Porous silicon in NO₂: A chemisorption mechanism for enhanced electrical conductivity

The interaction between NO₂ molecules and the array of Si nanowires composing the porous silicon skeleton is discussed. In a wide pressure regime ranging from 10^–2 to 10⁰ Torr, reactivation of the pristine acceptor atoms takes place provoking the generation of a considerable amount of free carriers inside the Si wires. At higher pressure, traces of species have been observed. Such processes also appear to be different in terms of reversibility. Chemisorption of NO₂ molecules is demonstrated to be the mechanism responsible for the recovery of the semiconducting character of porous silicon.