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Sample records for inas nanowire arrays

  1. Sub-100 nm Si nanowire and nano-sheet array formation by MacEtch using a non-lithographic InAs nanowire mask

    NASA Astrophysics Data System (ADS)

    Shin, Jae Cheol; Zhang, Chen; Li, Xiuling

    2012-08-01

    We report a non-lithographical method for the fabrication of ultra-thin silicon (Si) nanowire (NW) and nano-sheet arrays through metal-assisted-chemical-etching (MacEtch) with gold (Au). The mask used for metal patterning is a vertical InAs NW array grown on a Si substrate via catalyst-free, strain-induced, one-dimensional heteroepitaxy. Depending on the Au evaporation angle, the shape and size of the InAs NWs are transferred to Si by Au-MacEtch as is (NWs) or in its projection (nano-sheets). The Si NWs formed have diameters in the range of ˜25-95 nm, and aspect ratios as high as 250 in only 5 min etch time. The formation process is entirely free of organic chemicals, ensuring pristine Au-Si interfaces, which is one of the most critical requirements for high yield and reproducible MacEtch.

  2. Sub-100 nm Si nanowire and nano-sheet array formation by MacEtch using a non-lithographic InAs nanowire mask.

    PubMed

    Shin, Jae Cheol; Zhang, Chen; Li, Xiuling

    2012-08-01

    We report a non-lithographical method for the fabrication of ultra-thin silicon (Si) nanowire (NW) and nano-sheet arrays through metal-assisted-chemical-etching (MacEtch) with gold (Au). The mask used for metal patterning is a vertical InAs NW array grown on a Si substrate via catalyst-free, strain-induced, one-dimensional heteroepitaxy. Depending on the Au evaporation angle, the shape and size of the InAs NWs are transferred to Si by Au-MacEtch as is (NWs) or in its projection (nano-sheets). The Si NWs formed have diameters in the range of ∼25-95 nm, and aspect ratios as high as 250 in only 5 min etch time. The formation process is entirely free of organic chemicals, ensuring pristine Au-Si interfaces, which is one of the most critical requirements for high yield and reproducible MacEtch. PMID:22781145

  3. Short-wavelength infrared photodetector on Si employing strain-induced growth of very tall InAs nanowire arrays.

    PubMed

    Shin, Hyun Wook; Lee, Sang Jun; Kim, Doo Gun; Bae, Myung-Ho; Heo, Jaeyeong; Choi, Kyoung Jin; Choi, Won Jun; Choe, Jeong-woo; Shin, Jae Cheol

    2015-06-02

    One-dimensional crystal growth enables the epitaxial integration of III-V compound semiconductors onto a silicon (Si) substrate despite significant lattice mismatch. Here, we report a short-wavelength infrared (SWIR, 1.4-3 μm) photodetector that employs InAs nanowires (NWs) grown on Si. The wafer-scale epitaxial InAs NWs form on the Si substrate without a metal catalyst or pattern assistance; thus, the growth is free of metal-atom-induced contaminations, and is also cost-effective. InAs NW arrays with an average height of 50 μm provide excellent anti-reflective and light trapping properties over a wide wavelength range. The photodetector exhibits a peak detectivity of 1.9 × 10(8) cm · Hz(1/2)/W for the SWIR band at 77 K and operates at temperatures as high as 220 K. The SWIR photodetector on the Si platform demonstrated in this study is promising for future low-cost optical sensors and Si photonics.

  4. Thermal conductance of InAs nanowire composites.

    PubMed

    Persson, Ann I; Koh, Yee Kan; Cahill, David G; Samuelson, Lars; Linke, Heiner

    2009-12-01

    The ability to measure and understand heat flow in nanowire composites is crucial for applications ranging from high-speed electronics to thermoelectrics. Here we demonstrate the measurement of the thermal conductance of nanowire composites consisting of regular arrays of InAs nanowires embedded in PMMA using time-domain thermoreflectance (TDTR). On the basis of a proposed model for heat flow in the composite, we can, as a consistency check, extract the thermal conductivity Lambda of the InAs nanowires and find Lambda(NW) = 5.3 +/- 1.5 W m(-1) K(-1), in good agreement with theory and previous measurements of individual nanowires.

  5. Laser induced modification and ablation of InAs nanowires

    SciTech Connect

    He Jiayu; Chen Pingping; Lu Wei; Dai Ning; Zhu Daming

    2012-05-01

    InAs nanowires were irradiated locally under an ambient condition using a focused laser beam, which led to laser ablation and thinning of the nanowires. We show that the laser beam can induce a reduction of the local As concentration in an InAs nanowire; the change leads to a significant decrease of local melting temperature of InAs, which results in the thinning and eventually breaking of the nanowire. The results indicate that chemical and mechanical modifications of an InAs nanowire can be accomplished by using a confocal laser beam, which may prove to be a convenient approach in fabricating nanostructural materials and nanodevices.

  6. Ballistic InAs nanowire transistors.

    PubMed

    Chuang, Steven; Gao, Qun; Kapadia, Rehan; Ford, Alexandra C; Guo, Jing; Javey, Ali

    2013-02-13

    Ballistic transport of electrons at room temperature in top-gated InAs nanowire (NW) transistors is experimentally observed and theoretically examined. From length dependent studies, the low-field mean free path is directly extracted as ~150 nm. The mean free path is found to be independent of temperature due to the dominant role of surface roughness scattering. The mean free path was also theoretically assessed by a method that combines Fermi's golden rule and a numerical Schrödinger-Poisson simulation to determine the surface scattering potential with the theoretical calculations being consistent with experiments. Near ballistic transport (~80% of the ballistic limit) is demonstrated experimentally for transistors with a channel length of ~60 nm, owing to the long mean free path of electrons in InAs NWs. PMID:23256503

  7. Phase coherent transport in hollow InAs nanowires

    SciTech Connect

    Wenz, T.; Rosien, M.; Haas, F.; Rieger, T.; Lepsa, M. I.; Lüth, H.; Grützmacher, D.; Schäpers, Th.; Demarina, N.

    2014-09-15

    Hollow InAs nanowires are produced from GaAs/InAs core/shell nanowires by wet chemical etching of the GaAs core. At room temperature, the resistivity of several nanowires is measured before and after removal of the GaAs core. The observed change in resistivity is explained by simulating the electronic states in both structures. At cryogenic temperatures, quantum transport in hollow InAs nanowires is studied. Flux periodic conductance oscillations are observed when the magnetic field is oriented parallel to the nanowire axis.

  8. Coherent electron transport in InAs nanowires

    NASA Astrophysics Data System (ADS)

    Sourribes, Marion J. L.; Isakov, Ivan; Panfilova, Marina; Ercolani, Daniele; Giazotto, Francesco; Sorba, Lucia; Warburton, Paul A.

    2013-03-01

    Indium arsenide nanowires are of special interest since they exhibit high mobility, strong spin-orbit coupling and form ohmic contacts with metals which make them good candidates for the observation of Majorana fermions in semiconductor/superconductor hybrid systems. InAs nanowires have already been used as Josephson elements in superconducting devices. Here we report our low-temperature experiments on InAs nanowires grown by two methods: (i) gold-catalyzed chemical beam epitaxy on InAs (111) substrates; (ii) catalyst-free molecular beam epitaxy on Si (111) substrates. Contacts to the nanowires are defined by e-beam lithography. Before metallization of the contacts, the nanowire surface is deoxidized by an in situ sputter-cleaning process leading to a specific contact resistance of 9 . 8 ×10-9 Ω .cm2. These highly transparent contacts allowed the observation of proximity-induced superconductivity in InAs nanowires connected with Nb contacts. The critical current was tuned by changing the gate voltage. Both magnetic-field-dependent and gate-voltage-dependent measurements of universal conductance fluctuations were performed to extract information on the electron phase coherence.

  9. Hall effect measurements on InAs nanowires

    SciTech Connect

    Bloemers, Ch.; Grap, T.; Lepsa, M. I.; Moers, J.; Gruetzmacher, D.; Lueth, H.; Trellenkamp, St.; Schaepers, Th.

    2012-10-08

    We have processed Hall contacts on InAs nanowires grown by molecular beam epitaxy using an electron beam lithography process with an extremely high alignment accuracy. The carrier concentrations determined from the Hall effect measurements on these nanowires are lower by a factor of about 4 in comparison with those measured by the common field-effect technique. The results are used to evaluate quantitatively the charging effect of the interface and surface states.

  10. Direct observation of acoustic oscillations in InAs nanowires.

    PubMed

    Mariager, Simon O; Khakhulin, Dmitry; Lemke, Henrik T; Kjaer, Kasper S; Guerin, Laurent; Nuccio, Laura; Sørensen, Claus B; Nielsen, Martin M; Feidenhans'l, Robert

    2010-07-14

    Time-resolved X-ray diffraction and optical reflectivity are used to directly measure three different acoustic oscillations of InAs nanowires. The oscillations are excited by a femtosecond laser pulse and evolve at three different time scales. We measure the absolute scale of the initial radial expansion of the fundamental breathing eigenmode and determine the frequency by transient optical reflectivity. For the extensional eigenmode we measure the oscillations of the average radial and axial lattice constants and determine the amplitude of oscillations and the average extension. Finally we observe a bending motion of the nanowires. The frequencies of the eigenmodes are in good agreements with predictions made by continuum elasticity theory and we find no difference in the speed of sound between the wurtzite nanowires and cubic bulk crystals, but the measured strain is influenced by the interaction between different modes. The wurtzite crystal structure of the nanowires however has an anisotropic thermal expansion.

  11. Quality of epitaxial InAs nanowires controlled by catalyst size in molecular beam epitaxy

    SciTech Connect

    Zhang, Zhi; Xu, Hong-Yi; Guo, Ya-Nan; Liao, Zhi-Ming; Lu, Zhen-Yu; Chen, Ping-Ping; Shi, Sui-Xing; Lu, Wei; Zou, Jin

    2013-08-12

    In this study, the structural quality of Au-catalyzed InAs nanowires grown by molecular beam epitaxy is investigated. Through detailed electron microscopy characterizations and analysis of binary Au-In phase diagram, it is found that defect-free InAs nanowires can be induced by smaller catalysts with a high In concentration, while comparatively larger catalysts containing less In induce defected InAs nanowires. This study indicates that the structural quality of InAs nanowires can be controlled by the size of Au catalysts when other growth conditions remain as constants.

  12. Quality of epitaxial InAs nanowires controlled by catalyst size in molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi; Lu, Zhen-Yu; Chen, Ping-Ping; Xu, Hong-Yi; Guo, Ya-Nan; Liao, Zhi-Ming; Shi, Sui-Xing; Lu, Wei; Zou, Jin

    2013-08-01

    In this study, the structural quality of Au-catalyzed InAs nanowires grown by molecular beam epitaxy is investigated. Through detailed electron microscopy characterizations and analysis of binary Au-In phase diagram, it is found that defect-free InAs nanowires can be induced by smaller catalysts with a high In concentration, while comparatively larger catalysts containing less In induce defected InAs nanowires. This study indicates that the structural quality of InAs nanowires can be controlled by the size of Au catalysts when other growth conditions remain as constants.

  13. In-situ mechanical characterization of wurtzite InAs nanowires

    NASA Astrophysics Data System (ADS)

    Erdélyi, Róbert; Hannibal Madsen, Morten; Sáfrán, György; Hajnal, Zoltán; Endre Lukács, István; Fülöp, Gergő; Csonka, Szabolcs; Nygård, Jesper; Volk, János

    2012-10-01

    High aspect ratio vertical InAs nanowires were mechanically characterized in a scanning electron microscope equipped with two micromanipulators. One, equipped with a calibrated atomic force microscope probe, was used for in-situ static bending of single nanowires along the <11-20> crystallographic direction. The other one was equipped with a tungsten tip for dynamic resonance excitation of the same nanowires. This setup enabled a direct comparison between the two techniques. The crystal structure was analyzed using transmission electron microscopy, and for InAs nanowires with a hexagonal wutzite crystal structure, the bending modulus value was found to BM=43.5 GPa. This value is significantly lower than previously reported for both cubic zinc blende InAs bulk crystals and InAs nanowires. Besides, due to their high resonance quality factor (Q>1200), the wurtzite InAs nanowires are shown to be a promising candidate for sub-femtogram mass detectors.

  14. Ballistic modeling of InAs nanowire transistors

    NASA Astrophysics Data System (ADS)

    Jansson, Kristofer; Lind, Erik; Wernersson, Lars-Erik

    2016-01-01

    In this work, the intrinsic performance of InAs nanowire transistors is evaluated in the ballistic limit. A self-consistent Schrödinger-Poisson solver is utilized in the cylindrical geometry, while accounting for conduction band non-parabolicity. The transistor characteristics are derived from simulations of ballistic transport within the nanowire. Using this approach, the performance is calculated for a continuous range of nanowire diameters and the transport properties are mapped. A transconductance exceeding 4S /mm is predicted at a gate overdrive of 0.5V and it is shown that the performance is improved with scaling. Furthermore, the influence from including self-consistency and non-parabolicity in the band structure simulations is quantified. It is demonstrated that the effective mass approximation underestimates the transistor performance due to the highly non-parabolic conduction band in InAs. Neglecting self-consistency severely overestimates the device performance, especially for thick nanowires. The error introduced by both of these approximations gets increasingly worse under high bias conditions.

  15. Bandgap Energy of Wurtzite InAs Nanowires.

    PubMed

    Rota, Michele B; Ameruddin, Amira S; Fonseka, H Aruni; Gao, Qiang; Mura, Francesco; Polimeni, Antonio; Miriametro, Antonio; Tan, H Hoe; Jagadish, Chennupati; Capizzi, Mario

    2016-08-10

    InAs nanowires (NWs) have been grown on semi-insulating InAs (111)B substrates by metal-organic chemical vapor deposition catalyzed by 50, 100, and 150 nm-sized Au particles. The pure wurtzite (WZ) phase of these NWs has been attested by high-resolution transmission electron microscopy and selected area diffraction pattern measurements. Low temperature photoluminescence measurements have provided unambiguous and robust evidence of a well resolved, isolated peak at 0.477 eV, namely 59 meV higher than the band gap of ZB InAs. The WZ nature of this energy band has been demonstrated by high values of the polarization degree, measured in ensembles of NWs both as-grown and mechanically transferred onto Si and GaAs substrates, in agreement with the polarization selection rules for WZ crystals. The value of 0.477 eV found here for the bandgap energy of WZ InAs agrees well with theoretical calculations.

  16. Bandgap Energy of Wurtzite InAs Nanowires.

    PubMed

    Rota, Michele B; Ameruddin, Amira S; Fonseka, H Aruni; Gao, Qiang; Mura, Francesco; Polimeni, Antonio; Miriametro, Antonio; Tan, H Hoe; Jagadish, Chennupati; Capizzi, Mario

    2016-08-10

    InAs nanowires (NWs) have been grown on semi-insulating InAs (111)B substrates by metal-organic chemical vapor deposition catalyzed by 50, 100, and 150 nm-sized Au particles. The pure wurtzite (WZ) phase of these NWs has been attested by high-resolution transmission electron microscopy and selected area diffraction pattern measurements. Low temperature photoluminescence measurements have provided unambiguous and robust evidence of a well resolved, isolated peak at 0.477 eV, namely 59 meV higher than the band gap of ZB InAs. The WZ nature of this energy band has been demonstrated by high values of the polarization degree, measured in ensembles of NWs both as-grown and mechanically transferred onto Si and GaAs substrates, in agreement with the polarization selection rules for WZ crystals. The value of 0.477 eV found here for the bandgap energy of WZ InAs agrees well with theoretical calculations. PMID:27467011

  17. Metal free growth and characterization of InAs1-xPx nanowires

    SciTech Connect

    Mandl, Bernhard; Stangl, Julian; Brehm, Moritz; Fromherz, Thomas; Bauer, Guenther; Maartensson, Thomas; Samuelson, Lars; Seifert, Werner

    2007-04-10

    InAs nanowires have been grown without the use of Au or other metal particles as catalyst by metal-organic vapor phase epitaxy. The nanowires growth is initiated by a thin layer of SiOx. The wires exhibit a non-tapered shape with a hexagonal cross section. In addition to InAs also InAs1-xPx wires are grown and the incorporation of P is studied by photoluminescence.

  18. Switching current distributions in InAs nanowire Josephson junctions

    NASA Astrophysics Data System (ADS)

    Kim, Bum-Kyu; Doh, Yong-Joo

    2016-08-01

    We report on the switching current distributions in nano-hybrid Josephson junctions made of InAs semiconductor nanowires. The temperature dependence of the switching current distribution can be understood through the motion of Josephson phase particles escaping from a tilted washboard potential, and the data could be fitted well by using the macroscopic quantum tunneling, thermal activation or phase diffusion models, depending on temperature. Application of the gate voltage to tune the Josephson coupling strength enable us to adjust the effective temperature for the escape process, and holds promising for developing gate-tunable superconducting phase qubits.

  19. Defect-free thin InAs nanowires grown using molecular beam epitaxy.

    PubMed

    Zhang, Zhi; Chen, Ping-Ping; Lu, Wei; Zou, Jin

    2016-01-21

    In this study, we designed a simple method to achieve the growth of defect-free thin InAs nanowires with a lateral dimension well below their Bohr radius on different substrate orientations. By depositing and annealing a thin layer of Au thin film on a (100) substrate surface, we have achieved the growth of defect-free uniform-sized thin InAs nanowires. This study provides a strategy to achieve the growth of pure defect-free thin nanowires.

  20. Synthesis and structural characterization of vertical ferromagnetic MnAs/semiconducting InAs heterojunction nanowires

    NASA Astrophysics Data System (ADS)

    Kodaira, Ryutaro; Hara, Shinjiro; Kabamoto, Kyohei; Fujimagari, Hiromu

    2016-07-01

    The purpose of this study is to synthesize vertical ferromagnetic/semiconducting heterojunction nanowires by combing the catalyst-free selective-area growth of InAs nanowires and the endotaxial nanoclustering of MnAs and to structurally and magnetically characterize them. MnAs penetrates the InAs nanowires to form nanoclusters. The surface migration length of manganese adatoms on the nanowires, which is estimated to be 600 nm at 580 °C, is a key to the successful fabrication of vertical MnAs/InAs heterojunction nanowires with atomically abrupt heterointerfaces.

  1. InAs nanowire formation on InP(001)

    SciTech Connect

    Parry, H. J.; Ashwin, M. J.; Jones, T. S.

    2006-12-01

    The heteroepitaxial growth of InAs on InP(001) by solid source molecular beam epitaxy has been studied for a range of different growth temperatures and annealing procedures. Atomic force microscopy images show that nanowires are formed for deposition in the temperature range of 400-480 deg. C, and also following high temperature annealing (480 deg. C) after deposition at 400 deg. C. The wires show preferential orientation along <110> and often exhibit pronounced serpentine behavior due to the presence of kinks, an effect that is reduced at increasing growth temperature. The results suggest that the serpentine behavior is related to the degree of initial surface order. Kinks in the wires appear to act as nucleation centers for In adatoms migrating along the wires during annealing, leading to the coexistence of large three-dimensional islands.

  2. Growth of Catalyst-Free Epitaxial InAs Nanowires on Si Wafers Using Metallic Masks.

    PubMed

    Soo, M Teng; Zheng, Kun; Gao, Qiang; Tan, H Hoe; Jagadish, Chennupati; Zou, Jin

    2016-07-13

    Development of heteroepitaxy growth of catalyst-free vertical III-V nanowires on Si wafers is highly desirable for future nanoscale Si-based electronic and optoelectronic devices. In this study, a proof-of-concept approach is developed for catalyst-free heteroepitaxy growth of InAs nanowires on Si wafers. Before the growth of InAs nanowires, a Si-compatible metallic film with a thickness of several tens of nanometers was predeposited on a Si wafer and then annealed to form nanosize openings so as to obtain a metallic mask. These nano-openings exposed the surface of the Si wafer, which allowed subsequent nucleation and growth of epitaxial InAs nanowires directly on the surface of the Si wafer. The small size of the nano-openings limits the lateral growth of the nanostructures but promotes their axial growth. Through this approach, catalyst-free InAs nanowires were grown on both Si (111) and (001) wafers successfully at different growth temperatures. In particular, ultralong defect-free InAs nanowires with the wurtzite structure were grown the Si (111) wafers at 550 °C using the Ni mask. This study offers a simple, cost-effective, and scalable method to grow catalyst-free III-V nanowires on Si wafers. The simplicity of the approach opens a new avenue for the growth and integration of catalyst-free high-quality heteroepitaxial III-V nanowires on Si wafers.

  3. Growth of Catalyst-Free Epitaxial InAs Nanowires on Si Wafers Using Metallic Masks.

    PubMed

    Soo, M Teng; Zheng, Kun; Gao, Qiang; Tan, H Hoe; Jagadish, Chennupati; Zou, Jin

    2016-07-13

    Development of heteroepitaxy growth of catalyst-free vertical III-V nanowires on Si wafers is highly desirable for future nanoscale Si-based electronic and optoelectronic devices. In this study, a proof-of-concept approach is developed for catalyst-free heteroepitaxy growth of InAs nanowires on Si wafers. Before the growth of InAs nanowires, a Si-compatible metallic film with a thickness of several tens of nanometers was predeposited on a Si wafer and then annealed to form nanosize openings so as to obtain a metallic mask. These nano-openings exposed the surface of the Si wafer, which allowed subsequent nucleation and growth of epitaxial InAs nanowires directly on the surface of the Si wafer. The small size of the nano-openings limits the lateral growth of the nanostructures but promotes their axial growth. Through this approach, catalyst-free InAs nanowires were grown on both Si (111) and (001) wafers successfully at different growth temperatures. In particular, ultralong defect-free InAs nanowires with the wurtzite structure were grown the Si (111) wafers at 550 °C using the Ni mask. This study offers a simple, cost-effective, and scalable method to grow catalyst-free III-V nanowires on Si wafers. The simplicity of the approach opens a new avenue for the growth and integration of catalyst-free high-quality heteroepitaxial III-V nanowires on Si wafers. PMID:27248817

  4. Fabrication and optical properties of multishell InAs quantum dots on GaAs nanowires

    SciTech Connect

    Yan, Xin; Zhang, Xia Li, Junshuai; Cui, Jiangong; Ren, Xiaomin

    2015-02-07

    Hybrid nanostructures combining nanowires with quantum dots promote the development of nanoelectronic and nanophotonic devices with integrated functionalities. In this work, we present a complex nanostructure with multishell quantum dots grown on nanowires. 1–4 shells of Stranski-Krastanov InAs quantum dots are grown on the sidewalls of GaAs nanowires by metal organic chemical vapor deposition. Different dot shells are separated by 8 nm GaAs spacer shells. With increasing the number of shells, the quantum dots become sparser and tend to align in one array, which is caused by the shrinkage of facets on which dots prefer to grow as well as the strain fields produced by the lower set of dots which influences the migration of In adatoms. The size of quantum dots increases with the increase of shell number due to enhanced strain fields coupling. The spectra of multishell dots exhibit multiwavelength emission, and each peak corresponds to a dot shell. This hybrid structure may serve as a promising element in nanowire intermediate band solar cells, infrared nanolasers, and photodetectors.

  5. Ag-catalyzed InAs nanowires grown on transferable graphite flakes.

    PubMed

    Meyer-Holdt, Jakob; Kanne, Thomas; Sestoft, Joachim E; Gejl, Aske; Zeng, Lunjie; Johnson, Erik; Olsson, Eva; Nygård, Jesper; Krogstrup, Peter

    2016-09-01

    Semiconducting nanowires grown by quasi-van-der-Waals epitaxy on graphite flakes are a new class of hybrid materials that hold promise for scalable nanostructured devices within opto-electronics. Here we report on high aspect ratio and stacking fault free Ag-seeded InAs nanowires grown on exfoliated graphite flakes by molecular beam epitaxy. Ag catalyzes the InAs nanowire growth selectively on the graphite flakes and not on the underlying InAs substrates. This allows for easy transfer of the flexible graphite flakes with as-grown nanowire ensembles to arbitrary substrates by a micro-needle manipulator. Besides the possibilities for fabricating novel nanostructure device designs, we show how this method is used to study the parasitic growth and bicrystal match between the graphite flake and the nanowires by transmission electron microscopy.

  6. Ag-catalyzed InAs nanowires grown on transferable graphite flakes

    NASA Astrophysics Data System (ADS)

    Meyer-Holdt, Jakob; Kanne, Thomas; Sestoft, Joachim E.; Gejl, Aske; Zeng, Lunjie; Johnson, Erik; Olsson, Eva; Nygård, Jesper; Krogstrup, Peter

    2016-09-01

    Semiconducting nanowires grown by quasi-van-der-Waals epitaxy on graphite flakes are a new class of hybrid materials that hold promise for scalable nanostructured devices within opto-electronics. Here we report on high aspect ratio and stacking fault free Ag-seeded InAs nanowires grown on exfoliated graphite flakes by molecular beam epitaxy. Ag catalyzes the InAs nanowire growth selectively on the graphite flakes and not on the underlying InAs substrates. This allows for easy transfer of the flexible graphite flakes with as-grown nanowire ensembles to arbitrary substrates by a micro-needle manipulator. Besides the possibilities for fabricating novel nanostructure device designs, we show how this method is used to study the parasitic growth and bicrystal match between the graphite flake and the nanowires by transmission electron microscopy.

  7. Ag-catalyzed InAs nanowires grown on transferable graphite flakes.

    PubMed

    Meyer-Holdt, Jakob; Kanne, Thomas; Sestoft, Joachim E; Gejl, Aske; Zeng, Lunjie; Johnson, Erik; Olsson, Eva; Nygård, Jesper; Krogstrup, Peter

    2016-09-01

    Semiconducting nanowires grown by quasi-van-der-Waals epitaxy on graphite flakes are a new class of hybrid materials that hold promise for scalable nanostructured devices within opto-electronics. Here we report on high aspect ratio and stacking fault free Ag-seeded InAs nanowires grown on exfoliated graphite flakes by molecular beam epitaxy. Ag catalyzes the InAs nanowire growth selectively on the graphite flakes and not on the underlying InAs substrates. This allows for easy transfer of the flexible graphite flakes with as-grown nanowire ensembles to arbitrary substrates by a micro-needle manipulator. Besides the possibilities for fabricating novel nanostructure device designs, we show how this method is used to study the parasitic growth and bicrystal match between the graphite flake and the nanowires by transmission electron microscopy. PMID:27479073

  8. MBE growth of self-assisted InAs nanowires on graphene

    NASA Astrophysics Data System (ADS)

    Kang, Jung-Hyun; Ronen, Yuval; Cohen, Yonatan; Convertino, Domenica; Rossi, Antonio; Coletti, Camilla; Heun, Stefan; Sorba, Lucia; Kacman, Perla; Shtrikman, Hadas

    2016-11-01

    Self-assisted growth of InAs nanowires on graphene by molecular beam epitaxy is reported. Nanowires with diameter of ∼50 nm and aspect ratio of up to 100 were achieved. The morphological and structural properties of the nanowires were carefully studied by changing the substrate from bilayer graphene through buffer layer to quasi-free-standing monolayer graphene. The positional relation of the InAs NWs with the graphene substrate was determined. A 30° orientation configuration of some of the InAs NWs is shown to be related to the surface corrugation of the graphene substrate. InAs NW-based devices for transport measurements were fabricated, and the conductance measurements showed a semi-ballistic behavior. In Josephson junction measurements in the non-linear regime, multiple Andreev reflections were observed, and an inelastic scattering length of about 900 nm was derived.

  9. Structural characterization of nanowires and nanowire arrays

    NASA Astrophysics Data System (ADS)

    Becker, Catherine Rose

    synthesis of copper nanowires. The results of this research provide a link between the synthesis and performance of nanowire arrays and will aid in their rapid optimization for thermoelectric applications.

  10. Harmonic Generation in InAs Nanowire Double Quantum Dots

    NASA Astrophysics Data System (ADS)

    Schroer, M. D.; Jung, M.; Petersson, K. D.; Petta, J. R.

    2012-02-01

    InAs nanowires provide a useful platform for investigating the physics of confined electrons subjected to strong spin-orbit coupling. Using tunable, bottom-gated double quantum dots, we demonstrate electrical driving of single spin resonance.ootnotetextS. Nadj-Perge et al., Nature 468, 1084 (2010)^,ootnotetextM.D. Schroer et al., Phys. Rev. Lett. 107, 176811 (2011) We observe a standard spin response when the applied microwave frequency equals the Larmour frequency f0. However, we also observe an anomalous signal at frequencies fn= f0/ n for integer n up to n ˜5. This is equivalent to generation of harmonics of the spin resonance field. While a f0/2 signal has observed,ootnotetextE.A. Laird et al., Phys. Rev. Lett. 99, 246601 (2007) we believe this is the first observation of higher harmonics in spin resonance. Possible mechanisms will be discussed.ootnotetextE.I. Rashba, arXiv:1110.6569 (2011) Acknowledgements: Research supported by the Sloan and Packard Foundations, the NSF, and Army Research Office.

  11. Orientation Dependence of Electromechanical Characteristics of Defect-free InAs Nanowires.

    PubMed

    Zheng, Kun; Zhang, Zhi; Hu, Yibin; Chen, Pingping; Lu, Wei; Drennan, John; Han, Xiaodong; Zou, Jin

    2016-03-01

    Understanding the electrical properties of defect-free nanowires with different structures and their responses under deformation are essential for design and applications of nanodevices and strain engineering. In this study, defect-free zinc-blende- and wurtzite-structured InAs nanowires were grown using molecular beam epitaxy, and individual nanowires with different structures and orientations were carefully selected and their electrical properties and electromechanical responses were investigated using an electrical probing system inside a transmission electron microscope. Through our careful experimental design and detailed analyses, we uncovered several extraordinary physical phenomena, such as the electromechanical characteristics are dominated by the nanowire orientation, rather than its crystal structure. Our results provide critical insights into different responses induced by deformation of InAs with different structures, which is important for nanowire-based devices. PMID:26837494

  12. Photoelectrochemistry of Semiconductor Nanowire Arrays

    SciTech Connect

    Mallouk, Thomas E; Redwing, Joan M

    2009-11-10

    This project supported research on the growth and photoelectrochemical characterization of semiconductor nanowire arrays, and on the development of catalytic materials for visible light water splitting to produce hydrogen and oxygen. Silicon nanowires were grown in the pores of anodic aluminum oxide films by the vapor-liquid-solid technique and were characterized electrochemically. Because adventitious doping from the membrane led to high dark currents, silicon nanowire arrays were then grown on silicon substrates. The dependence of the dark current and photovoltage on preparation techniques, wire diameter, and defect density was studied for both p-silicon and p-indium phosphide nanowire arrays. The open circuit photovoltage of liquid junction cells increased with increasing wire diameter, reaching 350 mV for micron-diameter silicon wires. Liquid junction and radial p-n junction solar cells were fabricated from silicon nano- and microwire arrays and tested. Iridium oxide cluster catalysts stabilized by bidentate malonate and succinate ligands were also made and studied for the water oxidation reaction. Highlights of this project included the first papers on silicon and indium phosphide nanowire solar cells, and a new procedure for making ligand-stabilized water oxidation catalysts that can be covalently linked to molecular photosensitizers or electrode surfaces.

  13. Length distributions of Au-catalyzed and In-catalyzed InAs nanowires

    NASA Astrophysics Data System (ADS)

    Dubrovskii, V. G.; Sibirev, N. V.; Berdnikov, Y.; Gomes, U. P.; Ercolani, D.; Zannier, V.; Sorba, L.

    2016-09-01

    We present experimental data on the length distributions of InAs nanowires grown by chemical beam epitaxy with Au catalyst nanoparticles obtained by thermal dewetting of Au film, Au colloidal nanoparticles and In droplets. Poissonian length distributions are observed in the first case. Au colloidal nanoparticles produce broader and asymmetric length distributions of InAs nanowires. However, the distributions can be strongly narrowed by removing the high temperature annealing step. The length distributions for the In-catalyzed growth are instead very broad. We develop a generic model that is capable of describing the observed behaviors by accounting for both the incubation time for nanowire growth and secondary nucleation of In droplets. These results allow us to formulate some general recipes for obtaining more uniform length distributions of III-V nanowires.

  14. Length distributions of Au-catalyzed and In-catalyzed InAs nanowires.

    PubMed

    Dubrovskii, V G; Sibirev, N V; Berdnikov, Y; Gomes, U P; Ercolani, D; Zannier, V; Sorba, L

    2016-09-16

    We present experimental data on the length distributions of InAs nanowires grown by chemical beam epitaxy with Au catalyst nanoparticles obtained by thermal dewetting of Au film, Au colloidal nanoparticles and In droplets. Poissonian length distributions are observed in the first case. Au colloidal nanoparticles produce broader and asymmetric length distributions of InAs nanowires. However, the distributions can be strongly narrowed by removing the high temperature annealing step. The length distributions for the In-catalyzed growth are instead very broad. We develop a generic model that is capable of describing the observed behaviors by accounting for both the incubation time for nanowire growth and secondary nucleation of In droplets. These results allow us to formulate some general recipes for obtaining more uniform length distributions of III-V nanowires.

  15. Length distributions of Au-catalyzed and In-catalyzed InAs nanowires.

    PubMed

    Dubrovskii, V G; Sibirev, N V; Berdnikov, Y; Gomes, U P; Ercolani, D; Zannier, V; Sorba, L

    2016-09-16

    We present experimental data on the length distributions of InAs nanowires grown by chemical beam epitaxy with Au catalyst nanoparticles obtained by thermal dewetting of Au film, Au colloidal nanoparticles and In droplets. Poissonian length distributions are observed in the first case. Au colloidal nanoparticles produce broader and asymmetric length distributions of InAs nanowires. However, the distributions can be strongly narrowed by removing the high temperature annealing step. The length distributions for the In-catalyzed growth are instead very broad. We develop a generic model that is capable of describing the observed behaviors by accounting for both the incubation time for nanowire growth and secondary nucleation of In droplets. These results allow us to formulate some general recipes for obtaining more uniform length distributions of III-V nanowires. PMID:27501469

  16. Schottky barrier heights at the interfaces between pure-phase InAs nanowires and metal contacts

    NASA Astrophysics Data System (ADS)

    Feng, Boyong; Huang, Shaoyun; Wang, Jiyin; Pan, Dong; Zhao, Jianghua; Xu, H. Q.

    2016-02-01

    Understanding of the Schottky barriers formed at metal contact-InAs nanowire interfaces is of great importance for the development of high-performance InAs nanowire nanoelectronic and quantum devices. Here, we report a systematical study of InAs nanowire field-effect transistors (FETs) and the Schottky barrier heights formed at the contact-nanowire interfaces. The InAs nanowires employed are grown by molecular beam epitaxy and are high material quality single crystals, and the devices are made by directly contacting the nanowires with a series of metals of different work functions. The fabricated InAs nanowire FET devices are characterized by electrical measurements at different temperatures and the Schottky barrier heights are extracted from the measured temperature and gate-voltage dependences of the channel current. We show that although the work functions of the contact metals are widely spread, the Schottky barrier heights are determined to be distributed over 35-55 meV, showing a weak but not negligible dependence on the metals. The deduced Fermi level in the InAs nanowire channels is found to be in the band gap and very close to the conduction band. The physical origin of the results is discussed in terms of Fermi level pinning by the surface states of the InAs nanowires and a shift in pinned Fermi level induced by the metal-related interface states.

  17. Selective-Area Growth of InAs Nanowires on Ge and Vertical Transistor Application.

    PubMed

    Tomioka, Katsuhiro; Izhizaka, Fumiya; Fukui, Takashi

    2015-11-11

    III-V compound semiconductor and Ge are promising channel materials for future low-power and high-performance integrated circuits. A heterogeneous integration of these materials on the same platform, however, raises serious problem owing to a huge mismatch of carrier mobility. We proposed direct integration of perfectly vertically aligned InAs nanowires on Ge as a method for new alternative integrated circuits and demonstrated a high-performance InAs nanowire-vertical surrounding-gate transistor. Virtually 100% yield of vertically aligned InAs nanowires was achieved by controlling the initial surface of Ge and high-quality InAs nanowires were obtained regardless of lattice mismatch (6.7%). The transistor performance showed significantly higher conductivity with good gate control compared to Si-based conventional field-effect transistors: the drain current was 0.65 mA/μm, and the transconductance was 2.2 mS/μm at drain-source voltage of 0.50 V. These demonstrations are a first step for building alternative integrated circuits using vertical III-V/multigate planar Ge FETs.

  18. Coupled Array of Superconducting Nanowires

    NASA Astrophysics Data System (ADS)

    Ursache, Andrei

    2005-03-01

    We present experiments that investigate the collective behavior of arrays of superconducting lead nanowires with diameters smaller than the coherence length. The ultrathin (˜15nm) nanowires are grown by pulse electrodeposition into porous self-assembled P(S-b-MMA) diblock copolymer templates. The closely packed (˜24 nm spacing) 1-D superconducting nanowires stand vertically upon a thin normal (Au or Pt) film in a brush-like geometry. Thereby, they are coupled to each other by Andreev reflection at the S-N (Pb-Au) point contact interfaces. Magnetization measurements reveal that the ZFC/FC magnetic response of the coupled array system can be irreversible or reversible, depending on the orientation, perpendicular or parallel, of the applied magnetic field with respect to the coupling plane. As found by electric transport measurements, the coupled array system undergoes an in plane superconducting resistive transition at a temperature smaller than the Tc of an individual nanowire. Current-voltage characteristics throughout the transition region are also discussed. This work was supported by NSF grant DMI-0103024 and DMR-0213695.

  19. Improvement of Terahertz Wave Radiation for InAs Nanowires by Simple Dipping into Tap Water

    PubMed Central

    Park, Dong Woo; Bin Ji, Young; Hwang, Jehwan; Lee, Cheul-Ro; Lee, Sang Jun; Kim, Jun Oh; Noh, Sam Kyu; Oh, Seung Jae; Kim, Sang-Hoon; Jeon, Tae-In; Jeong, Kwang-Un; Kim, Jin Soo

    2016-01-01

    We report improvement of terahertz (THz) wave radiation for Si-based catalyst-free InAs nanowires (NWs) by simple dipping into tap water (DTW). In addition, the possibility of using InAs NWs as a cost-effective method for biomedical applications is discussed by comparison to bulk InAs. The peak-to-peak current signals (PPCSs) of InAs NWs measured from THz time-domain spectroscopy increased with increasing NW height. For example, the PPCS of 10 μm-long InAs NWs was 2.86 times stronger than that of 2.1 μm-long NWs. The THz spectra of the InAs NWs obtained by applying a fast Fourier transformation to the current signals showed a main frequency of 0.5 THz, which can be applied to a variety of medical imaging systems. After the DTW process, structural variation was not observed for 2.1 μm-long InAs NWs. However, the top region of several InAs NWs with heights of 4.6 and 5.8 μm merged into a conical structure. InAs NWs with a height of 10 μm resulted in a bundle feature forming above the conical shape, where the length of bundle region was 4 μm. After the DTW process, the PPCS for 10 μm-long InAs NWs increased by 15 percent compared to that of the as-grown case. PMID:27782220

  20. A transmission line method for evaluation of vertical InAs nanowire contacts

    SciTech Connect

    Berg, M. Svensson, J. Lind, E. Wernersson, L.-E.

    2015-12-07

    In this paper, we present a method for metal contact characterization to vertical semiconductor nanowires using the transmission line method (TLM) on a cylindrical geometry. InAs nanowire resistors are fabricated on Si substrates using a hydrogen silsesquioxane (HSQ) spacer between the bottom and top contact. The thickness of the HSQ is defined by the dose of an electron beam lithography step, and by varying the separation thickness for a group of resistors, a TLM series is fabricated. Using this method, the resistivity and specific contact resistance are determined for InAs nanowires with different doping and annealing conditions. The contacts are shown to improve with annealing at temperatures up to 300 °C for 1 min, with specific contact resistance values reaching down to below 1 Ω µm{sup 2}.

  1. Crystal Phase- and Orientation-Dependent Electrical Transport Properties of InAs Nanowires.

    PubMed

    Fu, Mengqi; Tang, Zhiqiang; Li, Xing; Ning, Zhiyuan; Pan, Dong; Zhao, Jianhua; Wei, Xianlong; Chen, Qing

    2016-04-13

    We report a systematic study on the correlation of the electrical transport properties with the crystal phase and orientation of single-crystal InAs nanowires (NWs) grown by molecular-beam epitaxy. A new method is developed to allow the same InAs NW to be used for both the electrical measurements and transmission electron microscopy characterization. We find both the crystal phase, wurtzite (WZ) or zinc-blende (ZB), and the orientation of the InAs NWs remarkably affect the electronic properties of the field-effect transistors based on these NWs, such as the threshold voltage (VT), ON-OFF ratio, subthreshold swing (SS) and effective barrier height at the off-state (ΦOFF). The SS increases while VT, ON-OFF ratio, and ΦOFF decrease one by one in the sequence of WZ ⟨0001⟩, ZB ⟨131⟩, ZB ⟨332⟩, ZB ⟨121⟩, and ZB ⟨011⟩. The WZ InAs NWs have obvious smaller field-effect mobility, conductivities, and electron concentration at VBG = 0 V than the ZB InAs NWs, while these parameters are not sensitive to the orientation of the ZB InAs NWs. We also find the diameter ranging from 12 to 33 nm shows much less effect than the crystal phase and orientation on the electrical transport properties of the InAs NWs. The good ohmic contact between InAs NWs and metal remains regardless of the variation of the crystal phase and orientation through temperature-dependent measurements. Our work deepens the understanding of the structure-dependent electrical transport properties of InAs NWs and provides a potential way to tailor the device properties by controlling the crystal phase and orientation of the NWs.

  2. Crystal Phase- and Orientation-Dependent Electrical Transport Properties of InAs Nanowires.

    PubMed

    Fu, Mengqi; Tang, Zhiqiang; Li, Xing; Ning, Zhiyuan; Pan, Dong; Zhao, Jianhua; Wei, Xianlong; Chen, Qing

    2016-04-13

    We report a systematic study on the correlation of the electrical transport properties with the crystal phase and orientation of single-crystal InAs nanowires (NWs) grown by molecular-beam epitaxy. A new method is developed to allow the same InAs NW to be used for both the electrical measurements and transmission electron microscopy characterization. We find both the crystal phase, wurtzite (WZ) or zinc-blende (ZB), and the orientation of the InAs NWs remarkably affect the electronic properties of the field-effect transistors based on these NWs, such as the threshold voltage (VT), ON-OFF ratio, subthreshold swing (SS) and effective barrier height at the off-state (ΦOFF). The SS increases while VT, ON-OFF ratio, and ΦOFF decrease one by one in the sequence of WZ ⟨0001⟩, ZB ⟨131⟩, ZB ⟨332⟩, ZB ⟨121⟩, and ZB ⟨011⟩. The WZ InAs NWs have obvious smaller field-effect mobility, conductivities, and electron concentration at VBG = 0 V than the ZB InAs NWs, while these parameters are not sensitive to the orientation of the ZB InAs NWs. We also find the diameter ranging from 12 to 33 nm shows much less effect than the crystal phase and orientation on the electrical transport properties of the InAs NWs. The good ohmic contact between InAs NWs and metal remains regardless of the variation of the crystal phase and orientation through temperature-dependent measurements. Our work deepens the understanding of the structure-dependent electrical transport properties of InAs NWs and provides a potential way to tailor the device properties by controlling the crystal phase and orientation of the NWs. PMID:27002386

  3. Nucleation and growth mechanism of self-catalyzed InAs nanowires on silicon

    NASA Astrophysics Data System (ADS)

    Gomes, U. P.; Ercolani, D.; Zannier, V.; David, J.; Gemmi, M.; Beltram, F.; Sorba, L.

    2016-06-01

    We report on the nucleation and growth mechanism of self-catalyzed InAs nanowires (NWs) grown on Si (111) substrates by chemical beam epitaxy. Careful choices of the growth parameters lead to In-rich conditions such that the InAs NWs nucleate from an In droplet and grow by the vapor-liquid-solid mechanism while sustaining an In droplet at the tip. As the growth progresses, new NWs continue to nucleate on the Si (111) surface causing a spread in the NW size distribution. The observed behavior in NW nucleation and growth is described within a suitable existing theoretical model allowing us to extract relevant growth parameters. We argue that these results provide useful guidelines to rationally control the growth of self-catalyzed InAs NWs for various applications.

  4. Field dependent transport properties in InAs nanowire field effect transistors.

    PubMed

    Dayeh, Shadi A; Susac, Darija; Kavanagh, Karen L; Yu, Edward T; Wang, Deli

    2008-10-01

    We present detailed studies of the field dependent transport properties of InAs nanowire field-effect transistors. Transconductance dependence on both vertical and lateral fields is discussed. Velocity-field plots are constructed from a large set of output and transfer curves that show negative differential conductance behavior and marked mobility degradation at high injection fields. Two dimensional electrothermal simulations at current densities similar to those measured in the InAs NWFET devices indicate that a significant temperature rise occurs in the channel due to enhanced phonon scattering that leads to the observed mobility degradation. Scanning transmission electron microscopy measurements on devices operated at high current densities reveal arsenic vaporization and crystal deformation in the subject nanowires.

  5. Strain-driven synthesis of <112> direction InAs nanowires in V-grooved trenches on Si using InP/GaAs buffer layers

    NASA Astrophysics Data System (ADS)

    Li, Shiyan; Zhou, Xuliang; Kong, Xiangting; Li, Mengke; Mi, Junping; Wang, Mengqi; Pan, Jiaoqing

    2016-09-01

    The catalyst-free metal organic vapor phase epitaxial growth of InAs nanowires on silicon (001) substrates is investigated by using selectively grown InP/GaAs buffer layers in V-grooved trenches. A strain-driven mechanism of self-aligned <112> direction InAs nanowires growing is proposed and demonstrated by the transmission electron microscopy measurement. The morphology of InAs nanowires is tapered in diameter and exhibits a hexagonal cross-section. The defect-free InAs nanowire shows a pure zinc blende crystal structure and an epitaxial relationship with InP buffer layer.

  6. Encapsulated gate-all-around InAs nanowire field-effect transistors

    NASA Astrophysics Data System (ADS)

    Sasaki, Satoshi; Tateno, Kouta; Zhang, Guoqiang; Suominen, Henri; Harada, Yuichi; Saito, Shiro; Fujiwara, Akira; Sogawa, Tetsuomi; Muraki, Koji

    2013-11-01

    We report the fabrication of lateral gate-all-around InAs nanowire field-effect transistors whose gate overlaps the source and drain electrodes and thus fully encapsulates the nanowire channel. They feature large drive current and transconductance that surpass those of conventional non-gate-overlap devices. The improved device characteristics can be attributed to the elimination of access resistance associated with ungated segments between the gate and source/drain electrodes. Our data also reveal a correlation between the normalized transconductance and the threshold voltage, which points to a beneficial effect of our wet-etching procedure performed prior to the atomic-layer-deposition of the gate dielectric.

  7. Encapsulated gate-all-around InAs nanowire field-effect transistors

    SciTech Connect

    Sasaki, Satoshi Tateno, Kouta; Zhang, Guoqiang; Suominen, Henri; Harada, Yuichi; Saito, Shiro; Fujiwara, Akira; Sogawa, Tetsuomi; Muraki, Koji

    2013-11-18

    We report the fabrication of lateral gate-all-around InAs nanowire field-effect transistors whose gate overlaps the source and drain electrodes and thus fully encapsulates the nanowire channel. They feature large drive current and transconductance that surpass those of conventional non-gate-overlap devices. The improved device characteristics can be attributed to the elimination of access resistance associated with ungated segments between the gate and source/drain electrodes. Our data also reveal a correlation between the normalized transconductance and the threshold voltage, which points to a beneficial effect of our wet-etching procedure performed prior to the atomic-layer-deposition of the gate dielectric.

  8. Anomalous photoconductive behavior of a single InAs nanowire photodetector

    SciTech Connect

    Li, Junshuai; Yan, Xin; Sun, Fukuan; Zhang, Xia Ren, Xiaomin

    2015-12-28

    We report on a bare InAs nanowire photodetector which exhibits an anomalous photoconductive behavior. Under low-power illumination, the current is smaller than the dark current, and monotonously decreases as the excitation power increases. When the excitation power is high enough, the current starts to increase normally. The phenomenon is attributed to different electron mobilities in the “core” and “shell” of a relatively thick nanowire originating from the surface effect, which result in a quickly dropped “core current” and slowly increased “shell current” under illumination.

  9. Theoretical interpretation of the electron mobility behavior in InAs nanowires

    SciTech Connect

    Marin, E. G. Ruiz, F. G. Godoy, A.; Tienda-Luna, I. M.; Martínez-Blanque, C.; Gámiz, F.

    2014-11-07

    This work studies the electron mobility in InAs nanowires (NWs), by solving the Boltzmann Transport Equation under the Momentum Relaxation Time approximation. The numerical solver takes into account the contribution of the main scattering mechanisms present in III-V compound semiconductors. It is validated against experimental field effect-mobility results, showing a very good agreement. The mobility dependence on the nanowire diameter and carrier density is analyzed. It is found that surface roughness and polar optical phonons are the scattering mechanisms that mainly limit the mobility behavior. Finally, we explain the origin of the oscillations observed in the mobility of small NWs at high electric fields.

  10. Single-electron transport in InAs nanowire quantum dots formed by crystal phase engineering

    NASA Astrophysics Data System (ADS)

    Nilsson, Malin; Namazi, Luna; Lehmann, Sebastian; Leijnse, Martin; Dick, Kimberly A.; Thelander, Claes

    2016-05-01

    We report electrical characterization of quantum dots formed by introducing pairs of thin wurtzite (WZ) segments in zinc blende (ZB) InAs nanowires. Regular Coulomb oscillations are observed over a wide gate voltage span, indicating that WZ segments create significant barriers for electron transport. We find a direct correlation of transport properties with quantum dot length and corresponding growth time of the enclosed ZB segment. The correlation is made possible by using a method to extract lengths of nanowire crystal phase segments directly from scanning electron microscopy images, and with support from transmission electron microscope images of typical nanowires. From experiments on controlled filling of nearly empty dots with electrons, up to the point where Coulomb oscillations can no longer be resolved, we estimate a lower bound for the ZB-WZ conduction-band offset of 95 meV.

  11. Graphitic platform for self-catalysed InAs nanowires growth by molecular beam epitaxy

    PubMed Central

    2014-01-01

    We report the self-catalysed growth of InAs nanowires (NWs) on graphite thin films using molecular beam epitaxy via a droplet-assisted technique. Through optimising metal droplets, we obtained vertically aligned InAs NWs with highly uniform diameter along their entire length. In comparison with conventional InAs NWs grown on Si (111), the graphite surface led to significant effects on the NWs geometry grown on it, i.e. larger diameter, shorter length with lower number density, which were ascribed to the absence of dangling bonds on the graphite surface. The axial growth rate of the NWs has a strong dependence on growth time, which increases quickly in the beginning then slows down after the NWs reach a length of approximately 0.8 μm. This is attributed to the combined axial growth contributions from the surface impingement and sidewall impingement together with the desorption of adatoms during the diffusion. The growth of InAs NWs on graphite was proposed following a vapour-solid mechanism. High-resolution transmission electron microscopy reveals that the NW has a mixture of pure zinc-blende and wurtzite insertions. PMID:25024683

  12. g-factor anisotropy in nanowire-based InAs quantum dots

    SciTech Connect

    D'Hollosy, Samuel; Fábián, Gábor; Baumgartner, Andreas; Schönenberger, Christian; Nygård, Jesper

    2013-12-04

    The determination and control of the electron g-factor in semiconductor quantum dots (QDs) are fundamental prerequisites in modern concepts of spintronics and spin-based quantum computation. We study the dependence of the g-factor on the orientation of an external magnetic field in quantum dots (QDs) formed between two metallic contacts on stacking fault free InAs nanowires. We extract the g-factor from the splitting of Kondo resonances and find that it varies continuously in the range between |g*| = 5 and 15.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    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.

  14. 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

  15. 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.

  16. Ballistic Transport and Exchange Interaction in InAs Nanowire Quantum Point Contacts.

    PubMed

    Heedt, S; Prost, W; Schubert, J; Grützmacher, D; Schäpers, Th

    2016-05-11

    One-dimensional ballistic transport is demonstrated for a high-mobility InAs nanowire device. Unlike conventional quantum point contacts (QPCs) created in a two-dimensional electron gas, the nanowire QPCs represent one-dimensional constrictions formed inside a quasi-one-dimensional conductor. For each QPC, the local subband occupation can be controlled individually between zero and up to six degenerate modes. At large out-of-plane magnetic fields Landau quantization and Zeeman splitting emerge and comprehensive voltage bias spectroscopy is performed. Confinement-induced quenching of the orbital motion gives rise to significantly modified subband-dependent Landé g factors. A pronounced g factor enhancement related to Coulomb exchange interaction is reported. Many-body effects of that kind also manifest in the observation of the 0.7·2e(2)/h conductance anomaly, commonly found in planar devices. PMID:27104768

  17. Electronic properties of GaAs, InAs and InP nanowires studied by terahertz spectroscopy.

    PubMed

    Joyce, Hannah J; Docherty, Callum J; Gao, Qiang; Tan, H Hoe; Jagadish, Chennupati; Lloyd-Hughes, James; Herz, Laura M; Johnston, Michael B

    2013-05-31

    We have performed a comparative study of ultrafast charge carrier dynamics in a range of III-V nanowires using optical pump-terahertz probe spectroscopy. This versatile technique allows measurement of important parameters for device applications, including carrier lifetimes, surface recombination velocities, carrier mobilities and donor doping levels. GaAs, InAs and InP nanowires of varying diameters were measured. For all samples, the electronic response was dominated by a pronounced surface plasmon mode. Of the three nanowire materials, InAs nanowires exhibited the highest electron mobilities of 6000 cm² V⁻¹ s⁻¹, which highlights their potential for high mobility applications, such as field effect transistors. InP nanowires exhibited the longest carrier lifetimes and the lowest surface recombination velocity of 170 cm s⁻¹. This very low surface recombination velocity makes InP nanowires suitable for applications where carrier lifetime is crucial, such as in photovoltaics. In contrast, the carrier lifetimes in GaAs nanowires were extremely short, of the order of picoseconds, due to the high surface recombination velocity, which was measured as 5.4 × 10⁵  cm s⁻¹. These findings will assist in the choice of nanowires for different applications, and identify the challenges in producing nanowires suitable for future electronic and optoelectronic devices.

  18. Measurements of the spin-orbit interaction and Landé g factor in a pure-phase InAs nanowire double quantum dot in the Pauli spin-blockade regime

    NASA Astrophysics Data System (ADS)

    Wang, Jiyin; Huang, Shaoyun; Lei, Zijin; Pan, Dong; Zhao, Jianhua; Xu, H. Q.

    2016-08-01

    We demonstrate direct measurements of the spin-orbit interaction and Landé g factors in a semiconductor nanowire double quantum dot. The device is made from a single-crystal pure-phase InAs nanowire on top of an array of finger gates on a Si/SiO2 substrate and the measurements are performed in the Pauli spin-blockade regime. It is found that the double quantum dot exhibits a large singlet-triplet energy splitting of ΔST ˜ 2.3 meV, a strong spin-orbit interaction of ΔSO ˜ 140 μeV, and a large and strongly level-dependent Landé g factor of ˜12.5. These results imply that single-crystal pure-phase InAs nanowires are desired semiconductor nanostructures for applications in quantum information technologies.

  19. Self-seeded, position-controlled InAs nanowire growth on Si: A growth parameter study

    PubMed Central

    Mandl, Bernhard; Dey, Anil W.; Stangl, Julian; Cantoro, Mirco; Wernersson, Lars-Erik; Bauer, Günther; Samuelson, Lars; Deppert, Knut; Thelander, Claes

    2011-01-01

    In this work, the nucleation and growth of InAs nanowires on patterned SiO2/Si(111) substrates is studied. It is found that the nanowire yield is strongly dependent on the size of the etched holes in the SiO2, where openings smaller than 180 nm lead to a substantial decrease in nucleation yield, while openings larger than ≈500nm promote nucleation of crystallites rather than nanowires. We propose that this is a result of indium particle formation prior to nanowire growth, where the size of the indium particles, under constant growth parameters, is strongly influenced by the size of the openings in the SiO2 film. Nanowires overgrowing the etched holes, eventually leading to a merging of neighboring nanowires, shed light into the growth mechanism. PMID:22053114

  20. Plasmon resonant cavities in vertical nanowire arrays

    SciTech Connect

    Bora, M; Bond, T; Behymer, E; Chang, A

    2010-02-23

    We investigate tunable plasmon resonant cavity arrays in paired parallel nanowire waveguides. Resonances are observed when the waveguide length is an odd multiple of quarter plasmon wavelengths, consistent with boundary conditions of node and antinode at the ends. Two nanowire waveguides satisfy the dispersion relation of a planar metal-dielectric-metal waveguide of equivalent width equal to the square field average weighted gap. Confinement factors over 103 are possible due to plasmon focusing in the inter-wire space.

  1. Phase-coherent transport and spin relaxation in InAs nanowires grown by molecule beam epitaxy

    SciTech Connect

    Wang, L. B.; Guo, J. K.; Kang, N. E-mail: hqxu@pku.edu.cn; Li, Sen; Fan, Dingxun; Pan, Dong; Zhao, Jianhua; Xu, H. Q. E-mail: hqxu@pku.edu.cn

    2015-04-27

    We report low-temperature magnetotransport studies of individual InAs nanowires grown by molecule beam epitaxy. At low magnetic fields, the magnetoconductance characteristics exhibit a crossover between weak antilocalization and weak localization by changing either the gate voltage or the temperature. The observed crossover behavior can be well described in terms of relative scales of the transport characteristic lengths extracted based on the quasi-one-dimensional theory of weak localization in the presence of spin-orbit interaction. The spin relaxation length extracted from the magnetoconductance data is found to be in the range of 80–100 nm, indicating the presence of strong spin-orbit coupling in the InAs nanowires. Moreover, the amplitude of universal conductance fluctuations in the nanowires is found to be suppressed at low temperatures due to the presence of strong spin-orbit scattering.

  2. Suspended InAs nanowire gate-all-around field-effect transistors

    SciTech Connect

    Li, Qiang; Huang, Shaoyun E-mail: hqxu@pku.edu.cn; Wang, Jingyun; Pan, Dong; Zhao, Jianhua; Xu, H. Q. E-mail: hqxu@pku.edu.cn

    2014-09-15

    Gate-all-around field-effect transistors are realized with thin, single-crystalline, pure-phase InAs nanowires grown by molecular beam epitaxy. At room temperature, the transistors show a desired high on-state current I{sub on} of ∼10 μA and an on-off current ratio I{sub on}/I{sub off} of as high as 10{sup 6} at source-drain bias voltage of 50 mV and gate length of 1 μm with a gate underlap spacing of 1 μm from the source and from the drain. At low temperatures, the on-state current I{sub on} is only slightly reduced, while the ratio I{sub on}/I{sub off} is increased to 10{sup 7}. The field-effect mobility in the nanowire channels is also investigated and found to be ∼1500 cm{sup 2}/V s at room temperature and ∼2000 cm{sup 2}/V s at low temperatures. The excellent performance of the transistors is explained in terms of strong electrostatic and quantum confinements of carriers in the nanowires.

  3. Nanowire sensor, sensor array, and method for making the same

    NASA Technical Reports Server (NTRS)

    Yun, Minhee (Inventor); Myung, Nosang (Inventor); Vasquez, Richard (Inventor); Homer, Margie (Inventor); Ryan, Margaret (Inventor); Yen, Shiao-Pin (Inventor); Fleurial, Jean-Pierre (Inventor); Bugga, Ratnakumar (Inventor); Choi, Daniel (Inventor); Goddard, William (Inventor)

    2012-01-01

    The present invention relates to a nanowire sensor and method for forming the same. More specifically, the nanowire sensor comprises at least one nanowire formed on a substrate, with a sensor receptor disposed on a surface of the nanowire, thereby forming a receptor-coated nanowire. The nanowire sensor can be arranged as a sensor sub-unit comprising a plurality of homogeneously receptor-coated nanowires. A plurality of sensor subunits can be formed to collectively comprise a nanowire sensor array. Each sensor subunit in the nanowire sensor array can be formed to sense a different stimulus, allowing a user to sense a plurality of stimuli. Additionally, each sensor subunit can be formed to sense the same stimuli through different aspects of the stimulus. The sensor array is fabricated through a variety of techniques, such as by creating nanopores on a substrate and electrodepositing nanowires within the nanopores.

  4. Giant thermovoltage in single InAs nanowire field-effect transistors.

    PubMed

    Roddaro, Stefano; Ercolani, Daniele; Safeen, Mian Akif; Suomalainen, Soile; Rossella, Francesco; Giazotto, Francesco; Sorba, Lucia; Beltram, Fabio

    2013-08-14

    Millivolt range thermovoltage is demonstrated in single InAs nanowire based field effect transistors. Thanks to a buried heating scheme, we drive both a large thermal bias ΔT > 10 K and a strong field-effect modulation of electric conductance on the nanostructures. This allows the precise mapping of the evolution of the Seebeck coefficient S as a function of the gate-controlled conductivity σ between room temperature and 100 K. Based on these experimental data a novel estimate of the electron mobility is given. This value is compared with the result of standard field-effect based mobility estimates and discussed in relation to the effect of charge traps in the devices. PMID:23869467

  5. Noise thermometry applied to thermoelectric measurements in InAs nanowires

    NASA Astrophysics Data System (ADS)

    Tikhonov, E. S.; Shovkun, D. V.; Ercolani, D.; Rossella, F.; Rocci, M.; Sorba, L.; Roddaro, S.; Khrapai, V. S.

