Bk. Tay et al., OPTICAL-PROPERTIES OF TETRAHEDRAL AMORPHOUS-CARBON FILMS DETERMINED BY SPECTROSCOPIC ELLIPSOMETRY, Thin solid films, 308, 1997, pp. 268-272
The optical and microstructural properties of tetrahedral amorphous ca
rbon (ta-C) thin films prepared by filtered cathodic vacuum are (FCVA)
have been investigated as a function of the ion energy. The films wer
e characterized by spectroscopic phase modulated ellipsometry (SPME) f
or the first time. The optical property of the ta-C layer was derived
from the Forouhi and Bloomer amorphous semiconductor model. An effecti
ve medium approximation and a linear regression analysis have been use
d to determine the microstructure of thin ta-C films on silicon. The m
icrostructure of these films deposited on silicon wafers was simulated
by a four-layer model consisting of a roughness layer, a ta-C layer,
a graded ta-C:Si layer and the silicon substrate. The graded layer con
sisting of the mixture of ta-C and silicon simulates the carbon ion im
pinging/diffusion into the surface of the silicon substrate. The compl
ex refraction index, N = n - ik over the range of 250-900 nm, for ta-C
had been determined. The Tauc (optical) band gap as a function of ion
energy was also studied. (C) 1997 Elsevier Science S.A.