Plasma Deposition of Diamond at Low Pressures: A Review

Abstract

Plasma deposition techniques of nanocrystalline and microcrystalline diamond and related mechanisms at pressures below 0.1 torr are reviewed. The mechanism of nucleation and growth of diamond in low-pressure conditions is discussed theoretically and experimentally along with the role of radicals and ions in two different ion-energy ranges. For ion impact energies below 20-30 eV, diamond deposition occurs on a surface. The growth process is limited by the substrate temperature and the flux of hydrogen radicals when the ion energy is reduced enough to several eV as shown by a kinetic rate analysis for radical species. The nucleation process is limited mainly by the degree of carbon saturation and, hence, the flux of carboncontaining species. For ion impact energies above 20-30 eV, diamond deposition occurs beneath a surface. Renucleation hinders the growth and diamond nanocrystals are embedded in an amorphous carbon matrix. The nucleation process depends strongly upon the ion energy, ion-to-depositing flux ratio, and substrate temperature as shown by the film density increment based on the subplantation model.Index Terms-Amorphous carbon, chemical vapor deposition (CVD), diamond-like carbon (DLC), epitaxy, hydrogen, ion bombardment, nanocrystalline diamond, nanodiamond, physical vapor deposition (PVD), plasma diagnostics, subplantation. 0093-3813

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