Improvement of n-type conductivity in hexagonal boron nitride monolayers by doping, strain and adsorption

Abstract

The n-type conductivity of hexagonal boron nitride (h-BN) monolayers has been studied using state-of-the-art first-principles calculations. We adopt three different methods, which are C, S, Si and Si–nO (n = 1, 2, 3) doping, applying strain and alkali metal (AM) atom (Li, Na, K and Rb) adsorption, to improve the n-type conductivity of h-BN monolayers. Three important results are obtained. First, as donor dopants, the activation energies (E_D) of C_B, S_N and Si_B are 1.22, 0.50 and 0.86 eV, respectively. The E_D of Si can be further reduced via Si–nO codoping with an increasing O-atom number and it decreases to 0.39 eV for Si–3O. Second, E_D can be effectively reduced by applying strain. The Si–3O has the lowest activation energy of 0.06 eV under 4% compressive biaxial strain. Finally, there is an obvious charge transfer from adsorbed AM atoms to h-BN monolayers, which results in an enhancement of electron concentration and improvement of n-type conductivity. This charge transfer is insensitive to the strain. The present results are significant for improving the performance of h-BN based two-dimensional optoelectronic nanodevices.