{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/77409"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/77409","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Fluctuations in dc SQUIDs: Quantum Noise Effects, Low Frequency Noise, and Single Electron Trapping","abstract":"We have studied the signal and noise properties of extremely sensitive dc SQUIDs composed of submicron area tunnel junctions. At high frequencies, the flux resolution is expected to be limited by intrinsic quantum fluctuations, making these devices prime candidates for ideal quantum-limited detectors. The observed signal properties are excellent and a minimum for energy resolution of 1.6$\\hbar$ was measured at 1.5K, the lowest value reported to date. At low frequencies, we observe broad, Lorentzian features superimposed on a background which is always much flatter than 1/f ($\\sim {\\rm f}\\sp{-2/3}$). When these features are strongest, the real-time voltage noise displays discrete switching behavior which results from the trapping and untrapping of single electrons into localized defect states residing within the tunneling barrier. The weak temperature of the trap lifetimes reveals that the trapping process displays tunneling kinetics. In contrast, the voltage bias dependence of the lifetimes is consistent with a simple nonequilibrium model in which the bias strongly enhances the rate for electrons to tunnel in from one side of the barrier and exit out the other side. Some junctions show clear evidence of interactions between traps, and for certain bias conditions, the noise displays predominantly series kinetics. These observations show that the low frequency noise in this system cannot always be described by a simple parallel kinetics model composed of independent fluctuators.","abstract_html":"We have studied the signal and noise properties of extremely sensitive dc SQUIDs composed of submicron area tunnel junctions. At high frequencies, the flux resolution is expected to be limited by intrinsic quantum fluctuations, making these devices prime candidates for ideal quantum-limited detectors. The observed signal properties are excellent and a minimum for energy resolution of 1.6$\\hbar$ was measured at 1.5K, the lowest value reported to date. At low frequencies, we observe broad, Lorentzian features superimposed on a background which is always much flatter than 1/f ($\\sim {\\rm f}\\sp{-2/3}$). When these features are strongest, the real-time voltage noise displays discrete switching behavior which results from the trapping and untrapping of single electrons into localized defect states residing within the tunneling barrier. The weak temperature of the trap lifetimes reveals that the trapping process displays tunneling kinetics. In contrast, the voltage bias dependence of the lifetimes is consistent with a simple nonequilibrium model in which the bias strongly enhances the rate for electrons to tunnel in from one side of the barrier and exit out the other side. Some junctions show clear evidence of interactions between traps, and for certain bias conditions, the noise displays predominantly series kinetics. These observations show that the low frequency noise in this system cannot always be described by a simple parallel kinetics model composed of independent fluctuators.","abstract_has_math":true,"creators":["Wakai, Ronald Tatsuya"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Physics","degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-05-13T15:41:57Z","date_published":"2015-05-13T15:41:57Z","updated_at":"2026-07-22T22:26:10Z","subjects":["Physics, Condensed Matter"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(UMI)AAI8721778"],"render_values":[{"text":"(UMI)AAI8721778","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/77409","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Wakai, Ronald Tatsuya"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-05-13T15:41:57Z","1987"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Physics"]},{"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":["Physics, Condensed Matter"]}]},{"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/2142/77409","(UMI)AAI8721778"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["We have studied the signal and noise properties of extremely sensitive dc SQUIDs composed of submicron area tunnel junctions. At high frequencies, the flux resolution is expected to be limited by intrinsic quantum fluctuations, making these devices prime candidates for ideal quantum-limited detectors. The observed signal properties are excellent and a minimum for energy resolution of 1.6$\\hbar$ was measured at 1.5K, the lowest value reported to date. At low frequencies, we observe broad, Lorentzian features superimposed on a background which is always much flatter than 1/f ($\\sim {\\rm f}\\sp{-2/3}$). When these features are strongest, the real-time voltage noise displays discrete switching behavior which results from the trapping and untrapping of single electrons into localized defect states residing within the tunneling barrier. The weak temperature of the trap lifetimes reveals that the trapping process displays tunneling kinetics. In contrast, the voltage bias dependence of the lifetimes is consistent with a simple nonequilibrium model in which the bias strongly enhances the rate for electrons to tunnel in from one side of the barrier and exit out the other side. Some junctions show clear evidence of interactions between traps, and for certain bias conditions, the noise displays predominantly series kinetics. These observations show that the low frequency noise in this system cannot always be described by a simple parallel kinetics model composed of independent fluctuators.","Made available in DSpace on 2015-05-13T15:41:57Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 8721778.PDF: 4810008 bytes, checksum: 1c4bd727d0ed71db71d2de8352d8736b (MD5) Previous issue date: 1987","Embargo set by: Seth Robbins for item 78620 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Open Restriction set for Item 78620 on 2021-06-09T13:37:27Z with date null by madinag@illinois.edu.","Open Restriction set for Item 78620 on 2021-06-09T13:37:31Z with date null by madinag@illinois.edu.","Open","164 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987."]},{"key":"dc:title","label":"Title","values":["Fluctuations in dc SQUIDs: Quantum Noise Effects, Low Frequency Noise, and Single Electron Trapping"]}]}],"canonical_facts":{"dc:creator":["Wakai, Ronald Tatsuya"],"dc:date":["2015-05-13T15:41:57Z","1987"],"dc:description":["We have studied the signal and noise properties of extremely sensitive dc SQUIDs composed of submicron area tunnel junctions. At high frequencies, the flux resolution is expected to be limited by intrinsic quantum fluctuations, making these devices prime candidates for ideal quantum-limited detectors. The observed signal properties are excellent and a minimum for energy resolution of 1.6$\\hbar$ was measured at 1.5K, the lowest value reported to date. At low frequencies, we observe broad, Lorentzian features superimposed on a background which is always much flatter than 1/f ($\\sim {\\rm f}\\sp{-2/3}$). When these features are strongest, the real-time voltage noise displays discrete switching behavior which results from the trapping and untrapping of single electrons into localized defect states residing within the tunneling barrier. The weak temperature of the trap lifetimes reveals that the trapping process displays tunneling kinetics. In contrast, the voltage bias dependence of the lifetimes is consistent with a simple nonequilibrium model in which the bias strongly enhances the rate for electrons to tunnel in from one side of the barrier and exit out the other side. Some junctions show clear evidence of interactions between traps, and for certain bias conditions, the noise displays predominantly series kinetics. These observations show that the low frequency noise in this system cannot always be described by a simple parallel kinetics model composed of independent fluctuators.","Made available in DSpace on 2015-05-13T15:41:57Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 8721778.PDF: 4810008 bytes, checksum: 1c4bd727d0ed71db71d2de8352d8736b (MD5) Previous issue date: 1987","Embargo set by: Seth Robbins for item 78620 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Open Restriction set for Item 78620 on 2021-06-09T13:37:27Z with date null by madinag@illinois.edu.","Open Restriction set for Item 78620 on 2021-06-09T13:37:31Z with date null by madinag@illinois.edu.","Open","164 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987."],"dc:identifier":["http://hdl.handle.net/2142/77409","(UMI)AAI8721778"],"dc:language":["eng"],"dc:subject":["Physics, Condensed Matter"],"dc:title":["Fluctuations in dc SQUIDs: Quantum Noise Effects, Low Frequency Noise, and Single Electron Trapping"],"dc:type":["text"],"thesis:degree_discipline":["Physics"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:26:10Z"}