{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/34427"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/34427","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Real-time atomic resolution dynamics of glass surfaces","abstract":"Although glasses are commonplace materials found in every walk of life, they have managed to remain mysterious for centuries. The origins of the defining characteristic of glasses, the glass transition, remain unknown. The glass transition is accompanied by a catastrophic increase in viscosity with a superexponential pace whose underlying reason has been difficult to pin down. Cooperatively rearranging regions (CRR) are playing an increasingly important role in explaining these phenomena. As CRR are only a few nanometers in size, much information can be gained by imaging studies of glasses at the atomic scale. This thesis employs the atomic resolution capabilities of scanning tunneling microscopy (STM) to study glass surfaces in real-time. Initial experiments on metallic glass surfaces discovered localized two-state dynamics of atomic clusters (2-8 atomic diameters) active even below the glass transition temperature (Tg). Atomic scale evidence of spatial and temporal heterogeneity was acquired. After multiple metallic glass surfaces were shown to exhibit these dynamics, it was proposed to be a universal phenomenon on glass surfaces with similar size distribution in terms of their average weighted diameter. The clusters were also shown to be thermally-activated by studying their temperature behavior. Similar dynamics were discovered on amorphous-silicon, which is an important electronic material, amidst the debate whether or not it is a glass. Further, the two-state dynamics were demonstrated to be quenched after the incorporation of hydrogen during the growth process. Individual CRRs are studied while simultaneously ramping their temperature. The single cluster traces showed marked shifts in the local equilibria illustrating a temperature-sensitive energy landscape. It was deduced that spatial heterogeneity (differences in rates at different sites) is the major contributor to the non-exponential glassy relaxations rather than temporal heterogeneity (differences in rate at single sites with time). Studies performed on metallic glasses with ultra-low Tg of 376 K near its glass transition to above its crystallization temperature (433 K) showed the glass surfaces are robust and their amorphous nature indestructible via heat treatments above their bulk melting point. Temperature dependence of surface dynamics was found to be weak, supporting the view that the mobile surface layer is able to find progressively deeper minima with increasing temperature.","abstract_html":"Although glasses are commonplace materials found in every walk of life, they have managed to remain mysterious for centuries. The origins of the defining characteristic of glasses, the glass transition, remain unknown. The glass transition is accompanied by a catastrophic increase in viscosity with a superexponential pace whose underlying reason has been difficult to pin down. Cooperatively rearranging regions (CRR) are playing an increasingly important role in explaining these phenomena. As CRR are only a few nanometers in size, much information can be gained by imaging studies of glasses at the atomic scale. This thesis employs the atomic resolution capabilities of scanning tunneling microscopy (STM) to study glass surfaces in real-time. Initial experiments on metallic glass surfaces discovered localized two-state dynamics of atomic clusters (2-8 atomic diameters) active even below the glass transition temperature (Tg). Atomic scale evidence of spatial and temporal heterogeneity was acquired. After multiple metallic glass surfaces were shown to exhibit these dynamics, it was proposed to be a universal phenomenon on glass surfaces with similar size distribution in terms of their average weighted diameter. The clusters were also shown to be thermally-activated by studying their temperature behavior. Similar dynamics were discovered on amorphous-silicon, which is an important electronic material, amidst the debate whether or not it is a glass. Further, the two-state dynamics were demonstrated to be quenched after the incorporation of hydrogen during the growth process. Individual CRRs are studied while simultaneously ramping their temperature. The single cluster traces showed marked shifts in the local equilibria illustrating a temperature-sensitive energy landscape. It was deduced that spatial heterogeneity (differences in rates at different sites) is the major contributor to the non-exponential glassy relaxations rather than temporal heterogeneity (differences in rate at single sites with time). Studies performed on metallic glasses with ultra-low Tg of 376 K near its glass transition to above its crystallization temperature (433 K) showed the glass surfaces are robust and their amorphous nature indestructible via heat treatments above their bulk melting point. Temperature dependence of surface dynamics was found to be weak, supporting the view that the mobile surface layer is able to find progressively deeper minima with increasing temperature.","abstract_has_math":false,"creators":["Ashtekar, Sumit"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Chemistry","degree_department":null,"school":null,"contributors":["Gruebele, Martin","Martin Gruebele","Lyding, Joseph W.","Jain, Prashant K.","McCall, Benjamin J."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2012,"date_issued":"2012-09-18T21:16:20Z","date_published":"2012-09-18T21:16:20Z","updated_at":"2026-07-22T22:25:31Z","subjects":["Glass Transition","Two-state Dynamics","Metallic Glasses","Scanning Tunneling Microscopy","Cooperatively Rearranging Regions","Aging","Fragility","Amorphous Silicon","Surface Dynamics"],"languages":["en"],"rights":["Copyright 2012 Sumit Ashtekar"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/34427","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Gruebele, Martin","Martin Gruebele","Lyding, Joseph W.","Jain, Prashant K.","McCall, Benjamin J."]