Characteristics of thin film tin disulfide depending on its thickness

Abstract

Thin film tin disulfide (SnS2) was deposited via a thermal atomic layer deposition (ALD) method at low temperatures and characterized depending on its film thickness. The physical, chemical, and electrical characteristics of SnS2 were examined. Thin films of SnS2 exhibited (001) a hexagonal plane peak at 14.9° according to X-ray diffraction (XRD), and a Raman peak of A1g at 311 cm-1 was examined. X-ray photoelectron spectroscopy (XPS) analysis revealed that the films consisted of Sn4+ and S2- in terms of valence states. We examined the SnS2 film thickness with a transmission electron microscope (TEM) and its ALD growth rate per cycle (GPC) was measured at approximately 0.51 Å/cycle. The thin film of SnS2 that was grown at 150 °C showed a crystalline phase at 22.4 nm thickness. Both the optical band gap and transmittance of SnS2 were observed to decrease as the film thickness increased. The band gap was changed from 2.99 to 2.37 eV, and the transmittance of SnS2 changed from 85 to 32 % at the 400 nm wavelength, as the film thickness increased from 2.3 nm to 44.8 nm. In addition, the resistivity of the thin film SnS2 decreased from 1011 to 106 Ω·cm as the film thickness increased.