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. sputtering at room temperature. The working pressure was 5 mTorr, adjusted by changing Ar and O-2 flow from 1:1 to 10:1. Post annealing was performed at the temperatures of 200 degreesC, 300 degreesC, 400 degreesC, 450 degreesC, and 500 degreesC. Electrical resistivities of VOx films were measured at various temperatures from 25 degreesC to 80 degreesC and the temperature coefficient of resistance (TCR) was calculated for each film. The resistivity decreases with the increase of the annealing temperature and shows two steps of critical drops at 300 degreesC and 450 degreesC, respectively. This is attributed to the phase transitions of the as-deposited VOx as characterized by X-ray diffraction (XRD). Considering both the TCR and resistivities, it is concluded that the optimum oxygen concentration, x ill the VOx films approaches to 2.25 (V4O9). (C) 2001 Elsevier Science B.V. All rights reserved.