Nanostructures in various Au ion-implanted ZnO facets modified using energetic O ions

Noble metal nanoparticles dispersed in semiconductors, mainly in ZnO, have been intensively investigated. Au dispersion and possible precipitation as well as damage growth were studied in ZnO of various orientations, a-plane (112[combining macron]0) and c-plane (0001), using 1 MeV Au⁺-ion implantation with an ion fluence of 1.5 × 10¹⁶ cm^-2 and subsequently annealed at 600 °C in an ambient atmosphere for one hour. Afterwards, irradiation with 10 MeV O³⁺ at a fluence of 5 × 10¹⁴ cm^-2 was used to modify Au distribution and internal morphology as well as to follow the structural modification of ZnO under high-energy light-ion irradiation. Rutherford backscattering spectrometry in the channelling mode (RBS-C) and Raman spectroscopy show that O irradiation with high electronic energy transfer distinctly modifies the implanted Au layer in various ZnO facets; it introduces additional displacement and disorder in the O sublattice mainly in the a-plane while not creating an additional strain in this facet. This has been confirmed by XRD analysis, identifying the appearance of an additional phase (nanocrystallites) after Au implantation, which diminishes after O irradiation, and RBS-C has identified decreased disorder in the Zn-sublattice. Unlike in c-plane ZnO, it has been possible to observe a local compressive deformation around spherical defects, which is more pronounced after O irradiation simultaneously with the vertical strain introduced in the Au-implanted and annealed layer. Transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS) was employed to investigate the interior morphology, showing the occurrence of Au-hcp clusters of the small sizes of about 4-10 nm; neither the cluster sizes nor their shapes are significantly affected by the O irradiation.