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Sample records for aligned silicon nanowires

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2007-09-01

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

  3. 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).

  4. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

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

    PubMed

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

    2015-05-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  9. Self-aligned nanoforest in silicon nanowire for sensitive conductance modulation.

    PubMed

    Seol, Myeong-Lok; Ahn, Jae-Hyuk; Choi, Ji-Min; Choi, Sung-Jin; Choi, Yang-Kyu

    2012-11-14

    A self-aligned and localized nanoforest structure is constructed in a top-down fabricated silicon nanowire (SiNW). The surface-to-volume ratio (SVR) of the SiNW is enhanced due to the local nanoforest formation. The conductance modulation property of the SiNWs, which is an important characteristic in sensor and charge transfer based applications, can be largely enhanced. For the selective modification of the channel region, localized Joule-heating and subsequent metal-assisted chemical etching (mac-etch) are employed. The nanoforest is formed only in the channel region without misalignment due to the self-aligned process of Joule-heating. The modified SiNW is applied to a porphyrin-silicon hybrid device to verify the enhanced conductance modulation. The charge transfer efficiency between the porphyrin and the SiNW, which is caused by external optical excitation, is clearly increased compared to the initial SiNW. The effect of the local nanoforest formation is enhanced when longer etching times and larger widths are used. PMID:23066892

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  11. Vertically aligned crystalline silicon nanowires with controlled diameters for energy conversion applications: Experimental and theoretical insights

    SciTech Connect

    Razek, Sara Abdel; Swillam, Mohamed A.; Allam, Nageh K.

    2014-05-21

    Vertically orientated single crystalline silicon nanowire (SiNW) arrays with controlled diameters are fabricated via a metal-assisted chemical etching method. The diameter of the fabricated nanowires is controlled by simply varying the etching time in HF/H{sub 2}O{sub 2} electrolytes. The fabricated SiNWs have diameters ranging from 117 to 650 nm and lengths from 8 to 18 μm. The optical measurements showed a significant difference in the reflectance/absorption of the SiNWs with different diameters, where the reflectance increases with increasing the diameter of the SiNWs. The SiNWs showed significant photoluminescence (PL) emission spectra with peaks lying between 380 and 670 nm. The PL intensity increases as the diameter increases and shows red shift for peaks at ∼670 nm. The increase or decrease of reflectivity is coincident with PL intensity at wavelength ∼660 nm. The x-ray diffraction patterns confirm the high crystallinity of the fabricated SiNWs. In addition, the Raman spectra showed a shift in the first order transverse band toward lower frequencies compared to that usually seen for c-Si. Finite difference time domain simulations have been performed to confirm the effect of change of diameter on the optical properties of the nanowires. The simulation results showed good agreement with the experimental results for the SiNWs of different diameters.

  12. Silicon Nanowire Devices

    NASA Astrophysics Data System (ADS)

    Kamins, Theodore

    2006-03-01

    Metal-catalyzed, self-assembled, one-dimensional semiconductor nanowires are being considered as possible device elements to augment and supplant conventional electronics and to extend the use of CMOS beyond the physical and economic limits of conventional technology. Such nanowires can create nanostructures without the complexity and cost of extremely fine scale lithography. The well-known and controllable properties of silicon make silicon nanowires especially attractive. Easy integration with conventional electronics will aid their acceptance and incorporation. For example, connections can be formed to both ends of a nanowire by growing it laterally from a vertical surface formed by etching the top silicon layer of a silicon-on-insulator structure into isolated electrodes. Field-effect structures are one class of devices that can be readily built in silicon nanowires. Because the ratio of surface to volume in a thin nanowire is high, conduction through the nanowire is very sensitive to surface conditions, making it effective as the channel of a field-effect transistor or as the transducing element of a gas or chemical sensor. As the nanowire diameter decreases, a greater fraction of the mobile charge can be modulated by a given external charge, increasing the sensitivity. Having the gate of a nanowire transistor completely surround the nanowire also enhances the sensitivity. For a field-effect sensor to be effective, the charge must be physically close to the nanowire so that the majority of the compensating charge is induced in the nanowire and so that ions in solution do not screen the charge. Because only induced charge is being sensed, a coating that selectively binds the target species should be added to the nanowire surface to distinguish between different species in the analyte. The nanowire work at Hewlett-Packard Laboratories was supported in part by the Defense Advanced Research Projects Agency.

  13. Multicolored Vertical Silicon Nanowires

    SciTech Connect

    Seo, Kwanyong; Wober, Munib; Steinvurzel, P.; Schonbrun, E.; Dan, Yaping; Ellenbogen, T.; Crozier, K. B.

    2011-04-13

    We demonstrate that vertical silicon nanowires take on a surprising variety of colors covering the entire visible spectrum, in marked contrast to the gray color of bulk silicon. This effect is readily observable by bright-field microscopy, or even to the naked eye. The reflection spectra of the nanowires each show a dip whose position depends on the nanowire radii. We compare the experimental data to the results of finite difference time domain simulations to elucidate the physical mechanisms behind the phenomena we observe. The nanowires are fabricated as arrays, but the vivid colors arise not from scattering or diffractive effects of the array, but from the guided mode properties of the individual nanowires. Each nanowire can thus define its own color, allowing for complex spatial patterning. We anticipate that the color filter effect we demonstrate could be employed in nanoscale image sensor devices.

  14. Electroluminescence from silicon nanowires

    NASA Astrophysics Data System (ADS)

    Huo, J.; Solanki, R.; Freeouf, J. L.; Carruthers, J. R.

    2004-12-01

    Room temperature electroluminescence has been demonstrated from undoped silicon nanowires that were grown from disilane. Ensembles of nanowires were excited by capacitively coupling them to an ac electric field. The emission peak occurred at about 600 nm from wires of average diameter of about 4 nm. The emission appears to result from band-to-band electron-hole recombination.

  15. Self-aligned process for forming microlenses at the tips of vertical silicon nanowires by atomic layer deposition

    SciTech Connect

    Dan, Yaping Chen, Kaixiang; Crozier, Kenneth B.

    2015-01-01

    The microlens is a key enabling technology in optoelectronics, permitting light to be efficiently coupled to and from devices such as image sensors and light-emitting diodes. Their ubiquitous nature motivates the development of new fabrication techniques, since existing methods face challenges as microlenses are scaled to smaller dimensions. Here, the authors demonstrate the formation of microlenses at the tips of vertically oriented silicon nanowires via a rapid atomic layer deposition process. The nature of the process is such that the microlenses are centered on the nanowires, and there is a self-limiting effect on the final sizes of the microlenses arising from the nanowire spacing. Finite difference time domain electromagnetic simulations are performed of microlens focusing properties, including showing their ability to enhance visible-wavelength absorption in silicon nanowires.

  16. Multimode silicon nanowire transistors.

    PubMed

    Glassner, Sebastian; Zeiner, Clemens; Periwal, Priyanka; Baron, Thierry; Bertagnolli, Emmerich; Lugstein, Alois

    2014-11-12

    The combined capabilities of both a nonplanar design and nonconventional carrier injection mechanisms are subject to recent scientific investigations to overcome the limitations of silicon metal oxide semiconductor field effect transistors. In this Letter, we present a multimode field effect transistors device using silicon nanowires that feature an axial n-type/intrinsic doping junction. A heterostructural device design is achieved by employing a self-aligned nickel-silicide source contact. The polymorph operation of the dual-gate device enabling the configuration of one p- and two n-type transistor modes is demonstrated. Not only the type but also the carrier injection mode can be altered by appropriate biasing of the two gate terminals or by inverting the drain bias. With a combined band-to-band and Schottky tunneling mechanism, in p-type mode a subthreshold swing as low as 143 mV/dec and an ON/OFF ratio of up to 10(4) is found. As the device operates in forward bias, a nonconventional tunneling transistor is realized, enabling an effective suppression of ambipolarity. Depending on the drain bias, two different n-type modes are distinguishable. The carrier injection is dominated by thermionic emission in forward bias with a maximum ON/OFF ratio of up to 10(7) whereas in reverse bias a Schottky tunneling mechanism dominates the carrier transport. PMID:25303290

  17. Roll up nanowire battery from silicon chips.

    PubMed

    Vlad, Alexandru; Reddy, Arava Leela Mohana; Ajayan, Anakha; Singh, Neelam; Gohy, Jean-François; Melinte, Sorin; Ajayan, Pulickel M

    2012-09-18

    Here we report an approach to roll out Li-ion battery components from silicon chips by a continuous and repeatable etch-infiltrate-peel cycle. Vertically aligned silicon nanowires etched from recycled silicon wafers are captured in a polymer matrix that operates as Li(+) gel-electrolyte and electrode separator and peeled off to make multiple battery devices out of a single wafer. Porous, electrically interconnected copper nanoshells are conformally deposited around the silicon nanowires to stabilize the electrodes over extended cycles and provide efficient current collection. Using the above developed process we demonstrate an operational full cell 3.4 V lithium-polymer silicon nanowire (LIPOSIL) battery which is mechanically flexible and scalable to large dimensions. PMID:22949696

  18. Roll up nanowire battery from silicon chips

    PubMed Central

    Vlad, Alexandru; Reddy, Arava Leela Mohana; Ajayan, Anakha; Singh, Neelam; Gohy, Jean-François; Melinte, Sorin; Ajayan, Pulickel M.

    2012-01-01

    Here we report an approach to roll out Li-ion battery components from silicon chips by a continuous and repeatable etch-infiltrate-peel cycle. Vertically aligned silicon nanowires etched from recycled silicon wafers are captured in a polymer matrix that operates as Li+ gel-electrolyte and electrode separator and peeled off to make multiple battery devices out of a single wafer. Porous, electrically interconnected copper nanoshells are conformally deposited around the silicon nanowires to stabilize the electrodes over extended cycles and provide efficient current collection. Using the above developed process we demonstrate an operational full cell 3.4 V lithium-polymer silicon nanowire (LIPOSIL) battery which is mechanically flexible and scalable to large dimensions. PMID:22949696

  19. Single crystalline mesoporous silicon nanowires

    SciTech Connect

    Hochbaum, A.I.; Gargas, Daniel; Jeong Hwang, Yun; Yang, Peidong

    2009-08-04

    Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. These porous nanowires also retain the crystallographic orientation of the wafer from which they are etched. Electron microscopy and diffraction confirm their single-crystallinity and reveal the silicon surrounding the pores is as thin as several nanometers. Confocal fluorescence microscopy showed that the photoluminescence (PL) of these arrays emanate from the nanowires themselves, and their PL spectrum suggests that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices.

  20. Nanowire lithography on silicon.

    PubMed

    Colli, Alan; Fasoli, Andrea; Pisana, Simone; Fu, Yongqing; Beecher, Paul; Milne, William I; Ferrari, Andrea C

    2008-05-01

    Nanowire lithography (NWL) uses nanowires (NWs), grown and assembled by chemical methods, as etch masks to transfer their one-dimensional morphology to an underlying substrate. Here, we show that SiO2 NWs are a simple and compatible system to implement NWL on crystalline silicon and fabricate a wide range of architectures and devices. Planar field-effect transistors made of a single SOI-NW channel exhibit a contact resistance below 20 kOmega and scale with the channel width. Further, we assess the electrical response of NW networks obtained using a mask of SiO2 NWs ink-jetted from solution. The resulting conformal network etched into the underlying wafer is monolithic, with single-crystalline bulk junctions; thus no difference in conductivity is seen between a direct NW bridge and a percolating network. We also extend the potential of NWL into the third dimension, by using a periodic undercutting that produces an array of vertically stacked NWs from a single NW mask. PMID:18386934

  1. Single crystalline mesoporous silicon nanowires

    SciTech Connect

    Hochbaum, Allon; Dargas, Daniel; Hwang, Yun Jeong; Yang, Peidong

    2009-08-18

    Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. The photoluminescence of these nanowires suggest they are composed of crystalline silicon with small enough dimensions such that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices. A better understanding of this electroless route to mesoporous silicon could lead to facile and general syntheses of different narrow bandgap semiconductor nanostructures for various applications.

  2. Fabrication and characterization of porous silicon nanowires

    NASA Astrophysics Data System (ADS)

    Jung, Daeyoon; Cho, Soo Gyeong; Moon, Taeho; Sohn, Honglae

    2016-01-01

    We report the synthesis of porous silicon nanowires through the metalassisted chemical etching of porous silicon in a solution of hydrofluoric acid and hydrogen peroxide. The morphology of porous silicon nanowires was characterized by scanning electron microscopy and transmission electron microscopy. The etch rate of the porous silicon nanowires was faster than that of silicon nanowires, but slower than that of porous silicon. The porous silicon nanowires distributed uniformly on the entire porous silicon layer and the tips of the porous silicon nanowires congregated together. The single crystalline and sponge-like porous structure with the pore diameters of less than 5 nm was confirmed for the porous silicon nanowires. [Figure not available: see fulltext.

  3. Optical absorption of silicon nanowires

    SciTech Connect

    Xu, T.; Lambert, Y.; Krzeminski, C.; Grandidier, B.; Stievenard, D.; Leveque, G.; Akjouj, A.; Pennec, Y.; Djafari-Rouhani, B.

    2012-08-01

    We report on simulations and measurements of the optical absorption of silicon nanowires (NWs) versus their diameter. We first address the simulation of the optical absorption based on two different theoretical methods: the first one, based on the Green function formalism, is useful to calculate the scattering and absorption properties of a single or a finite set of NWs. The second one, based on the finite difference time domain (FDTD) method, is well-adapted to deal with a periodic set of NWs. In both cases, an increase of the onset energy for the absorption is found with increasing diameter. Such effect is experimentally illustrated, when photoconductivity measurements are performed on single tapered Si nanowires connected between a set of several electrodes. An increase of the nanowire diameter reveals a spectral shift of the photocurrent intensity peak towards lower photon energies that allow to tune the absorption onset from the ultraviolet radiations to the visible light spectrum.

  4. Circular photogalvanic effect in silicon nanowires

    NASA Astrophysics Data System (ADS)

    Dhara, Sajal; Mele, E. J.; Agarwal, Ritesh

    Circular photogalvanic effect (CPGE), the generation of a photocurrent whose magnitude and polarity depends on chirality of optical excitation, is demonstrated in the visible optical range in silicon nanowires, a bulk non-gyrotropic material with weak spin-orbit coupling. CPGE, which is absent in bulk Si is found to arise from interband transitions only at the metal-semiconductor contacts to Si nanowires where inversion symmetry is broken by a Schottky electric field. Furthermore, by applying a bias voltage that modulates this field, the sign and magnitude of the CPGE can be controlled. From excitation energy dependent measurements and symmetry considerations, it is argued that the [10] surface states due to Si chains that are not aligned with the nanowire growth direction and the Schottky field produce an artificial gyrotropic optical medium that supports CPGE. This work reveals the role of the surface states in the generation of chirality-dependent photocurrents in silicon with a purely orbital-based mechanism, and also opens up new possibilities of engineering new functionalities in Si that can be integrated with conventional electronics.

  5. Synthesis and characterization of germanium nanowires and germanium/silicon radially heterostructured nanowires

    NASA Astrophysics Data System (ADS)

    Goldthorpe, Irene Anne

    Semiconductor nanowires offer new opportunities to study physical phenomena in low-dimensional nanostructures. They also possess technologically useful properties for applications in electronics, optics, sensing, and thermoelectrics. Germanium nanowires are of particular interest, because of germanium's compatibility with standard silicon integrated circuit fabrication processes, its high electronic carrier mobilities, and the low temperature required for germanium nanowire growth. In this work, epitaxially-aligned germanium nanowires are grown on silicon substrates by chemical vapor deposition through the vapor-liquid-solid mechanism. Uniform nanowire diameters between 5 and 50 nm are obtained through the use of monodisperse gold colloids as catalysts. The crystallographic orientation of the nanowires, their strain, and their heteroepitaxial relationship with the substrate are characterized with transmission electron microscopy (TEM) and x-ray diffraction (XRD). A process for removing the gold catalysts from the tips of the germanium nanowires is demonstrated. Silicon shells are then heteroepitaxially deposited around the wires to fabricate radial heterostructures. These shells passivate the germanium nanowire surface, create electronic band offsets to confine holes away the surface where they can scatter or recombine, and induce strain which could allow for the engineering of properties such as band gap and carrier mobilities. However, analogous to planar heteroepitaxy, surface roughening and misfit dislocations can relax this strain. The effects of coaxial dimensions on strain relaxation in these structures are analyzed quantitatively by TEM and synchrotron XRD, and these results are related to continuum elasticity models. Lessons learned generated two successful strategies for synthesizing coherent core-shell nanowires with large misfit strain: chlorine surface passivation and growth of nanowires with low-energy sidewall facets. Both approaches avoid the strain

  6. Silicon carbide nanowires synthesized with phenolic resin and silicon powders

    NASA Astrophysics Data System (ADS)

    Zhao, Hongsheng; Shi, Limin; Li, Ziqiang; Tang, Chunhe

    2009-02-01

    Large-scale silicon carbide nanowires with the lengths up to several millimeters were synthesized by a coat-mix, moulding, carbonization, and high-temperature sintering process, using silicon powder and phenolic resin as the starting materials. Ordinary SiC nanowires, bamboo-like SiC nanowires, and spindle SiC nanochains are found in the fabricated samples. The ordinary SiC nanowire is a single-crystal SiC phase with a fringe spacing of 0.252 nm along the [1 1 1] growth direction. Both of the bamboo-like SiC nanowires and spindle SiC nanochains exhibit uniform periodic structures. The bamboo-like SiC nanowires consist of amorphous stem and single-crystal knots, while the spindle SiC nanochains consist of uniform spindles which grow uniformly on the entire nanowires.

  7. Mechanical properties of Silicon Carbide Nanowires

    NASA Astrophysics Data System (ADS)

    Alkhateeb, Abdullah; Zhang, Daqing; McIlroy, David; Aston, David Eric

    2004-05-01

    Silicon carbide nanowires could be potentially useful for high strength materials which lead to the interest in understanding their mechanical properties. In this report we use the digital pulse force microscopy to analyze the mechanical properties of SiC nanowires .Stiffness and adhesion images of SiC nanowires on silicon grating were obtained and calibrated force-distance curves were plotted along the wire which spans on a 1.5 micron trench. Moreover, spring constant and Young's modules have been calculated from the linear part of the force-distance curves.

  8. Electric-field assisted growth and self-assembly of intrinsic silicon nanowires.

    PubMed

    Englander, Ongi; Christensen, Dane; Kim, Jongbaeg; Lin, Liwei; Morris, Stephen J S

    2005-04-01

    Electric-field assisted growth and self-assembly of intrinsic silicon nanowires, in-situ, is demonstrated. The nanowires are seen to respond to the presence of a localized DC electric field set up between adjacent MEMS structures. The response is expressed in the form of improved nanowire order, alignment, and organization while transcending a gap. This process provides a simple yet reliable method for enhanced control over intrinsic one-dimensional nanostructure placement and handling. PMID:15826112

  9. Synthesis of silicon and germanium nanowires.

    SciTech Connect

    Clement, Teresa J.; Hsu, Julia W. P.

    2007-11-01

    The vapor-liquid-solid growth process for synthesis of group-IV semiconducting nanowires using silane, germane, disilane and digermane precursor gases has been investigated. The nanowire growth process combines in situ gold seed formation by vapor deposition on atomically clean silicon (111) surfaces, in situ growth from the gaseous precursor(s), and real-time monitoring of nanowire growth as a function of temperature and pressure by a novel optical reflectometry technique. A significant dependence on precursor pressure and growth temperature for the synthesis of silicon and germanium nanowires is observed, depending on the stability of the specific precursor used. Also, the presence of a nucleation time for the onset of nanowire growth has been found using our new in situ optical reflectometry technique.

  10. Superconductive silicon nanowires using gallium beam lithography.

    SciTech Connect

    Henry, Michael David; Jarecki, Robert Leo,

    2014-01-01

    This work was an early career LDRD investigating the idea of using a focused ion beam (FIB) to implant Ga into silicon to create embedded nanowires and/or fully suspended nanowires. The embedded Ga nanowires demonstrated electrical resistivity of 5 m-cm, conductivity down to 4 K, and acts as an Ohmic silicon contact. The suspended nanowires achieved dimensions down to 20 nm x 30 nm x 10 m with large sensitivity to pressure. These structures then performed well as Pirani gauges. Sputtered niobium was also developed in this research for use as a superconductive coating on the nanowire. Oxidation characteristics of Nb were detailed and a technique to place the Nb under tensile stress resulted in the Nb resisting bulk atmospheric oxidation for up to years.

  11. Oxide-assisted growth of silicon nanowires by carbothermal evaporation

    NASA Astrophysics Data System (ADS)

    Hutagalung, Sabar D.; Yaacob, Khatijah A.; Aziz, Azma F. Abdul

    2007-11-01

    Silicon nanowires (SiNWs) have successfully been synthesized by carbothermal evaporation method. By ramping-up the furnace system at 20 °C min -1 to 1100 °C for 6 h, the vertically aligned coexist with crooked SiNWs were achieved on the silicon substrate located at 12 cm from source material. The processing parameters such as temperature, heating rate, duration, substrate position and location are very important to produce SiNWs. Morphology and chemical composition of deposited products were investigated by field-emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray analysis (EDX). The existence of small sphere silicon oxide capped nanowires suggested that the formation of SiNWs was governed by oxide-assisted growth (OAG) mechanism.

  12. Fabrication and characterization of copper oxide-silicon nanowire heterojunction photodiodes

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    In this study, copper oxide (CuO) thin film/silicon (Si) nanowire heterojunctions have been fabricated and their optoelectronic performances have been investigated. Vertically aligned n-type Si nanowires have been fabricated using metal-assisted etching (MAE) technique. CuO thin films were synthesized by the sol-gel method and deposited onto the nanowires through spin-coating. Fabricated nanowire heterojunction devices exhibited excellent diode behaviour compared to the planar heterojunction control device. The rectification ratios were found to be 105 and 101 for nanowire and planar heterojunctions, respectively. The improved electrical properties and photosensitivity of the nanowire heterojunction diode was observed, which was related to the three-dimensional nature of the interface between the Si nanowires and the CuO film. Results obtained in this work reveal the potential of Si nanowire-based heterojunctions for various optoelectronic devices.

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

    SciTech Connect

    Venkatesh, P. Sundara; Jeganathan, K.

    2013-04-15

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

  14. 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. PMID:26672801

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

    DOEpatents

    Wang, George T; Li, Qiming

    2014-11-25

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

  16. Anomalous piezoresistance effect in ultrastrained silicon nanowires.

    PubMed

    Lugstein, A; Steinmair, M; Steiger, A; Kosina, H; Bertagnolli, E

    2010-08-11

    In this paper we demonstrate that under ultrahigh strain conditions p-type single crystal silicon nanowires possess an anomalous piezoresistance effect. The measurements were performed on vapor-liquid-solid (VLS) grown Si nanowires, monolithically integrated in a microelectro-mechanical loading module. The special setup enables the application of pure uniaxial tensile strain along the <111> growth direction of individual, 100 nm thick Si nanowires while simultaneously measuring the resistance of the nanowires. For low strain levels (nanowire elongation less than 0.8%), our measurements revealed the expected positive piezoresistance effect, whereas for ultrahigh strain levels a transition to anomalous negative piezoresistance was observed. For the maximum tensile strain of 3.5%, the resistance of the Si nanowires decreased by a factor of 10. Even at these high strain amplitudes, no fatigue failures are observed for several hundred loading cycles. The ability to fabricate single-crystal nanowires that are widely free of structural defects will it make possible to apply high strain without fracturing to other materials as well, therefore in any application where crystallinity and strain are important, the idea of making nanowires should be of a high value. PMID:20698638

  17. Silicon nanowires: Growth, transport and device physics

    NASA Astrophysics Data System (ADS)

    Garnett, Erik Christian

    2009-11-01

    Silicon is the second most abundant element in the earth's crust and has been the backbone of the information technology revolution. It is the most well-studied material in all of solid-state chemistry and physics and has been used to make a variety of devices including transistors, resonators, and solar cells. Nanowires could provide advantages over bulk silicon; however, there are many fundamental challenges that must be overcome in order to use them in high-performance, reproducible devices. The first chapter of this dissertation gives an introduction to nanoscience with an emphasis on the working principles of the nanowire devices that are discussed later and the problems that face nanowire implementation. Chapter two demonstrates that platinum nanoparticles can be substituted for gold as the nanowire growth catalyst without sacrificing crystalline quality, epitaxial growth or electrical properties. Replacing gold with a clean-room compatible material such as platinum is important to allow for nanowire integration into microfabricated devices. Chapter three focuses on making horizontal surround-gate field effect transistors for capacitance-voltage measurements. These devices are used to extract the dopant profile and density of interface states from individual nanowires, showing results consistent with planar control samples and simulations. The results are encouraging because they suggest low surface recombination velocities (similar to bulk planar wafers) should be possible as long as the nanowire surface is smooth and well-faceted. Chapter four demonstrates two low-cost, scalable methods for fabricating silicon nanowire photovoltaics. Because of the rough surface induced by the electroless etching process and the poor junction quality from the nanocrystalline chemical vapor deposition film, the efficiency of cells made with the first approach is relatively low at about 0.5%. The second approach, using an assembly of silica beads, deep reactive ion etching

  18. Networks of silicon nanowires: A large-scale atomistic electronic structure analysis

    NASA Astrophysics Data System (ADS)

    Keleş, Ümit; Liedke, Bartosz; Heinig, Karl-Heinz; Bulutay, Ceyhun

    2013-11-01

    Networks of silicon nanowires possess intriguing electronic properties surpassing the predictions based on quantum confinement of individual nanowires. Employing large-scale atomistic pseudopotential computations, as yet unexplored branched nanostructures are investigated in the subsystem level as well as in full assembly. The end product is a simple but versatile expression for the bandgap and band edge alignments of multiply-crossing Si nanowires for various diameters, number of crossings, and wire orientations. Further progress along this line can potentially topple the bottom-up approach for Si nanowire networks to a top-down design by starting with functionality and leading to an enabling structure.

  19. Networks of silicon nanowires: A large-scale atomistic electronic structure analysis

    SciTech Connect

    Keleş, Ümit; Bulutay, Ceyhun; Liedke, Bartosz; Heinig, Karl-Heinz

    2013-11-11

    Networks of silicon nanowires possess intriguing electronic properties surpassing the predictions based on quantum confinement of individual nanowires. Employing large-scale atomistic pseudopotential computations, as yet unexplored branched nanostructures are investigated in the subsystem level as well as in full assembly. The end product is a simple but versatile expression for the bandgap and band edge alignments of multiply-crossing Si nanowires for various diameters, number of crossings, and wire orientations. Further progress along this line can potentially topple the bottom-up approach for Si nanowire networks to a top-down design by starting with functionality and leading to an enabling structure.

  20. Multispectral imaging with vertical silicon nanowires

    PubMed Central

    Park, Hyunsung; Crozier, Kenneth B.

    2013-01-01

    Multispectral imaging is a powerful tool that extends the capabilities of the human eye. However, multispectral imaging systems generally are expensive and bulky, and multiple exposures are needed. Here, we report the demonstration of a compact multispectral imaging system that uses vertical silicon nanowires to realize a filter array. Multiple filter functions covering visible to near-infrared (NIR) wavelengths are simultaneously defined in a single lithography step using a single material (silicon). Nanowires are then etched and embedded into polydimethylsiloxane (PDMS), thereby realizing a device with eight filter functions. By attaching it to a monochrome silicon image sensor, we successfully realize an all-silicon multispectral imaging system. We demonstrate visible and NIR imaging. We show that the latter is highly sensitive to vegetation and furthermore enables imaging through objects opaque to the eye. PMID:23955156

  1. Synthesis and characterization of silicon and germanium nanowires, silica nanotubes, and germanium telluride/tellurium nanostructures

    NASA Astrophysics Data System (ADS)

    Tuan, Hsing-Yu

    A supercritical fluid-liquid solid (SFLS) nanowire growth process using alkanethiol-coated Au nanoparticles to seed silicon nanowires was developed for synthesizing silicon nanowires in solution. The organic solvent was found to significantly influence the silicon precursor decomposition in solution. 46.8 mg of silicon nanowires with 63% yield of silicon nanowire synthesis were achieved while using benzene as a solvent. The most widely used metal for seeding Si and Ge nanowires is Au. However, Au forms deep trap in both Si and Ge and alternative metal seeds are more desirable for electronic applications. Different metal nanocrystals were studied for Si and Ge nanowire synthesis, including Co, Ni, CuS, Mn, Ir, MnPt 3, Fe2O3, and FePt. All eight metals have eutectic temperatures with Si and Ge that are well above the nanowire growth temperature. Unlike Au nanocrystals, which seed nanowire growth through the formation of a liquid Au:Si (Au:Ge) alloy, these other metals seed nanowires by forming solid silicide alloys, a process we have called "supercritical fluid-solid-solid" (SFSS) growth. Moreover, Co and Ni nanoparticles were found to catalyze the decomposition of various silane reactants that do not work well to make Si nanowires using Au seeds. In addition to seeding solid nanowires, CuS nanoparticles were found to seed silica nanotubes via a SFSS like mechanism. 5% of synthesized silica nanotubes were coiled. Heterostructured nanomaterials are interesting since they merge the properties of the individual materials and can be used in diverse applications. GeTe/Te heterostructures were synthesized by reacting diphenylgermane (DPG) and TOP-Te in the presence of organic surfactants. Aligned Te nanorods were grown on the surface facets of micrometer-size germanium telluride particles.

  2. Hydrogen passivation of silicon nanowire structures

    NASA Astrophysics Data System (ADS)

    Aouida, S.; Benabderrahmane Zaghouani, R.; Bachtouli, N.; Bessais, B.

    2016-05-01

    In this work, we focus on hydrogen passivation of silicon nanowire structures (SiNWs) obtained by metal assisted chemical etching (MACE) intended to be used in silicon-based solar cells. SiNWs present high surface defects density causing the minority carrier lifetime reduction. Our results show that hydrogen passivation of SiNWs ameliorates minority carrier lifetime by reducing the dangling bonds and then the surface recombination velocity. This enhancement is limited by SiNWs distribution.

  3. Silicon nanowires for photovoltaic solar energy conversion.

    PubMed

    Peng, Kui-Qing; Lee, Shuit-Tong

    2011-01-11

    Semiconductor nanowires are attracting intense interest as a promising material for solar energy conversion for the new-generation photovoltaic (PV) technology. In particular, silicon nanowires (SiNWs) are under active investigation for PV applications because they offer novel approaches for solar-to-electric energy conversion leading to high-efficiency devices via simple manufacturing. This article reviews the recent developments in the utilization of SiNWs for PV applications, the relationship between SiNW-based PV device structure and performance, and the challenges to obtaining high-performance cost-effective solar cells. PMID:20931630

  4. Self-aligned silicon quantum wires on Ag(1 1 0)

    NASA Astrophysics Data System (ADS)

    Leandri, C.; Lay, G. Le; Aufray, B.; Girardeaux, C.; Avila, J.; Dávila, M. E.; Asensio, M. C.; Ottaviani, C.; Cricenti, A.

    2005-01-01

    Upon deposition of silicon onto the (1 1 0) surface of a silver crystal we have grown massively parallel one-dimensional Si nanowires. They are imaged in scanning tunnelling microscopy as straight, high aspect ratio, nanostructures, all with the same characteristic width of 16 Å, perfectly aligned along the atomic troughs of the bare surface. Low energy electron diffraction confirms the massively parallel assembly of these self-organized nanowires. Photoemission reveals striking quantized states dispersing only along the length of the nanowires, and extremely sharp, two-components, Si 2p core levels. This demonstrates that in the large ensemble each individual nanowire is a well-defined quantum object comprising only two distinct silicon atomic environments. We suggest that this self-assembled array of highly perfect Si nanowires provides a simple, atomically precise, novel template that may impact a wide range of applications.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  7. 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

  8. Fabrication and properties of silicon carbide nanowires

    NASA Astrophysics Data System (ADS)

    Shim, Hyun Woo

    2008-12-01

    Silicon carbide (SiC), with excellent electrical, thermal, and mechanical properties, is a promising material candidate for future devices such as high-temperature electronics and super-strong lightweight structures. Combined with superior intrinsic properties, the nanomaterials of SiC show further advantages thanks to nanoscale effects. This thesis reports the growth mechanism, the self-integration, and the friction of SiC nanowires. The study involves nanowires fabrication using thermal evaporation, structure characterization using electron microscopy, friction measurement, and theoretical modeling. The study on nanowire growth mechanism requires understanding of the surfaces and interfaces of nanowire crystal. The catalyzed growth of SiC nanowires involves interfaces between source vapor, catalytic liquid, and nanowire solid. Our experimental observation includes the periodical twinning in a faceted SiC nanowire and three stage structure transitions during the growth. The proposed theoretical model shows that such phenomenon is the result of surface energy minimization process during the catalytic growth. Surface interactions also exist between nanowires, leading to their self-integration. Our parametric growth study reveals novel self-integration of SiC-SiO 2 core-shell nanowires as a result of SiO2 joining. Attraction between nanowires through van der Waals force and enhanced SiO2 diffusion at high temperature transform individual nanowires to the integrated nanojunctions, nanocables, and finally nanowebs. We also show that such joining process becomes effective either during growth or by annealing. The solid friction is a result of the interaction between two solid surfaces, and it depends on the adhesion and the deformation of two contacting solids among other factors. Having strong adhesion as shown from gecko foot-hairs, nanostructured materials should also have strong friction; this study is the first to investigate friction of nanostructures under

  9. Novel synthetic methodology for controlling the orientation of zinc oxide nanowires grown on silicon oxide substrates.

