Guo Yuwei, Sun Xin, Jiang Jie, Wang Baiwei, Chen Xinchun, Yin Xuan, Qi Wei, Gao Lei, Zhang Lifu, Lu Zonghuan, Jia Ru, Pendse Saloni, Hu Yang, Chen Zhizhong, Wertz Esther, Gall Daniel, Feng Jing, Lu Toh-Ming, Shi Jian
Department of Materials Science and Engineering , Rensselaer Polytechnic Institute , Troy , New York 12180 , United States.
Department of Physics, Applied Physics, and Astronomy , Rensselaer Polytechnic Institute , Troy , New York 12180 , United States.
Nano Lett. 2020 Jan 8;20(1):33-42. doi: 10.1021/acs.nanolett.9b02696. Epub 2019 Dec 4.
The reconfigurability of the electrical heterostructure featured with external variables, such as temperature, voltage, and strain, enabled electronic/optical phase transition in functional layers has great potential for future photonics, computing, and adaptive circuits. VO has been regarded as an archetypal phase transition building block with superior metal-insulator transition characteristics. However, the reconfigurable VO-based heterostructure and the associated devices are rare due to the fundamental challenge in integrating high-quality VO in technologically important substrates. In this report, for the first time, we show the remote epitaxy of VO and the demonstration of a vertical diode device in a graphene/epitaxial VO/single-crystalline BN/graphite structure with VO as a reconfigurable phase-change material and hexagonal boron nitride (h-BN) as an insulating layer. By diffraction and electrical transport studies, we show that the remote epitaxial VO films exhibit higher structural and electrical quality than direct epitaxial ones. By high-resolution transmission electron microscopy and Cs-corrected scanning transmission electron microscopy, we show that a graphene buffered substrate leads to a less strained VO film than the bare substrate. In the reconfigurable diode, we find that the Fermi level change and spectral weight shift along with the metal-insulator transition of VO could modify the transport characteristics. The work suggests the feasibility of developing a single-crystalline VO-based reconfigurable heterostructure with arbitrary substrates and sheds light on designing novel adaptive photonics and electrical devices and circuits.
具有温度、电压和应变等外部变量特性的电异质结构的可重构性，使功能层中的电子/光学相变成为未来光子学、计算和自适应电路的巨大潜力。VO被认为是具有卓越金属-绝缘体转变特性的典型相变构建块。然而，由于在技术上重要的衬底中集成高质量VO存在根本性挑战，基于VO的可重构异质结构及相关器件很少见。在本报告中，我们首次展示了VO的远程外延，并在以VO作为可重构相变材料、六方氮化硼（h-BN）作为绝缘层的石墨烯/外延VO/单晶BN/石墨结构中演示了垂直二极管器件。通过衍射和电输运研究，我们表明远程外延VO薄膜比直接外延的薄膜具有更高的结构和电学质量。通过高分辨率透射电子显微镜和Cs校正扫描透射电子显微镜，我们表明石墨烯缓冲衬底导致的VO薄膜应变比裸衬底小。在可重构二极管中，我们发现费米能级变化和光谱权重转移以及VO的金属-绝缘体转变可以改变输运特性。这项工作表明了开发具有任意衬底的单晶VO基可重构异质结构的可行性，并为设计新型自适应光子学和电气器件及电路提供了思路。
