Radio-frequency controlled crystalline phase transformation of MoS2 thin film fabricated by unique vapour-plasma mixing technique

Abstract

Successful fabrication of molybdenum disulfide thin films on silicon substrates by a unique vapour-plasma mixing technique at a relatively low temperature of 300 °C is reported. This mixing technique involves simultaneous sputtering of a molybdenum target and thermal evaporation of sulphur flakes to form MoS2 molecules. Raman studies confirm the formation of MoS2 with characteristic E12g and A1g modes observed at ∼384 and ∼408 cm−1. The effects of radio frequency (RF) power on the physical properties of MoS2 film at a constant sulphur evaporation rate are investigated. The Raman and X-Ray photon spectroscopy reveal that a controlled crystalline phase transition between metallic tetragonal (1 T-MoS2) and semiconducting hexagonal (2H–MoS2) has been successfully achieved upon variation of the RF power. Furthermore in X-Ray diffraction analysis, Scherrer's, Williamson-Hall and Size-Strain Plot methods are used to extract relevant correlations between structural properties (viz. Crystallite sizes, strains) and the thin film growth controlling parameters.