Deposition of SnS thin film using tetrakis(dimethylamido)tin(IV) and improvement of crystallinity by post annealing

Two-dimensional (2D) tin sulfides are promising materials to overcome the limitations of transition metal dichalcogenides (TMDCs). For tin sulfide to replace TMDCs, it must exhibit high crystallinity. Tin sulfide deposited by atomic layer deposition (ALD) tends to have low crystallinity due to the low deposition temperature. To improve crystallinity, methods such as pre-treatment, annealing, and seed layers have been studied, with annealing is most effective. In this study, we evaluated the effect of in-situ annealing on tin monosulfide (SnS) thin films deposited by ALD. Various structural parameters were calculated using grazing incidence X-ray diffraction (GI-XRD), and by comparing these values, we confirmed that crystallinity of the SnS thin films improved after in-situ annealing. Phase purity was confirmed through Raman spectroscopy. The 2D layered structure was observed with transmission electron microscopy (TEM), while Rutherford backscattering spectrometry (RBS) was used to confirm stoichiometry. The bonding states of the thin films were analyzed with X-ray photoelectron spectroscopy (XPS), and optical properties were confirmed using ultraviolet-visible spectroscopy (UV-vis) and ultraviolet photoelectron spectroscopy (UPS). Lastly, Hall measurements were performed to compare the electrical characteristics of as-deposited and annealed SnS thin films. Our results show that in-situ annealing effectively improves the crystallinity of SnS thin films.