【作者】 田雪松；

【导师】 王骐；

【作者基本信息】 哈尔滨工业大学 ， 物理电子学， 2008， 博士

【摘要】 目前,激光战术战略武器装备得到了快速的发展,对于3~5μm、8~12μm波段制导用中长波红外探测器的抗激光致盲技术的研究也变得越来越重要。氧化钒薄膜具有最接近室温的相变温度,相变前后透过率发生很大变化,适于应用在激光防护领域。本文对氧化钒薄膜开展了相变机理研究和理论计算,研究了相变前后光学性质变化以及组分改变相变温度的情况。在硒化锌基片上制备了氧化钒薄膜,对薄膜进行了X射线电子能谱测试和数据拟合,并对其进行了退火处理来调节薄膜内组分。实验测试了氧化钒薄膜相变前后的光学特性变化,制得的薄膜基本满足要求。研究了通过退火工艺对组分控制的技术,探索到了一种新的非掺杂改变相变温度的技术途径。采用Material studio模拟工具的Castep程序包,利用局域密度泛函近似与赝势技巧相结合的方法,采用BFGS算法对钒的氧化物体系的几何结构进行优化,赝势采用倒易空间晶格的超软赝势,对其电子结构(能带及态密度)、晶体的光学性质、点缺陷性质(取代掺杂)在小于7μm波长范围内进行了计算,并采用计算公式拓展对10.6μm下光学特性进行了尝试性计算,看到了一定的趋势。对掺杂改变相变温度机理进行尝试性计算,掺杂低价态Al、Ti、Sn的二氧化钒的能隙变大,可能提高VO2由半导体态向金属态转变温度。而掺杂高价态W、F、Mo的VO2的能隙变小,可能有利于VO2的相变温度降低。不同温度条件下的动力学模拟采用Castep模块中的动力学模拟程序,对其电子结构(能带及态密度)、晶体的光学性质以及组分对相变温度影响进行了计算。得到了各钒氧化合物能带和态密度曲线,吸光系数、折射率和透光率等光学参数,以及温度对各曲线的影响,不同组分对相变温度的影响。提出参数设计制造了JGP560C8型超高真空多功能磁控溅射设备,用直流磁控溅射方法在锗和硒化锌基片上制备了氧化钒薄膜。采用在预处理室内对基片进行反溅处理的工艺解决了硒化锌基片与氧化钒薄膜结合不好的难题,得到了氧氩流量比0.11、基片温度450℃、溅射时气压2.2 Pa、溅射电流0.5 A、电压330 V、功率165 W和溅射时间180 s等最佳制备参数,经过X射线电子能谱测试及数据拟合来得到薄膜内组分情况。进行了退火工艺的探索,通过对薄膜进行4小时、450℃充氧或不充氧的退火处理,有效地改变了氧化钒薄膜的组分。用吸收膜特征矩阵方法对符合相变前透过率82%,相变后透过率5%的薄膜厚度进行了计算,膜层厚度应为103 nm。并采用实验室镀膜设备的参数及经验公式计算溅射产额,进而定量说明磁控溅射可以通过改变工作参数调节镀膜速率,指导了氧化钒薄膜的制备,再用3分钟制备时间的系数制备薄膜。用轮廓仪测得氧化钒薄膜厚度为125 nm,用红外分光光度计测得薄膜相变前后透过率分别为79.2%和12.3%,计算结果与实际测量值基本相等。搭建实验平台,分别用CO2激光器和Nicolet8700型红外分光光度计测试不同温度下氧化钒薄膜在10.6μm的透过率,得到其相变前后的光学性能变化情况及相变温度等参数,氧化钒薄膜的透过率可以从相变前半导体态的70.8%,降低到相变后金属态的11.3%,相变响应时间小于50 ns。测试了激光对氧化钒薄膜相变的作用。光学特性变化幅度很大,且相变过程具有重复性。如果作成器件放置于探测器前,可以起到兼顾激光防护与接收信号的功能。观察并研究氧化钒薄膜不同组分降低相变温度的情况,以及它对热滞回线和相变前后透过率变化幅度等参数的影响,并在机理上进行了一定的解释。并可实现通过退火工艺来控制组分的变化,可以说本论文探索到了一种新的非掺杂改变相变温度的技术途径。更多还原

