| 학회 | 한국재료학회 |
| 학술대회 | 2020년 가을 (11/18 ~ 11/20, 휘닉스 제주 섭지코지) |
| 권호 | 26권 1호 |
| 발표분야 | G. 나노/박막 재료 분과 |
| 제목 | Low-voltage SEM characterization of the number of layers and defects in MoS2 film |
| 초록 | Two dimensional (2D) materials are gaining importance for the past 16 years due to its atomic level thickness which makes it a promising candidate material for flexible electronics and in the fabrication of NEMS. The electronic properties mostly rely on the thickness of these 2D materials, so that it is critical to identify the number of layers for their application. The methods like optical microscopy, Raman spectroscopy, atomic force microscopy (AFM) & transmission electron microscopy (TEM) are commonly used to identify the number of layers. But they have their own inherent limitations. TEM is destructive. In Raman spectroscopy, laser beam irradiation may degrade the structure of 2D material. AFM has the issue of the speed and reproducibility. For optical microscopy, 2D material should be supported by sufficiently thick silicon dioxide. Further Raman spectroscopy & optical microscopy are limited in resolution to around one micrometer due to the diffraction limits of light. To compensate the existing techniques, we are studying a technique to measure the number of layers, & simultaneously to identify their defects on the nanometer scale, using scanning electron microscopy (SEM). Especially low voltage SEM, 1 kV in this study, is advantageous considering both the surface sensitivity & charging. The 2D material used is molybdenum disulphide (MoS2), which is an inorganic compound consisting of molybdenum & sulphur atoms. It is a semiconducting material at its monolayer with a bandgap of 1.9 eV. When exposed to air, MoS2 combines with oxygen & water in the surrounding environment to create defects. The high spatial resolution in identifying the defects cannot be achieved non-destructively by other methods mentioned above. The 2 types of specimen used are: exfoliated MoS2 on conductive Si & on non-conductive SiO2/Si. The thickness of SiO2 is approximately 300 nm. The SE images of the MoS2/Si revealed that MoS2 is the semiconductor with a bandgap energy of about 1.9 eV and less according to the number of layers. The MoS2/SiO2/Si sample produce a significant surface, so backscattering electron (BSE) images were taken instead. We found out that the contrast of BSE images is also the function of the number of layers. As expected, low-voltage SEM was very useful to identify the MoS2 film defects in the nm scale. |
| 저자 | Rakesh Sadanand Sharbidre1, Seong-Gu Hong2, Yung Ho Kahng1, Taik Nam Kim2, Byong Chon Park3 |
| 소속 | 1Division of Industrial Metrology, 2Korea Research Institute of Standards and Science, 3Department of Physical Education |
| 키워드 | number of MoS<SUB>2</SUB> layers; low voltage SEM; backscattering electrons |
