film on the WC (Co) chip, (b) SEM image on the A-region, and (c) SEM image on the B-region.\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/e8c9895e578162340a90e070.jpg"},{"id":70648549,"identity":"979b5889-fa59-4b0e-b275-f695564edb65","added_by":"auto","created_at":"2024-12-05 08:41:18","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":36920,"visible":true,"origin":"","legend":"\u003cp\u003eAn energy profile of light element analyzed by EDS.\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/771de8e1c532a0ae2acc77a7.jpg"},{"id":70647398,"identity":"0f16dea2-4097-48d6-a463-f31cd06e1082","added_by":"auto","created_at":"2024-12-05 08:33:18","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":45651,"visible":true,"origin":"","legend":"\u003cp\u003eNitrogen mapping on the ion-sliced sample of N-doped, MCSed SiC coating.\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/c8e3f5ecf994a2b5f269e281.jpg"},{"id":70647395,"identity":"6be4ce42-8b08-4c29-91c4-2c63933ae357","added_by":"auto","created_at":"2024-12-05 08:33:17","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":49879,"visible":true,"origin":"","legend":"\u003cp\u003eMicrostructure of the N-doped, MCSed SiC coating. The blue arrow indicates the stacking faults induced in the inside of SiC grain, penetrating from one end on its grain boundary to the other end. The red arrow points at the carbon rich cluster. Electric diffraction pattern was also inserted into Fig. 8.\u003c/p\u003e","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/c35a27373c5ed260a3996840.jpg"},{"id":70648776,"identity":"741e0c58-fa60-4684-8242-61a45970e1a6","added_by":"auto","created_at":"2024-12-05 08:49:18","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":93134,"visible":true,"origin":"","legend":"\u003cp\u003eSTEM image on the induced stacking faults into the 6H-structured SiC grain.. (a) A stacking fault band in low magnification image, and (b) stacking faults in the 6H-structured SiC crystallographic alignment.\u003c/p\u003e","description":"","filename":"9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/eb9101965246199b052f964a.jpg"},{"id":70650007,"identity":"ddd3fa72-0484-4356-89bd-918bd464b488","added_by":"auto","created_at":"2024-12-05 08:57:18","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":47268,"visible":true,"origin":"","legend":"\u003cp\u003eSTEM image and carbon mapping on the carbon rich clusters along the SiC grain boundaries.\u003c/p\u003e","description":"","filename":"10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/c7ca991acab4818bd8c71811.jpg"},{"id":70647401,"identity":"9208dbd9-64a4-4d5d-81b2-fe52dca24b14","added_by":"auto","created_at":"2024-12-05 08:33:18","extension":"jpg","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":71674,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of STEM images on the microstructure between the undoped and N-doped MCSed SiC coatings.\u003c/p\u003e","description":"","filename":"11.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/a847677f9ef47b34c411154a.jpg"},{"id":70647415,"identity":"0f709eb0-ea48-4924-9ea0-583f76e1d128","added_by":"auto","created_at":"2024-12-05 08:33:18","extension":"jpg","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":53736,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of carbon rich cluster distribution in the inner grains and along the grain boundaries between the undoped and N-doped MCSed SiC coatings.\u003c/p\u003e","description":"","filename":"12.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/db0a1a02821ac644ba11f87c.jpg"},{"id":70647442,"identity":"cbc48663-dcc9-4627-bd28-7a712d33b130","added_by":"auto","created_at":"2024-12-05 08:33:20","extension":"jpg","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":40693,"visible":true,"origin":"","legend":"\u003cp\u003eGrowth of carbon rich clusters along the grain boundaries analyzed by STEM.\u003c/p\u003e","description":"","filename":"13.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/ff6a25941b5e9c09d56545a5.jpg"},{"id":70648561,"identity":"ee0db4a5-7979-4c09-8c66-8f9cb22ad0d0","added_by":"auto","created_at":"2024-12-05 08:41:19","extension":"jpg","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":78561,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of morphology and population for carbon rich clusters between the undoped and N-doped MCSed SiC coatings.\u003c/p\u003e","description":"","filename":"14.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/8b492b3bbbe355ec902875b4.jpg"},{"id":101691236,"identity":"7298109d-307c-4bf5-abd7-fc35e443e4cf","added_by":"auto","created_at":"2026-02-02 16:13:10","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1349931,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/a997f434-55aa-48fe-b211-7a9cdccc2af0.pdf"},{"id":70648547,"identity":"c5436417-b9e8-4896-af90-7076f895936d","added_by":"auto","created_at":"2024-12-05 08:41:18","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":30978,"visible":true,"origin":"","legend":"","description":"","filename":"Tables.docx","url":"https://assets-eu.researchsquare.com/files/rs-5435418/v1/a4d20ae9ac39a74cb2fcd388.