Electronic properties and electron-electron interaction effects in transition metal dichalcogenides

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dc.contributor.advisorTutuc, Emanuel, 1974-
dc.contributor.committeeMemberBanerjee, Sanjay K
dc.contributor.committeeMemberMacDonald, Allan H
dc.contributor.committeeMemberRegister, Leonard F
dc.contributor.committeeMemberShi, Li
dc.creatorLarentis, Stefano
dc.date.accessioned2018-10-03T19:25:21Z
dc.date.available2018-10-03T19:25:21Z
dc.date.created2018-08
dc.date.issued2018-08-09
dc.date.submittedAugust 2018
dc.date.updated2018-10-03T19:25:21Z
dc.description.abstractTransition metal dichalcogenides (TMDs) are a new class of two-dimensional layered materials characterized by a MX₂ chemical formula, where M (X) stands for a transition metal (chalcogen). MoS₂, MoSe₂ and MoTe₂ are semiconducting TMDs, which at the monolayer limit possess bandgaps >1 eV, rendering them attractive as possible channel material for scaled transistors. The bandstructures of monolayers feature coupled spin and valley degrees of freedom, thanks to large spin-orbit interaction, and large effective masses (m*), suggesting that electron-electron interaction effects are expected to be important in these semiconductors. In this dissertation we discuss the fabrication and electrical characterization of TMD-based electronic devices, with a focus on their electronic properties, including scattering mechanisms contributing to the mobility, carriers' effective mass, band offset in heterostructures, electronic compressibility, and spin susceptibility. We begin studying the four-point field-effect mobilities of few-layers MoS₂, MoSe₂ and MoTe₂ field effect transistors (FETs), in top-contact, bottom-gate architectures. Using hexagonal boron-nitride dielectrics, we fabricate FETs with an improved bottom-contact, dual-gate architecture to probe transport at low temperatures in monolayer MoS₂, and mono- and bilayer MoSe₂. From conductivity and carrier density measurements we determine the Hall mobility, which shows strong temperature dependence, consistent with phonon scattering, and saturates at low temperatures because of impurity scattering. High mobility MoSe₂ samples probed in perpendicular magnetic field, at low temperatures show Shubnikov-de Haas oscillations. Using magnetotransport we probe carriers in spin split bands at the K point in the conduction band and extract their m* = 0.8m [subscript e]; m [subscript e] is the bare electron mass. Quantum Hall states emerging at either odd or even filling factors are explained by a density dependent, interaction enhanced Zeeman splitting. Gated graphene-MoS₂ heterostructures reveal a saturating electron branch conductivity at the onset of MoS₂ population. Magnetotransport measurements probe the graphene electron density, which saturates and decreases as MoS₂ populates, a finding associated with the negative compressibility of MoS₂ electrons, modeled by a decreasing chemical potential, where many-body contributions dominate. Using a multi-gate architecture in monolayer MoTe₂ FETs, that allows for independent contact resistance and threshold voltage tuning, we integrate reconfigurable n- and p-FETs, and demonstrate a complementary inverter.
dc.description.departmentElectrical and Computer Engineering
dc.format.mimetypeapplication/pdf
dc.identifierdoi:10.15781/T2CV4C99J
dc.identifier.urihttp://hdl.handle.net/2152/68682
dc.language.isoen
dc.subjectTMD
dc.subjectMoS2
dc.subjectMoSe2
dc.subjectMoTe2
dc.subjectMobility
dc.subjectTemperature dependence
dc.subjectPhotoluminescence
dc.subjectFew-layer
dc.subjectMonolayer
dc.subjectBilayer
dc.subjecthBN: Graphene
dc.subjectChacogenides
dc.subjectHeterostructures
dc.subjectNgative compressibility
dc.subjectBand offset
dc.subjectEffective mass
dc.subjectG-factor
dc.subjectInteraction effects
dc.subjectElectronic properties
dc.subjectZeeman energy
dc.subjectMagnetotransport
dc.subjectLandau level
dc.subjectBandstructure
dc.subjectSpin splitting
dc.subjectTransition metal dichalcogenides
dc.subjectTransistor
dc.subjectReconfigurable
dc.titleElectronic properties and electron-electron interaction effects in transition metal dichalcogenides
dc.typeThesis
dc.type.materialtext
thesis.degree.departmentElectrical and Computer Engineering
thesis.degree.disciplineElectrical and Computer Engineering
thesis.degree.grantorThe University of Texas at Austin
thesis.degree.levelDoctoral
thesis.degree.nameDoctor of Philosophy

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