    2016-10-01

    We apply noise thermometry to characterize charge and thermoelectric transport in single InAs nanowires (NWs) at a bath temperature of 4.2 K. Shot noise measurements identify elastic diffusive transport in our NWs with negligible electron-phonon interaction. This enables us to set up a measurement of the diffusion thermopower. Unlike previous approaches, we make use of a primary electronic noise thermometry to calibrate a thermal bias across the NW. In particular, this enables us to apply a contact heating scheme, which is much more efficient in creating the thermal bias as compared to conventional substrate heating. The measured thermoelectric Seebeck coefficient exhibits strong mesoscopic fluctuations in dependence on the back-gate voltage that is used to tune the NW carrier density. We analyze the transport and thermoelectric data in terms of an approximate Mott's thermopower relation and evaluate a gate-voltage to the Fermi energy conversion factor.

  6. Mechanical properties of individual InAs nanowires studied by tensile tests

    SciTech Connect

    Li, X.; Wei, X. L. E-mail: qingchen@pku.edu.cn; Xu, T. T.; Ning, Z. Y.; Shu, J. P.; Chen, Q. E-mail: qingchen@pku.edu.cn; Wang, X. Y.; Pan, D.; Zhao, J. H.; Yang, T.

    2014-03-10

    Mechanical properties of individual InAs nanowires (NWs) synthesized by metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) methods are studied by in-situ tensile tests in a scanning electron microscope and their fracture strength and Young's modulus are obtained. The two types of NWs both exhibit brittle fracture with a maximum elastic strain up to ∼10%. Their fracture strength distributes in a similar range of ∼2–5 GPa with a general trend of increasing with NW volume decrease, which is well described by Weibull statistic with a smaller Weibull modulus and a higher characteristic strength for MOCVD NWs. Young's modulus is determined to be 16–78 GPa with an average value of 45 GPa and no dependence on NW diameter for MOCVD NWs and 34–79 GPa with an average value of 58 GPa for MBE NWs.

  7. Mechanical properties of individual InAs nanowires studied by tensile tests

    NASA Astrophysics Data System (ADS)

    Li, X.; Wei, X. L.; Xu, T. T.; Ning, Z. Y.; Shu, J. P.; Wang, X. Y.; Pan, D.; Zhao, J. H.; Yang, T.; Chen, Q.

    2014-03-01

    Mechanical properties of individual InAs nanowires (NWs) synthesized by metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) methods are studied by in-situ tensile tests in a scanning electron microscope and their fracture strength and Young's modulus are obtained. The two types of NWs both exhibit brittle fracture with a maximum elastic strain up to ˜10%. Their fracture strength distributes in a similar range of ˜2-5 GPa with a general trend of increasing with NW volume decrease, which is well described by Weibull statistic with a smaller Weibull modulus and a higher characteristic strength for MOCVD NWs. Young's modulus is determined to be 16-78 GPa with an average value of 45 GPa and no dependence on NW diameter for MOCVD NWs and 34-79 GPa with an average value of 58 GPa for MBE NWs.

  8. InAs nanowire growth modes on Si (111) by gas source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Robson, M. T.; LaPierre, R. R.

    2016-02-01

    InAs nanowires (NWs) were grown on silicon substrates by gas source molecular beam epitaxy using five different growth modes: (1) Au-assisted growth, (2) positioned (patterned) Au-assisted growth, (3) Au-free growth, (4) positioned Au-assisted growth using a patterned oxide mask, and (5) Au-free selective-area epitaxy (SAE) using a patterned oxide mask. Optimal growth conditions (temperature, V/III flux ratio) were identified for each growth mode for control of NW morphology and vertical NW yield. The highest yield (72%) was achieved with the SAE method at a growth temperature of 440 °C and a V/III flux ratio of 4. Growth mechanisms are discussed for each of the growth modes.

  9. Time evolution studies of laser induced chemical changes in InAs nanowire using Raman spectroscopy

    SciTech Connect

    Pal, Suparna; Aggarwal, R.; Kumari Gupta, Vandna; Ingale, Alka

    2014-07-07

    We report the study of time evolution of chemical changes on the surface of an InAs nanowire (NW) on laser irradiation in different power density regime, using Raman spectroscopy for a time span of 8–16 min. Mixture of metastable oxides like InAsO{sub 4,} As{sub 2}O{sub 3} are formed upon oxidation, which are reflected as sharp Raman peaks at ∼240–254 and 180–200 cm{sup −1}. Evidence of removal of arsenic layer by layer is also observed at higher power density. Position controlled laser induced chemical modification on a nanometer scale, without changing the core of the NW, can be useful for NW based device fabrication.

  10. Signature of topological transition in InAs nanowire Josephson junctions

    NASA Astrophysics Data System (ADS)

    Strambini, Elia; Paajaste, J.; Amado, M.; Roddaro, S.; San-Jose, P.; Aguado, R.; Bergeret, S.; Ercolani, D.; Sorba, L.; Giazotto, F.

    The coupling of a conventional s-wave superconductors to semiconductors with strong spin-orbit (SO) coupling, like e. g. InAs or InSb nanowires (NWs), gives rise to unconventional p-wave superconductivity that may become a topological superconductor (TS), which is a natural host for exotic edge modes with Majorana character. Recently the enhancement of the critical supercurrent Ic in a strong SO semiconducting Josephson junction (JJ) have been proposed as a new evidence of the sought-after Majorana bound states. Here we report on the first observation of the colossal Ic enhancement induced by an external magnetic field on a mesoscopic JJ formed by InAs NWs and Ti/Al leads. This anomalous enhancement appears precisely above a threshold magnetic field Bth orthogonal to the substrate and in junctions of different lengths, suggesting that the origin of the enhancement is intrinsic, i.e. it is not related to geometrical resonances in the junction. None of the standard phenomenon known in JJ, including e. g. Fraunhofer patterns or π-junction behavior, can explain this colossal enhancement while a topological transition at Bth is qualitatively compatible with the observed phenomenology.

  11. 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.

  12. 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.

  13. Structural and electrical properties of catalyst-free Si-doped InAs nanowires formed on Si(111).

    PubMed

    Park, Dong Woo; Jeon, Seong Gi; Lee, Cheul-Ro; Lee, Sang Jun; Song, Jae Yong; Kim, Jun Oh; Noh, Sam Kyu; Leem, Jae-Young; Kim, Jin Soo

    2015-11-19

    We report structural and electrical properties of catalyst-free Si-doped InAs nanowires (NWs) formed on Si(111) substrates. The average diameter of Si-doped InAs NWs was almost similar to that of undoped NWs with a slight increase in height. In the previous works, the shape and size of InAs NWs formed on metallic catalysts or patterned structures were significantly changed by introducing dopants. Even though the external shape and size of the Si-doped NWs in this work were not changed, crystal structures inside the NWs were significantly changed. For the undoped InAs NWs, both zincblende (ZB) and wurzite (WZ) structures were observed in transmission-electron microscope images, where the portion of WZ structure was estimated to be more than 30%. However, only ZB was observed with an increase in stacking fault (SF) for the Si-doped NWs. The undoped and Si-doped InAs NWs were used as channels of four-point electrical measurements with Al/Ni electrodes to investigate electrical properties. The resistivity calculated from the current-voltage curve of a Si-doped InAs NW showed 1.32 × 10(-3) Ωcm, which was dramatically decreased from 10.14 × 10(-3) Ωcm for the undoped InAs NW. A relatively low resistivity of catalyst-free Si-doped InAs NWs was achieved without significant change in structural dimensions.

  14. Plasmon resonant cavities in vertical nanowire arrays

    DOEpatents

    Bora, Mihail; Bond, Tiziana C.; Fasenfest, Benjamin J.; Behymer, Elaine M.

    2014-07-15

    Tunable plasmon resonant cavity arrays in paired parallel nanowire waveguides are presented. Resonances can be observed when the waveguide length is an odd multiple of quarter plasmon wavelengths, consistent with boundary conditions of node and antinode at the ends. Two nanowire waveguides can satisfy the dispersion relation of a planar metal-dielectric-metal waveguide of equivalent width equal to the square field average weighted gap. Confinement factors of over 10.sup.3 are possible due to plasmon focusing in the inter-wire space.

  15. Templated Synthesis of Uniform Perovskite Nanowire Arrays.

    PubMed

    Ashley, Michael J; O'Brien, Matthew N; Hedderick, Konrad R; Mason, Jarad A; Ross, Michael B; Mirkin, Chad A

    2016-08-17

    While the chemical composition of semiconducting metal halide perovskites can be precisely controlled in thin films for photovoltaic devices, the synthesis of perovskite nanostructures with tunable dimensions and composition has not been realized. Here, we describe the templated synthesis of uniform perovskite nanowires with controlled diameter (50-200 nm). Importantly, by providing three examples (CH3NH3PbI3, CH3NH3PbBr3, and Cs2SnI6), we show that this process is composition general and results in oriented nanowire arrays on transparent conductive substrates. PMID:27501464

  16. Thermal conductivity of bulk and nanowire InAs, AlN, and BeO polymorphs from first principles

    SciTech Connect

    Li, Wu; Mingo, Natalio

    2013-11-14

    We compute the thermal conductivity of the alternative zincblende (ZB) and wurtzite (WZ) phases of InAs, AlN, and BeO. The bulk thermal conductivity of the ZB phase of BeO is predicted to be even higher than that of its WZ phase (the highest amongst all ceramics used in electronic technology). Our calculations agree well with the available experimental measurements for bulk ZB InAs, WZ AlN, WZ BeO, and WZ and ZB InAs nanowires, and we provide predictions for the remaining cases. The predicted good thermal conductor ZB BeO might have interesting applications in improved heat sinks for high performance semiconductor electronics.

  17. X-ray diffraction strain analysis of a single axial InAs1–xPx nanowire segment

    PubMed Central

    Keplinger, Mario; Mandl, Bernhard; Kriegner, Dominik; Holý, Václav; Samuelsson, Lars; Bauer, Günther; Deppert, Knut; Stangl, Julian

    2015-01-01

    The spatial strain distribution in and around a single axial InAs1–xPx hetero-segment in an InAs nanowire was analyzed using nano-focused X-ray diffraction. In connection with finite-element-method simulations a detailed quantitative picture of the nanowire’s inhomogeneous strain state was achieved. This allows for a detailed understanding of how the variation of the nanowire’s and hetero-segment’s dimensions affect the strain in its core region and in the region close to the nanowire’s side facets. Moreover, ensemble-averaging high-resolution diffraction experiments were used to determine statistical information on the distribution of wurtzite and zinc-blende crystal polytypes in the nanowires. PMID:25537589

  18. Nanowire sensors and arrays for chemical/biomolecule detection

    NASA Technical Reports Server (NTRS)

    Yun, Minhee; Lee, Choonsup; Vasquez, Richard P.; Ramanathan, K.; Bangar, M. A.; Chen, W.; Mulchandan, A.; Myung, N. V.

    2005-01-01

    We report electrochemical growth of single nanowire based sensors using e-beam patterned electrolyte channels, potentially enabling the controlled fabrication of individually addressable high density arrays. The electrodeposition technique results in nanowires with controlled dimensions, positions, alignments, and chemical compositions. Using this technique, we have fabricated single palladium nanowires with diameters ranging between 75 nm and 300 nm and conducting polymer nanowires (polypyrrole and polyaniline) with diameters between 100 nm and 200 nm. Using these single nanowires, we have successfully demonstrated gas sensing with Pd nanowires and pH sensing with polypirrole nanowires.

  19. Porous InP array-directed assembly of InAs nanostructure

    NASA Astrophysics Data System (ADS)

    Che, Xiao-Ling; Li, Lu; Liu, Feng-Qi; Huang, Xiu-Qi; Wang, Zhan-Guo

    2006-06-01

    Fascinating features of porous InP array-directed assembly of InAs nanostructures are presented. Strained InAs nanostructures are grown by molecular-beam epitaxy on electrochemical etched porous InP substrate. Identical porous substrate with different pore depths defines different growth modes. Shallow pores direct the formation of closely spaced InAs dots at the bottom. Deep pores lead to progressive covering of the internal surface of pores by epitaxial material followed by pore mouth shrinking. For any depth an obvious dot depletion feature occurs on top of the pore framework. This growth method presages a pathway to engineer quantum-dot molecules and other nanoelements for fancy physical phenomena.

  20. Chemical beam epitaxy growth of III-V semiconductor nanowires

    NASA Astrophysics Data System (ADS)

    Mohummed Noori, Farah T.

    2013-12-01

    Indium- Arsenide (InAs) nanowires were grown in a high vacuum chemical beam epitaxy (CBE) unit on InAs(111) wafers substrates at 425-454°C. Two types of nanogold were used as orientation catalyst, 40nm and 80nm. The measurements were performed using scanning electron microscopy showed that uniform nanowires. The nanowires orient vertically in the InAs nanowire scanning electron microscopy of an array 80nm diameter InAs nanowire with length is in the range 0.5-1 μm and of an array 40nm diameter with length is in the range 0.3-0.7μm. The nanowire length with growth time shows that the linear increase of nanowires start to grow as soon as TMIn is available. The growth rate with temperature was studied.

  1. Chemical beam epitaxy growth of III–V semiconductor nanowires

    SciTech Connect

    Mohummed Noori, Farah T.

    2013-12-16

    Indium- Arsenide (InAs) nanowires were grown in a high vacuum chemical beam epitaxy (CBE) unit on InAs(111) wafers substrates at 425–454°C. Two types of nanogold were used as orientation catalyst, 40nm and 80nm. The measurements were performed using scanning electron microscopy showed that uniform nanowires. The nanowires orient vertically in the InAs nanowire scanning electron microscopy of an array 80nm diameter InAs nanowire with length is in the range 0.5–1 μm and of an array 40nm diameter with length is in the range 0.3–0.7μm. The nanowire length with growth time shows that the linear increase of nanowires start to grow as soon as TMIn is available. The growth rate with temperature was studied.

  2. Novel microwave properties and "memory effect" in magnetic nanowire array

    NASA Astrophysics Data System (ADS)

    Kou, Xiaoming

    2011-12-01

    Ferromagnetic nanowire arrays embedded in insulating matrices have attracted great attention in recent years for their rich physics and potential as sensor and microwave applications. Magnetic nanowires made of 3d transitional metals or their alloys have the advantages of high saturation magnetizations, limited eddy current loss, and guaranteed microwave penetration due to nanometer size. The nanowire arrays can also have high ferromagnetic resonance (FMR) frequencies due to shape anisotropy. In this work, the following new phenomena of magnetic nanowire arrays are demonstrated and explained with a theoretical model. (1) A simple theoretical analysis indicates that high permeability is possible in nanowire arrays with the magnetocrystalline anisotropy comparable to the demagnetization energy and its easy axis perpendicular to the nanowire. With proper conditions, we have fabricated Co nanowire arrays with a crystalline easy axis perpendicular to the nanowire. For Co nanowire arrays with certain geometries, high permeability and low losses have been achieved. (2) Magnetic materials with tunable FMR are highly desirable in microwave devices. We demonstrate that the natural FMR of Ni90Fe10 nanowire array can be tuned continuously from 8.2 to 11.7 GHz by choosing different remanent state. Theoretical model based on dipolar interaction among nanowires has been developed to explain the observed phenomena. A double FMR feature caused by dipolar interaction in magnetic nanowire array was predicted and verified in Co nanowires. (3) A memory effect has also been demonstrated in magnetic nanowire arrays. The magnetic nanowire array has the ability to record the maximum magnetic field that the array has been exposed to after the field has been turned off. The origin of the memory effect is the strong magnetic dipole interaction among the nanowires. Based on the memory effect, a novel and extremely low cost EMP detection scheme is proposed. It has the potential to measure

  3. Thermal conductivity in porous silicon nanowire arrays

    PubMed Central

    2012-01-01

    The nanoscale features in silicon nanowires (SiNWs) can suppress phonon propagation and strongly reduce their thermal conductivities compared to the bulk value. This work measures the thermal conductivity along the axial direction of SiNW arrays with varying nanowire diameters, doping concentrations, surface roughness, and internal porosities using nanosecond transient thermoreflectance. For SiNWs with diameters larger than the phonon mean free path, porosity substantially reduces the thermal conductivity, yielding thermal conductivities as low as 1 W/m/K in highly porous SiNWs. However, when the SiNW diameter is below the phonon mean free path, both the internal porosity and the diameter significantly contribute to phonon scattering and lead to reduced thermal conductivity of the SiNWs. PMID:23039084

  4. Thermal conductivity in porous silicon nanowire arrays.

    PubMed

    Weisse, Jeffrey M; Marconnet, Amy M; Kim, Dong Rip; Rao, Pratap M; Panzer, Matthew A; Goodson, Kenneth E; Zheng, Xiaolin

    2012-10-06

    The nanoscale features in silicon nanowires (SiNWs) can suppress phonon propagation and strongly reduce their thermal conductivities compared to the bulk value. This work measures the thermal conductivity along the axial direction of SiNW arrays with varying nanowire diameters, doping concentrations, surface roughness, and internal porosities using nanosecond transient thermoreflectance. For SiNWs with diameters larger than the phonon mean free path, porosity substantially reduces the thermal conductivity, yielding thermal conductivities as low as 1 W/m/K in highly porous SiNWs. However, when the SiNW diameter is below the phonon mean free path, both the internal porosity and the diameter significantly contribute to phonon scattering and lead to reduced thermal conductivity of the SiNWs.

  5. Thermal conductivity in porous silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Weisse, Jeffrey M.; Marconnet, Amy M.; Kim, Dong Rip; Rao, Pratap M.; Panzer, Matthew A.; Goodson, Kenneth E.; Zheng, Xiaolin

    2012-10-01

    The nanoscale features in silicon nanowires (SiNWs) can suppress phonon propagation and strongly reduce their thermal conductivities compared to the bulk value. This work measures the thermal conductivity along the axial direction of SiNW arrays with varying nanowire diameters, doping concentrations, surface roughness, and internal porosities using nanosecond transient thermoreflectance. For SiNWs with diameters larger than the phonon mean free path, porosity substantially reduces the thermal conductivity, yielding thermal conductivities as low as 1 W/m/K in highly porous SiNWs. However, when the SiNW diameter is below the phonon mean free path, both the internal porosity and the diameter significantly contribute to phonon scattering and lead to reduced thermal conductivity of the SiNWs.

  6. Development of nanowire arrays for neural probe

    NASA Astrophysics Data System (ADS)

    Abraham, Jose K.; Xie, Jining; Varadan, Vijay K.

    2005-05-01

    It is already established that functional electrical stimulation is an effective way to restore many functions of the brain in disabled individuals. The electrical stimulation can be done by using an array of electrodes. Neural probes stimulate or sense the biopotentials mainly through the exposed metal sites. These sites should be smaller relative to the spatial potential distribution so that any potential averaging in the sensing area can be avoided. At the same time, the decrease in size of these sensing sites is limited due to the increase in impedance levels and the thermal noise while decreasing its size. It is known that current density in a planar electrode is not uniform and a higher current density can be observer around the perimeter of the electrodes. Electrical measurements conducted on many nanotubes and nanowires have already proved that it could be possible to use for current density applications and the drawbacks of the present design in neural probes can be overcome by incorporating many nanotechnology solutions. In this paper we present the design and development of nanowire arrays for the neural probe for the multisite contact which has the ability to collect and analyze isolated single unit activity. An array of vertically grown nanowires is used as contact site and many of such arrays can be used for stimulating as well as recording sites. The nanolevel interaction and wireless communication solution can extend to applications involving the treatment of many neurological disorders including Parkinson"s disease, Alzheimer"s disease, spinal injuries and the treatment of blindness and paralyzed patients with minimal or no invasive surgical procedures.

  7. Defect-free zinc-blende structured InAs nanowires realized by in situ two V/III ratio growth in molecular beam epitaxy.

    PubMed

    Zhang, Zhi; Lu, Zhen-Yu; Chen, Ping-Ping; Lu, Wei; Zou, Jin

    2015-08-01

    In this study, we devised a two-V/III-ratio procedure to control the Au-assisted growth of defect-free InAs nanowires in molecular beam epitaxy. The demonstrated two V/III ratio procedure consists of a first high V/III ratio growth step to prepare the nanowire foundation on the substrate surface, followed by a low V/III ratio step to induce the nanowire growth. By manipulating the V/III ratios in different steps, we have achieved the controlled growth of pure defect-free zinc-blende structured InAs nanowires on the GaAs {1̄1̄1̄} substrates. This study provides an approach to control not only the crystal structure of semiconductor nanowires, but also their structural qualities.

  8. Amplified Thermionic Cooling Using Arrays of Nanowires

    NASA Technical Reports Server (NTRS)

    Yang, Eui-Hyeok; Choi, Daniel; Shcheglov, Kirill; Hishinuma, Yoshikazu

    2007-01-01

    A class of proposed thermionic cooling devices would incorporate precise arrays of metal nanowires as electron emitters. The proposed devices could be highly miniaturized, enabling removal of heat from locations, very close to electronic devices, that have previously been inaccessible for heat-removal purposes. The resulting enhancement of removal of heat would enable operation of the devices at higher power levels and higher clock speeds. Moreover, the mass, complexity, and bulk of electronic circuitry incorporating these highly miniaturized cooling devices could be considerably reduced, relative to otherwise equivalent circuitry cooled by conventional electromechanical, thermoelectric, and fluidic means. In thermionic cooling, one exploits the fact that because only the highest-energy electrons are thermionically emitted, collecting those electrons to prevent their return to the emitting electrode results in the net removal of heat from that electrode. Collection is effected by applying an appropriate positive bias potential to another electrode placed near the emitting electrode. The concept underlying the proposal is that the thermionic-emission current and, hence, the cooling effect attainable by use of an array of nanowires could be significantly greater than that attainable by use of a single emitting electrode or other electron- emitting surface. The wires in an array according to the proposal would protrude perpendicularly from a planar surface and their heights would be made uniform to within a sub-nanometer level of precision

  9. Magnetic interactions in compositionally modulated nanowire arrays

    NASA Astrophysics Data System (ADS)

    Palmero, Ester M.; Béron, Fanny; Bran, Cristina; del Real, Rafael P.; Vázquez, Manuel

    2016-10-01

    Series of high hexagonally ordered compositionally modulated nanowire arrays, with different Cu layer and FeCoCu segment thicknesses and a constant diameter of 35 nm, were fabricated by electroplating from a single electrolytic bath into anodic aluminum oxide membranes. The objective of the study was to determine the influence of ferromagnetic (FM) segment and non-ferromagnetic (NFM) layer thickness on the magnetic properties, particularly coercivity and magnetic interactions. First-order reversal curve (FORC) measurements and simulations were performed to quantify the effect of the inter-/intra-nanowire magnetostatic interactions on the coercivity and interaction field distributions. The FORC coercivity increases for a thick NFM layer and long FM segments due to decoupling of the the FM segments and the increased shape anisotropy, respectively. On the other hand, the interaction field presents a parallel strong reduction for a thick NFM layer and thin FM segments, which is ascribed to a similar NFM/FM thickness ratio and degree of FM segment decoupling along the nanowire.

  10. Electrodeposition and device incorporation of bismuth antimony nanowire arrays

    NASA Astrophysics Data System (ADS)

    Keyani, Jennifer

    Thermoelectric materials have the unique property where the application of a potential difference across the material results in the formation of a temperature gradient, and vice versa. There is continued interest in bulk thermoelectric materials for power generation and refrigeration applications, however these materials are not currently in widespread use due to their low conversion efficiency. It has been predicted that nanostructured thermoelectric materials will show enhanced performance over their bulk counterparts. In this study, bismuth antimony (Bi1-xSbx) nanowire arrays have been synthesized and assembled into devices in order to demonstrate an enhanced performance in nanostructured thermoelectric materials. Bi1-xSbx nanowire arrays were fabricated by potentiostatic electrodeposition into porous alumina templates from a dimethyl sulfoxide (DMSO) solution. The nanowire composition and texture were studied as a function of the electrodeposition conditions in order to maximize their thermoelectric performance. Energy dispersive spectrometry and electron microprobe analysis were used to study the nanowire composition as a function of the electroactive and non-electroactive species in solution. Texturing in the nanowire arrays was observed by X-ray diffraction and controlled by the applied voltage and presence of supporting electrolyte. The nanowire arrays were also optimized for device incorporation by maximizing the number of nanowires and minimizing their length distribution. The areal density of nanowire arrays was on the order of 1010 wires/cm2 due to the high density of pores in the alumina and the high degree to which those pores were filled with electrodeposited material. A narrow distribution of nanowire lengths was observed by scanning electron microscopy across millimeter-length portions of the arrays. A hybrid nanowire-bulk thermoelectric device was assembled after electrical contacts were electrodeposited over Bi1-xSbx nanowire arrays. Nickel was

  11. 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

  12. Modifying the emission of light from a semiconductor nanowire array

    NASA Astrophysics Data System (ADS)

    Anttu, Nicklas

    2016-07-01

    Semiconductor nanowire arrays have been identified as a promising platform for future light emitting diodes (LEDs), for example, due to the materials science freedom of combining lattice-mismatched materials in them. Furthermore, the emission of light from nanowires can be tailored by designing their geometry. Such tailoring could optimize the emission of light to the top side as well as enhance the emission rate through the Purcell effect. However, the possibility for enhanced light extraction from III-V nanowire arrays over a conventional bulk-like LED has not been investigated systematically. Here, we use electromagnetic modeling to study the emission of light from nanowire arrays. We vary both the diameter of the nanowires and the array period to show the benefit of moving from a bulk-like LED to a nanowire array LED. We study the fraction of light emitted to the top air side and to the substrate at wavelength λ. We find several diameter-dependent resonant peaks for which the emission to the top side is maximized. For the strongest such peak, by increasing the array period, the fraction of emitted light that is extracted at the top air side can be enhanced by a factor of 30 compared to that in a planar bulk LED. By modeling a single nanowire, we confirm that it is beneficial to place the nanowires further apart to enhance the emission to the top side. Furthermore, we predict that for a nanowire diameter D > λ/2, a majority of the emitted power ends up in the substrate. Our results offer direction for the design and optimization of nanowire-array based light emitting diodes.

  13. 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.

  14. Generic nano-imprint process for fabrication of nanowire arrays.

    PubMed

    Pierret, Aurélie; Hocevar, Moïra; Diedenhofen, Silke L; Algra, Rienk E; Vlieg, E; Timmering, Eugene C; Verschuuren, Marc A; Immink, George W G; Verheijen, Marcel A; Bakkers, Erik P A M

    2010-02-10

    A generic process has been developed to grow nearly defect-free arrays of (heterostructured) InP and GaP nanowires. Soft nano-imprint lithography has been used to pattern gold particle arrays on full 2 inch substrates. After lift-off organic residues remain on the surface, which induce the growth of additional undesired nanowires. We show that cleaning of the samples before growth with piranha solution in combination with a thermal anneal at 550 degrees C for InP and 700 degrees C for GaP results in uniform nanowire arrays with 1% variation in nanowire length, and without undesired extra nanowires. Our chemical cleaning procedure is applicable to other lithographic techniques such as e-beam lithography, and therefore represents a generic process.

  15. Generic nano-imprint process for fabrication of nanowire arrays

    NASA Astrophysics Data System (ADS)

    Pierret, Aurélie; Hocevar, Moïra; Diedenhofen, Silke L.; Algra, Rienk E.; Vlieg, E.; Timmering, Eugene C.; Verschuuren, Marc A.; Immink, George W. G.; Verheijen, Marcel A.; Bakkers, Erik P. A. M.

    2010-02-01

    A generic process has been developed to grow nearly defect-free arrays of (heterostructured) InP and GaP nanowires. Soft nano-imprint lithography has been used to pattern gold particle arrays on full 2 inch substrates. After lift-off organic residues remain on the surface, which induce the growth of additional undesired nanowires. We show that cleaning of the samples before growth with piranha solution in combination with a thermal anneal at 550 °C for InP and 700 °C for GaP results in uniform nanowire arrays with 1% variation in nanowire length, and without undesired extra nanowires. Our chemical cleaning procedure is applicable to other lithographic techniques such as e-beam lithography, and therefore represents a generic process.

  16. Gold nanowire electrodes in array: simulation study and experiments.

    PubMed

    Wahl, Amélie; Dawson, Karen; MacHale, John; Barry, Seán; Quinn, Aidan J; O'Riordan, Alan

    2013-01-01

    Recent developments in nanofabrication have enabled fabrication of robust and reproducible nanoelectrodes with enhanced performance, when compared to microelectrodes. A hybrid electron beam/photolithography technique is shown that permits discrete gold nanowire electrode arrays to be routinely fabricated at reasonable cost. Fabricated devices include twelve gold nanowire working electrode arrays, an on-chip gold counter electrode and an on-chip platinum pseudo reference electrode. Using potential sweep techniques, when diffusionally independent, these nanowires exhibit measurable currents in the nanoAmpere regime and display steady-state voltammograms even at very high scan rates (5000 mV s(-1)) indicative of fast analyte mass transport to the electrode. Nanowire electrode arrays offer the potential for enhancements in electroanalysis including increased signal to noise ratio and increased sensitivity while also allowing quantitative detection at much lower concentrations. However, to achieve this goal a full understanding of the diffusion profiles existing at nanowire arrays is required. To this end, we simulate the effects of altering inter-electrode separations on analyte diffusion for a range of scan rates at nanowire electrode arrays, and perform the corresponding experiments. We show that arrays with diffusionally independent concentration profiles demonstrate superior electrochemical performance compared to arrays with overlapping diffusion profiles when employing sweep voltammetric techniques. By contrast, we show that arrays with diffusionally overlapping profiles exhibit enhanced performance when employing step voltammetric techniques.

  17. Enhanced photothermal conversion in vertically oriented gallium arsenide nanowire arrays.

    PubMed

    Walia, Jaspreet; Dhindsa, Navneet; Flannery, Jeremy; Khodabad, Iman; Forrest, James; LaPierre, Ray; Saini, Simarjeet S

    2014-10-01

    The photothermal properties of vertically etched gallium arsenide nanowire arrays are examined using Raman spectroscopy. The nanowires are arranged in square lattices with a constant pitch of 400 nm and diameters ranging from 50 to 155 nm. The arrays were illuminated using a 532 nm laser with an incident energy density of 10 W/mm(2). Nanowire temperatures were highly dependent on the nanowire diameter and were determined by measuring the spectral red-shift for both TO and LO phonons. The highest temperatures were observed for 95 nm diameter nanowires, whose top facets and sidewalls heated up to 600 and 440 K, respectively, and decreased significantly for the smaller or larger diameters studied. The diameter-dependent heating is explained by resonant coupling of the incident laser light into optical modes of the nanowires, resulting in increased absorption. Photothermal activity in a given nanowire diameter can be optimized by proper wavelength selection, as confirmed using computer simulations. This demonstrates that the photothermal properties of GaAs nanowires can be enhanced and tuned by using a photonic lattice structure and that smaller nanowire diameters are not necessarily better to achieve efficient photothermal conversion. The diameter and wavelength dependence of the optical coupling could allow for localized temperature gradients by creating arrays which consist of different diameters.

  18. High-density gold nanowire arrays by lithographically patterned nanowire electrodeposition.

    PubMed

    Hujdic, Justin E; Sargisian, Alan P; Shao, Jingru; Ye, Tao; Menke, Erik J

    2011-07-01

    Here we describe a new method for preparing multiple arrays of parallel gold nanowires with dimensions and separation down to 50 nm. This method uses photolithography to prepare an electrode consisting of a patterned nickel film on glass, onto which a gold and nickel nanowire array is sequentially electrodeposited. After the electrodeposition, the nickel is stripped away, leaving behind a gold nanowire array, with dimensions governed by the gold electrodeposition parameters, spacing determined by the nickel electrodeposition parameters, and overall placement and shape dictated by the photolithography.

  19. Magnetic nanowire arrays in anodic alumina membranes: Rutherford backscattering characterization

    NASA Astrophysics Data System (ADS)

    Hernández-Vélez, M.; Pirota, K. R.; Pászti, F.; Navas, D.; Climent, A.; Vázquez, M.

    2005-05-01

    Systematic study of magnetic nanowire arrays grown in anodic alumina membranes (AAM) has been done by means of Rutherford backscattering spectroscopy (RBS). The AAM used as templates were morphologically characterized by using high resolution scanning electron microscopy (HRSEM), fast Fourier transform (FFT) and atomic force microscopy (AFM). The highly ordered templates with a mean pore diameter size of 30 nanometers, a mean inter-pore spacing of 100 nm and lengths ranging from 4 to 180 microns were obtained through two-steps anodization process, and the Ni and Co nanowire arrays were grown by electrodeposition techniques. The main attention is addressed to Ni nanowire arrays. RBS results allowed us to determine the real depth profile of atomic composition of the obtained nanowire arrays. In addition, the RBS spectra fitting showed that the porosity increased from the top to the bottom of the samples. Two phenomenological models are proposed to understand the apparition of that secondary porosity and a linear relation between the total amount of electrodeposited Ni and the electrodeposition time was obtained. As an example, it is also reported the relation between RBS results and magnetic properties, such as coercive field and remanence/saturation magnetization ratio of the samples. Particularly, for Ni nanowires arrays obtained by using voltage pulses, it is demonstrated that the larger the nanowires, the higher the definition for easy axis parallel to the nanowire length is possible.

  20. Nanowire array and nanowire solar cells and methods for forming the same

    DOEpatents

    Yang, Peidong; Greene, Lori E.; Law, Matthew

    2009-06-09

    Homogeneous and dense arrays of nanowires are described. The nanowires can be formed in solution and can have average diameters of 40-300 nm and lengths of 1-3 .mu.m. They can be formed on any suitable substrate. Photovoltaic devices are also described.

  1. Nanowire array and nanowire solar cells and methods for forming the same

    DOEpatents

    Yang, Peidong; Greene, Lori; Law, Matthew

    2007-09-04

    Homogeneous and dense arrays of nanowires are described. The nanowires can be formed in solution and can have average diameters of 40-300 nm and lengths of 1-3 .mu.m. They can be formed on any suitable substrate. Photovoltaic devices are also described.

  2. Photovoltaic properties of GaAs:Be nanowire arrays

    SciTech Connect

    Bouravleuv, A. D.; Beznasyuk, D. V.; Gilstein, E. P.; Tchernycheva, M.; Luna Bugallo, A. De; Rigutti, L.; Yu, L.; Proskuryakov, Yu.; Shtrom, I. V.; Timofeeva, M. A.; Samsonenko, Yu. B.; Khrebtov, A. I.; Cirlin, G.

    2013-06-15

    Arrays of GaAs:Be nanowires are synthesized by molecular beam epitaxy on GaAs(111)B substrates. Prototypes of photovoltaic converters in which the grown nanowire arrays are used as active layers are produced by means of successive photolithography, etching, and metallization processes. Studying the photovoltaic properties of the fabricated structures using a solar radiation simulator demonstrates that the solarenergy conversion efficiency is about 0.1%. The value of the efficiency recalculated with the area occupied by the p-type nanowires on the surface of the n-type GaAs substrate taken into account amounts to 1.1%.

  3. Oriented Mn-doped CuO nanowire arrays

    NASA Astrophysics Data System (ADS)

    Han, Dongqiang; Wu, Zhaofeng; Wang, Zhihe; Yang, Shaoguang

    2016-04-01

    Using anodic aluminum oxide membranes as the nanoreactors and controller, oriented nanowire arrays of the diluted magnetic semiconductor Mn-doped CuO have been successfully fabricated using Mn(NO3)2 · 4H2O and Cu(NO3)2 · 3H2O as the starting materials. X-ray diffraction measurements showed that the as-prepared oriented nanowire arrays are of high purity. Scanning electron microscope and transmission electron microscope studies showed the nanowires are oriented, continuous and uniform with a diameter and length of about 170 nm and several tens of micrometers, respectively, and thus of a high aspect ratio. Low-temperature magnetic measurements showed the ferromagnetic property of the oriented Mn-doped CuO nanowire arrays with the critical temperature at around 80 K, which will endow them with great potential applications in spintronics in the future.

  4. Controlled growth of Si nanowire arrays for device integration.

    PubMed

    Hochbaum, Allon I; Fan, Rong; He, Rongrui; Yang, Peidong

    2005-03-01

    Silicon nanowires were synthesized, in a controlled manner, for their practical integration into devices. Gold colloids were used for nanowire synthesis by the vapor-liquid-solid growth mechanism. Using SiCl4 as the precursor gas in a chemical vapor deposition system, nanowire arrays were grown vertically aligned with respect to the substrate. By manipulating the colloid deposition on the substrate, highly controlled growth of aligned silicon nanowires was achieved. Nanowire arrays were synthesized with narrow size distributions dictated by the seeding colloids and with average diameters down to 39 nm. The density of wire growth was successfully varied from approximately 0.1-1.8 wires/microm2. Patterned deposition of the colloids led to confinement of the vertical nanowire growth to selected regions. In addition, Si nanowires were grown directly into microchannels to demonstrate the flexibility of the deposition technique. By controlling various aspects of nanowire growth, these methods will enable their efficient and economical incorporation into devices. PMID:15755094

  5. Influence of the oxide layer for growth of self-assisted InAs nanowires on Si(111)

    PubMed Central

    2011-01-01

    The growth of self-assisted InAs nanowires (NWs) by molecular beam epitaxy (MBE) on Si(111) is studied for different growth parameters and substrate preparations. The thickness of the oxide layer present on the Si(111) surface is observed to play a dominant role. Systematic use of different pre-treatment methods provides information on the influence of the oxide on the NW morphology and growth rates, which can be used for optimizing the growth conditions. We show that it is possible to obtain 100% growth of vertical NWs and no parasitic bulk structures between the NWs by optimizing the oxide thickness. For a growth temperature of 460°C and a V/III ratio of 320 an optimum oxide thickness of 9 ± 3 Å is found. PMID:21880130

  6. Magneto-transport properties of InAs nanowires laterally-grown by selective area molecular beam epitaxy on GaAs (110) masked substrates

    SciTech Connect

    Akabori, M.; Yamada, S.

    2013-12-04

    We prepared InAs nanowires (NWs) by lateral growth on GaAs (110) masked substrates in molecular beam epitaxy. We measured magneto-transport properties of the InAs NWs. In spite of parallel-NW multi-channels, we observed fluctuating magneto-conductance. From the fluctuation, we evaluated phase coherence length as a function of measurement temperature, and found decrease in the length with increase in the temperature. We also evaluate phase coherence length as a function of gate voltage.

  7. Highly stretchable, printable nanowire array optical polarizers.

    PubMed

    Kwon, Soonshin; Lu, Dylan; Sun, Zhelin; Xiang, Jie; Liu, Zhaowei

    2016-09-21

    Designing optical components such as polarizers on substrates with high mechanical deformability have potential to realize new device platforms in photonics, wearable electronics, and sensors. Conventional manufacturing approaches that rely highly on top-down lithography, deposition and the etching process can easily confront compatibility issues and high fabrication complexity. Therefore, an alternative integration scheme is necessary. Here, we demonstrate fabrication of highly flexible and stretchable wire grid polarizers (WGPs) by printing bottom-up grown Ge or Ge/Si core/shell nanowires (NWs) on device substrates in a highly dense and aligned fashion. The maximum contrast ratio of 104 between transverse electric (TE) and transverse magnetic (TM) fields and above 99% (maximum 99.7%) of light blocking efficiency across the visible spectrum range are achieved. Further systematic analyses are performed both in experimental and numerical models to reveal the correspondence between physical factors (coverage ratio of NW arrays and diameter) and polarization efficiency. Moreover, we demonstrate distinctive merits of our approach: (i) high flexibility in the choice of substrates such as glass, plastic, or elastomer; (ii) easy combination with additional novel functionalities, for example, air permeability, flexibility/stretchability, biocompatibility, and a skin-like low mechanical modulus; (iii) selective printing of polarizers on a designated local area. PMID:27537105

  8. Highly stretchable, printable nanowire array optical polarizers.

    PubMed

    Kwon, Soonshin; Lu, Dylan; Sun, Zhelin; Xiang, Jie; Liu, Zhaowei

    2016-09-21

    Designing optical components such as polarizers on substrates with high mechanical deformability have potential to realize new device platforms in photonics, wearable electronics, and sensors. Conventional manufacturing approaches that rely highly on top-down lithography, deposition and the etching process can easily confront compatibility issues and high fabrication complexity. Therefore, an alternative integration scheme is necessary. Here, we demonstrate fabrication of highly flexible and stretchable wire grid polarizers (WGPs) by printing bottom-up grown Ge or Ge/Si core/shell nanowires (NWs) on device substrates in a highly dense and aligned fashion. The maximum contrast ratio of 104 between transverse electric (TE) and transverse magnetic (TM) fields and above 99% (maximum 99.7%) of light blocking efficiency across the visible spectrum range are achieved. Further systematic analyses are performed both in experimental and numerical models to reveal the correspondence between physical factors (coverage ratio of NW arrays and diameter) and polarization efficiency. Moreover, we demonstrate distinctive merits of our approach: (i) high flexibility in the choice of substrates such as glass, plastic, or elastomer; (ii) easy combination with additional novel functionalities, for example, air permeability, flexibility/stretchability, biocompatibility, and a skin-like low mechanical modulus; (iii) selective printing of polarizers on a designated local area.

  9. Vertical nanowire arrays as a versatile platform for protein detection and analysis

    NASA Astrophysics Data System (ADS)

    Rostgaard, Katrine R.; Frederiksen, Rune S.; Liu, Yi-Chi C.; Berthing, Trine; Madsen, Morten H.; Holm, Johannes; Nygård, Jesper; Martinez, Karen L.

    2013-10-01

    Protein microarrays are valuable tools for protein assays. Reducing spot sizes from micro- to nano-scale facilitates miniaturization of platforms and consequently decreased material consumption, but faces inherent challenges in the reduction of fluorescent signals and compatibility with complex solutions. Here we show that vertical arrays of nanowires (NWs) can overcome several bottlenecks of using nanoarrays for extraction and analysis of proteins. The high aspect ratio of the NWs results in a large surface area available for protein immobilization and renders passivation of the surface between the NWs unnecessary. Fluorescence detection of proteins allows quantitative measurements and spatial resolution, enabling us to track individual NWs through several analytical steps, thereby allowing multiplexed detection of different proteins immobilized on different regions of the NW array. We use NW arrays for on-chip extraction, detection and functional analysis of proteins on a nano-scale platform that holds great promise for performing protein analysis on minute amounts of material. The demonstration made here on highly ordered arrays of indium arsenide (InAs) NWs is generic and can be extended to many high aspect ratio nanostructures.Protein microarrays are valuable tools for protein assays. Reducing spot sizes from micro- to nano-scale facilitates miniaturization of platforms and consequently decreased material consumption, but faces inherent challenges in the reduction of fluorescent signals and compatibility with complex solutions. Here we show that vertical arrays of nanowires (NWs) can overcome several bottlenecks of using nanoarrays for extraction and analysis of proteins. The high aspect ratio of the NWs results in a large surface area available for protein immobilization and renders passivation of the surface between the NWs unnecessary. Fluorescence detection of proteins allows quantitative measurements and spatial resolution, enabling us to track individual

  10. Magnetostatic interaction in electrodeposited Ni/Au multilayer nanowire arrays

    NASA Astrophysics Data System (ADS)

    He, Li-Zhong; Qin, Li-Rong; Zhao, Jian-Wei; Yin, Ying-Ying; Yang, Yu; Li, Guo-Qing

    2016-08-01

    Ordered Ni/Au multilayer nanowire arrays are successfully fabricated inside the nanochannels of anodic aluminum oxide template by pulse electrodeposition method. The thickness of the alternating layers is controlled to examine the magnetostatic interaction in Ni/Au multilayer nanowires. The magnetic easy axis parallel to the nanowires indicates that here the magnetostatic coupling along the wire axis dominates over the interactions perpendicular to the nanowires. However, the magnetostatic interaction between adjacent nanowires with larger magnetic layers is enhanced, leading to the existence of an optimum coercivity value. Project supported by the National Natural Science Foundation of China (Grant No. 11204246) and the Natural Science Foundation of CQCSTC (Grant No. cstc2014jcyjA50027).

  11. Magnetostatic interaction in electrodeposited Ni/Au multilayer nanowire arrays

    NASA Astrophysics Data System (ADS)

    He, Li-Zhong; Qin, Li-Rong; Zhao, Jian-Wei; Yin, Ying-Ying; Yang, Yu; Li, Guo-Qing

    2016-08-01

    Ordered Ni/Au multilayer nanowire arrays are successfully fabricated inside the nanochannels of anodic aluminum oxide template by pulse electrodeposition method. The thickness of the alternating layers is controlled to examine the magnetostatic interaction in Ni/Au multilayer nanowires. The magnetic easy axis parallel to the nanowires indicates that here the magnetostatic coupling along the wire axis dominates over the interactions perpendicular to the nanowires. However, the magnetostatic interaction between adjacent nanowires with larger magnetic layers is enhanced, leading to the existence of an optimum coercivity value. Project supported by the National Natural Science Foundation of China (Grant No. 11204246) and the Natural Science Foundation of CQCSTC (Grant No. cstc2014jcyjA50027).

  12. Field emission from crystalline copper sulphide nanowire arrays

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Deng, S. Z.; Xu, N. S.; Wang, Suhua; Wen, Xiaogang; Yang, Shihe; Yang, Chunlei; Wang, Jiannong; Ge, Weikun

    2002-05-01

    Straight crystalline copper sulphide (Cu2S) nanowire arrays have been grown by using a simple gas-solid reaction at room temperature. These were demonstrated to exhibit semiconductor properties. Field emission was observed at a field of ˜6 MV/m, and its current-field characteristics deviate from Fowler-Nordheim theory, i.e., showing a nonlinear Fowler-Nordheim plot. The uniform emission from the whole arrays was observed using transparent anode technique, and their variation with applied field was recorded. The emission from individual nanowires was also studied using a field emission microscope, and was found to consist of a number of spatially resolved diffuse spots. Finally, stable emission current at different levels and over time was recorded. These findings indicate that semiconductor nanowires as cold cathode have a potential future, worthy of further comprehensive investigation. The technical importance of using semiconductor nanowires as cold cathode emitter is given.

  13. Dimensional Tailoring of Hydrothermally Grown Zinc Oxide Nanowire Arrays.

    PubMed

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

    2016-01-13

    Hydrothermally synthesized ZnO nanowire arrays are critical components in a range of nanostructured semiconductor devices. The device performance is governed by relevant nanowire morphological parameters that cannot be fully controlled during bulk hydrothermal synthesis due to its transient nature. Here, we maintain homeostatic zinc concentration, pH, and temperature by employing continuous flow synthesis and demonstrate independent tailoring of nanowire array dimensions including areal density, length, and diameter on device-relevant length scales. By applying diffusion/reaction-limited analysis, we separate the effect of local diffusive transport from the c-plane surface reaction rate and identify direct incorporation as the c-plane growth mechanism. Our analysis defines guidelines for precise and independent control of the nanowire length and diameter by operating in rate-limiting regimes. We validate its utility by using surface adsorbents that limit reaction rate to obtain spatially uniform vertical growth rates across a patterned substrate. PMID:26708095

  14. Anomalous polarization conversion in arrays of ultrathin ferromagnetic nanowires

    NASA Astrophysics Data System (ADS)

    Stashkevich, Andrey A.; Roussigné, Yves; Poddubny, Alexander N.; Chérif, S.-M.; Zheng, Y.; Vidal, Franck; Yagupov, Ilya V.; Slobozhanyuk, Alexei P.; Belov, Pavel A.; Kivshar, Yuri S.

    2015-12-01

    We study the optical properties of arrays of ultrathin cobalt nanowires by means of the Brillouin scattering of light on magnons. We employ the Stokes/anti-Stokes scattering asymmetry to probe the circular polarization of a local electric field induced inside nanowires by linearly polarized light waves. We observe the anomalous polarization conversion of the opposite sign than that in a bulk medium or thick nanowires with a great enhancement of the degree of circular polarization attributed to the unconventional refraction in a nanowire medium. A rigorous simulation of the electric field polarization as a function of the wire diameter and spacing reveals the reversed polarization for a thin sparse wire array, in full quantitative agreement with experimental results.

  15. Molecular beam epitaxy of InAs nanowires in SiO2 nanotube templates: challenges and prospects for integration of III–Vs on Si

    NASA Astrophysics Data System (ADS)

    Vukajlovic-Plestina, Jelena; Dubrovskii, Vladimir G.; Tütüncuoǧlu, Gözde; Potts, Heidi; Ricca, Ruben; Meyer, Frank; Matteini, Federico; Leran, Jean-Baptiste; Morral, Anna Fontcuberta i.

    2016-11-01

    Guided growth of semiconductor nanowires in nanotube templates has been considered as a potential platform for reproducible integration of III–Vs on silicon or other mismatched substrates. Herein, we report on the challenges and prospects of molecular beam epitaxy of InAs nanowires in SiO2/Si nanotube templates. We show how and under which conditions the nanowire growth is initiated by In-assisted vapor–liquid–solid growth enabled by the local conditions inside the nanotube template. The conditions for high yield of vertical nanowires are investigated in terms of the nanotube depth, diameter and V/III flux ratios. We present a model that further substantiates our findings. This work opens new perspectives for monolithic integration of III–Vs on the silicon platform enabling new applications in the electronics, optoelectronics and energy harvesting arena.

  16. Study of spin dynamics and damping on the magnetic nanowire arrays with various nanowire widths

    NASA Astrophysics Data System (ADS)

    Cho, Jaehun; Fujii, Yuya; Konioshi, Katsunori; Yoon, Jungbum; Kim, Nam-Hui; Jung, Jinyong; Miwa, Shinji; Jung, Myung-Hwa; Suzuki, Yoshishige; You, Chun-Yeol

    2016-07-01

    We investigate the spin dynamics including Gilbert damping in the ferromagnetic nanowire arrays. We have measured the ferromagnetic resonance of ferromagnetic nanowire arrays using vector-network analyzer ferromagnetic resonance (VNA-FMR) and analyzed the results with the micromagnetic simulations. We find excellent agreement between the experimental VNA-FMR spectra and micromagnetic simulations result for various applied magnetic fields. We find that the same tendency of the demagnetization factor for longitudinal and transverse conditions, Nz (Ny) increases (decreases) as increasing the nanowire width in the micromagnetic simulations while Nx is almost zero value in transverse case. We also find that the Gilbert damping constant increases from 0.018 to 0.051 as the increasing nanowire width for the transverse case, while it is almost constant as 0.021 for the longitudinal case.

  17. Optical Sensing with Simultaneous Electrochemical Control in Metal Nanowire Arrays

    PubMed Central

    MacKenzie, Robert; Fraschina, Corrado; Sannomiya, Takumi; Auzelyte, Vaida; Vörös, Janos

    2010-01-01

    This work explores the alternative use of noble metal nanowire systems in large-scale array configurations to exploit both the nanowires’ conductive nature and localized surface plasmon resonance (LSPR). The first known nanowire-based system has been constructed, with which optical signals are influenced by the simultaneous application of electrochemical potentials. Optical characterization of nanowire arrays was performed by measuring the bulk refractive index sensitivity and the limit of detection. The formation of an electrical double layer was controlled in NaCl solutions to study the effect of local refractive index changes on the spectral response. Resonance peak shifts of over 4 nm, a bulk refractive index sensitivity up to 115 nm/RIU and a limit of detection as low as 4.5 × 10−4 RIU were obtained for gold nanowire arrays. Simulations with the Multiple Multipole Program (MMP) confirm such bulk refractive index sensitivities. Initial experiments demonstrated successful optical biosensing using a novel form of particle-based nanowire arrays. In addition, the formation of an ionic layer (Stern-layer) upon applying an electrochemical potential was also monitored by the shift of the plasmon resonance. PMID:22163441

  18. A simple approach for fabricating polypyrrole nanowire arrays

    NASA Astrophysics Data System (ADS)

    Cheng, F. L.; Zhang, M.; Zhang, M. l.

    2005-01-01

    Highly ordered nanoporous anodic aluminum oxide (AAO) templates were prepared, which had 35 nm average porous diameter and 4.8 × 1010 pores cm-2 porous density. The AAO template was affixed tightly to the surface of glass carbon electrode (GCE). Cyclic voltammetry (CV) and direct current electrodeposits (DCED) method were utilized to fabricate polypyrrole nanowire arrays. Experimental results indicated that DCED methods were simpler and more efficient than CV. Furthermore, the prepared polypyrrole nanowire arrays were characterized by high-resolution scan electron micrograph (HRSEM).

  19. Thermal conductivity of silicon nanowire arrays with controlled roughness

    SciTech Connect

    Feser, JP; Sadhu, JS; Azeredo, BP; Hsu, KH; Ma, J; Kim, J; Seong, M; Fang, NX; Li, XL; Ferreira, PM; Sinha, S; Cahill, DG

    2012-12-01

    A two-step metal assisted chemical etching technique is used to systematically vary the sidewall roughness of Si nanowires in vertically aligned arrays. The thermal conductivities of nanowire arrays are studied using time domain thermoreflectance and compared to their high-resolution transmission electron microscopy determined roughness. The thermal conductivity of nanowires with small roughness is close to a theoretical prediction based on an upper limit of the mean-free-paths of phonons given by the nanowire diameter. The thermal conductivity of nanowires with large roughness is found to be significantly below this prediction. Raman spectroscopy reveals that nanowires with large roughness also display significant broadening of the one-phonon peak; the broadening correlates well with the reduction in thermal conductivity. The origin of this broadening is not yet understood, as it is inconsistent with phonon confinement models, but could derive from microstructural changes that affect both the optical phonons observed in Raman scattering and the acoustic phonons that are important for heat conduction. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4767456

  20. Thermal conductivity of silicon nanowire arrays with controlled roughness

    NASA Astrophysics Data System (ADS)

    Feser, Joseph P.; Sadhu, Jyothi S.; Azeredo, Bruno P.; Hsu, Keng H.; Ma, Jun; Kim, Junhwan; Seong, Myunghoon; Fang, Nicholas X.; Li, Xiuling; Ferreira, Placid M.; Sinha, Sanjiv; Cahill, David G.

    2012-12-01

    A two-step metal assisted chemical etching technique is used to systematically vary the sidewall roughness of Si nanowires in vertically aligned arrays. The thermal conductivities of nanowire arrays are studied using time domain thermoreflectance and compared to their high-resolution transmission electron microscopy determined roughness. The thermal conductivity of nanowires with small roughness is close to a theoretical prediction based on an upper limit of the mean-free-paths of phonons given by the nanowire diameter. The thermal conductivity of nanowires with large roughness is found to be significantly below this prediction. Raman spectroscopy reveals that nanowires with large roughness also display significant broadening of the one-phonon peak; the broadening correlates well with the reduction in thermal conductivity. The origin of this broadening is not yet understood, as it is inconsistent with phonon confinement models, but could derive from microstructural changes that affect both the optical phonons observed in Raman scattering and the acoustic phonons that are important for heat conduction.

  1. Efficient Multiterminal Spectrum Splitting via a Nanowire Array Solar Cell

    PubMed Central

    2015-01-01

    Nanowire-based solar cells opened a new avenue for increasing conversion efficiency and rationalizing material use by growing different III–V materials on silicon substrates. Here, we propose a multiterminal nanowire solar cell design with a theoretical conversion efficiency of 48.3% utilizing an efficient lateral spectrum splitting between three different III–V material nanowire arrays grown on a flat silicon substrate. This allows choosing an ideal material combination to achieve the proper spectrum splitting as well as fabrication feasibility. The high efficiency is possible due to an enhanced absorption cross-section of standing nanowires and optimization of the geometric parameters. Furthermore, we propose a multiterminal contacting scheme that can be fabricated with a technology close to standard CMOS. As an alternative we also consider a single power source with a module level voltage matching. These new concepts open avenues for next-generation solar cells for terrestrial and space applications. PMID:26878027

  2. Ferromagnetic resonance in low interacting permalloy nanowire arrays

    NASA Astrophysics Data System (ADS)

    Raposo, V.; Zazo, M.; Flores, A. G.; Garcia, J.; Vega, V.; Iñiguez, J.; Prida, V. M.

    2016-04-01

    Dipolar interactions on magnetic nanowire arrays have been investigated by various techniques. One of the most powerful techniques is the ferromagnetic resonance spectroscopy, because the resonance field depends directly on the anisotropy field strength and its frequency dependence. In order to evaluate the influence of magnetostatic dipolar interactions among ferromagnetic nanowire arrays, several densely packed hexagonal arrays of NiFe nanowires have been prepared by electrochemical deposition filling self-ordered nanopores of alumina membranes with different pore sizes but keeping the same interpore distance. Nanowires' diameter was changed from 90 to 160 nm, while the lattice parameter was fixed to 300 nm, which was achieved by carefully reducing the pore diameter by means of Atomic Layer Deposition of conformal Al2O3 layers on the nanoporous alumina templates. Field and frequency dependence of ferromagnetic resonance have been studied in order to obtain the dispersion diagram which gives information about anisotropy, damping factor, and gyromagnetic ratio. The relationship between resonance frequency and magnetic field can be explained by the roles played by the shape anisotropy and dipolar interactions among the ferromagnetic nanowires.

  3. Fully Tunable Silicon Nanowire Arrays Fabricated by Soft Nanoparticle Templating.

    PubMed

    Rey, By Marcel; Elnathan, Roey; Ditcovski, Ran; Geisel, Karen; Zanini, Michele; Fernandez-Rodriguez, Miguel-Angel; Naik, Vikrant V; Frutiger, Andreas; Richtering, Walter; Ellenbogen, Tal; Voelcker, Nicolas H; Isa, Lucio

    2016-01-13

    We demonstrate a fabrication breakthrough to produce large-area arrays of vertically aligned silicon nanowires (VA-SiNWs) with full tunability of the geometry of the single nanowires and of the whole array, paving the way toward advanced programmable designs of nanowire platforms. At the core of our fabrication route, termed "Soft Nanoparticle Templating", is the conversion of gradually compressed self-assembled monolayers of soft nanoparticles (microgels) at a water-oil interface into customized lithographical masks to create VA-SiNW arrays by means of metal-assisted chemical etching (MACE). This combination of bottom-up and top-down techniques affords excellent control of nanowire etching site locations, enabling independent control of nanowire spacing, diameter and height in a single fabrication route. We demonstrate the fabrication of centimeter-scale two-dimensional gradient photonic crystals exhibiting continuously varying structural colors across the entire visible spectrum on a single silicon substrate, and the formation of tunable optical cavities supported by the VA-SiNWs, as unambiguously demonstrated through numerical simulations. Finally, Soft Nanoparticle Templating is combined with optical lithography to create hierarchical and programmable VA-SiNW patterns.

  4. First-principles study of quantum confinement and surface effects on the electronic properties of InAs nanowires

    SciTech Connect

    Ning, Feng; Tang, Li-Ming Zhang, Yong; Chen, Ke-Qiu

    2013-12-14

    We have used first principles methods to systematically investigate the quantum confinement effect on the electronic properties of zinc-blende (ZB) and wurtzite (WZ) InAs nanowires (NWs) with different orientations and diameters, and compared their electronic properties before and after pseudo-hydrogen passivation. The results show that the calculated carrier effective masses are dependent on the NW diameter, except for [110] ZB NWs, and the hole effective masses of [111] ZB NWs are larger than the electron effective masses when the NW diameter is ≥26 Å. The band alignments of [111] ZB and [0001] WZ NWs reveal that the effect of quantum confinement on the conduction bands is greater than on the valence bands, and the position of the valence band maximum level changes little with increasing NW diameter. The pseudo-hydrogen passivated NWs have larger band gaps than the corresponding unpassivated NWs. The carrier effective masses and mobilities can be adjusted by passivating the surface dangling bonds.

  5. Low temperature transport in p-doped InAs nanowires

    SciTech Connect

    Upadhyay, S.; Jespersen, T. S.; Madsen, M. H.; Krogstrup, P.; Nygård, J.

    2013-10-14

    We present low temperature electrical measurements of p-type Indium Arsenide nanowires grown via molecular beam epitaxy using Beryllium as a dopant. Growth of p-type wires without stacking faults is demonstrated. Devices in field-effect geometries exhibit ambipolar behavior, and the temperature dependence of electron and hole field effect mobilities are extracted. At low temperatures, we observe reproducible conductance fluctuations as a result of quantum interference, and magnetoconductance data show weak antilocalization.

  6. Near-unity broadband absorption designs for semiconducting nanowire arrays via localized radial mode excitation.

    PubMed

    Fountaine, Katherine T; Kendall, Christian G; Atwater, Harry A

    2014-05-01

    We report design methods for achieving near-unity broadband light absorption in sparse nanowire arrays, illustrated by results for visible absorption in GaAs nanowires on Si substrates. Sparse (<5% fill fraction) nanowire arrays achieve near unity absorption at wire resonant wavelengths due to coupling into 'leaky' radial waveguide modes of individual wires and wire-wire scattering processes. From a detailed conceptual development of radial mode resonant absorption, we demonstrate two specific geometric design approaches to achieve near unity broadband light absorption in sparse nanowire arrays: (i) introducing multiple wire radii within a small unit cell array to increase the number of resonant wavelengths, yielding a 15% absorption enhancement relative to a uniform nanowire array and (ii) tapering of nanowires to introduce a continuum of diameters and thus resonant wavelengths excited within a single wire, yielding an 18% absorption enhancement over a uniform nanowire array.

  7. New Applications of Electrochemically Produced Porous Semiconductors and Nanowire Arrays

    PubMed Central

    2010-01-01

    The growing demand for electro mobility together with advancing concepts for renewable energy as primary power sources requires sophisticated methods of energy storage. In this work, we present a Li ion battery based on Si nanowires, which can be produced reliable and cheaply and which shows superior properties, such as a largely increased capacity and cycle stability. Sophisticated methods based on electrochemical pore etching allow to produce optimized regular arrays of nanowires, which can be stabilized by intrinsic cross-links, which serve to avoid unwanted stiction effects and allow easy processing. PMID:20730118

  8. Integrating Different Types of Nanowire Sensors in a Large Array

    NASA Astrophysics Data System (ADS)

    Dan, Yaping; Evoy, Stephane; Johnson, A. T. Charlie

    2008-03-01

    Biological olfactory systems have a key structural feature: different types of sensors in a large array. Humans, for example, possess several hundred distinct types of sensing cells, a level of sensor diversity not yet achieved in artificial olfactory systems. Here, we demonstrate a simple and low-cost electrochemical approach to integrate large numbers of different types of nanowire sensors in an array on the same silicon wafer. In our approach, nanowires are grown inside an on-chip nanochannel template by electrochemistry with each horizontal channel connected to a gold electrode. This design allows for addressable synthesis of a specific type of nanowire in specified channels by providing a voltage to the electrodes connecting to those channels. The process can be further repeated to produce different types of nanowires in other channels using different electroplating solutions. The scale and diversity of this array have a potential to compete with those of biological olfactory systems and the synthesis process is cost-effective enough for commercialization.

