Deactivation of Li by vacancy clusters in ion implanted and flash-annealed ZnO

Li is present in hydrothermally grown ZnO at high concentrations and is known to compensate both n- and p-type doping due to its amphoteric nature. However, Li can be manipulated by annealing and ion implantation in ZnO. Fast, 20ms flash anneals in the 900–1400°C range result in vacancy cluster formation and, simultaneously, a low-resistive layer in the implanted part of the He- and Li-implanted ZnO. The vacancy clusters, involving 3-4 Zn vacancies, trap and deactivate Li, leaving other in-grown donors to determine the electrical properties. Such clusters are not present in sufficient concentrations after longer (1h) anneals because of a relatively low dissociation barrier ∼2.6±0.3eV, so ZnO remains compensated until Li diffuses out after 1250°C anneals.