Thermal annealing of sequentially deposited SnS thin films; pp. 488–494Full article in PDF format | doi: 10.3176/proc.2015.4.04
The influence of thermal treatment with the number of deposition cycles on the properties of SnS films on CdS and ZnS substrates was investigated. Annealing under an argon atmosphere made amorphous SnS films formed in one deposition cycle crystalline, but did not markedly change the crystallinity of SnS films formed after multiple deposition cycles. All annealed films were consistent with the orthorhombic phase of herzenbergite SnS, and no additional Sn-containing phases were identified. The CdS/SnS films maintained their initial stoichiometric composition of tin monosulphide after annealing. The films deposited on ZnS substrate films were rich in tin and poor in sulphur and their composition was unaffected by thermal annealing. Both the deposited and thermally annealed films possessed uniform pinhole-free surfaces. Only minor changes in the optical transmittance and reflectance spectra of the CdS/SnS films were observed after annealing, whereas the spectra of the ZnS/SnS films exhibited substantial changes after annealing. As the annealing temperature increased, the absorption edge of the ZnS/SnS films shifted to a longer wavelength. The optical bandgap of the CdS/SnS films was indirect and decreased from 1.28 eV for the three-deposition-cycle CdS/SnS film to 1.22 eV after annealing at 460 °C. The ZnS/SnS films showed a similar change: the bandgap of 1.39 eV for the unannealed films decreased to 1.23 eV after annealing. All deposited and annealed SnS films showed p-type conductivity and their photoconductivity increased with the increasing annealing temperature. Solar cells with reverse structures were fabricated; their performance decreased with the increasing annealing temperature of the SnS film.
1. Jeong, S., Lee, B.-S., Ahn, S. J., Yoon, K. H., Seo, Y. H., and Choi, Y. An 8.2% efficient solution-processed CuInSe2 solar cell based on multiphase CuInSe2 nanoparticles. Energy Environ. Sci., 2012, 5, 7539–7542.
2. Hussain, K. M. A., Podder, J., Saha, D. K., and Ichmura, M. Structural, electrical and optical characterization of CuInS2 thin films deposited by spray pyrolysis. Indian J. Pure Appl. Phy., 2012, 50, 117–122.
3. Mohammed, W. F., Daoud, O., and Al-Tikriti, M. Power conversion enhancement of CdS/CdTe solar cell interconnected with tunnel diode. Circuits and Systems, 2012, 3, 230–237.
4. Schneikart, A., Schimper, H.-J., Klein, A., and Jaegermann, W. Efficiency limitations of thermally evaporated thin-film SnS solar cells. J. Phys. D: Appl. Phys., 2013, 46, 305109.
5. Andersson, B. A. Materials availability for large-scale thin-film photovoltaics. Prog. Photovolt. Res. Appl., 2000, 8, 61–76.
6. Mariappan, R., Ragavendar, M., and Ponnuswamy, V. Structural and optical characterization of SnS thin films by electrodeposition technique. Opt. Appl., 2011, XLI, 988–997.
7. Reddy, K. T. R., Reddy, P. P., Miles, R. W., and Datta, P. K. Investigations on SnS films deposited by spray pyrolysis. Opt. Mater., 2001, 17(1–2), 295–298.
8. Hartman, K., Johnson, J. L., Bertoni, M. I., Recht, D., Aziz, M. J., and Scarpulla, M. A. SnS thin-films by RF sputtering at room temperature. Thin Solid Films, 2011, 519, 7421–7424.
9. Ghosh, B., Das, M., Banerjee, P., and Das, S. Fabrication of vacuum-evaporated SnS/CdS heterojunction for PV applications. Sol. Energ. Mat. Sol. C., 2008, 92, 1099–1104.
10. Sreedevi, G. and Reddy, K. T. R. Properties of tin monosulphide films grown by chemical bath deposition. Conference Papers in Energy, 2013, 2013, Article ID 528724.
11. Ming Du, Xuesong Yin, and Hao Gong. Effects of triethanolamine on the morphology and phase of chemically deposited tin sulfide. Mater. Lett., 2015, 152, 40–44.
12. Sreedevi Gedi, Vasudeva Reddy Minnam Reddy, Chinho Park, Jeon Chan-Wook, and Ramakrishna Reddy, K. T. Comprehensive optical studies on SnS layers synthesized by chemical bath deposition. Opt. Mater., 2015, 42, 468–475.
13. Patel, T. H. Influence of deposition time on structural and optical properties of chemically deposited SnS thin films. The Open Surface Science Journal, 2012, 4, 6–13.
14. Ragina, A. J., Preetha, K. C., Murali, K. V., Deepa, K., and Remadevi, T. L. Wet chemical synthesis and characterization of tin sulphide thin films from different host solutions. Advances in Applied Science Research, 2011, 2(3), 438–444.
15. Chao Gao, Honglie Shen, and Lei Sun. Preparation and properties of zinc blende and orthorhombic SnS films by chemical bath deposition. Appl. Surf. Sci., 2011, 257, 6750–6755.
16. Safonova, M., Nair, P., Mellikov, E., Garcia, A., Kerm, K., Revathi, N., Romann, T., Mikli, V., and Volobujeva, O. Chemical bath deposition of SnS thin films on ZnS and CdS substrates. J. Mater. Sci.–Mater. El., 2014, 25, 3160.
17. Arenas, O. L., Nair, M. T. S., and Nair, P. K. Chemical bath deposition of ZnS thin films and modification by air annealing. Semicond. Sci. Tech., 1997, 12, 1323.
18. Nair, P. K., Daza, O. G., Readigos, A. A.-C., Campos, J., and Nair, M. T. S. Formation of conductive CdO layer on CdS thin films during air heating. Semicond. Sci. Tech., 2001, 16, 651–656.
19. Leite, R. C. C. and Porto, S. P. S. Enhancement of Raman cross section in CdS due to resonant absorption. Phys. Rev. Lett., 1966, 17, 10.
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