Science.gov

Sample records for ag doped zno

  1. Synthesis of highly efficient antibacterial agent Ag doped ZnO nanorods: Structural, Raman and optical properties

    SciTech Connect

    Jan, Tariq; Iqbal, Javed; Ismail, Muhammad; Mahmood, Arshad

    2014-04-21

    Here, synthesis, structural, morphological, Raman, optical properties and antibacterial activity of undoped and Ag doped ZnO nanorods by chemical co-precipitation technique have been reported. Structural analysis has revealed that Ag doping cannot deteriorate the structure of ZnO and wurtzite phase is maintained. Lattice constants are found to be decreased with the Ag doping. Fourier transform infrared and Raman spectroscopy also confirm the X-ray diffraction results. Scanning electron microscopy results have demonstrated the formation of ZnO nanorods with average diameter and length of 96 nm and 700 nm, respectively. Raman spectroscopy results suggest that the Ag doping enhances the number of defects in ZnO crystal. It has been found from optical study that Ag doping results in positional shift of band edge absorption peak. This is attributed to the successful incorporation of Ag dopant into ZnO host matrix. The antibacterial activity of prepared nanorods has been determined by two different methods and compared to that of undoped ZnO nanorods. Ag doped ZnO nanorods exhibit excellent antibacterial activity as compared to that of undoped ZnO nanorods. This excellent antibacterial activity may be attributed to the presence of oxygen vacancies and Zn{sup 2+} interstitial defects. Our preliminary findings suggest that Ag doped ZnO nanorods can be used externally to control the spreading of infections related with tested bacterial strains.

  2. Theory of doping properties of Ag acceptors in ZnO

    NASA Astrophysics Data System (ADS)

    Volnianska, O.; Boguslawski, P.; Kaczkowski, J.; Jakubas, P.; Jezierski, A.; Kaminska, E.

    2009-12-01

    Doping properties of Ag in ZnO were analyzed by first-principles calculations within both the local-density and generalized gradient approximations. The ionization energy of AgZn , about 0.2 eV, is comparable to that of the commonly used group-V acceptors, and is lower than that of two other IB species, Cu and Au. Formation energy of Ag in the favorable O-rich conditions is 0.85 eV, which corresponds to the solubility limit of about 1018cm-3 at 700°C . Formation of Ag-rich second phases is predicted for high Ag concentrations. Energetics of the onset of this process is analyzed and AgZn display a tendency to form aggregates of AgO with the wurtzite structure. Formation of such nanoinclusions is shown to affect the lattice constant of ZnO:Ag. Two “wrong” incorporation channels, i.e., at the interstitial sites and at the oxygen sites as AgO , are predicted to be nonefficient due to the high formation energies. The calculated magnetic coupling between Ag ion reveals an unexpected dependence on the Ag-Ag distance; the interaction between the nearest-neighbor AgZn pair vanishes while that for the more distant pairs is weakly ferromagnetic.

  3. Structural and nonlinear optical behavior of Ag-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Tan, Ming-Yue; Yao, Cheng-Bao; Yan, Xiao-Yan; Li, Jin; Qu, Shu-Yang; Hu, Jun-Yan; Sun, Wen-Jun; Li, Qiang-Hua; Yang, Shou-Bin

    2016-01-01

    We present the structural and nonlinear optical behavior of Ag-doped ZnO (AZO) films prepared by magnetron sputtering. The structural of AZO films are systematically investigated by X-ray diffraction (XRD) and scanning electronic microscopy (SEM), respectively. The results show that AZO films can still retain a wurtzite structure, although the c-axis as preferred orientation is decreased by Ag doping. As the amounts of the Ag dopant were increased, the crystallinity as well as the absorptivity and optical band gap were increased. Moreover, the nonlinear optical characterized of the AZO films was studied using Z-scan technique. These samples show self-defocusing nonlinearity and good nonlinear absorption behavior which increases with increasing Ag volume fraction. AZO is a potential nanocomposite material for the development of nonlinear optical devices with a relatively small limiting threshold.

  4. Synthesis and Characterization of Varying Concentrations of Ag-doped ZnO Thin Films

    NASA Astrophysics Data System (ADS)

    Hachlica, Justin; Wadie-Ibrahim, Patrick; Sahiner, M. Alper

    Silver doped ZnO is a promising compound for photovoltaic solar cell use. Doping this compound with varying amounts of silver will theoretically make this type of thin film more efficient by reducing the overall resistance and increasing the voltage and current output. The extent of this promise is being tested experimentally, by analysis of both the electrical and the surface roughness properties of the cells. Ag-doped Zinc Oxide is deposited by method of Pulsed Laser Deposition (PLD) onto Indium Tin Oxide (ITO) coated Glass. Annealing effects were also observed by varying the temperature at which the annealing occurred after synthesis of the sample. Thickness is confirmed by use of Ellipsometery. X-Ray Diffraction (XRD) measurements confirmed a ZnO crystal structure on the thin films. The active dopant carrier concentrations were determined using a Hall Effect Measuring System. Finally, the photovoltaic properties of the film are recorded by using a Keithley Source Meter. The structural characterization and electrical results of the effect of Ag doping on ZnO will then be discussed.

  5. The synthesis and characterization of Ag-N dual-doped p-type ZnO: experiment and theory.

    PubMed

    Duan, Li; Wang, Pei; Yu, Xiaochen; Han, Xiao; Chen, Yongnan; Zhao, Peng; Li, Donglin; Yao, Ran

    2014-03-01

    Ag-N dual-doped ZnO films have been fabricated by a chemical bath deposition method. The p-type conductivity of the dual-doped ZnO:(Ag, N) is stable over a long period of time, and the hole concentration in the ZnO:(Ag, N) is much higher than that in mono-doped ZnO:Ag or ZnO:N. We found that this is because AgZn-NO complex acceptors can be formed in ZnO:(Ag, N). First-principles calculations show that the complex acceptors generate a fully occupied band above the valance band maximum, so the acceptor levels become shallower and the hole concentration is increased. Furthermore, the binding energy of the Ag-N complex in ZnO is negative, so ZnO:(Ag, N) can be stable. These results indicate that the Ag-N dual-doping may be expected to be a potential route to achieving high-quality p-type ZnO for use in a variety of devices. PMID:24448605

  6. Size dependent electron-phonon coupling in N, Li, In, Ga, F and Ag doped ZnO thin films.

    PubMed

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

    2012-12-01

    Polarized micro-Raman measurements are performed to study the phonon modes of N, Li, In, Ga, F and Ag doped ZnO thin films, grown by spray pyrolysis on corning glass substrates. The E(2)(high) mode displays a visible asymmetric line shape. The size and dopant dependence onto coupling strength between electron and LO phonon is experimentally estimated. PMID:23010630

  7. Photocatalytic activity of ZnO doped with Ag on the degradation of endocrine disrupting under UV irradiation and the investigation of its antibacterial activity

    NASA Astrophysics Data System (ADS)

    Bechambi, Olfa; Chalbi, Manel; Najjar, Wahiba; Sayadi, Sami

    2015-08-01

    Ag-doped ZnO photocatalysts with different Ag molar content (0.0, 0.5, 1.0, 2.0 and 4.0%) were prepared via hydrothermal method. The X-ray diffraction (XRD), Nitrogen physisorption at 77 K, Fourier transformed infrared spectroscopy (FTIR), UV--Visible spectroscopy, Photoluminescence spectra (PL) and Raman spectroscopy were used to characterize the structural, textural and optical properties of the samples. The results showed that Ag-doping does not change the average crystallite size with the Ag low content (≤1.0%) but slightly decreases with Ag high content (>1.0%). The specific surface area (SBET) increases with the increase of the Ag content. The band gap values of ZnO are decreased with the increase of the Ag doping level. The results of the photocatalytic degradation of bisphenol A (BPA) and nonylphenol (NP) in aqueous solutions under UV irradiation and in the presence of hydrogen peroxide (H2O2) showed that silver ions doping greatly improved the photocatalytic efficiency of ZnO. The TOC conversion BPA and NP are 72.1% and 81.08% respectively obtained using 1% Ag-doped ZnO. The enhancement of photocatalytic activity is ascribed to the fact that the modification of ZnO with an appropriate amount of Ag can increase the separation efficiency of the photogenerated electrons-holes in ZnO. The antibacterial activity of the catalysts which uses Escherichia coli as a model for Gram-negative bacteria confirmed that Ag-doped ZnO possessed more antibacterial activity than the pure ZnO.

  8. Aging and annealing effects on properties of Ag-N dual-acceptor doped ZnO thin films

    SciTech Connect

    Swapna, R.; Amiruddin, R.; Santhosh Kumar, M. C.

    2013-02-05

    Ag-N dual acceptor doping into ZnO has been proposed to realize p-ZnO thin film of different concentrations (1, 2 and 4 at.%) by spray pyrolysis at 623 K and then 4 at.% films annealed at 673 K and 723 K for 1 hr. X-ray diffraction studies reveal that all the films are preferentially oriented along (002) plane. Energy dispersive spectroscopy (EDS) confirms the presence of Ag and N in 2 at.% ZnO:(Ag, N) film. Hall measurement shows that 4 at.% ZnO:(Ag, N) film achieved minimum resistivity with high hole concentration. The p-type conductivity of the ZnO:(Ag, N) films is retained even after 180 days. Photoluminescence (PL) spectra of ZnO:(Ag, N) films show low density of native defects.

  9. Li and Ag Co-Doped ZnO Photocatalyst for Degradation of RO 4 Dye Under Solar Light Irradiation.

    PubMed

    Dhatshanamurthi, P; Shanthi, M

    2016-06-01

    The synthesis of Li doped Ag-ZnO (Li-Ag-ZnO) has been successfully achieved by a sonochemically assisted precipitation-decomposition method. The synthesized catalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), diffuse reflectance spectra (DRS), photoluminescence spectra (PL), X-ray photoelectron spectra (XPS) and BET surface area measurements. The photocatalytic activity of Li-Ag-ZnO was investigated for the degradation of Reactive orange 4 (RO 4) dye in aqueous solution under solar light irradiation. Co-dopants shift the absorbance of ZnO to the visible region. Li-Ag-ZnO is found to be more efficient than Ag-ZnO, Li-ZnO, commercial ZnO and prepared ZnO at pH 7 for the mineralization of RO 4 dye under solar light irradiation. The influences of operational parameters such as the amount of photocatalyst, dye concentration, initial pH on photo-mineralization of RO 4 have been analyzed. The mineralization of RO 4 dye has been confirmed by COD measurements. A degradation mechanism is proposed for the degradation of RO 4 under solar light. The catalyst was found to be more stable and reusable. PMID:27427652

  10. Tuning of Ag doped core-shell ZnO NWs/Cu2O grown by electrochemical deposition

    NASA Astrophysics Data System (ADS)

    Makhlouf, Houssin; Messaoudi, Olfa; Souissi, Ahmed; Ben Assaker, Ibtissem; Oueslati, Mihrez; Bechelany, Mikhael; Chtourou, Radhouane

    2015-09-01

    ZnO nanowires (NWs)/Cu2O-Ag core-shell nanostructures (NSs) have been synthesized by electrochemical deposition method on ITO-coated glass substrates in order to improve the efficiency of the type-II transition of core-shell ZnO NWs/Cu2O-Ag NSs. The morphologies of the obtained NSs were studied by scanning electron microscopy confirming the presence of core-shell NSs. The crystalline proprieties were analyzed by x-ray diffraction and micro-Raman measurement: wurtzite ZnO and cuprit Cu2O phase were founded. The presence of Ag content in core-shell NS was detected by EDX. Optical measurement reveals an additional contribution δE at about 1.72 eV attributed to the type-II interfacial transition between the valance band of cuprit-Cu2O and the conduction band of W-ZnO. The effect of the Ag doping into the type-II transition was investigated. A red shift of the type-II transition was detected according to the Ag concentration. These materials could have potential applications in photocatalytic and photovoltaic fields.

  11. 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. PMID:25990263

  12. Fabrication of Ag nanowire and Al-doped ZnO hybrid transparent electrodes

    NASA Astrophysics Data System (ADS)

    You, Sslimsearom; Park, Yong Seo; Choi, Hyung Wook; Kim, Kyung Hwan

    2016-01-01

    Among the materials used as transparent electrodes, silver nanowires (AgNWs) have attracted attention because of their high transmittance and excellent conductivity. However, AgNWs have shortcomings, including their poor adhesion, oxidation by atmospheric oxygen, and unstable characteristics at high temperature. To overcome these shortcomings, multi-layer thin films with an aluminum-doped zinc oxide (AZO)/AgNW/AZO structure were fabricated using facing targets sputtering. The samples heated to 350 °C exhibited stable electrical characteristics. In addition, the adhesion to the substrate was improved compared with AgNWs layer. The AZO/AgNW/AZO thin films with multilayer structure overcame the shortcomings of AgNWs, and we propose their use as transparent electrodes with excellent properties for optoelectronic applications.

  13. Low temperature preparation of Ag-doped ZnO nanowire arrays for sensor and light-emitting diode applications

    NASA Astrophysics Data System (ADS)

    Lupan, O.; Viana, B.; Cretu, V.; Postica, V.; Adelung, R.; Pauporté, T.

    2016-02-01

    Transition metal doped-oxide semiconductor nanostructures are important to achieve enhanced and new properties for advanced applications. We describe the low temperature preparation of ZnO:Ag nanowire/nanorod (NW/NR) arrays by electrodeposition at 90 °C. The NWs have been characterized by SEM, EDX, transmittance and photoluminescence (PL) measurements. The integration of Ag in the crystal is shown. Single nanowire/nanorod of ZnO:Ag was integrated in a nanosensor structure leading to new and enhanced properties. The ultraviolet (UV) response of the nanosensor was investigated at room temperature. Experimental results indicate that ZnO:Ag (0.75 μM) nanosensor possesses faster response/recovery time and better response to UV light than those reported in literature. The sensor structure has been also shown to give a fast response for the hydrogen detection with improved performances compared to pristine ZnO NWs. ZnO:Ag nanowire/nanorod arrays electrochemically grown on p-type GaN single crystal layer is also shown to act as light emitter in LED structures. The emission wavelength is red-shifted compared to pristine ZnO NW array. At low Ag concentration a single UV-blue emission is found whereas at higher concentration of dopant the emission is broadened and extends up to the red wavelength range. Our study indicates that high quality ZnO:Ag NW/NR prepared at low temperature by electrodeposition can serve as building nanomaterials for new sensors and light emitting diodes (LEDs) structures with low-power consumption.

  14. Photoluminescence study of p-type vs. n-type Ag-doped ZnO films

    SciTech Connect

    Myers, M. A.; Jian, J.; Khranovskyy, V.; Lee, J. H.; Wang, Han; Wang, Haiyan E-mail: hwang00@tamu.edu

    2015-08-14

    Silver doped ZnO films have been grown on sapphire (0001) substrates by pulsed laser deposition. Hall measurements indicate that p-type conductivity is realized for the films deposited at 500 °C and 750 °C. Transmission electron microscopy images show more obvious and higher density of stacking faults (SFs) present in the p-type ZnO films as compared to the n-type films. Top view and cross sectional photoluminescence of the n- and p-type samples revealed free excitonic emission from both films. A peak at 3.314 eV, attributed to SF emission, has been observed only for the n-type sample, while a weak neutral acceptor peak observed at 3.359 eV in the p-type film. The SF emission in the n-type sample suggests localization of acceptor impurities nearby the SFs, while lack of SF emission for the p-type sample indicates the activation of the Ag acceptors in ZnO.

  15. Ag-doped ZnO nanorods coated metal wire meshes as hierarchical photocatalysts with high visible-light driven photoactivity and photostability.

    PubMed

    Hsu, Mu-Hsiang; Chang, Chi-Jung

    2014-08-15

    Ag-doped ZnO nanorods were grown on stainless-steel wire meshes to fabricate the hierarchical photocatalysts with excellent visible light driven activity and anti-photocorrosion property. Effects of Ag doping and the surface structure on the surface chemistry, surface wetting properties, absorption band shift, photoelectrochemical response, and photocatalytic decolorization properties of the hierarchical photocatalysts, together with the stability of photocatalytic activity for recycled photocatalysts were investigated. Ag doping leads to red-shift in the absorption band and increased visible light absorption. Nanorods coated wire meshes hierarchical structure not only increases the surface area of photocatalysts but also makes the surface hydrophilic. The photocatalytic activity enhancement and reduced photocorrosion can be achieved because of increased surface area, enhanced hydrophilicity, and the interaction between the metal wire/ZnO and Ag/ZnO heterostructure interface which can improve the charge separation of photogenerated charge carriers. PMID:24997260

  16. Breakthrough of the p-type doping bottleneck in ZnO by inserting an ultrathin ZnX (X  =  S, Se and Te) layer doped with NX or AgZn

    NASA Astrophysics Data System (ADS)

    Jiang, Xin-he; Shi, Jun-jie; Zhang, Min; Zhong, Hong-xia; Huang, Pu; Ding, Yi-min; Cao, Xiong; Wu, Meng; Liao, Zhi-min

    2016-03-01

    The worldwide problem of p-type doping in ZnO is investigated based on first-principles calculations by combining the standard density functional theory and hybrid functional methods. We find that p-type doping can be realized by inserting an ultrathin ZnX (X  =  S, Se and Te) layer, doped with NX or AgZn, into ZnO to form short-period (ZnO) m /(ZnX) n (m  >  n) superlattices. The formation energy is the lowest for NX or AgZn in the ZnX layer. The Zn-rich (Zn-poor) condition is favourable for the formation of the NX (AgZn) defect. Compensation by the native defects can be avoided for the Ag-doped (ZnO) m /(ZnX) n under the Zn-poor condition. The N (Ag) acceptor activation energy can be reduced from 0.45 (0.43) eV in ZnO to 0.33 (0.32) eV in (ZnO)5/(ZnS)1, 0.20 (0.24) eV in (ZnO)5/(ZnSe)1 and 0.12 (0.13) eV in (ZnO)5/(ZnTe)1, which is caused by the ZnX-monolayer modulation to the local structure around the NX or AgZn defect and the high-lying p-derived valence bands. Moreover, the band gaps can be tuned from 3.40 eV of ZnO to 3.21 eV of (ZnO)5/(ZnS)1, 2.41 eV of (ZnO)5/(ZnSe)1 and 2.26 eV of (ZnO)5/(ZnTe)1, which is promising for the integration of ZnO-based white light-emitting diodes.

  17. Ab inito study of Ag-related defects in ZnO

    NASA Astrophysics Data System (ADS)

    Wan, Qixin; Xiong, Zhihua; Li, Dongmei; Liu, Guodong

    2008-12-01

    Using first-principles calculations, we investigated the structure and electronic properties of Ag-related defects in ZnO. The calculation results indicate that AgZn behaves as acceptor. Simultaneously, by comparing the formation energy and electronic structure of Ag-related defects in ZnO, Oi-AgZn behaves as acceptor in Ag-doped ZnO and it is better to gain p-type ZnO. However, Hi-AgZn complex has the lowest formation energy. Thus, the formation of the other point defects is greatly suppressed by the formation of Hi in Ag-doped ZnO. Moreover, the H atoms can be easily dissociated from hydrogen-passivated complexes by post-annealing at moderate temperatures, thus, codoping Ag with H may be a good method to achieve p-type in Ag-doped ZnO.

  18. Effect of Ag/Al co-doping method on optically p-type ZnO nanowires synthesized by hot-walled pulsed laser deposition

    PubMed Central

    2012-01-01

    Silver and aluminum-co-doped zinc oxide (SAZO) nanowires (NWs) of 1, 3, and 5 at.% were grown on sapphire substrates. Low-temperature photoluminescence (PL) was studied experimentally to investigate the p-type behavior observed by the exciton bound to a neutral acceptor (A0X). The A0X was not observed in the 1 at.% SAZO NWs by low-temperature PL because 1 at.% SAZO NWs do not have a Ag-O chemical bonding as confirmed by XPS measurement. The activation energies (Ea) of the A0X were calculated to be about 18.14 and 19.77 meV for 3 and 5 at.% SAZO NWs, respectively, which are lower than the activation energy of single Ag-doped NW which is about 25 meV. These results indicate that Ag/Al co-doping method is a good candidate to make optically p-type ZnO NWs. PMID:22647319

  19. Effect of silver doping on ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Gawai, U. P.; Khawal, H. A.; Bodke, M. R.; Dole, B. N.

    2016-05-01

    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 Zn1-xAgxO 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 FTIR 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-1.

  20. Al-doped ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Kadam, Pratibha; Agashe, Chitra; Mahamuni, Shailaja

    2008-11-01

    Al3+-doped ZnO nanocrystals were differently obtained by wet chemical and an electrochemical route. An increase in forbidden gap due to change in crystal size and also due to Al3+ doping in ZnO is critically analyzed. The Moss-Burstein type shift in Al3+-doped ZnO nanocrystals provides an evidence of successful Al3+ doping in ZnO nanocrystals. The possibility of varying the carrier concentration in ZnO nanocrystals is the indirect implication of the present investigations.

  1. First-principles study on distribution of Ag in ZnO

    NASA Astrophysics Data System (ADS)

    Wan, Qixin; Xiong, Zhihua; Li, Dongmei; Liu, Guodong; Peng, Jianfei

    2009-08-01

    Except for the group-V dopants, Ag, as a group IB element, could also act as an acceptor in ZnO, if incorporated on substitutional Zn sites. In this paper, first-principles density-functional calculations have been performed to investigate various distributions of Ag in ZnO. The first-principles calculations were carried out using the density functional theory with the generalized gradient approximation (GGA) and the projector augmented wave (PAW) pseudopotentials. The supercell employed contained 32 atoms that corresponded to a 2×2×2 supercell of ZnO. The various distributions of Ag in ZnO have been calculated corresponding to each possible location. In conclusion, the calculation results show that the formation energies of Ag on the substitutional Zn site (AgZn) and incorporation in the interstitial site (Agi) are smaller than that of Ag on the O site (AgO). When AgZn and Agi coexist and are partitioned by an oxygen atom layer, the formation energy and the total energy is the smallest. As a result, Ag prefers to distribute discretely in Ag doped ZnO. It is also found that our results are in agreement with other experimental results.

  2. Fabrication of ZnO and doped ZnO waveguides deposited by Spin Coating

    NASA Astrophysics Data System (ADS)

    Mohan, Rosmin Elsa; R, Neha P.; T, Shalu; C, Darshana K.; Sreelatha, K. S.

    2015-02-01

    In this paper, the synthesis of ZnO and doped Zn1-xAgxO (where x=0.03) nanoparticles by co- precipitation is reported. The precursors used were Zinc Nitrate and Potassium hydroxide pellets. For doping, 3% AgNO3 in ZnNO3 was considered as a separate buffer solution. The prepared nanoparticles were subsequently spin coated onto silica glass substrates at a constant chuck rate of 3000 rpm. The substrate acts as the lower cladding of a waveguide structure. The upper cladding is assumed to be air in the present investigation. The nanostructures of the ZnO powders in the doped and undoped cases were studied using X-ray Diffraction patterns. There was a decrease in the grain size with doping which increase the tunability of the powders to be used as photoluminescent devices. The optical characteristics of the sample were also investigated using UV-Visible spectrophotometer at 200-900 nm wavelengths. The photoluminescence peaks also report a dramatic increase in intensity at the same wavelength for the doped case compared to the undoped one.

  3. Sodium doping in ZnO crystals

    SciTech Connect

    Parmar, N. S. Lynn, K. G.

    2015-01-12

    ZnO bulk single crystals were doped with sodium by thermal diffusion. Positron annihilations spectroscopy confirms the filling of zinc vacancies, to >6 μm deep in the bulk. Secondary-ion mass spectrometry measurement shows the diffusion of sodium up to 8 μm with concentration (1–3.5) × 10{sup 17 }cm{sup −3}. Broad photoluminescence excitation peak at 3.1 eV, with onset appearance at 3.15 eV in Na:ZnO, is attributed to an electronic transition from a Na{sub Zn} level at ∼(220–270) meV to the conduction band. Resistivity in Na doped ZnO crystals increases up to (4–5) orders of magnitude at room temperature.

  4. A Novel Way for Synthesizing Phosphorus-Doped Zno Nanowires

    PubMed Central

    2011-01-01

    We developed a novel approach to synthesize phosphorus (P)-doped ZnO nanowires by directly decomposing zinc phosphate powder. The samples were demonstrated to be P-doped ZnO nanowires by using scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction spectra, X-ray photoelectron spectroscopy, energy dispersive spectrum, Raman spectra and photoluminescence measurements. The chemical state of P was investigated by electron energy loss spectroscopy (EELS) analyses in individual ZnO nanowires. P was found to substitute at oxygen sites (PO), with the presence of anti-site P on Zn sites (PZn). P-doped ZnO nanowires were high resistance and the related P-doping mechanism was discussed by combining EELS results with electrical measurements, structure characterization and photoluminescence measurements. Our method provides an efficient way of synthesizing P-doped ZnO nanowires and the results help to understand the P-doping mechanism.

  5. Preparation of new morphological ZnO and Ce-doped ZnO

    SciTech Connect

    Chelouche, A.; Djouadi, D.; Aksas, A.

    2013-12-16

    ZnO micro-tori and cerium doped hexangulars ZnO have been prepared by the sol-gel method under methanol hypercritical conditions of temperature and pressure. X-ray diffraction (XRD) measurement has revealed the high crystalline quality and the nanometric size of the samples. Scanning electron microscopy (SEM) has shown that the ZnO powder has a torus-like shape while that of ZnO:Ce has a hexangular-like shape, either standing free or inserted into the cores of ZnO tori. Transmission electron microscopy (TEM) has revealed that the ZnO particles have sizes between 25 and 30 nm while Ce-doped ZnO grains have diameters ranging from 75 nm to 100 nm. Photoluminescence spectra at room temperature of the samples have revealed that the introduction of cerium in ZnO reduces the emission intensity lines, particularly the ZnO red and green ones.

  6. Electrically conductive nanostructured silver doped zinc oxide (Ag:ZnO) prepared by solution-immersion technique

    NASA Astrophysics Data System (ADS)

    Afaah, A. N.; Asib, N. A. M.; Aadila, A.; Mohamed, R.; Rusop, M.; Khusaimi, Z.

    2016-07-01

    p-type ZnO films have been fabricated on ZnO-seeded glass substrate, using AgNO3 as a source of silver dopant by facile solution-immersion. Cleaned glass substrate were seeded with ZnO by mist-atomisation, and next the seeded substrates were immersed in Ag:ZnO solution. The effects of Ag doping concentration on the Ag-doped ZnO have been investigated. The substrates were immersed in different concentrations of Ag dopant with variation of 0, 1, 3, 5 and 7 at. %. The surface morphology of the films was characterized by field emission scanning electron microscope (FESEM). In order to investigate the electrical properties, the films were characterized by Current-Voltage (I-V) measurement. FESEM micrographs showed uniform distribution of nanostructured ZnO and Ag:ZnO. Besides, the electrical properties of Ag-doped ZnO were also dependent on the doping concentration. The I-V measurement result indicated the electrical properties of 1 at. % Ag:ZnO thin film owned highest electrical conductivity.

  7. Controlled doping of graphene using ZnO substrates

    NASA Astrophysics Data System (ADS)

    Si, Misuk; Choi, Won Jin; Jeong, Yoon Jang; Lee, Young Kuk; Kim, Ju-Jin; Lee, Jeong-O.

    2016-06-01

    We show that graphene device could be controllably doped by the bottom substrate by inserting atomic layer deposition grown ZnO between graphene and SiO2 substrate. To clarify the effect of bottom ZnO, length of the graphene transistor channel was varied from 20 to 200 μm, while that of ZnO was fixed to 10 μm. Graphene devices supported on ZnO film show marked difference from those supported on SiO2 substrates; bottom ZnO layer behave as an electron donor. UV illumination experiment on hybrid graphene-ZnO device reveals that the effect of doping from ZnO becomes negligible when the graphene channel length made about four times larger than that of ZnO stripe.

  8. Mass preparation and novel visible light photocatalytic activity of C and Ag Co-modified ZnO nanocrystals.

    PubMed

    Zhang, Xiao-Yan; Deng, Ya-Juan; Liu, Jin-Ku; Lu, Yi; Yang, Xiao-Hong

    2015-12-01

    A combustion method was developed to synthesize the C and Ag co-modified ZnO NCs to enhance its photocatalytic efficiency and practicability. The results showed that the doped Ag was significant to promote the photocatalytic activity, and the optimum content was 2% molar ratio of Ag to Zn atom. The degradation rate under visible light increased by 150% compared with C-ZnO NCs, while by more 1233.3% than pure ZnO photocatalyst. There were some new little particles with grain size about 10 nm on the C-ZnO NCs surface, which may state for the existence of Ag atoms. The synergy effect of Ag and carbon elements was proposed to explain the mechanism of enhanced photocatalytic performance under visible light irradiation. PMID:26254866

  9. Hydrothermal fabrication of selectively doped organic assisted advanced ZnO nanomaterial for solar driven photocatalysis.

    PubMed

    Namratha, K; Byrappa, K; Byrappa, S; Venkateswarlu, P; Rajasekhar, D; Deepthi, B K

    2015-08-01

    Hydrothermal fabrication of selectively doped (Ag(+)+Pd(3+)) advanced ZnO nanomaterial has been carried out under mild pressure temperature conditions (autogeneous; 150°C). Gluconic acid has been used as a surface modifier to effectively control the particle size and morphology of these ZnO nanoparticles. The experimental parameters were tuned to achieve optimum conditions for the synthesis of selectively doped ZnO nanomaterials with an experimental duration of 4 hr. These selectively doped ZnO nanoparticles were characterized using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy and scanning electron microscopy (SEM). The solar driven photocatalytic studies have been carried out for organic dyes, i.e., Procion MX-5B dye, Cibacron Brilliant Yellow dye, Indigo Carmine dye, separately and all three mixed, by using gluconic acid modified selectively doped advanced ZnO nanomaterial. The influence of catalyst, its concentration and initial dye concentration resulted in the photocatalytic efficiency of 89% under daylight. PMID:26257367

  10. Enhanced piezoelectric output voltage and Ohmic behavior in Cr-doped ZnO nanorods

    SciTech Connect

    Sinha, Nidhi; Ray, Geeta; Godara, Sanjay; Gupta, Manoj K.; Kumar, Binay

    2014-11-15

    Highlights: • Low cost highly crystalline Cr-doped ZnO nanorods were synthesized. • Enhancement in dielectric, piezoelectric and ferroelectric properties were observed. • A high output voltage was obtained in AFM. • Cr-doping resulted in enhanced conductivity and better Ohmic behavior in ZnO/Ag contact. - Abstract: Highly crystalline Cr-doped ZnO nanorods (NRs) were synthesized by solution technique. The size distribution was analyzed by high resolution tunneling electron microscope (HRTEM) and particle size analyzer. In atomic force microscope (AFM) studies, peak to peak 8 mV output voltage was obtained on the application of constant normal force of 25 nN. It showed high dielectric constant (980) with phase transition at 69 °C. Polarization vs. electric field (P–E) loops with remnant polarization (6.18 μC/cm{sup 2}) and coercive field (0.96 kV/cm) were obtained. In I–V studies, Cr-doping was found to reduce the rectifying behavior in the Ag/ZnO Schottky contact which is useful for field effect transistor (FET) and solar cell applications. With these excellent properties, Cr-doped ZnO NRs can be used in nanopiezoelectronics, charge storage and ferroelectric applications.

  11. Electrical and mechanical properties of ZnO doped silver-molybdate glass-nanocomposite system

    NASA Astrophysics Data System (ADS)

    Kundu, Ranadip; Roy, Debasish; Bhattacharya, Sanjib

    2016-05-01

    Zno doped silver-molybdate glass-nanocomposites, 0.3 Ag2O - 0.7 [0.075 ZnO - 0.925 MoO3] have been prepared by melt-quenching method. Ionic conductivity of these glass-nanocomposites has been measured in wide temperature and frequency windows. Vicker's hardness methods have been employed to study micro-hardness of the as-prepared samples. Heat-treated counterparts for this glass-nanocomposites system has been analyzed in different temperature to observe the changes in conductivity as well as micro-hardness for that system.

  12. Top electrode-dependent resistance switching behaviors of lanthanum-doped ZnO film memory devices

    NASA Astrophysics Data System (ADS)

    Xu, Dinglin; Xiong, Ying; Tang, Minghua; Zeng, Baiwen

    2014-03-01

    Lanthanum-doped ZnO (Zn0.99La0.01O) polycrystalline thin films were deposited on Pt/Ti/SiO2/Si substrates by a chemical solution deposition method. Metal/La-doped ZnO/Pt sandwich structures were constructed by depositing different top electrodes (Ag and Pt). Unipolar switching and bipolar switching characteristics were investigated in Pt/La-doped ZnO/Pt and Ag/La-doped ZnO/Pt structures, respectively. Compared with the undoped devices (Pt/ZnO/Pt and Ag/ZnO/Pt), the La-doped devices exhibits superior resistive switching performances, such as narrow distribution of the resistive switching properties ( R ON, R OFF, V Set, and V Reset), higher R OFF/ R ON ratio and sharp switching transition.

  13. Co doped ZnO nanowires as visible light photocatalysts

    NASA Astrophysics Data System (ADS)

    Šutka, Andris; Käämbre, Tanel; Pärna, Rainer; Juhnevica, Inna; Maiorov, Mihael; Joost, Urmas; Kisand, Vambola

    2016-06-01

    High aspect ratio cobalt doped ZnO nanowires showing strong photocatalytic activity and moderate ferromagnetic behaviour were successfully synthesized using a solvothermal method and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), vibrating sample magnetometry (VSM) and UV-visible absorption spectroscopy. The photocatalytic activities evaluated for visible light driven degradation of an aqueous methylene orange (MO) solution were higher than for Co doped ZnO nanoparticles at the same doping level and synthesized by the same synthesis route. The rate constant for MO visible light photocatalytic degradation was 1.9·10-3 min-1 in case of nanoparticles and 4.2·10-3 min-1 in case of nanowires. We observe strongly enhanced visible light photocatalytic activity for moderate Co doping levels, with an optimum at a composition of Zn0.95Co0.05O. The enhanced photocatalytic activities of Co doped ZnO nanowires were attributed to the combined effects of enhanced visible light absorption at the Co sites in ZnO nanowires, and improved separation efficiency of photogenerated charge carriers at optimal Co doping.

  14. Green emission in carbon doped ZnO films

    SciTech Connect

    Tseng, L. T.; Yi, J. B. Zhang, X. Y.; Xing, G. Z.; Luo, X.; Li, S.; Fan, H. M.; Herng, T. S.; Ding, J.; Ionescu, M.

    2014-06-15

    The emission behavior of C-doped ZnO films, which were prepared by implantation of carbon into ZnO films, is investigated. Orange/red emission is observed for the films with the thickness of 60–100 nm. However, the film with thickness of 200 nm shows strong green emission. Further investigations by annealing bulk ZnO single crystals under different environments, i.e. Ar, Zn or C vapor, indicated that the complex defects based on Zn interstitials are responsible for the strong green emission. The existence of complex defects was confirmed by electron spin resonance (ESR) and low temperature photoluminescence (PL) measurement.

  15. Green emission in carbon doped ZnO films

    NASA Astrophysics Data System (ADS)

    Tseng, L. T.; Yi, J. B.; Zhang, X. Y.; Xing, G. Z.; Fan, H. M.; Herng, T. S.; Luo, X.; Ionescu, M.; Ding, J.; Li, S.

    2014-06-01

    The emission behavior of C-doped ZnO films, which were prepared by implantation of carbon into ZnO films, is investigated. Orange/red emission is observed for the films with the thickness of 60-100 nm. However, the film with thickness of 200 nm shows strong green emission. Further investigations by annealing bulk ZnO single crystals under different environments, i.e. Ar, Zn or C vapor, indicated that the complex defects based on Zn interstitials are responsible for the strong green emission. The existence of complex defects was confirmed by electron spin resonance (ESR) and low temperature photoluminescence (PL) measurement.

  16. Ferromagnetism studies of Cu-doped and (Cu, Al) co-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Wu, S. Z.; Yang, H. L.; Xu, X. G.; Miao, J.; Jiang, Y.

    2011-01-01

    We have studied the room temperature ferromagnetism (FM) in Cu-doped and (Cu, Al) co-doped ZnO thin films which were grown on quartz substrates by chemical method based on a sol-gel process combining with spin-coating technology. X-ray diffraction (XRD) patterns demonstrate that both the Cu-doped and (Cu, Al) co-doped ZnO films have the hexagonal wurtzite structure with c-axis orientation. Alternating Gradient Magnetometer (AGM) measurements confirm that all the doped ZnO samples are ferromagnetic at room temperature. When the doped Cu content is 1 %, the Cu-doped ZnO film has the strongest FM. The FM significantly decreases in the (Cu, Al) co-doped ZnO films. The doping of Al ions suppresses the FM induced by the doped Cu ions.

  17. Luminance behavior of lithium-doped ZnO nanowires with p-type conduction characteristics.

    PubMed

    Ko, Won Bae; Lee, Jun Seok; Lee, Sang Hyo; Cha, Seung Nam; Sohn, Jung Inn; Kim, Jong Min; Park, Young Jun; Kim, Hyun Jung; Hong, Jin Pyo

    2013-09-01

    The present study describes the room-temperature cathodeluminescence (CL) and temperature-dependent photoluminescence (PL) properties of p-type lithium (Li)-doped zinc oxide (ZnO) nanowires (NWs) grown by hydrothermal doping and post-annealing processes. A ZnO thin film was used as a seed layer in NW growth. The emission wavelengths and intensities of undoped ZnO NWs and p-type Li-doped ZnO NWs were analyzed for comparison. CL and PL observations of post-annealed p-type Li-doped ZnO NWs clearly exhibited a dominant sharp band-edge emission. Finally, a n-type ZnO thin film/p-type annealed Li-doped ZnO NW homojunction diode was prepared to confirm the p-type conduction of annealed Li-doped ZnO NWs as well as the structural properties measured by transmission electron microscopy. PMID:24205635

  18. Enhancing blue luminescence from Ce-doped ZnO nanophosphor by Li doping

    PubMed Central

    2014-01-01

    Undoped ZnO, Ce-doped ZnO, and (Li, Ce)-codoped ZnO nanophosphors were prepared by a sol-gel process. The effects of the additional doping with Li ions on the crystal structure, particle morphology, and luminescence properties of Ce-doped ZnO were investigated by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy and photoluminescence spectroscopy. The results indicate that the obtained samples are single phase, and a nanorod shaped morphology is observed for (Li, Ce)-codoping. Under excitation with 325 nm light, Ce-doped ZnO phosphors show an ultraviolet emission, a green emission, and a blue emission caused by Zn interstitials. The spectrum of the sample codoped with a proper Li concentration features two additional emissions that can be attributed to the Ce3+ ions. With the increase of the Li doping concentration, the Ce3+ blue luminescence of (Li, Ce)-codoped ZnO is obviously enhanced, which results not only from the increase of the Ce3+ ion concentration itself but also from the energy transfer from the ZnO host material to the Ce3+ ions. This enhancement reaches a maximum at a Li content of 0.02, and then decreases sharply due to the concentration quench. These nanophosphors may promise for application to the visible-light-emitting devices. PACS 78.55.Et; 81.07.Wx; 81.20.Fw PMID:25258604

  19. Li doped ZnO thin films for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Sandeep, K. M.; Bhat, Shreesha; Serrao, F. J.; Dharmaprakash, S. M.

    2016-05-01

    We have prepared undoped (ZnO) and Li doped ZnO (LZO) thin films using cost effective sol gel spin coating method.The structural properties were analyzed by X-ray diffraction, and it showed that Li ions occupied interstitial positions in the LZO film. The optical properties like band bending effect, absorption length, band edge sharpness, which have direct impact on solar cell performance has been calculated. The room temperature photoluminescence spectra of the films showed dominant blue emission with CIE coordinate numbers (0.1384, 0.0836) for ZnO and (0.1356, 0.0910) for LZO. The dominating wavelength of the blue emission is present at 470.9 nm and 472.3 nm for ZnO and LZO films respectively. The structural and optical parameters determined in the present study could be used in LED applications.

  20. Ferromagnetism in Co- and Mn-doped ZnO

    NASA Astrophysics Data System (ADS)

    Theodoropoulou, N. A.; Hebard, A. F.; Norton, D. P.; Budai, J. D.; Boatner, L. A.; Lee, J. S.; Khim, Z. G.; Park, Y. D.; Overberg, M. E.; Pearton, S. J.; Wilson, R. G.

    2003-12-01

    Bulk single crystals of Sn-doped ZnO were implanted with Co or Mn at doses designed to produce transition metal concentrations of 3-5 at.% in the near-surface (˜2000 Å) region. The implantation was performed at ˜350 °C to promote dynamic annealing of ion-induced damage. Following annealing at 700 °C, temperature-dependent magnetization measurements showed ordering temperatures of ˜300 K for Co- and ˜250 K for Mn-implanted ZnO. Clear hysteresis loops were obtained at these temperatures. The coercive fields were ⩽100 Oe for all measurement temperatures. X-ray diffraction showed no detectable second phases in the Mn-implanted material. One plausible origin for the ferromagnetism in this case is a carrier-induced mechanism. By sharp contrast, the Co-implanted material showed evidence for the presence of Co precipitates with hexagonal symmetry, which is the cause of the room temperature ferromagnetism. Our results are consistent with the stabilization of ferromagnetic states by electron doping in transition metal-doped ZnO predicted by Sato and Katayama-Yoshida [Jpn. J. Appl. Phys. 40 (2001) L334]. This work shows the excellent promise of Mn-doped ZnO for potential room temperature spintronic applications.

  1. Cu-Doping of ZnO by Nuclear Transmutation

    SciTech Connect

    Selim, F. A.; Tarun, M. C.; Wall, D. E.; Boatner, Lynn A; McCluskey, M. D.

    2011-01-01

    Zinc oxide single crystals were doped with copper acceptors by means of the nuclear transmutation doping (NTD) method, which gives highly uniform dopant distributions and has a much higher probability of controlling the dopant locations in the lattice. The Cu doping was confirmed by the infrared absorption signature of Cu2+ at 5780 cm-1. Hall-effect measurements were performed to study the effect of CuZn on the electrical properties of ZnO. These measurements indicated that the Cu acceptor level lies 0.126 eV below the conduction-band minimum.

  2. Ferromagnetism in Sm doped ZnO nanorods by a hydrothermal method

    NASA Astrophysics Data System (ADS)

    Piao, Jingyuan; Tseng, Li-Ting; Yi, Jiabao

    2016-04-01

    Sm doped ZnO nanorods with various concentrations have been successfully synthesized using a hydrothermal method. XRD analysis indicates that there are no impurities or secondary phases in all the samples. The continuous expansion of d-spacing from XRD and TEM analysis suggests the effective corporation of Sm ions in ZnO. It is found that pure ZnO is paramagnetic. Both 1% and 5% Sm doped ZnO nanorods are ferromagnetic at room temperature. 5% Sm doped ZnO has a large paramagnetic signal at low temperature, suggesting the formation of the precipitation or clusters of samarium oxide.

  3. Electronic structure of Co-doped ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Neffati, Ahmed; Souissi, Hajer; Kammoun, Souha

    2012-10-01

    The optical transmission spectra, the photoluminescence (PL), and the photoluminescence excitation (PLE) spectra of the cobalt doped zinc oxide nanorods Zn1-xCoxO (x = 0.01, 0.10) were measured by Loan et al. [J. Phys. D: Appl. Phys. 42, 065412 (2009)] in the region 1.5-4 eV. These spectra exhibit a group of ultraviolet narrow lines in the region of 3.0-3.4 eV related to the near-band-edge emission of the host ZnO materials and a group of emission lines in the red region of 1.8-1.9 eV assigned to the radiative transitions within the tetrahedral Co2+ ions in the ZnO host crystal. The group of lines in the visible region provides important information about the electronic structure of the cobalt doped zinc oxide nanorods. This work investigates a theoretical crystal-field analysis of the visible lines associated to the Co2+ ion transition occupying a Td site symmetry in ZnO host crystal. A satisfactory correlations were obtained between experimental and calculated energy levels. The electronic structure was compared with the reported for cobalt transition ion doped in ZnO nanoparticles and bulk crystals [Volbers et al., Appl. Phys. A 88, 153 (2007) and H. J. Schulz and M. Thiede, Phys. Rev. B 35, 18 (1987)]. In order to explain the existence of excitation peaks observed near the band edge of the ZnO host, an energy transfer mechanism is proposed.

  4. Aluminum doping studies on high field ZnO varistors

    SciTech Connect

    Kimball, K.M.; Doughty, D.H.

    1987-08-01

    We have investigated the effect of Al doping on the physical and electronic properties of high field ZnO varistors. For this study, varistors containing 98.94 m/o ZnO, 0.25 m/o CoO, 0.25 m/o MnO, 0.56 m/o Bi/sub 2/O/sub 3/ and 0 to 200 ppM Al were prepared from powders obtained from solution precipitation techniques. Because of the amphoteric nature of aluminum oxides, precise control of pH and metal concentrations was necessary to assure complete incorporation of dopants. We observed inhibition of grain growth during sintering of varistor pellets at aluminum concentrations of 50 ppM and above. The measured electrical properties show increased switching fields and increased nonlinearity coefficients for Al doping levels of 50 to 200 ppM.

  5. Electrical property studies on chemically processed polypyrolle/aluminum doped ZnO based hybrid heterostructures

    NASA Astrophysics Data System (ADS)

    Mohan Kumar, G.; Ilanchezhiyan, P.; Madhan Kumar, A.; Yuldashev, Sh. U.; Kang, T. W.

    2016-04-01

    A hybrid structure based on p-type polypyrolle (PPy) and n-type aluminum (Al) doped ZnO nanorods was successfully constructed. The effect of Al doping on material properties of wurtzite structured ZnO were studied using several analytical techniques. To establish the desired hybrid structure, pyrrole monomers were polymerized on hydrothermally grown Al doped ZnO nanorods by chemical polymerization. The current-voltage characteristics on the fabricated PPy/Al doped ZnO heterostructures were found to exhibit excellent rectifying characteristics under dark and illumination conditions. The obtained results augment the prescribed architecture to be highly suitable for high-sensitivity optoelectronic applications.

  6. Opto-electrical properties of Sb-doped p-type ZnO nanowires

    SciTech Connect

    Kao, Tzu-Hsuan; Chen, Jui-Yuan; Chiu, Chung-Hua; Huang, Chun-Wei; Wu, Wen-Wei

    2014-03-17

    P-type ZnO nanowires (NWs) have attracted much attention in the past years due to the potential applications for optoelectronics and piezotronics. In this study, we have synthesized Sb-doped p-type ZnO NWs on Si (100) substrates by chemical vapor deposition with Aucatalyst. The Sb-doped ZnO NWs are single crystalline with high density, grown along [1-1-2] direction. The doping percentage of Sb is about 2.49%, which has been confirmed by X-ray photoelectron spectroscopy. The ZnO NW field effect transistor demonstrated its p-type characteristics. A high responsivity to ultraviolet photodetection was also observed. In addition, compared to intrinsic ZnO NWs, the conductivity of the Sb-doped ZnO NWs exhibited ∼2 orders of magnitude higher. These properties make the p-type ZnO NWs a promising candidate for electronic and optoelectronic devices.

  7. Controllable Growth of Ultrathin P-doped ZnO Nanosheets

    NASA Astrophysics Data System (ADS)

    Zhu, Yuankun; Yang, Hengyan; Sun, Feng; Wang, Xianying

    2016-04-01

    Ultrathin phosphor (P)-doped ZnO nanosheets with branched nanowires were controllably synthesized, and the effects of oxygen and phosphor doping on the structural and optical properties were systematically studied. The grown ZnO nanosheet exhibits an ultrathin nanoribbon backbone with one-side-aligned nanoteeth. For the growth of ultrathin ZnO nanosheets, both oxygen flow rate and P doping are essential, by which the morphologies and microstructures can be finely tuned. P doping induces strain relaxation to change the growth direction of ZnO nanoribbons, and oxygen flow rate promotes the high supersaturation degree to facilitate the growth of nanoteeth and widens the nanoribbons. The growth of P-doped ZnO in this work provides a new progress towards the rational control of the morphologies for ZnO nanostructures.

  8. Controllable Growth of Ultrathin P-doped ZnO Nanosheets.

    PubMed

    Zhu, Yuankun; Yang, Hengyan; Sun, Feng; Wang, Xianying

    2016-12-01

    Ultrathin phosphor (P)-doped ZnO nanosheets with branched nanowires were controllably synthesized, and the effects of oxygen and phosphor doping on the structural and optical properties were systematically studied. The grown ZnO nanosheet exhibits an ultrathin nanoribbon backbone with one-side-aligned nanoteeth. For the growth of ultrathin ZnO nanosheets, both oxygen flow rate and P doping are essential, by which the morphologies and microstructures can be finely tuned. P doping induces strain relaxation to change the growth direction of ZnO nanoribbons, and oxygen flow rate promotes the high supersaturation degree to facilitate the growth of nanoteeth and widens the nanoribbons. The growth of P-doped ZnO in this work provides a new progress towards the rational control of the morphologies for ZnO nanostructures. PMID:27033851

  9. Improving the ethanol gas-sensing properties of porous ZnO microspheres by Co doping

    SciTech Connect

    Xiao, Qi Wang, Tao

    2013-08-01

    Graphical abstract: - Highlights: • Co-doped porous ZnO microspheres were synthesized. • 3 mol% Co-doped ZnO sensor showed the highest response to ethanol. • 3 mol% Co-doped ZnO sensor exhibited fast recovery property. • 3 mol% Co-doped ZnO sensor exhibited good selectivity and long-term stability. - Abstract: Porous Co-doped ZnO microspheres were prepared by a simple hydrothermal method combined with post-annealing. Co species existed as a form of divalent state in the sample and substituted Zn{sup 2+} sites in ZnO crystal lattice, which was affirmed by X-ray diffraction, UV–vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The gas-sensing measurements demonstrated that the 3 mol% Co-doped ZnO sample showed the highest response value to 100 ppm ethanol at 350 °C, which were 5 folds higher than that of the pure ZnO sample. In addition, the 3 mol% Co-doped ZnO sensor exhibited fast recovery property, good quantitative determination, good selectivity and long-term stability. The superior sensing properties were contributed to high specific surface area combined with the large amount of oxygen vacancies originating from Co doping.

  10. Shape controlled Sn doped ZnO nanostructures for tunable optical emission and transport properties

    SciTech Connect

    Rakshit, T.; Manna, I.; Ray, S. K.

    2013-11-15

    Pure and Sn doped ZnO nanostructures have been grown on SiO{sub 2}/Si substrates by vapor-solid technique without using any catalysts. It has been found that the morphology of the nanostructures depend strongly on the growth temperature and doping concentration. By proper tuning of the growth temperature, morphology of pure ZnO can be changed from tetrapods to multipods. On the other hand, by varying the doping concentration of Sn in ZnO, the morphology can be tuned from tetrapods to flower-like multipods to nanowires. X-ray diffraction pattern reveals that the nanostructures have a preferred (0002) growth orientation, and they are tensile strained with the increase of Sn doping in ZnO. Temperature-dependent photoluminescence characteristics of these nanostructures have been investigated in the range from 10 to 300 K. Pure ZnO tetrapods exhibited less defect state emissions than that of pure ZnO multipods. The defect emission is reduced with low concentration of Sn doping, but again increases at higher concentration of doping because of increased defects. Transport properties of pure and Sn doped ZnO tetrapods have been studied using complex-plane impedance spectroscopy. The contribution from the arms and junctions of a tetrapod could be distinguished. Sn doped ZnO samples showed lower conductivity but higher relaxation time than that of pure ZnO tetrapods.

  11. The Antibacterial Activity of Ta-doped ZnO Nanoparticles

    NASA Astrophysics Data System (ADS)

    Guo, Bing-Lei; Han, Ping; Guo, Li-Chuan; Cao, Yan-Qiang; Li, Ai-Dong; Kong, Ji-Zhou; Zhai, Hai-Fa; Wu, Di

    2015-08-01

    A novel photocatalyst of Ta-doped ZnO nanoparticles was prepared by a modified Pechini-type method. The antimicrobial study of Ta-doped ZnO nanoparticles on several bacteria of Gram-positive Bacillus subtilis ( B. subtilis) and Staphylococcus aureus ( S. aureus) and Gram-negative Escherichia coli ( E. coli) and Pseudomonas aeruginosa ( P. aeruginosa) were performed using a standard microbial method. The Ta-doping concentration effect on the minimum inhibitory concentration (MIC) of various bacteria under dark ambient has been evaluated. The photocatalytical inactivation of Ta-doped ZnO nanoparticles under visible light irradiation was examined. The MIC results indicate that the incorporation of Ta5+ ions into ZnO significantly improve the bacteriostasis effect of ZnO nanoparticles on E. coli, S. aureus, and B. subtilis in the absence of light. Compared to MIC results without light irradiation, Ta-doped ZnO and pure ZnO nanoparticles show much stronger bactericidal efficacy on P. aeruginosa, E. coli, and S. aureus under visible light illumination. The possible antimicrobial mechanisms in Ta-doped ZnO systems under visible light and dark conditions were also proposed. Ta-doped ZnO nanoparticles exhibit more effective bactericidal efficacy than pure ZnO in dark ambient, which can be attributed to the synergistic effect of enhanced surface bioactivity and increased electrostatic force due to the incorporation of Ta5+ ions into ZnO. Based on the antibacterial tests, 5 % Ta-doped ZnO is a more effective antimicrobial agent than pure ZnO.

  12. Anomalous antibacterial activity and dye degradation by selenium doped ZnO nanoparticles.

    PubMed

    Dutta, Raj Kumar; Nenavathu, Bhavani Prasad; Talukdar, Soumita

    2014-02-01

    Selenium doped ZnO nanoparticles synthesized by mechanochemical method were spherically shaped of size distribution of 10.2±3.4 nm measured by transmission electron microscopy. Diffused reflectance spectroscopy revealed increase in the band gap, ranging between 3.47 eV and 3.63 eV due to Se doping in ZnO nanoparticles. The antibacterial activity of pristine and Se doped ZnO nanoparticles was attributed to ROS (reactive oxygen species) generation in culture media confirmed by TBARS assay. Compared to complete inhibition of growth by 0.45 mg/mL of pristine ZnO nanoparticles, the batches of 0.45 mg/mL of selenium doped ZnO nanoparticles exhibited only 51% inhibition of growth of Escherichia coli. The reduced antibacterial activity of selenium doped ZnO nanoparticles was attributed to two opposing factors, e.g., ROS generation for inhibition of growth, countered by sustaining growth of E. coli due to availability of Se micronutrients in culture media, confirmed by inductively coupled plasma mass spectrometer measurement. Higher ROS generation by selenium doped ZnO nanoparticles was attributed to creation of oxygen vacancies, confirmed from green emission peak observed at 565 nm. The impact of higher ROS generation by selenium doped ZnO nanoparticles was evident from enhanced photocatalytic degradation of trypan blue dye, than pristine ZnO nanoparticles. PMID:24200949

  13. Plasmonic enhanced optical characteristics of Ag nanostructured ZnO thin films

    NASA Astrophysics Data System (ADS)

    Sarkar, Arijit; Gogurla, Narendar; Shivakiran Bhaktha, B. N.; Ray, Samit K.

    2016-04-01

    We have demonstrated the enhanced photoluminescence and photoconducting characteristics of plasmonic Ag–ZnO films due to the light scattering effect from Ag nanoislands. Ag nanoislands have been prepared on ITO-coated glass substrates by thermal evaporation followed by annealing. Plasmonic Ag–ZnO films have been fabricated by depositing ZnO over Ag nanoislands by sol–gel process. The band-edge emission of ZnO is enhanced for 170 nm sized Ag nanoislands in ZnO as compared to pure ZnO. The defect emission is also found to be quenched simultaneously for plasmonic Ag–ZnO films. The enhancement and quenching of photoluminescence at different wavelengths for Ag–ZnO films can be well understood from the localized surface plasmon resonance of Ag nanoislands. The Ag–ZnO M–S–M photoconductor device showed a tenfold increment in photocurrent and faster photoresponse as compared to the control ZnO device. The enhancement in photoresponse of the device is due to the increased photon absorption in ZnO films via scattering of the incident illumination.

  14. Highly efficient yttrium-doped ZnO nanorods for quantum dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Kim, Soo-Kyoung; Gopi, Chandu V. V. M.; Srinivasa Rao, S.; Punnoose, Dinah; Kim, Hee-Je

    2016-03-01

    Yttrium-doped ZnO nanorod arrays were applied to photoanodes of quantum dot-sensitized solar cells (QDSCs). The introduction of yttrium to ZnO nanostructures facilitates the growth of ZnO nanorods and increases the amount of QD deposition with a large surface area. Furthermore, lower electrical resistance and longer electron lifetime were achieved with yttrium-doping owing to fewer defects and trap sites on the surface of yttrium-doped ZnO nanorods. As a result, the conversion efficiency of 3.3% was achieved with the optimized concentration of yttrium.

  15. Synthesis of nitrogen-doped ZnO nanoparticles by RF thermal plasma

    NASA Astrophysics Data System (ADS)

    Hiragino, Yuto; Tanaka, Toshimi; Takeuchi, Hiroshi; Takeuchi, Akira; Lin, Jie; Yoshida, Toshiyuki; Fujita, Yasuhisa

    2016-04-01

    The nitrogen-doped ZnO nanoparticles (NPs) were successfully synthesized by using an RF thermal plasma process which would be a promising technique to the massive production. XRD measurements revealed that the formation of the hexagonal ZnO wurtzite structure. The synthesized nitrogen-doped ZnO NPs showed the nitrogen and carbon concentrations of 3.1-4.6 × 1020 cm-3 and 1.1-1.2 × 1020 cm-3. The hole injection was confirmed by evaluating band edge electroluminescence from the LED structures using nitrogen doped ZnO NPs as a p-type layer.

  16. Effect of Li doping on the magnetic properties of ZnO nanomaterials

    NASA Astrophysics Data System (ADS)

    Rajamanickam, N.; Rajashabala, S.; Ramachandran, K.

    2013-06-01

    Zn1-xLixO (0 ≤ x ≥ 0.05) nanomaterials were synthesized by the solvothermal method and the influence of Li doping on the structural, optical, and magnetic properties was investigated. Morphological analysis by SEM revealed the formation of ZnO nanorods (NR) and Li-doped ZnO nanoparticles (NP), which indicate that doping of Li ions affects the morphology of ZnO. The magnetization curve of undoped ZnO indicates the co-existence of dia and antiferromagnetism, which changes to dia and ferrimagnetism with the addition of Li.

  17. Local structures of copper-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Ma, Qing; Buchholz, D. Bruce; Chang, Robert P. H.

    2008-12-01

    We report the local structures of a series of copper-doped zinc oxide films using polarization-dependent x-ray-absorption spectroscopy. The films were grown by pulsed-laser ablation under various conditions. The results show that films where copper exists solely as clusters are not ferromagnetic. The results also show that some of the copper-doped zinc oxide films are not ferromagnetic despite the fact that the copper substitution for zinc in the ZnO lattice is in the Cu2+ state, which provides the necessary unpaired spins for ferromagnetism. Therefore, Cu2+/Zn2+ substitution is not the only imperative condition for ferromagnetism to occur. We present characteristics unique to the electronic and atomic structure of ferromagnetic films and argue that the increased covalence of the CuZn-O bond found in these films is a prerequisite for the spin alignments in a substitutionally copper-doped zinc oxide film.

  18. Synthesis and characterization of Mn-doped ZnO column arrays

    NASA Astrophysics Data System (ADS)

    Yang, Mei; Guo, Zhixing; Qiu, Kehui; Long, Jianping; Yin, Guangfu; Guan, Denggao; Liu, Sutian; Zhou, Shijie

    2010-04-01

    Mn-doped ZnO column arrays were successfully synthesized by conventional sol-gel process. Effect of Mn/Zn atomic ratio and reaction time were investigated, and the morphology, tropism and optical properties of Mn-doped ZnO column arrays were characterized by SEM, XRD and photoluminescence (PL) spectroscopy. The result shows that a Mn/Zn atomic ratio of 0.1 and growth time of 12 h are the optimal condition for the preparation of densely distributed ZnO column arrays. XRD analysis shows that Mn-doped ZnO column arrays are highly c-axis oriented. As for Mn-doped ZnO column arrays, obvious increase of photoluminescence intensity is observed at the wavelength of ˜395 nm and ˜413 nm, compared to pure ZnO column arrays.

  19. Electron paramagnetic resonance in Cu-doped ZnO

    NASA Astrophysics Data System (ADS)

    Buchheit, R.; Acosta-Humánez, F.; Almanza, O.

    2016-04-01

    In this work, ZnO and Cu-doped ZnO nanoparticles (Zn1‑xCuxO, x = 3%), with a calcination temperature of 500∘C were synthesized using the sol-gel method. The particles were analyzed using atomic absorption spectroscopy (AAS), X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) at X-band, measurement in a temperature range from 90 K to room temperature. AAS confirmed a good correspondence between the experimental doping concentration and the theoretical value. XRD reveals the presence of ZnO phase in hexagonal wurtzite structure and a nanoparticle size for the samples synthesized. EPR spectroscopy shows the presence of point defects in both samples with g-values of g = 1.959 for shallow donors and g = 2.004 for ionized vacancies. It is important when these materials are required have been used as catalysts, as suggested that it is not necessary prepare them at higher temperature. A simulation of the Cu EPR signal using an anisotropic spin Hamiltonian was performed and showed good coincidence with the experimental spectra. It was shown that Cu2+ ions enter interstitial octahedral sites of orthorhombic symmetry in the wurtzite crystal structure. Temperature dependence of the EPR linewidth and signal intensity shows a paramagnetic behavior of the sample in the measurement range. A Néel temperature TN = 78 ± 19 K was determined.

  20. Piezoelectric and opto-electrical properties of silver-doped ZnO nanorods synthesized by low temperature aqueous chemical method

    SciTech Connect

    Nour, E. S. Echresh, A.; Willander, M.; Nur, O.; Liu, Xianjie; Broitman, E.

    2015-07-15

    In this paper, we have synthesized Zn{sub 1−x}Ag{sub x}O (x = 0, 0.03, 0.06, and 0.09) nanorods (NRs) via the hydrothermal method at low temperature on silicon substrate. The characterization and comparison between the different Zn{sub 1−x}Ag{sub x}O samples, indicated that an increasing Ag concentration from x = 0 to a maximum of x = 0.09; All samples show a preferred orientation of (002) direction with no observable change of morphology. As the quantity of the Ag dopant was changed, the transmittances, as well as the optical band gap were decreased. X-ray photoelectron spectroscopy data clearly indicate the presence of Ag in ZnO crystal lattice. A nanoindentation-based technique was used to measure the effective piezo-response of different concentrations of Ag for both direct and converse effects. The value of the piezoelectric coefficient (d{sub 33}) as well as the piezo potential generated from the ZnO NRs and Zn{sub 1−x}Ag{sub x}O NRs was found to decrease with the increase of Ag fraction. The finding in this investigation reveals that Ag doped ZnO is not suitable for piezoelectric energy harvesting devices.

  1. Doping of ZnO nanowires using phosphorus diffusion from a spin-on doped glass source

    SciTech Connect

    Bocheux, A.; Robin, I. C.; Bonaimé, J.; Hyot, B.; Feuillet, G.; Kolobov, A. V.; Fons, P.; Mitrofanov, K. V.; Tominaga, J.; Tamenori, Y.

    2014-05-21

    In this article, we report on ZnO nanowires that were phosphorus doped using a spin on dopant glass deposition and diffusion method. Photoluminescence measurements suggest that this process yields p-doped ZnO. The spatial location of P atoms was studied using x-ray near-edge absorption structure spectroscopy and it is concluded that the doping is amphoteric with P atoms located on both Zn and O sites.

  2. Doping of ZnO nanowires using phosphorus diffusion from a spin-on doped glass source

    NASA Astrophysics Data System (ADS)

    Bocheux, A.; Robin, I. C.; Bonaimé, J.; Hyot, B.; Kolobov, A. V.; Mitrofanov, K. V.; Fons, P.; Tominaga, J.; Tamenori, Y.; Feuillet, G.

    2014-05-01

    In this article, we report on ZnO nanowires that were phosphorus doped using a spin on dopant glass deposition and diffusion method. Photoluminescence measurements suggest that this process yields p-doped ZnO. The spatial location of P atoms was studied using x-ray near-edge absorption structure spectroscopy and it is concluded that the doping is amphoteric with P atoms located on both Zn and O sites.

  3. Fabrication of tunable hydrophobic surface of ZnO nanorods with Cu doping

    SciTech Connect

    Chakraborty, Mohua; Thangavel, R.

    2015-08-28

    In this work, tunable wettability of the Zinc Oxide (ZnO) nanorod surface with Cu doping prepared by a hydrothermal method. These grown samples were characterized by XRD, FESEM, AFM and water contact angle measurements. The wettability of the ZnO nanorods surface area was controlled and tuned by different concentration of copper doping. It was found that the hydrophobic surface of doped ZnO Nanorods shows a maximum and minimum contact angle of about 156.60° and 136.36° was achieved with doping concentration of 10 and 20 M % respectively. Further, the surface properties such as surface energy and work of adhesion were calculated for undoped and Cu doped ZnO nanostructure surfaces. These nanosructures can be potentially applicable to enlarge time honoured application of ZnO based electronic devices.

  4. Origins of conductivity improvement in fluoride-enhanced silicon doping of ZnO films.

    PubMed

    Rashidi, Nazanin; Vai, Alex T; Kuznetsov, Vladimir L; Dilworth, Jonathan R; Edwards, Peter P

    2015-06-01

    Fluoride in spray pyrolysis precursor solutions for silicon-doped zinc oxide (SiZO) transparent conductor thin films significantly improves their electrical conductivity by enhancing silicon doping efficiency and not, as previously assumed, by fluoride doping. Containing only earth-abundant elements, SiZO thus prepared rivals the best solution-processed indium-doped ZnO in performance. PMID:25879727

  5. Room temperature ferromagnetism in undoped and Fe doped ZnO nanorods: Microwave-assisted synthesis

    SciTech Connect

    Limaye, Mukta V.; Singh, Shashi B.; Das, Raja; Poddar, Pankaj; Kulkarni, Sulabha K.

    2011-02-15

    One-dimensional (1D) undoped and Fe doped ZnO nanorods of average length {approx}1 {mu}m and diameter {approx}50 nm have been obtained using a microwave-assisted synthesis. The magnetization (M) and coercivity (H{sub c}) value obtained for undoped ZnO nanorods at room temperature is {approx}5x10{sup -3} emu/g and {approx}150 Oe, respectively. The Fe doped ZnO samples show significant changes in M -H loop with increasing doping concentration. Both undoped and Fe doped ZnO nanorods exhibit a Curie transition temperature (T{sub c}) above 390 K. Electron spin resonance and Moessbauer spectra indicate the presence of ferric ions. The origin of ferromagnetism in undoped ZnO nanorods is attributed to localized electron spin moments resulting from surface defects/vacancies, where as in Fe doped samples is explained by F center exchange mechanism. -- Graphical abstract: Room temperature ferromagnetism has been reported in undoped and Fe doped ZnO nanorods of average length {approx}1 {mu}m and diameter {approx}50 nm. Display Omitted Research Highlights: {yields} Microwave-assisted synthesis of undoped and Fe doped ZnO nanorods. {yields} Observation of room temperature ferromagnetism in undoped and Fe doped ZnO nanorods. {yields} Transition temperature (T{sub c}) obtained in undoped and doped samples is above 390 K. {yields} In undoped ZnO origin of ferromagnetism is explained in terms of defects/vacancies. {yields} Ferromagnetism in Fe doped ZnO is explained by F-center exchange mechanism.

  6. First-principles study for ferromagnetism of Cu-doped ZnO with carrier doping

    SciTech Connect

    Kang, Byung-Sub; Kim, Kyeong-Sup; Yu, Seong-Cho; Chae, Heejoon

    2013-02-15

    We studied the effects on the ferromagnetism of carrier doping in Zn{sub 1-x}Cu{sub x}O with x=0.0277-0.0833 by using the first-principles calculations. The total magnetic moment of Cu is about 1, 2, and 3 {mu}{sub B}/cell at the concentration of 2.77%, 5.55%, and 8.33%, respectively. For Zn{sub 1-x}Cu{sub x}O{sub 1-y}N{sub y}, we obtained the ferromagnetic and half-metallic ground state. The Cu magnetic moment in low Cu concentration is increased by the N-doping. However, for the F-doping it decreases. The ferromagnetism in Cu-doped ZnO is controllable by changing the carrier density. The N 2p states hybridize well with Cu 3d states instead of the O 2p states. Due to the hybridization between N 2p and Cu 3d states, the holes are itinerant with keeping its 3d states. For (Cu,N)-codoped ZnO, it is recognized that the width of 3d states is larger than that of (Cu,F)-codoped ZnO. - Graphical abstract: Considered clean wurtzite ZnO structure, the Cu magnetic moments for Zn{sub 1-x}Cu{sub x}O{sub 1-y}N{sub y} or Zn{sub 1-x}Cu{sub x}O{sub 1-y}F{sub y} of the ferromagnetic state (left), and the charge density difference of Zn{sub 1-x}Cu{sub x}O (x=0.0277) (right). Highlights: Black-Right-Pointing-Pointer The ferromagnetism of Cu-doped ZnO is controllable by N or F carrier density. Black-Right-Pointing-Pointer The Cu magnetic moment in low Cu concentration is increased by hole doping. Black-Right-Pointing-Pointer The N 2p states hybridize well with the Cu 3d states instead of the O 2p states. Black-Right-Pointing-Pointer For (Cu,F)-codoped ZnO, the Cu 3d band is narrower than that for (Cu,N)-codoped ZnO.