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Nitrogen Doping into Thin and Thick Coatings for Nano-structuring and Nano-texturing by Plasma Immersion Nitriding","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eVarious types of coating have been utilized to prolong the manufacturing tool life [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], to protect the artificial medical and dental products from wearing and corrosion [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], to improve the bio-activeness for enhancement of bio-compatibility between metallic parts and cells [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], and to functionalize by themselves via the specified surface textures [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Furthermore, a post-treatment of these original coatings is effective to modify their surface morphology for further functionalization of coating materials [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. In the literature, several studies were reported on the functionalization of thin and thick films by the post-treatment. Thin gold film was modified to be nano-porous to pasteurize its surface [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Polycrystalline diamond (PCD) or nano-diamond coatings on the tools were nano-textured for fine shearing and machining via the femtosecond laser machining [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] and the FIB (Focused Ion Beam) [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The carbon-controlled thick SiC coating was also modified to have a composite microstructure where 6H-structured SiC grains with lots of stacking faults align themselves with carbon-rich clusters along their grain boundaries [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAmong these post-treatments, the nitrogen doping process has a capability to make efficient surface modification of thin and thick coatings [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Three approaches of N-doping process are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. When impinging the nitrogen or carbon ions, or, nitrogen \u0026ndash; hydrogen or carbon \u0026ndash; hydrogen radicals into metallic films, they are supersaturated by nitrogen or carbon solutes with high content. As theoretically studied in [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], most of these nitrogen or carbon solutes occupy the octahedral vacancy sites in the crystalline lattices of coating materials. Then, each crystal lattice with the supersaturated nitrogen or carbon solutes is strained in anisotropic as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea. Any deposit such as cells and bacterium onto this thin film, is physically influenced by this lattice straining. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb, a nanotexturing of coating layers is highlighted as the second approach. When the thin and thick inorganic films are intensely irradiated by ion beams via the ion implantation and the intensified plasma bombardment, their structure is modified to have nanotextures and nanoporous as pointed in [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. In particular, these convex nanotextures induced by intense ion beam irradiation, works as a new type of sensors [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Nano-composites [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] are formed by selectively nitrogen ion impinging the dissimilar solute atoms into original granular structure as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec.\u003c/p\u003e \u003cp\u003eIn the present paper, three thin and thick coatings are prepared for N-doping to describe their modified surface conditions and to investigate the N-doping effect to each coating. The plasma immersion nitriding system is utilized in common for this N-doping. Thin gold film with the thickness of 200 nm is N-doped to have high nitrogen solute content and hardness. Thick PCD coating on the WC (Co) chip with the thickness of 15 \u0026micro;m is N-doped to have an array of acicular textures via self-organization. Thick carbon-controlled SiC coating with the thickness of 4 mm is also N-doped to reduce the SiC grain size and to increase the stacking faults density in the 6H-structured SiC grains as well as the carbon-rich clusters along the SiC grain boundaries. This crystallographic modification results in the selective reduction of electric resistivity to the unmasked surfaces.\u003c/p\u003e"},{"header":"2. Methods and Materials","content":"\u003cp\u003eThree types of thin and thick coatings were prepared for nitrogen doping process via the plasma immersion nitriding system. In addition to materials characterization on the N-doped coatings, the micro-Vickers testing was employed to measure the hardness of coatings. Furthermore, the masking technique was used to analyze the N-doping effect on the electric resistivity.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Preparation of thin and thick coatings for post-treatment\u003c/h2\u003e \u003cp\u003eThree types of thin and thick coatings were prepared for nitrogen doping experiments as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea shows a thin gold film with the average thickness of 200 nm onto the AISI304 stainless steel substrate. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb depicts a thick polycrystalline diamond (PCD) film with the thickness of 15 \u0026micro;m onto the WC (Co) chips. A thick 6H-structured SiC coating plate with the thickness of 4 mm is also prepared as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec. Thin gold film was deposited onto the substrate by sputtering method. PCD film was synthesized by PE-CVD (Plasma Enhanced Chemical vapor Deposition) method onto the WC (Co) chip before polishing. Thick SiC coating with supersaturated carbon content was once synthesized onto a dummy sintered SiC substrate by thermal CVD method and cut to only SiC coating specimen. After chemical cleansing, all these films were used as a specimen for N-doping.