快速热处理制备相变氧化钒薄膜及其特性研究

采用直流对靶磁控溅射在Si<100>基底上沉积金属V薄膜, 然后分别在纯氧气环境和纯氮气环境下进行快速热处理制备具有 金属-半导体相变特性的氧化钒(VO_X)薄膜, 热处理条件分别为纯氧气环境下430℃/40 s, 450℃/40 s, 470℃/40 s, 450℃/30 s, 450℃/50 s, 纯氮气环境下500℃/15 s. 用X射线衍射仪、X射线光电子能谱、原子力显微镜 和扫描电子显微镜对薄膜的结晶结构、钒的价态和组分以及微观形貌进行分析. 利用四探针薄膜电阻测量方法和THz时域频谱技术分析薄膜的电学特性和光学特性. 结果表明: 金属V薄膜经过纯氧气环境450℃/40 s快速热处理 后形成了具有低相变特性的VO_X薄膜, 升温前后薄膜方块电阻变化幅度达到两个数量级, THz透射强度变化幅度较小. 为了提高薄膜的相变特性, 对制备的VO_X薄膜采用纯氮气环境500℃/15 s快速热处理, 薄膜的相变特性有了明显提升, 相变前后方块电阻变化达到3个数量级, THz透射强度变化达到56.33%.     

氧化钒薄膜的微结构及阻变特性研究

采用射频反应溅射法于室温下在Cu/Ti/SiO₂/Si基底上制备了氧化钒薄膜. X-射线衍射、X射线光电子能谱分析仪及原子力显微镜结果表明, 室温下制备的氧化钒薄膜除微弱的V₂O₅ (101)和V₂O₃ (110)峰外, 没有明显的结晶取向, 是VO₂, V₂O₅, V₂O₃及VO的混合相薄膜, 且薄膜表面颗粒大小均匀, 表面均方根粗糙度约为1 nm. 采用半导体参数分析仪对薄膜的电开关特性进行测试. 结果表明薄膜具有较低的开关电压(V_Set<1 V, V_Reset<-0.5 V), 并且具有稳定的可逆开关特性. 薄膜从低阻态转变为高阻态的电流(I_Reset)随限流的增大而增大.通过高低阻态时I-V对数曲线的拟合(高阻态斜率>1, 低阻态斜率=1), 认为Cu离子在薄膜中扩散形成的导电细丝是该体系发生电阻转变的主要机制. 关键词： 氧化钒薄膜 电阻开关 电阻式非挥发存储器 导电细丝     

溶胶凝胶制备氧化钒薄膜的生长机理及光电特性

采用溶胶凝胶法, 在不同的退火温度下制备了不同的氧化钒薄膜. 利用扫描电子显微镜、X射线衍射仪、高阻仪、紫外-可见分光光度计和傅里叶红外光谱仪等, 对薄膜的形貌、晶态、电学和光学特性进行了分析. 结果表明, 溶胶凝胶法获取V₂O₅薄膜的最佳退火温度为430 ℃, 低于此温度不利于使有机溶剂充分分解, 高于此温度则V–O键发生裂解、形成更多的低价态氧化钒. 本文制备的氧化钒薄膜具有较高的电阻温度系数和光吸收率, 适合应用在非制冷红外探测器中. 本文揭示了溶胶凝胶法制备氧化钒薄膜的生长机理. 关键词： 氧化钒薄膜 溶胶凝胶 光电特性 生长机理     

纳秒激光作用下二氧化钒薄膜相变特性

采用脉冲激光沉积法制备了VO2薄膜,应用X射线衍射和X射线光电子能谱分析表明样品为多晶薄膜。采用泵浦-探针方法研究了二氧化钒薄膜的相变特性,实验结果表明当激光重复频率为160 Hz时,样品最小相变响应为12ns,相变恢复时间与激光能量按照自然指数关系变化。仿真结果表明当激光能量一定时,二氧化钒薄膜相变恢复时间与衬底材料的热导率、热扩散系数有关。     