【Abstract】 With the rapid development of tactical and strategic laser weapons, the research in anti-laser blinding technology for 3~5μm and 8~12μm infrared detector used in missile guidance has become more and more important. The vanadium oxide thin film is suitable to laser protection for the nearest room-temperature phase-changing temperature and the sharp difference in reflectivity after phase change. In this dissertation, the mechanism of phase change and the theoretical calculation for vanadium oxide thin films are investigated, and contrasts in the optical characteristics after phase change and the phase change temperature’s dependence on component are also studied. The vanadium oxide thin films are prepared on zinc selenide by DC magnet sputtering method. The X-ray photoelectron spectroscopy (XPS) test and data fit are performed and the components control in the films is realized by annealing. The experimental contrasts in optical characteristics after phase change demonstrate that our films can meet the demand. The components controlling technology by annealing is studied, and a novel technological way of changing the phase transition temperature without doping is explored.By utilizing the Castep program package of the Material Studio simulation tool, based on local density function approximation and pseudo-potential method, optimization for the geometric structure of vanadium oxides is accomplished with the BFGS calculate way. Using the super soft pseudo-potential of reciprocal space lattice, the electronic structure (energy band and density of states), optical characteristics of crystal, and point defect’s feature are calculated within the 7μm scope. Furthermore, some trends can be concluded from the extended estimation for the optical characteristics at 10.6μm by formula. We find that the low-valence (Al, Ti, Sn) doped VO2 have broader energy gaps, possibly increase the phase transition temperature from semiconductor state to metal state; while the high-valence (W, F, Mo) doped VO2 have tighter energy gaps, possibly good for the reduction in the phase transition temperature.Based on the dynamic simulation process in Castep module, the electronic structure (energy band and state density), optical characteristics of crystal and the influence of components on phase-change temperature are calculated. As a result, the energy band and state density curves, the optical parameters such as absorption coefficient, refractive index and transmittance for vanadium oxides are obtained. Furthermore, the influence of temperature in all these curves, different components in phase transition temperatures are also got.The JGP560C8 super high vacuum multi-functional magnet sputtering instrument is designed and built, consequently, the vanadium oxide thin films are prepared on germanium and zinc selenide base by DC magnet sputtering method. Using opposite spluttering technique for the base in the pre-processing room, the mal-contact problem between zinc selenide base and the film is solved, and the optimized preparation parameters are achieved. That is, the flux ratio of oxygen-to-argon is 0.11, the temperature of base is 450℃, the gas pressure when sputtering is 2.2 Pa, the spluttering current is 0.5 A, the spluttering voltage is 330 V, the spluttering power is 165 W, and the spluttering time is 180 s. Internal components are analyzed by XPS test and data fit, For investigating the annealing technique, the films are processed in the oxygen-on and absent conditions for 4 hours under the temperature of 450℃.The expected results exhibits that the films’components has been effectively changed.Based on the absorption film’s eigenmatrix method, under the pretext that the corresponding transmittances are 82% and 5% for the condition before and after phase transition, the film’s thickness is calculated to be 103 nm. Also the spluttering product is estimated according to the parameters of coating equipment and experienced formula, which permits quantitative illumination that the coating rate could be controlled by adjusting the working parameters in magnet sputtering. The film thickness is 125 nm measured by profile meter. Transmittances measured by the infrared spectrometer are 79.2% and 12.3% before and after phase transition. The data calculated is in well agreement with the measured data.The transmittances of VO2 at 10.6μm under different temperatures are tested by employing CO2 laser and Nicolet8700 infrared spectrometer, respectively. Thus, parameters such as changes in the optical characteristics after phase transition and the phase transition temperature are attained. From these data, it can be seen that the transmittance could be reduced from 70.8% to 11.3% after phase transition, with a phase-transition response time less than 50 ns. The function of laser on the phase transition of VO2 film is examined. As a result, sharp difference occurs in the optical characteristics after phase transition. What’s more, the phase transition process exhibits good repetivity. Therefore, it can be expected that the film can play both laser protection and signal receiver roles when placed before the detector.Observation and investigation are performed in the dependence of phase transition temperature on components in the VO2, so as its influence on parameters such as heat stagnation curve and the variation amplitude in transmittance after phase transition. Certain explanation is made basically from mechanism. By controlling the components through annealing technique, a novel technological way on the changes of non-doping phase transition temperature has been explored.更多还原