Effect of high-density plasma etching on the optical properties and surface stoichiometry of ZnO

Abstract

Bulk, single-crystalZnO was etched in Cl 2 / Ar and CH 4 / H 2 / Ar inductively coupled plasmas as a function of ion impact energy. For CH 4 / H 2 / Ar , the etch rate (R) increases with ion energy (E) as predicted from a model of ion enhanced sputtering by a collision–cascade process, R∝(E 0.5 −E TH 0.5 ), where the threshold energy, E TH , is ∼96 eV . Band edge photoluminescence intensity decreases with incident ion energy in both chemistries, with a 70% decrease even for low energies (∼116 eV ). Surface roughness is also a function of ion energy with a minimum at ∼250 eV , where Auger electron spectroscopy shows there is no measurable change in near-surface stoichiometry from that of unetched control samples.