  7. Growth and characterization of Cl-doped ZnO hexagonal nanodisks

    SciTech Connect

    Yousefi, Ramin; Zak, A.K.; Mahmoudian, M.R.

    2011-10-15

    Cl-doped ZnO nanodisks were grown on a Si(111) substrate using a thermal evaporation method. The prepared nanodisks exhibited a hexagonal shape with an average thickness of 50 nm and average diagonal of 270 nm. In addition, undoped ZnO disks with hexagonal shape were grown under the same conditions, but the sizes of these undoped ZnO disks were on the micrometer order. A possible mechanism was proposed for the growth of the Cl-doped ZnO nanodisks, and it was shown that the Cl{sup 1-} anions play a crucial role in controlling the size. X-ray diffraction and Raman spectroscopy clearly showed an extension in the crystal lattice of ZnO because of the presence of chlorine. In addition, these nanodisks produced a strong photoluminescence emission peak in the ultraviolet (UV) region and a weak peak in the green region of the electromagnetic spectrum. Furthermore, the UV peak of the Cl-doped ZnO nanodisks was blueshifted with respect to that of the undoped ZnO disks. - Graphical abstract: Cl-doped ZnO nanodisks and undoped ZnO microdisks have been grown using a thermal evaporation method. Highlights: > Cl-doped ZnO nanodisks with hexagonal shape are grown using a thermal evaporation method. > It is shown that the Cl{sup 1-} anions play a crucial role in controlling the size of the nanodisks. > XRD and Raman results showed that the Cl-doped ZnO nanodisks structure is under a biaxial stress. > UV peak of the PL spectrum is blueshifted for the Cl-doped ZnO nanodisks.

  8. Sodium acceptor doping of ZnO crystals

    NASA Astrophysics Data System (ADS)

    Parmar, Narendra S.; Joni, I. Made; Lynn, Kelvin G.

    2016-02-01

    ZnO bulk single crystals were doped with sodium by thermal diffusion using sodium dispensers. Secondary-ion mass spectrometry measurement shows the diffusion of sodium with concentration ˜1×1018 cm-3 in near surface region. Photoluminescence (PL) measurements show donor acceptor pair (DAP) emission at 408 nm at room temperature which exhibits a blue-shift to 404 nm at 9 K. DC Hall measurements show the mixed conduction due to low Hall voltage in these samples. PL measurements and variable temperature resistivity measurements suggest that the sodium acceptor activation energy is ˜0.300 eV.

  9. Synthesis of Fe Doped ZnO Nanowire Arrays that Detect Formaldehyde Gas.

    PubMed

    Jeon, Yoo Sang; Seo, Hyo Won; Kim, Su Hyo; Kim, Young Keun

    2016-05-01

    Owing to their chemical and thermal stability and doping effects on providing electrons to the conduction band, doped ZnO nanowires have generated interest for use in electronic devices. Here we report hydrothermally grown Fe-doped ZnO nanowires and their gas-sensing properties. The synthesized nanowires have a high crystallinity and are 60 nm in diameter and 1.7 μm in length. Field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) are employed to understand the doping effects on the microstructures and gas sensing properties. When the Fe-doped ZnO nanowire arrays were evaluated for gas sensing, responses were recorded through changes in temperature and gas concentration. Gas sensors consisting of ZnO nanowires doped with 3-5 at.% Fe showed optimum formaldehyde (HCHO) sensing performance at each working temperature. PMID:27483827

  10. Mechanism of Photoinduced Charge Transfer in Co(Li)-Doped ZnO Film

    NASA Astrophysics Data System (ADS)

    Kobayashi, Kenkichiro; Maeda, Tatsuro; Matsushima, Shigenori; Okada, Genji

    1992-08-01

    A three-layer film consisting of In-doped ZnO, Co(Li)-doped ZnO and Li-doped NiO has been fabricated by means of a sputtering technique. The photocurrent spectrum of the Co(Li)-doped ZnO has been measured by applying a bias voltage between the In-doped ZnO and Li-doped NiO electrodes. A broad peak around 640 nm in the photocurrent spectrum is assigned to photothermal ionization of Co2+ ions. The time dependence of photocurrents indicates that the concentration of Co2+ ions is decreased by the irradiation of 500 nm and is recovered to the initial value by turning off the bias voltage.

  11. Highly active lanthanum doped ZnO nanorods for photodegradation of metasystox.

    PubMed

    Korake, P V; Dhabbe, R S; Kadam, A N; Gaikwad, Y B; Garadkar, K M

    2014-01-01

    La-doped ZnO nanorods with different La contents were synthesized by microwave assisted method and characterized by various sophisticated techniques such as XRD, UV-Vis., EDS, XPS, SEM and TEM. The XRD patterns of the La-doped ZnO indicate hexagonal crystal structure with an average crystallite size of 30nm. It was found that the crystallite size of La-doped ZnO is much smaller as compared to pure ZnO and decreases with increasing La content. The photocatalytic activity of 0.5mol% La-doped ZnO in the degradation of metasystox was studied. It was observed that degradation efficiency of metasystox over La-doped ZnO increases up to 0.5mol% doping then decreases for higher doping levels. Among the catalyst studied, the 0.5mol% La-doped ZnO was the most active, showing high photocatalytic activity for the degradation of metasystox. The maximum reduction of concentration of metasystox was observed under static condition at pH 8. Reduction in the Chemical Oxygen Demand (COD) of metasystox was observed after 150min. The cytotoxicological studies of meristematic root tip cells of Allium cepa were studied. The results obtained indicate that photocatalytically degraded products of metasystox were less toxic as compared to metasystox. PMID:24231392

  12. Enhanced photocatalytic performance of Ga{sup 3+}-doped ZnO

    SciTech Connect

    Zhong, Jun Bo; Li, Jian Zhang; Zeng, Jun; He, Xi Yang; Hu, Wei; Shen, Yue Cheng

    2012-11-15

    Graphical abstract: In general, the strong SPS response corresponds to the high separation rate of photoinduced charge carriers on the basis of the SPS principle. The photovoltage of Ga{sup 3+}-doped ZnO is higher than that of ZnO, thus it can be confirmed that the Ga{sup 3+}-doped ZnO has a higher charge separation rate than the ZnO sample. Among these samples, 1%Ga has highest charge separation rate. Display Omitted Highlights: ► Ga{sup 3+} has been employed to dope ZnO photocatalyst. ► Ga{sup 3+} increases the BET surface area and changes the morphology of ZnO. ► The photoinduced charge separation rate has been enhanced. ► The photocatalytic activity has been greatly promoted. -- Abstract: ZnO and Ga{sup 3+}-doped ZnO with different molar ratio of Ga/Zn (1%, 2% and 3%) were prepared by a parallel flow precipitation method. The photocatalysts prepared were characterized by BET surface area, X-ray diffraction (XRD), UV/vis diffuse reflectance spectroscopy (DRS), scanning electron microscope (SEM) and surface photovoltage spectroscopy (SPS), respectively. The results show that doping Ga{sup 3+} into ZnO increases the BET surface area. The XRD spectra of the photocatalysts calcined at 573 K show only the characteristic peaks of wurtzite-type. Ga{sup 3+}-doped ZnO absorbs much more light than ZnO in the visible light region. Doping Ga{sup 3+} into ZnO greatly changes the morphology of ZnO and enhances the photoinduced charge separation rate. The photocatalytic activity of ZnO and Ga{sup 3+}-doped ZnO for decolorization of methyl orange (MO) solution was evaluated, of all the photocatalysts prepared, the Ga{sup 3+}-doped ZnO with 1% possesses the best photocatalytic activity and the possible reason was discussed.

  13. Highly Sensitive and Selective Ethanol Sensor Fabricated with In-Doped 3DOM ZnO.

    PubMed

    Wang, Zhihua; Tian, Ziwei; Han, Dongmei; Gu, Fubo

    2016-03-01

    ZnO is an important n-type semiconductor sensing material. Currently, much attention has been attracted to finding an effective method to prepare ZnO nanomaterials with high sensing sensitivity and excellent selectivity. A three-dimensionally ordered macroporous (3DOM) ZnO nanostructure with a large surface area is beneficial to gas and electron transfer, which can enhance the gas sensitivity of ZnO. Indium (In) doping is an effective way to improve the sensing properties of ZnO. In this paper, In-doped 3DOM ZnO with enhanced sensitivity and selectivity has been synthesized by using a colloidal crystal templating method. The 3DOM ZnO with 5 at. % of In-doping exhibits the highest sensitivity (∼88) to 100 ppm ethanol at 250 °C, which is approximately 3 times higher than that of pure 3DOM ZnO. The huge improvement to the sensitivity to ethanol was attributed to the increase in the surface area and the electron carrier concentration. The doping by In introduces more electrons into the matrix, which is helpful for increasing the amount of adsorbed oxygen, leading to high sensitivity. The In-doped 3DOM ZnO is a promising material for a new type of ethanol sensor. PMID:26844815

  14. Investigation of Li-doped ferroelectric and piezoelectric ZnO films by electric force microscopy and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Ni, H. Q.; Lu, Y. F.; Liu, Z. Y.; Qiu, H.; Wang, W. J.; Ren, Z. M.; Chow, S. K.; Jie, Y. X.

    2001-08-01

    We have grown Li-doped ZnO films on silicon (100) using the rf planar magnetron sputtering method. The surface charges induced piezoelectrically by defect and by polarization can be observed by electric force microscopy. The Li-doped ZnO films have been proven to be ferroelectric. The Raman spectra of ZnO and Li-doped ZnO films have been measured.

  15. Luminescence dynamics of bound exciton of hydrogen doped ZnO nanowires

    DOE PAGESBeta

    Yoo, Jinkyoung; Yi, Gyu -Chul; Chon, Bonghwan; Joo, Taiha; Wang, Zhehui

    2016-04-11

    In this study, all-optical camera, converting X-rays into visible photons, is a promising strategy for high-performance X-ray imaging detector requiring high detection efficiency and ultrafast detector response time. Zinc oxide is a suitable material for all-optical camera due to its fast radiative recombination lifetime in sub-nanosecond regime and its radiation hardness. ZnO nanostructures have been considered as proper building blocks for ultrafast detectors with spatial resolution in sub-micrometer scale. To achieve remarkable enhancement of luminescence efficiency n-type doping in ZnO has been employed. However, luminescence dynamics of doped ZnO nanostructures have not been thoroughly investigated whereas undoped ZnO nanostructures havemore » been employed to study their luminescence dynamics. Here we report a study of luminescence dynamics of hydrogen doped ZnO nanowires obtained by hydrogen plasma treatment. Hydrogen doping in ZnO nanowires gives rise to significant increase in the near-band-edge emission of ZnO and decrease in averaged photoluminescence lifetime from 300 to 140 ps at 10 K. The effects of hydrogen doping on the luminescent characteristics of ZnO nanowires were changed by hydrogen doping process variables.« less

  16. Optical and electrical properties of p-type Li-doped ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Sáaedi, Abdolhossein; Yousefi, Ramin; Jamali-Sheini, Farid; Cheraghizade, Mohsen; Khorsand Zak, A.; Huang, Nay Ming

    2013-09-01

    Undoped and Li-doped ZnO nanowires were grown on Si(1 1 1) substrates using a thermal evaporation method. Undoped and Li-doped ZnO nanoparticles, which were prepared using a sol-gel method, were used as material sources to grow the undoped and Li-doped ZnO nanowires, respectively. X-ray diffraction patterns clearly indicated hexagonal structures for all of the products. The nanowires were completely straight, with non-aligned arrays, and were tapered. Field emission Auger spectrometer indicated lithium element in the nanowires structures. Photoluminescence (PL) studies showed lower optical properties for the Li-doped ZnO nanowires compared to the undoped ZnO nanowires. Furthermore, the UV peak of the Li-doped ZnO nanowires was red-shifted compared to the undoped ZnO nanowires. Two probe method results proved that the Li-doped ZnO nanowires exhibited p-type properties.

  17. Synthesis, structural and optical characterization of undoped, N-doped ZnO and co-doped ZnO thin films

    SciTech Connect

    Pathak, Trilok Kumar Kumar, R.; Purohit, L. P.

    2015-05-15

    ZnO, N-doped ZnO and Al-N co-doped ZnO thin films were deposited on ITO coated corning glass by spin coater using sol-gel method. The films were annealed in air at 450°C for one hour. The crystallographic structure and morphology of the films were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The X-ray diffraction results confirm that the thin films are of wurtzite hexagonal with a very small distortion. The optical properties were investigated by transmission spectra of different films using spectrophotometer (Shimadzu UV-VIS-NIR 3600). The results indicate that the N doped ZnO thin films have obviously enhanced transmittance in visible region. Moreover, the thickness of the films has strong influences on the optical constants.

  18. Enhanced deposition of ZnO films by Li doping using radio frequency reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Chen, Liang-xian; Liu, Sheng; Li, Cheng-ming; Wang, Yi-chao; Liu, Jin-long; Wei, Jun-jun

    2015-10-01

    Radio frequency (RF) reactive magnetron sputtering was utilized to deposit Li-doped and undoped zinc oxide (ZnO) films on silicon wafers. Various Ar/O2 gas ratios by volume and sputtering powers were selected for each deposition process. The results demonstrate that the enhanced ZnO films are obtained via Li doping. The average deposition rate for doped ZnO films is twice more than that of the undoped films. Both atomic force microscopy and scanning electron microscopy studies indicate that Li doping significantly contributes to the higher degree of crystallinity of wurtzite-ZnO. X-ray diffraction analysis demonstrates that Li doping promotes the (002) preferential orientation in Li-doped ZnO films. However, an increase in the ZnO lattice constant, broadening of the (002) peak and a decrease in the peak integral area are observed in some Li-doped samples, especially as the form of Li2O. This implies that doping with Li expands the crystal structure and thus induces the additional strain in the crystal lattice. The oriented-growth Li-doped ZnO will make significant applications in future surface acoustic wave devices.

  19. Semiconducting properties of Al doped ZnO thin films.

    PubMed

    Al-Ghamdi, Ahmed A; Al-Hartomy, Omar A; El Okr, M; Nawar, A M; El-Gazzar, S; El-Tantawy, Farid; Yakuphanoglu, F

    2014-10-15

    Aluminum doped ZnO (AZO) thin films were successfully deposited via spin coating technique onto glass substrates. Structural properties of the films were analyzed by X-ray diffraction, atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy. X-ray diffraction results reveal that all the films are polycrystalline with a hexagonal wurtzite structure with a preferential orientation according to the direction (002) plane. The crystallite size of ZnO and AZO films was determined from Scherrer's formula and Williamson-Hall analysis. The lattice parameters of the AZO films were found to decrease with increasing Al content. Energy dispersive spectroscopy (EDX) results indicate that Zn, Al and O elements are present in the AZO thin films. The electrical conductivity, mobility carriers and carrier concentration of the films are increased with increasing Al doping concentration. The optical band gap (Eg) of the films is increased with increasing Al concentration. The AZO thin films indicate a high transparency in the visible region with an average value of 86%. These transparent AZO films may be open a new avenue for optoelectronic and photonic devices applications in near future. PMID:24840493

  20. One pot synthesis of Ag nanoparticle modified ZnO microspheres in ethylene glycol medium and their enhanced photocatalytic performance

    SciTech Connect

    Tian Chungui; Li Wei; Pan Kai; Zhang Qi; Tian Guohui; Zhou Wei; Fu Honggang

    2010-11-15

    Ag nanoparticles (NPs) modified ZnO microspheres (Ag/ZnO microspheres) were prepared by a facile one pot strategy in ethylene glycol (EG) medium. The EG played two important roles in the synthesis: it could act as a reaction media for the formation of ZnO and reduce Ag{sup +} to Ag{sup 0}. A series of the characterizations indicated the successful combination of Ag NPs with ZnO microspheres. It was shown that Ag modification could greatly enhance the photocatalytic efficiency of ZnO microspheres by taking the photodegradation of Rhodamine B as a model reaction. With appropriate ratio of Ag and ZnO, Ag/ZnO microspheres showed the better photocatalytic performance than commercial Degussa P-25 TiO{sub 2}. Photoluminescence and surface photovoltage spectra demonstrated that Ag modification could effectively inhibit the recombination of the photoinduced electron and holes of ZnO. This is responsible for the higher photocatalytic activity of Ag/ZnO composites. -- Graphical abstract: A 'one-pot' strategy was developed for preparing the Ag/ZnO microspheres in ethylene glycol. The composites exhibited superior photocatalytic performance for photodegradation of Rhodamine B dye in water. Display Omitted

  1. Potassium acceptor doping of ZnO crystals

    SciTech Connect

    Parmar, Narendra S. Lynn, K. G.; Corolewski, Caleb D.; McCluskey, Matthew D.

    2015-05-15

    ZnO bulk single crystals were doped with potassium by diffusion at 950°C. Positron annihilation spectroscopy confirms the filling of zinc vacancies and a different trapping center for positrons. Secondary ion mass spectroscopy measurements show the diffusion of potassium up to 10 μm with concentration ∼1 × 10{sup 16} cm{sup −3}. IR measurements show a local vibrational mode (LVM) at 3226 cm{sup −1}, at a temperature of 9 K, in a potassium doped sample that was subsequently hydrogenated. The LVM is attributed to an O–H bond-stretching mode adjacent to a potassium acceptor. When deuterium substitutes for hydrogen, a peak is observed at 2378 cm{sup −1}. The O-H peak is much broader than the O-D peak, perhaps due to an unusually low vibrational lifetime. The isotopic frequency ratio is similar to values found in other hydrogen complexes. Potassium doping increases the resistivity up to 3 orders of magnitude at room temperature. The doped sample has a donor level at 0.30 eV.

  2. Potassium acceptor doping of ZnO crystals

    NASA Astrophysics Data System (ADS)

    Parmar, Narendra S.; Corolewski, Caleb D.; McCluskey, Matthew D.; Lynn, K. G.

    2015-05-01

    ZnO bulk single crystals were doped with potassium by diffusion at 950°C. Positron annihilation spectroscopy confirms the filling of zinc vacancies and a different trapping center for positrons. Secondary ion mass spectroscopy measurements show the diffusion of potassium up to 10 μm with concentration ˜1 × 1016 cm-3. IR measurements show a local vibrational mode (LVM) at 3226 cm-1, at a temperature of 9 K, in a potassium doped sample that was subsequently hydrogenated. The LVM is attributed to an O-H bond-stretching mode adjacent to a potassium acceptor. When deuterium substitutes for hydrogen, a peak is observed at 2378 cm-1. The O-H peak is much broader than the O-D peak, perhaps due to an unusually low vibrational lifetime. The isotopic frequency ratio is similar to values found in other hydrogen complexes. Potassium doping increases the resistivity up to 3 orders of magnitude at room temperature. The doped sample has a donor level at 0.30 eV.

  3. Atomic layer deposition of Al-doped ZnO thin films

    SciTech Connect

    Tynell, Tommi; Yamauchi, Hisao; Karppinen, Maarit; Okazaki, Ryuji; Terasaki, Ichiro

    2013-01-15

    Atomic layer deposition has been used to fabricate thin films of aluminum-doped ZnO by depositing interspersed layers of ZnO and Al{sub 2}O{sub 3} on borosilicate glass substrates. The growth characteristics of the films have been investigated through x-ray diffraction, x-ray reflection, and x-ray fluorescence measurements, and the efficacy of the Al doping has been evaluated through optical reflectivity and Seebeck coefficient measurements. The Al doping is found to affect the carrier density of ZnO up to a nominal Al dopant content of 5 at. %. At nominal Al doping levels of 10 at. % and higher, the structure of the films is found to be strongly affected by the Al{sub 2}O{sub 3} phase and no further carrier doping of ZnO is observed.

  4. Properties of antimony doped ZnO thin films deposited by spray pyrolysis technique

    SciTech Connect

    Sadananda Kumar, N. Bangera, Kasturi V.; Shivakumar, G. K.

    2015-07-15

    Antimony (Sb) doped zinc oxide (ZnO) thin films were deposited on the glass substrate at 450°C using spray pyrolysis technique. Effect of Sb doping on surface morphology structural, optical and electrical properties were studied. X-ray diffraction (XRD) analysis showed that both the undoped and doped ZnO thin films are polycrystalline in nature with (101) preferred orientation. SEM analysis showed a change in surface morphology of Sb doped ZnO thin films. Doping results in a marked increase in conductivity without affecting the transmittance of the films. ZnO films prepared with 3 at % Sb shows the lowest resistivity of 0.185 Ohm cm with a Hall mobility of 54.05 cm{sup 2} V{sup –1} s{sup –1}, and a hole concentration of 6.25 × 10{sup 17} cm{sup –3}.

  5. Synthesis and characterization of Cu-doped ZnO nanorods chemically grown on flexible substrate

    NASA Astrophysics Data System (ADS)

    Shabannia, R.

    2016-08-01

    Vertically aligned undoped and Cu-doped ZnO nanorods array were successfully grown on flexible substrate by chemical bath deposition method at a low 0074emperature. The fabricated materials were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and photoluminescence (PL) spectroscopy. XRD analysis showed that Cu doping improves the crystallinity of the fabricated ZnO nanorods. The mean diameter and bending of the ZnO nanorods increase with an increase of Cu doping, but the density of Cu-doped ZnO nanorods almost unchanged. Room temperature PL measurement displayed increased intensity in UV peak and decreased visible peak after Cu doping.

  6. Nitrogen-doped ZnO shells: Studies on optical transparency and electrical conductivity

    SciTech Connect

    Gaikwad, Rajendra S.; Mane, Rajaram S.; Pawar, Bhagwat N.; Ambade, Rohan B.; Ahn, Hee Joon; Han, Sung-Hwan; Joo, Oh-Shim

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Chemical spray growth of high quality zinc oxide nitrogen-doped films is explored. Black-Right-Pointing-Pointer Effect of nitrogen doping on crystallinity, surface morphology, and optical properties is comprehensively studied. Black-Right-Pointing-Pointer ZnO structural properties are optimized. Black-Right-Pointing-Pointer Effect of nitrogen doping on a gas sensing application of ZnO is investigated. -- Abstract: Studies on optical and electrical conductivity in nitrogen (N)-doped ZnO shells are explored. On incorporating low levels of nitrogen, the (0 0 2) X-ray diffraction (XRD) peak was found to be intensified significantly. Closely packed spherical crystallites of ZnO were transformed into flat-flakes during 0.1-0.3 M nitrogen doping and finally to shells, flattered at the center and tapered at ends, at 0.4 M. Both pristine and N-doped ZnO films show hydrophilic character. It was also found that the degree of transparency and the nature of conductivity as estimated by optical absorbance and Hall measurement, respectively, were strongly influenced by the levels of N-doping. Higher nitrogen doping led to decline in electrical resistivity and mobility due to an enhancement of free charge carriers. Presence of both (N{sub 2}){sub O} donor and (N){sub O} acceptor peaks in X-ray photoelectron spectroscopy could be responsible for the formation of higher carrier concentration in ZnO films.

  7. Synthesis of Sn-doped ZnO nanorods and their photocatalytic properties

    SciTech Connect

    Wu, Changle; Shen, Li; Yu, Huaguang; Huang, Qingli; Zhang, Yong Cai

    2011-07-15

    Graphical abstract: Sn-doped ZnO nanorods have been fabricated by a hydrothermal route. Photocatalytic activity of the Sn-doped ZnO samples increases gradually with an increase of the Sn content. Highlights: {yields} Sn-doped ZnO nanorods were fabricated by a hydrothermal route. {yields} Solid-state NMR result confirms Sn{sup 4+} was incorporated into the lattice of ZnO. {yields} The visible luminescence intensity increased with increase in Sn concentration. {yields} Photocatalytic activity of Sn-doped ZnO increases with increasing Sn content. -- Abstract: Sn-doped ZnO nanorods were fabricated by a hydrothermal route, and characterized by X-ray diffraction, field emission scanning electron microscope, UV-vis spectroscopy, Raman spectra, solid-state nuclear magnetic resonance (NMR) spectra, and room temperature photoluminescence spectroscopy. Solid-state NMR result confirms that Sn{sup 4+} was successfully incorporated into the crystal lattice of ZnO. Room temperature photoluminescence showed that all the as-synthesized products exhibited a weak UV emission (380 nm) and a strong visible emission (540 nm), but the intensities of the latter emission increased with increase in Sn concentration. The improvement of visible emission at 540 nm in the Sn-doped ZnO samples was suggested to be a result of the lattice defects increased by doping of Sn in zinc oxide. In addition, the photocatalytic studies indicated that Sn-doped ZnO nanorods are a kind of promising photocatalyst in remediation of water polluted by some chemically stable azo dyes.

  8. Rapid synthesis of Co, Ni co-doped ZnO nanoparticles: Optical and electrochemical properties

    NASA Astrophysics Data System (ADS)

    Romeiro, Fernanda C.; Marinho, Juliane Z.; Lemos, Samantha C. S.; de Moura, Ana P.; Freire, Poliana G.; da Silva, Luis F.; Longo, Elson; Munoz, Rodrigo A. A.; Lima, Renata C.

    2015-10-01

    We report for the first time a rapid preparation of Zn1-2xCoxNixO nanoparticles via a versatile and environmentally friendly route, microwave-assisted hydrothermal (MAH) method. The Co, Ni co-doped ZnO nanoparticles present an effect on photoluminescence and electrochemical properties, exhibiting excellent electrocatalytic performance compared to undoped ZnO sample. Photoluminescence spectroscopy measurements indicated the reduction of the green-orange-red visible emission region after adding Co and Ni ions, revealing the formation of alternative pathways for the generated recombination. The presence of these metallic ions into ZnO creates different defects, contributing to a local structural disorder, as revealed by Raman spectra. Electrochemical experiments revealed that the electrocatalytic oxidation of dopamine on ZnO attached to multi-walled carbon nanotubes improved significantly in the Co, Ni co-doped ZnO samples when compared to pure ZnO.

  9. Fundamental understanding of the growth, doping and characterization of aligned ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Shen, Gang

    Zinc oxide (ZnO) is a II-VI semiconductor whose wide direct bandgap (3.37 eV) and large exciton binding energy (60 meV) make it compelling for optoelectronic devices such as light emitting diodes, lasers, photodetectors, solar cells, and mechanical energy harvesting devices. One dimensional structures of ZnO (nanowires) have become significant due to their unique physical properties arising from quantum confinement, and they are ideal for studying transport mechanisms in one-dimensional systems. In this doctoral research work, ZnO nanowire (NW) arrays were synthesized on sapphire substrates through carbo-thermal reduction of ZnO powders, and the effects of growth parameters on the properties of ZnO NW arrays were studied by scanning and transmission electron microscopy, X-ray diffraction, photoluminescence and Raman spectroscopy. Based on the phonon mode selection rules in wurtzite ZnO, confocal Raman spectroscopy was used to assess the alignment of ZnO NWs in an array, thereby complementing X-ray diffraction. Al doped ZnO NW arrays were achieved by mixing Al powder into the ZnO and graphite source mixture, and the presence of Al was confirmed by Energy-dispersive X-ray spectroscopy. The incorporation of Al had the effects of lowering the electrical resistivity, slightly deteriorating crystal quality and suppressing defect related green emission. Two models of ZnO NW growth were developed by establishing the relationship between NW length and diameter for undoped and Al doped ZnO NWs separately. The growth of undoped ZnO NWs followed the diffusion-induced model which was characterized by thin wires being longer than thick wires, while the growth of Al doped ZnO was controlled by Gibbs-Thomson effect which was characterized by thin wires being shorter than thin wires. Local electrode atom probe analysis of ZnO NWs was carried out to study the crystal stoichiometry and Al incorporation. Undoped ZnO NWs were found to be high purity with no detectable impurities

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

    SciTech Connect

    Kumar, Shalendra; Vats, Prashant; Gautam, S.; Gupta, V.P.; Verma, K.D.; Chae, K.H.; Hashim, Mohd; Choi, H.K.

    2014-11-15

    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 fine 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.

  11. Spectroscopic and fiber optic ethanol sensing properties Gd doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Noel, J. L.; Udayabhaskar, R.; Renganathan, B.; Muthu Mariappan, S.; Sastikumar, D.; Karthikeyan, B.

    2014-11-01

    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.

  12. 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. PMID:24892544

  13. Enhanced photovoltaic performance of quantum dot-sensitized solar cell fabricated using Al-doped ZnO nanorod electrode

    NASA Astrophysics Data System (ADS)

    Raja, M.; Muthukumarasamy, N.; Velauthapillai, Dhayalan; Balasundrapraphu, R.; Senthil, T. S.; Agilan, S.

    2015-04-01

    ZnO and Al doped ZnO nanorods have been successfully synthesized on ITO substrate via solgel dip coating method without using any catalyst. The X-ray diffraction studies showed that the Al doped ZnO samples are of hexagonal wurtzite structure. The Al ions were successfully incorporated into the ZnO lattice. Scanning electron microscopy images reveal that the average diameter of ZnO nanorods and Al doped ZnO nanorods are ∼300 nm and ∼200 nm respectively. The energy dispersive X-ray (EDS) analysis confirmed the presence Al in the ZnO thin films. The CdS quantum dot sensitized Al doped ZnO solar cell exhibited a power conversion efficiency of 1.5%.

  14. 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.

  15. Synthesis and characterization of sodium doped ZnO nanocrystals and its application to photocatalysis

    NASA Astrophysics Data System (ADS)

    Elangovan, S. V.; Chandramohan, V.; Sivakumar, N.; Senthil, T. S.

    2015-09-01

    Pure and Na-doped ZnO photocatalysts (Na-ZnO) were synthesized by simple wet chemical method using zinc acetate dehydrate as starting material and samples were annealed at 350 °C. The results of characterization techniques like XRD, SEM, EDXA and UV reveals that the prepared samples were nanometer in size and Na ions successfully doped into the ZnO lattice without change its wurtzite structure. The effect of addition of different concentration of sodium dopant on structural property, optical property, surface morphology and photo-catalytic activity of ZnO nanocrystals were analyzed. By using methylene blue as a model dye the photo-catalytic decolourisation was studied and the results shows that the sodium doped ZnO proves higher photo-catalytic decolourisation than the pure ZnO. This increase is possible as a result of sodium doping in the crystal structure of ZnO. A possible mechanism of the photocatalytic decolourisation of methylene blue on the sodium doped ZnO is suggested.

  16. Enhanced UV absorbance and photoluminescence properties of ultrasound assisted synthesized gold doped ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Sahu, Dojalisa; Panda, N. R.; Acharya, B. S.; Panda, A. K.

    2014-06-01

    Au doped ZnO (ZnO:Au) nanostructures were synthesized by ultrasound assisted wet chemical method. The concentration of dopant was varied and both structural and optical properties of ZnO:Au were investigated. The crystal structure and morphology of the samples were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). These results showed the formation of nanorods of ZnO:Au having wurtzite structure and c-axis orientation. Gradual increase in crystallite size and bond length was also observed with the increase in gold concentration in ZnO intending the expansion of lattice after gold doping. The optical absorption measurements showed high ultraviolet (UV) absorbance property of ZnO:Au with sharp and intense absorption band in this region as compared to pristine ZnO. Photoluminescence (PL) measurements showed excitonic emission band of ZnO around 390 nm for both undoped and Au doped ZnO nanoparticles. Further, a strong emission around 467 nm was observed in the PL spectra of ZnO/ZnO:Au which was attributed to the transitions related to excess of oxygen vacancies. Interestingly, a new band was observed at 582 nm for doped ZnO samples which grew in intensity with doping concentration. This band was ascribed to the gold nanoparticle adsorbed on the surface of ZnO.

  17. Synthesis, physical properties and catalytic activity of Cr-doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Djaja, Nadia Febiana; Noorhidayati, Annisa; Saleh, Rosari

    2016-03-01

    The present work studies the photocatalytic degradation of Cr-doped ZnO nanoparticles toward aqueous mixture of organic dyes, such as methyl orange, methylene blue and congo red. Cr-doped ZnO nanoparticles were synthesized using co-precipitation method and characterized by several method of measurements. Photocatalytic mechanism was investigated by measuring the photocatalytic degradation rate in the presence of scavenger. The results revealed that hydroxyl radical plays an important role in photocatalytic activity.

  18. Room temperature ferromagnetism in ZnO using non-magnetic dopants

    NASA Astrophysics Data System (ADS)

    Ali, Nasir; Atri, Asha; Singh, Budhi; Ghosh, Subhasis

    2016-05-01

    We studied the magnetic properties of Ag and Cu doped ZnO thin films deposited by magnetron sputtering. Robust room temperature ferromagnetism is observed in the films. Comparative to Cu doped films Ag doped films shows significant increase in ferromagnetism. Spectroscopic ellipsometry studies are also done to see the change in band structure with different metal doping content.

  19. Low switching voltage ZnO quantum dots doped polymer-dispersed liquid crystal film.

    PubMed

    Hsu, Chuan-Chun; Chen, Yi-Xuan; Li, Hui-Wen; Hsu, Jy-Shan

    2016-04-01

    This paper investigates the effects of ZnO nanoparticles (NPs) on the switching voltages of polymer dispersed liquid crystal (PDLC) films. The threshold and driving electric fields of PDLC film doped with 2.44 wt% ZnO NPs were 0.13 and 0.31 V/μm, respectively, with a contrast ratio of 26. The results of field emission scanning electron microscopy show that the size of the droplets in doped PDLC films increases with the doping concentration. The development of ZnO-doped PDLC films with low driving voltages greatly broadens the applicability of these devices. PMID:27137000

  20. Study of structural and optical properties of Al doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Mallika, A. N.; Ramachandra Reddy, A.

    2014-03-01

    This paper reports on the structural and optical properties of Al doped ZnO nanoparticles prepared through sol-gel method using poly vinyl alcohol as chelating agent. Al was effectively doped in ZnO with concentrations up to 6 atomic percent concentrations (at. %). X-ray diffraction (XRD) results revealed that all the samples do not have impurity phase indicating hexagonal wurtzite structure of ZnO formed, the average crystallite sizes were decreased with increasing Al concentrations. A compressive strain was induced with Al doping and was calculated with W-H plot analysis. The morphology of all the samples was studied from Field Emission Scanning Electron Microscope (FE-SEM). The energy band gap of the Al doped samples was estimated from UV-Vis spectrum showed an overall increase. The presence of functional groups and chemical bonding of ZnO with Al doping was confirmed by Fourier Transform Infrared Spectroscopy (FTIR) spectra, and in addition to this, the photoluminescence (PL) properties of Al doped ZnO nanoparticles were studied. This paper reports on the structural and optical properties of Al doped ZnO nanoparticles prepared through sol-gel method using poly vinyl alcohol as chelating agent. Al was effectively doped in ZnO with concentrations up to 6 atomic percent concentrations (at. %). X-ray diffraction (XRD) results revealed that all the samples do not have impurity phase indicating hexagonal wurtzite structure of ZnO formed, the average crystallite sizes were decreased with increasing Al concentrations. A compressive strain was induced with Al doping and was calculated with W-H plot analysis. The morphology of all the samples was studied from Field Emission Scanning Electron Microscope (FE-SEM). The energy band gap of the Al doped samples was estimated from UV-Vis spectrum showed an overall increase. The presence of functional groups and chemical bonding of ZnO with Al doping was confirmed by Fourier Transform Infrared Spectroscopy (FTIR) spectra, and in

  1. Fabrication of Al-Doped ZnO Film with High Conductivity Induced by Photocatalytic Activity

    NASA Astrophysics Data System (ADS)

    Hong, Jeongsoo; Katsumata, Ken-ichi; Matsushita, Nobuhiro

    2016-06-01

    We have fabricated Al-doped ZnO films by a spin-spray method, achieving high conductivity by Al-ion doping and photocatalytic activity of the ZnO. The surface morphology of the as-deposited films was varied by changing the Al concentration and addition of citrate ions. As-deposited Al-doped ZnO film without citrate ions showed rod array structure with increasing rod width as the Al concentration was increased. Meanwhile, Al-doped ZnO film deposited with addition of citrate ions changed to exhibit dense and continuous surface morphology with high transmittance of 85%. The lowest resistivity recorded for undoped and Al-doped ZnO film was 2.1 × 10-2 Ω cm and 5.9 × 10-3 Ω cm, after ultraviolet (UV) irradiation. The reason for the decreased resistivity is thought to be that Al-ion doping and the photocatalytic activity of ZnO contributed to improve the conductivity.

  2. Magnetic properties of high Li doped ZnO sol–gel thin films

    SciTech Connect

    Vettumperumal, R.; Kalyanaraman, S.; Santoshkumar, B.; Thangavel, R.

    2014-02-01

    Highlights: • Ferromagnetism in high Li doped ZnO films. • Magnetic properties observed by Guoy's and VSM method. • The rod and wrinkle like structures are observed from the surface of the films. • Band gap of ZnO does not get altered by high Li doping. - Abstract: Undoped and Li doped ZnO thin films were deposited on a glass substrate using the sol–gel dip coating method. The films were prepared at 5 mol.% and 10 mol.% of Li doped ZnO at 550 °C annealing temperature and the deposited films were characterized by X-ray diffraction (XRD), microscopic studies, Gouy's method, vibrating sample magnetometer (VSM) and UV–visible spectroscopy. All the deposited thin films had a hexagonal wurtzite structure with polycrystalline grains at random. Primarily magnetic properties of pure and Li doped ZnO films were observed by Guoy's method which depicted Dia and Para magnetic behavior at room temperature. VSM measurement reveals a coercivity of 97.7 Oe in the films. An inverse relative ferromagnetism was perceived in Li doped ZnO films which had an average transmission of <90%.

  3. Rapid synthesis of Co, Ni co-doped ZnO nanoparticles: Optical and electrochemical properties

    SciTech Connect

    Romeiro, Fernanda C.; Marinho, Juliane Z.; Lemos, Samantha C.S.; Moura, Ana P. de; Freire, Poliana G.; Silva, Luis F. da; Longo, Elson; Munoz, Rodrigo A.A.; Lima, Renata C.

    2015-10-15

    We report for the first time a rapid preparation of Zn{sub 1−2x}Co{sub x}Ni{sub x}O nanoparticles via a versatile and environmentally friendly route, microwave-assisted hydrothermal (MAH) method. The Co, Ni co-doped ZnO nanoparticles present an effect on photoluminescence and electrochemical properties, exhibiting excellent electrocatalytic performance compared to undoped ZnO sample. Photoluminescence spectroscopy measurements indicated the reduction of the green–orange–red visible emission region after adding Co and Ni ions, revealing the formation of alternative pathways for the generated recombination. The presence of these metallic ions into ZnO creates different defects, contributing to a local structural disorder, as revealed by Raman spectra. Electrochemical experiments revealed that the electrocatalytic oxidation of dopamine on ZnO attached to multi-walled carbon nanotubes improved significantly in the Co, Ni co-doped ZnO samples when compared to pure ZnO. - Graphical abstract: Rapid synthesis of Co, Ni co-doped ZnO nanoparticles: optical and electrochemical properties. Co, Ni co-doped ZnO hexagonal nanoparticles with optical and electrocatalytic properties were successfully prepared for the first time using a microwave hydrothermal method at mild conditions. - Highlights: • Co{sup 2+} and Ni{sup 2+} into ZnO lattice obtained a mild and environmentally friendly process. • The heating method strongly influences in the growth and shape of the particles. • Short-range defects generated by the ions insertion affects the photoluminescence. • Doped ZnO nanoparticles improve the electrocatalytic properties of pure oxide.

  4. Study of ZnO and Mg doped ZnO nanoparticles by sol-gel process

    SciTech Connect

    Ansari, Mohd Meenhaz Arshad, Mohd; Tripathi, Pushpendra

    2015-06-24

    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 absorption spectra was obtained and the band gap of the samples calculated.

  5. Dye-sensitized solar cells using ZnO nanotips and Ga-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Chen, Hanhong; Du Pasquier, Aurelien; Saraf, Gaurav; Zhong, Jian; Lu, Yicheng

    2008-04-01

    Ga-doped ZnO (GZO) transparent conducting films and well-aligned ZnO nanotips were sequentially grown on a glass substrate using metal-organic chemical vapor deposition (MOCVD). The morphology control of ZnO from dense films to nanotips was realized through temperature-modulated growth. The ZnO nanotips/GZO structure was sensitized with dye N719 to form photoelectrochemical cells. It is found that the power conversion efficiency linearly increases with the length of ZnO nanotips. For the 1.0 cm2 dye-sensitized solar cell built from 4.8 µm ZnO nanotips, a peak incident photo-to-current conversion efficiency of 79% (at ~530 nm) and a power conversion efficiency of 0.77% under the illumination of one sun-simulated sunlight were achieved. UV light harvesting directly by ZnO was observed. The I-V characteristics of the cells were analyzed using a one-diode equivalent circuit model.

  6. Magnetic and optical properties of Co-doped and Mn-doped ZnO nanocrystalline particles

    NASA Astrophysics Data System (ADS)

    Alsmadi, Abdel; Salameh, B.; Shatnawi, M.; Alnawashi, G.; Bsoul, I.

    We carried out a systematic study on the effect of Co doping and Mn doping on the structural, magnetic and optical properties of ZnO nanocrystalline particles, using x-ray diffraction, x-ray photoelectron spectroscopy (XPS), Quantum Design PPMS-9 magnetometry, and Ultra Violet-Visible spectroscopy. The Zn1- x CoxO and Zn1- x MnxO nanoparticles with 0 <= x <= 0 . 1 were successfully prepared by the formal solid-state reaction method. The XPS results and the XRD analysis with full structural Rietveld refinement reveal that both structures have hexagonal wurtzite structure. For all Co-doped ZnO nanoparticles under investigation, the field dependence of the magnetization curves exhibits ferromagnetic behavior with relatively small coercive fields at room temperature. In addition, we found a signature for antiferromagnetic ordering between the Co ions. For the Mn-doped ZnO nanoparticles, we observed ferromagnetic behavior only below 50 K. We also observed a strong correlation between the magnetic and optical behavior of the Co-doped ZnO nanoparticles. Optical diffuse reflectance and absorption spectra exhibit a red shift at room temperature in the absorption band edge with increasing Co-doping. The red shift is attributed to the sp-d exchange interaction between free charge carriers in ZnO band and the localized magnetic moments.

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

    SciTech Connect

    Kumar, Shalendra; Song, T.K.; Gautam, Sanjeev; Chae, K.H.; Kim, S.S.; Jang, K.W.

    2015-06-15

    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 scanning 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.

  8. Impact of ZnO and Ag Nanoparticles on Bacterial Growth and Viability

    NASA Astrophysics Data System (ADS)

    Olson, M. S.; Digiovanni, K. A.

    2007-12-01

    Hundreds of consumer products containing nanomaterials are currently available in the U.S., including computers, clothing, cosmetics, sports equipment, medical devices and product packaging. Metallic nanoparticles can be embedded in or coated on product surfaces to provide antimicrobial, deodorizing, and stain- resistant properties. Although these products have the potential to provide significant benefit to the user, the impact of these products on the environment remains largely unknown. The purpose of this project is to study the effect of metallic nanoparticles released to the environment on bacterial growth and viability. Inhibition of bacterial growth was tested by adding doses of suspended ZnO and Ag nanoparticles into luria broth prior to inoculation of Escherichia coli cells. ZnO particles (approximately 40 nm) were obtained commercially and Ag particles (12-14 nm) were fabricated by reduction of silver nitrate with sodium borohydride. Toxicity assays were performed to test the viability of E. coli cells exposed to both ZnO and Ag nanoparticles using the LIVE/DEAD BacLight bacterial viability kit (Invitrogen). Live cells stain green whereas cells with compromised membranes that are considered dead or dying stain red. Cells were first grown, stained, and exposed to varying doses of metallic nanoparticles, and then bacterial viability was measured hourly using fluorescence microscopy. Results indicate that both ZnO and Ag nanoparticles inhibit the growth of E. coli in liquid media. Preliminary results from toxicity assays confirm the toxic effect of ZnO and Ag nanoparticles on active cell cultures. Calculated death rates resulting from analyses of toxicity studies will be presented.

  9. Effect of Mg doping in ZnO buffer layer on ZnO thin film devices for electronic applications

    NASA Astrophysics Data System (ADS)

    Giri, Pushpa; Chakrabarti, P.

    2016-05-01

    Zinc Oxide (ZnO) thin films have been grown on p-silicon (Si) substrate using magnesium doped ZnO (Mg: ZnO) buffer layer by radio-frequency (RF) sputtering method. In this paper, we have optimized the concentration of Mg (0-5 atomic percent (at. %)) ZnO buffer layer to examine its effect on ZnO thin film based devices for electronic and optoelectronic applications. The crystalline nature, morphology and topography of the surface of the thin film have been characterized. The optical as well as electrical properties of the active ZnO film can be tailored by varying the concentration of Mg in the buffer layer. The crystallite size in the active ZnO thin film was found to increase with the Mg concentration in the buffer layer in the range of 0-3 at. % and subsequently decrease with increasing Mg atom concentration in the ZnO. The same was verified by the surface morphology and topography studies carried out with scanning electron microscope (SEM) and atomic electron microscopy (AFM) respectively. The reflectance in the visible region was measured to be less than 80% and found to decrease with increase in Mg concentration from 0 to 3 at. % in the buffer region. The optical bandgap was initially found to increase from 3.02 eV to 3.74 eV by increasing the Mg content from 0 to 3 at. % but subsequently decreases and drops down to 3.43 eV for a concentration of 5 at. %. The study of an Au:Pd/ZnO Schottky diode reveals that for optimum doping of the buffer layer the device exhibits superior rectifying behavior. The barrier height, ideality factor, rectification ratio, reverse saturation current and series resistance of the Schottky diode were extracted from the measured current voltage (I-V) characteristics.

  10. High temperature ferromagnetism and optical properties of Co doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Pal, Bappaditya; Giri, P. K.

    2010-10-01

    We report on the occurrence of high temperature ferromagnetism (FM) in ZnO nanoparticles (NPs) doped with Co-atoms. ZnO NPs of two different initial sizes are doped with 3% and 5% Co using ball milling and FM is studied at room temperature and above. 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 studies show change in band structure and photoluminescence studies show green emission band at 520 nm indicating incorporation of Co-atoms and presence of oxygen vacancy defects, respectively in ZnO lattice. Micro-Raman studies of doped samples shows defect related additional bands at 547 and 574 cm-1. XRD and Raman spectra provide clear evidence for strain in the doped ZnO NPs. The field dependence of magnetization (M-H curve) measured at room temperature exhibits the clear FM with saturation magnetization (Ms) and coercive field (Hc) of the order of 3-7 emu/g and 260 Oe, respectively. Temperature dependence of magnetization (M-T) measurement shows sharp ferromagnetic to paramagnetic transition with a high Curie temperature (Tc) of ˜800 K for 3% Co doped ZnO NPs. It is found that doping at 5% and higher concentration does not exhibit a proper magnetic transition. We attempt to fit the observed FM data with the bound magnetic polaron (BMP) model involving localized carriers and magnetic cations. However, calculated concentration of the BMPs is well below the typical percolation threshold in ZnO. We believe that observed high temperature FM is primarily mediated by defects in the strained NPs. ZnO NPs of lower initial size show enhanced FM that may be attributed to size dependent doping effect.

  11. 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.

  12. Ni, Fe Co-doped ZnO nanoparticles synthesized by solution combustion method

    SciTech Connect

    Dhiman, Pooja Chand, Jagdish Verma, S. Sarveena, Singh, M.

    2014-04-24

    This paper outlines the synthesis and characterization of Ni-Fe co-doped ZnO nanoparticles by facile solution combustion method. The structural characterization by XRD confirmed the phase purity of the samples. Surface morphology studied by scanning electron microscope revealed cubic type shape of grains. EDS analysis conformed the elemental composition. Higher value of DC electrical conductivity and less band gap for co-doped ZnO from UV-Vis studies confirmed the change in defect chemistry of ZnO Matrix.

  13. UV light sensing properties of Sm doped vertically aligned ZnO nanorod arrays

    SciTech Connect

    Kumar, D. Ranjith; Ranjith, K. S.; Rajendrakumar, R. T.

    2015-06-24

    Samarium doped ZnO nanorods were grown on silicon substrate by using vapor phase transport method (VPT) with the growth temperature of 950°C. The synthesized nanorods were characterized by XRD, field emission scanning electron microscopy, Raman spectra, and photocurrent measurements. The XRD result revealed that Sm was successfully doped into lattice plane of hexagonal ZnO nanorods. The FESEM result confirms the pure ZnO has nanorod like morphology with an average diameter and length of 130nm and 10µm respectively. The above observation is supported by the Micro-Raman spectroscopy result. The photocurrent in the visible region has been significantly enhanced due to deposition of Sm on the surface of the ZnO nanorods. Sm acts as a visible sensitizer because of its lower band gap compared to ZnO.

  14. Ag nanoparticles-decorated ZnO nanorod array on a mechanical flexible substrate with enhanced optical and antimicrobial properties.

    PubMed

    Chen, Yi; Tse, Wai Hei; Chen, Longyan; Zhang, Jin

    2015-01-01

    Heteronanostructured zinc oxide nanorod (ZnO NR) array are vertically grown on polydimethylsiloxane (PDMS) through a hydrothermal method followed by an in situ deposition of silver nanoparticles (Ag NPs) through a photoreduction process. The Ag-ZnO heterostructured nanorods on PDMS are measured with an average diameter of 160 nm and an average length of 2 μm. ZnO NRs measured by high-resolution transmission electron microscope (HRTEM) shows highly crystalline with a lattice fringe of 0.255 nm, which corresponds to the (0002) planes in ZnO crystal lattice. The average diameter of the Ag NPs in situ deposited on the ZnO NRs is estimated at 22 ± 2 nm. As compared to the bare ZnO NRs, the heterostructured Ag-ZnO nanorod array shows enhanced ultraviolet (UV) absorption at 440 nm, and significant emission in the visible region (λem = 542 nm). In addition, the antimicrobial efficiency of Ag-ZnO heterostructured nanorod array shows obvious improvement as compared to bare ZnO nanorod array. The cytotoxicity of ZnO nanorod array with and without Ag NPs was studied by using 3 T3 mouse fibroblast cell line. No significant toxic effect is imposed on the cells. PMID:25852401

  15. Charge Compensated (Al, N) Co-Doped Zinc Oxide (ZnO) Films for Photlelectrochemical Application

    SciTech Connect

    Shet, S.

    2012-01-01

    ZnO thin films with significantly reduced bandgaps were synthesized by doping N and co-doping Al and N at 100oC. All the films were synthesized by radio-frequency magnetron sputtering on F-doped tin-oxide-coated glass. We found that co-doped ZnO:(Al,N) thin films exhibited significantly enhanced crystallinity as compared to ZnO doped solely with N, ZnO:N, at the same growth conditions. Furthermore, annealed ZnO:(Al,N) thin films exhibited enhanced N incorporation over ZnO:N films. As a result, ZnO:(Al,N) films exhibited improved photocurrents than ZnO:N films grown with pure N doping, suggesting that charge-compensated donor-acceptor co-doping could be a potential method for bandgap reduction of wide-bandgap oxide materials to improve their photoelectrochemical performance.

  16. Correlated substitution in paramagnetic Mn{sup 2+}-doped ZnO epitaxial films.

    SciTech Connect

    Droubay, T. C.; Keavney, D. J.; Kaspar, T. C.; Heald, S. M.; Wang, C. M.; Johnson, C. A.; Whitaker, K. M.; Gamelin, D. R.; Chambers, S. A.; X-Ray Science Division; PNNL; Univ. of Washington

    2009-04-01

    Epitaxial films of Mn2+-doped ZnO were deposited by pulsed laser deposition on {alpha}-Al{sub 2}O{sub 3}(0001) using targets created from Mn{sup 2+}-doped ZnO nanoparticles. Using x-ray absorption spectroscopy and x-ray magnetic circular dichroism, Mn(II) was found to substitute for Zn(II) in the wuertzite ZnO lattice with only a paramagnetic dichroic component from the Mn and no magnetic component from either the O or Zn. The dichroism reveals that, while substitutional, the Mn{sup 2+} distribution in the ZnO lattice is not stochastic. Rather, Mn{sup 2+} has a tendency to substitute with higher effective local concentrations than anticipated from a stochastic doping model.

  17. Synthesis and characterization of Sb-doped ZnO microspheres by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Nagasaki, Fumiaki; Shimogaki, Tetsuya; Tanaka, Toshinobu; Ikebuchi, Tatsuya; Ueyama, Takeshi; Fujiwara, Yuki; Higashihata, Mitsuhiro; Nakamura, Daisuke; Okada, Tatsuo

    2016-08-01

    We succeeded in synthesizing antimony (Sb)-doped zinc oxide (ZnO) microspheres by ablating a sintered ZnO target containing Sb in air. The structural properties of the microspheres were investigated by Raman scattering studies. The Zn–Sb related local vibrational mode (LVM) was detected around 238 cm‑1. Room-temperature photoluminescence (PL) properties of the microspheres were investigated under cw and pulsed laser excitations, and ultraviolet (UV) emission and whispering-gallery-mode (WGM) lasing were observed from the microspheres. Furthermore, a p–n heterojunction was formed between a single Sb-doped ZnO microsphere and an n-Al-doped ZnO thin film, and a good rectifying property with a turn-on voltage of approximately 1.8 V was observed in the current–voltage (I–V) characteristics across the junction.

  18. Fabrication and Magnetic Properties of Sn-Doped ZnO Microstructures via Hydrothermal Method.

    PubMed

    Farooq, M Hassan; Hussain, Riaz; Iqbal, M Zubair; Shah, M W; Rana, Usman Ali; Khan, Salah Ud-Din

    2016-01-01

    Pure zinc oxide (ZnO) and Sn-doped ZnO hexagonal sheets were synthesized by template free hydrothermal growth mechanism with controlled morphology by using zinc acetate dihydrate (Zn(CH₃COO)₂· 2H₂O), tin chloride pentahydrate (SnCl₄ · 5H₂O), Polyvinylpyrrolidone (PVP) and H₂O as precursors. The structural, physical, chemical, and magnetic characteristics were investigated by X-ray diffraction, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy and alternating gradient magnetometer (AGM), respectively. The average crystalline size of hexagonal phase of ZnO sheets was calculated to be about 34 nm from XRD patterns. Energy dispersive spectroscopy provided the compositional analysis of pure and Sn-doped ZnO. Room temperature ferromagnetism (RTFM) was observed by AGM for pure and Sn-doped ZnO hexagonal plates. RTFM increases monotonically for Sn doping and reaches maximum saturation magnetization 0.045 emu/g for 3% Sn-doped ZnO. PMID:27398543

  19. 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

  20. Improved photovoltaic performance of multiple carbon-doped ZnO nanostructures under UV and visible light irradiation.

    PubMed

    Liu, Xianbin; Du, Hejun; Sun, Xiao Wei; Zhan, Zhaoyao; Sun, Gengzhi; Li, Fengji; Zheng, Lianxi; Zhang, Sam

    2014-09-01

    We report synthesis of multiple carbon-doped ZnO nanostructures by using carbon cloth as substrates to obtain multiple hollow ZnO microtube-nanowire structures. X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy analysis clearly show that carbon is doped into ZnO through substitution of carbon for oxygen in the growth and annealing processes. Upon exposure to 633-nm red laser, a distinct photoresponse can be observed, which indicates that carbon doping in ZnO can well extend its light harvesting to visible light region. Furthermore, a prototype of photovoltaic cell was fabricated to demonstrate the photovoltaic performance of multiple carbon-doped ZnO nanostructures under UV and visible light irradiation. This result shows that carbon-doped ZnO can act as effective photoactive materials for photoelectric components. PMID:25924372

  1. Structure and photocatalytic activity of Ni-doped ZnO nanorods

    SciTech Connect

    Zhao, Jing; Wang, Li; Yan, Xiaoqin; Yang, Ya; Lei, Yang; Zhou, Jing; Huang, Yunhua; Gu, Yousong; Zhang, Yue

    2011-08-15

    Graphical abstract: Degradation rates of rhodamine B by Zn{sub 1-x}Ni{sub x}O photocatalyst. Highlights: {yields} The Ni-doped ZnO nanorods show a new band at {approx}130 cm{sup -1} in Raman spectra at room temperature. We conclude this mode is caused by an ordered arrangement of Ni dopants in the ZnO lattice. {yields} When the Ni-doping concentration raises, the band gap first increases and then decreases. {yields} The ZnO nanorods with different Ni-doping concentraton all exhibited higher photocatalytic activity than un-doped ZnO. The order of photocatalytic activities is Zn{sub 0.95}Ni{sub 0.05}O > Zn{sub 0.9}Ni{sub 0.1}O > Zn{sub 0.98}Ni{sub 0.02}O > ZnO. -- Abstract: The one-dimensional (1D) Zn{sub 1-x}Ni{sub x}O (x = 0, 0.02, 0.05, 0.10) nanorods have been synthesized by a simple hydrothermal method. New bands show at {approx}130 cm{sup -1} in the Raman spectra of Ni-doped ZnO nanorods and their relative intensity depends on the doping concentration of nickel. The optical band gap of the ZnO nanorods have been tuned by Ni-doping, which is revealed by absorption spectra. The photocatalytic activity of Zn{sub 1-x}Ni{sub x}O was studied by comparing the degradation rate of rhodamine B (RB) under UV-light irradiation. It was found that Zn{sub 0.95}Ni{sub 0.05}O exhibited the highest photocatalytic degradation efficiency among the samples.

  2. Structural studies and band gap tuning of Cr doped ZnO nanoparticles

    SciTech Connect

    Srinet, Gunjan Kumar, Ravindra Sajal, Vivek

    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.

  3. Defect Chemistry Study of Nitrogen Doped ZnO Thin Films

    SciTech Connect

    Miami University: Dr. Lei L. Kerr Wright State University: Dr. David C. Look and Dr. Zhaoqiang Fang

    2009-11-29

    Our team has investigated the defect chemistry of ZnO:N and developed a thermal evaporation (vapor-phase) method to synthesis p-type ZnO:N. Enhanced p-type conductivity of nitrogen doped ZnO via nano/micro structured rods and Zn-rich Co-doping process were studied. Also, an extended X-Ray absorption fine structure study of p-type nitrogen doped ZnO was conducted. Also reported are Hall-effect, photoluminescence, and DLTS studies.

  4. Synthesis and magnetic properties of Zr doped ZnO Nanoparticles

    PubMed Central

    2011-01-01

    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. PMID:22074396

  5. Modification of the electrical properties of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) upon doping of ZnO nanoparticles of different content

    NASA Astrophysics Data System (ADS)

    Lin, Yow-Jon; Su, Yu-Chao

    2012-04-01

    A photocurrent decay model is presented that addresses the charge trapping and doping mechanisms for composite poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS) films having ZnO nanoparticles of different contents. It is shown that ZnO doping introduced changes in the chemical structure of PEDOT:PSS. Dark current proportional to ZnO doping was observed. For n-type Si/ZnO-doped PEDOT:PSS devices, the high photocurrent density originates from efficient hole transport combined with long-lifetime electron trapping.

  6. Electrical and optical properties of Ti doped ZnO films grown on glass substrate by atomic layer deposition

    SciTech Connect

    Wan, Zhixin; Kwack, Won-Sub; Lee, Woo-Jae; Jang, Seung-II; Kim, Hye-Ri; Kim, Jin-Woong; Jung, Kang-Won; Min, Won-Ja; Yu, Kyu-Sang; Park, Sung-Hun; Yun, Eun-Young; Kim, Jin-Hyock; Kwon, Se-Hun

    2014-09-15

    Highlights: • Ti doped ZnO films were prepared on Corning XG glass substrate by ALD. • The electrical properties and optical properties were systematically investigated. • An optimized Ti doped ZnO films had low resistivity and excellent optical transmittance. - Abstract: Titanium doped zinc oxide (Ti doped ZnO) films were prepared by atomic layer deposition methods at a deposition temperature of 200 °C. The Ti content in Ti doped ZnO films was varied from 5.08 at.% to 15.02 at.%. X-ray diffraction results indicated that the crystallinity of the Ti doped ZnO films had degraded with increasing Ti content. Transmission electron microscopy was used to investigate the microstructural evolution of the Ti doped ZnO films, showing that both the grain size and crystallinity reduced with increasing Ti content. The electrical resistivity of the Ti doped ZnO films showed a minimum value of 1.6 × 10{sup −3} Ω cm with the Ti content of 6.20 at.%. Furthermore, the Ti doped ZnO films exhibited excellent transmittance.

  7. In vitro antibacterial activity of ZnO and Nd doped ZnO nanoparticles against ESBL producing Escherichia coli and Klebsiella pneumoniae.

    PubMed

    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

  8. 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

  9. 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.

  10. Luminescence Properties of Sm3+/Eu3+ Co-Doped ZnO Quantum Dots.

    PubMed

    Liu, Fengyi; Li, Hong; Hu, Yajing; Na, Jin; Mou, Yun; Yang, Kun; Ye, Zuhu; Li, Mingyue; Xie, Ya-Hong

    2016-04-01

    In order to improve luminescence properties of semiconductor ZnO quantum dots (QDs), Sm3+/Eu3+ co-doped ZnO QDs have been controllably synthesized by sol-gel method in this paper. ZnO QDs have a spherical shape with mean diameter at about 5-6 nm, which was characterized by high-resolution transmission electron microscopy (HRTEM). ZnO QDs have hexagonal wurtzite structure with parts of Sm3+ and Eu3+ incorporated into the lattice, which was demonstrated by X-ray Diffraction (XRD). Luminescence properties at room temperature (RT) of different amount of Sm3+ and 2 mol% Eu3+ doped ZnO QDs were examined in-depth by optical spectra. In contrast to the Pr3+/Eu3+ co-doped fluorescent performance researched in our previous study, the photoluminescence (PL) spectra indicates the unique luminescence properties of Sm3+/Eu3+ co-doped ZnO QDs. In addition, fluorescence lifetimes were obtained to illustrate the luminous mechanism. PMID:27451672

  11. Study of Doped ZnO Films Synthesized by Combining Vapor Gases and Pulsed Laser Deposition

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, Ching-Hua; Lehoczky, Sandor L.; George, M. A.

    2000-01-01

    The properties and structure of the ZnO material are similar to those of the GaN. Since an excitonic binding energy of ZnO is about 60 meV, it has strong potential for excitonic lasing at the room temperature. This makes synthesizing ZnO films for applications attractive. However, there are several hurdles in fabricating electro-optical devices from ZnO. One of those is in growing doped p-type ZnO films. Although techniques have been developed for the doping of both p-type and n-type ZnO, this remains an area that can be improved. In this presentation, we will report the experimental results of using both thermal vapor and pulsed laser deposition to grow doped ZnO films. The films are deposited on (0001) sapphire, (001) Si and quartz substrates by ablating a ZnO target. The group III and V elements are introduced into the growth chamber using inner gases. Films are characterized by x-ray diffraction, scanning probe microscopy, energy dispersive spectroscopy, Auger electron spectroscopy, and electrical measurements. The full width at half maximum of theta rocking curves for epitaxial films is less than 0.5 deg. In textured films, it rises to several degrees. Film surface morphology reveals an island growth pattern, but the size and density of these islands vary with the composition of the reactive gases. The electrical resistivity also changes with the doped elements. The relationship between the doping elements, gas composition, and film properties will be discussed.

  12. Enhanced visible light photocatalytic performance of ZnO nanowires integrated with CdS and Ag2S.

    PubMed

    Chen, Chienhua; Li, Zhengcao; Lin, Hehnan; Wang, Guojing; Liao, Jiecui; Li, Mingyang; Lv, Shasha; Li, Wei

    2016-02-18

    A series of ZnO-CdS-Ag2S ternary nanostructures with different amounts of Ag2S were prepared using simple and low-cost successive ionic layer adsorption and reaction (SILAR) and a chemical precipitation method. The ZnO nanowires, with a diameter of ∼100 nm and a length of ∼1 μm, were modified by coating CdS and Ag2S. CdS has a high absorption coefficient and can efficiently match with the energy levels of ZnO, which can enhance the light absorption ability of the nanostructures. In addition, Ag2S with a narrow band gap was used as the main light absorber and played an important role in increasing the light absorption in the visible light region. The photocatalytic activity of the ZnO-CdS-Ag2S ternary nanostructures was investigated using the degradation of methyl orange (MO) in an aqueous solution under visible light. The ZnO-CdS-Ag2S ternary nanostructures were found to be more efficient than ZnO nanowires, ZnO-CdS nanowires, and ZnO-Ag2S nanowires. There is 7.68 times more photocatalytic activity for MO degradation in terms of the rate constant for ZnO-CdS-Ag2S 15-cycle ternary nanostructure compared to the as-grown ZnO. Furthermore, the effect of the amount of Ag2S and CdS on the ZnO surface on the photocatalytic activity was analyzed. The superior photo-absorption properties and photocatalytic performance of the ZnO-CdS-Ag2S ternary nanostructures can be ascribed to the heterostructure, which enhanced the separation of the photo-induced electron-hole pairs. In addition, visible light could be absorbed by ZnO-CdS-Ag2S ternary nanostructures rather than by ZnO. PMID:26815888

  13. Control of point defects and grain boundaries in advanced materials. Optical properties and diffusion induced by Li doping in ZnO

    NASA Astrophysics Data System (ADS)

    Nakagawa, Tsubasa; Sakaguchi, Isao; Matsunaga, Katsuyuki; Yamamoto, Takahisa; Haneda, Hajime; Ikuhara, Yuichi

    2005-05-01

    Nickel diffusion in non-doped and Li-doped polycrystalline ZnO was studied to investigate the dominant lattice defect introduced by the reaction of incorporated Li. Li-doped ZnO exhibited new emission at 393 nm. Li doping increased the Ni lattice diffusion coefficients in ZnO, but its effect on Ni grain boundary diffusion was very small. These results can be understood as Li incorporation in the ZnO lattice.

  14. Spectroscopic Study on Eu3+ Doped Borate Glasses Containing Ag Nanoparticles and Ag Aggregates.

    PubMed

    Fu, Shaobo; Zheng, Hui; Zhang, Jinsu; Li, Xiangping; Sun, Jiashi; Hua, Ruinian; Dong, Bin; Xia, Haiping; Chen, Baojiu

    2015-01-01

    Transparent Eu(3+)-doped borate glasses containing Ag nanoparticles and Ag aggregates with composition (40 - x) CaO-59.5B2O3-0.5Eu2O3-xAgNO3 were prepared by a simple one-step melt-quenching technique. The X-ray diffraction (XRD) patterns of the glasses reveal amorphous structural properties and no diffraction peaks belonging to metal Ag particles. Ag particles and Ag aggregates were observed from the absorption spectra. Effective energy transfers from the Ag aggregates to the Eu3+ ions were observed in the excitation spectra from monitoring the intrinsic emission of Eu3+x .5D0 --> 7F2. The glasses with higher Ag content can be effectively excited by light in a wide wavelength region, indicating that these glasses have potential application in the solid state lighting driven by semiconductor light emitting diodes (LEDs). The emission spectra of the samples with higher Ag contents exhibit plenteous spectral components covering the full visible region from violet to red, thus indicating that these glass materials possess an excellent and tunable color rendering index. The color coordinates for all the glass samples were calculated by using the intensity-corrected emission spectra and the standard data issued by the CIE (Commission International de l' Eclairage) in 1931. It was found that the color coordinates for most samples with higher Ag contents fall into the white region in the color space. PMID:26328363

  15. 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.

  16. Ferromagnetic behaviour of Fe-doped ZnO nanograined films

    PubMed Central

    Protasova, Svetlana G; Mazilkin, Andrei A; Tietze, Thomas; Goering, Eberhard; Schütz, Gisela; Straumal, Petr B; Baretzky, Brigitte

    2013-01-01

    Summary The influence of the grain boundary (GB) specific area s GB on the appearance of ferromagnetism in Fe-doped ZnO has been analysed. A review of numerous research contributions from the literature on the origin of the ferromagnetic behaviour of Fe-doped ZnO is given. An empirical correlation has been found that the value of the specific grain boundary area s GB is the main factor controlling such behaviour. The Fe-doped ZnO becomes ferromagnetic only if it contains enough GBs, i.e., if s GB is higher than a certain threshold value s th = 5 × 104 m2/m3. It corresponds to the effective grain size of about 40 μm assuming a full, dense material and equiaxial grains. Magnetic properties of ZnO dense nanograined thin films doped with iron (0 to 40 atom %) have been investigated. The films were deposited by using the wet chemistry “liquid ceramics” method. The samples demonstrate ferromagnetic behaviour with J s up to 0.10 emu/g (0.025 μB/f.u.ZnO) and coercivity H c ≈ 0.03 T. Saturation magnetisation depends nonmonotonically on the Fe concentration. The dependence on Fe content can be explained by the changes in the structure and contiguity of a ferromagnetic “grain boundary foam” responsible for the magnetic properties of pure and doped ZnO. PMID:23844341

  17. Influence of nitrogen and magnesium doping on the properties of ZnO films

    NASA Astrophysics Data System (ADS)

    Dong-hua, Li; Hui-Qiong, Wang; Hua, Zhou; Ya-Ping, Li; Zheng, Huang; Jin-Cheng, Zheng; Jia-Ou, Wang; Hai-jie, Qian; Kurash, Ibrahim; Xiaohang, Chen; Huahan, Zhan; Yinghui, Zhou; Junyong, Kang

    2016-07-01

    Undoped ZnO and doped ZnO films were deposited on the MgO(111) substrates using oxygen plasma-assisted molecular beam expitaxy. The orientations of the grown ZnO thin film were investigated by in situ reflection high-energy electron diffraction and ex situ x-ray diffraction (XRD). The film roughness was measured by atomic force microscopy, which was correlated with the grain sizes determined by XRD. Synchrotron-based x-ray absorption spectroscopy was performed to study the doping effect on the electronic properties of the ZnO films, compared with density functional theory calculations. It is found that, nitrogen doping would hinder the growth of thin film, and generate the NO defect, while magnesium doping promotes the quality of nitrogen-doped ZnO films, inhibiting (N2)O production and increasing nitrogen content. Project supported by the National Natural Science Foundation of China (Grant Nos. 11204253, U1332105, 61227009, and 91321102), the Fundamental Research Funds for Central Universities, China (Grant No. 20720160020), and the National High Technology Research and Development Program of China (Grant No. 2014AA052202).

