Search query: ZnO— nanostructures, defects, and devices Mater

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abstract: Zinc oxide and related compound semiconductors (CdO, MgO) have drawn considerable interest in recent years due to their suitability for visible and UV light emitters and detectors, as well as for high temperature electronics. This volume, first published in 2007, brings together researchers and technologists from academia, industry and government laboratories around the world, all working in various aspects of ZnO and related materials. In addition to fundamental materials science issues, the volume focuses on device design, processing, and technology of photonic and electronic devices including light emitting diodes and gas, chemical and biosensors. Topics include: devices; defects; spintronics and magnetism; growth; optical properties and nanostructures; doping and processing TFTs.
author_names: Jurgen Christen

Related Materials
title: Zinc oxide and related materials symposium held November 27 30, 2006, Boston, Massachusetts, U.S.A.
year: 2007

abstract: ZnO has received much attention over the past few years because it has a wide range of properties that depend on doping, including a range of conductivity from metallic to insulating (including n type and p type conductivity) high transparency, piezoelectricity, wide bandgap semiconductivity, room temperature ferromagnetism, and huge magneto optic and chemical sensing effects. Without much effort, it can be grown in many different nanoscale forms, thus allowing various novel devices to be achieved. We review recent studies of ZnO nanostructures, fabrication, novel device applications, and its potential as an electron acceptor material in hybrid solar cells. Control of its rich defect chemistry, which is critical for controlling properties but has not been widely addressed in the context of novel applications, is also discussed.
author_names: Lukas Schmidt-Mende

Judith L MacManus-Driscoll
title: ZnO nanostructures, defects, and devices
year: 2007

abstract: The interest in ZnO structures has increased drastically in recent years. Intense research by many different groups has focused on novel nanostructures with different shapes ranging from nanowires to nanobelts and even nanosprings. The number of reviews on ZnO is increasing (see for example1 9) The topic of p doping is especially difficult and has been investigated by different groups10 13. ZnO is a direct wide bandgap ~3.3 eV)2 material with a large exciton binding energy of 60 meV. This makes it interesting as a laser material based on exciton recombination at room temperature or even higher. Such a large amount of research on ZnO nanomaterials makes it hard to summarize the work in a systematic way. In this article, we first describe different synthesis routes toward a large variety of nanostructures. The first approach is chemical vapor deposition; certainly one of the most common routes for the synthesis of nanowires, nanobelts, nanosprings, and nanorings. Aqueous solution growth has also attracted great interest. This method allows growth of nanowires and other nanostructures at low temperatures. We describe this method in some detail. Similar to aqueous solution growth, electrodeposition of ZnO nanocolumns can be performed at low temperatures, and this is also briefly described. A very important issue is the doping of ZnO nanowires. We give an introduction into the defect states of ZnO and describe different examples where doping of ZnO nanowires and thin films has been performed. The last section focuses on applications of ZnO nanowires. We describe their use as sensors and cantilevers, as well as their ZnO has received much attention over the past few years because it has a wide range of properties that depend on doping, including a range of conductivity from metallic to insulating (including n type and p type conductivity) high transparency, piezoelectricity, wide bandgap semiconductivity, room temperature ferromagnetism, and huge magnetooptic and chemical sensing effects. Without much effort, it can be grown in many different nanoscale forms, thus allowing various novel devices to be achieved. We review recent studies of ZnO nanostructures, fabrication, novel device applications, and its potential as an electronacceptor material in hybrid solar cells. Control of its rich defect chemistry, which is critical for controlling properties but has not been widely addressed in the context of novel applications, is also discussed.
author_names: Lukas Schmidt-Mende

Judith L MacManus-Driscoll
title: ZnO nanostructures defects and devices REVIEW
year: 2007

abstract: Abstract The significant effect of electrically active defects present in the device, which limits the carrier mobility, generated due to cobalt doping via the co precipitation technique in a ZnO matrix, has been investigated on the basis of its structural, optical and charge transient behaviours. The variations observed in the absorbance and extinction coefficients as a function of wave length reveal the presence of defect states, a range of localized states and structural disorder. The presence of a non uniform trap centre density in the material has been measured on the basis of different operational modes in charge deep level transient spectroscopic analysis. A disparity of such a kind in the structures at the nanoscale will provide for a remarkable approach to improve the performance and reliability of the smart electronic, optoelectronics, photonics and sensing devices.
author_names: Amir Zia

