PHASE TRANSFORMATION AND R–T CHARACTERISTICS OF VACUUM ANNEALED VANADIUM OXIDE THIN FILMS

Abstract

Polycrystalline vanadium oxide ( VO x) thin films with mixed phases of V 6 O 13 + VO 2 (M) are deposited onto p-doped Si (100) substrates at 430°C using magnetron sputtering. By vacuum annealing on as-deposited VO x thin films at 450°C, at different annealing times we obtained nanoscale polycrystalline VO x thin films with two or more mixed phases. With the annealing time increasing, the phases of the films underwent the following transformation: V 6 O 13 + VO 2 ( M ) → VO 2 ( M ) + VO 2 ( B ) → VO 2 ( B ) + VO 2 ( M ) + V 5 O 9 → V 4 O 7 + V 5 O 9. The surface of VO x thin films prepared in different conditions is of high quality with mean grain size ranging from 80 to 300 nm and the R a being about 20nm. The lowest temperature coefficient of resistance at ambient temperature (20°C) of -2% K-1 is found in the VO x thin film annealed at 450°C for 8 h with mixed phases of VO 2 ( M ) + VO 2 ( B ), which can meet the needs of microbolometer materials.