Optical properties of diamond-like carbon thin films deposited by DC-PECVD
DOI:
https://doi.org/10.11113/mjfas.v7n1.201Keywords:
Diamond like carbon, DC-PECVD, Optical properties, Photoluminescence, Amorphous carbon,Abstract
Diamond-like carbon (DLC) thin films were deposited at different substrate temperatures using methane gas in DC-PECVD at 1x10-1 Torr. From the light
transmission using UV-VIS spectroscopy it was found that the optical transition had changed from allowed indirect transition to forbidden direct
transition as the substrate temperature increased. The photoluminescence study has shown that the recombination centre occurred at 1.738 eV. The
observation in the present work shows that the Urbach energy decreases with increasing substrate temperature provides evidence that such films have a
narrowed band tail. This decrease in Urbach energy is due to a more ordered structure with lower hydrogen concentration and larger cluster by the
increase in the degree of cross-linking of the C-C network. Distorted cluster which contribute to the broadening of the band tail may also contribute to the
PL peak width. As the substrate temperature increases, the cluster size in the tetrahedral hydrogenated amorphous carbon (ta-C:H) increases, resulting in
smaller band gap and the structure is more ordered as the decrease in Urbach energy, give the decrease in PL peak energy.
References
Werner M. and R Locher, Rep. Prog. Phys. 61(1998)1665
Davis R. F. (Ed.), Diamond Films and Coatings,William Andrew Publishing, Noyes, 1993.
Silinskas M., A. Grigonis, V. Kulikauskas and I. Manika, Thin Solid Films, 516(2008)1683–1692
Gupta, P., Singh, V. and Meletis, E.I., Tribology International. 37(2004)1019-1029.
Staryga E. and G. W. Bk, Diamond and Related Materials, 14(2005) 23-34
Smith, D. L., 1995, Thin film Deposition: Principles and Practice, McGraw-Hill, Boston.
Bewilogun, K., Wittorf, R., Thomsen, H., Weber, M., Thin Solid Films. 447-448 (2004)142-147.
Tauc, J., in Optical Properties of Solids, Abeles, F., Editors, North-Holland, Amsterdam, (1970).
Weiler, M., Sattel, S., Giessen, T., Jung, K. and Ehrhardt, H., Physical Review B. 53(3) (1996)1594-1608
Robertson, J., Diamond and Related Materials. 12(2003)79-84.
Manage, D.P., Structural and Optical Characterization of Hydrogenated Amorphous Carbon Thin Films. University of Toronto: Ph. D. Thesis,
(1998).
Rusli, Gehan, Amaratunga, A.J. and Silva, S.R.P., Thin Solid Films. 270(1995)160-164.
Koos, M., Pocsik, I., Erostyak, J. and Buzadi, Journal of Non-Crystalline Solids. 227-230(1998)579-582.
Anguita, J.V., Young, W.T., Khan, R.U., Silva, S.R.P., Haq, S., Sturland, I. and Pritchard A., Journal of Non-Crystalline Solids. 266-
(2000)821-824.
Fule, M., Toth, S., Veres, M., Pocsik, I. and Koos, M., Diamond and Related Materials. 14(2005)1041-1046.
Toth, S., Veres, M., Fule, M. and Koos, M., Diamond and Related Materials. 15(2006)967-971.