},{"key":"dc:creator","label":"Author","values":["Ashtekar, Sumit"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2012-09-18T21:16:20Z","2012-08"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Chemistry"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Glass Transition","Two-state Dynamics","Metallic Glasses","Scanning Tunneling Microscopy","Cooperatively Rearranging Regions","Aging","Fragility","Amorphous Silicon","Surface Dynamics"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2012 Sumit Ashtekar"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/34427"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Although glasses are commonplace materials found in every walk of life, they have managed to remain mysterious for centuries. The origins of the defining characteristic of glasses, the glass transition, remain unknown. The glass transition is accompanied by a catastrophic increase in viscosity with a superexponential pace whose underlying reason has been difficult to pin down. Cooperatively rearranging regions (CRR) are playing an increasingly important role in explaining these phenomena. As CRR are only a few nanometers in size, much information can be gained by imaging studies of glasses at the atomic scale. This thesis employs the atomic resolution capabilities of scanning tunneling microscopy (STM) to study glass surfaces in real-time. Initial experiments on metallic glass surfaces discovered localized two-state dynamics of atomic clusters (2-8 atomic diameters) active even below the glass transition temperature (Tg). Atomic scale evidence of spatial and temporal heterogeneity was acquired. After multiple metallic glass surfaces were shown to exhibit these dynamics, it was proposed to be a universal phenomenon on glass surfaces with similar size distribution in terms of their average weighted diameter. The clusters were also shown to be thermally-activated by studying their temperature behavior. Similar dynamics were discovered on amorphous-silicon, which is an important electronic material, amidst the debate whether or not it is a glass. Further, the two-state dynamics were demonstrated to be quenched after the incorporation of hydrogen during the growth process. Individual CRRs are studied while simultaneously ramping their temperature. The single cluster traces showed marked shifts in the local equilibria illustrating a temperature-sensitive energy landscape. It was deduced that spatial heterogeneity (differences in rates at different sites) is the major contributor to the non-exponential glassy relaxations rather than temporal heterogeneity (differences in rate at single sites with time). Studies performed on metallic glasses with ultra-low Tg of 376 K near its glass transition to above its crystallization temperature (433 K) showed the glass surfaces are robust and their amorphous nature indestructible via heat treatments above their bulk melting point. 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After multiple metallic glass surfaces were shown to exhibit these dynamics, it was proposed to be a universal phenomenon on glass surfaces with similar size distribution in terms of their average weighted diameter. The clusters were also shown to be thermally-activated by studying their temperature behavior. Similar dynamics were discovered on amorphous-silicon, which is an important electronic material, amidst the debate whether or not it is a glass. Further, the two-state dynamics were demonstrated to be quenched after the incorporation of hydrogen during the growth process. Individual CRRs are studied while simultaneously ramping their temperature. The single cluster traces showed marked shifts in the local equilibria illustrating a temperature-sensitive energy landscape. It was deduced that spatial heterogeneity (differences in rates at different sites) is the major contributor to the non-exponential glassy relaxations rather than temporal heterogeneity (differences in rate at single sites with time). Studies performed on metallic glasses with ultra-low Tg of 376 K near its glass transition to above its crystallization temperature (433 K) showed the glass surfaces are robust and their amorphous nature indestructible via heat treatments above their bulk melting point. Temperature dependence of surface dynamics was found to be weak, supporting the view that the mobile surface layer is able to find progressively deeper minima with increasing temperature.","Item withdrawn by Katherine Eriksen (eriksen3@illinois.edu) on 2012-07-09T20:50:56Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 11 Ashtekar_Sumit.docx: 12173965 bytes, checksum: e8aa836c7942b5a782fd3334db36046c (MD5) Movie 3.4 Silicon spatial heterogeneity.mov: 2818348 bytes, checksum: f5e9674fa5168290e645daaef1670377 (MD5) Movie 4.2 CRR Dynamics with temp ramp.mov: 14317205 bytes, checksum: 30e0b3475200a8aa3308ed74502ea21e (MD5) Movie 4.1 Atomic resolution of 3-state CRR.mov: 8633667 bytes, checksum: fdf00784e2529fb818cd3b865a58291b (MD5) Movie 3.3 Silicon Concerted Motion.mov: 3902801 bytes, checksum: c70f8680d387bbe23321471ecbd6bd82 (MD5) Movie 3.2 Silicon Vapor Two state dynamics.mov: 2851665 bytes, checksum: df986a1115f2ce866ce95624db5072b2 (MD5) Movie 3.1 Silion - ion two state dynamics.mov: 2886599 bytes, checksum: 680098dcb9fcdb2a79f72c8caa478398 (MD5) Movie 2.3 Temporal heterogeneity.mov: 9405895 bytes, checksum: 4760277f8b6fd5d4d944c9644e698728 (MD5) Movie 2.2 Spatial heterogeneity.mov: 10365732 bytes, checksum: 961ae4a9ee5446d48afedb58088d0da7 (MD5) Movie 2.1 Two state motion.mov: 6073977 bytes, checksum: 07f5b009d92b105ca200b40ce57fc095 (MD5) Ashtekar_Sumit.pdf: 4801414 bytes, checksum: 74d57048f4ff6b182f023ff121bae941 (MD5)","Made available in DSpace on 2012-09-18T21:16:20Z (GMT). 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