Effect of morphology modulation and interface engineering of SnS-MoS2 heterojunction on nonlinear optical response

Abstract

MoS2 base films with different morphologies were prepared by modulating the magnetron sputtering parameters, and the base films were used to induce the growth of SnS with different structures, forming columnar and worm-like SnS-MoS2 heterojunctions, which were found to have excellent nonlinear absorption properties and their properties could be modulated by the morphology of the films by Z-scanning tests. The tunable morphology and crystalline quality of the films were characterized using scanning electron microscopy, atomic force microscopy and X-ray diffraction techniques and explained using the Stranski-Krastanow growth mechanism. The Raman spectrum of the heterojunction shows the A1g vibrational peak at 320 cm−1 and the appearance of Sn4+ in the X-ray photoelectron spectroscopy confirms the existence of S-Sn-S charge transfer channels between the interfaces. The fine spectra of all the elements in the X-ray photoelectron spectroscopy data as well as the characteristic absorption peaks in the absorption spectra confirm the formation of heterojunctions, and the constructed heterojunctions are determined to be type-II heterojunctions using the method of the core energy level. Heterojunction was determined to be a type-II heterojunction by using the core energy level method. The photoluminescence peak quenching of the heterojunction indicates that there is a process of charge transfer between the interfaces, and the type-II heterostructure of SnS-MoS2 makes the nonlinear absorption performance in the 800 nm band regulated by the morphology of the material. The nonlinear optical absorption coefficient is two orders of magnitude higher than that of the pure materials, and the nonlinear absorption performance of the worm-like SnS-MoS2 heterojunction is superior to that of the columnar SnS-MoS2 heterojunction, which is attributed to the larger interfacial contact area, the better crystalline quality, and the more efficient carrier interfacial transport capability. These tunable type-II SnS-MoS2 heterojunctions with ultrafast nonlinear optical absorption have a positive impact on practical applications such as optical limiter devices and all-optical switching devices.