Estudos de primeiros princípios de fosfeto de boro hexagonal funcionalizado com moléculas DMBI e F4TCNQ

Abstract

The discovery of Graphene in 2004 opened the door to the realm of two-dimensional(2D) materials, which are structures as thick as an atom. Within this realm dwells materials other than graphene, such as phosphorene, borophene, germanene, silicene, hexagonal boron-nitride and many more. This kind of material has awakened in scientists a huge interest in recent decades due to their unique features and potential on being applied to nanoelectronic devices. Among those who are part of this flat world, the one studied in the present research is called hexagonal Boron-Phosphide. Recent studies show that h-BP is a strong candidate for application in future nanoelectronic devices, e.g., as an anode material for batteries based on Lithium and Potassium. Therefore, researches are being made in order to find 2D structures similar to graphene, however, with features that could supply the "shortcomings" of graphene. This research is an effort to experiment, investigate and compare what these two systems have to offer, and this was done through DFT calculations using two softwares, called SIESTA and Quantum Espresso. The calculations were performed on pristine graphene and h-BP to build the basic structure and the electronic information. After that, h-BP was doped with two different molecules: DMBI and F4TCNQ, which are N-type and P-type dopants on graphene, respectively. Then, the present work investigates the electronic and structural properties of hexagonal boron-phosphide, that is a graphene-like structure. The calculations results for Graphene were in agreement with the literature, which means that the method is good. Talking about the h-BP, it was shown that it is a semiconductor with an energy gap (not the case of graphene). When it adsorbs the DMBI molecule, it keeps the semiconductor behaviour and there is charge transfer from the molecule to the slab. When the F4TCNQ is adsorbed, an almost flat molecular state is introduced in its band structure (and it is also clear in its DOS graphics as a huge state near the Fermi level) but there is no charge transfer between the two structures. With both molecules, the h-BP sheet seems to works as a medium to transfer charge from the DMBI molecule to the F4TCNQ, as it happens with graphene. Key-words: Graphene, Hexagonal Boron-Phosphide, DMBI, F4TCNQ.