Mesoscopic transport in 2D materials and heterostructures

This thesis presents an experimental work on electronic transport in two-dimensional (2D) van der Waals systems. The variety of the physics of the chapters reflects the exploratory character of the Ph.D. study and demonstrates the versatility and the unique properties of some of the members of the vast group of van der Waals materials. In the experiments we explore the fundamental properties of carriers and states in 2D materials via electrical transport. The first three chapters include experimental work on planar transport in multiterminal devices from transition metal dichalcogenides (2H-MoS2) and trichalogenides (TiS3). In the fist chapter, we study how intravalley spin relaxation and the phase coherence affects weak localization in boron nitride encapsulatedMoS2. In TiS3 we explore its electronic properties and in order to avoid disorder induced localization, we protect the devices with hexagonal boron nitride. An improvement in the quality of the transport and signatures of charge-density-wave transition are observed. Lastly, multi-terminal transport in 1T/1T0-MoS2 and its carrier transport mechanism are investigated, with special emphasis on how to establish low-temperature electrical contacts to 2H-MoS2. The next part of the thesis shifts to vertical transport in van der Waals heterostructures. Firstly, we use WS2 as tunneling barrier between monolayer graphene and metal contact. We observe sequential tunneling through localized states. By studying the ground and excited states, we gain information about their spatial sizes and the magnetic moments of these states. Lastly, we explore heterostructures of graphene on WSe2 and potential effects on the band structure due to the dielectric environment and the proximity induced spin-orbit coupling.