Subplantation model for film growth from hyperthermal species.

Abstract

A model describing film growth from hyperthermal (\ensuremath{\sim}1--${10}^{3}$ eV) species impinging on substrates is presented. The model involves a shallow subsurface implantation process called ``subplantation,'' energy loss, preferential displacement of atoms with low displacement energy ${\mathit{E}}_{\mathit{d}}$, leaving the high-${\mathit{E}}_{\mathit{d}}$ atoms intact, sputtering of substrate material, and inclusion of a new phase due to incorporation of a high density of interstitials in a host matrix. Epitaxial or preferred orientation may result from the angular dependence of the ${\mathit{E}}_{\mathit{d}}$ and the boundary conditions imposed by the host matrix, i.e., the ``mold'' effect. The discussion focuses on deposition of carbon diamondlike films, but examples of other systems, such as Si, Ge, and Ag, are provided as well. The model is supported by classical-ion-trajectory calculations and experimental data. The calculations probe the role of ion range, local concentration, backscattering coefficient, sputtering yield, and ion-induced damage in film evolution. The experimental data emphasize in situ surface-analysis studies of film evolution. The physical parameters of the deposition process that are treated are as follows: (i) nature of bombarding species (${\mathrm{C}}^{+}$ versus ${\mathrm{C}}^{\mathrm{\ensuremath{-}}}$, ${\mathrm{C}}^{\mathrm{\ensuremath{-}}}$ versus ${\mathrm{C}}_{2}^{\mathrm{\ensuremath{-}}}$, ${\mathrm{C}}_{\mathit{n}}$${\mathrm{H}}_{\mathit{m}}^{+}$, ${\mathrm{Ar}}^{+}$, and ${\mathrm{H}}^{+}$), (ii) ion energy, (iii) type of substrate, and (iv) substrate temperature during deposition.