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

    NASA Astrophysics Data System (ADS)

    Singh, J.; Chanda, A.; Gupta, S.; Shukla, P.; Chandra, V.

    2016-05-01

    Cobalt doped ZnO nanoparticles of uniform sizes were prepared by a chemical method using ZnCl2 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. The absorption band at 857 cm-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.

  19. Structural, electronic and optical properties of Cu-doped ZnO: experimental and theoretical investigation

    NASA Astrophysics Data System (ADS)

    Horzum, S.; Torun, E.; Serin, T.; Peeters, F. M.

    2016-06-01

    Experiments are supplemented with ab initio density functional theory (DFT) calculations in order to investigate how the structural, electronic and optical properties of zinc oxide (ZnO) thin films are modified upon Cu doping. Changes in characteristic properties of doped thin films, that are deposited on a glass substrate by sol-gel dip coating technique, are monitored using X-ray diffraction (XRD) and UV measurements. Our ab initio calculations show that the electronic structure of ZnO can be well described by DFT+U/? method and we find that Cu atom substitutional doping in ZnO is the most favourable case. Our XRD measurements reveal that the crystallite size of the films decrease with increasing Cu doping. Moreover, we determine the optical constants such as refractive index, extinction coefficient, optical dielectric function and optical energy band gap values of the films by means of UV-Vis transmittance spectra. The optical band gap of ZnO the thin film linearly decreases from 3.25 to 3.20 eV at 5% doping. In addition, our calculations reveal that the electronic defect states that stem from Cu atoms are not optically active and the optical band gap is determined by the ZnO band edges. Experimentally observed structural and optical results are in good agreement with our theoretical results.

  20. Optical properties of Li-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Valentini, Antonio; Quaranta, Fabio; Vasanelli, Lorenzo; Piccolo, R.

    1991-03-01

    The difficulty to achieve a refractive index matching between active substrate and active layer grown on, is one of the main problem in integrated optical devices based on gallium arsenide, because of its high refractive index value. One possible solution could be an active layer whose refractive index is variable during the grown. Zinc oxide is a very interesting material because of its electro-optic and acousto- optic properties. It has a low cost and can be prepared by a variety of techniques. In this paper deposition of lithium doped zinc oxide films by reactive sputtering has been investigated in order to study the dependence of optical properties on lithium content and deposition parameters. A ZnO:Li target was used. The film depositions were performed varying the oxygen content in sputtering gas. For comparison undoped ZnO films were also prepared. We have performed optical and electrical measurement on films relating the results to Li contents and O/Zn ratio obtained by nuclear reaction and Rutherford backscattering measurements respectively. The film analysis has shown that dopant concentration is mainly controlled by gas mixture. The optical properties are dependent on deposition conditions. Optical waveguides have been prepared and characterized. The results are presented and discussed.

  1. Theoretical and experimental investigation of stability and spectra of doped Ag:ZnSe nanocrystals.

    PubMed

    Xu, Shuhong; Wang, Chunlei; Wang, Zhuyuan; Cui, Yiping

    2014-04-01

    In experiment, doped Ag:ZnSe nanocrystals (NCs) had better stability than that of ZnSe nanocrystals under ambient atmospheres in the presence of air and light illumination. However, it is difficult to explain the mechanism of better stability of Ag:ZnSe nanocrystals from the experiment perspective for doped nanocrystals are more unstable than corresponding pure nanocrystals in general. Using B3LYP/LANL2DZ method, we have investigated the geometrical structures, bonding characters, and molecular orbitals (MOs) of hexagonal and tetrahedral Ag doped ZnSe structures in theory. The results showed that the good stability of Ag:ZnSe nanocrystals can be attributed to the stronger binding between Ag and Se. Moreover, we have proved that Ag doped ZnSe nanocrystals synthesized in experiment should be substituting doped but not vacuity doped. Substituting Ag doped ZnSe molecules have the same configuration as that of the ZnSe structure, but vacuity doped Ag:ZnSe have completely different configuration than ZnSe structure due to the big size of Ag atom. In addition, through contrast of MO of ZnSe and Ag doped ZnSe, we have testified that Ag easily formed bonds with Se. The high binding energy and high probability of forming bonds with Se atom make Ag doped ZnSe nanocrystals have better stability than that of ZnSe nanocrystals. PMID:24633779

  2. Heteroepitaxial growth of nonpolar Cu-doped ZnO thin film on MnS-buffered (100) Si substrate

    NASA Astrophysics Data System (ADS)

    Nakamura, Tatsuru; Nguyen, Nam; Nagata, Takahiro; Takahashi, Kenichiro; Ri, Sung-Gi; Ishibashi, Keiji; Suzuki, Setsu; Chikyow, Toyohiro

    2015-06-01

    The preparation of nonpolar ZnO and Cu-doped ZnO thin films on Si substrates was studied for the application to the fabrication of green-light-emitting diodes. The use of rocksalt MnS and wurtzite AlN as buffer layers is a key technology for achieving the heteroepitaxial growth of nonpolar ZnO thin film on a (100) Si substrate. X-ray diffraction and photoluminescence measurements revealed that deposition under a high oxygen partial pressure (∼1 Torr) can enhance the nonpolar crystallization of undoped ZnO, and can simultaneously suppress the formation of defects such as oxygen vacancies. These techniques can be also applied to the growth of Cu-doped ZnO. A room-temperature photoluminescence study revealed that nonpolar [11\\bar{2}0]-oriented Cu-doped ZnO film exhibits enhanced green emission owing to the doped Cu ions.

  3. Tuning the properties of ZnO, hematite, and Ag nanoparticles by adjusting the surface charge.

    PubMed

    Zhang, Jianhui; Dong, Guanjun; Thurber, Aaron; Hou, Yayi; Gu, Min; Tenne, Dmitri A; Hanna, C B; Punnoose, Alex

    2012-03-01

    A poly (acryl acid) (PAA) post-treatment method is performed to modify the surface charge of ZnO nanospheres, hematite nanocubes, and Ag nanoprisms from highly positive to very negative by adjusting the PAA concentration, to and greatly modify their photoluminescence, cytotoxicity, magnetism, and surface plasmon resonance. This method provides a general way to tune the nanoparticle properties for broad physicochemical and biological applications. PMID:22298490

  4. Large lateral photovoltaic effect observed in nano Al-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Lu, Jing; Wang, Hui

    2011-07-01

    Zinc oxide (ZnO), including a variety of metal-doped ZnO, as one kind of most important photoelectric materials, has been widely investigated and received enormous attention for a series of applications. In this work, we report a new finding which we call as lateral photovoltaic effect (LPE) in a nano Al-doped ZnO (ZAO) film based on ZAO/SiO2/Si homo-heterostructure. This large and stable LPE observed in ZAO is an important supplement to the existing ZnO properties. In addition, all data and analyses demonstrate ZAO film can also be a good candidate for new type position-sensitive detector (PSD) devices.

  5. Effect of Ga-doping on the properties of ZnO nanowire

    SciTech Connect

    Ishiyama, Takeshi Nakane, Takaya Fujii, Tsutomu

    2015-02-27

    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 nm and green emission around 510 nm. Moreover, the green emission reduced in Ga-doped sample.

  6. Doping concentration driven morphological evolution of Fe doped ZnO nanostructures

    SciTech Connect

    Sahai, A.; Goswami, N.; Kumar, Y.; Agarwal, V.; Olive-Méndez, S. F.

    2014-10-28

    In this paper, systematic study of structural, vibrational, and optical properties of undoped and 1-10 at.% Fe doped ZnO nanostructures, synthesized adopting chemical precipitation route, has been reported. Prepared nanostructures were characterized employing an assortment of microscopic and spectroscopic techniques, namely Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray (EDX) Spectroscopy, X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Micro-Raman Spectroscopy (μRS), and UV-visible and Photoluminescence (PL) spectroscopy. With Fe incorporation, a gradual morphological transformation of nanostructures is demonstrated vividly through SEM/TEM characterizations. Interestingly, the morphology of nanostructures evolves with 1–10 at. % Fe doping concentration in ZnO. Nanoparticles obtained with 1 at. % Fe evolve to nanorods for 3 at. % Fe; nanorods transform to nanocones (for 5 at. % and 7 at. % Fe) and finally nanocones transform to nanoflakes at 10 at. % Fe. However, at all these stages, concurrence of primary hexagonal phase of Zn{sub 1-x}Fe{sub x}O along with the secondary phases of cubic ZnFe{sub 2}O{sub 4} and rhombohedric Fe{sub 2}O{sub 3}, is revealed through XRD analysis. Based on collective XRD, SEM, TEM, and EDX interpretations, a model for morphological evolution of nanostructures was proposed and the pivotal role of Fe dopant was deciphered. Furthermore, vibrational properties analyzed through Raman and FTIR spectroscopies unravel the intricacies of formation and gradual enhancement of secondary phases with increased Fe concentration. UV-visible and PL spectroscopic analyses provided further insight of optical processes altering with Fe incorporation. The blue shift and gradual quenching of visible photoluminescence with Fe doping was found in accordance with structural and vibrational analyses and explicated accordingly.

  7. Effect of Substrate Temperature on The Structural and Optical Properties of Non-doped ZnO Thin Films

    SciTech Connect

    Ilican, Saliha; Caglar, Mujdat; Caglar, Yasemin

    2007-04-23

    Transparent conducting non-doped zinc oxide (ZnO) thin films have been deposited by the spray pyrolysis method at different substrate temperatures. X-ray diffraction spectra of the films have shown that the films are polycrystalline and hexagonal wurtzite in structure. From these spectra, grain size and texture coefficient (TC) are calculated. The analytical method for calculating lattice constants is used to calculate a and c for the films. The preferred orientation of non-doped ZnO thin films was changed with substrate temperature. The average optical transmittance of non-doped ZnO thin films was over 80% in the visible range. The optical band gap and optical constants of the non-doped ZnO thin films were evaluated as dependent on the substrate temperatures. The substrate temperature have a significant effect on structural and optical properties of the non-doped ZnO thin films.

  8. Electrical and optical properties of in and Al doped ZnO thin film

    NASA Astrophysics Data System (ADS)

    Park, Sang-Uk; Koh, Jung-Hyuk

    2013-07-01

    In this study, to improve the electrical and optical properties of aluminium (Al) doped zinc oxide thin films, we have added small amounts of indium (In) to Al doped ZnO thin films. We will present the results of In and Al doped ZnO thin film on glass substrates prepared by the sol-gel processing method. A rapid thermal annealing process was applied to cure the thin film properties. Different amounts of In were used to dope the AZO thin films to find the optimum process condition. The effects of crystallinity were analyzed by an x-ray diffraction method. In addition, the optical transmittance and electrical proprties of In doped AZO thin films were investigated.

  9. 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

  10. La-doped ZnO nanoparticles: Simple solution-combusting preparation and applications in the wastewater treatment

    SciTech Connect

    Wu, Tingting; Ni, Yonghong; Ma, Xiang; Hong, Jianming

    2013-11-15

    Graphical abstract: La-doped ZnO nanoparticles have been successfully prepared by a simple solution combustion route and exhibit good adsorption for Cu and Pb ion from water systems. - Highlights: • La-doped ZnO nanoparticles were successfully prepared via a simple solution-combustion route. • The integration of La{sup 3+} ions into ZnO decreased the band-gap of ZnO nanoparticles. • La-doped ZnO nanoparticles could remove more Pb and Cu ions from water resources than undoped ZnO. - Abstract: La-doped ZnO nanoparticles have been successfully synthesized by a simple solution combustion method via employing a mixture of ethanol and ethyleneglycol (v/v = 60/40) as the solvent. Zinc acetate and oxygen gas in the atmosphere were used as zinc and oxygen sources, and La(NO{sub 3}){sub 3} as the doping reagent. The as-obtained product was characterized by means of powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectrometry and X-ray photoelectron spectroscopy. Experiments showed that La-doped ZnO nanoparticles exhibited the higher capacities for the removal of Pb{sup 2+} and Cu{sup 2+} ions in water resource than undoped ZnO nanoparticles.

  11. Structural and optical properties of cobalt doped ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Li, Meihui; Xu, Jianping; Chen, Ximing; Zhang, Xiaosong; Wu, Yanyu; Li, Ping; Niu, Xiping; Luo, Chengyuan; Li, Lan

    2012-10-01

    Zn1-xCoxO nanocrystals with nominal Co doping concentrations of x = 0-0.1 were synthesized through a simple solution route followed by a calcining process. The doping effects on the structural, morphological and optical properties were investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman, absorption and luminescence spectroscopy. The results indicated that a small amount of Co ions were incorporated into ZnO lattice structure, whereas the secondary phase of Co3O4 was segregated and precipitated at high Co doping concentrations, the solid solubility of Co ions in ZnO nanocrystals could be lower than 0.05. The spectra related to transitions within the tetrahedral Co2+ ions in the ZnO host crystal were observed in absorption and luminescence spectra.

  12. Role of Ni doping on transport properties of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Dar, Tanveer Ahmad; Agrawal, Arpana; Sen, Pratima

    2015-06-01

    Nickel doped (Ni=0.05) and undoped Zinc Oxide (ZnO) thin films have been prepared by Pulsed laser deposition (PLD) technique. The structural analysis of the films was done by X-ray diffraction (XRD) studies which reveal absence of any secondary phase in the prepared samples. UV transmission spectra show that Ni doping reduces the transparency of the films. X-ray Photoelectron spectroscopy (XPS) also shows the presence of metallic Ni along with +2 oxidation state in the sample. Low temperature magneto transport properties of the ZnO and NiZnO films are also discussed in view of Khosla fisher model. Ni doping in ZnO results in decrease in magnitude of negative MR.

  13. Role of Ni doping on transport properties of ZnO thin films

    SciTech Connect

    Dar, Tanveer Ahmad Agrawal, Arpana; Sen, Pratima

    2015-06-24

    Nickel doped (Ni=0.05) and undoped Zinc Oxide (ZnO) thin films have been prepared by Pulsed laser deposition (PLD) technique. The structural analysis of the films was done by X-ray diffraction (XRD) studies which reveal absence of any secondary phase in the prepared samples. UV transmission spectra show that Ni doping reduces the transparency of the films. X-ray Photoelectron spectroscopy (XPS) also shows the presence of metallic Ni along with +2 oxidation state in the sample. Low temperature magneto transport properties of the ZnO and NiZnO films are also discussed in view of Khosla fisher model. Ni doping in ZnO results in decrease in magnitude of negative MR.

  14. Fe doped ZnO thin film for mediator-less biosensing application

    NASA Astrophysics Data System (ADS)

    Saha, Shibu; Tomar, Monika; Gupta, Vinay

    2012-05-01

    Fe doped ZnO (FZO) thin film is prepared by pulsed laser deposition for its application as mediator-less biosensing matrix. Fe doping introduces redox centre in ZnO along with shallow donor level and promotes the electron transfer capability due to substitution of Fe at Zn sites. Glucose oxidase (GOx), chosen as model enzyme, was immobilized on surface of the prepared matrix. Cyclic voltammetry and photometric assay show that the developed bio-electrode, GOx/FZO/indium tin oxide/Glass is sensitive to glucose concentration with enhanced response (0.2 µA mM-1 cm-2) and low Km (3.01 mM). The results show promising application of Fe doped ZnO thin film as an attractive matrix for mediator-less biosensing.

  15. Room temperature ferromagnetism in Mg-doped ZnO nanoparticles

    SciTech Connect

    Singh, Jaspal Vashihth, A.; Gill, Pritampal Singh; Verma, N. K.

    2015-06-24

    Zn{sub 1-x}Mg{sub x}O (x = 0, 0,10) nanoparticles were successfully synthesized using sol-gel method. X-ray diffraction (XRD) confirms that the synthesized nanoparticles possess wurtzite phase having hexagonal structure. Morphological analysis was carried out using transmission electron microscopy (TEM) which depicts the spherical morphology of ZnO nanoparticles. Energy dispersive spectroscopy (EDS) showed the presence of Mg in ZnO nanoparticles. Electron spin resonance (ESR) signal was found to be decreasing with increasing of Mg-doping concentration. The room temperature ferromagnetism was observed in undoped and Mg-doped ZnO nanoparticles. The increase of Mg-doping concentration resulted in decrease of saturation magnetization value which could be attributed to decrease of oxygen vacancies present in host nanoparticles.

  16. Effect of Fe doping concentration on photocatalytic activity of ZnO nanosheets under natural sunlight

    SciTech Connect

    Khokhra, Richa; Kumar, Rajesh

    2015-05-15

    A facile room temperature, aqueous solution-based chemical method has been adopted for large-scale synthesis of Fe doped ZnO nanosheets. The XRD and SEM results reveal the as-synthesized products well crystalline and accumulated by large amount of interweave nanosheets, respectively. Energy dispersive spectroscopy data confirmed Fe doping of the ZnO nanosheets with a varying Fe concentration. The photoluminescence spectrum reveals a continuous suppression of defect related emissions intensity by increasing the concentration of the Fe ion. A photocatalytic activity using these samples under sunlight irradiation in the mineralization of methylene blue dye was investigated. The photocatalytic activity of Fe doped ZnO nanosheets depends upon the presence of surface oxygen vacancies.

  17. Fabrication of p-type Li-doped ZnO films by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Xiao, Bin; Ye, Zhizhen; Zhang, Yinzhu; Zeng, Yujia; Zhu, Liping; Zhao, Binghui

    2006-11-01

    p-Type ZnO thin films have been realized via doping Li as acceptor by using pulsed laser deposition. In our experiment, Li 2CO 3 was used as Li precursor, and the growth temperature was varied from 400 to 600 °C in pure O 2 ambient. The Li-doped ZnO film prepared at 450 °C possessed the lowest resistivity of 34 Ω cm with a Hall mobility of 0.134 cm 2 V -1 s -1 and hole concentration of 1.37 × 10 18 cm -3. X-ray diffraction (XRD) measurements showed that the Li-doped ZnO films grown at different substrate temperatures were of completely (0 0 2)-preferred orientation.

  18. Effect of Mn doping on the microstructures and sensing properties of ZnO nanofibers

    NASA Astrophysics Data System (ADS)

    Mao, Yuzhen; Ma, Shuyi; Li, Xiangbing; Wang, Caiyun; Li, Faming; Yang, Xiaohong; Zhu, Jing; Ma, Lin

    2014-04-01

    Zinc oxide (ZnO) nanofibers doped with manganese (Mn) are synthesized by electrospinning followed by calcinations at 580 °C for 150 min. The structure, morphology and element-composition are investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results show that the diameters of Mn-doped ZnO nanofibers are from 60 nm to 90 nm corresponding to the amount of Mn from 0 wt% to 2.0 wt%, respectively. XPS spectrum indicates that Mn2+ ions exist in divalent state. The gas sensing properties are significantly affected by the Mn-doped ZnO nanofibers and the operation temperature. The sensors exhibit excellent sensitivity, practical selectivity and stability to acetone with a fast response and recovery time at 340 °C.

  19. Gas sensing properties of Al-doped ZnO for UV-activated CO detection

    NASA Astrophysics Data System (ADS)

    Dhahri, R.; Hjiri, M.; El Mir, L.; Bonavita, A.; Iannazzo, D.; Latino, M.; Donato, N.; Leonardi, S. G.; Neri, G.

    2016-04-01

    Al-doped ZnO (AZO) samples were prepared using a modified sol-gel route and charaterized by means of trasmission electron microscopy, x-ray diffraction and photoluminescence analysis. Resistive planar devices based on thick films of AZO deposited on interdigitated alumina substrates were fabricated and investigated as UV light activated CO sensors. CO sensing tests were performed in both dark and illumination condition by exposing the samples to UV radiation (λ  =  400 nm).Under UV light, Al-doped ZnO gas sensors operated at lower temperature than in dark. Furthermore, by photoactivation we also promoted CO sensitivity and made signal recovery of AZO sensors faster. Results demonstrate that Al-doped ZnO might be a promising sensing material for the detection of CO under UV illumination.

  20. Morphological properties of Al-doped ZnO nano/microstructures

    NASA Astrophysics Data System (ADS)

    Kim, Kyung Ho; Umakoshi, Tomoyuki; Abe, Yoshio; Kawamura, Midori; Kiba, Takayuki

    2016-03-01

    We discussed the morphological properties of Al-doped zinc oxide (Al-ZnO) microrods grown on a ZnO seed layer and precipitation particles and compared them with undoped ZnO samples. The ZnO nanorods grown on a ZnO seed layer were dense and perpendicular to the surface of the substrate, i.e., fluorine-doped tin oxide (FTO). In contrast the Al-ZnO grew as larger microrods, and the rods were sparsely and obliquely arranged. Precipitation particles synthesized in the ZnO solution through homogeneous nucleation had flower-like structures assembled from the rods and individual rods with lengths of several micrometers. Al-ZnO precipitation particles consisted of rods with length of several micrometers and hexagonal nanoplates. Fourier transform infrared (FTIR) analysis results showed that the rods and precipitation particles had the good chemical properties of ZnO. Both size and morphology of the rods could be effectively controlled by adding aluminum nitrate (Al(NO3)3) as dopant in the ZnO rod solution.

  1. Influence Al doped ZnO nanostructure on structural and optical properties

    NASA Astrophysics Data System (ADS)

    Ramelan, Ari Handono; Wahyuningsih, Sayekti; Chasanah, Uswatul; Munawaroh, Hanik

    2016-04-01

    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 cause 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.

  2. Preparation and antibacterial properties of titanium-doped ZnO from different zinc salts

    PubMed Central

    2014-01-01

    To research the relationship of micro-structures and antibacterial properties of the titanium-doped ZnO powders and probe their antibacterial mechanism, titanium-doped ZnO powders with different shapes and sizes were prepared from different zinc salts by alcohothermal method. The ZnO powders were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED), and the antibacterial activities of titanium-doped ZnO powders on Escherichia coli and Staphylococcus aureus were evaluated. Furthermore, the tested strains were characterized by SEM, and the electrical conductance variation trend of the bacterial suspension was characterized. The results indicate that the morphologies of the powders are different due to preparation from different zinc salts. The XRD results manifest that the samples synthesized from zinc acetate, zinc nitrate, and zinc chloride are zincite ZnO, and the sample synthesized from zinc sulfate is the mixture of ZnO, ZnTiO3, and ZnSO4 · 3Zn (OH)2 crystal. UV-vis spectra show that the absorption edges of the titanium-doped ZnO powders are red shifted to more than 400 nm which are prepared from zinc acetate, zinc nitrate, and zinc chloride. The antibacterial activity of titanium-doped ZnO powders synthesized from zinc chloride is optimal, and its minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) are lower than 0.25 g L−1. Likewise, when the bacteria are treated by ZnO powders synthesized from zinc chloride, the bacterial cells are damaged most seriously, and the electrical conductance increment of bacterial suspension is slightly high. It can be inferred that the antibacterial properties of the titanium-doped ZnO powders are relevant to the microstructure, particle size, and the crystal. The powders can damage the

  3. Synthesis and characterization of ZnO and Ni doped ZnO nanorods by thermal decomposition method for spintronics application

    SciTech Connect

    Saravanan, R.; Santhi, Kalavathy; Sivakumar, N.; Narayanan, V.; Stephen, A.

    2012-05-15

    Zinc oxide nanorods and diluted magnetic semiconducting Ni doped ZnO nanorods were prepared by thermal decomposition method. This method is simple and cost effective. The decomposition temperature of acetate and formation of oxide were determined by TGA before the actual synthesis process. The X-ray diffraction result indicates the single phase hexagonal structure of zinc oxide. The transmission electron microscopy and scanning electron microscopy images show rod like structure of ZnO and Ni doped ZnO samples with the diameter {approx} 35 nm and the length in few micrometers. The surface analysis was performed using X-ray photoelectron spectroscopic studies. The Ni doped ZnO exhibits room temperature ferromagnetism. This diluted magnetic semiconducting Ni doped ZnO nanorods finds its application in spintronics. - Highlights: Black-Right-Pointing-Pointer The method used is very simple and cost effective compared to all other methods for the preparation DMS materials. Black-Right-Pointing-Pointer ZnO and Ni doped ZnO nanorods Black-Right-Pointing-Pointer Ferromagnetism at room temperature.

  4. Band Gap Narrowing and Widening of ZnO Nanostructures and Doped Materials.

    PubMed

    Kamarulzaman, Norlida; Kasim, Muhd Firdaus; Rusdi, Roshidah

    2015-12-01

    Band gap change in doped ZnO is an observed phenomenon that is very interesting from the fundamental point of view. This work is focused on the preparation of pure and single phase nanostructured ZnO and Cu as well as Mn-doped ZnO for the purpose of understanding the mechanisms of band gap narrowing in the materials. ZnO, Zn0.99Cu0.01O and Zn0.99Mn0.01O materials were prepared using a wet chemistry method, and X-ray diffraction (XRD) results showed that all samples were pure and single phase. UV-visible spectroscopy showed that materials in the nanostructured state exhibit band gap widening with respect to their micron state while for the doped compounds exhibited band gap narrowing both in the nano and micron states with respect to the pure ZnO materials. The degree of band gap change was dependent on the doped elements and crystallite size. X-ray photoelectron spectroscopy (XPS) revealed that there were shifts in the valence bands. From both UV-visible and XPS spectroscopy, it was found that the mechanism for band gap narrowing was due to the shifting of the valance band maximum and conduction band minimum of the materials. The mechanisms were different for different samples depending on the type of dopant and dimensional length scales of the crystallites. PMID:26319225

  5. Ruthenium Doped ZnO Semiconductor: Synthesis, Characterization and Photodegradation of Azo Dye

    NASA Astrophysics Data System (ADS)

    Aranganayagam, K. R.; Senthilkumaar, S.; Ganapathi Subramaniam, N.; Kang, T. Wang

    2013-04-01

    Ruthenium doped zinc oxide was synthesized by a simple sol-gel method via ultrasonication. The samples were characterized by X-ray diffraction, high resolution scanning electron microscopy (HR-SEM), high resolution transmission electron microscope (HR-TEM), energy dispersive spectroscopy (EDS) and UV-visible spectroscopy techniques and tested for the feasibility as a heterogeneous photocatalyst. The photocatalytic activity of Ru doped ZnO was tested using an azo dye, congo red (CR) in an aqueous solution, as a model compound. For comparison, the photocatalytic activity of pure ZnO was also performed. The parameters studied include the effect of initial CR concentration, photocatalyst weight and charge transfer phenomenon. The observed reaction mechanism was rationalized based on the elementary chemical reaction occurring in the irradiated heterogeneous reaction mixture. Total mineralization of CR was observed for both pure and Ru doped ZnO system. However, the photocatalytic activity of Ru doped ZnO was found to be higher than that of a pure ZnO.

  6. Development of a ReaxFF potential for Ag/Zn/O and application to Ag deposition on ZnO

    NASA Astrophysics Data System (ADS)

    Lloyd, A.; Cornil, D.; van Duin, A. C. T.; van Duin, D.; Smith, R.; Kenny, S. D.; Cornil, J.; Beljonne, D.

    2016-03-01

    A new empirical potential has been derived to model an Ag-Zn-O system. Additional parameters have been included into the reactive force field (ReaxFF) parameter set established for ZnO to describe the interaction between Ag and ZnO for use in molecular dynamics (MD) simulations. The reactive force field parameters have been fitted to density functional theory (DFT) calculations performed on both bulk crystal and surface structures. ReaxFF accurately reproduces the equations of state determined for silver, silver zinc alloy and silver oxide crystals via DFT. It also compares well to DFT binding energies and works of separation for Ag on a ZnO surface. The potential was then used to model single point Ag deposition on polar (000 1 bar) and non-polar (10 1 bar0) orientations of a ZnO wurtzite substrate, at different energies. Simulation results then predict that maximum Ag adsorption on a ZnO surface requires deposition energies of ≤ 10 eV.

  7. Growth of ferroelectric Li-doped ZnO thin films for metal-ferroelectric-semiconductor FET

    NASA Astrophysics Data System (ADS)

    Dhananjay; Nagaraju, J.; Choudhury, Palash Roy; Krupanidhi, S. B.

    2006-07-01

    A metal-ferroelectric-semiconductor structure has been developed by depositing Li-doped ZnO thin films (Zn1-xLixO, x = 0.25) on p-type Si substrates by the pulsed laser ablation technique. (002) preferential oriented films were deposited at a low growth temperature of 500 °C and 100 mTorr oxygen partial pressure. The dielectric response of the films has been studied over a temperature range 250 373 K. A dielectric anomaly was observed at 360 K. The capacitance voltage characteristics of Ag/Zn0.75Li0.25O/Si exhibited clockwise hysteresis loops with a memory window of 2 V. The films deposited at 100 mTorr pressure show a stable current density and a saturated polarization hysteresis loop with a remanent polarization of 0.09 µC cm-2 and coercive field of 25 kV cm-1. Leakage current measurements were done at elevated temperatures to provide evidence of the conduction mechanism present in these films. Ohmic behaviour was observed at low voltage, while higher voltages induced a bulk space charge. The optical properties of Zn0.75Li0.25O thin films were studied in the wavelength range 300 900 nm. The appearance of ferroelectric nature in Li-doped ZnO films adds an additional dimension to its applications.

  8. Ferromagnetism in Dilute Magnetic Semiconductors through Defect Engineering: Li-Doped ZnO

    NASA Astrophysics Data System (ADS)

    Yi, J. B.; Lim, C. C.; Xing, G. Z.; Fan, H. M.; van, L. H.; Huang, S. L.; Yang, K. S.; Huang, X. L.; Qin, X. B.; Wang, B. Y.; Wu, T.; Wang, L.; Zhang, H. T.; Gao, X. Y.; Liu, T.; Wee, A. T. S.; Feng, Y. P.; Ding, J.

    2010-04-01

    We demonstrate, both theoretically and experimentally, that cation vacancy can be the origin of ferromagnetism in intrinsic dilute magnetic semiconductors. The vacancies can be controlled to tune the ferromagnetism. Using Li-doped ZnO as an example, we found that while Li itself is nonmagnetic, it generates holes in ZnO, and its presence reduces the formation energy of Zn vacancy, and thereby stabilizes the zinc vacancy. Room temperature ferromagnetism with p type conduction was observed in pulsed laser deposited ZnO:Li films with certain doping concentration and oxygen partial pressure.

  9. Ferromagnetism in dilute magnetic semiconductors through defect engineering: Li-doped ZnO.

    PubMed

    Yi, J B; Lim, C C; Xing, G Z; Fan, H M; Van, L H; Huang, S L; Yang, K S; Huang, X L; Qin, X B; Wang, B Y; Wu, T; Wang, L; Zhang, H T; Gao, X Y; Liu, T; Wee, A T S; Feng, Y P; Ding, J

    2010-04-01

    We demonstrate, both theoretically and experimentally, that cation vacancy can be the origin of ferromagnetism in intrinsic dilute magnetic semiconductors. The vacancies can be controlled to tune the ferromagnetism. Using Li-doped ZnO as an example, we found that while Li itself is nonmagnetic, it generates holes in ZnO, and its presence reduces the formation energy of Zn vacancy, and thereby stabilizes the zinc vacancy. Room temperature ferromagnetism with p type conduction was observed in pulsed laser deposited ZnO:Li films with certain doping concentration and oxygen partial pressure. PMID:20481907

  10. Synthesis of manganese doped ZnO single crystals and their magnetization studies

    NASA Astrophysics Data System (ADS)

    Jayakumar, O. D.; Gopalakrishnan, I. K.; Sudakar, C.; Kulshreshtha, S. K.

    2006-09-01

    We report the synthesis of rod shaped Mn (2.2 at%) doped ZnO single crystals using the surfactant AOT (sodium bis (2-ethylhexyl) sulpho succinate) assisted solid-state synthesis route. The X-ray diffraction and transmission electron microsopy analyses showed the formation of impurity free single crystals of Mn doped ZnO with wurtzite structure. XPS data revealed that Mn exists in +2 oxidation state. DC magnetization measurements as a function of field and temperature showed that the sample is ferromagnetic above room temperature.

  11. Investigation of sol-gel yttrium doped ZnO thin films: structural and optical properties

    NASA Astrophysics Data System (ADS)

    Ivanova, T.; Harizanova, A.; Koutzarova, T.; Vertruyen, B.

    2016-02-01

    Nanostructured metal oxide films are extensively studied due to their numerous applications such as optoelectronic devices, sensors. In this work, we report the Y-Zn-O nanostructured films prepared by sol-gel technology from sols with different concentration of yttrium precursor, followed by post-annealing treatment. The Y doped ZnO thin films have been deposited on Si and quartz substrates by spin coating method, then treated at temperatures ranging from 300-800oC. XRD analysis reveals modification of the film structure and phases in the doped ZnO films.

  12. Local structure investigation of Co doped ZnO thin films prepared by RF sputtering technique

    NASA Astrophysics Data System (ADS)

    Yadav, A. K.; Haque, S. Maidul; Shukla, D.; Phase, D. M.; Jha, S. N.; Bhattacharyya, D.

    2016-05-01

    Co doped ZnO thin films have been prepared using rf magnetron sputtering technique with varying Co doping concentration. GIXRD has been used to probe long range order and Zn, Co and Oxygen K-edge XAFS measurements have been used for investigating local structure around Zn and Co atoms. GIXRD results show wurzite structure of the samples while XANES and EXAFS results at Zn and Co K edge show that Co is going at Zn site in ZnO matrix and no other phase is present. These results are further confirmed by O K edge and Co L2,3 edge XANES measurements.

  13. A facile green antisolvent approach to Cu2+-doped ZnO nanocrystals with visible-light-responsive photoactivities.

    PubMed

    Lu, Yi-Hsuan; Lin, Wei-Hao; Yang, Chao-Yao; Chiu, Yi-Hsuan; Pu, Ying-Chih; Lee, Min-Han; Tseng, Yuan-Chieh; Hsu, Yung-Jung

    2014-08-01

    An environmentally benign antisolvent method has been developed to prepare Cu(2+)-doped ZnO nanocrystals with controllable dopant concentrations. A room temperature ionic liquid, known as a deep eutectic solvent (DES), was used as the solvent to dissolve ZnO powders. Upon the introduction of the ZnO-containing DES into a bad solvent which shows no solvation to ZnO, ZnO was precipitated and grown due to the dramatic decrease of solubility. By adding Cu(2+) ions to the bad solvent, the growth of ZnO from the antisolvent process was accompanied by Cu(2+) introduction, resulting in the formation of Cu(2+)-doped ZnO nanocrystals. The as-prepared Cu(2+)-doped ZnO showed an additional absorption band in the visible range (400-800 nm), which conduced to an improvement in the overall photon harvesting efficiency. Time-resolved photoluminescence spectra, together with the photovoltage information, suggested that the doped Cu(2+) may otherwise trap photoexcited electrons during the charge transfer process, inevitably depressing the photoconversion efficiency. The photoactivity of Cu(2+)-doped ZnO nanocrystals for photoelectrochemical water oxidation was effectively enhanced in the visible region, which achieved the highest at 2.0 at% of Cu(2+). A further increase in the Cu(2+) concentration however led to a decrease in the photocatalytic performance, which was ascribed to the significant carrier trapping caused by the increased states given by excessive Cu(2+). The photocurrent action spectra illustrated that the enhanced photoactivity of the Cu(2+)-doped ZnO nanocrystals was mainly due to the improved visible photon harvesting achieved by Cu(2+) doping. These results may facilitate the use of transition metal ion-doped ZnO in other photoconversion applications, such as ZnO based dye-sensitized solar cells and magnetism-assisted photocatalytic systems. PMID:24954742

  14. Ultrasonic-assisted degradation of phenazopyridine with a combination of Sm-doped ZnO nanoparticles and inorganic oxidants.

    PubMed

    Eskandarloo, Hamed; Badiei, Alireza; Behnajady, Mohammad A; Ziarani, Ghodsi Mohammadi

    2016-01-01

    Pure and samarium doped ZnO nanoparticles were synthesized by a sonochemical method and characterized by TEM, SEM, EDX, XRD, Pl, and DRS techniques. The average crystallite size of pure and Sm-doped ZnO nanoparticles was about 20 nm. The sonocatalytic activity of pure and Sm-doped ZnO nanoparticles was considered toward degradation of phenazopyridine as a model organic contaminant. The Sm-doped ZnO nanoparticles with Sm concentration of 0.4 mol% indicated a higher sonocatalytic activity (59%) than the pure ZnO (51%) and other Sm-doped ZnO nanoparticles. It was believed that Sm(3+) ion with optimal concentration (0.4 mol%) can act as superficial trapping for electrons in the conduction band of ZnO and delayed the recombination of charge carriers. The influence of the nature and concentration of various oxidants, including periodate, hydrogen peroxide, peroxymonosulfate, and peroxydisulfate on the sonocatalytic activity of Sm-doped ZnO nanoparticles was studied. The influence of the oxidants concentration (0.2-1.4 g L(-1)) on the degradation rate was established by the 3D response surface and the 2D contour plots. The results demonstrated that the utilizing of oxidants in combination with Sm-doped ZnO resulting in rapid removal of contaminant, which can be referable to a dual role of oxidants; (i) scavenging the generated electrons in the conduction band of ZnO and (ii) creating highly reactive radical species under ultrasonic irradiation. It was found that the Sm-doped ZnO and periodate combination is the most efficient catalytic system under ultrasonic irradiation. PMID:26384896

  15. Visible WGM emissions from rare earth ion doped ZnO microspheres

    NASA Astrophysics Data System (ADS)

    K, Fabitha; Rao, M. S. Ramachandra

    ZnO is known to be an ideal candidate for short wavelength range opto-electronic device applications due to its wide and direct bandgap (3.37 eV) and high excitonic binding energy (60 meV). Apart from the UV emission at ~380 nm (free exciton emission) ZnO also possesses a broad emission band centered at ~530 nm which is expected to be originated from the oxygen vacancy (Vo) defects. In rare earth (RE) ion doped ZnO, emissions originate from the 4f levels of RE ions will be obtained in addition to the characteristic emissions of ZnO. Small micro/nanostructures made of ZnO with high crystalline quality show unique characteristics in light emission, especially in lasing applications. A micro/ nanostructured ZnO crystal generally has a wurtzite structure with a natural hexagonal cross section, which serves as a WGM lasing micro cavity owing to its high reflective index (~2). However, there exists a potential optical loss at corners of hexagons; therefore, an isotropic structure like spheres may be a better candidate to achieve efficient light confinement. In our work, highly smooth micro spheres with different diameters were grown. Raman spectroscopy measurements confirm the hexagonal wurtzite structure of ZnO, SEM and AFM studies shows the smooth surfaced spheres. WGM lasing characteristics of ZnO spheres have been investigated using optical pumping with 488 nm laser in a micro-PL system. Details of the results will be presented.

  16. 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.

  17. Characterization of co-doped (In, N): ZnO by indigenous thermopower measurement system

    NASA Astrophysics Data System (ADS)

    Kedia, Sanjay Kumar; Singh, Anil; Chaudhary, Sujeet

    2016-05-01

    The thermopower measurement of (In, N) co-doped ZnO thin films have been carried out using indigenous high and low temperature thermopower measurement system. The compact thermopower measurement system has been designed, developed, tested in house. The sensitivity and accuracy of indigenous thermopower system have been investigated by measuring thermopower of standard samples like Cu, Ni, Sb etc. It has been also investigated by the comparison of carrier concentration using Hall Effect and Thermopower measurement of these (In, N) co-doped ZnO thin films. The constant temperature gradient between hot and cold junction has been maintained by using the temperature controller. The room temperature and low temperature Seebeck coefficient measurements were performed on these co-doped ZnO samples. A series of experiments have been performed to detect the p-type conductivity in co-doped ZnO thin films, particularly at low temperature. The negative Seebeck coefficient observed down to 40 K established the n-type behavior in these co-doped samples.

  18. Al-doped ZnO nanocoatings obtained by sol-gel route

    NASA Astrophysics Data System (ADS)

    Mihaiu, S.; Toader, A.; Atkinson, I.; Anastasescu, M.; Vasilescu, M.; Zaharescu, M.; Plugaru, R.

    2010-11-01

    In recent years aluminum doped zinc oxide (AZO) film has attracted more attention due to many advantages including low cost, non-toxicity, and high stability to H2 plasma in comparison with indium tin oxide (ITO) film, the best known and used transparent conductive oxide (TCO) film. In this work, mono and multilayer Al-doped ZnO coatings have been obtained by dip coating sol-gel method on the glass and silicon supports. X-ray Diffraction, Atomic Force Microscopy (AFM) and Fluorescence Spectroscopy were used for the structural, morphological and optical characterization of the obtained coatings. The multilayer Al-doped ZnO coatings (after five layer depositions) on the silicon substrate present a polycrystalline wurtzite type structure with crystallite size of 20 nm. The AFM measurements have shown that no matter the support type, the Al-doped ZnO coatings present a similar morphology consisting in a smooth distribution of the circular grains leading also to similar values of the RMS roughness, around 2 nm. The photoluminescence properties of the Al-doped ZnO coatings depend on the number of depositions and type of substrate. Systematic study performed allows finding most suitable parameters for obtaining coatings with desired properties.

  19. Alternate deposition and hydrogen doping technique for ZnO thin films

    NASA Astrophysics Data System (ADS)

    Myong, Seung Yeop; Lim, Koeng Su

    2006-08-01

    We propose an alternate deposition and hydrogen doping (ADHD) technique for polycrystalline hydrogen-doped ZnO thin films, which is a sublayer-by-sublayer deposition based on metalorganic chemical vapor deposition and mercury-sensitized photodecomposition of hydrogen doping gas. Compared to conventional post-deposition hydrogen doping, the ADHD process provides superior electrical conductivity, stability, and surface roughness. Photoluminescence spectra measured at 10 K reveal that the ADHD technique improves ultraviolet and violet emissions by suppressing the green and yellow emissions. Therefore, the ADHD technique is shown to be very promising aid to the manufacture of improved transparent conducting electrodes and light emitting materials.

  20. p Doping in Expanded Phases of ZnO: An Ab Initio Study

    NASA Astrophysics Data System (ADS)

    Hapiuk, D.; Marques, Miguel A. L.; Melinon, P.; Flores-Livas, José A.; Botti, Silvana; Masenelli, B.

    2012-03-01

    The issue of p doping in nanostructured cagelike ZnO is investigated by state-of-the-art calculations. Our study is focused on one prototypical structure, namely, sodalite, for which we show that p-type doping is possible for elements of the V, VI, and VII columns of the periodic table. However, some dopants tend to form dimers, thus impairing the stability of this kind of doping. This difference of behavior is discussed, and two criteria are proposed to ensure stable p doping.

  1. First-principles study of diffusion of Li, Na, K and Ag in ZnO

    NASA Astrophysics Data System (ADS)

    Huang, Gui-Yang; Wang, Chong-Yu; Wang, Jian-Tao

    2009-08-01

    Based on ab initio total energy calculations, Li, Na and Ag interstitials are found to be stable with at least a 1.56 eV energy barrier to transform to a zinc substitutional site in ZnO, whereas K interstitial has a relatively small energy barrier at 0.79 eV. The isolated dopant substitutional defects (LiZn, NaZn, KZn and AgZn) are found to be rather stable, with at least a 3.4 eV energy barrier to transform to an interstitial site. All of the dopant interstitials (Lii, Nai, Ki and Agi) are fast diffusers. The diffusion of Li interstitial is isotropic, whereas the diffusion of Na, K and Ag interstitials is highly anisotropic. Fundamental processes of the vacancy-assisted mechanisms are systematically investigated and specific values of the energy barriers are obtained.

  2. The Synthesis of Ag-Doped Mesoporous TiO2

    SciTech Connect

    Li, Xiaohong S.; Fryxell, Glen E.; Wang, Chong M.; Engelhard, Mark H.

    2008-04-15

    Ag-doped mesoporous titanium oxide was prepared using non-ionic surfactants and easily handled titanium precursors, under mild reaction conditions. In contrast to the stabilizing effect of Cd-doping on mesoporous TiO2, Ag-doping was found to significantly destabilize the mesoporous structure.

  3. Effects of Oxide-Modified Spherical ZnO on Electrical Properties of Ag/ZnO Electrical Contact Material

    NASA Astrophysics Data System (ADS)

    Wei, Zhijun; Zhang, Lingjie; Shen, Tao; Qiao, Zhengyang; Yang, Hui; Fan, Xianping; Chen, Lawson

    2016-07-01

    Silver-zinc oxide (Ag/ZnO) electrical contact material is widely used as contacts of the medium duty switching devices. Effects of modified ZnO on properties of Ag/ZnO electrical contact material were investigated in this work. NiO and CuO were introduced to modify spherical ZnO by a chemical solution nano-coating method. Ag/ZnO contacts prepared using the modified spherical ZnO were produced by powder metallurgy (PM) method in a muffle furnace in temperature ranges from 750 to 900 °C. Results show that electrical conductivity, stability of relative density, and Vickers' hardness of Ag/ZnO electrical contact material can be improved by the addition of NiO because of the formation of NiO solid solution Zn0.2Ni0.8O. The addition of CuO to Ag/ZnO electrical contact material makes arcing energy and mass loss lower. Since this is attractive for a longer service life, using NiO and CuO co-modified ZnO as a second phase may be a promising way to improve properties of Ag/ZnO electrical contact material. Hence, the presented results could also be useful for the design of a new Ag/ZnO electrical contact material.

  4. Synthesis, structural and optical properties of pure ZnO and Co doped ZnO nanoparticles prepared by the co-precipitation method

    NASA Astrophysics Data System (ADS)

    Devi, P. Geetha; Velu, A. Sakthi

    2016-09-01

    Pure ZnO and Cobalt (Co) doped ZnO nanoparticles (NPs) were synthesized by the co-precipitation method. The synthesized nanoparticles retained the wurtzite hexagonal structure, which was confirmed by X-ray diffraction studies. From FESEM studies, ZnO and Co doped ZnO NPs showed Spherical and nanorod mixed phase and Spherical like morphology, respectively. The amount of dopant (Co2+) incorporated into ZnO sample was determined by EDAX. The FT-IR spectra confirmed the Zn-O stretching bands at 438 and 427 cm-1 for ZnO and Co doped ZnO NPs. From the UV-VIS spectroscopic measurements, the excitonic pecks were found around 376 and 370 nm for the respective samples. The photoluminescence measurements revealed that the broad emission was composed of seven different bands due to zinc vacancies, oxygen vacancies and surface defects. The dynamic light scattering (DLS) and Zeta potential measurements were used to find out the size and surface charges.

  5. Synthesis, structural and optical properties of pure ZnO and Co doped ZnO nanoparticles prepared by the co-precipitation method

    NASA Astrophysics Data System (ADS)

    Devi, P. Geetha; Velu, A. Sakthi

    2016-05-01

    Pure ZnO and Cobalt (Co) doped ZnO nanoparticles (NPs) were synthesized by the co-precipitation method. The synthesized nanoparticles retained the wurtzite hexagonal structure, which was confirmed by X-ray diffraction studies. From FESEM studies, ZnO and Co doped ZnO NPs showed Spherical and nanorod mixed phase and Spherical like morphology, respectively. The amount of dopant (Co2+) incorporated into ZnO sample was determined by EDAX. The FT-IR spectra confirmed the Zn-O stretching bands at 438 and 427 cm-1 for ZnO and Co doped ZnO NPs. From the UV-VIS spectroscopic measurements, the excitonic pecks were found around 376 and 370 nm for the respective samples. The photoluminescence measurements revealed that the broad emission was composed of seven different bands due to zinc vacancies, oxygen vacancies and surface defects. The dynamic light scattering (DLS) and Zeta potential measurements were used to find out the size and surface charges.

  6. Synthesis of nano-dimensional ZnO and Ga doped ZnO thin films by vapor phase transport and study as transparent conducting oxide.

    PubMed

    Ghosh, S; Saurav, M; Pandey, B; Srivastava, P

    2008-05-01

    We report synthesis of polycrystalline ZnO and Ga doped ZnO (ZnO:Ga) thin films (approximately 80 nm) on Si and quartz substrates in a non-vacuum muffle furnace, a simple and cost-effective route, without any catalyst/reactive carrier gases, at relatively low processing temperature of 550 degrees C. The crystalline phases of the films are identified by grazing angle X-ray diffraction (GAXRD). The growth of ZnO films is examined with scanning electron microscope (SEM) as a function of deposition time. An optical transmission of approximately 90% is observed for pure ZnO film having a resistivity of approximately 2.1 Omega-cm as measured by van der Pauw technique. Doping with Ga results in single phase ZnO:Ga films, retaining an optical transmission of about 80% and three orders of magnitude decrease in resistivity as compared to pure ZnO film. PMID:18572702

  7. Formation of Al-doped ZnO thin films on glass by sol-gel process and characterization

    NASA Astrophysics Data System (ADS)

    Shahid, M. U.; Deen, K. M.; Ahmad, A.; Akram, M. A.; Aslam, M.; Akhtar, W.

    2016-02-01

    In this study, pure ZnO and Al-doped ZnO thin films were developed on glass by sol-gel process followed by drying and annealing in air at 170 and 400 °C, respectively. The surface morphology and structural characteristics were determined through scanning electron microscopy, atomic force microscopy and X-ray diffraction. The Fourier transform infrared spectroscopy validated the formation of Al-doped ZnO film on glass substrate. It was evaluated that 1 at% aluminum (Al) doping in ZnO film showed low electrical resistivity and higher charge carrier concentration due to uniformly dispersed regular shape crystallites as compared to pure ZnO and 2 at% `Al'-doped thin films.

  8. Effects of Li doping on the performance and environmental stability of solution processed ZnO thin film transistors

    NASA Astrophysics Data System (ADS)

    Nayak, Pradipta K.; Jang, Jongsu; Lee, Changhee; Hong, Yongtaek

    2009-11-01

    We report the effects of lithium (Li) doping on the performance and environmental stability of solution processed zinc oxide (ZnO) thin film transistors (TFTs). It was found that appropriate amount of Li doping significantly reduced the background conductivity of ZnO films and also improved the orientation of ZnO crystallites along the c-axis. A highest field-effect mobility of 3.07 cm2/V s was found for the 5 at. % Li-doped ZnO TFTs. However, 15 and 25 at. % Li-doped ZnO TFTs showed good environmental stability of Ion/Ioff ratio with reasonable field-effect mobility.

  9. Room temperature ferromagnetism and photoluminescence in Cu-doped ZnO nanocrystals.

    PubMed

    Kong, Liming; Yu, Bin; Xu, Xiaoyong; Pan, Jing; Su, Yuanchang; Hu, Jingguo

    2014-08-01

    The Zn(1-x)Cu(x)O (x = 0.0-3.5%) nanocrystals have been synthesized by a simple sol-gel method. X-ray diffraction, optical absorption and photoluminescence measurements were employed to validate consistently the incorporation of Cu ions into the ZnO wurtzite lattice without formation of secondary phases for Zn(1-x)Cu(x)O (x < 2.0%). Meanwhile, it was found that the substituted Cu-doping leads to the reduction of the band gap and the appearance of the structured green emission. Magnetization measurement showed that the low Cu-doping (x < 1.0%) develops the ferromagnetism, but the high Cu-doping destroys sharply the ferromagnetism due to the formation of the antiferromagnetic coupling among the neighboring Cu ions. It is indicated that the rational Cu-doping can tune optical and magnetic properties in ZnO. PMID:25936047

  10. Effects of Mn doping on electrical properties of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Motevalizadeh, Leili; Shohany, Boshra Ghanbari; Abrishami, Majid Ebrahimizadeh

    2016-01-01

    In this paper, we have investigated the effect of Mn doping on the electrical properties of ZnO thin films. ZnO thin films with different amounts of Mn concentrations (0, 5, 10 and 15 mol.%) were prepared by spray pyrolysis technique. The crystal structure was examined by X-ray diffraction (XRD) analysis. XRD patterns showed that all the samples were crystallized in wurtzite structure while a decrease in crystallinity and switch in preferential orientations were observed in Mn-doped thin films comparing to undoped ZnO. The element composition of all thin films was detected by energy dispersive X-ray (EDX). The surface morphology of the films was investigated using field emission scanning electron microscope (FESEM) and optical properties were studied using UV-vis spectroscopy. UV-vis study revealed that the band gap blueshifts with the increase in Mn content and Eg increases with the increase in Mn concentration. The resistivity and activation energy were measured at room temperature and ranging from 373 K to 573 K. Comparing to undoped ZnO thin film, the resistivity of Mn-doped ZnO films increased because of different parameters such as increasing barrier height energy and reducing the oxygen deficiency.

  11. Investigation of the iron site localization in doped ZnO

    SciTech Connect

    Carvalho, M.D.; Borges, R.P.; Godinho, M.

    2012-01-15

    Iron doped (5%) ZnO powders were prepared by hydrothermal and combustion methods. Subsequent heating treatments on these samples were performed under air and also under a reductive atmosphere. Powder XRD, Moessbauer spectroscopy and magnetization studies were used to characterize the products and investigate the localization of iron ions in the ZnO lattice. It was shown that a mixture with a ZnFe{sub 2}O{sub 4} type phase was obtained when the sample was prepared by the hydrothermal method, while Fe{sup 3+} occupy tetrahedral sites of the ZnO lattice in the case of the sample obtained by the combustion method. The magnetic measurements show that no ferromagnetism was detected in the iron doped ZnO compound, neither in the as prepared state nor after reduction. - Graphical abstract: Zn{sub 0.95}Fe{sub 0.05}O obtained by a combustion method and after reduction under hydrogen atmosphere. Highlights: Black-Right-Pointing-Pointer Iron doped ZnO was successfully synthesized by a combustion method. Black-Right-Pointing-Pointer The Fe{sup 3+} tetrahedral coordination was deduced from Moessbauer results. Black-Right-Pointing-Pointer The wurtzite structure was maintained after partial reduction of Fe{sup 3+} to Fe{sup 2+}.

  12. Sn doping induced enhancement in the activity of ZnO nanostructures against antibiotic resistant S. aureus bacteria

    PubMed Central

    Jan, Tariq; Iqbal, Javed; Ismail, Muhammad; Zakaullah, M; Naqvi, Sajjad Haider; Badshah, Noor

    2013-01-01

    Highly ionic metal oxide nanostructures are attractive, not only for their physiochemical properties but also for antibacterial activity. Zinc oxide (ZnO) nanostructures are known to have inhibitory activity against many pathogens but very little is known about doping effects on it. The antibacterial activity of undoped ZnO and tin (Sn) doped ZnO nanostructures synthesized by a simple, versatile, and wet chemical technique have been investigated against Escherichia coli, methicillin-resistant Staphylococcus aureus, and Pseudomonas aeruginosa bacterial strains. It has been interestingly observed that Sn doping enhanced the inhibitory activity of ZnO against S. aureus more efficiently than the other two bacterial strains. From cytotoxicity and reactive oxygen species (ROS) production studies it is found that Sn doping concentration in ZnO does not alter the cytotoxicity and ROS production very much. It has also been observed that undoped and Sn doped ZnO nanostructures are biosafe and biocompatible materials towards SH-SY5Y Cells. The observed behavior of ZnO nanostructures with Sn doping is a new way to prevent bacterial infections of S. aureus, especially on skin, when using these nanostructures in creams or lotions in addition to their sunscreen property as an ultraviolet filter. Structural investigations have confirmed the formation of a single phase wurtzite structure of ZnO. The morphology of ZnO nanostructures is found to vary from spherical to rod shaped as a function of Sn doping. The excitation absorption peak of ZnO is observed to have a blue shift, with Sn doping leading toward a significant tuning in band gap. PMID:24109181

  13. Effects of N- and N-In doping on ZnO films prepared by using ultrasonic spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Wang, Qun; Park, Se-Jeong; Shin, Dong-Myeong; Kim, Hyung-Kook; Hwang, Yoon-Hwae; Zhang, Yiwen; Li, Xiaomin

    2014-12-01

    The effects of N-doping, and N-In co-doping on ZnO films were studied by analyzing the structural, electrical, and optical properties of the films prepared by using an ultrasonic spray pyrolysis (USP) method. According to scanning electron microscopy (SEM) data, all films had very complex surface structures. Their polycrystallinity were also proven by using an X-ray diffraction method. The Hall-effect measurement showed that both the undoped and the N-doped ZnO films exhibited n-type conductivity and that the N-In co-doped ZnO film showed p-type conductivity. In the extended X-ray absorption fine structure (EXAFS) analysis, the number of oxygen atoms in the N-In codoped ZnO films was found to be larger than that in the N-doped and the undoped ZnO films. The photoluminescence spectra also showed that the N-In co-doping suppressed the concentration of oxygen vacancies in the ZnO films. Through an effective incorporation of indium atoms, more oxygen atoms seem to have been introduced into the lattice of the N-In co-doped ZnO films.

  14. 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.

  15. Resistive switching characteristics of a compact ZnO nanorod array grown directly on an Al-doped ZnO substrate

    NASA Astrophysics Data System (ADS)

    Yoo, E. J.; Shin, J. Y.; Yoon, T. S.; Kang, C. J.; Choi, Y. J.

    2016-07-01

    ZnO’s resistive switching properties have drawn much attention because ZnO has a simple chemical composition and is easy to manipulate. The propulsion mechanism for resistive switching in ZnO is based on a conducting filament that consists of oxygen vacancies. In the case of film structure, the random formation of the conducting filaments occasionally leads to unstable switching characteristics. Limiting the direction in which the conducting filaments are formed is one way to solve this problem. In this study, we demonstrate reliable resistive switching behavior in a device with an Au/compact ZnO nanorod array/Al-doped ZnO structure with stable resistive switching over 105 cycles and a long retention time of 104 s by confining conducting filaments along the boundaries between ZnO nanorods. The restrictive formation of conducting filaments along the boundaries between ZnO nanorods is observed directly using conductive atomic force microscopy.

  16. Residual and intentional n-type doping of ZnO thin films grown by metal-organic vapor phase epitaxy on sapphire and ZnO substrates

    NASA Astrophysics Data System (ADS)

    Brochen, Stéphane; Lafossas, Matthieu; Robin, Ivan-Christophe; Ferret, Pierre; Gemain, Frédérique; Pernot, Julien; Feuillet, Guy

    2014-03-01

    ZnO epilayers usually exhibit high n-type residual doping which is one of the reasons behind the difficulties to dope this material p-type. In this work, we aimed at determining the nature of the involved impurities and their potential role as dopant in ZnO thin films grown by metalorganic vapor phase epitaxy (MOVPE) on sapphire and ZnO substrates. In both cases, secondary ion mass spectroscopy (SIMS) measurements give evidence for a strong diffusion of impurities from the substrate to the epilayer, especially for silicon and aluminum. In the case of samples grown on sapphire substrates, aluminum follows Fick's diffusion law on a wide growth temperature range (800-1000°C). Thus, the saturation solubility and the diffusion coefficient of aluminum in ZnO single crystals have been determined. Furthermore, the comparison between SIMS impurity and effective dopant concentrations determined by capacitance-voltage measurements highlights, on one hand a substitutional mechanism for aluminum diffusion, and on the other hand that silicon acts as a donor in ZnO and not as an amphoteric impurity. In addition, photoluminescence spectra exhibit excitonic recombinations at the same energy for aluminum and silicon, indicating that silicon behaves as an hydrogenic donor in ZnO. Based on these experimental observations, ZnO thin films with a controlled n-type doping in the 1016-1019cm-3 range have been carried out. These results show that MOVPE growth is fully compatible with the achievement of highly Al-doped n-type thin films, but also with the growth of materials with low residual doping, which is a crucial parameter to address ZnO p-type doping issues.

  17. High temperature ferromagnetism in Ni doped ZnO nanoparticles: Milling time dependence

    SciTech Connect

    Pal, Bappaditya Sarkar, D.; Giri, P. K.

    2014-04-24

    We report on the room temperature ferromagnetism (RT FM) in the Zn{sub 1−x}Ni{sub x}O (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 (M{sub s}) of 1.6–2.56 (emu/g) and coercive field (H{sub c}) 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{sup −1} in addition to 437 cm{sup −1} peak of pure ZnO. UV-Vis absorption spectra illustrate band gap shift due to doping. Alteration of M{sub s} value with the variation of doping concentration and milling time has been studied and discussed.

  18. Transparent conducting indium doped ZnO films by dc reactive S-gun magnetron sputtering.

    PubMed

    Ye, Z Z; Tang, J F

    1989-07-15

    Transparent conducting ZnO films have been prepared by modified S-gun reactive dc magnetron sputtering using an indium doped Zn target. Films with a resistivity of 1.08 x 10(-3) Omega cm and average transmittance of over 80% in the visible region were obtained. The influence of indium content at the surface of Zn target on the resistivity and transmittance of ZnO films was investigated. Optical properties of ZnO films in the 0.2-2.5-microm range were modeled by the Drude theory of free electrons. The reflectance of ZnO films in the 2.5-26.0-microm region was calculated. PMID:20555606

  19. Tunable surface plasmon resonance and enhanced electrical conductivity of In doped ZnO colloidal nanocrystals

    NASA Astrophysics Data System (ADS)

    Ghosh, Sirshendu; Saha, Manas; de, S. K.

    2014-05-01

    We report a new synthesis process of colloidal indium (In) doped zinc oxide (ZIO) nanocrystals by a hot injection technique. By fine tuning the synthesis we reached the same nucleation temperature for indium oxide and zinc oxide which helped us to study a dopant precursor dependent In incorporation into the ZnO matrix by using different In sources. The dopant induced shape evolution changes the hexagonal pyramid structured ZnO to a platelet like structure upon 8% In doping. The introduction of trivalent In3+ into the ZnO lattice and consequent substitution of divalent Zn2+ generates free electrons in the conduction band which produces a plasmonic resonance in the infrared region. The electron concentration controls plasmon frequency as well as the band gap of host ZnO. The variation of the band gap and the modification of the conduction band have been explained by the Burstein-Moss effect and Mie's theory respectively. The In dopant changes the defect chemistry of pure ZnO nanocrystals which has been studied by photoluminescence and other spectroscopic measurements. The nanocrystals are highly stable in the organic medium and can be deposited as a crack free thin film on different substrates. Careful ligand exchange and thermal annealing of the spin cast film lead to a good conductive film (720 Ω per square to 120 Ω per square) with stable inherent plasmonic absorption in the infrared and 90% transmittance in the visible region. A temperature induced metal-semiconductor transition was found for doped ZnO nanocrystals. The transition temperature shifts to a lower temperature with increase of the doping concentration.We report a new synthesis process of colloidal indium (In) doped zinc oxide (ZIO) nanocrystals by a hot injection technique. By fine tuning the synthesis we reached the same nucleation temperature for indium oxide and zinc oxide which helped us to study a dopant precursor dependent In incorporation into the ZnO matrix by using different In sources. The

  20. Structural and photoluminescence properties of Ce, Dy, Er-doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Jayachandraiah, C.; Kumar, K. Siva; Krishnaiah, G.

    2015-06-01

    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. PL 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.

  1. Enhanced luminescence in Eu-doped ZnO nanocrystalline films

    NASA Astrophysics Data System (ADS)

    Suzuki, Keigo; Murayama, Koji; Tanaka, Nobuhiko

    2015-07-01

    We found an enhancement of Eu3+ emissions in Eu-doped ZnO nanocrystalline films fabricated by microemulsion method. The Eu3+ emission intensities were increased by reducing annealing temperatures from 633 K to 533 K. One possible explanation for this phenomenon is that the size reduction enhances the energy transfer from ZnO nanoparticles to Eu3+ ions. Also, the shift of the charge-transfer band into the low-energy side of the absorption edge is found to be crucial, which seems to expedite the energy transfer from O atoms to Eu3+ ions. These findings will be useful for the material design of Eu-doped ZnO phosphors.

  2. Structural and photoluminescence properties of Ce, Dy, Er-doped ZnO nanoparticles

    SciTech Connect

    Jayachandraiah, C.; Kumar, K. Siva; Krishnaiah, G.

    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. PL 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.

  3. Analysis of defect luminescence in Ga-doped ZnO nanoparticles.

    PubMed

    Zhu, Wenliang; Kitamura, Shoichiro; Boffelli, Marco; Marin, Elia; Gaspera, Enrico Della; Sturaro, Marco; Martucci, Alessandro; Pezzotti, Giuseppe

    2016-04-14

    We applied cathodoluminescence (CL) spectroscopy to evaluate the defect-induced luminescence within ZnO and Ga-doped ZnO (GZO) nanoparticles. The observed emissions from defect sites present in the GZO lattice exhibited a strong dependence on both dopant content and synthesis methods. The strong and broad defect-induced emissions and inhomogeneous population of intrinsic defects in nano-sized ZnO particles could effectively be suppressed by Ga doping, although large dopant amounts caused the generation of negatively-charged defects, VZn and Oi, with a subsequent increase of the luminescence. Upon deconvolution of the retrieved CL spectra into individual sub-bands, the physical origin of all the sub-bands could be clarified, and related to sample composition and synthesis protocol. This study lays the foundation of quantitative CL evaluation of defects to assess the quality of GZO optoelectronic devices. PMID:26996752

  4. Enhanced luminescence in Eu-doped ZnO nanocrystalline films

    SciTech Connect

    Suzuki, Keigo Murayama, Koji; Tanaka, Nobuhiko

    2015-07-20

    We found an enhancement of Eu{sup 3+} emissions in Eu-doped ZnO nanocrystalline films fabricated by microemulsion method. The Eu{sup 3+} emission intensities were increased by reducing annealing temperatures from 633 K to 533 K. One possible explanation for this phenomenon is that the size reduction enhances the energy transfer from ZnO nanoparticles to Eu{sup 3+} ions. Also, the shift of the charge-transfer band into the low-energy side of the absorption edge is found to be crucial, which seems to expedite the energy transfer from O atoms to Eu{sup 3+} ions. These findings will be useful for the material design of Eu-doped ZnO phosphors.

  5. Thermal growth and cathodoluminescence of Bi doped ZnO nanowires and rods

    NASA Astrophysics Data System (ADS)

    Alemán, B.; Hidalgo, P.; Fernández, P.; Piqueras, J.

    2009-11-01

    Bi doped ZnO nanowires and rods have been grown by a catalyst free evaporation-deposition method with precursors containing either ZnO and Bi2O3 or ZnS and Bi2O3 powders. The use of ZnS as a precursor was found to lead to a higher density of nano- and microstructures at lower temperatures than by using ZnO. Energy dispersive x-ray spectroscopy (EDS) shows that the Bi content in the wires and rods is in the range 0.15-0.35 at%. Bi incorporation was found to induce a red shift of the near band gap luminescence but no quantitative correlation between the shift and the amount of Bi, as measured by EDS, was observed. The I-V curves of single Bi doped wires had linear behaviour at low current and non-linear behaviour for high currents, qualitatively similar to that of undoped wires.

  6. Optical and ferromagnetic properties of Cr doped ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Lin, Bao-Zhu; Zhou, Lin; Yuldashev, Sh. U.; Fu, De-Jun; Kang, Tae-Won

    2014-10-01

    ZnO nanorods doped with 1-2 wt% Cr were grown on Si substrates by hydrothermal method. Scanning electron spectroscopy and X-ray diffraction show the hexagonal structure of the nanorods with ZnO oriented along (1 0 0), (0 0 2), (1 0 1) and (1 0 2) and CrO2 along (2 1 1). Ionized donor bound exciton, neutral donor bound exciton, free exciton, two-electron-satellite of hydrogen donor bound exciton, and donor acceptor pairs were observed in low temperature photoluminescence spectra. The photoluminescence spectra along with XPS results confirm that Zni was formed in the low temperature hydrothermal process. Superconducting quantum interference device measurement reveals that the Cr-doped ZnO nanorods are ferromagnetic with saturation magnetization of 2.421 × 10-3 emu/g. The room temperature ferromagnetic properties are explained by defect-mediated bound magnetic polarons based on Zni.

  7. Enhanced the photocatalytic activity of Ni-doped ZnO thin films: Morphological, optical and XPS analysis

    NASA Astrophysics Data System (ADS)

    Abdel-wahab, M. Sh.; Jilani, Asim; Yahia, I. S.; Al-Ghamdi, Attieh A.

