Structure and morphology of magnetron sputter deposited ultrathin ZnO films on confined polymeric template

NASA Astrophysics Data System (ADS)

Singh, Ajaib; Schipmann, Susanne; Mathur, Aakash; Pal, Dipayan; Sengupta, Amartya; Klemradt, Uwe; Chattopadhyay, Sudeshna

2017-08-01

The structure and morphology of ultra-thin zinc oxide (ZnO) films with different film thicknesses on confined polymer template were studied through X-ray reflectivity (XRR) and grazing incidence small angle X-ray scattering (GISAXS). Using magnetron sputter deposition technique ZnO thin films with different film thicknesses (<10 nm) were grown on confined polystyrene with ∼2Rg film thickness, where Rg ∼ 20 nm (Rg is the unperturbed radius of gyration of polystyrene, defined by Rg = 0.272 √M0, and M0 is the molecular weight of polystyrene). The detailed internal structure, along the surface/interfaces and the growth direction of the system were explored in this study, which provides insight into the growth procedure of ZnO on confined polymer and reveals that a thin layer of ZnO, with very low surface and interface roughness, can be grown by DC magnetron sputtering technique, with approximately full coverage (with bulk like electron density) even in nm order of thickness, in 2-7 nm range on confined polymer template, without disturbing the structure of the underneath template. The resulting ZnO-polystyrene hybrid systems show strong ZnO near band edge (NBE) and deep-level (DLE) emissions in their room temperature photoluminescence spectra, where the contribution of DLE gets relatively stronger with decreasing ZnO film thickness, indicating a significant enhancement of surface defects because of the greater surface to volume ratio in thinner films.

ZnO nanofiber (NFs) growth from ZnO nanowires (NWs) by controlling growth temperature on flexible Teflon substrate by CBD technique for UV photodetector

NASA Astrophysics Data System (ADS)

Farhat, O. F.; Halim, M. M.; Ahmed, Naser M.; Qaeed, M. A.

2016-12-01

In this study, ZnO nanofibers (ZnO NFs) were successfully grown for the first time on Teflon substrates using CBD technique. The well-aligned ZnO nanorods (ZnO NRs) were transformed to ZnO nanofibers (NFs) by varying growth temperature and growth time. The high intensity and distinct growth orientation of peaks observed in the XRD spectra of the NFs indicate high crystal quality. The field emission scanning electron microscopy (FESEM) revealed high density of small diameter sized and long ZnO nanofibers (NFs) that are distributed in random directions. Raman analyses revealed a high E2 (high) peak at 436 nm, which indicates the wurtzite structure of ZnO. A flexible ZnO nanofiber (NFs)-based metal-semiconductor-metal UV detector was fabricated and analyzed for photo response and sensitivity under low power illumination (375 nm, 1.5 mW/cm2). The results showed a sensitivity of 4045% which can be considered a relatively high response and baseline recovery for UV detection.

Influence of External Gaseous Environments on the Electrical Properties of ZnO Nanostructures Obtained by a Hydrothermal Method

PubMed Central

Procek, Marcin; Pustelny, Tadeusz; Stolarczyk, Agnieszka

2016-01-01

This paper deals with experimental investigations of ZnO nanostructures, consisting of a mixture of nanoparticles and nanowires, obtained by the chemical (hydrothermal) method. The influences of both oxidizing (NO2) and reducing gases (H2, NH3), as well as relative humidity (RH) on the physical and chemical properties of ZnO nanostructures were tested. Carrier gas effect on the structure interaction with gases was also tested; experiments were conducted in air and nitrogen (N2) atmospheres. The effect of investigated gases on the resistance of the ZnO nanostructures was tested over a wide range of concentrations at room temperature (RT) and at 200 °C. The impact of near- ultraviolet (UV) excitation (λ = 390 nm) at RT was also studied. These investigations indicated a high response of ZnO nanostructures to small concentrations of NO2. The structure responses to 1 ppm of NO2 amounted to about: 600% in N2/230% in air at 200 °C (in dark conditions) and 430% in N2/340% in air at RT (with UV excitation). The response of the structure to the effect of NO2 at 200 °C is more than 105 times greater than the response to NH3, and more than 106 times greater than that to H2 in the relation of 1 ppm. Thus the selectivity of the structure for NO2 is very good. What is more, the selectivity to NO2 at RT with UV excitation increases in comparison at elevated temperature. This paper presents a great potential for practical applications of ZnO nanostructures (including nanoparticles) in resistive NO2 sensors. PMID:28335355

Room temperature synthesis and optical properties of small diameter (5 nm) ZnO nanorod arrays.

PubMed

Cho, Seungho; Jang, Ji-Wook; Lee, Jae Sung; Lee, Kun-Hong

2010-10-01

We report a simple wet-chemical synthesis of ∼5 nm diameter ZnO nanorod arrays at room temperature (20 °C) and normal atmospheric pressure (1 atm) and their optical properties. They were single crystalline in nature, and grew in the [001] direction. These small diameter ZnO nanorod arrays can also be synthesized at 0 °C. Control experiments were also conducted. On the basis of the results, we propose a mechanism for the spontaneous growth of the small diameter ZnO structures. The optical properties of the 5 nm diameter ZnO nanorod arrays synthesized using this method were probed by UV-Visible diffuse reflectance spectroscopy. A clear blue-shift, relative to the absorption band from 50 nm diameter ZnO nanorod arrays, was attributed to the quantum confinement effects caused by the small nanocrystal size in the 5 nm diameter ZnO nanorods.

Fabrication and photoluminescence properties of graphite fiber/ZnO nanorod core-shell structures.

PubMed

Liu, Xianbin; Du, Hejun; Liu, Bo; Wang, Jianxiong; Sun, Xiao Wei; Sun, Handong

2011-08-01

Graphite fiber/ZnO nanorod core-shell structures were synthesized by thermal evaporation process. The core-shell hybrid architectures were comprised of ZnO nanorods grown on the surface of graphite fiber. In addition, Hollow ZnO hierarchical structure can be obtained by oxidizing the graphite fiber. Room temperature photoluminescence (PL) of the as-made graphite fiber/ZnO nanorod structures shows two UV peaks at around 3.274 eV and 3.181 eV. The temperature-dependent photoluminescence spectra demonstrate the two UV emissions are attributed to the intrinsic optical transitions and extrinsic defect-related emissions in ZnO. These hybrid structures may be used as the building block for fabrication of nanodevices.

Structural morphology of zinc oxide structures with antibacterial application of calamine lotion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ann, Ling Chuo; Mahmud, Shahrom; Bakhori, Siti Khadijah Mohd

In this study, we report the structural morphology of a zinc oxide (ZnO) sample and antibacterial application of the ZnO structures in calamine lotion. Antibacterial activities of the calamine lotion towards Staphylococcus aureus and Pseudomonas aeruginosa were investigated. The structural morphology of ZnO sample was studied using a transmission electron microscope (TEM) and a field-emission scanning electron microscope (FESEM). The morphologies of the ZnO structure consisted of many rod and spherical structures. The particle sizes of the sample ranged from 40 nm to 150 nm. A calamine lotion was prepared through mixing the ZnO structures with other constituents in suitable proportion. Themore » energy-dispersive x-ray spectroscopy (EDS) revealed the presence of large amount of ZnO structures whiles the X-ray diffraction (XRD) results showed a good crystalline property of ZnO in the calamine lotion mixture. The morphological structures of ZnO were found to remain unchanged in the calamine lotion mixture through FESEM imaging. In the antibacterial test, prepared calamine lotion exhibited a remarkable bacterial inhibition on Staphylococcus aureus and Pseudomonas aeruginosa after 24 h of treatment. The bactericidal capability of calamine lotion was largely due to the presence of ZnO structures which induce high toxicity and killing effect on the bacteria.« less

Magnetically addressable fluorescent Fe3O4/ZnO nanocomposites: Structural, optical and magnetization studies

NASA Astrophysics Data System (ADS)

Roychowdhury, A.; Pati, S. P.; Mishra, A. K.; Kumar, S.; Das, D.

2013-06-01

Fe3O4/ZnO nanocomposites (NCs) are prepared by a wet chemical route. X-ray diffraction, transmission electron microscopy and Fourier transform infrared spectroscopy studies confirm the coexistence of Fe3O4 and ZnO phases in the NCs. The UV-vis absorption spectra show a red shift of the absorption peak with increase in Fe3O4 content indicating a modification of the band structure of ZnO in the NCs. Photoluminescence emission spectra of the NCs display strong excitonic emission in the UV region along with weak emission bands in the visible range caused by electronic transitions involving defect-related energy levels in the band gap of ZnO. Positron annihilation lifetimes indicate that cation vacancies in the ZnO structure are the strong traps for positrons and the overall defect concentration in the NCs decreases with increase in Fe3O4 content. Dc magnetization measurements reveal an anomalous temperature dependence of the coercivity of the NCs that is argued to be due to the anomalous variation of magnetocrystalline anisotropy at lower temperature. The irreversibility observed in the temperature dependent ZFC-FC magnetization points to the presence of a spin-glass phase in the NCs.

Structure, morphology and optical properties of undoped and MN-doped ZnO(1-x)Sx nano-powders prepared by precipitation method

NASA Astrophysics Data System (ADS)

Dejene, F. B.; Onani, M. O.; Koao, L. F.; Wako, A. H.; Motloung, S. V.; Yihunie, M. T.

2016-01-01

The undoped and Mn-doped ZnO(1-x)Sx nano-powders were successfully synthesized by precipitation method without using any capping agent. Its structure, morphology, elemental analysis, optical and luminescence properties were determined by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), UV-vis spectroscopy (UV) and photoluminescence spectroscopy (PL). A typical SEM image of the un-doped ZnO(1-x)Sx nanoparticles exhibit flake like structures that changes to nearly spherical particles with Mn-doping. The XRD of undoped and Mn doped ZnO(1-x)Sx pattern reveals the formation of a product indexed to the hexagonal wurtzite phase of ZnS. The nanopowders have crystallite sizes estimated from XRD measurements were in the range of 10-20 nm. All the samples showed absorption maximum of ZnO(1-x)Sx at 271 nm and high transmittance in UV and visible region, respectively. The undoped ZnO(1-x)Sx nanoparticles show strong room-temperature photoluminescence with four emission bands centering at 338 nm, 384 nm, 448 nm and 705 nm that may originate to the impurity of ZnO(1-x)Sx, existence of oxide related defects. The calculated bandgap of the nanocrystalline ZnO(1-x)Sx showed a blue-shift with respect to the Mn-doping. The PL spectra of the Mn-doped samples exhibit a strong orange emission at around 594 nm attributed to the 4T1-6A1 transition of the Mn2+ ions.

Structural, optical and magnetic properties of Co doped ZnO DMS nanoparticles by microwave irradiation method

NASA Astrophysics Data System (ADS)

Guruvammal, D.; Selvaraj, S.; Meenakshi Sundar, S.

2018-04-01

Microwave irradiation method is employed to synthesis of Zn1-xCoxO (x = 0.001-0.004) nanoparticles and investigate their structural, optical and magnetic properties using various characterization techniques. Structural studies reveal single phase hexagonal structure with average crystallite size 18-28 nm. FTIR study identifies the functional group present in the samples. The incorporation of Co2+ ions into the ZnO lattice is confirmed through XRD and UV-Vis studies. PL spectra exhibit a strong emission peak in UV region and a defect related visible emission peak in orange red region. These peaks are attributed to near band edge emission and the presence of oxygen related defects in the samples respectively. The blue shift observed in the UV emission peak shows an increase in the carrier concentration caused by the interstitial incorporation of ions into the ZnO lattice. The oxygen related defect is also confirmed through a peak obtained around g factor 1.9933 in ESR studies. Further, the number of spin contributing the ESR signal demonstrates the dependence of the strength of ferromagnetism on the concentration of oxygen ion vacancies. The VSM, ESR and PL measurements confirm the origin of RTFM of Co doped ZnO nanoparticles from the exchange interaction between the localized spin moments resulting from oxygen vacancies. The reason for the obtained super paramagnetic nature for x = 0.002 and x = 0.003 may be either due to some of nanoparticles or due to the weakly coupled Co ions in the Zn2+ site in the ZnO lattice. Further, the ferromagnetic behavior arises again for x = 0.004 due to the incorporation of Co2+ ions in the interstitial positions.

Theoretical prediction of low-density hexagonal ZnO hollow structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tuoc, Vu Ngoc, E-mail: tuoc.vungoc@hust.edu.vn; Huan, Tran Doan; Thao, Nguyen Thi

2016-10-14

Along with wurtzite and zinc blende, zinc oxide (ZnO) has been found in a large number of polymorphs with substantially different properties and, hence, applications. Therefore, predicting and synthesizing new classes of ZnO polymorphs are of great significance and have been gaining considerable interest. Herein, we perform a density functional theory based tight-binding study, predicting several new series of ZnO hollow structures using the bottom-up approach. The geometry of the building blocks allows for obtaining a variety of hexagonal, low-density nanoporous, and flexible ZnO hollow structures. Their stability is discussed by means of the free energy computed within the lattice-dynamicsmore » approach. Our calculations also indicate that all the reported hollow structures are wide band gap semiconductors in the same fashion with bulk ZnO. The electronic band structures of the ZnO hollow structures are finally examined in detail.« less

A study on different morphological structures of zinc oxide nanostructures for humidity sensing application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ismail, A. S., E-mail: kyrin-samaxi@yahoo.com; Mamat, M. H., E-mail: mhmamat@salam.uitm.edu.my; Rusop, M., E-mail: rusop@salam.uitm.my

2016-07-06

Effects of different morphological structures of ZnO to the performance of the device in the humidity sensing have been studied. Two different kinds of nanostructures were obtained which are nanords and nanoflakes. From the surface morphology image, the ZnO nanoflakes has lower diameter size of 100 nm compared to ZnO nanorods of 250 nm. The ZnO nanoflakes are not aligned and has low porous structure compared to ZnO nanorods. The humidity sensor performance of ZnO nanorods has superior performance compared to ZnO nanoflakes. The sensitivity of the ZnO nanorods sensor is 3.20 which are almost two times higher than themore » ZnO nanoflakes of 1.65. The structural properties of the samples have been characterized using field emission scanning electron microscopy (FESEM) electrical properties has been characterized using current voltage (I-V) measurement.« less

Structural, optical, and LED characteristics of ZnO and Al doped ZnO thin films

NASA Astrophysics Data System (ADS)

Sandeep, K. M.; Bhat, Shreesha; Dharmaprakash, S. M.

2017-05-01

ZnO (pristine) and Al doped ZnO (AZO) films were prepared using sol-gel spin coating method. The XRD analysis showed the enhanced compressive stress in AZO film. The presence of extended states below the conduction band edge in AZO accounts for the redshift in optical bandgap. The PL spectra of AZO showed significant blue emission due to the carrier recombination from defect states. The TRPL curves showed the dominant DAP recombination in ZnO film, whereas defect related recombination in Al doped ZnO film. Color parameters viz: the dominant wavelength, color coordinates (x,y), color purity, luminous efficiency and correlated color temperature (CCT) of ZnO and AZO films are calculated using 1931 (CIE) diagram. Further, a strong blue emission with color purity more than 96% is observed in both the films. The enhanced blue emission in AZO significantly increased the luminous efficiency (22.8%) compared to ZnO film (10.8%). The prepared films may be used as blue phosphors in white light generation.

Bi-layer channel structure-based oxide thin-film transistors consisting of ZnO and Al-doped ZnO with different Al compositions and stacking sequences

NASA Astrophysics Data System (ADS)

Cho, Sung Woon; Yun, Myeong Gu; Ahn, Cheol Hyoun; Kim, So Hee; Cho, Hyung Koun

2015-03-01

Zinc oxide (ZnO)-based bi-layers, consisting of ZnO and Al-doped ZnO (AZO) layers grown by atomic layer deposition, were utilized as the channels of oxide thin-film transistors (TFTs). Thin AZO layers (5 nm) with different Al compositions (5 and 14 at. %) were deposited on top of and beneath the ZnO layers in a bi-layer channel structure. All of the bi-layer channel TFTs that included the AZO layers showed enhanced stability (Δ V Th ≤ 3.2 V) under a positive bias stress compared to the ZnO single-layer channel TFT (Δ V Th = 4.0 V). However, the AZO/ZnO bi-layer channel TFTs with an AZO interlayer between the gate dielectric and the ZnO showed a degraded field effect mobility (0.3 cm2/V·s for 5 at. % and 1.8 cm2/V·s for 14 at. %) compared to the ZnO single-layer channel TFT (5.5 cm2/V·s) due to increased scattering caused by Al-related impurities near the gate dielectric/channel interface. In contrast, the ZnO/AZO bi-layer channel TFTs with an AZO layer on top of the ZnO layer exhibited an improved field effect mobility (7.8 cm2/V·s for 14 at. %) and better stability. [Figure not available: see fulltext.

Structural, Optical, and Photocatalytic Properties of Quasi-One-Dimensional Nanocrystalline ZnO, ZnOC:nC Composites, and C-doped ZnO

NASA Astrophysics Data System (ADS)

Shalaeva, E. V.; Gyrdasova, O. I.; Krasilnikov, V. N.; Melkozerova, M. A.; Baklanova, I. V.; Buldakova, L. Yu.

Various thermolysis rotes of zinc glicolate complexes are considered for the synthesis of quasi-one-dimensional nanostructured aggregates ZnO and Zn-O-C used as photocatalysts. Structural features of quasi-one-dimensional aggregates Zn-O-C and ZnO are investigated in detail. Transmission electron microscopy, Raman spectroscopy, and electron paramagnetic resonance spectroscopy methods demonstrate that the aggregates Zn-O-C have either composite structure (ZnO crystallites in amorphous carbon matrix) or a C-doped ZnO single-phase structure depending on heat treatment conditions, and that all the aggregates exhibit as a rule a tubular morphology, a nanocrystalline structure with a high specific surface area, and a high concentration of singly charged oxygen vacancies. The mechanism of the nanocrystalline structure formation is discussed and the effect of thermolysis condition on the formation of the textured structure of aggregates is investigated. The results of examination of the photocatalytic and optical absorption properties of the synthesized aggregates are presented. The photocatalytic activity for the hydroquinone oxidation reaction under ultraviolet and visible light increases in the series: the reference ZnO powder, quasi-one-dimensional ZnO, quasi-one-dimensional aggregates C-doped ZnO, and this tendency correlates with the reduction of the optical gap width. As a result of our studies, we have arrived at an important conclusion that thermal treatment of ZnO:nC composites allows a C-doped ZnO with high catalytic activity. This increasing photoactivity of C-doped ZnO aggregates is attributed to the optimal specific surface area and electron-energy spectrum restructuring to be produced owing to the presence of singly charged oxygen vacancies and carbon dissolved in the ZnO lattice.

Fabrication of thin ZnO films with wide-range tuned optical properties by reactive magnetron sputtering

NASA Astrophysics Data System (ADS)

Davydova, A.; Tselikov, G.; Dilone, D.; Rao, K. V.; Kabashin, A. V.; Belova, L.

2018-02-01

We report the manufacturing of thin zinc oxide films by reactive magnetron sputtering at room temperature, and examine their structural and optical properties. We show that the partial oxygen pressure in DC mode can have dramatic effect on absorption and refractive index (RI) of the films in a broad spectral range. In particular, the change of the oxygen pressure from 7% to 5% can lead to either conventional crystalline ZnO films having low absorption and characteristic descending dependence of RI from 2.4-2.7 RIU in the visible to 1.8-2 RIU in the near-infrared (1600 nm) range, or to untypical films, composed of ZnO nano-crystals embedded into amorphous matrix, exhibiting unexpectedly high absorption in the visible-infrared region and ascending dependence of RI with values varying from 1.5 RIU in the visible to 4 RIU in the IR (1600 nm), respectively. Untypical optical characteristics in the second case are explained by defects in ZnO structure arising due to under-oxidation of ZnO crystals. We also show that the observed defect-related film structure remains stable even after annealing of films under relatively high temperatures (30 min under 450 °C). We assume that both types of films can be of importance for photovoltaic (as contact or active layers, respectively), as well as for chemical or biological sensing, optoelectronics etc.

Structural, Electrical and Optical Properties of Cd Doped ZnO Thin Films by Reactive dc Magnetron Sputtering

NASA Astrophysics Data System (ADS)

Kumar, A. Guru Sampath; Obulapathi, L.; Sarmash, T. Sofi; Rani, D. Jhansi; Maddaiah, M.; Rao, T. Subba; Asokan, K.

2015-04-01

Thin films of cadmium (Cd) (0 wt.%, 2 wt.%, 4 wt.% and 10 wt.%) doped zinc oxide (ZnO) have been deposited on a glass substrate by reactive DC magnetron sputtering. The synthesized films are characterized by glancing angle x-ray diffraction (GAXRD), UV-Vis-NIR spectroscopy, four probe resistivity measurement, Hall measurement system, field emission-scanning electron microscopy and energy dispersive analysis by x-rays. A systematic study has been made on the structure, electrical and optical properties of Cd doped ZnO thin films as a function of Cd concentration (0 wt.%, 2 wt.%, 4 wt.% and 10 wt.%). All these films have a hexagonal wurtzite ZnO structure with (0 0 2) orientation without any Cd related phase from the GAXRD patterns. The grain size was increased and maximum appears at 4 wt.% Cd concentration. The electrical resistivity of the films decreased with the Cd doping and minimum resistivity was observed at 4 wt.% Cd concentration. UV-Vis-NIR studies showed that the optical band gap of ZnO (3.37 eV) was reduced to 3.10 eV which is at 4 wt.% Cd concentration.

Nanoparticle Self-Assembled Grain Like Curcumin Conjugated ZnO: Curcumin Conjugation Enhances Removal of Perylene, Fluoranthene, and Chrysene by ZnO

PubMed Central

Moussawi, Rasha N.; Patra, Digambara

2016-01-01

Curcumin conjugated ZnO, referred as Zn(cur)O, nanostructures have been successfully synthesized, these sub-micro grain-like structures are actually self-assemblies of individual needle-shaped nanoparticles. The nanostructures as synthesized possess the wurtzite hexagonal crystal structure of ZnO and exhibit very good crystalline quality. FT-Raman and TGA analysis establish that Zn(cur)O is different from curcumin anchored ZnO (ZnO@cur), which is prepared by physically adsorbing curcumin on ZnO surfaces. Chemically Zn(cur)O is more stable than ZnO@cur. Diffuse reflectance spectroscopy indicates Zn(cur)O have more impurities compared to ZnO@cur. The solid-state photoluminescence of Zn(cur)O has been investigated, which demonstrates that increase of curcumin concentration in Zn(cur)O suppresses visible emission of ZnO prepared through the same method, this implies filling ZnO defects by curcumin. However, at excitation wavelength 425 nm the emission is dominated by fluorescence from curcumin. The study reveals that Zn(cur)O can remove to a far extent high concentrations of perylene, fluoranthene, and chrysene faster than ZnO. The removal depends on the extent of curcumin conjugation and is found to be faster for PAHs having smaller number of aromatic rings, particularly, it is exceptional for fluoranthene with 93% removal after 10 minutes in the present conditions. The high rate of removal is related to photo-degradation and a mechanism has been proposed. PMID:27080002

Falling Leaves Inspired ZnO Nanorods-Nanoslices Hierarchical Structure for Implant Surface Modification with Two Stage Releasing Features.

PubMed

Liao, Hang; Miao, Xinxin; Ye, Jing; Wu, Tianlong; Deng, Zhongbo; Li, Chen; Jia, Jingyu; Cheng, Xigao; Wang, Xiaolei

2017-04-19

Inspired from falling leaves, ZnO nanorods-nanoslices hierarchical structure (NHS) was constructed to modify the surfaces of two widely used implant materials: titanium (Ti) and tantalum (Ta), respectively. By which means, two-stage release of antibacterial active substances were realized to address the clinical importance of long-term broad-spectrum antibacterial activity. At early stages (within 48 h), the NHS exhibited a rapid releasing to kill the bacteria around the implant immediately. At a second stage (over 2 weeks), the NHS exhibited a slow releasing to realize long-term inhibition. The excellent antibacterial activity of ZnO NHS was confirmed once again by animal test in vivo. According to the subsequent experiments, the ZnO NHS coating exhibited the great advantage of high efficiency, low toxicity, and long-term durability, which could be a feasible manner to prevent the abuse of antibiotics on implant-related surgery.

Cross-section imaging and p-type doping assessment of ZnO/ZnO:Sb core-shell nanowires by scanning capacitance microscopy and scanning spreading resistance microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Lin, E-mail: lin.wang@insa-lyon.fr; Brémond, Georges; Sallet, Vincent

2016-08-29

ZnO/ZnO:Sb core-shell structured nanowires (NWs) were grown by the metal organic chemical vapor deposition method where the shell was doped with antimony (Sb) in an attempt to achieve ZnO p-type conduction. To directly investigate the Sb doping effect in ZnO, scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM) were performed on the NWs' cross-sections mapping their two dimensional (2D) local electrical properties. Although no direct p-type inversion in ZnO was revealed, a lower net electron concentration was pointed out for the Sb-doped ZnO shell layer with respect to the non-intentionally doped ZnO core, indicating an evident compensating effectmore » as a result of the Sb incorporation, which can be ascribed to the formation of Sb-related acceptors. The results demonstrate SCM/SSRM investigation being a direct and effective approach for characterizing radial semiconductor one-dimensional (1D) structures and, particularly, for the doping study on the ZnO nanomaterial towards its p-type realization.« less

Structural studies of ZnO nanostructures by varying the deposition parameters

NASA Astrophysics Data System (ADS)

Yunus, S. H. A.; Sahdan, M. Z.; Ichimura, M.; Supee, A.; Rahim, S.

2017-01-01

The effect of Zinc Oxide (ZnO) thin film on the growth of ZnO nanorods (NRs) was investigated. The structures of ZnO NRs were synthesized by chemical bath deposition (CBD) method in aqueous solution of N2O6Zn.6H2O and C6H12N4 at 90°C of deposition temperature. One of the ZnO NRs samples was deposited on a ZnO seed layer coated on a glass substrate to investigate the properties of ZnO NRs without receiving effect of other materials. Next, for diode application, the ZnO NRs was deposited on tin monosulfide (SnS) coated on indium-tin-oxide (ITO) coated glass substrate (SnS/ITO). The next, the ZnO structural properties were studied from surface morphology, X-ray diffractometer (XRD) spectra, and chemical composition by using field emission scanning electron microscope (FESEM), XRD and energy dispersive X-ray Spectroscopy (EDX). The growth of ZnO NRs on ZnO seed layer was investigated by ZnO seed layer condition while the growth of ZnO NRs on SnS/ITO was investigated by deposition time and deposition temperature parameters. From FESEM images, aligned ZnO NRs were obtained, and the diameters of ZnO NRs were 0.024-3.94 µm. The SnS thin film was affected by the diameter of ZnO NRs which are the ZnO NRs grow on SnS thin films has a larger diameter compared to ZnO NRs grow on ZnO seed layer. Besides that, all of ZnO peaks observed from XRD corresponding to the wurzite structure and preferentially oriented along the c-axis. In addition, EDX shows a high composition of zinc (Zn) and oxygen (O) signals, which indicated that the NRs are indeed made up of Zn and O.

Effect of thermal annealing on the structure and magnetism of Fe-doped ZnO nanocrystals synthesized by solid state reaction

NASA Astrophysics Data System (ADS)

Wang, Dong; Chen, Z. Q.; Wang, D. D.; Gong, J.; Cao, C. Y.; Tang, Z.; Huang, L. R.

2010-11-01

High purity Fe 2O 3/ZnO nanocomposites were annealed in air at different temperatures between 100 and 1200 °C to get Fe-doped ZnO nanocrystals. The structure and grain size of the Fe 2O 3/ZnO nanocomposites were investigated by X-ray diffraction 2θ scans. Annealing induces an increase of the grain size from 25 to 195 nm and appearance of franklinite phase of ZnFe 2O 4. Positron annihilation measurements reveal large number of vacancy defects in the interface region of the Fe 2O 3/ZnO nanocomposites, and they are gradually recovered with increasing annealing temperature. After annealing at temperatures higher than 1000 °C, the number of vacancies decreases to the lower detection limit of positrons. Room temperature ferromagnetism can be observed in Fe-doped ZnO nanocrystals using physical properties measurement system. The ferromagnetism remains after annealing up to 1000 °C, suggesting that it is not related with the interfacial defects.

Electrochemical route to the synthesis of ZnO microstructures: its nestlike structure and holding of Ag particles

NASA Astrophysics Data System (ADS)

Ding, Ling; Zhang, Ruixue; Fan, Louzhen

2013-02-01

A simple and facile electrochemical route was developed for the shape-selective synthesis of large-scaled series of ZnO microstructures, including petal, flower, sphere, nest and clew aggregates of ZnO laminas at room temperature. This route is based on sodium citrate-directed crystallization. In the system, sodium citrate can greatly promote ZnO to nucleate and directly grow by selectively capping the specific ZnO facets because of its excellent adsorption ability. The morphology of ZnO is tuned by readily adjusting the concentration of sodium citrate and the electrodeposition time. Among the series structures, the remarkable ZnO nestlike structure can be used as a container to hold not only the interlaced ZnO laminas but also Ag nanoparticles in the center. The special heterostructures of nestlike ZnO holding Ag nanoparticles were found to display the superior properties on the surface-enhanced Raman scattering. This work has signified an important methodology to produce a wide assortment of desired microstructures of ZnO.

Synthesis of ZnO nanopencils using wet chemical method and its investigation as LPG sensor

NASA Astrophysics Data System (ADS)

Shimpi, Navinchandra G.; Jain, Shilpa; Karmakar, Narayan; Shah, Akshara; Kothari, D. C.; Mishra, Satyendra

2016-12-01

ZnO nanopencils (NPCs) were prepared by a novel wet chemical process, using triethanolamine (TEA) as a mild base, which is relatively simple and cost effective method as compared to hydrothermal method. ZnO NPCs were characterized using powder X-ray diffraction (XRD), Fourier Transform Infra-Red (FTIR) spectroscopy in mid-IR and far-IR regions, X-ray Photoelectron Spectroscopy (XPS), UV-vis (UV-vis) absorption spectroscopy, room temperature Photoluminescence (PL) spectroscopy and Field Emission Scanning Electron Microscopy (FESEM). ZnO NPCs obtained, were highly pure, uniform and monodispersed.XRD pattern indicated hexagonal unit cell structure with preferred orientation along the c-axis. Sensing behaviour of ZnO NPCs was studied towards Liquefied Petroleum Gas (LPG) at different operating temperatures. The study shows that ZnO NPCs were most sensitive and promising candidate for detection of LPG at 250 °C with gas sensitivity > 60%. The high response towards LPG is due to high surface area of ZnO NPCs and their parallel alignment.

Ab Initio Study of Structural and Electronic Properties of (ZnO) n "Magical" Nanoclusters n = (34, 60)

NASA Astrophysics Data System (ADS)

Bovhyra, Rostyslav; Popovych, Dmytro; Bovgyra, Oleg; Serednytski, Andrew

2017-01-01

Density functional theory studies of the structural and electronic properties of nanoclusters (ZnO) n ( n = 34, 60) in different geometric configurations were conducted. For each cluster, an optimization (relaxation) of structure geometry was performed, and the basic properties of the band structure were investigated. It was established that for the (ZnO)34 nanoclusters, the most stable are fullerene-like hollow structures that satisfy the rule of six isolated quadrangles. For the (ZnO)60 nanoclusters, different types of isomers, including hollow structures and sodalite-like structures composed from (ZnO)12 nanoclusters, were investigated. It was determined that the most energetically favorable structure was sodalite-type structure composed of seven (ZnO)12 clusters with common quadrangle edges.

Tuning the optical properties of ZnO nanorods by variation of precursor concentration through hydrothermal method

NASA Astrophysics Data System (ADS)

Kumari, Lakshmi; Kar, Asit Kumar

2018-05-01

ZnO nanorods with varying precursor concentration have been successfully synthesized by the hydrothermal method. The effect of the precursor concentration on the structural, morphological and optical properties of the resulting nanorods was investigated by means of X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), UV-Vis spectroscopy and photoluminescence (PL) spectroscopy. The crystalline structural characterization demonstrated that the synthesized materials crystallize in pure ZnO wurtzite structure without any other secondary phase. SEM micrographs demonstrate nanorod type features in all the samples. In addition, they show that increase of precursor concentration changes the length and diameter of nanorods. The UV-Vis studies show a strong absorption band in UV region at 373 nm attributed to the band-edge absorption of wurtzite hexagonal ZnO, blue shifted relative to its bulk form (380 nm). The PL spectra of obtained nanorods excited at 360 nm present broad visible emission. Moreover, as the visible region (from 510 to 550 nm) is concerned, it is speculated that the increase of the precursor concentration affects strongly the kind of interstitial defects (Oi, Zni and Vo) formed in ZnO nanorods. The luminescence intensity decreases with the increase of precursor concentration.

The Impact of Iron Adsorption on the Electronic and Photocatalytic Properties of the Zinc Oxide (0001) Surface: A First-Principles Study.

PubMed

Cheng, Jingsi; Wang, Ping; Hua, Chao; Yang, Yintang; Zhang, Zhiyong

2018-03-12

The structural stability, electronic structure, and optical properties of an iron-adsorbed ZnO (0001) surface with three high-symmetry adsorption sites are investigated with first-principle calculations on the basis of density functional theory and the Hubbard-U method. It is found that the iron adatom in the H₃ adsorption site of ZnO (0001) surface has the lowest adsorption energy of -5.665 eV compared with T₄ and Top sites. For the Top site, compared with the pristine ZnO (0001) surface, the absorption peak located at 1.17 eV has a red shift, and the elevation of the absorption coefficient is more pronounced in the visible-light region, because the Fe-related levels are introduced in the forbidden band and near the Fermi level. The electrostatic potential computation reveals that the work function of the ZnO (0001) surface is significantly decreased from 2.340 to 1.768 eV when iron is adsorbed on the Top site. Furthermore, the degradation mechanism based on the band structure is analyzed. It can be concluded that the adsorption of iron will promote the separation of photoinduced carriers, thus improving the photocatalytic activity of ZnO (0001) surface. Our study benefits research on the photocatalytic activity of ZnO and the utilization rate of solar energy.

Understanding lattice defects to influence ferromagnetic order of ZnO nanoparticles by Ni, Cu, Ce ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verma, Kuldeep Chand, E-mail: dkuldeep.physics@gmail.com; Kotnala, R.K., E-mail: rkkotnala@gmail.com

Future spintronics technologies based on diluted magnetic semiconductors (DMS) will rely heavily on a sound understanding of the microscopic origins of ferromagnetism in such materials. It remains unclear, however, whether the ferromagnetism in DMS is intrinsic - a precondition for spintronics - or due to dopant clustering. For this, we include a simultaneous doping from transition metal (Ni, Cu) and rare earth (Ce) ions in ZnO nanoparticles that increase the antiferromagnetic ordering to achieve high-T{sub c} ferromagnetism. Rietveld refinement of XRD patterns indicate that the dopant ions in ZnO had a wurtzite structure and the dopants, Ni{sup 2+}, Cu{sup 2+},more » Ce{sup 3+} ions, are highly influenced the lattice constants to induce lattice defects. The Ni, Cu, Ce ions in ZnO have nanoparticles formation than nanorods was observed in pure sample. FTIR involve some organic groups to induce lattice defects and the metal-oxygen bonding of Zn, Ni, Cu, Ce and O atoms to confirm wurtzite structure. Raman analysis evaluates the crystalline quality, structural disorder and defects in ZnO lattice with doping. Photoluminescence spectra have strong near-band-edge emission and visible emission bands responsible for defects due to oxygen vacancies. The energy band gap is calculated using Tauc relation. Room temperature ferromagnetism has been described due to bound magnetic polarons formation with Ni{sup 2+}, Cu{sup 2+}, Ce{sup 3+} ions in ZnO via oxygen vacancies. The zero field and field cooling SQUID measurement confirm the strength of antiferromagnetism in ZnO. The field cooling magnetization is studied by Curie-Weiss law that include antiferromagnetic interactions up to low temperature. The XPS spectra have involve +3/+4 oxidation states of Ce ions to influence the observed ferromagnetism. - Graphical abstract: The lattice defects/vacancies attributed by Ni and Ce ions in the wurtzite ZnO structure are responsible in high T{sub c} -ferromagnetism due to long-range magnetic interactions with cluster and spin-glass type growth. - Highlights: • Lattice defects/vacancies attributed high T{sub c} –ferromagnetism. • Transition metal and rare earth ions deform the wurtzite ZnO lattice to induce defects. • Oxygen vacancies are more favorable than Zn with Ni, Cu, Ce into ZnO. • Defects assisted long-range ferromagnetism of doped ZnO include cluster and spin-glass growth.« less

Electrochemical route to the synthesis of ZnO microstructures: its nestlike structure and holding of Ag particles

PubMed Central

2013-01-01

Abstract A simple and facile electrochemical route was developed for the shape-selective synthesis of large-scaled series of ZnO microstructures, including petal, flower, sphere, nest and clew aggregates of ZnO laminas at room temperature. This route is based on sodium citrate-directed crystallization. In the system, sodium citrate can greatly promote ZnO to nucleate and directly grow by selectively capping the specific ZnO facets because of its excellent adsorption ability. The morphology of ZnO is tuned by readily adjusting the concentration of sodium citrate and the electrodeposition time. Among the series structures, the remarkable ZnO nestlike structure can be used as a container to hold not only the interlaced ZnO laminas but also Ag nanoparticles in the center. The special heterostructures of nestlike ZnO holding Ag nanoparticles were found to display the superior properties on the surface-enhanced Raman scattering. This work has signified an important methodology to produce a wide assortment of desired microstructures of ZnO. PACS 81 Materials science 81.07.-b nanoscale materials and structures Fabrication Characterization 81.15.-z Methods of deposition of films Coatings Film growth and epitaxy. PMID:23414592

Single-crystalline twinned ZnO nanoleaf structure via a facile hydrothermal process.

PubMed

Qiu, Jijun; Lil, Xiaomin; Gao, Xiangdong; Gan, Xiaoyan; He, Weizhen; Kim, Hyung-Kook; Hwang, Yoon-Hwae

2011-03-01

A single-crystalline twinned ZnO nanostructure with a 2-dimensional leaf-like morphology (nanoleaves) was synthesized using a facile hydrothermal strategy. The ZnO nanoleaves had 2-fold symmetric branches, which were identified by the existence of an inversion domain boundary (IDB) along the [2110] growth direction of the ribbon-like stems with both side surfaces of the stems terminated with a chemically active Zn-(0001) plane. A proposed growth mechanism suggested that the formation of IDB and the leaf-like shape are related to the dissolution of seed particles on the substrate surfaces and an OH- shielding effect in solution, respectively. Optical measurements revealed visible emission, suggesting the possession of defects in the as-grown and annealed ZnO nanoleaves. In addition, various ZnO nanostructures were synthesized by simply controlling the fabrication conditions.

Angle-dependent photodegradation over ZnO nanowire arrays on flexible paper substrates

PubMed Central

2014-01-01

In this study, we grew zinc oxide (ZnO) nanowire arrays on paper substrates using a two-step growth strategy. In the first step, we formed single-crystalline ZnO nanoparticles of uniform size distribution (ca. 4 nm) as seeds for the hydrothermal growth of the ZnO nanowire arrays. After spin-coating of these seeds onto paper, we grew ZnO nanowire arrays conformally on these substrates. The crystal structure of a ZnO nanowire revealed that the nanowires were single-crystalline and had grown along the c axis. Further visualization through annular bright field scanning transmission electron microscopy revealed that the hydrothermally grown ZnO nanowires possessed Zn polarity. From photocatalytic activity measurements of the ZnO nanowire (NW) arrays on paper substrate, we extracted rate constants of 0.415, 0.244, 0.195, and 0.08 s-1 for the degradation of methylene blue at incident angles of 0°, 30°, 60°, and 75°, respectively; that is, the photocatalytic activity of these ZnO nanowire arrays was related to the cosine of the incident angle of the UV light. Accordingly, these materials have promising applications in the design of sterilization systems and light-harvesting devices. PMID:25593556

Atomic Layer Deposition of Nickel on ZnO Nanowire Arrays for High-Performance Supercapacitors.

PubMed

Ren, Qing-Hua; Zhang, Yan; Lu, Hong-Liang; Wang, Yong-Ping; Liu, Wen-Jun; Ji, Xin-Ming; Devi, Anjana; Jiang, An-Quan; Zhang, David Wei

2018-01-10

A novel hybrid core-shell structure of ZnO nanowires (NWs)/Ni as a pseudocapacitor electrode was successfully fabricated by atomic layer deposition of a nickel shell, and its capacitive performance was systemically investigated. Transmission electron microscopy and X-ray photoelectron spectroscopy results indicated that the NiO was formed at the interface between ZnO and Ni where the Ni was oxidized by ZnO during the ALD of the Ni layer. Electrochemical measurement results revealed that the Ti/ZnO NWs/Ni (1500 cycles) electrode with a 30 nm thick Ni-NiO shell layer had the best supercapacitor properties including ultrahigh specific capacitance (∼2440 F g -1 ), good rate capability (80.5%) under high current charge-discharge conditions, and a relatively better cycling stability (86.7% of the initial value remained after 750 cycles at 10 A g -1 ). These attractive capacitive behaviors are mainly attributed to the unique core-shell structure and the combined effect of ZnO NW arrays as short charge transfer pathways for ion diffusion and electron transfer as well as conductive Ni serving as channel for the fast electron transport to Ti substrate. This high-performance Ti/ZnO NWs/Ni hybrid structure is expected to be one of a promising electrodes for high-performance supercapacitor applications.

Synthesis and magnetic properties of Zr doped ZnO Nanoparticles.

PubMed

Zhang, Jing; Gao, Daqiang; Yang, Guijin; Zhang, Jinlin; Shi, Zhenhua; Zhang, Zhaohui; Zhu, Zhonghua; Xue, Desheng

2011-11-10

Zr doped ZnO nanoparticles are prepared by the sol-gel method with post-annealing. X-ray diffraction results show that all samples are the typical hexagonal wurtzite structure without any other new phase, as well as the Zr atoms have successfully entered into the ZnO lattices instead of forming other lattices. Magnetic measurements indicate that all the doping samples show room temperature ferromagnetism and the pure ZnO is paramagneism. The results of Raman and X-ray photoelectron spectroscopy indicate that there are a lot of oxygen vacancies in the samples by doping element of Zr. It is considered that the observed ferromagnetism is related to the doping induced oxygen vacancies.

Influence of hydrogen on the structure and stability of ultra-thin ZnO on metal substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bieniek, Bjoern; Hofmann, Oliver T.; Institut für Festkörperphysik, TU Graz, 8010 Graz

2015-03-30

We investigate the atomic and electronic structure of ultra-thin ZnO films (1 to 4 layers) on the (111) surfaces of Ag, Cu, Pd, Pt, Ni, and Rh by means of density-functional theory. The ZnO monolayer is found to adopt an α-BN structure on the metal substrates with coincidence structures in good agreement with experiment. Thicker ZnO layers change into a wurtzite structure. The films exhibit a strong corrugation, which can be smoothed by hydrogen (H) adsorption. An H over-layer with 50% coverage is formed at chemical potentials that range from low to ultra-high vacuum H{sub 2} pressures. For the Agmore » substrate, both α-BN and wurtzite ZnO films are accessible in this pressure range, while for Cu, Pd, Pt, Rh, and Ni wurtzite films are favored. The surface structure and the density of states of these H passivated ZnO thin films agree well with those of the bulk ZnO(0001{sup ¯})-2×1-H surface.« less

Enhanced Structural and Luminescent Properties of Carbon-Assisted ZnO Nanorod Arrays on (100) Si Substrate

NASA Astrophysics Data System (ADS)

Yoon, Im Taek; Cho, Hak Dong; Lee, Sejoon; Roshchupkin, Dmitry V.

2018-02-01

We have fabricated as-grown ZnO nanorods (NRs) and carbon-assisted NR arrays on semi-insulating (100)-oriented Si substrates. We compared the structural and luminescent properties of them. High-resolution transmission microscopy, field emission scanning electron microscopy, x-ray diffraction and energy-dispersive x-ray revealed that the as-grown ZnO NRs and carbon-assisted ZnO NRs were single crystals with a hexagonal wurtzite structure, and grew with a c-axis orientation perpendicular to the Si substrate. These measurements show that the carbon-assisted ZnO NRs were better synthesized vertically on an Si substrate compared to the as-grown ZnO NRs. Photoluminescence measurements showed that luminescence intensity of the carbon-assisted ZnO NRs was enhanced compared to the as-grown ZnO NRs. The enhanced luminescence intensity of the carbon-assisted ZnO demonstrates the possible improvement in the performance of photovoltaic nanodevices based on ZnO-like materials. This method can be applied to the fabrication of well-aligned ZnO NRs used widely in optoelectronic devices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shang Yazhuo; Hu Jun; Liu Honglai, E-mail: yazhuoshang@ecust.edu.c

Novel large-scale hollow ZnO spherical shells were synthesized by ionic liquids assisted hydrothermal oxidization of pure zinc powder without any catalyst at a relatively low temperature of 160 deg. C. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) patterns show that the shells are composed of ZnO and the structure of the shells is very unique. Textured flower-like ZnO consisting of ZnO rods is grown on the outer surfaces of shells forming a triple assembly. Room-temperature photoluminescence spectra of the oxidized material show a sharp peak at 379 nm and a wider broad peak centeredmore » at 498 nm. The possible growth mechanism of the triple assembly of ZnO is discussed in detail. - Graphical abstract: A proposed growth mechanism of large scale hollow ZnO. Bubbles provide the aggregation center for ionic liquids that leads to the formation of hollow Zn particle-dotted shells, buoyancy promotes shells to go upward, the breach occurs when shells are subjected to overpressure.« less

Elemental, morphological, structural, optical, and magnetic properties of erbium doped ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Poornaprakash, B.; Chalapathi, U.; Purusottam Reddy, B.; Prabhakar Vattikuti, S. V.; Siva Pratap Reddy, M.; Park, Si-Hyun

2018-03-01

The sensible tuning of the structural, optical, and magnetic properties of ZnO nanoparticles (NPs) with suitable doping can enhance their applicability in diverse fields. In this study, we synthesized ZnO NPs with Er (0-4 at%) doping and their elemental, structural, optical, and magnetic properties were studied. Both field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) studies of the suspensions consist of hexagonal shaped NPs. All the prepared NPs exhibited hexagonal phase as demonstrated by powder x-ray diffraction studies. A blue shift was observed in the Er doped ZnO NPs compared to pure ZnO, indicating the increased optical bandgap. Vibrating sample magnetometer studies exhibited the pure ZnO NPs was typical diamagnetic feature whereas all the Er doped ZnO NPs were paramagnetic feature at 300 K. This is the first paramagnetic report on Er doped ZnO NPs.

Nanostructured ZnO - its challenging properties and potential for device applications

NASA Astrophysics Data System (ADS)

Dimova-Malinovska, D.

2017-01-01

Nanostructured ZnO possessing interesting structural and optical properties offers challenging opportunities for innovative applications. In this lecture the review of the optical and structural properties of ZnO nanostructured layers is presented. It is shown that they have a direct impact on the parameters of devices involving ZnO. An analysis of current trends in the photovoltaic (PV) field shows that improved light harvesting and efficiency of solar cells can be obtained by implementing nanostructured ZnO layers to process advanced solar cell structures. Because of amenability to doping, high chemical stability, sensitivity to different adsorbed gases, nontoxicity and low cost ZnO attracted much attention for application as gas sensors. The sensitivity of nano-grain ZnO gas elements is comparatively high because of the grain-size effect. Application of nanostructured ZnO for gas sensors and for increasing of light harvesting in solar cells is demonstrated.

Study of vertical type organic light emitting transistor using ZnO

NASA Astrophysics Data System (ADS)

Iechi, Hiroyuki; Watanabe, Yasuyuki; Kudo, Kazuhiro

2006-04-01

We propose a new type organic light emitting transistor (OLET) combining static induction transistor (SIT) with double hetero junction type organic light emitting diodes (OLED) using n-type zinc oxide (ZnO) films which works as a transparent and electron injection layer. The device characteristics of newly developed OLED and ZnO-SIT showed relatively high luminance of about 500 cd/m2 at 7.6 mA/cm2 and is able to control by gate voltage as low as a few volts, respectively. The crystal structures of the ZnO films as a function of Ar/O II flow ratio and the basic characteristics of the thin film transistor (TFT) and SIT depending on the ZnO sputtering conditions are investigated. The results obtained here show that the OLET using ZnO film is a suitable element for flexible sheet displays.

Structural characterization of ZnO thin films grown on various substrates by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Novotný, M.; Čížek, J.; Kužel, R.; Bulíř, J.; Lančok, J.; Connolly, J.; McCarthy, E.; Krishnamurthy, S.; Mosnier, J.-P.; Anwand, W.; Brauer, G.

2012-06-01

ZnO thin films were grown by pulsed laser deposition on three different substrates: sapphire (0 0 0 1), MgO (1 0 0) and fused silica (FS). The structure and morphology of the films were characterized by x-ray diffraction and scanning electron microscopy and defect studies were carried out using slow positron implantation spectroscopy (SPIS). Films deposited on all substrates studied in this work exhibit the wurtzite ZnO structure and are characterized by an average crystallite size of 20-100 nm. However, strong differences in the microstructure of films deposited on various substrates were found. The ZnO films deposited on MgO and sapphire single-crystalline substrates exhibit local epitaxy, i.e. a well-defined relation between film crystallites and the substrate. Domains with different orientation relationships with the substrate were found in both films. On the other hand, the film deposited on the FS substrate exhibits fibre texture with random lateral orientation of crystallites. Extremely high compressive in-plane stress of σ ˜ 14 GPa was determined in the film deposited on the MgO substrate, while the film deposited on sapphire is virtually stress-free, and the film deposited on the FS substrate exhibits a tensile in-plane stress of σ ˜ 0.9 GPa. SPIS investigations revealed that the concentration of open-volume defects in the ZnO films is substantially higher than that in a bulk ZnO single crystal. Moreover, the ZnO films deposited on MgO and sapphire single-crystalline substrates exhibit a significantly higher density of defects than the film deposited on the amorphous FS substrate.

Room temperature photoluminescence properties of ZnO nanorods grown by hydrothermal reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iwan, S., E-mail: iwan-sugihartono@unj.ac.id; Prodi Ilmu Material, Departemen Fisika, FMIPA, Universitas Indonesia, Kampus UI Depok; Fauzia, Vivi

Zinc oxide (ZnO) nanorods were fabricated by a hydrothermal reaction on silicon (Si) substrate at 95 °C for 6 hours. The ZnO seed layer was fabricated by depositing ZnO thin films on Si substrates by ultrasonic spray pyrolisis (USP). The annealing effects on crystal structure and optical properties of ZnO nanorods were investigated. The post-annealing treatment was performed at 800 °C with different environments. The annealed of ZnO nanorods were characterized by X-ray diffraction (XRD) and photoluminescence (PL) in order to analyze crystal structure and optical properties, respectively. The results show the orientations of [002], [101], [102], and [103] diffractionmore » peaks were observed and hexagonal wurtzite structure of ZnO nanorods were vertically grown on Si substrates. The room temperature PL spectra show ultra-violet (UV) and visible emissions. The annealed of ZnO nanorods in vacuum condition (3.8 × 10{sup −3} Torr) has dominant UV emission. Meanwhile, non-annealed of ZnO nanorods has dominant visible emission. It was expected that the annealed of ZnO in vacuum condition suppresses the existence of native defects in ZnO nanorods.« less

Reaction mechanism of a PbS-on-ZnO heterostructure and enhanced photovoltaic diode performance with an interface-modulated heterojunction energy band structure.

PubMed

Li, Haili; Jiao, Shujie; Ren, Jinxian; Li, Hongtao; Gao, Shiyong; Wang, Jinzhong; Wang, Dongbo; Yu, Qingjiang; Zhang, Yong; Li, Lin

2016-02-07

A room temperature successive ionic layer adsorption and reaction (SILAR) method is introduced for fabricating quantum dots-on-wide bandgap semiconductors. Detailed exploration of how SILAR begins and proceeds is performed by analyzing changes in the electronic structure of related elements at interfaces by X-ray photoelectric spectroscopy, together with characterization of optical properties and X-ray diffraction. The distribution of PbS QDs on ZnO, which is critical for optoelectrical applications of PbS with a large dielectric constant, shows a close relationship with the dipping order. A successively deposited PbS QDs layer is obtained when the sample is first immersed in Na2S solution. This is reasonable because the initial formation of different chemical bonds on ZnO nanorods is closely related to dangling bonds and defect states on surfaces. Most importantly, dipping order also affects their optoelectrical characteristics greatly, which can be explained by the heterojunction energy band structure related to the interface. The formation mechanism for PbS QDs on ZnO is confirmed by the fact that the photovoltaic diode device performance is closely related to the dipping order. Our atomic-scale understanding emphasises the fundamental role of surface chemistry in the structure and tuning of optoelectrical properties, and consequently in devices.

Direct Growth of Feather-Like ZnO Structures by a Facile Solution Technique for Photo-Detecting Application

NASA Astrophysics Data System (ADS)

Jiang, Yurong; Liu, Xingbing; Cai, Fangmin; Liu, Hairui

2017-08-01

The feather-like hierarchical zinc oxide (ZnO) was synthesized via successive ionic layer adsorption and reaction without any seed layer or metal catalyst. A possible growth mechanism is proposed to explain the forming process of ZnO feather-like structures. Meanwhile, the photo-electronic performances of the feather-like ZnO have been investigated with the UV-vis-NIR spectroscopy, I-V and I-tmeasurements. The results indicate that feather-like ZnO hierarchical structures have good anti-reflection and excellent photo-sensitivity. All results suggest that the direct growth processing of novel feather-like ZnO is envisaged to have promising application in the field of photo-detector devices.

Spectroscopic Ellipsometry Studies of n-i-p Hydrogenated Amorphous Silicon Based Photovoltaic Devices

PubMed Central

Karki Gautam, Laxmi; Junda, Maxwell M.; Haneef, Hamna F.; Collins, Robert W.; Podraza, Nikolas J.

2016-01-01

Optimization of thin film photovoltaics (PV) relies on characterizing the optoelectronic and structural properties of each layer and correlating these properties with device performance. Growth evolution diagrams have been used to guide production of materials with good optoelectronic properties in the full hydrogenated amorphous silicon (a-Si:H) PV device configuration. The nucleation and evolution of crystallites forming from the amorphous phase were studied using in situ near-infrared to ultraviolet spectroscopic ellipsometry during growth of films prepared as a function of hydrogen to reactive gas flow ratio R = [H2]/[SiH4]. In conjunction with higher photon energy measurements, the presence and relative absorption strength of silicon-hydrogen infrared modes were measured by infrared extended ellipsometry measurements to gain insight into chemical bonding. Structural and optical models have been developed for the back reflector (BR) structure consisting of sputtered undoped zinc oxide (ZnO) on top of silver (Ag) coated glass substrates. Characterization of the free-carrier absorption properties in Ag and the ZnO + Ag interface as well as phonon modes in ZnO were also studied by spectroscopic ellipsometry. Measurements ranging from 0.04 to 5 eV were used to extract layer thicknesses, composition, and optical response in the form of complex dielectric function spectra (ε = ε1 + iε2) for Ag, ZnO, the ZnO + Ag interface, and undoped a-Si:H layer in a substrate n-i-p a-Si:H based PV device structure. PMID:28773255

Effects of different surface modifying agents on the cytotoxic and antimicrobial properties of ZnO nanoparticles.

PubMed

Esparza-González, S C; Sánchez-Valdés, S; Ramírez-Barrón, S N; Loera-Arias, M J; Bernal, J; Meléndez-Ortiz, H Iván; Betancourt-Galindo, R

2016-12-01

Zinc oxide (ZnO) nanoparticles (NPs) have received considerable attention in the medical field because of their antibacterial properties, primarily for killing and reducing the activity of numerous microorganisms. The purpose of this study was to determine whether surface-modified ZnO NPs exhibit different properties compared with unmodified ZnO. The antimicrobial and cytotoxic properties of modified ZnO NPs as well as their effects on inflammatory cytokine production were evaluated. ZnO NPs were prepared using a wet chemical method. Then, the surfaces of these NPs were modified using 3-aminopropyltriethoxysilane (APTES) and dimethyl sulfoxide (DMSO) as modifying agents via a chemical hydrolysis method. According to infrared spectroscopy analysis (FTIR), the structure of the ZnO remained unchanged after modification. Antibacterial assays demonstrated that APTES modification is more effective at inducing an antimicrobial effect against Gram-negative bacteria than against Gram-positive bacteria. Cytotoxicity studies showed that cell viability was dose-dependent; moreover, pristine and APTES-modified ZnO exhibited low cytotoxicity, whereas DMSO-modified ZnO exhibited toxicity even at a low NP concentration. An investigation of inflammatory cytokine production demonstrated that the extent of stimulation was related to the ZnO NP concentration but not to the surface modification, except for IFN-γ and IL-10, which were not detected even at high NP concentrations. Copyright © 2016 Elsevier B.V. All rights reserved.

Ultraviolet Electroluminescence from ZnS@ZnO Core-Shell Nanowires/p-GaN Introduced by Exciton Localization.

PubMed

Fang, Xuan; Wei, Zhipeng; Yang, Yahui; Chen, Rui; Li, Yongfeng; Tang, Jilong; Fang, Dan; Jia, Huimin; Wang, Dengkui; Fan, Jie; Ma, Xiaohui; Yao, Bin; Wang, Xiaohua

2016-01-27

We investigate the electroluminescence (EL) from light emitting diodes (LEDs) of ZnO nanowires/p-GaN structure and ZnS@ZnO core-shell nanowires/p-GaN structure. With the increase of forward bias, the emission peak of ZnO nanowires/p-GaN structure heterojunction shows a blue-shift, while the ZnS@ZnO core-shell nanowires/p-GaN structure demonstrates a changing EL emission; the ultraviolet (UV) emission at 378 nm can be observed. This discrepancy is related to the localized states introduced by ZnS particles, which results in a different carrier recombination process near the interfaces of the heterojunction. The localized states capture the carriers in ZnO nanowires and convert them to localized excitons under high forward bias. A strong UV emission due to localized excitons can be observed. Our results indicated that utilizing localized excitons should be a new route toward ZnO-based ultraviolet LEDs with high efficiency.

Fabrication and characterization of nano-gas sensor arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hassan, H. S., E-mail: hassan.shokry@gmail.com; Kashyout, A. B., E-mail: hady8@yahoo.com; Morsi, I., E-mail: drimanmorsi@yahoo.com

2015-03-30

A novel structures of Nanomaterials gas sensors array constructed using ZnO, and ZnO doped with Al via sol-gel technique. Two structure arrays are developed; the first one is a double sensor array based on doping with percentages of 1% and 5%. The second is a quadrature sensor array based on several doping ratios concentrations (0%, 1%, 5% and 10%). The morphological structures of prepared ZnO were revealed using scanning electron microscope (SEM). X-ray diffraction (XRD) patterns reveal a highly crystallized wurtzite structure and used for identifying phase structure and chemical state of both ZnO and ZnO doped with Al undermore » different preparation conditions and different doping ratios. Chemical composition of Al-doped ZnO nanopowders was performed using energy dispersive x-ray (EDS) analysis. The electrical characteristics of the sensor are determined by measuring the two terminal sensor’s output resistance for O{sub 2}, H{sub 2} and CO{sub 2} gases as a function of temperature.« less

ZrO{sub 2}-ZnO composite thin films for humidity sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velumani, M., E-mail: velumanimohan@gmail.com; Sivacoumar, R.; Alex, Z. C.

2016-05-23

ZrO{sub 2}-ZnO composite thin films were grown by reactive DC magnetron sputtering. X-ray diffraction studies reveal the composite nature of the films with separate ZnO and ZrO{sub 2} phase. Scanning electron microscopy studies confirm the nanocrystalline structure of the films. The films were studied for their impedometric relative humidity (RH) sensing characteristics. The complex impedance plot was fitted with a standard equivalent circuit consisting of an inter-granular resistance and a capacitance in parallel. The DC resistance was found to be decreasing with increase in RH.

Effects of Eu doping and O vacancy on the magnetic and optical properties of ZnO

NASA Astrophysics Data System (ADS)

Ling-Feng, Qu; Qing-Yu, Hou; Xiao-Fang, Jia; Zhen-Chao, Xu; Chun-Wang, Zhao

2018-02-01

We calculated the electronic structure and optical properties of Eu mono-doped ZnO systems with or without O vacancy. We also determined the relative energy of ferromagnetic and antiferromagnetic orders of Eu-double-doped ZnO systems. The double-doped systems possess high Curie temperature and achieve room temperature ferromagnetism. The magnetism in the Eu mono-doped system without O vacancy is caused by the -Eu3+-O2--Eu3+- bound magnetopolaron (BMP) model. The magnetism of Eu mono-doped ZnO systems with O vacancy is more stable than that without O vacancy, and such magnetism is attributed to the -Eu3+-VO++-Eu3+- BMP model. The absorption spectrum for mono-doped systems is red shifted, and this finding confirms that Eu-mono-doped ZnO is a candidate photocatalyst for various applications. Therefore, Eu-double-doped ZnO can be practically used as an unambiguous diluted magnetic semiconductor.

Hydrothermal Growth of ZnO Nanowires on UV-Nanoimprinted Polymer Structures.

PubMed

Park, Sooyeon; Moore, Sean A; Lee, Jaejong; Song, In-Hyouk; Farshchian, Bahador; Kim, Namwon

2018-05-01

Integration of zinc oxide (ZnO) nanowires on miniaturized polymer structures can broaden its application in multi-functional polymer devices by taking advantages of unique physical properties of ZnO nanowires and recent development of polymer microstructures in analytical systems. In this paper, we demonstrate the hydrothermal growth of ZnO nanowires on polymer microstructures fabricated by UV nanoimprinting lithography (NIL) using a polyurethane acrylate (PUA). Since PUA is a siloxane-urethane-acrylate compound containing the alpha-hydroxyl ketone, UV-cured PUA include carboxyl groups, which inhibit and suppress the nucleation and growth of ZnO nanowires on polymer structures. The presence of carboxyl groups in UV-cured PUA was substantiated by Fourier transform infrared spectroscopy (FTIR), and a Ag thin film was deposited on the nanoimprinted polymer structures to limit their inhibitive influence on the growth of ZnO nanowires. Furthermore, the naturally oxidized Ag layer (Ag2O) reduced crystalline lattice mismatches at the interface between ZnO-Ag during the seed annealing process. The ZnO nanowires grown on the Ag-deposited PUA microstructures were found to have comparable morphological characteristics with ZnO nanowires grown on a Si wafer.

Effects of surface morphology of ZnO seed layers on growth of ZnO nanostructures prepared by hydrothermal method and annealing.

PubMed

Yim, Kwang Gug; Kim, Min Su; Leem, Jae-Young

2013-05-01

ZnO nanostructures were grown on Si (111) substrates by a hydrothermal method. Prior to growing the ZnO nanostructures, ZnO seed layers with different post-heat temperatures were prepared by a spin-coating process. Then, the ZnO nanostructures were annealed at 500 degrees C for 20 min under an Ar atmosphere. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out at room temperature (RT) to investigate the structural and optical properties of the as-grown and annealed ZnO nanostructures. The surface morphologies of the seed layers changed from a smooth surface to a mountain chain-like structure as the post-heating temperatures increased. The as-grown and annealed ZnO nanostructures exhibited a strong (002) diffraction peak. Compared to the as-grown ZnO nanostructures, the annealed ZnO nanostructures exhibited significantly strong enhancement in the PL intensity ratio by almost a factor of 2.

Origin of luminescence from ZnO/CdS core/shell nanowire arrays

NASA Astrophysics Data System (ADS)

Wang, Zhiqiang; Wang, Jian; Sham, Tsun-Kong; Yang, Shaoguang

2014-07-01

Chemical imaging, electronic structure and optical properties of ZnO/CdS nano-composites have been investigated using scanning transmission X-ray microscopy (STXM), X-ray absorption near-edge structure (XANES) and X-ray excited optical luminescence (XEOL) spectroscopy. STXM and XANES results confirm that the as-prepared product is ZnO/CdS core/shell nanowires (NWs), and further indicate that ZnS was formed on the surface of ZnO NWs as the interface between ZnO and CdS. The XEOL from ZnO/CdS NW arrays exhibits one weak ultraviolet (UV) emission at 375 nm, one strong green emission at 512 nm, and two broad infrared (IR) emissions at 750 and 900 nm. Combining XANES and XEOL, it is concluded that the UV luminescence is the near band gap emission (BGE) of ZnO; the green luminescence comes from both the BGE of CdS and defect emission (DE, zinc vacancies) of ZnO; the IR luminescence is attributed to the DE (bulk defect related to the S site) of CdS; ZnS contributes little to the luminescence of the ZnO/CdS NW arrays. Interestingly, the BGE and DE from oxygen vacancies of ZnO in the ZnO/CdS nano-composites are almost entirely quenched, while DE from zinc vacancies changes little.Chemical imaging, electronic structure and optical properties of ZnO/CdS nano-composites have been investigated using scanning transmission X-ray microscopy (STXM), X-ray absorption near-edge structure (XANES) and X-ray excited optical luminescence (XEOL) spectroscopy. STXM and XANES results confirm that the as-prepared product is ZnO/CdS core/shell nanowires (NWs), and further indicate that ZnS was formed on the surface of ZnO NWs as the interface between ZnO and CdS. The XEOL from ZnO/CdS NW arrays exhibits one weak ultraviolet (UV) emission at 375 nm, one strong green emission at 512 nm, and two broad infrared (IR) emissions at 750 and 900 nm. Combining XANES and XEOL, it is concluded that the UV luminescence is the near band gap emission (BGE) of ZnO; the green luminescence comes from both the BGE of CdS and defect emission (DE, zinc vacancies) of ZnO; the IR luminescence is attributed to the DE (bulk defect related to the S site) of CdS; ZnS contributes little to the luminescence of the ZnO/CdS NW arrays. Interestingly, the BGE and DE from oxygen vacancies of ZnO in the ZnO/CdS nano-composites are almost entirely quenched, while DE from zinc vacancies changes little. Electronic supplementary information (ESI) available: PL spectra of the ZnO NW arrays before/after CdS coating. S K-edge XANES spectra of the ZnO/CdS core/shell NW arrays. See DOI: 10.1039/c4nr02231a

Defect mediated magnetic interaction and high Tc ferromagnetism in Co doped ZnO nanoparticles.

PubMed

Pal, Bappaditya; Giri, P K

2011-10-01

Structural, optical and magnetic studies have been carried out for the Co-doped ZnO nanoparticles (NPs). ZnO NPs are doped with 3% and 5% Co using ball milling and ferromagnetism (FM) is studied at room temperature and above. A high Curie temperature (Tc) has been observed from the Co doped ZnO NPs. X-ray diffraction and high resolution transmission electron microscopy analysis confirm the absence of metallic Co clusters or any other phase different from würtzite-type ZnO. UV-visible absorption and photoluminescence studies on the doped samples show change in band structure and oxygen vacancy defects, respectively. Micro-Raman studies of doped samples shows defect related additional strong bands at 547 and 574 cm(-1) confirming the presence of oxygen vacancy defects in ZnO lattice. The field dependence of magnetization (M-H curve) measured at room temperature exhibits the clear M-H loop with saturation magnetization and coercive field of the order of 4-6 emu/g and 260 G, respectively. Temperature dependence of magnetization measurement shows sharp ferromagnetic to paramagnetic transition with a high Tc = 791 K for 3% Co doped ZnO NPs. Ferromagnetic ordering is interpreted in terms of overlapping of polarons mediated through oxygen vacancy defects based on the bound magnetic polaron (BMP) model. We show that the observed FM data fits well with the BMP model involving localised carriers and magnetic cations.

Dual-Color Emission in Hybrid III-Nitride/ZnO Light Emitting Diodes

NASA Astrophysics Data System (ADS)

Namkoong, Gon; Trybus, Elaissa; Cheung, Maurice C.; Doolittle, W. Alan; Cartwright, Alexander N.; Ferguson, Ian; Seong, Tae-Yeon; Nause, Jeff

2010-02-01

We report dual-color production of the blue and green regions using hybrid nitride/ZnO light emitting diode (LED) structures grown on ZnO substrates. The blue emission is ascribed to the near-band edge transition in InGaN while green emission is related to Zn-related defect levels formed by the unintentional interdiffusion of Zn into the InGaN active layer from the ZnO substrates.

MOF-Derived ZnO Nanoparticles Covered by N-Doped Carbon Layers and Hybridized on Carbon Nanotubes for Lithium-Ion Battery Anodes.

PubMed

Zhang, Hui; Wang, Yunsong; Zhao, Wenqi; Zou, Mingchu; Chen, Yijun; Yang, Liusi; Xu, Lu; Wu, Huaisheng; Cao, Anyuan

2017-11-01

Metal-organic frameworks (MOFs) have many promising applications in energy and environmental areas such as gas separation, catalysis, supercapacitors, and batteries; the key toward those applications is controlled pyrolysis which can tailor the porous structure, improve electrical conductivity, and expose metal ions in MOFs. Here, we present a systematic study on the structural evolution of zeolitic imidazolate frameworks hybridized on carbon nanotubes (CNTs) during the carbonization process. We show that a number of typical products can be obtained, depending on the annealing time, including (1) CNTs wrapped by relatively thick carbon layers, (2) CNTs grafted by ZnO nanoparticles which are covered by thin nitrogen-doped carbon layers, and (3) CNTs grafted by aggregated ZnO nanoparticles. We also investigated the electrochemical properties of those hybrid structures as freestanding membrane electrodes for lithium ion batteries, and the second one (CNT-supported ZnO covered by N-doped carbon) shows the best performance with a high specific capacity (850 mA h/g at a current density of 100 mA/g) and excellent cycling stability. Our results indicate that tailoring and optimizing the MOF-CNT hybrid structure is essential for developing high-performance energy storage systems.

ZnO:Gd nanocrystals for fluorescent applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Divya, N. K., E-mail: divyank90@gmail.com; Pradyumnan, P. P.

2016-05-23

Gadolinium doped ZnO crystals within the solubility limit of gadolinium in ZnO matrix were prepared by solid state reaction technique. The method is relatively less expense and enables the production in large scale. The samples were characterised by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), UV/Vis diffuse reflectance spectroscopy and photoluminescence techniques. Fluorescent property studies of gadolinium doped ZnO at room temperature show enhanced visible light emission due to the defects and oxygen vacancies produced via doping. This work reports the impact of gadolinium doping in the structural, optical and luminescent properties of ZnO inmore » detail.« less

Photoelectrochemical properties of highly mobilized Li-doped ZnO thin films.

PubMed

Shinde, S S; Bhosale, C H; Rajpure, K Y

2013-03-05

Li-doped ZnO thin films with preferred (002) orientation have been prepared by spray pyrolysis technique in aqueous medium on to the corning glass substrates. The effect of Li-doping on to the photoelectrochemical, structural, morphological, optical, luminescence, electrical and thermal properties has been investigated. XRD and Raman study indicates that the films have hexagonal crystal structure. The transmittance, reflectance, refractive index, extinction coefficient and bandgap have been analyzed by optical study. PL spectra consist of a near band edge and visible emission due to the electronic defects, which are related to deep level emissions, such as oxide antisite (OZn), interstitial zinc (Zni), interstitial oxygen (Oi) and zinc vacancy (VZn). The Li-doped ZnO films prepared for 1at% doping possesses the highest electron mobility of 102cm(2)/Vs and carrier concentration of 3.62×10(19)cm(-3). Finally, degradation of 2,4,6-Trinitrotoluene using Li-doped ZnO thin films has been reported. Copyright © 2013 Elsevier B.V. All rights reserved.

Effects of Al-Impurity Type on Formation Energy, Crystal Structure, Electronic Structure, and Optical Properties of ZnO by Using Density Functional Theory and the Hubbard-U Method.

PubMed

Wu, Hsuan-Chung; Chen, Hsing-Hao; Zhu, Yu-Ren

2016-08-01

We systematically investigated the effects of Al-impurity type on the formation energy, crystal structure, charge density, electronic structure, and optical properties of ZnO by using density functional theory and the Hubbard-U method. Al-related defects, such as those caused by the substitution of Zn and O atoms by Al atoms (Al s(Zn) and Al s(O) , respectively) and the presence of an interstitial Al atom at the center of a tetrahedron (Al i(tet) ) or an octahedron (Al i(oct) ), and various Al concentrations were evaluated. The calculated formation energy follows the order E f (Al s(Zn) ) < E f (Al i(tet) ) < E f (Al i(oct) ) < E f (Al s(O) ). Electronic structure analysis showed that the Al s(Zn) , Al s(O) , Al i(tet) , and Al i(oct) models follow n -type conduction, and the optical band gaps are higher than that of pure ZnO. The calculated carrier concentrations of the Al s(O) and Al i(tet) /Al i(oct) models are higher than that of the Al s(Zn) model. However, according to the curvature of the band structure, the occurrence of interstitial Al atoms or the substitution of O atoms by Al atoms results in a high effective mass, possibly reducing the carrier mobility. The average transmittance levels in the visible light and ultraviolet (UV) regions of the Al s(Zn) model are higher than those of pure ZnO. However, the presence of an interstitial Al atom within the ZnO crystal reduces transmittance in the visible light region; Al s(O) substantially reduces the transmittance in the visible light and UV regions. In addition, the properties of ZnO doped with various Al s(Zn) concentrations were analyzed.

Hydrogen-related complexes in Li-diffused ZnO single crystals

DOE PAGES

Corolewski, Caleb D.; Parmar, Narendra S.; Lynn, Kelvin G.; ...

2016-07-21

Zinc oxide (ZnO) is a wide band gap semiconductor and a potential candidate for next generation white solid state lighting applications. In this work, hydrogen-related complexes in lithium diffused ZnO single crystals were studied. In addition to the well-known Li-OH complex, several other hydrogen defects were observed. When a mixture of Li 2O and ZnO is used as the dopant source, zinc vacancies are suppressed and the bulk Li concentration is very high (>10 19 cm -3). In that case, the predominant hydrogen complex has a vibrational frequency of 3677 cm -1, attributed to surface O-H species. When Li 2COmore » 3 is used, a structured blue luminescence band and O-H mode at 3327 cm -1 are observed at 10K. These observations, along with positron annihilation measurements, suggest a zinc vacancy–hydrogen complex, with an acceptor level 0.3 eV above the valence-band maximum. In conclusion, this relatively shallow acceptor could be beneficial for p-type ZnO.« less

Effect of deposition parameters on the structural properties of ZnO nanopowders prepared by microwave-assisted hydrothermal synthesis.

PubMed

Caglar, Yasemin; Gorgun, Kamuran; Aksoy, Seval

2015-03-05

ZnO nanopowders were synthesized via microwave-assisted hydrothermal method at different deposition (microwave irradiation) times and pH values. The effects of pH and deposition (microwave irradiation) time on the crystalline structure and orientation of the ZnO nanopowders have been investigated by X-ray diffraction (XRD) study. XRD observations showed that the crystalline quality of ZnO nanopowders increased with increasing pH value. The crystallite size and texture coefficient values of ZnO nanopowders were calculated. The structural quality of ZnO nanopowder was improved by deposition parameters. Field emission scanning electron microscope (FESEM) was used to analyze the surface morphology of the ZnO nanopowders. Microwave irradiation time and pH value showed a significant effect on the surface morphology. Copyright © 2014 Elsevier B.V. All rights reserved.

