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Sample records for ag-doped zno thin

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. Influence of oxygen partial pressure on the physical properties of Ag doped NiO thin films

    NASA Astrophysics Data System (ADS)

    Reddy, Y. Ashok Kumar; Reddy, A. Sivasankar; Reddy, P. Sreedhara

    2013-06-01

    Ag doped p-type NiO thin films were successfully deposited by DC reactive magnetron sputtering technique at different oxygen partial pressures in the range 1 × 10-4 - 9 × 10-4 mbar. The structural and morphological properties of the films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). All the deposited films were of polycrystalline nature and exhibited cubic structure with preferential growth. The morphological studies revealed that the surface roughness was increased with increasing oxygen partial pressure up to 5 × 10-4 mbar and decreased at higher oxygen partial pressures.

  8. Thermally induced effect on sub-band gap absorption in Ag doped CdSe thin films

    NASA Astrophysics Data System (ADS)

    Kaur, Jagdish; Sharma, Kriti; Bharti, Shivani; Tripathi, S. K.

    2015-05-01

    Thin films of Ag doped CdSe have been prepared by thermal evaporation using inert gas condensation (IGC) method taking Argon as inert gas. The prepared thin films are annealed at 363 K for one hour. The sub-band gap absorption spectra in the as deposited and annealed thin films have been studied using constant photocurrent method (CPM). The absorption coefficient in the sub-band gap region is described by an Urbach tail in both as deposited and annealed thin films. The value of Urbach energy and number density of trap states have been calculated from the absorption coefficient in the sub-band gap region which have been found to increase after annealing treatment indicating increase in disorderness in the lattice. The energy distribution of the occupied density of states below Fermi level has also been studied using derivative procedure of absorption coefficient.

  9. 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

  10. 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.

  11. 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.

  12. Structural and optical properties of Ag-doped copper oxide thin films on polyethylene napthalate substrate prepared by low temperature microwave annealing

    SciTech Connect

    Das, Sayantan; Alford, T. L.

    2013-06-28

    Silver doped cupric oxide thin films are prepared on polyethylene naphthalate (flexible polymer) substrates. Thin films Ag-doped CuO are deposited on the substrate by co-sputtering followed by microwave assisted oxidation of the metal films. The low temperature tolerance of the polymer substrates led to the search for innovative low temperature processing techniques. Cupric oxide is a p-type semiconductor with an indirect band gap and is used as selective absorption layer solar cells. X-ray diffraction identifies the CuO phases. Rutherford backscattering spectrometry measurements confirm the stoichiometry of each copper oxide formed. The surface morphology is determined by atomic force microscopy. The microstructural properties such as crystallite size and the microstrain for (-111) and (111) planes are calculated and discussed. Incorporation of Ag led to the lowering of band gap in CuO. Consequently, it is determined that Ag addition has a strong effect on the structural, morphological, surface, and optical properties of CuO grown on flexible substrates by microwave annealing. Tauc's plot is used to determine the optical band gap of CuO and Ag doped CuO films. The values of the indirect and direct band gap for CuO are found to be 2.02 eV and 3.19 eV, respectively.

  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. Microstructure and temperature dependence of microwave penetration depth of Ag doped Y 1Ba 2Cu 3O 7- x thin films

    NASA Astrophysics Data System (ADS)

    Kaur, Davinder; Pai, S. P.; Jesudasan, J.; Pinto, R.

    2004-06-01

    We report the measurements of magnetic penetration depth λ( T) of Ag-doped YBa 2Cu 3O 7- δ (YBCO) thin films in the thickness range 1500-4000 A and temperature range 18-88 K. The films are in situ grown by laser ablation on <1 0 0> LaAlO 3 substrates. The penetration depth measurements are performed by microstrip resonator technique. A correlation of λ( T) with the film microstructure observed with atomic force microscopy has shown that λ( T) depends critically on the film microstructure. Temperature dependence of magnetic penetration depth has also been studied for best quality films. The experimental results are discussed in terms of BCS theory (s-wave pairing) and d-wave Pairing with and without unitary scattering. The results are found to be best fitted to the d-wave model with unitary scattering limit. Near Tc, we have also compare the (3D) XY critical regime and the Ginzburg-Landau (GL) behaviour.

  15. Thermally deposited Ag-doped CdS thin film transistors with high-k rare-earth oxide Nd{sub 2}O{sub 3} as gate dielectric

    SciTech Connect

    Gogoi, P.

    2013-03-15

    The performance of thermally deposited CdS thin film transistors doped with Ag has been reported. Ag-doped CdS thin films have been prepared using chemical method. High dielectric constant rare earth oxide Nd{sub 2}O{sub 3} has been used as gate insulator. The thin film trasistors are fabricated in coplanar electrode structure on ultrasonically cleaned glass substrates with a channel length of 50 {mu}m. The thin film transistors exhibit a high mobility of 4.3 cm{sup 2} V{sup -1} s{sup -1} and low threshold voltage of 1 V. The ON-OFF ratio of the thin film transistors is found as 10{sup 5}. The TFTs also exhibit good transconductance and gain band-width product of 1.15 Multiplication-Sign 10{sup -3} mho and 71 kHz respectively.

  16. 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.

  17. 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.

  18. Dye-Sensitization Of Nanocrystalline ZnO Thin Films

    NASA Astrophysics Data System (ADS)

    Ajimsha, R. S.; Tyagi, M.; Das, A. K.; Misra, P.; Kukreja, L. M.

    2010-12-01

    Nannocrystalline and nanoporus thin films of ZnO were synthesized on glass substrates by using wet chemical drop casting method. X-ray diffraction measurements on these samples confirmed the formation of ZnO nanocrystallites in hexagonal wurtzite phase with mean size of ˜20 nm. Photo sensitization of these nanostructured ZnO thin films was carried out using three types of dyes Rhodamine 6 G, Chlorophyll and cocktail of Rhodamine 6 G and Chlorophyll in 1:1 ratio. Dye sensitized ZnO thin films showed enhanced optical absorption in visible spectral region compared to the pristine ZnO thin films.

  19. Dye-Sensitization Of Nanocrystalline ZnO Thin Films

    SciTech Connect

    Ajimsha, R. S.; Tyagi, M.; Das, A. K.; Misra, P.; Kukreja, L. M.

    2010-12-01

    Nannocrystalline and nanoporus thin films of ZnO were synthesized on glass substrates by using wet chemical drop casting method. X-ray diffraction measurements on these samples confirmed the formation of ZnO nanocrystallites in hexagonal wurtzite phase with mean size of {approx}20 nm. Photo sensitization of these nanostructured ZnO thin films was carried out using three types of dyes Rhodamine 6 G, Chlorophyll and cocktail of Rhodamine 6 G and Chlorophyll in 1:1 ratio. Dye sensitized ZnO thin films showed enhanced optical absorption in visible spectral region compared to the pristine ZnO thin films.

  20. Synthesis and characterization of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Anilkumar T., S.; Girija M., L.; Venkatesh, J.

    2016-05-01

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

  1. 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.

  2. ZnO Thin Film Electronics for More than Displays

    NASA Astrophysics Data System (ADS)

    Ramirez, Jose Israel

    Zinc oxide thin film transistors (TFTs) are investigated in this work for large-area electronic applications outside of display technology. A constant pressure, constant flow, showerhead, plasma-enhanced atomic layer deposition (PEALD) process has been developed to fabricate high mobility TFTs and circuits on rigid and flexible substrates at 200 °C. ZnO films and resulting devices prepared by PEALD and pulsed laser deposition (PLD) have been compared. Both PEALD and PLD ZnO films result in densely packed, polycrystalline ZnO thin films that were used to make high performance devices. PEALD ZnO TFTs deposited at 300 °C have a field-effect mobility of ˜ 40 cm2/V-s (and > 20 cm2/V-S deposited at 200 °C). PLD ZnO TFTs, annealed at 400 °C, have a field-effect mobility of > 60 cm2/V-s (and up to 100 cm2/V-s). Devices, prepared by either technique, show high gamma-ray radiation tolerance of up to 100 Mrad(SiO2) with only a small radiation-induced threshold voltage shift (VT ˜ -1.5 V). Electrical biasing during irradiation showed no enhanced radiation-induced effects. The study of the radiation effects as a function of material stack thicknesses revealed the majority of the radiation-induced charge collection happens at the semiconductor-passivation interface. A simple sheet-charge model at that interface can describe the radiation-induced charge in ZnO TFTs. By taking advantage of the substrate-agnostic process provided by PEALD, due to its low-temperature and excellent conformal coatings, ZnO electronics were monolithically integrated with thin-film complex oxides. Application-based examples where ZnO electronics provide added functionality to complex oxide-based devices are presented. In particular, the integration of arrayed lead zirconate titanate (Pb(Zr, Ti)O3 or PZT) thin films with ZnO electronics for microelectromechanical systems (MEMs) and deformable mirrors is demonstrated. ZnO switches can provide voltage to PZT capacitors with fast charging and slow

  3. A high power ZnO thin film piezoelectric generator

    NASA Astrophysics Data System (ADS)

    Qin, Weiwei; Li, Tao; Li, Yutong; Qiu, Junwen; Ma, Xianjun; Chen, Xiaoqiang; Hu, Xuefeng; Zhang, Wei

    2016-02-01

    A highly efficient and large area piezoelectric ZnO thin film nanogenerator (NG) was fabricated. The ZnO thin film was deposited onto a Si substrate by pulsed laser ablation at a substrate temperature of 500 °C. The deposited ZnO film exhibited a preferred c-axis orientation and a high piezoelectric value of 49.7 pm/V characterized using Piezoelectric Force Microscopy (PFM). Thin films of ZnO were patterned into rectangular power sources with dimensions of 0.5 × 0.5 cm2 with metallic top and bottom electrodes constructed via conventional semiconductor lithographic patterning processes. The NG units were subjected to periodic bending/unbending motions produced by mechanical impingement at a fixed frequency of 100 Hz at a pressure of 0.4 kg/cm2. The output electrical voltage, current density, and power density generated by one ZnO NG were recorded. Values of ∼95 mV, 35 μA cm-2 and 5.1 mW cm-2 were recorded. The level of power density is typical to that produced by a PZT NG on a flexible substrate. Higher energy NG sources can be easily created by adding more power units either in parallel or in series. The thin film ZnO NG technique is highly adaptable with current semiconductor processes, and as such, is easily integrated with signal collecting circuits that are compatible with mass production. A typical application would be using the power harvested from irregular human foot motions to either to operate blue LEDs directly or to drive a sensor network node in mille-power level without any external electric source and circuits.

  4. Role of ZnO thin film in the vertically aligned growth of ZnO nanorods by chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Son, Nguyen Thanh; Noh, Jin-Seo; Park, Sungho

    2016-08-01

    The effect of ZnO thin film on the growth of ZnO nanorods was investigated. ZnO thin films were sputter-deposited on Si substrate with varying the thickness. ZnO nanorods were grown on the thin film using a chemical bath deposition (CBD) method at 90 °C. The ZnO thin films showed granular structure and vertical roughness on the surface, which facilitated the vertical growth of ZnO nanorods. The average grain size and the surface roughness of ZnO film increased with an increase in film thickness, and this led to the increase in both the average diameter and the average length of vertically grown ZnO nanorods. In particular, it was found that the average diameter of ZnO nanorods was very close to the average grain size of ZnO thin film, confirming the role of ZnO film as a seed layer for the vertical growth of ZnO nanorods. The CBD growth on ZnO seed layers may provide a facile route to engineering vertically aligned ZnO nanorod arrays.

  5. Surface Engineering of ZnO Thin Film for High Efficiency Planar Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Tseng, Zong-Liang; Chiang, Chien-Hung; Wu, Chun-Guey

    2015-09-01

    Sputtering made ZnO thin film was used as an electron-transport layer in a regular planar perovskite solar cell based on high quality CH3NH3PbI3 absorber prepared with a two-step spin-coating. An efficiency up to 15.9% under AM 1.5G irradiation is achieved for the cell based on ZnO film fabricated under Ar working gas. The atmosphere of the sputtering chamber can tune the surface electronic properties (band structure) of the resulting ZnO thin film and therefore the photovoltaic performance of the corresponding perovskite solar cell. Precise surface engineering of ZnO thin film was found to be one of the key steps to fabricate ZnO based regular planar perovskite solar cell with high power conversion efficiency. Sputtering method is proved to be one of the excellent techniques to prepare ZnO thin film with controllable properties.

  6. 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

  7. Surface Morphological and Nanomechanical Properties of PLD-Derived ZnO Thin Films

    PubMed Central

    2008-01-01

    This study reports the surface roughness and nanomechanical characteristics of ZnO thin films deposited on the various substrates, obtained by means of atomic force microscopy (AFM), nanoindentation and nanoscratch techniques. ZnO thin films are deposited on (a- and c-axis) sapphires and (0001) 6H-SiC substrates by using the pulsed-laser depositions (PLD) system. Continuous stiffness measurements (CSM) technique is used in the nanoindentation tests to determine the hardness and Young’s modulus of ZnO thin films. The importance of the ratio (H/Efilm) of elastic to plastic deformation during nanoindentation of ZnO thin films on their behaviors in contact-induced damage during fabrication of ZnO-based devices is considered. In addition, the friction coefficient of ZnO thin films is also presented here.

  8. 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.

  9. Synthesis and annealing study of RF sputtered ZnO thin film

    NASA Astrophysics Data System (ADS)

    Singh, Shushant Kumar; Sharma, Himanshu; Singhal, R.; Kumar, V. V. Siva; Avasthi, D. K.

    2016-05-01

    In this paper, we have investigated the annealing effect on optical and structural properties of ZnO thin films, synthesized by RF magnetron sputtering. ZnO thin films were deposited on glass and silicon substrates simultaneously at a substrate temperature of 300 °C using Argon gas in sputtering chamber. Thickness of as deposited ZnO thin film was found to be ~155 nm, calculated by Rutherford backscattering spectroscopy (RBS). These films were annealed at 400 °C and 500 °C temperature in the continuous flow of oxygen gas for 1 hour in tube furnace. X-ray diffraction analysis confirmed the formation of hexagonal wurtzite structure of ZnO thin film along the c-axis (002) orientation. Transmittance of thin films was increased with increasing the annealing temperature estimated by UV-visible transmission spectroscopy. Quality and texture of the thin films were improved with annealing temperature, estimated by Raman spectroscopy.

  10. Influence of stress in ZnO thin films on its biosensing application.

    PubMed

    Saha, Shibu; Tomar, Monika; Gupta, Vinay

    2015-11-01

    Highly c-axis oriented zinc oxide (ZnO) thin films deposited by radio frequency (RF) magnetron sputtering, under varying ambient atmosphere (oxygen and argon reactive gas mixture), were studied for biosensing application. The as-grown ZnO thin films were found to be under compressive stress. Glucose oxidase was chosen as model enzyme for studying biosensing response properties of the ZnO thin films. The present study reveals a good correlation between stress induced during thin film growth and its biosensing response characteristic. The bio-electrodes based on ZnO thin films which are under the influence of higher stress, show better sensitivity and higher enzyme loading along with a prolonged shelf life. The study highlights the importance of physical properties of thin film matrix on its biosensing application. PMID:26320716

  11. Laser nanostructuring of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Nedyalkov, N.; Koleva, M.; Nikov, R.; Atanasov, P.; Nakajima, Y.; Takami, A.; Shibata, A.; Terakawa, M.

    2016-06-01

    In this work, results on laser processing of thin zinc oxide films deposited on metal substrate are presented. ZnO films are obtained by classical nanosecond pulsed laser deposition method in oxygen atmosphere on tantalum substrate. The produced films are then processed by nanosecond laser pulses at wavelength of 355 nm. The laser processing parameters and the film thickness are varied and their influence on the fabricated structures is estimated. The film morphology after the laser treatment is found to depend strongly on the laser fluence as two regimes are defined. It is shown that at certain conditions (high fluence regime) the laser treatment of the film leads to formation of a discrete nanostructure, composed of spherical like nanoparticles with narrow size distribution. The dynamics of the melt film on the substrate and fast cooling are found to be the main mechanisms for fabrication of the observed structures. The demonstrated method is an alternative way for direct fabrication of ZnO nanostructures on metal which can be easy implemented in applications as resistive sensor devices, electroluminescent elements, solar cell technology.

  12. Buffer-enhanced room-temperature growth and characterization of epitaxial ZnO thin films

    SciTech Connect

    Sasaki, Atsushi; Hara, Wakana; Matsuda, Akifumi; Tateda, Norihiro; Otaka, Sei; Akiba, Shusaku; Saito, Keisuke; Yodo, Tokuo; Yoshimoto, Mamoru

    2005-06-06

    The room-temperature epitaxial growth of ZnO thin films on NiO buffered sapphire (0001) substrate was achieved by using the laser molecular-beam-epitaxy method. The obtained ZnO films had the ultrasmooth surface reflecting the nanostepped structure of the sapphire substrate. The crystal structure at the surface was investigated in situ by means of coaxial impact-collision ion scattering spectroscopy. It was proved that the buffer-enhanced epitaxial ZnO thin films grown at room temperature had +c polarity, while the polarity of high-temperature grown ZnO thin films on the sapphire was -c. Photoluminescence spectra at room temperature were measured for the epitaxial ZnO films, showing only the strong ultraviolet emission near 380 nm.

  13. Comparative study of ZnO nanorods and thin films for chemical and biosensing applications and the development of ZnO nanorods based potentiometric strontium ion sensor

    NASA Astrophysics Data System (ADS)

    Khun, K.; Ibupoto, Z. H.; Chey, C. O.; Lu, Jun.; Nur, O.; Willander, M.

    2013-03-01

    In this study, the comparative study of ZnO nanorods and ZnO thin films were performed regarding the chemical and biosensing properties and also ZnO nanorods based strontium ion sensor is proposed. ZnO nanorods were grown on gold coated glass substrates by the hydrothermal growth method and the ZnO thin films were deposited by electro deposition technique. ZnO nanorods and thin films were characterised by field emission electron microscopy [FESEM] and X-ray diffraction [XRD] techniques and this study has shown that the grown nanostructures are highly dense, uniform and exhibited good crystal quality. Moreover, transmission electron microscopy [TEM] was used to investigate the quality of ZnO thin film and we observed that ZnO thin film was comprised of nano clusters. ZnO nanorods and thin films were functionalised with selective strontium ionophore salicylaldehyde thiosemicarbazone [ST] membrane, galactose oxidase, and lactate oxidase for the detection of strontium ion, galactose and L-lactic acid, respectively. The electrochemical response of both ZnO nanorods and thin films sensor devices was measured by using the potentiometric method. The strontium ion sensor has exhibited good characteristics with a sensitivity of 28.65 ± 0.52 mV/decade, for a wide range of concentrations from 1.00 × 10-6 to 5.00 × 10-2 M, selectivity, reproducibility, stability and fast response time of 10.00 s. The proposed strontium ion sensor was used as indicator electrode in the potentiometric titration of strontium ion versus ethylenediamine tetra acetic acid [EDTA]. This comparative study has shown that ZnO nanorods possessed better performance with high sensitivity and low limit of detection due to high surface area to volume ratio as compared to the flat surface of ZnO thin films.

  14. Selective growth of ZnO thin film nanostructures: Structure, morphology and tunable optical properties

    NASA Astrophysics Data System (ADS)

    Krishnakanth, Katturi Naga; Rajesh, Desapogu; Sunandana, C. S.

    2016-05-01

    The ZnO nanostructures (spherical, rod shape) have been successfully fabricated via a thermal evaporation followed by dip coating method. The pure, doped ZnO thin films were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM) and UV-Vis spectroscopy, respectively. A possible growth mechanism of the spherical, rod shape ZnO nanostructures are discussed. XRD patterns revealed that all films consist of pure ZnO phase and were well crystallized with preferential orientation towards (002) direction. Doping by PVA, PVA+Cu has effective role in the enhancement of the crystalline quality and increases in the band gap.

  15. ZnO Thin Films Deposited on Textile Material Substrates for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Duta, L.; Popescu, A. C.; Dorcioman, G.; Mihailescu, I. N.; Stan, G. E.; Zgura, I.; Enculescu, I.; Dumitrescu, I.

    We report on the coating with ZnO adherent thin films of cotton woven fabrics by Pulsed laser deposition technique in order to obtain innovative textile materials, presenting protective effects against UV radiations and antifungal action.

  16. Effect of ZnO Nanostructured Thin Films on Pseudomonas Putida Cell Division

    NASA Astrophysics Data System (ADS)

    Ivanova, I.; Lukanov, A.; Angelov, O.; Popova, R.; Nichev, H.; Mikli, V.; Dimova-Malinovska, Doriana; Dushkin, C.

    In this report we study the interaction between the bacteria Pseudomonas putida and nanostructured ZnO and ZnO:H thin films prepared by magnetron sputtering of a ZnO target. The nanostructured ZnO and ZnO:H thin films possess some biological-active properties when in contact with bacteria. Our experimental data show that these films have no destructive effect on the cell division of Pseudomonas putida in poor liquid medium and can be applied in biosensor devices.

  17. 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}.

  18. 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.

  19. Improved performance of Ag-doped TiO2 synthesized by modified sol-gel method as photoanode of dye-sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Gupta, Arun Kumar; Srivastava, Pankaj; Bahadur, Lal

    2016-08-01

    Ag-doped TiO2 with Ag content ranging from 1 to 7 mol% was synthesized by a modified sol-gel route, and its performance as the photoanode of dye-sensitized solar cells (DSSCs) was compared with undoped TiO2 photoanode. Titanium(IV)isopropoxide was used as precursor and hexamethylenetetramine as the capping agent. XRD results show the formation of TiO2 nanoparticles with an average crystallite size of 5 nm (1 % Ag-doped TiO2) and 9 nm (undoped TiO2), respectively. The TiO2 nanopowder was used to prepare its thin film photoelectrode using doctor's blade method. Significant improvement in light-to-energy conversion efficiency was achieved when thin films of 1 % Ag-doped TiO2 were applied as photoanode in DSSC taking N719 as the sensitizer dye. As evidenced by EIS measurements, the electron lifetime of DSSC with Ag-doped TiO2 increased from 1.33 (for undoped TiO2) to 2.05 ms. The short-circuit current density ( J sc), open-circuit voltage ( V oc), fill factor (FF) and the overall energy conversion efficiency ( η) were 1.07 mA cm-2, 0.72 V, 0.73 and 0.40 %, respectively, with the use of 1 % Ag-doped TiO2 photoanode, whereas with undoped TiO2 under similar conditions, J sc = 0.63 mA cm-2, V oc = 0.70 V, fill factor 0.45 and conversion efficiency 0.14 % could be obtained. Therefore, compared with the reference DSSC containing an undoped TiO2 photoanode, the power conversion efficiency of the cell based on Ag-doped TiO2 has been remarkably enhanced by ~70 %. The substantial improvement in the device performance is attributed to the reduced band-gap energy, retarded charge recombination and greater surface coverage of the sensitizing dye over Ag-doped TiO2, which ultimately resulted in improved IPCE, J SC and η values.

  20. Pulsed-laser deposition of ZnO and related compound thin films for optoelectronics

    NASA Astrophysics Data System (ADS)

    Millon, Eric; Perrière, Jacques; Tricot, Sylvain; Boulmer-Leborgne, Chantal

    2008-05-01

    ZnO is a wide and direct band-gap material (3.37 eV at room temperature) making this compound very suitable for UV photodetector applications as well as for UV and blue light emitting devices. As an electronic conductor, ZnO may be used as transparent and conducting electrodes for flat panel displays and solar cells. ZnO doped with various atoms can also lead to new or enhanced functional properties. For example, doping with Al, Ga, In, Si or H allows decreasing its resistivity to below 10-4 Ω.cm, while keeping the high optical transparency. Rare-earth doped ZnO thin films have been studied for optics and optoelectronics such as visible or infrared emitting devices, planar optical waveguide amplifiers. Ferromagnetic semiconductors can be obtained by doping ZnO with transition metal atoms (Mn, Co, Ni...) that could be used as spin injectors in spintronics. These new and exciting properties of pure and doped ZnO request the use of thin films or multilayer structures. ZnO thin film growth by pulsed-laser deposition (PLD) with or without any dopants or alloyed atoms has been intensively studied. In this paper, we will review the aspects of ZnO thin films grown by PLD, in order to prepare dense, stoichiometric and crystalline epitaxied ZnO layers or to form nanocrystalline films. Then, the optical and electrical properties will be discussed with a special emphasis on the growth conditions in relation to the physical properties for applications in p-n junctions, light emission devices, spintronics and bandgap tuning.

  1. Ohmic-Rectifying Conversion of Ni Contacts on ZnO and the Possible Determination of ZnO Thin Film Surface Polarity

    PubMed Central

    Saw, Kim Guan; Tneh, Sau Siong; Tan, Gaik Leng; Yam, Fong Kwong; Ng, Sha Shiong; Hassan, Zainuriah

    2014-01-01

    The current-voltage characteristics of Ni contacts with the surfaces of ZnO thin films as well as single crystal (0001) ZnO substrate are investigated. The ZnO thin film shows a conversion from Ohmic to rectifying behavior when annealed at 800°C. Similar findings are also found on the Zn-polar surface of (0001) ZnO. The O-polar surface, however, only shows Ohmic behavior before and after annealing. The rectifying behavior observed on the Zn-polar and ZnO thin film surfaces is associated with the formation of nickel zinc oxide (Ni1-xZnxO, where x = 0.1, 0.2). The current-voltage characteristics suggest that a p-n junction is formed by Ni1-xZnxO (which is believed to be p-type) and ZnO (which is intrinsically n-type). The rectifying behavior for the ZnO thin film as a result of annealing suggests that its surface is Zn-terminated. Current-voltage measurements could possibly be used to determine the surface polarity of ZnO thin films. PMID:24466144

  2. Influence of surface defects in ZnO thin films on its biosensing response characteristic

    SciTech Connect

    Saha, Shibu; Gupta, Vinay

    2011-09-15

    Highly c-axis oriented zinc oxide (ZnO) thin films deposited by rf magnetron sputtering under varying processing pressure (20-50 mT) in a reactive gas mixture of argon and oxygen were studied for biosensing application. The as-deposited ZnO thin films were in a state of compressive stress having defects related to interstitial Zn and antisite oxygen. Glucose oxidase has been chosen as the model enzyme in the present study and was immobilized on the surface of ZnO thin films deposited on indium tin oxide coated Corning Glass substrate. The studies reveal a correlation between the biosensing characteristic and the presence of defects in the ZnO films. The ZnO films deposited under high pressure (50 mT) are found to be more sensitive for biosensing application due to availability of more surface area for effective immobilization of biomolecules and exhibits a suitable microenvironment with good electron transfer characteristic. The obtained results highlight the importance of desired microstate besides availability of suitable native defects in the ZnO thin film for exhibiting enhanced biosensing response.

  3. Surface Engineering of ZnO Thin Film for High Efficiency Planar Perovskite Solar Cells

    PubMed Central

    Tseng, Zong-Liang; Chiang, Chien-Hung; Wu, Chun-Guey

    2015-01-01

    Sputtering made ZnO thin film was used as an electron-transport layer in a regular planar perovskite solar cell based on high quality CH3NH3PbI3 absorber prepared with a two-step spin-coating. An efficiency up to 15.9% under AM 1.5G irradiation is achieved for the cell based on ZnO film fabricated under Ar working gas. The atmosphere of the sputtering chamber can tune the surface electronic properties (band structure) of the resulting ZnO thin film and therefore the photovoltaic performance of the corresponding perovskite solar cell. Precise surface engineering of ZnO thin film was found to be one of the key steps to fabricate ZnO based regular planar perovskite solar cell with high power conversion efficiency. Sputtering method is proved to be one of the excellent techniques to prepare ZnO thin film with controllable properties. PMID:26411577

  4. Surface Engineering of ZnO Thin Film for High Efficiency Planar Perovskite Solar Cells.

    PubMed

    Tseng, Zong-Liang; Chiang, Chien-Hung; Wu, Chun-Guey

    2015-01-01

    Sputtering made ZnO thin film was used as an electron-transport layer in a regular planar perovskite solar cell based on high quality CH3NH3PbI3 absorber prepared with a two-step spin-coating. An efficiency up to 15.9% under AM 1.5G irradiation is achieved for the cell based on ZnO film fabricated under Ar working gas. The atmosphere of the sputtering chamber can tune the surface electronic properties (band structure) of the resulting ZnO thin film and therefore the photovoltaic performance of the corresponding perovskite solar cell. Precise surface engineering of ZnO thin film was found to be one of the key steps to fabricate ZnO based regular planar perovskite solar cell with high power conversion efficiency. Sputtering method is proved to be one of the excellent techniques to prepare ZnO thin film with controllable properties. PMID:26411577

  5. Cytotoxic evaluation of nanostructured zinc oxide (ZnO) thin films and leachates.

    PubMed

    Petrochenko, Peter E; Zhang, Qin; Bayati, Reza; Skoog, Shelby A; Phillips, K Scott; Kumar, Girish; Narayan, Roger J; Goering, Peter L

    2014-09-01

    Nanostructured ZnO films have potential use as coatings on medical devices and food packaging due to their antimicrobial and UV-protection properties. However, their influence on mammalian cells during clinical use is not fully understood. This study investigated the potential cytotoxicity of ZnO thin films in RAW 264.7 macrophages. ZnO thin films (∼96nm thick with a 50nm grain) were deposited onto silicon wafers using pulsed laser deposition. Cells grown directly on ZnO thin film coatings exhibited less toxicity than cells exposed to extracts of the coatings. Cells on ZnO thin films exhibited a 43% and 68% decrease in cell viability using the MTT and 7-AAD/Annexin V flow cytometry assays, respectively, after a 24-h exposure as compared to controls. Undiluted 100% 24- and 48-h extracts decreased viability by 89%, increased cell death by LDH release to 76% 24h after treatment, and increased ROS after 5-24h of exposure. In contrast, no cytotoxicity or ROS were observed for 25% and 50% extracts, indicating a tolerable concentration. Roughly 24 and 34μg/m(2) Zn leached off the surfaces after 24 and 48h of incubation, respectively. ZnO coatings may produce gradual ion release which becomes toxic after a certain level and should be evaluated using both direct exposure and extraction methods. PMID:24878115

  6. 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.

  7. Investigation of thin ZnO layers in view of laser desorption-ionization

    NASA Astrophysics Data System (ADS)

    Grechnikov, A. A.; Georgieva, V. B.; Alimpiev, S. S.; Borodkov, A. S.; Nikiforov, S. M.; Simanovsky, Ya O.; Dimova-Malinovska, D.; Angelov, O. I.

    2010-04-01

    Thin zinc oxide films (ZnO) were developed as a matrix-free platform for surface assisted laser desorption-ionization (SALDI) time-of-flight mass spectrometry. The ZnO films were deposited by RF magnetron sputtering of ZnO ceramic targets in Ar atmospheres on monocrystalline silicon. The generation under UV (355 nm) laser irradiation of positive ions of atenolol, reserpine and gramicidin S from the ZnO layers deposited was studied. All analytes tested were detected as protonated molecules with no or very structure-specific fragmentation. The mass spectra obtained showed low levels of chemical background noise. All ZnO films studied exhibited high stability and good reproducibility. The detection limits for test analytes are in the 10 femtomol range.

  8. Rectifying properties of ZnO thin films deposited on FTO by electrodeposition technique

    NASA Astrophysics Data System (ADS)

    Lv, Jianguo; Sun, Yue; Zhao, Min; Cao, Li; Xu, Jiayuan; He, Gang; Zhang, Miao; Sun, Zhaoqi

    2016-03-01

    ZnO thin films were successfully grown on fluorine-doped tin oxide glass by electrodeposition technique. The crystal structure, surface morphology and optical properties of the thin films were investigated. The average crystallite size and intensity of A1(LO) mode increase with improving the absolute value of deposition potential. The best preferential orientation along c-axis and the richest oxygen interstitial defects have been observed in the sample deposited at -0.8 V. A heterojunction device consisting of ZnO thin film and n-type fluorine-doped tin oxide was fabricated. The current-voltage (I-V) characteristic of the p-n heterojunction device deposited at -0.8 V shows the best rectifying diode behavior. The p-type conductivity of the ZnO thin film could be attributed to complex defect of unintentional impurity and interstitial oxygen.

  9. Synthesis of Imine-Bearing ZnO Nanoparticle Thin Films and Characterization of Their Structural, Morphological and Optical Properties.

    PubMed

    Kaur, Narinder; Sharma, Sanjeev K; Kim, Deuk Young; Sharma, Hemant; Singh, Narinder

    2015-10-01

    We are presenting the first report on the fabrication of imine-bearing ZnO nanoparticle thin films grown on Corning glass by spin coating. The sol was prepared by dissolving imine-bearing ZnO nanoparticles in dimethylsulfoxide (DMSO). The thickness of the films was manipulated to be 125-200 nm. The X-ray diffraction (XRD) analysis showed hexagonal wurtzite structure of imine-bearing ZnO nanoparticles thin films with a (002) preferential orientation. The stretching of chemical bonds of the imine linkage and Zn-O in imine-bearing ZnO nanoparticle thin films was confirmed by Fourier transform infrared spectroscopy (FTIR). The grain size of the films increased with increasing the thickness of the films due to the number of coatings and subsequently dried at 200 °C. The transmittance of imine-bearing ZnO nanoparticle thin films was observed to be ≥94%, which was in close agreement to pure ZnO thin films in the visible region. The bandgap of imine-bearing ZnO nanoparticle thin films (3.04 eV), evaluated from Tauc's plot, was observed to be lower than that of pure ZnO (3.21 eV), which is attributed to the interaction of the ZnO nanoparticles with the imine receptor. PMID:26726472

  10. Fabrication of superhydrophobic surface of hierarchical ZnO thin films by using stearic acid

    NASA Astrophysics Data System (ADS)

    Wang, Yanfen; Li, Benxia; Xu, Chuyang

    2012-01-01

    Flower-like hierarchical ZnO microspheres were successfully synthesized by a simple, template-free, and low-temperature aqueous solution route. The morphology and microstructure of the ZnO microspheres were examined by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The bionic films with hydrophobicity were fabricated by the hierarchical ZnO microspheres modified by stearic acid. It was found that the hydrophobicity of the thin films was very sensitive to the added amount of stearic acid. The thin films modified with 8% stearic acid took on strong superhydrophobicity with a water contact angle (CA) almost to be 178° and weak adhersion. The remarkable superhydrophobicity could be attributed to the synergistic effect of micro/nano hierarchical structure of ZnO and low surface energy of stearic acid.

  11. Formation of ST12 phase Ge nanoparticles in ZnO thin films

    NASA Astrophysics Data System (ADS)

    Ceylan, Abdullah; Gumrukcu, Emre; Ozcan, Sadan

    2015-03-01

    In this work, we investigate the effects of reactive and nonreactive growth of ZnO on the rapid thermal annealing (RTA) induced formation of Ge nanoparticles (Ge-np) in ZnO: Ge nanocomposite thin films. The samples were deposited by sequential sputtering of ZnO and Ge thin film layers with a total thickness of about 600 nm on Si substrates followed by an ex-situ (RTA) at 600°C for 30, 60, 90, 120, 150, 180, and 210 s under forming gas atmosphere. In order for the reactive sputtering of ZnO layer, 5 mTorr Oxygen was introduced to the growth chamber. XRD and Raman analyses were utilized to investigate the effect of RTA time on the structural evolution of the samples. It has been realized that crystal structure of Ge nanoparticles is significantly affected by the growth method of the embedding ZnO layer. While reactive deposition of ZnO layers results in a mixture of diamond cubic (DC) and simple tetragonal (ST12) Ge-np, nonreactive deposition of ZnO layers leads to the formation of pure DC Ge-np upon RTA process. Formation of these two phases has been discussed based on the existence of native point defects such as oxygen vacancies and Zn interstitials.

  12. Selective Purcell enhancement of defect emission in ZnO thin films

    SciTech Connect

    Lawrie, Benjamin J; Mu, Richard; HaglundJr., Richard F

    2012-01-01

    A zinc interstitial defect present but unobservable in ZnO thin films annealed at 500 C in oxygen or in atmosphere was selectively detected by interaction of the film with an Ag surface-plasmon polariton. The time-dependent differential reflectivity of the ZnO near the ZnO/MgO interface exhibited a subpicosecond decay followed by a several nanosecond recovery, consistent with the Purcell-enhanced Zn interstitial luminescence seen in Ag ZnO heterostructures. Heterostructures annealed at other temperatures showed significantly greater band-edge photoluminescence and no evidence of the Zn interstitial defect.

  13. Slow positron beam study of hydrogen ion implanted ZnO thin films

    NASA Astrophysics Data System (ADS)

    Hu, Yi; Xue, Xudong; Wu, Yichu

    2014-08-01

    The effects of hydrogen related defect on the microstructure and optical property of ZnO thin films were investigated by slow positron beam, in combination with x-ray diffraction, infrared and photoluminescence spectroscopy. The defects were introduced by 90 keV proton irradiation with doses of 1×1015 and 1×1016 ions cm-2. Zn vacancy and OH bonding (VZn+OH) defect complex were identified in hydrogen implanted ZnO film by positron annihilation and infrared spectroscopy. The formation of these complexes led to lattice disorder in hydrogen implanted ZnO film and suppressed the luminescence process.

  14. Fabrication of nanostructured Al-doped ZnO thin film for methane sensing applications

    NASA Astrophysics Data System (ADS)

    Shafura, A. K.; Sin, N. D. Md.; Azhar, N. E. I.; Saurdi, I.; Uzer, M.; Mamat, M. H.; Shuhaimi, A.; Alrokayan, Salman A. H.; Khan, Haseeb A.; Rusop, M.

    2016-07-01

    CH4 gas sensor was fabricated using spin-coating method of the nanostructured ZnO thin film. Effect of annealing temperature on the electrical and structural properties of the film was investigated. Dense nanostructured ZnO film are obtained at higher annealing temperature. The optimal condition of annealing temperature is 500°C which has conductivity and sensitivity value of 3.3 × 10-3 S/cm and 11.5%, respectively.

  15. Oxygen glow treating of ZnO electrode for thin film silicon solar cell

    SciTech Connect

    Elias, E.; Knapp, K.E.

    1989-10-10

    This patent describes an improvement in a process for production of a photoconductive device wherein a first conductive layer comprising ZnO is applied to a substrate, and a thin film silicon hydrogen alloy is applied to the first conductive layer. The improvement comprising: after applying the first conductive layer comprising ZnO to the substrate, treating the first conductive layer with a glow discharge in a gas containing a source of oxygen.

  16. 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.

  17. 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.

  18. 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.

  19. Optical Properties of MEH-PPV Thin Films Containing ZnO Nanoparticles

    SciTech Connect

    Zayana, N. Y.; Shariffudin, S. S.; Jumali, N. S.; Shaameri, Z.; Hamzah, A. S.; Rusop, M.

    2011-05-25

    Thin films of poly [2-methoxy-5(2'-ethyl hexyloxy)-phenylene vinylene](MEH-PPV) containing different weight percent of ZnO nanoparticles were deposited by spin coating from THF solutions and their optical properties were investigated. Optical characterization of the nanocomposite thin films were performed by Ultraviolet-Visible Spectrophotometer (UV-Vis) and Photoluminescence Spectrometer while the thickness of the thin films was measured by using Surface Profiler. The UV-Vis absorption spectra of MEH-PPV: ZnO films showed a small red shift as compared with pure MEH-PPV. Similarly, a small red shift was found in PL emission spectra with increasing the content of ZnO nanoparticles.

  20. Third generation biosensing matrix based on Fe-implanted ZnO thin film

    NASA Astrophysics Data System (ADS)

    Saha, Shibu; Gupta, Vinay; Sreenivas, K.; Tan, H. H.; Jagadish, C.

    2010-09-01

    Third generation biosensor based on Fe-implanted ZnO (Fe-ZnO) thin film has been demonstrated. Implantation of Fe in rf-sputtered ZnO thin film introduces redox center along with shallow donor level and thereby enhance its electron transfer property. Glucose oxidase (GOx), chosen as model enzyme, has been immobilized on the surface of the matrix. Cyclic voltammetry and photometric assay show that the prepared bioelectrode, GOx/Fe-ZnO/ITO/Glass is sensitive to the glucose concentration with enhanced response of 0.326 μA mM-1 cm-2 and low Km of 2.76 mM. The results show promising application of Fe-implanted ZnO thin film as an attractive matrix for third generation biosensing.

  1. Laser-assisted sol-gel growth and characteristics of ZnO thin films

    SciTech Connect

    Kim, Min Su; Kim, Soaram; Leem, Jae-Young

    2012-06-18

    ZnO thin films were grown on Si(100) substrates by a sol-gel method assisted by laser beam irradiation with a 325 nm He-Cd laser. In contrast to conventional sol-gel ZnO thin films, the surface morphology of the laser-assisted sol-gel thin films was much smoother, and the residual stress in the films was relaxed by laser irradiation. The luminescent properties of the films were also enhanced by laser irradiation, especially, by irradiation during the deposition and post-heat treatment stages. The incident laser beam is thought to play several roles, such as annihilating defects by accelerating crystallization during heat treatment, enhancing the surface migration of atoms and molecules, and relaxing the ZnO matrix structure during crystallization.

  2. Third generation biosensing matrix based on Fe-implanted ZnO thin film

    SciTech Connect

    Saha, Shibu; Gupta, Vinay; Sreenivas, K.; Tan, H. H.; Jagadish, C.

    2010-09-27

    Third generation biosensor based on Fe-implanted ZnO (Fe-ZnO) thin film has been demonstrated. Implantation of Fe in rf-sputtered ZnO thin film introduces redox center along with shallow donor level and thereby enhance its electron transfer property. Glucose oxidase (GOx), chosen as model enzyme, has been immobilized on the surface of the matrix. Cyclic voltammetry and photometric assay show that the prepared bioelectrode, GOx/Fe-ZnO/ITO/Glass is sensitive to the glucose concentration with enhanced response of 0.326 {mu}A mM{sup -1} cm{sup -2} and low Km of 2.76 mM. The results show promising application of Fe-implanted ZnO thin film as an attractive matrix for third generation biosensing.

  3. 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.

  4. 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%.

  5. Low temperature atomic layer deposited ZnO photo thin film transistors

    SciTech Connect

    Oruc, Feyza B.; Aygun, Levent E.; Donmez, Inci; Biyikli, Necmi; Okyay, Ali K.; Yu, Hyun Yong

    2015-01-01

    ZnO thin film transistors (TFTs) are fabricated on Si substrates using atomic layer deposition technique. The growth temperature of ZnO channel layers are selected as 80, 100, 120, 130, and 250 °C. Material characteristics of ZnO films are examined using x-ray photoelectron spectroscopy and x-ray diffraction methods. Stoichiometry analyses showed that the amount of both oxygen vacancies and interstitial zinc decrease with decreasing growth temperature. Electrical characteristics improve with decreasing growth temperature. Best results are obtained with ZnO channels deposited at 80 °C; I{sub on}/I{sub off} ratio is extracted as 7.8 × 10{sup 9} and subthreshold slope is extracted as 0.116 V/dec. Flexible ZnO TFT devices are also fabricated using films grown at 80 °C. I{sub D}–V{sub GS} characterization results showed that devices fabricated on different substrates (Si and polyethylene terephthalate) show similar electrical characteristics. Sub-bandgap photo sensing properties of ZnO based TFTs are investigated; it is shown that visible light absorption of ZnO based TFTs can be actively controlled by external gate bias.

  6. Optical, Electrical, and Adhesive Properties of ZnO Thin Films.

    PubMed

    Chen, Yuan-Tsung

    2016-01-01

    ZnO films were sputtered onto glass substrates to thicknesses from 100 A to 500 A under the following conditions; (a) as-deposited films were maintained at room temperature (RT); (b) films were post-annealed at 150 °C for 1 h, and (c) films were post-annealed at 250 °C for 1 h. X-ray diffraction (XRD) result thus obtained demonstrate that ZnO has a wurtzite structure with a (002) texture diffraction peak with a 2θ of 34° range. The intensity of the ZnO (002) peak increased with film thickness and upon post-annealing. As the ZnO thin film thickness increased and post-annealing was carried out, the grains became larger. A spectral analyzer was utilized to measure transmittance for various thicknesses. Post-annealing treatment promoted the growth of grains, yielding a large mean grain size and, therefore, low transmittance. The as-deposited ZnO thin film with a thickness of 100 Å had a transmittance maximum of approximately 88% and a reflectance minimum of around 12%. Additionally, the four-point probe measurements revealed that p decreased as the ZnO thickness increased and with post-annealing treatment because grain boundaries and the surface of thin films scatter electrons, so thinner films have a greater resistance. ZnO with a thickness of 500 Å that underwent post-annealing treatment at 250 °C had a minimum resistivity of 7.6 x 10⁻³ Ω · cm. Adhesion critically influences the surface energy of films. The surface energy of as-deposited ZnO films was higher than that following post-annealing treatments, revealing that the adhesion of the as-deposited ZnO films was stronger than that following post-annealing treatment because the degree of crystallinity was lower. Accordingly, the thickness and crystallinity of ZnO importantly affects its optical, electrical, and adhesive characteristics. Finally, thinner as-deposited ZnO films exhibited better optical and adhesive properties. PMID:27398504

  7. 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.

  8. Structural, electronic and magnetic properties of Er implanted ZnO thin films

    NASA Astrophysics Data System (ADS)

    Murmu, P. P.; Kennedy, J.; Ruck, B. J.; Leveneur, J.

    2015-09-01

    We report the structural, electronic and magnetic properties of Er implanted and annealed ZnO thin films. The effect of annealing in oxygen-deficient and oxygen-rich conditions was investigated. Rutherford backscattering spectrometry results revealed that the Er atoms are located at the implantation depth of around 13 nm, and annealing conditions had no adverse effect on the Er concentration in the layer. Raman spectroscopy results showed peak related to E2(high) mode of ZnO indicating enhanced crystalline quality of the Er implanted and annealed ZnO films. X-ray absorption near edge spectroscopy results demonstrated pre-edge features in O K-edge which are attributed to the structural defects in the films. Room temperature magnetic ordering was observed in Er implanted and annealed films, and is mainly assigned to the intrinsic defects in ZnO.

  9. Structural and optical characterization of high-quality ZnO thin films deposited by reactive RF magnetron sputtering

    SciTech Connect

    Zhang, X.L.; Hui, K.N.; Hui, K.S.; Singh, Jai

    2013-03-15

    Highlights: ► High-quality ZnO thin films were deposited at room temperature. ► Effect of O{sub 2} flow and RF sputtering voltages on properties of ZnO films were studied. ► O{sub 2}/Ar ratios played a key role in controlling optical properties of ZnO films. ► Photoluminescence intensity of the ZnO films strongly depended on O{sub 2}/Ar ratios. ► Crystallite size, stress and strain strongly depended on O{sub 2}/Ar ratios. - Abstract: ZnO thin films were deposited onto quartz substrates by radio frequency (RF) reactive magnetron sputtering using a Zn target. The structural and optical properties of the ZnO thin films were investigated comprehensively by X-ray diffraction (XRD), ultraviolet–visible and photoluminescence (PL) measurements. The effects of the oxygen content of the total oxygen–argon mixture and sputtering voltage in the sputtering process on the structural and optical properties of the ZnO films were studied systemically. The microstructural parameters, such as the lattice constant, crystallite size, stress and strain, were also calculated and correlated with the structural and optical properties of the ZnO films. In addition, the results showed that the crystalline quality of ZnO thin films improved with increasing O{sub 2}/Ar gas flow ratio from 2:8 to 8:2. XRD and PL spectroscopy revealed 800 V to be the most appropriate sputtering voltage for ZnO thin film growth. High-quality ZnO films with a good crystalline structure, tunable optical band gap as well as high transmittance could be fabricated easily by RF reactive magnetron sputtering, paving the way to obtaining cost-effective ZnO thin films transparent conducting oxides for optoelectronics applications.

  10. 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.

  11. Influence of Substrate Nature and Annealing on Electro-Optical Properties of ZnO Thin Films

    SciTech Connect

    Iacomi, Felicia; Baban, C.; Prepelita, Petronela; Luca, D.; Iftimie, Nicoleta

    2007-04-23

    ZnO thin films were grown on different substrates (glass, quartz, silicon wafers, etc) by vacuum thermal evaporation. Different thermal treatments were performed in order to obtain transparent and conductive or high resistive ZnO thin films. The optical and electrical properties of ZnO thin films are dependent on the crucible temperature, annealing conditions and on the substrate nature. The thin films are transparent and have an electrical resistivity in 10-4 {omega}m regio. The annealing process performed in vacuum at 573K or under UV irradiation determines a decrease in the electrical resistivity of films.

  12. Laser ablated ZnO thin film for amperometric detection of urea

    NASA Astrophysics Data System (ADS)

    Batra, Neha; Tomar, Monika; Jain, Prateek; Gupta, Vinay

    2013-09-01

    Zinc oxide (ZnO) thin films deposited onto indium tin oxide (ITO) coated corning glass substrates using pulsed laser deposition (PLD) technique at two different oxygen pressures (50 mT and 100 mT) have been used as efficient matrix for realization of efficient urea biosensors after immobilization of urease (Urs) enzyme onto ZnO film surface. The bioelectrode Urs/ZnO/ITO/glass having ZnO matrix grown at 100 mT is found to be exhibiting an enhanced sensitivity of 36 μΑ mΜ-1 cm-2 for urea over a wide detection range of 5-200 mg/dl. The relatively low value of Michaelis-Menten constant (Km = 0.82 mM) indicates high affinity of the immobilized urease towards the analyte (urea). The prepared sensor exhibits high selectivity towards detection of urea and retains 90% of its activity for more than 12 weeks. The observed enhanced response characteristics of bioelectrode is attributed to the growth of highly c-axis oriented ZnO thin film by PLD at 100 mT oxygen pressure with desired rough and porous surface morphology besides high electron communication feature. The results confirm the promising application of PLD grown ZnO thin film as an efficient matrix for urea detection.

  13. Preparation and characterization of double layer thin films ZnO/ZnO:Ag for methylene blue photodegradation

    NASA Astrophysics Data System (ADS)

    Wibowo, Singgih; Sutanto, Heri

    2016-02-01

    Double layer (DL) thin films of zinc oxide and silver-doped zinc oxide (ZnO/ZnO:Ag) were deposited on glass substrate by sol-gel spray coating technique. The prepared thin films were subjected for optical and photocatalytic studies. UV-visible transmission spectra shows that the subtitution of Ag in ZnO leads to band gap reduction. The influence of Ag doping on the photocatalytic activity of ZnO for the degradation of methylene blue dye was studied under solar radiation. The light absorption over an extended visible region by Ag ion doping in ZnO film contributed equally to improve the photocatalytic activity up to 98.29%.

  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. Hydrogen treatment of undoped ZnO thin film using photo-chemical vapor deposition

    SciTech Connect

    Baik, S.J.; Lim, K.S.; Song, J.

    1996-12-31

    To obtain high quality ZnO thin films for use as transparent electrodes of amorphous silicon solar cells, hydrogen treatment of the films using photo-chemical vapor deposition was performed for the first time. The as-deposited ZnO thin film was irradiated by UV light during the flow of hydrogen molecules in the presence of photo-sensitizers of mercury. As the treatment time increased, resistivity decreased from 1 {times} 10{sup {minus}2}{Omega}cm to 2 {times} 10{sup {minus}3}{Omega}cm. Moreover, haze ratio increased from 20% to 48%. Hydrogen radicals were thought to be playing various roles on the neighborhood of the surface region and the grain boundary region. This new trial gave us new understanding into the relation between hydrogen and ZnO. Moreover, these results could be applied to the process of amorphous silicon solar cells and a possible increase of efficiency is expected.

  16. 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.

  17. 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.

  18. 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.

  19. Growth and characterization of seed layer-free ZnO thin films deposited on porous silicon by hydrothermal method

    NASA Astrophysics Data System (ADS)

    Kim, Min Su; Yim, Kwang Gug; Kim, Do Yeob; Kim, Soaram; Nam, Giwoong; Lee, Dong-Yul; Kim, Sung-O.; Kim, Jin Soo; Kim, Jong Su; Son, Jeong-Sik; Leem, Jae-Young

    2012-02-01

    Catalyst- and seed layer-free zinc oxide (ZnO) thin films were grown on porous silicon (PS) by a hydrothermal method. Atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and photoluminescence (PL) were carried out to investigate the structural and optical properties of the PS and the ZnO thin films. The ZnO thin films have an extraordinary tendency to grow along the a-axis with a hexagonal wurtzite structure. The growth rate of the ZnO thin films was increased with the increase in the precursor concentration. The crystal quality of the ZnO thin films was improved, and the residual stress was decreased as their thickness increased. Monochromatic indigo and red light emission peaks were observed from the ZnO thin films and the PS, respectively. At an excessively high precursor concentration, a green light emission peak was also observed in the ZnO thin films. The luminescent efficiency of the indigo light emission peak was enhanced with the increase in the precursor concentration.

  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. 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.

  2. 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

  3. A comparative study of ultraviolet photoconductivity relaxation in zinc oxide (ZnO) thin films deposited by different techniques

    SciTech Connect

    Yadav, Harish Kumar; Gupta, Vinay

    2012-05-15

    Photoresponse characteristics of ZnO thin films deposited by three different techniques namely rf diode sputtering, rf magnetron sputtering, and electrophoretic deposition has been investigated in the metal-semiconductor-metal (MSM) configuration. A significant variation in the crystallinity, surface morphology, and photoresponse characteristics of ZnO thin film with change in growth kinetics suggest that the presence of defect centers and their density govern the photodetector relaxation properties. A relatively low density of traps compared to the true quantum yield is found very crucial for the realization of practical ZnO thin film based ultraviolet (UV) photodetector.

  4. Controlling growth rate anisotropy for formation of continuous ZnO thin films from seeded substrates.

    PubMed

    Zhang, R H; Slamovich, E B; Handwerker, C A

    2013-05-17

    Solution-processed zinc oxide (ZnO) thin films are promising candidates for low-temperature-processable active layers in transparent thin film electronics. In this study, control of growth rate anisotropy using ZnO nanoparticle seeds, capping ions, and pH adjustment leads to a low-temperature (90 ° C) hydrothermal process for transparent and high-density ZnO thin films. The common 1D ZnO nanorod array was grown into a 2D continuous polycrystalline film using a short-time pure solution method. Growth rate anisotropy of ZnO crystals and the film morphology were tuned by varying the chloride (Cl(-)) ion concentration and the initial pH of solutions of zinc nitrate and hexamethylenetetramine (HMTA), and the competitive adsorption effects of Cl(-) ions and HMTA ligands on the anisotropic growth behavior of ZnO crystals were proposed. The lateral growth of nanorods constituting the film was promoted by lowering the solution pH to accelerate the hydrolysis of HMTA, thereby allowing the adsorption effects from Cl(-) to dominate. By optimizing the growth conditions, a dense ∼100 nm thickness film was fabricated in 15 min from a solution of [Cl(-)]/[Zn(2+)] = 1.5 and pH=  4.8 ± 0.1. This film shows >80% optical transmittance and a field-effect mobility of 2.730 cm(2) V(-1) s(-1) at zero back-gate bias. PMID:23595114

  5. Growth of non-polar ZnO thin films with different working pressures by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Chao, Chung-Hua; Wei, Da-Hua

    2014-11-01

    Non-polar coexisting m-plane (10\\bar{1}0) and a-plane (11\\bar{2}0) zinc oxide (ZnO) thin films have been synthesized onto commercial silicon (100) substrates by using plasma enhanced chemical vapor deposition (PECVD) system at different working pressures. The effects of the working pressure on crystal orientation, microstructure, surface morphology, and optical properties of the ZnO thin films were investigated. From the X-ray diffraction patterns, the non-polar ZnO thin films were successfully synthesized at the working pressures of 6 and 9 Torr, respectively. The non-polar ZnO thin films showed stripes-like surface morphology and with smooth surface roughness (˜3.53 nm) was performed by field emission scanning electron microscope (FE-SEM) and atomic force microscope (AFM), respectively. All the ZnO films show a remarkable near-band-edge (NBE) emission peak located at ultraviolet (UV) band accompanying a negligible deep-level (DL) emission at visible region detected by photoluminescence (PL) spectra at room temperature. From the above systematic measurement analysis, indicating the better crystallinity and optical character of ZnO thin film was improved with reducing the working pressure. The wettability of non-polar ZnO thin films was also explored in this presented article.

  6. Second harmonic generation in ZnO thin films fabricated by metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Liu, C. Y.; Zhang, B. P.; Binh, N. T.; Segawa, Y.

    2004-07-01

    Second harmonic generation (SHG) from ZnO thin films fabricated by metalorganic chemical vapor deposition (MOCVD) technique was carried out. By comparing the second harmonic signal generated in a series of ZnO films with different deposition temperatures, we conclude that a significant part of second harmonic signal is generated at the film deposited with appropriate temperature. The second-order susceptibility tensor χ(2)zzz=9.2 pm/V was deduced for a film deposited at 250 °C.

  7. ZrO2-ZnO composite thin films for humidity sensing

    NASA Astrophysics Data System (ADS)

    Velumani, M.; Meher, S. R.; Balakrishnan, L.; Sivacoumar, R.; Alex, Z. C.

    2016-05-01

    ZrO2-ZnO composite thin films were grown by reactive DC magnetron sputtering. X-ray diffraction studies reveal the composite nature of the films with separate ZnO and ZrO2 phase. Scanning electron microscopy studies confirm the nanocrystalline structure of the films. The films were studied for their impedometric relative humidity (RH) sensing characteristics. The complex impedance plot was fitted with a standard equivalent circuit consisting of an inter-granular resistance and a capacitance in parallel. The DC resistance was found to be decreasing with increase in RH.

  8. 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.

  9. 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.

  10. Nanoscale heterogeniety and workfunction variations in ZnO thin films

    NASA Astrophysics Data System (ADS)

    Sharma, Anirudh; Untch, Maria; Quinton, Jamie S.; Berger, Rüdiger; Andersson, Gunther; Lewis, David A.

    2016-02-01

    Nano-roughened, sol-gel derived polycrystalline ZnO thin films prepared by a thermal ramping procedure were found to exhibit different work function values on a sub-micrometer scale. By Kelvin probe force microscopy (KPFM) two distinct nanoscale regions with work function differing by over 0.1 eV were detected which did not coincide with the nano-roughened surface topography. In contrast, a flat ZnO surface displayed a single, uniform distribution. Ultraviolet photoelectron spectroscopy (UPS) studies showed that the average workfunction across a flat ZnO surface was 3.7 eV while ZnO with a nano-roughened morphology had a lower workfunction of 3.4 eV with indications of electronic heterogeneity across the surface, supporting the KPFM results. Scanning Auger Nanoprobe measurements showed that the chemical composition was uniform across the surface in all samples, suggesting the work function heterogeneity was due to variations in crystallinity or crystal orientation on the surface of these thin films. Such heterogeneity in the electronic properties of materials in thin film devices can significantly influence the interfacial charge transport across materials.

