| 초록 |
The advances in atomically thin two-dimensional transition metal dichalcogenides (2D TMD’s) have led to a variety of promising technologies in nanoelectronics, photonics, sensing, energy storage, and optoelectronics. TMD’s like molybdenum disulfide (MoS2) are finding applications for next generations electronic and optoelectronic devices relying on ultimate atomic thicknesses. Here we investigate a new characterization technique to identify the number of MoS2 layers on SiO2/Si substrate using commercially available scanning electron microscopy (SEM) at low voltage. With the help of mechanical exfoliation, MoS2 samples were prepared on SiO2/Si substrate and then characterized by Raman spectroscopy and atomic force microscopy respectively. The optimized conditions of SEM imaging carried out at 1 kV in a double-channel mode (registering secondary electrons type 1 (SE1) and backscattered electrons (BSE) images in a single scan) allowed for the visualization of grey contrast in MoS2 flake with a different number of layers. The grey contrast in SEM images varied with the number of MoS2 layers, which form a linear relation with the MoS2 layers. With this linear relationship, we can identify the number of MoS2 layers up to four for an unknown MoS2 flake easily, rapidly, spatially, accurately and in a non-destructive manner. This method is also superior to the conventional optical methods in terms of its capability to characterize MoS2 flakes with sub-micrometer squares in the area on SiO2/Si substrate. Also, this technique can be further applied to other 2D materials on various substrates. |