  9. Silver nanowire array-polymer composite as thermal interface material

    NASA Astrophysics Data System (ADS)

    Xu, Ju; Munari, Alessio; Dalton, Eric; Mathewson, Alan; Razeeb, Kafil M.

    2009-12-01

    Silver nanowire arrays embedded inside polycarbonate templates are investigated as a viable thermal interface material for electronic cooling applications. The composite shows an average thermal diffusivity value of 1.89×10-5 m2 s-1, which resulted in an intrinsic thermal conductivity of 30.3 W m-1 K-1. The nanowires' protrusion from the film surface enables it to conform to the surface roughness to make a better thermal contact. This resulted in a 61% reduction in thermal impedance when compared with blank polymer. An ˜30 nm Au film on the top of the composite was found to act as a heat spreader, reducing the thermal impedance further by 35%. A contact impedance model was employed to compare the contact impedance of aligned silver nanowire-polymer composites with that of aligned carbon nanotubes, which showed that the Young's modulus of the composite is the defining factor in the overall thermal impedance of these composites.

  10. Three Dimensional Sculpturing of Vertical Nanowire Arrays by Conventional Photolithography.

    PubMed

    Shi, Run; Huang, Chengzi; Zhang, Linfei; Amini, Abbas; Liu, Kai; Shi, Yuan; Bao, Shuhan; Wang, Ning; Cheng, Chun

    2016-01-05

    Ordered nanoarchitectures have attracted an intense research interest recently because of their promising device applications. They are always fabricated by self-assembling building blocks such as nanowires, nanodots. This kind of bottom up approaches is limited in poor control over height, lateral resolution, aspect ratio, and patterning. Here, we break these limits and realize 3D sculpturing of vertical ZnO nanowire arrays (NAs) based on the conventional photolithography approach. These are achieved by immersing nanowire NAs in thick photoresist (PR) layers, which enable the cutting and patterning of ZnO NAs as well as the tailoring of NAs. Our strategy of 3D sculpturing of NAs promisingly paves the way for designing novel NAs-based nanoarchitectures.

  11. Three Dimensional Sculpturing of Vertical Nanowire Arrays by Conventional Photolithography

    NASA Astrophysics Data System (ADS)

    Shi, Run; Huang, Chengzi; Zhang, Linfei; Amini, Abbas; Liu, Kai; Shi, Yuan; Bao, Shuhan; Wang, Ning; Cheng, Chun

    2016-01-01

    Ordered nanoarchitectures have attracted an intense research interest recently because of their promising device applications. They are always fabricated by self-assembling building blocks such as nanowires, nanodots. This kind of bottom up approaches is limited in poor control over height, lateral resolution, aspect ratio, and patterning. Here, we break these limits and realize 3D sculpturing of vertical ZnO nanowire arrays (NAs) based on the conventional photolithography approach. These are achieved by immersing nanowire NAs in thick photoresist (PR) layers, which enable the cutting and patterning of ZnO NAs as well as the tailoring of NAs. Our strategy of 3D sculpturing of NAs promisingly paves the way for designing novel NAs-based nanoarchitectures.

  12. Three Dimensional Sculpturing of Vertical Nanowire Arrays by Conventional Photolithography

    PubMed Central

    Shi, Run; Huang, Chengzi; Zhang, Linfei; Amini, Abbas; Liu, Kai; Shi, Yuan; Bao, Shuhan; Wang, Ning; Cheng, Chun

    2016-01-01

    Ordered nanoarchitectures have attracted an intense research interest recently because of their promising device applications. They are always fabricated by self-assembling building blocks such as nanowires, nanodots. This kind of bottom up approaches is limited in poor control over height, lateral resolution, aspect ratio, and patterning. Here, we break these limits and realize 3D sculpturing of vertical ZnO nanowire arrays (NAs) based on the conventional photolithography approach. These are achieved by immersing nanowire NAs in thick photoresist (PR) layers, which enable the cutting and patterning of ZnO NAs as well as the tailoring of NAs. Our strategy of 3D sculpturing of NAs promisingly paves the way for designing novel NAs-based nanoarchitectures. PMID:26729069

  13. Fabrication of highly-ordered nanopatterned copper nanowire arrays by photolithography.

    PubMed

    Li, Xiaoru; Wang, Yiqian; Song, Guojun; She, Xilin; Peng, Zhi; Wang, Shulong; Li, Jianjiang

    2010-07-01

    Two different patterns, one being circular and the other being QDU, of copper (Cu) nanowire arrays were successfully produced by electrochemical deposition and photolithography. The highly-ordered patterns of Cu nanowire arrays were observed to stand freely on the substrate using scanning electron microscopy (SEM). Chemical analyses have been performed on Cu nanowires using energy dispersive X-ray spectroscopy (EDS). The results confirmed that it is mainly composed of Cu. Selected-area electron diffraction (SAED) pattern indicated the nanowires are single crystalline and the growth direction of the nanowires is along the [220] direction. With the deposition time increasing, the length of Cu nanowires increaseed.

  14. 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.

  15. Absence of vapor-liquid-solid growth during molecular beam epitaxy of self-induced InAs nanowires on Si

    NASA Astrophysics Data System (ADS)

    Hertenberger, S.; Rudolph, D.; Bolte, S.; Döblinger, M.; Bichler, M.; Spirkoska, D.; Finley, J. J.; Abstreiter, G.; Koblmüller, G.

    2011-03-01

    The growth mechanism of self-induced InAs nanowires (NWs) grown on Si (111) by molecular beam epitaxy was investigated by in situ reflection high energy electron diffraction and ex situ scanning and transmission electron microscopy. Abrupt morphology transition and in-plane strain relaxation revealed that InAs NWs nucleate without any significant delay and under the absence of indium (In) droplets. These findings are independent of the As/In-flux ratio, revealing entirely linear vertical growth rate and nontapered NWs. No evidence of In droplets nor associated change in the NW apex morphology was observed for various growth termination procedures. These results highlight the absence of vapor-liquid-solid growth, providing substantial benefits for realization of atomically abrupt doping and composition profiles in future axial InAs-based NW heterostructures on Si.

  16. Absence of vapor-liquid-solid growth during molecular beam epitaxy of self-induced InAs nanowires on Si

    SciTech Connect

    Hertenberger, S.; Rudolph, D.; Bichler, M.; Spirkoska, D.; Finley, J. J.; Koblmueller, G.; Bolte, S.; Doeblinger, M.; Abstreiter, G.

    2011-03-21

    The growth mechanism of self-induced InAs nanowires (NWs) grown on Si (111) by molecular beam epitaxy was investigated by in situ reflection high energy electron diffraction and ex situ scanning and transmission electron microscopy. Abrupt morphology transition and in-plane strain relaxation revealed that InAs NWs nucleate without any significant delay and under the absence of indium (In) droplets. These findings are independent of the As/In-flux ratio, revealing entirely linear vertical growth rate and nontapered NWs. No evidence of In droplets nor associated change in the NW apex morphology was observed for various growth termination procedures. These results highlight the absence of vapor-liquid-solid growth, providing substantial benefits for realization of atomically abrupt doping and composition profiles in future axial InAs-based NW heterostructures on Si.

  17. Prediction of phonon thermal transport in thin GaAs, InAs and InP nanowires by molecular dynamics simulations: influence of the interatomic potential.

    PubMed

    Carrete, J; Longo, R C; Gallego, L J

    2011-05-01

    A number of different potentials are currently being used in molecular dynamics simulations of semiconductor nanostructures. Confusion can arise if an inappropriate potential is used. To illustrate this point, we performed direct molecular dynamics simulations to predict the room temperature lattice thermal conductivity λ of thin GaAs, InAs and InP nanowires. In each case, simulations performed using the classical Harrison potential afforded values of λ about an order of magnitude smaller than those obtained using more elaborate potentials (an Abell-Tersoff, as parameterized by Hammerschmidt et al for GaAs and InAs, and a potential of Vashishta type for InP). These results will be a warning to those wishing to use computer simulations to orient the development of quasi-one-dimensional systems as heat sinks or thermoelectric devices. PMID:21427474

  18. Dendritic Heterojunction Nanowire Arrays for High-Performance Supercapacitors

    PubMed Central

    Zou, Rujia; Zhang, Zhenyu; Yuen, Muk Fung; Hu, Junqing; Lee, Chun-Sing; Zhang, Wenjun

    2015-01-01

    Herein, we designed and synthesized for the first time a series of 3D dendritic heterojunction arrays on Ni foam substrates, with NiCo2S4 nanowires as cores and NiCo2O4, NiO, Co3O4, and MnO2 nanowires as branches, and studied systematically their electrochemical performance in comparison with their counterparts in core/shell structure. Attributed to the following reasons: (1) both core and branch are pseudocapacitively active materials, (2) the special dendritic structure with considerable inter-nanowire space enables easy access of electrolyte to the core and branch surfaces, and (3) the highly conductive NiCo2S4 nanowire cores provide “superhighways” for charge transition, NiCo2S4-cored dendritic heterojunction electrodes synergistically lead to ultrahigh specific capacitance, good rate capability, and excellent cycling life. These results of core/branch dentritic heterojunction arrays is universially superior to their core/shell conterparts, thus this is a significant improvement of overall electrochemical performance. PMID:25597402

  19. Polaronic transport and current blockades in epitaxial silicide nanowires and nanowire arrays.

    PubMed

    Iancu, Violeta; Zhang, X-G; Kim, Tae-Hwan; Menard, Laurent D; Kent, P R C; Woodson, Michael E; Ramsey, J Michael; Li, An-Ping; Weitering, Hanno H

    2013-08-14

    Crystalline micrometer-long YSi2 nanowires with cross sections as small as 1 × 0.5 nm(2) can be grown on the Si(001) surface. Their extreme aspect ratios make electron conduction within these nanowires almost ideally one-dimensional, while their compatibility with the silicon platform suggests application as metallic interconnect in Si-based nanoelectronic devices. Here we combine bottom-up epitaxial wire synthesis in ultrahigh vacuum with top-down miniaturization of the electrical measurement probes to elucidate the electronic conduction mechanism of both individual wires and arrays of nanowires. Temperature-dependent transport through individual nanowires is indicative of thermally assisted tunneling of small polarons between atomic-scale defect centers. In-depth analysis of complex wire networks emphasize significant electronic crosstalk between the nanowires due to the long-range Coulomb fields associated with polaronic charge fluctuations. This work establishes a semiquantitative correlation between the density and distributions of atomic-scale defects and resulting current-voltage characteristics of nanoscale network devices. PMID:23902411

  20. Polaronic transport and current blockades in epitaxial silicide nanowires and nanowire arrays.

    PubMed

    Iancu, Violeta; Zhang, X-G; Kim, Tae-Hwan; Menard, Laurent D; Kent, P R C; Woodson, Michael E; Ramsey, J Michael; Li, An-Ping; Weitering, Hanno H

    2013-08-14

    Crystalline micrometer-long YSi2 nanowires with cross sections as small as 1 × 0.5 nm(2) can be grown on the Si(001) surface. Their extreme aspect ratios make electron conduction within these nanowires almost ideally one-dimensional, while their compatibility with the silicon platform suggests application as metallic interconnect in Si-based nanoelectronic devices. Here we combine bottom-up epitaxial wire synthesis in ultrahigh vacuum with top-down miniaturization of the electrical measurement probes to elucidate the electronic conduction mechanism of both individual wires and arrays of nanowires. Temperature-dependent transport through individual nanowires is indicative of thermally assisted tunneling of small polarons between atomic-scale defect centers. In-depth analysis of complex wire networks emphasize significant electronic crosstalk between the nanowires due to the long-range Coulomb fields associated with polaronic charge fluctuations. This work establishes a semiquantitative correlation between the density and distributions of atomic-scale defects and resulting current-voltage characteristics of nanoscale network devices.

  1. Synthesis and magnetic properties of spinel CoFe 2O 4 nanowire arrays

    NASA Astrophysics Data System (ADS)

    Yuan, J. J.; Zhao, Q.; Xu, Y. S.; Liu, Z. G.; Du, X. B.; Wen, G. H.

    2009-09-01

    Spinel CoFe 2O 4 nanowire arrays were synthesized in nanopores of anodic aluminum oxide (AAO) template using aqueous solution of cobalt and iron nitrates as precursor. The precursor was filled into the nanopores by vacuum impregnation. After heat treatment, it transformed to spinel CoFe 2O 4 nanowires. The structure, morphology and magnetic properties of the sample were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The results indicate that the nanowire arrays are compact. And the individual nanowires have a high aspect ratio, which are about 80 nm in diameter and 10 μm in length. The nanowires are polycrystalline spinel phase. Magnetic measurements indicate that the nanowire arrays are nearly magnetic isotropic. The reason is briefly discussed. Moreover, the temperature dependence of the coercive force of the nanowire arrays was studied.

  2. In Situ Formation of Crystallographically Oriented Semiconductor Nanowire Arrays via Selective Vaporization for Optoelectronic Applications.

    PubMed

    Huang, Xing; Yu, Yongqiang; Jones, Travis; Fan, Hua; Wang, Lei; Xia, Jing; Wang, Zhu-Jun; Shao, Li-Dong; Meng, Xiang-Min; Willinger, Marc-Georg

    2016-09-01

    Direct transformation of bulk crystals to single-crystalline crystallographically oriented semiconductor nanowire arrays is presented. Real-time imaging during in situ environmental scanning electron microscopy experiment clearly demonstrates that the nanowire arrays form through a selective vaporization process with respect to the crystallography of wurtzite crystals. Due to the high quality of the prepared semiconductor nanowire arrays, photodetectors constructed from them can present superior optoelectronic performances. PMID:27373221

  3. Transport of fast electrons in a nanowire array with collisional effects included

    SciTech Connect

    Li, Boyuan; Zhang, Zhimeng; Wang, Jian; Zhang, Bo; Zhao, Zongqing; Shan, Lianqiang; Zhou, Weimin; Zhang, Baohan; Cao, Lihua; Gu, Yuqiu

    2015-12-15

    The transport of picosecond laser generated fast electrons in a nanowire array is studied with two-dimensional particle-in-cell simulations. Our simulations show that a fast electron beam is initially guided and collimated by strong magnetic filaments in the array. Subsequently, after the decomposition of the structure of nanowire array due to plasma expansion, the beam is still collimated by the resistive magnetic field. An analytical model is established to give a criterion for long-term beam collimation in a nanowire array; it indicates that the nanowire cell should be wide enough to keep the beam collimated in picosecond scale.

  4. Generation of terahertz radiation in ordered arrays of GaAs nanowires

    SciTech Connect

    Trukhin, V. N.; Mustafin, I. A.; Bouravleuv, A. D.; Cirlin, G. E.; Kakko, J. P.; Huhtio, T.; Lipsanen, H.

    2015-06-22

    THz generation under excitation by ultrashort optical pulses in ordered arrays of GaAs nanowires is reported. It was found that the efficiency of THz radiation generation increases due to the resonant leaky mode excitation in nanowires. The maximum value of the THz field is achieved when the distance between the nanowires is of the order of the wavelength of exciting light.

  5. Ordering Ag nanowire arrays by spontaneous spreading of volatile droplet on solid surface

    PubMed Central

    Dai, Han; Ding, Ruiqiang; Li, Meicheng; Huang, Jinjer; Li, Yingfeng; Trevor, Mwenya

    2014-01-01

    Large-area Ag nanowires are ordered by spontaneous spreading of volatile droplet on a wettable solid surface. Compared with other nanowires orientation methods, radial shaped oriented Ag nanowires in a large ring region are obtained in an extremely short time. Furthermore, the radial shaped oriented Ag nanowires are transferred and aligned into one direction. Based on the hydrodynamics, the coactions among the microfluid, gravity effect and the adhesion of substrate on the orientation of the Ag nanowires are clearly revealed. This spreading method opens an efficient way for extreme economic, efficient and “green” way for commercial producing ordered nanowire arrays. PMID:25339118

  6. 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.

  7. Multi-spectral optical absorption in substrate-free nanowire arrays

    SciTech Connect

    Zhang, Junpeng; Chia, Andrew; Boulanger, Jonathan; LaPierre, Ray; Dhindsa, Navneet; Khodadad, Iman; Saini, Simarjeet

    2014-09-22

    A method is presented of fabricating gallium arsenide (GaAs) nanowire arrays of controlled diameter and period by reactive ion etching of a GaAs substrate containing an indium gallium arsenide (InGaP) etch stop layer, allowing the precise nanowire length to be controlled. The substrate is subsequently removed by selective etching, using the same InGaP etch stop layer, to create a substrate-free GaAs nanowire array. The optical absorptance of the nanowire array was then directly measured without absorption from a substrate. We directly observe absorptance spectra that can be tuned by the nanowire diameter, as explained with rigorous coupled wave analysis. These results illustrate strong optical absorption suitable for nanowire-based solar cells and multi-spectral absorption for wavelength discriminating photodetectors. The solar-weighted absorptance above the bandgap of GaAs was 94% for a nanowire surface coverage of only 15%.

  8. 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.

  9. 2D and 3D ordered arrays of Co magnetic nanowires

    NASA Astrophysics Data System (ADS)

    Garcia, J.; Prida, V. M.; Vega, V.; Rosa, W. O.; Caballero-Flores, R.; Iglesias, L.; Hernando, B.

    2015-06-01

    Cobalt nanowire arrays spatially distributed in 2D and 3D arrangements have been performed by pulsed electrodeposition into the pores of planar and cylindrical nanoporous anodic alumina membranes, respectively. Morphological characterization points out the good filling factor reached by electroplated Co nanowires in both kinds of alumina membranes exhibiting hexagonally self-ordered porous structures. Co nanowires grown in both kinds of alumina templates exhibit the same crystalline phases. DC magnetometry and First Order Reversal Curve (FORC) analysis were carried out in order to determine the overall magnetic behavior for both nanowire array geometries. It is found that when the Co nanowires of two kinds of arrays are perpendicularly magnetized, both hysteresis loops are identical, suggesting that neither the intrinsic magnetic behavior of the nanowires nor the collective one depend on the arrays geometry. FORC analysis performed along the radial direction of the Co nanowire arrays embedded in the cylindrical alumina template reveals that the contribution of each nanowire to the magnetization reversal process involves its specific orientation with respect to the applied field direction. Furthermore, the comparison between the magnetic properties for both kinds of Co nanowire arrays allows discussing about the effect of the cylindrical geometry of the template on the magnetostatic interaction among nanowires.

  10. Ordering Ag nanowire arrays by a glass capillary: a portable, reusable and durable SERS substrate.

    PubMed

    Liu, Jian-Wei; Wang, Jin-Long; Huang, Wei-Ran; Yu, Le; Ren, Xi-Feng; Wen, Wu-Cheng; Yu, Shu-Hong

    2012-01-01

    Assembly of nanowires into ordered macroscopic structures with new functionalities has been a recent focus. In this Letter, we report a new route for ordering hydrophilic Ag nanowires with high aspect ratio by flowing through a glass capillary. The present glass capillary with well-defined silver nanowire films inside can serve as a portable and reusable substrate for surface-enhanced Raman spectroscopy (SERS), which may provide a versatile and promising platform for detecting mixture pollutions. By controlling the flow parameters of nanowire suspensions, initially random Ag nanowires can be aligned to form nanowire arrays with tunable density, forming cambered nanowire films adhered onto the inner wall of the capillary. Compared with the planar ordered Ag nanowire films by the Langmuir-Blodgett (LB) technique, the cambered nanowire films show better SERS performance.

  11. Ordering Ag nanowire arrays by a glass capillary: A portable, reusable and durable SERS substrate

    PubMed Central

    Liu, Jian-Wei; Wang, Jin-Long; Huang, Wei-Ran; Yu, Le; Ren, Xi-Feng; Wen, Wu-Cheng; Yu, Shu-Hong

    2012-01-01

    Assembly of nanowires into ordered macroscopic structures with new functionalities has been a recent focus. In this Letter, we report a new route for ordering hydrophilic Ag nanowires with high aspect ratio by flowing through a glass capillary. The present glass capillary with well-defined silver nanowire films inside can serve as a portable and reusable substrate for surface-enhanced Raman spectroscopy (SERS), which may provide a versatile and promising platform for detecting mixture pollutions. By controlling the flow parameters of nanowire suspensions, initially random Ag nanowires can be aligned to form nanowire arrays with tunable density, forming cambered nanowire films adhered onto the inner wall of the capillary. Compared with the planar ordered Ag nanowire films by the Langmuir-Blodgett (LB) technique, the cambered nanowire films show better SERS performance. PMID:23248750

  12. Statistical magnetometry on isolated NiCo nanowires and nanowire arrays: a comparative study

    NASA Astrophysics Data System (ADS)

    Sergelius, Philip; Garcia Fernandez, Javier; Martens, Stefan; Zocher, Michael; Böhnert, Tim; Vega Martinez, Victor; de la Prida, Victor Manuel; Görlitz, Detlef; Nielsch, Kornelius

    2016-04-01

    The first-order reversal curve (FORC) method can be used to extract information about the interaction and switching field distribution of ferromagnetic nanowire arrays, yet it remains challenging to acquire reliable values. Within ordered pores of anodic alumina templates we electrochemically synthesize eight different Ni x Co1-x samples with x varying between 0.05 and 1. FORC diagrams are acquired using vibrating sample magnetometry. By dissolving the template and using the magneto-optical Kerr effect, we measure the hysteresis loops of up to 100 different and isolated nanowires for each sample to gain precise information about the intrinsic switching field distribution. Values of the interaction field are extracted from a deshearing of the major hysteresis loop. We present a comparative study between all methods in order to evaluate and reinforce current FORC theory with experimental findings.

  13. Preparation and magnetic behavior of arrays of electrodeposited Co nanowires

    NASA Astrophysics Data System (ADS)

    Rivas, J.; Kazadi Mukenga Bantu, A.; Zaragoza, G.; Blanco, M. C.; López-Quintela, M. A.

    2002-08-01

    Cobalt nanowires have been synthesized by electrodeposition into porous track-etched polycarbonate membranes with a quoted pore diameter of Dp≈200-400 nm and a thickness of L≈7 μm. Magnetization curves and torque experiments of arrays of Co wires confirm that when the lengths of the wires are increased a crossover takes place from a parallel easy direction of magnetization towards an easy direction perpendicular to the axis of the wire. This change in the easy direction of magnetization is analyzed considering the competition between demagnetizing field, magnetocrystalline anisotropy, and dipolar interaction among wires.

  14. Large-scale, heterogeneous integration of nanowire arrays for image sensor circuitry

    PubMed Central

    Fan, Zhiyong; Ho, Johnny C.; Jacobson, Zachery A.; Razavi, Haleh; Javey, Ali

    2008-01-01

    We report large-scale integration of nanowires for heterogeneous, multifunctional circuitry that utilizes both the sensory and electronic functionalities of single crystalline nanomaterials. Highly ordered and parallel arrays of optically active CdSe nanowires and high-mobility Ge/Si nanowires are deterministically positioned on substrates, and configured as photodiodes and transistors, respectively. The nanowire sensors and electronic devices are then interfaced to enable an all-nanowire circuitry with on-chip integration, capable of detecting and amplifying an optical signal with high sensitivity and precision. Notably, the process is highly reproducible and scalable with a yield of ≈80% functional circuits, therefore, enabling the fabrication of large arrays (i.e., 13 × 20) of nanowire photosensor circuitry with image-sensing functionality. The ability to interface nanowire sensors with integrated electronics on large scales and with high uniformity presents an important advance toward the integration of nanomaterials for sensor applications. PMID:18685094

  15. Cell membrane conformation at vertical nanowire array interface revealed by fluorescence imaging

    NASA Astrophysics Data System (ADS)

    Berthing, Trine; Bonde, Sara; Rostgaard, Katrine R.; Hannibal Madsen, Morten; Sørensen, Claus B.; Nygård, Jesper; Martinez, Karen L.

    2012-10-01

    The perspectives offered by vertical arrays of nanowires for biosensing applications in living cells depend on the access of individual nanowires to the cell interior. Recent results on electrical access and molecular delivery suggest that direct access is not always obtained. Here, we present a generic approach to directly visualize the membrane conformation of living cells interfaced with nanowire arrays, with single nanowire resolution. The method combines confocal z-stack imaging with an optimized cell membrane labelling strategy which was applied to HEK293 cells interfaced with 2-11 μm long and 3-7 μm spaced nanowires with various surface coatings (bare, aminosilane-coated or polyethyleneimine-coated indium arsenide). We demonstrate that, for all commonly used nanowire lengths, spacings and surface coatings, nanowires generally remain enclosed in a membrane compartment, and are thereby not in direct contact with the cell interior.

  16. Silica Nanowire Arrays for Diffraction-Based Bioaffinity Sensing

    PubMed Central

    Loget, Gabriel; Corn, Robert M.

    2014-01-01

    Arrays of electrodeposited silica nanowires (SiO2 NWs) have been fabricated over large areas (cm2) on fluoropolymer thin films attached to glass substrates by a combination of photolithography and electrochemically triggered sol-gel nanoscale deposition. Optical and SEM measurements revealed that the SiO2 NW arrays had an average spacing of 10 micrometers and an average width of 700 nm with a significant grain structure that was a result of the sol-gel deposition process. The optical diffraction properties at 633 nm of the SiO2 NWs arrays were characterized when placed in contact with solutions using a prism-coupled total internal reflection geometry; quantification of changes in these diffraction properties was applied in various sensing applications. Bulk refractive index sensing using the SiO2 NWs grating was demonstrated with a refractive index resolution of 1.30 × 10−5 RIU. Toposelectively chemically-modified SiO2 NW arrays were used for diffraction biosensing measurements of surface binding events, such as the electrostatic adsorption of gold nanoparticles and the bioaffinity adsorption of streptavidin onto a biotin monolayer. Finally, the application of the SiO2 NWs arrays for practical medical diagnostic applications was demonstrated by monitoring the diffraction of SiO2 NWs arrays functionalized with a single-stranded DNA aptamer in order to detect human α-thrombin from solutions at sub-pathologic nanomolar concentrations. PMID:24590560

  17. 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

  18. 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.

  19. Vertical group III-V nanowires on si, heterostructures, flexible arrays and fabrication

    DOEpatents

    Wang, Deli; Soci, Cesare; Bao, Xinyu; Wei, Wei; Jing, Yi; Sun, Ke

    2015-01-13

    Embodiments of the invention provide a method for direct heteroepitaxial growth of vertical III-V semiconductor nanowires on a silicon substrate. The silicon substrate is etched to substantially completely remove native oxide. It is promptly placed in a reaction chamber. The substrate is heated and maintained at a growth temperature. Group III-V precursors are flowed for a growth time. Preferred embodiment vertical Group III-V nanowires on silicon have a core-shell structure, which provides a radial homojunction or heterojunction. A doped nanowire core is surrounded by a shell with complementary doping. Such can provide high optical absorption due to the long optical path in the axial direction of the vertical nanowires, while reducing considerably the distance over which carriers must diffuse before being collected in the radial direction. Alloy composition can also be varied. Radial and axial homojunctions and heterojunctions can be realized. Embodiments provide for flexible Group III-V nanowire structures. An array of Group III-V nanowire structures is embedded in polymer. A fabrication method forms the vertical nanowires on a substrate, e.g., a silicon substrate. Preferably, the nanowires are formed by the preferred methods for fabrication of Group III-V nanowires on silicon. Devices can be formed with core/shell and core/multi-shell nanowires and the devices are released from the substrate upon which the nanowires were formed to create a flexible structure that includes an array of vertical nanowires embedded in polymer.

  20. Ultra-long metal nanowire arrays on solid substrate with strong bonding

    PubMed Central

    2011-01-01

    Ultra-long metal nanowire arrays with large circular area up to 25 mm in diameter were obtained by direct electrodeposition on metalized Si and glass substrates via a template-based method. Nanowires with uniform length up to 30 μm were obtained. Combining this deposition process with lithography technology, micrometre-sized patterned metal nanowire array pads were successfully fabricated on a glass substrate. Good adhesion between the patterned nanowire array pads and the substrate was confirmed using scanning acoustic microscopy characterization. A pull-off tensile test showed strong bonding between the nanowires and the substrate. Conducting atomic force microscopy (C-AFM) measurements showed that approximately 95% of the nanowires were electrically connected with the substrate, demonstrating its viability to use as high-density interconnect. PMID:21906311

  1. Reversal modes in FeCoNi nanowire arrays: Correlation between magnetostatic interactions and nanowires length

    NASA Astrophysics Data System (ADS)

    Samanifar, S.; Almasi Kashi, M.; Ramazani, A.; Alikhani, M.

    2015-03-01

    FeCoNi nanowire arrays (175 nm in diameter and lengths ranging from 5 to 40 μm) were fabricated into nanopores of hard-anodized aluminum oxide templates using pulsed ac electrodeposition technique. Increasing the length had no considerable effect on the composition and crystalline characteristics of Fe47Co38Ni15 nanowires (NWs). By eliminating the dendrites formed at the bottom of the pores, we report a careful investigation on the effect of magnetostatic interactions on magnetic properties and the effect of nanowire length on reversal modes. Hysteresis loop measurements indicated that increasing the length decreases coercivity and squareness values. On the other hand, first-order reversal curve measurements show a linear correlation between the magnetostatic interactions and length of NWs. Comparing reversal modes of the NWs both experimentally and theoretically using angular dependence of coercivity, we find that when L≤22 μm, a vortex domain wall mode is only occurred. When L>22 μm, a non-monotonic behavior indicates a transition from the vortex to transverse domain wall propagation. As a result, a critical length was found above which the transition between the reversal modes is occurred due the enhanced interactions. The transition angle also shifts toward a lower angle as the length increases. Moreover, with increasing length from 22 to 31 μm, the single domain structure of NWs changes to a pseudo single domain state. A multidomain-like behavior is also found for the longest NWs length.

  2. Patterned arrays of capped platinum nanowires with quasi-elastic mechanical response to lateral force

    SciTech Connect

    Hottes, M. Muench, F.; Rauber, M.; Stegmann, C.; Ensinger, W.; Dassinger, F.; Schlaak, H. F.

    2015-02-02

    In this Letter, we describe the electrodeposition of capped, micro-sized Pt nanowire arrays in ion-track etched polymer templates and measure their collective mechanical response to an external force. By using an aperture mask during the irradiation process, it was possible to restrict the creation of pores in the templates to defined areas, allowing the fabrication of small nanowire arrays in different geometries and sizes. The simultaneous and highly reliable formation of many nanowire arrays was achieved using a pulsed electrodeposition technique. After deposition, the polymer matrix was removed using a gentle, dry oxygen plasma treatment, resulting in an excellent preservation of the array nanostructure as confirmed by scanning electron microscopy. A force measuring station was set up to perform mechanical characterization series on free-standing arrays. The nanowire arrays show a high robustness and respond sensitively to the applied force, making them attractive as spring elements in miniaturized inertial sensors, for example.

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

    PubMed Central

    2014-01-01

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

  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. A facile fabrication of Cu2O nanowire arrays on Cu substrates

    NASA Astrophysics Data System (ADS)

    Xu, Zhichuan; Bi, Zhuanfang; Shen, Chengmin

    2012-09-01

    Nanomaterials play an important role in modern science and engineering. The ability to fabricate nanomaterials with high quality and low cost is a primary stage for further discovering their applications. This research article presents a facile fabrication of Cu2O nanowires on Cu substrate. It was found that simply heating Cu in air leads to the growth of Cu2O nanowires. The Cu2O nanowires are aligned in one direction and vertically grown on the Cu substrate. The growth process of nanowires was tracked by SEM and the root at the initial stage was observed by HRTEM. The access to oxygen is critical to the growth of Cu2O nanowires and the patterned nanowire arrays can be readily fabricated by using a mask. The method reported here offers a great potential route toward a large scale manufacture of Cu2O nanowires.

  6. Resonant absorption in semiconductor nanowires and nanowire arrays: Relating leaky waveguide modes to Bloch photonic crystal modes

    SciTech Connect

    Fountaine, Katherine T.; Whitney, William S.; Atwater, Harry A.

    2014-10-21

    We present a unified framework for resonant absorption in periodic arrays of high index semiconductor nanowires that combines a leaky waveguide theory perspective and that of photonic crystals supporting Bloch modes, as array density transitions from sparse to dense. Full dispersion relations are calculated for each mode at varying illumination angles using the eigenvalue equation for leaky waveguide modes of an infinite dielectric cylinder. The dispersion relations along with symmetry arguments explain the selectivity of mode excitation and spectral red-shifting of absorption for illumination parallel to the nanowire axis in comparison to perpendicular illumination. Analysis of photonic crystal band dispersion for varying array density illustrates that the modes responsible for resonant nanowire absorption emerge from the leaky waveguide modes.

  7. Self-assembled nanowire array capacitors: capacitance and interface state profile.

    PubMed

    Li, Qiliang; Xiong, Hao D; Liang, Xuelei; Zhu, Xiaoxiao; Gu, Diefeng; Ioannou, Dimitris E; Baumgart, Helmut; Richter, Curt A

    2014-04-01

    Direct characterization of the capacitance and interface states is very important for understanding the electronic properties of a nanowire transistor. However, the capacitance of a single nanowire is too small to precisely measure. In this work we have fabricated metal-oxide-semiconductor capacitors based on a large array of self-assembled Si nanowires. The capacitance and conductance of the nanowire array capacitors are directly measured and the interface state profile is determined by using the conductance method. We demonstrate that the nanowire array capacitor is an effective platform for studying the electronic properties of nanoscale interfaces. This approach provides a useful and efficient metrology for the study of the physics and device properties of nanoscale metal-oxide-semiconductor structures.

  8. Size effect on morphology and optical properties of branched ZnO/Si nanowire arrays

    NASA Astrophysics Data System (ADS)

    Yang, Qianqian; Li, Dingguo; Yu, Binbin; Huang, Shengli; Wang, Jiayuan; Li, Shuping; Kang, Junyong

    2016-03-01

    Branched ZnO/Si nanowire arrays have been synthesized by integration of metal-assisted chemical etching and hydrothermal growth. Experiments for different etching duration and hydrothermal growth time were carried out to investigate their effect on the final morphology of the heterogeneous material as well as its photoluminescence and antireflectance. The results demonstrated that the Si nanowires got longer with extending etching period, on which the branched ZnO nanowires were shorter in length and smaller in diameter in the set time period. The branched ZnO nanowires became longer and gradually filled up the interval among Si nanowires with prolonging hydrothermal growth. The emission spectra indicated that the nanostructure became better with less defects and impurities for the long Si nanowires. The diffuse reflectance spectra of the ZnO/Si nanowires showed an optimal growth period for the reflectivity lower than 4% in the visible region. In this article, possible mechanisms for the nanowire arrays growth and optical properties and their evolution were also discussed, which might provide guidance for the architecture and application of the heterogeneous tree-like nanowire arrays.

  9. Fabrication and assessment of structure, composition, and electronic properties of nanowire arrays

    NASA Astrophysics Data System (ADS)

    Sander, Melissa

    2001-07-01

    Nanocomposite materials consisting of arrays of parallel, uniform-diameter nanowires within a supporting matrix have a variety of potential applications. The focus of this work is on two nanowire array systems, bismuth and bismuth telluride nanowires in alumina templates. These systems are both promising for thermoelectric applications due to an expected increase in thermoelectric efficiency with reduced dimensionality. Bismuth telluride nanowire arrays were fabricated by electrochemical deposition of Bi2Te3 into porous anodic alumina templates. A process has been developed that allows for the production of high density (˜5 x 109/cm2), high aspect-ratio (>1000), ordered nanowire arrays over large areas (>1mm2), which will enable routine assessment of the array properties as well as potential incorporation into existing device structures. High spatial resolution characterization techniques, including imaging, diffraction, and energy-dispersive spectroscopy in the transmission electron microscope (TEM), have been employed to assess the structure and composition in the arrays. The nanowires are dense, polycrystalline Bi2Te3 with strong texturing along the wire axis. A short (<5 mum) Te-rich composition gradient was identified at the base of the pores. In addition, the composition, structure, and electronic properties of pressure-injected bismuth nanowire arrays have been assessed at high spatial resolution by employing imaging, diffraction, and electron energy loss spectrometry (EELS) in the TEM. The nanowires are polycrystalline with high aspect-ratio grains, and there is evidence of internal localized strain fields. The Bi-Al 2O3 interface in the arrays is compositionally abrupt, with a narrow interphase region dominated by Bi-O bonding. Low-loss EELS studies indicate that the volume plasmon loss peak in individual Bi nanowires shifts to higher energy and broadens as the wire diameter decreases from 90 to 35nm. A low-loss excitation is present in spectra from the

  10. Nanowire Array Gratings with ZnO Combs

    SciTech Connect

    Pan, Zhengwei; Mahurin, Shannon Mark; Dai, Sheng; Lowndes, Douglas H

    2005-01-01

    Diffraction gratings are mainly manufactured by mechanical ruling, interference lithography, or resin replication, which generally require expensive equipment, complicated procedures, and a stable environment. We describe the controlled growth of self-organized microscale ZnO comb gratings by a simple one-step thermal evaporation and condensation method. The ZnO combs consist of an array of very uniform, perfectly aligned, evenly spaced and long single-crystalline ZnO nanowires or nanobelts with periods in the range of 0.2 to 2 {mu}m. Diffraction experiments show that the ZnO combs can function as a tiny three-beam divider that may find applications in miniaturized integrated optics such as three-beam optical pickup systems.

  11. Excitation of surface plasmons in graphene-coated nanowire arrays

    NASA Astrophysics Data System (ADS)

    Xia, Sheng-Xuan; Zhai, Xiang; Wang, Ling-Ling; Liu, Jian-Ping; Li, Hong-Ju; Liu, Jian-Qiang; Pan, An-Lian; Wen, Shuang-Chun

    2016-09-01

    One of the important challenges that graphene must overcome before it can legitimately declare its irreplaceable position among the fields of plasmonic materials is to achieve efficiently coupling to external light. In this paper, we demonstrate an effective solution to this problem by exciting localized surface plasmon polaritons (SPPs) on graphene-coated nanowire arrays (GCNAs). These SPPs are analyzed by introducing a universal scaling law that considerably simplifies the understanding of these modes. Meanwhile, numerical experiments are carried out to demonstrate the theoretical analysis of plasmon excitations. The excited SPPs permit the control through both geometrical and physical properties. The proposed structure can be used as a tunable optical filter, a highly sensitive refractive index sensor, and other plasmonic modulation devices.

  12. Tunable remanent state resonance frequency in arrays of magnetic nanowires

    NASA Astrophysics Data System (ADS)

    Encinas, Armando; Demand, Marc; Vila, Laurent; Piraux, Luc; Huynen, Isabelle

    2002-09-01

    The zero-field microwave absorption, or natural ferromagnetic resonance, spectra in arrays of electrodeposited magnetic nanowires is studied as a function of the saturation magnetization of NiCu, NiFe, CoNiFe, and CoFe alloys of several compositions. Measurements show that due to the shape anisotropy, these systems present strong absorption peaks in the absence of an applied magnetic field in the GHz range due to the ferromagnetic resonance. Furthermore, the zero-field resonance frequency is observed to be independent of the wire diameter and density as well as the magnetic history and its value depends only on the material, through the saturation magnetization and the gyromagnetic factor. It is shown that, using different electrolytic solutions and depositing at different electrostatic potentials, the alloy composition can be varied and the remanent state resonance frequency can be tailored quasicontinuously between 4 and 31 GHz.

  13. Stress-determined nucleation sites above GaAs-capped arrays of InAs quantum dots

    NASA Astrophysics Data System (ADS)

    Latini, V.; Placidi, E.; Arciprete, F.; Tisbi, E.; Patella, F.; Magri, R.

    2016-09-01

    We studied the stress field at the surface of GaAs capping layers of variable thicknesses burying InAs quantum dot arrays using the Finite Element method to solve numerically the equations of the elastic field. The aim is to determine the stress-determined favorable sites for dot nucleation. We show that: (i) depending on the cap thickness, dot distances, and array orientation, sudden transitions in the stress-strain fields occur, leading from a vertical alignment of the dots to an anti-aligned correlation. We find that just few determined positions are favorable for dot nucleation and exclude some other sites previously indicated as favorable in the literature; (ii) the critical thicknesses at which the switch between the vertical alignment and the anti-aligned positions occurs depend on the distance between the dots in a square array and on the ratio between the two different distances if the arrays are rectangular; (iii) the transitions occur within a few nanometer range of the capping layer thickness, and the elastic field undergoes large changes in its properties before and after the transition. This behavior has been revealed by a very accurate fit of the tangential stress field using appropriate fit functions. The fit and parameter functions allow to easily reproduce the stress field in different contexts and are useful in growth simulation models. The results suggest that by properly engineering the capping layer thicknesses in the layers of a stack, it is possible to obtain different three-dimensional quantum dot lattices starting from an initial fixed dot array. Our results are in agreement with the available experimental data.

  14. The catalyst-free synthesis of large-area tungsten oxide nanowire arrays on ITO substrate and field emission properties

    SciTech Connect

    Huang Kai; Pan Qingtao; Yang Feng; Ni Shibi; He Deyan

    2008-04-01

    Tungsten oxide nanowire arrays have been grown on indium tin oxide coated glass substrate using tungsten trioxide powders as source by thermal evaporation approach without any catalysts. When the O{sub 2}/Ar flow rate ratio was 1/100, large-scale, high-density and uniformly distributed tungsten oxide nanowire arrays were obtained. The morphology and structure properties of the tungsten oxide nanowires were characterized by scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The influences of the oxygen concentration on the growth, density, shape and structure of the nanowires were investigated. The possible growth mechanism which governs the various types of nanowire arrays as the O{sub 2}/Ar flow rate ratios changed is also discussed. Field emission properties of tungsten oxide nanowire arrays were studied at a poor vacuum condition. The remarkable performance reveals that the tungsten oxide nanowire arrays can be served as a good candidate for commercial application as electron emitters.

  15. Developing high coercivity in large diameter cobalt nanowire arrays

    NASA Astrophysics Data System (ADS)

    Montazer, A. H.; Ramazani, A.; Almasi Kashi, M.; Zavašnik, J.

    2016-11-01

    Regardless of the synthetic method, developing high magnetic coercivity in ferromagnetic nanowires (NWs) with large diameters has been a challenge over the past two decades. Here, we report on the synthesis of highly coercive cobalt NW arrays with diameters of 65 and 80 nm, which are embedded in porous anodic alumina templates with high-aspect-ratio pores. Using a modified electrochemical deposition method enabled us to reach room temperature coercivity and remanent ratio up to 3000 Oe and 0.70, respectively, for highly crystalline as-synthesized hcp cobalt NW arrays with a length of 8 μm. The first-order reversal curve (FORC) analysis showed the presence of both soft and hard magnetic phases along the length of the resulting NWs. To develop higher coercive fields, the length of the NWs was then gradually reduced in order from bottom to top, thereby reaching NW sections governed by the hard phase. Consequently, this resulted in record high coercivities of 4200 and 3850 Oe at NW diameters of 65 and 80 nm, respectively. In this case, the FORC diagrams confirmed a significant reduction in interactions between the magnetic phases of the remaining sections of NWs. At this stage, x-ray diffraction (XRD) and dark-field transmission electron microscopy analyses indicated the formation of highly crystalline bamboo-like sections along the [0 0 2] direction during a progressive pulse-controlled electrochemical growth of NW arrays under optimized parameters. Our results both provide new insights into the growth process, crystalline characteristics and magnetic phases along the length of large diameter NW arrays and, furthermore, develop the performance of pure 3d transition magnetic NWs.

  16. Controlling the directional emission of light by periodic arrays of heterostructured semiconductor nanowires.

    PubMed

    Diedenhofen, Silke L; Janssen, Olaf T A; Hocevar, Moïra; Pierret, Aurélie; Bakkers, Erik P A M; Urbach, H Paul; Rivas, Jaime Gómez

    2011-07-26

    We demonstrate experimentally the directional emission of light by InAsP segments embedded in InP nanowires. The nanowires are arranged in a periodic array, forming a 2D photonic crystal slab. The directionality of the emission is interpreted in terms of the preferential decay of the photoexcited nanowires and the InAsP segments into Bloch modes of the periodic structure. By simulating the emission of arrays of nanowires with the emitting segments located at different heights, we conclude that the position of this active region strongly influences the directionality and efficiency of the emission. Our results will help to improve the design of nanowire based LEDs and single photon sources.

  17. GaN nanowire arrays by a patterned metal-assisted chemical etching

    NASA Astrophysics Data System (ADS)

    Wang, K. C.; Yuan, G. D.; Wu, R. W.; Lu, H. X.; Liu, Z. Q.; Wei, T. B.; Wang, J. X.; Li, J. M.; Zhang, W. J.

    2016-04-01

    We developed an one-step and two-step metal-assisted chemical etching method to produce self-organized GaN nanowire arrays. In one-step approach, GaN nanowire arrays are synthesized uniformly on GaN thin film surface. However, in a two-step etching processes, GaN nanowires are formed only in metal uncovered regions, and GaN regions with metal-covering show nano-porous sidewalls. We propose that nanowires and porous nanostructures are tuned by sufficient and limited etch rate, respectively. PL spectra shows a red-shift of band edge emission in GaN nanostructures. The formation mechanism of nanowires was illustrated by two separated electrochemical reactions occur simultaneously. The function of metals and UV light was illustrated by the scheme of potential relationship between energy bands in Si, GaN and standard hydrogen electrode potential of solution and metals.

  18. A force sensor using nanowire arrays to understand biofilm formation (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Sahoo, Prasana K.; Cavalli, Alessandro; Pelegati, Vitor B.; Murillo, Duber M.; Souza, Alessandra A.; Cesar, Carlos L.; Bakkers, Erik P. A. M.; Cotta, Monica A.

    2016-03-01

    Understanding the cellular signaling and function at the nano-bio interface can pave the way towards developing next-generation smart diagnostic tools. From this perspective, limited reports detail so far the cellular and subcellular forces exerted by bacterial cells during the interaction with abiotic materials. Nanowire arrays with high aspect ratio have been used to detect such small forces. In this regard, live force measurements were performed ex-vivo during the interaction of Xylella fastidiosa bacterial cells with InP nanowire arrays. The influence of nanowire array topography and surface chemistry on the response and motion of bacterial cells was studied in detail. The nanowire arrays were also functionalized with different cell adhesive promoters, such as amines and XadA1, an afimbrial protein of X.fastidiosa. By employing the well-defined InP nanowire arrays platform, and single cell confocal imaging system, we were able to trace the bacterial growth pattern, and show that their initial attachment locations are strongly influenced by the surface chemistry and nanoscale surface topography. In addition, we measure the cellular forces down to few nanonewton range using these nanowire arrays. In case of nanowire functionalized with XadA1, the force exerted by vertically and horizontally attached single bacteria on the nanowire is in average 14% and 26% higher than for the pristine array, respectively. These results provide an excellent basis for live-cell force measurements as well as unravel the range of forces involved during the early stages of bacterial adhesion and biofilm formation.

  19. Sensors and devices containing ultra-small nanowire arrays

    DOEpatents

    Xiao, Zhili

    2014-09-23

    A network of nanowires may be used for a sensor. The nanowires are metallic, each nanowire has a thickness of at most 20 nm, and each nanowire has a width of at most 20 nm. The sensor may include nanowires comprising Pd, and the sensor may sense a change in hydrogen concentration from 0 to 100%. A device may include the hydrogen sensor, such as a vehicle, a fuel cell, a hydrogen storage tank, a facility for manufacturing steel, or a facility for refining petroleum products.

  20. Morphology and composition of oxidized InAs nanowires studied by combined Raman spectroscopy and transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Tanta, Rawa; Kanne, Thomas; Amaduzzi, Francesca; Liao, Zhiyu; Madsen, Morten H.; Alarcón-Lladó, Esther; Krogstrup, Peter; Johnson, Erik; Morral, Anna Fontcuberta i.; Vosch, Tom; Nygård, Jesper; Jespersen, Thomas S.

    2016-07-01

    Any device exposed to ambient conditions will be prone to oxidation. This may be of particular importance for semiconductor nanowires because of the high surface-to-volume ratio and only little is known about the consequences of oxidation for these systems. Here, we study the properties of indium arsenide nanowires which were locally oxidized using a focused laser beam. Polarization dependent micro-Raman measurements confirmed the presence of crystalline arsenic, and transmission electron microscopy diffraction showed the presence of indium oxide. The surface dependence of the oxidation was investigated in branched nanowires grown along the [0001] and [01\\bar{1}0] wurtzite crystal directions exhibiting different surface facets. The oxidation did not occur at the [01\\bar{1}0] direction. The origin of this selectivity is discussed in terms transition state kinetics of the free surfaces of the different crystal families of the facets and numerical simulations of the laser induced heating.

  1. Ultra-sensitive detection of adipocytokines with CMOS-compatible silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Pui, Tze-Sian; Agarwal, Ajay; Ye, Feng; Tou, Zhi-Qiang; Huang, Yinxi; Chen, Peng

    2009-09-01

    Perfectly aligned arrays of single-crystalline silicon nanowires were fabricated using top-down CMOS-compatible techniques. We demonstrate that these nanowire devices are able to detect adipocytokines secreted by adipose cells with femtomolar sensitivity, high specificity, wide detection range, and ability for parallel monitoring. The nanowire sensors also provide a novel tool to reveal the poorly understood signaling mechanisms of these newly recognized signaling molecules, as well as their relevance in common diseases such as obesity and diabetes.Perfectly aligned arrays of single-crystalline silicon nanowires were fabricated using top-down CMOS-compatible techniques. We demonstrate that these nanowire devices are able to detect adipocytokines secreted by adipose cells with femtomolar sensitivity, high specificity, wide detection range, and ability for parallel monitoring. The nanowire sensors also provide a novel tool to reveal the poorly understood signaling mechanisms of these newly recognized signaling molecules, as well as their relevance in common diseases such as obesity and diabetes. Electronic supplementary information (ESI) available: Process diagram of nanowire fabrication; specificity of nanowire detection; induced differentiation of 3T3-L1 cells. See DOI: 10.1039/b9nr00092e

  2. Electrodeposition of bismuth:tellurium nanowire arrays into porous alumina templates for thermoelectric applications

    NASA Astrophysics Data System (ADS)

    Trahey, Lynn

    Bismuth telluride is a well-known thermoelectric material for refrigeration applications. Thermoelectrics possess several advantages over conventional refrigeration and power generation devices, yet are not widely-used due to low efficiencies. It has been predicted and shown experimentally that the efficiency of thermoelectric devices increases when the semiconducting materials have reduced dimensions. Therefore, the aim of this research was to show enhanced thermoelectric efficiency in one-dimensional nanowires. The nanowires were synthesized via electrochemical deposition into porous alumina templates. Electrodeposition is a versatile technique that ensures electrical continuity in the deposited material. The nanowire templates, porous alumina, were made by the double anodization of high-purity aluminum foil in oxalic acid solutions. This technique produces parallel, hexagonally packed, and nanometer-range diameter pores that can reach high aspect ratios (greater than 2000:1). The main anodization variables (electrolyte concentration, applied potential, 2nd anodization time, and temperature) were studied systematically in order to deconvolute their effects on the resulting pores and to obtain high aspect ratio pores. The porous alumina is of great importance because the pore dimensions determine the dimensions of the electrodeposited nanowires, which influence the thermoelectric performance of the nanowire arrays. Nanowire arrays were characterized in several ways. Powder X-ray diffraction was used to assess crystallinity and preferred orientation of the nanowires, revealing that the nanowires are highly crystalline and grow with strong preferred orientation such that the material is suited for optimal thermoelectric performance. Scanning electron microscopy was used to evaluate the nanowire nucleation percentage and growth-front uniformity, both of which were enhanced by pulsed-potential electrodeposition. Compositional analysis via electron microprobe indicates

  3. 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

  4. Low bandgap mid-infrared thermophotovoltaic arrays based on InAs

    NASA Astrophysics Data System (ADS)

    Krier, A.; Yin, M.; Marshall, A. R. J.; Kesaria, M.; Krier, S. E.; McDougall, S.; Meredith, W.; Johnson, A. D.; Inskip, J.; Scholes, A.

    2015-11-01

    We demonstrate the first low bandgap thermophotovoltaic (TPV) arrays capable of operating with heat sources at temperatures as low as 345 °C, which is the lowest ever reported. The individual array elements are based on narrow band gap InAs/InAs0.61Sb0.13P0.26 photodiode structures. External power conversion efficiency was measured to be ∼3% from a single element at room temperature, using a black body at 950 °C. Both 25-element and 65-element arrays were fabricated and exhibited a TPV response at different source temperatures in the range 345-950 °C suitable for electricity generation from waste heat and other applications.

  5. 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.

  6. 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.

  7. 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

  8. A near-infrared 64-pixel superconducting nanowire single photon detector array with integrated multiplexed readout

    SciTech Connect

    Allman, M. S. Verma, V. B.; Stevens, M.; Gerrits, T.; Horansky, R. D.; Lita, A. E.; Mirin, R.; Nam, S. W.; Marsili, F.; Beyer, A.; Shaw, M. D.; Kumor, D.

    2015-05-11

    We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon detectors optimized for high detection efficiency in the near-infrared range. An integrated, readily scalable, multiplexed readout scheme is employed to reduce the number of readout lines to 16. The cryogenic, optical, and electronic packaging to read out the array as well as characterization measurements are discussed.

  9. Amorphous Alumina Nanowire Array Efficiently Delivers Ac-DEVD-CHO to Inhibit Apoptosis of Dendritic Cells

    PubMed Central

    Lampert, Lester; Timonen, Brittany; Smith, Sean; Davidge, Brittney; Li, Haiyan; Conley, John F.; Singer, Jeffrey D.; Jiao, Jun

    2014-01-01

    To create an effective well-ordered delivery platform still remains a challenge. Herein we fabricate vertically aligned alumina nanowire arrays via atomic layer deposition templated by carbon nanotubes. Using these arrays, a caspase-3/7 inhibitor was delivered into DC 2.4 cells and blocked apoptosis, as confirmed by fluorescence microscopy. PMID:24336780

  10. Extremely stable field emission from AlZnO nanowire arrays

    NASA Astrophysics Data System (ADS)

    Xue, X. Y.; Li, L. M.; Yu, H. C.; Chen, Y. J.; Wang, Y. G.; Wang, T. H.

    2006-07-01

    Extremely stable electric field emission from well-aligned AlZnO nanowire arrays is realized. The emission current density is up to 6.5mA/cm2, and no current saturation is observed. The turn-on field is 2.9V/μm as d (distance between the nanowire emitters and anode) is 0.64mm. After aging for two days, the emission current is extremely stable with the fluctuations of ±0.4%. The high stability arises from the high crystal quality with few surface states of the nanowires and the in situ fabrication of cathodes. The field emission behaviors are in excellent agreement with Fowler-Nordheim theory, and the relationship between the field enhancement factor β and d follows a universal equation. Our results imply that AlZnO nanowire arrays are promising candidates for field emission displays.

  11. Efficient CoO nanowire array photocatalysts for H2 generation

    NASA Astrophysics Data System (ADS)

    Zhan, Xueying; Wang, Zhenxing; Wang, Fengmei; Cheng, Zhongzhou; Xu, Kai; Wang, Qisheng; Safdar, Muhammad; He, Jun

    2014-10-01

    CoO nanowire arrays for efficient water-splitting were fabricated via a facile hydrothermal and subsequent annealing method. The CoO nanowire is composed of assembled CoO nanoparticles and the particle size can be controlled by annealing temperatures. CoO nanowire array exhibits advantages of easy fabrication, recyclability, and high stability. The origin of the difference of photocatalytic activity among CoO bulk, CoO nanowires annealed under different temperatures, can be contributed to remarkable shift in the position of the band edge due to different CoO particle sizes. Our finding may provide an avenue in design and fabrication of Co-based nanosturctures for practical applications.

  12. Patterned polymer nanowire arrays as an effective protein immobilizer for biosensing and HIV detection

    NASA Astrophysics Data System (ADS)

    Shen, Yue; Liu, Yingyi; Zhu, Guang; Fang, Hao; Huang, Yunhui; Jiang, Xingyu; Wang, Zhong L.

    2012-12-01

    We report an array of polymeric nanowires for effectively immobilizing biomolecules on biochips owing to the large surface area. The nanowires were fabricated in predesigned patterns using an inductively coupled plasma (ICP) etching process. Microfluidic biochips integrated using the substrates with arrays of nanowires and polydimethylsiloxane channels have been demonstrated to be effective for detecting antigens, and a detection limit of antigens at 0.2 μg mL-1 has been achieved, which is improved by a factor of 50 compared to that based on flat substrates without the nanowires. In addition, the high sensitivity for clinical detection of human immunodeficiency virus (HIV) antibody has also been demonstrated, showing a 20 times enhancement in fluorescent signal intensity between the samples with positive and negative HIV.

  13. E{sub 1} Gap of Wurtzite InAs Single Nanowires Measured by Means of Resonant Raman Spectroscopy

    SciTech Connect

    Moeller, M.; Lima, M. M. Jr. de; Cantarero, A.; Dacal, L. C. O.; Iikawa, F.; Chiaramonte, T.; Cotta, M. A.

    2011-12-23

    Indium arsenide nanowires were synthesized with an intermixing of wurtzite and zincblende structure by chemical beam epitaxy with the vapor-liquid-solid mechanism. Resonant Raman spectroscopy of the transverse optical phonon mode at 215 cm{sup -1} reveals an E{sub 1} gap of 2.47 eV which is assigned to the electronic band gap at the A point in the indium arsenide wurtzite phase.

  14. Distortions of the coulomb blockade conductance line in scanning gate measurements of inas nanowire based quantum dots

    SciTech Connect

    Zhukov, A. A.; Volk, Ch.; Winden, A.; Hardtdegen, H.; Schaepers, Th.

    2013-01-15

    We performed measurements at helium temperatures of the electronic transport in the linear regime in an InAs quantum wire in the presence of a charged tip of an atomic force microscope (AFM) at low electron concentration. We show that at certain concentration of electrons, only two closely placed quantum dots, both in the Coulomb blockade regime, govern conductance of the whole wire. Under this condition, two types of peculiarities-wobbling and splitting-arise in the behavior of the lines of the conductance peaks of Coulomb blockade. These peculiarities are measured in quantum-wire-based structures for the first time. We explain both peculiarities as an interplay of the conductance of two quantum dots present in the wire. Detailed modeling of wobbling behavior made in the framework of the orthodox theory of Coulomb blockade demonstrates good agreement with the obtained experimental data.

  15. PKP simulation of size effect on interaction field distribution in highly ordered ferromagnetic nanowire arrays

    NASA Astrophysics Data System (ADS)

    Dobrotă, Costin-Ionuţ; Stancu, Alexandru

    2012-12-01

    Perpendicular structured nanowire arrays interaction field distributions (IFDs), as revealed from first-order reversal curves (FORC) diagrams, are related to the presence of the demagnetizing field in the system. Despite the similarity between the geometric properties of bit patterned media and mentioned nanowire arrays, FORC diagrams of these two types of systems are not similar essentially due to the different number of magnetic entities influencing the switch of an individual element. We show that one Preisach-Krasnosel'skii-Pokrovskii (PKP) symmetrical hysteron can be representative of an ideal infinite nanowire array when the field is applied along the wires. Starting from this observation, we present a very simple model based on PKP symmetrical hysterons that can be applied to real finite ferromagnetic nanowire arrays, and is able to describe a wide class of experimentally observed FORC distributions, revealing features due to size effects. We also present IFDs modeled for different geometric characteristics such as array size, interwire distance, and nanowire dimensions, and an identification procedure for the proposed model.

  16. Magnetic hysteresis in small-grained CoxPd1-x nanowire arrays

    NASA Astrophysics Data System (ADS)

    Viqueira, M. S.; Pozo-López, G.; Urreta, S. E.; Condó, A. M.; Cornejo, D. R.; Fabietti, L. M.

    2015-11-01

    Co-Pd nanowires with small grain size are fabricated by AC electrodeposition into hexagonally ordered alumina pores, 20-35 nm in diameter and about 1 μm long. The effects of the alloy composition, the nanowire diameter and the grain size on the hysteresis properties are considered. X-ray diffraction indicates that the nanowires are single phase, a fcc Co-Pd solid solution; electron microscopy results show that they are polycrystalline, with randomly oriented grains (7-12 nm), smaller than the wire diameter. Nanowire arrays are ferromagnetic, with an easy magnetization axis parallel to the nanowire long axis. Both, the coercive field and the loop squareness monotonously increase with the Co content and with the grain size, but no clear correlation with the wire diameter is found. The Co and Co-rich nanowire arrays exhibit coercive fields and reduced remanence values quite insensitive to temperature in the range 4 K-300 K; on the contrary, in Pd-rich nanowires both magnitudes are smaller and they largely increase during cooling below 100 K. These behaviors are systematized by considering the strong dependences displayed by the magneto-crystalline anisotropy and the saturation magnetostriction on composition and temperature. At low temperatures the effective anisotropy value and the domain-wall width to grain size ratio drastically change, promoting less cooperative and harder nucleation modes.

  17. Electronic transport mechanisms in scaled gate-all-around silicon nanowire transistor arrays

    SciTech Connect

    Clément, N. E-mail: guilhem.larrieu@laas.fr; Han, X. L.; Larrieu, G. E-mail: guilhem.larrieu@laas.fr

    2013-12-23

    Low-frequency noise is used to study the electronic transport in arrays of 14 nm gate length vertical silicon nanowire devices. We demonstrate that, even at such scaling, the electrostatic control of the gate-all-around is sufficient in the sub-threshold voltage region to confine charges in the heart of the wire, and the extremely low noise level is comparable to that of high quality epitaxial layers. Although contact noise can already be a source of poor transistor operation above threshold voltage for few nanowires, nanowire parallelization drastically reduces its impact.