  11. Growth and optical characteristics of high-quality ZnO thin films on graphene layers

    SciTech Connect

    Park, Suk In; Tchoe, Youngbin; Baek, Hyeonjun; Hyun, Jerome K.; Yi, Gyu-Chul E-mail: gcyi@snu.ac.kr; Heo, Jaehyuk; Jo, Janghyun; Kim, Miyoung; Kim, Nam-Jung E-mail: gcyi@snu.ac.kr

    2015-01-01

    We report the growth of high-quality, smooth, and flat ZnO thin films on graphene layers and their photoluminescence (PL) characteristics. For the growth of high-quality ZnO thin films on graphene layers, ZnO nanowalls were grown using metal-organic vapor-phase epitaxy on oxygen-plasma treated graphene layers as an intermediate layer. PL measurements were conducted at low temperatures to examine strong near-band-edge emission peaks. The full-width-at-half-maximum value of the dominant PL emission peak was as narrow as 4 meV at T = 11 K, comparable to that of the best-quality films reported previously. Furthermore, the stimulated emission of ZnO thin films on the graphene layers was observed at the low excitation energy of 180 kW/cm{sup 2} at room temperature. Their structural and optical characteristics were investigated using X-ray diffraction, transmission electron microscopy, and PL spectroscopy.

  12. Photoluminescence Spectra of thin Zno films grown by ALD technology

    NASA Astrophysics Data System (ADS)

    Akopyan, I. Kh.; Davydov, V. Yu.; Labzovskaya, M. E.; Lisachenko, A. A.; Mogunov, Ya. A.; Nazarov, D. V.; Novikov, B. V.; Romanychev, A. I.; Serov, A. Yu.; Smirnov, A. N.; Titov, V. V.; Filosofov, N. G.

    2015-09-01

    The photoluminescence of ZnO films grown by atomic layer deposition (ALD) on silicon substrates has been investigated. A new broad photoluminescence band has been revealed in the exciton region of the spectrum. The properties of the band in the spectra of the films with different crystallographic orientations of substrates have been studied in a wide temperature range at different excitation levels. A model describing the origin of the new band has been proposed.

  13. Enhanced optical band-gap of ZnO thin films by sol-gel technique

    NASA Astrophysics Data System (ADS)

    Raghu, P.; Naveen, C. S.; Shailaja, J.; Mahesh, H. M.

    2016-05-01

    Transparent ZnO thin films were prepared using different molar concentration (0.1 M, 0.2 M & 0.8 M) of zinc acetate on soda lime glass substrates by the sol-gel spin coating technique. The optical properties revealed that the transmittance found to decrease with increase in molar concentration. Absorption edge showed that the higher concentration film has increasingly red shifted. An increased band gap energy of the thin films was found to be direct allowed transition of ˜3.9 eV exhibiting their relevance for photovoltaic applications. The extinction coefficient analysis revealed maximum transmittance with negligible absorption coefficient in the respective wavelengths. The results of ZnO thin film prepared by sol-gel technique reveal its suitability for optoelectronics and as a window layer in solar cell applications.

  14. 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.

  15. 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.

  16. 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.

  17. Electrical characteristics of ZnO nanorods reinforced polymer nanocomposite thin films

    SciTech Connect

    Bhattacharjee, Snigdha; Roy, Asim

    2015-05-15

    ZnO nanorods have been prepared by simple chemical method, which is used to fabricate organic bistable devices (OBDs). OBDs are fabricated by incorporating different weight percent (wt %) of chemically synthesized Zinc Oxide (ZnO) nanorods into polymethylmethacrylate (PMMA). Current-voltage (I-V) measurements of the spin coated ZnO+PMMA nanocomopsite thin film on indium tin oxide (ITO) coated glass substrate showed current hysteresis behaviour, which is an indication of memory effect. The samples exhibit two distinct resistance states, ON and OFF states, characterised by relatively low and high resistance of the OBDs, respectively. It is also observed that with change in ZnO dopant concentration the value of ON/OFF current changes. Higher ON/OFF current ratio is desired for practical applications. Current conduction mechanism of the devices has been explained invoking various existing models, and it has been found that the trapped-charge-limited conduction mechanism was dominant in our samples.

  18. Micro-patterned ZnO semiconductors for high performance thin film transistors via chemical imprinting with a PDMS stamp.

    PubMed

    Seong, Kieun; Kim, Kyongjun; Park, Si Yun; Kim, Youn Sang

    2013-04-01

    Chemical imprinting was conducted on ZnO semiconductor films via a chemical reaction at the contact regions between a micro-patterned PDMS stamp and ZnO films. In addition, we applied the chemical imprinting on Li doped ZnO thin films for high performance TFTs fabrication. The representative micro-patterned Li doped ZnO TFTs showed a field effect mobility of 4.2 cm(2) V(-1) s(-1) after sintering at 300 °C. PMID:23439918

  19. Characterization of Flexible CIGS Thin Film Solar Cells or Stainless Steel with Intrinsic ZnO Diffusion Barriers.

    PubMed

    Kim, Chae-Woong; Kim, Hye Jin; Kim, Jin Hyeok; Jeong, Chaehwan

    2016-05-01

    ZnO diffusion barrier layer was deposited by RF magnetron sputtering by using the same method as intrinsic ZnO layer. The CIGS solar cells were fabricated on stainless steel substrate. The 50-200 nm thin ZnO diffusion barriers effectively reduced the diffusion of Fe and Cr, from stainless steel substrates into the CIGS absorbers. The CIGS solar cells with ZnO diffusion barriers increased the J(sc) and FF, which resulted in an increase of cell efficiency from 5.9% up to 9.06%. PMID:27483885

  20. 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.

  1. Microfluidic pumps employing surface acoustic waves generated in ZnO thin films

    SciTech Connect

    Du, X. Y.; Flewitt, A. J.; Milne, W. I.; Fu, Y. Q.; Luo, J. K.

    2009-01-15

    ZnO thin film based surface acoustic wave (SAW) devices have been utilized to fabricate microfluidic pumps. The SAW devices were fabricated on nanocrystalline ZnO piezoelectric thin films deposited on Si substrates using rf magnetron sputtering and use a Sezawa wave mode for effective droplet motion. The as-deposited ZnO surface is hydrophilic, with a water contact angle of {approx}75 deg., which prevents droplet pumping. Therefore, the ZnO surface was coated using a self-assembled monolayer of octadecyltrichlorosilane which forms a hydrophobic surface with a water contact angle of {approx}110 deg. Liquid droplets between 0.5 and 1 {mu}l in volume were successfully pumped on the hydrophobic ZnO surface at velocities up to 1 cm s{sup -1}. Under acoustic pressure, the water droplet on an hydrophilic surface becomes deformed, and the asymmetry in the contact angle at the trailing and leading edges allow the force acting upon the droplet to be calculated. These forces, which increase with input voltage above a threshold level, are found to be in the range of {approx}100 {mu}N. A pulsed rf signal has also been used to demonstrate precision manipulation of the liquid droplets. Furthermore, a SAW device structure is demonstrated in which the ZnO piezoelectric only exists under the input and output transducers. This structure still permits pumping, while avoiding direct contact between the piezoelectric material and the fluid. This is of particular importance for biological laboratory-on-a-chip applications.

  2. Investigation of chemical bath deposition of ZnO thin films using six different complexing agents

    NASA Astrophysics Data System (ADS)

    Khallaf, Hani; Chai, Guangyu; Lupan, Oleg; Heinrich, Helge; Park, Sanghoon; Schulte, Alfons; Chow, Lee

    2009-07-01

    Chemical bath deposition of ZnO thin films using six different complexing agents, namely ammonia, hydrazine, ethanolamine, methylamine, triethanolamine and dimethylamine, is investigated. As-grown films were mainly ZnO2 with a band gap around 4.3 eV. Films annealed at 400 °C were identified as ZnO with a band gap around 3.3 eV. X-ray diffraction and micro-Raman spectroscopy revealed that as-grown films consist mainly of cubic zinc peroxide that was transformed into hexagonal ZnO after annealing. Rutherford backscattering spectroscopy (RBS) detected excess oxygen content in ZnO films after annealing. Fourier transform infrared spectroscopy of as-grown films showed a broad absorption band around 3300 cm-1 suggesting that the as-grown films may consist of a mixture of zinc peroxide and zinc hydroxide. X-ray photoelectron spectroscopy multiplex spectra of the O 1s peak were found to be consistent with film stoichiometry revealed by RBS. High-resolution transmission electron micrographs showed small variations of the order of 10 nm in film thickness which corresponds to the average grain size. A carrier density as high as 2.24×1019 cm-3 and a resistivity as low as 6.48 × 10-1 Ω cm were obtained for films annealed at 500 °C in argon ambient.

  3. Effect of defect content on the unipolar resistive switching characteristics of ZnO thin film memory devices

    NASA Astrophysics Data System (ADS)

    Zhang, Feng; Li, Xiaomin; Gao, Xiangdong; Wu, Liang; Zhuge, Fuwei; Wang, Qun; Liu, Xinjun; Yang, Rui; He, Yong

    2012-09-01

    In this study, unipolar resistive switching (URS) characteristics in ZnO thin film memory devices were systematically investigated with variable defect content. ZnO films displayed typically URS behavior while oxygen-deficient ZnO1-x films did not show resistive switching effects. The devices with two intentional Ohmic interfaces still show URS. These results show that appearance of URS behavior can be dominated by initial oxygen vacancy content in ZnO thin films. Modest increase in oxygen vacancy content in ZnO films will lead to forming-free and narrower distributions of switching parameters (set and reset voltage, high and low resistance states). It indicates that controlling the initial oxygen vacancy content was an effective method to enhance the URS performance.

  4. 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.

  5. A comparative study of physico-chemical properties of CBD and SILAR grown ZnO thin films

    SciTech Connect

    Jambure, S.B.; Patil, S.J.; Deshpande, A.R.; Lokhande, C.D.

    2014-01-01

    Graphical abstract: Schematic model indicating ZnO nanorods by CBD (Z{sub 1}) and nanograins by SILAR (Z{sub 2}). - Highlights: • Simple methods for the synthesis of ZnO thin films. • Comparative study of physico-chemical properties of ZnO thin films prepared by CBD and SILAR methods. • CBD outperforms SILAR method. - Abstract: In the present work, nanocrystalline zinc oxide (ZnO) thin films have been successfully deposited onto glass substrates by simple and economical chemical bath deposition (CBD) and successive ionic layer adsorption reaction (SILAR) methods. These films were further characterized for their structural, optical, surface morphological and wettability properties. The X-ray diffraction (XRD) patterns for both CBD and SILAR deposited ZnO thin films reveal the highly crystalline hexagonal wurtzite structure. From optical studies, band gaps obtained are 2.9 and 3.0 eV for CBD and SILAR deposited thin films, respectively. The scanning electron microscope (SEM) patterns show growth of well defined randomly oriented nanorods and nanograins on the CBD and SILAR deposited samples, respectively. The resistivity of CBD deposited films (10{sup 2} Ω cm) is lower than that of SILAR deposited films (10{sup 5} Ω cm). Surface wettability studies show hydrophobic nature for both films. From the above results it can be concluded that CBD grown ZnO thin films show better properties as compared to SILAR method.

  6. ZnO thin film piezoelectric MEMS vibration energy harvesters with two piezoelectric elements for higher output performance.

    PubMed

    Wang, Peihong; Du, Hejun

    2015-07-01

    Zinc oxide (ZnO) thin film piezoelectric microelectromechanical systems (MEMS) based vibration energy harvesters with two different designs are presented. These harvesters consist of a silicon cantilever, a silicon proof mass, and a ZnO piezoelectric layer. Design I has a large ZnO piezoelectric element and Design II has two smaller and equally sized ZnO piezoelectric elements; however, the total area of ZnO thin film in two designs is equal. The ZnO thin film is deposited by means of radio-frequency magnetron sputtering method and is characterized by means of XRD and SEM techniques. These ZnO energy harvesters are fabricated by using MEMS micromachining. The natural frequencies of the fabricated ZnO energy harvesters are simulated and tested. The test results show that these two energy harvesters with different designs have almost the same natural frequency. Then, the output performance of different ZnO energy harvesters is tested in detail. The effects of series connection and parallel connection of two ZnO elements on the load voltage and power are also analyzed. The experimental results show that the energy harvester with two ZnO piezoelectric elements in parallel connection in Design II has higher load voltage and higher load power than the fabricated energy harvesters with other designs. Its load voltage is 2.06 V under load resistance of 1 MΩ and its maximal load power is 1.25 μW under load resistance of 0.6 MΩ, when it is excited by an external vibration with frequency of 1300.1 Hz and acceleration of 10 m/s(2). By contrast, the load voltage of the energy harvester of Design I is 1.77 V under 1 MΩ resistance and its maximal load power is 0.98 μW under 0.38 MΩ load resistance when it is excited by the same vibration. PMID:26233403

  7. ZnO thin film piezoelectric MEMS vibration energy harvesters with two piezoelectric elements for higher output performance

    NASA Astrophysics Data System (ADS)

    Wang, Peihong; Du, Hejun

    2015-07-01

    Zinc oxide (ZnO) thin film piezoelectric microelectromechanical systems (MEMS) based vibration energy harvesters with two different designs are presented. These harvesters consist of a silicon cantilever, a silicon proof mass, and a ZnO piezoelectric layer. Design I has a large ZnO piezoelectric element and Design II has two smaller and equally sized ZnO piezoelectric elements; however, the total area of ZnO thin film in two designs is equal. The ZnO thin film is deposited by means of radio-frequency magnetron sputtering method and is characterized by means of XRD and SEM techniques. These ZnO energy harvesters are fabricated by using MEMS micromachining. The natural frequencies of the fabricated ZnO energy harvesters are simulated and tested. The test results show that these two energy harvesters with different designs have almost the same natural frequency. Then, the output performance of different ZnO energy harvesters is tested in detail. The effects of series connection and parallel connection of two ZnO elements on the load voltage and power are also analyzed. The experimental results show that the energy harvester with two ZnO piezoelectric elements in parallel connection in Design II has higher load voltage and higher load power than the fabricated energy harvesters with other designs. Its load voltage is 2.06 V under load resistance of 1 MΩ and its maximal load power is 1.25 μW under load resistance of 0.6 MΩ, when it is excited by an external vibration with frequency of 1300.1 Hz and acceleration of 10 m/s2. By contrast, the load voltage of the energy harvester of Design I is 1.77 V under 1 MΩ resistance and its maximal load power is 0.98 μW under 0.38 MΩ load resistance when it is excited by the same vibration.

  8. Recent advances in the transparent conducting ZnO for thin-film Si solar cells

    NASA Astrophysics Data System (ADS)

    Moon, Taeho; Shin, Gwang Su; Park, Byungwoo

    2015-11-01

    The key challenge for solar-cell development lies in the improvement of power-conversion efficiency and the reduction of fabrication cost. For thin-film Si solar cells, researches have been especially focused on the light trapping for the breakthrough in the saturated efficiencies. The ZnO-based transparent conducting oxides (TCOs) have therefore received strong attention because of their excellent light-scattering capability by the texture-etched surface and cost effectiveness through in-house fabrication. Here, we have highlighted our recent studies on the transparent conducting ZnO for thin-film Si solar cells. From the electrical properties and their degradation mechanisms, bilayer deposition and organic-acid texturing approaches for enhancing the light trapping, and finally the relation between textured ZnO and electrical cell performances are sequentially introduced in this review article. [Figure not available: see fulltext.

  9. Improved sensing response of photo activated ZnO thin film for hydrogen peroxide detection.

    PubMed

    Parthasarathy, S; Nandhini, V; Jeyaprakash, B G

    2016-11-15

    The nanostructured ZnO thin films were deposited using spray pyrolysis technique. Formation of polycrystalinity with hexagonal wurtzite structure was observed from the structural study. Highly dense spherical shaped nanoparticles with fine crystallites were observed from the surface morphological studies. The light induced hydrogen peroxide vapour sensing was done using chemi-resistive method and its effect on the sensing response was studied and reported. PMID:27491004

  10. 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.

  11. Optical and electrical studies of ZnO thin films heavily implanted with silver ions

    NASA Astrophysics Data System (ADS)

    Lyadov, N. M.; Gumarov, A. I.; Valeev, V. F.; Nuzhdin, V. I.; Khaibullin, R. I.; Faizrakhmanov, I. A.

    2014-12-01

    Thin films of zinc oxide (ZnO) with the thickness of 200 nm have been deposited on quartz substrates by using ion-beam sputtering technique. Then Ag+ ions with the energy of 30 keV have been implanted into as-deposited ZnO films to the fluences in the range of (0.25-1.00)×1017 ions/cm2 to form ZnO:Ag composite layers with different concentrations of the silver impurity. The analysis of the microstructure has shown that the thickness of the ZnO film decreases, and the Ag dopant concentration tends to the saturation with increasing Ag implantation fluence. The ZnO:Ag composite layers reveal the optical selective absorption at the wavelength of the surface plasmon resonance that is typical for silver nanoparticles dispersed in the ZnO matrix. The red shift of the plasmon resonance peak from 480 to 500 nm is observed with the increase in the implantation fluence to 0.75×1017 Ag ions/cm2. Then the absorption peak position starts the backward motion, and the absorption intensity decreases with the subsequent increase in the implantation fluence. The non-monotonic dependence of the absorption peak position on the implantation fluence has been analyzed within of Maxwell Garnet theory and taking into account the strong sputtering of ZnO films during implantation. The ZnO:Ag composite layers exhibit the p-type conductivity indicating that a part of Ag+ ions is in the form of acceptor impurities implanted into the ZnO lattice.

  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. Structural and optical properties of Ni added ZnO thin films deposited by sol-gel method

    SciTech Connect

    Murugan, R.; Vijayaprasath, G.; Anandhan, N. E-mail: gravicrc@gmail.com; Ravi, G. E-mail: gravicrc@gmail.com; Mahalingam, T.

    2014-04-24

    Pure and Ni added zinc oxide thin films were prepared by sol-gel method using spin-coating technique on glass substrates. The influences of nickel on ZnO thin films are characterized by Powder X-ray diffraction study. Pure and Ni added thin films are hexagonal wurtzite structure without any secondary phase in c-axis orientation. The SEM images of thin films show uniform sphere like particles covered completely on glass substrates. All the films exhibit transmittance of 85-95% in the visible range up to 800nm and cut-off wavelength observed at 394 nm corresponding to the fundamental absorption of ZnO. The photoluminescence property for pure and Ni added ZnO thin films has been studied and results are presented in detail.

  14. 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 (

  15. Fabrication and Characterization of High-Crystalline Nanoporous ZnO Thin Films by Modified Thermal Evaporation System

    NASA Astrophysics Data System (ADS)

    Islam, M. S.; Hossain, M. F.; Razzak, S. M. A.; Haque, M. M.; Saha, D. K.

    2016-05-01

    The aim of this work is to fabricate high-crystalline nanoporous zinc oxide (ZnO) thin films by a modified thermal evaporation system. First, zinc thin films have been deposited on bare glass substrate by the modified thermal evaporation system with pressure of 0.05mbar, source-substrate distance of 3cm and source temperature 700∘C. Then, high-crystalline ZnO thin film is obtained by annealing at 500∘C for 2h in atmosphere. The prepared ZnO films are characterized with various deposition times of 10min and 20min. The structural property was investigated by X-ray diffractometer (XRD). The optical bandgap and absorbance/transmittance of these films are examined by ultraviolet/visible spectrophotometer. The surface morphological property has been observed by scanning electron microscope (SEM). ZnO films have showed uniform nanoporous surface with high-crystalline hexagonal wurtzite structure. The ZnO films prepared with 20min has excitation absorption-edge at 369nm, which is blueshifted with respect to the bulk absorption-edge appearing at 380nm. The gap energy of ZnO film is decreased from 3.14eV to 3.09eV with increase of the deposition time, which can enhance the excitation of ZnO films by the near visible light, and is suitable for the application of photocatalyst of waste water cleaning and polluted air purification.

  16. 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.

  17. Characterization of ZnO Thin Films Prepared by Thermal Oxidation of Zn

    NASA Astrophysics Data System (ADS)

    Bouanane, I.; Kabir, A.; Boulainine, D.; Zerkout, S.; Schmerber, G.; Boudjema, B.

    2016-07-01

    Zinc oxide thin films were prepared by thermal oxidation of zinc films at a temperature of 500°C for 2 h. The Zn films were deposited onto glass substrates by magnetron RF sputtering. The sputtering time varied from 2.5 min to 15 min. The physico-chemical characterization of the ZnO films was carried out depending on the Zn sputtering time. According to x-ray diffraction, ZnO films were polycrystalline and the Zn-ZnO phase transformation was direct. The mean transmittance of the ZnO films was around 80% and the band gap increased from 3.15 eV to 3.35 eV. Photoluminescence spectra show ultraviolet, visible, and infrared emission bands. The increase of the UV emission band was correlated with the improvement of the crystalline quality of the ZnO films. The concentration of native defects was found to decrease with increasing Zn sputtering time. The decrease of the electrical resistivity as a function of Zn sputtering time was linked to extrinsic hydrogen-related defects.

  18. Characterization of ZnO Thin Films Prepared by Thermal Oxidation of Zn

    NASA Astrophysics Data System (ADS)

    Bouanane, I.; Kabir, A.; Boulainine, D.; Zerkout, S.; Schmerber, G.; Boudjema, B.

    2016-04-01

    Zinc oxide thin films were prepared by thermal oxidation of zinc films at a temperature of 500°C for 2 h. The Zn films were deposited onto glass substrates by magnetron RF sputtering. The sputtering time varied from 2.5 min to 15 min. The physico-chemical characterization of the ZnO films was carried out depending on the Zn sputtering time. According to x-ray diffraction, ZnO films were polycrystalline and the Zn-ZnO phase transformation was direct. The mean transmittance of the ZnO films was around 80% and the band gap increased from 3.15 eV to 3.35 eV. Photoluminescence spectra show ultraviolet, visible, and infrared emission bands. The increase of the UV emission band was correlated with the improvement of the crystalline quality of the ZnO films. The concentration of native defects was found to decrease with increasing Zn sputtering time. The decrease of the electrical resistivity as a function of Zn sputtering time was linked to extrinsic hydrogen-related defects.

  19. Electrode loading effect and high temperature performance of ZnO thin film ultrasonic transducers

    NASA Astrophysics Data System (ADS)

    Zhou, X. S.; Zhang, J.; Hou, R.; Zhao, C.; Kirk, K. J.; Hutson, D.; Hu, P. A.; Peng, S. M.; Zu, X. T.; Fu, Y. Q.

    2014-10-01

    Nanocrystalline ZnO films of 5.8 μm thick were sputter-deposited on ferritic carbon steel plates (25 × 25 × 3 mm3) and characterized for use as ultrasonic transducers at both room temperature and high temperatures. Electrode loading effects have been studied using two types of electrodes, i.e., sputtered Cr/Au (5/50 nm) and silver paste, with electrode diameters 0.7-2.5 mm. Longitudinal and transverse waves were obtained in pulse-echo tests using both types of electrodes. With a silver paste top electrode, a dominant longitudinal mode was obtained, but with a thin Cr/Au film as the top electrode, shear waves were more dominant. Pulse-echo tests of the ZnO transducers were also performed at elevated temperatures up to 450 °C using a carbon paste electrodes. The sputtered ZnO films maintained a stable crystalline structure and orientation at the elevated temperatures, and ZnO devices on ferritic carbon steel could be used successfully up to 400 °C. However, when the temperature was increased further, rapid surface oxidation of the ferritic carbon steel caused the failure of the transducer.

  20. Photocatalytic efficiency of reusable ZnO thin films deposited by sputtering technique

    NASA Astrophysics Data System (ADS)

    Ahumada-Lazo, R.; Torres-Martínez, L. M.; Ruíz-Gómez, M. A.; Vega-Becerra, O. E.; Figueroa-Torres, M. Z.

    2014-12-01

    The photocatalytic activity of ZnO thin films with different physicochemical characteristics deposited by RF magnetron sputtering on glass substrate was tested for the decolorization of orange G dye aqueous solution (OG). The crystalline phase, surface morphology, surface roughness and the optical properties of these ZnO films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV-visible spectroscopy (UV-Vis), respectively. The dye photodecolorization process was studied at acid, neutral and basic pH media under UV irradiation of 365 nm. Results showed that ZnO films grow with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a (002) preferential crystalline orientation. A clear relationship between surface morphology and photocatalytic activity was observed for ZnO films. Additionally, the recycling photocatalytic abilities of the films were also evaluated. A promising photocatalytic performance has been found with a very low variation of the decolorization degree after five consecutive cycles at a wide range of pH media.

  1. Improved UV photoresponse properties of high-quality ZnO thin films through the use of a ZnO buffer layer on flexible polyimide substrates

    NASA Astrophysics Data System (ADS)

    Kim, Mincheol; Leem, Jae-Young; Son, Jeong-Sik

    2016-03-01

    An oxidized ZnO buffer layer was prepared by using thermal oxidation of a Zn buffer layer on a polyimide (PI) substrate; then, ZnO thin films with (sample 1) and without (sample 2) an oxidized ZnO buffer layer were grown by using the sol-gel spin-coating method. The intensities of the ZnO (002) diffraction peaks observed in sample 1 were stronger than those observed in sample 2, implying that the crystal quality was enhanced by the oxidized ZnO buffer layer. Moreover, the residual stress of sample 1 was reduced compared to that of sample 2 due to the decreased number of defects. Sample 2 exhibited defect-related deep-level orange-yellow emissions, which almost disappeared with the introduction of the ZnO buffer layer (sample 1). The values of the responsivity were 0.733 (sample 1) and 0.066 (sample 2) mA/W; therefore, the proposed method could provide a pathway to the easy fabrication of fast-response UV sensors.

  2. 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.

  3. 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.

  4. Excitonic transition dynamics on front and back surfaces of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Lee, Sun-Kyun; Kwon, Bong-Joon; Cho, Yong-Hoon; Ko, Hang-Ju; Yao, Takafumi

    2011-11-01

    We report strong excitonic transitions and exciton-phonon couplings in the photoluminescence (PL) of ZnO thin films grown on MgO/sapphire (buffer/substrate) by plasma-assisted molecular-beam epitaxy. The room temperature (RT) PL spectra showed that the dominant emission contributions from the front surface area (FS) and the back surface area (BS) are the free exciton (FX) emission and its first longitudinal optical (LO)-phonon replica, respectively. We found that the one LO-phonon replica at the BS of ZnO can be even more intense than the direct (zero-phonon) FX transition at elevated temperatures. Time-resolved PL spectra revealed that the lifetime of FX recombination from FS is longer than that from BS, which is attributed to the reduction of nonradiative recombination at FS. This indicates that the existence of native defects or trap centers, which can be reduced by the proper initial growth condition, and the exciton-phonon interaction couplings play important roles in the excitonic transition properties of ZnO thin films.

  5. 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

  6. Characteristics of Sputtered ZnO Thin Films for an Inverted Organic Solar Cell.

    PubMed

    Park, Yong Seob; Park, Chul Min; Lee, Jaehyeong

    2016-05-01

    Several research groups have claimed high energy conversion efficiency in organic solar cells. However, it still has low efficiency and is unstable, because organic materials are easily oxidized by atmospheric humidity and UV light. In this work, ZnO thin film as the blocking layer attributed to the interference of the injection of the hole from the P3HT and no charge carrier recombination. We obtained the maximum power conversion efficiency of 1.9% under AM 1.5 G spectral illumination of 100 MWcm(-2), when we used a ZnO film of 60 nm and the optimized P3HT:PCBM, and Au as the back electrode to solve the reaction problem of Al electrode and to control the work function between the HOMO level of P3HT and the energy level of the metal electrode. Power conversion efficiency of inverted organic solar cell (IOSC) is significantly dependent on the thickness of the ZnO thin film deposited by unbalanced magnetron sputtering method. Also, the stability of IOSC is measured under ambient conditions. PMID:27483875

  7. 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

  8. Homobuffer thickness effect on the conduction type of non-polar ZnO thin films

    NASA Astrophysics Data System (ADS)

    Pan, X. H.; Ding, P.; Huang, J. Y.; He, H. P.; Ye, Z. Z.; Lu, B.

    2014-10-01

    Non-polar (101bar0) ZnO thin films were epitaxially grown on m-plane sapphire substrates by plasma-assisted molecular beam epitaxy. The homobuffer thickness effect on the conduction type of undoped ZnO thin films is carefully investigated. With a relatively thicker buffer layer, weak p-type conductivity with a hole concentration of 1.6×1016 cm-3, a Hall mobility of 0.33 cm2 V-1 s-1, and a resistivity of 1.2×103 Ω cm are achieved for the film. By careful analysis of results from low temperature photoluminescence and transmission electron microscopy measurements, a correlation of the 3.32-eV emission to the p-type conductivity in the undoped non-polar ZnO films is revealed and discussed. The results are important to help deepen understanding of the origin of p-type behavior in ZnO-based materials.

  9. Flexible pH sensors based on polysilicon thin film transistors and ZnO nanowalls

    NASA Astrophysics Data System (ADS)

    Maiolo, L.; Mirabella, S.; Maita, F.; Alberti, A.; Minotti, A.; Strano, V.; Pecora, A.; Shacham-Diamand, Y.; Fortunato, G.

    2014-09-01

    A fully flexible pH sensor using nanoporous ZnO on extended gate thin film transistor (EGTFT) fabricated on polymeric substrate is demonstrated. The sensor adopts the Low Temperature Polycrystalline Silicon (LTPS) TFT technology for the active device, since it allows excellent electrical characteristics and good stability and opens the way towards the possibility of exploiting CMOS architectures in the future. The nanoporous ZnO sensitive film, consisting of very thin (20 nm) crystalline ZnO walls with a large surface-to-volume ratio, was chemically deposited at 90 °C, allowing simple process integration with conventional TFT micro-fabrication processes compatible with wide range of polymeric substrates. The pH sensor showed a near-ideal Nernstian response (˜59 mV/pH), indicating an ideality factor α ˜ 1 according to the conventional site binding model. The present results can pave the way to advanced flexible sensing systems, where sensors and local signal conditioning circuits will be integrated on the same flexible substrate.

  10. Distribution pattern and allocation of defects in hydrogenated ZnO thin films.

    PubMed

    Gurylev, Vitaly; Su, Chung-Yi; Perng, Tsong-Pyng

    2016-06-21

    A polycrystalline ZnO thin film prepared by atomic layer deposition was annealed in hydrogen at 10 bar and 350-450 °C. Hydrogenation induced simultaneous formation of oxygen and zinc vacancies whose concentrations were closely related to the temperature of treatment. Spatial distributions of these defects were analyzed by photoluminescence confocal mapping which revealed that their localized appearances are linked to each other. It was also demonstrated that nanomechanical mapping of elastic modulus distribution could be used to assess the allocation of accumulated defects on the topmost surface of ZnO with a depth resolution of only several atomic layers. The higher the temperature of hydrogenation, the higher the concentration, and more uniform the distribution of surface defects. In addition, the correlation between the surface morphology and the accumulated defects was established. PMID:27244648

  11. Exciton and core-level electron confinement effects in transparent ZnO thin films

    PubMed Central

    Mosquera, Adolfo A.; Horwat, David; Rashkovskiy, Alexandr; Kovalev, Anatoly; Miska, Patrice; Wainstein, Dmitry; Albella, Jose M.; Endrino, Jose L.

    2013-01-01

    The excitonic light emission of ZnO films have been investigated by means of photoluminescence measurements in ultraviolet-visible region. Exciton confinement effects have been observed in thin ZnO coatings with thickness below 20 nm. This is enhanced by a rise of the intensity and a blue shift of the photoluminescence peak after extraction of the adsorbed species upon annealing in air. It is found experimentally that the free exciton energy (determined by the photoluminescence peak) is inversely proportional to the square of the thickness while core-level binding energy is inversely proportional to the thickness. These findings correlate very well with the theory of kinetic and potential confinements.

  12. Structural and optical characterization of MOCVD-grown ZnO thin films

    NASA Astrophysics Data System (ADS)

    Pagni, O.; James, G. R.; Leitch, A. W. R.

    2004-03-01

    We report on the characterization of ZnO thin films grown by metal organic chemical vapor deposition (MOCVD) using diethyl zinc (DEZ) and tert-butanol (TBOH) as precursors. Substrate temperature proved to be a crucial factor in the crystallization process, as it vastly impacted the structural properties of the samples studied. Highly c-axis oriented films with large grain size (52 nm), low tensile strain (0.6%), uniform substrate coverage and a columnar structure devoid of hexagonal needles were successfully deposited on n-Si (100) substrates. The temperature-dependent luminescence spectra recorded confirmed the excellent quality of the material obtained in this work. Our results so far set TBOH apart as an outstanding oxygen source for the MOCVD growth of ZnO.

  13. 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.

  14. Perovskite solar cells based on nanocolumnar plasma-deposited ZnO thin films.

    PubMed

    Ramos, F Javier; López-Santos, Maria C; Guillén, Elena; Nazeeruddin, Mohammad Khaja; Grätzel, Michael; Gonzalez-Elipe, Agustin R; Ahmad, Shahzada

    2014-04-14

    ZnO thin films having a nanocolumnar microstructure are grown by plasma-enhanced chemical vapor deposition at 423 K on pre-treated fluorine-doped tin oxide (FTO) substrates. The films consist of c-axis-oriented wurtzite ZnO nanocolumns with well-defined microstructure and crystallinity. By sensitizing CH3NH3PbI3 on these photoanodes a power conversion of 4.8% is obtained for solid-state solar cells. Poly(triarylamine) is found to be less effective when used as the hole-transport material, compared to 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD), while the higher annealing temperature of the perovskite leads to a better infiltration in the nanocolumnar structure and an enhancement of the cell efficiency. PMID:24643984

  15. 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

  16. Study of deposition parameters for the fabrication of ZnO thin films using femtosecond laser

    NASA Astrophysics Data System (ADS)

    Hashmi, Jaweria Zartaj; Siraj, Khurram; Latif, Anwar; Murray, Mathew; Jose, Gin

    2016-08-01

    Femtosecond (fs) pulsed laser deposition (fs-PLD) of ZnO thin film on borosilicate glass substrates is reported in this work. The effect of important fs-PLD parameters such as target-substrate distance, laser pulse energy and substrate temperature on structure, morphology, optical transparency and luminescence of as-deposited films is discussed. XRD analysis reveals that all the films grown using the laser energy range 120-230 μJ are polycrystalline when they are deposited at room temperature in a ~10-5 Torr vacuum. Introducing 0.7 mTorr oxygen pressure, the films show preferred c-axis growth and transform into a single-crystal-like film when the substrate temperature is increased to 100 °C. The scanning electron micrographs show the presence of small nano-size grains at 25 °C, which grow in size to the regular hexagonal shape particles at 100 °C. Optical transmission of the ZnO film is found to increase with an increase in crystal quality. Maximum transmittance of 95 % in the wavelength range 400-1400 nm is achieved for films deposited at 100 °C employing a laser pulse energy of 180 μJ. The luminescence spectra show a strong UV emission band peaked at 377 nm close to the ZnO band gap. The shallow donor defects increase at higher pulse energies and higher substrate temperatures, which give rise to violet-blue luminescence. The results indicate that nano-crystalline ZnO thin films with high crystalline quality and optical transparency can be fabricated by using pulses from fs lasers.

  17. ZnO thin films and nanostructures for emerging optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Rogers, D. J.; Teherani, F. H.; Sandana, V. E.; Razeghi, M.

    2010-02-01

    ZnO-based thin films and nanostructures grown by PLD for various emerging optoelectronic applications. AZO thin films are currently displacing ITO for many TCO applications due to recent improvements in attainable AZO conductivity combined with processing, cost and toxicity advantages. Advances in the channel mobilities and Id on/off ratios in ZnO-based TTFTs have opened up the potential for use as a replacement for a-Si in AM-OLED and AM-LCD screens. Angular-dependent specular reflection measurements of self-forming, moth-eye-like, nanostructure arrays grown by PLD were seen to have <0.5% reflectivity over the whole visible spectrum for angles of incidence between 10 and 60 degrees. Such nanostructures may be useful for applications such as AR coatings on solar cells. Compliant ZnO layers on mismatched/amorphous substrates were shown to have potential for MOVPE regrowth of GaN. This approach could be used as a means to facilitate lift-off of GaN-based LEDs from insulating sapphire substrates and could allow the growth of InGaN-based solar cells on cheap substrates. The green gap in InGaN-based LEDs was combated by substituting low Ts PLD n-ZnO for MOCVD n-GaN in inverted hybrid heterojunctions. This approach maintained the integrity of the InGaN MQWs and gave LEDs with green emission at just over 510 nm. Hybrid n-ZnO/p-GaN heterojunctions were also seen to have the potential for UV (375 nm) EL, characteristic of ZnO NBE emission. This suggests that there was significant hole injection into the ZnO and that such LEDs could profit from the relatively high exciton binding energy of ZnO.

  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. Physical Property Evaluation of ZnO Thin Film Fabricated by Low-Temperature Process for Flexible Transparent TFT.

    PubMed

    Khafe, Adie Bin Mohd; Watanabe, Hiraku; Yamauchi, Hiroshi; Kuniyoshi, Shigekazu; Iizuka, Masaaki; Sakai, Masatoshi; Kudo, Kazuhiro

    2016-04-01

    The usual silicon-based display back planes require fairly high process temperature and thus the development of a low temperature process is needed on flexible plastic substrates. A new type of flexible organic light emitting transistor (OLET) had been proposed and investigated in the previous work. By using ultraviolet/ozone (UV/O3) assisted thermal treatments on wet processed zinc oxide field effect transistor (ZnO-FET), through low-process temperature, ZnO-FETs were fabricated which succeeded to achieve target drain current value and mobility. In this study, physical property evaluation of ZnO was conducted in term of their crystallinity, the increase composition of ZnO formed inside the thin film and the decrease of the carbon impurities originated from aqueous solution of the ZnO itself. The X-ray diffraction (XRD) evaluation showed UV/03 assisted thermal treatment has no obvious effect towards crystallinity of ZnO in the range of low process temperature. Moreover, through X-ray photoelectron spectroscopy (XPS) evaluation and Fourier transform infrared (FT-IR) spectroscopy evaluation, more carbon impurities disappeared from the ZnO thin film and the increase of composition amount of ZnO, when the thin film was subjected to UV/O3 assisted thermal treatment. Therefore, UV/O3 assisted thermal treatment contributed in carbon impurities elimination and accelerate ZnO formation in ZnO thin film, which led to the improvement in the electrical property of ZnO-FET in the low-process temperature. PMID:27451599

  20. 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.

  1. Annealing temperature dependency of ZnO thin films memristive behavior

    NASA Astrophysics Data System (ADS)

    Shaari, N. A. A.; Kasim, S. M. M.; Rusop, M.; Herman, S. H.

    2016-07-01

    The work focuses on the effect of different annealing temperature on the ZnO-based memristive device. Zinc oxide was deposited on the ITO substrate by sol-gel spincoating technique. The deposited ZnO thin films were then annealed from 50°C to 450°C in a furnace for 60 minutes each. The electrodes Platinum (Pt) were sputtered by using JEOL JFC-1600 Auto Fine Coater. The thin film thicknesses were measured by Veeco Dektak 150 Surface Profiler. The thickness of the thin film annealed at 350°C is the thinnest, which is 54.78nm and from the electrical characterization it also shown the switching characteristic behavior. The surface morphology and topology to examine the existence of nanoparticles

  2. Synthesis of ZnO nanowires for thin film network transistors

    NASA Astrophysics Data System (ADS)

    Dalal, S. H.; Unalan, H. E.; Zhang, Y.; Hiralal, Pritesh; Gangloff, L.; Flewitt, Andrew J.; Amaratunga, Gehan A. J.; Milne, William I.

    2008-08-01

    Zinc oxide nanowire networks are attractive as alternatives to organic and amorphous semiconductors due to their wide bandgap, flexibility and transparency. We demonstrate the fabrication of thin film transistors (TFT)s which utilize ZnO nanowires as the semiconducting channel. These thin film transistors can be transparent and flexible and processed at low temperatures on to a variety of substrates. The nanowire networks are created using a simple contact transfer method that is easily scalable. Apparent nanowire network mobility values can be as high as 3.8 cm2/Vs (effective thin film mobility: 0.03 cm2/Vs) in devices with 20μm channel lengths and ON/OFF ratios of up to 104.

  3. Characterization of nanostructured ZnO thin films deposited through vacuum evaporation

    PubMed Central

    Maldonado, Arturo; Juarez, Héctor; Pacio, Mauricio; Perez, Rene

    2015-01-01

    Summary This work presents a novel technique to deposit ZnO thin films through a metal vacuum evaporation technique using colloidal nanoparticles (average size of 30 nm), which were synthesized by our research group, as source. These thin films had a thickness between 45 and 123 nm as measured by profilometry. XRD patterns of the deposited thin films were obtained. According to the HRSEM micrographs worm-shaped nanostructures are observed in samples annealed at 600 °C and this characteristic disappears as the annealing temperature increases. The films obtained were annealed from 25 to 1000 °C, showing a gradual increase in transmittance spectra up to 85%. The optical band gaps obtained for these films are about 3.22 eV. The PL measurement shows an emission in the red and in the violet region and there is a correlation with the annealing process. PMID:25977868

  4. Influence of water content in mixed solvent on surface morphology, wettability, and photoconductivity of ZnO thin films

    PubMed Central

    2014-01-01

    ZnO thin films have been synthesized by means of a simple hydrothermal method with different solvents. The effect of deionized water content in the mixed solvents on the surface morphology, crystal structure, and optical property has been investigated by scanning electron microscopy, X-ray diffraction, and UV-Vis spectrophotometer. A large number of compact and well-aligned hexagonal ZnO nanorods and the maximal texture coefficient have been observed in the thin film, which is grown in the mixed solvent with x = 40%. A lot of sparse, diagonal, and pointed nanorods can be seen in the ZnO thin film, which is grown in the 40-mL DI water solution. The optical band gap decreases firstly and then increases with the increase of x. Reversible wettability of ZnO thin films were studied by home-made water contact angle apparatus. Reversible transition between hydrophobicity and hydrophilicity may be attributed to the change of surface chemical composition, surface roughness and the proportion of nonpolar planes on the surface of ZnO thin films. Photocurrent response of ZnO thin films grown at different solvents were measured in air. The response duration of the thin film, which is grown in the solvent with x = 40%, exhibits a fast growth in the beginning but cannot approach the saturate current value within 100 s. The theoretical mechanism for the slower growth or decay duration of the photocurrent has been discussed in detail. PMID:25249823

  5. 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.

  6. Nitrogen-doped ZnO thin films by use of laser ablation of ZnO(1-x)Nx targets

    NASA Astrophysics Data System (ADS)

    Okato, Takeshi; Osada, Takenori; Obara, Minoru

    2005-04-01

    ZnO is inherently a strong n-type semiconductor due to its intrinsic defects. Among the group V elements (N, As, P, Sb), nitrogen is considered as teh most hopeful dopant for p-type ZnO, because substitute N (N0) is a relatively shallow acceptor. However, technical issues of the low solubility for the desirable defect and compensations from undesirable donor-like defects are imposed on the development of high mobility and low resistivity p-type ZnO. Breaking through these issues is accompanied by the optimization of dopant concentration and reduction of intrinsic defects. In this study, we have investigated the dependence of the nitrogen concentration on its electrical properties. Home-made ZnO1-xNx targets were prepared and used for KrF excimer pulsed-laser deposition (PLD) at precisely controlled growth conditions. Thin films were deposited on c-cut sapphire substrates. The nitrogen concentration was tuned by adjusting the amount of nitrogen in the ablation targets. The film properties were characterized by x-ray diffraction (XRD) and x-ray photoemission spectroscopy (XPS). The electrical properties were measured by van der Pauw method. The as-grown ZnO:N films showed n-type conductivity, however, they were converted to p-type upon post-deposition thermal treatment. Further improvement was demonstrated by introducing a ZnO low-temperature buffer layer which realized the lattice mismatch relaxation.

  7. 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.

  8. 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.

  9. Effect of substrate temperature on residual stress of ZnO thin films prepared by ion beam deposition

    NASA Astrophysics Data System (ADS)

    Jeon, Ju-Won; Kim, Myoung; Jang, Lee-Woon; Hoffman, J. L.; Kim, Nam Soo; Lee, In-Hwan

    2012-02-01

    We have investigated the effect of substrate temperature on micro-structural properties of ZnO thin films prepared by ion beam deposition technique. ZnO thin films were deposited on AlN-buffered Si (111) and sapphire (001) substrates at various substrate temperatures. The structural properties and surface morphologies were examined by high resolution X-ray diffraction (XRD) and field emission scanning electron microscopy, respectively. The RMS roughness was measured by atomic force microscopy. XRD measurements confirmed that the ZnO thin films were grown well on the AlN-buffered Si (111) and sapphire (001) substrates along the c-axis. Minimization of residual stress was carried out by tuning the substrate temperature. The structural properties were notably improved with increasing substrate temperature.

  10. Pulsed-laser deposition of inclined ZnO, of GaPO4 and of novel composite thin films

    NASA Astrophysics Data System (ADS)

    Pedarnig, J. D.; Peruzzi, M.; Vrejoiu, I.; Matei, D. G.; Dinescu, M.; Bäuerle, D.

    2005-07-01

    Pulsed-laser deposition of different novel thin film materials is reported. Pure ZnO, Al-doped and Li-doped ZnO thin films and double-layers with inclined crystal orientation and very strong texture were achieved. The inclined ZnO heterostructures consisted of pure and doped layers of strongly different electrical resistivity. Polycrystalline GaPO4 thin films were grown by F2-laser ablation of ceramic GaPO4. Layers of a novel composite material were produced from BaTiO3/polytetrafluoroethylene mixed targets. The composite films revealed a giant dielectric permittivity, ɛr’≤ 15000, and a strong dependence of permittivity on the thickness of the layers.

  11. Electrical and optical properties of p-type codoped ZnO thin films prepared by spin coating technique

    NASA Astrophysics Data System (ADS)

    Pathak, Trilok Kumar; Kumar, Vinod; Swart, H. C.; Purohit, L. P.

    2016-03-01

    Undoped, doped and codoped ZnO thin films were synthesized on glass substrates using a spin coating technique. Zinc acetate dihydrate, ammonium acetate and aluminum nitrate were used as precursor for zinc, nitrogen and aluminum, respectively. X-ray diffraction shows that the thin films have a hexagonal wurtzite structure for the undoped, doped and co-doped ZnO. The transmittance of the films was above 80% and the band gap of the film varied from 3.20 eV to 3.24 eV for undoped and doped ZnO. An energy band diagram to describe the photoluminescence from the thin films was also constructed. This diagram includes the various defect levels and possible quasi-Fermi levels. A minimum resistivity of 0.0834 Ω-cm was obtained for the N and Al codoped ZnO thin films with p-type carrier conductivity. These ZnO films can be used as a window layer in solar cells and in UV lasers.

  12. 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.

  13. Photoelectrocatrocatalytic hydrolysis of starch by using sprayed ZnO thin films

    NASA Astrophysics Data System (ADS)

    Sapkal, R. T.; Shinde, S. S.; Rajpure, K. Y.; Bhosale, C. H.

    2013-05-01

    Thin films of zinc oxide have been deposited onto glass/FTO substrates at optimized 400 °C by using a chemical spray pyrolysis technique. Deposited films are character photocatalytic activity by using XRD, an SEM, a UV-vis spectrophotometer, and a PEC single-cell reactor. Films are polycrystalline and have a hexagonal (wurtzite) crystal structure with c-axis (002) orientation growth perpendicular to the substrate surface. The observed direct band gap is about 3.22 eV for typical films prepared at 400 °C. The photocatalytic activity of starch with a ZnO photocatalyst has been studied by using a novel photoelectrocatalytic process.

  14. Self-erasing and rewritable wettability patterns on ZnO thin films

    SciTech Connect

    Kekkonen, Ville; Hakola, Antti; Kajava, Timo; Ras, Robin H. A.; Sahramo, Elina; Malm, Jari; Karppinen, Maarit

    2010-07-26

    Self-erasing patterns allow a substrate to be patterned multiple times or could store temporary information for secret communications, and are mostly based on photochromic molecules to change the color of the pattern. Herein we demonstrate self-erasing patterns of wettability on thin ZnO films made by atomic layer deposition. Hydrophilic patterns are written using UV light and decay spontaneously, i.e. become hydrophobic, or are erased aided by vacuum conditions or heat. We demonstrate that these patterns can be applied for channels to confine flow of water without physical walls.

  15. The Electrical Properties of Co-Doped ZnO Thin Films

    SciTech Connect

    Hamid, H. A.; Abdullah, M. J.; Aziz, A. A.

    2010-03-11

    Codoped ZnO thin films were prepared on silicon (111) substrates by cosputtering of aluminium rods and zinc target using DC magnetron sputtering followed by heat treatment at 400 deg. C for 1 hour at different ratios of oxygen and nitrogen gas. Results indicate that gas ratios influenced the film conduction properties, which had the lowest resistivity of 7.985x10{sup -3} cm{sup -3} and highest carrier concentration of 6.89x10{sup 21} cm{sup -3}.

  16. Photoelectrocatalytic decolorization and degradation of textile effluent using ZnO thin films.

    PubMed

    Sapkal, R T; Shinde, S S; Mahadik, M A; Mohite, V S; Waghmode, T R; Govindwar, S P; Rajpure, K Y; Bhosale, C H

    2012-09-01

    Zinc oxide (ZnO) thin films have been successfully deposited onto fluorine doped tin oxide coated glass at substrate temperature of 400 °C and used as electrode in photoelectrocatalytic reactor. The untreated textile effluent was circulated through photoelectrocatalytic reactor under UVA illumination for the decolorization and degradation. Textile effluent was decolorized by 93% within 3h at room temperature with significant reduction in COD (69%). High performance liquid chromatography (HPLC) and Fourier transform infrared spectroscopy (FTIR) analysis of samples before and after decolorization confirmed the degradation of dyes molecules from textile effluent into simpler oxidizable products. Phytotoxicity study revealed reduction in toxic nature of textile effluent after treatment. PMID:22727863

  17. Surface excitons on a ZnO (000-1) thin film

    SciTech Connect

    Kuehn, S. Friede, S.; Elsaesser, T.; Sadofev, S.; Blumstengel, S.; Henneberger, F.

    2013-11-04

    Elementary excitations at the polar (000-1) surface of a 20 nm pseudomorphically grown ZnO thin film are examined by steady state and time-resolved photoluminescence spectroscopy at low temperature. We control the density of emission centers through the deposition of prototypical organic molecules with a carboxylic acid anchor group by the Langmuir-Blodgett technique. Knowledge of the precise film thickness, defect concentrations and number density of deposited molecules leads us to associate the surface exciton emission to defect-related localization centers that are generated through a photochemical process.

  18. 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.

  19. 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.

  20. 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.

  1. Synthesis and characterization of porous structured ZnO thin film for dye sensitized solar cell applications

    NASA Astrophysics Data System (ADS)

    Marimuthu, T.; Anandhan, N.; Mummoorthi, M.; Dharuman, V.

    2016-05-01

    Zinc oxide (ZnO) and zinc oxide/eosin yellow (ZnO/EY) thin films were potentiostatically deposited onto fluorine doped tin oxide (FTO) glass substrate. Effect of eosin yellow dye on structural, morphological and optical properties was studied. X-ray diffraction patterns, micro Raman spectra and photoluminescence (PL) spectra reveal hexagonal wurtzite structure with less atomic defects in 101 plane orientation of the ZnO/EY film. Scanning electron microscopy (SEM) images show flower for ZnO and porous like structure for ZnO/EY thin film, respectively. DSSC was constructed and evaluated by measuring the current density verses voltage curve.

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

    SciTech Connect

    Bieniek, Bjoern; Hofmann, Oliver T.; Rinke, Patrick

    2015-03-30

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

  3. 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

  4. Evidence of Negative Capacitance in Piezoelectric ZnO Thin Films Sputtered on Interdigital Electrodes.

    PubMed

    Laurenti, Marco; Verna, Alessio; Chiolerio, Alessandro

    2015-11-11

    The scaling paradigm known as Moore's Law, with the shrinking of transistors and their doubling on a chip every two years, is going to reach a painful end. Another less-known paradigm, the so-called Koomey's Law, stating that the computing efficiency doubles every 1.57 years, poses other important challenges, since the efficiency of rechargeable energy sources is substantially constant, and any other evolution is based on device architecture only. How can we still increase the computational power/reduce the power consumption of our electronic environments? A first answer to this question comes from the quest for new functionalities. Within this aim, negative capacitance (NC) is becoming one of the most intriguing and studied phenomena since it can be exploited for reducing the aforementioned limiting effects in the downscaling of electronic devices. Here we report the evidence of negative capacitance in 80 nm thick ZnO thin films sputtered on Au interdigital electrodes (IDEs). Highly (002)-oriented ZnO thin films, with a fine-grained surface nanostructure and the desired chemical composition, are deposited at room temperature on different IDEs structures. Direct-current electrical measurements highlighted the semiconducting nature of ZnO (current density in the order of 1 × 10(-3) A/cm(2)). When turned into the alternating current regime (from 20 Hz to 2 MHz) the presence of NC values is observed in the low-frequency range (20-120 Hz). The loss of metal/semiconductor interface charge states under forward bias conditions, together with the presence of oxygen vacancies and piezoelectric/electrostriction effects, is believed to be at the basis of the observed negative behavior, suggesting that ZnO thin-film-based field-effect transistors can be a powerful instrument to go beyond the Boltzmann limit and the downscaling of integrated circuit elements required for the fabrication of portable and miniaturized electronic devices, especially for electric household

  5. Photoluminescence and photoconductivity studies on amorphous and crystalline ZnO thin films obtained by sol-gel method

    NASA Astrophysics Data System (ADS)

    Valverde-Aguilar, G.; Manríquez Zepeda, J. L.

    2015-03-01

    Amorphous and crystalline ZnO thin films were obtained by the sol-gel process. A precursor solution of ZnO was synthesized by using zinc acetate dehydrate as inorganic precursor at room temperature. The films were spin-coated on silicon and glass wafers and gelled in humid air. The films were calcined at 450 °C for 15 min to produce ZnO nanocrystals with a wurtzite structure. Crystalline ZnO film exhibits an absorption band located at 359 nm (3.4 eV). Photoconductivity technique was used to determine the charge transport mechanism on both kinds of films. Experimental data were fitted with straight lines at darkness and under illumination at 355 and 633 nm wavelengths. This indicates an ohmic behavior. The photovoltaic and photoconductivity parameters were determined from the current density versus the applied electrical field results.

  6. 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.

  7. Synthesis, characterization, and hydrogen gas sensing properties of AuNs-catalyzed ZnO sputtered thin films

    NASA Astrophysics Data System (ADS)

    Drmosh, Q. A.; Yamani, Z. H.

    2016-07-01

    Hydrogen present in concentration up to 4 vol.% forms an explosive mixture with air. Its propensity to escape in the event of leak, could lead to quick build-up and formation of an explosive mixture with air in confined spaces, such as an automobile. This necessitates its detection at very low concentration. Zinc oxide (ZnO) is a well-known wide band gap (∼3.37 eV) semiconducting oxide that has been widely used for gas sensing applications. This work reports on the fabrication, characterization and gas sensing performance of nanogold decorated ZnO thin films made by DC reactive sputtering. The sensor films were fabricated by depositing a very thin layer of gold on the sputtered ZnO thin film. The as deposited Au@ZnO films were converted into highly crystalline ZnO film covered with gold nanostructures (AuNs@ZnO) by mild heat treatment. The structural and morphological as well as the compositional homogeneity of the as-deposited and heat-treated ZnO, Au@ZnO and AuNs@ZnO thin films were ascertained. The gas sensing behavior of the AuNs@ZnO thin films towards hydrogen as a function of temperature at different H2 concentrations was investigated and compared with that of pure and heat-treated ZnO films. The effect of the presence of gold nanoparticles on imparting improvement (in terms of higher response signal, high reproducibility and complete reversibility) was established; the optimal operating temperature was about 400 °C. A plausible mechanism for the observed enhancement in the sensing behavior of AuNs@ZnO films towards H2 is proposed.

  8. Characterization of piesoelectric ZnO thin films and the fabrication of piezoelectric micro-cantilevers

    SciTech Connect

    Johnson, Raegan Lynn

    2005-08-01

    In Atomic Force Microscopy (AFM), a microcantilever is raster scanned across the surface of a sample in order to obtain a topographical image of the sample's surface. In a traditional, optical AFM, the sample rests on a bulk piezoelectric tube and a control loop is used to control the tip-sample separation by actuating the piezo-tube. This method has several disadvantages--the most noticeable one being that response time of the piezo-tube is rather long which leads to slow imaging speeds. One possible solution aimed at improving the speed of imaging is to incorporate a thin piezoelectric film on top of the cantilever beam. This design not only improves the speed of imaging because the piezoelectric film replaces the piezo-tube as an actuator, but the film can also act as a sensor. In addition, the piezoelectric film can excite the cantilever beam near its resonance frequency. This project aims to fabricate piezoelectric microcantilevers for use in the AFM. Prior to fabricating the cantilevers and also part of this project, a systematic study was performed to examine the effects of deposition conditions on the quality of piezoelectric ZnO thin films deposited by RF sputtering. These results will be presented. The deposition parameters that produced the highest quality ZnO film were used in the fabrication of the piezoelectric cantilevers. Unfortunately, the fabricated cantilevers warped due to the intrinsic stress of the ZnO film and were therefore not usable in the AFM. The complete fabrication process will be detailed, the results will be discussed and reasons for the warping will be examined.

  9. Different magnetic origins of (Mn, Fe)-codoped ZnO powders and thin films

    SciTech Connect

    Fan, Jiuping; Jiang, Fengxian; Quan, Zhiyong; Qing, Xiufang; Xu, Xiaohong

    2012-11-15

    Graphical abstract: The effects of the sample forms, fabricated methods, and process conditions on the structural and magnetic properties of (Mn, Fe)-codoped ZnO powders and films were systematically studied. The origins of ferromagnetism in the vacuum-annealed powder and PLD-deposited film are different. The former originates from the impurities of magnetic clusters, whereas the latter comes from the almost homogenous phase. Highlights: ► The magnetic natures of Zn{sub 0.98}Mn{sub 0.01}Fe{sub 0.01}O powders and thin films come from different origins. ► The ferromagnetism of the powder is mainly from the contribution of magnetic clusters. ► Whereas the ferromagnetic behavior of the film comes from the almost homogenous phase. -- Abstract: The structural and magnetic properties of (Mn, Fe)-codoped ZnO powders as well as thin films were investigated. The X-ray diffraction and magnetic measurements indicated that the higher sintering temperature facilitates more Mn and Fe incorporation into ZnO. Magnetic measurements indicated that the powder sintered in air at 800 °C showed paramagnetic, but it exhibited obvious room temperature ferromagnetism after vacuum annealing at 600 °C. The results revealed that magnetic clusters were the major contributors to the observed ferromagnetism in vacuum-annealed Zn{sub 0.98}Mn{sub 0.01}Fe{sub 0.01}O powder. Interestingly, the room temperature ferromagnetism was also observed in the Zn{sub 0.98}Mn{sub 0.01}Fe{sub 0.01}O film deposited via pulsed laser deposition from the air-sintered paramagnetic target, but the secondary phases in the film were not detected from X-ray diffraction, transmission electron microscopy, and zero-field cooling and field cooling. Apparently, the magnetic natures of powders and films come from different origins.

  10. Role of indium in highly crystalline ZnO thin films

    SciTech Connect

    Singh, Anil; Chaudhary, Sujeet; Pandya, Dinesh K.