    2016-06-01

    Pure and Ni-doped ZnO thin films with different concentration of Ni (3.5 wt%, 5 wt%, 7 wt%) were prepared by DC/RF magnetron sputtering technique. The X-rays diffraction pattern showed the polycrystalline nature of pure and Ni-doped ZnO thin films. The surface morphology of pure and Ni doped ZnO thin films were investigated through atomic force microscope, which indicated the increase in the grain dimension and surface roughness with increasing the Ni doping. The UV-Visible transmission spectra showed the decrease in the transmittance of doped ZnO thin films with the incorporation of Ni dopants. The surface and chemical state analysis of pure and Ni doped ZnO thin films were investigated by X-rays photoelectron spectroscopy (XPS). The photocatalytic activities were evaluated by an aqueous solution of methyl green dye. The tungsten lamp of 500 W was used as a source of visible light for photocatalytic study. The degradation results showed that the Ni-doped ZnO thin films exhibit highly enhanced photocatalytic activity as compared to the pure ZnO thin films. The enhanced photocatalytic activities of Ni-doped ZnO thin films were attributed to the enhanced surface area (surface defects), surface roughness and decreasing the band gap of Ni-doped ZnO thin films. Our work supports the applications of thin film metal oxides in waste water treatment.

  8. Solvothermal synthesis of nanorods of ZnO, N-doped ZnO and CdO

    SciTech Connect

    Varghese, Neenu; Panchakarla, L.S.; Hanapi, M.; Govindaraj, A.; Rao, C.N.R.

    2007-12-04

    ZnO nanorods with diameters in the 80-800 nm range are readily synthesized by the reaction of zinc acetate, ethanol and ethylenediamine under solvothermal conditions. The best products are obtained at 330 deg. C with a slow heating rate. Addition of the surfactant Triton -X 100 gave nanorods of uniform (300 nm) diameter. By adding a small amount of liquid NH{sub 3} to the reaction mixture, N-doped ZnO nanorods, with distinct spectroscopic features are obtained. CdO nanorods of 80 nm diameter have been prepared under solvothermal conditions using a mixture of cadmium cupferronate, ethylenediamine and ethanol at 330 deg. C. Similarly, Zn{sub 1-x}Cd{sub x}O nanorods of a 70 nm diameter are obtained under solvothermal conditions starting with a mixture of zinc acetate, cadmium cupferronate, ethanol and ethylenediamine.

  9. Highly textured and transparent RF sputtered Eu2O3 doped ZnO films.

    PubMed

    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

  10. Tunable surface plasmon resonance and enhanced electrical conductivity of In doped ZnO colloidal nanocrystals.

    PubMed

    Ghosh, Sirshendu; Saha, Manas; De, S K

    2014-06-21

    We report a new synthesis process of colloidal indium (In) doped zinc oxide (ZIO) nanocrystals by a hot injection technique. By fine tuning the synthesis we reached the same nucleation temperature for indium oxide and zinc oxide which helped us to study a dopant precursor dependent In incorporation into the ZnO matrix by using different In sources. The dopant induced shape evolution changes the hexagonal pyramid structured ZnO to a platelet like structure upon 8% In doping. The introduction of trivalent In(3+) into the ZnO lattice and consequent substitution of divalent Zn(2+) generates free electrons in the conduction band which produces a plasmonic resonance in the infrared region. The electron concentration controls plasmon frequency as well as the band gap of host ZnO. The variation of the band gap and the modification of the conduction band have been explained by the Burstein-Moss effect and Mie's theory respectively. The In dopant changes the defect chemistry of pure ZnO nanocrystals which has been studied by photoluminescence and other spectroscopic measurements. The nanocrystals are highly stable in the organic medium and can be deposited as a crack free thin film on different substrates. Careful ligand exchange and thermal annealing of the spin cast film lead to a good conductive film (720 Ω per square to 120 Ω per square) with stable inherent plasmonic absorption in the infrared and 90% transmittance in the visible region. A temperature induced metal-semiconductor transition was found for doped ZnO nanocrystals. The transition temperature shifts to a lower temperature with increase of the doping concentration. PMID:24842309

  11. 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

  12. Indium-doped ZnO nanowires with infrequent growth orientation, rough surfaces and low-density surface traps

    PubMed Central

    2013-01-01

    Indium-doped ZnO nanowires have been prepared by vapor transport deposition. With increasing In content, the growth orientation of the nanowires switches from [101_0] to infrequent [022_3] and the surface becomes rough. No surface-related exciton emission is observed in these nanowires. The results indicate that large surface-to-volume ratio, high free electron concentration, and low density of surface traps can be achieved simultaneously in ZnO nanowires via In doping. These unique properties make In-doped ZnO nanowire a potential material for photocatalysis application, which is demonstrated by the enhanced photocatalytic degradation of Rhodamine B. PMID:24256997

  13. Ferromagnetism of Mn-doped ZnO nanoparticles prepared by sol-gel process at room temperature

    NASA Astrophysics Data System (ADS)

    Huang, Gui-Jun; Wang, Jin-Bin; Zhong, Xiang-Li; Zhou, Gong-Cheng; Yan, Hai-Long

    2006-11-01

    Mn-doped ZnO diluted magnetic semiconductor nanoparticles are prepared by an ultrasonic assisted solgel process. Transmission electron microscopy shows pseudo-hexagonal nanoparticles with an average size of about 24 nm. From the analysis of X-ray diffraction, the Mn-doped ZnO nanoparticles are identified to be a wurtzite structure without any impurity phases. The magnetic properties are measured by using superconducting quantum interference device. For the ZnO with 2% Mn doping concentration, a good hysteresis loop indicates fine ferromagnetism with a Curie temperature higher than 350 K.

  14. Ag-doped titanium dioxide gas sensor

    NASA Astrophysics Data System (ADS)

    Alaei Sheini, Navid; Rohani, Mahsa

    2016-03-01

    Titanium dioxide has been utilized for the fabrication of oxygen sensitive ceramic bodies. In this work, disk-shaped TiO2 pellets are fabricated by the sintering of the press- formed anatase powder at 1000°C. Two silver contacts are printed on one of the top base of each sample. Silver wire segments are connected to the printed electrodes. It is shown that the gradual diffusion of silver into titanium dioxide from the electrodes profoundly affects the resistive properties of the ceramic samples. SEM, XRD and EDAX analyses are carried out to determine the position of the silver diffused in the structure. At 35°C, before silver diffusion, the electrical resistance of the device decreases ten times in response to the presence of 3000 ppm ethanol contamination. Sensitivity (Rair/Rgas) to reducing gases is severely affected by the silver doping level in the titanium dioxide. The progress of silver diffusion continuously decreases the sensitivity till it become less than one. Further progress in silver diffusion brings the devices to the condition at which the resistance increases at the presents of reducing gases. In this condition, inverse sensitivities (Rgas/Rair) as large as 103 are demonstrated.

  15. Pulsed laser deposited cobalt-doped ZnO thin film

    NASA Astrophysics Data System (ADS)

    Wang, Li; Su, Xue-qiong; Lu, Yi; Chen, Jiang-bo

    2013-09-01

    To realize the room-temperature ferromagnetism (RTFM) in diluted magnetic semiconductors (DMS), we prepared a series of Cobalt-doped ZnO thin films using pulsed laser deposition (PLD) at deposition temperatures 500°C under oxygen pressure from 2.5×10-4 Pa to 15 Pa. To elucidate the physical origin of RTFM, Co 2p spectra of cobalt-doped ZnO thin films was measured by X-ray photoelectron spectroscopy (XPS). The magnetic properties of films were measured by an alternating gradient magnetometer (AGM), and the electrical properties were detected by a Hall Effect instrument using the Van der Pauw method. XPS analysis shows that the Co2+ exists and Co clusters and elemental content change greatly in samples under various deposition oxygen pressures. Not only the valence state and elemental content but also the electrical and magnetic properties were changed. In the case of oxygen pressure 10 Pa, an improvement of saturation magnetic moment about one order of magnitude over other oxygen pressure experiments, and the film exhibits ferromagnetism with a curie temperature above room temperature. It was found that the value of carrier concentration in the Co-doped ZnO film under oxygen pressure 10Pa increases about one order of magnitude than the values of other samples under different oxygen pressure. Combining XPS with AGM measurements, we found that the ferromagnetic signals in cobalt-doped ZnO thin film deposited at 500 °C under oxygen pressure 10 Pa only appear with the detectable Co2+ spectra from incompletely oxidized Co metal or Co cluster. So oxygen pressure 10 Pa can be thought the best condition to obtain room-temperature dilute magnetic semiconductor about cobalt-doped ZnO thin films.

  16. The shift of optical band gap in W-doped ZnO with oxygen pressure and doping level

    SciTech Connect

    Chu, J.; Peng, X.Y.; Dasari, K.; Palai, R.; Feng, P.

    2014-06-01

    Highlights: • CVD–PLD co-deposition technique was used. • Better crystalline of the ZnO samples causes the redshift of the optical band gap. • Higher W concentration induces blueshift of the optical band gap. - Abstract: Tungsten-doped (W-doped) zinc oxide (ZnO) nanostructures were synthesized on quartz substrates by pulsed laser and hot filament chemical vapor co-deposition technique under different oxygen pressures and doping levels. We studied in detail the morphological, structural and optical properties of W-doped ZnO by SEM, XPS, Raman scattering, and optical transmission spectra. A close correlation among the oxygen pressure, morphology, W concentrations and the variation of band gaps were investigated. XPS and Raman measurements show that the sample grown under the oxygen pressure of 2.7 Pa has the maximum tungsten concentration and best crystalline structure, which induces the redshift of the optical band gap. The effect of W concentration on the change of morphology and shift of optical band gap was also studied for the samples grown under the fixed oxygen pressure of 2.7 Pa.

  17. Crystallinity-dependent substitutional nitrogen doping in ZnO and its improved visible light photocatalytic activity.

    PubMed

    Yu, Zongbao; Yin, Li-Chang; Xie, Yingpeng; Liu, Gang; Ma, Xiuliang; Cheng, Hui-Ming

    2013-06-15

    Increasing visible light absorption of wide-bandgap photocatalysts (for example, ZnO and TiO2) plays a pivotal role in improving their photocatalytic activity. In this work, we show that substitutional nitrogen doping can be realized in semi-crystalline zinc oxide (ZnO) nanoparticles but fails for highly crystalline ZnO by heating the ZnO at a temperature of 400°C in gaseous ammonia atmosphere. The results suggest that substitutional nitrogen for lattice oxygen is strongly dependent on the crystallinity of ZnO. The nitrogen doped ZnO obtained shows an improved visible light photocatalytic activity in the degradation of organic dyes due to its increased visible light absorption. The origin of the increased visible light absorption is theoretically attributed to the formed N 2p localized states in the bandgap. PMID:23561822

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

    PubMed

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

    2013-03-01

    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. PMID:23416707

  19. Photoluminescence, ellipsometric, optical and morphological studies of sprayed Co-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Gençyılmaz, O.; Atay, F.; Akyüz, I.

    2016-06-01

    In this study, undoped and cobalt (Co)-doped zinc oxide (ZnO) films were successfully produced by ultrasonic spray pyrolysis (USP) technique at low temperature (350°C). The optical and surface properties were investigated as a function of Co content. The optical parameters (thickness, refractive index and extinction coefficient) were determined using spectroscopic ellipsometry (SE) and it was seen that the refractive index and extinction coefficient values of Co-doped ZnO films decreased slightly depending on the increasing of Co doping. For investigation, the transmittance and photoluminescence (PL) spectra of the films, UV-Vis spectrophotometer and PL spectroscopy were used at room temperature. The transmittance spectra show that transmittance values decreased and Co+2 ions substitute Zn+2 ions of ZnO lattice. The optical band gap values decreased from 3.26 eV to 2.85 eV with the changing of Co content. The results of PL spectra exhibit the position of the different emission peaks unchanged but the intensity of peaks increased with increasing Co doping. Also, the surface properties of the films were obtained by atomic force microscopy (AFM) and these results indicated that the surface morphology and roughness values were prominently changed with Co doping.

  20. Zn interstitial defects induced magnetic nature in Fe ions doped ZnO based DMS

    SciTech Connect

    Pazhanivelu, V. Selvadurai, A. Paul Blessington; Murugaraj, R.

    2015-06-24

    This paper describes the synthesis of Fe doped ZnO samples Zn{sub 1-x}Fe{sub x}0, where x various from 0.01≤x≤0.05 (in steps of 0.01) by solution method. The effect of Fe ions doping on the structural, optical and magnetic properties was investigated using X-ray diffraction (XRD), Photoluminescence and vibrating sample magnetometer (VSM) measurements. The observed result indicates that the samples are single phase formation of the wurtzite structure without any significant secondary phase in it. The photoluminescence spectra reveals the presence of Zn vacancies. The magnetic property of prepared samples was studied using a vibrating sample magnetometer and the observed results revealed a super-paramagnetic behavior for the Fe doped ZnO samples.

  1. Zn interstitial defects induced magnetic nature in Fe ions doped ZnO based DMS

    NASA Astrophysics Data System (ADS)

    Pazhanivelu, V.; Selvadurai, A. Paul Blessington; Murugaraj, R.

    2015-06-01

    This paper describes the synthesis of Fe doped ZnO samples Zn1-xFex0, where x various from 0.01≤x≤0.05 (in steps of 0.01) by solution method. The effect of Fe ions doping on the structural, optical and magnetic properties was investigated using X-ray diffraction (XRD), Photoluminescence and vibrating sample magnetometer (VSM) measurements. The observed result indicates that the samples are single phase formation of the wurtzite structure without any significant secondary phase in it. The photoluminescence spectra reveals the presence of Zn vacancies. The magnetic property of prepared samples was studied using a vibrating sample magnetometer and the observed results revealed a super-paramagnetic behavior for the Fe doped ZnO samples.

  2. The magnetic ordering in high magnetoresistance Mn-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Venkatesh, S.; Baras, A.; Lee, J.-S.; Roqan, I. S.

    2016-03-01

    We studied the nature of magnetic ordering in Mn-doped ZnO thin films that exhibited ferromagnetism at 300 K and superparamagnetism at 5 K. We directly inter-related the magnetisation and magnetoresistance by invoking the polaron percolation theory and variable range of hopping conduction below the metal-to-insulator transition. By obtaining a qualitative agreement between these two models, we attribute the ferromagnetism to the s-d exchange-induced spin splitting that was indicated by large positive magnetoresistance (˜40 %). Low temperature superparamagnetism was attributed to the localization of carriers and non-interacting polaron clusters. This analysis can assist in understanding the presence or absence of ferromagnetism in doped/un-doped ZnO.

  3. Evaluation of gas-sensing properties of ZnO nanostructures electrochemically doped with Au nanophases

    PubMed Central

    Penza, Michele; Alvisi, Marco; Di Franco, Cinzia; Palmisano, Francesco; Torsi, Luisa

    2016-01-01

    Summary A one-step electrochemical method based on sacrificial anode electrolysis (SAE) was used to deposit stabilized gold nanoparticles (Au NPs) directly on the surface of nanostructured ZnO powders, previously synthesized through a sol–gel process. The effect of thermal annealing temperatures (300 and 550 °C) on chemical, morphological, and structural properties of pristine and Au-doped ZnO nancomposites (Au@ZnO) was investigated. Transmission and scanning electron microscopy (TEM and SEM), as well as X-ray photoelectron spectroscopy (XPS), revealed the successful deposition of nanoscale gold on the surface of spherical and rod-like ZnO nanostructures, obtained after annealing at 300 and 550 °C, respectively. The pristine ZnO and Au@ZnO nanocomposites are proposed as active layer in chemiresistive gas sensors for low-cost processing. Gas-sensing measurements towards NO2 were collected at 300 °C, evaluating not only the Au-doping effect, but also the influence of the different ZnO nanostructures on the gas-sensing properties. PMID:26925349

  4. Microstructure and Luminescence Properties of Tb3+ Doped ZnO Quantum Dots.

    PubMed

    Jin, Na; Li, Hong; Liu, Fengyi; Xie, Ya-Hong

    2016-04-01

    In order to increase the exchange efficiency of solar cells by down-conversion, Tb3+ doped ZnO quantum dots (QDs) were successfully synthesized by sol-gel process. The X-ray diffraction (XRD) results indicate that ZnO QDs have hexagonal wurtzite structure. ZnO QDs have a spherical shape and diameter around 5 nm, which was confirmed by high-resolution transmission electron microscopy (HRTEM). The intensity of visible light emission peaks becomes strengthened and then weakened with the increase of Tb3+ doping concentration. When the concentration is more than 1%, because of the decrease of surface defects and concentration quenching effect, the emissive intensity is weakened. The enhancement of the PL emission peaks at 542 nm, 582 nm, and 619 nm was assigned to energy transfer between TbS+ ions and ZnO QDs host. Moreover, the absorption spectra also demonstrates energy transfers from Tb3+ ions to ZnO QDs. PMID:27451671

  5. Optical Properties of Cu-Doped ZnO Films Prepared by Cu Solution Coating.

    PubMed

    Allabergenov, Bunyod; Chung, Seok-Hwan; Kim, Sungjin; Choi, Byeongdae

    2015-10-01

    This work demonstrates the fabrication of Cu-doped ZnO films by Cu solution coating method. Cu ink was spin coated on ZnO thin films prepared by e-beam deposition. After curing and annealing at high temperatures, structural, morphological and optical properties of the films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and spectrofluorometer, respectively. The XRD results showed that ZnO films formed polycrystalline with a hexagonal wurtzite structure, and the grain size increased with increasing the annealing temperature from 500 to 850 °C. The changes in lattice parameters were caused by grain size, strain, and residual stress. Morphological analysis have revealed that the Cu-doped ZnO film after annealing at 500 °C has flat surface with uniformly distributed grain size, which became porous after higher temperature annealing process. Energy dispersive spectroscopy (EDS) and photoluminescence spectras have shown the presence of Zn, Cu, and O elements, and combined violet, blue, green and weak red emissions between 350 and 650 nm in the ZnO films, respectively. PMID:26726392

  6. Hybrid Modulation-Doping of Solution-Processed Ultrathin Layers of ZnO Using Molecular Dopants.

    PubMed

    Schießl, Stefan P; Faber, Hendrik; Lin, Yen-Hung; Rossbauer, Stephan; Wang, Qingxiao; Zhao, Kui; Amassian, Aram; Zaumseil, Jana; Anthopoulos, Thomas D

    2016-05-01

    An alternative doping approach that exploits the use of organic donor/acceptor molecules for the effective tuning of the free electron concentration in quasi-2D ZnO transistor channel layers is reported. The method relies on the deposition of molecular dopants/formulations directly onto the ultrathin ZnO channels. Through careful choice of materials combinations, electron transfer from the dopant molecule to ZnO and vice versa is demonstrated. PMID:26437002

  7. Interplay of hydrogen treatment and nitrogen doping in ZnO nanoparticles: a first-principles study

    NASA Astrophysics Data System (ADS)

    Gutjahr, Johann; Sakong, Sung; Kratzer, Peter

    2014-04-01

    With the help of density functional calculations using the HSE and PBE functionals, it is shown that incorporation of nitrogen into ZnO nanoparticles is energetically less costly compared to ZnO bulk, due to charge transfer between Zn dangling bonds and the NO impurity. Neutral NO results after full passivation of the doped nanoparticles by a treatment with atomic hydrogen. A nanocomposite made from such ZnO particles could show thermally activated p-type hopping conductivity.

  8. Control of Li configuration and electrical properties of Li-doped ZnO

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Knutsen, K. E.; Merz, T.; Kuznetsov, A. Yu; Svensson, B. G.; Brillson, L. J.

    2012-09-01

    Li-doped ZnO after different thermal treatments was characterized by depth-resolved cathodoluminescence spectroscopy (DRCLS), secondary ion mass spectrometry, surface photovoltage spectroscopy (SPS), coupled with other surface science techniques. It is found that the Li configuration and electrical properties of Li-doped ZnO could be controlled by different thermal processes. Within a 500-600 °C annealing temperature range, subsequent quenching of ZnO leaves Li as interstitial donors, resulting in n-type low room temperature resistivity. In contrast, slower cooling in air enables these interstitials to fill Zn vacancies, forming Li acceptors 3.0 eV below the conduction band edge. Emergence of this acceptor and the resultant resistivity increase agree with the calculated diffusion lengths based on published diffusion coefficients. In general, these acceptors are compensated by residual intrinsic and extrinsic donors, resulting in a semi-insulating material. DRCL spectra exhibit a 3.0 eV optical signature of the LiZn acceptor and its depth distribution in slow-cooled ZnO. A 3.0 eV SPS absorption feature corresponding to a conduction band-to-acceptor level transition confirms this acceptor assignment. Nanoscale SPS spectra reveal p-type band bending localized near ZnO surface nano-mounds, where VZn and LiZn acceptor densities increase. The slow-cooled and quenched Li-doped ZnO spectra display an inverse relationship between the optical emission densities of lithium on zinc versus zinc vacancy sites, demonstrating the time dependence of Li interstitial diffusion to reach zinc vacancies and form substitutional Li acceptors.

  9. High-resolution photoluminescence spectroscopy of Sn-doped ZnO single crystals

    DOE PAGESBeta

    Kumar, E. Senthil; Mohammadbeigi, F.; Boatner, Lynn A.; Watkins, S. P.

    2016-01-01

    Here, Group IV donors in ZnO are poorly understood, despite evidence that they are effective n-dopants. We present high-resolution photoluminescence spectroscopy studies of unintentionally doped and Sn doped ZnO single crystals grown by the chemical vapor transport method. Doped samples showed greatly increased emission from the I10 bound exciton transition which was recently proven to be related to the incorporation of Sn impurities based on radio-isotope studies. PL linewidths are exceptionally sharp for these samples, enabling clear identification of several donor species. Temperature dependent PL measurements of the I10 line emission energy and intensity dependence reveal a behavior similar tomore » other shallow donors in ZnO. Ionized donor bound exciton and two electron satellite transitions of the I10 transition are unambiguously identified and yield a donor binding energy of 71 meV. In contrast to recent reports of Ge-related donors in ZnO, the spectroscopic binding energy for the Sn-related donor bound exciton follows a linear relationship with donor binding energy (Haynes rule), confirming the shallow nature of this defect center, which we attribute to a SnZn double donor compensated by an unknown single acceptor.« less

  10. Towards p-type doping of ZnO by ion implantation

    SciTech Connect

    Coleman, V; Tan, H H; Jagadish, C; Kucheyev, S; Phillips, M; Zou, J

    2005-01-18

    Zinc oxide is a very attractive material for a range of optoelectronic devices including blue light-emitting diodes and laser diodes. Though n-type doping has been successfully achieved, p-type doing of ZnO is still a challenge that must be overcome before p-n junction devices can be realized. Ion implantation is widely used in the microelectronics industry for selective area doping and device isolation. Understanding damage accumulation and recrystallization processes is important for achieving selective area doping. In this study, As (potential p-type dopant) ion implantation and annealing studies were carried out. ZnO samples were implanted with high dose (1.4 x 10{sup 17} ions/cm{sup 2}) 300 keV As ions at room temperature. Furnace annealing of samples in the range of 900 C to 1200 C was employed to achieve recrystallization of amorphous layers and electrical activation of the dopant. Rutherford backscattering/channeling spectrometry, transmission electron microscopy and cathodolumiescence spectroscopy were used to monitor damage accumulation and annihilation behavior in ZnO. Results of this study have significant implications for p-type doing of ZnO by ion implantation.

  11. High-resolution photoluminescence spectroscopy of Sn-doped ZnO single crystals

    SciTech Connect

    Kumar, E. Senthil; Mohammadbeigi, F.; Boatner, Lynn A.; Watkins, S. P.

    2016-01-01

    Here, Group IV donors in ZnO are poorly understood, despite evidence that they are effective n-dopants. We present high-resolution photoluminescence spectroscopy studies of unintentionally doped and Sn doped ZnO single crystals grown by the chemical vapor transport method. Doped samples showed greatly increased emission from the I10 bound exciton transition which was recently proven to be related to the incorporation of Sn impurities based on radio-isotope studies. PL linewidths are exceptionally sharp for these samples, enabling clear identification of several donor species. Temperature dependent PL measurements of the I10 line emission energy and intensity dependence reveal a behavior similar to other shallow donors in ZnO. Ionized donor bound exciton and two electron satellite transitions of the I10 transition are unambiguously identified and yield a donor binding energy of 71 meV. In contrast to recent reports of Ge-related donors in ZnO, the spectroscopic binding energy for the Sn-related donor bound exciton follows a linear relationship with donor binding energy (Haynes rule), confirming the shallow nature of this defect center, which we attribute to a SnZn double donor compensated by an unknown single acceptor.

  12. Preparation and characterization of undoped and cobalt doped ZnO for antimicrobial use.

    PubMed

    Stoica, Angelica Oprea; Andronescu, Ecaterina; Ghitulica, Cristina Daniela; Voicu, Georgeta; Grumezescu, Alexandru Mihai; Popa, Marcela; Chifiriuc, Mariana Carmen

    2016-08-30

    The objective of this study was to carry out the synthesis by sol-gel method of undoped and cobalt doped ZnO, with different cobalt concentrations (0.5-5mol%), using as stabilizer monoethanolamine (MEA) in a molar ratio ZnO:MEA=1:2. The dry gel was thermally treated at 500°C/5h, respectively at 1100°C/30min. All the thermal treated samples were of wurtzite type with an hexagonal structure. The doping with Co(2+) induced change of lattice parameters and of crystallite size, proving the successful interleaving of Co(2+) into the ZnO lattice. From the morphological point of view, the thermal treatment at 1100°C/30min led to a higher degree of compactness of the ZnO granules. At 500°C/5h there were formed polyhedral or spherical nanometric particles (25-50nm) which have been agglomerated into aggregates with sizes over 1μm. From the biological point of view, the quantitative analyses of antimicrobial activity have shown that the ZnO doped with cobalt has inhibited the ability of the Bacillus subtilis and Escherichia coli bacterial strains to colonize the inert substrate and therefore, can be used in the design of new antimicrobial strategies. PMID:26394121

  13. Synthesis and photoluminescence properties of aligned Zn{sub 2}GeO{sub 4} coated ZnO nanorods and Ge doped ZnO nanocombs

    SciTech Connect

    Su Yong; Meng Xia Chen Yiqing; Li Sen; Zhou Qingtao; Liang Xuemei; Feng Yi

    2008-07-01

    Aligned Zn{sub 2}GeO{sub 4} coated ZnO nanorods and Ge doped ZnO nanocombs were synthesized on a silicon substrate by a simple thermal evaporation method. The structure and morphology of the as-synthesized nanostructure were characterized using scanning electron microscopy and transmission electron microscopy. The growth of aligned Zn{sub 2}GeO{sub 4} coated ZnO nanorods and Ge doped ZnO nanocombs follows a vapor-solid (VS) process. Photoluminescence properties were also investigated at room temperature. The photoluminescence spectrum reveals the nanostructures have a sharp ultraviolet luminescence peak centered at 382 nm and a broad green luminescence peak centered at about 494 nm.

  14. Effect of Sb-doping on the morphology and dielectric properties of chrysanthemum-like ZnO nanowire clusters

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    Chrysanthemum-like ZnO nanowire clusters with different Sb-doping concentrations were prepared using a hydrothermal process. The microstructures, morphologies, and dielectric properties of the as-prepared products were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), field emission environment scanning electron microscope (FEESEM), and microwave vector network analyzer respectively. The results indicate that the as-prepared products are Sb-doped ZnO single crystallines with a hexagonal wurtzite structure, the flower bud saturation degree Fd is obviously different from that of the pure ZnO nanowire clusters, the good dielectric loss property is found in Sb-doped ZnO products with low density, and the dielectric loss tangent tanδe increases with the increase of the Sb-doping concentration in a certain concentration range.

  15. Selective photochemical synthesis of Ag nanoparticles on position-controlled ZnO nanorods for the enhancement of yellow-green light emission

    NASA Astrophysics Data System (ADS)

    Park, Hyeong-Ho; Zhang, Xin; Lee, Keun Woo; Sohn, Ahrum; Kim, Dong-Wook; Kim, Joondong; Song, Jin-Won; Choi, Young Su; Lee, Hee Kwan; Jung, Sang Hyun; Lee, In-Geun; Cho, Young-Dae; Shin, Hyun-Beom; Sung, Ho Kun; Park, Kyung Ho; Kang, Ho Kwan; Park, Won-Kyu; Park, Hyung-Ho

    2015-12-01

    A novel technique for the selective photochemical synthesis of silver (Ag) nanoparticles (NPs) on ZnO nanorod arrays is established by combining ultraviolet-assisted nanoimprint lithography (UV-NIL) for the definition of growth sites, hydrothermal reaction for the position-controlled growth of ZnO nanorods, and photochemical reduction for the decoration of Ag NPs on the ZnO nanorods. During photochemical reduction, the size distribution and loading of Ag NPs on ZnO nanorods can be tuned by varying the UV-irradiation time. The photochemical reduction is hypothesized to facilitate the adsorbed citrate ions on the surface of ZnO, allowing Ag ions to preferentially form Ag NPs on ZnO nanorods. The ratio of visible emission to ultraviolet (UV) emission for the Ag NP-decorated ZnO nanorod arrays, synthesized for 30 min, is 20.5 times that for the ZnO nanorod arrays without Ag NPs. The enhancement of the visible emission is believed to associate with the surface plasmon (SP) effect of Ag NPs. The Ag NP-decorated ZnO nanorod arrays show significant SP-induced enhancement of yellow-green light emission, which could be useful in optoelectronic applications. The technique developed here requires low processing temperatures (120 °C and lower) and no high-vacuum deposition tools, suitable for applications such as flexible electronics.A novel technique for the selective photochemical synthesis of silver (Ag) nanoparticles (NPs) on ZnO nanorod arrays is established by combining ultraviolet-assisted nanoimprint lithography (UV-NIL) for the definition of growth sites, hydrothermal reaction for the position-controlled growth of ZnO nanorods, and photochemical reduction for the decoration of Ag NPs on the ZnO nanorods. During photochemical reduction, the size distribution and loading of Ag NPs on ZnO nanorods can be tuned by varying the UV-irradiation time. The photochemical reduction is hypothesized to facilitate the adsorbed citrate ions on the surface of ZnO, allowing Ag ions to

  16. Many-body electronic structure calculations of Eu-doped ZnO

    NASA Astrophysics Data System (ADS)

    Lorke, M.; Frauenheim, T.; da Rosa, A. L.

    2016-03-01

    The formation energies and electronic structure of europium-doped zinc oxide has been determined using DFT and many-body G W methods. In the absence of intrisic defects, we find that the europium-f states are located in the ZnO band gap with europium possessing a formal charge of 2+. On the other hand, the presence of intrinsic defects in ZnO allows intraband f -f transitions otherwise forbidden in atomic europium. This result corroborates with recently observed photoluminescence in the visible red region S. Geburt et al. [Nano Lett. 14, 4523 (2014), 10.1021/nl5015553].

  17. Research Update: Doping ZnO and TiO2 for solar cells

    NASA Astrophysics Data System (ADS)

    Hoye, Robert L. Z.; Musselman, Kevin P.; MacManus-Driscoll, Judith L.

    2013-12-01

    ZnO and TiO2 are two of the most commonly used n-type metal oxide semiconductors in new generation solar cells due to their abundance, low-cost, and stability. ZnO and TiO2 can be used as active layers, photoanodes, buffer layers, transparent conducting oxides, hole-blocking layers, and intermediate layers. Doping is essential to tailor the materials properties for each application. The dopants used and their impact in solar cells are reviewed. In addition, the advantages, disadvantages, and commercial potential of the various fabrication methods of these oxides are presented.

  18. Microstructural and conductivity comparison of Ag films grown on amorphous TiO2 and polycrystalline ZnO

    SciTech Connect

    Dannenberg, Rand; Stach, Eric; Glenn, Darin; Sieck, Peter; Hukari, Kyle

    2001-03-26

    8 nm thick Ag films were sputter deposited onto amorphous TiO{sub 2} underlayers 25 nm thick, and also amorphous TiO{sub 2} (25 nm)/ZnO (5 nm) multiunderlayers. The substrates were back-etched Si with a 50 nm thick LPCVD Si{sub 3}N{sub 4} electron transparent membrane. The ZnO, sputtered onto amorphous TiO{sub 2}, formed a continuous layer with a grain size of 5 nm in diameter, on the order of the film thickness. There are several microstructural differences in the Ag dependent on the underlayers, revealed by TEM. First a strong {l_brace}0001{r_brace} ZnO to {l_brace}111{r_brace} Ag fibre-texture relationship exists. On TiO{sub 2} the Ag microstructure shows many abnormal grains whose average diameter is about 60-80 nm, whereas the films on ZnO show few abnormal grains. The background matrix of normal grains on the TiO{sub 2} is roughly 15 nm, while the normal grain size on the ZnO is about 25 nm. Electron diffraction patterns show that the film on ZnO has a strong {l_brace}111{r_brace} orientation, and dark field images with this diffraction condition have a grain size of about 30 nm. In a region near the center of the TEM grid where there is the greatest local heating during deposition, Ag films grown on amorphous TiO{sub 2} are discontinuous, whereas on ZnO, the film is continuous. When films 8 nm films are grown on solid glass substrates, those with ZnO underlayers have sheet resistances of 5.68 {Omega}/, whereas those on TiO{sub 2} are 7.56 {Omega}/, and when 16 nm thick, the corresponding sheet resistances are 2.7 {Omega}/ and 3.3 {Omega}/. The conductivity difference is very repeatable. The improved conductivity is thought to be a combined effect of reduced grain boundary area per unit volume, the predominance of low grain boundary resistivity Coincidence Site Lattice boundaries from the Ag {l_brace}111{r_brace} orientation, and Ag planarization on ZnO resulting in less groove formation on deposition, concluded from atomic force microscopy.

  19. Effect of Zr doping on the electrical and optical properties of ZnO

    NASA Astrophysics Data System (ADS)

    Hou, Qingyu; Zhao, Chunwang; Xu, Zhenchao

    2016-08-01

    Within 0.02083-0.04167 Zr doping amount, there are contradictory reports on the experimental results of ZnO doping system in absorption spectrum distribution. However, there is no reasonable theoretical explanation until now. To solve this problem, density functional theory-based generalized gradient approximation plane wave ultra-soft pseudopotential GGA + U method is utilized in this paper and the first-principles are adopted to construct the supercell models with three different doping amounts, Zn0.97917Zr0.02083O, Zn0.96875Zr0.03125O and Zn0.95833Zr0.04167O. On the basis of geometrical optimization of all the models, band structure distribution, density of states distribution and absorption spectrum distribution are calculated and the calculation results show that within the limited doping amount, the higher the Zr doping amount is, the higher the doping system volume is, the higher the total energy is, the lower the system stability is, the higher the formation energy is, and the more difficult doping is. With all the doping systems converted into n-type degenerate semiconductor, the wider the doping system band gap is, the more significant the absorption spectrum blueshift is, the lower the absorption intensity is, the higher the electronic effective mass is, the higher the electronic concentration is, the lower the electronic mobility is, the higher the electronic conductivity is, and the more significant the doping system conductivity is. The calculation results and the experiment results are consistent.

  20. Effect of substrate temperature on the structural and optical properties of ZnO and Al-doped ZnO thin films prepared by dc magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Li, Xue-Yong; Li, Hong-Jian; Wang, Zhi-Jun; Xia, Hui; Xiong, Zhi-Yong; Wang, Jun-Xi; Yang, Bing-Chu

    2009-01-01

    ZnO and Al-doped ZnO(ZAO) thin films have been prepared on glass substrates by direct current (dc) magnetron sputtering from 99.99% pure Zn metallic and ZnO:3 wt%Al 2O 3 ceramic targets, the effects of substrate temperature on the crystallization behavior and optical properties of the films have been studied. It shows that the surface morphologies of ZAO films exhibit difference from that of ZnO films, while their preferential crystalline growth orientation revealed by X-ray diffraction remains always the (0 0 2). The optical transmittance and photoluminescence (PL) spectra of both ZnO and ZAO films are obviously influenced by the substrate temperature. All films exhibit a transmittance higher than 86% in the visible region, while the optical transmittance of ZAO films is slightly smaller than that of ZnO films. More significantly, Al-doping leads to a larger optical band gap ( Eg) of the films. It is found from the PL measurement that near-band-edge (NBE) emission and deep-level (DL) emission are observed in pure ZnO thin films. However, when Al was doped into thin films, the DL emission of the thin films is depressed. As the substrate temperature increases, the peak of NBE emission has a blueshift to region of higher photon energy, which shows a trend similar to the Eg in optical transmittance measurement.

  1. XPS studies and photocurrent applications of alkali-metals-doped ZnO nanoparticles under visible illumination conditions

    NASA Astrophysics Data System (ADS)

    Saáedi, Abdolhossein; Yousefi, Ramin; Jamali-Sheini, Farid; Zak, Ali Khorsand; Cheraghizade, Mohsen; Mahmoudian, M. R.; Baghchesara, Mohammad Amin; Dezaki, Abbas Shirmardi

    2016-05-01

    The present work is a study about a relationship between X-ray photoelectron spectrometer (XPS) results and photocurrent intensity of alkali-metals-elements doped ZnO nanoparticles, which is carried out under visible illumination conditions. The nanoparticles were synthesized by a simple sol-gel method. Structure and morphology studies of the NPs were carried out by X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The effect of doping on the optical band-gap was investigated by using UV-visible spectrometer. The absorption peak of the doped ZnO NPs was red-shifted with respect to that of the undoped ZnO NPs. After that, the photocurrent application of the products was examined under a white light source at 2 V bias. The photocurrent results showed that, the current intensity of the ZnO NPs was increased by doping materials. However, K-doped ZnO NPs showed the highest photocurrent intensity. Finally, a discussion was carried out about the obtained photocurrent results by the O-1s spectra of the XPS of the samples. Our results suggest that the alkali-metals-doped ZnO NPs exhibit considerable promise for highly sensitive visible-light photodetectors.

  2. The preparation of a Eu3+-doped ZnO bi-functional layer and its application in organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Wu, Na; Luo, Qun; Qiao, Xvsheng; Ma, Chang-Qi

    2015-12-01

    Recently, spectra conversion has been used to minimize energy loss in photovoltaic devices. In this work, we explore the development of a novel Eu3+-doped ZnO bi-functional layer for use in organic solar cells. The bi-functional layer acts as both a spectra conversion and an electron transporting layer. Compared to conventional spectra conversion layers, it has a simpler device structure, is easier to fabricate, and has a wider spectrum-sensitized region. A series of Eu3+-doped ZnO nanocrystals were synthesized using the simple solution route. X-ray powder diffraction patterns (XRD), transmission electron microscopy (TEM), and UV-visible absorbance spectra were used to characterize the obtained ZnO nanocrystals. The results reveal that the size and bandgap of ZnO nanocrystals can be controlled through regulation of the doping concentration of Eu3+ ions. The energy transfer of ZnO → Eu3+ is observed by photoluminescence (PL) spectra. At a bandgap excitation of around 300-400 nm, a typical emission band from the Eu3+ is obtained. By employing the Eu3+- doped ZnO nanocrystals as a buffer layer in a P3HT:PC61BM bulk heterojunction device, the obtained performance is similar to the undoped ZnO device, indicating that the electrical properties of ZnO are not affected by Eu3+ doping. Due to the down-conversion energy transfer between ZnO and Eu3+, the external quantum efficiency of the ZnO:Eu3+ device at 300-400 nm is higher than that of the pure ZnO device, which subsequently leads to an increase in short circuit current density (J SC). This work proves that it is possible to improve the solar spectrum response in the ultraviolet region of organic solar cells effectively by incorporating the bi-functional layer.

  3. Transition metal doped ZnO nanoclusters for carbon monoxide detection: DFT studies.

    PubMed

    Aslanzadeh, Saeed

    2016-07-01

    Metal doped ZnO nanomaterials have attracted considerable attention as a chemical sensor for toxic gases. Here, the electronic sensitivity of pristine and Sc-, Ti-, V-, Cr-, Mn-, and Fe-doped Zn12O12 nanoclusters toward CO gas is investigated using density functional theory calculations. It is found that replacing a Zn atom by a Sc or Ti atom does not change the sensitivity of cluster but doping V and Cr atoms significantly increase the sensitivity. Also, Mn, or Fe doping slightly improves the sensitivity. It is predicted that among all, the Cr-doped ZnO cluster may be the most favorable sensor for CO detection because its electrical conductivity considerably changes after the CO adsorption, thereby, generating an electrical signal. The calculated Gibbs free energy change for the adsorption of CO molecule on the Cr-doped cluster is about -51.2 kcal mol(-1) at 298.15 K and 1 atm, and the HOMO-LUMO gap of the adsorbent is changed by about 117.8 %. PMID:27316701

  4. Influence of Fe-Doping on the Structural, Morphological, Optical, Magnetic and Antibacterial Effect of ZnO Nanostructures.

    PubMed

    Basith, N Mohamed; Vijaya, J Judith; Kennedy, L John; Bououdina, M; Shenbhagaraman, R; Jayavel, R

    2016-02-01

    Pure and Fe-doped ZnO nanostructures with different weight ratios (0.5, 1.0, 1.5, and 2.0 at wt% of Fe) were successfully synthesized by a facile microwave combustion method using urea as a fuel. The detailed structural characterization was performed by means of X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). XRD patterns refined by the Rietveld method indicated that Fe-doped ZnO have a single pure phase with wurtzite structure, suggesting that Fe ions are successfully incorporated into ZnO crystal lattice by occupying Zn ionic sites. Interestingly, the morphology was found to change substantially from grains to nanoflakes and then into nanorods with the variation of Fe-content. The optical band gap estimated using DRS was found to be red-shifted from 3.220 eV for the pure ZnO nanostructures, then decreases up to 3.200 eV with increasing Fe-content. Magnetic studies showed that Fe-doped ZnO nanostructures exhibit room temperature ferromagnetism (RTFM) and the saturation magnetization attained a maximum value of 8.154 x 10(-3) emu/g for the highest Fe-content. The antibacterial activity of pure and Fe-doped ZnO nanostructures against a Gram-positive bacteria and Gram-negative bacteria was investigated. Pure ZnO and Fe-doped ZnO exhibited antibacterial activity, but it was considerably more effective in the 1.5 wt% Fe-doped ZnO nanostructures. PMID:27433623

  5. Photocatalytic degradation of acid blue 74 in water using Ag-Ag2O-Zno nanostuctures anchored on graphene oxide

    NASA Astrophysics Data System (ADS)

    Umukoro, Eseoghene H.; Peleyeju, Moses G.; Ngila, Jane C.; Arotiba, Omotayo A.

    2016-01-01

    Water pollution due to industrial effluents from industries which utilize dyes in the manufacturing of their products has serious implications on aquatic lives and the general environment. Thus, there is need for the removal of dyes from wastewater before being discharged into the environment. In this study, a nanocomposite consisting of silver, silver oxide (Ag2O), zinc oxide (ZnO) and graphene oxide (GO) was synthesized, characterized and photocatalytically applied in the degradation (and possibly mineralization) of organic pollutants in water treatment process. The Ag-Ag2O-ZnO nanostructure was synthesized by a co-precipitation method and calcined at 400 °C. It was functionalized using 3-aminopropyl triethoxysilane and further anchored on carboxylated graphene oxide via the formation of an amide bond to give the Ag-Ag2O-ZnO/GO nanocomposite. The prepared nanocomposite was characterized by UV-Vis diffuse reflectance spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electronic microscopy (SEM), energy dispersive X-ray spectrometry (EDX), Fourier transformed infrared spectroscopy (FTIR), and Raman spectroscopy. The applicability of Ag-Ag2O-ZnO/GO nanocomposite as a photocatalyst was investigated in the photocatalytic degradation of acid blue 74 dye under visible light irradiation in synthetic wastewater containing the dye. The results indicated that Ag-Ag2O-ZnO/GO nanocomposite has a higher photocatalytic activity (90% removal) compared to Ag-Ag2O-ZnO (85% removal) and ZnO (75% removal) respectively and thus lends itself to application in water treatment, where the removal of organics is very important.

  6. Impacts of Co doping on ZnO transparent switching memory device characteristics

    NASA Astrophysics Data System (ADS)

    Simanjuntak, Firman Mangasa; Prasad, Om Kumar; Panda, Debashis; Lin, Chun-An; Tsai, Tsung-Ling; Wei, Kung-Hwa; Tseng, Tseung-Yuen

    2016-05-01

    The resistive switching characteristics of indium tin oxide (ITO)/Zn1-xCoxO/ITO transparent resistive memory devices were investigated. An appropriate amount of cobalt dopant in ZnO resistive layer demonstrated sufficient memory window and switching stability. In contrast, pure ZnO devices demonstrated a poor memory window, and using an excessive dopant concentration led to switching instability. To achieve suitable memory performance, relying only on controlling defect concentrations is insufficient; the grain growth orientation of the resistive layer must also be considered. Stable endurance with an ON/OFF ratio of more than one order of magnitude during 5000 cycles confirmed that the Co-doped ZnO device is a suitable candidate for resistive random access memory application. Additionally, fully transparent devices with a high transmittance of up to 90% at wavelength of 550 nm have been fabricated.

  7. Unexpected positive role of oxygen vacancies in Na-doped ZnO

    NASA Astrophysics Data System (ADS)

    Yang, X. P.; Lu, J. G.; Zhang, H. H.; Lu, B.; Huang, J. Y.; Ye, C. L.; Ye, Z. Z.

    2012-12-01

    The interaction of Na impurities and O vacancies (VO) in ZnO was studied in theory and experiment. The VO facilitated substitutional Na (NaZn/NaZn-) acceptors with inhibiting interstitial Na (Nai/Nai+) donors, which may benefit the p-type conductivity. The formed (NaZn-VO)+/0 complexes induced the change of band structures of ZnO, with the broadening of gap energies and disappearance of the VO2+-related impurity level, which confirmed by the blue shift of the near-band-edge (NBE) UV emission and the decay of the visible emission in PL spectra. The strong and dominant NBE UV emission suggested acceptable luminescence behaviors of Na-doped ZnO.

  8. Luminescence of defects in Li-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Potek, Z.; Bryknar, Z.; Ptáek, P.; Hubika, Z.

    2005-01-01

    Photoluminescence of pure ZnO and ZnO:Li thin films prepared in the plasmachemical reactor with the hollow cathode can be observed after annealing of samples in the hydrogen atmosphere at temperatures within the range 300-600 °C. Photoluminescence was excited by light with the photon energy higher than 3.1 eV. Considering the differences between photoluminescence emission spectra of pure and doped ZnO thin films investigated in the spectral region (260-1000 nm) at temperature 12 K, it was concluded (i) photoluminescence emission from the region 3.10-1.77 eV is originated from the intrinsic centers of pure ZnO and (ii) the emission near 1.68 eV is associated with a transition from a state at bottom of the conduction band to a hole trapped in a localized state introduced by Li.

  9. Homojunction p-n photodiodes based on As-doped single ZnO nanowire

    SciTech Connect

    Cho, H. D.; Zakirov, A. S.; Yuldashev, Sh. U.; Kang, T. W.; Ahn, C. W.; Yeo, Y. K.

    2013-12-04

    Photovoltaic device was successfully grown solely based on the single ZnO p-n homojunction nanowire. The ZnO nanowire p-n diode consists of an as-grown n-type segment and an in-situ arsenic doped p-type segment. This p-n homojunction acts as a good photovoltaic cell, producing a photocurrent almost 45 times larger than the dark current under reverse-biased condition. Our results demonstrate that present ZnO p-n homojunction nanowire can be used as a self-powered ultraviolet photodetector as well as a photovoltaic cell, which can also be used as an ultralow electrical power source for nano-scale electronic, optoelectronic, and medical devices.

  10. Influence of ZnO nanorod on the luminescent and electrical properties of fluorescent dye-doped polymer nanocomposite

    NASA Astrophysics Data System (ADS)

    Zhang, T.; Xu, Z.; Qian, L.; Tao, D. L.; Teng, F.; Xu, X. R.

    2006-11-01

    The luminescent properties of fluorescent dye-doped polymer dispersed with ZnO nanorods were investigated. Embedding ZnO nanorods in blend film results in a blue-shifted emission of fluorescent dye. It is accounted for in terms of the difference in permittivity between inorganic oxide nano-material and dye-doped polymer. Moreover, polymer light-emitting diodes with the addition of ZnO nanorods showed the lower threshold voltage and the higher charge current and electroluminescence efficiency.

  11. Enhanced photocatalytic ability from carbon-doped ZnO photocatalyst synthesized without an external carbon precursor

    NASA Astrophysics Data System (ADS)

    Zhang, Dong En; Wang, Ming Yan; Ma, Juan Juan; Han, Gui Quan; Li, Shu An; Zhao, Hong; Zhao, Bin Yuan; Tong, Zhi Wei

    2014-03-01

    We report a simple synthesis of C-doped ZnO composite nanoparticles by a solvothermal treatment of Zn(OAc)2 ṡ 2H2O that provides a source of both zinc and carbon. The photocatalytic activities of the composites were evaluated by the degree of degradation rhodamine B in aqueous solutions at room temperature with near UV light irradiation. These nanocomposites exhibit higher photocatalytic activity compared with pure ZnO nanoparticles. The enhancement of photocatalytic activity of C-doped ZnO nanoparticles is mainly attributed to their absorbed more photons and reduced electron hole pair recombination.

  12. Self-assembled Ag nanoparticle network passivated by a nano-sized ZnO layer for transparent and flexible film heaters

    SciTech Connect

    Seo, Ki-Won; Kim, Han-Ki; Kim, Min-Yi; Chang, Hyo-Sik

    2015-12-15

    We investigated a self-assembled Ag nanoparticle network electrode passivated by a nano-sized ZnO layer for use in high-performance transparent and flexible film heaters (TFFHs). The low temperature atomic layer deposition of a nano-sized ZnO layer effectively filled the uncovered area of Ag network and improved the current spreading in the self-assembled Ag network without a change in the sheet resistance and optical transmittance as well as mechanical flexibility. The time-temperature profiles and heat distribution analysis demonstrate that the performance of the TFTH with the ZnO/Ag network is superior to that of a TFFH with Ag nanowire electrodes. In addition, the TFTHs with ZnO/Ag network exhibited better stability than the TFFH with a bare Ag network due to the effective current spreading through the nano-sized ZnO layer.

  13. Electrodeposition of zinc oxide nanowires: Growth, doping, and physical properties

    NASA Astrophysics Data System (ADS)

    Thomas, Matthew Allan

    As a transparent, wide bandgap semiconductor, ZnO offers an expansive range of potential uses in various technological arenas such as electronics, optoelectronics, photonics, sensors, and energy conversion. However, a current obstacle to the realization of ZnO based electronics and optoelectronics is the lack of a reliable and reproducible method for fabricating high quality p-type ZnO. In addition, there remains a difficulty in tuning the various properties of ZnO materials, especially nanostructures, via low cost and low temperature deposition techniques. In this work, some of these deficiencies have been addressed. Undoped and Ag-doped ZnO nanowires, as well as highly uniform and dense ZnO films, were obtained by an inexpensive, low temperature, electrochemical technique in aqueous solution. The effects of electrochemical growth conditions and Ag-doping on the structural, optical, and electrical properties of the ZnO nanowires were investigated in detail. Ag-doping was found to induce significant changes in the various physical properties of the ZnO nanowires. Importantly, a range of experimental and theoretical results indicate Ag is doped into the ZnO nanowire structure and leads to p-type properties of the nanowires. The room temperature photoluminescence (PL) of the nanowires illustrates bandgap reduction, while intense emissions from a free electron to neutral acceptor were induced in the low temperature PL upon Ag-doping. The electrical properties of the Ag-doped nanowires were probed with photoelectrochemical cell measurements, providing further evidence for their p-type nature. The mechanism of Ag-doping in the nanowires was explored with cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. Interestingly, the presence of Ag+ in the growth process catalyzes and enhances the electrochemistry, shifting the ZnO growth conditions to an O-rich environment. These conditions enable a more efficient Ag

  14. A dual-colored bio-marker made of doped ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Wu, Y. L.; Fu, S.; Tok, A. I. Y.; Zeng, X. T.; Lim, C. S.; Kwek, L. C.; Boey, F. C. Y.

    2008-08-01

    Bio-compatible ZnO nanocrystals doped with Co, Cu and Ni cations, surface capped with two types of aminosilanes and titania are synthesized by a soft chemical process. Due to the small particle size (2-5 nm), surface functional groups and the high photoluminescence emissions at the UV and blue-violet wavelength ranges, bio-imaging on human osteosarcoma (Mg-63) cells and histiocytic lymphoma U-937 monocyte cells showed blue emission at the nucleus and bright turquoise emission at the cytoplasm simultaneously. This is the first report on dual-color bio-images labeled by one semiconductor nanocrystal colloidal solution. Bright green emission was detected on mung bean seedlings labeled by all the synthesized ZnO nanocrystals. Cytotoxicity tests showed that the aminosilanes capped nanoparticles are non-toxic. Quantum yields of the nanocrystals varied from 79% to 95%. The results showed the potential of the pure ZnO and Co-doped ZnO nanocrystals for live imaging of both human cells and plant systems.

  15. Enhancement of dielectric constant in transition metal doped ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Singh, Swati; Dey, P.; Roy, J. N.; Mandal, S. K.

    2014-09-01

    We have presented dielectric studies on Zn1-xCoxO, Zn1-xFexO, and Zn1-xFex/2Cox/2O (x = doping level) semiconducting nanoparticles (˜2-40 nm). For all those samples, dielectric constant (є) is found to exhibit a maximum with x. Enhancement of є is found to be ˜250 times for Zn0.85Co0.15O and ˜400 times for Zn0.8Fe0.1Co0.1O from that of ZnO. Presence of effective higher oxidation state of transition metals ions in ZnO due to Fe/Co doping resulting in space charge polarization possibly yields this effect. The simultaneous existence of high є, semiconducting, and ferromagnetic like behaviour at 300 K seems to propose Zn0.8Fe0.1Co0.1O, promising for technological application.

  16. Microstructural and optical studies on sonochemically synthesized Cu doped ZnO nanoparticles

    SciTech Connect

    Sahu, Dojalisa Panda, Nihar Ranjan Panda, A. K.; Acharya, B. S.

    2014-04-24

    Copper doped ZnO nanoparticles were synthesized by sonochemical method varying the concentration of the impurity. Systematic investigations like X-ray diffraction (XRD) and Transmission electron microscopy (TEM) were carried out to understand the microstructural properties. The average particle sizes and all the crystallographic parameters were calculated from XRD results. This shows the formation of wurtzite phase of ZnO with average size of the particles as 53 nm and an increase of particle size with dopant concentration was also been observed. UV absorption and Fourier transformed infrared spectroscopy (FTIR) spectra revealed the absorption at wavelength < 370 nm with a remarkable red shift of absorption band and a linear decrease of transmittance with increase in doping concentrations respectively.

  17. Lithium related deep and shallow acceptors in Li-doped ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Rauch, C.; Gehlhoff, W.; Wagner, M. R.; Malguth, E.; Callsen, G.; Kirste, R.; Salameh, B.; Hoffmann, A.; Polarz, S.; Aksu, Y.; Driess, M.

    2010-01-01

    We study the existence of Li-related shallow and deep acceptor levels in Li-doped ZnO nanocrystals using electron paramagnetic resonance (EPR) and photoluminescence (PL) spectroscopy. ZnO nanocrystals with adjustable Li concentrations between 0% and 12% have been prepared using organometallic precursors and show a significant lowering of the Fermi energy upon doping. The deep Li acceptor with an acceptor energy of 800 meV could be identified in both EPR and PL measurements and is responsible for the yellow luminescence at 2.2 eV. Additionally, a shallow acceptor state at 150 meV above the valence band maximum is made responsible for the observed donor-acceptor pair and free electron-acceptor transitions at 3.235 and 3.301 eV, possibly stemming from the formation of Li-related defect complexes acting as acceptors.

  18. Growth and characterization of Li-doped ZnO thin films on nanocrystalline diamond substrates

    NASA Astrophysics Data System (ADS)

    Huang, Jian; Xia, Yiben; Wang, Linjun; Xu, Jinyong; Hu, Guang; Zhu, Xuefeng; Shi, Weimin

    2008-02-01

    Nanocrystalline diamond(NCD) films with a mean surface roughness of 23.8 nm were grown on silicon substrates in a hot filament chemical vapor deposition(HFCVD) system. Then, Zn 1-xLi xO (x=0, 0.05, 0.10, 0.15) films were deposited on these NCD films by radio-frequency(RF) reactive magnetron sputtering method. When x was 0.1, the Li-doped ZnO film had a larger resistivity more than 10 8Ω•cm obtained from Hall effect measurement. All the Zn 1-xLi xO films had a strong c-axis orientation structure determined by X-ray diffraction (XRD). The above results suggested that the Li-doped ZnO film/NCD structure prepared in this work was attractive for the application of high frequency surface acoustic wave (SAW) devices.

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

    SciTech Connect

    Prajapati, C.S.; Kushwaha, Ajay; Sahay, P.P.

    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-doped 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.

  20. Effect of seed layer on the self assembly of spray pyrolyzed Al-doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Dwivedi, Charu; Dutta, V.

    2013-03-01

    Al-doped ZnO (AlZO) nanorod arrays and nanostructures were fabricated on seed coated glass substrates via CoSP (Continuous Spray Pyrolysis) reactor. The as-synthesized aluminium doped ZnO nanoparticles and nanorods were analyzed through different characterization techniques. There were no significant changes found in the structure with doping of Al but the morphology of the film changed to branched nanorods and nanosheets with the change in seed solution and annealing temperature, respectively. Also, the current-voltage curves of the ZnO and AZO nanorod arrays was measured and it was found that the current response of AZO nanorods was higher than that of ZnO nanorods, proving the Al incorporation as a dopant.

  1. Preparation and XRD analyses of Na-doped ZnO nanorod arrays based on experiment and theory

    NASA Astrophysics Data System (ADS)

    Yang, X. P.; Lu, J. G.; Zhang, H. H.; Chen, Y.; Kan, B. T.; Zhang, J.; Huang, J.; Lu, B.; Zhang, Y. Z.; Ye, Z. Z.

    2012-03-01

    ZnO nanorod arrays (NRAs) with different Na contents were prepared by thermal evaporation. Sodium pyrophosphate was adopted as the Na source. The Na contents in NRAs were determined by X-ray photoelectron spectra to be 0, 6.1, and 9.4 at.%. X-ray diffraction (XRD) analyses of Na-doped ZnO NRAs were performed in experiment and by first-principle calculation with the assumption of Na substitutions. A couple of typical changes were found in XRD patterns of Na-doped ZnO. The simulation results well agreed with the experimental data, which revealed that Na mainly located at the substitutional sites in Na-doped ZnO NRAs.

  2. Synthesis and properties of boron doped ZnO nanorods on silicon substrate by low-temperature hydrothermal reaction

    NASA Astrophysics Data System (ADS)

    Yu, Qi; Li, Liuan; Li, Hongdong; Gao, Shiyong; Sang, Dandan; Yuan, Jujun; Zhu, Pinwen

    2011-05-01

    Boron doped ZnO nanorods were fabricated by hydrothermal technique on silicon substrate covered with a ZnO seed layer. It is found that the concentration of boric acid in the reaction solution plays a key role in varying the morphology and properties of the products. The growth rate along the [0 0 0 1] orientation (average size in diameter) of the doped ZnO nanorods decreased (increased) with the increase of boric acid concentration. Based on the results of XRD, EDX and XPS, it is demonstrated that the boron dopants tend to occupy the octahedral interstice sites. The photoluminescence of the ZnO nanorods related to boron doping are investigated.

  3. Study of the negative magneto-resistance of single proton-implanted lithium-doped ZnO microwires.

    PubMed

    Lorite, I; Zandalazini, C; Esquinazi, P; Spemann, D; Friedländer, S; Pöppl, A; Michalsky, T; Grundmann, M; Vogt, J; Meijer, J; Heluani, S P; Ohldag, H; Adeagbo, W A; Nayak, S K; Hergert, W; Ernst, A; Hoffmann, M

    2015-07-01

    The magneto-transport properties of single proton-implanted ZnO and of Li(7%)-doped ZnO microwires have been studied. The as-grown microwires were highly insulating and not magnetic. After proton implantation the Li(7%) doped ZnO microwires showed a non-monotonous behavior of the negative magneto-resistance (MR) at temperature above 150 K. This is in contrast to the monotonous NMR observed below 50 K for proton-implanted ZnO. The observed difference in the transport properties of the wires is related to the amount of stable Zn vacancies created at the near surface region by the proton implantation and Li doping. The magnetic field dependence of the resistance might be explained by the formation of a magnetic/non-magnetic heterostructure in the wire after proton implantation. PMID:26043764

  4. Study of the negative magneto-resistance of single proton-implanted lithium-doped ZnO microwires

    NASA Astrophysics Data System (ADS)

    Lorite, I.; Zandalazini, C.; Esquinazi, P.; Spemann, D.; Friedländer, S.; Pöppl, A.; Michalsky, T.; Grundmann, M.; Vogt, J.; Meijer, J.; Heluani, S. P.; Ohldag, H.; Adeagbo, W. A.; Nayak, S. K.; Hergert, W.; Ernst, A.; Hoffmann, M.

    2015-06-01

    The magneto-transport properties of single proton-implanted ZnO and of Li(7%)-doped ZnO microwires have been studied. The as-grown microwires were highly insulating and not magnetic. After proton implantation the Li(7%) doped ZnO microwires showed a non-monotonous behavior of the negative magneto-resistance (MR) at temperature above 150 K. This is in contrast to the monotonous NMR observed below 50 K for proton-implanted ZnO. The observed difference in the transport properties of the wires is related to the amount of stable Zn vacancies created at the near surface region by the proton implantation and Li doping. The magnetic field dependence of the resistance might be explained by the formation of a magnetic/non-magnetic heterostructure in the wire after proton implantation.

  5. Room temperature enhanced red emission from novel Eu(3+) doped ZnO nanocrystals uniformly dispersed in nanofibers.

    PubMed

    Zhang, Yongzhe; Liu, Yanxia; Li, Xiaodong; Wang, Qi Jie; Xie, Erqing

    2011-10-14

    Achieving red emission from ZnO-based materials has long been a goal for researchers in order to realize, for instance, full-color display panels and solid-state light-emitting devices. However, the current technique using Eu(3+) doped ZnO for red emission generation has a significant drawback in that the energy transfer from ZnO to Eu(3+) is inefficient, resulting in a low intensity red emission. In this paper, we report an efficient energy transfer scheme for enhanced red emission from Eu(3+) doped ZnO nanocrystals by fabricating polymer nanofibers embedded with Eu(3+) doped ZnO nanocrystals to facilitate the energy transfer. In the fabrication, ZnO nanocrystals are uniformly dispersed in polymer nanofibers prepared by the high electrical field electrospinning technique. Enhanced red emission without defect radiation from the ZnO matrix is observed. Three physical mechanisms for this observation are provided and explained, namely a small ZnO crystal size, uniformity distribution of ZnO nanocrystals in polymers (PVA in this case), and strong bonding between ZnO and polymer through the -OH group bonding. These explanations are supported by high resolution transmission emission microscopy measurements, resonant Raman scattering characterizations, photoluminescence spectra and photoluminescence excitation spectra measurements. In addition, two models exploring the 'accumulation layer' and 'depletion layer' are developed to explain the reasons for the more efficient energy transfer in our ZnO nanocrystal system compared to that in the previous reports. This study provides an important approach to achieve enhanced energy transfer from nanocrystals to ions which could be widely adopted in rare earth ion doped materials. These discoveries also provide more insights into other energy transfer problems in, for example, dye-sensitized solar cells and quantum dot solar cells. PMID:21914938

  6. Room temperature enhanced red emission from novel Eu3 + doped ZnO nanocrystals uniformly dispersed in nanofibers

    NASA Astrophysics Data System (ADS)

    Zhang, Yongzhe; Liu, Yanxia; Li, Xiaodong; Jie Wang, Qi; Xie, Erqing

    2011-10-01

    Achieving red emission from ZnO-based materials has long been a goal for researchers in order to realize, for instance, full-color display panels and solid-state light-emitting devices. However, the current technique using Eu3 + doped ZnO for red emission generation has a significant drawback in that the energy transfer from ZnO to Eu3 + is inefficient, resulting in a low intensity red emission. In this paper, we report an efficient energy transfer scheme for enhanced red emission from Eu3 + doped ZnO nanocrystals by fabricating polymer nanofibers embedded with Eu3 + doped ZnO nanocrystals to facilitate the energy transfer. In the fabrication, ZnO nanocrystals are uniformly dispersed in polymer nanofibers prepared by the high electrical field electrospinning technique. Enhanced red emission without defect radiation from the ZnO matrix is observed. Three physical mechanisms for this observation are provided and explained, namely a small ZnO crystal size, uniformity distribution of ZnO nanocrystals in polymers (PVA in this case), and strong bonding between ZnO and polymer through the -OH group bonding. These explanations are supported by high resolution transmission emission microscopy measurements, resonant Raman scattering characterizations, photoluminescence spectra and photoluminescence excitation spectra measurements. In addition, two models exploring the 'accumulation layer' and 'depletion layer' are developed to explain the reasons for the more efficient energy transfer in our ZnO nanocrystal system compared to that in the previous reports. This study provides an important approach to achieve enhanced energy transfer from nanocrystals to ions which could be widely adopted in rare earth ion doped materials. These discoveries also provide more insights into other energy transfer problems in, for example, dye-sensitized solar cells and quantum dot solar cells.

  7. Annealed Ce3+-doped ZnO flower-like morphology synthesized by chemical bath deposition method

    NASA Astrophysics Data System (ADS)

    Koao, Lehlohonolo F.; Dejene, Francis B.; Tsega, Moges; Swart, Hendrik C.

    2016-01-01

    We have successfully synthesized ZnO:xmol% Ce3+ (0≤x≤10 mol%) doped nanopowders via the chemical bath deposition method (CBD) technique at low temperature (80 °C) and annealed in air at 700 °C. The X-ray diffraction patterns showed that all the undoped and Ce-doped ZnO nanopowders have a hexagonal wurtzite polycrystalline structure with an average crystallite size of about 46 nm. Weak diffraction peaks related mainly to cerium oxide were also detected at higher concentrations of Ce3+ (x=5-10 mol%). The scanning electron microscopy study revealed that the nanopowder samples were assembled in flower-shaped undoped ZnO and pyramid-shaped Ce3+-doped ZnO nanostructures. The UV-vis spectra showed that the absorption edges shifted slightly to the longer wavelengths with the increase in the Ce3+ ions concentration. Moreover, the photoluminescence (PL) results showed a relative weak visible emission for the Ce3+-doped ZnO nanoparticles compared to the undoped ZnO. The effects of Ce3+-doping on the structure and PL of ZnO nanopowders are discussed in detail.

  8. Magnetic and dielectric studies of Li-Cu co-doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Vivek, S.; Ajith, S. K.; Chitralekha, C. S.; Nair, Swapna S.

    2016-05-01

    Room temperature ferromagnetism has been observed in Li-Cu co-doped ZnO nanoparticles prepared by sol-gel route. Our studies indicated that the observed ferromagnetism is a surface phenomenon which depends on oxygen vacancy and the nature of the dopants. Dependence of ferromagnetism on the annealing temperature indicated the role of oxygen vacancy, and the decrease in coercivity as the particle size increases indicates the surface dependence of ferromagnetism. It is found that the addition of dopants also enhanced ferromagnetism. Dielectric studies indicated an increase in dielectric constant as the doping concentration is increased.

  9. Microstructure evolution of highly Ga-doped ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Oh, S. J.; Jung, M. N.; Ha, S. Y.; Choi, S. G.; Kim, J. J.; Kobayashi, K.; Lee, S. T.; Lee, H. C.; Cho, Y. R.; Yao, T.; Chang, J. H.

    2008-10-01

    Ga-doped zinc oxide (ZnO) (ZnO:Ga) nanocrystals were synthesized by the vapor-solidification method to investigate morphological and structural evolution induced by Ga-incorporation. Ga-content was controlled in the full composition range (0-100%). As the Ga-content increased, the shape of nanocrystals changed from tetrapod- to rod-type. Hard X-ray photoemission spectroscopy (HXPES) measurement indicates that highly Ga-doped uniphase ZnO:Ga nanocrystals without a serious deterioration of morphology are achieved, which strongly suggests the feasibility of Ga as a successful n-type dopant for ZnO-based nanocrystals.

  10. Synthesis of wheatear-like ZnO nanoarrays decorated with Ag nanoparticles and its improved SERS performance through hydrogenation.

    PubMed

    Shan, Yufeng; Yang, Yong; Cao, Yanqin; Fu, Chaoli; Huang, Zhengren

    2016-04-01

    Semiconductor/noble metal composite SERS substrates have been extensively studied due to their unique bifunctionality. In this work, wheatear-like ZnO nanoarrarys have been fabricated via a modified low-temperature solution method. The hierarchical nanostructures that are constructed by stacked nanoflakes and long whiskers of ZnO possess a substantial number of characteristic nano corners and edges, which are proved to be beneficial to deposit more Ag nanoparticles (NPs). Furthermore, hydrogenated wheatear-like ZnO/AgNP composite substrates are achieved via a safe and facile solid hydrogen source (NaBH4). The hydrogenated ZnO/AgNPs (H-ZnO/Ag) substrates exhibit greatly improved SERS activity in detecting R6G molecules with an enhancement factor (EF) up to ∼0.49 × 10(8), over two orders of magnitude higher than that of the substrates before hydrogenation. The outstanding SERS performance of wheatear-like H-ZnO/Ag substrates benefits from the emerging porous structure of ZnO and abundant surface defects introduced by hydrogenation. In addition, the as-prepared substrates also show high detection sensitivity, good repeatability and recyclability, indicating great potential for practical applications. PMID:26916627

  11. Origin of carrier scattering in polycrystalline Al-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Jia, Junjun; Oka, Nobuto; Kusayanagi, Minehide; Nakatomi, Satoshi; Shigesato, Yuzo

    2014-10-01

    We observed the carrier transport phenomena in polycrystalline Al-doped ZnO (AZO) films with carrier densities ranging from 2.0 × 1019 to 1.1 × 1021 cm-3. A comparison of the optical carrier density and Hall carrier density indicates that the conduction band in AZO films is nonparabolic above 2.0 × 1020 cm-3. A transition from grain boundary scattering to ionized impurity scattering is observed at a doping level of ˜4.0 × 1020 cm-3. The trap density at the grain boundary increases with increasing Al concentration in the films, implying that the doping level plays a decisive role in the trap density. The excellent fitting of the optical mobility and carrier density using the Brooks-Herring model shows that the acceptor concentration increases with increasing doping level.