  18. Defect-engineered GaN:Mg nanowire arrays for overall water splitting under violet light

    SciTech Connect

    Kibria, M. G.; Chowdhury, F. A.; Zhao, S.; Mi, Z.; Trudeau, M. L.; Guo, H.

    2015-03-16

    We report that by engineering the intra-gap defect related energy states in GaN nanowire arrays using Mg dopants, efficient and stable overall neutral water splitting can be achieved under violet light. Overall neutral water splitting on Rh/Cr{sub 2}O{sub 3} co-catalyst decorated Mg doped GaN nanowires is demonstrated with intra-gap excitation up to 450 nm. Through optimized Mg doping, the absorbed photon conversion efficiency of GaN nanowires reaches ∼43% at 375–450 nm, providing a viable approach to extend the solar absorption of oxide and non-oxide photocatalysts.

  19. The influence of the droplet composition on the vapor-liquid-solid growth of InAs nanowires on GaAs (111)B by metal-organic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Bauer, Jens; Gottschalch, Volker; Wagner, Gerald

    2008-12-01

    The heteroepitaxial growth of InAs nanowires (NWs) on GaAs (1¯1¯1¯)B substrate was investigated by metal-organic vapor phase epitaxy. The vapor-liquid-solid (VLS) growth mechanism was applied with gold as seed material. InAs NW with two types of morphology were observed. The first morphology type exhibited a tapered NW shape. In a distinct region below the alloy particle the shape was influenced by the precursor surface diffusion. The NW growth was attributed to Au-rich liquid alloy particles containing gallium as a result of the initial Au-GaAs interaction. Differential scanning calorimetry measurements revealed the lowest eutectic temperature of the Au-Ga-In liquid alloy for different compositions. For a considerable amount of gallium inside the ternary alloy, the eutectic temperature was found to be below the InAs NW growth temperature window. A second type of morphology with a more columnlike shape was related to a very high indium fraction inside the liquid alloy particle during VLS growth. These NW exhibited a change in the side facet orientation from {2¯11} to {1¯10} below the droplet. Additionally, the sample structure was studied by transmission electron microscopy. A change in the InAs NW crystal structure from sphalerite-type to mainly wurtzite-type was observed with an increase in the growth temperature.

  20. Controlling the growth and field emission properties of silicide nanowire arrays by direct silicification of Ni foil

    NASA Astrophysics Data System (ADS)

    Liu, Zhihong; Zhang, Hui; Wang, Lei; Yang, Deren

    2008-09-01

    Nickel silicide nanowire arrays have been achieved by the decomposition of SiH4 on Ni foil at 650 °C. It is indicated that the nickel silicide nanowires consist of roots with diameter of about 100-200 nm and tips with diameter of about 10-50 nm. A Ni diffusion controlled mechanism is proposed to explain the formation of the nickel silicide nanowires. Field emission measurement shows that the turn-on field of the nickel silicide nanowire arrays is low, at about 3.7 V µm-1, and the field enhancement factor is as high as 4280, so the arrays have promising applications as emitters.

  1. Simulation Analysis on Photoelectric Conversion Characteristics of Silicon Nanowire Array Photoelectrodes.

    PubMed

    Zhao, Yong; Yu, Jin; Fang, Li-Guang; Zheng, Jun; Wang, Hui-Qin; Yuan, Ji-Ren; Wu, Shaolong; Cheng, Guo-An

    2015-12-01

    Semiconductor nanowire photoelectrochemical cells have attracted extensive attention in the light-conversion field owing to the low-cost preparation, excellent optical absorption, and short distance of carrier collection. Although there are numbers of experimental investigations to improve the device performance, the understanding of the detailed process of photoelectric conversion needs to be further improved. In this work, a thorough optoelectronic simulation is employed to figure out how the nanowire diameter, doping concentration, and illumination wavelength affect the photoelectric conversion characteristics of the silicon nanowire array photoelectrodes. We find that two balances should be carefully weighted between optical absorption and photogenerated-carrier collection, along with between short-circuit photocurrent density and open-circuit voltage. For the small-diameter nanowire array photoelectrodes, the overall absorption is higher than that of the larger-diameter ones with the most contribution from the nanowires. However, the substrate shows increasing absorption with increasing illumination wavelength. Higher doping density leads to a larger open-circuit voltage; while lower doping density can guarantee a relatively higher short-circuit photocurrent. To obtain high-light-conversion-efficiency photoelectrodes, the doping density should be carefully chosen with considerations of illumination wavelength and surface recombination. Suppressing the surface recombination velocity can effectively enhance the short-circuit photocurrent (open-circuit voltage) for the lightly (heavily) doped nanowire array photoelectrodes. Our systematical results provide a theoretical guidance for the photoelectrochemical devices based on semiconductor nanostructures.

  2. Simulation Analysis on Photoelectric Conversion Characteristics of Silicon Nanowire Array Photoelectrodes

    NASA Astrophysics Data System (ADS)

    Zhao, Yong; Yu, Jin; Fang, Li-Guang; Zheng, Jun; Wang, Hui-Qin; Yuan, Ji-Ren; Wu, Shaolong; Cheng, Guo-An

    2015-06-01

    Semiconductor nanowire photoelectrochemical cells have attracted extensive attention in the light-conversion field owing to the low-cost preparation, excellent optical absorption, and short distance of carrier collection. Although there are numbers of experimental investigations to improve the device performance, the understanding of the detailed process of photoelectric conversion needs to be further improved. In this work, a thorough optoelectronic simulation is employed to figure out how the nanowire diameter, doping concentration, and illumination wavelength affect the photoelectric conversion characteristics of the silicon nanowire array photoelectrodes. We find that two balances should be carefully weighted between optical absorption and photogenerated-carrier collection, along with between short-circuit photocurrent density and open-circuit voltage. For the small-diameter nanowire array photoelectrodes, the overall absorption is higher than that of the larger-diameter ones with the most contribution from the nanowires. However, the substrate shows increasing absorption with increasing illumination wavelength. Higher doping density leads to a larger open-circuit voltage; while lower doping density can guarantee a relatively higher short-circuit photocurrent. To obtain high-light-conversion-efficiency photoelectrodes, the doping density should be carefully chosen with considerations of illumination wavelength and surface recombination. Suppressing the surface recombination velocity can effectively enhance the short-circuit photocurrent (open-circuit voltage) for the lightly (heavily) doped nanowire array photoelectrodes. Our systematical results provide a theoretical guidance for the photoelectrochemical devices based on semiconductor nanostructures.

  3. Simulation Analysis on Photoelectric Conversion Characteristics of Silicon Nanowire Array Photoelectrodes.

    PubMed

    Zhao, Yong; Yu, Jin; Fang, Li-Guang; Zheng, Jun; Wang, Hui-Qin; Yuan, Ji-Ren; Wu, Shaolong; Cheng, Guo-An

    2015-12-01

    Semiconductor nanowire photoelectrochemical cells have attracted extensive attention in the light-conversion field owing to the low-cost preparation, excellent optical absorption, and short distance of carrier collection. Although there are numbers of experimental investigations to improve the device performance, the understanding of the detailed process of photoelectric conversion needs to be further improved. In this work, a thorough optoelectronic simulation is employed to figure out how the nanowire diameter, doping concentration, and illumination wavelength affect the photoelectric conversion characteristics of the silicon nanowire array photoelectrodes. We find that two balances should be carefully weighted between optical absorption and photogenerated-carrier collection, along with between short-circuit photocurrent density and open-circuit voltage. For the small-diameter nanowire array photoelectrodes, the overall absorption is higher than that of the larger-diameter ones with the most contribution from the nanowires. However, the substrate shows increasing absorption with increasing illumination wavelength. Higher doping density leads to a larger open-circuit voltage; while lower doping density can guarantee a relatively higher short-circuit photocurrent. To obtain high-light-conversion-efficiency photoelectrodes, the doping density should be carefully chosen with considerations of illumination wavelength and surface recombination. Suppressing the surface recombination velocity can effectively enhance the short-circuit photocurrent (open-circuit voltage) for the lightly (heavily) doped nanowire array photoelectrodes. Our systematical results provide a theoretical guidance for the photoelectrochemical devices based on semiconductor nanostructures. PMID:26123274

  4. Piezo-Phototronic Enhanced UV Sensing Based on a Nanowire Photodetector Array.

    PubMed

    Han, Xun; Du, Weiming; Yu, Ruomeng; Pan, Caofeng; Wang, Zhong Lin

    2015-12-22

    A large array of Schottky UV photodetectors (PDs) based on vertical aligned ZnO nanowires is achieved. By introducing the piezo-phototronic effect, the performance of the PD array is enhanced up to seven times in photoreponsivity, six times in sensitivity, and 2.8 times in detection limit. The UV PD array may have applications in optoelectronic systems, adaptive optical computing, and communication.

  5. Silicon nanowire arrays coupled with cobalt phosphide spheres as low-cost photocathodes for efficient solar hydrogen evolution.

    PubMed

    Bao, Xiao-Qing; Fatima Cerqueira, M; Alpuim, Pedro; Liu, Lifeng

    2015-07-01

    We demonstrate the first example of silicon nanowire array photocathodes coupled with hollow spheres of the emerging earth-abundant cobalt phosphide catalysts. Compared to bare silicon nanowire arrays, the hybrid electrodes exhibit significantly improved photoelectrochemical performance toward the solar-driven H2 evolution reaction.

  6. Morphology-dependent field emission properties and wetting behavior of ZnO nanowire arrays

    PubMed Central

    2011-01-01

    The fabrication of three kinds of ZnO nanowire arrays with different structural parameters over Au-coated silicon (100) by facile thermal evaporation of ZnS precursor is reported, and the growth mechanism are proposed based on structural analysis. Field emission (FE) properties and wetting behavior were revealed to be strongly morphology dependent. The nanowire arrays in small diameter and high aspect ratio exhibited the best FE performance showing a low turn-on field (4.1 V/μm) and a high field-enhancement factor (1745.8). The result also confirmed that keeping large air within the films was an effective way to obtain super water-repellent properties. This study indicates that the preparation of ZnO nanowire arrays in an optimum structural model is crucial to FE efficiency and wetting behavior. PMID:21711609

  7. Transparently wrap-gated semiconductor nanowire arrays for studies of gate-controlled photoluminescence

    SciTech Connect

    Nylund, Gustav; Storm, Kristian; Torstensson, Henrik; Wallentin, Jesper; Borgström, Magnus T.; Hessman, Dan; Samuelson, Lars

    2013-12-04

    We present a technique to measure gate-controlled photoluminescence (PL) on arrays of semiconductor nanowire (NW) capacitors using a transparent film of Indium-Tin-Oxide (ITO) wrapping around the nanowires as the gate electrode. By tuning the wrap-gate voltage, it is possible to increase the PL peak intensity of an array of undoped InP NWs by more than an order of magnitude. The fine structure of the PL spectrum reveals three subpeaks whose relative peak intensities change with gate voltage. We interpret this as gate-controlled state-filling of luminescing quantum dot segments formed by zincblende stacking faults in the mainly wurtzite NW crystal structure.

  8. Wurtzite InP nanowire arrays grown by selective area MOCVD

    SciTech Connect

    Chu, Hyung-Joon; Yeh, Ting-Wei; Stewart, Lawrence; Dapkus, P. Daniel

    2010-06-22

    InP nanowires are a unique material phase because this normally zincblende material forms in the wurtzite crystal structure below a critical diameter owing to the contribution of sidewalls to the total formation energy. This may allow control of the carrier transport and optical properties of InP nanowires for applications such as nano scale transistors, lasers and detectors. In this work, we describe the fabrication of InP nanowire arrays by selective area growth using MOCVD in the diameter range where the wurtzite structure is formed. The spatial growth rate in selective area growth is modeled by a diffusion model for the precursors. The proposed model achieves an average error of 9%. Electron microscopy shows that the grown InP nanowires are in the wurtzite crystal phase with many stacking faults. The threshold diameter of the crystal phase transition of InP nanowires is larger than the thermodynamic estimation. In order to explain this tendency, we propose a surface kinetics model based on a 2×2 reconstruction. This model can explain the increased tendency for wurtzite nanowire formation on InP (111)A substrates and the preferred growth direction of binary III-V compound semiconductor nanowires.

  9. Transmission electron microscopy assisted in-situ joule heat dissipation study of individual InAs nanowires

    NASA Astrophysics Data System (ADS)

    Xu, T. T.; Wei, X. L.; Shu, J. P.; Chen, Q.

    2013-11-01

    Managing heat transport at nanoscale is an important and challenging task for nanodevice applications and nanostructure engineering. Herein, through in-situ engineering nanowire (NW)-electrode contacts with electron beam induced carbon deposition in a transmission electron microscope, Joule heat dissipation along individual suspended Indium Arsenide NWs is well managed to obtain pre-designed temperature profiles along NWs. The temperature profiles are experimentally determined by the breakdown site of NWs under Joule heating and breakdown temperature measurement. A model with NW-electrode contacts being well considered is proposed to describe heat transport along a NW. By fitting temperature profiles with the model, thermal conductance at NW-electrode contacts is obtained. It is found that, the temperature profile along a specific NW is mainly governed by the relative thermal conductance at the two NW-electrode contacts, which is engineered in experiments.

  10. Simultaneous Selective-Area and Vapor-Liquid-Solid Growth of InP Nanowire Arrays.

    PubMed

    Gao, Qian; Dubrovskii, Vladimir G; Caroff, Philippe; Wong-Leung, Jennifer; Li, Li; Guo, Yanan; Fu, Lan; Tan, Hark Hoe; Jagadish, Chennupati

    2016-07-13

    Selective-area epitaxy is highly successful in producing application-ready size-homogeneous arrays of III-V nanowires without the need to use metal catalysts. Previous works have demonstrated excellent control of nanowire properties but the growth mechanisms remain rather unclear. Herein, we report a detailed growth study revealing that fundamental growth mechanisms of pure wurtzite InP ⟨111⟩A nanowires can indeed differ significantly from the simple picture of a facet-limited selective-area growth process. A dual growth regime with and without metallic droplet is found to coexist under the same growth conditions for different diameter nanowires. Incubation times and highly nonmonotonous growth rate behaviors are revealed and explained within a dedicated kinetic model. PMID:27253040

  11. Enhanced magnetic performance of metal-organic nanowire arrays by FeCo/polypyrrole co-electrodeposition

    NASA Astrophysics Data System (ADS)

    Luo, X. J.; Xia, W. B.; Gao, J. L.; Zhang, S. Y.; Li, Y. L.; Tang, S. L.; Du, Y. W.

    2013-05-01

    FeCo/polypyrrole (PPy) composite nanowire array, which shows enhanced magnetic remanence and coercivity along the nanowires, was fabricated by AC electrodeposition using anodic aluminum oxide templates. High resolution transmission electron microscopy shows that PPy grows on the surface of FeCo nanowires forming a coaxial nanowire structure, with a coating layer of about 4 nm. It suggests that the decreased dipolar interaction due to the reduced nanowire diameters is responsible for the enhancement of magnetic performance. The possible mechanism of this coating may be that PPy is inclined to nucleate along the pore wall of the templates.

  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. Vertical Si nanowire arrays fabricated by magnetically guided metal-assisted chemical etching

    NASA Astrophysics Data System (ADS)

    Chun, Dong Won; Kim, Tae Kyoung; Choi, Duyoung; Caldwell, Elizabeth; Kim, Young Jin; Paik, Jae Cheol; Jin, Sungho; Chen, Renkun

    2016-11-01

    In this work, vertically aligned Si nanowire arrays were fabricated by magnetically guided metal-assisted directional chemical etching. Using an anodized aluminum oxide template as a shadow mask, nanoscale Ni dot arrays were fabricated on an Si wafer to serve as a mask to protect the Si during the etching. For the magnetically guided chemical etching, we deposited a tri-layer metal catalyst (Au/Fe/Au) in a Swiss-cheese configuration and etched the sample under the magnetic field to improve the directionality of the Si nanowire etching and increase the etching rate along the vertical direction. After the etching, the nanowires were dried with minimal surface-tension-induced aggregation by utilizing a supercritical CO2 drying procedure. High-resolution transmission electron microscopy (HR-TEM) analysis confirmed the formation of single-crystal Si nanowires. The method developed here for producing vertically aligned Si nanowire arrays could find a wide range of applications in electrochemical and electronic devices.

  15. Writing and functionalisation of suspended DNA nanowires on superhydrophobic pillar arrays.

    PubMed

    Miele, Ermanno; Accardo, Angelo; Falqui, Andrea; Marini, Monica; Giugni, Andrea; Leoncini, Marco; De Angelis, Francesco; Krahne, Roman; Di Fabrizio, Enzo

    2015-01-01

    Nanowire arrays and networks with precisely controlled patterns are very interesting for innovative device concepts in mesoscopic physics. In particular, DNA templates have proven to be versatile for the fabrication of complex structures that obtained functionality via combinations with other materials, for example by functionalisation with molecules or nanoparticles, or by coating with metals. Here, the controlled motion of the a three-phase contact line (TCL) of DNA-loaded drops on superhydrophobic substrates is used to fabricate suspended nanowire arrays. In particular, the deposition of DNA wires is imaged in situ, and different patterns are obtained on hexagonal pillar arrays by controlling the TCL velocity and direction. Robust conductive wires and networks are achieved by coating the wires with a thin layer of gold, and as proof of concept conductivity measurements are performed on single suspended wires. The plastic material of the superhydrophobic pillars ensures electrical isolation from the substrate. The more general versatility of these suspended nanowire networks as functional templates is outlined by fabricating hybrid organic-metal-semiconductor nanowires by growing ZnO nanocrystals onto the metal-coated nanowires.

  16. Writing and functionalisation of suspended DNA nanowires on superhydrophobic pillar arrays.

    PubMed

    Miele, Ermanno; Accardo, Angelo; Falqui, Andrea; Marini, Monica; Giugni, Andrea; Leoncini, Marco; De Angelis, Francesco; Krahne, Roman; Di Fabrizio, Enzo

    2015-01-01

    Nanowire arrays and networks with precisely controlled patterns are very interesting for innovative device concepts in mesoscopic physics. In particular, DNA templates have proven to be versatile for the fabrication of complex structures that obtained functionality via combinations with other materials, for example by functionalisation with molecules or nanoparticles, or by coating with metals. Here, the controlled motion of the a three-phase contact line (TCL) of DNA-loaded drops on superhydrophobic substrates is used to fabricate suspended nanowire arrays. In particular, the deposition of DNA wires is imaged in situ, and different patterns are obtained on hexagonal pillar arrays by controlling the TCL velocity and direction. Robust conductive wires and networks are achieved by coating the wires with a thin layer of gold, and as proof of concept conductivity measurements are performed on single suspended wires. The plastic material of the superhydrophobic pillars ensures electrical isolation from the substrate. The more general versatility of these suspended nanowire networks as functional templates is outlined by fabricating hybrid organic-metal-semiconductor nanowires by growing ZnO nanocrystals onto the metal-coated nanowires. PMID:25131422

  17. Pulse electrodeposition and electrochemical quartz crystal microbalance techniques for high perpendicular magnetic anisotropy cobalt nanowire arrays

    NASA Astrophysics Data System (ADS)

    Ursache, Andrei; Goldbach, James T.; Russell, Thomas P.; Tuominen, Mark T.

    2005-05-01

    This research is focused on the development of pulse electrodeposition techniques to fabricate a high-density array of vertically oriented, high-magnetic anisotropy cobalt nanowires using a porous polymer film template. This type of array is a competitive candidate for future perpendicular magnetic media capable of storage densities exceeding 1Terabit/in.2 The polymer template, derived from a self-assembling P(S-b-MMA) diblock copolymer film, provides precise control over the nanowire diameter (15nm) and interwire spacing (24nm), whereas nanowire length (typically 50to1000nm) is controlled accurately with the aid of real-time electrochemical quartz crystal monitoring. Pulse and pulse-reversed electrodeposition techniques, as compared to dc, are shown to significantly enhance the perpendicular magnetic anisotropy of the magnetic nanowire array and ultimately result in coercivity as large as 2.7kOe at 300K. Magnetic and structural characterizations suggest that these properties arise from an improved degree of magnetocrystalline anisotropy (due to c-axis oriented crystal growth and improvements in crystal quality) that strongly supplements the basic shape anisotropy of the nanowires. Low temperature magnetometry is used to investigate exchange bias effects due to the incorporation of CoO antiferromagnetic impurities during the electrodeposition process and subsequent Co oxidation in air.

  18. Microwave properties of ferromagnetic nanowire arrays patterned with periodic and quasi-periodic structures

    NASA Astrophysics Data System (ADS)

    Lei, Yuxiong; Chen, Zheng; Li, Liangliang

    2015-05-01

    Microwave properties of ferromagnetic nanowire arrays patterned with periodic and quasi-periodic structures were investigated in this study. The periodic and quasi-periodic structures were designed based on Fibonacci sequence and golden ratio. Ni nanowires arrays were electrodeposited in anodic aluminum oxide (AAO) templates with patterned Cu electrodes, and then the AAO templates were attached to the coplanar waveguide lines fabricated on quartz substrate for measurement. The S21 of both periodic and quasi-periodic structure-patterned Ni nanowire arrays showed an extra absorption peak besides the absorption peak due to the ferromagnetic resonance of Ni nanowires. The frequency of the absorption peak caused by the patterned structure could be higher than 40 GHz when the length and arrangement of the structural units were modified. In addition, the frequency of the absorption peak due to the quasi-periodic structure was calculated based on a simple analytical model, and the calculated value was consistent with the measured one. The experimental data showed that it could be a feasible approach to tune the performance of microwave devices by patterning ferromagnetic nanowires.

  19. 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

  20. Magnetoelectrolysis of Co nanowire arrays grown in a track-etched polycarbonate membrane

    NASA Astrophysics Data System (ADS)

    Sánchez-Barriga, J.; Lucas, M.; Rivero, G.; Marin, P.; Hernando, A.

    2007-05-01

    Arrays of Cobalt nanowires with a controlled length of 6 μm have been fabricated by electrochemical deposition into the pores of track-etched polycarbonate membranes with a nominal pore diameter of 30 nm. The magnetic properties of Co-deposited nanowires and the effects of a magnetic field applied during electrodeposition of the arrays have been studied. An enhancement of the mass deposition rate due to the presence of a 50 Oe magnetic field along the nanowire axis has been observed by measuring the experimental development of the current in the electrochemical cell during the fabrication process. X-ray diffraction measurements reveal a different polycrystalline degree for each deposition configuration, indicating that the crystalline structure of the deposited material has been substantially modified. Magnetic measurements show a clear dependence of the anisotropy directions on the orientation of the magnetic field applied during the electrodeposition.

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

    NASA Astrophysics Data System (ADS)

    Kuo, Shou-Yi; Lin, Hsin-I.

    2014-02-01

    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.

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

    PubMed

    Kuo, Shou-Yi; Lin, Hsin-I

    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

  3. Porous silicon nanowire arrays decorated by Ag nanoparticles for surface enhanced Raman scattering study

    NASA Astrophysics Data System (ADS)

    Su, L.; Xu, H. J.; Chan, Y. F.; Sun, X. M.

    2012-02-01

    A large scale and highly ordered Ag nanoparticle-decorated porous silicon nanowire array was fabricated for a uniform and reproducible surface-enhanced Raman scattering (SERS) substrate. The overall process for the proposed structure is simple and reliable with the use of only chemical etching and metal reduction processes. The SERS sensitivity of the novel substrate as low as 10-16 M for rhodamine 6G (R6G) and the Raman enhancement factor as high as 10^14 were obtained. The excellent SERS performances were mainly attributed to the strong local electromagnetic effect which is associated with the formation of large-quantity Ag nanoparticles on porous silicon nanowire array and the existence of semiconductor silicon nanowires. Significantly, the quadratic relation between the logarithmic concentrations and the logarithmic integrated Raman peak intensities provided quantitative detection of R6G. Our results open new possibilities for applying SERS to trace detection of low-concentration biomolecules.

  4. Enzyme electrodes immobilized on hetero-structured metallic nanowire array for glucose sensing

    NASA Astrophysics Data System (ADS)

    Yoon, Hargsoon; Deshpande, Devesh; Chintakuntla, Ritesh R.; Varadan, Vijay K.

    2007-12-01

    The fabrication of hetero-structured vertically aligned nanowire arrays and enzyme immobilization on their surface is presented for a glucose sensor with high sensitivity. Hetero-structured nanowires of gold and platinum are fabricated by hybrid polycarbonate membrane assembly and electrochemical deposition processes and glucose oxidase are attached on their surface by covalent immobilization. Platinum and gold hetero-structured nanoelectrodes with enzyme are evaluated to detect hydrogen peroxide produced in the enzyme reaction without the need for the artificial redox mediator, which is not viable on a homogenous gold electrode. Chronoamperometric current behavior is demonstrated with various concentrations from 0.5 mM to 28 mM. In this research, the combination of enzyme immobilization and sensing surfaces on nanowire arrays has shown superior performance with regards to the sensitivity and response time.

  5. Metallic nanowires can lead to wavelength-scale microlenses and microlens arrays.

    PubMed

    Zaiba, Soraya; Kouriba, Timothe; Ziane, Omar; Stéphan, Olivier; Bosson, Jocelyne; Vitrant, Guy; Baldeck, Patrice L

    2012-07-01

    We theoretically and experimentally demonstrate that the diffraction of microstructures based on silver nanowires leads to very efficient microfocusing effects. Pairs of parallel nanowires act as ultrasmall cylindrical microlenses with diffraction-limited resolution in the Fresnel region. This is a new diffraction scheme to make micron-sized optical lenses with higher transmittance than plasmonic microlens based on nano-aperture arrays. Calculations based on the scalar Rayleigh-Sommerfeld integral highlights the pure scalar diffractive contribution. Thus, the plasmon contribution is negligible in such micron-sized metallic geometry. We demonstrate that two-dimensional grids of nanowires can be used to fabricate dense arrays of microlenses, i.e. 10000x10000 DPI (dots per inch).

  6. A facile chemical route to synthesize ZnO nanoarrays: one-dimensional nanowire arrays and two-dimensional porous nanosheet arrays.

    PubMed

    Hua, Guomin; Sun, Li; Tian, Yue; Chen, Xiaomeng; Zhang, Lide; Dai, Jun; Hu, Linhua; Dai, Songyuan

    2011-04-01

    A facile chemical route is presented to synthesize ZnO nanoarrays including one-dimensional nanowire arrays and two-dimensional porous nanosheet arrays. Large-scale ZnO nanowire arrays with the length of 5 microm and aspect ratio of 42 were achieved by cyclic growth in aqueous solution. After being immerged in the zinc acetate solution for 24 h, the ZnO nanowire arrays converted to sheet-like Zn5(OH)8(CH3COO)2 arrays. Subsequently, the sheet-like Zn5(OH)8(CH3COO)2 arrays converted to the porous ZnO nanosheet arrays by annealing treatment. As demonstrated by the performance of dye-sensitized solar cells (DSC), the porous ZnO nanosheet arrays can improve the efficiency of DSC effectively. In addition, the synthesized ZnO nanoarrays have potential applications in solar cells, catalysis, sensors and other nanodevices.

  7. Antibacterial activity of single crystalline silver-doped anatase TiO2 nanowire arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangyu; Li, Meng; He, Xiaojing; Hang, Ruiqiang; Huang, Xiaobo; Wang, Yueyue; Yao, Xiaohong; Tang, Bin

    2016-05-01

    Well-ordered, one-dimensional silver-doped anatase TiO2 nanowire (AgNW) arrays have been prepared through a hydrothermal growth process on the sputtering-deposited AgTi layers. Electron microscope analyses reveal that the as-synthesized AgNW arrays exhibit a single crystalline phase with highly uniform morphologies, diameters ranging from 85 to 95 nm, and lengths of about 11 μm. Silver is found to be doped into TiO2 nanowire evenly and mainly exists in the zerovalent state. The AgNW arrays show excellent efficient antibacterial activity against Escherichia coli (E. coli), and all of the bacteria can be killed within 1 h. Additionally, the AgNW arrays can still kill E. coli after immersion for 60 days, suggesting the long-term antibacterial property. The technique reported here is environmental friendly for formation of silver-containing nanostructure without using any toxic organic solvents.

  8. An Ultralong, Highly Oriented Nickel-Nanowire-Array Electrode Scaffold for High-Performance Compressible Pseudocapacitors.

    PubMed

    Xu, Chao; Li, Ziheng; Yang, Cheng; Zou, Peichao; Xie, Binghe; Lin, Ziyin; Zhang, Zhexu; Li, Baohua; Kang, Feiyu; Wong, Ching-Ping

    2016-06-01

    Ultralong, highly oriented Ni nanowire arrays are used as the electrode scaffold to support metal-oxide- and conductive-polymer-based electrode materials with a high mass loading; the as-obtained asymmetric supercapacitor can be compressed by fourfold and exhibits superior energy and power densities with ultrahigh cycle stability.

  9. Fabrication and properties of a branched (NH₄)xWO₃ nanowire array film and a porous WO3 nanorod array film.

    PubMed

    Liu, Ya; Zhao, Liang; Su, Jinzhan; Li, Mingtao; Guo, Liejin

    2015-02-18

    We describe the successful fabrication of a three-dimensional branched (NH4)xWO3 nanowire array film on fluorine-doped tin oxide coated glass by a facile one-step hydrothermal method. The porous WO3 nanorod array film formed after heat treatment and recrystallization. Specifically, the branched (NH4)xWO3 nanowire array film has very thin nanowires that were about 10 nm in diameter. The results of an optical and photoelectrochemical test show that the branched (NH4)xWO3 nanowire array film could be used as a near-infrared shielder, while the porous WO3 nanorod array film can be used as a photoanode for water splitting. Moreover, the morphology, structure, and composition of the as-prepared films are revealed, and the related changes caused by heat treatment are discussed in detail. PMID:25623076

  10. Fast growth of well-aligned ZnO nanowire arrays by a microwave heating method and their photocatalytic properties.

    PubMed

    Cao, Guangxia; Hong, Kunquan; Wang, Wenda; Liu, Liqing; Xu, Mingxiang

    2016-10-28

    The fast growth of aligned ZnO nanowire arrays with optimized structure is attractive for electrical and optical devices. In this paper, we report a controllable and rapid growth of ZnO nanowire arrays by a microwave-assisted hydrothermal method. When using different zinc salts as the precursors, the morphology of the samples changes a lot and the length growth rate is several times different. The growth mechanism is also investigated. It is found that the solution near neutral pH value is ideal for fast nanowire growth, in which the length of the nanowires increases linearly with growth time and the growth rate is over ten times faster than that in the traditional hydrothermal method. Therefore, aligned ZnO nanowire arrays can grow up to tens of microns in a few hours, while the density and sizes of these nanowires can be well controlled. The ZnO nanowire arrays used as photocatalysts present good photocatalytic performance to the degradation of methyl orange (MO) due to the large surface area. So this paper provides an effective method to obtain vertically aligned ZnO nanowire arrays for practical applications. PMID:27655230

  11. Fast growth of well-aligned ZnO nanowire arrays by a microwave heating method and their photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Cao, Guangxia; Hong, Kunquan; Wang, Wenda; Liu, Liqing; Xu, Mingxiang

    2016-10-01

    The fast growth of aligned ZnO nanowire arrays with optimized structure is attractive for electrical and optical devices. In this paper, we report a controllable and rapid growth of ZnO nanowire arrays by a microwave-assisted hydrothermal method. When using different zinc salts as the precursors, the morphology of the samples changes a lot and the length growth rate is several times different. The growth mechanism is also investigated. It is found that the solution near neutral pH value is ideal for fast nanowire growth, in which the length of the nanowires increases linearly with growth time and the growth rate is over ten times faster than that in the traditional hydrothermal method. Therefore, aligned ZnO nanowire arrays can grow up to tens of microns in a few hours, while the density and sizes of these nanowires can be well controlled. The ZnO nanowire arrays used as photocatalysts present good photocatalytic performance to the degradation of methyl orange (MO) due to the large surface area. So this paper provides an effective method to obtain vertically aligned ZnO nanowire arrays for practical applications.

  12. Fast growth of well-aligned ZnO nanowire arrays by a microwave heating method and their photocatalytic properties.

    PubMed

    Cao, Guangxia; Hong, Kunquan; Wang, Wenda; Liu, Liqing; Xu, Mingxiang

    2016-10-28

    The fast growth of aligned ZnO nanowire arrays with optimized structure is attractive for electrical and optical devices. In this paper, we report a controllable and rapid growth of ZnO nanowire arrays by a microwave-assisted hydrothermal method. When using different zinc salts as the precursors, the morphology of the samples changes a lot and the length growth rate is several times different. The growth mechanism is also investigated. It is found that the solution near neutral pH value is ideal for fast nanowire growth, in which the length of the nanowires increases linearly with growth time and the growth rate is over ten times faster than that in the traditional hydrothermal method. Therefore, aligned ZnO nanowire arrays can grow up to tens of microns in a few hours, while the density and sizes of these nanowires can be well controlled. The ZnO nanowire arrays used as photocatalysts present good photocatalytic performance to the degradation of methyl orange (MO) due to the large surface area. So this paper provides an effective method to obtain vertically aligned ZnO nanowire arrays for practical applications.

  13. Copper indium diselenide nanowire arrays by electrodeposition in porous alumina templates

    NASA Astrophysics Data System (ADS)

    Phok, Sovannary; Rajaputra, Suresh; Singh, Vijay P.

    2007-11-01

    A simple template assisted approach for fabricating I-III-VI semiconductor nanowire arrays is presented. Vertically aligned arrays of CuInSe2 (CIS) nanowires of controllable diameter and length were synthesized by pulse cathodic electrodeposition from a novel acidic electrolyte solution into anodized alumina (AAO) templates, followed by annealing at 220 °C in vacuum. Scanning electron microscopy revealed that the nanowires were dense and compact. Depending on the dimensions of the starting AAO template, the diameters ranged from 5 to 40 nm and the lengths ranged from 600 nm to 5 µm the grain size was estimated to be less than 5 nm. The composition of the nanowires was analyzed by energy dispersive x-ray (EDX) spectroscopy, and was found to be close to stoichiometric CuInSe2 within the limit of the resolution of the EDX technique. High resolution transmission electron microscopy and x-ray diffraction revealed high purity CuInSe2 nanowires with a preferred [112] orientation.

  14. 15% Power Conversion Efficiency from a Gated Nanotube/Silicon Nanowire Array Solar Cell

    NASA Astrophysics Data System (ADS)

    Petterson, Maureen K.; Lemaitre, Maxime G.; Shen, Yu; Wadhwa, Pooja; Hou, Jie; Vasilyeva, Svetlana V.; Kravchenko, Ivan I.; Rinzler, Andrew G.

    2015-03-01

    Despite their enhanced light trapping ability the performance of silicon nanowire array solar cells have, been stagnant with power conversion efficiencies barely breaking 10%. The problem is understood to be the consequence of a high photo-carrier recombination at the large surface area of the Si nanowire sidewalls. Here, by exploiting 1) electronic gating via an ionic liquid electrolyte to induce inversion in the n-type Si nanowires and 2) using a layer of single wall carbon nanotubes engineered to contact each nanowire tip and extract the minority carriers, we demonstrate silicon nanowire array solar cells with power conversion efficiencies of 15%. Our results allow for discrimination between the two principle means of avoiding front surface recombination: surface passivation and the use of local fields. A deleterious electrochemical reaction of the silicon due to the electrolyte gating is shown to be caused by oxygen/water entrained in the ionic liquid electrolyte. While encapsulation can avoid the issue a non-encapsulation based solution is also described. We gratefully acknowledge support from the National Science Foundation under ECCS-1232018.

  15. Solar energy harnessing in hexagonally arranged Si nanowire arrays and effects of array symmetry on optical characteristics.

    PubMed

    Li, Junshuai; Yu, HongYu; Li, Yali

    2012-05-17

    Investigation of solar energy harvesting in hexagonally arranged Si nanowire (NW) arrays is performed through optimizing the structural parameters, such as array periodicity (P), Si NW diameter (D) and length (L). The results demonstrate that there exist wide P and D/P 'windows' for the Si NW arrays, locating around 600 nm and 0.833 (i.e., D=500 nm), respectively, for achieving enhanced light absorption compared to their thin film counterparts with the same thickness, but with much less materials consumption. Calculation of the ultimate efficiency (UE) indicates that the light trapping capability is not monotonically increased with L, and that UE vibration is found when L is >1000 nm. Comparison of the light absorption spectra for hexagonally and squarely arranged Si NW arrays demonstrates that these two most widely employed array symmetries in practice have little impact on the light trapping capability.

  16. 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

    2016-03-24

    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.

  17. 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

  18. 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

  19. Arrays of nanowires of magnetic metals and multilayers: Perpendicular GMR and magnetic properties

    NASA Astrophysics Data System (ADS)

    Piraux, L.; Dubois, S.; Duvail, J. L.; Ounadjela, K.; Fert, A.

    1997-11-01

    The template strategy combined with electrodeposition techniques have been used to fabricate arrays of nanowires of magnetic metals and multilayers in the cylindrical pores of track-etched polymer membranes. The giant magnetoresistance effects have been investigated in two different types of multilayered nanowires systems: Co/Cu and Ni 80Fe 20/Cu. In addition, a comparative study of the magnetic properties of sub-micron Ni, Co, Fe and Ni 80Fe 20 wires is made by means of anisotropic magnetoresistance and magnetization experiments.

  20. Application of Polyethylenimine-Grafted Silicon Nanowire Arrays for Gene Transfection.

    PubMed

    Wang, Hongwei; Pan, Jingjing; Chen, Hong; Yuan, Lin

    2016-01-01

    Polyplexes are one of the most important and promising approaches to deliver exogenous DNA into cells. However, it is severely restricted by the aggregation of polyplexes. Surface-tethered polyplexes can inhibit the aggregation effect and increase the local concentrations of DNA, exhibiting an excellent potential in gene transfection. Since silicon nanowires have the ability to penetrate the cell membrane, branched polyethylenimine (bPEI)-grafted silicon nanowire arrays (SiNWAs) can stimulate gene transfection to a great extent. Herein, the method for the preparation of bPEI-grafted SiNWAs, as an example of surface-tethered polyplexes, is introduced in detail. PMID:27436326

  1. Interactions and reversal-field memory in complex magnetic nanowire arrays

    NASA Astrophysics Data System (ADS)

    Rotaru, Aurelian; Lim, Jin-Hee; Lenormand, Denny; Diaconu, Andrei; Wiley, John. B.; Postolache, Petronel; Stancu, Alexandru; Spinu, Leonard

    2011-10-01

    Interactions and magnetization reversal of Ni nanowire arrays have been investigated by the first-order reversal curve (FORC) method. Several series of samples with controlled spatial distribution were considered including simple wires of different lengths and diameters (70 and 110 nm) and complex wires with a single modulated diameter along their length. Subtle features of magnetic interactions are revealed through a quantitative analysis of the local interaction field profile distributions obtained from the FORC method. In addition, the FORC analysis indicates that the nanowire systems with a mean diameter of 70 nm appear to be organized in symmetric clusters indicative of a reversal-field memory effect.

  2. One-pot synthesis of Bi-Ni nanowire and nanocable arrays by coelectrodeposition approach

    PubMed Central

    2012-01-01

    A novel and convenient one-pot electrodeposition approach has been developed for precisely controlled fabrication of large-scale Bi-Ni nanowire and nanocable arrays. Using porous anodic aluminum oxide as a shape-directing template, by simply changing the electrochemical deposition mode, desired Bi-Ni hybrid nanowires and Bi-Ni core-shell nanocables have been obtained in the CV and CC modes, respectively. The structure, morphology, and composition of the as-prepared samples were characterized using X-ray powder diffraction, transmission electron microscopy, elemental mapping, and energy-dispersive X-ray spectrometry. PMID:22336749

  3. Nonlithographic nanowire-array tunnel device: Fabrication, zero-bias anomalies, and Coulomb blockade

    NASA Astrophysics Data System (ADS)

    Davydov, D. N.; Haruyama, J.; Routkevitch, D.; Statt, B. W.; Ellis, D.; Moskovits, M.; Xu, J. M.

    1998-06-01

    Coulomb blockade (CB) was observed in Al/aluminum oxide/Ni nanowire single-junction arrays fabricated by electrochemical deposition of Ni into porous aluminum oxide nanotemplates. The bias dependence of the tunneling current and the temperature dependence of the zero-bias anomalies observed in the tunneling spectra are shown to accord well with the theory of Nazarov for CB in systems where the leads play a significant role. Direct scanning tunneling microscopy measurements of the nanowire leads resistance confirms it to be the regime required by the theory.

  4. Versatile Particle-Based Route to Engineer Vertically Aligned Silicon Nanowire Arrays and Nanoscale Pores.

    PubMed

    Elnathan, Roey; Isa, Lucio; Brodoceanu, Daniel; Nelson, Adrienne; Harding, Frances J; Delalat, Bahman; Kraus, Tobias; Voelcker, Nicolas H

    2015-10-28

    Control over particle self-assembly is a prerequisite for the colloidal templating of lithographical etching masks to define nanostructures. This work integrates and combines for the first time bottom-up and top-down approaches, namely, particle self-assembly at liquid-liquid interfaces and metal-assisted chemical etching, to generate vertically aligned silicon nanowire (VA-SiNW) arrays and, alternatively, arrays of nanoscale pores in a silicon wafer. Of particular importance, and in contrast to current techniques, including conventional colloidal lithography, this approach provides excellent control over the nanowire or pore etching site locations and decouples nanowire or pore diameter and spacing. The spacing between pores or nanowires is tuned by adjusting the specific area of the particles at the liquid-liquid interface before deposition. Hence, the process enables fast and low-cost fabrication of ordered nanostructures in silicon and can be easily scaled up. We demonstrate that the fabricated VA-SiNW arrays can be used as in vitro transfection platforms for transfecting human primary cells.

  5. Enhanced field emission from ZnO nanowires grown on a silicon nanoporous pillar array

    NASA Astrophysics Data System (ADS)

    Xu, Hai Jun; Chan, Yu Fei; Su, Lei; Li, De Yao; Sun, Xiao Ming

    2010-12-01

    A large scale heterostructure array of ZnO nanowires/silicon nanoporous pillar array (Si-NPA) was prepared by a self-catalytic thermal evaporation and vapor-phase transport method, and an ultrahigh field emission current density of 1.55 mA cm-2 was obtained under an operating electric field of 4.0 V μm-1, with a low turn-on field of 1.65 V μm-1. The enhancement factor calculated according to the Fowler-Nordheim theory was ˜3141. The excellent field emission performance was attributed to the unique structure of ZnO/Si-NPA, especially the formation of ZnO nanowires on regular Si pillar array. Our work indicated that ZnO/Si-NPA might be an ideal candidate cathode of potential applications in flat panel displays and high brightness electron sources.

  6. Influence of the adatom diffusion on selective growth of GaN nanowire regular arrays

    NASA Astrophysics Data System (ADS)

    Gotschke, T.; Schumann, T.; Limbach, F.; Stoica, T.; Calarco, R.

    2011-03-01

    Molecular beam epitaxy (MBE) on patterned Si/AlN/Si(111) substrates was used to obtain regular arrays of uniform-size GaN nanowires (NWs). The silicon top layer has been patterned with e-beam lithography, resulting in uniform arrays of holes with different diameters (dh) and periods (P). While the NW length is almost insensitive to the array parameters, the diameter increases significantly with dh and P till it saturates at P values higher than 800 nm. A diffusion induced model was used to explain the experimental results with an effective diffusion length of the adatoms on the Si, estimated to be about 400 nm.

  7. Photovoltaic properties of Zr(x)Ti(1-x)O2 solid solution nanowire arrays.

    PubMed

    Gu, Xuehui; Liu, Guohua; Zhang, Min; Zhang, Haifeng; Zhou, Jingran; Guo, Wenbin; Chen, Yu; Ruan, Shengping

    2014-05-01

    In this paper, Zr(0.05Ti(0.95)O2 solid solution nanowire arrays (NWs) were prepared by a low temperature hydrothermal method. The as-prepared NWs were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-visible (UV-vis) spectroscopy. With the doping of Zr content, the band gap of the composite can be varied in a wide range and excellent photoelectric properties of the arrays could be obtained. Moreover, a preliminary study on the photoelectric properties was conducted, which indicates potential applications of the arrays for fabricating high performance ultraviolet photodetectors.

  8. Effective piezoelectric response of substrate-integrated ZnO nanowire array devices on galvanized steel.

    PubMed

    Velazquez, By Jesus M; Baskaran, Sivapalan; Gaikwad, Anil V; Ngo-Duc, Tam-Triet; He, Xiangtong; Oye, Michael M; Meyyappan, M; Rout, Tapan K; Fu, John Y; Banerjee, Sarbajit

    2013-11-13

    Harvesting waste energy through electromechanical coupling in practical devices requires combining device design with the development of synthetic strategies for large-area controlled fabrication of active piezoelectric materials. Here, we show a facile route to the large-area fabrication of ZnO nanostructured arrays using commodity galvanized steel as the Zn precursor as well as the substrate. The ZnO nanowires are further integrated within a device construct and the effective piezoelectric response is deduced based on a novel experimental approach involving induction of stress in the nanowires through pressure wave propagation along with phase-selective lock-in detection of the induced current. The robust methodology for measurement of the effective piezoelectric coefficient developed here allows for interrogation of piezoelectric functionality for the entire substrate under bending-type deformation of the ZnO nanowires.

  9. Fabrication of Carbon Nanowire Arrays Using Inhomogeneous Dissolution-Diffusion Kinetics and Photoresist Pyrolysis.

    PubMed

    Gao, Kunpeng; Zhu, Zhuanghui; Yan, Jinyi; Liao, Lingying; Cheng, Ji; Li, Gang; Jin, Qinghui; Zhao, Jianlong

    2015-09-01

    We report a simple and efficient method to fabricate carbon nanowire (CNW) arrays with precise locations and spatial arrangements. This method is based on a phenomenon in photoresist (PR) development that if the exposed posts are close-spaced they are linked by some undissolved resist filaments. Pyrolysis made the residual resist filaments to shrink and form CNWs under an inert atmosphere. Scanning electron microscope (SEM) showed that these nanowires had orderly arrangement and precise location. The formation of the CNWs was studied by simulation and experiment, which indicated the nanowire was influenced by the thickness of PR, the spacing distance between exposed posts, the diameter of posts and the developing time. We also investigated the composition and electrical properties of the resultant CNWs. The results showed that the CNW had characteristics of p type semiconductor.

  10. Hypersonic crystal band gaps in Ni/Cu superlattice nanowire arrays

    NASA Astrophysics Data System (ADS)

    Hu, Jia-Guang; Shen, Tie

    2016-03-01

    The hexagonal and tetragonal ordered arrays were prepared by Ni/Cu superlattice nanowires on the porous anodic alumina membrane template, and their phonon band structures were calculated by using the plane wave expansion method. Numerical results show that the hypersonic band gaps can be acquired by adjusting the structural parameters. Along the different wave-vector directions, the width and position of band gap would vary. If the nanowires'filling fraction is increased continuously, the width of the first band gap firstly increases and then decreases within a certain range. The height of superlattice nanowire elementary unit can only affect the width of band gap within a quite narrow range. When the height of elementary unit remains unchanged, the decrease of the Cu-component ratio can contribute to the formation of a wider band gap. Additionally, the wide band gap is more easily formed in tetragonal structure than in hexagonal structure.

  11. Laser Modified ZnO/CdSSe Core-Shell Nanowire Arrays for Micro-Steganography and Improved Photoconduction

    NASA Astrophysics Data System (ADS)

    Lu, Junpeng; Liu, Hongwei; Zheng, Minrui; Zhang, Hongji; Lim, Sharon Xiaodai; Tok, Eng Soon; Sow, Chorng Haur

    2014-09-01

    Arrays of ZnO/CdSSe core/shell nanowires with shells of tunable band gaps represent a class of interesting hybrid nanomaterials with unique optical and photoelectrical properties due to their type II heterojunctions and chemical compositions. In this work, we demonstrate that direct focused laser beam irradiation is able to achieve localized modification of the hybrid structure and chemical composition of the nanowire arrays. As a result, the photoresponsivity of the laser modified hybrid is improved by a factor of ~3. A 3D photodetector with improved performance is demonstrated using laser modified nanowire arrays overlaid with monolayer graphene as the top electrode. Finally, by controlling the power of the scanning focused laser beam, micropatterns with different fluorescence emissions are created on a substrate covered with nanowire arrays. Such a pattern is not apparent when imaged under normal optical microscopy but the pattern becomes readily revealed under fluorescence microscopy i.e. a form of Micro-Steganography is achieved.

  12. Laser modified ZnO/CdSSe core-shell nanowire arrays for Micro-Steganography and improved photoconduction.

    PubMed

    Lu, Junpeng; Liu, Hongwei; Zheng, Minrui; Zhang, Hongji; Lim, Sharon Xiaodai; Tok, Eng Soon; Sow, Chorng Haur

    2014-01-01

    Arrays of ZnO/CdSSe core/shell nanowires with shells of tunable band gaps represent a class of interesting hybrid nanomaterials with unique optical and photoelectrical properties due to their type II heterojunctions and chemical compositions. In this work, we demonstrate that direct focused laser beam irradiation is able to achieve localized modification of the hybrid structure and chemical composition of the nanowire arrays. As a result, the photoresponsivity of the laser modified hybrid is improved by a factor of ~3. A 3D photodetector with improved performance is demonstrated using laser modified nanowire arrays overlaid with monolayer graphene as the top electrode. Finally, by controlling the power of the scanning focused laser beam, micropatterns with different fluorescence emissions are created on a substrate covered with nanowire arrays. Such a pattern is not apparent when imaged under normal optical microscopy but the pattern becomes readily revealed under fluorescence microscopy i.e. a form of Micro-Steganography is achieved.

  13. 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.

  14. 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.

  15. Magnetic properties of Ni-Fe nanowire arrays: effect of template material and deposition conditions

    SciTech Connect

    Singleton, John; Aravamudhan, Shyan; Goddard, Paul A; Bhansali, Shekhar

    2008-01-01

    The objective of this work is to study the magnetic properties of arrays of Ni-Fe nanowires electrodeposited in different template materials such as porous silicon, polycarbonate and alumina. Magnetic properties were studied as a function of template material, applied magnetic field (parallel and perpendicular) during deposition, wire length, as well as magnetic field orientation during measurement. The results show that application of magnetic field during deposition strongly influences the c-axis preferred orientation growth of Ni-Fe nanowires. The samples with magnetic field perpendicular to template plane during deposition exhibits strong perpendicular anisotropy with greatly enhanced coercivity and squareness ratio, particularly in Ni-Fe nanowires deposited in polycarbonate templates. In case of polycarbonate template, as magnetic field during deposition increases, both coercivity and squareness ratio also increase. The wire length dependence was also measured for polycarbonate templates. As wire length increases, coercivity and squarness ratio decrease, but saturation field increases. Such magnetic behavior (dependence on template material, magnetic field, wire length) can be qualitatively explained by preferential growth phenomena, dipolar interactions among nanowires, and perpendicular shape anisotropy in individual nanowires.

  16. Large-scale parallel arrays of silicon nanowires via block copolymer directed self-assembly.

    PubMed

    Farrell, Richard A; Kinahan, Niall T; Hansel, Stefan; Stuen, Karl O; Petkov, Nikolay; Shaw, Matthew T; West, Laetitia E; Djara, Vladimir; Dunne, Robert J; Varona, Olga G; Gleeson, Peter G; Jung, Soon-Jung; Kim, Hye-Young; Koleśnik, Maria M; Lutz, Tarek; Murray, Christopher P; Holmes, Justin D; Nealey, Paul F; Duesberg, Georg S; Krstić, Vojislav; Morris, Michael A

    2012-05-21

    Extending the resolution and spatial proximity of lithographic patterning below critical dimensions of 20 nm remains a key challenge with very-large-scale integration, especially if the persistent scaling of silicon electronic devices is sustained. One approach, which relies upon the directed self-assembly of block copolymers by chemical-epitaxy, is capable of achieving high density 1 : 1 patterning with critical dimensions approaching 5 nm. Herein, we outline an integration-favourable strategy for fabricating high areal density arrays of aligned silicon nanowires by directed self-assembly of a PS-b-PMMA block copolymer nanopatterns with a L(0) (pitch) of 42 nm, on chemically pre-patterned surfaces. Parallel arrays (5 × 10(6) wires per cm) of uni-directional and isolated silicon nanowires on insulator substrates with critical dimension ranging from 15 to 19 nm were fabricated by using precision plasma etch processes; with each stage monitored by electron microscopy. This step-by-step approach provides detailed information on interfacial oxide formation at the device silicon layer, the polystyrene profile during plasma etching, final critical dimension uniformity and line edge roughness variation nanowire during processing. The resulting silicon-nanowire array devices exhibit Schottky-type behaviour and a clear field-effect. The measured values for resistivity and specific contact resistance were ((2.6 ± 1.2) × 10(5)Ωcm) and ((240 ± 80) Ωcm(2)) respectively. These values are typical for intrinsic (un-doped) silicon when contacted by high work function metal albeit counterintuitive as the resistivity of the starting wafer (∼10 Ωcm) is 4 orders of magnitude lower. In essence, the nanowires are so small and consist of so few atoms, that statistically, at the original doping level each nanowire contains less than a single dopant atom and consequently exhibits the electrical behaviour of the un-doped host material. Moreover this indicates that the processing

  17. Angular dependence of the coercivity and remanence of ferromagnetic nanowire arrays

    NASA Astrophysics Data System (ADS)

    Han, G. C.; Zong, B. Y.; Luo, P.; Wu, Y. H.

    2003-06-01

    Magnetization properties of magnetic nanowire arrays are studied on various ferromagnetic materials grown in anodic alumina (alumite) and track etched polycarbonate (PCTE) membranes by pulsed electrodeposition. Magnetization curves were measured as functions of wire material, field orientation, and wire length. The coercivity (Hc) and remanent squareness (S) of the various wire arrays were derived from hysteresis loops as a function of angle (θ) between the field and wire axis. For PCTE membranes, Hc(θ) curves for CoNiFe, NiFe, and Co nanowire arrays all show an otherwise-bell-type variation, while they change shapes from the otherwise bell to bell type for Ni nanowire arrays as the wire diameter decreases to 30 nm. These characteristics can be understood based on different magnetization reversal mechanisms of small wires. The effect of magnetostatic interaction among wires on the magnetic properties was examined by changing the wire lengths in alumite membranes. It is found that the interaction reduces Hc and S values significantly and may cause the overall easy axis change from parallel to perpendicular to the wire axis. However, the interaction is much weaker than expected from an independent precession theory. The strong coupling among the wire may also induce a change of magnetization reversal mechanism.

  18. Directly-grown and square-patterned arrays of metal oxide nanowires for high-performance catalyst support platforms.

    PubMed

    Lee, Sang Ho; Lim, Eun Ja; Jo, Yong-Ryun; Kim, Bong-Joong; Kim, Won Bae

    2014-12-10

    This research reports novel and efficient electrocatalyst support systems. Tin dioxide nanowires grown directly on current collecting substances are introduced as high-performance support platforms. For this propose, palladium or platinum catalysts are impregnated on these nanowire scaffolds and exhibit improved electrocatalytic performance for methanol oxidation in alkaline and acidic environments. These nanowire support platforms could be demonstrated to maximize the electrocatalytic activity because of the effective charge transport provided by the direct connection between the nanowire supports and current collectors. More significantly, grid-patterned nanowire arrays grown directly on current collectors are, for the first time, demonstrated as a milestone to enhance the electrocatalytic performance. The empty space between the patterned nanowire arrays acts as a channel to facilitate the electrolyte diffusion. The metal catalysts incorporated into the patterned nanowire supports show an 8-fold improvement in the catalytic performance for methanol electrooxidation, most likely because of the synergetic effects of the enhanced charge transport and mass transfer attributed to the structural advantages of the patterned nanowire array supports. PMID:25405935

  19. Fabrication of Ni-silicide/Si heterostructured nanowire arrays by glancing angle deposition and solid state reaction

    PubMed Central

    2013-01-01

    This work develops a method for growing Ni-silicide/Si heterostructured nanowire arrays by glancing angle Ni deposition and solid state reaction on ordered Si nanowire arrays. Samples of ordered Si nanowire arrays were fabricated by nanosphere lithography and metal-induced catalytic etching. Glancing angle Ni deposition deposited Ni only on the top of Si nanowires. When the annealing temperature was 500°C, a Ni3Si2 phase was formed at the apex of the nanowires. The phase of silicide at the Ni-silicide/Si interface depended on the diameter of the Si nanowires, such that epitaxial NiSi2 with a {111} facet was formed at the Ni-silicide/Si interface in Si nanowires with large diameter, and NiSi was formed in Si nanowires with small diameter. A mechanism that is based on flux divergence and a nucleation-limited reaction is proposed to explain this phenomenon of size-dependent phase formation. PMID:23663726

  20. Effects of various hydrogenated treatments on formation and photocatalytic activity of black TiO2 nanowire arrays.

    PubMed

    Wang, Chih-Chieh; Chou, Po-Hsun

    2016-08-12

    The effects of hydrogen thermal and plasma treatment on the formation and photocatalytic activities of black TiO2 nanowire arrays were investigated and discussed. After either the hydrogen thermal or plasma treatment, the TiO2 nanowires remained. However, in contrast to the plasma treated nanowires, the diameter of the thermal treated TiO2 nanowires reduced more significantly, which was attributed to a thicker surface amorphous layer and more oxygen vacancies. A higher photoresponse in both UV and visible light regions and more hydroxide groups were also observed for the thermal treated nanowires. In addition, the black nanowires possessed greater carrier concentration, leading to a more efficient separation of electron-hole pairs. As a consequence, much enhanced photoelectrochemical water splitting and photocatalytic degradation of methylene blue were obtained. PMID:27354433

  1. Effects of various hydrogenated treatments on formation and photocatalytic activity of black TiO2 nanowire arrays

    NASA Astrophysics Data System (ADS)

    Wang, Chih-Chieh; Chou, Po-Hsun

    2016-08-01

    The effects of hydrogen thermal and plasma treatment on the formation and photocatalytic activities of black TiO2 nanowire arrays were investigated and discussed. After either the hydrogen thermal or plasma treatment, the TiO2 nanowires remained. However, in contrast to the plasma treated nanowires, the diameter of the thermal treated TiO2 nanowires reduced more significantly, which was attributed to a thicker surface amorphous layer and more oxygen vacancies. A higher photoresponse in both UV and visible light regions and more hydroxide groups were also observed for the thermal treated nanowires. In addition, the black nanowires possessed greater carrier concentration, leading to a more efficient separation of electron–hole pairs. As a consequence, much enhanced photoelectrochemical water splitting and photocatalytic degradation of methylene blue were obtained.

  2. Effects of various hydrogenated treatments on formation and photocatalytic activity of black TiO2 nanowire arrays

    NASA Astrophysics Data System (ADS)

    Wang, Chih-Chieh; Chou, Po-Hsun

    2016-08-01

    The effects of hydrogen thermal and plasma treatment on the formation and photocatalytic activities of black TiO2 nanowire arrays were investigated and discussed. After either the hydrogen thermal or plasma treatment, the TiO2 nanowires remained. However, in contrast to the plasma treated nanowires, the diameter of the thermal treated TiO2 nanowires reduced more significantly, which was attributed to a thicker surface amorphous layer and more oxygen vacancies. A higher photoresponse in both UV and visible light regions and more hydroxide groups were also observed for the thermal treated nanowires. In addition, the black nanowires possessed greater carrier concentration, leading to a more efficient separation of electron-hole pairs. As a consequence, much enhanced photoelectrochemical water splitting and photocatalytic degradation of methylene blue were obtained.

  3. Low temperature magnetoresistance measurements on bismuth nanowire arrays

    NASA Astrophysics Data System (ADS)

    Kaiser, Ch; Weiss, G.; Cornelius, T. W.; Toimil-Molares, M. E.; Neumann, R.

    2009-05-01

    We present low temperature resistance R(T) and magnetoresistance measurements for Bi nanowires with diameters between 100 and 500 nm, which are close to being single-crystalline. The nanowires were fabricated by electrochemical deposition in pores of polycarbonate membranes. R(T) varies as T2 in the low temperature range 1.5 K

  4. Periodically porous top electrodes on vertical nanowire arrays for highly sensitive gas detection.

    PubMed

    In, Hyun Jin; Field, Christopher R; Pehrsson, Pehr E

    2011-09-01

    Nanowires of various materials and configurations have been shown to be highly effective in the detection of chemical and biological species. In this paper, we report a novel, nanosphere-enabled approach to fabricating highly sensitive gas sensors based on ordered arrays of vertically aligned silicon nanowires topped with a periodically porous top electrode. The vertical array configuration helps to greatly increase the sensitivity of the sensor while the pores in the top electrode layer significantly improve sensing response times by allowing analyte gases to pass through freely. Herein, we show highly sensitive detection to both nitrogen dioxide (NO(2)) and ammonia (NH(3)) in humidified air. NO(2) detection down to 10 parts per billion (ppb) is demonstrated and an order-of-magnitude improvement in sensor response time is shown in the detection of NH(3).

  5. [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.

  6. 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.

  7. 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.

  8. 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

  9. Ultrahigh density array of vertically aligned small-molecular organic nanowires on arbitrary substrates.

    PubMed

    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

  10. 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

  11. Optical properties of silicon nanocrystals covered by periodic array of gold nanowires

    NASA Astrophysics Data System (ADS)

    Dyakov, S. A.; Zhigunov, D. M.; Marinins, A.; Shcherbakov, M. R.; Fedyanin, A. A.; Vorontsov, A. S.; Kashkarov, P. K.; Popov, S.; Qiu, M.; Zacharias, M.; Tikhodeev, S. G.; Gippius, N. A.