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Nitrogen doping procedure\u003c/h2\u003e \u003cp\u003eThe RF (Radio-Frequency) \u0026ndash; DC (Direct Current) plasma immersion nitriding system with the use of the hollow cathode, was utilized for N-doping experiments to film specimens as schematically illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea. Owing to the hollow cathode device, the nitrogen ion and NH (Nitrogen \u0026ndash; Hydrogen) - radical densities were enhanced in the hollow as studied in [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. After its plasma diagnosis, the ion density reached 4 x 10\u003csup\u003e18\u003c/sup\u003e ions/m\u003csup\u003e3\u003c/sup\u003e under the gas flow ratio of nitrogen gas by 160 mL/min to hydrogen gas flow by 30 mL/min. The RF-DC powers were automatically controlled with prompt response less than 1 ms to the spatial impedance change in plasmas by adjusting the frequency of RF power as well as the DC-bias voltage. Heater was embedded into the supporting plate below the DC-biased plate.\u003c/p\u003e \u003cp\u003eIn the following experiments, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb, the chamber was evacuated down to the base pressure of 0.1 Pa after setting the specimen into the hollow. The plasma immersion nitriding conditions were optimized for adaptive N-doping process to each specimen. As listed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, five items were main nitriding parameters; the RF-voltage, the DC-bias, the holding temperature, the total gas pressure, and the N-doping duration. Two procedures were employed for N-doping to thin gold film specimens; e.g., G1 and G2 procedures. In the G1-procedure, the specimen was preheat-treated at 673 K for 7.2 ks before N-doping. The RF-voltage, the DC-bias and the duration were varied in G1 and G2 procedures.\u003c/p\u003e \u003cp\u003eHigher RF-voltage and DC-bias were employed in the PCD procedure at 473 K. The thermocouples embedded onto the DC-biased plate, was used to monitor the temporal transients of temperature. In the SiC procedure, the processing temperature was increased up to 673 K. After presputtering in the nitrogen atmosphere for 1.8 ks at 673 K, the SiC coating specimen was immersed in the nitrogen \u0026ndash; hydrogen plasma at 50 Pa under the specified gas flow ratio by 160 mL for nitrogen to 30 mL for hydrogen gas at 673 K for 14.4 ks. After every N-doping process, the specimen was cooled down in the nitrogen atmosphere.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Materials and mechanical characterization\u003c/h2\u003e \u003cp\u003eSEM (Scanning Electron Microscopy; JEOL, Tokyo, Japan) \u0026ndash; EDS (Electron Dispersive X-ray Spectroscopy) were respectively used for microstructure observation and element mapping. STEM (Scanning Transmission Electron Microscopy; JEOL, Tokyo, Japan) was also utilized for precise analysis of crystallographic structure including defects. This Cs-corrected STEM attains high spatial resolution in 0.08 nm. In this STEM, the raster-scanned electron beam transmits through the specimen to provide three types of TEM images; LAADF (Low-Angle Annular Dark Field), HAADF (High-Angle Annular Dark Field), and ABF (Annular Bright Field) images. A series of steps were used in preparation for a sample for STEM analysis. The N-doped and undoped specimens were mechanically cut and polished. Then both sides of specimens were argon-ion-milled using the masking belt. Finally, the argon-ion slicer (JEOL, Tokyo, Japan) was used to build up the specimens for STEM analysis.\u003c/p\u003e \u003cp\u003eA nano-indenter (Shimazu; Kyoto, Japan) and a micro-Vickers hardness tester (Mitsutoyo, Co., Ltd., Yokohama, Japan) were respectively used for N-doped thin and thick coated specimen.\u003c/p\u003e \u003cp\u003eElectric resistivity was measured at the masked and unmasked regions using the insulation resistor (SM-8125; HIOKI, Co., Ltd. Nagano, Japan) to describe the nitrogen doping effect on the electric properties.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cp\u003eThree film specimens were N-doped at each plasma-immersion nitriding condition to yield the massively nitrogen-supersaturated (MNSed) samples for materials and mechanical characterization. In particular, precise analyses were performed on the MNSed CVD-SiC film with carbon control by using STEM and EDS.\u003c/p\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.1 N-doping into thin gold film\u003c/h2\u003e \u003cp\u003eTwo N-doping procedures were employed to investigate the N-doping effect on the supersaturated nitrogen solute content and the measured hardness. In the G1 procedure at Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, a heating treatment was added as a preliminary step to N-doping process. As depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, the original gold thin film changed its surface color from gold to red through this heat treatment, as pointed in [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. On the other hand, the original gold color turned to be more dark gold after the G2 procedure, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb. The measured nitrogen content and surface hardness of these G1- and G2-specimens were listed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The N-doped gold film is latticed strained via the massive nitrogen supersaturation (MNS) by 3\u0026ndash;5% in tension because of higher supersaturated nitrogen content than 1 mass%. This enrichment of nitrogen solutes significantly hardens the thin gold film up to 300 HV. In particular, the G2 procedure provides an efficient N-doping process with very little damage into a thin gold film.