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Sample records for aligned zno nanowires

  1. 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.

  2. Wafer-scale high-throughput ordered growth of vertically aligned ZnO nanowire arrays.

    PubMed

    Wei, Yaguang; Wu, Wenzhuo; Guo, Rui; Yuan, Dajun; Das, Suman; Wang, Zhong Lin

    2010-09-01

    This article presents an effective approach for patterned growth of vertically aligned ZnO nanowire (NW) arrays with high throughput and low cost at wafer scale without using cleanroom technology. Periodic hole patterns are generated using laser interference lithography on substrates coated with the photoresist SU-8. ZnO NWs are selectively grown through the holes via a low-temperature hydrothermal method without using a catalyst and with a superior control over orientation, location/density, and as-synthesized morphology. The development of textured ZnO seed layers for replacing single crystalline GaN and ZnO substrates extends the large-scale fabrication of vertically aligned ZnO NW arrays on substrates of other materials, such as polymers, Si, and glass. This combined approach demonstrates a novel method of manufacturing large-scale patterned one-dimensional nanostructures on various substrates for applications in energy harvesting, sensing, optoelectronics, and electronic devices. PMID:20681617

  3. Growth, modulation and photoresponse characteristics of vertically aligned ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Kar, J. P.; Das, S. N.; Choi, J. H.; Lee, T. I.; Seo, J.; Lee, T.; Myoung, J. M.

    2011-03-01

    Vertically aligned, c-axis oriented zinc oxide (ZnO) nanowires were grown on Si substrate by metal organic chemical vapor deposition (MOCVD) technique, where sputtered aluminum nitride (AlN) film was used as an intermediate layer and thermally evaporated barium fluoride (BaF 2) film as a sacrificial layer. The aspect ratio and density of the nanowires were also varied using only Si microcavity without any interfacial or sacrificial layer. The UV detectors inside the microcavity have shown the higher on-off current ratio and fast photoresponse characteristics. The photoresponse characteristics were significantly varied with the aspect ratio and the density of nanowires.

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

    NASA Astrophysics Data System (ADS)

    Shen, Gang

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

  5. Field emission behavior of vertically aligned ZnO nanowire planar cathodes

    SciTech Connect

    Semet, V.; Binh, Vu Thien; Pauporte, Th.; Joulaud, L.; Vermersch, F. J.

    2011-03-01

    A field emission (FE) study by scanning anode field emission microscopy was performed to evaluate the FE properties of vertically aligned zinc oxide (ZnO) nanowire arrays electrodeposited on a plane conductive surface. The specific FE behaviors of the cathode observed experimentally are (1) a turn-on macroscopic field of about 6 V/{mu}m for a FE current density J{sub FE} 5 x 10{sup -4} A/cm{sup 2}, (2) a stable FE characteristics for 5 x 10{sup -4} < J{sub FE} < 5 x 10{sup -2} A/cm{sup 2}, and (3) a brutal shut down of FE when J{sub FE} crossed a limiting value of {approx}0.05 A/cm{sup 2} due to a rapid evolution of the nanowires toward a bulbous tip geometry or a complete melting. A physical process of FE from ZnO nanostructures is proposed from the experimental data analyses. An effective surface barrier of about 1 eV was determined from the experimental Fowler-Nordheim plot and the presence of a Zn enriched surface was assumed in considering the possibility of important modifications of the crystallography and charge transfers at the surface of ZnO nanowires during the application of the strong electric field required for FE.

  6. Enhanced UV photosensitivity from rapid thermal annealed vertically aligned ZnO nanowires

    PubMed Central

    2011-01-01

    We report on the major improvement in UV photosensitivity and faster photoresponse from vertically aligned ZnO nanowires (NWs) by means of rapid thermal annealing (RTA). The ZnO NWs were grown by vapor-liquid-solid method and subsequently RTA treated at 700°C and 800°C for 120 s. The UV photosensitivity (photo-to-dark current ratio) is 4.5 × 103 for the as-grown NWs and after RTA treatment it is enhanced by a factor of five. The photocurrent (PC) spectra of the as-grown and RTA-treated NWs show a strong peak in the UV region and two other relatively weak peaks in the visible region. The photoresponse measurement shows a bi-exponential growth and bi-exponential decay of the PC from as-grown as well as RTA-treated ZnO NWs. The growth and decay time constants are reduced after the RTA treatment indicating a faster photoresponse. The dark current-voltage characteristics clearly show the presence of surface defects-related trap centers on the as-grown ZnO NWs and after RTA treatment it is significantly reduced. The RTA processing diminishes the surface defect-related trap centers and modifies the surface of the ZnO NWs, resulting in enhanced PC and faster photoresponse. These results demonstrated the effectiveness of RTA processing for achieving improved photosensitivity of ZnO NWs. PMID:21859456

  7. Low-Cost, Large-Area, Facile, and Rapid Fabrication of Aligned ZnO Nanowire Device Arrays.

    PubMed

    Cadafalch Gazquez, Gerard; Lei, Sidong; George, Antony; Gullapalli, Hemtej; Boukamp, Bernard A; Ajayan, Pulickel M; Ten Elshof, Johan E

    2016-06-01

    Well aligned nanowires of ZnO have been made with an electrospinning technique using zinc acetate precursor solutions. Employment of two connected parallel collector plates with a separating gap of 4 cm resulted in a very high degree of nanowire alignment. By adjusting the process parameters, the deposition density of the wires could be controlled. Field effect transistors were prepared by depositing wires between two gold electrodes on top of a heavily doped Si substrate covered with a 300 nm oxide layer. These devices showed good FET characteristics and photosensitivity under UV-illumination. The method provides a fast and scalable fabrication route for functional nanowire arrays with a high degree of alignment and control over nanowire spacing. PMID:27173007

  8. Alignment nature of ZnO nanowires grown on polished and nanoscale etched lithium niobate surface through self-seeding thermal evaporation method

    SciTech Connect

    Mohanan, Ajay Achath; Parthiban, R.; Ramakrishnan, N.

    2015-08-15

    Highlights: • ZnO nanowires were grown directly on LiNbO{sub 3} surface for the first time by thermal evaporation. • Self-alignment of the nanowires due to step bunching of LiNbO{sub 3} surface is observed. • Increased roughness in surface defects promoted well-aligned growth of nanowires. • Well-aligned growth was then replicated in 50 nm deep trenches on the surface. • Study opens novel pathway for patterned growth of ZnO nanowires on LiNbO{sub 3} surface. - Abstract: High aspect ratio catalyst-free ZnO nanowires were directly synthesized on lithium niobate substrate for the first time through thermal evaporation method without the use of a buffer layer or the conventional pre-deposited ZnO seed layer. As-grown ZnO nanowires exhibited a crisscross aligned growth pattern due to step bunching of the polished lithium niobate surface during the nanowire growth process. On the contrary, scratches on the surface and edges of the substrate produced well-aligned ZnO nanowires in these defect regions due to high surface roughness. Thus, the crisscross aligned nature of high aspect ratio nanowire growth on the lithium niobate surface can be changed to well-aligned growth through controlled etching of the surface, which is further verified through reactive-ion etching of lithium niobate. The investigations and discussion in the present work will provide novel pathway for self-seeded patterned growth of well-aligned ZnO nanowires on lithium niobate based micro devices.

  9. Direct synthesis of vertically aligned ZnO nanowires on FTO substrates using a CVD method and the improvement of photovoltaic performance

    PubMed Central

    2012-01-01

    In this work, we report a direct synthesis of vertically aligned ZnO nanowires on fluorine-doped tin oxide-coated substrates using the chemical vapor deposition (CVD) method. ZnO nanowires with a length of more than 30 μm were synthesized, and dye-sensitized solar cells (DSSCs) based on the as-grown nanowires were fabricated, which showed improvement of the device performance compared to those fabricated using transferred ZnO nanowires. Dependence of the cell performance on nanowire length and annealing temperature was also examined. This synthesis method provided a straightforward, one-step CVD process to grow relatively long ZnO nanowires and avoided subsequent nanowire transfer process, which simplified DSSC fabrication and improved cell performance. PMID:22673046

  10. Vertically Well-Aligned ZnO Nanowire Arrays Directly Synthesized from Zn Vapor Deposition Without Catalyst

    NASA Astrophysics Data System (ADS)

    Van Khai, Tran; Van Thu, Le; Huu, Nguyen The; Lam, Tran Dai

    2016-05-01

    Vertically well-aligned ZnO nanowire (NW) arrays with high density have been successfully synthesized on sapphire substrate by thermal evaporation of the zinc powders without catalysts or additives. The ZnO NWs were characterized by scanning electron microscopy, transmission electronic microscopy (TEM), x-ray diffraction, ultraviolet-visible, photoluminescence, Raman, and x-ray photoelectron spectroscopy. The results showed that the obtained ZnO NWs had diameters in the range of 100-130 nm, lengths over several micrometers and well aligned in the direction perpendicular to the substrate surface. The as-synthesized ZnO NWs, which were single crystalline in a hexagonal structure, showed uniform morphology, faceted planes at the tips of the NWs, and grown along the [001] direction. The as-synthesized NW arrays had a good crystal quality with excellent optical properties, showing a sharp and strong ultraviolet emission at 380 nm and a weak visible emission at around 500 nm.

  11. Low-temperature growth of well-aligned ZnO nanorods/nanowires on flexible graphite sheet and their photoluminescence properties

    SciTech Connect

    Zhong, Guo; Kalam, Abul; Al-Shihri, Ayed Sad; Su, Qingmei; Li, Jie; Du, Gaohui

    2012-06-15

    Highlights: ► Well-aligned ZnO nanostructures were grown on flexible graphite sheets at 500–650 °C. ► ZnO nanostructures are formed via self-catalytic vapor–solid process assisted by immiscibility of ZnO with graphite. ► The ZnO nanostructures show intensive green emission. ► The photoluminescence property can be easily tuned by changing growth condition or annealing treatment. -- Abstract: We have grown large-scale well-aligned ZnO nanorods/nanowires on commercial flexible graphite sheet (FGS) at low temperature via chemical vapor deposition method. The products were characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. The effects of the growth temperature and oxygen flow rate on the morphology of ZnO nanostructures have been investigated. The growth mechanism of ZnO is found to be a self-catalytic vapor–solid process assisted by the immiscibility of ZnO with graphite. The as-grown ZnO/FGS products show strong green emission and their photoluminescence properties can be tuned by changing growth condition or annealing treatment.

  12. Large-scale fabrication of vertically aligned ZnO nanowire arrays

    DOEpatents

    Wang, Zhong L; Das, Suman; Xu, Sheng; Yuan, Dajun; Guo, Rui; Wei, Yaguang; Wu, Wenzhuo

    2013-02-05

    In a method for growing a nanowire array, a photoresist layer is placed onto a nanowire growth layer configured for growing nanowires therefrom. The photoresist layer is exposed to a coherent light interference pattern that includes periodically alternately spaced dark bands and light bands along a first orientation. The photoresist layer exposed to the coherent light interference pattern along a second orientation, transverse to the first orientation. The photoresist layer developed so as to remove photoresist from areas corresponding to areas of intersection of the dark bands of the interference pattern along the first orientation and the dark bands of the interference pattern along the second orientation, thereby leaving an ordered array of holes passing through the photoresist layer. The photoresist layer and the nanowire growth layer are placed into a nanowire growth environment, thereby growing nanowires from the nanowire growth layer through the array of holes.

  13. Use of distributed Bragg reflectors to enhance Fabry-Pérot lasing in vertically aligned ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Kong, Jieying; Chu, Sheng; Huang, Jian; Olmedo, Mario; Zhou, Weihang; Zhang, Long; Chen, Zhanghai; Liu, Jianlin

    2013-01-01

    An optically pumped ZnO nanowire laser with a 10-period SiO2/SiN x distributed Bragg reflector (DBR) was demonstrated. Stimulated emissions with equally distributed Fabry-Pérot lasing modes were observed at pumping powers larger than 121 kW/cm2. This result, when compared to nanowires of the same length and without a DBR structure, shows that a lower threshold of pumping power, higher quality factor, and larger cavity finesse can be achieved due to the high reflectivity of the DBR in the designed wavelength range. A coexistence of stimulated and spontaneous emissions was also observed above threshold and was attributed to partially confined waveguide modes in nanowires with diameters smaller than 100 nm.

  14. Large-scale fabrication of vertically aligned ZnO nanowire arrays

    DOEpatents

    Wang, Zhong Lin; Hu, Youfan; Zhang, Yan; Xu, Chen; Zhu, Guang

    2014-09-09

    A generator includes a substrate, a first electrode layer, a dense plurality of vertically-aligned piezoelectric elongated nanostructures, an insulating layer and a second electrode layer. The substrate has a top surface and the first electrode layer is disposed on the top surface of the substrate. The dense plurality of vertically-aligned piezoelectric elongated nanostructures extends from the first electrode layer. Each of the nanostructures has a top end. The insulating layer is disposed on the top ends of the nanostructures. The second electrode layer is disposed on the non-conductive layer and is spaced apart from the nanostructures.

  15. Catalyst-free synthesis of well-aligned ZnO nanowires on In0.2Ga0.8N, GaN, and Al0.25Ga0.75N substrates.

    PubMed

    Yang, W Q; Dai, L; You, L P; Zhang, B R; Shen, B; Qin, G G

    2006-12-01

    Well-aligned ZnO nanowires have been synthesized vertically on In0.2Ga0.8N, GaN, and Al0.25Ga0.75N substrates, using a catalyst-free carbon thermal-reduction vapor phase deposition method for the first time. The as-synthesized nanowires are single crystalline wurtzite structure, and have a growth direction of [0001]. Each nanowire has a smooth surface, and uniform diameter along the growth direction. The average diameter and length of these nanowires are 120-150 nm, and 3-10 )m, respectively. We suggest that the growth mechanism follow a self-catalyzing growth model. Excitonic emission peaked around 385 nm dominates the room-temperature photoluminescence spectra of these nanowires. The room-temperature photoluminescence and Raman scattering spectra show that these nanowires have good optical quality with very less structural defects. PMID:17256330

  16. Liquid crystal alignment on zinc oxide nanowire arrays for LCDs applications.

    PubMed

    Chen, Mu-Zhe; Chen, Wei-Sheng; Jeng, Shie-Chang; Yang, Sheng-Hsiung; Chung, Yueh-Feng

    2013-12-01

    The zinc oxide (ZnO) nanowire arrays on the indium tin oxide (ITO) glass substrates were fabricated by using the two-step hydrothermal method. A high transmittance ~92% of ZnO nanowire arrays on ITO substrate in the visible region was obtained. It was observed that the liquid crystal (LC) directors were aligned vertically to the (ZnO) nanowire arrays. The properties of ZnO nanowire arrays as vertical liquid crystal (LC) alignment layers and their applications for hybrid-aligned nematic LC modes were investigated in this work. PMID:24514480

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  18. Growth of vertically aligned ZnO nanorods using textured ZnO films

    PubMed Central

    2011-01-01

    A hydrothermal method to grow vertical-aligned ZnO nanorod arrays on ZnO films obtained by atomic layer deposition (ALD) is presented. The growth of ZnO nanorods is studied as function of the crystallographic orientation of the ZnO films deposited on silicon (100) substrates. Different thicknesses of ZnO films around 40 to 180 nm were obtained and characterized before carrying out the growth process by hydrothermal methods. A textured ZnO layer with preferential direction in the normal c-axes is formed on substrates by the decomposition of diethylzinc to provide nucleation sites for vertical nanorod growth. Crystallographic orientation of the ZnO nanorods and ZnO-ALD films was determined by X-ray diffraction analysis. Composition, morphologies, length, size, and diameter of the nanorods were studied using a scanning electron microscope and energy dispersed x-ray spectroscopy analyses. In this work, it is demonstrated that crystallinity of the ZnO-ALD films plays an important role in the vertical-aligned ZnO nanorod growth. The nanorod arrays synthesized in solution had a diameter, length, density, and orientation desirable for a potential application as photosensitive materials in the manufacture of semiconductor-polymer solar cells. PACS 61.46.Hk, Nanocrystals; 61.46.Km, Structure of nanowires and nanorods; 81.07.Gf, Nanowires; 81.15.Gh, Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.) PMID:21899743

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

    SciTech Connect

    Ishiyama, Takeshi Nakane, Takaya Fujii, Tsutomu

    2015-02-27

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

  20. Synthesis, optical and electrochemical properties of ZnO nanowires/graphene oxide heterostructures

    PubMed Central

    2013-01-01

    Large-scale vertically aligned ZnO nanowires with high crystal qualities were fabricated on thin graphene oxide films via a low temperature hydrothermal method. Room temperature photoluminescence results show that the ultraviolet emission of nanowires grown on graphene oxide films was greatly enhanced and the defect-related visible emission was suppressed, which can be attributed to the improved crystal quality and possible electron transfer between ZnO and graphene oxide. Electrochemical property measurement results demonstrated that the ZnO nanowires/graphene oxide have large integral area of cyclic voltammetry loop, indicating that such heterostructure is promising for application in supercapacitors. PMID:23522184

  1. Synthesis, optical and electrochemical properties of ZnO nanowires/graphene oxide heterostructures

    NASA Astrophysics Data System (ADS)

    Zeng, Huidan; Cao, Ying; Xie, Shufan; Yang, Junhe; Tang, Zhihong; Wang, Xianying; Sun, Luyi

    2013-03-01

    Large-scale vertically aligned ZnO nanowires with high crystal qualities were fabricated on thin graphene oxide films via a low temperature hydrothermal method. Room temperature photoluminescence results show that the ultraviolet emission of nanowires grown on graphene oxide films was greatly enhanced and the defect-related visible emission was suppressed, which can be attributed to the improved crystal quality and possible electron transfer between ZnO and graphene oxide. Electrochemical property measurement results demonstrated that the ZnO nanowires/graphene oxide have large integral area of cyclic voltammetry loop, indicating that such heterostructure is promising for application in supercapacitors.

  2. Visible electroluminescence from a ZnO nanowires/p-GaN heterojunction light emitting diode.

    PubMed

    Baratto, C; Kumar, R; Comini, E; Faglia, G; Sberveglieri, G

    2015-07-27

    In the current paper we apply catalyst assisted vapour phase growth technique to grow ZnO nanowires (ZnO nws) on p-GaN thin film obtaining EL emission in reverse bias regime. ZnO based LED represents a promising alternative to III-nitride LEDs, as in free devices: the potential is in near-UV emission and visible emission. For ZnO, the use of nanowires ensures good crystallinity of the ZnO, and improved light extraction from the interface when the nanowires are vertically aligned. We prepared ZnO nanowires in a tubular furnace on GaN templates and characterized the p-n ZnO nws/GaN heterojunction for LED applications. SEM microscopy was used to study the growth of nanowires and device preparation. Photoluminescence (PL) and Electroluminescence (EL) spectroscopies were used to characterize the heterojunction, showing that good quality of PL emission is observed from nanowires and visible emission from the junction can be obtained from the region near ZnO contact, starting from onset bias of 6V. PMID:26367556

  3. Investigations on the growth and characterization of vertically aligned zinc oxide nanowires by radio frequency magnetronsputtering

    SciTech Connect

    Venkatesh, P. Sundara; Jeganathan, K.

    2013-04-15

    Undoped vertically aligned ZnO nanowires have been grown on silicon (111) substrates by the rf magnetron sputtering technique without metal catalyst. The diameter, length and density distributions of the nanowires have been analyzed with respect to the different growth durations. The tapering of the nanowires is observed for the growth duration of 120 min owing to the insufficient adatoms on the growth front. In the X-ray diffraction pattern, the dominant (002) peak with narrow full width at half maximum (FWHM) of ZnO nanowires indicates the c-axis orientation and high crystalline nature with hexagonal wurtzite crystal structure. The narrow FWHM of E{sub 2}{sup low} and E{sub 2}{sup high} phonon modes (1.4 and 9.1 cm{sup −1}) provide an additional evidence for the high crystalline and optical properties of the nanowires. The low temperature photoluminescence spectra are dominated by the green emission at∼2.28 eV induced by the electron transitions between shallow donor and acceptor energy levels. - Graphical abstract: Coalescence free vertically aligned ZnO nanowires have been grown on silicon (111) substrate by the radio frequency magnetron sputtering technique. Highlights: ► ZnO nanowires have been grown by rf magnetron sputtering. ► A morphologically superior and coalescence free ZnO nanowires have been realized. ► ZnO nanowires exhibit hexagonal wurtzite crystal structure. ► A dominant visible emission indicates the presence of point defects in nanowires.

  4. The nitridation of ZnO nanowires

    PubMed Central

    2012-01-01

    ZnO nanowires (NWs) with diameters of 50 to 250 nm and lengths of several micrometres have been grown by reactive vapour transport via the reaction of Zn with oxygen on 1 nm Au/Si(001) at 550°C under an inert flow of Ar. These exhibited clear peaks in the X-ray diffraction corresponding to the hexagonal wurtzite crystal structure of ZnO and a photoluminescence spectrum with a peak at 3.3 eV corresponding to band edge emission close to 3.2 eV determined from the abrupt onset in the absorption-transmission through ZnO NWs grown on 0.5 nm Au/quartz. We find that the post growth nitridation of ZnO NWs under a steady flow of NH3 at temperatures ≤600°C promotes the formation of a ZnO/Zn3N2 core-shell structure as suggested by the suppression of the peaks related to ZnO and the emergence of new ones corresponding to the cubic crystal structure of Zn3N2 while maintaining their integrity. Higher temperatures lead to the complete elimination of the ZnO NWs. We discuss the effect of nitridation time, flow of NH3, ramp rate and hydrogen on the conversion and propose a mechanism for the nitridation. PMID:22397754

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

    PubMed Central

    2011-01-01

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

  6. In-plane trapping and manipulation of ZnO nanowires by a hybrid plasmonic field.

    PubMed

    Zhang, Lichao; Dou, Xiujie; Min, Changjun; Zhang, Yuquan; Du, Luping; Xie, Zhenwei; Shen, Junfeng; Zeng, Yujia; Yuan, Xiaocong

    2016-05-14

    In general, when a semiconductor nanowire is trapped by conventional laser beam tweezers, it tends to be aligned with the trapping beam axis rather than confined in the horizontal plane, and this limits the application of these nanowires in many in-plane nanoscale optoelectronic devices. In this work, we achieve the in-plane trapping and manipulation of a single ZnO nanowire by a hybrid plasmonic tweezer system on a flat metal surface. The gap between the nanowire and the metallic substrate leads to an enhanced gradient force caused by deep subwavelength optical energy confinement. As a result, the nanowire can be securely trapped in-plane at the center of the excited surface plasmon polariton field, and can also be dynamically moved and rotated by varying the position and polarization direction of the incident laser beam, which cannot be performed using conventional optical tweezers. The theoretical results show that the focused plasmonic field induces a strong in-plane trapping force and a high rotational torque on the nanowire, while the focused optical field produces a vertical trapping force to produce the upright alignment of the nanowire; this is in good agreement with the experimental results. Finally, some typical ZnO nanowire structures are built based on this technique, which thus further confirms the potential of this method for precise manipulation of components during the production of nanoelectronic and nanophotonic devices. PMID:27117313

  7. Nonvolatile resistive switching in single crystalline ZnO nanowires.

    PubMed

    Yang, Yuchao; Zhang, Xiaoxian; Gao, Min; Zeng, Fei; Zhou, Weiya; Xie, Sishen; Pan, Feng

    2011-04-01

    We demonstrate nonvolatile resistive switching in single crystalline ZnO nanowires with high ON/OFF ratios and low threshold voltages. Unlike the mechanism of continuous metal filament formation along grain boundaries in polycrystalline films, the resistive switching in single crystalline ZnO nanowires is speculated to be induced by the formation of a metal island chain on the nanowire surface. Resistive memories based on bottom-up semiconductor nanowires hold potential for next generation ultra-dense nonvolatile memories. PMID:21394361

  8. Power generation from base excitation of a Kevlar composite beam with ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Malakooti, Mohammad H.; Hwang, Hyun-Sik; Sodano, Henry A.

    2015-04-01

    One-dimensional nanostructures such as nanowires, nanorods, and nanotubes with piezoelectric properties have gained interest in the fabrication of small scale power harvesting systems. However, the practical applications of the nanoscale materials in structures with true mechanical strengths have not yet been demonstrated. In this paper, piezoelectric ZnO nanowires are integrated into the fiber reinforced polymer composites serving as an active phase to convert the induced strain energy from ambient vibration into electrical energy. Arrays of ZnO nanowires are grown vertically aligned on aramid fibers through a low-cost hydrothermal process. The modified fabrics with ZnO nanowires whiskers are then placed between two carbon fabrics as the top and the bottom electrodes. Finally, vacuum resin transfer molding technique is utilized to fabricate these multiscale composites. The fabricated composites are subjected to a base excitation using a shaker to generate charge due to the direct piezoelectric effect of ZnO nanowires. Measuring the generated potential difference between the two electrodes showed the energy harvesting application of these multiscale composites in addition to their superior mechanical properties. These results propose a new generation of power harvesting systems with enhanced mechanical properties.

  9. High mobility ZnO nanowires for terahertz detection applications

    NASA Astrophysics Data System (ADS)

    Liu, Huiqiang; Peng, Rufang; Chu, Sheng; Chu, Shijin

    2014-07-01

    An oxide nanowire material was utilized for terahertz detection purpose. High quality ZnO nanowires were synthesized and field-effect transistors were fabricated. Electrical transport measurements demonstrated the nanowire with good transfer characteristics and fairly high electron mobility. It is shown that ZnO nanowires can be used as building blocks for the realization of terahertz detectors based on a one-dimensional plasmon detection configuration. Clear terahertz wave (˜0.3 THz) induced photovoltages were obtained at room temperature with varying incidence intensities. Further analysis showed that the terahertz photoresponse is closely related to the high electron mobility of the ZnO nanowire sample, which suggests that oxide nanoelectronics may find useful terahertz applications.

  10. Development of multifunctional fiber reinforced polymer composites through ZnO nanowire arrays

    NASA Astrophysics Data System (ADS)

    Malakooti, Mohammad H.; Patterson, Brendan A.; Hwang, Hyun-Sik; Sodano, Henry A.

    2016-04-01

    Piezoelectric nanowires, in particular zinc oxide (ZnO) nanowires, have been vastly used in the fabrication of electromechanical devices to convert wasted mechanical energy into useful electrical energy. Over recent years, the growth of vertically aligned ZnO nanowires on various structural fibers has led to the development of fiber-based nanostructured energy harvesting devices. However, the development of more realistic energy harvesters that are capable of continuous power generation requires a sufficient mechanical strength to withstand typical structural loading conditions. Yet, a durable, multifunctional material system has not been developed thoroughly enough to generate electrical power without deteriorating the mechanical performance. Here, a hybrid composite energy harvester is fabricated in a hierarchical design that provides both efficient power generating capabilities while enhancing the structural properties of the fiber reinforced polymer composite. Through a simple and low-cost process, a modified aramid fabric with vertically aligned ZnO nanowires grown on the fiber surface is embedded between woven carbon fabrics, which serve as the structural reinforcement as well as the top and the bottom electrodes of the nanowire arrays. The performance of the developed multifunctional composite is characterized through direct vibration excitation and tensile strength examination.

  11. Selective growth of ZnO nanowires on substrates patterned by photolithography and inkjet printing

    NASA Astrophysics Data System (ADS)

    Laurenti, M.; Verna, A.; Fontana, M.; Quaglio, M.; Porro, S.

    2014-05-01

    Zinc oxide nanowires (ZnO NWs) were grown by a two-step growth method, involving the deposition of a patterned ZnO thin seeding layer and the chemical vapor deposition (CVD) of ZnO NWs. Two ways of patterning the seed layer were performed. The seeding solution containing ZnO precursors was deposited by sol-gel/spin-coating technique and patterned by photolithography. In the other case, the seeding solution was directly printed by inkjet printing only on selected portion of the substrate areas. In both cases, crystallization of the seed layer was achieved by thermal annealing in ambient air. Vertically aligned ZnO NWs were then grown by CVD on patterned, seeded substrates. The structure and morphology of ZnO NWs was analyzed by means of X-ray diffraction and field emission scanning electron microscopy measurements, respectively, while the vibrational properties were evaluated through Raman spectroscopy. Results showed that less-defective, vertically aligned, c-axis oriented ZnO NWs were grown on substrates patterned by photolithography while more defective nanostructures were grown on printed seed layer. A feature size of 30 µm was transferred into the patterned seed layer, and a good selectivity in growing ZnO NWs was obtained.

  12. Fluorescent security markers on ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Warren, Kristy; Tzolov, Marian

    2012-02-01

    Zink oxide is an efficient emitter of light thanks to the large exciton binding energy of 60 meV. The narrow emission lines from ZnO nanowires can be used as an enhanced security feature in documents and can be easily recognized from the background originating from the paper itself. We have studied the emission properties of ZnO nanowires in the UV range and how they can be implemented into paper products for document security. The zinc oxide nanowires were synthesized by chemical vapor transport and postprocessed in solution. The nanowires were dispersed using a sonicator into nitric acid water solutions with a pH of 2 and 4, and ammonium hydroxide water solution with a pH of 5 and 7. The morphology of the dispersed ZnO nanowires was imaged under a scanning electron microscope. Fluorescence measurements have shown better light emission from the nanoparticles dispersed in the basic pH solution. This material was then implemented into crafted paper and viewed under UV lamps and with a spectrometer. We have studied the loading of the paper with ZnO nanoparticles. A comparison was done with equivalently processed material of ZnO in powder form. The implementation of zinc oxide nanowires into paper products can advance document security at a relatively low cost.

  13. Selective growth of catalyst-free ZnO nanowire arrays on Al:ZnO for device application

    SciTech Connect

    Chung, T. F.; Luo, L. B.; He, Z. B.; Leung, Y. H.; Shafiq, I.; Yao, Z. Q.; Lee, S. T.

    2007-12-03

    Vertically aligned ZnO nanowire (NW) arrays have been synthesized selectively on patterned aluminum-doped zinc oxide (AZO) layer deposited on silicon substrates without using any metal catalysts. The growth region was defined by conventional photolithography with an insulating template. Careful control of the types of template materials and growth conditions allows good alignment and growth selectivity for ZnO NW arrays. Sharp ultraviolet band-edge peak observed in the photoluminescence spectra of the patterned ZnO NW arrays reveals good optical qualities. The current-voltage characteristics of ZnO NWs/AZO/p-Si device suggest that patterned and aligned ZnO NW arrays on AZO may be used in optoelectronic devices.

  14. ZnO Nanoparticles and Nanowire Arrays with Liquid Crystals for Photovoltaic Apprications

    NASA Astrophysics Data System (ADS)

    Salamanca-Riba, Lourdes; Weadock, Nicholas; Martinez-Miranda, Luz

    2011-03-01

    Liquid crystals are small monodisperse molecules with high mobilities and are easy and cheap to process. In addition, some of their phases exhibit molecular orientation that can provide a path for the electrons, or holes, to move from one electrode to the other. We have mixed a smectic A liquid crystal (8CB) with varying concentrations of ZnO nanoparticles of ~ 5 nm in diameter and have observed a photovoltaic effect as a function of the concentration of ZnO. The liquid crystal is believed to enhance the alignment of the nanoparticles and aid in the diffusion of electrons through the particles to the collection electrode. We have also made PV cells of ZnO nanowire arrays grown on Au layers on Si substrates. The nanowire arrays are covered with 8CB liquid crystal for hole conduction. We compare the light absorption of the PV cells as a function of wavelength of the light for the ZnO nanoparticle and the ZnO nanowire cells. We present a detailed study of the structure of the two systems. Supported by the National Science Foundation under the University of Maryland MRSEC DMR 0520471.

  15. Vertically aligned zinc oxide nanowires electrodeposited within porous polycarbonate templates for vibrational energy harvesting

    NASA Astrophysics Data System (ADS)

    Boughey, Francesca L.; Davies, Timothy; Datta, Anuja; Whiter, Richard A.; Sahonta, Suman-Lata; Kar-Narayan, Sohini

    2016-07-01

    A piezoelectric nanogenerator has been fabricated using a simple, fast and scalable template-assisted electrodeposition process, by which vertically aligned zinc oxide (ZnO) nanowires were directly grown within a nanoporous polycarbonate (PC) template. The nanowires, having average diameter 184 nm and length 12 μm, are polycrystalline and have a preferred orientation of the [100] axis parallel to the long axis. The output power density of a nanogenerator fabricated from the as-grown ZnO nanowires still embedded within the PC template was found to be 151 ± 25 mW m‑3 at an impedance-matched load, when subjected to a low-level periodic (5 Hz) impacting force akin to gentle finger tapping. An energy conversion efficiency of ∼4.2% was evaluated for the electrodeposited ZnO nanowires, and the ZnO–PC composite nanogenerator was found to maintain good energy harvesting performance through 24 h of continuous fatigue testing. This is particularly significant given that ZnO-based nanostructures typically suffer from mechanical and/or environmental degradation that otherwise limits their applicability in vibrational energy harvesting. Our template-assisted synthesis of ZnO nanowires embedded within a protective polymer matrix through a single growth process is thus attractive for the fabrication of low-cost, robust and stable nanogenerators.

  16. Vertically aligned zinc oxide nanowires electrodeposited within porous polycarbonate templates for vibrational energy harvesting.

    PubMed

    Boughey, Francesca L; Davies, Timothy; Datta, Anuja; Whiter, Richard A; Sahonta, Suman-Lata; Kar-Narayan, Sohini

    2016-07-15

    A piezoelectric nanogenerator has been fabricated using a simple, fast and scalable template-assisted electrodeposition process, by which vertically aligned zinc oxide (ZnO) nanowires were directly grown within a nanoporous polycarbonate (PC) template. The nanowires, having average diameter 184 nm and length 12 μm, are polycrystalline and have a preferred orientation of the [100] axis parallel to the long axis. The output power density of a nanogenerator fabricated from the as-grown ZnO nanowires still embedded within the PC template was found to be 151 ± 25 mW m(-3) at an impedance-matched load, when subjected to a low-level periodic (5 Hz) impacting force akin to gentle finger tapping. An energy conversion efficiency of ∼4.2% was evaluated for the electrodeposited ZnO nanowires, and the ZnO-PC composite nanogenerator was found to maintain good energy harvesting performance through 24 h of continuous fatigue testing. This is particularly significant given that ZnO-based nanostructures typically suffer from mechanical and/or environmental degradation that otherwise limits their applicability in vibrational energy harvesting. Our template-assisted synthesis of ZnO nanowires embedded within a protective polymer matrix through a single growth process is thus attractive for the fabrication of low-cost, robust and stable nanogenerators. PMID:27256619

  17. Flexible Dye-Sensitized Solar Cell based on Vertical ZnO Nanowire Arrays

    SciTech Connect

    Chu, Sheng; Li, Dongdong; Chang, Pai-Chun; Lu, Jia Grace

    2010-09-26

    Flexible dye-sensitized solar cells are fabricated using vertically aligned ZnO nanowire arrays that are transferred onto ITO-coated poly(ethylene terephthalate) substrates using a simple peel-off process. The solar cells demonstrate an energy conversion efficiency of 0.44% with good bending tolerance. This technique paves a new route for building large-scale cost-effective flexible photovoltaic and optoelectronic devices.

  18. In-plane trapping and manipulation of ZnO nanowires by a hybrid plasmonic field

    NASA Astrophysics Data System (ADS)

    Zhang, Lichao; Dou, Xiujie; Min, Changjun; Zhang, Yuquan; Du, Luping; Xie, Zhenwei; Shen, Junfeng; Zeng, Yujia; Yuan, Xiaocong

    2016-05-01

    In general, when a semiconductor nanowire is trapped by conventional laser beam tweezers, it tends to be aligned with the trapping beam axis rather than confined in the horizontal plane, and this limits the application of these nanowires in many in-plane nanoscale optoelectronic devices. In this work, we achieve the in-plane trapping and manipulation of a single ZnO nanowire by a hybrid plasmonic tweezer system on a flat metal surface. The gap between the nanowire and the metallic substrate leads to an enhanced gradient force caused by deep subwavelength optical energy confinement. As a result, the nanowire can be securely trapped in-plane at the center of the excited surface plasmon polariton field, and can also be dynamically moved and rotated by varying the position and polarization direction of the incident laser beam, which cannot be performed using conventional optical tweezers. The theoretical results show that the focused plasmonic field induces a strong in-plane trapping force and a high rotational torque on the nanowire, while the focused optical field produces a vertical trapping force to produce the upright alignment of the nanowire; this is in good agreement with the experimental results. Finally, some typical ZnO nanowire structures are built based on this technique, which thus further confirms the potential of this method for precise manipulation of components during the production of nanoelectronic and nanophotonic devices.In general, when a semiconductor nanowire is trapped by conventional laser beam tweezers, it tends to be aligned with the trapping beam axis rather than confined in the horizontal plane, and this limits the application of these nanowires in many in-plane nanoscale optoelectronic devices. In this work, we achieve the in-plane trapping and manipulation of a single ZnO nanowire by a hybrid plasmonic tweezer system on a flat metal surface. The gap between the nanowire and the metallic substrate leads to an enhanced gradient force

  19. Gold as an intruder in ZnO nanowires.

    PubMed

    Méndez-Reyes, José M; Monroy, B Marel; Bizarro, Monserrat; Güell, Frank; Martínez, Ana; Ramos, Estrella

    2015-09-01

    Several techniques for obtaining ZnO nanowires (ZnO NWs) have been reported in the literature. In particular, vapour-liquid-solid (VLS) with Au as a catalyst is widely used. During this process, Au impurities in the ZnO NWs can be incorporated accidentally, and for this reason we named these impurities as intruders. It is thought that these intruders may produce interesting alterations in the electronic characteristics of nanowires. In the experiment, it is not easy to detect either Au atoms in these nanowires, or the modification that intruders produce in different electrical, optical and other properties. For this reason, in this density functional theory investigation, the effect of Au intruders on ZnO NWs is analysed. Au extended (thread) and point defects (atoms replacing Zn or O, or Au interstitials) are used to simulate the presence of gold atoms. Optimised geometries, band-gaps and density of states indicate that the presence of small amounts of Au drastically modifies the electronic states of ZnO NWs. The results reported here clearly indicate that small amounts of Au have a strong impact on the electronic properties of ZnO NWs, introducing states in the band edges that may promote transitions in the visible spectral region. The presence of Au as an intruder in ZnO NWs enhances the potential use of this system for photonic and photovoltaic applications. PMID:26219752

  20. Homoepitaxial regrowth habits of ZnO nanowire arrays

    PubMed Central

    2011-01-01

    Synthetic regrowth of ZnO nanowires [NWs] under a similar chemical vapor transport and condensation [CVTC] process can produce abundant ZnO nanostructures which are not possible by a single CVTC step. In this work, we report three different regrowth modes of ZnO NWs: axial growth, radial growth, and both directions. The different growth modes seem to be determined by the properties of initial ZnO NW templates. By varying the growth parameters in the first-step CVTC process, ZnO nanostructures (e.g., nanoantenna) with drastically different morphologies can be obtained with distinct photoluminescence properties. The results have implications in guiding the rational synthesis of various ZnO NW heterostructures. PMID:22151820

  1. Noise in ZnO nanowire field effect transistors.

    PubMed

    Xiong, Hao D; Wang, Wenyong; Suehle, John S; Richter, Curt A; Hong, Woong-Ki; Lee, Takhee

    2009-02-01

    The noise power spectra in ZnO nanowire field effect transistors (FETs) were experimentally investigated and showed a classical 1/f dependence. A Hooge's constant of 5 x 10(-3) was estimated. This value is within the range reported for CMOS FETs with high-k dielectrics, supporting the concept that nanowires can be utilized for future beyond-CMOS electronic applications from the point of view of device noise properties. ZnO FETs measured in a dry O2 environment displayed elevated noise levels compared to in vacuum. At low temperature, random telegraph signals are observed in the drain current. PMID:19441450

  2. ZnO nanowire-based CO sensor

    NASA Astrophysics Data System (ADS)

    Ho, Mon-Shu; Chen, Wei-Hao; Chen, Yu-Lin; Chang, Meng-Fan

    This study applied ZnO nanowires to the fabrication of a CO gas sensor operable at room temperature. Following the deposition of a seed layer by spin coating, an aqueous solution method was used to grow ZnO nanowires. This was followed by the self-assembly of an electrode array via dielectrophoresis prior to the fabrication of the CO sensing device. The material characteristics were analyzed using FE-SEM, EDS, GIXRD, FE-TEM, and the measurement of photoluminescence (PL). Our results identified the ZnO nanowires as a single crystalline wurtzite structure. Extending the growth period from 30 min to 360 min led to an increase in the length and diameter of the nanowires. After two hours, the ZnO presented a preferred crystal orientation of [002]. Sensor chips were assembled using 60 pairs of electrodes with gaps of 2 μm, over which were lain nanowires to complete the sensing devices. The average sensing response was 48.37 s and the average recovery time was 65.61 s, with a sensing response magnitude of approximately 6.8% at room temperature.

  3. Synthesis and characterization of ZnO nanowires for nanosensor applications

    SciTech Connect

    Lupan, O.; Emelchenko, G.A.; Ursaki, V.V.; Chai, G.; Redkin, A.N.; Gruzintsev, A.N.; Tiginyanu, I.M.; Chow, L.; Ono, L.K.; and others

    2010-08-15

    In this paper we report the synthesis of ZnO nanowires via chemical vapor deposition (CVD) at 650 {sup o}C. It will be shown that these nanowires are suitable for sensing applications. ZnO nanowires were grown with diameters ranging from 50 to 200 nm depending on the substrate position in a CVD synthesis reactor and the growth regimes. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and Raman spectroscopy (RS) have been used to characterize the ZnO nanowires. To investigate the suitability of the CVD synthesized ZnO nanowires for gas sensing applications, a single ZnO nanowire device (50 nm in diameter) was fabricated using a focused ion beam (FIB). The response to H{sub 2} of a gas nanosensor based on an individual ZnO nanowire is also reported.

  4. Structural, mechanical, and electronic properties of ultrathin ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Wang, Baolin; Zhao, Jijun; Jia, Jianming; Shi, Daning; Wan, Jianguo; Wang, Guanghou

    2008-07-01

    We report a structural transformation between the regular wurtzite and the unbuckled wurtzite (hexagonal) structure for ultrathin single-crystalline [0001] ZnO nanowires under uniaxial elongation and compression. Our density functional calculations show that hexagonal structure corresponds to a distinct minimum on the transformation path. Young's moduli of the ZnO nanowires with the hexagonal structures are larger than those with the wurtzite structures at the same size. Within the nanowire size range considered, Young's moduli of the ZnO nanowires decrease with increasing wire diameter. The electronic properties of these two types of ZnO nanowires exhibit distinctly different behaviors.

  5. In situ probing electrical response on bending of ZnO nanowires inside transmission electron microscope

    NASA Astrophysics Data System (ADS)

    Liu, K. H.; Gao, P.; Xu, Z.; Bai, X. D.; Wang, E. G.

    2008-05-01

    In situ electrical transport measurements on individual bent ZnO nanowires have been performed inside a high-resolution transmission electron microscope, where the crystal structures of ZnO nanowires were simultaneously imaged. A series of consecutively recorded current-voltage (I-V) curves along with an increase in nanowire bending show the striking effect of bending on their electrical behavior. The bending-induced changes of resistivity, electron concentration, and carrier mobility of ZnO nanowires have been retrieved based on the experimental I-V data, which suggests the applications of ZnO nanowires as nanoelectromechanical sensors.

  6. Co doped ZnO nanowires as visible light photocatalysts

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  7. Buffer layer effect on ZnO nanorods growth alignment

    NASA Astrophysics Data System (ADS)

    Zhao, Dongxu; Andreazza, Caroline; Andreazza, Pascal; Ma, Jiangang; Liu, Yichun; Shen, Dezhen

    2005-06-01

    Vertical aligned ZnO nanorods array was fabricated on Si with introducing a ZnO thin film as a buffer layer. Two different nucleation mechanisms were found in growth process. With using Au catalyst, Zn vapor could diffuse into Au nanoclusters with forming a solid solution. Then the ZnO nucleation site is mainly on the catalyst by oxidation of Au/Zn alloy. Without catalyst, nucleation could occur directly on the surface of buffer layer by homoepitaxy. The density and the size of ZnO nanorods could be governed by morphological character of catalyst and buffer layer. The nanorods growth is followed by vapor-solid mechanism.

  8. Oligo and Poly-thiophene/Zno Hybrid Nanowire Solar Cells

    SciTech Connect

    Briseno, Alejandro L.; Holcombe, Thomas W.; Boukai, Akram I.; Garnett, Erik C.; Shelton, Steve W.; Frechet, Jean J. M.; Yang, Peidong

    2009-11-03

    We demonstrate the basic operation of an organic/inorganic hybrid single nanowire solar cell. End-functionalized oligo- and polythiophenes were grafted onto ZnO nanowires to produce p-n heterojunction nanowires. The hybrid nanostructures were characterized via absorption and electron microscopy to determine the optoelectronic properties and to probe the morphology at the organic/inorganic interface. Individual nanowire solar cell devices exhibited well-resolved characteristics with efficiencies as high as 0.036percent, Jsc = 0.32 mA/cm2, Voc = 0.4 V, and a FF = 0.28 under AM 1.5 illumination with 100 mW/cm2 light intensity. These individual test structures will enable detailed analysis to be carried out in areas that have been difficult to study in bulk heterojunction devices.

  9. Role of Au in the growth and nanoscale optical properties of ZnO nanowires

    SciTech Connect

    Brewster, M.; Zhou, Xiang; Lim, S. K.; Gradecak, S.

    2011-03-17

    Metallic nanoparticles play a crucial role in nanowire growth and have profound consequences on nanowire morphology and their physical properties. Here, we investigate the evolving role of the Au nanoparticle during ZnO nanowire growth and its effects on nanoscale photoemission of the nanowires. We observe the transition from Au-assisted to non-assisted growth mechanisms during a single nanowire growth, with significant changes in growth rates during these two regimes. This transition occurs through the reduction of oxygen partial pressure, which modifies the ZnO facet stability and increases Au diffusion. Nanoscale quenching of ZnO cathodoluminescence occurs near the Au nanoparticle due to excited electron diffusion to the nanoparticle. Thus, the Au nanoparticle is critically linked to the nanowire growth mechanism and corresponding growth rate through the energy of its interface with the ZnO nanowire, and its presence modifies nanowire optical properties on the nanoscale.

  10. The growth of porous ZnO nanowires by thermal oxidation of ZnS nanowires.

    PubMed

    Hung, Chih-Cheng; Lin, Wen-Tai; Wu, Kuen-Hsien

    2011-12-01

    The growth of porous ZnO nanowires (NWs) via phase transformation of ZnS NWs at 500-850 degrees C in air was studied. The ZnS NWs were first synthesized by thermal evaporation of ZnS powder at 1100 degrees C in Ar. On subsequent annealing at 500 degrees C in air, discrete ZnO epilayers formed on the surface of ZnS NWs. At 600 degrees C, polycrystalline ZnO and the crack along the (0001) interface between the ZnO epilayer and ZnS NW were observed. At 700-750 degrees C ZnS NWs transformed to ZnO NWs, meanwhile nanopores and interfacial cracks were observed in the ZnO NWs. Two factors, the evaporation of SO2 and SO3 and the stress induced by the incompatible structure at the interface of ZnO epilayer and ZnS NW, can be responsible for the formation of porous ZnO NWs from ZnS NW templates on annealing at 700-750 degrees C in air. Rapid growth of ZnO at 850 degrees C could heal the pores and cracks and thus resulted in the well-crystallized ZnO NWs. PMID:22409083

  11. Localized ultraviolet photoresponse in single bent ZnO micro/nanowires

    SciTech Connect

    Guo Wen; Yang Ya; Qi Junjie; Zhao Jing; Zhang Yue

    2010-09-27

    The localized ultraviolet photoresponse in single bent ZnO micro/nanowires bridging two Ohmic contacts has been investigated. The ZnO micro/nanowire has a higher photoresponse sensitivity of about 190% at the bent region (bending strain: about 4%) than that at the straight region (about 50%). The rise and decay time constants are almost the same in the straight and bent regions of the ZnO micro/nanowire. A possible mechanism has been proposed and discussed. The bent ZnO micro/nanowires could be potentially useful for fabricating the coupled piezoelectric and optoelectronic nanodevices.

  12. Optical attenuation coefficient in individual ZnO nanowires.

    PubMed

    Little, Anree; Hoffman, Abigail; Haegel, Nancy M

    2013-03-11

    Attenuation coefficient measurements for the propagation of bandedge luminescence are made on individual ZnO nanowires by combining the localized excitation capability of a scanning electron microscope (SEM) with near-field scanning optical microscopy (NSOM) to record the distribution and intensity of wave-guided emission. Measurements were made for individual nanostructures with triangular cross-sections ranging in diameter from 680 to 2300 nm. The effective attenuation coefficient shows an inverse dependence on nanowire diameter (d(-1)), indicating scattering losses due to non-ideal waveguiding behavior. PMID:23482201

  13. Method of fabricating vertically aligned group III-V nanowires

    DOEpatents

    Wang, George T; Li, Qiming

    2014-11-25

    A top-down method of fabricating vertically aligned Group III-V micro- and nanowires uses a two-step etch process that adds a selective anisotropic wet etch after an initial plasma etch to remove the dry etch damage while enabling micro/nanowires with straight and smooth faceted sidewalls and controllable diameters independent of pitch. The method enables the fabrication of nanowire lasers, LEDs, and solar cells.

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

    PubMed Central

    2016-01-01

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

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

    PubMed

    Ou, Canlin; Sanchez-Jimenez, Pedro E; Datta, Anuja; Boughey, Francesca L; Whiter, Richard A; Sahonta, Suman-Lata; Kar-Narayan, Sohini

    2016-06-01

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

  16. Thermal-electric model for piezoelectric ZnO nanowires.

    PubMed

    Araneo, Rodolfo; Bini, Fabiano; Rinaldi, Antonio; Notargiacomo, Andrea; Pea, Marialilia; Celozzi, Salvatore

    2015-07-01

    The behavior of ZnO nanowires under uniaxial loading is characterized by means of a numerical model that accounts for all coupled mechanical, electrical, and thermal effects. The paper shows that thermal effects in the nanowires may greatly impact the predicted performance of piezoelectric and piezotronic nanodevices. The pyroelectric effect introduces new equivalent volumic charge in the body of the nanowire and surface charges at the boundaries, where Kapitza resistances are located, that act together with the piezoelectric charges to improve the predicted performance. It is shown that the proposed model is able to reproduce several effects experimentally observed by other research groups, and is a promising tool for the design of ultra-high efficient nanodevices. PMID:26059217

  17. Highly Ordered Vertical Arrays of TiO2/ZnO Hybrid Nanowires: Synthesis and Electrochemical Characterization.

    PubMed

    Gujarati, Tanvi P; Ashish, Ajithan G; Rai, Maniratnam; Shaijumon, Manikoth M

    2015-08-01

    We report the fabrication of vertically aligned hierarchical arrays of TiO2/ZnO hybrid nanowires, consisting of ZnO nanowires grown directly from within the pores of TiO2 nanotubes, through a combination of electrochemical anodization and hydrothermal techniques. These novel nano-architectured hybrid nanowires with its unique properties show promise as high performance supercapacitor electrodes. The electrochemical behaviour of these hybrid nanowires has been studied using Cyclic voltammetry, Galvanostatic charge-discharge and Electrochemical impedance spectroscopy (EIS) measurements using 1.5 M tetraethylammoniumtetrafluoroborate in acetonitrile as the electrolyte. Excellent electrochemical performances with a maximum specific capacitance of 2.6 mF cm-2 at a current density of 10 µA cm-2, along with exceptional cyclic stability, have been obtained for TiO2/ZnO-1 h hybrid material. The obtained results demonstrate the possibility of fabricating new geometrical architectures of inorganic hybrid nanowires with well adhered interfaces for the development of hybrid energy devices. PMID:26369158

  18. Synthesis of ZnO nanowires and their applications as an ultraviolet photodetector.

    PubMed

    Lin, Chih-Cheng; Lin, Wang-Hua; Li, Yuan-Yao

    2009-05-01

    High purity ZnO nanowire arrays were synthesized uniformly on a 1.5 cm x 2 cm tin-doped indium oxide (ITO) glass substrate. The ZnO nanowire arrays were formed with a uniform diameter distribution of 30-50 nm and a length of about 5 microm, synthesized via thermal decomposition of zinc acetate at 300 degrees C in air. Analysis by X-ray diffraction and transmission electron microscopy showed that the ZnO nanowires are of single crystal structure with a preferred growth orientation of [001]. A study of the growth mechanism showed that it is a vapor-solid (VS) growth process. The synthesis of these nanowires begins with the processes of dehydration, vaporization, decomposition, and oxidation of the zinc acetate. Next, the ZnO clusters are deposited to form seeds that give rise to selective epitaxial growth of the ZnO nanowires. Optical analysis of ZnO nanowires was performed by UV-visible and fluorescence spectrophotometry, investigating both the photocurrent characteristics and UV photoresponse of the ZnO nanowire photodetectors. A study of optical properties showed that the as-produced ZnO nanowires have great potential as UV photodetectors/sensors. PMID:19452935

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

    PubMed

    Lu, Ming-Yen; Tseng, Yen-Ti; Chiu, Cheng-Yao

    2014-01-01

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

  20. Black-colored ZnO nanowires with enhanced photocatalytic hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Zhang, Nan; Shan, Chong-Xin; Tan, Hua-Qiao; Zhao, Qi; Wang, Shuang-Peng; Sun, Zai-Cheng; Xia, Yong-de; Shen, De-Zhen

    2016-06-01

    Black-colored ZnO nanowires have been prepared in a metal–organic chemical vapor deposition system by employing a relatively low growth temperature and oxygen-deficient conditions. X-ray photoelectron spectroscopy reveals the incorporation of carbon into the nanowires. The photocatalytic hydrogen evolution activity of the black-colored ZnO nanowires is over 2.5 times larger than that of the pristine ZnO nanowires under simulated solar illumination conditions, and the enhanced photocatalytic activity can be attributed to the higher absorption of visible light by the black color and better carrier separation at the ZnO/carbon interface.

  1. Black-colored ZnO nanowires with enhanced photocatalytic hydrogen evolution.

    PubMed

    Zhang, Nan; Shan, Chong-Xin; Tan, Hua-Qiao; Zhao, Qi; Wang, Shuang-Peng; Sun, Zai-Cheng; Xia, Yong-de; Shen, De-Zhen

    2016-06-01

    Black-colored ZnO nanowires have been prepared in a metal-organic chemical vapor deposition system by employing a relatively low growth temperature and oxygen-deficient conditions. X-ray photoelectron spectroscopy reveals the incorporation of carbon into the nanowires. The photocatalytic hydrogen evolution activity of the black-colored ZnO nanowires is over 2.5 times larger than that of the pristine ZnO nanowires under simulated solar illumination conditions, and the enhanced photocatalytic activity can be attributed to the higher absorption of visible light by the black color and better carrier separation at the ZnO/carbon interface. PMID:27109699

  2. Effect of Intrinsic Point Defect on the Magnetic Properties of ZnO Nanowire

    PubMed Central

    Yun, Jiangni; Zhang, Zhiyong; Yin, Tieen

    2013-01-01

    The effect of intrinsic point defect on the magnetic properties of ZnO nanowire is investigated by the first-principles calculation based on the density functional theory (DFT). The calculated results reveal that the pure ZnO nanowire without intrinsic point defect is nonmagnetic and ZnO nanowire with VO, Zni, Oi, OZn, or ZnO point defect also is nonmagnetic. However, a strong spin splitting phenomenon is observed in ZnO nanowire with VZn defect sitting on the surface site. The Mulliken population analysis reveals that the oxygen atoms which are close to the VZn defect do major contribution to the magnetic moment. Partial density states calculation further suggests that the appearance of the half-metallic ferromagnetism in ZnO nanorod with VZn originates from the hybridization of the O2p states with Zn 3d states. PMID:24396300

  3. Site-specific growth of ZnO nanowires from patterned Zn via compatible semiconductor processing

    NASA Astrophysics Data System (ADS)

    Law, J. B. K.; Boothroyd, C. B.; Thong, J. T. L.

    2008-05-01

    An alternative method for site-selective growth of ZnO nanowires without the use of an Au catalyst or a ZnO thin-film seed layer is presented. Using conventional lithography and metallization semiconductor processing steps, regions for selective nanowire growth are defined using Zn, which acts as a self-catalyst for subsequent ZnO nanowire growth via a simple thermal oxidation process. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction reveal that the nanowires grown by this technique are single-crystalline wurtzite ZnO. Room temperature photoluminescence exhibits strong ultraviolet emission from these nanowires, indicating good optical properties. A series of experiments was conducted to elucidate the unique growth behavior of these nanowires directly from the Zn grains and a growth model is proposed.

  4. Attachment-driven morphology evolvement of rectangular ZnO nanowires.

    PubMed

    Zhang, Dong-Feng; Sun, Ling-Dong; Yin, Jia-Lu; Yan, Chun-Hua; Wang, Rong-Ming

    2005-05-12

    The rectangular cross-sectional ZnO nanowires were synthesized in a solution method. An attachment-driven growth mechanism was proposed for the morphology evolvement of ZnO nanocrystals from nanoparticles to nanoplates and eventually to nanowires. Due to the pileup attachment of the nanoplates to recrystallize into nanowires, unique one-dimensional (1D) ZnO nanowires with the rectangular cross section were obtained, which is different from those nanowires in the previous reports. It is the first time the evidence that "oriented attachment" can occur not only for nanoparticles but also for nanoplates was obtained, suggesting that "oriented attachment" is an intrinsic behavior for nanosized materials. According to the growth model proposed based on the direct TEM observations, ZnO nanocrystals can be easily controlled as nanoparticles, nanoplates, or nanowires by tuning the synthetic parameters. PMID:16852043

  5. Efficient nitrogen incorporation in ZnO nanowires

    PubMed Central

    Stehr, Jan E.; Chen, Weimin M.; Reddy, Nandanapalli Koteeswara; Tu, Charles W.; Buyanova, Irina A.

    2015-01-01

    One-dimensional ZnO nanowires (NWs) are a promising materials system for a variety of applications. Utilization of ZnO, however, requires a good understanding and control of material properties that are largely affected by intrinsic defects and contaminants. In this work we provide experimental evidence for unintentional incorporation of nitrogen in ZnO NWs grown by rapid thermal chemical vapor deposition, from electron paramagnetic resonance spectroscopy. The incorporated nitrogen atoms are concluded to mainly reside at oxygen sites (NO). The NO centers are suggested to be located in proximity to the NW surface, based on their reduced optical ionization energy as compared with that in bulk. This implies a lower defect formation energy at the NW surface as compared with its bulk value, consistent with theoretical predictions. The revealed facilitated incorporation of nitrogen in ZnO nanostructures may be advantageous for realizing p-type conducting ZnO via N doping. The awareness of this process can also help to prevent such unintentional doping in structures with desired n-type conductivity. PMID:26299157

  6. Efficient nitrogen incorporation in ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Stehr, Jan E.; Chen, Weimin M.; Reddy, Nandanapalli Koteeswara; Tu, Charles W.; Buyanova, Irina A.

    2015-08-01

    One-dimensional ZnO nanowires (NWs) are a promising materials system for a variety of applications. Utilization of ZnO, however, requires a good understanding and control of material properties that are largely affected by intrinsic defects and contaminants. In this work we provide experimental evidence for unintentional incorporation of nitrogen in ZnO NWs grown by rapid thermal chemical vapor deposition, from electron paramagnetic resonance spectroscopy. The incorporated nitrogen atoms are concluded to mainly reside at oxygen sites (NO). The NO centers are suggested to be located in proximity to the NW surface, based on their reduced optical ionization energy as compared with that in bulk. This implies a lower defect formation energy at the NW surface as compared with its bulk value, consistent with theoretical predictions. The revealed facilitated incorporation of nitrogen in ZnO nanostructures may be advantageous for realizing p-type conducting ZnO via N doping. The awareness of this process can also help to prevent such unintentional doping in structures with desired n-type conductivity.

  7. Excitonic effects in ZnO nanowires and hollow nanotubes

    NASA Astrophysics Data System (ADS)

    Willander, M.; Lozovik, Y. E.; Zhao, Q. X.; Nur, O.; Hu, Q.-H.; Klason, P.

    2007-02-01

    Energy levels and wave functions of ground and excited states of an exciton are calculated by the method of imaginary time. Energy levels as functions of radius of single and double wall nanotube are studied. Asymptotic behavior of energy levels at large and small values of the radius using perturbation theory and adiabatic approximation is considered. Spatially indirect exciton in semiconductor nanowire is also investigated. Experimental result from high quality reproducible ZnO nanowires grown by low temperature chemical engineering is presented. State of the art high brightness white light emitting diodes (HB-LEDs) are demonstrated from the grown ZnO nano-wires. The color temperature and color rendering index (CRI) of the HB-LEDs values was found to be (3250 K, 82), and (14000 K, 93), for the best LEDs, which means that the quality of light is superior to one obtained from GaN LEDs available on the market today. The role of V Zn and V ° on the emission responsible for the white light band as well as the peak position of this important wide band is thoroughly investigated in a systematic way.

  8. Spatially controlled growth of highly crystalline ZnO nanowires by an inkjet-printing catalyst-free method

    NASA Astrophysics Data System (ADS)

    Güell, Frank; Martínez-Alanis, Paulina R.; Khachadorian, Sevak; Zamani, Reza R.; Franke, Alexander; Hoffmann, Axel; Wagner, Markus R.; Santana, Guillermo

    2016-02-01

    High-density arrays of uniform ZnO nanowires with a high-crystal quality have been synthesized by a catalyst-free vapor-transport method. First, a thin ZnO film was deposited on a Si substrate as nucleation layer for the ZnO nanowires. Second, spatially selective and mask-less growth of ZnO nanowires was achieved using inkjet-printed patterned islands as the nucleation sites on a SiO2/Si substrate. Raman scattering and low temperature photoluminescence measurements were applied to characterize the structural and optical properties of the ZnO nanowires. The results reveal negligible amounts of strain and defects in the mask-less ZnO nanowires as compared to the ones grown on the ZnO thin film, which underlines the potential of the inkjet-printing approach for the growth of high-crystal quality ZnO nanowires.

  9. Energy harvesting from vertically aligned PZT nanowire arrays

    NASA Astrophysics Data System (ADS)

    Malakooti, Mohammad H.; Zhou, Zhi; Sodano, Henry A.

    2016-04-01

    In this paper, a nanostructured piezoelectric beam is fabricated using vertically aligned lead zirconate titanate (PZT) nanowire arrays and its capability of continuous power generation is demonstrated through direct vibration tests. The lead zirconate titanate nanowires are grown on a PZT thin film coated titanium foil using a hydrothermal reaction. The PZT thin film serves as a nucleation site while the titanium foil is used as the bottom electrode. Electromechanical frequency response function (FRF) analysis is performed to evaluate the power harvesting efficiency of the fabricated device. Furthermore, the feasibility of the continuous power generation using the nanostructured beam is demonstrated through measuring output voltage from PZT nanowires when beam is subjected to a sinusoidal base excitation. The effect of tip mass on the voltage generation of the PZT nanowire arrays is evaluated experimentally. The final results show the great potential of synthesized piezoelectric nanowire arrays in a wide range of applications, specifically power generation at nanoscale.

  10. Optical modulation of persistent photoconductivity in ZnO nanowires

    SciTech Connect

    Wang Yao; Liao Zhaoliang; Chen Dongmin; She Guangwei; Mu Lixuan; Shi Wensheng

    2011-05-16

    In this study, ZnO nanowires (ZNWs)-based optoelectric devices are found to exhibit strong persistent photoconductivity (PPC) effect. An optical modulation on the PPC effect of the ZNWs with 980 nm infrared (IR) laser has been investigated. It was found that the decay time for the PPC can be significantly shortened by IR irradiation. The modulation mechanism related with the oxygen vacancies and the subband gap excitation is proposed. Based on this mechanism, the modulation behavior of the IR can be well explained. The present optical modulation on the PPC is suggested to have potential applications in enhancing the performance of ZnO-based photodetectors.

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

    PubMed

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

    2016-05-01

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

  12. Towards high-performance, low-cost quartz sensors with high-density, well-separated, vertically aligned ZnO nanowires by low-temperature, seed-less, single-step, double-sided growth.

    PubMed

    Orsini, Andrea; Medaglia, Pier Gianni; Scarpellini, David; Pizzoferrato, Roberto; Falconi, Christian

    2013-09-01

    Resonant sensors with nanostructured surfaces have long been considered as an emergent platform for high-sensitivity transduction because of the potentially very large sensing areas. Nevertheless, until now only complex, time-consuming, expensive and sub-optimal fabrication procedures have been described; in fact, especially with reference to in-liquid applications, very few devices have been reported. Here, we first demonstrate that, by immersing standard, ultra-low-cost quartz resonators with un-polished silver electrodes in a conventional zinc nitrate/HMTA equimolar nutrient solution, the gentle contamination from the metallic package allows direct growth on the electrodes of arrays of high-density (up to 10 μm⁻²) and well-separated (no fusion at the roots) ZnO nanowires without any seed layer or thermal annealing. The combination of high-density and good separation is ideal for increasing the sensing area; moreover, this uniquely simple, single-step process is suitable for conventional, ultra-low-cost and high-frequency quartzes, and results in devices that are already packaged and ready to use. As an additional advantage, the process parameters can be effectively optimized by measuring the quartz admittance before and after growth. As a preliminary test, we show that the sensitivity to the liquid properties of high-frequency (i.e. high sensitivity) quartzes can be further increased by nearly one order of magnitude and thus show the highest ever reported frequency shifts of an admittance resonance in response to immersion in both ethanol and water. PMID:23924776

  13. Tribological characteristics of ZnO nanowires investigated by atomic force microscope

    NASA Astrophysics Data System (ADS)

    Chung, Koo-Hyun; Kim, Hyun-Joon; Lin, Li-Yu; Kim, Dae-Eun

    2008-08-01

    Zinc oxide (ZnO) nanowires have attracted great interest in nanodevices. In this work, the tribological characteristics of vertically grown ZnO nanowires obtained by metalorganic chemical vapor deposition were investigated by using an atomic force microscope (AFM). The ZnO nanowires were slid against flattened silicon and diamond-coated AFM probes under 50 150 nN normal force while monitoring the frictional force. The wear of the ZnO nanowires was observed by a scanning electron microscope and quantified based on Archard’s wear law. Also, the wear debris accumulated on the silicon probe was analyzed by using a transmission electron microscope (TEM). The results showed that the wear of ZnO nanowires slid against the silicon probe was extremely small. However, when the ZnO nanowires were slid against the diamond-coated probe, the wear coefficients ranged from 0.006 to 0.162, which correspond to the range of severe wear at the macroscale. It was also shown that the friction coefficient decreased from 0.30 to 0.25 as the sliding cycles increased. From TEM observation, it was found that the ZnO wear debris was mainly amorphous in structure. Also, crystalline ZnO nanoparticles were observed among the wear debris.