  12. Realization of p-type conductivity in ZnO by (N, Ag) dual acceptor codoping: a first-principles study

    NASA Astrophysics Data System (ADS)

    Xiong, Zhihua; Chen, Lanli; Wan, Qixin; Li, Dongmei

    2010-10-01

    Ag monodoped, N monodoped and (nN, Ag) codoped ZnO have been investigated by the first-principles calculations, where the formation energies and ionization energies of various complexes and the electronic structure for 3N-Ag complex are studied. The calculated results are that N prefers to substitute O site, and Ag substitutes Zn site under the most growth condition, which indicate NO and AgZn all act as acceptors. Meanwhile, it's shown that N-Ag, 2N-Ag complex contribute little to p-type conduction because of the relatively higher ionization energy. However, 3N-Ag complex may have the lowest ionization energy among various complexes, while the formation energy of 3N-Ag is lower than that of N monodoped, Ag monodoped, N-Ag and 2N-Ag complex under the Zn-rich condition, which indicates that 3N-Ag complex is energetically favorable for the formation of p-type ZnO. Furthermore, by studying the electronic structure of 3N-Ag complex, it may generate an additional impurity band above the valence band maximum of ZnO. It is found that NO generated holes around the top of the valence band, and at the same time, N 2p states hybridized with 4d states of AgZn at the Fermi energy, and the hybridization lowered the repulsive interaction between the two dual acceptors, which enhance the concentration of impurities and the stability of the system, indicating that the dual acceptors evidently improve p-type conductivity of ZnO. Thus, it is found that 3N-Ag complex is the better dopant configuration. That can gain a better quality p-type ZnO under the Zn-rich condition. Our theoretical results are consistent with the experiment results.

  13. Effect of band gap energy on the electrical conductivity in doped ZnO thin film

    NASA Astrophysics Data System (ADS)

    Benramache, Said; Belahssen, Okba; Ben Temam, Hachemi

    2014-07-01

    The transparent conductive pure and doped zinc oxide thin films with aluminum, cobalt and indium were deposited by ultrasonic spray technique on glass substrate at 350 °C. This paper is to present a new approach to the description of correlation between electrical conductivity and optical gap energy with dopants' concentration of Al, Co and In. The correlation between the electrical and optical properties with doping level suggests that the electrical conductivity of the films is predominantly estimated by the band gap energy and the concentrations of Al, Co and In. The measurement in the electrical conductivity of doped films with correlation is equal to the experimental value, the error of this correlation is smaller than 13%. The minimum error value was estimated in the cobalt-doped ZnO thin films. This result indicates that such Co-doped ZnO thin films are chemically purer and have far fewer defects and less disorder owing to an almost complete chemical decomposition.

  14. Effect of neodymium doping on structure, electrical and optical properties of nanocrystalline ZnO

    SciTech Connect

    Roy, B.; Chakrabarty, S.; Mondal, O.; Pal, M.; Dutta, A.

    2012-08-15

    In this paper, we report effect of Nd doping on structure, electrical and optical properties of nanocrystalline ZnO prepared through a modified ceramic route. The X-ray diffraction and transmission electron microscopy studies reveal that annealed samples are single phase, pure nanocrystalline ZnO. The optical band gap for different compositions, estimated from ultraviolet-visible spectroscopy study, shows a little increasing tendency while doped with Nd for the samples annealed at lower temperature. The dc electrical conductivity of the samples decreases with the increase in Nd concentration. The ac electrical measurements prove the hopping conduction as the dominant mechanism. The results are being explained on the basis of band structural change due to Nd doping in the host lattice and by Correlated Barrier Hopping model. - Highlights: Black-Right-Pointing-Pointer Particle size increases when it is doped (from XRD). Black-Right-Pointing-Pointer XRD peak shifted to lower angle when doped. Black-Right-Pointing-Pointer The dc conductivity decreases with the increase of Nd dopant concentrations. Black-Right-Pointing-Pointer The temperature dependent ac conductivity follows the universal power law.

  15. Structural, microstructural, optical and magnetic properties of Mn-doped ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Fabbiyola, S.; Kennedy, L. John; Dakhel, A. A.; Bououdina, M.; Vijaya, J. Judith; Ratnaji, T.

    2016-04-01

    Pure and Mn2+ doped ZnO nanoparticles (Zn1-xMnxO with 0 ≤ x ≤ 0.2) were prepared by co-precipitation method followed by drying at 200 °C. A non-ionic surfactant, Tween-80, was used during preparation process to control the particles growth. X-ray diffraction analysis revealed the formation of hexagonal wurtzite for pure and Mn2+ doped ZnO samples with a minor secondary phase. The Rietveld analysis confirmed the formation of hexagonal wurtzite structure as well as the secondary phase as Mn3O4 for all doping levels. Morphological observations showed the formation of nanoparticles with remarkable morphologies of which spherical nanostructures seem to be more dominant. The quantitative analysis from EDAX confirmed the purity of the as-prepared nanopowders and that the chemical composition of Zn, Mn and O seem to be close to the starting stoichiometries. Emission bands in both UV and visible regions were revealed by photoluminescence spectra, which were due to defect centers acting as trap levels. The diffuse reflectance spectroscopy (DRS) indicated a decrease in the value of bandgap with increasing Mn doping concentration. The ferromagnetic behaviour was very clear from the Magnetisation-Field (M-H) hysteresis curves, where the magnetic characteristics such as coercivity and saturation magnetization values, were found to be sensitive to Mn doping level.

  16. Growth and properties of electrodeposited transparent Al-doped ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Baka, O.; Mentar, L.; Khelladi, M. R.; Azizi, A.

    2015-12-01

    Al-doped zinc oxide (AZO) nanostructures were fabricated on fluorine-doped tin-oxide (FTO)- coated glass substrates by using electrodeposition. The effects of the doping concentration of Al on the morphological, microstructural, electrical and optical properties of the nanostructures were investigated. From the field emission scanning electron microscopy (FE-SEM) observation, when the amount of Al was increased in the solution, the grains size was observed to decreases. The observed changes in the morphology indicate that Al acts as nucleation centers in the vacancy sites of ZnO and destroys the crystalline structure at high doping level. Effectively, the X-ray diffraction (XRD) analysis indicated that the undoped and the doped ZnO nanostructures has a polycrystalline nature and a hexagonal wurtzite structure with a (002) preferential orientation. The photoluminescence (PL) room-temperature measurements showed that the incorporation of Al in the Zn lattice can improve the intensity of ultraviolet (UV) emission, thus suggesting its greater prospects for use in UV optoelectronic devices.

  17. Hexagonal core-shell and alloy Au/Ag nanodisks on ZnO nanorods and their optical enhancement effect

    PubMed Central

    2014-01-01

    Au and Ag hybrid hexagonal nanodisks were synthesized on ZnO nanorods' (0002) surface via a new two-step deposition-annealing method. The structural, compositional, as well as optical investigations were carried out systematically to find out the nanodisks' formation mechanism and optical enhancement effect. It was shown that the core-shell Au/Ag nanodisk can be formed under rapid annealing temperature of 500°C, while Au/Ag alloy nanodisks are formed if higher temperatures (>550°C) are applied. The optical effect from these nanodisks was studied through photoluminescence and absorption spectroscopy. It was found that the carrier-plasmon coupling together and carrier transfer between metal and ZnO contribute to the emission enhancement. Furthermore, the results suggest that the composition of nanodisk on the vicinity of metal/ZnO interface plays an important role in terms of the enhancement factors. PMID:24936157

  18. Mechanical, structural and thermal properties of Ag-Cu and ZnO reinforced polylactide nanocomposite films.

    PubMed

    Ahmed, Jasim; Arfat, Yasir Ali; Castro-Aguirre, Edgar; Auras, Rafael

    2016-05-01

    Plasticized polylactic acid (PLA) based nanocomposite films were prepared by incorporating polyethylene glycol (PEG) and two selected nanoparticles (NPs) [silver-copper (Ag-Cu) alloy (<100 nm) and zinc oxide (ZnO) (<50 and <100 nm)] through solvent casting method. Incorporation of Ag-Cu alloy into the PLA/PEG matrix increased the glass transition temperature (Tg) significantly. The crystallinity of the nanocomposites (NCs) was significantly influenced by NP incorporation as evidenced from differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis. The PLA nanocomposite reinforced with NPs exhibited much higher tensile strength than that of PLA/PEG blend. Melt rheology of NCs exhibited a shear-thinning behavior. The mechanical property drastically reduced with a loading of NPs, which is associated with degradation of PLA. SEM micrographs exhibited that both Ag-Cu alloy and ZnO NPs were dispersed well in the PLA film matrix. PMID:26893045

  19. Characteristics of ZnO thin films doped by various elements

    NASA Astrophysics Data System (ADS)

    Kahraman, S.; Çakmak, H. M.; Çetinkaya, S.; Bayansal, F.; Çetinkara, H. A.; Güder, H. S.

    2013-01-01

    We have investigated the effects of Al, K and Co dopant elements on the properties of ZnO thin films deposited by CBD method on glass substrates. Changing in morphology, structural parameters, ionization energies of impurity levels, absorption behavior and optical band gap values were investigated through scanning electron microscopy (SEM), X-Ray diffraction (XRD), resistance-temperature measurement (R-T) and ultraviolet-visible spectroscopy (UV-vis) techniques. From the SEM observations, various morphologies (rod-like, flower-like and rice-like) were observed. Those morphological variations were attributed to the change in stable growth mechanism of intrinsic ZnO, induced by different atomic radius and different electronegativity of dopants. XRD results indicated that all orientations are well indexed to hexagonal phase crystalline ZnO. The impurity level ionization energy values (ΔE) were estimated as 0.32/0.13/0.07 eV; 0.34/0.15 eV; 0.40/0.13 eV and 0.48/0.22 eV for the Al, K, Co doped samples and i-ZnO, respectively. Optical band gap values were found that the doped samples' were higher than the intrinsic one's. This increasing (blue shift) was attributed to a deterioration which occurred in the lattice of the structures after doping. This effect was also supported by the structural results.

  20. Photovoltaic performance of Gallium-doped ZnO thin film/Si nanowires heterojunction diodes

    NASA Astrophysics Data System (ADS)

    Akgul, Guvenc; Aksoy Akgul, Funda; Emrah Unalan, Husnu; Turan, Rasit

    2016-04-01

    In this work, photovoltaic performance of Ga-doped ZnO thin film/Si NWs heterojunction diodes was investigated. Highly dense and vertically well-aligned Si NW arrays were successfully synthesised on a p-type (1 0 0)-oriented Si wafer through cost-effective metal-assisted chemical etching technique. Ga-doped ZnO thin films were deposited onto Si NWs via radio frequency magnetron sputtering to construct three-dimensional heterostructures. Photovoltaic characteristics of the fabricated diodes were determined with current density (J)-voltage (V) measurements under simulated solar irradiation of AM 1.5 G. The optimal open-circuit voltage, short-circuit current density, fill factor and power conversion efficiency were found to be 0.37 V, 3.30 mA cm-2, 39.00 and 0.62%, respectively. Moreover, photovoltaic diodes exhibited relatively high external quantum efficiency over the broadband wavelengths between 350 and 1100 nm interval of the spectrum. The observed photovoltaic performance in this study clearly indicates that the investigated device structure composed of Ga-doped ZnO thin film/Si NWs heterojunctions could facilitate an alternative pathway for optoelectronic applications in future, and be a promising alternative candidate for high-performance low-cost new-generation photovoltaic diodes.

  1. Ferromagnetism in Gd doped ZnO nanowires: A first principles study

    SciTech Connect

    Aravindh, S. Assa; Schwingenschloegl, Udo E-mail: iman.roqan@kaust.edu.sa; Roqan, Iman S. E-mail: iman.roqan@kaust.edu.sa

    2014-12-21

    In several experimental studies, room temperature ferromagnetism in Gd-doped ZnO nanostructures has been achieved. However, the mechanism and the origin of the ferromagnetism remain controversial. We investigate the structural, magnetic, and electronic properties of Zn{sub 48}O{sub 48} nanowires doped with Gd, using density functional theory. Our findings indicate that substitutionally incorporated Gd atoms prefer occupying the surface Zn sites. Moreover, the formation energy increases with the distance between Gd atoms, signifying that no Gd-Gd segregation occurs in the nanowires within the concentration limit of ≤2%. Gd induces ferromagnetism in ZnO nanowires with magnetic coupling energy up to 21 meV in the neutral state, which increases with additional electron and O vacancy, revealing the role of carriers in magnetic exchange. The potential for achieving room temperature ferromagnetism and high T{sub C} in ZnO:Gd nanowires is evident from the large ferromagnetic coupling energy (200 meV) obtained with the O vacancy. Density of states shows that Fermi level overlaps with Gd f states with the introduction of O vacancy, indicating the possibility of s-f coupling. These results will assist in understanding experimental findings in Gd-doped ZnO nanowires.

  2. Photo-degradation of methylene blue using Ta-doped ZnO nanoparticle

    SciTech Connect

    Kong Jizhou; Li Aidong; Li Xiangyu; Zhai Haifa; Zhang Wenqi; Gong Youpin; Li Hui; Wu Di

    2010-06-15

    A photocatalyst of Ta-doped ZnO was prepared by a modified Pechini-type method. The structural, morphological properties and photocatalytic activity of 1 mol % Ta-doped ZnO samples annealed at different temperatures were characterized. The photo-oxidation of methylene blue under the visible-light irradiation followed the pseudo-first-order kinetics according to the Langmuir-Hinshelwood model. It is found that the photocatalysis of 1% Ta-doped ZnO annealed at 700 {sup o}C showed excellent performance of the photodegradation of methylene blue, which was attributed to a competitive trade-off among the crystallinity, surface hydroxyl groups, and specific surface area. The processing parameter such as the pH value also played an important role in tuning the photocatalytic activity. The maximum photodecomposed rate was achieved at pH=8, and an novel model about the absorption of methylene blue on the surface of the catalysts was proposed. - Graphical abstract: This model describes the adsorption between the amphoteric behavior of the metal oxide and the cationic dye methylene blue (MB) on the surface of the catalyst at the acidic and alkaline condition.

  3. Comparative studies of Al-doped ZnO and Ga-doped ZnO transparent conducting oxide thin films

    PubMed Central

    2012-01-01

    We have investigated the influences of aluminum and gallium dopants (0 to 2.0 mol%) on zinc oxide (ZnO) thin films regarding crystallization and electrical and optical properties for application in transparent conducting oxide devices. Al- and Ga-doped ZnO thin films were deposited on glass substrates (corning 1737) by sol–gel spin-coating process. As a starting material, AlCl3⋅6H2O, Ga(NO3)2, and Zn(CH3COO)2⋅2H2O were used. A lowest sheet resistance of 3.3 × 103 Ω/□ was obtained for the GZO thin film doped with 1.5 mol% of Ga after post-annealing at 650°C for 60 min in air. All the films showed more than 85% transparency in the visible region. We have studied the structural and microstructural properties as a function of Al and Ga concentrations through X-ray diffraction and scanning electron microscopy analysis. In addition, the optical bandgap and photoluminescence were estimated. PMID:23173885

  4. Deposition of F-doped ZnO transparent thin films using ZnF2-doped ZnO target under different sputtering substrate temperatures

    PubMed Central

    2014-01-01

    Highly transparent and conducting fluorine-doped ZnO (FZO) thin films were deposited onto glass substrates by radio-frequency (RF) magnetron sputtering, using 1.5 wt% zinc fluoride (ZnF2)-doped ZnO as sputtering target. Structural, electrical, and optical properties of the FZO thin films were investigated as a function of substrate temperature ranging from room temperature (RT) to 300°C. The cross-sectional scanning electron microscopy (SEM) observation and X-ray diffraction analyses showed that the FZO thin films were of polycrystalline nature with a preferential growth along (002) plane perpendicular to the surface of the glass substrate. Secondary ion mass spectrometry (SIMS) analyses of the FZO thin films showed that there was incorporation of F atoms in the FZO thin films, even if the substrate temperature was 300°C. Finally, the effect of substrate temperature on the transmittance ratio, optical energy gap, Hall mobility, carrier concentration, and resistivity of the FZO thin films was also investigated. PMID:24572004

  5. Lateral photovoltaic effect co-observed with unipolar resistive switching behavior in Cu-doped ZnO film

    NASA Astrophysics Data System (ADS)

    Lu, Jing; Li, Zheng; Yin, Guilin; Ge, Meiying; He, Dannong; Wang, Hui

    2014-09-01

    Unipolar resistive switching (RS) behavior was first observed in Cu-doped ZnO film based on ZnO/SiO2/Si structure, which was a novel phenomenon as memory films grown on Si substrate usually showed a bipolar one. The results demonstrate Cu-doped ZnO a new candidate for memory material. By introducing an external electric-field before the sweeping process, we have verified that the RS behavior was a localized effect. The non-linear I-V character, which suggested a junction of the proposed Cu-doped ZnO/SiO2/Si structure, leads to the lateral photovoltaic effect (LPE) investigation. In photovoltaic mode, which is the simplest configuration, the position sensitivity of lateral photovoltage observed on Cu-doped ZnO film achieves 24.82 mV/mm and the nonlinearity is within 9.95%, indicating that Cu-doped ZnO could serve as a LPE material directly. The dual effects accommodate functions of detector and memristor in the same structure and make Cu-doped ZnO a competitive material for advanced multi-functional device.

  6. Photocatalytic degradation of humic substances in aqueous solution using Cu-doped ZnO nanoparticles under natural sunlight irradiation.

    PubMed

    Maleki, Afshin; Safari, Mahdi; Shahmoradi, Behzad; Zandsalimi, Yahya; Daraei, Hiua; Gharibi, Fardin

    2015-11-01

    In this study, Cu-doped ZnO nanoparticles were investigated as an efficient synthesized catalyst for photodegradation of humic substances in aqueous solution under natural sunlight irradiation. Cu-doped ZnO nanocatalyst was prepared through mild hydrothermal method and was characterized using FT-IR, powder XRD and SEM techniques. The effect of operating parameters such as doping ratio, initial pH, catalyst dosage, initial concentrations of humic substances and sunlight illuminance were studied on humic substances degradation efficiency. The results of characterization analyses of samples confirmed the proper synthesis of Cu-doped ZnO nanocatalyst. The experimental results indicated the highest degradation efficiency of HS (99.2%) observed using 1.5% Cu-doped ZnO nanoparticles at reaction time of 120 min. Photocatalytic degradation efficiency of HS in a neutral and acidic pH was much higher than that at alkaline pH. Photocatalytic degradation of HS was enhanced with increasing the catalyst dosage and sunlight illuminance, while increasing the initial HS concentration led to decrease in the degradation efficiency of HS. Conclusively, Cu-doped ZnO nanoparticles can be used as a promising and efficient catalyst for degradation of HS under natural sunlight irradiation. PMID:26104905

  7. Improved Exciton Dissociation at Semiconducting Polymer:ZnO Donor:Acceptor Interfaces via Nitrogen Doping of ZnO

    PubMed Central

    Musselman, Kevin P; Albert-Seifried, Sebastian; Hoye, Robert L Z; Sadhanala, Aditya; Muñoz-Rojas, David; MacManus-Driscoll, Judith L; Friend, Richard H

    2014-01-01

    Exciton dissociation at the zinc oxide/poly(3-hexylthiophene) (ZnO/P3HT) interface as a function of nitrogen doping of the zinc oxide, which decreases the electron concentration from approximately 1019 cm−3 to 1017 cm−3, is reported. Exciton dissociation and device photocurrent are strongly improved with nitrogen doping. This improved dissociation of excitons in the conjugated polymer is found to result from enhanced light-induced de-trapping of electrons from the surface of the nitrogen-doped ZnO. The ability to improve the surface properties of ZnO by introducing a simple nitrogen dopant has general applicability. PMID:25520604

  8. Growth and optical properties of ZnO nanorod arrays on Al-doped ZnO transparent conductive film

    PubMed Central

    2013-01-01

    ZnO nanorod arrays (NRAs) on transparent conductive oxide (TCO) films have been grown by a solution-free, catalyst-free, vapor-phase synthesis method at 600°C. TCO films, Al-doped ZnO films, were deposited on quartz substrates by magnetron sputtering. In order to study the effect of the growth duration on the morphological and optical properties of NRAs, the growth duration was changed from 3 to 12 min. The results show that the electrical performance of the TCO films does not degrade after the growth of NRAs and the nanorods are highly crystalline. As the growth duration increases from 3 to 8 min, the diffuse transmittance of the samples decreases, while the total transmittance and UV emission enhance. Two possible nanorod self-attraction models were proposed to interpret the phenomena in the sample with 9-min growth duration. The sample with 8-min growth duration has the highest total transmittance of 87.0%, proper density about 75 μm−2, diameter about 26 nm, and length about 500 nm, indicating that it can be used in hybrid solar cells. PMID:23566567

  9. ZnO nanowires array grown on Ga-doped ZnO single crystal for dye-sensitized solar cells.

    PubMed

    Hu, Qichang; Li, Yafeng; Huang, Feng; Zhang, Zhaojun; Ding, Kai; Wei, Mingdeng; Lin, Zhang

    2015-01-01

    High quality ZnO nanowires arrays were homoepitaxial grown on Ga-doped ZnO single crystal (GZOSC), which have the advantages of high conductivity, high carrier mobility and high thermal stability. When it was employed as a photoanode in the DSSCs, the cell exhibited a 1.44% power-conversion efficiency under the illumination of one sun (AM 1.5G). The performance is superior to our ZnO nanowires/FTO based DSSCs under the same condition. This enhanced performance is mainly attributed to the perfect interface between the ZnO nanowires and the GZOSC substrate that contributes to lower carrier scattering and recombination rates compared with that grown on traditional FTO substrate. PMID:26099568

  10. ZnO nanowires array grown on Ga-doped ZnO single crystal for dye-sensitized solar cells

    PubMed Central

    Hu, Qichang; Li, Yafeng; Huang, Feng; Zhang, Zhaojun; Ding, Kai; Wei, Mingdeng; Lin, Zhang

    2015-01-01

    High quality ZnO nanowires arrays were homoepitaxial grown on Ga-doped ZnO single crystal (GZOSC), which have the advantages of high conductivity, high carrier mobility and high thermal stability. When it was employed as a photoanode in the DSSCs, the cell exhibited a 1.44% power-conversion efficiency under the illumination of one sun (AM 1.5G). The performance is superior to our ZnO nanowires/FTO based DSSCs under the same condition. This enhanced performance is mainly attributed to the perfect interface between the ZnO nanowires and the GZOSC substrate that contributes to lower carrier scattering and recombination rates compared with that grown on traditional FTO substrate. PMID:26099568

  11. Vertically aligned nanostructures based on Na-doped ZnO nanorods for wide band gap semiconductor memory applications.

    PubMed

    Huang, Jian; Qi, Jing; Li, Zonglin; Liu, Jianlin

    2013-10-01

    Vertically aligned undoped ZnO nanotips, nanotubes and nanorods were synthesized on the top facets of Na-doped ZnO nanorods without catalytic assistance under different growth times in a chemical vapor deposition system. The growth mechanism is discussed. The Na-doped nanorods were grown on a ZnO seed layer on Si. The p-type conductivity of the Na-doped nanorods was studied by temperature-dependent photoluminescence and nanorod back-gated field effect transistor measurements. The undoped nanorods, Na-doped nanorods and undoped seed layer form an n-p-n memory structure. The programming and retention characteristics have been demonstrated. PMID:24013400

  12. Structural and electronic properties of ni-doped ZnO in zinc-blende phase: A DFT investigations

    NASA Astrophysics Data System (ADS)

    Haq, Bakhtiar Ul; Ahmed, R.; Afaq, A.; Shaari, A.; Zarshenas, M.

    2012-09-01

    In the present work investigations of structural and electronic properties of nickel doped ZnO in zinc-blende phase have been done in the framework of density functional theory. In doping process 25% cations (Zn atoms) have been replaced by Ni atoms. Wu-Cohen parameterized Generalized Gradient Approximation (GGA-WC) is used for exchange and correlation energy functional treatment. Our calculations for structural properties reveal a reduction in lattice constant with Ni doping. Whereas the spin polarized electronic structures show metallic behavior of ZnO in the presence of Ni impurity atoms for both up and down spin configuration. Moreover we present calculated density of states to understand the effect of Ni doping on ZnO.

  13. Tailoring Energy Bandgap of Al Doped ZnO Thin Films Grown by Vacuum Thermal Evaporation Method.

    PubMed

    Vyas, Sumit; Singh, Shaivalini; Chakrabarti, P

    2015-12-01

    The paper presents the results of our experimental investigation pertaining to tailoring of energy bandgap and other associated characteristics of undoped and Al doped ZnO (AZO) thin film by varying the atomic concentration of Al in ZnO. Thin films of ZnO and ZnO doped with Al (1, 3, and 5 atomic percent (at.%)) were deposited on silicon substrate for structural characterization and on glass substrate for optical characterization. The dependence of structural and optical properties of Al doped ZnO on the atomic concentration of Al added to ZnO has been reported. On the basis of the experimental results an empirical formula has been proposed to calculate the energy bandgap of AZO theoretically in the range of 1 to 5 at.% of Al. The study revealed that AZO films are composed of smaller and larger number of grains as compared to pure ZnO counterpart and density of the grains was found to increase as the Al concentration increased (from 1 to 5 at.%). The transmittance in the visible region was greater than 90% and found to increase with increasing Al concentration up to 5 at.%. The optical bandgap was found to increase initially with increase in atomic concentration of Al concentration up to 3 at.% and decrease thereafter with increasing concentration of Al. PMID:26682390

  14. Synthesis, Characterization, and Gas Sensing Properties of Pure and Mn-doped ZnO Nanocrystalline Particles

    NASA Astrophysics Data System (ADS)

    Saydi, J.; Karimi, M.; Mazhdi, M.; Seidi, J.; Mazhdi, F.

    2014-10-01

    Nanocrystalline ZnO and Mn (1 wt.%)-doped ZnO particles have been synthesized via reverse micelle method. The structural, particulate, and optical properties of the synthesized nanoparticles have been studied by XRD, TEM, UV-Vis, and PL spectroscopy. The obtained data indicate the synthesis of the pure nanoparticles structure with wurtzite structure, average particle size of 18-21 nm, and high optical quality. Gas sensing properties of the nanocrystalline ZnO and Mn-doped ZnO particles toward gasoline and ethanol vapors have been investigated at different temperatures and concentrations. The results show that the optimum working temperature of the gas sensors based on ZnO and Mn-doped ZnO particles are about 633 and 620 K toward ethanol vapor and about 560 and 608 K toward gasoline vapor, respectively. Based on the results, although Mn impurities reduce the sensitivity of the ZnO gas sensor, they cause sensor to saturate at much higher gas concentration.

  15. Evidence for multi-polymorphic islands during epitaxial growth of ZnO on Ag(1 1 1)

    NASA Astrophysics Data System (ADS)

    Demiroglu, Ilker; Bromley, Stefan T.

    2016-06-01

    A range of models of free standing and Ag(1 1 1)-supported stoichiometric ZnO films with coverages between 2-3 monolayers are studied using density functional calculations. Following experimental observations we focus on stoichiometric hexagonal and triangular ad-layer islands grown on top of two complete ZnO monolayers. The adlayer islands display distinct edge and corner reconstructions and are found to induce a structural transition extending from the island core to the layered phase below. Based on our results we propose a general model of ad-layer triangular island structure based on seven regions exhibiting four distinct polymorphs.

  16. Evidence for multi-polymorphic islands during epitaxial growth of ZnO on Ag(1 1 1).

    PubMed

    Demiroglu, Ilker; Bromley, Stefan T

    2016-06-01

    A range of models of free standing and Ag(1 1 1)-supported stoichiometric ZnO films with coverages between 2-3 monolayers are studied using density functional calculations. Following experimental observations we focus on stoichiometric hexagonal and triangular ad-layer islands grown on top of two complete ZnO monolayers. The adlayer islands display distinct edge and corner reconstructions and are found to induce a structural transition extending from the island core to the layered phase below. Based on our results we propose a general model of ad-layer triangular island structure based on seven regions exhibiting four distinct polymorphs. PMID:26979335

  17. Enhanced photoluminescence and Raman properties of Al-Doped ZnO nanostructures prepared using thermal chemical vapor deposition of methanol assisted with heated brass.

    PubMed

    Thandavan, Tamil Many K; Gani, Siti Meriam Abdul; San Wong, Chiow; Md Nor, Roslan

    2015-01-01

    Vapor phase transport (VPT) assisted by mixture of methanol and acetone via thermal evaporation of brass (CuZn) was used to prepare un-doped and Al-doped zinc oxide (ZnO) nanostructures (NSs). The structure and morphology were characterized by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). Photoluminescence (PL) properties of un-doped and Al-doped ZnO showed significant changes in the optical properties providing evidence for several types of defects such as zinc interstitials (Zni), oxygen interstitials (Oi), zinc vacancy (Vzn), singly charged zinc vacancy (VZn-), oxygen vacancy (Vo), singly charged oxygen vacancy (Vo+) and oxygen anti-site defects (OZn) in the grown NSs. The Al-doped ZnO NSs have exhibited shifted PL peaks at near band edge (NBE) and red luminescence compared to the un-doped ZnO. The Raman scattering results provided evidence of Al doping into the ZnO NSs due to peak shift from 145 cm-1 to an anomalous peak at 138 cm-1. Presence of enhanced Raman signal at around 274 and 743 cm-1 further confirmed Al in ZnO NSs. The enhanced D and G band in all Al-doped ZnO NSs shows possible functionalization and doping process in ZnO NSs. PMID:25756598

  18. Enhanced Photoluminescence and Raman Properties of Al-Doped ZnO Nanostructures Prepared Using Thermal Chemical Vapor Deposition of Methanol Assisted with Heated Brass

    PubMed Central

    Thandavan, Tamil Many K.; Gani, Siti Meriam Abdul; San Wong, Chiow; Md. Nor, Roslan

    2015-01-01

    Vapor phase transport (VPT) assisted by mixture of methanol and acetone via thermal evaporation of brass (CuZn) was used to prepare un-doped and Al-doped zinc oxide (ZnO) nanostructures (NSs). The structure and morphology were characterized by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). Photoluminescence (PL) properties of un-doped and Al-doped ZnO showed significant changes in the optical properties providing evidence for several types of defects such as zinc interstitials (Zni), oxygen interstitials (Oi), zinc vacancy (Vzn), singly charged zinc vacancy (VZn-), oxygen vacancy (Vo), singly charged oxygen vacancy (Vo+) and oxygen anti-site defects (OZn) in the grown NSs. The Al-doped ZnO NSs have exhibited shifted PL peaks at near band edge (NBE) and red luminescence compared to the un-doped ZnO. The Raman scattering results provided evidence of Al doping into the ZnO NSs due to peak shift from 145 cm-1 to an anomalous peak at 138 cm-1. Presence of enhanced Raman signal at around 274 and 743 cm-1 further confirmed Al in ZnO NSs. The enhanced D and G band in all Al-doped ZnO NSs shows possible functionalization and doping process in ZnO NSs. PMID:25756598

  19. Effect of doping on structural and optical properties of ZnO nanoparticles: study of antibacterial properties

    NASA Astrophysics Data System (ADS)

    Maddahi, P.; Shahtahmasebi, N.; Kompany, A.; Mashreghi, M.; Safaee, S.; Roozban, F.

    2014-06-01

    Sol-gel method was successfully used for synthesis of ZnO nanoparticles doped with 10 % Mg or Cu. The structure, morphology and optical properties of the prepared nanoparticles were studied as a function of doping content. The synthesized ZnO:(Mg/Cu) samples were characterized using XRD, TEM, FTIR and UV-Vis spectroscopy techniques. The samples show hexagonal wurtzite structure, and the phase segregation takes place for Cu doping. Optical studies revealed that Mg doping increases the energy band gap while Cu incorporation results in decrease of the band gap. The antibacterial activities of the nanoparticles were tested against Escherichia coli (Gram negative bacteria) cultures. It was found that both pure and doped ZnO nanosuspensions show good antibacterial activity which increases with copper doping, and slightly decreases with adding Mg.

  20. Synthesis and characterization of Cr-doped ZnO nanorod-array photocatalysts with improved activity

    SciTech Connect

    Chang, Chi-Jung Yang, Tsung-Lin; Weng, Yu-Ching

    2014-06-01

    Immobilized photocatalysts with high catalytic activity under UV light were prepared by growing Cr-doped ZnO nanorods on glass substrates by a hydrothermal method. The effects of Cr dopant on the surface texture, crystallinity, surface chemistry, and photoinduced charge separation and their relation with the photocatalytic degradation of Cr-doped ZnO were investigated by scanning electron microscopy, diffuse reflectance spectra, photoelectrochemical scanning electrochemical microscopy, and X-ray photoemission spectroscopy. Adding the appropriate amount of Cr dopant is a powerful way to enhance the separation of charge carriers in ZnO photocatalyst. The photocatalytic activity was improved due to the increase in surface oxygen vacancies, the separation of charge carriers, modification of the band gap, and the large surface area of the doped ZnO nanorod photocatalyst. - Graphical abstract: Photoinduced charge separation and its relation with the photocatalytic degradation activity of Cr-doped ZnO were investigated by photoelectrochemical scanning electrochemical microscopy. - Highlights: • Cr dopant enhances separation of charge carries in ZnO nanorod photocatalyst. • Photoinduced charge carries separation monitored by PEC-SECM. • The higher the photocurrent is, the higher the photocatalytic activity is. • Degradation of DB86 dye solutions under visible light finished within 50 min. • Higher activity due to more oxygen vacancy, tuned band gap and more surface area.

  1. An optical study of the D—D neutron irradiation-induced defects in Co- and Cu-doped ZnO wafers

    NASA Astrophysics Data System (ADS)

    Wang, Yun-Bo; Li, Gong-Ping; Xu, Nan-Nan; Pan, Xiao-Dong

    2013-03-01

    Room-temperature photoluminescence and optical transmittance spectroscopy of Co-doped (1 × 1014, 5 × 1016, and 1 × 1017 cm-2) and Cu-doped (5 × 1016 cm-2) ZnO wafers irradiated by D—D neutrons (fluence of 2.9 × 1010 cm-2) have been investigated. After irradiation, the Co or Cu metal and oxide clusters in doped ZnO wafers are dissolved, and the würtzite structure of ZnO substrate for each sample remains unchanged and keeps in high c-axis preferential orientation. The degree of irradiation-induced crystal disorder reflected from the absorption band tail parameter (E0) is far greater for doped ZnO than the undoped one. Under the same doping concentration, the Cu-doped ZnO wafer has much higher irradiation-induced disorder than the Co-doped one. Photoluminescence measurements indicate that the introduction rate of both the zinc vacancy and the zinc interstitial is much higher for the doped ZnO wafer with a high doping level than the undoped one. In addition, both crystal lattice distortion and defect complexes are suggested to be formed in doped ZnO wafers. Consequently, the Co- or Cu-doped ZnO wafer (especially with a high doping level) exhibits very low radiation hardness compared with the undoped one, and the Cu-doped ZnO wafer is much less radiation-hard than the Co-doped one.

  2. Exploration of Al-Doped ZnO in Photovoltaic Thin Films

    NASA Astrophysics Data System (ADS)

    Ciccarino, Christopher; Sahiner, M. Alper

    The electrical properties of Al doped ZnO-based thin films represent a potential advancement in the push for increasing solar cell efficiency. Doping with Aluminum will theoretically decrease resistivity of the film and therefore achieve this potential as a viable option in the P-N junction phase of photovoltaic cells. The n-type semi-conductive characteristics of the ZnO layer will theoretically be optimized with the addition of Aluminum carriers. In this study, Aluminum doping concentrations ranging from 1-3% by mass were produced, analyzed, and compared. Films were developed onto ITO coated glass using the Pulsed Laser Deposition technique. Target thickness was 250 nm and ellipsometry measurements showed uniformity and accuracy in this regard. Active dopant concentrations were determined using Hall Effect measurements. Efficiency measurements showed possible applications of this doped compound, with upwards of 7% efficiency measured, using a Keithley 2602 SourceMeter set-up. XRD scans showed highly crystalline structures, with effective Al intertwining of the hexagonal wurtzile ZnO molecular structure. This alone indicates a promising future of collaboration between these two materials.

  3. Ga-doped ZnO conducting antireflection coatings for crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Estrich, N. A.; Hook, D. H.; Smith, A. N.; Leonard, J. T.; Laughlin, B.; Maria, J.-P.

    2013-06-01

    Transparent, conductive gallium-doped ZnO thin films are evaluated for application as conducting antireflection coatings (ARC) for crystalline silicon solar cells as a means to enhance efficiency by reducing the overall resistivity of the photovoltaic circuit. All Ga-doped ZnO thin films in this study were deposited using pulsed laser deposition. Synthesis conditions were first optimized for maximum electrical resistivity and minimal visible light absorption. The ideal combination contained 1 mol. % Ga doping and exhibited ˜90% transmission, with resistivity in the 1 × 10-3 ohm-cm range. Optimized films were prepared on reference flat silicon wafers with known dopant densities and on commercially obtained solar cell emitters without ARCs. Circular transmission line method measurements were used to measure specific contact resistivity (ρc). For n-type doped solar cell emitters, contact resistivity values of 0.1 mΩ cm2 were observed repeatedly. These values are consistent with, or lower than, contact resistivities associated with conventional silver paste metallization.

  4. Dominant ferromagnetic coupling over antiferromagnetic in Ni doped ZnO: First-principles calculations

    NASA Astrophysics Data System (ADS)

    Haq, Bakhtiar Ul; Ahmed, Rashid; Abdellatif, Galila; Shaari, Amiruddin; Butt, Faheem K.; Kanoun, Mohammed Benali; Goumri-Said, Souraya

    2016-02-01

    The low magnetic moment (MM) in diluted magnetic semiconductors (DMS) at low impurity doping levels has triggered considerable research into condensed magnetic semiconductors (CMS).This work reports an ab-initio investigation of the electronic structures and magnetic properties of ZnO in a zinc-blende (ZB) structure doped with nickel ions. Ni-doped ZnO-based DMS and CMS exhibit a dominance of ferromagnetic coupling over antiferromagnetic. A robust increase in the magnetization has been observed as a function of Ni impurity levels. This material favors short-range magnetic interactions at the ground state, suggesting that the observed ferromagnetism is defined by the double exchange mechanism. The spin-polarized density of states (DOS) of Ni-doped ZnO characterizes it as half-metallic with a considerable energy gap for up-spin components and as metallic for-down spins. Half-metallic Ni:ZnO based magnetic semiconductors with high magnetization are expected to have potential applications in spintronics.

  5. Effect of Ag doping and annealing on thermoelectric properties of PbTe

    SciTech Connect

    Bala, Manju Tripathi, T. S.; Avasthi, D. K.; Asokan, K.; Gupta, Srashti

    2015-06-24

    The present study reveals that annealing Ag doped PbTe thin films enhance thermoelectric properties. Phase formation was identified by using X-ray diffraction measurement. Annealing increases the crystallinity of both undoped and Ag doped PbTe. Electrical resistivity and thermoelectric power measurements are done using four probe and bridge method respectively. The increase in thermoelectric power of Ag doped PbTe is 29 % in comparison to undoped PbTe and it further increases to 34 % after annealing at 250{sup o} C for 1 hour whereas thermoelectric power increases by 14 % on annealing undoped PbTe thin films at same temperature.

  6. Enhancement in the antibacterial efficiency of ZnO nanopowders by tuning the shape of the nanograins through fluorine doping

    NASA Astrophysics Data System (ADS)

    Ravichandran, K.; Snega, S.; Jabena Begum, N.; Swaminathan, K.; Sakthivel, B.; Rene Christena, L.; Chandramohan, G.; Ochiai, Shizuyasu

    2014-05-01

    Fluorine doped ZnO nanopowders were synthesized from starting solutions having different doping levels of F (0, 5, … , 20 at.%) using a simple soft chemical route and the effects of the doping level on the structural, optical, surface morphological and antibacterial properties were investigated. The XRD studies reveal that all the products have preferential orientation along the (1 0 1) plane. The PL studies show that all the samples exhibit strong visible emission with a peak at 425 nm. The enhancement in the visible emission indicates an increasing number of surface defects caused by the doping of F. The obtained FTIR spectra confirm the incorporation of F into ZnO lattice. From the SEM studies, it is observed that the ZnO nanowires formed at 10 at.% of F doping level exhibit excellent antibacterial activities. Antibacterial activity of F doped ZnO nanopowders against Staphylococcus aureus was found to be significantly higher than that against the Escherichia coli and Pseudomonas aeruginosa micro-organisms. All the physical properties were corroborated well with the findings related to antibacterial activity. Finally, we conclude that, the analysis of all the results shows that F doping level of 10 at.% is optimal in all respects and is suitable for antibacterial applications.

  7. First-principle study on Ag-2N heavy codoped of p-type graphene-like ZnO nanosheet

    NASA Astrophysics Data System (ADS)

    Zhang, W. X.; Li, T.; He, C.; Wu, X. L.; Duan, L.; Li, H.; Xu, L.; Gong, S. B.

    2015-02-01

    In this article, two different Ag-2N heavy codoped of graphene-like ZnO nanosheets have been investigated based on first-principles density-functional theory. The geometric optimization, Density of States (DOS) and Band structure (BS) for all models are calculated, respectively. The results indicate that Ag substituted on the cation site (AgZn) exhibit a strong attractive interaction with a nitrogen acceptor located at the nearest-neighbor oxygen site, forming passive Ag-N complex. This study can be a theoretical guidance to improve the electrical conductivity of p-type graphene-like ZnO nanosheet by heavy codoping.

  8. Effect of Co Doping on the Structural, Optical and Magnetic Properties of ZnO Nanoparticles

    SciTech Connect

    Hays, Jason; Reddy, K. M.; Graces, N. Y.; Engelhard, Mark H.; Shutthanandan, V.; Luo, M.; Xu, Changqing; Giles, N. C.; Wang, Chong M.; Thevuthasan, Suntharampillai; Punnoose, Alex

    2007-07-04

    We report the results of a detailed investigation of sol-gel synthesized nanoscale Zn1-xCoxO powders processed at 350 °C with 0 @ x @ 0.12 to understand how the structural, morphological, optical and magnetic properties of ZnO are modified by Co doping, in addition to searching for the theoretically predicated ferromagnetism. With x increasing to 0.03, both lattice parameters a and c of the hexagonal ZnO decreased suggesting substitutional doping of Co at the tetrahedral Zn2+ sites. For x > 0.03, these trends reversed and the lattice showed a gradual expansion as x approached 0.12, probably due to additional interstitial incorporation of Co. Raman spectroscopy measurements showed a rapid change in the ZnO peak positions for x > 0.03 suggesting significant disorder and changes in the ZnO structure, in support of additional interstitial Co doping possibility. Combined x-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance spectroscopy, photoluminescence spectroscopy and diffuse reflectance spectroscopy showed clear evidence for tetrahedrally coordinated high spin Co2+ ions occupying the lattice sites of ZnO host system, which became saturated for x > 0.03. Magnetic measurements showed a paramagnetic behavior in Zn1-xCoxO with increasing antiferromagnetic interactions as x increased to 0.10. Surprisingly, a weak ferromagnetic behavior was observed for the sample with x = 0.12 with a characteristic hysteresis loop showing a coercivity Hc ~ 350 Oe, 25% remanence Mr, a low saturation magnetization Ms ~ 0.04 emu/g and with a Curie temperature Tc ~ 540 K. The XPS data collected from Zn1-xCoxO samples showed a gradual increase in the oxygen concentration, changing the oxygen deficient undoped ZnO to an excess oxygen state for x = 0.12. This indicates that such high Co concentrations and appropriate oxygen stoichiometry may be needed to achieve adequate ferromagnetic exchange coupling between the incorporated Co2+ ions.

  9. Photocatalytic degradation of Reactive Black 5 and Malachite Green with ZnO and lanthanum doped nanoparticles

    NASA Astrophysics Data System (ADS)

    Kaneva, N.; Bojinova, A.; Papazova, K.

    2016-02-01

    Here we report the preparation of ZnO particles with different concentrations of La3+ doping (0, 0.5 and 1 wt%) via sol-gel method. The nanoparticles are synthesized directly from Zn(CH3COO)2.2H2O in the presence of 1-propanol and triethylamine at 80°C. The conditions are optimized to obtain particles of uniform size, easy to isolate and purify. The nanoparticles are characterized by SEM, XRD and UV-Vis analysis. The photocatalytic properties of pure and La-doped ZnO are studied in the photobleaching of Malachite Green (MG) and Reactive Black 5 (RB5) dyes in aqueous solutions upon UV illumination. It is observed that the rate constant increases with the La loading up to 1 wt%. The doping helps to achieve complete mineralization of MG within a short irradiation time. 1 wt% La-doped ZnO nanoparticles show highest photocatalytic activity. The La3+ doped ZnO particles degrade faster RB5 than MG. The reason is weaker N=N bond in comparison with the C-C bond between the central carbon atom and N,N-dimethylaminobenzyl in MG. The as-prepared ZnO particles can find practical application in photocatalytic purification of textile wastewaters.

  10. Mid-infrared extraordinary transmission through Ga-doped ZnO films with 2D hole arrays

    NASA Astrophysics Data System (ADS)

    Cleary, Justin W.; Nader Esfahani, Nima; Vangala, Shiva; Guo, Junpeng; Hendrickson, Joshua R.; Leedy, Kevin D.; Look, David C.

    2014-03-01

    Extraordinary optical transmission (EOT), through highly conductive ZnO films with sub-wavelength hole arrays is investigated in the long-wavelength infrared regime. EOT is facilitated by the excitation of surface plasmon polaritons (SPPs) on Ga-Doped ZnO films and can be tuned utilizing the physical parameters such as film thickness, period, hole size, and hole shape, as well as doping of the film. Analytical and finite-difference time-domain calculations are completed for 1 micron thick films with square, circular, and triangular hole arrays demonstrating SPP coupling and EOT. The fundamental plasmonic modes are observed in each of these hole shapes at wavelengths that correspond to strong EOT peaks. Doping tunability for these structures is also observed. Ga-doped ZnO films are grown via pulsed laser deposition (PLD) on silicon with plasma frequencies in the near-infrared. The sub-wavelength 2D hole arrays are fabricated in the Ga-doped ZnO films via standard lithography and etching processes. This highly conductive ZnO EOT structure may prove useful in novel integrated components such as tunable biosensors or surface plasmon coupling mechanisms.

  11. The magnetic ordering in high magnetoresistance Mn-doped ZnO thin films

    DOE PAGESBeta

    Venkatesh, S.; Baras, A.; Lee, J. -S.; Roqan, I. S.

    2016-03-24

    Here, we studied the nature of magnetic ordering in Mn-doped ZnO thin films that exhibited ferromagnetism at 300 K and superparamagnetism at 5 K. We directly inter-related the magnetisation and magnetoresistance by invoking the polaronpercolation theory and variable range of hopping conduction below the metal-to-insulator transition. By obtaining a qualitative agreement between these two models, we attribute the ferromagnetism to the s-d exchange-induced spin splitting that was indicated by large positive magnetoresistance (~40 %). Low temperature superparamagnetism was attributed to the localization of carriers and non-interacting polaron clusters. This analysis can assist in understanding the presence or absence of ferromagnetismmore » in doped/un-doped ZnO.« less

  12. Significant mobility enhancement in extremely thin highly doped ZnO films

    SciTech Connect

    Look, David C.; Heller, Eric R.; Yao, Yu-Feng; Yang, C. C.

    2015-04-13

    Highly Ga-doped ZnO (GZO) films of thicknesses d = 5, 25, 50, and 300 nm, grown on 160-nm ZnO buffer layers by molecular beam epitaxy, had 294-K Hall-effect mobilities μ{sub H} of 64.1, 43.4, 37.0, and 34.2 cm{sup 2}/V-s, respectively. This extremely unusual ordering of μ{sub H} vs d is explained by the existence of a very high-mobility Debye tail in the ZnO, arising from the large Fermi-level mismatch between the GZO and the ZnO. Scattering theory in conjunction with Poisson analysis predicts a Debye-tail mobility of 206 cm{sup 2}/V-s at the interface (z = d), falling to 58 cm{sup 2}/V-s at z = d + 2 nm. Excellent fits to μ{sub H} vs d and sheet concentration n{sub s} vs d are obtained with no adjustable parameters.

  13. Synthesis and Characterization of Mg-doped ZnO Nanorods for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Gemar, H.; Das, N. C.; Wanekaya, A.; Delong, R.; Ghosh, K.

    2013-03-01

    Nanomaterials research has become a major attraction in the field of advanced materials research in the area of Physics, Chemistry, and Materials Science. Bio-compatible and chemically stable metal nanoparticles have biomedical applications that includes drug delivery, cell and DNA separation, gene cloning, magnetic resonance imaging (MRI). This research is aimed at the fabrication and characterization of Mg-doped ZnO nanorods. Hydrothermal synthesis of undoped ZnO and Mg-doped ZnO nanorods is carried out using aqueous solutions of Zn(NO3)2 .6H2O, MgSO4, and using NH4OH as hydrolytic catalyst. Nanomaterials of different sizes and shapes were synthesized by varying the process parameters such as molarity (0.15M, 0.3M, 0.5M) and pH (8-11) of the precursors, growth temperature (130°C), and annealing time during the hydrothermal Process. Structural, morphological, and optical properties are studied using various techniques such as XRD, SEM, UV-vis and PL spectroscopy. Detailed structural, and optical properties will be discussed in this presentation. This work is partially supported by National Cancer Institute (1 R15 CA139390-01).

  14. High-quality ZnO growth, doping, and polarization effect

    NASA Astrophysics Data System (ADS)

    Kun, Tang; Shulin, Gu; Jiandong, Ye; Shunming, Zhu; Rong, Zhang; Youdou, Zheng

    2016-03-01

    The authors have reported their recent progress in the research field of ZnO materials as well as the corresponding global advance. Recent results regarding (1) the development of high-quality epitaxy techniques, (2) the defect physics and the Te/N co-doping mechanism for p-type conduction, and (3) the design, realization, and properties of the ZnMgO/ZnO hetero-structures have been shown and discussed. A complete technology of the growth of high-quality ZnO epi-films and nano-crystals has been developed. The co-doping of N plus an iso-valent element to oxygen has been found to be the most hopeful path to overcome the notorious p-type hurdle. High mobility electrons have been observed in low-dimensional structures utilizing the polarization of ZnMgO and ZnO. Very different properties as well as new physics of the electrons in 2DEG and 3DES have been found as compared to the electrons in the bulk. Project supported by the National Natural Science Foundation of China (Nos. 61025020, 61274058, 61322403, 61504057, 61574075), the Natural Science Foundation of Jiangsu Province (Nos. BK2011437, BK20130013, BK20150585), the Priority Academic Program Development of Jiangsu Higher Education Institutions, and the Fundamental Research Funds for the Central Universities.

  15. Defect characterization and magnetic properties in un-doped ZnO thin film annealed in a strong magnetic field

    NASA Astrophysics Data System (ADS)

    Ning, Shuai; Zhan, Peng; Wang, Wei-Peng; Li, Zheng-Cao; Zhang, Zheng-Jun

    2014-12-01

    Highly c-axis oriented un-doped zinc oxide (ZnO) thin films, each with a thickness of ~ 100 nm, are deposited on Si (001) substrates by pulsed electron beam deposition at a temperature of ~ 320 °C, followed by annealing at 650 °C in argon in a strong magnetic field. X-ray photoelectron spectroscopy (XPS), positron annihilation analysis (PAS), and electron paramagnetic resonance (EPR) characterizations suggest that the major defects generated in these ZnO films are oxygen vacancies. Photoluminescence (PL) and magnetic property measurements indicate that the room-temperature ferromagnetism in the un-doped ZnO film originates from the singly ionized oxygen vacancies whose number depends on the strength of the magnetic field applied in the thermal annealing process. The effects of the magnetic field on the defect generation in the ZnO films are also discussed.

  16. Co and Cu co-doped ZnO epitaxial films—A magnetically soft nano-composite

    NASA Astrophysics Data System (ADS)

    Ney, V.; Venkataraman, V.; Henne, B.; Ollefs, K.; Wilhelm, F.; Rogalev, A.; Ney, A.

    2016-04-01

    A series of Co/Cu co-doped ZnO epitaxial films has been grown on sapphire substrates to investigate the possibilities of tailoring the magnetic properties in functional ZnO-Co/Cu nano-composites. The growth was performed using reactive magnetron sputtering varying the oxygen partial pressure to tune the incorporation of the dopants and the resulting valence state. At high oxygen pressures, Co2+ is formed and the resulting magnetic properties are very similar to phase pure paramagnetic Co-doped ZnO samples. However, the formation of a secondary CuO phase reduces the overall structural quality of the layers and virtually no substitutional incorporation of Cu2+ in ZnO could be evidenced. At low oxygen pressures, a significant fraction of metallic Co and Cu forming nanometer-sized superparamagnetic precipitates of a Co/Cu alloy can be evidenced which are embedded in a ZnO host matrix.

  17. A facile green antisolvent approach to Cu2+-doped ZnO nanocrystals with visible-light-responsive photoactivities

    NASA Astrophysics Data System (ADS)

    Lu, Yi-Hsuan; Lin, Wei-Hao; Yang, Chao-Yao; Chiu, Yi-Hsuan; Pu, Ying-Chih; Lee, Min-Han; Tseng, Yuan-Chieh; Hsu, Yung-Jung

    2014-07-01

    An environmentally benign antisolvent method has been developed to prepare Cu2+-doped ZnO nanocrystals with controllable dopant concentrations. A room temperature ionic liquid, known as a deep eutectic solvent (DES), was used as the solvent to dissolve ZnO powders. Upon the introduction of the ZnO-containing DES into a bad solvent which shows no solvation to ZnO, ZnO was precipitated and grown due to the dramatic decrease of solubility. By adding Cu2+ ions to the bad solvent, the growth of ZnO from the antisolvent process was accompanied by Cu2+ introduction, resulting in the formation of Cu2+-doped ZnO nanocrystals. The as-prepared Cu2+-doped ZnO showed an additional absorption band in the visible range (400-800 nm), which conduced to an improvement in the overall photon harvesting efficiency. Time-resolved photoluminescence spectra, together with the photovoltage information, suggested that the doped Cu2+ may otherwise trap photoexcited electrons during the charge transfer process, inevitably depressing the photoconversion efficiency. The photoactivity of Cu2+-doped ZnO nanocrystals for photoelectrochemical water oxidation was effectively enhanced in the visible region, which achieved the highest at 2.0 at% of Cu2+. A further increase in the Cu2+ concentration however led to a decrease in the photocatalytic performance, which was ascribed to the significant carrier trapping caused by the increased states given by excessive Cu2+. The photocurrent action spectra illustrated that the enhanced photoactivity of the Cu2+-doped ZnO nanocrystals was mainly due to the improved visible photon harvesting achieved by Cu2+ doping. These results may facilitate the use of transition metal ion-doped ZnO in other photoconversion applications, such as ZnO based dye-sensitized solar cells and magnetism-assisted photocatalytic systems.An environmentally benign antisolvent method has been developed to prepare Cu2+-doped ZnO nanocrystals with controllable dopant concentrations. A room

  18. Optical properties of Ag- and AgI-doped Ge-Ga-Te far-infrared chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Cheng, Ci; Wang, Xunsi; Xu, Tiefeng; Sun, Lihong; Pan, Zhanghao; Liu, Shuo; Zhu, Qingde; Liao, Fangxing; Nie, Qiuhua; Dai, Shixun; Shen, Xiang; Zhang, Xianghua; Chen, Wei

    2016-05-01

    Te-based glasses are ideal material for life detection and infrared-sensing applications because of their excellent far-infrared properties. In this study, the influence of Ag- and AgI- doped Te-based glasses were discussed. Thermal and optical properties of the prepared glasses were evaluated using X-ray diffraction, differential scanning calorimetry, and Fourier transform infrared spectroscopy. Results show that these glass samples have good amorphous state and thermal stability. However, Ge-Ga-Te-Ag and Ge-Ga-Te-AgI glass systems exhibit completely different in optical properties. With an increase of Ag content, the absorption cut-off edge of Ge-Ga-Te-Ag glass system has a red shift. On the contrary, a blue shift appears in Ge-Ga-Te-AgI glass system with an increase of AgI content. Moreover, the transmittance of Ge-Ga-Te-Ag glass system deteriorates while that of Ge-Ga-Te-AgI glass system ameliorates. All glass samples have wide infrared transmission windows and the far-infrared cut-off wavelengths of these glasses are beyond 25 μm. The main absorption peaks of these glasses are eliminated through a purifying method.

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

    SciTech Connect

    Iribarren, A.; Hernández-Rodríguez, E.; Maqueira, L.

    2014-12-15

    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 to 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.

  20. Control of p- and n-type conductivities in Li-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Lu, J. G.; Zhang, Y. Z.; Ye, Z. Z.; Zeng, Y. J.; He, H. P.; Zhu, L. P.; Huang, J. Y.; Wang, L.; Yuan, J.; Zhao, B. H.; Li, X. H.

    2006-09-01

    Li-doped ZnO films were prepared by pulsed laser deposition. The carrier type could be controlled by adjusting the growth conditions. In an ionized oxygen atmosphere, p-type ZnO was achieved, with the hole concentration of 6.04×1017cm-3 at an optimal Li content of 0.6at.%, whereas ZnO exhibited n-type conductivity in a conventional O2 growth atmosphere. At a Li content of more than 1.2at.% only high-resistivity ZnO was obtained. The amount of Li introduced into ZnO and the relative concentrations of such defects as Li substitutions and interstitials could play an important role in determining the conductivity of films.

  1. Structural, photoluminescence and picosecond nonlinear optical effect of In-doped ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Yan, Xiao-Yan; Yao, Cheng-Bao; Li, Jin; Hu, Jun-Yan; Li, Qiang-Hua; Yang, Shou-Bin

    2016-05-01

    In-doped ZnO (IZO) nanowires were grown using the chemical vapour deposition method. The IZO nanowires have been characterized by scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and UV-Visible spectroscopy. The PL results demonstrated a larger band-gap for the IZO nanowires in comparison to the undoped ZnO. Two major emission peaks were observed for the IZO nanowires, one originated from the free exciton recombination (ultraviolet emission) and another possibly related to the deep-level emission (visible emission). Furthermore, the nonlinear optical characteristic of the nanowires was studied using picosecond Z-scan technique. The experimental results show that the two and three-photon absorption coefficient of samples were able to be observed. These studies make the promising potential applications of the samples in the development of multifunctional all-optical devices.

  2. Thermal process dependence of Li configuration and electrical properties of Li-doped ZnO

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Knutsen, K. E.; Merz, T.; Kuznetsov, A. Yu.; Svensson, B. G.; Brillson, L. J.

    2012-01-01

    We used depth-resolved cathodoluminescence spectroscopy (DRCLS) to describe the strong dependence of Li acceptor formation on thermal treatment in Li-doped ZnO. Within a 500-600 °C annealing temperature range, subsequent quenching ZnO leaves Li as interstitial donors, resulting in low room temperature resistivity, while slow cooling in air allows these interstitials to fill Zn vacancies forming Li acceptors 3.0 eV below the conduction band edge. DRCLS reveals an inverse relationship between the optical emission densities of lithium on zinc sites versus zinc vacancy sites, demonstrating the time dependence of Li interstitials to combine with zinc vacancies in order to form substitutional Li acceptors.

  3. Search for ferromagnetism in transition-metal-doped piezoelectric ZnO

    NASA Astrophysics Data System (ADS)

    Spaldin, Nicola A.

    2004-03-01

    We present results of a computational study of ZnO in the presence of Co and Mn substitutional impurities. The goal of our work is to identify potential ferromagnetic ground states within the (Zn,Co)O or (Zn,Mn)O material systems that are also good candidates for piezoelectricity. We find that robust ferromagnetism is not obtained by substitution of Co or Mn on the Zn site, unless additional carriers (holes) are also incorporated. This is consistent with the conventional wisdom that carriers are required to induce ferromagnetism in diluted magnetic semiconductors, but in contrast to a previous theoretical prediction for this system [K. Sato and H. Katayama-Yoshida, Jpn. J. Appl. Phys., Part 2 39, L555 (2000); K. Sato and H. Katayama-Yoshida, Phys. Status Solidi B 229, 673 (2002)]. We propose a practical scheme for achieving such p-type doping in ZnO.

  4. Fabrication and photoelectric properties of La-doped p-type ZnO nanofibers and crossed p-n homojunctions by electrospinning.

    PubMed

    Zhang, H D; Yu, M; Zhang, J C; Sheng, C H; Yan, X; Han, W P; Liu, Y C; Chen, S; Shen, G Z; Long, Y Z

    2015-06-21

    La-doped p-type ZnO nanofibers were successfully synthesized by electrospinning, followed by calcination. The microstructure and morphology of the La-doped ZnO nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The field effect curve of individual nanofibers confirms that the resulting La-doped ZnO fibers are p-type semiconductors. The doping mechanism is discussed. Furthermore, crossed p-n homojunction nanofibers were also prepared based on electrospun La-doped p-type ZnO and n-type pure ZnO fibers. The current-voltage curve shows the typical rectifying characteristic of a p-n homojunction device. The turn-on voltage appears at about 2.5 V under the forward bias and the reverse current is impassable. PMID:26008851

  5. Effect of deposition parameters and strontium doping on characteristics of nanostructured ZnO thin film by chemical bath deposition method

    NASA Astrophysics Data System (ADS)

    Sheeba, N. H.; Naduvath, J.; Abraham, A.; Weiss, M. P.; Diener, Z. J.; Remillard, S. K.; DeYoung, P. A.; Philip, R. R.

    2014-10-01

    Polycrystalline thin films of ZnO and Sr-doped ZnO (ZnO:Sr) on ultrasonically cleaned soda lime glass substrates are synthesized through successive ionic layer adsorption and reaction. The XRD profiles of ZnO and ZnO:Sr films prepared at different number of deposition cycles exhibit hexagonal wurtzite structure with preferred orientation along (002) direction. The crystallites are found to be nano sized, having variation in size with the increase in number of depositions cycles and also with Sr doping. Optical absorbance studies reveal a systematically controllable blueshift in band gap of Sr-doped ZnO films. SEM images indicate enhanced assembling of crystallites to form elongated rods as number of dips increased in Sr doped ZnO. The films are found to be n-type with the Sr doping having little effect on the electrical properties.

  6. Effect of deposition parameters and strontium doping on characteristics of nanostructured ZnO thin film by chemical bath deposition method

    SciTech Connect

    Sheeba, N. H.; Naduvath, J.; Abraham, A. Philip, R. R.; Weiss, M. P. E-mail: zachary.diener@hope.edu E-mail: deyoung@hope.edu; Diener, Z. J. E-mail: zachary.diener@hope.edu E-mail: deyoung@hope.edu; Remillard, S. K. E-mail: zachary.diener@hope.edu E-mail: deyoung@hope.edu; DeYoung, P. A. E-mail: zachary.diener@hope.edu E-mail: deyoung@hope.edu

    2014-10-15

    Polycrystalline thin films of ZnO and Sr-doped ZnO (ZnO:Sr) on ultrasonically cleaned soda lime glass substrates are synthesized through successive ionic layer adsorption and reaction. The XRD profiles of ZnO and ZnO:Sr films prepared at different number of deposition cycles exhibit hexagonal wurtzite structure with preferred orientation along (002) direction. The crystallites are found to be nano sized, having variation in size with the increase in number of depositions cycles and also with Sr doping. Optical absorbance studies reveal a systematically controllable blueshift in band gap of Sr-doped ZnO films. SEM images indicate enhanced assembling of crystallites to form elongated rods as number of dips increased in Sr doped ZnO. The films are found to be n-type with the Sr doping having little effect on the electrical properties.

  7. Aluminum doping tunes band gap energy level as well as oxidative stress-mediated cytotoxicity of ZnO nanoparticles in MCF-7 cells

    NASA Astrophysics Data System (ADS)

    Akhtar, Mohd Javed; Alhadlaq, Hisham A.; Alshamsan, Aws; Majeed Khan, M. A.; Ahamed, Maqusood

    2015-09-01

    We investigated whether Aluminum (Al) doping tunes band gap energy level as well as selective cytotoxicity of ZnO nanoparticles in human breast cancer cells (MCF-7). Pure and Al-doped ZnO nanoparticles were prepared by a simple sol-gel method. Characterization study confirmed the formation of single phase of AlxZn1-xO nanocrystals with the size range of 33-55 nm. Al-doping increased the band gap energy of ZnO nanoparticles (from 3.51 eV for pure to 3.87 eV for Al-doped ZnO). Al-doping also enhanced the cytotoxicity and oxidative stress response of ZnO nanoparticles in MCF-7 cells. The IC50 for undoped ZnO nanoparticles was 44 μg/ml while for the Al-doped ZnO counterparts was 31 μg/ml. Up-regulation of apoptotic genes (e.g. p53, bax/bcl2 ratio, caspase-3 & caspase-9) along with loss of mitochondrial membrane potential suggested that Al-doped ZnO nanoparticles induced apoptosis in MCF-7 cells through mitochondrial pathway. Importantly, Al-doping did not change the benign nature of ZnO nanoparticles towards normal cells suggesting that Al-doping improves the selective cytotoxicity of ZnO nanoparticles toward MCF-7 cells without affecting the normal cells. Our results indicated a novel approach through which the inherent selective cytotoxicity of ZnO nanoparticles against cancer cells can be further improved.

  8. Aluminum doping tunes band gap energy level as well as oxidative stress-mediated cytotoxicity of ZnO nanoparticles in MCF-7 cells.

