Research On Microstructure And Noise Properties Of Vanadium Oxide Film

Development of uncooled infrared detectors is very quickly. Temperature coefficient of resistance and noise property of thin film materials are the key factors that determine the performance of uncooled infrared detector. A nd the noise of vanadium oxide films is an important source of the noise of uncooled infrared detectors. Exploring the noise of vanadium oxide thin films is an important task for fabricating infrared detectors with high performance.This thesis focuses on the relationship between the noise property and microstructure of vanadium oxide thermal sensitive thin film. Vanadium oxide thin films were prepared by reactive magnetron sputtering method. The surface morphology and microstructure of the films were characterized and analyzed by using atomic force microscopy(AFM), scanning electron microscopy(SEM), X-ray diffraction(XRD), Raman spectral analysis, electron paramagnetic resonance(EPR) and other analysis tools. A system for measuring noise of thermal sensitive thin film was designed and built, The noise of vanadium oxide thin films with different microstructures was analyzed and the relationship between noise property and microstructure of the vanadium oxide thin film was explored. The main results obtained are as follows:Firstly, as for requirements of noise test for thin film materials used for uncooled infrared detectors, the noise- measuring system was designed and built using multi-channel data acquisition card made by American NI company, Lab View software and electromagnetic and heat shield. Validation tests show that the results from the system are reproducible. This ensures the reliability of noise evaluation.Secondly, vanadium oxide thin films deposited at different substrate temperatures were sputtered in order to investigate how the substrate temperature influence the microstructure and noise property of vanadium oxide thin films. As the substrate temperature increases, the particle size of vanadium oxide thin film increases, the distribution of the particle size becomes narrow, the degree of order of films increases, and the stability of the film microstructure increases. These effects reduce the noise parameters of films.Thirdly, the effect of Y-doping on the microstructure and noise of vanadium oxide film was studied. With Y-doping, the vanadium oxide film increases the surface uniformity and the particles of film become smaller. Y-doping also reduces the short-range order of the vanadium oxide thin films. At the same time, Y-doping makes the noise parameter of vanadium oxide film smaller. This means that the Y-doped vanadium oxide film may be an excellent thermal sensitive film material.Finally, the impact of Ag-doping on micro-structure and properties of vanadium oxide thin films was explored for the first time. O n the one hand, Ag-doping makes the particles of vanadium oxide film larger, the roughness of the film worse, peak-valley value of the film greater significantly, the sheet resistance smaller and the noise of the film larger. O n the other hand, the magnitude of the phase transition of the film reduces after Ag-doping. With increasing amounts of Ag doping, s heet resistance of vanadium oxide film in semiconductor phase reduces. With increasing the Ag concentration up to a certain level, the phase transition of vanadium oxide film disappears.