  14. Gate-tunable photocurrent in ZnO nanowires mediated by nanowire-substrate interface states

    NASA Astrophysics Data System (ADS)

    Yang, Liangliang; Wang, Qiaoming; Tao, Xin; Taylor, Shelby P.; Gu, Yi

    2015-03-01

    We report the observation of gate-tunable photocurrent in ZnO nanowires under optical excitation in the visible regime. Particularly, the photocurrent can be tuned by one order of magnitude with moderate changes in the backgate voltages (from -10 V to 10 V), and by more than two orders of magnitude within an extended range of the backgate voltage (several tens of volts). Using scanning photocurrent microscopy, single-nanowire photocurrent spectroscopy, and numerical calculations, we suggest that this gate tunability originates from the nanowire/substrate (Si3N4) interface states, where the electron occupation of these states and the excitation of electrons are controlled by the backgate voltage. This external gate tunability of the photocarrier generation facilitated by interface states provides an additional way to control photodetecting and photovoltaic properties, and this approach can also be extended to other nanostructures, such as two-dimensional semiconductors, where the surface effects are significant.

  15. Fabrication and characterization of hexagonally patterned quasi-1D ZnO nanowire arrays

    PubMed Central

    2014-01-01

    Quasi-one-dimensional (quasi-1D) ZnO nanowire arrays with hexagonal pattern have been successfully synthesized via the vapor transport process without any metal catalyst. By utilizing polystyrene microsphere self-assembled monolayer, sol–gel-derived ZnO thin films were used as the periodic nucleation sites for the growth of ZnO nanowires. High-quality quasi-1D ZnO nanowires were grown from nucleation sites, and the original hexagonal periodicity is well-preserved. According to the experimental results, the vapor transport solid condensation mechanism was proposed, in which the sol–gel-derived ZnO film acting as a seed layer for nucleation. This simple method provides a favorable way to form quasi-1D ZnO nanostructures applicable to diverse fields such as two-dimensional photonic crystal, nanolaser, sensor arrays, and other optoelectronic devices. PMID:24521308

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

    PubMed Central

    2012-01-01

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

  17. Enhanced photocatalytic activity of ultra-high aspect ratio ZnO nanowires due to Cu induced defects

    NASA Astrophysics Data System (ADS)

    Pasupathi Sugavaneshwar, Ramu; Duy Dao, Thang; Nanda, Karuna Kar; Nagao, Tadaaki; Hishita, Shunichi; Sakaguchi, Isao

    2015-12-01

    We report the synthesis of ZnO nanowires in ambient air at 650°C by a single-step vapor transport method using two different sources Zn (ZnO nanowires-I) and Zn:Cu (ZnO nanowires-II). The Zn:Cu mixed source co-vaporize Zn with a small amount of Cu at temperatures where elemental Cu source does not vaporize. This method provides us a facile route for Cu doping into ZnO. The aspect ratio of the grown ZnO nanowires-II was found to be higher by more than five times compared ZnO nanowires-I. Photocatalytic activity was measured by using a solar simulator and its ultraviolet-filtered light. The ZnO nanowires-II shows higher catalytic activity due to increased aspect ratio and higher content of surface defects because of incorporation of Cu impurities.

  18. Optical and morphological properties of graphene sheets decorated with ZnO nanowires via polyol enhancement

    SciTech Connect

    Sharma, Vinay Rajaura, Rajveer Singh; Sharma, Preetam K.; Srivastava, Subodh; Vijay, Y. K.; Sharma, S. S.

    2014-04-24

    Graphene-ZnO nanocomposites have proven to be very useful materials for photovoltaic and sensor applications. Here, we report a facile, one-step in situ polymerization method for synthesis of graphene sheets randomly decorated with zinc oxide nanowires using ethylene glycol as solvent. We have used hydrothermal treatment for growth of ZnO nanowires. UV-visible spectra peak shifting around 288nm and 307 nm shows the presence of ZnO on graphene structure. Photoluminiscence spectra (PL) in 400nm-500nm region exhibits the luminescence quenching effect. Scanning electron microscopy (SEM) image confirms the growth of ZnO nanowires on graphene sheets.

  19. Resistive switching characteristics of ZnO nanowires.

    PubMed

    Yoo, Eun Ji; Shin, Il Kwon; Yoon, Tae Sik; Choi, Young Jin; Kang, Chi Jung

    2014-12-01

    Binary transition metal oxides such as ZnO, TiO2, and MnO; and their various structures such as thin film, nanowire, and nanoparticle assembly; have been widely investigated for use in insulators in resistive random access memory (ReRAM), considered a next-generation nonvolatile memory device. Among the various driving mechanisms of resistive switching in insulating materials, the conductive filament model is one of the most widely accepted. Studies on spatially confined structures such as one-dimensional nanostructures and zero-dimensional nanoparticles to reveal the detailed filament constructing mechanism are warranted because low-dimensional nanostructures can provide more localized properties with a narrow dispersion of operational parameter values compared with thin-film structures. We investigated the resistive switching characteristics of ZnO nanowire (NW) structures. The NWs were grown on an Au/Ti/SiO2/Si substrate via the hydrothermal method. The empty space between the top and bottom electrodes was filled with a photoresist to prevent direct connection between the electrodes. The top electrode (Cr) and bottom electrode (Au), both with a thickness of -100 nm, were deposited by DC sputtering. The current-voltage (I-V) measurements were performed using a semiconductor characterization system. Additionally, the local current image and the point I-V characteristics for each NW were examined by replacing the top electrode with a conducting atomic force microscope tip. The Au-ZnO NW-Cr devices exhibited bipolar resistive switching behavior. PMID:25971083

  20. Synthesis of Ni(OH)2 nanoflakes on ZnO nanowires by pulse electrodeposition for high-performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Lo, I.-Hsiang; Wang, Jun-Yi; Huang, Kuo-Yen; Huang, Jin-Hua; Kang, Weng P.

    2016-03-01

    A high-performance supercapacitor based on Ni(OH)2 nanoflakes modified ZnO nanowires (NWs) was developed. The well-aligned ZnO NWs were synthesized by chemical bath deposition, followed by pulse electrodeposition of Ni(OH)2 nanoflakes on the surface of ZnO NWs at 1 mA cm-2 current density. The effects of the pulse electrodeposition conditions were systematically investigated. Both the pulse time and relaxation time were found to affect the size and interspacing of the nanoflakes, while the deposition cycle number determines the thickness of the Ni(OH)2 nanoflake shell. The ZnO/Ni(OH)2 nanocomposite electrode fabricated under the optimal pulse electrodeposition conditions has exhibited a large specific capacitance of 1830 F g-1, a high energy density of 51.5 Wh kg-1, and a high power density of 9 kW kg-1, revealing its potential application in electrochemical capacitors.

  1. Rapid large-scale preparation of ZnO nanowires for photocatalytic application.

    PubMed

    Ma, Chunyu; Zhou, Zhihua; Wei, Hao; Yang, Zhi; Wang, Zhiming; Zhang, Yafei

    2011-01-01

    ZnO nanowires are a promising nanomaterial for applications in the fields of photocatalysis, nano-optoelectronics, and reinforced composite materials. However, the challenge of producing large-scale ZnO nanowires has stunted the development and practical utilization of ZnO nanowires. In this study, a modified carbothermal reduction method for preparing large-scale ZnO nanowires in less than 5 min is reported. The preparation was performed in a quartz tube furnace at atmospheric pressure without using any catalysts. A mixed gas of air and N2 with a volume ratio of 45:1 was used as the reactive and carrier gas. About 0.8 g ZnO nanowires was obtained using 1 g ZnO and 1 g graphite powder as source materials. The obtained nanowires exhibited a hexagonal wurtzite crystal structure with an average diameter of about 33 nm. Good photocatalytic activity of the nanowires toward the photodegradation of methylene blue dye under UV irradiation was also demonstrated. PMID:21968032

  2. Rapid large-scale preparation of ZnO nanowires for photocatalytic application

    PubMed Central

    2011-01-01

    ZnO nanowires are a promising nanomaterial for applications in the fields of photocatalysis, nano-optoelectronics, and reinforced composite materials. However, the challenge of producing large-scale ZnO nanowires has stunted the development and practical utilization of ZnO nanowires. In this study, a modified carbothermal reduction method for preparing large-scale ZnO nanowires in less than 5 min is reported. The preparation was performed in a quartz tube furnace at atmospheric pressure without using any catalysts. A mixed gas of air and N2 with a volume ratio of 45:1 was used as the reactive and carrier gas. About 0.8 g ZnO nanowires was obtained using 1 g ZnO and 1 g graphite powder as source materials. The obtained nanowires exhibited a hexagonal wurtzite crystal structure with an average diameter of about 33 nm. Good photocatalytic activity of the nanowires toward the photodegradation of methylene blue dye under UV irradiation was also demonstrated. PMID:21968032

  3. Anisotropic third-order optical nonlinearity of a single ZnO micro/nanowire.

    PubMed

    Wang, Kai; Zhou, Jun; Yuan, Longyan; Tao, Yuting; Chen, Jian; Lu, Peixiang; Wang, Zhong Lin

    2012-02-01

    We report a systematic study about the anisotropic third-order optical nonlinearity of a single ZnO micro/nanowire by using the Z-scan method with a femtosecond laser. The two-photon absorption coefficient and nonlinear refraction index, which are measured as a function of polarization angle and sample orientation angle, exhibit oscillation curves with a period of π/2, indicating a highly polarized optical nonlinearity of the ZnO micro/nanowire. Further studies show that the polarized optical nonlinearity of the ZnO micro/nanowire is highly size-dependent. The results indicate that ZnO nanowire has great potential in applications of nanolasers, all-optical switching and polarization-sensitive photodetectors. PMID:22214490

  4. Flexible high-output nanogenerator based on lateral ZnO nanowire array.

    PubMed

    Zhu, Guang; Yang, Rusen; Wang, Sihong; Wang, Zhong Lin

    2010-08-11

    We report here a simple and effective approach, named scalable sweeping-printing-method, for fabricating flexible high-output nanogenerator (HONG) that can effectively harvesting mechanical energy for driving a small commercial electronic component. The technique consists of two main steps. In the first step, the vertically aligned ZnO nanowires (NWs) are transferred to a receiving substrate to form horizontally aligned arrays. Then, parallel stripe type of electrodes are deposited to connect all of the NWs together. Using a single layer of HONG structure, an open-circuit voltage of up to 2.03 V and a peak output power density of approximately 11 mW/cm(3) have been achieved. The generated electric energy was effectively stored by utilizing capacitors, and it was successfully used to light up a commercial light-emitting diode (LED), which is a landmark progress toward building self-powered devices by harvesting energy from the environment. This research opens up the path for practical applications of nanowire-based piezoelectric nanogeneragtors for self-powered nanosystems. PMID:20698630

  5. Graphene cathode-based ZnO nanowire hybrid solar cells.

    PubMed

    Park, Hyesung; Chang, Sehoon; Jean, Joel; Cheng, Jayce J; Araujo, Paulo T; Wang, Mingsheng; Bawendi, Moungi G; Dresselhaus, Mildred S; Bulović, Vladimir; Kong, Jing; Gradečak, Silvija

    2013-01-01

    Growth of semiconducting nanostructures on graphene would open up opportunities for the development of flexible optoelectronic devices, but challenges remain in preserving the structural and electrical properties of graphene during this process. We demonstrate growth of highly uniform and well-aligned ZnO nanowire arrays on graphene by modifying the graphene surface with conductive polymer interlayers. On the basis of this structure, we then demonstrate graphene cathode-based hybrid solar cells using two different photoactive materials, PbS quantum dots and the conjugated polymer P3HT, with AM 1.5G power conversion efficiencies of 4.2% and 0.5%, respectively, approaching the performance of ITO-based devices with similar architectures. Our method preserves beneficial properties of graphene and demonstrates that it can serve as a viable replacement for ITO in various photovoltaic device configurations. PMID:23205637

  6. Epitaxial growth of aligned AlGalnN nanowires by metal-organic chemical vapor deposition

    DOEpatents

    Han, Jung; Su, Jie

    2008-08-05

    Highly ordered and aligned epitaxy of III-Nitride nanowires is demonstrated in this work. <1010> M-axis is identified as a preferential nanowire growth direction through a detailed study of GaN/AlN trunk/branch nanostructures by transmission electron microscopy. Crystallographic selectivity can be used to achieve spatial and orientational control of nanowire growth. Vertically aligned (Al)GaN nanowires are prepared on M-plane AlN substrates. Horizontally ordered nanowires, extending from the M-plane sidewalls of GaN hexagonal mesas or islands demonstrate new opportunities for self-aligned nanowire devices, interconnects, and networks.

  7. Imaging Single ZnO Vertical Nanowire Laser Cavities using UV-Laser Scanning Confocal Microscopy

    SciTech Connect

    Gargas, D.J.; Toimil-Molares, M.E.; Yang, P.

    2008-11-17

    We report the fabrication and optical characterization of individual ZnO vertical nanowire laser cavities. Dilute nanowire arrays with interwire spacing>10 ?m were produced by a modified chemical vapor transport (CVT) method yielding an ideal platform for single nanowire imaging and spectroscopy. Lasing characteristics of a single vertical nanowire are presented, as well as high-resolution photoluminescence imaging by UV-laser scanning confocal microscopy. In addition, three-dimensional (3D) mapping of the photoluminescence emission performed in both planar and vertical dimensions demonstrates height-selective imaging useful for vertical nanowires and heteronanostructures emerging in the field of optoelectronics and nanophotonics.

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

    PubMed Central

    2013-01-01

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

  9. 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

  10. Electrical anisotropy in coatings of aligned silver nanowires

    NASA Astrophysics Data System (ADS)

    Xu, Ye; Galderon-Ortiz, Gabriel; Exarhos, Annemarie; Alsayed, Ahmed; Winey, Karen; Kikkawa, Jay; Yodh, Arjun

    2015-03-01

    Conductive and transparent coatings consisting of silver nanowires (AgNWs) have been suggested as a promising candidate to replace traditional ITO coatings for emerging flexible electronics applications. The electrical properties of such AgNW coatings depend strongly on the structure of nanowire networks formed by various processing methods. In this work, we study how the alignment of nanowires affects the electrical anisotropy in AgNW coatings. Specifically, we introduce a robust method to prepare coatings of well-aligned AgNWs on glass substrates; the method utilizes the rapid flow of AgNW suspensions through a confined geometry. The angle-dependent sheet resistance of the coatings was measured, and large anisotropy in surface conductivity was found to characterize the aligned AgNW networks. We also explore the degree of alignment and surface coverage of AgNWs in the networks, thereby establishing connections between microscopy network structures and macroscopic electrical anisotropy. This work was supported by the NSF DMR12-05463, DMR-1305199, PENN MRSEC DMR11-20901, NASA NNX08AO0G grants, and Solvay.

  11. ZnO nanowire UV photodetectors with high internal gain.

    PubMed

    Soci, C; Zhang, A; Xiang, B; Dayeh, S A; Aplin, D P R; Park, J; Bao, X Y; Lo, Y H; Wang, D

    2007-04-01

    ZnO nanowire (NW) visible-blind UV photodetectors with internal photoconductive gain as high as G approximately 108 have been fabricated and characterized. The photoconduction mechanism in these devices has been elucidated by means of time-resolved measurements spanning a wide temporal domain, from 10-9 to 102 s, revealing the coexistence of fast (tau approximately 20 ns) and slow (tau approximately 10 s) components of the carrier relaxation dynamics. The extremely high photoconductive gain is attributed to the presence of oxygen-related hole-trap states at the NW surface, which prevents charge-carrier recombination and prolongs the photocarrier lifetime, as evidenced by the sensitivity of the photocurrrent to ambient conditions. Surprisingly, this mechanism appears to be effective even at the shortest time scale investigated of t < 1 ns. Despite the slow relaxation time, the extremely high internal gain of ZnO NW photodetectors results in gain-bandwidth products (GB) higher than approximately 10 GHz. The high gain and low power consumption of NW photodetectors promise a new generation of phototransistors for applications such as sensing, imaging, and intrachip optical interconnects. PMID:17358092

  12. Electrical properties of ZnO single nanowires

    NASA Astrophysics Data System (ADS)

    Stiller, Markus; Barzola-Quiquia, José; Zoraghi, Mahsa; Esquinazi, Pablo

    2015-10-01

    We have investigated the electrical resistance R(T) of ZnO nanowires of ≈ 400 nm diameter as a function of temperature, between 30 K and 300 K, and frequency in the range 40 Hz to 30 MHz. The measurements were done on the as-prepared and after low-energy proton implantation at room temperature. The temperature dependence of the resistance of the wire, before proton implantation, can be well described by two processes in parallel. One process is the fluctuation induced tunneling conductance (FITC) and the other the usual thermally activated process. The existence of a tunneling conductance was also observed in the current-voltage (I-V) results, and can be well described by the FITC model. Impedance spectroscopy measurements in the as-prepared state and at room temperature, indicate and support the idea of two contributions of these two transport processes in the nanowires. Electron backscatter diffraction confirms the existence of different crystalline regions. After the implantation of H+ a third thermally activated process is found that can be explained by taking into account the impurity band splitting due to proton implantation.

  13. Single ZnO nanowire ultraviolet detector with free-recovered contact performance

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Wang, Liang; Li, Xin; Li, Zhenhu; Feng, Shuanglong; Lu, Wenqiang

    2016-06-01

    In this paper, a single ZnO nanowire ultraviolet detector was firstly fabricated by a single ZnO nanowire and silver paint, which can be free-recovered from a Schottky contact to an Ohmic contact. Key effect factors such as the illumination and bias voltage of the free-recovered performance were also investigated. Meanwhile, the reason for the recoverable contact was further confirmed in detail. This result is beneficial for developing the highly sensitive ZnO based ultraviolet detector.

  14. Efficient production of ZnO nanowires by a ball milling and annealing method

    NASA Astrophysics Data System (ADS)

    Glushenkov, A. M.; Zhang, H. Z.; Zou, J.; Lu, G. Q.; Chen, Y.

    2007-05-01

    ZnO powder was mechanically milled in a ball mill. This procedure was found to greatly increase its evaporation ability. The anomalous evaporation behaviour was caused by the disordered structure of the milled material and was not related to the increase in its surface area after milling. ZnO nanowires were synthesized by evaporation of this milled precursor. Nanowires with smooth and rough surfaces were present in the sample; the latter morphology was dominant. A green emission band centred at 510 nm was dominant in the cathodoluminescence spectrum of the nanowires.

  15. Photovoltaic effect and charge storage in single ZnO nanowires

    SciTech Connect

    Liao Zhimin; Xu Jun; Zhang Jingmin; Yu Dapeng

    2008-07-14

    Asymmetric Schottky barriers between ZnO nanowire and metal electrode have been fabricated at the two ends of the nanowire. An obvious photocurrent generated from the device at zero voltage bias can be switched on/off with quick response by controlling the light irradiation. Moreover, the device can still afford a current at zero bias after switching off light illumination, which is ascribed to the charge storage effect in single ZnO nanowires. The underlying mechanisms related to the photovoltaic effect and charge storage were discussed.

  16. Fabrication of ZnO nanowires through thermal heating of metallic Zn by solar energy

    NASA Astrophysics Data System (ADS)

    Lee, Geun-Hyoung

    2011-04-01

    ZnO nanowires were synthesized in a short time of a few seconds through a simple thermal evaporation of Zn powder using solar energy under air atmosphere. The Zn powder was heated by focusing sunlight on the Zn powder employing a magnifying lens. This strategy heated Zn to its evaporation temperature resulting in its oxidation in air. This procedure formed ZnO nanowires of ˜10 nm diameter and ˜2 μm length. As only Zn powder without any catalysts was used as the source material, it is suggested that the growth of the nanowires occurs through a vapor-solid mechanism. The cathodoluminescence (CL) spectrum from such ZnO nanowires showed strong ultraviolet emission indicating their highly crystalline quality besides good optical properties.

  17. Highly aligned vertical GaN nanowires using submonolayer metal catalysts

    DOEpatents

    Wang, George T.; Li, Qiming; Creighton, J. Randall

    2010-06-29

    A method for forming vertically oriented, crystallographically aligned nanowires (nanocolumns) using monolayer or submonolayer quantities of metal atoms to form uniformly sized metal islands that serve as catalysts for MOCVD growth of Group III nitride nanowires.

  18. Large hexagonal arrays of aligned ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Banerjee, D.; Rybczynski, J.; Huang, J. Y.; Wang, D. Z.; Kempa, K.; Ren, Z. F.

    2005-02-01

    Large-scale truly periodic arrays of vertically aligned zinc oxide nanorods were grown on pre-patterned and pre-annealed gold dots on a-plane sapphire substrates via the vapor liquid solid mechanism. Periodic arrays of triangular gold islands were first patterned on the a-plane sapphire substrates by the nanosphere self-assembly technique. Zinc has been found to be an effective interfacial modifier between gold and sapphire to form single catalytic dots from triangular islands. The successful fabrication of zinc oxide nanowires in truly periodic arrays opens up the possibility of achieving enhanced room-temperature ultraviolet lasing and photonic crystal based devices and sensors.

  19. ZnO quantum dots-decorated ZnO nanowires for the enhancement of antibacterial and photocatalytic performances

    NASA Astrophysics Data System (ADS)

    Wu, Jyh Ming; Tsay, Li-Yi

    2015-10-01

    We demonstrate highly antibacterial activities for killing off Staphylococcus aureus and Escherichia coli using ZnO nanowires decorated with ZnO quantum dots (so-called ZnO QDs/NWs) under visible-light irradiation and dark conditions. The average size of the ZnO QDs is in the range of 3-5 nm; these were uniformly dispersed on the ZnO nanowires’ surface to form the ZnO QDs/NWs. A significant blue-shift effect was observed using photoluminescence (PL) spectra. The size of the ZnO QDs is strongly dependent on the material’s synthesis time. The ZnO QDs/NWs exhibited an excellent photocatalytic activity under visible-light irradiation. The ZnO QDs’ active sites (i.e. the O-H bond and Zn2+) accelerate the photogenerated-carrier migration from the QDs to the NWs. As a consequence, the electrons reacted with the dissolved oxygen to form oxygen ions and produced hydroperoxyl radicals to enhance photocatalytic activity. The antibacterial activities (as indicated by R-factor-inhibiting activity) of the ZnO QDs/NWs for killing off Staphylococcus aureus and Escherichia coli is around 4.9 and 5.5 under visible-light irradiation and dark conditions, respectively. The hydroxyl radicals served as an efficient oxidized agent for decomposing the organic dye and microorganism species. The antibacterial activities of the ZnO QDs/NWs in the dark may be attributed to the Zn2+ ions that were released from the ZnO QDs and infused into the microbial solution against the growth of bacteria thus disrupting the microorganism. The highly antibacterial and photocatalytic activity of the ZnO QDs/NWs can be well implanted on a screen window, thus offering a promising solution to inhibit the spread of germs under visible-light and dark conditions.

  20. Gate-tunable photocurrent in ZnO nanowires mediated by nanowire-substrate interface states

    SciTech Connect

    Yang, Liangliang; Wang, Qiaoming; Tao, Xin; Taylor, Shelby P.; Gu, Yi

    2015-03-02

    We report the observation of gate-tunable photocurrent in ZnO nanowires under optical excitation in the visible regime. Particularly, the photocurrent can be tuned by one order of magnitude with moderate changes in the backgate voltages (from −10 V to 10 V), and by more than two orders of magnitude within an extended range of the backgate voltage (several tens of volts). Using scanning photocurrent microscopy, single-nanowire photocurrent spectroscopy, and numerical calculations, we suggest that this gate tunability originates from the nanowire/substrate (Si{sub 3}N{sub 4}) interface states, where the electron occupation of these states and the excitation of electrons are controlled by the backgate voltage. This external gate tunability of the photocarrier generation facilitated by interface states provides an additional way to control photodetecting and photovoltaic properties, and this approach can also be extended to other nanostructures, such as two-dimensional semiconductors, where the surface effects are significant.

  1. Structural, photoluminescence and picosecond nonlinear optical effect of In-doped ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Yan, Xiao-Yan; Yao, Cheng-Bao; Li, Jin; Hu, Jun-Yan; Li, Qiang-Hua; Yang, Shou-Bin

    2016-05-01

    In-doped ZnO (IZO) nanowires were grown using the chemical vapour deposition method. The IZO nanowires have been characterized by scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and UV-Visible spectroscopy. The PL results demonstrated a larger band-gap for the IZO nanowires in comparison to the undoped ZnO. Two major emission peaks were observed for the IZO nanowires, one originated from the free exciton recombination (ultraviolet emission) and another possibly related to the deep-level emission (visible emission). Furthermore, the nonlinear optical characteristic of the nanowires was studied using picosecond Z-scan technique. The experimental results show that the two and three-photon absorption coefficient of samples were able to be observed. These studies make the promising potential applications of the samples in the development of multifunctional all-optical devices.

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

    DOE PAGESBeta

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

    2016-04-11

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

  3. Conducting properties of nearly depleted ZnO nanowire UV sensors fabricated by dielectrophoresis

    NASA Astrophysics Data System (ADS)

    García Núñez, C.; García Marín, A.; Nanterne, P.; Piqueras, J.; Kung, P.; Pau, J. L.

    2013-10-01

    ZnO nanowires (NWs) with different radii (rNW) have been aligned between pre-patterned electrodes using dielectrophoresis (DEP) for the fabrication of high gain UV sensors. The DEP conditions (voltage amplitude and frequency) and electrode material, geometry and size were optimized to enhance the efficiency during the DEP process. To understand the alignment mechanism of the ZnO NWs, the dielectrophoretic force (FDEP) was analyzed as a function of the DEP conditions and NW dimensions. These studies showed that the DEP alignment process tends to trap NWs with a smaller radius. The effects of NW size on device performance were analyzed by means of I-V measurements in darkness and under illumination (200 nm < λ < 600 nm). In darkness, the NW resistance increases as rNW decreases due to the reduction of the conduction volume, until saturation is reached for rNW < 65 nm. On the other hand, the NW spectral photoresponse shows high values around 108 A W-1 (measured at 5 V and λ < 370 nm) and follows a linear trend as a function of the NW cross section. In addition, the cut-off wavelength depends on rNW, presenting a clear blue-shift for NWs with a lower radius (rNW < 50 nm). Transient photoresponse studies show that NWs with lower radii have longer rise times and shorter decay times mainly due to surface trapping effects. Regardless of NW size, passivation of the surface using a dielectric capping layer of SiO2 reduces the dynamic range of the photoresponse due to a strong increase of the dark current.

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

    SciTech Connect

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

    2014-03-17

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

  5. Nanoparticulate PdZn as a Novel Catalyst for ZnO Nanowire Growth

    PubMed Central

    2010-01-01

    ZnO nanowires have been grown by chemical vapour deposition (CVD) using PdZn bimetallic nanoparticles to catalyse the process. Nanocatalyst particles with mean particle diameters of 2.6 ± 0.3 nm were shown to catalyse the growth process, displaying activities that compare well with those reported for sputtered systems. Since nanowire diameters are linked to catalyst morphology, the size-control we are able to exhibit during particle preparation represents an advantage over existing approaches in terms of controlling nanowire dimensions, which is necessary in order to utilize the nanowires for catalytic or electrical applications. (See supplementary material 1) PMID:20672032

  6. Enhanced photoelectric performance in self-powered UV detectors based on ZnO nanowires with plasmonic Au nanoparticles scattered electrolyte

    NASA Astrophysics Data System (ADS)

    Zeng, Yiyu; Ye, Zhizhen; Lu, Bin; Dai, Wei; Pan, Xinhua

    2016-04-01

    Vertically aligned ZnO nanowires (NWs) were grown on a fluorine-doped tin-oxide-coated glass substrate by a hydrothermal method. Au nanoparticles were well dispersed in the mixed solution of ethanol and deionized water. A simple self-powered ultraviolet detector based on solid-liquid heterojunction was fabricated, utilizing ZnO NWs as active photoanode and such prepared mixed solution as electrolyte. The introduction of Au nanoparticles results in considerable improvements in the responsivity and sensitivity of the device compared with the one using deionized water as electrolyte, which is attributed to the enhanced light harvesting by Au nanoparticles.

  7. Microfabricated environmental barrier using ZnO nanowire on metal mesh

    NASA Astrophysics Data System (ADS)

    Shin, Young-Min; Lee, Seung-Ki; Lee, Joo-Yong; Kim, Jun-Ho; Park, Jae-Hyoung; Ji, Chang-Hyeon

    2013-12-01

    In this study, a waterproof environmental barrier for microsensor package has been developed using metal mesh covered with zinc oxide (ZnO) nanowire. A near superhydrophobic surface with two-dimensional array of holes has been fabricated by hydrothermal growth of ZnO nanowire on an off-the-shelf steel use stainless (SUS) mesh. For a twill-woven SUS wire mesh having wire thickness of 30 µm and gap of 33 µm, a maximum contact angle of 160.40° and a minimum contact angle hysteresis of 15.23° have been achieved using ZnO nanowire grown on the wire surface and further deposition of FC film. The mesh was able to withstand a maximum water pressure of 2,459.8 Pa. The measured height of ZnO nanowire was approximately 2-3 µm. The fabricated SUS mesh covered with ZnO nanowire has been assembled with a microphone package, and waterproof characteristics have been measured by cyclic dipping test at various water levels. For a microphone package having two acoustic ports on top and bottom covered with fabricated mesh, no visible change in acoustic characteristics has been observed up to 1,372.9 Pa of water pressure. Total volume of the package was 6.8 × 9.8 × 1.9 mm3.

  8. Direct growth of densely aligned ZnO nanorods on graphene

    NASA Astrophysics Data System (ADS)

    Honda, Mitsuhiro; Okumura, Ryuji; Ichikawa, Yo

    2016-08-01

    Densely aligned ZnO nanorods were directly grown on graphene sheets. On graphene prepared via a chemical vapor deposition technique, ZnO nanorods were synthesized by a hydrothermal method. The rod density was ∼1.4 × 109/cm2 and the nanorods were observed to be well aligned on graphene by scanning electron microscopy. The formation of such ZnO structures is considered to be induced by carbon vacancies in graphene in accordance with Raman spectroscopic results.

  9. Strain Loading Mode Dependent Bandgap Deformation Potential in ZnO Micro/Nanowires.

    PubMed

    Fu, Xuewen; Liao, Zhi-Min; Liu, Ren; Lin, Fang; Xu, Jun; Zhu, Rui; Zhong, Wei; Liu, Yingkai; Guo, Wanlin; Yu, Dapeng

    2015-12-22

    The electronic-mechanical coupling in semiconductor nanostructures under different strain loading modes can modulate their photoelectric properties in different manners. Here, we report the systematic investigation on the strain mode dependent bandgap deformation potential of ZnO micro/nanowires under both uniaxial tensile and bending strains at room temperature. Uniaxial stretching-photoluminescence results show that the deformation potential of the smaller ZnO nanowire (with diameter d = 260 nm) is -30.6 meV/%, and is close to the bulk value, whereas it deviates the bulk value and becomes to be -10.6 meV/% when the wire diameter is increased to d = 2 μm. This unconventional size dependence stems from surface effect induced inhomogeneous strain in the surface layer and the core of the ZnO micro/nanowires under uniaxial tension. For bending load mode, the in situ high-resolution transmission electron microscope analysis reveals that the local strain distributes linearly in the bending cross section. Further cathodoluminescence measurements on a bending ZnO microwire (d = 1.8 μm) demonstrate that the deformation potential is -27 meV/%, whose absolute value is much larger than that of the ZnO microwire under uniaxial tension. Further analysis reveals that the distinct deformation potentials originate from the different deforming modes in ZnO micro/nanowires under bending or uniaxial tensile strains. Our results should facilitate the design of flexible optoelectronic nanodevices. PMID:26517647

  10. Tuning the electronic properties of ZnO nanowire field effect transistors via surface functionalization.

    PubMed

    Han, Cheng; Xiang, Du; Zheng, Minrui; Lin, Jiadan; Zhong, Jianqiang; Sow, Chorng Haur; Chen, Wei

    2015-03-01

    Using in situ field effect transistor (FET) characterization combined with the molecular beam epitaxy technique, we demonstrate a significant depletion of electron charge carriers in single zinc oxide (ZnO) nanowire through the surface modification with molybdenum trioxide (MoO3) and 1, 4, 5, 8, 9, 11-hexaazatriphenylene hexacarbonitrile (HATCN) layers. The electron mobility of ZnO nanowire was found to sharply decrease after the surface modification with MoO3; in contrast, the electron mobility significantly increased after functionalization with HATCN layers. Such depletion of n-type conduction originates from the interfacial charge transfer, corroborated by in situ photoelectron spectroscopy studies. The air exposure effect on MoO(3-) and HATCN-coated ZnO nanowire devices was also investigated. PMID:25676393

  11. Tuning the electronic properties of ZnO nanowire field effect transistors via surface functionalization

    NASA Astrophysics Data System (ADS)

    Han, Cheng; Xiang, Du; Zheng, Minrui; Lin, Jiadan; Zhong, Jianqiang; Haur Sow, Chorng; Chen, Wei

    2015-03-01

    Using in situ field effect transistor (FET) characterization combined with the molecular beam epitaxy technique, we demonstrate a significant depletion of electron charge carriers in single zinc oxide (ZnO) nanowire through the surface modification with molybdenum trioxide (MoO3) and 1, 4, 5, 8, 9, 11-hexaazatriphenylene hexacarbonitrile (HATCN) layers. The electron mobility of ZnO nanowire was found to sharply decrease after the surface modification with MoO3; in contrast, the electron mobility significantly increased after functionalization with HATCN layers. Such depletion of n-type conduction originates from the interfacial charge transfer, corroborated by in situ photoelectron spectroscopy studies. The air exposure effect on MoO3- and HATCN-coated ZnO nanowire devices was also investigated.

  12. "High Quantum Efficiency of Band-Edge Emission from ZnO Nanowires"

    SciTech Connect

    GARGAS, DANIEL; GAO, HANWEI; WANG, HUNGTA; PEIDONG, YANG

    2010-12-01

    External quantum efficiency (EQE) of photoluminescence as high as 20 percent from isolated ZnO nanowires were measured at room temperature. The EQE was found to be highly dependent on photoexcitation density, which underscores the importance of uniform optical excitation during the EQE measurement. An integrating sphere coupled to a microscopic imaging system was used in this work, which enabled the EQE measurement on isolated ZnO nanowires. The EQE values obtained here are significantly higher than those reported for ZnO materials in forms of bulk, thin films or powders. Additional insight on the radiative extraction factor of one-dimensional nanostructures was gained by measuring the internal quantum efficiency of individual nanowires. Such quantitative EQE measurements provide a sensitive, noninvasive method to characterize the optical properties of low-dimensional nanostructures and allow tuning of synthesis parameters for optimization of nanoscale materials.

  13. High quantum efficiency of band-edge emission from ZnO nanowires.

    PubMed

    Gargas, Daniel J; Gao, Hanwei; Wang, Hungta; Yang, Peidong

    2011-09-14

    External quantum efficiency (EQE) of photoluminescence as high as 20% from isolated ZnO nanowires were measured at room temperature. The EQE was found to be highly dependent on photoexcitation density, which underscores the importance of uniform optical excitation during the EQE measurement. An integrating sphere coupled to a microscopic imaging system was used in this work, which enabled the EQE measurement on isolated ZnO nanowires. The EQE values obtained here are significantly higher than those reported for ZnO materials in forms of bulk, thin films or powders. Additional insight on the radiative extraction factor of one-dimensional nanostructures was gained by measuring the internal quantum efficiency of individual nanowires. Such quantitative EQE measurements provide a sensitive, noninvasive method to characterize the optical properties of low-dimensional nanostructures and allow tuning of synthesis parameters for optimization of nanoscale materials. PMID:21859081

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

    SciTech Connect

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

    2013-12-04

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

  15. Tunable Surface Wettability of ZnO Nanoparticle Arrays for Controlling the Alignment of Liquid Crystals.

    PubMed

    Chung, Yueh-Feng; Chen, Mu-Zhe; Yang, Sheng-Hsiung; Jeng, Shie-Chang

    2015-05-13

    The control of the liquid crystal (LC) alignment is very important for both academic research and practical applications. LC molecules aligned on the ZnO nanoparticle arrays (ZnO NPAs) are demonstrated and the pretilt angles of LCs can be controlled by using ZnO NPAs with different surface wettability. The wettability of ZnO NPAs fabricated by the solution-based hydrothermal method can be controlled by changing the annealing temperature of the as-prepared ZnO NPAs. The measurements of the energy-dispersive spectra and photoluminescence have shown that the chemical properties of ZnO NPAs have been changed with the annealing temperature. Our results show that the pretilt angle of LCs can be tuned continuously from ∼0 to ∼90° as the contact angle of water on ZnO NPAs changes from 33 to 108°. PMID:25895105

  16. Carrier density driven lasing dynamics in ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Wille, Marcel; Sturm, Chris; Michalsky, Tom; Röder, Robert; Ronning, Carsten; Schmidt-Grund, Rüdiger; Grundmann, Marius

    2016-06-01

    We report on the temporal lasing dynamics of high quality ZnO nanowires using the time-resolved micro-photoluminescence technique. The temperature dependence of the lasing characteristics and of the corresponding decay constants demonstrate the formation of an electron–hole plasma to be the underlying gain mechanism in the considered temperature range from 10 K to 300 K. We found that the temperature-dependent emission onset-time ({t}{{on}}) strongly depends on the excitation power and becomes smallest in the lasing regime, with values below 5 ps. Furthermore, the observed red shift of the dominating lasing modes in time is qualitatively discussed in terms of the carrier density induced change of the refractive index dispersion after the excitation laser pulse. This theory is supported by extending an existing model for the calculation of the carrier density dependent complex refractive index for different temperatures. This model coincides with the experimental observations and reliably describes the evolution of the refractive index after the excitation laser pulse.

  17. Carrier density driven lasing dynamics in ZnO nanowires.

    PubMed

    Wille, Marcel; Sturm, Chris; Michalsky, Tom; Röder, Robert; Ronning, Carsten; Schmidt-Grund, Rüdiger; Grundmann, Marius

    2016-06-01

    We report on the temporal lasing dynamics of high quality ZnO nanowires using the time-resolved micro-photoluminescence technique. The temperature dependence of the lasing characteristics and of the corresponding decay constants demonstrate the formation of an electron-hole plasma to be the underlying gain mechanism in the considered temperature range from 10 K to 300 K. We found that the temperature-dependent emission onset-time ([Formula: see text]) strongly depends on the excitation power and becomes smallest in the lasing regime, with values below 5 ps. Furthermore, the observed red shift of the dominating lasing modes in time is qualitatively discussed in terms of the carrier density induced change of the refractive index dispersion after the excitation laser pulse. This theory is supported by extending an existing model for the calculation of the carrier density dependent complex refractive index for different temperatures. This model coincides with the experimental observations and reliably describes the evolution of the refractive index after the excitation laser pulse. PMID:27103563

  18. One step syntheses of S incorporated ZnO nanowires for photocatalysis applications

    NASA Astrophysics Data System (ADS)

    Awad, Madeha Ahmed; Ibrahim, Eslam Mohamed Mohamed; Ahmed, Ahmed Mohamed

    2015-12-01

    S incorporated ZnO nanowires (NWs) were prepared by vapor transport method using ZnS bulk precursor. Effects of S incorporation on the structural, morphological, optical as well as photocatalysis performance of ZnO NWs were studied. EDAX analysis revealed existence of S with low ratio. A deformation of the hexagonal nanowires was observed inasmuch to the S existence. X-ray diffraction analysis asserted the formation of a single phase of ZnO with the emergence of two weak peaks identifier for ZnS. The low value of the optical band gap (3.10 eV) was ascribed to the increase in the level of the valence band maximum induced by the S doping. The capability of S incorporated ZnO as a photocatalyst was tested by the decomposition of methylene blue.

  19. Single ZnO Nanowire-Based Gas Sensors to Detect Low Concentrations of Hydrogen.

    PubMed

    Cardoza-Contreras, Marlene N; Romo-Herrera, José M; Ríos, Luis A; García-Gutiérrez, R; Zepeda, T A; Contreras, Oscar E

    2015-01-01

    Low concentrations of hazardous gases are difficult to detect with common gas sensors. Using semiconductor nanostructures as a sensor element is an alternative. Single ZnO nanowire gas sensor devices were fabricated by manipulation and connection of a single nanowire into a four-electrode aluminum probe in situ in a dual-beam scanning electron microscope-focused ion beam with a manipulator and a gas injection system in/column. The electrical response of the manufactured devices shows response times up to 29 s for a 121 ppm of H₂ pulse, with a variation in the nanowire resistance appreciable at room temperature and at 373.15 K of approximately 8% and 14% respectively, showing that ZnO nanowires are good candidates to detect low concentrations of H₂. PMID:26690158

  20. Single ZnO Nanowire-Based Gas Sensors to Detect Low Concentrations of Hydrogen

    PubMed Central

    Cardoza-Contreras, Marlene N.; Romo-Herrera, José M.; Ríos, Luis A.; García-Gutiérrez, R.; Zepeda, T. A.; Contreras, Oscar E.

    2015-01-01

    Low concentrations of hazardous gases are difficult to detect with common gas sensors. Using semiconductor nanostructures as a sensor element is an alternative. Single ZnO nanowire gas sensor devices were fabricated by manipulation and connection of a single nanowire into a four-electrode aluminum probe in situ in a dual-beam scanning electron microscope-focused ion beam with a manipulator and a gas injection system in/column. The electrical response of the manufactured devices shows response times up to 29 s for a 121 ppm of H2 pulse, with a variation in the nanowire resistance appreciable at room temperature and at 373.15 K of approximately 8% and 14% respectively, showing that ZnO nanowires are good candidates to detect low concentrations of H2. PMID:26690158

  1. Study of faceted Au nanoparticle capped ZnO nanowires: antireflection, surface enhanced Raman spectroscopy and photoluminescence aspects

    NASA Astrophysics Data System (ADS)

    Ghosh, A.; Juluri, R. R.; Guha, P.; Sathyavathi, R.; Dash, Ajit; Jena, B. K.; Satyam, P. V.

    2015-02-01

    We report a single step growth process of faceted Au nanoparticles (NPs) on highly c-axis oriented ZnO nanowires (NWs) and report that a system with a lower antireflection coefficient also showed higher surface enhanced Raman spectroscopy (SERS) enhanced factors. Well-dispersed Au NPs are grown on silicon substrate using a thin film-in-air-annealing method (using 1 nm and 5 nm thick Au films on silicon and subsequent annealing in air at 800 °C) wherein enhanced oxide growth at the Au-Si interface was used to inhibit inter-diffusion to avoid Au-Si alloy formation (Au/SiOx/Si). These substrates are used to grow aligned ZnO NWs using a high temperature (≈900 °C) chemical vapour deposition method. Depending on the size and areal density of initial catalytic Au NPs, the resultant photoluminescence, reflectance characteristics, and effectiveness as SERS substrates of the faceted Au NP capped ZnO NWs coatings are systematically studied. The highly oriented and faceted Au NPs on ZnO NWs have been used as free standing SERS substrates to detect sub-micro molar crystal violet molecules with an analytical enhancement factor (AEF) of ≥104 and with high repeatability. The substrate with high-density Au-ZnO heterostructures (5 nm Au case) found to have larger AEF, very low reflectance (≈0.75%) and more green emission.

  2. Coexistence of strong and weak coupling in ZnO nanowire cavities

    NASA Astrophysics Data System (ADS)

    Michalsky, Tom; Franke, Helena; Buschlinger, Robert; Peschel, Ulf; Grundmann, Marius; Schmidt-Grund, Rüdiger

    2016-06-01

    We present a high quality two-dimensional cavity structure based on ZnO nanowires coated with concentrical Bragg reflectors. The spatial mode distribution leads to the simultaneous appearance of the weak and strong coupling regime even at room temperature. Photoluminescence (PL) measurements agree with finite difference time domain (FDTD) simulations. Furthermore the ZnO core nanowires allow for the observation of middle polariton branches between the A- and B-exciton ground state resonances. Further, lasing emission up to room temperature is detected in excitation dependent photoluminescence measurements. Supplementary online material is available in electronic form at http://www.epjap.org

  3. Self-assembled ZnO agave-like nanowires and anomalous superhydrophobicity

    NASA Astrophysics Data System (ADS)

    Yang, Y. H.; Li, Z. Y.; Wang, B.; Wang, C. X.; Chen, D. H.; Yang, G. W.

    2005-09-01

    Thin films of ZnO agave-like nanowires were prepared on amorphous carbon thin layers on silicon substrates using thermal chemical vapour transport and condensation without any metal catalysts. The unusual superhydrophobicity of the fabricated surface was measured; the water contact angle reaches 151.1°. On the basis of experimental and theoretical analyses, it appears likely that the biomimetic microcomposite and nanocomposite surfaces of the prepared thin films of ZnO agave-like nanowires are responsible for the excellent superhydrophobicity.

  4. Facile route to high-density, ordered ZnO nanowire arrays and their photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Tao, Xiaoming; Liu, Yuyang; Sun, Xiaohong; Hu, Zhigang; Fei, Bin

    2006-10-01

    A simple template-directed wet chemistry route based on traditional thermal decomposition technique has been developed for the preparation of high-density, ordered ZnO nanowire arrays. The fabrication was performed at relative low temperature without involving complex procedures, sophisticated equipment and rigorous experiment conditions, thereby providing a straightforward and mild method to produce metal/metal oxide ordered nanostructures. The nanowire array system was evaluated by SEM, XRD, TEM and PL. A stable luminescence at 425 nm was present.

  5. ZnO Nanowire-Based Corona Discharge Devices Operated Under Hundreds of Volts

    NASA Astrophysics Data System (ADS)

    Yang, Wenming; Zhu, Rong; Zong, Xianli

    2016-02-01

    Minimizing the voltage of corona discharges, especially when using nanomaterials, has been of great interest in the past decade or so. In this paper, we report a new corona discharge device by using ZnO nanowires operated in atmospheric air to realize continuous corona discharge excited by hundreds of volts. ZnO nanowires were synthesized on microelectrodes using electric-field-assisted wet chemical method, and a thin tungsten film was deposited on the microchip to enhance discharging performance. The testing results showed that the corona inception voltages were minimized greatly by using nanowires compared to conventional dischargers as a result of the local field enhancement of nanowires. The corona could be continuously generated and self-sustaining. It was proved that the law of corona inception voltage obeyed the conventional Peek's breakdown criterion. An optimal thickness of tungsten film coated over ZnO nanowires was figured out to obtain the lowest corona inception voltage. The ion concentration of the nanowire-based discharger attained 1017/m3 orders of magnitude, which is practicable for most discharging applications.

  6. ZnO Nanowire-Based Corona Discharge Devices Operated Under Hundreds of Volts.

    PubMed

    Yang, Wenming; Zhu, Rong; Zong, Xianli

    2016-12-01

    Minimizing the voltage of corona discharges, especially when using nanomaterials, has been of great interest in the past decade or so. In this paper, we report a new corona discharge device by using ZnO nanowires operated in atmospheric air to realize continuous corona discharge excited by hundreds of volts. ZnO nanowires were synthesized on microelectrodes using electric-field-assisted wet chemical method, and a thin tungsten film was deposited on the microchip to enhance discharging performance. The testing results showed that the corona inception voltages were minimized greatly by using nanowires compared to conventional dischargers as a result of the local field enhancement of nanowires. The corona could be continuously generated and self-sustaining. It was proved that the law of corona inception voltage obeyed the conventional Peek's breakdown criterion. An optimal thickness of tungsten film coated over ZnO nanowires was figured out to obtain the lowest corona inception voltage. The ion concentration of the nanowire-based discharger attained 10(17)/m(3) orders of magnitude, which is practicable for most discharging applications. PMID:26880727

  7. Chemical bath deposition of ZnO nanowires at near-neutral pH conditions without hexamethylenetetramine (HMTA): understanding the role of HMTA in ZnO nanowire growth.

    PubMed

    McPeak, Kevin M; Le, Thinh P; Britton, Nathan G; Nickolov, Zhorro S; Elabd, Yossef A; Baxter, Jason B

    2011-04-01

    Chemical bath deposition (CBD) is an inexpensive and reproducible method for depositing ZnO nanowire arrays over large areas. The aqueous Zn(NO(3))(2)-hexamethylenetetramine (HMTA) chemistry is one of the most common CBD chemistries for ZnO nanowire synthesis, but some details of the reaction mechanism are still not well-understood. Here, we report the use of in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy to study HMTA adsorption from aqueous solutions onto ZnO nanoparticle films and show that HMTA does not adsorb on ZnO. This result refutes earlier claims that the anisotropic morphology arises from HMTA adsorbing onto and capping the ZnO {10 1 0} faces. We conclude that the role of HMTA in the CBD of ZnO nanowires is only to control the saturation index of ZnO. Furthermore, we demonstrate the first deposition of ZnO nanowire arrays at 90 °C and near-neutral pH conditions without HMTA. Nanowires were grown using the pH buffer 2-(N-morpholino)ethanesulfonic acid (MES) and continuous titratation with KOH to maintain the same pH conditions where growth with HMTA occurs. This semi-batch synthetic method opens many new opportunities to tailor the ZnO morphology and properties by independently controlling temperature and pH. PMID:21361384

  8. Direct selective growth of ZnO nanowire arrays from inkjet-printed zinc acetate precursor on a heated substrate

    PubMed Central

    2013-01-01

    Inkjet printing of functional materials has drawn tremendous interest as an alternative to the conventional photolithography-based microelectronics fabrication process development. We introduce direct selective nanowire array growth by inkjet printing of Zn acetate precursor ink patterning and subsequent hydrothermal ZnO local growth without nozzle clogging problem which frequently happens in nanoparticle inkjet printing. The proposed process can directly grow ZnO nanowires in any arbitrary patterned shape, and it is basically very fast, low cost, environmentally benign, and low temperature. Therefore, Zn acetate precursor inkjet printing-based direct nanowire local growth is expected to give extremely high flexibility in nanomaterial patterning for high-performance electronics fabrication especially at the development stage. As a proof of concept of the proposed method, ZnO nanowire network-based field effect transistors and ultraviolet photo-detectors were demonstrated by direct patterned grown ZnO nanowires as active layer. PMID:24252130

  9. Thermal conductivity of a ZnO nanowire/silica aerogel nanocomposite

    NASA Astrophysics Data System (ADS)

    Xie, Jing; Frachioni, Anthony; Williams, D. S.; White, B. E.

    2013-05-01

    The thermal conductivity of 100 nm zinc oxide nanowires embedded in silica aerogel was measured using the 3ω method over a temperature range of 150 K to 300 K. Compared to 100 nm ZnO nanowires alone, the thermal conductivity of the nanocomposite was reduced by over an order of magnitude throughout this temperature range. We attribute this reduction to the scattering of ballistic phonons at the nanowire surface and the subsequent emission of and transport of energy by the scattered phonon into the silica aerogel, as predicted by the diffuse mismatch model.

  10. Electrically pumped near-ultraviolet lasing from ZnO Nanowire Based Heterojunctions

    NASA Astrophysics Data System (ADS)

    Mu, Richard; Xu, Haiyang; Liu, Yichun

    2014-03-01

    ZnO with a band gap (3.37 eV) and an exciton binding energy (60 meV) is a promising material for ultraviolet (UV) light-emitting diodes (LEDs) and low-threshold lasing diodes. Much progress has been made recently to enhance band edge emission of ZnO nanowire (NW) structure through surface passivation and local surface plasmon enahncement with metal nanparticles. Efforts have been made to fabricate electrically pumped near-ultraviolet lasing devices with metal/insulator/semiconductor laser diode based on ZnO/MgO core/shell nanowires with and without metal nanoparticle presences. The nanowire diode shows higher emission intensity at relatively low operating current density compared with the planar device. The improved efficiency is attributed to enhanced exciton oscillator strength and superior carrier transport properties of single-crystalline ZnO nanowires, and effective surface passivation by MgO coating. Random laser action was confirmed by the calculation of quality factor and the real-time changes of lasing spectra. The results reveal that the MgO coating serves as electron blocking, hole supplying and surface passivation layer for the nanowire heterostructure. Other approaches will also be presented and discussed in the presentation. DMR-0423914, NSF-CREST HRD-0420516, and DOD W911NF-11-1-0156 and -13-1-0153.

  11. Effect of Surface Elasticity on the Piezoelectric Potential of a Bent ZnO Nanowire

    NASA Astrophysics Data System (ADS)

    Yao, Haiyan; Yun, Guohong; Bai, Narsu; Li, Jiangang

    2012-07-01

    The influence of surface elasticity on the piezoelectric potential distribution of a deformed ZnO nanowire is investigated by the effective Young's modulus based upon elastic and piezoelectric theory. When the nanowire in radius 25 nm subjects to an lateral applied force 5 nN, the maximum piezoelectric potential of the nanowire we derived is about 13.8 mV, which approaches much more closely to the experiment measurement value (˜10 mV) [Z. L. Wang and J. H. Song: Science 312 (2006) 242]. Moreover, a comprehensive analysis of maximum piezoelectric potential between the cases with and without the effect of surface elasticity is analyzed. The results show that the values of piezoelectric potential generated in ZnO nanowires are decreased due to the surface stiffening. From the theoretical analysis, the effect of surface elasticity has a significant impact on the piezoelectric potential for a bent ZnO nanowire, actually it reduces the gap between theoretical estimation and experiment measurements.

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

    SciTech Connect

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

    2014-12-21

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

  13. Hydrothermal Synthesis of ZnO Structures Formed by High-Aspect-Ratio Nanowires for Acetone Detection

    NASA Astrophysics Data System (ADS)

    Cao, Zhen; Wang, Yong; Li, Zhanguo; Yu, Naisen

    2016-07-01

    Snowflake-like ZnO structures originating from self-assembled nanowires were prepared by a low-temperature aqueous solution method. The as-grown hierarchical ZnO structures were investigated by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The results showed that the snowflake-like ZnO structures were composed of high-aspect-ratio nanowires. Furthermore, gas-sensing properties to various testing gases of 10 and 50 ppm were measured, which confirms that the ZnO structures were of good selectivity and response to acetone and could serve for acetone sensor to detect low-concentration acetone.

  14. Terahertz detectors arrays based on orderly aligned InN nanowires

    PubMed Central

    Chen, Xuechen; Liu, Huiqiang; Li, Qiuguo; Chen, Hao; Peng, Rufang; Chu, Sheng; Cheng, Binbin

    2015-01-01

    Nanostructured terahertz detectors employing a single semiconducting nanowire or graphene sheet have recently generated considerable interest as an alternative to existing THz technologies, for their merit on the ease of fabrication and above-room-temperature operation. However, the lack of alignment in nanostructure device hindered their potential toward practical applications. The present work reports ordered terahertz detectors arrays based on neatly aligned InN nanowires. The InN nanostructures (nanowires and nano-necklaces) were achieved by chemical vapor deposition growth, and then InN nanowires were successfully transferred and aligned into micrometer-sized groups by a “transfer-printing” method. Field effect transistors on aligned nanowires were fabricated and tested for terahertz detection purpose. The detector showed good photoresponse as well as low noise level. Besides, dense arrays of such detectors were also fabricated, which rendered a peak responsivity of 1.1 V/W from 7 detectors connected in series. PMID:26289498

  15. Investigation of Nucleation Mechanism and Tapering Observed in ZnO Nanowire Growth by Carbothermal Reduction Technique

    PubMed Central

    2011-01-01

    ZnO nanowire nucleation mechanism and initial stages of nanowire growth using the carbothermal reduction technique are studied confirming the involvement of the catalyst at the tip in the growth process. Role of the Au catalyst is further confirmed when the tapering observed in the nanowires can be explained by the change in the shape of the catalyst causing a variation of the contact area at the liquid–solid interface of the nanowires. The rate of decrease in nanowire diameter with length on the average is found to be 0.36 nm/s and this rate is larger near the base. Variation in the ZnO nanowire diameter with length is further explained on the basis of the rate at which Zn atoms are supplied as well as the droplet stability at the high flow rates and temperature. Further, saw-tooth faceting is noticed in tapered nanowires, and the formation is analyzed crystallographically.

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

    PubMed

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  18. Nanogenerators based on vertically aligned InN nanowires.

    PubMed

    Liu, Guocheng; Zhao, Songrui; Henderson, Robert D E; Leonenko, Zoya; Abdel-Rahman, Eihab; Mi, Zetian; Ban, Dayan

    2016-01-28

    Piezoelectric nanogenerators (NGs) based on vertically aligned InN nanowires (NWs) are fabricated, characterized, and evaluated. In these NGs, arrays of p-type and intrinsic InN NWs prepared by plasma-assisted molecular beam epitaxy (MBE) demonstrate similar piezoelectric properties. The p-type NGs show 160% more output current and 70% more output power product than the intrinsic NGs. The features driving performance enhancement are reduced electrostatic losses due to better NW array morphology, improved electromechanical energy conversion efficiency due to smaller NW diameters, and the higher impedance of intrinsic NGs due to elevated NW surface charge levels. These findings highlight the potential of InN based NGs as a power source for self-powered systems and the importance of NW morphology and surface state in overall NG performance. PMID:26700694

  19. Plasma versus thermal annealing for the Au-catalyst growth of ZnO nanocones and nanowires on Al-doped ZnO buffer layers

    NASA Astrophysics Data System (ADS)

    Güell, Frank; Martínez-Alanis, Paulina R.; Roso, Sergio; Salas-Pérez, Carlos I.; García-Sánchez, Mario F.; Santana, Guillermo; Marel Monroy, B.

    2016-06-01

    We successfully synthesized ZnO nanocones and nanowires over polycrystalline Al-doped ZnO (AZO) buffer layers on fused silica substrates by a vapor-transport process using Au-catalyst thin films. Different Au film thicknesses were thermal or plasma annealed in order to analyze their influence on the ZnO nanostructure growth morphology. Striking differences have been observed. Thermal annealing generates a distribution of Au nanoclusters and plasma annealing induces a fragmentation of the Au thin films. While ZnO nanowires are found in the thermal-annealed samples, ZnO nanocones and nanowires have been obtained on the plasma-annealed samples. Enhancement of the preferred c-axis (0001) growth orientation was demonstrated by x-ray diffraction when the ZnO nanocones and nanowires have been grown over the AZO buffer layer. The transmittance spectra of the ZnO nanocones and nanowires show a gradual increase from 375 to 900 nm, and photoluminescence characterization pointed out high concentration of defects leading to observation of a broad emission band in the visible range from 420 to 800 nm. The maximum emission intensity peak position of the broad visible band is related to the thickness of the Au-catalyst for the thermal-annealed samples and to the plasma power for the plasma-annealed samples. Finally, we proposed a model for the plasma versus thermal annealing of the Au-catalyst for the growth of the ZnO nanocones and nanowires. These results are promising for renewable energy applications, in particular for its potential application in solar cells.

  20. Opto-mechano-electrical tripling in ZnO nanowires probed by photocurrent spectroscopy in a high-resolution transmission electron microscope

    SciTech Connect

    Zhang, C.; Golberg, D. E-mail: golberg.dmitri@nims.go.jp; Xu, Z. E-mail: golberg.dmitri@nims.go.jp; Kvashnin, D. G.; Tang, D.-M.; Xue, Y. M.; Bando, Y.; Sorokin, P. B.

    2015-08-31

    Photocurrent spectroscopy of individual free-standing ZnO nanowires inside a high-resolution transmission electron microscope (TEM) is reported. By using specially designed optical in situ TEM system capable of scanning tunneling microscopy probing paired with light illumination, opto-mechano-electrical tripling phenomenon in ZnO nanowires is demonstrated. Splitting of photocurrent spectra at around 3.3 eV under in situ TEM bending of ZnO nanowires directly corresponds to nanowire deformation and appearance of expanded and compressed nanowire sides. Theoretical simulation of a bent ZnO nanowire has an excellent agreement with the experimental data. The splitting effect could be explained by a change in the valence band structure of ZnO nanowires due to a lattice strain. The strain-induced splitting provides important clues for future flexible piezo-phototronics.

  1. Strain-induced band alignment in wurtzite/zinc-blende InAs heterostructured nanowires

    NASA Astrophysics Data System (ADS)

    Panda, Jaya Kumar; Roy, Anushree; Chakraborty, Arup; Dasgupta, Indra; Hasanu, Elena; Ercolani, Daniele; Sorba, Lucia; Gemmi, Mauro

    2015-11-01

    We study band alignment in wurtzite/zinc-blende polytype InAs heterostructured nanowires using temperature-dependent resonance Raman measurements. Nanowires having two different wurtzite fractions are investigated. Using visible excitation wavelengths in resonance Raman measurements, we probe the electronic band alignment of these semiconductor nanowires near a high-symmetry point of the Brillouin zone (E1 gap). The strain in the crystal structure, as revealed from the shift of the phonon mode, explains the observed band alignment at the wurtzite/zinc-blende interface. Our experimental results are further supported by electronic-structure calculations for such periodic heterostructured interface.

  2. Three-dimensional mesoscale heterostructures of ZnO nanowire arrays epitaxially grown on CuGaO2 nanoplates as individual diodes.

    PubMed

    Forticaux, Audrey; Hacialioglu, Salih; DeGrave, John P; Dziedzic, Rafal; Jin, Song

    2013-09-24

    We report a three-dimensional (3D) mesoscale heterostructure composed of one-dimensional (1D) nanowire (NW) arrays epitaxially grown on two-dimensional (2D) nanoplates. Specifically, three facile syntheses are developed to assemble vertical ZnO NWs on CuGaO2 (CGO) nanoplates in mild aqueous solution conditions. The key to the successful 3D mesoscale integration is the preferential nucleation and heteroepitaxial growth of ZnO NWs on the CGO nanoplates. Using transmission electron microscopy, heteroepitaxy was found between the basal planes of CGO nanoplates and ZnO NWs, which are their respective (001) crystallographic planes, by the observation of a hexagonal Moiré fringes pattern resulting from the slight mismatch between the c planes of ZnO and CGO. Careful analysis shows that this pattern can be described by a hexagonal supercell with a lattice parameter of almost exactly 11 and 12 times the a lattice constants for ZnO and CGO, respectively. The electrical properties of the individual CGO-ZnO mesoscale heterostructures were measured using a current-sensing atomic force microscopy setup to confirm the rectifying p-n diode behavior expected from the band alignment of p-type CGO and n-type ZnO wide band gap semiconductors. These 3D mesoscale heterostructures represent a new motif in nanoassembly for the integration of nanomaterials into functional devices with potential applications in electronics, photonics, and energy. PMID:23952783

  3. 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.

  4. Steering epitaxial alignment of Au, Pd, and AuPd nanowire arrays by atom flux change.

    PubMed

    Yoo, Youngdong; Seo, Kwanyong; Han, Sol; Varadwaj, Kumar S K; Kim, Hyun You; Ryu, Ji Hoon; Lee, Hyuck Mo; Ahn, Jae Pyoung; Ihee, Hyotcherl; Kim, Bongsoo

    2010-02-10

    We have synthesized epitaxial Au, Pd, and AuPd nanowire arrays in vertical or horizontal alignment on a c-cut sapphire substrate. We show that the vertical and horizontal nanowire arrays grow from half-octahedral seeds by the correlations of the geometry and orientation of seed crystals with those of as-grown nanowires. The alignment of nanowires can be steered by changing the atom flux. At low atom deposition flux vertical nanowires grow, while at high atom flux horizontal nanowires grow. Similar vertical/horizontal epitaxial growth is also demonstrated on SrTiO(3) substrates. This orientation-steering mechanism is visualized by molecular dynamics simulations. PMID:20050692

  5. Photoluminescence based H2 and O2 gas sensing by ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Yadav, Kavita; Gahlaut, Shashank K.; Mehta, B. R.; Singh, J. P.

    2016-02-01

    Gas sensing properties of ZnO nanowires prepared via thermal chemical vapor deposition method were investigated by analyzing change in their photoluminescence (PL) spectra. The as-synthesized nanowires show two different PL peaks positioned at 380 nm and 520 nm. The 380 nm emission is ascribed to near band edge emission, and the green peak (520 nm) appears due to the oxygen vacancy defects. The intensity of the green PL signal enhances upon hydrogen gas exposure, whereas it gets quenched upon oxygen gas loading. The ZnO nanowires' sensing response values were observed as about 54% for H2 gas and 9% for O2 gas at room temperature for 50 sccm H2/O2 gas flow rate. The sensor response was also analyzed as a function of sample temperature ranging from 300 K to 400 K. A conclusion was derived from the observations that the H2/O2 gases affect the adsorbed oxygen species on the surface of ZnO nanowires. The adsorbed species result in the band bending and hence changes the depletion region which causes variation in PL signal. A photoluminescence based gas sensing technique has advantage over a conductometric technique due to its higher sensitivity and faster response time.

  6. Highly aligned arrays of high aspect ratio barium titanate nanowires via hydrothermal synthesis

    SciTech Connect

    Bowland, Christopher C.; Zhou, Zhi; Malakooti, Mohammad H.; Sodano, Henry A.

    2015-06-01

    We report on the development of a hydrothermal synthesis procedure that results in the growth of highly aligned arrays of high aspect ratio barium titanate nanowires. Using a multiple step, scalable hydrothermal reaction, a textured titanium dioxide film is deposited on titanium foil upon which highly aligned nanowires are grown via homoepitaxy and converted to barium titanate. Scanning electron microscope images clearly illustrate the effect the textured film has on the degree of orientation of the nanowires. The alignment of nanowires is quantified by calculating the Herman's Orientation Factor, which reveals a 58% improvement in orientation as compared to growth in the absence of the textured film. The ferroelectric properties of barium titanate combined with the development of this scalable growth procedure provide a powerful route towards increasing the efficiency and performance of nanowire-based devices in future real-world applications such as sensing and power harvesting.