    PubMed

    Akhtar, Mohd Javed; Alhadlaq, Hisham A; Alshamsan, Aws; Majeed Khan, M A; Ahamed, Maqusood

    2015-01-01

    We investigated whether Aluminum (Al) doping tunes band gap energy level as well as selective cytotoxicity of ZnO nanoparticles in human breast cancer cells (MCF-7). Pure and Al-doped ZnO nanoparticles were prepared by a simple sol-gel method. Characterization study confirmed the formation of single phase of Al(x)Zn(1-x)O nanocrystals with the size range of 33-55 nm. Al-doping increased the band gap energy of ZnO nanoparticles (from 3.51 eV for pure to 3.87 eV for Al-doped ZnO). Al-doping also enhanced the cytotoxicity and oxidative stress response of ZnO nanoparticles in MCF-7 cells. The IC50 for undoped ZnO nanoparticles was 44 μg/ml while for the Al-doped ZnO counterparts was 31 μg/ml. Up-regulation of apoptotic genes (e.g. p53, bax/bcl2 ratio, caspase-3 &caspase-9) along with loss of mitochondrial membrane potential suggested that Al-doped ZnO nanoparticles induced apoptosis in MCF-7 cells through mitochondrial pathway. Importantly, Al-doping did not change the benign nature of ZnO nanoparticles towards normal cells suggesting that Al-doping improves the selective cytotoxicity of ZnO nanoparticles toward MCF-7 cells without affecting the normal cells. Our results indicated a novel approach through which the inherent selective cytotoxicity of ZnO nanoparticles against cancer cells can be further improved. PMID:26347142

  9. Aluminum doping tunes band gap energy level as well as oxidative stress-mediated cytotoxicity of ZnO nanoparticles in MCF-7 cells

    PubMed Central

    Akhtar, Mohd Javed; Alhadlaq, Hisham A.; Alshamsan, Aws; Majeed Khan, M.A.; Ahamed, Maqusood

    2015-01-01

    We investigated whether Aluminum (Al) doping tunes band gap energy level as well as selective cytotoxicity of ZnO nanoparticles in human breast cancer cells (MCF-7). Pure and Al-doped ZnO nanoparticles were prepared by a simple sol-gel method. Characterization study confirmed the formation of single phase of AlxZn1-xO nanocrystals with the size range of 33–55 nm. Al-doping increased the band gap energy of ZnO nanoparticles (from 3.51 eV for pure to 3.87 eV for Al-doped ZnO). Al-doping also enhanced the cytotoxicity and oxidative stress response of ZnO nanoparticles in MCF-7 cells. The IC50 for undoped ZnO nanoparticles was 44 μg/ml while for the Al-doped ZnO counterparts was 31 μg/ml. Up-regulation of apoptotic genes (e.g. p53, bax/bcl2 ratio, caspase-3 & caspase-9) along with loss of mitochondrial membrane potential suggested that Al-doped ZnO nanoparticles induced apoptosis in MCF-7 cells through mitochondrial pathway. Importantly, Al-doping did not change the benign nature of ZnO nanoparticles towards normal cells suggesting that Al-doping improves the selective cytotoxicity of ZnO nanoparticles toward MCF-7 cells without affecting the normal cells. Our results indicated a novel approach through which the inherent selective cytotoxicity of ZnO nanoparticles against cancer cells can be further improved. PMID:26347142

  10. Realization of Cu-Doped p-Type ZnO Thin Films by Molecular Beam Epitaxy.

    PubMed

    Suja, Mohammad; Bashar, Sunayna B; Morshed, Muhammad M; Liu, Jianlin

    2015-04-29

    Cu-doped p-type ZnO films are grown on c-sapphire substrates by plasma-assisted molecular beam epitaxy. Photoluminescence (PL) experiments reveal a shallow acceptor state at 0.15 eV above the valence band edge. Hall effect results indicate that a growth condition window is found for the formation of p-type ZnO thin films, and the best conductivity is achieved with a high hole concentration of 1.54 × 10(18) cm(-3), a low resistivity of 0.6 Ω cm, and a moderate mobility of 6.65 cm(2) V(-1) s(-1) at room temperature. Metal oxide semiconductor capacitor devices have been fabricated on the Cu-doped ZnO films, and the characteristics of capacitance-voltage measurements demonstrate that the Cu-doped ZnO thin films under proper growth conditions are p-type. Seebeck measurements on these Cu-doped ZnO samples lead to positive Seebeck coefficients and further confirm the p-type conductivity. Other measurements such as X-ray diffraction, X-ray photoelectron, Raman, and absorption spectroscopies are also performed to elucidate the structural and optical characteristics of the Cu-doped p-type ZnO films. The p-type conductivity is explained to originate from Cu substitution of Zn with a valency of +1 state. However, all p-type samples are converted to n-type over time, which is mostly due to the carrier compensation from extrinsic defects of ZnO. PMID:25835032

  11. Fabrication and characterization of silicon wire solar cells having ZnO nanorod antireflection coating on Al-doped ZnO seed layer

    PubMed Central

    2012-01-01

    In this study, we have fabricated and characterized the silicon [Si] wire solar cells with conformal ZnO nanorod antireflection coating [ARC] grown on a Al-doped ZnO [AZO] seed layer. Vertically aligned Si wire arrays were fabricated by electrochemical etching and, the p-n junction was prepared by spin-on dopant diffusion method. Hydrothermal growth of the ZnO nanorods was followed by AZO film deposition on high aspect ratio Si microwire arrays by atomic layer deposition [ALD]. The introduction of an ALD-deposited AZO film on Si wire arrays not only helps to create the ZnO nanorod arrays, but also has a strong impact on the reduction of surface recombination. The reflectance spectra show that ZnO nanorods were used as an efficient ARC to enhance light absorption by multiple scattering. Also, from the current-voltage results, we found that the combination of the AZO film and ZnO nanorods on Si wire solar cells leads to an increased power conversion efficiency by more than 27% compared to the cells without it. PMID:22222067

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

    SciTech Connect

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

    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 of 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.

  13. Fabrication and photoelectric properties of Er3+ and Yb3+ co-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Feng, Wei; Wang, Xiangfu; Meng, Lan; Yan, Xiaohong

    2016-01-01

    In this paper, the Er3+ and Yb3+ co-doped ZnO films deposited by a novel thermal decomposition method under different annealing temperature process have been reported. The effects of annealing temperature on the morphology and properties of the films are systematically studied. The resulting spectra demonstrate that the Er3+ and Yb3+ co-doped ZnO films possessed the property of up-conversion, converting IR light into visible light that can be absorbed by amorphous silicon solar cell. After all, inner photoelectric effect of the Er3+ and Yb3+ co-doped ZnO films in the amorphous as a light scattering layer are also found with an infrared 980 nm laser as excitation source.

  14. Enhanced mobility of Li-doped ZnO thin film transistors fabricated by mist chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Jeon, Hye-ji; Lee, Seul-Gi; Kim, H.; Park, Jin-Seong

    2014-05-01

    Mist chemical vapor deposition (mist-CVD)-processed, lithium (Li)-doped ZnO thin film transistors (TFTs) are investigated. Li doping significantly increases the field-effect mobility in TFTs up to ˜100 times greater than that of undoped ZnO. The addition of Li into mist-CVD-grown ZnO semiconductors leads to improved film quality, which results from the enhanced crystallinity and reduced defect states, including oxygen vacancies. Our results suggest that Li doping of ZnO-based oxide semiconductors could serve as an effective strategy for high-performance, mist-CVD-processed oxide TFTs with low-cost and low-temperature fabrication.

  15. The design of Cu-doped ZnO thermoelectric module (simulation study)

    NASA Astrophysics Data System (ADS)

    Hadi, Syamsul; Suratwan, Agus; Kurniawan, Agus; Budiana, Eko Prasetya; Suyitno

    2016-03-01

    The p-type semiconductor of Cu-doped ZnO-based thermoelectric material has already been synthesized and studied as an energy harvester. The next challenge is manufacturing the thermoelectric module in the development of thermoelectric as an eco-friendly material in the future. This research aims to investigate the effect of thermoelectric geometric design on the electrical output power and voltage and to recommend the most appropriate thermoelectric geometric design. The design of thermoelectric generator (TEG) includes the determinations of dimension (width, length, and height), number of modules, and semiconductor materials. The simulation used the coupled-field analysis of ANSYS APDL 14.5 in the steady state condition. The p- and n- type thermoelectric material used Cu-doped ZnO and Al-doped ZnO, respectively. The width of element and the number of thermoelectric module were varied to obtain a thermoelectric design, which produces the largest current, power, and voltage. The result of research shows that the t hermoelectric generator with the element widths of 0.94 mm, 1.125 mm, 1.05 mm, and 1.2 mm generates the largest power output and voltage, namely: 0.32 W and 0.89 V, 0.38 W and 0.98 V, 0.45 W and 1.06 V, and 0.52 W and 1.13 V, respectively.

  16. Correlation between structural, optical and magnetic properties of Mn-doped ZnO

    NASA Astrophysics Data System (ADS)

    Kumar, Pawan; Singh, Bipin K.; Pal, Bhola N.; Pandey, Praveen C.

    2016-08-01

    We have investigated the structural, optical and magnetic properties of Mn-doped ZnO nanoparticles with different doping concentrations (0, 2, 4 and 6 %) synthesised by sol-gel method. Lattice parameters, cell volume, atomic packing fraction, crystallite size and confirmation of hexagonal wurtzite crystal structure have been studied by X-ray diffraction data. Surface morphology as well as grain size and the presence of all the elements have been confirmed by scanning electron microscope and energy-dispersive X-ray spectroscopy, respectively. The decrease in lattice parameters ratio ( c/ a) with Mn concentration indicates lattice distortion with the incorporation of Mn2+ ions at Zn2+ site of ZnO structure, which has been confirmed by Raman analysis. It has been observed that microstructure defects induced some extra Raman vibration modes. Ultraviolet-visible analysis shows that absorption edge lies in visible region, and encroachment in visible region increases, while energy band gap decreases with the increase in Mn concentrations. We have recorded FTIR spectra at room temperature to study the vibrational bands present in Zn1- x Mn x O samples. The magnetic study of samples indicates ferromagnetic behaviour at room temperature. The magnetic properties increases with doping concentration due to small lattice distortion and defects.

  17. Ag-Modified In2O3/ZnO Nanobundles with High Formaldehyde Gas-Sensing Performance

    PubMed Central

    Fang, Fang; Bai, Lu; Song, Dongsheng; Yang, Hongping; Sun, Xiaoming; Sun, Hongyu; Zhu, Jing

    2015-01-01

    Ag-modified In2O3/ZnO bundles with micro/nano porous structures have been designed and synthesized with by hydrothermal method continuing with dehydration process. Each bundle consists of nanoparticles, where nanogaps of 10–30 nm are present between the nanoparticles, leading to a porous structure. This porous structure brings high surface area and fast gas diffusion, enhancing the gas sensitivity. Consequently, the HCHO gas-sensing performance of the Ag-modified In2O3/ZnO bundles have been tested, with the formaldehyde-detection limit of 100 ppb (parts per billion) and the response and recover times as short as 6 s and 3 s, respectively, at 300 °C and the detection limit of 100 ppb, response time of 12 s and recover times of 6 s at 100 °C. The HCHO sensing detect limitation matches the health standard limitation on the concentration of formaldehyde for indoor air. Moreover, the strategy to synthesize the nanobundles is just two-step heating and easy to scale up. Therefore, the Ag-modified In2O3/ZnO bundles are ready for industrialization and practical applications. PMID:26287205

  18. Ferromagnetic ordering in Mn-doped ZnO nanoparticles

    PubMed Central

    2014-01-01

    Zn1 - x Mn x O nanoparticles have been synthesized by hydrothermal technique. The doping concentration of Mn can reach up to 9 at% without precipitation or secondary phase, confirmed by electron spin resonance (ESR) and synchrotron X-ray diffraction (XRD). Room-temperature ferromagnetism is observed in the as-prepared nanoparticles. However, the room-temperature ferromagnetism disappears after post-annealing in either argon or air atmosphere, indicating the importance of post-treatment for nanostructured magnetic semiconductors. PMID:25435834

  19. Giant temperature coefficient of resistance in Co-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Zhou, X. F.; Zhang, H.; Yan, H.; He, C. L.; Lu, M. H.; Hao, R. Y.

    2014-03-01

    A novel high-performance thermistor material based on Co-doped ZnO thin films is presented. The films were deposited by the pulsed laser deposition technique on Si (111) single-crystal substrates. The structural and electronic transport properties were correlated as a function of parameters such as substrate temperature and Co-doped content for Zn1- x Co x O ( x=0.005,0.05,0.10 and 0.15) to prepare these films. The Zn1- x Co x O films were deposited at various substrate temperatures between 20 and 280 °C. A value of 20 %/K for the negative temperature coefficient of resistance (TCR) with a wide range near room temperature was obtained. It was found that both TCR vs. temperature behavior and TCR value were strongly affected by cobalt doping level and substrate temperature. In addition, a maximal TCR value of over 20 % K-1 having a resistivity value of 3.6 Ω cm was observed in a Zn0.9Co0.1O film near 260 °C, which was deposited at 120 °C and shown to be amorphous by X-ray diffraction. The result proved that the optimal Co concentration could help us to achieve giant TCR in Co-doped ZnO films. Meanwhile, the resistivities of the films ranged from 0.4 to 270 Ω cm. A Co-doped ZnO/Si film is a strong candidate of thermometric materials for non-cooling and high-performance bolometric applications.

  20. Plasma versus thermal annealing for the Au-catalyst growth of ZnO nanocones and nanowires on Al-doped ZnO buffer layers

    NASA Astrophysics Data System (ADS)

    Güell, Frank; Martínez-Alanis, Paulina R.; Roso, Sergio; Salas-Pérez, Carlos I.; García-Sánchez, Mario F.; Santana, Guillermo; Marel Monroy, B.

    2016-06-01

    We successfully synthesized ZnO nanocones and nanowires over polycrystalline Al-doped ZnO (AZO) buffer layers on fused silica substrates by a vapor-transport process using Au-catalyst thin films. Different Au film thicknesses were thermal or plasma annealed in order to analyze their influence on the ZnO nanostructure growth morphology. Striking differences have been observed. Thermal annealing generates a distribution of Au nanoclusters and plasma annealing induces a fragmentation of the Au thin films. While ZnO nanowires are found in the thermal-annealed samples, ZnO nanocones and nanowires have been obtained on the plasma-annealed samples. Enhancement of the preferred c-axis (0001) growth orientation was demonstrated by x-ray diffraction when the ZnO nanocones and nanowires have been grown over the AZO buffer layer. The transmittance spectra of the ZnO nanocones and nanowires show a gradual increase from 375 to 900 nm, and photoluminescence characterization pointed out high concentration of defects leading to observation of a broad emission band in the visible range from 420 to 800 nm. The maximum emission intensity peak position of the broad visible band is related to the thickness of the Au-catalyst for the thermal-annealed samples and to the plasma power for the plasma-annealed samples. Finally, we proposed a model for the plasma versus thermal annealing of the Au-catalyst for the growth of the ZnO nanocones and nanowires. These results are promising for renewable energy applications, in particular for its potential application in solar cells.

  1. Interplay between chemical state, electric properties, and ferromagnetism in Fe-doped ZnO films

    SciTech Connect

    Chen, G.; Peng, J. J.; Song, C.; Zeng, F.; Pan, F.

    2013-03-14

    Valence state of Fe ions plays an important role in the physical properties of Fe doped ZnO films. Here, a series of Zn{sub 1-x}Fe{sub x}O films with different Fe concentrations (x = 0, 2.3, 5.4, 7.1, and 9.3 at. %) were prepared to investigate their structural, piezoelectric, ferroelectric, bipolar resistive switching properties, and electrical-control of ferromagnetism at room temperature. The structure characterizations indicate that the chemical state of Fe ions substituting Zn{sup 2+} site changes from Fe{sup 3+} to Fe{sup 2+} with the increase of Fe dopant concentration. We found enhanced piezoelectric and ferroelectric properties in Zn{sub 0.977}Fe{sub 0.023}O films with more Fe{sup 3+} due to the smaller Fe{sup 3+} ionic size in comparison with Zn{sup 2+} while the increase of Fe{sup 2+} concentration by a larger amount of Fe dopant results in the worse ferroelectric and piezoelectric performance. All Pt/Zn{sub 1-x}Fe{sub x}O/Pt devices show bipolar resistive switching properties. Especially, devices with lower Fe dopant concentration exhibit better endurance properties due to their higher crystalline quality. The variation of oxygen vacancies during resistive switching provides an opportunity to tune ferromagnetism of Fe-doped ZnO films, giving rise to the integration of charge and spin into a simple Pt/Zn{sub 1-x}Fe{sub x}O/Pt devices. The multifunctional properties of Fe-doped ZnO films are promising for communication systems and information storage devices.

  2. Structural, morphological, optical and photocatalytic investigation of Ag-doped TiO2

    NASA Astrophysics Data System (ADS)

    Kundu, Virender Singh; Singh, Davender; Maan, A. S.; Tanwar, Amit

    2016-05-01

    The pure and Ag-doped TiO2 nanoparticles were prepared by using Titanium isoproxide (TTIP), silver nitrate sodium hydroxide and sodium hydroxide. The calcined nanoparticles at 400°C were characterized by means of X-ray diffraction (XRD). XRD analyses reveal that the nanoparticles of various doping concentration were having anatase phase. The particle size was calculated by Scherrer formula and was found 11.08 nm for pure TiO2 and 8.86 nm for 6 mol % Ag doped TiO2. The morphology and nature of nanoparticles was analyzed by using scanning electron microscope (SEM), the optical absorption spectra of pure TiO2 and Ag-doped TiO2 nanoparticles showed that absorption edge increases towards longer wavelength from 390 nm (pure) to 450 nm (doped), also band gap energy calculated from Tauc's plot decrease from 3.20eV to 2.92eV with increase in doing. The measurement of photocatalytic properties of pure TiO2 and Ag-doped TiO2 nanoparticles showed that Ag-doped TiO2 degrades MB dye more efficiently than pure TiO2.

  3. An asymmetric Zn//Ag doped polyaniline microparticle suspension flow battery with high discharge capacity

    NASA Astrophysics Data System (ADS)

    Wu, Sen; Zhao, Yongfu; Li, Degeng; Xia, Yang; Si, Shihui

    2015-02-01

    In this study, the effect of oxygen on the potential of reduced polyaniline (PANI) was investigated. In order to enhance the air oxidation of reduced PANI, several composites of PANI doped with co-catalysts were prepared, and a reasonable flow Zn//PANI suspension cell system was designed to investigate the discharge capacity of obtained PANI composite microparticle suspension cathodes. Compared with PANI doped with Cu2+, La+, Mn2+ and zinc protoporphyrin, Ag doped PANI composite at 0.90 weight percent doping of Ag gave the highest value of discharge capacity for the half-cell potential from the initial value to -0.20 V (vs. SCE). A comparison study on the electrochemical properties of both PANI and Ag doped PANI microparticle suspension was done by using cyclic voltammetry, AC Impedance. Due to partial utilization of Zn//air fuel cell, the discharge capacity for Ag doped PANI reached 470 mA h g-1 at the current density of 20 mA cm-2. At 15 mA cm-2, the discharge capacity even reached up to 1650 mA h g-1 after 220 h constant current discharge at the final discharge voltage of 0.65 V. This work demonstrates an effective and feasible approach toward obtaining high energy and power densities by a Zn//Ag-doped PANI suspension flow battery system combined with Zn//air fuel cell.

  4. Defect-band mediated ferromagnetism in Gd-doped ZnO thin films

    SciTech Connect

    Venkatesh, S.; Roqan, I. S.; Franklin, J. B.; Ryan, M. P.; McLachlan, M. A.; Alford, N. M.; Lee, J.-S.; Ohldag, Hendrik

    2015-01-07

    Gd-doped ZnO thin films prepared by pulsed laser deposition with Gd concentrations varying from 0.02–0.45 atomic percent (at. %) showed deposition oxygen pressure controlled ferromagnetism. Thin films prepared with Gd dopant levels (

  5. Structural and optical studies on Nd doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Deepa Rani, T.; Tamilarasan, K.; Elangovan, E.; Leela, S.; Ramamurthi, K.; Thangaraj, K.; Himcinschi, C.; Trenkmann, I.; SchuIze, S.; Hietschold, M.; Liebig, A.; Salvan, G.; Zahn, D. R. T.

    2015-01-01

    Thin films of Zn1-xNdxO were deposited by spray pyrolysis on Si(111) substrates preheated at 400 °C temperature and were studied as a function of neodymium (Nd)-doping concentration. X-ray diffraction (XRD) patterns confirmed that the deposited films possess hexagonal wurtzite ZnO structure. Further, it is observed that the doped films show a preferential orientation along the c-axis (0 0 2), which is perpendicular to the substrate. The un-doped films seem to be having a bit low-crystallinity, which is corroborated by the scanning electron microscope (SEM) analysis that showed nano-crystalline like features. Further, SEM analysis showed that the Nd doping triggers the formation bubble-like structure on top of the nano-crystalline structure. The SEM microstructures are interpreted with the Micro-Raman studies. Photoluminescence (PL) and XRD characterizations indicate that above 5 at.% doping concentrations, the Nd atoms preferentially agglomerate in the large islands.

  6. Effect of doping concentration on the conductivity and optical properties of p-type ZnO thin films

    NASA Astrophysics Data System (ADS)

    Pathak, Trilok Kumar; Kumar, Vinod; Swart, H. C.; Purohit, L. P.

    2016-01-01

    Nitrogen doped ZnO (NZO) thin films were synthesized on glass substrates by the sol-gel and spin coating method. Zinc acetate dihydrates and ammonium acetate were used as precursors for zinc and nitrogen, respectively. X-ray diffraction study showed that the thin films have a hexagonal wurtzite structure corresponding (002) peak for undoped and doped ZnO thin films. The transmittance of the films was above 80% and the band gap of the film varies from 3.21±0.03 eV for undoped and doped ZnO. The minimum resistivity of NZO thin films was obtained as 0.473 Ω cm for the 4 at% of nitrogen (N) doping with a mobility of 1.995 cm2/V s. The NZO thin films showed p-type conductivity at 2 and 3 at% of N doping. The AC conductivity measurements that were carried out in the frequency range 10 kHz to 0.1 MHz showed localized conduction in the NZO thin films. These highly transparent ZnO films can be used as a possible window layer in solar cells.

  7. Ag-doped carbon aerogels for removing halide ions in water treatment.

    PubMed

    Sánchez-Polo, M; Rivera-Utrilla, J; Salhi, E; von Gunten, U

    2007-03-01

    The objective of this study was to analyze the efficiency of silver(Ag)-doped carbon aerogels for the removal of bromide (Br(-)) and iodide (I(-)) from drinking waters. Textural characterization of Ag-doped aerogels showed that an increase in the Ag dose added during the preparation process produced: (i) a reduction in the surface area (S(BET)) and (ii) an increase in mesopore (V(2)) and macropore (V(3)) volumes. Chemical characterization of the materials revealed an acidic surface (pH of point of zero charge, pH(PZC)=4.5, O(surface)=20%). The oxidation state of Ag was +1 and the surface concentration of this element ranged from 4% to 10%. The adsorption capacity (X(m)) and affinity of adsorbent (BX(m)) increased with a reduction in the radius of the halogenide. Furthermore, an increase in the adsorption capacity was observed with higher Ag concentrations on the aerogel surface. The high adsorption capacity of the aerogel may be due to the presence of Ag(I) on its surface, with the formation of the corresponding Ag halides. Our observations indicate that the halogenides adsorption on commercial activated carbon (Sorbo-Norit) is much lower than that of the Ag-doped carbon aerogels. The presence of chloride and natural organic matter (NOM) in the medium reduced the adsorption capacity of Br(-) and I(-) on Ag carbon aerogels. PMID:16970974

  8. Improved solar-driven photocatalytic performance of Ag3PO4/ZnO composites benefiting from enhanced charge separation with a typical Z-scheme mechanism

    NASA Astrophysics Data System (ADS)

    Zhong, Junbo; Li, Jianzhang; Wang, Tao; Zeng, Jun; Si, Yujun; Cheng, Chaozhu; Li, Minjiao; Wang, Pei; Ding, Jie

    2016-01-01

    In this work, efficient simulated solar-driven Ag3PO4/ZnO photocatalysts with different molar ratios of Ag/Zn have been prepared by a precipitation method and characterized by X-ray diffraction, UV-Vis diffuse reflectance spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy and surface photovoltage (SPV) spectroscopy. Under simulated sunlight illumination, the Ag3PO4/ZnO composites exhibit enhanced photocatalytic activity compared with the pure ZnO toward the decolorization of rhodamine B (RhB) aqueous solution, and the Ag3PO4/ZnO composite with 4 % Ag/Zn molar ratio exhibits the highest activity. The quenching effects of scavengers indicate that O2•- plays the major role in RhB decolorization. Ag3PO4 deposited on the ZnO surface can promote the separation rate of photoinduced charge carriers, proven by the SPV results. Based on all the observations, the charge separation mechanism with a typical Z-scheme was proposed.

  9. The effect of Ag adsorption on the structural, electronic, and optical properties of the ZnO (10 1 ̅ 0) surface: A first-principles study

    NASA Astrophysics Data System (ADS)

    Lahmer, M. A.

    2016-09-01

    The effect of the Ag adsorption on the structural, electronic and optical properties of the clean ZnO(10 1 ̅ 0) surface was investigated using the first principles method. The obtained results show that adsorbed Ag atoms transfer charge to the surface which results in a charge accumulation in near-surface region accompanied with a decrease of the work function. On the other hand, our results show that the adsorption of Ag atoms leads also to the new optical absorption peaks in the visible region which could improve ZnO photocatalytical properties.

  10. Indium doped ZnO nano-powders prepared by RF thermal plasma treatment of In2O3 and ZnO

    NASA Astrophysics Data System (ADS)

    Lee, Mi-Yeon; Song, Min-Kyung; Seo, Jun-Ho; Kim, Min-Ho

    2015-06-01

    Indium doped ZnO nano-powders were synthesized by the RF thermal plasma treatment of In2O3 and ZnO. For this purpose, micron-sized ZnO powder was mixed with In2O3 powder at the In/Zn ratios of 0.0, 1.2, and 2.4 at. % by ball milling for 1 h, after which the mixtures were injected into RF thermal plasma generated at the plate power level of ˜140 kV A. As observed from the field emission scanning electron microscopy (FE-SEM) images of the RF plasma-treated powders, hexagonal prism-shaped nano-crystals were mainly obtained along with multi-pod type nano-particles, where the number of multi-pods decreased with increasing In/Zn ratios. In addition, the X-ray diffraction (XRD) data for the as-treated nano-powders showed the diffraction peaks for the In2O3 present in the precursor mixture to disappear, while the crystalline peaks for the single phase of ZnO structure shifted toward lower Bragg angles. In the UV-vis absorption spectra of the as-treated powders, redshifts were also observed with increases of the In/Zn ratios. Together with the FE-SEM images and the XRD data, the redshifts were indicative of the doping process of ZnO with indium, which took place during the RF thermal plasma treatment of In2O3 and ZnO.

  11. Mechanical and transparent conductive properties of ZnO and Ga-doped ZnO films sputtered using electron-cyclotron-resonance plasma on polyethylene naphtalate substrates

    SciTech Connect

    Akazawa, Housei

    2014-03-15

    Transparent conductive ZnO and Ga-doped ZnO (GZO) films were deposited on polyethylene naphtalate (PEN) sheet substrates using electron cyclotron resonance plasma sputtering. Both ZnO and GZO films were highly adhesive to the PEN substrates without inserting an intermediate layer in the interface. When compared at the same thickness, the transparent conductive properties of GZO films on PEN substrates were only slightly inferior to those on glass substrates. However, the carrier concentration of ZnO films on PEN substrates was 1.5 times that of those on glass substrates, whereas their Hall mobility was only 60% at a thickness of 300 nm. The depth profile of elements measured by secondary ion mass spectroscopy revealed the diffusion of hydrocarbons out of the PEN substrate into the ZnO film. Hence, doped carbons may act as donors to enhance carrier concentration, and the intermixing of elements at the interface may deteriorate the crystallinity, resulting in the lower Hall mobility. When the ZnO films were thicker than 400 nm, cracks became prevalent because of the lattice mismatch strain between the film and the substrate, whereas GZO films were free of cracks. The authors investigated how rolling the films around a cylindrical pipe surface affected their conductive properties. Degraded conductivity occurred at a threshold pipe radius of 10 mm when tensile stress was applied to the film, but it occurred at a pipe radius of 5 mm when compressive stress was applied. These values are guidelines for bending actual devices fabricated on PEN substrates.

  12. On the impact of Ag doping on performance and reliability of GeS2-based conductive bridge memories

    NASA Astrophysics Data System (ADS)

    Longnos, F.; Vianello, E.; Cagli, C.; Molas, G.; Souchier, E.; Blaise, P.; Carabasse, C.; Rodriguez, G.; Jousseaume, V.; De Salvo, B.; Dahmani, F.; Verrier, P.; Bretegnier, D.; Liebault, J.

    2013-06-01

    In this work, we study the impact of Ag doping on GeS2-based CBRAM devices employing Ag as active electrode. Several devices with Ag doping varying between 10% and 24% are extensively analyzed. First, we assess switching voltages and time-to-set as a function of Ag concentration in the electrolyte layer. Subsequently, we evaluate the two most important reliability aspects of RRAM devices: endurance and data retention at different temperatures. The results show that an increase of Ag doping in the GeS2 layer yields a strong improvement to both endurance and data retention performances. The extrapolated temperature allowing for 10 years data retention increases from 75 °C for the 10% Ag-doped sample to 109 °C for the 24% Ag-doped one.

  13. Co-doping effects of Gd and Ag on YBCO films derived by metalorganic deposition

    NASA Astrophysics Data System (ADS)

    Sun, Meijuan; Liu, Zhiyong; Bai, Chuanyi; Guo, Yanqun; Lu, Yuming; Fan, Feng; Cai, Chuanbing

    2015-12-01

    Y1-xGdxBa2Cu3O7-δ-Ag (x = 0, 0.25, 0.5, 0.75, 1) thin films were prepared on oxide buffered Hastelloy substrates by low fluorine metalorganic depostion (MOD) process. The effects of co-doping of Ag and Gd on the microstructures and superconducting properties of YBCO thin films are investigated with respect to improvement on texture and superconducting performance in case of optimized doping content. It is found that optimum addition of Ag and Gd may lead to better c-axis orientation, superior surface microstructure and finally give rise to much improvement of superconducting performance.

  14. Influence of Te and Se doping on ZnO films growth by SILAR method

    NASA Astrophysics Data System (ADS)

    Güney, Harun; Duman, Ćaǧlar

    2016-04-01

    The AIP Successive ionic layer adsorption and reaction (SILAR) is an economic and simple method to growth thin films. In this study, SILAR method is used to growth Selenium (Se) and Tellurium (Te) doped zinc oxide (ZnO) thin films with different doping rates. For characterization of the films X-ray diffraction (XRD), absorbance and scanning electron microscopy (SEM) are used. XRD results are showed well-defined strongly (002) oriented crystal structure for all samples. Also, absorbance measurements show, Te and Se concentration are proportional and inversely proportional with band gap energy, respectively. SEM measurements show that the surface morphology and thickness of the material varied with Se and/or Te and varying concentrations.

  15. Optical and electrical characterization of aluminium doped ZnO layers

    NASA Astrophysics Data System (ADS)

    Major, C.; Nemeth, A.; Radnoczi, G.; Czigany, Zs.; Fried, M.; Labadi, Z.; Barsony, I.

    2009-08-01

    Al doped ZnO (ZAO) thin films (with Al-doping levels 2 at.%) were deposited at different deposition parameters on silicon substrate by reactive magnetron sputtering for solar cell contacts, and samples were investigated by transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS) and spectroscopic ellipsometry (SE). Specific resistances were measured by the well known 4-pin method. Well visible columnar structure and in most cases voided other regions were observed at the grain boundaries by TEM. EELS measurements were carried out to characterize the grain boundaries, and the results show spacing voids between columnar grains at samples with high specific resistance, while no spacing voids were observed at highly conductive samples. SE measurements were evaluated by using the analytical expression suggested by Yoshikawa and Adachi [H. Yoshikawa, S. Adachi, Japanese Journal of Applied Physics 36 (1997) 6237], and the results show correlation between specific resistance and band gap energy and direct exciton strength parameter.

  16. Direct observation of Li diffusion in Li-doped ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Li, Guohua; Yu, Lei; Hudak, Bethany M.; Chang, Yao-Jen; Baek, Hyeonjun; Sundararajan, Abhishek; Strachan, Douglas R.; Yi, Gyu-Chul; Guiton, Beth S.

    2016-05-01

    The direct observation of Li diffusion in Li-doped zinc oxide nanowires (NWs) was realized by using in situ heating in the scanning transmission electron microscope (STEM). A continuous increase of low atomic mass regions within a single NW was observed between 200 °C and 600 °C when heated in vacuum, which was explained by the conversion of interstitial to substitutional Li in the ZnO NW host lattice. A kick-out mechanism is introduced to explain the migration and conversion of the interstitial Li (Lii) to Zn-site substitutional Li (LiZn), and this mechanism is verified with low-temperature (11 K) photoluminescence measurements on as-grown and annealed Li-doped zinc oxide NWs, as well as the observation of an increase of NW surface roughing with applied bias.

  17. Influence of Y-doped induced defects on the optical and magnetic properties of ZnO nanorod arrays prepared by low-temperature hydrothermal process

    PubMed Central

    2012-01-01

    One-dimensional pure zinc oxide (ZnO) and Y-doped ZnO nanorod arrays have been successfully fabricated on the silicon substrate for comparison by a simple hydrothermal process at the low temperature of 90°C. The Y-doped nanorods exhibit the same c-axis-oriented wurtzite hexagonal structure as pure ZnO nanorods. Based on the results of photoluminescence, an enhancement of defect-induced green-yellow visible emission is observed for the Y-doped ZnO nanorods. The decrease of E2(H) mode intensity and increase of E1(LO) mode intensity examined by the Raman spectrum also indicate the increase of defects for the Y-doped ZnO nanorods. As compared to pure ZnO nanorods, Y-doped ZnO nanorods show a remarked increase of saturation magnetization. The combination of visible photoluminescence and ferromagnetism measurement results indicates the increase of oxygen defects due to the Y doping which plays a crucial role in the optical and magnetic performances of the ZnO nanorods. PMID:22768847

  18. Ferromagnetism in Li doped ZnO nanoparticles: The role of interstitial Li

    NASA Astrophysics Data System (ADS)

    Ullah Awan, Saif; Hasanain, S. K.; Bertino, Massimo F.; Hassnain Jaffari, G.

    2012-11-01

    ZnO nanoparticles doped with Li (Zn1-yLiyO, y ≤ 0.1) have been investigated with emphasis on the correlation between their magnetic, electronic, and structural properties. In particular, defects such as interstitial Li and Zn atoms, substitutional Li atoms, and oxygen vacancies have been identified by X-ray photoelectron spectroscopy (XPS) and their respective roles in stabilization of the magnetic moment are discussed. X-ray diffraction (XRD) and XPS give clear evidence of Li presence at both substitutional and interstitial sites. XPS studies further show that the amount of substitutional Li defects (Lizn) and interstitial Li defects (Lii) vary non-monotonically with the Li concentration, with the Lii defects being noticeably high for the y = 0.02, 0.08, and 0.10 concentrations, in agreement with the XRD results. Magnetization studies show room temperature ferromagnetism in these nanoparticles with the moment being largest for the particles with high concentration of interstitial lithium and vice versa. Both interstitial Zn (Zni) defects and Zn-O bonds were determined from the Zn LMM Auger peaks; however, the variation of these with Li concentrations was not large. Oxygen vacancies (Vo) concentrations are estimated to be relatively constant over the entire Li concentration range. We relate the Lii and Zni defects to the formation and stabilization of Zn vacancies and thus stabilizing the p-type ferromagnetism predicted for cation (zinc) vacancy in the ZnO type oxides.

  19. Electron transport in Al-doped ZnO nanolayers obtained by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Blagoev, B. S.; Dimitrov, D. Z.; Mehandzhiev, V. B.; Kovacheva, D.; Terziyska, P.; Pavlic, J.; Lovchinov, K.; Mateev, E.; Leclercq, J.; Sveshtarov, P.

    2016-03-01

    Al-doped ZnO thin films with different Al content were prepared by atomic layer deposition (ALD). To carry out thermal ALD, diethyl zinc (DEZ) and tri-methyl aluminium (TMA) were used as Zn and Al precursors, respectively, and water vapor as oxidant. Various numbers n of DEZ and m TMA cycles was used to obtain different [ZnO] n [Al2O3] m films, where n = 100 – 95, m = 1 – 5. The X-ray diffraction analysis showed a predominantly (100) oriented polycrystalline phase for the ZnO:Al films with a low Al content (m = 1 – 3) and an amorphous structure for pure Al2O3. In ZnO:Al with a higher Al content (m = 4 – 6) the (100) reflection disappeared and the (002) peak increased. The resistivity of the films decreased with the increase in the Al content, reaching a minimum of 3.3×10-3 Ω cm at about 1.1 % Al2O3 for the [ZnO]99[Al2O3]2 sample; for higher dopant concentrations, the resistivity increased because of the increased crystal inhomogeneity due to axis reorientation.

  20. NEXAFS and XMCD studies of single-phase Co doped ZnO thin films.

    PubMed

    Singh, Abhinav Pratap; Kumar, Ravi; Thakur, P; Brookes, N B; Chae, K H; Choi, W K

    2009-05-01

    A study of the electronic structure and magnetic properties of Co doped ZnO thin films synthesized by ion implantation followed by swift heavy ion irradiation is presented using near-edge x-ray absorption fine structure (NEXAFS) and x-ray magnetic circular dichroism (XMCD) measurements. The spectral features of NEXAFS at the Co L(3,2)-edge show entirely different features than that of metallic Co clusters and other Co oxide phases. The atomic multiplet calculations are performed to determine the valence state, symmetry and the crystal field splitting, which show that in the present system Co is in the 2+ state and substituted at the Zn site in tetrahedral symmetry with 10Dq = -0.6 eV. The ferromagnetic character of these materials is confirmed through XMCD spectra. To rule out the possibilities of defect induced magnetism, the results are compared with Ar annealed and Ar-ion implanted pure ZnO thin films. The presented results confirm the substitution of Co at the Zn site in the ZnO matrix, which is responsible for room temperature ferromagnetism. PMID:21825451

  1. Optical, electrical and structural characterization of chloride-doped ZnO nanopillars obtained by electrodeposition

    NASA Astrophysics Data System (ADS)

    Berruet, M.; Gau, D. L.; Dalchiele, E. A.; Vázquez, M.; Marotti, R. E.

    2016-06-01

    As-grown and chloride-doped ZnO nanopillars were electrodeposited onto bare FTO/glass and ZnO-compact layer/FTO/glass substrates. To analyse the effect of the presence of chloride ions in the electrolytic bath, NH4Cl was progressively added up to 0.02 mol l‑1. As a preliminary examination, the morphology of ZnO nanostructures was analysed by SEM micrographs and chlorine incorporation was detected by EDS. Then, a detailed analysis comprising structural, electrical, optical and defect properties was constructed using XRD, electrical resistance measurements and UV–Vis–IR spectroscopy. As the chlorine concentration in the film increases, XRD reveals a displacement of diffracted planes due to macrostrain of the ZnO lattice and the electrical resistance diminishes. Also, the UV optical absorption edge shifts to higher energies due to the Moss–Burstein effect, which corresponds to electron densities in the order of 1–6  ×  1019 cm‑3, and the infrared spectra reveal the presence of free electrons, allowing a more precise determination of the free electron densities.

  2. Ultrafast photoluminescence features analysis of In-doped ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Zhao, Qingming

    2011-08-01

    ZnO has been researched for its excellent properties for optoelectronic, sensing, piezoelectric application, solar cells, light emitting diodes and laser diodes. Transparent oxide semiconductor (TOS) thin films made of ZnO nanocomposites, which are used as transparent electrodes in optoelectronic devices, have been widely reported. Among the TOSs, the thin films of a homologous compound, with a so-called superlattice structure have attracted considerable interest. Because of the spatial confinement of conductive electrons in the two dimensional layer, their interesting electronic, optical, and magnetic properties, along with small size and chemical reactivity, have led to a wide range of applications in nano-optoelectronics, medical diagnostics, catalysis, and chemical sensing. In this paper, the ultrafast dynamics and the nonlinear optical response of metal nanocomposites were investigated. Heat treatment has been proven to be a feasible way to improve the performance of ultrafast response for this kind of materials. Based on the experimental results of In-doped ZnO materials excited by intense fs pulses near 800 nm, nonlinear optical effects that may emerge under an intense field are attributed to be responsible for the efficient two-photon absorption process under detuned excitation.

  3. Effect of In doping on the properties and antibacterial activity of ZnO films prepared by spray pyrolysis.

    PubMed

    Manoharan, C; Pavithra, G; Dhanapandian, S; Dhamodharan, P

    2015-01-01

    Pure and In-doped ZnO thin films were deposited onto glass substrates by spray pyrolysis technique. XRD results showed that all films were polycrystalline in nature with the wurzite structure. A change in preferential orientation from (002) to (101) plane was observed with increase in content of Indium. A reduce in crystallite size was observed with increase of In content. The small sized grains with the porous nature of the film was observed from SEM analysis. AFM study depicted polycrystalline nature and uniformly distributed grains with small pores in the doped film. A decrease in band gap was noticed with increase in In content. The absence of green emission in PL spectra indicated the decreased oxygen defects. The decrease in the resistivity with increase of Hall mobility was noted for the doped film. A better antibacterial activity was observed against Staphylococcus aureus by doped ZnO thin film. PMID:25997176

  4. Local structure investigation of (Co, Cu) co-doped ZnO nanocrystals and its correlation with magnetic properties

    NASA Astrophysics Data System (ADS)

    Tiwari, N.; Doke, S.; Lohar, A.; Mahamuni, Shailaja; Kamal, C.; Chakrabarti, Aparna; Choudhary, R. J.; Mondal, P.; Jha, S. N.; Bhattacharyya, D.

    2016-03-01

    Pure, Co doped and (Co, Cu) co-doped ZnO nanocrystals have been prepared by wet chemical route at room temperature to investigate the effect of Cu doping in Co doped ZnO nanocrystals . The nanocrystals have initially been characterized by X-ray diffraction, FTIR, Raman, optical absorption and EPR spectroscopy and the results were corroborated with DFT based electronic structure calculations. Magnetic properties of the samples have been investigated by studying their magnetic hysteresis behavior and temperature dependence of susceptibilities. Finally the local structure at the host and dopant sites of the nanocrystals have been investigated by Zn, Co and Cu K edges EXAFS measurements with synchrotron radiation to explain their experimentally observed magnetic properties.

  5. Microstructural and Optical properties of transition metal (Cu) doped ZnO diluted magnetic semiconductor nano thin films fabricated by sol gel method

    NASA Astrophysics Data System (ADS)

    Ozturk, Ozgur; Asikuzun, Elif; Tasci, A. Tolga; Arda, Lutfi; Demirozu Senol, Sevim; Celik, Sukru; Terzioglu, Cabir

    Undoped and Cu (Copper) doped ZnO (Zn1-xCuxO) semiconductor thin films were produced by using sol-gel method. Cu was doped 1%, 2%, 3%, 4% and 5% ratio. Methanol and monoethanolamine (MEA) were used as solvent and stabilizer. In this study, the effect of Cu doping was investigated on microstructural and optical properties of ZnO DMS thin films. XRD, SEM, AFM and UV-VIS spectrometer measurements were performed for the microstructural and optical characterization. XRD, SEM and AFM results were showed that all of Cu doped ZnO based thin films have a hexagonal structure. The grain size of Cu doped ZnO thin films and morphology of surface were changed with increasing Cu doping. The optical transmittance of transition metal (Cu) doped ZnO thin films were decreased with doping. Keywords:Diluted Magnetic Semiconductor (DMS), Thin Film, Cu-doping, Bandgap Energy, ZnO. This research has been supported by the Kastamonu University Scientific Research Projects Coordination Department under the Grant No. KU-BAP-05/2015-12 and the Scientific and Technological Research Council of Turkey (TUBITAK) Project No. 114F259.

  6. Red luminescence of Eu3+ doped ZnO nanoparticles fabricated by laser ablation in aqueous solution

    NASA Astrophysics Data System (ADS)

    Katsuki, Daichi; Sato, Toshiyuki; Suzuki, Ryoji; Nanai, Yasushi; Kimura, Seiji; Okuno, Tsuyoshi

    2012-08-01

    Fabrication of Eu3+-doped ZnO nanoparticles by laser ablation in liquid medium is reported. Sintered disks made of mixed powders of ZnO and Eu2O3 are used for targets, and surfactant of sodium dodecyl sulfate or LiOH is included in solution. Round-shaped nanoparticles with the diameter of 5˜30 nm are synthesized. When the ZnO host is photoexcited, broad green photoluminescence (PL) of oxygen vacancies in the ZnO host as well as red PL of Eu3+ is observed at room temperature. The red PL peak of Eu3+ included in the ZnO host lattice is different from that of the source material of Eu2O3. Energy transfer from the ZnO host to Eu3+ is demonstrated in site-selectively excited PL spectra and its excitation spectra. This result shows that the liquid-phase laser ablation is useful for doping active centers into nanoparticles.

  7. Investigation of structural and optical properties of ZnO films co-doped with fluorine and indium

    NASA Astrophysics Data System (ADS)

    Keskenler, E. F.; Turgut, G.; Doğan, S.

    2012-07-01

    Undoped ZnO film and ZnO films, which are co-doped with F and In (FIZO) at different concentrations, were synthesized by sol-gel technique and the effects of co-doping of F and In on structural and optical properties of ZnO thin films were investigated. The concentration ratio of [F]/[Zn] was altered from 0.25 to 1.75 with 0.50 step at.% mole and [In]/[Zn] was altered from 0.25 to 1.00 with 0.25 step at.% mole. X-ray diffraction analysis indicates that the films have polycrystalline nature and the (0 0 2) preferred orientation is the stronger peak. No extra phases involving zinc, fluorine and indium compounds were observed even at high F and In content. The grain size of undoped ZnO and FIZO thin films varied between 15 and 20 nm with a small fluctuation. From the SEM images, although the undoped ZnO had a smooth and particle-shaped surface, FIZO films had nanofiber-networks shapes over the surface with average size of 500 nm. The surface morphologies and crystallite sizes for the F and In doped films were slightly different from than those of undoped film. From the optical study, a slight shrinkage of band gap was backwardly observed from 3.36 to 3.25 eV with the increasing of F and In content.

  8. AgII doped MIL-101 and its adsorption of iodine with high speed in solution

    NASA Astrophysics Data System (ADS)

    Mao, Ping; Qi, Bingbing; Liu, Ying; Zhao, Lei; Jiao, Yan; Zhang, Yi; Jiang, Zheng; Li, Qiang; Wang, Jinfeng; Chen, Shouwen; Yang, Yi

    2016-05-01

    In order to improve the adsorption speed of iodine from water, MIL-101 with extra-large specific surface area (3054 m2/g) was chosen as a base material, and then, Ag was doped into MIL-101 to enhance its adsorption capacity through an incipient-wetness impregnation method. With the characterization of SEM-EDS, TEM, XRD, XPS, TGA, IR, and BET techniques, the resulting Ag was identified to be stay in the framework of MIL-101 stably in the form of AgII (generally, AgII cation is not stable). However, after the adsorption of I- anions, AgII stay in the cages of MIL-101 in the form of AgI/AgI3. It is important to note that, all adsorbents show high adsorption speed of iodine in solution. The equilibrium adsorption time of the adsorbents were acquired by only a few minutes, which can be attributed to its large BET surface area. An interesting note is that, when the doping amount of Ag is less than 9%, the iodine anions adsorption capacity of Ag@MIL-101 is greater than its theoretical adsorption capacity. It shows that both physical adsorption and chemical adsorption are existed in the adsorption process. This study hopefully leads to a new and highly efficient Ag-based adsorbent for iodide adsorb from solutions.

  9. Doped nanocrystalline ZnO powders for non-linear resistor applications by spray pyrolysis method.

    PubMed

    Hembram, Kaliyan; Vijay, R; Rao, Y S; Rao, T N

    2009-07-01

    Homogeneous and doped nanocrystalline ZnO powders (30-200 nm) were synthesized by spray pyrolysis technique. The spray pyrolysed powders were calcined in the temperature range of 500-750 degrees C. Formation of insulating pyrochlore phase started from 700 degrees C during the calcination itself. The calcined powders were compacted and sintered at different temperatures ranging from 900-1200 degrees C for 0.5-4 h. The densification behavior was found to be dependent on calcination temperature of the nanopowder. The resulting discs were found to have density (5.34-5.62 g/cc) in the range of 96-99% of theoretical density. The breakdown voltage value obtained for the nanopowder based non-linear resistor is 10.3 kV/cm with low leakage current density of 0.7 microA/cm2 and coefficient of nonlinearity as high as 193. The activation energy for grain growth of the doped ZnO nanopowder powders is 449.4 +/- 15 kJ/mol. PMID:19916460

  10. Electronic transport properties of In-doped ZnO nanobelts with different concentration.

    PubMed

    Su, Jia; Li, Huifeng; Huang, Yunhua; Xing, Xiujun; Zhao, Jing; Zhang, Yue

    2011-05-01

    In this paper, zinc oxide (ZnO) nanobelts with five different indium (In) concentrations (1.98, 2.73, 3.33, 4.20, and 5.16 wt%) were prepared by simple vapor deposition with HAuCl(4) (1% solution) as catalyst. Detailed structural and compositional characterizations were performed by XRD, TEM, EDS, PL, and Raman spectroscopy. Moreover, the current-voltage (I-V) characteristics of In-doped ZnO nanobelts with different In concentrations were determined by nano-manipulation and measurement systems. The results show that the resistivity of these nanobelts decreases with increasing In concentration when the doping concentration of In is lower than 4.20%, but, on the contrary, when the In concentration is higher than 4.20% their resistivity increases. Also, all of the nanobelts keep ohmic contact very well. Simultaneously, the influence of electron beam irradiation (20 kV) on the nanobelts was studied, and it was found that electron beam irradiation can improve the conductivity of the nanobelts. Under the same voltage, the current increased gradually during irradiation until equilibrium was reached. The degree of influence of the irradiation on the resistivity of the nanobelts is the greatest when the In dopant concentration is 4.20%, which is suitable for making irradiation sensors. PMID:21445421

  11. Low temperature electron transport in phosphorus-doped ZnO films grown on Si substrates

    NASA Astrophysics Data System (ADS)

    Zhang, K.; Hao, M. R.; Guo, W.; Heeg, T.; Schlom, D. G.; Shen, W. Z.; Pan, X. Q.

    2012-07-01

    Low temperature magneto-transport properties and electron dephasing mechanisms of phosphorus-doped ZnO thin films grown on (1 1 1) Si substrates with Lu2O3 buffer layers using pulsed laser deposition were investigated in detail by quantum interference and weak localization theories under magnetic fields up to 10 T. The dephasing length follows the temperature dependence with an index p≈1.6 at higher temperatures indicating electron-electron interaction, yet becomes saturated at lower temperatures. Consistent with photoluminescence measurements and the multi-band simulation of the electron concentration, such behavior was associated with the dislocation densities obtained from x-ray diffraction and mobility fittings, where charged edge dislocations acting as inelastic Coulomb scattering centers were affirmed responsible for electron dephasing. Owing to the temperature independence of the dislocation density, the phosphorus-doped ZnO film maintained a Hall mobility of 4.5 cm2 V-1 s-1 at 4 K.

  12. Transparent conductive Al-doped ZnO thin films grown at room temperature

    SciTech Connect

    Wang Yuping; Lu Jianguo; Bie Xun; Gong Li; Li Xiang; Song Da; Zhao Xuyang; Ye Wenyi; Ye Zhizhen

    2011-05-15

    Aluminum-doped ZnO (ZnO:Al, AZO) thin films were prepared on glass substrates by dc reactive magnetron sputtering from a Zn-Al alloy target at room temperature. The effects of the Ar-to-O{sub 2} partial pressure ratios on the structural, electrical, and optical properties of AZO films were studied in detail. AZO films grown using 100:4 to 100:8 Ar-to-O{sub 2} ratio result in acceptable quality films with c-axis orientated crystals, uniform grains, 10{sup -3} {Omega} cm resistivity, greater than 10{sup 20} cm{sup -3} electron concentration, and high transmittance, 90%, in the visible region. The lowest resistivity of 4.11x10{sup -3} {Omega} cm was obtained under the Ar-to-O{sub 2} partial pressure ratio of 100:4. A relatively strong UV emission at {approx}3.26 eV was observed in the room-temperature photoluminescence spectrum. X-ray photoelectron spectroscopy analysis confirmed that Al was introduced into ZnO and substitutes for Zn and doped the film n-type.

  13. Temperature dependent dual hydrogen sensor response of Pd nanoparticle decorated Al doped ZnO surfaces

    SciTech Connect

    Gupta, D.; Barman, P. B.; Hazra, S. K.; Dutta, D.; Kumar, M.; Som, T.

    2015-10-28

    Sputter deposited Al doped ZnO (AZO) thin films exhibit a dual hydrogen sensing response in the temperature range 40 °C–150 °C after surface modifications with palladium nanoparticles. The unmodified AZO films showed no response in hydrogen in the temperature range 40 °C–150 °C. The operational temperature windows on the low and high temperature sides have been estimated by isolating the semiconductor-to-metal transition temperature zone of the sensor device. The gas response pattern was modeled by considering various adsorption isotherms, which revealed the dominance of heterogeneous adsorption characteristics. The Arrhenius adsorption barrier showed dual variation with change in hydrogen gas concentration on either side of the semiconductor-to-metal transition. A detailed analysis of the hydrogen gas response pattern by considering the changes in nano palladium due to hydrogen adsorption, and semiconductor-to-metal transition of nanocrystalline Al doped ZnO layer due to temperature, along with material characterization studies by glancing incidence X-ray diffraction, atomic force microscopy, and transmission electron microscopy, are presented.

  14. Optical analysis of doped ZnO thin films using nonparabolic conduction-band parameters

    NASA Astrophysics Data System (ADS)

    Kim, J. S.; Jeong, J.-h.; Park, J. K.; Baik, Y. J.; Kim, I. H.; Seong, T.-Y.; Kim, W. M.

    2012-06-01

    The optical properties of impurity doped ZnO thin films were analyzed by taking into account the nonparabolicity in the conduction-band and the optically determined carrier concentration and mobility were correlated with those measured by Hall measurement. The Drude parameters obtained by applying a simple Drude model combined with the Lorentz oscillator model for the optical transmittance and reflectance spectrum were analyzed by using the carrier density dependent bare band effective mass determined by the first-order nonparabolicity approximation. The squared plasma energy multiplied by the carrier density dependent effective mass yielded fairly linear relationship with respect to the carrier concentration in wide carrier density range of 1019 - 1021 cm-3, verifying the applicability of the nonparabolicity parameter for various types of impurity doped ZnO thin films. The correlation between the optical and Hall analyses was examined by taking the ratios of optical to Hall measurements for carrier density, mobility, and resistivity by introducing a parameter, Rdl, which represents the ratio of the resistances to electron transport from the inside of the lattice and from the crystallographic defects. For both the carrier concentration and mobility, the ratios of optical to Hall measurements were shown to exhibit a monotonically decreasing function of Rdl, indicating that the parameter Rdl could be used as a yardstick in correlating the optically determined carrier density and mobility with those measured by Hall analysis.

  15. Hybrid Hartree-Fock density functional study of transition-metal doped ZnO

    NASA Astrophysics Data System (ADS)

    Betancourt, Jesuan; Kalitsov, Alan; Velev, Julian

    2012-02-01

    Dilute magnetic semiconductors (DMS) obtained by doping semiconductors with transition metals (TM) hold much promise for spintronics. Transition metal doped ZnO (ZnO:TM) has been investigated for a possible room-temperature DMS. Density functional theory gives incorrect prediction for the band gap of ZnO which leads to diverging interpretations for the magnetic behavior of ZnO:TM [1,2]. Here we report Heyd-Scuseria-Ernzerhof (HSE) hybrid functional study of the electronic structure of ZnO:TM (TM=Cu, Ni, Co, Fe, Mn). The hybrid functional corrects for both the bandgap problem on the host and the lack of correlation in the impurity, without the use of ad-hoc intra-atomic potentials. Our results show although the HSE opens the band gap of the host, the Hubbard splitting of the impurity levels makes the empty impurity levels reside in the host conduction band. This leaves open the possibility for spin polarized carriers. We discuss the validity of the results and explore their implications for the magnetic behavior of ZnO:TM. [1] H. Raebiger, S. Lany, and A. Zunger, Physical Review B 79, 165202 (2009). [2] P. Gopal and N. A. Spaldin, Phys.l Review B 74, 094418 (2006).

  16. Sonocatalytic performance of Er-doped ZnO for degradation of a textile dye.

    PubMed

    Khataee, Alireza; Saadi, Shabnam; Safarpour, Mahdie; Joo, Sang Woo

    2015-11-01

    Pure and erbium (Er)-doped ZnO samples were synthesized through a sonochemical method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis spectroscopy, and X-ray photoelectron spectroscopy (XPS) analysis. The synthesized samples were used as a catalyst for the sonocatalytic decolorization of Reactive Orange 29 (RO29) as a model organic pollutant. The decolorization efficiency was 63%, 68%, 88%, and 75% for undoped, 2%, 4%, and 6% Er-doped ZnO, respectively. The effect of different experimental parameters including catalyst content, dye concentration and ultrasound power was investigated on the sonocatalytic decolorization of RO29. Among several radical scavengers (i.e. chloride, carbonate and sulfate anions and t-butanol), the chloride anion showed the most inhibitive effect on the sonocatalysis performance. Improvement of the sonocatalytic process by K2S2O8 and H2O2 enhancers was also studied. The reusability of the synthesized sonocatalyst was evaluated in several consecutive runs, and a decline of only 4% was observed in the process performance after five runs. The intermediates produced during the degradation of RO29 were identified by GC-MS analysis. PMID:26186857

  17. Room temperature ferromagnetism in Eu-doped ZnO nanoparticulate powders prepared by combustion reaction method

    NASA Astrophysics Data System (ADS)

    Franco, A.; Pessoni, H. V. S.; Soares, M. P.

    2014-04-01

    Nanoparticulate powders of Eu-doped ZnO with 1.0, 1.5, 2.0 and 3.0 at% Eu were synthesized by combustion reaction method using zinc nitrate, europium nitrate and urea as fuel without subsequent heat treatments. X-ray diffraction patterns (XRD) of all samples showed broad peaks consistent with the ZnO wurtzite structure. The absence of extra reflections in the diffraction patterns ensures the phase purity, except for x=0.03 that exhibits small reflection corresponding to Eu2O3 phase. The average crystallite size determined from the most prominent (1 0 1) peak of the diffraction using Scherrer's equation was in good agreement with those determined by transmission electron microscopy (TEM); being ~26 nm. The magnetic properties measurements were performed using a vibrating sample magnetometer (VSM) in magnetic fields up to 2.0 kOe at room temperature. The hysteresis loops, typical of magnetic behaviors, indicating that the presence of an ordered magnetic structure can exist in the Eu-doped ZnO wurtzite structure at room temperature. The room temperature ferromagnetism behavior increases with the Eu3+ doping concentration. All samples exhibited the same Curie temperature (TC) around ~726 K, except for x=0.01; TC~643 K. High resolution transmission electron microscopy (HRTEM) images revealed defects/strain in the lattice and grain boundaries of Eu-doped ZnO nanoparticulate powders. The origin of room temperature ferromagnetism in Eu-doped ZnO nanoparticulate powders was discussed in terms of these defects, which increase with the Eu3+ doping concentration.

  18. Study on Solid-Phase Crystallization of Amorphized Vanadium-Doped ZnO Thin Films

    NASA Astrophysics Data System (ADS)

    Watanabe, Akihiro; Chiba, Hiroshi; Kawashima, Tomoyuki; Washio, Katsuyoshi

    2016-04-01

    The effects of post-annealing and film thickness on the solid-phase crystallization (SPC) of amorphized vanadium-doped ZnO (VZO) thin films were investigated. The 2-500-nm-thick VZO (V of about 4 at.%) thin films were deposited on a c-face sapphire substrate at room temperature by RF magnetron sputtering and subsequently were annealed at an annealing temperature (T A) from 700°C to 900°C in a nitrogen atmosphere. From in-plane x-ray diffraction (XRD) measurements, the as-deposited VZO film had a faint in-plane orientation at the initial stage of deposition. However, the ZnO(100) XRD intensity weakened with increasing film thickness and no diffraction peak was seen over 35-nm thick. That is, the pseudo-amorphous film was fabricated. By annealing the 100-nm-thick VZO film over 700°C, the sixfold symmetry appeared. The ZnO(100) XRD intensity increased sharply at a T A of 800°C and was saturated at a higher T A. The c axis orientation reached a peak at a T A of 800°C according to the ZnO(002) XRD intensity. Concerning the effect of film thickness in the case of T A = 800°C, both the in-plane and c axis orientation improved up to 100-nm thick and deteriorated over it. At a T A ≥ 850°C or film thickness ≥200 nm, where the c axis orientation was deteriorated, the secondary phase-like Zn3V2O8 was formed. As a result, it is found that the careful selection of the T A and film thickness is necessary to avoid the formation of secondary phase-like Zn3V2O8 to fabricate the high-quality buffer layer via SPC.

  19. Temperature dependence anomalous dielectric relaxation in Co doped ZnO nanoparticles

    SciTech Connect

    Ansari, Sajid Ali; Nisar, Ambreen; Fatma, Bushara; Khan, Wasi; Chaman, M.; Azam, Ameer; Naqvi, A.H.

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► We prepared Co doped ZnO by facile gel-combustion method. ► Studied temperature dependent dielectric properties in detail. ► Relaxation time shifts toward the higher temperature as increase in Co content. ► SEM analysis shows formation and agglomeration of nanoparticles. ► Dielectric constants, loss and ac conductivity increases with rise in temperature. ► The dielectric constant, loss and ac conductivity decreases as Co ion increases. -- Abstract: We have reported temperature and frequency dependence of dielectric behavior of nanocrystalline Zn{sub 1−x}Co{sub x}O (x = 0.0, 0.01, 0.05 and 0.1) samples prepared by gel-combustion method. The synthesized samples were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and LCR-meter, respectively. The XRD analysis reveals that ZnO has a hexagonal (wurtzite) crystal structure. The morphology and size of the nanoparticles (∼10–25 nm) were observed by SEM for 5% Co doped ZnO sample. In dielectric properties, complex permittivity (ε{sup *} = ε′ − jε″), loss tangent (tan δ) and ac conductivity (σ{sub ac}) in the frequency range 75 kHz to 5 MHz were analyzed with temperature range 150–400 °C. The experimental results indicate that ε′, ε″, tan δ and σ{sub ac} decreases with increase in frequency and temperature. The transition temperature as obtained in dispersion curve of dielectric constant shifts toward higher temperature with increase Co content.

  20. Cr-Doped ZnO Nanoparticles: Synthesis, Characterization, Adsorption Property, and Recyclability.

    PubMed

    Meng, Alan; Xing, Jing; Li, Zhenjiang; Li, Qingdang

    2015-12-16

    In this paper, a mild solvothermal method has been employed to successfully synthesize a series of Cr-doped ZnO nanoparticles (NPs) with different Cr(3+) contents, which is a kind of novel and high-efficiency absorbent for the removal of acid dye methyl orange (MO) from aqueous solution. The as-prepared products were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Brunauer, Emmet, and Teller (BET), and Zeta potential measurements. In accordance with the adsorption capacity of the products, the obtained optimal Cr/Zn molar ratio is 6%. The adsorption process of MO on Cr-doped ZnO was investigated by kinetics, thermodynamics, and isotherm technologies, which, respectively, indicated that the adsorption was fast (adsorption reached equilibrium in 2 h) and followed a pseudo-second-order model, that the adsorption process was spontaneous and endothermic, and that it agreed well with the Langmuir isotherm with a maximum adsorption capacity of 310.56 mg g(-1). Moreover, a reasonable mechanism was proposed to elucidate the reasons for their adsorption behavior. In addition, a simple and low-cost chemical method was developed to separate and recycle ZnO and MO from the used adsorbent, effectively avoiding the secondary pollution. This work can not only describe efficient experimental approaches for obtaining novel adsorbents and recycling them but also offer valuable clues for the preparation and property study of other semiconductor adsorbents. PMID:26600320

  1. Fabrication and characterization of pristine and annealed Ga doped ZnO thin films using sputtering

    NASA Astrophysics Data System (ADS)

    Mishra, Abhisek; Mohapatra, Saswat; Gouda, Himanshu Sekhar; Singh, Udai P.

    2016-05-01

    ZnO is a wide-band gap, transparent, polar semiconductor with unparalleled optoelectronic, piezoelectric, thermal and transport properties, which make it the material of choice for a wide range of applications such as blue/UV optoelectronics, energy conversion, transparent electronics, spintronic, plasmonic and sensor devices. We report, three sets of Ga doped Zinc Oxide (GZO) were fabricated in different sputtering power (100 watt, 200 watt and 300 watt). Thereafter films were annealed in nitrogen ambient for 30 minutes at 400° C. From the optical absorption spectroscopy it was found that pristine films are showing a 75% transmittance in the visible region of light and it increases after the annealing. However, for 300 W grown sample opposite trend has been achieved for the post annealed sample. X-ray diffraction pattern of all the pristine and annealed films showed a preferable growth orientation at (002) phase. Some other weak peaks were also appeared in different angle which indicates that films are polycrystalline in nature. XRD data also reveals that crystallite size increases with sputtering power up to 200 W and thereafter it decreases with the deposition power. It also noted that the crystallite size of the annealed film increases with compare to the non annealed films. At room temperature an enhancement in electrical properties of Ga doped ZnO thin films was noted for the annealed ZnO films except for the film deposited at 300 watt. More significantly, it was found that annealed thin films showed the resistivity in the range of 10-3 ˜ 10-4 ohm-cm. Such a high optical transmittance and conducting zinc-oxide thin film can be used as a window layer in solar cell.

  2. Low-temperature ferromagnetic properties in Co-doped Ag{sub 2}Se nanoparticles

    SciTech Connect

    Yang, Fengxia E-mail: xia9020@hust.edu.cn; Yu, Gen; Han, Chong; Liu, Tingting; Zhang, Duanming; Xia, Zhengcai E-mail: xia9020@hust.edu.cn

    2014-01-06

    β-Ag{sub 2}Se is a topologically nontrivial insulator. The magnetic properties of Co-doped Ag{sub 2}Se nanoparticles with Co concentrations up to 40% were investigated. The cusp of zero-field-cooling magnetization curves and the low-temperature hysteresis loops were observed. With increasing concentration of Co{sup 2+} ions mainly substituting Ag{sub I} sites in the Ag{sub 2}Se structure, the resistivity, Curie temperature T{sub c}, and magnetization increased. At 10 T, a sharp drop of resistance near T{sub c} was detected due to Co dopants. The ferromagnetic behavior in Co-doped Ag{sub 2}Se might result from the intra-layer ferromagnetic coupling and surface spin. This magnetic semiconductor is a promising candidate in electronics and spintronics.

  3. Photoluminescence of Ag-doped ZnSe nanowires synthesized by metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhang, X. T.; Ip, K. M.; Li, Quan; Hark, S. K.

    2005-05-01

    Photoluminescence of Ag-doped ZnSe nanowires synthesized by metalorganic chemical vapor deposition is investigated in the temperature range from 10to300K. Ag impurities were introduced into the ZnSe nanowires during the growing process. Some dominating Ag-related centers are found. Especially, the strong zero-phonon bound exciton luminescence with energy near 2.747eV is attributed to a neutral AgZn acceptor complex. This is because the emission peak at the same energy is observed only in the photoluminescence spectrum of the Ag-doped bulk ZnSe. A new luminescence peak at 2.842eV is attributed to the recombination of excitons bound to ionized acceptors (I2h) in the hexagonal phase of ZnSe nanowires. The physical origins of the emissions are briefly discussed.

  4. Oxygen reduction reaction on Cu-doped Ag cluster for fuel-cell cathode.

    PubMed

    Ma, Wenqiang; Chen, Fuyi; Zhang, Nan; Wu, Xiaoqiang

    2014-10-01

    The development of fuel cells as clean-energy technologies is largely limited by the prohibitive cost of the noble-metal catalysts needed for catalyzing the oxygen reduction reaction (ORR) in fuel cells. A fundamental understanding of catalyst design principle that links material structures to the catalytic activity can accelerate the search for highly active and abundant bimetallic catalysts to replace platinum. Here, we present a first-principles study of ORR on Ag12Cu cluster in alkaline environment. The adsorptions of O2, OOH, and OH on Cu-doped Ag13 are stronger than on Ag13. The d-band centers of adsorption sites show the Cu-doping makes d-electrons transferred to higher energy state, and improves O2 dissociation. ORR processes on Ag12Cu and Ag13 indicate Cu-doping can strongly promote ORR, and ORR process can be better preformed on Ag12Cu than on Ag13. For four-electron transfer, the effective reversible potential is 0.401 V/RHE on Ag12Cu in alkaline medium. PMID:25227449

  5. In situ photo sonosynthesis and characterize nonmetal/metal dual doped honeycomb-like ZnO nanocomposites on wool fabric.

    PubMed

    Behzadnia, Amir; Montazer, Majid; Rad, Mahnaz Mahmoudi

    2015-11-01

    In this work, nonmetal/metal dual-doped honeycomb-like N-Ag/ZnO nanocomposites were successfully photo sonosynthesized and sonoimmobilized on wool fabric through a facile one-step method under ambient pressure at low temperature as a novel photo-catalyst nanocomposite on textile material. Introducing nitrogen and silver on the sonoprepared nano ZnO particles led to superior photocatalytic activity. The homogenous distribution of the honeycomb-like nanocomposites on the fiber surface was confirmed by FE-SEM, EDX and X-ray mapping. X-ray diffraction patterns also proved the presence of silver metal with a crystal size of 54Å on the photo sonotreated sample with nonmetal/metal dual-doped honeycomb-like N-Ag/ZnO nanocomposites. The defect analysis based on XPS confirmed the composition of the nanocomposite. Ultraviolet-blocking was examined through reflectance spectra in the range of 200-800 nm showing reasonable transmittance property. The sonoloaded wool sample indicated excellent antibacterial/antifungal properties with low negative effect on human dermal fibroblasts. The role of both zinc acetate and silver nitrate concentration on diverse properties of the fabric was investigated and the optimized conditions introduced using response surface methodology. Finally a superior quality wool fabric with multifunctional properties was introduced for using special clothing in different environment. PMID:26186838

  6. Nucleation, Growth Mechanism, and Controlled Coating of ZnO ALD onto Vertically Aligned N-Doped CNTs.

    PubMed

    Silva, R M; Ferro, M C; Araujo, J R; Achete, C A; Clavel, G; Silva, R F; Pinna, N

    2016-07-19

    Zinc oxide thin films were deposited on vertically aligned nitrogen-doped carbon nanotubes (N-CNTs) by atomic layer deposition (ALD) from diethylzinc and water. The study demonstrates that doping CNTs with nitrogen is an effective approach for the "activation" of the CNTs surface for the ALD of metal oxides. Conformal ZnO coatings are already obtained after 50 ALD cycles, whereas at lower ALD cycles an island growth mode is observed. Moreover, the process allows for a uniform growth from the top to the bottom of the vertically aligned N-CNT arrays. X-ray photoelectron spectroscopy demonstrates that ZnO nucleation takes place at the N-containing species on the surface of the CNTs by the formation of the Zn-N bonds at the interface between the CNTs and the ZnO film. PMID:27333190

  7. p-type ZnO films with solid-source phosphorus doping by molecular-beam epitaxy

    SciTech Connect

    Xiu, F.X.; Yang, Z.; Mandalapu, L.J.; Liu, J.L.; Beyermann, W. P.