    PubMed

    Cho, Jinhyun; Salleh, Najah; Blanco, Carlos; Yang, Sungwoo; Lee, Chul-Jin; Kim, Young-Woo; Kim, Jungsang; Liu, Jie

    2014-04-01

    This study presents a simple method to reproducibly obtain well-aligned vertical ZnO nanowire arrays on silicon oxide (SiOx) substrates using seed crystals made from a mixture of ammonium hydroxide (NH4OH) and zinc acetate (Zn(O2CCH3)2) solution. In comparison, high levels of OH(-) concentration obtained using NaOH or KOH solutions lead to incorporation of Na or K atoms into the seed crystals, destroying the c-axis alignment of the seeds and resulting in the growth of misaligned nanowires. The use of NH4OH eliminates the metallic impurities and ensures aligned nanowire growth in a wide range of OH(-) concentrations in the seed solution. The difference of crystalline orientations between NH4OH- and NaOH-based seeds is directly observed by lattice-resolved images and electron diffraction patterns using a transmission electron microscope (TEM). This study obviously suggests that metallic impurities incorporated into the ZnO nanocrystal seeds are one of the factors that generates the misaligned ZnO nanowires. This method also enables the use of silicon oxide substrates for the growth of vertically aligned nanowires, making ZnO nanostructures compatible with widely used silicon fabrication technology. PMID:24584438

  10. Silicon on insulator self-aligned transistors

    DOEpatents

    McCarthy, Anthony M.

    2003-11-18

    A method for fabricating thin-film single-crystal silicon-on-insulator (SOI) self-aligned transistors. Standard processing of silicon substrates is used to fabricate the transistors. Physical spaces, between the source and gate, and the drain and gate, introduced by etching the polysilicon gate material, are used to provide connecting implants (bridges) which allow the transistor to perform normally. After completion of the silicon substrate processing, the silicon wafer is bonded to an insulator (glass) substrate, and the silicon substrate is removed leaving the transistors on the insulator (glass) substrate. Transistors fabricated by this method may be utilized, for example, in flat panel displays, etc.

  11. Enhanced thermoelectric properties in silicon nanowires

    NASA Astrophysics Data System (ADS)

    Mitrovic, Slobodan; Yu, Jen-Kan; Boukai, Akram; Tahir-Kheli, Jamil; Goddard, William A., III; Heath, James R.

    2008-03-01

    Recently, we demonstrated that silicon nanowires can be designed and fabricated to achieve an approximately 100-fold enhancement in thermoelectric efficiency compared to bulk silicon. Independent measurements of thermoelectric power, and thermal and electrical conductivities suggest that this improvement is due to phonon effects rather than quantum confinement. Here, we present the study of the scaling laws (i.e. nanowire length/width dependence) for the phonon dynamics and transport. We investigate the influence of the phonon drag, carrier mobility and doping on the thermoelectric properties, and the universality of these findings. This work is supported by the Office of Naval Research, the Department of Energy, the National Science Foundation, and the Defense Advanced Research Projects Agency.

  12. High sensitivity silicon single nanowire junctionless phototransistor

    NASA Astrophysics Data System (ADS)

    Das, Samaresh; Dhyani, Veerendra; Georgiev, Yordan M.; Williams, David A.

    2016-02-01

    A high-gain photodetector based on junctionless MOSEFT has been presented in this work. Tri-gate junctionless nanowire phototransistors were fabricated on (100) silicon-on-insulator wafers with a buried oxide of thickness 145 nm and top silicon layer of thickness 10 nm. The gate stack consisted of a 10 nm SiO2 dielectric and a 50 nm poly-Si gate electrode. The channel length and doping concentration of junctionless n-MOSFETs was 1 μm and 3 × 1019 cm-3, respectively. The dark current of this device measured at room temperature was less than 1 pA. The measured internal gain of the device was about 35 for 860 nm light illumination. The photocurrent was 300 times larger than the dark current for only 30 nW incident power on the nanowire at 300 mV drain bias.

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

    PubMed Central

    2012-01-01

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

  14. The influence of H2O2 concentration to the structure of silicon nanowire growth by metal-assisted chemical etching

    NASA Astrophysics Data System (ADS)

    Omar, Hafsa; Jani, Abdul Mutalib Md.; Rusop, Mohamad; Abdullah, Saifollah

    2016-07-01

    A simple and low cost method to produce well aligned silicon nanowires at large areas using Ag-assisted chemical etching at room temperature were presented. The structure of silicon nanowires growth by metal-assisted chemical etching was observed. Prior to the etching, the silicon nanowires were prepared by electroless metal deposited (EMD) in solution containing hydrofluoric acid and hydrogen peroxide in Teflon vessel. The silver particle was deposited on substrate by immersion in hydrofluoric acid and silver nitrate solution for sixty second. The silicon nanowires were growth in different hydrogen peroxide concentration which are 0.3M, 0.4M, 0.5M and 0.6M and 0.7M.The influence of hydrogen peroxide concentration to the formation of silicon nanowires was studied. The morphological properties of silicon nanowires were investigated using field emission scanning electron microscopy (FESEM) and Energy Dispersive X-Ray Spectroscopy (EDS).

  15. Reliable Fabrication of Metal Contacts on Silicon Nanowire Forests.

    PubMed

    Dimaggio, Elisabetta; Pennelli, Giovanni

    2016-07-13

    We present a technique for the fabrication of an electrical (and thermal) contact on the top ends of a large number of vertical silicon nanowires, which are fabricated perpendicularly to a silicon wafer (silicon nanowire forest). The technique is based on electrochemical deposition of copper and has been developed on silicon nanowire forests, fabricated by metal assisted chemical etching. We demonstrate that copper grows selectively only on the top end of the silicon nanowires, forming a layer onto the top of the forest. The presence of a predeposited metal seed is fundamental for the selective growth, meanwhile the process is very strong with respect to other parameters, such as concentration of the electrolytic solution and current density, used during the metal deposition. Typical I-V characteristics of top-to-bottom conduction through silicon nanowire forests with different n-doping are shown and discussed. PMID:27351210

  16. Synthesis of silicon and germanium nanowires and silicon/germanium nanowire heterostructures

    NASA Astrophysics Data System (ADS)

    Clement, Teresa J.

    2007-12-01

    The vapor-liquid-solid growth process for synthesis of group-IV semiconducting nanowires using silane, germane, disilane and digermane precursor gases has been investigated. The nanowire growth process combines in situ gold seed formation by vapor deposition on atomically clean silicon (111) surfaces, in situ growth from the gaseous precursor(s), and real-time monitoring of nanowire growth as a function of temperature and pressure by a novel optical reflectometry technique. A significant dependence on precursor pressure and growth temperature for the synthesis of silicon and germanium nanowires is observed, depending on the stability of the specific precursor used. Also, the presence of a nucleation time for the onset of nanowire growth has been found using our new in situ optical reflectometry technique. Thermal annealing of the deposited gold seeds prior to nanowire growth is shown to lead to ripening of the gold seeds and the formation of pillars several nanometers in height under the seeds. These pillars are demonstrated to result from the catalytic collection of surface Si adatoms and provide a method to obtain 100% vertical growth of nanowires on Si (111) substrates. The growth of nanowire heterostructures has also been investigated with specific attention paid to the strain induced within these structures. Strain in axial and core-shell Si/Ge nanowire heterostructures provides a unique opportunity for modifying bandstructures of specific nanoscale heterostructures. Specific precursor selection adds an additional control by which we are able to grow specific heterostructures---axial or core-shell. Axial heterowires form more easily by catalyzing silane at the Au eutectic seed, while core-shell heterowires grow more easily by stabilizing lateral growth using disilane or digermane. Strain mapping of nanowires based on geometric phase analysis of high-resolution transmission electron microscopy lattice imaging reveals large strains present in core-shell Si

  17. Selective plating for junction delineation in silicon nanowires.

    PubMed

    Eichfeld, Chad M; Wood, Carolyn; Liu, Bangzhi; Eichfeld, Sarah M; Redwing, Joan M; Mohney, Suzanne E

    2007-09-01

    The in situ growth of p-n junctions in silicon nanowires enables the fabrication of a variety of nanoscale electronic devices. We have developed a method for selective coating of Au onto n-type segments of silicon nanowire p-n junctions. Selective plating allows for quick verification of the position of p-n junctions along the nanowire using electron microscopy and allows for measurement of segment length. PMID:17696558

  18. Growth of epitaxial silicon nanowires on a Si substrate by a metal-catalyst-free process

    NASA Astrophysics Data System (ADS)

    Ishiyama, Takeshi; Nakagawa, Shuhei; Wakamatsu, Toshiki

    2016-07-01

    The growth of epitaxial Si nanowires by a metal-catalyst-free process has been investigated as an alternative to the more common metal-catalyzed vapor–liquid–solid process. The well-aligned Si nanowires are successfully grown on a (111)-oriented Si substrate without any metal catalysts by a thermal treatment using silicon sulfide as a Si source at approximately 1200 °C. The needle-shaped Si nanowires, which have a core–shell structure that consists of a single-crystalline Si core along the <111> direction consistent with the substrate direction and a surface coating of silicon oxide, are grown by a metal-catalyst-free process. In this process, the silicon sulfide in the liquid phase facilitates the nucleation and nanowire growth. In contrast, oxygen-rich nanowires that consist of crystalline Si at the tip and lumpy silicon oxide on the body are observed in a sample grown at 1300 °C, which disturbs the epitaxial growth of Si nanowires.

  19. Growth of epitaxial silicon nanowires on a Si substrate by a metal-catalyst-free process.

    PubMed

    Ishiyama, Takeshi; Nakagawa, Shuhei; Wakamatsu, Toshiki

    2016-01-01

    The growth of epitaxial Si nanowires by a metal-catalyst-free process has been investigated as an alternative to the more common metal-catalyzed vapor-liquid-solid process. The well-aligned Si nanowires are successfully grown on a (111)-oriented Si substrate without any metal catalysts by a thermal treatment using silicon sulfide as a Si source at approximately 1200 °C. The needle-shaped Si nanowires, which have a core-shell structure that consists of a single-crystalline Si core along the <111> direction consistent with the substrate direction and a surface coating of silicon oxide, are grown by a metal-catalyst-free process. In this process, the silicon sulfide in the liquid phase facilitates the nucleation and nanowire growth. In contrast, oxygen-rich nanowires that consist of crystalline Si at the tip and lumpy silicon oxide on the body are observed in a sample grown at 1300 °C, which disturbs the epitaxial growth of Si nanowires. PMID:27465800

  20. Growth of epitaxial silicon nanowires on a Si substrate by a metal-catalyst-free process

    PubMed Central

    Ishiyama, Takeshi; Nakagawa, Shuhei; Wakamatsu, Toshiki

    2016-01-01

    The growth of epitaxial Si nanowires by a metal-catalyst-free process has been investigated as an alternative to the more common metal-catalyzed vapor–liquid–solid process. The well-aligned Si nanowires are successfully grown on a (111)-oriented Si substrate without any metal catalysts by a thermal treatment using silicon sulfide as a Si source at approximately 1200 °C. The needle-shaped Si nanowires, which have a core–shell structure that consists of a single-crystalline Si core along the <111> direction consistent with the substrate direction and a surface coating of silicon oxide, are grown by a metal-catalyst-free process. In this process, the silicon sulfide in the liquid phase facilitates the nucleation and nanowire growth. In contrast, oxygen-rich nanowires that consist of crystalline Si at the tip and lumpy silicon oxide on the body are observed in a sample grown at 1300 °C, which disturbs the epitaxial growth of Si nanowires. PMID:27465800

  1. Strain in silicon nanowire beams

    NASA Astrophysics Data System (ADS)

    Ureña, Ferran; Olsen, Sarah H.; Šiller, Lidija; Bhaskar, Umesh; Pardoen, Thomas; Raskin, Jean-Pierre

    2012-12-01

    In this work, strain in silicon free standing beams loaded in uniaxial tension is experimentally and theoretically investigated for strain values ranging from 0 to 3.6%. The fabrication method allows multiple geometries (and thus strain values) to be processed simultaneously on the same wafer while being studied independently. An excellent agreement of strain determined by two non-destructive characterization techniques, Raman spectroscopy and mechanical displacement using scanning electron microscopy (SEM) markers, is found for all the sample lengths and widths. The measured data also show good agreement with theoretical predictions of strain based upon continuum mechanical considerations, giving validity to both measurement techniques for the entire range of strain values. The dependence of Young's modulus and fracture strain on size has also been analyzed. The Young's modulus is determined using SEM and compared with that obtained by resonance-based methods. Both methods produced a Young's modulus value close to that of bulk silicon with values obtained by resonance-based methods being slightly lower. Fracture strain is analyzed in 40 sets of samples with different beam geometries, yielding values up to 3.6%. The increase in fracture strain with decreasing beam width is compared with previous reports. Finally, the role of the surface on the mechanical properties is analyzed using UV and visible lasers having different penetration depths in silicon. The observed dependence of Raman shift on laser wavelength is used to assess the thermal conductivity of deformed silicon.

  2. Electrically controlled giant piezoresistance in silicon nanowires.

    PubMed

    Neuzil, Pavel; Wong, Chee Chung; Reboud, Julien

    2010-04-14

    Herein we demonstrate giant piezoresistance in silicon nanowires (NWs) by the modulation of an electric field-induced with an external electrical bias. Positive bias for a p-type device (negative for an n-type) partially depleted the NWs forming a pinch-off region, which resembled a funnel through which the electrical current squeezed. This region determined the total current flowing through the NWs. In this report, we combined the electrical biasing with the application of mechanical stress, which impacts the charge carriers' concentration, to achieve an electrically controlled giant piezoresistance in nanowires. This phenomenon was used to create a stress-gated field-effect transistor, exhibiting a maximum gauge factor of 5000, 2 orders of magnitude increase over bulk value. Giant piezoresistance can be tailored to create highly sensitive mechanical sensors operating in a discrete mode such as nanoelectromechanical switches. PMID:20192246

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

    DOEpatents

    Han, Jung; Su, Jie

    2008-08-05

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

  4. Magnetic resonance characterization of silicon nanowires

    NASA Astrophysics Data System (ADS)

    Fanciulli, Marco; Belli, Matteo; Vellei, Antonio; Canevali, Carmen; Rotta, Davide; Paleari, Stefano; Basini, Martina

    2012-02-01

    Silicon nanowires (SiNWs) have been extensively investigated in the last decades. The interest in these nanostructures stems from both fundamental and applied research motivations. The functional properties of one- and zero-dimensional silicon structures are significantly different, at least below a certain critical dimension, from those well known in the bulk. The key and peculiar functional properties of SiNWs find applications in nanoelectronics, classical and quantum information processing and storage, optoelectronics, photovoltaics, thermoelectric, battery technology, nano-biotechnology, and neuroelectronics. We report our work on the characterization by continuous wave (CW) and pulse electron spin resonance (CW, FT-EPR) and electrically detected magnetic resonance (EDMR) measurements of silicon nanowires (SiNWs) produced by different top-down processes. SiNWs were fabricated starting from SOI wafers using standard e-beam lithography and anisotropic wet etching or by metal-assisted chemical etching. Further oxidation was used to reduce the wire cross section. Different EDMR implementations were used to address the electronic wave function of donors (P, As) and to characterize point defects at the SiNWs/SiO2 interface.

  5. Atomic scale investigation of silicon nanowires and nanoclusters

    PubMed Central

    2011-01-01

    In this study, we have performed nanoscale characterization of Si-clusters and Si-nanowires with a laser-assisted tomographic atom probe. Intrinsic and p-type silicon nanowires (SiNWs) are elaborated by chemical vapor deposition method using gold as catalyst, silane as silicon precursor, and diborane as dopant reactant. The concentration and distribution of impurity (gold) and dopant (boron) in SiNW are investigated and discussed. Silicon nanoclusters are produced by thermal annealing of silicon-rich silicon oxide and silica multilayers. In this process, atom probe tomography (APT) provides accurate information on the silicon nanoparticles and the chemistry of the nanolayers. PMID:21711788

  6. Electrical anisotropy in coatings of aligned silver nanowires

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  7. Highly aligned vertical GaN nanowires using submonolayer metal catalysts

    DOEpatents

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

    2010-06-29

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

  8. Studies of Epitaxial Silicon Nanowire Growth at Low Temperature

    NASA Astrophysics Data System (ADS)

    Joun, Hee-Joung

    Silicon nanowires were grown epitaxially on Si (100) and (111) surfaces using the Vapor-Liquid-Solid (VLS) mechanism under both thermal and plasma enhanced growth conditions. Nanowire morphology was investigated as a function of temperature, time, disilane partial pressure and substrate preparation. Silicon nanowires synthesized in low temperature plasma typically curved compared to the linear nanowires grown under simple thermal conditions. The nanowires tended bend more with increasing disilane partial gas pressure up to 25 x10 -3 mTorr. The nanowire curvature measured geometrically is correlated with the shift of the main silicon peak obtained in Raman spectroscopy. A mechanistic hypothesis was proposed to explain the bending during plasma activated growth. Additional driving forces related to electrostatic and Van der Waals forces were also discussed. Deduced from a systematic variation of a three-step experimental protocol, the mechanism for bending was associated with asymmetric deposition rate along the outer and inner wall of nanowire. The conditions leading to nanowire branching were also examined using a two-step growth process. Branching morphologies were examined as a function of plasma powers between 1.5 W and 3.5 W. Post-annealing thermal and plasma-assisted treatments in hydrogen were compared to understand the influences in the absence of an external silicon source (otherwise supplied by disilane). Longer and thicker nanowires were associated with longer annealing times due to an Ostwald-like ripening effect. The roles of surface diffusion, gas diffusion, etching and deposition rates were examined.

  9. Facile Pyrolytic Synthesis of Silicon Nanowires

    PubMed Central

    Chan, Joo C.; Tran, Hoang; Pattison, James W.; Rananavare, Shankar B.

    2010-01-01

    One-dimensional nanostructures such as silicon nanowires (SiNW) are attractive candidates for low power density electronic and optoelectronic devices including sensors. A new simple method for SiNW bulk synthesis[1, 2] is demonstrated in this work, which is inexpensive and uses low toxicity materials, thereby offering a safe, energy efficient and green approach. The method uses low flammability liquid phenylsilanes, offering a safer avenue for SiNW growth compared with using silane gas. A novel, duo-chamber glass vessel is used to create a low-pressure environment where SiNWs are grown through vapor-liquid-solid mechanism using gold nanoparticles as a catalyst. The catalyst decomposes silicon precursor vapors of diphenylsilane and triphenylsilane and precipitates single crystal SiNWs, which appear to grow parallel to the substrate surface. This opens up possibilities for synthesizing nano-junctions amongst wires which is important for the grid architecture of nanoelectronics proposed by Likharev[3]. Even bulk synthesis of SiNW is feasible using sacrificial substrates such as CaCO3 that can be dissolved post-synthesis. Furthermore, by dissolving appropriate dopants in liquid diphenylsilane, a controlled doping of the nanowires is realized without the use of toxic gases and expensive mass flow controllers. Upon boron doping, we observe a characteristic red shift in photoluminescence spectra. In summary, an inexpensive and versatile method for SiNW is presented that makes these exotic materials available to any lab at low cost. PMID:20711489

  10. Facile Pyrolytic Synthesis of Silicon Nanowires.

    PubMed

    Chan, Joo C; Tran, Hoang; Pattison, James W; Rananavare, Shankar B

    2010-10-01

    One-dimensional nanostructures such as silicon nanowires (SiNW) are attractive candidates for low power density electronic and optoelectronic devices including sensors. A new simple method for SiNW bulk synthesis[1, 2] is demonstrated in this work, which is inexpensive and uses low toxicity materials, thereby offering a safe, energy efficient and green approach. The method uses low flammability liquid phenylsilanes, offering a safer avenue for SiNW growth compared with using silane gas. A novel, duo-chamber glass vessel is used to create a low-pressure environment where SiNWs are grown through vapor-liquid-solid mechanism using gold nanoparticles as a catalyst. The catalyst decomposes silicon precursor vapors of diphenylsilane and triphenylsilane and precipitates single crystal SiNWs, which appear to grow parallel to the substrate surface. This opens up possibilities for synthesizing nano-junctions amongst wires which is important for the grid architecture of nanoelectronics proposed by Likharev[3]. Even bulk synthesis of SiNW is feasible using sacrificial substrates such as CaCO(3) that can be dissolved post-synthesis. Furthermore, by dissolving appropriate dopants in liquid diphenylsilane, a controlled doping of the nanowires is realized without the use of toxic gases and expensive mass flow controllers. Upon boron doping, we observe a characteristic red shift in photoluminescence spectra. In summary, an inexpensive and versatile method for SiNW is presented that makes these exotic materials available to any lab at low cost. PMID:20711489

  11. Synthesis, characterizations, and applications of carbon nanotubes and silicon nanowires

    NASA Astrophysics Data System (ADS)

    Xiong, Guangyong

    Carbon nanotubes (CNTs) have received great attention because of their unique structure and promising applications in microelectronic devices such as field electron emitters. Silicon nanowires (SiNWs) are also very popular because Si is a well established electronic material. This thesis will present my effort on synthesis, characterizations, and applications of CNTs and SiNWs by thermal chemical vapor deposition (CVD) method. For CNTs growth, block copolymer micelles were used as a template to create large area arrays of metal nanoclusters as catalysts for patterned arrays, and Fe/Al/Fe sandwich film on single crystal magnesium oxide (MgO) substrate was used as the catalyst for growth of long length aligned CNTs by CVD. The factors that affect the structure and length of CNTs have been investigated. CNTs were also grown on etched Si substrate by PECVD method. Continuous dropwise condensation was achieved on a biomimetic two-tier texture with short CNTs deposited on micromachined pillars. Superhydrophobic condensation model was studied. For SiNWs growth, hydrogen gold tetrachloride was uniformly mixed into the salt and decomposed into gold nanoparticles at the growth temperature and acted as the catalyst particles to start the growth of Si nanowires. The as-grown Si nanowires are about 70--90 nm in diameter and up to 200 micrometers long. The salt was completely removed by water rinse after growth. Field emission of aligned CNTs grown on Si substrates and SiNWs on Si substrates and carbon clothes has been studied. A post growth annealing procedure has been found to drastically improve the field emission performance of these CNTs and SiNWs.

  12. Controllable deformation of silicon nanowires with strain up to 24%

    SciTech Connect

    Walavalkar, Sameer S.; Homyk, Andrew P.; Henry, M. David; Scherer, Axel

    2010-06-15

    Fabricated silicon nanostructures demonstrate mechanical properties unlike their macroscopic counterparts. Here we use a force mediating polymer to controllably and reversibly deform silicon nanowires. This technique is demonstrated on multiple nanowire configurations, which undergo deformation without noticeable macroscopic damage after the polymer is removed. Calculations estimate a maximum of nearly 24% strain induced in 30 nm diameter pillars. The use of an electron activated polymer allows retention of the strained configuration without any external input. As a further illustration of this technique, we demonstrate nanoscale tweezing by capturing 300 nm alumina beads using circular arrays of these silicon nanowires.

  13. Platinum nanoparticle decorated silicon nanowires for efficient solar energy conversion.

    PubMed

    Peng, Kui-Qing; Wang, Xin; Wu, Xiao-Ling; Lee, Shuit-Tong

    2009-11-01

    High-density aligned n-type silicon nanowire (SiNW) arrays decorated with discrete 5-10 nm platinum nanoparticles (PtNPs) have been fabricated by aqueous electroless Si etching followed by an electroless platinum deposition process. Coating of PtNPs on SiNW sidewalls yielded a substantial enhancement in photoconversion efficiency and an apparent energy conversion efficiency of up to 8.14% for the PtNP-decorated SiNW-based photoelectrochemical solar cell using a liquid electrolyte containing Br(-)/Br(2) redox couple. The results demonstrate PtNP-decorated SiNWs to be a promising hybrid system for solar energy conversion. PMID:19807069

  14. Aluminum-catalyzed silicon nanowires: Growth methods, properties, and applications

    NASA Astrophysics Data System (ADS)

    Hainey, Mel F.; Redwing, Joan M.

    2016-12-01

    Metal-mediated vapor-liquid-solid (VLS) growth is a promising approach for the fabrication of silicon nanowires, although residual metal incorporation into the nanowires during growth can adversely impact electronic properties particularly when metals such as gold and copper are utilized. Aluminum, which acts as a shallow acceptor in silicon, is therefore of significant interest for the growth of p-type silicon nanowires but has presented challenges due to its propensity for oxidation. This paper summarizes the key aspects of aluminum-catalyzed nanowire growth along with wire properties and device results. In the first section, aluminum-catalyzed nanowire growth is discussed with a specific emphasis on methods to mitigate aluminum oxide formation. Next, the influence of growth parameters such as growth temperature, precursor partial pressure, and hydrogen partial pressure on nanowire morphology is discussed, followed by a brief review of the growth of templated and patterned arrays of nanowires. Aluminum incorporation into the nanowires is then discussed in detail, including measurements of the aluminum concentration within wires using atom probe tomography and assessment of electrical properties by four point resistance measurements. Finally, the use of aluminum-catalyzed VLS growth for device fabrication is reviewed including results on single-wire radial p-n junction solar cells and planar solar cells fabricated with nanowire/nanopyramid texturing.

  15. Bubble-Regulated Silicon Nanowire Synthesis on Micro-Structured Surfaces by Metal-Assisted Chemical Etching.

    PubMed

    Li, Yinxiao; Duan, Chuanhua

    2015-11-10

    In this work, we study silicon nanowire synthesis via one-step metal-assisted chemical etching (MACE) on microstructured silicon surfaces with periodic pillar/cavity array. It is found that hydrogen gas produced from the initial anodic reaction can be trapped inside cavities and between pillars, which serves as a mask to prevent local etching, and leads to the formation of patterned vertically aligned nanowire array. A simple model is presented to demonstrate that such bubble entrapment is due to the significant adhesion energy barrier, which is a function of pillar/cavity geometry, contact angle, and nanowire length to be etched. The bubble entrapment can be efficiently removed when extra energy is introduced by sonication to overcome this energy barrier, resulting in nanowire growth in all exposed surfaces. This bubble-regulated MACE process on microstructured surfaces can be used to fabricate nanowire arrays with desired morphologies. PMID:26411775

  16. Phonon Trapping in Pearl-Necklace-Shaped Silicon Nanowires.

    PubMed

    Miao, Chunyang; Tai, Guoan; Zhou, Jianxin; Guo, Wanlin

    2015-12-22

    A pearl-necklace-shaped silicon nanowire, in contrast to a smooth nanowire, presents a much lower thermal conductivity due to the phonon trapping effect. By precisely controlling the pearl size and density, this reduction can be more than 70% for the structures designed in the study, which provides a unique approach for designing high-performance nanoscale thermoelectric devices. PMID:26577864

  17. Reversible Modulation of Spontaneous Emission by Strain in Silicon Nanowires

    PubMed Central

    Shiri, Daryoush; Verma, Amit; Selvakumar, C. R.; Anantram, M. P.

    2012-01-01

    We computationally study the effect of uniaxial strain in modulating the spontaneous emission of photons in silicon nanowires. Our main finding is that a one to two orders of magnitude change in spontaneous emission time occurs due to two distinct mechanisms: (A) Change in wave function symmetry, where within the direct bandgap regime, strain changes the symmetry of wave functions, which in turn leads to a large change of optical dipole matrix element. (B) Direct to indirect bandgap transition which makes the spontaneous photon emission to be of a slow second order process mediated by phonons. This feature uniquely occurs in silicon nanowires while in bulk silicon there is no change of optical properties under any reasonable amount of strain. These results promise new applications of silicon nanowires as optoelectronic devices including a mechanism for lasing. Our results are verifiable using existing experimental techniques of applying strain to nanowires. PMID:22708056

  18. Silicon nanowire synthesis by a vapor-liquid-solid approach

    NASA Technical Reports Server (NTRS)

    Mao, Aaron; Ng, H. T.; Nguyen, Pho; McNeil, Melanie; Meyyappan, M.

    2005-01-01

    Synthesis of silicon nanowires is studied by using a vapor-liquid-solid growth technique. Silicon tetrachloride reduction with hydrogen in the gas phase is used with gold serving as catalyst to facilitate growth. Only a narrow set of conditions of SiCl4 concentration and temperature yield straight nanowires. High concentrations and temperatures generally result in particulates, catalyst coverage and deactivation, and coatinglike materials.

  19. Photoresponsive properties of ultrathin silicon nanowires

    SciTech Connect

    Tran, Duy P.; Macdonald, Thomas J.; Nann, Thomas; Thierry, Benjamin E-mail: benjamin.thierry@unisa.edu.au; Wolfrum, Bernhard; Stockmann, Regina; Offenhäusser, Andreas E-mail: benjamin.thierry@unisa.edu.au

    2014-12-08

    Functional silicon nanowires (SiNWs) are promising building blocks in the design of highly sensitive photodetectors and bio-chemical sensors. We systematically investigate the photoresponse properties of ultrathin SiNWs (20 nm) fabricated using a size-reduction method based on e-beam lithography and tetramethylammonium hydroxide wet-etching. The high-quality SiNWs were able to detect light from the UV to the visible range with excellent sensitivity (∼1 pW/array), good time response, and high photoresponsivity (R ∼ 2.5 × 10{sup 4 }A/W). Improvement of the ultrathin SiNWs' photoresponse has been observed in comparison to 40 nm counter-part nanowires. These properties are attributable to the predominance surface-effect due to the high surface-to-volume ratio of ultrathin SiNWs. Long-term measurements at different temperatures in both the forward and reverse bias directions demonstrated the stability and reliability of the fabricated device. By sensitizing the fabricated SiNW arrays with cadmium telluride quantum dots (QDs), hybrid QD SiNW devices displayed an improvement in photocurrent response under UV light, while preserving their performance in the visible light range. The fast, stable, and high photoresponse of these hybrid nanostructures is promising towards the development of optoelectronic and photovoltaic devices.

  20. Photoresponsive properties of ultrathin silicon nanowires

    NASA Astrophysics Data System (ADS)

    Tran, Duy P.; Macdonald, Thomas J.; Wolfrum, Bernhard; Stockmann, Regina; Nann, Thomas; Offenhäusser, Andreas; Thierry, Benjamin

    2014-12-01

    Functional silicon nanowires (SiNWs) are promising building blocks in the design of highly sensitive photodetectors and bio-chemical sensors. We systematically investigate the photoresponse properties of ultrathin SiNWs (20 nm) fabricated using a size-reduction method based on e-beam lithography and tetramethylammonium hydroxide wet-etching. The high-quality SiNWs were able to detect light from the UV to the visible range with excellent sensitivity (˜1 pW/array), good time response, and high photoresponsivity (R ˜ 2.5 × 104 A/W). Improvement of the ultrathin SiNWs' photoresponse has been observed in comparison to 40 nm counter-part nanowires. These properties are attributable to the predominance surface-effect due to the high surface-to-volume ratio of ultrathin SiNWs. Long-term measurements at different temperatures in both the forward and reverse bias directions demonstrated the stability and reliability of the fabricated device. By sensitizing the fabricated SiNW arrays with cadmium telluride quantum dots (QDs), hybrid QD SiNW devices displayed an improvement in photocurrent response under UV light, while preserving their performance in the visible light range. The fast, stable, and high photoresponse of these hybrid nanostructures is promising towards the development of optoelectronic and photovoltaic devices.

  1. Assembly and magnetic properties of nickel nanoparticles on silicon nanowires

    SciTech Connect

    Picraux, Samuel T; Manandhar, Pradeep; Nazaretski, E; Thompson, J

    2009-01-01

    The directed assembly of magnetic Ni nanoparticles at the tips of silicon nanowires is reported. Using electrodeposition Ni shells of thickness from 10 to 100 nm were selectively deposited on Au catalytic seeds at the ends of nanowires. Magnetic characterization confirms a low coercivity ({approx}115 Oe) ferromagnetic behavior at 300 K. This approach to multifunctional magnetic-semiconducting nanostructure assembly could be extended to electrodeposition of other materials on the nanowire ends, opening up novel ways of device integration. Such magnetically functionalized nanowires offer a new approach to developing novel highly localized magnetic probes for high resolution magnetic resonance force microscopy.