  7. Genetic patterns of Zn 2GeO 4 coated ZnO nanowires from phase texture distribution of biphase brass substrate

    NASA Astrophysics Data System (ADS)

    Chen, Yiqing; Liu, Lizhu; Zhang, Xinhua; Guo, Taibo; Jia, Chong; Su, Yong; Li, Qiang; Wei, Meiqin

    2010-08-01

    Based on the natural patterns of phase texture distribution of (α+β) biphase brass substrate, we synthesize the patterned quasi-aligned Zn 2GeO 4 coated ZnO nanowires by one-step thermal evaporation of the mixture powders of GeO 2 and C, and characterize the products by means of X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, optical microscopy and photoluminescence spectroscopy. It is observed that following the self-catalyzed effect of the Zn clusters, quasi-aligned Zn 2GeO 4 coated ZnO nanowires grow site-selectively on the surface of island-shaped α phase and form novel patterns which inherit the distribution of α phase on the substrate. According to the pattern and feature of phase texture distribution of the alloy substrate, we can synthesize the patterned nanowires arrays with controlled location and distribution in a more effective way.

  8. First principles investigations on the electronic structure of anchor groups on ZnO nanowires and surfaces

    SciTech Connect

    Dominguez, A.; Lorke, M.; Rosa, A. L.; Frauenheim, Th.; Schoenhalz, A. L.; Dalpian, G. M.; Rocha, A. R.

    2014-05-28

    We report on density functional theory investigations of the electronic properties of monofunctional ligands adsorbed on ZnO-(1010) surfaces and ZnO nanowires using semi-local and hybrid exchange-correlation functionals. We consider three anchor groups, namely thiol, amino, and carboxyl groups. Our results indicate that neither the carboxyl nor the amino group modify the transport and conductivity properties of ZnO. In contrast, the modification of the ZnO surface and nanostructure with thiol leads to insertion of molecular states in the band gap, thus suggesting that functionalization with this moiety may customize the optical properties of ZnO nanomaterials.

  9. Photoelectric properties and charge dynamics in ZnO nanowires/Cu4Bi4S9 and ZnO nanowires/In2O3/Cu4Bi4S9 heterostructures

    NASA Astrophysics Data System (ADS)

    Liu, Xiangyang; Wang, Shun; Zhang, Jingwei; Zhang, Jiwei; Gu, Yuzong

    2014-12-01

    ZnO nanowires arrays were preformed in a horizontal double-tube system. Two types of heterostructures (ZnO nanowires/Cu4Bi4S9 and ZnO nanowires/In2O3/Cu4Bi4S9) and three-dimensional solar cells were fabricated with ZnO nanowires arrays as working electrode, In2O3 as buffer layer, and Cu4Bi4S9 as inorganic dye and hole collector. It is suggested that two types of heterostructures have the similar absorption properties with single Cu4Bi4S9. However, the results of steady state and electric field-induced surface photovoltage indicate that ZnO nanowires/In2O3/Cu4Bi4S9 exhibits the higher photovoltaic response than ZnO nanowires/Cu4Bi4S9. Using the transient surface photovoltage spectroscopy, we further studied the separation and transport mechanism of photogenerated charges. Furthermore, Cu4Bi4S9/In2O3/ZnO cells presents the better performance than Cu4Bi4S9/ZnO cells and the highest efficiencies are about 6.4% and 5.2%, respectively. It is suggested that direct paths, interface barrier, built-in electric field, and double energy level matchings between conduction bands (Cu4Bi4S9 and In2O3, In2O3 and ZnO) have obvious effect on the separation of photogenerated charges. Then we discussed the synthetic action on the charge dynamics from these factors.

  10. Programmable ZnO nanowire transistors using switchable polarization of ferroelectric liquid crystal

    NASA Astrophysics Data System (ADS)

    Hong, Woong-Ki; Inn Sohn, Jung; Cha, SeungNam; Min Kim, Jong; Park, Jong-Bae; Seok Choi, Su; Coles, Harry J.; Welland, Mark E.

    2013-02-01

    We demonstrate modulations of electrical conductance and hysteresis behavior in ZnO nanowire transistors via electrically polarized switching of ferroelectric liquid crystal (FLC). After coating a nanowire channel in the transistors with FLCs, we observed large increases in channel conductance and hysteresis width, and a strong dependence of hysteresis loops on the polarization states associated with the orientation of electric dipole moments along the direction of the gate electric field. Furthermore, the reversible switching and retention characteristics provide the feasibility of creating a hybrid system with switch and memory functions.

  11. Low-Temperature Preparation of Ag-Doped ZnO Nanowire Arrays, DFT Study, and Application to Light-Emitting Diode.

    PubMed

    Pauporté, Thierry; Lupan, Oleg; Zhang, Jie; Tugsuz, Tugba; Ciofini, Ilaria; Labat, Frédéric; Viana, Bruno

    2015-06-10

    Doping ZnO nanowires (NWs) by group IB elements is an important challenge for integrating nanostructures into functional devices with better and tuned performances. The growth of Ag-doped ZnO NWs by electrodeposition at 90 °C using a chloride bath and molecular oxygen precursor is reported. Ag acts as an electrocatalyst for the deposition and influences the nucleation and growth of the structures. The silver atomic concentration in the wires is controlled by the additive concentration in the deposition bath and a content up to 3.7 atomic % is reported. XRD analysis shows that the integration of silver enlarges the lattice parameters of ZnO. The optical measurements also show that the direct optical bandgap of ZnO is reduced by silver doping. The bandgap shift and lattice expansion are explained by first principle calculations using the density functional theory (DFT) on the silver impurity integration as an interstitial (Ag(i)) and as a substitute of zinc atom (Ag(Zn)) in the crystal lattice. They notably indicate that Ag(Zn) doping forms an impurity band because of Ag 4d and O 2p orbital interactions, shifting the Fermi level toward the valence band. At least, Ag-doped ZnO vertically aligned nanowire arrays have been epitaxially grown on GaN(001) substrate. The heterostructure has been inserted in a light emitting device. UV-blue light emission has been achieved with a low emission threshold of 5 V and a tunable red-shifted emission spectrum related to the bandgap reduction induced by silver doping of the ZnO emitter material. PMID:25990263

  12. In-situ optical transmission electron microscope study of exciton phonon replicas in ZnO nanowires by cathodoluminescence

    SciTech Connect

    Yang, Shize; Tian, Xuezeng; Wang, Lifen; Wei, Jiake; Qi, Kuo; Li, Xiaomin; Xu, Zhi E-mail: xdbai@iphy.ac.cn Wang, Wenlong; Zhao, Jimin; Bai, Xuedong E-mail: xdbai@iphy.ac.cn; Wang, Enge E-mail: xdbai@iphy.ac.cn

    2014-08-18

    The cathodoluminescence spectrum of single zinc oxide (ZnO) nanowires is measured by in-situ optical Transmission Electron Microscope. The coupling between exciton and longitudinal optical phonon is studied. The band edge emission varies for different excitation spots. This effect is attributed to the exciton propagation along the c axis of the nanowire. Contrary to free exciton emission, the phonon replicas are well confined in ZnO nanowire. They travel along the c axis and emit at the end surface. Bending strain increases the relative intensity of second order phonon replicas when excitons travel along the c-axis.

  13. Integration of ZnO and CuO nanowires into a thermoelectric module.

    PubMed

    Zappa, Dario; Dalola, Simone; Faglia, Guido; Comini, Elisabetta; Ferroni, Matteo; Soldano, Caterina; Ferrari, Vittorio; Sberveglieri, Giorgio

    2014-01-01

    Zinc oxide (ZnO, n-type) and copper oxide (CuO, p-type) nanowires have been synthesized and preliminarily investigated as innovative materials for the fabrication of a proof-of-concept thermoelectric device. The Seebeck coefficients, electrical conductivity and thermoelectric power factors (TPF) of both semiconductor materials have been determined independently using a custom experimental set-up, leading to results in agreement with available literature with potential improvement. Combining bundles of ZnO and CuO nanowires in a series of five thermocouples on alumina leads to a macroscopic prototype of a planar thermoelectric generator (TEG) unit. This demonstrates the possibility of further integration of metal oxide nanostructures into efficient thermoelectric devices. PMID:24991531

  14. High degree of polarization of the near-band-edge photoluminescence in ZnO nanowires

    PubMed Central

    2011-01-01

    We investigated the polarization dependence of the near-band-edge photoluminescence in ZnO strain-free nanowires grown by vapor phase technique. The emission is polarized perpendicular to the nanowire axis with a large polarization ratio (as high as 0.84 at 4.2 K and 0.63 at 300 K). The observed polarization ratio is explained in terms of selection rules for excitonic transitions derived from the k·p theory for ZnO. The temperature dependence of the polarization ratio evidences a gradual activation of the XC excitonic transition. PACS: 78.55.Cr, 77.22.Ej, 81.07.Gf. PMID:21854578

  15. Integration of ZnO and CuO nanowires into a thermoelectric module

    PubMed Central

    Dalola, Simone; Faglia, Guido; Comini, Elisabetta; Ferroni, Matteo; Soldano, Caterina; Ferrari, Vittorio; Sberveglieri, Giorgio

    2014-01-01

    Summary Zinc oxide (ZnO, n-type) and copper oxide (CuO, p-type) nanowires have been synthesized and preliminarily investigated as innovative materials for the fabrication of a proof-of-concept thermoelectric device. The Seebeck coefficients, electrical conductivity and thermoelectric power factors (TPF) of both semiconductor materials have been determined independently using a custom experimental set-up, leading to results in agreement with available literature with potential improvement. Combining bundles of ZnO and CuO nanowires in a series of five thermocouples on alumina leads to a macroscopic prototype of a planar thermoelectric generator (TEG) unit. This demonstrates the possibility of further integration of metal oxide nanostructures into efficient thermoelectric devices. PMID:24991531

  16. 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.

  17. Flow-enabled self-assembly of large-scale aligned nanowires.

    PubMed

    Li, Bo; Zhang, Chuchu; Jiang, Beibei; Han, Wei; Lin, Zhiqun

    2015-03-27

    One-dimensional nanowires enable the realization of optical and electronic nanodevices that may find applications in energy conversion and storage systems. Herein, large-scale aligned DNA nanowires were crafted by flow-enabled self-assembly (FESA). The highly oriented and continuous DNA nanowires were then capitalized on either as a template to form metallic nanowires by exposing DNA nanowires that had been preloaded with metal salts to an oxygen plasma or as a scaffold to direct the positioning and alignment of metal nanoparticles and nanorods. The FESA strategy is simple and easy to implement and thus a promising new method for the low-cost synthesis of large-scale one-dimensional nanostructures for nanodevices. PMID:25689374

  18. Aligned epitaxial SnO2 nanowires on sapphire: growth and device applications.

    PubMed

    Wang, Xiaoli; Aroonyadet, Noppadol; Zhang, Yuzheng; Mecklenburg, Matthew; Fang, Xin; Chen, Haitian; Goo, Edward; Zhou, Chongwu

    2014-06-11

    Semiconducting SnO2 nanowires have been used to demonstrate high-quality field-effect transistors, optically transparent devices, photodetectors, and gas sensors. However, controllable assembly of rutile SnO2 nanowires is necessary for scalable and practical device applications. Here, we demonstrate aligned, planar SnO2 nanowires grown on A-plane, M-plane, and R-plane sapphire substrates. These parallel nanowires can reach 100 μm in length with sufficient density to be patterned photolithographically for field-effect transistors and sensor devices. As proof-of-concept, we show that transistors made this way can achieve on/off current ratios on the order of 10(6), mobilities around 71.68 cm(2)/V·s, and sufficiently high currents to drive external organic light-emitting diode displays. Furthermore, the aligned SnO2 nanowire devices are shown to be photosensitive to UV light with the capability to distinguish between 254 and 365 nm wavelengths. Their alignment is advantageous for polarized UV light detection; we have measured a polarization ratio of photoconductance (σ) of 0.3. Lastly, we show that the nanowires can detect NO2 at a concentration of 0.2 ppb, making them a scalable, ultrasensitive gas sensing technology. Aligned SnO2 nanowires offer a straightforward method to fabricate scalable SnO2 nanodevices for a variety of future electronic applications. PMID:24837617

  19. Transmission type flat-panel X-ray source using ZnO nanowire field emitters

    SciTech Connect

    Chen, Daokun; Song, Xiaomeng; Zhang, Zhipeng; Chen, Jun; Li, Ziping; She, Juncong; Deng, Shaozhi; Xu, Ningsheng

    2015-12-14

    A transmission type flat-panel X-ray source in diode structure was fabricated. Large-scale patterned ZnO nanowires grown on a glass substrate by thermal oxidation were utilized as field emitters, and tungsten thin film coated on silica glass was used as the transmission anode. Uniform distribution of X-ray generation was achieved, which benefited from the uniform electron emission from ZnO nanowires. Self-ballasting effect induced by the intrinsic resistance of ZnO nanowire and decreasing of screening effect caused by patterned emitters account for the uniform emission. Characteristic X-ray peaks of W-L lines and bremsstrahlung X-rays have been observed under anode voltages at a range of 18–20 kV, the latter of which were the dominant X-ray signals. High-resolution X-ray images with spatial resolution less than 25 μm were obtained by the flat-panel X-ray source. The high resolution was attributed to the small divergence angle of the emitted X-rays from the transmission X-ray source.

  20. Transmission type flat-panel X-ray source using ZnO nanowire field emitters

    NASA Astrophysics Data System (ADS)

    Chen, Daokun; Song, Xiaomeng; Zhang, Zhipeng; Li, Ziping; She, Juncong; Deng, Shaozhi; Xu, Ningsheng; Chen, Jun

    2015-12-01

    A transmission type flat-panel X-ray source in diode structure was fabricated. Large-scale patterned ZnO nanowires grown on a glass substrate by thermal oxidation were utilized as field emitters, and tungsten thin film coated on silica glass was used as the transmission anode. Uniform distribution of X-ray generation was achieved, which benefited from the uniform electron emission from ZnO nanowires. Self-ballasting effect induced by the intrinsic resistance of ZnO nanowire and decreasing of screening effect caused by patterned emitters account for the uniform emission. Characteristic X-ray peaks of W-L lines and bremsstrahlung X-rays have been observed under anode voltages at a range of 18-20 kV, the latter of which were the dominant X-ray signals. High-resolution X-ray images with spatial resolution less than 25 μm were obtained by the flat-panel X-ray source. The high resolution was attributed to the small divergence angle of the emitted X-rays from the transmission X-ray source.

  1. Hierarchically structured nanowires on and nanosticks in ZnO microtubes

    PubMed Central

    Rivaldo-Gómez, C. M.; Cabrera-Pasca, G. A.; Zúñiga, A.; Carbonari, A. W.; Souza, J. A.

    2015-01-01

    We report both coaxial core-shell structured microwires and ZnO microtubes with growth of nanosticks in the inner and nanowires on the outer surface as a novel hierarchical micro/nanoarchitecture. First, a core-shell structure is obtained—the core is formed by metallic Zn and the semiconducting shell is comprised by a thin oxide layer covered with a high density of nanowires. Such Zn/ZnO core-shell array showed magnetoresistance effect. It is suggested that magnetic moments in the nanostructured shell superimposes to the external magnetic field enhancing the MR effect. Second, microtubes decorated with nanowires on the external surface are obtained. In an intermediate stage, a hierarchical morphology comprised of discrete nanosticks in the inner surface of the microtube has been found. Hyperfine interaction measurements disclosed the presence of confined metallic Zn regions at the interface between linked ZnO grains forming a chain and a ZnO thicker layer. Surprisingly, the metallic clusters form highly textured thin flat regions oriented parallel to the surface of the microtube as revealed by the electrical field gradient direction. The driving force to grow the internal nanosticks has been ascribed to stress-induced migration of Zn ions due to compressive stress caused by the presence of these confined regions. PMID:26456527

  2. Wireless Remote Monitoring of Glucose Using a Functionalized ZnO Nanowire Arrays Based Sensor

    PubMed Central

    Ali, Syed M. Usman; Aijazi, Tasuif; Axelsson, Kent; Nur, Omer; Willander, Magnus

    2011-01-01

    This paper presents a prototype wireless remote glucose monitoring system interfaced with a ZnO nanowire arrays-based glucose sensor, glucose oxidase enzyme immobilized onto ZnO nanowires in conjunction with a Nafion® membrane coating, which can be effectively applied for the monitoring of glucose levels in diabetics. Global System for Mobile Communications (GSM) services like General Packet Radio Service (GPRS) and Short Message Service (SMS) have been proven to be logical and cost effective methods for gathering data from remote locations. A communication protocol that facilitates remote data collection using SMS has been utilized for monitoring a patient’s sugar levels. In this study, we demonstrate the remote monitoring of the glucose levels with existing GPRS/GSM network infra-structures using our proposed functionalized ZnO nanowire arrays sensors integrated with standard readily available mobile phones. The data can be used for centralized monitoring and other purposes. Such applications can reduce health care costs and allow caregivers to monitor and support to their patients remotely, especially those located in rural areas. PMID:22164087

  3. Gallium ion implantation greatly reduces thermal conductivity and enhances electronic one of ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Xia, Minggang; Cheng, Zhaofang; Han, Jinyun; Zheng, Minrui; Sow, Chorng-Haur; Thong, John T. L.; Zhang, Shengli; Li, Baowen

    2014-05-01

    The electrical and thermal conductivities are measured for individual zinc oxide (ZnO) nanowires with and without gallium ion (Ga+) implantation at room temperature. Our results show that Ga+ implantation enhances electrical conductivity by one order of magnitude from 1.01 × 103 Ω-1m-1 to 1.46 × 104 Ω-1m-1 and reduces its thermal conductivity by one order of magnitude from 12.7 Wm-1K-1 to 1.22 Wm-1K-1 for ZnO nanowires of 100 nm in diameter. The measured thermal conductivities are in good agreement with those in theoretical simulation. The increase of electrical conductivity origins in electron donor doping by Ga+ implantation and the decrease of thermal conductivity is due to the longitudinal and transverse acoustic phonons scattering by Ga+ point scattering. For pristine ZnO nanowires, the thermal conductivity decreases only two times when its diameter reduces from 100 nm to 46 nm. Therefore, Ga+-implantation may be a more effective method than diameter reduction in improving thermoelectric performance.

  4. Fabrication and photoresponse of ZnO nanowires/CuO coaxial heterojunction

    PubMed Central

    2013-01-01

    The fabrication and properties of n-ZnO nanowires/p-CuO coaxial heterojunction (CH) with a photoresist (PR) blocking layer are reported. In our study, c-plane wurtzite ZnO nanowires were grown by aqueous chemical method, and monoclinic CuO (111) was then coated on the ZnO nanowires by electrochemical deposition to form CH. To improve the device performance, a PR layer was inserted between the ZnO buffer layer and the CuO film to serve as a blocking layer to block the leakage current. Structural investigations of the CH indicate that the sample has good crystalline quality. It was found that our refined structure possesses a better rectifying ratio and smaller reverse leakage current. As there is a large on/off ratio between light on and off and the major light response is centered at around 424 nm, the experimental results suggest that the PR-inserted ZnO/CuO CH can be used as a good narrow-band blue light detector. PMID:24044381

  5. MOCVD growth of vertically aligned InGaN nanowires

    NASA Astrophysics Data System (ADS)

    Kuo, H. C.; Su Oh, Tae; Ku, P.-C.

    2013-05-01

    In this work, we report the growth of vertically aligned bulk InGaN nanowires (NWs) on r-plane sapphire substrate by metal organic chemical vapor deposition (MOCVD). Through the optimization process of growth conditions, such as growth temperature and pressure, we obtained high density InGaN NWs consisting of one (0001) polar- and two equivalent {1101} semi-polar planes. We have shown the highest InGaN NWs wire density of 8×108 cm-2,with an average diameter of 300 nm and a length of 2 μm. From results of photoluminescence (PL) at 30 K and 300 K, we observed the intense and broad emission peak from InGaN NWs at around 595 nm, and confirmed that the luminescence could be tuned from 580 nm to 660 nm by controlling the indium flow (TMIn) rate. Our results indicate that MOCVD-grown InGaN NWs can be effective absorbers of the blue-green range of solar spectrum and may be one of the good candidates for high efficiency photovoltaic devices targeting at blue-green photons.

  6. Thermal Conduction in Vertically Aligned Copper Nanowire Arrays and Composites.

    PubMed

    Barako, Michael T; Roy-Panzer, Shilpi; English, Timothy S; Kodama, Takashi; Asheghi, Mehdi; Kenny, Thomas W; Goodson, Kenneth E

    2015-09-01

    The ability to efficiently and reliably transfer heat between sources and sinks is often a bottleneck in the thermal management of modern energy conversion technologies ranging from microelectronics to thermoelectric power generation. These interfaces contribute parasitic thermal resistances that reduce device performance and are subjected to thermomechanical stresses that degrade device lifetime. Dense arrays of vertically aligned metal nanowires (NWs) offer the unique combination of thermal conductance from the constituent metal and mechanical compliance from the high aspect ratio geometry to increase interfacial heat transfer and device reliability. In the present work, we synthesize copper NW arrays directly onto substrates via templated electrodeposition and extend this technique through the use of a sacrificial overplating layer to achieve improved uniformity. Furthermore, we infiltrate the array with an organic phase change material and demonstrate the preservation of thermal properties. We use the 3ω method to measure the axial thermal conductivity of freestanding copper NW arrays to be as high as 70 W m(-1) K(-1), which is more than an order of magnitude larger than most commercial interface materials and enhanced-conductivity nanocomposites reported in the literature. These arrays are highly anisotropic, and the lateral thermal conductivity is found to be only 1-2 W m(-1) K(-1). We use these measured properties to elucidate the governing array-scale transport mechanisms, which include the effects of morphology and energy carrier scattering from size effects and grain boundaries. PMID:26284489

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

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

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

  8. [101̅0] oriented multichannel ZnO nanowire arrays with enhanced optoelectronic device performance.

    PubMed

    He, Dongqing; Sheng, Xia; Yang, Jie; Chen, Liping; Zhu, Kai; Feng, Xinjian

    2014-12-01

    Crystallographic orientation and microstructure of metal oxide nanomaterials have great impact on their properties and applications. Here, we report [101̅0] oriented ZnO nanowire (NW) arrays with a multichannel mesostructure. The NW has a preferential growth of low energy (101̅0) crystal plane and exhibits 2-3 orders of magnitude faster electron transport rate than that in nanoparticle (NP) films. Furthermore, the surface area of the as-prepared NW arrays is about 5 times larger than that of conventional NW arrays with similar thickness. These lead to the highest power conversion efficiency of ZnO NW array-based sensitized solar cells. We anticipate that the unique crystallographic orientation and mesostructure will endow ZnO NW arrays new properties and expand their application fields. PMID:25411922

  9. 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

  10. The Modulation of Optical Property and its Correlation with Microstructures of ZnO Nanowires

    PubMed Central

    2009-01-01

    ZnO nanowires with both good crystallinity and oxygen vacancies defects were synthesized by thermal oxidation of Zn substrate pretreated in concentrated sulfuric acid under the air atmosphere, Ar- and air-mixed gas stream. The photoluminescence spectra reveal that only near-band-edge (NBE) emission peak was observed for the sample grown in the air atmosphere; the broad blue–green and the red-shifted NBE emission peaks were observed for the sample grown in the mixed gas stream, indicating that the sample grown in the mixed gas stream has a defective structure and its optical properties can be modulated by controlling its structure. The high-resolution transmission electron microscope and the corresponding structural simulation confirm that the oxygen vacancies exist in the crystal of the nanowires grown in the mixed gas stream. The ZnO nanowires with oxygen vacancies defects exhibit better photocatalytic activity than the nanowires with good crystallinity. The photocatalytic process obeys the rules of first-order kinetic reaction, and the rate constants were calculated. PMID:20596485

  11. MOF-Based Membrane Encapsulated ZnO Nanowires for Enhanced Gas Sensor Selectivity.

    PubMed

    Drobek, Martin; Kim, Jae-Hun; Bechelany, Mikhael; Vallicari, Cyril; Julbe, Anne; Kim, Sang Sub

    2016-04-01

    Gas sensors are of a great interest for applications including toxic or explosive gases detection in both in-house and industrial environments, air quality monitoring, medical diagnostics, or control of food/cosmetic properties. In the area of semiconductor metal oxides (SMOs)-based sensors, a lot of effort has been devoted to improve the sensing characteristics. In this work, we report on a general methodology for improving the selectivity of SMOx nanowires sensors, based on the coverage of ZnO nanowires with a thin ZIF-8 molecular sieve membrane. The optimized ZnO@ZIF-8-based nanocomposite sensor shows markedly selective response to H2 in comparison with the pristine ZnO nanowires sensor, while showing the negligible sensing response to C7H8 and C6H6. This original MOF-membrane encapsulation strategy applied to nanowires sensor architecture pave the way for other complex 3D architectures and various types of applications requiring either gas or ion selectivity, such as biosensors, photo(catalysts), and electrodes. PMID:27003470

  12. Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties.

    PubMed

    Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao

    2016-01-01

    In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA. PMID:27023546

  13. Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties

    PubMed Central

    Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao

    2016-01-01

    In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA. PMID:27023546

  14. Developing Seedless Growth of ZnO Micro/Nanowire Arrays towards ZnO/FeS2/CuI P-I-N Photodiode Application

    NASA Astrophysics Data System (ADS)

    Yang, Zhi; Wang, Minqiang; Shukla, Sudhanshu; Zhu, Yue; Deng, Jianping; Ge, Hu; Wang, Xingzhi; Xiong, Qihua

    2015-06-01

    A seedless hydrothermal method is developed to grow high density and vertically aligned ZnO micro/nanowire arrays with low defect density on metal films under the saturated nutrition solution. In particular, the mechanism of seedless method is discussed here. A buffer layer can be confirmed by transmission electron microscopy (TEM), which may release the elastic strain between ZnO and substrate to achieve this highly mismatched heteroepitaxial structures. Based on ZnO micro/nanowire arrays with excellent wettability surface, we prepared ZnO-FeS2-CuI p-i-n photodiode by all-solution processed method with the high rectifying ratio of 197 at ±1 V. Under AM 1.5 condition, the Jsc of 0.5 mA/cm2, on-off current ratio of 371 and fast photoresponse at zero bias voltage were obtained. This good performance comes from excellent collection ability of photogenerated electrons and holes due to the increased depletion layer width for p-i-n structure. Finally, the high responsivity around 900 nm shows the potential as near infrared photodetectors applications.

  15. Developing Seedless Growth of ZnO Micro/Nanowire Arrays towards ZnO/FeS2/CuI P-I-N Photodiode Application

    PubMed Central

    Yang, Zhi; Wang, Minqiang; Shukla, Sudhanshu; Zhu, Yue; Deng, Jianping; Ge, Hu; Wang, Xingzhi; Xiong, Qihua

    2015-01-01

    A seedless hydrothermal method is developed to grow high density and vertically aligned ZnO micro/nanowire arrays with low defect density on metal films under the saturated nutrition solution. In particular, the mechanism of seedless method is discussed here. A buffer layer can be confirmed by transmission electron microscopy (TEM), which may release the elastic strain between ZnO and substrate to achieve this highly mismatched heteroepitaxial structures. Based on ZnO micro/nanowire arrays with excellent wettability surface, we prepared ZnO-FeS2-CuI p-i-n photodiode by all-solution processed method with the high rectifying ratio of 197 at ±1 V. Under AM 1.5 condition, the Jsc of 0.5 mA/cm2, on-off current ratio of 371 and fast photoresponse at zero bias voltage were obtained. This good performance comes from excellent collection ability of photogenerated electrons and holes due to the increased depletion layer width for p-i-n structure. Finally, the high responsivity around 900 nm shows the potential as near infrared photodetectors applications. PMID:26077658

  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. Length-dependent charge generation from vertical arrays of high-aspect-ratio ZnO nanowires.

    PubMed

    Rivera, Vivian Farías; Auras, Florian; Motto, Paolo; Stassi, Stefano; Canavese, Giancarlo; Celasco, Edvige; Bein, Thomas; Onida, Barbara; Cauda, Valentina

    2013-10-18

    Aqueous chemical growth of zinc oxide nanowires is a flexible and effective approach to obtain dense arrays of vertically oriented nanostructures with high aspect ratio. Herein we present a systematic study of the different synthesis parameters that influence the ZnO seed layer and thus the resulting morphological features of the free-standing vertically oriented ZnO nanowires. We obtained a homogeneous coverage of transparent conductive substrates with high-aspect-ratio nanowire arrays (length/diameter ratio of up to 52). Such nanostructured vertical arrays were examined to assess their electric and piezoelectric properties, and showed an electric charge generation upon mechanical compressive stress. The principle of energy harvesting with these nanostructured ZnO arrays was demonstrated by connecting them to an electronic charge amplifier and storing the generated charge in a series of capacitors. We found that the generated charge and the electrical behavior of the ZnO nanowires are strictly dependent on the nanowire length. We have shown the importance of controlling the morphological properties of such ZnO nanostructures for optimizing a nanogenerator device. PMID:24027171

  18. Scalable alignment and transfer of nanowires in a Spinning Langmuir Film.

    PubMed

    Zhu, Ren; Lai, Yicong; Nguyen, Vu; Yang, Rusen

    2014-10-21

    Many nanomaterial-based integrated nanosystems require the assembly of nanowires and nanotubes into ordered arrays. A generic alignment method should be simple and fast for the proof-of-concept study by a researcher, and low-cost and scalable for mass production in industries. Here we have developed a novel Spinning-Langmuir-Film technique to fulfill both requirements. We used surfactant-enhanced shear flow to align inorganic and organic nanowires, which could be easily transferred to other substrates and ready for device fabrication in less than 20 minutes. The aligned nanowire areal density can be controlled in a wide range from 16/mm(-2) to 258/mm(-2), through the compression of the film. The surface surfactant layer significantly influences the quality of alignment and has been investigated in detail. PMID:25177924

  19. In situ observation of size-scale effects on the mechanical properties of ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Asthana, A.; Momeni, K.; Prasad, A.; Yap, Y. K.; Yassar, R. S.

    2011-07-01

    In this investigation, the size-scale in mechanical properties of individual [0001] ZnO nanowires and the correlation with atomic-scale arrangements were explored via in situ high-resolution transmission electron microscopy (TEM) equipped with atomic force microscopy (AFM) and nanoindentation (NI) systems. The Young's modulus was determined to be size-scale-dependent for nanowires with diameter, d, in the range of 40 nm <= d <= 110 nm, and reached the maximum of ~ 249 GPa for d = 40 nm. However, this phenomenon was not observed for nanowires in the range of 200 nm <= d <= 400 nm, where an average constant Young's modulus of ~ 147.3 GPa was detected, close to the modulus value of bulk ZnO. A size-scale dependence in the failure of nanowires was also observed. The thick ZnO nanowires (d >= 200 nm) were brittle, while the thin nanowires (d <= 110 nm) were highly flexible. The diameter effect and enhanced Young's modulus observed in thin ZnO nanowires are due to the combined effects of surface relaxation and long-range interactions present in ionic crystals, which leads to much stiffer surfaces than bulk wires. The brittle failure in thicker ZnO wires was initiated from the outermost layer, where the maximum tensile stress operates and propagates along the (0001) planes. After a number of loading and unloading cycles, the highly compressed region of the thinner nanowires was transformed from a crystalline to an amorphous phase, and the region near the neutral zone was converted into a mixture of disordered atomic planes and bent lattice fringes as revealed by high-resolution images.

  20. Plasmon-mediated photocatalytic activity of wet-chemically prepared ZnO nanowire arrays.

    PubMed

    Dao, Thang Duy; Han, Gui; Arai, Nono; Nabatame, Toshihide; Wada, Yoshiki; Hoang, Chung Vu; Aono, Masakazu; Nagao, Tadaaki

    2015-03-21

    We report on measurements and simulations of the efficient sunlight-driven and visible-active photocatalysts composed of plasmonic metal nanoparticles and ZnO nanowire (NW) arrays fabricated via an all-wet-chemical route. Because of the coupling between the ZnO dielectric response and the excitation of the Ag or Au nanoparticles, efficient electronic excitation can be induced in the vicinity of the metal-ZnO interfaces because optically-excited plasmonic particles can not only concentrate the electromagnetic field at the ZnO/particle interface, but also act as efficient sources of plasmonic hot electrons to be injected into the conduction band of the ZnO catalyst. The catalytic activities of the fabricated ZnO NWs are examined by photodegradation of methylene blue and by photocurrent measurements in a photovoltaic configuration. Numerical electromagnetic simulations were used to understand the behavior of the light on the nanometer-scale to clarify the catalytic enhancement mechanisms in both the ultraviolet (UV) and visible (VIS) regions. In addition, simulation results indicated that a near-surface normal but slightly tilted ZnO NW array geometry would provide an increased optical path length and enhanced multiple scattering and absorption processes arising from the localized surface plasmon resonances of the nanoparticles. The results obtained here clarify the role of the plasmon resonance and provide us with useful knowledge for the development of metal-oxide nano-hybrid materials for solar energy conversion. PMID:25700130

  1. ZnO Nanowires for PV: Size Control and Scalability Studies

    NASA Astrophysics Data System (ADS)

    Gunther, Darlene; Lawrie, Jenifer; Ueda, Akira; Mu, Richard

    2007-11-01

    Our research attempts to understand the carbothermal vapor- solid growth process for novel ZnO nanowires (NW's). In addition to being a relatively simple growth process, the ZnO NW's, most often n- type, have high electron mobility and a large bandgap (3.4 eV). This makes them an attractive electron conductor. Our team expects these ZnO NW's to provide a means of reducing the charge recombination problems currently hampering the efficiencies of photovoltaic (PV) cells. Current growth methods are limited to small sample sizes in a horizontal tube furnace. We propose an innovative vertical design that provides optimal control of the growth parameters, allowing us to study each of the factors to determine their role in growing the required ZnO structures, e.g. gas flow turbulence, oxygen supply, distance from source to substrate, temperature control and uniform density. We report the results of our initial experiments where we grew dense ZnO nw's on a large (11.3 x 44.8 mm) silicon substrate (100).

  2. Electro-physical characterization of individual and arrays of ZnO nanowires

    SciTech Connect

    Mallampati, Bhargav; Singh, Abhay; Philipose, U.; Shik, Alex; Ruda, Harry E.

    2015-07-21

    Capacitance measurements were made on an array of parallel ZnO nanowires embedded in a polymer matrix and provided with two electrodes perpendicular to the nanowires. The capacitance monotonically increased, and saturated at large negative (depleting) and large positive (accumulating) voltages. A qualitative explanation for this behavior is presented, taking into account specific features of quasi-one-dimensional screening. The increasing or decreasing character of the capacitance-voltage characteristics were determined by the conductivity type of the nanowires, which in our case was n-type. A dispersion of the experimental capacitance was observed over the entire frequency range of 1 kHz to 5 MHz. This phenomenon is explained by the slow discharge of the nanowires through the thin dielectric layer that separates them from the top electrode. Separate measurements on individual identical nanowires in a field effect transistor configuration yielded an electron concentration and mobility of approximately 10{sup 17 }cm{sup −3} and 150 cm{sup 2}/Vs, respectively, at room temperature.

  3. Solution Processing of Ordered Thin Film Nanowire Composites by Magnetic Field Alignment

    NASA Astrophysics Data System (ADS)

    Singer, Jonathan; Pelligra, Candice; Huang, Su; Osuji, Chinedum

    2014-03-01

    Vertically aligned nanowire forests are a desirable geometry for many applications, including as electrodes, heterojunctions, and high surface energy interfaces. Most conventional aligned nanowire structures, however, are generated by methods that require (i) high temperatures, (ii) a specific substrate, or (iii) high cost lithographic techniques. We seek to utilize the magnetic alignment of cobalt-doped zinc oxide nanowires to enable the solution processing of thin films of aligned nanowires on a generalized substrate at a fraction of the cost of other methods. By functionalization of the nanowires with various surface modifications, they can be dispersed in several solvent systems and aligned by a 6 T field. Further, by including polymer in the wire solution, we can both control the areal density and also incorporate additional functionalities to the final composite device. As an example, the use of a conjugated polymer (such as poly(3-hexylthiophene-2,5-diyl) (P3HT)) allows for the final structures to act as inorganic-organic ordered heterojunction solar cells. While final device quality depends on the simultaneous optimization of several key processing parameters, the process does not rely on top-down fabrication or costly materials. Supported by ONR YIP Award N000141210657.

  4. Fast and enhanced broadband photoresponse of a ZnO nanowire array/reduced graphene oxide film hybrid photodetector from the visible to the near-infrared range.

    PubMed

    Liu, Hao; Sun, Qi; Xing, Jie; Zheng, Zhiyuan; Zhang, Zhili; Lü, Zhiqing; Zhao, Kun

    2015-04-01

    In the present work, a ZnO nanowire array/reduced graphene oxide film hybrid nanostructure was realized, and the photovoltaic responses from the visible to the near-infrared range were investigated. Compared with the pure ZnO nanowire array and rGO thin film, the hybrid composite exhibited a fast and greatly enhanced broadband photovoltaic response that resulted from the formation of interfacial Schottky junctions between ZnO and rGO. PMID:25768384

  5. Low-Frequency Self-Powered Footstep Sensor Based on ZnO Nanowires on Paper Substrate.

    PubMed

    Nour, E S; Bondarevs, A; Huss, P; Sandberg, M; Gong, S; Willander, M; Nur, O

    2016-12-01

    In this work, we design and fabricate a wireless system with the main operating device based on zinc oxide (ZnO) nanowires. The main operating device is based on piezoelectric nanogenerator (NG) achieved using ZnO nanowires grown hydrothermally on paper substrate. The fabricated NG is capable of harvesting ambient mechanical energy from various kinds of human motion, e.g., footsteps. The harvested electric output has been used to serve as a self-powered pressure sensor. Without any storage device, the signal from a single footstep has successfully triggered a wireless sensor node circuit. This study demonstrates the feasibility of using ZnO nanowire piezoelectric NG as a low-frequency self-powered sensor, with potential applications in wireless sensor networks. PMID:27000024

  6. Low-Frequency Self-Powered Footstep Sensor Based on ZnO Nanowires on Paper Substrate

    NASA Astrophysics Data System (ADS)

    Nour, E. S.; Bondarevs, A.; Huss, P.; Sandberg, M.; Gong, S.; Willander, M.; Nur, O.

    2016-03-01

    In this work, we design and fabricate a wireless system with the main operating device based on zinc oxide (ZnO) nanowires. The main operating device is based on piezoelectric nanogenerator (NG) achieved using ZnO nanowires grown hydrothermally on paper substrate. The fabricated NG is capable of harvesting ambient mechanical energy from various kinds of human motion, e.g., footsteps. The harvested electric output has been used to serve as a self-powered pressure sensor. Without any storage device, the signal from a single footstep has successfully triggered a wireless sensor node circuit. This study demonstrates the feasibility of using ZnO nanowire piezoelectric NG as a low-frequency self-powered sensor, with potential applications in wireless sensor networks.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

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

    PubMed

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

    2014-02-01

    High quality ZnO nanowires (NWs) were grown on a graphene layer by a hydrothermal method. The ZnO NWs revealed higher uniform surface morphology and better structural properties than ZnO NWs grown on SiO2/Si substrate. A low dark current metal-semiconductor-metal photodetector based on ZnO NWs with Au Schottky contact has also been fabricated. The photodetector displays a low dark current of 1.53 nA at 1 V bias and a large UV-to-visible rejection ratio (up to four orders), which are significantly improved compared to conventional ZnO NW photodetectors. The improvement in UV detection performance is attributed to the existence of a surface plasmon at the interface of the ZnO and the graphene. PMID:24407201

  9. Piezotronic effect in solution-grown p-type ZnO nanowires and films.

    PubMed

    Pradel, Ken C; Wu, Wenzhuo; Zhou, Yusheng; Wen, Xiaonan; Ding, Yong; Wang, Zhong Lin

    2013-06-12

    Investigating the piezotronic effect in p-type piezoelectric semiconductor is critical for developing a complete piezotronic theory and designing/fabricating novel piezotronic applications with more complex functionality. Using a low temperature solution method, we were able to produce ultralong (up to 60 μm in length) Sb doped p-type ZnO nanowires on both rigid and flexible substrates. For the p-type nanowire field effect transistor, the on/off ratio, threshold voltage, mobility, and carrier concentration of 0.2% Sb-doped sample are found to be 10(5), 2.1 V, 0.82 cm(2)·V(-1)·s(-1), and 2.6 × 10(17) cm(-3), respectively, and the corresponding values for 1% Sb doped samples are 10(4), 2.0 V, 1.24 cm(2)·V(-1)·s(-1), and 3.8 × 10(17) cm(-3). We further investigated the universality of piezotronic effect in the as-synthesized Sb-doped p-type ZnO NWs and reported for the first time strain-gated piezotronic transistors as well as piezopotential-driven mechanical energy harvesting based on solution-grown p-type ZnO NWs. The results presented here broaden the scope of piezotronics and extend the framework for its potential applications in electronics, optoelectronics, smart MEMS/NEMS, and human-machine interfacing. PMID:23635319

  10. Characterization and modeling of a ZnO nanowire ultraviolet photodetector with graphene transparent contact

    SciTech Connect

    Zhang, H.; Lavenus, P.; Julien, F. H.; Tchernycheva, M.; Babichev, A. V.; Jacopin, G.; Egorov, A. Yu.

    2013-12-21

    We report the demonstration of a ZnO nanowire ultraviolet photodetector with a top transparent electrode made of a few-layered graphene sheet. The nanowires have been synthesized using a low-cost electrodeposition method. The detector is shown to be visible-blind and to present a responsivity larger than 10{sup 4} A/W in the near ultraviolet range thanks to a high photoconductive gain in ZnO nanowires. The device exhibits a peak responsivity at 370 nm wavelength and shows a sub bandgap response down to 415 nm explained by an Urbach tail with a characteristic energy of 83 meV. The temporal response of the detector and the power dependence are discussed. A model of the photoconductive mechanism is proposed showing that the main process responsible for the photoconductive gain is the modulation of the conducting surface due to the variation of the surface depletion layer and not the reduction of recombination efficiency stemming from the electron-hole spatial separation. The gain is predicted to decrease at high incident power due to the flattening of the lateral band bending in agreement with experimental data.

  11. Shadow mask assisted direct growth of ZnO nanowires as a sensing medium for surface acoustic wave devices using a thermal evaporation method

    NASA Astrophysics Data System (ADS)

    Achath Mohanan, Ajay; Parthiban, R.; Ramakrishnan, N.

    2016-02-01

    Zinc oxide (ZnO) nanowires were directly synthesized on high temperature stable one-port surface acoustic wave (SAW) resonators made of LiNbO3 substrate and Pt/Ti electrodes using a self-seeding catalyst-free thermal evaporation method. To enhance post-growth device functionality, one half of an SAW resonator was masked along the interdigital transducer aperture length during the nanowire growth process using a stainless steel shadow mask, while the other half was used as the ZnO nanowire growth site. This was achieved by employing a precisely machined stainless steel sleeve to house the chip and mask in the reaction chamber during the nanowire growth process. The ZnO nanowire integrated SAW resonator exhibited ultraviolet radiation sensing abilities which indicated that the ZnO nanowires grown on the SAW device were able to interact with SAW propagation on the substrate even after the device was exposed to extremely harsh conditions during the nanowire growth process. The use of a thermal evaporation method, instead of the conventionally used solution-grown method for direct growth of ZnO nanowires on SAW devices, paves the way for future methods aimed at the fabrication of highly sensitive ZnO nanowire-LiNbO3 based SAW sensors utilizing coupled resonance phenomenon at the nanoscale.

  12. Tunable transport properties of n-type ZnO nanowires by Ti plasma immersion ion implantation

    SciTech Connect

    Liao, L.; Zhang, Z.; Yan, B.; Li, G. P.; Wu, T.; Shen, Z. X.; Yu, T.; Yang, Y.; Cao, H. T.; Chen, L. L.; Tay, B. K.; Sun, X. W.

    2008-10-01

    Single-crystalline, transparent conducting ZnO nanowires were obtained simply by Ti plasma immersion ion implantation (PIII). Electrical transport characterizations demonstrate that the n-type conduction of ZnO nanowire could be tuned by appropriate Ti-PIII. When the energy of PIII is increased, the resistivity of ZnO decreases from 4x10{sup 2} to 3.3x10{sup -3} {omega} cm, indicating a semiconductor-metal transition. The failure-current densities of the metallic ZnO could be up to 2.75x10{sup 7} A/cm{sup 2}. Therefore, this facile method may provide an inexpensive alternative to tin doped indium oxide as transparent conducting oxide materials.

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

  14. Hydrothermal Synthesis of ZnO Structures Formed by High-Aspect-Ratio Nanowires for Acetone Detection.

    PubMed

    Cao, Zhen; Wang, Yong; Li, Zhanguo; Yu, Naisen

    2016-12-01

    Snowflake-like ZnO structures originating from self-assembled nanowires were prepared by a low-temperature aqueous solution method. The as-grown hierarchical ZnO structures were investigated by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The results showed that the snowflake-like ZnO structures were composed of high-aspect-ratio nanowires. Furthermore, gas-sensing properties to various testing gases of 10 and 50 ppm were measured, which confirms that the ZnO structures were of good selectivity and response to acetone and could serve for acetone sensor to detect low-concentration acetone. PMID:27460595

  15. 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.

  16. Exploring the Potential of Turbulent Flow Control Using Vertically Aligned Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    Bailey, Sean; Calhoun, John; Guskey, Christopher; Seigler, Michael; Koka, Aneesh; Sodano, Henry

    2012-11-01

    We present evidence that turbulent flow can be influenced by oscillating nanowires. A substrate coated with vertically aligned nanowires was installed in the boundary wall of fully-developed turbulent channel flow, and the substrate was excited by a piezoceramic actuator to oscillate the nanowires. Because the nanowires are immersed in the viscous sublayer, it was previously unclear whether the small scale flow oscillations imparted into the bulk flow by the nanowires would influence the turbulent flow or be dissipated by the effects of viscosity. Our experiments demonstrated that the nanowires produced perturbations in the flow and contributed energy throughout the depth of the turbulent layer. A parallel investigation using a dynamically scaled surface of vertically aligned wires in laminar flow found that, even at low Reynolds numbers, significant momentum transport can be produced in the flow by the introduction of a travelling wave motion into the surface. These findings reflect the potential for using oscillating nanowires as a novel method of near-wall turbulent flow control. This work was supported by the Air Force Office of Scientific Research under FA9550-11-1-0140.

  17. Vertically Aligned ZnO Nanorods: Effect of Synthesis Parameters.

    PubMed

    Rehman, Zeeshan Ur; Heo, Si-Nae; Cho, Hyeon Ji; Koo, Bon Heun

    2016-06-01

    This report is devoted to the synthesis of high quality nanorods using spin coating technique for seed layer growth. Effect of different parameter i.e., spins coating counts, spin coating speed, and the effect of temperature during the drying process was analyzed. Hot plate and furnace technique was used for heating purpose and the difference in the morphology was carefully observed. It is worthy to mention here that there is a substantial effect of all the above mentioned parameters on the growth and morphology of the ZnO nanostructure. The ZnO nanorods were finally synthesized using wet chemical method. The morphological properties of the obtained nanostructures were analyzed by using FESEM technique. PMID:27427752

  18. An advanced fabrication method of highly ordered ZnO nanowire arrays on silicon substrates by atomic layer deposition.

    PubMed

    Subannajui, Kittitat; Güder, Firat; Danhof, Julia; Menzel, Andreas; Yang, Yang; Kirste, Lutz; Wang, Chunyu; Cimalla, Volker; Schwarz, Ulrich; Zacharias, Margit

    2012-06-15

    In this work, the controlled fabrication of highly ordered ZnO nanowire (NW) arrays on silicon substrates is reported. Si NWs fabricated by a combination of phase shift lithography and etching are used as a template and are subsequently substituted by ZnO NWs with a dry-etching technique and atomic layer deposition. This fabrication technique allows the vertical ZnO NWs to be fabricated on 4 in Si wafers. Room temperature photoluminescence and micro-photoluminescence are used to observe the optical properties of the atomic layer deposition (ALD) based ZnO NWs. The sharp UV luminescence observed from the ALD ZnO NWs is unexpected for the polycrystalline nanostructure. Surprisingly, the defect related luminescence is much decreased compared to an ALD ZnO film deposited at the same time ona plane substrate. Electrical characterization was carried out by using nanomanipulators. With the p-type Si substrate and the n-type ZnO NWs the nanodevices represent p–n NW diodes.The nanowire diodes show a very high breakthrough potential which implies that the ALD ZnO NWs can be used for future electronic applications. PMID:22609898

  19. Type II band alignment in InAs zinc-blende/wurtzite heterostructured nanowires.

    PubMed

    Panda, Jaya Kumar; Chakraborty, Arup; Ercolani, Daniele; Gemmi, Mauro; Sorba, Lucia; Roy, Anushree

    2016-10-14

    In this article we demonstrate type-II band alignment at the wurtzite/zinc-blende hetero-interface in InAs polytype nanowires using resonance Raman measurements. Nanowires were grown with an optimum ratio of the above mentioned phases, so that in the electronic band alignment of such NWs the effect of the difference in the crystal structure dominates over other perturbing effects (e.g. interfacial strain, confinement of charge carriers and band bending due to space charge). Experimental results are compared with the band alignment obtained from density functional theory calculations. In resonance Raman measurements, the excitation energies in the visible range probe the band alignment formed by the E 1 gap of wurtzite and zinc-blende phases. However, we expect our claim to be valid also for band alignment near the fundamental gap at the heterointerface. PMID:27586817

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

    SciTech Connect

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

    2014-05-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  2. Catalyst-Free Synthesis of ZnO Nanowires on Oxidized Silicon Substrate for Gas Sensing Applications.

    PubMed

    Behera, B; Chandra, S

    2015-06-01

    In the present work, we report the synthesis of nanostructured ZnO by oxidation of zinc film without using a seed or catalyst layer. The zinc films were deposited on oxidized Si substrates by RF magnetron sputtering process. These were oxidized in dry and wet air/oxygen ambient. The optimized process yielded long nanowires of ZnO having diameter of around 60-70 nm and spread uniformly over the surface. The effect of oxidation temperature, time, Zn film thickness and the ambient has strong influence on the morphology of resulting nanostruxctured ZnO film. The films were characterized by scanning electron microscopy for morphological studies and X-ray diffraction (XRD) analysis to study the phase of the nanostructured ZnO. Room temperature photoluminescence (PL) measurements of the nanowires show UV and green emission. A sensor was designed and fabricated using nanostructured ZnO film, incorporating inter-digital-electrode (IDE) for the measurement of resistance of the sensing layer. The gas sensing properties were investigated from the measurement of change in resistance when exposed to vapours of different volatile organic compound (VOC) such as acetone, ethanol, methanol and 2-propanol. The results suggest that ZnO nanowires fabricated by this method have potential application in gas sensors. PMID:26369077

  3. ZnO nanowire array growth on precisely controlled patterns of inkjet-printed zinc acetate at low-temperatures

    NASA Astrophysics Data System (ADS)

    Tsangarides, Constantinos P.; Ma, Hanbin; Nathan, Arokia

    2016-06-01

    ZnO nanowires have been fabricated through the hydrothermal method on inkjet-printed patterns of zinc acetate dihydrate. The silicon substrate used was heated accordingly during the printing period in order to maintain good spatial uniformity of the zinc acetate nanoparticles, responsible for the pattern morphology. Printing more than one pass of precursor ink leads to an increase in seed layer thickness that subsequently alters the density and dimensions of nanowires. It has been demonstrated that with the right inkjet-printing parameters and substrate temperature, ZnO nanowires can be effortlessly fabricated in accordance with the desired pattern variations under low temperature and mild conditions that ensures promising applications in optoelectronic devices.ZnO nanowires have been fabricated through the hydrothermal method on inkjet-printed patterns of zinc acetate dihydrate. The silicon substrate used was heated accordingly during the printing period in order to maintain good spatial uniformity of the zinc acetate nanoparticles, responsible for the pattern morphology. Printing more than one pass of precursor ink leads to an increase in seed layer thickness that subsequently alters the density and dimensions of nanowires. It has been demonstrated that with the right inkjet-printing parameters and substrate temperature, ZnO nanowires can be effortlessly fabricated in accordance with the desired pattern variations under low temperature and mild conditions that ensures promising applications in optoelectronic devices. Electronic supplementary information (ESI) available: Printing parameters in detail and extra figures. See DOI: 10.1039/c6nr02962k

  4. Fabrication of ZnO Nanowire Based Piezoelectric Generators and Related Structures

    NASA Astrophysics Data System (ADS)

    Opoku, Charles; Dahiya, Abhishek Singh; Oshman, Christopher; Cayrel, Frederic; Poulin-Vittrant, Guylaine; Alquier, Daniel; Camara, Nicolas

    Using vertically grown hydrothermal ZnO nanowires, we demonstrate the assembly of fully functional piezoelectric energy harvesters on plastics substrates. A seedless hydrothermal process is employed for the growth of single crystalline vertically orientated ZnO NWs at around 100oC. Flexible NG are assembled using ∼7 μm thick PDMS polymer matrix on a 3x3cm substrate. A representative device with an active area of 4cm2 is characterised revealing average output voltage generation of ∼22mV (±1.2) and -32mV (±0.16) in the positive and negative cycles after 3-4mm periodic deflection at 20Hz. A power density of ∼288nW/cm3 is estimated for the device. It is envisaged that such energy scavengers may find potential applications targeting self-powered systems, sensors and on-body charging of electronics.

  5. CL from ZnO nanowires and microneedles Co-doped with N and Mn

    NASA Astrophysics Data System (ADS)

    Herrera, M.; Morales, A.; Díaz, J. A.

    2014-05-01

    Cathodoluminescence (CL) was used to study the luminescence emission of ZnO : N, Mn nanowires and microneedles grown by thermal evaporation. CL spectra acquired at room temperature showed the presence of near band edge and defect-related emissions. The defect related emission comprised two bands centered at 2.28 and 2.5 eV. The first component was attributed to the formation of spinel ZnMn2O4 and the second to the well-known ZnO green emission. CL spectra acquired at 100 K showed two emissions centered at 3.22 and 3.25 eV that were attributed to donor-acceptor pair (DAP) and FA transitions, respectively. It was proposed that substitutional nitrogen (NO) and zinc interstitial (Zni) were acceptor and shallow-donor centers in the DAP transition.

  6. Weak localization and electron-electron interactions in indium-doped ZnO nanowires.

    PubMed

    Thompson, Richard S; Li, Dongdong; Witte, Christopher M; Lu, Jia G

    2009-12-01

    Single crystal ZnO nanowires doped with indium are synthesized via the laser-assisted chemical vapor deposition method. The conductivity of the nanowires is measured at low temperatures in magnetic fields with directions both perpendicular and parallel to the wire axes. A quantitative fit of our data is obtained, consistent with the theory of a quasi-one-dimensional metallic system with quantum corrections due to weak localization and electron-electron interactions. The anisotropy of the magneto-conductivity agrees with theory. The two quantum corrections are of approximately equal magnitude with respective temperature dependences of T(-1/3)and T(-1/2). The alternative model of quasi-two-dimensional surface conductivity is excluded by the absence of oscillations in the magneto-conductivity in parallel magnetic fields. PMID:19831413

  7. Direct fabrication of superhydrophobic ceramic surfaces with ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Chung, Jihoon; Lee, Sukyung; Yong, Hyungseok; Lee, Sangmin; Park, Yong Tae

    2016-02-01

    Super-hydrophobic surfaces having contact angles > 150° for water are of great interest due to their potential use in a wide variety of applications. Although many reports on the wettability of different surfaces have been published, few or no studies have been done on the formation of a super-hydrophobic surface on a ceramic substrate. In this paper, we demonstrate the creation of a super-hydrophobic surface on a ceramic substrate by using zinc oxide nanowires (ZnO NWs) prepared by using a direct hydrothermal method. A self-assembled monolayer of heptadecafluoro- 1,1,2,2-tetrahydrodecyl trichlorosilane (HDFS) lowered the surface energy between the water droplet and the nano-textured surface. The length of the ZnO NWs was found to play a key role in the formation of a nanostructure that increased the surface roughness of the substrate. Furthermore, the length of the ZnO NWs could be controlled by changing the growth time, and HDFS-coated ZnO NWs were found to be super-hydrophobic after a growth time of 3 h. We have demonstrated the potential application of this nanostructure for ceramic tableware by introducing a ZnO-NW-textured surface on a ceramic cup, which resulted in water and alcohol repellency. This method is a simple and practical way to achieve a super-hydrophobic surface; hence, our method is expected to be widely used in various ceramic applications.

  8. Novel nonvolatile memory with multibit storage based on a ZnO nanowire transistor.

    PubMed

    Sohn, Jung Inn; Choi, Su Seok; Morris, Stephen M; Bendall, James S; Coles, Harry J; Hong, Woong-Ki; Jo, Gunho; Lee, Takhee; Welland, Mark E

    2010-11-10

    We demonstrate a room temperature processed ferroelectric (FE) nonvolatile memory based on a ZnO nanowire (NW) FET where the NW channel is coated with FE nanoparticles. A single device exhibits excellent memory characteristics with the large modulation in channel conductance between ON and OFF states exceeding 10(4), a long retention time of over 4 × 10(4) s, and multibit memory storage ability. Our findings provide a viable way to create new functional high-density nonvolatile memory devices compatible with simple processing techniques at low temperature for flexible devices made on plastic substrates. PMID:20945844

  9. Ultrafast spectroscopy of stimulated emission in single ZnO tetrapod nanowires

    NASA Astrophysics Data System (ADS)

    Djurisic, A. B.; Kwok, W. M.; Leung, Y. H.; Chan, W. K.; Phillips, D. L.; Lin, M. S.; Gwo, S.

    2006-01-01

    Stimulated emission from single ZnO tetrapod nanowires was studied by time-resolved photoluminescence (TRPL) spectroscopy. The samples were excited by a 300 fs pulse and the emission spectra collected as a function of time. The spectra exhibit a change in the position and the shape of the emission peak with time. The time evolution of the emission spectra was studied for different pump excitation fluences. The spectra exhibited a blue shift with increasing pump fluence, while for all pump fluences a red shift of the peaks with time was obtained. Possible reasons for the observed behaviour are discussed.

  10. Plasma enhanced multistate storage capability of single ZnO nanowire based memory

    NASA Astrophysics Data System (ADS)

    Lai, Yunfeng; Xin, Pucong; Cheng, Shuying; Yu, Jinling; Zheng, Qiao

    2015-01-01

    Multiple-state storage (MSS) is common for resistive random access memory, but the effects of plasma treatment on the MSS and the switching properties have been scarcely investigated. We have demonstrated a stable four-state storage capability of single zinc oxide nanowire (ZnO NW) treated by argon plasma. The electrical switching is attributed to the electron trapping and detrapping from the oxygen vacancies (Vos). The MSS relates to the electrical-thermal induced distribution of the Vos which determines electron transport behavior to show different resistance states. Additionally, programming (set and reset) voltages decrease with plasma treatment due to the thickness modulation of the interface barrier.

  11. A ZnO nanowire-based photo-inverter with pulse-induced fast recovery

    NASA Astrophysics Data System (ADS)

    Ali Raza, Syed Raza; Lee, Young Tack; Hosseini Shokouh, Seyed Hossein; Ha, Ryong; Choi, Heon-Jin; Im, Seongil

    2013-10-01

    We demonstrate a fast response photo-inverter comprised of one transparent gated ZnO nanowire field-effect transistor (FET) and one opaque FET respectively as the driver and load. Under ultraviolet (UV) light the transfer curve of the transparent gate FET shifts to the negative side and so does the voltage transfer curve (VTC) of the inverter. After termination of UV exposure the recovery of photo-induced current takes a long time in general. This persistent photoconductivity (PPC) is due to hole trapping on the surface of ZnO NWs. Here, we used a positive voltage short pulse after UV exposure, for the first time resolving the PPC issue in nanowire-based photo-detectors by accumulating electrons at the ZnO/dielectric interface. We found that a pulse duration as small as 200 ns was sufficient to reach a full recovery to the dark state from the UV induced state, realizing a fast UV detector with a voltage output.We demonstrate a fast response photo-inverter comprised of one transparent gated ZnO nanowire field-effect transistor (FET) and one opaque FET respectively as the driver and load. Under ultraviolet (UV) light the transfer curve of the transparent gate FET shifts to the negative side and so does the voltage transfer curve (VTC) of the inverter. After termination of UV exposure the recovery of photo-induced current takes a long time in general. This persistent photoconductivity (PPC) is due to hole trapping on the surface of ZnO NWs. Here, we used a positive voltage short pulse after UV exposure, for the first time resolving the PPC issue in nanowire-based photo-detectors by accumulating electrons at the ZnO/dielectric interface. We found that a pulse duration as small as 200 ns was sufficient to reach a full recovery to the dark state from the UV induced state, realizing a fast UV detector with a voltage output. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03801g

  12. ZnO homojunction photodiodes based on Sb-doped p-type nanowire array and n-type film for ultraviolet detection

    SciTech Connect

    Wang Guoping; Chu Sheng; Zhan Ning; Liu Jianlin; Lin Yuqing; Chernyak, Leonid

    2011-01-24

    ZnO p-n homojunctions based on Sb-doped p-type nanowire array and n-type film were grown by combining chemical vapor deposition (for nanowires) with molecular-beam epitaxy (for film). Indium tin oxide and Ti/Au were used as contacts to the ZnO nanowires and film, respectively. Characteristics of field-effect transistors using ZnO nanowires as channels indicate p-type conductivity of the nanowires. Electron beam induced current profiling confirmed the existence of ZnO p-n homojunction. Rectifying I-V characteristic showed a turn-on voltage of around 3 V. Very good response to ultraviolet light illumination was observed from photocurrent measurements.

  13. Aligned ZnO nanorod arrays growth on GaN QDs for excellent optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Sang, Dandan; Li, Hongdong; Wang, Qinglin

    2016-02-01

    Uniformly aligned ZnO nanorod (NR) arrays grown on GaN quantum dots (QDs) as preferred nucleation sites are imperative for designing field emission emitters, ultraviolet photodetectors and light-emitting diodes for a wide range of new optoelectronic applications. In a recent study (2015 Nanotechnology 26 415601), Qi et al reported a novel method of fabricating ZnO NRs arrays with uniform shape, the density of which is easily tunable by adjusting the density of GaN QDs. This approach opens a door to obtaining a combination of 0D and 1D structures for optoelectronic applications.

  14. Polymer chain alignment and transistor properties of nanochannel-templated poly(3-hexylthiophene) nanowires

    NASA Astrophysics Data System (ADS)

    Oh, Seungjun; Hayakawa, Ryoma; Pan, Chengjun; Sugiyasu, Kazunori; Wakayama, Yutaka

    2016-08-01

    Nanowires of semiconducting poly(3-hexylthiophene) (P3HT) were produced by a nanochannel-template technique. Polymer chain alignment in P3HT nanowires was investigated as a function of nanochannel widths (W) and polymer chain lengths (L). We found that the ratio between chain length and channel width (L/W) was a key parameter as regards promoting polymer chain alignment. Clear dichroism was observed in polarized ultraviolet-visible (UV-Vis) absorption spectra only at a ratio of approximately L/W = 2, indicating that the L/W ratio must be optimized to achieve uniaxial chain alignment in the nanochannel direction. We speculate that an appropriate L/W ratio is effective in confining the geometries and conformations of polymer chains. This discussion was supported by theoretical simulations based on molecular dynamics. That is, the geometry of the polymer chains, including the distance and tilting angles of the chains in relation to the nanochannel surface, was dominant in determining the longitudinal alignment along the nanochannels. Thus prepared highly aligned polymer nanowire is advantageous for electrical carrier transport and has great potential for improving the device performance of field-effect transistors. In fact, a one-order improvement in carrier mobility was observed in a P3HT nanowire transistor.

  15. Fabrication and characterization of ultraviolet photosensors from ZnO nanowires prepared using chemical bath deposition method

    NASA Astrophysics Data System (ADS)

    Al-Asadi, Ahmed S.; Henley, Luke Alexander; Ghosh, Sujoy; Quetz, Abdiel; Dubenko, Igor; Pradhan, Nihar; Balicas, Luis; Perea-Lopez, Nestor; Carozo, Victor; Lin, Zhong; Terrones, Mauricio; Talapatra, Saikat; Ali, Naushad

    2016-02-01

    Highly crystalline zinc oxide (ZnO) nanowires (NWs) were synthesized through chemical bath deposition (CBD) method by using a simple seeding technique. The process includes dispersion of commercially available ZnO nanoparticles through spraying on a desired substrate prior to the CBD growth. A typical growth period of 16 h produced ZnO NW assemblies with an average diameter of ˜45 nm and lengths of 1-1.3 μm, with an optical band gap of ˜3.61 eV. The as-prepared ZnO NWs were photoactive under ultra violet (UV) illumination. Photodetector devices fabricated using these NW assemblies demonstrated a high photoresponse factor of ˜40 and 120 at room temperature under moderate UV illumination power of ˜250 μW/cm2. These findings indicate the possibility of using ZnO NWs, grown using the simple method discussed in this paper, for various opto-electronic applications.

  16. Self-aligned multi-channel silicon nanowire field-effect transistors

    NASA Astrophysics Data System (ADS)

    Zhu, Hao; Li, Qiliang; Yuan, Hui; Baumgart, Helmut; Ioannou, Dimitris E.; Richter, Curt A.

    2012-12-01

    Si nanowire field effect transistors (SiNW FETs) with multiple nanowire channels and different gate lengths have been fabricated by using a directed assembly approach combined with a standard photolithographic process. The electrical characteristics of SiNW FETs containing different numbers of nanowire channels were measured and compared. The multi-channel SiNW FETs show excellent performance: small subthreshold slope (≈75 mV/dec), large ON/OFF ratio (≈108), good break-down voltage (>30 V) and good carrier mobility (μp ≈ 100 cm2 V-1s-1). These excellent device properties were achieved by using a clean self-alignment process and an improved device structure with Schottky barriers at the source and drain contacts. Such high-performance multi-nanowire FETs are attractive for logic, memory, and sensor applications.

