Visible photoluminescence in ZnO tetrapod and multipod structures

The investigation of the properties of ZnO tetrapod and multipod structures using scanning electron microscopy, X-ray diffraction, photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopy was discussed. The ZnO samples were fabricated by heating a mixture of ZnO, GeO2 and graphite at 1100°C in order to modify the morphology of the fabricated structures. The room temperature of PL was measured by using a HeCd laser excitation source (325 nm). It was found that the green PL was due to transition between a shallow donor and deep acceptor in the absence of g ≈ 1.96 EPR signal and transition between the conduction band and deep acceptor in the absence of g ≈ 1.96 EPR signal.published_or_final_versio

NiOZnO light emitting diodes by solution-based growth

Heterojunction NiOZnO light emitting diodes have been fabricated using low temperature solution-based growth methods. While negligible light emission has been obtained for the as-grown NiO film, devices with annealed NiO film exhibit room-temperature electroluminescence (EL), which was attributed to the detrimental effects of nickel oxide hydroxide in as-grown NiO layers. The device performance can be further modified by insertion of the organic layers between NiO and ZnO and the EL spectra exhibited dependence on the bias voltage. For higher bias voltages, strong UV-violet emission peak can be obtained in spite of the dominance of defect emission in the photoluminescence spectra. © 2008 American Institute of Physics.published_or_final_versio

Change of the emission spectra in organic light-emitting diodes by layer thickness modification

The electroluminescence (EL) and photoluminescence properties of organic light-emitting diodes (LED) were analyzed using layer thickness modification. Investigations show that the EL spectra exhibited significant variation with the increase of the viewing angle. It was found that multiple peak emission could be achieved for a certain range of thickness values. It was concluded that near white emission with CIE coordinates (0.32, 0.43) could be obtained for optimized device thickness.published_or_final_versio

Nitrogen doped-ZnO/n-GaN heterojunctions

Nitrogen-doped ZnO nanorods were prepared by electrodeposition using two different Zn precursors (zinc nitrate and zinc acetate), while all other growth conditions (dopant precursor, concentration, growth temperature, and bias) were identical. We have shown that the precursor used affects the properties of the ZnO nanorods, and that the presence of rectifying properties in n-GaN/N:ZnO heterojunctions is strongly related to the use of nitrate precursor for ZnO growth. The difference in the properties of ZnO obtained from two precursors is attributed to the differences in native defect and impurity concentrations, which could affect the electronic properties of the samples. © 2011 American Institute of Physics.published_or_final_versio

Effect of annealing on the performance of CrO3/ZnO light emitting diodes

Heterojunction CrO3/ZnO light emitting diodes have been fabricated. Their performance was investigated for different annealing temperature for ZnO nanorods. Annealing in oxygen atmosphere had significant influence on carrier concentration in the nanorods, as well as on the emission spectra of the nanorods. Surprisingly, annealing conditions, which yield the lowest band edge-to-defect emission ratio in the photoluminescence spectra, result in the highest band edge-to-defect emission ratio in the electroluminescence spectra. The influence of the native defects on ZnO light emitting diode performance is discussed. © 2009 American Institute of Physics.published_or_final_versio

Topological Homogeneity for Electron Microscopy Images

In this paper, the concept of homogeneity is defined, from a topological perspective, in order to analyze how uniform is the material composition in 2D electron microscopy images. Topological multiresolution parameters are taken into account to obtain better results than classical techniques.Ministerio de Economía y Competitividad MTM2016-81030-PMinisterio de Economía y Competitividad TEC2012-37868-C04-0

Solution-based growth of ZnO nanorods for light-emitting devices: Hydrothermal vs. electrodeposition

ZnO nanorods have been grown by two inexpensive, solution-based, low-temperature methods: hydrothermal growth and electrodeposition. Heterojunction n-ZnO nanorods/p-GaN light-emitting diodes have been studied for different nanorod growth methods and different preparation of the seed layer. We demonstrate that both the nanorod properties and the device performance are strongly dependent on the growth method and seed layer. All the devices exhibit light emission under both forward and reverse bias, and the emission spectra can be tuned by ZnO nanorod deposition conditions. Electrodeposition of rods or a seed layer results in yellow emission, while conventional hydrothermal growth results in violet emission. © The Author(s) 2010. This article is published with open access at Springerlink.com.published_or_final_versionSpringer Open Choice, 01 Dec 201

Gallium vacancy in GaSb studied by positron lifetime spectroscopy and photoluminescence

Positron lifetime technique and photoluminescence (PL) were employed to study the vacancy type defects in p-type Zn-doped and undoped GaSh samples. In the positron lifetime study, Ga vacancy related defect was identified in these materials and it was found to anneal out at temperature of about 350°C. For the PL measurement on the as-grown undoped sample performed at 10 K, a transition peak having a photon energy of about 777 meV was observed. This transition peak was observed to disappear after a 400°C annealing. Our results is consistent with the general belief that the 777 meV transition is related to the V GaGa sb defect, which is the proposed residual acceptor of GaSb.published_or_final_versio

Nitrogen doped-ZnO/n-GaN heterojunctions

Author name used in this publication: Aleksandra B. DjurišičAuthor name used in this publication: Kok Wai CheahAuthor name used in this publication: Chi Chung LingAuthor name used in this publication: Wai Kin ChanAuthor name used in this publication: Patrick W. K. FongAuthor name used in this publication: Hsian Fei Lui2011-2012 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe