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

非技术描述：当地震发生时，它会摇动建筑物：能量从地面转移到建筑物上，如果建筑物设计不当，它们无法摆脱这些能量，从而损坏或倒塌。这个研究项目使用类似的方法来研究一类特殊的新型半导体材料，称为过渡金属二硫族化合物。通常，这些材料只有一个原子层厚，它们为下一代电子设备提供了巨大的机会，因为它们可以以硅无法达到的厚度用于晶体管，同时允许光通信。这种方法利用表面内的声波——类似于地震时震动地面的声波——来震动半导体薄层，并研究其中的载流子如何耗散能量。这种方法提供了关于载流子动态特性的独特知识，以及它们如何自由移动，从而使它们能够维持快速的电子应用。这种技术的最大优点是它不需要制造电触点或将电线连接到所研究的材料上。由于这种材料非常薄，金属导线会对使用更传统技术的测量结果产生巨大影响。本研究探索了将这些材料集成到电子器件中的新策略。加州大学河滨分校是一所西班牙裔服务机构，每三名学生中就有一名是西班牙裔，其他每一名学生都是家里第一个上大学的学生。该研究项目由一名西班牙裔研究生进行，为加州大学河滨分校的多元化学生群体提供了本科研究机会。技术描述：本研究主要是利用表面声波光谱技术研究二维（2D）过渡金属二硫族化合物的输运性质。该方法是无接触的，并且提供了对传输特性调制的洞察，而没有替代方法所需的电接触引起的任何扰动。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。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。研究小组探索了晶界、横向和垂直界面以及其他材料扰动对局部电导率的影响。该项目是跨学科的，结合了加州大学河滨分校的制备技术和德国奥格斯堡大学的国际合作者的专业知识。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。

Non-technical Description: When an earthquake hits it shakes the buildings: energy is transferred from the ground to the buildings and - if the buildings are not designed appropriately - they cannot get rid of that energy and become damaged or collapsed. This research project uses a similar approach to study a particular class of novel semiconducting materials called transition metal dichalcogenides. Usually, these materials are only a single atomic layer thick and they hold tremendous opportunity for next generation electronic devices, because they can serve in a transistor at a thinness unattainable by silicon while at the same time allowing for optical communication. This method uses sound waves within surfaces - waves much akin to those that shake the ground during earthquakes - to rock the semiconductor thin layers and to study how the charge carriers in them dissipate the energy. The approach provides unique knowledge about the dynamic properties of charge carriers and how free they are to move around so that they can sustain fast electronic applications. The great advantage of this technique is that it does not require fabrication of electrical contacts or attaching wires to the material under investigation. Because the material is so thin, the metal of the wires can have a huge impact on the results of measurements using more conventional techniques. This research explores novel strategies for the integration of these materials into electronic devices. The University of California at Riverside is a Hispanic serving institution with every third student being Hispanic and every other student being the first in the family to attend college. This research project is conducted by a Hispanic graduate student and offers undergraduate research opportunity to UC Riverside's diverse student body.Technical Description: This research is focused on studying the transport properties of two-dimensional (2D) transition metal dichalcogenides by applying surface acoustic wave spectroscopy. The method is contactless and provides insight into the transport properties modulations in absence of any perturbation caused by electrical contacts 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. 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 research team explores the impact of grain boundaries, lateral and vertical interfaces, and other material perturbations on the local conductivity. The project is interdisciplinary, combining the preparative techniques available at the University of California, Riverside, with the expertise of an international collaborator from University of Augsburg, Germany. 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.