Formation of Acceptor States on the Silicon Hydroxylated Surface Upon NO2 Molecules Adsorption

It is shown that the hypothesis of reactivation of subsurface boron atoms in porous silicon (PS) by NO2 molecules at their adsorption on the surface dangling bonds cannot explain the reversible increase of free holes concentration in n-type PS and in p-n junctions with oxidized surface. The alternative model of hole conduction emergence in silicon structures upon adsorption of NO2 molecules is proposed. Density functional theory (DFT) calculations show that fixing NO2 molecules on the hydroxyl groups of silicon or its oxide surface can produce acceptor states and, therefore, free holes.