Plasma deposition of amorphous SiC:H,F alloys from SiF4‐CH4‐H2 mixtures under modulated conditions (original) (raw)
Journal of Applied Physics
https://doi.org/10.1063/1.362473
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Abstract
Fluorinated and hydrogenated amorphous silicon‐carbon alloys (a‐SiC:H,F) are produced by glow discharge decomposition of SiF 4 ‐CH 4 ‐H 2 mixture. Small amount of CH 4 in SiF 4 ‐H 2 mixture are enough to produce silicon carbon alloys having optical gap ranging between 1.8 and 2.6 eV. Materials, having 1.95 eV band gap and exhibiting optoelectronic properties typical of state of art a‐SiC:H, are deposited under plasma modulation conditions. © 1996 American Institute of Physics.
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References (17)
- Y.-M. Li, in Amorphous Silicon Technology-1993, edited by E. A. Schiff, M. J. Thompson, A. Madan, K. Tanaka, and P. G. LeComber, Mater. Res. Soc. Symp. Proc. 297 ͑MRS, Pittsburgh, 1993͒, p. 803.
- R. Galloni, R. Rizzoli, C. Summonte, F. DeMichelis, F. Giorgis, C. F. Pirri, E. Tresso, G. Ambrosone, C. Catalanotti, U. Coscia, P. Rava, G. Della Mea, V. Rigato, A. Madan, and F. Zignani, in Amorphous Silicon Technology-1994, edited by E. A. Schiff, M. Hack, A. Madan, M. Powell, and A. Matsuda, Mater. Res. Soc. Symp. Proc. 336 ͑MRS, Pitts- burgh, 1994͒, p. 517.
- Y.-M. Li and B. F. Fieselmann, Appl. Phys. Lett. 59, 1720 ͑1991͒.
- A. H. Mahan, D. L. Williamson, M. Ruth, and P. Raboisson, J. Non-Cryst. Solids 77/78, 861 ͑1985͒.
- D. M. Bhusari, A.S. Kumbhar, and S.T. Kshirsagar, J. Appl. Phys. 77,5 4 ͑ 1995͒.
- G. Ganguly, J. Dutta, S. Ray, and K. Barua, Phys. Rev. B 40, 3830 ͑1989͒.
- N. Shibata, N. Shida, A. Tanabe, J. Hanna, and I. Shimizu, 8th Interna- tional Symposium on Plasma Chemistry ͑ISPC-8͒, Tokyo, Japan, Vol. III, edited by K. Akashi and A. Kinbara, 1987, p. 1496.
- Y. Catherine, G. Turban, and G. Grolleau, Plasma Chem. Plasma Proc. 2, 81 ͑1982͒.
- K. Tachibana, H. Harima, and Y. Urano, 8th International Symposium on Plasma Chemistry ͑ISPC-8͒, Tokyo, Japan, Vol. I, edited by K. Akashi and A. Kinbara, 1987, p. 590.
- G. Cicala, G. Bruno, and P. Capezzuto, Pure and Appl. Chem. 68 ͑1996͒.
- H. Wieder, M. Cardona, and C. R. Guarnieri, Phys. Status Solidi B 92,99 ͑1979͒.
- G. Lucovsky, Solid State Commun. 29, 571 ͑1979͒.
- R. Dutta, P. K. Banerjee, and S. S. Mitra, Phys. Rev. B 27, 5032 ͑1983͒.
- A. Madan, S. R. Ovshinksy, and E. Benn, Philos. Mag. 40, 259 ͑1979͒.
- G. Lucovsky, J. Yang, S. S. Chao, J. E. Tyler, and W. Czubatyi, Phys. Rev. B 28, 3225 ͑1983͒.
- A. H. Mahan, B. von Roedern, D. L. Williamson, and A. Madan, J. Appl. Phys. 57, 2717 ͑1985͒.
- N. Amer and W. B. Jackson, in Semiconductors and Semimetals, Vol. 21, Part B, edited by J. Pankove ͑Academic, Orlando, FL, 1984͒,p .8 3 .
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