Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
ACS Nano. 2017 May 23;11(5):5179-5185. doi: 10.1021/acsnano.7b02521. Epub 2017 May 8.
Recently, there has been considerable research interest in two-dimensional (2D) transition-metal dichalcogenides (TMDCs) for future optoelectronic applications. It has been shown that surface passivation with the organic nonoxidizing superacid bis(trifluoromethane)sulfonamide (TFSI) produces MoS and WS monolayers whose recombination is at the radiative limit, with a photoluminescence (PL) quantum yield (QY) of ∼100%. While the surface passivation persists under ambient conditions, exposure to conditions such as water, solvents, and low pressure found in typical semiconductor processing degrades the PL QY. Here, an encapsulation/passivation approach is demonstrated that yields near-unity PL QY in MoS and WS monolayers which are highly stable against postprocessing. The approach consists of two simple steps: encapsulation of the monolayers with an amorphous fluoropolymer and a subsequent TFSI treatment. The TFSI molecules are able to diffuse through the encapsulation layer and passivate the defect states of the monolayers. Additionally, we demonstrate that the encapsulation layer can be patterned by lithography and is compatible with subsequent fabrication processes. Therefore, our work presents a feasible route for future fabrication of highly efficient optoelectronic devices based on TMDCs.
最近，二维（2D）过渡金属二卤化物（TMDC）在未来光电子应用方面的研究引起了相当大的兴趣。研究表明，用有机非氧化性超强酸双（三氟甲烷）磺酰胺（TFSI）进行表面钝化可以得到 MoS 和 WS 单层，其复合处于辐射极限，光致发光（PL）量子产率（QY）约为 100%。虽然在环境条件下表面钝化仍然存在，但在典型半导体处理中发现的水、溶剂和低压等条件下暴露会降低 PL QY。在这里，演示了一种封装/钝化方法，该方法可使 MoS 和 WS 单层的 PL QY 接近 100%，并且在经过后处理后仍具有高度稳定性。该方法包括两个简单的步骤：用非晶氟聚合物和随后的 TFSI 处理对单层进行封装。TFSI 分子能够通过封装层扩散并钝化单层的缺陷态。此外，我们证明了封装层可以通过光刻进行图案化，并且与后续的制造工艺兼容。因此，我们的工作为基于 TMDC 的高效光电设备的未来制造提供了一条可行的途径。
