The Role of Ions for the Deposition of Hydrocarbon Films, investigated by In-Situ Ellipsometry
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their kinetic energy to the adsorbed species to overcome the activation barrier for a new chemical bond. The temperature dependence of this coverage leads to a temperature dependent growth by incorporated neutral species. In a combined modelling for the surface and the plasma good agreement is achieved with the measurement of deposition rates and the measurement of CHdensities by laser induced fluorescence (LIF) [11]. However this model has been contradicted by recent experiments: The temperature dependence of the net deposition rate is due to a temperature dependent erosion by atomic hydrogen [12,13]. This temperature dependent erosion step has been neglected for simplicity in the modelling by an 'adsorbed layer'. Based on these new results it is not necessary to postulate an 'adsorbed layer' of radicals on the growing C:H-film to describe the temperature dependence of the measured total growth rate. If we assume that this adsorbed layer does not exist, the synergetic effect between ions and neutrals on the growing film may be modelled alternatively by the creation of 'activated sites' on the film surface: The impinging ions create in a first step dangling bonds on the growing film by the displacement of bonded hydrogen. In a second step neutral species immediately chemisorb at these 'activated surface sites'. The film properties are strongly dependent on the ion energy during deposition. Hard carbon films with a low hydrogen content are deposited using high ion energies (>100 eV) and soft polymer-like films with a large hydrogen content are deposited using low ion energies (
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