Transmission Electron Microscopy of Surface Damages Resulting from Wet Polishing in a Polycrystalline Aluminum Nitride Substrate

AlN polycrystalline specimens were wet-polished with Al2O3 and Cr2O3 abrasives. A flat surface with a roughness of 100nm was achieved, while the surface layer was heavily damaged. High-voltage electron microscopy revealed that the damaged and/or dislocated layer was about 0.5μm thick and a few dislocations propagated deeper. The source of dislocation such as free surface and grain boundary was discussed.