S Ahmed

M Umair Ali
title: Defects anomaly in cobalt doped ZnO nanostructures using optical and charge transient analysis
venue: Chinese Journal of Physics
year: 2019

abstract: Zinc oxide (ZnO) nanostructures were synthesized in the form of nanoparticles, nanoflowers and nanourchins. Structural, electronic and optical characterization of the samples was performed via standard techniques such as X ray diffraction (XRD) scanning electron microscopy (SEM) photoluminescence, Raman and ultraviolet visible (UV Vis) spectroscopy. Point defect structures which are specific to each morphology have been investigated in terms of their concentration and location via state of the art electron paramagnetic resonance (EPR) spectroscopy. According to the core shell model, all the samples revealed core defects; however, the defects on the surface are smeared out. Finally, all three morphologies have been tested as electrode materials in a real supercapacitor device and the performance of the device, in particular, the specific capacitance and the storage mechanism, has been mediated by the point defects. Morphology dependent defective ZnO electrodes enable the monitoring of the working principle of the supercapacitor device ranging from electric double layer capacitors (EDLC) to pseudo supercapacitors.
author_names: Sumaiyah Najib

Feray Bakan

Nazrin Abdullayeva

Rahim Bahariqushchi

Sibel Kasap

G Franzo

Mehmet Sankir

Nurdan Demirci Sankir

Salvo Mirabella

Emre Erdem
title: Tailoring morphology to control defect structures in ZnO electrodes for high performance supercapacitor devices.
venue: Nanoscale
year: 2020

abstract: One dimensional (1D) ZnO nanostructures have shown great potential in electronics, optoelectronics and electromechanical devices owing to their unique physical and chemical properties. Most of these nanostructures were grown by equilibrium processes where the defects density is controlled by thermodynamic equilibrium. In this work, flash sintering, a non equilibrium field assisted processing method, has been used to synthesize ZnO nanostructures. By applying a high electric field and limiting a low current flow, ZnO nanorods grew uniformly by a vapor liquid solid mechanism due to the extreme temperatures achieved near the hot spot. A high density of basal stacking faults in the nanorods along with ultraviolet excitonic emission and a yellow red emission under room temperature demonstrate the potential of defect engineering in nanostructures via the field assisted growth method.
author_names: Xin Li Phuah

Jaehun Cho

Akriti Akriti

Letian Dou

Wolfgang Rheinheimer

Edwin R Garcia

Xingtong Zhang

Haiyan Wang
title: Field assisted growth of one dimensional ZnO nanostructures with high defect density.
venue: Nanotechnology
year: 2020

abstract: Abstract The observation of feeble ferroelectricity and giant piezoelectricity in doped II VI ZnO binary semiconductor has inspired a great deal of research interest, which could pave the way to reduce the toxic effects on the environment, and to develop small molecule ferroelectrics and flexible piezoelectric nanogenerator. The main challenge for practical application of the ZnO is the attainment of a high Curie temperature to be compatible with junction temperatures. This review focuses primarily on the piezoelectric and ferroelectric properties of zinc oxide (ZnO) nanostructures. One of the desirable outcomes is to provide a useful insight into various processes which may induce ferroelectricity and enhance piezoelectricity in non ferroelectric and weak piezoelectric ZnO. Taking into consideration the recent progress in this area, topics such as local switchable polarization, effects of defects, ionic charge of the dopant and ionic size of the dopant, and their contributions to piezoelectric and ferroelectric properties of ZnO are discussed. A critical review of the question dealing with the origin of ferroelectricity in ZnO is given. In a similar vein, methods for enhancing piezoelectric coefficient of ZnO are briefly discussed, followed by their applications in potential devices. From this review, it can be concluded that ZnO (a lead free and biocompatible material) on being doped with suitable dopants show king sized piezoelectric response and feeble ferroelectric response, which possibly make ZnO an attractive alternative to lead based perovskites for specific applications. This subject is of current interest to various scientists worldwide and hence, motivated us to write a review article with an aim that it would give further momentum to the scientists already working in this field.
author_names: Sahil Goel

