Fabrication Of Phase Transition Vanadium Oxide Thin Film And Research On Rapid Thermal Process

Vanadium dioxide(VO2) thin films have excellent Semiconductor-Metal phase transition with huge mutation in electrical and optical (terahertz(THz) band) properties, which could be the ideal function materials used in optical switch and THz modulator. The fabrication of high performance VO2 thin films is a focus of research.In this paper, Vanadium oxide(VOx) thin films with good phase transition property were prepared on SiO2/Si and single crystal Si substrate by reactive magnetron sputtering and rapid thermal process. Two preparation conditions of sputtering time and the ratio of Argon Oxygen flow(Ar/O2) were discussed about the impact on phase transition property of VOx. The four-point probe method and terahertz time domain spectroscopy (THz-TDS) were employed to measure the resistance-temperature characteristic and THz optical properties of the films before and after the rapid thermal process. Modern microscopic measures were used to analyze the surface morphology、microstructure、crystalline state of the VOx and phase composition in films. The results reveal that monoclinic vanadium dioxide(VO2) with (011) crystal orientation occupied the main component in the films is the reason for the phase transition.When the gas flow ratio of Ar/O2 was 48:1.2(sccm) and the sputtering time was 15 minutes and 30minutes, VOx thin films deposited on SiO2/Si substrate had a Semiconductor-Metal phase transition after rapid thermal process at 500℃for 30s. The VOx films with the sputtering time of 15 minutes had a better phase transition performance, accompanied by a sheet resistance drop of 3 magnitude orders and a 70% reduction in the amplitude of THz time domain pulse signal. And the THz optical phase transition had a higher temperature and a wider temperature range than the electrical phase transition during the heating and cooling period.The VOx films deposited on the Si substrate showed phase transition property after the rapid thermal process when the gas flow ratio of Ar/O2 was 48:1.2(sccm) and the sputtering time was 15 minutes、20 minutes and 25 minutes. The VOx films sputtered for 25 minutes had the best phase transition performance while the main component in the films is also VO2 (011) with monoclinic structure. With the rising of rapid thermal temperature, the partical and grain size on the surface of VOx films grew larger.Finally, THz-TDS was employed to research the light-induced phase transition of VOx thin films deposited on Si substrate. Results showed that, with the rising of optical power from OmW to 502mW, the THz time and frequency domain signal both had a reduction up to 25.6% when the THz wave passed through VOx films.