Radiation induced modification in nanoscale hardness of ZnO cone structures

In this paper, the effect of ion irradiation on nanoscale hardness of ZnO microcones is reported. The hardness of ZnO cones determined by nanoindentation using atomic force microscope initially increases from 4.7 +/- 1.4 to 9.5 +/- 1.6 GPa after irradiation with 1.2 MeV Ar(+8) ions at an ion fluence of 10(15) ions cm(-2) and then decreases with increasing ion fluence. This change in mechanical hardness has been correlated with the residual stress of the sample revealed by Raman peak shift in the E(2)(H) mode. These results show that the generally reported radiation-hard nature of ZnO depends critically on irradiation conditions, especially the irradiation temperature. (c) 2010 American Institute of Physics. [doi:10.1063/1.3482026]