Disentangling the structural and electronic phase transitions in ultrathin vanadium dioxide

解开超薄二氧化钒中的结构和电子相变

• 批准号: 1409912
• 负责人: Louis Piper
• 金额: $ 20万
• 依托单位: SUNY at Binghamton
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-15 至 2017-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1409912&HistoricalAwards=false
• 关键词: Disentangling; structural; electronic; phase; transitions

NON-TECHNICAL DESCRIPTION: The project addresses the science that underpins the reversible switch from insulating to metallic behavior in extremely thin vanadium dioxide. The goal of this research is to determine what happens at the nanometer scale during the thermally driven transition, and how to control it. Understanding and controlling transitions between the various possible phases of vanadium dioxide will enable advances to be made in the development of energy-efficient computers, and smart windows that regulate the heating and cooling of buildings. Extended international visits to Bremen University in Germany to perform experiments complement the development of joint on-line courses between universities in Binghamton and Bremen. Undergraduate researchers from underrepresented minorities are involved with the research activities, including dedicated field trips to national research facilities, such as Brookhaven National Laboratory. A K-12 educational outreach to attract younger students to science and engineering employs on-line video demonstrations and infographics. TECHNICAL DETAILS: The abrupt metal insulator transition of vanadium dioxide is an archetypal example of the complex interplay between the electrons and the lattice. A structural phase transition accompanies the electronic transition, which can be triggered by small thermal perturbations near room temperature. Additional phases are expected to exist during the transition or may be stabilized by strained thin films. However, the exact nature and presence of these phases is a hot topic of debate. The advent of high quality ultrathin films, newly developed nanoscale spectromicroscopy techniques, and recent sophisticated computational studies present an ideal opportunity to explore these phases. Nanoscale resolution spectromicroscopy techniques can determine exactly and simultaneously the electronic and geometric configurations in phase-separated regions that coexist through the phase transitions of vanadium dioxide. The research objective is to determine whether the structural and electronic phase transitions in nanoscale vanadium dioxide are intrinsically decoupled, as suggested by the presence of intermediate states, or whether the material can be tailored to be so by strain and doping. Measured parameters, such as lattice constants, density of states, and vanadium coordination are used as inputs and constraints for band structure calculations of vanadium dioxide. Students, at both the graduate and undergraduate level, are being trained in cutting-edge low-energy/photoelectron electron microscopy and small-spot X-ray spectroscopy at national research facilities in the US and abroad.

非技术描述：该项目解决了基于极度薄钒剂中从绝缘行为到金属行为的可逆切换的科学。 这项研究的目的是确定热驱动过渡期间纳米尺度上发生的情况，以及如何控制它。 理解和控制二氧化钒的各个可能阶段之间的过渡将使能够在节能计算机的开发以及调节建筑物加热和冷却的智能窗口中取得进步。 扩展了国际访问德国不来梅大学的实验，以补充宾厄姆顿大学和不来梅大学之间联合在线课程的发展。 来自代表性不足的少数民族的本科研究人员参与了研究活动，包括前往国家研究设施的专门实地考察，例如布鲁克黑文国家实验室。 K-12教育宣传，吸引年轻的学生进入科学和工程学，采用在线视频演示和信息图表。技术细节：二氧化钒的突然金属绝缘子过渡是电子与晶格之间复杂相互作用的原型例子。电子过渡伴随着电子过渡，可以通过室温附近的小热扰动触发。预计过渡期间将存在其他阶段，或者可能通过紧张的薄膜稳定。但是，这些阶段的确切性质和存在是辩论的热门话题。高质量的超薄膜的出现，新开发的纳米级光镜技术以及最近的复杂计算研究为探索这些阶段提供了理想的机会。纳米级分辨率光谱镜技术可以准确地确定相位分离区域中通过二氧化钒的相变相处的相分开区域中的电子和几何构型。研究目标是确定纳米级二氧化钒中的结构和电子相跃迁是否本质上是脱钩的，如存在中间状态所暗示的，还是可以通过应变和掺杂来量身定制材料。 测得的参数，例如晶格常数，状态的密度和钒协调，用作二氧化钒的带结构计算的输入和约束。 在研究生和本科级别的学生都接受了美国和国外国家研究设施的尖端低能/光电电子显微镜和小点X射线光谱的培训。