{"id":{"repo_id":"umn","oai_identifier":"oai:conservancy.umn.edu:11299/224983"},"canonical_url":"https://search.dev.ndltd.org/etd/umn/oai:conservancy.umn.edu:11299/224983","repository":{"repo_id":"umn","name":"University of Minnesota","base_url":"https://conservancy.umn.edu/server/oai/request"},"display":{"title":"Phase-Engineered Field-Effect Transistors Based on Two-Dimensional Transition Metal Dichalcogenides","abstract":"Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are layered materials in which each unit consists of a transition metal (Mo, and W) layer sandwiched between two chalcogen (S, Se, and Te) atomic layers. They can exist in either a semiconducting or metallic phase. Semiconducting TMDC based field-effect transistors (FETs) are considered promising candidates for post-Si electronics owing to their ultra-thin body enabling ultimate scalability. However, the large contact resistance at the metal/TMDC interface limits their drive current for high-performance applications. The large contact resistance is due to an enlarged schottky barrier height resulting from strong fermi-level pinning and the existence of van der Waal gaps at the metal/TMDC interface and in-between TMDC layers. The ultimate solution to the contact issue is to utilize lateral metallic-semiconducting TMDC junctions as 2D edge contacts. Thanks to the small free energy difference between its semiconducting 2H and metallic 1T’ phases, lateral 2H/1T’ MoTe2 homojunctions can be synthesized in situ by flux-controlled phase engineering. In this dissertation, a comprehensive study combining detailed structural and electrical properties of in-situ-grown lateral MoTe2 homojunctions formed via the flux-controlled technique is presented. MoTe2 p-MOSFETs with phase-engineered 1T’ contacts which showed significantly improved performance over devices with metal/2H contacts are demonstrated. In order to employ this flux-controlled technique for large-scale CMOS fabrication, a two-step lithographic synthesis approach for creating various lateral TMDC junctions is developed. Lateral 2H/1T′ MoTe2 homojunction p-MOSFETs and 2H-MoS2/1T′-MoTe2 heterojunction n-MOSFETs are fabricated using the two-step approach. Besides, a reversible phase transition between 2H and 1T’ MoS2 by gate-controlled Li+ intercalation through a solid PEO:LiClO4 electrolyte is demonstrated, which could allow the use of lateral metallic-semiconducting TMDC junctions for phase-change memory applications.","abstract_html":"Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are layered materials in which each unit consists of a transition metal (Mo, and W) layer sandwiched between two chalcogen (S, Se, and Te) atomic layers. They can exist in either a semiconducting or metallic phase. Semiconducting TMDC based field-effect transistors (FETs) are considered promising candidates for post-Si electronics owing to their ultra-thin body enabling ultimate scalability. However, the large contact resistance at the metal/TMDC interface limits their drive current for high-performance applications. The large contact resistance is due to an enlarged schottky barrier height resulting from strong fermi-level pinning and the existence of van der Waal gaps at the metal/TMDC interface and in-between TMDC layers. The ultimate solution to the contact issue is to utilize lateral metallic-semiconducting TMDC junctions as 2D edge contacts. Thanks to the small free energy difference between its semiconducting 2H and metallic 1T’ phases, lateral 2H/1T’ MoTe2 homojunctions can be synthesized in situ by flux-controlled phase engineering. In this dissertation, a comprehensive study combining detailed structural and electrical properties of in-situ-grown lateral MoTe2 homojunctions formed via the flux-controlled technique is presented. MoTe2 p-MOSFETs with phase-engineered 1T’ contacts which showed significantly improved performance over devices with metal/2H contacts are demonstrated. In order to employ this flux-controlled technique for large-scale CMOS fabrication, a two-step lithographic synthesis approach for creating various lateral TMDC junctions is developed. Lateral 2H/1T′ MoTe2 homojunction p-MOSFETs and 2H-MoS2/1T′-MoTe2 heterojunction n-MOSFETs are fabricated using the two-step approach. Besides, a reversible phase transition between 2H and 1T’ MoS2 by gate-controlled Li+ intercalation through a solid PEO:LiClO4 electrolyte is demonstrated, which could allow the use of lateral metallic-semiconducting TMDC junctions for phase-change memory applications.","abstract_has_math":false,"creators":["Ma, Rui"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2020,"date_issued":"2020-08","date_published":"2020-08","updated_at":"2026-07-24T05:19:52Z","subjects":["chemical vapor deposition","field-effect Transistor","lateral homojunction","phase engineering","Schottky barrier height","transition metal dichalcogenide"],"languages":["en"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/11299/224983","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Ma, Rui"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2021-10-13T17:55:49Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2021-10-13T17:55:49Z"]},{"key":"dc:date.issued","label":"Date","values":["2020-08"]},{"key":"dc:type","label":"Dc Type","values":["Thesis or Dissertation"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["chemical vapor deposition","field-effect Transistor","lateral homojunction","phase engineering","Schottky barrier height","transition metal dichalcogenide"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/11299/224983"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["University of Minnesota Ph.D. dissertation. August 2020. Major: Electrical/Computer Engineering. Advisor: Steven Koester. 