Bilayer Lateral Heterostructures of Transition-Metal Dichalcogenides and Their Optoelectronic Response
Bilayer Lateral Heterostructures of Transition-Metal Dichalcogenides and Their Optoelectronic Response
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DOI：
10.1021/acsnano.9b04957
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发表时间：
2019-11-01
期刊：
影响因子：
17.1
通讯作者：
Gutierrez, Humberto Rodriguez
中科院分区：
文献类型：
--
作者：
Sahoo, Prasana Kumar;Memaran, Shahriar;Gutierrez, Humberto Rodriguez
基于单层过渡金属二硫属化物（TMD）的二维横向异质结受到越来越多的关注，因为它们的直接带隙使其对光电应用非常有吸引力。尽管双层TMD具有间接带隙，但与单层相比，其电学特性预计不易受环境条件影响，具有更高的迁移率和态密度。双层和几层单域器件已经在射频和光传感应用中展示了更高的性能。尽管有这些优点，但基于双层域的横向异质结构的研究较少。在这里，我们报告了基于MoS2-WS2和MoSe2-WSe2单域的多结双层横向异质结构的受控合成。异质结是通过在第一层和第二层同时发生的顺序横向边缘外延形成的。提出了一种现象学机制来解释在特定生长条件窗口内发生的自限厚度生长模式。相对于生长的单层结构，双层横向异质结构产生的整流电流高出近 1 个数量级。除了室温电致发光之外，它们还表现出清晰的光伏响应，短路电流比从生长的单层中提取的电流大 103 倍。双层异质结构性能的改进显着扩展了二维材料用于光电子学的潜力。
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 MoS2-WS2 and MoSe2-WSe2 monodomains. The heterojunctions are created via 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 103 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.