    2006-01-30

    Phosphorus-doped p-type ZnO films were grown on r-plane sapphire substrates using molecular-beam epitaxy with a solid-source GaP effusion cell. X-ray diffraction spectra and reflection high-energy electron diffraction patterns indicate that high-quality single crystalline (1120) ZnO films were obtained. Hall and resistivity measurements show that the phosphorus-doped ZnO films have high hole concentrations and low resistivities at room temperature. Photoluminescence (PL) measurements at 8 K reveal a dominant acceptor-bound exciton emission with an energy of 3.317 eV. The acceptor energy level of the phosphorus dopant is estimated to be 0.18 eV above the valence band from PL spectra, which is also consistent with the temperature dependence of PL measurements.

  8. Magnetic structure and interaction in (Sb, Co) co-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Samanta, K.; Sardar, M.; Singh, S. P.; Katiyar, R. S.

    2014-10-01

    The magnetic behaviour of (Co, Sb) co-doped ZnO thin films grown by pulsed laser deposition is investigated. The irreversibility (ZFC-FC bifurcation) in low field (H = 100 Oe) magnetization and small hysteresis below 300 K are similar in samples with or without Sb co-doping. Both the phenomena originate from the presence of blocked supermoments in the samples. Incorporation of Sb only increases the saturation magnetization and coercivity. The quantitative increase in moment due to Sb co-doping suggests a transfer of electrons from Co ions to Sb-related acceptor complexes. This is supported by a decrease in the number of electronic transitions from Co d electrons to the conduction band seen in optical transmission spectroscopy when Sb is added. The high field susceptibility data show the existence of supermoments with antiferromagnetic interaction between them. We find that the value of the effective antiferromagnetic molecular field constant decreases with increasing Co concentration, revealing that the supermoments are bound magnetic polarons around intrinsic donors, rather than coming from Co precipitates. True ferromagnetism (overlapping polarons) can emerge either with larger intrinsic donors, or with acceptors with shallower levels, than those created by Sb co-doping. Our results suggest that Sb-related acceptor states may be unstable towards accepting electrons from deep d levels of Co ions.

  9. Hydrothermal growth and conductivity enhancement of (Al, Cu) co-doped ZnO nanorods thin films

    NASA Astrophysics Data System (ADS)

    Chakraborty, Mohua; Mahapatra, Preetilata; Thangavel, R.

    2016-05-01

    The incorporation of Al, Cu co-doping in ZnO host lattice plays an important role in modification of structural, optical and electrical properties in optoelectronic devices. In the present work, we were grown one dimensional ZnO nanorods (NRs) doped with different concentration of Al (0%~5%) and Cu was kept 20 M% on ITO glass substrates using a facile hydrothermal method, and investigated the effect of the codoping on the surface morphology and the electrical and optical performances of the doped ZnO NRs as photo anodes for solar water splitting applications. The crystallite size of NRs shows tuning in the band gap between 3.194 (Zn0.79Al0.01Cu0.2O) to 3.212 eV (Zn0.75Al0.05Cu0.2O) with Aluminium doping concentration and a remarkable improvement in current density (J) from 0.05 mA/cm2 to 4.98 mA/cm2 was achieved by incorporating Al and Cu has a critical effect of ZnO nanorods.

  10. Defects Energetics and Electronic Properties of Li Doped ZnO: A Hybrid Hartree-Fock and Density Functional Study

    NASA Astrophysics Data System (ADS)

    Sun, Xu; Gu, You-song; Wang, Xue-qiang; Zhang, Yue

    2012-06-01

    The electronic properties and stability of Li-doped ZnO with various defects have been studied by calculating the electronic structures and defect formation energies via first-principles calculations using hybrid Hartree-Fock and density functional methods. The results from formation energy calculations show that Li pair complexes have the lowest formation energy in most circumstances and they consume most of the Li content in Li doped ZnO, which make the p-type conductance hard to obtain. The formation of Li pair complexes is the main obstacle to realize p-type conductance in Li doped ZnO. However, the formation energy of LiZn decreases as environment changes from Zn-rich to O-rich and becomes more stable than that of Li-pair complexes at highly O-rich environment. Therefore, p-type conductance can be obtained by Li doped ZnO grown or post annealed in oxygen rich atmosphere.

  11. Effect of Mn-doping on the growth mechanism and electromagnetic properties of chrysanthemum-like ZnO nanowire clusters

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

    Chrysanthemum-like ZnO nanowire clusters with different Mn-doping concentrations are prepared by a hydrothermal process. The microstructure, morphology and electromagnetic properties are characterized by x-ray diffractometer high-resolution transmission electron microscopy (HRTEM), a field emission environment scanning electron microscope (FEESEM) and a microwave vector network analyser respectively. The experimental results indicate that the as-prepared products are Mn-doped ZnO single crystalline with a hexagonal wurtzite structure, that the growth habit changes due to Mn-doping and that a good magnetic loss property is found in the Mn-doped ZnO products, and the average magnetic loss tangent tanδm is up to 0.170099 for 3% Mn-doping, while the dielectric loss tangent tanδe is weakened, owing to the fact that ions Mn2+ enter the crystal lattice of ZnO.

  12. Synthesis and characterization of aluminum–boron co-doped ZnO nanostructures

    SciTech Connect

    Kumar, Vinod; Singh, R.G.; Singh, Neetu; Kapoor, Avinashi; Mehra, R.M.; Purohit, L.P.

    2013-02-15

    Graphical abstract: In this paper, we have reported the development of aluminum boron co-doped ZnO (AZB) nanostructures deposited by sol–gel method using spin coating technique. The structure of AZB nanostructure films has been found to exhibit the hexagonal wurtzite structure. The shape of nanostructures has been changed from seed structure to tetra-pods, tetra-pods to nanorods and finally nanorods to nanofiber with variation in Al concentration. The structural, electrical and optical properties of AZB nanostructures are tuned with shape and size of the nanostructures. The effect of Al concentration on the resistivity (ρ), carrier concentration (n) and mobility (μ) of nanostructure films is shown in graph below. A minimum resistivity of 6.8 × 10{sup −4} Ω cm is obtained in AZB films at doping concentration of B 0.6 at.% and Al 0.4 at.% with a sheet resistance of 24 Ω/□ and transmittance of ∼88% for nanorods structure. These nanostructures could be applicable for a various nano-regime devices such as photovolatics, gas sensing and field emission device. Display Omitted Highlights: ► Synthesis of Al and B co-doped ZnO (AZB) nanostructures. ► Minimum resistivity (ρ) of 6.8 × 10{sup −4} Ω cm in AZB films. ► Minimum sheet resistance (R{sub s}) 24 Ω/□ in nanorods (NRs). ► Maximum transmittance ∼88% in NRs. ► Application in nano-electronic devices. -- Abstract: In this paper, we have reported the development of aluminum boron co-doped ZnO (AZB) nanostructures deposited by sol–gel method using spin coating technique. The structure of AZB nanostructure films has been found to exhibit the hexagonal wurtzite structure. The shape of AZB nanostructures has changed from seed structure to tetra-pods, tetra-pods to nanorods and finally to nanofibers with increase in aluminum concentration. The structural, electrical and optical properties of AZB films are tuned with shape and size of the nanostructures. These AZB nanostructures could be

  13. Photosensitization of ZnO by AgBr and Ag2CO3: Nanocomposites with tandem n-n heterojunctions and highly enhanced visible-light photocatalytic activity.

    PubMed

    Pirhashemi, Mahsa; Habibi-Yangjeh, Aziz

    2016-07-15

    Facile ultrasonic-irradiation method was applied for photosensitization of ZnO by combining with AgBr and Ag2CO3 particles through preparation of novel ternary nanocomposites. The prepared samples were characterized by XRD, SEM, TEM, EDX, UV-Vis DRS, FT-IR, BET, and PL techniques. Photocatalytic activity was investigated by degradation of rhodamine B under visible-light irradiation. It was found that photocatalytic activity of the ZnO was greatly enhanced by coupling with AgBr and Ag2CO3 particles, as narrow band gap semiconductors, through formation of tandem n-n heterojunctions. The nanocomposite with 20% of Ag2CO3 displayed the highest photocatalytic activity with the degradation rate constants which are nearly 122, 31, and 25 times higher than those of the ZnO, ZnO/AgBr, and ZnO/Ag2CO3 samples, respectively. Moreover, the trapping experiments confirmed that superoxide ion radicals and holes are the main active species responsible for the degradation reaction. Finally, it was also demonstrated that the ternary ZnO/AgBr/Ag2CO3 (20%) nanocomposite has enhanced activity in degradation of methylene blue and methyl orange. Hence, this work shows a great potential of the ternary photocatalyst for purification of contaminated water from organic pollutants. PMID:27111379

  14. Optoelectronic Characterization of Ta-Doped ZnO Thin Films by Pulsed Laser Deposition.

    PubMed

    Koo, Horng-Show; Peng, Jo-Chi; Chen, Mi; Chin, Hung-I; Chen, Jaw-Yeh; Wu, Maw-Kuen

    2015-11-01

    Transparent conductive oxide of Ta-doped ZnO (TZO) film with doping amount of 3.0 wt% have been deposited on glass substrates (Corning Eagle XG) at substrate temperatures of 100 to 500 degrees C by the pulsed laser deposition (PLD) technique. The effect of substrate temperature on the structural, optical and electronic characteristics of Ta-doped ZnO (TZO) films with 3.0 wt% dopant of tantalum oxide (Ta2O5) was measured and demonstrated in terms of X-ray diffraction (XRD), ultraviolet-visible spectrometer (UV-Vis), four-probe and Hall-effect measurements. X-ray diffraction pattern shows that TZO films grow in hexagonal crystal structure of wurtzite phase with a preferred orientation of the crystallites along (002) direction and exhibits better physical characteristics of optical transmittance, electrical conductivity, carrier concentration and mobility for the application of window layer in the optoelectronic devices of solar cells, OLEDs and LEDs. The lowest electrical resistivity (ρ) and the highest carrier concentration of the as-deposited film deposited at 300 degrees C are measured as 2.6 x 10(-3) Ω-cm and 3.87 x 10(-20) cm(-3), respectively. The highest optical transmittance of the as-deposited film deposited at 500 degrees C is shown to be 93%, compared with another films deposited below 300 degrees C. It is found that electrical and optical properties of the as-deposited TZO film are greatly dependent on substrate temperature during laser ablation deposition. PMID:26726672

  15. Thermoelectric Properties of CuAgSe doped with Co, Cr

    NASA Astrophysics Data System (ADS)

    Czajka, Peter; Yao, Mengliang; Opeil, Cyril

    Thermoelectric materials represent one way that reliable cooling below the boiling point of nitrogen can be realized. Current materials do not exhibit sufficiently high efficiencies at cryogenic temperatures, but significant progress is being made. One material that has generated significant interest recently is CuAgSe. It has been demonstrated (Ishiwata et al., Nature Mater. 2013) that doping CuAgSe with 10% Ni at the Cu sites increases the material's thermoelectric figure of merit (ZT) at 100 K from 0.02 to 0.10. This is intriguing not just because of the dramatic effect that the Ni doping produces, but also because CuAgSe is a semimetal and semimetals are not usually able to exhibit the kind of asymmetric carrier activation necessary for strong thermoelectric performance. In order to further investigate the unusual nature of thermoelectricity in CuAgSe and its strong dependence on chemical composition, we have synthesized and measured the thermoelectric properties of a series of CuAgSe samples doped with Co and Cr. Temperature-dependent magnetic and thermoelectric transport properties of CuAgSe as a function of Co and Cr doping will be discussed. This work is supported by the Department of Defense, AFOSR, MURI Program Contract # FA9550-10-1-0533 and the Trustees of Boston College.

  16. Ag- and Cu-doped multifunctional bioactive nanostructured TiCaPCON films

    NASA Astrophysics Data System (ADS)

    Shtansky, D. V.; Batenina, I. V.; Kiryukhantsev-Korneev, Ph. V.; Sheveyko, A. N.; Kuptsov, K. A.; Zhitnyak, I. Y.; Anisimova, N. Yu.; Gloushankova, N. A.

    2013-11-01

    A key property of multicomponent bioactive nanostructured Ti(C,N)-based films doped with Ca, P, and O (TiCaPCON) that can be improved further is their antibacterial effect that should be achieved without compromising the implant bioactivity and biocompatibility. The present work is focused on the study of structure, chemical, mechanical, tribological, and biological properties of Ag- and Cu-doped TiCaPCON films. The films with Ag (0.4-4 at.%) and Cu (13 at.%) contents were obtained by simultaneous sputtering of a TiC0.5-Ca3(PO4)2 target and either an Ag or a Cu target. The film structure was studied using X-ray diffraction, transmission and scanning electron microscopy, energy dispersive X-ray spectroscopy, glow discharge optical emission spectroscopy, and Raman-shift and IR spectroscopy. The films were characterized in terms of their hardness, elastic modulus, dynamic impact resistance, friction coefficient and wear rate (both in air and normal saline), surface wettability, electrochemical behavior and Ag or Cu ion release in normal saline. Particular attention was paid to the influence of inorganic bactericides (Ag and Cu ions) on the bactericidal activity against unicellular yeast fungus Saccharomyces cerevisiae and gram-positive bacteria Lactobacillus acidophilus, as well as on the attachment, spreading, actin cytoskeleton organization, focal adhesions, and early stages of osteoblastic cell differentiation. The obtained results show that the Ag-doped films are more suitable for the protection of metallic surfaces against bacterial infection compared with their Cu-doped counterpart. In particular, an excellent combination of mechanical, tribological, and biological properties makes Ag-doped TiCaPCON film with 1.2 at.% of Ag very attractive material for bioengineering and modification of load-bearing metal implant surfaces.

  17. Ag{sub 3}PO{sub 4}/ZnO: An efficient visible-light-sensitized composite with its application in photocatalytic degradation of Rhodamine B

    SciTech Connect

    Liu, Wei; Wang, Mingliang; Xu, Chunxiang; Chen, Shifu; Fu, Xianliang

    2013-01-15

    Graphical abstract: The free OH radicals generated in the VB of ZnO play the primary role in the visible-light photocatalytic degradation of RhB in Ag{sub 3}PO{sub 4}/ZnO system. The accumulated electrons in the CB of Ag{sub 3}PO{sub 4} can be transferred to O{sub 2} adsorbed on the surface of the composite semiconductors and H{sub 2}O{sub 2} yields. H{sub 2}O{sub 2} reacts with electrons in succession to produce active ·OH to some extent. Display Omitted Highlights: ► Efficient visible-light-sensitized Ag{sub 3}PO{sub 4}/ZnO composites were successfully prepared. ► Effect of Ag{sub 3}PO{sub 4} content on the catalytic activity of Ag{sub 3}PO{sub 4}/ZnO is studied in detail. ► Rate constant of RhB degradation over Ag{sub 3}PO{sub 4}(3.0 wt.%)/ZnO is 3 times that of Ag{sub 3}PO{sub 4}. ► The active species in RhB degradation are examined by adding a series of scavengers. ► Visible light degradation mechanism of RhB over Ag{sub 3}PO{sub 4}/ZnO is systematically studied. -- Abstract: The efficient visible-light-sensitized Ag{sub 3}PO{sub 4}/ZnO composites with various weight percents of Ag{sub 3}PO{sub 4} were prepared by a facile ball milling method. The photocatalysts were characterized by XRD, DRS, SEM, EDS, XPS, and BET specific area. The ·OH radicals produced during the photocatalytic reaction was detected by the TA–PL technique. The photocatalytic property of Ag{sub 3}PO{sub 4}/ZnO was evaluated by photocatalytic degradation of Rhodamine B under visible light irradiation. Significantly, the results revealed that the photocatalytic activity of the composites was much higher than that of pure Ag{sub 3}PO{sub 4} and ZnO. The rate constant of RhB degradation over Ag{sub 3}PO{sub 4}(3.0 wt.%)/ZnO is 3 times that of single-phase Ag{sub 3}PO{sub 4}. The optimal percentage of Ag{sub 3}PO{sub 4} in the composite is 3.0 wt.%. It is proposed that the ·OH radicals produced in the valence band of ZnO play the leading role in the photocatalytic degradation of

  18. Understanding the role of iron in the magnetism of Fe doped ZnO nanoparticles.

    PubMed

    Beltrán, J J; Barrero, C A; Punnoose, A

    2015-06-21

    The actual role of transition metals like iron in the room temperature ferromagnetism (RTFM) of Fe doped ZnO nanoparticles is still an unsolved problem. While some studies concluded that the Fe ions participate in the magnetic interaction, others in contrast do not believe Fe to play a direct role in the magnetic exchange interaction. To contribute to the understanding of this issue, we have carefully investigated the structural, optical, vibrational and magnetic properties of sol-gel synthesized Zn1-xFexO (0 < x < 0.10) nanoparticles. No Fe(2+) was detected in any sample. We found that high spin Fe(3+) ions are substitutionally incorporated at the Zn(2+) in the tetrahedral-core sites and in pseudo-octahedral surface sites in ZnO. Superficial OH(-) was observed in all samples. For x ≤ 0.03, an increment in Fe doping concentration decreased a and c lattice parameters, average Zn-O bond length, average crystallite size and band gap; while it increased the degree of distortion and quadrupole splitting. Undoped ZnO nanoparticles exhibited very weak RTFM with a saturation magnetization (Ms) of ∼0.47 memu g(-1) and this value increased to ∼2.1 memu g(-1) for Zn0.99Fe0.01O. Very interestingly, the Ms for Zn0.99Fe0.01O and Zn0.97Fe0.03O increased by a factor of about ∼2.3 by increasing annealing for 1 h to 3 h. For x ≥ 0.05, ferrimagnetic disordered spinel ZnFe2O4 was formed and this phase was found to become more ordered with increasing annealing time. Fe does not contribute directly to the RTFM, but its presence promoted the formation of additional single charged oxygen vacancies, zinc vacancies, and more oxygen-ended polar terminations at the nanoparticle surface. These defects, which are mainly superficial, altered the electronic structure and are considered as the main sources of the observed ferromagnetism. PMID:25994044

  19. Sol-gel derived Al-Ga co-doped transparent conducting oxide ZnO thin films

    NASA Astrophysics Data System (ADS)

    Serrao, Felcy Jyothi; Sandeep, K. M.; Bhat, Shreesha; Dharmaprakash, S. M.

    2016-05-01

    Transparent conducting ZnO doped with Al, Ga and co-doped Al and Ga (1:1) (AGZO) thin films were grown on glass substrates by cost effective sol-gel spin coating method. The XRD results showed that all the films are polycrystalline in nature and highly textured along the (002) plane. Enhanced grain size was observed in the case of AGZO thin films. The transmittance of all the films was more than 83% in the visible region of light. The electrical properties such as carrier concentration and mobility values are increased in case of AGZO compared to that of Al and Ga doped ZnO thin films. The minimum resistivity of 2.54 × 10-3 Ω cm was observed in AGZO thin film. The co-doped AGZO thin films exhibited minimum resistivity and high optical transmittance, indicate that co-doped ZnO thin films could be used in transparent electronics mainly in display applications.

  20. Transparent and conductive Al/F and In co-doped ZnO thin films deposited by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Hadri, A.; Taibi, M.; El hat, A.; Mzerd, A.

    2016-02-01

    In doped ZnO (IZO), In-Al co-doped ZnO (IAZO) and In-F co-doped ZnO (IFZO) were deposited on glass substrates at 350 °C by spray pyrolysis technique. The structural, optical and electrical properties of as-deposited thin films were investigated and compared. A polycrystalline and (002) oriented wurtzite crystal structure was confirmed by X-ray patterns for all films; and the full width at half -maximum (FWHM) of (002) diffraction peak increased after co-doping. The investigation of the optical properties was performed using Uv-vis spectroscopy. The average transmittances of all the films were between 70 and 85%. Hall Effect measurements showed that the electrical conductivity of co-doped films increased as compared with IZO thin film. The highest conductivity of about 16.39 Ω-1 cm-1 was obtained for as-deposited IFZO thin film. In addition, the thin films were annealed at 350 °C for two hour under Ar atmosphere and their optical, electrical properties and the associated photoluminescence (PL) responses of selected films were analysed. After annealing, the electrical conductivity of all thin films was improved and the optical transmittance remained above 70%. Room temperature PL revealed that the annealed IAZO thin film had a strong green emission than that of IZO film.

  1. Synergistic effect of N-decorated and Mn(2+) doped ZnO nanofibers with enhanced photocatalytic activity.

    PubMed

    Wang, Yuting; Cheng, Jing; Yu, Suye; Alcocer, Enric Juan; Shahid, Muhammad; Wang, Ziyuan; Pan, Wei

    2016-01-01

    Here we report a high efficiency photocatalyst, i.e., Mn(2+)-doped and N-decorated ZnO nanofibers (NFs) enriched with vacancy defects, fabricated via electrospinning and a subsequent controlled annealing process. This nanocatalyst exhibits excellent visible-light photocatalytic activity and an apparent quantum efficiency up to 12.77%, which is 50 times higher than that of pure ZnO. It also demonstrates good stability and durability in repeated photocatalytic degradation experiments. A comprehensive structural analysis shows that high density of oxygen vacancies and nitrogen are introduced into the nanofibers surface. Hence, the significant enhanced visible photocatalytic properties for Mn-ZnO NFs are due to the synergetic effects of both Mn(2+) doping and N decorated. Further investigations exhibit that the Mn(2+)-doping facilitates the formation of N-decorated and surface defects when annealing in N2 atmosphere. N doping induce the huge band gap decrease and thus significantly enhance the absorption of ZnO nanofibers in the range of visible-light. Overall, this paper provides a new approach to fabricate visible-light nanocatalysts using both doping and annealing under anoxic ambient. PMID:27600260

  2. Synergistic effect of N-decorated and Mn2+ doped ZnO nanofibers with enhanced photocatalytic activity

    PubMed Central

    Wang, Yuting; Cheng, Jing; Yu, Suye; Alcocer, Enric Juan; Shahid, Muhammad; Wang, Ziyuan; Pan, Wei

    2016-01-01

    Here we report a high efficiency photocatalyst, i.e., Mn2+-doped and N-decorated ZnO nanofibers (NFs) enriched with vacancy defects, fabricated via electrospinning and a subsequent controlled annealing process. This nanocatalyst exhibits excellent visible-light photocatalytic activity and an apparent quantum efficiency up to 12.77%, which is 50 times higher than that of pure ZnO. It also demonstrates good stability and durability in repeated photocatalytic degradation experiments. A comprehensive structural analysis shows that high density of oxygen vacancies and nitrogen are introduced into the nanofibers surface. Hence, the significant enhanced visible photocatalytic properties for Mn-ZnO NFs are due to the synergetic effects of both Mn2+ doping and N decorated. Further investigations exhibit that the Mn2+-doping facilitates the formation of N-decorated and surface defects when annealing in N2 atmosphere. N doping induce the huge band gap decrease and thus significantly enhance the absorption of ZnO nanofibers in the range of visible-light. Overall, this paper provides a new approach to fabricate visible-light nanocatalysts using both doping and annealing under anoxic ambient. PMID:27600260

  3. Room temperature ferromagnetism and luminescent behavior of Ni doped ZnO nanoparticles prepared by coprecipitation method

    NASA Astrophysics Data System (ADS)

    Arora, Deepawali; Ashokan, K.; Mahajan, Aman; Kaur, Parvinder; Singh, Gurinder Pal; Kumar, Sunil; Singh, D. P.

    2016-05-01

    The samples of Zn1-xNixO (x= 0.00 and 0.05) were prepared using coprecipitation method and annealed at different temperatures. The effect of Ni ion substitution on the structural and optical properties has been studied using X-ray Diffraction, UV-Visible, Photoluminescence and Magnetic measurements. XRD measurements demonstrate that all the prepared samples are wurtzite polycrystalline single phase in nature, ruling out the presence of any secondary phase formation. Ultraviolet visible measurements showed a decrease in band gap with the increase in annealing temperature and doping concentration. The PL data shows the red shift in all the samples and luminescence quenching with Ni doping. Compared to undoped ZnO, Ni doped ZnO showed room temperature ferromagnetism

  4. Improved conversion efficiency of Ag2S quantum dot-sensitized solar cells based on TiO2 nanotubes with a ZnO recombination barrier layer

    PubMed Central

    2011-01-01

    We improve the conversion efficiency of Ag2S quantum dot (QD)-sensitized TiO2 nanotube-array electrodes by chemically depositing ZnO recombination barrier layer on plain TiO2 nanotube-array electrodes. The optical properties, structural properties, compositional analysis, and photoelectrochemistry properties of prepared electrodes have been investigated. It is found that for the prepared electrodes, with increasing the cycles of Ag2S deposition, the photocurrent density and the conversion efficiency increase. In addition, as compared to the Ag2S QD-sensitized TiO2 nanotube-array electrode without the ZnO layers, the conversion efficiency of the electrode with the ZnO layers increases significantly due to the formation of efficient recombination layer between the TiO2 nanotube array and electrolyte. PMID:21777458

  5. Growth and conduction mechanism of As-doped p-type ZnO thin films deposited by MOCVD

    SciTech Connect

    Ma, Y.; Gao, Q.; Wu, G.G.; Li, W.C.; Gao, F.B.; Yin, J.Z.; Zhang, B.L.; Du, G.T.

    2013-03-15

    Highlight: ► P-type As-doped ZnO thin films was fabricated by MOCVD after post-growth annealing. ► The formation mechanism of p-ZnO with high hole concentration above 10{sup 19} cm{sup −3} was elucidated. ► Besides As{sub Zn}–2V{sub Zn} complex, C impurities also played an important role in realizing p-ZnO. ► The formations of As{sub O} and O-C-O complex were partially contributed to the p-type ZnO: As films. - Abstract: As-doped p-type ZnO thin films were fabricated by metal organic chemical vapor deposition (MOCVD) after in situ annealing in a vacuum. The p-type conduction mechanism was suggested by the analysis of X-ray photoelectron spectroscopy and ultraviolet photoemission spectroscopy. It was found that most of the As dopants in p-ZnO thin films formed As{sub Zn}–2V{sub Zn} shallow acceptor complex, simultaneously, carbon impurities also played an important role in realizing p-type conductivity in ZnO. Substitutional carbon on oxygen site created passivated defect bands by combining with Ga atoms due to the donor-acceptor pair Coulomb binding, which shifted the valence-band maximum upwards for ZnO and thus increased the hole concentration.

  6. Microstress, strain, band gap tuning and photocatalytic properties of thermally annealed and Cu-doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Prasad, Neena; V. M. M, Saipavitra; Swaminathan, Hariharan; Thangaraj, Pandiyarajan; Ramalinga Viswanathan, Mangalaraja; Balasubramanian, Karthikeyan

    2016-06-01

    ZnO nanoparticles and Cu-doped ZnO nanoparticles were prepared by co-precipitation method. Also, a part of the pure ZnO nanoparticles were annealed at 750 °C for 3, 6, and 9 h. X-ray diffraction studies were carried out and the lattice parameters, unit cell volume, interplanar spacing, and Young's modulus were calculated for all the samples, and also the crystallite size was found using the Scherrer method. X-ray peak broadening analysis was used to estimate the crystallite sizes and the strain using the Williamson-Hall (W-H) method and the size-strain plot (SSP) method. Stress and the energy density were calculated using the W-H method assuming different models such as uniform deformation model, uniform strain deformation model, uniform deformation energy density model, and the SSP method. Optical absorption properties of the samples were understood from their UV-visible spectra. Photocatalytic activities of ZnO and 5 % Cu-doped ZnO were observed by the degradation of methylene blue dye in aqueous medium under the irradiation of 20-W compact fluorescent lamp for an hour.

  7. Morphology and electrochemical behavior of Ag-Cu nanoparticle-doped amalgams.

    PubMed

    Chung, Kwok-Hung; Hsiao, Li-Yin; Lin, Yu-Sheng; Duh, Jenq-Gong

    2008-05-01

    The aim of this study was to introduce Ag-Cu phase nanopowder as an additive to improve the corrosion behavior of dental amalgams. A novel Ag-Cu nanopowder was synthesized by the precipitation method. An amalgam alloy powder (World-Cap) was added and mixed with 5 wt.% and 10 wt.% of Ag-Cu nanopowders, respectively, to form experimental amalgam alloy powders. The original alloy powder was used as a control. Alloy powders were examined using X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy and electron probe microanalysis. Amalgam disk specimens of metallurgically prepared were tested in 0.9% NaCl solution using electrochemical methods. The changes in the corrosion potential and anodic polarization characteristics were determined. Corrosion potential data were analyzed statistically (n=3, analysis of variance, Tukey's test, p<0.05). The diameters of lamellar structure Ag-Cu nanoparticles were measured to be approximately 30 nm. The composition of the Ag-Cu nanoparticles determined by TEM-energy-dispersive spectroscopy was 56.28 at.% Ag-43.72 at.% Cu. A light-shaded phase was found mixing with dark Cu-Sn reaction particles in the reaction zones of Ag-Cu nanoparticle-doped amalgams. The Ag-Cu nanoparticle-doped amalgams exhibited zero current potentials more positive than the control (p<0.05) and no current peak was observed at -325mV that related to Ag-Hg phase and Cu6Sn5 phase in anodic polarization curves. The results indicated that the corrosion resistance of high-copper single-composition amalgam could be improved by Ag-Cu nanoparticle-doping. PMID:18321799

  8. The Origin of Ferromagnetism in Ni-DOPED ZnO and SnO2

    NASA Astrophysics Data System (ADS)

    Felner, I.; Herber, R.; Acharya, Somobrata; Awana, V. P. S.

    We present a detailed study of the ferromagnetism in nano-Ni-doped SnO2 and ZnO. It is shown that the ferromagnetic behavior is not an intrinsic property of the systems but rather associated with the presence of nNi particles in both matrices. The ferromagnetic transition of all Ni-doped samples is at 631(2) K, the same as the TC value for bulk Ni and nano-Ni powder. The saturation moments of the nano-Ni-doped samples scale with the Ni concentration and are much lower than that of pure Ni. This is due to the large surface area of nano-Ni particles which are partially oxidized due to nano-NiO. 119Sn Mössbauer spectroscopy studies on Sn0.96Ni0.04O2 do not show any transferred hyperfine field on the Sn nuclei, confirming that the magnetic properties stem from a different phase.

  9. Local investigation of hyperfine interactions in pure and Co-doped ZnO

    NASA Astrophysics Data System (ADS)

    Mercurio, M. E.; Carbonari, A. W.; Cordeiro, M. R.; Saxena, R. N.; D'Agostino, L. Z.

    2010-05-01

    In the present work bulk samples of pure as well as Co-doped ZnO with different concentrations were prepared by sol-gel method from highly pure metallic Zn (99.9999%) and Co (99.9999%). The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray microanalysis (EDS) and perturbed gamma-gamma angular correlation (PAC) spectroscopy. Carrier-free 111In nuclei were introduced during preparation of the samples and used as probe nuclei at Zn sites for PAC measurements. PAC results show that both pure and Zn1-xCoxO ( x≤0.15) samples have the same electric quadrupole frequency when Co-doped samples are annealed in air, argon or nitrogen atmosphere at 1173 K. SEM and EDS results showed that Co-doped samples are homogeneous without any secondary Co phases. These observations indicate that Co ions are substituted for Zn ions and have a similar electronic structure of Zn ions. A weak local magnetism was observed at temperatures below about 300 K for Co concentration of 10% when sample was annealed in Nitrogen.

  10. Selective Divalent Cobalt Ions Detection Using Ag2O3-ZnO Nanocones by ICP-OES Method for Environmental Remediation

    PubMed Central

    Rahman, Mohammed M.; Khan, Sher Bahadar; Marwani, Hadi M.; Asiri, Abdullah M.

    2014-01-01

    Here, we have synthesized Ag2O3-ZnO nanocones (NCs) by a wet-chemical route using reducing agents at low temperature. The structural, optical and morphological properties of Ag2O3-ZnO NCs were investigated by several conventional techniques such as powder XRD, XPS, FESEM, XEDS, FTIR and UV/vis. spectroscopy. The analytical parameters of prepared NCs were also calculated for a selective detection of divalent cobalt [Co(II)] prior to its determination by inductively coupled plasma-optical emission spectrometry (ICP-OES). The selectivity of NCs toward various metal ions, including Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Ni(II), and Zn(II) was studied. Results of the selectivity study demonstrated that Ag2O3-ZnO NC phase was the most selective towards Co(II) ion. The uptake capacity for Co(II) ion was experimentally calculated to be ∼76.69 mgg−1. Moreover, adsorption isotherm data provided that the adsorption process was mainly monolayer on homogeneous adsorbent surfaces of Ag2O3-ZnO NCs. Kinetic study revealed that the adsorption of Co(II) on Ag2O3-ZnO NCs phase followed the pseudo-second-order kinetic model. In addition, thermodynamic results provided that the adsorption mechanism of Co(II) ions on Ag2O3-ZnO NCs was a spontaneous process and thermodynamically favorable. Finally, the proposed method was validated by applying it to real environmental water samples with reasonable results. PMID:25464507

  11. Magnetic and optical properties of Mn-doped ZnO vertically aligned nanorods synthesized by hydrothermal technique

    NASA Astrophysics Data System (ADS)

    Panda, J.; Sasmal, I.; Nath, T. K.

    2016-03-01

    In this paper we have reported the synthesis of high quality vertically aligned undoped and Mn-doped ZnO single crystalline nanorods arrays on Si (100) substrates using two steps process, namely, initial slow seed layer formation followed by solution growth employing wet chemical hydrothermal method. The shapes of the as grown single crystalline nanorods are hexagonal. The diameter and length of the as grown undoped ZnO nanorods varies in the range of 80-150 nm and 1.0 - 1.4 μm, respectively. Along with the lattice parameters of the hexagonal crystal structure, the diameter and length of Mn doped ZnO nanorods are found to increase slightly as compared to the undoped ZnO nanorods. The X-ray photoelectron spectroscopy confirms the presence of Mn atoms in Mn2+ state in the single crystalline ZnO nanorods. The recorded photoluminescence spectrum contains two emissions peaks having UV exciton emissions along with a green-yellow emission. The green-yellow emissions provide the evidence of singly ionized oxygen vacancies. The magnetic field dependent magnetization measurements [M (H)] and zero field cooled (ZFC) and field cooled (FC) magnetization [M(T)] measurements have been carried out at different isothermal conditions in the temperature range of 5-300 K. The Mn doped ZnO nanorods clearly show room temperature ferromagnetic ordering near room temperature down to 5 K. The observed magnetization may be attributed to the long range ferromagnetic interaction between bound magnetic polarons led by singly charged oxygen vacancies.

  12. High-performance flexible Ag nanowire electrode with low-temperature atomic-layer-deposition fabrication of conductive-bridging ZnO film.

    PubMed

    Duan, Ya-Hui; Duan, Yu; Chen, Ping; Tao, Ye; Yang, Yong-Qiang; Zhao, Yi

    2015-01-01

    As material for flexible transparent electrodes for organic photoelectric devices, the silver nanowires (AgNWs) have been widely studied. In this work, we propose a hybrid flexible anode with photopolymer substrate, which is composed of spin-coating-processed AgNW meshes and of zinc oxide (ZnO) prepared by low-temperature (60°C) atomic layer deposition. ZnO effectively fills in the voids of the AgNW mesh electrode, which is thus able to contact to the device all over the active area, to allow for efficient charge extraction/injection. Furthermore, ZnO grown by low temperature mainly relies on hole conduction to make the anode play a better role. Hole-only devices are fabricated to certify the functionality of the low-temperature ZnO film. Finally, we confirm that the ZnO film grown at a low temperature bring a significant contribution to the performance of the modified AgNW anode. PMID:25852386

  13. High-performance flexible Ag nanowire electrode with low-temperature atomic-layer-deposition fabrication of conductive-bridging ZnO film

    NASA Astrophysics Data System (ADS)

    Duan, Ya-Hui; Duan, Yu; Chen, Ping; Tao, Ye; Yang, Yong-Qiang; Zhao, Yi

    2015-02-01

    As material for flexible transparent electrodes for organic photoelectric devices, the silver nanowires (AgNWs) have been widely studied. In this work, we propose a hybrid flexible anode with photopolymer substrate, which is composed of spin-coating-processed AgNW meshes and of zinc oxide (ZnO) prepared by low-temperature (60°C) atomic layer deposition. ZnO effectively fills in the voids of the AgNW mesh electrode, which is thus able to contact to the device all over the active area, to allow for efficient charge extraction/injection. Furthermore, ZnO grown by low temperature mainly relies on hole conduction to make the anode play a better role. Hole-only devices are fabricated to certify the functionality of the low-temperature ZnO film. Finally, we confirm that the ZnO film grown at a low temperature bring a significant contribution to the performance of the modified AgNW anode.

  14. TiO2 nanotube composite layers as delivery system for ZnO and Ag nanoparticles - an unexpected overdose effect decreasing their antibacterial efficacy.

    PubMed

    Roguska, A; Belcarz, A; Pisarek, M; Ginalska, G; Lewandowska, M

    2015-06-01

    Enhancement of biocompatibility and antibacterial properties of implant materials is potentially beneficial for their practical value. Therefore, the use of metallic and metallic oxide nanoparticles as antimicrobial coatings components which induce minimized antibacterial resistance receives currently particular attention. In this work, TiO2 nanotubes layers loaded with ZnO and Ag nanoparticles were designed for biomedical coatings and delivery systems and evaluated for antimicrobial activity. TiO2 nanotubes themselves exhibited considerable and diameter-dependent antibacterial activity against planktonic Staphylococcus epidermidis cells but favored bacterial adhesion. Loading of nanotubes with moderate amount of ZnO nanoparticles significantly diminished S. epidermidis cell adhesion and viability just after 1.5h contact with modified surfaces. However, an increase of loaded ZnO amount unexpectedly altered the structure of nanoparticle-nanolayer, caused partial closure of nanotube interior and significantly reduced ZnO solubility and antibacterial efficacy. Co-deposition of Ag nanoparticles enhanced the antibacterial properties of synthesized coatings. However, the increase of ZnO quantity on Ag nanoparticles co-deposited surfaces favored the adhesion of bacterial cells. Thus, ZnO/Ag/TiO2 nanotube composite layers may be promising delivery systems for combating post-operative infections in hard tissue replacement procedures. However, the amount of loaded antibacterial agents must be carefully balanced to avoid the overdose and reduced efficacy. PMID:25842121

  15. High-mobility Sb-doped p-type ZnO by molecular-beam epitaxy

    SciTech Connect

    Xiu, F.X.; Yang, Z.; Mandalapu, L.J.; Zhao, D.T.; Liu, J.L.; Beyermann, W.P.

    2005-10-10

    Reproducible Sb-doped p-type ZnO films were grown on n-Si (100) by electron-cyclotron-resonance-assisted molecular-beam epitaxy. The existence of Sb in ZnO:Sb films was confirmed by low-temperature photoluminescence measurements. An acceptor-bound exciton (A deg. X) emission was observed at 3.358 eV at 8 K. The acceptor energy level of the Sb dopant is estimated to be 0.2 eV above the valence band. Temperature-dependent Hall measurements were performed on Sb-doped ZnO films. At room temperature, one Sb-doped ZnO sample exhibited a low resistivity of 0.2 {omega} cm, high hole concentration of 1.7x10{sup 18} cm{sup -3} and high mobility of 20.0 cm{sup 2}/V s. This study suggests that Sb is an excellent dopant for reliable and reproducible p-type ZnO fabrication.

  16. Structural and Luminescence Features of Lithium-Doped p-Type Film-Like ZnO Nanorods.

    PubMed

    Ko, Wonbae; Lee, Sanghyo; Hong, Jin Pyo

    2015-11-01

    We report the structural and optical characteristics of p-type lithium (Li)-doped ZnO film-like nano-structures prepared by utilizing a simple hydro-thermal method in an aqueous solution at a low temperature (< 90 degrees C). The diameters and densities of the Li-doped ZnO nanostructures were controlled by adjusting the molar concentration. A relatively high molar concentration resulted in hexagonal and flat surface-shaped ZnO nanostructures. In addition, a post-annealing process in the range of 400 to 600 degrees C effectively leads to the incorporation of lithium dopant as an acceptor, resulting in optical p-type behavior. The p-type features of synthesized Li-doped ZnO nanostructures were analyzed using a photoluminescence measurement using a He-Cd laser as an excitation source at 10 K. Closer investigation of the fine donor- and acceptor-bound exciton emission peaks from the low temperature PL spectra revealed the occurrence of several peaks related to free excitons (FX), excitons bound to acceptor (A(0)X), free electron to the acceptor transition peak (FA), and its LO phonon replicas. PMID:26726574

  17. Improve efficiency of perovskite solar cells by using Magnesium doped ZnO and TiO2 compact layers

    NASA Astrophysics Data System (ADS)

    Baktash, Ardeshir; Amiri, Omid; Sasani, Alireza

    2016-05-01

    Here the effect of Magnesium doped TiO2 and ZnO as hole blocking layers (HBLs) are investigated by using solar cell capacitance simulator (SCAPS). The Impact of Magnesium concentration into the TiO2 and ZnO and effect of operating temperature on the performance of the perovskite solar cell are investigated. Best cell performance for both TiO2 and ZnO HBLs (with cell efficiencies of 19.86% and 19.57% respectively) are concluded for the doping level of 10% of Mg into the structure of HBLs. Increase in operating temperature from 300 K to 400 K are decreased the performance of the perovskite solar cell with both pure and Mg-doped HBLs. However, the cells with pure ZnO layer and with Zn0.9 Mg0.1O layer show the highest (with a decline of 8.88% in efficiency) and the lowest stability (with a decline of 50.49% in efficiency) at higher temperatures respectively. Moreover, the cell with Ti0.9 Mg0.1O2 layer shows better stability (with 21.85% reduction in efficiency) than the cell with pure TiO2 compact layer (with 23.28% reduction in efficiency) at higher operating temperatures.

  18. Structure and Properties of Al and Ga- Doped ZnO

    NASA Astrophysics Data System (ADS)

    Temizer, Namik Kemal

    Recently there is tremendous interest in Transparent conducting oxide (TCO) research due to the unlimited and exciting application areas. Current research is mostly focused on finding alternative low cost and sustainable materials in order to replace indium tin oxide (ITO), which caused serious concern due to the increasing cost of indium and chemical stability issues of ITO. The primary aim of this research is to develop alternative TCO materials with superior properties in order to increase the efficiency in optoelectronic applications, as well as to study the properties of these materials to fully characterize them. We have grown Al and Ga-doped ZnO films with an optimized composition under different deposition conditions in order to understand the effect of processing parameters on the film properties. We report a detailed investigation on the structure-property correlations in Ga and Al codoped ZnO films on c-sapphire substrates where the thin film microstructure varies from nanocrystalline to single crystal. We have achieved highly epitaxial films with very high optical transmittance (close to 90%) and low resistivity (˜110muO-cm) values. The films grown in an ambient oxygen partial pressure (PO2 ) of 50 mTorr and at growth temperatures from room temperature to 600°C showed semiconducting behavior, whereas samples grown at a Po2 of 1 mTorr showed metallic nature. The most striking feature is the occurrence of resistivity minima at relatively high temperatures around 110 K in films deposited at high temperatures. The structure-property correlations reveal that point defects play an important role in modifying the structural, optical, electrical and magnetic properties and such changes in physical properties are controlled predominantly by the defect content. To gain a better understanding of the conduction processes in doped ZnO thin films, we have studied the temperature variation of resistivity of some selected samples that showed some interesting behavior

  19. Study on the doping effect of Sn-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Ajili, Mejda; Castagné, Michel; Turki, Najoua Kamoun

    2013-01-01

    Tin doped zinc oxide (ZnO:Sn) thin films were deposited onto Pyrex glass substrates by chemical spray pyrolysis technique starting from zinc acetate (CH3CO2)2Znṡ2H2O and tin chloride SnCl2. The effect of Sn doping on structural, optical and electrical properties was investigated. The atomic percentages of dopant in ZnO-based solution were y = [Sn4+]/[Zn2+] = 0%, 0.2%, 0.6% and 1%. It was found that all the thin films have a preferential c-axis orientation. With increase of Sn doping, the peak position of the (0 0 2) plane was shifted to the high 2θ values. ZnO:Sn demonstrated obviously improved surface roughness, reduced average crystallite size, enhanced Hall mobility and reduced resistivity. Among all of the tin doped zinc oxide in this study, films doped with 0.6 at.% Sn concentration exhibited the best properties, namely a Hall mobility of 9.22 cm2 V-1 s-1, an RMS roughness of 37.15 nm and a resistivity of 8.32 × 10-2 Ω cm.

  20. Physical properties of FePt nanocomposite doped with Ag atoms: First-principles study

    NASA Astrophysics Data System (ADS)

    Jia, Yong-Fei; Shu, Xiao-Lin; Xie, Yong; Chen, Zi-Yu

    2014-07-01

    L10 FePt nanocomposite with high magnetocrystalline anisotropy energy has been extensively investigated in the fields of ultra-high density magnetic recording media. However, the order—disorder transition temperature of the nanocomposite is higher than 600 °C, which is a disadvantage for the use of the material due to the sustained growth of FePt grain under the temperature. To address the problem, addition of Ag atoms has been proposed, but the magnetic properties of the doped system are still unclear so far. Here in this paper, we use first-principles method to study the lattice parameters, formation energy, electronic structure, atomic magnetic moment and order—disorder transition temperature of L10 FePt with Ag atom doping. The results show that the formation energy of a Ag atom substituting for a Pt site is 1.309 eV, which is lower than that of substituting for an Fe site 1.346 eV. The formation energy of substituting for the two nearest Pt sites is 2.560 eV lower than that of substituting for the further sites 2.621 eV, which indicates that Ag dopants tend to segregate L10 FePt. The special quasirandom structures (SQSs) for the pure FePt and the FePt doped with two Ag atoms at the stable Pt sites show that the order—disorder transition temperatures are 1377 °C and 600 °C, respectively, suggesting that the transition temperature can be reduced with Ag atom, and therefore the FePt grain growth is suppressed. The saturation magnetizations of the pure FePt and the two Ag atoms doped FePt are 1083 emu/cc and 1062 emu/cc, respectively, indicating that the magnetic property of the doped system is almost unchanged.

  1. Origin of p-type conductivity of Sb-doped ZnO nanorods and the local structure around Sb ions

    SciTech Connect

    Liang, J. K.; Su, H. L. E-mail: ycwu@hfut.edu.cn Wu, Y. C. E-mail: ycwu@hfut.edu.cn; Chuang, P. Y.; Kuo, C. L.; Huang, S. Y.; Chan, T. S.; Huang, J. C. A. E-mail: ycwu@hfut.edu.cn

    2015-05-25

    To probe the origin of p-type conductivity in Sb-doped ZnO, a careful and detailed synchrotron radiation study was performed. The extended X-ray absorption fine structure and X-ray photoelectron spectroscopy investigations provided the evidence for the formation of the complex defects comprising substitution Sb ions at Zn sites (Sb{sub Zn}) and Zn vacancies within the Sb-doped ZnO lattice. Such complex defects result in the increases of Sb-O coordination number and the Sb valence and thereby lead to the p-type conductivity of Sb-doped ZnO. The back-gate field-effect-transistors based on single nanorod of Sb-doped ZnO were constructed, and the stable p-type conduction behavior was confirmed.

  2. Electrical and Structural Analyses of Solution-Processed Li-Doped ZnO Thin Film Transistors Exposed to Ambient Conditions

    NASA Astrophysics Data System (ADS)

    Kang, Tae Sung; Koo, Ja Hyun; Kim, Tae Yoon; Hong, Jin Pyo

    2013-01-01

    We report the electrical and structural features of various Li-doped ZnO thin-film transistors (TFTs) grown via a chemical solution process at low temperature. The time-dependent transfer curves for the 10 at. % Li-doped ZnO TFTs, including second-order lowered off-current magnitude, exhibited only a negative shift of -1.07 V for 25 days, compared with a -21.83 V negative shift of undoped ZnO TFTs. Secondary ion mass spectroscopy and X-ray photoelectron spectroscopy observations clearly demonstrated the structure of Li dopants and the reduction of oxygen vacancies after appropriate doping processes. Finally, the nature of improved stability in the Li-doped ZnO TFTs is described.

  3. Induced structural defects in Ti-doped ZnO and its two-photon-excitation

    NASA Astrophysics Data System (ADS)

    Martínez Julca, Milton A.; Rivera, Ivonnemary; Santillan Mercado, Jaime; Sierra, Heidy; Perales-Pérez, Oscar

    2016-03-01

    ZnO is a well-known luminescent material that reacts with light to generate free radicals enabling its use in cancer treatment by Photodynamic Therapy (PDT). Unfortunately, up to know, the photo-excitation of ZnO-based materials' requires excitation with ultraviolet light, which limits their biomedical applications. In this regard, this work investigates the effect of Ti species incorporation into the lattice of ZnO nanoparticles (NPs) with the aim of improving the corresponding optical properties and enabling the two-photoexcitation with 690nm-light (near infrared light). A modified polyol-based route was used to synthesize pure and Ti-doped (9% at.) ZnO NPs. X-ray diffraction confirmed the formation of ZnO-wurtzite whereas Scanning Electron Microscopy confirmed the formation of monodispersed 100-nm NPs. Raman Spectroscopy measurements evidenced the presence of zinc interstitials (Zni) and oxygen vacancies (VO) in the host oxide strcuture. Asynthesized NPs were excited using the technique of two-photon fluorescence microscopy (TPFM). The photoluminescence (PL) spectra generated from the analysis of TPFM images revealed a high emission peak presence in the green region (555 nm) that was assigned to VO. Also, a weak but noticeable band at 420 nm was detected, which is attributed to electron transition from the shallow donor level of Zni to the valence band. These PL transitions will favor triplet states formation necessary to yield cytotoxic reactive oxygen species. Furthermore, the presence of the PL peaks confirmed the Ti-ZnO NPs capacity to be excited by 690-nm light, thus, opening new possibilities for this NPs to be used in lightinduced bio-medical applications.

  4. Soft x-ray absorption spectroscopy on Co doped ZnO: structural distortions and electronic structure

    NASA Astrophysics Data System (ADS)

    Kowalik, I. A.; Guziewicz, E.; Godlewski, M.; Arvanitis, D.

    2016-05-01

    We present soft x-ray absorption spectra from a series of Co doped ZnO films. We discuss systematic variations of the Co L-edge white line intensity and multiplet features for this series of samples. We document sizeable differences in the electronic state of the Co ionic cores, as well as in the local environment of the host lattice atoms, characterised by means of x-ray absorption spectra at the O K-edge and Zn L-edges. Model calculations allow to correlate the observed effects to small structural distortions of the ZnO lattice.

  5. Investigation of As-doped ZnO films synthesized via thermal annealing of ZnSe/GaAs heterostructures

    NASA Astrophysics Data System (ADS)

    Maksimov, O.; Liu, B. Z.

    2008-06-01

    We synthesized ZnO films via oxidative annealing of ZnSe/GaAs heterostructures and investigated their structural and optical properties. Films were polycrystalline, c-axis oriented and exhibited superior optical properties. In addition, we detected nanometer-size As clusters into the ZnO film and a Ga xO y layer at the ZnO/GaAs interface. Formation of an interfacial layer can prevent use of this technique for p-type doping and complicates identification of the origin of p-type response in the annealed ZnO/GaAs heterostructures.

  6. Synthesis, structural characterisation and antibacterial activity of Ag+-doped fluorapatite nanomaterials prepared by neutralization method

    NASA Astrophysics Data System (ADS)

    Stanić, Vojislav; Radosavljević-Mihajlović, Ana S.; Živković-Radovanović, Vukosava; Nastasijević, Branislav; Marinović-Cincović, Milena; Marković, Jelena P.; Budimir, Milica D.

    2015-05-01

    Silver doped fluorapatite nanopowders were synthesised by neutralization method, which consists of dissolving Ag2O in solution of HF and H3PO4 and addition to suspension of Ca(OH)2. The powder XRD, SEM and FTIR studies indicated the formation of a fluorapatite nanomaterials with average length of the particles is about 80 nm and a width of about 15 nm. The FTIR studies show that carbonate content in samples is very small and carbonte ions substitute both phosphate and hydroxyl groups in the crystal structure of samples, forming AB-type fluorapatite. Antibacterial studies have demonstrated that all Ag+-doped fluorapatite samples exhibit bactericidal effect against pathogens: Staphylococcus aureus, Micrococcus luteus and Kllebsiela pneumoniae. Antibacterial activity increased with the increase of Ag+ in the samples. The atomic force microscopy studies revealed extensive damage to the bacterial cell envelops in the presence of Ag+-doped fluorapatite particles which may lead to their death. The synthesized Ag+-doped fluorapatite nanomaterials are promising as antibacterial biomaterials in orthopedics and dentistry.

  7. Defects responsible for abnormal n-type conductivity in Ag-excess doped PbTe thermoelectrics

    SciTech Connect

    Ryu, Byungki Lee, Jae Ki; Lee, Ji Eun; Joo, Sung-Jae; Kim, Bong-Seo; Min, Bok-Ki; Lee, Hee-Woong; Park, Su-Dong; Oh, Min-Wook

    2015-07-07

    Density functional calculations have been performed to investigate the role of Ag defects in PbTe thermoelectric materials. Ag-defects can be either donor, acceptor, or isovalent neutral defect. When Ag is heavily doped in PbTe, the neutral (Ag-Ag) dimer defect at Pb-site is formed and the environment changes to the Pb-rich/Te-poor condition. Under Pb-rich condition, the ionized Ag-interstitial defect (Ag{sub I}{sup +}) becomes the major donor. The formation energy of Ag{sub I}{sup +} is smaller than other native and Ag-related defects. Also it is found that Ag{sub I}{sup +} is an effective dopant. There is no additional impurity state near the band gap and the conduction band minimum. The charge state of Ag{sub I}{sup +} defect is maintained even when the Fermi level is located above the conduction band minimum. The diffusion constant of Ag{sub I}{sup +} is calculated based on the temperature dependent Fermi level, formation energy, and migration energy. When T > 550 K, the diffusion length of Ag within a few minutes is comparable to the grain size of the polycrystalline PbTe, implying that Ag is dissolved into PbTe and this donor defect is distributed over the whole lattice in Ag-excess doped polycrystalline PbTe. The predicted solubility of Ag{sub I}{sup +} well explains the increased electron carrier concentration and electrical conductivity reported in Ag-excess doped polycrystalline PbTe at T = 450–750 K [Pei et al., Adv. Energy Mater. 1, 291 (2011)]. In addition, we suggest that this abnormal doping behavior is also found for Au-doped PbTe.

  8. AC conductivity and structural properties of Mg-doped ZnO ceramic

    NASA Astrophysics Data System (ADS)

    Othman, Zayani Jaafar; Hafef, Olfa; Matoussi, Adel; Rossi, Francesca; Salviati, Giancarlo

    2015-11-01

    Undoped ZnO and Zn1- x Mg x O ceramic pellets were synthesized by the standard sintering method at the temperature of 1200 °C. The influence of Mg doping on the morphological, structural and electrical properties was studied. The scanning electron microscopy images revealed rough surface textured by grain boundaries and compacted grains having different shapes and sizes. Indeed, the X-ray diffraction reveals the alloying of hexagonal ZnMgO phase and the segregation of cubic MgO phase. The crystallite size, strain and stress were studied using Williamson-Hall (W-H) method. The results of mean particle size of Zn1- x Mg x O composites showed an inter-correlation with W-H analysis and Sherrer method. The electrical conductivity of the films was measured from 173 to 373 K in the frequency range of 0.1 Hz-1 MHz to identify the dominant conductivity mechanism. The DC conductivity is thermally activated by electron traps having activation energy of about 0.09 to 0.8 eV. The mechanisms of AC conductivity are controlled by the correlated barrier hopping model for the ZnO sample and the small polaron tunneling (SPT) model for Zn0.64Mg0.36O and Zn0.60Mg0.40O composites.

  9. Role of quantum confinement and hyperfine splitting in lithium-doped ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Kwak, Hyunwook; Tiago, Murilo L.; Chan, Tzu-Liang; Chelikowsky, James R.

    2008-11-01

    The role of quantum confinement on the electronic properties of Li interstitial impurities in ZnO nanocrystals was examined using a real-space pseudopotential-density-functional method. The Li impurity was found to be partially ionized resulting in a significant charge transfer around the impurity site. To calculate the hyperfine interaction for this system using pseudopotentials, we modified Van de Walle and Blöchl’s method to include explicitly the off-site contribution of the Li impurity wave function. Our modifications dramatically enhanced the agreement between the calculated and the measured isotropic hyperfine splitting constants. Our analysis with an effective-mass model demonstrates that the partial ionization of the impurity atom plays an important role both in the binding energy and in the shape of its wave function. Comparison between calculations using the local-density approximation (LDA) with LDA+U indicates that the local Coulomb correlation does not play a significant role in altering the impurity electronic states of interstitial Li-doped ZnO nanocrystals.

  10. Room Temperature Ferromagnetism in Transition Metal Doped CVD-Grown ZnO Films and Nanostructures

    NASA Astrophysics Data System (ADS)

    Hill, D. H.; Gateau, R.; Bartynski, R. A.; Wu, P.; Lu, Y.; Wielunski, L.; Poltavets, V.; Greenblatt, M.; Arena, D. A.; Dvorak, J.; Calvin, S.

    2006-03-01

    We have characterized the chemical, compositional, and magnetic properties of Mn- and Fe-ion implanted epitaxial ZnO films and single crystal nanostructures grown by MOCVD as candidate room temperature diluted magnetic semiconductors. X-ray absorption spectroscopy (SXAS) shows that Mn-implanted films contain Mn^2+ ions which convert to a mixture of Mn^3+ and Mn^4+ upon annealing. Fe-implanted films contain a mixture of Fe^2+ and Fe^3+ which converts to a higher concentration of Fe^3+ upon annealing. XAS and preliminary analysis of EXAFS data indicate that the TM ions are substitutional for Zn. SQUID magnetometry shows that as-implanted films are ferromagnetic at 5K and the annealed films are ferromagnetic at room temperature. X-ray diffraction shows that the annealed films remain epitaxial with excellent long range order. Rutherford backscattering spectrometry indicates a substantial recovery of local order upon annealing as well. The properties of in-situ Fe-doped MOCVD-grown ZnO epitaxial films and nanostructures will also be discussed.

  11. Tunable antireflection from conformal Al-doped ZnO films on nanofaceted Si templates

    PubMed Central

    2014-01-01

    Photon harvesting by reducing reflection loss is the basis of photovoltaic devices. Here, we show the efficacy of Al-doped ZnO (AZO) overlayer on ion beam-synthesized nanofaceted silicon for suppressing reflection loss. In particular, we demonstrate thickness-dependent tunable antireflection (AR) from conformally grown AZO layer, showing a systematic shift in the reflection minima from ultraviolet to visible to near-infrared ranges with increasing thickness. Tunable AR property is understood in light of depth-dependent refractive index of nanofaceted silicon and AZO overlayer. This improved AR property significantly increases the fill factor of such textured heterostructures, which reaches its maximum for 60-nm AZO compared to the ones based on planar silicon. This thickness matches with the one that shows the maximum reduction in surface reflectance. PACS 81.07.-b; 42.79.Wc; 81.16.Rf; 81.15.Cd PMID:24808799

  12. Weak localization and electron-electron interactions in indium-doped ZnO nanowires.

    PubMed

    Thompson, Richard S; Li, Dongdong; Witte, Christopher M; Lu, Jia G

    2009-12-01

    Single crystal ZnO nanowires doped with indium are synthesized via the laser-assisted chemical vapor deposition method. The conductivity of the nanowires is measured at low temperatures in magnetic fields with directions both perpendicular and parallel to the wire axes. A quantitative fit of our data is obtained, consistent with the theory of a quasi-one-dimensional metallic system with quantum corrections due to weak localization and electron-electron interactions. The anisotropy of the magneto-conductivity agrees with theory. The two quantum corrections are of approximately equal magnitude with respective temperature dependences of T(-1/3)and T(-1/2). The alternative model of quasi-two-dimensional surface conductivity is excluded by the absence of oscillations in the magneto-conductivity in parallel magnetic fields. PMID:19831413

  13. Bi-stable resistive switching characteristics in Ti-doped ZnO thin films

    PubMed Central

    2013-01-01

    Ti-doped ZnO (ZnO/Ti) thin films were grown on indium tin oxide substrates by a facile electrodeposition route. The morphology, crystal structure and resistive switching properties were examined, respectively. The morphology reveals that grains are composed of small crystals. The (002) preferential growth along c-axis of ZnO/Ti could be observed from structural analysis. The XPS study shows the presence of oxygen vacancies in the prepared films. Typical bipolar and reversible resistance switching effects were observed. High ROFF/RON ratios (approximately 14) and low operation voltages within 100 switching cycles are obtained. The filament theory and the interface effect are suggested to be responsible for the resistive switching phenomenon. PMID:23557254

  14. Annealing induced reorientation of crystallites in Sn doped ZnO films

    NASA Astrophysics Data System (ADS)

    Ravichandran, K.; Vasanthi, M.; Thirumurugan, K.; Sakthivel, B.; Karthika, K.

    2014-11-01

    Tin doped ZnO thin films were prepared by employing a simplified spray pyrolysis technique using a perfume atomizer and subsequently annealed under different temperatures from 350 °C to 500 °C in steps of 50 °C. The structural, optical, electrical, photoluminescence and surface morphological properties of the as-deposited films were studied and compared with that of the annealed films. The X-ray diffraction studies showed that as-deposited film exhibits preferential orientation along the (0 0 2) plane and it changes in favour of (1 0 0) plane after annealing. The increase in crystallite size due to annealing is explained on the basis of Ostwald ripening effect. It is found that the optical transmittance and band gap increases with increase in annealing temperature. A slight decrease in resistivity caused by annealing is discussed in correlation with annealing induced defect modifications and surface morphology.

  15. Structural and Morphological Properties of Al doped ZnO Nanoparticles

    NASA Astrophysics Data System (ADS)

    Akdağ, A.; Budak, H. F.; Yılmaz, M.; Efe, A.; Büyükaydın, M.; Can, M.; Turgut, G.; Sönmez, E.

    2016-04-01

    Zinc oxide nanoparticles have a wide area of use because of their unique properties such as catalytic, electrical, and optical properties and low cost. Since the suitable additive materials can be changed the electrical and optical properties of zinc oxide, the demand of the industrial commercial area to the zinc oxide increased. In this study, Al doped ZnO nanoparticles produced by using the methods of reduction thought having materials of the Zn(NO)3, AlCl3 and NaOH. XRD, SEM and EDS used for making analyzing of structural and dimensional of particles. The analyses show that the large amount of the Al3+ ions did nut substitute with Zn2+ successfully with the reduction method. XRD and EDS results confirm this situation.

  16. Growth of ZnO thin films doped with (Mn & Co) by spin coating technique

    NASA Astrophysics Data System (ADS)

    Dhruvashi, Rawat, Kusum; Shishodia, P. K.

    2016-05-01

    ZnO thin films co-doped with Mn and Co have been deposited on glass substrates by spin coating technique. Structural, optical and magnetic properties have been investigated as a function of dopant concentration. X-ray diffraction has confirmed the growth of c-axis oriented polycrystalline thin films. No impurity phases have been detected corresponding to metal oxides within the limitation of x-ray diffraction. The optical bandgap has been evaluated from tauc's plots derived from the transmittance spectra in the wavelength range 350-900 nm. Surface morphology of the films has been observed by field emission scanning electron microscope. The field dependence of magnetization (M-H curve) measured by vibrating sample magnetometer shows the ferromagnetic behavior of the films at room temperature. The magnetization versus temperature (M-T) curve has also been measured under zero field cooled and field cooled conditions.

  17. Sputter deposition of Al-doped ZnO films with various incident angles

    SciTech Connect

    Sato, Yasushi; Yanagisawa, Kei; Oka, Nobuto; Nakamura, Shin-ichi; Shigesato, Yuzo

    2009-09-15

    Al-doped ZnO (AZO) films were sputter deposited on glass substrates heated at 200 degree sign C under incident angles of sputtered particles at 0 degree sign (incidence normal to substrate), 20 deg., 40 deg., 60 deg., and 80 deg. In the case of normal incidence, x-ray diffraction pole figures show a strong [001] preferred orientation normal to the film surface. In contrast, in the case wherein the incident angles were higher than 60 degree sign , the [001] orientation inclined by 25 deg. - 35 deg. toward the direction of sputtered particles. Transmission electron microscopy revealed that the tilt angle of the [001] orientation increased with increasing angle of the incident sputtered particles, whereas the columnar structure did not show any sign of inclination with respect to the substrate plane.

  18. Tunable antireflection from conformal Al-doped ZnO films on nanofaceted Si templates

    NASA Astrophysics Data System (ADS)

    Basu, Tanmoy; Kumar, Mohit; Sahoo, Pratap Kumar; Kanjilal, Aloke; Som, Tapobrata

    2014-04-01

    Photon harvesting by reducing reflection loss is the basis of photovoltaic devices. Here, we show the efficacy of Al-doped ZnO (AZO) overlayer on ion beam-synthesized nanofaceted silicon for suppressing reflection loss. In particular, we demonstrate thickness-dependent tunable antireflection (AR) from conformally grown AZO layer, showing a systematic shift in the reflection minima from ultraviolet to visible to near-infrared ranges with increasing thickness. Tunable AR property is understood in light of depth-dependent refractive index of nanofaceted silicon and AZO overlayer. This improved AR property significantly increases the fill factor of such textured heterostructures, which reaches its maximum for 60-nm AZO compared to the ones based on planar silicon. This thickness matches with the one that shows the maximum reduction in surface reflectance.

  19. Identification of acceptor states in Li-doped p-type ZnO thin films

    NASA Astrophysics Data System (ADS)

    Zeng, Y. J.; Ye, Z. Z.; Lu, J. G.; Xu, W. Z.; Zhu, L. P.; Zhao, B. H.; Limpijumnong, Sukit

    2006-07-01

    We investigate photoluminescence from reproducible Li-doped p-type ZnO thin films prepared by dc reactive magnetron sputtering. The LiZn acceptor state, with an energy level located at 150meV above the valence band maximum, is identified from free-to-neutral-acceptor transitions. Another deeper acceptor state located at 250meV emerges with the increased Li concentration. A broad emission centered at 2.96eV is attributed to a donor-acceptor pair recombination involving zinc vacancy. In addition, two chemical bonding states of Li, evident in x-ray photoelectron spectroscopy, are probably associated with the two acceptor states observed.

  20. Room-temperature ferromagnetism in Li-doped p -type luminescent ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Chawla, Santa; Jayanthi, K.; Kotnala, R. K.

    2009-03-01

    We have observed ferromagnetism in Li-doped ZnO nanorods with Curie temperature up to 554 K. Li forms shallow acceptor states in substitutional zinc sites giving rise to p -type conductivity. An explicit correlation emerges between increase in hole concentration with decrease in magnetization and Curie temperature in ZnO:Li. Occurrence of ferromagnetism at room temperature has been established with observed magnetic domain formation in ZnO:Li pellets in magnetic force microscopy and prominent ferromagnetic resonance signal in electron paramagnetic resonance spectrum. Magnetic ZnO:Li nanorods are luminescent, showing strong near UV emission. Substitutional Li atoms can induce local moments on neighboring oxygen atoms, which when considered in a correlated model for oxygen orbitals with random potentials introduced by dopant atom could explain the observed ferromagnetism and high Curie temperature in ZnO:Li nanorods.

  1. Effect of Co doping on the structural and dielectric properties of ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Ram, Mast; Bala, Kanchan; Sharma, Hakikat; Negi, N. S.

    2016-05-01

    This paper reports on the synthesis of Co doped Zn1-xCoxO (x= 0.0, 0.01, 0.02, 0.03 and 0.05) nanoparticles by solution combustion method using urea as a fuel. The Structural and dielectric properties of the samples were studied. Crystallite sizes were obtained from X-ray diffraction (XRD) patterns whose values decreased with increase in Co concentration. The XRD study reveals that Co2+ ions substitute the Zn2+ ion without changing the wurtzite structure of pristine ZnO up to Co concentrations of 5%. The dielectric constants, dielectric loss (tanδ) and ac conductivity (σac) were studied as the function of frequency and composition, which have been explained by Maxwell-Wagner type interfacial polarization and discussed Koops phenomenological theory.

  2. Local vibrational modes competitions in Mn-doped ZnO epitaxial films with tunable ferromagnetism

    SciTech Connect

    Cao, Qiang; Fu, Maoxiang; Liu, Guolei Zhang, Huaijin; Yan, Shishen; Chen, Yanxue; Mei, Liangmo; Jiao, Jun

    2014-06-28

    We reported spectroscopic investigations of high quality Mn-doped ZnO (ZnMnO) films grown by oxygen plasma-assisted molecular beam epitaxy. Raman scattering spectra revealed two local vibrational modes (LVMs) associated with Mn dopants at 523 and 712 cm{sup −1}. The LVMs and magnetic properties of ZnMnO films can be synchronously modulated by post annealing processing or by introducing tiny Co. The relative intensity of two LVMs clearly shows competitions arising from uncompensated acceptor and donor defects competition for ferromagnetic and nonmagnetic films. The experimental results indicated that LVM at 523 cm{sup −1} is attributed to Mn—(Zinc-vacancy) complexes, while LVM at 712 cm{sup −1} is attributed to Mn—(Oxygen-vacancy) complexes.

