This thesis focuses on the transport and magneto-transport properties of graphene p-n-p junctions, such as the pronounced quantum Hall effect, a well-defined plateau-plateau transition point, and scaling behavior. In addition, it demonstrates persistent photoconductivity (PPC) in the monolayer MoS2 devices, an effect that can be attributed to random localized potential fluctuations in the devices.

Further, it studies scaling behavior at zeroth Landau level and high performance of fractional values of quantum Hall plateaus in these graphene p-n-p devices. Moreover, it demonstrates a unique and efficient means of controlling the PPC effect in monolayer MoS2. This PPC effect may offer novel functionalities for MoS2-based optoelectronic applications in the future.

Autorentext

Cheng-Hua Liu graduated from National Taiwan University with a major in Physics. He obtained his Ph.D. in May 2016. His research projects involve investigations on the graphene p-n-p junction and the MoS2 thin-film transistor using the resistor-free fabrication method. His main project is based in Prof. Chi-Te Liang's lab at National Taiwan University and Wei-Hua Wang's lab at the Institute of Atomic and Molecular Sciences.

Inhalt
Introduction.- Theoretical background.- Experimental methods.- Distinctive magnetotransport of graphene p-n-p junctions via resist-free fabrication and controlled diffusion of metallic contact.- Observation of quantum Hall plateau-plateau transition and scaling behavior of the zeroth Landau level in graphene p-n-p junction.- Extrinsic Origin of Persistent Photoconductivity in Monolayer MoS2 Field Effect.- Conclusion.