    2013-02-05

    Zinc oxide and indium doped zinc oxide (ZnO:In) transparent conducting thin films were deposited on glass substrates by pulsed DC magnetron sputtering using separate Zn and In targets. The independent control of the In content in ZnO has helped us to explore the role of indium in influencing the oriented (002) growth, crystallinity, conductivity and mobility of the doped films. The lowest resistivity of ZnO:In thin film is 2.73 Multiplication-Sign 10{sup -3} ohm-cm. At the optimal condition of high (002) orientation, ZnO:In films with electrical resistivity of 7.63 Multiplication-Sign 10{sup -3} ohm.cm and mobility of 126.4 cm{sup 2}/V.s are achieved.

  11. Role of indium in highly crystalline ZnO thin films

    NASA Astrophysics Data System (ADS)

    Singh, Anil; Chaudhary, Sujeet; Pandya, Dinesh K.

    2013-02-01

    Zinc oxide and indium doped zinc oxide (ZnO:In) transparent conducting thin films were deposited on glass substrates by pulsed DC magnetron sputtering using separate Zn and In targets. The independent control of the In content in ZnO has helped us to explore the role of indium in influencing the oriented (002) growth, crystallinity, conductivity and mobility of the doped films. The lowest resistivity of ZnO:In thin film is 2.73×10-3 ohm-cm. At the optimal condition of high (002) orientation, ZnO:In films with electrical resistivity of 7.63×10-3 ohm.cm and mobility of 126.4 cm2/V.s are achieved.

  12. Resistive switching behavior of RF magnetron sputtered ZnO thin films

    NASA Astrophysics Data System (ADS)

    Rajalakshmi, R.; Angappane, S.

    2015-06-01

    The resistive switching characteristics of RF magnetron sputtered zinc oxide thin films have been studied. The x-ray diffraction studies confirm the formation of crystalline ZnO on Pt/TiO2/SiOx/Si substrate. We have fabricated Cu/ZnO/Pt device using a shadow masking technique for resistive switching study. Our Cu/ZnO/Pt device exhibits a unipolar resistive switching behaviour. The switching observed in our device could be related to oxygen vacancies or Cu ions that generate the conducting filaments responsible for resistive switching. We found HRS to LRS resistance ratio of as high as ˜200 for our Cu/ZnO/Pt device. The higher resistance ratio and stability of Cu/ZnO/Pt device would make our RF magnetron sputtered zinc oxide thin films suitable for non volatile memory applications.

  13. Enhanced stimulated emission in ZnO thin films using microdisk top-down structuring

    SciTech Connect

    Nomenyo, K.; Kostcheev, S.; Lérondel, G.; Gadallah, A.-S.; Rogers, D. J.

    2014-05-05

    Microdisks were fabricated in zinc oxide (ZnO) thin films using a top-down approach combining electron beam lithography and reactive ion etching. These microdisk structured thin films exhibit a stimulated surface emission between 3 and 7 times higher than that from a reference film depending on the excitation power density. Emission peak narrowing, reduction in lasing threshold and blue-shifting of the emission wavelength were observed along with enhancement in the emitted intensity. Results indicate that this enhancement is due to an increase in the internal quantum efficiency combined with an amplification of the stimulated emission. An analysis in terms of waveguiding is presented in order to explain these effects. These results demonstrate that very significant gains in emission can be obtained through conventional microstructuration without the need for more onerous top-down nanostructuration techniques.

  14. Electrophoretic deposition of transparent ZnO thin films from highly stabilized colloidal suspensions.

    PubMed

    Verde, M; Peiteado, M; Caballero, A C; Villegas, M; Ferrari, B

    2012-05-01

    The parameters that control the stability of ZnO-nanoparticles suspensions and their deposition by electrophoretic deposition were studied, so as to organize the assembly and compaction of nanoparticles. The addition of cationic polyelectrolyte - Polyethylenimine (PEI) - with different molecular weights was investigated, in order to study their effectiveness and the influence of the molecular weight of the organic chain on suspensions dispersion. It was found that PEI with the highest molecular weight provided better dispersion conditions. Cathodic EPD was performed under previously optimized suspensions conditions and over electropolished stainless steel substrates. Experimental results showed that the EPD process in these conditions allows obtaining dense transparent ZnO thin films. Deposition times and intensities were optimized by analyzing the resulting thin films characteristics. Finally, the deposits were characterized by FE-SEM, AFM, and different spectroscopic techniques. PMID:21999953

  15. 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.

  16. Resistive switching behavior of RF magnetron sputtered ZnO thin films

    SciTech Connect

    Rajalakshmi, R.; Angappane, S.

    2015-06-24

    The resistive switching characteristics of RF magnetron sputtered zinc oxide thin films have been studied. The x-ray diffraction studies confirm the formation of crystalline ZnO on Pt/TiO{sub 2}/SiO{sub x}/Si substrate. We have fabricated Cu/ZnO/Pt device using a shadow masking technique for resistive switching study. Our Cu/ZnO/Pt device exhibits a unipolar resistive switching behaviour. The switching observed in our device could be related to oxygen vacancies or Cu ions that generate the conducting filaments responsible for resistive switching. We found HRS to LRS resistance ratio of as high as ∼200 for our Cu/ZnO/Pt device. The higher resistance ratio and stability of Cu/ZnO/Pt device would make our RF magnetron sputtered zinc oxide thin films suitable for non volatile memory applications.

  17. Fabrication and characterization of ZnO nanowires by wet oxidation of Zn thin film deposited on Teflon substrate

    NASA Astrophysics Data System (ADS)

    Farhat, O. F.; Halim, M. M.; Abdullah, M. J.; Ali, M. K. M.; Ahmed, Naser M.; Bououdina, M.

    2015-10-01

    In this study, ZnO nanowires (NWs) were successfully grown for the first time on to Teflon substrate by a wet oxidation of a Zn thin film coated by RF sputtering technique. The sputtered Zn thin film was oxidized at 100 °C for 5 h under water-vapour using a horizontal furnace. This oxidation process transformed Zn thin film into ZnO with wire-like nanostructure. XRD analysis confirms the formation of single nanocrystalline ZnO phase having a low compressive strain. FESEM observations reveal high density of ZnO NWs with diameter ranging from 34 to 52 nm and length about 2.231 μm, which are well distributed in different direction. A flexible ZnO NWs-based metal-semiconductor-metal UV photodetector was fabricated. Photo-response and sensitivity measurements under low power illumination (375 nm, 1.5 mW/cm2) showed a high sensitivity of 2050%, which can be considered a relatively fast response and baseline recovery for UV detection.

  18. 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.

  19. ZnO transparent conductive oxide for thin film silicon solar cells

    NASA Astrophysics Data System (ADS)

    Söderström, T.; Dominé, D.; Feltrin, A.; Despeisse, M.; Meillaud, F.; Bugnon, G.; Boccard, M.; Cuony, P.; Haug, F.-J.; Faÿ, S.; Nicolay, S.; Ballif, C.

    2010-03-01

    There is general agreement that the future production of electric energy has to be renewable and sustainable in the long term. Photovoltaic (PV) is booming with more than 7GW produced in 2008 and will therefore play an important role in the future electricity supply mix. Currently, crystalline silicon (c-Si) dominates the market with a share of about 90%. Reducing the cost per watt peak and energy pay back time of PV was the major concern of the last decade and remains the main challenge today. For that, thin film silicon solar cells has a strong potential because it allies the strength of c-Si (i.e. durability, abundancy, non toxicity) together with reduced material usage, lower temperature processes and monolithic interconnection. One of the technological key points is the transparent conductive oxide (TCO) used for front contact, barrier layer or intermediate reflector. In this paper, we report on the versatility of ZnO grown by low pressure chemical vapor deposition (ZnO LP-CVD) and its application in thin film silicon solar cells. In particular, we focus on the transparency, the morphology of the textured surface and its effects on the light in-coupling for micromorph tandem cells in both the substrate (n-i-p) and superstrate (p-i-n) configurations. The stabilized efficiencies achieved in Neuchâtel are 11.2% and 9.8% for p-i-n (without ARC) and n-i-p (plastic substrate), respectively.

  20. Substrate Temperature Effects on Room Temperature Sensing Properties of Nanostructured ZnO Thin Films.

    PubMed

    Reddy, Jonnala Rakesh; Mani, Ganesh Kumar; Shankar, Prabakaran; Rayappan, John Bosco Balaguru

    2016-01-01

    Zinc oxide (ZnO) thin films were deposited on glass substrates using chemical spray pyrolysis technique at different substrate temperatures such as 523, 623 and 723 K. X-ray diffraction (XRD) patterns confirmed the formation of polycrystalline films with hexagonal wurtzite crystal structure and revealed the change in preferential orientation of the crystal planes. Scanning electron micrographs showed the formation of uniformly distributed spherical shaped grains at low deposition temperature and pebbles like structure at the higher temperature. Transmittance of 85% was observed for the film deposited at 723 K. The band gap of the films was found to be increased from 3.15 to 3.23 eV with a rise in deposition temperature. The electrical conductivity of the films was found to be improved with an increase in substrate temperature. Surface of ZnO thin films deposited at 523 K, 623 K and 723 K were found to be hydrophobic with the contact angles of 92°, 105° and 128° respectively. The room temperature gas sensing characteristics of all the films were studied and found that the film deposited at 623 K showed a better response towards ammonia vapour. PMID:27398478

  1. Synthesis of Various Nanopatterns of ZnO Thin Film Using Sol Gel Method

    NASA Astrophysics Data System (ADS)

    Julia, Sri; Yuliarto, Brian; Nugraha

    2010-10-01

    In order to achieve the different types of nanostructures of Zinc Oxide thin film using the low cost method, this research applied sol gel method and varying volume of solvent composition as the parameter. The volume of solvent composition was varying in amount of 75% distilled water + 25% ethanol, 50% distilled water + ethanol, and 25% distilled water + 75% ethanol. These compositions yield the different in pH value of solution, consequently yield the different of nanopatterns. Other parameter which also used is varying the substrates. In this investigation, kind of substrates used were glass, alumina and silicon. Through these parameters, the morphology of ZnO thin films was formed in various nanopatterns and observed by X-ray diffraction (XRD) and Scanning Electron Microscopic (SEM). X-ray diffraction determined all of the grown films are true ZnO, with wurtzite hexagonal crystal phase. Various patterns that obtained from SEM investigation are nanorod, flowerlike, nanoball and nanofiber. Uniquely, our flowerlike structure is arranged by nanosheet and nanofiber. The particle size of nanorods and nanoballs is about ±250 nm, while particle size of nanosheets is found to be ±500 nm and nanofiber is in the range of ± hundreds nm.

  2. 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.

  3. Effect of different sol concentrations on the properties of nanocrystalline ZnO thin films grown on FTO substrates by sol-gel spin-coating

    NASA Astrophysics Data System (ADS)

    Kim, Ikhyun; Kim, Younggyu; Nam, Giwoong; Kim, Dongwan; Park, Minju; Kim, Haeun; Lee, Wookbin; Leem, Jae-Young; Kim, Jong Su; Kim, Jin Soo

    2014-08-01

    Nanocrystalline ZnO thin films grown on fluorine-doped tinoxide (FTO) substrates were fabricated using the spin-coating method. The structural and the optical properties of the ZnO thin films prepared using different sol concentrations were investigated by using field-emission scanning electron microscopy (FE-SEM), X-ray diffractometry (XRD), photoluminescence (PL) measurements, and ultraviolet-visible (UV-vis) spectrometry. The surface morphology of the ZnO thin films, as observed in the SEM images, exhibited a mountain-chain structure. XRD results indicated that the thin films were preferentially orientated along the direction of the c-axis and that the grain size of the ZnO thin films increased with increasing sol concentration. The PL spectra showed a strong ultraviolet emission peak at 3.22 eV and a broad orange emission peak at 2.0 eV. The intensities of deep-level emission (DLE) gradually increased with increasing sol concentration from 0.4 to 1.0 M. The transmittance spectra of the ZnO thin films showed that the ZnO thin films were transparent (~85%) in the visible region and exhibited sharp absorption edges at 375 nm. Thus, The Urbach energy of ZnO thin films decreased with increasing sol concentration.

  4. SEM and XRD Characterization of ZnO Nanostructured Thin Films Prepared by Sol-Gel Method with Various Annealing Temperatures

    NASA Astrophysics Data System (ADS)

    Amizam, S.; Abdullah, N.; Rafaie, H. A.; Rusop, M.

    2010-03-01

    ZnO thin films were fabricated by the sol-gel method using Zn(CH3COO)2.2H2O (zinc acetate) as starting material. A homogenous and stable solution was prepared by dissolving the zinc acetate in a solution of ethanol and ethanolamine. Deposition of ZnO solution on Si substrate was performed by spin-coating technique and annealed at various temperatures from 200° C to 600° C. The surface morphologies and structural properties of the obtained product were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). SEM analysis showed that the surface boundaries of ZnO thin films were decreased with the increasing of annealing temperature. X-ray analysis showed that the crystallinity of ZnO thin films increased with increasing annealing temperature. The effect of annealing temperature of ZnO thin films was studied.

  5. Single phase formation of Co-implanted ZnO thin films by swift heavy ion irradiation: Optical studies

    SciTech Connect

    Kumar, Ravi; Singh, Fouran; Angadi, Basavaraj; Choi, Ji-Won; Choi, Won-Kook; Jeong, Kwangho; Song, Jong-Han; Khan, M. Wasi; Srivastava, J. P.; Kumar, Ajay; Tandon, R. P.

    2006-12-01

    Low temperature photoluminescence and optical absorption studies on 200 MeV Ag{sup +15} ion irradiated Co-implanted ZnO thin films were studied. The Co clusters present in as implanted samples were observed to be dissolved using 200 MeV Ag{sup +15} ion irradiation with a fluence of 1x10{sup 12} ions/cm{sup 2}. The photoluminescence spectrum of pure ZnO thin film was characterized by the I{sub 4} peak due to the neutral donor bound excitons and the broad green emission. The Co-doped ZnO films show three sharp levels and two shoulders corresponding to 3t{sub 2g} and 2e{sub g} levels of crystal field splitted Co d orbitals, respectively. The ultraviolet-visible absorption spectroscopy also shows the systematic variation of band gap after 200 MeV Ag{sup +15} ion irradiation.

  6. The porous nature of ZnO thin films deposited by sol-gel Spin-Coating technique

    NASA Astrophysics Data System (ADS)

    Karyaoui, M.; Ben Jaballah, A.; Mechiak, R.; Chtourou, R.

    2012-02-01

    Zinc oxide (ZnO) thin films were deposited on silicon and quartz substrates, by sol-gel method, using zinc acetate dehydrate [Zn(CH3COO)2.2H2O] dissolved in isopropanol and glycerol. The structural, morphologic and optical properties of ZnO thin films subsequently annealed at 700°C in air for 30 min have leads to a porous nature of these films. To calculate, the refraction index and the extinction coefficient values, Cauchy formalism is used to evaluate the Spectroscopic Ellipsometry results. Two distinct configurations were proposed for each sample: in the first, the film is considered as mixture of randomly distributed voids and ZnO crystallites while in the second, the effect of porosity gradient is highlighted. This optical analysis gives a better agreement between experiment and theory for a wide range of wavelengths regarding the second configuration.

  7. The influence of substrate curvature on structural, optical properties of Cu, Co codoped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Liu, Huilian; Li, Weijun; Li, Hongbo; Sun, Yunfei; Song, Junlin; Yang, Jinghai; Gao, Ming; Liu, Xiaoyan

    2015-07-01

    The influence of substrate curvature on structural, optical properties of Cu, Co codoped ZnO thin films were investigated in this study. XRD analysis indicated that the crystal quality of the ZnO films could been influenced by the substrate curvature. The biaxial stress of our samples was measured by side-inclination X-ray diffraction technique. The results indicated that the type of the stress was biaxial compressive stress. Optical absorption spectra showed the absorption edge of our samples displayed blueshift with decreasing substrate curvature. Gauss fit for PL emission spectra showed that the substrate curvature affected the PL properties of the Cu, Co codoped ZnO thin films deposited on polystyrene particles. The various substrates induced defect-related emission increased in visible region.

  8. Polar dependent in-plane electric transport of epitaxial ZnO thin films on SrTiO(3) substrates.

    PubMed

    Sun, Gaofeng; Zhao, Kehan; Wu, Yunlong; Wang, Yuhang; Liu, Na; Zhang, Liuwan

    2012-07-25

    Polar (001) and nonpolar (110) ZnO epitaxial thin films were grown on SrTiO(3) substrates by the pulsed laser deposition method and the in-plane electric transport was investigated. Both films display semiconducting behavior. The polar thin films have linear I-V relations with mobility increasing almost linearly with temperature. In contrast, for nonpolar ZnO thin films, the I-V curves are symmetric and nonlinear with room temperature resistivity 30 times larger than that of polar thin films. We conclude that in nonpolar ZnO thin films the bound polarization charge induced barrier limits the carrier transport. Instead, for polar thin films, the polar effect on the in-plane transport is negligible, and the charged dislocation scattering is dominant. Our observations suggest the polar effect should be considered in the design of ZnO related devices. PMID:22713690

  9. Polar dependent in-plane electric transport of epitaxial ZnO thin films on SrTiO3 substrates

    NASA Astrophysics Data System (ADS)

    Sun, Gaofeng; Zhao, Kehan; Wu, Yunlong; Wang, Yuhang; Liu, Na; Zhang, Liuwan

    2012-07-01

    Polar (001) and nonpolar (110) ZnO epitaxial thin films were grown on SrTiO3 substrates by the pulsed laser deposition method and the in-plane electric transport was investigated. Both films display semiconducting behavior. The polar thin films have linear I-V relations with mobility increasing almost linearly with temperature. In contrast, for nonpolar ZnO thin films, the I-V curves are symmetric and nonlinear with room temperature resistivity 30 times larger than that of polar thin films. We conclude that in nonpolar ZnO thin films the bound polarization charge induced barrier limits the carrier transport. Instead, for polar thin films, the polar effect on the in-plane transport is negligible, and the charged dislocation scattering is dominant. Our observations suggest the polar effect should be considered in the design of ZnO related devices.

  10. Study of p-type ZnO and MgZnO Thin Films for Solid State Lighting

    SciTech Connect

    Liu, Jianlin

    2015-07-31

    This project on study of p-type ZnO and MgZnO thin films for solid state lighting was carried out by research group of Prof. Jianlin Liu of UCR during the four-year period between August 2011 and July 2015. Tremendous progress has been made on the proposed research. This final report summarizes the important findings.

  11. Conductive ZnO:Zn Composites for High-Rate Sputtering Deposition of ZnO Thin Films

    NASA Astrophysics Data System (ADS)

    Zhou, Li Qin; Dubey, Mukul; Simões, Raul; Fan, Qi Hua; Neto, Victor

    2015-02-01

    We report an electrically conductive composite prepared by sintering ZnO and metallic Zn powders. Microstructure analysis combined with electrical conductivity studies indicated that when the proportion of metallic Zn reached a threshold (˜20 wt.%), a metal matrix was formed in accordance with percolation theory. This composite has potential as a sputtering target for deposition of high-quality ZnO. Use of the ZnO:Zn composite completely eliminates target poisoning effects in reactive sputtering of the metal, and enables deposition of thin ZnO films at rates much higher than those obtained by sputtering of pure ZnO ceramic targets. The optical transmittance of the ZnO films prepared by use of this composite is comparable with that of films produced by radio frequency sputtering of pure ZnO ceramic targets. The sputtering characteristics of the conductive ZnO:Zn composite target are reported, and possible mechanisms of the high rate of deposition are also discussed.

  12. 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.

  13. 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.

  14. Annealing effect on the optical and electrical properties of ZnO thin film grown on inp substrate

    NASA Astrophysics Data System (ADS)

    Ghosh, K.; Majumdar, S.; Bhunia, S.

    2012-06-01

    ZnO thin films have been fabricated by sublimation process on indium phosphide (InP) (111) substrates. These films were annealed at various temperatures in order to study the annealing effect on the optical and electrical properties of ZnO thin film grown on InP substrate. From photoluminescence study it was observed that the near band edge peak, i.e., excitonic peak, decreases drastically with the increase of annealing temperature. This indicates that at higher annealing temperature the recombinations are taking place in non-radiative way. It was also observed that the defect related broad peak around 500 nm, i.e., green luminescence peak for ZnO, increases at higher annealing temperatures. As O vacancy is responsible for the green luminescence, so more oxygen vacancies have been introduced at higher annealing temperatures. The electrical characterization of ZnO film revealed that the resistivity of the film increases with the increasing annealing temperatures. Ionised Zn interstitials contribute to carrier concentration in ZnO. Evaporation of Zn interstitials at higher annealing temperatures may have decreased the carrier concentration which in tern had increased the resistivity.

  15. 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

  16. Effects of Precursor Concentration on Structural and Optical Properties of ZnO Thin Films Grown on Muscovite Mica Substrates by Sol-Gel Spin-Coating.

    PubMed

    Kim, Younggyu; Leem, Jae-Young

    2016-05-01

    The structural and optical properties of the ZnO thin films grown on mica substrates for different precursor concentrations were investigated. The surface morphologies of all the samples indicated that they consisted of granular structures with spherical nano-sized crystallites. The thickness of the ZnO thin films increased significantly and the optical band gap exhibited a blue shift with an increase in the precursor concentration. It is remarkable that the highest I(NBE)/I(DLE) ratio was observed for the ZnO thin film with 0.8 M precursor concentration, even though cracks formed on the surface of this film. PMID:27483897

  17. 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.

  18. 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.

  19. Tuning of undoped ZnO thin film via plasma enhanced atomic layer deposition and its application for an inverted polymer solar cell

    NASA Astrophysics Data System (ADS)

    Jin, Mi-jin; Jo, Junhyeon; Neupane, Guru P.; Kim, Jeongyong; An, Ki-Seok; Yoo, Jung-Woo

    2013-10-01

    We studied the tuning of structural and optical properties of ZnO thin film and its correlation to the efficiency of inverted solar cell using plasma-enhanced atomic layer deposition (PEALD). The sequential injection of DEZn and O2 plasma was employed for the plasma-enhanced atomic layer deposition of ZnO thin film. As the growth temperature of ZnO film was increased from 100 °C to 300 °C, the crystallinity of ZnO film was improved from amorphous to highly ordered (002) direction ploy-crystal due to self crystallization. Increasing oxygen plasma time in PEALD process also introduces growing of hexagonal wurtzite phase of ZnO nanocrystal. Excess of oxygen plasma time induces enhanced deep level emission band (500 ˜ 700 nm) in photoluminescence due to Zn vacancies and other defects. The evolution of structural and optical properties of PEALD ZnO films also involves in change of electrical conductivity by 3 orders of magnitude. The highly tunable PEALD ZnO thin films were employed as the electron conductive layers in inverted polymer solar cells. Our study indicates that both structural and optical properties rather than electrical conductivities of ZnO films play more important role for the effective charge collection in photovoltaic device operation. The ability to tune the materials properties of undoped ZnO films via PEALD should extend their functionality over the wide range of advanced electronic applications.

  20. 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.

  1. Evaluation of transverse piezoelectric coefficient of ZnO thin films deposited on different flexible substrates: a comparative study on the vibration sensing performance.

    PubMed

    Joshi, Sudeep; Nayak, Manjunatha M; Rajanna, K

    2014-05-28

    We report on the systematic comparative study of highly c-axis oriented and crystalline piezoelectric ZnO thin films deposited on four different flexible substrates for vibration sensing application. The flexible substrates employed for present experimental study were namely a metal alloy (Phynox), metal (aluminum), polyimide (Kapton), and polyester (Mylar). ZnO thin films were deposited by an RF reactive magnetron sputtering technique. ZnO thin films of similar thicknesses of 700 ± 30 nm were deposited on four different flexible substrates to have proper comparative studies. The crystallinity, surface morphology, chemical composition, and roughness of ZnO thin films were evaluated by respective material characterization techniques. The transverse piezoelectric coefficient (d31) value for assessing the piezoelectric property of ZnO thin films on different flexible substrates was measured by a four-point bending method. ZnO thin films deposited on Phynox alloy substrate showed relatively better material characterization results and a higher piezoelectric d31 coefficient value as compared to ZnO films on metal and polymer substrates. In order to experimentally verify the above observations, vibration sensing studies were performed. As expected, the ZnO thin film deposited on Phynox alloy substrate showed better vibration sensing performance. It has generated the highest peak to peak output voltage amplitude of 256 mV as compared to that of aluminum (224 mV), Kapton (144 mV), and Mylar (46 mV). Therefore, metal alloy flexible substrate proves to be a more suitable, advantageous, and versatile choice for integrating ZnO thin films as compared to metal and polymer flexible substrates for vibration sensing applications. The present experimental study is extremely important and helpful for the selection of a suitable flexible substrate for various applications in the field of sensor and actuator technology. PMID:24773266

  2. Spin-polarized transport current in n-type codoped ZnO thin films measured by Andreev spectroscopy.

    SciTech Connect

    Yates, K. A.; Behan, A. J.; Neal, J. R.; Score, D. S.; Blythe, H. J.; Gehring, G. A.; Heald, S. M.; Branford, W. R.; Cohen, L. F.; Imperial Coll.; Univ. of Sheffield

    2009-12-01

    We use point-contact Andreev-reflection measurements to determine the spin polarization of the transport current in pulse laser deposited thin films of ZnO with 1% Al and with and without 2% Mn. Only films with Mn are ferromagnetic and show spin polarization of the transport current of up to 55 {+-} 0.5% at 4.2 K, in sharp contrast to measurements of the nonmagnetic films without Mn where the polarization is consistent with zero. Our results imply strongly that ferromagnetism in these Al-doped ZnO films requires the presence of Mn.

  3. Investigations of rapid thermal annealing induced structural evolution of ZnO: Ge nanocomposite thin films via GISAXS

    NASA Astrophysics Data System (ADS)

    Ceylan, Abdullah; Ozcan, Yusuf; Orujalipoor, Ilghar; Huang, Yen-Chih; Jeng, U.-Ser; Ide, Semra

    2016-06-01

    In this work, we present in depth structural investigations of nanocomposite ZnO: Ge thin films by utilizing a state of the art grazing incidence small angle x-ray spectroscopy (GISAXS) technique. The samples have been deposited by sequential r.f. and d.c. sputtering of ZnO and Ge thin film layers, respectively, on single crystal Si(100) substrates. Transformation of Ge layers into Ge nanoparticles (Ge-np) has been initiated by ex-situ rapid thermal annealing of asprepared thin film samples at 600 °C for 30, 60, and 90 s under forming gas atmosphere. A special attention has been paid on the effects of reactive and nonreactive growth of ZnO layers on the structural evolution of Ge-np. GISAXS analyses have been performed via cylindrical and spherical form factor calculations for different nanostructure types. Variations of the size, shape, and distributions of both ZnO and Ge nanostructures have been determined. It has been realized that GISAXS results are not only remarkably consistent with the electron microscopy observations but also provide additional information on the large scale size and shape distribution of the nanostructured components.

  4. 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

  5. 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

  6. Fabrication of ZnO thin films by the photochemical deposition method

    SciTech Connect

    Azuma, Masaki; Ichimura, Masaya

    2008-12-01

    ZnO thin films were fabricated by the photochemical deposition (PCD) method. The deposition solution contains ZnSO{sub 4}, Na{sub 2}SO{sub 3}, Na{sub 2}S{sub 2}O{sub 3} and a small amount of NH{sub 4}OH for pH adjustment. We blew oxygen or oxygen + ozone (O{sub 3}) gas into the solution to increase the dissolved oxygen content and enhance the oxidation reaction. The films were characterized by Auger electron and optical spectroscopy, and a photoelectrochemical (PEC) measurement. On an indium-tin-oxide (ITO) substrate, the films showed high optical transmission in the visible range. In a current-voltage measurement for films on a p-Si substrate, the O{sub 3} bubbling sample showed rectification properties and photovoltaic effects.

  7. 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.

  8. Vibration optimization of ZnO thin film bulk acoustic resonator with ring electrodes

    NASA Astrophysics Data System (ADS)

    Zhao, Zinan; Qian, Zhenghua; Wang, Bin

    2016-04-01

    A rectangular ZnO thin film bulk acoustic resonator with ring electrodes is presented in this paper to demonstrate the existence of a nearly uniform displacement distribution at the central part of this typical resonator. The variational formulation based on two-dimensional scalar differential equations provides a theoretical foundation for the Ritz method adopted in our analysis. The resonant frequencies and vibration distributions for the thickness-extensional modes of this ring electrode resonator are obtained. The structural parameters are optimized to achieve a more uniform displacement distribution and therefore a uniform mass sensitivity, which guarantee the high accuracy and repeatable measurement for sensor detection in an air or a liquid environment. These results provide a fundamental reference for the design and optimization of the high quality sensor.

  9. 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.

  10. 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

  11. 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.

  12. Preparation of dye-adsorbing ZnO thin films by electroless deposition and their photoelectrochemical properties.

    PubMed

    Nagaya, Satoshi; Nishikiori, Hiromasa

    2013-09-25

    Dye-adsorbing ZnO thin films were prepared on ITO films by electroless deposition. The films were formed in an aqueous solution containing zinc nitrate, dimethylamine-borane, and eosin Y at 328 K. The film thickness was 1.2-2.0 μm. Thinner and larger-plane hexagonal columns were produced from the solution containing a higher concentration of eosin Y. A photocurrent was observed in the electrodes containing such ZnO films during light irradiation. The photoelectrochemical performance of the film was improved by increasing the concentration of eosin Y because of increases in the amount of absorbed photons and the electronic conductivity of ZnO. PMID:24020721

  13. 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.

  14. 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

  15. Pretreatment of polyethylene terephthalate substrate for the growth of Ga-doped ZnO thin film.

    PubMed

    Kim, D W; Kang, J H; Lim, Y S; Lee, M H; Seo, W S; Park, H H; Seo, K H; Park, M G

    2011-02-01

    The effect of the pretreatment of polyethylene terephthalate (PET) substrate on the growth of transparent conducting Ga-doped ZnO (GZO) thin film was investigated. Because of its high gas and moisture absorption and easy gas permeation, PET substrate was annealed at 100 degrees C in a vacuum chamber prior to the sputtering growth of GZO thin film for the outgassing of impurity gases. GZO thin film was deposited on the pretreated PET substrate by rf-magnetron sputtering and significantly improved electrical properties of GZO thin film was achieved. Electrical and structural characterizations of the GZO thin films were carried out by 4-point probe, Hall measurement, and scanning electron microscopy, and the effects of the pretreatment on the improved properties of GZO thin films were discussed. This result is not only useful to PET substrate, but also could be applicable to other plastic substrates which inevitably containing the moisture and impurity gases. PMID:21456250

  16. Spontaneous shape transition of thin films into ZnO nanowires with high structural and optical quality.

    PubMed

    Guillemin, Sophie; Sarigiannidou, Eirini; Appert, Estelle; Donatini, Fabrice; Renou, Gilles; Bremond, Georges; Consonni, Vincent

    2015-10-28

    ZnO nanowires are usually formed by physical and chemical deposition techniques following the bottom-up approach consisting in supplying the reactants on a nucleation surface heated at a given temperature. We demonstrate an original alternative approach for the formation of ZnO nanowire arrays with high structural and optical quality, which is based on the spontaneous transformation of a ZnO thin film deposited by sol-gel process following a simple annealing. The development of these ZnO nanowires occurs through successive shape transitions, including the intermediate formation of pyramid-shaped islands. Their nucleation under near-equilibrium conditions is expected to be governed by thermodynamic considerations via the total free energy minimization related to the nanowire shape. It is further strongly assisted by the drastic reordering of the matter and by recrystallization phenomena through the massive transport of zinc and oxygen atoms towards the localized growth areas. The spontaneous shape transition process thus combines the easiness and low-cost of sol-gel process and simple annealing with the assets of the vapor phase deposition techniques. These findings cast a light on the fundamental mechanisms driving the spontaneous formation of ZnO nanowires and, importantly, reveal the great technological potential of the spontaneous shape transition process as a promising alternative approach to the more usual bottom-up approach. PMID:26416227

  17. Transparent conducting impurity-doped ZnO thin films prepared using oxide targets sintered by millimeter-wave heating

    SciTech Connect

    Minami, Tadatsugu; Okada, Kenji; Miyata, Toshihiro; Nomoto, Juni-chi; Hara, Youhei; Abe, Hiroshi

    2009-07-15

    The preparation of transparent conducting impurity-doped ZnO thin films by both pulsed laser deposition (PLD) and magnetron sputtering deposition (MSD) using impurity-doped ZnO targets sintered with a newly developed energy saving millimeter-wave (28 GHz) heating technique is described. Al-doped ZnO (AZO) and V-co-doped AZO (AZO:V) targets were prepared by sintering with various impurity contents for 30 min at a temperature of approximately 1250 degree sign C in an air or Ar gas atmosphere using the millimeter-wave heating technique. The resulting resistivity and its thickness dependence obtainable in thin films prepared by PLD using millimeter-wave-sintered AZO targets were comparable to those obtained in thin films prepared by PLD using conventional furnace-sintered AZO targets; a low resistivity on the order of 3x10{sup -4} {Omega} cm was obtained in AZO thin films prepared with an Al content [Al/(Al+Zn) atomic ratio] of 3.2 at. % and a thickness of 100 nm. In addition, the resulting resistivity and its spatial distribution on the substrate surface obtainable in thin films prepared by rf-MSD using a millimeter-wave-sintered AZO target were almost the same as those obtained in thin films prepared by rf-MSD using a conventional powder AZO target. Thin films prepared by PLD using millimeter-wave-sintered AZO:V targets exhibited an improved resistivity stability in a high humidity environment. Thin films deposited with a thickness of approximately 100 nm using an AZO:V target codoped with an Al content of 4 at. % and a V content [V/(V+Zn) atomic ratio] of 0.2 at. % were sufficiently stable when long-term tested in air at 90% relative humidity and 60 degree sign C.

  18. ZnO thin film deposition using colliding plasma plumes and single plasma plume: Structural and optical properties

    SciTech Connect

    Gupta, Shyam L. Thareja, Raj K.

    2013-12-14

    We report the comparative study on synthesis of thin films of ZnO on glass substrates using IR laser ablated colliding plasma plumes and conventional pulsed laser deposition using 355 nm in oxygen ambient. The optical properties of deposited films are characterized using optical transmission in the UV-visible range of spectrum and photoluminescence measurements. X-ray diffraction and atomic force microscopy are used to investigate the surface morphology of synthesized ZnO films. The films synthesized using colliding plumes created with 1064 nm are non-polar a-plane ZnO with transmission in UV-visible (300–800 nm) region ∼60% compared to polycrystalline thin film deposited using single plume which has chunk deposition and poor optical response. However, deposition with 355 nm single plume shows polar c-axis oriented thin film with average roughness (∼thickness) of ∼86 nm (∼850 nm) compared to ∼2 nm (∼3 μm) for 1064 nm colliding plumes. These observed differences in the quality and properties of thin films are attributed to the flux of mono-energetic plasma species with almost uniform kinetic energy and higher thermal velocity reaching the substrate from interaction/stagnation zone of colliding plasma plumes.

  19. Sol-Gel and Thermally Evaporated Nanostructured Thin ZnO Films for Photocatalytic Degradation of Trichlorophenol

    NASA Astrophysics Data System (ADS)

    Abdel Aal, A.; Mahmoud, Sawsan A.; Aboul-Gheit, Ahmed K.

    2009-07-01

    In the present work, thermal evaporation and sol-gel coating techniques were applied to fabricate nanostructured thin ZnO films. The phase structure and surface morphology of the obtained films were investigated by X-ray diffractometer (XRD) and scanning electron microscope (SEM), respectively. The topography and 2D profile of the thin ZnO films prepared by both techniques were studied by optical profiler. The results revealed that the thermally evaporated thin film has a comparatively smoother surface of hexagonal wurtzite structure with grain size 12 nm and 51 m2/g. On the other hand, sol-gel films exhibited rough surface with a strong preferred orientation of 25 nm grain size and 27 m2/g surface area. Following deposition process, the obtained films were applied for the photodegradation of 2,4,6-trichlorophenol (TCP) in water in presence of UV irradiation. The concentrations of TCP and its intermediates produced in the solution during the photodegradation were determined by high performance liquid chromatography (HPLC) at defined irradiation times. Complete decay of TCP and its intermediates was observed after 60 min when the thermal evaporated photocatalyst was applied. However, by operating sol-gel catalyst, the concentration of intermediates initially increased and then remained constant with irradiation time. Although the degradation of TCP followed first-order kinetic for both catalysts, higher photocatalytic activity was exhibited by the thermally evaporated ZnO thin film in comparison with sol-gel one.

  20. Optical and electrical properties of transparent conducting B-doped ZnO thin films prepared by various deposition methods

    SciTech Connect

    Nomoto, Jun-ichi; Miyata, Toshihiro; Minami, Tadatsugu

    2011-07-15

    B-doped ZnO (BZO) thin films were prepared with various thicknesses up to about 500 nm on glass substrates at 200 deg. C by dc or rf magnetron sputtering deposition, pulsed laser deposition (PLD), and vacuum arc plasma evaporation (VAPE) methods. Resistivities of 4-6 x 10{sup -4}{Omega} cm were obtained in BZO thin films prepared with a B content [B/(B + Zn) atomic ratio] around 1 at. % by PLD and VAPE methods: Hall mobilities above 40 cm{sup 2}/Vs and carrier concentrations on the order of 10{sup 20} cm{sup -3}. All 500-nm-thick-BZO thin films prepared with a resistivity on the order of 10{sup -3}-10{sup -4}{Omega} cm exhibited an averaged transmittance above 80% in the wavelength range of 400-1100 nm. The resistivity in BZO thin films prepared with a thickness below about 500 nm was found to increase over time with exposure to various high humidity environments. In heat-resistance tests, the resistivity stability of BZO thin films was found to be nearly equal to that of Ga-doped ZnO thin films, so these films were judged suitable for use as a transparent electrode for thin-film solar cells.

  1. Towards solution-processed ambipolar hybrid thin-film transistors based on ZnO nanoparticles and P3HT polymer

    NASA Astrophysics Data System (ADS)

    Diallo, Abdou Karim; Gaceur, Meriem; Berton, Nicolas; Margeat, Olivier; Ackermann, Jörg; Videlot-Ackermann, Christine

    2013-06-01

    Solution-processed n-channel oxide semiconductor thin-film transistors (TFTs) were fabricated using zinc oxide (ZnO) nanoparticles. Polycrystalline fused-ZnO nanoparticle films were produced by spin-coating ZnO nanosphere dispersions following by a subsequent heat treatment. The solution-processable semiconductor ink based on ZnO was prepared by dispersing the synthesized ZnO nanospheres in isopropanol mixed with ethanolamine to various concentrations from 20 to 80 mg/mL. Such concentration dependence on morphology and microstructure of thin films was studied on spin-coated ZnO films by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Spin-coated ZnO films involved as active layers in transistor configuration delivered an almost ideal output characteristic (Id-Vd) with an electron mobility up to 3 × 10-2 cm2/V s. As a p-channel semiconductor, a poly(3-hexylthiophene) (P3HT) solution-processable ink was deposited by spin-coating on top of closely packed ZnO nanoparticles-based films to form an uniform overlying layer. A hybrid (inorganic-organic) interface was formed by the direct contact between ZnO and P3HT leading to carrier redistribution. Such solution-processed hybrid thin-film transistors delivered in air well balanced electron and hole mobilities as 3.9 × 10-5 and 2 × 10-5 cm2/V s, respectively.

  2. Effect of GaN interlayer on polarity control of epitaxial ZnO thin films grown by molecular beam epitaxy

    SciTech Connect

    Wang, X. Q.; Sun, H. P.; Pan, X. Q.

    2010-10-11

    Epitaxial ZnO thin films were grown on nitrided (0001) sapphire substrates with an intervening GaN layer by rf-plasma-assisted molecular beam epitaxy. It was found that polarity of the ZnO epilayer could be controlled by modifying the GaN interlayer. ZnO grown on a distorted 3-nm-thick GaN interlayer has Zn-polarity while ZnO on a 20-nm-thick GaN interlayer with a high structural quality has O-polarity. High resolution transmission electron microscopy analysis indicates that the polarity of ZnO epilayer is controlled by the atomic structure of the interface between the ZnO buffer layer and the intervening GaN layer.

  3. Application of Thin ZnO ALD Layers in Fiber-Optic Fabry-Pérot Sensing Interferometers.

    PubMed

    Majchrowicz, Daria; Hirsch, Marzena; Wierzba, Paweł; Bechelany, Michael; Viter, Roman; Jędrzejewska-Szczerska, Małgorzata

    2016-01-01

    In this paper we investigated the response of a fiber-optic Fabry-Pérot sensing interferometer with thin ZnO layers deposited on the end faces of the optical fibers forming the cavity. Standard telecommunication single-mode optical fiber (SMF-28) segments were used with the thin ZnO layers deposited by Atomic Layer Deposition (ALD). Measurements were performed with the interferometer illuminated by two broadband sources operating at 1300 nm and 1550 nm. Reflected interference signal was acquired by an optical spectrum analyzer while the length of the air cavity was varied. Thickness of the ZnO layers used in the experiments was 50 nm, 100 nm, and 200 nm. Uncoated SMF-28 fiber was also used as a reference. Based on the results of measurements, the thickness of the ZnO layers and the length of the cavity were selected in order to achieve good visibility. Following, the interferometer was used to determine the refractive index of selected liquids. PMID:27011188

  4. Application of Thin ZnO ALD Layers in Fiber-Optic Fabry-Pérot Sensing Interferometers

    PubMed Central

    Majchrowicz, Daria; Hirsch, Marzena; Wierzba, Paweł; Bechelany, Michael; Viter, Roman; Jędrzejewska‑Szczerska, Małgorzata

    2016-01-01

    In this paper we investigated the response of a fiber-optic Fabry-Pérot sensing interferometer with thin ZnO layers deposited on the end faces of the optical fibers forming the cavity. Standard telecommunication single-mode optical fiber (SMF-28) segments were used with the thin ZnO layers deposited by Atomic Layer Deposition (ALD). Measurements were performed with the interferometer illuminated by two broadband sources operating at 1300 nm and 1550 nm. Reflected interference signal was acquired by an optical spectrum analyzer while the length of the air cavity was varied. Thickness of the ZnO layers used in the experiments was 50 nm, 100 nm, and 200 nm. Uncoated SMF-28 fiber was also used as a reference. Based on the results of measurements, the thickness of the ZnO layers and the length of the cavity were selected in order to achieve good visibility. Following, the interferometer was used to determine the refractive index of selected liquids. PMID:27011188

  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. Sol-gel derived ZnO thin films: Effect of amino-additives

    NASA Astrophysics Data System (ADS)

    Hosseini Vajargah, P.; Abdizadeh, H.; Ebrahimifard, R.; Golobostanfard, M. R.

    2013-11-01

    Zinc oxide thin films were dip-coated from an alcoholic sol of zinc acetate with different amino-additives including monoethanolamine, diethanolamine, triethanolamine, triethylamine, and ethylenediamine. Sol-gel behavior, crystal structure, optoelectronic and morphological properties of thin films were investigated with focus on the effects of different amines and drying conditions. Investigations explicate the role of chemical and physical properties of amines such as organic chains, polarity, and boiling point as the main factors that cause distinct sol-gel behavior and film properties. It is shown that different amines in different molar ratios together with drying temperature cause dramatic impacts on sol transparency, stability, and consequently on structural, optoelectronic, and morphological properties of films. Notably, monoethanolamine and triethylamine films demonstrate a preferred orientation stimulated by increased molar ratio of amines. Further investigations indicated the positive effect of elevated drying temperature particularly on those films prepared from sols with high-boiling-point stabilizers. The variation of film optoelectronics seems to depend mainly on heat treatment, whereas sol chemistry influences the optical properties indirectly through the structural alteration. Peculiar morphologies in the ethylenediamine films disappeared with adjusting the drying conditions. The size of ZnO grains were approximately independent of amine types and primarily affected by the heat treatment

  7. An economic approach to fabricate photo sensor based on nanostructured ZnO thin films

    NASA Astrophysics Data System (ADS)

    Huse, Nanasaheb; Upadhye, Deepak; Sharma, Ramphal

    2016-05-01

    Nanostructural ZnO Thin Films have been synthesized by simple and economic Chemical Bath Deposition technique onto glass substrate with bath temperature at 60°C for 1 hour. Structural, Optical, Electrical and topographical properties of the prepared Thin Films were investigated by GIXRD, I-V Measurement System, UV-Visible Spectrophotometer and AFM respectively. Calculated lattice parameters are in good agreement with the standard JCPDS card (36-1451) values, exhibits Hexagonal Wurtzite crystal structure. I-V Measurement curve has shown ohmic nature in dark condition and responds to light illumination which reveals Photo sensor properties. After illumination of 60W light, decrease in resistance was observed from 110.9 KΩ to 104.4 KΩ. The change in current and calculated Photo sensitivity was found to be 3.51 µA and 6.3% respectively. Optical band gap was found to be 3.24 eV. AFM images revealed uniform deposition over entire glass substrate with 32.27 nm average roughness of the film.

  8. 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.

  9. Characterization of the quality of ZnO thin films using reflective second harmonic generation

    SciTech Connect

    Huang, Y.-J.; Chu, S.-Y.; Lo, K.-Y.; Liu, C.-W.; Liu, C.-C.

    2009-08-31

    A polar mirror symmetrical contribution originated from the arrangement of grain boundaries existing in the ZnO film is detected by reflective second harmonic generation pattern. The ordering of ZnO grain boundary is dependent on the kinetic energy of deposited atoms and affects the quality of ZnO films. The net direction of the grain boundary in ZnO film trends toward the [110] direction of Si(111) to reach the minimum grain energy for better quality ZnO film. The polar structure of the mirrorlike boundaries under the optically macroscopic viewpoint presents a correlation with film quality.

  10. 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.

  11. 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.

  12. Hybrid ZnO nanowire/a-Si:H thin-film radial junction solar cells using nanoparticle front contacts

    SciTech Connect

    Pathirane, M. Iheanacho, B.; Lee, C.-H.; Wong, W. S.; Tamang, A.; Knipp, D.; Lujan, R.

    2015-10-05

    Hydrothermally synthesized disordered ZnO nanowires were conformally coated with a-Si:H thin-films to fabricate three dimensional hybrid nanowire/thin-film structures. The a-Si:H layer formed a radial junction p-i-n diode solar cell around the ZnO nanowire. The cylindrical hybrid solar cells enhanced light scattering throughout the UV-visible-NIR spectrum (300 nm–800 nm) resulting in a 22% increase in short-circuit current density compared to the reference planar p-i-n device. A fill factor of 69% and a total power conversion efficiency of 6.5% were achieved with the hybrid nanowire solar cells using a spin-on indium tin oxide nanoparticle suspension as the top contact.

  13. Tailoring the coercivity in ferromagnetic ZnO thin films by 3d and 4f elements codoping

    SciTech Connect

    Lee, J. J.; Xing, G. Z. Yi, J. B.; Li, S.; Chen, T.; Ionescu, M.

    2014-01-06

    Cluster free, Co (3d) and Eu (4f) doped ZnO thin films were prepared using ion implantation technique accompanied by post annealing treatments. Compared with the mono-doped ZnO thin films, the samples codoped with Co and Eu exhibit a stronger magnetization with a giant coercivity of 1200 Oe at ambient temperature. This was further verified through x-ray magnetic circular dichroism analysis, revealing the exchange interaction between the Co 3d electrons and the localized carriers induced by Eu{sup 3+} ions codoping. The insight gained with modulating coercivity in magnetic oxides opens up an avenue for applications requiring non-volatility in spintronic devices.

  14. Effect of Fe incorporation on the optical behavior of ZnO thin films prepared by sol-gel derived spin coating techniques

    NASA Astrophysics Data System (ADS)

    Rakkesh, R. Ajay; Malathi, R.; Balakumar, S.

    2013-02-01

    In this work, Fe doped Zinc Oxide (ZnO) thin films were fabricated on the glass substrate by sol-gel derived spin coating technique. X-ray Diffraction studies revealed that the obtained pure and Fe doped ZnO thin films were in the wurtzite and spinel phase respectively. The three well defined Raman lines at 432, 543 and 1091 cm-1 also confirmed the lattice structure of the ZnO thin film has wurtzite symmetry. While doping Fe atoms in the ZnO, there was a significant change in the phase from wurtzite to spinel structure; owing to Fe (III) ions being incorporated into the lattice through substitution of Zn (II) ions. Room temperature PL spectra showed that the role of defect mediated red emissions at 612 nm was due to radial recombination of a photogenerated hole with an electron that belongs to the Fe atoms, which were discussed in detail.

  15. Influence of Gas Flow Rate for Formation of Aligned Nanorods in ZnO Thin Films for Solar-Driven Hydrogen Production

    SciTech Connect

    Shet, S.; Chen, L.; Tang, H.; Nuggehalli, R.; Wang, H.; Yan, Y.; Turner, J.; Al-Jassim, M.

    2012-04-01

    ZnO thin films have been deposited in mixed Ar/N{sub 2} gas ambient at substrate temperature of 500 C by radiofrequency sputtering of ZnO targets. We find that an optimum N{sub 2}-to-Ar ratio in the deposition ambient promotes the formation of well-aligned nanorods. ZnO thin films grown in ambient with 25% N{sub 2} gas flow rate promoted nanorods aligned along c-axis and exhibit significantly enhanced photoelectrochemical (PEC) response, compared with ZnO thin films grown in an ambient with different N{sub 2}-to-Ar gas flow ratios. Our results suggest that chamber ambient is critical for the formation of aligned nanostructures, which offer potential advantages for improving the efficiency of PEC water splitting for H{sub 2} production.

  16. Effect of the gate metal work function on water-gated ZnO thin-film transistor performance

    NASA Astrophysics Data System (ADS)

    Singh, Mandeep; Yusuf Mulla, Mohammad; Vittoria Santacroce, Maria; Magliulo, Maria; Di Franco, Cinzia; Manoli, Kyriaki; Altamura, Davide; Giannini, Cinzia; Cioffi, Nicola; Palazzo, Gerardo; Scamarcio, Gaetano; Torsi, Luisa

    2016-07-01

    ZnO thin films, prepared using a printing-compatible sol–gel method involving a thermal treatment below 400 °C, are proposed as active layers in water-gated thin-film transistors (WG-TFTs). The thin-film structure and surface morphology reveal the presence of contiguous ZnO crystalline (hexagonal wurtzite) with isotropic nano-grains as large as 10 nm characterized by a preferential orientation along the a-axis. The TFT devices are gated through a droplet of deionized water by means of electrodes characterized by different work functions. The high capacitance of the electrolyte allowed operation below 0.5 V. While the Ni, Pd, Au and Pt gate electrodes are electrochemically stable in the inspected potential range, electrochemical activity is revealed for the W one. Such an occurrence leads to an increase of capacitance (and current), which is ascribed to a high output current from the dissolution of a lower capacitance W-oxide layer. The environmental stability of the ZnO WG-TFTs is quite good over a period of five months.

  17. Characterization of ZnO thin films grown on different p-Si substrate elaborated by solgel spin-coating method

    SciTech Connect

    Chebil, W.; Fouzri, A.; Fargi, A.; Azeza, B.; Zaaboub, Z.; and others

    2015-10-15

    Highlights: • High quality ZnO thin films grown on different p-Si substrates were successful obtained by sol–gel process. • PL measurement revealed that ZnO thin film grown on porous Si has the better optical quality. • I–V characteristics for all heterojunctions exhibit successful diode formation. • The diode ZnO/PSi shows a better photovoltaic effect under illumination with a maximum {sub Voc} of 0.2 V. - Abstract: In this study, ZnO thin films are deposited by sol–gel technique on p-type crystalline silicon (Si) with [100] orientation, etched silicon and porous silicon. The structural analyses showed that the obtained thin films were polycrystalline with a hexagonal wurtzite structure and preferentially oriented along the c-axis direction. Morphological study revealed the presence of rounded and facetted grains irregularly distributed on the surface of all samples. PL spectra at room temperature revealed that ZnO thin film grown on porous Si has a strong UV emission with low defects in the visible region comparing with ZnO grown on plat Si and etched Si surface. The heterojunction parameters were evaluated from the (I–V) under dark and illumination at room temperature. The ideality factor, barrier height and series resistance of heterojunction grown on different p-Si substrates are determined by using different methods. Best electrical properties are obtained for ZnO layer deposited on porous silicon.

  18. Effect of depth of traps in ZnO polycrystalline thin films on ZnO-TFTs performance

    NASA Astrophysics Data System (ADS)

    Medina-Montes, Maria I.; Baldenegro-Perez, Leonardo A.; Sanchez-Zeferino, Raul; Rojas-Blanco, Lizeth; Becerril-Silva, Marcelino; Quevedo-Lopez, Manuel A.; Ramirez-Bon, Rafael

    2016-09-01

    ZnO thin films were processed by radio frequency magnetron sputtering at room temperature on p-Si/SiO2 substrates under pure argon (Ar:O2 = 100:0 vol.%) and argon-oxygen mixture (Ar:O2 = 99:1 vol.%) gas environment. Morphological, optical and electrical characteristics of the ZnO films are reported, and they show a clear relationship with the gas mixture employed for the sputtering process. Scanning Electron Microscopy revealed the formation of grains of 15.3 and 19.9 nm average sizes and thicknesses of 59 nm and 82 nm for films growth in pure argon and argon-oxygen, respectively. Photoluminescence measurements at room temperature showed the violet emission band (centered at 3 eV) which was only detected in the ZnO film grown under pure argon. From thermally stimulated conductivity measurements two traps with 0.27 and 0.14 eV activation energies were identified for films grown in pure argon and argon-oxygen mixture, respectively. The trap at 0.27 eV is associated with a level located below the conduction band edge and it is supported by the PL band centered at 3 eV. Both types of ZnO films were used as the active channel layer in thin film transistors with thermal SiO2 as gate dielectric. Field effect mobility, threshold voltage and current ratio were improved in the devices with ZnO channel deposited with the argon-oxygen mixture (99% Ar/1% O2 vol.). Threshold voltage decreased from 25 V to 15 V, field effect mobility and current ratio increased from 0.8 to 2.4 cm2/Vs and from 102 to 106, in that order.

  19. Photo-Patternable ZnO Thin Films Based on Cross-Linked Zinc Acrylate for Organic/Inorganic Hybrid Complementary Inverters.

    PubMed

    Jeong, Yong Jin; An, Tae Kyu; Yun, Dong-Jin; Kim, Lae Ho; Park, Seonuk; Kim, Yebyeol; Nam, Sooji; Lee, Keun Hyung; Kim, Se Hyun; Jang, Jaeyoung; Park, Chan Eon

    2016-03-01

    Complementary inverters consisting of p-type organic and n-type metal oxide semiconductors have received considerable attention as key elements for realizing low-cost and large-area future electronics. Solution-processed ZnO thin-film transistors (TFTs) have great potential for use in hybrid complementary inverters as n-type load transistors because of the low cost of their fabrication process and natural abundance of active materials. The integration of a single ZnO TFT into an inverter requires the development of a simple patterning method as an alternative to conventional time-consuming and complicated photolithography techniques. In this study, we used a photocurable polymer precursor, zinc acrylate (or zinc diacrylate, ZDA), to conveniently fabricate photopatternable ZnO thin films for use as the active layers of n-type ZnO TFTs. UV-irradiated ZDA thin films became insoluble in developing solvent as the acrylate moiety photo-cross-linked; therefore, we were able to successfully photopattern solution-processed ZDA thin films using UV light. We studied the effects of addition of a tiny amount of indium dopant on the transistor characteristics of the photopatterned ZnO thin films and demonstrated low-voltage operation of the ZnO TFTs within ±3 V by utilizing Al2O3/TiO2 laminate thin films or ion-gels as gate dielectrics. By combining the ZnO TFTs with p-type pentacene TFTs, we successfully fabricated organic/inorganic hybrid complementary inverters using solution-processed and photopatterned ZnO TFTs. PMID:26840992

  20. Growth of vertically aligned one-dimensional ZnO nanowire arrays on sol-gel derived ZnO thin films

    NASA Astrophysics Data System (ADS)

    Kitazawa, Nobuaki; Aono, Masami; Watanabe, Yoshihisa

    2014-11-01

    Vertically aligned one-dimensional ZnO nanowire arrays have been synthesized by a hydrothermal method on sol-gel derived ZnO films. Sol-gel derived ZnO films and corresponding ZnO nanowire arrays have been characterized by X-ray diffraction and field-emission scanning electron microscopy. The effect of sol-gel derived ZnO film surface on the morphology of ZnO nanowire arrays has been investigated. The authors suggest from our investigation that sol-gel derived ZnO films affect the growth of one-dimensional ZnO nanostructures. Not only crystalline ZnO films but also amorphous ones can act as a scaffold for ZnO nucleus. Tilted ZnO micro-rods are grown on ZnO gel films, whereas vertically aligned ZnO nanowire arrays are grown on nanometer-sized ZnO grains. The average diameter of ZnO nanowire arrays are correlated strongly with the grain size of sol-gel derived ZnO films.

  1. Electrochemical Synthesis of ZnO Nanorods/Nanotubes/Nanopencils on Transparent Aluminium-Doped Zinc Oxide Thin Films for Photocatalytic Applications.

    PubMed

    Le, Thi Ngoc Tu; Pham, Tan Thi; Ngo, Quang Minh; Vu, Thi Hanh Thu

    2015-09-01

    We report an electrochemical synthesis of homogeneous and well-aligned ZnO nanorods (NRs) on transparent conducting aluminium-doped zinc oxide (AZO) thin films as electrodes. The selected ZnO NRs was then chemically corroded in HCl and KCl aqueous solutions to form nanopencils (NPs), and nanotubes (NTs), respectively. A DC magnetron sputtering was employed to fabricate AZO thin films at various thicknesses. The obtained AZO thin films have a c-direction orientation, transmittance above 80% in visible region, and sheet resistance approximately 40 Ω/sq. They are considered to be relevant as electrodes and seeding layers for electrochemical. The ZnO NRs are directly grown on the AZOs without a need of catalysts or additional seeding layers at temperature as low as 85 degrees C. Their shapes are strongly associated with the AZO thickness that provides a valuable way to control the diameter of ZnO NRs grown atop. With the addition of HCI and KCl aqueous solutions, ZnO NRs were modified their shape to NPs and NTs with the reaction time, respectively. All the ZnO NRs, NPs, and NTs are preferred to grow along c-direction that indicates a lattice matching between AZO thin films and ZnO nanostructrures. Photoluminescence spectra and XRD patterns show that they have good crystallinities. A great photocatalytic activity of ZnO nanostructures promises potential application in environmental treatment and protection. The ZnO NTs exhibits a higher photocatalysis than others possibly due to the oxygen vacancies on the surface and the polarizability of Zn2+ and O2-. PMID:26716213

  2. ZnO Nanoparticles/Reduced Graphene Oxide Bilayer Thin Films for Improved NH3-Sensing Performances at Room Temperature

    NASA Astrophysics Data System (ADS)

    Tai, Huiling; Yuan, Zhen; Zheng, Weijian; Ye, Zongbiao; Liu, Chunhua; Du, Xiaosong

    2016-03-01

    ZnO nanoparticles and graphene oxide (GO) thin film were deposited on gold interdigital electrodes (IDEs) in sequence via simple spraying process, which was further restored to ZnO/reduced graphene oxide (rGO) bilayer thin film by the thermal reduction treatment and employed for ammonia (NH3) detection at room temperature. rGO was identified by UV-vis absorption spectra and X-ray photoelectron spectroscope (XPS) analyses, and the adhesion between ZnO nanoparticles and rGO nanosheets might also be formed. The NH3-sensing performances of pure rGO film and ZnO/rGO bilayer films with different sprayed GO amounts were compared. The results showed that ZnO/rGO film sensors exhibited enhanced response properties, and the optimal GO amount of 1.5 ml was achieved. Furthermore, the optimal ZnO/rGO film sensor showed an excellent reversibility and fast response/recovery rate within the detection range of 10-50 ppm. Meanwhile, the sensor also displayed good repeatability and selectivity to NH3. However, the interference of water molecules on the prepared sensor is non-ignorable; some techniques should be researched to eliminate the effect of moisture in the further work. The remarkably enhanced NH3-sensing characteristics were speculated to be attributed to both the supporting role of ZnO nanoparticles film and accumulation heterojunction at the interface between ZnO and rGO. Thus, the proposed ZnO/rGO bilayer thin film sensor might give a promise for high-performance NH3-sensing applications.