Fe-tannic acid complex dye as photo sensitizer for different morphological ZnO based DSSCs

NASA Astrophysics Data System (ADS)

Çakar, Soner; Özacar, Mahmut

2016-06-01

In this paper we have synthesized different morphological ZnO nanostructures via microwave hydrothermal methods at low temperature within a short time. We described different morphologies of ZnO at different Zn(NO3)2/KOH mole ratio. The ZnO nanostructures were characterized via X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and UV-vis spectrophotometry. All ZnO structures have hexagonal wurtzite type structures. The FESEM images showed various morphologies of ZnO such as plate, rod and nanoparticles. Dye sensitized solar cells have been assembled by these different morphological structures photo electrode and tannic acid or Fe-tannic acid complex dye as sensitizer. We have achieved at maximum efficiencies of photovoltaic cells prepared with ZnO plate in all dye systems. The conversion efficiencies of dye sensitized solar cells are 0.37% and 1.00% with tannic acid and Fe-tannic acid complex dye, respectively.

Hydrodynamic fabrication of structurally gradient ZnO nanorods.

PubMed

Kim, Hyung Min; Youn, Jae Ryoun; Song, Young Seok

2016-02-26

We studied a new approach where structurally gradient nanostructures were fabricated by means of hydrodynamics. Zinc oxide (ZnO) nanorods were synthesized in a drag-driven rotational flow in a controlled manner. The structural characteristics of nanorods such as orientation and diameter were determined by momentum and mass transfer at the substrate surface. The nucleation of ZnO was induced by shear stress which plays a key role in determining the orientation of ZnO nanorods. The nucleation and growth of such nanostructures were modeled theoretically and analyzed numerically to understand the underlying physics of the fabrication of nanostructures controlled by hydrodynamics. The findings demonstrated that the precise control of momentum and mass transfer enabled the formation of ZnO nanorods with a structural gradient in diameter and orientation.

The effect of concentration ratio and type of functional group on synthesis of CNT-ZnO hybrid nanomaterial by an in situ sol-gel process

NASA Astrophysics Data System (ADS)

Hosseini Largani, Sekineh; Akbarzadeh Pasha, Mohammad

2017-12-01

In this research, MWCNT-ZnO hybrid nanomaterials were synthesized by a simple sol-gel process using Zn(CH3COO)2·2H2O and functionalized MWCNT with carboxyl(COOH) and hydroxyl(OH) groups. Three different mass ratios of MWCNT:ZnO = 3:1, 1:1 and 1:3 were examined. The prepared nanomaterials were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR). Successful growth of MWCNT-ZnO hybrids for both COOH and OH functional groups and all the three mass ratios were obtained. The ZnO nanoparticles attached on the surfaces of CNTs have rather spherical shapes and hexagonal crystal structure. By increasing the concentration of ZnO, the number and average size of ZnO nanoparticles decorated the body of CNTs in hybrid structures increase. By increasing the ZnO precursor, the distribution of ZnO nanoparticles that appeared on the surface of CNTs becomes more uniform. The SEM observation beside EDX analysis revealed that at the same concentration ratio the amount of ZnO loading on the surface of MWCNT-COOH is more than MWCNT-OH. Moreover, the average size of ZnO nanoparticles attached on the surface of COOH functionalized CNTs is relatively smaller than that of OH functionalized ones.

Effect of Co doping concentration on structural properties and optical parameters of Co-doped ZnO thin films by sol-gel dip-coating method.

PubMed

Nam, Giwoong; Yoon, Hyunsik; Kim, Byunggu; Lee, Dong-Yul; Kim, Jong Su; Leem, Jae-Young

2014-11-01

The structural and optical properties of Co-doped ZnO thin films prepared by a sol-gel dip-coating method were investigated. X-ray diffraction analysis showed that the thin films were grown with a c-axis preferred orientation. The position of the (002) peak was almost the same in all samples, irrespective of the Co concentration. It is thus clear that Co doping had little effect on the position of the (002) peak. To confirm that Co2+ was substituted for Zn2+ in the wurtzite structure, optical measurements were conducted at room temperature by a UV-visible spectrometer. Three absorption peaks are apparent in the Co-doped ZnO thin films that do not appear for the undoped ZnO thin film. As the Co concentration was increased, absorption related to characteristic Co2+ transitions increased because three absorption band intensities and the area underneath the absorption wells between 500 and 700 nm increased with increasing Co concentration. The optical band gap and static dielectric constant decreased and the Urbach energy and extinction coefficient increased with increasing Co concentration.

Excitation Dependent Phosphorous Property and New Model of the Structured Green Luminescence in ZnO

NASA Astrophysics Data System (ADS)

Ye, Honggang; Su, Zhicheng; Tang, Fei; Wang, Mingzheng; Chen, Guangde; Wang, Jian; Xu, Shijie

2017-02-01

The copper induced green luminescence (GL) with two sets of fine structures in ZnO crystal has been found for several decades (i.e., R. Dingle, Phys. Rev. Lett. 23, 579 (1969)), but the physical origin of the doublet still remains as an open question up to now. In this paper, we provide new insight into the mechanism of the structured GL band in terms of new experimental findings and theoretical calculations. It is found, for the first time, that the GL signal exhibits persistent afterglow for tens of minutes after the switch-off of below-band-gap excitation light but it cannot occur under above-band-gap excitation. Such a phosphorous property may be interpreted as de-trapping and feeding of electrons from a shallow trapping level via the conduction band to the Cu-related luminescence centers where the Cu3+ ion is proposed to work as the final state of the GL emission. From first-principles calculation, such a Cu3+ ion in wurtzite ZnO prefers a high spin 3d8 state with two non-degenerated half-filled orbitals due to the Jahn-Teller effect, probably leading to the double structures in photoluminescence spectrum. Therefore, this model gives a comprehensively new understanding on the mechanism of the structured GL band in ZnO.

Effect of Ag doping on the properties of ZnO thin films for UV stimulated emission

NASA Astrophysics Data System (ADS)

Razeen, Ahmed S.; Gadallah, A.-S.; El-Nahass, M. M.

2018-06-01

Ag doped ZnO thin films have been prepared using sol-gel spin coating method, with different doping concentrations. Structural and morphological properties of the films have been investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Thin films have been optically pumped and stimulated emission has been observed with strong peaks in the UV region. The UV stimulated emission is found to be due to exciton-exciton scattering, and Ag doping promoted this process by increasing the excitons concentrations in the ZnO lattice. Output-input intensity relation and peak emission, FWHM, and quantum efficiency relations with pump intensity have been reported. The threshold for which stimulated emission started has been evaluated to be about 18 MW/cm2 with quantum efficiency of about 58.7%. Mechanisms explaining the role of Ag in enhancement of stimulated emission from ZnO thin films have been proposed.

Nanoporous structures on ZnO thin films

NASA Astrophysics Data System (ADS)

Gür, Emre; Kılıç, Bayram; Coşkun, C.; Tüzemen, S.; Bayrakçeken, Fatma

2010-01-01

Porous structures were formed on ZnO thin films which were grown by an electrochemical deposition (ECD) method. The growth processes were carried out in a solution of dimethylsulfoxide (DMSO) zinc perchlorate, Zn(ClO 4) 2, at 120 ∘C on indium tin oxide (ITO) substrates. Optical and structural characterizations of electrochemically grown ZnO thin films have shown that the films possess high (0002) c-axis orientation, high nucleation, high intensity and low FWHM of UV emission at the band edge region and a sharp UV absorption edge. Nanoporous structures were formed via self-assembled monolayers (SAMs) of hexanethiol (C 6SH) and dodecanethiol (C 12SH). Scanning electron microscope (SEM) measurements showed that while a nanoporous structure (pore radius 20 nm) is formed on the ZnO thin films by hexanathiol solution, a macroporous structure (pore radius 360 nm) is formed by dodecanethiol solution. No significant variation is observed in X-ray diffraction (XRD) measurements on the ZnO thin films after pore formation. However, photoluminescence (PL) measurements showed that green emission is observed as the dominant emission for the macroporous structures, while no variation is observed for the thin film nanoporous ZnO sample.

Structural, optical and field emission properties of urchin-shaped ZnO nanostructures.

PubMed

Al-Heniti, Saleh; Umar, Ahmad

2013-01-01

In this work, well-crystallized urchin-shaped ZnO structures were synthesized on silicon substrate by simple non-catalytic thermal evaporation process by using metallic zinc powder in the presence of oxygen as source materials for zinc and oxygen, respectively. The synthesized ZnO structures were characterized in detail in terms of their morphological, structural, optical and field emission properties. The detailed morphological investigations revealed that the synthesized structures possess urchin-shape and grown in high-density over the substrate surface. The detailed structural and optical characterizations revealed that the synthesized urchin-shaped ZnO structures are well-crystallized and exhibiting good optical properties. The field emission analysis for urchin-shaped ZnO structures exhibits a turn-on field of 4.6 V/microm. The emission current density reached to 0.056 mA/cm2 at an applied electrical field of 6.4 V/microm and shows no saturation. The calculated field enhancement factor 'beta', from the F-N plot, was found to be approximately 2.2 x 10(3).

Direct growth of ZnO tetrapod on glass substrate by Chemical Vapor Deposition Technique

NASA Astrophysics Data System (ADS)

Fadzil, M. F. M.; Rahman, R. A.; Azhar, N. E. A.; Aziz, T. N. T. A.; Zulkifli, Z.

2018-03-01

This research demonstrates the growth of ZnO tetrapod structure on glass substrate for different types of flow gas and at different growth temperatures. The study on the morphological structure and electrical properties of ZnO thin film growth by Chemical Vapour Deposition (CVD) technique showed that the optimum growth temperature was obtained at 750°C with ZnO nanotetrapod morphological structure. Introducing Nitrogen gas flow during the growth process exhibited leg-to-leg linking ZnO tetrapods morphology. The electrical properties of ZnO tetrapods film were measured by using two point probes and it shows that, the sample growth in Ar and O2 atmosphere have better I-V characteristic.

Blue emitting ZnO nanostructures grown through cellulose bio-templates.

PubMed

Oudhia, Anjali; Sharma, Savita; Kulkarni, Pragya; Kumar, Rajesh

2016-06-01

This paper presents a green and cost-effective recipe for the synthesis of blue-emitting ZnO nanoparticles (NPs) using cellulose bio-templates. Azadirachta indica (neem) leaf extract prepared in different solvents were used as biological templates to produce nanostructures of wurtzite ZnO with a particle size ~12-36 nm. A cellulose-driven capping mechanism is used to describe the morphology of ZnO NPs. The scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infra-red (FTIR) and photoluminescence (PL) studies showed that solvents affect the growth process and the capping mechanism of bio-template severely. Structural changes in ZnO NPs were evident with variation in pH, dielectric constants (DC) and boiling points (BP) of solvents. Furthermore, an energy band model is proposed to explain the origin of the blue emission in the as-obtained ZnO NPs. PL excitation studies and the theoretical enthalpy values of individual defects were used to establish the association between the interstitial-zinc-related defect levels and the blue emission. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Nanocrystalline-to-amorphous transition in nanolaminates grown by low temperature atomic layer deposition and related mechanical properties

NASA Astrophysics Data System (ADS)

Raghavan, R.; Bechelany, M.; Parlinska, M.; Frey, D.; Mook, W. M.; Beyer, A.; Michler, J.; Utke, I.

2012-05-01

We report on a comprehensive structural and nanoindentation study of nanolaminates of Al2O3 and ZnO synthesized by atomic layer deposition (ALD). By reducing the bilayer thickness from 50 nm to below 1 nm, the nanocrystal size could be controlled in the nanolaminate structure. The softer and more compliant response of the multilayers as compared to the single layers of Al2O3 and ZnO is attributed to the structural change from nanocrystalline to amorphous at smaller bilayer thicknesses. It is also shown that ALD is a unique technique for studying the inverse Hall-Petch softening mechanism (E. Voce and D. Tabor, J. Inst. Metals 79(12), 465 (1951)) related to grain size effects in nanomaterials.

Fabrication of Well-Aligned ZnO Nanorods Using a Composite Seed Layer of ZnO Nanoparticles and Chitosan Polymer.

PubMed

Khun, Kimleang; Ibupoto, Zafar Hussain; AlSalhi, Mohamad S; Atif, Muhammad; Ansari, Anees A; Willander, Magnus

2013-09-30

In this study, by taking the advantage of both inorganic ZnO nanoparticles and the organic material chitosan as a composite seed layer, we have fabricated well-aligned ZnO nanorods on a gold-coated glass substrate using the hydrothermal growth method. The ZnO nanoparticles were characterized by the Raman spectroscopic techniques, which showed the nanocrystalline phase of the ZnO nanoparticles. Different composites of ZnO nanoparticles and chitosan were prepared and used as a seed layer for the fabrication of well-aligned ZnO nanorods. Field emission scanning electron microscopy, energy dispersive X-ray, high-resolution transmission electron microscopy, X-ray diffraction, and infrared reflection absorption spectroscopic techniques were utilized for the structural characterization of the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods on a gold-coated glass substrate. This study has shown that the ZnO nanorods are well-aligned, uniform, and dense, exhibit the wurtzite hexagonal structure, and are perpendicularly oriented to the substrate. Moreover, the ZnO nanorods are only composed of Zn and O atoms. An optical study was also carried out for the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods, and the obtained results have shown that the fabricated ZnO nanorods exhibit good crystal quality. This study has provided a cheap fabrication method for the controlled morphology and good alignment of ZnO nanorods, which is of high demand for enhancing the working performance of optoelectronic devices.

Fabrication of Well-Aligned ZnO Nanorods Using a Composite Seed Layer of ZnO Nanoparticles and Chitosan Polymer

PubMed Central

Khun, Kimleang; Ibupoto, Zafar Hussain; AlSalhi, Mohamad S.; Atif, Muhammad; Ansari, Anees A.; Willander, Magnus

2013-01-01

In this study, by taking the advantage of both inorganic ZnO nanoparticles and the organic material chitosan as a composite seed layer, we have fabricated well-aligned ZnO nanorods on a gold-coated glass substrate using the hydrothermal growth method. The ZnO nanoparticles were characterized by the Raman spectroscopic techniques, which showed the nanocrystalline phase of the ZnO nanoparticles. Different composites of ZnO nanoparticles and chitosan were prepared and used as a seed layer for the fabrication of well-aligned ZnO nanorods. Field emission scanning electron microscopy, energy dispersive X-ray, high-resolution transmission electron microscopy, X-ray diffraction, and infrared reflection absorption spectroscopic techniques were utilized for the structural characterization of the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods on a gold-coated glass substrate. This study has shown that the ZnO nanorods are well-aligned, uniform, and dense, exhibit the wurtzite hexagonal structure, and are perpendicularly oriented to the substrate. Moreover, the ZnO nanorods are only composed of Zn and O atoms. An optical study was also carried out for the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods, and the obtained results have shown that the fabricated ZnO nanorods exhibit good crystal quality. This study has provided a cheap fabrication method for the controlled morphology and good alignment of ZnO nanorods, which is of high demand for enhancing the working performance of optoelectronic devices. PMID:28788336

Dimensional-Hybrid Structures of 2D Materials with ZnO Nanostructures via pH-Mediated Hydrothermal Growth for Flexible UV Photodetectors.

PubMed

Lee, Young Bum; Kim, Seong Ku; Lim, Yi Rang; Jeon, In Su; Song, Wooseok; Myung, Sung; Lee, Sun Sook; Lim, Jongsun; An, Ki-Seok

2017-05-03

Complementary combination of heterostructures is a crucial factor for the development of 2D materials-based optoelectronic devices. Herein, an appropriate solution for fabricating complementary dimensional-hybrid nanostructures comprising structurally tailored ZnO nanostructures and 2D materials such as graphene and MoS 2 is suggested. Structural features of ZnO nanostructures hydrothermally grown on graphene and MoS 2 are deliberately manipulated by adjusting the pH value of the growing solution, which will result in the formation of ZnO nanowires, nanostars, and nanoflowers. The detailed growth mechanism is further explored for the structurally tailored ZnO nanostructures on the 2D materials. Furthermore, a UV photodetector based on the dimensional-hybrid nanostructures is fabricated, which demonstrates their excellent photocurrent and mechanical durability. This can be understood by the existence of oxygen vacancies and oxygen-vacancies-induced band narrowing in the ZnO nanostructures, which is a decisive factor for determining their photoelectrical properties in the hybrid system.

Growth of catalyst-free high-quality ZnO nanowires by thermal evaporation under air ambient

PubMed Central

2012-01-01

ZnO nanowires have been successfully fabricated on Si substrate by simple thermal evaporation of Zn powder under air ambient without any catalyst. Morphology and structure analyses indicated that ZnO nanowires had high purity and perfect crystallinity. The diameter of ZnO nanowires was 40 to 100 nm, and the length was about several tens of micrometers. The prepared ZnO nanowires exhibited a hexagonal wurtzite crystal structure. The growth of the ZnO nanostructure was explained by the vapor-solid mechanism. The simplicity, low cost and fewer necessary apparatuses of the process would suit the high-throughput fabrication of ZnO nanowires. The ZnO nanowires fabricated on Si substrate are compatible with state-of-the-art semiconductor industry. They are expected to have potential applications in functional nanodevices. PMID:22502639

ZnO thin film piezoelectric micromachined microphone with symmetric composite vibrating diaphragm

NASA Astrophysics Data System (ADS)

Li, Junhong; Wang, Chenghao; Ren, Wei; Ma, Jun

2017-05-01

Residual stress is an important factor affecting the sensitivity of piezoelectric micromachined microphone. A symmetric composite vibrating diaphragm was adopted in the micro electro mechanical systems piezoelectric microphone to decrease the residual stress and improve the sensitivity of microphone in this paper. The ZnO film was selected as piezoelectric materials of microphone for its higher piezoelectric coefficient d 31 and lower relative dielectric constant. The thickness optimization of piezoelectric film on square diaphragm is difficult to be fulfilled by analytic method. To optimize the thickness of ZnO films, the stress distribution in ZnO film was analyzed by finite element method and the average stress in different thickness of ZnO films was given. The ZnO films deposited using dc magnetron sputtering exhibits a densely packed structure with columnar crystallites preferentially oriented along (002) plane. The diaphragm of microphone fabricated by micromachining techniques is flat and no wrinkling at corners, and the sensitivity of microphone is higher than 1 mV Pa-1. These results indicate the diaphragm has lower residual stress.

Observations of two-dimensional monolayer zinc oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sahoo, Trilochan, E-mail: trilochansahoo@gmail.com; Nayak, Sanjeev K.; Chelliah, Pandian

2016-03-15

Highlights: • Synthesis of planer ZnO nanostructure. • Observation of multilayered and monolayer ZnO. • DFT calculation of (10-10), (11-20) and (0 0 0 1) planes of ZnO. • Stability of non-polar (10-10) and (11-20) planes of ZnO. - Abstract: This letter reports the observations of planar two-dimensional ZnO synthesized using the hydrothermal growth technique. High-resolution transmission electron microscopy revealed the formation of a two-dimensional honeycomb lattice and aggregated structures of layered ZnO. The nonpolar (10-10) and (11-20) planes were present in the X-ray diffraction patterns, but the characteristic (0 0 0 1) peak of bulk ZnO was absent. Themore » study found that nonpolar freestanding ZnO structures composed of a single or few layers may be more stable and may have a higher probability of formation than their polar counterparts. The stability of the nonpolar two-dimensional hexagonal ZnO slabs is supported by density functional theory studies.« less

Structural, optical, and magnetic studies of manganese-doped zinc oxide hierarchical microspheres by self-assembly of nanoparticles.

PubMed

Hao, Yao-Ming; Lou, Shi-Yun; Zhou, Shao-Min; Yuan, Rui-Jian; Zhu, Gong-Yu; Li, Ning

2012-02-02

In this study, a series of manganese [Mn]-doped zinc oxide [ZnO] hierarchical microspheres [HMSs] are prepared by hydrothermal method only using zinc acetate and manganese acetate as precursors and ethylene glycol as solvent. X-ray diffraction indicates that all of the as-obtained samples including the highest Mn (7 mol%) in the crystal lattice of ZnO have a pure phase (hexagonal wurtzite structure). A broad Raman spectrum from as-synthesized doping samples ranges from 500 to 600 cm-1, revealing the successful doping of paramagnetic Mn2+ ions in the host ZnO. Optical absorption analysis of the samples exhibits a blueshift in the absorption band edge with increasing dopant concentration, and corresponding photoluminescence spectra show that Mn doping suppresses both near-band edge UV emission and defect-related blue emission. In particular, magnetic measurements confirm robust room-temperature ferromagnetic behavior with a high Curie temperature exceeding 400 K, signifying that the as-formed Mn-doped ZnO HMSs will have immense potential in spintronic devices and spin-based electronic technologies.

Hexagonal and prismatic nanowalled ZnO microboxes.

PubMed

Zhao, Fenghua; Lin, Wenjiao; Wu, Mingmei; Xu, Ningsheng; Yang, Xianfeng; Tian, Z Ryan; Su, Qiang

2006-04-17

We hereby report hydrothermal syntheses of new microstructures of semiconducting ZnO. Single-crystalline prismatic ZnO microboxes formed by nanowalls and hexagonal hollow microdisks closed by plates with micron-sized inorganic fullerene-like structures have been made in a base-free medium through a one-step hydrothermal synthesis with the help of n-butanol (NB). Structures and morphologies of the products were confirmed by results from powder X-ray diffraction and scanning electron microscopy. NB has been found to play a crucial role in the growth of these hollow structures. It is indicated that these hollow ZnO crystals were grown from redissolution of interiors. These ZnO microboxes exhibit a band emission in the visible range, implying the possession of a high content of defects.

Characterization of Zinc Oxide (ZnO) piezoelectric properties for Surface Acoustic Wave (SAW) device

NASA Astrophysics Data System (ADS)

Rosydi Zakaria, Mohd; Johari, Shazlina; Hafiz Ismail, Mohd; Hashim, Uda

2017-11-01

In fabricating Surface Acoustic Wave (SAW) biosensors device, the substrate is one of important factors that affected to performance device. there are many types of piezoelectric substrate in the markets and the cheapest is zinc Oxide substrate. Zinc Oxide (ZnO) with its unique properties can be used as piezoelectric substrate along with SAW devices for detection of DNA in this research. In this project, ZnO thin film is deposited onto silicon oxide substrate using electron beam evaporation (E-beam) and Sol-Gel technique. Different material structure is used to compare the roughness and best piezoelectric substrate of ZnO thin film. Two different structures of ZnO target which are pellet and granular are used for e-beam deposition and one sol-gel liquid were synthesize and compared. Parameter for thickness of ZnO e-beam deposition is fixed to a 0.1kÅ for both materials structure and sol-gel was coat using spin coat technique. After the process is done, samples are annealed at temperature of 500°C for 2 hours. The structural properties of effect of post annealing using different material structure of ZnO are studied using Atomic Force Microscopic (AFM) for surface morphology and X-ray Diffraction (XRD) for phase structure.

Identification of F impurities in F-doped ZnO by synchrotron X-ray absorption near edge structures

NASA Astrophysics Data System (ADS)

Na-Phattalung, Sutassana; Limpijumnong, Sukit; Min, Chul-Hee; Cho, Deok-Yong; Lee, Seung-Ran; Char, Kookrin; Yu, Jaejun

2018-04-01

Synchrotron X-ray absorption near edge structure (XANES) measurements of F K-edge in conjunction with first-principles calculations are used to identify the local structure of the fluorine (F) atom in F-doped ZnO. The ZnO film was grown by pulsed laser deposition with an Nd:YAG laser, and an oxyfluoridation method was used to introduce F ions into the ZnO films. The measured XANES spectrum of the sample was compared against the first-principles XANES calculations based on various models for local atomic structures surrounding F atoms. The observed spectral features are attributed to ZnF2 and FO defects in wurtzite bulk ZnO.

Eosin-Y sensitized core-shell TiO2-ZnO nano-structured photoanodes for dye-sensitized solar cell applications.

PubMed

Manikandan, V S; Palai, Akshaya K; Mohanty, Smita; Nayak, Sanjay K

2018-06-01

In the current investigation, TiO 2 and TiO 2 -ZnO (core-shell) spherical nanoparticles were synthesized by simple combined hydrolysis and refluxing method. A TiO 2 core nanomaterial on the shell material of ZnO was synthesized by utilizing variable ratios of ZnO. The structural characterization of TiO 2 -ZnO core/shell nanoparticles were done by XRD analysis. The spherical structured morphology of the TiO 2 -ZnO has been confirmed through field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) studies. The UV-visible spectra of TiO 2 -ZnO nanostructures were also compared with the pristine TiO 2 to investigate the shift of wavelength. The TiO 2 -ZnO core/shell nanoparticles at the interface efficiently collect the photogenarated electrons from ZnO and also ZnO act a barrier for reduced charge recombination of electrolyte and dye-nanoparticles interface. This combination improved the light absorption which induced the charge transfer ability and dye loading capacity of core-shell nanoparticles. An enhancement in the short circuit current (J sc ) from 1.67 mA/cm 2 to 2.1 mA/cm 2 has been observed for TiO 2 -ZnObased photoanode (with platinum free counter electrode), promises an improvement in the energy conversion efficiency by 57% in comparison with that of the DSSCs based on the pristine TiO 2 . Henceforth, TiO 2 -ZnO photoelectrode in ZnO will effectively act as barrier at the interface of TiO 2 -ZnO and TiO 2 , ensuring the potential for DSSC application. Copyright © 2018 Elsevier B.V. All rights reserved.

Effects of different compositions from magnetic and nonmagnetic dopants on structural and electrical properties of ZnO nanoparticles-based varistor ceramics

NASA Astrophysics Data System (ADS)

Sendi, Rabab Khalid

2018-03-01

In the current study, 20 nm zinc oxide (ZnO) nanoparticles were used to manufacture high-density ZnO discs doped with Mn and Sn via the conventional ceramic processing method, and their properties were characterized. Results show that the dopants were found to have significant effects on the ZnO varistors, especially on the shape and size of grains, which are significantly different for both dopants. The strong solid-state reaction in the varistor from the 20 nm ZnO powder during the sintering process may be attributed to the high surface area of the 20 nm ZnO nanoparticles. Although Mn and Sn do not affect the well-known peaks related to the wurtzite structure of ZnO ceramics, a few of the additional peaks could be formed at high doping content (≥2.0) due to the formation of other unknown phases during the sintering process. Both additives also significantly affect the electrical properties of the varistor, with a marked changed in the breakdown voltage from 415 V to 460 V for Sn and from 400 V to 950 V for Mn. Interestingly, the electrical behaviors of the varistors, such as breakdown voltage, nonlinear coefficient, and barrier height, are higher for Mn- than Sn-doping samples, and the opposite behaviors hold for hardness, leakage currents, and electrical conductivities. Results show that the magnetic moment and valence state of the two additive dopants are responsible for all demonstrated differences in the electrical characteristics between the two dopants.

Buckminsterfullerene hybridized zinc oxide tetrapods: defects and charge transfer induced optical and electrical response.

PubMed

Smazna, Daria; Rodrigues, Joana; Shree, Sindu; Postica, Vasile; Neubüser, Gero; Martins, A F; Ben Sedrine, N; Jena, Naresh K; Siebert, Leonard; Schütt, Fabian; Lupan, Oleg; Ahuja, Rajeev; Correia, M R; Monteiro, Teresa; Kienle, Lorenz; Yang, Ya; Adelung, Rainer; Mishra, Yogendra Kumar

2018-05-21

Buckminster fullerene (C60) based hybrid metal oxide materials are receiving considerable attention because of their excellent fundamental and applied aspects, like semiconducting, electron transfer, luminescent behaviors, etc. and this work briefly discusses the successful fabrication of C60 decorated ZnO tetrapod materials and their detailed structure-property relationships including device sensing applications. The electron microscopy investigations indicate that a quite dense surface coverage of ZnO tetrapods with C60 clusters is achieved. The spectroscopy studies confirmed the identification of the C60 vibrational modes and the C60 induced changes in the absorption and luminescence properties of the ZnO tetrapods. An increased C60 concentration on ZnO results in steeper ZnO bandgap absorption followed by well-defined free exciton and 3.31 eV line emissions. As expected, higher amounts of C60 increase the intensity of C60-related visible absorption bands. Pumping the samples with photons with an energy corresponding to these absorption band maxima leads to additional emission from ZnO showing an effective charge transfer phenomenon from C60 to the ZnO host. The density of states model obtained from DFT studies for pure and C60 coated ZnO surfaces confirms the experimental observations. The fabricated C60-ZnO hybrid tetrapod based micro- and nanodevices showed interesting ethanol gas sensing characteristics.

Dye anchored ZnO nanoparticles: The positive and negative photoluminescence quenching effects

NASA Astrophysics Data System (ADS)

Ganesh, T.; Kim, Jong Hoon; Yoon, Seog Joon; Lee, Sangjin; Lee, Wonjoo; Mane, Rajaram S.; Han, Jin Wook; Han, Sung-Hwan

2009-10-01

The positive and negative photoluminescence quenching effects in dye [BCMoxo and BCtCM (curcumin-derived molecules)] anchored ZnO nanoparticles (NPs) are investigated using the optical and electronic properties. The photoluminescence, band gap (BCMoxo, 2.2 eV; BCtCM, 2.3 eV), and wettability studies confirm an optical quenching, well-matched electronic structure and relative hydrophobic nature, respectively, in the presence of dicarboxylic anchor groups (BCtCM) on ZnO NPs in contrast to that of keto groups (BCMoxo). Systematic change in UV-visible absorption band edge is noticeable for the BCtCM and BCMoxo-anchored ZnO NPs. The atomic absorption spectroscopy and inductively coupled-mass-spectroscopy analysis quantitatively verifies the amount of BCtCM dye molecules present on ZnO NPs surface area about three times higher than that of BCMoxo dye molecule without anchor groups.

Enhanced ultraviolet photo-response in Dy doped ZnO thin film

NASA Astrophysics Data System (ADS)

Kumar, Pawan; Singh, Ranveer; Pandey, Praveen C.

2018-02-01

In the present work, a Dy doped ZnO thin film deposited by the spin coating method has been studied for its potential application in a ZnO based UV detector. The investigations on the structural property and surface morphology of the thin film ensure that the prepared samples are crystalline and exhibit a hexagonal crystal structure of ZnO. A small change in crystallite size has been observed due to Dy doping in ZnO. AFM analysis ascertains the grain growth and smooth surface of the thin films. The Dy doped ZnO thin film exhibits a significant enhancement in UV region absorption as compared to the pure ZnO thin film, which suggests that Dy doped ZnO can be used as a UV detector. Under UV irradiation of wavelength 325 nm, the photocurrent value of Dy doped ZnO is 105.54 μA at 4.5 V, which is 31 times greater than that of the un-doped ZnO thin film (3.39 μA). The calculated value of responsivity is found to increase significantly due to the incorporation of Dy in the ZnO lattice. The observed higher value of photocurrent and responsivity could be attributed to the substitution of Dy in the ZnO lattice, which enhances the conductivity, electron mobility, and defects in ZnO and benefits the UV sensing property.

Complex and oriented ZnO nanostructures.

PubMed

Tian, Zhengrong R; Voigt, James A; Liu, Jun; McKenzie, Bonnie; McDermott, Matthew J; Rodriguez, Mark A; Konishi, Hiromi; Xu, Huifang

2003-12-01

Extended and oriented nanostructures are desirable for many applications, but direct fabrication of complex nanostructures with controlled crystalline morphology, orientation and surface architectures remains a significant challenge. Here we report a low-temperature, environmentally benign, solution-based approach for the preparation of complex and oriented ZnO nanostructures, and the systematic modification of their crystal morphology. Using controlled seeded growth and citrate anions that selectively adsorb on ZnO basal planes as the structure-directing agent, we prepared large arrays of oriented ZnO nanorods with controlled aspect ratios, complex film morphologies made of oriented nanocolumns and nanoplates (remarkably similar to biomineral structures in red abalone shells) and complex bilayers showing in situ column-to-rod morphological transitions. The advantages of some of these ZnO structures for photocatalytic decompositions of volatile organic compounds were demonstrated. The novel ZnO nanostructures are expected to have great potential for sensing, catalysis, optical emission, piezoelectric transduction, and actuations.

Anisotropic properties of periodically polarity-inverted zinc oxide structures

NASA Astrophysics Data System (ADS)

Park, J. S.; Minegishi, T.; Lee, J. W.; Hong, S. K.; Song, J. H.; Lee, J. Y.; Yoon, E.; Yao, T.

2010-06-01

We report on the anisotropic structural properties of periodically polarity-inverted (PPI) ZnO structures grown on patterned templates. The etching and growth rates along ⟨112¯0⟩ direction of ZnO structures are higher than those of ⟨101¯0⟩ direction of ZnO films. From the strain evaluation by Raman spectroscopy, compressive strains are observed in all PPI ZnO samples with different stripe pattern size and the smaller pattern size is more effective to residual stress relaxation. The detailed structures at transition region show relationship with the anisotropic crystal quality.

Effect of Pressure on the Stability and Electronic Structure of ZnO0.5S0.5 and ZnO0.5Se0.5

NASA Astrophysics Data System (ADS)

Manotum, R.; Klinkla, R.; Phaisangittisakul, N.; Pinsook, U.; Bovornratanaraks, T.

2017-12-01

Structures and high-pressure phase transitions in ZnO0.5S0.5 and ZnO0.5Se0.5 have been investigated using density functional theory calculations. The previously proposed structures of ZnO0.5S0.5 and ZnO0.5Se0.5 which are chalcopyrite ( I\\bar{4}2d ), rocksalt ( Fm3m ), wurtzite ( P63 mc ) and CuAu-I ( P\\bar{4}m2 ) have been fully investigated. Stabilities of these materials have been systematically studied up to 40 GPa using various approaches. We have confirmed the stability of the chalcopyrite structure up to 30 GPa for which the CuAu-I structure has been previously proposed. However, our calculation revealed that CuAu-I is not a stable structure under 32 GPa and 33 GPa for both ZnO0.5S0.5 and ZnO0.5Se0.5, respectively, which could explain the failure in several attempts to fabricate these materials under such conditions. We have also examined the pressure-dependence of the bandgap and electronic structure up to 30 GPa. We can conclude from our PDOS analysis that the applied pressure does not change the atomic state characters of electronic states near the top of valence and the bottom of conduction bands, but mainly modifies the dominant Zn-3d atomic state of the deep Bloch state at -1 eV below Fermi level.

Hierarchical ZnO Nanowires-loaded Sb-doped SnO2-ZnO Micrograting Pattern via Direct Imprinting-assisted Hydrothermal Growth and Its Selective Detection of Acetone Molecules

NASA Astrophysics Data System (ADS)

Choi, Hak-Jong; Choi, Seon-Jin; Choo, Soyoung; Kim, Il-Doo; Lee, Heon

2016-01-01

We propose a novel synthetic route by combining imprinting transfer of a Sb-doped SnO2 (ATO)-ZnO composite micrograting pattern (MP), i.e., microstrip lines, on a sensor substrate and subsequent hydrothermal growth of ZnO nanowires (NWs) for producing a hierarchical ZnO NW-loaded ATO-ZnO MP as an improved chemo-resistive sensing layer. Here, ATO-ZnO MP structure with 3-μm line width, 9-μm pitch, and 6-μm height was fabricated by direct transfer of mixed ATO and ZnO nanoparticle (NP)-dispersed resists, which are pre-patterned on a polydimethylsiloxane (PDMS) mold. ZnO NWs with an average diameter of less than 50 nm and a height of 250 nm were quasi-vertically grown on the ATO-ZnO MP, leading to markedly enhanced surface area and heterojunction composites between each ATO NP, ZnO NP, and ZnO NW. A ZnO NW-loaded MP sensor with a relative ratio of 1:9 between ATO and ZnO (1:9 ATO-ZnO), exhibited highly sensitive and selective acetone sensing performance with 2.84-fold higher response (Rair/Rgas = 12.8) compared to that (Rair/Rgas = 4.5) of pristine 1:9 ATO-ZnO MP sensor at 5 ppm. Our results demonstrate the processing advantages of direct imprinting-assisted hydrothermal growth for large-scale homogeneous coating of hierarchical oxide layers, particularly for applications in highly sensitive and selective chemical sensors.

Hierarchical ZnO Nanowires-loaded Sb-doped SnO2-ZnO Micrograting Pattern via Direct Imprinting-assisted Hydrothermal Growth and Its Selective Detection of Acetone Molecules.

PubMed

Choi, Hak-Jong; Choi, Seon-Jin; Choo, Soyoung; Kim, Il-Doo; Lee, Heon

2016-01-08

We propose a novel synthetic route by combining imprinting transfer of a Sb-doped SnO2 (ATO)-ZnO composite micrograting pattern (MP), i.e., microstrip lines, on a sensor substrate and subsequent hydrothermal growth of ZnO nanowires (NWs) for producing a hierarchical ZnO NW-loaded ATO-ZnO MP as an improved chemo-resistive sensing layer. Here, ATO-ZnO MP structure with 3-μm line width, 9-μm pitch, and 6-μm height was fabricated by direct transfer of mixed ATO and ZnO nanoparticle (NP)-dispersed resists, which are pre-patterned on a polydimethylsiloxane (PDMS) mold. ZnO NWs with an average diameter of less than 50 nm and a height of 250 nm were quasi-vertically grown on the ATO-ZnO MP, leading to markedly enhanced surface area and heterojunction composites between each ATO NP, ZnO NP, and ZnO NW. A ZnO NW-loaded MP sensor with a relative ratio of 1:9 between ATO and ZnO (1:9 ATO-ZnO), exhibited highly sensitive and selective acetone sensing performance with 2.84-fold higher response (R air/R gas = 12.8) compared to that (R air/R gas = 4.5) of pristine 1:9 ATO-ZnO MP sensor at 5 ppm. Our results demonstrate the processing advantages of direct imprinting-assisted hydrothermal growth for large-scale homogeneous coating of hierarchical oxide layers, particularly for applications in highly sensitive and selective chemical sensors.

Hierarchical ZnO Nanowires-loaded Sb-doped SnO2-ZnO Micrograting Pattern via Direct Imprinting-assisted Hydrothermal Growth and Its Selective Detection of Acetone Molecules

PubMed Central

Choi, Hak-Jong; Choi, Seon-Jin; Choo, Soyoung; Kim, Il-Doo; Lee, Heon

2016-01-01

We propose a novel synthetic route by combining imprinting transfer of a Sb-doped SnO2 (ATO)-ZnO composite micrograting pattern (MP), i.e., microstrip lines, on a sensor substrate and subsequent hydrothermal growth of ZnO nanowires (NWs) for producing a hierarchical ZnO NW-loaded ATO-ZnO MP as an improved chemo-resistive sensing layer. Here, ATO-ZnO MP structure with 3-μm line width, 9-μm pitch, and 6-μm height was fabricated by direct transfer of mixed ATO and ZnO nanoparticle (NP)-dispersed resists, which are pre-patterned on a polydimethylsiloxane (PDMS) mold. ZnO NWs with an average diameter of less than 50 nm and a height of 250 nm were quasi-vertically grown on the ATO-ZnO MP, leading to markedly enhanced surface area and heterojunction composites between each ATO NP, ZnO NP, and ZnO NW. A ZnO NW-loaded MP sensor with a relative ratio of 1:9 between ATO and ZnO (1:9 ATO-ZnO), exhibited highly sensitive and selective acetone sensing performance with 2.84-fold higher response (Rair/Rgas = 12.8) compared to that (Rair/Rgas = 4.5) of pristine 1:9 ATO-ZnO MP sensor at 5 ppm. Our results demonstrate the processing advantages of direct imprinting-assisted hydrothermal growth for large-scale homogeneous coating of hierarchical oxide layers, particularly for applications in highly sensitive and selective chemical sensors. PMID:26743814

ZnO deposition on metal substrates: Relating fabrication, morphology, and wettability

NASA Astrophysics Data System (ADS)

Beaini, Sara S.; Kronawitter, Coleman X.; Carey, Van P.; Mao, Samuel S.

2013-05-01

It is not common practice to deposit thin films on metal substrates, especially copper, which is a common heat exchanger metal and practical engineering material known for its heat transfer properties. While single crystal substrates offer ideal surfaces with uniform structure for compatibility with oxide deposition, metallic surfaces needed for industrial applications exhibit non-idealities that complicate the fabrication of oxide nanostructure arrays. The following study explored different ZnO fabrication techniques to deposit a (super)hydrophobic thin film of ZnO on a metal substrate, specifically copper, in order to explore its feasibility as an enhanced condensing surface. ZnO was selected for its non-toxicity, ability to be made (super)hydrophobic with hierarchical roughness, and its photoinduced hydrophilicity characteristic, which could be utilized to pattern it to have both hydrophobic-hydrophilic regions. We investigated the variation of ZnO's morphology and wetting state, using SEMs and sessile drop contact angle measurements, as a function of different fabrication techniques: sputtering, pulsed laser deposition (PLD), electrodeposition and annealing Zn. We successfully fabricated (super)hydrophobic ZnO on a mirror finish, commercially available copper substrate using the scalable electrodeposition technique. PLD for ZnO deposition did not prove viable, as the ZnO samples on metal substrates were hydrophilic and the process does not lend itself to scalability. The annealed Zn sheets did not exhibit consistent wetting state results.

Investigation of Optical Cavity Modes and Ultrafast Carrier Dynamics in Zinc Oxide Rods Using Second-Harmonic Generation and Transient Absorption Pump-Probe Microscopy

NASA Astrophysics Data System (ADS)

Mehl, Brian Peter

The polydispersity intrinsic to nanoscale and microscale semiconductor materials poses a major challenge to using individual objects as building blocks for device applications. The ability to manipulate the shape of ZnO structures is enormous, making it an ideal material for studying shape-dependent phenomena. We have built a nonlinear microscope used to directly image optical cavity modes in ZnO rods using second-harmonic generation. Images of second-harmonic generation in needle-shaped ZnO rods obtained from individual structures show areas of enhanced second-harmonic intensity along the longitudinal axis of the rod that are periodically distributed and symmetrically situated relative to the rod midpoint. The spatial modulation is a direct consequence of the fundamental optical field coupling into standing wave resonator modes of the ZnO structure, leading to an enhanced backscattered second-harmonic condition that cannot be achieved in bulk ZnO. A more complicated second-harmonic image is observed when excitation is below the band gap, which is attributed to whispering gallery modes. Additionally, the nonlinear microscope was combined with transient absorption pump-probe to follow the electron-hole recombination dynamics at different points within individual needle-shaped ZnO rods to characterize spatial differences in dynamical behavior. The results from pump-probe experiments are correlated with spatially resolved ultrafast emission measurements, and scanning electron microscopy provides structural details. Dramatically different electron-hole recombination dynamics are observed in the narrow tips compared to the interior, with the ends exhibiting a greater propensity for electron-hole plasma formation and faster recombination of carriers across the band gap that stem from a physical confinement of the charge carriers. In the interior of the rod, a greater fraction of the electron-hole recombination is trap-mediated and occurs on a significantly longer time scale.

Effect of Er3+ doping on structural, morphological and photocatalytical properties of ZnO thin films

NASA Astrophysics Data System (ADS)

Bouhouche, S.; Bensouici, F.; Toubane, M.; Azizi, A.; Otmani, A.; Chebout, K.; Kezzoula, F.; Tala-Ighil, R.; Bououdina, M.

2018-05-01

In this research work, structure, microstructure, optical and photocatalytic properties of undoped and Erbium doped nanostructured ZnO thin films prepared by sol-gel dip-coating are investigated. X-ray diffraction (XRD) analysis indicates that the deposited films crystallize within the hexagonal wurtzite-type structure with a preferential growth orientation along (002) plane. Morphological observations using scanning electron microscopy (SEM) reveal important influence of Er concentration; displaying homogeneous and dense aspect for undoped to 0.3% then grid-like morphology for 0.4 and 0.5%. UV/vis/NIR transmittance spectroscopy spectra display a transmittance over 70%, and small variation in the energy gap energy 3.263–3.278 eV. Wettability test of ZnO thin films surface ranges from hydrophilic aspect for pure ZnO to hydrophobic one for Er doped ZnO, and the contact angle is found to increase from 58.7° for pure ZnO up to 98.4° for 0.4% Er doped ZnO. The photocatalytic activity measurements evaluated using the degradation of methylene blue (MB) under UV light irradiation demonstrate that undoped ZnO film shows higher photocatalytic activity compared to Er doped ZnO films, which may be attributed to the deterioration of films’crystallinity resulting in lower transmittance.

Effects of Chromium Dopant on Ultraviolet Photoresponsivity of ZnO Nanorods

NASA Astrophysics Data System (ADS)

Mokhtari, S.; Safa, S.; Khayatian, A.; Azimirad, R.

2017-07-01

Structural and optical properties of bare ZnO nanorods, ZnO-encapsulated ZnO nanorods, and Cr-doped ZnO-encapsulated ZnO nanorods have been investigated. Encapsulated ZnO nanorods were grown using a simple two-stage method in which ZnO nanorods were first grown on a glass substrate directly from a hydrothermal bath, then encapsulated with a thin layer of Cr-doped ZnO by dip coating. Comparative study of x-ray diffraction patterns showed that Cr was successfully incorporated into the shell layer of ZnO nanorods. Moreover, energy-dispersive x-ray spectroscopy confirmed presence of Cr in this sample. It was observed that the thickness of the shell layer around the core of the ZnO nanorods was at least about 20 nm. Transmission electron microscopy of bare ZnO nanorods revealed single-crystalline structure. Based on optical results, both the encapsulation process and addition of Cr dopant decreased the optical bandgap of the samples. Indeed, the optical bandgap values of Cr-doped ZnO-encapsulated ZnO nanorods, ZnO-encapsulated ZnO nanorods, and bare ZnO nanorods were 2.89 eV, 3.15 eV, and 3.34 eV, respectively. The ultraviolet (UV) parameters demonstrated that incorporation of Cr dopant into the shell layer of ZnO nanorods considerably facilitated formation and transportation of photogenerated carriers, optimizing their performance as a practical UV detector. As a result, the photocurrent of the Cr-doped ZnO-encapsulated ZnO nanorods was the highest (0.6 mA), compared with ZnO-encapsulated ZnO nanorods and bare ZnO nanorods (0.21 mA and 0.06 mA, respectively).

ZnO nanoparticles obtained by ball milling technique: Structural, micro-structure, optical and photo-catalytic properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balamurugan, S., E-mail: scandium.chemistry@gmail.com; Joy, Josny; Godwin, M. Anto

The ZnO nanoparticles were obtained by ball milling of commercial grade ZnO powder at 250 rpm for 20 h and studied their structural, micro-structure, optical and photo-catalytic properties. Due to ball milling significant decrease in lattice parameters and average crystalline size is noticed for the as-milled ZnO nano powder. The HRSEM images of the as-milled powder consist of agglomerated fine spherical nanoparticles in the range of ~10-20 nm. The room temperature PL spectrum of as-milled ZnO nano powder excited under 320 nm reveals two emission bands at ~406 nm (violet emission) and ~639 nm (green emission). Interestingly about 98 % of photo degradation of methylene (MB)more » by the ZnO catalyst is achieved at 100 minutes of solar light irradiation.« less

Synthesis of uniformly distributed single- and double-sided zinc oxide (ZnO) nanocombs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Altintas Yildirim, Ozlem; Liu, Yuzi; Petford-Long, Amanda K.

Uniformly distributed single- and double-sided zinc oxide (ZnO) nanocomb structures have been prepared by a vapor-liquid-solid technique from a mixture of ZnO nanoparticles and graphene nanoplatelets. The ZnO seed nanoparticles were synthesized via a simple precipitation method. The structure of the ZnO nanocombs could easily be controlled by tuning the carrier-gas flow rate during growth. Higher flow rate resulted in the formation of uniformly-distributed single-sided comb structures with nanonail-shaped teeth, as a result of the self-catalysis effect of the catalytically active Zn-terminated polar (0001) surface. Lower gas flow rate was favorable for production of double-sided comb structures with the twomore » sets of teeth at an angle of similar to 110 degrees to each other along the comb ribbon, which was attributed to the formation of a bicrystal nanocomb ribbon. Lastly, the formation of such a double-sided structure with nanonail-shaped teeth has not previously been reported.« less

Synthesis of uniformly distributed single- and double-sided zinc oxide (ZnO) nanocombs

DOE PAGES

Altintas Yildirim, Ozlem; Liu, Yuzi; Petford-Long, Amanda K.

2015-08-21

Uniformly distributed single- and double-sided zinc oxide (ZnO) nanocomb structures have been prepared by a vapor-liquid-solid technique from a mixture of ZnO nanoparticles and graphene nanoplatelets. The ZnO seed nanoparticles were synthesized via a simple precipitation method. The structure of the ZnO nanocombs could easily be controlled by tuning the carrier-gas flow rate during growth. Higher flow rate resulted in the formation of uniformly-distributed single-sided comb structures with nanonail-shaped teeth, as a result of the self-catalysis effect of the catalytically active Zn-terminated polar (0001) surface. Lower gas flow rate was favorable for production of double-sided comb structures with the twomore » sets of teeth at an angle of similar to 110 degrees to each other along the comb ribbon, which was attributed to the formation of a bicrystal nanocomb ribbon. Lastly, the formation of such a double-sided structure with nanonail-shaped teeth has not previously been reported.« less

The optoelectronic properties and role of Cu concentration on the structural and electrical properties of Cu doped ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Omri, K.; Bettaibi, A.; Khirouni, K.; El Mir, L.

2018-05-01

In the current study, we synthesized a Cu-doped ZnO (CZO) nanoparticles material using a sol-gel method with different doping concentrations of Cu (0, 2, 3 and 4 at.%). The control of the Cu concentration on structural, electrical and optical properties of CZO nanoparticles was investigated in detail. The XRD analysis of the CZO nanoparticles reveals the formation of ZnO hexagonal wurtzite structure for all samples which confirm the incorporation of Cu2+ ions into the ZnO lattice by substitution. Furthermore, CZO nanoparticles showed a small red shift of absorption band with the incorporation of Cu from 0 to 4 at.%; i.e. a decreased band gap value from 3.34 eV to 3.27 eV with increasing of Cu doping content. The frequency dispersion of the electric conductivity were studied using the Jonscher universal power law, according to relation σ(ω) = σDC + A ωs(T). Alternative current conductivity increases with increasing Cu content in spite of the decrease the activation energy with copper loading. It was found that the conductivity reached its maximum value for critical Cu concentration of 3 at.%. The frequency relaxation phenomenon was also investigated and all results were discussed in term of the copper doping concentration.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hou, Kun; Gao, Ziwei, E-mail: zwgao@snnu.edu.cn; Da, Min

Highlights: Black-Right-Pointing-Pointer Highly oriented and well-defined ZnO urchin-like crystals were successfully fabricated by a facile and effective hydrotherm method. Black-Right-Pointing-Pointer Polyvinylpyrrolidone- and hydrogen peroxide-assisted synthesis of ZnO could optimize its crystalline quality and the obtained ZnO have smooth surface, radial growth of morphology, obvious crystal edges and decreased defects. Black-Right-Pointing-Pointer The physicochemical properties of samples were studied by analysis of its structure, morphology, surface and optical properties. Black-Right-Pointing-Pointer This study represented a multistep mechanism based on [Zn(OH){sub 4}]{sup 2-} growth units about formation such urchin-like structure. -- Abstract: The urchin-like ZnO microcrystals with high crystallinity decomposed from [Zn(OH){sub 4}]{sup 2-}more » directly were obtained via a hydrothermal method. The morphology, particle size, crystalline structure and fluorescence of the as-prepared ZnO were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) analyses. The results demonstrated that the urchin-like ZnO crystals with wurtzite structure had a narrow distribution in size, which could be adjusted in the range of 30-80 {mu}m by varying reaction time. Broad visible light emission peak was also observed in the PL spectra of the synthesized ZnO products. A multistep growth process about how to form such a structure was proposed.« less

Structure of (Ga2O3)2(ZnO)13 and a unified description of the homologous series (Ga2O3)2(ZnO)(2n + 1).

PubMed

Michiue, Yuichi; Kimizuka, Noboru; Kanke, Yasushi; Mori, Takao

2012-06-01

The structure of (Ga(2)O(3))(2)(ZnO)(13) has been determined by a single-crystal X-ray diffraction technique. In the monoclinic structure of the space group C2/m with cell parameters a = 19.66 (4), b = 3.2487 (5), c = 27.31 (2) Å, and β = 105.9 (1)°, a unit cell is constructed by combining the halves of the unit cell of Ga(2)O(3)(ZnO)(6) and Ga(2)O(3)(ZnO)(7) in the homologous series Ga(2)O(3)(ZnO)(m). The homologous series (Ga(2)O(3))(2)(ZnO)(2n + 1) is derived and a unified description for structures in the series is presented using the (3+1)-dimensional superspace formalism. The phases are treated as compositely modulated structures consisting of two subsystems. One is constructed by metal ions and another is by O ions. In the (3 + 1)-dimensional model, displacive modulations of ions are described by the asymmetric zigzag function with large amplitudes, which was replaced by a combination of the sawtooth function in refinements. Similarities and differences between the two homologous series (Ga(2)O(3))(2)(ZnO)(2n + 1) and Ga(2)O(3)(ZnO)(m) are clarified in (3 + 1)-dimensional superspace. The validity of the (3 + 1)-dimensional model is confirmed by the refinements of (Ga(2)O(3))(2)(ZnO)(13), while a few complex phenomena in the real structure are taken into account by modifying the model.

Gas-sensing performances of Cd-doped ZnO nanoparticles synthesized by a surfactant-mediated method for n-butanol gas

NASA Astrophysics Data System (ADS)

Zhao, Rongjun; Li, Kejin; Wang, Zhezhe; Xing, Xinxin; Wang, Yude

2018-01-01

Zinc oxide nanoparticles with the different Cd doping contents were prepared by with a surfactant-mediated method in this paper. The effects of Cd doping on the gas sensing properties of the ZnO nanoparticles were studied. The morphology and microstructure of as-prepared samples were characterized by X-ray diffraction (XRD); scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM), respectively. The results reveal that all the products are the high crystalline hexagonal wurtzite ZnO crystal structure. The gas-sensing characteristics of the Cd doped ZnO nanoparticles for volatile organic compounds (VOCs) were investigated. At its optimal operation temperature of 300 °C, the sensing properties of the Cd doped ZnO nanoparticles for n-butanol gas exhibit a high-performance gas sensing performances including high gas response, good selectivity, response/recovery time, and repeatability as well as stability. Especially, its response reaches 130 for 100 ppm n-butanol of ZnO nanoparticles with 2.5% Cd doping. Those values demonstrate the potential of using as-prepared Cd doped ZnO nanoparticles for n-butanol gas detection, making them to be promising candidates for practical detectors to n-butanol gas. Apart from these, the mechanism related to the advanced properties was also investigated and presented.

Surfactant-assisted growth and optical properties of ZnO hexagonal bilayer disk-like microstructures

NASA Astrophysics Data System (ADS)

Zhu, Q. P.; Shen, X. Y.; Wang, L. L.; Zhu, L. P.; Wang, L. J.; Liao, G. H.

2018-01-01

ZnO hexagonal bilayer disk-like microstructures are successfully fabricated using a simple solvothermal method assisted with surfactant. The structure and morphology were investigated by XRD, SEM, and EDS. XRD result indicated that the as-obtained samples were well-crystallized wurtzite hexagonal ZnO structure. SEM images showed that the ZnO hexagonal bilayer disk-like assembles consist of two uniform and smooth disks with an average edge length of 6 μm and thickness of ˜4 μm. UV-vis spectrum reveals that ZnO sampls show an appreciable red shift and the band gap energy of the obtained ZnO samples were about 3.15 eV. A very strong UV emission at the ultraviolet (UV) region was observed in the photoluminescence (PL) spectrum of the as-prepared ZnO samples tested at room-temperature. A possible growth process of the ZnO hexagonal bilayer disk-like microstructures was schematically illustrated.

Semiconductor hierarchically structured flower-like clusters for dye-sensitized solar cells with nearly 100% charge collection efficiency.

PubMed

Xin, Xukai; Liu, Hsiang-Yu; Ye, Meidan; Lin, Zhiqun

2013-11-21

By combining the ease of producing ZnO nanoflowers with the advantageous chemical stability of TiO2, hierarchically structured hollow TiO2 flower-like clusters were yielded via chemical bath deposition (CBD) of ZnO nanoflowers, followed by their conversion into TiO2 flower-like clusters in the presence of TiO2 precursors. The effects of ZnO precursor concentration, precursor amount, and reaction time on the formation of ZnO nanoflowers were systematically explored. Dye-sensitized solar cells fabricated by utilizing these hierarchically structured ZnO and TiO2 flower clusters exhibited a power conversion efficiency of 1.16% and 2.73%, respectively, under 100 mW cm(-2) illumination. The intensity modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) studies suggested that flower-like structures had a fast electron transit time and their charge collection efficiency was nearly 100%.

Investigation of intrinsic and extrinsic defects effective role on producing intense red emission in ZnO:Eu nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Najafi, Mehrdad, E-mail: najafi@shahroodut.ac.ir; Haratizadeh, Hamid

2015-05-15

Highlights: • Effective role of defects on producing red emission at indirect excitation. • V{sub Zn} and V{sub O} defects have important role on energy transfer. • Mg related defects and Zn{sub i} defects were responsible for blue emission. • Extrinsic and intrinsic defects mediated energy transfer to sensitize Eu{sup 3+} ions. • Decrease of red emission because of diminishing in oxygen vacancy. - Abstract: Europium doped ZnO nanorads and nanosheets were synthesized by hydrothermal method. Effects of Mg doping, morphology and annealing in oxygen ambient on structural and optical properties of ZnO nanostructures were investigated using X-ray diffraction (XRD),more » particle size analysis (PSA), thermo gravimetric analysis (TGA), differential thermal analysis (DTA), differential thermo gravimetry (DTG), scanning electron microscopy (SEM) and photoluminescence spectroscopy (PL). This study recommends that both of intrinsic and extrinsic defects facilitate energy transfer (ET) from the ZnO host to Eu{sup 3+} ions and consequently have efficient role on producing intense red emission at indirect excitation. The results also showed that annealing process improved the crystal structure of ZnO nanosheets due to decrease of surface defects; however decreased ET and red emission because of diminishing in oxygen vacancy. In addition in ZnO nanorods sample with more surface area in comparison with ZnO nanosheets sample deep level emissions are enhanced.« less

Structural, surface wettability and antibacterial properties of HPMC-ZnO nanocomposite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rao, B. Lakshmeesha; Asha, S.; Madhukumar, R.

The developed hydroxypropyl methylcellulose (HPMC)/Zinc oxide (ZnO) nanocomposite films were examined for structural property and surface wettability using X-ray diffraction and contact angle measurement. Antibacterial activity of these films was evaluated as a function of ZnO concentration. The microstructuralline parameters ( and (g in %)) decreased with increasing concentration of ZnO nanoparticles and there was increase in hydrophilicity. Addition of ZnO nanoparticles in films resulted in antimicrobial activity against tested microorganisms.

Multi-tip nano-prisms: Controlled growth and emission enhancement properties

NASA Astrophysics Data System (ADS)

Liu, Ming; Meng, Cong; Xue, Zheng-Hong; Xiong, Xiang; Shu, Da-Jun; Peng, Ru-Wen; Wu, Qiang; Hu, Zheng; Wang, Mu

2013-10-01

We report here the experimental observations that the tip topography of ZnO nano-prisms sensitively depends on the percentage of oxygen in the flux of the carrying gas in vapor growth. At a relatively high oxygen concentration, a number of thin filaments can be nucleated atop nano-prisms, forming a unique fish-spear-like multi-tip morphology. The length and density of the “spear tines” depend on the flux of the carrying gas. The field emission properties of the nanorod array with different tip morphology are investigated. The structures with longer and denser spear tines possess lower turn-on electric field and higher electric current density. The cathodoluminescence properties of the ZnO nano-prisms have also been studied. The luminescence related to defects in multi-tip nano-prisms possesses the strongest intensity, and the nanorod without any tine structure possesses the lowest defect luminescence intensity. The intrinsic luminescence of ZnO around 385 nm, however, has the opposite tendency. We suggest that our observation is inspiring in optimizing the emission properties of the nanowire devices.

Hierarchical core-shell structure of ZnO nanorod@NiO/MoO₂ composite nanosheet arrays for high-performance supercapacitors.

PubMed

Hou, Sucheng; Zhang, Guanhua; Zeng, Wei; Zhu, Jian; Gong, Feilong; Li, Feng; Duan, Huigao

2014-08-27

A hierarchical core-shell structure of ZnO nanorod@NiO/MoO2 composite nanosheet arrays on nickel foam substrate for high-performance supercapacitors was constructed by a two-step solution-based method involving two hydrothermal processes followed by a calcination treatment. Compared to one composed of pure NiO/MoO2 composite nanosheets, the hierarchical core-shell structure electrode displays better pseudocapacitive behaviors in 2 M KOH, including high areal specific capacitance values of 1.18 F cm(-2) at 5 mA cm(-2) and 0.6 F cm(-2) at 30 mA cm(-2) as well as relatively good rate capability at high current densities. Furthermore, it also shows remarkable cycle stability, remaining at 91.7% of the initial value even after 4000 cycles at a current density of 10 mA cm(-2). The enhanced pseudocapacitive behaviors are mainly due to the unique hierarchical core-shell structure and the synergistic effect of combining ZnO nanorod arrays and NiO/MoO2 composite nanosheets. This novel hierarchical core-shell structure shows promise for use in next-generation supercapacitors.

Microwave Synthesized ZnO Nanorod Arrays for UV Sensors: A Seed Layer Annealing Temperature Study.

PubMed

Pimentel, Ana; Ferreira, Sofia Henriques; Nunes, Daniela; Calmeiro, Tomas; Martins, Rodrigo; Fortunato, Elvira

2016-04-20

The present work reports the influence of zinc oxide (ZnO) seed layer annealing temperature on structural, optical and electrical properties of ZnO nanorod arrays, synthesized by hydrothermal method assisted by microwave radiation, to be used as UV sensors. The ZnO seed layer was produced using the spin-coating method and several annealing temperatures, ranging from 100 to 500 °C, have been tested. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and spectrophotometry measurements have been used to investigate the structure, morphology, and optical properties variations of the produced ZnO nanorod arrays regarding the seed layer annealing temperatures employed. After the growth of ZnO nanorod arrays, the whole structure was tested as UV sensors, showing an increase in the sensitivity with the increase of seed layer annealing temperature. The UV sensor response of ZnO nanorod arrays produced with the seed layer annealed temperature of 500 °C was 50 times superior to the ones produced with a seed layer annealed at 100 °C.

Microwave Synthesized ZnO Nanorod Arrays for UV Sensors: A Seed Layer Annealing Temperature Study

PubMed Central

Pimentel, Ana; Ferreira, Sofia Henriques; Nunes, Daniela; Calmeiro, Tomas; Martins, Rodrigo; Fortunato, Elvira

2016-01-01

The present work reports the influence of zinc oxide (ZnO) seed layer annealing temperature on structural, optical and electrical properties of ZnO nanorod arrays, synthesized by hydrothermal method assisted by microwave radiation, to be used as UV sensors. The ZnO seed layer was produced using the spin-coating method and several annealing temperatures, ranging from 100 to 500 °C, have been tested. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and spectrophotometry measurements have been used to investigate the structure, morphology, and optical properties variations of the produced ZnO nanorod arrays regarding the seed layer annealing temperatures employed. After the growth of ZnO nanorod arrays, the whole structure was tested as UV sensors, showing an increase in the sensitivity with the increase of seed layer annealing temperature. The UV sensor response of ZnO nanorod arrays produced with the seed layer annealed temperature of 500 °C was 50 times superior to the ones produced with a seed layer annealed at 100 °C. PMID:28773423

Implementation of ZnO/ZnMgO strained-layer superlattice for ZnO heteroepitaxial growth on sapphire

NASA Astrophysics Data System (ADS)

Petukhov, Vladimir; Bakin, Andrey; Tsiaoussis, Ioannis; Rothman, Johan; Ivanov, Sergey; Stoemenos, John; Waag, Andreas

2011-05-01

The main challenge in fabrication of ZnO-based devices is the absence of reliable p-type material. This is mostly caused by insufficient crystalline quality of the material and not well-enough-developed native point defect control of ZnO. At present high-quality ZnO wafers are still expensive and ZnO heteroepitaxial layers on sapphire are the most reasonable alternative to homoepitaxial layers. But it is still necessary to improve the crystalline quality of the heteroepitaxial layers. One of the approaches to reduce defect density in heteroepitaxial layers is to introduce a strained-layer superlattice (SL) that could stop dislocation propagation from the substrate-layer interface. In the present paper we have employed fifteen periods of a highly strained SL structure. The structure was grown on a conventional double buffer layer comprising of high-temperature MgO/low-temperature ZnO on sapphire. The influence of the SLs on the properties of the heteroepitaxial ZnO layers is investigated. Electrical measurements of the structure with SL revealed very high values of the carrier mobility up to 210 cm2/Vs at room temperature. Structural characterization of the obtained samples showed that the dislocation density in the following ZnO layer was not reduced. The high mobility signal appears to come from the SL structure or the SL/ZnO interface.

The structural properties of flower-like ZnO nanostructures on porous silicon

NASA Astrophysics Data System (ADS)

Eswar, Kevin Alvin; Suhaimi, Mohd Husairi Fadzillah; Guliling, Muliyadi; Mohamad, Maryam; Khusaimi, Zuraida; Rusop, M.; Abdullah, Saifollah

2018-05-01

The flower-like zinc oxide (ZnO) were successfully synthesized on porous silicon (PSi) via hydrothermal method. The characteristic of ZnO nanostructures was investigated using field emission scanning microscopy (FESEM) and X-ray diffraction (X-Ray). The FESEM images show the flower-like ZnO nanostructures composed ZnO nanoparticles. The X-ray diffraction shows that strong intensity of (100), (002) and (101) peaks. The structural analysis revealed that the peaks angles were shifted due to the stress or imperfection of the crystalline of ZnO nanostructures. The crystalline sizes in range of 42.60 to 54.09 nm were produced.

The structural, electronic and optical properties of Nd doped ZnO using first-principles calculations

NASA Astrophysics Data System (ADS)

Wen, Jun-Qing; Zhang, Jian-Min; Chen, Guo-Xiang; Wu, Hua; Yang, Xu

2018-04-01

The density functional theory calculations using general gradient approximation (GGA) applying Perdew-Burke-Ernzerhof (PBE) as correlation functional have been systematically performed to research the formation energy, the electronic structures, band structures, total and partial DOS, and optical properties of Nd doping ZnO with the content from 6.25% to 12.5%. The formation energies are negative for both models, which show that two structures are energetically stable. Nd doping ZnO crystal is found to be a direct band gap semiconductor and Fermi level shifts upward into conduction band, which show the properties of n-type semiconductor. Band structures are more compact after Nd doping ZnO, implying that Nd doping induces the strong interaction between different atoms. Nd doping ZnO crystal presents occupied states at near Fermi level, which mainly comes from the Nd 4f orbital. The calculated optical properties imply that Nd doping causes a red-shift of absorption peaks, and enhances the absorption of the visible light.

Effect of intrinsic zinc oxide coating on the properties of Al-doped zinc oxide nanorod arrays

NASA Astrophysics Data System (ADS)

Saidi, S. A.; Mamat, M. H.; Ismail, A. S.; Malek, M. F.; Yusoff, M. M.; Sin, N. D. Md.; Zoolfakar, A. S.; Khusaimi, Z.; Rusop, M.

2018-05-01

The aim of this study was to explore the influence of intrinsic zinc oxide (ZnO) coating fabricated by a simple immersion method. X-ray powder diffraction (XRD) analysis indicated that the Al-doped ZnO nanorod arrays films had a hexagonal wurtzite structure, similar to that of an intrinsic ZnO coating. Structural properties of the samples were characterised using field emission scanning electron microscopy (FESEM; JEOL JSM-7600F) and optical properties using X-ray diffraction (XRD). The XRD results showed that all films were crystallized under hexagonal wurtzite structure and presented a preferential orientation along the c-axis (002) was obtained. The XRD results showed that the intrinsic ZnO coating material had a strong orientation, whereas the ZnO was randomly oriented. Overall these results indicate that intrinsic ZnO coating are pontetial for the creation of functional materials such as barrier protection, optoelectronic devices, humidity sensor and ultraviolet photoconductive sensor.

In-vitro antibacterial study of zinc oxide nanostructures on Streptococcus sobrinus

NASA Astrophysics Data System (ADS)

Bakhori, Siti Khadijah Mohd; Mahmud, Shahrom; Ann, Ling Chuo; Sirelkhatim, Amna; Hasan, Habsah; Mohamad, Dasmawati; Masudi, Sam'an Malik; Seeni, Azman; Rahman, Rosliza Abd

2014-10-01

Zinc oxide nanostructures were prepared using a pilot plant of zinc oxide boiling furnace. Generally, it produced two types of nanostructures different in morphology; one is rod-like shaped (ZnO-1) and a plate-like shape (ZnO-2). The properties of ZnO were studied by structural, optical and morphological using XRD, PL and FESEM respectively. The XRD patterns confirmed the wurtzite structures of ZnO with the calculated crystallite size of 41 nm (ZnO-1) and 42 nm (ZnO-2) using Scherrer formula. The NBE peaks were determined by photoluminescence spectra which reveal peak at 3.25 eV and 3.23 eV for ZnO-1 and ZnO-2 respectively. Prior to that, the morphologies for both ZnO-1 and ZnO-2 were demonstrated from FESEM micrographs. Subsequently the antibacterial study was conducted using in-vitro broth dilution technique towards a gram positive bacterium Streptococcus sobrinus (ATCC 33478) to investigate the level of antibacterial effect of zinc oxide nanostructures as antibacterial agent. Gradual increment of ZnO concentrations from 10-20 mM affected the inhibition level after twenty four hours of incubation. In conjunction with concentration increment of ZnO, the percentage inhibition towards Streptococcus sobrinus was also increased accordingly. The highest inhibition occurred at 20 mM of ZnO-1 and ZnO-2 for 98% and 77% respectively. It showed that ZnO has good properties as antibacterial agent and relevancy with data presented by XRD, PL and FESEM were determined.

Hydrothermal temperature effect on crystal structures, optical properties and electrical conductivity of ZnO nanostructures

NASA Astrophysics Data System (ADS)

Dhafina, Wan Almaz; Salleh, Hasiah; Daud, Mohd Zalani; Ghazali, Mohd Sabri Mohd; Ghazali, Salmah Mohd

2017-09-01

ZnO is an wide direct band gap semiconductor and possess rich family of nanostructures which turned to be a key role in the nanotechnology field of applications. Hydrothermal method was proven to be simple, robust and low cost among the reported methods to synthesize ZnO nanostructures. In this work, the properties of ZnO nanostructures were altered by varying temperatures of hydrothermal process. The changes in term of morphological, crystal structures, optical properties and electrical conductivity were investigated. A drastic change of ZnO nanostructures morphology and decreases of 002 diffraction peak were observed as the hydrothermal temperature increased. The band gap of samples decreased as the size of ZnO nanostructure increased, whereas the electrical conductivity had no influence on the band gap value but more on the morphology of ZnO nanostructures instead.

Gas-sensing behaviour of ZnO/diamond nanostructures.

PubMed

Davydova, Marina; Laposa, Alexandr; Smarhak, Jiri; Kromka, Alexander; Neykova, Neda; Nahlik, Josef; Kroutil, Jiri; Drahokoupil, Jan; Voves, Jan

2018-01-01

Microstructured single- and double-layered sensor devices based on p-type hydrogen-terminated nanocrystalline diamond (NCD) films and/or n-type ZnO nanorods (NRs) have been obtained via a facile microwave-plasma-enhanced chemical vapour deposition process or a hydrothermal growth procedure. The morphology and crystal structure of the synthesized materials was analysed with scanning electron microscopy, X-ray diffraction measurements and Raman spectroscopy. The gas sensing properties of the sensors based on i) NCD films, ii) ZnO nanorods, and iii) hybrid ZnO NRs/NCD structures were evaluated with respect to oxidizing (i.e., NO 2 , CO 2 ) and reducing (i.e., NH 3 ) gases at 150 °C. The hybrid ZnO NRs/NCD sensor showed a remarkably enhanced NO 2 response compared to the ZnO NRs sensor. Further, inspired by this special hybrid structure, the simulation of interaction between the gas molecules (NO 2 and CO 2 ) and hybrid ZnO NRs/NCD sensor was studied using DFT calculations.

Effects of 8-mer acidic peptide concentration on the morphology and photoluminescence of synthesized ZnO nanomaterials

NASA Astrophysics Data System (ADS)

Moon, Chung Hee; Tousi, Marzieh; Cheeney, Joseph; Ngo-Duc, Tam-Triet; Zuo, Zheng; Liu, Jianlin; Haberer, Elaine D.

2015-11-01

An 8-mer ZnO-binding peptide, VPGAAEHT, was identified using a M13 pVIII phage display library and employed as an additive during aqueous-based ZnO synthesis at 65 °C. Unlike most other well-studied ZnO-binding sequences which are strongly basic (pI > pH 7), the 8-mer peptide was overall acidic (pI < pH 7) in character, including only a single basic residue. The selected peptide strongly influenced ZnO nanostructure formation. Morphology and optical emission properties were found to be dependent on the concentration of peptide additive. Using lower peptide concentrations (<0.1 mM), single crystal hexagonal rods and platelets were produced, and using higher peptide concentrations (≥0.1 mM), polycrystalline layered platelets, yarn-like structures, and microspheres were assembled. Photoluminescence analysis revealed a characteristic ZnO band-edge peak, as well as sub-bandgap emission peaks. Defect-related green emission, typically associated with surface-related oxygen and zinc vacancies, was significantly reduced by the peptide additive, while blue emission, attributable to oxygen and zinc interstitials, emerged with increased peptide concentrations. Peptide-directed synthesis of ZnO materials may be useful for gas sensing and photocatalytic applications in which properly engineered morphology and defect levels have demonstrated enhanced performance.

Electrical and structural properties of ZnO synthesized via infiltration of lithographically defined polymer templates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang-Yong Nam; Stein, Aaron; Kisslinger, Kim

We investigate the electrical and structural properties of infiltration-synthesized ZnO. In-plane ZnO nanowire arrays with prescribed positional registrations are generated by infiltrating diethlyzinc and water vapor into lithographically defined SU-8 polymer templates and removing organic matrix by oxygen plasma ashing. Transmission electron microscopy reveals that homogeneously amorphous as-infiltrated polymer templates transform into highly nanocrystalline ZnO upon removal of organic matrix. Field-effect transistor device measurements show that the synthesized ZnO after thermal annealing displays a typical n-type behavior, ~1019 cm -3 carrier density, and ~0.1 cm 2 V -1 s -1 electron mobility, reflecting highly nanocrystalline internal structure. The results demonstratemore » the potential application of infiltration synthesis in fabricating metal oxide electronic devices.« less

Electrical and structural properties of ZnO synthesized via infiltration of lithographically defined polymer templates

DOE PAGES

Chang-Yong Nam; Stein, Aaron; Kisslinger, Kim; ...

2015-11-17

We investigate the electrical and structural properties of infiltration-synthesized ZnO. In-plane ZnO nanowire arrays with prescribed positional registrations are generated by infiltrating diethlyzinc and water vapor into lithographically defined SU-8 polymer templates and removing organic matrix by oxygen plasma ashing. Transmission electron microscopy reveals that homogeneously amorphous as-infiltrated polymer templates transform into highly nanocrystalline ZnO upon removal of organic matrix. Field-effect transistor device measurements show that the synthesized ZnO after thermal annealing displays a typical n-type behavior, ~1019 cm -3 carrier density, and ~0.1 cm 2 V -1 s -1 electron mobility, reflecting highly nanocrystalline internal structure. The results demonstratemore » the potential application of infiltration synthesis in fabricating metal oxide electronic devices.« less

Highly sensitive hydrogen detection of catalyst-free ZnO nanorod networks suspended by lithography-assisted growth.

