Polarity-dependence of the defect formation in <italic>c</italic>-axis oriented ZnO by the irradiation of an 8 MeV proton beam.

The polarity dependence of the radiation hardness of single-crystalline ZnO bulk crystals is studied by irradiating the Zn-polar and O-polar <italic>c</italic>-planes with an 8 MeV proton beam up to the fluence of 4.2 × 1016 p/cm2. To analyze the hardness, radiation-induced defects were evaluated using positron annihilation (PA) analysis, and the recovery by post-annealing was examined using continuous-wave photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurements. It was suggested by the PA and PL analyses that the major defects in both polarities were VZnVO divacancies. While the PA data did not show the clear dependence on the polarity, the PL and TRPL results showed that the Zn-polar <italic>c</italic>-plane had a little higher radiation tolerance than that of the O-polar <italic>c</italic>-plane, which was consistent with the result that the increase in the electrical resistance by proton beam irradiation was smaller for the former one. Considering these results in total, the polarity dependence is considered to be not so large, but the Zn-polar <italic>c</italic>-plane has a little higher tolerance than that of the O-polar one. [ABSTRACT FROM AUTHOR]