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 Å. 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.