Flux method growth of bulk MoS2 single crystals and their application as a saturable absorber

Abstract

Molybdenum disulfide (MoS₂) has attracted a great deal of attention because of its outstanding physical, chemical and optoelectronic properties. The method used to prepare large sized MoS₂ crystals of very high quality is still an important issue for determining the feasibility of its application. Herein, we propose a novel Sn flux method to grow single crystal MoS₂, and bulk MoS₂ single crystals with a size of 3 mm × 5 mm were successfully obtained by using a cooling rate of 2–4 °C h⁻¹. The growth mechanism of the MoS₂ crystal in Sn flux was investigated in detail using optical microscopy and atomic force microscopy (AFM). The obvious screw dislocation steps that are revealed suggest that the growth of MoS₂ is controlled by a screw-dislocation-driven (SDD) spiral growth mechanism. The flux-grown MoS₂ crystals were exfoliated to produce high-quality large-scale films using the liquid-phase exfoliation method. Using ultrathin MoS₂ films as a saturable absorber, a passively Q-switched laser at a wavelength of 1.06 μm was constructed and operated, with a narrow pulse width of 326 ns.