Low temperature conductivity in plasma deposited amorphous dielectric films

Investigations on electrical properties of amorphous dielectric films have revealed, in some cases, a measurable conductivity at low temperatures (down to 77 K). This effect was attributed to variable range hopping between states lying near the Fermi level and was described by Mott's law. Subsequent studies, however, carried out over much broader temperature ranges, have shown that Mott's law is not satisfied and the conductivity at a given electric field becomes completely temperature independent below a critical temperature. This phenomenon is studied based on measured DC conductivity at low temperatures and voltage-pulse-induced time-domain depolarization (VPITDD) experiments. Samples of films deposited by plasma decomposition of hexamethyldisilazane, hexamethyldisiloxane, and tetramethylsilane were investigated. Although the results obtained seem to confirm the existence of a second transport channel in some amorphous dielectric films, the nature of states responsible for this mechanism is not yet known.<
>