Thickness-dependent structure and properties of SnS₂ thin films prepared by atomic layer deposition

Abstract

Tin disulfide (SnS₂) thin films were deposited by a thermal atomic layer deposition (ALD) method at low temperatures. The physical, chemical, and electrical characteristics of SnS₂ were investigated as a function of the film thickness. SnS₂ exhibited a (001) hexagonal plane peak at 14.9 ° in the X-ray diffraction (XRD) results and an A(1g) peak at 311 cm⁻¹ in the Raman spectra. These results demonstrate that SnS₂ thin films grown at 150 °C showed a crystalline phase at film thicknesses above 11.2nm. The crystallinity of the SnS₂ thin films was evaluated by a transmission electron microscope (TEM). The X-ray photoelectron spectroscopy (XPS) analysis revealed that SnS₂ consisted of Sn⁴⁺ and S²⁻ valence states. Both the optical band gap and the transmittance of SnS₂ decreased as the film thickness increased. The band gap of SnS₂ decreased from 3.0 to 2.4 eV and the transmittance decreased from 85 to 32% at a wavelength of 400nm. In addition, the resistivity of the thin film SnS₂ decreased from 10¹¹ to 10⁶ Ω·cm as the film thickness increased.