Sharma Yogesh, Balachandran Janakiraman, Sohn Changhee, Krogel Jaron T, Ganesh Panchapakesan, Collins Liam, Ievlev Anton V, Li Qian, Gao Xiang, Balke Nina, Ovchinnikova Olga S, Kalinin Sergei V, Heinonen Olle, Lee Ho Nyung
Materials Science and Technology Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States.
Center for Nanophase Materials Sciences , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States.
ACS Nano. 2018 Jul 24;12(7):7159-7166. doi: 10.1021/acsnano.8b03031. Epub 2018 Jun 22.
Strongly correlated vanadium dioxide (VO) is one of the most promising materials that exhibits a temperature-driven, metal-insulator transition (MIT) near room temperature. The ability to manipulate the MIT at nanoscale offers both insight into understanding the energetics of phase transition and a promising potential for nanoelectronic devices. In this work, we study nanoscale electrochemical modifications of the MIT in epitaxial VO thin films using a combined approach with scanning probe microscopy (SPM) and theoretical calculations. We find that applying electric voltages of different polarity through an SPM tip locally changes the contact potential difference and conductivity on the surface of VO by modulating the oxygen stoichiometry. We observed nearly 2 orders of magnitude change in resistance between positive and negative biased-tip written areas of the film, demonstrating the electric field modulated MIT behavior at the nanoscale. Density functional theory calculations, benchmarked against more accurate many-body quantum Monte Carlo calculations, provide information on the formation energetics of oxygen defects that can be further manipulated by strain. This study highlights the crucial role of oxygen vacancies in controlling the MIT in epitaxial VO thin films, useful for developing advanced electronic and iontronic devices.
强关联二氧化钒（VO₂）是最具前景的材料之一，在室温附近呈现出温度驱动的金属-绝缘体转变（MIT）。在纳米尺度上操控这种转变的能力，既有助于深入理解相变的能量学原理，也为纳米电子器件带来了广阔的潜在应用前景。在这项工作中，我们采用扫描探针显微镜（SPM）与理论计算相结合的方法，研究外延VO₂薄膜中MIT的纳米尺度电化学修饰。我们发现，通过SPM针尖施加不同极性的电压，能够通过调节氧化学计量比，局部改变VO₂表面的接触电势差和电导率。我们观察到，薄膜正负偏置针尖写入区域之间的电阻变化近2个数量级，证明了纳米尺度下电场调制的MIT行为。密度泛函理论计算以更精确的多体量子蒙特卡罗计算为基准，提供了关于可通过应变进一步操控的氧缺陷形成能量学的信息。这项研究突出了氧空位在控制外延VO₂薄膜中的MIT方面的关键作用，这对于开发先进的电子和离子电子器件非常有用。
