ENERGY DEPOSITIONS OF PROTONS IN ALLOTROPIC CARBON ULTRATHIN FILMS

We present the effects of structure, chemical binding, and number of l ayers on stopping for clean, unreconstructed diamond (100) one- to fou r-layer films with lattice constants fixed at crystalline values, and for graphite mono- and dilayers at their optimized bond lengths. First Born approximation stopping cross sections for protons incident norma lly on the films were obtained from orbital versions of the kinetic th eory of stopping and of the local plasma approximation. The required e lectron momentum density was generated from the real space Kohn-Sham o rbitals. We find a strong static quantum size effect in the stopping o f diamond ultra-thin films as opposed to graphite, for which the stopp ing is only very weakly dependent on the layer number. (C) 1994 John W iley & Sons, Inc.