  2. Synthesis of silicon nitride nanowires by the pyrolysis of perhydropolysilazane.

    PubMed

    Qi, Gong-Jin; Zhang, Chang-Rui; Hu, Hai-Feng

    2006-05-01

    Silicon nitride nanowires synthesized by the pyrolysis of perhydropolysilazane without using any catalysts are reported. After pyrolysis at 1073 K in N2/NH3 atmosphere, the synthetic nanowires are discrete and curly with diameters about tens of nanometers and lengths of hundreds of nanometers. While after post-treatment at 1873 K in N2 atmosphere, the nanowires are continuous and randomly distributed with diameters about tens of nanometers and several microns in length. There are no bulbs or droplets on the tips of the nanowires, and two gas-solid mechanisms are proposed to explain their growth. PMID:16792386

  3. Bottom-up silicon nanowire-based thermoelectric microgenerators

    NASA Astrophysics Data System (ADS)

    Dávila, D.; Huber, R.; Hierold, C.

    2015-12-01

    In this work, bottom-up intrinsic crystalline Si nanowire arrays in combination with top-down microfabrication techniques and a vertical device architecture have been proposed to develop an all-silicon nanostructured thermoelectric generator. To fabricate this device, a suitable vertical integration of Si NWs on patterned microstructures, which define the thermoelectric legs of the generator, has been achieved by bonding top and bottom silicon structures through nanowires. The process has been proven to be a feasible approach that employs a regrowth process of the nanowires for bonding purposes.

  4. SiC nanowires synthesized from graphene and silicon vapors

    NASA Astrophysics Data System (ADS)

    Weichenpei, Luo; Gong-yi, Li; Zengyong, Chu; Tianjiao, Hu; Xiaodong, Li; Xuefei, Zhang

    2016-04-01

    The preparation of silicon carbide (SiC) nanowires is basically important for its potential applications in nanodevices, nanocomposites, etc. In the present work, a simple route was reported to synthesize SiC nanowires by heating commercial graphene with silicon vapors and no catalyst. Characterization by scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, electron energy scattering, X-ray diffraction, and Raman dispersive spectrum demonstrates the products are composed of β-SiC crystal. The SiC nanowires have the average diameter of about 50 nm and length of tens of micrometers. The vapor-solid mechanism was employed to interpret the SiC nanowires growth. Gaseous SiO which was produced by the reaction of Si powders with its surface oxidation reacted with the solid graphene to form SiC crystal nuclei. And SiC crystal nuclei would act as active sites for further growing into nanowires.

  5. Indirect measurement of thermal conductivity in silicon nanowires

    SciTech Connect

    Pennelli, Giovanni Nannini, Andrea; Macucci, Massimo

    2014-02-28

    We report indirect measurements of thermal conductivity in silicon nanostructures. We have exploited a measurement technique based on the Joule self-heating of silicon nanowires. A standard model for the electron mobility has been used to determine the temperature through the accurate measurement of the nanowire resistance. We have applied this technique to devices fabricated with a top-down process that yields nanowires together with large silicon areas used both as electrical and as thermal contacts. As there is crystalline continuity between the nanowires and the large contact areas, our thermal conductivity measurements are not affected by any temperature drop due to the contact thermal resistance. Our results confirm the observed reduction of thermal conductivity in nanostructures and are comparable with those previously reported in the literature, achieved with more complex measurement techniques.

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  7. High-performance silicon nanowire bipolar phototransistors

    NASA Astrophysics Data System (ADS)

    Tan, Siew Li; Zhao, Xingyan; Chen, Kaixiang; Crozier, Kenneth B.; Dan, Yaping

    2016-07-01

    Silicon nanowires (SiNWs) have emerged as sensitive absorbing materials for photodetection at wavelengths ranging from ultraviolet (UV) to the near infrared. Most of the reports on SiNW photodetectors are based on photoconductor, photodiode, or field-effect transistor device structures. These SiNW devices each have their own advantages and trade-offs in optical gain, response time, operating voltage, and dark current noise. Here, we report on the experimental realization of single SiNW bipolar phototransistors on silicon-on-insulator substrates. Our SiNW devices are based on bipolar transistor structures with an optically injected base region and are fabricated using CMOS-compatible processes. The experimentally measured optoelectronic characteristics of the SiNW phototransistors are in good agreement with simulation results. The SiNW phototransistors exhibit significantly enhanced response to UV and visible light, compared with typical Si p-i-n photodiodes. The near infrared responsivities of the SiNW phototransistors are comparable to those of Si avalanche photodiodes but are achieved at much lower operating voltages. Compared with other reported SiNW photodetectors as well as conventional bulk Si photodiodes and phototransistors, the SiNW phototransistors in this work demonstrate the combined advantages of high gain, high photoresponse, low dark current, and low operating voltage.

  8. Silicon Nanowire Growth at Chosen Positions and Orientations

    NASA Technical Reports Server (NTRS)

    Getty, Stephanie A.

    2009-01-01

    It is now possible to grow silicon nanowires at chosen positions and orientations by a method that involves a combination of standard microfabrication processes. Because their positions and orientations can be chosen with unprecedented precision, the nanowires can be utilized as integral parts of individually electronically addressable devices in dense arrays. Nanowires made from silicon and perhaps other semiconductors hold substantial promise for integration into highly miniaturized sensors, field-effect transistors, optoelectronic devices, and other electronic devices. Like bulk semiconductors, inorganic semiconducting nanowires are characterized by electronic energy bandgaps that render them suitable as means of modulating or controlling electronic signals through electrostatic gating, in response to incident light, or in response to molecules of interest close to their surfaces. There is now potential for fabricating arrays of uniform, individually electronically addressable nanowires tailored to specific applications. The method involves formation of metal catalytic particles at the desired positions on a substrate, followed by heating the substrate in the presence of silane gas. The figure illustrates an example in which a substrate includes a silicon dioxide surface layer that has been etched into an array of pillars and the catalytic (in this case, gold) particles have been placed on the right-facing sides of the pillars. The catalytic thermal decomposition of the silane to silicon and hydrogen causes silicon columns (the desired nanowires) to grow outward from the originally catalyzed spots on the substrate, carrying the catalytic particles at their tips. Thus, the position and orientation of each silicon nanowire is determined by the position of its originally catalyzed spot on the substrate surface, and the orientation of the nanowire is perpendicular to the substrate surface at the originally catalyzed spot.

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

    PubMed

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

    2013-12-01

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

  10. Plasmon-loss imaging of chains of crystalline-silicon nanospheres and silicon nanowires

    PubMed

    Kohno; Takeda; Tanaka

    2000-01-01

    Nanostructures in chains of crystalline-silicon nanospheres and silicon nanowires were investigated using energy-filtered transmission electron microscopy (TEM). Observation of the shape of the silicon nanospheres in the chains provided the direct evidence that the chains were formed via the surface oxidation process, which may preferentially work at the necks. The diverse nanostructures in silicon nanowires were revealed, and we found smooth-shaped wires which have periodically modulated silicon cores. Nanostructures in wire-chain transition regions were also investigated for the first time. The wire-chain transition is not a simple junction of a silicon nanowire and a chain of silicon nanospheres, but has a periodically modulated silicon core in the wire region near the transition position. PMID:11108050

  11. True reference nanosensor realized with silicon nanowires.

    PubMed

    Tarasov, A; Wipf, M; Bedner, K; Kurz, J; Fu, W; Guzenko, V A; Knopfmacher, O; Stoop, R L; Calame, M; Schönenberger, C

    2012-06-26

    Conventional gate oxide layers (e.g., SiO(2), Al(2)O(3), or HfO(2)) in silicon field-effect transistors (FETs) provide highly active surfaces, which can be exploited for electronic pH sensing. Recently, great progress has been achieved in pH sensing using compact integrateable nanowire FETs. However, it has turned out to be much harder to realize a true reference electrode, which--while sensing the electrostatic potential--does not respond to the proton concentration. In this work, we demonstrate a highly effective reference sensor, a so-called reference FET, whose proton sensitivity is suppressed by as much as 2 orders of magnitude. To do so, the Al(2)O(3) surface of a nanowire FET was passivated with a self-assembled monolayer of silanes with a long alkyl chain. We have found that a full passivation can be achieved only after an extended period of self-assembling lasting several days at 80 °C. We use this slow process to measure the number of active proton binding sites as a function of time by a quantitative comparison of the measured nonlinear pH-sensitivities to a theoretical model (site-binding model). Furthermore, we have found that a partially passivated surface can sense small changes in the number of active binding sites reaching a detection limit of δN(s) ≈ 170 μm(-2) Hz(-1/2) at 10 Hz and pH 3. PMID:22631046

  12. Silicon Nanowire Fabric as a Lithium Ion Battery Electrode Material

    SciTech Connect

    Chockla, Aaron M.; Harris, Justin T.; Akhavan, Vahid A.; Bogart, Timothy D.; Holmberg, Vincent C.; Steinhagen, Chet; Mullins, C. Buddie; Stevenson, Keith J.; Korgel, Brian A.

    2011-11-09

    A nonwoven fabric with paperlike qualities composed of silicon nanowires is reported. The nanowires, made by the supercritical-fluid–liquid–solid process, are crystalline, range in diameter from 10 to 50 nm with an average length of >100 μm, and are coated with a thin chemisorbed polyphenylsilane shell. About 90% of the nanowire fabric volume is void space. Thermal annealing of the nanowire fabric in a reducing environment converts the polyphenylsilane coating to a carbonaceous layer that significantly increases the electrical conductivity of the material. This makes the nanowire fabric useful as a self-supporting, mechanically flexible, high-energy-storage anode material in a lithium ion battery. Anode capacities of more than 800 mA h g{sup –1} were achieved without the addition of conductive carbon or binder.

  13. Large area, dense silicon nanowire array chemical sensors

    SciTech Connect

    Talin, A. Alec; Hunter, Luke L.; Leonard, Francois; Rokad, Bhavin

    2006-10-09

    The authors present a simple top-down approach based on nanoimprint lithography to create dense arrays of silicon nanowires over large areas. Metallic contacts to the nanowires and a bottom gate allow the operation of the array as a field-effect transistor with very large on/off ratios. When exposed to ammonia gas or cyclohexane solutions containing nitrobenzene or phenol, the threshold voltage of the field-effect transistor is shifted, a signature of charge transfer between the analytes and the nanowires. The threshold voltage shift is proportional to the Hammett parameter and the concentration of the nitrobenzene and phenol analytes.

  14. A deep etching mechanism for trench-bridging silicon nanowires.

    PubMed

    Tasdemir, Zuhal; Wollschläger, Nicole; Österle, Werner; Leblebici, Yusuf; Alaca, B Erdem

    2016-03-01

    Introducing a single silicon nanowire with a known orientation and dimensions to a specific layout location constitutes a major challenge. The challenge becomes even more formidable, if one chooses to realize the task in a monolithic fashion with an extreme topography, a characteristic of microsystems. The need for such a monolithic integration is fueled by the recent surge in the use of silicon nanowires as functional building blocks in various electromechanical and optoelectronic applications. This challenge is addressed in this work by introducing a top-down, silicon-on-insulator technology. The technology provides a pathway for obtaining well-controlled silicon nanowires along with the surrounding microscale features up to a three-order-of-magnitude scale difference. A two-step etching process is developed, where the first shallow etch defines a nanoscale protrusion on the wafer surface. After applying a conformal protection on the protrusion, a deep etch step is carried out forming the surrounding microscale features. A minimum nanowire cross-section of 35 nm by 168 nm is demonstrated in the presence of an etch depth of 10 μm. Nanowire cross-sectional features are characterized via transmission electron microscopy and linked to specific process steps. The technology allows control on all dimensional aspects along with the exact location and orientation of the silicon nanowire. The adoption of the technology in the fabrication of micro and nanosystems can potentially lead to a significant reduction in process complexity by facilitating direct access to the nanowire during surface processes such as contact formation and doping. PMID:26854570

  15. A deep etching mechanism for trench-bridging silicon nanowires

    NASA Astrophysics Data System (ADS)

    Tasdemir, Zuhal; Wollschläger, Nicole; Österle, Werner; Leblebici, Yusuf; Erdem Alaca, B.

    2016-03-01

    Introducing a single silicon nanowire with a known orientation and dimensions to a specific layout location constitutes a major challenge. The challenge becomes even more formidable, if one chooses to realize the task in a monolithic fashion with an extreme topography, a characteristic of microsystems. The need for such a monolithic integration is fueled by the recent surge in the use of silicon nanowires as functional building blocks in various electromechanical and optoelectronic applications. This challenge is addressed in this work by introducing a top-down, silicon-on-insulator technology. The technology provides a pathway for obtaining well-controlled silicon nanowires along with the surrounding microscale features up to a three-order-of-magnitude scale difference. A two-step etching process is developed, where the first shallow etch defines a nanoscale protrusion on the wafer surface. After applying a conformal protection on the protrusion, a deep etch step is carried out forming the surrounding microscale features. A minimum nanowire cross-section of 35 nm by 168 nm is demonstrated in the presence of an etch depth of 10 μm. Nanowire cross-sectional features are characterized via transmission electron microscopy and linked to specific process steps. The technology allows control on all dimensional aspects along with the exact location and orientation of the silicon nanowire. The adoption of the technology in the fabrication of micro and nanosystems can potentially lead to a significant reduction in process complexity by facilitating direct access to the nanowire during surface processes such as contact formation and doping.

  16. Terahertz detectors arrays based on orderly aligned InN nanowires

    PubMed Central

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

    2015-01-01

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

  17. Hydrogenated microcrystalline silicon electrodes connected by indium phosphide nanowires

    NASA Astrophysics Data System (ADS)

    Kobayashi, Nobuhiko P.; VJ, Logeeswaran; Saif Islam, M.; Li, Xuema; Straznicky, Joseph; Wang, Shih-Yuan; Stanley Williams, R.; Chen, Yong

    2007-09-01

    The authors report the connection of two planar hydrogenated silicon (Si:H) electrodes by intersecting and bridging indium phosphide nanowires (InP NWs). A simple metal-semiconductor-metal photoconductor was used as a test vehicle to measure electrical and optical characteristics of the connected InP NWs. This implementation of III-V compound semiconductor nanowires on Si:H combines the characteristics of a direct bandgap semiconductor with the flexible fabrication processes of non-single-crystal silicon platforms that do not require single-crystal substrates.

  18. Nanogenerators based on vertically aligned InN nanowires.

    PubMed

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

    2016-01-28

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

  19. Electrical properties of phosphorus in situ doped Au-catalyst vapor liquid solid silicon nanowires

    NASA Astrophysics Data System (ADS)

    Pichon, L.; Rogel, R.; Jacques, E.

    2015-11-01

    N-type in-situ doped silicon nanowire-based resistors are fabricated following a CMOS process fabrication. Silicon nanowires are prepared by a Vapour Liquid Solid (VLS) method using gold as the catalyst. The doping level is adjusted by varying the phosphine to silane mole ratio during silicon nanowire growth. A macroscopic electrical model is presented to extract the average silicon nanowire electrical resistivity over a large doping level range (varying from undoped to highly doped nanowires). Carrier transport is strongly affected by the trapping effect of gold impurities into silicon nanowires, and silicon nanowire electrical resistivity is three decades higher than for silicon bulk at low doping levels. The technological requirement in terms of doping level control for the fabrication of devices based on a gold catalyst VLS is demonstrated.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  1. 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

  2. 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.

  3. Sub-diffraction Laser Synthesis of Silicon Nanowires

    PubMed Central

    Mitchell, James I.; Zhou, Nan; Nam, Woongsik; Traverso, Luis M.; Xu, Xianfan

    2014-01-01

    We demonstrate synthesis of silicon nanowires of tens of nanometers via laser induced chemical vapor deposition. These nanowires with diameters as small as 60 nm are produced by the interference between incident laser radiation and surface scattered radiation within a diffraction limited spot, which causes spatially confined, periodic heating needed for high resolution chemical vapor deposition. By controlling the intensity and polarization direction of the incident radiation, multiple parallel nanowires can be simultaneously synthesized. The nanowires are produced on a dielectric substrate with controlled diameter, length, orientation, and the possibility of in-situ doping, and therefore are ready for device fabrication. Our method offers rapid one-step fabrication of nano-materials and devices unobtainable with previous CVD methods. PMID:24469704

  4. Raman spectra of silicon carbide small particles and nanowires

    NASA Astrophysics Data System (ADS)

    Wieligor, Monika; Wang, Yuejian; Zerda, T. W.

    2005-04-01

    Two manufacturing protocols of silicon carbide (SiC) nanowires are discussed. The Raman spectra of produced SiC nanowires are compared with spectra of SiC powders of various grain sizes. The temperature and pressure dependence of the Raman spectra for powders is similar to that of bulk crystals, but is different for nanowires. Frequency shifts, band broadenings and the presence of shoulders are discussed in terms of crystal size, character of defects and their population. The concentration of defects in synthesized nanowires depends on the sintering method. Raman intensity enhancement of the LO phonon was observed when the wavelength of the excitation laser was changed from 780 to 514 nm.

  5. Atomistic modeling of bending properties of oxidized silicon nanowires

    SciTech Connect

    Ilinov, Andrey Kuronen, Antti

    2014-03-14

    In this work, we have modeled a three point bending test of monocrystalline Si nanowires using molecular dynamics simulations in order to investigate their elastic properties. Tested nanowires were about 30 nm in length and had diameters from 5 to 9 nm. To study the influence of a native oxide layer, nanowires were covered with a 1 nm thick silica layer. The bending force was applied by a carbon diamond half-sphere with a 5 nm diameter. The Si-O parametrization for the Tersoff potential was used to describe atomic interactions between Si and O atoms. In order to remove the indentation effect of the diamond half-sphere and to obtain a pure bending behavior, we have also performed a set of simulations with fixed bottoms of the nanowires. Our results show that the oxide layer reduces the nanowire stiffness when compared with a pure Si nanowire with the same number of silicon atoms—in spite of the fact that the oxidized nanowires had larger diameters.

  6. Lithium Ion Battery Performance of Silicon Nanowires With Carbon Skin

    SciTech Connect

    Bogart, Timothy D.; Oka, Daichi; Lu, Xiaotang; Gu, Meng; Wang, Chong M.; Korgel, Brian A.

    2013-12-06

    Silicon (Si) nanomaterials have emerged as a leading candidate for next generation lithium-ion battery anodes. However, the low electrical conductivity of Si requires the use of conductive additives in the anode film. Here we report a solution-based synthesis of Si nanowires with a conductive carbon skin. Without any conductive additive, the Si nanowire electrodes exhibited capacities of over 2000 mA h g-1 for 100 cycles when cycled at C/10 and over 1200 mA h g-1 when cycled more rapidly at 1C against Li metal.. In situ transmission electron microscopy (TEM) observation reveals that the carbon skin performs dual roles: it speeds lithiation of the Si nanowires significantly, while also constraining the final volume expansion. The present work sheds light on ways to optimize lithium battery performance by smartly tailoring the nanostructure of composition of materials based on silicon and carbon.

  7. Anomalous Plastic Deformation and Sputtering of Ion Irradiated Silicon Nanowires

    PubMed Central

    2015-01-01

    Silicon nanowires of various diameters were irradiated with 100 keV and 300 keV Ar+ ions on a rotatable and heatable stage. Irradiation at elevated temperatures above 300 °C retains the geometry of the nanostructure and sputtering can be gauged accurately. The diameter dependence of the sputtering shows a maximum if the ion range matches the nanowire diameter, which is in good agreement with Monte Carlo simulations based on binary collisions. Nanowires irradiated at room temperature, however, amorphize and deform plastically. So far, plastic deformation has not been observed in bulk silicon at such low ion energies. The magnitude and direction of the deformation is independent of the ion-beam direction and cannot be explained with mass-transport in a binary collision cascade but only by collective movement of atoms in the collision cascade with the given boundary conditions of a high surface to volume ratio. PMID:25951108

  8. Interdigitated design of a thermoelectric microgenerator based on silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    Silicon nanowires thermoelectric properties are much better than those of silicon bulk. Taking advantage of silicon microfabrication techniques and compatibilizing the device fabrication with the CVD-VLS silicon nanowire growth, we present a thermoelectric microgenerator based on silicon nanowire arrays with interdigitated structures which enhance the power density compared to previous designs presented by the authors. The proposed design features a thermally isolated silicon platform on the silicon device layer of an SOI silicon wafer. This silicon platform has vertical walls exposing <111< planes where gold nanoparticles are deposited by galvanic displacement. These gold nanoparticles act as seeds for the silicon nanowires. The growth takes place in a CVD with silane precursor, and uses the Vapor-Solid-Liquid synthesis. Once the silicon nanowires are grown, they connect the silicon platform with the silicon bulk. The proposed thermoelectric generator is unileg, which means that only one type of semiconductor is used, and the second connection is made through a metal. In addition, to improve the thermal isolation of the silicon platform, multiple trenches of silicon nanowire arrays are used, up to a maximum of nine. After packaging the device with nanowires, we are able to measure the Seebeck voltage and the power obtained with different operation modes: harvesting mode, where the bottom device is heated up, and the silicon platform is cooled down by natural or forced convection, and test mode, where a heater integrated on the silicon platform is used to produce a thermal gradient.

  9. Spray-coating route for highly aligned and large-scale arrays of nanowires.

    PubMed

    Assad, Ossama; Leshansky, Alexander M; Wang, Bin; Stelzner, Thomas; Christiansen, Silke; Haick, Hossam

    2012-06-26

    Technological implementation of nanowires (NWs) requires these components to be organized with controlled orientation and density on various substrates. Here, we report on a simple and efficient route for the deposition of highly ordered and highly aligned NW arrays on a wide range of receiver substrates, including silicon, glass, metals, and flexible plastics with controlled density. The deposition approach is based on spray-coating of a NW suspension under controlled conditions of the nozzle flow rate, droplet size of the sprayed NWs suspension, spray angle, and the temperature of the receiver substrate. The dynamics of droplet generation is understood by a combined action of shear forces and capillary forces. Provided that the size of the generated droplet is comparable to the length of the single NW, the shear-driven elongation of the droplets results presumably in the alignment of the confined NW in the spraying direction. Flattening the droplets upon their impact with the substrate yields fast immobilization of the spray-aligned NWs on the surface due to van der Waals attraction. The availability of the spray-coating technique in the current microelectronics technology would ensure immediate implementation in production lines, with minimal changes in the fabrication design and/or auxiliary tools used for this purpose. PMID:22554272

  10. Multifunctional devices and logic gates with undoped silicon nanowires.

    PubMed

    Mongillo, Massimo; Spathis, Panayotis; Katsaros, Georgios; Gentile, Pascal; De Franceschi, Silvano

    2012-06-13

    We report on the electronic transport properties of multiple-gate devices fabricated from undoped silicon nanowires. Understanding and control of the relevant transport mechanisms was achieved by means of local electrostatic gating and temperature-dependent measurements. The roles of the source/drain contacts and of the silicon channel could be independently evaluated and tuned. Wrap gates surrounding the silicide-silicon contact interfaces were proved to be effective in inducing a full suppression of the contact Schottky barriers, thereby enabling carrier injection down to liquid helium temperature. By independently tuning the effective Schottky barrier heights, a variety of reconfigurable device functionalities could be obtained. In particular, the same nanowire device could be configured to work as a Schottky barrier transistor, a Schottky diode, or a p-n diode with tunable polarities. This versatility was eventually exploited to realize a NAND logic gate with gain well above one. PMID:22594644

  11. Giant piezoresistance effects in silicon nanowires and microwires.

    PubMed

    Milne, J S; Rowe, A C H; Arscott, S; Renner, Ch

    2010-11-26

    The giant piezoresistance (PZR) previously reported in silicon nanowires is experimentally investigated in a large number of depleted silicon nano- and microstructures. The resistance is shown to vary strongly with time due to electron and hole trapping at the sample surfaces independent of the applied stress. Importantly, this time-varying resistance manifests itself as an apparent giant PZR identical to that reported elsewhere. By modulating the applied stress in time, the true PZR of the structures is found to be comparable with that of bulk silicon. PMID:21231411

  12. Reconfigurable quadruple quantum dots in a silicon nanowire transistor

    NASA Astrophysics Data System (ADS)

    Betz, A. C.; Tagliaferri, M. L. V.; Vinet, M.; Broström, M.; Sanquer, M.; Ferguson, A. J.; Gonzalez-Zalba, M. F.

    2016-05-01

    We present a reconfigurable metal-oxide-semiconductor multi-gate transistor that can host a quadruple quantum dot in silicon. The device consists of an industrial quadruple-gate silicon nanowire field-effect transistor. Exploiting the corner effect, we study the versatility of the structure in the single quantum dot and the serial double quantum dot regimes and extract the relevant capacitance parameters. We address the fabrication variability of the quadruple-gate approach which, paired with improved silicon fabrication techniques, makes the corner state quantum dot approach a promising candidate for a scalable quantum information architecture.

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

    PubMed

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

    2015-03-27

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

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

    PubMed

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

    2014-06-11

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

  15. 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.

  16. Microscopic theory of thermoelectric properties of silicon nanowires

    SciTech Connect

    Vo, T; Williamson, A; Lordi, V; Galli, G

    2007-06-14

    We present predictions of the thermoelectric figure of merit (ZT) of Si nanowires, as obtained using Boltzman transport equation and ab-initio electronic structure calculations. We find that ZT is strongly dependent on the nanowire growth direction and surface reconstruction and we discuss general rules to select silicon based nanostructures with combined n-type and p-type optimal ZT. In particular, our calculations indicate that 1 nm wires grown in the [001] and [011] directions can attain ZT values which are about twice as high as those of ordinary thermoelectric materials.

  17. Silicon nanowire arrays as learning chemical vapour classifiers.

    PubMed

    Niskanen, A O; Colli, A; White, R; Li, H W; Spigone, E; Kivioja, J M

    2011-07-22

    Nanowire field-effect transistors are a promising class of devices for various sensing applications. Apart from detecting individual chemical or biological analytes, it is especially interesting to use multiple selective sensors to look at their collective response in order to perform classification into predetermined categories. We show that non-functionalised silicon nanowire arrays can be used to robustly classify different chemical vapours using simple statistical machine learning methods. We were able to distinguish between acetone, ethanol and water with 100% accuracy while methanol, ethanol and 2-propanol were classified with 96% accuracy in ambient conditions. PMID:21673389

  18. Electrical shielding for silicon nanowire biosensor in microchannels

    NASA Astrophysics Data System (ADS)

    Chen, Songyue; Xie, Yanbo; De, Arpita; van den Berg, Albert; Carlen, Edwin T.

    2013-10-01

    When integrating silicon nanowire biosensors with a microfluidic sample delivery system, additional challenges are introduced. Noise and erroneous signal generation induced by sample fluidic handling such as flow rate fluctuations during sample switching reduce the quality and reliability of the measurement system. In this paper, we propose an effective electrical shielding method to improve the stability and reliability of the setup by placing double electrodes instead of a single electrode that is traditionally used for nanowire sensors. Experimental results show that with proper shielding electrical measurements are not influenced by flow speed variations or during sample switching.

  19. Silicon-nanowire based attachment of silicon chips for mouse embryo labelling.

    PubMed

    Durán, S; Novo, S; Duch, M; Gómez-Martínez, R; Fernández-Regúlez, M; San Paulo, A; Nogués, C; Esteve, J; Ibañez, E; Plaza, J A

    2015-03-21

    The adhesion of small silicon chips to cells has many potential applications as direct interconnection of the cells to the external world can be accomplished. Hence, although some typical applications of silicon nanowires integrated into microsystems are focused on achieving a cell-on-a-chip strategy, we are interested in obtaining chip-on-a-cell systems. This paper reports the design, technological development and characterization of polysilicon barcodes featuring silicon nanowires as nanoscale attachment to identify and track living mouse embryos during their in vitro development. The chips are attached to the outer surface of the Zona Pellucida, the cover that surrounds oocytes and embryos, to avoid the direct contact between the chip and the embryo cell membrane. Two attachment methodologies, rolling and pushpin, which allow two entirely different levels of applied forces to attach the chips to living embryos, are evaluated. The former consists of rolling the mouse embryos over one barcode with the silicon nanowires facing upwards, while in the latter, the barcode is pushed against the embryo with a micropipette. The effect on in vitro embryo development and the retention rate related to the calculated applied forces are stated. Field emission scanning electron microscopy inspection, which allowed high-resolution imaging, also confirms the physical attachment of the nanowires with some of them piercing or wrapped by the Zona Pellucida and revealed extraordinary bent silicon nanowires. PMID:25609565

  20. MOCVD growth of vertically aligned InGaN nanowires

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  1. 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

  2. Atomistic modeling of metallic nanowires in silicon.

    PubMed

    Ryu, Hoon; Lee, Sunhee; Weber, Bent; Mahapatra, Suddhasatta; Hollenberg, Lloyd C L; Simmons, Michelle Y; Klimeck, Gerhard

    2013-09-21

    Scanning tunneling microscope (STM) lithography has recently demonstrated the ultimate in device scaling with buried, conducting nanowires just a few atoms wide and the realization of single atom transistors, where a single P atom has been placed inside a transistor architecture with atomic precision accuracy. Despite the dimensions of the critical parts of these devices being defined by a small number of P atoms, the device electronic properties are influenced by the surrounding 10(4) to 10(6) Si atoms. Such effects are hard to capture with most modeling approaches, and prior to this work no theory existed that could explore the realistic size of the complete device in which both dopant disorder and placement are important. This work presents a comprehensive study of the electronic and transport properties of ultra-thin (<10 nm wide) monolayer highly P δ-doped Si (Si:P) nanowires in a fully atomistic self-consistent tight-binding approach. This atomistic approach covering large device volumes allows for a systematic study of disorder on the physical properties of the nanowires. Excellent quantitative agreement is observed with recent resistance measurements of STM-patterned nanowires [Weber et al., Science, 2012, 335, 64], confirming the presence of metallic behavior at the scaling limit. At high doping densities the channel resistance is shown to be insensitive to the exact channel dopant placement highlighting their future use as metallic interconnects. This work presents the first theoretical study of Si:P nanowires that are realistically extended and disordered, providing a strong theoretical foundation for the design and understanding of atomic-scale electronics. PMID:23897026

  3. 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.

  4. Fabricating vertically aligned sub-20 nm Si nanowire arrays by chemical etching and thermal oxidation.

    PubMed

    Li, Luping; Fang, Yin; Xu, Cheng; Zhao, Yang; Zang, Nanzhi; Jiang, Peng; Ziegler, Kirk J

    2016-04-22

    Silicon nanowires (SiNWs) are appealing building blocks in various applications, including photovoltaics, photonics, and sensors. Fabricating SiNW arrays with diameters <100 nm remains challenging through conventional top-down approaches. In this work, chemical etching and thermal oxidation are combined to fabricate vertically aligned, sub-20 nm SiNW arrays. Defect-free SiNWs with diameters between 95 and 200 nm are first fabricated by nanosphere (NS) lithography and chemical etching. The key aspects for defect-free SiNW fabrication are identified as: (1) achieving a high etching selectivity during NS size reduction; (2) retaining the circular NS shape with smooth sidewalls; and (3) using a directional metal deposition technique. SiNWs with identical spacing but variable diameters are demonstrated by changing the reactive ion etching power. The diameter of the SiNWs is reduced by thermal oxidation, where self-limiting oxidation is encountered after oxidizing the SiNWs at 950 °C for 1 h. A second oxidation is performed to achieve vertically aligned, sub-20 nm SiNW arrays. Si/SiO2 core/shell NWs are obtained before removing the oxidized shell. HRTEM imaging shows that the SiNWs have excellent crystallinity. PMID:26953775

  5. Oxide mediated liquid-solid growth of high aspect ratio aligned gold silicide nanowires on Si(110) substrates.

    PubMed

    Bhatta, Umananda M; Rath, Ashutosh; Dash, Jatis K; Ghatak, Jay; Yi-Feng, Lai; Liu, Chuan-Pu; Satyam, P V

    2009-11-18

    Silicon nanowires grown using the vapor-liquid-solid method are promising candidates for nanoelectronics applications. The nanowires grow from an Au-Si catalyst during silicon chemical vapor deposition. In this paper, the effect of temperature, oxide at the interface and substrate orientation on the nucleation and growth kinetics during formation of nanogold silicide structures is explained using an oxide mediated liquid-solid growth mechanism. Using real time in situ high temperature transmission electron microscopy (with 40 ms time resolution), we show the formation of high aspect ratio ( approximately 15.0) aligned gold silicide nanorods in the presence of native oxide at the interface during in situ annealing of gold thin films on Si(110) substrates. Steps observed in the growth rate and real time electron diffraction show the existence of liquid Au-Si nano-alloy structures on the surface besides the un-reacted gold nanostructures. These results might enable us to engineer the growth of nanowires and similar structures with an Au-Si alloy as a catalyst. PMID:19843987

  6. Oxide mediated liquid-solid growth of high aspect ratio aligned gold silicide nanowires on Si(110) substrates

    NASA Astrophysics Data System (ADS)

    Bhatta, Umananda M.; Rath, Ashutosh; Dash, Jatis K.; Ghatak, Jay; Yi-Feng, Lai; Liu, Chuan-Pu; Satyam, P. V.