新型AgInSbTe相变薄膜的光学及记录性能

利用直流磁控溅射法制备了一种新型AgInSbTe相变薄膜。示差扫描量热(DSC)实验测定的结晶峰温度为193．92℃。X射线衍射(XRD)表明未经热处理的沉积态薄膜是非晶态,而经过200℃热处理,X射线衍射图出现衍射峰,薄膜从非晶态转变到晶态。同时,研究了晶态和非晶态相变薄膜的吸收率、透射率和反射率随波长的变化。测定了650nm激光作用下的相变薄膜的记录性能,分析了记录功率、记录脉宽对薄膜反射率衬比度的影响,在同一记录脉宽条件下,记录功率越大,反射率衬比度也越大;在同一记录功率条件下,随记录脉宽的增加,反射率衬比度也增大。结果表明,新型AgInSbTe相变薄膜在激光作用下具有较高的反射率衬比度,可获得良好的记录性能。     

花状掺杂W-VO_2/ZnO热致变色纳米复合薄膜研究

为解决掺杂引起的二氧化钒薄膜的红外调制幅度下降以及二氧化钒复合薄膜相变温度需要进一步降低等问题,采用纳米结构、掺杂改性和复合结构等多种机理协同作用的方案,利用共溅射氧化法,先在石英玻璃上制备高(002)取向的Zn O薄膜,再在Zn O层上室温共溅射沉积钒钨金属薄膜,最后经热氧化处理获得双层钨掺杂W-VO2/Zn O纳米复合薄膜.利用X射线衍射、X射线光电子能谱、扫描电镜和变温光谱分析等对薄膜的结构、组分、形貌和光学特性进行了分析.结果显示,W-VO2/Zn O纳米复合薄膜呈花状结构,取向性提高,在保持掺杂薄膜相变温度(约39?C)和热滞回线宽度(约6?C)较低的情况下,其相变前后的红外透过率差量增加近2倍,热致变色性能得到协同增强.     

中频孪生磁控溅射WO3薄膜及变色性能研究

采用先进的中频孪生非平衡磁控溅射技术,以金属钨为靶材,制备非晶态WO3电致变色薄膜。用X射线衍射(XRD)、X射线光电子能谱(XPS)、紫外分光光度计等测试手段分析薄膜的结构、表面形貌、成分以及透射光谱特性。研究了氧气流量比及热处理温度对WO3薄膜变色性能的影响。结果表明,中频孪生非平衡磁控溅射技术是制备WO3变色薄膜的一种有效方法;室温条件下沉积获得的原始态薄膜为非晶态WO3;提高氧气流量比和适当热处理温度能有效改善薄膜的电致变色性能。实验中在较高氧气流量比,200℃热处理条件下制备的薄膜在380~780 nm的可见光范围内着色态和褪色态平均透光率差值高达50%以上,表现出较好的电致变色性能。     

溶胶-凝胶VO2薄膜转换特性研究

利用溶胶凝胶法在SiO2Si衬底上沉积高取向的V2O5薄膜,在压强低于2Pa,温度高于400℃的条件下,对V2O5薄膜进行真空烘烤,获得了电阻率变化3个数量级以上、弛豫宽度为62℃的VO2多晶薄膜.以X射线衍射(XRD)、扫描电子显微镜(SEM)图和电阻率转换特性等实验结果为依据,详细分析了溶胶凝胶薄膜在真空烘烤时从V2O5向VO2的转化,它经历了从VnO2n+1(n=2,3,4,6)到VO2的过程.实验证明,根据选择合适的成膜热处理条件和真空烘烤条件是实现溶胶凝胶V2O5结构向VO2结构成功转换的关键 关键词： 溶胶-凝胶法 氧化钒薄膜 VO2膜转换特性     

基片温度与氧分压对磁控溅射制备氧化钒薄膜的影响

采用磁控溅射工艺制备了V₂O₅薄膜.通过改变制备工艺中基片温度和氧分压两个条件，研究了薄膜的晶相组成、表观形貌以及氧化物中钒和氧元素的化合价态.当基片温度升高时，V₂O₅薄膜中颗粒结晶由细长针状转变为平行于基片的片状，V⁵⁺状态保持不变，但723 K时氧结合能向高键能态移动.氧分压较低时，薄膜表面有部分V⁴⁺态存在，但存在较多的高键能氧，此时薄膜中晶粒尺寸较小.随着氧分压的提 关键词： 氧化钒 磁控溅射 相变薄膜 X射线光电子能谱     

