Formation of D–VZn complex defects and possible p-type conductivity of ZnO nanoparticle via hydrogen adsorption

Abstract

The hydrogen adsorption on surfaces and on defect sites of ZnO nanoparticles (NPs) has been studied by using Raman and Fourier transform infrared spectroscopic methods. The presence of hydrogen at defect sites bound to zinc vacancy with different coordinations has been confirmed. To further identify the existence of isolated VZn and H–VZn complexes in the ZnO NPs, coincidence Doppler broadening (CDB) spectroscopic studies have been performed with respect to the CDB spectra of a 99.9999% pure Al single crystal. The broad momentum dip ρL showed between 15–17 × 10−3 m0c suggests the trapping of positrons with the core electrons of 3p Zn. However, positron annihilation takes place between ρL 20–25 × 10−3 m0c and this may occur with an electron belonging to OH bonds (VZn–Hi–O). Here the lattice hydrogen H+ ion acts as a compensating centre, and it can bind with the VZn around the dislocation and stacking faults (SFs) core, which may produce the acceptor-type complex defect for p-type conductivity. Finally, the existence of SFs and dislocation defects, including edges and steps, was confirmed by transmission electron microscopy.