    2009-11-01

    Silicon nanowires grown using the vapor-liquid-solid method are promising candidates for nanoelectronics applications. The nanowires grow from an Au-Si catalyst during silicon chemical vapor deposition. In this paper, the effect of temperature, oxide at the interface and substrate orientation on the nucleation and growth kinetics during formation of nanogold silicide structures is explained using an oxide mediated liquid-solid growth mechanism. Using real time in situ high temperature transmission electron microscopy (with 40 ms time resolution), we show the formation of high aspect ratio (≈15.0) aligned gold silicide nanorods in the presence of native oxide at the interface during in situ annealing of gold thin films on Si(110) substrates. Steps observed in the growth rate and real time electron diffraction show the existence of liquid Au-Si nano-alloy structures on the surface besides the un-reacted gold nanostructures. These results might enable us to engineer the growth of nanowires and similar structures with an Au-Si alloy as a catalyst.

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

    PubMed

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

    2014-10-21

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

  8. Approaching the ideal elastic strain limit in silicon nanowires.

    PubMed

    Zhang, Hongti; Tersoff, Jerry; Xu, Shang; Chen, Huixin; Zhang, Qiaobao; Zhang, Kaili; Yang, Yong; Lee, Chun-Sing; Tu, King-Ning; Li, Ju; Lu, Yang

    2016-08-01

    Achieving high elasticity for silicon (Si) nanowires, one of the most important and versatile building blocks in nanoelectronics, would enable their application in flexible electronics and bio-nano interfaces. We show that vapor-liquid-solid-grown single-crystalline Si nanowires with diameters of ~100 nm can be repeatedly stretched above 10% elastic strain at room temperature, approaching the theoretical elastic limit of silicon (17 to 20%). A few samples even reached ~16% tensile strain, with estimated fracture stress up to ~20 GPa. The deformations were fully reversible and hysteresis-free under loading-unloading tests with varied strain rates, and the failures still occurred in brittle fracture, with no visible sign of plasticity. The ability to achieve this "deep ultra-strength" for Si nanowires can be attributed mainly to their pristine, defect-scarce, nanosized single-crystalline structure and atomically smooth surfaces. This result indicates that semiconductor nanowires could have ultra-large elasticity with tunable band structures for promising "elastic strain engineering" applications. PMID:27540586

  9. Approaching the ideal elastic strain limit in silicon nanowires

    PubMed Central

    Zhang, Hongti; Tersoff, Jerry; Xu, Shang; Chen, Huixin; Zhang, Qiaobao; Zhang, Kaili; Yang, Yong; Lee, Chun-Sing; Tu, King-Ning; Li, Ju; Lu, Yang

    2016-01-01

    Achieving high elasticity for silicon (Si) nanowires, one of the most important and versatile building blocks in nanoelectronics, would enable their application in flexible electronics and bio-nano interfaces. We show that vapor-liquid-solid–grown single-crystalline Si nanowires with diameters of ~100 nm can be repeatedly stretched above 10% elastic strain at room temperature, approaching the theoretical elastic limit of silicon (17 to 20%). A few samples even reached ~16% tensile strain, with estimated fracture stress up to ~20 GPa. The deformations were fully reversible and hysteresis-free under loading-unloading tests with varied strain rates, and the failures still occurred in brittle fracture, with no visible sign of plasticity. The ability to achieve this “deep ultra-strength” for Si nanowires can be attributed mainly to their pristine, defect-scarce, nanosized single-crystalline structure and atomically smooth surfaces. This result indicates that semiconductor nanowires could have ultra-large elasticity with tunable band structures for promising “elastic strain engineering” applications. PMID:27540586

  10. Funnel-shaped silicon nanowire for highly efficient light trapping.

    PubMed

    Hussein, Mohamed; Hameed, Mohamed Farhat O; Areed, Nihal F F; Yahia, Ashraf; Obayya, S S A

    2016-03-01

    In this Letter, funnel-shaped silicon nanowires (SiNWs) are newly introduced for highly efficient light trapping. The proposed designs of nanowires are inspired by the funnel shape, which enhances the light trapping with reduced reflections in the wavelength range from 300 to 1100 nm. Composed of both cylindrical and conical units, the funnel nanowires increase the number of leaky mode resonances, yielding an absorption enhancement relative to a uniform nanowire array. The optical properties of the suggested nanowires have been numerically investigated using the 3D finite difference time domain (FDTD) method and compared to cylindrical and conical counterparts. The structural geometrical parameters are studied to maximize the ultimate efficiency and hence the short-circuit current. Carefully engineered structure geometry is shown to yield improved light absorption useful for solar cell applications. The proposed funnel-shaped SiNWs offer an ultimate efficiency of 41.8%, with an enhancement of 54.8% relative to conventional cylindrical SiNWs. Additionally, short-circuit current of 34.2  mA/cm2 is achieved using the suggested design. PMID:26974103

  11. Silicon nanowires: where mechanics and optics meet at the nanoscale.

    PubMed

    Ramos, Daniel; Gil-Santos, Eduardo; Malvar, Oscar; Llorens, Jose M; Pini, Valerio; San Paulo, Alvaro; Calleja, Montserrat; Tamayo, Javier

    2013-01-01

    Mechanical transducers based on nanowires promise revolutionary advances in biological sensing and force microscopy/spectroscopy. A crucial step is the development of simple and non-invasive techniques able to detect displacements with subpicometer sensitivity per unit bandwidth. Here, we design suspended tapered silicon nanowires supporting a range of optical resonances that confine and efficiently scatter light in the visible range. Then, we develop an optical method for efficiently coupling the evanescent field to the regular interference pattern generated by an incoming laser beam and the reflected beam from the substrate underneath the nanowire. This optomechanical coupling is here applied to measure the displacement of 50 nm wide nanowires with sensitivity on the verge of 1 fm/Hz(1/2) at room temperature with a simple laser interferometry set-up. This method opens the door to the measurement of the Brownian motion of ultrashort nanowires for the detection of single biomolecular recognition events in liquids, and single molecule spectroscopy in vacuum. PMID:24309472

  12. Epitaxial growth of silicon nanowires using an aluminium catalyst.

    PubMed

    Wang, Yewu; Schmidt, Volker; Senz, Stephan; Gösele, Ulrich

    2006-12-01

    Silicon nanowires have been identified as important components for future electronic and sensor nanodevices. So far gold has dominated as the catalyst for growing Si nanowires via the vapour-liquid-solid (VLS) mechanism. Unfortunately, gold traps electrons and holes in Si and poses a serious contamination problem for Si complementary metal oxide semiconductor (CMOS) processing. Although there are some reports on the use of non-gold catalysts for Si nanowire growth, either the growth requires high temperatures and/or the catalysts are not compatible with CMOS requirements. From a technological standpoint, a much more attractive catalyst material would be aluminium, as it is a standard metal in Si process lines. Here we report for the first time the epitaxial growth of Al-catalysed Si nanowires and suggest that growth proceeds via a vapour-solid-solid (VSS) rather than a VLS mechanism. It is also found that the tapering of the nanowires can be strongly reduced by lowering the growth temperature. PMID:18654184

  13. Electric field effect thermoelectric transport in individual silicon and germanium/silicon nanowires

    NASA Astrophysics Data System (ADS)

    Brovman, Yuri M.; Small, Joshua P.; Hu, Yongjie; Fang, Ying; Lieber, Charles M.; Kim, Philip

    2016-06-01

    We have simultaneously measured conductance and thermoelectric power (TEP) of individual silicon and germanium/silicon core/shell nanowires in the field effect transistor device configuration. As the applied gate voltage changes, the TEP shows distinctly different behaviors while the electrical conductance exhibits the turn-off, subthreshold, and saturation regimes, respectively. At room temperature, peak TEP value of ˜300 μ V/K is observed in the subthreshold regime of the Si devices. The temperature dependence of the saturated TEP values is used to estimate the carrier doping of Si nanowires.

  14. Graphene/silicon nanowire Schottky junction for enhanced light harvesting.

    PubMed

    Fan, Guifeng; Zhu, Hongwei; Wang, Kunlin; Wei, Jinquan; Li, Xinming; Shu, Qinke; Guo, Ning; Wu, Dehai

    2011-03-01

    Schottky junction solar cells are assembled by directly coating graphene films on n-type silicon nanowire (SiNW) arrays. The graphene/SiNW junction shows enhanced light trapping and faster carrier transport compared to the graphene/planar Si structure. With chemical doping, the SiNW-based solar cells showed energy conversion efficiencies of up to 2.86% at AM1.5 condition, opening a possibility of using graphene/semiconductor nanostructures in photovoltaic application. PMID:21323376

  15. Enhanced thermoelectric performance of rough silicon nanowires.

    PubMed

    Hochbaum, Allon I; Chen, Renkun; Delgado, Raul Diaz; Liang, Wenjie; Garnett, Erik C; Najarian, Mark; Majumdar, Arun; Yang, Peidong

    2008-01-10

    Approximately 90 per cent of the world's power is generated by heat engines that use fossil fuel combustion as a heat source and typically operate at 30-40 per cent efficiency, such that roughly 15 terawatts of heat is lost to the environment. Thermoelectric modules could potentially convert part of this low-grade waste heat to electricity. Their efficiency depends on the thermoelectric figure of merit ZT of their material components, which is a function of the Seebeck coefficient, electrical resistivity, thermal conductivity and absolute temperature. Over the past five decades it has been challenging to increase ZT > 1, since the parameters of ZT are generally interdependent. While nanostructured thermoelectric materials can increase ZT > 1 (refs 2-4), the materials (Bi, Te, Pb, Sb, and Ag) and processes used are not often easy to scale to practically useful dimensions. Here we report the electrochemical synthesis of large-area, wafer-scale arrays of rough Si nanowires that are 20-300 nm in diameter. These nanowires have Seebeck coefficient and electrical resistivity values that are the same as doped bulk Si, but those with diameters of about 50 nm exhibit 100-fold reduction in thermal conductivity, yielding ZT = 0.6 at room temperature. For such nanowires, the lattice contribution to thermal conductivity approaches the amorphous limit for Si, which cannot be explained by current theories. Although bulk Si is a poor thermoelectric material, by greatly reducing thermal conductivity without much affecting the Seebeck coefficient and electrical resistivity, Si nanowire arrays show promise as high-performance, scalable thermoelectric materials. PMID:18185582

  16. In situ tensile and creep testing of lithiated silicon nanowires

    SciTech Connect

    Boles, Steven T.; Kraft, Oliver; Thompson, Carl V.; Mönig, Reiner

    2013-12-23

    We present experimental results for uniaxial tensile and creep testing of fully lithiated silicon nanowires. A reduction in the elastic modulus is observed when silicon nanowires are alloyed with lithium and plastic deformation becomes possible when the wires are saturated with lithium. Creep testing was performed at fixed force levels above and below the tensile strength of the material. A linear dependence of the strain-rate on the applied stress was evident below the yield stress of the alloy, indicating viscous deformation behavior. The observed inverse exponential relationship between wire radius and strain rate below the yield stress indicates that material transport was controlled by diffusion. At stress levels approaching the yield strength of fully lithiated silicon, power-law creep appears to govern the strain-rate dependence on stress. These results have direct implications on the cycling conditions, rate-capabilities, and charge capacity of silicon and should prove useful for the design and construction of future silicon-based electrodes.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  18. Electronic Structure of Silicon Nanowires Matrix from Ab Initio Calculations.

    PubMed

    Monastyrskii, Liubomyr S; Boyko, Yaroslav V; Sokolovskii, Bogdan S; Potashnyk, Vasylyna Ya

    2016-12-01

    An investigation of the model of porous silicon in the form of periodic set of silicon nanowires has been carried out. The electronic energy structure was studied using a first-principle band method-the method of pseudopotentials (ultrasoft potentials in the basis of plane waves) and linearized mode of the method of combined pseudopotentials. Due to the use of hybrid exchange-correlation potentials (B3LYP), the quantitative agreement of the calculated value of band gap in the bulk material with experimental data is achieved. The obtained results show that passivation of dangling bonds with hydrogen atoms leads to substantial transformation of electronic energy structure. At complete passivation of the dangling silicon bonds by hydrogen atoms, the band gap value takes the magnitude which substantially exceeds that for bulk silicon. The incomplete passivation gives rise to opposite effect when the band gap value decreases down the semimetallic range. PMID:26768147

  19. High-stability Finite-Length Silicon Nanowires: A Real Space Theoretical Study

    NASA Astrophysics Data System (ADS)

    Koukaras, E. N.; Zdetsis, A. D.; Garoufalis, C. S.

    2007-12-01

    We demonstrate by real-space density functional calculations that unreconstructed low-stability finite size hydrogenated silicon nanowires could bend through relaxation under the influence of internal strains, contrary to high-stability "magic" nanowires. The strains and the resulting bending depend on the distribution and orientation of silicon dihydrides on the nanowire's surface. This and other related effects cannot be accounted for by the usual k-space supercell techniques. We also demonstrate that reconstructed (2×1) nanowires, although bend they are practically as stable as the "magic" unreconstructed nanowires. Our calculations are in full agreement with the experimental work of Ma et al. [Science 299, 1874, (2003)].

  20. Expanding the versatility of silicon carbide thin films and nanowires

    NASA Astrophysics Data System (ADS)

    Luna, Lunet

    Silicon carbide (SiC) based electronics and sensors hold promise for pushing past the limits of current technology to achieve small, durable devices that can function in high-temperature, high-voltage, corrosive, and biological environments. SiC is an ideal material for such conditions due to its high mechanical strength, excellent chemical stability, and its biocompatibility. Consequently, SiC thin films and nanowires have attracted interest in applications such as micro- and nano-electromechanical systems, biological sensors, field emission cathodes, and energy storage devices. However to fully realize SiC in such technologies, the reliability of metal contacts to SiC at high temperatures must be improved and the nanowire growth mechanism must be understood to enable strict control of nanowire crystal structure and orientation. Here, we present a novel metallization scheme, utilizing solid-state graphitization of SiC, to improve the long-term reliability of Pt/Ti contacts to polycrystalline n-type SiC films at high temperature. The metallization scheme includes an alumina protection layer and exhibits low, stable contact resistivity even after long-term (500 hr) testing in air at 450 ºC. We also report the crystal structure and growth mechanism of Ni-assisted silicon carbide nanowires using single-source precursor, methyltrichlorosilane. The effects of growth parameters, such as substrate and temperature, on the structure and morphology of the resulting nanowires will also be presented. Overall, this study provides new insights towards the realization of novel SiC technologies, enabled by advanced electron microscopy techniques located in the user facilities at the Molecular Foundry in Berkeley, California. This work was performed in part at the Molecular Foundry, supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

  1. Nano-silicide formation through point contact reaction, nickel-silicon/silicon/nickel-silicon and platinum-silicon/silicon/platinum-silicon nanowire heterostructures for nanodevices

    NASA Astrophysics Data System (ADS)

    Lu, Kuo-Chang

    very sharp interfaces were produced in a Si nanowire. Owing to the supply-limited point contact reaction, we propose that the nucleation and growth of the bamboo-type NiSi grains start at the middle of the point contacts between two Ni nanodots and a Si nanowire. The reaction happens by the dissolution of Ni into the Si nanowire at the point contacts and by interstitial diffusion of Ni atoms within a Si nanowire. The growth of NiSi stops as the amount of Ni in the Ni nanodots is consumed. The fabricated multi-nano-heterostructures may enhance the development of circuit elements in nano-scale electronic devices. Additionally, the formation of PtSi nanowires, PtSi/Si/PtSi nanowire heterostructures, and nanodevices from such heterostructures are demonstrated. Scanning electron microscopy studies show that silicon nanowires can be converted into PtSi nanowires through controlled reactions between lithographically defined platinum pads and silicon nanowires. High-resolution transmission electron microscopy studies show that PtSi/Si/PtSi heteorstructure has an atomically sharp interface with epitaxial relationships of Si [1-10]//PtSi [010] and Si (111)//PtSi (101). Electrical measurements show that the pure PtSi nanowires have low resistivities ˜28.6 muO·cm and high breakdown current densities >1 x 108 A/cm 2. Furthermore, using single crystal PtSi/Si/PtSi nanowire heterostructures with atomically sharp interfaces, we have fabricated high-performance nanoscale field-effect transistors from intrinsic silicon nanowires, in which the source and drain contacts are defined by the metallic PtSi nanowire regions, and the gate length is defined by the Si nanowire region. Electrical measurements show nearly perfect p-channel enhancement mode transistor behavior with a normalized transconductance of 0.3 mS/mum, field-effect hole mibility of 168 cm2/V·s, and on/off ratio >10 7, demonstrating the best performing device from intrinsic silicon nanowires.

  2. ASM stepper alignment through thick epitaxial silicon films

    NASA Astrophysics Data System (ADS)

    Black, Iain

    1999-04-01

    High voltage bipolar and BiCMOS processes often use thick epitaxially grown layers of silicon. These films 12-24 micrometers thick offer a considerable challenge to the alignment of subsequent process layers due to the 'wash out' and image distortion, caused to any underlying pattern, which render automatic alignment mark recognition difficult it not impossible. Historically using projection aligner technology these immediately post Epi layers have been manually aligned with future automatic alignment target defined at the first opportunity post Epi. This is not possible using ASM steppers, as these depend upon marks etched into the silicon, before first processing, to create marks, to which all subsequent layers are registered. To allow the stepper to run wafers with these Epi films a new approach was required.

  3. Raman study of phase transformation from diamond structure to wurtzite structure in the silicon nanowires

    NASA Astrophysics Data System (ADS)

    Shukla, A. K.; Dixit, Saurabh

    2016-07-01

    Hexagonal silicon has emerged as an exciting material due to its novel vibrational and electronic properties. Synthesis of the wurtzite silicon nanowires (w-SiNWs) is studied here using metal assisted chemical etching (MACE) technique. Stress induced in the SiNWs during wet chemical etching is attributed to formation of the w-SiNWs. Presence of the w-SiNWs is revealed by first-order and second-order Raman spectra. The effect of variation of deposition time of silver (catalyst) is explicitly studied for growth of w-SiNWs. The deposition time enhances the density of SiNWs in an island of vertically aligned SiNWs. Absorption coefficient studies of the w-SiNWs are also conducted using UV–vis spectroscopy as a function of deposition time. Increase in the absorption coefficient in SiNWs is noticed with increasing deposition time. The prominent quantum confinement along with stress and porosity is shown to be mainly responsible for the transformation from diamond structure to wurtzite structure in the silicon nanowires.

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

  6. Electrical properties of nominally undoped silicon nanowires grown by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Bauer, Jan; Fleischer, Frank; Breitenstein, Otwin; Schubert, Luise; Werner, Peter; Gösele, Ulrich; Zacharias, Margit

    2007-01-01

    Single undoped Si nanowires were electrically characterized. The nanowires were grown by molecular-beam epitaxy on n+ silicon substrates and were contacted by platinum/iridium tips. I-V curves were measured and electron beam induced current investigations were performed on single nanowires. It was found that the nanowires have an apparent resistivity of 0.85Ωcm, which is much smaller than expected for undoped Si nanowires. The conductance is explained by hopping conductivity at the Si -SiO2 interface of the nanowire surface.

  7. Fabrication of sub-12 nm thick silicon nanowires by processing scanning probe lithography masks

    SciTech Connect

    Kyoung Ryu, Yu; Garcia, Ricardo; Aitor Postigo, Pablo; Garcia, Fernando

    2014-06-02

    Silicon nanowires are key elements to fabricate very sensitive mechanical and electronic devices. We provide a method to fabricate sub-12 nm silicon nanowires in thickness by combining oxidation scanning probe lithography and anisotropic dry etching. Extremely thin oxide masks (0.3–1.1 nm) are transferred into nanowires of 2–12 nm in thickness. The width ratio between the mask and the silicon nanowire is close to one which implies that the nanowire width is controlled by the feature size of the nanolithography. This method enables the fabrication of very small single silicon nanowires with cross-sections below 100 nm{sup 2}. Those values are the smallest obtained with a top-down lithography method.

  8. 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

  9. Structural and electrical properties of trimethylboron-doped silicon nanowires

    NASA Astrophysics Data System (ADS)

    Lew, Kok-Keong; Pan, Ling; Bogart, Timothy E.; Dilts, Sarah M.; Dickey, Elizabeth C.; Redwing, Joan M.; Wang, Yanfeng; Cabassi, Marco; Mayer, Theresa S.; Novak, Steven W.

    2004-10-01

    Trimethylboron (TMB) was investigated as a p-type dopant source for the vapor-liquid-solid growth of boron-doped silicon nanowires (SiNWs). The boron concentration in the nanowires was measured using secondary ion mass spectrometry and results were compared for boron-doping using TMB and diborane (B2H6) sources. Boron concentrations ranging from 1×1018 to 4×1019cm-3 were obtained by varying the inlet dopant/SiH4 gas ratio. TEM characterization revealed that the B2H6-doped SiNWs consisted of a crystalline core with a thick amorphous Si coating, while the TMB-doped SiNWs were predominantly single crystal even at high boron concentrations. The difference in structural properties was attributed to the higher thermal stability and reduced reactivity of TMB compared to B2H6. Four-point resistivity and gate-dependent conductance measurements were used to confirm p-type conductivity in the TMB-doped nanowires and to investigate the effect of dopant concentration on nanowire resistivity.

  10. Growth of epitaxial silicon and germanium nanowires using the gold catalyzed vapor-liquid-solid mechanism

    NASA Astrophysics Data System (ADS)

    Dailey, Eric J.

    The growth of silicon and germanium nanowires and their nanowire heterostructures has been investigated using the gold catalyzed vapor-liquid-solid (VLS) mechanism. The Au catalyst particles were deposited under ultra high vacuum (UHV) conditions onto vicinal Si(111) surfaces using physical vapor deposition. Nanowires were grown in a home built UHV-chemical vapor deposition (CVD) chamber using silane, disilane, germane, and digermane as gas precursors. Silicon nanowire morphology was determined to be dependent on the stability of the gold catalyst particle at the tip of the nanowire. Specifically, silicon nanowires grow along <111> orientations when gold wets the nanowire sidewalls and along <112> orientations when gold does not wet the nanowire sidewalls except under a very narrow pressure range. The dependence of gold coverage on CVD parameters on the sidewalls of <111> and <112> silicon nanowires was also determined revealing a liquid metal wetting of cylinders phenomenon. A new "seedless" VLS mechanism for nanowire growth was also determined in which the Stranski-Krastanov planar gold layer on Si(111) dewets under certain CVD conditions resulting in 15 nm diameter gold seeds that then form nanowires via the VLS mechanism. Both core/shell and axial nanowire heterostructures were also investigated with a focus on the effect of nanowire orientation on heterostructure formation. For core/shell heterostructures, only the <110> germanium core/silicon shell heterostructures were determined to form with smooth shell deposition while all other orientations underwent shell roughening. Various germanium core diameters and silicon shell thicknesses for <110> germanium core/silicon shell heterostructures were analyzed to determine the effect of nanowire diameter on shell coherency limits and to determine the strain within the nanowire heterostructures. Lastly, axial nanowire heterostructures were investigated to determine the ability to form axial heterostructures using

  11. Investigation of functionalized silicon nanowires by self-assembled monolayer

    NASA Astrophysics Data System (ADS)

    Hemed, Nofar Mintz; Convertino, Annalisa; Shacham-Diamand, Yosi

    2016-03-01

    The functionalization using self assembled monolayer (SAM) of silicon nanowires (SiNW) fabricated by plasma enhanced chemical vapor deposition (PECVD) is reported here. The SAM is being utilized as the first building block in the functionalization process. The morphology of the SiNW comprises a polycrystalline core wrapped by an hydrogenated amorphous silicon (α-Si:H) shell. Since most of the available methods for SAM verification and characterization are suitable only for flat substrates; therefore, in addition to the SiNW α-Si:H on flat samples were produced in the same system as the SiNWs. First we confirmed the SAM's presence on the flat α-Si:H samples using the following methods: contact angle measurement to determine the change in surface energy; atomic force microscopy (AFM) to determine uniformity and molecular coverage. Spectroscopic ellipsometry and X-ray reflectivity (XRR) were performed to measure SAM layer thickness and density. X-ray photoelectron spectroscopy (XPS) was applied to study the chemical states of the surface. Next, SiNW/SAM were tested by electrochemical impedance spectroscopy (EIS), and the results were compared to α-Si:H/SAM. The SAM electrical coverage on SiNW and α-Si:H was found to be ∼37% and ∼65 ± 3%, respectively. A model, based on transmission line theory for the nanowires is presented to explain the disparity in results between the nanowires and flat surface of the same materials.

  12. Elliptic cylindrical silicon nanowire hybrid surface plasmon polariton waveguide.

    PubMed

    Zhang, Li; Xiong, Qiulin; Li, Xiaopeng; Ma, Junxian

    2015-08-10

    We researched an elliptic cylindrical silicon nanowire hybrid surface plasmon polariton waveguide and evaluated its mode characteristics using the finite element method software COMSOL. The waveguide consists of three parts: an elliptic cylindrical silicon nanowire, a silver film layer, and a silica covering layer between them. All of the components are surrounded by air. After optimizing the geometrical parameters of the waveguide, we can achieve the waveguide's strong field confinement (ranging from λ2/270 to λ2/27) and long propagation distances (119-485 μm). In order to further understand the impact of the waveguide's architecture on its performance, we also studied the ridge hybrid waveguide. The results show that the ridge waveguide has moderate local field confinement ranging from λ2/190 to λ2/20 and its maximum propagation distance is about 340 μm. We compared the elliptic cylindrical and ridge nanowire hybrid waveguides with the cylindrical hybrid waveguide that we studied before. The elliptic cylindrical waveguide achieves a better trade-off between reasonable mode confinement and maximum propagation length in the three waveguides. The researched hybrid surface plasmon polaritons waveguides are useful to construct devices such as a directional coupler and may find potential applications in photonic integrated circuits or other novel SPP devices. PMID:26368373

  13. Synthesis and Photoluminescence Property of Silicon Carbide Nanowires Via Carbothermic Reduction of Silica

    PubMed Central

    2010-01-01

    Silicon carbide nanowires have been synthesized at 1400 °C by carbothermic reduction of silica with bamboo carbon under normal atmosphere pressure without metallic catalyst. X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy and Fourier transformed infrared spectroscopy were used to characterize the silicon carbide nanowires. The results show that the silicon carbide nanowires have a core–shell structure and grow along <111> direction. The diameter of silicon carbide nanowires is about 50–200 nm and the length from tens to hundreds of micrometers. The vapor–solid mechanism is proposed to elucidate the growth process. The photoluminescence of the synthesized silicon carbide nanowires shows significant blueshifts, which is resulted from the existence of oxygen defects in amorphous layer and the special rough core–shell interface. PMID:20651911

  14. Synthesis and Photoluminescence Property of Silicon Carbide Nanowires Via Carbothermic Reduction of Silica

    NASA Astrophysics Data System (ADS)

    Luo, Xiaogang; Ma, Wenhui; Zhou, Yang; Liu, Dachun; Yang, Bin; Dai, Yongnian

    2010-01-01

    Silicon carbide nanowires have been synthesized at 1400 °C by carbothermic reduction of silica with bamboo carbon under normal atmosphere pressure without metallic catalyst. X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy and Fourier transformed infrared spectroscopy were used to characterize the silicon carbide nanowires. The results show that the silicon carbide nanowires have a core-shell structure and grow along <111> direction. The diameter of silicon carbide nanowires is about 50-200 nm and the length from tens to hundreds of micrometers. The vapor-solid mechanism is proposed to elucidate the growth process. The photoluminescence of the synthesized silicon carbide nanowires shows significant blueshifts, which is resulted from the existence of oxygen defects in amorphous layer and the special rough core-shell interface.

  15. Synthesis and Photoluminescence Property of Silicon Carbide Nanowires Via Carbothermic Reduction of Silica.

    PubMed

    Luo, Xiaogang; Ma, Wenhui; Zhou, Yang; Liu, Dachun; Yang, Bin; Dai, Yongnian

    2009-01-01

    Silicon carbide nanowires have been synthesized at 1400 degrees C by carbothermic reduction of silica with bamboo carbon under normal atmosphere pressure without metallic catalyst. X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy and Fourier transformed infrared spectroscopy were used to characterize the silicon carbide nanowires. The results show that the silicon carbide nanowires have a core-shell structure and grow along <111> direction. The diameter of silicon carbide nanowires is about 50-200 nm and the length from tens to hundreds of micrometers. The vapor-solid mechanism is proposed to elucidate the growth process. The photoluminescence of the synthesized silicon carbide nanowires shows significant blueshifts, which is resulted from the existence of oxygen defects in amorphous layer and the special rough core-shell interface. PMID:20651911

  16. Self-heated silicon nanowires for high performance hydrogen gas detection.

    PubMed

    Ahn, Jae-Hyuk; Yun, Jeonghoon; Moon, Dong-Il; Choi, Yang-Kyu; Park, Inkyu

    2015-03-01

    Self-heated silicon nanowire sensors for high-performance, ultralow-power hydrogen detection have been developed. A top-down nanofabrication method based on well-established semiconductor manufacturing technology was utilized to fabricate silicon nanowires in wafer scale with high reproducibility and excellent compatibility with electronic readout circuits. Decoration of palladium nanoparticles onto the silicon nanowires enables sensitive and selective detection of hydrogen gas at room temperature. Self-heating of silicon nanowire sensors allows us to enhance response and recovery performances to hydrogen gas, and to reduce the influence of interfering gases such as water vapor and carbon monoxide. A short-pulsed heating during recovery was found to be effective for additional reduction of operation power as well as recovery characteristics. This self-heated silicon nanowire gas sensor will be suitable for ultralow-power applications such as mobile telecommunication devices and wireless sensing nodes. PMID:25670503

  17. Self-heated silicon nanowires for high performance hydrogen gas detection

    NASA Astrophysics Data System (ADS)

    Ahn, Jae-Hyuk; Yun, Jeonghoon; Moon, Dong-Il; Choi, Yang-Kyu; Park, Inkyu

    2015-03-01

    Self-heated silicon nanowire sensors for high-performance, ultralow-power hydrogen detection have been developed. A top-down nanofabrication method based on well-established semiconductor manufacturing technology was utilized to fabricate silicon nanowires in wafer scale with high reproducibility and excellent compatibility with electronic readout circuits. Decoration of palladium nanoparticles onto the silicon nanowires enables sensitive and selective detection of hydrogen gas at room temperature. Self-heating of silicon nanowire sensors allows us to enhance response and recovery performances to hydrogen gas, and to reduce the influence of interfering gases such as water vapor and carbon monoxide. A short-pulsed heating during recovery was found to be effective for additional reduction of operation power as well as recovery characteristics. This self-heated silicon nanowire gas sensor will be suitable for ultralow-power applications such as mobile telecommunication devices and wireless sensing nodes.

  18. Transport Measurements on Sb doped Silicon Nanowires

    NASA Astrophysics Data System (ADS)

    Nukala, Prathyusha; Zare, Marzieh; Sapkota, Gopal; Gali, Pradeep; Philipose, Usha

    2011-03-01

    Semiconductor nanowires (NWs) present an alternative approach for device scaling. N-type Si NWs are generally grown with silane as source with phosphine and arsenic as dopants, all of which are toxic in nature. We present a safe, cost-effective approach for synthesis of n- doped Si NWs using Sb. Structural and compositional characterization using electron microscopy and X-ray spectroscopy will be presented for crystallographic information on the quality and morphology. Ohmic contacts established to a single and on an array of doped and undoped NWs in an FET type of device configuration will provide information on several parameters such as type of majority carriers, mobility and concentration. We will highlight the promise of Sb doped Si NWs for electronic applications such as nano-scale field effect transistors and sensors.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  20. Silicon nanowire sensor by mix and match lithography process: Fabrication and characterization

    NASA Astrophysics Data System (ADS)

    Hashim, U.

    2012-11-01

    Silicon nanowires (SiNWs) have attracted significant interest in the study because of their potential to impact applications from nanoscale electronics to biomedical engineering. E-Beam Lithography couple with standard CMOS process is employed to fabricate the device. The exposure doses for the resist layer are varied in the range of 50 μC/cm2 to 180 μC/cm2 at 20 kV accelerating voltage with a beam current of 0.075 nA. The nanowires resist masks are well developed with dimension of less than 100 nm in width for the dose exposure parameters of 80 μC/cm2, 100 μC/cm2 and 120 μC/cm2. It is found that, the smallest SiNW with diameter of 65 nm is well aligned with electrode pads. In terms of sensitivity, the device with smaller nanowire is found to be more sensitive as a result of the high surface-to-volume ratio. These results demonstrate that the in-house fabricated SiNWs biosensor is capable as a platform for label-free biosensing.