    2016-05-01

    Extinction and photoluminescence spectra are experimentally and theoretically studied for a periodic array of gold nanowires deposited on top of a dielectric substrate containing silicon nanocrystals. Quasiguided modes are observed in the substrate resulting in modification of optical properties of silicon nanocrystals. Our calculations of extinction and photoluminescence spectra are in good agreement with experimental results. The periodicity provides a powerful tool for achieving a high photoluminescence outcoupling efficiency of silicon nanocrystals.

  12. Photoelectric properties of an array of axial GaAs/AlGaAs nanowires

    NASA Astrophysics Data System (ADS)

    Grigor'ev, R. V.; Shtrom, I. V.; Grigor'eva, N. R.; Novikov, B. V.; Soshnikov, I. P.; Samsonenko, Yu. B.; Khrebtov, A. I.; Buravleuv, A. D.; Cirlin, G. E.

    2015-05-01

    The results of studies of photoelectric properties of an array of axial n-type GaAs/Al x Ga1 - x As ( x ≈ 0.3) nanowires grown using molecular beam epitaxy on a p-type silicon substrate are presented. The ability to separate charges efficiently in a wide spectral range (from 450 to 1100 nm) is demonstrated. Such properties are important for designing active elements of photodetectors and solar cells.

  13. Carbon-layer-protected cuprous oxide nanowire arrays for efficient water reduction.

    PubMed

    Zhang, Zhonghai; Dua, Rubal; Zhang, Lianbin; Zhu, Haibo; Zhang, Hongnan; Wang, Peng

    2013-02-26

    In this work, we propose a solution-based carbon precursor coating and subsequent carbonization strategy to form a thin protective carbon layer on unstable semiconductor nanostructures as a solution to the commonly occurring photocorrosion problem of many semiconductors. A proof-of-concept is provided by using glucose as the carbon precursor to form a protective carbon coating onto cuprous oxide (Cu₂O) nanowire arrays which were synthesized from copper mesh. The carbon-layer-protected Cu₂O nanowire arrays exhibited remarkably improved photostability as well as considerably enhanced photocurrent density. The Cu₂O nanowire arrays coated with a carbon layer of 20 nm thickness were found to give an optimal water splitting performance, producing a photocurrent density of -3.95 mA cm⁻² and an optimal photocathode efficiency of 0.56% under illumination of AM 1.5G (100 mW cm⁻²). This is the highest value ever reported for a Cu₂O-based electrode coated with a metal/co-catalyst-free protective layer. The photostability, measured as the percentage of the photocurrent density at the end of 20 min measurement period relative to that at the beginning of the measurement, improved from 12.6% on the bare, nonprotected Cu₂O nanowire arrays to 80.7% on the continuous carbon coating protected ones, more than a 6-fold increase. We believe that the facile strategy presented in this work is a general approach that can address the stability issue of many nonstable photoelectrodes and thus has the potential to make a meaningful contribution in the general field of energy conversion.

  14. Flexible Dye-Sensitized Solar Cell Based on Vertical ZnO Nanowire Arrays

    PubMed Central

    2011-01-01

    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. PMID:27502660

  15. Fabrication of ordered NiO coated Si nanowire array films as electrodes for a high performance lithium ion battery.

    PubMed

    Qiu, M C; Yang, L W; Qi, X; Li, Jun; Zhong, J X

    2010-12-01

    Highly ordered NiO coated Si nanowire array films are fabricated as electrodes for a high performance lithium ion battery via depositing Ni on electroless-etched Si nanowires and subsequently annealing. The structures and morphologies of as-prepared films are characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. When the potential window versus lithium was controlled, the coated NiO can be selected to be electrochemically active to store and release Li+ ions, while highly conductive crystalline Si cores function as nothing more than a stable mechanical support and an efficient electrical conducting pathway. The hybrid nanowire array films exhibit superior cyclic stability and reversible capacity compared to that of NiO nanostructured films. Owing to the ease of large-scale fabrication and superior electrochemical performance, these hybrid nanowire array films will be promising anode materials for high performance lithium-ion batteries.

  16. Controlling the growth and field emission properties of silicide nanowire arrays by direct silicification of Ni foil.

    PubMed

    Liu, Zhihong; Zhang, Hui; Wang, Lei; Yang, Deren

    2008-09-17

    Nickel silicide nanowire arrays have been achieved by the decomposition of SiH(4) on Ni foil at 650 °C. It is indicated that the nickel silicide nanowires consist of roots with diameter of about 100-200 nm and tips with diameter of about 10-50 nm. A Ni diffusion controlled mechanism is proposed to explain the formation of the nickel silicide nanowires. Field emission measurement shows that the turn-on field of the nickel silicide nanowire arrays is low, at about 3.7 V µm(-1), and the field enhancement factor is as high as 4280, so the arrays have promising applications as emitters.

  17. Controlling the growth and field emission properties of silicide nanowire arrays by direct silicification of Ni foil.

    PubMed

    Liu, Zhihong; Zhang, Hui; Wang, Lei; Yang, Deren

    2008-09-17

    Nickel silicide nanowire arrays have been achieved by the decomposition of SiH(4) on Ni foil at 650 °C. It is indicated that the nickel silicide nanowires consist of roots with diameter of about 100-200 nm and tips with diameter of about 10-50 nm. A Ni diffusion controlled mechanism is proposed to explain the formation of the nickel silicide nanowires. Field emission measurement shows that the turn-on field of the nickel silicide nanowire arrays is low, at about 3.7 V µm(-1), and the field enhancement factor is as high as 4280, so the arrays have promising applications as emitters. PMID:21832554

  18. Self-assembled and highly selective sensors based on air-bridge-structured nanowire junction arrays.

    PubMed

    Park, Won Jeong; Choi, Kyung Jin; Kim, Myung Hwa; Koo, Bon Hyeong; Lee, Jong-Lam; Baik, Jeong Min

    2013-08-14

    We describe a strategy for creating an air-bridge-structured nanowire junction array platform that capable of reliably discriminating between three gases (hydrogen, carbon monoxide, and nitrogen dioxide) in air. Alternatively driven dual nanowire species of ZnO and CuO with the average diameter of ∼30 nm on a single substrate are used and decorated with metallic nanoparticles to form two-dimensional microarray, which do not need to consider the post fabrications. Each individual nanowires in the array form n-n, p-p, and p-n junctions at the micro/nanoscale on single substrate and the junctions act as electrical conducting path for carriers. The adsorption of gas molecules to the surface changes the potential barrier height formed at the junctions and the carrier transport inside the straight semiconductors, which provide the ability of a given sensor array to differentiate among the junctions. The sensors were tested for their ability to distinguish three gases (H2, CO, and NO2), which they were able to do unequivocally when the data was classified using linear discriminant analysis. PMID:23841667

  19. Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells

    NASA Astrophysics Data System (ADS)

    Du, Shangfeng; Lin, Kaijie; Malladi, Sairam K.; Lu, Yaxiang; Sun, Shuhui; Xu, Qiang; Steinberger-Wilckens, Robert; Dong, Hanshan

    2014-09-01

    In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support surface, significantly promoting the uniform growth of tiny Pt nuclei which directs the growth of ultrathin single-crystal Pt nanowire (2.5-3 nm in diameter) arrays, forming a three-dimensional (3D) nano-architecture. Pt nanowire arrays in-situ grown on the large-area gas diffusion layer (GDL) (5 cm2) can be directly used as the catalyst electrode in fuel cells. The unique design brings in an extremely thin electrocatalyst layer, facilitating the charge transfer and mass transfer properties, leading to over two times higher power density than the conventional Pt nanoparticle catalyst electrode in real fuel cell environment. Due to the similar challenges faced with other nanostructures and the high availability of ASP for other material surfaces, this work will provide valuable insights and guidance towards the development of other new nano-architectures for various practical applications.

  20. Single crystalline cylindrical nanowires - toward dense 3D arrays of magnetic vortices.

    PubMed

    Ivanov, Yurii P; Chuvilin, Andrey; Vivas, Laura G; Kosel, Jurgen; Chubykalo-Fesenko, Oksana; Vázquez, Manuel

    2016-03-31

    Magnetic vortex-based media have recently been proposed for several applications of nanotechnology; however, because lithography is typically used for their preparation, their low-cost, large-scale fabrication is a challenge. One solution may be to use arrays of densely packed cobalt nanowires that have been efficiently fabricated by electrodeposition. In this work, we present this type of nanoscale magnetic structures that can hold multiple stable magnetic vortex domains at remanence with different chiralities. The stable vortex state is observed in arrays of monocrystalline cobalt nanowires with diameters as small as 45 nm and lengths longer than 200 nm with vanishing magnetic cross talk between closely packed neighboring wires in the array. Lorentz microscopy, electron holography and magnetic force microscopy, supported by micromagnetic simulations, show that the structure of the vortex state can be adjusted by varying the aspect ratio of the nanowires. The data we present here introduce a route toward the concept of 3-dimensional vortex-based magnetic memories.

  1. Single crystalline cylindrical nanowires – toward dense 3D arrays of magnetic vortices

    PubMed Central

    Ivanov, Yurii P.; Chuvilin, Andrey; Vivas, Laura G.; Kosel, Jurgen; Chubykalo-Fesenko, Oksana; Vázquez, Manuel

    2016-01-01

    Magnetic vortex-based media have recently been proposed for several applications of nanotechnology; however, because lithography is typically used for their preparation, their low-cost, large-scale fabrication is a challenge. One solution may be to use arrays of densely packed cobalt nanowires that have been efficiently fabricated by electrodeposition. In this work, we present this type of nanoscale magnetic structures that can hold multiple stable magnetic vortex domains at remanence with different chiralities. The stable vortex state is observed in arrays of monocrystalline cobalt nanowires with diameters as small as 45 nm and lengths longer than 200 nm with vanishing magnetic cross talk between closely packed neighboring wires in the array. Lorentz microscopy, electron holography and magnetic force microscopy, supported by micromagnetic simulations, show that the structure of the vortex state can be adjusted by varying the aspect ratio of the nanowires. The data we present here introduce a route toward the concept of 3-dimensional vortex-based magnetic memories. PMID:27030143

  2. Angular dependence of coercivity and remanence of Ni nanowire arrays and its relevance to magnetoviscosity

    NASA Astrophysics Data System (ADS)

    Günther, A.; Monz, S.; Tschöpe, A.; Birringer, R.; Michels, A.

    Ni nanowire arrays with varying wire dimensions (diameter d, length l) and center-to-center distances dCC were synthesized by pulsed electrodeposition of Ni in porous Al templates. The magnetization-reversal behavior of the arrays was investigated by means of magnetometry for different angles θ between the wire axes and the applied magnetic field. The functional dependences of the characteristic parameters coercivity HC( θ) and reduced remanence mR/mS( θ) exhibit a strong dependence on the wire dimensions and the center-to-center distance. For instance, for nanowire arrays with d=40 nm, dCC=100 nm, and for θ=0°, the coercivity takes on a rather large value of μ0HC=85 mT and mR/mS≅94%; reducing dCC to 30 nm and d to 17 nm results in μ0HC=49 mT and mR/mS≅57%, an observation which suggests an increasing magnetostatic interwire interaction at increased ( d/ dCC)-ratio. The potential application of nanowires as the constituents of ferrofluids is discussed.

  3. Wafer-scale assembly of highly ordered semiconductor nanowire arrays by contact printing.

    PubMed

    Fan, Zhiyong; Ho, Johnny C; Jacobson, Zachery A; Yerushalmi, Roie; Alley, Robert L; Razavi, Haleh; Javey, Ali

    2008-01-01

    Controlled and uniform assembly of "bottom-up" nanowire (NW) materials with high scalability presents one of the significant bottleneck challenges facing the integration of nanowires for electronic applications. Here, we demonstrate wafer-scale assembly of highly ordered, dense, and regular arrays of NWs with high uniformity and reproducibility through a simple contact printing process. The assembled NW pitch is shown to be readily modulated through the surface chemical treatment of the receiver substrate, with the highest density approaching approximately 8 NW/mum, approximately 95% directional alignment, and wafer-scale uniformity. Such fine control in the assembly is attained by applying a lubricant during the contact printing process which significantly minimizes the NW-NW mechanical interactions, therefore enabling well-controlled transfer of nanowires through surface chemical binding interactions. Furthermore, we demonstrate that our printing approach enables large-scale integration of NW arrays for various device structures on both rigid silicon and flexible plastic substrates, with a controlled semiconductor channel width ranging from a single NW ( approximately 10 nm) up to approximately 250 microm, consisting of a parallel array of over 1250 NWs and delivering over 1 mA of ON current.

  4. Direct electrodeposition of cable-like CuO@Cu nanowires array for non-enzymatic sensing.

    PubMed

    Dong, Junping; Ren, Linxiao; Zhang, Yuan; Cui, Xiaoli; Hu, Pengfei; Xu, Jiaqiang

    2015-01-01

    Vertically aligned cable-like CuO@Cu nanowires array was synthesized using a template-directed electrodeposition strategy. The morphology, crystal structure, and surface property of nanowires array were investigated by SEM, HRTEM, XRD, and XPS, respectively. It is found that the free standing namowires are highly dense, and possess about 20 μm in length and 200 nm in diameter. The bulk Cu nanowires are assembled by a number of single crystalline Cu nanoparticles and surface is wrapped by a thin layer of amorphous CuO with size of 2.5 nm. Electrocatalytic activity of the nanowires array towards glucose oxidation was investigated by cyclic voltammetry and amperometry in alkaline media. The nanowires array with 3×3 mm(2) was then used to fabricate a non-enzymatic glucose sensor. The sensor exhibits a wide concentration range of 1×10(-6)M-1×10(-2) M for glucose, with an ultra-high sensitivity of 1250.8 μA mM(-1) cm(-2) and excellent anti-interference ability. The good sensing performances could be attributed to the integration of the superior electrocatalysis of high density of Cu nanowires array and the outer shell of negatively charged CuO against interferences.

  5. Dense, Regular GaAs Nanowire Arrays by Catalyst-Free Vapor Phase Epitaxy for Light Harvesting.

    PubMed

    Jin, Jiehong; Stoica, Toma; Trellenkamp, Stefan; Chen, Yang; Anttu, Nicklas; Migunov, Vadim; Kawabata, Rudy M S; Buenconsejo, Pio J S; Lam, Yeng M; Haas, Fabian; Hardtdegen, Hilde; Grützmacher, Detlev; Kardynał, Beata E

    2016-08-31

    Density dependent growth and optical properties of periodic arrays of GaAs nanowires (NWs) by fast selective area growth MOVPE are investigated. As the period of the arrays is decreased from 500 nm down to 100 nm, a volume growth enhancement by a factor of up to four compared with the growth of a planar layer is observed. This increase is explained as resulting from increased collection of precursors on the side walls of the nanowires due to the gas flow redistribution in the space between the NWs. Normal spectral reflectance of the arrays is strongly reduced compared with a flat substrate surface in all fabricated arrays. Electromagnetic modeling reveals that this reduction is caused by antireflective action of the nanowire arrays and nanowire-diameter dependent light absorption. Irrespective of the periodicity and diameter, Raman scattering and grazing angle X-ray diffraction show signal from zinc blende and wurtzite phases, the latter originating from stacking faults as observed by high resolution transmission electron microscopy. Raman spectra contain intense surface phonons peaks, whose intensity depends strongly on the nanowire diameters as a result of potential structural changes and as well as variations of optical field distribution in the nanowires. PMID:27504951

  6. An ordered Si nanowire with NiSi2 tip arrays as excellent field emitters.

    PubMed

    Liu, Chun-Yi; Li, Wun-Shan; Chu, Li-Wei; Lu, Ming-Yen; Tsai, Cho-Jen; Chen, Lih-Juann

    2011-02-01

    A method was developed to grow ordered silicon nanowire with NiSi(2) tip arrays by reacting nickel thin films on silica-coated ordered Si nanowire (NW) arrays. The coating of thin silica shell on Si NW arrays has the effect of limiting the diffusion of nickel during the silicidation process to achieve the single crystalline NiSi(2) NWs. In the meantime, it relieves the distortion of the NWs caused by the strain associated with formation of NiSi(2) to maintain the straightness of the nanowire and the ordering of the arrays. Other nickel silicide phases such as Ni(2)Si and NiSi were obtained if the silicidation processes were conducted on the ordered Si NWs without a thin silica shell. Excellent field emission properties were found for NiSi(2)/Si NW arrays with a turn on field of 0.82 V µm(-1) and a threshold field of 1.39 V µm(-1). The field enhancement factor was calculated to be about 2440. The stability test showed a fluctuation of about 7% with an applied field of 2.6 V µm(-1) for a period of 24 h. The excellent field emission characteristics are attributed to the well-aligned and highly ordered arrangement of the single crystalline NiSi(2)/Si heterostructure field emitters. In contrast to other growth methods, the present growth of ordered nickel silicide/Si NWs on silicon is compatible with silicon nanoelectronics device processes, and also provides a facile route to grow other well-aligned metal silicide NW arrays. The advantages will facilitate its applications as field emission devices. PMID:21178255

  7. 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

  8. Bi-stable resistive switching in an array of nanowires

    NASA Astrophysics Data System (ADS)

    Gayen, Sirshendu; Sanyal, Milan K.; Sarma, Abhisakh; Satpati, Biswarup

    2015-01-01

    A resistive switching system comprising of metal-insulator-metal sandwich-structured nanowires embedded within polycarbonate membrane has been investigated. The system switches from non-Ohmic high resistive state (HRS) to Ohmic low resistive state on application of a critical bias of 2.5 V. The bipolar switching can be performed by applying current bias as well. Driving two suitable currents, and we observe highly reproducible switching between two stable resistive states. The switching is initiated by establishment of filamentary conduction path commonly formed in oxide materials. However, the main charge transport in the HRS is governed with modified activated behavior, which is obvious from the antisymmetric, reversible I-V characteristic following where a, b and are constants. The exponential term corresponds to charge generation by field-enhanced thermal activation process, whereas the linear term is related to mobility.

  9. Process Development of Gallium Nitride Phosphide Core-Shell Nanowire Array Solar Cell

    NASA Astrophysics Data System (ADS)

    Chuang, Chen

    Dilute Nitride GaNP is a promising materials for opto-electronic applications due to its band gap tunability. The efficiency of GaNxP1-x /GaNyP1-y core-shell nanowire solar cell (NWSC) is expected to reach as high as 44% by 1% N and 9% N in the core and shell, respectively. By developing such high efficiency NWSCs on silicon substrate, a further reduction of the cost of solar photovoltaic can be further reduced to 61$/MWh, which is competitive to levelized cost of electricity (LCOE) of fossil fuels. Therefore, a suitable NWSC structure and fabrication process need to be developed to achieve this promising NWSC. This thesis is devoted to the study on the development of fabrication process of GaNxP 1-x/GaNyP1-y core-shell Nanowire solar cell. The thesis is divided into two major parts. In the first parts, previously grown GaP/GaNyP1-y core-shell nanowire samples are used to develop the fabrication process of Gallium Nitride Phosphide nanowire solar cell. The design for nanowire arrays, passivation layer, polymeric filler spacer, transparent col- lecting layer and metal contact are discussed and fabricated. The property of these NWSCs are also characterized to point out the future development of Gal- lium Nitride Phosphide NWSC. In the second part, a nano-hole template made by nanosphere lithography is studied for selective area growth of nanowires to improve the structure of core-shell NWSC. The fabrication process of nano-hole templates and the results are presented. To have a consistent features of nano-hole tem- plate, the Taguchi Method is used to optimize the fabrication process of nano-hole templates.

  10. Thickness dependent self limiting 1-D tin oxide nanowire arrays by nanosecond pulsed laser irradiation

    SciTech Connect

    Shirato, N.; Strader, J.; Kumar, Amit; Vincent, A.; Zhang, P.; Karakoti, Ajay S.; Nachimuthu, Ponnusamy; Cho, H-J.; Seal, Sudipta; Kalyanaraman, R.

    2011-01-23

    Fast, sensitive and discriminating detection of hydrogen at room temperature is crucial for storage, transportation, and distribution of hydrogen as an energy source. One dimensional nanowires of SnO2 are potential candidates for improved H2 sensor performance. The single directional conducting continuous nanowires can decrease electrical noise, and their large active surface area could improve the response and recovery time of the sensor. In this work we discuss synthesis and characterization of nanowire arrays made using nanosecond ultraviolet wavelength (266 nm) laser interference processing of ultrathin SnO2 films on SiO2 substrates. The laser energy was chosen to be above the melting point of the films. The results show that the final nanowire formation is dominated by preferential evaporation as compared to thermocapillary flow. The nanowire height (and hence wire aspect ratio) increased with increasing initial film thickness ho and with increasing laser energy density Eo. Furthermore, a self-limiting effect was observed where-in the wire formation ceased at a specific final remaining thickness of SnO2 that was almost independent of ho for a given Eo. To understand these effects, finite element modeling of the nanoscale laser heating was performed. This showed that the temperature rise under laser heating was a strong non-monotonic function of film thickness. As a result, the preferential evaporation rate varies as wire formation occurs, eventually leading to a shut-off of evaporation at a characteristic thickness. This results in the stoppage of wire formation. This combination of nanosecond pulsed laser experiments and thermal modeling shows that several unique synthesis approaches can be utilized to control the nanowire characteristics.

  11. Temperature-dependent structure and phase variation of nickel silicide nanowire arrays prepared by in situ silicidation

    SciTech Connect

    Liu, Hailong; She, Guangwei; Mu, Lixuan; Shi, Wensheng

    2012-12-15

    Graphical abstract: Display Omitted Highlight: ► Nickel silicides nanowire arrays prepared by a simple in situ silicidation method. ► Phases of nickel silicides could be varied by tuning the reaction temperature. ► A growth model was proposed for the nickel silicides nanowires. ► Diffusion rates of Ni and Si play a critical role for the phase variation. -- Abstract: In this paper, we report an in situ silicidizing method to prepare nickel silicide nanowire arrays with varied structures and phases. The in situ reaction (silicidation) between Si and NiCl{sub 2} led to conversion of Si nanowires to nickel silicide nanowires. Structures and phases of the obtained nickel silicides could be varied by changing the reaction temperature. At a relatively lower temperature of 700 °C, the products are Si/NiSi core/shell nanowires or NiSi nanowires, depending on the concentration of NiCl{sub 2} solution. At a higher temperature (800 °C and 900 °C), other phases of the nickel silicides, including Ni{sub 2}Si, Ni{sub 31}Si{sub 12}, and NiSi{sub 2}, were obtained. It is proposed that the different diffusion rates of Ni and Si atoms at different temperatures played a critical role in the formation of nickel silicide nanowires with different phases.

  12. Manufacturing a nanowire-based sensing system via flow-guided assembly in a microchannel array template

    NASA Astrophysics Data System (ADS)

    Chen, Juan; Zu, Yingbo; Rajagopalan, Kartik Kumar; Wang, Shengnian

    2015-06-01

    A novel flow-guided assembly approach is presented to accurately align and position nanowire arrays in pre-defined locations with high throughput and large-scale manufacturing capability. In this approach, a polymer solution is first filled in an array of microfluidic channels. Then a gas flow is introduced to blow out most of the solution while pushing a little leftover against the channel wall for assembly into polymer nanowires. In this way, highly ordered nanowires are conveniently aligned in the flow direction and patterned along both sides of the microchannels. In this study, we demonstrated this flow-guided assembly process by producing millimetre-long nanowires across a 5 × 12 mm area in the same orientation and with basic ‘I-shape’, ‘T-shape’, and ‘cross’ patterns. The assembled polymer nanowires were further converted to conductive carbon nanowires through a standard carbonization process. After being integrated into electronic sensors, high sensitivity was found in model protein sensing tests. This new nanowire manufacturing approach is anticipated to open new doors to the fabrication of nanowire-based sensing systems and serve as good manufacturing practice for its simplicity, low cost, alignment reliability, and high throughput.

  13. Manufacturing a nanowire-based sensing system via flow-guided assembly in a microchannel array template.

    PubMed

    Chen, Juan; Zu, Yingbo; Kumar Rajagopalan, Kartik; Wang, Shengnian

    2015-06-12

    A novel flow-guided assembly approach is presented to accurately align and position nanowire arrays in pre-defined locations with high throughput and large-scale manufacturing capability. In this approach, a polymer solution is first filled in an array of microfluidic channels. Then a gas flow is introduced to blow out most of the solution while pushing a little leftover against the channel wall for assembly into polymer nanowires. In this way, highly ordered nanowires are conveniently aligned in the flow direction and patterned along both sides of the microchannels. In this study, we demonstrated this flow-guided assembly process by producing millimetre-long nanowires across a 5 × 12 mm area in the same orientation and with basic 'I-shape', 'T-shape', and 'cross' patterns. The assembled polymer nanowires were further converted to conductive carbon nanowires through a standard carbonization process. After being integrated into electronic sensors, high sensitivity was found in model protein sensing tests. This new nanowire manufacturing approach is anticipated to open new doors to the fabrication of nanowire-based sensing systems and serve as good manufacturing practice for its simplicity, low cost, alignment reliability, and high throughput.

  14. New Insights into the Origins of Sb-Induced Effects on Self-Catalyzed GaAsSb Nanowire Arrays.

    PubMed

    Ren, Dingding; Dheeraj, Dasa L; Jin, Chengjun; Nilsen, Julie S; Huh, Junghwan; Reinertsen, Johannes F; Munshi, A Mazid; Gustafsson, Anders; van Helvoort, Antonius T J; Weman, Helge; Fimland, Bjørn-Ove

    2016-02-10

    Ternary semiconductor nanowire arrays enable scalable fabrication of nano-optoelectronic devices with tunable bandgap. However, the lack of insight into the effects of the incorporation of Vy element results in lack of control on the growth of ternary III-V(1-y)Vy nanowires and hinders the development of high-performance nanowire devices based on such ternaries. Here, we report on the origins of Sb-induced effects affecting the morphology and crystal structure of self-catalyzed GaAsSb nanowire arrays. The nanowire growth by molecular beam epitaxy is changed both kinetically and thermodynamically by the introduction of Sb. An anomalous decrease of the axial growth rate with increased Sb2 flux is found to be due to both the indirect kinetic influence via the Ga adatom diffusion induced catalyst geometry evolution and the direct composition modulation. From the fundamental growth analyses and the crystal phase evolution mechanism proposed in this Letter, the phase transition/stability in catalyst-assisted ternary III-V-V nanowire growth can be well explained. Wavelength tunability with good homogeneity of the optical emission from the self-catalyzed GaAsSb nanowire arrays with high crystal phase purity is demonstrated by only adjusting the Sb2 flux. PMID:26726825

  15. Enhanced field emission from ZnO nanowire arrays utilizing MgO buffer between seed layer and silicon substrate

    NASA Astrophysics Data System (ADS)

    Chen, Si; Chen, Jiangtao; Liu, Jianlin; Qi, Jing; Wang, Yuhua

    2016-11-01

    Field emitters based on ZnO nanowires and other nanomaterials are promising high-brightness electron sources for field emission display, microscopy and other applications. The performance of a ZnO nanowire field emitter is linked to the quality, conductivity and alignment of the nanowires on a substrate, therefore requiring ways to improve these parameters. Here, ZnO nanowire arrays were grown on ZnO seed layer on silicon substrate with MgO buffer between the seed layer and Si. The turn-on field and enhancement factor of these nanowire arrays are 3.79 V/μm and 3754, respectively. These properties are improved greatly compared to those of ZnO nanowire arrays grown on ZnO seed layer without MgO buffer, which are 5.06 V/μm and 1697, respectively. The enhanced field emission properties can be attributed to better electron transport in seed layer, and better nanowire alignment because of MgO buffer.

  16. Study of the magnetization behavior of ferromagnetic nanowire array: Existence of growth defects revealed by micromagnetic simulations

    NASA Astrophysics Data System (ADS)

    Nguyen Vien, G.; Rioual, S.; Gloaguen, F.; Rouvellou, B.; Lescop, B.

    2016-03-01

    High aspect ratio nanowires were electrodeposited in nanoporous anodic alumina template by a potentiostatic method. The angular dependence of the coercive field and remanence magnetization extracted from magnetometry measurements are compared with micromagnetic simulations. Inclusion of magnetostatic interactions between Ni nanowires in simulations is required to explain some of the properties of the magnetization reversal. However, it is not sufficient to reproduce fully the angular dependence of the coercive field. Due to the polycrystalline nature of nanowires and thus to the presence of grain boundaries, defects are included in simulations. A good agreement between theory and experiment is then clearly highlighted, in particular in the nanowire easy axis direction. The achieved results allow a description of several experimental data published in the literature and consequently to get a better understanding of reversal mechanisms that operate in such nanowire arrays. A complementary study of composite nanowire array is successfully performed to prove the adequacy of the simulations method to describe the magnetic properties of nanowire array.

  17. Raman spectroscopy and electrical properties of InAs nanowires with local oxidation enabled by substrate micro-trenches and laser irradiation

    SciTech Connect

    Tanta, R.; Krogstrup, P.; Nygård, J.; Jespersen, T. S.; Madsen, M. H.; Liao, Z.; Vosch, T.

    2015-12-14

    The thermal gradients along indium arsenide nanowires were engineered by a combination of fabricated micro-trenches in the supporting substrate and focused laser irradiation. This allowed local spatial control of thermally activated oxidation reactions of the nanowire on the scale of the diffraction limit. The locality of the oxidation was detected by micro-Raman mapping, and the results were found to be consistent with numerical simulations of the temperature profile. Applying the technique to nanowires in electrical devices the locally oxidized nanowires remained conducting with a lower conductance as expected for an effectively thinner conducting core.

  18. Raman spectroscopy and electrical properties of InAs nanowires with local oxidation enabled by substrate micro-trenches and laser irradiation

    NASA Astrophysics Data System (ADS)

    Tanta, R.; Madsen, M. H.; Liao, Z.; Krogstrup, P.; Vosch, T.; Nygârd, J.; Jespersen, T. S.

    2015-12-01

    The thermal gradients along indium arsenide nanowires were engineered by a combination of fabricated micro-trenches in the supporting substrate and focused laser irradiation. This allowed local spatial control of thermally activated oxidation reactions of the nanowire on the scale of the diffraction limit. The locality of the oxidation was detected by micro-Raman mapping, and the results were found to be consistent with numerical simulations of the temperature profile. Applying the technique to nanowires in electrical devices the locally oxidized nanowires remained conducting with a lower conductance as expected for an effectively thinner conducting core.

  19. Synthesis of ordered ZnO nanowire arrays from aqueous solution using AAO template

    NASA Astrophysics Data System (ADS)

    Kumar, Nagesh; Varma, G. D.; Nath, R.; Srivastava, A. K.

    2011-09-01

    In this paper we report a simple method that enables the easy fabrication of ordered ZnO nanowire arrays using Anodic Aluminium Oxide (AAO) template. We have used a vacuum injection technique to fill solution into the pores of an AAO template. The AAO template has been fabricated by a two-step anodization process using 0.3 M oxalic acid (H2C2O4) solution under a constant voltage of 40 V. The AAO template formed through this process has been detached from Al substrate via an anodic voltage pulse using perchloric acid (HClO4) solution (70%). The nanowires of ZnO have been synthesized by injecting the saturated Zn(NO3)2 solution into the pores of the detached AAO template using a vacuum pump. The ZnO nanowires synthesized by this technique have been found dense & continuous with uniform diameter throughout the length of the wire. The structural characteristics of AAO template and ZnO nanowires have been studied by Field Emission Scanning Electron Microscope (FESEM), Atomic force microscope (AFM) and Transmission Electron Microscope (TEM).

  20. Fabrication of single crystalline, uniaxial single domain Co nanowire arrays with high coercivity

    NASA Astrophysics Data System (ADS)

    Ramazani, A.; Almasi Kashi, M.; Montazer, A. H.

    2014-03-01

    Whilst Co nanorods with high coercivity were synthesized during recent years, they did not achieve the same results as for Co nanowires embedded in solid templates. In the present work, Co nanowire arrays (NWAs) with high coercivity were successfully fabricated in porous aluminum oxide template under optimum conditions by using pulsed ac electrodeposition technique. Magnetic properties and crystalline characteristics of the nanowires were investigated by hysteresis loop measurements, first-order reversal curve (FORC) analysis, X-ray diffraction (XRD), and selected area electron diffraction (SAED) patterns. Hysteresis loop measurements showed high coercivity of about 4.8 kOe at room temperature together with optimum squareness of 1, resulting in an increase of the previous maximum coercivity for Co NWAs up to 45%. XRD and SAED patterns revealed a single crystalline texture along the [0002] direction, indicating the large magnetocrystalline anisotropy. On the other hand, FORC analysis confirmed a single domain structure for the Co NWAs. In addition, the reversal mechanism of the single crystalline, single domain Co NWAs was studied which resulted in the fixed easy axis with a coherent rotation. Accordingly, these nanowires might offer promising applications in high density bit patterned media and low power logic devices.

  1. Fabrication of single crystalline, uniaxial single domain Co nanowire arrays with high coercivity

    SciTech Connect

    Ramazani, A. Almasi Kashi, M.; Montazer, A. H.

    2014-03-21

    Whilst Co nanorods with high coercivity were synthesized during recent years, they did not achieve the same results as for Co nanowires embedded in solid templates. In the present work, Co nanowire arrays (NWAs) with high coercivity were successfully fabricated in porous aluminum oxide template under optimum conditions by using pulsed ac electrodeposition technique. Magnetic properties and crystalline characteristics of the nanowires were investigated by hysteresis loop measurements, first-order reversal curve (FORC) analysis, X-ray diffraction (XRD), and selected area electron diffraction (SAED) patterns. Hysteresis loop measurements showed high coercivity of about 4.8 kOe at room temperature together with optimum squareness of 1, resulting in an increase of the previous maximum coercivity for Co NWAs up to 45%. XRD and SAED patterns revealed a single crystalline texture along the [0002] direction, indicating the large magnetocrystalline anisotropy. On the other hand, FORC analysis confirmed a single domain structure for the Co NWAs. In addition, the reversal mechanism of the single crystalline, single domain Co NWAs was studied which resulted in the fixed easy axis with a coherent rotation. Accordingly, these nanowires might offer promising applications in high density bit patterned media and low power logic devices.

  2. 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

  3. 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

  4. Synthesis and field emission of β-SiC nanowires on silicon nanoporous pillar array

    NASA Astrophysics Data System (ADS)

    Wang, Haiyan; Li, Zijiong; Kang, Liping; Li, Xinjian

    2012-10-01

    Nonaligned β-SiC nanowires (nw-SiC) were grown on silicon nanoporous pillar array (Si-NPA) by a chemical vapor deposition (CVD) method with nickel as the catalyst. The curly hair like SiC nanowires and the silicon pillar array formed a nanometer-micron hierarchy structure. The field-emission measurements to nw-SiC/Si-NPA showed that a lower turn-on field of 2.9 V μm-1 was obtained, and the enhancement factor of nw-SiC/Si-NPA according to the Fowler-Nordheim (F-N) theory reached 5200. The excellent field-emission performance was attributed to the nanometer-micron hierarchy structure of nw-SiC/Si-NPA, including the high aspect ratio of the SiC nanowires and the regular surface undulation of Si-NPA which increased the emission sites density and might have reduced the electrostatic shielding among the emitters.

  5. Controlled Growth of Platinum Nanowire Arrays on Sulfur Doped Graphene as High Performance Electrocatalyst

    PubMed Central

    Wang, Rongyue; Higgins, Drew C.; Hoque, Md Ariful; Lee, DongUn; Hassan, Fathy; Chen, Zhongwei

    2013-01-01

    Graphene supported Pt nanostructures have great potential to be used as catalysts in electrochemical energy conversion and storage technologies; however the simultaneous control of Pt morphology and dispersion, along with ideally tailoring the physical properties of the catalyst support properties has proven very challenging. Using sulfur doped graphene (SG) as a support material, the heterogeneous dopant atoms could serve as nucleation sites allowing for the preparation of SG supported Pt nanowire arrays with ultra-thin diameters (2–5 nm) and dense surface coverage. Detailed investigation of the preparation technique reveals that the structure of the resulting composite could be readily controlled by fine tuning the Pt nanowire nucleation and growth reaction kinetics and the Pt-support interactions, whereby a mechanistic platinum nanowire array growth model is proposed. Electrochemical characterization demonstrates that the composite materials have 2–3 times higher catalytic activities toward the oxygen reduction and methanol oxidation reaction compared with commercial Pt/C catalyst. PMID:23942256

  6. Selective growth of vertical silicon nanowire array guided by anodic aluminum oxide template

    NASA Astrophysics Data System (ADS)

    Hoang Nguyen, Van; Hoshi, Yusuke; Usami, Noritaka; Konagai, Makoto

    2015-09-01

    We report on the selective growth of vertical silicon nanowire arrays guided by an anodic aluminum oxide (AAO) template without the introduction of any metallic catalyst. Gas-source molecular beam epitaxy using disilane as a source gas was carried out. The growth conditions such as flow rate and growth temperature were changed to optimize the Si nanowire growth. It was found that the selective growth was promoted at a flow rate of 0.5 sccm, whereas the selective growth was poor at high flow rates of 1 and 2 sccm. One-micrometer-long Si nanowire arrays were obtained at a low flow rate of 0.5 sccm only at the growth temperature of 700 °C. The obtained Si grown at a temperature of 650 °C exhibited conglomerated structures with Si grains piled up inside the nanopores of the AAO template. We found that increasing the growth temperature and decreasing the flow rate are useful for improving the growth selectivity.

  7. 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).

  8. 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).

  9. 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

  10. A four-pixel single-photon pulse-position array fabricated from WSi superconducting nanowire single-photon detectors

    SciTech Connect

    Verma, V. B. Horansky, R.; Lita, A. E.; Mirin, R. P.; Nam, S. W.; Marsili, F.; Stern, J. A.; Shaw, M. D.

    2014-02-03

    We demonstrate a scalable readout scheme for an infrared single-photon pulse-position camera consisting of WSi superconducting nanowire single-photon detectors. For an N × N array, only 2 × N wires are required to obtain the position of a detection event. As a proof-of-principle, we show results from a 2 × 2 array.

  11. Ultra-dense silicon nanowire array solar cells by nanoimprint lithography

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Liu, Pei; Siontas, Stylianos; Zaslavsky, Alexander; Pacifici, Domenico; Ha, Jong-Yoon; Krylyuk, Sergiy; Davydov, Albert

    Nanowire (NW) solar cells have been attracting increasing interest due to their potentially superior light absorption compared to thin bulk films. In order to improve light trapping, we have used nanoimprint lithography (NIL) to fabricate high-density NW arrays with deep sub-micron pitch (P) and diameter (D). We have grown dense vertical arrays of Si axial p - i - n junction NWs of D = 170 nm and P = 500 nm by vapor-liquid-solid epitaxy on seed arrays produced by NIL. The NWs were 9 µm length long with a 5 µm intrinsic section. The NW arrays were planarized using SU-8 photoresist, followed by reactive ion etching to expose the NW tips. Top n-contact was realized by sputter deposition of a transparent 200 nm IZO layer. The nanoimprinted NW array samples measured under AM 1.5 G illumination showed a peak external quantum efficiency of ~8% and internal quantum efficiency of ~90% in the visible spectral range. Three-dimensional finite-difference time-domain simulations of Si NW periodic arrays with varying P confirm the importance of high NW density. Specifically, due to diffractive scattering and light trapping, absorption efficiency close to 100% in the 400-650 nm spectral range is predicted for a Si NW array with an even smaller P = 250 nm, significantly outperforming a blanket Si film of the same thickness. Such pitch values are accessible to NIL and work on such arrays is in progress. National Science Foundation.

  12. High Density n-Si/n-TiO2 Core/Shell Nanowire Arrays with Enhanced Photoactivity

    SciTech Connect

    Hwang, Yun Jeong; Boukai, Akram; Yang, Peidong

    2008-11-15

    There are currently great needs to develop low-cost inorganic materials that can efficiently perform solar water splitting as photoelectrolysis of water into hydrogen and oxygen has significant potential to provide clean energy. We investigate the Si/TiO2 nanowire heterostructures to determine their potential for the photooxidation of water. We observed that highly dense Si/TiO2 core/shell nanowire arrays enhanced the photocurrent by 2.5 times compared to planar Si/TiO2 structure due to their low reflectance and high surface area. We also showed that n-Si/n-TiO2 nanowire arrays exhibited a larger photocurrent and open circuit voltage than p-Si/n-TiO2 nanowires due to a barrier at the heterojunction.

  13. Design for strong absorption in a nanowire array tandem solar cell

    NASA Astrophysics Data System (ADS)

    Chen, Yang; Pistol, Mats-Erik; Anttu, Nicklas

    2016-08-01

    Semiconductor nanowires are a promising candidate for next-generation solar cells. However, the optical response of nanowires is, due to diffraction effects, complicated to optimize. Here, we optimize through optical modeling the absorption in a dual-junction nanowire-array solar cell in terms of the Shockley-Quessier detailed balance efficiency limit. We identify efficiency maxima that originate from resonant absorption of photons through the HE11 and the HE12 waveguide modes in the top cell. An efficiency limit above 40% is reached in the band gap optimized Al0.10Ga0.90As/In0.34Ga0.66As system when we allow for different diameter for the top and the bottom nanowire subcell. However, for experiments, equal diameter for the top and the bottom cell might be easier to realize. In this case, we find in our modeling a modest 1–2% drop in the efficiency limit. In the Ga0.51In0.49P/InP system, an efficiency limit of η = 37.3% could be reached. These efficiencies, which include reflection losses and sub-optimal absorption, are well above the 31.0% limit of a perfectly-absorbing, idealized single-junction bulk cell, and close to the 42.0% limit of the idealized dual-junction bulk cell. Our results offer guidance in the choice of materials and dimensions for nanowires with potential for high efficiency tandem solar cells.

  14. Design for strong absorption in a nanowire array tandem solar cell.

    PubMed

    Chen, Yang; Pistol, Mats-Erik; Anttu, Nicklas

    2016-08-30

    Semiconductor nanowires are a promising candidate for next-generation solar cells. However, the optical response of nanowires is, due to diffraction effects, complicated to optimize. Here, we optimize through optical modeling the absorption in a dual-junction nanowire-array solar cell in terms of the Shockley-Quessier detailed balance efficiency limit. We identify efficiency maxima that originate from resonant absorption of photons through the HE11 and the HE12 waveguide modes in the top cell. An efficiency limit above 40% is reached in the band gap optimized Al0.10Ga0.90As/In0.34Ga0.66As system when we allow for different diameter for the top and the bottom nanowire subcell. However, for experiments, equal diameter for the top and the bottom cell might be easier to realize. In this case, we find in our modeling a modest 1-2% drop in the efficiency limit. In the Ga0.51In0.49P/InP system, an efficiency limit of η = 37.3% could be reached. These efficiencies, which include reflection losses and sub-optimal absorption, are well above the 31.0% limit of a perfectly-absorbing, idealized single-junction bulk cell, and close to the 42.0% limit of the idealized dual-junction bulk cell. Our results offer guidance in the choice of materials and dimensions for nanowires with potential for high efficiency tandem solar cells.

  15. Design for strong absorption in a nanowire array tandem solar cell

    PubMed Central

    Chen, Yang; Pistol, Mats-Erik; Anttu, Nicklas

    2016-01-01

    Semiconductor nanowires are a promising candidate for next-generation solar cells. However, the optical response of nanowires is, due to diffraction effects, complicated to optimize. Here, we optimize through optical modeling the absorption in a dual-junction nanowire-array solar cell in terms of the Shockley-Quessier detailed balance efficiency limit. We identify efficiency maxima that originate from resonant absorption of photons through the HE11 and the HE12 waveguide modes in the top cell. An efficiency limit above 40% is reached in the band gap optimized Al0.10Ga0.90As/In0.34Ga0.66As system when we allow for different diameter for the top and the bottom nanowire subcell. However, for experiments, equal diameter for the top and the bottom cell might be easier to realize. In this case, we find in our modeling a modest 1–2% drop in the efficiency limit. In the Ga0.51In0.49P/InP system, an efficiency limit of η = 37.3% could be reached. These efficiencies, which include reflection losses and sub-optimal absorption, are well above the 31.0% limit of a perfectly-absorbing, idealized single-junction bulk cell, and close to the 42.0% limit of the idealized dual-junction bulk cell. Our results offer guidance in the choice of materials and dimensions for nanowires with potential for high efficiency tandem solar cells. PMID:27574019

  16. Design for strong absorption in a nanowire array tandem solar cell.

    PubMed

    Chen, Yang; Pistol, Mats-Erik; Anttu, Nicklas

    2016-01-01

    Semiconductor nanowires are a promising candidate for next-generation solar cells. However, the optical response of nanowires is, due to diffraction effects, complicated to optimize. Here, we optimize through optical modeling the absorption in a dual-junction nanowire-array solar cell in terms of the Shockley-Quessier detailed balance efficiency limit. We identify efficiency maxima that originate from resonant absorption of photons through the HE11 and the HE12 waveguide modes in the top cell. An efficiency limit above 40% is reached in the band gap optimized Al0.10Ga0.90As/In0.34Ga0.66As system when we allow for different diameter for the top and the bottom nanowire subcell. However, for experiments, equal diameter for the top and the bottom cell might be easier to realize. In this case, we find in our modeling a modest 1-2% drop in the efficiency limit. In the Ga0.51In0.49P/InP system, an efficiency limit of η = 37.3% could be reached. These efficiencies, which include reflection losses and sub-optimal absorption, are well above the 31.0% limit of a perfectly-absorbing, idealized single-junction bulk cell, and close to the 42.0% limit of the idealized dual-junction bulk cell. Our results offer guidance in the choice of materials and dimensions for nanowires with potential for high efficiency tandem solar cells. PMID:27574019

  17. Sensitive and Selective Detection of HIV-1 RRE RNA Using Vertical Silicon Nanowire Electrode Array

    NASA Astrophysics Data System (ADS)

    Lee, Jaehyung; Hong, Min-Ho; Han, Sanghun; Na, Jukwan; Kim, Ilsoo; Kwon, Yong-Joon; Lim, Yong-beom; Choi, Heon-Jin

    2016-07-01

    In this study, HIV-1 Rev response element (RRE) RNA was detected via an Au-coated vertical silicon nanowire electrode array (VSNEA). The VSNEA was fabricated by combining bottom-up and top-down approaches and then immobilized by artificial peptides for the recognition of HIV-1 RRE. Differential pulse voltammetry (DPV) analysis was used to measure the electrochemical response of the peptide-immobilized VSNEA to the concentration and types of HIV-1 RRE RNA. DPV peaks showed linearity to the concentration of RNA with a detection limit down to 1.513 fM. It also showed the clear different peaks to the mutated HIV-1 RRE RNA. The high sensitivity and selectivity of VSNEA for the detection of HIV-1 RRE RNA may be attributed to the high surface-to-volume ratio and total overlap diffusion mode of ions of the one-dimensional nanowire electrodes.

  18. Vertical nanowire electrode arrays as a scalable platform for intracellular interfacing to neuronal circuits

    PubMed Central

    Robinson, Jacob T.; Jorgolli, Marsela; Shalek, Alex K.; Yoon, Myung-Han; Gertner, Rona S.; Park, Hongkun

    2014-01-01

    Deciphering the neuronal code - the rules by which neuronal circuits store and process information - is a major scientific challenge1,2. Currently, these efforts are impeded by a lack of experimental tools that are sensitive enough to quantify the strength of individual synaptic connections and also scalable enough to simultaneously measure and control a large number of mammalian neurons with single-cell resolution3,4. Here, we report a scalable intracellular electrode platform based on vertical nanowires that affords parallel electrical interfacing to multiple mammalian neurons. Specifically, we show that our vertical nanowire electrode arrays (VNEAs) can intracellularly record and stimulate neuronal activity in dissociated cultures of rat cortical neurons and can also be used to map multiple individual synaptic connections. The scalability of this platform, combined with its compatibility with silicon nanofabrication techniques, provides a clear path toward simultaneous, high-fidelity interfacing with hundreds of individual neurons. PMID:22231664

  19. Sensitive and Selective Detection of HIV-1 RRE RNA Using Vertical Silicon Nanowire Electrode Array.

    PubMed

    Lee, Jaehyung; Hong, Min-Ho; Han, Sanghun; Na, Jukwan; Kim, Ilsoo; Kwon, Yong-Joon; Lim, Yong-Beom; Choi, Heon-Jin

    2016-12-01

    In this study, HIV-1 Rev response element (RRE) RNA was detected via an Au-coated vertical silicon nanowire electrode array (VSNEA). The VSNEA was fabricated by combining bottom-up and top-down approaches and then immobilized by artificial peptides for the recognition of HIV-1 RRE. Differential pulse voltammetry (DPV) analysis was used to measure the electrochemical response of the peptide-immobilized VSNEA to the concentration and types of HIV-1 RRE RNA. DPV peaks showed linearity to the concentration of RNA with a detection limit down to 1.513 fM. It also showed the clear different peaks to the mutated HIV-1 RRE RNA. The high sensitivity and selectivity of VSNEA for the detection of HIV-1 RRE RNA may be attributed to the high surface-to-volume ratio and total overlap diffusion mode of ions of the one-dimensional nanowire electrodes.

  20. Combined flame and electrodeposition synthesis of energetic coaxial tungsten-oxide/aluminum nanowire arrays.

    PubMed

    Dong, Zhizhong; Al-Sharab, Jafar F; Kear, Bernard H; Tse, Stephen D

    2013-09-11

    A nanostructured thermite composite comprising an array of tungsten-oxide (WO2.9) nanowires (diameters of 20-50 nm and lengths of >10 μm) coated with single-crystal aluminum (thickness of ~16 nm) has been fabricated. The method involves combined flame synthesis of tungsten-oxide nanowires and ionic-liquid electrodeposition of aluminum. The geometry not only presents an avenue to tailor heat-release characteristics due to anisotropic arrangement of fuel and oxidizer but also eliminates or minimizes the presence of an interfacial Al2O3 passivation layer. Upon ignition, the energetic nanocomposite exhibits strong exothermicity, thereby being useful for fundamental study of aluminothermic reactions as well as enhancing combustion characteristics.

  1. Nanoimprint-lithography patterned epitaxial Fe nanowire arrays with misaligned magnetocrystalline and shape anisotropies

    SciTech Connect

    Zhang, Wei; Bowden, Mark E.; Krishnan, Kannan M.

    2013-01-01

    We fabricated large area (>1 × 1 cm2), epitaxial Fe nanowire arrays on MgO(001) substrates by nanoimprint lithography with a direct metallization of epitaxial materials through a metallic mask, which avoided the disadvantageous metal-etching process in conventional methods. The magnetization reversals, as revealed by magneto-optic Kerr effect, showed competing effects between Fe cubic magnetocrystalline anisotropy and lithographically induced uniaxial shape anisotropy. Unlike the weakly induced uniaxial anisotropy observed in continuous films, both the magnitude and direction of the uniaxial shape anisotropy can be easily modulated in the nanowires. Complex magnetization reversal processes including two-step and three-step loops were observed when magnetizing the samples along different Fe cubic easy axes, respectively. Finally, these modified magnetization reversal processes were explained by the nucleation and propagation of the domain walls along the non-superimposed easy axes of the competing magnetocrystalline and shape anisotropies.

  2. A Robust Highly Aligned DNA Nanowire Array-Enabled Lithography for Graphene Nanoribbon Transistors.

    PubMed

    Kang, Seok Hee; Hwang, Wan Sik; Lin, Zhiqun; Kwon, Se Hun; Hong, Suck Won

    2015-12-01

    Because of its excellent charge carrier mobility at the Dirac point, graphene possesses exceptional properties for high-performance devices. Of particular interest is the potential use of graphene nanoribbons or graphene nanomesh for field-effect transistors. Herein, highly aligned DNA nanowire arrays were crafted by flow-assisted self-assembly of a drop of DNA aqueous solution on a flat polymer substrate. Subsequently, they were exploited as "ink" and transfer-printed on chemical vapor deposited (CVD)-grown graphene substrate. The oriented DNA nanowires served as the lithographic resist for selective removal of graphene, forming highly aligned graphene nanoribbons. Intriguingly, these graphene nanoribbons can be readily produced over a large area (i.e., millimeter scale) with a high degree of feature-size controllability and a low level of defects, rendering the fabrication of flexible two terminal devices and field-effect transistors.

  3. Vertically p-n-junctioned GaN nano-wire array diode fabricated on Si(111) using MOCVD.

    PubMed

    Park, Ji-Hyeon; Kim, Min-Hee; Kissinger, Suthan; Lee, Cheul-Ro

    2013-04-01

    We demonstrate the fabrication of n-GaN:Si/p-GaN:Mg nanowire arrays on (111) silicon substrate by metal organic chemical vapor deposition (MOCVD) method .The nanowires were grown by a newly developed two-step growth process. The diameter of as-grown nanowires ranges from 300-400 nm with a density of 6-7 × 10(7) cm(-2). The p- and n-type doping of the nanowires is achieved with Mg and Si dopant species. Structural characterization by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) indicates that the nanowires are relatively defect-free. The room-temperature photoluminescence emission with a strong peak at 370 nm indicates that the n-GaN:Si/p-GaN:Mg nanowire arrays have potential application in light-emitting nanodevices. The cathodoluminscence (CL) spectrum clearly shows a distinct optical transition of GaN nanodiodes. The nano-n-GaN:Si/p-GaN:Mg diodes were further completed using a sputter coating approach to deposit Au/Ni metal contacts. The polysilazane filler has been etched by a wet chemical etching process. The n-GaN:Si/p-GaN:Mg nanowire diode was fabricated for different Mg source flow rates. The current-voltage (I-V) measurements reveal excellent rectifying properties with an obvious turn-on voltage at 1.6 V for a Mg flow rate of 5 sccm (standard cubic centimeters per minute).

  4. Carbonization-assisted integration of silica nanowires to photoresist-derived three-dimensional carbon microelectrode arrays

    NASA Astrophysics Data System (ADS)

    Liu, Dan; Shi, Tielin; Tang, Zirong; Zhang, Lei; Xi, Shuang; Li, Xiaoping; Lai, Wuxing

    2011-11-01

    We propose a novel technique of integrating silica nanowires to carbon microelectrode arrays on silicon substrates. The silica nanowires were grown on photoresist-derived three-dimensional carbon microelectrode arrays during carbonization of patterned photoresist in a tube furnace at 1000 °C under a gaseous environment of N2 and H2 in the presence of Cu catalyst, sputtered initially as a thin layer on the structure surface. Carbonization-assisted nucleation and growth are proposed to extend the Cu-catalyzed vapor-liquid-solid mechanism for the nanowire integration behaviour. The growth of silica nanowires exploits Si from the etched silicon substrate under the Cu particles. It is found that the thickness of the initial Cu coating layer plays an important role as catalyst on the morphology and on the amount of grown silica nanowires. These nanowires have lengths of up to 100 µm and diameters ranging from 50 to 200 nm, with 30 nm Cu film sputtered initially. The study also reveals that the nanowire-integrated microelectrodes significantly enhance the electrochemical performance compared to blank ones. A specific capacitance increase of over 13 times is demonstrated in the electrochemical experiment. The platform can be used to develop large-scale miniaturized devices and systems with increased efficiency for applications in electrochemical, biological and energy-related fields.

  5. 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.

  6. CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: The effect of substrate on magnetic properties of Co/Cu multilayer nanowire arrays

    NASA Astrophysics Data System (ADS)

    Ren, Yong; Wang, Jian-Bo; Liu, Qing-Fang; Han, Xiang-Hua; Xue, De-Sheng

    2009-08-01

    Ordered Co/Cu multilayer nanowire arrays have been fabricated into anodic aluminium oxide templates with Ag and Cu substrate by direct current electrodeposition. This paper studies the morphology, structure and magnetic properties by transmission electron microscopy, selective area electron diffraction, x-ray diffraction, and vibrating sample magnetometer. X-ray diffraction patterns reveal that both as-deposited nanowire arrays films exhibit face-centred cubic structure. Magnetic measurements indicate that the easy magnetization direction of Co/Cu multilayer nanowire arrays films on Ag substrate is perpendicular to the long axis of nanowire, whereas the easy magnetization direction of the sample with Cu substrate is parallel to the long axis of nanowire. The change of easy magnetization direction attributed to different substrates, and the magnetic properties of the nanowire arrays are discussed.

  7. Magnetic properties of planar nanowire arrays of Co fabricated on oxidized step-bunched silicon templates.

    PubMed

    Arora, S K; O'Dowd, B J; Ballesteros, B; Gambardella, P; Shvets, I V

    2012-06-15

    Planar nanowire (NW) arrays of Co grown on oxidized step-bunched Si(111) templates exhibit room temperature ferromagnetic behaviour for wire widths down to 25 nm. Temperature and thickness dependent magnetization studies on these polycrystalline NW arrays show that the magnetic anisotropy of the NW array is dominated by shape anisotropy, which keeps the magnetization in-plane with easy axis parallel to the wires. This shape related uniaxial anisotropy is preserved even at low temperatures (10 K). Thickness dependent studies reveal that the magnetization reversal is governed by the curling mode reversal for thick wires whereas thinner wires exhibit a more complex behaviour which is related to thermal effects and size distribution of the crystal grains that constitute the NWs.

  8. Influence of the adatom diffusion on selective growth of GaN nanowire regular arrays

    SciTech Connect

    Gotschke, T.; Schumann, T.; Limbach, F.; Calarco, R.; Stoica, T.

    2011-03-07

    Molecular beam epitaxy (MBE) on patterned Si/AlN/Si(111) substrates was used to obtain regular arrays of uniform-size GaN nanowires (NWs). The silicon top layer has been patterned with e-beam lithography, resulting in uniform arrays of holes with different diameters (d{sub h}) and periods (P). While the NW length is almost insensitive to the array parameters, the diameter increases significantly with d{sub h} and P till it saturates at P values higher than 800 nm. A diffusion induced model was used to explain the experimental results with an effective diffusion length of the adatoms on the Si, estimated to be about 400 nm.

  9. Broadband light absorption of silicon nanowires embedded in Ag nano-hole arrays

    NASA Astrophysics Data System (ADS)

    Rao, Lei; Ji, Chun-Lei; Li, Ming

    2016-09-01

    Silicon nanowires (SiNWs) embedded in Ag nano-hole arrays with broadband light absorption is proposed in this paper. Finite Difference Time Domain (FDTD) simulations were utilized to obtain absorptivity and band diagrams for both SiNWs and SiNWs embedded in Ag nano-hole arrays. A direct relationship between waveguide modes and extraordinary absorptivity is established qualitatively, which helps to optimal design the structure parameters to achieve broadband absorptivity. After introducing Ag nano-hole arrays at the rear side of SiNWs, the band modes are extended into leaky regions and light energy can be fully absorbed, resulting in high absorptivity at long wavelength. Severe reflection is also suppressed by light trapping capability of SiNWs at short wavelength. Over 70% average absorptivity from 400 nm to 1100 nm is realized finally. This kinds of design give promising route for high efficiency solar cells and optical absorbers.

  10. Microscopic structure and magnetic behavior of arrays of electrodeposited Ni and Fe nanowires

    SciTech Connect

    Xu, X.; Zangari, G.

    2005-05-15

    Arrays of Ni and Fe nanowires with length up to 6 {mu}m were fabricated by voltage controlled electrodeposition within track etched polycarbonate membranes with nominal pore diameter 50 nm, using dc or pulsed voltage. Magnetostatic interactions between wires are found to be important in determining magnetic properties and switching processes. Ni arrays switch by quasicoherent rotation when the magnetic field is applied near to the average wire axis, and by curling at large angles. The importance of curling processes increases with wire length, due to the larger demagnetizing field. The properties of Fe wires are dominated by magnetostatic interactions; these arrays switch by curling and no definite easy axis is observed in pulse-plated, amorphous wires.

  11. Synthesis and characterizations of ternary InGaAs nanowires by a two-step growth method for high-performance electronic devices.

    PubMed

    Hou, Jared J; Han, Ning; Wang, Fengyun; Xiu, Fei; Yip, Senpo; Hui, Alvin T; Hung, TakFu; Ho, Johnny C

    2012-04-24

    InAs nanowires have been extensively studied for high-speed and high-frequency electronics due to the low effective electron mass and corresponding high carrier mobility. However, further applications still suffer from the significant leakage current in InAs nanowire devices arising from the small electronic band gap. Here, we demonstrate the successful synthesis of ternary InGaAs nanowires in order to tackle this leakage issue utilizing the larger band gap material but at the same time not sacrificing the high electron mobility. In this work, we adapt a two-step growth method on amorphous SiO(2)/Si substrates which significantly reduces the kinked morphology and surface coating along the nanowires. The grown nanowires exhibit excellent crystallinity and uniform stoichiometric composition along the entire length of the nanowires. More importantly, the electrical properties of those nanowires are found to be remarkably impressive with I(ON)/I(OFF) ratio >10(5), field-effect mobility of ∼2700 cm(2)/(V·s), and ON current density of ∼0.9 mA/μm. These nanowires are then employed in the contact printing and achieve large-scale assembly of nanowire parallel arrays which further illustrate the potential for utilizing these high-performance nanowires on substrates for the fabrication of future integrated circuits.

  12. Enhanced optical properties in inclined GaAs nanowire arrays for high-efficiency solar cells

    NASA Astrophysics Data System (ADS)

    Wang, Yile; Zhang, Xu; Sun, Xiaohong; Qi, Yongle; Wang, Zhen; Wang, Hua

    2016-11-01

    The inclined Gallium Arsenide (GaAs) nanowire arrays (NWAs) as light absorbing structures for solar photovoltaics are proposed. The influence of geometric parameters on the optical absorption properties is systematically investigated, and the optimal geometric parameters of the proposed structure are determined by using rigorous coupled wave analysis (RCWA) and the finite element method. It is found that the absorption efficiency of the optimized structure can be improved significantly compared with vertical NWAs and thin film layer structure. The optimized structure yields a photocurrent of 30.3 mA/cm2, which is much higher than that of vertical NWAs and thin film layer with the same geometric configurations.

