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

非技术描述：当地震袭击建筑物时，它会震动建筑物：能量从地面转移到建筑物，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。这项研究项目使用了一种类似的方法来研究一类特殊的新型半导体材料，称为过渡金属二卤化物。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，因为它们可以在晶体管中以硅无法达到的厚度服务，同时允许光学通信。这种方法使用表面中的声波--与地震时震动地面的声波非常相似--来震动半导体薄层，并研究其中的载流子是如何耗散能量的。该方法提供了关于载流子的动态性质以及它们可以自由移动的独特知识，以便它们能够维持快速的电子应用。这项技术的最大优点是它不需要制造电触点或将电线连接到被研究的材料上。由于材料很薄，导线的金属可能会对使用更传统技术的测量结果产生巨大影响。这项研究探索了将这些材料集成到电子设备中的新策略。加州大学河滨分校是一所为拉美裔学生服务的机构，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。这项研究项目是由一名西班牙裔研究生进行的，为加州大学河滨分校不同的学生群体提供了本科生的研究机会。技术描述：本研究重点是通过应用表面声波光谱来研究二维(2D)过渡金属二卤化物的输运性质。该方法是非接触式的，在没有替代方法所需的电接触引起的任何扰动的情况下，提供了对传输特性调制的洞察。该方法利用叉指换能器产生和记录的表面声波，这些换能器与被调查的胶片相距几毫米。光激发被用来改变薄膜的输运性质，其衍射极限空间分辨率可与目前的光致发光和拉曼光谱相媲美。这使得对过渡金属二卤化物薄膜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准备技术和德国奥格斯堡大学的国际合作者的专业知识。这项研究有望加深对含缺陷、异质结或其他局域变化的过渡金属二卤化物薄膜中载流子输运的理解。所获得的知识是设计将这种薄膜的异质结作为功能元件的新型器件的基础。

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.