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.2 N-doping into PCD film on the WC (Co) chip\u003c/h2\u003e \u003cp\u003ePCD film was N-doped at 473 K by 50 Pa for 10.8 ks. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea, the PCD surface was modified into two colored regions. The inner region, A, in PCD, was gray-colored while the vicinity to PCD surface, B-region, was colored in black. SEM was used to analyze each region. In both regions, the original PCD surface was shaped into an alignment of acicular micro-textures, as respectively shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb and \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec. In the A-region, the acicular microtextures with lower height, align themselves in high density, as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb. While, in the B-region, the acicular microtextures with higher aspect ratio, align themselves in low density. This difference of acicular texture array reflects on the color change in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e shows the energy spectrum of elements in the N-doped PCD into B-region by EDS. Carbon was detected as a main component of PCD together with the impurities of iron and the constituent of WC substrate. Nitrogen was detected together with the impurity of oxygen. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e summarizes the chemical composition detected by this EDS analysis. The nitrogen solute content reaches 10 at%. This reveals that carbon sites in PCD are substituted by nitrogen atoms\u003c/p\u003e \u003cp\u003eThese acicular microtextures are formed by the physical bombardment with selective substitution of nitrogen atoms to carbon sites in PCD with high nitrogen content. The nitrogen solute supersaturates into the grain boundaries of PCD and substitutes into the carbon sites of tetragonal diamond. Then, as suggested in [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], the supersaturated and substituted PCD zones with high content nitrogen solutes remain as an acicular microtexture during N-doping. While, less supersaturated and substituted PCD zones are physically etched away during N-doping. Regularity in these acicular textures in Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb and \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec proves that this nitrogen supersaturation and substation advances selectively in the self-organization manner with much dependence on the nitrogen content distribution during N-doping. The difference of aspect ratios in the acicular microtextures between A and B regions, comes from the ion and radical density distribution in the plasma sheath. At the vicinity of PCD chip edges, more nitrogen ions and NH-radicals concentrate to make deeper etching by their physical bombardment.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.3 N-doping into MCSed thick SiC coating\u003c/h2\u003e \u003cp\u003eA thick MCSed SiC coating is nitrogen-doped at 673 K for 14.4 ks by plasma immersion nitriding. STEM\u003c/p\u003e \u003cp\u003e-EDS was first utilized to describe the nitrogen solute distribution in the inside of MNSed top layer. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, the nitrogen solutes uniformly distribute in the SiC grains and grain boundaries. This implies that the impinged nitrogen solutes have substitutional interaction with the bound carbon atoms in SiC as well as the carbon-rich clusters, synthesized by CVD deposition process with carbon enrichment [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. STEM was further utilized to analyze the microstructure of N-doped, MCSed SiC coating. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, the stacking faults are induced in the inside of SiC grains from one end of its grain boundary (GB) to the other end of its GB, as indicated by the blue arrow. The carbon-rich clusters are also synthesized mainly along the SiC GBs as pointed by the red arrow. This microstructure resembles to that before N-doping; however, more stacking faults and clusters is induced by N-doping. In particular, many stacking faults are induced in each SiC grain by this N-doping. As shown in the electric diffraction pattern inserted into Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, a halo-pattern proves that these carbon clusters are unbound in SiC.\u003c/p\u003e \u003cp\u003eA precise analysis on the SiC crystallographic structure and the grain boundary structure was performed using STEM and EDS. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ea, lots of stacking faults are formed into the SiC in a defect band. In fact, Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eb proves that wide stacking faults band is formed in the 6H-structured SiC granular structure. This reveals that many carbon solute atoms are exiled from the inside of SiC grain to its GBs through this stacking fault bands during the N-doping process. Figure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e shows the STEM image and carbon mapping along the SiC GBs. Many carbon-rich clusters are also formed especially along the SiC GBs. This proves that lots of bound carbon to SiC grains are exiled from the inside of SiC Grains to their GBs via homogeneous nitrogen substitution to SiC grains, and, that these exiled carbon solutes agglomerate with the pre-existing clusters and grow to a larger carbon-rich cluster.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Comparison of microstructure between masked and unmasked MCSed-SiC coating\u003c/h2\u003e \u003cp\u003eThe masking technique was employed to analyze the difference in microstructure between the N-doped and undoped SiC coatings. Three STEM images were compared under the same magnification between the undoped and N-doped MCSed SiC coatings in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e. The average SiC grain size is reduced by N-doping. Much more carbon rich clusters are induced along the grain boundaries. To be discussed later, more stacking faults are induced by N-doping, and, most of them are formed into the inner grains in bands. Since several stacking faults are formed all together with them, these stacking fault bands turn to be a new SiC GB so that the grain size is reduced.\u003c/p\u003e \u003cp\u003eThe carbon rich cluster distribution is compared between the undoped and N-doped regions. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e, more carbon rich clusters distribute not only in the inner SiC grains but also along their GBs in both regions. To be noticed, the number of clusters is much increased by N-doping in this image. This increase of carbon rich clusters as well as increase of stacking faults bands reveals that more carbon solutes are exiled by substation of nitrogen solutes to carbon sites in SiC and that these carbon solutes diffuse through the stacking faults and agglomerate themselves along the GBs.\u003c/p\u003e \u003cp\u003eThe carbon solute transportation from inner SiC grains to their GBs might well be enhanced by N-doping. Each carbon cluster before doping is expected to grow itself during N-doping. Fig, 13 depicts HAADf, ABF and LAADF images analyzed by STEM, respectively. Each carbon rich cluster grew up to have nearly the same size of SiC grains. That is, the SiC grains are partially surrounded by carbon rich clusters. This carbon rich cluster distribution is also compared before and after N-doping. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e., the grown-up carbon clusters surround each SiC grain boundary. Figures\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003e and \u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e reveal that most of N-doped SiC grains have GBs including the carbon rich clusters. This coverage of carbon rich clusters onto SiC grains reflects on the functional properties of SiC.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Comparison of electric resistivity between masked and unmasked MCSed-SiC coatings.\u003c/h2\u003e \u003cp\u003eSilicon carbide, especially 6H-strcutured SiC, has high resistivity as reviewed in [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Various approaches were developed to reduce or control this electric resistivity by microstructure modification. The electric resistivity was measured and compared between the N-doped and undoped regions in the MCSed SiC specimen in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec. As listed in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, the electric resistivity is reduced by 1/3 to 1/2 of original resistivity to 6H-structure SiC. This is attributed to the coverage of SiC GBs by carbon-rich clusters, the density of which is increased by N-doping.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eN-doping process has been utilized in industries with the use of ion implantation technique [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The accelerated nitrogen ions are impinged into the thin and thick coatings with the specified kinetic energy in 100 keV to MeV order. Even under this intense ion bombardment, the affected layer thickness by nitrogen ion implantation is still limited by 1 to 2 \u0026micro;m [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The present N-doping process via the plasma immersion nitriding builds up a thicker affected layer up to 10 to 100 \u0026micro;m range through the nitrogen solute diffusion with modification of microstructure of original coatings. This modification by N-doping is discussed with reference to three N-doping experiments.\u003c/p\u003e \u003cp\u003eA nitrogen doping process into thin and thick coatings is characterized by massive nitrogen supersaturation. The nitrogen content [N] reaches 1 mass% in the N-doped thin gold film while [N]\u0026thinsp;~\u0026thinsp;10 mass% in the N-doped PCD film. As theoretically explained in [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], this MNS induces an anisotropic lattice expansion into the N-doped films. In case of the N-doped gold thin films, this lattice strain reaches\u0026thinsp;+\u0026thinsp;3 to +\u0026thinsp;5% in tension. As stated in [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], the surface strains of nano-porous gold film induced the polarization into the cells for inactivation. This suggests that N-doped gold thin film works as a bioactive coating to pasteurize the gold-coated parts and tools even in vivo. In parallel to lattice-straining effect, the N-doping process significantly harden the soft metals like pure gold. The hardness of 300 HV in the N-doped gold films via G1 and G2 procedures exceeds the hardness of aluminum alloys. This implies that MNS directly drives to harden the gold crystallographic structure by lattice distortion.