Defect emissions in ZnO nanostructures

Abstract

Defects in three different types of ZnO nanostructures before and after annealing under different conditions were studied. The annealing atmosphere and temperature were found to strongly affect the yellow and orange-red defect emissions, while green emission was not significantly affected by annealing. The defect emissions exhibited a strong dependence on the temperature and excitation wavelength, with some defect emissions observable only at low temperatures and for certain excitation wavelengths. The yellow emission in samples prepared by a hydrothermal method is likely due to the presence of OH groups, instead of the commonly assumed interstitial oxygen defect. The green and orange-red emissions are likely due to donor acceptor transitions involving defect complexes, which likely include zinc vacancy complexes in the case of orange-red emissions.

ZnO nanorod/GaN light-emitting diodes: The origin of yellow and violet emission bands under reverse and forward bias

“…The broad long wavelength emission is typically attributed to the defect emission in ZnO based on comparisons with the PL spectra 4,14 since ZnO commonly exhibits broad visible emissions due to native defects. 44 However, while the exact peak positions for yellow/orange emission, blue emission, and UV EL emission differ for devices with ZnO and with Ag, we can clearly observe that emissions absent in the PL spectrum of P1-P3 (Ref. 37) can occur in absence of ZnO.…”

Defects induced luminescence and tuning of bandgap energy narrowing in ZnO nanoparticles doped with Li ions

“…5,11 The yellow emission (550-650 nm) for undoped ZnO can be due to the Zn(OH) 2 or OH group. 46,52 The peak "f" observed at 615 nm in our ZnO sample corresponds to yellow emission. The yellow luminescence in doped nanoparticles can be due to both Li Zn and Li i defects.…”

Carrier recombination in sonochemically synthesized ZnO powders

“…It is quite obvious that the observed changes are due to complicated defect chemistry relevant to the sonochemical processing. As reported in the literature [1,10,[27][28][29], room-temperature PL of ZnO can exhibit one emission peak in the UV region which is due to the recombination of free excitons, and one or more peaks in the visible region. The latter ones are commonly associated with the defectrelated emissions, such that the defect properties strongly affect optical spectra of ZnO.…”

“…ZnO is a wide band gap semiconductor with a high exciton binding energy which attracts considerable scientific and applied interest with respect to exploiting its optical properties [1][2][3][4][5]. For example, high thermal and chemical stability, simple tunability of the optical and electrical properties are widely applicable in optoelectronic devices [6,7].…”