PubMed

Huh, Junghwan; Park, Jonghyurk; Kim, Gyu Tae; Park, Jeong Young

2011-02-25

We have successfully demonstrated a ZnO nanorod-based 3D nanostructure to show a high sensitivity and very fast response/recovery to hydrogen gas. ZnO nanorods have been synthesized selectively over the pre-defined area at relatively low temperature using a simple self-catalytic solution process assisted by a lithographic method. The conductance of the ZnO nanorod device varies significantly as the concentration of the hydrogen is changed without any additive metal catalyst, revealing a high sensitivity to hydrogen gas. Its superior performance can be explained by the porous structure of its three-dimensional network and the enhanced surface reaction of the hydrogen molecules with the oxygen defects resulting from a high surface-to-volume ratio. It was found that the change of conductance follows a power law depending on the hydrogen concentration. A Langmuir isotherm following an ideal power law and a cross-over behavior of the activation energy with respect to hydrogen concentration were observed. This is a very novel and intriguing phenomenon on nanostructured materials, which suggests competitive surface reactions in ZnO nanorod gas sensors.

AuNPs Hybrid Black ZnO Nanorods Made by a Sol-Gel Method for Highly Sensitive Humidity Sensing

PubMed Central

Zhang, Min; Lin, Cunchong; Zhang, Jun

2018-01-01

A highly sensitive self-powered humidity sensor has been realized from AuNPs hybrid black zinc oxide (ZnO) nanorods prepared through a sol-gel method. XRD pattern reveals that both ZnO and ZnO/AuNPs exhibit a wurtzite structure. ZnO/AuNPs nanorods grow in a vertical alignment, which possesses high uniformity and forms dense arrays with a smaller diameter than that of ZnO nanoparticles. All ZnO/AuNPs and pure black ZnO show lower band gap energy than the typically reported 3.34 eV of pure ZnO. Furthermore, the band gap of ZnO/AuNPs nanocomposites is effectively influenced by the amount of AuNPs. The humidity sensing tests clearly prove that all the ZnO/AuNPs humidity sensors exhibit much higher response than that of ZnO sensors, and the sensitivity of such ZnO/AuNPs nanorods (6 mL AuNPs) display a change three orders higher than that of pure ZnO with relative humidity (RH) ranging from 11% to 95% at room temperature. The response and recovery time of the ZnO/AuNPs are 5.6 s and 32.4 s, respectively. This study of the construction of semiconductor/noble metal sensors provides a rational way to control the morphology of semiconductor nanomaterials and to design a humidity sensor with high performance. PMID:29342860

AuNPs Hybrid Black ZnO Nanorods Made by a Sol-Gel Method for Highly Sensitive Humidity Sensing.

PubMed

Zhang, Hongyan; Zhang, Min; Lin, Cunchong; Zhang, Jun

2018-01-13

A highly sensitive self-powered humidity sensor has been realized from AuNPs hybrid black zinc oxide (ZnO) nanorods prepared through a sol-gel method. XRD pattern reveals that both ZnO and ZnO/AuNPs exhibit a wurtzite structure. ZnO/AuNPs nanorods grow in a vertical alignment, which possesses high uniformity and forms dense arrays with a smaller diameter than that of ZnO nanoparticles. All ZnO/AuNPs and pure black ZnO show lower band gap energy than the typically reported 3.34 eV of pure ZnO. Furthermore, the band gap of ZnO/AuNPs nanocomposites is effectively influenced by the amount of AuNPs. The humidity sensing tests clearly prove that all the ZnO/AuNPs humidity sensors exhibit much higher response than that of ZnO sensors, and the sensitivity of such ZnO/AuNPs nanorods (6 mL AuNPs) display a change three orders higher than that of pure ZnO with relative humidity (RH) ranging from 11% to 95% at room temperature. The response and recovery time of the ZnO/AuNPs are 5.6 s and 32.4 s, respectively. This study of the construction of semiconductor/noble metal sensors provides a rational way to control the morphology of semiconductor nanomaterials and to design a humidity sensor with high performance.

Effect of aluminium doping on structural and optical properties of ZnO thin films by sol-gel method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vijayaprasath, G.; Murugan, R.; Ravi, G., E-mail: raviganesa@rediffmail.com, E-mail: gravicrc@gmail.com

2015-06-24

We systematically investigated the structural, morphological and optical properties of 0.05 mol % Al doped ZnO (Al:ZnO) thin films deposited on glass substrates by sol-gel spin coating method. The influences of Al doping in ZnO thin films are characterized by Powder X-ray diffraction study. ZnO and Al:ZnO thin films have showed hexagonal wurtzite structure without any secondary phase in c-axis (002) orientation. The SEM images also proved the hexagonal rod like morphologies for both films. All the films exhibited transmittance of 70-80% in the visible range up to 800 nm and cut-off wavelength observed at ∼390 nm corresponding to the fundamental absorption ofmore » ZnO. The band gap of the ZnO thin films slightly widened with the Al doping. The photoluminescence properties have been studied for Al: ZnO thin films and the results are presented in detail.« less

Design of hybrid nanoheterostructure systems for enhanced quantum and solar conversion efficiencies in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Kılıç, Bayram; Telli, Hakan; Tüzemen, Sebahattin; Başaran, Ali; Pirge, Gursev

2015-04-01

Dye sensitized solar cells (DSSCs) with an innovative design involving controlled-morphology vertically aligned (VA) ZnO nanowires within mesoporous TiO2 structures with ultrahigh surface area for implementation as photoanodes are herein reported. Although TiO2 nanostructures exhibit excellent power conversion efficiency, the electron transport rate is low owing to low electron mobility. To overcome this, ZnO nanowires with high electron mobility have been investigated as potential candidates for photoanodes. However, the power conversion efficiency of ZnO nanowires is still lower than that of TiO2 owing to their low internal surface area. Consequently, in this work, vertical growth of ZnO nanowires within mesoporous TiO2 structures is carried out to increase their solar power conversion efficiency. The photovoltaic performance of solar cells using ZnO nanowires, mesoporous TiO2, and TiO2/ZnO hybrid structures are compared. The VA TiO2/ZnO hybrid structures are found to provide direct electron transfer compared with the tortuous pathway of zero-dimensional nanostructures, resulting in an increased conversion efficiency. It is demonstrated that the light scattering of the photoanode film is increased and electron recombination is decreased when an appropriate amount of mesoporous TiO2 is used as a substrate for ZnO nanowires. The DSSC fabricated with the TiO2/ZnO hybrid photoanode prepared with 15.8 wt. % TiO2 showed the highest conversion efficiency of 7.30%, approximately 5%, 18%, and 40% higher than that of DSSCs fabricated with 3.99 wt. % TiO2, pure TiO2, and pure ZnO photoanodes, respectively.

Study of cobalt effect on structural and optical properties of Dy doped ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Kumar, Pawan; Pandey, Praveen C.

2018-05-01

The present study has been carried out to investigate the effect of Co doping on structural and optical properties of Dy doped ZnO nanoparticles. We have prepared pure Zinc oxide, Dy (1%) doped ZnO and Dy (1%) doped ZnO co-doped with Co(2%) with the help of simple sol-gel combustion method. The structural analysis carried out using X-ray diffraction spectra (XRD) indicates substitution of Dy and Co at Zn site of ZnO crystal structure and hexagonal crystal structure without any secondary phase formation in all the samples. The surface morphology was analyzed by transmission electron microscopy (TEM). Absorption study indicates that Dy doping causes a small shift in band edge, while Co co-doping results significant change is absorption edge as well as introduce defect level absorption in the visible region. The band gap of samples decreases due to Dy and Co doping, which can be attributed to defect level formation below the conduction band in the system.

An efficient BTX sensor based on ZnO nanoflowers grown by CBD method

NASA Astrophysics Data System (ADS)

Acharyya, D.; Bhattacharyya, P.

2015-04-01

In this paper, sensing performance of ZnO nanoflower like structures derived by chemical bath deposition method (CBD), towards Benzene Toluene and Xylene (BTX) vapors is reported. Relatively higher bath temperature (110 °C) and high pH value (pH: 11) of solution escort to higher growth rate along [0 0 0 1] plane of ZnO, which eventually resulted in pointed edge nanorod based flower like structures after 3 h. After detailed structural characterizations (field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD)), existence of different defect states (viz. oxygen vacancy (Vo), Zinc vacancy (VZn) and Zinc interstitials (Zni)) were authenticated by Photoluminescence (PL) spectroscopy. BTX sensing performance, employing the nanoflowers as the sensing layer, was carried out in resistive mode with two Pd lateral electrodes. The sensor study was performed at different temperatures (150-350 °C) in the concentration range of 0.5-700 ppm of the respective vapors. The highest normalized resistance response (NRR%) was achieved at 200 °C. At this optimum temperature, normalized resistance responses (39.3/92.6%, 45.8/96.9%, and 47.8/99% respectively) were found to be promising towards 0.5/700 ppm of benzene, toluene and xylene. The response time of the sensor towards the target species were also found to be appreciably fast (15 s, 6 s, and 5 s) towards 700 ppm of benzene, toluene and xylene respectively. Detailed sensing mechanism for BTX with such flower like ZnO structures was explained with the help of interaction of band structures (of ZnO) with the corresponding highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the target species.

Structural and optical properties of ZnO nanorods synthesized via template free approach

NASA Astrophysics Data System (ADS)

Kajal, Priyanka; D, Pooja; Jaggi, Neena

2016-06-01

In this paper, we report a novel method for synthesis of semiconducting ZnO nanorods using Zinc acetate dehydrate precursor in a methanol—de-ionized (1:5) mixture via template free approach. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of as synthesized nanorods revealed hexagonal symmetry of rods, whereas x-ray diffraction (XRD) analysis for structure and phase has shown high crystallinity with wurtzite crystal structure. The structural characterization by FT-IR analysis revealed presence of various groups on as synthesized ZnO nanorods, whereas the UV-Vis analysis has shown a blue shift in the absorption spectra as compared to bulk ZnO due to quantum confinement of charge carriers. Photoluminescence (PL) spectroscopy study has also been performed revealing a good degree of phosphorescence in the ZnO nanorods. Further, thermo gravimetric analysis (TGA) revealed that as synthesized nanorods by present method are highly stable at high temperature (1000 °C). This study provides an alternative, less expensive and a very simple method for the fabrication of ZnO nanorods in abundance, which can be further used for various sensing applications, in particular, gas sensing.

Structural, chemical and optical evaluation of Cu-doped ZnO nanoparticles synthesized by an aqueous solution method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iribarren, A., E-mail: augusto@imre.oc.uh.cu; Hernández-Rodríguez, E.; Maqueira, L.

Highlights: • Cu-doped ZnO nanoparticles obtained by chemical synthesis. • Substitutional or interstitial Cu into ZnO lead specific structural, chemical, and optical changes. • Incorporation efficiency of Cu atoms in ZnO as a function of the Cu concentration in the precursor dissolution. - Abstract: In this work a study of ZnO and Cu-doped ZnO nanoparticles obtained by chemical synthesis in aqueous media was carried out. Structural analysis gave the dominant presence of wurtzite ZnO phase forming a solid solution Zn{sub 1−x}Cu{sub x}O. For high Cu doping CuO phase is also present. For low Cu concentration the lattice shrinks due tomore » Cu atoms substitute Zn atoms. For high Cu concentration the lattice enlarges due to predominance of interstitial Cu. From elemental analysis we determined and analyzed the incorporation efficiency of Cu atoms in Zn{sub 1−x}Cu{sub x}O as a function of the Cu concentration in the precursor dissolution. Combining structural and chemical results we described the Cu/Zn precursor concentrations r{sub w} in which the solid solution of Cu in ZnO is predominant. In the region located at r{sub w} ≈ 0.2–0.3 it is no longer valid. For Cu/Zn precursor concentration r{sub w} > 0.3 interstitial Cu dominates, and some amount of copper oxide appears. As the Cu concentration increases, the effective size of nanoparticles decreases. Photoluminescence (PL) measurements of the Cu-doped ZnO nanoparticles were carried out and analyzed.« less

A Surfactant-Free Synthesis Technique of Coral-Like Zno Hierarchical Structures for Photocatalytic Degradation of Resorcinol under UV Irradiation

NASA Astrophysics Data System (ADS)

Sin, Jin-Chung; Lam, Sze-Mun; Chin, Ying-Hui

2018-01-01

Hierarchical coral-like ZnO structures were successfully prepared by a surfactant-free wet chemical method. Various characterization tests were carried out to analyze the as-prepared ZnO samples. The coral-like ZnO was used to degrade resorcinol at three different solution pH values (pH 5.0, pH 8.0 and pH 11.0). It was observed that the resorcinol adsorption onto the ZnO was strongly dependent on the electrical charge properties of both photocatalyst and resorcinol. Photocatalytic degradation of resorcinol reached the highest at pH 11.0 due to high concentration of hydroxyl ions for hydroxyl radicals generation.

New Insights into Mechanism of Surface Reactions of ZnO Nanorods During Electrons Beam Irradiation.

PubMed

Cho, Youngseung; Ji, Hyunjin; Kim, Hyoungsub; Yoon, Jinsuop; Choi, Byoungdeog

2018-09-01

This study provides new insight into mechanisms of ionic reactions on the surface of ZnO nanorod networks, which could result in enhanced performance in optical or molecular sensors. The current- voltage characteristics of ZnO nanorod network devices exhibit typical nonlinear behavior in air, which implies the formation of a Schottky barrier when metals are used as contacts. The conductance of the device increased significantly in vacuum, which can be explained by the desorption of hydroxyl groups at very low pressure. While physisorbed water or oxygen-related ions can detach from the ZnO surface during evacuation, exposure to high energy in the electron beam is believed to detach the chemisorbed anions of O- and O-2 from the surface of ZnO nanorods, which releases more electrons into the channel. The increase in available electrons enhances the conductance of the ZnO nanorods. Slow initialization of the conductance under ambient conditions indicates that the ionic re-adsorption is inactive under these conditions. Thus, the electron irradiation process can be used to reset the surface ionic molecules on metal oxide nano-structures by tuning the surface potential prior to the passivation process.

Low-temperature synthesis of rose-like ZnO nanostructures using surfactin and their photocatalytic activity.

PubMed

Reddy, A Satyanarayana; Kuo, Yi-Hao; Atla, Shashi B; Chen, Chien-Yen; Chen, Chien-Cheng; Shih, Ruey-Chyuan; Chang, Young-Fo; Maity, Jyoti Prakash; Chen, How-Ji

2011-06-01

Rose-like ZnO nanostructures were synthesized by the precipitation method using a biosurfactant (surfactin) as a templating-agent stabilizer. The concentration of surfactin in the precursor solution significantly influenced the thickness and density of the petals in the rose-like structures, and all samples were of a wurtzite phase. The thickness of the petal was found to decrease with increasing surfactin concentration. The average thickness of the petals was found to be between 10 and 13 nm. Photocatalytic degradation of methylene blue using rose-like ZnO nanostuctures was investigated, and the morphology, density and thickness of the ZnO petals were found to influence the photodegradation activity. The samples with loosely-spread petals, or plate-like ZnO structures, brought about the strongest photodegradation in comparison with the dense rose-like structures. The greater activity of the loose-petal structures was correlated with their higher absorption in the UV region in comparison with the other samples. The ZnO samples prepared using low surfactin concentrations had higher rate constant values, i.e., 9.1 x 10(-3) min(-1), which revealed that the photodegradation of methylene blue under UV irradiation progressed by a pseudo first-order kinetic reaction.

Enhancement of Si solar cell efficiency using ZnO nanowires with various diameters

NASA Astrophysics Data System (ADS)

Gholizadeh, A.; Reyhani, A.; Parvin, P.; Mortazavi, S. Z.; Mehrabi, M.

2018-01-01

Here, Zinc Oxide nanowires are synthesized using thermal chemical vapor deposition of a Zn granulate source and used to enhance a significant Si-solar cell efficiency with simple and low cost method. The nanowires are grown in various O2 flow rates. Those affect the shape, yield, structure and the quality of ZnO nanowires according to scanning electron microscopy and x-ray diffraction analyses. This delineates that the ZnO nanostructure is dependent on the synthesis conditions. The photoluminescence spectroscopy of ZnO indicates optical emission at the Ultra-Violet and blue-green regions whose intensity varies as a function of diameter of ZnO nano-wires. The optical property of ZnO layer is measured by UV-visible and diffuse reflection spectroscopy that demonstrate high absorbance at 280-550 nm. Furthermore, the photovoltaic characterization of ZnO nanowires is investigated based on the drop casting on Si-solar cell. The ZnO nanowires with various diameters demonstrate different effects on the efficiency of Si-solar cells. We have shown that the reduction of the spectral reflectance and down-shifting process as well as the reduction of photon trapping are essential parameters on the efficiency of Si-solar cells. However, the latter is dominated here. In fact, the trapped photons during the electron-hole generation are dominant due to lessening the absorption rate in ZnO nano-wires. The results indicate that the mean diameters reduction of ZnO nanowires is also essential to improve the fill factor. The external and internal quantum efficiency analyses attest the efficiency improvement over the blue region which is related to the key parameters above.

Physico-chemical characteristics of ZnO nanoparticles-based discs and toxic effect on human cervical cancer HeLa cells

NASA Astrophysics Data System (ADS)

Sirelkhatim, Amna; Mahmud, Shahrom; Seeni, Azman; Kaus, Noor Haida Mohd.; Sendi, Rabab

2014-10-01

In this study, we investigated physico-chemical properties of zinc oxide nanoparticles (ZnO NPs)-based discs and their toxicity on human cervical cancer HeLa cell lines. ZnO NPs (80 nm) were produced by the conventional ceramic processing method. FESEM analysis indicated dominant structure of nanorods with dimensions 100-500 nm in length, and 20-100 nm in diameter. The high content of ZnO nanorods in the discs probably played significant role in toxicity towards HeLa cells. Structural defects (oxygen vacancies and zinc/oxygen interstitials) were revealed by PL spectra peaks at 370-376 nm and 519-533 nm for the ZnO discs. The structural, optical and electrical properties of prepared sample have influenced the toxicological effects of ZnO discs towards HeLa cell lines via the generation of reactive oxygen species (ROS), internalization, membrane damage, and eventually cell death. The larger surface to volume area of the ZnO nanorods, combined with defects, stimulated enhanced toxicity via ROS generation hydrogen peroxide, hydroxyl radicals, and superoxide anion. The preliminary results confirmed the ZnO-disc toxicity on HeLa cells was significantly associated with the unique physicochemical properties of ZnO NPs and to our knowledge, this is the first cellular study for treatment of HeLa cells with ZnO discs made from 80 nm ZnO particles.

ZnO nanorods for electronic and photonic device applications

NASA Astrophysics Data System (ADS)

Yi, Gyu-Chul; Yoo, Jinkyoung; Park, Won Il; Jung, Sug Woo; An, Sung Jin; Kim, H. J.; Kim, D. W.

2005-11-01

We report on catalyst-free growth of ZnO nanorods and their nano-scale electrical and optical device applications. Catalyst-free metalorganic vapor-phase epitaxy (MOVPE) enables fabrication of size-controlled high purity ZnO single crystal nanorods. Various high quality nanorod heterostructures and quantum structures based on ZnO nanorods were also prepared using the MOVPE method and characterized using scanning electron microscopy, transmission electron microscopy, and optical spectroscopy. From the photoluminescence spectra of ZnO/Zn 0.8Mg 0.2O nanorod multi-quantum-well structures, in particular, we observed a systematic blue-shift in their PL peak position due to quantum confinement effect of carriers in nanorod quantum structures. For ZnO/ZnMgO coaxial nanorod heterostructures, photoluminescence intensity was significantly increased presumably due to surface passivation and carrier confinement. In addition to the growth and characterizations of ZnO nanorods and their quantum structures, we fabricated nanoscale electronic devices based on ZnO nanorods. We report on fabrication and device characteristics of metal-oxidesemiconductor field effect transistors (MOSFETs), Schottky diodes, and metal-semiconductor field effect transistors (MESFETs) as examples of the nanodevices. In addition, electroluminescent devices were fabricated using vertically aligned ZnO nanorods grown p-type GaN substrates, exhibiting strong visible electroluminescence.

Structural, morphological and magnetic properties of pure and Ni-doped ZnO nanoparticles synthesized by sol-gel method

NASA Astrophysics Data System (ADS)

Undre, Pallavi G.; Birajdar, Shankar D.; Kathare, R. V.; Jadhav, K. M.

2018-05-01

In this work pure and Ni-doped ZnO nanoparticles have been prepared by sol-gel method. Influence of nickel doping on structural, morphological and magnetic properties of prepared nanoparticles was investigated by X-ray diffraction technique (XRD), Scanning electron microscopy (SEM) and Pulse field magnetic hysteresis loop. X-ray diffraction pattern shows the formation of a single phase with hexagonal wurtzite structure of both pure and Ni-doped ZnO nanoparticles. The lattice parameters `an' and `c' of Ni-doped ZnO is slightly less than that of pure ZnO nanoparticles. The crystalline size of prepared nanoparticles is found to be in 29 and 31 nm range. SEM technique used to examine the surface morphology of samples, SEM image confirms the nanocrystalline nature of present samples. From the pulse field hysteresis loop technique pure and Ni-doped ZnO nanoparticles show diamagnetic and ferromagnetic behavior at room temperature respectively.

Environmentally induced chemical and morphological heterogeneity of zinc oxide thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Hua; Chou, Kang Wei; Petrash, Stanislas

Zinc oxide (ZnO) thin films have been reported to suffer from degradation in electrical properties, when exposed to elevated heat and humidity, often leading to failures of electronic devices containing ZnO films. This degradation appears to be linked to water and oxygen penetration into the ZnO film. However, a direct observation in the ZnO film morphological evolution detailing structural and chemical changes has been lacking. Here, we systematically investigated the chemical and morphological heterogeneities of ZnO thin films caused by elevated heat and humidity, simulating an environmental aging. X-ray fluorescence microscopy, X-ray absorption spectroscopy, grazing incidence small angle and widemore » angle X-ray scattering, scanning electron microscopy (SEM), ultra-high-resolution SEM, and optical microscopy were carried out to examine ZnO and Al-doped ZnO thin films on two different substrates—silicon wafers and flexible polyethylene terephthalate (PET) films. In the un-doped ZnO thin film, the simulated environmental aging is resulting in pin-holes. In the Al-doped ZnO thin films, significant morphological changes occurred after the treatment, with an appearance of platelet-shaped structures that are 100–200 nm wide by 1 μm long. Synchrotron x-ray characterization further confirmed the heterogeneity in the aged Al-doped ZnO, showing the formation of anisotropic structures and disordering. X-ray diffraction and X-ray absorption spectroscopy indicated the formation of a zinc hydroxide in the aged Al-doped films. Utilizing advanced characterization methods, our studies provided information with an unprecedented level of details and revealed the chemical and morphologically heterogeneous nature of the degradation in ZnO thin films.« less

Environmentally induced chemical and morphological heterogeneity of zinc oxide thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Hua; Chou, Kang Wei; Petrash, Stanislas

Zinc oxide (ZnO) thin films have been reported to suffer from degradation in electrical properties, when exposed to elevated heat and humidity, often leading to failures of electronic devices containing ZnO films. This degradation appears to be linked to water and oxygen penetration into the ZnO film. However, a direct observation in the ZnO film morphological evolution detailing structural and chemical changes has been lacking. Here, we systematically investigated the chemical and morphological heterogeneities of ZnO thin films caused by elevated heat and humidity, simulating an environmental aging. X-ray fluorescence microscopy, X-ray absorption spectroscopy, grazing incidence small angle and widemore » angle X-ray scattering, scanning electron microscopy (SEM), ultra-high-resolution SEM, and optical microscopy were carried out to examine ZnO and Al-doped ZnO thin films on two different substrates—silicon wafers and flexible polyethylene terephthalate (PET) films. In the un-doped ZnO thin film, the simulated environmental aging is resulting in pin-holes. In the Al-doped ZnO thin films, significant morphological changes occurred after the treatment, with an appearance of platelet-shaped structures that are 100–200 nm wide by 1μm long. Synchrotron x-ray characterization further confirmed the heterogeneity in the aged Al-doped ZnO, showing the formation of anisotropic structures and disordering. X-ray diffraction and X-ray absorption spectroscopy indicated the formation of a zinc hydroxide in the aged Al-doped films. In conclusion, utilizing advanced characterization methods, our studies provided information with an unprecedented level of details and revealed the chemical and morphologically heterogeneous nature of the degradation in ZnO thin films.« less

Environmentally induced chemical and morphological heterogeneity of zinc oxide thin films

DOE PAGES

Jiang, Hua; Chou, Kang Wei; Petrash, Stanislas; ...

2016-09-02

Zinc oxide (ZnO) thin films have been reported to suffer from degradation in electrical properties, when exposed to elevated heat and humidity, often leading to failures of electronic devices containing ZnO films. This degradation appears to be linked to water and oxygen penetration into the ZnO film. However, a direct observation in the ZnO film morphological evolution detailing structural and chemical changes has been lacking. Here, we systematically investigated the chemical and morphological heterogeneities of ZnO thin films caused by elevated heat and humidity, simulating an environmental aging. X-ray fluorescence microscopy, X-ray absorption spectroscopy, grazing incidence small angle and widemore » angle X-ray scattering, scanning electron microscopy (SEM), ultra-high-resolution SEM, and optical microscopy were carried out to examine ZnO and Al-doped ZnO thin films on two different substrates—silicon wafers and flexible polyethylene terephthalate (PET) films. In the un-doped ZnO thin film, the simulated environmental aging is resulting in pin-holes. In the Al-doped ZnO thin films, significant morphological changes occurred after the treatment, with an appearance of platelet-shaped structures that are 100–200 nm wide by 1μm long. Synchrotron x-ray characterization further confirmed the heterogeneity in the aged Al-doped ZnO, showing the formation of anisotropic structures and disordering. X-ray diffraction and X-ray absorption spectroscopy indicated the formation of a zinc hydroxide in the aged Al-doped films. In conclusion, utilizing advanced characterization methods, our studies provided information with an unprecedented level of details and revealed the chemical and morphologically heterogeneous nature of the degradation in ZnO thin films.« less

Mechanical and Electrical Performance of Thermally Stable Au-ZnO films

DOE PAGES

Schoeppner, Rachel L.; Goeke, Ronald S.; Moody, Neville R.; ...

2015-03-28

The mechanical properties, thermal stability, and electrical performance of Au–ZnO composite thin films are determined in this work. The co-deposition of ZnO with Au via physical vapor deposition leads to grain refinement over that of pure Au; the addition of 0.1 vol.% ZnO reduces the as-grown grain size by over 30%. The hardness of the as-grown films doubles with 2% ZnO, from 1.8 to 3.6 GPa as measured by nanoindentation. Films with ZnO additions greater than 0.5% show no significant grain growth after annealing at 350 °C, while pure gold and smaller additions do exhibit grain growth and subsequent mechanicalmore » softening. Films with 1% and 2% ZnO show a decrease of approximately 50% in electrical resistivity and no change in hardness after annealing. A model accounting for both changes in the interface structure between dispersed ZnO particles and the Au matrix captures the changes in mechanical and electrical resistivity. Furthermore, the addition of 1–2% ZnO co-deposited with Au provides a method to create mechanically hard and thermally stable films with a resistivity less than 80 nΩ-m. Our results complement previous studies of other alloying systems, suggesting oxide dispersion strengthened (ODS) gold shows a desirable hardness–resistivity relationship that is relatively independent of the particular ODS chemistry.« less

Optical and magneto-optical properties of zinc-oxide nanostructures grown by the low-temperature chemical route

NASA Astrophysics Data System (ADS)

Willander, M.; Alnoor, H.; Savoyant, A.; Adam, Rania E.; Nur, O.

2018-02-01

We demonstrate that the low temperature synthesis chemical route can be utilized to control the functionality of zinc oxide (ZnO) nanoparticles (NPs) and nanorods (NRs) for optical and magneto-optical performance. Different structural, optical, electro- and magneto-optical results will be displayed and analyzed. In the first part, we show how high quality ZnO NPs can be efficient for photodegradation using ultra-violet radiation. In the second part we will present our recent results on the control of the core defects in cobalt doped ZnO NR. Here and by using electron paramagnetic resonance (EPR) measurements, the substitution of Co2+ ions in the ZnO NRs crystal is shown. The relation between the incorporation and core defects concentration will be discussed. The findings give access to the magnetic anisotropy of ZnO NRs grown by the low temperature chemical route and can lead to demonstrate room temperature ferromagnetism in nanostructures with potential for different device applications.

Theoretical investigation on thermodynamic properties of ZnO1-x Te x alloys

NASA Astrophysics Data System (ADS)

Long, Debing; Li, Mingkai; Luo, Minghai; Zhu, Jiakun; Yang, Hui; Huang, Zhongbing; Ahuja, Rajeev; He, Yunbin

2017-05-01

In this study, the formation energy, phase diagram (with/without phonon contribution) and the relationship between bond stiffness and bond length for wurtzite (WZ) and zincblende (ZB) structures of ZnO1-x Te x (0  ⩽  x  ⩽  1) alloys have been investigated by combining first-principles calculations and cluster expansion method. The formation energy of ZnO1-x Te x alloys is very high in both structures, which means that it is difficult for ZnO and ZnTe to form stable ternary alloys ZnO1-x Te x . In the phase diagrams, both structures do not have stable phase of ternary alloys and ZnO1-x Te x ternary alloys can only exist in the form of metastable phase. These results indicate that ZnO and ZnTe easily form solid solubility gap when they form alloys. After considering vibrational free energy, we found the solubility of Te in ZnO and O in ZnTe was increased and the vibrational entropy improved the solubility furthermore. The phonon contribution is not ignorable to improve solid solubility. The phonon density of states was analyzed for ZnO1-x Te x alloys and the contribution from vibrational entropy was discussed.

Concentration specific and tunable photoresponse of bismuth vanadate functionalized hexagonal ZnO nanocrystals based photoanodes for photoelectrochemical application

NASA Astrophysics Data System (ADS)

Singh, Sonal; Ruhela, Aakansha; Rani, Sanju; Khanuja, Manika; Sharma, Rishabh

2018-02-01

In the present work, dual layer BiVO4/ZnO photoanode is instigated for photo-electrochemical (PEC) water splitting applications. Two different photocatalytic layers ZnO and BiVO4, reduces charge carrier recombination and charge transfer resistance at photoanode/electrolyte junction. The concentration-specific, tunable and without 'spike and overshoot' features, photocurrent density response is originated by varying BiVO4 concentration in the BiVO4/ZnO photoanode. The crystal structure of ZnO (hexagonal wurtzite structure) and BiVO4 (monoclinic scheelite structure) is confirmed by X-ray diffraction studies. The band gap of BiVO4/ZnO was estimated to be ca. 2.42 eV through Kubler-Munk function F(R∞) using diffuse reflectance spectroscopy. Electrochemical behavior of samples was analyzed with photocurrent measurements, electrochemical impedance, Mott-Schottky plots, bulk separation efficiency and surface transfer efficiency. The maximum photocurrent density of BiVO4/ZnO photoanode was found to be 2.3 times higher than pristine ZnO sample.0.038 M BiVO4/ZnO exhibited the highest separation efficiency of 72% and surface transfer efficiency of 64.7% at +1.23 V vs. RHE. Mott-Schottky study revealed the maximum charge carrier density in the same sample.

Structural, magnetic and electronic structure properties of Co doped ZnO nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Shalendra, E-mail: shailuphy@gmail.com; School of Materials Science and Engineering, Changwon National University, Changwon, Gyeongnam 641-773; Song, T.K., E-mail: tksong@changwon.ac.kr

Highlights: • XRD and HR-TEM results show the single phase nature of Co doped ZnO nanoparticles. • XMCD and dc magnetization results indicate the RT-FM in Co doped ZnO nanoparticles. • Co L{sub 3,2} NEXAFS spectra infer that Co ions are in 2+ valence state. • O K edge NEXAFS spectra show that O vacancy increases with Co doping in ZnO. - Abstract: We reported structural, magnetic and electronic structure studies of Co doped ZnO nanoparticles. Doping of Co ions in ZnO host matrix has been studied and confirmed using various methods; such as X-ray diffraction (XRD), field emission scanningmore » electron microscopy (FE-SEM), energy dispersed X-ray (EDX), high resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), near edge X-ray absorption fine structure (NEXAFS) spectroscopy, magnetic hysteresis loop measurements and X-ray magnetic circular dichroism (XMCD). From the XRD and HR-TEM results, it is observed that Co doped ZnO nanoparticles have single phase nature with wurtzite structure and exclude the possibility of secondary phase formation. FE-SEM and TEM micrographs show that pure and Co doped nanoparticles are nearly spherical in shape. O K edge NEXAFS spectra indicate that O vacancies increase with Co doping. The Co L{sub 3,2} edge NEXAFS spectra revealed that Co ions are in 2+ valence state. DC magnetization hysteresis loops and XMCD results clearly showed the intrinsic origin of temperature ferromagnetism in Co doped ZnO nanoparticles.« less

Characterization of structural and electrical properties of ZnO tetrapods

NASA Astrophysics Data System (ADS)

Gu, Yu-Dong; Mai, Wen-Jie; Jiang, Peng

2011-12-01

ZnO tetrapods were synthesized by a typical thermal vapor-solid deposition method in a horizontal tube furnace. Structural characterization was carried out by transmission electron microscopy (TEM) and select-area electron diffraction (SAED), which shows the presence of zinc blende nucleus in the center of tetrapods while the four branches taking hexagonal wurtzite structure. The electrical transport property of ZnO tetrapods was investigated through an in-situ nanoprobe system. The three branches of a tetrapod serve as source, drain, and "gate", respectively; while the fourth branch pointing upward works as the force trigger by vertically applying external force downward. The conductivity of each branch of ZnO-tetrapods increases 3-4 times under pressure. In such situation, the electrical current through the branches of ZnO tetrapods can be tuned by external force, and therefore a simple force sensor based on ZnO tetrapods has been demonstrated for the first time.

Effect of K-doping on structural and optical properties of ZnO thin films

NASA Astrophysics Data System (ADS)

Xu, Linhua; Li, Xiangyin; Yuan, Jun

2008-09-01

In this work, K-doped ZnO thin films were prepared by a sol-gel method on Si(111) and glass substrates. The effect of different K-doping concentrations on structural and optical properties of the ZnO thin films was studied. The results showed that the 1 at.% K-doped ZnO thin film had the best crystallization quality and the strongest ultraviolet emission ability. When the concentration of K was above 1 at.%, the crystallization quality and ultraviolet emission ability dropped. For the K-doped ZnO thin films, there was not only ultraviolet emission, but also a blue emission signal in their photoluminescent spectra. The blue emission might be connected with K impurity or/and the intrinsic defects (Zn interstitial and Zn vacancy) of the ZnO thin films.

Template-Assisted Hydrothermal Growth of Aligned Zinc Oxide Nanowires for Piezoelectric Energy Harvesting Applications

PubMed Central

2016-01-01

A flexible and robust piezoelectric nanogenerator (NG) based on a polymer-ceramic nanocomposite structure has been successfully fabricated via a cost-effective and scalable template-assisted hydrothermal synthesis method. Vertically aligned arrays of dense and uniform zinc oxide (ZnO) nanowires (NWs) with high aspect ratio (diameter ∼250 nm, length ∼12 μm) were grown within nanoporous polycarbonate (PC) templates. The energy conversion efficiency was found to be ∼4.2%, which is comparable to previously reported values for ZnO NWs. The resulting NG is found to have excellent fatigue performance, being relatively immune to detrimental environmental factors and mechanical failure, as the constituent ZnO NWs remain embedded and protected inside the polymer matrix. PMID:27172933

Seed/catalyst-free vertical growth of high-density electrodeposited zinc oxide nanostructures on a single-layer graphene

NASA Astrophysics Data System (ADS)

Aziz, Nur Suhaili Abd; Mahmood, Mohamad Rusop; Yasui, Kanji; Hashim, Abdul Manaf

2014-02-01

We report the seed/catalyst-free vertical growth of high-density electrodeposited ZnO nanostructures on a single-layer graphene. The absence of hexamethylenetetramine (HMTA) and heat has resulted in the formation of nanoflake-like ZnO structure. The results show that HMTA and heat are needed to promote the formation of hexagonal ZnO nanostructures. The applied current density plays important role in inducing the growth of ZnO on graphene as well as in controlling the shape, size, and density of ZnO nanostructures. High density of vertically aligned ZnO nanorods comparable to other methods was obtained. The quality of the ZnO nanostructures also depended strongly on the applied current density. The growth mechanism was proposed. According to the growth timing chart, the growth seems to involve two stages which are the formation of ZnO nucleation and the enhancement of the vertical growth of nanorods. ZnO/graphene hybrid structure provides several potential applications in electronics and optoelectronics such as photovoltaic devices, sensing devices, optical devices, and photodetectors.

Optical study of gamma irradiated sodium metaphosphate glasses containing divalent metal oxide MO (ZnO or CdO)

NASA Astrophysics Data System (ADS)

Nabhan, E.; Abd-Allah, W. M.; Ezz-El-Din, F. M.

Sodium metaphosphate glasses containing divalent metal oxide, ZnO or CdO with composition 50 P2O5 - (50 - x) Na2O - x MO (ZnO, or CdO) where x = 0, 10, 20 (mol%) were prepared by conventional melt method. UV/visible spectroscopy and FTIR spectroscopy are measured before and after exposing to successive gamma irradiation doses (5-80 kGy). The optical absorption spectra results of the samples before irradiation reveal a strong UV absorption band at (∼230 nm) which is related to unavoided iron impurities. The effects of gamma irradiation on the optical spectral properties of the various glasses have been compared. From the optical absorption spectral data, the optical band gap is evaluated. The main structural groups and the influence of both divalent metal oxide and gamma irradiation effect on the structural vibrational groups are realized through IR spectroscopy. The FTIR spectra of γ-irradiated samples are characterized by the stability of the number and position for the main characteristic band of phosphate groups. To better understood the structural changes during γ-irradiation, a deconvolution of FTIR spectra in the range 650-1450 cm-1 is made. The FTIR deconvolution results found evidence that, the changes occurring after gamma irradiation have been related to irradiation induced structural defects and compositional changes.

Influence of amines as surfactant on the optical, thermal, and structural properties of nanostructured ZnO

NASA Astrophysics Data System (ADS)

Sehgal, Preeti; Narula, A. K.

2015-06-01

Zinc oxide nanoparticles were synthesized by precipitation method using triethanolamine (TEA) and hexamine (HA) as capping agents, and their effects on the optical, thermal, and morphological properties were analyzed. We have also analyzed the role of solvents on the aforementioned properties of ZnO nanoparticles. The optical properties of capped zinc oxide nanoparticles were investigated by UV-visible and fluorescent techniques. The HA@ZnO and TEA@ZnO that showed blueshift in comparison with ZnO without surfactant revealed the role of surfactant in reducing the trap sites by forming defect-free nanoparticles. TG-DTA curves indicated that optimum annealing temperature for ZnO nanoparticles was in the range of 360-469 °C depending upon the surfactant and solvent; no weight loss was observed above 469 °C. Synthesized ZnO nanoparticles had pure wurtzite structure as elucidated by X-ray diffraction studies (XRD). Scanning electron microscope revealed that the ZnO synthesized in isopropyl alcohol had spherical morphology, whereas ZnO nanoparticles synthesized in methanol had agglomerate sheet-like structure. The average size of the nanocrystal was estimated around 85-169 nm for ZnO.

Tailoring surface and photocatalytic properties of ZnO and nitrogen-doped ZnO nanostructures using microwave-assisted facile hydrothermal synthesis

NASA Astrophysics Data System (ADS)

Rangel, R.; Cedeño, V.; Ramos-Corona, A.; Gutiérrez, R.; Alvarado-Gil, J. J.; Ares, O.; Bartolo-Pérez, P.; Quintana, P.

2017-08-01

Microwave hydrothermal synthesis, using an experimental 23 factorial design, was used to produce tunable ZnO nano- and microstructures, and their potential as photocatalysts was explored. Photocatalytic reactions were conducted in a microreactor batch system under UV and visible light irradiation, while monitoring methylene blue degradation, as a model system. The variables considered in the microwave reactor to produce ZnO nano- or microstructures, were time, NaOH concentration and synthesis temperature. It was found that, specific surface area and volume/surface area ratio were affected as a consequence of the synthesis conditions. In the second stage, the samples were plasma treated in a nitrogen atmosphere, with the purpose of introducing nitrogen into the ZnO crystalline structure. The central idea is to induce changes in the material structure as well as in its optical absorption, to make the plasma-treated material useful as photocatalyst in the visible region of the electromagnetic spectrum. Pristine ZnO and nitrogen-doped ZnO compounds were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area (BET), XPS, and UV-Vis diffuse reflectance spectroscopy. The results show that the methodology presented in this work is effective in tailoring the specific surface area of the ZnO compounds and incorporation of nitrogen into their structure, factors which in turn, affect its photocatalytic behavior.

Self-Assembly of ZnO Nanoplatelets into Hierarchical Mesocrystals and Their Photocatalytic Property

NASA Astrophysics Data System (ADS)

Yang, Yongqiang; Wang, Qinsheng; Liu, Zheng; Jin, Ling; Ou, Bingxian; Han, Pengju; Wang, Qun; Cheng, Xiaobao; Liu, Wenjun; Wen, Yu; Liu, Yuan; Zhao, Weifang

2018-03-01

In this work, a simple chemical procedure was developed for the preparation of mesocrystals consisiting of ZnO nanoplateletes. By simple mixing the aqueous solutions Zn(NO3)2, NaOH and ethanol at certain temperatures, the hierarchical mesocrystals with big at both ends but small in the middle were obtained. After being annealed in air at certain temperatures, the same structured ZnO mesocrystals were generated. The morphology, crystalline structure and chemical composition were characterized using SEM, XRD FT-IR and Raman. The photocatalytic properties of the ZnO mesocrystals were also investigated. It was illustrated that the ZnO mesocrystals show decent photocatalytic performance to the photodegradation of methyl blue.

High-quality ZnO inverse opals and related heterostructures as photocatalysts produced by atomic layer deposition

NASA Astrophysics Data System (ADS)

Long, Jie; Fu, Ming; Li, Caixia; Sun, Cuifeng; He, Dawei; Wang, Yongsheng

2018-10-01

ZnO with various nanostructures is widely investigated for high photoelectrochemical (PEC) catalysis performances due to its abundant and inert semiconducting properties with elevated electronic mobility and variable morphologies. Because the solar energy conversion efficiencies could possibly be further enhanced by the introduction of nanophotonic structures with larger surface ratios, high-quality ZnO inverse opals (IOs) were achieved by ALD method using O3 as the oxidant. The intrinsic UV emission peaks and PEC currents of ZnO IOs produced by O3 atomic layer deposition (ALD) method were much improved when compared to those made by H2O ALD and electrodeposition. ALD at higher temperatures (240 °C) can further enhance the crystalline quality and PEC performances. The optimal ALD thickness and filling fraction obtained by controlling ALD cycles, as well as the optimal photonic stop band position obtained by colloidal crystals with different sphere diameters were also discussed. It was found that conformally coated samples with TiO2 protection layers by ALD method using titanium tetrachloride as a precursor enhanced the photochemical stability of ZnO IOs. The photocorrosion was further reduced by inserting ALD Al2O3 inside the TiO2 protection layers. Heterostructured photonic crystals with double-layer IO structures with different pore periodicities were also developed for enhancing the PEC performances.

Morphology control, defect engineering and photoactivity tuning of ZnO crystals by graphene oxide--a unique 2D macromolecular surfactant.

PubMed

Pan, Xiaoyang; Yang, Min-Quan; Xu, Yi-Jun

2014-03-28

Zinc oxide (ZnO) nanostructured materials have received significant attention because of their unique physicochemical and electronic properties. In particular, the functional properties of ZnO are strongly dependent on its morphology and defect structure, particularly for a semiconductor ZnO-based photocatalyst. Here, we demonstrate a simple strategy for simultaneous morphology control, defect engineering and photoactivity tuning of semiconductor ZnO by utilizing the unique surfactant properties of graphene oxide (GO) in a liquid phase. By varying the amount of GO added during the synthesis process, the morphology of ZnO gradually evolves from a one dimensional prismatic rod to a hexagonal tube-like architecture while GO is converted into reduced GO (RGO). In addition, the introduction of GO can create oxygen vacancies in the lattice of ZnO crystals. As a result, the absorption edge of the wide band gap semiconductor ZnO is effectively extended to the visible light region, which thus endows the RGO-ZnO nanocomposites with visible light photoactivity; in contrast, the bare ZnO nanorod is only UV light photoactive. The synergistic integration of the unique morphology and the presence of oxygen vacancies imparts the RGO-ZnO nanocomposite with remarkably enhanced visible light photoactivity as compared to bare ZnO and its counterpart featuring different structural morphologies and the absence of oxygen vacancies. Our promising results highlight the versatility of the 2D GO as a solution-processable macromolecular surfactant to fabricate RGO-semiconductor nanocomposites with tunable morphology, defect structure and photocatalytic performance in a system-materials-engineering way.

Structural and photoluminescence studies on catalytic growth of silicon/zinc oxide heterostructure nanowires

PubMed Central

2013-01-01

Silicon/zinc oxide (Si/ZnO) core-shell nanowires (NWs) were prepared on a p-type Si(111) substrate using a two-step growth process. First, indium seed-coated Si NWs (In/Si NWs) were synthesized using a plasma-assisted hot-wire chemical vapor deposition technique. This was then followed by the growth of a ZnO nanostructure shell layer using a vapor transport and condensation method. By varying the ZnO growth time from 0.5 to 2 h, different morphologies of ZnO nanostructures, such as ZnO nanoparticles, ZnO shell layer, and ZnO nanorods were grown on the In/Si NWs. The In seeds were believed to act as centers to attract the ZnO molecule vapors, further inducing the lateral growth of ZnO nanorods from the Si/ZnO core-shell NWs via a vapor-liquid-solid mechanism. The ZnO nanorods had a tendency to grow in the direction of [0001] as indicated by X-ray diffraction and high resolution transmission electron microscopy analyses. We showed that the Si/ZnO core-shell NWs exhibit a broad visible emission ranging from 400 to 750 nm due to the combination of emissions from oxygen vacancies in ZnO and In2O3 structures and nanocrystallite Si on the Si NWs. The hierarchical growth of straight ZnO nanorods on the core-shell NWs eventually reduced the defect (green) emission and enhanced the near band edge (ultraviolet) emission of the ZnO. PMID:23590803

Biosynthesis and characterization of ZnO nanoparticles using the aqueous leaf extract of Imperata cylindrica L.

NASA Astrophysics Data System (ADS)

Saputra, I. S.; Yulizar, Y.

2017-04-01

ZnO nanoparticles (ZnO NPs) were biosynthesized.The growth was observed by a sol-gel method. ZnO were successfully formed through the reaction of zinc nitrate tetrahydrate Zn(NO3)2.4H2O precursor with aqueous leaf extract of Imperata cylindrica L (ICL). The structural and optical properties of ZnO were investigated. The as-synthesized products were characterized by UV-Visible (UV-Vis), UV diffuse reflectance spectroscopy (UV-DRS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). UV-Vis absorption data showed hydrolysis and characteristic of absorption peak at 300 nm of Zn(OH)2. UV-DRS confirmed that ZnO NPs has the indirect band gap at 3.13 eV. FTIR spectrum revealed the functional groups and indicated the presence of protein as the capping and stabilizing agent on the ZnO surface. Powder XRD studies indicated the formation of pure wurtzite hexagonal structure with particle size of 11.9 nm. The detailed morphological and structural characterizations revealed that the synthesized products were hexagonal nanochip.

Experimental study of optical and electrical properties of ZnO nano composites electrodeposited on n-porous silicon substrate for photovoltaic applications

NASA Astrophysics Data System (ADS)

Selmane, Naceur; Cheknane, Ali; Gabouze, Nourddine; Maloufi, Nabila; Aillerie, Michel

2017-11-01

ZnO films deposited on silicon porous substrates (PS) were prepared by electro-deposition anodization on n type (100) silicon wafer. This ZnO/PS structure combines substrates having specific structural and optical properties (IR emission), with nano-composites of ZnO potentially interesting due to their functional properties (UV emission) to be integrated as constitutive elements of devices in various optoelectronic applications mainly in blue light emitters. With this combined structure, the blue shift in the PL peak is possible and easy to obtain (467nm). The vibration modes of PS and ZnO films on PS substrates (ZnO /PS) were investigated by infrared (FTIR) measurements and their behaviors were analyzed and discussed by considering the structural properties characterized by X-ray diffraction (DRX) and scanning electronic microscopy (MEB).

Tartaric acid assisted hydrothermal synthesis of different flower-like ZnO hierarchical architectures with tunable optical and oxygen vacancy-induced photocatalytic properties

NASA Astrophysics Data System (ADS)

Liu, Tingzhi; Li, Yangyang; Zhang, Hao; Wang, Min; Fei, Xiaoyan; Duo, Shuwang; Chen, Ying; Pan, Jian; Wang, Wei

2015-12-01

Different flower-like ZnO hierarchical architectures were prepared by tartaric acid assisted hydrothermal synthesis, especially four flower-like ZnO nanostructures were obtained simultaneously under the same reaction condition. The cauliflower-like ZnO is assembled by spherical shaped nanoparticles, and the chrysanthemum-like and other flower-like ZnO nanostructures are assembled by hexagonal rods/prisms with from planar to semi-pyramid, and to pyramid tips. TA acts as a capping agent and structure-directing agent during the synthesis. All ZnO possess the hexagonal wurtzite structure. The PL spectra can be tuned by changing TA concentration. XRD, PL and Raman spectra confirmed that oxygen vacancies mainly come from the ZnO surface. The flower-like samples of 1:4.5 and 1:3 with the largest aspect ratios have highest photocatalytic performance. They decompose 85% MB within 60 min. Combining PL Gaussian fitting with K, the higher content of oxygen vacancy is, the higher photocatalytic activity is. The enhanced photocatalytic performance is mainly induced by oxygen vacancy of ZnO. The possible formation mechanism, growth and change process of flower-like ZnO were proposed.

CuO-Decorated ZnO Hierarchical Nanostructures as Efficient and Established Sensing Materials for H2S Gas Sensors

PubMed Central

Vuong, Nguyen Minh; Chinh, Nguyen Duc; Huy, Bui The; Lee, Yong-Ill

2016-01-01

Highly sensitive hydrogen sulfide (H2S) gas sensors were developed from CuO-decorated ZnO semiconducting hierarchical nanostructures. The ZnO hierarchical nanostructure was fabricated by an electrospinning method following hydrothermal and heat treatment. CuO decoration of ZnO hierarchical structures was carried out by a wet method. The H2S gas-sensing properties were examined at different working temperatures using various quantities of CuO as the variable. CuO decoration of the ZnO hierarchical structure was observed to promote sensitivity for H2S gas higher than 30 times at low working temperature (200 °C) compared with that in the nondecorated hierarchical structure. The sensing mechanism of the hybrid sensor structure is also discussed. The morphology and characteristics of the samples were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis absorption, photoluminescence (PL), and electrical measurements. PMID:27231026

Chemical lift-off and direct wafer bonding of GaN/InGaN P-I-N structures grown on ZnO

NASA Astrophysics Data System (ADS)

Pantzas, K.; Rogers, D. J.; Bove, P.; Sandana, V. E.; Teherani, F. H.; El Gmili, Y.; Molinari, M.; Patriarche, G.; Largeau, L.; Mauguin, O.; Suresh, S.; Voss, P. L.; Razeghi, M.; Ougazzaden, A.

2016-02-01

p-GaN/i-InGaN/n-GaN (PIN) structures were grown epitaxially on ZnO-buffered c-sapphire substrates by metal organic vapor phase epitaxy using the industry standard ammonia precursor for nitrogen. Scanning electron microscopy revealed continuous layers with a smooth interface between GaN and ZnO and no evidence of ZnO back-etching. Energy Dispersive X-ray Spectroscopy revealed a peak indium content of just under 5 at% in the active layers. The PIN structure was lifted off the sapphire by selectively etching away the ZnO buffer in an acid and then direct bonded onto a glass substrate. Detailed high resolution transmission electron microscoy and grazing incidence X-ray diffraction studies revealed that the structural quality of the PIN structures was preserved during the transfer process.

Impact of Substrate Types on Structure and Emission of ZnO Nanocrystalline Films

NASA Astrophysics Data System (ADS)

Ballardo Rodriguez, I. Ch.; El Filali, B.; Díaz Cano, A. I.; Torchynska, T. V.

2018-02-01

Zinc oxide (ZnO) films were simultaneously synthesized by an ultrasonic spray pyrolysis (USP) method on p-type Si (100), silicon carbide polytype [6H-SiC (0001)], porous 6H-SiC and amorphous glass substrates with the aim of studying the impact of substrate types on the structure and emission of ZnO nanocrystalline films. Porous silicon carbide (P-SiC) was prepared by the electrochemical anodization method at a constant potential of 20 V and etching time of 12 min. ZnO films grown on the SiC and P-SiC substrates are characterized by a wurtzite crystal structure with preferential growth along the (002) direction and with grain sizes of 90-180 and 70-160 nm, respectively. ZnO films grown on the Si substrate have just some small irregular hexagonal islands. The amorphous glass substrate did not promote the formation of any regular crystal forms. The obtained x-ray diffraction and photoluminescence (PL) results have shown that the better ZnO film crystallinity and high PL intensity of near-band edge emissions were achieved in the films grown on the porous SiC and SiC substrates. The preferential growth and crystalline nature of ZnO films on the SiC substrate have been discussed from the point of view of the lattice parameter compatibility between ZnO and SiC crystals.

Influence Al doped ZnO nanostructure on structural and optical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramelan, Ari Handono, E-mail: aramelan@mipa.uns.ac.id; Wahyuningsih, Sayekti; Chasanah, Uswatul

2016-04-19

The preparation of Al-doped ZnO (AZO) thin films prepared by the spin-coating method was reported. Preparation of AZO was conducted by annealing treatment at a temperature of 700°C. While the spin-coating process of AZO thin films were done at 2000 and 3000 rpm respectively. The structural properties of ZnO were determined by X- ray diffraction (XRD) analysis. ZnOnanostructure was formed after annealed at atemperature of 400°C.The morphology of ZnO was determined by Scanning Electron Microscopy (SEM) showed the irregular morphology about 30-50µm in size. Al doped on ZnO influenced the optical properties of those material. Increasing Al contain on ZnO causemore » of shifting to the lower wavelength. The optical properties of the ZnO as well as AZO films showed that higher reflectance on the ultraviolet region so those materials were used as anti-reflecting agent.Al addition significantly enhance the optical transparency and induce the blue-shift in optical bandgap of ZnO films.« less

Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers.

PubMed

Willander, M; Nur, O; Zhao, Q X; Yang, L L; Lorenz, M; Cao, B Q; Zúñiga Pérez, J; Czekalla, C; Zimmermann, G; Grundmann, M; Bakin, A; Behrends, A; Al-Suleiman, M; El-Shaer, A; Che Mofor, A; Postels, B; Waag, A; Boukos, N; Travlos, A; Kwack, H S; Guinard, J; Le Si Dang, D

2009-08-19

Zinc oxide (ZnO), with its excellent luminescent properties and the ease of growth of its nanostructures, holds promise for the development of photonic devices. The recent advances in growth of ZnO nanorods are discussed. Results from both low temperature and high temperature growth approaches are presented. The techniques which are presented include metal-organic chemical vapour deposition (MOCVD), vapour phase epitaxy (VPE), pulse laser deposition (PLD), vapour-liquid-solid (VLS), aqueous chemical growth (ACG) and finally the electrodeposition technique as an example of a selective growth approach. Results from structural as well as optical properties of a variety of ZnO nanorods are shown and analysed using different techniques, including high resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), photoluminescence (PL) and cathodoluminescence (CL), for both room temperature and for low temperature performance. These results indicate that the grown ZnO nanorods possess reproducible and interesting optical properties. Results on obtaining p-type doping in ZnO micro- and nanorods are also demonstrated using PLD. Three independent indications were found for p-type conducting, phosphorus-doped ZnO nanorods: first, acceptor-related CL peaks, second, opposite transfer characteristics of back-gate field effect transistors using undoped and phosphorus doped wire channels, and finally, rectifying I-V characteristics of ZnO:P nanowire/ZnO:Ga p-n junctions. Then light emitting diodes (LEDs) based on n-ZnO nanorods combined with different technologies (hybrid technologies) are suggested and the recent electrical, as well as electro-optical, characteristics of these LEDs are shown and discussed. The hybrid LEDs reviewed and discussed here are mainly presented for two groups: those based on n-ZnO nanorods and p-type crystalline substrates, and those based on n-ZnO nanorods and p-type amorphous substrates. Promising electroluminescence characteristics aimed at the development of white LEDs are demonstrated. Although some of the presented LEDs show visible emission for applied biases in excess of 10 V, optimized structures are expected to provide the same emission at much lower voltage. Finally, lasing from ZnO nanorods is briefly reviewed. An example of a recent whispering gallery mode (WGM) lasing from ZnO is demonstrated as a way to enhance the stimulated emission from small size structures.

Synthesis of ALD zinc oxide and thin film materials optimization for UV photodetector applications

NASA Astrophysics Data System (ADS)

Tapily, Kandabara Nouhoum

Zinc oxide (ZnO) is a direct, wide bandgap semiconductor material. It is thermodynamically stable in the wurtzite structure at ambient temperature conditions. ZnO has very interesting optical and electrical properties and is a suitable candidate for numerous optoelectronic applications such as solar cells, LEDs and UV-photodetectors. ZnO is a naturally n-type semiconductor. Due to the lack of reproducible p-type ZnO, achieving good homojunction ZnO-based photodiodes such as UV-photodetectors remains a challenge. Meanwhile, heterojunction structures of ZnO with p-type substrates such as SiC, GaN, NiO, AlGaN, Si etc. are used; however, those heterojunction diodes suffer from low efficiencies. ZnO is an n-type material with numerous intrinsic defect levels responsible for the electrical and optical behaviors. Presently, there is no clear consensus about the origin of those defects. In this work, ZnO was synthesized by atomic layer deposition (ALD). ALD is a novel deposition technique suitable for nanotechnology engineering that provides unique features such as precise control of ZnO thin film with atomic resolution, high uniformity, good conformity and high aspect ratio. Using this novel deposition technique, the ALD ZnO deposition process was developed and optimized using diethyl zinc as the precursor for zinc and water vapor as the oxygen source. In order to optimize the film quality for use in electronic applications, the physical, mechanical and electrical properties were investigated. The structural and mechanical properties of the ALD ZnO thin films were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning electron microscopy (SEM), spectroscopic Ellipsometry, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV-VIS absorption and nanoindentation. The electrical characterizations were performed using C-V, I-V, DLTS, Hall Effect, and four-point probe. The intrinsic defects responsible for the electrical and optical properties of the ALD ZnO films were analyzed and identified. ALD ZnO based electronic devices were fabricated, optimized and their electrical characteristics measured. The photocurrent characteristics of ALD ZnO were also optimized, and high efficiency UV-photodetectors were achieved.

The effects of Mg incorporation and annealing temperature on the physicochemical properties and antibacterial activity against Listeria monocytogenes of ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Shadan, Nima; Ziabari, Ali Abdolahzadeh; Meraat, Rafieh; Jalali, Kamyar Mazloum

2017-02-01

In this paper, Mg-doped ZnO nanoparticles were synthesized by the facile sol-gel method. The crystalline structure, characteristic absorption bands and morphology of the obtained Mg-doped ZnO nanoparticles were studied by XRD, FTIR and TEM. The thermal degradation behaviour of the samples was investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG). The effect of Mg concentrations and annealing temperatures on the antibacterial properties of the obtained nanoparticles was investigated in detail. The results indicated that doping Mg ions into ZnO lattice could enhance its antibacterial activity. Antibacterial assay demonstrated that Mg-doped ZnO with 7% Mg content annealed at 400 ∘C had the strongest antibacterial activity against Listeria monocytogenes (98.7%). This study indicated that the inhibition rate of ZnO nanoparticles increased with the formation of granular structure and the decrease of ZnO size due to the doping of Mg ions into the ZnO lattice.

Electronic structure, magnetic and structural properties of Ni doped ZnO nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Shalendra, E-mail: shailuphy@gmail.com; Vats, Prashant; Gautam, S.

Highlights: • XRD, and HR-TEM results show the single phase nature of Ni doped ZnO nanoparticles. • dc magnetization results indicate the RT-FM in Ni doped ZnO nanoparticles. • Ni L{sub 3,2} edge NEXAFS spectra infer that Ni ions are in +2 valence state. • O K edge NEXAFS spectra show that O vacancy increases with Ni doping in ZnO. - Abstract: We report structural, magnetic and electronic structural properties of Ni doped ZnO nanoparticles prepared by auto-combustion method. The prepared nanoparticles were characterized by using X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), near edge X-ray absorption finemore » structure (NEXAFS) spectroscopy, and dc magnetization measurements. The XRD and HR-TEM results indicate that Ni doped ZnO nanoparticles have single phase nature with wurtzite lattice and exclude the presence of secondary phase. NEXAFS measurements performed at Ni L{sub 3,2}-edges indicates that Ni ions are in +2 valence state and exclude the presence of Ni metal clusters. O K-edge NEXAFS spectra indicate an increase in oxygen vacancies with Ni-doping, while Zn L{sub 3,2}-edge show the absence of Zn-vacancies. The magnetization measurements performed at room temperature shows that pure and Ni doped ZnO exhibits ferromagnetic behavior.« less

Electrical and structural properties of ZnO synthesized via infiltration of lithographically defined polymer templates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nam, Chang-Yong, E-mail: cynam@bnl.gov; Stein, Aaron; Kisslinger, Kim

We investigate the electrical and structural properties of infiltration-synthesized ZnO. In-plane ZnO nanowire arrays with prescribed positional registrations are generated by infiltrating diethlyzinc and water vapor into lithographically defined SU-8 polymer templates and removing organic matrix by oxygen plasma ashing. Transmission electron microscopy reveals that homogeneously amorphous as-infiltrated polymer templates transform into highly nanocrystalline ZnO upon removal of organic matrix. Field-effect transistor device measurements show that the synthesized ZnO after thermal annealing displays a typical n-type behavior, ∼10{sup 19 }cm{sup −3} carrier density, and ∼0.1 cm{sup 2} V{sup −1} s{sup −1} electron mobility, reflecting highly nanocrystalline internal structure. The results demonstrate themore » potential application of infiltration synthesis in fabricating metal oxide electronic devices.« less

Improvement of antimony sulfide photo absorber performance by interface modification in Sb2S3-ZnO hybrid nanostructures

NASA Astrophysics Data System (ADS)

Ali, Asad; Hasanain, Syed Khurshid; Ali, Tahir; Sultan, Muhammad

2017-03-01

Metal-oxide chalcogenide nanostructures as part of hybrid systems are very important for photovoltaic and optoelectronic applications. It is however known that the various interfaces within the hybrid structures play a crucial role in limiting the efficiency of these devices. Here we report on the improvement of Sb2S3 structure through modification of interface between Zn-oxide nanostructures and chalcogenides. ZnO nanorods were grown on fluorine doped tin oxide (FTO) substrate by chemical bath deposition (CBD) method. X-ray diffraction (XRD) and SEM analysis confirmed the single phase wurtzite structure and c-axis orientation of the ZnO nanorod arrays. Antimony tri-sulfide (Sb2S3) was deposited on ZnO nanords by CBD and subsequently annealed at 300 °C in argon environment for 30 min. XRD and the XPS analysis of ZnO-Sb2S3 system showed the dominant presence of Sb2O3 rather than Sb2S3. Since oxidation of Sb2S3 is understood to proceed mainly from the ZnO-Sb2S3 interface, a ZnS interlayer was introduced between ZnO nanorods and Sb2S3 by chemical route. The subsequent structural and optical properties of the ZnO-ZnS-Sb2S3 system are analyzed in detail. The introduction of sulfide interlayer prevents the oxidation of Sb2S3 which is evident from reduced oxide phase in Sb2S3. Significant improvement in the structural and optical properties of Sb2S3 are reported as compared to the parent ZnO-Sb2S3 system. This gain in the optical properties of hybrid ZnO-ZnS-Sb2S3 nanostructures is explained as being related to successful prevention of Sb2O3 formation at the Sb-ZnO interface and stabilization of the desired Sb2S3.

Synthesis of ZnO Photocatalysts Using Various Surfactants

NASA Astrophysics Data System (ADS)

Yao, Chengli; Zhu, Jinmiao; Li, Hongying; Zheng, Bin; Wei, Yanxin

2017-12-01

Zinc oxide (ZnO) nanostructured materials have received significant attention because of their unique physicochemical and electronic properties. In particular, the functional properties of ZnO are owed to its morphology and defect structure. ZnO particles were successfully synthesized by chemical precipitation. CTAB (cetyltrimethylammonium bromide), BS-12 (dodecyl dimethyl betaine) and graphene oxide (GO) were selected as templates to induce the formation of ZnO, respectively. By varying the amount of surfactant added during the synthesis process, the structural properties and the crystalline phase of the synthesized nanospheres were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet and visible spectrophotometry (UV‒Vis). Simultaneously, photo catalytic degradation of Rhodamine B (RhB) was carried out under natural sunlight irradiation while ZnO or ZnO/GO particles were used as catalyst. GO is prone to induce formation of wurtzite hexagonal phase of ZnO. Compared with CTAB and BS-12, ZnO/GO composites had a remarkably photocatalytic degradation.

Deposition of undoped and Al doped ZnO thin films using RF magnetron sputtering and study of their structural, optical and electrical properties

NASA Astrophysics Data System (ADS)

Parvathy Venu, M.; Shrisha B., V.; Balakrishna, K. M.; Naik, K. Gopalakrishna

2017-05-01

Undoped ZnO and Al doped ZnO thin films were deposited on glass and p-Si(100) substrates by RF magnetron sputtering technique at room temperature using homemade targets. ZnO target containing 5 at% of Al2O3 as doping source was used for the growth of Al doped ZnO thin films. XRD revealed that the films have hexagonal wurtzite structure with high crystallinity. Morphology and chemical composition of the films have been indicated by FESEM and EDAX studies. A blue shift of the band gap energy and higher optical transmittance has been observed in the case of Al doped ZnO (ZnO:Al) thin films with respect to the ZnO thin films. The as deposited films on p-Si were used to fabricate n-ZnO/p-Si(100) and n-ZnO:Al/p-Si(100) heterojunction diodes and their room temperature current-voltage characteristics were studied.

Characteristics of one-port surface acoustic wave resonator fabricated on ZnO/6H-SiC layered structure

NASA Astrophysics Data System (ADS)

Li, Qi; Qian, Lirong; Fu, Sulei; Song, Cheng; Zeng, Fei; Pan, Feng

2018-04-01

Characteristics of one-port surface acoustic wave (SAW) resonators fabricated on ZnO/6H-SiC layered structure were investigated experimentally and theoretically. Phase velocities (V p), electromechanical coupling coefficients (K 2), quality factors (Q), and temperature coefficients of frequency (TCF) of Rayleigh wave (0th mode) and first- and second-order Sezawa wave (1st and 2nd modes, respectively) for different piezoelectric film thickness-to-wavelength (h ZnO /λ) ratios were systematically studied. Results demonstrated that one-port SAW resonators fabricated on the ZnO/6H-SiC layered structure were promising for high-frequency SAW applications with moderate K 2 and TCF values. A high K 2 of 2.44% associated with a V p of 5182 m s‑1 and a TCF of  ‑41.8 ppm/°C was achieved at h ZnO /λ  =  0.41 in the 1st mode, while a large V p of 7210 m s‑1 with a K 2 of 0.19% and a TCF of  ‑36.4 ppm/°C was obtained for h ZnO /λ  =  0.31 in the 2nd mode. Besides, most of the parameters were reported for the first time and will be helpful for the future design and optimization of SAW devices fabricated on ZnO/6H-SiC layered structures.

Synthesis and characterization of ZnO thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anilkumar, T. S., E-mail: anil24march@gmail.com; Girija, M. L., E-mail: girija.ml.grt1@gmail.com; Venkatesh, J., E-mail: phph9502@yahoo.com

2016-05-06

Zinc oxide (ZnO) Thin films were deposited on glass substrate using Spin coating method. Zinc acetate dehydrate, Carbinol and Mono-ethanolamine were used as the precursor, solvent and stabilizer respectively to prepare ZnO Thin-films. The molar ratio of Monoethanolamine to Zinc acetate was maintained as approximately 1. The thickness of the films was determined by Interference technique. The optical properties of the films were studied by UV Vis-Spectrophotometer. From transmittance and absorbance curve, the energy band gap of ZnO is found out. Electrical Conductivity measurements of ZnO are carried out by two probe method and Activation energy for the electrical conductivitymore » of ZnO are found out. The crystal structure and orientation of the films were analyzed by XRD. The XRD patterns show that the ZnO films are polycrystalline with wurtzite hexagonal structure.« less

Control of ZnO Nanorod Defects to Enhance Carrier Transportation in p-Cu₂O/i-ZnO Nanorods/n-IGZO Heterojunction.

PubMed

Ke, Nguyen Huu; Trinh, Le Thi Tuyet; Mung, Nguyen Thi; Loan, Phan Thi Kieu; Tuan, Dao Anh; Truong, Nguyen Huu; Tran, Cao Vinh; Hung, Le Vu Tuan

2017-01-01

The p-Cu₂O/i-ZnO nanorods/n-IGZO heterojunctions were fabricated by electrochemical and sputtering method. ZnO nanorods were grown on conductive indium gallium zinc oxide (IGZO) thin film and then p-Cu₂O layer was deposited on ZnO nanorods to form the heterojunction. ZnO nanorods play an important role in carrier transport mechanisms and performance of the junction. The changing of defects in ZnO nanorods by annealing samples in air and vacuum have studied. The XRD, photoluminescence (PL) spectroscopy, and FTIR were used to study about structure, and defects in ZnO nanorods. The SEM, i–V characteristics methods were also used to define structure, electrical properties of the heterojunctions layers. The results show that the defects in ZnO nanorods affected remarkably on performance of heterojunctions of solar cells.

Effect of Material of Metal Sublayer and Deposition Configuration on the Texture Formation in the Piezoactive ZnO Films

NASA Astrophysics Data System (ADS)

Veselov, A. G.; Elmanov, V. I.; Kiryasova, O. A.; Nikulin, Yu. V.

2018-01-01

Effect of material of metal sublayer (aluminum, vanadium, chromium, iron, cobalt, nickel, and copper) and deposition configuration on the formation of the oblique and straight texture in the ZnO films is studied. The films that are synthesized in a dc magnetron sputtering system. It is shown that the piezoactive ZnO films with oblique texture that can generate shear waves are formed on the Cr and V metal sublayers in the shifted deposition configuration when the substrate is shifted relative to the magnetron axis toward the region of the target erosion. The piezoactive ZnO films with the straight structure that can generate longitudinal waves are formed on a chemically pure Al sublayer in the symmetric deposition configuration when the substrate is centered with respect to the target. Changes of the sublayer material in both deposition configurations or preliminary oxidation of the sublayer lead to the formation of the piezoactive ZnO films with mixed texture that excite shear and longitudinal waves. Chemical etching is used to show that the ZnO films with the oblique and straight textures exhibit piezoactive properties and can generate hypersound at thicknesses of no less than about 0.3 and about 0.9 μm, respectively.

The effect of cation doping on the morphology, optical and structural properties of highly oriented wurtzite ZnO-nanorod arrays grown by a hydrothermal method

NASA Astrophysics Data System (ADS)

Hassanpour, A.; Guo, P.; Shen, S.; Bianucci, P.

2017-10-01

Undoped and C-doped (C: Mg2+, Ni2+, Mn2+, Co2+, Cu2+, Cr3+) ZnO nanorods were synthesized by a hydrothermal method at temperatures as low as 60 °C. The effect of doping on the morphology of the ZnO nanorods was visualized by taking their cross section and top SEM images. The results show that the size of nanorods was increased in both height and diameter by cation doping. The crystallinity change of the ZnO nanorods due to each doping element was thoroughly investigated by an x-ray diffraction (XRD). The XRD patterns show that the wurtzite crystal structure of ZnO nanorods was maintained after cation addition. The optical Raman-active modes of undoped and cation-doped nanorods were measured with a micro-Raman setup at room temperature. The surface chemistry of samples was investigated by x-ray photoelectron spectroscopy and energy-dispersive x-ray spectroscopy. Finally, the effect of each cation dopant on band-gap shift of the ZnO nanorods was investigated by a photoluminescence setup at room temperature. Although the amount of dopants (Mg2+, Ni2+, and Co2+) was smaller than the amount of Mn2+, Cu2+, and Cr3+ in the nanorods, their effect on the band structure of the ZnO nanorods was profound. The highest band-gap shift was achieved for a Co-doped sample, and the best crystal orientation was for Mn-doped ZnO nanorods. Our results can be used as a comprehensive reference for engineering of the morphological, structural and optical properties of cation-doped ZnO nanorods by using a low-temperature synthesis as an economical mass-production approach.

Au functionalized ZnO rose-like hierarchical structures and their enhanced NO2 sensing performance

NASA Astrophysics Data System (ADS)

Shingange, K.; Swart, H. C.; Mhlongo, G. H.

2018-04-01

Herein, we present ZnO rose-like hierarchical nanostructures employed as support to Au nanoparticles to produce Au functionalized three dimensional (3D) ZnO hierarchical nanostructures (Au/ZnO) for NO2 detection using a microwave-assisted method. Comparative analysis of NO2 sensing performance between the pristine ZnO and Au/ZnO rose-like structures at 300 °C revealed improved NO2 response and rapid response-recovery times with Au incorporation owing to a combination of high surface accessibility induced by hierarchical nanostructure design and catalytic activity of the small Au nanoparticles. Structural and optical analyses acquired from X-ray diffraction, scanning electron microscopy, transmission electron microscope and photoluminescence spectroscopy were also performed.

Effects of annealing on the ferromagnetism and photoluminescence of Cu-doped ZnO nanowires.

PubMed

Xu, H J; Zhu, H C; Shan, X D; Liu, Y X; Gao, J Y; Zhang, X Z; Zhang, J M; Wang, P W; Hou, Y M; Yu, D P

2010-01-13

Room temperature ferromagnetic Cu-doped ZnO nanowires have been synthesized using the chemical vapor deposition method. By combining structural characterizations and comparative annealing experiments, it has been found that both extrinsic (CuO nanoparticles) and intrinsic (Zn(1-x)Cu(x)O nanowires) sources are responsible for the observed ferromagnetic ordering of the as-grown samples. As regards the former, annealing in Zn vapor led to a dramatic decrease of the ferromagnetism. For the latter, a reversible switching of the ferromagnetism was observed with sequential annealings in Zn vapor and oxygen ambience respectively, which agreed well with previous reports for Cu-doped ZnO films. In addition, we have for the first time observed low temperature photoluminescence changed with magnetic properties upon annealing in different conditions, which revealed the crucial role played by interstitial zinc in directly mediating high T(c) ferromagnetism and indirectly modulating the Cu-related structured green emission via different charge transfer transitions.

Ferroelectric behavior and reproducible Bi-stable resistance switching property in K-doped ZnO thin films as candidate for application in non-volatile memories

NASA Astrophysics Data System (ADS)

Lee, J. W.; Subramaniam, N. G.; Kang, T. W.; Shon, Yoon; Kim, E. K.

2015-05-01

Potassium-doped ZnO thin films electrodeposited on indium tin oxide (ITO) coated glass substrates exhibited ferroelectric behavior with a remnant polarization of 0.2 μC/cm2. Especially, wave forms showing the applied input voltage Vi and output voltage Vo were obtained for Al/ZnO:K/ITO structure. It exhibits a superposition of Vi (input) and Vo (output) signal from Al/ZnO:K/ITO structure with a clear phase shift between the two wave forms which again confirms that the observed ferroelectric hysteresis curve is not related to leaky dielectric materials. The current-voltage characteristics of Al/ZnO:K/ITO structures measured for several cycles revealed bi-stable switching characteristics. The reproducible bi-stable switching characteristics for the mentioned structures had good retention in one particular resistance state. Around one order of switching was realized between low and high resistance states. The switching property thought to be polarization induced originating out from the ferroelectric properties of the potassium doped ZnO thin film. The switching between ZnO:K/ITO interface is assumed to be critical for stability in switching for several cycles. Possible application of this structure in non-volatile memories is explored.

