Laser Thermal Lab, Department of Mechanical Engineering , University of California , Berkeley , California 94720 , United States.
Department of Mechanical Engineering , Tsinghua University , Beijing 100084 , People's Republic of China.
ACS Appl Mater Interfaces. 2019 Oct 23;11(42):39385-39393. doi: 10.1021/acsami.9b14306. Epub 2019 Oct 8.
Various exotic optoelectronic properties of two-dimensional (2D) transition metal dichalcogenides (TMDCs) strongly depend on their number of layers, and typically manifest in ultrathin few-layer or monolayer formats. Thus, precise manipulation of thickness and shape is essential to fully access their potential in optoelectronic applications. Here, we demonstrate site-selective atomic layer precision thinning of exfoliated MoS flake by laser. The oxidation mediated anisotropic chemical etching initiated from edge defects and progressed by controlled scanning of the laser beam. Thereby, the topmost layer can be preferentially removed in designed patterns without damaging the bottom flake. In addition, we could monitor the deceleration of the thinning by in situ reflectance measurement. The apparent slow down of the thinning rate is attributed to the sharp reduction in the temperature of the flake due to thickness dependent optical properties. Fabrication of monolayer stripes by laser thinning suggests potential applications in nonlinear optical gratings. The proposed thinning method would offer a unique and rather straightforward way to obtain arbitrary shape and thickness of a TMDCs flake for various optoelectronic applications.
二维（2D）过渡金属二卤化物（TMDCs）的各种奇特光电特性强烈依赖于其层数，并且通常以超薄的少层或单层形式表现出来。因此，精确控制厚度和形状对于充分发挥其在光电应用中的潜力至关重要。在这里，我们通过激光演示了剥离的 MoS 薄片的选择性原子层精确减薄。氧化介导的各向异性化学蚀刻从边缘缺陷开始，并通过激光束的受控扫描进行。从而，可以在不损坏底部薄片的情况下，以预定图案优先去除最顶层。此外，我们可以通过原位反射率测量监测减薄的减速。减薄速率明显减慢归因于薄片温度因厚度相关光学性质而急剧降低。通过激光减薄制作的单层条纹表明其在非线性光学光栅中的潜在应用。所提出的减薄方法将为各种光电应用提供一种独特且相当简单的方法来获得 TMDCs 薄片的任意形状和厚度。
