Facile fabrication of wafer-scale MoS2 neat films with enhanced third-order nonlinear optical performance

Abstract

Wafer-scale MoS₂ neat films with controllable thicknesses were successfully fabricated by vacuum filtering liquid-exfoliated MoS₂ dispersions. The obtained MoS₂ filtered thin films were systematically characterized by UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM). It was found that the fabricated scalable MoS₂ films have a smooth surface and high optical homogeneity verified by AFM and a collimated 532 nm beam, respectively. We investigated the ultrafast nonlinear optical (NLO) properties of the filtered films by an open aperture Z-scan method using 515 and 1030 nm femtosecond laser pulses. Saturable absorption was observed at both 515 and 1030 nm with the figure of merit (FOM) values as ∼3.3 × 10⁻¹² esu cm and ∼3.4 × 10⁻¹⁴ esu cm, respectively. The observation of ultrafast NLO performance of the MoS₂ filtered films indicates that vacuum filtration is a feasible method for the fabrication of optical thin films, which can be expanded to fabricate other two-dimensional films from the corresponding dispersions. This easy film fabrication technology will greatly enlarge the application of graphene analogues including graphene in photonic devices, especially of MoS₂ as a saturable absorber.