Tensile strain is intrinsic to monolayer crystals of transition metal disulfides such as Mo(W)S₂ grown on oxidized silicon substrates by chemical vapor deposition (CVD) owing to the much larger thermal expansion coefficient of Mo(W)S₂ than that of silica. Here we report fascinating fluorescent variation in intensity with aging time in CVD-grown triangular monolayer WS₂ crystals on SiO₂ (300 nm)/Si substrates and formation of interesting concentric triangular fluorescence patterns in monolayer crystals of large size. The novel fluorescence aging behavior is recognized to be induced by the partial release of intrinsic tensile strain after CVD growth and the induced localized variations or gradients of strain in the monolayer crystals. The results demonstrate that strain has a dramatic impact on the fluorescence and photoluminescence of monolayer WS₂ crystals and thus could potentially be utilized to tune electronic and optoelectronic properties of monolayer transition metal disulfides.

中文翻译：

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应变释放诱导CVD生长的单层WS ₂晶体中的新型荧光变化。

拉伸应变是固有的过渡金属二硫化物的单层晶体如Mo（W）S ₂上通过化学气相沉积（CVD）由于钼（W）的大得多的热膨胀系数S氧化的硅衬底上生长₂比二氧化硅的。在这里，我们报道了在SiO ₂上由CVD生长的三角形单层WS ₂晶体中强度随老化时间的引人入胜的荧光变化（300 nm）/ Si衬底，并在大尺寸单层晶体中形成有趣的同心三角形荧光图案。新型的荧光老化行为被认为是由CVD生长后固有的拉伸应变的部分释放以及在单层晶体中引起的局部应变变化或梯度引起的。结果表明，应变对单层WS ₂晶体的荧光和光致发光具有显着影响，因此可以潜在地用于调节单层过渡金属二硫化物的电子和光电性能。