Assessment of subsurface damage in polished II–VI semiconductors by ion channeling

Surfaces of bulk single crystal CdS, ZnSe and ZnO were prepared by mechanical polishing with 1 and 1/4 μm diamond abrasive slurries and by chemomechanical polishing with sodium hypochlorite:colloidal silica. Etched surfaces, indicative of original crystalline quality were also prepared. Near surface damage was investigated by ion channeling with He ions using incident beam energies of 2 and 5 MeV and detector positions of 75° and 13°. Damage depths were found to be significantly higher for ZnSe when compared to CdS or ZnO. The chemomechanical polishing process was seen to introduce small but measurable subsurface damage in CdS and ZnSe. However, channeling was unable to detect any damage for the chemomechanically polished ZnO surfaces, a result which was supported by cross-section transmission electron microscopy (XTEM). The presence of damage beyond that identified by the surface peak for the mechanically polished ZnSe surfaces was indicated by the dechanneling behavior below the surface.