The effect of water on the electronic and field emission properties of inorganic AlN nanocones: Computational study

Abstract

Using density functional theory calculations, we explored the effect of water adsorption on the electronic and field emission properties of AlN nanocones (AlNN) at the presence and absence of a uniform electric field (EF) about ±0.02a.u. in direction of Z-axis. At zero EF, the H2O molecule tends to be adsorbed from its O atom at the apex of AlNN with adsorption energy about −23.2kcal/mol so that its effect on the electronic and field emission properties of AlNN is negligible. Both EFs increase the electrical conductivity of AlNN. At the + and −EFs, the adsorption energy changes to −40.6 and −4.1kcal/mol, respectively. At the +EF, the HOMO level of AlNN largely shifts up from −3.69 to −3.08eV, and thus, the gap significantly decreases by about 31.6%. As a result, the Fermi level (FL) shifts to higher energies, and the work function (Φ) of AlNN decreases by about 12.0%. Therefore, it can be concluded that H2O molecules can increase the field emission current density (EECD) from the surface of AlNN. But at the −EF, after the H2O adsorption, the LUMO level of AlNN largely shifts down and the gap is meaningfully decreased by about 59.4%. As a result, the FL shifts to lower energies and the Φ of AlNN increases by about 14.0%. Thus, H2O molecules decrease the EECD from the surface of AlNN at −EF.