Surface effects on heterogeneous nucleation of metal at the atomic scale

Surface effects on heterogeneous nucleation of metal at the atomic scale | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Surface effects on heterogeneous nucleation of metal at the atomic scale Kecheng Cao, Pu Yan, Kaijun Sun, Yan Mi, Jing Feng, Wengdi Zheng, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5396960/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Agglomerationand crystallization of atoms are the key processes in nucleation. For heterogeneous nucleation, investigating the influence of the substrate surface on agglomeration and crystallization, and then understanding the related mechanism at the atomic scale is crucial to material synthesis. Here, electron beam in transmission electron microscopy is utilized to decompose BiOCl material for generating dissociative Bi atoms. We observe the heterogeneous nucleation process of Bi nanocrystals at the surface of BiOCl from the side view with atomic spatial resolution and millisecond temporal resolution. The nucleation and crystallization of Bi nanocrystal is found to occur at the concave sites of the surface with angles ranging from 91° to 157° and form stable nucleus with sizes of 1 to 2 nanometers, while the pre-agglomerated Bi clusters dissociate again on the flat and convex surface. We demonstrate the collision between the Bi atoms and the concave structure helps Bi atoms release kinetic energy and form nucleus, and then the concave surface further stabilizes the nucleus and promotes crystallization. Physical sciences/Nanoscience and technology/Nanoscale materials/Nanoparticles Physical sciences/Chemistry/Materials chemistry Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Main Nucleation, the common yet mysterious phenomenon in nature, serves as the pyramid foundation of the material science in the construction of human civilization 1-4 . In recent years, several non-classical multi-step nucleation theories beyond the classical nucleation theory have been introduced and developed 5-12 . The identification of metastable intermediate states preceding the formation of crystal nucleus improves the understanding of homogeneous nucleation 6 . Apart from homogeneous nucleation, heterogeneous nucleation is a more common nucleation mode, during which pre-nucleation matters attach to substrate surfaces to reduce total free energy and then nucleate and crystallize 7,13 . The properties of the substrate surface, including surface chemical constructions and physical roughness, significantly influence the interaction between the surface and pre-nucleation matters. These further affect the site, density, and rate of nucleation, as well as the size and even orientation of the nucleated crystal 14,15 . To understand these surface effects on heterogeneous nucleation, various techniques such as transmission electron microscopy (TEM) 16 , small-angle X-ray scattering 17 , atomic force microscopy 18 , and scanning electron microscopy (SEM) 19 have been employed to investigate the dynamics of heterogeneous nucleation at diverse surfaces. Nevertheless, the atomic mechanisms of the surface effects, especially how the pre-nucleation matter interacts with the surface and how the nucleation sites are selectively determined at the atomic scale, remain unclear. Advanced aberration-corrected high resolution TEM (AC-HRTEM) with temporal resolution at the millisecond scale and sub-atomic spatial resolution has contributed to deepening the understandings of crystal nucleation mechanisms 20 . Furthermore, the electron beam in TEM has been directly employed as initiators to trigger the nucleation of crystal in liquid or vacuum. 21-25 Compared with the liquid environment, studying the nucleation process stimulated by electron beam under vacuum possesses higher spatial resolution. 21 Accordingly, the atomic structure of the small primary clusters or nuclei with size smaller than 2 nm at the initial stage of nucleation can be observed. By utilizing low-contrast substrates such as single-walled carbon nanotubes or graphene combined with the electron beam trigger technology, the two-step nucleation mechanism and the reversible transformation phenomenon for nucleation of metals have been unveiled. 21,26 Here, we reveal surface effects on heterogeneous nucleation of metal at the atomic scale using bismuth (Bi) crystal as model. The electron beam in AC-HRTEM is used to stimulate the dissociation of BiOCl nanocrystals as starting material for generating discrete Bi atoms. Thereby we have realized the direct observations of Bi nanocrystal heterogeneous nucleation at the BiOCl surface from the side view with atomic spatial resolution and millisecond time resolution. Our results demonstrated that the concave sites on surfaces play significant roles in facilitating the formation of amorphous clusters via kinetic energy relaxation by collisions. Moreover, these concave sites contribute to the subsequent nucleation, growth, and stabilization of the as-formed crystals. Bismuth, a metal with low melting point and high electron beam irradiation sensitivity 27 , is an ideal candidate for investigating surface effects on heterogeneous nucleation in real time by AC-HRTEM. We applied an electron beam sensitive compound, BiOCl, as starting material, and then irradiated and observed it utilizing parallel 80 keV electron beam in AC-HRTEM. The characterizations of BiOCl including x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), SEM images, AC-HRTEM images, SAED patterns, energy-dispersive X-ray spectroscopy (EDS) mapping, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and electron energy loss spectroscopy (EELS) are shown in Supplementary Figs. 1-7. Fig. 1a shows the typical time-series images acquired from continuous Supplementary Movies 1-4, presenting the real-time stimulation and observations for the dissociation and nucleation process of a Bi nanocrystal under 80 keV electron beam irradiation (Supplementary Fig. 8). The whole process lasted over 252,400 ms, and can be divided into three stages: (1) beginning of dissociation of BiOCl and diffusion of Bi atoms; (2) atom relaxation and pre-nucleation stage; (3) metastable cluster nucleation, nuclei growth, and amorphous-crystalline (A-C) changing stage. At the initial state (0 ms), an intrinsic concave site with an angle of 98.4° and a depth of 2 nm was observed at the surface of BiOCl. Under electron beam irradiation during AC-HRTEM imaging, the chemical bonds in BiOCl were activated and broken due to synergistical ionization and knock-on processes via inelastic and elastic scattering of incident electrons 28 . The corresponding elastic and inelastic cross section and ionization potentials calculated by aug-cc-PVQZ-DK3 method are shown in Supplementary Fig. 9 and Supplementary Table 1 and Table 2. Under 80 keV electron beam irradiation, the maximum transferred kinetic energy ( E Tmax ) from 80 keV electron to a Bi, O, and Cl atom is 0.9036 eV, 11.8 eV, and 5.326 eV, respectively, as shown in Supplementary Table 3, resulting in the dissociation of BiOCl and generation of discrete Bi atoms (Fig. 1b). The breaking of chemical bonds lead to the increase of the free energy of Bi atom, making them migrate out and then be physically and chemically absorbed at the surface. We verified that BiOCl was dissociated into O 2 and Cl 2 besides discrete Bi atoms under 80 keV electron beam irradiation, by in situ electron beam irradiation-mass spectrometry experiment on our home-made electron beam molecular engineering (EBME) system (Methods, Extended Data Figs. 1-5, Supplementary Figs. 10-11 and Supplementary Table 4). Thus, we found these discrete Bi atoms freely diffusing on the BiOCl surface during the whole irradiation and observation processes. The electron-beam induced dissociation process ran through the whole investigation, consistently providing Bi atoms for further nucleation processes. The electron beam irradiation acts as an energy source, providing kinetic energy for the whole process, which is similar to conventional thermal driven heterogeneous nucleation via interatomic or intermolecular collisions. From 0 ms to 7,680 ms, a few of the Bi atoms (less than 10) consecutively diffused to the bottom of the defective structure. These Bi atoms gathered together and overcame the first energy barrier of nucleation 29 , forming an observable amorphous cluster