Preparation and characteristics of vanadium oxide thin films by controlling the sputtering voltage

• In reactive sputtering process of VOx films, the sputtering voltage performed a special behavior.
• Contrary to generally accepted idea, ISEE coefficient of VOx is lower than that of the vanadium metal.
• The S–M phase transition temperature decreased with decreasing the sputtering voltage.
• The lower the sputtering voltage, the lower the corresponding temperature of the maximum TCR.
• O/V ratio, R, and TCR of VOx films can be easy controlled by controlling the sputtering voltage.

Influence of sputtering voltage on the deposition process and characteristics of vanadium oxide thin films prepared by reactive DC magnetron sputtering is investigated. The target surface cleaning is controlled by adjusting the sputtering voltage. During the sputtering process, the sputtering voltage increases faster with larger O2 gas flow rate. The sputtering voltage is easy to be stable with larger sputtering voltage. The measured sputtering voltage is correlated to the ion induced secondary electron emission (ISEE) coefficient of the target material. The ISEE coefficient of the oxidized vanadium target surface is lower than the ISEE coefficient of the vanadium metal. The semiconductor to metal (S–M) phase transition temperature decreases with the sputtering voltage, leading to the lower the corresponding temperature of the maximum temperature coefficient of resistance (TCR). By this way, O/V ratio, R, and TCR of VOx films can be controlled by adjusting the sputtering voltage.