Long-Range Interaction Between NO2 Molecules, Impurity Boron Atoms and Si Atoms with Dangling Bonds in Porous Silicon

Density functional theory (DFT) simulation show that in p-doped porous silicon (PS), boron (B) atoms are passivated by surface dangling bonds of Si atoms (p(b)-centers) at distances up to 25 angstrom. A positive charge of the p(b)-centers leads to the appearance of an increased potential region and a Coulomb blockade (CB) of free holes. When a NO2 molecule is adsorbed on a surface OH group near the p(b)-center, a shallow acceptor state arises. This state is related to the NO2 molecule and not to the B atom. When an electron is captured from the valence band by the NO2 molecule, the potential around it and the p(b)-center decreases, which removes CB.