Synthesis and Properties of Vanadium Dioxide Thin Films for use as Optical Switches

互联网主要运行在光纤通信网络上，只有光纤才能满足人们的需求 对带宽的需求不断增加。光纤电缆的每一端都有各种设备，用于 操纵光束，包括光束多路复用器和其他转向、切换和选择装置。 有各种技术用于设计这些器件，例如MEMS、液晶、声光、 最好的技术之一是利用其光学特性随另一种材料而改变的材料 电信号或光信号。例如，具有可变折射率的材质可用于 干涉仪从相长干涉变为相消干涉，从而影响光开关。或者，一个 光束选择器可以由反射率随电场变化的材料制成。基于材料的 与其他技术相比，设备坚固耐用、反应迅速、体积小、制造相对简单。这个 这个项目的整体想法是让新技术的光开关由一种电子设备控制 输入。这些光开关将基于一种新技术(描述的相变技术 并将提高光网络中的光交换的效率。过渡金属氧化物 对本项目特别感兴趣的(Mo)材料体系是钒的氧化物。氧化钒 存在于许多化学计量中。二氧化VO2的晶相从单斜晶系转变为 在340K时为四方相；(低温)单斜相为绝缘相，四方相为金属相。 在外加电场的作用下，VO2中的金属-绝缘体转变也可以发生。因此，VO2是一个质数 适用于电子控制的光开关。研究将分为三个部分：准备 VO2薄膜、表征和原型器件的开发和测试。准备工作将在 真空沉积--在氧气存在的情况下从钒靶上溅射。VO2薄膜的沉积 通过溅射和在有无电场的情况下考察它们的光学性质，来探索 这些器件中的场感应光开关。

The internet primarily runs on optical fibre communication networks; only optical fibers can satisfy the ever increasing demands for bandwidth. At each end of the fibre optic cable are a variety of devices for manipulating the light beam including beam multiplexers and other steering, switching, and selecting devices. There are a variety of technologies for designing these devices such as MEMS, liquid crystals, acousto-optics, etc. One of the best technologies utilizes materials whose optical properties change in response to another electrical or optical signal. For example, a material with a variable index of refraction can be used in an interferometer to change from constructive to destructive interference thereby effecting an optical switch. Or, a beam selector can be made from a material whose reflectivity changes with electric field. Materials based devices are robust, fast-acting, small, and relatively simple to manufacture compared to other technologies. The whole idea in this project is to have new-technology optical switches that will be controlled by an electrical input. These optical switches would be based on a new technology (phase transition technology described below) and would be enhancing the efficiency of optical switching in optical networks. Transition metal oxide (MO) material system that is of particular interest in this project is the oxides of vanadium. Vanadium oxide exists in a number of stoichiometries. The dioxide VO2 has a crystalline phase transition from monoclinic to tetragonal at 340K; the (low-temperature) monoclinic phase is insulating and the tetragonal phase is metallic. The metal-insulator transition in VO2 can also be induced by an applied electric field. Thus VO2 is a prime candidate for use in an electronically controlled optical switch. The research will have three parts: preparation of VO2 thin films, characterization, and prototype device development and testing. The preparation will be by vacuum deposition - sputtering from a vanadium target in the presence of oxygen gas. VO2 films be deposited by sputtering and their optical properties will be examined with and without an electric field to explore the field induced optical switching in these devices.