  3. ZnO Nanoparticles/Reduced Graphene Oxide Bilayer Thin Films for Improved NH3-Sensing Performances at Room Temperature.

    PubMed

    Tai, Huiling; Yuan, Zhen; Zheng, Weijian; Ye, Zongbiao; Liu, Chunhua; Du, Xiaosong

    2016-12-01

    ZnO nanoparticles and graphene oxide (GO) thin film were deposited on gold interdigital electrodes (IDEs) in sequence via simple spraying process, which was further restored to ZnO/reduced graphene oxide (rGO) bilayer thin film by the thermal reduction treatment and employed for ammonia (NH3) detection at room temperature. rGO was identified by UV-vis absorption spectra and X-ray photoelectron spectroscope (XPS) analyses, and the adhesion between ZnO nanoparticles and rGO nanosheets might also be formed. The NH3-sensing performances of pure rGO film and ZnO/rGO bilayer films with different sprayed GO amounts were compared. The results showed that ZnO/rGO film sensors exhibited enhanced response properties, and the optimal GO amount of 1.5 ml was achieved. Furthermore, the optimal ZnO/rGO film sensor showed an excellent reversibility and fast response/recovery rate within the detection range of 10-50 ppm. Meanwhile, the sensor also displayed good repeatability and selectivity to NH3. However, the interference of water molecules on the prepared sensor is non-ignorable; some techniques should be researched to eliminate the effect of moisture in the further work. The remarkably enhanced NH3-sensing characteristics were speculated to be attributed to both the supporting role of ZnO nanoparticles film and accumulation heterojunction at the interface between ZnO and rGO. Thus, the proposed ZnO/rGO bilayer thin film sensor might give a promise for high-performance NH3-sensing applications. PMID:26956599

  4. Stable and High-Performance Flexible ZnO Thin-Film Transistors by Atomic Layer Deposition.

    PubMed

    Lin, Yuan-Yu; Hsu, Che-Chen; Tseng, Ming-Hung; Shyue, Jing-Jong; Tsai, Feng-Yu

    2015-10-14

    Passivation is a challenging issue for the oxide thin-film transistor (TFT) technologies because it requires prolonged high-temperature annealing treatments to remedy defects produced in the process, which greatly limits its manufacturability as well as its compatibility with temperature-sensitive materials such as flexible plastic substrates. This study investigates the defect-formation mechanisms incurred by atomic layer deposition (ALD) passivation processes on ZnO TFTs, based on which we demonstrate for the first time degradation-free passivation of ZnO TFTs by a TiO2/Al2O3 nanolaminated (TAO) film deposited by a low-temperature (110 °C) ALD process. By combining the TAO passivation film with ALD dielectric and channel layers into an integrated low-temperature ALD process, we successfully fabricate flexible ZnO TFTs on plastics. Thanks to the exceptional gas-barrier property of the TAO film (water vapor transmission rate (WVTR)<10(-6) g m(-2) day(-1)) as well as the defect-free nature of the ALD dielectric and ZnO channel layers, the TFTs exhibit excellent device performance with high stability and flexibility: field-effect mobility>20 cm2 V(-1) s(-1), subthreshold swing<0.4 V decade(-1) after extended bias-stressing (>10,000 s), air-storage (>1200 h), and bending (1.3 cm radius for 1000 times). PMID:26436832

  5. Adopting Novel Strategies in Achieving High-Performance Single-Layer Network Structured ZnO Nanorods Thin Film Transistors.

    PubMed

    Park, Ji-Hyeon; Park, Jee Ho; Biswas, Pranab; Kwon, Do Kyun; Han, Sun Woong; Baik, Hong Koo; Myoung, Jae-Min

    2016-05-11

    High-performance, solution-processed transparent and flexible zinc oxide (ZnO) nanorods (NRs)-based single layer network structured thin film transistors (TFTs) were developed on polyethylene terephthalate (PET) substrate at 100 °C. Keeping the process-temperature under 100 °C, we have improved the device performance by introducing three low temperature-based techniques; regrowing ZnO to fill the void spaces in a single layer network of ZnO NRs, passivating the back channel with polymer, and adopting ZrO2 as the high-k dielectric. Notably, high-k amorphous ZrO2 was synthesized and deposited using a novel method at an unprecedented temperature of 100 °C. Using these methods, the TFTs exhibited a high mobility of 1.77 cm(2)/V·s. An insignificant reduction of 2.18% in mobility value after 3000 cycles of dynamic bending at a radius of curvature of 20 mm indicated the robust mechanical nature of the flexible ZnO NRs SLNS TFTs. PMID:27096706

  6. Tuning of structural, optical, and magnetic properties of ultrathin and thin ZnO nanowire arrays for nano device applications

    NASA Astrophysics Data System (ADS)

    Shrama, Satinder K.; Saurakhiya, Neelam; Barthwal, Sumit; Kumar, Rudra; Sharma, Ashutosh

    2014-03-01

    One-dimensional (1-D) ultrathin (15 nm) and thin (100 nm) aligned 1-D (0001) and ([InlineEquation not available: see fulltext.]) oriented zinc oxide (ZnO) nanowire (NW) arrays were fabricated on copper substrates by one-step electrochemical deposition inside the pores of polycarbonate membranes. The aspect ratio dependence of the compressive stress because of the lattice mismatch between NW array/substrate interface and crystallite size variations is investigated. X-ray diffraction results show that the polycrystalline ZnO NWs have a wurtzite structure with a = 3.24 Å, c = 5.20 Å, and [002] elongation. HRTEM and SAED pattern confirmed the polycrystalline nature of ultrathin ZnO NWs and lattice spacing of 0.58 nm. The crystallite size and compressive stress in as-grown 15- and 100-nm wires are 12.8 nm and 0.2248 GPa and 22.8 nm and 0.1359 GPa, which changed to 16.1 nm and 1.0307 GPa and 47.5 nm and 1.1677 GPa after annealing at 873 K in ultrahigh vacuum (UHV), respectively. Micro-Raman spectroscopy showed that the increase in E2 (high) phonon frequency corresponds to much higher compressive stresses in ultrathin NW arrays. The minimum-maximum magnetization magnitude for the as-grown ultrathin and thin NW arrays are approximately 8.45 × 10-3 to 8.10 × 10-3 emu/g and approximately 2.22 × 10-7 to 2.190 × 10-7 emu/g, respectively. The magnetization in 15-nm NW arrays is about 4 orders of magnitude higher than that in the 100 nm arrays but can be reduced greatly by the UHV annealing. The origin of ultrathin and thin NW array ferromagnetism may be the exchange interactions between localized electron spin moments resulting from oxygen vacancies at the surfaces of ZnO NWs. The n-type conductivity of 15-nm NW array is higher by about a factor of 2 compared to that of the 100-nm ZnO NWs, and both can be greatly enhanced by UHV annealing. The ability to tune the stresses and the structural and relative occupancies of ZnO NWs in a wide range by annealing has important

  7. Optical characterization of Mg-doped ZnO thin films deposited by RF magnetron sputtering technique

    NASA Astrophysics Data System (ADS)

    Singh, Satyendra Kumar; Hazra, Purnima; Tripathi, Shweta; Chakrabarti, P.

    2016-05-01

    This paper reports the in-depth analysis on optical characteristics of magnesium (Mg) doped zinc oxide (ZnO) thin films grown on p-silicon (Si) substrates by RF magnetron sputtering technique. The variable angle ellipsometer is used for the optical characterization of as-deposited thin films. The optical reflectance, transmission spectra and thickness of as-deposited thin films are measured in the spectral range of 300-800 nm with the help of the spectroscopic ellipsometer. The effect of Mg-doping on optical parameters such as optical bandgap, absorption coefficient, absorbance, extinction coefficient, refractive Index and dielectric constant for as-deposited thin films are extracted to show its application in optoelectronic and photonic devices.

  8. Effects of oxygen ion implantation in spray-pyrolyzed ZnO thin films

    NASA Astrophysics Data System (ADS)

    Vijayakumar, K. P.; Ratheesh Kumar, P. M.; Sudha Kartha, C.; Wilson, K. C.; Singh, F.; Nair, K. G. M.; Kashiwaba, Y.

    2006-04-01

    ZnO thin films, prepared using the chemical spray pyrolysis technique, were implanted using 100 keV O+ ions. Both pristine and ion-implanted samples were characterized using X-ray diffraction, optical absorption, electrical resistivity measurements, thermally stimulated current measurements and photoluminescence. Samples retained their crystallinity even after irradiation at a fluence of 1015 ions/cm2. However, at a still higher fluence of 2 × 1016 ions/cm2, the films became totally amorphous. The optical absorption edge remained unaffected by implantation and optical absorption spectra indicated two levels at 460 and 510 nm. These were attributed to defect levels corresponding to zinc vacancies (VZn) and oxygen antisites (OZn), respectively. Pristine samples had a broad photoluminescence emission centred at 517 nm, which was depleted on implantation. In the case of implanted samples, two additional emissions appeared at 425 and 590 nm. These levels were identified as due to zinc vacancies (VZn) and oxygen vacancies (VO), respectively. The electrical resistivity of implanted samples was much higher than that of pristine, while photosensitivity decreased to a very low value on implantation. This can be utilized in semiconductor device technology for interdevice isolation. Hall measurements showed a marked decrease in mobility due to ion implantation, while carrier concentration slightly increased.

  9. Structural, morphological and optical studies of ripple-structured ZnO thin films

    NASA Astrophysics Data System (ADS)

    Navin, Kumar; Kurchania, Rajnish

    2015-11-01

    Ripple-structured ZnO thin films were prepared on Si (100) substrate by sol-gel spin-coating method with different heating rates during preheating process and finally sintered at 500 °C for 2 h in ambient condition. The structural, morphological and photoluminescence (PL) properties of the nanostructured films were analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and PL spectroscopy. XRD analysis revealed that films have hexagonal wurtzite structure and texture coefficient increases along (002) plane with preheating rate. The faster heating rate produced higher crystallization and larger average crystallite size. The AFM and SEM images indicate that all the films have uniformly distributed ripple structure with skeletal branches. The number of ripples increases, while the rms roughness, amplitude and correlation length of the ripple structure decrease with preheating rates. The PL spectra show the presence of different defects in the structure. The ultraviolet emission improved with the heating rate which indicates its better crystallinity.

  10. Ferromagnetism and Conductivity in Hydrogen Irradiated Co-Doped ZnO Thin Films.

    PubMed

    Di Trolio, A; Alippi, P; Bauer, E M; Ciatto, G; Chu, M H; Varvaro, G; Polimeni, A; Capizzi, M; Valentini, M; Bobba, F; Di Giorgio, C; Amore Bonapasta, A

    2016-05-25

    Impressive changes in the transport and ferromagnetic properties of Co-doped ZnO thin films have been obtained by postgrowth hydrogen irradiation at temperatures of 400 °C. Hydrogen incorporation increases the saturation magnetization by one order of magnitude (up to ∼1.50 μB/Co) and increases the carrier density and mobility by about a factor of two. In addition to the magnetic characterization, the transport and structural properties of hydrogenated ZnO:Co have been investigated by Hall effect, local probe conductivity measurements, micro-Raman, and X-ray absorption spectroscopy. Particular care has been given to the detection of Co oxides and metal Co nanophases, whose influence on the increase in the transport and ferromagnetic properties can be excluded on the ground of the achieved results. The enhancement in ferromagnetism is directly related to the dose of H introduced in the samples. On the contrary, despite the shallow donor character of H atoms, the increase in carrier density n is not related to the H dose. These apparently contradictory effects of H are fully accounted for by a mechanism based on a theoretical model involving Co-VO (Co-O vacancy) pairs. PMID:27123761

  11. 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.

  12. 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.

  13. Effect of reduced graphene oxide-hybridized ZnO thin films on the photoinactivation of Staphylococcus aureus and Salmonella enterica serovar Typhi.

    PubMed

    Teh, Swe Jyan; Yeoh, Soo Ling; Lee, Kian Mun; Lai, Chin Wei; Abdul Hamid, Sharifah Bee; Thong, Kwai Lin

    2016-08-01

    The immobilization of photocatalyst nanoparticles on a solid substrate is an important aspect for improved post-treatment separation and photocatalyst reactor design. In this study, we report the simple preparation of reduced graphene oxide (rGO)-hybridized zinc oxide (ZnO) thin films using a one-step electrochemical deposition, and investigated the effect of rGO-hybridization on the photoinactivation efficiency of ZnO thin films towards Staphylococcus aureus (S. aureus) and Salmonella enterica serovar Typhi (S. Typhi) as target bacterial pathogens. Field-emission scanning electron microscopy (FESEM) revealed the formation of geometric, hexagonal flakes of ZnO on the ITO glass substrate, as well as the incorporation of rGO with ZnO in the rGO/ZnO thin film. Raman spectroscopy indicated the successful incorporation of rGO with ZnO during the electrodeposition process. Photoluminescence (PL) spectroscopy indicates that rGO hybridization with ZnO increases the amount of oxygen vacancies, evidenced by the shift of visible PL peak at 650 to 500nm. The photoinactivation experiments showed that the thin films were able to reduce the bacterial cell density of Staph. aureus and S. Typhi from an initial concentration of approximately 10(8) to 10(3)CFU/mL within 15min. The rGO/ZnO thin film increased the photoinactivation rate for S. aureus (log[N/No]) from -5.1 (ZnO) to -5.9. In contrast, the application of rGO/ZnO thin film towards the photoinactivation of S. Typhi did not improve its photoinactivation rate, compared to the ZnO thin film. We may summarise that (1) rGO/ZnO was effective to accelerate the photoinactivation of S. aureus but showed no difference to improve the photoinactivation of S. Typhi, in comparison to the performance of ZnO thin films, and (2) the photoinactivation in the presence of ZnO and rGO/ZnO was by ROS damage to the extracellular wall. PMID:27203568

  14. 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.

  15. Solution-processed flexible ZnO transparent thin-film transistors with a polymer gate dielectric fabricated by microwave heating

    NASA Astrophysics Data System (ADS)

    Yang, Chanwoo; Hong, Kipyo; Jang, Jaeyoung; Chung, Dae Sung; An, Tae Kyu; Choi, Woon-Seop; Eon Park, Chan

    2009-11-01

    We report the development of solution-processed zinc oxide (ZnO) transparent thin-film transistors (TFTs) with a poly(2-hydroxyethyl methacrylate) (PHEMA) gate dielectric on a plastic substrate. The ZnO nanorod film active layer, prepared by microwave heating, showed a highly uniform and densely packed array of large crystal size (58 nm) in the [002] direction of ZnO nanorods on the plasma-treated PHEMA. The flexible ZnO TFTs with the plasma-treated PHEMA gate dielectric exhibited an electron mobility of 1.1 cm2 V-1 s-1, which was higher by a factor of ~8.5 than that of ZnO TFTs based on the bare PHEMA gate dielectric.

  16. 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.

  17. 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

  18. 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.

  19. Electrical properties of solution-deposited ZnO thin-film transistors by low-temperature annealing.

    PubMed

    Lim, Chul; Oh, Ji Young; Koo, Jae Bon; Park, Chan Woo; Jung, Soon-Won; Na, Bock Soon; Chu, Hye Yong

    2014-11-01

    Flexible oxide thin-film transistors (Oxide-TFTs) have emerged as next generation transistors because of their applicability in electronic device. In particular, the major driving force behind solution-processed zinc oxide film research is its prospective use in printing for electronics. A low-temperature process to improve the performance of solution-processed n-channel ZnO thin-film transistors (TFTs) fabricated via spin-coating and inkjet-printing is introduced here. ZnO nanoparticles were synthesized using a facile sonochemical method that was slightly modified based on a previously reported method. The influence of the annealing atmosphere on both nanoparticle-based TFT devices fabricated via spin-coating and those created via inkjet printing was investigated. For the inkjet-printed TFTs, the characteristics were improved significantly at an annealing temperature of 150 degrees C. The field effect mobility, V(th), and the on/off current ratios were 3.03 cm2/Vs, -3.3 V, and 10(4), respectively. These results indicate that annealing at 150 degrees C 1 h is sufficient to obtain a mobility (μ(sat)) as high as 3.03 cm2/Vs. Also, the active layer of the solution-based ZnO nanoparticles allowed the production of high-performance TFTs for low-cost, large-area electronics and flexible devices. PMID:25958581

  20. 7-Octenyltrichrolosilane/trimethyaluminum hybrid dielectrics fabricated by molecular-atomic layer deposition on ZnO thin film transistors

    NASA Astrophysics Data System (ADS)

    Huang, Jie; Lee, Mingun; Lucero, Antonio T.; Cheng, Lanxia; Ha, Min-Woo; Kim, Jiyoung

    2016-06-01

    We demonstrate the fabrication of 7-octenytrichlorosilane (7-OTS)/trimethylaluminum (TMA) organic–inorganic hybrid films using molecular-atomic layer deposition (MALD). The properties of 7-OTS/TMA hybrid films are extensively investigated using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and electrical measurements. Our results suggest that uniform and smooth amorphous hybrid thin films with excellent insulating properties are obtained using the MALD process. Films have a relatively high dielectric constant of approximately 5.0 and low leakage current density. We fabricate zinc oxide (ZnO) based thin film transistors (TFTs) using 7-OTS/TMA hybrid material as a back gate dielectric with the top ZnO channel layer deposited in-situ via MALD. The ZnO TFTs exhibit a field effect mobility of approximately 0.43 cm2 V‑1 s‑1, a threshold voltage of approximately 1 V, and an on/off ratio of approximately 103 under low voltage operation (from ‑3 to 9 V). This work demonstrates an organic–inorganic hybrid gate dielectric material potentially useful in flexible electronics application.

  1. The Preparation and Properties of Al-Doped ZnO Thin Films as Transparent Electrodes for Solar Cell

    NASA Astrophysics Data System (ADS)

    Ding, J. N.; Tan, C. B.; Yuan, N. Y.; Feng, X. W.; Chang, X. Y.; Ye, F.

    Transparent conductive oxides based on ZnO are promising materials for application in thin-film solar photovoltaic cells. Al-doped ZnO thin films with a large area of 1 m × 1.5 m were prepared by magnetic sputtering on glass substrate using a ceramic target (98 wt. % ZnO, 2 wt. % Al2O3) in different Ar+H2 ambient at different substrate temperature. SiO2 layer with a thickness of 20 nm was deposited as a resistant layer. To investigate the influence of H2-flow on the properties of AZO films, H2-flow rate was changed during the growth process with a fixed Ar-flow rate. The effect of the substrate temperature and the H2-flow rate on the structure, electrical and optical properties was studied. In order to enhance light scattering and absorption inside the cell, suitable surface texture is needed. The influence of wet chemical etching on surface roughness and haze of AZO were also investigated.

  2. Crystal Structure and Optical Properties of Al-Doped ZnO Large-Area Thin Films Using 1500 mm Dual Cylindrical Cathodes.

    PubMed

    Lee, JinJu; Ha, Jong-Yoon; Yim, Haena; Choi, Won-Kook; Choi, Ji-Won

    2015-11-01

    The large-area Al-doped ZnO thin films are successfully deposited at room temperature on polycarbonate substrate using a 1500 mm dual cylindrical cathodes sputtering system. Those thin films have smooth surfaces (RMS: 9.6 nm) and lower thicknesses deviation (Uniformity: 98.6%) despite of high RF power. The optical transmittance properties of 3.13 wt% Al doped ZnO thin films have above 85% in visible region. A dual cylindrical cathodes sputtering system can fabricate transparent electrode on flexible electronic devices at room temperature for mass production of 6th generation solar cell and display industry. PMID:26726519

  3. Modification of opto-electronic properties of ZnO by incorporating metallic tin for buffer layer in thin film solar cells

    SciTech Connect

    Deepu, D. R.; Jubimol, J.; Kartha, C. Sudha; Louis, Godfrey; Vijayakumar, K. P.; Kumar, K. Rajeev

    2015-06-24

    In this report, the effect of incorporation of metallic tin (Sn) on opto-electronic properties of ZnO thin films is presented. ZnO thin films were deposited through ‘automated chemical spray pyrolysis’ (CSP) technique; later different quantities of ‘Sn’ were evaporated on it and subsequently annealed. Vacuum annealing showed a positive effect on crystallinity of films. Creation of sub band gap levels due to ‘Sn’ diffusion was evident from the absorption and PL spectra. The tin incorporated films showed good photo response in visible region. Tin incorporated ZnO thin films seem to satisfy the desirable criteria for buffer layer in thin film solar cells.

  4. Surfactant mediated one- and two-dimensional ZnO nanostructured thin films for dye sensitized solar cell application

    NASA Astrophysics Data System (ADS)

    Marimuthu, T.; Anandhan, N.; Thangamuthu, R.; Mummoorthi, M.; Rajendran, S.; Ravi, G.

    2015-01-01

    One-dimensional (1D) and two-dimensional (2D) nanostructured zinc oxide (ZnO) thin films were electrodeposited from aqueous zinc chloride on FTO glass substrates. The effects of organic surfactant such as cetyltrimethyl ammonium bromide (CTAB) and polyvinyl alcohol (PVA) on structural, morphological, crystal quality and optical properties of electrodeposited ZnO films were investigated. The x-ray diffraction pattern revealed that the prepared thin films were pure wutrzite hexagonal structure. The thin films deposited using organic surfactant in this work showed different morphologies such as nanoplatelet and flower. The hexagonal platelet and flower-like nanostructures were obtained in the presence of CTAB and PVA surfactant, respectively. The crystal quality and atomic vacancies of the prepared nanostructured thin films were investigated by micro Raman spectroscopic technique. The emission properties and optical quality of the films were studied by photoluminescence spectrometry. PEMA-LiClO4-EC gel polymer electrolyte has been used to replace the liquid electrolyte for reducing the leakage problem. Graphene counter electrode was used as an alternative for platinum electrode. Eosin yellow dye was used as a sensitizer. J-V characterizations were carried out for different 1D and 2D nanostructures. The nanoflower structure exhibited higher efficiency (η = 0.073%) than the other two nanostructures.

  5. Effect of Ag doping and insulator buffer layer on the memory mechanism of polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Kaur, Ramneek; Kaur, Jagdish; Tripathi, S. K.

    2015-07-01

    Resistive memory devices based on nanocomposites have attracted great potential for future applications in electronic and optoelectronic devices. The successful synthesis of aqueous CdSe nanoparticles has been provided with UV-Vis and Photoluminescence spectroscopy. The two terminal planar devices of CdSe nanocomposite have been fabricated. The effect of Ag doping and additional dielectric buffer layers on the memory devices have been studied by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The devices show hysteresis loops in both positive and negative bias directions. The memory window has been found to be increased with both Ag doping and PVA layer addition. The charge carrier transport mechanism in the memory devices has been studied by fitting the I-V characteristics with the theoretical model, Space charge conduction model (SCLC). C-V hysteresis loop in both positive and negative bias directions indicate that both the electrons and holes are responsible for memory mechanism of the devices. The switching mechanism of the memory devices has been explained by charge trapping/detrapping model. The retention characteristics show good stability and reliability of the devices.

  6. 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.

  7. 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.

  8. Control of the threshold voltage in ZnO nanobelt field-effect transistors by using MoO x thin film

    NASA Astrophysics Data System (ADS)

    Qian, Haolei; Fang, Yanjun; Gu, Lin; Lu, Ren; Zhao, Ming; Wang, Wei; Wang, Yewu; Sha, Jian

    2016-07-01

    We report on the feasible control of the threshold voltage (V th) in ultra-thin ZnO nanobelt FETs by using substoichiometric molybdenum trioxide (MoO x , x < 3) either as a modification layer on the surface of ZnO nanobelts or as electrodes instead of the widely used Ti/Au. ZnO nanobelt FETs using Ti/Au as the electrodes usually exhibit a negative threshold voltage, indicating n-channel depletion mode behavior, whereas ZnO FETs with MoO x /Au electrodes instead of Ti/Au show a positive shift of threshold voltage, exhibiting an n-channel type enhancement mode, which can be explained by a high Schottky barrier created at the interface of MoO x and the ZnO channel. In contrast, the decoration on the surface of ZnO channel by MoO x significantly increases the zero-bias conductivity and electron carrier concentration, and then negatively shifts the threshold voltage. We propose that MoO x thin film may play a passivation effect role, much more so than the doping effect role, due to the large amount of adsorbed species on as-grown ZnO nanobelts, especially oxygen species.

  9. Control of the threshold voltage in ZnO nanobelt field-effect transistors by using MoO x thin film.

    PubMed

    Qian, Haolei; Fang, Yanjun; Gu, Lin; Lu, Ren; Zhao, Ming; Wang, Wei; Wang, Yewu; Sha, Jian

    2016-07-01

    We report on the feasible control of the threshold voltage (V th) in ultra-thin ZnO nanobelt FETs by using substoichiometric molybdenum trioxide (MoO x , x < 3) either as a modification layer on the surface of ZnO nanobelts or as electrodes instead of the widely used Ti/Au. ZnO nanobelt FETs using Ti/Au as the electrodes usually exhibit a negative threshold voltage, indicating n-channel depletion mode behavior, whereas ZnO FETs with MoO x /Au electrodes instead of Ti/Au show a positive shift of threshold voltage, exhibiting an n-channel type enhancement mode, which can be explained by a high Schottky barrier created at the interface of MoO x and the ZnO channel. In contrast, the decoration on the surface of ZnO channel by MoO x significantly increases the zero-bias conductivity and electron carrier concentration, and then negatively shifts the threshold voltage. We propose that MoO x thin film may play a passivation effect role, much more so than the doping effect role, due to the large amount of adsorbed species on as-grown ZnO nanobelts, especially oxygen species. PMID:27196112

  10. Effect of post-annealing temperature on structural and optical properties of ZnO thin films grown on mica substrates using sol-gel spin-coating

    NASA Astrophysics Data System (ADS)

    Kim, Younggyu; Leem, Jae-Young

    2015-09-01

    ZnO thin films were grown on flexible muscovite mica substrates using sol-gel spin-coating. The structural and optical properties of the sol-gel-derived ZnO thin films annealed at temperatures between 300 - 600 °C were investigated. The surface morphology of the ZnO thin films was found to depend slightly on the annealing temperature. In the photoluminescence spectra, the position of the near-band-edge (NBE) peak was shifted towards a lower energy by the post-annealing process, and the full width at half maximum (FWHM) values of the NBE peaks for the annealed ZnO thin films were significantly lower than those for the as-grown film. Defect-related deep-level peaks exhibiting green and red emissions were observed only for the annealed ZnO thin films. The Urbach energy and optical band gap of the films decreased with an increase in annealing temperatures up to 500 °C.

  11. 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.

  12. Competition between (001) and (111) MgO thin film growth on Al-doped ZnO by oxygen plasma assisted pulsed laser deposition

    SciTech Connect

    Xiao, Bo; Yang, Qiguang; Walker, Brandon; Gonder, Casey A.; Romain, Gari C.; Mundle, Rajeh; Bahoura, Messaoud; Pradhan, A. K.

    2013-06-07

    We report on the study of epitaxial MgO thin films on (0001) Al-doped ZnO (Al: ZnO) underlayers, grown by oxygen plasma assisted pulsed laser deposition technique. A systematic investigation of the MgO thin films was performed by X-ray diffraction and atomic force microscopy, along with the current-voltage characteristics. A distinguished behavior was observed that the preferred MgO orientation changes from (111) to (001) in the films as the growth temperature increases. Two completely different in-plane epitaxial relationships were also determined from X-ray diffraction as: [110]MgO//[1120]Al: ZnO and [110]MgO//[1100]Al: ZnO for (001) MgO with 60 Degree-Sign rotated triplet domains, and [110]MgO//[1120]Al: ZnO for (111) MgO with 180 Degree-Sign rotated twin. The pronounced temperature dependence indicates a reconciliation of the nucleation driving forces among surface, interfacial, and strain energy for heteroepitaxy of cubic MgO on hexagonal Al: ZnO. The related interfacial atomic registry is considered to be important to the formation of unusual (001) MgO on hexagonal crystals. In addition, the electrical characterization revealed a dramatic reduction of the leakage current in (001) MgO thin films, whereas the small grain size of (111) MgO is identified by atomic force microscopy as a main cause of large leakage current.

  13. Research Update: Atmospheric pressure spatial atomic layer deposition of ZnO thin films: Reactors, doping, and devices

    SciTech Connect

    Hoye, Robert L. Z. E-mail: jld35@cam.ac.uk; MacManus-Driscoll, Judith L. E-mail: jld35@cam.ac.uk; Muñoz-Rojas, David; Nelson, Shelby F.; Illiberi, Andrea; Poodt, Paul

    2015-04-01

    Atmospheric pressure spatial atomic layer deposition (AP-SALD) has recently emerged as an appealing technique for rapidly producing high quality oxides. Here, we focus on the use of AP-SALD to deposit functional ZnO thin films, particularly on the reactors used, the film properties, and the dopants that have been studied. We highlight how these films are advantageous for the performance of solar cells, organometal halide perovskite light emitting diodes, and thin-film transistors. Future AP-SALD technology will enable the commercial processing of thin films over large areas on a sheet-to-sheet and roll-to-roll basis, with new reactor designs emerging for flexible plastic and paper electronics.

  14. Oxygen partial pressure dependent electrical conductivity type conversion of phosphorus-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Lee, S.; Jeong, Y. E.; Lee, D.; Bae, J. S.; Lee, W. J.; Park, K. H.; Bu, S. D.; Park, S.

    2014-02-01

    In this study, the oxygen partial pressure dependent physical properties of phosphorous-doped ZnO thin films were investigated. All thin films, grown on Al2O3(0 0 0 1) substrates using pulsed laser deposition, exhibited (0 0 2) orientation regardless of the oxygen partial pressure. However, as the oxygen partial pressure increased, the degree of crystallinity and the concentration of oxygen vacancies in the films decreased. All the thin-film samples showed n-type characteristics except for a sample grown at 100 mTorr, which exhibited p-type characteristics. The optical band gap energy also changed with the oxygen partial pressure. The feasible microscopic mechanism of conductivity conversion is explained in terms of the lattice constant, crystallinity, and the relative roles of the substituted phosphorous in the Zn-site and/or oxygen vacancies depending on the oxygen partial pressure.

  15. Effect of precursor on epitaxially grown of ZnO thin film on p-GaN/sapphire (0 0 0 1) substrate by hydrothermal technique

    SciTech Connect

    Sahoo, Trilochan; Ju, Jin-Woo; Kannan, V.; Kim, Jin Soo; Yu, Yeon-Tae; Han, Myung-Soo; Park, Young-Sik; Lee, In-Hwan

    2008-03-04

    Single crystalline ZnO thin film on p-GaN/sapphire (0 0 0 1) substrate, using two different precursors by hydrothermal route at a temperature of 90 deg. C were successfully grown. The effect of starting precursor on crystalline nature, surface morphology and optical emission of the films were studied. ZnO thin films were grown in aqueous solution of zinc acetate and zinc nitrate. X-ray diffraction analysis revealed that all the thin films were single crystalline in nature and exhibited wurtzite symmetry and c-axis orientation. The thin films obtained with zinc nitrate had a more pitted rough surface morphology compared to the film grown in zinc acetate. However the thickness of the films remained unaffected by the nature of the starting precursor. Sharp luminescence peaks were observed from the thin films almost at identical energies but deep level emission was slightly prominent for the thin film grown in zinc nitrate.

  16. Investigation on the Electrical and Methane Gas-Sensing Properties of ZnO Thin Films Produced by Different Methods

    NASA Astrophysics Data System (ADS)

    Teimoori, F.; Khojier, K.; Dehnavi, N. Z.

    2016-06-01

    In this work, the influence of deposition method on the structural, electrical, and methane gas-sensing properties of ZnO thin films is investigated. Sol-gel spin coating, direct current (DC) magnetron sputtering, and e-beam evaporation techniques are employed for production of Zn thin films post-annealed at 500°C with a constant flow of oxygen. Detailed morphological, chemical, and structural investigations are carried out on all samples by field emission electron microscopy (FESEM) and x-ray diffraction (XRD) analyses. DC electrical resistivity of the samples was measured using a four-point probe instrument while a Hall effect instrument was used for the Hall effect measurements. The sensing performance was optimized with respect to the deposition method as well as the operating temperature. Detection limit, reproducibility, and stability of all samples produced using different methods are also identified. An optimum operating temperature of 350°C is obtained. The best sensitivity was attributed to the deposited film by the e-beam evaporation method due to its different surface morphology, which provided a larger ratio of surface-to-bulk area, and a lower carrier concentration, which caused higher electrical resistance. All ZnO thin films deposited by different methods also showed good reproducibility and stability.

  17. Ag-doped FeSe0.94 polycrystalline samples obtained through hot isostatic pressing with improved grain connectivity

    NASA Astrophysics Data System (ADS)

    Gajda, G.; Morawski, A.; Rogacki, K.; Cetner, T.; Zaleski, A. J.; Buchkov, K.; Nazarova, E.; Balchev, N.; Hossain, M. S. A.; Diduszko, R.; Gruszka, K.; Przysłupski, P.; Fajfrowski, Ł.; Gajda, D.

    2016-09-01

    We evaluate the effects of high pressure during annealing on the structural and superconducting properties of Ag-doped FeSe bulks. The results obtained in this work indicate that the annealing at high pressure increases the critical temperature, upper critical field and irreversibility field due to the improved uniformity and grain connectivity.

  18. Nano-structural Characteristics of N-doped ZnO Thin Films and Fabrication of Film Bulk Acoustic Resonator Devices

    SciTech Connect

    Lee, E. J.; Zhang, R. R.; Yoon, G. W.; Park, J. D.

    2011-12-23

    N-doped ZnO thin films (ZnO:N) with c-axis preferred orientation were prepared on p-Si(100) wafers, using an RF magnetron sputter deposition. For ZnO deposition, N{sub 2}O gas was employed as a dopant source and various deposition conditions such as N{sub 2}O gas fraction and RF power were applied. In addition, the film bulk acoustic resonator (FBAR) devices with three kinds of top electrodes patterns were fabricated by using the N-doped ZnO thin films as the piezoelectric layers. The depth profiles of the nitrogen [N] atoms incorporated into the ZnO thin films were investigated by an Auger Electron Spectroscopy (AES) and the nano-scale structural characteristics of the N-doped ZnO (ZnO:N) thin films were also investigated by a scanning electron microscope (SEM) technique. The fabricated resonators were evaluated by measuring the return loss (S{sub 11}) characteristics using a probe station and E8361A PNA Network Analyzer.

  19. Enhancement of photo sensor properties of nanocrystalline ZnO thin film by swift heavy ion irradiation

    SciTech Connect

    Mahajan, S. V.; Upadhye, D. S.; Bagul, S. B.; Shaikh, S. U.; Birajadar, R. B.; Siddiqui, F. Y.; Huse, N. P.; Sharma, R. B. E-mail: rps.phy@gmail.com

    2015-06-24

    Nanocrystalline Zinc Oxide (ZnO) thin film prepared by Low cost Successive Ionic Layer Adsorption and Reaction (SILAR) method. This film was irradiated by 120 MeV Ni{sup 7+} ions with the fluence of 5x10{sup 12}ions/cm{sup 2}. The X-ray diffraction study was shows polycrystalline nature with wurtzite structure. The optical properties as absorbance were determined using UV-Spectrophotometer and band gap was also calculated. The Photo Sensor nature was calculated by I-V characteristics with different sources of light 40W, 60W and 100W.

  20. Resistive switching characteristics of ZnO thin film grown on stainless steel for flexible nonvolatile memory devices

    SciTech Connect

    Lee, Seunghyup; Kim, Heejin; Yong, Kijung; Yun, Dong-Jin; Rhee, Shi-Woo

    2009-12-28

    This paper reports a resistive switching device of Au/ZnO/stainless steel (SS) and its applicability as a flexible resistive random access memory (ReRAM). The Au/ZnO/SS structure was fabricated by radio frequency sputtering deposition of a ZnO thin film on the SS substrate. The fabricated device showed stable unipolar and bipolar resistive switching behaviors with reliable switching responses over 100 cycles. The device performance was not degraded upon bending, which indicates high potential for flexible ReRAM applications.

  1. Ferroelectric behavior of Li-doped ZnO thin films on Si(100) by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Joseph, M.; Tabata, H.; Kawai, T.

    1999-04-01

    Thin films of Li-doped ZnO of different compositions (Zn1-xLix)O, x=0.1, 0.17, and 0.3 have been prepared on Si(100) substrates, with no buffer layer, by the pulsed laser deposition method. Ferroelectric behavior with a memory window of 1.2 V has been observed in capacitance-voltage measurements. The peak maximum in the capacitance-temperature curve suggests that the ferroelectric phase transition occurs around 340 K.

  2. Broad-band three dimensional nanocave ZnO thin film photodetectors enhanced by Au surface plasmon resonance.

    PubMed

    Sun, Mengwei; Xu, Zhen; Yin, Min; Lin, Qingfeng; Lu, Linfeng; Xue, Xinzhong; Zhu, Xufei; Cui, Yanxia; Fan, Zhiyong; Ding, Yiling; Tian, Li; Wang, Hui; Chen, Xiaoyuan; Li, Dongdong

    2016-04-28

    ZnO semiconductor films with periodic 3D nanocave patterns were fabricated by the thermal nanoimprinting technology, which is promising for photodetectors with enhanced light harvesting capability. The Au nanoparticles were further introduced into the ZnO films, which boosts the UV response of ZnO films and extends the photodetection to visible regions. The best UV photoresponse was detected on the 3D nanocave ZnO-Au hybrid films, attributing to the light trapping mechanism of 3D periodic structures and the driving force of the Schottky barrier at the ZnO/Au interface, while the high visible photoresponse of ZnO-Au hybrid films mainly results from the hot electron generation and injection process over the Schottky junctions mediated by Au surface plasmon resonances. The work provides a cost-effective pathway to develop large-scale periodic 3D nanopatterned thin film photodetectors and is promising for the future deployment of high performance optoelectronic devices. PMID:27073045

  3. Comparison of Magnetic Property of Cu-, Al-, and Li-DOPED ZnO Dilute Magnetic Semiconductor Thin Films

    NASA Astrophysics Data System (ADS)

    van, L. H.; Ding, J.; Hong, M. H.; Fan, Z. C.; Wang, L.

    The properties of Cu-, Al-, and Li-doped ZnO dilute magnetic semiconductor (DMS) have been analyzed and compared. Zincite with wurtzite structures have been synthesized successfully on SiO2 (101) and SiO2 (110) substrates in both the Cu-ZnO and Li-ZnO DMS. The highly textured ZnO (002) peaks were able to form in the Cu-ZnO system at 400°C. However, it formed at even much lower temperature in the Li-ZnO system, that is only 25°C. ZnO (002) peaks in both systems were formed without any impurity phases. However, no crystalline structure is synthesized in the Al-ZnO system. The thin films formed are amorphous. The structural and related magnetic properties of the films were analyzed by XRD, AFM, and VSM. The films were found to be at their highest magnetism at the value of 3.1 emu/cm3 for Co-ZnO and 2.5 emu/cm3 for Li-ZnO, synthesized at 400°C, and under 1 × 10-4 Torr oxygen partial pressure.

  4. EXAFS and XANES investigation of (Li, Ni) codoped ZnO thin films grown by pulsed laser deposition.

    PubMed

    Mino, Lorenzo; Gianolio, Diego; Bardelli, Fabrizio; Prestipino, Carmelo; Senthil Kumar, E; Bellarmine, F; Ramanjaneyulu, M; Lamberti, Carlo; Ramachandra Rao, M S

    2013-09-25

    Ni doped, Li doped and (Li, Ni) codoped ZnO thin films were successfully grown using a pulsed laser deposition technique. Undoped and doped ZnO thin films were investigated using extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge spectroscopy (XANES). Preliminary investigations on the Zn K-edge of the undoped and doped ZnO thin films revealed that doping has not influenced the average Zn-Zn bond length and Debye-Waller factor. This shows that both Ni and Li doping do not appreciably affect the average local environment of Zn. All the doped ZnO thin films exhibited more than 50% of substitutional Ni, with a maximum of 77% for 2% Ni and 2% Li doped ZnO thin film. The contribution of Ni metal to the EXAFS signal clearly reveals the presence of Ni clusters. The Ni-Ni distance in the Ni(0) nanoclusters, which are formed in the film, is shorter with respect to the reference Ni metal foil and the Debye-Waller factor is higher. Both facts perfectly reflect what is expected for metal nanoparticles. At the highest doping concentration (5%), the presence of Li favors the growth of a secondary NiO phase. Indeed, 2% Ni and 5% Li doped ZnO thin film shows %Nisub = 75 ± 11, %Nimet = 10 ± 8, %NiO = 15 ± 8. XANES studies further confirm that the substitutional Ni is more than 50% in all the samples. These results explain the observed magnetic properties. PMID:23988792

  5. 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.

  6. Broad-band three dimensional nanocave ZnO thin film photodetectors enhanced by Au surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Sun, Mengwei; Xu, Zhen; Yin, Min; Lin, Qingfeng; Lu, Linfeng; Xue, Xinzhong; Zhu, Xufei; Cui, Yanxia; Fan, Zhiyong; Ding, Yiling; Tian, Li; Wang, Hui; Chen, Xiaoyuan; Li, Dongdong

    2016-04-01

    ZnO semiconductor films with periodic 3D nanocave patterns were fabricated by the thermal nanoimprinting technology, which is promising for photodetectors with enhanced light harvesting capability. The Au nanoparticles were further introduced into the ZnO films, which boosts the UV response of ZnO films and extends the photodetection to visible regions. The best UV photoresponse was detected on the 3D nanocave ZnO-Au hybrid films, attributing to the light trapping mechanism of 3D periodic structures and the driving force of the Schottky barrier at the ZnO/Au interface, while the high visible photoresponse of ZnO-Au hybrid films mainly results from the hot electron generation and injection process over the Schottky junctions mediated by Au surface plasmon resonances. The work provides a cost-effective pathway to develop large-scale periodic 3D nanopatterned thin film photodetectors and is promising for the future deployment of high performance optoelectronic devices.ZnO semiconductor films with periodic 3D nanocave patterns were fabricated by the thermal nanoimprinting technology, which is promising for photodetectors with enhanced light harvesting capability. The Au nanoparticles were further introduced into the ZnO films, which boosts the UV response of ZnO films and extends the photodetection to visible regions. The best UV photoresponse was detected on the 3D nanocave ZnO-Au hybrid films, attributing to the light trapping mechanism of 3D periodic structures and the driving force of the Schottky barrier at the ZnO/Au interface, while the high visible photoresponse of ZnO-Au hybrid films mainly results from the hot electron generation and injection process over the Schottky junctions mediated by Au surface plasmon resonances. The work provides a cost-effective pathway to develop large-scale periodic 3D nanopatterned thin film photodetectors and is promising for the future deployment of high performance optoelectronic devices. Electronic supplementary information

  7. Dye-sensitized solar cell using sprayed ZnO nanocrystalline thin films on ITO as photoanode.

    PubMed

    Dhamodharan, P; Manoharan, C; Dhanapandian, S; Venkatachalam, P

    2015-02-01

    ZnO thin films had been successfully prepared by spray pyrolysis (SP) technique on ITO/Glass substrates at different substrate temperature in the range 250-400°C using Zinc acetylacetonate as precursor. The X-ray diffraction studies confirmed the hexagonal wurtzite structure with preferred orientation along (002) plane at substrate temperature 350°C and the crystallite size was found to vary from 18 to 47nm. The morphology of the films revealed the porous nature with the roughness value of 8-13nm. The transmittance value was found to vary from 60% to 85% in the visible region depending upon the substrate temperature and the band gap value for the film deposited at 350°C was 3.2eV. The obtained results revealed that the structures and properties of the films were greatly affected by substrate temperature. The near band edge emission observed at 398nm in PL spectra showed better crystallinity. The measured electrical resistivity for ZnO film was ∼3.5×10(-4)Ωcm at the optimized temperature 350°C and was of n-type semiconductor. The obtained porous nature with increased surface roughness of the film and good light absorbing nature of the dye paved way for implementation of quality ZnO in DSSCs fabrication. DSSC were assembled using the prepared ZnO film on ITO coated glass substrate as photoanode and its photocurrent - voltage performance was investigated. PMID:25459731

  8. Dye-sensitized solar cell using sprayed ZnO nanocrystalline thin films on ITO as photoanode

    NASA Astrophysics Data System (ADS)

    Dhamodharan, P.; Manoharan, C.; Dhanapandian, S.; Venkatachalam, P.

    2015-02-01

    ZnO thin films had been successfully prepared by spray pyrolysis (SP) technique on ITO/Glass substrates at different substrate temperature in the range 250-400 °C using Zinc acetylacetonate as precursor. The X-ray diffraction studies confirmed the hexagonal wurtzite structure with preferred orientation along (0 0 2) plane at substrate temperature 350 °C and the crystallite size was found to vary from 18 to 47 nm. The morphology of the films revealed the porous nature with the roughness value of 8-13 nm. The transmittance value was found to vary from 60% to 85% in the visible region depending upon the substrate temperature and the band gap value for the film deposited at 350 °C was 3.2 eV. The obtained results revealed that the structures and properties of the films were greatly affected by substrate temperature. The near band edge emission observed at 398 nm in PL spectra showed better crystallinity. The measured electrical resistivity for ZnO film was ∼3.5 × 10-4 Ω cm at the optimized temperature 350 °C and was of n-type semiconductor. The obtained porous nature with increased surface roughness of the film and good light absorbing nature of the dye paved way for implementation of quality ZnO in DSSCs fabrication. DSSC were assembled using the prepared ZnO film on ITO coated glass substrate as photoanode and its photocurrent - voltage performance was investigated.

  9. Bromide and iodide removal from waters under dynamic conditions by Ag-doped aerogels.

    PubMed

    Sánchez-Polo, M; Rivera-Utrilla, J; von Gunten, U

    2007-02-01

    The objective of this study was to analyze the efficiency of Ag-doped aerogels in the removal of bromide and iodide from water. To test the applicability of these aerogels in water treatment, adsorption of bromide and iodide was studied under dynamic conditions using waters from Lake Zurich and a mineral water. The results obtained by using these waters showed a high breakthrough volume (V(0.02)=0.4 L) of the columns, while the height of the mass transfer zone (H(MTZ)=6.8 cm) was low, regardless of the anion under study. Bromide- and iodide-saturated columns were regenerated with NH4OH. No change in the column characteristics was observed after two regeneration treatments, regardless of the type of water considered. PMID:17109877

  10. Local order origin of thermal stability enhancement in amorphous Ag doping GeTe

    SciTech Connect

    Xu, L.; Li, Y.; Yu, N. N.; Zhong, Y. P.; Miao, X. S.

    2015-01-19

    We demonstrate the impacts of Ag doping on the local atomic structure of amorphous GeTe phase-change material. The variations of phonon vibrational modes, boding nature, and atomic structure are shown by Raman, X-ray photoelectron spectroscopy, and ab initio calculation. Combining the experiments and simulations, we observe that the number of Ge atoms in octahedral site decreases and that in tetrahedral site increases. This modification in local order of GeTe originating from the low valence element will affect the crystallization behavior of amorphous GeTe, which is verified by differential scanning calorimetry and transmission electron microscope results. This work not only gives the analysis on the structural change of GeTe with Ag dopants but also provides a method to enhance the thermal stability of amorphous phase-change materials for memory and brain-inspired computing applications.

  11. A study of the applicability of ZnO thin-films as anti-reflection coating on Cu{sub 2}ZnSnS{sub 4} thin-films solar cell

    SciTech Connect

    Ray, Abhijit; Patel, Malkeshkumar; Tripathi, Brijesh; Kumar, Manoj

    2012-06-25

    Transparent ZnO thin-films are prepared using the RF magnetron sputtering and spray pyrolysis techniques on the glass substrates. Reflectance spectra and thin films heights are measured using spectrophotometer and stylus surface profiler, respectively. Measured optical data is used for investigating the effect of the ZnO prepared by above two processes on the performance of Cu{sub 2}ZnSnS{sub 4} (CZTS) thin films solar cell (TFSC). One dimensional simulation approach is considered using the simulation program, SCAPS. External quantum efficiency and J-V characteristics of CZTS TFSC is simulated on the basis of optical reflectance data of ZnO films with and without ZnO thin-films as antireflection coating (ARC). Study shows that ARC coated CZTS TFSC provides a better fill factor (FF) as compared to other ARC material such as MgF{sub 2}. Sprayed ZnO thin-films as ARC show comparable performance with the sputtered samples.

  12. 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.

  13. Evaluation of the interface of thin GaN layers on c- and m-plane ZnO substrates by Rutherford backscattering

    SciTech Connect

    Izawa, Y.; Oga, T.; Ida, T.; Kuriyama, K.; Hashimoto, A.; Kotake, H.; Kamijoh, T.

    2011-07-11

    Lattice distortion at the interfaces between thin GaN layers with {approx}400 nm in thickness and ZnO substrates with non-polar m-plane (10-10) and polar c-plane (0001) is studied using Rutherford backscattering/ion channeling techniques. The interface between GaN/m-plane ZnO is aligned clearly to m-axis, indicating no lattice distortion, while between GaN/c-plane ZnO causes the lattice distortion in the GaN layer due to the piezoelectric field. The range of distortion exceeds {approx}90 nm from the interface of GaN/c-plane ZnO. These results are confirmed by x-ray diffraction and reflection high energy electron diffraction studies.

  14. Investigation of ZnO thin films deposited on ferromagnetic metallic buffer layer by molecular beam epitaxy toward realization of ZnO-based magnetic tunneling junctions

    SciTech Connect

    Belmoubarik, M.; Nozaki, T.; Sahashi, M.; Endo, H.

    2013-05-07

    Deposition of ZnO thin films on a ferromagnetic metallic buffer layer (Co{sub 3}Pt) by molecular beam epitaxy technique was investigated for realization of ZnO-based magnetic tunneling junctions with good quality hexagonal ZnO films as tunnel barriers. For substrate temperature of 600 Degree-Sign C, ZnO films exhibited low oxygen defects and high electrical resistivity of 130 {Omega} cm. This value exceeded that of hexagonal ZnO films grown by sputtering technique, which are used as tunnel barriers in ZnO-MTJs. Also, the effect of oxygen flow during deposition on epitaxial growth conditions and Co{sub 3}Pt surface oxidation was discussed.

  15. Effects of rapid thermal annealing on the structural and local atomic properties of ZnO: Ge nanocomposite thin films

    SciTech Connect

    Ceylan, Abdullah Ozcan, Sadan; Rumaiz, Abdul K.; Caliskan, Deniz; Ozbay, Ekmel; Woicik, J. C.

    2015-03-14

    We have investigated the structural and local atomic properties of Ge nanocrystals (Ge-ncs) embedded ZnO (ZnO: Ge) thin films. The films were deposited by sequential sputtering of ZnO and Ge thin film layers on z-cut quartz substrates followed by an ex-situ rapid thermal annealing (RTA) at 600 °C for 30, 60, and 90 s under forming gas atmosphere. Effects of RTA time on the evolution of Ge-ncs were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), hard x-ray photoelectron spectroscopy (HAXPES), and extended x-ray absorption fine structure (EXAFS). XRD patterns have clearly shown that fcc diamond phase Ge-ncs of sizes ranging between 18 and 27 nm are formed upon RTA and no Ge-oxide peak has been detected. However, cross-section SEM images have clearly revealed that after RTA process, Ge layers form varying size nanoclusters composed of Ge-ncs regions. EXAFS performed at the Ge K-edge to probe the local atomic structure of the Ge-ncs has revealed that as prepared ZnO:Ge possesses Ge-oxide but subsequent RTA leads to crystalline Ge structure without the oxide layer. In order to study the occupied electronic structure, HAXPES has been utilized. The peak separation between the Zn 2p and Ge 3d shows no significant change due to RTA. This implies little change in the valence band offset due to RTA.

  16. Environmental stability of solution processed Al-doped ZnO naoparticulate thin films using surface modification technique

    NASA Astrophysics Data System (ADS)

    Vunnam, Swathi; Ankireddy, Krishnamraju; Kellar, Jon; Cross, William

    2014-12-01

    The environmental stability of solution processed Al-doped ZnO (AZO) thin films was enhanced by functionalizing the film surface with a thin self-assembled molecular layer. Functionalization of AZO films was performed using two types of molecules having identical 12-carbon alkyl chain termination but different functional groups: dodecanethiol (DDT) and dodecanoic acid (DDA). Surface modified AZO films were examined using electrical resistivity measurements, contact angle measurements and quantitative nanomechanical property mapping atomic force microscopy. The hydrophobic layer inhibits the penetration of oxygen and water into the AZO's grain boundaries thus significantly increasing the environmental stability over unmodified AZO. Surface modified AZO films using DDT exhibited lower electrical resistivity compared to DDA functionalized AZO films. Our study demonstrates a new approach for improving the physical properties of oxide based nanoparticulate films for device applications.

  17. Effect of 8 MeV Si ions irradiation and thermal annealing in ZnO thin films

    NASA Astrophysics Data System (ADS)

    Hernández-Socorro, D. R.; Montiel-González, Z.; Rodil-Posada, S. E.; Flores-Morales, L.; Cruz-Manjarrez, H.; Hernández-Alcántara, J. M.; Rodríguez-Fernández, L.

    2012-09-01

    ZnO thin films deposited by RF magnetron sputtering on silicon (100) wafers were irradiated by 8 MeV Si ions and thermal annealed in order to study optical properties. The presence of defects inside thin films as well as their implications was discussed by Photoluminescence and Spectroscopic Ellipsometry. Photoluminescence confirmed presence of energy states in forbidden band-gap associates with ultraviolet emission and Zni, Oi and OZn defects according to the treatment received. Spectroscopic Ellipsometry using the Tauc-Lorentz model plus a Lorentz oscillator was found to be the best model to describe the properties of irradiated samples that did not receive a second thermal annealing treatment. Through this model, it was possible to obtain optical band-gap in the range of 3.1-3.3 eV and excellent approximation of position in energy of the oscillator.

  18. ZnO thin film transistors and electronic connections for adjustable x-ray mirrors: SMART-X telescope

    NASA Astrophysics Data System (ADS)

    Johnson-Wilke, R. L.; Wilke, R. H. T.; Wallace, M.; Ramirez, J. I.; Prieskorn, Z.; Nikoleyczik, J.; Cotroneo, V.; Allured, R.; Schwartz, D. A.; McMuldroch, S.; Reid, P. B.; Burrows, D. N.; Jackson, T. N.; Trolier-McKinstry, S.

    2014-09-01

    The proposed SMART-X telescope consists of a pixelated array of a piezoelectric lead zirconate titanate (PZT) thin film deposited on flexible glass substrates. These cells or pixels are used to actively control the overall shape of the mirror surface. It is anticipated that the telescope will consist of 8,000 mirror panels with 400-800 cells on each panel. This creates an enormous number (6.4 million) of traces and contacts needed to address the PZT. In order to simplify the design, a row/column addressing scheme using ZnO thin film transistors (TFTs) is proposed. In addition, connection of the gate and drain lines on the mirror segment to an external supply via a flexible cable was investigated through use of an anisotropic conductive film (ACF). This paper outlines the design of the ZnO TFTs, use of ACF for bonding, and describes a specially designed electronics box with associated software to address the desired cells.

  19. Post-annealing effect on the room-temperature ferromagnetism in Cu-doped ZnO thin films

    SciTech Connect

    Hu, Yu-Min Kuang, Chein-Hsiun; Han, Tai-Chun; Yu, Chin-Chung; Li, Sih-Sian

    2015-05-07

    In this work, we investigated the structural and magnetic properties of both as-deposited and post-annealed Cu-doped ZnO thin films for better understanding the possible mechanisms of room-temperature ferromagnetism (RT-FM) in ZnO-based diluted magnetic oxides. All of the films have a c-axis-oriented wurtzite structure and display RT-FM. X-ray photoelectron spectroscopy results showed that the incorporated Cu ions in as-deposited films are in 1+ valence state merely, while an additional 2+ valence state occurs in post-annealed films. The presence of Cu{sup 2+} state in post-annealed film accompanies a higher magnetization value than that of as-deposited film and, in particular, the magnetization curves at 10 K and 300 K of the post-annealed film separate distinctly. Since Cu{sup 1+} ion has a filled 3d band, the RT-FM in as-deposited Cu-doped ZnO thin films may stem solely from intrinsic defects, while that in post-annealed films is enhanced due to the presence of CuO crystallites.

  20. Resistive switching: An investigation of the bipolar–unipolar transition in Co-doped ZnO thin films

    SciTech Connect

    Santos, Daniel A.A.; Zeng, Hao; Macêdo, Marcelo A.

    2015-06-15

    Highlights: • A purely bipolar behavior on a Co-doped ZnO thin film has been demonstrated. • We have shown what can happen if a unipolar test is performed in a purely bipolar device. • An explanation for how a sample can show a purely bipolar switching behavior was suggested. • An important open issue about resistive switching effect was put in debate. - Abstract: In order to investigate the resistive switching effect we built devices in a planar structure in which two Al contacts were deposited on the top of the film and separated by a small gap using a shadow mask. Therefore, two samples of 10% Co-doped ZnO thin films were sputtered on glass substrate. High resolution X-ray diffraction (HRXRD) revealed a highly c-axis oriented crystalline structure, without secondary phase. The high resolution scanning electron microscopy (HRSEM) showed a flat surface with good coverage and thickness about 300 nm. A Keithley 2425 semiconductor characterization system was used to perform the resistive switching tests in the bipolar and unipolar modes. Considering only the effect of compliance current (CC), the devices showed a purely bipolar behavior since an increase in CC did not induce a transition to unipolar behavior.

  1. 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.

  2. Fabrication and resistive switching characteristics of high compact Ga-doped ZnO nanorod thin film devices

    NASA Astrophysics Data System (ADS)

    Yao, I.-Chuan; Lee, Dai-Ying; Tseng, Tseung-Yuen; Lin, Pang

    2012-04-01

    This study investigates the resistive switching behavior of Ga-doped ZnO (GZO) nanorod thin films with various Ga/Zn molar ratios. Vertically well-aligned and uniform GZO nanorod thin films were successfully grown on Au/Ti/SiO2/p-Si substrates using an aqueous solution method. X-ray diffraction (XRD) results indicate that GZO nanorods have [0001] highly preferred orientation. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show the formation of highly ordered and dense nanorod thin films. These compact GZO nanorod thin films can be used to make resistive switching memory devices. Such memory devices can be reversibly switched between ON and OFF states, with a stable resistance ratio of ten times, narrow dispersion of ON and OFF voltages, and good endurance performance of over 100 cycles. The resistive switching mechanism in these devices is related to the formation and rupture of conducting filaments consisting of oxygen vacancies, occurring at interfaces between GZO nanorods (grain boundaries). Results show that the resulting compact GZO nanorod thin films have a high potential for resistive memory applications.

