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 VO x films deposited by the pulsed reactive magnetron sputtering of a V target in an Ar/O 2 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/O 2 gas mixture during the deposition Г O2 , and the temperature of annealing in an O 2 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 V 4 O 9 to the mixed phase VO 2 /VO x /V 2 O 5 and then to the higher oxide V 2 O 5 . The character of changes in p , TCR and Egof films coming from the change in the annealing temperature is complex and largely determined by Г O2 . It was established that with the view of using VO x films as thermosensitive layers, the following conditions of deposition and annealing would be preferable: films deposited at the oxygen concentration 25 % in Ar/O 2 gas mixture and annealed at a temperature of 250–275 °C in an O 2 atmosphere for 10 min. Under these conditions VO x films with the following properties were obtained: p = (1.0 – 3.0) . 10 -2 Ohm . m, TCR = 2.05 %/°C, and E g = 3.76–3.78 eV.