METAL-SEMICONDUCTOR TRANSITION IN ELECTROFORMED CHROMIUM AMORPHOUS-SILICON VANADIUM THIN-FILM STRUCTURES

The electrical properties of electroformed Cr/hydrogenated amorphous Si/V thin-film analogue memory structures change from a semiconducting behaviour to a metallic behaviour as a result of systematically decreasing the resistance of the analogue memory state or changing the temperature for a fixed memory state. The transition has been studied in a temperature range from 13 to 300 K using d.c. and a.c. conductivity. The value of minimum metallic conductance was found to be of the order of G(0) = 1 x 10(-3) Ohm(-1). The metal-non-metal transition is found to be a second-order Anderson-type transition. The experimental results and theoretical considerations suggest that the conduction in the analogue memory states is restricted to a filamentary diameter of a size of a few tens of Angstroms.