  1. Significant thermal conductivity reduction of silicon nanowire forests through discrete surface doping of germanium

    SciTech Connect

    Pan, Ying; Hong, Guo; Raja, Shyamprasad N.; Zimmermann, Severin; Poulikakos, Dimos; Tiwari, Manish K.

    2015-03-02

    Silicon nanowires (SiNWs) are promising materials for the realization of highly-efficient and cost effective thermoelectric devices. Reduction of the thermal conductivity of such materials is a necessary and viable pathway to achieve sufficiently high thermoelectric efficiencies, which are inversely proportional to the thermal conductivity. In this article, vertically aligned forests of SiNW and germanium (Ge)-doped SiNW with diameters around 100 nm have been fabricated, and their thermal conductivity has been measured. The results show that discrete surface doping of Ge on SiNW arrays can lead to 23% reduction in thermal conductivity at room temperature compared to uncoated SiNWs. Such reduction can be further enhanced to 44% following a thermal annealing step. By analyzing the binding energy changes of Ge-3d and Si-2p using X-ray photoelectron spectroscopy, we demonstrate that surface doped Ge interacts strongly with Si, enhancing phonon scattering at the Si-Ge interface as has also been shown in non-equilibrium molecular dynamics studies of single nanowires. Overall, our results suggest a viable pathway to improve the energy conversion efficiency of nanowire-forest thermoelectric nanomaterials.

  2. Monolithically Integrated High-β Nanowire Lasers on Silicon.

    PubMed

    Mayer, B; Janker, L; Loitsch, B; Treu, J; Kostenbader, T; Lichtmannecker, S; Reichert, T; Morkötter, S; Kaniber, M; Abstreiter, G; Gies, C; Koblmüller, G; Finley, J J

    2016-01-13

    Reliable technologies for the monolithic integration of lasers onto silicon represent the holy grail for chip-level optical interconnects. In this context, nanowires (NWs) fabricated using III-V semiconductors are of strong interest since they can be grown site-selectively on silicon using conventional epitaxial approaches. Their unique one-dimensional structure and high refractive index naturally facilitate low loss optical waveguiding and optical recirculation in the active NW-core region. However, lasing from NWs on silicon has not been achieved to date, due to the poor modal reflectivity at the NW-silicon interface. We demonstrate how, by inserting a tailored dielectric interlayer at the NW-Si interface, low-threshold single mode lasing can be achieved in vertical-cavity GaAs-AlGaAs core-shell NW lasers on silicon as measured at low temperature. By exploring the output characteristics along a detection direction parallel to the NW-axis, we measure very high spontaneous emission factors comparable to nanocavity lasers (β = 0.2) and achieve ultralow threshold pump energies ≤11 pJ/pulse. Analysis of the input-output characteristics of the NW lasers and the power dependence of the lasing emission line width demonstrate the potential for high pulsation rates ≥250 GHz. Such highly efficient nanolasers grown monolithically on silicon are highly promising for the realization of chip-level optical interconnects. PMID:26618638

  3. Reduction of heat capacity and phonon group velocity in silicon nanowires

    NASA Astrophysics Data System (ADS)

    Marchbanks, Christopher; Wu, Zhigang

    2015-02-01

    We report on ab initio linear-response calculations of lattice vibrations in narrow silicon nanowires on the order of 1 nm along the [001], [011], and [111] growth directions. The confinement and nanowire structure substantially alter phonon distributions, resulting in an 15% to 23% reduction in heat capacity and an averaged decrease of 31% in acoustic velocities compared with bulk silicon. Based on these, we estimate an improvement up to 4 fold on thermoelectric performance due solely to the modified lattice vibrations in narrow silicon nanowires over bulk silicon.

  4. Optical biosensor based on silicon nanowire ridge waveguide

    NASA Astrophysics Data System (ADS)

    Gamal, Rania; Ismail, Yehia; Swillam, Mohamed A.

    2015-02-01

    Optical biosensors present themselves as an attractive solution for integration with the ever-trending lab-on-a-chip devices. This is due to their small size, CMOS compatibility, and invariance to electromagnetic interference. Despite their many benefits, typical optical biosensors rely on evanescent field detection, where only a small portion of the light interacts with the analyte. We propose to use a silicon nanowire ridge waveguide (SNRW) for optical biosensing. This structure is comprised of an array of silicon nanowires, with the envelope of a ridge, on an insulator substrate. The SNRW maximizes the overlap between the analyte and the incident light wave by introducing voids to the otherwise bulk structure, and strengthens the contribution of the material under test to the overall modal effective index will greatly augment the sensitivity. Additionally, the SNRW provides a fabrication convenience as it covers the entire substrate, ensuring that the etching process would not damage the substrate. FDTD simulations were conducted and showed that the percentage change in the effective index due to a 1% change in the surrounding environment was more than 170 times the amount of change perceived in an evanescent detection based bulk silicon ridge waveguide.

  5. Automatic Release of Silicon Nanowire Arrays with a High Integrity for Flexible Electronic Devices

    PubMed Central

    Wu, Luo; Li, Shuxin; He, Weiwei; Teng, Dayong; Wang, Ke; Ye, Changhui

    2014-01-01

    Automatic release and vertical transferring of silicon/silicon oxide nanowire arrays with a high integrity are demonstrated by an Ag-assisted ammonia etching method. By adding a water steaming step between Ag-assisted HF/H2O2 and ammonia etching to form a SiOx protective layer sheathing Si nanowires, we can tune the composition of the nanowires from SiOx (0 ≤ x ≤ 2) to Si nanowires. Ag plays a key role to the neat and uniform release of Si/SiOx nanowire arrays from Si wafer in the ammonia etching process. The vertical Si nanowire array device, with both sides having high-quality Ohmic contact, can be transferred to arbitrary substrates, especially on a flexible substrate. The method developed here offers a facile method to realize flexible Si nanowire array functional devices. PMID:24487460

  6. Automatic release of silicon nanowire arrays with a high integrity for flexible electronic devices.

    PubMed

    Wu, Luo; Li, Shuxin; He, Weiwei; Teng, Dayong; Wang, Ke; Ye, Changhui

    2014-01-01

    Automatic release and vertical transferring of silicon/silicon oxide nanowire arrays with a high integrity are demonstrated by an Ag-assisted ammonia etching method. By adding a water steaming step between Ag-assisted HF/H2O2 and ammonia etching to form a SiOx protective layer sheathing Si nanowires, we can tune the composition of the nanowires from SiOx (0 ≤ x ≤ 2) to Si nanowires. Ag plays a key role to the neat and uniform release of Si/SiOx nanowire arrays from Si wafer in the ammonia etching process. The vertical Si nanowire array device, with both sides having high-quality Ohmic contact, can be transferred to arbitrary substrates, especially on a flexible substrate. The method developed here offers a facile method to realize flexible Si nanowire array functional devices. PMID:24487460

  7. SERS detection and antibacterial activity from uniform incorporation of Ag nanoparticles with aligned Si nanowires

    NASA Astrophysics Data System (ADS)

    Chen, Chia-Yun; Hsu, Li-Jen; Hsiao, Po-Hsuan; Yu, Chang-Tze Ricky

    2015-11-01

    We present a facile, reliable and controllable two-steps electroless deposition for uniformly decorating the silver (Ag) nanoparticles (NPs) on the highly aspect ratio of silicon (Si) nanowire arrays. Different from the direct Ag-loading process, which is normally challenged by the non-uniform coating of Ag, the formation of Ag NPs using such innovative electroless process is no longer to be limited at top nanowire surfaces solely; instead, each Ag+/Si interface can initiate the galvanic reduction of Ag+ ions, thus resulting in the uniform formation of Ag NPs on the entire Si nanowire arrays. In addition, systematic explorations of surface-enhanced Raman scattering (SERS) capability as well as antibacterial activity of the Ag/Si-incorporated nanostructures were performed, and the optimized Ag loadings on Si nanowire-based substrates along with the kinetic investigations were further revealed, which may benefit their practical applications in sensing, medical and biological needs.

  8. Tunable metallic silicon nanowires and quantum dots with tailored dimensions and spacing

    NASA Astrophysics Data System (ADS)

    Zhang, Liangchi; Mylvaganam, Kausala

    2013-06-01

    Metallic silicon nanowire and quantum dots are promising low dimensional materials for a great range of applications. A critical issue is their quality-controlled, cost-effective fabrication. This paper presents a simple method for making seamlessly integrated tunable metallic silicon nanowires and quantum dots in the subsurface of mono-crystalline silicon by mechanical scratching. The study predicted, with the aid of the molecular dynamics analysis, that arrays of stable metallic bct-5 silicon nanowires and conductive quantum dots could be produced in the subsurface of silicon by scratching the {001} surface along a ⟨110⟩ direction. The dimension and spacing of the nanowires and quantum dots can easily be controlled by adjusting the distance between scratching tips, the size of the tips, and their depth-of-cut. It was also shown that the metallic bct-5 silicon is stable under a residual octahedral shear stress of 5 to 8 GPa.

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

    PubMed

    Wu, Yuchen; Su, Bin; Jiang, Lei

    2012-10-23

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

  10. Vapor-Induced Solid-Liquid-Solid Process for Silicon-based Nanowire Growth

    SciTech Connect

    Zhang, Jiguang; Liu, Jun; Wang, Donghai; Choi, Daiwon; Fifield, Leonard S.; Wang, Chong M.; Xia, Guanguang; Nie, Zimin; Yang, Zhenguo; Pederson, Larry R.; Graff, Gordon L.

    2010-03-10

    Silicon based nanowires have been grown from commercial silicon powders under conditions of differing oxygen and carbon activities. Nanowires grown in the presence of carbon sources consisted of a crystalline SiC core with an amorphous SiOx shell. The thickness of SiOx shell decreased as the oxygen concentration in the precursor gases was lowered. Nanowires grown in a carbon-free environment consisted of amorphous silicon oxide with a typical composition of SiO1.8. The growth rate of nanowires decreased with decreasing oxygen content in the precursor gases. SiO1.8 nanowires exhibited an initial discharge capacity of ~ 1,300 mAh/g and better stability than those of silicon powders. A Vapor Induced Solid-Liquid-Solid (VI-SLS) mechanism is proposed to explain the nanowire growth (including silicon and other metal based nanowires) from powder sources. In this approach, both a gas source and a solid powder source are required for nanowire growth. This mechanism is consistent with experimental observations and can also be used to guide the design and growth of other nanowires.

  11. 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

  12. Silicon nanowires integrated with CMOS circuits for biosensing application

    NASA Astrophysics Data System (ADS)

    Jayakumar, G.; Asadollahi, A.; Hellström, P.-E.; Garidis, K.; Östling, M.

    2014-08-01

    We describe a silicon nanowire (SiNW) biosensor fabricated in a fully depleted SOI CMOS process. The sensor array consists of N by N pixel matrix (N2 pixels or test sites) and 8 input-output (I/O) pins. In each pixel a single crystalline SiNW with 75 by 20 nm cross-section area is defined using sidewall transfer lithography in the SOI layer. The key advantage of the design is that each individual SiNWs can be read-out sequentially and used for real-time charge based detection of molecules in liquids or gases.

  13. 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.

  14. First-principles study of structural & electronic properties of pyramidal silicon nanowire

    NASA Astrophysics Data System (ADS)

    Jariwala, Pinank; Singh, Deobrat; Sonvane, Y. A.; Gupta, Sanjeev K.; Thakor, P. B.

    2016-05-01

    We have investigated the stable structural and electronic properties of Silicon (Si) nanowires having different cross-sections with 5-7 Si atoms per unit cell. These properties of the studied Si nanowires were significantly changed from those of diamond bulk Si structure. The binding energy increases as increasing atoms number per unit cell in different SiNWs structures. All the nanowires structures are behave like metallic rather than semiconductor in bulk systems. In general, the number of conduction channels increases when the nanowire becomes thicker. The density of charge revealed delocalized metallic bonding for all studied Si nanowires.

  15. Displacement detection of silicon nanowires by polarization-enhanced fiber-optic interferometry

    SciTech Connect

    Nichol, John M.; Budakian, Raffi; Hemesath, Eric R.; Lauhon, Lincoln J.

    2008-11-10

    We describe the displacement detection of freestanding silicon [111] nanowires by fiber-optic interferometry. We observe approximately a 50-fold enhancement in the scattered intensity for nanowires 40-60 nm in diameter for incident light polarized parallel to the nanowire axis, as compared to perpendicular polarization. This enhancement enables us to achieve a displacement sensitivity of 0.5 pm/{radical}(Hz) for 15 {mu}W of light incident on the nanowire. The nanowires exhibit ultralow mechanical dissipation in the range of (2x10{sup -15})-(2x10{sup -14}) kg/s and could be used as mechanical sensors for ultrasensitive scanning probe force measurements.

  16. Thermal Transport in Silicon Nanowires at High Temperature up to 700 K.

    PubMed

    Lee, Jaeho; Lee, Woochul; Lim, Jongwoo; Yu, Yi; Kong, Qiao; Urban, Jeffrey J; Yang, Peidong

    2016-07-13

    Thermal transport in silicon nanowires has captured the attention of scientists for understanding phonon transport at the nanoscale, and the thermoelectric figure-of-merit (ZT) reported in rough nanowires has inspired engineers to develop cost-effective waste heat recovery systems. Thermoelectric generators composed of silicon target high-temperature applications due to improved efficiency beyond 550 K. However, there have been no studies of thermal transport in silicon nanowires beyond room temperature. High-temperature measurements also enable studies of unanswered questions regarding the impact of surface boundaries and varying mode contributions as the highest vibrational modes are activated (Debye temperature of silicon is 645 K). Here, we develop a technique to investigate thermal transport in nanowires up to 700 K. Our thermal conductivity measurements on smooth silicon nanowires show the classical diameter dependence from 40 to 120 nm. In conjunction with Boltzmann transport equation, we also probe an increasing contribution of high-frequency phonons (optical phonons) in smooth silicon nanowires as the diameter decreases and the temperature increases. Thermal conductivity of rough silicon nanowires is significantly reduced throughout the temperature range, demonstrating a potential for efficient thermoelectric generation (e.g., ZT = 1 at 700 K). PMID:27243378

  17. High efficiency silicon solar cell based on asymmetric nanowire

    PubMed Central

    Ko, Myung-Dong; Rim, Taiuk; Kim, Kihyun; Meyyappan, M.; Baek, Chang-Ki

    2015-01-01

    Improving the efficiency of solar cells through novel materials and devices is critical to realize the full potential of solar energy to meet the growing worldwide energy demands. We present here a highly efficient radial p-n junction silicon solar cell using an asymmetric nanowire structure with a shorter bottom core diameter than at the top. A maximum short circuit current density of 27.5 mA/cm2 and an efficiency of 7.53% were realized without anti-reflection coating. Changing the silicon nanowire (SiNW) structure from conventional symmetric to asymmetric nature improves the efficiency due to increased short circuit current density. From numerical simulation and measurement of the optical characteristics, the total reflection on the sidewalls is seen to increase the light trapping path and charge carrier generation in the radial junction of the asymmetric SiNW, yielding high external quantum efficiency and short circuit current density. The proposed asymmetric structure has great potential to effectively improve the efficiency of the SiNW solar cells. PMID:26152914

  18. Orientation, alignment, and polytype control in epitaxial growth of SiC nanowires for electronics application in harsh environments

    NASA Astrophysics Data System (ADS)

    Koshka, Yaroslav; Thirumalai, Rooban Venkatesh K. G.; Krishnan, Bharat K.; Levin, Igor; Merrett, J. Neil; Davydov, Albert V.

    2013-09-01

    SiC nanowires (NWs) are attractive building blocks for the next generation electronic devices since silicon carbide is a wide bandgap semiconductor with high electrical breakdown strength, radiation resistance, mechanical strength, thermal conductivity, chemical stability and biocompatibility. Epitaxial growth using metal-catalyst-based vapor-liquid-solid mechanism was employed for SiC NW growth in this work. 4H-SiC substrates having different crystallographic orientations were used in order to control NW alignment and polytype. A new technique based on vapor-phase delivery of the metal catalyst was developed to facilitate control of the NW density. Both 4H and 3C polytypes with a strong stacking disorder were obtained. The 4H and 3C NWs had different orientations with respect to the substrate. 4H NWs grew perpendicular to the c-plane of the substrate. The stacking faults (SFs) in these nanowires were perpendicular to the [0001] nanowire axes. All 3C NWs grew at 20° with respect to the substrate c-plane, and their projections on the c-plane corresponded to one of the six equivalent ⟨101-0⟩ crystallographic directions. All six orientations were obtained simultaneously when growing NWs on the (0001) substrate surface, while only one or two NW orientations were observed when growing NWs on any particular crystallographic plane parallel to the c-axis of the substrate. Growth on {101-0} surfaces resulted in only one NW orientation, thereby producing well-aligned NW arrays. Preliminary measurements of the NW electrical conductivity are reported utilizing two-terminal device geometry.

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

    PubMed

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

    2008-05-01

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

  20. Bulk synthesis of silicon nanowires using a low-temperature vapor-liquid-solid method

    NASA Astrophysics Data System (ADS)

    Sunkara, M. K.; Sharma, S.; Miranda, R.; Lian, G.; Dickey, E. C.

    2001-09-01

    Silicon nanowires will find applications in nanoscale electronics and optoelectronics both as active and passive components. Here, we demonstrate a low-temperature vapor-liquid-solid synthesis method that uses liquid-metal solvents with low solubility for silicon and other elemental semiconductor materials. This method eliminates the usual requirement of quantum-sized droplets in order to obtain quantum-scale one-dimensional structures. Specifically, we synthesized silicon nanowires with uniform diameters distributed around 6 nm using gallium as the molten solvent, at temperatures less than 400 °C in hydrogen plasma. The potential exists for bulk synthesis of silicon nanowires at temperatures significantly lower than 400 °C. Gallium forms a eutectic with silicon near room temperature and offers a wide temperature range for bulk synthesis of nanowires. These properties are important for creating monodispersed one-dimensional structures capable of yielding sharp hetero- or homointerfaces.

  1. Assessing charge carrier trapping in silicon nanowires using picosecond conductivity measurements.

    PubMed

    Ulbricht, Ronald; Kurstjens, Rufi; Bonn, Mischa

    2012-07-11

    Free-standing semiconductor nanowires on bulk substrates are increasingly being explored as building blocks for novel optoelectronic devices such as tandem solar cells. Although carrier transport properties, such as mobility and trap densities, are essential for such applications, it has remained challenging to quantify these properties. Here, we report on a method that permits the direct, contact-free quantification of nanowire carrier diffusivity and trap densities in thin (∼25 nm wide) silicon nanowires-without any additional processing steps such as transfer of wires onto a substrate. The approach relies on the very different terahertz (THz) conductivity response of photoinjected carriers within the silicon nanowires from those in the silicon substrate. This allows quantifying both the picosecond dynamics and the efficiency of charge carrier transport from the silicon nanowires into the silicon substrate. Varying the excitation density allows for quantification of nanowire trap densities: for sufficiently low excitation fluences the diffusion process stalls because the majority of charge carriers become trapped at nanowire surface defects. Using a model that includes these effects, we determine both the diffusion constant and the nanowire trap density. The trap density is found to be orders of magnitude larger than the charge carrier density that would be generated by AM1.5 sunlight. PMID:22738182

  2. A silicon-nanowire memory driven by optical gradient force induced bistability

    NASA Astrophysics Data System (ADS)

    Dong, B.; Cai, H.; Chin, L. K.; Huang, J. G.; Yang, Z. C.; Gu, Y. D.; Ng, G. I.; Ser, W.; Kwong, D. L.; Liu, A. Q.

    2015-12-01

    In this paper, a bistable optical-driven silicon-nanowire memory is demonstrated, which employs ring resonator to generate optical gradient force over a doubly clamped silicon-nanowire. Two stable deformation positions of a doubly clamped silicon-nanowire represent two memory states ("0" and "1") and can be set/reset by modulating the light intensity (<3 mW) based on the optical force induced bistability. The time response of the optical-driven memory is less than 250 ns. It has applications in the fields of all optical communication, quantum computing, and optomechanical circuits.

  3. A silicon-nanowire memory driven by optical gradient force induced bistability

    SciTech Connect

    Dong, B.; Cai, H. Gu, Y. D.; Kwong, D. L.; Chin, L. K.; Ng, G. I.; Ser, W.; Huang, J. G.; Yang, Z. C.; Liu, A. Q.

    2015-12-28

    In this paper, a bistable optical-driven silicon-nanowire memory is demonstrated, which employs ring resonator to generate optical gradient force over a doubly clamped silicon-nanowire. Two stable deformation positions of a doubly clamped silicon-nanowire represent two memory states (“0” and “1”) and can be set/reset by modulating the light intensity (<3 mW) based on the optical force induced bistability. The time response of the optical-driven memory is less than 250 ns. It has applications in the fields of all optical communication, quantum computing, and optomechanical circuits.

  4. DRIE process optimization to fabricate vertical silicon nanowires using gold nanoparticles as masks

    NASA Astrophysics Data System (ADS)

    Bui, Thanh Tung; Phuc Tu, Hoan; Chien Dang, Mau

    2015-12-01

    Silicon nanowires have applications in various fields, e.g. vertical transistors, chemical or biological sensors, energy conversion, and storage devices. So far they have typically been obtained by bottom-up methods such as vapor-liquid-solid (VLS) synthesis, starting from metal nanoparticles. In this study, silicon nanowires are fabricated by dry reactive-ion etching using gold nanoparticles as a mask. Starting with the Bosch process, the cycle of SF6 plasma etching and C4F8 plasma deposition was optimized to control the quality of the resulting silicon nanowires.

  5. Manganese dioxide modified silicon nanowires and their excellent catalysis in the decomposition of methylene blue

    NASA Astrophysics Data System (ADS)

    Gao, Weiwei; Shao, Mingwang; Yang, Li; Zhuo, Shujuan; Ye, Shiyong; Lee, Shuit-tong

    2012-02-01

    A redox between hydrofluoric acid and ammonium fluoride-treated silicon nanowires and potassium permanganate solution was investigated. The results showed that MnO2 nanoparticles might grow on the surface of silicon nanowires, which was confirmed with the transmission electron microscope. These MnO2 modified silicon nanowires were employed as catalysts in the decomposition of methylene blue using sodium borohydride as the reducing agent, which exhibited excellent catalysis with its reaction rate 6 times larger than the unsupported MnO2.

  6. 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

  7. 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

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

    PubMed

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

    2015-07-01

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

  9. The mechanisms of platinum-catalyzed silicon nanowire growth

    NASA Astrophysics Data System (ADS)

    Hibst, N.; Knittel, P.; Biskupek, J.; Kranz, C.; Mizaikoff, B.; Strehle, S.

    2016-02-01

    Platinum (Pt) has been known as a catalyst material for vapor-liquid-solid (VLS) synthesis since the mid 1960s with the potential to grow electronic grade silicon nanowires (SiNWs). In contrast to gold-based growth, Pt-catalyzed SiNW synthesis has rarely been studied, most likely due to higher synthesis temperatures and the formation of multiple Pt silicide phases. Here we present the growth of SiNWs from a Pt catalyst deposited by a focused ion or electron beam, which opens new strategies for the assembly of Pt-catalyzed SiNW-based devices, as well as SiNW growth from Pt nanoparticles and thin films. We show that single-crystalline SiNWs exhibit either the well-known catalyst tip or a polycrystalline silicon tip so far not reported. The local Pt concentration was found to be one key parameter triggering the growth mode. The proposed growth model for both types of SiNWs is based on a solid-state silicide-mediated crystallization rather than VLS. The discussion of the growth modes is supported by a variation of several growth parameters and SiNW synthesis using the substrate materials silicon nitride, single-crystalline silicon, fused silica, and sapphire.

  10. Odd electron diffraction patterns in silicon nanowires and silicon thin films explained by microtwins and nanotwins

    PubMed Central

    Cayron, Cyril; Den Hertog, Martien; Latu-Romain, Laurence; Mouchet, Céline; Secouard, Christopher; Rouviere, Jean-Luc; Rouviere, Emmanuelle; Simonato, Jean-Pierre

    2009-01-01

    Odd electron diffraction patterns (EDPs) have been obtained by transmission electron microscopy (TEM) on silicon nanowires grown via the vapour–liquid–solid method and on silicon thin films deposited by electron beam evaporation. Many explanations have been given in the past, without consensus among the scientific community: size artifacts, twinning artifacts or, more widely accepted, the existence of new hexagonal Si phases. In order to resolve this issue, the microstructures of Si nanowires and Si thin films have been characterized by TEM, high-resolution transmission electron microscopy (HRTEM) and high-resolution scanning transmission electron microscopy. Despite the differences in the geometries and elaboration processes, the EDPs of the materials show great similarities. The different hypotheses reported in the literature have been investigated. It was found that the positions of the diffraction spots in the EDPs could be reproduced by simulating a hexagonal structure with c/a = 12(2/3)1/2, but the intensities in many EDPs remained unexplained. Finally, it was established that all the experimental data, i.e. EDPs and HRTEM images, agree with a classical cubic silicon structure containing two microstructural defects: (i) overlapping Σ3 microtwins which induce extra spots by double diffraction, and (ii) nanotwins which induce extra spots as a result of streaking effects. It is concluded that there is no hexagonal phase in the Si nanowires and the Si thin films presented in this work. PMID:22477767

  11. Nanoscale contact engineering for Silicon/Silicide nanowire devices

    NASA Astrophysics Data System (ADS)

    Lin, Yung-Chen

    Metal silicides have been used in silicon technology as contacts to achieve high device performance and desired device functions. The growth and applications of silicide materials have recently attracted increasing interest for nanoscale device applications. Nanoscale silicide materials have been demonstrated with various synthetic approaches. Solid state reaction wherein high quality silicides form through diffusion of metal atoms into silicon nano-templates and the subsequent phase transformation caught significant attention for the fabrication of nanoscale Si devices. Very interestingly, studies on the diffusion and phase transformation processes at nanoscale have indicated possible deviations from the bulk and the thin film system. Here we studied growth kinetics, electronic properties and device applications of nanoscale silicides formed through solid state reaction. We have grown single crystal PtSi nanowires and PtSi/Si/PtSi nanowire heterostructures through solid state reaction. TEM studies show that the heterostructures have atomically sharp interfaces free of defects. Electrical measurement of PtSi nanowires shows a low resistivity of ˜28.6 μΩ·cm and a high breakdown current density beyond 108 A/cm2. Furthermore, using single-crystal PtSi/Si/PtSi nanowire heterostructures with atomically clean interfaces, we have fabricated p-channel enhancement mode transistors with the best reported performance for intrinsic silicon nanowires to date. In our results, silicide can provide a clean and no Fermi level pinning interface and then silicide can form Ohmic-contact behavior by replacing the source/drain metal with PtSi. It has been proven by our experiment by contacting PtSi with intrinsic Si nanowires (no extrinsic doping) to achieve high performance p-channel device. By utilizing the same approach, single crystal MnSi nanowires and MnSi/Si/MnSi nanowire heterojunction with atomically sharp interfaces can also been grown. Electrical transport studies on Mn

  12. Beam-deposited platinum as versatile catalyst for bottom-up silicon nanowire synthesis

    SciTech Connect

    Hibst, N.; Strehle, S.; Knittel, P.; Kranz, C.; Mizaikoff, B.

    2014-10-13

    The controlled localized bottom-up synthesis of silicon nanowires on arbitrarily shaped surfaces is still a persisting challenge for functional device assembly. In order to address this issue, electron beam and focused ion beam-assisted catalyst deposition have been investigated with respect to platinum expected to form a PtSi alloy catalyst for a subsequent bottom-up nanowire synthesis. The effective implementation of pure platinum nanoparticles or thin films for silicon nanowire growth has been demonstrated recently. Beam-deposited platinum contains significant quantities of amorphous carbon due to the organic precursor and gallium ions for a focused ion beam-based deposition process. Nevertheless, silicon nanowires could be grown on various substrates regardless of the platinum purity. Additionally, p-type doping could be realized with diborane whereas n-type doping suppressed a nanowire growth. The rational utilization of this beam-assisted approach enables us to control the localized synthesis of single silicon nanowires at planar surfaces but succeeded also in single nanowire growth at the three-dimensional apex of an atomic force microscopy tip. Therefore, this catalyst deposition method appears to be a unique extension of current technologies to assemble complex nanowire-based devices.

  13. Glucose-Derived Porous Carbon-Coated Silicon Nanowires as Efficient Electrodes for Aqueous Micro-Supercapacitors.

    PubMed

    Devarapalli, Rami Reddy; Szunerits, Sabine; Coffinier, Yannick; Shelke, Manjusha V; Boukherroub, Rabah

    2016-02-24

    In this study, we report on carbon coating of vertically aligned silicon nanowire (SiNWs) arrays via a simple hydrothermal process using glucose as carbon precursor. Using this process, a thin carbon layer is uniformly deposited on the SiNWs. Under optimized conditions, the coated SiNWs electrode showed better electrochemical energy storage capacity as well as exceptional stability in aqueous system as compared to uncoated SiNWs. The as-measured capacitance reached 25.64 mF/cm(2) with a good stability up to 25000 charging/discharging cycles in 1 M Na2SO4 aqueous solution. PMID:26866275

  14. Synthesize of barium ferrite nanowire array by self-fabricated porous silicon template

    NASA Astrophysics Data System (ADS)

    Zheng, Hui; Han, Mangui; Deng, Jiangxia; Zheng, Liang; Wu, Jun; Deng, Longjiang; Qin, Huibin

    2014-08-01

    In this work, we synthesize barium ferrite (BaFe12O19) nanowire array in porous silicon template. The porous silicon templates are prepared via gold-assisted chemical etching method. The gold (Au) nanoparticles with mean diameter of 30 nm and distance of 100 nm were ordered on the surface of Si substrate through the Polystyrene (510000)-block-poly (2-vinylpyridine) (31000) (PS510000-b-P2VP31000) diblock copolymer. Porous silicon templates with mean diameter of 500 nm and distance between the pores of 500 nm were fabricated by two etching steps. BaFe12O19 nanowires with mean diameter of 200 nm were synthesized into a porous silicon template by a sol-gel method. Magnetic hysteresis loops show an isotropic feature of the BaFe12O19 nanowires array. The coercivity (Hc) and squareness ratio (Mr/Ms) of nanowire arrays are 2560 Oe and 0.6, respectively.