at 10,410 ms. At this concave site, the discrete Bi atoms collided with the atoms on the surface and other stacked Bi atoms, resulting in the relaxation of their free energy, as illustrated in Fig. 1b (Note the collisions and diffusions of Bi atoms can be observed more clearly in Supplementary Movies 1-4). Therefore, this concave site acted as a potential well for the diffusing Bi atoms, which further promoted the subsequent aggregation of discrete Bi atoms. Consequently, it served as the nucleation site for the further nucleation and growth of Bi crystal. During this stage, the as-formed tiny amorphous cluster kept changing structure but did not dissociate under 80 keV electron beam irradiation. From 10,410 ms to 16,990 ms, more Bi atoms diffused and then integrated into the tiny cluster, forming a pre-nucleation nucleus with size of 1-2 nm. In this stage, the cluster was completely amorphous showing dynamical and indistinguishable atomic structure. From 17,890 ms to 240,990 ms, the growing cluster overcame the second energy barrier for metal nucleation and then nucleated into an unstable Bi nanocrystal 21 . The Bi nanocrystal showed dynamical atomic structure switching between amorphous and crystalline states under electron beam irradiation. The energy transferred from incident electron to the Bi atoms is inconstant which relates to the scattering angle as presented in Supplementary Fig. 9. The transferred energy stimulated the free energy fluctuation of the Bi nanoparticle, resulting in the oscillation of its atomic structure. From 245,680 ms to 252,400 ms, this particle kept on growing and transformed into a bigger single crystal with lower free energy per Bi atom. The Bi nanocrystal became more stable but still undergone a reversible transformation between amorphous and crystalline states due to the transfer of kinetic energy from the incident electron 30 . At this stage, the concave site was fully filled by the Bi nanocrystal. The crystallinity and projected area of the nucleating and growing Bi nanoparticle are quantitatively analyzed and plotted in Fig. 1c. The crystallinity was quantified by analyzing the FFT patterns of the nanoparticle, demonstrating the amorphous nature of the pre-nucleation cluster before 17,910 ms and the structural oscillation of the nucleated nanoparticle after 17,910 ms. In addition, by quantifying the projection area of nucleated Bi nanocrystal and assuming the nanocrystal is spherical, we estimated the volume and the total atomic number of the nanocrystal in Fig. 1c. The growth rate of the nanocrystal is approximately 4 Bi atoms per 10 seconds from the quantification result. To investigate the relation between the nanoscale flatness and nucleation sites on the surface of substrate, we systematically analyzed the distribution of nucleation sites and corresponding surface structure (Fig. 2, Supplementary Figs. 12-13). Fig. 2a and Fig. 2b display the overall surface morphology of the BiOCl substrate. The surface was generally flat at micrometer scale but pitted with nanoscale concave and convex sites. Five representative intrinsic concave sites with angles from 98.8° to 129.5° and depths from 1 nm to 2 nm at the surface of BiOCl are shown in Fig. 2c. Fig. 2d shows the nucleation of Bi nanocrystals occurred at these intrinsic concave sites after 80 keV or 300 keV electron beam irradiation with dose rate ranging from 1.52×10 4 e Å -2 s -1 to 2.33×10 4 e Å -2 s -1 and time from 65 to 201 seconds. Fig. 2e presents 6 more typical cases in which the Bi nanocrystals formed at the concave sites. The dissociation of BiOCl and the subsequent atomic migration and nucleation processes at concave sites were common phenomena during our observations. Hence, we made statistical analysis of the angles of sites where Bi atoms nucleated and grew into nanocrystals based on 100 stochastic cases. We found 99% Bi nanocrystals formed at the concave sites with angles from 90 to 150 degrees, while only one Bi nanocrystal formed at the concave site with an angle of 156 degree. In addition, no Bi nanocrystal was found nucleated at flat or convex sites. Note that due to the thermodynamic equilibrium process during BiOCl material growth, concaves with angles smaller than 90 degrees are not stable and thus do not exist on the surface of BiOCl. Compared with the concave substrate surface, the behavior of discrete Bi atoms on the relatively smooth surface was noticeably different. We conducted in situ AC-HRTEM and HAADF-STEM experiments under the acceleration voltages of 80 keV or 300 keV (Supplementary Movies 5-6, Supplementary Figs. 14-16). Then we found that the dissociated discrete Bi atoms on the smooth surface were able to agglomerate and form tiny clusters, but they eventually dissociated again. As shown in Fig. 3a and Fig. 3b, at 80 keV, the time series AC-HRTEM images from recorded video Supplementary Movie 5 begins with an already formed tiny Bi cluster containing several atoms on the surface. However, this Bi cluster was unstable under e-beam irradiation, changing structure and dissociating into discrete atoms after 1,010 ms. In this relatively smooth area containing two neighboring concave sites with angles of 147.2° and 136.2°, we found tiny Bi clusters with less than 6 atoms formed and eventually dissociated, which repeated 24 times in the following 53,930 ms, as clearly shown in Supplementary Movie 5. We have analyzed the surface atomic migration before and after 20 ms in the whole process. Through the line profile of the intensity in the enlarged image in Fig. 3a, we find that the positions of the surface atoms change quickly within 10 ms under the irradiation of the electron beam, demonstrating the fast and frequent atomic diffusion on the surface. Fig. 3c and Fig. 3d present the similar phenomenon observed at 300 keV on a convex surface with angle of 200.8°. At the convex site, the discrete Bi atoms agglomerated into tiny clusters and soon dissociated again in 1 second. Thus, for the discrete Bi atoms diffusing on a relatively smooth surface, they could only form unstable amorphous cluster within 3-7 atoms which are not able to nucleate and grow into crystal under electron beam irradiation. In contrast with the concave sites with smaller angles (Fig. 1a and 2), the smooth and convex sites provided relatively open space for the diffusion of Bi atoms. Namely, potential wells for the motion of Bi atoms and clusters did not exist at these sites. The Bi atoms cannot effectively release free energy by impacting on the substrate surface. Therefore, the as-formed tiny clusters still possessed high free energy, which were subsequently dissociated into atoms by electron beam irradiation. The consequence was the free Bi atoms would not nucleate and grow into crystal on relatively smooth and convex surfaces where cannot provide nucleation site as a low energy potential well. The nucleated Bi nanocrystals on the substrate surface were still unstable under electron beam irradiation in Fig. 1a (245,680-252,400 ms) and Fig. 4a. They changed between amorphous and crystalline states as shown in Fig. 4b and c and even can move on the surface in Supplementary Fig. 17. We found such kind of nucleated Bi nanocrystal could be stabilized by further interacting with uneven surfaces of the substrate. A nanocrystal kept changing its state continually for over 34 times in the first 2,000 ms, as counted and presented in Fig. 4a and 4d (with frames acquired from Supplementary Movie 7). We found when the Bi nanocrystal switched from crystalline to amorphous state, it elongated and increased the contact area to the surface, thereby reducing its surface free energy. From 20,300 ms to 20,320 ms, the Bi nanocrystal became amorphous and began to contact the boundary from the bottom side (green arrows). In the following 60 ms, the Bi nanoparticle sufficiently contacted with the boundary and crystallized again owing to the reduction of surface free energy. From 20,380 ms to 21,720 ms, the Bi nanocrystal kept increasing its crystallinity, and then recrystallized into a single crystal with sharp surface. We quantified and presented the change of crystallinity for this Bi nanoparticle in Fig. 4c by using FFT patterns shown in Fig. 4a. The result shows a reversible transition between amorphous and crystalline states of the Bi nanoparticle before contacting the boundary. After contacted with the boundary, the Bi nanoparticle