Disorder induced violet/blue luminescence in rf‐deposited ZnO films

Abstract

In this work ZnO thin films were deposited on different substrates, glass, silicon (100), and MgO (100) using rf‐magnetron sputtering at low temperature in order to promote a large defect density, aiming to study a possible correlation with the observed violet/blue emission band. The peak position, width and low energy band shape asymmetry of the violet/blue band was found to be dependent on the deposition temperature and oxygen partial pressure. The structural analysis of deposited films reveals an epitaxial relationship for the a ‐oriented ZnO/MgO while for the c ‐oriented ZnO/Si no epitaxial relation was found with the substrate. The dependence of the violet/blue band on temperature displays always a shift of the peak position to lower energies, discarding the hypothesis of a free to bound transition. The sublinear dependence of the emission intensity with the excitation intensity suggests that the violet/blue bands on both samples could have a donor‐acceptor pair nature. However, the unusually strong shift of the peak position to lower energies for the ZnO/MgO films and the emphasised asymmetric band shape for the ZnO/Si samples suggest that potential fluctuations in the electronic bands, due to disorder induced charged defects, could also be considered as an alternative recombination model for the violet/blue band. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Structural, Optical Constants and Photoluminescence of ZnO Thin Films Grown by Sol-Gel Spin Coating

“…S2 shows three bands peaked at around 398 nm, 520 nm, and 730 nm. The violet/blue at 398 nm could be attributed to donoracceptor pair transition [30], and the green emission centered at about 520 nm is attributed to transition from conduction band to oxygen antisite level. The broad band centered at around 730 nm with a full width at half maximum (FWHM) of about 155.5 nm might be due to transition from conduction band to oxygen vacancy level; we refer to Figure 13.…”

“…using CW He-Cd laser with power up to 1 W/cm 2 and at high excitation regime using pulsed third harmonic Nd:YAG laser with power up to 1.3 MW/cm 2 . The photoluminescence intensity PL is related to the excitation intensity I 0 through [30,31]…”

Temperature-dependent photoluminescence and Raman investigation of Cu-incorporated ZnO nanorods

“…Except for doping, disorder can also introduce violet/blue emission into ZnO [26,27]. Peres et al have deposited ZnO films on different substrates to promote a large defect density, and found that violet/ blue emission was related to the defects and disorder in the ZnO films [26]. In this study, we incorporate Cu into ZnO nanorod by hydrothermal method.…”

“…Xu et al studied the PL properties of Cu-doped ZnO nanowires and observed broad structured emission band ranging from 370 to 650 nm [25]. Except for doping, disorder can also introduce violet/blue emission into ZnO [26,27]. Peres et al have deposited ZnO films on different substrates to promote a large defect density, and found that violet/ blue emission was related to the defects and disorder in the ZnO films [26].…”

One-Step Synthesis, Structural and Optical Characterization of Self-Assembled ZnO Nanoparticle Clusters with Quench-Induced Defects

“…5), associated with interface trap in the grain boundaries, 52 and dislocations. 53 Also, the coexistence of interstitial sites with different energy configurations such as isolated or split interstitials is highly possible, which can result in closely spaced energy levels. 54 Considering the area under the peaks, it can be observed from…”