Raman Analysis of trans-Polyacetylene Chains in Hydrogenated Amorphous Carbon Films

Abstract

Hydrogenated amorphous carbon (a-C:H) films were deposited using a RF magnetron sputtering system in H2/He plasma. The bonding hydrogen concentration (nH), optical gap, hardness and Raman spectrum of these a-C:H films were measured. Two significant peaks centered at ∼1150 and ∼1450 cm-1 were observed in the Raman spectra of the a-C:H films with a high nH. The two Raman peaks are attributed to the vibration modes of trans-polyacetylene (trans-PA), and the ∼1150 cm-1 peak is used to analyze the trans-PA chaining configuration. As a result, it is found that as the nH 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 nH. In this paper, we show that the chaining configuration of the a-C:H films can be analyzed using the ∼1150 cm-1 peak in the Raman spectrum.