\u003c/p\u003e \u003cp\u003eThick SCD (Single Crystal Diamond) and PCD films have been widely utilized not only as a machining chip and tool but also as a semi-conductor working at the elevated temperature. In addition to their intrinsic high hardness, their electric properties are also attractive to industrial applications. In particular, as stated in [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], various new functionalities and performances were induced into SCD and PCD films by nanostructuring processes. A regularized defect introduced by nitrogen doping induces the nitrogen \u0026ndash; vacancy centers for luminescence [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. After [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], micro- and nano-textures were built on the machining tools and piercing punch. In particular, a fully burnished hole surface with mirror-like surface condition was attained by using the nanotextured punch. The nanotexturing morphology of SCD and PCD by those laser and FIB machining processes is limited to have low aspect ratio. As recently reported in [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], needle-like monocrystalline diamonds with higher aspect ratio than 14, was synthesized by self-organization with aid of catalysis. This fine control of morphology in the diamond coating suggests that the present nitrogen doping approach is effective to yield the acicular diamond nanotextures with higher aspect ratio onto the SCD and PCD films and deposits.\u003c/p\u003e \u003cp\u003eA thick MCSed SiC coating by thermal CVD with carbon control, consists of the 6H-structured SiC grains with a few stacking faults in the SiC grains and a few carbon-rich clusters along the grain boundaries. Under the present N-doping, this composite microstructure is enhanced to have much more stacking faults in the inside SiC grains and more carbon-rich clusters along their grain boundaries. These defects and clusters are induced by nitrogen substitution into carbon sites in SiC binding state and by transportation of exiled carbon solutes to grain boundaries. As summarized in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, increase of stacking fault density reduces the SiC grain size. This proves that the staking fault bands induced by N-doping form new grain boundaries and result in the reduction of SiC grain size. The carbon rich cluster density and size increase nu N-doping. This implies that SiC grain boundaries are gradually covered by these clusters. Due to this coverage, the electric resistivity is reduced by N-doping.\u003c/p\u003e \u003cp\u003eN-doping to thin metallic coating is characterized by lattice straining and solid solution hardening. In case of N-doping to thin gold films, no nitrides are synthesized as a precipitate so that gold film is physically hardened by nitrogen solid solution into gold crystallographic structure. This high strained gold surface is attractive to bio-active coating of medical tools. This hardening prolongs the engineering durability of gold-coated pins and connectors. When the transition or refractory metal coating is N-doped, fine precipitation of nitrides could contribute to hardening of these thin metallic films. The carbon-base coatings such as DLC (Diamond Liker Carbon) and CVD diamond films, might well be N-doped to provide the acicularly textured DLC and diamond films with high aspect ratio. This tremendous surface area extension is attractive to sensing the nanoparticles and to radiate the current into solutions. The surface composite layer of 6H-structured SiC grains and carbon-rich grain boundaries, works as a mold in hot stamping of oxide glasses into optical lens and element due its high wear endurance of SiC grains at the elevated temperature and its electric and thermal conductivity with aid of carbon grain boundary network.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThin and thick coating materials were nitrogen doped to describe the microstructure and mechanical change before and after doping. The N-doped thin gold film is lattice-strained by nitrogen supersaturation with the nitrogen solute content up to 1 mass%. It has high hardness of 300 HV. High surface straining and high hardening provides an engineering way to functionalize the gold-coated parts and tools. The N-doped PCD film has an acicular microtexture with high aspect ratio via the self-organization in the nitrogen selective-substitution of carbon sites in PCD. The extraordinary surface extension of PCD film works as a sensitive sensor to nano-particles and bacterium and as a tiny electrode for wet plating. SiC microstructure is significantly modified by N-doping to have lots of stacking fault defects in the inside of grains and carbon rich clusters along the grain boundaries. A CVD-synthesized thick SiC substrate turns to have fine-grained crystallographic composite with carbon-rich grain boundaries. This composite surface layer has mechanical stability and strength original to 6H-structure SiC and conductive grain boundaries.