Theoretical characterization of graphene and other 2D materials

Abstract

In this thesis, various aspects of graphene and other 2D materials were studied by means of first-principles density functional theory (DFT) calculations. Initially, we propose two types of doping models in graphene for efficient band gap opening. In addition, we study triple dopants in graphene for the first time which is useful for the designing of the electronic properties and increasing the chemical reactivity of graphene. We also design several mono-doped and dual-doped graphene as potential anode materials for alkali-based (lithium, sodium, and potassium) batteries. Moreover, it is found that hexagonal boron phosphide (hBP) and hexagonal boron arsenide (hBAs) possess excelent electrochemical properties that are desirable for efficient anode materials. All of these proposed systems offer large storage capacities in comparison with the other famous anode materials. In addition, we report monolayer BX (X=P, As) derivatives, monolayer beryllium-nitride (Be3N2), and 2D holey boroxine (B3O3). In detail, the structural, thermal, dynamical, mechanical, electronic, and optical properties were systematically investigated and carefully examined. These theoretical investigations considerably upgrade the family of 2D materials. We inspect the stability and the electronic and optical properties of various vdWheterostructures including (hBP), (hBAs), and their derivatives which offer tunable optoelectronic properties. Additionally, we consider SiC3-hBN (vdW-heterostructure, and encapsulated SiC3 in hBN) as a potential replacement for graphene in nanoelectronics. Furthermore, the external electric field provides a great tunability of the gaps which is somewhat missing (or weaker) in the graphene-hBN bilayer. Finally, we investigate the effect of substitutional doping in single layer hBN. The induced impurity level structure is quite exotic and strongly dependent on the sublattice position and its behavior as a donor or an acceptor. For example, for an acceptor replacing a nitrogen atom, a strong intervalley interaction is observed with a strong valley and spin splitting. Conversely, when a boron atom is replaced with an acceptor, a much weaker intervalley interaction is observed with near-valley-degenerate levels. The behavior of the donor impurities is found to be the same.