Ž . Diamond and Related Materials 10 2001 993997 Electron paramagnetic resonance study of ion implantation induced defects in amorphous hydrogenated carbon B.J. Jones a,  , R.C. Barklie a , R.U.A. Khan b , J.D. Carey b , S.R.P. Silva b a Physics Department, Trinity College, Dublin 2, Ireland b School of Electronic Engineering, I.T. and Mathematics, Uni  ersity of Surrey, Guildford, GU2 7XH, UK Abstract Ž . Ž . Electron paramagnetic resonance EPR measurements have been made of defects in amorphous hydrogenated carbon a-C:H thin films. The films were grown on silicon substrates on the earthed electrode of an rf-powered plasma enhanced chemical vapour deposition reactor and were subsequently implanted with a range of doses of boron, carbon or nitrogen ions with energies Ž. from 20 keV to 32.5 keV. Two paramagnetic centres are observed, the carbon defect in the film with g 2.0028 1 and a silicon Ž. defect in the substrate with g 2.0058 6 . The volume concentration of the carbon defect increases approximately linearly with dose, from approximately 3 10 17 cm 3 for unimplanted samples to 2.7 10 20 cm 3 at the highest implantation of 2 10 16 B  2 Ž . ions cm . The increase in dose over this range also causes a narrowing of the EPR line from 0.83 mT to 0.13 mT and a Ž 5 8 . significant decrease in the spin-lattice relaxation time from 3 10 s to 6 10 s which approaches the spin  spin relaxation time at the highest dose. The narrowing is attributed to motional averaging produced by either exchange or hopping. We also report the effects of annealing samples implanted with a range of boron doses. The prime novelty of this paper is that it is the first EPR study of defects produced by the implantation of a range of ions into polymer-like amorphous hydrogenated carbon.  2001 Elsevier Science B.V. All rights reserved. Keywords: Amorphous hydrogenated carbon; Defect; Ion implantation; Annealing 1. Introduction The unimplanted material under study in this work is Ž . ‘polymer-like’ amorphous carbon PAC , one of the many different forms of hydrogenated amorphous car- Ž . bon a-C:H that can be prepared. This has a high Ž . hydrogen content  50 at.% , a wide band gap, a high sp 3 content and a strong room temperature photolumi-   nescence 1  3 , which probably reflects the compara-  Corresponding author. Tel.: 353-1-6081988; fax: 353-1- 6711759. Ž . E-mail address: bjones@tcd.ie B.J. Jones . tively low unpaired spin density of the order of 10 17 3  cm 4 in this type of carbon film. Ion implantation is one method by which ion species can be added to the film. Utilising this method enables the controlled addi- tion of a known quantity and distribution of ions; further advantages are the lack of significant alloying of   the material and the wide range of possible ions 5,6 .   In previous works 6,7 measurements were made of the optical band gap, conductivity, hydrogen content and refractive index of ion implanted PAC films. In this Ž . paper we use electron paramagnetic resonance EPR to study for the first time the effect of varying implan- tation dose on the population and nature of defects in PAC films, including measurements of the relaxation 0925-963501$ - see front matter  2001 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 9 2 5 - 9 6 3 5 00 00364-2