{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/82789"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/82789","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Optical and Electronic Properties, Nanoscale Structural Order, and Transformation Kinetics of Phase Change Materials","abstract":"One long standing puzzle was that, for a fixed composition, there may be different amorphous states that have greatly different crystallization kinetics. We provided clear evidence for the existence of nanoscale structural order in all amorphous states of Ge2Sb2Te5 and AgInSbTe, using Fluctuation electron microscopy (FEM) carried out in the transmission electron microscope. The nanoscale order is higher in the thermally annealed amorphous states than in the as-deposited (sputtered) state. Higher nanoscale order corresponds to more or larger ordered regions; then the structure has a greater probability to have supercritical nuclei that later grow into crystalline grains. The crystallization speeds of the annealed states are indeed higher than that of the as-deposited states. The greatly different effects of annealing on Ge2Sb2Te5 and AgInSbTe were explained by the difference in the nucleation rates. We also demonstrated that melt-quenched amorphous Ge2Sb2Te5 has clearly indexable crystalline particles of several nanometers, in addition to the amorphous matrix with high nanoscale order; the nanoparticles can act as supercritical nuclei that result in an order of magnitude faster crystallization.","abstract_html":"One long standing puzzle was that, for a fixed composition, there may be different amorphous states that have greatly different crystallization kinetics. We provided clear evidence for the existence of nanoscale structural order in all amorphous states of Ge2Sb2Te5 and AgInSbTe, using Fluctuation electron microscopy (FEM) carried out in the transmission electron microscope. The nanoscale order is higher in the thermally annealed amorphous states than in the as-deposited (sputtered) state. Higher nanoscale order corresponds to more or larger ordered regions; then the structure has a greater probability to have supercritical nuclei that later grow into crystalline grains. The crystallization speeds of the annealed states are indeed higher than that of the as-deposited states. The greatly different effects of annealing on Ge2Sb2Te5 and AgInSbTe were explained by the difference in the nucleation rates. We also demonstrated that melt-quenched amorphous Ge2Sb2Te5 has clearly indexable crystalline particles of several nanometers, in addition to the amorphous matrix with high nanoscale order; the nanoparticles can act as supercritical nuclei that result in an order of magnitude faster crystallization.","abstract_has_math":false,"creators":["Lee, Bong-Sub"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Materials Science and Engineering","degree_department":null,"school":null,"contributors":["Abelson, John R."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-09-25T20:53:01Z","date_published":"2015-09-25T20:53:01Z","updated_at":"2026-07-22T22:26:18Z","subjects":["Engineering, Materials Science"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(MiAaPQ)AAI3242913"],"render_values":[{"text":"(MiAaPQ)AAI3242913","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/82789","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Abelson, John R."]},{"key":"dc:creator","label":"Author","values":["Lee, Bong-Sub"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-09-25T20:53:01Z","10000-01-01","2006"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Materials Science and Engineering"]},{"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":["Engineering, Materials Science"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/82789","(MiAaPQ)AAI3242913"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["One long standing puzzle was that, for a fixed composition, there may be different amorphous states that have greatly different crystallization kinetics. We provided clear evidence for the existence of nanoscale structural order in all amorphous states of Ge2Sb2Te5 and AgInSbTe, using Fluctuation electron microscopy (FEM) carried out in the transmission electron microscope. The nanoscale order is higher in the thermally annealed amorphous states than in the as-deposited (sputtered) state. Higher nanoscale order corresponds to more or larger ordered regions; then the structure has a greater probability to have supercritical nuclei that later grow into crystalline grains. The crystallization speeds of the annealed states are indeed higher than that of the as-deposited states. The greatly different effects of annealing on Ge2Sb2Te5 and AgInSbTe were explained by the difference in the nucleation rates. We also demonstrated that melt-quenched amorphous Ge2Sb2Te5 has clearly indexable crystalline particles of several nanometers, in addition to the amorphous matrix with high nanoscale order; the nanoparticles can act as supercritical nuclei that result in an order of magnitude faster crystallization.","Made available in DSpace on 2015-09-25T20:53:01Z (GMT). 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We provided clear evidence for the existence of nanoscale structural order in all amorphous states of Ge2Sb2Te5 and AgInSbTe, using Fluctuation electron microscopy (FEM) carried out in the transmission electron microscope. The nanoscale order is higher in the thermally annealed amorphous states than in the as-deposited (sputtered) state. Higher nanoscale order corresponds to more or larger ordered regions; then the structure has a greater probability to have supercritical nuclei that later grow into crystalline grains. The crystallization speeds of the annealed states are indeed higher than that of the as-deposited states. The greatly different effects of annealing on Ge2Sb2Te5 and AgInSbTe were explained by the difference in the nucleation rates. We also demonstrated that melt-quenched amorphous Ge2Sb2Te5 has clearly indexable crystalline particles of several nanometers, in addition to the amorphous matrix with high nanoscale order; the nanoparticles can act as supercritical nuclei that result in an order of magnitude faster crystallization.","Made available in DSpace on 2015-09-25T20:53:01Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 3242913.pdf: 3289354 bytes, checksum: e766153c1e7c3aeb02ff46f2e75b7bc8 (MD5) Previous issue date: 2006","Embargo set by: Seth Robbins for item 84070 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","122 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006."],"dc:identifier":["http://hdl.handle.net/2142/82789","(MiAaPQ)AAI3242913"],"dc:language":["eng"],"dc:subject":["Engineering, Materials Science"],"dc:title":["Optical and Electronic Properties, Nanoscale Structural Order, and Transformation Kinetics of Phase Change Materials"],"dc:type":["text"],"thesis:degree_discipline":["Materials Science and Engineering"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:26:18Z"}