Mula Raju, Wan Meher, Sen Supriti, Jacob Chacko
Materials Science Centre, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, INDIA.
Advanced Technology Development Centre, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, INDIA.
Nanotechnology. 2020 Oct 9. doi: 10.1088/1361-6528/abbfd3.
High-quality, ultrathin 2D- MoS2 layers with large area were grown on SiO2/Si substrates by using chemical vapor deposition (CVD) at elevated temperatures. The growth precursors (MoO3 and S) were placed separately inside the double zone furnace to control the growth parameters individually for better flexibility in the growth process. In this study, it was found that the shape and edge structure of the evolved MoS2 flakes were significantly influenced by the chemical potential of the Mo and S precursor concentration. In keeping with the concentration gradient of Mo precursor (MoO3) on the substrate surface, the shape of MoS2 flakes changed from hexagonal to truncated triangle and then to triangular shapes owing to the Mo-rich to S-rich conditions. The surface roughness and thickness of the differently shaped MoS2 flakes were studied by using an atomic force microscope (AFM). Additionally, Raman and photoluminescence (PL) techniques were employed to characterize the crystalline quality, a number of grown layers and optical performance of the as-grown MoS2 layers. Auger electron spectroscopy (AES) analysis and scanning electron microscopy (SEM) confirmed that the equilibrium crystal shape of the MoS2 was hexagonal under Mo rich conditions. However, the shape of the MoS2 crystal changed to a triangle under S rich conditions. Furthermore, the influence of chemical potential on the edge structure of the monolayer MoS2 and its effect on the equilibrium shape of the crystal were studied.
通过在高温下使用化学气相沉积（CVD），在SiO2/Si衬底上生长出了高质量、大面积的超薄二维MoS2层。生长前驱体（MoO3和S）分别放置在双区炉内，以便在生长过程中分别控制生长参数，从而具有更好的灵活性。在本研究中，发现所生成的MoS2薄片的形状和边缘结构受到Mo和S前驱体浓度化学势的显著影响。与衬底表面上Mo前驱体（MoO3）的浓度梯度一致，由于从富Mo到富S的条件，MoS2薄片的形状从六边形变为截顶三角形，然后变为三角形。使用原子力显微镜（AFM）研究了不同形状的MoS2薄片的表面粗糙度和厚度。此外，采用拉曼光谱和光致发光（PL）技术来表征所生长的MoS2层的晶体质量、生长层数和光学性能。俄歇电子能谱（AES）分析和扫描电子显微镜（SEM）证实，在富Mo条件下，MoS2的平衡晶体形状为六边形。然而，在富S条件下，MoS2晶体的形状变为三角形。此外，还研究了化学势对单层MoS2边缘结构的影响及其对晶体平衡形状的作用。
