Enhancement of the Ultraviolet Luminescence Intensity from Cd-Doped ZnO Films Caused by Exciton Binding

Abstract

ZnO films doped with the cadmium (0.4-0.6%) were grown on crystalline sapphire c-Al 2 O 3 substrates applying radiofrequency magnetron sputtering at the temperature of 400• C in Ar-O 2 atmosphere. The as-grown films were investigated in detail using X-ray diffraction, X-ray photoelectron spectroscopy, and cathodoluminescence spectra. The X-ray diffraction analysis revealed that the films possess a hexagonal wurtzite-type structure with the dominant crystallite orientation along the c axis. It was found that the small concentration of the cadmium significantly enhances the ultraviolet emission associated with excitonic transitions. We suggest that this enhancement effect mainly results from appearance of the cadmium isoelectronic traps, which may bind an exciton, thereby increasing the probability of radiation recombination. The effect of Cd isoelectronic impurity on structural and luminescent properties of ZnO films is discussed.

Swift Xe26+Ion Irradiation Effect on Luminescent Properties of Undoped and Cd-Doped ZnO Films

“…The analysis of CL spectra of as-grown samples was discussed in our previous work [5]. Figure 1 illustrates the CL spectra of as-grown and irradiated undoped and Cd-doped ZnO lms.…”

“…In this study we report the use of cathodoluminescence The doping by isoelectronic impurities can signicantly increase the chances of applications [5,6]. In particular, it was found that the small concentration of the cadmium (0.4 at.%) signicantly enhances the ultraviolet emission associated with excitonic transitions.…”

“…In particular, it was found that the small concentration of the cadmium (0.4 at.%) signicantly enhances the ultraviolet emission associated with excitonic transitions. The enhancement eect mainly results from an appearance of the cadmium isoelectronic traps, which may bind an exciton, thereby increasing the probability of radiation recombination [5].…”

Effect of Se Isoelectronic Impurity on the Luminescence Features of the ZnO

“…Powder targets (pressured mixture of the zinc and selenium oxides) were used for the sputtering process. The atomic concentration of Se concentration varied from 0.6 to 0.8 at.% and was determined from the X-ray photoelectron spectroscopy (XPS) peak intensities, similarly to approach, which was presented in [6]. XPS spectra were collected by means of the UHV-Analysis--System SPECS (Germany).…”

“…In this case, the quantum eciency can be increased up to 1540%. Recently, we have already investigated the eect of the cadmium isoelectronic impurity on the properties of ZnO thin lms and have revealed that the Cd content of 0.4 at.% leads to an increase of the luminescence eciency [6]. Earlier, it was established that the substitution of a small fraction of the anion atoms with an isoelectronic element of distinctly dierent electronegativity and/or size leads to * corresponding author; e-mail: V.Khomyak@chnu.edu.ua a dramatic enhancement of the high radiative recombination eciency [7,8].…”