Electrical Conduction in Amorphous and Semicrystalline Ni–Cr–SiO Films

Abstract

A resistance maximum with respect to temperature has been observed in 40 Ni-10 Cr-50 SiO v/0 films of thickness 500–2200-Å vacuum coevaporated onto amorphous SiO2 substrates maintained at room temperature. The maximum occurs at a temperature TM between 275° and 325°C. On successive thermal cycling to 500°C the resistivity of the film decreases and the resistivity peak shifts to somewhat higher temperatures. The phenomena are attributed to short-range ordering processes occurring in the temperature range 200°–350°C due to the absence of significant oxidation. When the films of resistivity 200–1000Ω per square were deposited onto substrates maintained at 300°C, the resistivity maximum disappears and the films showed a near zero temperature coefficient of resistivity and excellent cyclic stability from 25° to 350°C. All films were apparently amorphous as determined by transmission electron microscopy and electron diffraction. Depositions and annealing of films at temperatures up to 600°C led to crystalline films and to the general rule that films of up to a thousand ohms per square deposited or annealed at a temperature TM exceeding 300°C are cyclically stable at least up to TM and exhibit near zero temperature coefficient of resistance.