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eT.A. wrote the main manuscript text.T.F. checked this text.T.A. ad T.F. prepared the samples and made experiments.All authors reviewed this manusript incuding figures and tables\u003c/p\u003e\u003cp\u003e[Acknowledgements]\u003c/p\u003e\n\u003cp\u003eThe authors would like to express their gratitude to T. Koyama, M. Saito, H. Yoshida, and Y. Ikuhara (University of Tokyo) for their sincere efforts in STEM analysis., and to Nasu T. (Ebinax, Co., Ltd.) for his help in measurement.\u003c/p\u003e\n\u003cp\u003e[Funding] Authore received no funding to the present research.\u003c/p\u003e\n\u003cp\u003e[Confliction of Interests] All authors declared that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest .\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAurich J. C., Kieren-Ehses S., Mayer T., Bohley M., Kirsch B., An investigation of the influence of the coating on the tool lifetime and surface quality for ultra-small micro end mills with different diameters. CIRP J. Manufact. Sci. Eng. 37 (2022) 92-102.\u003c/li\u003e\n\u003cli\u003eS\u0026ouml;derholm K-J. M., Coatings in dentistry\u0026mdash;A review of some basic principles. Coatings 2 (4) (2012) 138-159.\u003c/li\u003e\n\u003cli\u003eKim S-J., Lee D-S., Kim I-G,, Sohn D-W., Park J-Y., Choi B-K., Kim S-W., Evaluation of the biocompatibility of a coating material for an implantable bladder volume sensor. Kaohsiung J. Med. Si. 28 (3) (2012) 123-129.\u003c/li\u003e\n\u003cli\u003eWu F., Liu N., Ma Y., Zhang X., Han Y., Research on the influence of diamond coating microtexture on graphitization law and friction coefficient. Diamond Related Materials 127 (2022) 109153.\u003c/li\u003e\n\u003cli\u003eAizawa T., Inohara T., Yoshino T., Suzuki Y., Shiratori T., Laser treatment of CVD diamond coated punch for ultra-fine piercing of metallic sheets. Ch. 4 in Engineering Applications of Diamond, Intech Open, UK, London (2021).\u003c/li\u003e\n\u003cli\u003eWu P., Yanagi K., Yokota K., Hakamada M., Mabuchi M., Unusual effects of a nanoporous gold substrate on cell adhesion and differentiation because of independent multi-branch signaling of focal adhesions. J Mater. Sci.: Materials in Medicine 34 (2023) 54.\u003c/li\u003e\n\u003cli\u003eAizawa T., Shiratori T., Kira Y., Inohara T., Simultaneous nano-texturing onto a CVD-diamond coated piercing punch with femtosecond laser trimming. J. Applied Sciences 10, 2674 (2020) 1-12.\u003c/li\u003e\n\u003cli\u003eTuğrul \u0026Ouml;zel T., Biermann D., Enomoto T., Mativenga P., Structured and textured cutting tool surfaces for machining applications. CIRP Annal. 70 (6) (2021).\u003c/li\u003e\n\u003cli\u003eAizawa T., Fukuda T., Nitrogen doping into 6H-structured carbon supersaturated SiC coating via plasma immersion nitriding. Proc. 7\u003csup\u003eth\u003c/sup\u003e WCMNM (September 19\u003csup\u003eth\u003c/sup\u003e, 2024; Pattaya, Thai) 120-124.\u003c/li\u003e\n\u003cli\u003eTomastik J., Ctvrtlik R., Ingr T., Manak J., Opletalova A., Effect of nitrogen doping and temperature on mechanical durability of silicon carbide thin films. Sci. Rep. 8 (2018) 10428.\u003c/li\u003e\n\u003cli\u003eDomain C.; Becquart C. S., Foct J., Ab initio study of foreign interstitial atom (C, N) interactions with intrinsic point defects in \u0026alpha;-Fe. Physical Review B. 2004; 69: 144122.\u003c/li\u003e\n\u003cli\u003eCivantos A., Mesa-Restrepo A., Torres Y., Shetty A. R., Cheng M. K., Jaramillo-Correa C., Aditya T., Allain J. P., Nanotextured porous titanium scaffolds by argon ion irradiation: Toward conformal nanopatterning and improved implant osseointegration. J. Bio. Mater. Res. 111 (12) (2023) 1850-1865. \u003c/li\u003e\n\u003cli\u003eTeranishi N., Fuse G., Sugitani M., A review of Ion Implantation Technology for Image Sensors. Sensors 18(7) (2018) 2358.\u003c/li\u003e\n\u003cli\u003eKim D-S., Jeong W. S., Ko H., Lee J-S., Byun D., Pretreatment by selective ion-implantation for epitaxial lateral overgrowth of GaN on patterned sapphire substrate. Thin Solid Films 641 (2017) 2-7.\u003c/li\u003e\n\u003cli\u003eSharma, M.K.; Saikia, B.K.; Bujarbarua, S. Optical Emission Spectroscopy of DC Pulsed Plasmas Used for Steel Nitriding. Surf. Coat. Technol. 2008, 203, 229\u0026ndash;233\u003c/li\u003e\n\u003cli\u003eAizawa T., Rsadi I., Yunata E. E., High density RF-DC plasma nitriding under optimized conditions by plasma diagnosis. Appl. Sci. 12, 3706; 2022: 1-12.\u003c/li\u003e\n\u003cli\u003eŁapiński M., Piotr Dr\u0026oacute;żdż P., Gołębiowski M., Gołębiowski M., Piotr Okoczuk P., Karczewski J., Sobanska M., Pietruczik A., Zytkiewicz A. R., Zdyb R., Sadowski W., Kościelska B., Thermal Instability of gold thin films. Coatings 13(8) (2023) 1306. \u003c/li\u003e\n\u003cli\u003eNguyen K. G., Hu\u0026scaron; M., Baragau I-A., Bowen J., Heil T., Nicolaev A., Abramiuc L. E., Sapelkin A., Sajjad M. T., Kellici S., Nitrogen-doped carbon quantum dots: tailoring optical and chemical properties through selection of nitrogen precursors. Nano-Micro-Small (2024) 10587.\u003c/li\u003e\n\u003cli\u003eAizawa T., Fukuda T., Ito K-I., Carbon controlled CVD of 6H-structured fine polycrystalline SiC coating dies for galling-free micro-forging. Proc. 7\u003csup\u003eth\u003c/sup\u003e WCMNM (19\u003csup\u003eth\u003c/sup\u003e September, 2024; Pattaya, Thai) 116-119.\u003c/li\u003e\n\u003cli\u003eAnwar M. S., Bukhari S. Z. A., Ha J-H., Lee J., Song I-H., Kim Y-W., Controlling the electrical resistivity of porous silicon carbide ceramics and their applications: A review. Appl. Ceram. Technol. 