Direct Heteroepitaxial Growth of ZnO over GaN Crystal in Aqueous Solution

NASA Astrophysics Data System (ADS)

Hamada, Takahiro; Ito, Akihiro; Nagao, Nobuaki; Suzuki, Nobuyasu; Fujii, Eiji; Tsujimura, Ayumu

2013-04-01

We report on the structural and electrical properties of ZnO films grown on surface-treated GaN/Al2O3 substrates by chemical bath deposition. X-ray diffraction analysis indicated that the ZnO films had a single-crystalline wurtzite structure with c-axis orientation. The ZnO film exhibited n-type conduction with a carrier concentration of 6.9 ×1018 cm-3, an electron mobility of 41 cm2/(V.s), and a resistivity of 2.2 ×10-2 Ω.cm. A low specific contact resistivity of 4.3 ×10-3 Ω.cm2 was obtained at the ZnO/n-GaN interface. Additionally, the ZnO film exhibited high transparency in the visible and infrared region.

3-D matrix template-assisted growth of oriented oxide nanowire arrays using glancing angle pulsed laser deposition

NASA Astrophysics Data System (ADS)

Wright, N.; Mateo-Feliciano, D.; Ostoski, A.; Mukherjee, P.; Witanachchi, S.

Nanosphere lithography is a combination of different methods to nanofabrication. In this work nanosphere lithography is used to study the growth of Zinc Oxide Nano-columns (ZnO NCs) on different diameter Silica Nanosphere (SNS) self-assembled templates. ZnO NCs are promising building blocks for many existing and emerging optical, electrical, and piezoelectric devices, specifically, the seeded growth of other oxide materials. Recently, reports have shown a ferroelectric phase of zinc stannate (ZnSnO3) and while lead zirconium titanate oxide (PZT) has been the main material of interest in ferroelectric and piezoelectric applications, the toxicity of lead has been of great concern. The possibility of developing lead free piezoelectric materials is of great interest in the ferroelectric community. Langmuir-Blodgett method was used to construct a self-assembled monolayer of SNSs on silicon substrates. Oriented ZnO NCs were grown on top of the spheres using the glancing angle pulsed laser deposition technique. Columns were formed in a spatially ordered closed-packed hexagonal configuration. Growth of ZnO NCs was studied as function of ambient Oxygen pressure with SNS size ranging from 250-1000 nm. Cross-sectional Scanning Electron Microscopy and X-ray diffraction (XRD) were used to study the template structure. Relative aspect ratios were studied and showed tunability of column dimensions with sphere size. XRD revealed ZnO NC arrays were c-axis oriented with hexagonal wurtzite structure.

Nanostructured ZnO films on stainless steel are highly safe and effective for antimicrobial applications.

PubMed

Shim, Kyudae; Abdellatif, Mohamed; Choi, Eunsoo; Kim, Dongkyun

2017-04-01

The safety and effectiveness of antimicrobial ZnO films must be established for general applications. In this study, the antimicrobial activity, skin irritation, elution behavior, and mechanical properties of nanostructured ZnO films on stainless steel were evaluated. ZnO nanoparticle (NP) and ZnO nanowall (NW) structures were prepared with different surface roughnesses, wettability, and concentrations using an RF magnetron sputtering system. The thicknesses of ZnO NP and ZnO NW were approximately 300 and 620 nm, respectively, and ZnO NW had two diffraction directions of [0002] and [01-10] based on high-resolution transmission electron microscopy. The ZnO NW structure demonstrated 99.9% antimicrobial inhibition against Escherichia coli, Staphylococcus aureus, and Penicillium funiculosum, and no skin irritation was detected using experimental rabbits. Approximately 27.2 ± 3.0 μg L -1 Zn ions were eluted from the ZnO NW film at 100 °C for 24 h, which satisfies the WHO guidelines for drinking water quality. Furthermore, the Vickers hardness and fracture toughness of ZnO NW films on stainless steel were enhanced by 11 and 14% compared to those of the parent stainless steel. Based on these results, ZnO NW films on STS316L sheets are useful for household supplies, such as water pipes, faucets, and stainless steel containers.

Growth of High-Density Zinc Oxide Nanorods on Porous Silicon by Thermal Evaporation

PubMed Central

Rusli, Nurul Izni; Tanikawa, Masahiro; Mahmood, Mohamad Rusop; Yasui, Kanji; Hashim, Abdul Manaf

2012-01-01

The formation of high-density zinc oxide (ZnO) nanorods on porous silicon (PS) substrates at growth temperatures of 600–1000 °C by a simple thermal evaporation of zinc (Zn) powder in the presence of oxygen (O2) gas was systematically investigated. The high-density growth of ZnO nanorods with (0002) orientation over a large area was attributed to the rough surface of PS, which provides appropriate planes to promote deposition of Zn or ZnOx seeds as nucleation sites for the subsequent growth of ZnO nanorods. The geometrical morphologies of ZnO nanorods are determined by the ZnOx seed structures, i.e., cluster or layer structures. The flower-like hexagonal-faceted ZnO nanorods grown at 600 °C seem to be generated from the sparsely distributed ZnOx nanoclusters. Vertically aligned hexagonal-faceted ZnO nanorods grown at 800 °C may be inferred from the formation of dense arrays of ZnOx clusters. The formation of disordered ZnO nanorods formed at 1000 °C may due to the formation of a ZnOx seed layer. The growth mechanism involved has been described by a combination of self-catalyzed vapor-liquid-solid (VLS) and vapor-solid (VS) mechanism. The results suggest that for a more precise study on the growth of ZnO nanostructures involving the introduction of seeds, the initial seed structures must be taken into account given their significant effects.

Superhydrophilic poly (styrene co acrylonitrile)-ZnO nanocomposite surfaces for UV shielding and self-cleaning applications

NASA Astrophysics Data System (ADS)

Singh, Rajender; Sharma, Ramesh; Barman, P. B.; Sharma, Dheeraj

2017-11-01

UV shielding based super hydrophilic material is developed in the present formulation by in situ emulsion polymerization of poly (styrene-acrylonitrile) with ZnO nanoparticles. The ESI-MS technique confirms the structure of polymer nanocomposite by their mass fragments. The XRD study confirms the presence of ZnO phase in polymer matrix. PSAN/ZnO nanocomposite leads to give effective UV shielding (upto 375 nm) and visible luminescence with ZnO content in polymer matrix. The FESEM and TEM studies confirm the symmetrical, controlled growth of PNs. The incorporation of ZnO nanofillers into PSAN matrix lead to restructuring the PNs surfaces into superhydrophilic surfaces in water contact angle (WCA) from 70° to 10°. We believe our synthesized PSAN/ZnO nanocomposite could be potential as UV shielding, luminescent and super hydrophilic nature based materials in related commercial applications.

Polarization-dependent DANES study on vertically-aligned ZnO nanorods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Chengjun; Park, Chang-In; Jin, Zhenlan

2016-05-01

The local structural and local density of states of vertically-aligned ZnO nanorods were examined by using a polarization-dependent diffraction anomalous near edge structure (DANES) measurements from c-oriented ZnO nanorods at the Zn K edge with the incident x-ray electric field parallel and perpendicular to the x-ray momentum transfer direction. Orientation-dependent local structures determined by DANES were comparable with polarization-dependent EXAFS results. Unlike other techniques, polarization-dependent DANES can uniquely describe the orientation-dependent local structural properties and the local density of states of a selected element in selected-phased crystals of compounds or mixed-phased structures.

The SL-assisted synthesis of hierarchical ZnO nanostructures and their enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Miao, Ting-Ting; Guo, Yuan-Ru; Pan, Qing-Jiang

2013-06-01

Hierarchical ZnO nanoparticle-bar, nanomesh-lamina, and quasi-nanosphere structures have been successfully synthesized by the precipitation method with assistance of sodium lignosulphonate (SL). It is shown that the obtained ZnO nanomaterials are well crystallized and possess hexagonal wurtzite structure after calcination. Morphologies of ZnO with particle sizes ranging from 50 to 200 nm can be fabricated by tuning the SL amount in our synthetic route. Plenty of pores have been observed both in nanoparticle-bar and nanomesh-lamina ZnO. This may provide scaffold microenvironments to enhance their photocatalytic activity. It is evident that the synthesized ZnO exhibits good photocatalytic activity of degrading methylene blue, even under a very low-power UV illumination, which allows for the treatment of wastewater containing organic pollutants in an effective way. Among our synthesized nanomaterials, the nanomesh-lamina ZnO has the highest photodegradation efficiency, achieving nearly 100 % degradation only within 1.5 h (UV irradiation power of 12 W). As these ZnO nanomaterials are simply synthesized using SL which is a pulp industry by-product and their intrinsic hierarchical nanostructures show outstanding photocatalytic behavior, we expect the present controllable, environment-friendly, and cost-effective approach to be applied in the synthesis of small-sized ZnO materials.

Electronic properties of two-dimensional zinc oxide in hexagonal, (4,4)-tetragonal, and (4,8)-tetragonal structures by using Hybrid Functional calculation

NASA Astrophysics Data System (ADS)

Supatutkul, C.; Pramchu, S.; Jaroenjittichai, A. P.; Laosiritaworn, Y.

2017-09-01

This work reports the structures and electronic properties of two-dimensional (2D) ZnO in hexagonal, (4,8)-tetragonal, and (4,4)-tetragonal monolayer using GGA and HSE-hybrid functional. The calculated results show that the band gaps of 2D ZnO sheets are wider than those of the bulk ZnO. The hexagonal and (4,8)-tetragonal phases yield direct band gaps, which are 4.20 eV, and 4.59 eV respectively, while the (4,4)-tetragonal structure has an indirect band gap of 3.02 eV. The shrunken Zn-O bond lengths in the hexagonal and (4,8)-tetragonal indicate that they become more ionic in comparison with the bulk ZnO. In addition, the hexagonal ZnO sheet is the most energetically favourable. The total energy differences of (4,8)-tetragonal and (4,4)-tetragonal sheets from that of hexagonal monolayer (per formula unit) are 197 meV and 318 meV respectively.

Hierarchical structures of ZnO spherical particles synthesized solvothermally

NASA Astrophysics Data System (ADS)

Saito, Noriko; Haneda, Hajime

2011-12-01

We review the solvothermal synthesis, using a mixture of ethylene glycol (EG) and water as the solvent, of zinc oxide (ZnO) particles having spherical and flower-like shapes and hierarchical nanostructures. The preparation conditions of the ZnO particles and the microscopic characterization of the morphology are summarized. We found the following three effects of the ratio of EG to water on the formation of hierarchical structures: (i) EG restricts the growth of ZnO microcrystals, (ii) EG promotes the self-assembly of small crystallites into spheroidal particles and (iii) the high water content of EG results in hollow spheres.

Eradication of Multi-drug Resistant Bacteria by Ni Doped ZnO Nanorods: Structural, Raman and optical characteristics

NASA Astrophysics Data System (ADS)

Jan, Tariq; Iqbal, Javed; Ismail, Muhammad; Mansoor, Qaisar; Mahmood, Arshad; Ahmad, Amaar

2014-07-01

In this paper, ZnO nanorods doped with varying amounts of Ni have been prepared by chemical co-precipitation technique. Structural investigations provide the evidence that Ni is successfully doped into ZnO host matrix without having any secondary phases. Scanning electron microscopy (SEM) images reveal the formation of rodlike structure of undoped ZnO with average length and diameter of 1 μm and 80 nm, respectively. Raman spectroscopy results show that the E1LO phonons mode band shifts to the higher values with Ni doping, which is attributed to large amount of crystal defects. Ni doping is also found to greatly influence the optical properties of ZnO nanorods. The influence of Ni doping on antibacterial characteristics of ZnO nanorods have been studied by measuring the growth curves of Escherichia coli (E. coli), Methicillin-resistant Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) bacteria in the presence of prepared nanorods. ZnO nanorods antibacterial potency is found to increase remarkably with Ni doping against S. aureus and P. aeruginosa microbials, which might possibly be due to the increase in reactive oxygen species (ROS) generation. Interestingly, it is observed that Ni doped ZnO nanorods completely eradicates these multi-drug resistant bacteria.

Multilayer ZnO/Pd/ZnO Structure as Sensing Membrane for Extended-Gate Field-Effect Transistor (EGFET) with High pH Sensitivity

NASA Astrophysics Data System (ADS)

Rasheed, Hiba S.; Ahmed, Naser M.; Matjafri, M. Z.; Al-Hardan, Naif H.; Almessiere, Munirah Abdullah; Sabah, Fayroz A.; Al-Hazeem, Nabeel Z.

2017-10-01

Metal oxide nanostructures have attracted considerable attention as pH-sensitive membranes because of their unique advantages. Specifically, the special properties of ZnO thin film, including high surface-to-volume ratio, nontoxicity, thermal stability, chemical stability, electrochemical activity, and high mechanical strength, have attracted massive interest. ZnO exhibits wide bandgap of 3.37 eV, good biocompatibility, high reactivity, robustness, and environmental stability. These unique properties explain why ZnO has the most applications among all nanostructured metal oxides based on its structure and properties. Moreover, ZnO has excellent electrical characteristics, enabling its use in accurate sensors with rapid response. ZnO nanostructures can be used in novel pH and biomedical sensing applications. However, ZnO thin film exhibits large sheet resistance and low conductivity. Increasing the conductivity or reducing the resistivity of ZnO sensing membranes is important to achieve low impedance. We propose herein a new design using a multilayer ZnO/Pd/ZnO structure as a pH-sensing membrane. Multiple layers were deposited by radio frequency (RF) sputtering for ZnO and direct current (DC) sputtering for Pd to achieve low sheet resistance. These multilayers with low sheet resistance of 15.8 Ω/sq were then successfully used to control the conductivity in extended-gate field-effect transistors (EGFETs). The resulting multilayered EGFET pH-sensor demonstrated improved sensing performance. The measured sensitivity of the pH sensor was 40 μA/pH and 52 mV/pH within the pH range from 2 to 12, rendering this structure suitable for use in various applications, including pH sensors and biosensors.

Microstructure and dielectric properties of cellulose acetate-ZnO/ITO composite films based on water hyacinth

NASA Astrophysics Data System (ADS)

Diantoro, M.; Mustikasari, A. A.; Wijayanti, N.; Yogihati, C.; Taufiq, A.

2017-05-01

The electrical properties of Cellulose Acetate (CA), especially extracted from water hyacinth, is rarely informed. CA is generally more stable compared to its cellulose. It has a good potential for electronic application with specific modifications such as inducing metal oxide. A combination of intrinsic properties of Zinc Oxide (ZnO) and CA is expected as a great potential for electrical and optical applications. CA-ZnO/ITO composite film was investigated in relation with its structure, dielectric constant, and the effect of light intensity on their dielectric constant. CA-ZnO composite films were prepared with different mass of ZnO i.e. 0; 0,02; 0,04; 0,06 and 0,08 grams. CA-ZnO solution was synthesized via the mixing method with PEG:DMF solvents by using a magnetic hotplate stirrer with the rotation rate of 1500 rpm at 80°C. The CA-ZnO solution was then deposited onto ITO/glass substrate by using spin coating technique. The CA-ZnO/ITO films were annealed at 160°C to remove the remaining solvents. The effects of ZnO composition on the structure (crystallinity and morphology) and dielectric constant properties were investigated by using X-Ray Diffractometer, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, and LCR meter. It was shown that cellulose can be isolated from water hyacinth with the yield of 67,72 % by Chesson method and can further be transformed into CA. The X-ray diffraction pattern showed that there are 2 phases formed i.e. CA and ZnO. Furthermore, greater ZnO amount increased the crystallinity of composite films. The CA-ZnO films exhibit porous films with ZnO distributed on the CA surface films. Therefore, ZnO increases the dielectric constant of CA-ZnO composite films.

Absolute surface energy calculations of Wurtzite (0001)/(000-1): a study of ZnO and GaN

NASA Astrophysics Data System (ADS)

Zhang, Jingzhao; Zhang, Yiou; Tse, Kinfai; Deng, Bei; Xu, Hu; Zhu, Junyi

The accurate absolute surface energies of (0001)/(000-1) surfaces of wurtzite structures are crucial in determining the thin film growth mode of important energy materials. However, the surface energies still remain to be solved due to the intrinsic difficulty of calculating dangling bond energy of asymmetrically bonded surface atoms. We used a pseudo-hydrogen passivation method to estimate the dangling bond energy and calculate the polar surfaces of ZnO and GaN. The calculations were based on the pseudo chemical potentials obtained from a set of tetrahedral clusters or simple pseudo-molecules, using density functional theory approaches, for both GGA and HSE. And the surface energies of (0001)/(000-1) surfaces of wurtzite ZnO and GaN we obtained showed relatively high self-consistencies. A wedge structure calculation with a new bottom surface passivation scheme of group I and group VII elements was also proposed and performed to show converged absolute surface energy of wurtzite ZnO polar surfaces. Part of the computing resources was provided by the High Performance Cluster Computing Centre, Hong Kong Baptist University. This work was supported by the start-up funding and direct Grant with the Project code of 4053134 at CUHK.

Structural, morphological, optical and electrical properties of Schottky diodes based on CBD deposited ZnO:Cu nanorods

NASA Astrophysics Data System (ADS)

Mwankemwa, Benard S.; Legodi, Matshisa J.; Mlambo, Mbuso; Nel, Jackie M.; Diale, Mmantsae

2017-07-01

Undoped and copper doped zinc oxide (ZnO) nanorods have been synthesized by a simple chemical bath deposition (CBD) method at a temperature of 90 °C. Structural, morphological, optical and electrical properties of the synthesized ZnO nanorods were found to be dependent on the Cu doping percentage. X-ray diffraction (XRD) patterns revealed strong diffraction peaks of hexagonal wurtzite of ZnO, and no impurity phases from metallic zinc or copper. Scanning electron microscopy (SEM) images showed changes in diameter and shape of nanorods, where by those doped with 2 at.% and 3 at.% aggregated and became compact. Selected area electron diffraction (SAED) patterns indicates high quality, single crystalline wurtzite structure ZnO and intensities of bright spots varied with copper doping concentration. UV-visible absorption peaks of ZnO red shifted with increasing copper doping concentration. Raman studies demonstrated among others, strong and sharp E2 (low) and E2 (high) optical phonon peaks confirming crystal structure of ZnO. Current-voltage measurements based on the gold/ZnO nanorods/ITO showed good rectifying behavior of the Schottky diode. The predicted Schottky barrier height of 0.60 eV was obtained which is not far from the theoretical Schottky-Mott value of 0.80 eV.

First-principles approach to calculating energy level alignment at aqueous semiconductor interfaces.

PubMed

Kharche, Neerav; Muckerman, James T; Hybertsen, Mark S

2014-10-24

A first-principles approach is demonstrated for calculating the relationship between an aqueous semiconductor interface structure and energy level alignment. The physical interface structure is sampled using density functional theory based molecular dynamics, yielding the interface electrostatic dipole. The  GW approach from many-body perturbation theory is used to place the electronic band edge energies of the semiconductor relative to the occupied 1b1 energy level in water. The application to the specific cases of nonpolar (101¯0) facets of GaN and ZnO reveals a significant role for the structural motifs at the interface, including the degree of interface water dissociation and the dynamical fluctuations in the interface Zn-O and O-H bond orientations. These effects contribute up to 0.5 eV.

Structural enhancement of ZnO on SiO2 for photonic applications

NASA Astrophysics Data System (ADS)

Ruth, Marcel; Meier, Cedrik

2013-07-01

Multi-layer thin films are often the basis of photonic devices. Zinc oxide (ZnO) with its excellent optoelectronic properties can serve as a high quality emitter in structures like microdisks or photonic crystals. Here, we present a detailed study on the enhancement of the structural properties of low-temperature MBE grown ZnO on silica (SiO2). By thermal annealing a grain coalescence of the initially polycrystalline layer leads to an enhancement of the electronic structure, indicated by a blue shift of the photoluminescence (PL) signal maximum. Oxygen atmosphere during the annealing process prevents the creation of intrinsic defects by out-diffusion. Pre-annealing deposited SiO2 capping layers instead obstruct the recrystallization and lead to less intense emission. While thin capping layers partially detach from the ZnO film at high temperatures and cause higher surface roughness and the weakest emission, thicker layers remain smoother and exhibit a significantly stronger photoluminescence.

Comparative optical studies of ZnO and ZnO-TiO2 - Metal oxide nanoparticle

NASA Astrophysics Data System (ADS)

Vijayalakshmi, R. Vanathi; Asvini, V.; Kumar, P. Praveen; Ravichandran, K.

2018-05-01

A comparative study was carried out to show the enhancement in optical activity of bimetal oxide nanoparticle (ZnO - TiO2) than metal oxide nanoparticle (ZnO), which can preferably be used for optical applications. The samples were prepared by wet chemical method and crystalline structure of the samples as hexagonal - primitive for ZnO and tetragonal - bcc for ZnO-TiO2 was confirmed by XRD measurements. The average grain size of ZnO - 19.89nm and ZnO-TiO2- 49.89 nm was calculated by Debye- Scherrer formula. The structure and particle size of the sample was analyzed by FESEM images. The direct band gap energy of ZnO (3.9eV) and ZnO - TiO2(4.68eV) was calculated by Kubelka-Munk Function, from which it is clear that the band gap energy increases in bimetal oxide to a desired level than in its pure form. The photoluminescence study shows that the emitted wavelength of the samples lies exactly around the visible region.

Comparative study of textured and epitaxial ZnO films

NASA Astrophysics Data System (ADS)

Ryu, Y. R.; Zhu, S.; Wrobel, J. M.; Jeong, H. M.; Miceli, P. F.; White, H. W.

2000-06-01

ZnO films were synthesized by pulsed laser deposition (PLD) on GaAs and α-Al 2O 3 substrates. The properties of ZnO films on GaAs and α-Al 2O 3 have been investigated to determine the differences between epitaxial and textured ZnO films. ZnO films on GaAs show very strong emission features associated with exciton transitions as do ZnO films on α-Al 2O 3, while the crystalline structural qualities for ZnO films on α-Al 2O 3 are much better than those for ZnO films on GaAs. The properties of ZnO films are studied by comparing highly oriented, textured ZnO films on GaAs with epitaxial ZnO films on α-Al 2O 3 synthesized along the c-axis.

Low temperature synthesis of hexagonal ZnO nanorods and their hydrogen sensing properties

NASA Astrophysics Data System (ADS)

Qurashi, Ahsanulhaq; Faiz, M.; Tabet, N.; Alam, Mir Waqas

2011-08-01

The growth of hexagonal ZnO nanorods was demonstrated by low temperature chemical synthesis approach. X-ray diffraction (XRD) analysis revealed a wurtzite hexagonal structure of the ZnO nanorods. The optical properties were measured by UV-vis spectrophotometer at room temperature. X-ray photoelectron spectroscopy (XPS) confirmed high purity of the ZnO nanorods. The hydrogen sensor made of the ZnO nanorods showed reversible response. The hydrogen gas tests were carried out in presence of ambient air and the influence of operation temperature on the hydrogen gas sensing property of ZnO nanorods was also investigated.

Controllable synthesis of mesoporous multi-shelled ZnO microspheres as efficient photocatalysts for NO oxidation

NASA Astrophysics Data System (ADS)

Chen, Xiaolang; Zhang, Huiqiang; Zhang, Dieqing; Miao, Yingchun; Li, Guisheng

2018-03-01

The successful application of hierarchically porous structure in environmental treatment has provided new insights for solving environmental problems. Hierarchically structured semiconductor materials were considered as promising photocatalysts for NO oxidation in gas phase. Multi-shelled ZnO microspheres (MMSZ) were controllably shaped with hierarchically porous structures via a facile hydrothermal route using amino acid (N-Acetyl-D-Proline) as template and post-calcination treatment. Symmetric Ostwald ripening was used to explain the morphological evolution of hierarchical nanostructure. MMSZ was proved highly efficient for oxidizing NO (400 ppb) in gas phase under UV light irradiation with a much higher photocatalytic removal rate (77.3%) than that of the as-obtained ZnO crystals with other hierachically porous structures, owing to its higher photocurrent intensity. Such greatly enhanced photocatalytic activity can be assigned to the enhanced crystallinity of ZnO, mesopores and unique multi-shelled structure. Enhanced crystallinity promotes photogenerated charges under light irradiation. Mesoporous porosity can ensure enough light scattering between the shells. Multi-shelled structure endows ZnO with higher specific surface area and high frequency of multiple light reflection, resulting in more exposed active sites, higher light utilization efficiency, and fast separation efficiency of photogenerated charge carriers. The experimental results demonstrated that the photogenerated holes (h+) are the main active species. Hierarchically structured ZnO is not only contributed to directly use solar energy to solving various problems caused by atmospheric pollution, but also has potential applications in energy converse and storage including solar cells, lithium batteries, water-splitting, etc.

Facile one-step synthesis of magnesium-doped ZnO nanoparticles: optical properties and their device applications

NASA Astrophysics Data System (ADS)

Oh, Ji-Young; Lim, Sang-Chul; Ahn, Seong Deok; Lee, Sang Seok; Cho, Kyoung-Ik; Bon Koo, Jae; Choi, Rino; Hasan, Musarrat

2013-07-01

In this study, magnesium-doped (Mg-doped) zinc oxide (ZnO) nanoparticles were successfully synthesized by a sonochemical process under mild conditions. The x-ray diffraction pattern indicated that the Mg-doped ZnO nanoparticles maintain a wurtzite structure without impurities. We observed a blue-shift of the bandgap of the Mg-doped ZnO nanoparticles as the Mg-doping ratio increased. We also fabricated thin-film transistor (TFT) devices with the doped-ZnO nanoparticles. Devices using Mg-doped ZnO nanoparticles as a channel layer showed insensibility to white-light irradiation compared with undoped ZnO TFTs.

Crystallographic tilt and in-plane anisotropies of an a-plane InGaN/GaN layered structure grown by MOCVD on r-plane sapphire using a ZnO buffer

NASA Astrophysics Data System (ADS)

Liu, H. F.; Liu, W.; Guo, S.; Chi, D. Z.

2016-03-01

High-resolution x-ray diffraction (HRXRD) was used to investigate the crystallographic tilts and structural anisotropies in epitaxial nonpolar a-plane InGaN/GaN grown by metal-organic chemical vapor deposition on r-plane sapphire using a ZnO buffer. The substrate had an unintentional miscut of 0.14° towards its [-4 2 2 3] axis. However, HRXRD revealed a tilt of 0.26° (0.20°) between the ZnO (GaN) (11-20) and the Al2O3 (1-102) atomic planes, with the (11-20) axis of ZnO (GaN) tilted towards its c-axis, which has a difference of 163° in azimuth from that of the substrate’s miscut. Excess broadenings in the GaN/ZnO (11-20) rocking curves (RCs) were observed along its c-axis. Specific analyses revealed that partial dislocations and anisotropic in-plane strains, rather than surface-related effects, wafer curvature or stacking faults, are the dominant factors for the structural anisotropy. The orientation of the partial dislocations is most likely affected by the miscut of the substrate, e.g. via tilting of the misfit dislocation gliding planes created during island coalescences. Their Burgers vector components in the growth direction, in turn, gave rise to crystallographic tilts in the same direction as that of the excess RC-broadenings.

Synthesis of stable ZnO nanocolloids with enhanced optical limiting properties via simple solution method

NASA Astrophysics Data System (ADS)

Ramya, M.; Nideep, T. K.; Vijesh, K. R.; Nampoori, V. P. N.; Kailasnath, M.

2018-07-01

In present work, we report the synthesis of stable ZnO nanocolloids through a simple solution method which exhibit enhanced optical limiting threshold. The influences of reaction temperature on the crystal structure as well as linear and nonlinear optical properties of prepared ZnO nanoparticles were carried out. The XRD and Raman analysis reveal that the prepared ZnO nanoparticles retain the hexagonal wurtzite crystal structure. HRTEM analysis confirms the effect of reaction temperature, solvent effect on crystallinity as well as nanostructure of ZnO nanoparticles. It has been found that crystallinity and average diameter increase with reaction temperature where ethylene glycol act as both solvent and growth inhibiter. EDS spectra shows formation of pure ZnO nanoparticles. The direct energy band gap of the nanoparticles increases with decrease in particle size due to quantum confinement effect. The third order nonlinear optical properties of ZnO nanoparticles were investigated by z scan technique using a frequency doubled Nd-YAG nanosecond laser at 532 nm wavelength. The z-scan result reveals that the prepared ZnO nanoparticles exhibit self - defocusing nonlinearity. The two photon absorption coefficient and third - order nonlinear optical susceptibility increases with increasing particle size. The third-order susceptibility of the ZnO nanoparticles is found to be in the order of 10-10 esu, which is at least three order magnitude greater than the bulk ZnO. The optical limiting threshold of the nanoparticles varies in the range of 54 to 17 MW/cm2. The results suggest that ZnO nanoparticles considered as a promising candidates for the future photonic devices.

ZnO Schottky barriers and Ohmic contacts

NASA Astrophysics Data System (ADS)

Brillson, Leonard J.; Lu, Yicheng

2011-06-01

ZnO has emerged as a promising candidate for optoelectronic and microelectronic applications, whose development requires greater understanding and control of their electronic contacts. The rapid pace of ZnO research over the past decade has yielded considerable new information on the nature of ZnO interfaces with metals. Work on ZnO contacts over the past decade has now been carried out on high quality material, nearly free from complicating factors such as impurities, morphological and native point defects. Based on the high quality bulk and thin film crystals now available, ZnO exhibits a range of systematic interface electronic structure that can be understood at the atomic scale. Here we provide a comprehensive review of Schottky barrier and ohmic contacts including work extending over the past half century. For Schottky barriers, these results span the nature of ZnO surface charge transfer, the roles of surface cleaning, crystal quality, chemical interactions, and defect formation. For ohmic contacts, these studies encompass the nature of metal-specific interactions, the role of annealing, multilayered contacts, alloyed contacts, metallization schemes for state-of-the-art contacts, and their application to n-type versus p-type ZnO. Both ZnO Schottky barriers and ohmic contacts show a wide range of phenomena and electronic behavior, which can all be directly tied to chemical and structural changes on an atomic scale.

Observation of the origin of d0 magnetism in ZnO nanostructures using X-ray-based microscopic and spectroscopic techniques

NASA Astrophysics Data System (ADS)

Singh, Shashi B.; Wang, Yu-Fu; Shao, Yu-Cheng; Lai, Hsuan-Yu; Hsieh, Shang-Hsien; Limaye, Mukta V.; Chuang, Chen-Hao; Hsueh, Hung-Chung; Wang, Hsaiotsu; Chiou, Jau-Wern; Tsai, Hung-Ming; Pao, Chih-Wen; Chen, Chia-Hao; Lin, Hong-Ji; Lee, Jyh-Fu; Wu, Chun-Te; Wu, Jih-Jen; Pong, Way-Faung; Ohigashi, Takuji; Kosugi, Nobuhiro; Wang, Jian; Zhou, Jigang; Regier, Tom; Sham, Tsun-Kong

2014-07-01

Efforts have been made to elucidate the origin of d0 magnetism in ZnO nanocactuses (NCs) and nanowires (NWs) using X-ray-based microscopic and spectroscopic techniques. The photoluminescence and O K-edge and Zn L3,2-edge X-ray-excited optical luminescence spectra showed that ZnO NCs contain more defects than NWs do and that in ZnO NCs, more defects are present at the O sites than at the Zn sites. Specifically, the results of O K-edge scanning transmission X-ray microscopy (STXM) and the corresponding X-ray-absorption near-edge structure (XANES) spectroscopy demonstrated that the impurity (non-stoichiometric) region in ZnO NCs contains a greater defect population than the thick region. The intensity of O K-edge STXM-XANES in the impurity region is more predominant in ZnO NCs than in NWs. The increase in the unoccupied (occupied) density of states at/above (at/below) the conduction-band minimum (valence-band maximum) or the Fermi level is related to the population of defects at the O sites, as revealed by comparing the ZnO NCs to the NWs. The results of O K-edge and Zn L3,2-edge X-ray magnetic circular dichroism demonstrated that the origin of magnetization is attributable to the O 2p orbitals rather than the Zn d orbitals. Further, the local density approximation (LDA) + U verified that vacancies in the form of dangling or unpaired 2p states (due to Zn vacancies) induced a significant local spin moment in the nearest-neighboring O atoms to the defect center, which was determined from the uneven local spin density by analyzing the partial density of states of O 2p in ZnO.Efforts have been made to elucidate the origin of d0 magnetism in ZnO nanocactuses (NCs) and nanowires (NWs) using X-ray-based microscopic and spectroscopic techniques. The photoluminescence and O K-edge and Zn L3,2-edge X-ray-excited optical luminescence spectra showed that ZnO NCs contain more defects than NWs do and that in ZnO NCs, more defects are present at the O sites than at the Zn sites. Specifically, the results of O K-edge scanning transmission X-ray microscopy (STXM) and the corresponding X-ray-absorption near-edge structure (XANES) spectroscopy demonstrated that the impurity (non-stoichiometric) region in ZnO NCs contains a greater defect population than the thick region. The intensity of O K-edge STXM-XANES in the impurity region is more predominant in ZnO NCs than in NWs. The increase in the unoccupied (occupied) density of states at/above (at/below) the conduction-band minimum (valence-band maximum) or the Fermi level is related to the population of defects at the O sites, as revealed by comparing the ZnO NCs to the NWs. The results of O K-edge and Zn L3,2-edge X-ray magnetic circular dichroism demonstrated that the origin of magnetization is attributable to the O 2p orbitals rather than the Zn d orbitals. Further, the local density approximation (LDA) + U verified that vacancies in the form of dangling or unpaired 2p states (due to Zn vacancies) induced a significant local spin moment in the nearest-neighboring O atoms to the defect center, which was determined from the uneven local spin density by analyzing the partial density of states of O 2p in ZnO. Electronic supplementary information (ESI) available: Scanning photoelectron microscopy (SPEM) results of ZnO NCs and NWs. Computational details and calculated total and partial density of states (PDOS) of bulk wurtzite ZnO with oxygen anion vacancies (VO). See DOI: 10.1039/c4nr01961j

Ferroelectric enhancement in heterostructured ZnO /BiFeO3-PbTiO3 film

NASA Astrophysics Data System (ADS)

Yu, Shengwen; Chen, Rui; Zhang, Guanjun; Cheng, Jinrong; Meng, Zhongyan

2006-11-01

The authors have prepared heterostructured ZnO /BiFeO3-PbTiO3 (BFO-PT) composite film and BFO-PT film on Pt /Ti/SiO2/Si substrates by pulsed-laser deposition. The structure and morphologies of the films were characterized by x-ray diffraction (XRD) and scanning electron microscope. XRD results show that both films are perovskite structured last with different orientations. The leakage current density in the ZnO /BFO-PT film was found to be nearly two orders of magnitude lower. This could be due to the introduced ZnO layer behaving as a Schottky barrier between the BFO-PT film and top electrodes. The dramatic ferroelectric enhancement in ZnO /BFO-PT film is mostly ascribed to the improved insulation.

Thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap semiconductors SiC, GaN, and ZnO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Zheng; Lü, Tie-Yu; Wang, Hui-Qiong

We have investigated the thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap(n-type) semiconductors SiC, GaN, and ZnO based on first-principles calculations and Boltzmann transport theory. Our results show that the thermoelectric performance increases from 3C to 6H, 4H, and 2H structures with an increase of hexagonality for SiC. However, for GaN and ZnO, their power factors show a very weak dependence on the polytype. Detailed analysis of the thermoelectric properties with respect to temperature and carrier concentration of 4H-SiC, 2H-GaN, and 2H-ZnO shows that the figure of merit of these three compounds increases with temperature,more » indicating the promising potential applications of these thermoelectric materials at high temperature. The significant difference of the polytype-dependent thermoelectric properties among SiC, GaN, and ZnO might be related to the competition between covalency and ionicity in these semiconductors. Our calculations may provide a new way to enhance the thermoelectric properties of wide-band-gap semiconductors through atomic structure design, especially hexagonality design for SiC.« less

Structural studies and band gap tuning of Cr doped ZnO nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Srinet, Gunjan, E-mail: gunjansrinet@gmail.com; Kumar, Ravindra, E-mail: gunjansrinet@gmail.com; Sajal, Vivek, E-mail: gunjansrinet@gmail.com

2014-04-24

Structural and optical properties of Cr doped ZnO nanoparticles prepared by the thermal decomposition method are presented. X-ray diffraction studies confirmed the substitution of Cr on Zn sites without changing the wurtzite structure of ZnO. Modified form of W-H equations was used to calculate various physical parameters and their variation with Cr doping is discussed. Significant red shift was observed in band gap, i.e., a band gap tuning is achieved by Cr doping which could eventually be useful for optoelectronic applications.

Effect of cobalt doping on structural and optical properties of ZnO nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, J.; Chanda, A., E-mail: anupamamatsc@gmail.com; Gupta, S.

Cobalt doped ZnO nanoparticles of uniform sizes were prepared by a chemical method using ZnCl{sub 2} and NaOH as the source materials. The formation of Co-doped ZnO nanoparticles was confirmed by transmission electron microscopy (TEM), high resolution TEM (HR-TEM) and selected area electron diffraction (SAED) studies. The optical properties of obtained products were examined using room temperature UV-visible and FTIR spectroscopy. SAED of cobalt doped ZnO nanoparticles shows homogeneous distribution of nanoparticles with hexagonal structure. The HRTEM image of the Co-doped ZnO nanoparticles reveals a clear lattice spacing of 0.52 nm corresponding to the interplanar spacing of wurtzite ZnO (002) plane.more » The absorption band at 857 cm{sup −1} in FTIR spectra confirmed the tetrahedral coordination of Zn and a shift of absorption peak to shorter wavelength region and decrease in absorbance with Co doping.is observed in UV-Visible spectra.« less

Electronic structure of gadolinium complexes in ZnO in the GW approximation

NASA Astrophysics Data System (ADS)

Rosa, A. L.; Frauenheim, Th.

2018-04-01

The role of intrinsic defects has been investigated to determine binding energies and the electronic structure of Gd complexes in ZnO. We use density-functional theory and the GW method to show that the presence of vacancies and interstitials affect the electronic structure of Gd doped ZnO. However, the strong localization of the Gd-f and d states suggest that carrier mediated ferromagnetism in this material may be difficult to achieve.

Tunable, flexible antireflection layer of ZnO nanowires embedded in PDMS.

PubMed

Kim, Min Kyu; Yi, Dong Kee; Paik, Ungyu

2010-05-18

In this article, we report the fabrication of ordered hybrid structures composed of ZnO nanowires and a polymeric matrix with a polymer precursor infiltrating the nanowire arrays. The antireflective properties of the resulting ZnO nanowire-embedded polydimethylsiloxane composite (ZPC) were investigated at various ZnO nanowire lengths and ZPC bending angles. Interestingly, we found that whereas the antireflective properties showed a strong dependence on the length of the embedded ZnO nanowires in PDMS, the bending of ZPC has little effect on the antireflective properties.

Novel Gas Sensor Based on ZnO Nanorod Circular Arrays for C2H5OH Gas Detection.

PubMed

Jianjiao, Zhang; Hongyan, Yue; Erjun, Guo; Shaolin, Zhang; Liping, Wang; Chunyu, Zhang; Xin, Gao; Jing, Chang; Hong, Zhang

2015-03-01

Novel side-heating gas sensor based on ZnO nanorod circular arrays was firstly fabricated by hydrothermal treatment assisted with a kind of simple dip-coating technique. The structure and morphologies of ZnO nanorods were characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), respectively. XRD result indicates that the obtained ZnO nanorods have good crystalline with the hexagonal wurtzite structure. SEM result indicates that ZnO nanorod arrays are vertically growth on the surface of ceramic tube of side-heating sensor with controlled diameter and length, narrow size distribution and high orientation. The gas sensing properties of ZnO nanorod circular arrays are also evaluated. Comparative to the sensor based on scattered ZnO nanorods responding to 25 ppm H2, CO, C6H5CH3 and C2H5OH gas, respectively, the sensing values of high orientation gas sensor are generally increased by 5%. This novel sensor has good application promising for the fabrication of cost effective and high performance gas sensors.

A comparative analysis of green synthesis approach starch capped metal oxides (ZnO & CdO) nanoparticles and its bacterial activity

NASA Astrophysics Data System (ADS)

Vidhya, K.; Devarajan, V. P.; Viswanathan, C.; Nataraj, D.; Bhoopathi, G.

2013-06-01

In this study, we have investigated the bacterial activity of starch capped ZnO & CdO NPs. The NPs were prepared through green technique under room temperature and then obtained samples were characterized by using XRD and PL techniques. XRD pattern confirms the crystal nature it shows hexagonal structure for ZnO NPs and monoclinic structure for CdO NPs and their average particle size is ±20 nm. Further, the optical properties of NPs were investigated using PL technique in which the starch capped ZnO NPs shows maximum emission at 440 nm whereas starch capped CdO NPs shows maximum emission at 545 nm. Finally, toxic test was performed with E.coli bacteria and their results were investigated. Hence, starch capped ZnO NPs induced less killing effect when compared with starch capped CdO NPs. Therefore, we conclude that the starch capped ZnO NPs may be less toxic to microorganisms when compared with starch capped CdO NPs. In addition, starch capped ZnO NPs is also suitable for anti-microbial activity.

Characterization of thermal destruction behavior of hybrid composites based on polyoxymethylene, ethylene-octene copolymer impact modifier and ZnO nanofiller

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meri, Remo Merijs; Zicans, Janis; Abele, Agnese

Hybrid polymer nanocomposites, composed of polyoxymethylene (POM), ethylene octene copolymer (EOC) and plasma synthesized tetrapod shaped zinc oxide (ZnO), were prepared by using melt compounding. The content of EOC in the POM based composites was varied between 10 and 50 mass %, while the content of ZnO was constant (2 mass %). Thermal behaviour of POM based systems was studied by using thermogravimetric analysis coupled with Fourier transform infrared spectroscopy. The influence of the elastomer content and/or ZnO addition on the thermal stability of POM based systems was evaluated. The influence of the α-octene content in the elastomer on themore » thermal decomposition behaviour of POM and its nanocomposites with ZnO was also evaluated. Results of thermogravimetric analysis showed that, by rising either the elastomer or ZnO content, thermal stability of the investigated POM composites was increased. The modifying effect of EOC17 in respect of thermal resistance was somewhat larger than that of EOC38 because of the smaller amount of tertiary carbon atoms in the macromolecular structure of the former elastomer. Improved thermal resistance of ZnO containing POM based composites was because of impermeable structure the inorganic nanofiller allowing decrease gas exchange rate and facilitating non-combustible gases, such as CO{sub 2}, stay in the zone of burning. Addition of ZnO have a potential to influence structure of the polymer blend matrix itself by improving its barrier characteristics.« less

Multi-angle ZnO microstructures grown on Ag nanorods array for plasmon-enhanced near-UV-blue light emitter

NASA Astrophysics Data System (ADS)

Pal, Anil Kumar; Bharathi Mohan, D.

2017-10-01

Metal enhanced ultraviolet light emission has been explored in ZnO/Ag hybrid structures prepared by hydrothermal growth of multi-angled ZnO nanorods on slanted Ag nanorods array fabricated by the thermal evaporation technique. Slanted Ag nanorods are realized to be the stacking of non-spherical Ag nanoparticles, resulting in asymmetric surface plasmon resonance spectra. The surface roughness of Ag nanorod array films significantly influences the growth mechanism of ZnO nanorods, leading to the formation of multi-angled ZnO microflowers. ZnO/Ag hybrid structures facilitate the interfacial charge transfer from Ag to ZnO with the realization of negative shift in binding energy of Ag 3d orbitals by ˜0.8 eV. These high quality ZnO nanorods in ZnO/Ag hybrid nanostructures exhibit strong ultraviolet emission in the 383-396 nm region without broad deep level emission, which can be explained by a suitable band diagram. The metal enhanced photoluminescence is witnessed mainly due to interfacial charge transfer with its dependence on surface roughness of bottom layer Ag nanorods, number density of ZnO nanorods and diversity in the interfacial area between Ag and ZnO nanorods. The existence of strong ultraviolet light with minor blue light emission and appearance of CIE shade in strong violet-blue region by ZnO/Ag hybrid structures depict exciting possibilities towards near UV-blue light emitting devices.

Multi-angle ZnO microstructures grown on Ag nanorods array for plasmon-enhanced near-UV-blue light emitter.

PubMed

Pal, Anil Kumar; Mohan, D Bharathi

2017-10-13

Metal enhanced ultraviolet light emission has been explored in ZnO/Ag hybrid structures prepared by hydrothermal growth of multi-angled ZnO nanorods on slanted Ag nanorods array fabricated by the thermal evaporation technique. Slanted Ag nanorods are realized to be the stacking of non-spherical Ag nanoparticles, resulting in asymmetric surface plasmon resonance spectra. The surface roughness of Ag nanorod array films significantly influences the growth mechanism of ZnO nanorods, leading to the formation of multi-angled ZnO microflowers. ZnO/Ag hybrid structures facilitate the interfacial charge transfer from Ag to ZnO with the realization of negative shift in binding energy of Ag 3d orbitals by ∼0.8 eV. These high quality ZnO nanorods in ZnO/Ag hybrid nanostructures exhibit strong ultraviolet emission in the 383-396 nm region without broad deep level emission, which can be explained by a suitable band diagram. The metal enhanced photoluminescence is witnessed mainly due to interfacial charge transfer with its dependence on surface roughness of bottom layer Ag nanorods, number density of ZnO nanorods and diversity in the interfacial area between Ag and ZnO nanorods. The existence of strong ultraviolet light with minor blue light emission and appearance of CIE shade in strong violet-blue region by ZnO/Ag hybrid structures depict exciting possibilities towards near UV-blue light emitting devices.

Effect of Eu3+ doping on the structural, morphological and luminescence properties ZnO nanostructures

NASA Astrophysics Data System (ADS)

Vinoditha, U.; Balakrishna, K. M.; Sarojini, B. K.; Narayana, B.; Kumara, K.

2018-05-01

Pure and Eu3+ ions (1, 3, 5 atomic wt%) doped ZnO nanostructures are synthesized by a surfactant assisted hydrothermal method. The effect of doping concentrations on structural, morphological and optical properties of ZnO nanostructures is studied. The XRD analysis shows good crystallinity and the phase purity of the ZnO nanostructures. A shift in the standard Zn-O stretching mode after Eu3+ doping is observed in the FTIR spectra. The images of FESEM demonstrate the morphological variations from hexagonal nanorods to nanoflowers on varying the dopant concentrations. Substitution of Eu3+ ions into Zn2+ sites is confirmed by EDX analysis. The dominance of particle shape over the UV-Visible absorption properties of the prepared samples is noticed. The photoluminescence (PL) emission of undoped and doped ZnO nanostructures show dominant near band edge emission (NBE) in the UV region and minor defect induced deep level emissions in the visible region.

Effects of Na Doping on Structural, Optical, and Electronic Properties of ZnO Thin Films Fabricated by Sol-Gel Technique

NASA Astrophysics Data System (ADS)

Fan, Heliang; Yao, Zhen; Xu, Cheng; Wang, Xinqiang; Yu, Zhichao

2018-04-01

Undoped and Na-doped ZnO thin films were fabricated by sol-gel technique on quartz glass substrates and annealed at 500°C for 1 h. The structural properties of the films were characterized using x-ray diffraction analysis, which revealed hexagonal wurtzite structure with no peaks corresponding to Na2O or other Na phases being found. Surface morphology observations by scanning electron microscopy revealed that the crystallite size and topographical properties of the ZnO films were influenced by the Na doping concentration. X-ray photoelectron spectra revealed presence of Na+ in ZnO regime. The transmittance spectra indicated that the average transmittance of Na-doped ZnO film was above 80% in the visible range, superior to that of the undoped film. There was a blue-shift in the ultraviolet absorption edge with increase of the Na content. Photoluminescence spectra illustrated two peaks, corresponding to ultraviolet near-band-edge and visible emission.

Studies on visible light photocatalytic and antibacterial activities of nanostructured cobalt doped ZnO thin films prepared by sol-gel spin coating method.

PubMed

Poongodi, G; Anandan, P; Kumar, R Mohan; Jayavel, R

2015-09-05

Nanostructured cobalt doped ZnO thin films were deposited on glass substrate by sol-gel spin coating technique and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and UV-Vis spectroscopy. The XRD results showed that the thin films were well crystalline with hexagonal wurtzite structure. The results of EDAX and XPS revealed that Co was doped into ZnO structure. FESEM images revealed that the films possess granular morphology without any crack and confirm that Co doping decreases the grain size. UV-Vis transmission spectra show that the substitution of Co in ZnO leads to band gap narrowing. The Co doped ZnO films were found to exhibit improved photocatalytic activity for the degradation of methylene blue dye under visible light in comparison with the undoped ZnO film. The decrease in grain size and extending light absorption towards the visible region by Co doping in ZnO film contribute equally to the improved photocatalytic activity. The bactericidal efficiency of Co doped ZnO films were investigated against a Gram negative (Escherichia coli) and a Gram positive (Staphylococcus aureus) bacteria. The optical density (OD) measurement showed better bactericidal activity at higher level of Co doping in ZnO. Copyright © 2015 Elsevier B.V. All rights reserved.

A metal-semiconductor-metal detector based on ZnO nanowires grown on a graphene layer.

PubMed

Xu, Qiang; Cheng, Qijin; Zhong, Jinxiang; Cai, Weiwei; Zhang, Zifeng; Wu, Zhengyun; Zhang, Fengyan

2014-02-07

High quality ZnO nanowires (NWs) were grown on a graphene layer by a hydrothermal method. The ZnO NWs revealed higher uniform surface morphology and better structural properties than ZnO NWs grown on SiO2/Si substrate. A low dark current metal-semiconductor-metal photodetector based on ZnO NWs with Au Schottky contact has also been fabricated. The photodetector displays a low dark current of 1.53 nA at 1 V bias and a large UV-to-visible rejection ratio (up to four orders), which are significantly improved compared to conventional ZnO NW photodetectors. The improvement in UV detection performance is attributed to the existence of a surface plasmon at the interface of the ZnO and the graphene.

Toward hydrogen detection at room temperature with printed ZnO nanoceramics films activated with halogen lighting

NASA Astrophysics Data System (ADS)

Nguyen, Van Son; Jubera, Véronique; Garcia, Alain; Debéda, Hélène

2015-12-01

Though semiconducting properties of ZnO have been extensively investigated under hazardous gases, research is still necessary for low-cost sensors working at room temperature. Study of printed ZnO nanopowders-based sensors has been undertaken for hydrogen detection. A ZnO paste made with commercial nanopowders is deposited onto interdigitated Pt electrodes and sintered at 400 °C. The ZnO layer structure and morphology are first examined by XRD, SEM, AFM and emission/excitation spectra prior to the study of the effect of UV-light on the electrical conduction of the semiconductor oxide. The response to hydrogen exposure is subsequently examined, showing that low UV-light provided by halogen lighting enhances the gas response and allows detection at room temperature with gas responses similar to those obtained in dark conditions at 150 °C. A gas response of 44% (relative change in current) under 300 ppm is obtained at room temperature. Moreover, it is demonstrated that very low UV-light power (15 μW/mm2) provided by the halogen lamp is sufficient to give sensitivities as high as those for much higher powers obtained with a UV LED (7.7 mW/mm2). These results are comparable to those obtained by others for 1D or 2D ZnO nanostructures working at room temperature or at temperatures up to 250 °C.

Branched ZnO wire structures for water collection inspired by cacti.

PubMed

Heng, Xin; Xiang, Mingming; Lu, Zhihui; Luo, Cheng

2014-06-11

In this work, motivated by an approach used in a cactus to collect fog, we have developed an artificial water-collection structure. This structure includes a large ZnO wire and an array of small ZnO wires that are branched on the large wire. All these wires have conical shapes, whose diameters gradually increase from the tip to the root of a wire. Accordingly, a water drop that is condensed on the tip of each wire is driven to the root by a capillary force induced by this diameter gradient. The lengths of stem and branched wires in the synthesized structures are in the orders of 1 mm and 100 μm, respectively. These dimensions are, respectively, comparable to and larger than their counterparts in the case of a cactus. Two groups of tests were conducted at relative humidity of 100% to compare the amounts of water collected by artificial and cactus structures within specific time durations of 2 and 35 s, respectively. The amount of water collected by either type of structures was in the order of 0.01 μL. However, on average, what has been collected by the artificial structures was 1.4-5.0 times more than that harvested by the cactus ones. We further examined the mechanism that a cactus used to absorb a collected water drop into its stem. On the basis of the gained understanding, we developed a setup to successfully collect about 6 μL of water within 30 min.

Hydrothermal process assists undoped and Cr-doped semiconducting ZnO nanorods: Frontier of dielectric property

NASA Astrophysics Data System (ADS)

Debnath, Tanumoy; Saha, Papiya; Patra, Nesla; Das, Sukhen; Sutradhar, Soumyaditya

2018-05-01

The influence of the hydrothermal synthesis route on the grain morphology and thereby the modulation of dielectric response of undoped and Cr3+ ion doped semiconducting ZnO nanoparticles is investigated in this report. The X-ray diffraction study reveals that all the samples are in a polycrystalline single phase of a hexagonal wurtzite structure of ZnO. The field emission scanning electron microscopy study reveals the rod like structure of all the samples. The formation of synthesis route dependent morphology and the morphology dependent physical property of all the samples are the characteristic features of the present work and to date it has not been considered as the specific tool of dielectric property modulation by anyone else. The ultraviolet-visible measurement signifies the superior control over the charge density of the host semiconducting material due to the presence of Cr3+ ions in the structure of ZnO. In the photoluminescence measurement, no significant peak has been observed in the visible region. The frequency and temperature dependent dielectric constants of all the samples were investigated. The consequences of the dielectric measurement suggest that the hydrothermal synthesis route influences the growth mechanism of the semiconducting nanoparticles mostly towards the rod like structure and the doping element influences the charge density, nature of defects, and the defect densities inside the structure of ZnO nanomaterials. All these factors together make the semiconducting ZnO nanomaterials more effective for tailor made applications in magneto-dielectric devices.

Structural and optical properties of ZnO nanorods on Mg0.2Zn0.8O seed layers grown by hydrothermal method.

PubMed

Kim, Min Su; Kim, Do Yeob; Kim, Sung-O; Leem, Jae-Young

2013-05-01

ZnO nanorods were grown on the Mg0.2Zn0.8O seed layers with different thickness by hydrothermal method. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out to investigate the effects of the Mg0.2Zn0.8O seed layer thickness on the structural and the optical properties of the ZnO nanorods. The residual stress in the Mg0.2Zn0.8O seed layers was depended on the thickness while the texture coefficient of the Mg0.2Zn0.8O seed layers was not affected significantly. The smaller full width at half maximum (FWHM) of the ZnO (002) diffraction and near-band-edge emission (NBE) peak and the larger average grain size were observed from the ZnO nanorods grown on the Mg0.2Zn0.8O seed layers with 5 layers (thickness of 350 nm), which indicate the enhancement the structural and the optical properties of the ZnO nanorods.

On-chip surface modified nanostructured ZnO as functional pH sensors

NASA Astrophysics Data System (ADS)

Zhang, Qing; Liu, Wenpeng; Sun, Chongling; Zhang, Hao; Pang, Wei; Zhang, Daihua; Duan, Xuexin

2015-09-01

Zinc oxide (ZnO) nanostructures are promising candidates as electronic components for biological and chemical applications. In this study, ZnO ultra-fine nanowire (NW) and nanoflake (NF) hybrid structures have been prepared by Au-assisted chemical vapor deposition (CVD) under ambient pressure. Their surface morphology, lattice structures, and crystal orientation were investigated by scanning electron microscopy (SEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM). Two types of ZnO nanostructures were successfully integrated as gate electrodes in extended-gate field-effect transistors (EGFETs). Due to the amphoteric properties of ZnO, such devices function as pH sensors. We found that the ultra-fine NWs, which were more than 50 μm in length and less than 100 nm in diameter, performed better in the pH sensing process than NW-NF hybrid structures because of their higher surface-to-volume ratio, considering the Nernst equation and the Gouy-Chapman-Stern model. Furthermore, the surface coating of (3-Aminopropyl)triethoxysilane (APTES) protects ZnO nanostructures in both acidic and alkaline environments, thus enhancing the device stability and extending its pH sensing dynamic range.

Investigation of the structural, optical and piezoelectric properties of ALD ZnO films on PEN substrates

NASA Astrophysics Data System (ADS)

Blagoev, B. S.; Aleksandrova, M.; Terziyska, P.; Tzvetkov, P.; Kovacheva, D.; Kolev, G.; Mehandzhiev, V.; Denishev, K.; Dimitrov, D.

2018-03-01

We present the results of studies on the structural, optical and piezoelectric properties of ZnO thin films deposited by ALD on flexible polyethylene naphthalate (PEN) substrates. Changes were observed in the optical transmission and crystal structures as the deposition temperature was varied. The electromechanical behavior, dielectric losses and voltage generated from ZnO flexible devices were investigated and discussed, in order to estimate their suitability for potential application as microgenerators activated by human motion.

First-principles approach to calculating energy level alignment at aqueous semiconductor interfaces

DOE PAGES

Kharche, Neerav; Muckerman, James T.; Hybertsen, Mark S.

2014-10-21

A first-principles approach is demonstrated for calculating the relationship between an aqueous semiconductor interface structure and energy level alignment. The physical interface structure is sampled using density functional theory based molecular dynamics, yielding the interface electrostatic dipole. The GW approach from many-body perturbation theory is used to place the electronic band edge energies of the semiconductor relative to the occupied 1 b₁ energy level in water. The application to the specific cases of nonpolar (101¯0 ) facets of GaN and ZnO reveals a significant role for the structural motifs at the interface, including the degree of interface water dissociation andmore » the dynamical fluctuations in the interface Zn-O and O-H bond orientations. As a result, these effects contribute up to 0.5 eV.« less

The structural, magnetic and optical properties of TMn@(ZnO)42 (TM = Fe, Co and Ni) hetero-nanostructure.

PubMed

Hu, Yaowen; Ji, Chuting; Wang, Xiaoxu; Huo, Jinrong; Liu, Qing; Song, Yipu

2017-11-28

The magnetic transition-metal (TM) @ oxide nanoparticles have been of great interest due to their wide range of applications, from medical sensors in magnetic resonance imaging to photo-catalysis. Although several studies on small clusters of TM@oxide have been reported, the understanding of the physical electronic properties of TM n @(ZnO) 42 is far from sufficient. In this work, the electronic, magnetic and optical properties of TM n @(ZnO) 42 (TM = Fe, Co and Ni) hetero-nanostructure are investigated using the density functional theory (DFT). It has been found that the core-shell nanostructure Fe 13 @(ZnO) 42 , Co 15 @(ZnO) 42 and Ni 15 @(ZnO) 42 are the most stable structures. Moreover, it is also predicted that the variation of the magnetic moment and magnetism of Fe, Co and Ni in TM n @ZnO 42 hetero-nanostructure mainly stems from effective hybridization between core TM-3d orbitals and shell O-2p orbitals, and a magnetic moment inversion for Fe 15 @(ZnO) 42 is investigated. Finally, optical properties studied by calculations show a red shift phenomenon in the absorption spectrum compared with the case of (ZnO) 48 .

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishiyama, Takeshi, E-mail: ishiyama@ee.tut.ac.jp; Nakane, Takaya, E-mail: ishiyama@ee.tut.ac.jp; Fujii, Tsutomu, E-mail: ishiyama@ee.tut.ac.jp

Arrays of single-crystal zinc oxide (ZnO) nanowires have been synthesized on silicon substrates by vapor-liquid-solid growth techniques. The effect of growth conditions including substrate temperature and Ar gas flow rate on growth properties of ZnO nanowire arrays were studied. Structural and optical characterization was performed using scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. SEM images of the ZnO nanowire arrays grown at various Ar gas flow rates indicated that the alignment and structural features of ZnO nanowires were affected by the gas flow rate. The PL of the ZnO nanowire arrays exhibited strong ultraviolet (UV) emission at 380 nmmore » and green emission around 510 nm. Moreover, the green emission reduced in Ga-doped sample.« less

On the possibility of room temperature ferromagnetism on chunk-shape BaSnO3/ZnO core/shell nanostructures

NASA Astrophysics Data System (ADS)

Rajamanickam, N.; Jayakumar, K.; Ramachandran, K.

2018-04-01

Core/shell BaSnO3/ZnO (BS-ZO) nanostructures were prepared by oxalate precipitation method and wet-chemical method. BaSnO3 (BSO) cubic perovskite structure and ZnO hexagonal wurtzite structure were confirmed by X-ray diffraction (XRD). The crystallite sizes is 23 nm, 29 nm and 27 nm for BSO, ZnO and BS-ZO, respectively. Chunk-shape and cuboids morphology observed from scanning electron microscopy (SEM) analysis. The magnetic properties were studied by VSM for bare and core-shell nano systems and the room temperature ferromagnetism observed for core-shell nanostructures. The BSO/ZnO shows enhanced coercivity and saturated magnetization as compared with BSO and ZnO nanostructures.

Study of defects and vacancies in structural properties of Mn, co-doped oxides: ZnO

NASA Astrophysics Data System (ADS)

Kumar, Harish; Kaushik, A.; Alvi, P. A.; Dalela, B.; Dalela, S.

2018-05-01

The paper deals with the Structural properties on Mn, Co doped oxides ZnO samples using XRD, Positron Annihilation Lifetime (PAL) Spectra and Raman Spectra. The Mn, Co doped ZnO samples crystallize in a wurtzite structure without any impurity phases in XRD Spectra. The defect state of these samples has been investigated by using positron annihilation lifetime (PAL) spectroscopy technique in which all the relevant lifetime parameters are measured for all the spectra. The results are explained in the direction of doping concentration in these samples in terms of defects structure on Zn lattice site VZn and oxygen defects Vo.

Effect of an Electrochemically Oxidized ZnO Seed Layer on ZnO Nanorods Grown by using Electrodeposition

NASA Astrophysics Data System (ADS)

Jeon, Woosung; Leem, Jae-Young

2018-05-01

ZnO nanorods were prepared on a Si substrate with and without a ZnO seed layer formed by electro-oxidation to investigate the effect of the seed layer on their growth. The ZnO nanorods grown on the ZnO seed layer had top surfaces that were flat whereas those grown without it had rough top surfaces, as observed in field-emission scanning electron microscopy images. In the Xray diffraction analysis, all ZnO nanorods showed preferential orientation with the (002) plane. In the case of ZnO nanorods prepared with a ZnO seed layer, the residual stress decreased, and the full width at half maximum of the ZnO (002) plane peak decreased. The photoluminescence spectra show a strong and narrow near-band-edge emission peak and high near-band-edge emission to deep-level emission peak ratio for the ZnO nanorods prepared with the seed layer. With respect to the photoresponse properties, the ZnO nanorods grown with the ZnO seed layer showed higher responsivity and faster rise/decay curves than those grown without it. Thus, the ZnO seed layer formed by electro-oxidation improves the structural, optical, and photoresponse properties of the ZnO nanorods formed on it. This method could serve as a new route for improving the properties of optoelectronic devices.

ZnO nanorods/graphene/Ni/Au hybrid structures as transparent conductive layer in GaN LED for low work voltage and high light extraction

NASA Astrophysics Data System (ADS)

Xu, Kun; Xie, Yiyang; Ma, Huali; Du, Yinxiao; Zeng, Fanguang; Ding, Pei; Gao, Zhiyuan; Xu, Chen; Sun, Jie

2016-12-01

In this paper, by virtue of one-dimensional ZnO nanorods and two-dimensional graphene film hybrid structures, both the enhanced current spreading and enhanced light extraction were realized at the same time. A 1 nm/1 nm Ni/Au layer was used as an interlayer between graphene and pGaN to form ohmic contact, which makes the device have a good forward conduction properties. Through the comparison of the two groups of making ZnO nanorods or not, it was found that the 30% light extraction efficiency of the device was improved by using the ZnO nanorods. By analysis key parameters of two groups such as the turn-on voltage, work voltage and reverse leakage current, it was proved that the method for preparing surface nano structure by hydrothermal method self-organization growth ZnO nanorods applied in GaN LEDs has no influence to device's electrical properties. The hybrid structure application in GaN LED, make an achievement of a good ohmic contact, no use of ITO and enhancement of light extraction at the same time, meanwhile it does not change the device structure, introduce additional process, worsen the electrical properties.

Influence of Fe doping on the structural, optical and acetone sensing properties of sprayed ZnO thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prajapati, C.S.; Kushwaha, Ajay; Sahay, P.P., E-mail: dr_ppsahay@rediffmail.com

2013-07-15

Graphical abstract: All the films are found to be polycrystalline ZnO possessing hexagonal wurtzite structure. The intensities of all the peaks are diminished strongly in the Fe-doped films, indicating their lower crystallinity as compared to the undoped ZnO film. The average crystallite size decreases from 35.21 nm (undoped sample) to 15.43 nm (1 at% Fe-doped sample). - Highlights: • Fe-doped ZnO films show smaller crystallinity with crystallite size: 15–26 nm. • Optical band gap in ZnO films decreases on Fe doping. • Fe-doped films exhibit the normal dispersion for the wavelength range 450–600 nm. • PL spectra of the Fe-dopedmore » films show quenching of the broad green-orange emission. • Acetone response of the Fe-doped films increases considerably at 300 °C. - Abstract: The ZnO thin films (undoped and Fe-doped) deposited by chemical spray pyrolysis technique have been analyzed by X-ray powder diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Results show that all the films possess hexagonal wurtzite structure of zinc oxide having crystallite sizes in the range 15–36 nm. On 1 at% Fe doping, the surface roughness of the film increases which favors the adsorption of atmospheric oxygen on the film surface and thereby increase in the gas response. Optical studies reveal that the band gap decreases due to creation of some defect energy states below the conduction band edge, arising out of the lattice disorder in the doped films. The refractive index of the films decreases on Fe doping and follows the Cauchy relation of normal dispersion. Among all the films examined, the 1 at% Fe-doped film exhibits the maximum response (∼72%) at 300 °C for 100 ppm concentration of acetone in air.« less

Fabrication and characterization of high mobility spin-coated zinc oxide thin film transistors

NASA Astrophysics Data System (ADS)

Singh, Shaivalini; Chakrabarti, P.

2012-10-01

A ZnO based thin film transistor (TFT) with bottom-gate configuration and SiO2 as insulating layer has been fabricated and characterized. The ZnO thin film was prepared by spin coating the sol-gel solution on the p-type Si wafers. The optical and structural properties of ZnO films were investigated using UV measurements and scanning electron microscope (SEM). The result of UV-visible study confirms that the films have a good absorbance in UV region and relatively low absorbance in the visible region. The TFT exhibited an off-current of 2.5×10-7 A. The values of field effect channel mobility and on/off current ratio extracted for the device, measured 11 cm2/V.s and ~102 respectively. The value of threshold voltage was found to be 1.3 V.

One-dimensional ZnO nanostructures.

PubMed

Jayadevan, K P; Tseng, T Y

2012-06-01

The wide-gap semiconductor ZnO with nanostructures such as nanoparticle, nanorod, nanowire, nanobelt, nanotube has high potential for a variety of applications. This article reviews the fundamentals of one-dimensional ZnO nanostructures, including processing, structure, property, application and their processing-microstructure-property correlation. Various fabrication methods of the ZnO nanostructures including vapor-liquid-solid process, vapor-solid growth, solution growth, solvothermal growth, template-assisted growth and self-assembly are introduced. The characterization and properties of the ZnO nanostructures are described. The possible applications of these nanostructures are also discussed.

Structure and thermoelectric properties of Al-doped ZnO films prepared by thermal oxidization under high magnetic field

NASA Astrophysics Data System (ADS)

Liu, Shiying; Peng, Sunjuan; Ma, Jun; Li, Guojian; Qin, Xuesi; Li, Mengmeng; Wang, Qiang

2017-04-01

This paper studies the effects of high magnetic field (HMF) on the structure, optical and thermoelectric properties of the doped ZnO thin films. The results show that both Al dopant and application of HMF can affect the crystal structure, surface morphology, elemental distribution and so on. The particles of the thin films become small and regular by doping Al. The ZnO films oxidized from the Au/Zn bilayer have needle structure. The ZnO films oxidized from the Au/Zn-Al bilayer transform to spherical from hexagonal due to the application of HMF. The transmittance decreases with doping Al because of the opaque of Al element and decreases with the application of HMF due to the dense structure obtained under HMF. Electrical resistivity (ρ) of the ZnO films without Al decreases with increasing measurement temperature (T) and is about 1.5 × 10-3 Ω·m at 210 °C. However, the ρ of the Al-doped ZnO films is less than 10-5 Ω·m. The Seebeck coefficient (S) of the films oxidized from the Au/Zn-Al films reduces with increasing T. The S values oxidized under 0 T and 12 T conditions are 2.439 μV/K and -3.415 μV/K at 210 °C, respectively. Power factor reaches the maximum value (3.198 × 10-4 W/m·K2) at 210 °C for the film oxidized under 12 T condition. These results indicate that the Al dopant and the application of HMF can be used to control structure and thermoelectric properties of doped ZnO films.

Contrastive Study on the Structure and the Ultraviolet Absorption Property of Multiple-Doped and Element-Doped ZnO Thin Films

NASA Astrophysics Data System (ADS)

Xu, Yunyun; Zhang, Tao; Lin, Zhenrong; Tian, Yanfeng; Zhou, Shandan

Sb2O3- and CeO2-doped ZnO thin films were prepared by RF magnetron sputtering technique. The influence of Sb2O3 and CeO2 on the structure and ultraviolet (UV) absorption properties was studied by X-ray diffraction and UV-Vis spectrophotometry. Results show that multiple doping of films had a prominent effect on the development of crystal grains and the UV absorption property. Ce and Sb exist in many forms in the ZnO film. The multiple-doped films also show enhanced UVA absorption, and the UV absorption peak widens and the absorption intensity increases. Sb plays a dominant role on the structure and UV absorption of ZnO thin films, which are enhanced by Ce.

Effects of substrate on the structure and orientation of ZnO thin film grown by rf-magnetron sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, H. F.; Chua, S. J.; Hu, G. X.

2007-10-15

X-ray diffractions, Nomarski microscopy, scanning electron microscopy, and photoluminescence have been used to study the effects of substrate on the structure and orientation of ZnO thin films grown by rf-magnetron sputtering. GaAs(001), GaAs(111), Al{sub 2}O{sub 3}(0002) (c-plane), and Al{sub 2}O{sub 3}(1102) (r-plane) wafers have been selected as substrates in this study. X-ray diffractions reveal that the ZnO film grown on GaAs(001) substrate is purely textured with a high c-axis orientation while that grown on GaAs(111) substrate is a single ZnO(0002) crystal; a polycrystalline structure with a large-single-crystal area of ZnO(0002) is obtained on a c-plane Al{sub 2}O{sub 3} substrate whilemore » a ZnO(1120) single crystal is formed on an r-plane Al{sub 2}O{sub 3} substrate. There is absence of significant difference between the photoluminescence spectra collected from ZnO/GaAs(001), ZnO/GaAs(111), and ZnO/Al{sub 2}O{sub 3}(0002), while the photoluminescence from ZnO/Al{sub 2}O{sub 3}(1102) shows a reduced intensity together with an increased linewidth, which is, likely, due to the increased incorporation of native defects during the growth of ZnO(1120)« less

Investigation and characterization of ZnO single crystal microtubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Al-Naser, Qusay A.H.; Zhou, Jian, E-mail: jianzhou@whut.edu.cn; Liu, Guizhen

2016-04-15

Morphological, structural, and optical characterization of microwave synthesized ZnO single crystal microtubes were investigated in this work. The structure and morphology of the ZnO microtubes are characterized using X-ray diffraction (XRD), single crystal diffraction (SCD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The results reveal that the as-synthesized ZnO microtube has a highly regular hexagonal cross section and smooth surfaces with an average length of 650–700 μm, an average outer diameter of 50 μm and wall thickness of 1–3 μm, possessing a single crystal wurtzite hexagonal structure. Optical properties of ZnOmore » single crystal microtubes were investigated by photoluminescence (PL) and ultraviolet-visible (UV-vis) absorption techniques. Room-temperature PL spectrum of the microtube reveal a strong UV emission peak at around 375.89 nm and broad and a weak visible emission with a main peak identified at 577 nm, which was assigned to the nearest band-edge emission and the deep-level emission, respectively. The band gap energy of ZnO microtube was found to be 3.27 eV. - Highlights: • ZnO microtube length of 650–700 μm, diameter of 50 μm, wall thickness of 1–3 μm • ZnO microtube possesses a single crystal wurtzite hexagonal structure. • The crystal system is hexahedral oriented along a-axis with indices of (100). • A strong and sharp UV emission at 375.89 nm (3.29 eV) • One prominent absorption band around 378.88 nm (3.27 eV)« less

Preparation, characterization and properties of ZnO nanomaterials

NASA Astrophysics Data System (ADS)

Luo, Jiaolian; Zhang, Xiaoming; Chen, Ruxue; Wang, Xiaohui; Zhu, Ji; Wang, Xiaomin

2017-06-01

In this paper, using the hydrothermal synthesis method, NaOH, Zn(NO3)2, anhydrous ethanol, deionized water as raw material to prepare ZnO nanomaterial, and by X ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy (PL) on the synthesis of nano materials, surface morphology and phase luminescence characterization. The results show that the nano materials synthesized for single-phase ZnO, belonging to the six wurtzite structure; material surface shaped, arranged evenly distributed, and were the top six party structure; ZnO nano materials synthesized with strong emission spectra, emission peak is located at 394nm.

Novel Structure for High Performance UV Photodetector Based on BiOCl/ZnO Hybrid Film.

PubMed

Teng, Feng; Ouyang, Weixin; Li, Yanmei; Zheng, Lingxia; Fang, Xiaosheng

2017-06-01

A novel type of high performance ultraviolet (UV) photodetector (PD) based on a ZnO film has been prepared by incorporating a BiOCl nanostructure into the film. The responsivity of the BiOCl/ZnO hybrid film PD in UV region can reach 182.87 mA W -1 , which is about 2.72 and 6.87 times for that of TiO 2 /ZnO hybrid film PD and pure ZnO film PD. The rise/decay time of BiOCl/ZnO hybrid film PD is 25.83/11.25 s, which is much shorter than that of TiO 2 /ZnO hybrid film PD (51.94/26.05 s) and pure ZnO film PD (69.34/>120 s). The BiOCl nanostructure can inject photogenerated electrons into the ZnO film under UV light illumination, leading to the increase of photocurrent, and forms barriers to block the straight transmission of electrons between electrodes, resulting in the decrease of decay time. The results of control experiment show that the transfer path of photogenerated electrons formed by p-n junction will be cut off after depositing gold nanoparticles on the film surface, which means this hybrid film is a unique and novel structure to improve the optoelectronic performance of photodetectors. This novel BiOCl/ZnO hybrid structure paves new route for the development of film PDs based on ZnO film. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Template-free hydrothermal synthesis of beaded nanochain bundles of ZnO and their application as photoanode in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Ballal, Reshma; Shinde, Manish; Waghadkar, Yogesh; Arbuj, Sudhir; Rane, Sunit; Chauhan, Ratna

2018-02-01

ZnO shows promising candidature as photoanode material for dye-sensitized solar cells (DSSCs) due to its high bulk electron mobility and easily tailorable geometrical structures. The objective of this study is to facilitate the development of highly porous hierarchical ZnO for enhanced power conversion efficiency in dye-sensitized solar cells (DSSC) due to its greater dye adsorption. This study investigated the influence of reaction temperatures of 120 °C (sample Z-1) and 180 °C (sample Z-2) in hydrothermal synthesis on structural, morphological and optical properties of resultant ZnO nanostructures and their performance as photoanode material in DSSCs. The synthesized beaded nanochain bundles of ZnO, with multilayered and highly ordered texture, have diameters of several micrometers. Structural and morphological analysis shows that the ZnO beaded nanochain-like architectures possess wurtzite crystalline nature. These morphological improvements (beaded nanochains) of ZnO were found to exhibit higher dye loading and conversion efficiency due to increase in the surface area while reducing charge recombination. The maximum conversion efficiency was obtained with Z-1 and Z-2 is 2.95 and 3.56% with photocurrent of 7.73 and 9.24 mA/cm2, respectively. The obtained results pertaining to the DSSC performance studies were corroborated by the impedance spectroscopy data.