  15. Directed deposition of silicon nanowires using neopentasilane as precursor and gold as catalyst

    PubMed Central

    Kämpken, Britta; Wulf, Verena; Auner, Norbert; Winhold, Marcel; Huth, Michael; Rhinow, Daniel

    2012-01-01

    Summary In this work the applicability of neopentasilane (Si(SiH3)4) as a precursor for the formation of silicon nanowires by using gold nanoparticles as a catalyst has been explored. The growth proceeds via the formation of liquid gold/silicon alloy droplets, which excrete the silicon nanowires upon continued decomposition of the precursor. This mechanism determines the diameter of the Si nanowires. Different sources for the gold nanoparticles have been tested: the spontaneous dewetting of gold films, thermally annealed gold films, deposition of preformed gold nanoparticles, and the use of “liquid bright gold”, a material historically used for the gilding of porcelain and glass. The latter does not only form gold nanoparticles when deposited as a thin film and thermally annealed, but can also be patterned by using UV irradiation, providing access to laterally structured layers of silicon nanowires. PMID:23019549

  16. Silicon oxide nanowire growth mechanisms revealed by real-time electron microscopy

    NASA Astrophysics Data System (ADS)

    Kolíbal, Miroslav; Novák, Libor; Shanley, Toby; Toth, Milos; Šikola, Tomáš

    2015-12-01

    Growth of one-dimensional materials is possible through numerous mechanisms that affect the nanowire structure and morphology. Here, we explain why a wide range of morphologies is observed when silicon oxide nanowires are grown on silicon substrates using liquid gallium catalyst droplets. We show that a gallium oxide overlayer is needed for nanowire nucleation at typical growth temperatures, and that it can decompose during growth and, hence, dramatically alter the nanowire morphology. Gallium oxide decomposition is attributed to etching caused by hydrogen that can be supplied by thermal dissociation of H2O (a common impurity). We show that H2O dissociation is catalyzed by silicon substrates at temperatures as low as 320 °C, identify the material supply pathways and processes that rate-limit nanowire growth under dry and wet atmospheres, and present a detailed growth model that explains contradictory results reported in prior studies. We also show that under wet atmospheres the Ga droplets can be mobile and promote nanowire growth as they traverse the silicon substrate.Growth of one-dimensional materials is possible through numerous mechanisms that affect the nanowire structure and morphology. Here, we explain why a wide range of morphologies is observed when silicon oxide nanowires are grown on silicon substrates using liquid gallium catalyst droplets. We show that a gallium oxide overlayer is needed for nanowire nucleation at typical growth temperatures, and that it can decompose during growth and, hence, dramatically alter the nanowire morphology. Gallium oxide decomposition is attributed to etching caused by hydrogen that can be supplied by thermal dissociation of H2O (a common impurity). We show that H2O dissociation is catalyzed by silicon substrates at temperatures as low as 320 °C, identify the material supply pathways and processes that rate-limit nanowire growth under dry and wet atmospheres, and present a detailed growth model that explains

  17. Conductive-probe atomic force microscopy characterization of silicon nanowire

    PubMed Central

    2011-01-01

    The electrical conduction properties of lateral and vertical silicon nanowires (SiNWs) were investigated using a conductive-probe atomic force microscopy (AFM). Horizontal SiNWs, which were synthesized by the in-plane solid-liquid-solid technique, are randomly deployed into an undoped hydrogenated amorphous silicon layer. Local current mapping shows that the wires have internal microstructures. The local current-voltage measurements on these horizontal wires reveal a power law behavior indicating several transport regimes based on space-charge limited conduction which can be assisted by traps in the high-bias regime (> 1 V). Vertical phosphorus-doped SiNWs were grown by chemical vapor deposition using a gold catalyst-driving vapor-liquid-solid process on higly n-type silicon substrates. The effect of phosphorus doping on the local contact resistance between the AFM tip and the SiNW was put in evidence, and the SiNWs resistivity was estimated. PMID:21711623

  18. Nanoscale contact engineering for Silicon/Silicide nanowire devices

    NASA Astrophysics Data System (ADS)

    Lin, Yung-Chen

    Metal silicides have been used in silicon technology as contacts to achieve high device performance and desired device functions. The growth and applications of silicide materials have recently attracted increasing interest for nanoscale device applications. Nanoscale silicide materials have been demonstrated with various synthetic approaches. Solid state reaction wherein high quality silicides form through diffusion of metal atoms into silicon nano-templates and the subsequent phase transformation caught significant attention for the fabrication of nanoscale Si devices. Very interestingly, studies on the diffusion and phase transformation processes at nanoscale have indicated possible deviations from the bulk and the thin film system. Here we studied growth kinetics, electronic properties and device applications of nanoscale silicides formed through solid state reaction. We have grown single crystal PtSi nanowires and PtSi/Si/PtSi nanowire heterostructures through solid state reaction. TEM studies show that the heterostructures have atomically sharp interfaces free of defects. Electrical measurement of PtSi nanowires shows a low resistivity of ˜28.6 μΩ·cm and a high breakdown current density beyond 108 A/cm2. Furthermore, using single-crystal PtSi/Si/PtSi nanowire heterostructures with atomically clean interfaces, we have fabricated p-channel enhancement mode transistors with the best reported performance for intrinsic silicon nanowires to date. In our results, silicide can provide a clean and no Fermi level pinning interface and then silicide can form Ohmic-contact behavior by replacing the source/drain metal with PtSi. It has been proven by our experiment by contacting PtSi with intrinsic Si nanowires (no extrinsic doping) to achieve high performance p-channel device. By utilizing the same approach, single crystal MnSi nanowires and MnSi/Si/MnSi nanowire heterojunction with atomically sharp interfaces can also been grown. Electrical transport studies on Mn

  19. Directed assembly of gold nanowires on silicon via reorganization and simultaneous fusion of randomly distributed gold nanoparticles.

    PubMed

    Reinhardt, Hendrik M; Bücker, Kerstin; Hampp, Norbert A

    2015-05-01

    Laser-induced reorganization and simultaneous fusion of nanoparticles is introduced as a versatile concept for pattern formation on surfaces. The process takes advantage of a phenomenon called laser-induced periodic surface structures (LIPSS) which originates from periodically alternating photonic fringe patterns in the near-field of solids. Associated photonic fringe patterns are shown to reorganize randomly distributed gold nanoparticles on a silicon wafer into periodic gold nanostructures. Concomitant melting due to optical heating facilitates the formation of continuous structures such as periodic gold nanowire arrays. Generated patterns can be converted into secondary structures using directed assembly or self-organization. This includes for example the rotation of gold nanowire arrays by arbitrary angles or their fragmentation into arrays of aligned gold nanoparticles. PMID:25969286

  20. Anomalous Stagewise Lithiation of Gold-Coated Silicon Nanowires: A Combined In Situ Characterization and First-Principles Study.

    PubMed

    Chou, Chia-Yun; Seo, Jong-Hyun; Tsai, Yu-Hao; Ahn, Jae-Pyoung; Paek, Eunsu; Cho, Mann-Ho; Choi, In-Suk; Hwang, Gyeong S

    2015-08-12

    Through a combined density functional theory and in situ scanning electron microscopy study, the effects of presence of gold (Au) spreading on the lithiation process of silicon nanowire (SiNW) were systematically examined. Different from a pristine SiNW, an Au-coated SiNW (Au-SiNW) is lithiated in three distinct stages; Li atoms are found to be incorporated preferentially in the Au shell, whereas the thin AuSi interface layer may serve as a facile diffusion path along the nanowire axial direction, followed by the prompt lithiation of the Si core in the radial direction. The underlying mechanism of the intriguing stagewise lithiation behavior is explained through our theoretical analysis, which appears well-aligned with the experimental evidence. PMID:26194088

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

    PubMed

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

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

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

    PubMed

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

    2016-07-15

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

  4. Atomistic design of thermoelectric properties of silicon nanowires.

    PubMed

    Vo, Trinh T M; Williamson, Andrew J; Lordi, Vincenzo; Galli, Giulia

    2008-04-01

    We present predictions of the thermoelectric figure of merit ( ZT) of Si nanowires with diameter up to 3 nm, based upon the Boltzman transport equation and ab initio electronic structure calculations. We find that ZT depends significantly on the wire growth direction and surface reconstruction, and we discuss how these properties can be tuned to select silicon based nanostructures with combined n-type and p-type optimal ZT. Our calculations show that only by reducing the ionic thermal conductivity by about 2 or 3 orders of magnitudes with respect to bulk values, one may attain ZT larger than 1, for 1 or 3 nm wires, respectively. We also find that ZT of p-doped wires is considerably smaller than that of their n-doped counterparts with the same size and geometry. PMID:18302325

  5. Self-stopping effects of lithium penetration into silicon nanowires.

    PubMed

    Lang, Li; Dong, Chuanding; Chen, Guohong; Yang, Jihui; Gu, Xiao; Xiang, Hongjun; Wu, Ruqian; Gong, Xingao

    2013-12-21

    Using first-principles molecular dynamics simulations, we demonstrate that the penetration of lithium atoms into a silicon nanowire (SiNW) self-stops once a metallic amorphous Li-Si shell forms. This explains the extended life of crystalline Si cores in SiNW battery electrodes observed in experiments. Metallic Li-Si shells grasp Li atoms and prohibit them from directly segregating through interstitial channels toward the crystalline center of SiNWs. Meanwhile, high pressure develops on the core as it shrinks, due to the expansion and tension in the amorphous shell, which eventually frustrate the step-forward amorphization. We also elucidate the reasons why H-passivated SiNWs are not suitable for studies of lithiation processes. PMID:24162503

  6. Silicon nanowires for high-sensitivity glucose detection

    NASA Astrophysics Data System (ADS)

    Chen, Weiwei; Yao, Hui; Tzang, Chi Hung; Zhu, Junjie; Yang, Mengsu; Lee, Shuit-Tong

    2006-05-01

    Silicon nanowires (SiNWs) were investigated as supporting matrices for enzyme immobilization to construct glucose biosensors. Glucose oxidase was adsorbed onto SiNWs after different treatments, either as grown, HF etched, or carboxylic acid (COOH) functionalized. The amperometric biosensor with COOH-functionalized SiNWs performed the best with a detection limit of 0.01mM glucose (signal-to-noise ratio=3). For real-time detection of glucose, SiNW biosensor showed a linear response in the range of 0.1-15mM. This work demonstrates the utility of SiNWs as a biosensor component and provides a general method to modify the surface of semiconducting nanomaterials for potential biomedical applications.

  7. Epitaxial insertion of gold silicide nanodisks during the growth of silicon nanowires.

    PubMed

    Um, Han-Don; Jee, Sang-Won; Park, Kwang-Tae; Jung, Jin-Young; Guo, Zhongyi; Lee, Jung-Ho

    2011-07-01

    Nanodisk-shaped, single-crystal gold silicide heterojunctions were inserted into silicon nanowires during vapor-liquid-solid growth using Au as a catalyst within a specific range of chlorine-to-hydrogen atomic ratio. The mechanism of nanodisk formation has been investigated by changing the source gas ratio of SiCl4 to H2. We report that an over-supply of silicon into the Au-Si liquid alloy leads to highly supersaturated solution and enhances the precipitation of Au in the silicon nanowires due to the formation of unstable phases within the liquid alloy. It is shown that the gold precipitates embedded in the silicon nanowires consisted of a metastable gold silicide. Interestingly, faceting of gold silicide was observed at the Au/Si interfaces, and silicon nanowires were epitaxially grown on the top of the nanodisk by vapor-liquid-solid growth. High resolution transmission electron microscopy confirmed that gold silicide nanodisks are epitaxially connected to the silicon nanowires in the direction of growth direction. These gold silicide nanodisks would be useful as nanosized electrical junctions for future applications in nanowire interconnections. PMID:22121669

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

    PubMed

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

    2010-09-16

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

  9. Tensile and compressive mechanical behavior of twinned silicon carbide nanowires

    SciTech Connect

    Wang, Zhiguo; Li, Jingbo; Gao, Fei; Weber, William J.

    2010-04-01

    Molecular dynamics simulations with the Tersoff potential were used to study the response of twinned SiC nanowires under tensile and compressive strains. The critical strain of the twinned nanowires can be enhanced by twin-stacking faults, and their critical strains are larger than those of perfect nanowires with the same diameters. Under axial tensile strain, the bonds of the nanowires are just stretched before failure. The failure behavior is found to depend on the twin segment thickness and the diameter of the nanowires. An atomic chain is observed for the thin nanowires with small twin segment thickness under tension strain. Under axial compressive strain, the collapse of the twinned SiC nanowires exhibits two differently failure modes, depending on the length and diameter of the nanowires, i.e. shell buckling for short length nanowires and columnar buckling for longer length nanowires.

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

    PubMed

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

    2016-05-11

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

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

    PubMed

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

    2015-01-01

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

  12. Transparent, high-performance thin-film transistors with an InGaZnO/aligned-SnO2 -nanowire composite and their application in photodetectors.

    PubMed

    Liu, Xingqiang; Liu, Xi; Wang, Jingli; Liao, Chongnan; Xiao, Xiangheng; Guo, Shishang; Jiang, Changzhong; Fan, Zhiyong; Wang, Ti; Chen, Xiaoshuang; Lu, Wei; Hu, Weida; Liao, Lei

    2014-11-19

    A high mobility of 109.0 cm(2) V(-1) s(-1) is obtained by thin-film transistors (TFTs) comprising a composite made by aligning SnO2 nanowires (NWs) in amorphous InGaZnO (a-IGZO) thin films. This composite TFT reaches an on-current density of 61.4 μA μm(-1) with a 10 μm channel length. Its performance surpasses that of single-crystalline InGaZnO and is comparable with that of polycrystalline silicon. PMID:25236580

  13. Filter-free image sensor pixels comprising silicon nanowires with selective color absorption.

    PubMed

    Park, Hyunsung; Dan, Yaping; Seo, Kwanyong; Yu, Young J; Duane, Peter K; Wober, Munib; Crozier, Kenneth B

    2014-01-01

    The organic dye filters of conventional color image sensors achieve the red/green/blue response needed for color imaging, but have disadvantages related to durability, low absorption coefficient, and fabrication complexity. Here, we report a new paradigm for color imaging based on all-silicon nanowire devices and no filters. We fabricate pixels consisting of vertical silicon nanowires with integrated photodetectors, demonstrate that their spectral sensitivities are governed by nanowire radius, and perform color imaging. Our approach is conceptually different from filter-based methods, as absorbed light is converted to photocurrent, ultimately presenting the opportunity for very high photon efficiency. PMID:24588103

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

    PubMed

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

    2015-09-30

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

  15. Chemically Etched Silicon Nanowires as Anodes for Lithium-Ion Batteries

    SciTech Connect

    West, Hannah Elise

    2015-08-01

    This study focused on silicon as a high capacity replacement anode for Lithium-ion batteries. The challenge of silicon is that it expands ~270% upon lithium insertion which causes particles of silicon to fracture, causing the capacity to fade rapidly. To account for this expansion chemically etched silicon nanowires from the University of Maine were studied as anodes. They were built into electrochemical half-cells and cycled continuously to measure the capacity and capacity fade.

  16. Comparison of ordered and disordered silicon nanowire arrays: experimental evidence of photonic crystal modes.

    PubMed

    Dhindsa, Navneet; Saini, Simarjeet S

    2016-05-01

    We experimentally compared the reflectance between ordered and disordered silicon nanowires to observe the evidence of photonic crystal modes. For similar diameters, the resonance peaks for the ordered nanowires at a spacing of 400 nm was at a shorter wavelength than the disordered nanowires, consistent to the excitation of photonic crystal modes. Furthermore, the resonant wavelength didn't shift while changing the density of the disordered nanowires, whereas there was a significant shift observed in the ordered ones. At an ordered spacing of 800 nm, the resonance wavelength approached that of the disordered structures, indicating that the ordered structures were starting to behave like individual waveguides. To our knowledge, this is the first direct experimental observation of photonic crystal modes in vertical periodic silicon nanowire arrays. PMID:27128070

  17. A new approach for two-terminal electronic memory devices - Storing information on silicon nanowires

    NASA Astrophysics Data System (ADS)

    Saranti, Konstantina; Alotaibi, Sultan; Paul, Shashi

    2016-06-01

    The work described in this paper focuses on the utilisation of silicon nanowires as the information storage element in flash-type memory devices. Silicon nanostructures have attracted attention due to interesting electrical and optical properties, and their potential integration into electronic devices. A detailed investigation of the suitability of silicon nanowires as the charge storage medium in two-terminal non-volatile memory devices are presented in this report. The deposition of the silicon nanostructures was carried out at low temperatures (less than 400 °C) using a previously developed a novel method within our research group. Two-terminal non-volatile (2TNV) memory devices and metal-insulator-semiconductor (MIS) structures containing the silicon nanowires were fabricated and an in-depth study of their characteristics was carried out using current-voltage and capacitance techniques.

  18. A new approach for two-terminal electronic memory devices - Storing information on silicon nanowires.

    PubMed

    Saranti, Konstantina; Alotaibi, Sultan; Paul, Shashi

    2016-01-01

    The work described in this paper focuses on the utilisation of silicon nanowires as the information storage element in flash-type memory devices. Silicon nanostructures have attracted attention due to interesting electrical and optical properties, and their potential integration into electronic devices. A detailed investigation of the suitability of silicon nanowires as the charge storage medium in two-terminal non-volatile memory devices are presented in this report. The deposition of the silicon nanostructures was carried out at low temperatures (less than 400 °C) using a previously developed a novel method within our research group. Two-terminal non-volatile (2TNV) memory devices and metal-insulator-semiconductor (MIS) structures containing the silicon nanowires were fabricated and an in-depth study of their characteristics was carried out using current-voltage and capacitance techniques. PMID:27279431

  19. A new approach for two-terminal electronic memory devices - Storing information on silicon nanowires

    PubMed Central

    Saranti, Konstantina; Alotaibi, Sultan; Paul, Shashi

    2016-01-01

    The work described in this paper focuses on the utilisation of silicon nanowires as the information storage element in flash-type memory devices. Silicon nanostructures have attracted attention due to interesting electrical and optical properties, and their potential integration into electronic devices. A detailed investigation of the suitability of silicon nanowires as the charge storage medium in two-terminal non-volatile memory devices are presented in this report. The deposition of the silicon nanostructures was carried out at low temperatures (less than 400 °C) using a previously developed a novel method within our research group. Two-terminal non-volatile (2TNV) memory devices and metal-insulator-semiconductor (MIS) structures containing the silicon nanowires were fabricated and an in-depth study of their characteristics was carried out using current-voltage and capacitance techniques. PMID:27279431

  20. Silicon Alignment Pins: An Easy Way to Realize a Wafer-to-Wafer Alignment

    NASA Technical Reports Server (NTRS)

    Jung-Kubiak, Cecile; Reck, Theodore J.; Lin, Robert H.; Peralta, Alejandro; Gill, John J.; Lee, Choonsup; Siles, Jose; Toda, Risaku; Chattopadhyay, Goutam; Cooper, Ken B.; Mehdi, Imran; Thomas, Bertrand

    2013-01-01

    Submillimeter heterodyne instruments play a critical role in addressing fundamental questions regarding the evolution of galaxies as well as being a crucial tool in planetary science. To make these instruments compatible with small platforms, especially for the study of the outer planets, or to enable the development of multi-pixel arrays, it is essential to reduce the mass, power, and volume of the existing single-pixel heterodyne receivers. Silicon micromachining technology is naturally suited for making these submillimeter and terahertz components, where precision and accuracy are essential. Waveguide and channel cavities are etched in a silicon bulk material using deep reactive ion etching (DRIE) techniques. Power amplifiers, multiplier and mixer chips are then integrated and the silicon pieces are stacked together to form a supercompact receiver front end. By using silicon micromachined packages for these components, instrument mass can be reduced and higher levels of integration can be achieved. A method is needed to assemble accurately these silicon pieces together, and a technique was developed here using etched pockets and silicon pins to align two wafers together.

  1. Top-down fabrication of silicon nanowire devices for thermoelectric applications: properties and perspectives

    NASA Astrophysics Data System (ADS)

    Pennelli, Giovanni

    2015-05-01

    In this paper, the most recent achievements in the field of device fabrication, based on nanostructured silicon, will be reviewed. Top-down techniques for silicon nanowire production based on lithography, oxidation and highly anisotropic etching (wet, plasma and metal assisted) will be discussed, illustrating both advantages and drawbacks. In particular, fabrication processes for a massive production of silicon nanowires, organized and interconnected in devices with macroscopic dimensions, will be shown and discussed. These macroscopic devices offer the possibility of exploiting the nanoscale thermoelectric properties of silicon in practical applications. In particular, the reduced thermal conductivity of silicon nanowires, with respect to bulk silicon, makes possible to obtain high efficiencies in the direct conversion of heat into electrical power, with intriguing applications in the field of green energy harvesting. The main experiments elucidating the electrical and thermal properties of silicon nanowire devices will be shown and discussed, and compared with the recent theoretical works developed on the subject. Contribution to the Topical Issue "Silicon and Silicon-related Materials for Thermoelectricity", edited by Dario Narducci.

  2. 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

  3. Ab initio design of nanostructures for solar energy conversion: a case study on silicon nitride nanowire

    PubMed Central

    2014-01-01

    Design of novel materials for efficient solar energy conversion is critical to the development of green energy technology. In this work, we present a first-principles study on the design of nanostructures for solar energy harvesting on the basis of the density functional theory. We show that the indirect band structure of bulk silicon nitride is transferred to direct bandgap in nanowire. We find that intermediate bands can be created by doping, leading to enhancement of sunlight absorption. We further show that codoping not only reduces the bandgap and introduces intermediate bands but also enhances the solubility of dopants in silicon nitride nanowires due to reduced formation energy of substitution. Importantly, the codoped nanowire is ferromagnetic, leading to the improvement of carrier mobility. The silicon nitride nanowires with direct bandgap, intermediate bands, and ferromagnetism may be applicable to solar energy harvesting. PMID:25294975

  4. Detection of the early stage of recombinational DNA repair by silicon nanowire transistors.

    PubMed

    Chiesa, Marco; Cardenas, Paula P; Otón, Francisco; Martinez, Javier; Mas-Torrent, Marta; Garcia, Fernando; Alonso, Juan C; Rovira, Concepció; Garcia, Ricardo

    2012-03-14

    A silicon nanowire-based biosensor has been designed and applied for label-free and ultrasensitive detection of the early stage of recombinational DNA repair by RecA protein. Silicon nanowires transistors were fabricated by atomic force microscopy nanolithography and integrated into a microfluidic environment. The sensor operates by measuring the changes in the resistance of the nanowire as the biomolecular reactions proceed. We show that the nanoelectronic sensor can detect and differentiate several steps in the binding of RecA to a single-stranded DNA filament taking place on the nanowire-aqueous interface. We report relative changes in the resistance of 3.5% which are related to the interaction of 250 RecA·single-stranded DNA complexes. Spectroscopy data confirm the presence of the protein-DNA complexes on the functionalized silicon surfaces. PMID:22364265

  5. Generation of Reactive Oxygen Species from Silicon Nanowires

    PubMed Central

    Leonard, Stephen S; Cohen, Guy M; Kenyon, Allison J; Schwegler-Berry, Diane; Fix, Natalie R; Bangsaruntip, Sarunya; Roberts, Jenny R

    2014-01-01

    Processing and synthesis of purified nanomaterials of diverse composition, size, and properties is an evolving process. Studies have demonstrated that some nanomaterials have potential toxic effects and have led to toxicity research focusing on nanotoxicology. About two million workers will be employed in the field of nanotechnology over the next 10 years. The unknown effects of nanomaterials create a need for research and development of techniques to identify possible toxicity. Through a cooperative effort between National Institute for Occupational Safety and Health and IBM to address possible occupational exposures, silicon-based nanowires (SiNWs) were obtained for our study. These SiNWs are anisotropic filamentary crystals of silicon, synthesized by the vapor–liquid–solid method and used in bio-sensors, gas sensors, and field effect transistors. Reactive oxygen species (ROS) can be generated when organisms are exposed to a material causing cellular responses, such as lipid peroxidation, H2O2 production, and DNA damage. SiNWs were assessed using three different in vitro environments (H2O2, RAW 264.7 cells, and rat alveolar macrophages) for ROS generation and possible toxicity identification. We used electron spin resonance, analysis of lipid peroxidation, measurement of H2O2 production, and the comet assay to assess generation of ROS from SiNW and define possible mechanisms. Our results demonstrate that SiNWs do not appear to be significant generators of free radicals. PMID:25452695

  6. Graphitized silicon carbide microbeams: wafer-level, self-aligned graphene on silicon wafers

    NASA Astrophysics Data System (ADS)

    Cunning, Benjamin V.; Ahmed, Mohsin; Mishra, Neeraj; Ranjbar Kermany, Atieh; Wood, Barry; Iacopi, Francesca

    2014-08-01

    Currently proven methods that are used to obtain devices with high-quality graphene on silicon wafers involve the transfer of graphene flakes from a growth substrate, resulting in fundamental limitations for large-scale device fabrication. Moreover, the complex three-dimensional structures of interest for microelectromechanical and nanoelectromechanical systems are hardly compatible with such transfer processes. Here, we introduce a methodology for obtaining thousands of microbeams, made of graphitized silicon carbide on silicon, through a site-selective and wafer-scale approach. A Ni-Cu alloy catalyst mediates a self-aligned graphitization on prepatterned SiC microstructures at a temperature that is compatible with silicon technologies. The graphene nanocoating leads to a dramatically enhanced electrical conductivity, which elevates this approach to an ideal method for the replacement of conductive metal films in silicon carbide-based MEMS and NEMS devices.

  7. Graphitized silicon carbide microbeams: wafer-level, self-aligned graphene on silicon wafers.

    PubMed

    Cunning, Benjamin V; Ahmed, Mohsin; Mishra, Neeraj; Kermany, Atieh Ranjbar; Wood, Barry; Iacopi, Francesca

    2014-08-15

    Currently proven methods that are used to obtain devices with high-quality graphene on silicon wafers involve the transfer of graphene flakes from a growth substrate, resulting in fundamental limitations for large-scale device fabrication. Moreover, the complex three-dimensional structures of interest for microelectromechanical and nanoelectromechanical systems are hardly compatible with such transfer processes. Here, we introduce a methodology for obtaining thousands of microbeams, made of graphitized silicon carbide on silicon, through a site-selective and wafer-scale approach. A Ni-Cu alloy catalyst mediates a self-aligned graphitization on prepatterned SiC microstructures at a temperature that is compatible with silicon technologies. The graphene nanocoating leads to a dramatically enhanced electrical conductivity, which elevates this approach to an ideal method for the replacement of conductive metal films in silicon carbide-based MEMS and NEMS devices. PMID:25053702

  8. Silicon nanowire growth and transistor fabrication by self-assembling "grow-in-place" approach

    NASA Astrophysics Data System (ADS)

    Shan, Yinghui

    Nanowires have attracted much attention recently owing to their ability to serve as critical building blocks for emerging nanotechnologies. Silicon nanowires (SiNWs) are particularly promising because of the central role of silicon in semiconductor industry. SiNWs would allow device fabrication with high density and their high surface to volume ratio offers high sensitivity. In addition, the possible quantum confinement in SiNWs may further enhance device performances and open windows for exploiting fundamental properties. Intense researches have been carried out in SiNW growth and device fabrication. However, there are still challenges in SiNW growth controls, such as size, number, shape, position, orientation, and inter-wire spacings. To make devices from these SiNWs, post-growth processing steps are needed, such as SiNW collecting, picking, positioning, aligning, and assembling. Due to the extremely small size of SiNWs, there are also challenges in SiNW device fabrication. To solve these challenges in both SiNW growth control and device fabrication, we introduced a novel self-assembling "grow-in-place" approach. Our approach combined vapor-liquid-solid (VLS) nanowire growth mechanism and pre-fabricated nanochannel template. The VLS growth mechanism offers the ability of controlling nanowire size and shape by nanochannel templates. The pre-fabricated nanochannel template guides nanowire growth and offers good SiNW growth control. SiNWs and silicon nanoribbons (SiNRs) with different sizes have been successfully grown in our nanochannel templates. Characterizations on their size, shape, composition, and crystallinity of the SiNW/Rs have confirmed that our "grow-in-place" approach offers good controls on crystalline SiNW/Rs size, shape, number, orientation, position, and inter-wire spacing. So our approach solved the challenges in SiNW growth control. Our grow-in-place approach also solved the challenges in SiNW device fabrication. We introduced two versions of

  9. Synthesis, characterization and application of electroless metal assisted silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Sahoo, Sumanta Kumar; Marikani, Arumugam

    2015-12-01

    Vertically aligned silicon nanowire arrays (SiNWs) have been synthesized by electroless metal deposition process. The fabricated SiNWs have an average diameter of 75 nm and 3.5-4.0 μm length, as confirmed from scanning electron microscopy. A characteristic asymmetric peak broadening at 520 cm-1 from Raman spectroscopy was obtained for the SiNWs as compared to the bulk silicon crystal due to phonon confinement. The as-prepared SiNWs exhibit good electron field-emission properties with turn-on field of about 8.26 V μm-1 at a current density of 4.9 μA cm-2. The SiNWs was functionalized by coating with a thin gold metallic film for 60 s, and then used as bio-probe for the detection of bovine serum albumin (BSA) protein molecules. From the linear sweep voltammetry analysis, the Au coated SiNWs, exhibit linear response to the BSA analyte with increase in concentration. The minimum detection limit of the protein molecule was calculated of about 1.16 μM by the as-synthesized SiNWs probe.

  10. Surface trap mediated electronic transport in biofunctionalized silicon nanowires

    NASA Astrophysics Data System (ADS)

    Puppo, F.; Traversa, F. L.; Di Ventra, M.; De Micheli, G.; Carrara, S.

    2016-08-01

    Silicon nanowires (SiNWs), fabricated via a top-down approach and then functionalized with biological probes, are used for electrically-based sensing of breast tumor markers. The SiNWs, featuring memristive-like behavior in bare conditions, show, in the presence of biomarkers, modified hysteresis and, more importantly, a voltage memory component, namely a voltage gap. The voltage gap is demonstrated to be a novel and powerful parameter of detection thanks to its high-resolution dependence on charges in proximity of the wire. This unique approach of sensing has never been studied and adopted before. Here, we propose a physical model of the surface electronic transport in Schottky barrier SiNW biosensors, aiming at reproducing and understanding the voltage gap based behavior. The implemented model describes well the experimental I–V characteristics of the device. It also links the modification of the voltage gap to the changing concentration of antigens by showing the decrease of this parameter in response to increasing concentrations of the molecules that are detected with femtomolar resolution in real human samples. Both experiments and simulations highlight the predominant role of the dynamic recombination of the nanowire surface states, with the incoming external charges from bio-species, in the appearance and modification of the voltage gap. Finally, thanks to its compactness, and strict correlation with the physics of the nanodevice, this model can be used to describe and predict the I–V characteristics in other nanostructured devices, for different than antibody-based sensing as well as electronic applications.

  11. Surface trap mediated electronic transport in biofunctionalized silicon nanowires.

    PubMed

    Puppo, F; Traversa, F L; Ventra, M Di; Micheli, G De; Carrara, S

    2016-08-26

    Silicon nanowires (SiNWs), fabricated via a top-down approach and then functionalized with biological probes, are used for electrically-based sensing of breast tumor markers. The SiNWs, featuring memristive-like behavior in bare conditions, show, in the presence of biomarkers, modified hysteresis and, more importantly, a voltage memory component, namely a voltage gap. The voltage gap is demonstrated to be a novel and powerful parameter of detection thanks to its high-resolution dependence on charges in proximity of the wire. This unique approach of sensing has never been studied and adopted before. Here, we propose a physical model of the surface electronic transport in Schottky barrier SiNW biosensors, aiming at reproducing and understanding the voltage gap based behavior. The implemented model describes well the experimental I-V characteristics of the device. It also links the modification of the voltage gap to the changing concentration of antigens by showing the decrease of this parameter in response to increasing concentrations of the molecules that are detected with femtomolar resolution in real human samples. Both experiments and simulations highlight the predominant role of the dynamic recombination of the nanowire surface states, with the incoming external charges from bio-species, in the appearance and modification of the voltage gap. Finally, thanks to its compactness, and strict correlation with the physics of the nanodevice, this model can be used to describe and predict the I-V characteristics in other nanostructured devices, for different than antibody-based sensing as well as electronic applications. PMID:27418560

  12. Electrowetting properties of atomic layer deposited Al2O3 decorated silicon nanowires

    NASA Astrophysics Data System (ADS)

    Rajkumar, K.; Rajavel, K.; Cameron, D. C.; Mangalaraj, D.; Rajendrakumar, R. T.

    2015-06-01

    This paper reports the electrowetting properties of liquid droplet on superhydrophobic silicon nanowires with Atomic layer deposited (ALD) Al2O3 as dielectric layer. Silicon wafer were etched by metal assisted wet chemical etching with silver as catalyst. ALD Al2O3 films of 10nm thickness were conformally deposited over silicon nanowires. Al2O3 dielectric film coated silicon nanowires was chemically modified with Trichloro (1H, 1H, 2H, 2H-perfluorooctyl) silane to make it superhydrophobic(SHP). The contact angle was measured and all the samples exhibited superhydrophobic nature with maximum contact angles of 163° and a minimum contact angle hysteresis of 6°. Electrowetting induced a maximum reversible decrease of the contact angle of 20°at 150V in air.

  13. Silicon nanowires nanogenerator based on the piezoelectricity of alpha-quartz

    NASA Astrophysics Data System (ADS)

    Yin, Kui; Lin, Haiyang; Cai, Qian; Zhao, Yi; Lee, Shuit-Tong; Hu, Fei; Shao, Mingwang

    2013-11-01

    Silicon nanowires are important semiconductor with core/shell structure. In this work, the piezoelectric material alpha-quartz was grown in the interface of silicon nanowires by thermal treatment at 600 °C for 0.5 h. These nanowires were employed as starting materials to fabricate piezoelectric nanogenerators, which could convert kinetic energy into electrical one, exhibiting an output voltage of 36.5 V and a response current of 1.4 μA under a free-falling object of 300 g at a height of 30 cm.Silicon nanowires are important semiconductor with core/shell structure. In this work, the piezoelectric material alpha-quartz was grown in the interface of silicon nanowires by thermal treatment at 600 °C for 0.5 h. These nanowires were employed as starting materials to fabricate piezoelectric nanogenerators, which could convert kinetic energy into electrical one, exhibiting an output voltage of 36.5 V and a response current of 1.4 μA under a free-falling object of 300 g at a height of 30 cm. Electronic supplementary information (ESI) available: SEM, schematic diagram and video. See DOI: 10.1039/c3nr03838f

  14. Influence of Grain Size on the Thermoelectric Properties of Polycrystalline Silicon Nanowires

    NASA Astrophysics Data System (ADS)

    Suriano, F.; Ferri, M.; Moscatelli, F.; Mancarella, F.; Belsito, L.; Solmi, S.; Roncaglia, A.; Frabboni, S.; Gazzadi, G. C.; Narducci, D.

