Electrical Conductivity in Evaporated Silicon Oxide Films

Abstract

Evaporated silicon oxide films can be made with reproducible electrical conductivity when the evaporation rate, the oxygen pressure, the substrate temperature during the evaporation, and the subsequent heat treatment are controlled. In the high electric field region the conductivity follows a Schottky emission law and it is shown to be bulk limited. The conductivity is also shown to be a function of the degree of oxidation, and a variation in conductivity of a factor of 109 has been accomplished by varying the composition from SiO to SiOx, where x is between 1.5 and 2. At an electric field of 250 V/μ the variation is from 10−7 (Ω·cm)−1 to 10−16 (Ω·cm)−1. A model for the conduction mechanism is proposed, where the rate-limiting process is assumed to be Schottky emission from small silicon islands into a silica structure in which the silicon islands are imbedded.