Dry etching of bulk single-crystal ZnO in CH4/H2-based plasma chemistries

The effect of inert gas additive (He, Ar, Xe) to CH4/H2 discharges for dry etching of single crystal ZnO was examined. The etch rates were higher with Ar or Xe addition, compared to He but in all cases the CH4/H2-based mixtures showed little or no enhancement over pure physical sputtering under the same conditions. The etched surface morphologies were smooth, independent of the inert gas additive species and the Zn/O ratio in the near-surface region decreases as the mass number of the additive species increases, suggesting preferential sputtering of O. The plasma etching improved the band-edge photoluminescence intensity from the ZnO for the range of ion energies used here (290-355 eV), due possibly to removal of surface contamination layer.