Optical properties of hydrogenated hard carbon thin films

Characterization of a-C:H:N deposition from CH4/N2 rf plasmas using optical emission spectroscopy

“…The most striking observations from this study are the previously unidentified sharp nitrogen spectral lines which we ascribe to atomic N, the development of CN bands, the enhancement of N 2 second positive spectral line intensities with the addition of CH 4 , and the higher intensities of species originating from N 2 relative to those from CH 4 . These points, together with the variation of spectral line intensities under different plasma conditions, are discussed below.…”

“…Typical optical emission spectra of CH 4 , N 2 and CH 4 /N 2 plasmas are shown in Figs. 1͑a͒, 1͑b͒, and 1͑c͒, respectively.…”

“…The rate coefficient C X (E) is constant since the plasma parameters are fixed and the concentration of CH 4 is higher than that of N 2 . The difference in band intensities of species from N 2 and CH 4 must, therefore, be due to a higher excitation efficiency X of N 2 relative to CH 4 . This reflects the fact that the nitrogen species are principally generated by primary electron excitation ͓Table I, Eqs.…”

“…However, it is well known that with rf-PECVD-deposited undoped a-C:H, 4 film structure depends strongly on the ion bombardment energy of the species involved in the film growth which is a function of the deposition parameters, particularly bias voltage. Thus, it is relevant to ascertain the effects of bias variations on film properties of a-C:H:N. In this article we report on th optical emission spectroscopy ͑OES͒ of CH 4 /N 2 plasmas.…”

“…3 Further, the properties of the films are found to depend strongly on their microstructure, i.e., sp 3 /sp 2 ratio and H content. As well as varying the hydrocarbon feedstock, 4 additives such as hydrogen 5,6 and the inert gases [6][7][8][9] have been used in an attempt to further modify the structure of these films.…”