Vanadium Oxide Thin Film Microstructure Characterization Analysis And Control

Transition metal vanadium can be combined with oxygen to form the oxide with multiple valence states and it has become the current research focus at home and abroad due to its unique and excellent characters in photoelectric conversion and thermal properties. Vanadium oxide thin films have high application value and good prospects for development in optoelectronic switch, storage medium, micro bolometer and infrared detector.In our project, the method of dc reactive magnetron sputtering is adopted in the experiment and the vanadium metal films, vanadium oxide thin films, Y doped vanadium oxide thin films, Ti doped vanadium oxide thin films amd W/Ti doped vanadium oxide thin films are manufactured by using the K9Experimental glass as the substrate. The process conditions of using RF-reactive magnetron sputtering to manufacture metal films, undoped and doped Vanadium oxide thin films. Moreover, relative tests about the manufacture of thin films are analyzed, for example, the relationship between the resistance and the temperature, scanning electron microscope, ac impedance spectrascopy, X-ray diffraction (XRD) spectra, X-ray photoelectron spectroscopy and so on.According to the experimental investigations, the optimal manufacture process of vanadium oxide thin films is obtained which is a100:4ratio for oxygen and argon, a sputtering current of0.32A and a substrate temperature of100℃. Under this process condition, the phase change character with2～3phase change orders of magnitude appears in the temperture range of60～70℃.In the manufacture of Vanadium oxide thin films with different substrate temperatures, it can be found out from the study of ac impedance spectrascopy that with the increasement of substrate temperature, the grain size of the thin films increases and the contribution of grain resistance also increases. The high temperature annealing process should be conducted to the Vanadium oxide thin films obtained in the experiment and the Vanadium oxide thin films with relatively high TCR can be achieved when thay are annealed for one and a half hours in the atmospheric environment of450℃high temperature. It is indicated in the research that the phase change of vanadium oxide thin films obtained in the experiment appears when the temperature is about68℃and the electrical and optical properties of the thin film change severely after the phase change. If the optimal manufacture process condition is unchanged, the structural and electrical properties of the thin film change obviously when the elements such as Y, Ti and so on are doped in the manufacture process of vanadium oxide thin films. When the element Y is doped, the ratios of O element and V element increas according to the XPS analysis which makes the phase change of the thin films die away and disappear eventually while the TCR increases in the near room temperature. When the element Ti is doped, the grain size of the thin films increases with the increasement of the doping quantity and the shape of grain becomes bar-type which makes the phase change of the thin films die away and disappear eventually while the TCR increases in the near room temperature and the interval of Hysteresis becomes smaller. When the elements Y and Ti are both doped, the value of resistance of the thin films becomes smaller, the phase change disappears, TCR increases and the interval of Hysteresis become smaller. Doped Vanadium oxide thin films are investigated in this thesis and TCR in the near room temperature can reach-3%/K～-5%/K.