Modelling of the sp(3)/sp(2) ratio in ion beam and plasma-deposited carbon films
Model calculations are described which predict the fraction of tetrahedral (sp3) versus graphitic (sp2) bonding in ion beam or plasma-deposited amorphous carbon films on the basis of the preferential displacement of sp2 atoms. Displacement yields obtained from static TRIM simulations are used as input data for a simple analytical growing layer model of ion beam deposition. The sp3/sp2 ratio is found to increase with increasing carbon ion energy between 30 eV and 1 keV. Calculations assuming equal probabilities for a free (implanted or displaced) atom to become trapped at either sp2 or sp3 sites result in sp3/sp2 ratios between 1 and 3.5. More refined dynamic simulations with TRIDYN confirm the trends with slightly lower sp3/sp2 ratios for ion beam or plasma deposition, also involving hydrogen. A decrease of the sp3/sp2 ratio towards high energies cannot be explained by preferential displacement alone, in contrast to proposals in recent literature.
Bibliographic Reference: Article: Applied Physics Letters, Vol. 59 (1991) No. 19, pp. 2391-2393
Record Number: 199210207 / Last updated on: 1994-12-02
Original language: en
Available languages: en