  13. A palladium-nanoparticle and silicon-nanowire-array hybrid: a platform for catalytic heterogeneous reactions.

    PubMed

    Yamada, Yoichi M A; Yuyama, Yoshinari; Sato, Takuma; Fujikawa, Shigenori; Uozumi, Yasuhiro

    2014-01-01

    We report the development of a silicon nanowire array-stabilized palladium nanoparticle catalyst, SiNA-Pd. Its use in the palladium-catalyzed Mizoroki-Heck reaction, the hydrogenation of an alkene, the hydrogenolysis of nitrobenzene, the hydrosilylation of an α,β-unsaturated ketone, and the C-H bond functionalization reactions of thiophenes and indoles achieved a quantitative production with high reusability. The catalytic activity reached several hundred-mol ppb of palladium, reaching a TON of 2 000 000.

  14. N-doped carbon-coated tungsten oxynitride nanowire arrays for highly efficient electrochemical hydrogen evolution.

    PubMed

    Li, Qun; Cui, Wei; Tian, Jingqi; Xing, Zhicai; Liu, Qian; Xing, Wei; Asiri, Abdullah M; Sun, Xuping

    2015-08-10

    It is highly desired but still challenging to develop active nonprecious metal hydrogen evolution reaction (HER) electrocatalysts operating under all pH conditions. Herein, the development of three-dimensional N-doped carbon-coated tungsten oxynitride nanowire arrays on carbon cloth as a highly efficient and durable HER cathode was explored. The material delivers current densities of 10 and 100 mA cm(-2) at overpotentials of 106 and 172 mV, respectively, in acidic medium, and it also performs well in neutral and basic electrolytes.

  15. Smart integration of silicon nanowire arrays in all-silicon thermoelectric micro-nanogenerators

    NASA Astrophysics Data System (ADS)

    Fonseca, Luis; Santos, Jose-Domingo; Roncaglia, Alberto; Narducci, Dario; Calaza, Carlos; Salleras, Marc; Donmez, Inci; Tarancon, Albert; Morata, Alex; Gadea, Gerard; Belsito, Luca; Zulian, Laura

    2016-08-01

    Micro and nanotechnologies are called to play a key role in the fabrication of small and low cost sensors with excellent performance enabling new continuous monitoring scenarios and distributed intelligence paradigms (Internet of Things, Trillion Sensors). Harvesting devices providing energy autonomy to those large numbers of microsensors will be essential. In those scenarios where waste heat sources are present, thermoelectricity will be the obvious choice. However, miniaturization of state of the art thermoelectric modules is not easy with the current technologies used for their fabrication. Micro and nanotechnologies offer an interesting alternative considering that silicon in nanowire form is a material with a promising thermoelectric figure of merit. This paper presents two approaches for the integration of large numbers of silicon nanowires in a cost-effective and practical way using only micromachining and thin-film processes compatible with silicon technologies. Both approaches lead to automated physical and electrical integration of medium-high density stacked arrays of crystalline or polycrystalline silicon nanowires with arbitrary length (tens to hundreds microns) and diameters below 100 nm.

  16. Magnetic behavior of NiCu nanowire arrays: Compositional, geometry and temperature dependence

    SciTech Connect

    Palmero, E. M. Bran, C.; Real, R. P. del; Vázquez, M.; Magén, C.

    2014-07-21

    Arrays of Ni{sub 100−x}Cu{sub x} nanowires ranging in composition 0 ≤ x ≤ 75, diameter from 35 to 80 nm, and length from 150 nm to 28 μm have been fabricated by electrochemical co-deposition of Ni and Cu into self-ordered anodic aluminum oxide membranes. As determined by X-ray diffraction and Transmission Electron Microscopy, the crystalline structure shows fcc cubic symmetry with [111] preferred texture and preferential Ni or Cu lattice depending on the composition. Their magnetic properties such as coercivity and squareness have been determined as a function of composition and geometry in a Vibrating Sample Magnetometer in the temperature range from 10 to 290 K for applied magnetic fields parallel and perpendicular to the nanowires axis. Addition of Cu into the NiCu alloy up to 50% enhances both parallel coercivity and squareness. For the higher Cu content, these properties decrease and the magnetization easy axis becomes oriented perpendicular to the wires. In addition, coercivity and squareness increase by decreasing the diameter of nanowires which is ascribed to the increase of shape anisotropy. The temperature dependent measurements reflect a complex behavior of the magnetic anisotropy as a result of energy contributions with different evolution with temperature.

  17. Magnetic behavior of NiCu nanowire arrays: Compositional, geometry and temperature dependence

    NASA Astrophysics Data System (ADS)

    Palmero, E. M.; Bran, C.; del Real, R. P.; Magén, C.; Vázquez, M.

    2014-07-01

    Arrays of Ni100-xCux nanowires ranging in composition 0 ≤ x ≤ 75, diameter from 35 to 80 nm, and length from 150 nm to 28 μm have been fabricated by electrochemical co-deposition of Ni and Cu into self-ordered anodic aluminum oxide membranes. As determined by X-ray diffraction and Transmission Electron Microscopy, the crystalline structure shows fcc cubic symmetry with [111] preferred texture and preferential Ni or Cu lattice depending on the composition. Their magnetic properties such as coercivity and squareness have been determined as a function of composition and geometry in a Vibrating Sample Magnetometer in the temperature range from 10 to 290 K for applied magnetic fields parallel and perpendicular to the nanowires axis. Addition of Cu into the NiCu alloy up to 50% enhances both parallel coercivity and squareness. For the higher Cu content, these properties decrease and the magnetization easy axis becomes oriented perpendicular to the wires. In addition, coercivity and squareness increase by decreasing the diameter of nanowires which is ascribed to the increase of shape anisotropy. The temperature dependent measurements reflect a complex behavior of the magnetic anisotropy as a result of energy contributions with different evolution with temperature.

  18. Improvement of carrier diffusion length in silicon nanowire arrays using atomic layer deposition.

    PubMed

    Kato, Shinya; Kurokawa, Yasuyoshi; Miyajima, Shinsuke; Watanabe, Yuya; Yamada, Akira; Ohta, Yoshimi; Niwa, Yusuke; Hirota, Masaki

    2013-01-01

    To achieve a high-efficiency silicon nanowire (SiNW) solar cell, surface passivation technique is very important because a SiNW array has a large surface area. We successfully prepared by atomic layer deposition (ALD) high-quality aluminum oxide (Al2O3) film for passivation on the whole surface of the SiNW arrays. The minority carrier lifetime of the Al2O3-depositedSiNW arrays with bulk silicon substrate was improved to 27 μs at the optimum annealing condition. To remove the effect of bulk silicon, the effective diffusion length of minority carriers in the SiNW array was estimated by simple equations and a device simulator. As a result, it was revealed that the effective diffusion length in the SiNW arrays increased from 3.25 to 13.5 μm by depositing Al2O3 and post-annealing at 400°C. This improvement of the diffusion length is very important for application to solar cells, and Al2O3 deposited by ALD is a promising passivation material for a structure with high aspect ratio such as SiNW arrays. PMID:23968156

  19. From immobilized cells to motile cells on a bed-of-nails: effects of vertical nanowire array density on cell behaviour

    PubMed Central

    Persson, Henrik; Li, Zhen; Tegenfeldt, Jonas O.; Oredsson, Stina; Prinz, Christelle N.

    2015-01-01

    The field of vertical nanowire array-based applications in cell biology is growing rapidly and an increasing number of applications are being explored. These applications almost invariably rely on the physical properties of the nanowire arrays, creating a need for a better understanding of how their physical properties affect cell behaviour. Here, we investigate the effects of nanowire density on cell migration, division and morphology for murine fibroblasts. Our results show that few nanowires are sufficient to immobilize cells, while a high nanowire spatial density enables a ”bed-of-nails” regime, where cells reside on top of the nanowires and are fully motile. The presence of nanowires decreases the cell proliferation rate, even in the “bed-of-nails” regime. We show that the cell morphology strongly depends on the nanowire density. Cells cultured on low (0.1 μm−2) and medium (1 μm−2) density substrates exhibit an increased number of multi-nucleated cells and micronuclei. These were not observed in cells cultured on high nanowire density substrates (4 μm−2). The results offer important guidelines to minimize cell-function perturbations on nanowire arrays. Moreover, these findings offer the possibility to tune cell proliferation and migration independently by adjusting the nanowire density, which may have applications in drug testing. PMID:26691936

  20. A novel approach to titania nanowire arrays as photoanodes of back-illuminated dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Tao, Ru-Hua; Wu, Jin-Ming; Xue, Hong-Xing; Song, Xiao-Mei; Pan, Xu; Fang, Xia-Qin; Fang, Xiao-Dong; Dai, Song-Yuan

    Titania nanowire arrays have been deposited on Ti foils through direct oxidizing the Ti substrate with aqueous hydrogen peroxide solutions containing melamine and nitric acid, and the applicability of such nanowire arrays to back-illuminated dye-sensitized solar cells studied in parallel with titania nanotube arrays on Ti foils. The low-temperature nitrogen adsorption measurement reveals that the film with nanowires 25 nm in diameter and 1 μm in length possesses a BET specific surface area of 59.0 m 2 g -1, a value much larger than 26 m 2 g -1 calculated for the nanotube with an inner diameter of 80 nm, an outer diameter of 120 nm and a total length of 3 μm. Assuming an indirect transition between band gaps, the nanowire film exhibits a bandgap of 3.1 eV, slightly larger than that of 3.0 eV for the nanotube one. A detailed electrochemical study suggests that, in comparison with the nanotube film, the nanowire one exhibits much lower saturated photocurrent and poorer conductivity under the Xe-lamp irradiation. However, when utilized to construct back-side illuminated dye-sensitized solar cells, the cell with the 2 μm-thick nanowire photoanode possesses significantly higher efficiency than the one with the 3 μm-thick nanotube photoanode. The relatively high energy conversion efficiency is contributed to the high specific surface area and the unique mesoporous structure of the titania nanowire arrays, which favors the adsorption of dye molecules.

  1. Dense nanoimprinted silicon nanowire arrays with passivated axial p-i-n junctions for photovoltaic applications

    SciTech Connect

    Zhang, Peng; Liu, Pei; Siontas, Stylianos; Zaslavsky, A.; Pacifici, D.; Ha, Jong-Yoon; Krylyuk, S.; Davydov, A. V.

    2015-03-28

    We report on the fabrication and photovoltaic characteristics of vertical arrays of silicon axial p-i-n junction nanowire (NW) solar cells grown by vapor-liquid-solid (VLS) epitaxy. NW surface passivation with silicon dioxide shell is shown to enhance carrier recombination time, open-circuit voltage (V{sub OC}), short-circuit current density (J{sub SC}), and fill factor (FF). The photovoltaic performance of passivated individual NW and NW arrays was compared under 532 nm laser illumination with power density of ∼10 W/cm{sup 2}. Higher values of V{sub OC} and FF in the NW arrays are explained by enhanced light trapping. In order to verify the effect of NW density on light absorption and hence on the photovoltaic performance of NW arrays, dense Si NW arrays were fabricated using nanoimprint lithography to periodically arrange the gold seed particles prior to epitaxial growth. Compared to sparse NW arrays fabricated using VLS growth from randomly distributed gold seeds, the nanoimprinted NW array solar cells show a greatly increased peak external quantum efficiency of ∼8% and internal quantum efficiency of ∼90% in the visible spectral range. Three-dimensional finite-difference time-domain simulations of Si NW periodic arrays with varying pitch (P) confirm the importance of high NW density. Specifically, due to diffractive scattering and light trapping, absorption efficiency close to 100% in the 400–650 nm spectral range is calculated for a Si NW array with P = 250 nm, significantly outperforming a blanket Si film of the same thickness.

  2. Study of the Electrochemical System of Antimony-Tellurium in Dimethyl Sulfoxide for Growth of Nanowire Arrays, and an Innovative Method for Single Nanowire Measurements

    NASA Astrophysics Data System (ADS)

    Kalisman, Philip Taubman

    There is a strong interest in thermoelectric materials for energy production and savings. The properties which are integral to thermoelectric performance are typically linked, typically changing one of these properties for the better will change another for the worse. The intertwined nature of these properties has limited bulk thermoelectrics to low efficiencies, which has curbed their use to only niche applications. There has been theoretical and experimental work which has shown that limiting these materials in one or more dimensions will result in deconvolution of properties. Nanowires of well established thermoelectrics should show impressively high performance. Tellurium is attractive in many fields, including thermoelectrics. Nanowires of tellurium have been grown, but with limited success and with out the ability to dope the tellurium. Working on previous work with other systems, tellurium was studied in dimethyl sulfoxide (DMSO). The electrochemical system of tellurium was found to be quite dierent from its aqueous analog, but through comprehensive cyclic voltammetric study, all events were identified and explained. The binary antimony-tellurium system was also studied, as doping of tellurium is integral for many applications. Cyclic voltammograms of this system were studied, and the insight from these studies was used to grow nanowire arrays. Arrays of tellurium were grown and analysis showed that by using DMSO, antimony doped tellurium nanowire arrays could be grown. Furthermore, analysis showed that the antimony doped tellurium interstitially, resulting in a n-type material. Measurements were also performed on arrays and individual wires. Arrays of 1.15% antimony showed ZT of 0.092, with the low ZT attributed to poor contact methods. Although contacting was an obstacle towards measuring whole arrays, single wire measurements were also performed. Single wire measurements were done by a novel method which allows for easy, reproducible measurements of wire

  3. Fabrication of Si/ZnS radial nanowire heterojunction arrays for white light emitting devices on Si substrates.

    PubMed

    Katiyar, Ajit K; Sinha, Arun Kumar; Manna, Santanu; Ray, Samit K

    2014-09-10

    Well-separated Si/ZnS radial nanowire heterojunction-based light-emitting devices have been fabricated on large-area substrates by depositing n-ZnS film on p-type nanoporous Si nanowire templates. Vertically oriented porous Si nanowires on p-Si substrates have been grown by metal-assisted chemical etching catalyzed using Au nanoparticles. Isolated Si nanowires with needle-shaped arrays have been made by KOH treatment before ZnS deposition. Electrically driven efficient white light emission from radial heterojunction arrays has been achieved under a low forward bias condition. The observed white light emission is attributed to blue and green emission from the defect-related radiative transition of ZnS and Si/ZnS interface, respectively, while the red arises from the porous surface of the Si nanowire core. The observed white light emission from the Si/ZnS nanowire heterojunction could open up the new possibility to integrate Si-based optical sources on a large scale.

  4. Gold-Free Ternary III–V Antimonide Nanowire Arrays on Silicon: Twin-Free down to the First Bilayer

    PubMed Central

    2013-01-01

    With the continued maturation of III–V nanowire research, expectations of material quality should be concomitantly raised. Ideally, III–V nanowires integrated on silicon should be entirely free of extended planar defects such as twins, stacking faults, or polytypism, position-controlled for convenient device processing, and gold-free for compatibility with standard complementary metal–oxide–semiconductor (CMOS) processing tools. Here we demonstrate large area vertical GaAsxSb1–x nanowire arrays grown on silicon (111) by molecular beam epitaxy. The nanowires’ complex faceting, pure zinc blende crystal structure, and composition are mapped using characterization techniques both at the nanoscale and in large-area ensembles. We prove unambiguously that these gold-free nanowires are entirely twin-free down to the first bilayer and reveal their three-dimensional composition evolution, paving the way for novel infrared devices integrated directly on the cost-effective Si platform. PMID:24329502

  5. 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

  6. Transfer-free synthesis of highly ordered Ge nanowire arrays on glass substrates

    SciTech Connect

    Nakata, M.; Toko, K. Suemasu, T.; Jevasuwan, W.; Fukata, N.; Saitoh, N.; Yoshizawa, N.

    2015-09-28

    Vertically aligned Ge nanowires (NWs) are directly synthesized on glass via vapor-liquid-solid (VLS) growth using chemical-vapor deposition. The use of the (111)-oriented Ge seed layer, formed by metal-induced crystallization at 325 °C, dramatically improved the density, uniformity, and crystal quality of Ge NWs. In particular, the VLS growth at 400 °C allowed us to simultaneously achieve the ordered morphology and high crystal quality of the Ge NW array. Transmission electron microscopy demonstrated that the resulting Ge NWs had no dislocations or stacking faults. Production of high-quality NW arrays on amorphous insulators will promote the widespread application of nanoscale devices.

  7. Electrochemically reduced graphene oxide on silicon nanowire arrays for enhanced photoelectrochemical hydrogen evolution.

    PubMed

    Meng, Huan; Fan, Ke; Low, Jingxiang; Yu, Jiaguo

    2016-09-21

    Photoelectrochemical (PEC) water splitting into hydrogen and oxygen by sunlight is a promising approach to solve energy and environmental problems. In this work, silicon nanowire arrays (SiNWs) photocathodes decorated with reduced graphene oxide (rGO) for PEC water splitting were successfully prepared by a flexible and scalable electrochemical reduction method. The SiNWs photocathode with the optimized rGO decoration (SiNWs/rGO20) shows an enhanced activity with a much higher photocurrent density and significantly positive shift of onset potential compared to the bare SiNWs arrays for the hydrogen evolution reaction (HER). The enhanced PEC activity is ascribed to the high electrical conductivity of rGO and improved separation of the photogenerated charge carriers. This work not only demonstrates a facile, rapid and tunable electrochemical reduction method to produce rGO, but also exhibits an efficient protocol to enhance the PEC water splitting of silicon-based materials. PMID:27461187

  8. 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.

  9. Electrical properties of high density arrays of silicon nanowire field effect transistors

    NASA Astrophysics Data System (ADS)

    Kim, Hye-Young; Lee, Kangho; Lee, Jae Woo; Kim, Sangwook; Kim, Gyu-Tae; Duesberg, Georg S.

    2013-10-01

    Proximity effect corrected e-beam lithography of hydrogen silsesquioxane on silicon on insulator was used to fabricate multi-channel silicon nanowire field-effect transistors (SiNW FETs). Arrays of 15-channels with a line width of 18 nm and pitch as small as 50 nm, the smallest reported for electrically functional devices, were fabricated. These high density arrays were back-gated by the substrate and allowed for investigation of the effects of scaling on the electrical performance of this multi-channel SiNW FET. It was revealed that the drain current and the transconductance (gm) are both reduced with decreasing pitch size. The drain induced barrier lowering and the threshold voltage (Vth) are also decreased, whereas the subthreshold swing (S) is increased. The results are in agreement with our simulations of the electric potential profile of the devices. The study contains valuable information on SiNW FET integration and scaling for future devices.

  10. Electrochemically reduced graphene oxide on silicon nanowire arrays for enhanced photoelectrochemical hydrogen evolution.

    PubMed

    Meng, Huan; Fan, Ke; Low, Jingxiang; Yu, Jiaguo

    2016-09-21

    Photoelectrochemical (PEC) water splitting into hydrogen and oxygen by sunlight is a promising approach to solve energy and environmental problems. In this work, silicon nanowire arrays (SiNWs) photocathodes decorated with reduced graphene oxide (rGO) for PEC water splitting were successfully prepared by a flexible and scalable electrochemical reduction method. The SiNWs photocathode with the optimized rGO decoration (SiNWs/rGO20) shows an enhanced activity with a much higher photocurrent density and significantly positive shift of onset potential compared to the bare SiNWs arrays for the hydrogen evolution reaction (HER). The enhanced PEC activity is ascribed to the high electrical conductivity of rGO and improved separation of the photogenerated charge carriers. This work not only demonstrates a facile, rapid and tunable electrochemical reduction method to produce rGO, but also exhibits an efficient protocol to enhance the PEC water splitting of silicon-based materials.

  11. Two-fluid wetting behavior of a hydrophobic silicon nanowire array.

    PubMed

    Kim, Yongkwan; Chung, Yunsie; Tian, Ye; Carraro, Carlo; Maboudian, Roya

    2014-11-11

    The two-fluid wetting behavior of surfaces textured by an array of silicon nanowires is investigated systematically. The Si nanowire array is produced by a combination of colloidal patterning and metal-catalyzed etching, with control over its roughness depending upon the wire length. The nanowires are made hydrophobic and oleophobic by treatment with hydrocarbon and fluorinated self-assembled monolayers, respectively. Static, advancing, and receding contact angles are measured with water, hexadecane, and perfluorotripentylamine in both single-fluid (droplet on solid in an air environment) and two-fluid (droplet on solid in a liquid environment) configurations. The single-fluid measurements show wetting behavior similar to that expected by the Wenzel and Cassie-Baxter models, where the wetting or non-wetting behaviors are amplified with increasing roughness. The two-fluid systems on the rough surface exhibit more complex configurations because either the droplet or the environment fluid can penetrate the asperities depending upon the wettability of each fluid. It is observed that, when the Young contact angles are significantly increased or reduced from single-liquid to two-liquid systems, the effect of roughness is relatively minimal. However, when the Young contact angles are similar, roughness has almost identical influence on apparent contact angles in single- and two-liquid systems. The Wenzel and Cassie-Baxter models are modified to describe various two-fluid wetting states. In cases where metastable behavior is observed for the droplet, advancing and receding measurements are performed to suggest the equilibrium state of the droplet. PMID:25356959

  12. Two-fluid wetting behavior of a hydrophobic silicon nanowire array.

    PubMed

    Kim, Yongkwan; Chung, Yunsie; Tian, Ye; Carraro, Carlo; Maboudian, Roya

    2014-11-11

    The two-fluid wetting behavior of surfaces textured by an array of silicon nanowires is investigated systematically. The Si nanowire array is produced by a combination of colloidal patterning and metal-catalyzed etching, with control over its roughness depending upon the wire length. The nanowires are made hydrophobic and oleophobic by treatment with hydrocarbon and fluorinated self-assembled monolayers, respectively. Static, advancing, and receding contact angles are measured with water, hexadecane, and perfluorotripentylamine in both single-fluid (droplet on solid in an air environment) and two-fluid (droplet on solid in a liquid environment) configurations. The single-fluid measurements show wetting behavior similar to that expected by the Wenzel and Cassie-Baxter models, where the wetting or non-wetting behaviors are amplified with increasing roughness. The two-fluid systems on the rough surface exhibit more complex configurations because either the droplet or the environment fluid can penetrate the asperities depending upon the wettability of each fluid. It is observed that, when the Young contact angles are significantly increased or reduced from single-liquid to two-liquid systems, the effect of roughness is relatively minimal. However, when the Young contact angles are similar, roughness has almost identical influence on apparent contact angles in single- and two-liquid systems. The Wenzel and Cassie-Baxter models are modified to describe various two-fluid wetting states. In cases where metastable behavior is observed for the droplet, advancing and receding measurements are performed to suggest the equilibrium state of the droplet.

  13. External cavity laser using a InAs quantum dot gain chip and an arrayed-waveguide grating for T-band optical communications

    NASA Astrophysics Data System (ADS)

    Shibutani, Hideki; Tomomatsu, Yasunori; Sawado, Yoshinori; Yoshizawa, Katsumi; Asakura, Hideaki; Idris, Nazirul Afham; Tsuda, Hiroyuki

    2015-02-01

    Utilizing T-band (1000 nm to 1260 nm) for optical communications is promising for short reach, and large capacity networks, such as data centers or access networks. It is feasible to use this with low-cost coarse wavelength division multiplexing (WDM). However, a tunable wavelength light source is necessary for such applications. In this paper, we propose a new configuration for an external cavity laser, which uses a silica-based arrayed waveguide grating (AWG) for the wavelength selecting element. The external cavity laser consists of a gain chip with high reflection (HR) and anti-reflection (AR) coated facets, coupling lenses, an AWG with AR/HR coatings, and an output fiber. The AWG has 17 connection ports, which correspond to 17 wavelengths with a channel spacing of 1.67 nm. The width of the connection port waveguides was optimized to achieve high coupling efficiency. The AWG chip size is 15 mm x 30 mm. The active layer in the gain chip has InAs quantum dots. The spontaneous emission 3-dB bandwidth was 48 nm (1108 nm to 1156 nm) when a current of 150 mA was injected into the gain chip. The lasing wavelength of the external cavity laser was successfully tuned from 1129.9 nm to 1154.4 nm by selecting the connection ports of the AWG. The typical threshold current was about 130 mA.

  14. Rapid Synthesis of Thin and Long Mo17O47 Nanowire-Arrays in an Oxygen Deficient Flame

    NASA Astrophysics Data System (ADS)

    Allen, Patrick; Cai, Lili; Zhou, Lite; Zhao, Chenqi; Rao, Pratap M.

    2016-06-01

    Mo17O47 nanowire-arrays are promising active materials and electrically-conductive supports for batteries and other devices. While high surface area resulting from long, thin, densely packed nanowires generally leads to improved performance in a wide variety of applications, the Mo17O47 nanowire-arrays synthesized previously by electrically-heated chemical vapor deposition under vacuum conditions were relatively thick and short. Here, we demonstrate a method to grow significantly thinner and longer, densely packed, high-purity Mo17O47 nanowire-arrays with diameters of 20–60 nm and lengths of 4–6 μm on metal foil substrates using rapid atmospheric flame vapor deposition without any chamber or walls. The atmospheric pressure and 1000 °C evaporation temperature resulted in smaller diameters, longer lengths and order-of-magnitude faster growth rate than previously demonstrated. As explained by kinetic and thermodynamic calculations, the selective synthesis of high-purity Mo17O47 nanowires is achieved due to low oxygen partial pressure in the flame products as a result of the high ratio of fuel to oxidizer supplied to the flame, which enables the correct ratio of MoO2 and MoO3 vapor concentrations for the growth of Mo17O47. This flame synthesis method is therefore a promising route for the growth of composition-controlled one-dimensional metal oxide nanomaterials for many applications.

  15. Rapid Synthesis of Thin and Long Mo17O47 Nanowire-Arrays in an Oxygen Deficient Flame

    PubMed Central

    Allen, Patrick; Cai, Lili; Zhou, Lite; Zhao, Chenqi; Rao, Pratap M.

    2016-01-01

    Mo17O47 nanowire-arrays are promising active materials and electrically-conductive supports for batteries and other devices. While high surface area resulting from long, thin, densely packed nanowires generally leads to improved performance in a wide variety of applications, the Mo17O47 nanowire-arrays synthesized previously by electrically-heated chemical vapor deposition under vacuum conditions were relatively thick and short. Here, we demonstrate a method to grow significantly thinner and longer, densely packed, high-purity Mo17O47 nanowire-arrays with diameters of 20–60 nm and lengths of 4–6 μm on metal foil substrates using rapid atmospheric flame vapor deposition without any chamber or walls. The atmospheric pressure and 1000 °C evaporation temperature resulted in smaller diameters, longer lengths and order-of-magnitude faster growth rate than previously demonstrated. As explained by kinetic and thermodynamic calculations, the selective synthesis of high-purity Mo17O47 nanowires is achieved due to low oxygen partial pressure in the flame products as a result of the high ratio of fuel to oxidizer supplied to the flame, which enables the correct ratio of MoO2 and MoO3 vapor concentrations for the growth of Mo17O47. This flame synthesis method is therefore a promising route for the growth of composition-controlled one-dimensional metal oxide nanomaterials for many applications. PMID:27271194

  16. Rapid Synthesis of Thin and Long Mo17O47 Nanowire-Arrays in an Oxygen Deficient Flame.

    PubMed

    Allen, Patrick; Cai, Lili; Zhou, Lite; Zhao, Chenqi; Rao, Pratap M

    2016-01-01

    Mo17O47 nanowire-arrays are promising active materials and electrically-conductive supports for batteries and other devices. While high surface area resulting from long, thin, densely packed nanowires generally leads to improved performance in a wide variety of applications, the Mo17O47 nanowire-arrays synthesized previously by electrically-heated chemical vapor deposition under vacuum conditions were relatively thick and short. Here, we demonstrate a method to grow significantly thinner and longer, densely packed, high-purity Mo17O47 nanowire-arrays with diameters of 20-60 nm and lengths of 4-6 μm on metal foil substrates using rapid atmospheric flame vapor deposition without any chamber or walls. The atmospheric pressure and 1000 °C evaporation temperature resulted in smaller diameters, longer lengths and order-of-magnitude faster growth rate than previously demonstrated. As explained by kinetic and thermodynamic calculations, the selective synthesis of high-purity Mo17O47 nanowires is achieved due to low oxygen partial pressure in the flame products as a result of the high ratio of fuel to oxidizer supplied to the flame, which enables the correct ratio of MoO2 and MoO3 vapor concentrations for the growth of Mo17O47. This flame synthesis method is therefore a promising route for the growth of composition-controlled one-dimensional metal oxide nanomaterials for many applications. PMID:27271194

  17. Unique X-ray emission characteristics from volumetrically heated nanowire array plasmas

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    Highly anisotropic emission of hard X-ray radiation (h ν >10 keV) is observed when arrays of ordered nanowires (50 nm diameter wires of Au or Ni) are volumetrically heated by normal incidence irradiation with high contrast 50-60 fs laser pulses of relativistic intensity. The annular emission is in contrast with angular distribution of softer X-rays (h ν >1 KeV) from these targets and with the X-ray radiation emitted by polished flat targets, both of which are nearly isotropic. Model computations that make use the electron energy distribution computed by particle-in-cell simulations show that the unexpected annular distribution of the hard x-rays is the result of bremsstrahlung from fast electrons. Volumetric heating of Au nanowire arrays irradiated with an intensity of 2 x 10 19 W cm-2 is measured to convert laser energy into h ν>1KeV photons with a record efficiency of >8 percent into 2 π, creating a bright picosecond X-ray source for applications. Work supported by the Office of Fusion Energy Science of the U.S Department of Energy, and the Defense Threat Reduction Agency. A.P was supported by DFG project TR18.

  18. Ultrasensitive Detection of Dual Cancer Biomarkers with Integrated CMOS-Compatible Nanowire Arrays.

    PubMed

    Lu, Na; Gao, Anran; Dai, Pengfei; Mao, Hongju; Zuo, Xiaolei; Fan, Chunhai; Wang, Yuelin; Li, Tie

    2015-11-17

    A direct, rapid, highly sensitive and specific biosensor for detection of cancer biomarkers is desirable in early diagnosis and prognosis of cancer. However, the existing methods of detecting cancer biomarkers suffer from poor sensitivity as well as the requirement of enzymatic labeling or nanoparticle conjugations. Here, we proposed a two-channel PDMS microfluidic integrated CMOS-compatible silicon nanowire (SiNW) field-effect transistor arrays with potentially single use for label-free and ultrasensitive electrical detection of cancer biomarkers. The integrated nanowire arrays showed not only ultrahigh sensitivity of cytokeratin 19 fragment (CYFRA21-1) and prostate specific antigen (PSA) with detection to at least 1 fg/mL in buffer solution but also highly selectivity of discrimination from other similar cancer biomarkers. In addition, this method was used to detect both CYFRA21-1 and PSA real samples as low as 10 fg/mL in undiluted human serums. With its excellent properties and miniaturization, the integrated SiNW-FET device opens up great opportunities for a point-of-care test (POCT) for quick screening and early diagnosis of cancer and other complex diseases. PMID:26473941

  19. Polarization-tuned Dynamic Color Filters Incorporating a Dielectric-loaded Aluminum Nanowire Array

    PubMed Central

    Raj Shrestha, Vivek; Lee, Sang-Shin; Kim, Eun-Soo; Choi, Duk-Yong

    2015-01-01

    Nanostructured spectral filters enabling dynamic color-tuning are saliently attractive for implementing ultra-compact color displays and imaging devices. Realization of polarization-induced dynamic color-tuning via one-dimensional periodic nanostructures is highly challenging due to the absence of plasmonic resonances for transverse-electric polarization. Here we demonstrate highly efficient dynamic subtractive color filters incorporating a dielectric-loaded aluminum nanowire array, providing a continuum of customized color according to the incident polarization. Dynamic color filtering was realized relying on selective suppression in transmission spectra via plasmonic resonance at a metal-dielectric interface and guided-mode resonance for a metal-clad dielectric waveguide, each occurring at their characteristic wavelengths for transverse-magnetic and electric polarizations, respectively. A broad palette of colors, including cyan, magenta, and yellow, has been attained with high transmission beyond 80%, by tailoring the period of the nanowire array and the incident polarization. Thanks to low cost, high durability, and mass producibility of the aluminum adopted for the proposed devices, they are anticipated to be diversely applied to color displays, holographic imaging, information encoding, and anti-counterfeiting. PMID:26211625

  20. Polarization-tuned Dynamic Color Filters Incorporating a Dielectric-loaded Aluminum Nanowire Array

    NASA Astrophysics Data System (ADS)

    Raj Shrestha, Vivek; Lee, Sang-Shin; Kim, Eun-Soo; Choi, Duk-Yong

    2015-07-01

    Nanostructured spectral filters enabling dynamic color-tuning are saliently attractive for implementing ultra-compact color displays and imaging devices. Realization of polarization-induced dynamic color-tuning via one-dimensional periodic nanostructures is highly challenging due to the absence of plasmonic resonances for transverse-electric polarization. Here we demonstrate highly efficient dynamic subtractive color filters incorporating a dielectric-loaded aluminum nanowire array, providing a continuum of customized color according to the incident polarization. Dynamic color filtering was realized relying on selective suppression in transmission spectra via plasmonic resonance at a metal-dielectric interface and guided-mode resonance for a metal-clad dielectric waveguide, each occurring at their characteristic wavelengths for transverse-magnetic and electric polarizations, respectively. A broad palette of colors, including cyan, magenta, and yellow, has been attained with high transmission beyond 80%, by tailoring the period of the nanowire array and the incident polarization. Thanks to low cost, high durability, and mass producibility of the aluminum adopted for the proposed devices, they are anticipated to be diversely applied to color displays, holographic imaging, information encoding, and anti-counterfeiting.

  1. Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors

    PubMed Central

    Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

    2013-01-01

    Here we proposed a novel architectural design of a ternary MnO2-based electrode – a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2–based nanowire arrays for constructing next-generation supercapacitors. PMID:24132040

  2. Laser Modified ZnO/CdSSe Core-Shell Nanowire Arrays for Micro-Steganography and Improved Photoconduction

    PubMed Central

    Lu, Junpeng; Liu, Hongwei; Zheng, Minrui; Zhang, Hongji; Lim, Sharon Xiaodai; Tok, Eng Soon; Sow, Chorng Haur

    2014-01-01

    Arrays of ZnO/CdSSe core/shell nanowires with shells of tunable band gaps represent a class of interesting hybrid nanomaterials with unique optical and photoelectrical properties due to their type II heterojunctions and chemical compositions. In this work, we demonstrate that direct focused laser beam irradiation is able to achieve localized modification of the hybrid structure and chemical composition of the nanowire arrays. As a result, the photoresponsivity of the laser modified hybrid is improved by a factor of ~3. A 3D photodetector with improved performance is demonstrated using laser modified nanowire arrays overlaid with monolayer graphene as the top electrode. Finally, by controlling the power of the scanning focused laser beam, micropatterns with different fluorescence emissions are created on a substrate covered with nanowire arrays. Such a pattern is not apparent when imaged under normal optical microscopy but the pattern becomes readily revealed under fluorescence microscopy i.e. a form of Micro-Steganography is achieved. PMID:25213321

  3. Fabrication of silicon nanowire arrays by macroscopic galvanic cell-driven metal catalyzed electroless etching in aerated HF solution.

    PubMed

    Liu, Lin; Peng, Kui-Qing; Hu, Ya; Wu, Xiao-Ling; Lee, Shuit-Tong

    2014-03-01

    Macroscopic galvanic cell-driven metal catalyzed electroless etching (MCEE) of silicon in aqueous hydrofluoric acid (HF) solution is devised to fabricate silicon nanowire (SiNW) arrays with dissolved oxygen acting as the one and only oxidizing agent. The key aspect of this strategy is the use of a graphite or other noble metal electrode that is electrically coupled with silicon substrate.

  4. Heterogeneous NiCo2O4@polypyrrole core/sheath nanowire arrays on Ni foam for high performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Hu, Jing; Li, Minchan; Lv, Fucong; Yang, Mingyang; Tao, Pengpeng; Tang, Yougen; Liu, Hongtao; Lu, Zhouguang

    2015-10-01

    A novel heterogeneous NiCo2O4@PPy core/sheath nanowire arrays are directly grown on Ni foam involving three facile steps, hydrothermal synthesis and calcination of NiCo2O4 nanowire arrays and subsequent in-situ oxidative polymerization of polypyrrole (PPy). When investigated as binder- and conductive additive-free electrodes for supercapacitors (SCs) in 6 M KOH, the NiCo2O4@PPy core/sheath nanowire arrays exhibit high areal capacitance of 3.49 F cm-2 at a discharge current density of 5 mA cm-2, which is almost 1.5 times as much as the pristine NiCo2O4 (2.30 F cm-2). More importantly, it can remain 3.31 F cm-2 (94.8% retention) after 5000 cycles. The as-obtained electrode also displays excellent rate capability, whose areal capacitance can still remain 2.79 F cm-2 while the discharge current density is increased to 50 mA cm-2. The remarkable electrochemical performance is mainly attributed to the unique heterogeneous core/sheath nanowire-array architectures.

  5. 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.

  6. A technique for large-area position-controlled growth of GaAs nanowire arrays

    NASA Astrophysics Data System (ADS)

    Kauppinen, Christoffer; Haggren, Tuomas; Kravchenko, Aleksandr; Jiang, Hua; Huhtio, Teppo; Kauppinen, Esko; Dhaka, Veer; Suihkonen, Sami; Kaivola, Matti; Lipsanen, Harri; Sopanen, Markku

    2016-04-01

    We demonstrate a technique for fabricating position-controlled, large-area arrays of vertical semiconductor nanowires (NWs) with adjustable periods and NW diameters. In our approach, a Au-covered GaAs substrate is first coated with a thin film of photoresponsive azopolymer, which is exposed twice to a laser interference pattern forming a 2D surface relief grating. After dry etching, an array of polymer islands is formed, which is used as a mask to fabricate a matrix of gold particles. The Au particles are then used as seeds in vapour–liquid–solid growth to create arrays of vertical GaAs NWs using metalorganic vapour phase epitaxy. The presented technique enables producing NWs of uniform size distribution with high throughput and potentially on large wafer sizes without relying on expensive lithography techniques. The feasibility of the technique is demonstrated by arrays of vertical NWs with periods of 255–1000 nm and diameters of 50–80 nm on a 2 × 2 cm area. The grown NWs exhibit high long range order and good crystalline quality. Although only GaAs NWs were grown in this study, in principle, the presented technique is suitable for any material available for Au seeded NW growth.

  7. A technique for large-area position-controlled growth of GaAs nanowire arrays

    NASA Astrophysics Data System (ADS)

    Kauppinen, Christoffer; Haggren, Tuomas; Kravchenko, Aleksandr; Jiang, Hua; Huhtio, Teppo; Kauppinen, Esko; Dhaka, Veer; Suihkonen, Sami; Kaivola, Matti; Lipsanen, Harri; Sopanen, Markku

    2016-04-01

    We demonstrate a technique for fabricating position-controlled, large-area arrays of vertical semiconductor nanowires (NWs) with adjustable periods and NW diameters. In our approach, a Au-covered GaAs substrate is first coated with a thin film of photoresponsive azopolymer, which is exposed twice to a laser interference pattern forming a 2D surface relief grating. After dry etching, an array of polymer islands is formed, which is used as a mask to fabricate a matrix of gold particles. The Au particles are then used as seeds in vapour-liquid-solid growth to create arrays of vertical GaAs NWs using metalorganic vapour phase epitaxy. The presented technique enables producing NWs of uniform size distribution with high throughput and potentially on large wafer sizes without relying on expensive lithography techniques. The feasibility of the technique is demonstrated by arrays of vertical NWs with periods of 255-1000 nm and diameters of 50-80 nm on a 2 × 2 cm area. The grown NWs exhibit high long range order and good crystalline quality. Although only GaAs NWs were grown in this study, in principle, the presented technique is suitable for any material available for Au seeded NW growth.

  8. Synthesis and characterization of barium silicide (BaSi2) nanowire arrays for potential solar applications

    NASA Astrophysics Data System (ADS)

    Pokhrel, Ankit; Samad, Leith; Meng, Fei; Jin, Song

    2015-10-01

    In order to utilize nanostructured materials for potential solar and other energy-harvesting applications, scalable synthetic techniques for these materials must be developed. Herein we use a vapor phase conversion approach to synthesize nanowire (NW) arrays of semiconducting barium silicide (BaSi2) in high yield for the first time for potential solar applications. Dense arrays of silicon NWs obtained by metal-assisted chemical etching were converted to single-crystalline BaSi2 NW arrays by reacting with Ba vapor at about 930 °C. Structural characterization by X-ray diffraction and high-resolution transmission electron microscopy confirm that the converted NWs are single-crystalline BaSi2. The optimal conversion reaction conditions allow the phase-pure synthesis of BaSi2 NWs that maintain the original NW morphology, and tuning the reaction parameters led to a controllable synthesis of BaSi2 films on silicon substrates. The optical bandgap and electrochemical measurements of these BaSi2 NWs reveal a bandgap and carrier concentrations comparable to previously reported values for BaSi2 thin films.In order to utilize nanostructured materials for potential solar and other energy-harvesting applications, scalable synthetic techniques for these materials must be developed. Herein we use a vapor phase conversion approach to synthesize nanowire (NW) arrays of semiconducting barium silicide (BaSi2) in high yield for the first time for potential solar applications. Dense arrays of silicon NWs obtained by metal-assisted chemical etching were converted to single-crystalline BaSi2 NW arrays by reacting with Ba vapor at about 930 °C. Structural characterization by X-ray diffraction and high-resolution transmission electron microscopy confirm that the converted NWs are single-crystalline BaSi2. The optimal conversion reaction conditions allow the phase-pure synthesis of BaSi2 NWs that maintain the original NW morphology, and tuning the reaction parameters led to a controllable

  9. Highly organised and dense vertical silicon nanowire arrays grown in porous alumina template on <100> silicon wafers

    PubMed Central

    2013-01-01

    In this work, nanoimprint lithography combined with standard anodization etching is used to make perfectly organised triangular arrays of vertical cylindrical alumina nanopores onto standard <100>−oriented silicon wafers. Both the pore diameter and the period of alumina porous array are well controlled and can be tuned: the periods vary from 80 to 460 nm, and the diameters vary from 15 nm to any required diameter. These porous thin layers are then successfully used as templates for the guided epitaxial growth of organised mono-crystalline silicon nanowire arrays in a chemical vapour deposition chamber. We report the densities of silicon nanowires up to 9 × 109 cm−2 organised in highly regular arrays with excellent diameter distribution. All process steps are demonstrated on surfaces up to 2 × 2 cm2. Specific emphasis was made to select techniques compatible with microelectronic fabrication standards, adaptable to large surface samples and with a reasonable cost. Achievements made in the quality of the porous alumina array, therefore on the silicon nanowire array, widen the number of potential applications for this technology, such as optical detectors or biological sensors. PMID:23773702

  10. 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.

  11. 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

  12. High-resolution electroluminescent imaging of pressure distribution using a piezoelectric nanowire LED array

    NASA Astrophysics Data System (ADS)

    Pan, Caofeng; Dong, Lin; Zhu, Guang; Niu, Simiao; Yu, Ruomeng; Yang, Qing; Liu, Ying; Wang, Zhong Lin

    2013-09-01

    Emulation of the sensation of touch through high-resolution electronic means could become important in future generations of robotics and human-machine interfaces. Here, we demonstrate that a nanowire light-emitting diode-based pressure sensor array can map two-dimensional distributions of strain with an unprecedented spatial resolution of 2.7 µm, corresponding to a pixel density of 6,350 dpi. Each pixel is composed of a single n-ZnO nanowire/p-GaN light-emitting diode, the emission intensity of which depends on the local strain owing to the piezo-phototronic effect. A pressure map can be created by reading out, in parallel, the electroluminescent signal from all of the pixels with a time resolution of 90 ms. The device may represent a major step towards the digital imaging of mechanical signals by optical means, with potential applications in artificial skin, touchpad technology, personalized signatures, bio-imaging and optical microelectromechanical systems.

  13. Probing cellular traction forces with magnetic nanowires and microfabricated force sensor arrays.

    PubMed

    Lin, Yi-Chia; Kramer, Corinne M; Chen, Christopher S; Reich, Daniel H

    2012-02-24

    In this paper, the use of magnetic nanowires for the study of cellular response to force is demonstrated. High-aspect ratio Ni rods with diameter 300 nm and lengths up to 20 μm were bound to or internalized by pulmonary artery smooth muscle cells (SMCs) cultured on arrays of flexible micropost force sensors. Forces and torques were applied to the cells by driving the nanowires with AC magnetic fields in the frequency range 0.1-10 Hz, and the changes in cellular contractile forces were recorded with the microposts. These local stimulations yield global force reinforcement of the cells' traction forces, but this contractile reinforcement can be effectively suppressed upon addition of a calcium channel blocker, ruthenium red, suggesting the role of calcium channels in the mechanical response. The responsiveness of the SMCs to actuation depends on the frequency of the applied stimulation. These results show that the combination of magnetic nanoparticles and micropatterned, flexible substrates can provide new approaches to the study of cellular mechanotransduction.

  14. Probing cellular traction forces with magnetic nanowires and microfabricated force sensor arrays

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Chia; Kramer, Corinne M.; Chen, Christopher S.; Reich, Daniel H.

    2012-02-01

    In this paper, the use of magnetic nanowires for the study of cellular response to force is demonstrated. High-aspect ratio Ni rods with diameter 300 nm and lengths up to 20 μm were bound to or internalized by pulmonary artery smooth muscle cells (SMCs) cultured on arrays of flexible micropost force sensors. Forces and torques were applied to the cells by driving the nanowires with AC magnetic fields in the frequency range 0.1-10 Hz, and the changes in cellular contractile forces were recorded with the microposts. These local stimulations yield global force reinforcement of the cells’ traction forces, but this contractile reinforcement can be effectively suppressed upon addition of a calcium channel blocker, ruthenium red, suggesting the role of calcium channels in the mechanical response. The responsiveness of the SMCs to actuation depends on the frequency of the applied stimulation. These results show that the combination of magnetic nanoparticles and micropatterned, flexible substrates can provide new approaches to the study of cellular mechanotransduction.

  15. Band gap enhancement of glancing angle deposited TiO{sub 2} nanowire array

    SciTech Connect

    Chinnamuthu, P.; Mondal, A.; Singh, N. K.; Dhar, J. C.; Chattopadhyay, K. K.; Bhattacharya, Sekhar

    2012-09-01

    Vertically oriented TiO{sub 2} nanowire (NW) arrays were fabricated by glancing angle deposition technique. Field emission-scanning electron microscopy shows the formation of two different diameters {approx}80 nm and {approx}40 nm TiO{sub 2} NW for 120 and 460 rpm azimuthal rotation of the substrate. The x-ray diffraction and Raman scattering depicted the presence of rutile and anatase phase TiO{sub 2}. The overall Raman scattering intensity decreased with nanowire diameter. The role of phonon confinement in anatase and rutile peaks has been discussed. The red (7.9 cm{sup -1} of anatase E{sub g}) and blue (7.4 cm{sup -1} of rutile E{sub g}, 7.8 cm{sup -1} of rutile A{sub 1g}) shifts of Raman frequencies were observed. UV-vis absorption measurements show the main band absorption at 3.42 eV, 3.48 eV, and {approx}3.51 eV for thin film and NW prepared at 120 and 460 rpm, respectively. Three fold enhance photon absorption and intense light emission were observed for NW assembly. The photoluminescence emission from the NW assembly revealed blue shift in main band transition due to quantum confinement in NW structures.

  16. Microstructured Hydrogel Templates for the Formation of Conductive Gold Nanowire Arrays.

    PubMed

    Wünnemann, Patrick; Noyong, Michael; Kreuels, Klaus; Brüx, Roland; Gordiichuk, Pavlo; van Rijn, Patrick; Plamper, Felix A; Simon, Ulrich; Böker, Alexander

    2016-09-01

    Microstructured hydrogel allows for a new template-guided method to obtain conductive nanowire arrays on a large scale. To generate the template, an imprinting process is used in order to synthesize the hydrogel directly into the grooves of wrinkled polydimethylsiloxane (PDMS). The resulting poly(N-vinylimidazole)-based hydrogel is defined by the PDMS stamp in pattern and size. Subsequently, tetrachloroaurate(III) ions from aqueous solution are coordinated within the humps of the N-vinylimidazole-containing polymer template and reduced by air plasma. After reduction and development of the gold, to achieve conductive wires, the extension perpendicular to the long axis (width) of the gold strings is considerably reduced compared to the dimension of the parental hydrogel wrinkles (from ≈1 μm down to 200-300 nm). At the same time, the wire-to-wire distance and the overall length of the wires is preserved. The PDMS templates and hydrogel structures are analyzed with scanning force microscopy (SFM) and the gold structures via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy. The conductivity measurements of the gold nanowires are performed in situ in the SEM, showing highly conductive gold leads. Hence, this method can be regarded as a facile nonlithographic top-down approach from micrometer-sized structures to nanometer-sized features. PMID:27386787

  17. Plane wave scattering from a plasmonic nanowire array spacer-separated from a plasmonic film

    NASA Astrophysics Data System (ADS)

    Thomas, Arun; Trivedi, Rahul; Dhawan, Anuj

    2016-06-01

    In this paper, we present a theoretical analysis of the electromagnetic response of a plasmonic nanowire-spacer-plasmonic film system. The analytical solution presented in this paper is a full-wave solution, which is used to compute the fields scattered by the plasmonic nanostructure system on illumination by a plane electromagnetic wave. The physical structure comprises of an array of plasmonic nanowires made of a plasmonic metal such as gold or silver placed over a plasmonic film of the same material and separated from it by a dielectric spacer such as silica or alumina. Such a nanostructure exhibits a spectrum that is extremely sensitive to various geometric and electromagnetic parameters such as spacer thickness and spacer refractive index, which makes it favourable for various sensing applications such as chemical and biological sensing, strain sensing, position sensing, vibration sensing, and thickness sensing. We report a comparison of our analytical solution with a numerical rigorous coupled wave analysis of the same structure with the plasmonic medium being treated as local in nature.

  18. Band gap enhancement of glancing angle deposited TiO2 nanowire array

    NASA Astrophysics Data System (ADS)

    Chinnamuthu, P.; Mondal, A.; Singh, N. K.; Dhar, J. C.; Chattopadhyay, K. K.; Bhattacharya, Sekhar

    2012-09-01

    Vertically oriented TiO2 nanowire (NW) arrays were fabricated by glancing angle deposition technique. Field emission-scanning electron microscopy shows the formation of two different diameters ˜80 nm and ˜40 nm TiO2 NW for 120 and 460 rpm azimuthal rotation of the substrate. The x-ray diffraction and Raman scattering depicted the presence of rutile and anatase phase TiO2. The overall Raman scattering intensity decreased with nanowire diameter. The role of phonon confinement in anatase and rutile peaks has been discussed. The red (7.9 cm-1 of anatase Eg) and blue (7.4 cm-1 of rutile Eg, 7.8 cm-1 of rutile A1g) shifts of Raman frequencies were observed. UV-vis absorption measurements show the main band absorption at 3.42 eV, 3.48 eV, and ˜3.51 eV for thin film and NW prepared at 120 and 460 rpm, respectively. Three fold enhance photon absorption and intense light emission were observed for NW assembly. The photoluminescence emission from the NW assembly revealed blue shift in main band transition due to quantum confinement in NW structures.

  19. Layer-by-layer assembly synthesis of ZnO/SnO{sub 2} composite nanowire arrays as high-performance anode for lithium-ion batteries

    SciTech Connect

    Wang, Jiazheng; Du, Ning; Zhang, Hui; Yu, Jingxue; Yang, Deren

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer SnO{sub 2} nanoparticles was deposited on ZnO nanoarrays through layer-by-layer assembly. Black-Right-Pointing-Pointer The composite nanowire arrays show improved performance as anode for Li-ion battery. Black-Right-Pointing-Pointer Improved performance was attributed to the combining advantages of each ingredient. -- Abstract: A layer-by-layer approach has been developed to synthesize ZnO/SnO{sub 2} composite nanowire arrays on copper substrate. ZnO nanowire arrays have been first prepared on copper substrate through seed-assisted method, and then, the surface of ZnO nanowires have been modified by the polyelectrolyte. After oxidation-reduction reaction, SnO{sub 2} layer has been deposited onto the surface of ZnO nanowires. The as-synthesized ZnO/SnO{sub 2} composite nanowire arrays have been applied as anode for lithium-ion batteries, which show high reversible capacity and good cycling stability compared to pure ZnO nanowire arrays and SnO{sub 2} nanoparticles. It is believed that the improved performance may be attributed to the high capacity of SnO{sub 2} and the good cycling stability of the array structure on current collector.

  20. An effective surface-enhanced Raman scattering template based on gold nanoparticle/silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Wang, Ming-Li; Zhang, Chang-Xing; Wu, Zheng-Long; Jing, Xi-Li; Xu, Hai-Jun

    2014-06-01

    A large-scale Si nanowire array (SiNWA) is fabricated with gold (Au) nanoparticles by simple metal-assisted chemical etching and metal reduction processes. The three-dimensional nanostructured Au/SiNWA is evaluated as an active substrate for surface-enhanced Raman scattering (SERS). The results show that the detection limit for rhodamine 6G is as low as 10-7 M, and the Raman enhancement factor is as large as 105 with a relative standard deviation of less than 25%. After the calibration of the Raman peak intensities of rhodamine 6G and thiram, organic molecules could be quantitatively detected. These results indicate that Au/SiNWA is a promising SERS-active substrate for the detection of biomolecules present in low concentrations. Our findings are an important advance in SERS substrates to allow fast and quantitative detection of trace organic contaminants.

  1. Carbon-coated silicon nanowire array films for high-performance lithium-ion battery anodes

    NASA Astrophysics Data System (ADS)

    Huang, Rui; Fan, Xing; Shen, Wanci; Zhu, Jing

    2009-09-01

    Carbon-coated silicon nanowire array films prepared by metal catalytic etching of silicon wafers and pyrolyzing of carbon aerogel were used for lithium-ion battery anodes. The films exhibited an excellent first discharge capacity of 3344 mAh g-1 with a Coulombic efficiency of 84% at a rate of 150 mA g-1 between 2 and 0.02 V and a significantly enhanced cycling performance, i.e., a reversible capacity of 1326 mAh g-1 was retained after 40 cycles. These improvements were attributed to the uniform and continuous carbon coatings, which increased electronic contact and conduction and buffered large volume changes during lithium ion insertion/extraction.

  2. Indium tin oxide and indium phosphide heterojunction nanowire array solar cells

    SciTech Connect

    Yoshimura, Masatoshi Nakai, Eiji; Fukui, Takashi; Tomioka, Katsuhiro

    2013-12-09

    Heterojunction solar cells were formed with a position-controlled InP nanowire array sputtered with indium tin oxide (ITO). The ITO not only acted as a transparent electrode but also as forming a photovoltaic junction. The devices exhibited an open-circuit voltage of 0.436 V, short-circuit current of 24.8 mA/cm{sup 2}, and fill factor of 0.682, giving a power conversion efficiency of 7.37% under AM1.5 G illumination. The internal quantum efficiency of the device was higher than that of the world-record InP cell in the short wavelength range.

  3. Spin-on-doping for output power improvement of silicon nanowire array based thermoelectric power generators

    SciTech Connect

    Xu, B. Fobelets, K.

    2014-06-07

    The output power of a silicon nanowire array (NWA)-bulk thermoelectric power generator (TEG) with Cu contacts is improved by spin-on-doping (SOD). The Si NWAs used in this work are fabricated via metal assisted chemical etching (MACE) of 0.01–0.02 Ω cm resistivity n- and p-type bulk, converting ~4% of the bulk thickness into NWs. The MACE process is adapted to ensure crystalline NWs. Current-voltage and Seebeck voltage-temperature measurements show that while SOD mainly influences the contact resistance in bulk, it influences both contact resistance and power factor in NWA-bulk based TEGs. According to our experiments, using Si NWAs in combination with SOD increases the output power by an order of 3 under the same heating power due to an increased power factor, decreased thermal conductivity of the NWA and reduced Si-Cu contact resistance.

  4. Preparation of nickel nanowire arrays electrode for urea electro-oxidation in alkaline medium

    NASA Astrophysics Data System (ADS)

    Guo, Fen; Ye, Ke; Cheng, Kui; Wang, Guiling; Cao, Dianxue

    2015-03-01

    Fully metallic nickel nanowire arrays (NWAs) electrode is prepared by electrodepositing nickel within the pores and over-plating on the surface of polycarbonate template (PCT) with subsequent dissolution of the template in dichloromethane. The as-prepared electrode is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Urea electro-oxidation reaction in KOH solution on the nickel NWAs electrode is investigated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) tests. The results show that the nickel NWAs electrode achieves an onset oxidation potential of 0.25 V (vs. Ag/AgCl) and a peak current density of 160 mA cm-2 in 5 mol L-1 KOH and 0.33 mol L-1 urea accompanied with considerable stability.

  5. Optical simulations of P3HT/Si nanowire array hybrid solar cells

    PubMed Central

    2014-01-01

    An optical simulation of poly(3-hexylthiophene) (P3HT)/Si nanowire array (NWA) hybrid solar cells was investigated to evaluate the optical design requirements of the system by using finite-difference time-domain (FDTD) method. Steady improvement of light absorption was obtained with increased P3HT coating shell thickness from 0 to 80 nm on Si NWA. Further increasing the thickness caused dramatic decrease of the light absorption. Combined with the analysis of ultimate photocurrents, an optimum geometric structure with a coating P3HT thickness of 80 nm was proposed. At this structure, the hybrid solar cells show the most efficient light absorption. The optimization of the geometric structure and further understanding of the optical characteristics may contribute to the development for the practical experiment of the promising hybrid solar cells. PMID:24948883

  6. Effective electrocatalysis based on Ag2O nanowire arrays supported on a copper substrate.

    PubMed

    Ji, Rong; Wang, Lingling; Yu, Liutao; Geng, Baoyou; Wang, Guangfeng; Zhang, Xiaojun

    2013-11-13

    Silver oxide nanowire arrays (Ag2O NWAs) were first synthesized on a copper (Cu) rod by a simple and facile wet-chemistry approach without using any surfactants. The as-synthesized Ag2O NWA/Cu rod not only can be used as an integrated electrode (called a Ag2O NWA/CRIE) to detect hydrazine (HZ) but also can serve as the catalyst layer for a direct HZ fuel cell. The current density of HZ oxidation on Ag2O NWA (94.4 mA cm(-2)) is much bigger than that on a bare Cu rod (3.9 mA cm(-2)) at -0.6 V, and other Ag2O NWAs have the lowest onset potential (-0.85 V). This suggests that a Ag2O NWA integrated electrode has potential application in catalytic fields that contain the HZ fuel cell. PMID:23978111

  7. Fabrication of silicon nanowire arrays by near-field laser ablation and metal-assisted chemical etching.

    PubMed

    Brodoceanu, D; Alhmoud, H Z; Elnathan, R; Delalat, B; Voelcker, N H; Kraus, T

    2016-02-19

    We present an elegant route for the fabrication of ordered arrays of vertically-aligned silicon nanowires with tunable geometry at controlled locations on a silicon wafer. A monolayer of transparent microspheres convectively assembled onto a gold-coated silicon wafer acts as a microlens array. Irradiation with a single nanosecond laser pulse removes the gold beneath each focusing microsphere, leaving behind a hexagonal pattern of holes in the gold layer. Owing to the near-field effects, the diameter of the holes can be at least five times smaller than the laser wavelength. The patterned gold layer is used as catalyst in a metal-assisted chemical etching to produce an array of vertically-aligned silicon nanowires. This approach combines the advantages of direct laser writing with the benefits of parallel laser processing, yielding nanowire arrays with controlled geometry at predefined locations on the silicon surface. The fabricated VA-SiNW arrays can effectively transfect human cells with a plasmid encoding for green fluorescent protein. PMID:26778665

  8. Fabrication of silicon nanowire arrays by near-field laser ablation and metal-assisted chemical etching

    NASA Astrophysics Data System (ADS)

    Brodoceanu, D.; Alhmoud, H. Z.; Elnathan, R.; Delalat, B.; Voelcker, N. H.; Kraus, T.

    2016-02-01

    We present an elegant route for the fabrication of ordered arrays of vertically-aligned silicon nanowires with tunable geometry at controlled locations on a silicon wafer. A monolayer of transparent microspheres convectively assembled onto a gold-coated silicon wafer acts as a microlens array. Irradiation with a single nanosecond laser pulse removes the gold beneath each focusing microsphere, leaving behind a hexagonal pattern of holes in the gold layer. Owing to the near-field effects, the diameter of the holes can be at least five times smaller than the laser wavelength. The patterned gold layer is used as catalyst in a metal-assisted chemical etching to produce an array of vertically-aligned silicon nanowires. This approach combines the advantages of direct laser writing with the benefits of parallel laser processing, yielding nanowire arrays with controlled geometry at predefined locations on the silicon surface. The fabricated VA-SiNW arrays can effectively transfect human cells with a plasmid encoding for green fluorescent protein.

  9. Design of coated standing nanowire array solar cell performing beyond the planar efficiency limits

    NASA Astrophysics Data System (ADS)

    Zeng, Yang; Ye, Qinghao; Shen, Wenzhong

    2016-05-01

    The single standing nanowire (SNW) solar cells have been proven to perform beyond the planar efficiency limits in both open-circuit voltage and internal quantum efficiency due to the built-in concentration and the shifting of the absorption front. However, the expandability of these nano-scale units to a macro-scale photovoltaic device remains unsolved. The main difficulty lies in the simultaneous preservation of an effective built-in concentration in each unit cell and a broadband high absorption capability of their array. Here, we have provided a detailed theoretical guideline for realizing a macro-scale solar cell that performs furthest beyond the planar limits. The key lies in a complementary design between the light-trapping of the single SNWs and that of the photonic crystal slab formed by the array. By tuning the hybrid HE modes of the SNWs through the thickness of a coaxial dielectric coating, the optimized coated SNW array can sustain an absorption rate over 97.5% for a period as large as 425 nm, which, together with the inherited carrier extraction advantage, leads to a cell efficiency increment of 30% over the planar limit. This work has demonstrated the viability of a large-size solar cell that performs beyond the planar limits.

