Electronic Transport Properties in Single-layer CVD graphene

Abstract

Graphene is a two-dimensional material of carbon atoms possessing a metallic nature and the low-energy quasiparticles behave as massless Dirac fermions. The unique electronic properties of graphene inspire many researches in fundamental physics, and its extraordinary mechanical strength and high thermal and electrical conductivity make graphene as potential material in the nano-electronic devices. The chemical vapor deposition (CVD) has enabled a large scale growth of graphene, and the applications such as magnetic field sensors and tunnelling transistors rely on the scalable fabrication techniques. However, charge carrier mobilities of CVD graphene reported so far are still relatively lower than exfoliated graphene due to the conventional wet-transfer method, and the state of the art technique to overcome this is the dry transfer or the encapsulation of graphene with hexagonal boron nitride (hBN). This thesis presents an experimental study of electronic transport properties in single-layer graphene. Hall bars are fabricated with 1cm$^2$-sized commercial CVD graphene using photolithography and \ce{O_2} plasma etching. The electric field effect and the Dirac point in graphene are characterized by applying an external gate voltage, and the magnetotransport in graphene is measured. The gate-voltage dependence on the weak-localization in the measured magnetoresistance is studied. Graphene samples are \textit{in-situ} annealed with high current density to remove the impurities on graphene surface and its effect on the electronic transport is studied. Lastly, the resistance in Ni/Au and Pd contacts is compared.