Low metal-insulator transition temperature of Ni-doped vanadium oxide films

Elemental doping is the main means to regulate the phase transition of vanadium oxide (VO2); however, the effects of low valence elemental (<4+) doping on the phase transition of VO2 are still controversial. In the present work, Ni-doped VO2 films were prepared on quartz glass by direct current reactive magnetron sputtering and subsequent annealing. With the increase of the Ni doping content, the phase transition temperature of heating (TH) of the VO2 films decreased from 73.4 degrees C to 52.4 degrees C. The temperature required for the occurrence of phase transition (T-b) was lower than T-MIT. Different from the undoped VO2 film, the Ni-doped VO2 films had a T-b of around 30 degrees C. XRD and Raman results revealed that some rutile VO2 microcrystals appeared in the vanadium oxide films because of the lattice distortion by incorporated Ni. Hence, rutile VO2 micro-crystallinities signifi-cantly facilitated the phase transition of monoclinic VO2 to rutile one.