Large area synthesis of mono/few-layer MoS2 thin films on thermal oxide silicon substrate by pulsed laser deposition technique

Abstract

Two-dimensional molybdenum disulphide (2D MoS2) has emerged as an auspicious material in the development of optoelectronic devices owing to its remarkable similarities with graphene while possessing a definite bandgap. However, the production of these devices is restricted due to the difficulties in producing high-quality 2D MoS2 films on a large scale. Here we report the growth of mono/few layers of MoS2 - on thermal oxide silicon (Si/SiO2) substrate using pulsed laser deposition (PLD). The presence of Raman peaks corresponding to A1g and E12g modes of vibration confirmed the formation of 2D MoS2. The difference in Raman shift of A1g and E12g modes was used to find out the number of layers of the PLD-grown MoS2 thin films, which was found to be increasing with deposition time. Photoluminescence spectra also revealed the formation of mono/few-layered MoS2 thin films, and the thickness of the films was determined using atomic force microscopy. The MoS2 thin films were then deposited on a quartz substrate to record the absorption spectra of MoS2, and the existence of four excitonic peaks A, B and C, D further confirmed the formation of 2H MoS2. The calculation of the bandgap was done using Tauc plot studies, and a bandgap value of 1.77 eV was obtained for monolayer MoS2. The stoichiometry of Mo and S in the PLD-grown samples was determined using X-ray photoelectron spectroscopy analysis. The morphology and crystallinity of the monolayer MoS2 were studied by performing transmission electron microscopy analysis.