Probing phonon transport dynamics across an interface by electron microscopy

Probing phonon transport dynamics across an interface by electron microscopy | 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 Physical Sciences - Article Probing phonon transport dynamics across an interface by electron microscopy Peng Gao, Fachen Liu, Ruilin Mao, Zhiqiang Liu, Jinlong Du This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5420187/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 11 Jun, 2025 Read the published version in Nature → Version 1 posted You are reading this latest preprint version Abstract Understanding thermal transport mechanisms across material interfaces is crucial for advancing semiconductor technologies, particularly in miniaturized devices operating under extreme power densities1,2. Although the interface phonon-mediated processes are theoretically established3–6 as the dominant mechanism for interfacial thermal transport in semiconductors7, their nanoscale dynamics remain experimentally elusive due to challenges in measuring the temperature and non-equilibrium phonon distributions across the buried interface8–11. Here, we overcome these limitations by using in-situ vibrational electron energy-loss spectroscopy in an electron microscope to nanoscale profile temperature gradients across the AlN-SiC interface during thermal transport and map its non-equilibrium phonon occupations at sub-nanometer resolution. We observe a sharp temperature drop within ~2 nm across the interface, enabling direct extraction of relative interface thermal resistance. During thermal transport, the mismatch of phonon modes’ thermal conductivity at the interface causes substantial non-equilibrium phonons nearby, making the populations of interface modes different under forward and reverse heat flow, and also leading to significant changes in the modal temperature of AlN optical phonons within ~3 nm of the interface. These results reveal the phonon transport dynamics at the (sub-)nanoscale and establish the inelastic phonon scattering mechanism involved by interface modes, offering valuable insights into engineering of thermal interfaces. Physical sciences/Physics/Condensed-matter physics/Surfaces, interfaces and thin films Physical sciences/Nanoscience and technology/Techniques and instrumentation/Microscopy/Transmission electron microscopy Physical sciences/Materials science/Techniques and instrumentation/Characterization and analytical techniques Physical sciences/Materials science/Theory and computation/Atomistic models Physical sciences/Physics/Condensed-matter physics/Semiconductors Figures Figure 1 Figure 2 Figure 3 Full Text Additional Declarations There is NO Competing Interest. Supplementary Files SIrevised.pdf Supplementary Information for Probing phonon transport dynamics across an interface by electron microscopy TPRGao20241124089B.pdf Transparent Peer Review file Cite Share Download PDF Status: Published Journal Publication published 11 Jun, 2025 Read the published version in Nature → 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-5420187","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Physical Sciences - Article","associatedPublications":[],"authors":[{"id":442567665,"identity":"686c7fc6-b2b0-4b90-b780-4e1883a35c90","order_by":0,"name":"Peng Gao","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAt0lEQVRIiWNgGAWjYLCCDwwJIMqAeB2MM0jWwsxDkhZz/sUPH9vuSEtsYG/eJsFQc4ewFssZz4yNc8/kJDbwHCuTYDj2jLAWgxsHzKRz2yoSGyRyzCQYGw4To+X4N2lLkBb5N8RqOd9jJs3YBnSYBA+RWixn8BQb9p5JM27jSSu2SDhGhBZz/uMbH/zckSzbz354440PNcQ4TCIBGJcNDAxsIF4CYQ1ALfwHIFpGwSgYBaNgFOAEAKSTOfVw0X7VAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0001-9868-2115","institution":"International Center for Quantum Materials, and Electron Microscopy Laboratory, School of Physics, Peking University","correspondingAuthor":true,"prefix":"","firstName":"Peng","middleName":"","lastName":"Gao","suffix":""},{"id":442567666,"identity":"58ad0ee7-dfee-46a2-89af-0b3277685ab3","order_by":1,"name":"Fachen Liu","email":"","orcid":"","institution":"Academy for Advanced Interdisciplinary Studies, Peking University","correspondingAuthor":false,"prefix":"","firstName":"Fachen","middleName":"","lastName":"Liu","suffix":""},{"id":442567667,"identity":"3a0dd816-3e3b-4b50-a693-ef8deaa4b6ab","order_by":2,"name":"Ruilin