Ab initio theoretical study of hydrogen and its interaction with boron acceptors and nitrogen donors in single-wall silicon carbide nanotubes

Silicon carbide nanotubes have a great potential for biological applications. It is of interest to explore the electronic properties of these nanotubes, and how those are modified in the presence of impurities. Hydrogen is a common impurity that can appear during the growth of silicon carbide nanotubes or in the environment. In this paper we studied the properties of one and two hydrogen atoms in armchair and zigzag silicon carbide nanotubes by ab initio supercell calculations beyond the standard density functional theory. We found that a single hydrogen atom is an amphoteric defect: it can act as a donor as well as an acceptor, depending on the adsorption site. However, both sites are nearly equally stable; therefore these defects compensate each other in SiC nanotube semiconductors. We found that hydrogen can absorb onto SiC nanotubes when atomic hydrogen is present in the environment. In addition, we investigated the incorporation of hydrogen by applying BH and NH molecules in the environment of SiC nanotubes. The simulations predict that boron dissolves into SiC nanotubes together with hydrogen; thus boron can be used to raise the concentration of hydrogen in SiC nanotubes. Nitrogen is also incorporated with hydrogen. We predict that the shallow boron acceptor and the nitrogen donor may be activated in these processes.