【作者】 郭瑞；

【导师】 顾德恩；

【作者基本信息】 电子科技大学 ， 光学工程， 2015， 硕士

【摘要】 由于二氧化钒在室温附近(~68℃)半导体-金属相变带来的光电性能突变,使其在许多领域如光电开关、智能窗、光学存储等都有极大的应用潜力。但二氧化钒多晶薄膜普遍存在相变滞洄宽度大等问题,这将限制其在灵敏度要求高的温度响应特性场合的应用。因此,二氧化钒多晶薄膜相变特性的调控近年来受到国内外众多学者的广泛关注。本文围绕二氧化钒多晶薄膜相变特性,借助SEM、XRD、Raman、XPS等分析表征手段,探索Ti、Y掺杂对氧化钒薄膜微结构和相变特性的调控作用和机理。另外,由于氧化钒薄膜优良的性能而广泛用作高性能非制冷红外探测器的热敏薄膜材料,进一步提高其电阻温度系数(TCR)有助于提高器件灵敏度。本文基于Ti、Y掺杂对氧化钒薄膜性能的研究,以尝试寻求制备无相变、高TCR氧化钒热敏薄膜的新方法。论文主要研究内容及创新点归纳如下:(1)研究掺Ti对二氧化钒多晶薄膜微结构和相变特性的影响。结果表明:掺Ti对薄膜晶粒尺度有一定抑制作用。掺Ti对薄膜表面形貌的影响则表现出对掺杂量的依赖性:在掺Ti量较低(≤7.7at%)时,从未掺杂时的短蠕虫状颗粒变为球形或类球形颗粒;进一步增加掺Ti量,氧化钒薄膜的颗粒呈现出短棒和类球形相混合的形貌。掺Ti将显著抑制氧化钒薄膜的相变:相变滞洄宽度显著降低,相变幅度也明显降低。掺Ti量的进一步增加,将最终得到无相变高TCR(-4.42%/K)氧化钒薄膜。这为制备无相变高TCR的氧化钒热敏薄膜提供了一种新方法。(2)提出了通过掺Y制备无相变、高TCR氧化钒热敏薄膜的新方法。采用低温反应溅射工艺制备了不同Y含量的氧化钒薄膜。不退火的氧化钒薄膜呈现无定型结构特征,其电阻温度特性呈现无相变特征。掺Y后其TCR从未掺杂时的2.67%/K提高到3.63%/K;同时,掺Y也大大提高了氧化钒薄膜方阻的环境稳定性。(3)研究了掺Y对二氧化钒多晶薄膜微结构及相变特性的影响机制。采用低温反应溅射和原位气氛退火相结合的工艺,制备了掺Y二氧化钒多晶薄膜。薄膜中,Y以Y3+形式存在;掺Y和未掺杂二氧化钒薄膜都具有典型的单斜相晶体结构。掺Y显著抑制了薄膜颗粒尺度和晶粒尺度。但掺Y后氧化钒薄膜仍表现出典型相变特征。由于掺Y增加了相变时的异质成核密度,适当的掺杂可以将二氧化钒多晶薄膜的相变滞洄宽度从10.6℃降低至4.6℃。进一步增加掺Y量,其相变滞洄宽度又由于尺寸效应而逐渐增加,甚至接近于未掺杂氧化钒薄膜的相变滞洄宽度。更多还原

【Abstract】 Because of outstanding change of optical and electrical properties of vanadium dioxides resulting from semiconductor-metal phase transition(SMPT) at about room temperature(~ 68 ℃), it has great applications in many fields such as optical switches, smart windows, optical storage, etc. However, the wide hysteresis width of vanadium dioxide polycrystalline thin film is a big problem. This limits its application where high temperature-sensitivity is necessary, Therefore, the regulation of vanadium dioxide film polycrystalline phase transition has attracted many scholars’ attention in recent years. This paper focuses on phase transition properties of vanadium dioxide polycrystalline thin film, by means of SEM, XRD, Raman, XPS analysis and other characterization techniques to explore impact of Ti、Y-doping on the microstructure and phase transition features of vanadium oxide thin films. In addition, due to the excellent performance, vanadium oxide thin films can be widely used in high-sensitivity uncooled infrared detector. Further enhancing its temperature coefficient of resistance(TCR) will help improve the sensitivity of devices. This paper will try to seek new methods to prepare high TCR vanadium oxide films without SMPT based on the results about the impact of Ti、Y-doping on the electrical properties of vanadium oxide thin films. The main work and innovations are summarized as follows:(1) The influence of Ti-doping on the microstructure and phase transition characteristics of vanadium dioxide polycrystalline films was investigated. Ti-doping can decrease the grain size. For the lower concentration of Ti-doped(≤7.7at%), Ti-doping changes the morphologies of films from the short-worm-like particles to spherical or spherical particles. With further increasing the concentration of Ti-doping, vanadium oxide thin films shows mixed rod and spherical morphology. Ti-doping will significantly inhibit SMPT of vanadium oxide thin films: hysteresis width and transition amplitude are significantly reduced due to the introduction of Ti. As a result, high-TCR(-4.42%/K) vanadium oxide films without SMPT can be prepared with high Ti concentration. This provides a new method for preparation of high-TCR vanadium oxide thermal films without SMPT.(2) We firstly realize preparation high-TCR vanadium oxide thin films without SMPT through Y-doping. Different concentration of Y-doped vanadium oxide thin films was prepared by low-temperature reactively sputtering process. As-prepared vanadium oxide thin films are amorphous and no SMPT. Y-doping significantly enhances its TCR: from-2.67%/K to-3.63%/K. Moreover, Y-doping also greatly improvs the environmental stability of resistance of vanadium oxide thin films.(3) The effect of Y-doping on the microstructure and phase transition characteristics of vanadium dioxide polycrystalline thin films. Y-doped vanadium dioxide polycrystalline thin film with Y3 + form was fabricated by low-temperature reactively sputtering followed by annealing at high temperature. Y-doped and undoped vanadium dioxide films both have a typical monoclinic structure and typical SMPT feature. Y-doping significantly inhibits particle scale and grain size of films. The introduction of Y increases the heterogeneous nucleation density during SMPT, the appropriate concentration of Y can decrease hysteresis width of vanadium oxide thin film from 10.6 ℃ to 4.6 ℃. With further increasing the concentration of Y, the hysteresis width gradually increases and even becomes close to the one of undoped vanadium oxide thin films.更多还原