Influence of annealing on structure, phase and electrophysical properties of vanadium oxide films

Abstract

The aim of this work was to study the effect of the parameters of deposition process and subsequent annealing on the properties of vanadium oxide VOx films deposited by the pulsed reactive magnetron sputtering of a V target in an Ar/O2 gas mixture. The dependences of the structure, phase, temperature coefficient of resistance (TCR), resistivity p, band gap Egof the films on the oxygen concentration in Ar/O2 gas mixture during the deposition ГO2, and the temperature of annealing in an O2 atmosphere were obtained. The films were found to have an amorphous structure after deposition. Crystallization processes are observed at temperatures above 275 °C. In this case, depending on the temperature, polycrystalline films with a monoclinic, cubic or mixed crystal lattice are formed and a transition occurs from the intermediate oxide V4O9 to the mixed phase VO2/VOx/V2O5 and then to the higher oxide V2O5. The character of changes in p, TCR and Egof films coming from the change in the annealing temperature is complex and largely determined by ГO2. It was established that with the view of using VOx films as thermosensitive layers, the following conditions of deposition and annealing would be preferable: films deposited at the oxygen concentration 25 % in Ar/O2 gas mixture and annealed at a temperature of 250–275 °C in an O2 atmosphere for 10 min. Under these conditions VOx films with the following properties were obtained: p= (1.0 – 3.0).10-2 Ohm.m, TCR = 2.05 %/°C, and Eg= 3.76–3.78 eV.

Keywords

• microbolometer
• vanadium oxide
• thin films
• reactive magnetron sputtering
• annealing
• structure
• phase composition
• electrical properties