Author : Stefano Larentis
Publisher :
ISBN 13 :
Total Pages : 382 pages
Book Rating : 4.:/5 (15 download)
Book Synopsis Electronic Properties and Electron-electron Interaction Effects in Transition Metal Dichalcogenides by : Stefano Larentis
Download or read book Electronic Properties and Electron-electron Interaction Effects in Transition Metal Dichalcogenides written by Stefano Larentis and published by . This book was released on 2018 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transition 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.