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.