Raman analysis of trans-polyacetylene chains in hydrogenated amorphous carbon films

Hydrogenated amorphous carbon (a-C:H) films were deposited using a RF magnetron Sputtering system in H-2/He plasma. The bonding hydrogen concentration (n(H)), optical gap, hardness and Raman spectrum of these a-C:H films were measured. Two significant peaks centered at similar to 1150 and similar to 1450 cm(-1) were observed in the Raman spectra of the a-C:H films with a high n(H). The two Raman peaks are attributed to the vibration modes of trans-polyacetylene (trans-PA), and the similar to 1150 cm(-1) peak is used to analyze the trans-PA chaining configuration. As a result, it is found that as the n(H) increases, the relative intensity of this peak increases and its peak position downshifts. These results indicate that the trans-PA chain content and its conjugate length increase with n(H). In this paper, we show that the chaining configuration of the a-C:H films can be analyzed using the similar to 1150 cm(-1) peak in the Raman spectrum.