stayed in crystalline state as shown in Supplementary Fig. 18. Thus, the impact of surface flatness on the stability of the crystal structure has been assessed. The Bi nanocrystal releases surface free energy by contacting with multiple boundaries, thereby enhancing its crystallinity and stability. Through in situ observations at the atomic scale with high time resolution, we observed such process could be completed within 80 ms. Stabilization of nucleated Bi nanocrystal via boundary contacting is a common process during the heterogeneous nucleation. We presented and analyzed another similar observation in Supplementary Movie 8 and Supplementary Figs. 19-22. In addition, if the contacted boundary is a surface of another bigger Bi nanocrystal, the A-C changing Bi nanocrystal would coalesce into the Bi nanocrystal, which is the ripening of the Bi nanocrystals as we shown in Supplementary Figs. 23-24. Based on systematic experiments, we demonstrated the nanoscale concave sites on the substrate surface promote the heterogeneous nucleation of Bi nanocrystals by reducing the free energy via collisions and interactions between Bi atoms and the surface. In Fig. 5, we have summarized the change of Gibbs free energy per Bi atom ( G atom ) during different processes in our experiments to investigate how the structure of substrate surface influences the heterogeneous nucleation of metal at the atomic scale. During the whole observation processes, the incident electrons continually transfer kinetic energy to the BiOCl substrate, the discrete Bi atoms, and the nucleating metastable clusters. Thus, during the electron beam induced dissociation of BiOCl, the G atom significantly increased after the Bi atoms become discrete. Being chemically and physically absorbed on the substrate surface, some Bi atoms overcome the first energy barrier for nucleation and form tiny amorphous clusters with atom number less than 10, according to the two-step nucleation mechanism of metal 21,26,31 . However, the G atom of these clusters are still high, making them very sensitive to the disturbance from the environment, the continuous electron beam irradiation. On relatively flat and convex surfaces, these unstable clusters are dissociated into discrete Bi atoms again by the incident electrons. By contrast, at the concave sites, these unstable clusters and the discrete Bi atoms release kinetic energy via collision with the walls of concave sites. Thus, G atom of the tiny amorphous clusters is reduced, making them more stable under electron beam irradiation. Then these tiny amorphous clusters accept more discrete Bi atoms, and grow into bigger amorphous clusters with lower G atom . In other words, the concave sites act as potential walls helping to reduce the first energy barrier for nucleation of Bi nanocrystals from discrete Bi atoms. Being stabilized by the concave sites, the amorphous Bi clusters keep on accepting more discrete Bi atoms. They finally overcome the second energy barrier for nucleation and transform into crystalline structure with lower G atom . However, the G atom of nucleated Bi nanocrystals fluctuate under electron beam irradiation, leading to a reversible switching A-C changing state. When the Bi nanocrystal contact with the wall of concave sites during transformation, it immediately crystalizes due to the reduction of G atom via interfacial interaction. Based on our investigation at the atomic scale, we discovered that the nanoscale structure of the substrate surface significantly influences and even determines the nucleation site, nucleation rate and the structure of the nucleated crystal. We propose a function of the Gibbs free energy change ( ΔG ) for the heterogeneous nucleation of metal on substrate surface at atomic scale, as: here is the Gibbs free energy per atom for the nucleated nanocrystal, is the Gibbs free energy per atom for the convex or concave structure on the surface, is the Gibbs free energy per atom for the discrete metallic atom, is the Gibbs free energy per atom for the convex or concave structure with nucleating metallic nanoparticle on it, ΔH bond is the enthalpy of metal-metal bond formation, and n and n c are respectively the metal atom number during the nucleation process and the average coordination number of each metal atom in nucleating cluster or nucleated nanocrystal. ΔH interface is the enthalpy of each bond formation between surface atom and metal atom, and m is the number of this kind of bonds. ΔE is a function of the released kinetic energy owing to the collision between the metal atoms and the substrate, which is determined by the metal atom number and the angle of the convex or concave structure of the substrate surface. Conclusion In conclusion, we have stimulated and investigated heterogeneous nucleation of Bi nanocrystals on the surface of the BiOCl substrate at the atomic scale from the side view with vacuum background by AC-HRTEM. It has revealed the substrate surface structure at nanoscale significantly influences the heterogeneous nucleation on it. The nucleation of Bi nanocrystals only occurs at the concave sites with angles ranging from 98.4° to 157°, based on the data of over 100 stochastic cases. The discrete Bi atoms and the nucleating metastable clusters with sizes around 1–2 nm are confined in the concave sites acting as potential wells, helping them release kinetic energy by wall collisions. Therefore, they are stabilized by the concave site and further grow and crystalize into nanocrystals. However, at the relative flat and convex sites, all the formed metastable clusters possess high free energy and are eventually destroyed by the incident electrons. In addition, we have also proved the concave structure helps the formed nanoparticles stabilize the crystalline structure, thereby avoiding them being melted by the incident electrons. The nucleation site, nucleation rate, and the structure of the nucleated nanoparticle in heterogeneous nucleation processes are all influenced and determined by the substrate surface structure at the nanoscale. Based on our findings, we suggest, by designing and regulating the concave sites of the substrate surface for heterogeneous nucleation, the nucleation sites and nucleation processes of metals can be controlled and adjusted. Declarations Acknowledgements K.C. and Y.M. acknowledge financial support from the National Natural Science Foundation of China (22104092, 22376140, 22379032), and the Natural Science Foundation of Guangxi Province, China (2023GXNSFDA026022). Author contributions: P.Y. and K.C. conceived the idea and designed the experiment. P.Y. carried out the TEM experiments and made data analysis. J.F. and Y.M. prepared the BiOCl sample. K.J performed the theoretical calculations. P.Y. and Y.Y. processed the origin data and the schemes. P.Y., D.Z. and D.Y. carried out the electron beam irradiation experiments. W.D. and Y.D. performed the collection of the mass spectrum. P.Y., K.C., Y.H. discussed the results. K.C. and Y.H. supervised the research. All the authors have revised the manuscript. Competing interests: The authors declare no competing interests. Additional information: Supplementary Information is available for this paper. Correspondence and requests for materials should be addressed to K.C. or Y.H. Data availability All data needed to evaluate the conclusion herein are present in the article. References Chen, X. R. et al. Review on Li deposition in working batteries: from nucleation to early growth. Adv. Mater. 33 , 2004128 (2021). De Yoreo, J. J. et al. Crystallization by particle attachment in synthetic, biogenic, and geologic environments. Science 349 , aaa6760 (2015). Thiam, A. R. & Ikonen, E. Lipid droplet nucleation. Trends in Cell Biology 31 , 108-118 (2021). Zhang, R. et al. Nucleation and growth of nanoparticles in the atmosphere. Chem. Rev. 112 , 1957-2011 (2012). Cossairt, B. M. Shining light on indium phosphide quantum dots: understanding the interplay among precursor conversion, nucleation, and growth. 