  3. Transparent conducting Si-codoped Al-doped ZnO thin films prepared by magnetron sputtering using Al-doped ZnO powder targets containing SiC

    SciTech Connect

    Nomoto, Jun-ichi; Miyata, Toshihiro; Minami, Tadatsugu

    2009-07-15

    Transparent conducting Al-doped ZnO (AZO) thin films codoped with Si, or Si-codoped AZO (AZO:Si), were prepared by radio-frequency magnetron sputtering using a powder mixture of ZnO, Al{sub 2}O{sub 3}, and SiC as the target; the Si content (Si/[Si+Zn] atomic ratio) was varied from 0 to 1 at. %, but the Al content (Al/[Al+Zn] atomic ratio) was held constant. To investigate the effect of carbon on the electrical properties of AZO:Si thin films prepared using the powder targets containing SiC, the authors also prepared thin films using a mixture of ZnO, Al{sub 2}O{sub 3}, and SiO{sub 2} or SiO powders as the target. They found that when AZO:Si thin films were deposited on glass substrates at about 200 degree sign C, both Al and Si doped into ZnO acted as effective donors and the atomic carbon originating from the sputtered target acted as a reducing agent. As a result, sufficient improvement was obtained in the spatial distribution of resistivity on the substrate surface in AZO:Si thin films prepared with a Si content (Si/[Si+Zn] atomic ratio) of 0.75 at. % using powder targets containing SiC. The improvement in resistivity distribution was mainly attributed to increases in both carrier concentration and Hall mobility at locations on the substrate corresponding to the target erosion region. In addition, the resistivity stability of AZO: Si thin films exposed to air for 30 min at a high temperature was found to improve with increasing Si content.

  4. Nanoporous characteristics of sol—gel-derived ZnO thin film

    NASA Astrophysics Data System (ADS)

    Ansari, Anees A.; Khan, M. A. M.; Alhoshan, M.; Alrokayan, S. A.; Alsalhi, M. S.

    2012-04-01

    Sol—gel-derived nanoporous ZnO film has been successfully deposited on glass substrate at 200 °C and subsequently annealed at different temperatures of 300, 400 and 600 °C. Atomic force micrographs demonstrated that the film was crack-free, and that granular nanoparticles were homogenously distributed on the film surface. The average grain size of the nanoparticles and RMS roughness of the scanned surface area was 10 nm and 13.6 nm, respectively, which is due to the high porosity of the film. Photoluminescence (PL) spectra of the nanoporous ZnO film at room temperature show a diffused band, which might be due to an increased amount of oxygen vacancies on the lattice surface. The observed results of the nanoporous ZnO film indicates a promising application in the development of electrochemical biosensors due to the porosity of film enhancing the higher loading of biomacromolecules (enzyme and proteins).

  5. Enhanced ZnO Thin-Film Transistor Performance Using Bilayer Gate Dielectrics.

    PubMed

    Alshammari, Fwzah H; Nayak, Pradipta K; Wang, Zhenwei; Alshareef, Husam N

    2016-09-01

    We report ZnO TFTs using Al2O3/Ta2O5 bilayer gate dielectrics grown by atomic layer deposition. The saturation mobility of single layer Ta2O5 dielectric TFT was 0.1 cm(2) V(-1) s(-1), but increased to 13.3 cm(2) V(-1) s(-1) using Al2O3/Ta2O5 bilayer dielectric with significantly lower leakage current and hysteresis. We show that point defects present in ZnO film, particularly VZn, are the main reason for the poor TFT performance with single layer dielectric, although interfacial roughness scattering effects cannot be ruled out. Our approach combines the high dielectric constant of Ta2O5 and the excellent Al2O3/ZnO interface quality, resulting in improved device performance. PMID:27553091

  6. Tuning of structural, optical, and magnetic properties of ultrathin and thin ZnO nanowire arrays for nano device applications

    PubMed Central

    2014-01-01

    One-dimensional (1-D) ultrathin (15 nm) and thin (100 nm) aligned 1-D (0001) and (0001¯) oriented zinc oxide (ZnO) nanowire (NW) arrays were fabricated on copper substrates by one-step electrochemical deposition inside the pores of polycarbonate membranes. The aspect ratio dependence of the compressive stress because of the lattice mismatch between NW array/substrate interface and crystallite size variations is investigated. X-ray diffraction results show that the polycrystalline ZnO NWs have a wurtzite structure with a = 3.24 Å, c = 5.20 Å, and [002] elongation. HRTEM and SAED pattern confirmed the polycrystalline nature of ultrathin ZnO NWs and lattice spacing of 0.58 nm. The crystallite size and compressive stress in as-grown 15- and 100-nm wires are 12.8 nm and 0.2248 GPa and 22.8 nm and 0.1359 GPa, which changed to 16.1 nm and 1.0307 GPa and 47.5 nm and 1.1677 GPa after annealing at 873 K in ultrahigh vacuum (UHV), respectively. Micro-Raman spectroscopy showed that the increase in E2 (high) phonon frequency corresponds to much higher compressive stresses in ultrathin NW arrays. The minimum-maximum magnetization magnitude for the as-grown ultrathin and thin NW arrays are approximately 8.45 × 10−3 to 8.10 × 10−3 emu/g and approximately 2.22 × 10−7 to 2.190 × 10−7 emu/g, respectively. The magnetization in 15-nm NW arrays is about 4 orders of magnitude higher than that in the 100 nm arrays but can be reduced greatly by the UHV annealing. The origin of ultrathin and thin NW array ferromagnetism may be the exchange interactions between localized electron spin moments resulting from oxygen vacancies at the surfaces of ZnO NWs. The n-type conductivity of 15-nm NW array is higher by about a factor of 2 compared to that of the 100-nm ZnO NWs, and both can be greatly enhanced by UHV annealing. The ability to tune the stresses and the structural and relative occupancies of ZnO NWs in a wide range by annealing has

  7. X-ray Photoelectron Spectroscopy Study of Al- and N- Co-Doped p-Type ZnO Thin Films

    SciTech Connect

    Yuan, G. D.; Ye, Z. Z.; Huang, J. Y.; Zhu, L. P.; Perkins, C. L.; Zhang, S. B.

    2009-01-01

    The chemical state of nitrogen, aluminum, oxygen and zinc in Al-N co-doped p-type ZnO thin films was investigated by X-ray photoelectron spectroscopy (XPS). N{sub 1s} peak were detected in both the two p-type ZnO thin films, showing two components. The higher binding energy peak may be due to the Al-No-H species, and the lower one perhaps derive from the (NH{sub 2}){sup -} cluster for the ammonia introduction. These two peaks both contribute to the p-type behavior in the ZnO films. A symmetry 74.4 eV binding energy in Al{sub 2p3/2} photoelectron peaks revealed an Al-N bonding state, a key factor to the co-doping method.

  8. 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.

  9. Thin film epitaxy and structure property correlations for non-polar ZnO films

    SciTech Connect

    Pant, Punam; Budai, John D; Aggarwal, R; Narayan, Roger; Narayan, Jagdish

    2009-01-01

    Heteroepitaxial growth and strain relaxation were investigated in non-polar a-plane (11-20)ZnO films grown on r-plane (10-12)sapphire substrates in the temperature range 200-700 C by pulsed laser deposition. The lattice misfit in the plane of the film for this orientation varied from -1.26% in [0001] to ?18.52% in the [-1100] direction. The alignment of (11-20)ZnO planes parallel to (10-12)sapphire planes was confirmed by X-ray diffraction {theta}-2{theta} scans over the entire temperature range. X-ray {psi}-scans revealed the epitaxial relationship:[0001]ZnO[-1101]sap; [-1100]ZnO[-1-120]sap. Depending on the growth temperature, variations in the structural, optical and electrical properties were observed in the grown films. Room temperature photoluminescence for films grown at 700 C shows a strong band-edge emission. The ratio of the band-edge emission to green band emission is 135:1, indicating reduced defects and excellent optical quality of the films. The resistivity data for the films grown at 700 C shows semiconducting behavior with room temperature resistivity of 2.2 x 10{sup -3} {Omega}-cm.

  10. Effects of Annealing Temperature on Structural and Optical Properties of ZnO Thin Films

    NASA Astrophysics Data System (ADS)

    Xu, Jian-Ping; Shi, Shao-Bo; Li, Lan; Zhang, Xiao-Song; Wang, Ya-Xin; Chen, Xi-Ming

    2010-04-01

    The effects of annealing temperature on the structural and optical properties of ZnO films grown on Si (100) substrates by sol-gel spin-coating are investigated. The structural and optical properties are characterized by x-ray diffraction, scanning electron microscopy and photoluminescence spectra. X-ray diffraction analysis shows the crystal quality of ZnO films becomes better after annealing at high temperature. The grain size increases with the temperature increasing. It is found that the tensile stress in the plane of ZnO films first increases and then decreases with the annealing temperature increasing, reaching the maximum value of 1.8 GPa at 700°C. PL spectra of ZnO films annealed at various temperatures consists of a near band edge emission around 380 nm and visible emissions due to the electronic defects, which are related to deep level emissions, such as oxide antisite (OZn), interstitial oxygen (Oi), interstitial zinc (Zni) and zinc vacancy (V-Zn), which are generated during annealing process. The evolution of defects is analyzed by PL spectra based on the energy of the electronic transitions.

  11. 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.

  12. Highly transparent and conductive Al-doped ZnO nanoparticulate thin films using direct write processing

    NASA Astrophysics Data System (ADS)

    Vunnam, S.; Ankireddy, K.; Kellar, J.; Cross, W.

    2014-05-01

    Solution processable Al-doped ZnO (AZO) thin films are attractive candidates for low cost transparent electrodes. We demonstrate here an optimized nanoparticulate ink for the fabrication of AZO thin films using scalable, low-cost direct write processing (ultrasonic spray deposition) in air at atmospheric pressure. The thin films were made via thermal processing of as-deposited films. AZO films deposited using the proposed nanoparticulate ink with further reducing in vacuum and rf plasma of forming gas exhibited optical transparency greater than 95% across the visible spectrum, and electrical resistivity of 0.5 Ω cm and it drops down to 7.0 × 10-2 Ω cm after illuminating with UV light, which is comparable to commercially available tin doped indium oxide colloidal coatings. Various structural analyses were performed to investigate the influence of ink chemistry, deposition parameters, and annealing temperatures on the structural, optical, and electrical characteristics of the spray deposited AZO thin films. Optical micrographs confirmed the presence of surface defects and cracks using the AZO NPs ink without any additives. After adding N-(2-Aminoethyl)-3-aminopropylmethyldimethoxy silane to the ink, AZO films exhibited an optical transparency which was virtually identical to that of the plain glass substrate.

  13. Smart chemical sensors using ZnO semiconducting thin films for freshness detection of foods and beverages

    NASA Astrophysics Data System (ADS)

    Nanto, Hidehito; Kobayashi, Toshiki; Dougami, Naganori; Habara, Masaaki; Yamamoto, Hajime; Kusano, Eiji; Kinbara, Akira; Douguchi, Yoshiteru

    1998-07-01

    The sensitivity of the chemical sensor, based on the resistance change of Al2O3-doped and SnO2-doped ZnO (ZnO:Al and ZnO:SnO2) thin film, is studied for exposure to various gases. It is found that the ZnO:Al and ZnO:Sn thin film chemical sensor has a high sensitivity and excellent selectivity for amine (TMA and DMA) gas and ethanol gas, respectively. The ZnO:Al (5.0 wt%) thin film chemical sensor which exhibit a high sensitivity for exposure to odors from rotten sea foods, such as salmon, sea bream, oyster, squid and sardine, responds to the freshness change of these sea foods. The ZnO:SnO2 (78 wt%) thin film chemical sensor which exhibit a high sensitivity for exposure to aroma from alcohols, such as wine, Japanese sake, and whisky, responds to the freshness change of these alcohols.

  14. Highly transparent and conductive Al-doped ZnO nanoparticulate thin films using direct write processing.

    PubMed

    Vunnam, S; Ankireddy, K; Kellar, J; Cross, W

    2014-05-16

    Solution processable Al-doped ZnO (AZO) thin films are attractive candidates for low cost transparent electrodes. We demonstrate here an optimized nanoparticulate ink for the fabrication of AZO thin films using scalable, low-cost direct write processing (ultrasonic spray deposition) in air at atmospheric pressure. The thin films were made via thermal processing of as-deposited films. AZO films deposited using the proposed nanoparticulate ink with further reducing in vacuum and rf plasma of forming gas exhibited optical transparency greater than 95% across the visible spectrum, and electrical resistivity of 0.5 Ω cm and it drops down to 7.0 × 10(-2) Ω cm after illuminating with UV light, which is comparable to commercially available tin doped indium oxide colloidal coatings. Various structural analyses were performed to investigate the influence of ink chemistry, deposition parameters, and annealing temperatures on the structural, optical, and electrical characteristics of the spray deposited AZO thin films. Optical micrographs confirmed the presence of surface defects and cracks using the AZO NPs ink without any additives. After adding N-(2-Aminoethyl)-3-aminopropylmethyldimethoxy silane to the ink, AZO films exhibited an optical transparency which was virtually identical to that of the plain glass substrate. PMID:24763438

  15. Efficient inverted organic light-emitting devices with self or intentionally Ag-doped interlayer modified cathode

    SciTech Connect

    Liu, Wenbo; Liu, Shihao; Yu, Jing; Zhang, Wei; Wen, Xuemei; Yin, Yongming; Zhang, Letian; Chen, Ping; Xie, Wenfa

    2014-03-03

    Green phosphorescent inverted organic light-emitting devices (IOLEDs) with self or intentionally Ag-doped interlayer modified cathode were demonstrated. The IOLEDs show low driving voltage and high efficiency. For example, the efficiency of inverted bottom-emitting OLED with ITO cathode is comparable with the conventional bottom-emitting OLED with ITO anode. The top-emitting IOLED with Ag cathode shows high current efficiency of 76.4 cd/A which is 2.38 times of that of the conventional bottom-emitting OLED with ITO anode. The results indicate that the electron injection from cathode was observably improved by the Ag-doped interlayer and such interlayer is cathode independent relatively.

  16. Nanosecond laser switching of surface wettability and epitaxial integration of c-axis ZnO thin films with Si(111) substrates.

    PubMed

    Molaei, R; Bayati, M R; Alipour, H M; Estrich, N A; Narayan, J

    2014-01-01

    We have achieved integration of polar ZnO[0001] epitaxial thin films with Si(111) substrates where cubic yttria-stabilized zirconia (c-YSZ) was used as a template on a Si(111) substrate. Using XRD (θ-2θ and φ scans) and HRTEM techniques, the epitaxial relationship between the ZnO and the c-YSZ layers was shown to be [0001]ZnO || [111]YSZ and [21¯1¯0]ZnO || [1¯01](c-YSZ), where the [21¯1¯0] direction lies in the (0001) plane, and the [1¯01] direction lies in the (111) plane. Similar studies on the c-YSZ/Si interface revealed epitaxy as (111)YSZ || (111)Si and in-plane (110)YSZ || (110)Si. HRTEM micrographs revealed atomically sharp and crystallographically continuous interfaces. The ZnO epilayers were subsequently laser annealed by a single pulse of a nanosecond excimer KrF laser. It was shown that the hydrophobic behavior of the pristine sample became hydrophilic after laser treatment. XPS was employed to study the effect of laser treatment on surface stoichiometry of the ZnO epilayers. The results revealed the formation of oxygen vacancies, which are envisaged to control the observed hydrophilic behavior. Our AFM studies showed surface smoothing due to the coupling of the high energy laser beam with the surface. The importance of integration of c-axis ZnO with Si(111) substrates is emphasized using the paradigm of domain matching epitaxy on the c-YSZ[111] buffer platform along with their out-of-plane orientation, which leads to improvement of the performance of the solid-state devices. The observed ultrafast response and switching in photochemical characteristics provide new opportunities for application of ZnO in smart catalysts, sensors, membranes, DNA self-assembly and multifunctional devices. PMID:24275059

  17. Characterization of spray-deposited ZnO thin films for dye-sensitized solar cell application

    NASA Astrophysics Data System (ADS)

    Amala Rani, A.; Ernest, Suhashini

    2016-07-01

    ZnO films have been prepared on glass plates with concentrations of 0.025, 0.05 and 0.1 M each consisting of 50 ml of solution using the spray pyrolysis technique. A dye-sensitized solar cell (DSSC) was constructed by means of the obtained film for 0.1 M which was also coated above the ITO substrate. N-719, iodide and platinum-coated ITO glass plates were used as the dye, electrolyte and counter electrode, respectively. XRD confirms that the structure of the film was polycrystalline having wurtzite structure. The surface with pores was found from the FESEM studies. The DSSC shows an optical transmittance of approximately 70 % in the visible region. The photoluminescence study reveals the electronic structure of the material. The efficiency of the DSSC measured for a 0.1 M ZnO thin film by sensitizing every 2 h was η = 0.51, 0.80, 0.54, 1.12, 2.11, 2.71, 3.15 and 3.20 %, respectively.

  18. The high temperature photoluminescence and optical absorption of undoped ZnO single crystals and thin films

    SciTech Connect

    Margueron, Samuel; Clarke, David R.

    2014-11-21

    The photoluminescence of undoped ZnO single crystals up to 1350 °C and the optical absorption of stress-relaxed, epitaxial ZnO thin films up to 1100 °C are reported. The photoluminescence intensity and power dependence with illumination flux are related to the crystal growth methods and stabilize after high temperature annealing. The observation of excitonic recombination at very high temperatures requires high illumination flux. It is found that the zero phonon line model reproduces the shift and the band gap narrowing as well as the free excitonic transition up to the cross-over with a defect level at 2.83 eV that occurs at 800 °C. A phenomenological model of the excitonic recombination band shape, taking account exciton-phonon losses and defect levels provides an excellent fit up to 2.2–2.4 eV (1100 °C). At these cross-over temperatures, an energy transfer is observed between the free exciton transition and defect transitions. However, at temperature above 1100 °C, the decrease of the band gap and the increase of thermal radiation, as well as the restrictions of our experimental set-up and particularly the illumination flux of the exciting laser, limit the analysis of the photoluminescence spectra measurements.

  19. Epitaxial growth of non-polar m-plane ZnO thin films by pulsed laser deposition

    SciTech Connect

    Li, Yang; Zhang, Yinzhu; He, Haiping; Ye, Zhizhen; Jiang, Jie; Lu, Jianguo; Huang, Jingyun

    2012-09-15

    Highlights: ► Unique m-plane ZnO films were deposited on m-plane sapphire substrate by PLD. ► The epitaxial relationship between the film and the substrate was studied. ► The surface morphology showed stripes due to in-plane anisotropy. ► PL spectra showed strong NBE emission and weak deep level emission. -- Abstract: Non-polar ZnO thin films were deposited on m-plane sapphire substrates by pulsed laser deposition at various temperatures from 300 to 700 °C. The effects of growth temperature on surface morphology, structural, electrical, and optical properties of the films were investigated. All the films exhibited unique m-plane orientation indicated by X-ray diffraction and transmission electron microscopy. Based on the scanning electron microscopy and atomic force microscopy, the obtained films had smooth and highly anisotropic surface, and the root mean square roughness was less than 10 nm above 500 °C. The maximum electron mobility was ∼18 cm{sup 2}/V s, with resistivity of ∼0.26 Ω cm for the film grown at 700 °C. Room temperature photoluminescence of the m-plane films was also investigated.

  20. Structure and mechanical properties of 3dTM ion doped RF sputtered ZnO thin films on Si (100)

    SciTech Connect

    Venkaiah, M. Singh, R.

    2014-04-24

    Mn, Fe and Mn-Fe doped ZnO thin films were deposited on Si (100) substrates by rf- magnetron sputtering using ceramic target in pure oxygen gas environment. The X-ray diffraction shows the polycrystalline wurtzite structure films. The average grain size varies from 32-50 nm, with lower grain size for Fe doped ZnO films. The room temperature loading and unloading curve are continuous without any pop-in. The Young's modulus and hardness are in the range 156-178 GPa and 14-15.5 GPa respectively.

  1. Influence of Rare Earth Ho3+ Doping on Structural, Microstructure and Magnetic Properties of ZnO Bulk and Thin Film Systems

    NASA Astrophysics Data System (ADS)

    Murtaza Rai, Ghulam; Azhar Iqbal, Muhammad; Xu, Yongbing; Will, Iain Gordon; Zhang, Wen

    2011-06-01

    We have investigated the doping behavior of rare earth element holmium (Ho3+) in ZnO semiconductor. The structural, microstructure, and magnetic properties of Zn1-xHoxO (x=0.0, 0.04, and 0.05) thin films deposited on Si(100) substrate by thermal evaporation technique were studied. The ceramic targets were prepared by conventional solid state ceramic technique. The pallets used as target were final sintered at 900 °C in the presence of N2 atmosphere. The experimental results of X-ray diffraction (XRD) spectra, surface morphology, and magnetic properties show that the Ho3+ doped ZnO thin films has a strong influence on the materials properties. The higher angle shift in peak position and most preferred (101) orientation were observed in XRD pattern. These spectra confirmed the substitution of Ho3+ in ZnO lattice. The surface morphology and stoichiometry for both bulk and thin films were analyzed by scanning electron microscopy and energy dispersive spectroscopy. It was observed that grain size decreases with the increase of Ho3+. Room temperature ferromagnetism was observed for Zn0.95Ho0.05O films. The ferromagnetism might be attributed to the substitution of Ho ions for Zn2+ in ZnO lattices.

  2. Slope selection-driven Ostwald ripening in ZnO thin film growth

    NASA Astrophysics Data System (ADS)

    González-González, A.; Polop, C.; Vasco, E.

    2012-07-01

    The morphology evolution of polycrystalline ZnO films grown by pulsed laser deposition was investigated by atomic force microscopy and compared with morphologies simulated in 2 + 1 dimensions from a mesoscopic continuum model of selection of surface slopes. The distinctive feature of such an evolution is that the competition between grains gives rise to a singular grain coarsening mechanism, which although it matches the fingerprints of the Ostwald ripening, it remains operative under atypical growth conditions (temperatures as low as 0.28Tmelting and grains with sizes ranged between 20-500 nm) and is driven by the faceting of the grain faces. The resulting pyramidal single-crystalline grains from such a coarsening mechanism have been correlated with the enhanced ultraviolet lasing activity at room temperature of nanostructured ZnO.

  3. 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.

  4. X-ray absorption spectroscopy of Mn doped ZnO thin films prepared by rf sputtering technique

    SciTech Connect

    Yadav, Ashok Kumar; Jha, S. N.; Bhattacharyya, D.; Haque, Sk Maidul; Shukla, Dinesh; Choudhary, Ram Janay

    2015-11-15

    A set of r.f. sputter deposited ZnO thin films prepared with different Mn doping concentrations have been characterised by Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Spectroscopy (XANES) measurements at Zn, Mn and O K edges and at Mn L{sub 2,3} edges apart from long range structural characterisation by Grazing Incident X-ray Diffraction (GIXRD) technique. Magnetic measurements show room temperature ferromagnetism in samples with lower Mn doping which is however, gets destroyed at higher Mn doping concentration. The results of the magnetic measurements have been explained using the local structure information obtained from EXAFS and XANES measurements.

  5. Influence of baking method and baking temperature on the optical properties of ZnO thin films

    SciTech Connect

    Ng, Zi-Neng; Chan, Kah-Yoong

    2015-04-24

    In this work, sol-gel spin coating technique was utilised to coat ZnO thin films on glass substrates. During the intermediate 3 minutes baking process, either hotplate or convection oven was employed to bake the samples. The temperature for the baking process was varied from 150°C to 300°C for both instruments. Avantes Optical Spectrophotometer was used to characterise the optical property. The optical transmittances of hotplate-baked and oven-baked samples showed different trends with increasing baking temperatures, ranging from below 50% transmittance to over 90% transmittance in the visible range of wavelength. The difference in baking mechanisms using hotplate and convection oven will be discussed in this paper.

  6. 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.

  7. Effect of annealing on structural and optical properties of sol-gel prepared Cd doped ZnO thin films

    SciTech Connect

    Sahoo, Guruprasad Jain, Mahaveer K.; Meher, S. R.

    2015-06-24

    Zn{sub 1-x}Cd{sub x}O thin films have been prepared by sol-gel spin coating method. Structural analysis shows that the Cd substitution into the wutrzite ZnO lattice is achieved up to about 20 mol %. The optical band gap is found to decrease with the increase in Cd content. Increase in the annealing temperature up to a certain critical temperature leads to band gap narrowing because of the proper substitution of Zn by Cd and thereafter the band gap increases due to Cd re-evaporation from the lattice sites. This critical temperature lowers down with the increase in Cd doping concentration. The resistivity decreases with the increase in Cd content and increases with the increase in annealing temperature.

  8. Quantum corrections to temperature dependent electrical conductivity of ZnO thin films degenerately doped with Si

    SciTech Connect

    Das, Amit K. Ajimsha, R. S.; Kukreja, L. M.

    2014-01-27

    ZnO thin films degenerately doped with Si (Si{sub x}Zn{sub 1−x}O) in the concentrations range of ∼0.5% to 5.8% were grown by sequential pulsed laser deposition on sapphire substrates at 400 °C. The temperature dependent resistivity measurements in the range from 300 to 4.2 K revealed negative temperature coefficient of resistivity (TCR) for the 0.5%, 3.8%, and 5.8% doped Si{sub x}Zn{sub 1−x}O films in the entire temperature range. On the contrary, the Si{sub x}Zn{sub 1−x}O films with Si concentrations of 1.0%, 1.7%, and 2.0% showed a transition from negative to positive TCR with increasing temperature. These observations were explained using weak localization based quantum corrections to conductivity.

  9. Electrodeposition of Mg doped ZnO thin film for the window layer of CIGS solar cell

    NASA Astrophysics Data System (ADS)

    Wang, Mang; Yi, Jie; Yang, Sui; Cao, Zhou; Huang, Xiaopan; Li, Yuanhong; Li, Hongxing; Zhong, Jianxin

    2016-09-01

    Mg doped ZnO (ZMO) film with the tunable bandgap can adjust the conduction band offset of the window/chalcopyrite absorber heterointerface to positive to reduce the interface recombination and resulting in an increasement of chalcopyrite based solar cell efficiency. A systematic study of the effect of the electrodeposition potential on morphology, crystalline structure, crystallographic orientation and optical properties of ZMO films was investigated. It is interestingly found that the prepared doped samples undergo a significant morphological change induced by the deposition potential. With negative shift of deposition potential, an obvious morphology evolution from nanorod structrue to particle covered films was observed. A possible growth mechanism for explaining the morphological change is proposed and briefly discussed. The combined optical techniques including absorption, transmission and photoluminescence were used to study the obtained ZMO films deposited at different potential. The sample deposited at -0.9 V with the hexagonal nanorods morphology shows the highest optical transparency of 92%. The photoluminescence spectra reveal that the crystallization of the hexagonal nanorod ZMO thin film deoposited at -0.9 V is much better than the particles covered ZMO thin film. Combining the structural and optical properties analysis, the obtained normal hexagonal nanorod ZMO thin film could potentially be useful in nanostructured chalcopyrite solar cells to improve the device performance.

  10. Influence of Li-dopants on the luminescent and ferroelectric properties of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Zhang, Y. J.; Wang, J. B.; Zhong, X. L.; Zhou, Y. C.; Yuan, X. L.; Sekiguchi, T.

    2008-12-01

    Zn 1- xLi xO thin films ( 0.005≤x≤0.12) were prepared on Pt/Ti/SiO 2/Si substrates via a sol-gel spin coating method. Cathodoluminescence (CL) studies showed that the luminescent efficiency of specimens is degraded sharply with the increment of Li concentration, which indicates that non-radiative centers are introduced during the doping process. From low temperature CL studies, two luminescent peaks centered at 3.28 and 3.31 eV increase gradually with the increment of Li concentration, which are assigned to acceptor bound exciton transitions related to Li Zn and Li Zn-Li i complex, respectively. Ferroelectricity in Zn 1- xLi xO ( 0.08≤x≤0.12) thin films was found from the polarization hysteresis loop. The remnant polarization increases from 0.12 to 0.23 μC/cm 2 as the x increases from 0.08 to 0.12. Li Zn and Li Zn-Li i complex play important roles in the ferroelectric appearance of Li-doped ZnO thin films.

  11. 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.

  12. Dual role of boron in improving electrical performance and device stability of low temperature solution processed ZnO thin film transistors

    SciTech Connect

    Gandla, Srinivas; Gollu, Sankara Rao; Sharma, Ramakant; Sarangi, Venkateshwarlu; Gupta, Dipti

    2015-10-12

    In this paper, we have demonstrated the dual role of boron doping in enhancing the device performance parameters as well as the device stability in low temperatures (200 °C) sol-gel processed ZnO thin film transistors (TFTs). Our studies suggest that boron is able to act as a carrier generator and oxygen vacancy suppressor simultaneously. Boron-doped ZnO TFTs with 8 mol. % of boron concentration demonstrated field-effect mobility value of 1.2 cm{sup 2} V{sup −1} s{sup −1} and threshold voltage of 6.2 V, respectively. Further, these devices showed lower shift in threshold voltage during the hysteresis and bias stress measurements as compared to undoped ZnO TFTs.

  13. Evolution of dielectric function of Al-doped ZnO thin films with thermal annealing: effect of band gap expansion and free-electron absorption.

    PubMed

    Li, X D; Chen, T P; Liu, Y; Leong, K C

    2014-09-22

    Evolution of dielectric function of Al-doped ZnO (AZO) thin films with annealing temperature is observed. It is shown that the evolution is due to the changes in both the band gap and the free-electron absorption as a result of the change of free-electron concentration of the AZO thin films. The change of the electron concentration could be attributed to the activation of Al dopant and the creation/annihilation of the donor-like defects like oxygen vacancy in the thin films caused by annealing. PMID:25321779

  14. Transparent and conducting intrinsic ZnO thin films prepared at high growth-rate with c-axis orientation and pyramidal surface texture

    NASA Astrophysics Data System (ADS)

    Mondal, Praloy; Das, Debajyoti

    2013-12-01

    The growth of ZnO thin films has been optimized by adjusting the intrinsic ion vacancies, by controlling the RF power applied to the plasma in magnetron sputtering. Preferred c-axis oriented intrinsic ZnO films with largest grain size and a hexagonal wurtzite structure, exhibiting high room temperature conductivity, σ ∼ 1.37 S/cm, high transparency, ∼80-90% within 450-800 nm and ∼90-96% within 800-1900 nm, low reflectance (<5% in the visible range) was obtained at a very high deposition rate ∼214 nm/min, at 300 °C, by maintaining higher concentration of Zn interstitials or singly ionized oxygen vacancy, corresponding to an optimized RF power of 200 W. Films have lowest internal stress, smallest dissipation factor defined as ɛ2/ɛ1, and the specific pyramidal surface texture creates enough surface roughness that helps to improve the light scattering from the surface and makes it suitable for efficient use in thin-film silicon solar cells. With increasing RF power beyond 200 W, the Zn-O bond length reduces promptly and the internal stress increases monotonically approaching toward a virtual saturation. The preferred crystallographic alignment shifts from (0 0 2) to (1 0 3), i.e., from c to a-axis orientation, as the surface energy of ZnO crystal changes due to the increase in the Zn-to-ZnO ion ratio in the plasma caused by the plausible de-oxygenation of ZnO at elevated RF powers. Oxygen deficient ZnO films having the flower-like surface texture prepared with a very high deposition rate ∼554 nm/min at 500 W could indeed make the material suitable for gas and chemical sensing applications.

  15. Effects of sol concentration on structural, morphological and optical waveguiding properties of sol-gel ZnO nanostructured thin films

    NASA Astrophysics Data System (ADS)

    Tazerout, Mohand; Chelouche, Azeddine; Touam, Tahar; Djouadi, Djamel; Boudjouan, Fares; Khodja, Sebti; Ouhenia, Salim; Fischer, Alexis; Boudrioua, Azzedine

    2014-07-01

    Nanostructured ZnO thin films with different precursor concentrations (0.5-0.8 M) have been deposited on glass substrates by sol-gel dip coating technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-visible spectrophotometer, and m-lines spectroscopy have been employed to investigate the effect of solution concentration on structural, morphological, optical and waveguiding properties of the ZnO thin films. XRD spectra have shown that all the films are polycrystalline and exhibit the wurtzite hexagonal structure. SEM micrographs and AFM images have revealed that morphology and surface roughness of the thin films depend on sol concentration. The UV-visible transmittance results show a high transparency in the visible range and a shift of the maximum transmittance to the higher wavelength with increasing sol concentration. Waveguiding properties such as refractive index, number of propagating modes and attenuation coefficient measured at 632.8 nm wavelength by m-lines spectroscopy indicate that our ZnO slab waveguides are single mode and demonstrate optical losses estimated around 1.5 decibel per cm (dB/cm) for the thin film prepared with a sol concentration of 0.7 M.

  16. Structural, optical, and electrical properties of ZnO thin films deposited by sol-gel dip-coating process at low temperature

    NASA Astrophysics Data System (ADS)

    Kim, Soaram; Nam, Giwoong; Yoon, Hyunsik; Park, Hyunggil; Choi, Hyonkwang; Kim, Jong Su; Kim, Jin Soo; Kim, Do Yeob; Kim, Sung-O.; Leem, Jae-Young

    2014-07-01

    Sol-gel dip-coating was used to prepare ZnO thin films with relaxed residual stress by lowering the deposition temperature from room temperature (25°C) to -25°C. The effect of deposition temperature on the structural, optical, and electrical properties of the films was characterized using scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL), ultraviolet-visible (UV-Vis) spectroscopy and reflectance accessory, and the van der Pauw method. All the thin films were deposited successfully onto quartz substrates and exhibited fibrous root morphology. At low temperature, the deposition rate was higher than at room temperature (RT) because of enhanced viscosity of the films. Further, lowering the deposition temperature affected the structural, optical, and electrical properties of the ZnO thin films. The surface morphology, residual stress, PL properties, and optical transmittance and reflectance of the films were measured, and this information was used to determine the absorption coefficient, optical band gap, Urbach energy, refractive index, refractive index at infinite wavelength, extinction coefficient, single-oscillator energy, dispersion energy, average oscillator wavelength, moments M -1 and M -3, dielectric constant, optical conductivity, and electrical resistivity of the ZnO thin films.

  17. Impact of low temperature annealing on structural, optical, electrical and morphological properties of ZnO thin films grown by RF sputtering for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Purohit, Anuradha; Chander, S.; Sharma, Anshu; Nehra, S. P.; Dhaka, M. S.

    2015-11-01

    This paper presents effect of low temperature annealing on the physical properties of ZnO thin films for photovoltaic applications. The thin films of thickness 50 nm were grown on glass and indium tin oxide (ITO) coated glass substrates employing radio frequency magnetron sputtering technique followed by thermal annealing within low temperature range 150-450 °C. These as-grown and annealed films were subjected to the X-ray diffraction (XRD), UV-Vis spectrophotometer, source meter and scanning electron microscopy (SEM) for structural, optical, electrical and surface morphological analysis respectively. The compositional analysis of the as-grown ZnO film was also carried out using energy dispersive spectroscopy (EDS). The XRD patterns reveal that the films have wurtzite structure of hexagonal phase with preferred orientation (1 0 0) and polycrystalline in nature. The crystallographic and optical parameters are calculated and discussed in detail. The optical band gap was found in the range 3.30-3.52 eV and observed to decrease with annealing temperature except 150 °C. The current-voltage characteristics show that the films exhibit approximately ohmic behavior. The SEM studies show that the films are uniform, homogeneous and free from crystal defects and voids. The experimental results reveal that ZnO thin films may be used as alternative materials for eco-friendly buffer layer to the thin film solar cell applications.

  18. Synthesis and Characterization of High c-axis ZnO Thin Film by Plasma Enhanced Chemical Vapor Deposition System and its UV Photodetector Application.

    PubMed

    Chao, Chung-Hua; Wei, Da-Hua

    2015-01-01

    In this study, zinc oxide (ZnO) thin films with high c-axis (0002) preferential orientation have been successfully and effectively synthesized onto silicon (Si) substrates via different synthesized temperatures by using plasma enhanced chemical vapor deposition (PECVD) system. The effects of different synthesized temperatures on the crystal structure, surface morphologies and optical properties have been investigated. The X-ray diffraction (XRD) patterns indicated that the intensity of (0002) diffraction peak became stronger with increasing synthesized temperature until 400 (o)C. The diffraction intensity of (0002) peak gradually became weaker accompanying with appearance of (10-10) diffraction peak as the synthesized temperature up to excess of 400 (o)C. The RT photoluminescence (PL) spectra exhibited a strong near-band-edge (NBE) emission observed at around 375 nm and a negligible deep-level (DL) emission located at around 575 nm under high c-axis ZnO thin films. Field emission scanning electron microscopy (FE-SEM) images revealed the homogeneous surface and with small grain size distribution. The ZnO thin films have also been synthesized onto glass substrates under the same parameters for measuring the transmittance. For the purpose of ultraviolet (UV) photodetector application, the interdigitated platinum (Pt) thin film (thickness ~100 nm) fabricated via conventional optical lithography process and radio frequency (RF) magnetron sputtering. In order to reach Ohmic contact, the device was annealed in argon circumstances at 450 (o)C by rapid thermal annealing (RTA) system for 10 min. After the systematic measurements, the current-voltage (I-V) curve of photo and dark current and time-dependent photocurrent response results exhibited a good responsivity and reliability, indicating that the high c-axis ZnO thin film is a suitable sensing layer for UV photodetector application. PMID:26484561

  19. Transport and magnetotransport study of Mg doped ZnO thin films

    SciTech Connect

    Agrawal, Arpana; Dar, Tanveer A. Sen, Pratima; Phase, Deodatta M.

    2014-04-14

    We report negative magnetoresistance in pulsed laser deposited single phase ZnO and Mg{sub 0.268}Zn{sub 0.732}O films and attribute it to the presence of oxygen interstitials (O{sub i}) and zinc interstitials (Zn{sub i}) as observed in the X-ray photoelectron spectra of the films. An interesting feature of reduction of negative magnetoresistance at low temperatures and large fields in Mg{sub 0.268}Zn{sub 0.732}O film is observed and is explained by taking into account the localized scattering.

  20. Broadband light trapping based on periodically textured ZnO thin films

    NASA Astrophysics Data System (ADS)

    Liu, Bofei; Liang, Xuejiao; Liang, Junhui; Bai, Lisha; Gao, Haibo; Chen, Ze; Zhao, Ying; Zhang, Xiaodan

    2015-05-01

    Transparent conductive front electrodes (TCFEs) deployed in photovoltaic devices have been extensively studied for their significance in transporting carriers, coupling and trapping the incident photons in high-performing solar cells. The trade-off between the light-transmission, electrical, and scattering properties for TCFEs to achieve a broadband improvement in light absorption in solar cells while maintaining a high electrical performance has become the key issue to be tackled. In this paper, we employ self-assembled polystyrene (PS) spheres based on a sauna-like method as a template, followed by a double-layer deposition and then successfully fabricate highly-transparent, well-conductive, and large-scale periodically-textured ZnO TCFEs with broadband light trapping properties. A sheet resistance below 15 Ω sq-1 was achieved for the periodically-textured ZnO TCFEs, with a concomitant average transmission of 81% (including the glass substrate) in the 400-1100 nm spectral range, a haze improvement in a broadband spectral range, and a wider scattering angular domain. The proposed approach affords a promising alternative method to prepare periodically-textured TCFEs, which are essential for many optoelectronic device semiconductors, such as photovoltaic and display applications.Transparent conductive front electrodes (TCFEs) deployed in photovoltaic devices have been extensively studied for their significance in transporting carriers, coupling and trapping the incident photons in high-performing solar cells. The trade-off between the light-transmission, electrical, and scattering properties for TCFEs to achieve a broadband improvement in light absorption in solar cells while maintaining a high electrical performance has become the key issue to be tackled. In this paper, we employ self-assembled polystyrene (PS) spheres based on a sauna-like method as a template, followed by a double-layer deposition and then successfully fabricate highly-transparent, well

  1. Temperature Dependent Thermal Conductivity and Elastic Properties of a-InGaZnO4 and a-In2Ga2ZnO7 Thin Films

    NASA Astrophysics Data System (ADS)

    Thompson, W. D.; White, B. E.

    2016-06-01

    Amorphous In-Ga-Zn-O is an important oxide semiconductor in advanced display technologies. Despite its importance, little has been reported on the thermal and elastic properties of this material. Here, the temperature dependence of the thermal conductivity, shear modulus, and internal friction of a-InGaZnO4 and a-In2Ga2ZnO7 films are presented. The thermal conductivity of a-In2Ga2ZnO7, measured from 100 K to room temperature, was found to be larger than that of a-InGaZnO4 over the entire temperature range. At room temperature the thermal conductivities were 1.9 W/m K and 1.4 W/m K for the a-In2Ga2ZnO7 and a-InGaZnO4 films, respectively. The shear modulus and internal friction of these films were measured in the temperature range of 340 mK to 65 K. At 4.2 K the shear modulus of the a-InGaZnO4 and a-In2 Ga2ZnO7 films was 44 GPa and 42 GPa, respectively. The internal friction of thin films at each composition exhibited a temperature dependence and magnitude that is in agreement with that observed in all amorphous solids. As the self-heating effect is of concern in the development of amorphous In-Ga-Zn-O based thin film transistors on low thermal conductivity substrates, a thermal model of such a device utilizing a-In2Ga2ZnO7 or a-InGaZnO4 as the active layer was explored. It was found that the temperature increase of the thin film transistor channel is essentially independent of the thermal conductivity of the active layer.

  2. Effect of different dopant elements (Al, Mg and Ni) on microstructural, optical and electrochemical properties of ZnO thin films deposited by spray pyrolysis (SP)

    NASA Astrophysics Data System (ADS)

    Benzarouk, Hayet; Drici, Abdelaziz; Mekhnache, Mounira; Amara, Abdelaziz; Guerioune, Mouhamed; Bernède, Jean Christian; Bendjffal, Hacen

    2012-09-01

    In the present work we studied the influence of the dopant elements and concentration on the microstructural and electrochemical properties of ZnO thin films deposited by spray pyrolysis. Transparent conductive thin films of zinc oxide (ZnO) were prepared by the spray pyrolysis process using an aqueous solution of zinc acetate dehydrate [Zn(CH3COO)2·2H2O] on soda glass substrate heated at 400 ± 5 °C. AlCl3, MgCl2 and NiCl2 were used as dopant. The effect of doping percentage (2-4%) has been investigated. Afterwards the samples were thermally annealed in an ambient air during one hour at 500 °C. X-ray diffraction showed that films have a wurtzite structure with a preferential orientation along the (0 0 2) direction for doped ZnO. The lattice parameters a and c are estimated to be 3.24 and 5.20 Ǻ, respectively. Transmission allowed to estimate the band gaps of ZnO layers. The electrochemical studies revealed that the corrosion resistance of the films depended on the concentration of dopants.

  3. Structural, Electrical, and Optical Properties of ZnO Film Used as Buffer Layer for CIGS Thin-Film Solar Cell.

    PubMed

    Choi, Eun Chang; Cha, Ji-Hyun; Jung, Duk-Young; Hong, Byungyou

    2016-05-01

    The CuIn(x)Ga(1-x)Se2 (CIGS) using the solution-based fabrication method is attractive for thin film solar cells because of its possibilities for large-area and low-cost production. ZnO films between transparent conductive oxide (TCO) and the CdS films can improve the performances of CIGS thin-film solar cells. In this study, we investigated the characteristics of ZnO film between TCO and CIGS layers in a solar cell (AZO/ZnO/CdS/CIGS/Mo), which were deposited at various thicknesses to investigate the role of the films in CIGS solar cells. It was confirmed that the conversion efficiency of a CIGS solar cell depends on the ZnO film. For a ZnO film thickness of 80 nm, the highest power conversion efficiency that a solar cell achieved was J(sc) of 18.73 mA/cm2. PMID:27483877

  4. A Low Temperature, Solution-Processed Poly(4-vinylphenol), YO(x) Nanoparticle Composite/Polysilazane Bi-Layer Gate Insulator for ZnO Thin Film Transistor.

    PubMed

    Shin, Hyeonwoo; Kang, Chan-Mo; Chae, Hyunsik; Kim, Hyun-Gwan; Baek, Kyu-Ha; Choi, Hyoung Jin; Park, Man-Young; Do, Lee-Mi; Lee, Changhee

    2016-03-01

    Low temperature, solution-processed metal oxide thin film transistors (MEOTFTs) have been widely investigated for application in low-cost, transparent, and flexible electronics. To enlarge the application area, solution-processed gate insulators (GI) have been investigated in recent years. We investigated the effects of the organic/inorganic bi-layer GI to ZnO thin film transistors (TFTs). PVP, YO(x) nanoparticle composite, and polysilazane bi-layer showed low leakage current (-10(-8) A/cm2 in 2 MV), which are applicable in low temperature processed MEOTFTs. Polysilazane was used as an interlayer between ZnO and PVP, YO(x) nanoparticle composite as a good charge transport interface with ZnO. By applying the PVP, YO(x), nanoparticle composite/polysilazane bi-layer structure to ZnO TFTs, we successfully suppressed the off current (I(off)) to -10(-11) and fabricated good MEOTFTs in 180 degrees C. PMID:27455680

  5. Preparation of DC reactive magnetron sputtered ZnO thin film towards photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Prabhu, M.; Sivanantham, A.; Kannan, P. Karthick; Vishnukanthan, V.; Mayandi, J.

    2013-06-01

    Zinc oxide thin films deposited on glass and p-type silicon (100) substrates by DC reactive magnetron sputtering are reported here. The XRD investigations confirmed that the thin films deposited by this technique have hexagonal wurtzite structure. AFM results present the surface morphology and roughness of the deposited thin films. From the optical absorption spectrum, the band gap of the thin film is found to be ˜ 3.2 eV. The photoluminescence spectrum of the sample has an UV emission peak centered at 407 nm with broad visible emission in the range of 500-580 nm.

  6. Optical, Electrical, and UV Photoresponse Properties of Fluorine-Doped ZnO Thin Films Grown on Flexible Mica Substrates

    NASA Astrophysics Data System (ADS)

    Kim, Younggyu; Leem, Jae-Young

    2015-12-01

    Fluorine-doped ZnO (FZO) thin films have several potential applications, for instance, in low-cost optoelectronic devices; understanding how their optical, electrical, and photoresponse properties depend on and can be controlled via the synthesis conditions is essential for application of these systems. In this study, FZO thin films with different annealing temperatures were grown on muscovite mica substrates via sol-gel spin-coating. In photoluminescence measurements, a strong peak in the ultraviolet (UV) region and a broad peak in the visible region were observed for all films, being strongly dependent on the annealing temperature. The transmittance of the annealed films was slightly higher than that of as-grown film, and the absorption edges in the transmittance spectra red-shifted with increasing annealing temperature. The optical bandgap and Urbach energy of the films were calculated from the absorption coefficient values, using the Tauc and Urbach relations, respectively. Finally, the electrical (i.e., resistivity and carrier concentration) and photoresponse properties of the films were investigated to assess their applicability for use in FZO-based UV detectors.

  7. Infrared detection of hydrogen-generated free carriers in polycrystalline ZnO thin films

    SciTech Connect

    Wolden, Colin A.; Barnes, Teresa M.; Baxter, Jason B.; Aydil, Eray S.

    2005-02-15

    The changes in the free-carrier concentration in polycrystalline ZnO films during exposure to H{sub 2} and O{sub 2} plasmas were studied using in situ attenuated total reflection Fourier transform infrared spectroscopy. The carrier concentration and mobility were extracted from the free-carrier absorption in the infrared using a model for the dielectric function. The electron density in polycrystalline zinc oxide films may be significantly increased by >10{sup 19} cm{sup -3} by brief exposures to hydrogen plasma at room temperature and decreased by exposure to O{sub 2} plasmas. Room-temperature oxygen plasma removes a fraction of the H at donor sites but both elevated temperatures ({approx}225 deg. C) and O{sub 2} plasma were required to remove the rest. We demonstrate that combinations of O{sub 2} and H{sub 2} plasma treatments can be used to manipulate the carrier density in ZnO films. However, we also show the existence of significant drifts ({approx}15%) in the carrier concentrations over very long time scales (hours). Possible sites for H incorporation in polycrystalline films and reasons for the observed carrier-concentration changes are proposed.

  8. Broadband light trapping based on periodically textured ZnO thin films.

    PubMed

    Liu, Bofei; Liang, Xuejiao; Liang, Junhui; Bai, Lisha; Gao, Haibo; Chen, Ze; Zhao, Ying; Zhang, Xiaodan

    2015-06-01

    Transparent conductive front electrodes (TCFEs) deployed in photovoltaic devices have been extensively studied for their significance in transporting carriers, coupling and trapping the incident photons in high-performing solar cells. The trade-off between the light-transmission, electrical, and scattering properties for TCFEs to achieve a broadband improvement in light absorption in solar cells while maintaining a high electrical performance has become the key issue to be tackled. In this paper, we employ self-assembled polystyrene (PS) spheres based on a sauna-like method as a template, followed by a double-layer deposition and then successfully fabricate highly-transparent, well-conductive, and large-scale periodically-textured ZnO TCFEs with broadband light trapping properties. A sheet resistance below 15 Ω sq(-1) was achieved for the periodically-textured ZnO TCFEs, with a concomitant average transmission of 81% (including the glass substrate) in the 400-1100 nm spectral range, a haze improvement in a broadband spectral range, and a wider scattering angular domain. The proposed approach affords a promising alternative method to prepare periodically-textured TCFEs, which are essential for many optoelectronic device semiconductors, such as photovoltaic and display applications. PMID:25963950

  9. Assessment of structural, optical and conduction properties of ZnO thin films in the presence of acceptor impurities

    NASA Astrophysics Data System (ADS)

    Plugaru, R.; Plugaru, N.

    2016-06-01

    The structural, optical and electrical conduction properties of (Li/Cu,N):ZnO codoped thin films synthesized by the sol–gel method were investigated by field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), transmission and absorption, photoluminescence (PL) and I–V measurements in order to bring evidence of the formation of acceptor centers by dual-acceptor codoping processes. The (Li 3%,N 5%):ZnO films consist of crystallites with average size of 15 nm, show 95% transmission in the visible region, and an optical band gap of 3.22 eV. The PL spectra show emission maxima at 3.21 and 2.96 eV which are related to the emission of acceptor centers and the presence of defects, respectively. Li occupies interstitial sites and may form Lii–N(O) defect complexes that act as acceptor centers. The (Cu 3%,N 5%):ZnO films consist of crystallites with average size of 12 nm, and exhibit 90% transmission in the visible region. The PL spectra reveal band edge emission at 3.23 eV and defect related emission at 2.74 eV. In the (Cu,N) codoped films, copper substitutes zinc and adopts mainly the Cu1+ state. A possible defect complex involving Cu and N determines the transition from n- to p-type conductivity. These findings are in agreement with results of electronic structure calculations at the GGA-PBE level.

  10. Assessment of structural, optical and conduction properties of ZnO thin films in the presence of acceptor impurities.

    PubMed

    Plugaru, R; Plugaru, N

    2016-06-01

    The structural, optical and electrical conduction properties of (Li/Cu,N):ZnO codoped thin films synthesized by the sol-gel method were investigated by field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), transmission and absorption, photoluminescence (PL) and I-V measurements in order to bring evidence of the formation of acceptor centers by dual-acceptor codoping processes. The (Li 3%,N 5%):ZnO films consist of crystallites with average size of 15 nm, show 95% transmission in the visible region, and an optical band gap of 3.22 eV. The PL spectra show emission maxima at 3.21 and 2.96 eV which are related to the emission of acceptor centers and the presence of defects, respectively. Li occupies interstitial sites and may form Lii-N(O) defect complexes that act as acceptor centers. The (Cu 3%,N 5%):ZnO films consist of crystallites with average size of 12 nm, and exhibit 90% transmission in the visible region. The PL spectra reveal band edge emission at 3.23 eV and defect related emission at 2.74 eV. In the (Cu,N) codoped films, copper substitutes zinc and adopts mainly the Cu(1+) state. A possible defect complex involving Cu and N determines the transition from n- to p-type conductivity. These findings are in agreement with results of electronic structure calculations at the GGA-PBE level. PMID:26979467

  11. Controlling the surface nanostructure of ZnO and Al-doped ZnO thin films using electrostatic spraying for their application in 12% efficient perovskite solar cells.

    PubMed

    Mahmood, Khalid; Swain, Bhabani Sankar; Jung, Hyun Suk

    2014-08-01

    In this paper, ZnO and Al-doped ZnO films were deposited using the electrospraying method and studied for the first time as photoanodes for efficient perovskite solar cells. Effects of substrate temperature, deposition time, applied voltage, substrate-to-nozzle distance and flow rate (droplet size) on the morphology of ZnO were studied with the help of FE-SEM images. The major factors such as the droplet size of the spray, substrate temperature and substrate-to-nozzle distance at deposition control the film morphology. Indeed, these factors determine the density of the film, its smoothness and the flow of solution over the substrate. The droplet size was controlled by the flow rate of the spray. The substrate-to-nozzle distance and flow rate will both regulate the solution amount deposited on the surface of the substrate. The most favorable conditions for a good quality ZnO thin film were a long substrate-to-nozzle distance and lower solution flow rates. In situ droplet size measurement shows that the size and dispersion of particles were narrowed. The method was shown to have a high deposition rate and efficiency relative to well-established thin film deposition techniques such as chemical and physical vapor deposition. In addition, it also allows easy control of the microstructure and stoichiometry of the deposits. The pure ZnO film produced under optimum conditions (440 nm thick) demonstrated a high power conversion efficiency (PCE) of 10.8% when used as a photoanode for perovskite solar cells, owing to its high porosity, uniform morphology and efficient electron transport. For thicker films a drastic decrease in PCE was observed due to their low porosity. We also observed that the open-circuit voltage increases from 1010 mV to 1045 mV and also the PCE increases from 10.8% to 12.0% when pure ZnO films were doped with aluminum (Al). Under atmospheric pressure, the electrospraying system produces the reasonably uniform-sized droplets of smaller size, so the films

  12. Investigation of the biaxial stress of Al-doped ZnO thin films on a flexible substrate with RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Huang, Kuo-Ting; Chen, Hsi-Chao; Cheng, Po-Wei; Chang, Jhe-Ming

    2016-01-01

    Transparent conductive Al-doped ZnO (AZO) thin films were deposited onto poly(ethylene terephthalate) (PET) substrate, using the radio frequency (RF) magnetron sputtering method. The residual stress of flexible electronics was investigated by a double beam shadow moiré interferometer with phase shifting interferometry (PSI). Moreover, the biaxial stress of AZO thin films can be graphically represented by using Mohr’s circle of stress. The residual stress of AZO thin films becomes more compressive with the increase in sputtering power. The maximum residual stress is -1115.74 MPa, and the shearing stress is 490.57 MPa at a sputtering power of 200 W. The trends of residual stress were evidenced by the X-ray diffraction (XRD) patterns and optical properties of AZO thin films. According to the evaluation results of the refractive index and the extinction coefficient, the AZO thin films have better quality when the sputtering power less than 100 W.

  13. Studies on the Controlling of the Microstructural and Morphological Properties of Al Doped ZnO Thin Films Prepared by Hydrothermal Method

    NASA Astrophysics Data System (ADS)

    Gil Gang, Myeng; Shin, Seung Wook; Gurav, K. V.; Wang, YinBo; Agawane, G. L.; Lee, Jeong Yong; Moon, Jong-Ha; Hyeok Kim, Jin

    2013-10-01

    Al doped ZnO (AZO) thin films were prepared on ZnO coated glass substrates by hydrothermal synthesis technique using aqueous solutions containing zinc nitrate hexahydrate, ammonium hydroxide, and different sodium citrate concentrations at 60 °C for 6 h. The effects of different trisodium citrate concentrations on the microstructural, crystallinity, morphological, optical, and chemical properties of thin films were investigated. X-ray diffraction studies showed that the AZO thin films were grown as a polycrystalline wurtzite hexagonal phase with a c-axis preferred orientation and without an unwanted second phase regardless of trisodium citrate concentrations. The thickness and grain sizes of AZO thin films decreased with increasing trisodium citrate concentration. The microstructure of AZO thin films was changed from flat to needle shaped and the morphology was smoother with increasing trisodium citrate concentrations. The AZO thin films have a high transmittance in the visible region ranging from 75 to 85% and a sharp edge from 366 to 374 nm.

  14. Bendable ZnO thin film surface acoustic wave devices on polyethylene terephthalate substrate

    SciTech Connect

    He, Xingli; Guo, Hongwei; Chen, Jinkai; Wang, Wenbo; Xuan, Weipeng; Xu, Yang E-mail: jl2@bolton.ac.uk; Luo, Jikui E-mail: jl2@bolton.ac.uk

    2014-05-26

    Bendable surface acoustic wave (SAW) devices were fabricated using high quality c-axis orientation ZnO films deposited on flexible polyethylene terephthalate substrates at 120 °C. Dual resonance modes, namely, the zero order pseudo asymmetric (A{sub 0}) and symmetric (S{sub 0}) Lamb wave modes, have been obtained from the SAW devices. The SAW devices perform well even after repeated flexion up to 2500 με for 100 times, demonstrating its suitability for flexible electronics application. The SAW devices are also highly sensitive to compressive and tensile strains, exhibiting excellent anti-strain deterioration property, thus, they are particularly suitable for sensing large strains.

  15. Spectroscopy and control of near-surface defects in conductive thin film ZnO.

    PubMed

    Kelly, Leah L; Racke, David A; Schulz, Philip; Li, Hong; Winget, Paul; Kim, Hyungchul; Ndione, Paul; Sigdel, Ajaya K; Brédas, Jean-Luc; Berry, Joseph J; Graham, Samuel; Monti, Oliver L A

    2016-03-01

    The electronic structure of inorganic semiconductor interfaces functionalized with extended π-conjugated organic molecules can be strongly influenced by localized gap states or point defects, often present at low concentrations and hard to identify spectroscopically. At the same time, in transparent conductive oxides such as ZnO, the presence of these gap states conveys the desirable high conductivity necessary for function as electron-selective interlayer or electron collection electrode in organic optoelectronic devices. Here, we report on the direct spectroscopic detection of a donor state within the band gap of highly conductive zinc oxide by two-photon photoemission spectroscopy. We show that adsorption of the prototypical organic acceptor C60 quenches this state by ground-state charge transfer, with immediate consequences on the interfacial energy level alignment. Comparison with computational results suggests the identity of the gap state as a near-surface-confined oxygen vacancy. PMID:26871256

  16. Optical, structural and morphological studies of (ZnO) nano-rod thin films for biosensor applications using sol gel technique

    NASA Astrophysics Data System (ADS)

    Wahab, H. A.; Salama, A. A.; El-Saeid, A. A.; Nur, O.; Willander, M.; Battisha, I. K.