  17. Fabrication of Si3N4 nanowire membranes: free standing disordered nanopapers and aligned nanowire assemblies

    NASA Astrophysics Data System (ADS)

    Liu, Haitao; Fang, Minghao; Huang, Zhaohui; Huang, Juntong; Liu, Yan-gai; Wu, Xiaowen

    2016-08-01

    Herein, ultralong silicon nitride nanowires were synthesized via a chemical vapor deposition method by using the low-cost quartz and silicon powder as raw materials. Simple processes were used for the fabrication of disordered and ordered nanowire membranes of pure silicon nitride nanowires. The nanowires in the disordered nanopapers are intertwined with each other to form a paper-like structure which exhibit excellent flame retardancy and mechanical properties. Fourier-transform infrared spectroscopy and thermal gravity analysis were employed to characterize the refractory performance of the disordered nanopapers. Highly ordered nanowire membranes were also assembled through a three-phase assembly approach which make the Si3N4 nanowires have potential use in textured ceramics and semiconductor field. Moreover, the surface nanowires can also be modified to be hydrophobic; this characteristic make the as-prepared nanowires have the potential to be assembled by the more effective Langmuir–Blodgett method and also make the disordered nanopapers possess a super-hydrophobic surface.

  18. Smartly aligning nanowires by a stretching strategy and their application as encoded sensors.

    PubMed

    Wu, Yuchen; Su, Bin; Jiang, Lei

    2012-10-23

    The nanotechnology world is being more and more attracted toward high aspect ratio one-dimensional nanostructures due to their potentials as building blocks for electronic/optical devices. Here, we propose a novel method to generate nanowire patterns with assistance of superhydrophobic flexible polydimethylsiloxane (PDMS) substrates. Micropillar gaps are tunable via a stretching process of the PDMS surface; thus, diverse nanowire patterns can be formed by stretching the same PDMS surface in various ways. Importantly, square nanowire loops with alternative compositions can be generated through a double-stretching process, showing an advanced methodology in controlling the alignment of nanowires. Since alternative fluorescent molecules will be quenched by diverse chemical substances, this alternative nanowire loop shows a selective detection for diverse target compounds, which greatly improves the application of this nanowire patterning approach. Furthermore, such alternative nanowire patterns can be transferred from pillar-structured surfaces to flat films, indicating further potentials in microcircuits, sensitive sensors, and other organic functional nanodevices. PMID:22984829

  19. Horizontal transfer of aligned Si nanowire arrays and their photoconductive performance

    PubMed Central

    2014-01-01

    An easy and low-cost method to transfer large-scale horizontally aligned Si nanowires onto a substrate is reported. Si nanowires prepared by metal-assisted chemical etching were assembled and anchored to fabricate multiwire photoconductive devices with standard Si technology. Scanning electron microscopy images showed highly aligned and successfully anchored Si nanowires. Current-voltage tests showed an approximately twofold change in conductivity between the devices in dark and under laser irradiation. Fully reversible light switching ON/OFF response was also achieved with an ION/IOFF ratio of 230. Dynamic response measurement showed a fast switching feature with response and recovery times of 10.96 and 19.26 ms, respectively. PMID:25520603

  20. Gate tunable spin exchange interaction and inversion of magnetoresistance in ferromagnetic ZnO nanowire

    NASA Astrophysics Data System (ADS)

    Modepalli, Vijayakumar; Jin, Mi-Jin; Park, Jungmin; Jo, Junhyeon; Kim, Ji-Hyun; Baik, Jeong Min; Kim, Jeongyong; Yoo, Jung-Woo

    Tuning magnetism in diluted magnetic semiconductor (DMS) is one of the central issue to the development of future spintronic device applications. Particularly, realizing such control in nanostructure has received growing attention. Here, we report the dramatic change of MR in ferromagnetic ZnO nanowire with varied gate voltages (+50 V to -40 V) at different temperatures (2 K to 50 K). The MR signal was greatly influenced by the gate voltage induced carrier concentrations which results the inversion of MR from positive to negative sign while pertaining the coexistence of both parts before inversion in the range of -2T to 2T. The origin of negative MR is mainly due to spin scattering while the positive one is due to a field induced change in relative populations of conduction bands with different conductivities. The extracted spin exchange related parameter was well tuned with the varied gate voltages at different temperatures. More importantly this type of gate tuning of spin exchange interactions in ferromagnetic single ZnO nanowire is well suitable for future spintronic device applications.

  1. Schottky-contacted vertically self-aligned ZnO nanorods for hydrogen gas nanosensor applications

    SciTech Connect

    Ranwa, Sapana; Kumar, Mohit; Kumar, Mahesh; Singh, Jitendra; Fanetti, Mattia

    2015-07-21

    Vertically well aligned ZnO nanorods (NRs) were grown on Si(100) substrate using RF magnetron sputtering technique. Scanning electron microscopy images confirms uniform distribution of NRs on 2 in. wafer with average diameter, height and density being ∼75 nm, ∼850 nm, and ∼1.5 × 10{sup 10} cm{sup −2}, respectively. X-ray diffraction reveals that the ZnO NRs are grown along c-axis direction with wurtzite crystal structure. Cathodoluminescence spectroscopy, which shows a single strong peak around 3.24 eV with full width half maxima 130 meV, indicates the high crystalline and optical quality of ZnO and very low defect density. Vertically aligned nanosensors were fabricated by depositing gold circular Schottky contacts on ZnO NRs. Resistance responses of nanosensors were observed in the range from 50 to 150 °C in 1% and 5% hydrogen in argon environment, which is below and above the explosive limit (4%) of hydrogen in air. The nanosensor's sensitivity increases from 11% to 67% with temperature from 50 to 150 °C and also shows fast response time (9–16 s) and moderate recovery time (100–200 s). A sensing mechanism is proposed based on Schottky barrier changes at heterojunctions and change in depletion region of NRs.

  2. Schottky-contacted vertically self-aligned ZnO nanorods for hydrogen gas nanosensor applications

    NASA Astrophysics Data System (ADS)

    Ranwa, Sapana; Kumar, Mohit; Singh, Jitendra; Fanetti, Mattia; Kumar, Mahesh

    2015-07-01

    Vertically well aligned ZnO nanorods (NRs) were grown on Si(100) substrate using RF magnetron sputtering technique. Scanning electron microscopy images confirms uniform distribution of NRs on 2 in. wafer with average diameter, height and density being ˜75 nm, ˜850 nm, and ˜1.5 × 1010 cm-2, respectively. X-ray diffraction reveals that the ZnO NRs are grown along c-axis direction with wurtzite crystal structure. Cathodoluminescence spectroscopy, which shows a single strong peak around 3.24 eV with full width half maxima 130 meV, indicates the high crystalline and optical quality of ZnO and very low defect density. Vertically aligned nanosensors were fabricated by depositing gold circular Schottky contacts on ZnO NRs. Resistance responses of nanosensors were observed in the range from 50 to 150 °C in 1% and 5% hydrogen in argon environment, which is below and above the explosive limit (4%) of hydrogen in air. The nanosensor's sensitivity increases from 11% to 67% with temperature from 50 to 150 °C and also shows fast response time (9-16 s) and moderate recovery time (100-200 s). A sensing mechanism is proposed based on Schottky barrier changes at heterojunctions and change in depletion region of NRs.

  3. Catalyst-Free, Selective Growth of ZnO Nanowires on SiO2 by Chemical Vapor Deposition for Transfer-Free Fabrication of UV Photodetectors.

    PubMed

    Xu, Liping; Li, Xin; Zhan, Zhaoyao; Wang, Liang; Feng, Shuanglong; Chai, Xiangyu; Lu, Wenqiang; Shen, Jun; Weng, Zhankun; Sun, Jie

    2015-09-16

    Catalyst-free, selective growth of ZnO nanowires directly on the commonly used dielectric SiO2 layer is of both scientific significance and application importance, yet it is still a challenge. Here, we report a facile method to grow single-crystal ZnO nanowires on a large scale directly on SiO2/Si substrate through vapor-solid mechanism without using any predeposited metal catalyst or seed layer. We found that a rough SiO2/Si substrate surface created by the reactive ion etching is critical for ZnO growth without using catalyst. ZnO nanowire array exclusively grows in area etched by the reactive ion etching method. The advantages of this method include facile and safe roughness-assisted catalyst-free growth of ZnO nanowires on SiO2/Si substrate and the subsequent transfer-free fabrication of electronic or optoelectronic devices. The ZnO nanowire UV photodetector fabricated by a transfer-free process presented high performance in responsivity, quantum efficiency and response speed, even without any post-treatments. The strategy shown here would greatly reduce the complexity in nanodevice fabrication and give an impetus to the application of ZnO nanowires in nanoelectronics and optoelectronics. PMID:26308593

  4. ZnO nanowire array growth on precisely controlled patterns of inkjet-printed zinc acetate at low-temperatures.

    PubMed

    Tsangarides, Constantinos P; Ma, Hanbin; Nathan, Arokia

    2016-06-01

    ZnO nanowires have been fabricated through the hydrothermal method on inkjet-printed patterns of zinc acetate dihydrate. The silicon substrate used was heated accordingly during the printing period in order to maintain good spatial uniformity of the zinc acetate nanoparticles, responsible for the pattern morphology. Printing more than one pass of precursor ink leads to an increase in seed layer thickness that subsequently alters the density and dimensions of nanowires. It has been demonstrated that with the right inkjet-printing parameters and substrate temperature, ZnO nanowires can be effortlessly fabricated in accordance with the desired pattern variations under low temperature and mild conditions that ensures promising applications in optoelectronic devices. PMID:27223061

  5. Physical properties of annealed ZnO nanowire/CuSCN heterojunctions for self-powered UV photodetectors.

    PubMed

    Garnier, Jérôme; Parize, Romain; Appert, Estelle; Chaix-Pluchery, Odette; Kaminski-Cachopo, Anne; Consonni, Vincent

    2015-03-18

    The low-cost fabrication of ZnO nanowire/CuSCN heterojunctions is demonstrated by combining chemical bath deposition with impregnation techniques. The ZnO nanowire arrays are completely filled by the CuSCN layer from their bottoms to their tops. The CuSCN layer is formed of columnar grains that are strongly oriented along the [003] direction owing to the polymeric form of the β-rhombohedral crystalline phase. Importantly, an annealing step is found essential in a fairly narrow range of low temperatures, not only for outgassing the solvent from the CuSCN layer, but also for reducing the density of interfacial defects. The resulting electrical properties of annealed ZnO nanowire/CuSCN heterojunctions are strongly improved: a maximum rectification ratio of 2644 at ±2 V is achieved following annealing at 150 °C under air atmosphere, which is related to a strong decrease in the reverse current density. Interestingly, the corresponding self-powered UV photodetectors exhibit a responsivity of 0.02 A/W at zero bias and at 370 nm with a UV-to-visible (370-500 nm) rejection ratio of 100 under an irradiance of 100 mW/cm(2). The UV selectivity at 370 nm can also be readily modulated by tuning the length of ZnO nanowires. Eventually, a significant photovoltaic effect is revealed for this type of heterojunctions, leading to an open circuit voltage of 37 mV and a short circuit current density of 51 μA/cm(2), which may be useful for the self-powering of the complete device. These findings show the underlying physical mechanisms at work in ZnO nanowire/CuSCN heterojunctions and reveal their high potential as self-powered UV photodetectors. PMID:25706583

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

    PubMed

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

    2016-02-18

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

  7. Leapfrog cracking and nanoamorphization of ZnO nanowires during in situ electrochemical lithiation.

    PubMed

    Kushima, Akihiro; Liu, Xiao Hua; Zhu, Guang; Wang, Zhong Lin; Huang, Jian Yu; Li, Ju

    2011-11-01

    The lithiation reaction of single ZnO nanowire (NW) electrode in a Li-ion nanobattery configuration was observed by in situ transmission electron microscopy. Upon first charge, the single-crystalline NW was transformed into a nanoglass with multiple glassy nanodomains (Gleiter, H. MRS Bulletin2009, 34, 456) by an intriguing reaction mechanism. First, partial lithiation of crystalline NW induced multiple nanocracks ∼70 nm ahead of the main lithiation front, which traversed the NW cross-section and divided the NW into multiple segments. This was followed by rapid surface diffusion of Li(+) and solid-state amorphization along the open crack surfaces. Finally the crack surfaces merged, leaving behind a glass-glass interface (GGI). Such reaction front instability also repeated in the interior of each divided segment, further subdividing the NW into different nanoglass domains (nanoamorphization). Instead of the profuse dislocation plasticity seen in SnO(2) NWs (Science2010, 330, 1515), no dislocation was seen and the aforementioned nanocracking was the main precursor to the electrochemically driven solid-state amorphization in ZnO. Ab initio tensile decohesion calculations verified dramatic lithium embrittlement effect in ZnO, but not in SnO(2). This is attributed to the aliovalency of Sn cation (Sn(IV), Sn(II)) in contrast to the electronically more rigid Zn(II) cation. PMID:21942500

  8. Contact properties and surface reaction kinetics of single ZnO nanowire devices fabricated by dielectrophoresis

    NASA Astrophysics Data System (ADS)

    Pau, J. L.; García Núñez, C.; García Marín, A.; Guerrero, C.; Rodríguez, P.; Borromeo, S.; Piqueras, J.

    2014-03-01

    This work describes the development of ZnO nanowire (NW) devices for ultraviolet detection and cost-effective gas sensing. A dielectrophoresis (DEP) flow cell fabricated for the integration of NWs on different substrates is presented. The system includes the possibility to set characteristic parameters such as alternating current (AC) frequency, amplitude or flow speed in order to control NW trapping on specific sites defined by micro-gapped electrodes. The electrical characteristics of the rectifying metal/NW contact fabricated by DEP are investigated in darkness and under direct illumination of the metal-NW interface through the ZnO NW. A significant downshift of the turn-on voltage is observed in the current-voltage characteristics during the illumination with photon energies higher than the ZnO bandgap. The reduction is attributed to a barrier height lowering induced by interface charge emission. The effects of AC bias on the thermal drift of the DC average current in NW devices are also discussed. Finally, the reaction kinetics of ethanol and water vapors on the NW surface are compared through the analysis of the DC current under direct exposure to gas flows. Device responses to more complex compound mixtures such as coffee or mint are also monitored over time, showing different performance in both cases.

  9. Diameter and location control of ZnO nanowires using electrodeposition and sodium citrate

    NASA Astrophysics Data System (ADS)

    Lifson, Max L.; Levey, Christopher G.; Gibson, Ursula J.

    2013-10-01

    We report single-step growth of spatially localized ZnO nanowires of controlled diameter to enable improved performance of piezoelectric devices such as nanogenerators. This study is the first to demonstrate the combination of electrodeposition with zinc nitrate and sodium citrate in the growth solution. Electrodeposition through a thermally-grown silicon oxide mask results in localization, while the growth voltage and solution chemistry are tuned to control the nanowire geometry. We observe a competition between lateral (relative to the (0001) axis) citrate-related morphology and voltage-driven vertical growth which enables this control. High aspect ratios result with either pure nitrate or nitrate-citrate mixtures if large voltages are used, but low growth voltages permit the growth of large diameter nanowires in solution with citrate. Measurements of the current density suggest a two-step growth process. An oxide mask blocks the electrodeposition, and suppresses nucleation of thermally driven growth, permitting single-step lithography on low cost p-type silicon substrates.

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

    SciTech Connect

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

    2008-07-01

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

  11. The role of substrate surface alteration in the fabrication of vertically aligned CdTe nanowires.

    PubMed

    Neretina, S; Hughes, R A; Devenyi, G A; Sochinskii, N V; Preston, J S; Mascher, P

    2008-05-01

    Previously we have described the deposition of vertically aligned wurtzite CdTe nanowires derived from an unusual catalytically driven growth mode. This growth mode could only proceed when the surface of the substrate was corrupted with an alcohol layer, although the role of the corruption was not fully understood. Here, we present a study detailing the remarkable role that this substrate surface alteration plays in the development of CdTe nanowires; it dramatically improves the size uniformity and largely eliminates lateral growth. These effects are demonstrated to arise from the altered surface's ability to limit Ostwald ripening of the catalytic seed material and by providing a surface unable to promote the epitaxial relationship needed to sustain a lateral growth mode. The axial growth of the CdTe nanowires is found to be exclusively driven through the direct impingement of adatoms onto the catalytic seeds leading to a self-limiting wire height associated with the sublimation of material from the sidewall facets. The work presented furthers the development of the mechanisms needed to promote high quality substrate-based vertically aligned CdTe nanowires. With our present understanding of the growth mechanism being a combination of selective area epitaxy and a catalytically driven vapour-liquid-solid growth mode, these results also raise the intriguing possibility of employing this growth mode in other material systems in an effort to produce superior nanowires. PMID:21825689

  12. Effects of Nanowire Length and Surface Roughness on the Electrochemical Sensor Properties of Nafion-Free, Vertically Aligned Pt Nanowire Array Electrodes.

    PubMed

    Li, Zhiyang; Leung, Calvin; Gao, Fan; Gu, Zhiyong

    2015-01-01

    In this paper, vertically aligned Pt nanowire arrays (PtNWA) with different lengths and surface roughnesses were fabricated and their electrochemical performance toward hydrogen peroxide (H₂O₂) detection was studied. The nanowire arrays were synthesized by electroplating Pt in nanopores of anodic aluminum oxide (AAO) template. Different parameters, such as current density and deposition time, were precisely controlled to synthesize nanowires with different surface roughnesses and various lengths from 3 μm to 12 μm. The PtNWA electrodes showed better performance than the conventional electrodes modified by Pt nanowires randomly dispersed on the electrode surface. The results indicate that both the length and surface roughness can affect the sensing performance of vertically aligned Pt nanowire array electrodes. Generally, longer nanowires with rougher surfaces showed better electrochemical sensing performance. The 12 μm rough surface PtNWA presented the largest sensitivity (654 μA·mM⁻¹·cm⁻²) among all the nanowires studied, and showed a limit of detection of 2.4 μM. The 12 μm rough surface PtNWA electrode also showed good anti-interference property from chemicals that are typically present in the biological samples such as ascorbic, uric acid, citric acid, and glucose. The sensing performance in real samples (river water) was tested and good recovery was observed. These Nafion-free, vertically aligned Pt nanowires with surface roughness control show great promise as versatile electrochemical sensors and biosensors. PMID:26404303

  13. Effects of Nanowire Length and Surface Roughness on the Electrochemical Sensor Properties of Nafion-Free, Vertically Aligned Pt Nanowire Array Electrodes

    PubMed Central

    Li, Zhiyang; Leung, Calvin; Gao, Fan; Gu, Zhiyong

    2015-01-01

    In this paper, vertically aligned Pt nanowire arrays (PtNWA) with different lengths and surface roughnesses were fabricated and their electrochemical performance toward hydrogen peroxide (H2O2) detection was studied. The nanowire arrays were synthesized by electroplating Pt in nanopores of anodic aluminum oxide (AAO) template. Different parameters, such as current density and deposition time, were precisely controlled to synthesize nanowires with different surface roughnesses and various lengths from 3 μm to 12 μm. The PtNWA electrodes showed better performance than the conventional electrodes modified by Pt nanowires randomly dispersed on the electrode surface. The results indicate that both the length and surface roughness can affect the sensing performance of vertically aligned Pt nanowire array electrodes. Generally, longer nanowires with rougher surfaces showed better electrochemical sensing performance. The 12 μm rough surface PtNWA presented the largest sensitivity (654 μA·mM−1·cm−2) among all the nanowires studied, and showed a limit of detection of 2.4 μM. The 12 μm rough surface PtNWA electrode also showed good anti-interference property from chemicals that are typically present in the biological samples such as ascorbic, uric acid, citric acid, and glucose. The sensing performance in real samples (river water) was tested and good recovery was observed. These Nafion-free, vertically aligned Pt nanowires with surface roughness control show great promise as versatile electrochemical sensors and biosensors. PMID:26404303

  14. Realization of Vertically Aligned, Ultrahigh Aspect Ratio InAsSb Nanowires on Graphite.

    PubMed

    Anyebe, E A; Sanchez, A M; Hindmarsh, S; Chen, X; Shao, J; Rajpalke, M K; Veal, T D; Robinson, B J; Kolosov, O; Anderson, F; Sundaram, R; Wang, Z M; Falko, V; Zhuang, Q

    2015-07-01

    The monolithic integration of InAs(1-x)Sb(x) semiconductor nanowires on graphitic substrates holds enormous promise for cost-effective, high-performance, and flexible devices in optoelectronics and high-speed electronics. However, the growth of InAs(1-x)Sb(x) nanowires with high aspect ratio essential for device applications is extremely challenging due to Sb-induced suppression of axial growth and enhancement in radial growth. We report the realization of high quality, vertically aligned, nontapered and ultrahigh aspect ratio InAs(1-x)Sb(x) nanowires with Sb composition (xSb(%)) up to ∼12% grown by indium-droplet assisted molecular beam epitaxy on graphite substrate. Low temperature photoluminescence measurements show that the InAs(1-x)Sb(x) nanowires exhibit bright band-to-band related emission with a distinct redshift as a function of Sb composition providing further confirmation of successful Sb incorporation in as-grown nanowires. This study reveals that the graphite substrate is a more favorable platform for InAs(1-x)Sb(x) nanowires that could lead to hybrid heterostructures possessing potential device applications in optoelectronics. PMID:26086785

  15. 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

  16. High-efficiency solid-state dye-sensitized solar cells based on TiO(2)-coated ZnO nanowire arrays.

    PubMed

    Xu, Chengkun; Wu, Jiamin; Desai, Umang V; Gao, Di

    2012-05-01

    Replacing the liquid electrolytes in dye-sensitized solar cells (DSCs) with solid-state hole-transporting materials (HTMs) may solve the packaging challenge and improve the long-term stability of DSCs. The efficiencies of such solid-state DSCs (ss-DSCs), however, have been far below the efficiencies of their counterparts that use liquid electrolytes, primarily due to the challenges in filling HTMs into thick enough sensitized films based on sintered TiO(2) nanoparticles. Here we report fabrication of high-efficiency ss-DSCs using multilayer TiO(2)-coated ZnO nanowire arrays as the photoanodes. The straight channel between the vertically aligned nanostructures combined with a newly developed multistep HTM filling process allows us to effectively fill sensitized films as thick as 50 μm with the HTMs. The resulting ss-DSCs yield an average power conversion efficiency of 5.65%. PMID:22486787

  17. Effect of atomic layer deposition temperature on the performance of top-down ZnO nanowire transistors

    PubMed Central

    2014-01-01

    This paper studies the effect of atomic layer deposition (ALD) temperature on the performance of top-down ZnO nanowire transistors. Electrical characteristics are presented for 10-μm ZnO nanowire field-effect transistors (FETs) and for deposition temperatures in the range 120°C to 210°C. Well-behaved transistor output characteristics are obtained for all deposition temperatures. It is shown that the maximum field-effect mobility occurs for an ALD temperature of 190°C. This maximum field-effect mobility corresponds with a maximum Hall effect bulk mobility and with a ZnO film that is stoichiometric. The optimized transistors have a field-effect mobility of 10 cm2/V.s, which is approximately ten times higher than can typically be achieved in thin-film amorphous silicon transistors. Furthermore, simulations indicate that the drain current and field-effect mobility extraction are limited by the contact resistance. When the effects of contact resistance are de-embedded, a field-effect mobility of 129 cm2/V.s is obtained. This excellent result demonstrates the promise of top-down ZnO nanowire technology for a wide variety of applications such as high-performance thin-film electronics, flexible electronics, and biosensing. PMID:25276107

  18. A MEMS based acetone sensor incorporating ZnO nanowires synthesized by wet oxidation of Zn film

    NASA Astrophysics Data System (ADS)

    Behera, Bhagaban; Chandra, Sudhir

    2015-01-01

    In this work, we report a simple and efficient method for synthesis of ZnO nanowires by thermal oxidation of Zn film and their integration with MEMS technologies to fabricate a sensor for acetone vapour detection. ZnO nanowires were prepared by thermal oxidation of sputter deposited Zn film. The nanostructured ZnO was characterized by x-ray diffraction, a scanning electron microscope and room temperature photoluminescence measurements. The ZnO nanowires synthesis process was integrated with MEMS technologies to obtain a sensor for volatile organic compounds, incorporating an on-chip Ni microheater and an interdigited electrode structure. To reduce the heat loss from the on-chip microheater, the sensor was made on a thin silicon diaphragm obtained via a modified reactive ion etching process. This resulted in considerable power saving during sensor operation. For this, a three-mask process was used. The performance of the microheater was simulated on COMSOL and validated experimentally. The sensor has been tested for acetone vapour sensing and the operating parameters were optimized. The sensor has the ability to detect acetone vapour at 5 parts per million (ppm) concentrations when operated at 100 °C. The sensor consumed only 36 mW power and showed a high-sensitivity value of 26.3% for 100 ppm of acetone vapour.

  19. Field emission from in situ-grown vertically aligned SnO2 nanowire arrays

    PubMed Central

    2012-01-01

    Vertically aligned SnO2 nanowire arrays have been in situ fabricated on a silicon substrate via thermal evaporation method in the presence of a Pt catalyst. The field emission properties of the SnO2 nanowire arrays have been investigated. Low turn-on fields of 1.6 to 2.8 V/μm were obtained at anode-cathode separations of 100 to 200 μm. The current density fluctuation was lower than 5% during a 120-min stability test measured at a fixed applied electric field of 5 V/μm. The favorable field-emission performance indicates that the fabricated SnO2 nanowire arrays are promising candidates as field emitters. PMID:22330800

  20. Molten Pb as a catalyst for large-scale growth of highly aligned silicon oxide nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Jiang, Feihong; Yang, Yongdong; Li, Jianping

    2007-09-01

    Low melting point metal Pb can be used as an effective catalyst for the large-scale growth of highly aligned silicon oxide nanowire balls. Unlike any previously observed results using Au or Fe as catalyst, the molten Pb-catalyzed vapor-liquid-solid (VLS) growth exhibits many amazing growth phenomena. The scan electron microscopy (SEM) data indicate that the silicon oxide nanowires grow out perpendicularly from the surface of the metal Pb balls. For each ball, numerous nanowires simultaneously nucleate, grow at nearly the same rate and direction, and simultaneously stop growing. The pear-like, flower-like, chrysanthemum-like, and echinus-like SiO 2 nanostructures were formed. A growth model was proposed. The experimental results further expand the low melting point metal-catalyzed VLS mechanism to a broader range.

  1. Input/output pulse operation of ZnO nanowire threshold integrators.

    PubMed

    White, Richard; Colli, Alan; Li, Hongwei; Kivioja, Jani

    2011-01-14

    Integrating more functionality into individual nano-components is a key step to exploit alternative architectures for energy-efficient computation, such as, for instance, neuromorphic computing. Here, we show how to configure ZnO nanowire field-effect transistors as light pulse integrators with programmable threshold. We demonstrate that these single-component devices can be operated as both synchronous and asynchronous neuron-like structures, where the firing threshold and the form of the output signal, either step-like or spiked, can be controlled by using several operational parameters, including the environment in which the device operates. A detailed study showing how environmental variables, such as relative humidity, ambient light and temperature, affect device operation is presented. PMID:21139191

  2. Plasma enhanced multistate storage capability of single ZnO nanowire based memory

    SciTech Connect

    Lai, Yunfeng Xin, Pucong; Cheng, Shuying; Yu, Jinling; Zheng, Qiao

    2015-01-19

    Multiple-state storage (MSS) is common for resistive random access memory, but the effects of plasma treatment on the MSS and the switching properties have been scarcely investigated. We have demonstrated a stable four-state storage capability of single zinc oxide nanowire (ZnO NW) treated by argon plasma. The electrical switching is attributed to the electron trapping and detrapping from the oxygen vacancies (V{sub o}s). The MSS relates to the electrical-thermal induced distribution of the V{sub o}s which determines electron transport behavior to show different resistance states. Additionally, programming (set and reset) voltages decrease with plasma treatment due to the thickness modulation of the interface barrier.

  3. Direct observation of Li diffusion in Li-doped ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Li, Guohua; Yu, Lei; Hudak, Bethany M.; Chang, Yao-Jen; Baek, Hyeonjun; Sundararajan, Abhishek; Strachan, Douglas R.; Yi, Gyu-Chul; Guiton, Beth S.

    2016-05-01

    The direct observation of Li diffusion in Li-doped zinc oxide nanowires (NWs) was realized by using in situ heating in the scanning transmission electron microscope (STEM). A continuous increase of low atomic mass regions within a single NW was observed between 200 °C and 600 °C when heated in vacuum, which was explained by the conversion of interstitial to substitutional Li in the ZnO NW host lattice. A kick-out mechanism is introduced to explain the migration and conversion of the interstitial Li (Lii) to Zn-site substitutional Li (LiZn), and this mechanism is verified with low-temperature (11 K) photoluminescence measurements on as-grown and annealed Li-doped zinc oxide NWs, as well as the observation of an increase of NW surface roughing with applied bias.

  4. Hierarchical ZnO Nanowire Growth with Tunable Orientations on Versatile Substrates Using Atomic Layer Deposition Seeding

    SciTech Connect

    Bielinski, Ashley R.; Kazyak, Eric; Schleputz, Christian M.; Jung, Hee Joon; Wood, Kevin N.; Dasgupta, Neil P.

    2015-07-14

    The ability to synthesize semiconductor nanowires with deterministic and tunable control of orientation and morphology on a wide range of substrates, while high precision and repeatability are maintained, is a challenge currently faced for the development of many nanoscale material systems. Here we show that atomic layer deposition (ALD) presents a reliable method of surface and interfacial modification to guide nanowire orientation on a variety of substrate materials and geometries, including high-aspect-ratio, three-dimensional templates. We demonstrate control of the orientation and geometric properties of hydrothermally grown single crystalline ZnO nanowires via the deposition of a ZnO seed layer by ALD. The crystallographic texture and roughness of the seed layer result in tunable preferred nanowire orientations and densities for identical hydrothermal growth conditions. The structural and chemical relationship between the ALD layers and nanowires was investigated with synchrotron X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy to elucidate the underlying mechanisms of orientation and morphology control. The resulting control parameters were utilized to produce hierarchical nanostructures with tunable properties on a wide range of substrates, including vertical micropillars, paper fibers, porous polymer membranes, and biological substrates. This illustrates the power of ALD for interfacial engineering of heterogeneous material systems at the nanoscale, to provide a highly controlled and scalable seeding method for bottom-up synthesis of integrated nanosystems.

  5. Growth and characterization of vertically aligned ZnO nanorods grown on porous silicon: Effect of precursor concentration

    NASA Astrophysics Data System (ADS)

    Shabannia, R.; Abu Hassan, H.

    2013-10-01

    Vertically aligned ZnO nanorods were successfully synthesized on porous silicon (PS) substrates by chemical bath deposition method at low temperature. The effect of precursor concentration on the growth of ZnO nanorods were systematically characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), low and high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and Raman spectroscopy. The XRD results reveal that all the as-grown ZnO nanorod arrays grew preferentially oriented along the c-axis with a hexagonal wurtzite structure. The FESEM images show that the ZnO nanorods grown perpendicular to the PS substrates had diameters and lengths ranging from 13 nm to 69 nm and from 85 nm to 208 nm, respectively. The low-resolution TEM image indicates that the ZnO nanorod arrays had a uniform diameter along their whole length and a smooth surface. PL and Raman analyses reveal that the aligned ZnO nanorods exhibited a sharp ultraviolet peak and high E2 (high) at around 390 nm and 433.8 cm-1, respectively. Furthermore, the ZnO nanorods grew vertically under 0.050 M precursor concentration, resulting in a high structural and optical quality. These ZnO nanorods can be potentially used for fabricating nanoelectronic and nano-optical devices.

  6. Optical and Electrical Characteristics of Hybrid ZnO Nanowire/a-Si:H Solar Cells on Flexible Substrates under Mechanical Bending.

    PubMed

    Pathirane, Minoli K; Wong, William S

    2016-05-01

    Disordered 3-D hybrid ZnO nanowire/a-Si:H thin-film radial-junction solar cells are directly fabricated onto flexible substrates. A 41% reduction in optical reflectivity resulted in a 15% increase in the current density when the substrate is mechanically bent concave-up toward the incoming light. The light scattering of the nanowire devices was enhanced by decreasing the spacing between the nanowire solar cell by bending the substrate. PMID:27028309

  7. Towards a full integration of vertically aligned silicon nanowires in MEMS using silane as a precursor

    NASA Astrophysics Data System (ADS)

    Gadea, G.; Morata, A.; Santos, J. D.; Dávila, D.; Calaza, C.; Salleras, M.; Fonseca, L.; Tarancón, A.

    2015-05-01

    Silicon nanowires present outstanding properties for electronics, energy, and environmental monitoring applications. However, their integration into microelectromechanical systems (MEMS) is a major issue so far due to low compatibility with mainstream technology, which complicates patterning and controlled morphology. This work addresses the growth of <111> aligned silicon nanowire arrays fully integrated into standard MEMS processing by means of the chemical vapor deposition-vapor liquid solid method (CVD-VLS) using silane as a precursor. A reinterpretation of the galvanic displacement method is presented for selectively depositing gold nanoparticles of controlled size and shape. Moreover, a comprehensive analysis of the effects of synthesis temperature and pressure on the growth rate and alignment of nanowires is presented for the most common silicon precursor, i.e., silane. Compared with previously reported protocols, the redefined galvanic displacement together with a silane-based CVD-VLS growth methodology provides a more standard and low-temperature (<650 °C) synthesis scheme and a compatible route to reliably grow Si nanowires in MEMS for advanced applications.

  8. Towards a full integration of vertically aligned silicon nanowires in MEMS using silane as a precursor.

    PubMed

    Gadea, G; Morata, A; Santos, J D; Dávila, D; Calaza, C; Salleras, M; Fonseca, L; Tarancón, A

    2015-05-15

    Silicon nanowires present outstanding properties for electronics, energy, and environmental monitoring applications. However, their integration into microelectromechanical systems (MEMS) is a major issue so far due to low compatibility with mainstream technology, which complicates patterning and controlled morphology. This work addresses the growth of 〈111〉 aligned silicon nanowire arrays fully integrated into standard MEMS processing by means of the chemical vapor deposition-vapor liquid solid method (CVD-VLS) using silane as a precursor. A reinterpretation of the galvanic displacement method is presented for selectively depositing gold nanoparticles of controlled size and shape. Moreover, a comprehensive analysis of the effects of synthesis temperature and pressure on the growth rate and alignment of nanowires is presented for the most common silicon precursor, i.e., silane. Compared with previously reported protocols, the redefined galvanic displacement together with a silane-based CVD-VLS growth methodology provides a more standard and low-temperature (<650 °C) synthesis scheme and a compatible route to reliably grow Si nanowires in MEMS for advanced applications. PMID:25902702

  9. Synthesis of Vertically Aligned ZnO Nanorods on Ni-Based Buffer Layers Using a Thermal Evaporation Process

    NASA Astrophysics Data System (ADS)

    Kuo, Dong-Hau; He, Jheng-Yu; Huang, Ying-Sheng

    2012-03-01

    Uniform, vertically aligned ZnO nanorods have been grown mainly on Au-coated and ZnO-coated sapphire substrates, ZnO- and GaN-coated substrates, or self-catalyzing substrates. Conventionally, Ni-coated substrates have resulted in thick rods with diameter more than 250 nm, rods with nonuniform distribution in diameter, or rods with an alignment problem. In the best result in this paper, slender, uniform, vertically aligned, solely UV-emitting ZnO nanorods with diameter of 110 ± 25 nm and length of 30 ± 10 μm have been successfully grown at 700°C for 2 h on sapphire substrates covered with Ni-based buffer layers by using metallic zinc and oxygen as reactants. Scanning electron microscopy and room-temperature photoluminescence have been used to investigate the effects of process conditions on the slenderness and vertical alignment of the ZnO rods. To develop the desired ZnO nanorods, etched sapphire substrates, a second metallic Sn buffer layer on top of a spin-coated nickel oxide layer, polyvinyl alcohol binder at 10% concentration in solution of iron nitrate, and pyrolysis and reduction reactions were involved. Defect photoemission for thick ZnO rods is attributed to insufficient oxygen supply during the growth process with fixed oxygen flow rate.

  10. Alignment, rotation, and spinning of single plasmonic nanoparticles and nanowires using polarization dependent optical forces.

    PubMed

    Tong, Lianming; Miljković, Vladimir D; Käll, Mikael

    2010-01-01

    We demonstrate optical alignment and rotation of individual plasmonic nanostructures with lengths from tens of nanometers to several micrometers using a single beam of linearly polarized near-infrared laser light. Silver nanorods and dimers of gold nanoparticles align parallel to the laser polarization because of the high long-axis dipole polarizability. Silver nanowires, in contrast, spontaneously turn perpendicular to the incident polarization and predominantly attach at the wire ends, in agreement with electrodynamics simulations. Wires, rods, and dimers all rotate if the incident polarization is turned. In the case of nanowires, we demonstrate spinning at an angular frequency of approximately 1 Hz due to transfer of spin angular momentum from circularly polarized light. PMID:20030391

  11. High-speed graphene transistors with a self-aligned nanowire gate.

    PubMed

    Liao, Lei; Lin, Yung-Chen; Bao, Mingqiang; Cheng, Rui; Bai, Jingwei; Liu, Yuan; Qu, Yongquan; Wang, Kang L; Huang, Yu; Duan, Xiangfeng

    2010-09-16

    Graphene has attracted considerable interest as a potential new electronic material. With its high carrier mobility, graphene is of particular interest for ultrahigh-speed radio-frequency electronics. However, conventional device fabrication processes cannot readily be applied to produce high-speed graphene transistors because they often introduce significant defects into the monolayer of carbon lattices and severely degrade the device performance. Here we report an approach to the fabrication of high-speed graphene transistors with a self-aligned nanowire gate to prevent such degradation. A Co(2)Si-Al(2)O(3) core-shell nanowire is used as the gate, with the source and drain electrodes defined through a self-alignment process and the channel length defined by the nanowire diameter. The physical assembly of the nanowire gate preserves the high carrier mobility in graphene, and the self-alignment process ensures that the edges of the source, drain and gate electrodes are automatically and precisely positioned so that no overlapping or significant gaps exist between these electrodes, thus minimizing access resistance. It therefore allows for transistor performance not previously possible. Graphene transistors with a channel length as low as 140 nm have been fabricated with the highest scaled on-current (3.32 mA μm(-1)) and transconductance (1.27 mS μm(-1)) reported so far. Significantly, on-chip microwave measurements demonstrate that the self-aligned devices have a high intrinsic cut-off (transit) frequency of f(T) = 100-300 GHz, with the extrinsic f(T) (in the range of a few gigahertz) largely limited by parasitic pad capacitance. The reported intrinsic f(T) of the graphene transistors is comparable to that of the very best high-electron-mobility transistors with similar gate lengths. PMID:20811365

  12. Electronic structures and optical properties of GaN and ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Akiyama, T.; Freeman, A. J.; Nakamura, K.; Ito, T.

    2007-03-01

    GaN and ZnO are promising semiconductor materials that exhibit many outstanding physical and chemical properties. Recently, their one-dimensional nanowires (NWs) are also attracting much interest due to their significant potential for optoelectronic nano-devices; they always take the wurtizte structure while other compound semiconductor NWs also exhibit other polytypes. However, little is known about their electronic and optical properties. Here we investigate the electronic structures and optical properties of GaN and ZnO [0001] NWs by using the highly precise full-potential linearized augmented plane wave (FLAPW) method. Our calculations demonstrate that the band gap energy of both the unpassivated and passivated NWs becomes large compared with the bulk energy gap due to quantum confinement effects; surface states crucially affect the electronic structure of unpassivated NWs. Further, we find peculiar features of their dielectric functions that exhibit strong anisotropy in the calculated optical properties. Work supported by the U.S. NSF (through its MRSEC Program at NU). Zhong et al., Nano Lett. 3, 343 (2003); Ng et al., APL 82, 2023 (2003); Akiyama et al., JJAP 45, L275 (2006); PRB 73, 235308 (2006). Wimmer, Krakauer, Weinert, Freeman, PRB 24, 864 (1981).

  13. Enhanced field-emission of silver nanoparticle-graphene oxide decorated ZnO nanowire arrays.

    PubMed

    Wang, Guojing; Li, Zhengcao; Li, Mingyang; Liao, Jiecui; Chen, Chienhua; Lv, Shasha; Shi, Chuanqing

    2015-12-21

    This work presents a new method to improve the field emission (FE) properties of semiconductors decorated with low-cost graphene oxide (GO) nanosheets and trace amounts of noble metal. The Ag/GO/ZnO composite emitter exhibited efficient FE properties with a low turn-on field of 1.4 V μm(-1) and a high field enhancement factor of 7018. The excellent FE properties of the Ag/GO/ZnO composite can be attributed to the tunneling effect of electrons through the heterojunction. The FE properties of the Ag/GO/ZnO composite are slightly better than those of the Ag/ZnO composite which forms an energy well that collects electrons on interfaces when an electric field is applied. This behavior is associated with heterostructures that offer more contact points and protrusions between ZnO nanowire arrays (NWAs) and Ag/GO, which leads to easier electron transfer. High-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterise the connection and evolution of the ZnO NWAs and Ag/GO composites. PMID:26565977

  14. Energy Level Alignment at Aqueous GaN and ZnO Interfaces

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    Electronic energy level alignment at semiconductor-electrolyte interfaces is fundamental to electrochemical activity. Motivated in particular by the search for new materials that can be more efficient for photocatalysis, we develop a first principles method to calculate this alignment at aqueous interfaces and demonstrate it for the specific case of non-polar GaN and ZnO interfaces with water. In the first step, density functional theory (DFT) based molecular dynamics is used to sample the physical interface structure and to evaluate the electrostatic potential step at the interface. In the second step, the GW approach is used to evaluate the reference electronic energy level separately in the bulk semiconductor (valence band edge energy) and in bulk water (the 1b1 energy level), relative to the internal electrostatic energy reference. Use of the GW approach naturally corrects for errors inherent in the use of Kohn-Sham energy eigenvalues to approximate the electronic excitation energies in each material. With this predicted interface alignment, specific redox levels in water, with potentials known relative to the 1b1 level, can then be compared to the semiconductor band edge positions. Our results will be discussed in the context of experiments in which photoexcited GaN and ZnO drive the hydrogen evolution reaction. Research carried out at Brookhaven National Laboratory under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.

  15. Microwave Characterization of a Field Effect Transistor with Dielectrophoretically-Aligned Single Silicon Nanowire

    NASA Astrophysics Data System (ADS)

    Kang, Myung-Gil; Ahn, Jae-Hyun; Lee, Jongwoon; Hwang, Dong-Hoon; Kim, Hee-Tae; Rieh, Jae-Seong; Whang, Dongmok; Son, Maeng-Ho; Ahn, Doyeol; Yu, Yun-Seop; Hwang, Sung-Woo

    2010-06-01

    Microwave (MW) characteristics of a field effect transistor (FET) incorporating a single silicon nanowire (SiNW) were obtained from S-parameter measurements in the frequency range of 0.05 to 20 GHz. The single SiNW was aligned, using the alternating current (ac) dielectrophoresis alignment method, between the drain and source electrode forming a coplanar waveguide (CPW) structure. Analysis of the FET was performed using equivalent circuit modeling by advanced device system (ADS) simulation. By fitting the measured data with the simulation results, the parameters of the single SiNW FET were obtained and the cutoff frequency was derived.

  16. Versatile Fabrication of Self-Aligned Nanoscale Hall Devices Using Nanowire Masks.

    PubMed

    Tang, Jianshi; Yu, Guoqiang; Wang, Chiu-Yen; Chang, Li-Te; Jiang, Wanjun; He, Congli; Wang, Kang L

    2016-05-11

    In this work, we present an ingenious method to fabricate self-aligned nanoscale Hall devices using chemically synthesized nanowires as both etching and deposition masks. This versatile method can be extensively used to make nanoribbons out of arbitrary thin films without the need for extremely high alignment accuracy to define the metal contacts. The fabricated nanoribbon width scales with the mask nanowire width (diameter), and it can be easily reduced down to tens of nanometers. The self-aligned metal contacts from the sidewall extend to the top surface of the nanoribbon, and the overlap can be controlled by tuning the deposition recipe. To demonstrate the feasibility, we have fabricated Ta/CoFeB/MgO nanoribbons sputtered on a SiO2/Si substrate with different metal contacts, using synthesized SnO2 nanowires as masks. Anomalous Hall effect measurements have been carried out on the fabricated nanoscale Hall device in order to study the current-induced magnetization switching in the nanoscale heavy metal/ferromagnet heterostructure, which has shown distinct switching behaviors from micron-scale devices. The developed method provides a useful fabrication platform to probe the charge and spin transport in the nanoscale regime. PMID:27046777

  17. Large-area alignment of tungsten oxide nanowires over flat and patterned substrates for room-temperature gas sensing.

    PubMed

    Cheng, Wei; Ju, Yanrui; Payamyar, Payam; Primc, Darinka; Rao, Jingyi; Willa, Christoph; Koziej, Dorota; Niederberger, Markus

    2015-01-01

    Alignment of nanowires over a large area of flat and patterned substrates is a prerequisite to use their collective properties in devices such as gas sensors. In this work, uniform single-crystalline ultrathin W18 O49 nanowires with diameters less than 2 nm and aspect ratios larger than 100 have been synthesized, and, despite their flexibility, assembled into thin films with high orientational order over a macroscopic area by the Langmuir-Blodgett technique. Alignment of the tungsten oxide nanowires was also possible on top of sensor substrates equipped with electrodes. Such sensor devices were found to exhibit outstanding sensitivity to H2 at room temperature. PMID:25412600

  18. Tunable local excitation of surface plasmon polaritons by sum-frequency generation in ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Brincker, Mads; Pedersen, Kjeld; Skovsen, Esben

    2015-12-01

    Tunable local excitation of surface plasmon polaritons (SPP) by sum-frequency generation (SFG) in Zinc Oxide (ZnO) nanowires on a smooth and thin silver film has been studied by applying angle resolved leakage radiation spectroscopy. SFG between an infrared (IR) source, with a variable wavelength in the telecom range between 1350 nm and 1550 nm, and a near-infrared (NIR) source with a fixed wavelength of 790 nm resulted in the excitation of SPP's at wavelengths between 498 nm and 523 nm. The SFG to SPP coupling efficiency was studied as a function of the excitation angle and the wavelength of the IR source. It was shown that the SPP coupling was most efficient at oblique excitation angles, and that SFG in ZnO nanowires allows for the coherent conversion of optical signals at telecom frequencies to SPP's with frequencies within the visible range.

  19. Investigation of novel heterojunction: P-type SnS coated n-type ZnO nanowire

    NASA Astrophysics Data System (ADS)

    Bu, Ian Y. Y.

    2015-12-01

    SnS coated ZnO nanowires heterojunctional solar cells were fabricated using a combination of hydrothermal synthesis and chemical bath deposition (CBD) method. The synthesized materials and devices were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), photoluminescence emission spectroscopy, Uv-Vis spectroscopy and electrical measurements. SEM imaging of the sample revealed that the CBD SnS coating bunches the underlying ZnO nanowires due to the large capillary force it experiences during the drying process. Both of the EDS and XRD measurements confirm the presence of SnS and SnO2. Optoelectronic measurement confirms that the fabricated device exhibit high absorbance (∼80%) and exhibit photovoltaic behaviour.

  20. Identifying individual n- and p-type ZnO nanowires by the output voltage sign of piezoelectric nanogenerator

    NASA Astrophysics Data System (ADS)

    Lin, S. S.; Song, J. H.; Lu, Y. F.; Wang, Z. L.

    2009-09-01

    Based on a comparative study between the piezoelectric outputs of n-type nanowires (NWs) and n-core/p-shell NWs along with the previous study (Lu et al 2009 Nano. Lett. 9 1223), we demonstrate a one-step technique for identifying the conductivity type of individual ZnO nanowires (NWs) based on the output of a piezoelectric nanogenerator without destroying the sample. A negative piezoelectric output voltage indicates an NW is n-type and it appears after the tip scans across the center of the NW, while a positive output voltage reveals p-type conductivity and it appears before the tip scans across the central line of the NW. This atomic force microscopy based technique is reliable for statistically mapping the majority carrier type in ZnO NWs arrays. The technique may also be applied to other wurtzite semiconductors, such as GaN, CdS and ZnS.

  1. Microchannel Wetting for Controllable Patterning and Alignment of Silver Nanowire with High Resolution.

    PubMed

    Yang, Bo-Ru; Cao, Wu; Liu, Gui-Shi; Chen, Hui-Jiuan; Noh, Yong-Young; Minari, Takeo; Hsiao, Hsiang-Chih; Lee, Chia-Yu; Shieh, Han-Ping D; Liu, Chuan

    2015-09-30

    Patterning and alignment of conductive nanowires are essential for good electrical isolation and high conductivity in various applications. Herein a facile bottom-up, additive technique is developed to pattern and align silver nanowires (AgNWs) by manipulating wetting of dispersions in microchannels. By forming hydrophobic/hydrophilic micropatterns down to 8 μm with fluoropolymer (Cytop) and SiO2, the aqueous AgNW dispersions with the optimized surface tension and viscosity self-assemble into microdroplets and then dry to form anisotropic AgNW networks. The alignment degree characterized by the full width at half-maximum (FWHM) can be well-controlled from 39.8° to 84.1° by changing the width of microchannels. A mechanism is proposed and validated by statistical analysis on AgNW alignment, and a static model is proposed to guide the patterning of general NWs. The alignment reduced well the electrical resistivity of AgNW networks by a factor of 5 because of the formation of efficient percolation path for carrier conduction. PMID:26340378

  2. Large-scale growth of density-tunable aligned ZnO nanorods arrays on GaN QDs

    NASA Astrophysics Data System (ADS)

    Qi, Zhiqiang; Li, Senlin; Sun, Shichuang; Zhang, Wei; Ye, Wei; Fang, Yanyan; Tian, Yu; Dai, Jiangnan; Chen, Changqing

    2015-10-01

    An effective approach for growing large-scale, uniformly aligned ZnO nanorods arrays is demonstrated. The synthesis uses a GaN quantum dot (QD) template produced by a self-assembled Stranski-Krastanow mode in metal organic chemical vapor deposition, which serves as a nucleation site for ZnO owing to the QD’s high surface free energy. The resultant ZnO nanorods with uniform shape and length align vertically on the template, while their density is easily tunable by adjusting the density of GaN QDs, which can be adjusted by simply varying growth interruption. By controlling the density of ZnO nanorod arrays, their optical performance can also be improved. This approach opens the possibility of combining one-dimensional (1D) with 0D nanostructures for applications in sensor arrays, piezoelectric antenna arrays, optoelectronic devices, and interconnects.

  3. 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.

  4. Microstructural and optical properties of nanocrystalline ZnO deposited onto vertically aligned carbon nanotubes by physical vapor deposition

    SciTech Connect

    Borkar, Tushar; Chang, Won Seok; Hwang, Jun Yeon; Shepherd, Nigel D.; Banerjee, Rajarshi

    2012-10-15

    Nanocrystalline ZnO films with thicknesses of 5 nm, 10 nm, 20 nm, and 50 nm were deposited via magnetron sputtering onto the surface of vertically aligned multi-walled carbon nanotubes (MWCNTs). The ZnO/CNTs heterostructures were characterized by scanning electron microscopy, high resolution transmission electron microscopy, and X-ray diffraction studies. No structural degradation of the CNTs was observed and photoluminescence (PL) measurements of the nanostructured ZnO layers show that the optical properties of these films are typical of ZnO deposited at low temperatures. The results indicate that magnetron sputtering is a viable technique for growing heterostructures and depositing functional layers onto CNTs.

  5. Gate-Tunable Spin Exchange Interactions and Inversion of Magnetoresistance in Single Ferromagnetic ZnO Nanowires.

    PubMed

    Modepalli, Vijayakumar; Jin, Mi-Jin; Park, Jungmin; Jo, Junhyeon; Kim, Ji-Hyun; Baik, Jeong Min; Seo, Changwon; Kim, Jeongyong; Yoo, Jung-Woo

    2016-04-26

    Electrical control of ferromagnetism in semiconductor nanostructures offers the promise of nonvolatile functionality in future semiconductor spintronics. Here, we demonstrate a dramatic gate-induced change of ferromagnetism in ZnO nanowire (NW) field-effect transistors (FETs). Ferromagnetism in our ZnO NWs arose from oxygen vacancies, which constitute deep levels hosting unpaired electron spins. The magnetic transition temperature of the studied ZnO NWs was estimated to be well above room temperature. The in situ UV confocal photoluminescence (PL) study confirmed oxygen vacancy mediated ferromagnetism in the studied ZnO NW FET devices. Both the estimated carrier concentration and temperature-dependent conductivity reveal the studied ZnO NWs are at the crossover of the metal-insulator transition. In particular, gate-induced modulation of the carrier concentration in the ZnO NW FET significantly alters carrier-mediated exchange interactions, which causes even inversion of magnetoresistance (MR) from negative to positive values. Upon sweeping the gate bias from -40 to +50 V, the MRs estimated at 2 K and 2 T were changed from -11.3% to +4.1%. Detailed analysis on the gate-dependent MR behavior clearly showed enhanced spin splitting energy with increasing carrier concentration. Gate-voltage-dependent PL spectra of an individual NW device confirmed the localization of oxygen vacancy-induced spins, indicating that gate-tunable indirect exchange coupling between localized magnetic moments played an important role in the remarkable change of the MR. PMID:26964013

  6. Epitaxial growth of ZnO Nanodisks with large exposed polar facets on nanowire arrays for promoting photoelectrochemical water splitting.

    PubMed

    Chen, Haining; Wei, Zhanhua; Yan, Keyou; Bai, Yang; Zhu, Zonglong; Zhang, Teng; Yang, Shihe

    2014-11-01

    Single-crystalline and branched 1D arrays, ZnO nanowires/nanodisks (NWs/NDs) arrays, are fabricated to significantly enhance the performance of photoelectrochemical (PEC) water splitting. The epitaxial growth of the ZnO NDs with large exposed polar facets on ZnO NWs exhibits a laminated structure, which dramatically increases the light scattering capacity of the NWs arrays, especially in the wavelength region around 400 nm. The ND branching of the 1D arrays in the epitaxial fashion not only increase surface area and light utilization, but also support fast charge transport, leading to the considerable increase of photocurrent. Moreover, the tiny size NDs can facilitate charge separation and reduce charge recombination, while the large exposed polar facets of NDs reduce the external potential bias needed for water splitting. These advantages land the ZnO NWs/NDs arrays a four times higher power conversion efficiency than the ZnO NWs arrays. By sensitizing the ZnO NWs/NDs with CdS and CdSe quantum dots, the PEC performance can be further improved. This work advocates a trunk/leaf in forest concept for the single-crystalline NWs/NDs in array with enlarged exposure of polar facets, which opens the way for optimizing light harvesting and charge separation and transport, and thus the PEC water splitting. PMID:24990800

  7. Piezotronic Effect Enhanced Label-Free Detection of DNA Using a Schottky-Contacted ZnO Nanowire Biosensor.

    PubMed

    Cao, Xiaotao; Cao, Xia; Guo, Huijuan; Li, Tao; Jie, Yang; Wang, Ning; Wang, Zhong Lin

    2016-08-23

    A sensitive and in situ selective label-free DNA sensor based on a Schottky-contacted ZnO nanowire (NW) device has been developed and utilized to detect the human immunodeficiency virus 1 gene in this work. Piezotronic effect on the performance of the DNA sensor is studied by measuring its output current under different compressive strains and target complementary DNA concentrations. By applying a -0.59% compressive strain to a ZnO NW-based DNA sensor, the relative current response is greatly enhanced by 454%. A theoretical model is proposed to explain the observed behaviors of the DNA sensor. This study provides a piezotronically modified method to effectively improve the overall performance of the Schottky-contacted ZnO NW-based DNA sensor. PMID:27478905

  8. Enhanced non-volatile resistive switching in suspended single-crystalline ZnO nanowire with controllable multiple states

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Pang, Wei; Zhang, Qing; Chen, Yan; Chen, Xuejiao; Feng, Zhihong; Yang, Jianhua; Zhang, Daihua

    2016-08-01

    Resistive switching nanostructures are a promising candidate for next-generation non-volatile memories. In this report, we investigate the switching behaviors of single-crystalline ZnO nanowires suspended in air. They exhibit significantly higher current density, lower switching voltage, and more pronounced multiple conductance states compared to nanowires in direct contact with substrate. We attribute the effect to enhanced Joule heating efficiency, reduced surface scattering, and more significantly, the positive feedback established between the current density and local temperature in the suspended nanowires. The proposed mechanism has been quantitatively examined by finite element simulations. We have also demonstrated an innovative approach to initiating the current–temperature mutual enhancement through illumination by ultraviolet light, which further confirmed our hypothesis and enabled even greater enhancement. Our work provides further insight into the resistive switching mechanism of single-crystalline one-dimensional nanostructures, and suggests an effective means of performance enhancement and device optimization.

  9. Fe solubility, growth mechanism, and luminescence of Fe doped ZnO nanowires and nanorods grown by evaporation-deposition

    NASA Astrophysics Data System (ADS)

    Alemán, Belén; Ortega, Yanicet; García, José Ángel; Fernández, Paloma; Piqueras, Javier

    2011-07-01

    Fe doped ZnO nanowires, nanorods, and urchin-like nanostructures have been grown using an evaporation-deposition method with compacted mixtures of ZnS and Fe2O3 powders, with different Fe contents as precursors. Treatments at 950 °C under argon flow lead to the growth of iron doped nanowires, nanorods, and other nanostructures on the surface of the compacted sample. The incorporation of iron into the nanostructures has been investigated via energy dispersive spectroscopy as well as by cathodoluminescence in a scanning electron microscope and photoluminescence in an optical microscope. The iron content in the structures is limited to the range of 0.5-0.7 at.% and does not depend on the content in the precursor. Bright and dark field imaging and twist contour analysis via transmission electron microscopy support the possibility of a dislocation driven growth of the nanowires.

  10. 2D XANES-XEOL mapping: observation of enhanced band gap emission from ZnO nanowire arrays

    NASA Astrophysics Data System (ADS)

    Wang, Zhiqiang; Guo, Xiaoxuan; Sham, Tsun-Kong

    2014-05-01

    Using 2D XANES-XEOL spectroscopy, it is found that the band gap emission of ZnO nanowire arrays is substantially enhanced i.e. that the intensity ratio between the band gap and defect emissions increases by more than an order of magnitude when the excitation energy is scanned across the O K-edge. Possible mechanisms are discussed.Using 2D XANES-XEOL spectroscopy, it is found that the band gap emission of ZnO nanowire arrays is substantially enhanced i.e. that the intensity ratio between the band gap and defect emissions increases by more than an order of magnitude when the excitation energy is scanned across the O K-edge. Possible mechanisms are discussed. Electronic supplementary information (ESI) available: XEOL spectra with different excitation energies. X-ray attenuation length vs. photon energy. Details of surface defects in ZnO NWs. The second O K-edge and Zn L-edge 2D XANES-XEOL maps. Comparison of the first and second TEY at O K-edge and Zn L-edge scans, respectively. Raman spectra of the ZnO NWs with different IBGE/IDE ratios. See DOI: 10.1039/c4nr01049c

  11. Challenges in the simulation of dye-sensitized ZnO solar cells: quantum confinement, alignment of energy levels and excited state nature at the dye/semiconductor interface.

    PubMed

    Amat, Anna; De Angelis, Filippo

    2012-08-14

    We report a first principles density functional theory/time-dependent density functional theory (DFT/TDDFT) computational investigation on a prototypical perylene dye anchored to realistic ZnO nanostructures, approaching the size of the ZnO nanowires used in dye-sensitized solar cells devices. DFT calculations were performed on (ZnO)(n) clusters of increasing size, with n up to 222, of 1.3 × 1.5 × 3.4 nm dimensions, and for the related dye-sensitized models. We show that quantum confinement in the ZnO nanostructures substantially affects the dye/semiconductor alignment of energy levels, with smaller ZnO models providing unfavourable electron injection. An increasing broadening of the dye LUMO is found moving to larger substrates, substantially contributing to the interfacial electronic coupling. TDDFT excited state calculations for the investigated dye@(ZnO)(222) system are fully consistent with experimental data, quantitatively reproducing the red-shift and broadening of the visible absorption spectrum observed for the ZnO-anchored dye compared to the dye in solution. TDDFT calculations on the fully interacting system also introduce a contribution to the dye/semiconductor admixture, due to configurational excited state mixing. Our results highlight the importance of quantum confinement in dye-sensitized ZnO interfaces, and provide the fundamental insight lying at the heart of the associated DSC devices. PMID:22743544

  12. Investigation on P-N dual acceptor doped p-type ZnO thin films and subsequent growth of pencil-like nanowires

    NASA Astrophysics Data System (ADS)

    Amiruddin, R.; Devasia, Sebin; Mohammedali, D. K.; Santhosh Kumar, M. C.

    2015-03-01

    Phosphorous and nitrogen dual acceptor doped p-type ZnO (PNZO) have been deposited by spray pyrolysis method on glass substrates. An equimolar doping concentration of P and N were varied from 0.25-1.25 at% with a step of 0.25 at%. Preferred orientation along (002) planes with hexagonal wurzite structure was observed from structural analysis. Morphological analysis reveals uniform distributions of grains. Electrical studies showed dual acceptor doping of P and N in ZnO results in p-type behavior. The optimum doping concentration of P and N was found to be 0.75 at% which exhibited hole concentration of 4.48 × 1018 cm-3 and low resistivity value of 9.6 Ω.cm. Photoluminescence (PL) studies revealed that, as-deposited films exhibit strong UV emission at 383 nm of the spectrum. The surface morphology of the optimum PNZO (0.75 at%) samples were further modified in the form of vertically aligned pencil-like nanowires by modified aqueous chemical growth (ACG) process. During ACG process, more acceptor related defects such as oxygen interstitials (Oi) were formed in the PNZO nanopencils. These acceptor defects induce enhanced emission in the visible region (400 nm to 700 nm) and also promote stable p-type characteristics.

  13. Fabrication of high performance field-effect transistors and practical Schottky contacts using hydrothermal ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Opoku, Charles; Singh Dahiya, Abhishek; Oshman, Christopher; Daumont, Christophe; Cayrel, Frederic; Poulin-Vittrant, Guylaine; Alquier, Daniel; Camara, Nicolas

    2015-09-01

    The production of large quantities of single crystalline semiconducting ZnO nanowires (NWs) at low cost can offer practical solutions to realizing several novel electronic/optoelectronic and sensor applications on an industrial scale. The present work demonstrates high-density single crystalline NWs synthesized by a multiple cycle hydrothermal process at ˜100 °C. The high carrier concentration in such ZnO NWs is greatly suppressed by a simple low cost thermal annealing step in ambient air at ˜450 °C. Single ZnO NW FETs incorporating these modified NWs are characterized, revealing strong metal work function-dependent charge transport, unobtainable with as-grown hydrothermal ZnO NWs. Single ZnO NW FETs with Al as source and drain (s/d) contacts show excellent performance metrics, including low off-state currents (fA range), high on/off ratio (105-107), steep subthreshold slope (<600 mV/dec) and excellent field-effect carrier mobility (5-11 cm2/V-s). Modified ZnO NWs with platinum s/d contacts demonstrate excellent Schottky transport characteristics, markedly different from a reference ZnO NW device with Al contacts. This included abrupt reverse bias current-voltage saturation characteristics and positive temperature coefficient (˜0.18 eV to 0.13 eV). This work is envisaged to benefit many areas of hydrothermal ZnO NW research, such as NW FETs, piezoelectric energy recovery, piezotronics and Schottky diodes.

  14. Electrical characteristics and rectification performance of wet chemically synthesized vertically aligned n-ZnO nanowire/p-Si heterojunction

    NASA Astrophysics Data System (ADS)

    Gayen, R. N.; Bhattacharyya, S. R.

    2016-03-01

    Vertically well-aligned n-ZnO nanowire (NW) thin films were deposited onto p-Si substrates by a two-step wet chemical technique to form a p-n heterojunction diode. The morphological and structural characteristics of the ZnO NW performed by scanning electron microscopy (SEM) and x-ray diffraction (XRD) revealed well-aligned h-ZnO NW with a wurtzite structure. A direct optical band gap of 3.30 eV was calculated from the transmittance trace obtained using a UV-VIS-NIR spectrophotometer. The electrical characteristics of the heterojunction diode were studied by capacitance-voltage (C-V) measurement at room temperature, and current-voltage-temperature (I-V-T) measurements performed in the 300-400 K range. The C-V measurements yield a carrier concentration of 1.3  ×  1016 c.c.-1 for the ZnO NW thin film. The ideality factor (n) was found to decrease, while the barrier height (φ b0) increased with the increase in temperature, when calculated using a thermionic emission model from the non-linear I-V-T plots. The series resistance (R s) calculated by the Cheung-Cheung method decreased with the increase in temperature. The mean barrier height (0.718 eV) and modified Richardson constant (28.4 A cm-2 K-2) calculated using a Gaussian distribution of barrier heights (considering barrier height inhomogeneity) were closer to the theoretical value than those calculated from the linear approximation of the ln(I s/T 2) versus 1000/T plot. The variation of the density of interface states with interface state energy was also studied. The n-ZnO NW/p-Si heterojunction diode performed very good half wave rectification in the frequency range 50 Hz-10 kHz, when a sinusoidal ac voltage of amplitude 4.5 V was applied across it.

  15. Effect of surface energy and seed layer annealing temperature on ZnO seed layer formation and ZnO nanowire growth

    NASA Astrophysics Data System (ADS)

    Park, Ji-Sub; Mahmud, Imtiaz; Shin, Han Jae; Park, Min-Kyu; Ranjkesh, Amid; Lee, Do Kyung; Kim, Hak-Rin

    2016-01-01

    We discuss the effects of surface energy and seed layer annealing temperature (Tannealing) on seed layer growth and hydrothermally-grown zinc oxide (ZnO) nanowires (NWs). In this work, by varying the ultraviolet ozone (UVO) treatment times on a silicon surface, the surface energy conditions for the seed layer formation changed and the seed layer was annealed under different Tannealing conditions. Under a lower surface energy condition of the substrate, with increasing Tannealing, the coverage density and the average thickness of the seed layer increased, but island-like growth was observed. This case was inevitably accompanied by an increase in surface roughness, which resulted in agglomerated low density growth of ZnO NWs. After sufficient UVO treatment, hydroxyl groups on the silicon surface activated the ZnO seed layer formation in the chemical reaction and increased the bonding energy between the active nucleation sites of the seed layer and the substrate surface. This ensured higher coverage density of the seed layer with lower surface roughness under the same Tannealing condition, thereby providing the ZnO NW growth with an enhanced density and aspect ratio as well as good crystallinity.