Binay Kumar
title: A review on piezo /ferro electric properties of morphologically diverse ZnO nanostructures
year: 2020

abstract: In this work, a highly visible blind UV photodetector with a large photo responsivity using ZnO nanostructures is demonstrated. A large photoconductive gain of 2050 and external quantum efficiency of <inline formula> <tex math notation="LaTeX"$2.05\times 10 {5} /tex math>/inline formula> at 350 nm (illumination intensity of 1 mW/cm<sup>2</sup> incident radiation has been successfully achieved by morphological transition engineering i.e. growth of nanoplates around the nanorods. Further, by suppression of intrinsic defect states during the growth of nanostructures, high UV to visible rejection ratio of <inline formula> <tex math notation="LaTeX"$4.78\times 10 {5} /tex math>/inline formula> and photoresponsivity of 578 A/W has been accomplished. The device has demonstrated high selectivity for UV A radiations, with a sharp responsivity peak at 350 nm of 60 nm FWHM. Moreover, the specific photo detectivity was calculated to be as high as <inline formula> <tex math notation="LaTeX"$2.15\times 10 \mathbf {15} /tex math>/inline formula> cmHz<inline formula> <tex math notation="LaTeX"{1/2}\text{W} 1} /tex math>/inline formula> The proposed device has the capability to establish ZnO as a potential candidate for the variety of commercial applications, where high responsivity along with large UV to visible rejection ratio are the major requirements.
author_names: Jitesh Agrawal

Tejendra Dixit

I A Palani

Vipul Singh
title: Highly Visible Blind ZnO Photodetector by Customizing Nanostructures With Controlled Defects
venue: IEEE Photonics Technology Letters
year: 2020

abstract: Abstract Kinetically controlled growth of low dimensional zinc oxide (ZnO) nanostructures like nanorods, nanoflowers etc. have been demonstrated with enhanced photoluminescent emission by tuning of the hydroxide ion concentration in the precursor irrespective of the synthesis techniques. Change in concentration of the hydroxide ions in the precursor during the synthesis of ZnO nanostructured samples has been found to tune the aspect ratio of the nanostructures, viz. nanorods grown by electrodeposition, and morphology of nanoflowers to nanogranules synthesized by direct precipitation method. The photoluminescent emission from these samples has been found to increase synchronously with the increase in the concentration of hydroxide ions in the precursor. Observed enhancement in photoluminescence has been proposed to be due to the formation of superoxide O 2 charge transfer (CT) states C T O 2 due to the adsorption of molecular oxygen directly at grain boundaries or induced by hydroxide ions adsorbed over the surface of the nanostructures. The results are in contradiction to the established role of defect states behind photoluminescent emission from ZnO nanostructures. In this work, mathematical modelling has been used to establish the dominant role that superoxide CT states can play in enhancing the efficiency of ZnO based optoelectronic devices such as light emitting diodes and photodiodes.
author_names: Dhritiman Banerjee

Asit Kumar Kar
title: Influence of oxygen related surface adsorbates on the growth of low dimensional nanostructures and enhanced luminescence due to superoxide charge transfer states in ZnO for application in optoelectronic devices
year: 2020

abstract: Abstract The article reports a novel and highly efficient methodology for the development of surface defects free zinc oxide (ZnO) nanostructures, which are highly useful for various optoelectronic and electronic devices. Using this approach, we have developed high quality ZnO nanostructures with comparable physical and chemical properties to high temperature grown ones. Initially, ZnO nanostructures were developed by low temperature chemical bath deposition, and the surface defects passivated structures were obtained by atomic layer deposition of homo molecular clusters, i.e. Zn and O atomic layers. The surface passivated ZnO nanostructures exhibited excellent chemical stoichiometry between their constituents with enhanced crystalline quality. These nanostructures also showed improved light transmittance in the wavelengths range of 450 1000 nm, and light emission in the ultraviolet region. Further, the surface passivated nanostructures exhibited remarkable device performance as photoanodes with a greatly improved photocurrent density, more than 3 times, and reduced cathodic current of 6.17 x 10 7 A@ 0.4 V. Significantly, the light to dark current ratio of the PEC devices fabricated with passivated ZnO nanostructures is found to be 1761.
author_names: Koteeswara Reddy Nandanapalli

Devika Mudusu

Sungwon Lee
title: Defects free single crystalline zinc oxide nanostructures for efficient photoelectrochemical solar hydrogen generation
year: 2020