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Nucleation and growth of amino acid and peptide supramolecular polymers through liquid–liquid phase separation. Angew. Chem. Int. Ed. 58 , 18116-18123 (2019). Jeon, S. et al. Reversible disorder-order transitions in atomic crystal nucleation. Science 371 , 498-503 (2021). Chang, X. et al. Insights into the growth of bismuth nanoparticles on 2D structured BiOCl photocatalysts: an in situ TEM investigation. Dalton Transactions 44 , 15888-15896 (2015). Egerton, R., Li, P. & Malac, M. Radiation damage in the TEM and SEM. Micron 35 , 399-409 (2004). De Yoreo, J. J. & Vekilov, P. G. Principles of crystal nucleation and growth. Reviews in mineralogy and geochemistry 54 , 57-93 (2003). Li, Y. et al. In situ study on atomic mechanism of melting and freezing of single bismuth nanoparticles. Nat. Commun. 8 , 14462 (2017). Loh, N. D. et al. Multistep nucleation of nanocrystals in aqueous solution. Nat. Chem. 9 , 77-82 (2017). Methods BiOCl synthesis. Typically, 0.4850 g Bi(NO 3 ) 3 ·5H 2 O, 0.4000 g PVP, 0.4550 g D-Mannitol and 25 mL deionized water were added into a 50 mL beaker under continues stirring at room temperature. After it turns into a clear and transparent solution, 2 mL of saturated KCl solution was dropwise added in while stirring. After 10 more minutes of stirring, the mixture was transferred into a 25 mL Teflon-lined autoclave, and placed at 160℃ for 3 h. Subsequently, the autoclave was cooled to room temperature naturally. The resulted white product was collected and washed by deionized water and ethanol for several times. Finally obtained the BiOCl by freeze drying. TEM characterization. The BiOCl powder was dispersed in ethyl alcohol and drop-cast onto carbon coated copper TEM grids. Time-series AC-HRTEM images in Supplementary Moves S1-S8 were carried out on a double Cs-corrected JEOL Grand ARM-300F with OneView camera operated at 80 keV and 300 keV at room temperature. STEM-HAADF images, EDS mapping and EELS were collected on JEOL Grand ARM-300F equipped with an HAADF probe detector and a K2 summit direct electron counting detector. SEM images were collected on a JEOL JSM-7800F scanning electron microscopy at 5 keV. In situ electron beam irradiation characterization. In order to study the dissociation of BiOCl under electronic beam irradiation, home-made electron beam molecular engineering system (EBME) with RGA mass spectrometry was used in the experiment. The voltage was set up under the same conditions as TEM experiment, and BiOCl powder were pressed on a specific sample holder and a control group was set up as shown in Extended Data Fig. 3. Note The apparent atomic collision process is more obvious observed in the video, because the exposure time for each frame is 10 ms making contrast of the moving atoms very low. Additional Declarations There is NO Competing Interest. Supplementary Files Supplementarymovie1.mp4 Supplementary movie 1 Supplementarymovie2.mp4 Supplementary movie 2 Supplementarymovie3.mp4 Supplementary movie 3 Supplementarymovie4.mp4 Supplementary movie 4 Supplementarymovie5.mp4 Supplementary movie 5 Supplementarymovie6.mp4 Supplementary movie 6 Supplementarymovie7.mp4 Supplementary movie 7 Supplementarymovie8.mp4 Supplementary movie 8 SupplementaryInformationSubstrateeffectsonheterogeneousnucleationofmetalatatomicscale.docx ExtendedDataFig.docx Cite Share Download PDF Status: Posted Version 1 posted 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. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5396960","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":388038344,"identity":"7301934c-0140-4a72-a746-7c6c3e5f6ff7","order_by":0,"name":"Kecheng 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University","correspondingAuthor":false,"prefix":"","firstName":"Jing","middleName":"","lastName":"Feng","suffix":""},{"id":388038349,"identity":"cf2c8801-a75f-4389-9a2c-0d018c06a8f1","order_by":5,"name":"Wengdi Zheng","email":"","orcid":"","institution":"ShanghaiTech University","correspondingAuthor":false,"prefix":"","firstName":"Wengdi","middleName":"","lastName":"Zheng","suffix":""},{"id":388038350,"identity":"698b5152-6385-416c-be38-37f23e671ed0","order_by":6,"name":"Yue Yang","email":"","orcid":"","institution":"Shanghai Tech University","correspondingAuthor":false,"prefix":"","firstName":"Yue","middleName":"","lastName":"Yang","suffix":""},{"id":388038351,"identity":"0ca9ddb8-a846-4acc-8ec9-e6222433ef29","order_by":7,"name":"Dong Zhang","email":"","orcid":"","institution":"ShanghaiTech University","correspondingAuthor":false,"prefix":"","firstName":"Dong","middleName":"","lastName":"Zhang","suffix":""},{"id":388038352,"identity":"657e72c9-2e01-46fe-a6a6-3993fb345b9e","order_by":8,"name":"Yadong Li","email":"","orcid":"","institution":"ShanghaiTech University","correspondingAuthor":false,"prefix":"","firstName":"Yadong","middleName":"","lastName":"Li","suffix":""},{"id":388038353,"identity":"00c87c33-0705-46bd-82af-0cbfbea36c42","order_by":9,"name":"Yifei Dang","email":"","orcid":"","institution":"ShanghaiTech University","correspondingAuthor":false,"prefix":"","firstName":"Yifei","middleName":"","lastName":"Dang","suffix":""},{"id":388038354,"identity":"d5b8f2df-17f9-48c8-afc7-b715374bcd55","order_by":10,"name":"Dongyu Li","email":"","orcid":"","institution":"ShanghaiTech University","correspondingAuthor":false,"prefix":"","firstName":"Dongyu","middleName":"","lastName":"Li","suffix":""},{"id":388038355,"identity":"63cd64aa-4e91-4233-82f5-1f65bf5a49f0","order_by":11,"name":"Yuan Hu","email":"","orcid":"","institution":"ShanghaiTech University","correspondingAuthor":false,"prefix":"","firstName":"Yuan","middleName":"","lastName":"Hu","suffix":""}],"badges":[],"createdAt":"2024-11-05 16:20:39","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5396960/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5396960/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":78883620,"identity":"f7588665-0b58-45f5-bac6-3d64dbf0a882","added_by":"auto","created_at":"2025-03-20 09:10:02","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":910254,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHeterogeneous nucleation of Bi nanocrystal at concave site. a\u003c/strong\u003e, Time series raw AC-HRTEM images of the Bi nanocrystal nucleation process acquired from consecutive Supplementary Movies 1-4. \u003cstrong\u003eb\u003c/strong\u003e, Schematic showing the diffusion of discrete Bi atoms, and the relaxation by impacting. \u003cstrong\u003ec\u003c/strong\u003e, Quantification of the projection area, nanocrystal volume, number of atoms, and the crystallinity of the nucleating and growing Bi nanocrystal in \u003cstrong\u003ea\u003c/strong\u003e. Scale bar for AC-HRTEM images is 5 nm, and the scale bar for corresponding FFT images is 5 nm\u003csup\u003e-1\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5396960/v1/0ad60de3ef3cc81623078043.png"},{"id":78883618,"identity":"2d1be141-54b0-49d8-aaec-d45e6ece99f4","added_by":"auto","created_at":"2025-03-20 09:10:02","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":788128,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMorphology of the substrate and statistical analysis of the nucleation sites.\u003c/strong\u003e \u003cstrong\u003ea,b, \u003c/strong\u003eThe morphology of BiOCl substrate and nucleation sites on the surface. \u003cstrong\u003ec,d,\u003c/strong\u003eTypical nucleation sites on substrate surface and sequentially formed nm-scale clusters. \u003cstrong\u003ee,\u003c/strong\u003e Typical formed relatively large Bi nanocrystals at concave sites. \u003cstrong\u003ef,\u003c/strong\u003e The statistical analysis of the angles of nucleation sites based on 100 stochastic Bi nanocrystal nucleation cases; the detailed angles are listed below the 0 axis. Scale bars in \u003cstrong\u003ea\u003c/strong\u003e, \u003cstrong\u003eb\u003c/strong\u003e, \u003cstrong\u003ec\u003c/strong\u003e and \u003cstrong\u003ee\u003c/strong\u003e are respectively 5 μm, 5 nm, 2 nm and 5nm.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5396960/v1/fa5cafca14782bb65fc33899.png"},{"id":78883616,"identity":"8d454bba-42e5-495f-a95e-2277e87eeee4","added_by":"auto","created_at":"2025-03-20 09:10:02","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1016162,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDiffusion of the Bi atoms on relative flat and convex surface.