Analysis of amorphous carbon thin films by spectroscopic ellipsometry

Determination of optical properties of nitrogen-doped hydrogenated amorphous carbon films by spectroscopic ellipsometry

“…%. The increase in k with increased nitrogen incorporation is due to the graphitization effect which decreases the optical gap resulting in higher k. The values of n obtained here are much lower than those reported in the literature for unhydrogenated a-C. 10 The existence of C-H bonds explains the lower indices of refraction for these films. Smith has reported n values of 1.75 Ϯ0.02 in the spectral range of 1.45-4.86 eV for the as deposited a-C film and observed a density of only 1.35 g/cm 3 for his film which is even lower than those of other disordered forms of carbon, such as, evaporated carbon films ͑1.35-2.4 g/cm 3 ͒, carbon chars ͑1.4 -2.05 g/cm 3 ͒, and glassy carbon ͑1.47 g/cm 3 ͒.…”

“…[7][8][9] However, there has been no simultaneous study of the optical constant and depth profile of the films in order to better understand their optical properties. Lee et al 10 have analyzed ellipsometric data of a-C films from 1.5 to 5 eV by applying Bruggeman effective-medium theory with isotopic screening, assuming a model of the material as a composite with sp 2 and sp 3 carbon components. However, they did not investigate the degree of inhomogeneity of the films.…”

The Clarification of Low Friction Mechanism for Hydrogenated Amorphous Carbon by In-Situ Observation of Frictional Area

“…Therefore we estimated n and k by effective medium approximation which describe in the next section, then we estimated d by using the estimated n and k. and C-H bond in transformed layer from optical properties J. Lee et al reported that the effective medium approximation (EMA) which consists of C-Csp 2 and C-Csp 3 in amorphous carbon coating was used to estimate C-Csp 3 fraction in amorphous carbon coating, the EMA showed a good monotonic correlation with those obtained by electron energy-loss spectroscopy (EELS) [6]. From this report, it is expected that we can estimate hydrogen concentrations of transformed layer from volume fraction of C-H bond.…”

Modification Processes for Highly Hydrogenated Diamond-Like Carbon Thin Films by Soft X-ray Irradiation

“…(26,27) Recently, many researchers have reported the optical properties of DLC films using spectroscopic ellipsometry (SE), which is a powerful optical technique that enables the measurement and interpretation of changes in the polarization state of polarized light undergoing oblique reflection from a sample surface. (28)(29)(30)(31)(32)(33)(34) The technique is used to determine the films reflective index, n, and extinction coefficient, k, film thickness, and the surface roughness. Recently, the relation of optical constants to the local structure of DLC films attracted attention.…”