    Uniformly distributed ZnO nano-rods (NRs) with diameters in nano-scale have been successfully grown in two stages; the first at annealing temperature (250-300 °C) for seed layer preparation on glass substrate by using sol gel technique and the second at low temperature (90-95 °C) by aqueous chemical growth (ACG) method. The same prepared thin film samples were grown on the surface of silver wire (0.25 mm in diameters) to produce electrochemical nano-sensors. The structure and the morphology of the prepared samples will be evaluated using XRD, Scanning electron microscope SEM. The absorption coefficient (α) and the band gap (Eg) for ZnO NRs thin films were determined. (α) was decreased by increasing the annealing temperature due to the increase of the surface roughness caused by higher temperature, where the creation of surface roughness gives rise to multi-reflections which, capture the reflected radiation and enhance the absorptivity. We are presenting an iron ion (Fe3+) potentiometric sensor based on functionalized ZnO nano-rods with selective iono-phore (18 crown 6). Zinc oxide nanorods (NRs) thin films with a diameter of about 68 up to 94 nm were grown on silver wire and gold coated glass.

  17. 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

  18. Roughness-based monitoring of transparency and conductivity in boron-doped ZnO thin films prepared by spray pyrolysis

    SciTech Connect

    Gaikwad, Rajendra S.; Bhande, Sambhaji S.; Mane, Rajaram S.; Pawar, Bhagwat N.; Gaikwad, Sanjay L.; Han, Sung-Hwan; Joo, Oh-Shim

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► We report surface roughness dependent transparency and conductivity in ZnO films. ► The surface roughness with respected to boron doping concentrations is studied. ► Boron doped and pristine Zinc oxide thin films have showed ≥95% transmittance. ► Increased carrier concentration of 9.21 × 10{sup 21} cm{sup −3} revealed from Hall measurement. -- Abstract: Sprayed polycrystalline ZnO and boron-doped ZnO thin films composed of spherical grains of 25–32 nm in diameters are used in roughness measurement and further correlated with the transparency and the conductivity characteristics. The surface roughness is increased up to Zn{sub 0.98}B{sub 0.02}O and then declined at higher boron concentrations. The sprayed ZnO films revealed ≥95% transmittance in the visible wavelength range, 1.956 × 10{sup −4} Ω cm electrical resistivity, 46 cm{sup 2}/V s Hall mobility and 9.21 × 10{sup 21} cm{sup −3} charge carrier concentration. The X-ray photoelectron spectroscopy study has confirmed 0.15 eV binding energy change for Zn 2p{sub 3/2} when 2 at% boron content is mixed without altering electro-optical properties substantially. Finally, using soft modeling importance of these textured ZnO over non-textured films for enhancing the solar cells performance is explored.

  19. Spectroscopic Ellipsometry Studies of Ag and ZnO Thin Films and Their Interfaces for Thin Film Photovoltaics

    NASA Astrophysics Data System (ADS)

    Sainju, Deepak

    Many modern optical and electronic devices, including photovoltaic devices, consist of multilayered thin film structures. Spectroscopic ellipsometry (SE) is a critically important characterization technique for such multilayers. SE can be applied to measure key parameters related to the structural, optical, and electrical properties of the components of multilayers with high accuracy and precision. One of the key advantages of this non-destructive technique is its capability of monitoring the growth dynamics of thin films in-situ and in real time with monolayer level precision. In this dissertation, the techniques of SE have been applied to study the component layer materials and structures used as back-reflectors and as the transparent contact layers in thin film photovoltaic technologies, including hydrogenated silicon (Si:H), copper indium-gallium diselenide (CIGS), and cadmium telluride (CdTe). The component layer materials, including silver and both intrinsic and doped zinc oxide, are fabricated on crystalline silicon and glass substrates using magnetron sputtering techniques. These thin films are measured in-situ and in real time as well as ex-situ by spectroscopic ellipsometry in order to extract parameters related to the structural properties, such as bulk layer thickness and surface roughness layer thickness and their time evolution, the latter information specific to real time measurements. The index of refraction and extinction coefficient or complex dielectric function of a single unknown layer can also be obtained from the measurement versus photon energy. Applying analytical expressions for these optical properties versus photon energy, parameters that describe electronic transport, such as electrical resistivity and electron scattering time, can be extracted. The SE technique is also performed as the sample is heated in order to derive the effects of annealing on the optical properties and derived electrical transport parameters, as well as the

  20. Controlling the surface nanostructure of ZnO and Al-doped ZnO thin films using electrostatic spraying for their application in 12% efficient perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Mahmood, Khalid; Swain, Bhabani Sankar; Jung, Hyun Suk

    2014-07-01

    In this paper, ZnO and Al-doped ZnO films were deposited using the electrospraying method and studied for the first time as photoanodes for efficient perovskite solar cells. Effects of substrate temperature, deposition time, applied voltage, substrate-to-nozzle distance and flow rate (droplet size) on the morphology of ZnO were studied with the help of FE-SEM images. The major factors such as the droplet size of the spray, substrate temperature and substrate-to-nozzle distance at deposition control the film morphology. Indeed, these factors determine the density of the film, its smoothness and the flow of solution over the substrate. The droplet size was controlled by the flow rate of the spray. The substrate-to-nozzle distance and flow rate will both regulate the solution amount deposited on the surface of the substrate. The most favorable conditions for a good quality ZnO thin film were a long substrate-to-nozzle distance and lower solution flow rates. In situ droplet size measurement shows that the size and dispersion of particles were narrowed. The method was shown to have a high deposition rate and efficiency relative to well-established thin film deposition techniques such as chemical and physical vapor deposition. In addition, it also allows easy control of the microstructure and stoichiometry of the deposits. The pure ZnO film produced under optimum conditions (440 nm thick) demonstrated a high power conversion efficiency (PCE) of 10.8% when used as a photoanode for perovskite solar cells, owing to its high porosity, uniform morphology and efficient electron transport. For thicker films a drastic decrease in PCE was observed due to their low porosity. We also observed that the open-circuit voltage increases from 1010 mV to 1045 mV and also the PCE increases from 10.8% to 12.0% when pure ZnO films were doped with aluminum (Al). Under atmospheric pressure, the electrospraying system produces the reasonably uniform-sized droplets of smaller size, so the films

  1. Bipolar Switching Behavior of ZnO x Thin Films Deposited by Metalorganic Chemical Vapor Deposition at Various Growth Temperatures

    NASA Astrophysics Data System (ADS)

    Bae, Seonho; Kim, Dae-Sik; Jung, Seojoo; Jeong, Woo Seop; Lee, Jee Eun; Cho, Seunghee; Park, Junsung; Byun, Dongjin

    2015-11-01

    The bipolar resistive switching behaviors of ZnO films grown at various temperatures by metalorganic chemical vapor deposition have been investigated. The ZnO films were grown on Pt/Ti/SiO2/Si(100) substrate, and the ZnO growth temperature was varied from 300°C to 500°C in steps of 100°C. Rutherford backscattering spectroscopy analysis results showed that the chemical compositions of the ZnO films were oxygen-poor Zn1O0.9 at 300°C, stoichiometric Zn1O1 at 400°C, and oxygen-rich Zn1O1.3 at 500°C. Resistive switching properties were observed in the ZnO films grown at 300°C and 400°C. In contrast, high current, without switching properties, was found in the ZnO film grown at 500°C. The ZnO film grown at 500°C had higher concentration of both nonlattice oxygen (4.95%) and oxygen vacancy (3.23%) than those grown at 300°C or 400°C. The resistive switching behaviors of ZnO films are related to the ZnO growth temperature via the relative amount of oxygen vacancies in the film. Pt/ZnO/Pt devices showed asymmetric resistive switching with narrow dispersion of switching voltage.

  2. Semipolar r-plane ZnO films on Si(100) substrates: Thin film epitaxy and optical properties

    PubMed Central

    Aggarwal, Ravi; Zhou, Honghui; Jin, Chunming; Narayan, J.; Narayan, Roger J.

    2010-01-01

    We report heteroepitaxial growth of (101¯2) oriented (r-plane) ZnO films on Si(100) substrates. The films were grown by pulsed laser deposition and integration of ZnO with silicon was achieved using a tetragonal yttria stabilized zirconia (YSZ) buffer layer. It was observed that ZnO films grown at temperatures in the range of 700–750 °C with relatively high oxygen pressure (∼70 mTorr) were (101¯2) oriented. ZnO films deposited with lower oxygen pressures were found to be purely (0002) orientated. Experiments carried out to elucidate the role of oxygen pressure indicated that the crystallographic orientation of ZnO depends on the nature of atomic termination of YSZ layer. It has been proposed that crystallographic orientation of ZnO is controlled by chemical free energy associated with ZnO-YSZ interface. Detailed x-ray diffraction and transmission electron microscopy studies showed existence of four types of in-plane domains in r-plane ZnO films. Optical characterization demonstrated that photoluminescence of r-plane ZnO films was superior to that of c-plane ZnO films grown under similar conditions. PMID:20634966

  3. On the sol pH and the structural, optical and electrical properties of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Meziane, K.; El Hichou, A.; El Hamidi, A.; Mansori, M.; Liba, A.; Almaggoussi, A.

    2016-05-01

    Zinc oxide thin films were prepared by the sol-gel method and deposed on glass substrate using spin coating technique. The variation of the structural, optical and electrical properties with various pH values is investigated. pH values of the sol were adjusted with glacial acetic acid and ammonia. X-ray diffraction analysis showed that the films with alkaline sol are crystallized while those with acidic sol are amorphous. High values of texture coefficient and a high diffraction intensity of the (002) peak, ensuring better growth along c-axis, were obtained for an optimal pH value of 9.5. The crystallite size of the obtained films strongly depends on the sol pH. Scanning Electron Microscopy (SEM) images confirm that the morphology and grain size of the films are affected significantly by pH. The optical transmission was recorded to analyze the optical properties of the studied films. It was found that the optical gap increased with pH. The electrical properties were measured by Hall-effect and reveal an increase of the resistivity when the sol pH increases. A minimum residual intrinsic electrons density suitable for p-type ZnO was reached.

  4. Investigation of the Gate Bias Stress Instability in ZnO Thin Film Transistors by Low-Frequency Noise Analysis

    NASA Astrophysics Data System (ADS)

    Jeong, Kwang-Seok; Yun, Ho-Jin; Kim, Yu-Mi; Yang, Seung-Dong; Lee, Sang-Youl; Kim, Young-Su; Lee, Hi-Deok; Lee, Ga-Won

    2013-04-01

    To investigate the electrical instability mechanism under the application of gate bias stress and relaxation, the 1/f noise spectra of two different ZnO thin-film transistors (TFTs) were analyzed. In terms of gate bias dependence (SIDS/IDS), both devices followed a mobility fluctuation model based on the traps in their channel layers prior to and after stress. Device A (channel thickness: 20 nm), recovered its initial noise parameter (αapp) after relaxation, in exact agreement with the current-voltage (I-V) measurement results; this shows that in device A, the dominant phenomenon under the application of stress was temporary charge trapping at grain boundary traps. However, in device B (channel thickness: 80 nm), αapp did not recover its initial values after relaxation, and transfer parameters, such as VTH, mobility, SS, and Nt, degraded after the gate bias stress. Moreover, after the stress, device B showed a reduced gate insulator breakdown voltage. The electrical degradation seen in device B can be explained by trap creation and/or charge injection near channel/gate oxide interfaces, including those within the channel layer.

  5. Electronic transport in highly conducting Si-doped ZnO thin films prepared by pulsed laser deposition

    SciTech Connect

    Kuznetsov, Vladimir L.; Vai, Alex T.; Edwards, Peter P.; Al-Mamouri, Malek; Stuart Abell, J.; Pepper, Michael

    2015-12-07

    Highly conducting (ρ = 3.9 × 10{sup −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){sub 1−x}(SiO{sub 2}){sub 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. Enhancement Of Free Exciton Peak Intensity In Reactively Sputtered ZnO Thin Films On (0001) Al2O3

    SciTech Connect

    Tuezemen, S.; Guer, Emre; Yildirim, T.; Xiong, G.; Williams, R. T.

    2007-04-23

    Wide bandgap materials such as GaN with its direct bandgap structure have been developed rapidly for applications in short wavelength light emission. ZnO, II-VI oxide semiconductor, is also promising for various technological applications, especially for optoelectronic light emitting devices in the visible and ultraviolet (UV) range of the electromagnetic spectrum. Above-band-edge absorption spectra of reactively sputtered Zn- and O-rich samples exhibit free exciton (FX) and neutral acceptor bound exciton (A deg. X) features. It is shown that the residual acceptors which bind excitons with an energy of 75 meV reside about 312 meV above the valence band, according to effective mass theory. An intra-bandgap absorption feature peaking at 2.5 eV shows correlation with the characteristically narrow A-free exciton peak intensity. Relevant annealing processes are presented as a function of time and temperature dependently for both Zn- and O- rich thin films. Enhancement of the free exciton peak intensity is observed without disturbing the residual shallow acceptor profile which is necessary for at least background p-type conductivity.

  7. Quantifying charge carrier concentration in ZnO thin films by Scanning Kelvin Probe Microscopy

    PubMed Central

    Maragliano, C.; Lilliu, S.; Dahlem, M. S.; Chiesa, M.; Souier, T.; Stefancich, M.

    2014-01-01

    In the last years there has been a renewed interest for zinc oxide semiconductor, mainly triggered by its prospects in optoelectronic applications. In particular, zinc oxide thin films are being widely used for photovoltaic applications, in which the determination of the electrical conductivity is of great importance. Being an intrinsically doped material, the quantification of its doping concentration has always been challenging. Here we show how to probe the charge carrier density of zinc oxide thin films by Scanning Kelvin Probe Microscopy, a technique that allows measuring the contact potential difference between the tip and the sample surface with high spatial resolution. A simple electronic energy model is used for correlating the contact potential difference with the doping concentration in the material. Limitations of this technique are discussed in details and some experimental solutions are proposed. Two-dimensional doping concentration images acquired on radio frequency-sputtered intrinsic zinc oxide thin films with different thickness and deposited under different conditions are reported. We show that results inferred with this technique are in accordance with carrier concentration expected for zinc oxide thin films deposited under different conditions and obtained from resistivity and mobility measurements. PMID:24569599

  8. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Structural and Electrical Properties of Single Crystalline Ga-Doped ZnO Thin Films Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Lu, Zhong-Lin; Zou, Wen-Qin; Xu, Ming-Xiang; Zhang, Feng-Ming; Du, You-Wei

    2009-11-01

    High-quality Ga-doped ZnO (ZnO:Ga) single crystalline films with various Ga concentrations are grown on a-plane sapphire substrates using molecular-beam epitaxy. The site configuration of doped Ga atoms is studied by means of x-ray absorption spectroscopy. It is found that nearly all Ga can substitute into ZnO lattice as electrically active donors, a generating high density of free carriers with about one electron per Ga dopant when the Ga concentration is no more than 2%. However, further increasing the Ga doping concentration leads to a decrease of the conductivity due to partial segregation of Ga atoms to the minor phase of the spinel ZnGa2O4 or other intermediate phase. It seems that the maximum solubility of Ga in the ZnO single crystalline film is about 2 at.% and the lowest resistivity can reach 1.92 × 10-4 Ω·cm at room temperature, close to the best value reported. In contrast to ZnO:Ga thin film with 1% or 2% Ga doping, the film with 4% Ga doping exhibits a metal semiconductor transition at 80 K. The scattering mechanism of conducting electrons in single crystalline ZnO:Ga thin film is discussed.

  9. Structural, electrical and optical properties of a Li-doped ZnO thin film fabricated on a Pt(111)/Ti/SiO2/Si(100) substrate

    NASA Astrophysics Data System (ADS)

    Raghavan, C. M.; Kim, J. W.; Jang, K. W.; Kim, S. S.

    2015-04-01

    A Li-doped ZnO (Zn1- x Li x O1- δ , x = 0.12) thin film was fabricated on a Pt(111)/Ti/SiO2/Si(100) substrate by using a chemical solution deposition method. The formation of a wurtzite hexagonal structure was confirmed by an X-ray diffraction and a Raman spectroscopic analysis. Typical hexagonal microcrystalline grains were observed from the surface morphological studies. Room-temperature ferroelectricity with a remnant polarization (2 P r ) of 0.05 μC/cm2 and a coercive field (2 E c ) of 170 kV/cm at an applied electric field of 200 kV/cm was observed in the Li-doped ZnO thin film. The measured leakage current density for the thin film was 1.09 × 10 -4 A/cm2 at an applied electric field of 100 kV/cm. A sharp near-band-edge emission was observed in the photoluminescence spectrum at a wavelength of 375 nm for the thin film.

  10. Highly transparent and reproducible nanocrystalline ZnO and AZO thin films grown by room temperature pulsed-laser deposition on flexible Zeonor plastic substrates

    NASA Astrophysics Data System (ADS)

    Inguva, Saikumar; Vijayaraghavan, Rajani K.; McGlynn, Enda; Mosnier, Jean-Paul

    2015-09-01

    Zeonor plastics are highly versatile due to exceptional optical and mechanical properties which make them the choice material in many novel applications. For potential use in flexible transparent optoelectronic applications, we have investigated Zeonor plastics as flexible substrates for the deposition of highly transparent ZnO and AZO thin films. Films were prepared by pulsed laser deposition at room temperature in oxygen ambient pressures of 75, 150 and 300 mTorr. The growth rate, surface morphology, hydrophobicity and the structural, optical and electrical properties of as-grown films with thicknesses ˜65-420 nm were recorded for the three oxygen pressures. The growth rates were found to be highly linear both as a function of film thickness and oxygen pressure, indicating high reproducibility. All the films were optically smooth, hydrophobic and nanostructured with lateral grain shapes of ˜150 nm wide. This was found compatible with the deposition of condensed nanoclusters, formed in the ablation plume, on a cold and amorphous substrate. Films were nanocrystalline (wurtzite structure), c-axis oriented, with average crystallite size ˜22 nm for ZnO and ˜16 nm for AZO. In-plane compressive stress values of 2-3 GPa for ZnO films and 0.5 GPa for AZO films were found. Films also displayed high transmission greater than 95% in some cases, in the 400-800 nm wavelength range. The low temperature photoluminescence spectra of all the ZnO and AZO films showed intense near band edge emission. A considerable spread from semi-insulating to n-type conductive was observed for the films, with resistivity ˜103 Ω cm and Hall mobility in 4-14 cm2 V-1 s-1 range, showing marked dependences on film thickness and oxygen pressure. Applications in the fields of microfluidic devices and flexible electronics for these ZnO and AZO films are suggested.

  11. Ferromagnetism in 200-MeV Ag{sup +15}-ion-irradiated Co-implanted ZnO thin films

    SciTech Connect

    Angadi, Basavaraj; Jung, Y.S.; Choi, Won-Kook; Kumar, Ravi; Jeong, K.; Shin, S.W.; Lee, J.H.; Song, J.H.; Wasi Khan, M.; Srivastava, J.P.

    2006-04-03

    Structural, electrical resistivity, and magnetization properties of 200-MeV Ag{sup +15}-ion-irradiated Co-implanted ZnO thin films are presented. The structural studies show the presence of Co clusters whose size is found to increase with increase of Co implantation. The implanted films were irradiated with 200-MeV Ag{sup +15} ions to fluence of 1x10{sup 12} ions/cm{sup 2}. The Co clusters on irradiation dissolve in the ZnO matrix. The electrical resistivity of the irradiated samples is lowered to half. The magnetization hysteresis measurements show ferromagnetic behavior at 300 K, and the coercive field increases with the Co implantation. The ferromagnetism at room temperature is confirmed by magnetic force microscopy measurements. The results are explained on the basis of the close interplay between the electrical and the magnetic properties.

  12. 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.

  13. Characterization of deep acceptor level in as-grown ZnO thin film by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Asghar, M.; K., Mahmood; A. Hasan, M.; T. Ferguson, I.; Tsu, R.; Willander, M.

    2014-09-01

    We report deep level transient spectroscopy results from ZnO layers grown on silicon by molecular beam epitaxy (MBE). The hot probe measurements reveal mixed conductivity in the as-grown ZnO layers, and the current—voltage (I—V) measurements demonstrate a good quality p-type Schottky device. A new deep acceptor level is observed in the ZnO layer having activation energy of 0.49 ±0.03 eV and capture cross-section of 8.57 × 10-18 cm2. Based on the results from Raman spectroscopy, photoluminescence, and secondary ion mass spectroscopy (SIMS) of the ZnO layer, the observed acceptor trap level is tentatively attributed to a nitrogen-zinc vacancy complex in ZnO.

  14. The Effect of Mn Incorporation on the Structural, Morphological, Optical, and Electrical Features of Nanocrystalline ZnO Thin Films Prepared by Chemical Spray Pyrolysis Technique

    NASA Astrophysics Data System (ADS)

    Yilmaz, Mehmet; Aydoğan, Şakir

    2015-06-01

    Un-doped and Mn-doped ZnO nanocrystalline thin films and n-ZnO /n-Si heterojunction have been prepared by chemical spray pyrolysis technique. The microstructure, morphology, optical, and electrical properties have been studied. The X-ray analyses have revealed that all films are in single phase and have wurtzite structure. Besides, it has been indicated that there are not any secondary phases. The optical properties have been evaluated by UV-Vis measurement. It has shown that band gap decreases with Mn incorporation from 3.29 to 3.19 eV. Schottky diode applications of the films have been performed by evaporation of Au on pure and Mn-doped ZnO films. Current-voltage (I-V) and capacitance-voltage (C-V) measurements of the n-ZnO /n-Si heterojunction indicate good diode characteristic and the barrier heights have been calculated as 0.89 and 0.79 eV for un-doped and Mn 1 pct-doped ZnO films. Besides, schematic cross section of the Au/ n-ZnO/ n-Si/Al device and energy band diagram of n-ZnO/ n-Si heterojunction has been illustrated to clarify the transport mechanism. All results suggest that the characteristic properties of the ZnO thin films can be adjustable with the Mn doping and Al/ n-Si/ n-ZnO/Au diode can be used for UV detection application in photonic devices.

  15. Effect of substrate temperature on transparent conducting Al and F co-doped ZnO thin films prepared by rf magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Wang, Fang-Hsing; Chang, Chiao-Lu

    2016-05-01

    ZnO is a wide bandgap semiconductor that has many potential applications such as solar cells, thin film transistors, light emitting diodes, and gas/biological sensors. In this study, a composite ceramic ZnO target containing 1 wt% Al2O3 and 1.5 wt% ZnF2 was prepared and used to deposit transparent conducting Al and F co-doped zinc oxide (AFZO) thin films on glass substrates by radio frequency magnetron sputtering. The effect of substrate temperatures ranging from room temperature (RT) to 200 °C on structural, morphological, electrical, chemical, and optical properties of the deposited thin films were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), Hall effect measurement, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and UV-vis spectrophotometer. The XRD results showed that all the AFZO thin films had a (0 0 2) diffraction peak, indicating a typical wurtzite structure with a preferential orientation of the c-axis perpendicular to the substrate. The FE-SEM and AFM analyses indicated that the crystallinity and grain size of the films were enhanced while the surface roughness decreased as the substrate temperature increased. Results of Hall effect measurement showed that Al and F co-doping decreased the resistivity more effectively than single-doping (either Al or F doping) in ZnO thin films. The resistivity of the AFZO thin films decreased from 5.48 × 10-4 to 2.88 × 10-4 Ω-cm as the substrate temperature increased from RT to 200 °C due to the increased carrier concentration and Hall mobility. The optical transmittances of all the AFZO thin films were over 92% in the wavelength range of 400-800 nm regardless of substrate temperature. The blue-shift of absorption edge accompanied the rise of the optical band gap, which conformed to the Burstein-Moss effect. The developed AFZO thin films are suitable as transparent conducting electrodes for various optoelectronic

  16. X-ray absorption near edge structure investigation ofvanadium-doped ZnO thin films

    SciTech Connect

    Faiz, M.; Tabet, N.; Mekki, A.; Mun, B.S.; Hussain, Z.

    2006-05-11

    X-ray absorption near edge structure spectroscopy has beenused to investigate the electronic and atomic structure of vanadium-dopedZnO thin films obtained by reactive plasma. The results show no sign ofmetallic clustering of V atoms, +4 oxidation state of V, 4-foldcoordination of Zn in the films, and a secondary phase (possibly VO2)formation at 15 percent V doping. O K edge spectra show V 3d-O 2p and Zn4d-O 2p hybridization, and suggest that V4+ acts as electron donor thatfills the sigma* band.

  17. Effects of a seed layer on the structural properties of RF-sputtered ZnO thin films

    NASA Astrophysics Data System (ADS)

    Ur, Soon-Chul; Yi, Seung-Hwan

    2016-01-01

    Radio-frequency (RF) sputtered deposition combined with sol-gel spin coating has been applied to achieve a high-quality, c-axis-oriented ZnO film. The deposited ZnO films show only a c-axis-oriented ZnO (002) peak. The morphology, structure, and residual stress of the deposited ZnO films are found to depend strongly on the concentration of the precursor. As the concentration of the precursor is increased from 0.1-M to 0.6-M, the residual stress of the ZnO films changes from a compressive (-415 MPa) to a mild tensile (+90 MPa) mode. The deposited ZnO film interestingly shows facets when the concentration of the precursor is 0.6-M. We suggest that the residual stress in sputter-deposited ZnO films can be controlled by using the precursor concentration. This technique is believed to have been used for the first time, and can be applied to control the uniformity during micro speaker fabrication.

  18. 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.

  19. Structural, linear and nonlinear optical properties of co-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Shaaban, E. R.; El-Hagary, M.; Moustafa, El Sayed; Hassan, H. Shokry; Ismail, Yasser A. M.; Emam-Ismail, M.; Ali, A. S.

    2016-01-01

    Different compositions of Co-doped zinc oxide [(Zn(1- x)Co x O) ( x = 0, 0.02, 0.04, 0.06, 0.08 and 0.10)] thin films were evaporated onto highly clean glass substrates by thermal evaporation technique using a modified source. The structural properties investigated by X-ray diffraction revealed hexagonal wurtzite ZnO-type structure. The crystallite size of the films was found to decrease with increasing Co content. The optical characterization of the films has been carried out using spectral transmittance and reflectance obtained in the wavelength range from 300 to 2500 nm. The refractive index has been found to increase with increasing Co content. It was further found that optical energy gap decreases from 3.28 to 3.03 eV with increasing Co content from x = 0 to x = 0.10, respectively. The dispersion of refractive index has been analyzed in terms of Wemple-DiDomenico (WDD) single-oscillator model. The oscillator parameters, the single-oscillator energy ( E o), the dispersion energy ( E d), and the static refractive index ( n 0), were determined. The nonlinear refractive index of the Zn(1- x)Co x O thin films was calculated and revealed well correlation with the linear refractive index and WDD parameters which in turn depend on the density and molar volume of the system.

  20. Growth, structure, and electronic properties of nonpolar thin films on a polar substrate: Cr2O3 on ZnO (0001) and ZnO (000 1 ¯ )

    NASA Astrophysics Data System (ADS)

    Zhu, X.; Morales-Acosta, M. D.; Shen, J.; Walker, F. J.; Cha, J. J.; Altman, E. I.

    2015-10-01

    The growth and geometric and electronic structures of Cr2O3 layers on the polar ZnO surfaces were characterized to determine how polar substrates can influence the properties of nonpolar films. X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy (UPS), high resolution transmission electron microscopy (HRTEM), reflection high energy electron diffraction, low energy electron diffraction, x-ray diffraction (XRD), and x-ray reflectivity (XRR) were employed to characterize the growth mode, film quality, and interfacial electronic properties. Chromium oxide growth on ZnO (000 1 ¯ ) and (0001 ) followed the same trends: two-dimensional growth with initial disorder followed by the formation of epitaxial Cr2O3 (0001 ) . Despite the initial disorder, HRTEM and XRD/XRR measurements on thicker films revealed an abrupt interface with the Cr2O3 lattice extending all the way to the interface. This indicates that above a critical thickness of 10-15 Cr -O3-Cr repeat units, the entire film reorganizes into an ordered structure. It is postulated that the oxygen remained ordered throughout the growth but that the chromium initially filled interstices randomly in the oxygen sublattice, which allowed the film to eventually grow with a well-defined epitaxial relationship with the substrate. The polar interfaces showed a small band offset that decayed with increasing film thickness, suggesting that the compensating charges at the interface may partially migrate to the film surface. No evidence of formal changes in the Cr oxidation state at the interfaces was seen. On the other hand, statistical analyses of UPS valence band spectra revealed an enhanced density of states near the valence band edge for Cr2O3 on ZnO (0001 ) , consistent with stabilization of the positive interface by filling surface electronic states. In contrast, no significant valence band differences were observed between bulk Cr2O3 and thin Cr2O3 layers on ZnO (000 1 ¯ ) , suggesting a different

  1. Modulation of microstructure and optical properties of Mo-doped ZnO thin films by substrate temperature

    SciTech Connect

    Zhang, J.W.; He, G.; Li, T.S.; Liu, M.; Chen, X.S.; Liu, Y.M.; Sun, Z.Q.

    2015-05-15

    Highlights: • Mo-doped ZnO films are obtained by sputtering at various substrate temperatures. • High-quality MZO thin films with good crystalline have been obtained at 200 °C. • Deposition temperature affects the amount of defects in the crystalline structure - Abstract: Mo-doped ZnO(MZO) films were deposited on Si (1 1 1) substrates by radio frequency sputtering at different substrate temperatures of 200, 300 and 400 °C. The effect of the substrate temperature on the structural and optical properties of the MZO films has been investigated. X-ray diffraction results reveal that all the films are polycrystalline with a hexagonal wurtzite structure with a preferential orientation according to the direction (0 0 2) plane. The crystallinity and surface morphologies of the films are strongly dependent on the growth temperature, which in turn exerts a great effect on microstructural and optical properties of the MZO films. The optical absorption measurements show high ultraviolet (UV) absorbance property of MZO with sharp and intense absorption band in this region and the optical band gap (E{sub g}) are 3.18, 3.22, 3.25 and 3.21 eV for the films deposited at room temperature, 200, 300 and 400 °C. The photoluminescence (PL) intensity of a strong broad violet–blue emission from MZO nanostructures with increasing deposited temperature was also observed. X-ray photoelectron spectroscopy (XPS) was employed to investigate the surface chemical composition of growth products.

  2. Effect of Li substitution on dielectric and ferroelectric properties of ZnO thin films grown by pulsed-laser ablation

    NASA Astrophysics Data System (ADS)

    Dhananjay; Nagaraju, J.; Krupanidhi, S. B.

    2006-02-01

    Li-doped ZnO thin films (Zn1-xLixO, x=0.05-0.15) were grown by pulsed-laser ablation technique. Highly c-axis-oriented films were obtained at a growth temperature of 500 °C. Ferroelectricity in Zn1-xLixO was found from the temperature-dependent dielectric constant and from the polarization hysteresis loop. The transition temperature (Tc) varied from 290 to 330 K as the Li concentration increased from 0.05 to 0.15. It was found that the maximum value of the dielectric constant at Tc is a function of Li concentration. A symmetric increase in memory window with the applied gate voltage is observed for the ferroelectric thin films on a p-type Si substrate. A ferroelectric P-E hysteresis loop was observed for all the compositions. The spontaneous polarization (Ps) and coercive field (Ec) of 0.6 μC/cm2 and 45 kV/cm were obtained for Zn0.85Li0.15O thin films. These observations reveal that partial replacement of host Zn by Li ions induces a ferroelectric phase in the wurtzite-ZnO semiconductor. The dc transport studies revealed an Ohmic behavior in the lower-voltage region and space-charge-limited conduction prevailed at higher voltages. The optical constants were evaluated from the transmission spectrum and it was found that Li substitution in ZnO enhances the dielectric constant.

  3. Waveguiding-assisted random lasing in epitaxial ZnO thin film

    NASA Astrophysics Data System (ADS)

    Dupont, P.-H.; Couteau, C.; Rogers, D. J.; Hosseini Téhérani, F.; Lérondel, G.

    2010-12-01

    Zinc oxide thin films were grown on c-sapphire substrates using pulsed laser deposition. Pump power dependence of surface emission spectra, acquired using a quadrupled 266 nm laser, revealed room temperature stimulated emission (threshold of 900 kW/cm2). Time dependent spectral analysis plus gain measurements of single-shot, side-emission spectra pumped with a nitrogen laser revealed random lasing indicative of the presence of self-forming laser cavities. It is suggested that random lasing in an epitaxial system rather than a three-dimensional configuration of disordered scattering elements was due to waveguiding in the film. Waveguiding causes light to be amplified within randomly formed closed-loops acting as lasing cavities.

  4. Photocatalytic activity of undoped and Ag-doped TiO{sub 2}-supported zeolite for humic acid degradation and mineralization

    SciTech Connect

    Lazau, C.; Ratiu, C.; Orha, C.; Pode, R.; Manea, F.

    2011-11-15

    Highlights: {yields} Hybrid materials based on natural zeolite and TiO{sub 2} obtained by solid-state reaction. {yields} XRD proved the presence of anatase form of undoped and Ag-doped TiO{sub 2} onto zeolite. {yields} FT-IR spectra evidenced the presence on TiO{sub 2} bounded at the zeolite network. {yields} Ag-doped TiO{sub 2} onto zeolitic matrix exhibited an enhanced photocatalytic activity. -- Abstract: The hybrid materials based on natural zeolite and undoped and Ag-doped TiO{sub 2}, i.e., Z-Na-TiO{sub 2} and Z-Na-TiO{sub 2}-Ag, were successfully synthesized by solid-state reaction in microwave-assisted hydrothermal conditions. Undoped TiO{sub 2} and Ag-doped TiO{sub 2} nanocrystals were previously synthesized by sol-gel method. The surface characterization of undoped TiO{sub 2}/Ag-doped TiO{sub 2} and natural zeolite hybrid materials has been investigated by X-ray diffraction, DRUV-VIS spectroscopy, FT-IR spectroscopy, BET analysis, SEM microscopy and EDX analysis. The results indicated that anatase TiO{sub 2} is the dominant crystalline type as spherical form onto zeolitic matrix. The presence of Ag into Z-Na-TiO{sub 2}-Ag was confirmed by EDX analysis. The DRUV-VIS spectra showed that Z-Na-TiO{sub 2}-Ag exhibited absorption within the range of 400-500 nm in comparison with Z-Na-TiO{sub 2} catalyst. The enhanced photocatalytic activity of Z-Na-TiO{sub 2}-Ag catalyst is proved through the degradation and mineralization of humic acid under ultraviolet and visible irradiation.

  5. Investigation of correlation between the microstructure and electrical properties of sol-gel derived ZnO based thin films

    NASA Astrophysics Data System (ADS)

    Zhu, M. W.; Gong, J.; Sun, C.; Xia, J. H.; Jiang, X.

    2008-10-01

    Pure ZnO and aluminum doped ZnO films (ZAO) were prepared by sol-gel method and the effect of Al doping on the microstructure and electrical properties of the films was investigated. The results showed that the transformation from granular to columnar structure could be observed in pure ZnO films with the increase in heating time while in aluminum doped films little structural changes occurred even after a prolonged heating time. Additionally, measurements of electrical properties showed that both microstructural evolution and doping could significantly improve the conductivity of the films, which could be assigned to an increase both in Hall mobility and carrier concentration. The relationship between microstructure and the electrical properties of the films was discussed, and various scattering mechanisms were proposed for sol-gel derived ZnO and ZAO films as a function of the carrier concentration.

  6. Influences of pH and ligand type on the performance of inorganic aqueous precursor-derived ZnO thin film transistors.

    PubMed

    Jun, Taehwan; Jung, Yangho; Song, Keunkyu; Moon, Jooho

    2011-03-01

    The aqueous precursor-derived ZnO semiconductor is a promising alternative to organic semiconductors and amorphous silicon materials in applications requiring transparent thin-film transistors at low temperatures. The pH in the aqueous solution is an important factor in determining the device performance of ZnO-TFTs. Using a basic aqueous solution, the ZnO transistor annealed at 150 °C exhibited a high field-effect mobility (0.42 cm(2) V(-1) s(-1)) and an excellent on/off ratio (10(6)). In contrast, the ZnO layer annealed at 150 °C prepared from an acidic solution was inactive. Chemical and structural analyses confirmed that the variation of the device characteristics originates from the existing state difference of Zn in solution. The hydroxyo ligand is stable in basic conditions, which involves a lower energy pathway for the solution-to-solid conversion, whereas the hydrated zinc cation undergoes more complex reactions that occur at a higher temperature. Our results suggest that the pH and ligand type play critical roles in the preparation of aqueous precursor-based ZnO-TFTs which demonstrate high performance at low temperatures. PMID:21366236

  7. Observation of dopant-profile independent electron transport in sub-monolayer TiOx stacked ZnO thin films grown by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Saha, D.; Misra, P.; Das, Gangadhar; Joshi, M. P.; Kukreja, L. M.

    2016-01-01

    Dopant-profile independent electron transport has been observed through a combined study of temperature dependent electrical resistivity and magnetoresistance measurements on a series of Ti incorporated ZnO thin films with varying degree of static-disorder. These films were grown by atomic layer deposition through in-situ vertical stacking of multiple sub-monolayers of TiOx in ZnO. Upon decreasing ZnO spacer layer thickness, electron transport smoothly evolved from a good metallic to an incipient non-metallic regime due to the intricate interplay of screening of spatial potential fluctuations and strength of static-disorder in the films. Temperature dependent phase-coherence length as extracted from the magnetotransport measurement revealed insignificant role of inter sub-monolayer scattering as an additional channel for electron dephasing, indicating that films were homogeneously disordered three-dimensional electronic systems irrespective of their dopant-profiles. Results of this study are worthy enough for both fundamental physics perspective and efficient applications of multi-stacked ZnO/TiOx structures in the emerging field of transparent oxide electronics.

  8. Structural and physical properties of antibacterial Ag-doped nano-hydroxyapatite synthesized at 100°C

    PubMed Central

    2011-01-01

    Synthesis of nanosized particle of Ag-doped hydroxyapatite with antibacterial properties is in the great interest in the development of new biomedical applications. In this article, we propose a method for synthesized the Ag-doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionized water. Other phase or impurities were not observed. Silver-doped hydroxyapatite nanoparticles (Ag:HAp) were performed by setting the atomic ratio of Ag/[Ag + Ca] at 20% and [Ca + Ag]/P as 1.67. The X-ray diffraction studies demonstrate that powders made by co-precipitation at 100°C exhibit the apatite characteristics with good crystal structure and no new phase or impurity is found. The scanning electron microscopy (SEM) observations suggest that these materials present a little different morphology, which reveals a homogeneous aspect of the synthesized particles for all samples. The presence of calcium (Ca), phosphor (P), oxygen (O), and silver (Ag) in the Ag:HAp is confirmed by energy dispersive X-ray (EDAX) analysis. FT-IR and FT-Raman spectroscopies revealed that the presence of the various vibrational modes corresponds to phosphates and hydroxyl groups. The strain of Staphylococcus aureus was used to evaluate the antibacterial activity of the Ca10-xAgx(PO4)6(OH)2 (x = 0 and 0.2). In vitro bacterial adhesion study indicated a significant difference between HAp (x = 0) and Ag:HAp (x = 0.2). The Ag:Hap nanopowder showed higher inhibition. PMID:22136671

  9. Correlations between 1/f noise and thermal treatment of Al-doped ZnO thin films deposited by direct current sputtering

    SciTech Connect

    Barhoumi, A. Guermazi, S.; Leroy, G.; Gest, J.; Carru, J. C.; Yang, L.; Boughzala, H.; Duponchel, B.

    2014-05-28

    Al-doped ZnO thin films (AZO) have been deposited on amorphous glass substrates by DC sputtering at different substrate temperatures T{sub s}. X-Ray diffraction results reveal that AZO thin films have a hexagonal wurtzite structure with (002) preferred orientation. (002) peaks indicate that the crystalline structure of the films is oriented with c-axis perpendicular to the substrate. Three-dimensional (3D) atomic force microscopy images of AZO thin films deposited on glass substrate at 200 °C, 300 °C, and 400 °C, respectively, shows the improvement of the crystallinity and the homogeneity of AZO thin films with T{sub s} which is in agreement with the noise measurements. The noise was characterized between 1 Hz and 100 kHz and we have obtained 1/f spectra. The noise is very sensitive to the crystal structure especially to the orientation of the crystallites which is perpendicular to the substrate and to the grain boundaries which generate a high current flow and a sharp increase in noise. Through time, R{sub sh} and [αμ]{sub eff} increase with the modification of the crystallinity of AZO thin films. Study of noise aging shows that the noise is more sensitive than resistivity for all AZO thin films.

  10. Correlations between 1/f noise and thermal treatment of Al-doped ZnO thin films deposited by direct current sputtering

    NASA Astrophysics Data System (ADS)

    Barhoumi, A.; Leroy, G.; Yang, L.; Gest, J.; Boughzala, H.; Duponchel, B.; Guermazi, S.; Carru, J. C.

    2014-05-01

    Al-doped ZnO thin films (AZO) have been deposited on amorphous glass substrates by DC sputtering at different substrate temperatures Ts. X-Ray diffraction results reveal that AZO thin films have a hexagonal wurtzite structure with (002) preferred orientation. (002) peaks indicate that the crystalline structure of the films is oriented with c-axis perpendicular to the substrate. Three-dimensional (3D) atomic force microscopy images of AZO thin films deposited on glass substrate at 200 °C, 300 °C, and 400 °C, respectively, shows the improvement of the crystallinity and the homogeneity of AZO thin films with Ts which is in agreement with the noise measurements. The noise was characterized between 1 Hz and 100 kHz and we have obtained 1/f spectra. The noise is very sensitive to the crystal structure especially to the orientation of the crystallites which is perpendicular to the substrate and to the grain boundaries which generate a high current flow and a sharp increase in noise. Through time, Rsh and [αμ]eff increase with the modification of the crystallinity of AZO thin films. Study of noise aging shows that the noise is more sensitive than resistivity for all AZO thin films.

  11. Photocatalytic activity of V doped ZnO nanoparticles thin films for the removal of 2- chlorophenol from the aquatic environment under natural sunlight exposure.

    PubMed

    Salah, Numan; Hameed, A; Aslam, M; Babkair, Saeed S; Bahabri, F S

    2016-07-15

    Vanadium doped ZnO powders were used as precursors to deposit thin films of V(5+) incorporated ZnO nanoparticles on glass substrates by the pulsed laser deposition technique. The observed variations in Raman signals, visible region shift in the diffuse reflectance spectra along with a small shift in the (101) reflections of the X-ray diffraction (XRD) confirmed the insertion of V(5+) ions in ZnO lattice. No other additional reflection in the XRD results other than ZnO further endorsed the occupation of lattice positions by V entities rather than independent oxide formation. The asymmetric XPS peaks of Zn2p and V2p core levels confirmed the existence of both in the vicinity. The existence of minimal proportion of V(3+) along with V(5+) states varied the alteration of the oxidation states V in the synthetic route. The SEM images at various resolutions displayed the uniform distribution identical nanoparticles without the presence of additional phases in the deposited films. The SEM cross-section measurements revealed the uniform thickness of ∼90 nm of each film, whereas the surface studies of the films were performed by AFM. The as-synthesized films were tested for photocatalytic activity in sunlight illumination for the removal of 2-chlorophenol. The unique feature of the study was the estimation of the photocatalytic activity 20 ppm of 2-chlorophenol by exposing the low exposed area. The degradation of the substrate was measured by liquid phase UV-vis spectroscopy, whereas total organic carbon measurement revealed the mineralization of the substrate. The released Cl(-) ions were also measured by ion chromatography. The estimated flatband potentials and pHzpc values of the V doped materials, by Mott-Schottky analysis and zeta potential measurements respectively, were correlated with the photocatalytic activity. The kinetics of the photocatalytic degradation/mineralization process was estimated and results were correlated with the plausible mechanism. PMID

  12. Characteristics of the electromagnetic interference shielding effectiveness of Al-doped ZnO thin films deposited by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Choi, Yong-June; Gong, Su Cheol; Johnson, David C.; Golledge, Stephen; Yeom, Geun Young; Park, Hyung-Ho

    2013-03-01

    The structural, optical, and electrical properties of Al-doped ZnO (ZnO:Al) thin films deposited by atomic layer deposition (ALD) with a modified precursor pulse sequence were investigated to evaluate the electromagnetic interference shielding effectiveness (EMI-SE). A Zn-Al-O precursor exposure sequence was used in a modified ALD procedure to result in better distribution of Al3+ ions in the ZnO matrix with the aim of reducing the formation of complete nano-laminated structures that may form in the typical alternating ZnO and Al2O3 deposition procedure. The ALD dopant concentration of the ZnO:Al films was varied by adjusting the dopant deposition intervals of the ZnO:Znsbnd Alsbnd O precursor pulse cycle ratios among 24:1, 19:1, 14:1, and 9:1. The lowest obtained resistivity and average transmittance in the visible region (380-780 nm) were 5.876 × 10-4 Ω cm (carrier concentration of 6.02 × 1020 cm-3 and Hall mobility of 17.65 cm2/V s) and 85.93% in the 131 nm thick ZnO:Al(19:1) film, respectively. The average value of the EMI-SE in the range of 30 MHz to 1.5 GHz increased from 1.1 dB for the 121 nm thick undoped ZnO film to 6.5 dB for the 131 nm thick ZnO:Al(19:1) film.

  13. Energy and charge transfers between (Bu{sub 4}N){sub 2}(Ru)(dcbpyH){sub 2}(NCS){sub 2} (N719) and ZnO thin films

    SciTech Connect

    Ni Manman; Cheng Qiang; Zhang, W. F.

    2010-03-15

    ZnO thin films and (Bu{sub 4}N){sub 2}(Ru)(dcbpyH){sub 2}(NCS){sub 2} (called N719) sensitized ZnO thin films are grown on fluorine-doped tin oxide (FTO) conducting glass substrates using laser molecular beam epitaxy. Ultraviolet-visible absorption, photoluminescence (PL), surface photovoltage spectroscopy, and Raman scattering are employed to probe into the transition process of photogenerated charges and the interaction between ZnO and N719. The experimental results indicate that there is a significant electronic interaction between N719 and ZnO through chemiadsorption. The interaction greatly enhances the photogenerated charge separation and thus the photovoltaic response of the ZnO film but remarkedly weakens its radiative recombination, i.e., PL, implying strong energy and charge transfer occurring between N719 and ZnO. In addition, a new PL peak observed at about 720 nm in N719 sensitized ZnO/FTO is attributed to the electron-hole recombination of N719.

  14. Precise calibration of Mg concentration in Mg{sub x}Zn{sub 1-x}O thin films grown on ZnO substrates

    SciTech Connect

    Kozuka, Y.; Falson, J.; Tsukazaki, A.; Segawa, Y.; Makino, T.; Kawasaki, M.

    2012-08-15

    The growth techniques for Mg{sub x}Zn{sub 1-x}O thin films have advanced at a rapid pace in recent years, enabling the application of this material to a wide range of optical and electrical applications. In designing structures and optimizing device performances, it is crucial that the Mg content of the alloy be controllable and precisely determined. In this study, we have established laboratory-based methods to determine the Mg content of Mg{sub x}Zn{sub 1-x}O thin films grown on ZnO substrates, ranging from the solubility limit of x {approx} 0.4 to the dilute limit of x < 0.01. For the absolute determination of Mg content, Rutherford backscattering spectroscopy is used for the high Mg region above x = 0.14, while secondary ion mass spectroscopy is employed to quantify low Mg content. As a lab-based method to determine the Mg content, c-axis length is measured by x-ray diffraction and is well associated with Mg content. The interpolation enables the determination of Mg content to x = 0.023, where the peak from the ZnO substrate overlaps the Mg{sub x}Zn{sub 1-x}O peak in standard laboratory equipment, and thus limits quantitative determination. At dilute Mg contents below x = 0.023, the localized exciton peak energy of the Mg{sub x}Zn{sub 1-x}O films as measured by photoluminescence is found to show a linear Mg content dependence, which is well resolved from the free exciton peak of ZnO substrate down to x = 0.0043. Our results demonstrate that x-ray diffraction and photoluminescence in combination are appropriate methods to determine Mg content in a wide Mg range from x = 0.004 to 0.40 in a laboratory environment.

  15. Contrasting morphologies of O-rich ZnO epitaxy on Zn- and O-polar thin film surfaces: Phase-field model

    NASA Astrophysics Data System (ADS)

    Yu, Yan-Mei; Liu, Bang-Gui

    2008-05-01

    The island growths during the epitaxy of differently polar ZnO thin films under O-rich condition are simulated in terms of a phase-field model. The different island nucleation modes as well as the different atom migration and influx sticking ability are considered on the Zn-polar surfaces and the O-polar ones. By reproducing the morphological variation from the smooth two-dimensional island growth on the Zn-polar surfaces to the rough three-dimensional islands on the O-polar surfaces, our simulated results indicate that the surface morphology of the ZnO thin films is dependent not only on the migration ability and influx rate but also on the island nucleation kinetics. For the Zn-polarity, the easy island nucleation contributes to the smooth morphology as a result of the limited migration and fast influx. However, the reduced nucleation kinetics on the O-polar surfaces causes the developed three-dimensional island growth. This phase-field modeling should be applicable to other semiconductor epitaxial growths.

  16. Structural, electrical and optical properties of Al-Ti codoped ZnO (ZATO) thin films prepared by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Jiang, Minhong; Liu, Xinyu

    2008-12-01

    Al-Ti codoped ZnO (ZATO) thin films were grown on glass substrates at room temperature by radio frequency (RF) magnetron sputtering technique and annealed under vacuum (˜10 -1 Pa) at 400 °C for 3 h. The X-ray diffraction (XRD) patterns show that Al-doped ZnO (ZAO) and ZATO thin films are highly textured along the c-axis and perpendicular to the surface of the substrate. After annealing in a vacuum condition at 400 °C for 3 h, the lowest resistivity of 7.96 and 8.7 × 10 -4 Ω cm are observed for ZATO and ZAO films, respectively. But after annealing in air, the resistivity of ZATO and ZAO is higher than 10 5 Ω cm. In the visible region, the ZAO films show the average transmittance of the order of 90%, while ZATO films were of the order of 75%, which illustrates that the additional Ti doping reduces the optical properties. The optical band gap was found to be 3.46 eV for ZAO film and it increases to 3.53 eV for ZATO films.

  17. High Performance Flexible Actuator of Urchin-Like ZnO Nanostructure/Polyvinylenefluoride Hybrid Thin Film with Graphene Electrodes for Acoustic Generator and Analyzer.

    PubMed

    Cheong, Oug Jae; Lee, James S; Kim, Jae Hyun; Jang, Jyongsik

    2016-05-01

    A bass frequency response enhanced flexible polyvinylidene fluoride (PVDF) based thin film acoustic actuator is successfully fabricated. High concentrations of various zinc oxide (ZnO) is embedded in PVDF matrix, enhancing the β phase content and the dielectric property of the composite thin film. ZnO acts as a nucleation agent for the crystallization of PVDF. A chemical vapor deposition grown graphene is used as electrodes, enabling high electron mobility for the distortion free acoustic signals. The frequency response of the fabricated acoustic actuator is studied as a function of the film thickness and filler content. The optimized film has a thickness of 80 μm with 30 wt% filler content and shows 72% and 42% frequency response enhancement in bass and midrange compared to the commercial PVDF, respectively. Also, the total harmonic distortion decreases to 82% and 74% in the bass and midrange regions, respectively. Furthermore, the composite film shows a promising potential for microphone applications. Most of all, it is demonstrated that acoustic actuator performance is strongly influenced by degree of PVDF crystalline. PMID:27028524

  18. Growth, structural and optoelectronic properties tuning of nitrogen-doped ZnO thin films synthesized by means of reactive pulsed laser deposition

    SciTech Connect

    Naouar, M.; Ka, I.; Gaidi, M.; Alawadhi, H.; Bessais, B.; Khakani, M.A.El

    2014-09-15

    Highlights: • PLD technique has been used to elaborate N doped ZnO. • A maximum incorporation of 0.7 at.% has been achieved at a pressure of 25 mTorr. • Increasing the N{sub 2} pressure decreases the nitrogen content with the creation of more defects. • Optical transmission and PL spectra have confirmed the band gap narrowing. - Abstract: Pulsed laser deposition has been successfully used to achieve in-situ nitrogen doping of zinc oxide thin films at a temperature as low as 300 °C. Nitrogen-doped zinc oxide (ZnO:N) thin films with a maximum nitrogen content of 0.7 at.% were obtained by varying the nitrogen background pressure in the range of 0–150 mTorr. The ZnO:N thin films were found to present hexagonal crystalline structure with dense and smooth surface. X-ray photoelectron spectroscopy analysis confirms the effective incorporation of nitrogen into ZnO thin films. Optical transmission together with room temperature photoluminescence measurements show that the band gap of the ZnO:N films shifts from 3.3 eV to 3.1 eV as nitrogen concentration varies in the range of 0.2–0.7 at.%. The narrower band gap is obtained at an optimal nitrogen concentration of 0.22 at.%. This band gap narrowing is found to be caused by both nitrogen incorporation and nitrogen-induced defects in the ZnO:N films.

  19. Electronic structure of Al-doped ZnO transparent conductive thin films studied by x-ray absorption and emission spectroscopies

    SciTech Connect

    Huang, W. H.; Sun, S. J.; Chiou, J. W.; Chou, H.; Chan, T. S.; Lin, H.-J.; Kumar, Krishna; Guo, J.-H.

    2011-11-15

    This study used O K-, Zn L{sub 3}-, Zn K-, and Al K-edges x-ray absorption near-edge structure (XANES) and O K-edge x-ray emission spectroscopy (XES) measurements to investigate the electronic structure of transparent Al-doped ZnO (AZO) thin film conductors. The samples were prepared on glass substrates at a low temperature near 77 K by using a standard RF sputtering method. High-purity Ne (5N) was used as the sputtering gas. The crystallography of AZO thin films gradually transformed from the ZnO wurtize structure to an amorphous structure during sample deposition, which suggests the suitability to grow on flexible substrates, eliminating the severe degradation due to fragmentation by repeated bending. The O K- and Zn L{sub 3}-edges XANES spectra of AZO thin films revealed a decrease in the number of both O 2p and Zn 3d unoccupied states when the pressure of Ne was increased from 5 to 100 mTorr. In contrast, Al K-edges XANES spectra showed that the number of unoccupied states of Al 3p increased in conjunction with the pressure of Ne, indicating an electron transfer from Al to O atoms, and suggesting that Al doping increases the negative effective charge of oxygen ions. XES and XANES spectra of O 2p states at the O K-edge also revealed that Al doping not only raised the conduction-band-minimum, but also increased the valence-band-maximum and the band-gap. The results indicate that the reduction in conductivity of AZO thin films is due to the generation of ionic characters, the increase in band-gap, and the decrease in density of unoccupied states of oxygen.

  20. Thermoelectric properties optimization of Al-doped ZnO thin films prepared by reactive sputtering Zn-Al alloy target

    NASA Astrophysics Data System (ADS)

    Fan, Ping; Li, Ying-zhen; Zheng, Zhuang-hao; Lin, Qing-yun; Luo, Jing-ting; Liang, Guang-xing; Zhang, Miao-qin; Chen, Min-cong

    2013-11-01

    Al-doped ZnO (AZO) has practical applications in the industry for thermoelectric generation, owing to its nontoxicity, low-cost and stability at high temperatures. In this study, AZO thin films with high quality were deposited on BK7 glass substrates at room-temperature by direct current reactive magnetron sputtering using Zn-Al alloy target. The deposited thin films were annealed at various temperatures ranging from 623 K to 823 K with a space of 50 K. It is found that the absolute value of Seebeck coefficient of AZO thin film annealed at 723 K increases stably with increasing of measuring temperature and reaches a value of ∼60 μV/K at 575 K. After that, Al-doping content was varied to further optimize the thermoelectric properties of AZO thin films. The power factor of AZO thin films with Al content of 3 wt% increased with increase of measuring temperature and the maximum power factor of 1.54 × 10-4 W m-1K-2 was obtained at 550 K with the maximum absolute values of Seebeck coefficient of 99 μV/K, which is promising for high temperature thermoelectric application.

  1. Dye-sensitized solar cell based on spray deposited ZnO thin film: performance analysis through DFT approach.

    PubMed

    Parthiban, R; Balamurugan, D; Jeyaprakash, B G

    2015-02-01

    A dye-sensitized solar cell based on a spray deposited zinc oxide (ZnO) photoanode with Evans blue as a sensitizer was fabricated. Structural analysis confirms the hexagonal wurtzite phase of the ZnO photoanode with c-axis orientation. Surface morphology of the ZnO photoanode shows uniform distribution of spherically-shaped grains, ranging from 18 nm to 25 nm. The power conversion efficiency of the device was measured as 0.1%. Density functional theory was adopted to study the observed photovoltaic performance of the fabricated device. The analysis of the electronic properties of Evans blue dye showed that it has a pronounced effect on the observed device performance. PMID:25459624

  2. Influence of Incorporated Pt-Fe2O3 Core-Shell Nanoparticles on the Resistive Switching Characteristics of ZnO Thin Film.

    PubMed

    Yoo, E J; Kang, S Y; Shim, E L; Yoon, T S; Kang, C J; Choi, Y J

    2015-11-01

    The resistance-switching characteristics of metal oxides have attracted great interest for the non-volatile memory applications such as resistive random access memory. A basic resistive random access memory device has a metal/insulator/metal structure, and its memory effect is achieved by applying voltage to change the resistance of the insulating layer. One of the promising candidates for explaining the resistance-switching mechanism is the formation and rupture of nanoscale conductive filaments. However, this model has an issue that needs to be addressed: the wide distribution of switching voltage due to randomly formed filaments. Therefore, some researchers have reported a decrease in switching voltage distribution and an increase in switching stability by incorporating nanoparticles into the insulating layer. In this study, we investigated influence of incorporated Pt-Fe2O3 core-shell nanoparticles on the resistive switching characteristics of ZnO thin films. Devices were fabricated on SiO2 wafers. A 100-nm-thick Cr layer was used as the bottom electrode. A 50-nm-thick ZnO layer was deposited using the sputtering method, and Pt-Fe2O3 nanoparticles were deposited on it by the dip coating method. A 50-nm-thick ZnO layer was then deposited again. A top Cr electrode (size: 100 μm x 100 μm) was deposited using a shadow mask and sputtering system. All the devices showed bipolar resistance-switching behavior that is observed in Cr/ZnO/Cr structures. However, the on/off voltage was dramatically lowered by incorporating nanoparticles into the insulating layer when compared with that of the devices without nanoparticles. In addition, the switching stability of the devices was improved upon the incorporation of nanoparticles. On the basis of these results, we can conclude that Pt-Fe2O3 nanoparticles may be used to enhance the resistance switching properties of ZnO thin films by incorporating them into the films. PMID:26726563

  3. Synthesis and characterization of hierarchical multilayered flower-like assemblies of Ag doped Bi2WO6 and their photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Dumrongrojthanath, Phattharanit; Thongtem, Titipun; Phuruangrat, Anukorn; Thongtem, Somchai

    2013-12-01

    In this research, 0-3 mol% Ag doped Bi2WO6 hierarchical multilayered flower-like assemblies were successfully synthesized by a simple hydrothermal method at 180 °C for 24 h. The XRD, FE-SEM, FTIR and Raman analyses revealed the presence of flower-like Russellite Bi2WO6 structures which were constructed from a large number of orderly arranged 2D layers of interconnected nanoplates. Their photocatalytic activities were evaluated by photodegradation of rhodamine B (RhB) under Xe visible light irradiation (λ > 420 nm). The 3 mol% Ag doped Bi2WO6 showed the highest photocatalytic activities of 98.20% within 180 min.

