Sahoo Prasana Kumar, Memaran Shahriar, Nugera Florence Ann, Xin Yan, Díaz Márquez Tania, Lu Zhengguang, Zheng Wenkai, Zhigadlo Nikolai D, Smirnov Dmitry, Balicas Luis, Gutiérrez Humberto Rodríguez
Department of Physics , University of South Florida , Tampa , Florida 33620 , United States.
National High Magnetic Field Laboratory , Florida State University , Tallahassee , Florida 32310 , United States.
ACS Nano. 2019 Nov 26;13(11):12372-12384. doi: 10.1021/acsnano.9b04957. Epub 2019 Sep 23.
Two-dimensional lateral heterojunctions based on monolayer transition-metal dichalcogenides (TMDs) have received increasing attention given that their direct band gap makes them very attractive for optoelectronic applications. Although bilayer TMDs present an indirect band gap, their electrical properties are expected to be less susceptible to ambient conditions, with higher mobilities and density of states when compared to monolayers. Bilayers and few-layers single domain devices have already demonstrated higher performance in radio frequency and photosensing applications. Despite these advantages, lateral heterostructures based on bilayer domains have been less explored. Here, we report the controlled synthesis of multi-junction bilayer lateral heterostructures based on MoS-WS and MoSe-WSe monodomains. The heterojunctions are created sequential lateral edge-epitaxy that happens simultaneously in both the first and the second layers. A phenomenological mechanism is proposed to explain the growth mode with self-limited thickness that happens within a certain window of growth conditions. With respect to their as-grown monolayer counterparts, bilayer lateral heterostructures yield nearly 1 order of magnitude higher rectification currents. They also display a clear photovoltaic response, with short circuit currents ∼10 times larger than those extracted from the as-grown monolayers, in addition to room-temperature electroluminescence. The improved performance of bilayer heterostructures significantly expands the potential of two-dimensional materials for optoelectronics.
基于单层过渡金属二硫属化物（TMDs）的二维横向异质结受到了越来越多的关注，因为它们的直接带隙使其在光电子应用中极具吸引力。尽管双层TMDs呈现间接带隙，但其电学性质预计对环境条件的敏感度较低，与单层相比具有更高的迁移率和态密度。双层和少层单畴器件在射频和光电传感应用中已经展现出更高的性能。尽管有这些优点，但基于双层畴的横向异质结构的研究较少。在此，我们报告了基于MoS-WS和MoSe-WSe单畴的多结双层横向异质结构的可控合成。异质结通过顺序横向边缘外延形成，在第一层和第二层中同时发生。提出了一种唯象机制来解释在特定生长条件窗口内发生的具有自限厚度的生长模式。与生长态的单层对应物相比，双层横向异质结产生的整流电流高出近1个数量级。它们还表现出明显的光伏响应，短路电流比从生长态单层中提取的短路电流大~10倍，此外还具有室温电致发光。双层异质结构性能的提升显著扩展了二维材料在光电子学中的潜力。