  10. 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.

  11. Crystal Orientation Controlled Photovoltaic Properties of Multilayer GaAs Nanowire Arrays.

    PubMed

    Han, Ning; Yang, Zai-Xing; Wang, Fengyun; Yip, SenPo; Li, Dapan; Hung, Tak Fu; Chen, Yunfa; Ho, Johnny C

    2016-06-28

    In recent years, despite significant progress in the synthesis, characterization, and integration of various nanowire (NW) material systems, crystal orientation controlled NW growth as well as real-time assessment of their growth-structure-property relationships still presents one of the major challenges in deploying NWs for practical large-scale applications. In this study, we propose, design, and develop a multilayer NW printing scheme for the determination of crystal orientation controlled photovoltaic properties of parallel GaAs NW arrays. By tuning the catalyst thickness and nucleation and growth temperatures in the two-step chemical vapor deposition, crystalline GaAs NWs with uniform, pure ⟨110⟩ and ⟨111⟩ orientations and other mixture ratios can be successfully prepared. Employing lift-off resists, three-layer NW parallel arrays can be easily attained for X-ray diffraction in order to evaluate their growth orientation along with the fabrication of NW parallel array based Schottky photovoltaic devices for the subsequent performance assessment. Notably, the open-circuit voltage of purely ⟨111⟩-oriented NW arrayed cells is far higher than that of ⟨110⟩-oriented NW arrayed counterparts, which can be interpreted by the different surface Fermi level pinning that exists on various NW crystal surface planes due to the different As dangling bond densities. All this indicates the profound effect of NW crystal orientation on physical and chemical properties of GaAs NWs, suggesting the careful NW design considerations for achieving optimal photovoltaic performances. The approach presented here could also serve as a versatile and powerful platform for in situ characterization of other NW materials. PMID:27223050

  12. Crystal Orientation Controlled Photovoltaic Properties of Multilayer GaAs Nanowire Arrays.

    PubMed

    Han, Ning; Yang, Zai-Xing; Wang, Fengyun; Yip, SenPo; Li, Dapan; Hung, Tak Fu; Chen, Yunfa; Ho, Johnny C

    2016-06-28

    In recent years, despite significant progress in the synthesis, characterization, and integration of various nanowire (NW) material systems, crystal orientation controlled NW growth as well as real-time assessment of their growth-structure-property relationships still presents one of the major challenges in deploying NWs for practical large-scale applications. In this study, we propose, design, and develop a multilayer NW printing scheme for the determination of crystal orientation controlled photovoltaic properties of parallel GaAs NW arrays. By tuning the catalyst thickness and nucleation and growth temperatures in the two-step chemical vapor deposition, crystalline GaAs NWs with uniform, pure ⟨110⟩ and ⟨111⟩ orientations and other mixture ratios can be successfully prepared. Employing lift-off resists, three-layer NW parallel arrays can be easily attained for X-ray diffraction in order to evaluate their growth orientation along with the fabrication of NW parallel array based Schottky photovoltaic devices for the subsequent performance assessment. Notably, the open-circuit voltage of purely ⟨111⟩-oriented NW arrayed cells is far higher than that of ⟨110⟩-oriented NW arrayed counterparts, which can be interpreted by the different surface Fermi level pinning that exists on various NW crystal surface planes due to the different As dangling bond densities. All this indicates the profound effect of NW crystal orientation on physical and chemical properties of GaAs NWs, suggesting the careful NW design considerations for achieving optimal photovoltaic performances. The approach presented here could also serve as a versatile and powerful platform for in situ characterization of other NW materials.

  13. Silicon nanowire arrays with passivated axial p-i-n junctions for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Liu, Pei; Zaslavsky, Alexander; Pacifici, Domenico; Ha, Jong-Yoon; Krylyuk, Sergiy; Davydov, Albert

    2014-03-01

    Metal catalyst-assisted vapor-liquid-solid mechanism can be used to grow large areas of nanowires (NWs) with compositional and doping control in either axial or core-shell geometries. Here, we report on vertical arrays of Si axial p- i- n oxide-passivated NWs that were 12 microns long with a 4 micron intrinsic section. The NW arrays were planarized using SU-8 photoresist, followed by reactive ion etching to expose the NW tips. Top n-contact was realized by sputter deposition of a 200 nm IZO layer. The p-contact was made by backside metallization of the p-Si substrate. Under AM 1.5 illumination, unpassivated NW arrays exhibited an open-circuit voltage, VOC of 170 mV, a short-circuit current density JSC >3.7 mA/cm2 (with uncertainty due to the unknown fraction of properly contacted NWs), and a fill factor of 28.9%. After the passivation, VOC, JSC and FF increased to 250 mV, >9.2 mA/cm2 and 35.7%, respectively. The measured normal reflectance was around 6% over the 400-1000 nm spectral range, whereas the diffuse reflectance was around 20% over the same range, indicating strong light scattering and absorption by the NWs. The photovoltaic performance of passivated single NWs and NW arrays were compared using a 532 nm laser with a power density of about 10 W/cm2. Higher values of VOC and FF obtained for the latter are explained by light trapping in the NW arrays.

  14. Planar Gallium arsenide nanowire arrays for nanoelectronics: Controlled growth, doping, characterization, and devices

    NASA Astrophysics Data System (ADS)

    Dowdy, Ryan Stewart

    The Vapor-Liquid-Solid (VLS) mechanism is a bottom-up approach to produce onedimensional semiconductor structures, or nanowires. VLS nanowires are formed via a chemical or physical deposition process, where a metallic nanoparticle (seed) facilitates the growth. Nanowire growth diameter is strongly correlated to seed size, therefore top-down patterning can control site location and diameter of nanowire growth. Nanowires are sought after for their potential use as a manageable way produce small dimensioned semiconductor features without the need of expensive lithographic techniques. VLS nanowires commonly grow out-of-plane with respect to their growth substrate, resulting in difficulty with integrating VLS nanowires into existing device processing which is intended for planar geometries. Nanowires are typically removed from the substrate, which requires painstaking and uneconomical methods to pattern and align the nanowires. Planar nanowires are a potential solution to this issue; they grow in-plane on the substrate surface, epitaxially attached along its entire axis. Planar nanowires, as is, can be integrated into any preexisting planar semiconductor process, combining the advantages of nanowires with increased manufacturability. In this dissertation, planar GaAs nanowires are grown using metal organic chemical vapor deposition (MOCVD) with Au nanoparticles as the liquid metal seed. Growth occurs across multiple substrates to elucidate the mechanism behind planar nanowire growth direction. Knowledge gained by observing planar nanowire growth is used to precisely control nanowire growth direction. Subsequently the doping of planar nanowires is explored and unique phenomena related to the p-type doping of planar nanowires are investigated and discussed. The advantages of using planar nanowires are demonstrated through the controlled growth and doping of planar nanowires, and ultimately fabrication of electronic devices using conventional planar process techniques

  15. Influence of the packing fraction and host matrix on the magnetoelastic anisotropy in Ni nanowire composite arrays

    NASA Astrophysics Data System (ADS)

    Piraux, Luc; Hamoir, Gaël; Encinas, Armando; De La Torre Medina, Joaquin; Abreu Araujo, Flavio

    2013-09-01

    The influence of the packing fraction on thermally induced magnetoelastic effects has been studied in Ni nanowires embedded in polycarbonate, poly(vinylidene difluoride), and alumina nanoporous membranes of different porosities for temperatures between 77 K and 345 K. For nanowires embedded in polymer membranes, the contrasting shift in the ferromagnetic resonance frequency when the temperature is either above or below ambient temperature is consistent with the occurrence of uniaxial magnetoelastic anisotropy effects due to the large thermal expansion coefficient mismatch between the metal nanowires and the membrane. A model which considers the influence of the nanowires packing fraction and the membrane material on the magnetoelastic effects, arising from the matrix-assisted deformation process, is proposed. The model is able to successfully explain the experimentally observed effects for the Ni nanowire arrays embedded in the different porous membranes and their variation with the packing fraction. The possibility to modulate the magnetic anisotropy of such nanocomposites by an appropriate choice of membrane material, packing fraction, and sample temperature is of considerable importance to achieve magnetically tunable devices.

  16. Near-infrared quarter-waveplate with near-unity polarization conversion efficiency based on silicon nanowire array.

    PubMed

    Dai, Yanmeng; Cai, Hongbing; Ding, Huaiyi; Ning, Zhen; Pan, Nan; Zhu, Hong; Shi, Qinwei; Wang, Xiaoping

    2015-04-01

    Metasurfaces made of subwavelength resonators can modify the wave front of light within the thickness much less than free space wavelength, showing great promises in integrated optics. In this paper, we theoretically show that electric and magnetic resonances supported simultaneously by a subwavelength nanowire with high refractive-index can be utilized to design metasurfaces with near-unity transmittance. Taking silicon nanowire for instance, we design numerically a near-infrared quarter-waveplate with high transmittance using a subwavelength nanowire array. The operation bandwidth of the waveplate is 0.14 μm around the center wavelength of 1.71 μm. The waveplate can convert a 45° linearly polarized incident light to circularly polarized light with conversion efficiency ranging from 94% to 98% over the operation band. The performance of quarter waveplate can in principle be tuned and improved through optimizing the parameters of nanowire arrays. Its compatibility to microelectronic technologies opens up a distinct possibility to integrate nanophotonics into the current silicon-based electronic devices.

  17. Uniform Nickel Vanadate (Ni3V2O8) Nanowire Arrays Organized by Ultrathin Nanosheets with Enhanced Lithium Storage Properties

    PubMed Central

    Wang, Chang; Fang, Dong; Wang, Hong’en; Cao, Yunhe; Xu, Weilin; Liu, Xiaoqing; Luo, Zhiping; Li, Guangzhong; Jiang, Ming; Xiong, Chuanxi

    2016-01-01

    Development of three-dimensional nano-architectures on current collectors has emerged as an effective strategy for enhancing rate capability and cycling stability of the electrodes. Herein, a novel type of Ni3V2O8 nanowires, organized by ultrathin hierarchical nanosheets (less than 5 nm) on Ti foil, has been obtained by a two-step hydrothermal synthesis method. Studies on structural and thermal properties of the as-prepared Ni3V2O8 nanowire arrays are carried out and their morphology has changed obviously in the following heat treatment at 300 and 500 °C. As an electrode material for lithium ion batteries, the unique configuration of Ni3V2O8 nanowires presents enhanced capacitance, satisfying rate capability and good cycling stability. The reversible capacity of the as-prepared Ni3V2O8 nanowire arrays reaches 969.72 mAh·g−1 with a coulombic efficiency over 99% at 500 mA·g−1 after 500 cycles. PMID:26860692

  18. Near-infrared quarter-waveplate with near-unity polarization conversion efficiency based on silicon nanowire array.

    PubMed

    Dai, Yanmeng; Cai, Hongbing; Ding, Huaiyi; Ning, Zhen; Pan, Nan; Zhu, Hong; Shi, Qinwei; Wang, Xiaoping

    2015-04-01

    Metasurfaces made of subwavelength resonators can modify the wave front of light within the thickness much less than free space wavelength, showing great promises in integrated optics. In this paper, we theoretically show that electric and magnetic resonances supported simultaneously by a subwavelength nanowire with high refractive-index can be utilized to design metasurfaces with near-unity transmittance. Taking silicon nanowire for instance, we design numerically a near-infrared quarter-waveplate with high transmittance using a subwavelength nanowire array. The operation bandwidth of the waveplate is 0.14 μm around the center wavelength of 1.71 μm. The waveplate can convert a 45° linearly polarized incident light to circularly polarized light with conversion efficiency ranging from 94% to 98% over the operation band. The performance of quarter waveplate can in principle be tuned and improved through optimizing the parameters of nanowire arrays. Its compatibility to microelectronic technologies opens up a distinct possibility to integrate nanophotonics into the current silicon-based electronic devices. PMID:25968730

  19. Three-Dimensional Porous Iron Vanadate Nanowire Arrays as a High-Performance Lithium-Ion Battery.

    PubMed

    Cao, Yunhe; Fang, Dong; Liu, Ruina; Jiang, Ming; Zhang, Hang; Li, Guangzhong; Luo, Zhiping; Liu, Xiaoqing; Xu, Jie; Xu, Weilin; Xiong, Chuanxi

    2015-12-23

    Development of three-dimensional nanoarchitectures on current collectors has emerged as an effective strategy for enhancing rate capability and cycling stability of the electrodes. Herein, a new type of three-dimensional porous iron vanadate (Fe0.12V2O5) nanowire arrays on a Ti foil has been synthesized by a hydrothermal method. The as-prepared Fe0.12V2O5 nanowires are about 30 nm in diameter and several micrometers in length. The effect of reaction time on the resulting morphology is investigated and the mechanism for the nanowire formation is proposed. As an electrode material used in lithium-ion batteries, the unique configuration of the Fe0.12V2O5 nanowire arrays presents enhanced capacitance, satisfying rate capability and good cycling stability, as evaluated by cyclic voltammetry and galvanostatic discharge-charge cycling. It delivers a high discharge capacity of 293 mAh·g(-1) at 2.0-3.6 V or 382.2 mAh·g(-1) at 1.0-4.0 V after 50 cycles at 30 mA·g(-1).

  20. A nanoelectronic nose: a hybrid nanowire/carbon nanotube sensor array with integrated micromachined hotplates for sensitive gas discrimination.

    PubMed

    Chen, Po-Chiang; Ishikawa, Fumiaki N; Chang, Hsiao-Kang; Ryu, Koungmin; Zhou, Chongwu

    2009-03-25

    A novel hybrid chemical sensor array composed of individual In(2)O(3) nanowires, SnO(2) nanowires, ZnO nanowires, and single-walled carbon nanotubes with integrated micromachined hotplates for sensitive gas discrimination was demonstrated. Key features of our approach include the integration of nanowire and carbon nanotube sensors, precise control of the sensor temperature using the micromachined hotplates, and the use of principal component analysis for pattern recognition. This sensor array was exposed to important industrial gases such as hydrogen, ethanol and nitrogen dioxide at different concentrations and sensing temperatures, and an excellent selectivity was obtained to build up an interesting 'smell-print' library of these gases. Principal component analysis of the sensing results showed great discrimination of those three tested chemicals, and in-depth analysis revealed clear improvement of selectivity by the integration of carbon nanotube sensors. This nanoelectronic nose approach has great potential for detecting and discriminating between a wide variety of gases, including explosive ones and nerve agents. PMID:19420469

  1. ITO@Cu2S tunnel junction nanowire arrays as efficient counter electrode for quantum-dot-sensitized solar cells.

    PubMed

    Jiang, Yan; Zhang, Xing; Ge, Qian-Qing; Yu, Bin-Bin; Zou, Yu-Gang; Jiang, Wen-Jie; Song, Wei-Guo; Wan, Li-Jun; Hu, Jin-Song

    2014-01-01

    Quantum-dot-sensitized solar cell (QDSSC) has been considered as an alternative to new generation photovoltaics, but it still presents very low power conversion efficiency. Besides the continuous effort on improving photoanodes and electrolytes, the focused investigation on charge transfer at interfaces and the rational design for counter electrodes (CEs) are recently receiving much attention. Herein, core-shell nanowire arrays with tin-doped indium oxide (ITO) nanowire core and Cu2S nanocrystal shell (ITO@Cu2S) were dedicatedly designed and fabricated as new efficient CEs for QDSSCs in order to improve charge collection and transport and to avoid the intrinsic issue of copper dissolution in popular and most efficient Cu/Cu2S CEs. The high-quality tunnel junctions formed between n-type ITO nanowires and p-type Cu2S nanocrystals led to the considerable decrease in sheet resistance and charge transfer resistance and thus facilitated the electron transport during the operation of QDSSCs. The three-dimensional structure of nanowire arrays provided high surface area for more active catalytic sites and easy accessibility for an electrolyte. As a result, the power conversion efficiency of QDSSCs with the designed ITO@Cu2S CEs increased by 84.5 and 33.5% compared to that with planar Au and Cu2S CEs, respectively.

  2. Broadband High Efficiency Fractal-Like and Diverse Geometry Silicon Nanowire Arrays for Photovoltaic Applications

    NASA Astrophysics Data System (ADS)

    AL-Zoubi, Omar H.

    Solar energy has many advantages over conventional sources of energy. It is abundant, clean and sustainable. One way to convert solar energy directly into electrical energy is by using the photovoltaic solar cells (PVSC). Despite PVSC are becoming economically competitive, they still have high cost and low light to electricity conversion efficiency. Therefore, increasing the efficiency and reducing the cost are key elements for producing economically more competitive PVSC that would have significant impact on energy market and saving environment. A significant percentage of the PVSC cost is due to the materials cost. For that, thin films PVSC have been proposed which offer the benefits of the low amount of material and fabrication costs. Regrettably, thin film PVSC show poor light to electricity conversion efficiency because of many factors especially the high optical losses. To enhance conversion efficiency, numerous techniques have been proposed to reduce the optical losses and to enhance the absorption of light in thin film PVSC. One promising technique is the nanowire (NW) arrays in general and the silicon nanowire (SiNW) arrays in particular. The purpose of this research is to introduce vertically aligned SiNW arrays with enhanced and broadband absorption covering the entire solar spectrum while simultaneously reducing the amount of material used. To this end, we apply new concept for designing SiNW arrays based on employing diversity of physical dimensions, especially radial diversity within certain lattice configurations. In order to study the interaction of light with SiNW arrays and compute their optical properties, electromagnetic numerical modeling is used. A commercial numerical electromagnetic solver software package, high frequency structure simulation (HFSS), is utilized to model the SiNW arrays and to study their optical properties. We studied different geometries factors that affect the optical properties of SiNW arrays. Based on this study, we

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

    PubMed

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

    2014-08-21

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

  4. 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

  5. Defect level characterization of silicon nanowire arrays: Towards novel experimental paradigms

    SciTech Connect

    Carapezzi, Stefania; Castaldini, Antonio; Cavallini, Anna

    2014-02-21

    The huge amount of knowledge, and infrastructures, brought by silicon (Si) technology, make Si Nanowires (NWs) an ideal choice for nano-electronic Si-based devices. This, in turn, challenges the scientific research to adapt the technical and theoretical paradigms, at the base of established experimental techniques, in order to probe the properties of these systems. Metal-assisted wet-Chemical Etching (MaCE) [1, 2] is a promising fast, easy and cheap method to grow high aspect-ratio aligned Si NWs. Further, contrary to other fabrication methods, this method avoids the possible detrimental effects related to Au diffusion into NWs. We investigated the bandgap level diagram of MaCE Si NW arrays, phosphorous-doped, by means of Deep Level Transient Spectroscopy. The presence of both shallow and deep levels has been detected. The results have been examined in the light of the specificity of the MaCE growth. The study of the electronic levels in Si NWs is, of course, of capital importance in view of the integration of Si NW arrays as active layers in actual devices.

  6. Nanowire array chips for molecular typing of rare trafficking leukocytes with application to neurodegenerative pathology

    NASA Astrophysics Data System (ADS)

    Kwak, Minsuk; Kim, Dong-Joo; Lee, Mi-Ri; Wu, Yu; Han, Lin; Lee, Sang-Kwon; Fan, Rong

    2014-05-01

    Despite the presence of the blood-brain barrier (BBB) that restricts the entry of immune cells and mediators into the central nervous system (CNS), a small number of peripheral leukocytes can traverse the BBB and infiltrate into the CNS. The cerebrospinal fluid (CSF) is one of the major routes through which trafficking leukocytes migrate into the CNS. Therefore, the number of leukocytes and their phenotypic compositions in the CSF may represent important sources to investigate immune-to-brain interactions or diagnose and monitor neurodegenerative diseases. Due to the paucity of trafficking leucocytes in the CSF, a technology capable of efficient isolation, enumeration, and molecular typing of these cells in the clinical settings has not been achieved. In this study, we report on a biofunctionalized silicon nanowire array chip for highly efficient capture and multiplexed phenotyping of rare trafficking leukocytes in small quantities (50 microliters) of clinical CSF specimens collected from neurodegenerative disease patients. The antibody coated 3D nanostructured materials exhibited vastly improved rare cell capture efficiency due to high-affinity binding and enhanced cell-substrate interactions. Moreover, our platform creates multiple cell capture interfaces, each of which can selectively isolate specific leukocyte phenotypes. A comparison with the traditional immunophenotyping using flow cytometry demonstrated that our novel silicon nanowire-based rare cell analysis platform can perform rapid detection and simultaneous molecular characterization of heterogeneous immune cells. Multiplexed molecular typing of rare leukocytes in CSF samples collected from Alzheimer's disease patients revealed the elevation of white blood cell counts and significant alterations in the distribution of major leukocyte phenotypes. Our technology represents a practical tool for potentially diagnosing and monitoring the pathogenesis of neurodegenerative diseases by allowing an effective

  7. Nanowire array chips for molecular typing of rare trafficking leukocytes with application to neurodegenerative pathology

    NASA Astrophysics Data System (ADS)

    Kwak, Minsuk; Kim, Dong-Joo; Lee, Mi-Ri; Wu, Yu; Han, Lin; Lee, Sang-Kwon; Fan, Rong

    2014-05-01

    Despite the presence of the blood-brain barrier (BBB) that restricts the entry of immune cells and mediators into the central nervous system (CNS), a small number of peripheral leukocytes can traverse the BBB and infiltrate into the CNS. The cerebrospinal fluid (CSF) is one of the major routes through which trafficking leukocytes migrate into the CNS. Therefore, the number of leukocytes and their phenotypic compositions in the CSF may represent important sources to investigate immune-to-brain interactions or diagnose and monitor neurodegenerative diseases. Due to the paucity of trafficking leucocytes in the CSF, a technology capable of efficient isolation, enumeration, and molecular typing of these cells in the clinical settings has not been achieved. In this study, we report on a biofunctionalized silicon nanowire array chip for highly efficient capture and multiplexed phenotyping of rare trafficking leukocytes in small quantities (50 microliters) of clinical CSF specimens collected from neurodegenerative disease patients. The antibody coated 3D nanostructured materials exhibited vastly improved rare cell capture efficiency due to high-affinity binding and enhanced cell-substrate interactions. Moreover, our platform creates multiple cell capture interfaces, each of which can selectively isolate specific leukocyte phenotypes. A comparison with the traditional immunophenotyping using flow cytometry demonstrated that our novel silicon nanowire-based rare cell analysis platform can perform rapid detection and simultaneous molecular characterization of heterogeneous immune cells. Multiplexed molecular typing of rare leukocytes in CSF samples collected from Alzheimer's disease patients revealed the elevation of white blood cell counts and significant alterations in the distribution of major leukocyte phenotypes. Our technology represents a practical tool for potentially diagnosing and monitoring the pathogenesis of neurodegenerative diseases by allowing an effective

  8. Ultra high density three dimensional capacitors based on Si nanowires array grown on a metal layer

    NASA Astrophysics Data System (ADS)

    Morel, P. H.; Haberfehlner, G.; Lafond, D.; Audoit, G.; Jousseaume, V.; Leroux, C.; Fayolle-Lecocq, M.; Baron, T.; Ernst, T.

    2012-08-01

    We report the fabrication and the characterization of chemical vapor deposition (CVD) grown silicon nanowires capacitors using a complementary-metal-oxide-semiconductor (CMOS) circuit interconnect level compatible process. Silicon nanowires have been grown by CVD on metallic interconnect lines used in today's CMOS circuits at low temperature (<425 °C) and using copper as catalyst. The nanowire assembly develops a huge surface leading to very high measured capacitance densities reaching 18 μF/cm2, and featuring a ×23 gain when compared to the same structure without nanowires. This opens the path toward embedded capacitances technologies by using bottom-up nanowires.

  9. Significantly Enhanced Visible Light Photoelectrochemical Activity in TiO₂ Nanowire Arrays by Nitrogen Implantation.

    PubMed

    Wang, Gongming; Xiao, Xiangheng; Li, Wenqing; Lin, Zhaoyang; Zhao, Zipeng; Chen, Chi; Wang, Chen; Li, Yongjia; Huang, Xiaoqing; Miao, Ling; Jiang, Changzhong; Huang, Yu; Duan, Xiangfeng

    2015-07-01

    Titanium oxide (TiO2) represents one of most widely studied materials for photoelectrochemical (PEC) water splitting but is severely limited by its poor efficiency in the visible light range. Here, we report a significant enhancement of visible light photoactivity in nitrogen-implanted TiO2 (N-TiO2) nanowire arrays. Our systematic studies show that a post-implantation thermal annealing treatment can selectively enrich the substitutional nitrogen dopants, which is essential for activating the nitrogen implanted TiO2 to achieve greatly enhanced visible light photoactivity. An incident photon to electron conversion efficiency (IPCE) of ∼10% is achieved at 450 nm in N-TiO2 without any other cocatalyst, far exceeding that in pristine TiO2 nanowires (∼0.2%). The integration of oxygen evolution reaction (OER) cocatalyst with N-TiO2 can further increase the IPCE at 450 nm to ∼17% and deliver an unprecedented overall photocurrent density of 1.9 mA/cm(2), by integrating the IPCE spectrum with standard AM 1.5G solar spectrum. Systematic photoelectrochemical and electrochemical studies demonstrated that the enhanced PEC performance can be attributed to the significantly improved visible light absorption and more efficient charge separation. Our studies demonstrate the implantation approach can be used to reliably dope TiO2 to achieve the best performed N-TiO2 photoelectrodes to date and may be extended to fundamentally modify other semiconductor materials for PEC water splitting.

  10. Nanowire array chips for molecular typing of rare trafficking leukocytes with application to neurodegenerative pathology

    PubMed Central

    Kwak, Minsuk; Kim, Dong-Joo; Lee, Mi-Ri; Wu, Yu; Han, Lin; Lee, Sang-Kwon; Fan, Rong

    2014-01-01

    Despite the presence of the blood-brain barrier (BBB) that restricts the entry of immune cells and mediators into the central nervous system (CNS), a small number of peripheral leukocytes can traverse BBB and infiltrate into the CNS. Cerebrospinal fluid (CSF) is one of the major routes through which trafficking leukocytes migrate into the CNS. Therefore, the number of leukocytes and their phenotypic compositions in CSF may represent important sources to investigate immune-to-brain interaction, or diagnose and monitor neurodegenerative diseases. Due to the paucity of trafficking leucocytes in CSF, a technology capable of efficient isolation, enumeration, and molecular typing of these cells in the clinical settings has not been achieved. In this study, we report on a biofunctionalized silicon nanowire array chip for highly efficient capture and multiplexed phenotyping of rare trafficking leukocytes in small quantities (50 microliters) of clinical CSF specimens collected from neurodegenerative disease patients. The antibody-coated 3D nanostructured materials exhibited vastly improved rare cell capture efficiency due to high-affinity binding and enhanced cell-substrate interactions. Moreover, our platform creates multiple cell capture interfaces, each of which can selectively isolate specific leukocyte phenotype. Comparison with the traditional immunophenotyping using flow cytometry demonstrated that our novel silicon nanowire-based rare cell analysis platform can perform rapid detection and simultaneous molecular characterization of heterogeneous immune cells. Multiplexed molecular typing of rare leukocytes in CSF samples collected from Alzheimer’s disease patients revealed the elevation of white blood cell counts and significant alterations in the distribution of major leukocyte phenotypes. Our technology represents a practical tool potentially for diagnosing and monitoring the pathogenesis of neurodegenerative diseases by allowing an effective hematological

  11. Color-tunable, phosphor-free InGaN nanowire light-emitting diode arrays monolithically integrated on silicon.

    PubMed

    Wang, Renjie; Nguyen, Hieu P T; Connie, Ashfiqua T; Lee, J; Shih, Ishiang; Mi, Zetian

    2014-12-15

    We demonstrate controllable and tunable full color light generation through the monolithic integration of blue, green/yellow, and orange/red InGaN nanowire light-emitting diodes (LEDs). Such multi-color nanowire LED arrays are fabricated directly on Si substrate using a three-step selective area molecular beam epitaxy growth process. The lateral-arranged multi-color subpixels enable controlled light mixing at the chip-level and yield color-tunable light emission with CCT values in the range from 1900 K to 6800 K, while maintaining excellent color rendering capability. This work provides a viable approach for achieving micron and nanoscale tunable full-color LED arrays without the compromise between the device efficiency and light quality associated with conventional phosphor-based LEDs. PMID:25607491

  12. Color-tunable, phosphor-free InGaN nanowire light-emitting diode arrays monolithically integrated on silicon.

    PubMed

    Wang, Renjie; Nguyen, Hieu P T; Connie, Ashfiqua T; Lee, J; Shih, Ishiang; Mi, Zetian

    2014-12-15

    We demonstrate controllable and tunable full color light generation through the monolithic integration of blue, green/yellow, and orange/red InGaN nanowire light-emitting diodes (LEDs). Such multi-color nanowire LED arrays are fabricated directly on Si substrate using a three-step selective area molecular beam epitaxy growth process. The lateral-arranged multi-color subpixels enable controlled light mixing at the chip-level and yield color-tunable light emission with CCT values in the range from 1900 K to 6800 K, while maintaining excellent color rendering capability. This work provides a viable approach for achieving micron and nanoscale tunable full-color LED arrays without the compromise between the device efficiency and light quality associated with conventional phosphor-based LEDs.

  13. A high performance three-phase enzyme electrode based on superhydrophobic mesoporous silicon nanowire arrays for glucose detection

    NASA Astrophysics Data System (ADS)

    Xu, Chenlong; Song, Zhiqian; Xiang, Qun; Jin, Jian; Feng, Xinjian

    2016-03-01

    We describe here a high performance oxygen-rich three-phase enzyme electrode based on superhydrophobic mesoporous silicon nanowire arrays for glucose detection. We demonstrate that its linear detection upper limit is 30 mM, more than 15 times higher than that can be obtained on the normal enzyme-electrode. Notably, the three-phase enzyme electrode output is insensitive to the significant oxygen level fluctuation in analyte solution.We describe here a high performance oxygen-rich three-phase enzyme electrode based on superhydrophobic mesoporous silicon nanowire arrays for glucose detection. We demonstrate that its linear detection upper limit is 30 mM, more than 15 times higher than that can be obtained on the normal enzyme-electrode. Notably, the three-phase enzyme electrode output is insensitive to the significant oxygen level fluctuation in analyte solution. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08370b

  14. Fabrication and optical property of metal nanowire arrays embedded in anodic porous alumina membrane

    NASA Astrophysics Data System (ADS)

    Takase, Kouichi; Shimizu, Tomohiro; Sugawa, Kosuke; Aono, Takashige; Shirai, Yuma; Nishida, Tomohiko; Shingubara, Shoso

    2016-06-01

    Nanowires embedded in nanopores are potentially tough against surface scraping and agglomeration. In this study, we have fabricated Au and Ni nanowires embedded into anodic porous alumina (APA) and investigated their reflectance to study the effects of surface plasmon absorption properties and conversion from solar energy to thermal energy. Au nanowires embedded into APA show typical gold surface plasmon absorption at approximately 530 nm. On the other hand, Ni nanowires show quite a low reflectance under 600 nm. In the temperature elevation test, both Au and Ni nanowire samples present the same capability to warm up water. It means that Ni nanowires embedded into APA have almost the same photothermal activity as Au nanowires.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  16. A high performance three-phase enzyme electrode based on superhydrophobic mesoporous silicon nanowire arrays for glucose detection.

    PubMed

    Xu, Chenlong; Song, Zhiqian; Xiang, Qun; Jin, Jian; Feng, Xinjian

    2016-04-14

    We describe here a high performance oxygen-rich three-phase enzyme electrode based on superhydrophobic mesoporous silicon nanowire arrays for glucose detection. We demonstrate that its linear detection upper limit is 30 mM, more than 15 times higher than that can be obtained on the normal enzyme-electrode. Notably, the three-phase enzyme electrode output is insensitive to the significant oxygen level fluctuation in analyte solution.

  17. A high performance three-phase enzyme electrode based on superhydrophobic mesoporous silicon nanowire arrays for glucose detection.

    PubMed

    Xu, Chenlong; Song, Zhiqian; Xiang, Qun; Jin, Jian; Feng, Xinjian

    2016-04-14

    We describe here a high performance oxygen-rich three-phase enzyme electrode based on superhydrophobic mesoporous silicon nanowire arrays for glucose detection. We demonstrate that its linear detection upper limit is 30 mM, more than 15 times higher than that can be obtained on the normal enzyme-electrode. Notably, the three-phase enzyme electrode output is insensitive to the significant oxygen level fluctuation in analyte solution. PMID:26983941

  18. Piezo-generator integrating a vertical array of GaN nanowires

    NASA Astrophysics Data System (ADS)

    Jamond, N.; Chrétien, P.; Houzé, F.; Lu, L.; Largeau, L.; Maugain, O.; Travers, L.; Harmand, J. C.; Glas, F.; Lefeuvre, E.; Tchernycheva, M.; Gogneau, N.

    2016-08-01

    We demonstrate the first piezo-generator integrating a vertical array of GaN nanowires (NWs). We perform a systematic multi-scale analysis, going from single wire properties to macroscopic device fabrication and characterization, which allows us to establish for GaN NWs the relationship between the material properties and the piezo-generation, and to propose an efficient piezo-generator design. The piezo-conversion of individual MBE-grown p-doped GaN NWs in a dense array is assessed by atomic force microscopy (AFM) equipped with a Resiscope module yielding an average output voltage of 228 ± 120 mV and a maximum value of 350 mV generated per NW. In the case of p-doped GaN NWs, the piezo-generation is achieved when a positive piezo-potential is created inside the nanostructures, i.e. when the NWs are submitted to compressive deformation. The understanding of the piezo-generation mechanism in our GaN NWs, gained from AFM analyses, is applied to design a piezo-generator operated under compressive strain. The device consists of NW arrays of several square millimeters in size embedded into spin-on glass with a Schottky contact for rectification and collection of piezo-generated carriers. The generator delivers a maximum power density of ˜12.7 mW cm-3. This value sets the new state of the art for piezo-generators based on GaN NWs and more generally on nitride NWs, and offers promising prospects for the use of GaN NWs as high-efficiency ultra-compact energy harvesters.

  19. Piezo-generator integrating a vertical array of GaN nanowires.

    PubMed

    Jamond, N; Chrétien, P; Houzé, F; Lu, L; Largeau, L; Maugain, O; Travers, L; Harmand, J C; Glas, F; Lefeuvre, E; Tchernycheva, M; Gogneau, N

    2016-08-12

    We demonstrate the first piezo-generator integrating a vertical array of GaN nanowires (NWs). We perform a systematic multi-scale analysis, going from single wire properties to macroscopic device fabrication and characterization, which allows us to establish for GaN NWs the relationship between the material properties and the piezo-generation, and to propose an efficient piezo-generator design. The piezo-conversion of individual MBE-grown p-doped GaN NWs in a dense array is assessed by atomic force microscopy (AFM) equipped with a Resiscope module yielding an average output voltage of 228 ± 120 mV and a maximum value of 350 mV generated per NW. In the case of p-doped GaN NWs, the piezo-generation is achieved when a positive piezo-potential is created inside the nanostructures, i.e. when the NWs are submitted to compressive deformation. The understanding of the piezo-generation mechanism in our GaN NWs, gained from AFM analyses, is applied to design a piezo-generator operated under compressive strain. The device consists of NW arrays of several square millimeters in size embedded into spin-on glass with a Schottky contact for rectification and collection of piezo-generated carriers. The generator delivers a maximum power density of ∼12.7 mW cm(-3). This value sets the new state of the art for piezo-generators based on GaN NWs and more generally on nitride NWs, and offers promising prospects for the use of GaN NWs as high-efficiency ultra-compact energy harvesters. PMID:27363777

  20. Piezo-generator integrating a vertical array of GaN nanowires

    NASA Astrophysics Data System (ADS)

    Jamond, N.; Chrétien, P.; Houzé, F.; Lu, L.; Largeau, L.; Maugain, O.; Travers, L.; Harmand, J. C.; Glas, F.; Lefeuvre, E.; Tchernycheva, M.; Gogneau, N.

    2016-08-01

    We demonstrate the first piezo-generator integrating a vertical array of GaN nanowires (NWs). We perform a systematic multi-scale analysis, going from single wire properties to macroscopic device fabrication and characterization, which allows us to establish for GaN NWs the relationship between the material properties and the piezo-generation, and to propose an efficient piezo-generator design. The piezo-conversion of individual MBE-grown p-doped GaN NWs in a dense array is assessed by atomic force microscopy (AFM) equipped with a Resiscope module yielding an average output voltage of 228 ± 120 mV and a maximum value of 350 mV generated per NW. In the case of p-doped GaN NWs, the piezo-generation is achieved when a positive piezo-potential is created inside the nanostructures, i.e. when the NWs are submitted to compressive deformation. The understanding of the piezo-generation mechanism in our GaN NWs, gained from AFM analyses, is applied to design a piezo-generator operated under compressive strain. The device consists of NW arrays of several square millimeters in size embedded into spin-on glass with a Schottky contact for rectification and collection of piezo-generated carriers. The generator delivers a maximum power density of ∼12.7 mW cm‑3. This value sets the new state of the art for piezo-generators based on GaN NWs and more generally on nitride NWs, and offers promising prospects for the use of GaN NWs as high-efficiency ultra-compact energy harvesters.

  1. Piezo-generator integrating a vertical array of GaN nanowires.

    PubMed

    Jamond, N; Chrétien, P; Houzé, F; Lu, L; Largeau, L; Maugain, O; Travers, L; Harmand, J C; Glas, F; Lefeuvre, E; Tchernycheva, M; Gogneau, N

    2016-08-12

    We demonstrate the first piezo-generator integrating a vertical array of GaN nanowires (NWs). We perform a systematic multi-scale analysis, going from single wire properties to macroscopic device fabrication and characterization, which allows us to establish for GaN NWs the relationship between the material properties and the piezo-generation, and to propose an efficient piezo-generator design. The piezo-conversion of individual MBE-grown p-doped GaN NWs in a dense array is assessed by atomic force microscopy (AFM) equipped with a Resiscope module yielding an average output voltage of 228 ± 120 mV and a maximum value of 350 mV generated per NW. In the case of p-doped GaN NWs, the piezo-generation is achieved when a positive piezo-potential is created inside the nanostructures, i.e. when the NWs are submitted to compressive deformation. The understanding of the piezo-generation mechanism in our GaN NWs, gained from AFM analyses, is applied to design a piezo-generator operated under compressive strain. The device consists of NW arrays of several square millimeters in size embedded into spin-on glass with a Schottky contact for rectification and collection of piezo-generated carriers. The generator delivers a maximum power density of ∼12.7 mW cm(-3). This value sets the new state of the art for piezo-generators based on GaN NWs and more generally on nitride NWs, and offers promising prospects for the use of GaN NWs as high-efficiency ultra-compact energy harvesters.

  2. Carbon quantum dots decorated Cu2S nanowire arrays for enhanced photoelectrochemical performance

    NASA Astrophysics Data System (ADS)

    Li, Ming; Zhao, Renjie; Su, Yanjie; Yang, Zhi; Zhang, Yafei

    2016-04-01

    The photoelectrochemical (PEC) performance of Cu2S nanowire arrays (NWAs) has been demonstrated to be greatly enhanced by dipping-assembly of carbon quantum dots (CQDs) on the surfaces of Cu2S NWAs. Experimental results show that the pristine Cu2S NWAs with higher aspect ratios exhibit better PEC performance due to the longer length scale for light absorption and the shorter length scale for minority carrier diffusion. Importantly, the CQDs decorated Cu2S NWAs exhibit remarkably enhanced photocurrent density, giving a photocurrent density of 1.05 mA cm-2 at 0 V vs. NHE and an optimal photocathode efficiency of 0.148% under illumination of AM 1.5G (100 mW cm-2), which is 4 times higher than that of the pristine Cu2S NWAs. This can be attributed to the improved electron transfer and the energy-down-shift effect of CQDs. We believe that this inexpensive Cu2S/CQD photocathode with increased photocurrent density opens up new opportunities in PEC water splitting.The photoelectrochemical (PEC) performance of Cu2S nanowire arrays (NWAs) has been demonstrated to be greatly enhanced by dipping-assembly of carbon quantum dots (CQDs) on the surfaces of Cu2S NWAs. Experimental results show that the pristine Cu2S NWAs with higher aspect ratios exhibit better PEC performance due to the longer length scale for light absorption and the shorter length scale for minority carrier diffusion. Importantly, the CQDs decorated Cu2S NWAs exhibit remarkably enhanced photocurrent density, giving a photocurrent density of 1.05 mA cm-2 at 0 V vs. NHE and an optimal photocathode efficiency of 0.148% under illumination of AM 1.5G (100 mW cm-2), which is 4 times higher than that of the pristine Cu2S NWAs. This can be attributed to the improved electron transfer and the energy-down-shift effect of CQDs. We believe that this inexpensive Cu2S/CQD photocathode with increased photocurrent density opens up new opportunities in PEC water splitting. Electronic supplementary information (ESI) available

  3. Inorganic/organic hybrid solar cells: optimal carrier transport in vertically aligned silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Sato, Keisuke; Dutta, Mrinal; Fukata, Naoki

    2014-05-01

    Inorganic/organic hybrid radial heterojunction solar cells that combine vertically-aligned n-type silicon nanowires (SiNWs) with poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) have great potential for replacing commercial Si solar cells. The chief advantage of such solar cells is that they exhibit higher absorbance for a given thickness than commercial Si solar cells, due to incident light-trapping within the NW arrays, thus enabling lower-cost solar cell production. We report herein on the effects of NW length, annealing and surface electrode on the device performance of SiNW/PEDOT:PSS hybrid radial heterojunction solar cells. The power conversion efficiency (PCE) of the obtained SiNW/PEDOT:PSS hybrid solar cells can be optimized by tuning the thickness of the surface electrode, and the etching conditions during NW formation and post-annealing. The PCE of 9.3% is obtained by forming efficient transport pathways for photogenerated charge carriers to electrodes. Our approach is a significant contribution to design of high-performance and low-cost inorganic/organic hybrid heterojunction solar cells.Inorganic/organic hybrid radial heterojunction solar cells that combine vertically-aligned n-type silicon nanowires (SiNWs) with poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) have great potential for replacing commercial Si solar cells. The chief advantage of such solar cells is that they exhibit higher absorbance for a given thickness than commercial Si solar cells, due to incident light-trapping within the NW arrays, thus enabling lower-cost solar cell production. We report herein on the effects of NW length, annealing and surface electrode on the device performance of SiNW/PEDOT:PSS hybrid radial heterojunction solar cells. The power conversion efficiency (PCE) of the obtained SiNW/PEDOT:PSS hybrid solar cells can be optimized by tuning the thickness of the surface electrode, and the etching conditions during NW formation and

  4. 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.

  5. Effects of free carriers on piezoelectric nanogenerators and piezotronic devices made of GaN nanowire arrays.

    PubMed

    Wang, Chao-Hung; Liao, Wei-Shun; Ku, Nai-Jen; Li, Yi-Chang; Chen, Yen-Chih; Tu, Li-Wei; Liu, Chuan-Pu

    2014-11-01

    This study investigates the role of carrier concentration in semiconducting piezoelectric single-nanowire nanogenerators (SNWNGs) and piezotronic devices. Unintentionally doped and Si-doped GaN nanowire arrays with various carrier concentrations, ranging from 10(17) (unintentionally doped) to 10(19) cm(-3) (heavily doped), are synthesized. For SNWNGs, the output current of individual nanowires starts from a negligible level and rises to the maximum of ≈50 nA at a doping concentration of 5.63 × 10(18) cm(-3) and then falls off with further increase in carrier concentration, due to the competition between the reduction of inner resistance and the screening effect on piezoelectric potential. For piezotronic applications, the force sensitivity based on the change of the Schottky barrier height works best for unintentionally doped nanowires, reaching 26.20 ± 1.82 meV nN(-1) and then decreasing with carrier concentration. Although both types of devices share the same Schottky diode, they involve different characteristics in that the slope of the current-voltage characteristics governs SNWNG devices, while the turn-on voltage determines piezotronic devices. It is demonstrated that free carriers in piezotronic materials can influence the slope and turn-on voltage of the diode characteristics concurrently when subjected to strain. This work offers a design guideline for the optimum doping concentration in semiconductors for obtaining the best performance in piezotronic devices and SNWNGs.

  6. First order reversal curve investigation of the hard and soft magnetic phases of annealed CoFeCu nanowire arrays

    NASA Astrophysics Data System (ADS)

    Almasi-Kashi, M.; Ramazani, A.; Golafshan, E.; Arefpour, M.; Jafari-Khamse, E.

    2013-11-01

    (CoFe)1-xCux (x=0.12-0.84) nanowire arrays were ac-pulse electrodeposited into anodic aluminum oxide templates. The electrodeposition was performed in a constant electrolyte while Cu content was controlled by off-time between pulses. Nanowires with 30 nm diameter and the certain lengths with the both bcc-CoFe and fcc-Cu phases were obtained. Magnetization and coercivity of the nanowires decreased with increasing the Cu content. Annealing improved the coercivity and a remarkable increase in magnetization of nanowires with high Cu contents was observed. A two-phase treatment was seen for annealed samples with high Cu contents. First order reversal curves showed a hard magnetic phase with almost constant magnetic properties and coercivity of ~2500 Oe. The results showed that main source of the various magnetic behaviors of the samples may be attributed to increase in soft magnetic phase. A single domain treatment with a narrow interacting field and coercive field distributions was also observed for the annealed samples with high Cu content.

  7. Ultra-thin g-C{sub 3}N{sub 4} nanosheets wrapped silicon nanowire array for improved chemical stability and enhanced photoresponse

    SciTech Connect

    Wang, Beibei; Yu, Hongtao; Quan, Xie Chen, Shuo

    2014-11-15

    Highlights: • g-C{sub 3}N{sub 4}, as an oxygen free and metal free protective material for Si, was proposed. • g-C{sub 3}N{sub 4} nanosheets wrapped Si nanowire array was synthesized. • SiNW/g-C{sub 3}N{sub 4} exhibited enhancement of photoelectrochemical stability and photocurrent. - Abstract: In order to inhibit the oxidation of Si materials in aqueous solution, Si nanowire array was wrapped by ultra-thin g-C{sub 3}N{sub 4} nanosheets via an electrophoresis process. Scanning electron microscopy and transmission electron microscopy images showed that g-C{sub 3}N{sub 4} nanosheets were evenly distributed on the surface of Si nanowire array. X-ray diffraction patterns indicated that Si nanowire array/g-C{sub 3}N{sub 4} nanosheets were composed of Si (4 0 0 crystal plane) and g-C{sub 3}N{sub 4} (0 0 2 and 1 0 0 crystal planes). The cyclic voltammetry curves revealed that the corrosion of Si nanowire array was restrained under the protection of g-C{sub 3}N{sub 4} nanosheets. Furthermore, the photocurrent density of Si nanowire array/g-C{sub 3}N{sub 4} nanosheets increased by nearly 3 times compared to that of bare Si nanowire array due to the effective charge separation caused by the built-in electric field at the interface. This work will facilitate the applications of Si materials in aqueous solution, such as solar energy harvest and photocatalytic pollution control.

  8. Surface reconstruction of ZnO nanowire arrays via solvent-evaporation-induced self-assembly

    NASA Astrophysics Data System (ADS)

    Fang, Fang; Zhao, Dongxu; Li, Binghui; Zhang, Zhenzhong; Shen, Dezhen; Wang, Xiaohua

    2011-02-01

    Vertically aligned ZnO nanowires (NWs) can be reconstructed on large scales by a solvent-evaporation-induced method. The morphologies of the nanowires are regulated by changing the concentration of the solution. Possible mechanism, which the compressive residual stresses and wires/wires self-attraction can be responsible for the surface reconstruction, is addressed. Furthermore, we compare the structural properties of ZnO nanowires before and after reconstructed.

  9. Plane wave scattering from a plasmonic nanowire array spacer-separated from a plasmonic film

    NASA Astrophysics Data System (ADS)

    Thomas, Arun; Trivedi, Rahul; Dhawan, Anuj

    2016-06-01

    In this paper, we present a theoretical analysis of the electromagnetic response of a plasmonic nanowire–spacer–plasmonic film system. The analytical solution presented in this paper is a full-wave solution, which is used to compute the fields scattered by the plasmonic nanostructure system on illumination by a plane electromagnetic wave. The physical structure comprises of an array of plasmonic nanowires made of a plasmonic metal such as gold or silver placed over a plasmonic film of the same material and separated from it by a dielectric spacer such as silica or alumina. Such a nanostructure exhibits a spectrum that is extremely sensitive to various geometric and electromagnetic parameters such as spacer thickness and spacer refractive index, which makes it favourable for various sensing applications such as chemical and biological sensing, strain sensing, position sensing, vibration sensing, and thickness sensing. We report a comparison of our analytical solution with a numerical rigorous coupled wave analysis of the same structure with the plasmonic medium being treated as local in nature.

  10. Recyclable surface-enhanced Raman scattering template based on nanoporous gold film/Si nanowire arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Chang Xing; Liu, Luo; Jun Yin, Hong; Fang, Hui; Mei Zhao, Yong; Jian Bi, Chu; Jun Xu, Hai

    2014-07-01

    Nanoporous gold film (NPGF) composed of gold nanoparticles was used to cover a large Si nanowire array (SiNWA) by simple metal-assisted chemical etching and metal reduction processes. Three-dimensional SiNWA/NPGF was employed as an active substrate for surface-enhanced Raman scattering (SERS). The results show that the detection limit for crystal violet was as low as 10-12M, and the Raman enhancement factor was as large as 107 with a relative standard deviation of less than 20%. After calibrating the Raman peak intensities of crystal violet and thiram could be quantitatively detected. More importantly, the SERS substrates are recyclable and can be used for many gold surface adsorbates such as p-aminothiophenol, crystal violet, Rhodamine 6G, and methyl orange, which can all be rapidly and completely removed from the NPGF surface. Our findings are an important advance in SERS substrates and will allow the quantitative and recyclable detection of trace organic contaminants.

  11. Carbon quantum dots decorated Cu2S nanowire arrays for enhanced photoelectrochemical performance.

    PubMed

    Li, Ming; Zhao, Renjie; Su, Yanjie; Yang, Zhi; Zhang, Yafei

    2016-04-28

    The photoelectrochemical (PEC) performance of Cu2S nanowire arrays (NWAs) has been demonstrated to be greatly enhanced by dipping-assembly of carbon quantum dots (CQDs) on the surfaces of Cu2S NWAs. Experimental results show that the pristine Cu2S NWAs with higher aspect ratios exhibit better PEC performance due to the longer length scale for light absorption and the shorter length scale for minority carrier diffusion. Importantly, the CQDs decorated Cu2S NWAs exhibit remarkably enhanced photocurrent density, giving a photocurrent density of 1.05 mA cm(-2) at 0 V vs. NHE and an optimal photocathode efficiency of 0.148% under illumination of AM 1.5G (100 mW cm(-2)), which is 4 times higher than that of the pristine Cu2S NWAs. This can be attributed to the improved electron transfer and the energy-down-shift effect of CQDs. We believe that this inexpensive Cu2S/CQD photocathode with increased photocurrent density opens up new opportunities in PEC water splitting. PMID:26693806

  12. Growth and Photoelectrochemical Energy Conversion of Wurtzite Indium Phosphide Nanowire Arrays.

    PubMed

    Kornienko, Nikolay; Gibson, Natalie A; Zhang, Hao; Eaton, Samuel W; Yu, Yi; Aloni, Shaul; Leone, Stephen R; Yang, Peidong

    2016-05-24

    Photoelectrochemical (PEC) water splitting into hydrogen and oxygen is a promising strategy to absorb solar energy and directly convert it into a dense storage medium in the form of chemical bonds. The continual development and improvement of individual components of PEC systems is critical toward increasing the solar to fuel efficiency of prototype devices. Within this context, we describe a study on the growth of wurtzite indium phosphide (InP) nanowire (NW) arrays on silicon substrates and their subsequent implementation as light-absorbing photocathodes in PEC cells. The high onset potential (0.6 V vs the reversible hydrogen electrode) and photocurrent (18 mA/cm(2)) of the InP photocathodes render them as promising building blocks for high performance PEC cells. As a proof of concept for overall system integration, InP photocathodes were combined with a nanoporous bismuth vanadate (BiVO4) photoanode to generate an unassisted solar water splitting efficiency of 0.5%. PMID:27124203

  13. Disordered array of Au covered Silicon nanowires for SERS biosensing combined with electrochemical detection

    PubMed Central

    Convertino, Annalisa; Mussi, Valentina; Maiolo, Luca

    2016-01-01

    We report on highly disordered array of Au coated silicon nanowires (Au/SiNWs) as surface enhanced Raman scattering (SERS) probe combined with electrochemical detection for biosensing applications. SiNWs, few microns long, were grown by plasma enhanced chemical vapor deposition on common microscope slides and covered by Au evaporated film, 150 nm thick. The capability of the resulting composite structure to act as SERS biosensor was studied via the biotin-avidin interaction: the Raman signal obtained from this structure allowed to follow each surface modification step as well as to detect efficiently avidin molecules over a broad range of concentrations from micromolar down to the nanomolar values. The metallic coverage wrapping SiNWs was exploited also to obtain a dual detection of the same bioanalyte by electrochemical impedance spectroscopy (EIS). Indeed, the SERS signal and impedance modifications induced by the biomolecule perturbations on the metalized surface of the NWs were monitored on the very same three-electrode device with the Au/SiNWs acting as both working electrode and SERS probe. PMID:27112197

  14. Disordered array of Au covered Silicon nanowires for SERS biosensing combined with electrochemical detection

    NASA Astrophysics Data System (ADS)

    Convertino, Annalisa; Mussi, Valentina; Maiolo, Luca

    2016-04-01

    We report on highly disordered array of Au coated silicon nanowires (Au/SiNWs) as surface enhanced Raman scattering (SERS) probe combined with electrochemical detection for biosensing applications. SiNWs, few microns long, were grown by plasma enhanced chemical vapor deposition on common microscope slides and covered by Au evaporated film, 150 nm thick. The capability of the resulting composite structure to act as SERS biosensor was studied via the biotin-avidin interaction: the Raman signal obtained from this structure allowed to follow each surface modification step as well as to detect efficiently avidin molecules over a broad range of concentrations from micromolar down to the nanomolar values. The metallic coverage wrapping SiNWs was exploited also to obtain a dual detection of the same bioanalyte by electrochemical impedance spectroscopy (EIS). Indeed, the SERS signal and impedance modifications induced by the biomolecule perturbations on the metalized surface of the NWs were monitored on the very same three-electrode device with the Au/SiNWs acting as both working electrode and SERS probe.

  15. Disordered array of Au covered Silicon nanowires for SERS biosensing combined with electrochemical detection.

    PubMed

    Convertino, Annalisa; Mussi, Valentina; Maiolo, Luca

    2016-04-26

    We report on highly disordered array of Au coated silicon nanowires (Au/SiNWs) as surface enhanced Raman scattering (SERS) probe combined with electrochemical detection for biosensing applications. SiNWs, few microns long, were grown by plasma enhanced chemical vapor deposition on common microscope slides and covered by Au evaporated film, 150 nm thick. The capability of the resulting composite structure to act as SERS biosensor was studied via the biotin-avidin interaction: the Raman signal obtained from this structure allowed to follow each surface modification step as well as to detect efficiently avidin molecules over a broad range of concentrations from micromolar down to the nanomolar values. The metallic coverage wrapping SiNWs was exploited also to obtain a dual detection of the same bioanalyte by electrochemical impedance spectroscopy (EIS). Indeed, the SERS signal and impedance modifications induced by the biomolecule perturbations on the metalized surface of the NWs were monitored on the very same three-electrode device with the Au/SiNWs acting as both working electrode and SERS probe.

  16. Growth and Photoelectrochemical Energy Conversion of Wurtzite Indium Phosphide Nanowire Arrays.

    PubMed

    Kornienko, Nikolay; Gibson, Natalie A; Zhang, Hao; Eaton, Samuel W; Yu, Yi; Aloni, Shaul; Leone, Stephen R; Yang, Peidong

    2016-05-24

    Photoelectrochemical (PEC) water splitting into hydrogen and oxygen is a promising strategy to absorb solar energy and directly convert it into a dense storage medium in the form of chemical bonds. The continual development and improvement of individual components of PEC systems is critical toward increasing the solar to fuel efficiency of prototype devices. Within this context, we describe a study on the growth of wurtzite indium phosphide (InP) nanowire (NW) arrays on silicon substrates and their subsequent implementation as light-absorbing photocathodes in PEC cells. The high onset potential (0.6 V vs the reversible hydrogen electrode) and photocurrent (18 mA/cm(2)) of the InP photocathodes render them as promising building blocks for high performance PEC cells. As a proof of concept for overall system integration, InP photocathodes were combined with a nanoporous bismuth vanadate (BiVO4) photoanode to generate an unassisted solar water splitting efficiency of 0.5%.

  17. Inorganic/organic hybrid solar cells: optimal carrier transport in vertically aligned silicon nanowire arrays.

    PubMed

    Sato, Keisuke; Dutta, Mrinal; Fukata, Naoki

    2014-06-01

    Inorganic/organic hybrid radial heterojunction solar cells that combine vertically-aligned n-type silicon nanowires (SiNWs) with poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) have great potential for replacing commercial Si solar cells. The chief advantage of such solar cells is that they exhibit higher absorbance for a given thickness than commercial Si solar cells, due to incident light-trapping within the NW arrays, thus enabling lower-cost solar cell production. We report herein on the effects of NW length, annealing and surface electrode on the device performance of SiNW/PEDOT:PSS hybrid radial heterojunction solar cells. The power conversion efficiency (PCE) of the obtained SiNW/PEDOT:PSS hybrid solar cells can be optimized by tuning the thickness of the surface electrode, and the etching conditions during NW formation and post-annealing. The PCE of 9.3% is obtained by forming efficient transport pathways for photogenerated charge carriers to electrodes. Our approach is a significant contribution to design of high-performance and low-cost inorganic/organic hybrid heterojunction solar cells.

  18. Large current difference in Au-coated vertical silicon nanowire electrode array with functionalization of peptides

    PubMed Central

    2013-01-01

    Au-coated vertical silicon nanowire electrode array (VSNEA) was fabricated using a combination of bottom-up and top-down approaches by chemical vapor deposition and complementary metal-oxide-semiconductor process for biomolecule sensing. To verify the feasibility for the detection of biomolecules, Au-coated VSNEA was functionalized using peptides having a fluorescent probe. Cyclic voltammograms of the peptide-functionalized Au-coated VSNEA show a steady-state electrochemical current behavior. Because of the critically small dimension and vertically aligned nature of VSNEA, the current density of Au-coated VSNEA was dramatically higher than that of Au film electrodes. Au-coated VSNEA further showed a large current difference with and without peptides that was nine times more than that of Au film electrodes. These results indicate that Au-coated VSENA is highly effective device to detect peptides compared to conventional thin-film electrodes. Au-coated VSNEA can also be used as a divergent biosensor platform in many applications. PMID:24279451

  19. Tailoring magnetic properties in arrays of pulse-electrodeposited Co nanowires: The role of Cu additive

    NASA Astrophysics Data System (ADS)

    Esmaeili, A.; Almasi Kashi, M.; Ramazani, A.; Montazer, A. H.

    2016-01-01

    In this study, we aim to report the role of Cu additive in arrays of pulse-electrodeposited Co nanowires (NWs) with diameters from 30 to 75 nm, embedded in porous aluminum oxide templates. This features the role of Cu additive in composition and crystalline characteristics as well as in the magnetic properties of Co NWs. Increasing the duration of off-time between pulses during the electrodeposition of Co NWs made it possible to increase the amount of Cu content, so that Co-rich CoCu NWs were obtained. The parallel coercivity and squareness values increased up to 1500 Oe and 0.8 for 30 nm diameter Co94Cu6 NWs, starting from 500 Oe and 0.3 for pure Co NWs. On the other hand, although there was a substantial difference between the crystalline characteristics of 75 nm diameter pure Co and CoCu NWs, no considerable change in their magnetic properties was observed using hysteresis loop measurements. In this respect, the first-order reversal curve (FORC) analysis revealed strong inter-wire magnetostatic interactions for the CoCu NWs. Moreover, we studied the effect of thermal annealing, which resulted in an increase in the coercivity of CoCu NWs with different diameters up to 15%. As a result, the addition of small amount of Cu provides an alternative approach to tailoring the magnetic properties of Co NWs.

  20. Large current difference in Au-coated vertical silicon nanowire electrode array with functionalization of peptides.

    PubMed

    Kim, Ilsoo; Kim, So-Eun; Han, Sanghun; Kim, Hyungsuk; Lee, Jaehyung; Jeong, Du-Won; Kim, Ju-Jin; Lim, Yong-Beom; Choi, Heon-Jin

    2013-11-26

    Au-coated vertical silicon nanowire electrode array (VSNEA) was fabricated using a combination of bottom-up and top-down approaches by chemical vapor deposition and complementary metal-oxide-semiconductor process for biomolecule sensing. To verify the feasibility for the detection of biomolecules, Au-coated VSNEA was functionalized using peptides having a fluorescent probe. Cyclic voltammograms of the peptide-functionalized Au-coated VSNEA show a steady-state electrochemical current behavior. Because of the critically small dimension and vertically aligned nature of VSNEA, the current density of Au-coated VSNEA was dramatically higher than that of Au film electrodes. Au-coated VSNEA further showed a large current difference with and without peptides that was nine times more than that of Au film electrodes. These results indicate that Au-coated VSENA is highly effective device to detect peptides compared to conventional thin-film electrodes. Au-coated VSNEA can also be used as a divergent biosensor platform in many applications.