Achieving highly-enhanced UV photoluminescence and its origin in ZnO nanocrystalline films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thapa, Dinesh; Huso, Jesse; Morrison, John L.

ZnO is an efficient luminescent material in the UV-range ~3.4 eV with a wide range of applications in optical technologies. Sputtering is a cost-effective and relatively straightforward growth technique for ZnO films; however, most as-grown films are observed to contain intrinsic defects which can significantly diminish the desirable UV-emission. In this research the defect dynamics and optical properties of ZnO sputtered films were studied via post-growth annealing in Ar or O 2 ambient, with X-ray diffraction (XRD), imaging, transmission and Urbach analysis, Raman scattering, and photoluminescence (PL). The imaging, XRD, Raman and Urbach analyses indicate significant improvement in crystal morphologymore » and band-edge characteristics upon annealing, which is nearly independent of the annealing environment. The native defects specific to the as-grown films, which were analyzed via PL, are assigned to Zn i related centers that luminesce at 2.8 eV. Their presence is attributed to the nature of the sputtering growth technique, which supports Zn-rich growth conditions. After annealing, in either environment the 2.8 eV center diminished accompanied by morphology improvement, and the desirable UV-PL significantly increased. The O 2 ambient was found to introduce nominal O i centers while the Ar ambient was found to be the ideal environment for the enhancement of the UV-light emission: an enhancement of ~40 times was achieved. The increase in the UV-PL is attributed to the reduction of Zn i-related defects, the presence of which in ZnO provides a competing route to the UV emission. Also, the effect of the annealing was to decrease the compressive stress in the films. Lastly, the dominant UV-PL at the cold temperature regime is attributed to luminescent centers not associated with the usual excitons of ZnO, but rather to structural defects.« less

Achieving highly-enhanced UV photoluminescence and its origin in ZnO nanocrystalline films

DOE PAGES

Thapa, Dinesh; Huso, Jesse; Morrison, John L.; ...

2016-06-14

ZnO is an efficient luminescent material in the UV-range ~3.4 eV with a wide range of applications in optical technologies. Sputtering is a cost-effective and relatively straightforward growth technique for ZnO films; however, most as-grown films are observed to contain intrinsic defects which can significantly diminish the desirable UV-emission. In this research the defect dynamics and optical properties of ZnO sputtered films were studied via post-growth annealing in Ar or O 2 ambient, with X-ray diffraction (XRD), imaging, transmission and Urbach analysis, Raman scattering, and photoluminescence (PL). The imaging, XRD, Raman and Urbach analyses indicate significant improvement in crystal morphologymore » and band-edge characteristics upon annealing, which is nearly independent of the annealing environment. The native defects specific to the as-grown films, which were analyzed via PL, are assigned to Zn i related centers that luminesce at 2.8 eV. Their presence is attributed to the nature of the sputtering growth technique, which supports Zn-rich growth conditions. After annealing, in either environment the 2.8 eV center diminished accompanied by morphology improvement, and the desirable UV-PL significantly increased. The O 2 ambient was found to introduce nominal O i centers while the Ar ambient was found to be the ideal environment for the enhancement of the UV-light emission: an enhancement of ~40 times was achieved. The increase in the UV-PL is attributed to the reduction of Zn i-related defects, the presence of which in ZnO provides a competing route to the UV emission. Also, the effect of the annealing was to decrease the compressive stress in the films. Lastly, the dominant UV-PL at the cold temperature regime is attributed to luminescent centers not associated with the usual excitons of ZnO, but rather to structural defects.« less

Temperature- and frequency-dependent dielectric behaviors of insulator/semiconductor (Al2O3/ZnO) nanolaminates with various ZnO thicknesses

NASA Astrophysics Data System (ADS)

Li, Jin; Bi, Xiaofang

2016-07-01

Al2O3/ZnO nanolaminates (NLs) with various ZnO sublayer thicknesses were prepared by atomic layer deposition. The Al2O3 sublayers are characterized as amorphous and the ZnO sublayers have an oriented polycrystalline structure. As the ZnO thickness decreases to a certain value, each NL exhibits a critical temperature at which its dielectric constant starts to rise quickly. Moreover, this temperature increases as the ZnO thickness is decreased further. On the other hand, the permittivity demonstrates a large value of several hundred at a frequency  ⩽1000 Hz, followed by a steplike decrease at a higher frequency. The change in the cut-off frequency with ZnO thickness is characterized by a hook function. It is revealed that the Coulomb confinement effect becomes predominant in the dielectric behaviors of the NLs with very thin ZnO. As the ZnO thickness decreases to about the same as or even smaller than the Bohr radius of ZnO, a great change in the carrier concentration and effective mass of ZnO is induced, which is shown to be responsible for the peculiar dielectric behaviors of Al2O3/ZnO with very thin ZnO. These findings provide insight into the prevailing mechanisms to optimize the dielectric properties of semiconductor/insulator laminates with nanoscale sublayer thickness.

N doped ZnO and ZnO nanorods based p-n homojunction fabricated by ion implantation

NASA Astrophysics Data System (ADS)

Chakraborty, Mohua; Thangavel, R.; Asokan, K.

2018-05-01

Nitrogen (N) doped and undoped Zinc Oxide (ZnO) nanorod p-n homojunctions were fabricated by ion implantation method. The structural and optical characterizations showed that the N atoms doped into the ZnO crystal lattice. The UV-Vis absorption spectra revealed shift in optical absorption edge towards higher wavelength with ion implantation on ZnO, which attributed N acceptor levels above the valence band. The current-voltage (I-V) measurements exhibit a typical semiconductor rectification characteristic indicating the electrical conductivity of the N-doped ZnO nanorod have p-type conductivity. Moreover, a high photocurrent response has been observed with these p-n homojunctions.

Carrier transport in flexible organic bistable devices of ZnO nanoparticles embedded in an insulating poly(methyl methacrylate) polymer layer.

PubMed

Son, Dong-Ick; Park, Dong-Hee; Choi, Won Kook; Cho, Sung-Hwan; Kim, Won-Tae; Kim, Tae Whan

2009-05-13

The bistable effects of ZnO nanoparticles embedded in an insulating poly(methyl methacrylate) (PMMA) polymer single layer by using flexible polyethylene terephthalate (PET) substrates were investigated. Transmission electron microscopy (TEM) images revealed that ZnO nanoparticles were formed inside the PMMA polymer layer. Current-voltage (I-V) measurement on the Al/ZnO nanoparticles embedded in an insulating PMMA polymer layer/ITO/PET structures at 300 K showed a nonvolatile electrical bistability behavior with a flat-band voltage shift due to the existence of the ZnO nanoparticles, indicative of trapping, storing, and emission of charges in the electronic states of the ZnO nanoparticles. The carrier transport mechanism of the bistable behavior for the fabricated organic bistable device (OBD) structures is described on the basis of the I-V results by analyzing the effect of space charge.

Growth of well-aligned ZnO nanorods using auge catalyst by vapor phase transportation.

PubMed

Ha, S Y; Jung, M N; Park, S H; Ko, H J; Ko, H; Oh, D C; Yao, T; Chang, J H

2006-11-01

Well-aligned ZnO nanorods have been achieved using new alloy (AuGe) catalyst. Zn powder was used as a source material and it was transported in a horizontal tube furnace onto an AuGe deposited Si substrates. The structural and optical properties of ZnO nanorods were characterized by scanning electron microscopy, high resolution X-ray diffraction, and photoluminescence. ZnO nanorods grown at 650 degrees C on 53 nm thick AuGe layer show uniform shape with the length of 8 +/- 0.5 microm and the diameter of 150 +/- 5 nm. Also, the tilting angle of ZnO nanorods (+/- 5.5 degrees) is confirmed by HRXRD. High structural quality of the nanorods is conformed by the photoluminescence measurement. All samples show strong UV emission without considerable deep level emission. However, weak deep level emission appears at high (700 degrees C) temperature due to the increase of oxygen desertion.

Photoluminescent ZnO Nanoparticles and Their Biological Applications

PubMed Central

Zhang, Zheng-Yong; Xiong, Huan-Ming

2015-01-01

During the past decades, numerous achievements concerning luminescent zinc oxide nanoparticles (ZnO NPs) have been reported due to their improved luminescence and good biocompatibility. The photoluminescence of ZnO NPs usually contains two parts, the exciton-related ultraviolet (UV) emission and the defect-related visible emission. With respect to the visible emission, many routes have been developed to synthesize and functionalize ZnO NPs for the applications in detecting metal ions and biomolecules, biological fluorescence imaging, nonlinear multiphoton imaging, and fluorescence lifetime imaging. As the biological applications of ZnO NPs develop rapidly, the toxicity of ZnO NPs has attracted more and more attention because ZnO can produce the reactive oxygen species (ROS) and release Zn2+ ions. Just as a coin has two sides, both the drug delivery and the antibacterial effects of ZnO NPs become attractive at the same time. Hence, in this review, we will focus on the progress in the synthetic methods, luminescent properties, and biological applications of ZnO NPs.

Evaluation of Alternative Atomistic Models for the Incipient Growth of ZnO by Atomic Layer Deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chu, Manh-Hung; Tian, Liang; Chaker, Ahmad

ZnO thin films are interesting for applications in several technological fields, including optoelectronics and renewable energies. Nanodevice applications require controlled synthesis of ZnO structures at nanometer scale, which can be achieved via atomic layer deposition (ALD). However, the mechanisms governing the initial stages of ALD had not been addressed until very recently. Investigations into the initial nucleation and growth as well as the atomic structure of the heterointerface are crucial to optimize the ALD process and understand the structure-property relationships for ZnO. We have used a complementary suite of in situ synchrotron x-ray techniques to investigate both the structural andmore » chemical evolution during ZnO growth by ALD on two different substrates, i.e., SiO2 and Al2O3, which led us to formulate an atomistic model of the incipient growth of ZnO. The model relies on the formation of nanoscale islands of different size and aspect ratio and consequent disorder induced in the Zn neighbors' distribution. However, endorsement of our model requires testing and discussion of possible alternative models which could account for the experimental results. In this work, we review, test, and rule out several alternative models; the results confirm our view of the atomistic mechanisms at play, which influence the overall microstructure and resulting properties of the final thin film.« less

Anisotropic polaron localization and spontaneous symmetry breaking: Comparison of cation-site acceptors in GaN and ZnO

NASA Astrophysics Data System (ADS)

Sun, Y. Y.; Abtew, Tesfaye A.; Zhang, Peihong; Zhang, S. B.

2014-10-01

The behavior of cation substitutional hole doping in GaN and ZnO is investigated using hybrid density functional calculations. Our results reveal that Mg substitution for Ga (MgGa) in GaN can assume three different configurations. Two of the configurations are characterized by the formation of defect-bound small polaron (i.e., a large structural distortion accompanied by hole localization on one of the neighboring N atoms). The third one has a relatively small but significant distortion that is characterized by highly anisotropic polaron localization. In this third configuration, MgGa exhibits both effective-mass-like and noneffective-mass-like characters. In contrast, a similar defect in ZnO, LiZn, cannot sustain the anisotropic polaron in the hybrid functional calculation, but undergoes spontaneous breaking of a mirror symmetry through a mechanism driven by the hole localization. Finally, using NaZn in ZnO as an example, we show that the deep acceptor levels of the small-polaron defects could be made shallower by applying compressive strain to the material.

Influence of the morphology of ZnO nanostructures on luminescent and photovoltaic properties

NASA Astrophysics Data System (ADS)

Ibrayev, N. Kh.; Ilyassov, B. R.; Afanasyev, D. A.

2017-03-01

Arrays of ZnO nanorods and nanoplates are synthesized by the hydrothermal and electrochemical methods, respectively. The photoluminescence spectra indicate that the nanoplates have a more defective structure than the nanorods. The obtained ZnO nanostructures are used as the basis to construct dye-sensitized solar cells. The influence of morphology and defectiveness of ZnO nanostructures on the luminescent and photovoltaic properties of the cells is studied.

Theory and Device Modeling for Nano-Structured Transistor Channels

DTIC Science & Technology

2011-06-01

zinc oxide ( ZnO ) thin film transistors ( TFTs ) that contain nanocrystalline grains on the order of ~20nm. The authors of ref. 1 present results...problem in order to determine the threshold voltage. 15. SUBJECT TERMS nano-structured transistor , mesoscopic, zinc oxide , ZnO , field-effect...and R. Neidhard, “Microwave ZnO Thin - Film Transistors ”, IEEE Electron Dev. Lett. 29, 1024 (2008); doi: 10.1109/LED.2008.2001635.

REVIEW ARTICLE: Structure, microstructure and physical properties of ZnO based materials in various forms: bulk, thin film and nano

NASA Astrophysics Data System (ADS)

Singh, Shubra; Thiyagarajan, P.; Mohan Kant, K.; Anita, D.; Thirupathiah, S.; Rama, N.; Tiwari, Brajesh; Kottaisamy, M.; Ramachandra Rao, M. S.

2007-10-01

ZnO is a unique material that offers about a dozen different application possibilities. In spite of the fact that the ZnO lattice is amenable to metal ion doping (3d and 4f), the physics of doping in ZnO is not completely understood. This paper presents a review of previous research works on ZnO and also highlights results of our research activities on ZnO. The review pertains to the work on Al and Mg doping for conductivity and band gap tuning in ZnO followed by a report on transition metal (TM) ion doped ZnO. This review also highlights the work on the transport and optical studies of TM ion doped ZnO, nanostructured growth (ZnO polycrystalline and thin films) by different methods and the formation of unique nano- and microstructures obtained by pulsed laser deposition and chemical methods. This is followed by results on ZnO encapsulated Fe3O4 nanoparticles that show promising trends suitable for various applications. We have also reviewed the non-linear characteristic studies of ZnO based heterostructures followed by an analysis on the work carried out on ZnO based phosphors, which include mainly the nanocrystalline ZnO encapsulated SiO2, a new class of phosphor that is suitable for white light emission.

Zinc Oxide Nanoparticles Influence Microflora in Ileal Digesta and Correlate Well with Blood Metabolites.

PubMed

Feng, Yanni; Min, Lingjiang; Zhang, Weidong; Liu, Jing; Hou, Zhumei; Chu, Meiqiang; Li, Lan; Shen, Wei; Zhao, Yong; Zhang, Hongfu

2017-01-01

Zinc oxide nanoparticles (ZnO NPs) are used widely in consumer and industrial products, however, their influence on gut microbiota and metabolism and their mutual interactions are not fully understood. In this study, the effects of ZnO NPs on ileal bacterial communities, plasma metabolites, and correlations between them were investigated. Hens were fed with different concentrations of ZnO NPs [based on Zn; 0 mg/kg (control), 25 mg/kg, 50 mg/kg, and 100 mg/kg] for 9 weeks. Subsequently, ileal digesta and blood plasma were collected for analysis of microflora and metabolites, respectively. The V3-V4 region of the 16S rRNA gene of ileal digesta microbiota was sequenced using the Illumina HiSeq 2500 platform. The predominant bacterial community in the ileum belongs to the phylum Firmicutes. The richness of the bacterial community was negatively correlated with increasing amounts of ZnO NPs ( r = -0.636, P < 0.01); when ZnO NP levels were at 100 mg/kg, microbiota diversity was significantly decreased ( P < 0.05). The community structure determined by LEfSe analysis indicated that Bacilli, Fusobacteria, and Proteobacteria were changed, and Lactobacillus was reduced by ZnO NPs. Moreover, metabolism as analyzed by nuclear magnetic resonance (NMR) indicated that glucose, some amino acids, and other metabolites were changed by ZnO NPs. Choline, lactate, and methionine were positively correlated with bacterial richness. In summary, ZnO NPs could influence the levels of microflora in ileal digesta, particularly Lactobacillus . Furthermore, the richness of the microbiota was related to changes in choline, lactate, and methionine metabolism.

Novel synthesis and structural analysis of zinc oxide nanoparticles for the non enzymatic glucose biosensor.

PubMed

Dayakar, T; Venkateswara Rao, K; Bikshalu, K; Rajendar, V; Park, Si-Hyun

2017-06-01

A non-enzymatic glucose biosensor was developed by utilizing the zinc oxide nanoparticles (ZnO NPs) synthesized by a novel green method using the leaf extract of Ocimum tenuiflorum. The structural, optical and morphological properties of ZnO NPs characterized by means of X-ray diffraction (XRD), ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDAX) spectroscopy, and transmission electron microscopy (TEM). The XRD analysis revealed that the ZnO NPs were crystalline and had a hexagonal wurtzite structure. The crystallite size measured by XRD was the same as that measured using SEM and TEM. The UV-vis absorption spectrum estimates the band gap of ZnO NPs present in the range of 2.82 to 3.45eV. The reduction and formation of ZnO NPs mainly due to the involvement of leaf extract bio-molecular compounds analyzed from the FTIR spectra. The SEM result confirms the morphology of the NPs responsible from the various concentration of leaf extract in the synthesis process. HRTEM analysis depicts the spherical structure of ZnO NPs. The synthesized NPs have the average size ranges from 10 to 20nm. The fabricated GCE/ZnO glucose sensor represents superior electro catalytic activity that has been observed for ZnO NPs with a reproducible sensitivity of 631.30μAmM -1 cm -2 , correlation coefficient of R=0.998, linear dynamic range from 1-8.6mM, low detection limit of 0.043μM (S/N=3) and response time<4s. Copyright © 2017 Elsevier B.V. All rights reserved.

Morphology evolution of hierarchical ZnO nanostructures modulated by supersaturation and growth temperature

NASA Astrophysics Data System (ADS)

Yan, Youguo; Zhou, Lixia; Yu, Lianqing; Zhang, Ye

2008-07-01

Three kinds of ZnO hierarchical structures, nanocombs with tube- and needle-shaped teeth and hierarchical nanorod arrays, were successfully synthesized through the chemical vapor deposition method. Combining the experimental parameters, the microcosmic growing conditions (growth temperature and supersaturation) along the flux was discussed at length, and, based on the conclusions, three reasonable growth processes were proposed. The results and discussions were beneficial to further realize the relation between the growing behavior of the nanomaterial and microcosmic conditions, and the hierarchical nanostructures obtained were also expected to have potential applications as functional blocks in future nanodevices. Furthermore, the study of photoluminescence further indicated that the physical properties were strongly dependent on the crystal structure.

Surface structure, optoelectronic properties and charge transport in ZnO nanocrystal/MDMO-PPV multilayer films.

PubMed

Lian, Qing; Chen, Mu; Mokhtar, Muhamad Z; Wu, Shanglin; Zhu, Mingning; Whittaker, Eric; O'Brien, Paul; Saunders, Brian R

2018-05-07

Blends of semiconducting nanocrystals and conjugated polymers continue to attract major research interest because of their potential applications in optoelectronic devices, such as solar cells, photodetectors and light-emitting diodes. In this study we investigate the surface structure, morphological and optoelectronic properties of multilayer films constructed from ZnO nanocrystals (NCs) and poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV). The effects of layer number and ZnO concentration (C ZnO ) used on the multilayer film properties are investigated. An optimised solvent blend enabled well-controlled layers to be sequentially spin coated and the construction of multilayer films containing six ZnO NC (Z) and MDMO-PPV (M) layers (denoted as (ZM) 6 ). Contact angle data showed a strong dependence on C ZnO and indicated distinct differences in the coverage of MDMO-PPV by the ZnO NCs. UV-visible spectroscopy showed that the MDMO-PPV absorption increased linearly with the number of layers in the films and demonstrates highly tuneable light absorption. Photoluminescence spectra showed reversible quenching as well as a surprising red-shift of the MDMO-PPV emission peak. Solar cells were constructed to probe vertical photo-generated charge transport. The measurements showed that (ZM) 6 devices prepared using C ZnO = 14.0 mg mL -1 had a remarkably high open circuit voltage of ∼800 mV. The device power conversion efficiency was similar to that of a control bilayer device prepared using a much thicker MDMO-PPV layer. The results of this study provide insight into the structure-optoelectronic property relationships of new semiconducting multilayer films which should also apply to other semiconducting NC/polymer combinations.

A simple and transparent well-aligned ZnO nanowire array ultraviolet photodetector with high responsivity

NASA Astrophysics Data System (ADS)

Yin, Lei; Ding, Hesheng; Yuan, Zhaolin; Huang, Wendeng; Shuai, Chunjiang; Xiong, Zhaoxin; Deng, Jianping; Lv, Tengbo

2018-06-01

Well-aligned zinc oxide (ZnO) nanowire arrays were grown on an interdigital patterned fluorine tin oxide (FTO)-coated glass substrate by a facile chemical bath deposition at low temperature. Morphology, crystalline structure, and optical properties of the ZnO nanowire arrays were analyzed in detail. The results revealed that the ZnO nanowires had wurtzite structure, typically ∼40-60 nm in diameter, and ∼700-800 nm in length, a great number of highly uniform and dense nanowires grew vertically on the substrate to form the well-aligned ZnO nanowire arrays, which had very high optical transmission (>86%) in the visible light region. In addition, the performance of ZnO nanowire arrays ultraviolet (UV) photodetector was systematically examined. The photosensitivity (S), responsivity (R), response and decay time of the photodetector were 703 at +0.2 V, 113 A/W at +5 V, 23 s and 73 s respectively. Also, the photoresponse mechanism of the UV photodetector was illuminated in terms of the oxygen adsorption-photodesorption process.

Characteristics of surface acoustic waves in (11\\bar 2 0)ZnO film/ R-sapphire substrate structures

NASA Astrophysics Data System (ADS)

Wang, Yan; Zhang, ShuYi; Xu, Jing; Xie, YingCai; Lan, XiaoDong

2018-02-01

(11\\bar 2 0)ZnO film/ R-sapphire substrate structure is promising for high frequency acoustic wave devices. The propagation characteristics of SAWs, including the Rayleigh waves along [0001] direction and Love waves along [1ī00] direction, are investigated by using 3 dimensional finite element method (3D-FEM). The phase velocity ( v p), electromechanical coupling coefficient ( k 2), temperature coefficient of frequency ( TCF) and reflection coefficient ( r) of Rayleigh wave and Love wave devices are theoretically analyzed. Furthermore, the influences of ZnO films with different crystal orientation on SAW properties are also investigated. The results show that the 1st Rayleigh wave has an exceedingly large k 2 of 4.95% in (90°, 90°, 0°) (11\\bar 2 0)ZnO film/ R-sapphire substrate associated with a phase velocity of 5300 m/s; and the 0th Love wave in (0°, 90°, 0°) (11\\bar 2 0)ZnO film/ R-sapphire substrate has a maximum k 2 of 3.86% associated with a phase velocity of 3400 m/s. And (11\\bar 2 0)ZnO film/ R-sapphire substrate structures can be used to design temperature-compensated and wide-band SAW devices. All of the results indicate that the performances of SAW devices can be optimized by suitably selecting ZnO films with different thickness and crystal orientations deposited on R-sapphire substrates.

Efficient room temperature hydrogen sensor based on UV-activated ZnO nano-network

NASA Astrophysics Data System (ADS)

Kumar, Mohit; Kumar, Rahul; Rajamani, Saravanan; Ranwa, Sapana; Fanetti, Mattia; Valant, Matjaz; Kumar, Mahesh

2017-09-01

Room temperature hydrogen sensors were fabricated from Au embedded ZnO nano-networks using a 30 mW GaN ultraviolet LED. The Au-decorated ZnO nano-networks were deposited on a SiO2/Si substrate by a chemical vapour deposition process. X-ray diffraction (XRD) spectrum analysis revealed a hexagonal wurtzite structure of ZnO and presence of Au. The ZnO nanoparticles were interconnected, forming nano-network structures. Au nanoparticles were uniformly distributed on ZnO surfaces, as confirmed by FESEM imaging. Interdigitated electrodes (IDEs) were fabricated on the ZnO nano-networks using optical lithography. Sensor performances were measured with and without UV illumination, at room temperate, with concentrations of hydrogen varying from 5 ppm to 1%. The sensor response was found to be ˜21.5% under UV illumination and 0% without UV at room temperature for low hydrogen concentration of 5 ppm. The UV-photoactivated mode enhanced the adsorption of photo-induced O- and O2- ions, and the d-band electron transition from the Au nanoparticles to ZnO—which increased the chemisorbed reaction between hydrogen and oxygen. The sensor response was also measured at 150 °C (without UV illumination) and found to be ˜18% at 5 ppm. Energy efficient low cost hydrogen sensors can be designed and fabricated with the combination of GaN UV LEDs and ZnO nanostructures.

Electrochemical Sensing, Photocatalytic and Biological Activities of ZnO Nanoparticles: Synthesis via Green Chemistry Route

NASA Astrophysics Data System (ADS)

Yadav, L. S. Reddy; Archana, B.; Lingaraju, K.; Kavitha, C.; Suresh, D.; Nagabhushana, H.; Nagaraju, G.

2016-05-01

In this paper, we have successfully synthesized ZnO nanoparticles (Nps) via solution combustion method using sugarcane juice as the novel fuel. The structure and morphology of the synthesized ZnO Nps have been analyzed using various analytical tools. The synthesized ZnO Nps exhibit excellent photocatalytic activity for the degradation of methylene blue dye, indicating that the ZnO Nps are potential photocatalytic semiconductor materials. The synthesized ZnO Nps also show good electrochemical sensing of dopamine. ZnO Nps exhibit significant bactericidal activity against Klebsiella aerogenes, Pseudomonas aeruginosa, Eschesichia coli and Staphylococcus aureus using agar well diffusion method. Furthermore, the ZnO Nps show good antioxidant activity by potentially scavenging 1-diphenyl-2-picrylhydrazyl (DPPH) radicals. The above studies clearly demonstrate versatile applications of ZnO synthesized by simple eco-friendly route.

Inversion domain boundaries in ZnO with additions of Fe2O3 studied by high-resolution ADF imaging.

PubMed

Wolf, Frank; Freitag, Bert H; Mader, Werner

2007-01-01

Columns of metal atoms in the polytypoid compound Fe2O3(ZnO)15 could be resolved by high angle annular dark field imaging in a transmission electron microscopy (TEM)/STEM electron microscope--a result which could not be realized by high-resolution bright field imaging due to inherent strain from inversion domains and inversion domain boundaries (IDBs) in the crystals. The basal plane IDB was imaged in [11 00] yielding the spacing of the two adjacent ZnO domains, while imaging in [21 1 0] yields the position of single metal ions. The images allow the construction of the entire domain structure including the stacking sequence and positions of the oxygen ions. The IDB consists of a single layer of octahedrally co-ordinated Fe3+ ions, and the inverted ZnO domains are related by point symmetry at the iron position. The FeO6 octahedrons are compressed along the ZnO c-axis resulting in a FeO bond length of 0.208 nm which is in the range of FeO distances in iron containing oxides. The model of the basal plane boundary resembles that of the IDB in polytypoid ZnO-In2O3 compounds.

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Effect of polyacrylamide on morphology and electromagnetic properties of chrysanthemum-like ZnO particles

NASA Astrophysics Data System (ADS)

Yan, Jun-Feng; Zhang, Zhi-Yong; You, Tian-Gui; Zhao, Wu; Yun, Jiang-Ni; Zhang, Fu-Chun

2009-10-01

Through hydrothermal process, the chrysanthemum-like ZnO particles are prepared with zinc acetate dihydrate (Zn(CH3COO)2·2H2O) and sodium hydroxide (NaOH) used as main resources under the different concentrations of surfactant polyacrylamide (PAM). The microstructure, morphology and the electromagnetic properties of the as-prepared products are characterized by high-resolution transmissïon electron microscopy (HRTEM), field emission environment scanning electron microscope (FEESEM) and microwave vector network analyzer, respectively. The experimental results indicate that the as-prepared products are ZnO single crystalline with hexagona wurtzite structure, that the values of slenderness ratio Ld are different in different PAM concentrations, and that the good magnetic loss property is found in the ZnO products, and the average magnetic loss tangent tan δu increases with PAM concentration increasing, while the dielectric loss tangent tan δe decreases.

Facile synthesis of Zn1-xCoxO/ZnO core/shell nanostructures and their application to dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Manthina, Venkata; Agrios, Alexander G.

2017-04-01

Heterostructures consisting of Co-doped ZnO nanorod cores encased in an undoped ZnO shell were successfully synthesized to serve as photoanodes for dye-sensitized solar cells (DSSCs) by a two-step chemical bath deposition (CBD) technique. This yields a highly favorable structure in which electrons injected from the dye into the ZnO then step down in energy into the Co-doped core, where the electron is transported to the collector while the ZnO shell acts as a barrier to recombination with the electrolyte. Incorporation of the core/shell structures into DSSCs resulted in large improvements in photocurrent and photovoltage in comparison to pure ZnO nanorod-based DSSCs. SEM and XRD characterization indicate incorporation of the Co2+ into the ZnO matrix, without separation of the Co into other phases, providing no energy barriers. In addition, the ability of these heterostructures to reduce recombination rates in redox couples with fast recombination rates was probed by comparing DSSC device performance in both iodide/triiodide-based and ferrocene/ferrocenium-based electrolytes.

Structural, Optical, and Vibrational Properties of ZnO Microrods Deposited on Silicon Substrate

NASA Astrophysics Data System (ADS)

Lahlouh, Bashar I.; Ikhmayies, Shadia J.; Juwhari, Hassan K.

2018-03-01

Zinc oxide (ZnO) microrod films deposited by spray pyrolysis on silicon substrate at 350 ± 5°C have been studied and evaluated, and compared with thin films deposited by electron beam to confirm the identity of the studied samples. The films were characterized using different techniques. The microrod structure was studied and confirmed by scanning electron microscopy. Fourier-transform infrared (FTIR) spectroscopy and x-ray diffraction analysis confirmed successful deposition of ZnO thin films with the expected wurtzite structure. Reflectance data showed a substantial drop across the whole studied wavelength range. The photoluminescence (PL) spectra of the studied samples showed a peak at ˜ 360 nm, representing a signature of ZnO. The shift in the PL peak position is due to defects and other species present in the films, as confirmed by FTIR and energy-dispersive x-ray spectroscopy results.

Synthesis of ZnO thin film by sol-gel spin coating technique for H2S gas sensing application

NASA Astrophysics Data System (ADS)

Nimbalkar, Amol R.; Patil, Maruti G.

2017-12-01

In this present work, zinc oxide (ZnO) thin film synthesized by a simple sol-gel spin coating technique. The structural, morphology, compositional, microstructural, optical, electrical and gas sensing properties of the film were studied by using XRD, FESEM, EDS, XPS, HRTEM, Raman, FTIR and UV-vis techniques. The ZnO thin film shows hexagonal wurtzite structure with a porous structured morphology. Gas sensing performance of synthesized ZnO thin film was tested initially for H2S gas at different operating temperatures as well as concentrations. The maximum gas response is achieved towards H2S gas at 300 °C operating temperature, at 100 ppm gas concentration as compared to other gases like CH3OH, Cl2, NH3, LPG, CH3COCH3, and C2H5OH with a good stability.

Fabrication of GaN doped ZnO nanocrystallines by laser ablation.

PubMed

Gopalakrishnan, N; Shin, B C; Bhuvana, K P; Elanchezhiyan, J; Balasubramanian, T

2008-08-01

Here, we present the fabrication of pure and GaN doped ZnO nanocrystallines on Si(111) substrates by KrF excimer laser. The targets for the ablation have been prepared by conventional ceramic method. The fabricated nanocrystallines have been investigated by X-ray diffraction, photoluminescence and atomic force microscopy. The X-ray diffraction analysis shows that the crystalline size of pure ZnO is 36 nm and it is 41 nm while doped with 0.8 mol% of GaN due to best stoichiometry between Zn and O. Photoluminescence studies reveal that intense deep level emissions have been observed for pure ZnO and it has been suppressed for the GaN doped ZnO structures. The images of atomic force microscope show that the rms surface roughness is 27 nm for pure ZnO and the morphology is improved with decrease in rms roughness, 18 nm with fine crystallines while doped with 1 mol% GaN. The improved structural, optical and morphological properties of ZnO nanocrystalline due to GaN dopant have been discussed in detail.

Zinc oxide nanoparticles exhibit cytotoxicity and genotoxicity through oxidative stress responses in human lung fibroblasts and Drosophila melanogaster

PubMed Central

Ng, Cheng Teng; Yong, Liang Qing; Hande, Manoor Prakash; Ong, Choon Nam; Yu, Liya E; Bay, Boon Huat; Baeg, Gyeong Hun

2017-01-01

Background Although zinc oxide nanoparticles (ZnO NPs) have been widely used, there has been an increasing number of reports on the toxicity of ZnO NPs. However, study on the underlying mechanisms under in vivo conditions is insufficient. Methods In this study, we investigated the toxicological profiles of ZnO NPs in MRC5 human lung fibroblasts in vitro and in an in vivo model using the fruit fly Drosophila melanogaster. A comprehensive study was conducted to evaluate the uptake, cytotoxicity, reactive oxygen species (ROS) formation, gene expression profiling and genotoxicity induced by ZnO NPs. Results For in vitro toxicity, the results showed that there was a significant release of extracellular lactate dehydrogenase and decreased cell viability in ZnO NP-treated MRC5 lung cells, indicating cellular damage and cytotoxicity. Generation of ROS was observed to be related to significant expression of DNA Damage Inducible Transcript (DDIT3) and endoplasmic reticulum (ER) to nucleus signaling 1 (ERN1) genes, which are ER stress-related genes. Oxidative stress induced DNA damage was further verified by a significant release of DNA oxidation product, 8-hydroxydeoxyguanosine (8-OHdG), as well as by the Comet assay. For the in vivo study using the fruit fly D. melanogaster as a model, significant toxicity was observed in F1 progenies upon ingestion of ZnO NPs. ZnO NPs induced significant decrease in the egg-to-adult viability of the flies. We further showed that the decreased viability is closely associated with ROS induction by ZnO NPs. Removal of one copy of the D. melanogaster Nrf2 alleles further decreased the ZnO NPs-induced lethality due to increased production of ROS, indicating that nuclear factor E2-related factor 2 (Nrf2) plays important role in ZnO NPs-mediated ROS production. Conclusion The present study suggests that ZnO NPs induced significant oxidative stress-related cytotoxicity and genotoxicity in human lung fibroblasts in vitro and in D. melanogaster in vivo. More extensive studies would be needed to verify the safety issues related to increased usage of ZnO NPs by consumers. PMID:28280330

Zinc oxide nanoparticles exhibit cytotoxicity and genotoxicity through oxidative stress responses in human lung fibroblasts and Drosophila melanogaster.

PubMed

Ng, Cheng Teng; Yong, Liang Qing; Hande, Manoor Prakash; Ong, Choon Nam; Yu, Liya E; Bay, Boon Huat; Baeg, Gyeong Hun

2017-01-01

Although zinc oxide nanoparticles (ZnO NPs) have been widely used, there has been an increasing number of reports on the toxicity of ZnO NPs. However, study on the underlying mechanisms under in vivo conditions is insufficient. In this study, we investigated the toxicological profiles of ZnO NPs in MRC5 human lung fibroblasts in vitro and in an in vivo model using the fruit fly Drosophila melanogaster . A comprehensive study was conducted to evaluate the uptake, cytotoxicity, reactive oxygen species (ROS) formation, gene expression profiling and genotoxicity induced by ZnO NPs. For in vitro toxicity, the results showed that there was a significant release of extracellular lactate dehydrogenase and decreased cell viability in ZnO NP-treated MRC5 lung cells, indicating cellular damage and cytotoxicity. Generation of ROS was observed to be related to significant expression of DNA Damage Inducible Transcript ( DDIT3 ) and endoplasmic reticulum (ER) to nucleus signaling 1 ( ERN1 ) genes, which are ER stress-related genes. Oxidative stress induced DNA damage was further verified by a significant release of DNA oxidation product, 8-hydroxydeoxyguanosine (8-OHdG), as well as by the Comet assay. For the in vivo study using the fruit fly D. melanogaster as a model, significant toxicity was observed in F1 progenies upon ingestion of ZnO NPs. ZnO NPs induced significant decrease in the egg-to-adult viability of the flies. We further showed that the decreased viability is closely associated with ROS induction by ZnO NPs. Removal of one copy of the D. melanogaster Nrf2 alleles further decreased the ZnO NPs-induced lethality due to increased production of ROS, indicating that nuclear factor E2-related factor 2 (Nrf2) plays important role in ZnO NPs-mediated ROS production. The present study suggests that ZnO NPs induced significant oxidative stress-related cytotoxicity and genotoxicity in human lung fibroblasts in vitro and in D. melanogaster in vivo. More extensive studies would be needed to verify the safety issues related to increased usage of ZnO NPs by consumers.

Interfaces between hexagonal and cubic oxides and their structure alternatives

DOE PAGES

Zhou, Hua; Wu, Lijun; Wang, Hui-Qiong; ...

2017-11-14

Multi-layer structure of functional materials often involves the integration of different crystalline phases. The film growth orientation thus frequently exhibits a transformation, owing to multiple possibilities caused by incompatible in-plane structural symmetry. Nevertheless, the detailed mechanism of the transformation has not yet been fully explored. Here we thoroughly probe the heteroepitaxially grown hexagonal zinc oxide (ZnO) films on cubic (001)-magnesium oxide (MgO) substrates using advanced scanning transition electron microscopy, X-ray diffraction and first principles calculations, revealing two distinct interface models of (001) ZnO/(001) MgO and (100) ZnO/(001) MgO. Here we have found that the structure alternatives are controlled thermodynamically bymore » the nucleation, while kinetically by the enhanced Zn adsorption and O diffusion upon the phase transformation. Finally, this work not only provides a guideline for the interface fabrication with distinct crystalline phases but also shows how polar and non-polar hexagonal ZnO films might be manipulated on the same cubic substrate.« less

Mode of bindings of zinc oxide nanoparticles to myoglobin and horseradish peroxidase: A spectroscopic investigations

NASA Astrophysics Data System (ADS)

Mandal, Gopa; Bhattacharya, Sudeshna; Ganguly, Tapan

2011-07-01

The interactions between two heme proteins myoglobin (HMb) and horseradish peroxidase (HRP) with zinc oxide (ZnO) nanoparticles are investigated by using UV-vis absorption, steady state fluorescence, synchronous fluorescence, time-resolved fluorescence, FT-IR, atomic force microscopy (AFM) and circular dichroism (CD) techniques under physiological condition of pH˜7.4. The presence of mainly static mode in fluorescence quenching mechanism of HMb and HRP by ZnO nanoparticle indicates the possibility of formation of ground state complex. The processes of bindings of ZnO nanoparticles with the two proteins are spontaneous molecular interaction procedures. In both cases hydrogen bonding plays a major role. The circular dichroism (CD) spectra reveal that a helicity of the proteins is reduced by increasing ZnO nanoparticle concentration although the α-helical structures of HMb and HRP retain their identity. On binding to the ZnO nanoparticles the secondary structure of HRP molecules (or HMb molecules) remains unchanged while there is a substantial change in the environment of the tyrosin active site in case of HRP molecules and tryptophan active site in case of HMb molecules. Tapping mode atomic force microscopy (AFM) was applied for the investigation the structure of HRP adsorbed in the environment of nanoparticles on the silicon and on the bare silicon. HRP molecules adsorb and aggregate on the mica with ZnO nanoparticle. The aggregation indicates an attractive interaction among the adsorbed molecules. The molecules are randomly distributed on the bare silicon wafer. The adsorption of HRP in the environment of ZnO nanoparticle changes drastically the domains due to a strong interaction between HRP and ZnO nanoparticles. Similar situation is observed in case of HMb molecules. These findings demonstrate the efficacy of biomedical applications of ZnO nanoparticles as well as in elucidating their mechanisms of action as drugs in both human and plant systems.

Influence of rare earth ions on microstructural and optical properties of ZnO nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riyajuddin, Sk., E-mail: riyaj5303@gmail.com; Ahmad, Shabbir; Faizan, M.

2016-05-23

Pure and 3% rare earth ions (Nd{sup 3+} & Gd{sup 3+}) doped ZnO samples were synthesized by sol-gel method, followed by annealing at temperature 450°C for 2hr. The samples were characterized by XRD, FTIR and UV-visible spectroscopy. XRD result confirmed single phase nature of all samples with crystalline structure. The average crystallite size of the doped samples found to be decreases as caculated using Debye-Scherrer’s formula. FTIR spectra indicate absorption band centered at 464 cm{sup −1} which is attributed to Zn-O lattice vibration. It confirms the formaton of compounds. UV-visible spectroscopy was used to study the optical properties and band gapmore » of the synthesised materials using Tauc’s relation.« less

Growth of pure ZnO thin films prepared by chemical spray pyrolysis on silicon

NASA Astrophysics Data System (ADS)

Ayouchi, R.; Martin, F.; Leinen, D.; Ramos-Barrado, J. R.

2003-01-01

Structural, morphological, optical and electrical properties of ZnO thin films prepared by chemical spray pyrolysis from zinc acetate (Zn(CH 3COO) 2 2H 2O) aqueous solutions, on polished Si(1 0 0), and fused silica substrates for optical characterization, have been studied in terms of deposition time and substrate temperature. The growth of the films present three regimes depending on the substrate temperature, with increasing, constant and decreasing growth rates at lower, middle, and higher-temperature ranges, respectively. Growth rate higher than 15 nm min -1 can be achieved at Ts=543 K. ZnO film morphological and electrical properties have been related to these growth regimes. The films have been characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy.

Growth and characterization of textured well-faceted ZnO on planar Si(100), planar Si(111), and textured Si(100) substrates for solar cell applications.

PubMed

Tsai, Chin-Yi; Lai, Jyong-Di; Feng, Shih-Wei; Huang, Chien-Jung; Chen, Chien-Hsun; Yang, Fann-Wei; Wang, Hsiang-Chen; Tu, Li-Wei

2017-01-01

In this work, textured, well-faceted ZnO materials grown on planar Si(100), planar Si(111), and textured Si(100) substrates by low-pressure chemical vapor deposition (LPCVD) were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and cathode luminescence (CL) measurements. The results show that ZnO grown on planar Si(100), planar Si(111), and textured Si(100) substrates favor the growth of ZnO(110) ridge-like, ZnO(002) pyramid-like, and ZnO(101) pyramidal-tip structures, respectively. This could be attributed to the constraints of the lattice mismatch between the ZnO and Si unit cells. The average grain size of ZnO on the planar Si(100) substrate is slightly larger than that on the planar Si(111) substrate, while both of them are much larger than that on the textured Si(100) substrate. The average grain sizes (about 10-50 nm) of the ZnO grown on the different silicon substrates decreases with the increase of their strains. These results are shown to strongly correlate with the results from the SEM, AFM, and CL as well. The reflectance spectra of these three samples show that the antireflection function provided by theses samples mostly results from the nanometer-scaled texture of the ZnO films, while the micrometer-scaled texture of the Si substrate has a limited contribution. The results of this work provide important information for optimized growth of textured and well-faceted ZnO grown on wafer-based silicon solar cells and can be utilized for efficiency enhancement and optimization of device materials and structures, such as heterojunction with intrinsic thin layer (HIT) solar cells.

Influence of Co doping on combined photocatalytic and antibacterial activity of ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Anandan, M.; Dinesh, S.; Krishnakumar, N.; Balamurugan, K.

2016-11-01

The present work aims to investigate the structural, optical, photocatalyst and antibacterial properties of bare and cobalt doped ZnO nanoparticles (NPs) with different concentrations Zn1-x Co x O (x = 0, 0.03, 0.06 and 0.09) synthesized by co-precipitation method. The XRD patterns confirmed that all samples of cobalt doped ZnO nanostructures revealed the formation of single phase having hexagonal wurtzite structure with crystallite size in the range of 31-41 nm. Further, the decreasing trend in lattice parameters and grain sizes were also seen with increasing doping concentrations which confirms the incorporation of Co ions into the ZnO lattice. This result was further supported by the FT-IR data. HR-TEM images demonstrated the distinct hexagonal like morphology with small agglomeration. The UV-visible absorption spectra exhibits red shift with increase in Co doping concentration in ZnO while corresponding bandgap energy of cobalt doped ZnO NPs decreased with increased Co doping concentration. PL spectra showed a weak UV and visible emission band which may be ascribed to the reduction in oxygen vacancy and defects by cobalt doping. XPS and EDX spectral results confirm the composition and the purity of Co doped ZnO NPs. Furthermore, the Co doped ZnO NPs were found to exhibit lesser photocatalytic activity for the degradation of methyl green dye under UV light illumination in comparison with the bare ZnO NPs. Moreover, anti-bacterial studies reveals that the Co doped ZnO NPs possess more antibacterial effect against gram positive Basillus subtills and gram negative Klebsiella pneumoniae bacterial strains than the bare ZnO NPs.

Defect-induced ferromagnetism in ZnO nanoparticles prepared by mechanical milling

NASA Astrophysics Data System (ADS)

Phan, The-Long; Zhang, Y. D.; Yang, D. S.; Nghia, N. X.; Thanh, T. D.; Yu, S. C.

2013-02-01

Though ZnO is known as a diamagnetic material, recent studies have revealed that its nanostructures can be ferromagnetic (FM). The FM origin has been ascribed to intrinsic defects. This work shines light on an alternate method based on mechanical milling to induce defect-related ferromagnetism in ZnO nanoparticles (NPs) from initial diamagnetic ZnO powders. Our idea is motivated by the fact that mechanical milling introduces more defects to a ground material. We point out that the FM order increases with increasing the density of defects in ZnO NPs. The experimental results obtained from analyzing X-ray absorption, electron spin resonance, and Raman scattering spectra demonstrate that the ferromagnetism in ZnO NPs is due to intrinsic defects mainly related to oxygen and zinc vacancies. Among these, zinc vacancies play a decisive role in introducing a high FM order in ZnO NPs.

Local structure analysis of diluted magnetic semiconductor Co and Al co-doped ZnO nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hyodo, K.; Morimoto, S.; Yamazaki, T.

2016-02-01

In this study, Co and Al ions co-doped ZnO nanoparticles (Zn(Al, Co)O NPs) were prepared by our original chemical preparation method. The obtained samples prepared by this method, were encapsulated in amorphous SiO{sub 2}. X-ray diffraction (XRD) results showed Zn(Al, Co)O NPs had a single-phase nature with hexagonal wurtzite structure. These particle sizes could be controlled to be approximately 30 nm. We investigate the effect that the increase in the carrier has on the magnetization by doping Al to Co-doped ZnO NPs. The local structures were qualitatively analyzed using X-ray absorption fine structure (XAFS) measurements.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Shuning; Roy, Amitava; Lichtenberg, Henning

The micro-segmented flow technique was applied for continuous synthesis of ZnO micro- and nanoparticles with short residence times of 9.4 s and 21.4 s, respectively. The obtained particles were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Small angle X-ray scattering (SAXS) and photoluminescence spectroscopy were used to determine the size and optical properties of ZnO nanoparticles. In addition, extended X-ray absorption fine structure (EXAFS) spectroscopy was employed to investigate local structural properties. The EXAFS measurements reveal a larger degree of structural disorder in the nanoparticles than the microparticles. These structural changes should be taken into considerationmore » while evaluating the size-dependent visible emission of ZnO nanoparticles.« less

Lowest-energy cage structures of medium-sized ( ZnO )n clusters with n = 15 - 24

NASA Astrophysics Data System (ADS)

Tang, Lingli; Sai, Linwei; Zhao, Jijun; Qiu, Ruifeng

2015-01-01

Fullerene-like cage structures of medium-sized ( ZnO )n clusters with n = 15 - 24 were generated by spiral algorithm and optimized using density functional theory calculations. Most of these lowest-energy cage structures contain only four-membered and six-membered rings, whereas eight-membered rings were found in the lowest-energy cages of ( ZnO )n (n = 19, 20, 23, 24). Our best cage configurations either reproduce or prevail the previously reported ones. The size-dependent electronic properties were also discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu Changle; Qiao Xueliang; Luo Langli

Flower-like ZnO nano/microstructures have been synthesized by thermal treatment of Zn(NH{sub 3}){sub 4}{sup 2+} precursor in aqueous solvent, using ammonia as the structure directing agent. A number of techniques, including X-ray diffraction (XRD), field emission scan electron microscopy (FESEM), transmission electron microscopy (TEM), thermal analysis, and photoluminescence (PL) were used to characterize the obtained ZnO structures. The photoluminescence (PL) measurements indicated that the as-synthesized ZnO structures showed UV ({approx}375 nm), blue ({approx}465 nm), and yellow ({approx}585 nm) emission bands when they were excited by a He-Gd laser using 320 nm as the excitation source. Furthermore, it has been interestingly foundmore » that the intensity of light emission at {approx}585 nm remarkably decreased when the obtained ZnO nanocrystals were annealed at 600 deg. C for 3 h in air. The reason might be the possible oxygen vacancies and interstitials in the sample decreased at high temperature.« less

Evolution of crystal structure during the initial stages of ZnO atomic layer deposition

DOE PAGES

Boichot, R.; Tian, L.; Richard, M. -I.; ...

2016-01-05

In this study, a complementary suite of in situ synchrotron X-ray techniques is used to investigate both structural and chemical evolution during ZnO growth by atomic layer deposition. Focusing on the first 10 cycles of growth, we observe that the structure formed during the coalescence stage largely determines the overall microstructure of the film. Furthermore, by comparing ZnO growth on silicon with a native oxide with that on Al 2O 3(001), we find that even with lattice-mismatched substrates and low deposition temperatures, the crystalline texture of the films depend strongly on the nature of the interfacial bonds.

The transformation of ZnO submicron dumbbells into perfect hexagonal tubular structures using CBD: a post treatment route.

PubMed

Borade, P; Joshi, K U; Gokarna, A; Lerondel, G; Jejurikar, S M

2016-01-15

In this paper, we report the synthesis of dumbbell-shaped ZnO structures and their subsequent transformation into perfect hexagonal tubes by the extended chemical bath deposition (CBD) method, retaining all advantages such as reproducibility, simplicity, quickness and economical aspect. Well-dispersed sub-micron-sized dumbbell-shaped ZnO structures were synthesized on a SiO2/Si substrate by the CBD method. As an extension of the CBD process the synthesized ZnO dumbbells were exposed to the evaporate coming out of the chemical bath for a few minutes (simply by adjusting the height of the deposit so that it remained just above the solution) to convert them into hexagonal tubes via the dissolution process. The possible dissolution mechanism responsible for the observed conversion is discussed. The optical properties (photo-luminescence) recorded at low temperature on both the structures showed an intense, sharp excitonic peak located at ∼370 nm. The improved intensity and low FWHM of the UV peak observed in the hexagonal tubular structures assures high optical quality, and hence can be used for optoelectronic applications.

Ascorbic-acid-assisted growth of high quality M@ZnO: a growth mechanism and kinetics study.

PubMed

Yang, Yun; Han, Shuhua; Zhou, Guangju; Zhang, Lijie; Li, Xingliang; Zou, Chao; Huang, Shaoming

2013-12-07

We present a general route for synthesizing M@ZnO nanoparticles (NPs) by using ascorbic acid (AA) to induce deposition of ZnO on various shaped and structured cationic-surfactant-capped NP surfaces (noble, magnetic, semiconductor, rod-like, spherical, cubic, dendrite, alloy, core@shell). The results show that the complexing (AA and Zn(2+)) and cooperative effects (AA and CTAB) play important roles in the formation of polycrystalline ZnO shells. Besides, the growth kinetics of M@ZnO was systematically studied. It was found that the slow growth rate favors the successful formation of uniform core@ZnO NPs with relatively loose shells. An appropriate growth rate allows achieving high quality M@ZnO NPs with dense shells. However, very fast growth causes significant additional nucleation and the formation of pure ZnO NPs. This general method is suitable for preparing M@ZnO using seed NPs prepared in both water and organic phases. It might be an alternative route for functionalizing NPs for bioapplications (ZnO is biocompatible), modulating material properties as designed, or synthesizing template materials for building other nanostructures.

Structural classification of RAO3( MO) n compounds ( R =Sc, In, Y, or lanthanides; A =Fe(III), Ga, Cr, or Al; M =divalent cation; n = 1-11)

NASA Astrophysics Data System (ADS)

Kimizuka, Noboru; Mohri, Takahiko

1989-01-01

A series of new compounds RAO3( MO) n ( n = 1-11) having spinel, YbFe 2O 4, or InFeO 3(ZnO) n types of structures were newly synthesized ( R =Sc, In, Y, Lu, Yb, Tm, or Er; A =Fe(III), Ga, Cr, or Al; M =Mg, Mn, Fe(II), Co, Ni, Zn, or Cd) at elevated temperatures. The conditions of synthesis and the lattice constants for these compounds are reported. The stacking sequences of the InO 1.5, (FeZn)O 2.5, and ZnO layers for InFeO 3(ZnO) 10 and the TmO 1.5, (AlZn)O 2.5, and ZnO layers for TmAlO 3(ZnO) 11 are presented, respectively. The crystal structures of the( RAO3) m( MO) n phases ( R =Sc, In, Y, or lanthanide elements; A =Fe(III), Ga, Cr, or Al; M =divalent cation elements; m and n =integer) are classified into four crystal structure types (K 2NiF 4, CaFe 2O 4, YbFe 2O 4, and spinel), based upon the constituent cations R, A, and M

Surface potential driven dissolution phenomena of [0 0 0 1]-oriented ZnO nanorods grown from ZnO and Pt seed layers

NASA Astrophysics Data System (ADS)

Seo, Youngmi; Kim, Jung Hyeun

2011-06-01

Highly oriented ZnO nanorods are synthesized hydrothermally on ZnO and Pt seed layers, and they are dissolved in KOH solution. The rods grown on ZnO seed layer show uniform dissolution, but those grown on Pt seed layer are rod-selectively dissolved. The ZnO nanorods from both seed layers show the same crystalline structure through XRD and Raman spectrometer data. However, the surface potential analysis reveals big difference for ZnO and Pt seed cases. The surface potential distribution is very uniform for the ZnO seed case, but it is much fluctuated on the Pt seed case. It suggests that the rod-selective dissolution phenomena on Pt seed case are likely due to the surface energy difference.

Fabrication of Flower-like ZnO Micro/Nanostructures for Photodegradation of Pre-treated Palm Oil Mill Effluent

NASA Astrophysics Data System (ADS)

Lam, Sze-Mun; Wong, Kok-Ann; Sin, Jin-Chung

2018-01-01

Flower-like ZnO micro/nanostructures were fabricated by a simple and surfactant-free reflux method. X-ray diffraction findings showed that the prepared ZnO product was highly crystallite with hexagonal wurtzite structure. The band gap energy of ZnO sample was measured to be 3.18 eV via an optical reflectance spectrum. The flower-like morphological features of ZnO micro/nanostructures were witnessed through field-emission scanning electron microscopy. Such micro/nanoparticles could be used in the photodegradation of pre-treated palm oil mil effluent (POME) under UV irradiation.

Structural, morphological, optical and biological properties of pure ZnO and agar/zinc oxide nanocomposites.

PubMed

Magesh, G; Bhoopathi, G; Nithya, N; Arun, A P; Ranjith Kumar, E

2018-05-26

In this work, ZnO nanoparticles were prepared by in situ chemical precipitation method in the presence of Agar biopolymer. The influence of Agar concentrations on the structural, morphological and optical properties of ZnO have been investigated. The XRD pattern of Pure ZnO and Agar/ZnO nanocomposites indicates the hexagonal wurtzite phase of ZnO. The crystallite size of pure ZnO and Agar/ZnO nanocomposites was found to be in the range of 35.5 to 19.73 nm. Pure ZnO and Agar/ZnO nanocomposites showed nanospheroid and nanopaddy shaped morphology from FESEM studies. The interplanar distance observed from the HRTEM image confirms the plane of the prepared material. The elemental composition of the samples were characterized by EDX. The optical properties of Pure ZnO and Agar/ZnO nanocomposites were characterized by UV, FTIR and PL. The band gap of Agar/ZnO nanocomposites were varied with the Agar concentration. Oxygen vacancy induced photoluminescence of ZnO are observed and its intensity is found to be increased linearly with the Agar concentration. The antibacterial activity of ZnO and Agar/ZnO nanocomposites was evaluated by disc diffusion method against Gram-positive (B.subtilis) and Gram-negative (P. aeruginosa) bacteria. The cytotoxicity of Agar/ZnO nanocomposites was studied against Normal (L929) and Breast cancer cell line (MB231). The result of this investigation reveals that the Agar/ZnO nanocomposites deliver a dose dependent toxicity in normal and cancer cell line. Copyright © 2018. Published by Elsevier B.V.

Hydrothermal-electrochemical growth of heterogeneous ZnO: Co films

NASA Astrophysics Data System (ADS)

Yilmaz, Ceren; Unal, Ugur

2017-10-01

This study demonstrates the preparation of heterogeneous ZnO: Co nanostructures via hydrothermal-electrochemical deposition at 130 °C and -1.1 V (vs Ag/AgCl (satd)) in dimethyl sulfoxide (DMSO)-H2O mixture. Under the stated conditions, ZnO: Co nanostructures grow preferentially along (002) direction. Strength of directional growth progressively increases with the increasing concentration of Co(II) in the deposition bath. Films are composed of hexagonal Wurtzite ZnO, metallic cobalt, and mixed cobalt oxide on the surface and cobalt(II) oxide in deeper levels. Increasing the Co(II) concentration in the deposition bath results in different morphological features as well as phase separation. Platelets, sponge-like structures, cobalt-rich spheres, microislands of cobalt-rich spheres which are interconnected by ZnO network can be synthesized by adjusting [Co(II)]: [Zn(II)] ratio. Growth mechanisms giving rise to these particular structures, surface morphology, crystal structure, phase purity, chemical binding characteristics, and optical properties of the deposits are discussed in detail.

The photocatalytic investigation of methylene blue dye with Cr doped zinc oxide nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ray, Rajeev; Kumar, Ashavani, E-mail: ashavani@yahoo.com

2015-08-28

The present work reports eco-friendly and cost effective sol-gel technique for synthesis of Chromium doped ZnO nanoparticles at room temperature. In this process Zinc nitrate, Chromium nitrate were used as precursor. Structural as well as optical properties of Cr induced ZnO samples were analysed by X-ray diffraction technique (XRD), SEM, PL and UV-Visible spectroscopy (UV-Vis) respectively. XRD analysis shows that the samples have hexagonal (wurtzite) structure with no additional peak which suggests that Cr ions fit into the regular Zn sites of ZnO crystal structure. By using Scherrer’s formula for pure and Cr doped ZnO samples the average grain sizemore » was found to be 32 nm. Further band gap of pure and doped ZnO samples have been calculated by using UV-Vis spectra. The photo-catalytic degradation of methyl blue dye under UV irradiation was examined for synthesized samples. The results show that the concentration plays an important role in photo-catalytic activity.« less

Defect-driven interfacial electronic structures at an organic/metal-oxide semiconductor heterojunction.

PubMed

Winget, Paul; Schirra, Laura K; Cornil, David; Li, Hong; Coropceanu, Veaceslav; Ndione, Paul F; Sigdel, Ajaya K; Ginley, David S; Berry, Joseph J; Shim, Jaewon; Kim, Hyungchui; Kippelen, Bernard; Brédas, Jean-Luc; Monti, Oliver L A

2014-07-16

The electronic structure of the hybrid interface between ZnO and the prototypical organic semiconductor PTCDI is investigated via a combination of ultraviolet and X-ray photoelectron spectroscopy (UPS/XPS) and density functional theory (DFT) calculations. The interfacial electronic interactions lead to a large interface dipole due to substantial charge transfer from ZnO to 3,4,9,10-perylenetetracarboxylicdiimide (PTCDI), which can be properly described only when accounting for surface defects that confer ZnO its n-type properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultra-Fast Microwave Synthesis of ZnO Nanorods on Cellulose Substrates for UV Sensor Applications

PubMed Central

Pimentel, Ana; Samouco, Ana; Araújo, Andreia; Martins, Rodrigo; Fortunato, Elvira

2017-01-01

In the present work, tracing and Whatman papers were used as substrates to grow zinc oxide (ZnO) nanostructures. Cellulose-based substrates are cost-efficient, highly sensitive and environmentally friendly. ZnO nanostructures with hexagonal structure were synthesized by hydrothermal under microwave irradiation using an ultrafast approach, that is, a fixed synthesis time of 10 min. The effect of synthesis temperature on ZnO nanostructures was investigated from 70 to 130 °C. An Ultra Violet (UV)/Ozone treatment directly to the ZnO seed layer prior to microwave assisted synthesis revealed expressive differences regarding formation of the ZnO nanostructures. Structural characterization of the microwave synthesized materials was carried out by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The optical characterization has also been performed. The time resolved photocurrent of the devices in response to the UV turn on/off was investigated and it has been observed that the ZnO nanorod arrays grown on Whatman paper substrate present a responsivity 3 times superior than the ones grown on tracing paper. By using ZnO nanorods, the surface area-to-volume ratio will increase and will improve the sensor sensibility, making these types of materials good candidates for low cost and disposable UV sensors. The sensors were exposed to bending tests, proving their high stability, flexibility and adaptability to different surfaces. PMID:29140304

The magnetic and adsorption properties of ZnO1-xSx nanoparticles.

PubMed

Zhang, Huiyun; Liu, Guixian; Cao, Yanqiang; Chen, Jing; Shen, Kai; Kumar, Ashwini; Xu, Mingxiang; Li, Qi; Xu, Qingyu

2017-10-11

Sulfur is easy to be incorporated into ZnO nanoparticles by the solution-combustion method. Herein, the magnetic and adsorption properties of a series of ZnO 1-x S x (x = 0, 0.05, 0.1, 0.15, and 0.2) nanoparticles were systematically investigated. The X-ray diffraction patterns show that the as-prepared ZnO 1-x S x nanoparticles have the hexagonal wurtzite structure of ZnO with a low sulfur content that gradually transforms into the zinc blende structure of ZnS when the x value is greater than 0.1. PL spectra show several bands due to different transitions, which have been explained by the recombination of free excitons or defect-induced transitions. The introduction of sulfur not only modifies the bandgap of ZnO, but also impacts the concentration of Zn vacancies. The as-prepared ZnO shows weak room-temperature ferromagnetism, and the incorporation of sulfur improves the ferromagnetism owing to the increased concentration of Zn vacancies, which may be stabilized by the doped sulfur ions. The adsorption capability of ZnO 1-x S x nanoparticles has been significantly improved, and the process can be well described by the pseudo-first-order kinetic model and the Freundlich isotherm model. The mechanism has been confirmed to be due to the active sulfate groups existing in zinc oxysulfide nanoparticles.

Sol–gel synthesized zinc oxide nanorods and their structural and optical investigation for optoelectronic application

PubMed Central

2014-01-01

Nanostructured zinc oxide (ZnO) nanorods (NRs) with hexagonal wurtzite structures were synthesized using an easy and low-cost bottom-up hydrothermal growth technique. ZnO thin films were prepared with the use of four different solvents, namely, methanol, ethanol, isopropanol, and 2-methoxyethanol, and then used as seed layer templates for the subsequent growth of the ZnO NRs. The influences of the different solvents on the structural and optical properties were investigated through scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, and photoluminescence. The obtained X-ray diffraction patterns showed that the synthesized ZnO NRs were single crystals and exhibited a preferred orientation along the (002) plane. In addition, the calculated results from the specific models of the refractive index are consistent with the experimental data. The ZnO NRs that grew from the 2-methoxyethanol seeded layer exhibited the smallest grain size (39.18 nm), largest diffracted intensities on the (002) plane, and highest bandgap (3.21 eV). PMID:25221458

Effect of mesa structure formation on the electrical properties of zinc oxide thin film transistors.

PubMed

Singh, Shaivalini; Chakrabarti, P

2014-05-01

ZnO based bottom-gate thin film transistor (TFT) with SiO2 as insulating layer has been fabricated with two different structures. The effect of formation of mesa structure on the electrical characteristics of the TFTs has been studied. The formation of mesa structure of ZnO channel region can definitely result in better control over channel region and enhance value of channel mobility of ZnO TFT. As a result, by fabricating a mesa structured TFT, a better value of mobility and on-state current are achieved at low voltages. A typical saturation current of 1.85 x 10(-7) A under a gate bias of 50 V is obtained for non mesa structure TFT while for mesa structured TFT saturation current of 5 x 10(-5) A can be obtained at comparatively very low gate bias of 6.4 V.

Fabrication of ZnO Nanowire Based Piezoelectric Generators and Related Structures

NASA Astrophysics Data System (ADS)

Opoku, Charles; Dahiya, Abhishek Singh; Oshman, Christopher; Cayrel, Frederic; Poulin-Vittrant, Guylaine; Alquier, Daniel; Camara, Nicolas

Using vertically grown hydrothermal ZnO nanowires, we demonstrate the assembly of fully functional piezoelectric energy harvesters on plastics substrates. A seedless hydrothermal process is employed for the growth of single crystalline vertically orientated ZnO NWs at around 100oC. Flexible NG are assembled using ∼7 μm thick PDMS polymer matrix on a 3x3cm substrate. A representative device with an active area of 4cm2 is characterised revealing average output voltage generation of ∼22mV (±1.2) and -32mV (±0.16) in the positive and negative cycles after 3-4mm periodic deflection at 20Hz. A power density of ∼288nW/cm3 is estimated for the device. It is envisaged that such energy scavengers may find potential applications targeting self-powered systems, sensors and on-body charging of electronics.

Thickness dependence of crystal and optical characterization on ZnO thin film grown by atomic layer deposition

NASA Astrophysics Data System (ADS)

Baek, Seung-Hye; Lee, Hyun-Jin; Lee, Sung-Nam

2018-06-01

We studied the thickness dependence of the crystallographic and optical properties of ZnO thin films grown on c-plane sapphire substrate using atomic layer deposition. High-resolution X-ray diffraction (HR-XRD) revealed two peaks at 34.5° and 36.2° in the initial growth stage of ZnO on the sapphire substrate, corresponding to the (002) and (101) ZnO planes, respectively. However, as the thickness of the ZnO film increased, the XRD intensity of the (002) ZnO peak increased drastically, compared with that of the (101) ZnO peak. This indicated that (002) and (101) ZnO were simultaneously grown on the c-plane sapphire substrate in the initial growth stage, and that (002) ZnO was predominantly grown with the increase in the thickness of ZnO film. The ZnO thin film presented an anisotropic surface structure at the initial stage, whereas the isotropic surface morphology was developed with an increase in the film thickness of ZnO. These observations were consistent with the HR-XRD results.

Synthesis of nanocrystalline NiO/ZnO heterostructured composite powders by sol-gel auto combustion method and their characterizations

NASA Astrophysics Data System (ADS)

Tangcharoen, Thanit; Klysubun, Wantana; Kongmark, Chanapa

2018-03-01

Nanocrystalline NiO/ZnO heterostructured composite powders were prepared by the sol-gel auto combustion method, based on nickel and zinc nitrate precursors and using diethanolamine (DEA) as novel fuel. The composition of different NiO and ZnO ratios, ranging from 100/0, 95/5, 90/10, 80/20, 60/40, 50/50, 40/60, 20/80, 10/90, 5/95 to 0/100, were studied. The structural, chemical bonding, morphological, optical, and fluorescence properties including the local atomic structure of each calcined sample were systematically investigated by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), UV-visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence (PL) spectroscopy, and synchrotron X-ray absorption spectroscopy (XAS), respectively. For the ZnO concentration below 20%, both XRD and Raman spectroscopy results revealed only the NiO phase. This conformed to the observation of Zn K-edge and Ni K-edge X-ray absorption near edge structure (XANES). The Zn ions found in the samples of low ZnO concentration exhibited six-fold coordination with oxygen atoms rather than the four-fold coordination found in the wurtzite (WZ) structure of ZnO. In contrast, the Ni ions which are found in the samples of low NiO concentration (≤10%) are coordinated both tetrahedrally and octahedrally by four or six oxygen atoms, respectively, rather than the six-fold coordination which is usually observed for Ni ions in the rock salt (RS) form of NiO. All analytical results obtained from experimental XANES spectra were verified by the theoretical calculation of absorption spectra using the FEFF9.7 code. The UV-DRS results showed that there was an increase in the reflectance efficiency for both infrared and visible light conditions as the content of ZnO increases; meanwhile, the values for the energy gap (Eg) of all composite samples were higher than that of pure NiO and ZnO. In addition, the PL spectra revealed major blue emission bands observed at 490 nm when the excitation wavelength was 300 nm. As the ZnO phase developed, a variety of violet emission bands occurred within the range of 400 nm-450 nm, which was obviously related to the change in Eg. The intrinsic defects occurred in the NiO/ZnO composite powders were probably responsible for this phenomenon.

Gd{sup 3+} incorporated ZnO nanoparticles: A versatile material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Surender, E-mail: surender40@gmail.com; Sahare, P.D.

Graphical abstract: - Highlights: • Chemically synthesized Gd{sup 3+} doped ZnO nanoparticles. • The broad visible emission of the ZnO is dependent on the surface defects and can be tailored by Gd{sup 3+} doing. • PL and magnetic properties are modified by Gd{sup 3+} doping. • Photocatalysis experiment reveals that the ZnO: Gd{sup 3+} degrades the Rh B dye faster than the undoped ZnO. - Abstract: Gd{sup 3+} doped ZnO nanoparticles are synthesized by wet chemical route method and investigated through structural, optical, magnetic and photocatalytic properties. Transmission Electron Microscopy technique has been performed on undoped and Gd{sup 3+} dopedmore » ZnO nanoparticles. X-ray diffraction, X-ray photoelectron spectroscopy and Raman analyses are carried out in order to examine the desired phase formation and substitution of Gd{sup 3+} in the ZnO matrix. Gd{sup 3+} doped ZnO nanoparticles show enhanced photoluminescent and ferromagnetic properties as compared to undoped ZnO. The broad visible emission of ZnO is found to be largely dependent on the surface defects and these surface defects can be tailored by Gd{sup 3+} doping concentration. Furthermore, Gd{sup 3+} doped ZnO nanoparticles also show improved photocatalytic properties as compared with undoped ZnO nanoparticles under ultraviolet irradiation.« less

A hetero-homogeneous investigation of chemical bath deposited Ga-doped ZnO nanorods

NASA Astrophysics Data System (ADS)

Rakhsha, Amir Hosein; Abdizadeh, Hossein; Pourshaban, Erfan; Golobostanfard, Mohammad Reza

2018-01-01

One-dimensional nanostructures of zinc oxide (ZnO) have been in the center of attention, mostly for electronic applications due to their distinctive properties such as high electron mobility (100 cm2V-1s-1) and crystallinity. Thanks to its high density of vacancies and interstitial sites, wurtzite lattice of ZnO is a suitable host for gallium (Ga) as a dopant element. Herein, ZnO nanorod arrays (NRAs) are synthesized by a low-temperature chemical bath deposition (CBD) method with various concentrations of gallium nitrate hydrate as a dopant precursor. Structural and morphological analyses confirm that optimum properties of gallium-doped ZnO (GZO) are obtained at 1% (Ga to Zn molar ratio). Owing to the replacement of smaller Ga3+ ions with Zn2+ ions in the GZO structure, a slight shift of (002) peak to higher angles could be observed in XRD pattern of GZO NRAs. The scanning electron microscope images demonstrate a proliferation in the ZnO NRAs length from 650 nm for undoped ZnO (UZO) to 1200 nm for GZO-1%. However, increasing the dopant concentration above 2.5% results in formation of homogeneous zinc gallium oxide in the bulk solution, which is a sign of inefficient process of doping in GZO NRAs. Furthermore, photoluminescence spectroscopy is used to characterize the band-gap variation of the samples, which demonstrates a small red-shift in the UV emission peak and a decrease in visible emission peak intensity with introducing Ga in ZnO lattice. Lower resistivity for GZO-1% (1.1 MΩ) sample compared to UZO (1.4 MΩ) is recorded, which is compelling evidence for the presence of Ga3+ in ZnO lattice. The results suggest that incorporating Ga into ZnO lattice using CBD method is an easy and effective technique to improve the electrical properties of ZnO NRAs that is an essential factor for a broad range of devices.

Band-Gap Engineering in ZnO Thin Films: A Combined Experimental and Theoretical Study

NASA Astrophysics Data System (ADS)

Pawar, Vani; Jha, Pardeep K.; Panda, S. K.; Jha, Priyanka A.; Singh, Prabhakar

2018-05-01

Zinc oxide thin films are synthesized and characterized using x-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, and optical spectroscopy. Our results reveal that the structural, morphological, and optical properties are closely related to the stress of the sample provided that the texture of the film remains the same. The anomalous results are obtained once the texture is altered to a different orientation. We support this experimental observation by carrying out first-principles hybrid functional calculations for two different orientations of the sample and show that the effect of quantum confinement is much stronger for the (100) surface than the (001) surface of ZnO. Furthermore, our calculations provide a route to enhance the band gap of ZnO by more than 50% compared to the bulk band gap, opening up possibilities for wide-range industrial applications.

Effect of copper doping on the photocatalytic activity of ZnO thin films prepared by sol-gel method

NASA Astrophysics Data System (ADS)

Saidani, T.; Zaabat, M.; Aida, M. S.; Boudine, B.

2015-12-01

In the present work, we prepared undoped and copper doped ZnO thin films by the sol-gel dip coating method on glass substrates from zinc acetate dissolved in a solution of ethanol. The objective of our work is to study the effect of Cu doping with different concentrations on structural, morphological, optical properties and photocatalytic activity of ZnO thin films. For this purpose, we have used XRD to study the structural properties, and AFM to determine the morphology of the surface of the ZnO thin films. The optical properties and the photocatalytic degradation of the films were examined by UV-visibles spectrophotometer. The Tauc method was used to estimate the optical band gap. The XRD spectra indicated that the films have an hexagonal wurtzite structure, which gradually deteriorated with increasing Cu concentration. The results showed that the incorporation of Cu decreases the crystallite size. The AFM study showed that an increase of the concentration of Cu causes the decrease of the surface roughness, which passes from 20.2 for Un-doped ZnO to 12.16 nm for doped ZnO 5 wt% Cu. Optical measurements have shown that all the deposited films show good optical transmittance (77%-92%) in the visible region and increases the optical gap with increasing Cu concentration. The presence of copper from 1% to 5 wt% in the ZnO thin films is found to decelerate the photocatalytic process.

Hybrid structure of polyaniline/ZnO nanograss and its application in dye-sensitized solar cell with performance improvement

NASA Astrophysics Data System (ADS)

Zhu, Shibu; Wei, Wei; Chen, Xiangnan; Jiang, Man; Zhou, Zuowan

2012-06-01

Polyaniline (PANI) hybridized ZnO photoanode for dye-sensitized solar cell (DSSC) was primarily prepared via a two-step process which involved hydrothermal growth of ZnO nanograss on the fluorine-doped tin oxide (FTO) substrate and subsequently chemisorption of PANI on the surfaces of the ZnO nanorods. The PANI hybridized ZnO nanograss films were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectra (FT-IR), and the results indicated that there were chemical interactions between PANI and ZnO. Both pure ZnO nanograss and PANI hybridized ZnO nanograss were applied to DSSC. The results of photoelectrochemical measurement showed that the photocurrent density of PANI (100 mg/L) hybridized ZnO nanograss photoanode was significantly enhanced, and the overall light-conversion efficiency increased by 60%. The electrochemical impedance spectra (EIS) displayed that the electron densities in photoanodes of PANI hybridized ZnO nanograss were larger than that in pure ZnO nanograss. This is ascribed to more effective charge separation and faster interfacial charge transferring occurred in the hybrid photoanode.

