Investigation of zinc vacancies and their influence on N and Li related defect complexes in hydrothermal ZnO

Abstract

Hydrothermal ZnO samples having lithium concentration in the range of $3 \times 10^{14}$ -- $1 \times 10^{17}$\,Li/cm$^{3}$ were implanted with nitrogen. The variation of Li concentration was done by high temperature pre-anneals and controlled by secondary-ion mass spectrometry (SIMS). The efficiency of zinc vacancy clustering after ion implantation and post-implantation anneals was monitored by positron annihilation spectroscopy (PAS). It was found that the presence of Li enhances clustering of zinc vacancies considerably. In addition the resistivity evolution was monitored by scanning spreading resistance microscopy, and in combination with PAS, the results indicate the presence of a Li--N related doubly negative complex emerging at 800\,$^\circ$C. SIMS has also revealed the presence of additional processing induced defects acting as a Li traps with much lower diffusivity than un-trapped Li.