Atmospheric Pressure Chemical Vapor Deposition of Tin Sulfides (SnS, Sn₂S₃, and SnS₂) on Glass

Atmospheric pressure chemical vapor deposition of SnS2, Sn2S3, and SnS has been achieved onto glass substrates from the reaction of SnCl4 with H2S at 300−545 °C. The films show good uniformity and surface coverage, adherence, and a variety of colors (black, yellow, brown, and gray) dependent on deposition temperature and film thickness. Growth rates were on the order of 1−2 μm min-1. All the films were crystalline. For substrate temperatures of up to 500 °C single phase films with the hexagonal SnS2 structure (a = 3.65(1) Å, c = 5.88(1) Å) were formed. At 525 °C a film of mixed composition containing predominantly orthorhombic Sn2S3 (a = 8.83(1) Å, b = 3.76(1) Å, c = 14.03(1) Å) was formed together with some SnS2. At 545 °C films with orthorhombic SnS structure (a = 4.30(1) Å, b = 11.20(1) Å, c = 3.99(1) Å) were formed. Scanning electron microscopy (SEM) revealed a variety of different film thicknesses and morphologies, including needles, plates, and ovoids, dependent on the deposition temperature and time. Energy-dispersive X-ray analysis (EDX) and electron probe measurements on the films indicated elemental ratios close to those for tin disulfide (SnS1.98), ditin trisulfide (SnS1.60), and tin monosulfide (SnS1.10) and revealed no incorporation of chlorine. X-ray photoelectron spectroscopy (XPS) gave results in agreement with those from EDX and revealed binding energies of Sn 3d5/2 = 486.5(1) eV and S 2p = 161.6(2) eV for films grown at less than 500 °C (SnS2), and Sn 3d5/2 = 485.7 (1) eV and S 2p3/2 = 161.0 eV for the film grown at 545 °C (SnS). Raman microscopy showed that the films of SnS2 had bands at 315 and 215 cm-1, those of Sn2S3 had bands at 307, 251, 234, 183, 71, 60, and 52 cm-1, and those of SnS had bands at 288, 220, 189, 163, and 96 cm-1. The band gap of SnS2 was 2.14 eV. Sheet resistance measurements showed that all of the films were essentially insulating.