Photoluminescence Segmentation within Individual Hexagonal Monolayer Tungsten Disulfide Domains Grown by Chemical Vapor Deposition
Photoluminescence Segmentation within Individual Hexagonal Monolayer Tungsten Disulfide Domains Grown by Chemical Vapor Deposition
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DOI：
10.1021/acsami.6b16287
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发表时间：
2017-05-03
影响因子：
9.5
通讯作者：
Warner, Jamie H.
中科院分区：
文献类型：
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作者：
Sheng, Yuewen;Wang, Xiaochen;Warner, Jamie H.
我们证明，通过化学气相沉积（CVD）用粉末前驱体生长的单层二硫化钨（WS2）的六边形域可以在其光致发光（PL）发射强度上具有离散分段，形成具有交替亮区和暗区的对称图案。 PL 的二维图显示与六边形域最长边相关的片段显着减少。 PL 光谱分析显示激子与 Trion 比率的差异，表明激子复合动力学的变化。转移到新基底上的 WS2 六边形岛的单层仍然表现出这种 PL 分割，排除了该区域的局部应变作为主要原因。高功率激光照射导致明亮部分通过脱硫优先降解，表明存在氧化反应性较高的缺陷较多的区域。形貌和振幅模式的原子力显微镜 (AFM) 图像显示 WS2 域的厚度均匀，并且没有分割迹象。然而，AFM 相位图确实显示了与 PL 图相同的域分割，并表明它是由某种我们无法清楚识别的结构差异引起的。这些结果为了解这些 CVD 生长的过渡金属二硫族化物材料的空间变化特性提供了重要的见解，这对于它们在快速光电传感器和光开关中的有效实现可能很重要。
We show that hexagonal domains of monolayer tungsten disulfide (WS2) grown by chemical vapor deposition (CVD) with powder precursors can have discrete segmentation in their photoluminescence (PL) emission intensity, forming symmetric patterns with alternating bright and dark regions. Two-dimensional maps of the PL reveal significant reduction within the segments associated with the longest sides of the hexagonal domains. Analysis of the PL spectra shows differences in the exciton to trion ratio, indicating variations in the exciton recombination dynamics. Monolayers of WS2 hexagonal islands transferred to new substrates still exhibit this PL segmentation, ruling out local strain in the regions as the dominant cause. High-power laser irradiation causes preferential degradation of the bright segments by sulfur removal, indicating the presence of a more defective region that is higher in oxidative reactivity. Atomic force microscopy (AFM) images of topography and amplitude modes show uniform thickness of the WS2 domains and no signs of segmentation. However, AFM phase maps do show the same segmentation of the domain as the PL maps and indicate that it is caused by some kind of structural difference that we could not clearly identify. These results provide important insights into the spatially varying properties of these CVD-grown transition metal dichalcogenide materials, which may be important for their effective implementation in fast photo sensors and optical switches.