1] Laboratoire National des Champs Magnétiques Intenses, CNRS-UJF-UPS-INSA, 25 Rue des Martyrs, Grenoble 38042, France [2] Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw 02-093, Poland.
Laboratoire National des Champs Magnétiques Intenses, CNRS-UJF-UPS-INSA, 25 Rue des Martyrs, Grenoble 38042, France.
Nat Nanotechnol. 2015 Jun;10(6):503-6. doi: 10.1038/nnano.2015.67. Epub 2015 May 4.
Crystal structure imperfections in solids often act as efficient carrier trapping centres, which, when suitably isolated, act as sources of single photon emission. The best known examples of such attractive imperfections are well-width or composition fluctuations in semiconductor heterostructures (resulting in the formation of quantum dots) and coloured centres in wide-bandgap materials such as diamond. In the recently investigated thin films of layered compounds, the crystal imperfections may logically be expected to appear at the edges of commonly investigated few-layer flakes of these materials exfoliated on alien substrates. Here, we report comprehensive optical micro-spectroscopy studies of thin layers of tungsten diselenide (WSe2), a representative semiconducting dichalcogenide with a bandgap in the visible spectral range. At the edges of WSe2 flakes (transferred onto Si/SiO2 substrates) we discover centres that, at low temperatures, give rise to sharp emission lines (100 μeV linewidth). These narrow emission lines reveal the effect of photon antibunching, the unambiguous attribute of single photon emitters. The optical response of these emitters is inherently linked to the two-dimensional properties of the WSe2 monolayer, as they both give rise to luminescence in the same energy range, have nearly identical excitation spectra and have very similar, characteristically large Zeeman effects. With advances in the structural control of edge imperfections, thin films of WSe2 may provide added functionalities that are relevant for the domain of quantum optoelectronics.
固体中的晶体结构缺陷通常充当有效的载流子俘获中心，这些中心在适当隔离时，可作为单光子发射的来源。这种有吸引力的缺陷的最好例子是半导体异质结构中的宽化或组成波动（导致量子点的形成）以及宽带隙材料（如金刚石）中的色心。在最近研究的层状化合物薄膜中，晶体缺陷可能会出现在这些材料的常见少层薄片的边缘，这些薄片在异质衬底上剥落。在这里，我们报告了对钨硒化物（WSe2）的薄层层进行的综合光学微光谱研究，WSe2 是一种具有可见光谱范围内带隙的代表性半导体二卤化物。在 WSe2 薄片（转移到 Si/SiO2 衬底上）的边缘，我们发现了在低温下产生尖锐发射线（100μeV 线宽）的中心。这些窄发射线揭示了光子反聚束的效应，这是单光子发射器的明确属性。这些发射器的光学响应与 WSe2 单层的二维性质固有相关，因为它们在相同的能量范围内都产生发光，具有几乎相同的激发光谱，并且具有非常相似的、特征性大的塞曼效应。随着对边缘缺陷的结构控制的进展，WSe2 的薄膜可能会提供与量子光电领域相关的附加功能。