1 computer file (PDF); xii, 179 pages."]},{"key":"dc:description.abstract","label":"Abstract","values":["Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are layered materials in which each unit consists of a transition metal (Mo, and W) layer sandwiched between two chalcogen (S, Se, and Te) atomic layers. They can exist in either a semiconducting or metallic phase. Semiconducting TMDC based field-effect transistors (FETs) are considered promising candidates for post-Si electronics owing to their ultra-thin body enabling ultimate scalability. However, the large contact resistance at the metal/TMDC interface limits their drive current for high-performance applications. The large contact resistance is due to an enlarged schottky barrier height resulting from strong fermi-level pinning and the existence of van der Waal gaps at the metal/TMDC interface and in-between TMDC layers. The ultimate solution to the contact issue is to utilize lateral metallic-semiconducting TMDC junctions as 2D edge contacts. Thanks to the small free energy difference between its semiconducting 2H and metallic 1T’ phases, lateral 2H/1T’ MoTe2 homojunctions can be synthesized in situ by flux-controlled phase engineering. In this dissertation, a comprehensive study combining detailed structural and electrical properties of in-situ-grown lateral MoTe2 homojunctions formed via the flux-controlled technique is presented. MoTe2 p-MOSFETs with phase-engineered 1T’ contacts which showed significantly improved performance over devices with metal/2H contacts are demonstrated. In order to employ this flux-controlled technique for large-scale CMOS fabrication, a two-step lithographic synthesis approach for creating various lateral TMDC junctions is developed. Lateral 2H/1T′ MoTe2 homojunction p-MOSFETs and 2H-MoS2/1T′-MoTe2 heterojunction n-MOSFETs are fabricated using the two-step approach. Besides, a reversible phase transition between 2H and 1T’ MoS2 by gate-controlled Li+ intercalation through a solid PEO:LiClO4 electrolyte is demonstrated, which could allow the use of lateral metallic-semiconducting TMDC junctions for phase-change memory applications."]},{"key":"dc:title","label":"Title","values":["Phase-Engineered Field-Effect Transistors Based on Two-Dimensional Transition Metal Dichalcogenides"]}]}],"canonical_facts":{"dc:creator":["Ma, Rui"],"dc:date.accessioned":["2021-10-13T17:55:49Z"],"dc:date.available":["2021-10-13T17:55:49Z"],"dc:date.issued":["2020-08"],"dc:description":["University of Minnesota Ph.D. dissertation. August 2020. Major: Electrical/Computer Engineering. Advisor: Steven Koester. 1 computer file (PDF); xii, 179 pages."],"dc:description.abstract":["Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are layered materials in which each unit consists of a transition metal (Mo, and W) layer sandwiched between two chalcogen (S, Se, and Te) atomic layers. They can exist in either a semiconducting or metallic phase. Semiconducting TMDC based field-effect transistors (FETs) are considered promising candidates for post-Si electronics owing to their ultra-thin body enabling ultimate scalability. However, the large contact resistance at the metal/TMDC interface limits their drive current for high-performance applications. The large contact resistance is due to an enlarged schottky barrier height resulting from strong fermi-level pinning and the existence of van der Waal gaps at the metal/TMDC interface and in-between TMDC layers. The ultimate solution to the contact issue is to utilize lateral metallic-semiconducting TMDC junctions as 2D edge contacts. Thanks to the small free energy difference between its semiconducting 2H and metallic 1T’ phases, lateral 2H/1T’ MoTe2 homojunctions can be synthesized in situ by flux-controlled phase engineering. In this dissertation, a comprehensive study combining detailed structural and electrical properties of in-situ-grown lateral MoTe2 homojunctions formed via the flux-controlled technique is presented. MoTe2 p-MOSFETs with phase-engineered 1T’ contacts which showed significantly improved performance over devices with metal/2H contacts are demonstrated. In order to employ this flux-controlled technique for large-scale CMOS fabrication, a two-step lithographic synthesis approach for creating various lateral TMDC junctions is developed. Lateral 2H/1T′ MoTe2 homojunction p-MOSFETs and 2H-MoS2/1T′-MoTe2 heterojunction n-MOSFETs are fabricated using the two-step approach. Besides, a reversible phase transition between 2H and 1T’ MoS2 by gate-controlled Li+ intercalation through a solid PEO:LiClO4 electrolyte is demonstrated, which could allow the use of lateral metallic-semiconducting TMDC junctions for phase-change memory applications."],"dc:identifier.uri":["https://hdl.handle.net/11299/224983"],"dc:language.iso":["en"],"dc:subject":["chemical vapor deposition","field-effect Transistor","lateral homojunction","phase engineering","Schottky barrier height","transition metal dichalcogenide"],"dc:title":["Phase-Engineered Field-Effect Transistors Based on Two-Dimensional Transition Metal Dichalcogenides"],"dc:type":["Thesis or Dissertation"]},"updated_at":"2026-07-24T05:19:52Z"}