  16. Effects of precursor concentration on the properties of ZnO nanowires grown on (1-102) r-plane sapphire substrates by hydrothermal synthesis.

    PubMed

    Mun, D-H; Bak, S J; Ha, J-S; Lee, H-J; Lee, J K; Lee, S H; Moon, Y B

    2014-08-01

    In this study, we grew ZnO nanowires hydrothermally on (1-102) r-plane sapphire substrates in an aqueous solution which contained zinc nitrate hexahydrate and hexamethylenetetramine (HMT) at 90 °C. First, the AZO seed layer of 80 nm thickness was deposited on the r-plane sapphire substrate by a radio frequency magnetron sputter. After that, we grew the ZnO nanowires on the seed layer by changing the precursor concentration of the aqueous solution from 0.025 M to 0.01 M. When the molar concentration of the precursor was changed, the diameter, length, density and number of ZnO nanowires also changed significantly: diameter, length and density increased with increasing molar concentration but the number of ZnO nanowires decreased. The ZnO nanowires grown at the higher molar concentration tended to grow along with the c-axis direction, as revealed by atomic force microscope and X-ray diffraction peaks. Furthermore, the PL spectra measured at room-temperature revealed a UV emission of 380 nm which can be attributed to the radiative recombination of free and bound excitons (Near Band edge Emission). The NBE emission was also increased with increasing molar concentration. PMID:25936038

  17. Influence of Li-N and Li-F co-doping on defect-induced intrinsic ferromagnetic and photoluminescence properties of arrays of ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Ghosh, Shyamsundar; Gopal Khan, Gobinda; Varma, Shikha; Mandal, Kalyan

    2012-08-01

    The role of N/F co-doping on the defect-driven room-temperature d0 ferromagnetism in group-I element Li doped ZnO nanowire arrays has been investigated. The ferromagnetic signature of pristine ZnO nanowires has enhanced significantly after Li doping but the Li-N co-doping has found to be more effective in the stabilization and enhancement in room-temperature ferromagnetism in ZnO nanowires. Saturation magnetization in Li-doped ZnO nanowires found to increase from 0.63 to 2.52 emu/g and the Curie temperature rises up to 648 K when 10 at. % N is co-doped with 6 at. % Li. On the other hand, Li-F co-doping leads to exhibit much poor room-temperature ferromagnetic as well as visible luminescence properties. The valance state of the different dopants is estimated by x-ray photoelectron spectroscopy while the photoluminescence spectra indicate the gradual stabilization of Zn vacancy defects or defect complexes in presence of No acceptor states, which is found to be responsible for the enhancement of intrinsic ferromagnetism in ZnO:Li matrix. Therefore, the Li-N co-doping can be an effective parameter to stabilize, enhance, and tune zinc vacancy-induced room-temperature d0 ferromagnetism in ZnO nanowires, which can be an exciting approach to prepare new class of spintronic materials.

  18. Control of zinc oxide nanowire array properties with electron-beam lithography templating for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Nicaise, Samuel M.; Cheng, Jayce J.; Kiani, Amirreza; Gradečak, Silvija; Berggren, Karl K.

    2015-02-01

    Hydrothermally synthesized zinc oxide nanowire arrays have been used as nanostructured acceptors in emerging photovoltaic (PV) devices. The nanoscale dimensions of such arrays allow for enhanced charge extraction from PV active layers, but the device performance critically depends on the nanowire array pitch and alignment. In this study, we templated hydrothermally-grown ZnO nanowire arrays via high-resolution electron-beam-lithography defined masks, achieving the dual requirements of high-resolution patterning at a pitch of several hundred nanometers, while maintaining hole sizes small enough to control nanowire array morphology. We investigated several process conditions, including the effect of annealing sputtered and spincoated ZnO seed layers on nanowire growth, to optimize array property metrics—branching from individual template holes and off-normal alignment. We found that decreasing template hole size decreased branching prevalence but also reduced alignment. Annealing seed layers typically improved alignment, and sputtered seed layers yielded nanowire arrays superior to spincoated seed layers. We show that these effects arose from variation in the size of the template holes relative to the ZnO grain size in the seed layer. The quantitative control of branching and alignment of the nanowire array that is achieved in this study will open new paths toward engineering more efficient electrodes to increase photocurrent in nanostructured PVs. This control is also applicable to inorganic nanowire growth in general, nanomechanical generators, nanowire transistors, and surface-energy engineering.

  19. Control of zinc oxide nanowire array properties with electron-beam lithography templating for photovoltaic applications.

    PubMed

    Nicaise, Samuel M; Cheng, Jayce J; Kiani, Amirreza; Gradečak, Silvija; Berggren, Karl K

    2015-02-20

    Hydrothermally synthesized zinc oxide nanowire arrays have been used as nanostructured acceptors in emerging photovoltaic (PV) devices. The nanoscale dimensions of such arrays allow for enhanced charge extraction from PV active layers, but the device performance critically depends on the nanowire array pitch and alignment. In this study, we templated hydrothermally-grown ZnO nanowire arrays via high-resolution electron-beam-lithography defined masks, achieving the dual requirements of high-resolution patterning at a pitch of several hundred nanometers, while maintaining hole sizes small enough to control nanowire array morphology. We investigated several process conditions, including the effect of annealing sputtered and spincoated ZnO seed layers on nanowire growth, to optimize array property metrics-branching from individual template holes and off-normal alignment. We found that decreasing template hole size decreased branching prevalence but also reduced alignment. Annealing seed layers typically improved alignment, and sputtered seed layers yielded nanowire arrays superior to spincoated seed layers. We show that these effects arose from variation in the size of the template holes relative to the ZnO grain size in the seed layer. The quantitative control of branching and alignment of the nanowire array that is achieved in this study will open new paths toward engineering more efficient electrodes to increase photocurrent in nanostructured PVs. This control is also applicable to inorganic nanowire growth in general, nanomechanical generators, nanowire transistors, and surface-energy engineering. PMID:25642895

  20. Surface defects on ZnO nanowires: implications for design of sensors

    NASA Astrophysics Data System (ADS)

    Spencer, Michelle J. S.; Wong, Kester W. J.; Yarovsky, Irene

    2012-08-01

    Surface defects are commonly believed to be fundamentally important to gas-sensor performance. We examine the effect of gas coverage and ethanol orientation on its adsorption on the stoichiometric and oxygen deficient (1 0\\bar {1}0) nanowire surface. Our density functional theory calculations show that ethanol adsorbs in multiple stable configurations at coverages between 1/4 and 1 ML, highlighting the ability of ZnO to detect ethanol. Ethanol prefers to bind to a surface Zn via the adsorbate oxygen atom and, if a surface oxygen atom is in close proximity, the molecule is further stabilized by formation of a hydrogen bond between the hydrogen of the hydroxyl group and the surface oxygen. Two primary adsorption configurations were identified and have different binding strengths that could be distinguished experimentally by the magnitude of their OH stretching frequency. Our findings show that ethanol adsorbed on the oxygen deficient ZnO(1 0\\bar {1}0) surface has a reduced binding strength. This is due to either the lack of a hydrogen bond (due to a deficiency in surface oxygen) or to surface reconstruction that occurs on the defect surface that weakens the hydrogen bond interaction. This reduced binding on the oxygen deficient surface is in contrast to the defect enhanced gas-sensor interaction for other gases. Despite this difference, ethanol still acts as a reducing gas, donating electrons to the surface and decreasing the band gap. We show that multiple adsorbed ethanol molecules prefer to be orientated parallel to each other to facilitate the hydrogen bonding to the defect-free surface for enhanced interaction.

  1. 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.

  2. In situ fabrication of inorganic nanowire arrays grown from and aligned on metal substrates.

    PubMed

    Zhang, Weixin; Yang, Shihe

    2009-10-20

    The full potential of nanotechnology can be unleashed only when one is able not only to synthesize a rich variety of nanoscale building blocks but also assemble them into various patterns at the supramolecular and supracluster levels. In particular, the application of nanoparticle and nanowire materials often requires their assembly in the form of thin films, preferably on conductive surfaces for electrical addressing, control, and detection. Although a dazzling array of nanostructures has been fabricated by bottom-up approaches, one of the contemporary challenges is to assemble these nanostructures so that they introduce and realize functionalities. An alluring avenue is to simultaneously accomplish both the nanostructure synthesis and assembly on a useful substrate in a parallel fashion, affording the advantages of simplicity, low cost, and high throughput. In this Account, we review our recent work on growing inorganic nanowires (for example, metal sulfides, metal oxides, and so forth) directly from and on metal substrates in arrays without using templates and catalysts. This method of engineering nanowire arrays on metal substrates integrates the nanowire synthesis and assembly into a parallel process, both in time and in space, by exploiting in situ chemistry on the metal substrates. Both gas-phase and solution-phase approaches have been developed to synthesize the aligned nanowires; here, full advantage is taken of interfacial kinetics of restricted diffusion and surface-specific reactions, often accompanied by new interfacial growth mechanisms. The setting of nanowire arrays on metal substrates has allowed exploration of their application potentials in areas such as field electron emission and chemical sensing. The approaches described here are general, and we predict that they will be extended to more inorganic materials, such as metal halides. Moreover, as more control is achieved with synthetic methods, inorganic nanowire arrays should provide unusual

  3. Nucleation, Growth Mechanism, and Controlled Coating of ZnO ALD onto Vertically Aligned N-Doped CNTs.

    PubMed

    Silva, R M; Ferro, M C; Araujo, J R; Achete, C A; Clavel, G; Silva, R F; Pinna, N

    2016-07-19

    Zinc oxide thin films were deposited on vertically aligned nitrogen-doped carbon nanotubes (N-CNTs) by atomic layer deposition (ALD) from diethylzinc and water. The study demonstrates that doping CNTs with nitrogen is an effective approach for the "activation" of the CNTs surface for the ALD of metal oxides. Conformal ZnO coatings are already obtained after 50 ALD cycles, whereas at lower ALD cycles an island growth mode is observed. Moreover, the process allows for a uniform growth from the top to the bottom of the vertically aligned N-CNT arrays. X-ray photoelectron spectroscopy demonstrates that ZnO nucleation takes place at the N-containing species on the surface of the CNTs by the formation of the Zn-N bonds at the interface between the CNTs and the ZnO film. PMID:27333190

  4. Highly polarized light emission by isotropic quantum dots integrated with magnetically aligned segmented nanowires

    SciTech Connect

    Uran, Can; Erdem, Talha; Guzelturk, Burak; Perkgöz, Nihan Kosku; Jun, Shinae; Jang, Eunjoo; Demir, Hilmi Volkan

    2014-10-06

    In this work, we demonstrate a proof-of-concept system for generating highly polarized light from colloidal quantum dots (QDs) coupled with magnetically aligned segmented Au/Ni/Au nanowires (NWs). Optical characterizations reveal that the optimized QD-NW coupled structures emit highly polarized light with an s-to p-polarization (s/p) contrast as high as 15:1 corresponding to a degree of polarization of 0.88. These experimental results are supported by the finite-difference time-domain simulations, which demonstrate the interplay between the inter-NW distance and the degree of polarization.

  5. Alignment of nanoparticles, nanorods, and nanowires during chemical vapor deposition of silicon

    NASA Astrophysics Data System (ADS)

    Swain, Bhabani Sankar; Park, Jin-Woo; Yang, Seung-Min; Mahmood, Khalid; Swain, Bibhu Prasad; Lee, Jae-Gab; Hwang, Nong-Moon

    2015-09-01

    We fabricated silicon nanostructures (Si-NSs) on SiO x /Si substrate in chemical vapor deposition. During the synthesis of Si-NSs, Si sunflower-shaped structures of one to hundred microns were observed, therein the nanoparticles (NPs), nanowires, and nanorods were aligned in an ordered manner. We suggest that the NSs reported here are evolved by the electrostatic force exerted by charged NPs in gas phase. This NS would help in understanding the role of spontaneous charging of NPs in the gas phase and the role of charged NPs in the gas phase for NSs growth.

  6. Phonon processes in vertically aligned silicon nanowire arrays produced by low-cost all-solution galvanic displacement method

    NASA Astrophysics Data System (ADS)

    Banerjee, Debika; Trudeau, Charles; Gerlein, Luis Felipe; Cloutier, Sylvain G.

    2016-03-01

    The nanoscale engineering of silicon can significantly change its bulk optoelectronic properties to make it more favorable for device integration. Phonon process engineering is one way to enhance inter-band transitions in silicon's indirect band structure alignment. This paper demonstrates phonon localization at the tip of silicon nanowires fabricated by galvanic displacement using wet electroless chemical etching of a bulk silicon wafer. High-resolution Raman micro-spectroscopy reveals that such arrayed structures of silicon nanowires display phonon localization behaviors, which could help their integration into the future generations of nano-engineered silicon nanowire-based devices such as photodetectors and solar cells.

  7. Tuning quantum corrections and magnetoresistance in ZnO nanowires by ion implantation.

    PubMed

    Zeng, Y J; Pereira, L M C; Menghini, M; Temst, K; Vantomme, A; Locquet, J-P; Van Haesendonck, C

    2012-02-01

    Using ion implantation, the electrical as well as the magnetotransport properties of individual ZnO nanowires (NWs) can be tuned. The virgin NWs are configured as field-effect transistors which are in the enhancement mode. Al-implanted NWs reveal a three-dimensional metallic-like behavior, for which the magnetoresistance is well described by a semiempirical model that takes into account the presence of doping induced local magnetic moments and of two conduction bands. On the other hand, one-dimensional electron transport is observed in Co-implanted NWs. At low magnetic fields, the anisotropic magnetoresistance can be described in the framework of weak electron localization in the presence of strong spin-orbit scattering. From the weak localization, a large phase coherence length is inferred that reaches up to 800 nm at 2.5 K. The temperature-dependent dephasing is shown to result from a one-dimensional Nyquist noise-related mechanism. At the lowest temperatures, the phase coherence length becomes limited by magnetic scattering. PMID:22214218

  8. Carbon related donor bound exciton transitions in ZnO nanowires

    SciTech Connect

    Mohammadbeigi, F.; Kumar, E. Senthil; Alagha, S.; Anderson, I.; Watkins, S. P.

    2014-08-07

    Several shallow donor bound exciton photoluminescence (PL) transitions are reported in ZnO nanowires doped with carbon. The emission energies are in the range of 3360.8–3361.9 meV, close to previously reported emission lines due to excitons bound to donor point defects, such as Ga, Al, In, and H. The addition of small amounts of hydrogen during growth results in a strong enhancement of the PL of these carbon related emission lines, yet PL and annealing measurements indicate no appreciable bulk hydrogen. The observation of two electron satellites for these emission lines enables the determination of the donor binding energies. The dependence of exciton localization energy on donor binding energy departs somewhat from the usual linear relationship observed for group III donors, indicating a qualitatively different central cell potential, as one would expect for a complex. Emission lines due to excitons bound to ionized donors associated with these defects are also observed. The dependence of the PL emission intensities on temperature and growth conditions demonstrates that the lines are due to distinct complexes and not merely excited states of each other.

  9. Optical and Electrical Characterization of Quantum Dots Decorated ZnO Nanowires for Energy Conversion

    NASA Astrophysics Data System (ADS)

    Mu, Richard; Mayo, Anthony; Xu, Haiyang; Liu, Yichun

    2014-03-01

    Significant progress has been made recently in understanding optoelectronic properties of metallic and semiconducting quantum dots and their interactions with their surrounding nano-environments. It is shown that nanostructured photovoltaic devices do have clear advantages over the bulk counterparts to address energy challenges facing humanity. They require much less mass, not exclusively limited by materials of choice, and favoring integration for multifunctionality to be able to effectively harvest solar energy by tuning the optical gap and enhancing photon absorption across section through various nanomaterials syntheses. The other challenge is to be able to purposely control and manipulate the energy transfer pathways for particular needs. As for nanostructured photovotaic devices, charge and exciton transports must be carefully evaluated. The knowledge of charge and exciton mobility, coherent and incoherent hopping due to electronic coupling, energy redistribution and partition in may be the critical steps. CdTe and Si functionalized bare ZnO nanowires, and core/shell have been fabricated with Glazing Angle Deposition technique as the model systems. A series materials characterization techniques (confocal Raman, optical, photoluminancence and electrical) have been conducted to provide valuable information about the nanostructure. Results will be presented and discussed along with their scientific implications. NSF-STC DMR-0423914, NSF-CREST HRD-0420516, DOD W911NF-11-1-0156 and -13-1-0153, and China 111 Project

  10. Growth Conditions Control the Elastic and Electrical Properties of ZnO Nanowires.

    PubMed

    Wang, Xiaoguang; Chen, Kai; Zhang, Yongqiang; Wan, Jingchun; Warren, Oden L; Oh, Jason; Li, Ju; Ma, Evan; Shan, Zhiwei

    2015-12-01

    Great efforts have been made to synthesize ZnO nanowires (NWs) as building blocks for a broad range of applications because of their unique mechanical and mechanoelectrical properties. However, little attention has been paid to the correlation between the NWs synthesis condition and these properties. Here we demonstrate that by slightly adjusting the NW growth conditions, the cross-sectional shape of the NWs can be tuned from hexagonal to circular. Room temperature photoluminescence spectra suggested that NWs with cylindrical geometry have a higher density of point defects. In situ transmission electron microscopy (TEM) uniaxial tensile-electrical coupling tests revealed that for similar diameter, the Young's modulus and electrical resistivity of hexagonal NWs is always larger than that of cylindrical NWs, whereas the piezoresistive coefficient of cylindrical NWs is generally higher. With decreasing diameter, the Young's modulus and the resistivity of NWs increase, whereas their piezoresistive coefficient decreases, regardless of the sample geometry. Our findings shed new light on understanding and advancing the performance of ZnO-NW-based devices through optimizing the synthesis conditions of the NWs. PMID:26510098

  11. Optical memory effect in ZnO nanowire based organic bulk heterojunction devices

    NASA Astrophysics Data System (ADS)

    Santhanakrishna, Anand Kumar; Takshi, Arash

    2015-09-01

    Due to the required established field to separate photogenerated electrons and holes, the current- voltage (I-V) characteristic in almost all photovoltaic devices in dark is an exponential curve. Upon illumination, the shape of the curve remains almost the same, but the current shifts due to the photocurrent. Also, because of the lack of any storage mechanism, the I-V curve returns to the dark characteristic immediately after light cessation. Here, we are reporting a case study performed on a photo-electric memory effect in an organic bulk hetrojuction device made of ZnO nanowires as the electron transport layer under ambient conditions and within a sealed transfer box filled with nitrogen. The I-V characteristic in dark and light showed a unique change from a rectifying response in dark to a resistive behavior in light. Additionally, after light cessation, a memory effect was observed with a slow transition from the resistive to rectifying response same as the original dark characteristic. The memory effect and its I-V characteristics were tested for the two cases. For practical applications as a photo memory device, further experiments are required to gain a better understanding of the mechanism behind the observed memory effect for the two different cases.

  12. Complex tribomechanical characterization of ZnO nanowires: nanomanipulations supported by FEM simulations

    NASA Astrophysics Data System (ADS)

    Vlassov, Sergei; Polyakov, Boris; Oras, Sven; Vahtrus, Mikk; Antsov, Mikk; Šutka, Andris; Smits, Krisjanis; Dorogin, Leonid M.; Lõhmus, Rünno

    2016-08-01

    In the present work, we demonstrate a novel approach to nanotribological measurements based on the bending manipulation of hexagonal ZnO nanowires (NWs) in an adjustable half-suspended configuration inside a scanning electron microscope. A pick-and-place manipulation technique was used to control the length of the adhered part of each suspended NW. Static and kinetic friction were found by a ‘self-sensing’ approach based on the strain profile of the elastically bent NW during manipulation and its Young’s modulus, which was separately measured in a three-point bending test with an atomic force microscope. The calculation of static friction from the most bent state was completely reconsidered and a novel more realistic crack-based model was proposed. It was demonstrated that, in contrast to assumptions made in previously published models, interfacial stresses in statically bent NW are highly localized and interfacial strength is comparable to the bending strength of NW measured in respective bending tests.

  13. Complex tribomechanical characterization of ZnO nanowires: nanomanipulations supported by FEM simulations.

    PubMed

    Vlassov, Sergei; Polyakov, Boris; Oras, Sven; Vahtrus, Mikk; Antsov, Mikk; Šutka, Andris; Smits, Krisjanis; Dorogin, Leonid M; Lõhmus, Rünno

    2016-08-19

    In the present work, we demonstrate a novel approach to nanotribological measurements based on the bending manipulation of hexagonal ZnO nanowires (NWs) in an adjustable half-suspended configuration inside a scanning electron microscope. A pick-and-place manipulation technique was used to control the length of the adhered part of each suspended NW. Static and kinetic friction were found by a 'self-sensing' approach based on the strain profile of the elastically bent NW during manipulation and its Young's modulus, which was separately measured in a three-point bending test with an atomic force microscope. The calculation of static friction from the most bent state was completely reconsidered and a novel more realistic crack-based model was proposed. It was demonstrated that, in contrast to assumptions made in previously published models, interfacial stresses in statically bent NW are highly localized and interfacial strength is comparable to the bending strength of NW measured in respective bending tests. PMID:27377119

  14. ZnO dense nanowire array on a film structure in a single crystal domain texture for optical and photoelectrochemical applications

    NASA Astrophysics Data System (ADS)

    Zhong, Miao; Sato, Yukio; Kurniawan, Mario; Apostoluk, Aleksandra; Masenelli, Bruno; Maeda, Etsuo; Ikuhara, Yuichi; Delaunay, Jean-Jacques

    2012-12-01

    A single crystal domain texture quality (a unique in-plane and out-of-plane crystalline orientation over a large area) ZnO nanostructure of a dense nanowire array on a thick film has been homogeneously synthesized on a-plane sapphire substrates over large areas through a one-step chemical vapor deposition (CVD) process. The growth mechanism is clarified: a single crystal [0\\bar {2}1] oriented ZnAl2O4 buffer layer was formed at the ZnO film and the a-plane sapphire substrate interface via a diffusion reaction process during the CVD process, providing improved epitaxial conditions that enable the synthesis of the high crystalline quality ZnO nanowire array on a film structure. The high optoelectronic quality of the ZnO nanowire array on a film sample is evidenced by the free exitonic emissions in the low-temperature photoluminescence spectroscopy. A carrier density of ˜1017 cm-3 with an n-type conductivity of the ZnO nanowire array on a film sample is obtained by electrochemical impedance analysis. Finally, the ZnO nanowire array on a film sample is demonstrated to be an ideal template for a further synthesis of a single crystal quality ZnO-ZnGa2O4 core-shell nanowire array on a film structure. The fabricated ZnO-ZnGa2O4 sample revealed an enhanced anticorrosive ability and photoelectrochemical performance when used as a photoanode in a photoelectrochemical water splitting application.

  15. Metal Catalyst for Low-Temperature Growth of Controlled Zinc Oxide Nanowires on Arbitrary Substrates

    PubMed Central

    Kim, Baek Hyun; Kwon, Jae W.

    2014-01-01

    Zinc oxide nanowires generated by hydrothermal method present superior physical and chemical characteristics. Quality control of the growth has been very challenging and controlled growth is only achievable under very limited conditions using homogeneous seed layers with high temperature processes. Here we show the controlled ZnO nanowire growth on various organic and inorganic materials without the requirement of a homogeneous seed layer and a high temperature process. We also report the discovery of an important role of the electronegativity in the nanowire growth on arbitrary substrates. Using heterogeneous metal oxide interlayers with low-temperature hydrothermal methods, we demonstrate well-controlled ZnO nanowire arrays and single nanowires on flat or curved surfaces. A metal catalyst and heterogeneous metal oxide interlayers are found to determine lattice-match with ZnO and to largely influence the controlled alignment. These findings will contribute to the development of novel nanodevices using controlled nanowires. PMID:24625584

  16. A Pathway to Type-I Band Alignment in Ge/Si Core-Shell Nanowires.

    PubMed

    Kim, Jongseob; Lee, Jung Hoon; Hong, Ki-Ha

    2013-01-01

    We investigate the electronic band structures of Ge/Si core-shell nanowires (CSNWs) and devise a way to realize the electron quantum well at Ge core atoms with first-principles calculations. We reveal that the electronic band engineering by the quantum confinement and the lattice strain can induce the type-I/II band alignment transition, and the resulting type-I band alignment generates the electron quantum well in Ge/Si CSNWs. We also find that the type-I/II transition in Ge/Si CSNWs is highly related to the direct to indirect band gap transition through the analysis of charge density and band structures. In terms of the quantum confinement, for [100] and [111] directional Ge/Si CSNWs, the type-I/II transition can be obtained by decreasing the diameters, whereas a [110] directional CSNW preserves the type-II band alignment even at diameters as small as 1 nm. By applying a compressive strain on [110] CSNWs, the type-I band alignment can be formed. Our results suggest that Ge/Si CSNWs can have the type-I band alignment characteristics by the band structure engineering, which enables both n-type and p-type quantum-well transistors to be fabricated using Ge/Si CSNWs for high-speed logic applications. PMID:26291223

  17. Formation of crystalline InGaO3(ZnO) n nanowires via the solid-phase diffusion process using a solution-based precursor

    NASA Astrophysics Data System (ADS)

    Guo, Yujie; Van Bilzen, Bart; Locquet, Jean Pierre; Seo, Jin Won

    2015-12-01

    One-dimensional single crystalline InGaO3(ZnO) n (IGZO) nanostructures have great potential for various electrical and optical applications. This paper demonstrates for the first time, to our knowledge, a non-vacuum route for the synthesis of IGZO nanowires by annealing ZnO nanowires covered with solution-based IGZO precursor. This method results in nanowires with highly periodic IGZO superlattice structure. The phase transition of IGZO precursor during thermal treatment was systematically studied. Transmission electron microscopy studies reveal that the formation of the IGZO structure is driven by anisotropic inter-diffusion of In, Ga, and Zn atoms, and also by the crystallization of the IGZO precursor. Optical measurements using cathodoluminescence and UV-vis spectroscopy confirm that the nanowires consist of the IGZO compound with wide optical band gap and suppressed luminescence.

  18. Simple, Inexpensive, and Rapid Approach to Fabricate Cross-Shaped Memristors Using an Inorganic-Nanowire-Digital-Alignment Technique and a One-Step Reduction Process.

    PubMed

    Xu, Wentao; Lee, Yeongjun; Min, Sung-Yong; Park, Cheolmin; Lee, Tae-Woo

    2016-01-20

    A rapid, scalable, and designable approach to produce a cross-shaped memristor array is demonstrated using an inorganic-nanowire digital-alignment technique and a one-step reduction process. Two-dimensional arrays of perpendicularly aligned, individually conductive Cu-nanowires with a nanometer-scale Cux O layer sandwiched at each cross point are produced. PMID:26585580

  19. Room temperature-synthesized vertically aligned InSb nanowires: electrical transport and field emission characteristics

    PubMed Central

    2013-01-01

    Vertically aligned single-crystal InSb nanowires were synthesized via the electrochemical method at room temperature. The characteristics of Fourier transform infrared spectrum revealed that in the syntheses of InSb nanowires, energy bandgap shifts towards the short wavelength with the occurrence of an electron accumulation layer. The current–voltage curve, based on the metal–semiconductor–metal model, showed a high electron carrier concentration of 2.0 × 1017 cm−3 and a high electron mobility of 446.42 cm2 V−1 s−1. Additionally, the high carrier concentration of the InSb semiconductor with the surface accumulation layer induced a downward band bending effect that reduces the electron tunneling barrier. Consequently, the InSb nanowires exhibit significant field emission properties with an extremely low turn-on field of 1.84 V μm−1 and an estimative threshold field of 3.36 V μm−1. PMID:23399075

  20. Time limit for the efficient coupling of relativistic femtosecond laser pulses into aligned nanowire arrays

    NASA Astrophysics Data System (ADS)

    Hollinger, R.; Bargsten, C.; Shlyaptsev, V.; Keiss, D.; Townsend, A.; Rockwood, A.; Wang, Y.; Wang, S.; Rocca, J. J.; Pukhov, A.; Kaymak, V.; London, R.; Tommasini, R.

    2015-11-01

    Recent experiments at Colorado State University have demonstrated volumetric heating of near solid density plasmas to multi-keV temperatures by intense high contrast femtosecond laser irradiation of vertically aligned nanostructures. A key parameter is the time for the heated nanowires to expand and fill the inter-wire gaps with a super-critical density plasma. After this time the laser light can no longer penetrate deep into the array, effectively terminating volumetric heating. We have gained information on the gap closure time for arrays with different wire spacing by monitoring the intensity of He-like lines from arrays of nickel nanowires while varying the laser pulse width from 50 fs to 250 fs. Experiments conducted at constant laser energy show that He-like α line emission from arrays of 80 nm diameter nanowires separated by 205 nm is observed for pulse widths of 200 fs. It is possible to find an optimal wire separation to match the pulse width of the driving laser. The results are relevant to scaling the scheme to high energy laser facilities that are characterized by longer pulses. Work supported by the Office of Fusion Energy Science of the US Dept of Energy, and the DTRA. A.P was supported by DFG project TR18, and R.L. and R.T. by LLNL Contract No. DE-AC52-07NA27344.

  1. Vertically aligned GaAs nanowires on graphite and few-layer graphene: generic model and epitaxial growth.

    PubMed

    Munshi, A Mazid; Dheeraj, Dasa L; Fauske, Vidar T; Kim, Dong-Chul; van Helvoort, Antonius T J; Fimland, Bjørn-Ove; Weman, Helge

    2012-09-12

    By utilizing the reduced contact area of nanowires, we show that epitaxial growth of a broad range of semiconductors on graphene can in principle be achieved. A generic atomic model is presented which describes the epitaxial growth configurations applicable to all conventional semiconductor materials. The model is experimentally verified by demonstrating the growth of vertically aligned GaAs nanowires on graphite and few-layer graphene by the self-catalyzed vapor-liquid-solid technique using molecular beam epitaxy. A two-temperature growth strategy was used to increase the nanowire density. Due to the self-catalyzed growth technique used, the nanowires were found to have a regular hexagonal cross-sectional shape, and are uniform in length and diameter. Electron microscopy studies reveal an epitaxial relationship of the grown nanowires with the underlying graphitic substrates. Two relative orientations of the nanowire side-facets were observed, which is well explained by the proposed atomic model. A prototype of a single GaAs nanowire photodetector demonstrates a high-quality material. With GaAs being a model system, as well as a very useful material for various optoelectronic applications, we anticipate this particular GaAs nanowire/graphene hybrid to be promising for flexible and low-cost solar cells. PMID:22889019

  2. Aligned, ultra-long graphene nanoribbon network fabrication by nanowire etch masks

    NASA Astrophysics Data System (ADS)

    Wood, Joshua; Sivapalan, Sean; Dorgan, Vincent; Murphy, Catherine; Pop, Eric; Lyding, Joseph

    2011-03-01

    Patterning semi-metallic graphene into quasi one-dimensional structures known as nanoribbons (GNRs) can open a ~ 0.5 eV bandgap by quantum confinement. To circumvent GNR lithographic difficulties, Si nanowires (NWs) were used previously as an etch mask for exfoliated graphene, but with no scalability or alignment control. Conversely, we transfer ~ 1 in 2 graphene sheets off copper to silicon dioxide, giving us a template for array fabrication. We meniscus align both Au NWs (w > = 20 nm , l = 400 nm) andAgNWs (w > = 200 nm , l > = 10 μ m) , respectively , onthegraphenesurface . Byreactiveionetch (RIE) , weremovetheunmaskedgraphene , andweetchtheNWs . BasedonthestartingNWs , theresultingGNRarrayshavelengthsrangingfrom 200 nmtotensofmicrons , andwidthsfrom 10 nmto 250 nm . WecreatesingleGNRsthatcanspanmicron - separatedcontactsandGNRnetworks , similartoagraphenenanomesh . UsingatomicforcemicroscopyandRamanspectroscopy , wedeterminethatwehavemonolayerGNRswithahighdisorderintensityI D / I G ~ 1 , indicating rough edges and graphene grain boundaries, which are deleterious to transport.

  3. Enhanced power conversion efficiency of CdS quantum dot sensitized solar cells with ZnO nanowire arrays as the photoanodes

    NASA Astrophysics Data System (ADS)

    Qi, Junjie; Liu, Wang; Biswas, Chandan; Zhang, Guangjie; Sun, Lifang; Wang, Zengze; Hu, Xiaofeng; Zhang, Yue

    2015-08-01

    We report the fabrication of CdS quantum dot sensitized solar cells with ZnO nanowire arrays as the photoanodes. The influences of precursor solution temperature and sensitizing cycles on the performance of CdS quantum dots sensitized ZnO nanowires solar cells were studied. Successive ionic layer adsorption and reaction (SILAR) method was applied to deposit CdS quantum dots on the surface of ZnO nanowire arrays for assembling ZnO/CdS electrodes. The results of scanning electron microscopic (SEM), X-ray diffraction (XRD) patterns and UV-vis absorption spectroscopy indicated that the ZnO nanowires electrodes were well-covered with CdS quantum dots. The temperature of the ethanol sensitizing solutions significantly influenced the performance of ZnO/CdS electrodes by affecting the rate of deposition reaction and the penetration ability of ethanol solution. The CdS quantum dots sensitized ZnO-based solar cells exhibited a short-circuit current density (Jsc) of 3.1 mA/cm2, an open-circuit voltage (Voc) of 0.55 V and a photovoltaic conversion efficiency of 0.72%, which is much higher than that reported in literatures, under the illumination of one sun (AM 1.5, 100 mW/cm2) when the temperature of the ethanol solutions was 60 °C and ZnO arrays were sensitized for seven times.

  4. Alignment of human cardiomyocytes on laser patterned biphasic core/shell nanowire assemblies

    NASA Astrophysics Data System (ADS)

    Kiefer, Karin; Lee, Juseok; Haidar, Ayman; Martinez Miró, Marina; Akkan, Cagri Kaan; Veith, Michael; Cenk Aktas, Oral; Abdul-Khaliq, Hashim

    2014-12-01

    The management of end stage heart failure patients is only possible by heart transplantation or by the implantation of artificial hearts as a bridge for later transplantation. However, these therapeutic strategies are limited by a lack of donor hearts and by the associated complications, such as coagulation and infection, due to the used artificial mechanical circulatory assist devices. Therefore, new strategies for myocardial regenerative approaches are under extensive research to produce contractile myocardial tissue in the future to replace non-contractile myocardial ischemic and scarred tissue. Different approaches, such as cell transplantation, have been studied intensively. Although successful approaches have been observed, there are still limitations to the application. It is envisaged that myocardial tissue engineering can be used to help replace infarcted non-contractile tissue. The developed tissue should later mimic the aligned fibrillar structure of the extracellular matrix and provide important guidance cues for the survival, function and the needed orientation of cardiomyocytes. Nanostructured surfaces have been tested to provide a guided direction that cells can follow. In the present study, the cellular adhesion/alignment of human cardiomyocytes and the biocompatibility have been investigated after cultivation on different laser-patterned nanowires compared with unmodified nanowires. As a result, the nanostructured surfaces possessed good biocompatibility before and after laser modification. The laser-induced scalability of the pattern enabled the growth and orientation of the adhered myocardial tissue. Such approaches may be used to modify the surface of potential scaffolds to develop myocardial contractile tissue in the future.

  5. Catalyst-Free Direct Vapor-Phase Growth of Hexagonal ZnO Nanowires on α-Al2O3

    NASA Astrophysics Data System (ADS)

    Hullavarad, S. S.; Hullavarad, N. V.; Vispute, R. D.; Venkatesan, T.; Kilpatrick, S. J.; Ervin, M. H.; Nichols, B.; Wickenden, A. E.

    2010-08-01

    The evolution of ZnO nanowires has been studied under supersaturation of Zn metal species with and without a ZnO thin-film buffer layer on α-Al2O3 deposited by the pulsed laser ablation technique. The nanowires had diameters in the range of 30 nm to 50 nm and lengths in the range of 5 μm to 10 μm with clear hexagonal shape and [000bar{1}] , [10bar{1}1] , and [10bar{1}0] facets. X-ray diffraction (XRD) measurements indicated crystalline properties for the ZnO nanostructures grown on pulsed laser deposition (PLD) ZnO nucleation layers. The optical properties were analyzed by photoluminescence (PL) and cathodoluminescence (CL) measurements. The ZnO nanowires were found to emit strong ultraviolet (UV) light at 386 nm and weak green emission as observed by PL measurements. The stoichiometry of Zn and O was found to be close to 1 by x-ray photoelectron spectroscopy (XPS) measurements. The process-dependent growth properties of ZnO nanostructures can be harnessed for future development of nanoelectronic components including optically pumped lasers, optical modulators, detectors, electron emitters, and gas sensors.

  6. Non-classical logic inverter coupling a ZnO nanowire-based Schottky barrier transistor and adjacent Schottky diode.

    PubMed

    Hosseini Shokouh, Seyed Hossein; Raza, Syed Raza Ali; Lee, Hee Sung; Im, Seongil

    2014-08-21

    On a single ZnO nanowire (NW), we fabricated an inverter-type device comprising a Schottky diode (SD) and field-effect transistor (FET), aiming at 1-dimensional (1D) electronic circuits with low power consumption. The SD and adjacent FET worked respectively as the load and driver, so that voltage signals could be easily extracted as the output. In addition, NW FET with a transparent conducting oxide as top gate turned out to be very photosensitive, although ZnO NW SD was blind to visible light. Based on this, we could achieve an array of photo-inverter cells on one NW. Our non-classical inverter is regarded as quite practical for both logic and photo-sensing due to its performance as well as simple device configuration. PMID:24985947

  7. Characterization of planar pn heterojunction diodes constructed with Cu2O nanoparticle films and single ZnO nanowires.

    PubMed

    Kwak, Kiyeol; Cho, Kyoungah; Kim, Sangsig

    2013-05-01

    In this study, we fabricate planar pn heterojunction diodes composed of Cu2O nanoparticle (NP) films and single ZnO nanowires (NWs) on SiO2 (300 nm)/Si substrates and investigate their characteristics in the dark and under the illumination of white light and 325 nm wavelength light. The diode at bias voltages of +/- 1 V shows rectification ratios of 10 (in the dark) and 34 (under the illumination of white light). On the other hand, the diode exposed to the 325 nm wavelength light exhibits Ohmic characteristics which are associated with efficient photocurrent generation in both the Cu2O NP film and the single ZnO NW. PMID:23858873

  8. High-efficiency second harmonic generation from a single hybrid ZnO nanowire/Au plasmonic nano-oligomer.

    PubMed

    Grinblat, Gustavo; Rahmani, Mohsen; Cortés, Emiliano; Caldarola, Martín; Comedi, David; Maier, Stefan A; Bragas, Andrea V

    2014-11-12

    We introduce a plasmonic-semiconductor hybrid nanosystem, consisting of a ZnO nanowire coupled to a gold pentamer oligomer by crossing the hot-spot. It is demonstrated that the hybrid system exhibits a second harmonic (SH) conversion efficiency of ∼3 × 10(-5)%, which is among the highest values for a nanoscale object at optical frequencies reported so far. The SH intensity was found to be ∼1700 times larger than that from the same nanowire excited outside the hot-spot. Placing high nonlinear susceptibility materials precisely in plasmonic confined-field regions to enhance SH generation opens new perspectives for highly efficient light frequency up-conversion on the nanoscale. PMID:25347036

  9. Sandwiched assembly of ZnO nanowires between graphene layers for a self-powered and fast responsive ultraviolet photodetector.

    PubMed

    Boruah, Buddha Deka; Mukherjee, Anwesha; Misra, Abha

    2016-03-01

    A heterostructure of graphene and zinc oxide (ZnO) nanowires (NWs) is fabricated by sandwiching an array of ZnO NWs between two graphene layers for an ultraviolet (UV) photodetector. This unique structure allows NWs to be in direct contact with the graphene layers, minimizing the effect of the substrate or metal electrodes. In this device, graphene layers act as highly conducting electrodes with a high mobility of the generated charge carriers. An excellent sensitivity is demonstrated towards UV illumination, with a reversible photoresponse even for a short period of UV illumination. Response and recovery times of a few milliseconds demonstrated a much faster photoresponse than most of the conventional ZnO nanostructure-based photodetectors. It is shown that the generation of a built-in electric field between the interface of graphene and ZnO NWs effectively contributes to the separation of photogenerated electron-hole pairs for photocurrent generation without applying any external bias. Upon application of external bias voltage, the electric field further increases the drift velocity of photogenerated electrons by reducing the charge recombination rates, and results in an enhancement of the photocurrent. Therefore, the graphene-based heterostructure (G/ZnO NW/G) opens avenues to constructing a novel heterostructure with a combination of two functionally dissimilar materials. PMID:26857833

  10. Modification of the optical and structural properties of ZnO nanowires by low-energy Ar+ ion sputtering

    PubMed Central

    2013-01-01

    The effects of low-energy (≤2 kV) Ar+ irradiation on the optical and structural properties of zinc oxide (ZnO) nanowires (NWs) grown by a simple and cost-effective low-temperature technique were investigated. Both photoluminescence spectra from ZnO NW-coated films and cathodoluminescence analysis of individual ZnO NWs demonstrated obvious evidences of ultraviolet/visible luminescent enhancement with respect to irradiation fluence. Annihilation of the thinner ZnO NWs after the ion bombardment was appreciated by means of high-resolution scanning electron microscopy and transmission electron microscopy (TEM), which results in an increasing NW mean diameter for increasing irradiation fluences. Corresponding structural analysis by TEM pointed out not only significant changes in the morphology but also in the microstructure of these NWs, revealing certain radiation-sensitive behavior. The possible mechanisms accounting for the decrease of the deep-level emissions in the NWs with the increasing irradiation fluences are discussed according to their structural modifications. PMID:23570658

  11. Structural and optical properties of ZnMgO nanostructures formed by Mg in-diffused ZnO nanowires

    SciTech Connect

    Pan, C.-J.; Hsu, H.-C.; Cheng, H.-M.; Wu, C.-Y.; Hsieh, W.-F.

    2007-04-15

    ZnMgO nanostructures with wurtzite phase were prepared by thermal diffusion of Mg into the ZnO nanowires. As ZnO light-emitting devices have been operated by using ZnMgO layers as energy barrier layers to confine the carriers, it is essential to realize the characterization of ZnMgO particularly. In this work, the Mg content in Zn{sub 1} {sub -x} Mg {sub x} O alloy determined by X-ray diffraction (XRD) and photoluminescence (PL) shows a good coincidence. The variation of lattice constant and the blueshift of near-band-edge emission indicate that Zn{sup 2+} ions are successfully substituted by Mg{sup 2+} ions in the ZnO lattice. In Raman-scattering studies, the change of E {sub 2}(high) phonon line shape in ZnO:Mg nanostructures reveals the microscopic substitutional disorder. In addition to the host phonons of ZnO, two additional bands around 383 and 510 cm{sup -1} are presumably attributed to the Mg-related vibrational modes. - Graphical abstract: We reported the synthesis of the ZnMgO nanostructures prepared by a simple vapor transport method. Magnesium-related anomalous modes are observed by Raman spectra for the first time in ZnMgO system.

  12. Time Resolved Photoluminescence Studies of ZnO and Zn2SnO4 Nanowires for Solar Cells Applications

    NASA Astrophysics Data System (ADS)

    Yakami, Baichhabi Raj; Mahat, Meg; Chen, Jiajun; Lu, Liyou; Wang, Wenyong; Pikal, Jon M.

    2013-03-01

    Sensitized nanowires (NWs) are a promising option for solar cells. They serve as the support structure for the absorbing centers, provide interfacial charge separation, and transport to the anode. Most work has focused on binary oxides, but ternary oxides have advantages due to flexibility in the properties of the oxide. Here we report on the photoluminescence (PL) and Time Resolved PL (TRPL) of Zinc oxide (ZnO) and Zinc Tin Oxide (ZTO) NWs grown by Chemical Vapor Deposition. The ZnO NWs show strong band gap emission and weak but resolvable defect emission peaks. The PL from the ZTO NWs does not show any band gap emission and absorption measurements confirm that these NWs have a direct forbidden transition. The ZTO NWs do have a board visible emission peak, which is usually attributed defects and oxygen vacancies. TRPL of the band gap emission in ZnO NWs yield a carrier lifetime of 1.4ns. The TRPL of the defect peaks in ZTO NWs are more complicated, showing a multi-exponential decay but with an overall decay rate similar to the ZnO NWs. This indicates that the expected increase in carrier lifetime in the ZTO NWs is not currently realized likely due to defect recombination, and additional optimization of the NW growth process may yield improved performance. DOE

  13. Sandwiched assembly of ZnO nanowires between graphene layers for a self-powered and fast responsive ultraviolet photodetector

    NASA Astrophysics Data System (ADS)

    Deka Boruah, Buddha; Mukherjee, Anwesha; Misra, Abha

    2016-03-01

    A heterostructure of graphene and zinc oxide (ZnO) nanowires (NWs) is fabricated by sandwiching an array of ZnO NWs between two graphene layers for an ultraviolet (UV) photodetector. This unique structure allows NWs to be in direct contact with the graphene layers, minimizing the effect of the substrate or metal electrodes. In this device, graphene layers act as highly conducting electrodes with a high mobility of the generated charge carriers. An excellent sensitivity is demonstrated towards UV illumination, with a reversible photoresponse even for a short period of UV illumination. Response and recovery times of a few milliseconds demonstrated a much faster photoresponse than most of the conventional ZnO nanostructure-based photodetectors. It is shown that the generation of a built-in electric field between the interface of graphene and ZnO NWs effectively contributes to the separation of photogenerated electron-hole pairs for photocurrent generation without applying any external bias. Upon application of external bias voltage, the electric field further increases the drift velocity of photogenerated electrons by reducing the charge recombination rates, and results in an enhancement of the photocurrent. Therefore, the graphene-based heterostructure (G/ZnO NW/G) opens avenues to constructing a novel heterostructure with a combination of two functionally dissimilar materials.

  14. Effect of gamma irradiation on Schottky-contacted vertically aligned ZnO nanorod-based hydrogen sensor.

    PubMed

    Ranwa, Sapana; Barala, Surendra Singh; Fanetti, Mattia; Kumar, Mahesh

    2016-08-26

    We report the impact of gamma irradiation on the performance of a gold Schottky-contacted ZnO nanorod-based hydrogen sensor. RF-sputtered vertically aligned highly c-axis-oriented ZnO NRs were grown on Si(100) substrate. X-ray diffraction shows no significant change in crystal structure at low gamma doses from 1 to 5 kGy. As gamma irradiation doses increase to 10 kGy, the single crystalline ZnO structure converts to polycrystalline. The photoluminescence spectra also shows suppression of the near-band emission peak and the huge wide-band spectrum indicates the generation of structural defects at high gamma doses. At 1 kGy, the hydrogen sensor response was enhanced from 67% to 77% for 1% hydrogen in pure argon at a 150 °C operating temperature. However, at 10 kGy, the relative response decreases to 33.5%. High gamma irradiation causes displacement damage and defects in ZnO NRs, and as a result, degrades the sensor's performance as a result. Low gamma irradiation doses activate the ZnO NR surface through ionization, which enhances the sensor performance. The relative response of the hydrogen sensor was enhanced by ∼14.9% with respect to pristine ZnO using 1 kGy gamma ray treatment. PMID:27418478

  15. Effect of gamma irradiation on Schottky-contacted vertically aligned ZnO nanorod-based hydrogen sensor

    NASA Astrophysics Data System (ADS)

    Ranwa, Sapana; Singh Barala, Surendra; Fanetti, Mattia; Kumar, Mahesh

    2016-08-01

    We report the impact of gamma irradiation on the performance of a gold Schottky-contacted ZnO nanorod-based hydrogen sensor. RF-sputtered vertically aligned highly c-axis-oriented ZnO NRs were grown on Si(100) substrate. X-ray diffraction shows no significant change in crystal structure at low gamma doses from 1 to 5 kGy. As gamma irradiation doses increase to 10 kGy, the single crystalline ZnO structure converts to polycrystalline. The photoluminescence spectra also shows suppression of the near-band emission peak and the huge wide-band spectrum indicates the generation of structural defects at high gamma doses. At 1 kGy, the hydrogen sensor response was enhanced from 67% to 77% for 1% hydrogen in pure argon at a 150 °C operating temperature. However, at 10 kGy, the relative response decreases to 33.5%. High gamma irradiation causes displacement damage and defects in ZnO NRs, and as a result, degrades the sensor’s performance as a result. Low gamma irradiation doses activate the ZnO NR surface through ionization, which enhances the sensor performance. The relative response of the hydrogen sensor was enhanced by ∼14.9% with respect to pristine ZnO using 1 kGy gamma ray treatment.

  16. Capillary Printing of Highly Aligned Silver Nanowire Transparent Electrodes for High-Performance Optoelectronic Devices.

    PubMed

    Kang, Saewon; Kim, Taehyo; Cho, Seungse; Lee, Youngoh; Choe, Ayoung; Walker, Bright; Ko, Seo-Jin; Kim, Jin Young; Ko, Hyunhyub

    2015-12-01

    Percolation networks of silver nanowires (AgNWs) are commonly used as transparent conductive electrodes (TCEs) for a variety of optoelectronic applications, but there have been no attempts to precisely control the percolation networks of AgNWs that critically affect the performances of TCEs. Here, we introduce a capillary printing technique to precisely control the NW alignment and the percolation behavior of AgNW networks. Notably, partially aligned AgNW networks exhibit a greatly lower percolation threshold, which leads to the substantial improvement of optical transmittance (96.7%) at a similar sheet resistance (19.5 Ω sq(-1)) as compared to random AgNW networks (92.9%, 20 Ω sq(-1)). Polymer light-emitting diodes (PLEDs) using aligned AgNW electrodes show a 30% enhanced maximum luminance (33068 cd m(-2)) compared to that with random AgNWs and a high luminance efficiency (14.25 cd A(-1)), which is the highest value reported so far using indium-free transparent electrodes for fluorescent PLEDs. In addition, polymer solar cells (PSCs) using aligned AgNW electrodes exhibit a power conversion efficiency (PCE) of 8.57%, the highest value ever reported to date for PSCs using AgNW electrodes. PMID:26540011

  17. Correlation between SSM substrate effect and physical properties of ZnO nanowires electrodeposited with or without seed layer for enhanced photoelectrochemical applications

    NASA Astrophysics Data System (ADS)

    Lamouchi, A.; Slimi, B.; Ben Assaker, I.; Gannouni, M.; Chtourou, R.

    2016-06-01

    ZnO nanowires (NWs) were grown vertically by electrodeposition technique on a stainless-steel mesh (SSM) substrate in the presence and absence of seed layer. A new contribution to the knowledge of both substrate nature and seed layer dependence on structural, morphological, optical properties is reported. X-ray diffraction revealed that all the samples are mainly crystallized in the wurtzite ZnO phase. In the presence of seed layer onto the SSM substrate, the crystalline nature of ZnO NWs is improved by the enhancement of intensity in (002) peak, which indicates a preferential orientation along this peak. The scanning electron microscopy (SEM) images show that, in the presence of seed layer, nanowires appear uniform and stand perpendicular to the substrate with hexagonal shape, implying the occurrence of the wurtzite ZnO crystal structure. According to optical measurements, the decrease of the band-gap energy is due mainly to the seed layer effect and the SSM substrate contribution. To investigate the effect of seed layer and SSM substrate, a photoeletrochemical (PEC) analysis of ZnO NWs is performed. The photocurrent density produced by the ZnO NWs/ZnO/SSM electrode reached 0.2mA·cm^-2, about two times higher than that measured on the ZnO NWs/SSM electrode. These results indicate that both seed layer and substrate have great potential in photoelectrochemical devices.

  18. Chlorine Gas Sensing Performance of On-Chip Grown ZnO, WO3, and SnO2 Nanowire Sensors.

    PubMed

    Tran, Van Dang; Nguyen, Duc Hoa; Nguyen, Van Duy; Nguyen, Van Hieu

    2016-02-01

    Monitoring toxic chlorine (Cl2) at the parts-per-billion (ppb) level is crucial for safe usage of this gas. Herein, ZnO, WO3, and SnO2 nanowire sensors were fabricated using an on-chip growth technique with chemical vapor deposition. The Cl2 gas-sensing characteristics of the fabricated sensors were systematically investigated. Results demonstrated that SnO2 nanowires exhibited higher sensitivity to Cl2 gas than ZnO and WO3 nanowires. The response (RCl2/Rair) of the SnO2 nanowire sensor to 50 ppb Cl2 at 50 °C was about 57. Hence, SnO2 nanowires can be an excellent sensing material for detecting Cl2 gas at the ppb level under low temperatures. Abnormal sensing characteristics were observed in the WO3 and SnO2 nanowire sensors at certain temperatures; in particular, the response level of these sensors to 5 ppm of Cl2 was lower than that to 2.5 ppm of Cl2. The sensing mechanism of the SnO2 nanowire sensor was also elucidated by determining Cl2 responses under N2 and dry air as carrier gases. We proved that the Cl2 molecule was first directly adsorbed on the metal oxide surface and was then substituted for pre-adsorbed oxygen, followed by lattice oxygen. PMID:26816341

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

    PubMed

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

    2013-10-01

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

  20. High-gain subnanowatt power consumption hybrid complementary logic inverter with WSe2 nanosheet and ZnO nanowire transistors on glass.

    PubMed

    Shokouh, Seyed Hossein Hosseini; Pezeshki, Atiye; Ali Raza, Syed Raza; Lee, Hee Sung; Min, Sung-Wook; Jeon, Pyo Jin; Shin, Jae Min; Im, Seongil

    2015-01-01

    A 1D-2D hybrid complementary logic inverter comprising of ZnO nanowire and WSe2 nanosheet field-effect transistors (FETs) is fabricated on glass, which shows excellent static and dynamic electrical performances with a voltage gain of ≈60, sub-nanowatt power consumption, and at least 1 kHz inverting speed. PMID:25377731

  1. Low-Cost and High-Productivity Three-Dimensional Nanocapacitors Based on Stand-Up ZnO Nanowires for Energy Storage

    NASA Astrophysics Data System (ADS)

    Wei, Lei; Liu, Qi-Xuan; Zhu, Bao; Liu, Wen-Jun; Ding, Shi-Jin; Lu, Hong-Liang; Jiang, Anquan; Zhang, David Wei

    2016-04-01

    Highly powered electrostatic capacitors based on nanostructures with a high aspect ratio are becoming critical for advanced energy storage technology because of their high burst power and energy storage capability. We report the fabrication process and the electrical characteristics of high capacitance density capacitors with three-dimensional solid-state nanocapacitors based on a ZnO nanowire template. Stand-up ZnO nanowires are grown face down on p-type Si substrates coated with a ZnO seed layer using a hydrothermal method. Stacks of AlZnO/Al2O3/AlZnO are then deposited sequentially on the ZnO nanowires using atomic layer deposition. The fabricated capacitor has a high capacitance density up to 92 fF/μm2 at 1 kHz (around ten times that of the planar capacitor without nanowires) and an extremely low leakage current density of 3.4 × 10-8 A/cm2 at 2 V for a 5-nm Al2O3 dielectric. Additionally, the charge-discharge characteristics of the capacitor were investigated, indicating that the resistance-capacitance time constants were 550 ns for both the charging and discharging processes and the time constant was not dependent on the voltage. This reflects good power characteristics of the fabricated capacitors. Therefore, the current work provides an exciting strategy to fabricate low-cost and easily processable, high capacitance density capacitors for energy storage.

  2. Non-conformal decoration of semiconductor nanowire surfaces with boron nitride (BN) molecules for stability enhancement: degradation-resistant Zn3P2, ZnO and Mg2Si nanowires.

    PubMed

    Vasiraju, Venkata; Kang, Yongmin; Vaddiraju, Sreeram

    2014-08-14

    A simple and reliable strategy for stabilizing the surfaces of compound semiconductors was presented. The strategy involved decorating the surfaces of compound semiconductor nanowires non-conformally with small molecules of boron nitride (BN). More specifically, Zn3P2, ZnO and Mg2Si nanowires, highly useful in energy conversion device fabrication (e.g., photovoltaics and thermoelectrics), have been stabilized against air- and acid-assisted degradation by decorating their surfaces with small molecules of BN. It is believed that the decoration of the nanowire surfaces with BN molecules made the nanowire surfaces non-wettable to water and aqueous acid solutions, and thereby imparted them enhanced resistance against water- and acid-assisted degradation. This procedure did not alter the bandgap of the nanowires. Moreover, this procedure aided in retaining the electrical conduction between the nanowire interfaces when the nanowires are assembled into mats or pellets. This strategy solves one of the primary bottlenecks in the widespread use of nanowires in energy conversion device fabrication, namely their stability. It is believed that this strategy is applicable for stabilizing other compound semiconductor nanowires, including nitrides, sulfides, silicides and antimonides. PMID:24968211

  3. Chromium inhibition and size-selected Au nanocluster catalysis for the solution growth of low-density ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Errico, Vito; Arrabito, Giuseppe; Plant, Simon R.; Medaglia, Pier Gianni; Palmer, Richard E.; Falconi, Christian

    2015-07-01

    The wet chemical synthesis of nanostructures has many crucial advantages over high-temperature methods, including simplicity, low-cost, and deposition on almost arbitrary substrates. Nevertheless, the density-controlled solution growth of nanowires still remains a challenge, especially at the low densities (e.g. 1 to 10 nanowires/100 μm2) required, as an example, for intracellular analyses. Here, we demonstrate the solution-growth of ZnO nanowires using a thin chromium film as a nucleation inhibitor and Au size-selected nanoclusters (SSNCs) as catalytic particles for which the density and, in contrast with previous reports, size can be accurately controlled. Our results also provide evidence that the enhanced ZnO hetero-nucleation is dominated by Au SSNCs catalysis rather than by layer adaptation. The proposed approach only uses low temperatures (≤70 °C) and is therefore suitable for any substrate, including printed circuit boards (PCBs) and the plastic substrates which are routinely used for cell cultures. As a proof-of-concept we report the density-controlled synthesis of ZnO nanowires on flexible PCBs, thus opening the way to assembling compact intracellular-analysis systems, including nanowires, electronics, and microfluidics, on a single substrate.

  4. Hierarchical growth of TiO2 nanosheets on anodic ZnO nanowires for high efficiency dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Miles, David O.; Lee, Chang Soo; Cameron, Petra J.; Mattia, Davide; Kim, Jong Hak

    2016-09-01

    We present a novel route to hierarchical core-shell structures consisting of an anodic ZnO nanowire core surrounded by a shell of TiO2 nanosheets (ZNW@TNS). This material combines the beneficial properties of enhanced electron transport, provided by the nanowire core, with the high surface area and chemical stability of the TiO2 shell. Quasi-solid-state dye-sensitized solar cells (qssDSSCs) are prepared using different quantities of either the bare ZnO nanowires or the hierarchical nanowire structures and the effect on cell performance is examined. It is found that whilst the addition of the bare ZnO nanowires results in a decrease in cell performance, significant improvements can be achieved with the addition of small quantities of the hierarchical structures. Power conversion efficiencies of up to 7.5% are achieved under 1 Sun, AM 1.5 simulated sunlight, with a ∼30% increase compared to non-hierarchical mesoporous TiO2 films. A solid-state DSSC (ssDSSC) with a single component solid polymer also exhibits excellent efficiency of 7.2%. The improvement in cell performance is related to the improved light scattering, surface area and electron transport properties via the use of reflectance spectroscopy, BET surface area measurements and electrochemical impedance spectroscopy.

  5. Chromium inhibition and size-selected Au nanocluster catalysis for the solution growth of low-density ZnO nanowires

    PubMed Central

    Errico, Vito; Arrabito, Giuseppe; Plant, Simon R.; Medaglia, Pier Gianni; Palmer, Richard E.; Falconi, Christian

    2015-01-01

    The wet chemical synthesis of nanostructures has many crucial advantages over high-temperature methods, including simplicity, low-cost, and deposition on almost arbitrary substrates. Nevertheless, the density-controlled solution growth of nanowires still remains a challenge, especially at the low densities (e.g. 1 to 10 nanowires/100 μm2) required, as an example, for intracellular analyses. Here, we demonstrate the solution-growth of ZnO nanowires using a thin chromium film as a nucleation inhibitor and Au size-selected nanoclusters (SSNCs) as catalytic particles for which the density and, in contrast with previous reports, size can be accurately controlled. Our results also provide evidence that the enhanced ZnO hetero-nucleation is dominated by Au SSNCs catalysis rather than by layer adaptation. The proposed approach only uses low temperatures (≤70 °C) and is therefore suitable for any substrate, including printed circuit boards (PCBs) and the plastic substrates which are routinely used for cell cultures. As a proof-of-concept we report the density-controlled synthesis of ZnO nanowires on flexible PCBs, thus opening the way to assembling compact intracellular-analysis systems, including nanowires, electronics, and microfluidics, on a single substrate. PMID:26202588

  6. Spray-coating route for highly aligned and large-scale arrays of nanowires.

    PubMed

    Assad, Ossama; Leshansky, Alexander M; Wang, Bin; Stelzner, Thomas; Christiansen, Silke; Haick, Hossam

    2012-06-26

    Technological implementation of nanowires (NWs) requires these components to be organized with controlled orientation and density on various substrates. Here, we report on a simple and efficient route for the deposition of highly ordered and highly aligned NW arrays on a wide range of receiver substrates, including silicon, glass, metals, and flexible plastics with controlled density. The deposition approach is based on spray-coating of a NW suspension under controlled conditions of the nozzle flow rate, droplet size of the sprayed NWs suspension, spray angle, and the temperature of the receiver substrate. The dynamics of droplet generation is understood by a combined action of shear forces and capillary forces. Provided that the size of the generated droplet is comparable to the length of the single NW, the shear-driven elongation of the droplets results presumably in the alignment of the confined NW in the spraying direction. Flattening the droplets upon their impact with the substrate yields fast immobilization of the spray-aligned NWs on the surface due to van der Waals attraction. The availability of the spray-coating technique in the current microelectronics technology would ensure immediate implementation in production lines, with minimal changes in the fabrication design and/or auxiliary tools used for this purpose. PMID:22554272

  7. "Secondary Growth" in Hydrothermal Synthesis of Aligned ZnO Nanostructures and Its Application in Dye-Sensitized Solar Cells.

    PubMed

    Liu, Wenjun; Huang, Qiaoling; Huang, Tengji; Cao, Peijiang; Han, Shun; Jia, Fang; Zhu, Deliang; Ma, Xiaocui; Lul, Youming

    2016-04-01

    One-dimensional (1D) aligned ZnO nanostructures were prepared on ZnO film seeded substrates using a low-temperature hydrothermal method, and zinc nitrate and hexamethylenetetramine (HMT) precursors. It was observed that increasing the concentration ratio of Zn2+/HMT from 1 to 100 led to a "secondary growth," and a change in the morphologies of the ZnO nanostructures from arrays of thick nanorods to arrays of thin nanorod-step-thick nanorods. The morphological evolution of ZnO nanostructures with increased growth time at high Zn2+/HMT concentration ratios showed the same transformation. Dye-sensitized solar cells (DSSCs) were fabricated using ZnO nanostructures as the photoanodes, and the electron transport properties were determined by electrochemical impedance spectroscopy (EIS). Although the DSSCs showed low power conversion efficiencies due to the short lengths, the arrays of the thin nanorods demonstrated excellent electron transport with an electron diffusion coefficient (Dn) of 1.57 x 10(-3) cm2/s, and an effective diffusion length (L) of 140 µm. PMID:27451759

  8. Influence of electrodeposition parameters on the structure and morphology of ZnO nanowire arrays and networks synthesized in etched ion-track membranes

    NASA Astrophysics Data System (ADS)

    Movsesyan, Liana; Schubert, Ina; Yeranyan, Lilit; Trautmann, Christina; Toimil-Molares, Maria Eugenia

    2016-01-01

    This work presents the synthesis and characterization of two different zinc oxide (ZnO) nanowire assemblies: arrays of parallel-oriented cylindrical wires and three-dimensional (3D) networks of highly interconnected wires. Both are synthesized by electrochemical deposition in the pores of etched ion-track polycarbonate membranes. The crystallinity and crystallographic properties of the wires are influenced by the deposition parameters. In particular, we investigate how the diameter of the membrane nanopores and the deposition potential affect crystal orientation and morphology during nanowire growth. X-ray diffraction and energy dispersive x-ray analysis demonstrated that all wires are pure ZnO with a wurtzite hexagonal structure and free of impurities. The unique architecture of the synthesized 3D networks of nanowires with a high aspect ratio and enhanced mechanical stability is discussed.

