Hydrothermally synthesized 2H-MoS2 under optimized conditions - A structure and morphology analysis

Abstract

In this study, we obtained the optimized conditions to synthesize pure semiconducting 2H-MoS2 nanomaterial, using a facile and scalable hydrothermal route under the variation of growth parameters such as reaction temperature, reaction time and sulfur precursors. The structural and phase identification of obtained MoS2 powders was analysed using XRD and raman spectroscopy. The reproducible formation of pure 2H-MoS2 phase is reported for the optimized reaction time of 22 h at a temperature of 200 °C using thiourea as sulfur source, with a high yield of 77.4%. FESEM analysis revealed nanoflower-like morphology of average diameter of 300-400 nm with identifiable petals of thickness ∼25 nm for the formed 2H-MoS2 under the optimized conditions. The crystallite size, strain and dislocation density were estimated theoretically using Williamson-Hall plots for the MoS2 formed under the variation of growth temperatures. Tensile strain values were obtained for MoS2 formed using thiourea, which correlated only with phase transitions from mixed 1 T/2H-MoS2 to pure 2H-MoS2. In contrast, only mixed 1 T/2H-MoS2 phase were obtained for MoS2 powders using L-Cysteine, and correspondingly the strain values were extremely small, which may be due to no phase transition observed and presence of nanosheets without curved petal-like features. The results of this study provide optimized condition for the formation of semiconducting 2H-MoS2 nanomaterial by a scalable route. This is useful for low-cost fabrication of flexible nanoelectronic devices such as non-volatile ReRAMs, supercapacitors and sensors based on 2H-MoS2