Effects of Quantum Confinement in Photosensors from Transition Metal Dichalcogenides

非技术描述：只有一个原子厚的超薄材料和因其大幅减小的尺寸而产生的新物理学正在推动全球范围内的研究活动，为基础科学的发现和潜在的实际应用提供了巨大的机会，特别是在电子学和光子学领域。将电荷载流子（电子和“空穴”，或丢失的电子）限制到二维，即所谓的“量子限制”的一个例子，深刻影响了二维材料的特性及其与光的相互作用。该项目涉及研究如何通过层中的附加结构进一步修改这些类型材料的特性，例如，通过制作薄的“纳米带”或将层放置在纳米级孔的顶部，这些孔将局部影响电荷载流子。这项工作的结果将帮助我们更好地了解它们的特性，并可能导致光电晶体管和其他类型的光学探测器等设备的改进。该项目是与陆军研究实验室的一个小组合作，因此也将为学生提供一个很好的机会，让他们参与支持国防和光电子行业的前沿研究。技术描述：量子限制深刻影响了二维过渡金属二硫属化物（TMD）的性质及其与光的相互作用，产生了过多的光学激发，结合能大于零点几个电子伏。该项目将通过将这些材料图案化为纳米带，创建与其他TMD层堆叠的TMD纳米带异质结构，并图案化衬底以将这些材料悬浮在纳米级孔上，从而将这些材料的研究推向更强的量子限制。将2D材料纳米结构化为纳米带将在一维子带的开始处引入新的货车霍韦奇异性，与具有相同活性区域的2D通道相比，可能产生更强的光-物质相互作用和更高的响应度。 在TMD纳米带上堆叠不同的半导体TMD的层预期导致光吸收后的快速电荷转移和光门控，以及形成具有比层内激子更长寿命的层间激子。我们将研究激子凝聚的纳米带的空间限制的较长的寿命相结合的效果。最后，本计画将研究奈米图案化基底所造成的量子限制效应。在几个微米大小的孔上悬浮的TMD中观察到激子液体凝聚。该项目将研究将空穴尺寸减小到激子尺寸的几十或几百的尺寸的效果，从而研究激子液滴中的空间限制效果。优点审查声明：该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Nontechnical Description: Ultra-thin materials that are just one-atom-thick and the new physics arising from their drastically reduced dimensions are fueling intense research activity worldwide, with tremendous opportunities for discoveries in fundamental science and for potential practical applications, especially in electronics and photonics. The restriction of the charge carriers (electrons and “holes”, or missing electrons) to two dimensions, an example of so-called “quantum confinement”, deeply affects the properties of two-dimensional materials and their interaction with light. This project involves the study of how the properties of these types of materials can be further modified by additional structure in the layers, for example, by making thin “nanoribbons” or by placing the layers on top of nanoscale holes that will locally affect the charge carriers. The results of this work will help us understand their properties better, as well as potentially lead to improvements in devices such as phototransistors and other types of optical detectors. The project is a collaboration with a group at the Army Research Lab, and so will also provide an excellent opportunity for students to become involved with cutting-edge research that will support the national defense as well as the optoelectronics industry. Technical Description:Quantum confinement deeply affects the properties of two-dimensional transition metal dichalcogenides (TMDs) and their interaction with light, yielding a plethora of optical excitations with binding energies larger than a few tenths of an electron volt. This project will push studies of these materials towards even stronger quantum confinement by patterning them into nanoribbons, creating heterostructures of TMD nanoribbons stacked with other TMD layers, and patterning the substrates to suspend these materials on nanoscale holes. Nanostructuring 2D materials into nanoribbons will introduce new van Hove singularities at the onset of one-dimensional subbands, possibly yielding stronger light-matter interaction and higher responsivity compared to 2D channels with the same active area. Stacking a layer of a different semiconducting TMD on the TMD nanoribbons is expected to result in fast charge transfer and photogating after light absorption, as well as the formation of interlayer excitons having longer lifetimes than the intralayer excitons. We will study the effect of the longer lifetimes combined with the spatial confinement of the nanoribbons on the exciton condensation. Lastly, this project will study the effect of quantum confinement due to nanopatterning of the substrate. Exciton liquid condensation has been observed in TMD suspended on holes with size of a few microns. This project will study the effect of reducing the hole size to dimensions that are a few tens or hundreds of the exciton size, thereby studying the effect of spatial confinement in exciton droplets.Statement of merit review:This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.