    2015-01-01

    The thermoelectric properties of doped polycrystalline silicon nanowires have been investigated using doping techniques that impact grain growth in different ways during the doping process. In particular, As- and P-doped nanowires were fabricated using a process flow which enables the manufacturing of surface micromachined nanowires contacted by Al/Si pads in a four-terminal configuration for thermal conductivity measurement. Also, dedicated structures for the measurement of the Seebeck coefficient and electrical resistivity were prepared. In this way, the thermoelectric figure of merit of the nanowires could be evaluated. The As-doped nanowires were heavily doped by thermal doping from spin-on-dopant sources, whereas predeposition from POCl3 was utilized for the P-doped nanowires. The thermal conductivity measured on the nanowires appeared to depend on the doping type. The P-doped nanowires showed, for comparable cross-sections, higher thermal conductivity values than As-doped nanowires, most probably because of their finer grain texture, resulting from the inhibition effect that such doping elements have on grain growth during high-temperature annealing.

  15. 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.

  16. 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. PMID:26050844

  17. Molecular dynamics simulation overcoming the finite size effects of thermal conductivity of bulk silicon and silicon nanowires

    NASA Astrophysics Data System (ADS)

    Hou, Chaofeng; Xu, Ji; Ge, Wei; Li, Jinghai

    2016-05-01

    Nonequilibrium molecular dynamics simulation has been a powerful tool for studying the thermophysical properties of bulk silicon and silicon nanowires. Nevertheless, usually limited by the capacity and capability of computational resources, the traditional longitudinal and transverse simulation sizes are evidently restricted in a narrow range much less than the experimental scales, which seriously hinders the exploration of the thermal properties. In this research, based on a powerful and efficient molecular dynamics (MD) simulation method, the computation of thermal conductivity beyond the known Casimir size limits is realized. The longitudinal dimensions of the simulations significantly exceed the micrometer scale. More importantly, the lateral characteristic sizes are much larger than 10 nanometers, explicitly comparable with the silicon nanowires fabricated and measured experimentally, whereas the traditional simulation size is several nanometers. The powerful virtual experimental measurement provided in our simulations achieves the direct prediction of the thermal conductivity of bulk silicon and real-scale silicon nanowires, and delineates the complete longitudinal size dependence of their thermal conductivities, especially at the elusive mesoscopic scale. Furthermore, the presented measurement paves an exciting and promising way to explore in depth the thermophysical properties of other bulk covalent solids and their low-dimensional structures, such as nanowires and nanosheets.

  18. Tunable electronic transport properties of silicon-fullerene-linked nanowires: Semiconductor, conducting wire, and tunnel diode

    NASA Astrophysics Data System (ADS)

    Nishio, Kengo; Ozaki, Taisuke; Morishita, Tetsuya; Mikami, Masuhiro

    2010-03-01

    We explore the possibility of controllable tuning of the electronic transport properties of silicon-fullerene-linked nanowires by encapsulating guest atoms into their cages. Our first-principles calculations demonstrate that the guest-free nanowires are semiconductors, and do not conduct electricity. The iodine or sodium doping improves the transport properties, and makes the nanowires metallic. In the junctions of I-doped and Na-doped NWs, the current travels through the boundary by quantum tunneling. More significantly, the junctions have asymmetric I-Vb curves, which could be used as rectifiers. The current-voltage curves are interpreted by band-overlapping models. Tunable electronic transport properties of silicon-fullerene-linked nanowires could find many applications such as field-effect transistors, conducting wires, and tunnel diodes.

  19. Graphene Enhances Li Storage Capacity of Porous Single-crystalline Silicon Nanowires

    SciTech Connect

    Wang, X.; Han, W.

    2010-12-01

    We demonstrated that graphene significantly enhances the reversible capacity of porous silicon nanowires used as the anode in Li-ion batteries. We prepared our experimental nanomaterials, viz., graphene and porous single-crystalline silicon nanowires, respectively, using a liquid-phase graphite exfoliation method and an electroless HF/AgNO{sub 3} etching process. The Si porous nanowire/graphene electrode realized a charge capacity of 2470 mAh g{sup -1} that is much higher than the 1256 mAh g{sup -1} of porous Si nanowire/C-black electrode and 6.6 times the theoretical capacity of commercial graphite. This relatively high capacity could originate from the favorable charge-transportation characteristics of the combination of graphene with the porous Si 1D nanostructure.

  20. Fabrication of Metal-Semiconductor Heterostructures in Silicon Nanowires

    NASA Astrophysics Data System (ADS)

    Yang, Luyun

    The increasing demand for fossil fuels and the need to reduce greenhouse gases require clean energy sources and more efficient utilization of energy. Thermoelectric materials provide a means toward achieving these goals since they convert heat, including waste heat, directly into an electric potential difference. Metal-semiconductor heterostructures can work as Schottky barriers in thermoelectric materials to increase thermoelectric efficiency. In this project, nickel silicide phases were introduced into silicon nanowires (SiNWs) to build up the Schottky barrier. SiNW arrays were fabricated using a metal-assisted chemical process, creating SiNWs about 200 nm in diameter and 30im in length. Different methods were adopted for nickel deposition: electroless nickel deposition, electro nickel deposition, E-beam deposition, and thermal evaporation. The samples were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that depositing nickel on SiNWs in an aqueous solution without electricity is a simple way to deposit nickel particles, and the morphology of nickel particles depends on the concentration of the deposition bath. However, an aqueous solution will cause oxidation of the SiNWs and hinder the formation of nickel silicide. To solve this problem, depositing nickel on SiNWs in organic solutions inside an oxygen-free glove box is a way to prevent oxidation, and nickel can diffuse into silicon substrates easily via annealing when there no oxidation layer on the surface of SiNWs. The dominant phase formed in these samples is NiSi2 after being annealed at 650°C for one hour in a tube furnace.

  1. Photonic Torque Microscopy of the Nonconservative Force Field for Optically Trapped Silicon Nanowires.

    PubMed

    Irrera, Alessia; Magazzù, Alessandro; Artoni, Pietro; Simpson, Stephen H; Hanna, Simon; Jones, Philip H; Priolo, Francesco; Gucciardi, Pietro Giuseppe; Maragò, Onofrio M

    2016-07-13

    We measure, by photonic torque microscopy, the nonconservative rotational motion arising from the transverse components of the radiation pressure on optically trapped, ultrathin silicon nanowires. Unlike spherical particles, we find that nonconservative effects have a significant influence on the nanowire dynamics in the trap. We show that the extreme shape of the trapped nanowires yields a transverse component of the radiation pressure that results in an orbital rotation of the nanowire about the trap axis. We study the resulting motion as a function of optical power and nanowire length, discussing its size-scaling behavior. These shape-dependent nonconservative effects have implications for optical force calibration and optomechanics with levitated nonspherical particles. PMID:27280642

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

    PubMed

    Zhang, Weixin; Yang, Shihe

    2009-10-20

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

  3. 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

  4. Ultrafast Electrical Measurements of Isolated Silicon Nanowires and Nanocrystals.

    PubMed

    Bergren, Matthew R; Kendrick, Chito E; Neale, Nathan R; Redwing, Joan M; Collins, Reuben T; Furtak, Thomas E; Beard, Matthew C

    2014-06-19

    We simultaneously determined the charge carrier mobility and picosecond to nanosecond carrier dynamics of isolated silicon nanowires (Si NWs) and nanocrystals (Si NCs) using time-resolved terahertz spectroscopy. We then compared these results to data measured on bulk c-Si as a function of excitation fluence. We find >1 ns carrier lifetimes in Si NWs that are dominated by surface recombination with surface recombination velocities (SRV) between ∼1100-1700 cm s(-1) depending on process conditions. The Si NCs have markedly different decay dynamics. Initially, free-carriers are produced, but relax within ∼1.5 ps to form bound excitons. Subsequently, the excitons decay with lifetimes >7 ns, similar to free carriers produced in bulk Si. The isolated Si NWs exhibit bulk-like mobilities that decrease with increasing excitation density, while the hot-carrier mobilities in the Si NCs are lower than bulk mobilities and could only be measured within the initial 1.5 ps decay. We discuss the implications of our measurements on the utilization of Si NWs and NCs in macroscopic optoelectronic applications. PMID:26270492

  5. Silicon Nanowire Sensors Enable Diagnosis of Patients via Exhaled Breath.

    PubMed

    Shehada, Nisreen; Cancilla, John C; Torrecilla, Jose S; Pariente, Enrique S; Brönstrup, Gerald; Christiansen, Silke; Johnson, Douglas W; Leja, Marcis; Davies, Michael P A; Liran, Ori; Peled, Nir; Haick, Hossam

    2016-07-26

    Two of the biggest challenges in medicine today are the need to detect diseases in a noninvasive manner and to differentiate between patients using a single diagnostic tool. The current study targets these two challenges by developing a molecularly modified silicon nanowire field effect transistor (SiNW FET) and showing its use in the detection and classification of many disease breathprints (lung cancer, gastric cancer, asthma, and chronic obstructive pulmonary disease). The fabricated SiNW FETs are characterized and optimized based on a training set that correlate their sensitivity and selectivity toward volatile organic compounds (VOCs) linked with the various disease breathprints. The best sensors obtained in the training set are then examined under real-world clinical conditions, using breath samples from 374 subjects. Analysis of the clinical samples show that the optimized SiNW FETs can detect and discriminate between almost all binary comparisons of the diseases under examination with >80% accuracy. Overall, this approach has the potential to support detection of many diseases in a direct harmless way, which can reassure patients and prevent numerous unpleasant investigations. PMID:27383408

  6. Static friction between silicon nanowires and elastomeric substrates.

    PubMed

    Qin, Qingquan; Zhu, Yong

    2011-09-27

    This paper reports the first direct measurements of static friction force and interfacial shear strength between silicon (Si) nanowires (NWs) and poly(dimethylsiloxane) (PDMS). A micromanipulator is used to manipulate and deform the NWs under a high-magnification optical microscope in real time. The static friction force is measured based on "the most-bent state" of the NWs. The static friction and interface shear strength are found to depend on the ultraviolet/ozone (UVO) treatment of PDMS. The shear strength starts at 0.30 MPa without UVO treatment, increases rapidly up to 10.57 MPa at 60 min of treatment and decreases for longer treatment. Water contact angle measurements suggest that the UVO-induced hydrophobic-to-hydrophilic conversion of PDMS surface is responsible for the increase in the static friction, while the hydrophobic recovery effect contributes to the decrease. The static friction between NWs and PDMS is of critical relevance to many device applications of NWs including NW-based flexible/stretchable electronics, NW assembly and nanocomposites (e.g., supercapacitors). Our results will enable quantitative interface design and control for such applications. PMID:21815652

  7. A Highly Responsive Silicon Nanowire/Amplifier MOSFET Hybrid Biosensor

    PubMed Central

    Lee, Jieun; Jang, Jaeman; Choi, Bongsik; Yoon, Jinsu; Kim, Jee-Yeon; Choi, Yang-Kyu; Myong Kim, Dong; Hwan Kim, Dae; Choi, Sung-Jin

    2015-01-01

    This study demonstrates a hybrid biosensor comprised of a silicon nanowire (SiNW) integrated with an amplifier MOSFET to improve the current response of field-effect-transistor (FET)-based biosensors. The hybrid biosensor is fabricated using conventional CMOS technology, which has the potential advantage of high density and low noise performance. The biosensor shows a current response of 5.74 decades per pH for pH detection, which is 2.5 × 105 times larger than that of a single SiNW sensor. In addition, we demonstrate charged polymer detection using the biosensor, with a high current change of 4.5 × 105 with a 500 nM concentration of poly(allylamine hydrochloride). In addition, we demonstrate a wide dynamic range can be obtained by adjusting the liquid gate voltage. We expect that this biosensor will be advantageous and practical for biosensor applications which requires lower noise, high speed, and high density. PMID:26197105

  8. Effects of lithium insertion on thermal conductivity of silicon nanowires

    SciTech Connect

    Xu, Wen; Zhang, Gang; Li, Baowen

    2015-04-27

    Recently, silicon nanowires (SiNWs) have been applied as high-performance Li battery anodes, since they can overcome the pulverization and mechanical fracture during lithiation. Although thermal stability is one of the most important parameters that determine safety of Li batteries, thermal conductivity of SiNWs with Li insertion remains unclear. In this letter, using molecular dynamics simulations, we study room temperature thermal conductivity of SiNWs with Li insertion. It is found that compared with the pristine SiNW, there is as much as 60% reduction in thermal conductivity with 10% concentration of inserted Li atoms, while under the same impurity concentration the reduction in thermal conductivity of the mass-disordered SiNW is only 30%. With lattice dynamics calculations and normal mode decomposition, it is revealed that the phonon lifetimes in SiNWs decrease greatly due to strong scattering of phonons by vibrational modes of Li atoms, especially for those high frequency phonons. The observed strong phonon scattering phenomenon in Li-inserted SiNWs is similar to the phonon rattling effect. Our study serves as an exploration of thermal properties of SiNWs as Li battery anodes or weakly coupled with impurity atoms.

  9. A Highly Responsive Silicon Nanowire/Amplifier MOSFET Hybrid Biosensor.

    PubMed

    Lee, Jieun; Jang, Jaeman; Choi, Bongsik; Yoon, Jinsu; Kim, Jee-Yeon; Choi, Yang-Kyu; Kim, Dong Myong; Kim, Dae Hwan; Choi, Sung-Jin

    2015-01-01

    This study demonstrates a hybrid biosensor comprised of a silicon nanowire (SiNW) integrated with an amplifier MOSFET to improve the current response of field-effect-transistor (FET)-based biosensors. The hybrid biosensor is fabricated using conventional CMOS technology, which has the potential advantage of high density and low noise performance. The biosensor shows a current response of 5.74 decades per pH for pH detection, which is 2.5 × 10(5) times larger than that of a single SiNW sensor. In addition, we demonstrate charged polymer detection using the biosensor, with a high current change of 4.5 × 10(5) with a 500 nM concentration of poly(allylamine hydrochloride). In addition, we demonstrate a wide dynamic range can be obtained by adjusting the liquid gate voltage. We expect that this biosensor will be advantageous and practical for biosensor applications which requires lower noise, high speed, and high density. PMID:26197105

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

    SciTech Connect

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

    2014-10-06

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

  11. Nanomechanical detection of nuclear magnetic resonance using a silicon nanowire oscillator

    NASA Astrophysics Data System (ADS)

    Nichol, John M.; Hemesath, Eric R.; Lauhon, Lincoln J.; Budakian, Raffi

    2012-02-01

    The authors report the use of a radio frequency (rf) silicon nanowire mechanical oscillator as a low-temperature nuclear magnetic resonance force sensor to detect the statistical polarization of 1H spins in polystyrene. To couple the 1H spins to the nanowire oscillator, a magnetic resonance force detection protocol was developed that utilizes a nanoscale current-carrying wire to produce large time-dependent magnetic field gradients as well as the rf magnetic field. Under operating conditions, the nanowire experienced negligible surface-induced dissipation and exhibited an ultralow force noise near the thermal limit of the oscillator.

  12. Structural properties and magic structures in hydrogenated finite and infinite silicon nanowires

    NASA Astrophysics Data System (ADS)

    Zdetsis, A. D.; Koukaras, E. N.; Garoufalis, C. S.

    2007-11-01

    Unusual effects such as bending and "canting," related with the stability, have been identified by ab initio real-space calculations for hydrogenated silicon nanowires. We have examined in detail the electronic and structural properties of finite and infinite nanowires as a function of length (and width) and have developed stability and bending rules, demonstrating that "magic" wires do not bend. Reconstructed 2×1 nanowires are practically as stable as the magic ones. Our calculations are in good agreement with the experimental data of Ma et al. [Science 299, 1874 (2003).].

  13. Structural and optical properties of axial silicon-germanium nanowire heterojunctions

    NASA Astrophysics Data System (ADS)

    Wang, X.; Tsybeskov, L.; Kamins, T. I.; Wu, X.; Lockwood, D. J.

    2015-12-01

    Detailed studies of the structural and optical properties of axial silicon-germanium nanowire heterojunctions show that despite the 4.2% lattice mismatch between Si and Ge they can be grown without a significant density of structural defects. The lattice mismatch induced strain is partially relieved due to spontaneous SiGe intermixing at the heterointerface during growth and lateral expansion of the Ge segment of the nanowire. The mismatch in Ge and Si coefficients of thermal expansion and low thermal conductivity of Si/Ge nanowire heterojunctions are proposed to be responsible for the thermally induced stress detected under intense laser radiation in photoluminescence and Raman scattering measurements.

  14. Nanowire-integrated microporous silicon membrane for continuous fluid transport in micro cooling device

    SciTech Connect

    So, Hongyun; Pisano, Albert P.; Cheng, Jim C.

    2013-10-14

    We report an efficient passive micro pump system combining the physical properties of nanowires and micropores. This nanowire-integrated microporous silicon membrane was created to feed coolant continuously onto the surface of the wick in a micro cooling device to ensure it remains hydrated and in case of dryout, allow for regeneration of the system. The membrane was fabricated by photoelectrochemical etching to form micropores followed by hydrothermal growth of nanowires. This study shows a promising approach to address thermal management challenges for next generation electronic devices with absence of external power.

  15. Highly conductive indium nanowires deposited on silicon by dip-pen nanolithography

    SciTech Connect

    Kozhukhov, Anton; Volodin, Vladimir; Klimenko, Anatoliy; Shcheglov, Dmitriy; Karnaeva, Natalya; Latyshev, Alexander

    2015-04-14

    In this paper, we developed a new dip-pen nanolithography (DPN) method. Using this method, we fabricated conductive nanowires with diameters of 30–50 nm on silicon substrates. To accomplish this, indium was transferred from an atomic force microscopy tip to the surface by applying a potential difference between the tip and substrate. The fabricated indium nanowires were several micrometers in length. Unlike thermal DPN, our DPN method hardly oxidized the indium, producing nanowires with conductivities from 5.7 × 10{sup −3} to 4 × 10{sup −2} Ω cm.

  16. 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.

  17. Structural and optical properties of axial silicon-germanium nanowire heterojunctions

    SciTech Connect

    Wang, X.; Tsybeskov, L.; Kamins, T. I.; Wu, X.; Lockwood, D. J.

    2015-12-21

    Detailed studies of the structural and optical properties of axial silicon-germanium nanowire heterojunctions show that despite the 4.2% lattice mismatch between Si and Ge they can be grown without a significant density of structural defects. The lattice mismatch induced strain is partially relieved due to spontaneous SiGe intermixing at the heterointerface during growth and lateral expansion of the Ge segment of the nanowire. The mismatch in Ge and Si coefficients of thermal expansion and low thermal conductivity of Si/Ge nanowire heterojunctions are proposed to be responsible for the thermally induced stress detected under intense laser radiation in photoluminescence and Raman scattering measurements.

  18. Preparation of silicon@silicon oxide core-shell nanowires from a silica precursor toward a high energy density Li-ion battery anode.

    PubMed

    Zhang, Chuanjian; Gu, Lin; Kaskhedikar, Nitin; Cui, Guanglei; Maier, Joachim

    2013-12-11

    Bulk-quantity silicon@silicon oxide nanowires have been successfully synthesized via a facile high-temperature approach using environment-friendly silica mixed with titanium powders. It is confirmed that the obtained nanowires process a crystalline core and amorphous oxide sheath. The obtained nanowires grow along the [111] direction which catalyzed by spherical silicon@siilcon oxide nanoparticles. The unique one-dimensional structure and thin oxide sheath result in the favorable electrochemical performances, which may be beneficial to the high energy density silicon anode for lithium ion batteries. PMID:24229329

  19. Synthesis, Characterization and Kinetics of Epitaxial-Oriented Silicon Nanowire Arrays on Si Substrates

    NASA Astrophysics Data System (ADS)

    Wang, Z. L.; Bao, J. K.; Wan, Y. T.; Xia, W. W.; Wang, Y. W.; Sha, J.

    The fabrication of vertical-oriented, high aspect ratio silicon nanowires (SiNWs) with controllable density and length is of interest for the development of nanowire-based electronics and photovoltaic devices. Here we reported a both simple and economical method for synthesizing large-area epitaxial-oriented SiNW arrays, which was achieved on the Si (111) substrates by Au catalyzed vapor-liquid-solid mechanism using the conventional chemical vapor deposition furnace system. Their morphologies and microstructures were investigated with scanning electron microscopy and transmission electron microscopy, respectively. The results showed that most of nanowires were vertically grown on substrates, their density and length can be well controlled. As-grown SiNW is composed of a single crystalline silicon core and a thin amorphous silicon oxide coating layer. Furthermore, their growth kinetics was discussed in detail. It indicates that there are both the substrate-nanowire Si adatom surface diffusion and the slight radial growth during the upgrowth of nanowire, and besides, the migration of Au on the sidewall of nanowire was also found for such epitaxial-oriental SiNWs.

  20. Multichannel nonlinear distortion compensation using optical phase conjugation in a silicon nanowire.

    PubMed

    Vukovic, Dragana; Schröder, Jochen; Da Ros, Francesco; Du, Liang Bangyuan; Chae, Chang Joon; Choi, Duk-Yong; Pelusi, Mark D; Peucheret, Christophe

    2015-02-01

    We experimentally demonstrate compensation of nonlinear distortion caused by the Kerr effect in a 3 × 32-Gbaud quadrature phase-shift keying (QPSK) wavelength-division multiplexing (WDM) transmission system. We use optical phase conjugation (OPC) produced by four-wave mixing (FWM) in a 7-mm long silicon nanowire. A clear improvement in Q-factor is shown after 800-km transmission with high span input power when comparing the system with and without the optical phase conjugation module. The influence of OSNR degradation introduced by the silicon nanowire is analysed by comparing transmission systems of three different lengths. This is the first demonstration of nonlinear compensation using a silicon nanowire. PMID:25836216

  1. Fabrication of carbon-coated silicon nanowires and their application in dye-sensitized solar cells.

    PubMed

    Kim, Junhee; Lim, Jeongmin; Kim, Minsoo; Lee, Hae-Seok; Jun, Yongseok; Kim, Donghwan

    2014-11-12

    We report the fabrication of silicon/carbon core/shell nanowire arrays using a two-step process, involving electroless metal deposition and chemical vapor deposition. In general, foreign shell materials that sheath core materials change the inherent characteristics of the core materials. The carbon coating functionalized the silicon nanowire arrays, which subsequently showed electrocatalytic activities for the reduction of iodide/triiodide. This was verified by cyclic voltammetry and electrochemical impedance spectroscopy. We employed the carbon-coated silicon nanowire arrays in dye-sensitized solar cells as counter electrodes. We optimized the carbon shells to maximize the photovoltaic performance of the resulting devices, and subsequently, a peak power conversion efficiency of 9.22% was achieved. PMID:25319204

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

    PubMed

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

    2013-01-01

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

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

    PubMed

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

    2016-01-20

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

  4. Interference lithographically defined and catalytically etched, large-area silicon nanocones from nanowires.

    PubMed

    Dawood, M K; Liew, T H; Lianto, P; Hong, M H; Tripathy, S; Thong, J T L; Choi, W K

    2010-05-21

    We report a simple and cost effective method for the synthesis of large-area, precisely located silicon nanocones from nanowires. The nanowires were obtained from our interference lithography and catalytic etching (IL-CE) method. We found that porous silicon was formed near the Au catalyst during the fabrication of the nanowires. The porous silicon exhibited enhanced oxidation ability when exposed to atmospheric conditions or in wet oxidation ambient. Very well located nanocones with uniform sharpness resulted when these oxidized nanowires were etched in 10% HF. Nanocones of different heights were obtained by varying the doping concentration of the silicon wafers. We believe this is a novel method of producing large-area, low cost, well defined nanocones from nanowires both in terms of the control of location and shape of the nanocones. A wide range of potential applications of the nanocone array can be found as a master copy for nanoimprinted polymer substrates for possible biomedical research; as a candidate for making sharp probes for scanning probe nanolithography; or as a building block for field emitting tips or photodetectors in electronic/optoelectronic applications. PMID:20418606

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

    PubMed Central

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    SciTech Connect

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

    2011-03-01

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

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

    PubMed

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

    2012-09-12

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

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

    PubMed

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

    2010-09-01

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

  10. Silicon-Nanowire Based Lithium Ion Batteries for Vehicles With Double the Energy Density

    SciTech Connect

    Stefan, Ionel; Cohen, Yehonathan

    2015-03-31

    Amprius researched and developed silicon nanowire anodes. Amprius then built and delivered high-energy lithium-ion cells that met the project’s specific energy goal and exceeded the project’s energy density goal. But Amprius’ cells did not meet the project’s cycle life goal, suggesting additional manufacturing process development is required. With DOE support, Amprius developed a new anode material, silicon, and a new anode structure, nanowire. During the project, Amprius also began to develop a new multi-step manufacturing process that does not involve traditional anode production processes (e.g. mixing, drying and calendaring).

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  12. Microstructures of the silicon carbide nanowires obtained by annealing the mechanically-alloyed amorphous powders

    SciTech Connect

    Zhang, Pengfei Li, Xinli

    2015-07-15

    Silicon, graphite and boron nitride powders were mechanically alloyed for 40 h in argon. The as-milled powders were annealed at 1700 °C in nitrogen for 30 min. The annealed powders are covered by a thick layer of gray–green SiC nanowires, which are 300 nm to 1000 nm in diameter and several hundred microns in length. Trace iron in the raw powders acts as a catalyst, promoting the V–L–S process. It follows that the actual substances contributing to the growth of the SiC nanowires may be silicon, graphite and the metal impurities in the raw powders. The results from HRTEM and XRD reveal that the products contain both straight α/β-SiC nanowires and nodular α/β-SiC nanochains. It is interestingly found that 6H–SiC coexists with 3C–SiC in one nodular nanowire. This novel structure may introduce periodic potential field along the longitudinal direction of the nanowires, and may find applications in the highly integrated optoelectronic devices. - Graphical abstract: Display Omitted - Highlights: • SiC nanowires were prepared by annealing the mechanically alloyed amorphous powders. • SiC nanowires are 300 nm to 1000 nm in diameter and several hundred microns in length. • The products contain both straight α/β-SiC nanowires and nodular α/β-SiC nanochains. • Trace Fe in the raw powders acts as a catalyst, promoting the V–L–S process. • 6H–SiC coexists with 3C–SiC in one nodular SiC nanowire.

  13. Light trapping in horizontally aligned silicon microwire solar cells.

    PubMed

    Martinsen, Fredrik A; Smeltzer, Benjamin K; Ballato, John; Hawkins, Thomas; Jones, Max; Gibson, Ursula J

    2015-11-30

    In this study, we demonstrate a solar cell design based on horizontally aligned microwires fabricated from 99.98% pure silicon via the molten core fiber drawing method. A similar structure consisting of 50 μm diameter close packed wires (≈ 0.97 packing density) on a Lambertian white back-reflector showed 86 % absorption for incident light of wavelengths up to 850 nm. An array with a packing fraction of 0.35 showed an absorption of 58 % over the same range, demonstrating the potential for effective light trapping. Prototype solar cells were fabricated to demonstrate the concept. Horizontal wire cells offer several advantages as they can be flexible, and partially transparent, and absorb light efficiently over a wide range of incident angles. PMID:26698794

  14. Top-Down Nanofabrication and Characterization of 20 nm Silicon Nanowires for Biosensing Applications

    PubMed Central

    M. N, M. Nuzaihan; Hashim, U.; Md Arshad, M. K.; Ruslinda, A. Rahim; Rahman, S. F. A.; Fathil, M. F. M.; Ismail, Mohd. H.

    2016-01-01

    A top-down nanofabrication approach is used to develop silicon nanowires from silicon-on-insulator (SOI) wafers and involves direct-write electron beam lithography (EBL), inductively coupled plasma-reactive ion etching (ICP-RIE) and a size reduction process. To achieve nanometer scale size, the crucial factors contributing to the EBL and size reduction processes are highlighted. The resulting silicon nanowires, which are 20 nm in width and 30 nm in height (with a triangular shape) and have a straight structure over the length of 400 μm, are fabricated precisely at the designed location on the device. The device is applied in biomolecule detection based on the changes in drain current (Ids), electrical resistance and conductance of the silicon nanowires upon hybridization to complementary target deoxyribonucleic acid (DNA). In this context, the scaled-down device exhibited superior performances in terms of good specificity and high sensitivity, with a limit of detection (LOD) of 10 fM, enables for efficient label-free, direct and higher-accuracy DNA molecules detection. Thus, this silicon nanowire can be used as an improved transducer and serves as novel biosensor for future biomedical diagnostic applications. PMID:27022732

  15. Fabrication, electrical characterization and scanning gate microscopy of Schottky silicon nanowire devices

    NASA Astrophysics Data System (ADS)

    Melinte, Sorin; Iordanescu, Andra; Dutu, Constantin; Flandre, Denis; Faniel, Sebastien; Martins, Frederico; Hackens, Benoit; ICTM Team; IMCN Team

    2013-03-01

    We report the fabrication and the electrical characterization of Schottky silicon nanowire field effect transistors. Our devices are built with a top down approach on silicon-on-insulator wafers with (100) crystallographic orientation and 10 - 25 Ω.cm resistivity of the silicon top layer. The transistor's channel is assured by silicon nanowires patterned by electron beam lithography and wet etching. The nanowires have nominal cross sections down to 30 × 30nm2 . For example, platinum-silicon Schottky contacts are made by physical deposition of a platinum layer followed by an annealing at 500°C for 2 minutes in a N2 atmosphere. The devices are characterized at various temperatures by current-voltage measurements and scanning gate microscopy techniques. Varying the dimensionality and geometry of the contacts, the nature of metal-semiconductor junctions and the substrate strain, we get new insights into the influence of trapped charges at the Si -SiO2 interface on transport through SiO2-enclosed nanowires, at the nanometer scale.

  16. Top-Down Nanofabrication and Characterization of 20 nm Silicon Nanowires for Biosensing Applications.

    PubMed

    M Nuzaihan, M N; Hashim, U; Md Arshad, M K; Rahim Ruslinda, A; Rahman, S F A; Fathil, M F M; Ismail, Mohd H

    2016-01-01

    A top-down nanofabrication approach is used to develop silicon nanowires from silicon-on-insulator (SOI) wafers and involves direct-write electron beam lithography (EBL), inductively coupled plasma-reactive ion etching (ICP-RIE) and a size reduction process. To achieve nanometer scale size, the crucial factors contributing to the EBL and size reduction processes are highlighted. The resulting silicon nanowires, which are 20 nm in width and 30 nm in height (with a triangular shape) and have a straight structure over the length of 400 μm, are fabricated precisely at the designed location on the device. The device is applied in biomolecule detection based on the changes in drain current (Ids), electrical resistance and conductance of the silicon nanowires upon hybridization to complementary target deoxyribonucleic acid (DNA). In this context, the scaled-down device exhibited superior performances in terms of good specificity and high sensitivity, with a limit of detection (LOD) of 10 fM, enables for efficient label-free, direct and higher-accuracy DNA molecules detection. Thus, this silicon nanowire can be used as an improved transducer and serves as novel biosensor for future biomedical diagnostic applications. PMID:27022732

  17. A silicon carbide nanowire field effect transistor for DNA detection.

    PubMed

    Fradetal, L; Bano, E; Attolini, G; Rossi, F; Stambouli, V

    2016-06-10

    This work reports on the label-free electrical detection of DNA molecules for the first time, using silicon carbide (SiC) as a novel material for the realization of nanowire field effect transistors (NWFETs). SiC is a promising semiconductor for this application due to its specific characteristics such as chemical inertness and biocompatibility. Non-intentionally n-doped SiC NWs are first grown using a bottom-up vapor-liquid-solid (VLS) mechanism, leading to the NWs exhibiting needle-shaped morphology, with a length of approximately 2 μm and a diameter ranging from 25 to 60 nm. Then, the SiC NWFETs are fabricated and functionalized with DNA molecule probes via covalent coupling using an amino-terminated organosilane. The drain current versus drain voltage (I d-V d) characteristics obtained after the DNA grafting and hybridization are reported from the comparative and simultaneous measurements carried out on the SiC NWFETs, used either as sensors or references. As a representative result, the current of the sensor is lowered by 22% after probe DNA grafting and by 7% after target DNA hybridization, while the current of the reference does not vary by more than ±0.6%. The current decrease confirms the field effect induced by the negative charges of the DNA molecules. Moreover, the selectivity, reproducibility, reversibility and stability of the studied devices are emphasized by de-hybridization, non-complementary hybridization and re-hybridization experiments. This first proof of concept opens the way for future developments using SiC-NW-based sensors. PMID:27120971

  18. A silicon carbide nanowire field effect transistor for DNA detection

    NASA Astrophysics Data System (ADS)

    Fradetal, L.; Bano, E.; Attolini, G.; Rossi, F.; Stambouli, V.

