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Fundamental Study on Optical-electrical Properties and Applications of Vanadium Oxide Thin Films

Author: DaiJun
Tutor: WangXingZhi；YiXinJian
School: Huazhong University of Science and Technology
Course: Optical Engineering
Keywords: Vanadium oxide Thermal Optical switch Thermal hysteresis Phase change Uncooled infrared detector Porous silicon
CLC: O484.4
Type: PhD thesis
Year: 2009
Downloads: 506
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Abstract


This thesis is based on the optical and electrical properties of vanadium oxide films launched from both experimental and theoretical research. On the test, the paper focused on the preparation of the vanadium oxide film, the vanadium oxide films the infrared detector thermal layer preparation, as well as light switches and energy-saving glass expanded; micro-bridge thermal insulation around the vanadium oxide detectors structure using porous silicon sacrificial layer to produce micro-bridge structure of infrared detectors;, in theory, mainly around the VO 2 thin film phase change mechanism the explore and VO of 2 film thermal the laws governing the operation of the hysteresis loop analysis commenced. The dissertation contents including the following aspects: (1) application for vanadium oxide films in uncooled infrared focal plane to carry out the study of thin films of vanadium oxide thermal. By optimizing the film deposition process to meet the requirements of uncooled infrared detector thermal layer film prepared by reactive ion beam sputtering and dc magnetron sputtering. The use of field emission scanning electron microscope (F-SEM), X-ray diffraction (XRD) and Fourier spectrophotometer analysis of the surface characteristics of the film, the infrared characteristics of the crystal phase component and the heat-sensitive film. Thermal vanadium oxide films by reactive ion beam sputtering and annealing process after preparation, the annealing temperature 450 ℃, annealing time of 60min, the TCR of -2.26% / ℃ and sheet resistance 31kΩ / □ film. DC reactive magnetron sputtering at 210 ℃ at once prepared to meet the thermal performance of uncooled infrared focal plane required VO x film. Test, the film the VO 2 the V 3 O 5 , and V 2 O 3 < / sub> mixed phase composed of VO x film. Vanadium oxide prepared by magnetron sputtering film sheet resistance as 18.4kΩ / value of -2.05% / ° C TCR, a thickness of about 65nm. This is close to conclusion Honeywell Research Center reported. (2) In order to understand the cause of the phase change of the vanadium oxide, vanadium oxide using random impedance network model thin-film resistance temperature characteristic. In the simulation process, the film is equivalent to a semiconductor phase and the metal phase particles, the random distribution of the composite system. Assignment of parameters, the calculated results with the actual measurements of the resistance - temperature curve is more consistent in the entire temperature range. This result indicates that the vanadium oxide films occurs in the temperature change during the metal phase particles and the semiconductor phase particles, the phase separation occurs, and the semiconductor phase particles and metal phase between the particles with the results of the temperature changes in the process competing led vanadium oxide The thin film resistor of mutations at critical temperatures. Thus, the model further illustrate the polycrystalline thin film of vanadium oxide can be considered as the semiconductor phase particles and the metal phase particles composed of a mixed phase, the phase transition properties of the film of vanadium oxide can also to a certain extent through the model to obtain a reasonable explanation. (3) In order to understand the vanadium oxide films thermal hysteresis loop operation rules, Preisach model to study the characteristics of vanadium oxide films thermal hysteresis loops. As the classic Preisach model distributed in four quadrants, and symmetrical structure. VO 2 thin film thermal hysteresis loop distribution only in the resistance - temperature characteristics of the first quadrant, a non-symmetrical structure. Therefore, this paper uses a low phase transition point nano the VO 2 thin film resistor - temperature thermal hysteresis loop characteristics with Preisach VO 2 films thermal hysteresis loop modeling. The results show that the model can better simulate the output value after certain temperature cycling of vanadium oxide film resistors, give a true and reaction vanadium oxide thermal hysteresis loop trajectory. (4) for vanadium oxide film resistance temperature characteristic of metal - semiconductor phase transition characteristics of vanadium oxide film focuses on applications in the energy-saving glass and light switches in both directions. In the energy-saving glass applications, a low phase transition point vanadium oxide thin films were prepared on ordinary glass substrate, and the film was measured in the infrared and visible light transmission properties. In order to improve these two energy-saving glass, visible light transmission characteristic, using TFcale software simulates the thickness of the antireflective film is a silica film having antireflection effect, and verified by experiments. Coating as a light switch in the application of the optical switch, a nano-vanadium oxide film, and measuring the characteristics of the optical switch. After testing, the insertion loss of the optical switch is about-16dB. In order to measure the response time of the phase-change film, using ANSYS software to simulate the thermal effect of the laser heating film, and select the appropriate laser heating power according to the simulation results. Has been tested, the response time of the film is about 50.4ms. (5) oxide, vanadium uncooled infrared detectors in the heat insulating structure for improving the performance of the infrared detector has a very important significance. In this study, using porous silicon as a sacrificial layer, produced 128 yuan vanadium oxide micro-bridge structure of the infrared detectors, at the same time to do a more in-depth research on growth laws and characteristics of the porous silicon. Dual pool prepared porous silicon layer to the porous Si sacrificial layer is applied to the the uncooled detectors micro bridge vanadium oxide. Using different preparation process, and the morphology of the surface of porous silicon, and by changing the etching time and current density, the thickness of the sacrificial layer of porous silicon. Due to the presence of residual stress in the porous silicon layer will cause its surface cracking phenomenon, so using Raman spectroscopy analysis of the stress of the porous silicon layer is negative stress. This measuring method provides an analysis means for improving the quality of the porous silicon. Finally, the through standard detector preparation process, the structure of the porous silicon is successfully applied in the thermal insulation structure of the vanadium oxide detector, provides a method of thermal insulation for the vanadium oxide detectors.

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CLC: > Mathematical sciences and chemical > Physics > Solid State Physics > Thin Film Physics > The nature of the films
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