Mao","email":"","orcid":"","institution":"Peking University","correspondingAuthor":false,"prefix":"","firstName":"Ruilin","middleName":"","lastName":"Mao","suffix":""},{"id":442567668,"identity":"424e0954-a977-4c69-a8cc-f1b4238d7587","order_by":3,"name":"Zhiqiang Liu","email":"","orcid":"https://orcid.org/0000-0002-5341-0463","institution":"Institute of Semiconductors, Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Zhiqiang","middleName":"","lastName":"Liu","suffix":""},{"id":442567669,"identity":"14166262-016c-4ed6-9a36-8c3e94f2f318","order_by":4,"name":"Jinlong Du","email":"","orcid":"https://orcid.org/0000-0003-2776-0950","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Jinlong","middleName":"","lastName":"Du","suffix":""}],"badges":[],"createdAt":"2024-11-09 06:45:07","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5420187/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5420187/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41586-025-09108-6","type":"published","date":"2025-06-11T04:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":82126781,"identity":"f4820dc1-c80b-4b1c-a69b-b3ed2e49fe6c","added_by":"auto","created_at":"2025-05-07 04:17:18","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":358205,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eIn-situ STEM-EELS for probing phonon transport dynamics across an interface. a,\u003c/strong\u003e Schematic of the experimental setup for in-situ heating STEM-EELS, depicting an AlN-SiC heterostructure with a heated (hot) side and a cooled (cold) side to establish a temperature gradient across the interface. \u003cstrong\u003eb,\u003c/strong\u003e Schematic of temperature distribution near the interface in an idealized one-dimensional steady-state heat conduction model, where temperature drop (Δ\u003cem\u003eT=T\u003c/em\u003e\u003csub\u003e\u003cem\u003e2i\u003c/em\u003e\u003c/sub\u003e-\u003cem\u003eT\u003c/em\u003e\u003csub\u003e\u003cem\u003e1i\u003c/em\u003e\u003c/sub\u003e) at the interface is proportional to the interface thermal resistance (ITR). The characteristic interface length\u003csup\u003e20,44\u003c/sup\u003e that is defined as the spatial distance over which the bulk thermal resistance equals the ITR, is shown as (\u003cem\u003ex\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e-x\u003c/em\u003e\u003csub\u003e\u003cem\u003einter\u003c/em\u003e\u003c/sub\u003e) on the right side and (\u003cem\u003ex\u003c/em\u003e\u003csub\u003e\u003cem\u003einter\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e-x\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e)\u003csub\u003e \u003c/sub\u003eon the left. \u003cstrong\u003ec,\u003c/strong\u003e Electron energy loss (EEL) and energy gain (EEG) spectra acquired from hot AlN to cold SiC. The black dashed spectrum was acquired at the interface. For better visualization, the spectra were normalized to EEL signal intensity, with EEG spectra scaled by a factor of four. The inset shows the EEL signal mainly represent the phonon ground state, while the EEG signal reflects thermally excited-state phonons. \u003cstrong\u003ed,\u003c/strong\u003e Average excited-state phonon population \u0026nbsp;as the function of temperature and energy. The EEG signal intensity directly quantifies \u0026nbsp;(thermally excited-state phonons), whereas EEL signal intensity corresponds to the total phonon population 1+\u0026nbsp;(ground-state + thermally excited-state).\u003c/p\u003e","description":"","filename":"Fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-5420187/v1/1a25fac41b81037fa8abe093.png"},{"id":82126783,"identity":"18b5ce78-91c2-482b-95ca-518128534f0c","added_by":"auto","created_at":"2025-05-07 04:17:18","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":683978,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTemperature map and ITR characterization under AlN-to-SiC heat flow\u003c/strong\u003e. \u003cstrong\u003ea,\u003c/strong\u003e Low-magnification HAADF-STEM image (left) and atomic-resolution image (right) of the AlN-SiC interface. \u003cstrong\u003eb,\u003c/strong\u003e Linear plots of the logarithm of the ratio between