Scalable Thin-Film Fabrication for THz Optical Switching Devices in Vanadium Dioxide

二氧化钒中太赫兹光开关器件的可扩展薄膜制造

• 批准号: 1207507
• 负责人: Richard Haglund
• 金额: $ 43.23万
• 依托单位: Vanderbilt University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-06-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1207507&HistoricalAwards=false
• 关键词: Scalable; Thin; Film; Fabrication; THz

Technical Description: Vanadium dioxide exhibits a reversible insulator-to-metal transition that can be initiated optically with femtosecond lasers, and is thus potentially ideal for high-speed electronic, photonic and memory devices. This research project addresses two challenges to the realization of this potential: First, the insulator-to-metal transition is fast (sub-picosecond), but the metal-to-insulator transition is slow (sub-nanosecond) because it requires a rearrangement of crystal structure. Second, scalable low-temperature thin-film fabrication has not been demonstrated for epitaxial vanadium-dioxide films on technologically useful substrates. The activity addresses these issues by correlating materials properties (film morphology, substrate interactions, dopant concentration, lattice match, strain and crystalline phases) to the static and dynamic optical constants of the thin-film structures and to the time-dependent electronic response and lattice vibrations that govern the speed of the transition. The relative merits of sputter, electron-beam and atomic-layer film-deposition techniques are assessed and the equilibrium optical and physical properties of the films are characterized by ellipsometry, X-ray diffraction and by high-resolution transmission-electron, Raman and X-ray photoelectron microscopy. Dynamical optical properties are measured with femtosecond time resolution by visible, infrared and THz pump-probe spectroscopy, time-dependent ellipsometry, interferometric autocorrelation and photoelectron electron microscopy.Non-technical Description. Vanadium dioxide is a remarkable material that changes from an insulator to a metal in about a trillionth of a second when illuminated by a short burst of laser light, making it ideal for applications in telecommunications, electronics and optical computing. The goal of this project is to optimize vanadium dioxide properties to make the fastest possible optical switch while developing fabrication tools to make vanadium dioxide thin-film devices on a size scale suitable for real-world applications. The project promotes the development of the future science and engineering work force by training graduate students to think and work at the interdisciplinary boundary between science and engineering. The research fosters work-force diversity by recruiting a graduate student from, and collaborating with researchers at, two universities that serve underrepresented populations. Undergraduate students involved in the research present the concept of optical switching to local high school students through Vanderbilt Students Volunteering for Science. Statewide impact on future science and engineering undergraduates is fostered by a long-standing interaction between the graduate students and the annual Tennessee Governor's School for Emerging Technologies. The research project also motivates ongoing dialogue with industrial partners who are developing technologies based on vanadium dioxide.

技术描述：二氧化钒具有可逆的绝缘体到金属的转变，可以用飞秒激光光学启动，因此可能是高速电子、光子和存储设备的理想选择。这项研究项目解决了实现这一潜力的两个挑战：第一，绝缘体到金属的转变是快速的(亚皮秒)，但金属到绝缘体的转变是缓慢的(亚纳秒)，因为它需要重新排列晶体结构。其次，在技术上有用的衬底上，还没有证明可扩展的低温薄膜制造用于外延二氧化钒薄膜。该活动通过将材料属性(薄膜形态、衬底相互作用、掺杂浓度、晶格匹配、应变和晶相)与薄膜结构的静态和动态光学常数以及控制转变速度的依赖于时间的电子响应和晶格振动相关联来解决这些问题。评价了溅射、电子束和原子层薄膜沉积技术的优缺点，并用椭偏仪、X射线衍射仪、高分辨透射电子显微镜、拉曼光谱和X射线光电子显微镜对薄膜的平衡光学和物理性质进行了表征。通过可见光、红外和太赫兹泵浦探测光谱、含时椭圆偏振测量、干涉自相关和光电子显微镜，以飞秒时间分辨率测量动态光学性质。二氧化钒是一种非凡的材料，在短时间的激光照射下，它从绝缘体变成金属只需约万亿分之一秒，这使它成为电信、电子和光学计算应用的理想材料。该项目的目标是优化二氧化钒的性能，以制造尽可能快的光开关，同时开发制造工具，使二氧化钒薄膜器件的尺寸适合现实世界的应用。该项目通过培训研究生在科学和工程之间的跨学科边界上思考和工作来促进未来科学和工程工作的发展。这项研究通过从两所为代表性不足的人群提供服务的大学招聘一名研究生，并与这两所大学的研究人员合作，促进了劳动力的多样性。参与研究的本科生通过范德比尔特大学的科学志愿者向当地高中生介绍光交换的概念。全州范围内对未来科学和工程本科生的影响是由研究生和一年一度的田纳西州州长新兴技术学院之间的长期互动所培育的。该研究项目还推动了与正在开发以二氧化钒为基础的技术的工业伙伴的持续对话。