  4. Photocatalytic characteristics for the nanocrystalline TiO2 on the Ag-doped CaAl2O4:(Eu,Nd) phosphor

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Sik; Sung, Hyun-Je; Kim, Bum-Joon

    2015-04-01

    This study investigated the photocatalytic behavior of nanocrystalline TiO2 deposited on Ag-doped long-lasting phosphor (CaAl2O4:Eu2+,Nd3+). The CaAl2O4:Eu2+,Nd3+ phosphor powders were prepared via conventional sintering using CaCO3, Al2O3, Eu2O3, and Nd2O3 as raw materials according to the appropriate molar ratios. Silver nanoparticles were loaded on the phosphor by mixing with an aqueous Ag-dispersion solution. Nanocrystalline TiO2 was deposited on Ag-doped CaAl2O4:Eu2+,Nd3+ powders via low-pressure chemical vapor deposition (LPCVD). The TiO2 coated on the phosphor was actively photo-reactive under irradiation with visible light and showed much faster benzene degradation than pure TiO2, which is almost non-reactive. The coupling of TiO2 with phosphor may result in an energy band bending in the junction region, which then induces the TiO2 crystal at the interface to be photo-reactive under irradiation with visible light. In addition, the intermetallic compound of CaTiO3 that formed at the interface between TiO2 and the CaAl2O4:(Eu2+,Nd3+) phosphor results in the formation of oxygen vacancies and additional electrons that promote the photodecomposition of benzene gas. The addition of Ag nanoparticles enhanced the photocatalytic reactivity of the TiO2/CaAl2O4:Eu2+,Nd3+ phosphor. TiO2 on the Ag-doped phosphor presented a higher benzene gas decomposition rate than the TiO2 did on the phosphor without Ag-doping under both irradiation with ultraviolet and visible light.

  5. 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.

  6. Growth of Cu2O on Ga-doped ZnO and their interface energy alignment for thin film solar cells

    NASA Astrophysics Data System (ADS)

    Wong, L. M.; Chiam, S. Y.; Huang, J. Q.; Wang, S. J.; Pan, J. S.; Chim, W. K.

    2010-08-01

    Cu2O thin films are deposited by direct current reactive magnetron sputtering on borofloat glass and indium tin oxide (ITO) coated glass at room temperature. The effect of oxygen partial pressure on the structures and properties of Cu2O thin films are investigated. We show that oxygen partial pressure is a crucial parameter in achieving pure phases of CuO and Cu2O. Based on this finding, we fabricate heterojunctions of p-type Cu2O with n-type gallium doped ZnO (GZO) on ITO coated glass substrates by pulsed laser deposition for GZO thin films. The energy band alignment for thin films of Cu2O/GZO on ITO glass is characterized using high-resolution x-ray photoelectron spectroscopy. The energy band alignment for the Cu2O/GZO heterojunctions is determined to be type II with a valence band offset of 2.82 eV and shows negligible effects of variation with gallium doping. The higher conduction band of the Cu2O relative to that of GZO in the obtained band alignment shows that the heterojunctions are suitable for solar cell application based on energy levels consideration.

  7. Growth of Cu{sub 2}O on Ga-doped ZnO and their interface energy alignment for thin film solar cells

    SciTech Connect

    Wong, L. M.; Chiam, S. Y.; Wang, S. J.; Pan, J. S.; Huang, J. Q.; Chim, W. K.

    2010-08-15

    Cu{sub 2}O thin films are deposited by direct current reactive magnetron sputtering on borofloat glass and indium tin oxide (ITO) coated glass at room temperature. The effect of oxygen partial pressure on the structures and properties of Cu{sub 2}O thin films are investigated. We show that oxygen partial pressure is a crucial parameter in achieving pure phases of CuO and Cu{sub 2}O. Based on this finding, we fabricate heterojunctions of p-type Cu{sub 2}O with n-type gallium doped ZnO (GZO) on ITO coated glass substrates by pulsed laser deposition for GZO thin films. The energy band alignment for thin films of Cu{sub 2}O/GZO on ITO glass is characterized using high-resolution x-ray photoelectron spectroscopy. The energy band alignment for the Cu{sub 2}O/GZO heterojunctions is determined to be type II with a valence band offset of 2.82 eV and shows negligible effects of variation with gallium doping. The higher conduction band of the Cu{sub 2}O relative to that of GZO in the obtained band alignment shows that the heterojunctions are suitable for solar cell application based on energy levels consideration.

  8. Influence of film thickness and oxygen partial pressure on cation-defect-induced intrinsic ferromagnetic behavior in luminescent p-type Na-doped ZnO thin films.

    PubMed

    Ghosh, S; Khan, Gobinda Gopal; Varma, Shikha; Mandal, K

    2013-04-10

    In this article, we have investigated the effect of oxygen partial pressure (PO2) and film thickness on defect-induced room-temperature (RT) ferromagnetism (FM) of highly c-axis orientated p-type Na-doped ZnO thin films fabricated by pulse laser deposition (PLD) technique. We have found that the substitution of Na at Zn site (NaZn) can be effective to stabilize intrinsic ferromagnetic (FM) ordering in ZnO thin films with Curie temperature (TC) as high as 509 K. The saturation magnetization (MS) is found to decrease gradually with the increase in thickness of the films, whereas an increase in "MS" is observed with the increase in PO2 of the PLD chamber. The enhancement of ferromagnetic signature with increasing PO2 excludes the possibility of oxygen vacancy (VO) defects for the magnetic origin in Na-doped ZnO films. On the other hand, remarkable enhancement in the green emission (IG) are observed in the photoluminescence (PL) spectroscopic measurements due to Na-doping and that indicates the stabilization of considerable amount of Zn vacancy (VZn)-type defects in Na-doped ZnO films. Correlating the results of PL and X-ray photoelectron spectroscopy (XPS) studies with magnetic measurements we have found that VZn and Na substitutional (NaZn) defects are responsible for the hole-mediated FM in Na-doped ZnO films, which might be an effective candidate for modern spintronic technology. PMID:23461478

  9. Laser annealing of laser assisted molecular beam deposited ZnO thin films with application to metal-semiconductor-metal photodetectors

    SciTech Connect

    Li Meiya; Anderson, Wayne; Chokshi, Nehal; De Leon, Robert L.; Tompa, Gary

    2006-09-01

    We report on the effect of postdeposition laser annealing of undoped zinc oxide (ZnO) thin films grown by laser assisted molecular beam deposition. Hall-effect measurements show that some undoped ZnO films change from n type with mobility values in the range of 200 cm{sup 2} V{sup -1} s{sup -1} to p-type material with mobility value of 73 cm{sup 2} V{sup -1} s{sup -1}, after laser annealing. The photoconductive behavior was clearly seen on the laser-annealed samples, with values of 0.28 m{omega}{sup -1}. The structural and optical properties of the films were improved with laser annealing as shown by scanning electron microscopy, x-ray photoelectron spectroscopy analysis, and photoluminescence measurement. All of the nonlaser and laser annealed samples showed near-band emission at {approx}3.3 eV. Metal-semiconductor-metal photodetectors were fabricated from the films.

  10. Site location of Al-dopant in ZnO lattice by exploiting the structural and optical characterisation of ZnO:Al thin films

    NASA Astrophysics Data System (ADS)

    Nakrela, A.; Benramdane, N.; Bouzidi, A.; Kebbab, Z.; Medles, M.; Mathieu, C.

    The zinc oxide thin films, highly transparent, doped aluminium were prepared on glass substrates by the reactive chemical spray method. The incorporation nature of Al atoms in the ZnO lattice was determined by X-ray diffraction and optical analyses. Indeed, for low doping ⩽2%, the results of X-ray spectra analysis show a simultaneous reduction of lattice parameters (a and c), this variation, which follows VEGARD's law, tends to indicate a substitution of Zn by Al. By against for doping >2% the increase in the lattice parameters thus the grain sizes, in accordance with the VEGARD's law can be explained by occupation of the interstitial sites by Al atoms. Beyond 4%, the material tends to get disorderly and the crystallites orientation is random. The studied optical properties show that the variation of the optical gap follows a law of the x3/2 form for x < 3% (x is the aluminium atom fraction incorporated in the ZnO lattice). The granular structure is fairly visible and some local growths are disrupted. The crystallite size at low enlargement is coherent with the XRD results.

  11. Energy-transfer efficiency in Eu-doped ZnO thin films: the effects of oxidative annealing on the dynamics and the intermediate defect states.

    PubMed

    Ahmed, Samah M; Szymanski, Paul; El-Nadi, Lotfia M; El-Sayed, Mostafa A

    2014-02-12

    We have studied ultrafast dynamics in thin films of Eu-doped zinc oxide (ZnO), prepared by radio-frequency sputtering onto sapphire substrates. Following UV excitation of ZnO, a red emission is observed. Postdeposition annealing in an oxygen atmosphere improves the crystallinity and emission intensity of the films, which are highly sensitive to the dopant concentration. Transient-absorption spectroscopy shows that the excited semiconductor host transfers energy to rare-earth ions on a time scale of only a few picoseconds. The dynamics as a function of the probe wavelength change dramatically after annealing, with annealed films showing the fastest dynamics at much lower wavelengths. Our results show that annealing greatly affects the defect energy levels of the films and the dynamics of the trapped carriers. Unannealed films show dynamics consistent with energy transfer from O vacancies to the dopant, while energy transfer in annealed samples involves acceptor-type defects such as Zn vacancies as intermediates. PMID:24397538

  12. Effect of Sn Doping on the Properties of Nano-Structured ZnO Thin Films Deposited by Co-Sputtering Technique.

    PubMed

    Islam, M A; Rahman, K S; Haque, F; Khan, N A; Akhtaruzzaman, M; Alam, M M; Ruslan, H; Sopian, K; Amin, N

    2015-11-01

    In this study, tin doped zinc oxide (ZnO:Sn) nano-structured thin films were successfully deposited by co-sputtering of ZnO and Sn on top of glass substrate. The effect of Sn doping on the microstructure, phase, morphology, optical and electrical properties of the films were extensively investigated by means of XRD, EDX, SEM, AFM, Hall Effect measurement, and UV-Vis spectrometry. The results showed that the undoped ZnO film exhibited preferred orientation along the c-axis of the hexagonal wurtzite structure. With increase of Sn doping, the peak position of the (002) plane was shifted to the higher 20 values, and ultimately changed to amorphous structure. The absorption edge was shifted to blue region which confirmed the excitonic quantum confinement effect in the films. Consequently, improved surface morphology with optical bandgap, reduced average particle size, reduced resistivity, enhanced Hall mobility and carrier concentration were observed in the doped films after vacuum annealing. Among all of the as-deposited and annealed ZnO:Sn films investigated in this study, annealed film doped with 8 at.% of Sn concentration exhibited the best properties with a bandgap of 3.84 eV, RMS roughness of 2.51 nm, resistivity of 2.36 ohm-cm, and Hall mobility of 83 cm2 V(-1) s(-1). PMID:26726665

  13. Synthesis, characterizations and anti-bacterial activities of pure and Ag doped CdO nanoparticles by chemical precipitation method

    NASA Astrophysics Data System (ADS)

    Sivakumar, S.; Venkatesan, A.; Soundhirarajan, P.; Khatiwada, Chandra Prasad

    2015-02-01

    In the present study, synthesized pure and Ag (1%, 2%, and 3%) doped Cadmium Oxide (CdO) nanoparticles by chemical precipitation method. Then, the synthesized products were characterized by thermo gravimetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD) analysis, Fourier transform infrared (FT-IR) spectroscopy, Ultra violet-Vis diffused reflectance spectroscopy (UV-Vis-DRS), Scanning electron microscopy (SEM), Energy dispersive X-rays (EDX) spectroscopy, and anti-bacterial activities, respectively. The transition temperatures and phase transitions of Cd(OH)2 to CdO at 400 °C was confirmed by TG-DTA analysis. The XRD patterns show the cubic shape and average particle sizes are 21, 40, 34, and 37 nm, respectively for pure and Ag doped samples. FT-IR study confirmed the presence of CdO and Ag at 677 and 459 cm-1, respectively. UV-Vis-DRS study shows the variation on direct and indirect band gaps. The surface morphologies and elemental analysis have been confirmed from SEM and with EDX. In addition, the synthesized products have been characterized by antibacterial activities against Gram-positive and negative bacteria. Further, the present investigation suggests that CdO nanoparticles have the great potential applications on various industrial and medical fields of research.

  14. 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

  15. Bipolar resistive switching characteristics of low temperature grown ZnO thin films by plasma-enhanced atomic layer deposition

    SciTech Connect

    Zhang Jian; Yang Hui; Zhang Qilong; Dong Shurong; Luo, J. K.

    2013-01-07

    ZnO films deposited by plasma-enhanced atomic layer deposition (PEALD) have been used to investigate resistive memory behavior. The bipolar resistance switching properties were observed in the Al/PEALD-ZnO/Pt devices. The resistance ratio for the high and low resistance states (HRS/LRS) is more than 10{sup 3}, better than ZnO devices deposited by other methods. The dominant conduction mechanisms of HRS and LRS are trap-controlled space charge limited current and Ohmic behavior, respectively. The resistive switching behavior is induced upon the formation/disruption of conducting filaments. This study demonstrated that the PEALD-ZnO films have better properties for the application in 3D resistance random access memory.

  16. Dielectric function of very thin nano-granular ZnO layers with different states of growth.

    PubMed

    Gilliot, Mickaël; Hadjadj, Aomar; En Naciri, Aotmane

    2015-04-01

    Zinc oxide (ZnO) layers consisting of grains closely packed together are grown using a solgel synthesis and spin-coating deposition process. The morphologies are characterized by atomic force microscopy and X-ray diffraction, and their optical properties are investigated by spectroscopic ellipsometry at the different stages of the growth process. The optical observations are correlated with evolution of morphology and orientation. Two remarkable evolutions are observed: gradual evolution of morphology, crystallinity, and excitonic contribution with the first deposition steps; and transformation from a poorly oriented to a c-axis oriented crystalline state featuring a large contribution of bound excitons after thermal annealing. A modified Elliott model is used to obtain the optical parameters of ZnO, including bandgap and exciton energies. A simple growth mechanism is proposed to explain the evolution of the layers in accordance with the different deposition steps. PMID:25967220

  17. Study of multiple phonon behavior in Li-doped ZnO thin films fabricated using the sol-gel spin-coating technique

    NASA Astrophysics Data System (ADS)

    Kalyanaraman, Subramanian; Vettumperumal, Rajapandi; Thangavel, Rajalingam

    2013-03-01

    Undoped and lithium-doped zinc oxide (ZnO) thin films have been deposited on sapphire substrates (0001) using the sol-gel method. The effect of doping with various percentages of Li at a particular annealing temperature of 600 °C is studied. The samples are characterized using Xray diffraction (XRD), scanning electron microscopy (SEM), micro-photoluminescence (µ-PL) and Raman and polarized Raman (PR) spectroscopy. The X-ray diffraction and micro-Raman spectroscopy confirm the presence of lithium substitution for zinc. The wurtzite structure of the lattice is retained, and five multiple phonon Raman modes are observed. The values of the depolarization ratios are calculated from polarized Raman data. Photoluminescence shows a strong emission peak in the near UV at 3.276 eV and negligible visible emission. The PL peak positions in the doped samples nearly coincide with each other, suggesting very similar recombination mechanisms in the nanocrystals.

  18. In-situ post-annealing technique for improving piezoelectricity and ferroelectricity of Li-doped ZnO thin films prepared by radio frequency magnetron sputtering system

    NASA Astrophysics Data System (ADS)

    Lin, Chun-Cheng; Chang, Chia-Chiang; Wu, Chin-Jyi; Tseng, Zong-Liang; Tang, Jian-Fu; Chu, Sheng-Yuan; Chen, Yi-Chun; Qi, Xiaoding

    2013-03-01

    Li-doped zinc oxide (L0.03Z0.97O) thin films are deposited onto Pt/Ti/SiO2/Si substrates via the radio frequency magnetron sputtering method. The structure evolution with annealing temperature of the predominantly (002)-oriented Li-doped ZnO (LZO) films after in-situ post-annealing process is determined. The largest values of the piezoelectric coefficient (d33) and the remnant polarization (Pr) (22.85 pm/V and 0.655 μC/cm2, respectively) are obtained for LZO films post-annealed at 600 °C, which can be attributed to the predominant (002)-oriented crystalline structure, the release of intrinsic residual compressive stress, and less non-lattice oxygen.

  19. Optical properties and surface morphology of Li-doped ZnO thin films deposited on different substrates by DC magnetron sputtering method

    NASA Astrophysics Data System (ADS)

    Mohamed, Galal A.; Mohamed, El-Maghraby; Abu El-Fadl, A.

    2001-12-01

    Thin films of zinc oxide doped with Zn 1- xLi xO with x=0.2 (ZnO : Li), have been prepared on sapphire, MgO and quartz substrates by DC magnetron sputtering method at 5 mTorr. The substrate temperatures were fixed to about 573 K. We have measured the transmission and reflection spectra and determined the absorption coefficient, optical band-gap ( Egdopt), the high frequency dielectric constant ε‧ ∞ and the carrier concentration N for the as-prepared films at room temperature. The films show direct allowed optical transitions with Egdopt values of 3.38, 3.43 and 3.29 eV for films deposited on sapphire, MgO and quartz substrates, respectively. The dependence of the obtained results on the substrate type are discussed.

  20. Stress-induced anomalous shift of optical band gap in Ga-doped ZnO thin films: Experimental and first-principles study

    SciTech Connect

    Wang, Yaqin; Tang, Wu E-mail: lan.zhang@mail.xjtu.edu.cn; Liu, Jie; Zhang, Lan E-mail: lan.zhang@mail.xjtu.edu.cn

    2015-04-20

    In this work, highly c-axis oriented Ga-doped ZnO thin films have been deposited on glass substrates by RF magnetron sputtering under different sputtering times. The optical band gap is observed to shift linearly with the electron concentration and in-plane stress. The failure of fitting the shift of band gap as a function of electron concentration using the available theoretical models suggests the in-plane stress, instead of the electron concentration, be regarded as the dominant cause to this anomalous redshift of the optical band gap. And the mechanism of stress-dependent optical band gap is supported by the first-principles calculation based on density functional theory.

  1. Ultrafast dynamics of the dielectric functions of ZnO and BaTiO{sub 3} thin films after intense femtosecond laser excitation

    SciTech Connect

    Acharya, S.; Seifert, G.; Chouthe, S.; Graener, H.; Böntgen, T.; Sturm, C.; Schmidt-Grund, R.; Grundmann, M.

    2014-02-07

    The ultrafast carrier dynamics of epitaxial ZnO and BaTiO{sub 3} thin films after intense excitation at 3.10 eV and 4.66 eV photon energy has been studied by femtosecond absorption spectroscopy. Modelling the transient transmission changes on the basis of spectroscopic ellipsometry data and pertinent equilibrium model dielectric functions extended by additional terms for the effects at high carrier density (P-band luminescence and stimulated emission from electron-hole-plasma), a self-consistent parameterized description was obtained for both materials. Excited carrier lifetimes in the range of ≈2 to ≈60 ps and long-lived thermal effects after several hundred ps have been identified in both materials. These findings form a reliable basis to quantitatively describe future femtosecond studies on ZnO/BaTiO{sub 3} heterolayer systems.

  2. Development and characterization of ZnO, Au/ZnO and Pd/ZnO thin films through their adsorptive and catalytic properties.

    PubMed

    Giannoudakos, A; Agelakopoulou, T; Asteriadis, I; Kompitsas, M; Roubani-Kalantzopoulou, F

    2008-04-11

    In this paper, we report (a) the development of ZnO thin films prepared by pulsed laser deposition and partially covered with nano-particles Pd or Au and (b) their physicochemical study, in order to investigate their catalytic and/or adsorptive properties. It is the first time where two different and popular methods, namely pulsed laser deposition and reversed flow-inverse gas chromatography, are combined. The inverse gas chromatographic technique with the corresponding time-resolved analysis is used for the first time in order to characterise compounds in the nano-scale domain. We focus on the determination of physicochemical quantities mainly concerning the adsorption in thin films, with (Pd/ZnO) or without (Au/ZnO) catalytic behaviour. Thus, entropy and other important physicochemical quantities are calculated which reveal the mechanism of adsorption as well as of isomerization-hydrogenation of 1-butene and contribute to the study of heterogeneity of thin film surfaces. The programs used have been written in Fortran. An important achievement is also the determination of the standard deviations of the kinetic constants. PMID:18313683

  3. Highly Conducting Gallium-Doped ZnO Thin Film as Transparent Schottky Contact for Organic- Semiconductor-Based Schottky Diodes

    NASA Astrophysics Data System (ADS)

    Singh, Budhi; Ghosh, Subhasis

    2015-08-01

    Highly conducting and transparent Ga-doped ZnO (GZO) thin films have been grown on transparent substrates at different growth temperatures with Ga content varying from 0.01% to 10%. All films showed pronounced c-axis orientation corresponding to hexagonal wurtzite structure. The minimum resistivity of 4.3 × 10-4 Ω cm was reproducibly obtained in GZO thin film doped with 2% Ga and grown at 600°C. We have further shown that highly conducting transparent GZO thin film can be used as a Schottky contact in copper phthalocyanine (CuPc)-based Schottky diodes. The capacitance-voltage characteristics of the Al/CuPc/Au and GZO/CuPc/Au Schottky diodes show similar built-in potential ( V bi) of 0.98 V, which is close to the difference in work function between Au (5.2 eV) and Al or GZO (4.2 eV), establishing that GZO behaves as a metal electrode with work function similar to Al. Similar values of acceptor concentration (˜1015 cm-3) in CuPc were obtained from the capacitance-voltage characteristics of the Al/CuPc/Au and GZO/CuPc/Au Schottky diodes. These observations indicate the absence of interface states at the metal/organic interface in CuPc-based Schottky diodes.

  4. Doping effect on SILAR synthesized crystalline nanostructured Cu-doped ZnO thin films grown on indium tin oxide (ITO) coated glass substrates and its characterization

    NASA Astrophysics Data System (ADS)

    Dhaygude, H. D.; Shinde, S. K.; Velhal, Ninad B.; Takale, M. V.; Fulari, V. J.

    2016-08-01

    In the present study, a novel chemical route is used to synthesize the undoped and Cu-doped ZnO thin films in aqueous solution by successive ionic layer adsorption and reaction (SILAR) method. The synthesized thin films are characterized by x-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive x-ray analysis (EDAX), contact angle goniometer and UV–Vis spectroscopic techniques. XRD study shows that the prepared films are polycrystalline in nature with hexagonal crystal structure. The change in morphology for different doping is observed in the studies of FE-SEM. EDAX spectrum shows that the thin films consist of zinc, copper and oxygen elements. Contact angle goniometer is used to measure the contact angle between a liquid and a solid interface and after detection, the nature of the films is initiated from hydrophobic to hydrophilic. The optical band gap energy for direct allowed transition ranging between 1.60–2.91 eV is observed.

  5. Transparent conducting Al-doped ZnO thin films prepared by magnetron sputtering with dc and rf powers applied in combination

    SciTech Connect

    Minami, Tadatsugu; Ohtani, Yuusuke; Miyata, Toshihiro; Kuboi, Takeshi

    2007-07-15

    A newly developed Al-doped ZnO (AZO) thin-film magnetron-sputtering deposition technique that decreases resistivity, improves resistivity distribution, and produces high-rate depositions has been demonstrated by dc magnetron-sputtering depositions that incorporate rf power (dc+rf-MS), either with or without the introduction of H{sub 2} gas into the deposition chamber. The dc+rf-MS preparations were carried out in a pure Ar or an Ar+H{sub 2} (0%-2%) gas atmosphere at a pressure of 0.4 Pa by adding a rf component (13.56 MHz) to a constant dc power of 80 W. The deposition rate in a dc+rf-MS deposition incorporating a rf power of 150 W was approximately 62 nm/min, an increase from the approximately 35 nm/min observed in dc magnetron sputtering with a dc power of 80 W. A resistivity as low as 3x10{sup -4} {omega} cm and an improved resistivity distribution could be obtained in AZO thin films deposited on substrates at a low temperature of 150 deg. C by dc+rf-MS with the introduction of hydrogen gas with a content of 1.5%. This article describes the effects of adding a rf power component (i.e., dc+rf-MS deposition) as well as introducing H{sub 2} gas into dc magnetron-sputtering preparations of transparent conducting AZO thin films.

  6. Oxygen-dependent phosphorus networking in ZnO thin films grown by low temperature rf sputtering

    NASA Astrophysics Data System (ADS)

    Pugel, D. Elizabeth; Vispute, R. D.; Hullavarad, S. S.; Venkatesan, T.; Varughese, B.

    2007-03-01

    Radio frequency (rf) sputtered films of 10at.% P2O5-doped zinc oxide (ZnO) were deposited at temperatures (Td) below the sublimation point of P2O5 (Td<350°C) and at a range of oxygen pressures p(O2). Ultraviolet-visible optical transmission measurements, x-ray photoelectron spectroscopy (XPS), and x-ray diffraction were used to examine the effects of p(O2) during deposition on the band gap and on the bonding behavior of phosphorus. At both deposition temperatures studied (room temperature with unintentional heating and 125°C), an increase in phosphorus concentration with increasing p(O2) was observed. However, the dependence of the band gap behavior on p(O2) was observed to be dramatically different for the two deposition temperatures: room-temperature-deposited films show a redshift while films deposited at 125°C show a blueshift. Analysis of the oxygen 1s XPS peak shows a progressive formation of nonbridging (Zn-O-P) bond networks for room temperature films, whereas films grown at 125°C show increased (P-O-P) bond networks with increasing p(O2). This indicates that a small degree of thermal activation considerably modifies the bonding behavior of phosphorus in ZnO. Implications of these results for the use of phosphorus as a p-type dopant for ZnO are discussed.

  7. p-type conduction from Sb-doped ZnO thin films grown by dual ion beam sputtering in the absence of oxygen ambient

    SciTech Connect

    Kumar Pandey, Sushil; Kumar Pandey, Saurabh; Awasthi, Vishnu; Kumar, Ashish; Mukherjee, Shaibal; Deshpande, Uday P.; Gupta, Mukul

    2013-10-28

    Sb-doped ZnO (SZO) thin films were deposited on c-plane sapphire substrates by dual ion beam sputtering deposition system in the absence of oxygen ambient. The electrical, structural, morphological, and elemental properties of SZO thin films were studied for films grown at different substrate temperatures ranging from 200 °C to 600 °C and then annealed in situ at 800 °C under vacuum (pressure ∼5 × 10{sup −8} mbar). Films grown for temperature range of 200–500 °C showed p-type conduction with hole concentration of 1.374 × 10{sup 16} to 5.538 × 10{sup 16} cm{sup −3}, resistivity of 66.733–12.758 Ω cm, and carrier mobility of 4.964–8.846 cm{sup 2} V{sup −1} s{sup −1} at room temperature. However, the film grown at 600 °C showed n-type behavior. Additionally, current-voltage (I–V) characteristic of p-ZnO/n-Si heterojunction showed a diode-like behavior, and that further confirmed the p-type conduction in ZnO by Sb doping. X-ray diffraction measurements showed that all SZO films had (002) preferred crystal orientation. X-ray photoelectron spectroscopy analysis confirmed the formation of Sb{sub Zn}–2V{sub Zn} complex caused acceptor-like behavior in SZO films.

  8. Characterization of ZnO Interlayers for Organic Solar Cells: Correlation of Electrochemical Properties with Thin-Film Morphology and Device Performance.

    PubMed

    Ou, Kai-Lin; Ehamparam, Ramanan; MacDonald, Gordon; Stubhan, Tobias; Wu, Xin; Shallcross, R Clayton; Richards, Robin; Brabec, Christoph J; Saavedra, S Scott; Armstrong, Neal R

    2016-08-01

    This report focuses on the evaluation of the electrochemical properties of both solution-deposited sol-gel (sg-ZnO) and sputtered (sp-ZnO) zinc oxide thin films, intended for use as electron-collecting interlayers in organic solar cells (OPVs). In the electrochemical studies (voltammetric and impedance studies), we used indium-tin oxide (ITO) over coated with either sg-ZnO or sp-ZnO interlayers, in contact with either plain electrolyte solutions, or solutions with probe redox couples. The electroactive area of exposed ITO under the ZnO interlayer was estimated by characterizing the electrochemical response of just the oxide interlayer and the charge transfer resistance from solutions with the probe redox couples. Compared to bare ITO, the effective electroactive area of ITO under sg-ZnO films was ca. 70%, 10%, and 0.3% for 40, 80, and 120 nm sg-ZnO films. More compact sp-ZnO films required only 30 nm thicknesses to achieve an effective electroactive ITO area of ca. 0.02%. We also examined the electrochemical responses of these same ITO/ZnO heterojunctions overcoated with device thickness pure poly(3-hexylthiophehe) (P3HT), and donor/acceptor blended active layers (P3HT:PCBM). Voltammetric oxidation/reduction of pure P3HT thin films on ZnO/ITO contacts showed that pinhole pathways exist in ZnO films that permit dark oxidation (ITO hole injection into P3HT). In P3HT:PCBM active layers, however, the electrochemical activity for P3HT oxidation is greatly attenuated, suggesting PCBM enrichment near the ZnO interface, effectively blocking P3HT interaction with the ITO contact. The shunt resistance, obtained from dark current-voltage behavior in full P3HT/PCBM OPVs, was dependent on both (i) the porosity of the sg-ZnO or sp-ZnO films (as revealed by probe molecule electrochemistry) and (ii) the apparent enrichment of PCBM at ZnO/P3HT:PCBM interfaces, both effects conveniently revealed by electrochemical characterization. We anticipate that these approaches will be

  9. Effect of ZnO channel thickness on the device behaviour of nonvolatile memory thin film transistors with double-layered gate insulators of Al2O3 and ferroelectric polymer

    NASA Astrophysics Data System (ADS)

    Yoon, Sung-Min; Yang, Shin-Hyuk; Park, Sang-Hee Ko; Jung, Soon-Won; Cho, Doo-Hee; Byun, Chun-Won; Kang, Seung-Youl; Hwang, Chi-Sun; Yu, Byoung-Gon

    2009-12-01

    Poly(vinylidene fluoride trifluoroethylene) and ZnO were employed for nonvolatile memory thin film transistors as ferroelectric gate insulator and oxide semiconducting channel layers, respectively. It was proposed that the thickness of the ZnO layer be carefully controlled for realizing the lower programming voltage, because the serially connected capacitor by the formation of a fully depleted ZnO channel had a critical effect on the off programming voltage. The fabricated memory transistor with Al/P(VDF-TrFE) (80 nm)/Al2O3 (4 nm)/ZnO (5 nm) exhibits encouraging behaviour such as a memory window of 3.8 V at the gate voltage of -10 to 12 V, and 107 on/off ratio, and a gate leakage current of 10-11 A.

  10. Photocatalytic comparison of Cu- and Ag-doped TiO2/GF for bioaerosol disinfection under visible light

    NASA Astrophysics Data System (ADS)

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2015-12-01

    Photocatalysts, TiO2/glass fiber (TiO2/GF), Cu-doped TiO2/glass fiber (Cu-TiO2/GF) and Ag-doped TiO2/glass fiber (Ag-TiO2/GF), were synthesized by a sol-gel method. They were then used to disinfect Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in bioaerosols under visible light irradiation. TiO2/GF did not show any significant disinfection effect. Both Cu and Ag acted as intermediate agents to enhance separation efficiency of electron-hole pairs of TiO2, leading to improved photocatalytic activity of Cu-TiO2/GF and Ag-TiO2/GF under visible light. Cu in Cu-TiO2/GF acted as a defective agent, increasing the internal quantum efficiency of TiO2, while Ag in Ag-TiO2/GF acted as a sensitive agent, enhancing the transfer efficiency of the electrons generated. The highest disinfection efficiencies of E. coli and S. aureus by Cu-TiO2/GF were 84.85% and 65.21%, respectively. The highest disinfection efficiencies of E. coli and S. aureus by Ag-TiO2/GF were 94.46% and 73.12%, respectively. Among three humidity conditions - 40±5% (dry), 60±5% (moderate), and 80±5% (humid) - the moderate humidity condition showed the highest disinfection efficiency for both E. coli and S. aureus. This study also showed that a Gram-negative bacterium (E. coli) were more readily disinfected by the photocatalysts than a Gram-positive bacterium (S. aureus).

  11. Visible-Light-Responsive Photocatalysis: Ag-Doped TiO2 Catalyst Development and Reactor Design Testing

    NASA Technical Reports Server (NTRS)

    Coutts, Janelle L.; Hintze, Paul E.; Meier, Anne; Shah, Malay G.; Devor, Robert W.; Surma, Jan M.; Maloney, Phillip R.; Bauer, Brint M.; Mazyck, David W.

    2016-01-01

    In recent years, the alteration of titanium dioxide to become visible-light-responsive (VLR) has been a major focus in the field of photocatalysis. Currently, bare titanium dioxide requires ultraviolet light for activation due to its band gap energy of 3.2 eV. Hg-vapor fluorescent light sources are used in photocatalytic oxidation (PCO) reactors to provide adequate levels of ultraviolet light for catalyst activation; these mercury-containing lamps, however, hinder the use of this PCO technology in a spaceflight environment due to concerns over crew Hg exposure. VLR-TiO2 would allow for use of ambient visible solar radiation or highly efficient visible wavelength LEDs, both of which would make PCO approaches more efficient, flexible, economical, and safe. Over the past three years, Kennedy Space Center has developed a VLR Ag-doped TiO2 catalyst with a band gap of 2.72 eV and promising photocatalytic activity. Catalyst immobilization techniques, including incorporation of the catalyst into a sorbent material, were examined. Extensive modeling of a reactor test bed mimicking air duct work with throughput similar to that seen on the International Space Station was completed to determine optimal reactor design. A bench-scale reactor with the novel catalyst and high-efficiency blue LEDs was challenged with several common volatile organic compounds (VOCs) found in ISS cabin air to evaluate the system's ability to perform high-throughput trace contaminant removal. The ultimate goal for this testing was to determine if the unit would be useful in pre-heat exchanger operations to lessen condensed VOCs in recovered water thus lowering the burden of VOC removal for water purification systems.

  12. Ag doped hollow TiO2 nanoparticles as an effective green fungicide against Fusarium solani and Venturia inaequalis phytopathogens.

    PubMed

    Boxi, Siddhartha Sankar; Mukherjee, Khushi; Paria, Santanu

    2016-02-26

    Chemical-based pesticides are widely used in agriculture to protect crops from insect infestation and diseases. However, the excessive use of highly toxic pesticides causes several human health (neurological, tumor, cancer) and environmental problems. Therefore nanoparticle-based green pesticides have become of special importance in recent years. The antifungal activities of pure and Ag doped (solid and hollow) TiO2 nanoparticles are studied against two potent phytopathogens, Fusarium solani (which causes Fusarium wilt disease in potato, tomato, etc) and Venturia inaequalis (which causes apple scab disease) and it is found that hollow nanoparticles are more effective than the other two. The antifungal activities of the nanoparticles were further enhanced against these two phytopathogens under visible light exposure. The fungicidal effect of the nanoparticles depends on different parameters, such as particle concentration and the intensity of visible light. The minimum inhibitory dose of the nanoparticles for V. inaequalis and F. solani are 0.75 and 0.43 mg/plate. The presence of Ag as a dopant helps in the formation of stable Ag-S and disulfide bonds (R-S-S-R) in cellular protein, which leads to cell damage. During photocatalysis generated (•)OH radicals loosen the cell wall structure and this finally leads to cell death. The mechanisms of the fungicidal effect of nanoparticles against these two phytopathogens are supported by biuret and triphenyl tetrazolium chloride analyses and field emission electron microscopy. Apart from the fungicidal effect, at a very low dose (0.015 mg/plate) the nanoparticles are successful in arresting production of toxic napthoquinone pigment for F. solani which is related to the fungal pathogenecity. The nanoparticles are found to be effective in protecting potatoes affected by F. solani or other fungi from spoiling. PMID:26808118

  13. Ag doped hollow TiO2 nanoparticles as an effective green fungicide against Fusarium solani and Venturia inaequalis phytopathogens

    NASA Astrophysics Data System (ADS)

    Sankar Boxi, Siddhartha; Mukherjee, Khushi; Paria, Santanu

    2016-02-01

    Chemical-based pesticides are widely used in agriculture to protect crops from insect infestation and diseases. However, the excessive use of highly toxic pesticides causes several human health (neurological, tumor, cancer) and environmental problems. Therefore nanoparticle-based green pesticides have become of special importance in recent years. The antifungal activities of pure and Ag doped (solid and hollow) TiO2 nanoparticles are studied against two potent phytopathogens, Fusarium solani (which causes Fusarium wilt disease in potato, tomato, etc) and Venturia inaequalis (which causes apple scab disease) and it is found that hollow nanoparticles are more effective than the other two. The antifungal activities of the nanoparticles were further enhanced against these two phytopathogens under visible light exposure. The fungicidal effect of the nanoparticles depends on different parameters, such as particle concentration and the intensity of visible light. The minimum inhibitory dose of the nanoparticles for V. inaequalis and F. solani are 0.75 and 0.43 mg/plate. The presence of Ag as a dopant helps in the formation of stable Ag-S and disulfide bonds (R-S-S-R) in cellular protein, which leads to cell damage. During photocatalysis generated •OH radicals loosen the cell wall structure and this finally leads to cell death. The mechanisms of the fungicidal effect of nanoparticles against these two phytopathogens are supported by biuret and triphenyl tetrazolium chloride analyses and field emission electron microscopy. Apart from the fungicidal effect, at a very low dose (0.015 mg/plate) the nanoparticles are successful in arresting production of toxic napthoquinone pigment for F. solani which is related to the fungal pathogenecity. The nanoparticles are found to be effective in protecting potatoes affected by F. solani or other fungi from spoiling.

  14. A study on the evolution of dielectric function of ZnO thin films with decreasing film thickness

    SciTech Connect

    Li, X. D.; Chen, T. P. Liu, P.; Liu, Y.; Liu, Z.; Leong, K. C.

    2014-03-14

    Dielectric function, band gap, and exciton binding energies of ultrathin ZnO films as a function of film thickness have been obtained with spectroscopic ellipsometry. As the film thickness decreases, both real (ε{sub 1}) and imaginary (ε{sub 2}) parts of the dielectric function decrease significantly, and ε{sub 2} shows a blue shift. The film thickness dependence of the dielectric function is shown related to the changes in the interband absorption, discrete-exciton absorption, and continuum-exciton absorption, which can be attributed to the quantum confinement effect on both the band gap and exciton binding energies.

  15. Effect of deposition times on structure of Ga-doped ZnO thin films as humidity sensor

    SciTech Connect

    Khalid, Faridzatul Shahira; Awang, Rozidawati

    2014-09-03

    Gallium doped zinc oxide (GZO) has good electrical property. It is widely used as transparent electrode in photovoltaic devices, and sensing element in gas and pressure sensors. GZO thin film was prepared using magnetron sputtering. Film deposition times were set at 10, 15, 20, 25 and 30 minutes to get samples of different thickness. X-ray diffraction (XRD) was used to determine the structure of GZO thin films. Structure for GZO thin film is hexagonal wurtzite structure. Morphology and thickness of GZO thin films was observed from FESEM micrographs. Grain size and thickness of thin films improved with increasing deposition times. However, increasing the thickness of thin films occur below 25 minutes only. Electrical properties of GZO thin films were studied using a four-point probe technique. The changes in the structure of the thin films lead to the changed of their electrical properties resulting in the reduction of the film resistance. These thin films properties significantly implying the potential application of the sample as a humidity sensor.

  16. Domain matched epitaxial growth of (111) Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} thin films on (0001) Al{sub 2}O{sub 3} with ZnO buffer layer

    SciTech Connect

    Krishnaprasad, P. S. E-mail: mkj@cusat.ac.in; Jayaraj, M. K. E-mail: mkj@cusat.ac.in; Antony, Aldrin; Rojas, Fredy

    2015-03-28

    Epitaxial (111) Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} (BST) thin films have been grown by pulsed laser deposition on (0001) Al{sub 2}O{sub 3} substrate with ZnO as buffer layer. The x-ray ω-2θ, Φ-scan and reciprocal space mapping indicate epitaxial nature of BST thin films. The domain matched epitaxial growth of BST thin films over ZnO buffer layer was confirmed using Fourier filtered high resolution transmission electron microscope images of the film-buffer interface. The incorporation of ZnO buffer layer effectively suppressed the lattice mismatch and promoted domain matched epitaxial growth of BST thin films. Coplanar inter digital capacitors fabricated on epitaxial (111) BST thin films show significantly improved tunable performance over polycrystalline thin films.

  17. The effect of the solution flow rate on the properties of zinc oxide (ZnO) thin films deposited by ultrasonic spray

    NASA Astrophysics Data System (ADS)

    Attaf, A.; Benkhetta, Y.; Saidi, H.; Bouhdjar, A.; Bendjedidi, H.; Nouadji, M.; Lehraki, N.

    2015-03-01

    In this work, we used a system based on ultrasonic spray pyrolysis technique. By witch, we have deposited thin films of zinc oxide (ZnO) with the variation of solution flow rate from 50 ml / h to 150 ml / h, and set other parameters such as the concentration of the solution, the deposition time, substrate temperature and the nozzel -substrate distance. In order to study the influence of the solution flow rate on the properties of the films produced, we have several characterization techniques such as X-ray diffraction to determine the films structure, the scanning electron microscopy SEM for the morphology of the surfaces, EDS spectroscopy for the chemical composition, UV-Visible-Nir spectroscopy for determination the optical proprieties of thin films.The experimental results show that: the films have hexagonal structure at the type (wurtzite), the average size of grains varies from 20.11 to 32.45 nm, the transmittance of the films equals 80% in visible rang and the band gap is varied between 3.274 and 3.282 eV, when the solution flow rate increases from 50 to 150 ml/h.

  18. Growth Behavior of Ga-Doped ZnO Thin Films Deposited on Au/SiN/Si(001) Substrates by Radio Frequency Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Seo, Seon Hee; Kang, Hyon Chol

    2013-11-01

    This paper reports the growth behavior of Ga-doped ZnO (ZnO:Ga) thin films deposited on Au/SiN/Si(001) substrates by radio-frequency magnetron sputtering. The microstructures of the overgrown ZnO:Ga thin films were investigated by performing X-ray diffraction, scanning electron microcopy, and transmission electron microscopy analyses. It was confirmed that the growth process proceeds through three stages. In the first stage, nano-scale ZnO:Ga islands were grown on the SiN layer, while a fairly continuous flat structure was formed on the Au nanoparticles (NPs). In the second stage of the growth process, ZnO:Ga domains with different growth orientations, depending strongly on the crystalline planes of the host Au NPs, were nucleated. These domains then grew at different rates, resulting in a change in the morphology from the initial shape reflecting that of the Au NPs to a sunflower-type shape. In the final stage, columnar growth with a preferred (0002) orientation along the surface normal direction became dominant.

  19. The effect of the solution flow rate on the properties of zinc oxide (ZnO) thin films deposited by ultrasonic spray

    SciTech Connect

    Attaf, A. Benkhetta, Y.; Saidi, H.; Bouhdjar, A.; Bendjedidi, H.; Nouadji, M.; Lehraki, N.

    2015-03-30

    In this work, we used a system based on ultrasonic spray pyrolysis technique. By witch, we have deposited thin films of zinc oxide (ZnO) with the variation of solution flow rate from 50 ml / h to 150 ml / h, and set other parameters such as the concentration of the solution, the deposition time, substrate temperature and the nozzel -substrate distance. In order to study the influence of the solution flow rate on the properties of the films produced, we have several characterization techniques such as X-ray diffraction to determine the films structure, the scanning electron microscopy SEM for the morphology of the surfaces, EDS spectroscopy for the chemical composition, UV-Visible-Nir spectroscopy for determination the optical proprieties of thin films.The experimental results show that: the films have hexagonal structure at the type (wurtzite), the average size of grains varies from 20.11 to 32.45 nm, the transmittance of the films equals 80% in visible rang and the band gap is varied between 3.274 and 3.282 eV, when the solution flow rate increases from 50 to 150 ml/h.

  20. Influence of annealing on the linear and nonlinear optical properties of Mn doped ZnO thin films examined by z-scan technique in CW regime

    NASA Astrophysics Data System (ADS)

    Nagaraja, K. K.; Pramodini, S.; Poornesh, P.; Rao, Ashok; Nagaraja, H. S.

    2016-08-01

    We present the studies on the influence of annealing on the third-order nonlinear optical properties of RF magnetron sputtered manganese doped zinc oxide (MZO) thin films with different doping concentration. It is revealed that the incorporation of Mn into ZnO and annealing lead to prominent changes in the third order nonlinearity. Nonlinear optical measurements were carried out by employing the z-scan technique using a continuous wave (CW) Hesbnd Ne laser of 633 nm. The z-scan results reveal that the films exhibit self-defocusing thermal nonlinearity. The third-order nonlinear optical susceptibility χ(3) was found to be of the order of 10-3 esu and 10-2 esu for annealed MZO thin films at 200 °C and 400 °C respectively. The dependence of grain size on the observed nonlinearity was revealed by atomic force microscopy analysis. Optical limiting studies were carried out for a range of input power levels and an optical limiting of about ∼8 mW was observed indicating the possible application for photonic devices.

  1. Off-centered polarization and ferroelectric phase transition in Li-doped ZnO thin films grown by pulsed-laser ablation

    NASA Astrophysics Data System (ADS)

    Dhananjay, Nagaraju, J.; Krupanidhi, S. B.

    2007-05-01

    Li-doped ZnO (Zn1-xLixO, x=0.15) thin films have been grown on platinum-coated silicon substrates via pulsed-laser ablation. The films were grown at fixed substrate temperature of 500 °C and different partial pressure of oxygen (PO2˜100-300 mTorr). The films showed (002) preferred orientation. The doping concentration and built-in potential were estimated from the capacitance-voltage characteristics. In order to investigate the phase transition behavior of the films, dc conductivity and dielectric measurements were conducted. The phase transition temperature was found to be 330 K. The activation energy (dc) has been found to be 0.05 and 0.28 eV in ferroelectric and paraelectric phases, respectively. The Zn0.85Li015O thin films exhibited well-defined polarization hysteresis loop, with a remanent polarization of 0.2 μC/cm2 and coercive field of 25 kV/cm, at room temperature. The conduction mechanism of the laser ablated Zn0.85Li015O films was analyzed in the light of impedance spectroscopy.

  2. Effect of sputtering power on the electrical and optical properties of Ca-doped ZnO thin films sputtered from nanopowders compacted target

    NASA Astrophysics Data System (ADS)

    Mahdhi, H.; Ben Ayadi, Z.; Gauffier, J. L.; Djessas, K.; Alaya, S.

    2015-07-01

    In the present work, we have deposited calcium doped zinc oxide thin films by magnetron sputtering technique using nanocrystalline particles elaborated by sol-gel method as a target material. In the first step, the nanoparticles were synthesized by sol-gel method using supercritical drying in ethyl alcohol. The structural properties studied by X-ray diffractometry indicates that Ca doped ZnO has a polycrystalline hexagonal wurzite structure with a grain size of about 30 nm. Transmission electron microscopy (TEM) measurements have shown that the synthesized CZO is a nanosized powder. Then, thin films were deposited onto glass substrates by rf-magnetron sputtering at ambient temperature. The influence of RF sputtering power on structural, morphological, electrical, and optical properties were investigated. It has been found that all the films deposited were polycrystalline with a hexagonal wurtzite structure and preferentially oriented in the (0 0 2) crystallographic direction. They have a typical columnar structure and a very smooth surface. The as-deposited films show a high transmittance in the visible range over 85% and low electrical resistivity at room temperature.

  3. Suppression effect of silicon (Si) on Er3+ 1.54μm excitation in ZnO thin films

    NASA Astrophysics Data System (ADS)

    Xu, Bo; Lu, Fei; Ma, Changdong; Fan, Ranran

    2016-08-01

    We have investigated the photoluminescence (PL) characteristics of ZnO:Er thin films on Si (100) single crystal and SiO2-on-silicon (SiO2) substrates, synthesized by radio frequency magnetron sputtering. Rutherford backscattering/channeling spectrometry (RBS), X-ray diffraction (XRD) and atomic force microscope (AFM) were used to analyze the properties of thin films. The diffusion depth profiles of Si were determined by second ion mass spectrometry (SIMS). Infrared spectra were obtained from the spectrometer and related instruments. Compared with the results at room temperature (RT), PL (1.54μm) intensity increased when samples were annealed at 250°C and decreased when at 550°C. A new peak at 1.15μm from silicon (Si) appeared in 550°C samples. The Si dopants in ZnO film, either through the diffusion of Si from the substrate or ambient, directly absorbed the energy of pumping light and resulted in the suppression of Er3+ 1.54μm excitation. Furthermore, the energy transmission efficiency between Si and Er3+ was very low when compared with silicon nanocrystal (Si-NC). Both made the PL (1.54μm) intensity decrease. All the data in experiments proved the negative effects of Si dopants on PL at 1.54μm. And further research is going on.

  4. Influence of Fe-doping on the structural, optical, and magnetic properties of ZnO thin films prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Goktas, A.; Mutlu, I. H.; Yamada, Y.

    2013-05-01

    Zn1-xFexO thin films with different Fe (0 ⩽ x ⩽ 0.20) content were produced by sol-gel dip coating method. The influence of Fe doping on the structural, optical and magnetic properties of ZnO thin films was investigated. X-ray diffraction has shown that the films are polycrystalline and textured with c-axis of the hexagonal structure along the growth direction. Scanning electron microscope has indicated that the surface of the films is homogeneous with no cracking and the grain sizes tend to decrease with the increase of Fe-doping concentration. Ultraviolet-visible measurements show a reduction in band gap of the films with increase in Fe content from 3.27 eV to 3.10 eV. The magnetic measurements performed at 5, 100, 200 and 300 K using a SQUID magnetometer revealed the dominant paramagnetic behavior until Fe doping ratio of 10% and clear magnetic hysteresis loops at 5 and 100 K for the highest Fe doping ratio of 20%. The observed ferromagnetic behavior is likely related to a partial incorporation of Zn into the Fe3O4, i.e. Fe3-xZnxO4 composition or disorders as well as some defects.

  5. Inference on the Production Mechanism of ZnO Thin Films from Activated Water and Dimethylzinc Molecules

    NASA Astrophysics Data System (ADS)

    Umemoto, Hironobu; Ishikawa, Takuma; Nishihara, Yushin; Yasui, Kanji; Nishiyama, Hiroshi; Inoue, Yasunobu; Kashiwagi, Yusaku; Ushijima, Mitsuru

    2013-09-01

    The reaction of Zn(CH3)2 and activated H2O produced in a reaction of H2 and O2 on a Pt catalyst and effused from a nozzle was examined both experimentally and theoretically. This reaction has been shown to be effective in the preparation of high-quality ZnO films. Laser-induced fluorescence measurements showed that radical species, such as H atoms and OH radicals, do not play major roles. The rotational temperature of H2O, measured with a coherent anti-Stokes Raman scattering technique, was 250 K. This low rotational temperature suggests that H2O molecules must be accelerated along the beam axis and that the collisional energy between Zn(CH3)2 and H2O is as high as 43 kJ mol-1. This energy is higher than the potential barrier to produce HOZnCH3+CH4, 38 kJ mol-1, obtained by ab initio calculations at the MP2/LANL2DZ level of theory. HOZnCH3 thus produced can be the strongest candidate ZnO film precursor.

  6. 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.

  7. Preparation of ZnO nanoparticles for blend of P3HT:ZnO nanoparticles:PCBM thin film and its charge carrier dynamics characterization

    NASA Astrophysics Data System (ADS)

    Safriani, Lusi; Aprilia, Annisa; Bahtiar, Ayi; Risdiana, Kartawidjaja, Mariah; Apriani, Trisa; Kanazawa, Kei; Furukawa, Yukio

    2013-09-01

    Recently, many researchers have paid attention to develop active material of solar cell which plays an important role in absorbing solar spectrum. This active material should have an ability to transfer charge carrier resulted from the absorption of solar spectrum. The hybrid organic-inorganic solar cell has been developed due to the combining advantages between organic material Poly(3-hexylthiophene) (P3HT) and fullerene PCBM with inorganic material ZnO nanoparticles. The investigation of charge carrier dynamics in blend P3HT:ZnO nanoparticles:PCBM film as an active material of solar cell devices is an important things to enhance the solar cell performance. The charge carrier dynamics properties is needed to control the morphology of active material to produce an efficient and effective charge dissociation. In this study we synthezed the ZnO nanoparticles by using sol-gel methods. The size of nanoparticles resulted from the reflux process of zinc acetate in methanol by the presence of catalist sodium hydroxide is around 10 nm. Photo-induced Infra-red (PI-IR) Absorption Spectroscopy was used to investigate the charge carrier dynamics of P3HT:ZnO nanoparticles:PCBM thin film. Measurement of PI-IR Absorption Spectroscopy has been carried out under variation of temperature conditions from 78 to 300 K, using a 532-nm laser as a light source. At low temperature, the charge carrier recombination was performed by positive polarons along the intrachain of P3HT while at high temperature the charge carrier recombination was attributed to positive polarons along the interchain of P3HT.

  8. Improvement in optical and structural properties of ZnO thin film through hexagonal nanopillar formation to improve the efficiency of a Si–ZnO heterojunction solar cell

    NASA Astrophysics Data System (ADS)

    Maity, S.; Bhunia, C. T.; Sahu, P. P.

    2016-05-01

    We propose to use ZnO thin film with hexagonal nanopillars deposited on Si substrate to enhance the efficiency of a solar cell. It has been treated chemically and thermally and various crystal orientations have been obtained. X-ray diffraction of ZnO thin film shows relatively high intensity peak at 34.3° angle (0 0 2) compared to other orientations. Photoluminescence measurements also confirm a narrow full width at half maximum peak at 3.3 eV, which is more than that obtained for as-grown (broad emission peak around 3.0 eV). The alignment of nanorod structure made by adding a dopant of 0.15 mole fraction of magnesium increases both photon collection and electron collection efficiency. As a result, the solar cell efficiency is enhanced from 10% to 20%.

  9. The effect of dopant concentration on properties of transparent conducting Al-doped ZnO thin films for efficient Cu2ZnSnS4 thin-film solar cells prepared by electrodeposition method

    NASA Astrophysics Data System (ADS)

    Mkawi, E. M.; Ibrahim, K.; Ali, M. K. M.; Farrukh, M. A.; Mohamed, A. S.

    2015-11-01

    Al-doped ZnO (AZO) thin films were potentiostatically deposited on indium tin oxide substrates. The influence of the doping level of the ZnO:Al films was investigated. The results of the X-ray diffraction and scanning electron microscopy analysis revealed that the structural properties of the AZO films were found polycrystalline with a hexagonal wurtzite-type structure along the (002) plane. The grain size of the AZO films was observed as approximately 3 μm in the film doping with 4 mol% ZnO:Al concentration. The thin films also exhibited an optical transmittance as high as 90 % in the wavelength range of 100-1,000 nm. The optical band gap increased from 3.33 to 3.45 eV. Based on the Hall studies, the lowest resistivity (4.78 × 10-3 Ω cm) was observed in the film doping with 3 mol% ZnO:Al concentration. The sheet resistant, carrier concentration and Hall mobility values were found as 10.78 Ω/ square, 9.03 × 1018 cm-3 and 22.01 cm2/v s, respectively, which showed improvements in the properties of AZO thin films. The ZnO:Al thin films were used as a buffer layer in thin-film solar cells with the structure of soda-lime glass/Mo/Cu2ZnSnS4/ZnS/ZnO/Al grid. The best solar cell efficiency was 2.3 % with V OC of 0.430 V, J SC of 8.24 mA cm-2 and FF of 68.1 %.

  10. 700 keV Ni+2 ions induced modification in structural, surface, magneto-optic and optical properties of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Fiaz Khan, M.; Siraj, K.; Anwar, M. S.; Irshad, M.; Hussain, J.; Faiz, H.; Majeed, S.; Dosmailov, M.; Patek, J.; Pedarnig, J. D.; Rafique, M. S.; Naseem, S.

    2016-02-01

    We investigate the effect of 700 keV Ni+2 ions irradiation at different ion fluences (1 × 1013, 1 × 1014, 2 × 1014, 5 × 1014 ions/cm2) on the structural, surface, magneto-optic and optical properties of ZnO thin films. The X-ray diffraction (XRD) results show improved crystallinity when ion fluence is increased to 2 × 1014 ions/cm2, while deterioration is observed at the highest ion fluence of 5 × 1014 ions/cm2. Scanning electron micrographs (SEM) show the formation of small grains at ion fluence 1 × 1013 ions/cm2, micro-rods at fluences 1 × 1014 and 2 × 1014 ions/cm2 and ultimate fracturing of thin film surface at ion fluence 5 × 1014 ions/cm2. Faraday rotation measurements are also performed and show a decrease in Verdet constant from 53 to 31 rad/(T-m) when irradiated at 1 × 1013 ions/cm2, increasing up to 45 rad/(T-m) at 2 × 1014 ions/cm2, and then decreasing again to 36 rad/(T-m) at 5 × 1014 ions/cm2. The optical band gap energy of the films is determined using spectroscopic ellipsometry, which shows an increase in optical band gap energy (Eg) from 3.04 eV to 3.19 eV when the fluence increases to 2 × 1014 ions/cm2 and a decrease to 3 eV at fluence 5 × 1014 ions/cm2. We argue that these properties can be explained using ion heating effect of thin films.

  11. Effect of cation and anion defects on the resistive switching polarity of ZnO x thin films

    NASA Astrophysics Data System (ADS)

    Wu, Xinghui; Xu, Zhimou; Liu, Binbing; Sun, Tangyou; Zhao, Wenning; Liu, Sisi; Ma, Zhichao; Zhao, Fei; Wang, Shuangbao; Zhang, Xueming; Liu, Shiyuan; Peng, Jing

    2013-04-01

    In this paper, we achieve the resistive switching (RS) polarity from unipolar to bipolar in a simple Al/ZnO x /Al structure by moderating the oxygen content in the ZnO sputtering process. In a pure Ar sputtering, Al/ZnO x /Al shows unipolar behavior, as oxygen partial pressure increases, the RS polarity changes to bipolar, and the switch current decreases by about five orders of magnitude. The current transport properties of unipolar device show ohmic behavior under both high resistance (HRS) and low resistance states (LRS), but the bipolar device shows Schottky barrier modulated current transport properties. We study the defect types in the unipolar and bipolar devices through photoluminescence (PL) spectra. The PL results show that the interstitial zinc (Zni) and interstitial oxygen (Oi) are dominant in unipolar and bipolar devices, respectively. We attribute this phenomenon to Zni and Oi playing important role in unipolar (URS) and bipolar resistive switching (BRS), respectively.

