Room temperature magnetron sputtering and laser annealing of ultrathin amorphous sulfur-rich MoSx films

Abstract

Room temperature magnetron sputtering of an ultra-thin transition-metal dichalcogenide amorphous precursor and subsequent laser annealing-induced phase transformations were investigated for the synthesis of polycrystalline 2H-MoS2 semiconducting thin films. Radio frequency magnetron sputtering of a MoS3.6 target was used to produce amorphous precursors with S to Mo ratios greater than 2:1 on thermally annealed SiO2 substrates, glass, indium tin oxide coated glass, and amorphous boron-oxy-nitride. The influence of working pressure on the MoS2 and MoS3 interatomic bonding arrangements in amorphous MoSx films was explored with x-ray photoelectron spectroscopy. A 248 nm pulsed laser was used for annealing 1 cm2 sized areas of the amorphous precursor in an ambient atmosphere at fluences of 100–450 mJ for 1, 5, and 10 pulses to form a crystalline 2H-MoS2 phase. The role of laser fluence and substrate choice on phase transformation from the amorphous precursor to the 2H phase, as well as the competition between oxidation, elemental sulfur segregation, and ablation is discussed. Hall effect measurements confirmed p-type behavior of the produced semiconducting films and established mobility and charge carrier density characteristics of the laser-annealed films. The feasibility of scalable processing by combining sputtering from sulfur-rich targets and laser annealing for production of p-type 2H-MoS2 ultrathin films on various substrates is presented.