Ž . Thin Solid Films 389 2001 233238 Optical investigations and Raman scattering characterisation of carbon bonding in hard amorphous hydrogenated carbon films M. Lejeune, O. Durand-Drouhin, J. Henocque, R. Bouzerar, A. Zeinert, M. Benlahsen  Laboratoire de Physique de la Matiere Condensee, Faculte des Sciences d’Amiens, 33 rue Saint Leu, 80039 Amiens Cedex 2, France ` ´ ´ Received 18 August 2000; received in revised form 20 January 2001; accepted 19 February 2001 Abstract Ž . Hydrogenated amorphous carbon films were prepared by plasma enhanced chemical vapour deposition PECVD of Ž . Ž . methane  argon 5% gas mixtures at low pressure, in a dual electron cyclotron resonance ECR -rf glow discharge. Optical Ž . Ž . transmission spectroscopy, Raman spectroscopy, elastic recoil detection analysis ERDA and infra-red IR absorption spectra Ž . were combined to examine the relationship between the local microstructure C H and C C bonds and the optical properties at different negative bias voltage. The amount of bonded H, obtained by IR spectra, is higher in series deposited at low bias voltage, in qualitative agreement with the ERDA results. In all cases, most of the incorporated H is bonded to sp 3 C sites, with a predominance of CH methyl groups. These results are also consistent with the Raman spectroscopy measurements. The 3 positions, widths, and relative intensities of the two characteristic features, the D and G peaks are found to vary systematically Ž . with deposition conditions and film properties. The series prepared at high bias voltage shows a higher disorder D over the Ž . 2 graphitic G band ratio, which also indicates a structure with a high disorder form of Csp sites.  2001 Elsevier Science B.V. All rights reserved. Keywords: Amorphous materials; Optical properties; Raman scattering; Structural properties 1. Introduction Ž . Amorphous hydrogenated carbon a-C:H exhibits a wide range of electronic, optical and mechanical properties based on the proportion of sp 2 and sp 3   carbon bonding and the hydrogen content 1  5 . The properties of a-C:H films are also known to depend strongly upon both the deposition method and the   specific deposition conditions 6  8 . Modelling studies on the film growth and extensive experimental evidence show a direct link between the impact energy during the deposition process and the film microstructure. The  Corresponding author. Tel.: 33-322-82-76-65; fax: 33-322-82- 78-91. Ž E-mail address: benlahsen.mohamed@sc.u-picardie.fr M. Benlah- . sen . interaction of energetic ions with the surface of the growing film affects the hydrogen content and its incor- Ž poration and as a consequence the hybridisation type . of carbon bonding . The hydrogen incorporation de- pends on the amount of energy deposited in the film surface during the film growth, although a full under-   standing of this relationship does not yet exist 9  11 .  In the two phases model of Robertson 2 , the amor- phous carbon consists of sp 2 bonded planar carbon clusters embedded in a randomly oriented tetrahedrally sp 3 bonding matrix. The matrix connectivity largely controls the mechanical properties, while the rings  control the band gap 2 . The dissociation of the species after impact at the surface can produce surface defects and influences   mainly the optical response of the film 6,7 . The cre- ation of defects and ion-inducing disordering of the 0040-609001$ - see front matter  2001 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 0 4 0 - 6 0 9 0 01 00873-2