Surface Acoustic Wave Spectroscopy Offers Novel, Broadband, and Spatially-Resolved Insight into Transition Metal Dichalcogenides Films

这个德国和美国的双边项目主要研究二维（2D）过渡金属二硫族化合物的电输运性质。这种方法是无接触的，并且在没有任何由电接触引起的扰动的情况下，提供了对传输特性调制的洞察，这是替代方法所必需的。该方法利用表面声波产生和记录的数字间换能器，距离所研究的薄膜毫米远。在这个项目中研究的薄膜是使用完全可扩展的方法，化学气相沉积，在技术成熟和新兴的混合器件架构的功能基板上生长的。利用光激发来改变薄膜在衍射受限空间分辨率下的输运性质，与当前的光致发光和拉曼图相媲美。这使得人们对过渡金属二硫化物薄膜中输运性质的空间变化有了新的认识。德国-美国研究小组探索了过渡金属二硫族合金的成分梯度、晶界、横向界面和其他材料扰动对局部电导率的影响。该项目旨在揭示下一代先进过渡金属二硫化物异质结构在技术上极其重要的射频域（100 MHz至3 GHz）的基本电传输特性，从单片到基片级连续薄膜。重点将放在大面积薄膜的实际应用上。这些将被用作表面声波探测相机的主动探测介质。一种成分梯度薄膜将这种装置推向了光谱仪。这两种设备都与现有的表面声波技术完全兼容，可以通过射频识别标签无线通信进行接口和寻址。该项目结合了声光和声电光谱方面的专业知识，以及利用表面声波（Universität Augsburg）和加州大学河滨分校（University of California, Riverside）的制备技术控制光学活性纳米系统。该研究有望提高对具有缺陷、异质结或其他局部变化的过渡金属二硫化物薄膜中载流子输运的理解。所获得的知识是设计新型器件的基础，这些器件将这些薄膜的异质结作为功能元件。

This bi-national German-US project is focused on studying the electrical transport properties of two-dimensional (2D) transition metal dichalcogenides by applying surface acoustic wave spectroscopy. This method is contactless and provides insight into the transport properties modulations in absence of any perturbation caused by electrical contacts crucially needed for alternative methods. The approach utilizes surface acoustic waves generated and recorded by means of interdigital transducers that are spaced millimeters away from the films under investigation. The films studied in this project are grown using a fully scalable approach, chemical vapor deposition, on technologically mature and emerging functional substrates for hybrid device architectures. Optical excitation is used to modify the transport properties of the films at diffraction-limited spatial resolution rivaling that of current photoluminescence and Raman maps. This allows new insight into the spatial variation of transport properties in transition metal dichalcogenide films. The German-US research team explores the impact of composition gradients in alloys of transition metal dichalcogenides, grain boundaries, lateral interfaces, and other material perturbations on the local conductivity. It aims to unravel the fundamental electrical transport properties of these in the technologically extremely important radio frequency domain (100 MHz up to 3 GHz) of next-generation advanced transition metal dichalcogenide heterostructures, from single flakes to substrate-scale continuous films. Emphasis will be set on the practical application of large-area films. These will be applied as the active detection medium of a surface acoustic wave-interrogated camera. A composition-graded film advances this device towards a spectrometer. Both devices are fully compatible with existing surface acoustic wave technology and can be interfaced and addressed via RF-ID tagged wireless communication. The project combines the expertise on acousto-optic and acousto-electric spectroscopy and control of optically active nanosystems using surface acoustic waves at Universität Augsburg and preparative techniques available at the University of California, Riverside. The research is expected to enhance the understanding of carrier transport in transition metal dichalcogenide films with defects, heterojunctions or other local variations. The acquired knowledge is a foundation for design of novel devices that incorporate heterojunctions of such films as functional elements.