Extended-Defect-Related Photoluminescence Line at 3.33 eV in Nanostructured ZnO Thin Films

Abstract

International audienceThe 3.33 eV photoluminescence line is investigated in ZnO thin films deposited by dip coating. These films are oriented along the c-axis and exhibit basal-plane stacking faults and random grain boundaries. It is found that the relative intensity of the free exciton peak to the 3.33 eV line decreases as the nanoparticle size is reduced and that the corresponding Huang-Rhys factor is about 0.5. This reveals that excitons bound to extended defects at grain boundaries are involved. Also, post growth annealing strongly affects the photoluminescence spectra. In particular, the 3.31 eV line coming from stacking faults is enhanced at high annealing temperatur

The effect of silver oxidation on the photocatalytic activity of Ag/ZnO hybrid plasmonic/metal-oxide nanostructures under visible light and in the dark

“…The emission peak at 364 nm originates from a direct recombination of free excitons (FEs), while the emission peak at 378 nm is related to bound excitons (BEs) 44 . This recombination feature, which is caused by BEs, has been observed previously but its origin is still unknown 45–48 . It has been ascribed to different BEs from crystal defects such as donor BEs 49,50 , acceptor BEs 51 , and excitons bound to extended structural defects 46,52 .…”

The high temperature photoluminescence and optical absorption of undoped ZnO single crystals and thin films

“…The phonon emission is assumed to be represented by a Gaussian distribution shape with a variance r n . In the case of ZnO, the Huang-Rhys factor is rather small, 15 but the spectra cannot be represented by a symmetric shape. Moreover, Figure 6 shows that near room temperature the phonon side bands are barely observable and fitting with Eq.…”

“…6 The band edge transition has been analyzed as a function of doping in ZnO single crystals and thin films as well as nanostructures. [8][9][10][11][12][13][14][15] Other minor peaks have been associated with bound exciton transitions and impurities. 14,15 However, with increasing temperature, the probability of ionizing donor impurities increases and the spectral shape of ZnO become dominated by free exciton transitions.…”

“…[8][9][10][11][12][13][14][15] Other minor peaks have been associated with bound exciton transitions and impurities. 14,15 However, with increasing temperature, the probability of ionizing donor impurities increases and the spectral shape of ZnO become dominated by free exciton transitions. 1,16 The optical transition, however, has multi-phonon side bands.…”

Reversible quenching of luminescence in ZnO films by electric field action

“…A model in which one of the charge carriers is more weakly bound to the extended donor complex has been proposed to elucidate this phenomenon . However, this model cannot explain the change of the activation energy when films are annealed in different atmospheres . PL measurement under an electric field is a useful technique in understanding the optical and electronic properties of the material, both fundamental properties and those of defects.…”