  9. PLD-assisted VLS growth of aligned ferrite nanorods, nanowires, and nanobelts-synthesis, and properties.

    PubMed

    Morber, Jenny Ruth; Ding, Yong; Haluska, Michael Stephan; Li, Yang; Liu, J Ping; Wang, Zhong Lin; Snyder, Robert L

    2006-11-01

    We report here a systematic synthesis and characterization of aligned alpha-Fe2O3 (hematite), epsilon-Fe2O3, and Fe3O4 (magnetite) nanorods, nanobelts, and nanowires on alumina substrates using a pulsed laser deposition (PLD) method. The presence of spherical gold catalyst particles at the tips of the nanostructures indicates selective growth via the vapor-liquid-solid (VLS) mechanism. Through a series of experiments, we have produced a primitive "phase diagram" for growing these structures based on several designed pressure and temperature parameters. Transmission electron microscopy (TEM) analysis has shown that the rods, wires, and belts are single-crystalline and grow along <111>m or <110>h directions. X-ray diffraction (XRD) measurements confirm phase and structural analysis. Superconducting quantum interference device (SQUID) measurements show that the iron oxide structures exhibit interesting magnetic behavior, particularly at room temperature. This work is the first known report of magnetite 1D nanostructure growth via the vapor-liquid-solid (VLS) mechanism without using a template, as well as the first known synthesis of long epsilon-Fe2O3 nanobelts and nanowires. PMID:17064124

  10. Density Detection of Aligned Nanowire Arrays Using Terahertz Time-Domain Spectroscopy.

    PubMed

    Xiang, Wenfeng; Wang, Xin; Liu, Yuan; Zhang, JiaQi; Zhao, Kun

    2016-12-01

    A rapid technique is necessary to quantitatively detect the density of nanowire (NW) and nanotube arrays in one-dimensional devices which have been identified as useful building blocks for nanoelectronics, optoelectronics, biomedical devices, etc. Terahertz (THz) time-domain spectroscopy was employed in this research to detect the density of aligned Ni NW arrays. The transmitted amplitude of THz peaks and optical thickness of NW arrays was found to be the effective parameters to analyze the density change of NW arrays. Owing to the low multiple scattering and high order of Ni NW arrays, a linear relationship was observed for the transmitted amplitude and optical thickness regarding NW density, respectively. Therefore, THz technique may be used as a promising tool to characterize the density of one-dimensional structures in the large-scale integrated nanodevice fabrication. PMID:27431495

  11. Enhancing field emission performance of aligned Si nanowires via in situ partial oxidization.

    PubMed

    Qian, Zhongjian; Liu, Xianyun; Yang, Ye; Yin, Qiaoxia

    2014-08-01

    Partially oxidized Si nanowire (NW) arrays have been achieved via a combinatorial process of selectively etching Si wafer to obtain vertically aligned single crystalline Si NW arrays and subsequent in situ partially oxidizing the as-etched bare Si NWs. The resultant Si products are Si-SiOx nanocable-like structures consisting of single-crystalline Si NW inner cores and outer shells of insulating SiOx. Field emission measurements demonstrate that surface partial oxidization enhances the field emission current of the as-etched bare Si NWs effectively, which can be ascribed to the outer shell of insulating SiOx that has small electron affinity (0.6-0.8 eV) and can protect Si NW inner cores. The results indicate that the partially oxidized Si NW arrays would act as the excellent field emitters in the future vacuum micro- and nano-electronic devices. PMID:25936088

  12. Density Detection of Aligned Nanowire Arrays Using Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Xiang, Wenfeng; Wang, Xin; Liu, Yuan; Zhang, JiaQi; Zhao, Kun

    2016-07-01

    A rapid technique is necessary to quantitatively detect the density of nanowire (NW) and nanotube arrays in one-dimensional devices which have been identified as useful building blocks for nanoelectronics, optoelectronics, biomedical devices, etc. Terahertz (THz) time-domain spectroscopy was employed in this research to detect the density of aligned Ni NW arrays. The transmitted amplitude of THz peaks and optical thickness of NW arrays was found to be the effective parameters to analyze the density change of NW arrays. Owing to the low multiple scattering and high order of Ni NW arrays, a linear relationship was observed for the transmitted amplitude and optical thickness regarding NW density, respectively. Therefore, THz technique may be used as a promising tool to characterize the density of one-dimensional structures in the large-scale integrated nanodevice fabrication.

  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. Synthesis of Highly Stable Silver-Loaded Vertical ZnO Nanowires Array and its Acetylene Sensing Properties

    NASA Astrophysics Data System (ADS)

    Uddin, Abu Sadat Mohammad Iftekhar; Chung, Gwiy-Sang

    2016-09-01

    A silver-loaded one-dimensional (1D) vertical ZnO nanowires (NWs) array synthesized by a facile seed mediated hydrothermal-RF magnetron sputtering method has been investigated for the fabrication of a highly stable and reproducible acetylene (C2H2) gas sensor. Successful immobilization of silver nanoparticles (NPs) as a sensitizer on the ZnO NWs array significantly enhanced the C2H2 sensing properties and showed a stable sensing performance. The grown structure exhibited high response magnitude (30.8 at 1000ppm), short response time (43s) and excellent selectivity at 220∘C. The enhanced performance can probably be accounted for the effect of combining the highly orientated ZnO NWs and catalytically active silver-based network. The superior sensing features toward C2H2 along with broad detection range (1-1000ppm), outstanding stability and excellent reproducibility indicate that the sensor is a promising candidate for practical applications.

  15. Fabrication and Characterization of ZnO Nanowire-based Piezoelectric Nanogenerators for Low Frequency Mechanical Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Poulin-Vittrant, G.; Oshman, C.; Opoku, C.; Dahiya, A. S.; Camara, N.; Alquier, D.; Hue, L.-P. Tran Huu; Lethiecq, M.

    The present work investigates the possibility to charge a Lithium micro-battery (LiB) via direct conversion of ambient mechanical energy into electricity using piezoelectric ZnO nanowire (NW) based microgenerators (PGs). An estimate is provided for the power levels at the different stages of mechanical-to-electrical energy conversion chain, in the following areas: (1) PG output, (2) power management block and (3) LiB storage unit. Also covered in this work is the synthesis, which is a prerequisite for realising such PGs. ZnO NWs of 2 μm in length and 200 nm in diameter have been grown using a low temperature (<150 °C) hydrothermal process on 100 μm thick PET substrates (25 × 25 mm2). Substrates containing bi-layer metal layers with dissimilar electro-negativities functioned as a galvanic cell in the growth nutrients, which acted as an electrolyte medium. This necessitated ZnO NWs growth on conductive surfaces, even in the absence of seed layers and/or substrate with specific lattice parameters. Finally, the assembly steps undertaken to realise the fully functional PGs are discussed, and the performances of the final PG are described thereafter. Subjecting such devices to a 10 Hz sinusoidal bending force resulted in a measured PG output of ∼56 mV peak to peak, on 1 MΩ resistive load.

  16. Comparative study on CO2 and CO sensing performance of LaOCl-coated ZnO nanowires.

    PubMed

    Van Hieu, Nguyen; Khoang, Nguyen Duc; Trung, Do Dang; Toan, Le Duc; Van Duy, Nguyen; Hoa, Nguyen Duc

    2013-01-15

    Carbon dioxide (CO(2)) and carbon monoxide (CO) emissions from industries and combustion fuels such as coal, oil, hydrocarbon, and natural gases are increasing, thus causing environmental pollution and climate change. The selective detection of CO(2) and CO gases is important for environmental monitoring and industrial safety applications. In this work, LaOCl-coated ZnO nanowires (NWs) sensors are fabricated and characterized for the detection of CO(2) (250-4000 ppm) and CO (10-200 ppm) gases at different operating temperatures. The effects of the LaCl(3) coating concentration and calcination temperature of the sensors are studied. They are found to have a strong influence on the sensing performance to CO(2) gas, but a relatively slight influence on that to CO. The LaOCl coating enhances the response and shortens the response and recovery times to CO(2) compared with those to CO. The enhanced response of the LaOCl-coated ZnO NW sensors is attributed to the extension of the electron depletion layer due to the formation of p-LaOCl/n-ZnO junctions on the surfaces of the ZnO NWs. PMID:23246957

  17. Piezotronic-effect enhanced drug metabolism and sensing on a single ZnO nanowire surface with the presence of human cytochrome P450.

    PubMed

    Wang, Ning; Gao, Caizhen; Xue, Fei; Han, Yu; Li, Tao; Cao, Xia; Zhang, Xueji; Zhang, Yue; Wang, Zhong Lin

    2015-03-24

    Cytochromes P450 (CYPs) enzymes are involved in catalyzing the metabolism of various endogenous and exogenous compounds. A rapid analysis of drug metabolism reactions by CYPs is required because they can metabolize 95% of current drugs in drug development and effective therapies. Here, we describe a study of piezotronic-effect enhanced drug metabolism and sensing by utilizing a single ZnO nanowire (ZnO NW) device. Owing to the unique hydrophobic feature of a ZnO NW that provides a desirable "microenvironment" for the immobilization of biomolecules, our device can effectively stimulate the tolbutamide metabolism by decorating a ZnO NW with cytochrome P4502C9/CYPs reductase (CYP2C9/CPR) microsomes. By applying an external compressive strain to the ZnO nanowire, the piezotronic effect, which plays a primary role in tuning the transport behavior of a ZnO NW utilizing the created piezoelectric polarization charges at the local interface, can effectively enhance the performance of the device. A theoretical model is proposed using an energy band diagram to explain the experimental data. This study provides a potential approach to study drug metabolism and trace drug detection based on the piezotronic effect. PMID:25758259

  18. Novel synthetic methodology for controlling the orientation of zinc oxide nanowires grown on silicon oxide substrates.

    PubMed

    Cho, Jinhyun; Salleh, Najah; Blanco, Carlos; Yang, Sungwoo; Lee, Chul-Jin; Kim, Young-Woo; Kim, Jungsang; Liu, Jie

    2014-04-01

    This study presents a simple method to reproducibly obtain well-aligned vertical ZnO nanowire arrays on silicon oxide (SiOx) substrates using seed crystals made from a mixture of ammonium hydroxide (NH4OH) and zinc acetate (Zn(O2CCH3)2) solution. In comparison, high levels of OH(-) concentration obtained using NaOH or KOH solutions lead to incorporation of Na or K atoms into the seed crystals, destroying the c-axis alignment of the seeds and resulting in the growth of misaligned nanowires. The use of NH4OH eliminates the metallic impurities and ensures aligned nanowire growth in a wide range of OH(-) concentrations in the seed solution. The difference of crystalline orientations between NH4OH- and NaOH-based seeds is directly observed by lattice-resolved images and electron diffraction patterns using a transmission electron microscope (TEM). This study obviously suggests that metallic impurities incorporated into the ZnO nanocrystal seeds are one of the factors that generates the misaligned ZnO nanowires. This method also enables the use of silicon oxide substrates for the growth of vertically aligned nanowires, making ZnO nanostructures compatible with widely used silicon fabrication technology. PMID:24584438

  19. Surface-plasmon mediated photoluminescence enhancement of Pt-coated ZnO nanowires by inserting an atomic-layer-deposited Al2O3 spacer layer

    NASA Astrophysics Data System (ADS)

    Ren, Qing-Hua; Zhang, Yan; Lu, Hong-Liang; Chen, Hong-Yan; Zhang, Yuan; Li, De-Hui; Liu, Wen-Jun; Ding, Shi-Jin; Jiang, An-Quan; Zhang, David Wei

    2016-04-01

    Surface-plasmon mediated photoluminescence emission enhancement has been investigated for ZnO nanowire (NW)/Pt nanoparticle (NP) nanostructures by inserting an Al2O3 spacer layer. The thickness of the Al2O3 spacer layer and of the Pt NPs capped on the ZnO NWs are well controlled by atomic layer deposition. It is found that the photoluminescence property of the ZnO NW/Al2O3/Pt hybrid structure is highly tunable with respect to the thickness of the inserted Al2O3 spacer layer. The highest enhancement (˜14 times) of the near band emission of ZnO NWs is obtained with an optimized Al2O3 spacer layer thickness of 10 nm leading to a ultraviolet-visible emission ratio of 271.2 compared to 18.8 for bare ZnO NWs. The enhancement of emission is influenced by a Förster-type non-radiative energy transfer process of the exciton energy from ZnO NWs to Pt NPs as well as the coupling effect between excitons of ZnO NWs and surface plasmons of Pt NPs. The highly versatile and tunable photoluminescence properties of Pt-coated ZnO NWs achieved by introducing an Al2O3 spacer layer demonstrate their potential application in highly efficient optoelectronic devices.

  20. Surface-plasmon mediated photoluminescence enhancement of Pt-coated ZnO nanowires by inserting an atomic-layer-deposited Al₂O₃ spacer layer.

    PubMed

    Ren, Qing-Hua; Zhang, Yan; Lu, Hong-Liang; Chen, Hong-Yan; Zhang, Yuan; Li, De-Hui; Liu, Wen-Jun; Ding, Shi-Jin; Jiang, An-Quan; Zhang, David Wei

    2016-04-22

    Surface-plasmon mediated photoluminescence emission enhancement has been investigated for ZnO nanowire (NW)/Pt nanoparticle (NP) nanostructures by inserting an Al2O3 spacer layer. The thickness of the Al2O3 spacer layer and of the Pt NPs capped on the ZnO NWs are well controlled by atomic layer deposition. It is found that the photoluminescence property of the ZnO NW/Al2O3/Pt hybrid structure is highly tunable with respect to the thickness of the inserted Al2O3 spacer layer. The highest enhancement (∼14 times) of the near band emission of ZnO NWs is obtained with an optimized Al2O3 spacer layer thickness of 10 nm leading to a ultraviolet-visible emission ratio of 271.2 compared to 18.8 for bare ZnO NWs. The enhancement of emission is influenced by a Förster-type non-radiative energy transfer process of the exciton energy from ZnO NWs to Pt NPs as well as the coupling effect between excitons of ZnO NWs and surface plasmons of Pt NPs. The highly versatile and tunable photoluminescence properties of Pt-coated ZnO NWs achieved by introducing an Al2O3 spacer layer demonstrate their potential application in highly efficient optoelectronic devices. PMID:26963868

  1. Effect of TiO2 thickness on nanocomposited aligned ZnO nanorod/TiO2 for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Saurdi, I.; Shafura, A. K.; Azhar, N. E. A.; Ishak, A.; Malek, M. F.; Alrokayan, A. H. Salman; Khan, Haseeb A.; Mamat, M. H.; Rusop, M.

    2016-07-01

    The TiO2 films were deposited on glass substrate at different thicknesses with different deposition frequencies (1, 2, 3 and 4 times) using spin coating technique and their structural properties were investigated. Subsequently, the nanocomposited aligned ZnO nanorods and TiO2 were formed by deposited the TiO2 on top of aligned ZnO Nanorod on ITO-coated glass at different thicknesses using the same method of TiO2 deposited on glass substrate. The nanocomposited aligned ZnO nanorod/TiO2 were coated with different thicknesses of 900µm, 1815µm, 2710µm, 3620µm and ZnO without TiO2. The dye-sensitized solar cells were fabricated from the nanocomposited aligned ZnO nanorod/TiO2 with thickness of 900µm, 1815µm, 2710µm and 3620µm and ZnO without TiO2 and their photovoltaic properties of the DSSCs were investigated. From the solar simulator measurement the solar energy conversion efficiency (η) of 2.543% under AM 1.5 was obtained for the ZnO nanorod/TiO2 photoanode-2710µm Dye-Sensitized solar cell.

  2. Development of vertically aligned ZnO-nanowires scintillators for high spatial resolution x-ray imaging

    NASA Astrophysics Data System (ADS)

    Kobayashi, Masakazu; Komori, Jun; Shimidzu, Kaiji; Izaki, Masanobu; Uesugi, Kentaro; Takeuchi, Akihisa; Suzuki, Yoshio

    2015-02-01

    Newly designed scintillator of (0001)-oriented ZnO vertical nanowires (vnws) for X-ray imaging was prepared on a Ga-doped ZnO/soda-lime glass by electrodeposition, and the light emission feature was estimated in a synchrotron radiation facility. The ZnO-vnws scintillator revealed a strong light emission and improved resolution on CMOS image compared with that for the ZnO-layer scintillator, although the light emission performance was deteriorated in comparison to the Lu3Al5O12:Ce3+. The light emission property closely related to the nanostructure and the resultant photoluminescence characteristic.

  3. Development of vertically aligned ZnO-nanowires scintillators for high spatial resolution x-ray imaging

    SciTech Connect

    Kobayashi, Masakazu Komori, Jun; Shimidzu, Kaiji; Izaki, Masanobu; Uesugi, Kentaro; Takeuchi, Akihisa; Suzuki, Yoshio

    2015-02-23

    Newly designed scintillator of (0001)-oriented ZnO vertical nanowires (vnws) for X-ray imaging was prepared on a Ga-doped ZnO/soda-lime glass by electrodeposition, and the light emission feature was estimated in a synchrotron radiation facility. The ZnO-vnws scintillator revealed a strong light emission and improved resolution on CMOS image compared with that for the ZnO-layer scintillator, although the light emission performance was deteriorated in comparison to the Lu{sub 3}Al{sub 5}O{sub 12:}Ce{sup 3+}. The light emission property closely related to the nanostructure and the resultant photoluminescence characteristic.

  4. Fabricating vertically aligned sub-20 nm Si nanowire arrays by chemical etching and thermal oxidation

    NASA Astrophysics Data System (ADS)

    Li, Luping; Fang, Yin; Xu, Cheng; Zhao, Yang; Zang, Nanzhi; Jiang, Peng; Ziegler, Kirk J.

    2016-04-01

    Silicon nanowires (SiNWs) are appealing building blocks in various applications, including photovoltaics, photonics, and sensors. Fabricating SiNW arrays with diameters <100 nm remains challenging through conventional top-down approaches. In this work, chemical etching and thermal oxidation are combined to fabricate vertically aligned, sub-20 nm SiNW arrays. Defect-free SiNWs with diameters between 95 and 200 nm are first fabricated by nanosphere (NS) lithography and chemical etching. The key aspects for defect-free SiNW fabrication are identified as: (1) achieving a high etching selectivity during NS size reduction; (2) retaining the circular NS shape with smooth sidewalls; and (3) using a directional metal deposition technique. SiNWs with identical spacing but variable diameters are demonstrated by changing the reactive ion etching power. The diameter of the SiNWs is reduced by thermal oxidation, where self-limiting oxidation is encountered after oxidizing the SiNWs at 950 °C for 1 h. A second oxidation is performed to achieve vertically aligned, sub-20 nm SiNW arrays. Si/SiO2 core/shell NWs are obtained before removing the oxidized shell. HRTEM imaging shows that the SiNWs have excellent crystallinity.

  5. Self-aligned nanoforest in silicon nanowire for sensitive conductance modulation.

    PubMed

    Seol, Myeong-Lok; Ahn, Jae-Hyuk; Choi, Ji-Min; Choi, Sung-Jin; Choi, Yang-Kyu

    2012-11-14

    A self-aligned and localized nanoforest structure is constructed in a top-down fabricated silicon nanowire (SiNW). The surface-to-volume ratio (SVR) of the SiNW is enhanced due to the local nanoforest formation. The conductance modulation property of the SiNWs, which is an important characteristic in sensor and charge transfer based applications, can be largely enhanced. For the selective modification of the channel region, localized Joule-heating and subsequent metal-assisted chemical etching (mac-etch) are employed. The nanoforest is formed only in the channel region without misalignment due to the self-aligned process of Joule-heating. The modified SiNW is applied to a porphyrin-silicon hybrid device to verify the enhanced conductance modulation. The charge transfer efficiency between the porphyrin and the SiNW, which is caused by external optical excitation, is clearly increased compared to the initial SiNW. The effect of the local nanoforest formation is enhanced when longer etching times and larger widths are used. PMID:23066892

  6. Fabricating vertically aligned sub-20 nm Si nanowire arrays by chemical etching and thermal oxidation.

    PubMed

    Li, Luping; Fang, Yin; Xu, Cheng; Zhao, Yang; Zang, Nanzhi; Jiang, Peng; Ziegler, Kirk J

    2016-04-22

    Silicon nanowires (SiNWs) are appealing building blocks in various applications, including photovoltaics, photonics, and sensors. Fabricating SiNW arrays with diameters <100 nm remains challenging through conventional top-down approaches. In this work, chemical etching and thermal oxidation are combined to fabricate vertically aligned, sub-20 nm SiNW arrays. Defect-free SiNWs with diameters between 95 and 200 nm are first fabricated by nanosphere (NS) lithography and chemical etching. The key aspects for defect-free SiNW fabrication are identified as: (1) achieving a high etching selectivity during NS size reduction; (2) retaining the circular NS shape with smooth sidewalls; and (3) using a directional metal deposition technique. SiNWs with identical spacing but variable diameters are demonstrated by changing the reactive ion etching power. The diameter of the SiNWs is reduced by thermal oxidation, where self-limiting oxidation is encountered after oxidizing the SiNWs at 950 °C for 1 h. A second oxidation is performed to achieve vertically aligned, sub-20 nm SiNW arrays. Si/SiO2 core/shell NWs are obtained before removing the oxidized shell. HRTEM imaging shows that the SiNWs have excellent crystallinity. PMID:26953775

  7. Performance enhancement of multiple-gate ZnO metal-oxide-semiconductor field-effect transistors fabricated using self-aligned and laser interference photolithography techniques

    PubMed Central

    2014-01-01

    The simple self-aligned photolithography technique and laser interference photolithography technique were proposed and utilized to fabricate multiple-gate ZnO metal-oxide-semiconductor field-effect transistors (MOSFETs). Since the multiple-gate structure could improve the electrical field distribution along the ZnO channel, the performance of the ZnO MOSFETs could be enhanced. The performance of the multiple-gate ZnO MOSFETs was better than that of the conventional single-gate ZnO MOSFETs. The higher the drain-source saturation current (12.41 mA/mm), the higher the transconductance (5.35 mS/mm) and the lower the anomalous off-current (5.7 μA/mm) for the multiple-gate ZnO MOSFETs were obtained. PMID:24948884

  8. 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.

  9. Magnetic and optical properties of Mn-doped ZnO vertically aligned nanorods synthesized by hydrothermal technique

    NASA Astrophysics Data System (ADS)

    Panda, J.; Sasmal, I.; Nath, T. K.

    2016-03-01

    In this paper we have reported the synthesis of high quality vertically aligned undoped and Mn-doped ZnO single crystalline nanorods arrays on Si (100) substrates using two steps process, namely, initial slow seed layer formation followed by solution growth employing wet chemical hydrothermal method. The shapes of the as grown single crystalline nanorods are hexagonal. The diameter and length of the as grown undoped ZnO nanorods varies in the range of 80-150 nm and 1.0 - 1.4 μm, respectively. Along with the lattice parameters of the hexagonal crystal structure, the diameter and length of Mn doped ZnO nanorods are found to increase slightly as compared to the undoped ZnO nanorods. The X-ray photoelectron spectroscopy confirms the presence of Mn atoms in Mn2+ state in the single crystalline ZnO nanorods. The recorded photoluminescence spectrum contains two emissions peaks having UV exciton emissions along with a green-yellow emission. The green-yellow emissions provide the evidence of singly ionized oxygen vacancies. The magnetic field dependent magnetization measurements [M (H)] and zero field cooled (ZFC) and field cooled (FC) magnetization [M(T)] measurements have been carried out at different isothermal conditions in the temperature range of 5-300 K. The Mn doped ZnO nanorods clearly show room temperature ferromagnetic ordering near room temperature down to 5 K. The observed magnetization may be attributed to the long range ferromagnetic interaction between bound magnetic polarons led by singly charged oxygen vacancies.

  10. Effect of Mn-doping on the growth mechanism and electromagnetic properties of chrysanthemum-like ZnO nanowire clusters

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

    Chrysanthemum-like ZnO nanowire clusters with different Mn-doping concentrations are prepared by a hydrothermal process. The microstructure, morphology and electromagnetic properties are characterized by x-ray diffractometer high-resolution transmission electron microscopy (HRTEM), a field emission environment scanning electron microscope (FEESEM) and a microwave vector network analyser respectively. The experimental results indicate that the as-prepared products are Mn-doped ZnO single crystalline with a hexagonal wurtzite structure, that the growth habit changes due to Mn-doping and that a good magnetic loss property is found in the Mn-doped ZnO products, and the average magnetic loss tangent tanδm is up to 0.170099 for 3% Mn-doping, while the dielectric loss tangent tanδe is weakened, owing to the fact that ions Mn2+ enter the crystal lattice of ZnO.

  11. Nanofabrication of arrays of silicon field emitters with vertical silicon nanowire current limiters and self-aligned gates

    NASA Astrophysics Data System (ADS)

    Guerrera, S. A.; Akinwande, A. I.

    2016-07-01

    We developed a fabrication process for embedding a dense array (108 cm‑2) of high-aspect-ratio silicon nanowires (200 nm diameter and 10 μm tall) in a dielectric matrix and then structured/exposed the tips of the nanowires to form self-aligned gate field emitter arrays using chemical mechanical polishing (CMP). Using this structure, we demonstrated a high current density (100 A cm‑2), uniform, and long lifetime (>100 h) silicon field emitter array architecture in which the current emitted by each tip is regulated by the silicon nanowire current limiter connected in series with the tip. Using the current voltage characteristics and with the aid of numerical device models, we estimated the tip radius of our field emission arrays to be ≈4.8 nm, as consistent with the tip radius measured using a scanning electron microscope (SEM).

  12. Nanofabrication of arrays of silicon field emitters with vertical silicon nanowire current limiters and self-aligned gates.

    PubMed

    Guerrera, S A; Akinwande, A I

    2016-07-22

    We developed a fabrication process for embedding a dense array (10(8) cm(-2)) of high-aspect-ratio silicon nanowires (200 nm diameter and 10 μm tall) in a dielectric matrix and then structured/exposed the tips of the nanowires to form self-aligned gate field emitter arrays using chemical mechanical polishing (CMP). Using this structure, we demonstrated a high current density (100 A cm(-2)), uniform, and long lifetime (>100 h) silicon field emitter array architecture in which the current emitted by each tip is regulated by the silicon nanowire current limiter connected in series with the tip. Using the current voltage characteristics and with the aid of numerical device models, we estimated the tip radius of our field emission arrays to be ≈4.8 nm, as consistent with the tip radius measured using a scanning electron microscope (SEM). PMID:27292120

  13. Effect of indium on photovoltaic property of n-ZnO/p-Si heterojunction device prepared using solution-synthesized ZnO nanowire film

    NASA Astrophysics Data System (ADS)

    Kathalingam, Adaikalam; Kim, Hyun-Seok; Park, Hyung-Moo; Valanarasu, Santiyagu; Mahalingam, Thaiyan

    2015-01-01

    Preparation of n-ZnO/p-Si heterostructures using solution-synthesized ZnO nanowire films and their photovoltaic characterization is reported. The solution-grown ZnO nanowire film is characterized using scanning electron microscope, electron dispersive x-ray, and optical absorption studies. Electrical and photovoltaic properties of the fabricated heterostructures are studied using e-beam-evaporated aluminum as metal contacts. In order to use transparent contact and to simultaneously collect the photogenerated carriers, sandwich-type solar cells were fabricated using ZnO nanorod films grown on p-silicon and indium tin oxide (ITO) coated glass as ITO/n-ZnO NR/p-Si. The electrical properties of these structures are analyzed from current-voltage (I-V) characteristics. ZnO nanowire film thickness-dependent photovoltaic properties are also studied. Indium metal was also deposited over the ZnO nanowires and its effects on the photovoltaic response of the devices were studied. The results demonstrated that all the samples exhibit a strong rectifying behavior indicating the diode nature of the devices. The sandwich-type ITO/n-ZnO NR/p-Si solar cells exhibit improved photovoltaic performance over the Al-metal-coated n-ZnO/p-Si structures. The indium deposition is found to show enhancement in photovoltaic behavior with a maximum open-circuit voltage (Voc) of 0.3 V and short-circuit current (Isc) of 70×10-6 A under ultraviolet light excitation.

  14. Solution-processed Cu2ZnSnS4 superstrate solar cell using vertically aligned ZnO nanorods.

    PubMed

    Lee, Dongwook; Yong, Kijung

    2014-02-14

    One-dimensional (1D) zinc oxide (ZnO) nanostructures are considered to be promising materials for use in thin film solar cells because of their high light harvesting and charge collection efficiencies. We firstly report enhanced photovoltaic performances in Cu2ZnSnS4 (CZTS) thin film solar cells prepared using ZnO nanostructures. A CdS-coated, vertically well-aligned ZnO nanorod (NR) array was prepared via a hydrothermal reaction and nanocrystal layer deposition (NCLD) and was used as a transparent window/buffer layer in a CZTS thin film photovoltaic. A light absorber CZTS thin film was prepared on the CdS/ZnO NRs in air by depositing a non-toxic precursor solution that was annealed in two steps at temperatures up to 250 °C. The crystallized CZTS phase completely infiltrated the CdS/ZnO NR array. The nanostructured ZnO array provided improved light harvesting behavior compared to a thin film configuration by measuring UV-vis transmittance spectroscopy. The prepared CZTS/CdS/ZnO NR device exhibited a solar energy conversion efficiency of 1.2%, which is the highest efficiency yet reported for nanostructured superstrate CZTS solar cells. PMID:24434835

  15. Photoelectric properties and charge dynamics in ZnO nanowires/Cu{sub 4}Bi{sub 4}S{sub 9} and ZnO nanowires/In{sub 2}O{sub 3}/Cu{sub 4}Bi{sub 4}S{sub 9} heterostructures

    SciTech Connect

    Liu, Xiangyang E-mail: yzgu@henu.edu.cn; Wang, Shun; Gu, Yuzong E-mail: yzgu@henu.edu.cn; Zhang, Jingwei; Zhang, Jiwei

    2014-12-28

    ZnO nanowires arrays were preformed in a horizontal double-tube system. Two types of heterostructures (ZnO nanowires/Cu{sub 4}Bi{sub 4}S{sub 9} and ZnO nanowires/In{sub 2}O{sub 3}/Cu{sub 4}Bi{sub 4}S{sub 9}) and three-dimensional solar cells were fabricated with ZnO nanowires arrays as working electrode, In{sub 2}O{sub 3} as buffer layer, and Cu{sub 4}Bi{sub 4}S{sub 9} as inorganic dye and hole collector. It is suggested that two types of heterostructures have the similar absorption properties with single Cu{sub 4}Bi{sub 4}S{sub 9}. However, the results of steady state and electric field-induced surface photovoltage indicate that ZnO nanowires/In{sub 2}O{sub 3}/Cu{sub 4}Bi{sub 4}S{sub 9} exhibits the higher photovoltaic response than ZnO nanowires/Cu{sub 4}Bi{sub 4}S{sub 9}. Using the transient surface photovoltage spectroscopy, we further studied the separation and transport mechanism of photogenerated charges. Furthermore, Cu{sub 4}Bi{sub 4}S{sub 9}/In{sub 2}O{sub 3}/ZnO cells presents the better performance than Cu{sub 4}Bi{sub 4}S{sub 9}/ZnO cells and the highest efficiencies are about 6.4% and 5.2%, respectively. It is suggested that direct paths, interface barrier, built-in electric field, and double energy level matchings between conduction bands (Cu{sub 4}Bi{sub 4}S{sub 9} and In{sub 2}O{sub 3}, In{sub 2}O{sub 3} and ZnO) have obvious effect on the separation of photogenerated charges. Then we discussed the synthetic action on the charge dynamics from these factors.

  16. Study of Ac Dielectrophoretic Process of SiC Nanowires: A Universal Method for Alignment of Semiconductor Nanowires.

    PubMed

    Yao, Limei; Cui, Yan; Cong, Haining; Zheng, Jinju; Shang, Minghui; Yang, Zuobao; Yang, Weiyou; Wei, Guodong; Gao, Fengmei

    2016-04-01

    In this study, the dielectrophoretic processes of SiC nanowires suspended in three typical solvents, (highly purified water, ethanol and isopropanol) were systematically investigated. Optical microscope and SEM characterizations were used to observe the order of SiC nanowires on the surface of gold microchannels. The gold microchannels were induced by Ac dielectrophoresis of the corresponding dispersion solutions of SiC nanowires, with a concentration of 0.1 mg/mL. The study shows that the dielectrophoresis process is an effective way of synthesizing highly oriented SiC nanoarrays using isopropanol solution. The results also show that the arrangement of SiC nanowires on the interdigital electrode configuration not only depend on the kind of solvent used, but also on the applied frequency (1000 Hz~1 MHz) and voltage (1 V~20 V). PMID:27451739

  17. Structural characterization and low temperature growth of ferromagnetic Bi-Cu codoped ZnO bicrystal nanowires

    NASA Astrophysics Data System (ADS)

    Xu, C.; Chun, J.; Kim, D.; Chon, B.; Joo, T.

    2007-10-01

    Ferromagnetic Bi-Cu codoped ZnO nanowires were fabricated at temperatures as low as 300°C via a vapor phase transport using the mixture of Zn, BiI3 and CuI powders. They are grown as a bicrystal, along the [011¯2] direction, have a width of 40-150nm, and a length of a few microns. The investigation of the growth mechanism proposes that the synergy of BiCu and iodine/iodide induces the formation of bicrystallinity. The photoluminescence measurement shows the cooperative effect of Bi and Cu ions. The ferromagnetism observed in this study is the result of the combined effect of structural defects, the substitution of Cu into Zn site along the c axis, and codoping of Bi.

  18. Photoluminescence Analysis of Energy Level on Li-Doped ZnO Nanowires Grown by a Hydrothermal Method

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    The optical and structural properties of Li-doped ZnO nanowires grown by a hydrothermal method are reported herein. The low-temperature and temperature-dependent photoluminescence spectra clearly exhibited emission peaks that confirmed the presence of a lithium impurity as an acceptor dopant. Particularly, the acceptor energy level of the Li dopant was estimated to be 121 meV from the PL spectra. This value was also indicated from an Arrhenius plot of the integrated PL intensity of the A°X emission as a function of temperature. These results are in agreement with theoretical and experimental results of previously considered p-type dopants reported in other studies.

  19. Photoluminescence Analysis of Energy Level on Li-Doped ZnO Nanowires Grown by a Hydrothermal Method

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    The optical and structural properties of Li-doped ZnO nanowires grown by a hydrothermal method are reported herein. The low-temperature and temperature-dependent photoluminescence spectra clearly exhibited emission peaks that confirmed the presence of a lithium impurity as an acceptor dopant. Particularly, the acceptor energy level of the Li dopant was estimated to be 121 meV from the PL spectra. This value was also indicated from an Arrhenius plot of the integrated PL intensity of the A\\circX emission as a function of temperature. These results are in agreement with theoretical and experimental results of previously considered p-type dopants reported in other studies.

  20. Characteristics of Al substituted nanowires fabricated by self-aligned growth for future large scale integration interconnects

    NASA Astrophysics Data System (ADS)

    Kudo, Hiroshi; Kurahashi, Teruo

    2011-06-01

    Substituted Al nanowires for use in future large scale integration interconnects were fabricated by self-aligned growth. The resistivity of an Al substituted nanowire 80 nm in width, 100 nm in height, and 20 μm in length was 4.7 μΩ cm, which is 48% lower than that of an Al nanowire with the same dimensions fabricated using a bottom-up approach. The variation in the resistivity was in a narrow range (14%) over a Si wafer. The TEM imaging revealed that the Al substituted nanowire had a bamboo-like structure with grains larger than 1.6 μm. The electromigration activation energy was 0.72 eV, which is comparable to that of a pure Al wire with a bamboo-like structure. The product of the critical current density and wire length was 1.3 × 103 A/cm at 250 °C; 2.1 times higher than that of a pure Al wire with a polycrystalline structure. The acceleration of electromigration due to current density was 2.0, indicating that incubation time dominates electromigration lifetime. The prolonged incubation time observed in the electromigration test is attributed to the reduction in electromigration-induced mass transport due to the microstructure of the Al substituted nanowire. Even the formation of a small void immediately after incubation may be a fatal defect for nanoscale Al wires.

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

    SciTech Connect

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

    2015-06-24

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

  2. Growth, patterning and alignment of organolead iodide perovskite nanowires for optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Deng, Hui; Dong, Dongdong; Qiao, Keke; Bu, Lingling; Li, Bing; Yang, Dun; Wang, Hong-En; Cheng, Yibing; Zhao, Zhixin; Tang, Jiang; Song, Haisheng

    2015-02-01

    Organolead halide perovskites are becoming intriguing materials applied in optoelectronics. In the present work, organolead iodide perovskite (OIP) nanowires (NWs) have been fabricated by a one step self-assembly method. The controllable NW distributions were implemented by a series of facile techniques: monolayer and small diameter NWs were prepared by precursor concentration tuning; NW patterning was achieved via selected area treatment assisted by a mask; NW alignment was implemented by modified evaporation-induced self-assembly (EISA). The synthesized multifunctional NWs were further applied in photodetectors (PDs) and solar cells as application demos. The PD performances have reached 1.32 AW-1 for responsivity, 2.5 × 1012 Jones for detectivity and 0.3 ms for response speed, superior to OIP films and other typical inorganic NW based PD performances. An energy conversion efficiency of ~2.5% has been obtained for NW film based solar cells. The facile fabrication process, controllable distribution and optoelectronic applications make the OIP NWs promising building blocks for future optoelectronics, especially for low dimensional devices.Organolead halide perovskites are becoming intriguing materials applied in optoelectronics. In the present work, organolead iodide perovskite (OIP) nanowires (NWs) have been fabricated by a one step self-assembly method. The controllable NW distributions were implemented by a series of facile techniques: monolayer and small diameter NWs were prepared by precursor concentration tuning; NW patterning was achieved via selected area treatment assisted by a mask; NW alignment was implemented by modified evaporation-induced self-assembly (EISA). The synthesized multifunctional NWs were further applied in photodetectors (PDs) and solar cells as application demos. The PD performances have reached 1.32 AW-1 for responsivity, 2.5 × 1012 Jones for detectivity and 0.3 ms for response speed, superior to OIP films and other typical inorganic

  3. Island nucleation, optical and ferromagnetic properties of vertically aligned secondary growth ZnO : Cu nanorod arrays

    NASA Astrophysics Data System (ADS)

    Huang, Jun; Zhu, Liping; Hu, Liang; Liu, Shijiang; Zhang, Jie; Zhang, Honghai; Yang, Xiaopeng; Sun, Luwei; Li, Dehui; Ye, Zhizhen

    2012-02-01

    The paper reports an island nucleation and secondary growth of aligned ZnO : Cu nanorod arrays via thermal vapor phase transport. Results analysis indicates that the secondary segment is epitaxially grown on the ZnO : Cu nanorods with the radius strongly dependent on temperature and the concentration of zinc vapor. The modified characteristic radius (Rc) model is used to explain the nucleation and secondary growth process. Temperature-dependent photoluminescence spectra indicate that the band gap emission of the secondary growth nanorods is greatly restrained. A controversial 3.31 eV emission (A line) and two different donor-acceptor pair (DAP) recombinations at 3.24 eV and 2.48 eV are observed at 13 K. The A line shows a different behavior from the two DAP emissions during the heat-up process. Intrinsic room temperature ferromagnetism (RTFM) is observed in the secondary growth ZnO : Cu nanorods and it can be explained by oxygen vacancy and copper defects related to bound magnetic polar (BMP) or double exchange mechanism.The paper reports an island nucleation and secondary growth of aligned ZnO : Cu nanorod arrays via thermal vapor phase transport. Results analysis indicates that the secondary segment is epitaxially grown on the ZnO : Cu nanorods with the radius strongly dependent on temperature and the concentration of zinc vapor. The modified characteristic radius (Rc) model is used to explain the nucleation and secondary growth process. Temperature-dependent photoluminescence spectra indicate that the band gap emission of the secondary growth nanorods is greatly restrained. A controversial 3.31 eV emission (A line) and two different donor-acceptor pair (DAP) recombinations at 3.24 eV and 2.48 eV are observed at 13 K. The A line shows a different behavior from the two DAP emissions during the heat-up process. Intrinsic room temperature ferromagnetism (RTFM) is observed in the secondary growth ZnO : Cu nanorods and it can be explained by oxygen vacancy and copper

  4. Phototoxic effects of zinc oxide nanowires (ZnO NWs) complexed with 5-ALA in RD cell line

    NASA Astrophysics Data System (ADS)

    Fakhar-e-Alam, M.; Ali, S. M. U.; Ibupoto, Z. H.; Atif, M.; Willander, M.

    2011-12-01

    In this current study, we have manifested the photosensitizing effects of zinc oxide nanowires (ZnO NWs) in dark as well as under ultra violet light exposure with 240 nm of UV region, using human muscle cancer (Rhybdomyosarcoma cells, RD) as in vitro experimental model. We have fabricated ZnO-NWs on the tip of borosilicate glass capillaries (0.5 μm diameter) and were conjugated using 5-aminolevulinic acid (ALA) for the efficient intracellular drug delivery. When ZnO NWs were applied on tumor localizing drugs with non ionizing illumination, then excited drug liberates reactive oxygen species (ROS), effecting mitochondria and nucleus resulting in cell necrosis within few minutes. During investigations, we observed that when ZnO-NWs grown on intracellular tip was excited by using 240 nm of UV light, as a resultant 625 nm of emitted red light were used as appetizer in the presence of 5-ALA for chemical reaction, which produces singlet oxygen, responsible for cell necrosis. Morphological changes of necrosed cells were examined under microscopy. Moreover, Viability of controlled and treated RD cells with optimum dose of light (UV-Visible) has been assessed by MTT assay as well as reactive oxygen species (ROS) detection.

  5. Enhanced photocatalytic activity of hierarchical ZnO nanoplate-nanowire architecture as environmentally safe and facilely recyclable photocatalyst

    NASA Astrophysics Data System (ADS)

    Xu, Feng; Shen, Yuting; Sun, Litao; Zeng, Haibo; Lu, Yinong

    2011-12-01

    A hierarchical ZnO nanoplate-nanowire (ZNP-ZNW) architecture immobilized onto a substrate via a facile two-step synthesis strategy was used as an environmentally safe and recyclable photocatalyst. It showed greatly enhanced photocatalytic activity compared with a monomorphological ZnO nanoplate structure in the degradation of methyl orange (MO). The higher content of surface oxygen defects, which can capture the photogenerated electrons and holes separately and make them available for decomposing organic contaminants, is considered to play an important role in the degradation of MO and makes a major contribution to the enhanced photocatalysis. Increasing the surface-to-volume (S/V) ratio without limit cannot benefit the photocatalytic activity significantly if there are not enough defects to separate additional photogenerated charges caused by a larger S/V ratio. A detailed photocatalytic mechanism related to surface defects of the hierarchical architecture was clearly demonstrated. The present study provides a new paradigm for further understanding the photocatalytic mechanism and suggests a new direction to design high-efficiency photocatalysts based on increasing the number of surface defects of nanostructures.

  6. Design Concepts, Fabrication and Advanced Characterization Methods of Innovative Piezoelectric Sensors Based on ZnO Nanowires.

    PubMed

    Araneo, Rodolfo; Rinaldi, Antonio; Notargiacomo, Andrea; Bini, Fabiano; Pea, Marialilia; Celozzi, Salvatore; Marinozzi, Franco; Lovat, Giampiero

    2014-01-01

    Micro- and nano-scale materials and systems based on zinc oxide are expected to explode in their applications in the electronics and photonics, including nano-arrays of addressable optoelectronic devices and sensors, due to their outstanding properties, including semiconductivity and the presence of a direct bandgap, piezoelectricity, pyroelectricity and biocompatibility. Most applications are based on the cooperative and average response of a large number of ZnO micro/nanostructures. However, in order to assess the quality of the materials and their performance, it is fundamental to characterize and then accurately model the specific electrical and piezoelectric properties of single ZnO structures. In this paper, we report on focused ion beam machined high aspect ratio nanowires and their mechanical and electrical (by means of conductive atomic force microscopy) characterization. Then, we investigate the suitability of new power-law design concepts to accurately model the relevant electrical and mechanical size-effects, whose existence has been emphasized in recent reviews. PMID:25494351

  7. Design Concepts, Fabrication and Advanced Characterization Methods of Innovative Piezoelectric Sensors Based on ZnO Nanowires

    PubMed Central

    Araneo, Rodolfo; Rinaldi, Antonio; Notargiacomo, Andrea; Bini, Fabiano; Pea, Marialilia; Celozzi, Salvatore; Marinozzi, Franco; Lovat, Giampiero

    2014-01-01

    Micro- and nano-scale materials and systems based on zinc oxide are expected to explode in their applications in the electronics and photonics, including nano-arrays of addressable optoelectronic devices and sensors, due to their outstanding properties, including semiconductivity and the presence of a direct bandgap, piezoelectricity, pyroelectricity and biocompatibility. Most applications are based on the cooperative and average response of a large number of ZnO micro/nanostructures. However, in order to assess the quality of the materials and their performance, it is fundamental to characterize and then accurately model the specific electrical and piezoelectric properties of single ZnO structures. In this paper, we report on focused ion beam machined high aspect ratio nanowires and their mechanical and electrical (by means of conductive atomic force microscopy) characterization. Then, we investigate the suitability of new power-law design concepts to accurately model the relevant electrical and mechanical size-effects, whose existence has been emphasized in recent reviews. PMID:25494351

  8. Surface free-carrier screening effect on the output of a ZnO nanowire nanogenerator and its potential as a self-powered active gas sensor.

    PubMed

    Xue, Xinyu; Nie, Yuxin; He, Bin; Xing, Lili; Zhang, Yan; Wang, Zhong Lin

    2013-06-01

    The output of a piezoelectric nanogenerator (NG) fabricated using ZnO nanowire arrays is largely influenced by the density of the surface charge carriers at the nanowire surfaces. Adsorption of gas molecules could modify the surface carrier density through a screening effect, thus, the output of the NG is sensitive to the gas concentration. Based on such a mechanism, we first studied the responses of an unpackaged NG to oxygen, H2S and water vapor, and demonstrated its sensitivity to H2S to a level as low as 100 ppm. Therefore, the piezoelectric signal generated by a ZnO NWs NG can act not only as a power source, but also as a response signal to the gas, demonstrating a possible approach as a self-powered active gas sensor. PMID:23633477

  9. Insertion of Vertically Aligned Nanowires into Living Cells by Inkjet Printing of Cells.

    PubMed

    Lee, Donggyu; Lee, Daehee; Won, Yulim; Hong, Hyeonaug; Kim, Yongjae; Song, Hyunwoo; Pyun, Jae-Chul; Cho, Yong Soo; Ryu, Wonhyoung; Moon, Jooho

    2016-03-01

    Effective insertion of vertically aligned nanowires (NWs) into cells is critical for bioelectrical and biochemical devices, biological delivery systems, and photosynthetic bioenergy harvesting. However, accurate insertion of NWs into living cells using scalable processes has not yet been achieved. Here, NWs are inserted into living Chlamydomonas reinhardtii cells (Chlamy cells) via inkjet printing of the Chlamy cells, representing a low-cost and large-scale method for inserting NWs into living cells. Jetting conditions and printable bioink composed of living Chlamy cells are optimized to achieve stable jetting and precise ink deposition of bioink for indentation of NWs into Chlamy cells. Fluorescence confocal microscopy is used to verify the viability of Chlamy cells after inkjet printing. Simple mechanical considerations of the cell membrane and droplet kinetics are developed to control the jetting force to allow penetration of the NWs into cells. The results suggest that inkjet printing is an effective, controllable tool for stable insertion of NWs into cells with economic and scale-related advantages. PMID:26800021

  10. Wet etch methods for InAs nanowire patterning and self-aligned electrical contacts

    NASA Astrophysics Data System (ADS)

    Fülöp, G.; d’Hollosy, S.; Hofstetter, L.; Baumgartner, A.; Nygård, J.; Schönenberger, C.; Csonka, S.

    2016-05-01

    Advanced synthesis of semiconductor nanowires (NWs) enables their application in diverse fields, notably in chemical and electrical sensing, photovoltaics, or quantum electronic devices. In particular, indium arsenide (InAs) NWs are an ideal platform for quantum devices, e.g. they may host topological Majorana states. While the synthesis has been continously perfected, only a few techniques have been developed to tailor individual NWs after growth. Here we present three wet chemical etch methods for the post-growth morphological engineering of InAs NWs on the sub-100 nm scale. The first two methods allow the formation of self-aligned electrical contacts to etched NWs, while the third method results in conical shaped NW profiles ideal for creating smooth electrical potential gradients and shallow barriers. Low temperature experiments show that NWs with etched segments have stable transport characteristics and can serve as building blocks of quantum electronic devices. As an example we report the formation of a single electrically stable quantum dot between two etched NW segments.

  11. Aligned silver nanowire-based transparent electrodes for engineering polarisation-selective optoelectronics.

    PubMed

    Park, Byoungchoo; Bae, In-Gon; Huh, Yoon Ho

    2016-01-01

    We herein report on a remarkably simple, fast, and economic way of fabricating homogeneous and well oriented silver nanowires (AgNWs) that exhibit strong in-plane electrical and optical anisotropies. Using a small quantity of AgNW suspension, the horizontal-dip (H-dip) coating method was applied, in which highly oriented AgNWs were deposited unidirectionally along the direction of coating over centimetre-scale lengths very rapidly. In applying the H-dip-coating method, we adjusted the shear strain rate of the capillary flow in the Landau-Levich meniscus of the AgNW suspension, which induced a high degree of uniaxial orientational ordering (0.37-0.43) of the AgNWs, comparable with the ordering seen in archetypal nematic liquid crystal (LC) materials. These AgNWs could be used to fabricate not only transparent electrodes, but also LC-alignment electrodes for LC devices and/or polarising electrodes for organic photovoltaic devices, having the potential to revolutionise the architectures of a number of polarisation-selective opto-electronic devices for use in printed/organic electronics. PMID:26778621

  12. Massive transfer of vertically aligned Si nanowire array onto alien substrates and their characteristics

    NASA Astrophysics Data System (ADS)

    Shiu, Shu-Chia; Hung, Shih-Che; Chao, Jiun-Jie; Lin, Ching-Fuh

    2009-07-01

    Si nanowires (NWs) are promising materials for future electronic, photovoltaic, and sensor applications. So far the Si NWs are mainly formed on particular substrates or at high temperatures, greatly limiting their application flexibility. Here we report a low temperature process for forming and massively transferring vertically aligned Si NWs on alien substrates with a large density of about (3-5) × 10 7 NWs/mm 2. The X-ray diffraction spectrum reveals that the transferred NWs exhibit almost the same crystal property as the bulk Si. Our investigation further shows that the transferred NWs have exceptional optical characteristics. The transferred Si NWs of 12.14 μm exhibit the transmittance as low as 0.3% in the near infrared region and 0.07% in the visible region. The extracted absorption coefficient of Si NWs in the near infrared region is about 3 × 10 3 cm -1, over 30 times larger than that of the bulk Si. Because of the low temperature process, it enables a large variety of alien substrates such as glass and plastics to be used. In addition, the exceptional properties of the transferred NWs offer potential applications for photovoltaic, photo-detectors, sensors, and flexible electronics.

  13. Wet etch methods for InAs nanowire patterning and self-aligned electrical contacts.

    PubMed

    Fülöp, G; d'Hollosy, S; Hofstetter, L; Baumgartner, A; Nygård, J; Schönenberger, C; Csonka, S

    2016-05-13

    Advanced synthesis of semiconductor nanowires (NWs) enables their application in diverse fields, notably in chemical and electrical sensing, photovoltaics, or quantum electronic devices. In particular, indium arsenide (InAs) NWs are an ideal platform for quantum devices, e.g. they may host topological Majorana states. While the synthesis has been continously perfected, only a few techniques have been developed to tailor individual NWs after growth. Here we present three wet chemical etch methods for the post-growth morphological engineering of InAs NWs on the sub-100 nm scale. The first two methods allow the formation of self-aligned electrical contacts to etched NWs, while the third method results in conical shaped NW profiles ideal for creating smooth electrical potential gradients and shallow barriers. Low temperature experiments show that NWs with etched segments have stable transport characteristics and can serve as building blocks of quantum electronic devices. As an example we report the formation of a single electrically stable quantum dot between two etched NW segments. PMID:27040175

  14. Aligned silver nanowire-based transparent electrodes for engineering polarisation-selective optoelectronics

    NASA Astrophysics Data System (ADS)

    Park, Byoungchoo; Bae, In-Gon; Huh, Yoon Ho

    2016-01-01

    We herein report on a remarkably simple, fast, and economic way of fabricating homogeneous and well oriented silver nanowires (AgNWs) that exhibit strong in-plane electrical and optical anisotropies. Using a small quantity of AgNW suspension, the horizontal-dip (H-dip) coating method was applied, in which highly oriented AgNWs were deposited unidirectionally along the direction of coating over centimetre-scale lengths very rapidly. In applying the H-dip-coating method, we adjusted the shear strain rate of the capillary flow in the Landau-Levich meniscus of the AgNW suspension, which induced a high degree of uniaxial orientational ordering (0.37-0.43) of the AgNWs, comparable with the ordering seen in archetypal nematic liquid crystal (LC) materials. These AgNWs could be used to fabricate not only transparent electrodes, but also LC-alignment electrodes for LC devices and/or polarising electrodes for organic photovoltaic devices, having the potential to revolutionise the architectures of a number of polarisation-selective opto-electronic devices for use in printed/organic electronics.

  15. Aligned silver nanowire-based transparent electrodes for engineering polarisation-selective optoelectronics

    PubMed Central

    Park, Byoungchoo; Bae, In-Gon; Huh, Yoon Ho

    2016-01-01

    We herein report on a remarkably simple, fast, and economic way of fabricating homogeneous and well oriented silver nanowires (AgNWs) that exhibit strong in-plane electrical and optical anisotropies. Using a small quantity of AgNW suspension, the horizontal-dip (H-dip) coating method was applied, in which highly oriented AgNWs were deposited unidirectionally along the direction of coating over centimetre-scale lengths very rapidly. In applying the H-dip-coating method, we adjusted the shear strain rate of the capillary flow in the Landau-Levich meniscus of the AgNW suspension, which induced a high degree of uniaxial orientational ordering (0.37–0.43) of the AgNWs, comparable with the ordering seen in archetypal nematic liquid crystal (LC) materials. These AgNWs could be used to fabricate not only transparent electrodes, but also LC-alignment electrodes for LC devices and/or polarising electrodes for organic photovoltaic devices, having the potential to revolutionise the architectures of a number of polarisation-selective opto-electronic devices for use in printed/organic electronics. PMID:26778621

  16. Hydrothermal growth and characterization of vertically well-aligned and dense ZnO nanorods on glass and silicon using a simple optimizer system

    NASA Astrophysics Data System (ADS)

    Mohammad, Sabah M.; Hassan, Z.; Ahmed, Naser M.; Talib, Rawnaq A.; Abd-Alghafour, Nabeel M.; Omar, A. F.

    2016-07-01

    Vertically, well-aligned and high density ZnO nanorods were successfully hydrothermally grown on glass and silicon substrates using a simple and low cost system. The mechanism of synthesis of ZnO nanorods, generated with our system under hydrothermal conditions, is investigated in this report. Field-emission scanning electron microscopy indicated that the fabricated ZnO nanorods on both substrates have hexagonal shape with diameters ranging from 20 nm to 70 nm which grew vertically from the substrate. XRD analysis confirms the formation of wurtzite ZnO phase with a preferred orientation along (002) direction perpendicular on the substrate and enhanced crystallinity. The low value of the tensile strain (0.126 %) revealed that ZnO nanorods preferred to grow along the c-axis for both substrates. Photoluminescence spectra exhibited a strong, sharp UV near band edge emission peak with narrow FWHM values for both samples.

  17. Low-Cost and High-Productivity Three-Dimensional Nanocapacitors Based on Stand-Up ZnO Nanowires for Energy Storage.

    PubMed

    Wei, Lei; Liu, Qi-Xuan; Zhu, Bao; Liu, Wen-Jun; Ding, Shi-Jin; Lu, Hong-Liang; Jiang, Anquan; Zhang, David Wei

    2016-12-01

    Highly powered electrostatic capacitors based on nanostructures with a high aspect ratio are becoming critical for advanced energy storage technology because of their high burst power and energy storage capability. We report the fabrication process and the electrical characteristics of high capacitance density capacitors with three-dimensional solid-state nanocapacitors based on a ZnO nanowire template. Stand-up ZnO nanowires are grown face down on p-type Si substrates coated with a ZnO seed layer using a hydrothermal method. Stacks of AlZnO/Al2O3/AlZnO are then deposited sequentially on the ZnO nanowires using atomic layer deposition. The fabricated capacitor has a high capacitance density up to 92 fF/μm(2) at 1 kHz (around ten times that of the planar capacitor without nanowires) and an extremely low leakage current density of 3.4 × 10(-8) A/cm(2) at 2 V for a 5-nm Al2O3 dielectric. Additionally, the charge-discharge characteristics of the capacitor were investigated, indicating that the resistance-capacitance time constants were 550 ns for both the charging and discharging processes and the time constant was not dependent on the voltage. This reflects good power characteristics of the fabricated capacitors. Therefore, the current work provides an exciting strategy to fabricate low-cost and easily processable, high capacitance density capacitors for energy storage. PMID:27097913

  18. TEM Study of the Growth Mechanism, Phase Transformation, and Core/shell Structure of Semiconductor Nanowires

    NASA Astrophysics Data System (ADS)

    Wong, Tai Lun

    fast and completed instantly due to high temperature annealing. Furthermore, the phase transformation preferred to begin at the defect and bending region of the nanowires, as the nickel can easily diffuse through the native oxide on the Si nanowires rather than the other regions. By removing the native oxide on the Si nanowires using HF, the temperature required for the phase transformation was decreased significantly. However, without the native oxide, the phase transformation became a multi-site nucleation process, and the nanowire became a polycrystalline and multiphase nickel silicide nanowires after the reaction. A simple and effective method is developed for fabricating high-quality vertically aligned ZnO nanowire arrays using carbonized photoresists. ZnO nanowires fabricated by this method show excellent alignment, crystal quality, and optical properties that are independent of the substrates. We further fabricated vertically aligned ZnO/a-Si core-shell heterojunction nanowire arrays through direct chemical vapor deposition (CVD) of amorphous silicon on ZnO nanowire surfaces. The thickness of the a-Si shells linearly increases with deposition time and the deposition rate was about 5nm/min at 530 °C. Since the Si shell is p-type and the ZnO core is intrinsic n-type semiconductors, the ZnO/ amorphous silicon core-shell nanowires naturally formed hetero p-n junctions. The antireflection property of the ZnO/amorphous silicon core-shell nanowires is dramatically enhanced due to the rough interface between the ZnO and amorphous silicon. Additionally, the intensity of the Photoluminescence spectrum of ZnO/amorphous silicon core-shell structures is decreasing with the thickness of the amorphous silicon shell increases.

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

    PubMed Central

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  1. In situ ZnO nanowire growth to promote the PVDF piezo phase and the ZnO-PVDF hybrid self-rectified nanogenerator as a touch sensor.

    PubMed

    Li, Zetang; Zhang, Xu; Li, Guanghe

    2014-03-28

    A PVDF-ZnO nanowires (NWs) hybrid generator (PZHG) was designed. A simple, cost effective method to produce the PVDF β phase by nano force is introduced. With the ZnO NWs growing, the in situ nano extension force promotes the phase change. A theoretical analysis of the ZnO NWs acting as a self-rectifier of the nano generator is established. The ZnO NWs acted as a self-adjustment diode to control the current output of the PZHG by piezo-electric and semi-conductive effects. Based on the self-controllability of the piezoelectric output, three kinds of finger touching are distinguished by the output performances of the PZHG, which is applicable to an LCD touch pad. PMID:24515250

  2. Catalyst-free growth of ZnO nanowires on ITO seed/glass by thermal evaporation method: Effects of ITO seed layer thickness

    NASA Astrophysics Data System (ADS)

    Alsultany, Forat H.; Hassan, Z.; Ahmed, Naser M.

    2016-07-01

    A seed/catalyst-free growth of ZnO nanowires (ZnO-NWs) on a glass substrate were successfully fabricated using thermal evaporation technique. These nanowires were grown on ITO seed layers of different thicknesses of 25 and 75 nm, which were deposited on glass substrates by radio frequency (RF) magnetron sputtering. Prior to synthesized ITO nanowires, the sputtered ITO seeds were annealed using the continuous wave (CW) CO2 laser at 450 °C in air for 15 min. The effect of seed layer thickness on the morphological, structural, and optical properties of ZnO-NWs were systematically investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and UV-Vis spectrophotometer.

  3. Volumetric Heating of Ultra-High Energy Density Relativistic Plasmas by Ultrafast Laser Irradiation of Aligned Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    Bargsten, Clayton; Hollinger, Reed; Shlyaptsev, Vyacheslav; Pukhov, Alexander; Keiss, David; Townsend, Amanda; Wang, Yong; Wang, Shoujun; Prieto, Amy; Rocca, Jorge

    2014-10-01

    We have demonstrated the volumetric heating of near-solid density plasmas to keV temperatures by ultra-high contrast femtosecond laser irradiation of arrays of vertically aligned nanowires with an average density up to 30% solid density. X-ray spectra show that irradiation of Ni and Au nanowire arrays with laser pulses of relativistic intensities ionizes plasma volumes several micrometers in depth to the He-like and Co-like (Au 52 +) stages respectively. The penetration depth of the heat into the nanowire array was measured monitoring He-like Co lines from irradiated arrays in which the nanowires are composed of a Co segment buried under a selected length of Ni. The measurement shows the ionization reaches He-like Co for depth of up to 5 μm within the target. This volumetric plasma heating approach creates a new laboratory plasma regime in which extreme plasma parameters can be accessed with table-top lasers. Scaling to higher laser intensities promises to create plasmas with temperatures and pressures approaching those in the center of the sun. Work supported by the U.S Department of Energy, Fusion Energy Sciences and the Defense Threat Reduction Agency grant HDTRA-1-10-1-0079. A.P was supported by of DFG-funded project TR18.

  4. Vertically aligned ZnO nanorod core-polypyrrole conducting polymer sheath and nanotube arrays for electrochemical supercapacitor energy storage

    PubMed Central

    2014-01-01

    Nanocomposite electrodes having three-dimensional (3-D) nanoscale architecture comprising of vertically aligned ZnO nanorod array core-polypyrrole (PPy) conducting polymer sheath and the vertical PPy nanotube arrays have been investigated for supercapacitor energy storage. The electrodes in the ZnO nanorod core-PPy sheath structure are formed by preferential nucleation and deposition of PPy layer over hydrothermally synthesized vertical ZnO nanorod array by controlled pulsed current electropolymerization of pyrrole monomer under surfactant action. The vertical PPy nanotube arrays of different tube diameter are created by selective etching of the ZnO nanorod core in ammonia solution for different periods. Cyclic voltammetry studies show high areal-specific capacitance approximately 240 mF.cm-2 for open pore and approximately 180 mF.cm-2 for narrow 30-to-36-nm diameter PPy nanotube arrays attributed to intensive faradic processes arising from enhanced access of electrolyte ions through nanotube interior and exterior. Impedance spectroscopy studies show that capacitive response extends over larger frequency domain in electrodes with PPy nanotube structure. Simulation of Nyquist plots by electrical equivalent circuit modeling establishes that 3-D nanostructure is better represented by constant phase element which accounts for the inhomogeneous electrochemical redox processes. Charge-discharge studies at different current densities establish that kinetics of the redox process in PPy nanotube electrode is due to the limitation on electron transport rather than the diffusive process of electrolyte ions. The PPy nanotube electrodes show deep discharge capability with high coulomb efficiency and long-term charge-discharge cyclic studies show nondegrading performance of the specific areal capacitance tested for 5,000 cycles. PMID:25246867

  5. A reticulate superhydrophobic self-assembly structure prepared by ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Gong, Maogang; Xu, Xiaoliang; Yang, Zhou; Liu, Yuanyue; Lv, Haifei; Lv, Liu

    2009-04-01

    A simple hydrothermal self-assembly method was adopted to grow a newly reported superhydrophobic reticulate ZnO film with papillary nodes. The formation mechanism has also been explained by the tension junction model. This structure can extremely enhance the dewettability for the surface modification with low-surface-energy materials such as long chain fluorinated organic compounds. The surfaces of the ZnO thin film were superhydrophobic with a contact angle (CA) of 170° ± 1°, while the sliding angle (SA) is 2°. The samples were characterized by field emission scanning electron microscopy (FESEM).

  6. EFFECT OF PRE-ANNEALING TEMPERATURE ON THE GROWTH OF ALIGNED α-Fe2O3 NANOWIRES VIA A TWO-STEP THERMAL OXIDATION

    NASA Astrophysics Data System (ADS)

    Rashid, Norhana Mohamed; Kishi, Naoki; Soga, Tetsuo

    2016-03-01

    Pre-annealing as part of a two-step thermal oxidation process has a significant effect on the growth of hematite (α-Fe2O3) nanowires on Fe foil. High-density aligned nanowires were obtained on iron foils pre-annealed at 300∘C under a dry air flow for 30min. The X-ray diffraction (XRD) patterns indicate that the nanowires are transformed from the small α-Fe2O3 grains and uniquely grow in the (110) direction. The formation of a high-density of small grains by pre-annealing improved the alignment and density of the α-Fe2O3 nanowires.

  7. Application of Chemical Doping and Architectural Design Principles To Fabricate Nanowire Co2Ni3ZnO8 Arrays for Aqueous Asymmetric Supercapacitors.

    PubMed

    Liu, Qi; Yang, Bin; Liu, Jingyuan; Yuan, Yi; Zhang, Hongsen; Liu, Lianhe; Wang, Jun; Li, Rumin

    2016-08-10

    Electrode materials derived from transition metal oxides have a serious problem of low electron transfer rate, which restricts their practical application. However, chemically doped graphene transforms the chemical bonding configuration to enhance electron transfer rate and, therefore, facilitates the successful fabrication of Co2Ni3ZnO8 nanowire arrays. In addition, the Co2Ni3ZnO8 electrode materials, considered as Ni and Zn ions doped into Co3O4, have a high electron transfer rate and electrochemical response capability, because the doping increases the degree of crystal defect and reaction of Co/Ni ions with the electrolyte. Hence, the Co2Ni3ZnO8 electrode exhibits a high rate property and excellent electrochemical cycle stability, as determined by electrochemical analysis of the relationship between specific capacitance, IR drop, Coulomb efficiency, and different current densities. From the results of a three-electrode system of electrochemical measurement, the Co2Ni3ZnO8 electrode demonstrates a specific capacitance of 1115 F g(-1) and retains 89.9% capacitance after 2000 cycles at a current density of 4 A g(-1). The energy density of the asymmetric supercapacitor (AC//Co2Ni3ZnO8) is 54.04 W h kg(-1) at the power density of 3200 W kg(-1). PMID:27428712

  8. High-performance flexible Ag nanowire electrode with low-temperature atomic-layer-deposition fabrication of conductive-bridging ZnO film.

