Optimum oxygen concentration for the optoelectronic properties of IR sensitive VOx thin films

VOx films were fabricated on thermally grown SiO2 layers by reactive r.f. s puttering at room temperature. The working pressure was 5 mTorr, adjusted b y changing Ar and O-2 flow from 1:1 to 10:1. Post annealing was performed a t the temperatures of 200 degreesC, 300 degreesC, 400 degreesC, 450 degrees C, and 500 degreesC. Electrical resistivities of VOx films were measured at various temperatures from 25 degreesC to 80 degreesC and the temperature c oefficient of resistance (TCR) was calculated for each film. The resistivit y decreases with the increase of the annealing temperature and shows two st eps of critical drops at 300 degreesC and 450 degreesC, respectively. This is attributed to the phase transitions of the as-deposited VOx as character ized by X-ray diffraction (XRD). Considering both the TCR and resistivities , it is concluded that the optimum oxygen concentration, x ill the VOx film s approaches to 2.25 (V4O9). (C) 2001 Elsevier Science B.V. All rights rese rved.