Tuning the electronic properties of two-dimensional systems

The first isolation of graphene in 2004 opened a new area of 2D Van der Waals materials with one or several elements arranged in one plane with atomic thin thickness, which attracts great attention for the potential in the miniaturization of electronic devices. Various spectacular properties that do not exist in their 3D bulk form also provide opportunities for the design of novel electronic devices. In this thesis, by first principle calculations, I investigate the electronic properties of several typical 2D systems and explore the possibility to tune them for practical application. In chapter 2, I study the ferroelectric field effect on the two-dimensional electron gas at the n-type LAO/STO (001) interface through a ferroelectric substrate BaTiO3 (BTO). In chapter 3, I explore the possibility of making a semiconducting monolayer of MoS2 ferromagnetic by introducing holes into the narrow Mo d band that forms the top of the valence band. In chapter 4, I carry out a systematic study of the structural and electronic properties of single acceptor and double acceptor (V, Nb, Ta, Ti, Zr, Hf) doped MX2 (M = Cr;Mo;W, X = S; Se;Te) monolayers in the single impurity limit. In chapter 5, I study the structural reconstruction at the bare zigzag edge of 2D-Xene (X=Si, Ge, Sn).