    PubMed

    Duan, Ya-Hui; Duan, Yu; Chen, Ping; Tao, Ye; Yang, Yong-Qiang; Zhao, Yi

    2015-01-01

    As material for flexible transparent electrodes for organic photoelectric devices, the silver nanowires (AgNWs) have been widely studied. In this work, we propose a hybrid flexible anode with photopolymer substrate, which is composed of spin-coating-processed AgNW meshes and of zinc oxide (ZnO) prepared by low-temperature (60°C) atomic layer deposition. ZnO effectively fills in the voids of the AgNW mesh electrode, which is thus able to contact to the device all over the active area, to allow for efficient charge extraction/injection. Furthermore, ZnO grown by low temperature mainly relies on hole conduction to make the anode play a better role. Hole-only devices are fabricated to certify the functionality of the low-temperature ZnO film. Finally, we confirm that the ZnO film grown at a low temperature bring a significant contribution to the performance of the modified AgNW anode. PMID:25852386

  9. High-performance flexible Ag nanowire electrode with low-temperature atomic-layer-deposition fabrication of conductive-bridging ZnO film

    NASA Astrophysics Data System (ADS)

    Duan, Ya-Hui; Duan, Yu; Chen, Ping; Tao, Ye; Yang, Yong-Qiang; Zhao, Yi

    2015-02-01

    As material for flexible transparent electrodes for organic photoelectric devices, the silver nanowires (AgNWs) have been widely studied. In this work, we propose a hybrid flexible anode with photopolymer substrate, which is composed of spin-coating-processed AgNW meshes and of zinc oxide (ZnO) prepared by low-temperature (60°C) atomic layer deposition. ZnO effectively fills in the voids of the AgNW mesh electrode, which is thus able to contact to the device all over the active area, to allow for efficient charge extraction/injection. Furthermore, ZnO grown by low temperature mainly relies on hole conduction to make the anode play a better role. Hole-only devices are fabricated to certify the functionality of the low-temperature ZnO film. Finally, we confirm that the ZnO film grown at a low temperature bring a significant contribution to the performance of the modified AgNW anode.

  10. Development of novel implants with self-antibacterial performance through in-situ growth of 1D ZnO nanowire.

    PubMed

    Wang, Wenhao; Li, Tak Lung; Wong, Hoi Man; Chu, Paul K; Kao, Richard Y T; Wu, Shuilin; Leung, Frankie K L; Wong, Tak Man; To, Michael K T; Cheung, Kenneth M C; Yeung, Kelvin W K

    2016-05-01

    To prevent the attachment of bacteria to implant surfaces, the 1D zinc oxide nanowire-coating has been successfully developed on material surfaces by using a custom-made hydrothermal approach. The chemical nature, surface topography and wettability of spike-like 1D ZnO nanowire-coating are comprehensively investigated. The anti-adhesive and antimicrobial properties of 1D nanowire-coating are tested against Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli by using in vitro live/dead staining and scanning electron microscopy. We find that the adhesion of bacteria can be reduced via the special spike-like topography and that the release of Zn(2+) ions can help suppress the growth of attached bacteria. Furthermore, the antimicrobial effect is also evaluated under in vivo conditions by using a rat model infected with bioluminescent S. aureus. The amount of live bacteria in the rat implanted with a nanowire-coated sample is less than that of the control at various time points. Hence, it is believed that the nanowire-coated material is promising for application in orthopaedic implantation after the long-term animal studies have been completed. PMID:26918511

  11. Scalable synthesis of vertically aligned, catalyst-free gallium arsenide nanowire arrays: towards optimized optical absorption

    NASA Astrophysics Data System (ADS)

    Yao, Maoqing; Madaria, Anuj R.; Chi, ChunYung; Huang, Ningfeng; Lin, Chenxi; Povinelli, Michelle L.; Dapkus, P. Daniel; Zhou, Chongwu

    2012-06-01

    Recently nanostructure materials have emerged as a building block for constructing next generation of photovoltaic devices. Nanowire based semiconductor solar cells, among other candidates, have shown potential to produce high efficiency. In a radial pn junction light absorption and carrier collection can be decoupled. Also nanowires can increase choice of materials one can use to fabricate high efficiency tandem solar cells by relaxing the lattice-match constraint. Here we report synthesis of vertical III-V semiconducting nanowire arrays using Selective-Area Metal Organic Chemical Vapor Deposition (SA-MOCVD) technique, which can find application in various optoelectronic devices. We also demonstrate nanosphere lithography (NSL) patterning techniques to obtain ordered pattern for SAMOCVD. Reflection spectrum of nanowires array made by this technique shows excellent light absorption performance without additional anti-reflection coating layer. Thus, we show that highly ordered nanowire structure is 'not needed' to maximize the absorption in vertical nanowire array. Our scalable approach for synthesis of vertical semiconducting nanowire can have application in high throughput and low cost optoelectronic devices including photovoltaic devices.

  12. Polycrystalline nanowires of gadolinium-doped ceria via random alignment mediated by supercritical carbon dioxide

    PubMed Central

    Kim, Sang Woo; Ahn, Jae-Pyoung

    2013-01-01

    This study proposes a seed/template-free method that affords high-purity semiconducting nanowires from nanoclusters, which act as basic building blocks for nanomaterials, under supercritical CO2 fluid. Polycrystalline nanowires of Gd-doped ceria (Gd-CeO2) were formed by CO2-mediated non-oriented attachment of the nanoclusters resulting from the dissociation of single-crystalline aggregates. The unique formation mechanism underlying this morphological transition may be exploited for the facile growth of high-purity polycrystalline nanowires. PMID:23572061

  13. Ultrafast photoluminescence features analysis of In-doped ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Zhao, Qingming

    2011-08-01

    ZnO has been researched for its excellent properties for optoelectronic, sensing, piezoelectric application, solar cells, light emitting diodes and laser diodes. Transparent oxide semiconductor (TOS) thin films made of ZnO nanocomposites, which are used as transparent electrodes in optoelectronic devices, have been widely reported. Among the TOSs, the thin films of a homologous compound, with a so-called superlattice structure have attracted considerable interest. Because of the spatial confinement of conductive electrons in the two dimensional layer, their interesting electronic, optical, and magnetic properties, along with small size and chemical reactivity, have led to a wide range of applications in nano-optoelectronics, medical diagnostics, catalysis, and chemical sensing. In this paper, the ultrafast dynamics and the nonlinear optical response of metal nanocomposites were investigated. Heat treatment has been proven to be a feasible way to improve the performance of ultrafast response for this kind of materials. Based on the experimental results of In-doped ZnO materials excited by intense fs pulses near 800 nm, nonlinear optical effects that may emerge under an intense field are attributed to be responsible for the efficient two-photon absorption process under detuned excitation.

  14. Optical and Electrical Investigation of ZnO Nano-Wire Array to Micro-Flower from Hierarchical Nano-Rose Structures.

    PubMed

    Pal, Kaushik; Zhan, Bihong; Ma, Xiao; Wang, Guoping; Schirhagl, Romana; Murgasen, Priya

    2016-01-01

    We have demonstrated a simple solvo-chemical and solvo-thermal route to design various nano-structures growth of zinc oxide (ZnO). The shapes and morphologies can be easily controlled by using different ambient conditions. We successfully fabricated ZnO nano-wires array on ITO substrate. Those nano-wire array center gradually formed micro-flower like structure evolved in this solvo-chemical route. This novel synthesis happened under cationic surfactant CTAB in the solution helps to form hierarchical structures of ZnO. The length of nano-wire is around 2.0 µm, which formed micro-flower diameter 5.0 µm. Micro-flowers were scratched out from ITO substrate thin film and annealed at 650 °C in electric oven for 1 hour, eventually this micro-flower transformed to novel nano-rose structure confirmed by electron microscopic study. Synthesized nano-rose diameter was around 730 nm. Moreover, we found a drastic change of dielectric behavior and DC conductivity of ZnO nanostructures depending on geometry regulated by the duration of preparation. Interestingly enough, optical and electrical properties also changed due to different crystalline structure formation. The dielectric constant is higher at 7.5 also high threshold voltages at 4 V, corresponds to nano-wires array with micro-flower system. A detail dielectric analysis of one step behavior of broad single relaxation peak was obtained only shows the normal dispersion in this system from 1000 kHz to 10 MHz. While less dielectric constant 1.7 and low threshold voltage 1 V, investigated nano-wires with micro-flower, then nano-rose transition appeared in two step behaviors of double relaxations phenomenon appeared one at low frequency and other at higher frequency region. Besides, I~V response characteristics is new idea about different breakdown voltages and bi-stable DC switching capability. Our work demonstrates the possibility of a fast novel synthesis route using a Solvo-chemical process for this type of nanomaterials

  15. SERS detection and antibacterial activity from uniform incorporation of Ag nanoparticles with aligned Si nanowires

    NASA Astrophysics Data System (ADS)

    Chen, Chia-Yun; Hsu, Li-Jen; Hsiao, Po-Hsuan; Yu, Chang-Tze Ricky

    2015-11-01

    We present a facile, reliable and controllable two-steps electroless deposition for uniformly decorating the silver (Ag) nanoparticles (NPs) on the highly aspect ratio of silicon (Si) nanowire arrays. Different from the direct Ag-loading process, which is normally challenged by the non-uniform coating of Ag, the formation of Ag NPs using such innovative electroless process is no longer to be limited at top nanowire surfaces solely; instead, each Ag+/Si interface can initiate the galvanic reduction of Ag+ ions, thus resulting in the uniform formation of Ag NPs on the entire Si nanowire arrays. In addition, systematic explorations of surface-enhanced Raman scattering (SERS) capability as well as antibacterial activity of the Ag/Si-incorporated nanostructures were performed, and the optimized Ag loadings on Si nanowire-based substrates along with the kinetic investigations were further revealed, which may benefit their practical applications in sensing, medical and biological needs.

  16. Inorganic Nano Light-Emitting Transistor: p-Type Porous Silicon Nanowire/n-Type ZnO Nanofilm.

    PubMed

    Lee, Sang Hoon; Kim, Jong Woo; Lee, Tae Il; Myoung, Jae Min

    2016-08-01

    An inorganic nano light-emitting transistor (INLET) consisting of p-type porous Si nanowires (PoSiNWs) and an n-type ZnO nanofilm was integrated on a heavily doped p-type Si substrate with a thermally grown SiO2 layer. To verify that modulation of the Fermi level of the PoSiNWs is key for switchable light emitting, I-V and electroluminescent characteristics of the INLET are investigated as a function of gate bias (V g ). As the V g is changed from 0 V to -20 V, the current level and light-emission intensity in the orange-red range increase by three and two times, respectively, with a forward bias of 20 V in the p-n junction, compared to those at a V g of 0 V. On the other hand, as the V g approaches 10 V, the current level decreases and the emission intensity is reduced and then finally switched off. This result arises from the modulation of the Fermi level of the PoSiNWs and the built-in potential at the p-n junction by the applied gate electric field. PMID:27378257

  17. 3D branched ZnO nanowire arrays decorated with plasmonic au nanoparticles for high-performance photoelectrochemical water splitting.

    PubMed

    Zhang, Xing; Liu, Yang; Kang, Zhenhui

    2014-03-26

    Plasmonic photoelectrochemical (PEC) water splitting is very promising in the conversion of abundant solar energy into chemical energy. However, the solar-to-hydrogen efficiencies reported so far are still too low for practical use, which can be improved by optimizing the design and synthesis of individual blocks (i. e., the compositions, sizes, shapes of the metal and the coupling semiconductors) and the assembly of these blocks into targeted three-dimensional (3D) structures. Here, we constructed a composite plasmonic metal/semiconductor photoanode by decorating gold nanoparticles (Au NPs) on 3D branched ZnO nanowire arrays (B-ZnO NWs) through a series of simple solution chemical routes. The 3D ordered Au/B-ZnO NWs photoanodes exhibited excellent PEC activities in both ultraviolet and visible region. The improved photoactivities in visible region were demonstrated to be caused by the surface-plasmon-resonance effect of Au NPs. The photoconversion efficiency of Au/B-ZnO NWs photoanode reached 0.52% under simulated sunlight illumination. This is a high value of solar-to-hydrogen efficiencies reported till nowadays for plasmonic PEC water splitting, which was mainly benefit from the extensive metal/semiconductor interfaces for efficient extraction of hot electron from Au NPs and excellent charge-carries collection efficiency of the 3D ordered Au/B-ZnO NWs photoelectrode. PMID:24598779

  18. Self-powered ultraviolet photodetectors based on selectively grown ZnO nanowire arrays with thermal tuning performance.

    PubMed

    Bai, Zhiming; Chen, Xiang; Yan, Xiaoqin; Zheng, Xin; Kang, Zhuo; Zhang, Yue

    2014-05-28

    A self-powered Schottky-type ultraviolet photodetector with Al-Pt interdigitated electrodes has been fabricated based on selectively grown ZnO nanowire arrays. At zero bias, the fabricated photodetector exhibited high sensitivity and excellent selectivity to UV light illumination with a fast response time of 81 ms. By tuning the Schottky barrier height through the thermally induced variation of the interface chemisorbed oxygen, an ultrahigh sensitivity of 3.1 × 10(4) was achieved at 340 K without an external power source, which was 82% higher than that obtained at room temperature. According to the thermionic emission-diffusion theory and the solar cell theory, the changes in the photocurrent of the photodetector at zero bias with various system temperatures were calculated, which agreed well with the experimental data. This work demonstrates a promising approach to modulating the performance of a self-powered photodetector by heating and provides theoretical support for studying the thermal effect on the future photoelectric device. PMID:24728006

  19. Oxide mediated liquid-solid growth of high aspect ratio aligned gold silicide nanowires on Si(110) substrates.

    PubMed

    Bhatta, Umananda M; Rath, Ashutosh; Dash, Jatis K; Ghatak, Jay; Yi-Feng, Lai; Liu, Chuan-Pu; Satyam, P V

    2009-11-18

    Silicon nanowires grown using the vapor-liquid-solid method are promising candidates for nanoelectronics applications. The nanowires grow from an Au-Si catalyst during silicon chemical vapor deposition. In this paper, the effect of temperature, oxide at the interface and substrate orientation on the nucleation and growth kinetics during formation of nanogold silicide structures is explained using an oxide mediated liquid-solid growth mechanism. Using real time in situ high temperature transmission electron microscopy (with 40 ms time resolution), we show the formation of high aspect ratio ( approximately 15.0) aligned gold silicide nanorods in the presence of native oxide at the interface during in situ annealing of gold thin films on Si(110) substrates. Steps observed in the growth rate and real time electron diffraction show the existence of liquid Au-Si nano-alloy structures on the surface besides the un-reacted gold nanostructures. These results might enable us to engineer the growth of nanowires and similar structures with an Au-Si alloy as a catalyst. PMID:19843987

  20. Oxide mediated liquid-solid growth of high aspect ratio aligned gold silicide nanowires on Si(110) substrates

    NASA Astrophysics Data System (ADS)

    Bhatta, Umananda M.; Rath, Ashutosh; Dash, Jatis K.; Ghatak, Jay; Yi-Feng, Lai; Liu, Chuan-Pu; Satyam, P. V.

    2009-11-01

    Silicon nanowires grown using the vapor-liquid-solid method are promising candidates for nanoelectronics applications. The nanowires grow from an Au-Si catalyst during silicon chemical vapor deposition. In this paper, the effect of temperature, oxide at the interface and substrate orientation on the nucleation and growth kinetics during formation of nanogold silicide structures is explained using an oxide mediated liquid-solid growth mechanism. Using real time in situ high temperature transmission electron microscopy (with 40 ms time resolution), we show the formation of high aspect ratio (≈15.0) aligned gold silicide nanorods in the presence of native oxide at the interface during in situ annealing of gold thin films on Si(110) substrates. Steps observed in the growth rate and real time electron diffraction show the existence of liquid Au-Si nano-alloy structures on the surface besides the un-reacted gold nanostructures. These results might enable us to engineer the growth of nanowires and similar structures with an Au-Si alloy as a catalyst.

  1. Temperature dependent electrical transport studies of self-aligned ZnO nanorods/Si heterostructures deposited by sputtering

    SciTech Connect

    Ranwa, Sapana; Dixit, Vivek; Kumar, Mahesh; Kumar Kulriya, Pawan

    2014-06-21

    Self-aligned ZnO nanorods (NRs) were grown on n-Si(100) substrate by RF sputtering techniques. The NRs are uniformly grown on 2-inch wafer along [0001] direction. Single-crystalline wurtzite structure of ZnO NRs was confirmed by X-ray diffraction. The average diameter, height, and density of NRs are found 48 nm, 750 nm, and 1.26 × 10{sup 10} cm{sup −2}, respectively. The current-voltages (I-V) characteristics of ZnO NRs/Si heterojunction (HJ) were studied in the temperature range of 120–300 K and it shows a rectifying behavior. Barrier height (ϕ{sub B}) and ideality factor (η) were estimated from thermionic emission model and found to be highly temperature dependent in nature. Richardson constant (A{sup *}) was evaluated using Richardson plot of ln(I{sub o}/T{sup 2}) versus q/kT plot by linear fitting in two temperature range 120–180 K and 210–300 K. Large deviation in Richardson constant from its theoretical value of n-Si indicates the presence of barrier inhomogeneities at HJ. Double Gaussian distribution of barrier height with thermionic equation gives mean barrier heights of 0.55 ± 0.01 eV and 0.86 ± 0.02 eV for two different temperature regions 120–180 K and 210–300 K, respectively. Modified Richardson plot provided two values of Richardson constant for two temperature regions. However, for higher temperature range (210–300 K), the calculated value of Richardson constant ∼123 A cm{sup −2} K{sup −2} was close to the ideal Richardson constant for n-Si.

  2. Stable field emission from arrays of vertically aligned free-standing metallic nanowires

    NASA Astrophysics Data System (ADS)

    Xavier, Stephane; Mátéfi-Tempfli, Stefan; Ferain, Etienne; Purcell, Stephen; Enouz-Védrenne, Shaïma; Gangloff, Laurent; Minoux, Eric; Hudanski, Ludovic; Vincent, Pascal; Schnell, Jean-Philippe; Pribat, Didier; Piraux, Luc; Legagneux, Pierre

    2008-05-01

    We present a fully elaborated process to grow arrays of metallic nanowires with controlled geometry and density, based on electrochemical filling of nanopores in track-etched templates. Nanowire growth is performed at room temperature, atmospheric pressure and is compatible with low cost fabrication and large surfaces. This technique offers an excellent control of the orientation, shape and nanowires density. It is applied to fabricate field emission arrays with a good control of the emission site density. We have prepared Co, Ni, Cu and Rh nanowires with a height of 3 µm, a diameter of 80 nm and a density of ~107 cm-2. The electron field emission measurements and total energy distributions show that the as-grown nanowires exhibit a complex behaviour, first with emission activation under high field, followed by unstable emission. A model taking into account the effect of an oxide layer covering the nanowire surface is developed to explain this particular field emission behaviour. Finally, we present an in situ cleaning procedure by ion bombardment that collectively removes this oxide layer, leading to a stable and reproducible emission behaviour. After treatment, the emission current density is ~1 mA cm-2 for a 30 V µm-1 applied electric field.

  3. Controllable Growth of Ultrathin P-doped ZnO Nanosheets

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    PubMed

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

    2016-12-01

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

  5. Orientation, alignment, and polytype control in epitaxial growth of SiC nanowires for electronics application in harsh environments

    NASA Astrophysics Data System (ADS)

    Koshka, Yaroslav; Thirumalai, Rooban Venkatesh K. G.; Krishnan, Bharat K.; Levin, Igor; Merrett, J. Neil; Davydov, Albert V.

    2013-09-01

    SiC nanowires (NWs) are attractive building blocks for the next generation electronic devices since silicon carbide is a wide bandgap semiconductor with high electrical breakdown strength, radiation resistance, mechanical strength, thermal conductivity, chemical stability and biocompatibility. Epitaxial growth using metal-catalyst-based vapor-liquid-solid mechanism was employed for SiC NW growth in this work. 4H-SiC substrates having different crystallographic orientations were used in order to control NW alignment and polytype. A new technique based on vapor-phase delivery of the metal catalyst was developed to facilitate control of the NW density. Both 4H and 3C polytypes with a strong stacking disorder were obtained. The 4H and 3C NWs had different orientations with respect to the substrate. 4H NWs grew perpendicular to the c-plane of the substrate. The stacking faults (SFs) in these nanowires were perpendicular to the [0001] nanowire axes. All 3C NWs grew at 20° with respect to the substrate c-plane, and their projections on the c-plane corresponded to one of the six equivalent ⟨101-0⟩ crystallographic directions. All six orientations were obtained simultaneously when growing NWs on the (0001) substrate surface, while only one or two NW orientations were observed when growing NWs on any particular crystallographic plane parallel to the c-axis of the substrate. Growth on {101-0} surfaces resulted in only one NW orientation, thereby producing well-aligned NW arrays. Preliminary measurements of the NW electrical conductivity are reported utilizing two-terminal device geometry.

  6. Modulation of stimulated emission of ZnO nanowire based on electromechanical vibration.

    PubMed

    Li, Lijie

    2016-07-01

    An optical modulator is proposed using a double-clamped nanoelectromechanical resonator. Electromechanical-optical analysis has been performed to validate the idea. The electromechanical simulation involves the nonlocal effect as the resonator is in nanometer scale. Stimulated emission theory has been used to model the luminescence of the nanowire due to the addition of piezoelectric charges subjected to mechanical strains. Results successfully demonstrate both the intensity modulation and frequency filtering, providing an integrated solution in applications such as quantum entanglement experiments. PMID:27409201

  7. High performance non-volatile ferroelectric copolymer memory based on a ZnO nanowire transistor fabricated on a transparent substrate

    SciTech Connect

    Nedic, Stanko; Welland, Mark E-mail: mew10@cam.ac.uk; Tea Chun, Young; Chu, Daping E-mail: mew10@cam.ac.uk; Hong, Woong-Ki

    2014-01-20

    A high performance ferroelectric non-volatile memory device based on a top-gate ZnO nanowire (NW) transistor fabricated on a glass substrate is demonstrated. The ZnO NW channel was spin-coated with a poly (vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) layer acting as a top-gate dielectric without buffer layer. Electrical conductance modulation and memory hysteresis are achieved by a gate electric field induced reversible electrical polarization switching of the P(VDF-TrFE) thin film. Furthermore, the fabricated device exhibits a memory window of ∼16.5 V, a high drain current on/off ratio of ∼10{sup 5}, a gate leakage current below ∼300 pA, and excellent retention characteristics for over 10{sup 4} s.

  8. 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.

  9. Effect of Nb-doped TiO2 on nanocomposited aligned ZnO nanorod/TiO2:Nb for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Saurdi, I.; Shafura, A. K.; Azhar, N. E. A.; Ishak, A.; Malek, M. F.; Alrokayan, A. H. Salman; Khan, Haseeb A.; Mamat, M. H.; Rusop, M.

    2016-07-01

    The Nb-doped TiO2 films were deposited on glass substrate at different Nb concentrations of 0 at.%, 1 at.%, 3 at.%, 5 at.% and 7 at.%, respectively and their electrical and structural properties were investigated. Subsequently, the Nb-doped TiO2 films were deposited on top of aligned ZnO Nanorod on ITO glass substrates using spin coating technique. The nanocomposited aligned ZnO nanorod/Nb-doped TiO2 (TiO2:Nb) were coated with different Nb concentrations of 0 at.%, 1 at.%, 3 at.%, 5 at.% and 7 at.%, respectively. The Dye-sensitized solar cells were fabricated from the nanocomposited aligned ZnO nanorod/TiO2:Nb photoanodes and their effects on the performance of the DSSCs were investigated. From the solar simulator measurement of DSSC the solar energy conversion efficiency (η) of 5.376% under AM 1.5 was obtained for the ZnO nanorod/TiO2:Nb-5at.%.

  10. A Heterojunction Design of Single Layer Hole Tunneling ZnO Passivation Wrapping around TiO2Nanowires for Superior Photocatalytic Performance

    PubMed Central

    Ghobadi, Amir; Ulusoy, T. Gamze; Garifullin, Ruslan; Guler, Mustafa O.; Okyay, Ali K.

    2016-01-01

    Nanostructured hybrid heterojunctions have been studied widely for photocatalytic applications due to their superior optical and structural properties. In this work, the impact of angstrom thick atomic layer deposited (ALD) ZnO shell layer on photocatalytic activity (PCA) of hydrothermal grown single crystalline TiO2 nanowires (NWs) is systematically explored. We showed that a single cycle of ALD ZnO layer wrapped around TiO2 NWs, considerably boosts the PCA of the heterostructure. Subsequent cycles, however, gradually hinder the photocatalytic activity (PCA) of the TiO2 NWs. Various structural, optical, and transient characterizations are employed to scrutinize this unprecedented change. We show that a single atomic layer of ZnO shell not only increases light harvesting capability of the heterostructure via extension of the absorption toward visible wavelengths, but also mitigates recombination probability of carriers through reduction of surface defects density and introduction of proper charge separation along the core-shell interface. Furthermore, the ultrathin ZnO shell layer allows a strong contribution of the core (TiO2) valence band holes through tunneling across the ultrathin interface. All mechanisms responsible for this enhanced PCA of heterostructure are elucidated and corresponding models are proposed. PMID:27464476

  11. A Heterojunction Design of Single Layer Hole Tunneling ZnO Passivation Wrapping around TiO2Nanowires for Superior Photocatalytic Performance

    NASA Astrophysics Data System (ADS)

    Ghobadi, Amir; Ulusoy, T. Gamze; Garifullin, Ruslan; Guler, Mustafa O.; Okyay, Ali K.

    2016-07-01

    Nanostructured hybrid heterojunctions have been studied widely for photocatalytic applications due to their superior optical and structural properties. In this work, the impact of angstrom thick atomic layer deposited (ALD) ZnO shell layer on photocatalytic activity (PCA) of hydrothermal grown single crystalline TiO2 nanowires (NWs) is systematically explored. We showed that a single cycle of ALD ZnO layer wrapped around TiO2 NWs, considerably boosts the PCA of the heterostructure. Subsequent cycles, however, gradually hinder the photocatalytic activity (PCA) of the TiO2 NWs. Various structural, optical, and transient characterizations are employed to scrutinize this unprecedented change. We show that a single atomic layer of ZnO shell not only increases light harvesting capability of the heterostructure via extension of the absorption toward visible wavelengths, but also mitigates recombination probability of carriers through reduction of surface defects density and introduction of proper charge separation along the core-shell interface. Furthermore, the ultrathin ZnO shell layer allows a strong contribution of the core (TiO2) valence band holes through tunneling across the ultrathin interface. All mechanisms responsible for this enhanced PCA of heterostructure are elucidated and corresponding models are proposed.

  12. A Heterojunction Design of Single Layer Hole Tunneling ZnO Passivation Wrapping around TiO2Nanowires for Superior Photocatalytic Performance.

    PubMed

    Ghobadi, Amir; Ulusoy, T Gamze; Garifullin, Ruslan; Guler, Mustafa O; Okyay, Ali K

    2016-01-01

    Nanostructured hybrid heterojunctions have been studied widely for photocatalytic applications due to their superior optical and structural properties. In this work, the impact of angstrom thick atomic layer deposited (ALD) ZnO shell layer on photocatalytic activity (PCA) of hydrothermal grown single crystalline TiO2 nanowires (NWs) is systematically explored. We showed that a single cycle of ALD ZnO layer wrapped around TiO2 NWs, considerably boosts the PCA of the heterostructure. Subsequent cycles, however, gradually hinder the photocatalytic activity (PCA) of the TiO2 NWs. Various structural, optical, and transient characterizations are employed to scrutinize this unprecedented change. We show that a single atomic layer of ZnO shell not only increases light harvesting capability of the heterostructure via extension of the absorption toward visible wavelengths, but also mitigates recombination probability of carriers through reduction of surface defects density and introduction of proper charge separation along the core-shell interface. Furthermore, the ultrathin ZnO shell layer allows a strong contribution of the core (TiO2) valence band holes through tunneling across the ultrathin interface. All mechanisms responsible for this enhanced PCA of heterostructure are elucidated and corresponding models are proposed. PMID:27464476

  13. An excellent enzymatic lactic acid biosensor with ZnO nanowires-gated AlGaAs/GaAs high electron mobility transistor.

    PubMed

    Ma, Siwei; Liao, Qingliang; Liu, Hanshuo; Song, Yu; Li, Ping; Huang, Yunhua; Zhang, Yue

    2012-10-21

    An excellent biosensor with ZnO nanowires-gated AlGaAs/GaAs high electron mobility transistor (HEMT) was used to detect lactic acid. Due to the new structure, addition of the Si-doped GaAs cap layer, the HEMT biosensor could detect a wide range of lactic acid concentrations from 0.03 nM to 300 mM. The novel biosensor exhibiting good performance along with fast response, high sensitivity, wide detection range, and long-term stability, can be integrated with a commercially available transmitter to realize lactic acid detection. PMID:22951602

  14. ZnO nanowires with Au contacts characterised in the as-grown real device configuration using a local multi-probe method

    NASA Astrophysics Data System (ADS)

    Lord, Alex M.; Walton, Alex S.; Maffeis, Thierry G.; Ward, Michael B.; Davies, Peter; Wilks, Steve P.

    2014-10-01

    We demonstrate here a method using a multi-probe UHV instrument to isolate and measure individual metal contacts controllably fabricated on the tips of free standing ZnO nanowires (NWs). The measurements show Au can form reliable Ohmic and rectifying contacts by exercising control over the surface properties. In the as-grown state the Au contacts display low-resistance characteristics which are determined by the adsorbed species and defects on the NW surface. Subjecting the NWs to an oxidising agent (H2O2) increases the surface potential barrier creating more rectifying contacts. These developments are crucial for controllable NW array devices.

  15. Enhancement of the near-band-edge photoluminescence of ZnO nanowires: Important role of hydrogen incorporation versus plasmon resonances

    SciTech Connect

    Dev, A.; Richters, J. P.; Gutowski, J.; Voss, T.; Sartor, J.; Kalt, H.

    2011-03-28

    We investigated the photoluminescence properties of ZnO nanowires coated with Au, Ag, and Pt nanoparticles deposited by dc sputtering. A strong enhancement of the near-band-edge emission was observed in all metal-coated samples but also if the samples were treated with Ar plasma without any nanoparticle deposition. High-resolution photoluminescence spectroscopy revealed hydrogen-donor-bound-exciton emission in all samples indicating unintentional hydrogen incorporation. A shorter decay time of the near-band-edge emission was observed in all cases. The results indicate that unintentional hydrogen incorporation plays a dominant role when metal deposition is performed by sputtering.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  17. Rapid Charge Transport in Dye-Sensitized Solar Cells Made from Vertically Aligned Single-Crystal Rutile TiO2 Nanowires

    SciTech Connect

    Feng, X.; Zhu, K.; Frank, A. J.; Grimes, C. A.; Mallouk, T. E.

    2012-03-12

    A rapid solvothermal approach was used to synthesize aligned 1D single-crystal rutile TiO2 nanowire (NW) arrays on transparent conducting substrates as electrodes for dye-sensitized solar cells. The NW arrays showed a more than 200 times faster charge transport (see picture) and a factor four lower defect state density than conventional rutile nanoparticle films.

  18. Ultrahigh Density Array of Vertically Aligned Small-molecular Organic Nanowires on Arbitrary Substrates

    PubMed Central

    Starko-Bowes, Ryan; Pramanik, Sandipan

    2013-01-01

    In recent years π-conjugated organic semiconductors have emerged as the active material in a number of diverse applications including large-area, low-cost displays, photovoltaics, printable and flexible electronics and organic spin valves. Organics allow (a) low-cost, low-temperature processing and (b) molecular-level design of electronic, optical and spin transport characteristics. Such features are not readily available for mainstream inorganic semiconductors, which have enabled organics to carve a niche in the silicon-dominated electronics market. The first generation of organic-based devices has focused on thin film geometries, grown by physical vapor deposition or solution processing. However, it has been realized that organic nanostructures can be used to enhance performance of above-mentioned applications and significant effort has been invested in exploring methods for organic nanostructure fabrication. A particularly interesting class of organic nanostructures is the one in which vertically oriented organic nanowires, nanorods or nanotubes are organized in a well-regimented, high-density array. Such structures are highly versatile and are ideal morphological architectures for various applications such as chemical sensors, split-dipole nanoantennas, photovoltaic devices with radially heterostructured "core-shell" nanowires, and memory devices with a cross-point geometry. Such architecture is generally realized by a template-directed approach. In the past this method has been used to grow metal and inorganic semiconductor nanowire arrays. More recently π-conjugated polymer nanowires have been grown within nanoporous templates. However, these approaches have had limited success in growing nanowires of technologically important π-conjugated small molecular weight organics, such as tris-8-hydroxyquinoline aluminum (Alq3), rubrene and methanofullerenes, which are commonly used in diverse areas including organic displays, photovoltaics, thin film transistors

  19. Facile construction of vertically aligned ZnO nanorod/PEDOT:PSS hybrid heterojunction-based ultraviolet light sensors: efficient performance and mechanism

    NASA Astrophysics Data System (ADS)

    Ranjith, K. S.; Rajendra Kumar, R. T.

    2016-03-01

    We demonstrate a simple, planar manufacturing process-compatible fabrication of highly efficient UV sensors based on a hybrid heterojunction of an array of vertically aligned ZnO nanorods (NRs) and PEDOT:PSS. The ZnO NR array was grown by the solution growth process and the aspect ratio (length 1 to 4 μm, diameter ˜80 nm) of the rods was controlled by varying the growth time. UV sensors based on (i) naked ZnO NRs and (ii) ZnO NR/PEDOT:PSS heterojunctions were fabricated and tested. The UV sensitivity of bare ZnO NRs was found to increase with increasing aspect ratio of the NRs due to the increase in the photogenerated charge carriers as the fraction of material interacting with the light increases. Under 5 V bias, naked ZnO NR arrays showed a photocurrent of 8.84 × 10-5 A, a responsivity of 0.538 A W-1 and a sensitivity of 4.80 under UV (λ = 256 nm, 130 μW) illumination. ZnO NR/PEDOT:PSS hybrid heterojunctions showed diode-like behavior with a leakage current less than 2.54 × 10-8 A at -5 V and forward turn-on voltage of 1.1 V. ZnO NR/polymer-based hybrid heterojunctions show a photocurrent of 6.74 × 10-4 A, responsivity of 5.046 A W-1 and excellent sensitivity of 37.65 under UV (λ = 256 nm, 130 μW) illumination. Compared with bare ZnO NR arrays, the ZnO NR/polymer heterojunction device shows responsivity enhanced by a factor of 10, sensitivity enhanced by a factor of 8 and faster rise and decay time. The enhanced performance may be due to effective charge separation guided by the built-in potential formed at the interface between ZnO NRs and PEDOT:PSS.

  20. Spatial distribution of neutral oxygen vacancies on ZnO nanowire surfaces: An investigation combining confocal microscopy and first principles calculations

    NASA Astrophysics Data System (ADS)

    Mun Wong, Kin; Alay-e-Abbas, S. M.; Fang, Yaoguo; Shaukat, A.; Lei, Yong

    2013-07-01

    A qualitative approach using room-temperature confocal microscopy is employed to investigate the spatial distribution of shallow and deep oxygen vacancy (VO) concentrations on the polar (0001) and non-polar (101¯0) surfaces of zinc oxide (ZnO) nanowires (NWs). Using the spectral intensity variation of the confocal photoluminescence of the green emission at different spatial locations on the surface, the VO concentrations of an individual ZnO NW can be obtained. The green emission at different spatial locations on the ZnO NW polar (0001) and non-polar (101¯0) surfaces is found to have maximum intensity near the NW edges, decreasing to a minimum near the NW center. First-principles calculations using simple supercell-slab (SS) models are employed to approximate/model the defects on the ZnO NW (101¯0) and (0001) surfaces. These calculations give increased insight into the physical mechanism behind the green emission spectral intensity and the characteristics of an individual ZnO NW. The highly accurate density functional theory (DFT)-based full-potential linearized augmented plane-wave plus local orbitals (FP-LAPW + lo) method is used to compute the defect formation energy (DFE) of the SSs. Previously, using these SS models, it was demonstrated through the FP-LAPW + lo method that in the presence of oxygen vacancies at the (0001) surface, the phase transformation of the SSs in the graphite-like structure to the wurtzite lattice structure will occur even if the thickness of the graphite-like SSs are equal to or less than 4 atomic graphite-like layers [Wong et al., J. Appl. Phys. 113, 014304 (2013)]. The spatial profile of the neutral VO DFEs from the DFT calculations along the ZnO [0001] and [101¯0] directions is found to reasonably explain the spatial profile of the measured confocal luminescence intensity on these surfaces, leading to the conclusion that the green emission spectra of the NWs likely originate from neutral oxygen vacancies. Another significant

  1. Photoluminescence enhancement of ZnO nanowire arrays by atomic layer deposition of ZrO2 layers and thermal annealing.

    PubMed

    Zhang, Yuan; Lu, Hong-Liang; Wang, Tao; Ren, Qing-Hua; Chen, Hong-Yan; Zhang, Hao; Ji, Xin-Ming; Liu, Wen-Jun; Ding, Shi-Jin; Zhang, David Wei

    2016-06-28

    The effects of shell thickness and rapid thermal annealing on photoluminescence properties of one-dimensional ZnO/ZrO2 core/shell nanowires (NWs) are studied in this work. The ZnO/ZrO2 core/shell structures were synthesized by coating thin ZrO2 layers on the surface of ZnO NWs using atomic layer deposition. The morphological and structural characterization studies reveal that the ZrO2 shells have a polycrystalline structure, which are uniformly and conformally coated on the high quality single-crystal ZnO NWs. As compared with bare ZnO NWs, the ZnO/ZrO2 core/shell structures show a remarkable and continuous enhancement of ultraviolet (UV) emission in intensity with increasing ZrO2 shell thickness up to 10 nm. The great improvement mechanism of the UV emission arises from the surface passivation and the efficient carrier confinement effect of the type-I core/shell system. Moreover, it is observed that the UV emission of ZnO/ZrO2 core/shell structures after thermal annealing increases with increasing annealing temperature. The dominant surface exciton (SX) emission in the bare ZnO NWs and the ZnO/ZrO2 core/shell nanostructures has been detected in the low temperature photoluminescence spectra. A blue shift of the NBE emission peak as well as the varied decay rate of the SX emission intensity are also found in the ZnO NWs after the growth of ZrO2 shells and further thermal treatment. Our results suggest that the ZnO/ZrO2 core/shell nanostructures could be widely implemented in the optical and electronic devices in the future. PMID:27263423

  2. Silver Nanowires Binding with Sputtered ZnO to Fabricate Highly Conductive and Thermally Stable Transparent Electrode for Solar Cell Applications.

    PubMed

    Singh, Manjeet; Rana, Tanka R; Kim, SeongYeon; Kim, Kihwan; Yun, Jae Ho; Kim, JunHo

    2016-05-25

    Silver nanowire (AgNW) film has been demonstrated as excellent and low cost transparent electrode in organic solar cells as an alternative to replace scarce and expensive indium tin oxide (ITO). However, the low contact area and weak adhesion with low-lying surface as well as junction resistance between nanowires have limited the applications of AgNW film to thin film solar cells. To resolve this problem, we fabricated AgNW film as transparent conductive electrode (TCE) by binding with a thin layer of sputtered ZnO (40 nm) which not only increased contact area with low-lying surface in thin film solar cell but also improved conductivity by connecting AgNWs at the junction. The TCE thus fabricated exhibited transparency and sheet resistance of 92% and 20Ω/□, respectively. Conductive atomic force microscopy (C-AFM) study revealed the enhancement of current collection vertically and laterally through AgNWs after coating with ZnO thin film. The CuInGaSe2 solar cell with TCE of our AgNW(ZnO) demonstrated the maximum power conversion efficiency of 13.5% with improved parameters in comparison to solar cell fabricated with conventional ITO as TCE. PMID:27149372

  3. Morphology-tunable assembly of periodically aligned Si nanowire and radial pn junction arrays for solar cell applications

    NASA Astrophysics Data System (ADS)

    Li, Xiaocheng; Liang, Kun; Tay, Beng Kang; Teo, Edwin H. T.

    2012-06-01

    Large-area periodically aligned Si nanowire (PASiNW) arrays have been fabricated on Si substrates via a templated catalytic chemical etching process. The diameter, length, packing density, and even the shape of Si nanowires (SiNWs) could be precisely controlled and tuned. A local coupling redox mechanism involving the reduction of H2O2 on silver particles and the dissolution of Si is responsible for formation of SiNWs. With the as-prepared SiNWs as templates, three kinds of PASiNW radial pn junction structures were fabricated on Si substrates via a solid-state phosphorous diffusion strategy and their applications in solar cells were also explored. The PASiNW radial pn junction-based solar cell with big diameter and interspace shows the highest power conversion efficiency (PCE) of 4.10% among the three kinds of devices. Further optimization, including surface passivation and electrode contact, is still needed for the higher efficiency PASiNW radial pn junction-based solar cells in the future.

  4. TiO2/BiVO4 Nanowire Heterostructure Photoanodes Based on Type II Band Alignment

    PubMed Central

    2016-01-01

    Metal oxides that absorb visible light are attractive for use as photoanodes in photoelectrosynthetic cells. However, their performance is often limited by poor charge carrier transport. We show that this problem can be addressed by using separate materials for light absorption and carrier transport. Here, we report a Ta:TiO2|BiVO4 nanowire photoanode, in which BiVO4 acts as a visible light-absorber and Ta:TiO2 acts as a high surface area electron conductor. Electrochemical and spectroscopic measurements provide experimental evidence for the type II band alignment necessary for favorable electron transfer from BiVO4 to TiO2. The host–guest nanowire architecture presented here allows for simultaneously high light absorption and carrier collection efficiency, with an onset of anodic photocurrent near 0.2 V vs RHE, and a photocurrent density of 2.1 mA/cm2 at 1.23 V vs RHE. PMID:27163032

  5. Vertically Aligned Ge Nanowires on Flexible Plastic Films Synthesized by (111)-Oriented Ge Seeded Vapor-Liquid-Solid Growth.

    PubMed

    Toko, Kaoru; Nakata, Mitsuki; Jevasuwan, Wipakorn; Fukata, Naoki; Suemasu, Takashi

    2015-08-19

    Transfer-free fabrication of vertical Ge nanowires (NWs) on a plastic substrate is demonstrated using a vapor-liquid-solid (VLS) method. The crystal quality of Ge seed layers (50 nm thickness) prepared on plastic substrates strongly influenced the VLS growth morphology, i.e., the density, uniformity, and crystal quality of Ge NWs. The metal-induced layer exchange yielded a (111)-oriented Ge seed layer at 325 °C, which allowed for the VLS growth of vertically aligned Ge NWs. The Ge NW array had almost the same quality as that formed on a bulk Ge(111) substrate. Transmission electron microscopy demonstrated that the Ge NWs were defect-free single crystals. The present investigation paves the way for advanced electronic optical devices integrated on a low-cost flexible substrate. PMID:26230716

  6. A template and catalyst-free metal-etching-oxidation method to synthesize aligned oxide nanowire arrays: NiO as an example.

    PubMed

    Wei, Zhi Peng; Arredondo, Miryam; Peng, Hai Yang; Zhang, Zhou; Guo, Dong Lai; Xing, Guo Zhong; Li, Yong Feng; Wong, Lai Mun; Wang, Shi Jie; Valanoor, Nagarajan; Wu, Tom

    2010-08-24

    Although NiO is one of the canonical functional binary oxides, there has been no report so far on the effective fabrication of aligned single crystalline NiO nanowire arrays. Here we report a novel vapor-based metal-etching-oxidation method to synthesize high-quality NiO nanowire arrays with good vertical alignment and morphology control. In this method, Ni foils are used as both the substrates and the nickel source; NiCl(2) powder serves as the additional Ni source and provides Cl(2) to initiate mild etching. No template is deliberately employed; instead a nanograined NiO scale formed on the NiO foil guides the vapor infiltration and assists the self-assembled growth of NiO nanowires via a novel process comprising simultaneous Cl(2) etching and gentle oxidation. Furthermore, using CoO nanowires and Co-doped NiO as examples, we show that this general method can be employed to produce nanowires of other oxides as well as the doped counterparts. PMID:20614899

  7. X-ray photoelectron spectroscopy study of energy-band alignments of ZnO on buffer layer Lu2O3

    NASA Astrophysics Data System (ADS)

    Chen, Shanshan; Pan, Xinhua; Xu, Chenxiao; Huang, Jingyun; Ye, Zhizhen

    2016-02-01

    Lu2O3 was used as the buffer layer of the epitaxy of ZnO film on Si substrate by plasma-assisted molecular beam epitaxy. X-ray photoelectron spectroscopy was used to determine the band alignment at ZnO/Lu2O3 interface. The conduction band offset (CBO) and valence band offset (VBO) of the ZnO/Lu2O3 heterojunction are calculated to be 1.77 eV and 0.66 eV, respectively, with a type-I band alignment. And the ratio of CBO and VBO (ΔEc / ΔEv) is estimated to be about 2.68. The large ΔEv and ΔEc reveal that Lu2O3 is an ideal barrier layer in Si-based ZnO optoelectronic devices.

  8. Efficient Z-scheme charge separation in novel vertically aligned ZnO/CdSSe nanotrees.

    PubMed

    Li, Zhengxin; Nieto-Pescador, Jesus; Carson, Alexander J; Blake, Jolie C; Gundlach, Lars

    2016-04-01

    A new tree-like ZnO/CdSSe nanocomposite with CdSSe branches grown on ZnO nanowires prepared via a two-step chemical vapor deposition is presented. The nanotrees (NTs) are vertically aligned on a substrate. The CdSSe branches result in strong visible light absorption and form a type-II heterojunction with the ZnO stem that facilitates efficient electron transfer. A combination of photoluminescence spectroscopy and lifetime measurements indicates that the NTs are promising materials for applications that benefit from a Z-scheme charge transfer mechanism. Vertically aligned branched ZnO nanowires can provide direct electron transport pathways to substrates and allow for efficient charge separation. These advantages of nanoscale hierarchical heterostructures make ZnO/CdSSe NTs a promising semiconductor material for solar cells, and other opto-electronic devices. PMID:26894995

  9. Efficient Z-scheme charge separation in novel vertically aligned ZnO/CdSSe nanotrees

    NASA Astrophysics Data System (ADS)

    Li, Zhengxin; Nieto-Pescador, Jesus; Carson, Alexander J.; Blake, Jolie C.; Gundlach, Lars

    2016-04-01

    A new tree-like ZnO/CdSSe nanocomposite with CdSSe branches grown on ZnO nanowires prepared via a two-step chemical vapor deposition is presented. The nanotrees (NTs) are vertically aligned on a substrate. The CdSSe branches result in strong visible light absorption and form a type-II heterojunction with the ZnO stem that facilitates efficient electron transfer. A combination of photoluminescence spectroscopy and lifetime measurements indicates that the NTs are promising materials for applications that benefit from a Z-scheme charge transfer mechanism. Vertically aligned branched ZnO nanowires can provide direct electron transport pathways to substrates and allow for efficient charge separation. These advantages of nanoscale hierarchical heterostructures make ZnO/CdSSe NTs a promising semiconductor material for solar cells, and other opto-electronic devices.

  10. Au catalyst assisted growth of ZnO nanowires by vapour phase transport method on p-Si and fabrication of p-Si/n-ZnO heterojunction diode

    SciTech Connect

    Bhat, Shashidhara; V, Shrisha B.; Naik, K Gopalakrishna

    2015-06-24

    In this work ZnO nanowires were grown on p type silicon (p-Si) substrate using Vapor-Liquid-Solid (VLS) approach using Au as catalyst by vapor phase transport growth method. Surface morphology and structural properties of the grown ZnO nanowires were examined by Scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. Using the n-ZnO nanowires (NW) grown on p-type silicon, n-ZnO NW/p-Si heterojunction diode was fabricated. The rectification property of the fabricated diode was studied by room temperature as well as high temperature (up to 370 K) current-voltage (I-V) measurements.

  11. Vertically aligned crystalline silicon nanowires with controlled diameters for energy conversion applications: Experimental and theoretical insights

    SciTech Connect

    Razek, Sara Abdel; Swillam, Mohamed A.; Allam, Nageh K.

    2014-05-21

    Vertically orientated single crystalline silicon nanowire (SiNW) arrays with controlled diameters are fabricated via a metal-assisted chemical etching method. The diameter of the fabricated nanowires is controlled by simply varying the etching time in HF/H{sub 2}O{sub 2} electrolytes. The fabricated SiNWs have diameters ranging from 117 to 650 nm and lengths from 8 to 18 μm. The optical measurements showed a significant difference in the reflectance/absorption of the SiNWs with different diameters, where the reflectance increases with increasing the diameter of the SiNWs. The SiNWs showed significant photoluminescence (PL) emission spectra with peaks lying between 380 and 670 nm. The PL intensity increases as the diameter increases and shows red shift for peaks at ∼670 nm. The increase or decrease of reflectivity is coincident with PL intensity at wavelength ∼660 nm. The x-ray diffraction patterns confirm the high crystallinity of the fabricated SiNWs. In addition, the Raman spectra showed a shift in the first order transverse band toward lower frequencies compared to that usually seen for c-Si. Finite difference time domain simulations have been performed to confirm the effect of change of diameter on the optical properties of the nanowires. The simulation results showed good agreement with the experimental results for the SiNWs of different diameters.

  12. Highly flexible, transparent, conductive and antibacterial films made of spin-coated silver nanowires and a protective ZnO layer

    NASA Astrophysics Data System (ADS)

    Chen, Youxin; Lan, Wei; Wang, Junya; Zhu, Ranran; Yang, Zhiwei; Ding, Delei; Tang, Guomei; Wang, Kairong; Su, Qing; Xie, Erqing

    2016-02-01

    We prepared highly flexible, transparent, conductive and antibacterial film by spin coating a silver nanowire suspension on a poly (ethylene terephthalate) (PET) substrate. The ZnO layer covered the conductive silver nanowire (AgNW) network to protect the metal nanowires from oxidization and enhance both wire-to-wire adhesion and wire-to-substrate adhesion. It is found that the number of AgNW coatings correlates with both the sheet resistance (Rs) and the transmittance of the AgNW/ZnO composite films. An excellent 92% optical transmittance in the visible range and a surface sheet resistance of only 9 Ω sq-1 has been achieved, respectively. Even after bending 1000 times (5 mm bending radius), we found no significant change in the sheet resistance or optical transmittance. The real-time sheet resistance measured as a function of bending radius also remains stable even at the smallest measured bending radius (1 mm). The AgNW/ZnO composite films also show antibacterial effects which could be useful for the fabrication of wearable electronic devices.

  13. Catalyst-free growth of ZnO nanowires on ITO seed layer/glass by thermal evaporation method: Effects of ITO seed layer laser annealing temperature

    NASA Astrophysics Data System (ADS)

    Alsultany, Forat H.; Hassan, Z.; Ahmed, Naser M.

    2016-04-01

    Novel catalyst-free growth of ZnO nanowires (ZnO-NWs) on ITO seeds/glass substrate by thermal evaporation method, and effects of continuous wave CO2 laser thermal annealed seed layer on the morphology and properties of ZnO-NWs growth were investigated. The effects of sputtered ITO seed layer laser annealing temperature on the morphological, structural, and optical properties of ZnO-NWs was systematically investigated at temperatures 250, 350, and 450 °C, respectively. The surface morphology and structure of the seeds and the products of ZnO-NWs were characterized in detail by using field emission scanning electron microscopy, atomic force microscopy, and X-ray diffraction. Optical properties were further examined through photoluminescence, and UV-Vis spectrophotometer. A growth mechanism was proposed on the basis of obtained results. The results showed that the nanowires were strongly dependent on the seed layer annealing temperatures, which played an important role in nucleation and dissimilar growth of the nanowires with varying sizes and geometric shapes.

  14. Al-doped ZnO aligned nanorod arrays for opto-electronic and sensor applications

    NASA Astrophysics Data System (ADS)

    Holloway, T.; Mundle, R.; Dondapati, H.; Konda, R. B.; Bahoura, M.; Pradhan, A. K.

    2012-04-01

    We report on the growth of vertically aligned Al:ZnO nanorod arrays synthesized by the hydrothermal technique at considerably low temperature on a sputtered Al:ZnO seed layer. The morphology demonstrates that the nanorod arrays maintain remarkable alignment along the c-axis over a large area. The optoelectronic properties of nanorod arrays on Al:ZnO/p-Si seed layer with SiO2 have been illustrated. The photocurrent is significantly reduced in nanorod arrays on AZO/SiO2/p-Si heterojunction due to multiple scattering phenomena associated with the nanorod arrays. The optical properties of the AZO film with and without the AZO nanorod arrays were investigated. Also the effects of an intermediate layer in the AZO/P-Si heterojunction structure with and without the AZO nanorod array present were explored. All the various intermediate layers displayed photovoltaic effect behavior, especially with the AZO/SiO2/P-Si heterojunction structure, which exhibited ideal diode behavior. The optoelectronic properties of nanorod arrays on AZO/P-Si seed layer with SiO2 have been illustrated. The photocurrent is significantly reduced in nanorod arrays on AZO/SiO2/P-Si heterojunction due to multiple scattering phenomena associated with the nanorod arrays. The results have tremendous impact for sensor fabrication, including glucose sensor.

  15. Scanning tunneling microscopy of aligned coaxial nanowires of polyaniline passivated carbon nanotube

    NASA Astrophysics Data System (ADS)

    Hassanien, A.; Gao, M.; Tokumoto, M.; Dai, L.

    2001-11-01

    Various methods are used to grow carbon nanotubes aiming to optimize their structural properties. Among them CVD method proved to be very successful in growing well-aligned carbon nanotubes arrays, which offers great possibilities for applications. Here we present room temperature scanning tunneling microscopy (STM) investigations of well-aligned, polyaniline passivated, multiwall carbon nanotubes (MWCNT). STM topographic images show nanotubes are partially covered with the conducting polymer. On atomically resolved scale we observed array of caps with round shape that are separated by polyaniline. Differences in the electronic properties between nanotubes and the polymer suggest that this method could be used to synthesize large scale of nanodevices.

  16. Growth of aligned single-crystalline rutile TiO2 nanowires on arbitrary substrates and their application in dye-sensitized solar cells

    SciTech Connect

    Kumar, Akshay; Madaria, Anuj R.; Zhou, Chongwu

    2010-05-06

    TiO{sub 2} is a wide band gap semiconductor with important applications in photovoltaic cells and photocatalysis. In this paper, we report synthesis of single-crystalline rutile phase TiO{sub 2} nanowires on arbitrary substrates, including fluorine-doped tin oxide (FTO), glass slides, tin-doped indium oxide (ITO), Si/SiO{sub 2}, Si(100), Si(111), and glass rods. By controlling the growth parameters such as growth temperature, precursor concentrations, and so forth, we demonstrate that anisotropic growth of TiO{sub 2} is possible leading to various morphologies of nanowires. Optimization of the growth recipe leads to well-aligned vertical array of TiO{sub 2} nanowires on both FTO and glass substrates. Effects of various titanium precursors on the growth kinetics, especially on the growth rate of nanowires, are also studied. Finally, application of vertical array of TiO{sub 2} nanowires on FTO as the photoanode is demonstrated in dye-sensitized solar cell with an efficiency of 2.9 ± 0.2%.

  17. Shape control of nickel nanostructures incorporated in amorphous carbon films: From globular nanoparticles toward aligned nanowires

    NASA Astrophysics Data System (ADS)

    El Mel, A. A.; Bouts, N.; Grigore, E.; Gautron, E.; Granier, A.; Angleraud, B.; Tessier, P. Y.

    2012-06-01

    The growth of nickel/carbon nanocomposite thin films by a hybrid plasma process, which combines magnetron sputtering and plasma enhanced chemical vapor deposition, has been investigated. This study has shown that the films consist of nickel-rich nanostructures embedded in an amorphous carbon matrix. The size, the distribution, the density, and the shape of these nanostructures are directly dependent to the total carbon content within the films. At low carbon content (˜28 at. %), dense nanowire array perpendicularly oriented to the surface of the substrate can be fabricated. For an intermediate carbon concentration (˜35 at. %), the nickel phase was organized into elongated nanoparticles. These nanoparticles became spherical when reaching a higher carbon content (˜54 at. %). The extensive structural study allowed the representation of a structure zone diagram, as well as, the development of a scenario describing the growth mechanisms that take place during the deposition of such nanocomposite material.

  18. Controllable synthesis of branched ZnO/Si nanowire arrays with hierarchical structure

    PubMed Central

    2014-01-01

    A rational approach for creating branched ZnO/Si nanowire arrays with hierarchical structure was developed based on a combination of three simple and cost-effective synthesis pathways. The crucial procedure included growth of crystalline Si nanowire arrays as backbones by chemical etching of Si substrates, deposition of ZnO thin film as a seed layer by magnetron sputtering, and fabrication of ZnO nanowire arrays as branches by hydrothermal growth. The successful synthesis of ZnO/Si heterogeneous nanostructures was confirmed by morphologic, structural, and optical characterizations. The roles of key experimental parameters, such as the etchant solution, the substrate direction, and the seed layer on the hierarchical nanostructure formation, were systematically investigated. It was demonstrated that an etchant solution with an appropriate redox potential of the oxidant was crucial for a moderate etching speed to achieve a well-aligned Si nanowire array with solid and round surface. Meanwhile, the presence of gravity gradient was a key issue for the growth of branched ZnO nanowire arrays. The substrate should be placed vertically or facedown in contrast to the solution surface during the hydrothermal growth. Otherwise, only the condensation of the ZnO nanoparticles took place in a form of film on the substrate surface. The seed layer played another important role in the growth of ZnO nanowire arrays, as it provided nucleation sites and determined the growing direction and density of the nanowire arrays for reducing the thermodynamic barrier. The results of this study might provide insight on the synthesis of hierarchical three-dimensional nanostructure materials and offer an approach for the development of complex devices and advanced applications. PMID:25024688

  19. Polarity assignment in ZnTe, GaAs, ZnO, and GaN-AlN nanowires from direct dumbbell analysis.

    PubMed

    de la Mata, Maria; Magen, Cesar; Gazquez, Jaume; Utama, Muhammad Iqbal Bakti; Heiss, Martin; Lopatin, Sergei; Furtmayr, Florian; Fernández-Rojas, Carlos J; Peng, Bo; Morante, Joan Ramon; Rurali, Riccardo; Eickhoff, Martin; Fontcuberta i Morral, Anna; Xiong, Qihua; Arbiol, Jordi

    2012-05-01

    Aberration corrected scanning transmission electron microscopy (STEM) with high angle annular dark field (HAADF) imaging and the newly developed annular bright field (ABF) imaging are used to define a new guideline for the polarity determination of semiconductor nanowires (NWs) from binary compounds in two extreme cases: (i) when the dumbbell is formed with atoms of similar mass (GaAs) and (ii) in the case where one of the atoms is extremely light (N or O: ZnO and GaN/AlN). The theoretical fundaments of these procedures allow us to overcome the main challenge in the identification of dumbbell polarity. It resides in the separation and identification of the constituent atoms in the dumbbells. The proposed experimental via opens new routes for the fine characterization of nanostructures, e.g., in electronic and optoelectronic fields, where the polarity is crucial for the understanding of their physical properties (optical and electronic) as well as their growth mechanisms. PMID:22493937

  20. Improvement of electroluminescence performance by integration of ZnO nanowires and single-crystalline films on ZnO/GaN heterojunction

    SciTech Connect

    Shi, Zhifeng; Zhang, Yuantao Cui, Xijun; Wu, Bin; Zhuang, Shiwei; Yang, Fan; Zhang, Baolin; Du, Guotong; Yang, Xiaotian

    2014-03-31

    Heterojunction light-emitting diodes based on n-ZnO nanowires/ZnO single-crystalline films/p-GaN structure have been demonstrated for an improved electroluminescence performance. A highly efficient ultraviolet emission was observed under forward bias. Compared with conventional n-ZnO/p-GaN structure, high internal quantum efficiency and light extraction efficiency were simultaneously considered in the proposed diode. In addition, the diode can work continuously for ∼10 h with only a slight degradation in harsh environments, indicating its good reliability and application prospect in the future. This route opens possibilities for the development of advanced nanoscale devices in which the advantages of ZnO single-crystalline films and nanostructures can be integrated together.

  1. Interface studies of ZnO nanowire transistors using low-frequency noise and temperature-dependent I-V measurements

    NASA Astrophysics Data System (ADS)

    Ju, Sanghyun; Kim, Sunkook; Mohammadi, Saeed; Janes, David B.; Ha, Young-Geun; Facchetti, Antonio; Marks, Tobin J.

    2008-01-01

    Single ZnO nanowire (NW) transistors fabricated with self-assembled nanodielectric (SAND) and SiO2 gate insulators were characterized by low-frequency noise and variable temperature current-voltage (I-V ) measurements. According to the gate dependence of the noise amplitude, the extracted Hooge's constants (αH) are ˜3.3×10-2 for SAND-based devices and ˜3.5×10-1 for SiO2-based devices. Temperature-dependent I-V studies show that the hysteresis of the transfer curves and the threshold voltage shifts of SAND-based devices are significantly smaller than those of SiO2-based devices. These results demonstrate the improved SAND/ZnO NW interface quality (lower interface-trap states and defects) in comparison to those fabricated with SiO2.

  2. Well aligned ZnO nanorods growth on the gold coated glass substrate by aqueous chemical growth method using seed layer of Fe3O4 and Co3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Ibupoto, Z. H.; Khun, K.; Lu, Jun; Liu, Xianjie; AlSalhi, M. S.; Atif, M.; Ansari, Anees A.; Willander, M.

    2013-04-01

    In this study, Fe3O4 and Co3O4 nanoparticles were prepared by co-precipitation method and sol-gel method respectively. The synthesised nanoparticles were characterised by X-ray diffraction [XRD] and Raman spectroscopy techniques. The obtained results have shown the nanocrystalline phase of obtained Fe3O4 and Co3O4 nanoparticles. Furthermore, the Fe3O4 and Co3O4 nanoparticles were used as seed layer for the fabrication of well-aligned ZnO nanorods on the gold coated glass substrate by aqueous chemical growth method. Scanning electron microscopy (SEM), high resolution transmission electron microscopy [HRTEM], as well as XRD and energy dispersive X-ray techniques were used for the structural characterisation of synthesised ZnO nanorods. This study has explored highly dense, uniform, well-aligned growth pattern along 0001 direction and good crystal quality of the prepared ZnO nanorods. ZnO nanorods are only composed of Zn and O atoms. Moreover, X-ray photoelectron spectroscopy was used for the chemical analysis of fabricated ZnO nanorods. In addition, the structural characterisation and the chemical composition study and the optical investigation were carried out for the fabricated ZnO nanorods and the photoluminescence [PL] spectrum have shown strong ultraviolet (UV) peak at 381 nm for Fe3O4 nanoparticles seeded ZnO nanorods and the PL spectrum for ZnO nanorods grown with the seed layer of Co3O4 nanoparticles has shown a UV peak at 382 nm. The green emission and orange/red peaks were also observed for ZnO nanorods grown with both the seed layers. This study has indicated the fabrication of well aligned ZnO nanorods using the one inorganic nanomaterial on other inorganic nanomaterial due to their similar chemistry.

  3. Stereo-epitaxial growth of single-crystal Ni nanowires and nanoplates from aligned seed crystals

    NASA Astrophysics Data System (ADS)

    Lee, Hyoban; Yoo, Youngdong; Kang, Taejoon; Lee, Jiyoung; Kim, Eungwang; Fang, Xiaosheng; Lee, Sungyul; Kim, Bongsoo

    2016-05-01

    Epitaxially grown anisotropic Ni nanostructures are promising building blocks for the development of miniaturized and stereo-integrated data storage kits because they can store multiple magnetic domain walls (DWs). Here, we report stereo-epitaxially grown single-crystalline Ni nanowires (NWs) and nanoplates, and their magnetic properties. Vertical and inclined Ni NWs were grown at the center and edge regions of c-cut sapphire substrates, respectively. Vertical Ni nanoplates were grown on r-cut sapphire substrates. The morphology and growth direction of Ni nanostructures can be steered by seed crystals. Cubic Ni seeds grow into vertical Ni NWs, tetrahedral Ni seeds grow into inclined Ni NWs, and triangular Ni seeds grow into vertical Ni nanoplates. The shapes of the Ni seeds are determined by the interfacial energy between the bottom plane of the seeds and the substrates. The as-synthesized Ni NWs and nanoplates have blocking temperature values greater than 300 K at 500 Oe, verifying that these Ni nanostructures can form large magnetic DWs with high magnetic anisotropy properties. We anticipate that epitaxially grown Ni NWs and nanoplates will be used in various types of 3-dimensional magnetic devices.Epitaxially grown anisotropic Ni nanostructures are promising building blocks for the development of miniaturized and stereo-integrated data storage kits because they can store multiple magnetic domain walls (DWs). Here, we report stereo-epitaxially grown single-crystalline Ni nanowires (NWs) and nanoplates, and their magnetic properties. Vertical and inclined Ni NWs were grown at the center and edge regions of c-cut sapphire substrates, respectively. Vertical Ni nanoplates were grown on r-cut sapphire substrates. The morphology and growth direction of Ni nanostructures can be steered by seed crystals. Cubic Ni seeds grow into vertical Ni NWs, tetrahedral Ni seeds grow into inclined Ni NWs, and triangular Ni seeds grow into vertical Ni nanoplates. The shapes of the Ni

  4. ZnO nanorod/porous silicon nanowire hybrid structures as highly-sensitive NO2 gas sensors at room temperature.

    PubMed

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

    2016-02-01

    ZnO nanorod/porous silicon nanowire (ZnO/PSiNW) hybrids with three different structures as highly sensitive NO2 gas sensors were obtained. PSiNWs were first synthesized by metal-assisted chemical etching, and then seeded in three different ways. After that ZnO nanorods were grown on the seeded surface of PSiNWs using a hydrothermal procedure. ZnO/PSiNW hybrids showed excellent gas sensing performance for various NO2 concentrations (5-50 ppm) at room temperature, and the electrical resistance change rate reached as high as 35.1% when responding to 50 ppm NO2. The distinct enhancement was mainly attributed to the faster carrier transportation after combination, the increase in gas sensing areas and the oxygen vacancy (VO) concentration. Moreover, the p-type gas sensing behavior was explained by the gas sensing mechanism and the effect of VO concentration on gas sensing properties was also discussed concerning the photoluminescence (PL) spectra performance. PMID:26804157

  5. Hydrothermal treatment for the marked structural and optical quality improvement of ZnO nanowire arrays deposited on lightweight flexible substrates

    NASA Astrophysics Data System (ADS)

    Lupan, Oleg; Pauporté, Thierry

    2010-08-01

    ZnO nanowire arrays (NWs) have attracted great interest as the building blocks for emerging applications in new flexible and elastic electronic and optoelectronic devices (e.g. smart cards, light emitting diodes (LEDs), displays, etc.) with higher functionality. Since flexible plastic substrates (FPS) are important, soft post-growth treatments compatible with FPS must be found to significantly improve the properties of NWs deposited on it. We present an innovative low-temperature hydrothermal treatment in an autoclave to improve the structural and optical properties of ZnO NWs grown by electrochemical deposition at low temperature (80 °C) on transparent flexible polymer -based indium-tin-oxide (ITO) coated substrates. The layer characterizations by scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed the improvement of the wire surface smoothness and of their structural quality. The observed higher excitonic photoluminescence at 381 nm and the stronger optical phonon modes in the Raman spectra demonstrated the superior performance of the post-growth hydrothermal treatment compared to a conventional annealing at the same temperature. The presented results pave the way for the realization of new highly efficient ZnO-based optoelectronic devices on flexible plastic substrates or elastic foils.