The structural and optical properties of Y (Y  =  Al, B, Si and Ti)-doped ZnO nano thin films from the first principles calculations

NASA Astrophysics Data System (ADS)

Zhang, Wenshu; Hu, Huijun; Zhang, Caili; Li, Jianguo; Li, Yuping; Ling, Lixia; Han, Peide

2017-12-01

Based on the density functional theory, the structural stability and optical properties of undoped and Y (Y  =  Al, B, Si and Ti)-doped ZnO nano thin films are investigated. The good stability of the films based on the ZnO (0 0 0 1) can be obtained when the layer is larger than 12. Moreover, the dielectric function, refractive index, absorption, and reflectivity of doped ZnO nano thin films have been analyzed in detail. In the visible light range, the values of ZnO films from 12 to 24 layers are all smaller than those of the bulk. And with the augment of the layers, the values keep increasing. All the results signify that the nano film of 12 layers possesses the lowest reflectivity and weakest absorption. In addition, there is an evident impact of some doped element on the properties of nano films. The absorption and reflectivity of Ti, Si-doped ZnO nano thin films are higher than those of the clean films, while Al, B-doped are lower, especially B-doped. Moreover, the conductivity of the doped structure is better than that of the bulk. Thus, the B-doped ZnO nano thin films could be potential candidate materials of transparent conductive films.

Preparation of "Cauliflower-Like" ZnO Micron-Sized Particles.

PubMed

Gordon, Tamar; Grinblat, Judith; Margel, Shlomo

2013-11-14

Porous polydivinyl benzene (PDVB) microspheres of narrow size distribution were formed by a single-step swelling process of template uniform polystyrene microspheres with divinyl benzene (DVB), followed by polymerization of the DVB within the swollen template microspheres. The PDVB porous particles were then formed by dissolution of the template polystyrene polymer. Unique "cauliflower-like" ZnO microparticles were prepared by the entrapping of the ZnO precursor ZnCl₂ in the PDVB porous microspheres under vacuum, followed by calcination of the obtained ZnCl₂-PDVB microspheres in an air atmosphere. The morphology, crystallinity and fluorescence properties of those ZnO microparticles were characterized. This "cauliflower-like" shape ZnO particles is in contrast to a previous study demonstrated the preparation of spherical shaped porous ZnO and C-ZnO microparticles by a similar method, using zinc acetate (ZnAc) as a precursor. Two diverted synthesis mechanisms for those two different ZnO microparticles structures are proposed, based on studies of the distribution of each of the ZnO precursors within the PDVB microspheres.

Synthesis and characterization of Graphene oxide/Zinc oxide nanorods sandwich structure

NASA Astrophysics Data System (ADS)

Boukhoubza, I.; Khenfouch, M.; Achehboune, M.; Mouthudi, B.; Zorkani, I.; Jorio, A.

2018-03-01

Graphene-ZnO nanostructures composite materials have been used as very efficient candidates for various optoelectronic applications. Nowadays, the composite structure formation of ZnO nanostructures with graphene or graphene oxide is a novel, cost effective and efficient approach to control the morphology, surface defect states, band gap of ZnO nanocrystals. In this paper, we have prepared ZnO nanorods between two layers graphene oxide (GO/ZnO NRs/GO) via a simple hydrothermal method. Their morphology, structural and optical properties have been investigated. The obtained results of our composites GO/ZnO NRs/GO presented here showing an enhancement in the structural and optical properties. Thus may hold great promise to the development of the optoelectronic devices.

Effect of Cu-Dopant on the Structural, Magnetic and Electrical Properties of ZnO

NASA Astrophysics Data System (ADS)

Aryanto, D.; Kurniawan, C.; Subhan, A.; Sudiro, T.; Sebayang, P.; Ginting, M.; Siregar, S. M. K.; Nasruddin, M. N.

2017-05-01

Zn1- x Cu x O (x = 0, 2, 3, and 4 at.%) was synthesized by using solid-state reaction technique. The ZnO and CuO powders were mixed and then milled by using high-speed shaker mill. The influence of Cu dopants on the structure, magnetic, and electrical properties was investigated by using XRD, VSM, and I-V and C-V measurements. The XRD analysis showed that the Zn1- x Cu x O had hexagonal wurtzite polycrystalline. The diffraction intensity decreased and the peak position shifted directly to a higher 2θ angle with increasing the dopant concentration. Furthermore, the lattice parameters decreased when the ZnO was doped with x = 0.04, which indicated that the crystal structure changed. The increase of Cu dopants was believed to affect the magnetic and electrical properties of ZnO.

Influence of stress on the structural and dielectric properties of rf magnetron sputtered zinc oxide thin film

NASA Astrophysics Data System (ADS)

Menon, Rashmi; Sreenivas, K.; Gupta, Vinay

2008-05-01

Highly c axis oriented zinc oxide (ZnO) thin films have been prepared on 1737 Corning glass substrate by planar rf magnetron sputtering under varying pressure (10-50mTorr) and different oxygen percentage (40%-100%) in reactive gas mixtures. The as-grown ZnO thin films were found to have stress over a wide range from -6×1010to-9×107dynes/cm2. The presence of stress depends strongly on processing conditions, and films become almost stress free under a unique combination of sputtering pressure and reactive gas composition. The studies show a correlation of stress with structural and electrical properties of the ZnO thin film. The stressed films possess high electrical conductivity and exhibits strong dielectric dispersion over a wide frequency (1kHz-1MHz). The dielectric constant ɛ'(ω) of stress free ZnO film was almost frequency independent and was close to the bulk value. The measured value of dc conductivity, σdc(ω) and ac conductivity σac(ω) of stress free ZnO film was 1.3×10-9 and 6.8×10-5Ω-1cm-1, respectively. The observed variation in the structural and electrical properties of ZnO thin film with stress has been analyzed in the light of growth kinetics.

Structure evolution of zinc oxide thin films deposited by unbalance DC magnetron sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aryanto, Didik, E-mail: didi027@lipi.go.id; Materials Research Group, Physics Department, Universitas Negeri Semarang, Gunungpati, Semarang 50229 Jawa Tengah; Marwoto, Putut

Zinc oxide (ZnO) thin films are deposited on corning glass substrates using unbalanced DC magnetron sputtering. The effect of growth temperature on surface morphology and crystallographic orientation of ZnO thin film is studied using atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. The surface morphology and crystallographic orientation of ZnO thin film are transformed against the increasing of growth temperature. The mean grain size of film and the surface roughness are inversely and directly proportional towards the growth temperature from room temperature to 300 °C, respectively. The smaller grain size and finer roughness of ZnO thin film are obtainedmore » at growth temperature of 400 °C. The result of AFM analysis is in good agreement with the result of XRD analysis. ZnO thin films deposited in a series of growth temperatures have hexagonal wurtzite polycrystalline structures and they exhibit transformations in the crystallographic orientation. The results in this study reveal that the growth temperature strongly influences the surface morphology and crystallographic orientation of ZnO thin film.« less

Low-Temperature Preparation of Ag-Doped ZnO Nanowire Arrays, DFT Study, and Application to Light-Emitting Diode.

PubMed

Pauporté, Thierry; Lupan, Oleg; Zhang, Jie; Tugsuz, Tugba; Ciofini, Ilaria; Labat, Frédéric; Viana, Bruno

2015-06-10

Doping ZnO nanowires (NWs) by group IB elements is an important challenge for integrating nanostructures into functional devices with better and tuned performances. The growth of Ag-doped ZnO NWs by electrodeposition at 90 °C using a chloride bath and molecular oxygen precursor is reported. Ag acts as an electrocatalyst for the deposition and influences the nucleation and growth of the structures. The silver atomic concentration in the wires is controlled by the additive concentration in the deposition bath and a content up to 3.7 atomic % is reported. XRD analysis shows that the integration of silver enlarges the lattice parameters of ZnO. The optical measurements also show that the direct optical bandgap of ZnO is reduced by silver doping. The bandgap shift and lattice expansion are explained by first principle calculations using the density functional theory (DFT) on the silver impurity integration as an interstitial (Ag(i)) and as a substitute of zinc atom (Ag(Zn)) in the crystal lattice. They notably indicate that Ag(Zn) doping forms an impurity band because of Ag 4d and O 2p orbital interactions, shifting the Fermi level toward the valence band. At least, Ag-doped ZnO vertically aligned nanowire arrays have been epitaxially grown on GaN(001) substrate. The heterostructure has been inserted in a light emitting device. UV-blue light emission has been achieved with a low emission threshold of 5 V and a tunable red-shifted emission spectrum related to the bandgap reduction induced by silver doping of the ZnO emitter material.

Morphology-controllable of Sn doped ZnO nanorods prepared by spray pyrolysis for transparent electrode application

NASA Astrophysics Data System (ADS)

Hameed, M. Shahul; Princice, J. Joseph; Babu, N. Ramesh; Zahirullah, S. Syed; Deshmukh, Sampat G.; Arunachalam, A.

2018-05-01

Transparent conductive Sn doped ZnO nanorods have been deposited at various doping level by spray pyrolysis technique on glass substrate. The structural, surface morphological and optical properties of these films have been investigated with the help of X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM) and UV-Vis spectrophotometer respectively. XRD patterns revealed a successful high quality growth of single crystal ZnO nanorods with hexagonal wurtzite structure having (002) preferred orientation. The scanning electron microscope (SEM) image of the prepared films exposed the uniform distribution of Sn doped ZnO nanorod shaped grains. All these films were highly transparent in the visible region with average transmittance of 90%.

A facile method for synthesis of well-coated ZnO@graphene core/shell structure by self-assembly of amine-functionalized ZnO and graphene oxide

NASA Astrophysics Data System (ADS)

Zhang, Yunlong; Song, Lixin; Zhang, Yuzhi; Wang, Panpan; Liu, Yangqiao; Wu, Lingnan; Zhang, Tao

2016-06-01

The core/shell structure was formed by GO self-assembled with amine-functionalized commercial ZnO (CZO) and preparative hexagonal ZnO (HZO), respectively. Graphene-coated CZO and HZO were obtained after being reduced in Ar at 500 °C. The mechanism of the coating procedure was investigated by measuring their respective zeta potential values. Our characterizations demonstrate that graphene on HZO has better quality and fewer layers. An obvious band gap decrease of ZnO was observed for coating with graphene. Photoluminescence spectra of ZnO@graphene core/shell composites display the fluorescence quenching property, which indicates its good application prospect in optoelectronics, photocatalytic and other fields.

Structural, spectroscopic and anti-microbial inspection of PEG capped ZnO nanoparticles for biomedical applications

NASA Astrophysics Data System (ADS)

Meshram, J. V.; Koli, V. B.; Kumbhar, S. G.; Borde, L. C.; Phadatare, M. R.; Pawar, S. H.

2018-04-01

Zinc oxide (ZnO) nanoparticles (NPs) have a wide range of biomedical applications. Present study demonstrates the new methodology in sol-gel technology for synthesizing Polyethylene glycol (PEG) capped ZnO NPs and its size effect on anti-microbial activity. The reaction time was increased from 1 h to 5 h for the synthesis of ZnO NPs at 130 °C. The size of PEG capped ZnO NPs is increased from 10 to 84 nm by increasing the reaction upto 5 h. The x-ray diffraction studies and transmission electron microscopy analysis reveals the phase purity and hexagonal wurtzite crystal structure with uniform PEG capping on the surface of ZnO NPs. UV–visible spectroscopy exhibits the peak at 366 nm which is attributed to ZnO NPs. No adverse effect is observed in case of absorbance spectroscopy. Further, Fourier transforms infrared spectroscopy and thermo gravimetric analysis depicts the adsorption of PEG molecules on the ZnO NPs surface. The anti-microbial activities for both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria were studied by optical density (OD) mesurement. The remarkable anti-microbial activity was observed for PEG capped ZnO NPs synthesized at 1 h reaction time showing higher activity in comparison with that synthesized from 2 h to 5 h reaction time. The microbial growth was found to be inhibited after 10 h OD measurement for both the bacteria. The anti-microbial activity may be attributed to the generation of ROS and H2O2. However, these generated species plays a vital role in inhibition of microbial growth. Hence, PEG capped ZnO NPs has promising biomedical applications.

Site specific interaction between ZnO nanoparticles and tyrosine: A density functional theory study

NASA Astrophysics Data System (ADS)

Singh, Satvinder; Singh, Janpreet; Singh, Baljinder; Singh, Gurinder; Kaura, Aman; Tripathi, S. K.

2018-05-01

First Principles Calculations have been performed on ZnO/Tyrosine atomic complex to study site specific interaction of Tyrosine and ZnO nanoparticles. Calculated results shows that -COOH group present in Tyrosine is energetically more favorable than -NH2 group. Interactions show ionic bonding between ZnO and Tyrosine. All the calculations have been performed under the Density Functional Theory (DFT) framework. Structural and electronic properties of (ZnO)3/Tyrosine complex have been studied. Gaussian basis set approach has been adopted for the calculations. A ring type most stable (ZnO)3 atomic cluster has been modeled, analyzed and used for the calculations.

Optical properties of P ion implanted ZnO

NASA Astrophysics Data System (ADS)

Pong, Bao-Jen; Chou, Bo-Wei; Pan, Ching-Jen; Tsao, Fu-Chun; Chi, Gou-Chung

2006-02-01

Red and green emissions are observed from P ion implanted ZnO. Red emission at ~680 nm (1.82 eV) is associated with the donor-acceptor pair (DAP) transition, where the corresponding donor and acceptor are interstitial zinc (Zn i) and interstitial oxygen (O i), respectively. Green emission at ~ 516 nm (2.40 eV) is associated with the transition between the conduction band and antisite oxygen (O Zn). Green emission at ~516nm (2.403 eV) was observed for ZnO annealed at 800 oC under ambient oxygen, whereas, it was not visible when it was annealed in ambient nitrogen. Hence, the green emission is most likely not related to oxygen vacancies on ZnO sample, which might be related to the cleanliness of ZnO surface, a detailed study is in progress. The observed micro-strain is larger for N ion implanted ZnO than that for P ion implanted ZnO. It is attributed to the larger straggle of N ion implanted ZnO than that of P ion implanted ZnO. Similar phenomenon is also observed in Be and Mg ion implanted GaN.

Synthesis of Zinc Oxide Nanorods via the Formation of Sea Urchin Structures and Their Photoluminescence after Heat Treatment.

PubMed

Karlsson, Mattias E; Mamie, Yann C; Calamida, Andrea; Gardner, James M; Ström, Valter; Pourrahimi, Amir Masoud; Olsson, Richard T

2018-05-01

A protocol for the aqueous synthesis of ca. 1-μm-long zinc oxide (ZnO) nanorods and their growth at intermediate reaction progression is presented, together with photoluminescence (PL) characteristics after heat treatment at temperatures of up to 1000 °C. The existence of solitary rods after the complete reaction (60 min) was traced back to the development of sea urchin structures during the first 5 s of the precipitation. The rods primarily formed in later stages during the reaction due to fracture, which was supported by the frequently observed broken rod ends with sharp edges in the final material, in addition to tapered uniform rod ends consistent with their natural growth direction. The more dominant rod growth in the c direction (extending the length of the rods), together with the appearance of faceted surfaces on the sides of the rods, occurred at longer reaction times (>5 min) and generated zinc-terminated particles that were more resistant to alkaline dissolution. A heat treatment for 1 h at 600 or 800 °C resulted in a smoothing of the rod surfaces, and PL measurements displayed a decreased defect emission at ca. 600 nm, which was related to the disappearance of lattice imperfections formed during the synthesis. A heat treatment at 1000 °C resulted in significant crystal growth reflected as an increase in luminescence at shorter wavelengths (ca. 510 nm). Electron microscopy revealed that the faceted rod structure was lost for ZnO rods exposed to temperatures above 600 °C, whereas even higher temperatures resulted in particle sintering and/or mass redistribution along the initially long and slender ZnO rods. The synthesized ZnO rods were a more stable Wurtzite crystal structure than previously reported ball-shaped ZnO consisting of merging sheets, which was supported by the shifts in PL spectra occurring at ca. 200 °C higher annealing temperature, in combination with a smaller thermogravimetric mass loss occurring upon heating the rods to 800 °C.

Hierarchical porous ZnO microflowers with ultra-high ethanol gas-sensing at low concentration

NASA Astrophysics Data System (ADS)

Song, Liming; Yue, He; Li, Haiying; Liu, Li; Li, Yu; Du, Liting; Duan, Haojie; Klyui, N. I.

2018-05-01

Hierarchical porous and non-porous ZnO microflowers have been successfully fabricated by hydrothermal method. Their crystal structure, morphology and gas-sensing properties were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and chemical gas sensing intelligent analysis system (CGS). Compared with hierarchical non-porous ZnO microflowers, hierarchical porous ZnO microflowers exhibited ultra-high sensitivity with 50 ppm ethanol at 260 °C and the response is 110, which is 1.8 times higher than that of non-porous ZnO microflowers. Moreover, the lowest concentration limit of hierarchical porous ZnO microflowers (non-porous ZnO microflowers) to ethanol is 0.1 (1) ppm, the response value is 1.6 (1).

Study of ZnO and Mg doped ZnO nanoparticles by sol-gel process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ansari, Mohd Meenhaz, E-mail: meenhazphysics@gmail.com; Arshad, Mohd; Tripathi, Pushpendra

Nano-crystalline undoped and Mg doped ZnO (Mg-ZnO) nanoparticles with compositional formula Mg{sub x}Zn{sub 1-x}O (x=0,1,3,5,7,10 and 12 %) were synthesized using sol-gel process. The XRD diffraction peaks match with the pattern of the standard hexagonal structure of ZnO that reveals the formation of hexagonal wurtzite structure in all samples. SEM images demonstrates clearly the formation of spherical ZnO nanoparticles, and change of the morphology of the nanoparticles with the concentration of the magnesium, which is in close agreement with that estimated by Scherer formula based on the XRD pattern. To investigate the doping effect on optical properties, the UV–VIS absorptionmore » spectra was obtained and the band gap of the samples calculated.« less

Nanostructured zinc oxide photoelectrodes by green routes M-SILAR and electrodeposition for dye sensitized solar cell

NASA Astrophysics Data System (ADS)

Gaikwad, M. A.; Suryawanshi, M. P.; Maldar, P. S.; Dongale, T. D.; Moholkar, A. V.

2018-04-01

Surfactant-free, ultrasound assisted modified successive ionic layer adsorption and reaction (M-SILAR) method and home-made microcontroller based low-cost potentiostat system are employed to prepare zinc oxide (ZnO) nanostructure based thin films. The comparison between physicochemical as well as photoelectrochemical (PEC) properties of the nanostructures prepared via two different template free, simplistic and cost-effective green routes have been discussed in detail. X-ray diffraction and Raman analysis confirm the formation of phase pure ZnO with the hexagonal crystal structure. Surface morphology significantly affects the physicochemical as well as PEC properties of ZnO thin films. Nanorods (NRs) and nanosheets (NSs) based ZnO thin films sensitized with N3 dye have been directly used as photoelectrodes in the dye-sensitized solar cell (DSSC). The power conversion efficiency (PCE) of 0.59% is achieved with Jsc of 4.04 mA/cm2 and Voc of 0.44 V for the DSSC in which the M-SILAR deposited 1-D ZnO NRs based thin film is used as the photoanode. While relatively less PCE of 0.29% with Jsc of 2.53 mA/cm2 and Voc of 0.36 V is obtained for DSSC prepared using electrodeposited 2-D ZnO NSs. In the NSs like 2-D surface morphology, the presence of multiple grain boundaries are acted as traps for the diffusing electrons, which reduces the electron mobility through it.

Correlation of structural properties with energy transfer of Eu-doped ZnO thin films prepared by sol-gel process and magnetron reactive sputtering

PubMed Central

Petersen, Julien; Brimont, Christelle; Gallart, Mathieu; Schmerber, Guy; Gilliot, Pierre; Ulhaq-Bouillet, Corinne; Rehspringer, Jean-Luc; Colis, Silviu; Becker, Claude; Slaoui, Abdelillah; Dinia, Aziz

2010-01-01

We investigated the structural and optical properties of Eu-doped ZnO thin films made by sol-gel technique and magnetron reactive sputtering on Si (100) substrate. The films elaborated by sol-gel process are polycrystalline while the films made by sputtering show a strongly textured growth along the c-axis. X-ray diffraction patterns and transmission electron microscopy analysis show that all samples are free of spurious phases. The presence of Eu2+ and Eu3+ into the ZnO matrix has been confirmed by x-ray photoemission spectroscopy. This means that a small fraction of Europium substitutes Zn2+ as Eu2+ into the ZnO matrix; the rest of Eu being in the trivalent state. This is probably due to the formation of Eu2O3 oxide at the surface of ZnO particles. This is at the origin of the strong photoluminescence band observed at 2 eV, which is characteristic of the 5D0→7F2 Eu3+ transition. In addition the photoluminescence excitonic spectra showed efficient energy transfer from the ZnO matrix to the Eu3+ ion, which is qualitatively similar for both films although the sputtered films have a better structural quality compared to the sol-gel process grown films. PMID:20644657

Effect of morphology on the non-ohmic conduction in ZnO nanostructures

NASA Astrophysics Data System (ADS)

Praveen, E.; Jayakumar, K.

2016-05-01

Nanostructures of ZnO is synthesized with nanoflower like morphology by simple wet chemical method. The structural, morphological and electrical characterization have been carried out. The temperature dependent electrical characterization of ZnO pellets of thickness 1150 µm is made by the application of 925MPa pressure. The morphological dependence of non-ohmic conduction beyond some arbitrary tunneling potential and grain boundary barrier thickness is compared with the commercially available bulk ZnO. Our results show the suitability of nano-flower like ZnO for the devices like sensors, rectifiers etc.

Synthesis, structural and optical properties of ZnO spindle/reduced graphene oxide composites with enhanced photocatalytic activity under visible light irradiation

NASA Astrophysics Data System (ADS)

Prabhu, S.; Pudukudy, M.; Sohila, S.; Harish, S.; Navaneethan, M.; Navaneethan, D.; Ramesh, R.; Hayakawa, Y.

2018-05-01

In the present work, spindle-shaped ZnO and reduced graphene oxide sheets were successfully synthesized by a hydrothermal method and then ZnO/r-GO composite was prepared by a direct solution mixing method. Various characterization results confirmed the interior and surface decoration of spindle-shaped ZnO on the reduced graphene oxide sheets. The phase formation, crystalline structure, morphology, surface states and optical properties were characterized using Powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR) and UV-Vis spectroscopy. The X-ray diffraction analysis showed the formation of the hexagonal wurtzite crystalline structure of ZnO with high crystalline quality. The band gap of the ZnO/r-GO composite was found to be low (3.03eV) compared to the band gap of spindle shaped ZnO (3.13 eV), as calculated from optical studies. The spindle-like morphology of the single crystalline ZnO was clearly shown in the electron microscopic images. The chemical bonding and surface states of the samples were studied using XPS measurement. Moreover, a possible growth mechanism for the ZnO spindle was proposed. The catalytic activity of the as-synthesized samples was evaluated for the photodegradation of methylene blue under visible light irradiation. Among the synthesized samples, the ZnO/r-GO composite showed higher degradation efficiency of 93% and successfully reused for four consecutive run without any activity loss.

Effects of the ZnO layer on the structure and white light emission properties of a ZnS:Mn/GaN nanocomposite system.

PubMed

Wang, Cai-Feng; Hu, Bo

2017-10-01

ZnO films were inserted between the ZnS:Mn films and GaN substrates by pulsed laser deposition (PLD). The structure, morphology, and optical properties of the ZnS:Mn/ZnO/GaN nanocomposite systems have been investigated. X-ray diffraction results show that there are three diffraction peaks located at 28.4°, 34.4°, and 34.1°, which correspond to the β-ZnS(111), ZnO(002), and GaN(002) planes, respectively. Due to the insertion of ZnO films, the diffraction peak intensity of ZnS:Mn in ZnS:Mn/ZnO/GaN is stronger than that of ZnS:Mn in ZnS:Mn/GaN, and the full width at half-maximum is smaller. Though the transmittance of ZnS:Mn/ZnO films is slightly lower than that of ZnS:Mn films, the transmittance is still higher than 80%. Compared with ZnS:Mn/GaN, an ultraviolet (UV) emission at 387 nm (originated from the near-band emission of ZnO) and a green light emission at about 520 nm appeared in the photoluminescence (PL) spectra of ZnS:Mn/ZnO/GaN, in addition to the blue emission at 435 nm and the orange-red emission at 580 nm. The emission at 520 nm may be related to the deep-level emission from ZnO and the interface of ZnS:Mn/ZnO. The PL spectrum of ZnS:Mn/ZnO/GaN covers the visible region from the blue light to the red light (400-700 nm), and its color coordinate and color temperature are (0.3103,0.3063) and 6869 K, respectively, presenting strong white light emission.

A study of the effects of aligned vertically growth time on ZnO nanorods deposited for the first time on Teflon substrate

NASA Astrophysics Data System (ADS)

Farhat, O. F.; Halim, M. M.; Ahmed, Naser M.; Oglat, Ammar A.; Abuelsamen, A. A.; Bououdina, M.; Qaeed, M. A.

2017-12-01

In this study, ZnO nanorods (NRs) were well deposited on Teflon substrates (PTFE) via a chemical bath deposition (CBD) method at low temperature. The consequences of growth time (1 h-4 h) on the structural and optical properties of the aligned ZnO (NRs) were investigated through X-ray diffraction, field-emission scanning electron microscopy (FESEM), and photoluminescence (PL) analyses. The results show that the ZnO (NRs) were preferred to grew aligned along the c-axis as hexagonal wurtzite structure as proved by the sharp and strong ZnO (002) peaks of the ZnO (NRs). Irrespective of the growth continuation, FESEM photos confirmed that the ZnO nanorods arrays were fit to be aligned along the c-axis and perpendicular to (PTFE) substrates. The ZnO nanorods that exhibited the sharper stand most intense PL peaks among the sample were grown for 3hs as demonstrated by PL spectra. The device further showed a sensitivity of 4068 to low-power (1.25 mW/cm2) 375 nm light pulses without an external bias. The measurements of photoresponse demonstrated the highly reproducible characteristics of the fabricated UV detector with rapid response and baseline recovery times of 48.05 ms. Thus, this work introduced a simple, low-cost method of fabricating rapid-response, and highly photosensitive UV detectors with zero power consumption on Teflon substrates.

Infiltration of CdTe nano crystals into a ZnO wire vertical matrix by using the isothermal closed space technique

NASA Astrophysics Data System (ADS)

Larramendi, S.; Vaillant Roca, Lidice; Saint-Gregoire, Pierre; Ferraz Dias, Johnny; Behar, Moni

2017-10-01

A ZnO nanorod structure was grown by the hydrothermal method and interpenetrated with CdTe using the isothermal closed space sublimation technique. The obtained structure was studied by using the Rutherford backscattering spectrometry (RBS), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM). The X-ray Diffraction (XRD) technique confirmed the presence of CdTe nanocrystals (NCs) of very small size formed on the surface and in the interspaces between the ZnO nanorods. The RBS observations together with the SEM observations give information on the obtained structure. Finally the photoluminescence studies show a strong energy confinement effect on the grown CdTe NCs.

Formation of quasi-single crystalline porous ZnO nanostructures with a single large cavity

NASA Astrophysics Data System (ADS)

Cho, Seungho; Kim, Semi; Jung, Dae-Won; Lee, Kun-Hong

2011-09-01

We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 °C) and a stage in which the temperature is maintained at 120 °C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space.We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 °C) and a stage in which the temperature is maintained at 120 °C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space. Electronic supplementary information (ESI) available: TEM images and the corresponding SAED image of a ZnO nanostructure synthesized from the reaction without l(+)-ascorbic acid at the 85 °C time point (Fig. S1). See DOI: 10.1039/c1nr10609k

Calculation of DSSC parameters based on ZnO nanorod/TiO2 mesoporous photoanode

NASA Astrophysics Data System (ADS)

Safriani, L.; Nurrida, A.; Mulyana, C.; Susilawati, T.; Bahtiar, A.; Aprilia, A.

2017-07-01

Photoanode of dye sensitized solar cell (DSSC) plays an important role as electron transport media to accept photogenerated electron from excited state of dye. There are several physical properties that are required from photoanode of DSSC. It should be highly transparent, have large surface area, has a conduction band lower than LUMO of dye molecule, has high charge carrier mobility and finally has a good stability in redox electrolyte process. In this work, DSSC with structure FTO/ZnO nanorod/TiO2 mesoporous/Ru-dye/gel electrolyte/ Pt/FTO has been fabricated. In order to modified the structures of photoanode, ZnO nanorod was grown on aluminium doped ZnO seed layer by variation concentration of Al (0 wt%, 0.5 wt% and 1.0 wt%). Zinc nitrate hexahydrate and hexamethylenetetramine used as raw materials for ZnO nanorod growth solution and deposited by self-assembly methods on FTO/Al doped ZnO seed layer. It is then followed by deposition of titania (TiO2) paste by screen printing methods. DSSC parameters i.e. ideally factor (n), series resistance (RS ), and shunt resistance (RSH ) was derived from current density-voltage (I-V) curve using the simplify equation of ideal diode model. The influences of ZnO photoanode structures to the solar cell performance will be completely discussed.

Performance analysis of RF-sputtered ZnO/Si heterojunction UV photodetectors with high photo-responsivity

NASA Astrophysics Data System (ADS)

Singh, Satyendra Kumar; Hazra, Purnima; Tripathi, Shweta; Chakrabarti, P.

2016-03-01

In this paper, structural, electrical and ultraviolet photodetection parameters of RF sputtered-ZnO/Si heterojunction diodes are analyzed. In this work, ZnO thin film was deposited on bare Si substrate as well as Si substrate coated with ultrathin ZnO seed layer to exhibit the effect of seed layer on device performance. AFM image of as-grown ZnO films have exhibited the uniform growth ZnO film over the whole Si substrate with average roughness of 3.2 nm and 2.83 nm for ZnO with and without seed layer respectively. Stronger peak intensity along (002) direction, as shown in XRD spectra confirm that ZnO film grown on ZnO seed layer is having more stable wurtzite structure. Ti/Al point contacts were deposited on top of the ZnO film and a layer of Al was deposited on bottom of Si substrate for using as ohmic contacts for further device characterization at dark and under UV light of 365 nm wavelength. This process is repeated for both the films sequentially. The photo-responsivity of our proposed devices is calculated as 0.34 A/W for seed layer-mediated devices and 0.26 A/W for devices without seed layer. These values are very high as compare to the reported value of photo-responsivity for same kind of ZnO/Si heterojunction device prototypes prepared by other techniques.

Unravelling the origin of the giant Zn deficiency in wurtzite type ZnO nanoparticles

PubMed Central

Renaud, Adèle; Cario, Laurent; Rocquelfelte, Xavier; Deniard, Philippe; Gautron, Eric; Faulques, Eric; Das, Tilak; Cheviré, François; Tessier, Franck; Jobic, Stéphane

2015-01-01

Owing to its high technological importance for optoelectronics, zinc oxide received much attention. In particular, the role of defects on its physical properties has been extensively studied as well as their thermodynamical stability. In particular, a large concentration of Zn vacancies in ZnO bulk materials is so far considered highly unstable. Here we report that the thermal decomposition of zinc peroxide produces wurtzite-type ZnO nanoparticles with an extraordinary large amount of zinc vacancies (>15%). These Zn vacancies segregate at the surface of the nanoparticles, as confirmed by ab initio calculations, to form a pseudo core-shell structure made of a dense ZnO sphere coated by a Zn free oxo-hydroxide mono layer. In others terms, oxygen terminated surfaces are privileged over zinc-terminated surfaces for passivation reasons what accounts for the Zn off-stoichiometry observed in ultra-fine powdered samples. Such Zn-deficient Zn1-xO nanoparticles exhibit an unprecedented photoluminescence signature suggesting that the core-shell-like edifice drastically influences the electronic structure of ZnO. This nanostructuration could be at the origin of the recent stabilisation of p-type charge carriers in nitrogen-doped ZnO nanoparticles. PMID:26333510

Highly stable thin film transistors using multilayer channel structure

NASA Astrophysics Data System (ADS)

Nayak, Pradipta K.; Wang, Zhenwei; Anjum, D. H.; Hedhili, M. N.; Alshareef, H. N.

2015-03-01

We report highly stable gate-bias stress performance of thin film transistors (TFTs) using zinc oxide (ZnO)/hafnium oxide (HfO2) multilayer structure as the channel layer. Positive and negative gate-bias stress stability of the TFTs was measured at room temperature and at 60 °C. A tremendous improvement in gate-bias stress stability was obtained in case of the TFT with multiple layers of ZnO embedded between HfO2 layers compared to the TFT with a single layer of ZnO as the semiconductor. The ultra-thin HfO2 layers act as passivation layers, which prevent the adsorption of oxygen and water molecules in the ZnO layer and hence significantly improve the gate-bias stress stability of ZnO TFTs.

Self-assembled ultra small ZnO nanocrystals for dye-sensitized solar cell application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patra, Astam K.; Dutta, Arghya; Bhaumik, Asim, E-mail: msab@iacs.res.in

2014-07-01

We demonstrate a facile chemical approach to produce self-assembled ultra-small mesoporous zinc oxide nanocrystals using sodium salicylate (SS) as a template under hydrothermal conditions. These ZnO nanomaterials have been successfully fabricated as a photoanode for the dye-sensitized solar cell (DSSC) in the presence of N719 dye and iodine–triiodide electrolyte. The structural features, crystallinity, purity, mesophase and morphology of the nanostructure ZnO are investigated by several characterization tools. N{sub 2} sorption analysis revealed high surface areas (203 m{sup 2} g{sup −1}) and narrow pore size distributions (5.1–5.4 nm) for different samples. The mesoporous structure and strong photoluminescence facilitates the high dyemore » loading at the mesoscopic void spaces and light harvesting in DSSC. By utilizing this ultra-small ZnO photoelectrode with film thickness of about 7 μm in the DSSC with an open-circuit voltage (V{sub OC}) of 0.74 V, short-circuit current density (J{sub SC}) of 3.83 mA cm{sup −2} and an overall power conversion efficiency of 1.12% has been achieved. - Graphical abstract: Ultra-small ZnO nanocrystals have been synthesized with sodium salicylate as a template and using it as a photoanode in a dye-sensitized solar cell 1.12% power conversion efficiency has been observed. - Highlights: • Synthesis of self-assembled ultra-small mesoporous ZnO nanocrystals by using sodium salicylate as a template. • Mesoporous ZnO materials have high BET surface areas and void space. • ZnO nanoparticles serve as a photoanode for the dye-sensitized solar cell (DSSC). • Using ZnO nanocrystals as photoelectrode power conversion efficiency of 1.12% has been achieved.« less

Evaluation of anti-microbial activities of ZnO, citric acid and a mixture of both against Propionibacterium acnes.

PubMed

Bae, J Y; Park, S N

2016-12-01

In this study, anti-microbial activities of ZnO of three different particle sizes of citric acid (CA) and of mixtures of ZnO and CA were confirmed against Propionibacterium acnes. ZnO with the smallest particle size showed relatively high anti-microbial activity by disc diffusion assay and broth macrodilution assay. The mixtures of ZnO and CA also showed relatively high anti-microbial activity when the particle size of ZnO was the smallest. Furthermore, anti-microbial activities of ZnO, CA and the mixtures of ZnO and CA were compared through the checkerboard assay. The results indicated that a 1 : 1 ratio of ZnO and CA resulted in the highest anti-microbial activity. The substances were confirmed to have synergic anti-microbial effects. With the time-kill curve assay, the mixture of ZnO-containing CA reduced the surviving microbial content the most after 24 h. The results of our study suggest that ZnO may not only be an anti-microbial ingredient for the prevention of and treatment of acne. The results of our study suggest that ZnO may be an anti-microbial ingredient for the prevention of and treatment of acne when mixed with CA. © 2016 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Metal Oxide Nanowire Preparation and Their Integration into Chemical Sensing Devices at the SENSOR Lab in Brescia

PubMed Central

Bertuna, Angela; Faglia, Guido; Ferroni, Matteo; Kaur, Navpreet; Munasinghe Arachchige, Hashitha M. M.; Sberveglieri, Giorgio; Comini, Elisabetta

2017-01-01

Metal oxide 1D nanowires are probably the most promising structures to develop cheap stable and selective chemical sensors. The purpose of this contribution is to review almost two-decades of research activity at the Sensor Lab Brescia on their preparation during by vapor solid (n-type In2O3, ZnO), vapor liquid solid (n-type SnO2 and p-type NiO) and thermal evaporation and oxidation (n-type ZnO, WO3 and p-type CuO) methods. For each material we’ve assessed the chemical sensing performance in relation to the preparation conditions and established a rank in the detection of environmental and industrial pollutants: SnO2 nanowires were effective in DMMP detection, ZnO nanowires in NO2, acetone and ethanol detection, WO3 for ammonia and CuO for ozone. PMID:28468310

Thermal-induced structural and optical investigations of Agsbnd ZnO nanocomposite thin films

NASA Astrophysics Data System (ADS)

Singh, S. K.; Singhal, R.

2018-07-01

In the present paper, we have successfully synthesized Agsbnd ZnO nanocomposite thin films by RF-magnetron sputtering technique at room temperature. Systematic investigations of thermal-induced structural and optical modifications in Agsbnd ZnO thin films have been observed and described. The Agsbnd ZnO thin films were annealed at three different temperatures of 300 °C, 400 °C and 500 °C in vacuum to prevent the oxidation of Ag. The presence and formation of Ag nanoparticles were estimated by transmission electron microscopy. X-ray diffraction analysis revealed the structural information about the crystalline quality of ZnO. The crystallinity as well as the crystallite size of the films have been found to be improved with annealing temperatures. The estimated crystallite size was ∼15.8 nm for as-deposited film and 19.0 nm for the film at a higher temperature. The chemical composition and structural analysis of as-deposited film were carried out by X-ray photoelectron spectroscopy. A very sharp absorption band appeared at ∼540 nm for Ag NPs that is associated with the surface plasmon resonance band of Ag. A noticeable red shift of about ∼12 nm has been recorded for films annealed at 500 °C. Atomic force microscopy has been utilized to examine the surface morphology of the as-deposited and annealed films. The grain size was found to be increase with increasing annealing temperature, while no significant changes were observed in the roughness of Agsbnd ZnO thin films. Raman spectroscopy revealed lattice defects and disordering in the films after the thermal annealing.

Effect of Fe incorporation on the optical behavior of ZnO thin films prepared by sol-gel derived spin coating techniques

NASA Astrophysics Data System (ADS)

Rakkesh, R. Ajay; Malathi, R.; Balakumar, S.

2013-02-01

In this work, Fe doped Zinc Oxide (ZnO) thin films were fabricated on the glass substrate by sol-gel derived spin coating technique. X-ray Diffraction studies revealed that the obtained pure and Fe doped ZnO thin films were in the wurtzite and spinel phase respectively. The three well defined Raman lines at 432, 543 and 1091 cm-1 also confirmed the lattice structure of the ZnO thin film has wurtzite symmetry. While doping Fe atoms in the ZnO, there was a significant change in the phase from wurtzite to spinel structure; owing to Fe (III) ions being incorporated into the lattice through substitution of Zn (II) ions. Room temperature PL spectra showed that the role of defect mediated red emissions at 612 nm was due to radial recombination of a photogenerated hole with an electron that belongs to the Fe atoms, which were discussed in detail.

Toxicity evaluation of ZnO nanostructures on L929 fibroblast cell line using MTS assay

NASA Astrophysics Data System (ADS)

Bakhori, Siti Khadijah Mohd; Mahmud, Shahrom; Ann, Ling Chuo; Mohamed, Azman Seeni; Saifuddin, Siti Nazmin; Masudi, Sam'an Malik; Mohamad, Dasmawati

2015-04-01

ZnO has wide applications in medical and dentistry apart from being used as optoelectronic devices such as solar cells, photodetectors, sensors and light emitting diodes (LEDs). Therefore, the toxicity evaluation is important to know the toxicity level on normal cell line. The toxicity of two grades ZnO nanostructures, ZnO-4 and ZnO-8 have been carried out using cytotoxicity test of MTS assay on L929 rat fibroblast cell line. Prior to that, ZnO-4 and ZnO-8 were characterized for its morphology, structure and optical properties using FESEM, X-ray diffraction, and Photoluminescence respectively. The two groups revealed difference in morphology and exhibit slightly shifted of near band edge emission of Photoluminescence other than having a similar calculated crystallite size of nanostructures. The viability of cells after 72h were obtained and the statistical significance value was calculated using SPSS v20. The p value is more than 0.05 between untreated and treated cell with ZnO. This insignificant value of p>0.05 can be summarized as a non-toxic level of ZnO-4 and ZnO-8 on the L929 cell line.

In vitro toxicity of zinc oxide nanoparticles: a review

NASA Astrophysics Data System (ADS)

Pandurangan, Muthuraman; Kim, Doo Hwan

2015-03-01

The toxic effect of ZnO nanoparticles is due to their solubility. ZnO nanoparticles dissolve in the extracellular region, which in turn increases the intracellular [Zn2+] level. The mechanism for increased intracellular [Zn2+] level and ZnO nanoparticles dissolution in the medium is still unclear. Cytotoxicity, increased oxidative stress, increased intracellular [Ca2+] level, decreased mitochondrial membrane potential, and interleukin-8 productions occur in the BEAS-2B bronchial epithelial cells and A549 alveolar adenocarcinoma cells following the exposure of ZnO nanoparticles. Confluent C2C12 cells are more resistant to ZnO nanoparticles compared to the sparse monolayer. Loss of 3T3-L1 cell viability, membrane leakage, and morphological changes occurs due to exposure of ZnO nanoparticles. ZnO nanoparticle induces cytotoxicity and mitochondrial dysfunction in RKO colon carcinoma cells. The occurrence of apoptosis, increased ROS level, reduced mitochondrial activity and formation of tubular intracellular structures are reported following exposure of ZnO nanoparticles in skin cells. Macrophages, monocytes, and dendritic cells are affected by ZnO nanoparticles. In addition, genotoxicity is also induced. The present review summarizes the literature on in vitro toxicity of ZnO nanoparticles (10-100 nm) on various cell lines.

Toxicity evaluation of ZnO nanostructures on L929 fibroblast cell line using MTS assay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bakhori, Siti Khadijah Mohd; Mahmud, Shahrom; Ann, Ling Chuo

2015-04-24

ZnO has wide applications in medical and dentistry apart from being used as optoelectronic devices such as solar cells, photodetectors, sensors and light emitting diodes (LEDs). Therefore, the toxicity evaluation is important to know the toxicity level on normal cell line. The toxicity of two grades ZnO nanostructures, ZnO-4 and ZnO-8 have been carried out using cytotoxicity test of MTS assay on L929 rat fibroblast cell line. Prior to that, ZnO-4 and ZnO-8 were characterized for its morphology, structure and optical properties using FESEM, X-ray diffraction, and Photoluminescence respectively. The two groups revealed difference in morphology and exhibit slightly shiftedmore » of near band edge emission of Photoluminescence other than having a similar calculated crystallite size of nanostructures. The viability of cells after 72h were obtained and the statistical significance value was calculated using SPSS v20. The p value is more than 0.05 between untreated and treated cell with ZnO. This insignificant value of p>0.05 can be summarized as a non-toxic level of ZnO-4 and ZnO-8 on the L929 cell line.« less

Construction of Zinc Oxide into Different Morphological Structures to Be Utilized as Antimicrobial Agent against Multidrug Resistant Bacteria

PubMed Central

Elkady, M. F.; Shokry Hassan, H.; Hafez, Elsayed E.; Fouad, Ahmed

2015-01-01

Nano-ZnO has been successfully implemented in particles, rods, and tubes nanostructures via sol-gel and hydrothermal techniques. The variation of the different preparation parameters such as reaction temperature, time, and stabilizer agents was optimized to attain different morphological structures. The influence of the microwave annealing process on ZnO crystallinity, surface area, and morphological structure was monitored using XRD, BET, and SEM techniques, respectively. The antimicrobial activity of zinc oxide produced in nanotubes structure was examined against four different multidrug resistant bacteria: Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) strains. The activity of produced nano-ZnO was determined by disc diffusion technique and the results revealed that ZnO nanotubes recorded high activity against the studied strains due to their high surface area equivalent to 17.8 m2/g. The minimum inhibitory concentration (MIC) of ZnO nanotubes showed that the low concentrations of ZnO nanotubes could be a substitution for the commercial antibiotics when approached in suitable formula. Although the annealing process of ZnO improves the degree of material crystallinity, however, it declines its surface area and consequently its antimicrobial activity. PMID:26451136

Investigations of rapid thermal annealing induced structural evolution of ZnO: Ge nanocomposite thin films via GISAXS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ceylan, Abdullah, E-mail: aceylanabd@yahoo.com; Ozcan, Yusuf; Orujalipoor, Ilghar

2016-06-07

In this work, we present in depth structural investigations of nanocomposite ZnO: Ge thin films by utilizing a state of the art grazing incidence small angle x-ray spectroscopy (GISAXS) technique. The samples have been deposited by sequential r.f. and d.c. sputtering of ZnO and Ge thin film layers, respectively, on single crystal Si(100) substrates. Transformation of Ge layers into Ge nanoparticles (Ge-np) has been initiated by ex-situ rapid thermal annealing of asprepared thin film samples at 600 °C for 30, 60, and 90 s under forming gas atmosphere. A special attention has been paid on the effects of reactive and nonreactivemore » growth of ZnO layers on the structural evolution of Ge-np. GISAXS analyses have been performed via cylindrical and spherical form factor calculations for different nanostructure types. Variations of the size, shape, and distributions of both ZnO and Ge nanostructures have been determined. It has been realized that GISAXS results are not only remarkably consistent with the electron microscopy observations but also provide additional information on the large scale size and shape distribution of the nanostructured components.« less

Superhydrophobic Surface Based on a Coral-Like Hierarchical Structure of ZnO

PubMed Central

Wu, Jun; Xia, Jun; Lei, Wei; Wang, Baoping

2010-01-01

Background Fabrication of superhydrophobic surfaces has attracted much interest in the past decade. The fabrication methods that have been studied are chemical vapour deposition, the sol-gel method, etching technique, electrochemical deposition, the layer-by-layer deposition, and so on. Simple and inexpensive methods for manufacturing environmentally stable superhydrophobic surfaces have also been proposed lately. However, work referring to the influence of special structures on the wettability, such as hierarchical ZnO nanostructures, is rare. Methodology This study presents a simple and reproducible method to fabricate a superhydrophobic surface with micro-scale roughness based on zinc oxide (ZnO) hierarchical structure, which is grown by the hydrothermal method with an alkaline aqueous solution. Coral-like structures of ZnO were fabricated on a glass substrate with a micro-scale roughness, while the antennas of the coral formed the nano-scale roughness. The fresh ZnO films exhibited excellent superhydrophilicity (the apparent contact angle for water droplet was about 0°), while the ability to be wet could be changed to superhydrophobicity after spin-coating Teflon (the apparent contact angle greater than 168°). The procedure reported here can be applied to substrates consisting of other materials and having various shapes. Results The new process is convenient and environmentally friendly compared to conventional methods. Furthermore, the hierarchical structure generates the extraordinary solid/gas/liquid three-phase contact interface, which is the essential characteristic for a superhydrophobic surface. PMID:21209931

Anomalous luminescence phenomena of indium-doped ZnO nanostructures grown on Si substrates by the hydrothermal method

PubMed Central

2012-01-01

In recent years, zinc oxide (ZnO) has become one of the most popular research materials due to its unique properties and various applications. ZnO is an intrinsic semiconductor, with a wide bandgap (3.37 eV) and large exciton binding energy (60 meV) making it suitable for many optical applications. In this experiment, the simple hydrothermal method is used to grow indium-doped ZnO nanostructures on a silicon wafer, which are then annealed at different temperatures (400°C to 1,000°C) in an abundant oxygen atmosphere. This study discusses the surface structure and optical characteristic of ZnO nanomaterials. The structure of the ZnO nanostructures is analyzed by X-ray diffraction, the superficial state by scanning electron microscopy, and the optical measurements which are carried out using the temperature-dependent photoluminescence (PL) spectra. In this study, we discuss the broad peak energy of the yellow-orange emission which shows tendency towards a blueshift with the temperature increase in the PL spectra. This differs from other common semiconductors which have an increase in their peak energy of deep-level emission along with measurement temperature. PMID:22647253

Delocalization of π electrons and trapping action of ZnO nanoparticles in PPY matrix for hybrid solar cell application

NASA Astrophysics Data System (ADS)

Singh, Rajinder; Choudhary, Ram Bilash; Kandulna, Rohit

2018-03-01

Polypyrrole (PPY)-Zinc Oxide (ZnO) nanocomposites with varying concentration of ZnO (1:1-1:4) were prepared via in-situ polymerization technique by using pyrrole monomer in the presence of ammonium persulphate (APS) as oxidant. Globular morphology of PPY and sheet like structure of ZnO was examined using FESEM and EDAX. FTIR showed the presence of vibration modes in fingerprint region (1500 cm-1-500 cm-1) for metal oxides confirming the presence and interaction of ZnO with the polymer matrix in nanocomposites. Amorphous nature of PPY and hexagonal wurtzite structure of ZnO was confirmed using XRD with average crystallite size within 20 nm-30 nm. PANI-ZnO (1:1) exhibited blue shift in comparison to PPY (neat) and optimized optical band gap ∼ 1.81 eV. The effect of carrier concentration was investigated using electrochemical analyzer and maximum current was recorded for PANI-ZnO (1:1). The highest conductance was calculated for PANI-ZnO (1:1) ∼ 7.3242 × 10-3 S using current -voltage characteristics. Thermal stability was found to be increasing with the increase in ZnO concentration PANI-ZnO nanocomposite.

Clustered vacancies in ZnO: chemical aspects and consequences on physical properties

NASA Astrophysics Data System (ADS)

Pal, S.; Gogurla, N.; Das, Avishek; Singha, S. S.; Kumar, Pravin; Kanjilal, D.; Singha, A.; Chattopadhyay, S.; Jana, D.; Sarkar, A.

2018-03-01

The chemical nature of point defects, their segregation, cluster or complex formation in ZnO is an important area of investigation. The evolution of a defective state with MeV Ar ion irradiation fluence 1  ×  1014 and 1  ×  1016 ions cm-2 has been monitored here using x-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and Raman spectroscopy. The XPS study shows the presence of oxygen vacancies (V O) in Ar irradiated ZnO. Zn(LMM) Auger spectra clearly identifies a transition involving metallic zinc in the irradiated samples. An intense PL emission from interstitial Zn (I Zn)-related shallow donor bound excitons (DBX) is visible in the 10 K spectra for all samples. Although overall PL is largely reduced with irradiation disorder, DBX intensity is increased for the highest fluence irradiated sample. The Raman study indicates damage in both the zinc and oxygen sub-lattice by an energetic ion beam. Representative Raman modes from defect complexes involving V O, I Zn and I O are visible after irradiation with intermediate fluence. A further increase of fluence shows, to some extent, a homogenization of disorder. A huge reduction of resistance is also noted for this sample. Certainly, high irradiation fluence induces a qualitative modification of the conventional (and highly resistive) grain boundary (GB) structure of granular ZnO. A low resistive path, involving I Zn related shallow donors, across the GB can be presumed to explain resistance reduction. Open volumes (V Zn and V O) agglomerate more and more with increasing irradiation fluence and are finally transformed to voids. The results as a whole have been elucidated with a model which emphasizes the possible evolution of a new defect microstructure that is distinctively different from the GB-related disorder. Based on the model, qualitative explanations of commonly observed radiation hardness, colouration and ferromagnetism in disordered ZnO have been put forward. A coherent scenario on disorder accumulation in ZnO has been presented, which we believe will guide further discussion on this topic.

Structural characteristics of a non-polar ZnS layer on a ZnO buffer layer formed on a sapphire substrate by mist chemical vapor deposition

NASA Astrophysics Data System (ADS)

Okita, Koshi; Inaba, Katsuhiko; Yatabe, Zenji; Nakamura, Yusui

2018-06-01

ZnS is attractive as a material for low-cost light-emitting diodes. In this study, a non-polar ZnS layer was epitaxially grown on a sapphire substrate by inserting a ZnO buffer layer between ZnS and sapphire. The ZnS and ZnO layers were grown by a mist chemical vapor deposition system with a simple setup operated under atmospheric pressure. The sample was characterized by high-resolution X-ray diffraction measurements including 2θ/ω scans, rocking curves, and reciprocal space mapping. The results showed that an m-plane wurtzite ZnS layer grew epitaxially on an m-plane wurtzite ZnO buffer layer formed on the m-plane sapphire substrate to provide a ZnS/ZnO/sapphire structure.

Simple chemical synthesis of novel ZnO nanostructures: Role of counter ions

NASA Astrophysics Data System (ADS)

Pudukudy, Manoj; Yaakob, Zahira

2014-04-01

This article reports the synthesis, characterisation and photocatalytic activity of novel ZnO nanostructures prepared via the thermal decomposition of hydrozincite. Hydrozincites were obtained by the conventional precipitation route using different zinc salts such as acetate, nitrate, chloride and sulphate. The effect of counter ions (CH3COO-, Cl-, NO3-, and SO42-) on the structural, textural, morphological and optical properties was investigated. Various characterisations depicted the active role of counter ions in the properties of ZnO. Hexagonal wurtzite structure of ZnO with fine crystalline size was obvious from the XRD results, irrespective of the counter ions. Electron microscopic images indicated the role of counter ions in the surface and internal morphology of ZnO nanomaterials. Special coral like agglomerated morphology of elongated particles with high porosity was observed for the ZnO prepared from acetate precursor. Spherical, elongated and irregular shaped bigger lumps of ZnO nanoparticles with various novel morphologies were resulted for the sulphate, nitrate and chloride precursors respectively. Highly ordered porous micro disc like morphology was noted for the ZnO samples prepared from the sulphate and nitrate salts. Photoluminescence spectra showed the characteristic blue and green emission bands, depicting the presence of large crystal defects and high oxygen vacancies in the samples. Photocatalytic activity of the as-prepared ZnO catalysts was examined by the degradation of methylene blue under UV light irradiation. Degradation results indicated their substantial activity with respect to the counter ions. ZnO prepared from the acetate precursor showed highest photoactivity due to its high surface area, special morphology and high oxygen vacancies.

Flower-like ZnO nanorod arrays grown on HF-etched Si (111): constraining relation between ZnO seed layer and Si (111)

NASA Astrophysics Data System (ADS)

Brahma, Sanjaya; Liu, C.-W.; Huang, R.-J.; Chang, S.-J.; Lo, K.-Y.

2015-11-01

We demonstrate the formation of self-assembled homogenous flower-like ZnO nanorods over a ZnO seed layer deposited on a HF-etched Si (111) substrate. The typical flower-like morphology of ZnO nanorod arrays is ascribed to the formation of the island-like seed layer which is deposited by the drop method followed by annealing at 300 °C. The island-like ZnO seed layer consists of larger ZnO grains, and is built by constraining of the Si (111) surface due to pattern matching. Pattern matching of Si with ZnO determines the shape and size of the seed layer and this controls the final morphology of ZnO nanorods to be either flower like or vertically aligned. The high quality of the island-like ZnO seed layer enhances the diameter and length of ZnO nanorods. Besides, while the amorphous layer formed during the annealing process would influence the strained ZnO grain, that subsequent amorphous layer will not block the constraining between the ZnO grain and the substrate.

Efficiency of Nb-Doped ZnO Nanoparticles Electrode for Dye-Sensitized Solar Cells Application

NASA Astrophysics Data System (ADS)

Anuntahirunrat, Jirapat; Sung, Youl-Moon; Pooyodying, Pattarapon

2017-09-01

The technological of Dye-sensitized solar cells (DSSCs) had been improved for several years. Due to its simplicity and low cost materials with belonging to the part of thin films solar cells. DSSCs have numerous advantages and benefits among the other types of solar cells. Many of the DSSC devices had use organic chemical that produce by specific method to use as thin film electrodes. The organic chemical that widely use to establish thin film electrodes are Zinc Oxide (ZnO), Titanium Dioxide (TiO2) and many other chemical substances. Zinc oxide (ZnO) nanoparticles had been used in DSSCs applications as thin film electrodes. Nanoparticles are a part of nanomaterials that are defined as a single particles 1-100 nm in diameter. From a few year ZnO widely used in DSSC applications because of its optical, electrical and many others properties. In particular, the unique properties and utility of ZnO structure. However the efficiency of ZnO nanoparticles based solar cells can be improved by doped various foreign impurity to change the structures and properties. Niobium (Nb) had been use as a dopant of metal oxide thin films. Using specification method to doped the ZnO nanoparticles thin film can improved the efficiencies of DSSCs. The efficiencies of Nb-doped ZnO can be compared by doping 0 at wt% to 5 at wt% in ZnO nanoparticles thin films that prepared by the spin coating method. The thin film electrodes doped with 3 at wt% represent a maximum efficiencies with the lowest resistivity of 8.95×10-4 Ω·cm.

A vanadium-doped ZnO nanosheets-polymer composite for flexible piezoelectric nanogenerators

NASA Astrophysics Data System (ADS)

Shin, Sung-Ho; Kwon, Yang Hyeog; Lee, Min Hyung; Jung, Joo-Yun; Seol, Jae Hun; Nah, Junghyo

2016-01-01

We report high performance flexible piezoelectric nanogenerators (PENGs) by employing vanadium (V)-doped ZnO nanosheets (NSs) and the polydimethylsiloxane (PDMS) composite structure. The V-doped ZnO NSs were synthesized to overcome the inherently low piezoelectric properties of intrinsic ZnO. Ferroelectric phase transition induced in the V-doped ZnO NSs contributed to significantly improve the performance of the PENGs after the poling process. Consequently, the PENGs exhibited high output voltage and current up to ~32 V and ~6.2 μA, respectively, under the applied strain, which are sufficient to directly turn on a number of light emitting diodes (LEDs). The composite approach for PENG fabrication is scalable, robust, and reproducible during periodic bending/releasing over extended cycles. The approach introduced here extends the performance limits of ZnO-based PENGs and demonstrates their potential as energy harvesting devices.We report high performance flexible piezoelectric nanogenerators (PENGs) by employing vanadium (V)-doped ZnO nanosheets (NSs) and the polydimethylsiloxane (PDMS) composite structure. The V-doped ZnO NSs were synthesized to overcome the inherently low piezoelectric properties of intrinsic ZnO. Ferroelectric phase transition induced in the V-doped ZnO NSs contributed to significantly improve the performance of the PENGs after the poling process. Consequently, the PENGs exhibited high output voltage and current up to ~32 V and ~6.2 μA, respectively, under the applied strain, which are sufficient to directly turn on a number of light emitting diodes (LEDs). The composite approach for PENG fabrication is scalable, robust, and reproducible during periodic bending/releasing over extended cycles. The approach introduced here extends the performance limits of ZnO-based PENGs and demonstrates their potential as energy harvesting devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07185b

Elaboration, structural and optical investigations of ZnO/epoxy nanocomposites

NASA Astrophysics Data System (ADS)

Moussa, S.; Namouchi, F.; Guermazi, H.

2015-07-01

Hybrid nanocomposites were elaborated by incorporating ZnO nanoparticles into a transparent epoxy polymer matrix, using the direct dispersion method. The effect of the nanoparticles on the structural and optical properties of the polymer matrix was investigated using Fourier transform infrared (FTIR), Raman and UV-Visible spectroscopies. Nanocomposites FTIR spectra showed a variation of band intensities attributed to nanoparticles agglomeration within the polymer. The UV-Visible measurements showed a redshift on the band gap energy of the nanocomposites differently from neat epoxy resin, caused by interactions between ZnO NPs and polymer chains. Raman spectra confirm these interactions and the formation of hydrogen bonds in the nanocomposites. The UV-Visible transmittance spectra revealed that addition of a very low concentration (0.2wt%) of ZnO nanoparticles to a transparent epoxy matrix would maintain high visible-light transparency. The decrease of transmittance with increasing ZnO percentage is due to light scattering which originates from the agglomeration of nanoparticles in the matrix, the mismatch between the refractive index of ZnO and that of the epoxy matrix, and the increase of the surface roughness of the nanocomposite with increasing ZnO addition. Moreover, the UV-vis absorption spectra revealed that adding more than 1wt% ZnO leads to the improvement of the UV shielding properties of the nanocomposites. These results prove that the elaborated ZnO/epoxy nanocomposites can be used as UV shielding materials.

Structural and electrical properties of TiO{sub 2}/ZnO core–shell nanoparticles synthesized by hydrothermal method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vlazan, P.; Ursu, D.H.; Irina-Moisescu, C.

TiO{sub 2}/ZnO core–shell nanoparticles were successfully synthesized by hydrothermal method in two stages: first stage is the hydrothermal synthesis of ZnO nanoparticles and second stage the obtained ZnO nanoparticles are encapsulated in TiO{sub 2}. The obtained ZnO, TiO{sub 2} and TiO{sub 2}/ZnO core–shell nanoparticles were investigated by means of X-ray diffraction, transmission electron microscopy, Brunauer, Emmett, Teller and resistance measurements. X-ray diffraction analysis revealed the presence of both, TiO{sub 2} and ZnO phases in TiO{sub 2}/ZnO core–shell nanoparticles. According to transmission electron microscopy images, ZnO nanoparticles have hexagonal shapes, TiO{sub 2} nanoparticles have a spherical shape, and TiO{sub 2}/ZnO core–shellmore » nanoparticles present agglomerates and the shape of particles is not well defined. The activation energy of TiO{sub 2}/ZnO core–shell nanoparticles was about 101 meV. - Graphical abstract: Display Omitted - Highlights: • TiO{sub 2}/ZnO core–shell nanoparticles were synthesized by hydrothermal method. • TiO{sub 2}/ZnO core–shell nanoparticles were investigated by means of XRD, TEM and BET. • Electrical properties of TiO{sub 2}/ZnO core–shell nanoparticles were investigated. • The activation energy of TiO{sub 2}/ZnO core–shell nanoparticles was about E{sub a} = 101 meV.« less

Development of n-ZnO/p-Si single heterojunction solar cell with and without interfacial layer

NASA Astrophysics Data System (ADS)

Hussain, Babar

The conversion efficiency of conventional silicon (Si) photovoltaic cells has not been improved significantly during last two decades but their cost decreased dramatically during this time. However, the higher price-per-watt of solar cells is still the main bottleneck in their widespread use for power generation. Therefore, new materials need to be explored for the fabrication of solar cells potentially with lower cost and higher efficiency. The n-type zinc oxide (n-ZnO) and p-type Si (p-Si) based single heterojunction solar cell (SHJSC) is one of the several attempts to replace conventional Si single homojunction solar cell technology. There are three inadequacies in the literature related to n-ZnO/p-Si SHJSC: (1) a detailed theoretical analysis to evaluate potential of the solar cell structure, (2) inconsistencies in the reported value of open circuit voltage (VOC) of the solar cell, and (3) lower value of experimentally achieved VOC as compared to theoretical prediction based on band-bending between n-ZnO and p-Si. Furthermore, the scientific community lacks consensus on the optimum growth parameters of ZnO. In this dissertation, I present simulation and experimental results related to n-ZnO/p-Si SHJSC to fill the gaps mentioned above. Modeling and simulation of the solar cell structure are performed using PC1D and AFORS-HET software taking practical constraints into account to explore the potential of the structure. Also, unnoticed benefits of ZnO in solar cells such as an additional antireflection (AR) effect and low temperature deposition are highlighted. The growth parameters of ZnO using metal organic chemical vapor deposition and sputtering are optimized. The structural, optical, and electrical characterization of ZnO thin films grown on sapphire and Si substrates is performed. Several n-ZnO/p-Si SHJSC devices are fabricated to confirm the repeatability of the VOC. Moreover, the AR effect of ZnO while working as an n-type layer is experimentally verified. The spatial analysis for thickness uniformity and optical quality of ZnO films is carried out. These properties turn out to play a fundamental role in device performance and so far have been overlooked by the research community. Three different materials are used as a quantum buffer layer at the interface of ZnO and Si to suppress the interface states and improve the VOC. The best measured value of VOC of 359 mV is achieved using amorphous-ZnO (a-ZnO) as the buffer layer at the interface. Finally, supplementary simulations are performed to optimize the valence-band and conduction-band offsets by engineering the bandgap and electron affinity of ZnO. After we published our initial results related to the feasibility of n-ZnO/p-Si SHJSC [Sol. Energ. Mat. Sol. Cells 139 (2015) 95-100], different research groups have fabricated and reported the solar cell performance with the best efficiency of 7.1% demonstrated very recently by Pietruszka et al. [Sol. Energ. Mat. Sol. Cells 147 (2016) 164-170]. We conclude that major challenge in n-ZnO/p-Si SHJSC is to overcome Fermi-level pinning at the hetero-interface. A potential solution is to use the appropriate material as buffer layer which is confirmed by observing an improvement in VOC using a-ZnO at the interface as buffer layer. Once the interface quality is improved and the experimental value of VOC matched the theoretical prediction, the n-ZnO/p-Si SHJSC can potentially have significant contribution in solar cells industry.

Optimization of headspace solid phase microextraction based on nano-structured ZnO combined with gas chromatography-mass spectrometry for preconcentration and determination of ultra-traces of chlorobenzenes in environmental samples.

PubMed

Ghasemi, Ensieh; Sillanpää, Mika

2014-12-01

In this study, a simple, novel and efficient preconcentration method for the determination of some chlorobenzenes (monochlorobenzene (MCB), three isomeric forms of dichlorobenzene (diCB), 1,3,5-trichlorobenzene (triCB) and hexachlorobenze (hexaCB)) has been developed using a headspace solid phase microextraction (HS-SPME) based on nano-structured ZnO combined with capillary gas chromatography-mass spectrometry (GC-MS). ZnO nanorods have been grown on fused silica fibers using a hydrothermal process. The diameter of ZnO nanorods was in the range of 50-80 nm. The effect of different variables on the extraction efficiency was studied simultaneously using an experimental design. The variables of interest in the HS-SPME were stirring rate, desorption time and temperature, ionic strength, extraction time and temperature. For this purpose, a multivariate strategy was applied based on an experimental design using a Plackett-Burman design for screening and a Box-Behnken design for optimizing of the significant factors. The detection limit and relative standard deviation (RSD) (n=5) for the target analytes were in the range of 0.01-0.1 ng L(-1) and 4.3-7.6%, respectively. The developed technique was found to be successfully applicable to preconcentration and determination of the target analytes in environmental water and soil samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Structural, mechanical and optical investigations in the TeO2-rich part of the TeO2-GeO2-ZnO ternary glass system

NASA Astrophysics Data System (ADS)

Ghribi, N.; Dutreilh-Colas, M.; Duclère, J.-R.; Gouraud, F.; Chotard, T.; Karray, R.; Kabadou, A.; Thomas, P.

2015-02-01

Stable glasses are successfully synthesized in the TeO2-GeO2-ZnO system at 850 °C by the melt-quenching method and the glass forming domain is determined in the TeO2-rich part of the diagram. The thermal study, carried out using differential scanning calorimetry, reveals that the glass transition temperature, as well as the thermal stability, increases with the addition of ZnO or GeO2. Bulk glass samples are elaborated within two series of compositions, corresponding to fixed concentrations in GeO2 (respectively 5 or 10 mol. %), and to various contents in ZnO. Structural changes caused by the ZnO addition are discussed based on Raman spectroscopy data. A progressive but very moderate network depolymerization is shown with increasing amount of ZnO. However, two different regimes can be identified, depending on the ZnO content. It is believed that ZnO acts as a network modifier for compositions below 20 mol. %, and starts to participate as a glass network former over such concentration. It is well evidenced that GeO2 contributes to the increase in Young's modulus E, evaluated from ultrasonic echography measurements. In addition, this oxide favors the network reticulation detected by the decrease of the Poisson ratio and the increase of the fractal bond connectivity. However, the role of ZnO is more complicated and will be extensively discussed. The decrease in the atomic packing density Cg probably explains the global evolution of E as a function of ZnO content. The refractive indices and optical band gap energies are extracted from UV-Visible-NIR optical transmission data. For the studied glasses, it is found that the transmission threshold decreases with larger ZnO contents, reflecting the increase in the optical band gap value. Refractive index is finally seen to decrease as a function of both ZnO and GeO2 contents. Such variation is explained by the decrease of the molar electronic polarizability, and by the lower optical basicity values known for TeO3 entities in comparison to TeO4 units.

Hydrothermal Growth of Vertically Aligned ZnO Nanorods Using a Biocomposite Seed Layer of ZnO Nanoparticles.

PubMed

Ibupoto, Zafar Hussain; Khun, Kimleang; Eriksson, Martin; AlSalhi, Mohammad; Atif, Muhammad; Ansari, Anees; Willander, Magnus

2013-08-19

Well aligned ZnO nanorods have been prepared by a low temperature aqueous chemical growth method, using a biocomposite seed layer of ZnO nanoparticles prepared in starch and cellulose bio polymers. The effect of different concentrations of biocomposite seed layer on the alignment of ZnO nanorods has been investigated. ZnO nanorods grown on a gold-coated glass substrate have been characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. These techniques have shown that the ZnO nanorods are well aligned and perpendicular to the substrate, and grown with a high density and uniformity on the substrate. Moreover, ZnO nanorods can be grown with an orientation along the c -axis of the substrate and exhibit a wurtzite crystal structure with a dominant (002) peak in an XRD spectrum and possessed a high crystal quality. A photoluminescence (PL) spectroscopy study of the ZnO nanorods has revealed a conventional near band edge ultraviolet emission, along with emission in the visible part of the electromagnetic spectrum due to defect emission. This study provides an alternative method for the fabrication of well aligned ZnO nanorods. This method can be helpful in improving the performance of devices where alignment plays a significant role.

Hydrothermal Growth of Vertically Aligned ZnO Nanorods Using a Biocomposite Seed Layer of ZnO Nanoparticles

PubMed Central

Ibupoto, Zafar Hussain; Khun, Kimleang; Eriksson, Martin; AlSalhi, Mohammad; Atif, Muhammad; Ansari, Anees; Willander, Magnus

2013-01-01

Well aligned ZnO nanorods have been prepared by a low temperature aqueous chemical growth method, using a biocomposite seed layer of ZnO nanoparticles prepared in starch and cellulose bio polymers. The effect of different concentrations of biocomposite seed layer on the alignment of ZnO nanorods has been investigated. ZnO nanorods grown on a gold-coated glass substrate have been characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. These techniques have shown that the ZnO nanorods are well aligned and perpendicular to the substrate, and grown with a high density and uniformity on the substrate. Moreover, ZnO nanorods can be grown with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a dominant (002) peak in an XRD spectrum and possessed a high crystal quality. A photoluminescence (PL) spectroscopy study of the ZnO nanorods has revealed a conventional near band edge ultraviolet emission, along with emission in the visible part of the electromagnetic spectrum due to defect emission. This study provides an alternative method for the fabrication of well aligned ZnO nanorods. This method can be helpful in improving the performance of devices where alignment plays a significant role. PMID:28811454

Modification of optical and electrical properties of zinc oxide-coated porous silicon nanostructures induced by swift heavy ion

PubMed Central

2012-01-01

Morphological and optical characteristics of radio frequency-sputtered zinc aluminum oxide over porous silicon (PS) substrates were studied before and after irradiating composite films with 130 MeV of nickel ions at different fluences varying from 1 × 1012 to 3 × 1013 ions/cm2. The effect of irradiation on the composite structure was investigated by scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), and cathodoluminescence spectroscopy. Current–voltage characteristics of ZnO-PS heterojunctions were also measured. As compared to the granular crystallites of zinc oxide layer, Al-doped zinc oxide (ZnO) layer showed a flaky structure. The PL spectrum of the pristine composite structure consists of the emission from the ZnO layer as well as the near-infrared emission from the PS substrate. Due to an increase in the number of deep-level defects, possibly oxygen vacancies after swift ion irradiation, PS-Al-doped ZnO nanocomposites formed with high-porosity PS are shown to demonstrate a broadening in the PL emission band, leading to the white light emission. The broadening effect is found to increase with an increase in the ion fluence and porosity. XRD study revealed the relative resistance of the film against the irradiation, i.e., the irradiation of the structure failed to completely amorphize the structure, suggesting its possible application in optoelectronics and sensing applications under harsh radiation conditions. PMID:22748164

Self-Assembled ZnO Nanosheet-Based Spherical Structure as Photoanode in Dye-Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Ameri, Mohsen; Raoufi, Meysam; Zamani-Meymian, M.-R.; Samavat, Feridoun; Fathollahi, M.-R.; Mohajerani, Ezeddin

2018-03-01

High surface area and enhanced light scattering of ZnO nanosheet aggregates have made them a promising active layer candidate material for fabrication of nanostructure dye-sensitized solar cells. Here, we propose a facile preparation method of such ZnO nanosheet structures, and in order to verify their applicability as photoanode material for dye-sensitized solar cells, we employ morphological, optical, structural and electrical measurements. The results reveal the high surface area available for dye molecules for enhancing adsorption, high light scattering and competitive power conversion efficiencies compared to the works in literature. Finally, the device is optimized with respect to the photoanode thickness. The favorable features shown here can extend the application of the structure to other types of sensitization-based perovskite and quantum dot solar cells.

Origin of stress in radio frequency magnetron sputtered zinc oxide thin films

NASA Astrophysics Data System (ADS)

Menon, Rashmi; Gupta, Vinay; Tan, H. H.; Sreenivas, K.; Jagadish, C.

2011-03-01

Highly c-axis oriented ZnO thin films have been deposited on silicon substrates by planar rf magnetron sputtering under varying pressure (10-50 mTorr) and oxygen percentage (50-100%) in the reactive gas (Ar + O2) mixture. The as-grown films were found to be stressed over a wide range from -1 × 1011 to -2 × 108 dyne/cm2 that in turn depends strongly on the processing conditions, and the film becomes stress free at a unique combination of sputtering pressure and reactive gas composition. Raman spectroscopy and photoluminescence (PL) analyses identified the origin of stress as lattice distortion due to defects introduced in the ZnO thin film. FTIR study reveals that Zn-O bond becomes stronger with the increase in oxygen fraction in the reactive gas mixture. The lattice distortion or stress depends on the type of defects introduced during deposition. PL spectra show the formation of a shoulder in band emission with an increase in the processing pressure and are related to the presence of stress. The ratio of band emission to defect emission decreases with the increase in oxygen percentage from 50 to 100%. The studies show a correlation of stress with the structural, vibrational, and photoluminescence properties of the ZnO thin film. The systematic study of the stress will help in the fabrication of efficient devices based on ZnO film.

Fate of Zinc Oxide Nanoparticles Coated onto Macronutrient Fertilizers in an Alkaline Calcareous Soil

PubMed Central

Milani, Narges; Hettiarachchi, Ganga M.; Kirby, Jason K.; Beak, Douglas G.; Stacey, Samuel P.; McLaughlin, Mike J.

2015-01-01

Zinc oxide (ZnO) nanoparticles may provide a more soluble and plant available source of Zn in Zn fertilizers due to their greater reactivity compared to equivalent micron- or millimetre-sized (bulk) particles. However, the effect of soil on solubility, spatial distribution and speciation of ZnO nanoparticles has not yet been investigated. In this study, we examined the diffusion and solid phase speciation of Zn in an alkaline calcareous soil following application of nanoparticulate and bulk ZnO coated fertilizer products (monoammonium phosphate (MAP) and urea) using laboratory-based x-ray techniques and synchrotron-based μ-x-ray fluorescence (μ–XRF) mapping and absorption fine structure spectroscopy (μ–XAFS). Mapping of the soil-fertilizer reaction zones revealed that most of the applied Zn for all treatments remained on the coated fertilizer granule or close to the point of application after five weeks of incubation in soil. Zinc precipitated mainly as scholzite (CaZn2(PO4)2.2H2O) and zinc ammonium phosphate (Zn(NH4)PO4) species at the surface of MAP granules. These reactions reduced dissolution and diffusion of Zn from the MAP granules. Although Zn remained as zincite (ZnO) at the surface of urea granules, limited diffusion of Zn from ZnO-coated urea granules was also observed for both bulk and nanoparticulate ZnO treatments. This might be due to either the high pH of urea granules, which reduced solubility of Zn, or aggregation (due to high ionic strength) of released ZnO nanoparticles around the granule/point of application. The relative proportion of Zn(OH)2 and ZnCO3 species increased for all Zn treatments with increasing distance from coated MAP and urea granules in the calcareous soil. When coated on macronutrient fertilizers, Zn from ZnO nanoparticles (without surface modifiers) was not more mobile or diffusible compared to bulk forms of ZnO. The results also suggest that risk associated with the presence of ZnO NPs in calcareous soils would be the same as bulk sources of ZnO. PMID:25965385

Seed/catalyst-free growth of zinc oxide nanostructures on multilayer graphene by thermal evaporation

PubMed Central

2014-01-01

We report the seed/catalyst-free growth of ZnO on multilayer graphene by thermal evaporation of Zn in the presence of O2 gas. The effects of substrate temperatures were studied. The changes of morphologies were very significant where the grown ZnO structures show three different structures, i.e., nanoclusters, nanorods, and thin films at 600°C, 800°C, and 1,000°C, respectively. High-density vertically aligned ZnO nanorods comparable to other methods were obtained. A growth mechanism was proposed based on the obtained results. The ZnO/graphene hybrid structure provides several potential applications in electronics and optoelectronics. PMID:24533793

Photo-induced self-cleaning and sterilizing activity of Sm3+ doped ZnO nanomaterials.

PubMed

Saif, M; Hafez, H; Nabeel, A I

2013-01-01

Highly active samarium doped zinc oxide self-cleaning and biocidal surfaces (x mol% Sm(3+)/ZnO where x=0, 1, 2 and 4 mol%) with crystalline porous structures were synthesized by hydrothermal method. Sm(3+)/ZnO thin films were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersive spectroscopic (EDS), UV-visible diffuse reflectance and fluorescence (FL) spectroscopy. The combination between doping and hydrothermal treatments significantly altered the morphology of ZnO into rod and plate-like nanoshapes structure and enhanced its absorption and emission of ultraviolet radiation. The photo-activity in term of quantitative determination of the active oxidative species (()OH) produced on the thin film surfaces was evaluated using fluorescent probe method. The results showed that, the hydrothermally treated 2.0 mol% Sm(3+)/ZnO film (S2) is the highly active one. The optical, structural, morphology and photo-activity properties of the highly active thin film (S2) make it promising surface for self-cleaning and sterilizing applications. Copyright © 2012 Elsevier Ltd. All rights reserved.

Real structure of (Sb1/3Zn2/3)GaO3(ZnO)3, a member of the homologous series ARO3(ZnO)m with ordered site occupation

NASA Astrophysics Data System (ADS)

Garling, Jennifer; Assenmacher, Wilfried; Schmid, Herbert; Longo, Paolo; Mader, Werner

2018-02-01

The hitherto unknown compound (Sb1/3Zn2/3)GaO3(ZnO)3, a member of the homologous series with general formula ARO3(ZnO)m (A,R = trivalent metal cation), was prepared by solid state methods from the binary oxides in sealed Pt-tubes. The structure of (Sb1/3Zn2/3)GaO3(ZnO)3 has been determined by X-ray diffraction from flux-grown single crystals (R 3 ̅ m , Z = 3, aR = 3.2387(7) Å, cR = 41.78(1) Å. The analysis revealed that (Sb1/3Zn2/3)GaO3(ZnO)m is isostructural with InGaO3(ZnO)m, where In3+ on octahedral sites is replaced by Sb5+ and Zn2+ in a ratio of 1:2, preserving an average charge of 3+. (Sb1/3Zn2/3)GaO3(ZnO)3 was furthermore analyzed by electron diffraction, High Angle Annular Dark Field (HAADF) scanning TEM, and high precision EELS spectroscopic imaging, where a periodic ordering of SbO6 octahedra connected via edge sharing to six ZnO6 octahedra in the octahedral layers in a honeycomb motif is found. Due to the large lateral distance of ca. 1.4 nm between adjacent octahedral layers, electrostatic interaction might hardly dictate Sb and Zn positions in neighbouring layers, and hence is a characteristic of the real structure of (Sb1/3Zn2/3)GaO3(ZnO)3. A structure model of the compound in space group P3112 (Nr. 151) with strictly ordered and discrete Sb and Zn positions is derived by crystallographic transformations as closest approximant for the real structure of (Sb1/3Zn2/3)GaO3(ZnO)3. UV-vis measurements confirm this compound to be a transparent oxide with an optical band gap in the UV region with Eg = 3.15 eV.

Green synthesis and characterization of zinc oxide nanoparticle using insulin plant (Costus pictus D. Don) and investigation of its antimicrobial as well as anticancer activities

NASA Astrophysics Data System (ADS)

Suresh, Joghee; Pradheesh, Ganeshan; Alexramani, Vincent; Sundrarajan, Mahalingam; Hong, Sun Ig

2018-03-01

In this work we aim to synthesize biocompatible ZnO nanoparticles from the zinc nitrate via green process using leaf extracts of the Costus pictus D. Don medicinal plant. FTIR studies confirm the presence of biomolecules and metal oxides. X-ray diffraction (XRD) structural analysis reveals the formation of pure hexagonal phase structures of ZnO nanoparticles. The surface morphologies of ZnO nanoparticles observed under a scanning electron microscope (SEM) suggest that most ZnO crystallites are hexagonal. EDX analysis confirms the presence of primarily zinc and oxygen. TEM images show that biosynthesized zinc oxide nanoparticles are hexagonal and spherical. The plausible formation mechanisms of zinc oxide nanoparticles are also predicted. The biosynthesized zinc oxide nanoparticles exhibit strong antimicrobial behavior against bacterial and fungal species when employing the agar diffusion method. Synthesized ZnO nanoparticles exhibit anticancer activity against Daltons lymphoma ascites (DLA) cells as well as antimicrobial activity against some bacterial and fungal strains.

Tailoring the morphology of electrodeposited ZnO and its photoluminescence properties

NASA Astrophysics Data System (ADS)

Cui, H.; Mollar, M.; Marí, B.

2011-01-01

High density ZnO columnar films with well-aligned and well-perpendicular to the surface of film were electrodeposited on ITO substrates by using an electrolyte consisting of a mix of water and organic solvent namely dimethylsulfoxide (DMSO). The effect of mixing ratio of water and DMSO on the growth of film has been examined critically. SEM images have shown that well-oriented ZnO quasi-nano columns were formed perpendicular to the substrate. At the same time we found there are three kinds of competitions for growth of ZnO crystalmorphology i.e. column, rod and needle like. The needle like morphology has high density with well-aligned structure. The reasons for the growth of films of different morphology and their photoluminescence (PL) properties have been presented and discussed. It has been found that the three-dimensional (3D) ordered ZnO structure exhibits high intensity PL band which may shift their position and intensity with the varying conditions of depositions.

Sonochemical synthesis and photocatalytic property of zinc oxide nanoparticles doped with magnesium(II)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Xianyong, E-mail: xylu@buaa.edu.cn; Liu, Zhaoyue; Zhu, Ying

2011-10-15

Highlights: {yields} Mg-doped ZnO nanoparticles were synthesized by sonochemical strategy. {yields} Mg-doped ZnO nanoparticles present good photocatalytic properties. {yields} The change of band gap contributes to their high efficiency in photocatalyst. -- Abstract: Mg-doped ZnO nanoparticles were successfully synthesized by sonochemical method. The products were characterized by scan electron microscopy (SEM) and X-ray powder diffraction (XRD). SEM images revealed that ZnO doped with Mg(II) nanoparticles and ZnO nanoparticles synthesized by the same strategy all had spherical topography. XRD patterns showed that the doped nanoparticles had the same crystals structures as the pure ZnO nanoparticles. The Mg-doped ZnO nanoparticles had largermore » lattice volume than the un-doped nanoparticles. X-ray photoelectron spectroscopy (XPS) not only demonstrated the moral ratio of Mg and Zn element on the surface of nanoparticles, but their valence in nanoparticles as well. The Mg-doped ZnO nanoparticles presented good properties in photocatalyst compared with pure ZnO nanoparticles.« less

Improved luminescence intensity and stability of thermal annealed ZnO incorporated Alq3 composite films.

PubMed

Cuba, M; Muralidharan, G

2015-11-01

The 30 wt% of ZnO (weight percentage of ZnO has been optimised) incorporated tris- (8-hydroxyquinoline)aluminum (Alq3) has been synthesised and coated on to glass substrates using dip coating method. The structural and optical properties of the Alq3/ZnO composite film after thermal annealing from 50 to 300 °C insteps 50° has been studied and reported. XRD pattern reveals the presence of crystalline ZnO in all the annealed films. The films annealed above 150 °C reveal the presence of crystalline Alq3 along with crystalline ZnO. The FTIR spectra confirm the presence of hydroxyquinoline and ZnO vibration in all the annealed composite films. The composite films annealed above 150 °C show a partial sublimation and degradation of hydroxyquinoline compounds. The ZnO incorporated composite films (Alq3/ZnO) exhibit two emission peaks, one corresponding to ZnO at 487 nm and another at 513 nm due to Alq3. The films annealed at 200 °C exhibit maximum photoluminescence (PL) intensity than pristine film at 513 nm when excited at 390 nm.

Variation of microstructural and optical properties in SILAR grown ZnO thin films by thermal treatment.

PubMed

Valanarasu, S; Dhanasekaran, V; Chandramohan, R; Kulandaisamy, I; Sakthivelu, A; Mahalingam, T

2013-08-01

The influence of thermal treatment on the structural and morphological properties of the ZnO films deposited by double dip Successive ionic layer by adsorption reaction is presented. The effect of annealing temperature and time in air ambient is presented in detail. The deposited films were annealed from 200 to 400 degrees C in air and the structural properties were determined as a function of annealing temperature by XRD. The studies revealed that films were exhibiting preferential orientation along (002) plane. The other structural parameters like the crystallite size (D), micro strain (epsilon), dislocation density (delta) and stacking fault (alpha) of as-deposited and annealed ZnO films were evaluated and reported. The optical properties were also studied and the band gap of the ZnO thins films varied from 3.27 to 3.04 eV with the annealing temperature. SEM studies revealed that the hexagonal shaped grains with uniformly distributed morphology in annealed ZnO thin films. It has been envisaged using EDX analysis that the near stoichiometric composition of the film can be attained by thermal treatment during which microstructural changes do occur.

High-energy ball milling technique for ZnO nanoparticles as antibacterial material

PubMed Central

Salah, Numan; Habib, Sami S; Khan, Zishan H; Memic, Adnan; Azam, Ameer; Alarfaj, Esam; Zahed, Nabeel; Al-Hamedi, Salim

2011-01-01

Nanoparticles of zinc oxide (ZnO) are increasingly recognized for their utility in biological applications. In this study, the high-energy ball milling (HEBM) technique was used to produce nanoparticles of ZnO from its microcrystalline powder. Four samples were ball milled for 2, 10, 20, and 50 hours, respectively. The structural and optical modifications induced in the ‘as synthesized’ nanomaterials were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), and photoluminescence emission spectra (PL). SEM and TEM results show a gradual decrease in particle size from around 600 to ∼30 nm, with increased milling time. The initial microstructures had random shapes, while the final shape became quite spherical. XRD analysis showed ZnO in a hexagonal structure, broadening in the diffracted peaks and going from larger to smaller particles along with a relaxation in the lattice constant c. The value of c was found to increase from 5.204 to 5.217 Å with a decrease in particle size (600 to ∼30 nm). PL result showed a new band at around 365 nm, whose intensity is found to increase as the particles size decreases. These remarkable structural and optical modifications induced in ZnO nanoparticles might prove useful for various applications. The increase in c value is an important factor for increasing the antibacterial effects of ZnO, suggesting that the HEBM technique is quite suitable for producing these nanoparticles for this purpose. PMID:21720499

Polycrystalline ZnO and Mn-doped ZnO nanorod arrays with variable dopant content via a template based synthesis from Zn(II) and Mn(II) Schiff base type single source molecular precursors

NASA Astrophysics Data System (ADS)

Pashchanka, Mikhail; Hoffmann, Rudolf C.; Burghaus, Olaf; Corzilius, Björn; Cherkashinin, Gennady; Schneider, Jörg J.

2011-01-01

The synthesis and full characterisation of pure and Mn-doped polycrystalline zinc oxide nanorods with tailored dopant content are obtained via a single source molecular precursor approach using two Schiff base type coordination compounds is reported. The infiltration of precursor solutions into the cylindrical pores of a polycarbonate template and their thermal conversion into a ceramic green body followed by dissolution of the template gives the desired ZnO and Mn-doped ZnO nanomaterial as compact rods. The ZnO nanorods have a mean diameter between 170 and 180 nm or 60-70 nm, depending on the template pore size employed, comprising a length of 5-6 μm. These nanorods are composed of individual sub-5 nm ZnO nanocrystals. Exact doping of these hierarchically structured ZnO nanorods was achieved by introducing Mn(II) into the ZnO host lattice with the precursor complex Diaquo-bis[2-(meth-oxyimino)-propanoato]manganese, which allows to tailor the exact Mn(II) doping content of the ZnO rods. Investigation of the Mn-doped ZnO samples by XRD, TEM, XPS, PL and EPR, reveals that manganese occurs exclusively in its oxidation state + II and is distributed within the volume as well as on the surface of the ZnO host.

Simple fabrication process for 2D ZnO nanowalls and their potential application as a methane sensor.

PubMed

Chen, Tse-Pu; Chang, Sheng-Po; Hung, Fei-Yi; Chang, Shoou-Jinn; Hu, Zhan-Shuo; Chen, Kuan-Jen

2013-03-20

Two-dimensional (2D) ZnO nanowalls were prepared on a glass substrate by a low-temperature thermal evaporation method, in which the fabrication process did not use a metal catalyst or the pre-deposition of a ZnO seed layer on the substrate. The nanowalls were characterized for their surface morphology, and the structural and optical properties were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and photoluminescence (PL). The fabricated ZnO nanowalls have many advantages, such as low growth temperature and good crystal quality, while being fast, low cost, and easy to fabricate. Methane sensor measurements of the ZnO nanowalls show a high sensitivity to methane gas, and rapid response and recovery times. These unique characteristics are attributed to the high surface-to-volume ratio of the ZnO nanowalls. Thus, the ZnO nanowall methane sensor is a potential gas sensor candidate owing to its good performance.

Simple Fabrication Process for 2D ZnO Nanowalls and Their Potential Application as a Methane Sensor

PubMed Central

Chen, Tse-Pu; Chang, Sheng-Po; Hung, Fei-Yi; Chang, Shoou-Jinn; Hu, Zhan-Shuo; Chen, Kuan-Jen

2013-01-01

Two-dimensional (2D) ZnO nanowalls were prepared on a glass substrate by a low-temperature thermal evaporation method, in which the fabrication process did not use a metal catalyst or the pre-deposition of a ZnO seed layer on the substrate. The nanowalls were characterized for their surface morphology, and the structural and optical properties were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and photoluminescence (PL). The fabricated ZnO nanowalls have many advantages, such as low growth temperature and good crystal quality, while being fast, low cost, and easy to fabricate. Methane sensor measurements of the ZnO nanowalls show a high sensitivity to methane gas, and rapid response and recovery times. These unique characteristics are attributed to the high surface-to-volume ratio of the ZnO nanowalls. Thus, the ZnO nanowall methane sensor is a potential gas sensor candidate owing to its good performance. PMID:23519350

High temperature ferromagnetism in Ni doped ZnO nanoparticles: Milling time dependence

NASA Astrophysics Data System (ADS)

Pal, Bappaditya; Giri, P. K.; Sarkar, D.

2014-04-01

We report on the room temperature ferromagnetism (RT FM) in the Zn1-xNixO (x = 0, 0.03, and 0.05) nanoparticles (NPs) synthesized by a ball milling technique. X-ray diffraction analysis confirms the single crystalline ZnO wurtzite structure with presence of small intensity secondary phase related peak which disappear with increasing milling time for Ni doped samples. HRTEM lattice images show that the doped NPs are single crystalline with a dspacing of 2.44 Å. Energy-dispersive X-ray spectroscopy analysis confirms the presence of Ni ions in the ZnO matrix. Magnetic measurement (RT) exhibits the hysteresis loop with saturation magnetization (Ms) of 1.6-2.56 (emu/g) and coercive field (Hc) of 296-322 Oe. M-T measurement shows a Curie temperature of the order of 325°C for 3% Ni doped sample. Micro -Raman studies show doping/disorder induced additional modes at ˜510, 547, 572 cm-1 in addition to 437 cm-1 peak of pure ZnO. UV-Vis absorption spectra illustrate band gap shift due to doping. Alteration of Ms value with the variation of doping concentration and milling time has been studied and discussed.

Thermal and structural properties of zinc modified tellurite based glasses

NASA Astrophysics Data System (ADS)

Kundu, R. S.; Dhankhar, Sunil; Punia, R.; Dult, Meenakshi; Kishore, N.

2016-05-01

Glass system 60 TeO2 - 10 B2O3-(30-x) Bi2O3-x ZnO with mole fraction x = 10, 15, 20, 25 and 30 were synthesized by conventional melt quenching technique under controlled atmospheric conditions. The glass transition temperature (Tg) has been determined using differential scanning Calorimetry (DSC) and its value is observed to increase with increase in ZnO content. This increase may be due to the increase in the concentration of the bridging oxygen (BO) atoms. IR and Raman spectra of the present glass system indicate that ZnO acts as network modifier and exists in ZnO4 units. TeO2 exists as TeO3, TeO4, and TeO3+1 structural units. Bismuth plays the role of network modifier with BiO6 octahedral structural units whereas B2O3 exists in the form of BO3 trigonal and BO4 tetrahedral structural units.

Structural and optical properties of Na-doped ZnO films

NASA Astrophysics Data System (ADS)

Akcan, D.; Gungor, A.; Arda, L.

2018-06-01

Zn1-xNaxO (x = 0.0-0.05) solutions have been synthesized by the sol-gel technique using Zinc acetate dihydrate and Sodium acetate which were dissolved into solvent and chelating agent. Na-doped ZnO nanoparticles were obtained from solutions to find phase and crystal structure. Na-doped ZnO films have been deposited onto glass substrate by using sol-gel dip coating system. The effects of dopant concentration on the structure, morphology, and optical properties of Na-doped ZnO thin films deposited on glass substrate are investigated. Characterization of Zn1-xNaxO nanoparticles and thin films are examined using differential thermal analysis (DTA)/thermogravimetric analysis (TGA), Scanning electron microscope (SEM) and X-Ray diffractometer (XRD). Optical properties of Zn1-xNaxO thin films were obtained by using PG Instruments UV-Vis-NIR spectrophotometer in 190-1100 nm range. The structure, morphology, and optical properties of thin films are presented.

Structural, magnetic and optical properties of ZnO nanostructures converted from ZnS nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, Prayas Chandra; Ghosh, Surajit; Srivastava, P.C., E-mail: pcsrivastava50@gmail.com

Graphical abstract: The phase conversion of ZnS to highly crystalline hexagonal ZnO was done by heat treatment. - Highlights: • Phase change of cubic ZnS to hexagonal ZnO via heat treatment. • Band gap was found to decrease with increasing calcinations temperature. • ZnO samples have higher magnetic moment than ZnS. • Blocking Temperature of the samples is well above room temperature. • Maximum negative%MR with saturation value ∼38% was found for sample calcined at 600° C. - Abstract: The present work concentrates on the synthesis of cubic ZnS and hexagonal ZnO semiconducting nanoparticle from same precursor via co-precipitation method.more » The phase conversion of ZnS to highly crystalline hexagonal ZnO was done by heat treatment. From the analysis of influence of calcination temperature on the structural, optical and vibrational properties of the samples, an optimum temperature was found for the total conversion of ZnS nanoparticles to ZnO. Role of quantum confinement due to finite size is evident from the blue shift of the fundamental absorption in UV–vis spectra only in the ZnS nanoparticles. The semiconducting nature of the prepared samples is confirmed from the UV–vis, PL study and transport study. From the magnetic and transport studies, pure ZnO phase was found to be more prone to magnetic field.« less

Highly textured and transparent RF sputtered Eu2O3 doped ZnO films

PubMed Central

Sreedharan, Remadevi Sreeja; Ganesan, Vedachalaiyer; Sudarsanakumar, Chellappan Pillai; Bhavsar, Kaushalkumar; Prabhu, Radhakrishna; Mahadevan Pillai, Vellara Pappukutty Pillai

2015-01-01

Background Zinc oxide (ZnO) is a wide, direct band gap II-VI oxide semiconductor. ZnO has large exciton binding energy at room temperature, and it is a good host material for obtaining visible and infrared emission of various rare-earth ions. Methods Europium oxide (Eu2O3) doped ZnO films are prepared on quartz substrate using radio frequency (RF) magnetron sputtering with doping concentrations 0, 0.5, 1, 3 and 5 wt%. The films are annealed in air at a temperature of 773 K for 2 hours. The annealed films are characterized using X-ray diffraction (XRD), micro-Raman spectroscopy, atomic force microscopy, ultraviolet (UV)-visible spectroscopy and photoluminescence (PL) spectroscopy. Results XRD patterns show that the films are highly c-axis oriented exhibiting hexagonalwurtzite structure of ZnO. Particle size calculations using Debye-Scherrer formula show that average crystalline size is in the range 15–22 nm showing the nanostructured nature of the films. The observation of low- and high-frequency E2 modes in the Raman spectra supports the hexagonal wurtzite structure of ZnO in the films. The surface morphology of the Eu2O3 doped films presents dense distribution of grains. The films show good transparency in the visible region. The band gaps of the films are evaluated using Tauc plot model. Optical constants such as refractive index, dielectric constant, loss factor, and so on are calculated using the transmittance data. The PL spectra show both UV and visible emissions. Conclusion Highly textured, transparent, luminescent Eu2O3 doped ZnO films have been synthesized using RF magnetron sputtering. The good optical and structural properties and intense luminescence in the ultraviolet and visible regions from the films suggest their suitability for optoelectronic applications. PMID:25765728

Spectroscopic characterization of zinc oxide nanorods synthesized by solid-state reaction

NASA Astrophysics Data System (ADS)

Prasad, Virendra; D'Souza, Charlene; Yadav, Deepti; Shaikh, A. J.; Vigneshwaran, Nadanathangam

2006-09-01

Well-crystallized zinc oxide nanorods have been fabricated by single step solid-state reaction using zinc acetate and sodium hydroxide, at room temperature. The sodium lauryl sulfate (SLS) stabilized zinc oxide nanorods were characterized by using X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and photoluminescence spectroscopy. The X-ray diffraction revealed the wurtzite structure of zinc oxide. The size estimation by XRD and TEM confirmed that the ZnO nanorods are made of single crystals. The growth of zinc oxide crystals into rod shape was found to be closely related to its hexagonal nature. The mass ratio of SLS:ZnO in the nanorods was found to be 1:10 based on the thermogravimetric analysis. Blue shift of photoluminescence emission was noticed in the ZnO nanorods when compared to that of ZnO bulk. FT-IR analysis confirmed the binding of SLS with ZnO nanorods. Apart from ease of preparation, this method has the advantage of eco-friendliness since the solvent and other harmful chemicals were eliminated in the synthesis protocol.

Significant enhancement of yellow-green light emission of ZnO nanorod arrays using Ag island films

NASA Astrophysics Data System (ADS)

Lin, Chin-An; Tsai, Dung-Sheng; Chen, Cheng-Ying; He-Hau, Jr.

2011-03-01

Surface plasmon (SP) mediated emission from ZnO nanorod arrays (NRAs)/Ag/Si structures has been investigated. The ratio of visible emission to UV emission can be increased by over 30 times via coupling with SP without deterioration of the crystal quality. The fact that the effect of SP crucially depends on the size of Ag island films provides the feasibility to significantly enhance the yellow-green emission of the ZnO nanostructures without sacrificing the crystallinity of ZnO.Surface plasmon (SP) mediated emission from ZnO nanorod arrays (NRAs)/Ag/Si structures has been investigated. The ratio of visible emission to UV emission can be increased by over 30 times via coupling with SP without deterioration of the crystal quality. The fact that the effect of SP crucially depends on the size of Ag island films provides the feasibility to significantly enhance the yellow-green emission of the ZnO nanostructures without sacrificing the crystallinity of ZnO. Electronic supplementary information (ESI) available. See DOI: 10.1039/c0nr00732c

Pre-patterned ZnO nanoribbons on soft substrates for stretchable energy harvesting applications

NASA Astrophysics Data System (ADS)

Ma, Teng; Wang, Yong; Tang, Rui; Yu, Hongyu; Jiang, Hanqing

2013-05-01

Three pre-patterned ZnO nanoribbons in different configurations were studied in this paper, including (a) straight ZnO nanoribbons uniformly bonded on soft substrates that form sinusoidal buckles, (b) straight ZnO nanoribbons selectively bonded on soft substrates that form pop-up buckles, and (c) serpentine ZnO nanoribbons bonded on soft substrates via anchors. The nonlinear dynamics and random analysis were conducted to obtain the fundamental frequencies and to evaluate their performance in energy harvesting applications. We found that pop-up buckles and overhanging serpentine structures are suitable for audio frequency energy harvesting applications. Remarkably, almost unchanged fundamental natural frequency upon strain is achieved by properly patterning ZnO nanoribbons, which initiates a new and exciting direction of stretchable energy harvesting using nano-scale materials in audio frequency range.

Zinc interstitial threshold in Al-doped ZnO film: Effect on microstructure and optoelectronic properties

NASA Astrophysics Data System (ADS)

Singh, Chetan C.; Panda, Emila

2018-04-01

In order to know the threshold quantity of the zinc interstitials that contributes to an increase in carrier concentration in the Al-doped ZnO (AZO) films and their effect on the overall microstructure and optoelectronic properties of these films, in this work, Zn-rich-AZO and ZnO thin films are fabricated by adding excess zinc (from a zinc metallic target) during their deposition in RF magnetron sputtering and are then investigated using a wide range of experimental techniques. All these films are found to grow in a ZnO hexagonal wurtzite crystal structure with strong (002) orientation of the crystallites, with no indication of Al2O3, metallic Zn, and Al. The excessively introduced zinc in these AZO and/or ZnO films is found to increase the shallow donor level defects (i.e., zinc interstitials and oxygen-related electronic defect states), which is found to significantly increase the carrier concentration in these films. Additionally, aluminum is seen to enhance the creation of these electronic defect states in these films, thereby contributing more to the overall carrier concentration of these films. However, carrier mobility is found to decrease when the carrier concentration values are higher than 4 × 1020 cm-3, because of the electron-electron scattering. Whereas the optical band gap of the ZnO films is found to increase with increasing carrier concentration because of the Burstein-Moss shift, these decrease for the AZO films due to the band gap narrowing effect caused by excess carrier concentration.

Structure and properties of nanostructured ZnO arrays and ZnO/Ag nanocomposites fabricated by pulsed electrodeposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kopach, V. R.; Klepikova, K. S.; Klochko, N. P., E-mail: klochko-np@mail.ru

We investigate the structure, surface morphology, and optical properties of nanostructured ZnO arrays fabricated by pulsed electrodeposition, Ag nanoparticles precipitated from colloidal solutions, and a ZnO/Ag nanocomposite based on them. The electronic and electrical parameters of the ZnO arrays and ZnO/Ag nanocomposites are analyzed by studying the I–V and C–V characteristics. Optimal modes for fabricating the ZnO/Ag heterostructures with the high stability and sensitivity to ultraviolet radiation as promising materials for use in photodetectors, gas sensors, and photocatalysts are determined.

Micro-nano zinc oxide film fabricated by biomimetic mineralization: Designed architectures for SERS substrates

NASA Astrophysics Data System (ADS)

Lu, Fei; Guo, Yue; Wang, Yunxin; Song, Wei; Zhao, Bing

2018-05-01

In this study, we have investigated the effect of the surface morphologies of the zinc oxide (ZnO) substrates on surface enhanced Raman spectroscopy (SERS). During synthetic process, the self-assembly monolayers (SAMs) with different terminal groups are used as templates to induce the nucleation and growth of Zn(NO3)2·6H2O crystals, then different morphologies micro-nano ZnO powders are obtained by annealing Zn(NO3)2·6H2O crystals at 450 °C. The products obtained at different conditions are characterized by means of X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM) and Raman spectra. The as-prepared ZnO micro-sized particles have been used the efficient Surface enhanced Raman scattering (SERS) substrates, and the SERS signals of 4-mercaptopyridine (Mpy) probe molecules are much influenced by the morphologies of the ZnO structures. Results indicated that the more (0001) facets appear in the of ZnO morphology, the greater degree of charge-transfer (PCT) for the SERS enhancement on the surface of semiconductors is achieved. The chemical interaction between ZnO structures and Mpy molecules plays a very important role in the SERS enhancement.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gawai, U. P.; Dole, B. N.; Khawal, H. A.

Ag doped ZnO nanocrystals were synthesized by co-precipitation method with the nominal compositions (x=0.00, 0.02, 0.04, 0.06). The as-synthesized Ag doped ZnO nanocrystals were characterized by X-ray diffraction (XRD), FTIR and UV-Vis. From XRD patterns samples shows hexagonal structure. The average crystallite size is in the range of 41-47 nm. All as synthesized Zn{sub 1−x}Ag{sub x}O nanocrystals are highly textured, with wurtzite structure along the (101) growth direction. The energy band gap of pure and Ag doped ZnO were calculated from UV-Vis spectra. FTIR spectra were confirmed that Ag substituted into ZnO. Chemical species of the samples were detected using FTIRmore » spectra An increase in the hexagonal lattice parameters of ZnO is observed on increasing the Ag concentration. An optical absorption study shows an increment in the band gap with increasing Ag content. From optical study the samples determines blue shift. Atomic packing fraction (APF) and c/a ratio were calculated using XRD data. It confirms the formation of ZnO with the stretching vibrational mode around at 506 to 510 cm{sup −1}.« less

Structure, magnetic, and electrical properties of Zn1-xMnxO material

NASA Astrophysics Data System (ADS)

Sebayang, P.; Hulu, S. F.; Nasruddin, Aryanto, D.; Kurniawan, C.; Subhan, A.; Sudiro, T.; Ginting, M.

2017-07-01

ZnO and MnO2 powder were synthesized using solid state reaction method to produce Zn1-xMnxO materials. Effect of dopant concentrations at the material of Zn1-xMnxO (x = 0.015, 0.02, 0.025) to the change of crystal structure, electrical and magnetic properties was studied. The X-ray diffraction (XRD) result of the samples that were doped with Mn showed a hexagonal wurtzite polycrystalline structure. The addition of Mn dopant resulting the decrease of lattice parameters and peaks intensity. The significant increase of the peak intensity occurred at x = 0.02, which also indicated an increase in the crystal quality of ZnO. The change of the ZnO structure affected the electrical and magnetic properties of the samples.

Spectroscopic and fiber optic ethanol sensing properties Gd doped ZnO nanoparticles.

PubMed

Noel, J L; Udayabhaskar, R; Renganathan, B; Muthu Mariappan, S; Sastikumar, D; Karthikeyan, B

2014-11-11

We report the structural, optical and gas sensing properties of prepared pure and Gd doped ZnO nanoparticles through solgel method at moderate temperature. Structural studies are carried out by X-ray diffraction method confirms hexagonal wurtzite structure and doping induced changes in lattice parameters is observed. Optical absorption spectral studies shows red shift in the absorption peak corresponds to band-gap from 3.42 eV to 3.05 eV and broad absorption in the visible range after Gd doping is observed. Scanning electron microscopic studies shows increase in particle size where the particle diameters increase from few nm to micrometers after Gd doping. The clad modified ethanol fiber-optic sensor studies for ethanol sensing exhibits best sensitivity for the 3% Gd doped ZnO nanoparticles and the sensitivity get lowered incase of higher percentage of Gd doped ZnO sample. Copyright © 2014 Elsevier B.V. All rights reserved.

SHI irradiation effect on pure and Mn doped ZnO thin films

NASA Astrophysics Data System (ADS)

Khawal, H. A.; Raskar, N. D.; Dole, B. N.

2017-05-01

Investigated the structural, surface, electrical and modifications induced by Swift Heavy Ions (SHI) irradiation on pure and Mn substituted ZnO thin films were observed. Thin films of Zn1-xMnxO (x = 0.00, 0.04) were synthesized using the dip coating technique. All thin films irradiated by Li3+ swift heavy ions with fluence 5 × 1013 ions/cm2. The XRD peak reveals that all the samples exhibit wurtzite structures. Surface morphology of samples was investigated by SEM, it was observed that pristine samples of ZnO thin film shows spherical shape but for 4 % Mn substituted ZnO thin film with 5 × 1013 ions/cm2 fluence, it reveals that big grain spherical morphology like structure respectively. I-V characteristics were recorded in the voltage range -5 to 5 V. All curves were passed through origin and nearly linear exhibit ohmic in nature for the films.

Growth and characterization of zinc oxide and PZT films for micromachined acoustic wave devices

NASA Astrophysics Data System (ADS)

Yoon, Sang Hoon

The ability to detect the presence of low concentrations of harmful substances, such as biomolecular agents, warfare agents, and pathogen cells, in our environment and food chain would greatly advance our safety, provide more sensitive tools for medical diagnostics, and protect against terrorism. Acoustic wave (AW) devices have been widely studied for such applications due to several attractive properties, such as rapid response, reliability, portability, ease of use, and low cost. The principle of these sensors is based on a fundamental feature of the acoustic wave that is generated and detected by a piezoelectric material. The performance of the device, therefore, greatly depends on the properties of piezoelectric thin film. The required properties include a high piezoelectric coefficient and high electromechanical coefficients. The surface roughness and the mechanical properties, such as Young's modulus and hardness, are also factors that can affect the wave propagation of the device. Since the film properties are influenced by the structure of the material, understanding thin film structure is very important for the design of high-performance piezoelectric MEMS devices for biosensor applications. In this research, two piezoelectric thin film materials were fabricated and investigated. ZnO films were fabricated by CSD (Chemical Solution Deposition) and sputtering, and PZT films were fabricated by CSD only. The process parameters for solution derived ZnO and PZT films, such as the substrate type, the effect of the chelating agent, and heat treatment, were studied to find the relationship between process parameters and thin film structure. In the case of the sputtered ZnO films, the process gas types and their ratio, heat treatment in situ, and post deposition were investigated. The key results of systematic experiments show that the combined influence of chemical modifiers and substrates in chemical solution deposition have an effect on the crystallographic orientation of the films, which is explained by the phase transformation that occurs from amorphous pyrolized film to crystalline film. Sputtered ZnO films do not show a strong dependence on the parameters, possibly indicating a reduced energy barrier for the growth of ZnO film due to plasma energy. Based on an understanding of the relationship between process and thin film structure, the growth mechanism of CSD ZnO is proposed. The devices are fabricated on 4-inch silicon wafers by a microelectronic fabrication method. The fabrication procedure and issues relating to device fabrication are discussed.

Growth and dielectric properties of ZnO nanoparticles deposited by using electrophoretic deposition

NASA Astrophysics Data System (ADS)

Chung, Yoonsung; Park, Hyejin; Kim, Dong-Joo; Cho, Sung Baek; Yoon, Young Soo

2015-05-01

The deposition behavior of ZnO nanoparticles on metal plates and conductive fabrics was investigated using electrophoretic deposition (EPD). The deposition kinetics on both metal plates and fabrics were examined using the Hamaker equation. Fabric substrates give more deposited weight than flat substrates due to their rougher shape and higher surface area. The morphologies and the structures of the deposited ZnO layers showed uniform deposition without any preferred orientation on both substrates. The dielectric properties of the ZnO layers formed by using EPD showed values that were reduced, but comparable to those of bulk ZnO. This result suggests that EPD is a convenient method to deposit functional oxides on flexible substrates.

Hydrothermal synthesis of coral-like Au/ZnO catalyst and photocatalytic degradation of Orange II dye

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, P.K.; Lee, G.J.; Davies, S.H.

Highlights: ► Coral-like Au/ZnO was successfully prepared using green synthetic method. ► Gold nanoparticles were deposited on the ZnO structure using NaBH{sub 4} and β-D-glucose. ► Coral-like Au/ZnO exhibited superior photocatalytic activity to degrade Orange II. - Abstract: A porous coral-like zinc oxide (c-ZnO) photocatalyst was synthesized by the hydrothermal method. The coral-like structure was obtained by precipitating Zn{sub 4}(CO{sub 3})(OH){sub 6}·H{sub 2}O (ZnCH), which forms nanosheets that aggregate together to form microspheres with the coral-like structure. X-ray diffraction (XRD) studies indicate that after heating at 550 °C the ZnCH microspheres can be converted to ZnO microspheres with a morphologymore » similar to that of ZnCH microspheres. Thermogravimetric analysis (TGA) shows this conversion takes place at approximately 260 °C. A simple electrostatic self-assembly method has been employed to uniformly disperse Au nanoparticles (1 wt.%) on the ZnO surface. In this procedure β-D-glucose was used to stabilize the Au nanoparticles. Scanning electron microscope images indicate that the diameter of coral-like ZnO microspheres (c-ZnO) is about 8 μm. X-ray diffraction reveals that the ZnO is highly crystalline with a wurtzite structure and the Au metallic particles have an average size of about 13 nm. X-ray photoelectron spectroscopic (XPS) studies have confirmed the presence of ZnO and also showed that the Au is present in the metallic state. The photocatalytic degradation of Orange II dye, with either ultraviolet or visible light, is faster on Au/c-ZnO than on c-ZnO.« less

Analysis of ultraviolet photo-response of ZnO nanostructures prepared by electrodeposition and atomic layer deposition

NASA Astrophysics Data System (ADS)

Makhlouf, Houssin; Karam, Chantal; Lamouchi, Amina; Tingry, Sophie; Miele, Philippe; Habchi, Roland; Chtourou, Radhouane; Bechelany, Mikhael

2018-06-01

In this work, ZnO nanowires (ZnO NWs) and urchin-like ZnO nanowires (U-ZnO NWs) based on self-assembled ordered polystyrene sphere (PS) were successfully prepared by combining atomic layer deposition (ALD) and electrochemical deposition (ECD) processes to build UV photosensors. The photo-response of the prepared samples was investigated and compared. The growth of the nanowires on self-assembled, ordered PS introduces a significant modification on the morphology, crystal orientation and grain size of U-ZnO NWs compared to randomly, vertically aligned ZnO NWs, and therefore improves the photo-response of U-ZnO NWs. The photocurrent may be produced by either a surface or bulk-related process. For ZnO NW-based photosensors, the photocurrent was monitored by a surface related process, whereas, it was mainly governed by a bulk related process for U-ZnO NWs, resulting in a higher and faster photo-response. The study of the rise and decay time constants for both materials showed that these parameters were strikingly sensitive to the optical properties.

Observation of defects evolution in electronic materials

NASA Astrophysics Data System (ADS)

Jang, Jung Hun

Advanced characterization techniques have been used to obtain a better understanding of the microstructure of electronic materials. The structural evolution, especially defects, has been investigated during the film growth and post-growth processes. Obtaining the relation between the defect evolution and growth/post-growth parameters is very important to obtain highly crystalline films. In this work, the growth and post-growth related defects in GaN, ZnO, strained-Si/SiGe films have been studied using several advanced characterization techniques. First of all, the growth of related defects in GaN and p-type ZnO films have been studied. The effect of growth parameters, such as growth temperature, gas flow rate, dopants used during the deposition, on the crystalline quality of the GaN and ZnO layers was investigated by high resolution X-ray diffraction (HRXRD) and transmission electron microscopy (TEM). In GaN films, it was found that the edge and mixed type threading dislocations were the dominant defects so that the only relevant figure of merit (FOM) for the crystalline quality should be the FWHM value of o-RC of the surface perpendicular plane which could be determined by a grazing incidence x-ray diffraction (GIXD) technique as shown in this work. The understanding of the relationship between the defect evolution and growth parameters allowed for the growth of high crystalline GaN films. For ZnO films, it was found that the degree of texture and crystalline quality of P-doped ZnO films decreased with increasing the phosphorus atomic percent. In addition, the result from the x-ray diffraction line profile analysis showed that the 0.5 at % P-doped ZnO film showed much higher microstrain than the 1.0 at % P-doped ZnO film, which indicated that the phosphorus atoms were segregated with increasing P atomic percentage. Finally, post-growth related defects in strained-Si/SiGe films were investigated. Postgrowth processes used in this work included high temperature N2 annealing, ion-implantation, and thermal oxidation. Advanced characterization techniques have been used to obtain information about strain, relaxation, layer thickness, elemental composition, defects, surface/interface morphology changes and so on. Based on the understanding of defects behavior during the strain relaxation after post thermal processes, a new manufacturing process to obtain highly-relaxed and thin Si1-xGex layers, which could be used as virtual substrates for strained-Si applications, was found.

Structural, optical, morphological and electrical properties of undoped and Al-doped ZnO thin films prepared using sol—gel dip coating process

NASA Astrophysics Data System (ADS)

Boukhenoufa, N.; Mahamdi, R.; Rechem, D.

2016-11-01

In this work, sol—gel dip-coating technique was used to elaborate ZnO pure and ZnO/Al films. The impact of Al-doped concentration on the structural, optical, surface morphological and electrical properties of the elaborated samples was investigated. It was found that better electrical and optical performances have been obtained for an Al concentration equal to 5%, where the ZnO thin films exhibit a resistivity value equal to 1.64104 Ω·cm. Moreover, highest transparency has been recorded for the same Al concentration value. The obtained results from this investigation make the developed thin film structure a potential candidate for high optoelectronic performance applications.

ZnO twin-cones: synthesis, photoluminescence, and catalytic decomposition of ammonium perchlorate.

PubMed

Sun, Xuefei; Qiu, Xiaoqing; Li, Liping; Li, Guangshe

2008-05-19

ZnO twin-cones, a new member to the ZnO family, were prepared directly by a solvothermal method using a mixed solution of zinc nitrate and ethanol. The reaction and growth mechanisms of ZnO twin-cones were investigated by X-ray diffraction, UV-visible spectra, infrared and ion trap mass spectra, and transmission electron microscopy. All as-prepared ZnO cones consisted of tiny single crystals with lengths of several micrometers. With prolonging of the reaction time from 1.5 h to 7 days, the twin-cone shape did not change at all, while the lattice parameters increased slightly and the emission peak of photoluminescence shifted from the green region to the near orange region. ZnO twin-cones are also explored as an additive to promote the thermal decomposition of ammonium perchlorate. The variations of photoluminescence spectra and catalytic roles in ammonium perchlorate decomposition were discussed in terms of the defect structure of ZnO twin-cones.

Seedless-grown of ZnO thin films for photoelectrochemical water splitting application

NASA Astrophysics Data System (ADS)

Abdullah, Aidahani; Hamid, Muhammad Azmi Abdul; Chiu, W. S.

2018-04-01

We developed a seedless hydrothermal method to grow a flower like ZnO nanorods. Prior to the growth, a layer of Au thin film is sputtered onto the surface of indium tin oxide (ITO) coated glass substrate. The morphological, structural and optical properties of the ZnO nanostructures were characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and diffuse reflection measurement to understand the growth process of the working thin film. The photoelectrochemical (PEC) results suggest that the deposition of ZnO nanorods on Au nanoparticles plays an important role in enhancing the photoelectrode activity. H2 evolution from photo-splitting of water over Au-incorporated ZnO in the 0.1M NaOH liquid system was enhanced, compared to that over bare ZnO; particularly, the production of 15.5 µL of H2 gas after twenty five minutes exposure of ZnO grown on Au-coated thin film.

Sol-gel synthesized ZnO for optoelectronics applications: a characterization review

NASA Astrophysics Data System (ADS)

Harun, Kausar; Hussain, Fayaz; Purwanto, Agus; Sahraoui, Bouchta; Zawadzka, Anna; Azmin Mohamad, Ahmad

2017-12-01

The rapid growth in green technology has resulted in a marked increase in the incorporation of ZnO in energy and optoelectronic devices. Research involving ZnO is being given renewed attention in the quest to fully exploit its promising properties. The purity and state of defects in the ZnO system are optimized through several modifications to the synthesis conditions and the starting materials. These works have been verified through a series of characterizations. This review covers the essential characterization outcomes of pure ZnO nanoparticles. Emphasis is placed on recent techniques, examples and some issues concerning sol-gel synthesized ZnO nanoparticles. Thermal, phase, structural and morphological observations are combined to ascertain the level of purity of ZnO. The subsequent elemental and optical characterizations are also discussed. This review would be the collective information and suggestions at one place for investigators to focus on the best development of ZnO-based optical and energy devices.

Confocal Raman microscopy of one dimensional ZnO nanostructures

NASA Astrophysics Data System (ADS)

Singamaneni, Srikanth; Gupta, Maneesh; Yang, Rusen; Wang, Zhong; Tsukruk, Vladimir

2009-03-01

ZnO nanostructures with various shapes (vertically aligned nanorods, nanobelts, nanohelixes, nanorings) have been synthesized using both vapor phase and solution growth methods. In the simplest example of a nanobelt, the fast growth direction can be either (21 1 0) or (011 0) or (0001). Here, we show that confocal Raman microscopy can be employed as a fast and nondestructive analytical technique to identify the crystal planes and reveal the relative orientation of the ZnO nanostructure. Various features of the Raman spectrum of ZnO nanostructures (presence of the A1(TO) mode, width of the E2 mode) were found to be sensitive to relative orientation of the incident source laser and the crystal plane. Furthermore, owing to the optical anisotropy of ZnO, Raman scattering from the substrate is modulated (either enhanced or suppressed with respect to the background) depending on the polarization of the incident light with respect to orientation of the nanobelt. The results presented here describe a novel method to nondestructively identify the growth, relative orientation, and the waveguiding properties of the ZnO nanostructures.

Ultrasound assisted synthesis of WO3-ZnO nanocomposites for brilliant blue dye degradation.

PubMed

Hunge, Y M; Yadav, A A; Mathe, V L

2018-07-01

The present work deals with the preparation of WO 3 and WO 3 -ZnO nanocomposites in presence of ultrasonic irradiation, and its use in the sonocatalytic degradation of brilliant blue dye. WO 3 -ZnO nanocomposite is prepared using one step in-situ ultrasound assisted method. The successfully prepared WO 3 and WO 3 -ZnO nanocomposites were characterized using different characterization techniques such as XRD, Raman, BET, FE-SEM and EDS. The XRD pattern reveals that the formation of monoclinic and hexagonal crystal structures of WO 3 and ZnO respectively. BET study shows that WO 3 -ZnO nanocomposite have maximum surface area than that of the WO 3 . EDS study confirms the formation of WO 3 -ZnO nanocomposites. Further the use of the prepared WO 3 and WO 3 -ZnO nanocomposites as a sonocatalyst for the degradation of brilliant blue dye. The rate constant (k) was evaluated as a function of the initial concentration of brilliant blue dye. It is found that WO 3 -ZnO nanocomposites exhibits maximum sonocatalytic activity as compared to WO 3 photocatalyst. Copyright © 2018 Elsevier B.V. All rights reserved.

Structural and plasmonic properties of noble metal doped ZnO nanomaterials

NASA Astrophysics Data System (ADS)

Pathak, Trilok K.; Swart, H. C.; Kroon, R. E.

2018-04-01

Noble metal doped ZnO has been synthesized by the combustion method and the effect of different metals (Ag, Au, Pd) on the structural, morphological, optical, photoluminescence and localized surface plasmon resonance (LSPR) properties has been investigated. X-ray diffraction analysis revealed that the ZnO had a hexagonal wurtzite structure and the crystallite sizes were affected by the doping. The formation of noble metal nanoparticles (NPs) was investigated using transmission electron microscopy and diffuse reflectance spectra. The LSPR of the metallic NPs was predicted using Mie theory calculations. The absorption spectra were calculated using the Kubelka-Munk function and the optical bandgap varied from 3.06 to 3.18 eV for the different doping materials. The experimental results suggest that the origin of enhanced emission was due to direct interaction between the laser photons and the noble material NPs which in turn leads to photoemission transfer of electrons from the noble metals NPs to the conduction band of ZnO.

Low-temperature growth of aligned ZnO nanorods: effect of annealing gases on the structural and optical properties.

PubMed

Umar, Ahmad; Hahn, Yoon-Bong; Al-Hajry, A; Abaker, M

2014-06-01

Aligned ZnO nanorods were grown on ZnO/Si substrate via simple aqueous solution process at low-temperature of - 65 degrees C by using zinc nitrate and hexamethylenetetramine (HMTA). The detailed morphological and structural properties measured by FESEM, XRD, EDS and TEM confirmed that the as-grown nanorods are vertically aligned, well-crystalline possessing wurtzite hexagonal phase and grown along the [0001] direction. The room-temperature photoluminescence spectrum of the grown nanorods exhibited a strong and broad green emission and small ultraviolet emission. The as-prepared ZnO nanorods were post-annealed in nitrogen (N2) and oxygen (O2) environments and further characterized in terms of their morphological, structural and optical properties. After annealing the nanorods exhibit well-crystallinity and wurtzite hexagonal phase. Moreover, by annealing the PL spectra show the enhancement in the UV emission and suppression in the green emission. The presented results demonstrate that simply by post-annealing process, the optical properties of ZnO nanostructures can be controlled.

Structural and photoluminescence properties of Ce, Dy, Er-doped ZnO nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jayachandraiah, C.; Kumar, K. Siva; Krishnaiah, G., E-mail: ginnerik@gmail.com

2015-06-24

Undoped ZnO and rare earth elements (Ce, Dy and Er with 2 at. %) doped nanoparticles were synthesized by wet chemical co-precipitation method at 90°C with Polyvinylpyrrolidone (PVP) as capping agent. The structural, morphological, compositional and photoluminescence studies were performed with X-ray diffraction (XRD), Transmission electron microscopy (TEM), Energy dispersive spectroscopy (EDS), FTIR spectroscopy and Photoluminescence (PL) respectively. XRD results revealed hexagonal wurtzite structure with average particle size around 18 nm - 14 nm and are compatible with TEM results. EDS confirm the incorporation of Ce, Dy and Er elements into the host ZnO matrix and is validated by FTIR analysis. PLmore » studies showed a broad intensive emission peak at 558 nm in all the samples. The intensity for Er- doped ZnO found maximum with additional Er shoulder peaks at 516nm and 538 nm. No Ce, Dy emission centers were found in spectra.« less

Performance of Dye-Sensitized Solar Cells (DSSCs) Fabricated with Zinc Oxide (ZnO) Nanpowders and Nanorods

NASA Astrophysics Data System (ADS)

Chatterjee, Suman

2018-03-01

Due to their high efficiencies, along with lower production costs, many researchers are working on dye-sensitized solar cells (DSSCs) over last few decades as a substitute technology for nonconventional energy. Nanostructured ZnO has got many interesting properties such as wide band gap, large exciton binding energy, good exciton stability, and high breakdown strength, which are applicable as DSSC electrodes. This present work compares the device properties of DSSC fabricated using ZnO nanorods on a ZnO film and ZnO nanopowders. Different types of ZnO photoanode and dye combinations are used to study the stability and photovoltaic properties of the DSSC cell. The photovoltaic properties of the ZnO-based DSSC samples were systematically investigated. The photovoltaic properties of fabricated cell obtained are discussed in the light of band structure and density of states of different types of ZnO nanolayers. The ZnO nanorods fabricated through the sol-gel route have more uniform thickness resulting in enhanced photovoltaic properties of the fabricated device.

Gallium ion-assisted room temperature synthesis of small-diameter ZnO nanorods.

PubMed

Cho, Seungho; Kim, Semi; Lee, Kun-Hong

2011-09-15

We report a method for synthesizing small-diameter ZnO nanorods at room temperature (20 °C), under normal atmospheric pressure (1 atm), and using a relatively short reaction time (1 h) by adding gallium salts to the reaction solution. The ZnO nanorods were, on average, 92 nm in length and 9 nm in diameter and were single crystalline in nature. Quantitative analyses revealed that gallium atoms were not incorporated into the synthesized nanocrystals. On the basis of the experimental results, we propose a mechanism for the formation of small-diameter ZnO nanorods in the presence of gallium ions. The optical properties were probed by UV-Vis diffuse reflectance spectroscopy. The absorption band of the small-diameter ZnO nanorods was blue-shifted relative to the absorption band of the ~230 nm diameter ZnO nanorods (control samples). Control experiments demonstrated that the absence of metal ion-containing precipitants (except ZnO) at room temperature is essential, and that the ZnO nanorod diameter distributions were narrow for the stirred reaction solution and broad when prepared without stirring. Copyright © 2011 Elsevier Inc. All rights reserved.

Structural, electrical and optical properties of Al-Sn codoped ZnO transparent conducting layer deposited by spray pyrolysis technique

NASA Astrophysics Data System (ADS)

Bedia, A.; Bedia, F. Z.; Aillerie, M.; Maloufi, N.

2017-11-01

Low cost Al-Sn codoped ZnO (ATZO) Transparent Conductive Oxide films were deposited by spray pyrolysis on glass substrate. The influence of Al-Sn codoping on the structural, optical and electrical properties of ZnO thin films was studied by comparing the same properties obtained in undoped ZnO, Al doped ZnO (AZO) and Sn doped ZnO (TZO) thin films. The so-obtained films crystallized in hexagonal wurtzite structure. The morphology and structural defects have been investigated by both High resolution Field Effect Scanning Electron Microscopy (FE-SEM) and Raman spectroscopy at 532 nm excitation source. In the visible region, the undoped and doped films show an average transmittance of the order of 85%, while for ATZO thin film, it is of the order of 72%, which points out a degradation of the optical properties due to the co-doping. The optical band gap of ATZO thin film achieves 3.31eV and this shift, compared to the referred samples is attributed to the Burstein-Moss (BM) and band gap narrowing (BGN) opposite effects which is due to the increase of the carrier concentration in degenerate semiconductors. Within all the samples, the ATZO thin film exhibits the lowest electrical resistivity of 4.56 × 10-3 Ωcm with a Hall mobility equal to 2.13 cm2 V-1s-1, and the highest carrier concentration of 6.41 × 1020 cm-3. The performance of ATZO transparent conductive oxide film are determined by its figure of merit (φTC), found equal to 1.69 10-4 Ω-1, which is a suitable value for potentially high-performance solar cell applications.

Core-shell TiO2@ZnO nanorods for efficient ultraviolet photodetection

NASA Astrophysics Data System (ADS)

Panigrahi, Shrabani; Basak, Durga

2011-05-01

Core-shell TiO2@ZnO nanorods (NRs) have been fabricated by a simple two step method: growth of ZnO NRs' array by an aqueous chemical technique and then coating of the NRs with a solution of titanium isopropoxide [Ti(OC3H7)4] followed by a heating step to form the shell. The core-shell nanocomposites are composed of single-crystalline ZnO NRs, coated with a thin TiO2 shell layer obtained by varying the number of coatings (one, three and five times). The ultraviolet (UV) emission intensity of the nanocomposite is largely quenched due to an efficient electron-hole separation reducing the band-to-band recombinations. The UV photoconductivity of the core-shell structure with three times TiO2 coating has been largely enhanced due to photoelectron transfer between the core and the shell. The UV photosensitivity of the nanocomposite becomes four times larger while the photocurrent decay during steady UV illumination has been decreased almost by 7 times compared to the as-grown ZnO NRs indicating high efficiency of these core-shell structures as UV sensors.

Synthesis, Optical and Photoluminescence Properties of Cu-Doped Zno Nano-Fibers Thin Films: Nonlinear Optics

NASA Astrophysics Data System (ADS)

Ganesh, V.; Salem, G. F.; Yahia, I. S.; Yakuphanoglu, F.

2018-03-01

Different concentrations of copper-doped zinc oxide thin films were coated on a glass substrate by sol-gel/spin-coating technique. The structural properties of pure and Cu-doped ZnO films were characterized by different techniques, i.e., atomic force microscopy (AFM), photoluminescence and UV-Vis-NIR spectroscopy. The AFM study revealed that pure and doped ZnO films are formed as nano-fibers with a granular structure. The photoluminescence spectra of these films showed a strong ultraviolet emission peak centered at 392 nm and a strong blue emission peak cantered at 450 nm. The optical band gap of the pure and copper-doped ZnO thin films calculated from optical transmission spectra (3.29-3.23 eV) were found to be increasing with increasing copper doping concentration. The refractive index dispersion curve of pure and Cu-doped ZnO film obeyed the single-oscillator model. The optical dispersion parameters such as E o , E d , and n_{∞}2 were calculated. Further, the nonlinear refractive index and nonlinear optical susceptibility were also calculated and interpreted.

Synthesis of zinc oxide nanostructures on graphene/glass substrate by electrochemical deposition: effects of current density and temperature.

PubMed

Hambali, Nur Ashikyn; Yahaya, Hafizal; Mahmood, Mohamad Rusop; Terasako, Tomoaki; Hashim, Abdul Manaf

2014-01-01

The electrochemical growth of zinc oxide (ZnO) nanostructures on graphene on glass using zinc nitrate hexahydrate was studied. The effects of current densities and temperatures on the morphological, structural, and optical properties of the ZnO structures were studied. Vertically aligned nanorods were obtained at a low temperature of 75°C, and the diameters increased with current density. Growth temperature seems to have a strong effect in generating well-defined hexagonal-shape nanorods with a smooth top edge surface. A film-like structure was observed for high current densities above -1.0 mA/cm(2) and temperatures above 80°C due to the coalescence between the neighboring nanorods with large diameter. The nanorods grown at a temperature of 75°C with a low current density of -0.1 mA/cm(2) exhibited the highest density of 1.45 × 10(9) cm(-2). X-ray diffraction measurements revealed that the grown ZnO crystallites were highly oriented along the c-axis. The intensity ratio of the ultraviolet (UV) region emission to the visible region emission, I UV/I VIS, showed a decrement with the current densities for all grown samples. The samples grown at the current density below -0.5 mA/cm(2) showed high I UV/I VIS values closer to or higher than 1.0, suggesting their fewer structural defects. For all the ZnO/graphene structures, the high transmittance up to 65% was obtained at the light wavelength of 550 nm. Structural and optical properties of the grown ZnO structures seem to be effectively controlled by the current density rather than the growth temperature. ZnO nanorod/graphene hybrid structure on glass is expected to be a promising structure for solar cell which is a conceivable candidate to address the global need for an inexpensive alternative energy source.

Flexible cellulose and ZnO hybrid nanocomposite and its UV sensing characteristics

NASA Astrophysics Data System (ADS)

Mun, Seongcheol; Kim, Hyun Chan; Ko, Hyun-U.; Zhai, Lindong; Kim, Jung Woong; Kim, Jaehwan

2017-12-01

This paper reports the synthesis and UV sensing characteristics of a cellulose and ZnO hybrid nanocomposite (CEZOHN) prepared by exploiting the synergetic effects of ZnO functionality and the renewability of cellulose. Vertically aligned ZnO nanorods were grown well on a flexible cellulose film by direct ZnO seeding and hydrothermal growing processes. The ZnO nanorods have the wurtzite structure and an aspect ratio of 9 11. Photoresponse of the prepared CEZOHN was evaluated by measuring photocurrent under UV illumination. CEZOHN shows bi-directional, linear and fast photoresponse as a function of UV intensity. Electrode materials, light sources, repeatability, durability and flexibility of the prepared CEZOHN were tested and the photocurrent generation mechanism is discussed. The silver nanowire coating used for electrodes on CEZOHN is compatible with a transparent UV sensor. The prepared CEZOHN is flexible, transparent and biocompatible, and hence can be used for flexible and wearable UV sensors.

Fabrication of hierarchical ZnO nanostructures on cotton fabric for wearable device applications

NASA Astrophysics Data System (ADS)

Pandiyarasan, V.; Suhasini, S.; Archana, J.; Navaneethan, M.; Majumdar, Abhijit; Hayakawa, Y.; Ikeda, H.

2017-10-01

We have investigated ZnO nanostructures on cotton fabric (CF) s a flexible material for an application of wearable thermoelectric (TE) power generator which requires super-hydrophobicity, UV protection, and high TE efficiency. Field emission scanning electron microscopy images revealed that the formed ZnO nanostructures have a mixture of nanorods and nanosheets and are uniformly coated on the CF. XRD pattern and Raman spectra revealed that the ZnO nanostructure has a wurtzite structure. Contact angle measurements showed that the ZnO-nanostructures-coated CF possessed a high super hydrophobic nature with an angle of 132.5°. ZnO nanocomposite/CF sample exhibited an excellent UV protection factor 183.84. Seebeck coefficient, electrical resistivity and thermoelectric power factor of the ZnO nanostructures on cotton fabric were evaluated to be 28 μV/K, 0.04 Ω-cm, and 22 μW/m K2, respectively.

Superhydrophobic Ag decorated ZnO nanostructured thin film as effective surface enhanced Raman scattering substrates

NASA Astrophysics Data System (ADS)

Jayram, Naidu Dhanpal; Sonia, S.; Poongodi, S.; Kumar, P. Suresh; Masuda, Yoshitake; Mangalaraj, D.; Ponpandian, N.; Viswanathan, C.

2015-11-01

The present work is an attempt to overcome the challenges in the fabrication of super hydrophobic silver decorated zinc oxide (ZnO) nanostructure thin films via thermal evaporation process. The ZnO nanowire thin films are prepared without any surface modification and show super hydrophobic nature with a contact angle of 163°. Silver is further deposited onto the ZnO nanowire to obtain nanoworm morphology. Silver decorated ZnO (Ag@ZnO) thin films are used as substrates for surface enhanced Raman spectroscopy (SERS) studies. The formation of randomly arranged nanowire and silver decorated nanoworm structure is confirmed using FESEM, HR-TEM and AFM analysis. Crystallinity and existence of Ag on ZnO are confirmed using XRD and XPS studies. A detailed growth mechanism is discussed for the formation of the nanowires from nanobeads based on various deposition times. The prepared SERS substrate reveals a reproducible enhancement of 3.082 × 107 M for Rhodamine 6G dye (R6G) for 10-10 molar concentration per liter. A higher order of SERS spectra is obtained for a contact angle of 155°. Thus the obtained thin films show the superhydrophobic nature with a highly enhanced Raman spectrum and act as SERS substrates. The present nanoworm morphology shows a new pathway for the construction of semiconductor thin films for plasmonic studies and challenges the orderly arranged ZnO nanorods, wires and other nano structure substrates used in SERS studies.

Second-harmonic generation of ZnO nanoparticles synthesized by laser ablation of solids in liquids

NASA Astrophysics Data System (ADS)

Rocha-Mendoza, Israel; Camacho-López, Santiago; Luna-Palacios, Yryx Y.; Esqueda-Barrón, Yasmín; Camacho-López, Miguel A.; Camacho-López, Marco; Aguilar, Guillermo

2018-02-01

We report the synthesis of small zinc oxide nanoparticles (ZnO NPs) based colloidal suspensions and the study of second-harmonic generation from aggregated ZnO NPs deposited on glass substrates. The colloidal suspensions were obtained using the laser ablation of solids in liquids technique, ablating a Zn solid target immersed in acetone as the liquid medium, with ns-laser pulses (1064 nm) of a Nd-YAG laser. The per pulse laser fluence, the laser repetition rate frequency and the ablation time were kept constant. The absorption evolution of the obtained suspensions was optically characterized through absorption spectroscopy until stabilization. Raman spectroscopy, SEM and HRTEM were used to provide evidence of the ZnO NPs structure. HRTEM results showed that 5-8 nm spheroids ZnO NPs were obtained. Strong second-harmonic signal is obtained from random ZnO monocrystalline NPs and from aggregated ZnO NPs, suggesting that the high efficiency of the nonlinear process may not depend on the NPs size or aggregation state.

Low-Temperature Synthesis of Vertically Align ZnO Layer on ITO Glass: The Role of Seed Layer and Hydrothermal Process

NASA Astrophysics Data System (ADS)

Sholehah, Amalia; Achmad, NurSumiati; Dimyati, Arbi; Dwiyanti, Yanyan; Partuti, Tri

2017-05-01

ZnO thin layer has a broad potential application in optoelectronic devices. In the present study, vertically align ZnO layers on ITO glass were synthesized using wet chemical method. The seed layers were prepared using electrodeposition method at 3°C. After that, the growing process was carried out using chemical bath deposition (CBD) at 90°C. To improve the structural property of the ZnO layers, hydrothermal technique was used subsequently. Results showed that seeding layer has a great influence on the physical properties of the ZnO layers. Moreover, hydrothermal process conducted after the ZnO growth can enhance the morphological property of the layers. From the experiments, it is found that the ZnO layers has diameter of ∼60 nm with increasing thickness from ∼0.8 to 1.2 μm and band-gap energies of ∼3.2 eV.

Renewable Lignosulfonate-Assisted Synthesis of Hierarchical Nanoflake-Array-Flower ZnO Nanomaterials in Mixed Solvents and Their Photocatalytic Performance

NASA Astrophysics Data System (ADS)

Li, Yue; Zuo, Hong-Fen; Guo, Yuan-Ru; Miao, Ting-Ting; Pan, Qing-Jiang

2016-05-01

With the assistance of sodium lignosulfonate, hierarchical nanoflake-array-flower nanostructure of ZnO has been fabricated by a facile precipitation method in mixed solvents. The sodium lignosulfonate amount used in our synthetic route is able to fine-tune ZnO morphology and an abundance of pores have been observed in the nanoflake-array-flower ZnO, which result in specific surface area reaching as high as 82.9 m2 · g-1. The synthesized ZnO exhibits superior photocatalytic activity even under low-power UV illumination (6 W). It is conjectured that both nanoflake-array structure and plenty of pores embedded in ZnO flakes may provide scaffold microenvironments to enhance photocatalytic activity. Additionally, this catalyst can be used repeatedly without a significant loss in photocatalytic activity. The low-cost, simple synthetic approach as well as high photocatalytic and recycling efficiency of our ZnO nanomaterials allows for application to treat wastewater containing organic pollutants in an effective way.

Efficacy of saccharides bio-template on structural, morphological, optical and antibacterial property of ZnO nanoparticles.

PubMed

Dhanalakshmi, A; Palanimurugan, A; Natarajan, B

2018-09-01

Mono, di and polysaccharides of glucose (C 6 H 12 O 6 ), sucrose (C 12 H 24 O 12 ) and starch (C 6 H 12 O 6 ) n bio-template ZnO nanoparticles (NPs) has prepared by chemical precipitation method. Saccharides bio-template ZnO (SBts-ZnO) NPs were efficiently prepared for their structural and optical properties were examined by using XRD, FE-SEM, AFM, FTIR, UV and PL techniques. All the samples are polycrystalline nature with a preferential orientation depending on the (1 0 1) plane. The reduction of crystalline size by utilizing glucose, sucrose and starch bio-template of ZnO NPs. FE-SEM images revealed that the spherical and nano-rods like morphologies for ZnO and SBts-ZnO NPs respectively. AFM recorded images shows spherical features that confirmed and also the morphological changes were noticed with the addition of polymers. Interaction of bio-templated saccharides (glucose G 1 , sucrose S 2 & starch S n ) molecules was proved by FTIR study. Optical absorbance and emission behaviours were investigated using UV-Vis and photoluminescence techniques. The antibacterial study revealed that SBts-ZnO have excellent antibacterial effect than ZnO. The S n -ZnO sample has potent antibacterial activity against the Proteus vulgaris followed by Klebsiella pneumoniae, Escherichia coli and Staphylococcus aureus. Copyright © 2018 Elsevier B.V. All rights reserved.

Development of zinc oxide nanoparticle by sonochemical method and study of their physical and optical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, Samreen Heena, E-mail: samreen.heena.khan@gmail.com; Suriyaprabha, R.; Pathak, Bhawana, E-mail: bhawana.pathak@cug.ac.in

With the miniaturization of crystal size, the fraction of under-coordinated surface atoms becomes dominant, and hence, materials in the nano-regime behave very differently from the similar material in a bulk. Zinc oxide (ZnO), particularly, exhibits extraordinary properties such as a wide direct band gap (3.37 eV), large excitation binding energy (60 meV), low refractive index (1.9), stability to intense ultraviolet (UV) illumination, resistance to high-energy irradiation, and lower toxicity as compared to other semiconductors. This very property makes Zinc Oxide a potential candidate in many application fields, particularly as a prominent semiconductor. Zinc Oxide plays a significant role in manymore » technological advances with its application in semiconductor mediated photocatalytic processes and sensor, solar cells and others. In present study, Zinc Oxide (ZnO) has been synthesized using three different precursors by sonochemical method. Zinc Acetate Dihydrate, Zinc Nitrate Hexahydrate and Zinc Sulphate Heptahydrate used as a precursor for the synthesis process. The synthesized ZnO nanoparticle has been found under the range of ∼50 nm. Zinc oxide nanoparticles were characterized using different characterizing tools. The as-synthesized ZnO was characterized by Fourier Transform-Infrared Spectroscopy (FT-IR) for the determination of functional group; Scanning Electron Microscopy equipped with Energy Dispersive Spectroscopy (SEM-EDS) for Morphology and elemental detection respectively, Transmission Electron Microscopy for Particle size distribution and morphology and X-Ray Diffraction (XRD) for the confirmation of crystal structure of the nanomaterial. The optical properties of the ZnO were examined by UV-VIS spectroscopy equipped with Diffuse Reflectance spectroscopy (DRS) confirmed the optical band gap of ZnO-3 around 3.23 eV resembles with the band gap of bulk ZnO (3.37eV). The TEM micrograph of the as-synthesized material showed perfectly spherical shaped nanoparticle under the size range of 50nm. The XRD data showed that the ZnO-3 which was synthesized using Zinc Nitrate Hexahydrate as precursor showed the hexagonal wurtzite crystal structure. The XRD data obtained were compared with the JCPDS standard data. The precursor Zinc Nitrate Hexahydrate (ZnO-3) showed the good yield, monodispersity and size of nanoparticle under the range of 50 nm. The ZnO nanoparticles synthesize using different precursor was found effective in order of ZnO-3, followed by ZnO-1 & ZnO-2. The Synthesized ZnO has wider application in environmental remediation and clean-up as a potential nano-catalyst.« less

Enhanced antibacterial activity of zinc oxide nanoparticles synthesized using Petroselinum crispum extracts

NASA Astrophysics Data System (ADS)

Stan, Manuela; Popa, Adriana; Toloman, Dana; Silipas, Teofil-Danut; Vodnar, Dan Cristian; Katona, Gabriel

2015-12-01

The present contribution reports the synthesis of zinc oxide nanoparticles (ZnO NPs) using aqueous leaf and root extracts of Petroselinum crispum (parsley) and characterization of as-prepared samples. ZnO NPs are subjected to X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron paramagnetic resonance (EPR) studies. The XRD studies reveal a hexagonal wurtzite structure without supplementary diffraction lines for all ZnO samples. TEM analysis shows that the particle size is influenced by the type of plant extract. The EPR spectra indicate the presence of Mn2+ ions in ZnO sample synthesized using P. crispum leaf extract, while zinc vacancy complexes and oxygen vacancies are evidenced in all analyzed samples. ZnO NPs synthesized using P. crispum extracts exhibit increased (2-16 times) antibacterial activity as compared to chemically synthesized ZnO NPs.

Graphene-Based Transparent Electrodes for Dye Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Al-Rawashdeh, Nathir A. F.; Albiss, Borhan A.; Yousef, Mo'ath H. I.

2018-02-01

Several Zinc Oxide (ZnO) photo-anodes were prepared with different morphologies. For each morphology, two composites containing graphene oxide (GO) were prepared. ZnO sheet-flowers attained the highest efficiency among control samples, owing to the light diffraction that may be caused by such morphology. On the other hand, ZnO rods achieved lower performance than ZnO sheet-flowers, but higher than ZnO flowers, due to their porosity and structure, which may scatter light effectively. The effect of including GO in the photoanode matrix was studied and the results demonstrate a significant increase in short circuit current density (JSC). The addition of GO suggested an overall positive effect on cell performance, where samples of ZnO rods and Flowers had the most significant increase in their performance, due to the inhibition of charge recombination by GO.

Annealing effect on the structural, morphological and electrical properties of TiO2/ZnO bilayer thin films

NASA Astrophysics Data System (ADS)

Khan, M. I.; Imran, S.; Shahnawaz; Saleem, Muhammad; Ur Rehman, Saif

2018-03-01

The effect of annealing temperature on the structural, morphological and electrical properties of TiO2/ZnO (TZ) thin films has been observed. Bilayer thin films of TiO2/ZnO are deposited on FTO glass substrate by spray pyrolysis method. After deposition, these films are annealed at 573 K, 723 K and 873 K. XRD shows that TiO2 is present in anatase phase only and ZnO is present in hexagonal phase. No other phases of TiO2 and ZnO are present. Also, there is no evidence of other compounds like Zn-Ti etc. It also shows that the average grain size of TiO2/ZnO films is increased by increasing annealing temperature. AFM (Atomic force microscope) showed that the average roughness of TiO2/ZnO films is decreased at temperature 573-723 K and then increased at 873 K. The calculated average sheet resistivity of thin films annealed at 573 K, 723 K and 873 K is 152.28 × 102, 75.29 × 102 and 63.34 × 102 ohm-m respectively. This decrease in sheet resistivity might be due to the increment of electron concentration with increasing thickness and the temperature of thin films.

Synthesis and Characterization of Molybdenum Doped ZnO Thin Films by SILAR Deposition Method

NASA Astrophysics Data System (ADS)

Radha, R.; Sakthivelu, A.; Pradhabhan, D.

2016-08-01

Molybdenum (Mo) doped zinc oxide (ZnO) thin films were deposited on the glass substrate by Successive Ionic Layer Adsorption and Reaction (SILAR) deposition method. The effect of Mo dopant concentration of 5, 6.6 and 10 mol% on the structural, morphological, optical and electrical properties of n-type Mo doped ZnO films was studied. The X-ray diffraction (XRD) results confirmed that the Mo doped ZnO thin films were polycrystalline with wurtzite structure. The field emission scanning electron microscopy (FESEM) studies shows that the surface morphology of the films changes with Mo doping. A blue shift of the optical band gap was observed in the optical studies. Effect of Mo dopant concentration on electrical conductivity was studied and it shows comparatively high electrical conductivity at 10 mol% of Mo doping concentration.

Fast light-induced reversible wettability of a zinc oxide nanorod array coated with a thin gold layer

NASA Astrophysics Data System (ADS)

Wei, Yuefan; Du, Hejun; Kong, Junhua; Tran, Van-Thai; Koh, Jia Kai; Zhao, Chenyang; He, Chaobin

2017-11-01

Zinc oxide (ZnO) has gained much attention recently due to its excellent physical and chemical properties, and has been extensively studied in energy harvesting applications such as photovoltaic and piezoelectric devices. In recent years, its reversible wettability has also attracted increasing interest. The wettability of ZnO nanostructures with various morphologies has been studied. However, to the best of our knowledge, there is still a lack of investigations on further modifications on ZnO to provide more benefits than pristine ZnO. Comprehensive studies on the reversible wettability are still needed. In this study, a ZnO nanorod array was prepared via a hydrothermal process and subsequently coated with thin gold layers with varied thickness. The morphologies and structures, optical properties and wettability were investigated. It is revealed that the ZnO-Au system possesses recoverable wettability upon switching between visible-ultraviolet light and a dark environment, which is verified by the contact angle change. The introduction of the thin gold layer to the ZnO nanorod array effectively increases the recovery rate of the wettability. The improvements are attributed to the hierarchical structures, which are formed by depositing thin gold layers onto the ZnO nanorod array, the visible light sensitivity due to the plasmonic effect of the deposited gold, as well as the fast charge-induced surface status change upon light illumination or dark storage. The improvement is beneficial to applications in environmental purification, energy harvesting, micro-lenses, and smart devices.