\u003c/strong\u003e \u003cstrong\u003ea, c,\u003c/strong\u003e Time series raw AC-HRTEM images of the nucleation process in Supplementary movies 5-6 (\u003cstrong\u003ea\u003c/strong\u003e: black atom contrast, at 80 keV; \u003cstrong\u003ec\u003c/strong\u003e: white atom contrast, at 300 keV), the images in the lower left corner in \u003cstrong\u003ea\u003c/strong\u003e is the enlarged image of the green box and the bottom right corner in \u003cstrong\u003ea\u003c/strong\u003e and \u003cstrong\u003ec\u003c/strong\u003e is the yellow transparent line profile, \u003cstrong\u003eb, d,\u003c/strong\u003eSchematics showing the atom diffusion on relative flat and convex surface. (Scale bars in \u003cstrong\u003ea\u003c/strong\u003e and\u003cstrong\u003e c\u003c/strong\u003e: 5 nm)\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5396960/v1/32f5c1e0831c0601a12cefdd.png"},{"id":78884103,"identity":"029bba80-279b-4df7-9fb0-3ea79386073f","added_by":"auto","created_at":"2025-03-20 09:18:02","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":550057,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eBi nanoparticle increasing crystallinity and stability by contacting with boundary.\u003c/strong\u003e \u003cstrong\u003ea,\u003c/strong\u003e Time series raw AC-HRTEM images showing a Bi nanoparticle wit A-C changing state was stabilized by contacting with boundary as indicated by green arrow. The corresponding FFT patterns of the Bi nanoparticle in the yellow dash boxes showing the crystallinity changing. \u003cstrong\u003eb,\u003c/strong\u003e Schematics showing three states of Bi nanoparticle on the BiOCl surface. \u003cstrong\u003ec,\u003c/strong\u003e Quantification of the crystallinity by comparing the intensities of the reflection spots in the FFT patterns of Bi nanoparticle in the frames of Supplementary Movie 7. \u003cstrong\u003ed\u003c/strong\u003e, Trajectories of state transitions between amorphous and crystalline states from 18 s to 21 s as highlighted in \u003cstrong\u003ec\u003c/strong\u003e, including amorphous state, A-C changing state and crystalline state. At 20,380 ms, the Bi nanoparticle contacted with the boundary and became steadily crystalline. \u003cstrong\u003ee\u003c/strong\u003e, Schematic energy profile of the process for the stabilization of Bi nanoparticle by contacting with the boundary. Scale bar in AC-HRTEM image is 5 nm, and the scale bar in corresponding FFT image is 5 nm\u003csup\u003e-1\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5396960/v1/e9e175eac7deb1a213e24e32.png"},{"id":78884102,"identity":"4a3a0356-8899-47af-a3d7-6288810e50b8","added_by":"auto","created_at":"2025-03-20 09:18:02","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":180910,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSchematic energy profile of the heterogeneous nucleation of Bi nanocrystal.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5396960/v1/7742954b93fdd41e8f4c1789.png"},{"id":78885385,"identity":"2a378da9-b4bb-4f6b-8a83-fafc351dfb4f","added_by":"auto","created_at":"2025-03-20 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09:10:02","extension":"docx","order_by":10,"title":"","display":"","copyAsset":false,"role":"supplement","size":2203616,"visible":true,"origin":"","legend":"","description":"","filename":"ExtendedDataFig.docx","url":"https://assets-eu.researchsquare.com/files/rs-5396960/v1/99e3dec3da6e88a15ba380eb.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Surface effects on heterogeneous nucleation of metal at the atomic scale","fulltext":[{"header":"Main","content":"\u003cp\u003eNucleation, the common yet mysterious phenomenon in nature, serves as the pyramid foundation of the material science in the construction of human civilization\u003csup\u003e1-4\u003c/sup\u003e. In recent years, several non-classical multi-step nucleation theories beyond the classical nucleation theory have been introduced and developed\u003csup\u003e5-12\u003c/sup\u003e. The identification of metastable intermediate states preceding the formation of crystal nucleus improves the understanding of homogeneous nucleation\u003csup\u003e6\u003c/sup\u003e. Apart from homogeneous nucleation, heterogeneous nucleation is a more common nucleation mode, during which pre-nucleation matters attach to substrate surfaces to reduce total free energy and then nucleate and crystallize\u003csup\u003e7,13\u003c/sup\u003e. The properties of the substrate surface, including surface chemical constructions and physical roughness, significantly influence the interaction between the surface and pre-nucleation matters. These further affect the site, density, and rate of nucleation, as well as the size and even orientation of the nucleated crystal\u003csup\u003e14,15\u003c/sup\u003e. To understand these surface effects on heterogeneous nucleation, various techniques such as transmission electron microscopy (TEM)\u003csup\u003e16\u003c/sup\u003e, small-angle X-ray scattering\u003csup\u003e17\u003c/sup\u003e, atomic force microscopy\u003csup\u003e18\u003c/sup\u003e, and scanning electron microscopy (SEM)\u003csup\u003e19\u003c/sup\u003e have been employed to investigate the dynamics of heterogeneous nucleation at diverse surfaces. Nevertheless, the atomic mechanisms of the surface effects, especially how the pre-nucleation matter interacts with the surface and how the nucleation sites are selectively determined at the atomic scale, remain unclear.\u003c/p\u003e\n\u003cp\u003eAdvanced aberration-corrected high resolution TEM (AC-HRTEM) with temporal resolution at the millisecond scale and sub-atomic spatial resolution has contributed to deepening the understandings of crystal nucleation mechanisms\u003csup\u003e20\u003c/sup\u003e. Furthermore, the electron beam in TEM has been directly employed as initiators to trigger the nucleation of crystal in liquid or vacuum.\u003csup\u003e21-25\u003c/sup\u003e Compared with the liquid environment, studying the nucleation process stimulated by electron beam under vacuum possesses higher spatial resolution.\u003csup\u003e21\u003c/sup\u003e Accordingly, the atomic structure of the small primary clusters or nuclei with size smaller than 2 nm at the initial stage of nucleation can be observed. By utilizing low-contrast substrates such as single-walled carbon nanotubes or graphene combined with the electron beam trigger technology, the two-step nucleation mechanism and the reversible transformation phenomenon for nucleation of metals have been unveiled.\u003csup\u003e21,26\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eHere, we reveal surface effects on heterogeneous nucleation of metal at the atomic scale using bismuth (Bi) crystal as model. The electron beam in AC-HRTEM is used to stimulate the dissociation of BiOCl nanocrystals as starting material for generating discrete Bi atoms. Thereby we have realized the direct observations of Bi nanocrystal heterogeneous nucleation at the BiOCl surface from the side view with atomic spatial resolution and millisecond time resolution. Our results demonstrated that the concave sites on surfaces play significant roles in facilitating the formation of amorphous clusters via kinetic energy relaxation by collisions. Moreover, these concave sites contribute to the subsequent nucleation, growth, and stabilization of the as-formed crystals.\u003c/p\u003e\n\u003cp\u003eBismuth, a metal with low melting point and high electron beam irradiation sensitivity\u003csup\u003e27\u003c/sup\u003e, is an ideal candidate for investigating surface effects on heterogeneous nucleation in real time by AC-HRTEM. We applied an electron beam sensitive compound, BiOCl, as starting material, and then irradiated and observed it utilizing parallel 80 keV electron beam in AC-HRTEM. The characterizations of BiOCl including x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), SEM images, AC-HRTEM images, SAED patterns, energy-dispersive X-ray spectroscopy (EDS) mapping, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and electron energy loss spectroscopy (EELS) are shown in Supplementary Figs. 1-7. Fig. 1a shows the typical time-series images acquired from continuous Supplementary Movies 1-4, presenting the real-time stimulation and observations for the dissociation and nucleation process of a Bi nanocrystal under 80 keV electron beam irradiation (Supplementary Fig. 8). The whole process lasted over 252,400 ms, and can be divided into three stages: (1) beginning of dissociation of BiOCl and diffusion of Bi atoms; (2) atom relaxation and pre-nucleation stage; (3) metastable cluster nucleation, nuclei growth, and amorphous-crystalline (A-C) changing stage. At the initial state (0 ms), an intrinsic concave site with an angle of 98.4\u0026deg; and a depth of 2 nm was observed at the surface of BiOCl. Under electron beam irradiation during AC-HRTEM imaging, the