  12. Effect of cation and anion defects on the resistive switching polarity of ZnO x thin films

    NASA Astrophysics Data System (ADS)

    Wu, Xinghui; Xu, Zhimou; Liu, Binbing; Sun, Tangyou; Zhao, Wenning; Liu, Sisi; Ma, Zhichao; Zhao, Fei; Wang, Shuangbao; Zhang, Xueming; Liu, Shiyuan; Peng, Jing

    2014-03-01

    In this paper, we achieve the resistive switching (RS) polarity from unipolar to bipolar in a simple Al/ZnO x /Al structure by moderating the oxygen content in the ZnO sputtering process. In a pure Ar sputtering, Al/ZnO x /Al shows unipolar behavior, as oxygen partial pressure increases, the RS polarity changes to bipolar, and the switch current decreases by about five orders of magnitude. The current transport properties of unipolar device show ohmic behavior under both high resistance (HRS) and low resistance states (LRS), but the bipolar device shows Schottky barrier modulated current transport properties. We study the defect types in the unipolar and bipolar devices through photoluminescence (PL) spectra. The PL results show that the interstitial zinc (Zni) and interstitial oxygen (Oi) are dominant in unipolar and bipolar devices, respectively. We attribute this phenomenon to Zni and Oi playing important role in unipolar (URS) and bipolar resistive switching (BRS), respectively.

  13. Reversible Change in Electrical and Optical Properties in Epitaxially Grown Al-Doped ZnO Thin Films

    SciTech Connect

    Noh, J. H.; Jung, H. S.; Lee, J. K.; Kim, J. Y; Cho, C. M.; An, J.; Hong, K. S.

    2008-01-01

    Aluminum-doped ZnO (AZO) films were epitaxially grown on sapphire (0001) substrates using pulsed laser deposition. As-deposited AZO films had a low resistivity of 8.01 x 10{sup -4} {Omega} cm. However, after annealing at 450 C in air, the electrical resistivity of the AZO films increased to 1.97 x 10{sup -1} {Omega} cm because of a decrease in the carrier concentration. Subsequent annealing of the air-annealed AZO films in H{sub 2} recovered the electrical conductivity of the AZO films. In addition, the conductivity change was reversible upon repeated air and H{sub 2} annealing. A photoluminescence study showed that oxygen interstitial (O{sub i}) is a critical material parameter allowing for the reversible control of the electrical conducting properties of AZO films.

  14. Effects of NIR annealing on the characteristics of al-doped ZnO thin films prepared by RF sputtering.

    PubMed

    Jun, Min-Chul; Koh, Jung-Hyuk

    2012-01-01

    Aluminum-doped zinc oxide (AZO) thin films have been deposited on glass substrates by employing radio frequency (RF) sputtering method for transparent conducting oxide applications. For the RF sputtering process, a ZnO:Al2O3 (2 wt.%) target was employed. In this paper, the effects of near infrared ray (NIR) annealing technique on the structural, optical, and electrical properties of the AZO thin films have been researched. Experimental results showed that NIR annealing affected the microstructure, electrical resistance, and optical transmittance of the AZO thin films. X-ray diffraction analysis revealed that all films have a hexagonal wurtzite crystal structure with the preferentially c-axis oriented normal to the substrate surface. Optical transmittance spectra of the AZO thin films exhibited transmittance higher than about 80% within the visible wavelength region, and the optical direct bandgap (Eg) of the AZO films was increased with increasing the NIR energy efficiency. PMID:22673232

  15. Effects of NIR annealing on the characteristics of al-doped ZnO thin films prepared by RF sputtering

    PubMed Central

    2012-01-01

    Aluminum-doped zinc oxide (AZO) thin films have been deposited on glass substrates by employing radio frequency (RF) sputtering method for transparent conducting oxide applications. For the RF sputtering process, a ZnO:Al2O3 (2 wt.%) target was employed. In this paper, the effects of near infrared ray (NIR) annealing technique on the structural, optical, and electrical properties of the AZO thin films have been researched. Experimental results showed that NIR annealing affected the microstructure, electrical resistance, and optical transmittance of the AZO thin films. X-ray diffraction analysis revealed that all films have a hexagonal wurtzite crystal structure with the preferentially c-axis oriented normal to the substrate surface. Optical transmittance spectra of the AZO thin films exhibited transmittance higher than about 80% within the visible wavelength region, and the optical direct bandgap (Eg) of the AZO films was increased with increasing the NIR energy efficiency. PMID:22673232

  16. Ethanol-enriched low-pressure chemical vapor deposition ZnO bilayers: Properties and growth—A potential electrode for thin film solar cells

    NASA Astrophysics Data System (ADS)

    Messerschmidt, Daniel; Nicolay, Sylvain; Ding, Laura; Bugnon, Gregory; Meillaud, Fanny; Eberhardt, Jens; Ballif, Christophe

    2013-01-01

    Ethanol is used as a precursor during the growth of zinc oxide (ZnO) by low-pressure chemical vapor deposition (LPCVD). By adding ethanol, the surface of the deposited ZnO layer is flattened and its roughness is decreased about sevenfold. The layers become increasingly stressed and their resistivity grows significantly. We propose an explanation for the observed behavior based on the catalytic decomposition of ethanol at the ZnO surface and on the growth of selected crystal planes. By using ethanol for the last 10% of the total ZnO layer growth only, sheet resistance is maintained and roughness is slightly decreased. Our results indicate that such LPCVD ZnO bilayers could be a promising method to modify the ZnO surface morphology before cell deposition, thus, providing an alternative to argon plasma treatment, which is typically reported to improve solar cell parameters such as open-circuit voltage and fill factor.

  17. Ag Doping Effects on Y0.5Gd0.5Ba2Cu3O7-δ multilayers derived by low-fluorine metalorganic solution deposition

    NASA Astrophysics Data System (ADS)

    Sun, M. J.; Yang, W. T.; Liu, Z. Y.; Bai, C. Y.; Guo, Y. Q.; Lu, Y. M.; Lu, Q.; Cai, C. B.

    2015-09-01

    Various artificial multilayers consisting of Y0.5Gd0.5Ba2Cu3O7-δ (YGdBCO) superconducting films were built up on an oxide buffered Hastelloy substrate using the low-fluorine metallorganic deposition method (MOD). Microscopic and superconducting performances are studied on composite YGdBCO multilayer films with and without alternate ultrathin layers of Ag, which comparatively demonstrates the Ag doping effects in such architectures. X-ray diffraction and scanning electron microscopy imply that the growth thermodynamic parameters of the YGdBCO are modified, resulting in a better c-axis orientation and a higher in-plane texture, as well as a superior surface, and finally give rise to great improvement of superconducting performance. To understand the above Ag doping effects further, the critical Gibbs free energy ΔG*(r) on nucleation of MOD-YGdBCO films on the biaxially textured buffer layers is analyzed with respect to the additions of Ag, which shows the competition between a-axis and c-axis growths subject to supersaturation. As a consequence, Ag additions may reduce the supersaturation at the growth interfaces, and hence give rise to a wider window of c-axis nucleation.

  18. Origins of Highly Stable Al-evaporated Solution-processed ZnO Thin Film Transistors: Insights from Low Frequency and Random Telegraph Signal Noise.

    PubMed

    Kim, Joo Hyung; Kang, Tae Sung; Yang, Jung Yup; Hong, Jin Pyo

    2015-01-01

    One long-standing goal in the emerging field of flexible and transparent electronic devices is to meet the demand of key markets, such as enhanced output performance for metal oxide semiconductor thin film transistors (TFTs) prepared by a solution process. While solution-based fabrication techniques are cost-effective and ensure large-area coverage at low temperature, their utilization has the disadvantage of introducing large trap states into TFTs. Such states, the formation of which is induced by intrinsic defects initially produced during preparation, have a significant impact on electrical performance. Therefore, the ability to enhance the electrical characteristics of solution-processed TFTs, along with attaining a firm understanding of their physical nature, remains a key step towards extending their use. In this study, measurements of low-frequency noise and random telegraph signal noise are employed as generic alternative tools to examine the origins of enhanced output performance for solution-processed ZnO TFTs through the control of defect sites by Al evaporation. PMID:26525284

  19. Deposition and composition-control of Mn-doped ZnO thin films by combinatorial pulsed laser deposition using two delayed plasma plumes

    SciTech Connect

    Sanchez-Ake, C.; Camacho, R.; Moreno, L.

    2012-08-15

    Thin films of ZnO doped with manganese were deposited by double-beam, combinatorial pulsed laser deposition. The laser-induced plasmas were studied by means of fast photography and using a Langmuir probe, whereas the films were analyzed by x-ray-diffraction and energy-dispersive x-ray spectroscopy. The effect of the relative delay between plasma plumes on the characteristics of the films was analyzed. It was found that using this parameter, it is possible to control the dopant content keeping the oriented wurtzite structure of the films. The minimum content of Mn was found for plume delays between 0 and 10 {mu}s as the interaction between plasmas scatters the dopant species away from the substrate, thus reducing the incorporation of Mn into the films. Results suggest that for delays shorter than {approx}100 {mu}s, the expansion of the second plume through the region behind the first plume affects the composition of the film.

  20. Influence of annealing temperature on photoluminescence properties and optical constants of N-doped ZnO thin films grown on muscovite mica substrates

    NASA Astrophysics Data System (ADS)

    Kim, Younggyu; Leem, Jae-Young

    2015-11-01

    A sol-gel spin-coating method was used to synthesize N-doped ZnO (NZO) thin films on muscovite mica substrates; the films were then annealed at 200, 300, 400, and 500 °C. The effects of the annealing temperature on their photoluminescence properties and optical constants were investigated. All the films had strong UV emissions in their photoluminescence spectra, but the green emissions at ~2.4 eV were observed only for the annealed films. The average transmittance of all the films was about 80% in the visible range and the absorption edges in the UV range at 375 nm depended strongly on the annealing temperature. The optical band gap of the films decreased gradually as the annealing temperature was increased up to 400 °C, and the Urbach energy decreased significantly as the annealing temperature increased. Finally, the various optical constants, the dielectric constant, and the optical conductivity were measured for the un-annealed film and the film annealed at 500 °C.

  1. Effect of Channel Thickness, Annealing Temperature and Channel Length on Nanoscale Ga2O3-In2O3-ZnO Thin Film Transistor Performance.

    PubMed

    Kumaresan, Yogeenth; Pak, Yusin; Lim, Namsoo; Lee, Ryeri; Song, Hui; Kim, Tae Heon; Choi, Boran; Jung, Gun Young

    2016-06-01

    We demonstrated the effect of active layer (channel) thickness and annealing temperature on the electrical performances of Ga2O3-In2O3-ZnO (GIZO) thin film transistor (TFT) having nanoscale channel width (W/L: 500 nm/100 μm). We found that the electron carrier concentration of the channel was decreased significantly with increasing the annealing temperature (100 degrees C to 300 degrees C). Accordingly, the threshold voltage (V(T)) was shifted towards positive voltage (-12.2 V to 10.8 V). In case of channel thickness, the V(T) was shifted towards negative voltage with increasing the channel thickness. The device with channel thickness of 90 nm annealed at 200 degrees C revealed the best device performances in terms of mobility (10.86 cm2/Vs) and V(T) (0.8 V). The effect of channel length was also studied, in which the channel width, thickness and annealing temperature were kept constant such as 500 nm, 90 nm and 200 degrees C, respectively. The channel length influenced the on-current level significantly with small variation of V(T), resulting in lower value of on/off current ratio with increasing the channel length. The device with channel length of 0.5 μm showed enhanced on/off current ratio of 10(6) with minimum V(T) of 0.26 V. PMID:27427719

  2. Origins of Highly Stable Al-evaporated Solution-processed ZnO Thin Film Transistors: Insights from Low Frequency and Random Telegraph Signal Noise

    PubMed Central

    Kim, Joo Hyung; Kang, Tae Sung; Yang, Jung Yup; Hong, Jin Pyo

    2015-01-01

    One long-standing goal in the emerging field of flexible and transparent electronic devices is to meet the demand of key markets, such as enhanced output performance for metal oxide semiconductor thin film transistors (TFTs) prepared by a solution process. While solution-based fabrication techniques are cost-effective and ensure large-area coverage at low temperature, their utilization has the disadvantage of introducing large trap states into TFTs. Such states, the formation of which is induced by intrinsic defects initially produced during preparation, have a significant impact on electrical performance. Therefore, the ability to enhance the electrical characteristics of solution-processed TFTs, along with attaining a firm understanding of their physical nature, remains a key step towards extending their use. In this study, measurements of low-frequency noise and random telegraph signal noise are employed as generic alternative tools to examine the origins of enhanced output performance for solution-processed ZnO TFTs through the control of defect sites by Al evaporation. PMID:26525284

  3. Origins of Highly Stable Al-evaporated Solution-processed ZnO Thin Film Transistors: Insights from Low Frequency and Random Telegraph Signal Noise

    NASA Astrophysics Data System (ADS)

    Kim, Joo Hyung; Kang, Tae Sung; Yang, Jung Yup; Hong, Jin Pyo

    2015-11-01

    One long-standing goal in the emerging field of flexible and transparent electronic devices is to meet the demand of key markets, such as enhanced output performance for metal oxide semiconductor thin film transistors (TFTs) prepared by a solution process. While solution-based fabrication techniques are cost-effective and ensure large-area coverage at low temperature, their utilization has the disadvantage of introducing large trap states into TFTs. Such states, the formation of which is induced by intrinsic defects initially produced during preparation, have a significant impact on electrical performance. Therefore, the ability to enhance the electrical characteristics of solution-processed TFTs, along with attaining a firm understanding of their physical nature, remains a key step towards extending their use. In this study, measurements of low-frequency noise and random telegraph signal noise are employed as generic alternative tools to examine the origins of enhanced output performance for solution-processed ZnO TFTs through the control of defect sites by Al evaporation.

  4. Plasma-assisted hot filament chemical vapor deposition of AlN thin films on ZnO buffer layer: toward highly c-axis-oriented, uniform, insulative films

    NASA Astrophysics Data System (ADS)

    Alizadeh, M.; Mehdipour, H.; Ganesh, V.; Ameera, A. N.; Goh, B. T.; Shuhaimi, A.; Rahman, S. A.

    2014-12-01

    c-Axis-oriented aluminum nitride (AlN) thin film with improved quality was deposited on Si(111) substrate using ZnO buffer layer by plasma-assisted hot filament chemical vapor deposition. The optical and electrical properties and surface morphology as well as elemental composition of the AlN films deposited with and without ZnO buffer layer were investigated using a host of measurement techniques: X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, field emission scanning electron microscopy (FESEM), and current-voltage (I-V) characteristic measurement. The XRD and XPS results reveal that the AlN/ZnO/Si films are free of metallic Al particles. Also, cross-sectional FESEM observations suggest formation of a well-aligned, uniform, continuous, and highly (002) oriented structure for a bi-layered AlN film when Si(111) is covered with ZnO buffer. Moreover, a decrease in full width at half maximum of the E2 (high)-mode peak in Raman spectrum indicates a better crystallinity for the AlN films formed on ZnO/Si substrate. Finally, I-V curves obtained indicate that the electrical behavior of the AlN thin films switches from conductive to insulative when film is grown on a ZnO-buffered Si substrate.

  5. 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.

  6. Microstructure and micromorphology of ZnO thin films: Case study on Al doping and annealing effects

    NASA Astrophysics Data System (ADS)

    Ţălu, Ştefan; Bramowicz, Miroslaw; Kulesza, Slawomir; Solaymani, Shahram; Ghaderi, Atefeh; Dejam, Laya; Elahi, Seyed Mohammad; Boochani, Arash

    2016-05-01

    The aim of this work is to investigate the three-dimensional (3-D) surface texture of Aliminium doped Zinc Oxide (AZO) thin films deposited by Radio Frequency sputtering method on the quartz substrates. Deposited samples were annealed under argon flux at three different temperatures: 400 °C, 500 °C, and 600 °C, followed by gradual cooling down to room temperature. To characterize the structure of samples X-ray diffraction (XRD) patterns and Rutherford Back Scattering (RBS) spectra were applied. The Scanning electron microscope (SEM) and the atomic force microscope (AFM) were applied to study the samples' surface morphology. Then statistical, fractal and functional surface characteristics were computed. The analysis of 3-D surface texture of AZO thin films is crucial to control the 3-D surface topography features and to correct interpretate the surface topographic parameters. It also allows understanding the relationship between 3-D the surface topography and the functional (physical, chemical and mechanical) properties of AZO thin films.

  7. Sol-gel production of p-type ZnO thin film by using sodium doping

    NASA Astrophysics Data System (ADS)

    Bu, Ian Y. Y.

    2016-08-01

    In this study, ZnO:Na thin films doped with 1-5 at.% of Na were synthesized on glass substrates by the sol-gel deposition technique. The morphology and optoelectronic properties of the thin films were characterized by using the environmental scanning electron microscope (SEM), X-ray diffraction (XRD), UV-Vis spectroscopy and Hall effect measurements. The SEM images and XRD pattern both indicated a substantial change in the film structure as the Na content increases due to the oversupply of the OH- ions in the initial precursor solution. UV-Vis spectroscopy measurements revealed that the increase in Na doping resulted in the decreases of the optical transmittance and the optical band gap due to the formation recombination centers. Hall effect measurements confirmed that the ZnO:Na films doped with >2 at.% of Na are stable with p-type conduction behaviour. As a demonstration, a ZnO-based junction was fabricated using the synthesized ZnO:Na/ZnO thin films on indium tin oxide glass substrates.

  8. Room-temperature NH3 gas sensors based on Ag-doped γ-Fe2O3/SiO2 composite films with sub-ppm detection ability.

    PubMed

    Tang, Yongliang; Li, Zhijie; Zu, Xiaotao; Ma, Jinyi; Wang, Lu; Yang, Jing; Du, Bo; Yu, Qingkai

    2015-11-15

    In this report, NH3 gas sensors based on Ag-doped γ-Fe2O3/SiO2 composite films are investigated. The composite films were prepared with a sol-gel process, and the films' electrical resistance responded to the change of NH3 concentration in the environment. The SEM and AFM investigations showed that the films had a porous structure, and the XRD investigation indicated that the size of Ag particles changed with the modification of Ag loading content. Through a comparative gas sensing study among the Ag-doped composite films, undoped composite film, γ-Fe2O3 film, and SiO2 film, the Ag-doped composite films were found to be much more sensitive than the sensors based on the undoped composite film and γ-Fe2O3 film at room temperature, indicating the significant influences of the SiO2 and Ag on the sensing property. Moreover, the sensor based on Ag-doped (4%) γ-Fe2O3/SiO2 composite film was able to detect the NH3 gas at ppb level. Conversely, the responses of the sensor to other test gases (C2H5OH, CO, H2, CH4 and H2S) were all markedly low, suggesting excellent selectivity. PMID:26057440

  9. Hydrogen induced electric conduction in undoped ZnO and Ga-doped ZnO thin films: Creating native donors via reduction, hydrogen donors, and reactivating extrinsic donors

    SciTech Connect

    Akazawa, Housei

    2014-09-01

    The manner in which hydrogen atoms contribute to the electric conduction of undoped ZnO and Ga-doped ZnO (GZO) films was investigated. Hydrogen atoms were permeated into these films through annealing in an atmospheric H{sub 2} ambient. Because the creation of hydrogen donors competes with the thermal annihilation of native donors at elevated temperatures, improvements to electric conduction from the initial state can be observed when insulating ZnO films are used as samples. While the resistivity of conductive ZnO films increases when annealing them in a vacuum, the degree of increase is mitigated when they are annealed in H{sub 2}. Hydrogenation of ZnO crystals was evidenced by the appearance of OH absorption signals around a wavelength of 2700 nm in the optical transmittance spectra. The lowest resistivity that was achieved by H{sub 2} annealing was limited to 1–2 × 10{sup −2} Ω cm, which is one order of magnitude higher than that by native donors (2–3 × 10{sup −3} Ω cm). Hence, all native donors are converted to hydrogen donors. In contrast, GZO films that have resistivities yet to be improved become more conductive after annealing in H{sub 2} ambient, which is in the opposite direction of GZO films that become more resistive after vacuum annealing. Hydrogen atoms incorporated into GZO crystals should assist in reactivating Ga{sup 3+} donors.

  10. Compositional study of vacuum annealed Al doped ZnO thin films obtained by RF magnetron sputtering

    SciTech Connect

    Shantheyanda, B. P.; Todi, V. O.; Sundaram, K. B.; Vijayakumar, A.; Oladeji, I.

    2011-09-15

    Aluminum doped zinc oxide (AZO) thin films were obtained by RF magnetron sputtering. The effects of deposition parameters such as power, gas flow conditions, and substrate heating have been studied. Deposited and annealed films were characterized for composition as well as microstructure using x ray photoelectron spectroscopy and x ray diffraction. Films produced were polycrystalline in nature. Surface imaging and roughness studies were carried out using SEM and AFM, respectively. Columnar grain growth was predominantly observed. Optical and electrical properties were evaluated for transparent conducting oxide applications. Processing conditions were optimized to obtain highly transparent AZO films with a low resistivity value of 6.67 x 10{sup -4}{Omega} cm.

  11. Fabrication of tantalum and nitrogen codoped ZnO (Ta, N-ZnO) thin films using the electrospay: twin applications as an excellent transparent electrode and a field emitter.

    PubMed

    Mahmood, Khalid; Park, Seung Bin; Sung, Hyung Jin

    2013-05-01

    The realization of stable p-type nitrogen-doped ZnO thin films with durable and controlled growth is important for the fabrication of nanoscale electronic and optoelectronic devices. ZnO thin films codoped with tantalum and nitrogen (Ta, N-ZnO) were fabricated by using the electrospraying method at an atmospheric pressure. X-ray diffraction (XRD) studies demonstrated that all the prepared films were polycrystalline in nature with hexagonal wurtzite structure. In addition, a shift in the XRD patterns was observed, and the crystal orientation was changed at a certain amount of nitrogen (>6 at.%) in the starting solution. Analysis of X-ray diffraction patterns and X-ray photoelectron spectra revealed that nitrogen which was combined with the zinc atom (N-Zn) was successfully doped into the ZnO crystal lattice. It was also observed that 2 at.% tantalum and 6 at.% nitrogen (2 at.% Ta and 6 at.% N) were the optimal dopant amounts to achieve the minimum resistivity of about 9.70 × 10(-5) Ω cm and the maximum transmittance of 98% in the visible region. Consequently, the field-emission characteristics of such a Ta, N-ZnO emitter can exhibit the higher current density of 1.33 mA cm(-2), larger field-enhancement factor (β) of 4706, lower turn-on field of 2.6 V μm(-1), and lower threshold field of 3.5 V μm(-1) attributed to the enhanced conductivity and better crystallinity of films. Moreover, the obtained values of resistivity were closest to the lowest resistivity values among the doped ZnO films as well as to the indium tin oxide (ITO) resistivity values that were previously studied. We confirmed that the tantalum and nitrogen atoms substitution in the ZnO lattice induced positive effects in terms of enhancing the free carrier concentration which will further improve the electrical, optical, and field-emission properties. The proposed electrospraying method was well suitable for the fabrication of Ta, N-ZnO thin films at optimum conditions with superior electrical

  12. Improving yield and performance in ZnO thin-film transistors made using selective area deposition.

    PubMed

    Nelson, Shelby F; Ellinger, Carolyn R; Levy, David H

    2015-02-01

    We describe improvements in both yield and performance for thin-film transistors (TFTs) fabricated by spatial atomic layer deposition (SALD). These improvements are shown to be critical in forming high-quality devices using selective area deposition (SAD) as the patterning method. Selective area deposition occurs when the precursors for the deposition are prevented from reacting with some areas of the substrate surface. Controlling individual layer quality and the interfaces between layers is essential for obtaining good-quality thin-film transistors and capacitors. The integrity of the gate insulator layer is particularly critical, and we describe a method for forming a multilayer dielectric using an oxygen plasma treatment between layers that improves crossover yield. We also describe a method to achieve improved mobility at the important interface between the semiconductor and the gate insulator by, conversely, avoiding oxygen plasma treatment. Integration of the best designs results in wide design flexibility, transistors with mobility above 15 cm(2)/(V s), and good yield of circuits. PMID:25562441

  13. Aging effects of the precursor solutions on the properties of spin coated Ga-doped ZnO thin films

    SciTech Connect

    Serrao, Felcy Jyothi Dharmaprakash, S. M.

    2015-06-24

    In this study, gallium doped zinc oxide thin films (GZO) were grown on a glass substrate by a simple sol-gel process and spin coating technique using zinc acetate and gallium nitrate (3at%) as precursors for Zn and Ga ions respectively. The effects of aging time of the precursor solution on the structural and optical properties of the GZO films were investigated. The surface morphology, grain size, film thickness and optical properties of the GZO films were found to depend directly on the sol aging time. XRD studies reveal that the films are polycrystalline with a hexagonal wurtzite structure and show the c-axis grain orientation. Optical transmittance spectra of all the films exhibited transmittance higher than about 82% within the visible wavelength region. A sharp fundamental absorption edge with a slight blue shifting was observed with an increase in sol aging time which can be explained by Burstein-Moss effect. The result indicates that an appropriate aging time of the sol is important for the improvement of the structural and optical properties of GZO thin films derived from sol-gel method.

  14. Zinc vacancy and erbium cluster jointly promote ferromagnetism in erbium-doped ZnO thin film

    SciTech Connect

    Chen, Hong-Ming; Zhou, Ren-Wei; Li, Fei; Liu, Xue-Chao Zhuo, Shi-Yi; Shi, Er-Wei; Xiong, Ze

    2014-04-15

    Zn{sub 1-x}Er{sub x}O (0.005 ≤ x ≤ 0.04) thin films have been prepared by inductively coupled plasma enhanced physical vapor deposition method. Ferromagnetism, crystal structure, microstructure and photoluminescence properties of the films were characterized. It is found that the chemical valence state of Er is trivalent, and the Er{sup 3+} cations play an important role in ferromagnetism. Both saturated magnetization (M{sub s}) and zinc vacancy (V{sub Zn}) are decreased with the increase of x from 0.005 to 0.03. However, further increasing x to 0.04, the M{sub s} is quenched due to the generation of Er clusters. It reveals that the intensity of M{sub s} is not only associated with the V{sub Zn} concentration, but also related to the Er clusters. The V{sub Zn} concentration and the Er clusters can jointly boost the ferromagnetism in the Zn{sub 1-x}Er{sub x}O thin films.

  15. High-Pressure Synthesis and Superconductivity of Ag-Doped Topological Crystalline Insulator SnTe (Sn1-xAgxTe with x = 0-0.5)

    NASA Astrophysics Data System (ADS)

    Mizuguchi, Yoshikazu; Miura, Osuke

    2016-05-01

    We have synthesized single-phase polycrystalline samples of Sn1-xAgxTe, i.e., the Ag-doped topological crystalline insulator SnTe, with a range of x ≤ 0.5 by a high-pressure synthesis method. The crystal structure of Sn1-xAgxTe at room temperature is a cubic NaCl type structure, which does not vary upon Ag substitution. Bulk superconductivity with a transition temperature of 2.4 K was observed for x = 0.15-0.25, and the optimal Ag content was x = 0.2. The Sn1-xAgxTe superconducting phase will be useful for understanding the superconductive nature and mechanisms of the carrier-doped SnTe system.

  16. Deposition, structure, physical and invitro characteristics of Ag-doped β-Ca3(PO4)2/chitosan hybrid composite coatings on Titanium metal.

    PubMed

    Singh, Ram Kishore; Awasthi, Sharad; Dhayalan, Arunkumar; Ferreira, J M F; Kannan, S

    2016-05-01

    Pure and five silver-doped (0-5Ag) β-tricalcium phosphate [β-TCP, β-Ca3(PO4)2]/chitosan composite coatings were deposited on Titanium (Ti) substrates and their properties that are relevant for applications in hard tissue replacements were assessed. Silver, β-TCP and chitosan were combined to profit from their salient and complementary antibacterial and biocompatible features.The β-Ca3(PO4)2 powders were synthesized by co-precipitation. The characterization results confirmed the Ag(+) occupancy at the crystal lattice of β-Ca3(PO4)2. The Ag-dopedβ-Ca3(PO4)2/chitosan composite coatings deposited by electrophoresis showed good antibacterial activity and exhibited negative cytotoxic effects towards the human osteosarcoma cell line MG-63. The morphology of the coatings was observed by SEM and their efficiency against corrosion of metallic substrates was determined through potentiodynamic polarization tests. PMID:26952474

  17. One-pot synthesis of Ag+ doped BiVO4 microspheres with enhanced photocatalytic activity via a facile hydrothermal method

    NASA Astrophysics Data System (ADS)

    Zhu, Shiwen; Li, Quanguo; Li, Feng; Cao, Wei; Li, Taohai

    2016-05-01

    The Ag+/BiVO4 photocatalyst was fabricated through a facile hydrothermal method by using K6V10O28·9H2O as the vanadium source. The impact of Ag+ on the product's structure and morphology was studied. It was shown that the amount of Ag+ has no effect on the product's crystal phases but plays an important role on the morphology of the nanoparticles that construct the shell of BiVO4 microspheres. In addition, the Ag+-doped photocatalysts have much higher photocatalytic activities in removing RhB and MB under the UV light illumination than the pure BiVO4. A possible photocatalytic mechanism was proposed in photoexcitation of the BiVO4 electrons which subsequently captured by the dopant. The present work may offer a novel route to reach higher photocatalytic activity by doping the Ag+ in the semiconductor catalysts.

  18. Investigation of the antibacterial effects of silver-modified TiO2 and ZnO plasmonic photocatalysts embedded in polymer thin films.

    PubMed

    Tallósy, Szabolcs Péter; Janovák, László; Ménesi, Judit; Nagy, Elisabeth; Juhász, Ádám; Balázs, László; Deme, István; Buzás, Norbert; Dékány, Imre

    2014-10-01

    Nanosilver-modified TiO2 and ZnO photocatalysts were studied against methicillin-resistant Staphylococcus aureus on the surface and against naturally occurring airborne microorganisms. The photocatalysts/polymer nanohybrid films were prepared by spray coating technique on the surface of glass plates and on the inner surface of the reactive light source. The photoreactive surfaces were activated with visible light emitting LED light at λ = 405 nm. The optical properties of the prepared photocatalyst/polymer nanohybrid films were characterized by diffuse reflectance measurements. The photocatalytic properties were verified with the degradation of ethanol by gas chromatography measurements. The destruction of the bacterial cell wall component was examined with transmission electron microscope. The antibacterial effect of the photocatalyst/polymer nanohybrid films was tested with different methods and with the associated standard ISO 27447:2009. With the photoreactive coatings, an extensive disinfectant film was developed and successfully prepared. The cell wall component of S. aureus was degraded after 1 h of illumination. The antibacterial effect of the nanohybrid films has been proven by measuring the decrease of the number of methicillin-resistant S. aureus on the surface and in the air as the function of illumination time. The photocatalyst/polymer nanohybrid films could inactivate 99.9 % of the investigated bacteria on different thin films after 2 h of illumination with visible light source. The reactive light source with the inner-coated photocatalyst could kill 96 % of naturally occurring airborne microorganisms after 48 h of visible light illumination in indoor air sample. The TEM results and the microbiological measurements were completed with toxicity tests carried out with Vibrio fischeri bioluminescence bacterium. PMID:24497305

  19. Synthesis of Ag-doped TiO2 nanoparticles by combining laser decomposition of titanium isopropoxide and ablation of Ag for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Al-Kamal, Ahmed Kamal

    Nanostructured powders of TiO2 and Ag-doped TiO2 are synthesized by a novel pulsed-laser process that combines laser ablation of a silver (Ag) disc with laser decomposition of a titanium tetra-isopropoxide (TTIP) solution. Nanoparticles are formed by rapid condensation of vaporized species in the plasma plume generated by the high power laser, resulting in the formation of rapidly quenched Ag-doped TiO2 nanoparticles that have far-from-equilibrium or metastable structures. The uniqueness of the new ablation process is that it is a one-step process, in contrast to the two-step process developed by previous researchers in the field. Moreover, its ability to synthesize an extended-solid solution phase of Ag in TiO 2 may also be unique. The present work implies that other oxide phases, such as Al2O3, MgO and MgAl2O4, can be doped with normally insoluble metals, such as Pt and Ir, thus opening new opportunities for catalytic applications. Again, there is the prospect of being able to synthesize nanopowders of diamond, c-BN, and mixtures thereof, which are of interest for applications in machine tools, rock-drill bits, and lightweight armor. A wet-chemistry method is also investigated, which has much in common with that adopted by previous workers in the field. However, photo-voltaic properties do not measure up to expectations based on published data. A possible explanation is that the selected Ag concentrations are too high, so that recombination of holes and electrons occurs via a quantum-tunneling mechanism reduces photo-activity. Future work, therefore, will investigate lower concentrations of Ag dopant in TiO2, while also examining the effects of metastable states, including extended solid solution, amorphous, and semi-crystalline structures.

  20. Obtaining strong ferromagnetism in diluted Gd-doped ZnO thin films through controlled Gd-defect complexes

    SciTech Connect

    Roqan, I. S. Venkatesh, S.; Zhang, Z.; Hussain, S.; Bantounas, I.; Flemban, T. H.; Schwingenschlogl, U.; Franklin, J. B.; Zou, B.; Petrov, P. K.; Ryan, M. P.; Alford, N. M.; Lee, J.-S.

    2015-02-21

    We demonstrate the fabrication of reproducible long-range ferromagnetism (FM) in highly crystalline Gd{sub x}Zn{sub 1−x}O thin films by controlling the defects. Films are grown on lattice-matched substrates by pulsed laser deposition at low oxygen pressures (≤25 mTorr) and low Gd concentrations (x ≤ 0.009). These films feature strong FM (10 μ{sub B} per Gd atom) at room temperature. While films deposited at higher oxygen pressure do not exhibit FM, FM is recovered by post-annealing these films under vacuum. These findings reveal the contribution of oxygen deficiency defects to the long-range FM. We demonstrate the possible FM mechanisms, which are confirmed by density functional theory study, and show that Gd dopants are essential for establishing FM that is induced by intrinsic defects in these films.

  1. Spin wave study and optical properties in Fe-doped ZnO thin films prepared by spray pyrolysis technique

    NASA Astrophysics Data System (ADS)

    Lmai, F.; Moubah, R.; El Amiri, A.; Abid, Y.; Soumahoro, I.; Hassanain, N.; Colis, S.; Schmerber, G.; Dinia, A.; Lassri, H.

    2016-07-01

    We investigate the magnetic and optical properties of Zn1-xFexO (x = 0, 0.03, 0.05, and 0.07) thin films grown by spray pyrolysis technique. The magnetization as a function of temperature [M (T)] shows a prevailing paramagnetic contribution at low temperature. By using spin wave theory, we separate the M (T) curve in two contributions: one showing intrinsic ferromagnetism and one showing a purely paramagnetic behavior. Furthermore, it is shown that the spin wave theory is consistent with ab-initio calculations only when oxygen vacancies are considered, highlighting the key role played by structural defects in the mechanism driving the observed ferromagnetism. Using UV-visible measurements, the transmittance, reflectance, band gap energy, band tail, dielectric coefficient, refractive index, and optical conductivity were extracted and related to the variation of the Fe content.

  2. Achieving Antifingerprinting and Antibacterial Effects in Smart-Phone Panel Applications Using ZnO Thin Films without a Protective Layer.

    PubMed

    Choi, Hyung-Jin; Park, Byeong-Ju; Eom, Ji-Ho; Choi, Min-Ju; Yoon, Soon-Gil

    2016-01-13

    When crystalline ZnO films with a thickness of 30 nm and hydrophilic properties were deposited at room temperature onto a glass substrate via radio frequency sputtering, they exhibited antifingerprinting qualities following annealing treatment that was simple and accomplished at low temperature (100 °C). Hydrophobic properties were achieved using as-deposited ZnO films with hydrophilic properties via annealing treatment without the deposition of a protective layer with hydrophobic properties. The annealed 30 nm ZnO films showed a high transmittance (∼91.3%) comparable to that of a glass substrate at a wavelength of 550 nm. The annealed films showed strong antibacterial activity against E. coli and S. aureus bacteria. The ZnO films with a thickness of 30 nm showed predominant mechanical durability with strong antibacterial activity for smart-phone panel applications. PMID:26691534

  3. Effects of substrate conductivity on cell morphogenesis and proliferation using tailored, atomic layer deposition-grown ZnO thin films

    PubMed Central

    Choi, Won Jin; Jung, Jongjin; Lee, Sujin; Chung, Yoon Jang; Yang, Cheol-Soo; Lee, Young Kuk; Lee, You-Seop; Park, Joung Kyu; Ko, Hyuk Wan; Lee, Jeong-O

    2015-01-01

    We demonstrate that ZnO films grown by atomic layer deposition (ALD) can be employed as a substrate to explore the effects of electrical conductivity on cell adhesion, proliferation, and morphogenesis. ZnO substrates with precisely tunable electrical conductivity were fabricated on glass substrates using ALD deposition. The electrical conductivity of the film increased linearly with increasing duration of the ZnO deposition cycle (thickness), whereas other physical characteristics, such as surface energy and roughness, tended to saturate at a certain value. Differences in conductivity dramatically affected the behavior of SF295 glioblastoma cells grown on ZnO films, with high conductivity (thick) ZnO films causing growth arrest and producing SF295 cell morphologies distinct from those cultured on insulating substrates. Based on simple electrostatic calculations, we propose that cells grown on highly conductive substrates may strongly adhere to the substrate without focal-adhesion complex formation, owing to the enhanced electrostatic interaction between cells and the substrate. Thus, the inactivation of focal adhesions leads to cell proliferation arrest. Taken together, the work presented here confirms that substrates with high conductivity disturb the cell-substrate interaction, producing cascading effects on cellular morphogenesis and disrupting proliferation, and suggests that ALD-grown ZnO offers a single-variable method for uniquely tailoring conductivity. PMID:25897486

  4. Epitaxial growth of ZnO thin films on ScAlMgO 4 (0 0 0 1) by chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Wessler, B.; Steinecker, A.; Mader, W.

    2002-07-01

    Epitaxial zinc oxide films were produced on the low misfit (0.3%) substrate ScAlMgO 4 (0 0 0 1) by chemical solution deposition (CSD). Epitaxial growth of ZnO films was achieved by spin coating a precursor solution of zinc acetate dihydrate and ethanolamine in 2-methoxyethanol, heating at 300°C, then at 500°C, and finally at 850°C. X-ray diffraction ( θ/2 θ-scans/off-axis ϕ-scans) as well as electron diffraction show that the axes a and c of ZnO and ScAlMgO 4 are parallel. The absolute orientation of the ZnO film was determined by electron microdiffraction patterns to be [0 0 0 1¯] . Electron microscopy did not reveal any reaction between film and substrate. The structure of the interface between ZnO and ScAlMgO 4 was characterized in detail by high-resolution TEM methods. Exit wave reconstruction from focus series was carried out to localize the positions of atoms at the interface. It was found that the ZnO film coherently continues the terminating tetrahedral (Mg,Al)O 4 layer of the ScAlMgO 4 substrate to result in an ABAB stacking of the oxygen layers across the interface as in the wurtzite structure. The structural model is in agreement with the absolute orientation of the ZnO film.

  5. Structural and optical properties of dense vertically aligned ZnO nanorods grown onto silver and gold thin films by galvanic effect with iron contamination

    SciTech Connect

    Scarpellini, D.; Paoloni, S.; Medaglia, P.G.; Pizzoferrato, R.; Orsini, A.; Falconi, C.

    2015-05-15

    Highlights: • ZnO nanorods were grown on Au and Ag films in aqueous solution by galvanic effect. • The method is prone to metal contamination which can influence the ZnO properties. • Iron doping improves the lattice matching between ZnO and the substrate. • Energy levels of point defects are lowered and the light emission is red-shifted. • Galvanic-induced nucleation starts and proceeds continuously during the growth. - Abstract: Dense arrays of vertically aligned ZnO nanorods have been grown onto either silver or gold seedless substrates trough a simple hydrothermal method by exploiting the galvanic effect between the substrate and metallic parts. The nanorods exhibit larger bases and more defined hexagonal shapes, in comparison with standard non-galvanic wet-chemistry synthesis. X-ray diffraction (XRD) shows that the iron contamination, associated with the galvanic contact, significantly improves the in-plane compatibility of ZnO with the Au and Ag cubic lattice. Photoluminescence (PL) measurements indicate that the contamination does not affect the number density of localized defects, but lowers their energy levels uniformly; differently, the band-edge emission is not altered appreciably. Finally, we have found that the ZnO hetero-nucleation by galvanic effect initiates at different times in different sites of the substrate area. Our results can be useful for the fabrication of high performance piezonanodevices comprising high-density metal-to-ZnO nanoscaled junctions without intermediate polycrystalline layers.

  6. Fast classification of meat spoilage markers using nanostructured ZnO thin films and unsupervised feature learning.

    PubMed

    Längkvist, Martin; Coradeschi, Silvia; Loutfi, Amy; Rayappan, John Bosco Balaguru

    2013-01-01

    This paper investigates a rapid and accurate detection system for spoilage in meat. We use unsupervised feature learning techniques (stacked restricted Boltzmann machines and auto-encoders) that consider only the transient response from undoped zinc oxide, manganese-doped zinc oxide, and fluorine-doped zinc oxide in order to classify three categories: the type of thin film that is used, the type of gas, and the approximate ppm-level of the gas. These models mainly offer the advantage that features are learned from data instead of being hand-designed. We compare our results to a feature-based approach using samples with various ppm level of ethanol and trimethylamine (TMA) that are good markers for meat spoilage. The result is that deep networks give a better and faster classification than the feature-based approach, and we thus conclude that the fine-tuning of our deep models are more efficient for this kind of multi-label classification task. PMID:23353140

  7. Effects of deposition temperature on the effectiveness of hydrogen doping in Ga-doped ZnO thin films

    SciTech Connect

    Kim, Dong-Ho; Lee, Sung-Hun; Lee, Gun-Hwan; Kim, Hyun-Bum; Kim, Kwang Ho; Lee, Yoon-Gyu; Yu, Tae-Hwan

    2010-07-15

    Gallium-doped zinc oxide thin films were prepared on glass substrates by dc magnetron sputtering under various hydrogen contents in sputtering ambient. The carrier concentration of the films deposited at low-temperatures (80 and 160 deg. C) was increased due to the incorporation of hydrogen atoms, acting as shallow donors. A low resistivity of 4.0x10{sup -4} {Omega} cm was obtained for the film grown at 160 deg. C with H{sub 2} 10%, which has a carrier concentration of 8.2x10{sup 20}/cm{sup 3}. The beneficial effect of hydrogen doping was not observed for the films deposited at 270 deg. C. Both carrier concentration and mobility were decreased by the addition of hydrogen gas in the sputtering ambient. Variations in the electrical transport properties upon vacuum annealing showed that the difference is attributed to the thermal stability of interstitial hydrogen atoms in the films. The hydrogen incorporation was found to induce the lattice expansion and the free carrier absorption in near infrared range. The investigation of the structural and optical properties of the films upon annealing also revealed that the incorporated hydrogen atoms are unstable at high temperature, which is consistent with the results obtained in the electrical properties.

  8. Trajectory effect on the properties of large area ZnO thin films deposited by atmospheric pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Juang, Jia-Yang; Chou, Tung-Sheng; Lin, Hsin-Tien; Chou, Yuan-Fang; Weng, Chih-Chiang

    2014-09-01

    Large area (117 mm × 185 mm) gallium-doped zinc oxide (GZO) films are prepared on glass substrates by atmospheric pressure plasma jet (APPJ) technique. The uniformity of material properties, in particular the electrical resistivity, of the deposited film is of great importance in reducing design complexity of the electron devices. We investigate the effects of scanning trajectory recipe (speed, pitch and number of passes) on structural and electrical properties of GZO thin films. We find that the trajectory has significant effects on the magnitude and uniformity of sheet resistance over the glass substrates. For single pass, the resistance appears higher at the starting part of spray, whereas, for cases of multiple passes, the highest resistance appears in the central part of the substrate. XRD, SEM, Hall measurement and residual stress are used to study the film properties and identify root causes of the nonuniform distribution of sheet resistance. We conclude that annealing time is the dominant root cause of the nonuniform resistance distribution, and other factors such as residual stress and structural characteristics may also have contributions.

  9. Fast Classification of Meat Spoilage Markers Using Nanostructured ZnO Thin Films and Unsupervised Feature Learning

    PubMed Central

    Längkvist, Martin; Coradeschi, Silvia; Loutfi, Amy; Rayappan, John Bosco Balaguru

    2013-01-01

    This paper investigates a rapid and accurate detection system for spoilage in meat. We use unsupervised feature learning techniques (stacked restricted Boltzmann machines and auto-encoders) that consider only the transient response from undoped zinc oxide, manganese-doped zinc oxide, and fluorine-doped zinc oxide in order to classify three categories: the type of thin film that is used, the type of gas, and the approximate ppm-level of the gas. These models mainly offer the advantage that features are learned from data instead of being hand-designed. We compare our results to a feature-based approach using samples with various ppm level of ethanol and trimethylamine (TMA) that are good markers for meat spoilage. The result is that deep networks give a better and faster classification than the feature-based approach, and we thus conclude that the fine-tuning of our deep models are more efficient for this kind of multi-label classification task. PMID:23353140

  10. Superior adsorption performance for triphenylmethane dyes on 3D architectures assembled by ZnO nanosheets as thin as ∼1.5nm.

    PubMed

    Pei, Cuijin; Han, Guoping; Zhao, Yan; Zhao, Hua; Liu, Bin; Cheng, Lijuan; Yang, Heqing; Liu, Shengzhong

    2016-11-15

    The 3-dimensional hierarchical ZnO flower-like architectures have been synthesized in a Zn(Ac)2·2H2O-Na2SeO3-KBH4-pyridine solvothermal system at 100°C for 24h. The flower-like architecture is assembled from ZnO nanosheets with a thickness of ∼1.5nm, and the flower-like architecture specific surface area is 132m(2)/g. When the ZnO flower-like architecture is used as the adsorbent for acid fuschin (AF), malachite green (MG), basic fuchsin (BF), congo red (CR) and acid red (AR) in water, the adsorption capacities for AF, MG, BF, CR and AR are 7154.9, 2587.0, 1377.9, 85.0 and 38.0mg/g, respectively. Evidently, the as-obtained ZnO flower-like architectures show excellent adsorption performances for triphenylmethane dyes, and the adsorption capacity of 7154.9mg/g for AF is the highest of all adsorbents for dyes. The adsorption mechanism can be attributed to the electrostatic attraction and the formation of ion-association complex between triphenylmethane dyes and ZnO hierarchical flower-like architectures. PMID:27493012

  11. ZnO Films with Very High Haze Value for Use as Front Transparent Conductive Oxide Films in Thin-Film Silicon Solar Cells

    NASA Astrophysics Data System (ADS)

    Hongsingthong, Aswin; Krajangsang, Taweewat; Afdi Yunaz, Ihsanul; Miyajima, Shinsuke; Konagai, Makoto

    2010-05-01

    We successfully increased the haze value of zinc oxide (ZnO) films fabricated using metal-organic chemical vapor deposition (MOCVD) by conducting glass-substrate etching before film deposition. It was found that with increasing the glass treatment time, the surface morphology of ZnO films changed from conventional pyramid-like single texture to greater cauliflower-like multi texture. Further, the rms roughness and the haze value of the films increased remarkably. Using ZnO films with a high haze value as front transparent conductive oxide (TCO) films in hydrogenated microcrystalline silicon (µc-Si:H) solar cells, we improved the quantum efficiency of these cells particularly in the long-wavelength region.

  12. Epitaxial ZnO/LiNbO{sub 3}/ZnO stacked layer waveguide for application to thin-film Pockels sensors

    SciTech Connect

    Akazawa, Housei Fukuda, Hiroshi

    2015-05-15

    We produced slab waveguides consisting of a LiNbO{sub 3} (LN) core layer that was sandwiched with Al-doped ZnO cladding layers. The ZnO/LN/ZnO stacked layers were grown on sapphire C-planes by electron cyclotron resonance (ECR) plasma sputtering and were subjected to structural, electrical, and optical characterizations. X-ray diffraction confirmed that the ZnO and LN layers were epitaxial without containing misoriented crystallites. The presence of 60°-rotational variants of ZnO and LN crystalline domains were identified from X-ray pole figures. Cross-sectional transmission electron microscopy images revealed a c-axis orientated columnar texture for LN crystals, which ensured operation as electro-optic sensors based on optical anisotropy along longitudinal and transversal directions. The interfacial roughness between the LN core and ZnO bottom layers as well as that between the ZnO top and the LN core layers was less than 20 nm, which agreed with surface images observed with atomic force microscopy. Outgrowth of triangular LN crystalline domains produced large roughness at the LN film surface. The RMS roughness of the LN film surface was twice that of the same structure grown on sapphire A-planes. Vertical optical transmittance of the stacked films was higher than 85% within the visible and infrared wavelength range. Following the approach adopted by Teng and Man [Appl. Phys. Lett. 56, 1734 (1990)], ac Pockels coefficients of r{sub 33} = 24-28 pm/V were derived for c-axis oriented LN films grown on low-resistive Si substrates. Light propagation within a ZnO/LN/ZnO slab waveguide as well as within a ZnO single layer waveguide was confirmed. The birefringence of these waveguides was 0.11 for the former and 0.05 for the latter.

  13. Enhanced room temperature ferromagnetism in electrodeposited Co-doped ZnO nanostructured thin films by controlling the oxygen vacancy defects

    SciTech Connect

    Simimol, A.; Anappara, Aji A.; Greulich-Weber, S.; Chowdhury, Prasanta; Barshilia, Harish C.

    2015-06-07

    We report the growth of un-doped and cobalt doped ZnO nanostructures fabricated on FTO coated glass substrates using electrodeposition method. A detailed study on the effects of dopant concentration on morphology, structural, optical, and magnetic properties of the ZnO nanostructures has been carried out systematically by varying the Co concentration (c.{sub Co}) from 0.01 to 1 mM. For c.{sub Co }≤ 0.2 mM, h-wurtzite phase with no secondary phases of Co were present in the ZnO nanostructures. For c.{sub Co} ≤ 0.2 mM, the photoluminescence spectra exhibited a decrease in the intensity of ultraviolet emission as well as band-gap narrowing with an increase in dopant concentration. All the doped samples displayed a broad emission in the visible range and its intensity increased with an increase in Co concentration. It was found that the defect centers such as oxygen vacancies and zinc interstitials were the source of the visible emission. The X-ray photoelectron spectroscopy studies revealed, Co was primarily in the divalent state, replacing the Zn ion inside the tetrahedral crystal site of ZnO without forming any cluster or secondary phases of Co. The un-doped ZnO nanorods exhibited diamagnetic behavior and it remained up to a c.{sub Co} of 0.05 mM, while for c.{sub Co }> 0.05 mM, the ZnO nanostructures exhibited ferromagnetic behavior at room temperature. The coercivity increased to 695 G for 0.2 mM Co-doped sample and then it decreased for c.{sub Co }> 0.2 mM. Our results illustrate that up to a threshold concentration of 0.2 mM, the strong ferromagnetism is due to the oxygen vacancy defects centers, which exist in the Co-doped ZnO nanostructures. The origin of strong ferromagnetism at room temperature in Co-doped ZnO nanostructures is attributed to the s-d exchange interaction between the localized spin moments resulting from the oxygen vacancies and d electrons of Co{sup 2+} ions. Our findings provide a new insight for tuning the

  14. Role of substrate and annealing temperature on the structure of ZnO and AlxZn1-xO thin films for solar cell applications

    NASA Astrophysics Data System (ADS)

    Nambala, Fred Joe; Nel, Jacqueline M.; Machatine, Augusto G. J.; Mwakikunga, Bonex W.; Njoroge, Eric G.; Maabong, Kelebogile; Das, Arran G. M.; Diale, Mmantsae

    2016-01-01

    This paper reports on the deposition of pure and 5 at% Al doped ZnO (AZO) prepared by sol-gel and applied to the substrates by spin-coating, and the role of annealing temperature on the crystallinity of these layers. It is found that both ZnO and AZO are largely amorphous when coated on glass compared to n-Si(111), as substrates. On both substrates, X-ray diffraction (XRD) shows that the crystallinity improves as annealing temperature is raised from 200 to 600 °C with better crystallinity on Si substrates. The thickness of the films on substrates was determined as 120 nm by Rutherford backscattering spectroscopy (RBS). Specular ultra-violet visible (UV-vis) gives the direct transition optical band gaps (Eg) for AZO as-deposited films are 2.60 and 3.35 eV while that of 600 °C annealed films are 3.00 and 3.60 eV. The Eg calculated from diffuse reflectance spectroscopy (DRS) UV-vis are more diverse in ZnO- and AZO-Si than the ZnO- and AZO-glass samples, although in both sets the Eg tend to converge after annealing 600 °C. The Raman spectra of samples show multiphonon processes of higher order from the AZO and substrates. It is found that residual stresses are related to E2 Raman mode.

  15. Observation of the inverse spin Hall effect in ZnO thin films: An all-electrical approach to spin injection and detection

    SciTech Connect

    Prestgard, Megan C.; Tiwari, Ashutosh

    2014-03-24

    The inverse spin Hall effect (ISHE) is a newly discovered, quantum mechanical phenomenon where an applied spin current results in the generation of an electrical voltage in the transverse direction. It is anticipated that the ISHE can provide a more simple way of measuring spin currents in spintronic devices. The ISHE was first observed in noble metals that exhibit strong spin-orbit coupling. However, recently, the ISHE has been detected in conventional semiconductors (such as Si and Ge), which possess weak spin-orbit coupling. This suggests that large-spin orbit coupling is not a requirement for observing the ISHE. In this paper, we are reporting the observation of the ISHE in an alternative semiconductor material, zinc oxide (ZnO) using all-electrical means. In our study, we found that when a spin-polarized current is injected into the ZnO film from a NiFe ferromagnetic injector via an MgO tunnel barrier layer, a voltage transverse to both the direction of the current as well as its spin-polarization is generated in the ZnO layer. The polarity of this voltage signal was found to flip on reversing the direction of the injected current as well as on reversing the polarization of the current, consistent with the predictions of the ISHE process. Through careful analysis of the ISHE data, we determined a spin-Hall angle of approximately 1.651 × 10{sup −2} for ZnO, which is two orders of magnitude higher than that of silicon. Observation of a detectable room-temperature ISHE signal in ZnO via electrical injection and detection is a groundbreaking step that opens a path towards achieving transparent spin detectors for next-generation spintronic device technology.

  16. Fluorometric sensing of ultralow As(III) concentrations using Ag doped hollow CdS/ZnS bi-layer nanoparticles.

    PubMed

    Boxi, Siddhartha Sankar; Paria, Santanu

    2015-12-21

    Arsenic poisoning from drinking water has been an important global issue in recent years. Because of the high level toxicity of arsenic to human health, an easy, inexpensive, low level and highly selective detection technique is of great importance to take any early precautions. This study reports the synthesis of Ag doped hollow CdS/ZnS bi-layer (Ag-h-CdS/ZnS) nanoparticles for the easy fluorometric determination of As(iii) ions in the aqueous phase. The hollow bi-layer structures were synthesized by a sacrificial core method using AgBr as the sacrificial core and the core was removed by dissolution in an ammonium hydroxide solution. The synthesized nanoparticles were characterized using different instrumental techniques. A good linear relationship was obtained between fluorescence quenching intensity and As(iii) concentration in the range of 0.75-22.5 μg L(-1) at neutral pH with a limit of detection as low as 0.226 μg L(-1). PMID:26541652

  17. Control of Ag nanoparticle distribution influencing bioactive and antibacterial properties of Ag-doped mesoporous bioactive glass particles prepared by spray pyrolysis.

    PubMed

    Shih, Shao-Ju; Tzeng, Wei-Lung; Jatnika, Rifqi; Shih, Chi-Jen; Borisenko, Konstantin B

    2015-05-01

    Mesoporous bioactive glasses (MBGs) have become important bone implant materials because of their high specific surface area resulting in high bioactivity. Doping MBGs with Ag removes one of the remaining challenges to their applications, namely their lack of intrinsic antibacterial properties. In present work we demonstrate that Ag-doped MBGs can be prepared in one-step spray pyrolysis (SP) process. The SP preparation method offers the advantages of short processing times and continuous production over the sol-gel method previously used to prepare MBGs. Using scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction we demonstrate that the synthesized MBG particles have amorphous structure with nanocrystalline Ag inclusions. The scanning transmission electron microscopy-X-ray energy dispersive spectrometry of cross-sectional samples shows that the distribution of the Ag dopant nanoparticles within MBGs can be controlled by using the appropriate formulation of the precursors. The distribution of the Ag dopant nanoparticles within the MBG particles was found to affect their surface areas, bioactivities and antibacterial properties. Based on the observations, we propose a mechanism describing MBG particle formation and controlling dopant distribution. PMID:25171327

  18. 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

  19. The impact of oxygen incorporation during intrinsic ZnO sputtering on the performance of Cu(In,Ga)Se{sub 2} thin film solar cells

    SciTech Connect

    Lee, Kkotnim; Ok, Eun-A; Park, Jong-Keuk; Kim, Won Mok; Baik, Young-Joon; Jeong, Jeung-hyun; Kim, Donghwan

    2014-08-25

    We investigated the impact of incorporating 2% oxygen during intrinsic ZnO sputtering on the efficiency of Cu(In,Ga)Se{sub 2} solar cells. The added oxygen not only reduced the optical absorption loss of the Al-doped ZnO overlaying layer but also improved the electronic properties of the underlying CdS/Cu(In,Ga)Se{sub 2} by increasing carrier density, lowering defect level, and increasing diffusion length, eventually enhancing J{sub SC}, V{sub OC}, and fill factor. It was found that the Na doping concentration was significantly increased around the CdS/Cu(In,Ga)Se{sub 2} junction due to the plasma-activated oxygen. The improved electronic properties are better explained by the increased Na concentration than simply the oxygen-related defect passivation.

  20. Study on the microstructure, soft magnetic and high frequency properties of obliquely sputtered [Fe65Co35/ZnO]50 multilayer thin films

    NASA Astrophysics Data System (ADS)

    Yao, Dongsheng; Li, Wenchun; Sun, Yunbin; Wu, Hongye; Lu, Yi; Zhao, Jianjun; Feng, Liefeng; Liu, Xiaohong; Zhou, Xueyun

    2016-01-01

    The effect of ZnO layer thickness t on the structure, static magnetic properties and high frequency properties is systemically studied for [Fe65Co35/ZnO(t)]50 multilayer films. The gradually increasing crystallinity of ZnO layer with increasing t is observed in the XRD patterns. The VSM measurements show good soft magnetic properties are obtained in these multilayer films, even though the ZnO layer is thick (up to 3.6 nm). For the typical sample with t=3.6 nm, an obvious in-plane anisotropy field and comparatively small coercivity are achieved, and high electric resistivity up to 12.6 mΩ cm is obtained. The measurement of permeability spectra indicates that the multilayers have an invariable ferromagnetic resonance frequency fr about 4.0 GHz; however, the initial permeability μi can be adjusted from 48 to 136 by decreasing t from 3.6 nm to 1.0 nm. The phenomenon that fr is almost invariable is the result of the decreasing saturation magnetization 4πMs and the increasing dynamic anisotropy field Hk-dyn with increasing t. For our samples, the real part (μ'2G) of complex permeability at f=2.0 GHz remains a high value beyond 90, while the imaginary part (μ"2G) keeps a low value below 1.55, indicating that these multilayer films are promising for application in high frequency range.