硅基二氧化钒薄膜制备及在太赫兹开关器件方面的应用

发布时间：2018-04-17 22:27

本文选题：二氧化钒薄膜 + 电致相变　；参考：《电子科技大学》2015年硕士论文

【摘要】：太赫兹波(Terahertz,THz)是介于微波和红外波之间的电磁频谱。传统的高频电子器件和光学器件在THz频段不适用,因此对可应用在THz频段的功能材料和器件的研究备受关注。二氧化钒(VO2)在热、电、光等外场驱动下会发生金属态到半导体态相变,使得它在电磁波尤其是太赫兹波调控器件中具有重要应用价值。但到目前为止,基于热控和光控的VO2太赫兹器件存在操作不便,无法与高速电子系统相兼容等问题。本文主要针对太赫兹通信、成像等应用系统的实际需求,研究在硅(Si)衬底上制备高质量VO2相变薄膜的技术和方法,并以THz开关器件为代表,验证薄膜性能,形成实现电控型太赫兹功能器件的技术方案。首先研究了Si基底上VO2薄膜的制备技术。由于Si基底和VO2薄膜之间大的晶格失配度等原因,直接在Si基底上制备高取向、高质量的VO2薄膜相对困难,电阻变化约2个数量级。为了改善Si基VO2薄膜的性能,我们利用原子层沉积技术(ALD)在Si衬底上制备均匀致密的氧化铝(Al2O3)作为提高VO2薄膜性能的缓冲层。与直接在Si基底上制备的样品相比,缓冲层的引入使VO2薄膜发生相变时的电阻变化(ΔR)提高一个数量级,热滞回线宽度(ΔT)和弛豫时间(ΔH)均达到显著改善。同时,构建了基于VO2的二端平面器件,其电流-电压(I-V)特性显示,VO2薄膜具有明显的电致相变特性,VO2薄膜发生电致相变时电流跃迁幅度超过2个数量级,弛豫电压宽度约0.1V。基于Al2O3/VO2/n-Si结构,构建了一种“金属-氧化物-绝缘层-半导体”(MOIS)垂直器件结构。I-V测试表明由于Al2O3缓冲层的存在,该器件的漏电流降低到10μA,能够显著抑制相变过程中焦耳热的产生,有望实现超快开关。并对器件电容-电压特性(C-V)进行了分析。观测到在一定的偏压下,器件电容突然变小的现象,对电场触发VO2薄膜相变的Mott-Hurband机制起到一定的支撑作用。本文在制备的VO2样品表面制作微叉指电极阵列,构建了一种可应用在THz波段的电控开关器件。结果表明在0.2THz-1THz这个频段范围内,通过电驱动VO2相变而实现对THz波的有效开关效果,最大消光比为11dB,该开关操控简单,具有宽频特性,显示了Si基VO2薄膜在THz功能器件上的巨大应用潜力。
[Abstract]:Terahertzt THz) is an electromagnetic spectrum between microwave and infrared waves.Traditional high-frequency electronic devices and optical devices are not suitable in the THz band, so the research of functional materials and devices that can be used in the THz band has attracted much attention.Vanadium oxide (VO _ 2) is driven by thermal, electric and optical fields, which results in the phase transition from metal to semiconductor, which makes it valuable in electromagnetic wave control, especially in terahertz wave control devices.But up to now, VO2 terahertz devices based on thermal control and optical control are difficult to operate and can not be compatible with high speed electronic systems.In order to meet the practical requirements of terahertz communication, imaging and other applications, the techniques and methods of preparing high quality VO2 phase transition films on Si Si substrates are studied in this paper. The performance of the films is verified by using THz switch devices as the representative.The technical scheme of realizing electronic controlled terahertz functional device is formed.Firstly, the preparation technology of VO2 thin films on Si substrates was studied.Due to the large lattice mismatch between Si substrates and VO2 thin films, it is difficult to fabricate VO2 thin films with high orientation and high quality directly on Si substrates, and the resistance varies by about two orders of magnitude.In order to improve the properties of VO2 films on Si substrates, a uniform and dense Al 2O 3 film was prepared on Si substrate by atomic layer deposition (ALAD) as a buffer layer to improve the properties of VO2 thin films.Compared with the samples prepared directly on Si substrates, the addition of buffer layer increases the resistance (螖 R) of VO2 thin films by an order of magnitude, and the thermal hysteresis loop width (螖 T) and relaxation time (螖 H) are significantly improved.At the same time, a two-terminal planar device based on VO2 is constructed. Its current-voltage I-V) characteristics show that the VO _ 2 thin film has obvious electroinduced phase transition characteristics. The current transition amplitude of the VO _ 2 thin film is more than two orders of magnitude, and the relaxation voltage width is about 0.1 V.Based on Al2O3/VO2/n-Si structure, a kind of "metal-oxide-insulator-semiconductor" vertical device structure. I-V test shows that because of the existence of Al2O3 buffer layer,The leakage current of the device is reduced to 10 渭 A, which can significantly inhibit the Joule heat generation in the phase transition process and is expected to achieve ultra-fast switching.The capacitance-voltage characteristic of the device is analyzed.It is observed that the capacitance of the device suddenly decreases at a certain bias voltage, which plays a supporting role in the Mott-Hurband mechanism of the electric field triggering the phase transition of VO2 thin films.In this paper, a micro interDigital electrode array is fabricated on the surface of VO2 sample, and a kind of electronic control switch device can be used in THz band.The results show that in the frequency range of 0.2THz-1THz, the switch effect of THz wave is realized by electrically driving VO2 phase transition. The maximum extinction ratio is 11dB. the switch is easy to operate and has wide frequency characteristic.The application potential of Si-based VO2 thin films in THz functional devices is demonstrated.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ135.11;TB383.2

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