Optical detection of electron paramagnetic resonance for intrinsic defects produced in ZnO by 2.5-MeV electron irradiation in situ at 4.2 K

摘要

Intrinsic defects produced in ZnO by 2.5-MeV electron irradiation in situ at 4.2 K are studied by optical detection of electron paramagnetic resonance (ODEPR). Observed in the photoluminescence (PL) are ODEPR signals, which are identified with the oxygen vacancy, V_O~+, interstitial zinc, Zn_i~+, and zinc-vacancy-zinc-interstitial Frenkel pairs. The Frenkel pairs are primarily observed in their S = 1 exchange-coupled state, supplying strong evidence that interstitial zinc is a shallow effective mass double donor in ZnO. Annealing stages at ～65-119 K and ～145-170 K are observed for the defects associated with the zinc sublattice and are identified with the migration of interstitial zinc. Although interstitial' oxygen is not observed in the ODEPR, a higher-temperature annealing stage observed in the PL at ～160-230 K is tentatively identified with the onset of its migration. The oxygen vacancy is stable to ～400℃. The relationship between the spin-dependent processes producing the ODEPR signals and the PL of the material remains unclear.