Features of the vibrational spectra of diamond-like and polymer-like a-C:H films

Abstract

Comparative analysis of the IR spectra of multiple frustrated total internal reflection (MFTIR) in the range 4000–1000 cm−1 is performed for diamond-like and polymer-like a-C:H films with the refractive indices n ≥ 2.0 and n ≤ 1.7, respectively. The films are obtained by chemical-vapor deposition from octane, cyclohexane, toluene, and acetylene under various conditions using a dc glow discharge plasma. Characteristic features are found in the vibrational spectra of a-C:H films with different refractive indices. A peak at 1250 cm−1, which is independent of the initial hydrocarbon, is observed in the spectra of the diamond-like films. Additional peaks at 3400 and 1700 cm−1, due to O-H and C=H vibrations, are present in the spectra of the polymer-like films. It is shown that the integrated intensity of the band of CH vibrations peaked at ∼2900 cm−1 decreases exponentially by an order of magnitude with an increase in n from 1.55 to 2.4.