loss and gain scattering as a function of excitation energy. Color-coded spectra correspond to the acquisition positions marked by identical color dots in (a). \u003cstrong\u003ec, \u003c/strong\u003eTemperature map of the area marked by the white dashed box in (a), and the temperature profiles of each row. \u003cstrong\u003ed,\u003c/strong\u003e Corresponding isotherm diagram and temperature gradient field (black arrows), superimposed on the HAADF image to visualize thermal transport directionality. \u003cstrong\u003ee,\u003c/strong\u003e Interface-adjacent temperature profiles under varying heating currents from another sample (see Fig. S1a). Linear fits to bulk regions (colored text) yield temperature gradients, while the interface temperature drop (Δ\u003cem\u003eT\u003c/em\u003e) is denoted by black text. Colored shaded areas represent the standard deviation of the mean from multiple data points. \u003cstrong\u003ef,\u003c/strong\u003e Relative ITR is quantified by the interface characteristic length, derived from the relationship between the interface temperature drop and the bulk temperature gradient in AlN and SiC respectively.\u003c/p\u003e","description":"","filename":"Fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-5420187/v1/e5daa9e40e05178d81810512.png"},{"id":82126782,"identity":"05e21119-9e0c-4fbd-9ae3-98cc502a01ef","added_by":"auto","created_at":"2025-05-07 04:17:18","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":662606,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eNon-equilibrium phonon dynamics across the interface under forward (AlN→SiC) and reverse (SiC→AlN) heat flow\u003c/strong\u003e. \u003cstrong\u003ea, b,\u003c/strong\u003eExperimentally reconstructed temperature maps for forward and reverse heat flow conditions. \u003cstrong\u003ec, d,\u003c/strong\u003e EEG spectra acquired under forward and reverse heat flow. \u003cstrong\u003ee, f,\u003c/strong\u003e Corresponding EEL spectra. Overlaid lines denote the relative intensity of AlN TO phonon peak (81-85meV): solid white from EEG spectra and dashed gray from EEL spectra, respectively. \u003cstrong\u003eg,\u003c/strong\u003e Extracted phonon spectra at SiC (red line), AlN (blue line) and interface (green shade) from panels c-f. Calculated phonon density of states (DOS) is shown at the bottom. \u003cstrong\u003eh,\u003c/strong\u003eInterface residual spectra after removing the spectral components of bulk SiC and AlN using the least squared fitting (see Methods). \u003cstrong\u003ei,\u003c/strong\u003e Calculated spatial distribution of phonon modal temperatures near the interface. The thick solid line represents the averaged modal temperature profile. \u003cstrong\u003ej,\u003c/strong\u003e Schematic illustration of non-equilibrium phonon transport across the interface. Dispersion lines are color-coded by calculated modal temperatures along the ΓA direction (heat flow direction). The central colored band plots depict the interface residual spectra from the experimental EEG data, representing the interface mode population. Arrows denote the three-phonon scattering processes associated with the \u003cem\u003eα\u003c/em\u003e and \u003cem\u003eβ\u003c/em\u003e modes: green for absorption, gray for emission. Solid arrows indicate enhanced processes, while hollow arrows denote suppressed processes.\u003c/p\u003e","description":"","filename":"Fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-5420187/v1/56652556504a080503294798.png"},{"id":84452397,"identity":"72191af3-3eb0-4d3e-80d0-7971789eebbf","added_by":"auto","created_at":"2025-06-12 07:06:02","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1313704,"visible":true,"origin":"","legend":"","description":"","filename":"Manuscriptrevised.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5420187/v1_covered_744bae3b-d8b5-475b-bfc2-342a405176e3.pdf"},{"id":82126785,"identity":"2e150819-0be2-48e4-aa1e-668b479327e5","added_by":"auto","created_at":"2025-05-07 04:17:18","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":3306652,"visible":true,"origin":"","legend":"Supplementary Information for Probing phonon transport dynamics across an interface by electron microscopy","description":"","filename":"SIrevised.