Physico-Chemical nanomaterials science

Raman mapping few-layer MoS2 to develop flexible electronics
Qiu Y.1, Chen W.1, Babichuk I.S.1,2, Babichuk I.V.3, Yang J.1
1 Faculty of Intelligent Manufacturing, Wuyi University, 529020, Jiangmen, P.R. China. E-mail: 48489797@qq.com (Qiu), ivan@szu.edu.cn
2 V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, 03680, Kyiv, Ukraine.
3 National Center “Minor academy of sciences of Ukraine”, 04119, Kyiv, Ukraine.

Molybdenum disulfide (MoS2) as the most typical member of the transition metal dichalcogenides family has attracted increasing attention recently due to its extraordinarily different material properties compared with conventional bulk materials. The MoS2 possesses a high Young’s modulus, high strength, and outstanding carrier mobility. By exploiting the unique mechanical and mechanoelectrical transduction properties, MoS2 can be used in wide-ranging applications, including flexible electronics and strain sensors.
One of the main tasks at the beginning of the investigation was to optimize the parameters of the synthesis of MoS2 monolayer without defects over a large area. The synthesis of high-quality defect-free monolayer depends on many factors, such as the type of substrate, the quality of the starting material, pressure, temperature, gas flow, and so on. The chemical vapor deposition (CVD) method was used for the synthesis. Another direction was the development of a protocol for the transfer of these layers on the prepared flexible substrate. One of the transfer methods was the use of a layer of poly-(methyl methacrylate) (PMMA) coated by spin coating method on MoS2 and growth substrate (SiO2/Si) to lift off the PMMA/MoS2 stack.
The used of Raman spectroscopy demonstrated the mono and few-layer MoS2. Raman mapping showed the high-quality MoS2 monolayers (Fig. 1), but not a large areas and only flakes.

Fig. 1. (a) The optical photo of surface MoS2 flakes grown on SiO2/Si substrate by CVD method. (b) The mapping area of MoS2 flake. (c-d) The Raman mapping of E2g and A1g bands corresponds to the area in the optical photo.