Modification of structure and surface morphology in various ZnO facets via low fluence gold swift heavy ion irradiation
Abstract
The influence of low fluence high-energy ion irradiation on the modification of the ZnO surface structure and optical properties has been studied. ZnO samples of various orientations, namely, c-plane (0001), a-plane (11-20) and m-plane (10-10), have been implanted with 30-MeV Au ions with fluences ranging from 5 x 10(9) to 5 x 10(11) cm(-2).
Rutherford backscattering spectrometry in the channelling mode (RBS-C) and Raman spectroscopy has shown the distinct damage accumulation in the irradiated surface layer about 1 mu m depending on the ZnO facet being to larger extent evidenced in the m-plane ZnO. Contrary, the a-plane ZnO has been exhibited the lowest Zn disorder.
Using atomic force microscopy (AFM), a complex morphology was detected on the irradiated samples containing grains and exhibiting increased roughness, both growing with the Au implantation fluence mainly in m-plane ZnO. Positron annihilation spectroscopy (PAS) has shown distinct defect accumulation at the Au-ion fluence of 5 x 10(11) cm(-2), where RBS-C and Raman spectroscopy indicated sudden disorder increase in the irradiated layers, probably the creation of more complex clusters of Zn and O vacancies 4VZn + 8VO initiated in connection with an overlap of individual ion impacts.
Photoluminescence measurements have shown a distinct near-band-edge (NBE) luminescence, developing with the increasing Au-ion fluence in various ZnO orientations. The m-plane ZnO had the most progressively suppressed NBE in comparison with the other orientations.