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Implanted atoms can affect the evolution of ion-induced defects in radiation hard materials exhibiting a high dynamic annealing and these processes are poorly understood. Here, we study the thermal evolution of structural defects in wurtzite ZnO samples implanted at room temperature with a wide range of ion species (from 11B to 209Bi) to ion doses up to 2 × 1016 cm−2. The structural disorder was characterized by a combination of Rutherford backscattering spectrometry, nuclear reaction analysis, and transmission electron microscopy, while secondary ion mass spectrometry was used to monitor the behavior of both the implanted elements and residual impurities, such as Li. The results show that the damage formation and its thermal evolution strongly depend on the ion species. In particular, for F implanted samples, a strong out-diffusion of the implanted ions results in an efficient crystal recovery already at 600 °C, while co-implantation with B (via BF2) ions suppresses both the F out-diffusion and the lattice recovery at such low temperatures. The damage produced by heavy ions (such as Cd, Au, and Bi) exhibits a two-stage annealing behavior where efficient removal of point defects and small defect clusters occurs at temperatures ∼500 °C, while the second stage is characterized by a gradual and partial annealing of extended defects. These defects can persist even after treatment at 900 °C. In contrast, the defects produced by light and medium mass ions (O, B, and Zn) exhibit a more gradual annealing with increasing temperature without distinct stages. In addition, effects of the implanted species may lead to a nontrivial defect evolution during the annealing, with N, Ag, and Er as prime examples. In general, the obtained results are interpreted in terms of formation of different dopant-defect complexes and their thermal stability.

Electronic properties of defects induced by mechanical polishing in hydrothermally grown n-type ZnO have been investigated by capacitance versus voltage measurements and deep level transient spectroscopy (DLTS). The DLTS measurements have been performed in the temperature range 80-600 K enabling exploration of deep-level states in the vicinity of the middle of the energy bandgap. The results show that mechanical polishing forms defects in the near surface region which strongly compensate and/or passivate the dominant shallow donors. Two pronounced polishing-induced defects are revealed with energy level positions around 1.0 eV and 1.2 eV below the conduction band edge. These levels are assigned to vacancy-related defect centers and substantially reduced in strength by post-polishing etching in diluted hydrofluoric acid.

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