  1. Axially adjustable magnetic properties in arrays of multilayered Ni/Cu nanowires with variable segment sizes

    NASA Astrophysics Data System (ADS)

    Shirazi Tehrani, A.; Almasi Kashi, M.; Ramazani, A.; Montazer, A. H.

    2016-07-01

    Arrays of multilayered Ni/Cu nanowires (NWs) with variable segment sizes were fabricated into anodic aluminum oxide templates using a pulsed electrodeposition method in a single bath for designated potential pulse times. Increasing the pulse time between 0.125 and 2 s in the electrodeposition of Ni enabled the formation of segments with thicknesses ranging from 25 to 280 nm and 10-110 nm in 42 and 65 nm diameter NWs, respectively, leading to disk-shaped, rod-shaped and/or near wire-shaped geometries. Using hysteresis loop measurements at room temperature, the axial and perpendicular magnetic properties were investigated. Regardless of the segment geometry, the axial coercivity and squareness significantly increased with increasing Ni segment thickness, in agreement with a decrease in calculated demagnetizing factors along the NW length. On the contrary, the perpendicular magnetic properties were found to be independent of the pulse times, indicating a competition between the intrawire interactions and the shape demagnetizing field.

  2. 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.

  3. InGaAs axial-junction nanowire-array solar cells

    NASA Astrophysics Data System (ADS)

    Nakai, Eiji; Chen, Muyi; Yoshimura, Masatoshi; Tomioka, Katsuhiro; Fukui, Takashi

    2015-01-01

    Axial p-i-n junction nanowire (NW) solar cells (SCs) with a position-controlled GaAs-based NW array were fabricated by selective-area metal organic vapor phase epitaxy (SA-MOVPE). The measured electron-beam-induced current (EBIC) signals showed the formation of an axial p-i-n junction, which confirms power generation under sunlight illumination. The series resistance of the NW SCs is much higher than that of conventional planar SCs based on Si or other III-V compound semiconductors. The main difficulty concerning the fabrication of these NW SCs is the degradation of series resistance between the GaAs-based NWs and the indium-tin oxide (ITO) deposited as a transparent electrode. The series resistance of the fabricated GaAs-based NW SCs was reduced by introducing a tin doping contact layer between the ITO and the NW array, which is formed by pulse doping. As a result of this improved structure, the fabricated SCs exhibited an open-circuit voltage of 0.544 V, a short-circuit current of 18.2 mA/cm2, and a fill factor of 0.721 for an overall conversion efficiency of 7.14% under AM1.5G illumination. The series resistance of the SCs could be decreased to 0.132 Ω·cm2, which is one order of magnitude lower than that of the SC without a highly doped contact layer. This reduced series resistance indicates that nanostructure SCs with transparent electrodes and multijunction NW SCs with high efficiencies can be fabricated on a commercial basis in the near future.

  4. 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.

  5. Construction of high-capacitance 3D CoO@polypyrrole nanowire array electrode for aqueous asymmetric supercapacitor.

    PubMed

    Zhou, Cheng; Zhang, Yangwei; Li, Yuanyuan; Liu, Jinping

    2013-05-01

    We have developed a supercapacitor electrode composed of well-aligned CoO nanowire array grown on 3D nickel foam with polypyrrole (PPy) uniformly immobilized onto or firmly anchored to each nanowire surface to boost the pseudocapacitive performance. The electrode architecture takes advantage of the high electrochemical activity from both the CoO and PPy, the high electronic conductivity of PPy, and the short ion diffusion pathway in ordered mesoporous nanowires. These merits together with the elegant synergy between CoO and PPy lead to a high specific capacitance of 2223 F g(-1) approaching the theoretical value, good rate capability, and cycling stability (99.8% capacitance retention after 2000 cycles). An aqueous asymmetric supercapacitor device with a maximum voltage of 1.8 V fabricated by using our hybrid array as the positive electrode and activated carbon film as the negative electrode has demonstrated high energy density (~43.5 Wh kg(-1)), high power density (~5500 W kg(-1) at 11.8 Wh kg(-1)) and outstanding cycleability (~20,000 times). After charging for only ~10 s, two such 4 cm(2) asymmetric supercapacitors connected in series can efficiently power 5 mm diameter red, yellow, and green round LED indicators (lasting for 1 h for red LED) and drive a mini 130 rotation-motor robustly.

  6. Measuring photoluminescence spectra of self-assembly array nanowire of colloidal CdSe quantum dots using scanning near-field optics microscopy

    NASA Astrophysics Data System (ADS)

    Bai, Zhongchen; Hao, Licai; Zhang, Zhengping; Qin, Shuijie

    2016-05-01

    A novel periodic array CdSe nanowire is prepared on a substrate of the porous titanium dioxide by using a self-assembly method of the colloidal CdSe quantum dots (QDs). The experimental results show that the colloidal CdSe QDs have renewedly assembled on its space scale and direction in process of losing background solvent and form the periodic array nanowire. The main peak wavelength of Photoluminescence (PL) spectra, which is measured by using a 100-nm aperture laser beam spot on a scanning near-field optics microscopy, has shifted 60 nm with compared to the colloidal CdSe QDs. Furthermore, we have measured smaller ordered nanometer structure in thin QDs area as well, a 343-nm periodic nanowire in thick QDs area and the colloidal QDs in edge of well-ordered nanowire.

  7. The influence of passivation and photovoltaic properties of α-Si:H coverage on silicon nanowire array solar cells

    PubMed Central

    2013-01-01

    Silicon nanowire (SiNW) arrays for radial p-n junction solar cells offer potential advantages of light trapping effects and quick charge collection. Nevertheless, lower open circuit voltages (Voc) lead to lower energy conversion efficiencies. In such cases, the performance of the solar cells depends critically on the quality of the SiNW interfaces. In this study, SiNW core-shell solar cells have been fabricated by growing crystalline silicon (c-Si) nanowires via the metal-assisted chemical etching method and by depositing hydrogenated amorphous silicon (α-Si:H) via the plasma-enhanced chemical vapor deposition (PECVD) method. The influence of deposition parameters on the coverage and, consequently, the passivation and photovoltaic properties of α-Si:H layers on SiNW solar cells have been analyzed. PMID:24059343

  8. Magnetization mechanisms in ordered arrays of polycrystalline Fe{sub 100−x}Co{sub x} nanowires

    SciTech Connect

    Viqueira, M. S.; Bajales, N.; Urreta, S. E.; Bercoff, P. G.

    2015-05-28

    Magnetization reversal processes and coercivity mechanisms in polycrystalline Fe{sub 100−x}Co{sub x} nanowire arrays, resulting from an AC electrodeposition process, are investigated. The array coercivity is described on the basis of polarization reversal mechanisms operating in individual wires, under the effect of inter-wire dipolar interactions described by a mean field approximation. For individual wires, a reversal mechanism involving the nucleation and further expansion of domain-wall like spin configuration is considered. The wires have a mean grain size larger than both the nanowire diameter and the exchange length, so localized and non-cooperative nucleation modes are considered. As the Co content increases, the alloy saturation polarization gradually decreases, but the coercive field and the relative remanence of the arrays increase, indicating that they are not controlled by the shape anisotropy in all the composition range. The coercive field dependence on the angle between the applied field and the wire long axis is not well described by reversal mechanisms involving nucleation and further displacement of neither vortex nor transverse ideal domain walls. On the contrary, the angular dependence of the coercive field observed at room temperature is well predicted by a model considering nucleation of inverse domains by localized curling, in regions smaller than the grain size, exhibiting quite small aspect ratios as compared to those of the entire nanowire. In arrays with higher Co contents, a transition from an initial (small angle) localized curling nucleation mechanism to another one, involving localized coherent rotation is observed at about π/4.

  9. Visible-Light-Induced Self-Cleaning Property of Bi2Ti2O7-TiO2 Composite Nanowire Arrays.

    PubMed

    Liu, Hang; Chen, Yajie; Tian, Guohui; Ren, Zhiyu; Tian, Chungui; Fu, Honggang

    2015-06-01

    Bi2Ti2O7-TiO2 composite nanowire arrays were prepared via a two-step sequential solvothermal and subsequent calcination process. The morphology and structure of the Bi2Ti2O7-TiO2 composite nanowire array composite were characterized by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The UV-visible diffuse reflectance spectroscopy analysis indicated that the absorption spectrum of the Bi2Ti2O7-TiO2 composite nanowire array composite was extended to the visible-light region due to the existence of Bi2Ti2O7. The Bi2Ti2O7-TiO2 composite nanowire arrays exhibit superhydrophilicity with water contact angles of 0° after irradiation with visible light, and the superhydrophilic nature is retained for at least 15 days. This effect enables us to consider self-cleaning applications that do not require permanent UV exposure. Compared to pure Bi2Ti2O7 and TiO2, the vertically aligned Bi2Ti2O7-TiO2 composite nanowire arrays showed more significant visible-light self-cleaning performance due to the synergistic effect of superhydrophilicity and significant photocatalytic activity caused by effective electron-hole separation at the interfaces of the two semiconductors, which was confirmed by the electrochemical analysis and surface photovoltage technique.

  10. A hierarchical three-dimensional NiCo2O4 nanowire array/carbon cloth as an air electrode for nonaqueous Li-air batteries.

    PubMed

    Liu, Wei-Ming; Gao, Ting-Ting; Yang, Yin; Sun, Qian; Fu, Zheng-Wen

    2013-10-14

    A 3D NiCo2O4 nanowire array/carbon cloth (NCONW/CC) was employed as the cathode for Li-air batteries with a non-aqueous electrolyte. After its discharge, novel porous ball-like Li2O2 was found to be deposited on the tip of NiCo2O4 nanowires. The special structure of Li2O2 and active sites of catalysts are also discussed.

  11. Ordered arrays of shape tunable CuInS2 nanostructures, from nanotubes to nano test tubes and nanowires

    NASA Astrophysics Data System (ADS)

    Shi, Liang; Pei, Congjian; Li, Quan

    2010-10-01

    Well-aligned arrays of chalcopyrite CuInS2 one dimensional nanostructures have been prepared in a controllable manner via a convenient wet-chemical approach using anodic aluminium oxide (AAO) as a hard template. Highly oriented CuInS2 nanotubes, nano test tubes and nanowires arrays can be selectively grown by simply varying reaction conditions. Oleylamine (OLA) was found to play a key role in the synthesis and morphology control of the CuInS2 product. The structure, morphology, composition and optical absorption properties of the as-prepared samples were characterized using X-ray powder diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, scanning electron microscopy and UV-Vis spectrophotometry. The formation mechanism of the CuInS2 arrays is discussed.

  12. 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

  13. 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.

  14. Selective area growth of well-ordered ZnO nanowire arrays with controllable polarity.

    PubMed

    Consonni, Vincent; Sarigiannidou, Eirini; Appert, Estelle; Bocheux, Amandine; Guillemin, Sophie; Donatini, Fabrice; Robin, Ivan-Christophe; Kioseoglou, Joseph; Robaut, Florence

    2014-05-27

    Controlling the polarity of ZnO nanowires in addition to the uniformity of their structural morphology in terms of position, vertical alignment, length, diameter, and period is still a technological and fundamental challenge for real-world device integration. In order to tackle this issue, we specifically combine the selective area growth on prepatterned polar c-plane ZnO single crystals using electron-beam lithography, with the chemical bath deposition. The formation of ZnO nanowires with a highly controlled structural morphology and a high optical quality is demonstrated over large surface areas on both polar c-plane ZnO single crystals. Importantly, the polarity of ZnO nanowires can be switched from O- to Zn-polar, depending on the polarity of prepatterned ZnO single crystals. This indicates that no fundamental limitations prevent ZnO nanowires from being O- or Zn-polar. In contrast to their catalyst-free growth by vapor-phase deposition techniques, the possibility to control the polarity of ZnO nanowires grown in solution is remarkable, further showing the strong interest in the chemical bath deposition and hydrothermal techniques. The single O- and Zn-polar ZnO nanowires additionally exhibit distinctive cathodoluminescence spectra. To a broader extent, these findings open the way to the ultimate fabrication of well-organized heterostructures made from ZnO nanowires, which can act as building blocks in a large number of electronic, optoelectronic, and photovoltaic devices.

  15. Bright photoluminescence from ordered arrays of SiGe nanowires grown on Si(111)

    PubMed Central

    Rowell, N L; Benkouider, A; Ronda, A; Favre, L; Berbezier, I

    2014-01-01

    Summary We report on the optical properties of SiGe nanowires (NWs) grown by molecular beam epitaxy (MBE) in ordered arrays on SiO2/Si(111) substrates. The production method employs Au catalysts with self-limited sizes deposited in SiO2-free sites opened-up in the substrate by focused ion beam patterning for the preferential nucleation and growth of these well-organized NWs. The NWs thus produced have a diameter of 200 nm, a length of 200 nm, and a Ge concentration x = 0.15. Their photoluminescence (PL) spectra were measured at low temperatures (from 6 to 25 K) with excitation at 405 and 458 nm. There are four major features in the energy range of interest (980–1120 meV) at energies of 1040.7, 1082.8, 1092.5, and 1098.5 meV, which are assigned to the NW-transverse optic (TO) Si–Si mode, NW-transverse acoustic (TA), Si–substrate–TO and NW-no-phonon (NP) lines, respectively. From these results the NW TA and TO phonon energies are found to be 15.7 and 57.8 meV, respectively, which agree very well with the values expected for bulk Si1− xGex with x = 0.15, while the measured NW NP energy of 1099 meV would indicate a bulk-like Ge concentration of x = 0.14. Both of these concentrations values, as determined from PL, are in agreement with the target value. The NWs are too large in diameter for a quantum confinement induced energy shift in the band gap. Nevertheless, NW PL is readily observed, indicating that efficient carrier recombination is occurring within the NWs. PMID:25671145

  16. Metal-organic framework derived hybrid Co3O4-carbon porous nanowire arrays as reversible oxygen evolution electrodes.

    PubMed

    Ma, Tian Yi; Dai, Sheng; Jaroniec, Mietek; Qiao, Shi Zhang

    2014-10-01

    Hybrid porous nanowire arrays composed of strongly interacting Co3O4 and carbon were prepared by a facile carbonization of the metal-organic framework grown on Cu foil. The resulting material, possessing a high surface area of 251 m(2) g(-1) and a large carbon content of 52.1 wt %, can be directly used as the working electrode for oxygen evolution reaction without employing extra substrates or binders. This novel oxygen evolution electrode can smoothly operate in alkaline solutions (e.g., 0.1 and 1.0 M KOH), affording a low onset potential of 1.47 V (vs reversible hydrogen electrode) and a stable current density of 10.0 mA cm(-2) at 1.52 V in 0.1 M KOH solution for at least 30 h, associated with a high Faradaic efficiency of 99.3%. The achieved ultrahigh oxygen evolution activity and strong durability, with superior performance in comparison to the state-of-the-art noble-metal/transition-metal and nonmetal catalysts, originate from the unique nanowire array electrode configuration and in situ carbon incorporation, which lead to the large active surface area, enhanced mass/charge transport capability, easy release of oxygen gas bubbles, and strong structural stability. Furthermore, the hybrid Co3O4-carbon porous nanowire arrays can also efficiently catalyze oxygen reduction reaction, featuring a desirable four-electron pathway for reversible oxygen evolution and reduction, which is potentially useful for rechargeable metal-air batteries, regenerative fuel cells, and other important clean energy devices. PMID:25216300

  17. High-Resolution p-Type Metal Oxide Semiconductor Nanowire Array as an Ultrasensitive Sensor for Volatile Organic Compounds.

    PubMed

    Cho, Soo-Yeon; Yoo, Hae-Wook; Kim, Ju Ye; Jung, Woo-Bin; Jin, Ming Liang; Kim, Jong-Seon; Jeon, Hwan-Jin; Jung, Hee-Tae

    2016-07-13

    The development of high-performance volatile organic compound (VOC) sensor based on a p-type metal oxide semiconductor (MOS) is one of the important topics in gas sensor research because of its unique sensing characteristics, namely, rapid recovery kinetics, low temperature dependence, high humidity or thermal stability, and high potential for p-n junction applications. Despite intensive efforts made in this area, the applications of such sensors are hindered because of drawbacks related to the low sensitivity and slow response or long recovery time of p-type MOSs. In this study, the VOC sensing performance of a p-type MOS was significantly enhanced by forming a patterned p-type polycrystalline MOS with an ultrathin, high-aspect-ratio (∼25) structure (∼14 nm thickness) composed of ultrasmall grains (∼5 nm size). A high-resolution polycrystalline p-type MOS nanowire array with a grain size of ∼5 nm was fabricated by secondary sputtering via Ar(+) bombardment. Various p-type nanowire arrays of CuO, NiO, and Cr2O3 were easily fabricated by simply changing the sputtering material. The VOC sensor thus fabricated exhibited higher sensitivity (ΔR/Ra = 30 at 1 ppm hexane using NiO channels), as well as faster response or shorter recovery time (∼30 s) than that of previously reported p-type MOS sensors. This result is attributed to the high resolution and small grain size of p-type MOSs, which lead to overlap of fully charged zones; as a result, electrical properties are predominantly determined by surface states. Our new approach may be used as a route for producing high-resolution MOSs with particle sizes of ∼5 nm within a highly ordered, tall nanowire array structure.

  18. Metal-organic framework derived hybrid Co3O4-carbon porous nanowire arrays as reversible oxygen evolution electrodes.

    PubMed

    Ma, Tian Yi; Dai, Sheng; Jaroniec, Mietek; Qiao, Shi Zhang

    2014-10-01

    Hybrid porous nanowire arrays composed of strongly interacting Co3O4 and carbon were prepared by a facile carbonization of the metal-organic framework grown on Cu foil. The resulting material, possessing a high surface area of 251 m(2) g(-1) and a large carbon content of 52.1 wt %, can be directly used as the working electrode for oxygen evolution reaction without employing extra substrates or binders. This novel oxygen evolution electrode can smoothly operate in alkaline solutions (e.g., 0.1 and 1.0 M KOH), affording a low onset potential of 1.47 V (vs reversible hydrogen electrode) and a stable current density of 10.0 mA cm(-2) at 1.52 V in 0.1 M KOH solution for at least 30 h, associated with a high Faradaic efficiency of 99.3%. The achieved ultrahigh oxygen evolution activity and strong durability, with superior performance in comparison to the state-of-the-art noble-metal/transition-metal and nonmetal catalysts, originate from the unique nanowire array electrode configuration and in situ carbon incorporation, which lead to the large active surface area, enhanced mass/charge transport capability, easy release of oxygen gas bubbles, and strong structural stability. Furthermore, the hybrid Co3O4-carbon porous nanowire arrays can also efficiently catalyze oxygen reduction reaction, featuring a desirable four-electron pathway for reversible oxygen evolution and reduction, which is potentially useful for rechargeable metal-air batteries, regenerative fuel cells, and other important clean energy devices.

  19. 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.

  20. High-Resolution p-Type Metal Oxide Semiconductor Nanowire Array as an Ultrasensitive Sensor for Volatile Organic Compounds.

    PubMed

    Cho, Soo-Yeon; Yoo, Hae-Wook; Kim, Ju Ye; Jung, Woo-Bin; Jin, Ming Liang; Kim, Jong-Seon; Jeon, Hwan-Jin; Jung, Hee-Tae

    2016-07-13

    The development of high-performance volatile organic compound (VOC) sensor based on a p-type metal oxide semiconductor (MOS) is one of the important topics in gas sensor research because of its unique sensing characteristics, namely, rapid recovery kinetics, low temperature dependence, high humidity or thermal stability, and high potential for p-n junction applications. Despite intensive efforts made in this area, the applications of such sensors are hindered because of drawbacks related to the low sensitivity and slow response or long recovery time of p-type MOSs. In this study, the VOC sensing performance of a p-type MOS was significantly enhanced by forming a patterned p-type polycrystalline MOS with an ultrathin, high-aspect-ratio (∼25) structure (∼14 nm thickness) composed of ultrasmall grains (∼5 nm size). A high-resolution polycrystalline p-type MOS nanowire array with a grain size of ∼5 nm was fabricated by secondary sputtering via Ar(+) bombardment. Various p-type nanowire arrays of CuO, NiO, and Cr2O3 were easily fabricated by simply changing the sputtering material. The VOC sensor thus fabricated exhibited higher sensitivity (ΔR/Ra = 30 at 1 ppm hexane using NiO channels), as well as faster response or shorter recovery time (∼30 s) than that of previously reported p-type MOS sensors. This result is attributed to the high resolution and small grain size of p-type MOSs, which lead to overlap of fully charged zones; as a result, electrical properties are predominantly determined by surface states. Our new approach may be used as a route for producing high-resolution MOSs with particle sizes of ∼5 nm within a highly ordered, tall nanowire array structure. PMID:27304752

  1. Dye-sensitized InGaN nanowire arrays for efficient hydrogen production under visible light irradiation.

    PubMed

    Kibria, M G; Chowdhury, F A; Trudeau, M L; Guo, H; Mi, Z

    2015-07-17

    Solar water splitting is a key sustainable energy technology for clean, storable and renewable source of energy in the future. Here we report that Merocyanine-540 dye-sensitized and Rh nanoparticle-decorated molecular beam epitaxially grown In0.25Ga0.75N nanowire arrays have produced hydrogen from ethylenediaminetetraacetic acid (EDTA) and acetonitrile mixture solution under green, yellow and orange solar spectra (up to 610 nm) for the first time. An apparent quantum efficiency of 0.3% is demonstrated for wavelengths 525-600 nm, providing a viable approach to harness deep-visible and near-infrared solar energy for efficient and stable water splitting.

  2. Synthesis of high crystallinity ZnO nanowire array on polymer substrate and flexible fiber-based sensor.

    PubMed

    Liu, Jinmei; Wu, Weiwei; Bai, Suo; Qin, Yong

    2011-11-01

    Well aligned ZnO nanowire (NW) arrays are grown on Kevlar fiber and Kapton film via the chemical vapor deposition (CVD) method. These NWs have better crystallinity than those synthesized through the low-temperature hydrothermal method. The average length and diameter of ZnO NWs grown on Kevlar fiber can be controlled from 0.5 to 2.76 μm and 30 to 300 nm, respectively. A flexible ultraviolet (UV) sensor based on Kevlar fiber/ZnO NWs hybrid structure is made to detect UV illumination quantificationally.

  3. Dye-sensitized InGaN nanowire arrays for efficient hydrogen production under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Kibria, M. G.; Chowdhury, F. A.; Trudeau, M. L.; Guo, H.; Mi, Z.

    2015-07-01

    Solar water splitting is a key sustainable energy technology for clean, storable and renewable source of energy in the future. Here we report that Merocyanine-540 dye-sensitized and Rh nanoparticle-decorated molecular beam epitaxially grown In0.25Ga0.75N nanowire arrays have produced hydrogen from ethylenediaminetetraacetic acid (EDTA) and acetonitrile mixture solution under green, yellow and orange solar spectra (up to 610 nm) for the first time. An apparent quantum efficiency of 0.3% is demonstrated for wavelengths 525-600 nm, providing a viable approach to harness deep-visible and near-infrared solar energy for efficient and stable water splitting.

  4. Spatial mapping of efficiency of GaN/InGaN nanowire array solar cells using scanning photocurrent microscopy.

    PubMed

    Howell, Sarah L; Padalkar, Sonal; Yoon, KunHo; Li, Qiming; Koleske, Daniel D; Wierer, Jonathan J; Wang, George T; Lauhon, Lincoln J

    2013-11-13

    GaN-InGaN core-shell nanowire array devices are characterized by spectrally resolved scanning photocurrent microscopy (SPCM). The spatially resolved external quantum efficiency is correlated with structure and composition inferred from atomic force microscope (AFM) topography, scanning transmission electron microscope (STEM) imaging, Raman microspectroscopy, and scanning photocurrent microscopy (SPCM) maps of the effective absorption edge. The experimental analyses are coupled with finite difference time domain simulations to provide mechanistic understanding of spatial variations in carrier generation and collection, which is essential to the development of heterogeneous novel architecture solar cell devices.

  5. Earth-abundant oxygen evolution catalysts coupled onto ZnO nanowire arrays for efficient photoelectrochemical water cleavage.

    PubMed

    Jiang, Chaoran; Moniz, Savio J A; Khraisheh, Majeda; Tang, Junwang

    2014-09-26

    ZnO has long been considered as a model UV-driven photoanode for photoelectrochemical water splitting, but its performance has been limited by fast charge-carrier recombination, extremely poor stability in aqueous solution, and slow kinetics of water oxidation. These issues were addressed by applying a strategy of optimization and passivation of hydrothermally grown 1D ZnO nanowire arrays. The length and diameter of bare ZnO nanowires were optimized by varying the growth time and precursor concentration to achieve optimal photoelectrochemical performance. The addition of earth-abundant cobalt phosphate (Co-Pi) and nickel borate (Ni-B) oxygen evolution catalysts onto ZnO nanowires resulted in substantial cathodic shifts in onset potential to as low as about 0.3 V versus the reversible hydrogen electrode (RHE) for Ni-B/ZnO, for which a maximum photocurrent density of 1.1 mA cm(-2) at 0.9 V (vs. RHE) with applied bias photon-to-current efficiency of 0.4 % and an unprecedented near-unity incident photon-to-current efficiency at 370 nm. In addition the potential required for saturated photocurrent was dramatically reduced from 1.6 to 0.9 V versus RHE. Furthermore, the stability of these ZnO nanowires was significantly enhanced by using Ni-B compared to Co-Pi due to its superior chemical robustness, and it thus has additional functionality as a stable protecting layer on the ZnO surface. These remarkable enhancements in both photocatalytic activity and stability directly address the current severe limitations in the use of ZnO-based photoelectrodes for water-splitting applications, and can be applied to other photoanodes for efficient solar-driven fuel synthesis.

  6. Multi-functional CuO nanowire/TiO2 nanotube arrays photoelectrode synthesis, characterization, photocatalysis and SERS applications.

    PubMed

    Sheng, Pengtao; Li, Weili; Du, Pengwei; Cao, Kesheng; Cai, Qingyun

    2016-11-01

    Vertically aligned single crystalline CuO nanowire arrays (NWs) grown directly on TiO2 nanotube arrays (NTAs) supporting by Ti foil have been successfully fabricated using facile thermal oxidation of Cu nanocrystals in static air. CuO NWs growth behavior dependent on parent Cu nanocrystals sizes has been well investigated. Mass transport channel of Cu ions in horizontal and vertical for supporting CuO NWs diameter and length changes has been confirmed through a novel step-by-step surface diffusion process. CuO NWs, nano-mushrooms and nanosheets can be easily obtained by varying growth conditions. After photocatalytic synthesis of snow-like Ag nanocrystals upon CuO NWs/TiO2 NTAs, the hybrid photoelectrode exhibits superior catalytic property and detection sensitivity, which can clean themselves by photocatalytic degradation of RhB molecules adsorbed to the substrate under irradiation using surface enhanced Raman scattering (SERS) detection, a recycling can been achieved.

  7. Electron transport behaviors through donor-induced quantum dot array in heavily n-doped junctionless nanowire transistors

    SciTech Connect

    Ma, Liuhong; Han, Weihua Wang, Hao; Hong, Wenting; Lyu, Qifeng; Yang, Xiang; Yang, Fuhua

    2015-01-21

    We investigated single electron tunneling through a phosphorus donor-induced quantum dot array in heavily n-doped junctionless nanowire transistor. Seven subpeaks splitting in current oscillations are clearly observed due to the coupling of quantum dot array under the bias voltage below 1.0 mV at the temperature of 6 K. The conduction system can be well described by a two-band Hubbard model. The activation energy of phosphorus donors is tuned by the gate voltage to be 7.0 meV for the lower Hubbard band and 4.4 meV for the upper Hubbard band due to the localization effects below threshold voltage. The evolution of electron behaviors in the quantum dots is identified by adjusting the gate voltage from quantum-dot regime to one-dimensional regime.

  8. Reduction of Cr(VI) to Cr(III) using silicon nanowire arrays under visible light irradiation.

    PubMed

    Fellahi, Ouarda; Barras, Alexandre; Pan, Guo-Hui; Coffinier, Yannick; Hadjersi, Toufik; Maamache, Mustapha; Szunerits, Sabine; Boukherroub, Rabah

    2016-03-01

    We report an efficient visible light-induced reduction of hexavalent chromium Cr(VI) to trivalent Cr(III) by direct illumination of an aqueous solution of potassium dichromate (K2Cr2O7) in the presence of hydrogenated silicon nanowires (H-SiNWs) or silicon nanowires decorated with copper nanoparticles (Cu NPs-SiNWs) as photocatalyst. The SiNW arrays investigated in this study were prepared by chemical etching of crystalline silicon in HF/AgNO3 aqueous solution. The Cu NPs were deposited on SiNW arrays via electroless deposition technique. Visible light irradiation of an aqueous solution of K2Cr2O7 (10(-4)M) in presence of H-SiNWs showed that these substrates were not efficient for Cr(VI) reduction. The reduction efficiency achieved was less than 10% after 120 min irradiation at λ>420 nm. Addition of organic acids such as citric or adipic acid in the solution accelerated Cr(VI) reduction in a concentration-dependent manner. Interestingly, Cu NPs-SiNWs was found to be a very efficient interface for the reduction of Cr(VI) to Cr(III) in absence of organic acids. Almost a full reduction of Cr(VI) was achieved by direct visible light irradiation for 140 min using this photocatalyst.

  9. Integration of a highly ordered gold nanowires array with glucose oxidase for ultra-sensitive glucose detection.

    PubMed

    Cui, Jiewu; Adeloju, Samuel B; Wu, Yucheng

    2014-01-27

    A highly sensitive amperometric nanobiosensor has been developed by integration of glucose oxidase (GO(x)) with a gold nanowires array (AuNWA) by cross-linking with a mixture of glutaraldehyde (GLA) and bovine serum albumin (BSA). An initial investigation of the morphology of the synthesized AuNWA by field emission scanning electron microscopy (FESEM) and field emission transmission electron microscopy (FETEM) revealed that the nanowires array was highly ordered with rough surface, and the electrochemical features of the AuNWA with/without modification were also investigated. The integrated AuNWA-BSA-GLA-GO(x) nanobiosensor with Nafion membrane gave a very high sensitivity of 298.2 μA cm(-2) mM(-1) for amperometric detection of glucose, while also achieving a low detection limit of 0.1 μM, and a wide linear range of 5-6000 μM. Furthermore, the nanobiosensor exhibited excellent anti-interference ability towards uric acid (UA) and ascorbic acid (AA) with the aid of Nafion membrane, and the results obtained for the analysis of human blood serum indicated that the device is capable of glucose detection in real samples. PMID:24418144

  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. Flexible three-dimensional SnO2 nanowire arrays: atomic layer deposition-assisted synthesis, excellent photodetectors, and field emitters.

    PubMed

    Deng, Kaimo; Lu, Hao; Shi, Zhiwei; Liu, Qiong; Li, Liang

    2013-08-28

    Flexible three-dimensional SnO2 nanowire arrays were synthesized on a carbon cloth template in combination with atomic layer deposition and vapor transport. The as-grown nanostructures were assembled by high density quasi-aligned nanowires with a large aspect ratio. Nanoscale photodetectors based on the flexible nanostructure demonstrate excellent ultraviolet light selectivity, a high speed response time less than 0.3 s, and dark current as low as 2.3 pA. Besides, field emission measurements of the hierarchical structure show a rather low turn-on field (3.3 Vμm(-1)) and threshold field (4.5 Vμm(-1)), as well as an excellent field enhancment factor (2375) with a long-term stability up to 20 h. These results indicate that the flexible three-dimensional SnO2 nanowire arrays can be used as functional building blocks for efficient photodetectors and field emitters. PMID:23879602

  12. 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

  13. Facile synthesis of freestanding Si nanowire arrays by one-step template-free electro-deoxidation of SiO2 in a molten salt.

    PubMed

    Zhao, Ji; Li, Jun; Ying, Pinliang; Zhang, Wenhua; Meng, Lijian; Li, Can

    2013-05-18

    This communication presents a novel kind of silicon nanomaterial: freestanding Si nanowire arrays (Si NWAs), which are synthesized facilely by one-step template-free electro-deoxidation of SiO2 in molten CaCl2. The self-assembling growth process of this material is also investigated preliminarily.

  14. Wafer-Scale Precise Patterning of Organic Single-Crystal Nanowire Arrays via a Photolithography-Assisted Spin-Coating Method.

    PubMed

    Deng, Wei; Zhang, Xiujuan; Wang, Liang; Wang, Jincheng; Shang, Qixun; Zhang, Xiaohong; Huang, Liming; Jie, Jiansheng

    2015-12-01

    A photolithography-assisted spin-coating approach is developed to produce single-crystal organic nanowire (NW) arrays at designated locations with high precision and high efficiency. This strategy enables the large-scale fabrication of organic NW arrays with nearly the same accuracy, reliability, and flexibility as photolithography. The high mobilities of the organic NWs enable the control of the switch of multicolored light-emitting devices with good stability.

  15. Mechanical Resonance and Damping Properties of Gallium Nitride Nanowires in Selected-Area Growth Arrays Measured via Optical Bragg Scattering

    NASA Astrophysics Data System (ADS)

    Houlton, John; Brubaker, M. D.; Bertness, K. A.; Rogers, C. T.

    We report the use of optical Bragg scattering to measure the mechanical resonance frequencies and quality factors (Q) of gallium nitride (GaN) nanowires (NWs) in selected-area growth arrays. The GaN NWs are grown by catalyst-free molecular beam epitaxy on silicon (111) wafers. Hexagonal arrays of approximately 100 GaN NWs with pitch spacings of 400 - 1000 nm have been prepared. The NWs contained in such arrays have diameters ranging from 100-300 nm and lengths from 3 - 10 μm. A diode laser operating at 640 nm and 2 mW of optical power is used to perform Bragg scattering homodyne detection to passively read out the thermally induced Brownian mechanical motion of the NWs. The first order cantilever-mode mechanical resonance frequencies of these NWs have been measured to be between 2 - 12 MHz. We find that the optical readout via Bragg scattered light allows the simultaneous detection of all lowest order mechanical resonances in a given array. Q factors ranging from 1,000 - 12,000 have been seen at room temperature and 10-5 Torr pressures. Qs as high as 25,000 have been seen at temperatures of 80 K. These results show that the narrow mechanical resonances observed in freely-grown GaN NWs can also be seen in NWs prepared via selected-area growth. We gratefully acknowledge funding via NIST MSE Grant # 1553451.

  16. Si nanowires arrays fabricated by wet chemical etching for antireflection and self-cleaning

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Wang, Xiaotao; Lai, Wuxing; Tang, Zirong

    2011-11-01

    Here we report a simple and cost effective fabrication technique, which created large area vertical Si nanowires (diameter in ~200 nm) by means of silver induced wet chemical etching on single crystalline Si substrates. By this technique, Si nanowires were fabricated on single crystalline in aqueous 5M HF and 0.02M AgNO3 solution at room temperature. The scanning electron microscope (SEM) images indicate that etched silicon wafers consist of dense and nearly vertically aligned one-dimensional nanostructures. Length of Si nanowires was found to increase linearly with etching time (0-300 min). The mechanism of vertical nanowires formation can be understood as being a self-assembled Ag induced selective etching process based on the localized microscopic electrochemical cell model. A low reflectivity averaged ~1.7% from 450 to 790 nm was observed. The nanometer scale rough surface can make water droplet either in the so-called Wenzel or the Cassie regime, which can increase contact angle (CA). High CA makes the surface hydrophobicity and self-cleaning. Water CA (150°) was observed on the etched Si surface. Such antireflection (AR) and self-cleaning surface may have potential applications for silicon solar cells.

  17. Si nanowires arrays fabricated by wet chemical etching for antireflection and self-cleaning

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Wang, Xiaotao; Lai, Wuxing; Tang, Zirong

    2012-02-01

    Here we report a simple and cost effective fabrication technique, which created large area vertical Si nanowires (diameter in ~200 nm) by means of silver induced wet chemical etching on single crystalline Si substrates. By this technique, Si nanowires were fabricated on single crystalline in aqueous 5M HF and 0.02M AgNO3 solution at room temperature. The scanning electron microscope (SEM) images indicate that etched silicon wafers consist of dense and nearly vertically aligned one-dimensional nanostructures. Length of Si nanowires was found to increase linearly with etching time (0-300 min). The mechanism of vertical nanowires formation can be understood as being a self-assembled Ag induced selective etching process based on the localized microscopic electrochemical cell model. A low reflectivity averaged ~1.7% from 450 to 790 nm was observed. The nanometer scale rough surface can make water droplet either in the so-called Wenzel or the Cassie regime, which can increase contact angle (CA). High CA makes the surface hydrophobicity and self-cleaning. Water CA (150°) was observed on the etched Si surface. Such antireflection (AR) and self-cleaning surface may have potential applications for silicon solar cells.

  18. Vertical Nanowire Electrode Arrays as Novel Electrochemical Label-Free Immunosensors.

    PubMed

    Nasr, Babak; Chana, Gursharan; Lee, Ting Ting; Nguyen, Thanh; Abeyrathne, Chathurika; D'Abaco, Giovanna M; Dottori, Mirella; Skafidas, Efstratios

    2015-06-24

    A new method for the fabrication of a label-free electrochemical immunosensor based on vertical nanowires (VNWs) is proposed. The VNWs are functionalized to detect antibodies against a major astrocytic structural protein component, glial fibrillary acidic protein (GFAP). It is revealed that the interaction of GFAP-antibody with functionalized VNWs leads to a clear change in device conductance and the corresponding capacitance.

  19. Electrodeposited Co{sub 93.2}P{sub 6.8} nanowire arrays with core-shell microstructure and perpendicular magnetic anisotropy

    SciTech Connect

    Nasirpouri, F.; Peighambari, S. M.; Samardak, A. S. Ognev, A. V.; Sukovatitsina, E. V.; Modin, E. B.; Chebotkevich, L. A.; Komogortsev, S. V.; Bending, S. J.

    2015-05-07

    We demonstrate the formation of an unusual core-shell microstructure in Co{sub 93.2}P{sub 6.8} nanowires electrodeposited by alternating current (ac) in an alumina template. By means of transmission electron microscopy, it is shown that the coaxial-like nanowires contain amorphous and crystalline phases. Analysis of the magnetization data for Co-P alloy nanowires indicates that a ferromagnetic core is surrounded by a weakly ferromagnetic or non-magnetic phase, depending on the phosphor content. The nanowire arrays exhibit an easy axis of magnetization parallel to the wire axis. For this peculiar composition and structure, the coercivity values are 2380 ± 50 and 1260 ± 35 Oe, parallel and perpendicular to the plane directions of magnetization, respectively. This effect is attributed to the core-shell structure making the properties and applications of these nanowires similar to pure cobalt nanowires with an improved perpendicular anisotropy.

  20. Monolithic integration of a silicon nanowire field-effect transistors array on a complementary metal-oxide semiconductor chip for biochemical sensor applications.

    PubMed

    Livi, Paolo; Kwiat, Moria; Shadmani, Amir; Pevzner, Alexander; Navarra, Giulio; Rothe, Jörg; Stettler, Alexander; Chen, Yihui; Patolsky, Fernando; Hierlemann, Andreas

    2015-10-01

    We present a monolithic complementary metal-oxide semiconductor (CMOS)-based sensor system comprising an array of silicon nanowire field-effect transistors (FETs) and the signal-conditioning circuitry on the same chip. The silicon nanowires were fabricated by chemical vapor deposition methods and then transferred to the CMOS chip, where Ti/Pd/Ti contacts had been patterned via e-beam lithography. The on-chip circuitry measures the current flowing through each nanowire FET upon applying a constant source-drain voltage. The analog signal is digitized on chip and then transmitted to a receiving unit. The system has been successfully fabricated and tested by acquiring I-V curves of the bare nanowire-based FETs. Furthermore, the sensing capabilities of the complete system have been demonstrated by recording current changes upon nanowire exposure to solutions of different pHs, as well as by detecting different concentrations of Troponin T biomarkers (cTnT) through antibody-functionalized nanowire FETs.

  1. 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

  2. Carbon-Free CoO Mesoporous Nanowire Array Cathode for High-Performance Aprotic Li-O2 Batteries.

    PubMed

    Wu, Baoshan; Zhang, Hongzhang; Zhou, Wei; Wang, Meiri; Li, Xianfeng; Zhang, Huamin

    2015-10-21

    Although various kinds of catalysts have been developed for aprotic Li-O2 battery application, the carbon-based cathodes are still vulnerable to attacks from the discharge intermediates or products, as well as the accompanying electrolyte decomposition. To ameliorate this problem, the free-standing and carbon-free CoO nanowire array cathode was purposely designed for Li-O2 batteries. The single CoO nanowire formed as a special mesoporous structure, owing even comparable specific surface area and pore volume to the typical Super-P carbon particles. In addition to the highly selective oxygen reduction/evolution reactions catalytic activity of CoO cathodes, both excellent discharge specific capacity and cycling efficiency of Li-O2 batteries were obtained, with 4888 mAh gCoO(-1) and 50 cycles during 500 h period. Owing to the synergistic effect between elaborate porous structure and selective intermediate absorption on CoO crystal, a unique bimodal growth phenomenon of discharge products was occasionally observed, which further offers a novel mechanism to control the formation/decomposition morphology of discharge products in nanoscale. This research work is believed to shed light on the future development of high-performance aprotic Li-O2 batteries. PMID:26400109

  3. Reduction of spectral interferences using ultraclean gold nanowire arrays in the LDI-MS analysis of a model peptide.

    PubMed

    Colaianni, L; Kung, S C; Taggart, D K; Picca, R A; Greaves, J; Penner, R M; Cioffi, N

    2014-07-01

    The surface chemistry of gold nanowires (AuNWs) has been systematically assessed in terms of contamination and cleaning processes. The nanomaterial's surface quality was correlated to its performance in the matrix-free laser desorption ionization mass spectrometry (LDI-MS) analysis of low molecular weight analytes. Arrays of AuNWs were deposited on glass slides by means of the lithographically patterned nanowire electrodeposition technique. AuNWs were then characterized in terms of surface chemical composition and morphology using X-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy. AuNWs were subjected to a series of well-known cleaning procedures with the aim of producing the best performing surfaces for the LDI-MS detection of leucine enkephalin, chosen as a model analyte with a molar mass below 1,000 g/mol. Prolonged cyclic voltammetry in 2 M sulfuric acid and, most of all, oxygen plasma cleaning for 5 min provided the best results in terms of simpler (interference-free) and more intense mass spectrometry spectra of the reference compound. The analyte always ionized as the sodiated adduct, and leucine enkephalin limits of detection of 0.5 and 2.5 pmol were estimated for the positive and negative analysis modes, respectively. This study points out the tight correlation existing between the chemical status of the nanostructure surface and the AuNW-assisted LDI-MS performance in terms of reproducibility of spectra, intensity of analyte ions and reduction of interferences.

  4. The wavelength dependent photovoltaic effects caused by two different mechanisms in carbon nanotube film/CuO nanowire array heterodimensional contacts

    SciTech Connect

    Xu Jia; Xu Jinliang; Sun Jialin; Wei Jinquan

    2012-06-18

    Hetrodimensional contacts were fabricated by coating double-walled carbon nanotube (CNT) films on CuO nanowire arrays. Wavelength dependent photovoltaic effects by irradiating the devices with 405, 532, and 1064 nm lasers were observed. Two possible mechanisms responsible for the observed results were discussed. Photoexcitations within CuO nanowires and Schottky barriers in the heterojunctions dominate the photovoltaics in the 405 and 532 nm cases. For the 1064 nm case, the photovoltaic is the result of the excitation within the CNTs and of the heterodimensionality effect. Control experiments on CNT film/CuO granular film hetrodimensional contacts further show the relationship between these two mechanisms.

  5. AAO-assisted synthesis of highly ordered, large-scale TiO2 nanowire arrays via sputtering and atomic layer deposition.

    PubMed

    Yao, Zhao; Wang, Cong; Li, Yang; Kim, Nam-Young

    2015-01-01

    Highly ordered nanoporous anodic aluminum oxide (AAO) thin films were fabricated in oxalic acid under a constant voltage via a two-step anodization process. To investigate the high-aspect-ratio (7.5:1) filling process, both sputtering and atomic layer deposition (ALD) were used to form TiO2 nanowires. Field emission scanning electron microscopy and high-resolution transmission electron microscopy images indicated that mushroom-like TiO2 structures were sputtered onto the AAO template surface, and the ALD-coated TiO2 exhibited fine filling results and clear crystal grain boundaries. Large-scale and free-standing TiO2 nanowire arrays were liberated by selectively removing the aluminum substrate and AAO template via a wet etching process with no collapsing or agglomeration after the drying process. ALD-deposited TiO2 nanowire arrays that were 67 nm in diameter and 400 nm high were transferred from the AAO template. The ALD process enabled the rapid, simple synthesis of highly ordered TiO2 nanowire arrays with desired parameters such as diameter, density, and thickness determined using diverse AAO templates.

  6. AAO-assisted synthesis of highly ordered, large-scale TiO2 nanowire arrays via sputtering and atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Yao, Zhao; Wang, Cong; Li, Yang; Kim, Nam-Young

    2015-04-01

    Highly ordered nanoporous anodic aluminum oxide (AAO) thin films were fabricated in oxalic acid under a constant voltage via a two-step anodization process. To investigate the high-aspect-ratio (7.5:1) filling process, both sputtering and atomic layer deposition (ALD) were used to form TiO2 nanowires. Field emission scanning electron microscopy and high-resolution transmission electron microscopy images indicated that mushroom-like TiO2 structures were sputtered onto the AAO template surface, and the ALD-coated TiO2 exhibited fine filling results and clear crystal grain boundaries. Large-scale and free-standing TiO2 nanowire arrays were liberated by selectively removing the aluminum substrate and AAO template via a wet etching process with no collapsing or agglomeration after the drying process. ALD-deposited TiO2 nanowire arrays that were 67 nm in diameter and 400 nm high were transferred from the AAO template. The ALD process enabled the rapid, simple synthesis of highly ordered TiO2 nanowire arrays with desired parameters such as diameter, density, and thickness determined using diverse AAO templates.

  7. Synthesis of carbon nanotubes/Si nanowires core-sheath structure arrays and their field emission properties

    NASA Astrophysics Data System (ADS)

    Lu, M.; Li, M. K.; Zhang, Z. J.; Li, H. L.

    2003-09-01

    A new composite structure of carbon nanotubes (CNTs)/Si nanowires (SiNWs) arrays have been synthesized by chemical vapor deposition (CVD) within the pores of microporous alumina template. The results of scanning electron microscopy (SEM) and transmission electron microcopy (TEM) reveal that the obtained well-aligned composite structure has a core-sheath structure and the deposited material in the carbon sheath is polycrystalline silicon. Field emission from these CNTs-sheathed SiNWs exhibits significant enhancement compared to the pure SiNWs in turn-on field, total emission current and stability. The field emission characteristics of the composite structure are analyzed based on Fowler-Nordheim theory. The electron field emission increased with decreasing diameter of such structure. The well-aligned core-sheath structure provides an important means to fabricate emitter devices with chemically inert surface as well as with superior performance of field emission properties.

  8. Three-dimensionally grown thorn-like Cu nanowire arrays by fully electrochemical nanoengineering for highly enhanced hydrazine oxidation.

    PubMed

    Huang, Jianfei; Zhao, Shunan; Chen, Wei; Zhou, Ying; Yang, Xiaoling; Zhu, Yihua; Li, Chunzhong

    2016-03-21

    This communication reports fully electrochemical nanoengineering toward three-dimensionally grown thorn-like Cu nanowire arrays (CNWAs) as a highly efficient and durable electrocatalyst for hydrazine oxidation. Characterized by substantial negative shifting of the onset potential and an enlarged catalytic current density, the CNWAs afforded greatly enhanced hydrazine oxidation activity, even transcending that of the Pt/C catalyst at a higher reaction rate. The parameters of the electrochemical engineering and metallization methods were found to be essentially influential on the microstructure, and thus the electrocatalytic activity of the CNWAs. The present work typifies a flexible and expandible route toward integrated electrodes of metallic 1D nanostructures which are of interest in advancing the performance of cutting-edge electrochemical applications. PMID:26580842

  9. Silicon/hematite core/shell nanowire array decorated with gold nanoparticles for unbiased solar water oxidation.

    PubMed

    Wang, Xin; Peng, Kui-Qing; Hu, Ya; Zhang, Fu-Qiang; Hu, Bo; Li, Li; Wang, Meng; Meng, Xiang-Min; Lee, Shuit-Tong

    2014-01-01

    We report the facile fabrication of three-dimensional (3D) silicon/hematite core/shell nanowire arrays decorated with gold nanoparticles (AuNPs) and their potential application for sunlight-driven solar water splitting. The hematite and AuNPs respectively play crucial catalytic and plasmonic photosensitization roles, while silicon absorbs visible light and generates high photocurrent. Under simulated solar light illumination, solar water splitting with remarkable efficiency is achieved with no external bias applied. Such a nanocomposite photoanode design offers great promise for unassisted sunlight-driven water oxidation, and further stability and efficiency improvements to the device will lead to exciting prospects for practical solar water splitting and artificial photosynthesis.

  10. Core-shell heterojunction of silicon nanowire arrays and carbon quantum dots for photovoltaic devices and self-driven photodetectors.

    PubMed

    Xie, Chao; Nie, Biao; Zeng, Longhui; Liang, Feng-Xia; Wang, Ming-Zheng; Luo, Linbao; Feng, Mei; Yu, Yongqiang; Wu, Chun-Yan; Wu, Yucheng; Yu, Shu-Hong

    2014-04-22

    Silicon nanostructure-based solar cells have lately intrigued intensive interest because of their promising potential in next-generation solar energy conversion devices. Herein, we report a silicon nanowire (SiNW) array/carbon quantum dot (CQD) core-shell heterojunction photovoltaic device by directly coating Ag-assisted chemical-etched SiNW arrays with CQDs. The heterojunction with a barrier height of 0.75 eV exhibited excellent rectifying behavior with a rectification ratio of 10(3) at ±0.8 V in the dark and power conversion efficiency (PCE) as high as 9.10% under AM 1.5G irradiation. It is believed that such a high PCE comes from the improved optical absorption as well as the optimized carrier transfer and collection capability. Furthermore, the heterojunction could function as a high-performance self-driven visible light photodetector operating in a wide switching wavelength with good stability, high sensitivity, and fast response speed. It is expected that the present SiNW array/CQD core-shell heterojunction device could find potential applications in future high-performance optoelectronic devices.

  11. Electrochemical pore filling strategy for controlled growth of magnetic and metallic nanowire arrays with large area uniformity

    NASA Astrophysics Data System (ADS)

    Arefpour, M.; Almasi Kashi, M.; Ramazani, A.; Montazer, A. H.

    2016-07-01

    While a variety of template-based strategies have been developed in the fabrication of nanowires (NWs), a uniform pore filling across the template still poses a major challenge. Here, we present a large area controlled pore filling strategy in the reproducible fabrication of various magnetic and metallic NW arrays, embedded inside anodic aluminum oxide templates. Using a diffusive pulsed electrodeposition (DPED) technique, this versatile strategy relies on the optimized filling of branched nanopores at the bottom of templates with Cu. Serving the Cu filled nanopores as appropriate nucleation sites, the DPED is followed by a uniform and homogeneous deposition of magnetic (Ni and Fe) and metallic (Cu and Zn) NWs at a current density of 50 mA cm-2 for an optimal thickness of alumina barrier layer (˜18 nm). Our strategy provides large area uniformity (exceeding 400 μm2) in the fabrication of 16 μm long free-standing NW arrays. Using hysteresis loop measurements and scanning electron microscopy images, the electrodeposition efficiency (EE) and pore filling percentage (F p) are evaluated, leading to maximum EE and F p values of 91% and 95% for Ni and Zn, respectively. Moreover, the resulting NW arrays are found to be highly crystalline. Accordingly, the DPED technique is capable of cheaply and efficiently controlling NW growth over a large area, providing a tool for various nanoscale applications including biomedical devices, electronics, photonics, magnetic storage medium and nanomagnet computing.

  12. Optical properties of silicon nanowire arrays formed by metal-assisted chemical etching: evidences for light localization effect

    PubMed Central

    2012-01-01

    We study the structure and optical properties of arrays of silicon nanowires (SiNWs) with a mean diameter of approximately 100 nm and length of about 1–25 μm formed on crystalline silicon (c-Si) substrates by using metal-assisted chemical etching in hydrofluoric acid solutions. In the middle infrared spectral region, the reflectance and transmittance of the formed SiNW arrays can be described in the framework of an effective medium with the effective refractive index of about 1.3 (porosity, approximately 75%), while a strong light scattering for wavelength of 0.3 ÷ 1 μm results in a decrease of the total reflectance of 1%-5%, which cannot be described in the effective medium approximation. The Raman scattering intensity under excitation at approximately 1 μm increases strongly in the sample with SiNWs in comparison with that in c-Si substrate. This effect is related to an increase of the light-matter interaction time due to the strong scattering of the excitation light in SiNW array. The prepared SiNWs are discussed as a kind of ‘black silicon’, which can be formed in a large scale and can be used for photonic applications as well as in molecular sensing. PMID:23009051

  13. Electrochemical pore filling strategy for controlled growth of magnetic and metallic nanowire arrays with large area uniformity

    NASA Astrophysics Data System (ADS)

    Arefpour, M.; Almasi Kashi, M.; Ramazani, A.; Montazer, A. H.

    2016-07-01

    While a variety of template-based strategies have been developed in the fabrication of nanowires (NWs), a uniform pore filling across the template still poses a major challenge. Here, we present a large area controlled pore filling strategy in the reproducible fabrication of various magnetic and metallic NW arrays, embedded inside anodic aluminum oxide templates. Using a diffusive pulsed electrodeposition (DPED) technique, this versatile strategy relies on the optimized filling of branched nanopores at the bottom of templates with Cu. Serving the Cu filled nanopores as appropriate nucleation sites, the DPED is followed by a uniform and homogeneous deposition of magnetic (Ni and Fe) and metallic (Cu and Zn) NWs at a current density of 50 mA cm‑2 for an optimal thickness of alumina barrier layer (∼18 nm). Our strategy provides large area uniformity (exceeding 400 μm2) in the fabrication of 16 μm long free-standing NW arrays. Using hysteresis loop measurements and scanning electron microscopy images, the electrodeposition efficiency (EE) and pore filling percentage (F p) are evaluated, leading to maximum EE and F p values of 91% and 95% for Ni and Zn, respectively. Moreover, the resulting NW arrays are found to be highly crystalline. Accordingly, the DPED technique is capable of cheaply and efficiently controlling NW growth over a large area, providing a tool for various nanoscale applications including biomedical devices, electronics, photonics, magnetic storage medium and nanomagnet computing.

  14. Three-dimensionally grown thorn-like Cu nanowire arrays by fully electrochemical nanoengineering for highly enhanced hydrazine oxidation

    NASA Astrophysics Data System (ADS)

    Huang, Jianfei; Zhao, Shunan; Chen, Wei; Zhou, Ying; Yang, Xiaoling; Zhu, Yihua; Li, Chunzhong

    2016-03-01

    This communication reports fully electrochemical nanoengineering toward three-dimensionally grown thorn-like Cu nanowire arrays (CNWAs) as a highly efficient and durable electrocatalyst for hydrazine oxidation. Characterized by substantial negative shifting of the onset potential and an enlarged catalytic current density, the CNWAs afforded greatly enhanced hydrazine oxidation activity, even transcending that of the Pt/C catalyst at a higher reaction rate. The parameters of the electrochemical engineering and metallization methods were found to be essentially influential on the microstructure, and thus the electrocatalytic activity of the CNWAs. The present work typifies a flexible and expandible route toward integrated electrodes of metallic 1D nanostructures which are of interest in advancing the performance of cutting-edge electrochemical applications.This communication reports fully electrochemical nanoengineering toward three-dimensionally grown thorn-like Cu nanowire arrays (CNWAs) as a highly efficient and durable electrocatalyst for hydrazine oxidation. Characterized by substantial negative shifting of the onset potential and an enlarged catalytic current density, the CNWAs afforded greatly enhanced hydrazine oxidation activity, even transcending that of the Pt/C catalyst at a higher reaction rate. The parameters of the electrochemical engineering and metallization methods were found to be essentially influential on the microstructure, and thus the electrocatalytic activity of the CNWAs. The present work typifies a flexible and expandible route toward integrated electrodes of metallic 1D nanostructures which are of interest in advancing the performance of cutting-edge electrochemical applications. Electronic supplementary information (ESI) available: Experimental details, additional figures and table. See DOI: 10.1039/c5nr06512g

  15. Ordered Polypyrrole Nanowire Arrays Grown on a Carbon Cloth Substrate for a High-Performance Pseudocapacitor Electrode.

    PubMed

    Huang, Zi-Hang; Song, Yu; Xu, Xin-Xin; Liu, Xiao-Xia

    2015-11-18

    Highly aligned nanoarchitecture arrays directly grown on conducting substrates open up a new direction to accelerate Faradaic reactions for charge storage as well as address "dead volume" limitations for high-performance pseudocapacitor electrodes. Here we reported the electrochemical fabrication of well-ordered polypyrrole (PPy) nanowire arrays (NWAs) on surfaces of carbon fibers in an untreated carbon cloth to construct hierarchical structures constituted by the three-dimensional conductive carbon fiber skeleton and the atop well-ordered electroactive polymer nanowires. The morphologies, wetting behaviors, and charge-storage performances of the polymer were investigated by scanning electron microscopy, transmission electron microscopy, contact-angle measurement, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The well-ordered PPy NWA electrode exhibited a high specific capacitance of 699 F/g at 1 A/g with excellent rate capability, and 92.4% and 81.5% of its capacitance could be retained at 10 and 20 A/g, respectively. An extremely high energy density of 164.07 Wh/kg could be achieved by the PPy NWAs at a power density of 0.65 kW/kg. It also displayed a quite high energy density of 133.79 Wh/kg at a high power density of 13 kW/kg. The assembled symmetric supercapacitor of PPy NWAs//PPy NWAs also exhibited excellent rate capability, and only 19% of its energy density decreased when the power density increased 20 times from 0.65 to 13 kW/kg.

  16. Color generation and refractive index sensing using diffraction from 2D silicon nanowire arrays.

    PubMed

    Walia, Jaspreet; Dhindsa, Navneet; Khorasaninejad, Mohammadreza; Saini, Simarjeet Singh

    2014-01-15

    Tunable structural color generation from vertical silicon nanowires arranged in different square lattices is demonstrated. The generated colors are adjustable using well-defined Bragg diffraction theory, and only depend on the lattice spacing and angles of incidence. Vivid colors spanning from bright red to blue are easily achieved. In keeping with this, a single square lattice of silicon nanowires is also able to produce different colors spanning the entire visible range. It is also shown that the 2D gratings also have a third grating direction when rotated 45 degrees. These simple and elegant solutions to color generation from silicon are used to demonstrate a cost-effective refractive index sensor. The sensor works by measuring color changes resulting from changes in the refractive index of the medium surrounding the nanowires using a trichromatic RGB decomposition. Moreover, the sensor produces linear responses in the trichromatic decomposition values versus the surrounding medium index. An index resolution of 10(-4) is achieved by performing basic image processing on the collected images, without the need for a laser or a spectrometer. Spectral analysis enables an increase in the index resolution of the sensor to a value of 10(-6) , with a sensitivity of 400 nm/RIU. PMID:23784866

  17. Highly ordered nanowire arrays on plastic substrates for ultrasensitive flexible chemical sensors

    PubMed Central

    McAlpine, Michael C.; Ahmad, Habib; Wang, Dunwei; Heath, James R.

    2013-01-01

    The development of a robust method for integrating high-performance semiconductors on flexible plastics could enable exciting avenues in fundamental research and novel applications. One area of vital relevance is chemical and biological sensing, which if implemented on biocompatible substrates, could yield breakthroughs in implantable or wearable monitoring systems. Semiconducting nanowires (and nanotubes) are particularly sensitive chemical sensors because of their high surface-to-volume ratios. Here, we present a scalable and parallel process for transferring hundreds of pre-aligned silicon nanowires onto plastic to yield highly ordered films for low-power sensor chips. The nanowires are excellent field-effect transistors, and, as sensors, exhibit parts-per-billion sensitivity to NO2, a hazardous pollutant. We also use SiO2 surface chemistries to construct a ‘nano-electronic nose’ library, which can distinguish acetone and hexane vapours via distributed responses. The excellent sensing performance coupled with bendable plastic could open up opportunities in portable, wearable or even implantable sensors. PMID:17450146

  18. 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.

  19. 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

  20. Nanowire Photovoltaic Devices

    NASA Technical Reports Server (NTRS)

    Forbes, David

    2015-01-01

    Firefly Technologies, in collaboration with the Rochester Institute of Technology and the University of Wisconsin-Madison, developed synthesis methods for highly strained nanowires. Two synthesis routes resulted in successful nanowire epitaxy: direct nucleation and growth on the substrate and a novel selective-epitaxy route based on nanolithography using diblock copolymers. The indium-arsenide (InAs) nanowires are implemented in situ within the epitaxy environment-a significant innovation relative to conventional semiconductor nanowire generation using ex situ gold nanoparticles. The introduction of these nanoscale features may enable an intermediate band solar cell while simultaneously increasing the effective absorption volume that can otherwise limit short-circuit current generated by thin quantized layers. The use of nanowires for photovoltaics decouples the absorption process from the current extraction process by virtue of the high aspect ratio. While no functional solar cells resulted from this effort, considerable fundamental understanding of the nanowire epitaxy kinetics and nanopatterning process was developed. This approach could, in principle, be an enabling technology for heterointegration of dissimilar materials. The technology also is applicable to virtual substrates. Incorporating nanowires onto a recrystallized germanium/metal foil substrate would potentially solve the problem of grain boundary shunting of generated carriers by restricting the cross-sectional area of the nanowire (tens of nanometers in diameter) to sizes smaller than the recrystallized grains (0.5 to 1 micron(exp 2).