chemical bonds in BiOCl were activated and broken due to synergistical ionization and knock-on processes via inelastic and elastic scattering of incident electrons\u003csup\u003e28\u003c/sup\u003e. The corresponding elastic and inelastic cross section and ionization potentials calculated by \u003cem\u003eaug-cc-PVQZ-DK3\u003c/em\u003e method are shown in Supplementary Fig. 9 and Supplementary Table 1 and Table 2. Under 80 keV electron beam irradiation, the maximum transferred kinetic energy (\u003cem\u003eE\u003csub\u003eTmax\u003c/sub\u003e\u003c/em\u003e) from 80 keV electron to a Bi, O, and Cl atom is 0.9036 eV, 11.8 eV, and 5.326 eV, respectively, as shown in Supplementary Table 3, resulting in the dissociation of BiOCl and generation of discrete Bi atoms (Fig. 1b). The breaking of chemical bonds lead to the increase of the free energy of Bi atom, making them migrate out and then be physically and chemically absorbed at the surface. We verified that BiOCl was dissociated into O\u003csub\u003e2\u003c/sub\u003e and Cl\u003csub\u003e2\u003c/sub\u003e besides discrete Bi atoms under 80 keV electron beam irradiation, by \u003cem\u003ein situ\u003c/em\u003e electron beam irradiation-mass spectrometry experiment on our home-made electron beam molecular engineering (EBME) system (Methods, Extended Data Figs. 1-5, Supplementary Figs. 10-11 and Supplementary Table 4). Thus, we found these discrete Bi atoms freely diffusing on the BiOCl surface during the whole irradiation and observation processes. The electron-beam induced dissociation process ran through the whole investigation, consistently providing Bi atoms for further nucleation processes. The electron beam irradiation acts as an energy source, providing kinetic energy for the whole process, which is similar to conventional thermal driven heterogeneous nucleation via interatomic or intermolecular collisions.\u003c/p\u003e\n\u003cp\u003eFrom 0 ms to 7,680 ms, a few of the Bi atoms (less than 10) consecutively diffused to the bottom of the defective structure. These Bi atoms gathered together and overcame the first energy barrier of nucleation\u003csup\u003e29\u003c/sup\u003e, forming an observable amorphous cluster at 10,410 ms. At this concave site, the discrete Bi atoms collided with the atoms on the surface and other stacked Bi atoms, resulting in the relaxation of their free energy, as illustrated in Fig. 1b (Note the collisions and diffusions of Bi atoms can be observed more clearly in Supplementary Movies 1-4). Therefore, this concave site acted as a potential well for the diffusing Bi atoms, which further promoted the subsequent aggregation of discrete Bi atoms. Consequently, it served as the nucleation site for the further nucleation and growth of Bi crystal. During this stage,\u0026nbsp;the as-formed tiny amorphous cluster kept changing structure but did not dissociate under 80 keV electron beam irradiation. From 10,410 ms to 16,990 ms, more Bi atoms diffused and then integrated into the tiny cluster, forming a pre-nucleation nucleus with size of 1-2 nm. In this stage, the cluster was completely amorphous showing dynamical and indistinguishable atomic structure. From 17,890 ms to 240,990 ms, the growing cluster overcame the second energy barrier for metal nucleation and then nucleated into an unstable Bi nanocrystal\u003csup\u003e21\u003c/sup\u003e. The Bi nanocrystal showed dynamical atomic structure switching between amorphous and crystalline states under electron beam irradiation. The energy transferred from incident electron to the Bi atoms is inconstant which relates to the scattering angle as presented in Supplementary Fig. 9. The transferred energy stimulated the free energy fluctuation of the Bi nanoparticle, resulting in the oscillation of its atomic structure. From 245,680 ms to 252,400 ms, this particle kept on growing and transformed into a bigger single crystal with lower free energy per Bi atom. The Bi nanocrystal became more stable but still undergone a reversible transformation between amorphous and crystalline states due to the transfer of kinetic energy from the incident electron\u003csup\u003e30\u003c/sup\u003e. At this stage, the concave site was fully filled by the Bi nanocrystal. The crystallinity and projected area of the nucleating and growing Bi nanoparticle are quantitatively analyzed and plotted in Fig. 1c. The crystallinity was quantified by analyzing the FFT patterns of the nanoparticle, demonstrating the amorphous nature of the pre-nucleation cluster before 17,910 ms and the structural oscillation of the nucleated nanoparticle after 17,910 ms. In addition, by quantifying the projection area of nucleated Bi nanocrystal and assuming the nanocrystal is spherical, we estimated the volume and the total atomic number of the nanocrystal in Fig. 1c. The growth rate of the nanocrystal is approximately 4 Bi atoms per 10 seconds from the quantification result.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTo investigate the relation between the nanoscale flatness and nucleation sites on the surface of substrate, we systematically analyzed the distribution of nucleation sites and corresponding surface structure (Fig. 2, Supplementary Figs. 12-13).\u0026nbsp;Fig. 2a and Fig. 2b display the overall surface morphology of the BiOCl substrate. The surface was generally flat at micrometer scale but pitted with nanoscale concave and convex sites. Five representative intrinsic concave sites with angles from 98.8\u0026deg; to 129.5\u0026deg; and depths from 1 nm to 2 nm at the surface of BiOCl are shown in Fig. 2c. Fig. 2d shows the nucleation of Bi nanocrystals occurred at these intrinsic concave sites after 80 keV or 300 keV electron beam irradiation with dose rate ranging from 1.52\u0026times;10\u003csup\u003e4\u003c/sup\u003e e \u0026Aring;\u003csup\u003e-2\u0026nbsp;\u003c/sup\u003es\u003csup\u003e-1\u003c/sup\u003e to 2.33\u0026times;10\u003csup\u003e4\u003c/sup\u003e e \u0026Aring;\u003csup\u003e-2\u0026nbsp;\u003c/sup\u003es\u003csup\u003e-1\u003c/sup\u003e and time from 65 to 201 seconds. Fig. 2e presents 6 more typical cases in which the Bi nanocrystals formed at the concave sites. The dissociation of BiOCl and the subsequent atomic migration and nucleation processes at concave sites were common phenomena during our observations. Hence, we made statistical analysis of the angles of sites where Bi atoms nucleated and grew into nanocrystals based on 100 stochastic cases. We found 99% Bi nanocrystals formed at the concave sites with angles from 90 to 150 degrees, while only one Bi nanocrystal formed at the concave site with an angle of 156 degree. In addition, no Bi nanocrystal was found nucleated at flat or convex sites. Note that due to the thermodynamic equilibrium process during BiOCl material growth, concaves with angles smaller than 90 degrees are not stable and thus do not exist on the surface of BiOCl.\u003c/p\u003e\n\u003cp\u003eCompared with the concave substrate surface, the behavior of discrete Bi atoms on the relatively smooth surface was noticeably different. We conducted \u003cem\u003ein situ\u003c/em\u003e AC-HRTEM and HAADF-STEM experiments under the acceleration voltages of 80 keV or 300 keV (Supplementary Movies 5-6, Supplementary Figs. 14-16). Then we found that the dissociated discrete Bi atoms on the smooth surface were able to agglomerate and form tiny clusters, but they eventually dissociated again. As shown in Fig. 3a and Fig. 3b, at 80 keV, the time series AC-HRTEM images from recorded video Supplementary Movie 5 begins with an already formed tiny Bi cluster containing several atoms on the surface. However, this Bi cluster was unstable under e-beam irradiation, changing structure and dissociating into discrete atoms after 1,010 ms. In this relatively smooth area containing two neighboring concave sites with angles of 147.2\u0026deg; and 136.2\u0026deg;, we found tiny Bi clusters with less than 6 atoms formed and eventually dissociated, which repeated 24 times in the following 53,930 ms, as clearly shown in Supplementary Movie 5. We have analyzed the surface atomic migration before and after 20 ms in the whole process. Through the line profile of the intensity in the enlarged image in Fig. 3a, we find that the positions of the surface atoms change quickly within 10 ms under the irradiation of the electron beam, demonstrating the fast and frequent atomic diffusion on the surface. Fig. 3c and Fig. 3d present the similar phenomenon observed at 300 keV on a convex surface with angle of 200.8\u0026deg;. At the convex site, the discrete Bi atoms agglomerated into tiny clusters and soon dissociated again in 1 second. Thus, for the discrete Bi atoms diffusing on a relatively smooth surface, they could only form unstable amorphous cluster within 3-7 atoms which are not able to nucleate and grow into crystal under electron beam irradiation. In contrast with the concave sites with smaller angles (Fig. 1a and 2), the smooth and convex sites provided relatively open space for the diffusion of Bi atoms. Namely, potential wells for the motion of Bi atoms and clusters did not exist at these sites. The Bi atoms cannot effectively release free energy by impacting on the substrate surface. Therefore, the as-formed tiny clusters still possessed high free energy, which were subsequently dissociated into atoms by electron beam irradiation. The consequence was the free Bi atoms would not nucleate and grow into crystal on relatively smooth and convex surfaces where cannot provide nucleation site as a low energy potential well.