纳米二氧化钒薄膜的电学与光学相变特性

采用双离子束溅射氧化钒薄膜附加热处理的方式制备了纳米二氧化钒薄膜。在热驱动方式下,分别利用四探针测试技术和傅里叶变换红外光谱技术对纳米二氧化钒薄膜的电学与光学半导体-金属相变特性进行了测试与分析。实验结果表明,电学相变特性与光学相变特性之间存在明显的偏差,电学相变温度为63 ℃,高于光学相变温度,60 ℃;电学相变持续的温度宽度较光学相变持续温度宽度宽;在红外光波段,随着波长的增加,纳米二氧化钒薄膜的光学相变温度逐渐增大,由半导体相向金属相转变的初始温度逐渐升高,相变持续的温度宽度变窄。在红外光波段,纳米二氧化钒薄膜的光学相变特性可以通过光波波长进行调控,电学相变特性更适合表征纳米VO₂薄膜的半导体-金属相变特性。     

Effect of oxygen partial pressure and VO<Subscript>2</Subscript> content on hexagonal WO<Subscript>3</Subscript> thin films synthesized by pulsed laser deposition technique

We report on the effect of oxygen partial pressure and vacuum annealing on structural and optical properties of pulsed laser-deposited nanocrystalline WO₃ thin films. XRD results show the hexagonal phase of deposited WO₃ thin films. The crystallite size was observed to increase with increase in oxygen partial pressure. Vacuum annealing changed the transparent as-deposited WO₃ thin film to deep shade of blue color which increases the optical absorption of the film. The origin of this blue color could be due to the presence of oxygen vacancies associated with tungsten ions in lower oxidation states. In addition, the effects of VO₂ content on structural, electrochemical, and optical properties of (WO₃)_1−x (VO₂) _x nanocomposite thin films have also been systematically investigated. Cyclic voltammogram exhibits a modification with the appearance of an extra cathodic peak for VO₂–WO₃ thin film electrode with higher VO₂ content (x ≥ 0.2). Increase of VO₂ content in (WO₃)_1−x (VO₂) _x films leads to red shift in optical band gap.     

纳米VOx薄膜在空气中的电学特性退化研究

采用射频磁控溅射法在氮化硅衬底上沉积纳米VO_x薄膜,利用X射线衍射、原子力显微镜分别对薄膜的结晶形态及表面形貌进行表征.研究了纳米VO_x薄膜在空气中长时间暴露后的方块电阻、热滞回线等电学特性的变化情况,并分析这些变化给器件带来的影响.利用X射线光电子能谱仪、傅里叶变换红外光谱仪分析对比新制与久置薄膜的组分及分子结构差异.研究表明,暴露在空气中的纳米VO_x薄膜方块电阻增大是因为低价钒离子被吸附氧原子氧 关键词： x薄膜')" href="#">纳米VO_x薄膜 磁控溅射 电学特性 退化     

Comparative study of annealing and gold dopant effect on DC sputtered vanadium oxide films for bolometer applications

Vanadium oxide (VO_x) thin film has been widely used for IR detectors and it is one of the promising materials for THz detectors due to its high temperature coefficient of resistance (TCR) values. VO_x films with proper TCR values have also high resistance and it restricts bolometer performance especially for uncooled bolometers. To overcome this problem, deposition at elevated temperatures or annealing approach has been accepted and used but gold co-deposition approach has been proposed recently. In this study, vanadium oxide films were fabricated on high resistivity silicon substrates by reactive direct current magnetron sputtering in different O₂/Ar atmosphere at room temperature. We investigated influence of oxygen partial pressure during deposition process and fabricated VO_x thin films with sufficient TCR values for bolometer applications. In order to decrease resistivity of the deposited films, post annealing and gold doping approaches were performed separately. Effect of both post annealing process and gold doping process on structural and electrical properties of VO_x thin films deposited at room temperature were investigated and detailed comparison between these methods were presented. We obtained the best possible approach to obtain optimum conditions for the highly reproducible VO_x thin films which have the best resistivity and suitable TCR value for bolometer applications.     

硅基VO2纳米薄膜光致绝缘体—金属相变的THz时域频谱研究

利用THz时域频谱技术(THz-TDS)研究了硅基二氧化钒(VO₂)纳米薄膜的光致绝缘体—金属相变特性.在连续光激发下前后,观察到了非常明显的THz透过率变化,并通过薄膜近似计算出了THz波段金属态VO₂薄膜的电导率.根据实验结果建立了金属态VO₂薄膜的等效Drude模型,得到了复电导率,复电容率以及复折射率等相关的基本参数,并通过基于时域有限积分法模拟了THz波穿透硅基金属态VO₂薄膜的过程,验证了所建立的模型的正确 关键词： 二氧化钒 光致相变 Drude模型 THz时域频谱技术     

