Two-dimensional (2D) crystals have attracted much attention in recent years due to their unique physical, chemical, and mechanical properties. Semiconducting 2D crystals with van der Waals structures, such as transition metal dichalcogenides, are considered promising candidates for future device applications, as many have large band gaps, high carrier mobilities, and enable devices with immunity to short channel effects in addition to compatibility with silicon CMOS processes.^ In this thesis, the fundamental device implications of using semiconducting 2D crystals are investigated. This includes: 1) the optimization of device fabrication processing for better device performance, 2) comparing the device physics in 2D semiconductors based transistors and silicon MOSFET, and 3) circuit-level integration of devices using 2D semiconductors. A direct atomic layer deposition process was developed and investigated on various 2D crystals which allowed for the development of 2D semiconductor transistors. N-type MoS2 transistors with top and back gates were fabricated. The device performance of MoS2transistors with various channel lengths down to 50 nm was studied. Metal contacts on MoS2 and other TMD materials were also studied. They showed a strong Fermi-level pinning at the metal MoS 2 interface. Device performance based on single layer CVD MoS2 channel was studied and the device on/off switching was revealed to be dominated by Schottky barriers at metal contacts. Finally, the transport properties and device performance of p-type phosphorene crystals were investigated. Semiconducting 2D crystals are very promising candidates for future electronic and optoelectronic device applications.
","abstract_html":"<p>Two-dimensional (2D) crystals have attracted much attention in recent years due to their unique physical, chemical, and mechanical properties. Semiconducting 2D crystals with van der Waals structures, such as transition metal dichalcogenides, are considered promising candidates for future device applications, as many have large band gaps, high carrier mobilities, and enable devices with immunity to short channel effects in addition to compatibility with silicon CMOS processes.^ In this thesis, the fundamental device implications of using semiconducting 2D crystals are investigated. This includes: 1) the optimization of device fabrication processing for better device performance, 2) comparing the device physics in 2D semiconductors based transistors and silicon MOSFET, and 3) circuit-level integration of devices using 2D semiconductors. A direct atomic layer deposition process was developed and investigated on various 2D crystals which allowed for the development of 2D semiconductor transistors. N-type MoS<sub>2</sub> transistors with top and back gates were fabricated. The device performance of MoS<sub>2</sub>transistors with various channel lengths down to 50 nm was studied. Metal contacts on MoS<sub>2</sub> and other TMD materials were also studied. They showed a strong Fermi-level pinning at the metal MoS<sub> 2</sub> interface. Device performance based on single layer CVD MoS<sub>2 </sub>channel was studied and the device on/off switching was revealed to be dominated by Schottky barriers at metal contacts. Finally, the transport properties and device performance of p-type phosphorene crystals were investigated. Semiconducting 2D crystals are very promising candidates for future electronic and optoelectronic device applications.</p>","abstract_has_math":false,"creators":["Liu, Han"],"institution":null,"degree_name":"Doctor of Philosophy (PhD)","degree_level":"Dissertation","degree_discipline":"Electrical and Computer Engineering","degree_department":null,"school":null,"contributors":["Peide D. Ye","Mark S. Lundstrom","Muhammad A. Alam","Yong P. Chen"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2014,"date_issued":"2014-10-01T07:00:00Z","date_published":"2014-10-01T07:00:00Z","updated_at":"2026-07-24T03:53:34Z","subjects":["Electrical and Computer Engineering","Electrical and Electronics"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://docs.lib.purdue.edu/open_access_dissertations/324","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Peide D. Ye","Mark S. Lundstrom","Muhammad A. Alam","Yong P. Chen"]},{"key":"dc:creator","label":"Author","values":["Liu, Han"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"thesis:degree_discipline","label":"Discipline","values":["Electrical and Computer Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Electrical and Computer Engineering","Electrical and Electronics"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://docs.lib.purdue.edu/open_access_dissertations/324"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Two-dimensional (2D) crystals have attracted much attention in recent years due to their unique physical, chemical, and mechanical properties. Semiconducting 2D crystals with van der Waals structures, such as transition metal dichalcogenides, are considered promising candidates for future device applications, as many have large band gaps, high carrier mobilities, and enable devices with immunity to short channel effects in addition to compatibility with silicon CMOS processes.^ In this thesis, the fundamental device implications of using semiconducting 2D crystals are investigated. This includes: 1) the optimization of device fabrication processing for better device performance, 2) comparing the device physics in 2D semiconductors based transistors and silicon MOSFET, and 3) circuit-level integration of devices using 2D semiconductors. A direct atomic layer deposition process was developed and investigated on various 2D crystals which allowed for the development of 2D semiconductor transistors. N-type MoS2 transistors with top and back gates were fabricated. The device performance of MoS2transistors with various channel lengths down to 50 nm was studied. Metal contacts on MoS2 and other TMD materials were also studied. They showed a strong Fermi-level pinning at the metal MoS 2 interface. Device performance based on single layer CVD MoS2 channel was studied and the device on/off switching was revealed to be dominated by Schottky barriers at metal contacts. Finally, the transport properties and device performance of p-type phosphorene crystals were investigated. Semiconducting 2D crystals are very promising candidates for future electronic and optoelectronic device applications.
"]},{"key":"dc:title","label":"Title","values":["Material and device aspects of semiconducting two-dimensional crystals"]}]}],"canonical_facts":{"dc:contributor":["Peide D. Ye","Mark S. Lundstrom","Muhammad A. Alam","Yong P. Chen"],"dc:creator":["Liu, Han"],"dc:description.abstract":["Two-dimensional (2D) crystals have attracted much attention in recent years due to their unique physical, chemical, and mechanical properties. Semiconducting 2D crystals with van der Waals structures, such as transition metal dichalcogenides, are considered promising candidates for future device applications, as many have large band gaps, high carrier mobilities, and enable devices with immunity to short channel effects in addition to compatibility with silicon CMOS processes.^ In this thesis, the fundamental device implications of using semiconducting 2D crystals are investigated. This includes: 1) the optimization of device fabrication processing for better device performance, 2) comparing the device physics in 2D semiconductors based transistors and silicon MOSFET, and 3) circuit-level integration of devices using 2D semiconductors. A direct atomic layer deposition process was developed and investigated on various 2D crystals which allowed for the development of 2D semiconductor transistors. N-type MoS2 transistors with top and back gates were fabricated. The device performance of MoS2transistors with various channel lengths down to 50 nm was studied. Metal contacts on MoS2 and other TMD materials were also studied. They showed a strong Fermi-level pinning at the metal MoS 2 interface. Device performance based on single layer CVD MoS2 channel was studied and the device on/off switching was revealed to be dominated by Schottky barriers at metal contacts. Finally, the transport properties and device performance of p-type phosphorene crystals were investigated. Semiconducting 2D crystals are very promising candidates for future electronic and optoelectronic device applications.
"],"dc:identifier":["https://docs.lib.purdue.edu/open_access_dissertations/324"],"dc:subject":["Electrical and Computer Engineering","Electrical and Electronics"],"dc:title":["Material and device aspects of semiconducting two-dimensional crystals"],"thesis:degree_discipline":["Electrical and Computer Engineering"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-24T03:53:34Z"}