| Due to its excellent photoelectric properties, nanoscale metal oxide semiconductor is widely used as sensors and electrical devices. Among numerous semiconductor metal oxide nanomaterials, vanadium oxide system, with its low price and excellent optical, electrical and magnetic properties, has been widely used in photocatalysis, optoelectronic devices and lithium-ion batteries. Since the morphology and structure of the nanomaterials are closely related to their physical and chemical properties, and nanomaterials with different methods of synthesis show various physical and chemical properties, it is of great significance for exploring simple synthetic methods in research and application aspects. As a kind of transition metal elements, vanadium element has a variety of valence state and active chemical properties. The diversity of valence state has brought the diversity of vanadium oxides structures. Vanadium oxide system has many different stoichiometric ratios of phase structure, so how to control phase structures by fixing stoichiometric ratio in the synthesis of vanadium oxides system is important. This thesis mainly consists of synthesis of nanomaterials of vanadium oxides and optical properties of phases and structures. The main content and results are as follows:(1) The metastable tetragonal phase VO2(A) nanorods were prepared by a hydrothermal method. SEM analysis showed that the average diameter of nanorods is about200nm. XRD showed that its growth has obvious [110] direction tendency. The variable temperature XRD showed the structure phase transition of tetragonal phase VO2(A), and the lattice parameter c/a changed abruptly with increasing temperature. The thermal analysis proved that the phase transition was reversible and the thermal hysteresis was36℃. The evolution of V-O vibration peaks has been studied by FT-IR with increasing temperature. The Raman modes exhibit an obvious red shift. The driving mechanism of the phase transition involves an electron-phonon interaction. Based on one dimensional tetragonal phase VO2(A) nanorods, we designed the micro-nano photodetector devices, and studied the tetragonal VO2(A) response of the980nm infrared under different bias voltage. The devices show a high reversibility and stability characteristics.(2) We synthesized the nearly spherical monoclinic VO2(M) nanoparticles by a new preparation pathway, with the size of20～30nm. Doping W and Mo into the VO2(M) crystal lattice with different concentrations showed that, when W doping concentration was2.0%, the phase transition temperature of V02(M) nanoparticles fell to25.6℃, and when Mo doping concentration was4.0%, the phase transition temperature of VO2(M) nanoparticles fell to41.7℃; the phase transition temperature and doping concentrations show a good linear relationship:after W doping concentration increase1.0%, phase transition temperature was reduced by20.5℃, and after Mo doping concentration increase1.0%, phase transition temperature reduced by6.5℃. W and Mo doping can effectively reduce the phase transition of VO2(M) nanoparticles, but also weaken the feature of infrared spectra in the phase transition. By rapid thermal decomposition of tetragonal VO2(A) nanorods method, we studied the transformation relationship between the tetragonal VO2(A) and monoclinic VO2(M). We synthesized one dimension monoclinic VO2(M) nanomaterials with thermal treatment tetragonal VO2(A), and fabricated the micro-nano photodetectors based on the one dimension VO2(M). We also tested and analysised the one dimension VO2(M) nanomaterials by infrared spectrum.(3) One dimension VO2(B) nanomaterials were synthesized by using the hydrothermal method. SEM analysis showed that the nanorods width is about200nm, with the length several of micrometers. The relationship between metastable monoclinic VO2(B) and monoclinic VO2(M) has been studied under thermal treatment. TransformationfromVO2(B) to the monoclinic V02(M) was achieved, but the morphology of one dimension nanomaterials disappeared entirely. We fabricated an infrared photodetectors based on one dimension VO2(B) nanorods networks for the first time, to study the VO2(B) nanorods response characteristic of infrared light, and the explanation of the mechanism of photodetectors devices was given. |
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