  3. Photocatalysis using a Wide Range of the Visible Light Spectrum: Hydrogen Evolution from Doped AgGaS2.

    PubMed

    Yamato, Kohei; Iwase, Akihide; Kudo, Akihiko

    2015-09-01

    Doping of nickel into AgGaS2 yields a new absorption band, at a wavelength longer than the intrinsic absorption band of the AgGaS2 host. The doped nickel forms an electron donor level in a forbidden band of AgGaS2 . The nickel-doped AgGaS2 with rhodium co-catalyst shows photocatalytic activity for sacrificial H2 evolution under the light of up to 760 nm due to the transition from the electron donor level consisting of Ni(2+) to the conduction band of AgGaS2 . Apparent quantum yields for the sacrificial H2 evolution at 540-620 nm are about 1 %. Moreover, the nickel-doped AgGa0.75 In0.25 S2 also responds to near-IR light, up to 900 nm. PMID:26212706

  4. Hydrogen treatment-improved uniform deposition of Ag nanoparticles on ZnO nanorod arrays and their visible-light photocatalytic and surface-enhanced Raman scattering properties

    PubMed Central

    2013-01-01

    ZnO nanorod arrays were synthesized by chemical bath deposition. After heat treatment in hydrogen or air, Ag nanoparticles were deposited on ZnO nanorod arrays by photo-reduction method. The size of Ag nanoparticles as well as the surface morphology, structure, composition, and optical property of ZnO nanorod arrays before and after the deposition of Ag nanoparticles were characterized by SEM, XRD, EDS, and UV/VIS/NIR spectrophotometer. As compared to the samples with heat treatment in air or without heat treatment, the ZnO nanorod arrays after heat treatment in hydrogen allowed Ag nanoparticles to be deposited more uniformly, densely, and numerously. Also, they exhibited higher efficiency for the visible light-driven photocatalytic degradation of Rhodamine 6G (R6G) dye. The effects of the amount of Ag nanoparticles, initial dye concentration, and temperature on the photocatalytic degradation efficiency were investigated. Furthermore, they also exhibited better surface-enhanced Raman scattering property for the detection of R6G dyes. PMID:23866904

  5. Influence of Li-N and Li-F co-doping on defect-induced intrinsic ferromagnetic and photoluminescence properties of arrays of ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Ghosh, Shyamsundar; Gopal Khan, Gobinda; Varma, Shikha; Mandal, Kalyan

    2012-08-01

    The role of N/F co-doping on the defect-driven room-temperature d0 ferromagnetism in group-I element Li doped ZnO nanowire arrays has been investigated. The ferromagnetic signature of pristine ZnO nanowires has enhanced significantly after Li doping but the Li-N co-doping has found to be more effective in the stabilization and enhancement in room-temperature ferromagnetism in ZnO nanowires. Saturation magnetization in Li-doped ZnO nanowires found to increase from 0.63 to 2.52 emu/g and the Curie temperature rises up to 648 K when 10 at. % N is co-doped with 6 at. % Li. On the other hand, Li-F co-doping leads to exhibit much poor room-temperature ferromagnetic as well as visible luminescence properties. The valance state of the different dopants is estimated by x-ray photoelectron spectroscopy while the photoluminescence spectra indicate the gradual stabilization of Zn vacancy defects or defect complexes in presence of No acceptor states, which is found to be responsible for the enhancement of intrinsic ferromagnetism in ZnO:Li matrix. Therefore, the Li-N co-doping can be an effective parameter to stabilize, enhance, and tune zinc vacancy-induced room-temperature d0 ferromagnetism in ZnO nanowires, which can be an exciting approach to prepare new class of spintronic materials.

  6. Super-high photocatalytic activity, stability and improved photocatalytic mechanism of monodisperse AgBr doped with In.

    PubMed

    Song, Limin; Zhang, Shujuan; Zhang, Shuna

    2015-12-15

    Monodisperse In(3+) doped AgBr (In-AgBr) nanoparticles were synthesized by a hydrothermal route. The pure AgBr and In-AgBr samples were investigated by X-ray powder diffraction, transmission electron microscopy, ultraviolet-visible absorption spectroscopy, X-ray photoelectron spectroscopy, measurement of total organic carbon, and electron paramagnetic resonance spectrometry. In-AgBr was more photocatalytically active than pure AgBr in photodegradation of 20 mg/L methyl orange under visible light irradiation (λ>420 nm). The 0.05 mol/L In-AgBr sample showed the highest photodegradation efficiency and high stability. The doped In(3+) expanded the light absorption range, reduced the band gap of AgBr and improved the utilization of photons. The additional In(3+) can inhibit the formation of Ag particles on the surface of AgBr, which can further stabilize AgBr. The doped In(3+) in AgBr served as a temporary site for trapping of photoinduced electrons, and thereby obviously restrained the recombination of photoinduced electron-hole pairs on the surface of AgBr. The enhanced photocatalytic ability of In-AgBr may be mainly attributed to the improved separation efficiency of photogenerated charges. PMID:26259096

  7. Structural, electrical, and optical properties of Ti-doped ZnO films fabricated by atomic layer deposition

    PubMed Central

    2013-01-01

    High-quality Ti-doped ZnO films were grown on Si, thermally grown SiO2, and quartz substrates by atomic layer deposition (ALD) at 200°C with various Ti doping concentrations. Titanium isopropoxide, diethyl zinc, and deionized water were sources for Ti, Zn, and O, respectively. The Ti doping was then achieved by growing ZnO and TiO2 alternately. A hampered growth mode of ZnO on TiO2 layer was confirmed by comparing the thicknesses measured by spectroscopic ellipsometry with the expected. It was also found that the locations of the (100) diffraction peaks shift towards lower diffraction angles as Ti concentration increased. For all samples, optical transmittance over 80% was obtained in the visible region. The sample with ALD cycle ratio of ZnO/TiO2 being 20 had the lowest resistivity of 8.874 × 10−4 Ω cm. In addition, carrier concentration of the prepared films underwent an evident increase and then decreased with the increase of Ti doping concentration. PMID:23442766

  8. Effect of bismuth doping on the ZnO nanocomposite material and study of its photocatalytic activity under UV-light

    SciTech Connect

    Chandraboss, V.L.; Natanapatham, L.; Karthikeyan, B.; Kamalakkannan, J.; Prabha, S.; Senthilvelan, S.

    2013-10-15

    Graphical abstract: The hetero-junctions that are formed between the ZnO and the Bi provide an internal electric field that facilitates separation of the electron-hole pairs and induces faster carrier migration. Thus they often enhanced photocatalytic reaction. - Highlights: • Bi-doped ZnO nanocomposite material was prepared by precipitation method. • Characterized by XRD, HR-SEM with EDX, UV–visible DRS and FT-RAMAN analysis. • Bi-doped ZnO nanocomposite material was used to photodegradation of Congo red. • Mechanism and photocatalytic effect of nanocomposite material have been discussed. - Abstract: Bismuth (Bi)-doped ZnO nanocomposite material was prepared by precipitation method with doping precursors of bismuth nitrate pentahydrate and oxalic acid, characterized by X-ray diffraction (XRD), High Resolution-Scanning Electron Microscopy (HR-SEM) with Energy Dispersive X-ray (EDX) analysis, UV–visible Diffuse Reflectance Spectroscopy (UV–visible DRS) and Fourier Transform-Raman (FT-RAMAN) analysis. The enhanced photocatalytic activity of the Bi-doped ZnO is demonstrated through photodegradation of Congo red under UV-light irradiation. The mechanism of photocatalytic effect of Bi-doped ZnO nanocomposite material has been discussed.

  9. Plasmon enhanced CdS-quantum dot sensitized solar cell using ZnO nanorods array deposited with Ag nanoparticles as photoanode

    NASA Astrophysics Data System (ADS)

    Eskandari, M.; Ahmadi, V.; Yousefi rad, M.; Kohnehpoushi, S.

    2015-04-01

    CdS-quantum dot sensitized solar cell using ZnO nanorods (ZnO NRs) array deposited with Ag nanoparticles (Ag NPs) as photoanode was fabricated. Light absorption effect of Ag NPs on improvement of the cell performance was investigated. Performance improvement of metal nanoparticles (MNPs) was controlled by the structure design and architecture. Different decorations and densities of Ag NPs were utilized on the photoanode. Results showed that using 5% Ag NPs in the photoanode results in the increased efficiency, fill factor, and circuit current density from 0.28% to 0.60%, 0.22 to 0.29, and 2.18 mA/cm2 to 3.25 mA/cm2, respectively. Also, incident photon-to-current efficiencies (IPCE) results showed that cell performance improvement is related to enhanced absorption in the photoanode, which is because of the surface plasmonic resonance and light scattering of Ag NPs in the photoanode. Measurements of electrochemical impedance spectroscopy revealed that hole transfer kinetics increases with introduction of Ag NPs into photoanode. Also, it is shown that chemical capacitance increases with introduction of Ag NPs. Such increase can be attributed to the surface palsmonic resonance of Ag NPs which leads to absorption of more light in the photoanode and generation of more photoelectron in the photoanode.

  10. Thermoelectric properties of n-type Nb-doped Ag8SnSe6

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao; Zhang, Cheng-Long; Lin, Siqi; Lu, Hong; Pei, Yanzhong; Jia, Shuang

    2016-04-01

    Electrical and thermoelectric (TE) properties for n-type Ag8SnSe6 and ( Ag1- x Nb x ) 8 SnSe 6 are investigated. Ag8SnSe6 has the thermoelectric figure of merit (ZT) close to 1.1 at 803 K due to its intrinsic ultralow thermal conductivity ˜ 0.3 Wm - 1 K - 1 , relatively low resistivity ˜0.01 Ω cm, and high Seebeck coefficient ˜-200 μV/K. The ZT for pure Ag8SnSe6 drops to 0.02 at room temperature due to its large resistivity. Niobium doping increases the carrier concentration nearly 10 times and thus enhances its ZT to 0.11 at room temperature. Ag8SnSe6 is a promising n-type candidate of TE materials which needs further elaborations.

  11. Extranuclear dynamics of 111Ag(→111Cd) doped in AgI nanoparticles

    NASA Astrophysics Data System (ADS)

    Sato, W.; Mizuuchi, R.; Irioka, N.; Komatsuda, S.; Kawata, S.; Taoka, A.; Ohkubo, Y.

    2014-08-01

    Dynamic behavior of the extranuclear field relative to the 111Ag(→111Cd) probe nucleus introduced in a superionic conductor silver iodide (AgI) was investigated by means of the time-differential perturbed angular correlation technique. For poly-N-vinyl-2-pyrrolidone (PVP)-coated AgI nanoparticles, we observed nuclear spin relaxation of the probe at room temperature. This result signifies that Ag+ ions in the polymer-coated sample make hopping motion from site to site at this low temperature. The activation energy for the dynamic motion was successfully estimated to be 46(10) meV. The first atomic-level observation of the temperature-dependent dynamic behavior of Ag+ ions in the polymer-coated AgI is reported.

  12. Investigation on non-polar m-plane ZnO and Na-doped p-type ZnO films grown by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Chen, W.; Pan, X. H.; Chen, S. S.; He, H. P.; Huang, J. Y.; Lu, B.; Ye, Z. Z.

    2015-10-01

    Non-polar ZnO and Na-doped ZnO films were epitaxially grown on m-plane sapphire substrates by plasma-assisted molecular beam epitaxy. The films exhibit dominant () ( m-plane) orientation as identified by the X-ray diffraction pattern. The quality of the obtained m-plane ZnO film is evidenced by X-ray diffraction rocking curves full width at half maximum of 1125 arcsec for the () reflection and 1427 arcsec for the () reflection, respectively. Hall-effect measurements show that the m-plane Na-doped ZnO film exhibits p-type conductivity with a hole concentration of 2.50 × 1017 cm-3, while the m-plane ZnO film exhibits compensatory conductivity. Na atoms substituting for Zn atoms are believed to be the origin of p-type conductivity. The Na-related acceptor level is deduced to be ~120 meV by temperature-dependent photoluminescence, indicating the superiority of m-plane ZnO film in p-type doping compared with the polar ZnO film.

  13. Magnetism from 2p states in K-doped ZnO monolayer: A density functional study

    NASA Astrophysics Data System (ADS)

    Fang, D. Q.; Zhang, Y.; Zhang, S. L.

    2016-05-01

    Using density-functional–based methods, we have studied 2p-based magnetic moments and magnetic coupling in potassium (K)-doped ZnO monolayer. We find that the substitution of a K atom at a Zn site in a ZnO monolayer induces a magnetic moment of 1.0~μB per cell mainly originating from the O-2p states and has much lower formation energy than a magnetic Zn vacancy. A half-metallic electronic property and long-range ferromagnetic coupling between the magnetic moments are obtained based on the generalized gradient approximation (GGA) calculations, which is explained by a double-exchange–like mechanism. Moreover, with stronger correlation correction on 2p states, the structure of the substitutional K impurity undergoes a Jahn-Teller–like distortion. Incorporating magnetism into a two-dimensional ZnO monolayer will promote its application in nanodevices.

  14. Investigation of plasmon resonance tunneling through subwavelength hole arrays in highly doped conductive ZnO films

    SciTech Connect

    Nader, Nima Vangala, Shivashankar; Hendrickson, Joshua R.; Leedy, Kevin D.; Cleary, Justin W.; Look, David C.; Guo, Junpeng

    2015-11-07

    Experimental results pertaining to plasmon resonance tunneling through a highly conductive zinc oxide (ZnO) layer with subwavelength hole-arrays is investigated in the mid-infrared regime. Gallium-doped ZnO layers are pulsed-laser deposited on a silicon wafer. The ZnO has metallic optical properties with a bulk plasma frequency of 214 THz, which is equivalent to a free space wavelength of 1.4 μm. Hole arrays with different periods and hole shapes are fabricated via a standard photolithography process. Resonant mode tunneling characteristics are experimentally studied for different incident angles and compared with surface plasmon theoretical calculations and finite-difference time-domain simulations. Transmission peaks, higher than the baseline predicted by diffraction theory, are observed in each of the samples at wavelengths that correspond to the excitation of surface plasmon modes.

  15. Investigation of plasmon resonance tunneling through subwavelength hole arrays in highly doped conductive ZnO films

    NASA Astrophysics Data System (ADS)

    Nader, Nima; Vangala, Shivashankar; Hendrickson, Joshua R.; Leedy, Kevin D.; Look, David C.; Guo, Junpeng; Cleary, Justin W.

    2015-11-01

    Experimental results pertaining to plasmon resonance tunneling through a highly conductive zinc oxide (ZnO) layer with subwavelength hole-arrays is investigated in the mid-infrared regime. Gallium-doped ZnO layers are pulsed-laser deposited on a silicon wafer. The ZnO has metallic optical properties with a bulk plasma frequency of 214 THz, which is equivalent to a free space wavelength of 1.4 μm. Hole arrays with different periods and hole shapes are fabricated via a standard photolithography process. Resonant mode tunneling characteristics are experimentally studied for different incident angles and compared with surface plasmon theoretical calculations and finite-difference time-domain simulations. Transmission peaks, higher than the baseline predicted by diffraction theory, are observed in each of the samples at wavelengths that correspond to the excitation of surface plasmon modes.

  16. Homogeneous and stable p-type doping of graphene by MeV electron beam-stimulated hybridization with ZnO thin films

    SciTech Connect

    Song, Wooseok; Kim, Yooseok; Hwan Kim, Sung; Youn Kim, Soo; Cha, Myoung-Jun; Song, Inkyung; Jeon, Cheolho; Sung Jung, Dae; Lim, Taekyung; Lee, Sumi; Ju, Sanghyun; Chel Choi, Won; Wook Jung, Min; An, Ki-Seok; Park, Chong-Yun

    2013-02-04

    In this work, we demonstrate a unique and facile methodology for the homogenous and stable p-type doping of graphene by hybridization with ZnO thin films fabricated by MeV electron beam irradiation (MEBI) under ambient conditions. The formation of the ZnO/graphene hybrid nanostructure was attributed to MEBI-stimulated dissociation of zinc acetate dihydrate and a subsequent oxidation process. A ZnO thin film with an ultra-flat surface and uniform thickness was formed on graphene. We found that homogeneous and stable p-type doping was achieved by charge transfer from the graphene to the ZnO film.

  17. Characteristic properties of Raman scattering and photoluminescence on ZnO crystals doped through phosphorous-ion implantation

    NASA Astrophysics Data System (ADS)

    Jeong, T. S.; Yu, J. H.; Mo, H. S.; Kim, T. S.; Lim, K. Y.; Youn, C. J.; Hong, K. J.

    2014-02-01

    P-doped ZnO was fabricated by means of the ion-implantation method. At the Raman measurement, the blue shift of the E2high mode and A1(LO) phonon of the inactive mode were observed after the P-ion implantation. It suggested to be caused by the compressive stress. Thus, Hall effect measurement indicates that the acceptor levels exists in P-doped ZnO while still maintaining n-type ZnO. From the X-ray photoelectron spectroscopy, the chemical bond formation of the P2p3/2 spectrum consisted of 2(P2O5) molecules. Therefore, the implanted P ions were substituted to the Zn site in ZnO. From the photoluminescence (PL) spectra, P-related PL peaks were observed in the energy ranges of 3.1 and 3.5 eV, and its origin was analyzed at PZn-2VZn complexes, acting as a shallow acceptor. With increasing temperatures, the neutral-acceptor bound-exciton emission, (A0, X), shows a tendency to quench the intensity and extend the emission linewidth. From the relations of the intensity and the linewidth as a function of temperature, the broadening of linewidth was believed to the result that the vibration mode of E2high participates in the broadening process of (A0, X) and the change of luminescent intensity was attributed to the partial dissociation of (A0, X). Consequently, these facts indicate that the acceptor levels existed in P-doped ZnO layer by the ion implantation.

  18. Characteristic properties of Raman scattering and photoluminescence on ZnO crystals doped through phosphorous-ion implantation

    SciTech Connect

    Jeong, T. S.; Yu, J. H.; Mo, H. S.; Kim, T. S.; Lim, K. Y.; Youn, C. J.; Hong, K. J.

    2014-02-07

    P-doped ZnO was fabricated by means of the ion-implantation method. At the Raman measurement, the blue shift of the E{sub 2}{sup high} mode and A{sub 1}(LO) phonon of the inactive mode were observed after the P-ion implantation. It suggested to be caused by the compressive stress. Thus, Hall effect measurement indicates that the acceptor levels exists in P-doped ZnO while still maintaining n-type ZnO. From the X-ray photoelectron spectroscopy, the chemical bond formation of the P2p{sub 3/2} spectrum consisted of 2(P{sub 2}O{sub 5}) molecules. Therefore, the implanted P ions were substituted to the Zn site in ZnO. From the photoluminescence (PL) spectra, P-related PL peaks were observed in the energy ranges of 3.1 and 3.5 eV, and its origin was analyzed at P{sub Zn}-2V{sub Zn} complexes, acting as a shallow acceptor. With increasing temperatures, the neutral-acceptor bound-exciton emission, (A{sup 0}, X), shows a tendency to quench the intensity and extend the emission linewidth. From the relations of the intensity and the linewidth as a function of temperature, the broadening of linewidth was believed to the result that the vibration mode of E{sub 2}{sup high} participates in the broadening process of (A{sup 0}, X) and the change of luminescent intensity was attributed to the partial dissociation of (A{sup 0}, X). Consequently, these facts indicate that the acceptor levels existed in P-doped ZnO layer by the ion implantation.

  19. Preparation of transparent conducting B-doped ZnO films by vacuum arc plasma evaporation

    SciTech Connect

    Miyata, Toshihiro; Honma, Yasunori; Minami, Tadatsugu

    2007-07-15

    Highly transparent and conductive B-doped ZnO (BZO) thin films have been prepared by a newly developed vacuum arc plasma evaporation method that provided high-rate film depositions using sintered BZO pellets and fragments. The obtained electrical and optical properties of the deposited BZO thin films were considerably affected by the deposition conditions as well as the preparation method of the BZO pellets and fragments used. The lowest thin film resistivity was obtained with a B doping content [B/(B+Zn) atomic ratio] of approximately 1 at. %. A resistivity as low as 5x10{sup -4} {omega} cm and an average transmittance above about 80% in the wavelength range of 400-1300 nm were obtained in BZO films prepared with a thickness above approximately 400 nm at a substrate temperature of 200 deg. C. In addition, a low resistivity of 7.97x10{sup -4} {omega} cm and average transmittances above about 80% in the visible wavelength range were obtained in a BZO film prepared at a substrate temperature of 100 deg. C and an O{sub 2} gas flow rate of 10 SCCM (SCCM denotes cubic centimeter per minute at STP). The deposition rate of BZO films was typically 170 nm/min with a cathode plasma power of 4.5 kW.

  20. Boron doped ZnO embedded into reduced graphene oxide for electrochemical supercapacitors

    NASA Astrophysics Data System (ADS)

    Alver, Ü.; Tanrıverdi, A.

    2016-08-01

    In this work, reduced graphene oxide/boron doped zinc oxide (RGO/ZnO:B) composites were fabricated by a hydrothermal process and their electrochemical properties were investigated as a function of dopant concentration. First, boron doped ZnO (ZnO:B) particles was fabricated with different boron concentrations (5, 10, 15 and 20 wt%) and then ZnO:B particles were embedded into RGO sheets. The physical properties of sensitized composites were characterized by XRD and SEM. Characterization indicated that the ZnO:B particles with plate-like structure in the composite were dispersed on graphene sheets. The electrochemical properties of the RGO/ZnO:B composite were investigated through cyclic voltammetry, galvanostatic charge/discharge measurements in a 6 M KOH electrolyte. Electrochemical measurements show that the specific capacitance values of RGO/ZnO:B electrodes increase with increasing boron concentration. RGO/ZnO:B composite electrodes (20 wt% B) display the specific capacitance as high as 230.50 F/g at 5 mV/s, which is almost five times higher than that of RGO/ZnO (52.71 F/g).

  1. Sintering behavior of doped ZnO powders for high field varistors

    SciTech Connect

    Ghirlanda, M.

    1990-08-01

    The sintering of ZnO varistor precursor powders, doped with Co, Mn and different concentrations of Bi and Al, is investigated and discussed in relation with sintering models. One purpose of the present study is to provide information valuable for the fabrication of high field varistors. As the fundamental parameter of these electronic components is the breakdown voltage per unit of thickness, which is determined by the number of grain boundaries per linear dimension, the grain size and the sintered density are crucial variables, and the sintering is a central step in the manufacturing of such varistors. Sintering experiments performed at constant heating rate in a loading dilatometer provide data on the densification and creep of the compacted powders. Another goal of the present study is to provide an experimental basis for the interpretation of the evolution of the ratio between densification rate and creep rate in terms of competition between densification and microstructure coarsening. This is accomplished by taking advantage of the variety of sintering behaviors that takes place in the system ZnO-Bi-Al: the comparison of these behaviors allows us to correlate the macroscopic sintering parameters to the evolution of the microstructure. It results that, while in non-doped powders densification and coarsening develop in a balanced way, resulting in the constancy of the ratio between densification rate and creep rate, the effect of the dopants on the sintering kinetics alters such a balance, leading this ratio to vary. 17 figs.

  2. Synthesis of high-quality Al-doped ZnO nanoink

    NASA Astrophysics Data System (ADS)

    Thu, Tran V.; Maenosono, Shinya

    2010-01-01

    Al-doped ZnO (AZO) nanoparticles (NPs) have been synthesized via the thermal decomposition of metal acetylacetonate precursors in a nonoxygen and nonpolar solvent. Long-chain alkyl amines have been utilized to terminate the growth of AZO NPs and to stabilize them. The NPs have been characterized by a number of techniques as monocrystalline, exhibiting a hexagonal (wurtzite) structure with sizes from 8 to 13 nm. The composition of Al in the resulting NP is related solely to the composition of the reaction mixture and the size is controllable with the temperature of the reaction. The AZO NP dispersion has been proven to be stable over a 24 h period by dynamic light scattering measurements. The influence of the synthetic conditions, such as temperature, reaction time and the Al doping content, on the properties of NPs have also been investigated. An optically transparent AZO thin film was fabricated using the AZO nanoink by spin casting followed by annealing. The resulting film resistivity was measured to be 5.0×10-3 Ω cm.

  3. Structural, electrical, and optical properties of atomic layer deposition Al-doped ZnO films

    SciTech Connect

    Banerjee, P; Lee, W. J.; Bae, K. R.; Lee, Sang Bok; Rubloff, Gary W

    2010-01-01

    Al-doped ZnO (AZO) films of ∼100 nm thickness with various Aldoping were prepared at 150 °C by atomic layer deposition on quartz substrates. At low Aldoping, the films were strongly textured along the [100] direction, while at higher Aldoping the films remained amorphous. Atomic force microscopy results showed that Al–O cycles when inserted in a ZnOfilm, corresponding to a few atomic percent Al, could remarkably reduce the surface roughness of the films. Hall measurements revealed a maximum mobility of 17.7 cm{sup 2} /V s . Film resistivity reached a minima of 4.4×10{sup −3}  Ω cm whereas the carrier concentration reached a maxima of 1.7×10{sup 20}  cm{sup −3} , at 3 at. % Al. The band gap of AZO films varied from 3.23 eV for undoped ZnOfilms to 3.73 eV for AZO films with 24.6 at. % Al. Optical transmittance over 80% was obtained in the visible region. The detrimental impact of increased Al resulting in decreased conductivity due to doping past 3.0 at. % is evident in the x-ray diffraction data, as an abrupt increase in the optical band gap and as a deviation from the Burstein–Moss effect.

  4. Enhanced Ultraviolet Stability of Air-Processed Polymer Solar Cells by Al Doping of the ZnO Interlayer.

    PubMed

    Prosa, Mario; Tessarolo, Marta; Bolognesi, Margherita; Margeat, Olivier; Gedefaw, Desta; Gaceur, Meriem; Videlot-Ackermann, Christine; Andersson, Mats R; Muccini, Michele; Seri, Mirko; Ackermann, Jörg

    2016-01-27

    Photostability of organic photovoltaic devices represents a key requirement for the commercialization of this technology. In this field, ZnO is one of the most attractive materials employed as an electron transport layer, and the investigation of its photostability is of particular interest. Indeed, oxygen is known to chemisorb on ZnO and can be released upon UV illumination. Therefore, a deep analysis of the UV/oxygen effects on working devices is relevant for the industrial production where the coating processes take place in air and oxygen/ZnO contact cannot be avoided. Here we investigate the light-soaking stability of inverted organic solar cells in which four different solution-processed ZnO-based nanoparticles were used as electron transport layers: (i) pristine ZnO, (ii) 0.03 at %, (iii) 0.37 at %, and (iv) 0.8 at % aluminum-doped AZO nanoparticles. The degradation of solar cells under prolonged illumination (40 h under 1 sun), in which the ZnO/AZO layers were processed in air or inert atmosphere, is studied. We demonstrate that the presence of oxygen during the ZnO/AZO processing is crucial for the photostability of the resulting solar cell. While devices based on undoped ZnO were particularly affected by degradation, we found that using AZO nanoparticles the losses in performance, due to the presence of oxygen, were partially or totally prevented depending on the Al doping level. PMID:26751271

  5. Electronic transport in highly conducting Si-doped ZnO thin films prepared by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Vladimir L.; Vai, Alex T.; Al-Mamouri, Malek; Stuart Abell, J.; Pepper, Michael; Edwards, Peter P.

    2015-12-01

    Highly conducting (ρ = 3.9 × 10-4 Ωcm) and transparent (83%) polycrystalline Si-doped ZnO (SiZO) thin films have been deposited onto borosilicate glass substrates by pulsed laser deposition from (ZnO)1-x(SiO2)x (0 ≤ x ≤ 0.05) ceramic targets prepared using a sol-gel technique. Along with their structural, chemical, and optical properties, the electronic transport within these SiZO samples has been investigated as a function of silicon doping level and temperature. Measurements made between 80 and 350 K reveal an almost temperature-independent carrier concentration consistent with degenerate metallic conduction in all of these samples. The temperature-dependent Hall mobility has been modeled by considering the varying contribution of grain boundary and electron-phonon scattering in samples with different nominal silicon concentrations.

  6. Defects, stress and abnormal shift of the (0 0 2) diffraction peak for Li-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Lin, Yow-Jon; Wang, Mu-Shan; Liu, Chia-Jyi; Huang, Hsueh-Jung

    2010-10-01

    The effect of changes in Li content on the structural property of sol-gel Li-doped ZnO films was investigated in this study. The observed changes of the Li incorporation-induced strain along c-axis are closely related to the different ratios between the concentrations of Li interstitials (Li i) and Li substituting for Zn (Li Zn) in the films. According to the observed results from X-ray diffraction (XRD) and photoluminescence measurements, we found that the domination of the dissociative mechanism in the Li-doped ZnO films led to transformation from Li Zn to Li i, involving the formation of Zn vacancies (V Zn). In addition, the interaction between these defects (that is, Li Zn, Li i, V Zn and oxygen vacancy) and the crystal structure may lead to the abnormal shift of the (0 0 2) diffraction peak position determined from XRD measurements.

  7. Doping-induced stability in vanadium-doped ZnO quantum well wires (QWW): Combination of DFT calculations within experimental measurements

    NASA Astrophysics Data System (ADS)

    Yumak, A.; Goumri-Said, Souraya; Khan, Wilayat; Boubaker, Karem; Petkova, P.

    2016-07-01

    ZnO quantum well wires (QWW) have grown on glass substrates by an inexpensive, simplified and enhanced spray pyrolysis technique then doped by Vanadium. The effects of V-doping on the structural, morphological and optical properties of the QWW were investigated experimentally and theoretically. The accuracy of control can be achieved on functional performance by adjusting vanadium doping extent. The incorporation of Vanadium in ZnO-QWW induced the formation of band tailing in states. The interactions with phonons and the presence of a tail absorption profile are following the empirical Urbach law. The electronic structure using density functional theory have shown the changes induced by vanadium doping in ZnO-QWW, where the phonon band structure and density of states were reported. The DFT results showed a good agreement with the lattice compatibility theory as well as with the experimental results.

  8. 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

  9. Synthesis and optical properties of Eu3+ doped ZnO nanoparticles used for white light emitting diodes.

    PubMed

    Huang, Jinzhao; Liu, Shiyou; Gao, Baojun; Jiang, Tao; Zhao, Yongdan; Liu, Song; Kuang, Lei; Xu, Xijin

    2014-04-01

    ZnO nanoparticles doped with trivalent europium ions (Eu3+) were synthesized by the hydrothermal method. The structural properties of the samples were investigated by the X-ray diffraction (XRD). The results indicated that Eu3+ was incorporated into the lattice of ZnO. Photoluminescence (PL) measurements of ZnO:Eu3+ showed a strong red luminescence emission. Specially, the red emission can be obtained even under the nonresonant excitation of 320 nm, and it is explained by an energy transfer mechanism in which the energy is transferred from ZnO matrix to Eu3+. These results indicate that the ZnO:Eu3+ is the attractive candidate phosphor for the application in phosphor-converted light-emitting diodes (pc-LEDs) as red phosphor. The intensity of Eu3+ PL decreased with the increasing Eu3+ concentration and the concentration quenching mechanism was presented based on non-radiative recombination processes in ZnO and the energy back-transfer from the excited state of Eu3+ to the ZnO host. Moreover, the samples were synthesized under low temperature condition. PMID:24734733

  10. Structural, optical, vibrational, and magnetic properties of sol-gel derived Ni doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Srinet, Gunjan; Kumar, Ravindra; Sajal, Vivek

    2013-07-01

    With a view to study structural, optical, vibrational, and magnetic properties of solgel derived Zn1-xNixO (x = 0.02, 0.04, and 0.06) nanoparticles, systematic investigations have been carried out. The Rietveld refinement of X-ray powder diffraction data revealed a single hexagonal phase with space group P63mc. The secondary phase of NiO appeared only in 6% Ni doped sample. Phonon modes in Ni doped ZnO nanoparticles were studied through Fourier transform infrared measurements. Furthermore, the enhancement in optical band gap with Ni doping from 3.29 to 3.32 eV has been observed through UV-visible spectroscopic analysis. Photoluminescence spectra of Zn1-xNixO show the UV-emission peak showing the blue shift with increase in doping concentration followed by broad visible (blue) emission corresponding to the defect emission whose intensity decreased with increasing Ni concentration. A clear room temperature ferromagnetism is observed in all samples but saturation magnetization decreased with increasing Ni content. The suitability of bound magnetic polarons (BMP) model is checked and numbers of BMPs are found to be of the order 1015 per cm3, which is very small for the percolation in ZnO. In the present case, oxygen rich stoichiometry with enhanced Zn-O bonding favours the indirect Ni-O-Ni ferromagnetic exchange coupling and reduction of oxygen vacancies leading to strong hybridization of Ni in ZnO host matrix responsible for room temperature ferromagnetism.

  11. Facile one-step synthesis of N-doped ZnO micropolyhedrons for efficient photocatalytic degradation of formaldehyde under visible-light irradiation

    NASA Astrophysics Data System (ADS)

    Wu, Changle

    2014-11-01

    N-doped ZnO micropolyhedrons were fabricated by calcining the mixture of commercial ZnO (analytical grade) and NH4NO3 at 600 °C for 1.5 h, in which NH4NO3 was utilized as the nitrogen source. The structure, composition, BET specific surface area and optical properties of N-doped ZnO sample were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, wavelength dispersive X-ray fluorescence spectroscopy, field emission scanning electron microscopy, high resolution transmission electron microscopy, N2 adsorption-desorption isotherms, and UV-vis diffuse reflectance spectroscopy. The photocatalytic results demonstrated that the as-synthesized N-doped ZnO microcrystals possessed much higher photocatalytic activity than N-doped TiO2 (which was synthesized by calcining the mixture of P25 TiO2 and NH4NO3 at 600 °C for 1.5 h) and commercial pure ZnO in the decomposition of formaldehyde under visible-light (λ > 420 nm) irradiation. The present work suggests that NH4NO3 is a promising nitrogen source for one-step calcination synthesis of microcrystalline N-doped ZnO, which can be applied as a visible-light-activated photocatalyst in efficient utilization of solar energy for treating formaldehyde wastewater.

  12. Enhancement of two photon absorption with Ni doping in the dilute magnetic semiconductor ZnO crystalline nanorods

    SciTech Connect

    Rana, Amit Kumar; Kumar, Yogendra; Arjunan, M.S.; Sen, Somaditya; Shirage, Parasharam M. E-mail: paras.shirage@gmail.com; J, Aneesh; Adarsh, K. V.

    2015-12-07

    In this letter, we have investigated the third-order optical nonlinearities of high-quality Ni doped ZnO nanorods crystallized in wurtzite lattice, prepared by the wet chemical method. In our experiments, we found that the two photon absorption coefficient (β) increases by as much as 14 times, i.e., 7.6 ± 0.4 to 112 ± 6 cm/GW, when the Ni doping is increased from 0% to 10%. The substantial enhancement in β is discussed in terms of the bandgap scaling and Ni doping. Furthermore, we also show that the optical bandgap measured by UV-Vis and photoluminescence spectroscopies, continuously redshift with increasing Ni doping concentration. We envision that the strong nonlinear optical properties together with their dilute magnetic effects, they form an important class of materials for potential applications in magneto-optical and integrated optical chips.

  13. Enhancement of two photon absorption with Ni doping in the dilute magnetic semiconductor ZnO crystalline nanorods

    NASA Astrophysics Data System (ADS)

    Rana, Amit Kumar; J, Aneesh; Kumar, Yogendra; M. S, Arjunan; Adarsh, K. V.; Sen, Somaditya; Shirage, Parasharam M.

    2015-12-01

    In this letter, we have investigated the third-order optical nonlinearities of high-quality Ni doped ZnO nanorods crystallized in wurtzite lattice, prepared by the wet chemical method. In our experiments, we found that the two photon absorption coefficient (β) increases by as much as 14 times, i.e., 7.6 ± 0.4 to 112 ± 6 cm/GW, when the Ni doping is increased from 0% to 10%. The substantial enhancement in β is discussed in terms of the bandgap scaling and Ni doping. Furthermore, we also show that the optical bandgap measured by UV-Vis and photoluminescence spectroscopies, continuously redshift with increasing Ni doping concentration. We envision that the strong nonlinear optical properties together with their dilute magnetic effects, they form an important class of materials for potential applications in magneto-optical and integrated optical chips.

  14. Enhancement ZnO nanofiber as semiconductor for dye-sensitized solar cells by using Al doped

    NASA Astrophysics Data System (ADS)

    Sutanto, Bayu; Arifin, Zainal; Suyitno, Hadi, Syamsul; Pranoto, Lia Muliani; Agustia, Yuda Virgantara

    2016-03-01

    The purpose of this research is to produce Al-doped ZnO (AZO) nanofibers in order to enhance the performance of Dye-Sensitized Solar Cell (DSSC). AZO nanofiber semiconductor was manufactured by electrospinning process of Zinc Acetate Dehydrate (Zn(CH3COO)2) solution and precursor of Polyvinyl Acetate (PVA). The doping process of Al was built by dissolving 0-4 wt% in concentrations of AlCl3 to Zinc Acetate. AZO green fiber was sintered at temperature 500°C for an hour. The result shows that Al doped ZnO had capability to increase the electrical conductivity of semiconductor for doping 0, 1, 2, 3, and 4 wt% for 2,07×10-3; 3,71×10-3; 3,59 ×10-3; 3,10 ×10-3 and 2,74 ×10-3 S/m. The best performance of DSSC with 3 cm2 active area was obtained at 1 wt% Al-ZnO which the value of VOC, ISC, FF, and efficiency were 508,43 mV, 3,125 mA, 38,76%, and 0,411% respectively. These coincide with the electrical conductivity of semiconductor and the crystal size of XRD result that has the smallest size as compared to other doping variations.

  15. Structural and optical properties of highly crystalline Ce, Eu and co-doped ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Murugadoss, G.; Jayavel, R.; Rajesh Kumar, M.

    2015-06-01

    Different concentrations of europium (Eu), cerium (Ce) doped and co-doped ZnO:Eu (1%), Ce (1%) nanorods were successfully synthesized by chemical method using Polyvinylpyrrolidone as a surfactant. Crystalline phase, morphology, functional groups, optical absorption, emission and thermal properties of prepared samples were investigated by X-ray diffraction (XRD), X-ray photoelectron spectrometer (XPS), Scanning electron microscopy (SEM), High-resolution transmission electron microscopy (HR-TEM), Fourier transform infra-red (FT-IR), UV-visible, Photoluminescence (PL) spectrophotometer and thermogravimetry (TG) and differential thermal analysis (DTA) analysis. The XRD study showed high crystalline nature of the products with nanoscale regime. Optical study showed shifting the absorption and emission spectra toward higher wavelength side when increasing the doping concentrations. Mainly, this is first time observed a red emission peak at 660 nm for Ce (3%) doped ZnO. Additionally, co-doped ZnO:Eu (1%), Ce (1%) nanorods were synthesized and studied their optical properties. This work demonstrates that simply modified their optical absorption and emission of ZnO by introducing rare earth ions can be used as an effective electrode material in solar cell applications, optoelectronic devices and photocatalysis analysis.

  16. Li—N dual-doped ZnO thin films prepared by an ion beam enhanced deposition method

    NASA Astrophysics Data System (ADS)

    Xie, Jian-Sheng; Chen, Qiang

    2014-09-01

    Li—N dual-doped ZnO films [ZnO:(Li,N)] with Li doping concentrations of 3 at.%-5 at.% were grown on a glass substrate using an ion beam enhanced deposition (IBED) method. An optimal p-type ZnO:(Li,N) film with the resistivity of 11.4 Ω·cm was obtained by doping 4 at.% of Li and 5 sccm flow ratio of N2. The ZnO:(Li,N) films exhibited a wurtzite structure and good transmittance in the visible region. The p-type conductive mechanism of ZnO:(Li,N) films are attributed to the Li substitute Zn site (LiZn) acceptor. N doping in ZnO can forms the Lii—NO complex, which depresses the compensation of Li occupy interstitial site (Lii) donors for LiZn acceptor and helps to achieve p-type ZnO:(Li,N) films. Room temperature photoluminescence measurements indicate that the UV peak (381 nm) is due to the shallow acceptors LiZn in the p-type ZnO:(Li,N) films. The band gap of the ZnO:(Li,N) films has a red-shift after p-type doping.

  17. Spectral features and antibacterial properties of Cu-doped ZnO nanoparticles prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Alireza, Samavati; A, F. Ismail; Hadi, Nur; Z, Othaman; M, K. Mustafa

    2016-07-01

    Zn1‑x Cu x O (x = 0.00, 0.01, 0.03, and 0.05) nanoparticles are synthesized via the sol-gel technique using gelatin and nitrate precursors. The impact of copper concentration on the structural, optical, and antibacterial properties of these nanoparticles is demonstrated. Powder x-ray diffraction investigations have illustrated the organized Cu doping into ZnO nanoparticles up to Cu concentration of 5% (x = 0.05). However, the peak corresponding to CuO for x = 0.01 is not distinguishable. The images of field emission scanning electron microscopy demonstrate the existence of a nearly spherical shape with a size in the range of 30–52 nm. Doping Cu creates the Cu–O–Zn on the surface and results in a decrease in the crystallite size. Photoluminescence and absorption spectra display that doping Cu causes an increment in the energy band gap. The antibacterial activities of the nanoparticles are examined against Escherichia coli (Gram negative bacteria) cultures using optical density at 600 nm and a comparison of the size of inhibition zone diameter. It is found that both pure and doped ZnO nanoparticles indicate appropriate antibacterial activity which rises with Cu doping. Project supported by the Universiti Teknologi Malaysia (UTM) (Grant No. R. J1300000.7809.4F626). Dr. Samavati is thankful to RMC for postdoctoral grants.

  18. RETRACTED: Investigation of structural, optical and electronic properties in Al-Sn co-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Pan, Zhanchang; Tian, Xinlong; Wu, Shoukun; Yu, Xia; Li, Zhuliang; Deng, Jianfeng; Xiao, Chumin; Hu, Guanghui; Wei, Zhigang

    2013-01-01

    This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Figures 3 and 4 of this paper have also been presented as belonging to other materials in other publications. This observation is evidence of fraud and therefore it is not certain that the described research and conclusions of this paper belong to the presented images. Figures 3 and 4 of this paper can also be found in: Effect of annealing on the structures and properties of Al and F co-doped ZnO nanostructures, Materials Science in Semiconductor Processing, 2014, 17, 162-167, http://dx.doi.org/10.1016/j.mssp.2013.09.023 Highly transparent and conductive Sn/F and Al co-doped ZnO thin films prepared by sol-gel method, Journal of Alloys and Compounds, 2014,583, 32-38, http://dx.doi.org/10.1016/j.jallcom.2013.06.192 Properties of fluorine and tin co-doped ZnO thin films deposited by sol-gel method, Journal of Alloys and Compounds, 2013,576, 31-37, http://dx.doi.org/10.1016/j.jallcom.2013.04.132

  19. Influence of oxygen partial pressure on the microstructural and magnetic properties of Er-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Chen, Wei-Bin; Liu, Xue-Chao; Li, Fei; Chen, Hong-Ming; Zhou, Ren-Wei; Shi, Er-Wei

    2015-06-01

    Er-doped ZnO thin films have been prepared by using inductively coupled plasma enhanced physical vapor deposition at different O2:Ar gas flow ratio (R = 0:30, 1:30, 1:15, 1:10 and 1:6). The influence of oxygen partial pressure on the structural, optical and magnetic properties was studied. It is found that an appropriate oxygen partial pressure (R=1:10) can produce the best crystalline quality with a maximum grain size. The internal strain, estimated by fitting the X-ray diffraction peaks, varied with oxygen partial pressure during growth. PL measurements show that plenty of defects, especially zinc vacancy, exist in Er-doped ZnO films. All the samples show room-temperature ferromagnetism. Importantly, the saturation magnetization exhibits similar dependency on oxygen partial pressure with the internal strain, which indicates that internal strain has an important effect on the magnetic properties of Er-doped ZnO thin films.

  20. A sensitive and label-free photoelectrochemical aptasensor using Co-doped ZnO diluted magnetic semiconductor nanoparticles.

    PubMed

    Li, Hongbo; Qiao, Yunfei; Li, Jing; Fang, Hailin; Fan, Dahe; Wang, Wei

    2016-03-15

    Co-doped ZnO diluted magnetic semiconductor as a novel photoelectric beacon was first constructed for photoelectrochemical (PEC) aptasensor of acetamiprid. The fabricated PEC sensing is based on the specific binding of acetamiprid and its aptamer, which induces the decreasement of enhanced photocurrent produced by the electron donor of quercetin. Co(2+) doping has a beneficial effect in extending the band width of light absorption of ZnO into the visible region and to promote the separation of the photoinduced carriers due to the sp-d exchange interactions existing between the band electrons and the localized d electrons of Co(2+). The fabricated aptasensor was linear with the concentration of acetamiprid in the range of 0.5-800 nmolL(-1) with the detection limit of 0.18 nmolL(-1). The presence of same concentration of other conventional pesticides did not interfere in the detection of acetamiprid and the recovery is between 96.2% and 103.7%. This novel PEC aptasensor has good performances with high sensitivity, good selectivity, low cost and portable features. The strategy of Co-doped ZnO diluted magnetic semiconductor paves a new way to improve the performances of PEC aptasensor. PMID:26436325

  1. Optical parameters of boron-doped ZnO nanorods grown by low-temperature hydrothermal reaction.

    PubMed

    Kim, Soaram; Park, Hyunggil; Nam, Giwoong; Yoon, Hyunsik; Kim, Younggyu; Kim, Byunggu; Ji, Iksoo; Kim, Jong Su; Kim, Jin Soo; Kim, Do Yeob; Kim, Sung-O; Leem, Jae-Young

    2014-11-01

    Sol-gel spin-coating was used to deposit ZnO seed layers onto quartz substrates, and ZnO nanorods doped with various concentrations of B (i.e., BZO nanorods) ranging from 0 to 2.0 at% were hydrothermally grown on the ZnO seed layers. The effects of B doping on the absorption coefficient, optical band gap, Urbach energy, refractive index, extinction coefficient, single-oscillator energy, dispersion energy, average oscillator strength, average oscillator wavelength, dielectric constant, and optical conductivity of the hydrothermally grown BZO nanorods were investigated. The optical band gaps were 3.255, 3.243, 3.254, 3.258, and 3.228 eV for the nanorods grwon at 0, 0.5, 1.0, 1.5 and 2.0 at% B, respectively. B doping increased the Urbach energy from 40.7 to 65.1 meV for the nanorods grown at 0 and 2.0 at% B, respectively, and significantly affected the dispersion energy, the single-oscillator energy, the average oscillator wavelength, the average oscillator strength, the refractive index, and the optical conductivity of the hydrothermally grown BZO nanorods. PMID:25958555

  2. White-light luminescence properties of Mg and Sn doped ZnO prepared by thermal oxidation

    SciTech Connect

    Zeng, Jun; Fan, Huiqing; Xue, Jun; Wang, Yangli

    2014-02-01

    Graphical abstract: The PL spectrum of MgSnZnO was measured at room temperature through multi-peak Gaussian fitting, it is found that the broad emission is composed of six peaks. - Highlights: • Mg and Sn doped ZnO are synthesized by thermal oxidation of MgSnZn alloys. • The structure is characterized by XRD and micro-Raman scattering technology. • The optical properties are characterized by photoluminescence spectrum. • The resulting Mg and Sn doped ZnO shows white photoluminescence. - Abstract: This work reports that Mg and Sn doped ZnO (MgSnZnO) are synthesized by thermal oxidation of MgSnZn alloys. The structure and optical properties are characterized by X-ray diffraction (XRD), micro-Raman scattering technology and photoluminescence spectrum. Interestingly, the resulting MgSnZnO shows white photoluminescence. Additionally, the photoluminescence spectrum of MgSnZnO shows two broad emission bands ranging from 360 to 420 nm and 420 to 630 nm, respectively. Through multi-peak Gaussian fitting, it is found that the broad emission is composed of six Gaussian peaks. The six Gaussian peaks are centrered at 383 nm, 397 nm, 455 nm, 516 nm, 560 nm and 614 nm.

  3. A facile method for synthesis of N-doped ZnO mesoporous nanospheres and enhanced photocatalytic activity.

    PubMed

    Zhang, DongEn; Gong, JunYan; Ma, JuanJuan; Han, GuiQuan; Tong, ZhiWei

    2013-12-21

    A facile synthesis route is reported for preparation of N-doped mesoporous ZnO nanospheres by a solvothermal treatment of Zn(NO3)2·6H2O which provides a source of both zinc and nitrogen. A variety of different spectroscopic and analytical techniques, such as powder X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis and X-ray photoelectron (XPS) spectroscopies were used to characterize the physicochemical properties of catalysts. The photocatalytic activities of the composites were evaluated by the degree of degradation of rhodamine B in aqueous solutions at room temperature with near-UV light irradiation. These nanocomposites exhibit higher photocatalytic activity compared with pure ZnO nanoparticles. The enhancement of photocatalytic activity of N-doped ZnO nanoparticles is mainly attributed to their absorption of more photons and reduced electron-hole pair recombination. Our one-step, environmentally friendly synthetic method may provide a new means of designing and synthesizing series of N-doped metal oxide semiconductors for use in photo-assisted catalytic reactions. PMID:24068002

  4. Photocatalytic performance of Ag doped SnO2 nanoparticles modified with curcumin

    NASA Astrophysics Data System (ADS)

    Vignesh, K.; Hariharan, R.; Rajarajan, M.; Suganthi, A.

    2013-07-01

    Visible light active Ag doped SnO2 nanoparticles modified with curcumin (Cur-Ag-SnO2) have been prepared by a combined precipitation and chemical impregnation route. The optical properties, phase structures and morphologies of the as-prepared nanoparticles were characterized using UV-visible diffuse reflectance spectra (UV-vis-DRS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The surface area was measured by Brunauer. Emmett. Teller (B.E.T) analysis. Compared to bare SnO2, the surface modified photocatalysts (Ag-SnO2 and Cur-Ag-SnO2) showed a red shift in the visible region. The photocatalytic activity was monitored via the degradation of rose bengal (RB) dye and the results revealed that Cur-Ag-SnO2 shows better photocatalytic activity than that of Ag-SnO2 and SnO2. The superior photocatalytic activity of Cur-Ag-SnO2 could be attributed to the effective electron-hole separation by surface modification. The effect of photocatalyst concentration, initial dye concentration and electron scavenger on the photocatalytic activity was examined in detail. Furthermore, the antifungal activity of the photocatalysts and the reusability of Cur-Ag-SnO2 were tested.

  5. Effect of nitrogen as co-dopant in carbon and boron-doped ZnO clusters

    NASA Astrophysics Data System (ADS)

    Kapila, Neha; Sharma, Gaurav; Mudahar, Isha; Sharma, Hitesh

    2016-05-01

    The effect of N as co-dopant have been investigated on magnetic properties of C and B-doped (ZnO)n clusters (n = 1 - 16) using spin-polarized density functional theory. Total energy calculations show that C and N more stable when substituted at O site, whereas B is more stable at the Zn site. The B:N co-doping is energetically more stable than C:N which is more stable than N:N doping. C and N atoms do not show tendency to form clusters when doped separately. The magnetic moment (MM) of C-doped ZnO clusters is enhanced significantly with N co-doping. The MM of 2 μB, 1 μB and 1 μB per atom is induced due to C, N and B respectively. The MM of 3 μB or 5 μB and 2 μB or 4 μB are observed for co-doping of 2C:N and C:2N respectively. In contrary, the MM in 2B:N and B:2N co-doped (ZnO)n remains 1 μB for n=2-4, 12 and 16. The results are in agreement with the available theoretical results.

  6. Attempt of Deposition of Ag-Doped Amorphous Carbon Film by Ag-Cathode DC Plasma with CH4 Flow.

    PubMed

    Tsubota, Toshiki; Kuratsu, Kazuhiro; Murakami, Naoya; Ohno, Teruhisa

    2015-06-01

    A simple DC plasma apparatus having large Ag cathode with CH4 flow was used for the attempt to prepare Ag-doped amorphous carbon film. As the gaseous source, CH4 and the additive (N2 or Ar) were used for the plasma process. When N2 was the additive, the substrate surfaces after the plasma process were electrical conductor although high electrical resistance. The growth rate of the deposits decreased with increasing the amount of N2, and the deposits contained nitrogen. Although the small amount of silver was detected by XPS, the peak for Ag may not be in the carbon deposit but be in interlayer formed at Ar etching process. When Ar was the additive, the substrate surfaces after the plasma process were also electrical conductor although high electrical resistance. The growth rate of the deposits was almost independent of the amount of Ar, and the deposits contained no argon. The small XPS peaks for Ag may not be in the carbon deposit but be in interlayer formed at Ar etching process. Both the prepared samples had high antibiotic property. The method of this study could be used for the surface reforming with amorphous carbon coating having electrical conductivity and antibiotic property. PMID:26369089

  7. Structural and Optical properties of Er doped ZnO diluted magnetic semiconductor nano thin films produced by sol gel method

    NASA Astrophysics Data System (ADS)

    Tasci, A. Tolga; Ozturk, Ozgur; Asikuzun, Elif; Arda, Lutfi; Celik, Sukru; Terzioglu, Cabir

    Undoped and Er doped ZnO (Zn1-xErxO) transparent semiconductor thin films were coated using sol-gel method on non-alkali glass. Erbium was doped 1%, 2%, 3%, 4% and 5% ratio. Methanol and monoethanolamine were used as solvent and stabilizer. In this study, the effect of Er doping was examined on the structural and optical properties of ZnO DMS thin films. XRD, SEM and UV-VIS-NIR spectrometer measurements were performed for the structural and optical characterization. XRD results showed that, all of Er doped ZnO thin films have a hexagonal structure. The optical transmittance of rare earth element (Er) doped ZnO thin films were increased. The Er doped ZnO thin films showed high transparency (>84) in the visible region (400-700 nm). This research has been supported by the Kastamonu University Scientific Research Projects Coordination Department under the Grant No. KUBAP-03/2013-41 and the Scientific and Technological Research Council of Turkey (TUBITAK) Project No. 114F259.

  8. Morphological evolution and electronic alteration of ZnO nanomaterials induced by Ni/Fe co-doping

    NASA Astrophysics Data System (ADS)

    Fletcher, Cameron; Jiang, Yijiao; Sun, Chenghua; Amal, Rose

    2014-06-01

    Zinc oxide (ZnO) nanocrystals mono- and co-doped with nickel/iron were prepared using a facile solvothermal procedure. A significant change in the surface morphology from nanorods to plate-like nanoparticles was observed with an increase in the dopant concentration. The variations of their optical and electronic properties induced by metal dopants were investigated using a combination of characterization techniques and ab initio calculations. It is found that both nickel and iron atoms have been successfully incorporated into the crystal lattice rather than forming a secondary phase, suggesting good dispersion of dopants within the ZnO matrix. Doping with iron has red-shifted the absorption edges of ZnO towards the visible portion resulting in lower band gap energies with increasing dopant concentration. Evidenced by Raman and EPR spectroscopy, the addition of iron has been shown to promote the formation of more oxygen vacancy and crystal defects within the host lattice as well as increasing the free-electron density of the nanomaterial. The DFT plus Hubbard model calculations confirm that low concentration Ni-doping does not induce band gap narrowing but results in localized states. The calculations show that Fe-doping has the potential to greatly improve the optical absorption characteristics and lead to structural deformation, corroborating the UV-Vis, Raman, and EPR spectra.Zinc oxide (ZnO) nanocrystals mono- and co-doped with nickel/iron were prepared using a facile solvothermal procedure. A significant change in the surface morphology from nanorods to plate-like nanoparticles was observed with an increase in the dopant concentration. The variations of their optical and electronic properties induced by metal dopants were investigated using a combination of characterization techniques and ab initio calculations. It is found that both nickel and iron atoms have been successfully incorporated into the crystal lattice rather than forming a secondary phase

  9. Synthesis and characterization of cube-like Ag@AgCl-doped TiO2/fly ash cenospheres with enhanced visible-light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Liu, Shaomin; Zhu, Jinglin; Yang, Qing; Xu, Pengpeng; Ge, Jianhua; Guo, Xuetao

    2016-03-01

    A cube-like Ag@AgCl-doped TiO2/fly ash cenosphere composite (denoted Ag@AgCl-TiO2/fly ash cenospheres) was successfully synthesized via a two-step approach. The as-prepared catalysts were characterized by scanning electron microscopy, X-ray diffraction, diffuse reflectance ultraviolet-visible spectroscopy, Brunauer-Emmett-Teller, and X-ray photoelectron spectroscopy. The photocatalytic experiment showed that the rhodamine B degradation rate with Ag@AgCl-TiO2/fly ash cenospheres was 1.56 and 1.33 times higher than that with AgCl-TiO2/fly ash cenospheres and Ag@AgCl, respectively. The degradation ratio of rhodamine B with Ag@AgCl-TiO2/fly ash cenospheres was nearly 100% within 120 min under visible light. Analysis of active species indicated that radO2- and h+ dominated the reaction, and radOH participated in the photocatalytic reactions as an active species. A mechanism for the photocatalytic degradation by the Ag@AgCl-TiO2/fly-ash cenospheres was also proposed based on the experimental results.

  10. Effect of SnO, MgO and Ag2O Mix-doping on the Formation and Superconducting Properties of Bi-2223 Ag/tapes

    NASA Astrophysics Data System (ADS)

    Lu, X. Y.; Yi, D.; Chen, H.; Nagata, A.

    The Ag/tapes with the composition Bi1.8Pb0.4Sr1.9Ca2.1Cu3.5Oy + x wt% SnO + y wt% MgO + z wt% Ag2O (x = 0, 0.2, 0.4; y = 0, 0.2; z = 0, 0.2) were prepared by sintering at 835°C for 120 h after partial-melting at 845°C for 1 h. The individual SnO doping, SnO and Ag2O mix-doping, and SnO and MgO mix-doping all decrease the conversion of Bi-2212 phase to Bi-2223 phase. The tape with individual 0.4 wt% SnO doping shows the lowest conversion and the lowest critical current density. However, the SnO, MgO and Ag2O mix-doping increase the conversion of Bi-2212 phase to Bi-2223 phase. The tape with 0.2 wt% SnO, 0.2 wt% MgO and 0.2 wt%Ag2O mix-doping shows the highest proportion of Bi-2223 phase and the highest critical current density.

  11. Influence of Ag doping concentration on structural and optical properties of CdS thin film

    SciTech Connect

    Kumar, Pragati; Saxena, Nupur; Gupta, Vinay; Agarwal, Avinash

    2015-05-15

    This work shows the influence of Ag concentration on structural properties of pulsed laser deposited nanocrystalline CdS thin film. X-ray photoelectron spectroscopy (XPS) studies confirm the dopant concentration in CdS films and atomic concentration of elements. XPS studies show that the samples are slightly sulfur deficient. GAXRD scan reveals the structural phase transformation from cubic to hexagonal phase of CdS without appearance of any phase of CdO, Ag{sub 2}O or Ag{sub 2}S suggesting the substitutional doping of Ag ions. Photoluminescence studies illustrate that emission intensity increases with increase in dopant concentration upto 5% and then decreases for higher dopant concentration.

  12. Radiative properties of n-ZnSe single crystals doped with Ag

    NASA Astrophysics Data System (ADS)

    Ivanova, Galina N.; Kasiyan, Vladimir A.; Nedeoglo, Dmitri D.; Nedeoglo, Natalia D.

    1999-05-01

    Ag impurity exists in ZnSe as interstitial atoms Agi and substitution atoms Agzn. The structure of photoluminescence (PL) spectra of the ZnSe crystals doped with Ag depends on quantitative ratio of these defects in the crystal. Evidently, this is a cause of significant difference of PL spectra of n-ZnSe crystals doped with Ag either in the growing process or in the process of annealing in the Zn+Ag melt. The questions of electron configuration and of a charge state of Ag impurity in ZnSe is discussed also in the literature. Theoretical analysis of this problem allows the existence possibility of Ag multi-charged states in ZnSe, while the authors assume that Ag in ZnSe exists only in the single-charged state with d10-electron configuration. In this work, the PL spectra and photoluminescence excitation (PLE) spectra of n-ZnSe single crystals annealed in Zn melt with Ag contents from 0.1 at.% to 20 at.% are investigated in the temperature range from 82 K to 300 K. The annealing was made at the temperature of 950 degrees Celsius during the 100 h. At the termination of annealing the quartz ampoules were immersed in cold water for the sharp cooling of the samples. Luminescence was excited either by radiation of LGI-21 laser with the wavelength of 337 nm (Eexcit equals 3.68 eV) or by monochromatic light from VSU-1 monochromator with the halogen lamp. The investigation of PL spectra was carried out using MDR-23 monochromator with the line dispersion of 1.4 nm/mm in the wavelength region from 430 nm to 700 nm.

  13. Transport and pinning properties of Ag-doped FeSe0.94

    NASA Astrophysics Data System (ADS)

    Nazarova, E.; Balchev, N.; Nenkov, K.; Buchkov, K.; Kovacheva, D.; Zahariev, A.; Fuchs, G.

    2015-02-01

    We investigated the superconducting transition and the pinning properties of undoped and Ag-doped FeSe0.94 at magnetic fields up to 14 T. We established that, due to Ag addition, the hexagonal phase formation in melted FeSe0.94 samples is suppressed and the grain connectivity is strongly improved. The obtained superconducting zero-field transition becomes sharp, with a transition width below 1 K. Tc and the upper critical field were found to increase, while the normal-state resistivity was significantly reduced, becoming comparable with that of FeSe single crystals. In addition, a considerable magnetoresistance was observed due to Ag doping. The resistive transition of undoped and Ag-doped FeSe0.94 is dominated by a thermally activated flux flow. From the activation energy U versus H dependence, we found a crossover from single-vortex pinning to a collective-creep pinning behavior by increasing the magnetic field.

  14. 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

    2015-10-01

    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. PMID:26375476

  15. Low-Temperature Facile Synthesis of Sb-Doped p-Type ZnO Nanodisks and Its Application in Homojunction Light-Emitting Diode.

    PubMed

    Baek, Sung-Doo; Biswas, Pranab; Kim, Jong-Woo; Kim, Yun Cheol; Lee, Tae Il; Myoung, Jae-Min

    2016-05-25

    This study explores low-temperature solution-process-based seed-layer-free ZnO p-n homojunction light-emitting diode (LED). In order to obtain p-type ZnO nanodisks (NDs), antimony (Sb) was doped into ZnO by using a facile chemical route at 120 °C. The X-ray photoelectron spectra indicated the presence of (SbZn-2VZn) acceptor complex in the Sb-doped ZnO NDs. Using these NDs as freestanding templates, undoped n-type ZnO nanorods (NRs) were epitaxially grown at 95 °C to form ZnO p-n homojunction. The homojunction with a turn-on voltage of 2.5 V was found to be significantly stable up to 100 s under a constant voltage stress of 5 V. A strong orange-red emission was observed by the naked eye under a forward bias of 5 V. The electroluminescence spectra revealed three major peaks at 400, 612, and 742 nm which were attributed to the transitions from Zni to VBM, from Zni to Oi, and from VO to VBM, respectively. The presence of these deep-level defects was confirmed by the photoluminescence of ZnO NRs. This study paves the way for future applications of ZnO homojunction LEDs using low-temperature and low-cost solution processes with the controlled use of native defects. PMID:27160161

  16. Enhanced gas sensing performance of Li-doped ZnO nanoparticle film by the synergistic effect of oxygen interstitials and oxygen vacancies

    NASA Astrophysics Data System (ADS)

    Zhao, Jianwei; Xie, Changsheng; Yang, Li; Zhang, Shunping; Zhang, Guozhu; Cai, Ziming

    2015-03-01

    Li doped ZnO (Zn1-xLixO) nanoparticles with different content were synthesized. X-ray photoelectron spectroscopy (XPS) indicated that the ratio of oxygen to zinc for ZnO increased with increasing of Li content from x = 0 to 0.2, which had been attributed to the introduction of oxygen interstitial by Li dopant. The sensing performance and the temperature-dependent conductivity were investigated. It is observed that Li doped ZnO showed higher sensitivity and selectivity compared to the undoped ZnO. The 0.1 Li doped ZnO performed the maximum responses of 71.5 and 40.2 for 100 ppm methanol and formaldehyde, respectively, at 350 °C. The research showed that the oxygen vacancies served as active sites which supported the oxygen adsorption and reaction, oxygen interstitials served as active sites to oxidize the reducing gases and produce electrons. The enhanced sensing performance of Li doped ZnO was attributed to the synergistic effect of oxygen interstitials and oxygen vacancies.

  17. Controlled growth of ZnO nanorods on textured silicon wafer and the application for highly effective and recyclable SERS substrate by decorating Ag nanoparticles

    SciTech Connect

    Tao, Q.; Li, S.; Zhang, Q.Y. Kang, D.W.; Yang, J.S.; Qiu, W.W.; Liu, K.

    2014-06-01

    Highlights: • The growth behavior of ZnO nanorods (NRs) is studied on the textured Si wafer. • A new surface-enhanced Raman scattering (SERS) substrate has been achieved by assembling Ag nanoparticles onto the ZnO NRs. • The SERS substrate exhibits good performance in terms of high sensitivity, good reproducibility and recyclability. - Abstract: Based on the study of growth behavior of ZnO nanorods on the textured Si wafer, a new three-dimensional surface-enhanced Raman scattering substrate has been achieved by assembling Ag nanoparticles onto the ZnO nanorods to form a radial plasmonic nanostructure. It is found that the new substrate exhibits good performance in terms of high sensitivity and good reproducibility for surface-enhanced Raman scattering. The determined enhancement factor is in the order of 10{sup 7} and the Raman spectra exhibit the remarkable consistency with the deviation below 5.0%. Compared to the substrate fabricated with ZnO nanorod array on the flat Si wafer, the new substrates have the higher utility of excitation light. Meanwhile, the new substrate is demonstrated to be recyclable after the irradiation of ultraviolet light.

  18. Enhancement of photo-response via surface plasmon resonance induced by Ag nano-particles embedded in ZnO

    NASA Astrophysics Data System (ADS)

    Li, Gaoming; Zhang, Jingwen; Chen, Guangde; Ye, Honggang; Duan, Xiangyang; Hou, Xun

    2016-09-01

    Surface plasmon resonance can be exploited to improve the performance of the photodetectors. However, it may cause the increase of dark current as a side effect. The enhancement of responsivity is highly dependent on the device structure involving SPR and the situations of the metal nano-particles. In this paper, we reported the responsivity enhancement of the ZnO UV detectors with SPR based on a structure in which Ag nano-particles are embedded in ZnO film, without the apparent increase of dark current. We found that the characteristic wavelength for SPR absorption is 380 nm, well predicted by Mie theory. And the spectral responsivity peak value increases from 472 mA/W to 10.522 A/W, by 22.3 times. The good matching between enhancement spectra and SPR absorption spectra confirms that the responsivity enhancement is resulted from SPR. Our results are of great importance in improving the photodetectors based on SPR effects, which may be widely used in light detection.

  19. Effect of Al and Fe doping in ZnO on magnetic and magneto-transport properties

    NASA Astrophysics Data System (ADS)

    Kumar, Santosh; Deepika; Tripathi, Malvika; Vaibhav, Pratyush; Kumar, Aman; Kumar, Ritesh; Choudhary, R. J.; Phase, D. M.

    2016-12-01

    The structural, magnetic and magneto-transport of undoped ZnO, Zn0.97Al0.03O, Zn0.95Fe0.05O and Zn0.92Al0.03Fe0.05O thin films grown on Si(100) substrate using pulsed laser deposition were investigated. The single phase nature of the films is confirmed by X-ray diffraction and Raman spectroscopy measurements. The possibility of Fe metal cluster in Fe doped/co-doped films is ruled out by Fe 2p core level photoelectron spectra. From O 1s core level spectra it is observed that oxygen vacancy is present in all the films. The undoped ZnO film shows magnetic ordering below ∼175 K, whereas Fe doped/codoped samples show magnetic ordering even at 300 K. The Al doped sample reveals paramagnetic behavior. The magneto-transport measurements suggest that the mobile carriers undergo exchange interaction with local magnetic moments.

  20. Ag doped silicon nitride nanocomposites for embedded plasmonics

    NASA Astrophysics Data System (ADS)

    Bayle, M.; Bonafos, C.; Benzo, P.; Benassayag, G.; Pécassou, B.; Khomenkova, L.; Gourbilleau, F.; Carles, R.

    2015-09-01

    The localized surface plasmon-polariton resonance (LSPR) of noble metal nanoparticles (NPs) is widely exploited for enhanced optical spectroscopies of molecules, nonlinear optics, photothermal therapy, photovoltaics, or more recently in plasmoelectronics and photocatalysis. The LSPR frequency depends not only of the noble metal NP material, shape, and size but also of its environment, i.e., of the embedding matrix. In this paper, Ag-NPs have been fabricated by low energy ion beam synthesis in silicon nitride (SiNx) matrices. By coupling the high refractive index of SiNx to the relevant choice of dielectric thickness in a SiNx/Si bilayer for an optimum antireflective effect, a very sharp plasmonic optical interference is obtained in mid-range of the visible spectrum (2.6 eV). The diffusion barrier property of the host SiNx matrix allows for the introduction of a high amount of Ag and the formation of a high density of Ag-NPs that nucleate during the implantation process. Under specific implantation conditions, in-plane self-organization effects are obtained in this matrix that could be the result of a metastable coarsening regime.