  6. Individual Zn2SnO4-sheathed ZnO heterostructure nanowires for efficient resistive switching memory controlled by interface states

    PubMed Central

    Cheng, Baochang; Ouyang, Zhiyong; Chen, Chuan; Xiao, Yanhe; Lei, Shuijin

    2013-01-01

    Resistive switching (RS) devices are widely believed as a promising candidate for next generation nonvolatile resistance random access memory. Here, Zn2SnO4-sheathed ZnO core/shell heterostructure nanowires were constructed through a polymeric sol–gel approach followed by post-annealing. The back-to-back bipolar RS properties were observed in the Ohmic contact two-terminal devices based on individual core/shell nanowires. With increasing bias to about 1.5 V, it changes from high-resistance states (HRS) to low-resistance states, and however, it can be restored to HRS by reverse bias. We propose a new mechanism, which is attributed to the injection of electrons into/from interfacial states, arising from the lattice mismatch at ZnO/Zn2SnO4 heterointerface. Upon applying negative/positive voltage at one end of devices, where interfacial states are filled/emptied, barrier will be eliminated/created, resulting into symmetric RS characteristics. The behavior of storage and removal charges demonstrates that the heterostructures have excellent properties for the application in resistance random access memory. PMID:24247976

  7. Individual Zn2SnO4-sheathed ZnO heterostructure nanowires for efficient resistive switching memory controlled by interface states

    NASA Astrophysics Data System (ADS)

    Cheng, Baochang; Ouyang, Zhiyong; Chen, Chuan; Xiao, Yanhe; Lei, Shuijin

    2013-11-01

    Resistive switching (RS) devices are widely believed as a promising candidate for next generation nonvolatile resistance random access memory. Here, Zn2SnO4-sheathed ZnO core/shell heterostructure nanowires were constructed through a polymeric sol-gel approach followed by post-annealing. The back-to-back bipolar RS properties were observed in the Ohmic contact two-terminal devices based on individual core/shell nanowires. With increasing bias to about 1.5 V, it changes from high-resistance states (HRS) to low-resistance states, and however, it can be restored to HRS by reverse bias. We propose a new mechanism, which is attributed to the injection of electrons into/from interfacial states, arising from the lattice mismatch at ZnO/Zn2SnO4 heterointerface. Upon applying negative/positive voltage at one end of devices, where interfacial states are filled/emptied, barrier will be eliminated/created, resulting into symmetric RS characteristics. The behavior of storage and removal charges demonstrates that the heterostructures have excellent properties for the application in resistance random access memory.

  8. Field-Effect Modulation of Ambipolar Doping and Domain Wall Band Alignment in P-type Vanadium Dioxide Nanowires

    NASA Astrophysics Data System (ADS)

    Hou, Yasen; Peng, Xingyue; Yang, Yiming; Yu, Dong

    The sub-picosecond metal-insulator phase transition in vanadium dioxide (VO2) has attracted extensive attention with potential applications in ultrafast Mott transistors. However, the development of VO2-based transistors lags behind, owing to the lack of an efficient and hysteresis-free electrostatic doping control. Here we report the first synthesis of p-type single crystalline VO2nanowires via catalyst-free chemical vapor deposition. The p-type doping was unambiguously confirmed by both solid and electrochemical gating methods, and further evidenced by the scanning photocurrent microscopic measurements. Interestingly, we observed that the photocurrent spot polarity at the metal-insulator domain walls was reversibly switched by electrochemical gating, which indicates a band bending flipping. Furthermore, we eliminated the common hysteresis in gate sweep and greatly shortened the transistor response time via a hybrid gating method, which combines the merits of liquid ionic and solid gating. The capability of efficient field effect modulation of ambipolar conduction and band alignment offers new opportunities on understanding the phase transition mechanism and enables novel electronic applications based on VO2.

  9. Dye-sensitized solar cells with vertically aligned TiO2 nanowire arrays grown on carbon fibers.

    PubMed

    Cai, Xin; Wu, Hongwei; Hou, Shaocong; Peng, Ming; Yu, Xiao; Zou, Dechun

    2014-02-01

    One-dimensional semiconductor TiO2 nanowires (TNWs) have received widespread attention from solar cell and related optoelectronics scientists. The controllable synthesis of ordered TNW arrays on arbitrary substrates would benefit both fundamental research and practical applications. Herein, vertically aligned TNW arrays in situ grown on carbon fiber (CF) substrates through a facile, controllable, and seed-assisted thermal process is presented. Also, hierarchical TiO2 -nanoparticle/TNW arrays were prepared that favor both the dye loading and depressed charge recombination of the CF/TNW photoanode. An impressive conversion efficiency of 2.48 % (under air mass 1.5 global illumination) and an apparent efficiency of 4.18 % (with a diffuse board) due to the 3D light harvesting of the wire solar cell were achieved. Moreover, efficient and inexpensive wire solar cells made from all-CF electrodes and completely flexible CF-based wire solar cells were demonstrated, taking into account actual application requirements. This work may provide an intriguing avenue for the pursuit of lightweight, cost-effective, and high-performance flexible/wearable solar cells. PMID:24488679

  10. Stereo-epitaxial growth of single-crystal Ni nanowires and nanoplates from aligned seed crystals.

    PubMed

    Lee, Hyoban; Yoo, Youngdong; Kang, Taejoon; Lee, Jiyoung; Kim, Eungwang; Fang, Xiaosheng; Lee, Sungyul; Kim, Bongsoo

    2016-05-21

    Epitaxially grown anisotropic Ni nanostructures are promising building blocks for the development of miniaturized and stereo-integrated data storage kits because they can store multiple magnetic domain walls (DWs). Here, we report stereo-epitaxially grown single-crystalline Ni nanowires (NWs) and nanoplates, and their magnetic properties. Vertical and inclined Ni NWs were grown at the center and edge regions of c-cut sapphire substrates, respectively. Vertical Ni nanoplates were grown on r-cut sapphire substrates. The morphology and growth direction of Ni nanostructures can be steered by seed crystals. Cubic Ni seeds grow into vertical Ni NWs, tetrahedral Ni seeds grow into inclined Ni NWs, and triangular Ni seeds grow into vertical Ni nanoplates. The shapes of the Ni seeds are determined by the interfacial energy between the bottom plane of the seeds and the substrates. The as-synthesized Ni NWs and nanoplates have blocking temperature values greater than 300 K at 500 Oe, verifying that these Ni nanostructures can form large magnetic DWs with high magnetic anisotropy properties. We anticipate that epitaxially grown Ni NWs and nanoplates will be used in various types of 3-dimensional magnetic devices. PMID:27129106

  11. Self-assembled, aligned ZnO nanorod buffer layers for high-current-density, inverted organic photovoltaics.

    PubMed

    Rao, Arun D; Karalatti, Suresh; Thomas, Tiju; Ramamurthy, Praveen C

    2014-10-01

    Two different soft-chemical, self-assembly-based solution approaches are employed to grow zinc oxide (ZnO) nanorods with controlled texture. The methods used involve seeding and growth on a substrate. Nanorods with various aspect ratios (1-5) and diameters (15-65 nm) are grown. Obtaining highly oriented rods is determined by the way the substrate is mounted within the chemical bath. Furthermore, a preheat and centrifugation step is essential for the optimization of the growth solution. In the best samples, we obtain ZnO nanorods that are almost entirely oriented in the (002) direction; this is desirable since electron mobility of ZnO is highest along this crystallographic axis. When used as the buffer layer of inverted organic photovoltaics (I-OPVs), these one-dimensional (1D) nanostructures offer: (a) direct paths for charge transport and (b) high interfacial area for electron collection. The morphological, structural, and optical properties of ZnO nanorods are studied using scanning electron microscopy, X-ray diffraction, and ultraviolet-visible light (UV-vis) absorption spectroscopy. Furthermore, the surface chemical features of ZnO films are studied using X-ray photoelectron spectroscopy and contact angle measurements. Using as-grown ZnO, inverted OPVs are fabricated and characterized. For improving device performance, the ZnO nanorods are subjected to UV-ozone irradiation. UV-ozone treated ZnO nanorods show: (i) improvement in optical transmission, (ii) increased wetting of active organic components, and (iii) increased concentration of Zn-O surface bonds. These observations correlate well with improved device performance. The devices fabricated using these optimized buffer layers have an efficiency of ∼3.2% and a fill factor of 0.50; this is comparable to the best I-OPVs reported that use a P3HT-PCBM active layer. PMID:25238197

  12. Hydrothermal synthesis of highly crystalline ZnO nanorod arrays: Dependence of morphology and alignment on growth conditions

    NASA Astrophysics Data System (ADS)

    Azzez, Shrook A.; Hassan, Z.; Hassan, J. J.; Alimanesh, M.; Rasheed, Hiba S.; Sabah, Fayroz A.; Abdulateef, Sinan A.

    2016-07-01

    Highly oriented zinc oxide nanorod were successfully grown on seeded p-type silicone substrate by hydrothermal methode. The morphology and the crystallinty of ZnO c-axis (002) arrays were systematically studied using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) methods. The effect of seed layer pre-annealing on nanorods properties was explained according to the nucleation site of ZnO nanoparticles on silicon substrate. In addition, the variation of the equal molarity of zinc nitrate hexahydrate and hexamine concentrations in the reaction vessel play a crucial role related to the ZnO nanorods.

  13. The clash of mechanical and electrical size-effects in ZnO nanowires and a double power law approach to elastic strain engineering of piezoelectric and piezotronic devices.

    PubMed

    Rinaldi, Antonio; Araneo, Rodolfo; Celozzi, Salvatore; Pea, Marialilia; Notargiacomo, Andrea

    2014-09-10

    The piezoelectric performance of ultra-strength ZnO nanowires (NWs) depends on the subtle interplay between electrical and mechanical size-effects. "Size-dependent" modeling of compressed NWs illustrates why experimentally observed mechanical stiffening can indeed collide with electrical size-effects when the size shrinks, thereby lowering the actual piezoelectric function from bulk estimates. "Smaller" is not necessarily "better" in nanotechnology. PMID:25138083

  14. Seedless Pattern Growth of Quasi-Aligned ZnO Nanorod Arrays on Cover Glass Substrates in Solution

    NASA Astrophysics Data System (ADS)

    Ahsanulhaq, Q.; Kim, Jin Hwan; Kim, Jeong Hyun; Hahn, Y. B.

    2010-03-01

    A hybrid technique for the selective growth of ZnO nanorod arrays on wanted areas of thin cover glass substrates was developed without the use of seed layer of ZnO. This method utilizes electron-beam lithography for pattern transfer on seedless substrate, followed by solution method for the bottom-up growth of ZnO nanorod arrays on the patterned substrates. The arrays of highly crystalline ZnO nanorods having diameter of 60 ± 10 nm and length of 750 ± 50 nm were selectively grown on different shape patterns and exhibited a remarkable uniformity in terms of diameter, length, and density. The room temperature cathodluminescence measurements showed a strong ultraviolet emission at 381 nm and broad visible emission at 585-610 nm were observed in the spectrum.

  15. Aligned platinum nanowire networks from surface-oriented lipid cubic phase templates

    NASA Astrophysics Data System (ADS)

    Richardson, S. J.; Burton, M. R.; Staniec, P. A.; Nandhakumar, I. S.; Terrill, N. J.; Elliott, J. M.; Squires, A. M.

    2016-01-01

    Mesoporous metal structures featuring a bicontinuous cubic morphology have a wide range of potential applications and novel opto-electronic properties, often orientation-dependent. We describe the production of nanostructured metal films 1-2 microns thick featuring 3D-periodic `single diamond' morphology that show high out-of-plane alignment, with the (111) plane oriented parallel to the substrate. These are produced by electrodeposition of platinum through a lipid cubic phase (QII) template. Further investigation into the mechanism for the orientation revealed the surprising result that the QII template, which is tens of microns thick, is polydomain with no overall orientation. When thicker platinum films are grown, they also show increased orientational disorder. These results suggest that polydomain QII samples display a region of uniaxial orientation at the lipid/substrate interface up to approximately 2.8 +/- 0.3 μm away from the solid surface. Our approach gives previously unavailable information on the arrangement of cubic phases at solid interfaces, which is important for many applications of QII phases. Most significantly, we have produced a previously unreported class of oriented nanomaterial, with potential applications including metamaterials and lithographic masks.Mesoporous metal structures featuring a bicontinuous cubic morphology have a wide range of potential applications and novel opto-electronic properties, often orientation-dependent. We describe the production of nanostructured metal films 1-2 microns thick featuring 3D-periodic `single diamond' morphology that show high out-of-plane alignment, with the (111) plane oriented parallel to the substrate. These are produced by electrodeposition of platinum through a lipid cubic phase (QII) template. Further investigation into the mechanism for the orientation revealed the surprising result that the QII template, which is tens of microns thick, is polydomain with no overall orientation. When thicker

  16. Functionalized vertically aligned ZnO nanorods for application in electrolyte-insulator-semiconductor based pH sensors and label-free immuno-sensors

    NASA Astrophysics Data System (ADS)

    Kumar, Narendra; Senapati, Sujata; Kumar, Satyendra; Kumar, Jitendra; Panda, Siddhartha

    2016-04-01

    Vertically aligned ZnO nanorods were grown on a SiO2/Si surface by optimization of the temperature and atmosphere for annealing of the seed. The seed layer annealed at 500 °C in vacuum provided well separated and uniform seeds which also provided the best condition to get densely packed, uniformly distributed, and vertically aligned nanorods. These nanorods grown on the substrates were used to fabricate electrolyte-insulator-semiconductor (EIS) devices for pH sensing. Etching of ZnO at acidic pH prevents the direct use of nanorods for pH sensing. Therefore, the nanorods functionalised with 3-aminopropyltriethoxysilane (APTES) were utilized for pH sensing and showed the pH sensitivity of 50.1 mV/pH. APTES is also known to be used as a linker to immobilize biomolecules (such as antibodies). The EIS device with APTES functionalized nanorods was used for the label free detection of prostate-specific antigen (PSA). Finally, voltage shifts of 23 mV and 35 mV were observed with PSA concentrations of 1 ng/ml and 100 ng/ml, respectively.

  17. Transparent, high-performance thin-film transistors with an InGaZnO/aligned-SnO2 -nanowire composite and their application in photodetectors.

    PubMed

    Liu, Xingqiang; Liu, Xi; Wang, Jingli; Liao, Chongnan; Xiao, Xiangheng; Guo, Shishang; Jiang, Changzhong; Fan, Zhiyong; Wang, Ti; Chen, Xiaoshuang; Lu, Wei; Hu, Weida; Liao, Lei

    2014-11-19

    A high mobility of 109.0 cm(2) V(-1) s(-1) is obtained by thin-film transistors (TFTs) comprising a composite made by aligning SnO2 nanowires (NWs) in amorphous InGaZnO (a-IGZO) thin films. This composite TFT reaches an on-current density of 61.4 μA μm(-1) with a 10 μm channel length. Its performance surpasses that of single-crystalline InGaZnO and is comparable with that of polycrystalline silicon. PMID:25236580

  18. A laser-assisted process to produce patterned growth of vertically aligned nanowire arrays for monolithic microwave integrated devices

    NASA Astrophysics Data System (ADS)

    Van Kerckhoven, Vivien; Piraux, Luc; Huynen, Isabelle

    2016-06-01

    An experimental process for the fabrication of microwave devices made of nanowire arrays embedded in a dielectric template is presented. A pulse laser process is used to produce a patterned surface mask on alumina templates, defining precisely the wire growing areas during electroplating. This technique makes it possible to finely position multiple nanowire arrays in the template, as well as produce large areas and complex structures, combining transmission line sections with various nanowire heights. The efficiency of this process is demonstrated through the realisation of a microstrip electromagnetic band-gap filter and a substrate-integrated waveguide.

  19. A laser-assisted process to produce patterned growth of vertically aligned nanowire arrays for monolithic microwave integrated devices.

    PubMed

    Kerckhoven, Vivien Van; Piraux, Luc; Huynen, Isabelle

    2016-06-10

    An experimental process for the fabrication of microwave devices made of nanowire arrays embedded in a dielectric template is presented. A pulse laser process is used to produce a patterned surface mask on alumina templates, defining precisely the wire growing areas during electroplating. This technique makes it possible to finely position multiple nanowire arrays in the template, as well as produce large areas and complex structures, combining transmission line sections with various nanowire heights. The efficiency of this process is demonstrated through the realisation of a microstrip electromagnetic band-gap filter and a substrate-integrated waveguide. PMID:27138863

  20. Obtaining a Well-Aligned ZnO Nanotube Array Using the Hydrothermal Growth Method / Labi Sakārtotu Zno Nanocauruļu Kopu Iegūšana, Izmantojot Hidrotermālo Metodi

    NASA Astrophysics Data System (ADS)

    Krasovska, M.; Gerbreders, V.; Paskevics, V.; Ogurcovs, A.; Mihailova, I.

    2015-10-01

    Optimal growing parameters have been found using the hydrothermal method to obtain well-aligned vertical ZnO nanorod and nanotube arrays. The influence of different growing factors (such as temperature, growing solution concentration, method of obtaining seed layer and condition) on nanotube morphology and size is described in the paper. Well-structured ZnO nanotubes have been obtained by using a selfselective etching method with lowering temperatures of growth during the hydrothermal process. It is shown that the optical properties of the nanostructure arrays obtained are sensitive to the medium in which they are placed, which is why they can be used as sensors for pure substance detection and in different solutions for impurity determination. Dotajā darbā tika noteikti optimāli parametri labi sakārtotu ZnO nanocaurulīšu kopu iegūšanai, izmantojot hidrotermālo metodi ar temperatūras pazemināšanu, jeb t.s. selektīvu pa\\vskodināšanas metodi (self-selective etching), ir uzsvērtas šās metodes priekšrocības salīdzinājumā ar ķīmiskās kodināšanas metodi, kā arī tika aprakstīta dažādu augšanas faktora (tādu, ka darba šķīduma koncentrācija, augšanas temperatūra un laiks, iedīgļu slāņa iegūšanas veids un iegūšanas parametri) ietekme uz iegūtu nanostraktūra morfoloģiju. Tika konstatēts, ka noteicošu lomu ZnO nanocaurulīšu audzēšanas procesā spēlē iedīgļu slāņa graudu izmēri, kas savā staipā nosaka augošu nanostieņu izmērus un to tendenci pie pa\\vskodināšanas. Rentgenogrannnas parāda, ka iegūtām pie noteiktiem parametriem ZnO nanostruktūrām piemīt augsta kristāliskuma pakāpe un sakārtotība vertikālā virzienā. Optiskie mērījumi parāda, ka ZnO nanocauralītes ir jutīgas gan pret tīrām vielām (ūdens, spirts), gan pret dažādiem šķīdumiem, kas ļauj izmantot tos kā pie­jaukumu sensora. Salīdzinājumā ar ZnO nanostieņiem caurulīšu jūtība pieaug, jo pieaug nanostrakt

  1. Purely sonochemical route for oriented zinc oxide nanowire growth on arbitrary substrate

    NASA Astrophysics Data System (ADS)

    Nayak, Avinash P.; Katzenmeyer, Aaron M.; Kim, Ja-Yeon; Kwon, Min Ki; Gosho, Yasuhiro; Islam, M. Saif

    2010-04-01

    We report a simple sonochemical method for the seeding and synthesis of Zinc Oxide nanowire arrays that can be formed on a number of substrates that are stable in alcohol and aqueous solution. Vertically aligned ZnO NWs were synthesized from a single solution at room-ambient via ultrasonic excitation. Prior to the NW growth, a ZnO seed layer was deposited using the same system with a different solution. The optimal conditions to produce a high density of oriented wires along with their optical characteristics are presented for ZnO NWs with a significantly high growth rate compared with traditional growth techniques such as evaporation, chemical vapor deposition and sputtering. Our method promises a mass-manufacturable process for fast and inexpensive ZnO NW production for practical low cost electronics, photonics and energy conversion applications.

  2. Self-aligned process for forming microlenses at the tips of vertical silicon nanowires by atomic layer deposition

    SciTech Connect

    Dan, Yaping Chen, Kaixiang; Crozier, Kenneth B.

    2015-01-01

    The microlens is a key enabling technology in optoelectronics, permitting light to be efficiently coupled to and from devices such as image sensors and light-emitting diodes. Their ubiquitous nature motivates the development of new fabrication techniques, since existing methods face challenges as microlenses are scaled to smaller dimensions. Here, the authors demonstrate the formation of microlenses at the tips of vertically oriented silicon nanowires via a rapid atomic layer deposition process. The nature of the process is such that the microlenses are centered on the nanowires, and there is a self-limiting effect on the final sizes of the microlenses arising from the nanowire spacing. Finite difference time domain electromagnetic simulations are performed of microlens focusing properties, including showing their ability to enhance visible-wavelength absorption in silicon nanowires.

  3. Highly integrated synthesis of heterogeneous nanostructures on nanowire heater array

    NASA Astrophysics Data System (ADS)

    Jin, Chun Yan; Yun, Jeonghoon; Kim, Jung; Yang, Daejong; Kim, Dong Hwan; Ahn, Jae Hyuk; Lee, Kwang-Cheol; Park, Inkyu

    2014-11-01

    We have proposed a new method for the multiplexed synthesis of heterogeneous nanostructures using a top-down fabricated nanowire heater array. Hydrothermally synthesized nanostructures can be grown only on the heated nanowire through nanoscale temperature control using a Joule heated nanowire. We have demonstrated the selective synthesis of zinc oxide (ZnO) nanowires and copper oxide (CuO) nanostructures, as well as their surface modification with noble metal nanoparticles, using a nanowire heater array. Furthermore, we could fabricate an array of heterogeneous nanostructures via Joule heating of individual nanowire heaters and changing of the precursor solutions in a sequential manner. We have formed a parallel array of palladium (Pd) coated ZnO nanowires and gold (Au) coated ZnO nanowires, as well as a parallel array of ZnO nanowires and CuO nanospikes, in the microscale region by using the developed method.We have proposed a new method for the multiplexed synthesis of heterogeneous nanostructures using a top-down fabricated nanowire heater array. Hydrothermally synthesized nanostructures can be grown only on the heated nanowire through nanoscale temperature control using a Joule heated nanowire. We have demonstrated the selective synthesis of zinc oxide (ZnO) nanowires and copper oxide (CuO) nanostructures, as well as their surface modification with noble metal nanoparticles, using a nanowire heater array. Furthermore, we could fabricate an array of heterogeneous nanostructures via Joule heating of individual nanowire heaters and changing of the precursor solutions in a sequential manner. We have formed a parallel array of palladium (Pd) coated ZnO nanowires and gold (Au) coated ZnO nanowires, as well as a parallel array of ZnO nanowires and CuO nanospikes, in the microscale region by using the developed method. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04216f

  4. Hybrid core-shell nanowire electrodes utilizing vertically aligned carbon nanofiber arrays for high-performance energy storage

    NASA Astrophysics Data System (ADS)

    Klankowski, Steven Arnold

    Nanostructured electrode materials for electrochemical energy storage systems have been shown to improve both rate performance and capacity retention, while allowing considerably longer cycling lifetime. The nano-architectures provide enhanced kinetics by means of larger surface area, higher porosity, better material interconnectivity, shorter diffusion lengths, and overall mechanical stability. Meanwhile, active materials that once were excluded from use due to bulk property issues are now being examined in new nanoarchitecture. Silicon was such a material, desired for its large lithium-ion storage capacity of 4,200 mAh g-1 and low redox potential of 0.4 V vs. Li/Li+; however, a ˜300% volume expansion and increased resistivity upon lithiation limited its broader applications. In the first study, the silicon-coated vertically aligned carbon nanofiber (VACNF) array presents a unique core-shell nanowire (NW) architecture that demonstrates both good capacity and high rate performance. In follow-up, the Si-VACNFs NW electrode demonstrates enhanced power rate capabilities as it shows excellent storage capacity at high rates, attributed to the unique nanoneedle structure that high vacuum sputtering produces on the three-dimensional array. Following silicon's success, titanium dioxide has been explored as an alternative high-rate electrode material by utilizing the dual storage mechanisms of Li+ insertion and pseudocapacitance. The TiO 2-coated VACNFs shows improved electrochemical activity that delivers near theoretical capacity at larger currents due to shorter Li+ diffusion lengths and highly effective electron transport. A unique cell is formed with the Si-coated and TiO2-coated electrodes place counter to one another, creating the hybrid of lithium ion battery-pseudocapacitor that demonstrated both high power and high energy densities. The hybrid cell operates like a battery at lower current rates, achieving larger discharge capacity, while retaining one-third of

  5. Zinc oxide nanowire networks for macroelectronic devices

    NASA Astrophysics Data System (ADS)

    Unalan, Husnu Emrah; Zhang, Yan; Hiralal, Pritesh; Dalal, Sharvari; Chu, Daping; Eda, Goki; Teo, K. B. K.; Chhowalla, Manish; Milne, William I.; Amaratunga, Gehan A. J.

    2009-04-01

    Highly transparent zinc oxide (ZnO) nanowire networks have been used as the active material in thin film transistors (TFTs) and complementary inverter devices. A systematic study on a range of networks of variable density and TFT channel length was performed. ZnO nanowire networks provide a less lithographically intense alternative to individual nanowire devices, are always semiconducting, and yield significantly higher mobilites than those achieved from currently used amorphous Si and organic TFTs. These results suggest that ZnO nanowire networks could be ideal for inexpensive large area electronics.

  6. Band alignment at the interface between Ni-doped Cr2O3 and Al-doped ZnO: implications for transparent p-n junctions

    NASA Astrophysics Data System (ADS)

    Arca, Elisabetta; McInerney, Michael A.; Shvets, Igor V.

    2016-06-01

    The realization of transparent electronic and optoelectronic devices requires the use of transparent p-n junctions. In this context, understanding the band alignment at the interface between the p- and n-components represents a fundamental step towards the realization of high performance devices. In this work, the band alignment at the interface between Al-doped ZnO (AZO) and Ni-doped Cr2O3 has been analysed. The formation and evolution of the core levels as the interface progressively forms have been followed by means of x-ray Photoelectron Spectroscopy, x-ray diffraction and x-ray reflectivity. A type two (staggered) band alignment was identified, with the valence band offset and conduction band offset found to be 2.6 eV and 2.5 eV, respectively. The electrical behaviour will be discussed in terms of the position of the bands, the presence of band bending and the expected built-in potential and how these can be engineered in order to achieve the maximum performance for this hetero-structure.

  7. 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.

  8. 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.

  9. Band alignment at the interface between Ni-doped Cr2O3 and Al-doped ZnO: implications for transparent p-n junctions.

    PubMed

    Arca, Elisabetta; McInerney, Michael A; Shvets, Igor V

    2016-06-01

    The realization of transparent electronic and optoelectronic devices requires the use of transparent p-n junctions. In this context, understanding the band alignment at the interface between the p- and n-components represents a fundamental step towards the realization of high performance devices. In this work, the band alignment at the interface between Al-doped ZnO (AZO) and Ni-doped Cr2O3 has been analysed. The formation and evolution of the core levels as the interface progressively forms have been followed by means of x-ray Photoelectron Spectroscopy, x-ray diffraction and x-ray reflectivity. A type two (staggered) band alignment was identified, with the valence band offset and conduction band offset found to be 2.6 eV and 2.5 eV, respectively. The electrical behaviour will be discussed in terms of the position of the bands, the presence of band bending and the expected built-in potential and how these can be engineered in order to achieve the maximum performance for this hetero-structure. PMID:26952763

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

    PubMed Central

    2012-01-01

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

  11. Fluorinated copper phthalocyanine nanowires for enhancing interfacial electron transport in organic solar cells.

    PubMed

    Yoon, Seok Min; Lou, Sylvia J; Loser, Stephen; Smith, Jeremy; Chen, Lin X; Facchetti, Antonio; Marks, Tobin J; Marks, Tobin

    2012-12-12

    Zinc oxide is a promising candidate as an interfacial layer (IFL) in inverted organic photovoltaic (OPV) cells due to the n-type semiconducting properties as well as chemical and environmental stability. Such ZnO layers collect electrons at the transparent electrode, typically indium tin oxide (ITO). However, the significant resistivity of ZnO IFLs and an energetic mismatch between the ZnO and the ITO layers hinder optimum charge collection. Here we report that inserting nanoscopic copper hexadecafluorophthalocyanine (F(16)CuPc) layers, as thin films or nanowires, between the ITO anode and the ZnO IFL increases OPV performance by enhancing interfacial electron transport. In inverted P3HT:PC(61)BM cells, insertion of F(16)CuPc nanowires increases the short circuit current density (J(sc)) versus cells with only ZnO layers, yielding an enhanced power conversion efficiency (PCE) of ∼3.6% vs ∼3.0% for a control without the nanowire layer. Similar effects are observed for inverted PTB7:PC(71)BM cells where the PCE is increased from 8.1% to 8.6%. X-ray scattering, optical, and electrical measurements indicate that the performance enhancement is ascribable to both favorable alignment of the nanowire π-π stacking axes parallel to the photocurrent flow and to the increased interfacial layer-active layer contact area. These findings identify a promising strategy to enhance inverted OPV performance by inserting anisotropic nanostructures with π-π stacking aligned in the photocurrent flow direction. PMID:23181741

  12. Facile fabrication of hierarchical ZnO nanowire aggregates using rose-like peroxide precursor as the inorganic template

    NASA Astrophysics Data System (ADS)

    Gu, Yan; Yan, Fengwen; Guo, Cun-Yue; Yuan, Guoqing

    2016-08-01

    The complex rose-like inorganic templates assembled by the ZnO/ZnO2 hybrid nanosheets have been constructed with hydrogen peroxide as an additive to control the structure of a precursor. The surface morphologies of the inorganic templates can be controlled by varying the reaction time and the amount of hydrogen peroxide. The process of the precursor growth takes a dissolution-growth route under hydrothermal conditions. The chemical composition of the precursor is determined by X-ray diffraction (XRD) and Raman analyses, indicating the existence of peroxide in the precursor. Combined with transmission electron microscopy (TEM) data, the ZnO/ZnO2 hybrid precursor is proposed to act as an inorganic template for the growth of secondary crystal structures. The dandelion-like ZnO crystal is fabricated by using rose-like peroxide precursor as the inorganic template. The structural evolution of hierarchical ZnO crystal is studied by monitoring the influence of the reaction time.

  13. All-printable band-edge modulated ZnO nanowire photodetectors with ultra-high detectivity

    NASA Astrophysics Data System (ADS)

    Liu, Xi; Gu, Leilei; Zhang, Qianpeng; Wu, Jiyuan; Long, Yunze; Fan, Zhiyong

    2014-06-01

    High-performance photodetectors are critical for high-speed optical communication and environmental sensing, and flexible photodetectors can be used for a wide range of portable or wearable applications. Here we demonstrate the all-printable fabrication of polycrystalline nanowire-based high-performance photodetectors on flexible substrates. Systematic investigations have shown their ultra-high photoconductive gain, responsivity and detectivity up to 3.3 × 1017 Jones. Further analysis shows that their high performance originates from the unique band-edge modulation along the nanowire axial direction, where the existence of Schottky barriers in series leads to highly suppressed dark current of the device and also gives rise to fast photoelectric response to low-intensity optical signal owing to barrier height modulation. The discovered rationale in this work can be utilized as guideline to design high-performance photodetectors with other nanomaterial systems. The developed fabrication scheme opens up possibility for future flexible and high-performance integrated optoelectronic sensor circuitry.

  14. All-printable band-edge modulated ZnO nanowire photodetectors with ultra-high detectivity

    PubMed Central

    Liu, Xi; Gu, Leilei; Zhang, Qianpeng; Wu, Jiyuan; Long, Yunze; Fan, Zhiyong

    2014-01-01

    High-performance photodetectors are critical for high-speed optical communication and environmental sensing, and flexible photodetectors can be used for a wide range of portable or wearable applications. Here we demonstrate the all-printable fabrication of polycrystalline nanowire-based high-performance photodetectors on flexible substrates. Systematic investigations have shown their ultra-high photoconductive gain, responsivity and detectivity up to 3.3 × 1017 Jones. Further analysis shows that their high performance originates from the unique band-edge modulation along the nanowire axial direction, where the existence of Schottky barriers in series leads to highly suppressed dark current of the device and also gives rise to fast photoelectric response to low-intensity optical signal owing to barrier height modulation. The discovered rationale in this work can be utilized as guideline to design high-performance photodetectors with other nanomaterial systems. The developed fabrication scheme opens up possibility for future flexible and high-performance integrated optoelectronic sensor circuitry. PMID:24898081

  15. Comparative study of ultraviolet detectors based on ZnO nanostructures grown on different substrates

    NASA Astrophysics Data System (ADS)

    Abdulgafour, H. I.; Hassan, Z.; Ahmed, N. M.; Yam, F. K.

    2012-10-01

    Pd/ZnO/Pd metal-semiconductor-metal photodetectors have been successfully fabricated using a variety of high-quality ZnO nanostructures. The nanostructures used included well-aligned nanorods, tetrapod-like nanorods, and hair-like nanowires and were synthesized on Si (100), porous silicon (PS/Si), and quartz substrates, respectively, using a catalyst-free vapor-solid mechanism for comparison. The morphological, structural, and optical properties of these nanostructures were investigated. Upon illumination with ultraviolet light (365 nm), the responsivity values of the fabricated photodetectors on PS/Si, Si, and quartz substrates were 0.22, 0.073, and 0.053 A/W, which correspond to quantum efficiencies of 85%, 28%, and 20%, respectively, at an applied bias of 5 V. The present study demonstrated that ZnO nanowires/PS exhibited a relatively fast photoresponse, with a rise time of 0.089 s and fall time of 0.085 s. The ZnO nanorods/Si and ZnO nanotetrapods/quartz exhibited a slow response, with rise times of 0.128 and 0.194 s and fall times of 0.362 and 0.4 s, respectively. The study suggests that the response time of the ZnO nanostructures to ultraviolet exposure is dependent on the type of substrate used. Results show that these nanostructures are suitable for sensing applications.

  16. Synthesis and field emission properties of different ZnO nanostructure arrays

    PubMed Central

    2012-01-01

    In this article, zinc oxide (ZnO) nanostructures of different shapes were fabricated on silicon substrate. Well-aligned and long ZnO nanowire (NW) arrays, as well as leaf-like ZnO nanostructures (which consist of modulated and single-phase structures), were fabricated by a chemical vapor deposition (CVD) method without the assistance of a catalyst. On the other hand, needle-like ZnO NW arrays were first fabricated with the CVD process followed by chemical etching of the NW arrays. The use of chemical etching provides a low-cost and convenient method of obtaining the needle-like arrays. In addition, the field emission properties of the different ZnO NW arrays were also investigated where some differences in the turn-on field and the field-enhancement factors were observed for the ZnO nanostructures of different lengths and shapes. It was experimentally observed that the leaf-like ZnO nanostructure is most suitable for field emission due to its lowest turn-on and threshold field as well as its high field-enhancement factor among the different synthesized nanostructures. PMID:22444723

  17. Low-Temperature Growth of Well-Aligned ZnO Nanorod Arrays by Chemical Bath Deposition for Schottky Diode Application

    NASA Astrophysics Data System (ADS)

    Yuan, Zhaolin

    2015-04-01

    A well-aligned ZnO nanorod array (ZNRA) was successfully grown on an indium tin oxide (ITO) substrate by chemical bath deposition at low temperature. The morphology, crystalline structure, transmittance spectrum and photoluminescence spectrum of as-grown ZNRA were investigated by field emission scanning electron microscopy, x-ray diffraction, ultraviolet-visible spectroscopy and spectrophotometer, respectively. The results of these measurements showed that the ZNRA contained densely packed, aligned nanorods with diameters from 30 nm to 40 nm and a wurtzite structure. The ZNRA exhibited good optical transparency within the visible spectral range, with >80% transmission. Gold (Au) was deposited on top of the ZNRA, and the current-voltage characteristics of the resulting ITO/ZNRA/Au device in the dark were evaluated in detail. The ITO/ZNRA/Au device acted as a Schottky barrier diode with rectifying behaviour, low turn-on voltage (0.6 V), small reverse-bias saturation current (3.73 × 10-6 A), a high ideality factor (3.75), and a reasonable barrier height (0.65 V) between the ZNRA and Au.

  18. Controlled growth of semiconducting nanowire, nanowall, and hybrid nanostructures on graphene for piezoelectric nanogenerators.

    PubMed

    Kumar, Brijesh; Lee, Keun Young; Park, Hyun-Kyu; Chae, Seung Jin; Lee, Young Hee; Kim, Sang-Woo

    2011-05-24

    Precise control of morphologies of one- or two-dimensional nanostructures during growth has not been easy, usually degrading device performance and therefore limiting applications to various advanced nanoscale electronics and optoelectronics. Graphene could be a platform to serve as a substrate for both morphology control and direct use of electrodes due to its ideal monolayer flatness with π electrons. Here, we report that, by using graphene directly as a substrate, vertically well-aligned zinc oxide (ZnO) nanowires and nanowalls were obtained systematically by controlling gold (Au) catalyst thickness and growth time without inflicting significant thermal damage on the graphene layer during thermal chemical vapor deposition of ZnO at high temperature of about 900 °C. We clarify Au nanoparticle positions at graphene-ZnO heterojunctions that are very important in realizing advanced nanoscale electronic and optoelectronic applications of such nanostructures. Further, we demonstrate a piezoelectric nanogenerator that was fabricated from the vertically aligned nanowire-nanowall ZnO hybrid/graphene structure generates a new type of direct current through the specific electron dynamics in the nanowire-nanowall hybrid. PMID:21495657

  19. Investigating the energy harvesting capabilities of a hybrid ZnO nanowires/carbon fiber polymer composite beam.

    PubMed

    Masghouni, N; Burton, J; Philen, M K; Al-Haik, M

    2015-03-01

    Hybrid piezoelectric composite structures that are able to convert mechanical energy into electricity have gained growing attention in the past few years. In this work, an energy harvesting composite beam is developed by growing piezoelectric zinc oxide nanowires on the surface of carbon fiber prior to forming structural composites. The piezoelectric behavior of the composite beam was demonstrated under different vibration sources such as water bath sonicator and permanent magnet vibration shaker. The beam was excited at its fundamental natural frequency (43.2 Hz) and the open circuit voltage and the short circuit current were measured to be 3.1 mV and 23 nA, respectively. Upon connecting an optimal resistor (1.2 kΩ) in series with the beam a maximum power output 2.5 nW was achieved. PMID:25670370

  20. Field emission characteristics of zinc oxide nanowires synthesized by vapor-solid process

    PubMed Central

    2014-01-01

    Vertically aligned ZnO nanowire (NW) arrays have been synthesized on silicon substrates by chemical vapor deposition. The growth of ZnO NWs may be dominated by vapor-solid nucleation mechanism. Morphological, structural, optical, and field emission characteristics can be modified by varying the growth time. For growth time that reaches 120 min, the length and diameter of ZnO NWs are 1.5 μm and 350 nm, respectively, and they also show preferential growth orientation along the c-axis. Room-temperature photoluminescence spectra exhibit a sharp UV emission and broad green emission, and the enhanced UV-to-green emission ratio with increasing growth time might originate from the reduced concentration of surface defects. Furthermore, strong alignment and uniform distribution of ZnO NWs can also effectively enhance the antireflection to reach the average reflectance of 5.7% in the visible region. The field emission measurement indicated that the growth time plays an important role in density- and morphology-controlled ZnO NWs, and thus, ZnO NWs are expected to be used in versatile optoelectronic devices. PMID:24517113

  1. Type I band alignment in GaAs{sub 81}Sb{sub 19}/GaAs core-shell nanowires

    SciTech Connect

    Xu, T.; Wei, M. J.; Capiod, P.; Díaz Álvarez, A.; Han, X. L.; Troadec, D.; Nys, J. P.; Berthe, M.; Lefebvre, I.; Grandidier, B.; Patriarche, G.; Plissard, S. R.; Caroff, P.; and others

    2015-09-14

    The composition and band gap of the shell that formed during the growth of axial GaAs/GaAs{sub 81}Sb{sub 19}/ GaAs heterostructure nanowires have been investigated by transmission electron microscopy combined with energy dispersion spectroscopy, scanning tunneling spectroscopy, and density functional theory calculations. On the GaAs{sub 81}Sb{sub 19} intermediate segment, the shell is found to be free of Sb (pure GaAs shell) and transparent to the tunneling electrons, despite the (110) biaxial strain that affects its band gap. As a result, a direct measurement of the core band gap allows the quantitative determination of the band offset between the GaAs{sub 81}Sb{sub 19} core and the GaAs shell and identifies it as a type I band alignment.

  2. Characteristics of Al-doped ZnO films grown by atomic layer deposition for silicon nanowire photovoltaic device.

    PubMed

    Oh, Byeong-Yun; Han, Jin-Woo; Seo, Dae-Shik; Kim, Kwang-Young; Baek, Seong-Ho; Jang, Hwan Soo; Kim, Jae Hyun

    2012-07-01

    We report the structural, electrical, and optical characteristics of Al-doped ZnO (ZnO:Al) films deposited on glass by atomic layer deposition (ALD) with various Al2O3 film contents for use as transparent electrodes. Unlike films fabricated by a sputtering method, the diffraction peak position of the films deposited by ALD progressively moved to a higher angle with increasing Al2O3 film content. This indicates that Zn sites were effectively replaced by Al, due to layer-by-layer growth mechanism of ALD process which is based on alternate self-limiting surface chemical reactions. By adjusting the Al2O3 film content, a ZnO:Al film with low electrical resistivity (9.84 x 10(-4) Omega cm) was obtained at an Al2O3 film content of 3.17%, where the Al concentration, carrier mobility, optical transmittance, and bandgap energy were 2.8 wt%, 11.20 cm2 V(-1) s(-1), 94.23%, and 3.6 eV, respectively. Moreover, the estimated figure of merit value of our best sample was 8.2 m7Omega(-1). These results suggest that ZnO:Al films deposited by ALD could be useful for electronic devices in which especially require 3-dimensional conformal deposition of the transparent electrode and surface passivation. PMID:22966566

  3. Strain analysis of nanowire interfaces in multiscale composites

    NASA Astrophysics Data System (ADS)

    Malakooti, Mohammad H.; Zhou, Zhi; Spears, John H.; Shankwitz, Timothy J.; Sodano, Henry A.

    2016-04-01

    Recently, the reinforcement-matrix interface of fiber reinforced polymers has been modified through grafting nanostructures - particularly carbon nanotubes and ZnO nanowires - on to the fiber surface. This type of interface engineering has made a great impact on the development of multiscale composites that have high stiffness, interfacial strength, toughness, and vibrational damping - qualities that are mutually exclusive to a degree in most raw materials. Although the efficacy of such nanostructured interfaces has been established, the reinforcement mechanisms of these multiscale composites have not been explored. Here, strain transfer across a nanowire interphase is studied in order to gain a heightened understanding of the working principles of physical interface modification and the formation of a functional gradient. This problem is studied using a functionally graded piezoelectric interface composed of vertically aligned lead zirconate titanate nanowires, as their piezoelectric properties can be utilized to precisely control the strain on one side of the interface. The displacement and strain across the nanowire interface is captured using digital image correlation. It is demonstrated that the material gradient created through nanowires cause a smooth strain transfer from reinforcement phase into matrix phase that eliminates the stress concentration between these phases, which have highly mismatched elasticity.

  4. High surface-to-volume ratio ZnO microberets: low temperature synthesis, characterization, and photoluminescence.

    PubMed

    Lu, Hongbing; Liao, Lei; Li, Jinchai; Wang, Duofa; He, Hui; Fu, Qiang; Xu, Lei; Tian, Yu

    2006-11-23

    Novel hollow ZnO microstructures and ZnO microberets (ZMBs) with nanowires grown vertically on both the inner and outer surfaces of beret shells were synthesized on Si(100) substrates by simple thermal evaporation of pure zinc powder without any catalyst or template material at a relative low temperature of 490 degrees C. XRD, SAED, and HRTEM patterns show that the nanowires and shells of ZMBs are single-crystalline wurtzite structures. The growth mechanism of ZMBs is discussed in detail. The formation of these hollow microstructures depends on the optimum starting time of air introduction. It is a good way to grow well-aligned nanowires by using a nanoscale rough ZnO surface to realize a "self-catalyzed" vapor-liquid-solid process. The photoluminescence spectrum reveals a strong green emission related to the high surface-to-volume ratio of ZMBs. These types of special hollow high surface area structural ZMBs may find potential applications in functional architectural composite materials, solar cell photoanodes, and nanooptoelectronic devices. PMID:17107167

  5. Enhancing Photoresponsivity of Self-Aligned MoS2 Field-Effect Transistors by Piezo-Phototronic Effect from GaN Nanowires.

    PubMed

    Liu, Xingqiang; Yang, Xiaonian; Gao, Guoyun; Yang, Zhenyu; Liu, Haitao; Li, Qiang; Lou, Zheng; Shen, Guozhen; Liao, Lei; Pan, Caofeng; Lin Wang, Zhong

    2016-08-23

    We report high-performance self-aligned MoS2 field-effect transistors (FETs) with enhanced photoresponsivity by the piezo-phototronic effect. The FETs are fabricated based on monolayer MoS2 with a piezoelectric GaN nanowire (NW) as the local gate, and a self-aligned process is employed to define the source/drain electrodes. The fabrication method allows the preservation of the intrinsic property of MoS2 and suppresses the scattering center density in the MoS2/GaN interface, which results in high electrical and photoelectric performances. MoS2 FETs with channel lengths of ∼200 nm have been fabricated with a small subthreshold slope of 64 mV/dec. The photoresponsivity is 443.3 A·W(-1), with a fast response and recovery time of ∼5 ms under 550 nm light illumination. When strain is introduced into the GaN NW, the photoresponsivity is further enhanced to 734.5 A·W(-1) and maintains consistent response and recovery time, which is comparable with that of the mechanical exfoliation of MoS2 transistors. The approach presented here opens an avenue to high-performance top-gated piezo-enhanced MoS2 photodetectors. PMID:27447946

  6. The synthesis and electrical characterization of Cu2O/Al:ZnO radial p-n junction nanowire arrays

    NASA Astrophysics Data System (ADS)

    Kuo, Chien-Lin; Wang, Ruey-Chi; Huang, Jow-Lay; Liu, Chuan-Pu; Wang, Chun-Kai; Chang, Sheng-Po; Chu, Wen-Huei; Wang, Chao-Hung; Tu, Chia-hao

    2009-09-01

    Vertically aligned large-area p-Cu2O/n-AZO (Al-doped ZnO) radial heterojunction nanowire arrays were synthesized on silicon without using catalysts in thermal chemical vapor deposition followed by e-beam evaporation. Scanning electron microscopy and high-resolution transmission electron microscopy results show that poly-crystalline Cu2O nano-shells with thicknesses around 10 nm conformably formed on the entire periphery of pre-grown Al:ZnO single-crystalline nanowires. The Al doping concentration in the Al:ZnO nanowires with diameters around 50 nm were determined to be around 1.19 at.% by electron energy loss spectroscopy. Room-temperature photoluminescence spectra show that the broad green bands of pristine ZnO nanowires were eliminated by capping with Cu2O nano-shells. The current-voltage (I-V) measurements show that the p-Cu2O/n-AZO nanodiodes have well-defined current rectifying behavior. This paper provides a simple method to fabricate superior p-n radial nanowire arrays for developing nano-pixel optoelectronic devices and solar cells.

  7. The synthesis and electrical characterization of Cu2O/Al:ZnO radial p-n junction nanowire arrays.

    PubMed

    Kuo, Chien-Lin; Wang, Ruey-Chi; Huang, Jow-Lay; Liu, Chuan-Pu; Wang, Chun-Kai; Chang, Sheng-Po; Chu, Wen-Huei; Wang, Chao-Hung; Tu, Chia-Hao

    2009-09-01

    Vertically aligned large-area p-Cu(2)O/n-AZO (Al-doped ZnO) radial heterojunction nanowire arrays were synthesized on silicon without using catalysts in thermal chemical vapor deposition followed by e-beam evaporation. Scanning electron microscopy and high-resolution transmission electron microscopy results show that poly-crystalline Cu(2)O nano-shells with thicknesses around 10 nm conformably formed on the entire periphery of pre-grown Al:ZnO single-crystalline nanowires. The Al doping concentration in the Al:ZnO nanowires with diameters around 50 nm were determined to be around 1.19 at.% by electron energy loss spectroscopy. Room-temperature photoluminescence spectra show that the broad green bands of pristine ZnO nanowires were eliminated by capping with Cu(2)O nano-shells. The current-voltage (I-V) measurements show that the p-Cu(2)O/n-AZO nanodiodes have well-defined current rectifying behavior. This paper provides a simple method to fabricate superior p-n radial nanowire arrays for developing nano-pixel optoelectronic devices and solar cells. PMID:19687549

  8. Vertically-aligned sandwich nanowires enhance the photoelectrochemical reduction of hydrogen peroxide: hierarchical formation on carbon nanotubes of cadmium sulfide quantum dots and Prussian blue nanocoatings.

    PubMed

    Gong, Kuanping

    2015-07-01

    We describe a vertically-aligned array of sandwiched nanowires comprising Prussian blue (PB) nanocoating-carbon nanotube (CNT) core-shell structures with CdS particles positioning at the core/shell interface, viz. PB/CdS/CNT. The PB/CdS/CNT electrode thus constructed are noticeable in synchronically harvesting photon-, ionic-, and chemical-energies, respectively, from visible light radiation, K(+) uptaking and releasing, and the reduction of H2O2. In 0.2 M K2SO4 aqueous solution, the photoelectrocatalytic reduction of 1.5 mM H2O2 at PB/CdS/CNT delivered the current density as high as 1.91 mA/cm(2) at reduced overpotential, that is, three times that at the Pt/C. This superb performance is causally linked to the judicious choice of materials and their assembly into defining sandwich nanostructures wherein the three components closely cooperate with each other in the photoelectrocatalytic reduction of H2O2, including photo-induced charge separation in CdS, spontaneous electron injection into PB due to its relatively low Fermi level, and the electrocatalytic reduction of H2O2 by PB via an electrochemical-chemical-electrochemical reaction mechanism. The structural alignment of PB/CdS/CNT ensures the simplest pathway for the mass diffusion and electron shuttle, and a high surface area accessible to the chemical and electrochemical reactions, so as to minimize the concentration- and electrochemical-polarization and thus ensure the fast overall kinetics of the electrode reaction. PMID:25458868

  9. Self-Aligned Cu-Si Core-Shell Nanowire Array as a High-Performance Anode for Li-Ion Batteries

    SciTech Connect

    Qu, Jun; Li, Huaqing; Henry Jr, John James; Martha, Surendra K; Dudney, Nancy J; Lance, Michael J; Mahurin, Shannon Mark; Besmann, Theodore M; Dai, Sheng

    2012-01-01

    Silicon nanowires (NWs) have been reported as a promising anode that demonstrated high capacity without pulverization during cycling, however, they present some technical issues that remain to be solved. The high aspect ratio of the NWs and their small contact areas with the current collector cause high electrical resistance, which results in inefficient electron transport. The nano-size interface between a NW and the substrate experiences high shear stress during lithiation, causing the wire to separate from the current collector. In addition, most reported methods for producing silicon NWs involve high-temperature processing and require catalysts that later become contaminants. This study developed a new self-aligned Cu-Si core-shell NW array using a low-temperature, catalyst-free process to address the issues described. The silicon shell is amorphous as synthesized and accommodates Li-ions without phase transformation. The copper core functions as a built-in current collector to provide very short (nm) electron transport pathways as well as backbone to improve mechanical strength. Initial electrochemical evaluation has demonstrated good capacity retention and high Coulombic efficiency for this new anode material in a half-cell configuration. No wire fracture or core-shell separation was observed after cycling. However, electrolyte decomposition products largely covered the top surface of the NW array, restricting electrolyte access and causing capacity reduction at high charging rates.

  10. High Density of Aligned Nanowire Treated with Polydopamine for Efficient Gene Silencing by siRNA According to Cell Membrane Perturbation.

    PubMed

    Nair, Baiju G; Hagiwara, Kyoji; Ueda, Motoki; Yu, Hsiao-Hua; Tseng, Hsian-Rong; Ito, Yoshihiro

    2016-07-27

    High aspect ratio nanomaterials, such as vertically aligned silicon nanowire (SiNW) substrates, are three-dimensional topological features for cell manipulations. A high density of SiNWs significantly affects not only cell adhesion and proliferation but also the delivery of biomolecules to cells. Here, we used polydopamine (PD) that simply formed a thin coating on various material surfaces by the action of dopamine as a bioinspired approach. The PD coating not only enhanced cell adhesion, spreading, and growth but also anchored more siRNA by adsorption and provided more surface concentration for substrate-mediated delivery. By comparing plain and SiNW surfaces with the same amount of loaded siRNA, we quantitatively found that PD coating efficiently anchored siRNA on the surface, which knocked down the expression of a specific gene by RNA interference. It was also found that the interaction of SiNWs with the cell membrane perturbed the lateral diffusion of lipids in the membrane by fluorescence recovery after photobleaching. The perturbation was considered to induce the effective delivery of siRNA into cells and allow the cells to carry out their biological functions. These results suggest promising applications of PD-coated, high-density SiNWs as simple, fast, and versatile platforms for transmembrane delivery of biomolecules. PMID:27420034

  11. Vertically aligned InGaN nanowires with engineered axial In composition for highly efficient visible light emission

    PubMed Central

    Ebaid, Mohamed; Kang, Jin-Ho; Yoo, Yang-Seok; Lim, Seung-Hyuk; Cho, Yong-Hoon; Ryu, Sang-Wan

    2015-01-01

    We report on the fabrication of novel InGaN nanowires (NWs) with improved crystalline quality and high radiative efficiency for applications as nanoscale visible light emitters. Pristine InGaN NWs grown under a uniform In/Ga molar flow ratio (UIF) exhibited multi-peak white-like emission and a high density of dislocation-like defects. A phase separation and broad emission with non-uniform luminescent clusters were also observed for a single UIF NW investigated by spatially resolved cathodoluminescence. Hence, we proposed a simple approach based on engineering the axial In content by increasing the In/Ga molar flow ratio at the end of NW growth. This new approach yielded samples with a high luminescence intensity, a narrow emission spectrum, and enhanced crystalline quality. Using time-resolved photoluminescence spectroscopy, the UIF NWs exhibited a long radiative recombination time (τr) and low internal quantum efficiency (IQE) due to strong exciton localization and carrier trapping in defect states. In contrast, NWs with engineered In content demonstrated three times higher IQE and a much shorter τr due to mitigated In fluctuation and improved crystal quality. PMID:26585509

  12. Growth and characterization of ZnO/ZnTe core/shell nanowire arrays on transparent conducting oxide glass substrates

    PubMed Central

    2012-01-01

    We report the growth and characterization of ZnO/ZnTe core/shell nanowire arrays on indium tin oxide. Coating of the ZnTe layer on well-aligned vertical ZnO nanowires has been demonstrated by scanning electron microscope, tunneling electron microscope, X-ray diffraction pattern, photoluminescence, and transmission studies. The ZnO/ZnTe core/shell nanowire arrays were then used as the active layer and carrier transport medium to fabricate a photovoltaic device. The enhanced photocurrent and faster response observed in ZnO/ZnTe, together with the quenching of the UV emission in the PL spectra, indicate that carrier separation in this structure plays an important role in determining their optical response. The results also indicate that core/shell structures can be made into useful photovoltaic devices. PMID:22804871

  13. Novel Pulse Electrodeposited Co Cu ZnO Nanowire/tube Catalysts for C1 C4 Alcohols and C2 C6 (Except C5) Hydrocarbons from CO and H2

    SciTech Connect

    Gupta, Mayank; Schwartz, Viviane; Overbury, Steven {Steve} H; More, Karren Leslie; Meyer III, Harry M; Spivey, James J

    2012-01-01

    Co Cu ZnO nanowire/tube catalysts were synthesized using pulse electrodeposition technique from a single aqueous electrolyte solution using a template synthesis technique. They were then tested as catalysts for the hydrogenation of CO to alcohols and higher hydrocarbons. Nanowires/ tubes were grown inside the pores of membranes using a three-step sequential deposition process. First, a low current of 6.9 mA/cm2 was applied for 300 ms for Cu deposition, then a high current density of 11.5 mA/cm2 for t ms (t = 500, 600, 750 ms) was applied for Co deposition, and finally no current was applied for 1200 ms so that the ions near the cathode replenish. The surface had a significantly different composition than the bulk. On the surface, there was more Co, less Cu, and more Zn. The catalyst showed the alcohol (C1 C4) selectivity of 20.9 %C at H2/CO = 3/1, GHSV = 16 000 scc/h gcat, temperature = 270 C, pressure = 15 bar, and time-onstream = 65 h.

  14. Silver nanowires

    NASA Astrophysics Data System (ADS)

    Graff, A.; Wagner, D.; Ditlbacher, H.; Kreibig, U.

    2005-07-01

    Free silver nanowires were produced in aqueous electrolyte by a novel chemical reaction. Their diameters are about 27 nm, the lengths range up to more than 70 μm, yielding extreme length to thickness-ratios up to 2500. Their structure was identified by TEM analysis (SAED) and HRTEM to consist of a lattice aligned bundle of five monocrystalline rods of triangular cross-section forming an almost regular pentagonal cross-section. It is demonstrated that, for application purposes, single free nanowires can be mounted between contact areas. This manipulation is enabled by observing the nanowires in real time at atmosphere by Zsigmondy-Siedentopf farfield darkfield microscopy. Experimental results are presented concerning electrical dc conductivity and optical plasmon polariton excitation, the latter obtained from a single free wire without substrate and a single wire deposited on quartz glass. We also report about a present research cooperation with the Graz group of Aussenegg and Krenn which is devoted to investigate plasmon propagation in our Ag nanowires and to prove application possibilities as information guide fibers in analogy to optical fibers which may be integrated into micro- and nanoelectronic circuits.

  15. Thickness-controlled synthesis of vertically aligned c-axis oriented ZnO nanorod arrays: Effect of growth time via novel dual sonication sol-gel process

    NASA Astrophysics Data System (ADS)

    Firdaus Malek, Mohd; Hafiz Mamat, Mohamad; Soga, Tetsuo; Rahman, Saadah Abdul; Abu Bakar, Suriani; Syakirin Ismail, Ahmad; Mohamed, Ruziana; Alrokayan, Salman A. H.; Khan, Haseeb A.; Rusop Mahmood, Mohamad

    2016-01-01

    Zinc-oxide (ZnO) nanorod arrays were successfully prepared by using dual sonication sol-gel process. Field emission scanning electron microscopy revealed that the nanorods exhibited a hexagonal structure with a flat-end facet. The nanorods displayed similar surface morphologies and grew uniformly on the seed layer substrate, with the average diameter slightly increasing to the range of 65 to 80 nm after being immersed for varying growth times. Interestingly, thickness measurements indicated that the thicknesses of the samples increased as the growth time was extended. In addition, the X-ray diffraction spectra indicated that the prepared ZnO nanorods with a hexagonal wurtzite structure grew preferentially along the c-axis. Therefore, we can conclude that the diameter, length, and orientation of the ZnO nanorod arrays along the c-axis are controllable by adjusting the growth time, motivating us to further explore the growth mechanisms of ZnO nanorods.

  16. Solution processed semiconductor alloy nanowire arrays for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Shimpi, Paresh R.

    In this dissertation, we use ZnO nanowire as a model system to investigate the potential of solution routes for bandgap engineering in semiconductor nanowires. Excitingly, successful Mg-alloying into ZnO nanowire arrays has been achieved using a two-step sequential hydrothermal method at low temperature (<155°C) without using post-annealing process. Evidently, both room temperature and 40 K photoluminescence (PL) spectroscopy revealed enhanced and blue-shifted near-band-edge ultraviolet (NBE UV) emission in the Mg-alloyed ZnO (ZnMgO) nanowire arrays, compared with ZnO nanowires. The specific template of densely packed ZnO nanowires is found to be instrumental in achieving the Mg alloying in low temperature solution process. By optimizing the density of ZnO nanowires and precursor concentration, 8-10 at.% of Mg content has been achieved in ZnMgO nanowires. Post-annealing treatment is conducted in oxygen-rich and oxygen-deficient environment at different temperatures and time durations on silicon and quartz substrates in order to study the structural and optical property evolution in ZnMgO nanowire arrays. Vacuum annealed ZnMgO nanowires on both substrates retained their hexagonal structures and PL results showed the enhanced but red-shifted NBE UV emission compared to ZnO nanowires with visible emission nearly suppressed, suggesting the reduced defects concentration and improvement in crystallinity of the nanowires. On the contrast, for ambient annealed ZnMgO nanowires on silicon substrate, as the annealing temperature increased from 400°C to 900°C, intensity of visible emission peak across blue-green-yellow-red band (˜400-660 nm) increased whereas intensity of NBE UV peak decreased and completely got quenched. This might be due to interface diffusion of oxidized Si (SiOx) and formation of (Zn,Mg)1.7SiO4 epitaxially overcoated around individual ZnMgO nanowire. On the other hand, ambient annealed ZnMgO nanowires grown on quartz showed a ˜6-10 nm blue-shift in

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

    NASA Astrophysics Data System (ADS)

    Thomas, Matthew Allan

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

  18. Continuous wet-process growth of ZnO nanoarrays for wire-shaped photoanode of dye-sensitized solar cell.

    PubMed

    Tao, Pan; Guo, Wanwan; Du, Jun; Tao, Changyuan; Qing, Shenglan; Fan, Xing

    2016-09-15

    Well-aligned ZnO nanorod arrays have been grown on metal-plated polymer fiber via a mild wet process in a newly-designed continuous reactor, aiming to provide wire-shaped photoanodes for wearable dye-sensitized solar cells. The growth conditions were systematically optimized with the help of computational flow-field simulation. The flow field in the reactor will not only affect the morphology of the ZnO nanorod⧹nanowire but also affect the pattern distribution of nanoarray on the electrode surface. Unlike the sectional structure from the traditional batch-type reactor, ZnO nanorods with finely-controlled length and uniform morphology could be grown from the continuous reactor. After optimization, the wire-shaped ZnO-type photoanode grown from the continuous reactor exhibited better photovoltaic performance than that from the traditional batch-type reactor. PMID:27289432

  19. High Piezo-photocatalytic Efficiency of CuS/ZnO Nanowires Using Both Solar and Mechanical Energy for Degrading Organic Dye.

    PubMed

    Hong, Deyi; Zang, Weili; Guo, Xiao; Fu, Yongming; He, Haoxuan; Sun, Jing; Xing, Lili; Liu, Baodan; Xue, Xinyu

    2016-08-24

    High piezo-photocatalytic efficiency of degrading organic pollutants has been realized from CuS/ZnO nanowires using both solar and mechanical energy. CuS/ZnO heterostructured nanowire arrays are compactly/vertically aligned on stainless steel mesh by a simple two-step wet-chemical method. The mesh-supported nanocomposites can facilitate an efficient light harvesting due to the large surface area and can also be easily removed from the treated solution. Under both solar and ultrasonic irradiation, CuS/ZnO nanowires can rapidly degrade methylene blue (MB) in aqueous solution, and the recyclability is investigated. In this process, the ultrasonic assistance can greatly enhance the photocatalytic activity. Such a performance can be attributed to the coupling of the built-in electric field of heterostructures and the piezoelectric field of ZnO nanowires. The built-in electric field of the heterostructure can effectively separate the photogenerated electrons/holes and facilitate the carrier transportation. The CuS component can improve the visible light utilization. The piezoelectric field created by ZnO nanowires can further separate the photogenerated electrons/holes through driving them to migrate along opposite directions. The present results demonstrate a new water-pollution solution in green technologies for the environmental remediation at the industrial level. PMID:27494426

  20. EDITORIAL: Nanowires Nanowires

    NASA Astrophysics Data System (ADS)

    Jagadish, Chennupati

    2010-02-01

    Nanowires are considered as building blocks for the next generation of electronics, photonics, sensors and energy applications. One-dimensional nanostructures offer unique opportunities to control the density of states of semiconductors, and in turn their electronic and optical properties. Nanowires allow the growth of axial heterostructures without the constraints of lattice mismatch. This provides flexibility to create heterostructures of a broad range of materials and allows integration of compound semiconductor based optoelectronic devices with silicon based microelectronics. Nanowires are widely studied and the number of papers published in the field is growing exponentially with time. Already nanowire lasers, nanowire transistors, nanowire light emitting diodes, nanowire sensors and nanowire solar cells have been demonstrated. This special issue on semiconductor nanowires features 17 invited papers from leading experts in the field. In this special issue, the synthesis and growth of semiconductor nanowires of a broad range of materials have been addressed. Both axial and radial heterostructures and their structural properties have been discussed. Electrical transport properties of nanowires have been presented, as well as optical properties and carrier dynamics in a range of nanowires and nanowire heterostructures. Devices such as nanowire lasers and nanowire sensors have also been discussed. I would like to thank the Editorial Board of the journal for suggesting this special issue and inviting me to serve as the Guest Editor. Sincere thanks are due to all the authors for their contributions to this special issue. I am grateful to the reviewers and editorial staff at Semiconductor Science and Technology and the Institute of Physics Publishing for their excellent efforts. Special thanks are due to Dr Claire Bedrock for coordinating this special issue.