Influence of substrate temperature on the growth properties of Ag-doped SnS films deposited by sputtering method

• Published in: The Journal of physics and chemistry of solids 2021-08, Vol.155, p.110099, Article 110099
• Main Authors: Arepalli, Vinaya Kumar, Kim, Sung Jun, Kim, Jeha
• Format: Article
• Language: English
• Subjects: Ag-doped SnS; RF-sputtering; SnS thin films; SnS:Ag films
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/j.jpcs.2021.110099

The Ag-doped SnS films were obtained using a sputtering technique through a sub-sequential layer-by-layer SnS–Ag–SnS–Ag… approach. The structural, optical, and electrical properties of these films deposited at 200 °C, 250 °C, 300 °C, and 350 °C were investigated at a constant Ag concentration of ∼2 at. %. The XRD, Raman, and TEM confirmed that all the diffraction planes of the Ag-doped films belonged only to the orthorhombic crystal phase of the SnS. Based on the reduction in the crystal volume and the compressive type of micro-strain, it confirmed the substitutional doping of Ag into the Sn-vacancy sites in the SnS lattice. The SIMS analysis revealed that the Ag doping into SnS has occurred through the diffusion process with an increase in Ts. The XPS analysis confirmed the presence of the Sn2+, S2−, and Ag2+ oxidation states in the Ag-doped SnS films deposited at 200 °C. The direct optical band bap decreased from 1.44 to 1.42 eV with Ag doping at 200 °C, then it increased to 1.50 eV with rise in Ts (200–350 °C). All the undoped and Ag-doped SnS films exhibited a p-type conductivity. The hole carrier concentration increased from 6.65 × 1015 cm−3 to 5.74 × 1016 cm−3 with Ag doping at 200 °C, later it increased to 1.40 × 1017 cm−3 with an increase of Ts. While the hole mobility increased from 0.34 to 7.81 cm2/V.s with Ag doping at 200 °C, then as Ts increased to 350 °C it decreased to 0.35 cm2/V.s. Finally, the Ag-doped SnS grown at 200 °C exhibited the lowest resistivity (597 Ω cm) than the undoped SnS (2771 Ω cm). The Ag-doped SnS grown at 200 °C is suitable to be used as an efficient solar material. •All Ag-doped SnS films showed a constant Ag concentration (2 at. %) at substrate temperatures from 200 °C to 350 °C.•The Ag-doped SnS films exhibited a substitutional doping in the SnS lattice between 200–350 °C.•The Ag doping causes an increased crystallinity of the SnS films at 200 °C when compared to the undoped SnS.•The direct optical energy band gap of the Ag-doped SnS increased from 1.42 to 1.50 eV with increase in Ts from 200 °C to 350 °C.•The undoped and Ag-doped SnS showed the hole-carrier concentration between 6.65 × 1015 – 1.40 × 1017 cm−3.