Effects of oxygen content on the microstructures and optical properties of thermochromic vanadium oxide thin films

Reactive direct current magnetron sputtering and in situ thermal oxidation were used to prepare vanadium oxide (VO _X ) thin films with different oxygen contents. X-ray diffraction, Fourier transform infrared spectroscopy and a field emission scanning electron microscope were employed to characterize the films. The optical properties of the VO _X films at room temperature and 90 °C were investigated by applying an spectroscopic ellipsometer with a three-layer model of BEMA/Brendel–Bormann oscillator/substrate. It was demonstrated that the vanadium–oxygen bonds were strengthened, the film thickness and roughness decreased, while the grain size increased with increasing oxygen content. The increase in oxygen content had the effect of decreasing the near-infrared reflectance and free-electron concentration of the film at 90°C due to the decrease in the amount of VO₂.     

Ultrathin film growth and spectroscopic characterization of VOx (0.8x1.3) on Pt(1 1 1)

VO_x ultrathin epitaxial films (0.8x1.3) have been grown on Pt(1 1 1) by evaporating vanadium in a low and well-controlled water background (1×10⁻⁷ Pa). X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and X-ray excited auger electron spectroscopy data strongly indicate that vanadium(II) in the predominant oxidation state. Angle-scanned photoelectron diffraction data are compatible with a single domain film, bearing a rock-salt VO structure and exposing the (1 1 1) plane. Such films evolve toward more oxidized species within hours, probably due to oxidation by residual water in the chamber.     

The characteristics of Au:VO2 nanocomposite thin film for photo-electricity applications

Au nanoparticles have been fabricated on normal glass substrates using nanosphere lithography (NSL) method. Vanadium dioxide has been deposited on Au/glass by reactive radio frequency (rf) magnetron sputtering. The structure and composition were determined by X-ray diffraction and X-ray photoelectron spectroscope. Electrical and optical properties of bare VO₂ and Au:VO₂ nanocomposite thin films were measured. Typical hysteresis behavior and sharp phase transition were observed. Nanopartical Au could effectively reduce the transition temperature to 40 °C. The transmittance spectrum for both Au:VO₂ nanocomposite thin film shows high transmittance under transition temperature and low transmittance above transition temperature. The characteristics present the Au:VO₂ nanocomposite thin film can be used for applications, such as “smart window” or “laser protector”.     

Growth of b-axis oriented VO2 thin films on glass substrates using ZnO buffer layer

VO₂ thin films are grown on glass substrates by pulsed laser deposition using vanadium metal as a target. In this study, a ZnO thin film was used as a buffer layer for the growth of VO₂ thin films on glass substrates. X-ray diffraction studies showed that the VO₂ thin film had b-axis preferential orientation on a c-axis oriented ZnO buffer layer. The thickness of the ZnO buffer layer and the oxygen pressure during VO₂ deposition were optimized to grow highly b-axis oriented VO₂ thin films. The metal-insulator transition properties of the VO₂ film samples were investigated in terms of infrared reflectance and electrical resistance with varying temperatures.     

不同氮流量制备Mn3CuNx薄膜及其电、磁输运性质的研究

采用对靶磁控溅射方法在单晶Si(100)基片上制备了反钙钛矿结构的Mn₃CuN_x薄膜.通过控制制备过程中的反应气体氮气(N₂) 流量(N₂/Ar+N₂), 研究了氮含量对Mn₃CuN_x薄膜结构及物理性能的影响.分别利用X射线衍射仪、俄歇电子能谱、 原子力显微镜、X射线光电子能谱、物理性能测试系统和超导量子干涉仪, 对所制备薄膜的晶体结构、成分、表面形貌和电、磁输运性质进行了测试.结果表明:制备的薄膜均为反钙钛矿立方结构,且沿 (200) 晶面择优生长.随着氮含量的增大,薄膜表面粗糙度和颗粒度尺寸逐渐增大, 导致电阻率增加.氮含量对薄膜的电输运性质没有影响,所有薄膜电阻率均随着温度的降低逐渐增大, 呈现半导体型导电行为,这与对应的块体材料结果相反.Mn₃CuN_x薄膜随着测试温度的增大发生了 亚铁磁到顺磁的磁转变,且N含量的增大降低了磁有序转变温度,主要是由于N缺陷对Mn₆N八面体结构中 磁交换作用的影响所致.