19 (4) (2022) 1814-1840\u003c/li\u003e\n\u003cli\u003eKim I. K., Cha S., Hong S-M., Optimization of nitrogen ion implantation condition for \u0026beta;-Ga\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e vertical MOSFETs via process and device simulation. IEEE Trans, Electron Device 69 (12) (2022) 6948 \u0026ndash; 6955.\u003c/li\u003e\n\u003cli\u003eXie X., Chen C., Luo J., Xu J., Effect of nitrogen ion implantation energy on the mechanical and chemical properties of AISI M50 steel. Int. J. Chem. Eng. 12 (2021) 4630661.\u003c/li\u003e\n\u003cli\u003eDeguchi S., Hakamada M., Shingu J, Sakakibara S., Sugiyama H., Mabuchi M., Inactivation of HeLa cells on nanoporous gold. Materialia 7 (2021) 100370.\u003c/li\u003e\n\u003cli\u003eYang N., John S. Foord J. S., Xin Jiang X., Diamond electrochemistry at the nanoscale: A review. Carbon 99 (2016) 90-110.\u003c/li\u003e\n\u003cli\u003eSchirhagl R., Chang K., Loretz M., Degen C. L., Nitrogen-vacancy centers in diamond: nanoscale sensors for physics and biology. Annu. Rev. Phys. Chem. 65(1) (2014) 83-105.\u003c/li\u003e\n\u003cli\u003eHou S., Hao J., Deng L., Cui X., Mao R., Jiang N., The synthesis of needle-like monocrystalline diamonds with a high aspect ratio up to 14. Nano-Micro-Small (2024) 2405521.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 to 5 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-bio--and-tribo-corrosion","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jbtc","sideBox":"Learn more about [Journal of Bio- and Tribo-Corrosion](http://link.springer.com/journal/40735)","snPcode":"40735","submissionUrl":"https://submission.nature.com/new-submission/40735/3","title":"Journal of Bio- and Tribo-Corrosion","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Plasma immersion nitriding, Nitrogen doping, Gold film, Polycrystalline diamond coating, thick SiC coating, Nanostructuring","lastPublishedDoi":"10.21203/rs.3.rs-5435418/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5435418/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eA thin gold film, a poly-crystalline diamond (PCD) coating and a carbon-supersaturated thick SiC (Silicon Carbide) coating, were nitrogen-doped or N-doped by using the plasma immersion nitriding. The N-doped gold thin film was characterized by lattice straining up to 3\u0026ndash;5% and by hardening to 300 HV via the massive nitrogen supersaturation (MNS). The N-doped PCD was nano-textured to have a fine acicular-texture array on the PCD surface via self-organization process. The massively carbon supersaturated (MCSed) SiC thick coating was N-doped and characterized by the enrichment of carbon-rich clusters along the 6H-structured SiC grain boundaries. The masking technique was employed to describe the difference in microstructures and electric resistivity between the N-doped and undoped MCSed SiC coatings. N-doping induced the reduction of SiC grain size as well as the increase of stacking faults in the SiC grains as well as carbon-rich clusters along the SiC grain boundaries. The electric resistivity was reduced to 1/2 to 1/3 by this N-doping. Various functions were accommodated to thin and thick coatings by the nitrogen doping via the plasma immersion nitriding.\u003c/p\u003e","manuscriptTitle":"Nitrogen Doping into Thin and Thick Coatings for Nano-structuring and Nano-texturing by Plasma Immersion Nitriding","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-12-05 08:33:12","doi":"10.21203/rs.3.rs-5435418/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-12-11T03:35:56+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-12-10T13:48:20+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"212591258611633752270109035693345076847","date":"2024-12-09T14:06:12+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-12-09T04:38:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"333474922923037860230283294518114845665","date":"2024-12-03T03:01:41+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-11-14T10:04:02+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-11-14T04:23:03+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-11-13T01:41:02+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Bio- and Tribo-Corrosion","date":"2024-11-12T02:14:34+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-bio--and-tribo-corrosion","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jbtc","sideBox":"Learn more about [Journal of Bio- and Tribo-Corrosion](http://link.springer.com/journal/40735)","snPcode":"40735","submissionUrl":"https://submission.nature.com/new-submission/40735/3","title":"Journal of Bio- and Tribo-Corrosion","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"32209358-1660-460b-8c70-050371e1f163","owner":[],"postedDate":"December 5th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-02-02T16:09:41+00:00","versionOfRecord":{"articleIdentity":"rs-5435418","link":"https://doi.org/10.1007/s40735-025-00958-1","journal":{"identity":"journal-of-bio--and-tribo-corrosion","isVorOnly":false,"title":"Journal of Bio- and Tribo-Corrosion"},"publishedOn":"2026-01-26 15:58:12","publishedOnDateReadable":"January 26th, 2026"},"versionCreatedAt":"2024-12-05 08:33:12","video":"","vorDoi":"10.1007/s40735-025-00958-1","vorDoiUrl":"https://doi.org/10.1007/s40735-025-00958-1","workflowStages":[]},"version":"v1","identity":"rs-5435418","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5435418","identity":"rs-5435418","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}