Effect of growth parameters on the optical properties of ZnO nanostructures grown by simple solution methods

NASA Astrophysics Data System (ADS)

Kothari, Anjana

2017-05-01

ZnO, a wide band gap semiconductor is of significant interest for a range of practical applications. One of the highly attractive features of ZnO is to grow variety of nanostructures by using low-cost techniques. In this paper, we report deposition of ZnO nanostructure rod-arrays (NRA) via low-temperature, solution-based deposition techniques such as chemical bath deposition (CBD) and microwave-assisted chemical bath deposition (MACBD). A detailed study of film deposition parameters such as variation in concentration of precursors and deposition temperature has been carried out. Compositional and structural study of the films has been done by X-ray Diffractometer to know the phase and purity of the final product. Morphological study of these structures has been carried out by Scanning Electron Microscopy. Optical study such as transmittance and diffuse reflectance of the films has been carried out as a function of growth parameters.

Self-organized semiconductor nano-network on graphene

NASA Astrophysics Data System (ADS)

Son, Dabin; Kim, Sang Jin; Lee, Seungmin; Bae, Sukang; Kim, Tae-Wook; Kang, Jae-Wook; Lee, Sang Hyun

2017-04-01

A network structure consisting of nanomaterials with a stable structural support and charge path on a large area is desirable for various electronic and optoelectronic devices. Generally, network structures have been fabricated via two main strategies: (1) assembly of pre-grown nanostructures onto a desired substrate and (2) direct growth of nanomaterials onto a desired substrate. In this study, we utilized the surface defects of graphene to form a nano-network of ZnO via atomic layer deposition (ALD). The surface of pure and structurally perfect graphene is chemically inert. However, various types of point and line defects, including vacancies/adatoms, grain boundaries, and ripples in graphene are generated by growth, chemical or physical treatments. The defective sites enhance the chemical reactivity with foreign atoms. ZnO nanoparticles formed by ALD were predominantly deposited at the line defects and agglomerated with increasing ALD cycles. Due to the formation of the ZnO nano-network, the photocurrent between two electrodes was clearly changed under UV irradiation as a result of the charge transport between ZnO and graphene. The line patterned ZnO/graphene (ZnO/G) nano-network devices exhibit sensitivities greater than ten times those of non-patterned structures. We also confirmed the superior operation of a fabricated flexible photodetector based on the line patterned ZnO/G nano-network.

Electrically driven plasmon-exciton coupled random lasing in ZnO metal-semiconductor-metal devices

NASA Astrophysics Data System (ADS)

Suja, Mohammad; Debnath, Bishwajit; Bashar, Sunayna B.; Su, Longxing; Lake, Roger; Liu, Jianlin

2018-05-01

Electrically driven plasmon-exciton coupled random lasing is demonstrated by incorporating Ag nanoparticles on Cu-doped ZnO metal-semiconductor-metal (MSM) devices. Both photoluminescence and electroluminescence studies show that emission efficiencies have been enhanced significantly due to coupling between ZnO excitons and Ag surface plasmons. With the incorporation of Ag nanoparticles on ZnO MSM structures, internal quantum efficiency up to 6 times is demonstrated. Threshold current for lasing is decreased by as much as 30% while the output power is increased up to 350% at an injection current of 40 mA. A numerical simulation study reveals that hole carriers are generated in the ZnO MSM devices from impact ionization processes for subsequent plasmon-exciton coupled lasing.

Structural properties and gas sensing behavior of sol-gel grown nanostructured zinc oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajyaguru, Bhargav; Gadani, Keval; Kansara, S. B.

2016-05-06

In this communication, we report the results of the studies on structural properties and gas sensing behavior of nanostructured ZnO grown using acetone precursor based modified sol-gel technique. Final product of ZnO was sintered at different temperatures to vary the crystallite size while their structural properties have been studied using X-ray diffraction (XRD) measurement performed at room temperature. XRD results suggest the single phasic nature of all the samples and crystallite size increases from 11.53 to 20.96 nm with increase in sintering temperature. Gas sensing behavior has been studied for acetone gas which indicates that lower sintered samples are moremore » capable to sense the acetone gas and related mechanism has been discussed in the light of crystallite size, crystal boundary density, defect mechanism and possible chemical reaction between gas traces and various oxygen species.« less

Hexagonal ZnO porous plates prepared from microwave synthesized layered zinc hydroxide sulphate via thermal decomposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Machovsky, Michal, E-mail: machovsky@ft.utb.cz; Polymer Centre, Faculty of Technology, Tomas Bata University in Zlin, Nam. T.G. Masaryka 275, 762 72 Zlin; Kuritka, Ivo, E-mail: ivo@kuritka.net

2013-10-15

Graphical abstract: - Highlights: • Zinc hydroxy sulphate was synthesized in 3 min via microwave hydrothermal route. • Zinc hydroxy sulphate was converted into mesh like porous ZnO by calcining at 900°. • The process of transformation is topotactic. - Abstract: Layered zinc hydroxide sulphate (ZHS) was prepared by microwave-assisted hydrothermal precipitation of zinc sulphate monohydrate with hexamethylenetetramine. Under ambient conditions, the structure of ZHS determined by X-ray diffraction (XRD) was found to be a mixture of zinc hydroxide sulphate pentahydrate Zn{sub 4}SO{sub 4}(OH){sub 6}·5H{sub 2}O and tetrahydrate Zn{sub 4}SO{sub 4}(OH){sub 6}·4H{sub 2}O. Fourier transform infrared (FTIR) spectroscopy was usedmore » for characterization of the prepared materials. Based on the interpretation of ZHS's thermal decomposition profile obtained by thermogravimetric analysis, ZnO of high purity was prepared by calcination at 900 °C for 2 h. The structure of the resulting ZnO was confirmed by the XRD. The morphology examination by scanning electron microscopy revealed a porous mesh-like ZnO structure developed from the ZHS precursor at the expense of mass removal due to the release of water and sulphate during the calcination.« less

Trioctylphosphine-assisted morphology control of ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Hong, Yun-Kun; Cho, GeonHee; Park, YoonSu; Oh, Soong Ju; Ha, Don-Hyung

2018-06-01

This study investigates the morphological change in colloidal ZnO nanoparticles (NPs) synthesized with trioctylphosphine (TOP). The addition of TOP to the synthesis causes an evolution in the shape of ZnO NPs to tadpole-like particles from quasi-spherical particles at 300 °C. The total length of the tadpole-like ZnO NPs can be modified by controlling the molar ratio of TOP to oleylamine (OLAM). The tadpole-like particles are elongated as the concentration of TOP increased but decreased when the addition of TOP is excessive. These tadpole-like ZnO NPs transform to quasi-spherical NPs regardless of the amount of TOP at a reaction time of 3 h at 300 °C. At 200 °C, the effect of TOP on the ZnO NP synthesis differs from that at 300 °C. The ZnO NPs synthesized by controlling the molar ratios of surfactant ligands (TOP:OLAM = 2:100 and 70:100) at 200 °C share similar amorphous structures, while a crystalline ZnO phase is formed when the reaction time is 3 h. X-ray photoelectron spectroscopy analysis shows that TOP influences the oxidation of ZnO and suggests that a combination of OLAM and TOP plays a role in controlling the shape of ZnO NPs. These results provide critical insights to the utilization of TOP for a shape controlling ligand in ZnO NPs and suggest a new route to design oxide NPs.

Trioctylphosphine-assisted morphology control of ZnO nanoparticles.

PubMed

Hong, Yun-Kun; Cho, GeonHee; Park, YoonSu; Oh, Soong Ju; Ha, Don-Hyung

2018-06-01

This study investigates the morphological change in colloidal ZnO nanoparticles (NPs) synthesized with trioctylphosphine (TOP). The addition of TOP to the synthesis causes an evolution in the shape of ZnO NPs to tadpole-like particles from quasi-spherical particles at 300 °C. The total length of the tadpole-like ZnO NPs can be modified by controlling the molar ratio of TOP to oleylamine (OLAM). The tadpole-like particles are elongated as the concentration of TOP increased but decreased when the addition of TOP is excessive. These tadpole-like ZnO NPs transform to quasi-spherical NPs regardless of the amount of TOP at a reaction time of 3 h at 300 °C. At 200 °C, the effect of TOP on the ZnO NP synthesis differs from that at 300 °C. The ZnO NPs synthesized by controlling the molar ratios of surfactant ligands (TOP:OLAM = 2:100 and 70:100) at 200 °C share similar amorphous structures, while a crystalline ZnO phase is formed when the reaction time is 3 h. X-ray photoelectron spectroscopy analysis shows that TOP influences the oxidation of ZnO and suggests that a combination of OLAM and TOP plays a role in controlling the shape of ZnO NPs. These results provide critical insights to the utilization of TOP for a shape controlling ligand in ZnO NPs and suggest a new route to design oxide NPs.

Field evaporation of ZnO: A first-principles study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xia, Yu, E-mail: yuxia@dal.ca; Karahka, Markus; Kreuzer, H. J.

2015-07-14

With recent advances in atom probe tomography of insulators and semiconductors, there is a need to understand high electrostatic field effects in these materials as well as the details of field evaporation. We use density functional theory to study field effects in ZnO clusters calculating the potential energy curves, the local field distribution, the polarizability, and the dielectric constant as a function of field strength. We confirm that, as in MgO, the HOMO-LUMO gap of a ZnO cluster closes at the evaporation field strength signaling field-induced metallization of the insulator. Following the structural changes in the cluster at the evaporationmore » field strength, we can identify the field evaporated species, in particular, we show that the most abundant ion, Zn{sup 2+}, is NOT post-ionized but leaves the surface as 2+ largely confirming the experimental observations. Our results also help to explain problems related to stoichiometry in the mass spectra measured in atom probe tomography.« less

Differential gene expression in Daphnia magna suggests distinct modes of action and bioavailability for ZnO nanoparticles and Zn ions.

PubMed

Poynton, Helen C; Lazorchak, James M; Impellitteri, Christopher A; Smith, Mark E; Rogers, Kim; Patra, Manomita; Hammer, Katherine A; Allen, H Joel; Vulpe, Chris D

2011-01-15

Zinc oxide nanoparticles (ZnO NPs) are being rapidly developed for use in consumer products, wastewater treatment, and chemotherapy providing several possible routes for ZnO NP exposure to humans and aquatic organisms. Recent studies have shown that ZnO NPs undergo rapid dissolution to Zn(2+), but the relative contribution of Zn(2+) to ZnO NP bioavailability and toxicity is not clear. We show that a fraction of the ZnO NPs in suspension dissolves, and this fraction cannot account for the toxicity of the ZnO NP suspensions to Daphnia magna. Gene expression profiling of D. magna exposed to ZnO NPs or ZnSO(4) at sublethal concentrations revealed distinct modes of toxicity. There was also little overlap in gene expression between ZnO NPs and SiO(x) NPs, suggesting specificity for the ZnO NP expression profile. ZnO NPs effected expression of genes involved in cytoskeletal transport, cellular respiration, and reproduction. A specific pattern of differential expression of three biomarker genes including a multicystatin, ferritin, and C1q containing gene were confirmed for ZnO NP exposure and provide a suite of biomarkers for identifying environmental exposure to ZnO NPs and differentiating between NP and ionic exposure.

ZnO thin-film transistors with a polymeric gate insulator built on a polyethersulfone substrate

NASA Astrophysics Data System (ADS)

Hyung, Gun Woo; Park, Jaehoon; Koo, Ja Ryong; Choi, Kyung Min; Kwon, Sang Jik; Cho, Eou Sik; Kim, Yong Seog; Kim, Young Kwan

2012-03-01

Zinc oxide (ZnO) thin-film transistors (TFTs) with a cross-linked poly(vinyl alcohol) (c-PVA) insulator are fabricated on a polyethersulfone substrate. The ZnO film, formed by atomic layer deposition, shows a polycrystalline hexagonal structure with a band gap energy of about 3.37 eV. The fabricated ZnO TFT exhibits a field-effect mobility of 0.38 cm2/Vs and a threshold voltage of 0.2 V. The hysteresis of the device is mainly caused by trapped electrons at the c-PVA/ZnO interface, whereas the positive threshold voltage shift occurs as a consequence of constant positive gate bias stress after 5000 s due to an electron injection from the ZnO film into the c-PVA insulator.

Toward blue emission in ZnO based LED

NASA Astrophysics Data System (ADS)

Viana, Bruno; Pauporté, Thierry; Lupan, Oleg; Le Bahers, Tangui; Ciofini, Ilaria

2012-03-01

The bandgap engineering of ZnO nanowires by doping is of great importance for tunable light emitting diode (LED) applications. We present a combined experimental and computational study of ZnO doping with Cd or Cu atoms in the nanomaterial. Zn1-xTMxO (TM=Cu, Cd) nanowires have been epitaxially grown on magnesium-doped p-GaN by electrochemical deposition. The Zn1-xTMxO/p-GaN heterojunction was integrated in a LED structure. Nanowires act as the light emitters and waveguides. At room temperature, TM-doped ZnO based LEDs exhibit low-threshold emission voltage and electroluminescence emission shifted from ultraviolet to violet-blue spectral region compared to pure ZnO LEDs. The emission wavelength can be tuned by changing the transition metal (TM) content in the ZnO nanomaterial and the shift is discussed, including insights from DFT computational investigations.

Hydrothermal growth of ZnO nanowires on flexible fabric substrates

NASA Astrophysics Data System (ADS)

Hong, Gwang-Wook; Yun, Sang-Ho; Kim, Joo-Hyung

2016-04-01

ZnO nanowires (NWs) would provide significant enhancement in sensitivity due to high surface to volume ratio. We investigated the first methodical study on the quantitative relationship between the process parameters of solution concentration ratio, structure, and physical and properties of ZnO NWs grown on different flexible fabric surfaces. To develop a fundamental following concerning various substrates, we controlled the growth speed of ZnO NWs and nanowires on cotton surface with easy and moderate cost fabrication method. Using ammonium hydroxide as the reactant with zinc nitrate hexahydrate, ZnO NWs layer have been grown on metal layers, instead of seed layer. ZnO NWs fabrication was done on different fabric substrates such as wool, nylon and polypropylene (PP). After the ZnO NWs grown to each substrates, we coated insulating layer with polyurethane (PU) and ethyl cellulose for prevent external intervention. Detailed electrical characterization was subsequently performed to reveal the working characteristics of the hybrid fabric. For electrical verification of fabricated ZnO NWs, we implemented measurement impact test and material properties with FFT analyzer and LCR meter.

Morphological Influence of Solution-Processed Zinc Oxide Films on Electrical Characteristics of Thin-Film Transistors.

PubMed

Lee, Hyeonju; Zhang, Xue; Hwang, Jaeeun; Park, Jaehoon

2016-10-19

We report on the morphological influence of solution-processed zinc oxide (ZnO) semiconductor films on the electrical characteristics of ZnO thin-film transistors (TFTs). Different film morphologies were produced by controlling the spin-coating condition of a precursor solution, and the ZnO films were analyzed using atomic force microscopy, X-ray diffraction, X-ray photoemission spectroscopy, and Hall measurement. It is shown that ZnO TFTs have a superior performance in terms of the threshold voltage and field-effect mobility, when ZnO crystallites are more densely packed in the film. This is attributed to lower electrical resistivity and higher Hall mobility in a densely packed ZnO film. In the results of consecutive TFT operations, a positive shift in the threshold voltage occurred irrespective of the film morphology, but the morphological influence on the variation in the field-effect mobility was evident. The field-effect mobility in TFTs having a densely packed ZnO film increased continuously during consecutive TFT operations, which is in contrast to the mobility decrease observed in the less packed case. An analysis of the field-effect conductivities ascribes these results to the difference in energetic traps, which originate from structural defects in the ZnO films. Consequently, the morphological influence of solution-processed ZnO films on the TFT performance can be understood through the packing property of ZnO crystallites.

Morphological Influence of Solution-Processed Zinc Oxide Films on Electrical Characteristics of Thin-Film Transistors

PubMed Central

Lee, Hyeonju; Zhang, Xue; Hwang, Jaeeun; Park, Jaehoon

2016-01-01

We report on the morphological influence of solution-processed zinc oxide (ZnO) semiconductor films on the electrical characteristics of ZnO thin-film transistors (TFTs). Different film morphologies were produced by controlling the spin-coating condition of a precursor solution, and the ZnO films were analyzed using atomic force microscopy, X-ray diffraction, X-ray photoemission spectroscopy, and Hall measurement. It is shown that ZnO TFTs have a superior performance in terms of the threshold voltage and field-effect mobility, when ZnO crystallites are more densely packed in the film. This is attributed to lower electrical resistivity and higher Hall mobility in a densely packed ZnO film. In the results of consecutive TFT operations, a positive shift in the threshold voltage occurred irrespective of the film morphology, but the morphological influence on the variation in the field-effect mobility was evident. The field-effect mobility in TFTs having a densely packed ZnO film increased continuously during consecutive TFT operations, which is in contrast to the mobility decrease observed in the less packed case. An analysis of the field-effect conductivities ascribes these results to the difference in energetic traps, which originate from structural defects in the ZnO films. Consequently, the morphological influence of solution-processed ZnO films on the TFT performance can be understood through the packing property of ZnO crystallites. PMID:28773973

Growth of raspberry-, prism- and flower-like ZnO particles using template-free low-temperature hydrothermal method and their application as humidity sensors

NASA Astrophysics Data System (ADS)

Pál, Edit; Hornok, Viktória; Kun, Robert; Chernyshev, Vladimir; Seemann, Torben; Dékány, Imre; Busse, Matthias

2012-08-01

Zinc oxide particles with different morphologies were prepared by hydrothermal method at 60-90 °C. The structure formation was controlled by the addition rate and temperature of hydrolyzing agent, while the particles size (10 nm-2.5 μm) was influenced by the preparation (hydrothermal) temperature. Scanning electron microscopy studies showed that raspberry-, prism- and flower-like ZnO particles were prepared, whose average size decreased with increasing reaction temperature. X-ray diffraction investigations confirmed that ZnO particles with hexagonal crystal structure formed in all syntheses. The raspberry-, prism- and flower-like ZnO particles showed a weak UV-emission in the range of 390-395 nm and strong visible emission with a maximum at 586, 593 and 598 nm, respectively. Morphology effect on electrical and water vapour sensing properties of ZnO samples was investigated by impedance spectroscopy and quartz crystal microbalance, respectively. The absolute impedance of raspberry-, prism- and flower-like ZnO particles was found to be strong dependent on the morphology. Space-charge-limited conductivity transport mechanism was proved by the oscillatory behaviour of impedance. Humidity sensor tests also revealed morphology and specific surface area dependency on the sensitivity and water vapour adsorption property.

In vitro antibacterial activity of ZnO and Nd doped ZnO nanoparticles against ESBL producing Escherichia coli and Klebsiella pneumoniae

PubMed Central

Hameed, Abdulrahman Syedahamed Haja; Karthikeyan, Chandrasekaran; Ahamed, Abdulazees Parveez; Thajuddin, Nooruddin; Alharbi, Naiyf S.; Alharbi, Sulaiman Ali; Ravi, Ganasan

2016-01-01

Pure ZnO and Neodymium (Nd) doped ZnO nanoparticles (NPs) were synthesized by the co-precipitation method. The synthesized nanoparticles retained the wurtzite hexagonal structure. From FESEM studies, ZnO and Nd doped ZnO NPs showed nanorod and nanoflower like morphology respectively. The FT-IR spectra confirmed the Zn-O stretching bands at 422 and 451 cm−1 for ZnO and Nd doped ZnO NPs respectively. From the UV-VIS spectroscopic measurement, the excitonic peaks were found around 373 nm and 380 nm for the respective samples. The photoluminescence measurements revealed that the broad emission was composed of ten different bands due to zinc vacancies, oxygen vacancies and surface defects. The antibacterial studies performed against extended spectrum β-lactamases (ESBLs) producing strains of Escherichia coli and Klebsiella pneumoniae showed that the Nd doped ZnO NPs possessed a greater antibacterial effect than the pure ZnO NPs. From confocal laser scanning microscopic (CLSM) analysis, the apoptotic nature of the cells was confirmed by the cell shrinkage, disorganization of cell wall and cell membrane and dead cell of the bacteria. SEM analysis revealed the existence of bacterial loss of viability due to an impairment of cell membrane integrity, which was highly consistent with the damage of cell walls. PMID:27071382

In vitro antibacterial activity of ZnO and Nd doped ZnO nanoparticles against ESBL producing Escherichia coli and Klebsiella pneumoniae

NASA Astrophysics Data System (ADS)

Hameed, Abdulrahman Syedahamed Haja; Karthikeyan, Chandrasekaran; Ahamed, Abdulazees Parveez; Thajuddin, Nooruddin; Alharbi, Naiyf S.; Alharbi, Sulaiman Ali; Ravi, Ganasan

2016-04-01

Pure ZnO and Neodymium (Nd) doped ZnO nanoparticles (NPs) were synthesized by the co-precipitation method. The synthesized nanoparticles retained the wurtzite hexagonal structure. From FESEM studies, ZnO and Nd doped ZnO NPs showed nanorod and nanoflower like morphology respectively. The FT-IR spectra confirmed the Zn-O stretching bands at 422 and 451 cm-1 for ZnO and Nd doped ZnO NPs respectively. From the UV-VIS spectroscopic measurement, the excitonic peaks were found around 373 nm and 380 nm for the respective samples. The photoluminescence measurements revealed that the broad emission was composed of ten different bands due to zinc vacancies, oxygen vacancies and surface defects. The antibacterial studies performed against extended spectrum β-lactamases (ESBLs) producing strains of Escherichia coli and Klebsiella pneumoniae showed that the Nd doped ZnO NPs possessed a greater antibacterial effect than the pure ZnO NPs. From confocal laser scanning microscopic (CLSM) analysis, the apoptotic nature of the cells was confirmed by the cell shrinkage, disorganization of cell wall and cell membrane and dead cell of the bacteria. SEM analysis revealed the existence of bacterial loss of viability due to an impairment of cell membrane integrity, which was highly consistent with the damage of cell walls.

Spectroscopic Study of Deep Level Emissions from Acceptor Defects in ZnO Thin Films with Oxygen Rich Stoichiometry

NASA Astrophysics Data System (ADS)

Ilyas, Usman; Rawat, R. S.; Tan, T. L.

2013-10-01

This paper reports the tailoring of acceptor defects in oxygen rich ZnO thin films at different post-deposition annealing temperatures (500-800°C) and Mn doping concentrations. The XRD spectra exhibited the nanocrystalline nature of ZnO thin films along with inconsistent variation in lattice parameters suggesting the temperature-dependent activation of structural defects. Photoluminescence emission spectra revealed the temperature dependent variation in deep level emissions (DLE) with the presence of acceptors as dominating defects. The concentration of native defects was estimated to be increased with temperature while a reverse trend was observed for those with increasing doping concentration. A consistent decrease in DLE spectra, with increasing Mn content, revealed the quenching of structural defects in the optical band gap of ZnO favorable for good quality thin films with enhanced optical transparency.

Growth and characterization of ZnO multipods on functional surfaces with different sizes and shapes of Ag particles

NASA Astrophysics Data System (ADS)

A, Kamalianfar; S, A. Halim; Mahmoud Godarz, Naseri; M, Navasery; Fasih, Ud Din; J, A. M. Zahedi; Kasra, Behzad; K, P. Lim; A Lavari, Monghadam; S, K. Chen

2013-08-01

Three-dimensional ZnO multipods are successfully synthesized on functional substrates using the vapor transport method in a quartz tube. The functional surfaces, which include two different distributions of Ag nanoparticles and a layer of commercial Ag nanowires, are coated onto silicon substrates before the growth of ZnO nanostructures. The structures and morphologies of the ZnO/Ag heterostructures are investigated using X-ray diffraction and field emission scanning electron microscopy. The sizes and shapes of the Ag particles affect the growth rates and initial nucleations of the ZnO structures, resulting in different numbers and shapes of multipods. They also influence the orientation and growth quality of the rods. The optical properties are studied by photoluminescence, UV-vis, and Raman spectroscopy. The results indicate that the surface plasmon resonance strongly depends on the sizes and shapes of the Ag particles.

Growth of high-density ZnO nanorods on wood with enhanced photostability, flame retardancy and water repellency

NASA Astrophysics Data System (ADS)

Kong, Lizhuo; Tu, Kunkun; Guan, Hao; Wang, Xiaoqing

2017-06-01

Zinc oxide (ZnO) nanorod arrays were successfully assembled on the wood surface in situ via a two-step process consisting of formation of ZnO seeds and subsequent crystal growth under hydrothermal conditions at a low temperature. The morphology and crystalline structure of the formed ZnO nanorods were studied by field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). Highly dense and uniform arrays of ZnO nanorods with well-defined hexagonal facets were generated on the wood surface by tuning the concentration of the ZnO growth solution during the hydrothermal treatment. Accelerated weathering tests indicated that the assembled ZnO nanorod arrays were highly protective against UV radiation and greatly enhanced the photostability of the coated wood. Meanwhile, the ZnO nanorod-coated wood can withstand continuous exposure to flame with only minor smoldering in contrast with the pristine wood catching fire easily and burning rapidly. Moreover, when further modified with low-surface-energy stearic acid, the ZnO nanorod decorated wood surface can be transformed into a superhydrophobic surface, with a water contact angle (CA) of ∼154°. Such ZnO nanorod-modified woods with enhanced photostability, flame retardancy and water repellency offer an interesting alternative to conventional wood preservation strategies, highlighting their potential applications in some novel wood products.

ZnO nanomaterials based surface acoustic wave ethanol gas sensor.

PubMed

Wu, Y; Li, X; Liu, J H; He, Y N; Yu, L M; Liu, W H

2012-08-01

ZnO nanomaterials based surface acoustic wave (SAW) gas sensor has been investigated in ethanol environment at room temperature. The ZnO nanomaterials have been prepared through thermal evaporation of high-purity zinc powder. The as-prepared ZnO nanomaterials have been characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray Diffraction (XRD) techniques. The results indicate that the obtained ZnO nanomaterials, including many types of nanostructures such as nanobelts, nanorods, nanowires as well as nanosheets, are wurtzite with hexagonal structure and well-crystallized. The SAW sensor coated with the nanostructured ZnO materials has been tested in ethanol gas of various concentrations at room temperature. A network analyzer is used to monitor the change of the insertion loss of the SAW sensor when exposed to ethanol gas. The insertion loss of the SAW sensor varies significantly with the change of ethanol concentration. The experimental results manifest that the ZnO nanomaterials based SAW ethanol gas sensor exhibits excellent sensitivity and good short-term reproducibility at room temperature.

III-nitrides on oxygen- and zinc-face ZnO substrates

NASA Astrophysics Data System (ADS)

Namkoong, Gon; Burnham, Shawn; Lee, Kyoung-Keun; Trybus, Elaissa; Doolittle, W. Alan; Losurdo, Maria; Capezzuto, Pio; Bruno, Giovanni; Nemeth, Bill; Nause, Jeff

2005-10-01

The characteristics of III-nitrides grown on zinc- and oxygen-face ZnO by plasma-assisted molecular beam epitaxy were investigated. The reflection high-energy electron diffraction pattern indicates formation of a cubic phase at the interface between III-nitride and both Zn- and O-face ZnO. The polarity indicates that Zn-face ZnO leads to a single polarity, while O-face ZnO forms mixed polarity of III-nitrides. Furthermore, by using a vicinal ZnO substrate, the terrace-step growth of GaN was realized with a reduction by two orders of magnitude in the dislocation-related etch pit density to ˜108cm-2, while a dislocation density of ˜1010cm-2 was obtained on the on-axis ZnO substrates.

Structural and optical properties of DC magnetron sputtered ZnO films on glass substrate and their modification by Ag ions implantation

NASA Astrophysics Data System (ADS)

Ahmad, R.; Afzal, Naveed; Amjad, U.; Jabbar, S.; Hussain, T.; Hussnain, A.

2017-07-01

This work is focused on investigating the effects of deposition time and Ag ions implantation on structural and optical properties of ZnO film. The ZnO film was prepared on glass substrate by pulsed DC magnetron sputtering of pure Zn target in reactive oxygen environment for 2 h, 3 h, 4 h and 5 h respectively. X-ray diffraction results revealed polycrystalline ZnO film whose crystallinity was improved with increase of the deposition time. The morphological features indicated agglomeration of smaller grains into larger ones by increasing the deposition time. The UV-vis spectroscopy analysis depicted a small decrease in the band gap of ZnO from 3.36 eV to 3.27 eV with increase of deposition time. The Ag ions implantation in ZnO films deposited for 5 h on glass was carried out by using Pelletron Accelerator at different ions fluences ranging from 1  ×  1011 ions cm-2 to 2  ×  1012 ions cm-2. XRD patterns of Ag ions implanted ZnO did not show significant change in crystallite size by increasing ions fluence from 1  ×  1011 ions cm-2 to 5  ×  1011 ions cm-2. However, with further increase of the ions fluence, the crystallite size was decreased. The band gap of Ag ions implanted ZnO indicated anomalous variations with increase of the ions fluence.

Specifications of ZnO growth for heterostructure solar cell and PC1D based simulations

PubMed Central

Hussain, Babar; Ebong, Abasifreke

2015-01-01

This data article is related to our recently published article (Hussain et al., in press [1]) where we have proposed a new solar cell model based on n-ZnO as front layer and p-Si as rear region. The ZnO layer will act as an active n-layer as well as antireflection (AR) coating saving considerable processing cost. There are several reports presenting use of ZnO as window/antireflection coating in solar cells (Mansoor et al., 2015; Haq et al., 2014; Hussain et al., 2014; Matsui et al., 2014; Ding et al., 2014 [2], [3], [4], [5], [6]) but, here, we provide data specifically related to simultaneous use of ZnO as n-layer and AR coating. Apart from the information we already published, we provide additional data related to growth of ZnO (with and without Ga incorporation) layers using MOCVD. The data related to PC1D based simulation of internal and external quantum efficiencies with and without antireflection effects of ZnO as well as the effects of doping level in p-Si on current–voltage characteristics have been provided. PMID:26587557

First principles calculations for interaction of tyrosine with (ZnO)3 cluster

NASA Astrophysics Data System (ADS)

Singh, Satvinder; Singh, Gurinder; Kaura, Aman; Tripathi, S. K.

2018-04-01

First Principles Calculations have been performed to study interactions of Phenol ring of Tyrosine (C6H5OH) with (ZnO)3 atomic cluster. All the calculations have been performed under the Density Functional Theory (DFT) framework. Structural and electronic properties of (ZnO)3/C6H5OH have been studied. Gaussian basis set approach has been adopted for the calculations. A ring type most stable (ZnO)3 atomic cluster has been modeled, analyzed and used for the calculations. The compatibility of the results with previous studies has been presented here.

Emission and Structure-Varying ZnO and Carbon Nanocrystal Composite in Mechanical Processing

NASA Astrophysics Data System (ADS)

Torchynska, T.; Perez Millan, B.; Polupan, G.; Kakazey, M.

2018-03-01

Morphology, photoluminescence (PL), and Raman scattering spectra have been investigated for mixtures of ZnO+0.1%C nanocrystals (NCs) at different stages of mechanical processing (MP). The transformation of graphite into graphene monolayers covering the ZnO NC surface is revealed for the first MP stage. The interaction with oxygen has been detected in the second MP stage which leads to the dissolution of oxygen interstitials in the ZnO NCs and to the formation of graphene (graphite) oxides. Increasing the concentration of the oxygen interstitials in ZnO NCs also enhances the intensity stimulation of the orange PL band (2.18eV). Simultaneously, the PL band peaking at 2.82-2.90 eV is detected in the PL spectra of the ZnO+0.1%C NC mixture after MP for 9-90 min. Then, the variation of the ZnO NC shape, agglomeration of ZnO NCs, modification of ZnO defects and decreasing PL intensity have been detected after prolonged MP for 390 min. It is expected that short stages of MP can be useful for ZnO NC surface covering by graphene layers or graphene (graphite) oxides.

Synthesis of zinc oxide porous structures by anodization with water as an electrolyte

NASA Astrophysics Data System (ADS)

Shetty, Amitha; Nanda, Karuna Kar

2012-10-01

We report a simple, reliable and one-step method of synthesizing ZnO porous structures at room temperature by anodization of zinc (Zn) sheet with water as an electrolyte and graphite as a counter electrode. We observed that the de-ionized (DI) water used in the experiment is slightly acidic (pH=5.8), which is due to the dissolution of carbon dioxide from the atmosphere forming carbonic acid. Porous ZnO is characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and photoluminescence (PL) studies. The current-transient measurement is carried out using a Gamry Instruments Reference 3000 and the thickness of the deposited films is measured using a Dektak surface profilometer. The PL, Raman and X-ray photoelectron spectroscopy are used to confirm the presence of ZnO phase. We have demonstrated that the hybrid structures of ZnO and poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) exhibit good rectifying characteristics. The evaluated barrier height and the ideality factor are 0.45 eV and 3.6, respectively.

Diffusion Mechanisms of Ag atom in ZnO crystal: A First Principles Study

NASA Astrophysics Data System (ADS)

Masoumi, Saeed; Noori, Amirreza; Nadimi, Ebrahim

2017-12-01

Zinc oxide (ZnO) is currently under intensive investigation, as a result of its various applications in micro, nano and optoelectronics. However, a stable and reproducible p-type doping of ZnO is still a main challenging issue. Group IB elements such as Au, Cu and Ag, are promising candidates for p-type doping. Particularly, Ag atoms has been shown to be able to easily diffuse through the crystal structure of ZnO and lead to the p-type doping of the host crystal. However, the current understanding of Ag defects and their mobility in the ZnO crystal is still not fully explored. In this work, we report the results of our first-principles calculations based on density functional theory for Ag defects, particularly the interstitial and substitutional defects in ZnO crystal. Defect formation energies are calculated in different charged states as a function of Fermi energy in order to clarify the p-type behaviour of Ag-doped ZnO. We also investigate the diffusion behaviour and migration paths of Ag in ZnO crystal in the framework of density functional theory applying climbing image (CI) nudged elastic band method (NEB).

C-Axis-Oriented Hydroxyapatite Film Grown Using ZnO Buffer Layer

NASA Astrophysics Data System (ADS)

Sakoishi, Yasuhiro; Iguchi, Ryo; Nishikawa, Hiroaki; Hontsu, Shigeki; Hayami, Takashi; Kusunoki, Masanobu

2013-11-01

A method of fabricating c-axis-oriented hydroxyapatite film on a quartz crystal microbalance (QCM) sensor was investigated. ZnO was used as a template to obtain a hexagonal hydroxyapatite crystal of uniaxial orientation. The ZnO was grown as a c-axis film on a Au/quartz with the surface structure of a QCM sensor. Under optimized conditions, hydroxyapatite was deposited by pulsed laser deposition. X-ray diffraction showed the hydroxyapatite film to be oriented along the c-axis. Because Au and ZnO are applied to many devices, the anisotropic properties of hydroxyapatite may be incorporated into these devices as well as QCM sensors.

Strong compensation hinders the p-type doping of ZnO: a glance over surface defect levels

NASA Astrophysics Data System (ADS)

Huang, B.

2016-07-01

We propose a surface doping model of ZnO to elucidate the p-type doping and compensations in ZnO nanomaterials. With an N-dopant, the effects of N on the ZnO surface demonstrate a relatively shallow acceptor level in the band gap. As the dimension of the ZnO materials decreases, the quantum confinement effects will increase and render the charge transfer on surface to influence the shifting of Fermi level, by evidence of transition level changes of the N-dopant. We report that this can overwhelm the intrinsic p-type conductivity and transport of the ZnO bulk system. This may provide a possible route of using surface doping to modify the electronic transport and conductivity of ZnO nanomaterials.

Facile synthesis of one dimensional ZnO nanostructures for DSSC applications

NASA Astrophysics Data System (ADS)

Marimuthu, T.; Anandhan, N.

2016-05-01

Development of zinc oxide (ZnO) nanostructure based third generation dye sensitized solar cell is interesting compared to conventional silicon solar cells. ZnO nanostructured thin films were electrochemically deposited onto fluorine doped tin oxide (FTO) glass substrate. The effect of ethylene-diamine-tetra-acetic acid (EDTA) on structural, morphological and optical properties is investigated using X-ray diffraction (XRD) meter, field emission scanning electron microscope (FE-SEM) and micro Raman spectroscopy. XRD patterns reveal that the prepared nanostructures are hexagonal wutrzite structures with (101) plane orientation, the nanostructure prepared using EDTA exhibits better crystallinity. FE-SEM images illustrate that the morphological changes are observed from nanorod structure to cauliflower like structure as EDTA is added. Micro Raman spectra predict that cauliflower like structure possesses a higher crystalline nature with less atomic defects compared to nanorod structures. Dye sensitized solar cell (DSSC) is constructed for the optimized cauliflower structure, and open circuit voltage, short circuit density, fill factor and efficiency are estimated from the J-V curve.

Stability and band offsets between c-plane ZnO semiconductor and LaAlO3 gate dielectric

NASA Astrophysics Data System (ADS)

Wang, Jianli; Chen, Xinfeng; Wu, Shuyin; Tang, Gang; Zhang, Junting; Stampfl, C.

2018-03-01

Wurtzite-perovskite heterostructures composed of a high dielectric constant oxide and a wide bandgap semiconductor envision promising applications in field-effect transistors. In the present paper, the structural and electronic properties of LaAlO3/ZnO heterojunctions are investigated by first-principles calculations. We study the initial adsorption of La, Al, and oxygen atoms on ZnO (0001) and (000 1 ¯ ) surfaces and find that La atoms may occupy interstitial sites during the growth of stoichiometric ZnO (0001). The band gap of the stoichiometric ZnO (0001) surface is smaller than that of the stoichiometric ZnO (000 1 ¯ ) surface. The surface formation energy indicates that La or Al atoms may substitute Zn atoms at the nonstoichiometric ZnO (0001) surface. The atomic charges, electronic density of states, and band offsets are analyzed for the optimized LaAlO3/ZnO heterojunctions. There is a band gap for the LaAlO3/ZnO (000 1 ¯ ) heterostructures, and the largest variation in charge occurs at the surface or interface. Our results suggest that the Al-terminated LaAlO3/ZnO (000 1 ¯ ) interfaces are suitable for the design of metal oxide semiconductor devices because the valence and conduction band offsets are both larger than 1 eV and the interface does not produce any in-gap states.

Localized Surface Plasmon Resonance in Au Nanoparticles Embedded dc Sputtered ZnO Thin Films.

PubMed

Patra, Anuradha; Balasubrahmaniyam, M; Lahal, Ranjit; Malar, P; Osipowicz, T; Manivannan, A; Kasiviswanathan, S

2015-02-01

The plasmonic behavior of metallic nanoparticles is explicitly dependent on their shape, size and the surrounding dielectric space. This study encompasses the influence of ZnO matrix, morphology of Au nanoparticles (AuNPs) and their organization on the optical behavior of ZnO/AuNPs-ZnO/ZnO/GP structures (GP: glass plate). These structures have been grown by a multiple-step physical process, which includes dc sputtering, thermal evaporation and thermal annealing. Different analytical techniques such as scanning electron microscopy, glancing angle X-ray diffraction, Rutherford backscattering spectrometry and optical absorption have been used to study the structures. In-situ rapid thermal treatment during dc sputtering of ZnO film has been found to induce subtle changes in the morphology of AuNPs, thereby altering the profile of the plasmon band in the absorption spectra. The results have been contrasted with a recent study on the spectral response of dc magnetron sputtered ZnO films embedded with AuNPs. Initial simulation results indicate that AuNPs-ZnO/Au/GP structure reflects/absorbs UV and infrared radiations, and therefore can serve as window coatings.

Synthesis and photocatalytic property of Zinc Oxide (ZnO) fine particle using flame spray pyrolysis method

NASA Astrophysics Data System (ADS)

Widiyandari, Hendri; Ayu Ketut Umiati, Ngurah; Dwi Herdianti, Rizki

2018-05-01

Advance oxidation process (AOP) using photocatalysis constitute a promising technology for the treatment of wastewaters containing non-easily removable organic compound. Zinc oxide (ZnO) is one of efficient photocatalyst materials. This research reported synthesis of ZnO fine particle from zinc nitrate hexahydrate using Flame Spray Pyrolysis (FSP) method. In this method, oxygen (O2) gas were used as oxidizer and LPG (liquid petroleum gas) were used as fuel. The effect of O2 gas flow rate during ZnO particle fabrication to the microstructure, optical and photocatalytic properties were systematically discussed. The photocatalytic activity of ZnO was tested for the degradation of amaranth dye with initial concentration of 10 ppm under irradiation of solar simulator. The rate of decrease in amaranth concentration was measured using UV-Visible spectrophotometer. The ZnO synthesized using FSP has a hexagonal crystalline structure. Scanning electron microscope images showed that ZnO has a spherical formed which was the mixture of solid and hollow particles. The optimum condition for amaranth degradation was shown by ZnO produced at a flow rate of 1.5 L/min which able to degrade amaranth dye up to 95,3 % at 75 minutes irradiation.

Polarity in GaN and ZnO: Theory, measurement, growth, and devices

NASA Astrophysics Data System (ADS)

Zúñiga-Pérez, Jesús; Consonni, Vincent; Lymperakis, Liverios; Kong, Xiang; Trampert, Achim; Fernández-Garrido, Sergio; Brandt, Oliver; Renevier, Hubert; Keller, Stacia; Hestroffer, Karine; Wagner, Markus R.; Reparaz, Juan Sebastián; Akyol, Fatih; Rajan, Siddharth; Rennesson, Stéphanie; Palacios, Tomás; Feuillet, Guy

2016-12-01

The polar nature of the wurtzite crystalline structure of GaN and ZnO results in the existence of a spontaneous electric polarization within these materials and their associated alloys (Ga,Al,In)N and (Zn,Mg,Cd)O. The polarity has also important consequences on the stability of the different crystallographic surfaces, and this becomes especially important when considering epitaxial growth. Furthermore, the internal polarization fields may adversely affect the properties of optoelectronic devices but is also used as a potential advantage for advanced electronic devices. In this article, polarity-related issues in GaN and ZnO are reviewed, going from theoretical considerations to electronic and optoelectronic devices, through thin film, and nanostructure growth. The necessary theoretical background is first introduced and the stability of the cation and anion polarity surfaces is discussed. For assessing the polarity, one has to make use of specific characterization methods, which are described in detail. Subsequently, the nucleation and growth mechanisms of thin films and nanostructures, including nanowires, are presented, reviewing the specific growth conditions that allow controlling the polarity of such objects. Eventually, the demonstrated and/or expected effects of polarity on the properties and performances of optoelectronic and electronic devices are reported. The present review is intended to yield an in-depth view of some of the hot topics related to polarity in GaN and ZnO, a fast growing subject over the last decade.

Photoelectrocatalytic activity of a hydrothermally grown branched Zno nanorod-array electrode for paracetamol degradation.

PubMed

Lin, Chin Jung; Liao, Shu-Jun; Kao, Li-Cheng; Liou, Sofia Ya Hsuan

2015-06-30

Hierarchical branched ZnO nanorod (B-ZnR) arrays as an electrode for efficient photoelectrocatalytic degradation of paracetamol were grown on fluorine-doped tin oxide substrates using a solution route. The morphologic and structural studies show the ZnO trunks are single-crystalline hexagonal wurtzite ZnO with a [0001] growth direction and are densely covered by c-axis-oriented ZnO branches. The obvious enhancement in photocurrent response of the B-ZnR electrode was obtained than that in the ZnO nanoparticle (ZnO NP) electrode. For the photoelectrocatalytic degradation of paracetamol in 20 h, the conversion fraction of the drug increased from 32% over ZnO NP electrode to 62% over B-ZnR arrays with about 3-fold increase in initial reaction rate. The light intensity-dependent photoelectrocatalytic experiment indicated that the superior performance over the B-ZnR electrode was mainly ascribed to the increased specific surface area without significantly sacrificing the charge transport and pollutant diffusion efficiencies. Two aromatic intermediate compounds were observed and eventually converted into harmless carboxylic acids and ammonia. Hierarchical tree-like ZnO arrays can be considered effective alternatives to improve photoelectro degradation rates without the need for expensive additives. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis of SiO2-Coated Core-Shell ZnO Composites for Preparing High-Voltage Varistors

NASA Astrophysics Data System (ADS)

Qu, Xiao; Yao, Da-Chuan; Liu, Jin-Ran; Wang, Mao-Hua; Zhang, Han-Ping

2018-01-01

Monodispersed ZnO composite microspheres were successfully prepared by a facile ultrasound irradiation method. Then, the uniform core-shell structured composites were synthesized through the hydrolysis of tetraethyl orthosilicate on the surface of the ZnO composite microspheres. Microstructural studies of the as-obtained powders were carried out using the techniques of the x-ray powder diffraction, field emission scanning electron microscopy and transmission electron microscopy with energy dispersive x-ray spectroscopy. The results show that the pink ZnO composite powders as the core were spherical structures with the size of approximately 100 nm, and the SiO2 shell was fully coated on the surface of the core. On the basis of these results, the effect of SiO2 content on the thickness of the synthesized composites and microstructure, as well as the electrical properties of the ZnO varistors sintered in air at 1150°C for 2 h, were fully studied. In particular, the ZnO varistor prepared with the appropriate amount of the SiO2 coating (˜40 nm) leads to a superior electrical performance with the high breakdown voltage of 418 V mm-1 and an excellent nonlinear coefficient of 70.7, compared with the varistors obtained without the SiO2 coating. The high performance is attributed to the smaller and more homogeneous ZnO grains obtained via the SiO2 coating.

Fabrication and electrical properties of low temperature-processed thin-film-transistors with chemical-bath deposited ZnO layer.

PubMed

Ahn, Joo-Seob; Kwon, Ji-Hye; Yang, Heesun

2013-06-01

ZnO film was grown on ZnO quantum dot seed layer-coated substrate by a low-temperature chemical bath deposition, where sodium citrate serves as a complexing agent for Zn2+ ion. The ZnO film deposited under the optimal condition exhibited a highly uniform surface morphology with a thickness of approimately 30 nm. For the fabrication of thin-film-transistor with a bottom-gate structure, ZnO film was chemically deposited on the transparent substrate of a seed layer-coated SiN(x)/ITO (indium tin oxide)/glass. As-deposited ZnO channel was baked at low temperatures of 60-200 degrees C to investigate the effect of baking temperature on electrical performances. Compared to the device with 60 degrees C-baked ZnO channel, the TFT performances of one with 200 degrees C-baked channel were substantially improved, exhibiting an on-off current ratio of 3.6 x 10(6) and a saturated field-effect mobility of 0.27 cm2/V x s.

Structure and magnetic properties of Fe-doped ZnO prepared by the sol-gel method.

PubMed

Liu, Huilian; Yang, Jinghai; Zhang, Yongjun; Yang, Lili; Wei, Maobin; Ding, Xue

2009-04-08

Zn(0.97)Fe(0.03)O nanoparticles were synthesized by the sol-gel method. X-ray diffraction (XRD) and transmission electron microscope (TEM) analysis revealed that the samples had pure ZnO wurtzite structure and Fe ions were well incorporated into the ZnO crystal lattice. X-ray photoelectron spectroscopy (XPS) showed that both Fe(2+) and Fe(3+) existed in Zn(0.97)Fe(0.03)O. The result of x-ray absorption near-edge structure (XANES) further testified that Fe ions took the place of Zn sites in our samples. Magnetic measurements indicated that Zn(0.97)Fe(0.03)O was ferromagnetic at room temperature.

Mesoporous ZnO microcube derived from a metal-organic framework as photocatalyst for the degradation of organic dyes

NASA Astrophysics Data System (ADS)

Ban, Jin-jin; Xu, Guan-cheng; Zhang, Li; Lin, He; Sun, Zhi-peng; Lv, Yan; Jia, Dian-zeng

2017-12-01

A cube-like porous ZnO architecture was synthesized by direct two-step thermolysis of a zinc-based metal-organic framework [(CH3)2NH2][Zn(HCOO)3]. The obtained ZnO microcube was characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption and desorption isotherms. The mesoporous ZnO microcube was comprised by many nanoparticles, and inherited the cube shape from [(CH3)2NH2][Zn(HCOO)3] precursor. With large surface area and mesoporous structure, the ZnO microcube exhibits excellent photocatalytic activities against methyl orange (MO) and rhodamine B (RhB) under UV irradiation, and the degradation rates reached 99.7% and 98.1% within 120 min, respectively.

Insights into the effect of iron and cobalt doping on the structure of nanosized ZnO.

PubMed

Giuli, Gabriele; Trapananti, Angela; Mueller, Franziska; Bresser, Dominic; d'Acapito, Francesco; Passerini, Stefano

2015-10-05

Here we report an in-depth structural characterization of transition metal-doped zinc oxide nanoparticles that have recently been used as anode materials for Li-ion batteries. Structural refinement of powder X-ray diffraction (XRD) data allowed the determination of small though reproducible changes in the unit cell dimensions of four ZnO samples (wurtzite structure) prepared with different dopants or different synthesis conditions. Moreover, large variations of the full width at half-maximum of the XRD reflections indicate that the crystallinity of the samples decreases in the order ZnO, Zn0.9Co0.1O, Zn0.9Fe0.1O/C, and Zn0.9Fe0.1O (the crystallite sizes as determined by Williamson-Hall plots are 42, 29, 15, and 13 nm, respectively). X-ray absorption spectroscopy data indicate that Co is divalent, whereas Fe is purely trivalent in Zn0.9Fe0.1O and 95% trivalent (Fe(3+)/(Fe(3+) + Fe(2+)) ratio = 0.95) in Zn0.9Fe0.1O/C. The aliovalent substitution of Fe(3+) for Zn(2+) implies the formation of local defects around Fe(3+) such as cationic vacancies or interstitial oxygen for charge balance. The EXAFS (extended X-ray absorption fine structure) data, besides providing local Fe-O and Co-O bond distances, are consistent with a large amount of charge-compensating defects. The Co-doped sample displays similar EXAFS features to those of pure ZnO, suggesting the absence of a large concentration of defects as found in the Fe-doped samples. These results are of substantial importance for understanding and elucidating the modified electrochemical lithiation mechanism by introducing transition metal dopants into the ZnO structure for the application as lithium-ion anode material.

Effect of Doping Materials on the Low-Level NO Gas Sensing Properties of ZnO Thin Films

NASA Astrophysics Data System (ADS)

Çorlu, Tugba; Karaduman, Irmak; Yildirim, Memet Ali; Ateş, Aytunç; Acar, Selim

2017-07-01

In this study, undoped, Cu-doped, and Ni-doped ZnO thin films have been successfully prepared by successive ionic layer adsorption and reaction method. The structural, compositional, and morphological properties of the thin films are characterized by x-ray diffractometer, energy dispersive x-ray analysis (EDX), and scanning electron microscopy, respectively. Doping effects on the NO gas sensing properties of these thin films were investigated depending on gas concentration and operating temperature. Cu-doped ZnO thin film exhibited a higher gas response than undoped and Ni-doped ZnO thin film at the operating temperature range. The sensor with Cu-doped ZnO thin film gave faster responses and recovery speeds than other sensors, so that is significant for the convenient application of gas sensor. The response and recovery speeds could be associated with the effective electron transfer between the Cu-doped ZnO and the NO molecules.

Enhanced antibacterial activity of zinc oxide nanoparticles synthesized using Petroselinum crispum extracts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stan, Manuela, E-mail: manuela.stan@itim-cj.ro; Popa, Adriana; Toloman, Dana

The present contribution reports the synthesis of zinc oxide nanoparticles (ZnO NPs) using aqueous leaf and root extracts of Petroselinum crispum (parsley) and characterization of as-prepared samples. ZnO NPs are subjected to X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron paramagnetic resonance (EPR) studies. The XRD studies reveal a hexagonal wurtzite structure without supplementary diffraction lines for all ZnO samples. TEM analysis shows that the particle size is influenced by the type of plant extract. The EPR spectra indicate the presence of Mn{sup 2+} ions in ZnO sample synthesized using P. crispum leaf extract, while zinc vacancy complexes andmore » oxygen vacancies are evidenced in all analyzed samples. ZnO NPs synthesized using P. crispum extracts exhibit increased (2-16 times) antibacterial activity as compared to chemically synthesized ZnO NPs.« less

Template-Assisted Hydrothermal Growth of One-Dimensional Zinc Oxide Nanowires for Photocatalytic Application.

PubMed

Ma, Shuai-Shuai; Xu, Peng; Cai, Zhi-Lan; Li, Qing; Ye, Zhao-Lian; Zhou, Yu-Ming

2018-07-01

One-dimensional (1D) semiconductor ZnO nanowires have been successfully synthesized by a novel soft-chemical hydrothermal method with allylpolyethoxy amino carboxylate (AA-APEA) at low temperature. Their structure and properties have been characterized by a series of techniques, including X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and transmission electron microscopy (TEM). It was found that ZnO nanowires with diameters around 50 nm and lengths up to about several micrometers are well-distributed. The photocatalytic activity toward degradation of methylene blue (MB) aqueous solution under ultraviolet (UV) was investigated and the results showed that the ZnO nanowires exhibit a markedly higher photoactivity compared to the ZnO nanoparticles which were obtained without AA-APEA polymer assistant, and it can be ascribed to the special 1D morphology of the ZnO nanowires. In particular, the rate of degradation of the ZnO nanowires was 11 times faster than that of ZnO nanoparticles. In addition, the ZnO nanowires could be easily recycled in UV photocatalytic activity. These observations could promote new applications of photocatalyst for wastewater treatment utilizing oxide semiconductor nanostructures.

Doping induced c-axis oriented growth of transparent ZnO thin film

NASA Astrophysics Data System (ADS)

Mistry, Bhaumik V.; Joshi, U. S.

2018-04-01

c-Axis oriented In doped ZnO (IZO) transparent conducting thin films were optimized on glass substrate using sol gel spin coating method. The Indium content in ZnO was varied systematically and the structural parameters were studied. Along with the crystallographic properties, the optoelectronic and electrical properties of IZO thin films were investigated in detail. The IZO thin films revealed hexagonal wurtzite structure. It was found that In doping in ZnO promotes the c-axis oriented growth of the thin films deposited on amorphous substrate. The particle size of the IZO films were increase as doping content increases from 2% to 5%. The 2% In doped ZnO film show electrical resistivity of 0.11 Ω cm, which is far better than the reported value for ZnO thin film. Better than 75% average optical transmission was estimated in the wavelength range from 400-800 nm. Systematic variartions in the electron concentration and band gap was observed with increasing In doping. Note worthy finding is that, with suitable amount of In doping improves not only transparency and conductivity but also improves the preferred orientation of the oxide thin film.

Sulfate-based anionic diblock copolymer nanoparticles for efficient occlusion within zinc oxide

NASA Astrophysics Data System (ADS)

Ning, Y.; Fielding, L. A.; Andrews, T. S.; Growney, D. J.; Armes, S. P.

2015-04-01

Occlusion of copolymer particles within inorganic crystalline hosts not only provides a model for understanding the crystallisation process, but also may offer a direct route for the preparation of novel nanocomposite materials with emergent properties. In the present paper, a series of new well-defined anionic diblock copolymer nanoparticles are synthesised by polymerisation-induced self-assembly (PISA) via reversible addition-fragmentation chain transfer (RAFT) aqueous emulsion polymerisation and then evaluated as crystal habit modifiers for the in situ formation of ZnO in aqueous solution. Systematic studies indicate that both the chemical nature (i.e. whether sulfate-based or carboxylate-based) and the mean degree of polymerisation (DP) of the anionic stabiliser block play vital roles in determining the crystal morphology. In particular, sulfate-functionalised nanoparticles are efficiently incorporated within the ZnO crystals whereas carboxylate-functionalised nanoparticles are excluded, thus anionic character is a necessary but not sufficient condition for successful occlusion. Moreover, the extent of nanoparticle occlusion within the ZnO phase can be as high as 23% by mass depending on the sulfate-based nanoparticle concentration. The optical properties, chemical composition and crystal structure of the resulting nanocomposite crystals are evaluated and an occlusion mechanism is proposed based on the observed evolution of the ZnO morphology in the presence of sulfate-based anionic nanoparticles. Finally, controlled deposition of a 5 nm gold sol onto porous ZnO particles (produced after calcination of the organic nanoparticles) significantly enhances the rate of photocatalytic decomposition of a model rhodamine B dye on exposure to a relatively weak UV source.Occlusion of copolymer particles within inorganic crystalline hosts not only provides a model for understanding the crystallisation process, but also may offer a direct route for the preparation of novel nanocomposite materials with emergent properties. In the present paper, a series of new well-defined anionic diblock copolymer nanoparticles are synthesised by polymerisation-induced self-assembly (PISA) via reversible addition-fragmentation chain transfer (RAFT) aqueous emulsion polymerisation and then evaluated as crystal habit modifiers for the in situ formation of ZnO in aqueous solution. Systematic studies indicate that both the chemical nature (i.e. whether sulfate-based or carboxylate-based) and the mean degree of polymerisation (DP) of the anionic stabiliser block play vital roles in determining the crystal morphology. In particular, sulfate-functionalised nanoparticles are efficiently incorporated within the ZnO crystals whereas carboxylate-functionalised nanoparticles are excluded, thus anionic character is a necessary but not sufficient condition for successful occlusion. Moreover, the extent of nanoparticle occlusion within the ZnO phase can be as high as 23% by mass depending on the sulfate-based nanoparticle concentration. The optical properties, chemical composition and crystal structure of the resulting nanocomposite crystals are evaluated and an occlusion mechanism is proposed based on the observed evolution of the ZnO morphology in the presence of sulfate-based anionic nanoparticles. Finally, controlled deposition of a 5 nm gold sol onto porous ZnO particles (produced after calcination of the organic nanoparticles) significantly enhances the rate of photocatalytic decomposition of a model rhodamine B dye on exposure to a relatively weak UV source. Electronic supplementary information (ESI) available: Kinetic data for RAFT polymerisation of SEM, GPC traces of PSEM homopolymers, additional digital photographs and TEM images of various diblock copolymer nanoparticles. Length/width histograms for ZnO particles prepared in the absence of any additive (control), PSES73 homopolymer, and S73-B300 nanoparticle. Additional DCP and LUMiSizer® particle size distributions, N2 adsorption data and elemental microanalyses. See DOI: 10.1039/c5nr00535c

Electromechanical coupling coefficient k15 of polycrystalline ZnO films with the c-axes lie in the substrate plane.

PubMed

Yanagitani, Takahiko; Mishima, Natsuki; Matsukawa, Mami; Watanabe, Yoshiaki

2007-04-01

The (1120) textured polycrystalline ZnO films with a high shear mode electromechanical coupling coefficient k15 are obtained by sputter deposition. An over-moded resonator, a layered structure of metal electrode film/(1120) textured ZnO piezoelectric film/metal electrode film/silica glass substrate was used to characterize k15 by a resonant spectrum method. The (1120) textured ZnO piezoelectric films with excellent crystallite c-axis alignment showed an electromechanical coupling coefficient k15 of 0.24. This value was 92% of k15 value in single-crystal (k15 = 0.26).

EGCG assisted green synthesis of ZnO nanopowders: Photodegradative, antimicrobial and antioxidant activities

NASA Astrophysics Data System (ADS)

Suresh, D.; Udayabhanu; Nethravathi, P. C.; Lingaraju, K.; Rajanaika, H.; Sharma, S. C.; Nagabhushana, H.

2015-02-01

Zinc oxide nanopowders were synthesized by solution combustion method using Epigallocatechin gallate (EGCG) a tea catechin as fuel. The structure and morphology of the product was characterized by Powder X-ray Diffraction, Scanning Electron Microscopy, photoluminescence and UV-Visible spectroscopy. The nanopowders (Nps) were subjected to photocatalytic and biological activities such as antimicrobial and antioxidant studies. PXRD patterns demonstrate that the formed product belongs to hexagonal wurtzite system. SEM images show that the particles are agglomerated to form sponge like structure and the average crystallite sizes were found to be ∼10-20 nm. PL spectra exhibit broad and strong peak at 590 nm due to the Zn-vacancies, and O-vacancies. The prepared ZnO Nps exhibit excellent photocatalytic activity for the photodegradation of malachite green (MG) and methylene blue (MB) indicating that the ZnO NPs are potential photocatalytic semiconductor materials. ZnO NPs exhibit significant bactericidal activity against Klebsiella aerogenes, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus using the agar well diffusion method. Furthermore, the ZnO nano powders show good antioxidant activity by potentially scavenging DPPH radicals. The study successfully demonstrates synthesis of ZnO NPs by simple ecofriendly route employing EGCG as fuel that exhibit superior photodegradative, antibacterial and antioxidant activities.

In Situ X-ray Absorption Near-Edge Structure Spectroscopy of ZnO Nanowire Growth During Chemical Bath Deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

McPeak, Kevin M.; Becker, Matthew A.; Britton, Nathan G.

2010-12-03

Chemical bath deposition (CBD) offers a simple and inexpensive route to deposit semiconductor nanostructures, but lack of fundamental understanding and control of the underlying chemistry has limited its versatility. Here we report the first use of in situ X-ray absorption spectroscopy during CBD, enabling detailed investigation of both reaction mechanisms and kinetics of ZnO nanowire growth from zinc nitrate and hexamethylenetetramine (HMTA) precursors. Time-resolved X-ray absorption near-edge structure (XANES) spectra were used to quantify Zn(II) speciation in both solution and solid phases. ZnO crystallizes directly from [Zn(H{sub 2}O){sub 6}]{sup 2+} without long-lived intermediates. Using ZnO nanowire deposition as an example,more » this study establishes in situ XANES spectroscopy as an excellent quantitative tool to understand CBD of nanomaterials.« less

Variation of the coordination environment and its effect on the white light emission properties in a Mn-doped ZnO-ZnS complex structure.

PubMed

Cheng, Yan; Chen, Rui; Feng, Haifeng; Hao, Weichang; Xu, Huaizhe; Wang, Yu; Li, Jiong

2014-03-14

Mn-doped ZnO-ZnS complex nanocrystals were fabricated through coating of dodecanethiol on Mn-doped ZnO nanocrystals. The relationship between the component of white light emission and the coordination environments of Mn-dopants were experimentally investigated. It was shown that Mn ions mainly formed Mn(3+)O6 octahedra in as prepared Mn-doped ZnO, while the Mn(3+) ions on the surface of ZnO transferred into Mn(2+) ions at the interface between ZnO and ZnS after dodecanethiol coating. The Mn(2+)S4 tetrahedron density and the orange emission intensity increased upon enhancing the dodecanethiol content. These results provide an alternative way to optimize the white emission spectrum from nanocrystals of Mn-doped ZnS-ZnO complex structures through modulation of the coordination environment of Mn ions.

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Effect of Annealing Conditions on Properties of Sol-Gel Derived Al-Doped ZnO Thin Films

NASA Astrophysics Data System (ADS)

Gao, Mei-Zhen; Zhang, Feng; Liu, Jing; Sun, Hui-Na

2009-08-01

Transparent conductive Al-doped ZnO (AZO) thin films are prepared on normal glass substrates by the sol-gel spin coating method. The effects of drying conditions, annealing temperature and cooling rate on the structural, electrical and optical properties of AZO films are investigated by x-ray diffraction, scanning electron microscopy, the four-point probe method and UV-VIS spectrophotometry, respectively. The deposited films show a hexagonal wurtzite structure and high preferential c-axis orientation. As the drying temperature increases from 100°C to 300°C the resistivity of AZO films decreases dramatically. In contrast to the annealed films cooled in a furnace and in air, the resistivity of the annealed film which is cooled at -15°C is greatly reduced. Increasing the cooling rate dramatically increases the electrical conductivity of AZO films.

UV-light-assisted ethanol sensing characteristics of g-C3N4/ZnO composites at room temperature

NASA Astrophysics Data System (ADS)

Zhai, Jiali; Wang, Tao; Wang, Chuang; Liu, Dechen

2018-05-01

A highly efficient UV-light-assisted room temperature sensor based on g-C3N4/ZnO composites were prepared by an in situ precipitation method. The thermostability, composition, structure, and morphology properties of the as-prepared g-C3N4/ZnO composites were characterized by TGA, XRD, FT-IR, TEM, and XPS, respectively. And then, we studied the ethanol (C2H5OH) sensing performance of the g-C3N4/ZnO composites at the room temperature. Compared with pure ZnO and g-C3N4, the gas sensing activity of g-C3N4/ZnO composites was greatly improved at room temperature, for example, the g-C3N4/ZnO-8% composites showed an obvious response of 121-40 ppm C2H5OH at room temperature, which was 60 times higher than the pure ZnO based on the sensors under the same condition. The great enhancement of the C2H5OH sensing properties of composites can be understood by the efficient separation of photogenerated charge carriers of g-C3N4/ZnO heterogeneous and the UV-light catalytic effect. Finally, a possible mechanism for the gas sensing activity was proposed.

The effect of Cu doping on the mechanical and optical properties of zinc oxide nanowires synthesized by hydrothermal route.

PubMed

Robak, Elżbieta; Coy, Emerson; Kotkowiak, Michał; Jurga, Stefan; Załęski, Karol; Drozdowski, Henryk

2016-04-29

Zinc oxide (ZnO) is a wide-bandgap semiconductor material with applications in a variety of fields such as electronics, optoelectronic and solar cells. However, much of these applications demand a reproducible, reliable and controllable synthesis method that takes special care of their functional properties. In this work ZnO and Cu-doped ZnO nanowires are obtained by an optimized hydrothermal method, following the promising results which ZnO nanostructures have shown in the past few years. The morphology of as-prepared and copper-doped ZnO nanostructures is investigated by means of scanning electron microscopy and high resolution transmission electron microscopy. X-ray diffraction is used to study the impact of doping on the crystalline structure of the wires. Furthermore, the mechanical properties (nanoindentation) and the functional properties (absorption and photoluminescence measurements) of ZnO nanostructures are examined in order to assess their applicability in photovoltaics, piezoelectric and hybrids nanodevices. This work shows a strong correlation between growing conditions, morphology, doping and mechanical as well as optical properties of ZnO nanowires.

Bacteriorhodopsin–ZnO hybrid as a potential sensing element for low-temperature detection of ethanol vapour

PubMed Central

Kumar, Saurav; Bagchi, Sudeshna; Prasad, Senthil; Sharma, Anupma; Kumar, Ritesh; Kaur, Rishemjit; Singh, Jagvir

2016-01-01

Summary Zinc oxide (ZnO) and bacteriorhodopsin (bR) hybrid nanostructures were fabricated by immobilizing bR on ZnO thin films and ZnO nanorods. The morphological and spectroscopic analysis of the hybrid structures confirmed the ZnO thin film/nanorod growth and functional properties of bR. The photoactivity results of the bR protein further corroborated the sustainability of its charge transport property and biological activity. When exposed to ethanol vapour (reducing gas) at low temperature (70 °C), the fabricated sensing elements showed a significant increase in resistivity, as opposed to the conventional n-type behaviour of bare ZnO nanostructures. This work opens up avenues towards the fabrication of low temperature, photoactivated, nanomaterial–biomolecule hybrid gas sensors. PMID:27335741

Enhanced resolution imaging of ultrathin ZnO layers on Ag(111) by multiple hydrogen molecules in a scanning tunneling microscope junction

NASA Astrophysics Data System (ADS)

Liu, Shuyi; Shiotari, Akitoshi; Baugh, Delroy; Wolf, Martin; Kumagai, Takashi

2018-05-01

Molecular hydrogen in a scanning tunneling microscope (STM) junction has been found to enhance the lateral spatial resolution of the STM imaging, referred to as scanning tunneling hydrogen microscopy (STHM). Here we report atomic resolution imaging of 2- and 3-monolayer (ML) thick ZnO layers epitaxially grown on Ag(111) using STHM. The enhanced resolution can be obtained at a relatively large tip to surface distance and resolves a more defective structure exhibiting dislocation defects for 3-ML-thick ZnO than for 2 ML. In order to elucidate the enhanced imaging mechanism, the electric and mechanical properties of the hydrogen molecular junction (HMJ) are investigated by a combination of STM and atomic force microscopy. It is found that the HMJ shows multiple kinklike features in the tip to surface distance dependence of the conductance and frequency shift curves, which are absent in a hydrogen-free junction. Based on a simple modeling, we propose that the junction contains several hydrogen molecules and sequential squeezing of the molecules out of the junction results in the kinklike features in the conductance and frequency shift curves. The model also qualitatively reproduces the enhanced resolution image of the ZnO films.

Flexible, transparent and exceptionally high power output nanogenerators based on ultrathin ZnO nanoflakes

NASA Astrophysics Data System (ADS)

van Ngoc, Huynh; Kang, Dae Joon

2016-02-01

Novel nanogenerator structures composed of ZnO nanoflakes of less than 10 nm thickness were fabricated using a novel method involving a facile synthetic route and a rational design. The fabricated nanogenerators exhibited a short-circuit current density of 67 μA cm-2, a peak-to-peak open-circuit voltage of 110 V, and an overall output power density exceeding 1.2 mW cm-2, and to the best of our knowledge, these are the best values that have been reported so far in the literature on ZnO-based nanogenerators. We demonstrated that our nanogenerator design could instantaneously power 20 commercial green light-emitting diodes without any additional energy storage processes. Both the facile synthetic route for the ZnO nanoflakes and the straightforward device fabrication process present great scaling potential in order to power mobile and personal electronics that can be used in smart wearable systems, transparent and flexible devices, implantable telemetric energy receivers, electronic emergency equipment, and other self-powered nano/micro devices.Novel nanogenerator structures composed of ZnO nanoflakes of less than 10 nm thickness were fabricated using a novel method involving a facile synthetic route and a rational design. The fabricated nanogenerators exhibited a short-circuit current density of 67 μA cm-2, a peak-to-peak open-circuit voltage of 110 V, and an overall output power density exceeding 1.2 mW cm-2, and to the best of our knowledge, these are the best values that have been reported so far in the literature on ZnO-based nanogenerators. We demonstrated that our nanogenerator design could instantaneously power 20 commercial green light-emitting diodes without any additional energy storage processes. Both the facile synthetic route for the ZnO nanoflakes and the straightforward device fabrication process present great scaling potential in order to power mobile and personal electronics that can be used in smart wearable systems, transparent and flexible devices, implantable telemetric energy receivers, electronic emergency equipment, and other self-powered nano/micro devices. Electronic supplementary information (ESI) available: FE-SEM images of ZnO NFs grown on textile and FTO/glass substrates, XRD patterns of synthesized ZnO NFs, nitrogen adsorption isotherms for ZnO NWs and ZnO NFs, effect of different coating layers on ZnO NFNGs, P(VDF-TrFE) coating on ZnO NFs, output open-circuit voltages of a textile electrostatic NG based on P(VDF-TrFE) coated on ZnO NFs and a textile ZnO NFNG without an insulating layer generated by a sonic wave, NG-based triboelectric effects and PDMS-coated ZnO NF-based NGs grown on an ITO/PET substrate. See DOI: 10.1039/c5nr08324a

Physical study on Cobalt-Indium Co-doped ZnO nanofilms as hydrophobic surfaces

NASA Astrophysics Data System (ADS)

Mimouni, R.; Mahdhi, N.; Boubaker, K.; Madouri, A.; Amlouk, M.

2016-03-01

The present work reports some physical investigations on (Co,In) codoped zinc oxide nanofilms deposited on glass substrates at 460 °C by the spray pyrolysis technique. The effect of Co and In concentration on the structural, morphological, optical and surface wettability properties have been investigated using X-ray diffraction (XRD) patterns, Raman spectroscopy, SEM, optical measurement, photoluminescence spectroscopy as well as the measurement of hydrophobicity in terms of water contact angle. It is found that all films crystallized in würtzite ZnO phase, with a preferentially orientation towards (002) direction parallel to c-axis. The Raman spectra of the samples exhibit the presence of E2high characteristic mode of würtzite structure with high crystallinity as well as two dominant bands 1LO and 2LO. Also, no additional modes introduced by codopoing have been found. SEM micrographs show the uniform deposition of fine grains on surface films. Thicknesses of films are less than 100 nm. In addition, optical investigations indicate that the band gap narrowing of (Co,In) codoped ZnO thin films is due to the increase in the band tail width. Indeed, PL study indicates that (Co,In) codoped ZnO nanofilms exhibit a large decrease of the UV luminescence, which is assigned to the trapping of photo-generated electrons by both In3+ and Co2+ ions as well as an improvement of charge separation in the ZnO thin films. Finally, the (Co,In) codoping influences the surface wettability property and transform the ZnO character from hydrophilic (θ < 90°) for pure ZnO nanofilm to hydrophobic (θ > 90°) for (Co,In) codoped ZnO ones.

Effect of thermal treatment on Zn nanodisks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Acuña-Avila, Pedro E., E-mail: pacunaa004@alumno.uaemex.mx; López, Roberto; Vigueras-Santiago, Enrique

2015-06-15

Metallic Zn nanodisks with hexagonal morphology were obtained onto glass substrate under vacuum thermal evaporation. A thermal characterization of Zn nanodiks showed a lower oxidation temperature than source powder Zn. Different thermal treatment on Zn nanodisks played an important role on the morphology, crystal size and surface vibrational modes of ZnO. The growth of ZnO nanoneedles started at the edge of metallic zinc hexagonal structures according with SEM images, the higher temperature the longer needles were grown. XRD diffractogram confirmed the wurtzite structure of ZnO with metallic nuclei. A wide band between 530 and 580 cm{sup −1} of Raman scatteringmore » corresponded at surface vibrational modes not observed at higher temperature.« less

The correlation between radiative surface defect states and high color rendering index from ZnO nanotubes

PubMed Central

2011-01-01

Combined surface, structural and opto-electrical investigations are drawn from the chemically fashioned ZnO nanotubes and its heterostructure with p-GaN film. A strong correlation has been found between the formation of radiative surface defect states in the nanotubes and the pure cool white light possessing averaged eight color rendering index value of 96 with appropriate color temperature. Highly important deep-red color index value has been realized > 95 which has the capability to render and reproduce natural and vivid colors accurately. Diverse types of deep defect states and their relative contribution to the corresponding wavelengths in the broad emission band is suggested. PMID:21878100

Ti-doped ZnO Thin Films Prepared at Different Ambient Conditions: Electronic Structures and Magnetic Properties

PubMed Central

Yong, Zhihua; Liu, Tao; Uruga, Tomoya; Tanida, Hajime; Qi, Dongchen; Rusydi, Andrivo; Wee, Andrew T. S.

2010-01-01

We present a comprehensive study on Ti-doped ZnO thin films using X-ray Absorption Fine Structure (XAFS) spectroscopy. Ti K edge XAFS spectra were measured to study the electronic and chemical properties of Ti ions in the thin films grown under different ambient atmospheres. A strong dependence of Ti speciation, composition, and local structures upon the ambient conditions was observed. The XAFS results suggest a major tetrahedral coordination and a 4+ valence state. The sample grown in a mixture of 80% Ar and 20% O2 shows a portion of precipitates with higher coordination. A large distortion was observed by the Ti substitution in the ZnO lattice. Interestingly, the film prepared in 80% Ar, 20% O2 shows the largest saturation magnetic moment of 0.827 ± 0.013 µB/Ti.

Controllable synthesis and optical properties of novel ZnO cone arrays via vapor transport at low temperature.

PubMed

Han, Xinhai; Wang, Guanzhong; Jie, Jiansheng; Choy, Wallace C H; Luo, Yi; Yuk, T I; Hou, J G

2005-02-24

Novel ZnO cone arrays with controllable morphologies have been synthesized on silicon (100) substrates by thermal evaporation of metal Zn powder at a low temperature of 570 degrees C without a metal catalyst. Clear structure evolutions were observed using scanning electron microscopy: well-aligned ZnO nanocones, double-cones with growing head cones attached by stem cones, and cones with straight hexagonal pillar were obtained as the distance between the source and the substrates was increased. X-ray diffraction shows that all cone arrays grow along the c-axis. Raman and photoluminescence spectra reveal that the optical properties of the buffer layer between the ZnO cone arrays and the silicon substrates are better than those of the ZnO cone arrays due to high concentration of Zn in the heads of the ZnO cone arrays and higher growth temperature of the buffer layer. The growth of ZnO arrays reveals that the cone arrays are synthesized through a self-catalyzed vapor-liquid-solid (VLS) process.