\u003c/p\u003e\n\u003cp\u003eThe nucleated Bi nanocrystals on the substrate surface were still unstable under electron beam irradiation in Fig. 1a (245,680-252,400 ms) and Fig. 4a. They changed between amorphous and crystalline states as shown in Fig. 4b and c and even can move on the surface in Supplementary Fig. 17. We found such kind of nucleated Bi nanocrystal could be stabilized by further interacting with uneven surfaces of the substrate. A nanocrystal kept changing its state continually for over 34 times in the first 2,000 ms, as counted and presented in Fig. 4a and 4d (with frames acquired from Supplementary Movie 7). We found when the Bi nanocrystal switched from crystalline to amorphous state, it elongated and increased the contact area to the surface, thereby reducing its surface free energy. From 20,300 ms to 20,320 ms, the Bi nanocrystal became amorphous and began to contact the boundary from the bottom side (green arrows). In the following 60 ms, the Bi nanoparticle sufficiently contacted with the boundary and crystallized again owing to the reduction of surface free energy. From 20,380 ms to 21,720 ms, the Bi nanocrystal kept increasing its crystallinity, and then recrystallized into a single crystal with sharp surface. We quantified and presented the change of crystallinity for this Bi nanoparticle in Fig. 4c by using FFT patterns shown in Fig. 4a.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe result shows a reversible transition between amorphous and crystalline states of the Bi nanoparticle before contacting the boundary. After contacted with the boundary, the Bi nanoparticle stayed in crystalline state as shown in Supplementary Fig. 18. Thus, the impact of surface flatness on the stability of the crystal structure has been assessed. The Bi nanocrystal releases surface free energy by contacting with multiple boundaries, thereby enhancing its crystallinity and stability. Through \u003cem\u003ein situ\u003c/em\u003e observations at the atomic scale with high time resolution, we observed such process could be completed within 80 ms. Stabilization of nucleated Bi nanocrystal via boundary contacting is a common process during the heterogeneous nucleation. We presented and analyzed another similar observation in Supplementary Movie 8 and Supplementary Figs. 19-22. In addition, if the contacted boundary is a surface of another bigger Bi nanocrystal, the A-C changing Bi nanocrystal would coalesce into the Bi nanocrystal, which is the ripening of the Bi nanocrystals as we shown in Supplementary Figs. 23-24.\u003c/p\u003e\n\u003cp\u003eBased on systematic experiments, we demonstrated the nanoscale concave sites on the substrate surface promote the heterogeneous nucleation of Bi nanocrystals by reducing the free energy via collisions and interactions between Bi atoms and the surface. In Fig. 5, we have summarized the change of Gibbs free energy per Bi atom (\u003cem\u003eG\u003csub\u003eatom\u003c/sub\u003e\u003c/em\u003e) during different processes in our experiments to investigate how the structure of substrate surface influences the heterogeneous nucleation of metal at the atomic scale. During the whole observation processes, the incident electrons continually transfer kinetic energy to the BiOCl substrate, the discrete Bi atoms, and the nucleating metastable clusters. Thus, during the electron beam induced dissociation of BiOCl, the \u003cem\u003eG\u003csub\u003eatom\u003c/sub\u003e\u003c/em\u003e significantly increased after the Bi atoms become discrete. Being chemically and physically absorbed on the substrate surface, some Bi atoms overcome the first energy barrier for nucleation and form tiny amorphous clusters with atom number less than 10, according to the two-step nucleation mechanism of metal\u003csup\u003e21,26,31\u003c/sup\u003e. However, the \u003cem\u003eG\u003csub\u003eatom\u003c/sub\u003e\u003c/em\u003e of these clusters are still high, making them very sensitive to the disturbance from the environment, the continuous electron beam irradiation. On relatively flat and convex surfaces, these unstable clusters are dissociated into discrete Bi atoms again by the incident electrons. By contrast, at the concave sites, these unstable clusters and the discrete Bi atoms release kinetic energy via collision with the walls of concave sites. Thus, \u003cem\u003eG\u003csub\u003eatom\u003c/sub\u003e\u003c/em\u003e of the tiny amorphous clusters is reduced, making them more stable under electron beam irradiation. Then these tiny amorphous clusters accept more discrete Bi atoms, and grow into bigger amorphous clusters with lower \u003cem\u003eG\u003csub\u003eatom\u003c/sub\u003e\u003c/em\u003e. In other words, the concave sites act as potential walls helping to reduce the first energy barrier for nucleation of Bi nanocrystals from discrete Bi atoms. Being stabilized by the concave sites, the amorphous Bi clusters keep on accepting more discrete Bi atoms. They finally overcome the second energy barrier for nucleation and transform into crystalline structure with lower \u003cem\u003eG\u003csub\u003eatom\u003c/sub\u003e\u003c/em\u003e. However, the \u003cem\u003eG\u003csub\u003eatom\u003c/sub\u003e\u003c/em\u003e of nucleated Bi nanocrystals fluctuate under electron beam irradiation, leading to a reversible switching A-C changing state. When the Bi nanocrystal contact with the wall of concave sites during transformation, it immediately crystalizes due to the reduction of \u003cem\u003eG\u003csub\u003eatom\u003c/sub\u003e\u003c/em\u003e via interfacial interaction. Based on our investigation at the atomic scale, we discovered that the nanoscale structure of the substrate surface significantly influences and even determines the nucleation site, nucleation rate and the structure of the nucleated crystal. We propose a function of the Gibbs free energy change (\u003cem\u003e\u0026Delta;G\u003c/em\u003e) for the heterogeneous nucleation of metal on substrate surface at atomic scale, as:\u003c/p\u003e\n\u003cp\u003e\u003cimg 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\" width=\"571\" height=\"108\"\u003e\u003c/p\u003e\n\u003cp\u003ehere \u0026nbsp; is the Gibbs free energy per atom for the nucleated nanocrystal, \u0026nbsp;is the Gibbs free energy per atom for the convex or concave structure on the surface, \u0026nbsp; \u0026nbsp; \u0026nbsp;is the Gibbs free energy per atom for the discrete metallic atom, \u0026nbsp;is the Gibbs free energy per atom for the convex or concave structure with nucleating metallic nanoparticle on it, \u003cem\u003e\u0026Delta;H\u003csub\u003ebond\u003c/sub\u003e\u003c/em\u003e is the enthalpy of metal-metal bond formation, and \u003cem\u003en\u003c/em\u003e and \u003cem\u003en\u003csub\u003ec\u003c/sub\u003e\u003c/em\u003e are respectively the metal atom number during the nucleation process and the average coordination number of each metal atom in nucleating cluster or nucleated nanocrystal. \u003cem\u003e\u0026Delta;H\u003csub\u003einterface\u003c/sub\u003e\u003c/em\u003e is the enthalpy of each bond formation between surface atom and metal atom, and \u003cem\u003em\u003c/em\u003e is the number of this kind of bonds. \u003cem\u003e\u0026Delta;E\u003c/em\u003e is a function of the released kinetic energy owing to the collision between the metal atoms and the substrate, which is determined by the metal atom number and the angle of the convex or concave structure of the substrate surface.