Bonding and hydrogen incorporation in a-C/H studied by infrared spectroscopy

Infrared absorption spectroscopy is a powerful tool for the investigation of hydrogen bonding in a-C:H films. Analysis of the C-H stretch bands (near 3000 cm E-1) provides information on the total amount of bonded hydrogen and on the type of bonding (carbon hybridisation). The absorption bands of the CH sub m groups with sp(h) hydridisation (m, n = 1, 2, 3) have all been determined. For a typical hard a-C:H film (plasma deposited at high bias voltage) the result is sp3:sp2:sp1 = 63 : 30 : 2% and CH3 : CH2 : CH = 0 : 40 : 60%. For a typical polymerlike film (plasma deposited at low bias voltage) the result is CH3 : CH2 : CH = 25 : 60 : 15%, indicating frequent side chain termination. Bonding and hydrogen incorporation can be correlated with other properties of a-C:H, like optical gap and density. (IAF)