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5420187/v1/faada958cea025859f4c2f5a.pdf"},{"id":82127510,"identity":"27dfbb70-eb67-49be-906f-12890390022b","added_by":"auto","created_at":"2025-05-07 04:25:18","extension":"pdf","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":1749907,"visible":true,"origin":"","legend":"Transparent Peer Review file","description":"","filename":"TPRGao20241124089B.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5420187/v1/2507fd34b1adad885e1f9ff6.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Probing phonon transport dynamics across an interface by electron microscopy","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-5420187/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5420187/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Understanding thermal transport mechanisms across material interfaces is crucial for advancing semiconductor technologies, particularly in miniaturized devices operating under extreme power densities1,2. Although the interface phonon-mediated processes are theoretically established3–6 as the dominant mechanism for interfacial thermal transport in semiconductors7, their nanoscale dynamics remain experimentally elusive due to challenges in measuring the temperature and non-equilibrium phonon distributions across the buried interface8–11. Here, we overcome these limitations by using in-situ vibrational electron energy-loss spectroscopy in an electron microscope to nanoscale profile temperature gradients across the AlN-SiC interface during thermal transport and map its non-equilibrium phonon occupations at sub-nanometer resolution. We observe a sharp temperature drop within ~2 nm across the interface, enabling direct extraction of relative interface thermal resistance. During thermal transport, the mismatch of phonon modes’ thermal conductivity at the interface causes substantial non-equilibrium phonons nearby, making the populations of interface modes different under forward and reverse heat flow, and also leading to significant changes in the modal temperature of AlN optical phonons within ~3 nm of the interface. These results reveal the phonon transport dynamics at the (sub-)nanoscale and establish the inelastic phonon scattering mechanism involved by interface modes, offering valuable insights into engineering of thermal interfaces.","manuscriptTitle":"Probing phonon transport dynamics across an interface by electron microscopy","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-07 04:17:14","doi":"10.21203/rs.3.rs-5420187/v1","editorialEvents":[],"status":"published","journal":{"display":false,"email":"[email protected]","identity":"nature","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"nature","sideBox":"Learn more about [Nature](http://www.nature.com/nature/)","snPcode":"","submissionUrl":"","title":"Nature","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"132081ee-be2e-4861-88bb-f0749877b7a5","owner":[],"postedDate":"May 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":47113180,"name":"Physical sciences/Physics/Condensed-matter physics/Surfaces, interfaces and thin films"},{"id":47113181,"name":"Physical sciences/Nanoscience and technology/Techniques and instrumentation/Microscopy/Transmission electron microscopy"},{"id":47113182,"name":"Physical sciences/Materials science/Techniques and instrumentation/Characterization and analytical techniques"},{"id":47113183,"name":"Physical sciences/Materials science/Theory and computation/Atomistic models"},{"id":47113184,"name":"Physical sciences/Physics/Condensed-matter physics/Semiconductors"}],"tags":[],"updatedAt":"2025-06-12T07:05:52+00:00","versionOfRecord":{"articleIdentity":"rs-5420187","link":"https://doi.org/10.1038/s41586-025-09108-6","journal":{"identity":"nature","isVorOnly":false,"title":"Nature"},"publishedOn":"2025-06-11 04:00:00","publishedOnDateReadable":"June 11th, 2025"},"versionCreatedAt":"2025-05-07 04:17:14","video":"","vorDoi":"10.1038/s41586-025-09108-6","vorDoiUrl":"https://doi.org/10.1038/s41586-025-09108-6","workflowStages":[]},"version":"v1","identity":"rs-5420187","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5420187","identity":"rs-5420187","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}