\u003cem\u003e\u003cbr\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn conclusion, we have stimulated and investigated heterogeneous nucleation of Bi nanocrystals on the surface of the BiOCl substrate at the atomic scale from the side view with vacuum background by AC-HRTEM. It has revealed the substrate surface structure at nanoscale significantly influences the heterogeneous nucleation on it. The nucleation of Bi nanocrystals only occurs at the concave sites with angles ranging from 98.4\u0026deg; to 157\u0026deg;, based on the data of over 100 stochastic cases. The discrete Bi atoms and the nucleating metastable clusters with sizes around 1\u0026ndash;2 nm are confined in the concave sites acting as potential wells, helping them release kinetic energy by wall collisions. Therefore, they are stabilized by the concave site and further grow and crystalize into nanocrystals. However, at the relative flat and convex sites, all the formed metastable clusters possess high free energy and are eventually destroyed by the incident electrons. In addition, we have also proved the concave structure helps the formed nanoparticles stabilize the crystalline structure, thereby avoiding them being melted by the incident electrons. The nucleation site, nucleation rate, and the structure of the nucleated nanoparticle in heterogeneous nucleation processes are all influenced and determined by the substrate surface structure at the nanoscale. Based on our findings, we suggest, by designing and regulating the concave sites of the substrate surface for heterogeneous nucleation, the nucleation sites and nucleation processes of metals can be controlled and adjusted.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eK.C. and Y.M. acknowledge financial support from the National Natural Science Foundation of China (22104092, 22376140, 22379032), and the Natural Science Foundation of Guangxi Province, China (2023GXNSFDA026022).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eP.Y. and K.C. conceived the idea and designed the experiment. P.Y. carried out the TEM experiments and made data analysis. J.F. and Y.M. prepared the BiOCl sample. K.J performed the theoretical calculations. P.Y. and Y.Y. processed the origin data and the schemes. P.Y., D.Z. and D.Y. carried out the electron beam irradiation experiments. W.D. and Y.D. performed the collection of the mass spectrum. P.Y., K.C., Y.H. discussed the results. K.C. and Y.H. supervised the research. All the authors have revised the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdditional information:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSupplementary Information is available for this paper.\u003c/p\u003e\n\u003cp\u003eCorrespondence and requests for materials should be addressed to K.C. or Y.H.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data needed to evaluate the conclusion herein are present in the article.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eChen, X. R.\u003cem\u003e et al.\u003c/em\u003e Review on Li deposition in working batteries: from nucleation to early growth. \u003cem\u003eAdv. 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Principles of crystal nucleation and growth. \u003cem\u003eReviews in mineralogy and geochemistry\u003c/em\u003e \u003cstrong\u003e54\u003c/strong\u003e, 57-93 (2003).\u003c/li\u003e\n\u003cli\u003eLi, Y.\u003cem\u003e et al.\u003c/em\u003e In situ study on atomic mechanism of melting and freezing of single bismuth nanoparticles. \u003cem\u003eNat. Commun.\u003c/em\u003e \u003cstrong\u003e8\u003c/strong\u003e, 14462 (2017).\u003c/li\u003e\n\u003cli\u003eLoh, N. D.\u003cem\u003e et al.\u003c/em\u003e Multistep nucleation of nanocrystals in aqueous solution. \u003cem\u003eNat. Chem.\u003c/em\u003e \u003cstrong\u003e9\u003c/strong\u003e, 77-82 (2017).\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eBiOCl synthesis.\u0026nbsp;\u003c/strong\u003eTypically, 0.4850 g Bi(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e·5H\u003csub\u003e2\u003c/sub\u003eO, 0.4000 g PVP, 0.4550 g D-Mannitol and 25 mL deionized water were added into a 50 mL beaker under continues stirring at room temperature. After it turns into a clear and transparent solution, 2 mL of saturated KCl solution was dropwise added in while stirring. After 10 more minutes of stirring, the mixture was transferred into a 25 mL Teflon-lined autoclave, and placed at 160℃\u0026nbsp;for 3 h. Subsequently, the autoclave was cooled to room temperature naturally. The resulted white product was collected and washed by deionized water and ethanol for several times. Finally obtained the BiOCl by freeze drying.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTEM characterization.\u003c/strong\u003e The BiOCl powder was dispersed in ethyl alcohol and drop-cast onto carbon coated copper TEM grids. Time-series AC-HRTEM images in Supplementary Moves S1-S8 were carried out on a double Cs-corrected JEOL Grand ARM-300F with OneView camera operated at 80 keV and 300 keV at room temperature. STEM-HAADF images, EDS mapping and EELS were collected on JEOL Grand ARM-300F equipped with an HAADF probe detector and a K2 summit direct electron counting detector. SEM images were collected on a JEOL JSM-7800F scanning electron microscopy at 5 keV.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eIn situ\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;electron beam irradiation characterization.\u0026nbsp;\u003c/strong\u003eIn order to study the dissociation of BiOCl under electronic beam irradiation, home-made electron beam molecular engineering system (EBME) with RGA mass spectrometry was used in the experiment. The voltage was set up under the same conditions as TEM experiment, and BiOCl powder were pressed on a specific sample holder and a control group was set up as shown in Extended Data Fig. 3.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNote\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe apparent atomic collision process is more obvious observed in the video, because the exposure time for each frame is 10 ms making contrast of the moving atoms very low.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-5396960/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5396960/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAgglomerationand crystallization of atoms are the key processes in nucleation. For heterogeneous nucleation, investigating the influence of the substrate surface on agglomeration and crystallization, and then understanding the related mechanism at the atomic scale is crucial to material synthesis. Here, electron beam in transmission electron microscopy is utilized to decompose BiOCl material for generating dissociative Bi atoms. We observe the heterogeneous nucleation process of Bi nanocrystals at the surface of BiOCl from the side view with atomic spatial resolution and millisecond temporal resolution. The nucleation and crystallization of Bi nanocrystal is found to occur at the concave sites of the surface with angles ranging from 91° to 157° and form stable nucleus with sizes of 1 to 2 nanometers, while the pre-agglomerated Bi clusters dissociate again on the flat and convex surface. We demonstrate the collision between the Bi atoms and the concave structure helps Bi atoms release kinetic energy and form nucleus, and then the concave surface further stabilizes the nucleus and promotes crystallization.\u003c/p\u003e","manuscriptTitle":"Surface effects on heterogeneous nucleation of metal at the atomic scale","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-20 09:09:57","doi":"10.21203/rs.3.rs-5396960/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"cc910405-0d60-4bbf-be15-078a7aced023","owner":[],"postedDate":"March 20th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":41349453,"name":"Physical sciences/Nanoscience and technology/Nanoscale materials/Nanoparticles"},{"id":41349454,"name":"Physical sciences/Chemistry/Materials chemistry"}],"tags":[],"updatedAt":"2025-03-20T09:09:59+00:00","versionOfRecord":[],"versionCreatedAt":"2025-03-20 09:09:57","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5396960","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5396960","identity":"rs-5396960","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}