Modulation of microstructural and electrical properties of rapid thermally synthesized MoS2 thin films by the flow of H2 gas

Abstract

Two dimensional transition metal dichalcogenides (TMDC) have gained potential attention of the researchers, owing to their fascinating electronic and optoelectronic properties. Among the TMDC, the widely studied molybdenum disulphide (MoS2) stands out as a prototypical material. In this work, rapid thermal process (RTP) is adopted for the deposition of MoS2 thin film, using sputtered molybdenum (Mo) thin film and thermally evaporated sulphur (S) film. The microstructural and electrical characteristics of the MoS2 thin films were studied by varying the H2 flow rate in the rapid thermal processing furnace. Field Emission Scanning Electron Microscope images showed the improvement in the uniformity of the MoS2 thin films with the increase in the flow rate of H2 gas. The X-ray diffraction peak has been observed at 14.1°, corresponding to the (002) plane of the hexagonal MoS2 (2H). Raman spectra depict two peaks around 400 cm−1 for A1g and E2g1active modes, which a fingerprint of 2H MoS2. The FTIR studies also depicted the enhancement of MoS2 characteristics peaks with the increase in H2 flow rate. In order to study the effect of substrate, MoS2 films were grown on both Si and SiO2/Si substrates. Among the various H2 flow rates used during the RTP, MoS2 thin films grown with 20 sccm H2 gas at 800 °C has shown better microstructural properties. In order to study the semiconductor properties of MoS2 thin films, the carrier concentration has been calculated from the heterojunction capacitance and is found to be ~1016 cm−3. The comprehensive study on the effect of H2 flow rate on the properties of MoS2 thin films imparts the underlying role of hydrogen atoms in the deposition process, which paves a way for the controlled synthesis of low dimensional materials.