Defect evolution on the optical properties of H⁺-implanted ZnO whiskers

The interplay of intentionally doped H impurity with native defects as well as its influence on the microstructure and optical properties of ZnO whiskers was systematically studied by varying the H⁺ implantation fluencies from 1 × 10¹⁴ to 1 × 10¹⁶ ions cm ^-2. Higher dose of H⁺ implantation resulted in the serious deterioration of the crystallinity and introduction of more nonradiative V _O and Zn_i defects in the energy gap, as revealed by the X-ray diffraction (XRD), absorption spectra, Raman scattering, photoluminescence and electronic paramagnetic resonance (EPR) measurements. We demonstrate that H passivation of oxygen vacancies is in terms of forming V+0 defects rather than H+0 while deactivation of zinc vacancy related acceptor defects is through the process of hydrogen filling. The V+0 and ionized Zn_i defects are suggested to give rise to the H⁺-implantation induced blue band optical absorption.