    2016-06-01

    This work reports on the label-free electrical detection of DNA molecules for the first time, using silicon carbide (SiC) as a novel material for the realization of nanowire field effect transistors (NWFETs). SiC is a promising semiconductor for this application due to its specific characteristics such as chemical inertness and biocompatibility. Non-intentionally n-doped SiC NWs are first grown using a bottom-up vapor–liquid–solid (VLS) mechanism, leading to the NWs exhibiting needle-shaped morphology, with a length of approximately 2 μm and a diameter ranging from 25 to 60 nm. Then, the SiC NWFETs are fabricated and functionalized with DNA molecule probes via covalent coupling using an amino-terminated organosilane. The drain current versus drain voltage (I d–V d) characteristics obtained after the DNA grafting and hybridization are reported from the comparative and simultaneous measurements carried out on the SiC NWFETs, used either as sensors or references. As a representative result, the current of the sensor is lowered by 22% after probe DNA grafting and by 7% after target DNA hybridization, while the current of the reference does not vary by more than ±0.6%. The current decrease confirms the field effect induced by the negative charges of the DNA molecules. Moreover, the selectivity, reproducibility, reversibility and stability of the studied devices are emphasized by de-hybridization, non-complementary hybridization and re-hybridization experiments. This first proof of concept opens the way for future developments using SiC-NW-based sensors.

  19. 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

  20. Large current difference in Au-coated vertical silicon nanowire electrode array with functionalization of peptides

    NASA Astrophysics Data System (ADS)

    Kim, Ilsoo; Kim, So-Eun; Han, Sanghun; Kim, Hyungsuk; Lee, Jaehyung; Jeong, Du-Won; Kim, Ju-Jin; Lim, Yong-beom; Choi, Heon-Jin

    2013-11-01

    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.

  1. 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.

  2. Capillary Printing of Highly Aligned Silver Nanowire Transparent Electrodes for High-Performance Optoelectronic Devices.

    PubMed

    Kang, Saewon; Kim, Taehyo; Cho, Seungse; Lee, Youngoh; Choe, Ayoung; Walker, Bright; Ko, Seo-Jin; Kim, Jin Young; Ko, Hyunhyub

    2015-12-01

    Percolation networks of silver nanowires (AgNWs) are commonly used as transparent conductive electrodes (TCEs) for a variety of optoelectronic applications, but there have been no attempts to precisely control the percolation networks of AgNWs that critically affect the performances of TCEs. Here, we introduce a capillary printing technique to precisely control the NW alignment and the percolation behavior of AgNW networks. Notably, partially aligned AgNW networks exhibit a greatly lower percolation threshold, which leads to the substantial improvement of optical transmittance (96.7%) at a similar sheet resistance (19.5 Ω sq(-1)) as compared to random AgNW networks (92.9%, 20 Ω sq(-1)). Polymer light-emitting diodes (PLEDs) using aligned AgNW electrodes show a 30% enhanced maximum luminance (33068 cd m(-2)) compared to that with random AgNWs and a high luminance efficiency (14.25 cd A(-1)), which is the highest value reported so far using indium-free transparent electrodes for fluorescent PLEDs. In addition, polymer solar cells (PSCs) using aligned AgNW electrodes exhibit a power conversion efficiency (PCE) of 8.57%, the highest value ever reported to date for PSCs using AgNW electrodes. PMID:26540011

  3. Dopant profiling and surface analysis of silicon nanowires using capacitance-voltage measurements.

    PubMed

    Garnett, Erik C; Tseng, Yu-Chih; Khanal, Devesh R; Wu, Junqiao; Bokor, Jeffrey; Yang, Peidong

    2009-05-01

    Silicon nanowires are expected to have applications in transistors, sensors, resonators, solar cells and thermoelectric systems. Understanding the surface properties and dopant distribution will be critical for the fabrication of high-performance devices based on nanowires. At present, determination of the dopant concentration depends on a combination of experimental measurements of the mobility and threshold voltage in a nanowire field-effect transistor, a calculated value for the capacitance, and two assumptions--that the dopant distribution is uniform and that the surface (interface) charge density is known. These assumptions can be tested in planar devices with the capacitance-voltage technique. This technique has also been used to determine the mobility of nanowires, but it has not been used to measure surface properties and dopant distributions, despite their influence on the electronic properties of nanowires. Here, we measure the surface (interface) state density and the radial dopant profile of individual silicon nanowire field-effect transistors with the capacitance-voltage technique. PMID:19421217

  4. Carbon-assisted growth and high visible-light optical reflectivity of amorphous silicon oxynitride nanowires

    PubMed Central

    2011-01-01

    Large amounts of amorphous silicon oxynitride nanowires have been synthesized on silicon wafer through carbon-assisted vapor-solid growth avoiding the contamination from metallic catalysts. These nanowires have the length of up to 100 μm, with a diameter ranging from 50 to 150 nm. Around 3-nm-sized nanostructures are observed to be homogeneously distributed within a nanowire cross-section matrix. The unique configuration might determine the growth of ternary amorphous structure and its special splitting behavior. Optical properties of the nanowires have also been investigated. The obtained nanowires were attractive for their exceptional whiteness, perceived brightness, and optical brilliance. These nanowires display greatly enhanced reflection over the whole visible wavelength, with more than 80% of light reflected on most of the wavelength ranging from 400 to 700 nm and the lowest reflectivity exceeding 70%, exhibiting performance superior to that of the reported white beetle. Intense visible photoluminescence is also observed over a broad spectrum ranging from 320 to 500 nm with two shoulders centered at around 444 and 468 nm, respectively. PMID:21787429

  5. Chemical and molecular beam epitaxy of III-V nanowires on silicon for photovoltaic application

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, Gokul

    Nanowires, due to their unique structure and carrier transport abilities, have sparked huge interest in the semiconductor industry. An array of nanometric size wires inserted between the p and n conductivity regions of a conventional solar cell or core shell type p-n junction nanowires synergized with semiconductor nanocrystals can lead to faster carrier collection, thereby improving device performance. This work investigates the growth of GaAs and InP semiconductor nanowires on silicon (111) using Chemical Beam Epitaxy (CBE) and Molecular Beam Epitaxy (MBE). Uniform gold nanoparticles acting as growth centers in the Vapor Liquid Solid mode of growth were generated by using the cheap and rapid technique called Nanosphere Lithography (NSL). Variation of the experimental parameters during NSL resulted in honeycomb and hexagonal patterns of gold nanoparticles. A high degree of selectivity was obtained for CBE grown nanowires whereas the MBE grown GaAs nanowires revealed the formation of a thick polycrystalline wetting layer at the interface. The CBE grown InP nanowires mostly maintained the honeycomb structure although they were found to be oriented contrary to the expected <111> direction. SEM analysis of GaAs nanowires grown by CBE showed that during growth, the nanowires may coalesce with each other resulting in unique structures such as bipods, tripods and multipods. High resolution TEM analysis of single GaAs nanowires revealed periodic formation of contrasting materials. Diffraction patterns recorded at these dark contrast areas confirmed the formation of hexagonal wurtzite single crystal structures interspaced with cubic zincblende single crystal structures. These nanowires can be used for photovoltaic applications or as light emitting devices. In addition, the formation of superlattices of different crystal structures can pave the way for novel quantum confined optoelectronic devices.

  6. Random telegraph signal and spin characteristics of the gate-all-around poly-silicon nanowire

    SciTech Connect

    Lee, Tsung-Han; Li, Yan-Ting; Hu, Shu-Fen E-mail: sfhu.hu@gmail.com

    2014-11-07

    An arsenic (As)-doped poly-silicon nanowire gate-all-around transistor fabricated using standard semiconductor methods was used to measure the Coulomb blockade effect by applying a tunable gate voltage. Two-level trapping states due to the random telegraph signal of fluctuating drain current were observed in the silicon transport channel. Under high magnetic fields, the superposition points of differential conductance revealed weak 2-electron singlet-triplet splitting states of the arsenic magnetic impurity. The weak spin-orbital coupling suggests that the electron-spin-polarization in the As-doped silicon nanowire and the two-level trapping state coexisted in the Coulomb blockade oscillations. These characteristics indicate that a few arsenic donors strongly affect the quantum behavior of the poly-silicon material.

  7. A comprehensive study of thermoelectric and transport properties of β-silicon carbide nanowires

    SciTech Connect

    Valentín, L. A.; Betancourt, J.; Fonseca, L. F.; Pettes, M. T.; Shi, L.; Soszyński, M.; Huczko, A.

    2013-11-14

    The temperature dependence of the Seebeck coefficient, the electrical and thermal conductivities of individual β-silicon carbide nanowires produced by combustion in a calorimetric bomb were studied using a suspended micro-resistance thermometry device that allows four-point probe measurements to be conducted on each nanowire. Additionally, crystal structure and growth direction for each measured nanowire was directly obtained by transmission electron microscopy analysis. The Fermi level, the carrier concentration, and mobility of each nanostructure were determined using a combination of Seebeck coefficient and electrical conductivity measurements, energy band structure and transport theory calculations. The temperature dependence of the thermal and electrical conductivities of the nanowires was explained in terms of contributions from boundary, impurity, and defect scattering.

  8. Formation of silicon nanowire packed films from metallurgical-grade silicon powder using a two-step metal-assisted chemical etching method.

    PubMed

    Ouertani, Rachid; Hamdi, Abderrahmen; Amri, Chohdi; Khalifa, Marouan; Ezzaouia, Hatem

    2014-01-01

    In this work, we use a two-step metal-assisted chemical etching method to produce films of silicon nanowires shaped in micrograins from metallurgical-grade polycrystalline silicon powder. The first step is an electroless plating process where the powder was dipped for few minutes in an aqueous solution of silver nitrite and hydrofluoric acid to permit Ag plating of the Si micrograins. During the second step, corresponding to silicon dissolution, we add a small quantity of hydrogen peroxide to the plating solution and we leave the samples to be etched for three various duration (30, 60, and 90 min). We try elucidating the mechanisms leading to the formation of silver clusters and silicon nanowires obtained at the end of the silver plating step and the silver-assisted silicon dissolution step, respectively. Scanning electron microscopy (SEM) micrographs revealed that the processed Si micrograins were covered with densely packed films of self-organized silicon nanowires. Some of these nanowires stand vertically, and some others tilt to the silicon micrograin facets. The thickness of the nanowire films increases from 0.2 to 10 μm with increasing etching time. Based on SEM characterizations, laser scattering estimations, X-ray diffraction (XRD) patterns, and Raman spectroscopy, we present a correlative study dealing with the effect of the silver-assisted etching process on the morphological and structural properties of the processed silicon nanowire films. PMID:25349554

  9. Formation of silicon nanowire packed films from metallurgical-grade silicon powder using a two-step metal-assisted chemical etching method

    NASA Astrophysics Data System (ADS)

    Ouertani, Rachid; Hamdi, Abderrahmen; Amri, Chohdi; Khalifa, Marouan; Ezzaouia, Hatem

    2014-10-01

    In this work, we use a two-step metal-assisted chemical etching method to produce films of silicon nanowires shaped in micrograins from metallurgical-grade polycrystalline silicon powder. The first step is an electroless plating process where the powder was dipped for few minutes in an aqueous solution of silver nitrite and hydrofluoric acid to permit Ag plating of the Si micrograins. During the second step, corresponding to silicon dissolution, we add a small quantity of hydrogen peroxide to the plating solution and we leave the samples to be etched for three various duration (30, 60, and 90 min). We try elucidating the mechanisms leading to the formation of silver clusters and silicon nanowires obtained at the end of the silver plating step and the silver-assisted silicon dissolution step, respectively. Scanning electron microscopy (SEM) micrographs revealed that the processed Si micrograins were covered with densely packed films of self-organized silicon nanowires. Some of these nanowires stand vertically, and some others tilt to the silicon micrograin facets. The thickness of the nanowire films increases from 0.2 to 10 μm with increasing etching time. Based on SEM characterizations, laser scattering estimations, X-ray diffraction (XRD) patterns, and Raman spectroscopy, we present a correlative study dealing with the effect of the silver-assisted etching process on the morphological and structural properties of the processed silicon nanowire films.

  10. Formation of silicon nanowire packed films from metallurgical-grade silicon powder using a two-step metal-assisted chemical etching method

    PubMed Central

    2014-01-01

    In this work, we use a two-step metal-assisted chemical etching method to produce films of silicon nanowires shaped in micrograins from metallurgical-grade polycrystalline silicon powder. The first step is an electroless plating process where the powder was dipped for few minutes in an aqueous solution of silver nitrite and hydrofluoric acid to permit Ag plating of the Si micrograins. During the second step, corresponding to silicon dissolution, we add a small quantity of hydrogen peroxide to the plating solution and we leave the samples to be etched for three various duration (30, 60, and 90 min). We try elucidating the mechanisms leading to the formation of silver clusters and silicon nanowires obtained at the end of the silver plating step and the silver-assisted silicon dissolution step, respectively. Scanning electron microscopy (SEM) micrographs revealed that the processed Si micrograins were covered with densely packed films of self-organized silicon nanowires. Some of these nanowires stand vertically, and some others tilt to the silicon micrograin facets. The thickness of the nanowire films increases from 0.2 to 10 μm with increasing etching time. Based on SEM characterizations, laser scattering estimations, X-ray diffraction (XRD) patterns, and Raman spectroscopy, we present a correlative study dealing with the effect of the silver-assisted etching process on the morphological and structural properties of the processed silicon nanowire films. PMID:25349554

  11. Enhancing the Lithiation Rate of Silicon Nanowires by the Inclusion of Tin

    SciTech Connect

    Bogart, Timothy D.; Lu, Xiaotang; Gu, Meng; Wang, Chong M.; Korgel, Brian A.

    2014-10-30

    Silicon (Si) has a very high lithium storage capacity and is being explored as a negative electrode material in lithium-ion batteries (LIBs). Si nanowires can exhibit relatively stable performance for many cycles of charging; however, conductive carbon must often be added to the electrode layer to improve the rate capability due to the relatively low electrical conductivity of Si. The added carbon lowers the capacity of the electrode. Here, we show that the rate capability of Si in LIBs can be substantially enhanced by incorporating tin (Sn) into Si nanowires. The solubility of Sn in Si is very low (0.015 at%); yet, Sn used as a seed for supercritical fluid–liquid–solid (SFLS) growth can be trapped in Si nanowires with relatively high concentration (10 at%). Such Sn-containing Si nanowires and no added conductive carbon in the electrode layer, could be cycled in LIBs with high capacity (*1000 mA h g*1 over 100 cycles) at a current density of 2.8 A g*1 (1 C). Capacities exceeding that of graphite could still be reached at cycle rates as high as 2 C. Real-time in situ transmission electron microscopy (TEM) revealed that lithiation occurs five times faster in Si nanowires with significant amounts of Sn than in the Si nanowires without Sn, and twice as fast as in nanowires that were coated with carbon.

  12. Probing photo-carrier collection efficiencies of individual silicon nanowire diodes on a wafer substrate.

    PubMed

    Schmitt, S W; Brönstrup, G; Shalev, G; Srivastava, S K; Bashouti, M Y; Döhler, G H; Christiansen, S H

    2014-07-21

    Vertically aligned silicon nanowire (SiNW) diodes are promising candidates for the integration into various opto-electronic device concepts for e.g. sensing or solar energy conversion. Individual SiNW p-n diodes have intensively been studied, but to date an assessment of their device performance once integrated on a silicon substrate has not been made. We show that using a scanning electron microscope (SEM) equipped with a nano-manipulator and an optical fiber feed-through for tunable (wavelength, power using a tunable laser source) sample illumination, the dark and illuminated current-voltage (I-V) curve of individual SiNW diodes on the substrate wafer can be measured. Surprisingly, the I-V-curve of the serially coupled system composed of SiNW/wafers is accurately described by an equivalent circuit model of a single diode and diode parameters like series and shunting resistivity, diode ideality factor and photocurrent can be retrieved from a fit. We show that the photo-carrier collection efficiency (PCE) of the integrated diode illuminated with variable wavelength and intensity light directly gives insight into the quality of the device design at the nanoscale. We find that the PCE decreases for high light intensities and photocurrent densities, due to the fact that considerable amounts of photo-excited carriers generated within the substrate lead to a decrease in shunting resistivity of the SiNW diode and deteriorate its rectification. The PCE decreases systematically for smaller wavelengths of visible light, showing the possibility of monitoring the effectiveness of the SiNW device surface passivation using the shown measurement technique. The integrated device was pre-characterized using secondary ion mass spectrometry (SIMS), TCAD simulations and electron beam induced current (EBIC) measurements to validate the properties of the characterized material at the single SiNW diode level. PMID:24830733

  13. Synthesis of silicon oxide nanowires and nanotubes with cobalt-palladium or palladium catalysts

    NASA Astrophysics Data System (ADS)

    Esterina, Ria; Liu, X. M.; Ross, C. A.; Adeyeye, A. O.; Choi, W. K.

    2012-07-01

    The dewetting behaviors of cobalt (Co), cobalt palladium (CoPd), and palladium (Pd) thin films on oxidized silicon substrates were examined. We observed the formation of craters in the oxide layer and pits in the Si substrate for larger CoPd or Pd catalyst particles and thinner oxide. Nanowires and nanotubes were observed near the Si pits. The nanowires and nanotubes grow via a vapor-solid-solid or vapor-liquid-solid mechanism with the silicon vapor source provided from the substrate. The original Si atoms that form the nanowires or nanotubes were oxidized in situ by the residual oxygen atoms present in the chamber. Some of the nanotubes had a series of embedded sub-catalysts that formed branches from the primary nanotube.

  14. Donor wave functions delocalization in silicon nanowires: the peculiar [011] orientation.

    PubMed

    Petretto, Guido; Debernardi, Alberto; Fanciulli, Marco

    2013-10-01

    The localization of the donor electron wave function can be of key importance in various silicon applications, since for example it determines the interactions between neighboring donors. Interestingly, the physical confinement of the electrons in quasi-one-dimensional nanostructures, like silicon nanowires, noticeably affects this property. Using fully ab initio calculations, we show that the delocalization of the donor electron wave function along the axis of a nanowire is much greater in [011] oriented nanowires for phosphorus and selenium donors. We also demonstrate that its value can be controlled by applying a compressive or tensile uniaxial strain. Finally, we discuss the implications of these features from both an experimental and a theoretical point of view. PMID:23984940

  15. Radial junction amorphous silicon solar cells on PECVD-grown silicon nanowires

    NASA Astrophysics Data System (ADS)

    Yu, Linwei; O'Donnell, Benedict; Foldyna, Martin; Cabarrocas, Pere Roca i.

    2012-05-01

    Constructing radial junction hydrogenated amorphous silicon (a-Si:H) solar cells on top of silicon nanowires (SiNWs) represents a promising approach towards high performance and cost-effective thin film photovoltaics. We here develop an all-in situ strategy to grow SiNWs, via a vapour-liquid-solid (VLS) mechanism on top of ZnO-coated glass substrate, in a plasma-enhanced chemical vapour deposition (PECVD) reactor. Controlling the distribution of indium catalyst drops allows us to tailor the as-grown SiNW arrays into suitable size and density, which in turn results in both a sufficient light trapping effect and a suitable arrangement allowing for conformal coverage of SiNWs by subsequent a-Si:H layers. We then demonstrate the fabrication of radial junction solar cells and carry on a parametric study designed to shed light on the absorption and quantum efficiency response, as functions of the intrinsic a-Si:H layer thickness and the density of SiNWs. These results lay a solid foundation for future structural optimization and performance ramp-up of the radial junction thin film a-Si:H photovoltaics.

  16. Field Emission studies of Silicon nanowires grown by Vapor-Liquid-Solid (VLS) technique

    NASA Astrophysics Data System (ADS)

    Kulkarni, Niraj; Bae, Joonho; Stanley, Scott; Coffee, Shawn; Ekerdt, John; Yao, Zhen; Shih, Chih-Kang

    2004-03-01

    Semiconductor nanowires among other 1-D nanostructures are potential candidates for field emission applications by virtue of their small tip radii and large aspect ratios. In this regard field emission properties of silicon nanowires are investigated. Silicon as a material has processing advantages over others because it has been well researched over the past decades. Silicon nanowires are grown by hot wire chemical vapor deposition (CVD) of disilane at approximately 600 C. The growth takes place via vapor-liquid-solid (VLS) mechanism with a thin film (20 nm) of gold acting as a catalyst. VLS growth enables large area coverage and also offers scalability. Field emission studies of these samples will be reported. Preliminary studies indicate a threshold field of 10-15 V/μ m. As a consequence of VLS growth, the catalyst (gold) resides at the tip of the nanowire and can be etched away by aqua regia. The effect of gold removal on the field emission characteristics will be reported. Silicon also offers an additional degree of freedom in terms of doping to engineer the position of the Fermi level. The effect of doping on the field emission characteristics will also be reported.

  17. Gamma ray irradiated silicon nanowires: An effective model to investigate defects at the interface of Si/SiOx

    SciTech Connect

    Yin, Kui; Zhao, Yi; Liu, Liangbin; Lee, Shuit-Tong; Shao, Mingwang E-mail: xuegi@nju.edu.cn; Wang, Xiaoliang E-mail: xuegi@nju.edu.cn Xue, Gi E-mail: xuegi@nju.edu.cn

    2014-01-20

    The effect of gamma ray irradiation on silicon nanowires was investigated. Here, an additional defect emerged in the gamma-ray-irradiated silicon nanowires and was confirmed with electron spin resonance spectra. {sup 29}Si nuclear magnetic resonance spectroscopy showed that irradiation doses had influence on the Q{sup 4} unit structure. This phenomenon indicated that the unique core/shell structure of silicon nanowires might contribute to induce metastable defects under gamma ray irradiation, which served as a satisfactory model to investigate defects at the interface of Si/SiOx.

  18. High throughput nanofabrication of silicon nanowire and carbon nanotube tips on AFM probes by stencil-deposited catalysts.

    PubMed

    Engstrom, Daniel S; Savu, Veronica; Zhu, Xueni; Bu, Ian Y Y; Milne, William I; Brugger, Juergen; Boggild, Peter

    2011-04-13

    A new and versatile technique for the wafer scale nanofabrication of silicon nanowire (SiNW) and multiwalled carbon nanotube (MWNT) tips on atomic force microscope (AFM) probes is presented. Catalyst material for the SiNW and MWNT growth was deposited on prefabricated AFM probes using aligned wafer scale nanostencil lithography. Individual vertical SiNWs were grown epitaxially by a catalytic vapor-liquid-solid (VLS) process and MWNTs were grown by a plasma-enhanced chemical vapor (PECVD) process on the AFM probes. The AFM probes were tested for imaging micrometers-deep trenches, where they demonstrated a significantly better performance than commercial high aspect ratio tips. Our method demonstrates a reliable and cost-efficient route toward wafer scale manufacturing of SiNW and MWNT AFM probes. PMID:21446752

  19. Silicon carbide nanowires under external loads: An atomistic simulation study

    NASA Astrophysics Data System (ADS)

    Makeev, Maxim A.; Srivastava, Deepak; Menon, Madhu

    2006-10-01

    The nanomechanical response properties of 3C-SiC nanowires are investigated using molecular dynamics simulation with Tersoff bond-order interatomic potential. Under axial compression and tensile strain, the computed Young’s modulus and structural changes at elastic limit do not depend appreciably on the diameter of the nanowire except for the nanowire of the smallest diameter (≈1nm) under compression. The elastic modulus and structural failure near the elastic limit regime, for nonaxial bending and torsional strains, are found to depend strongly on the nanowire diameters through a power-law behavior. The exponent of the power-law behavior and mechanisms of the material failure under different types of loading strains are described in this work.

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

    SciTech Connect

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

    2015-08-15

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

  1. 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

  2. Electrocatalytic activity of NiO on silicon nanowires with a carbon shell and its application in dye-sensitized solar cell counter electrodes

    NASA Astrophysics Data System (ADS)

    Kim, Junhee; Jung, Cho-Long; Kim, Minsoo; Kim, Soomin; Kang, Yoonmook; Lee, Hae-Seok; Park, Jeounghee; Jun, Yongseok; Kim, Donghwan

    2016-03-01

    To improve the catalytic activity of a material, it is critical to maximize the effective surface area by directly contacting the electrolyte. Nanowires are a promising building block for catalysts in electrochemical applications because of their large surface area. Nickel oxide (NiO) decoration was achieved by drop-casting a nickel-dissolved solution onto vertically aligned silicon nanowire arrays with a carbon shell (SiNW/C). Based on the hybridization of the NiO and silicon nanowire arrays with a carbon shell this study aimed to achieve a synergic effect for the catalytic activity performance. This study demonstrated that the resulting nanomaterial exhibits excellent electrocatalytic activity and performs well as a counter electrode for dye-sensitized solar cells (DSSCs). The compositions of the materials were examined using X-ray diffraction, X-ray photoelectron spectroscopy, and energy dispersive spectroscopy. Their micro- and nano-structures were investigated using scanning electron microscopy and transmission electron microscopy. The electrochemical activity toward I-/I3- was examined using cyclic voltammetry and electrochemical impedance spectroscopy. The obtained peak power conversion efficiency of the DSSC based on the NiO@SiNW/C counter electrode was 9.49%, which was greater than that of the DSSC based on the Pt counter electrode.To improve the catalytic activity of a material, it is critical to maximize the effective surface area by directly contacting the electrolyte. Nanowires are a promising building block for catalysts in electrochemical applications because of their large surface area. Nickel oxide (NiO) decoration was achieved by drop-casting a nickel-dissolved solution onto vertically aligned silicon nanowire arrays with a carbon shell (SiNW/C). Based on the hybridization of the NiO and silicon nanowire arrays with a carbon shell this study aimed to achieve a synergic effect for the catalytic activity performance. This study demonstrated that the

  3. Studies of epitaxial silicon nanowire growth by the vapor-liquid-solid mechanism

    NASA Astrophysics Data System (ADS)

    Aella, Pavan Reddy K.

    2007-12-01

    Silicon nanowires were grown epitaxially on Si (100) and (111) surfaces using the Vapor-Liquid-Solid (VLS) mechanism under both thermal and plasma enhanced growth conditions. Silane and disilane were used as source gases. Plasma excitation at low growth temperatures is found to strongly enhance nanowire growth rates and promote the nucleation of smaller diameter <110> oriented silicon nanowires relative to the larger diameter <111> nanowires. The higher nucleation rate for <110> nanowires during plasma excitation is attributed to a plasma-induced increase in silicon chemical potential. From this study, plasma excitation can be concluded to enable an additional degree of control over nanowire orientation. In low power radio frequency silane plasma, SiH3 are the dominant radical species in the gas phase. These reactive radicals formed in the plasma "bypass" the SiH 4 → SiH3 decomposition step on the liquid AuSi interface required for growth under thermal growth conditions, thereby leading to faster incorporation rates into the melt and hence promoting higher growth rates. Also consistent with this interpretation is the strong reduction in nucleation times in the presence of plasma. The nanowire growth rate shows a linear dependence with plasma power. The activation energy decreases from 0.78 eV under thermal growth conditions to 0.23 eV for a 2.5 W radio frequency plasma stimulated conditions. This decreased activation energy for growth under plasma excitation indicates that the rate limiting step for VLS growth of Si nanowires using Au as a catalyst is at the vapor-liquid interface. The growth under plasma conditions is dominated by the plasma influenced decomposition step and this strong reduction in the activation energy under silane plasma is consistent with a change in the rate limiting step. Growth kinetics between silane and disilane reveals an incorporation coefficient of Si, 60 to 80 times higher with disilane. This results in higher growth rates with

  4. Fabrication of a Silicon Nanowire on a Bulk Substrate by Use of a Plasma Etching and Total Ionizing Dose Effects on a Gate-All-Around Field-Effect Transistor

    NASA Technical Reports Server (NTRS)

    Moon, Dong-Il; Han, Jin-Woo; Meyyappan, Meyya

    2016-01-01

    The gate all around transistor is investigated through experiment. The suspended silicon nanowire for the next generation is fabricated on bulk substrate by plasma etching method. The scallop pattern generated by Bosch process is utilized to form a floating silicon nanowire. By combining anisotropic and istropic silicon etch process, the shape of nanowire is accurately controlled. From the suspended nanowire, the gate all around transistor is demonstrated. As the silicon nanowire is fully surrounded by the gate, the device shows excellent electrostatic characteristics.

  5. PLD-assisted VLS growth of aligned ferrite nanorods, nanowires, and nanobelts-synthesis, and properties.

    PubMed

    Morber, Jenny Ruth; Ding, Yong; Haluska, Michael Stephan; Li, Yang; Liu, J Ping; Wang, Zhong Lin; Snyder, Robert L

    2006-11-01

    We report here a systematic synthesis and characterization of aligned alpha-Fe2O3 (hematite), epsilon-Fe2O3, and Fe3O4 (magnetite) nanorods, nanobelts, and nanowires on alumina substrates using a pulsed laser deposition (PLD) method. The presence of spherical gold catalyst particles at the tips of the nanostructures indicates selective growth via the vapor-liquid-solid (VLS) mechanism. Through a series of experiments, we have produced a primitive "phase diagram" for growing these structures based on several designed pressure and temperature parameters. Transmission electron microscopy (TEM) analysis has shown that the rods, wires, and belts are single-crystalline and grow along <111>m or <110>h directions. X-ray diffraction (XRD) measurements confirm phase and structural analysis. Superconducting quantum interference device (SQUID) measurements show that the iron oxide structures exhibit interesting magnetic behavior, particularly at room temperature. This work is the first known report of magnetite 1D nanostructure growth via the vapor-liquid-solid (VLS) mechanism without using a template, as well as the first known synthesis of long epsilon-Fe2O3 nanobelts and nanowires. PMID:17064124

  6. 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

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

    PubMed Central

    2016-01-01

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

  8. Enhancing field emission performance of aligned Si nanowires via in situ partial oxidization.

    PubMed

    Qian, Zhongjian; Liu, Xianyun; Yang, Ye; Yin, Qiaoxia

    2014-08-01

    Partially oxidized Si nanowire (NW) arrays have been achieved via a combinatorial process of selectively etching Si wafer to obtain vertically aligned single crystalline Si NW arrays and subsequent in situ partially oxidizing the as-etched bare Si NWs. The resultant Si products are Si-SiOx nanocable-like structures consisting of single-crystalline Si NW inner cores and outer shells of insulating SiOx. Field emission measurements demonstrate that surface partial oxidization enhances the field emission current of the as-etched bare Si NWs effectively, which can be ascribed to the outer shell of insulating SiOx that has small electron affinity (0.6-0.8 eV) and can protect Si NW inner cores. The results indicate that the partially oxidized Si NW arrays would act as the excellent field emitters in the future vacuum micro- and nano-electronic devices. PMID:25936088

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

    PubMed

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

    2016-06-01

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

  10. 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.

  11. Flexible silver nanowire meshes for high-efficiency microtextured organic-silicon hybrid photovoltaics.

    PubMed

    Chen, Ting-Gang; Huang, Bo-Yu; Liu, Hsiao-Wei; Huang, Yang-Yue; Pan, Huai-Te; Meng, Hsin-Fei; Yu, Peichen

    2012-12-01

    Hybrid organic-silicon heterojunction solar cells promise a significant reduction on fabrication costs by avoiding energy-intensive processes. However, their scalability remains challenging without a low-cost transparent electrode. In this work, we present solution-processed silver-nanowire meshes that uniformly cover the microtextured surface of hybrid heterojunction solar cells to enable efficient carrier collection for large device area. We systematically compare the characteristics and device performance with long and short nanowires with an average length/diameter of 30 μm/115 nm and 15 μm/45 nm, respectively, to those with silver metal grids. A remarkable power conversion efficiency of 10.1% is achieved with a device area of 1 × 1 cm(2) under 100 mW/cm(2) of AM1.5G illumination for the hybrid solar cells employing long wires, which represents an enhancement factor of up to 36.5% compared to the metal grid counterpart. The high-quality nanowire network displays an excellent spatial uniformity of photocurrent generation via distributed nanowire meshes and low dependence on efficient charge transport under a high light-injection condition with increased device area. The capability of silver nanowires as flexible transparent electrodes presents a great opportunity to accelerate the mass deployment of high-efficiency hybrid silicon photovoltaics via simple and rapid soluble processes. PMID:23167527

  12. Monolithic electrically injected nanowire array edge-emitting laser on (001) silicon.

    PubMed

    Frost, Thomas; Jahangir, Shafat; Stark, Ethan; Deshpande, Saniya; Hazari, Arnab; Zhao, Chao; Ooi, Boon S; Bhattacharya, Pallab

    2014-08-13

    A silicon-based laser, preferably electrically pumped, has long been a scientific and engineering goal. We demonstrate here, for the first time, an edge-emitting InGaN/GaN disk-in-nanowire array electrically pumped laser emitting in the green (λ = 533 nm) on (001) silicon substrate. The devices display excellent dc and dynamic characteristics with values of threshold current density, differential gain, T0 and small signal modulation bandwidth equal to 1.76 kA/cm(2), 3 × 10(-17) cm(2), 232 K, and 5.8 GHz respectively under continuous wave operation. Preliminary reliability measurements indicate a lifetime of 7000 h. The emission wavelength can be tuned by varying the alloy composition in the quantum disks. The monolithic nanowire laser on (001)Si can therefore address wide-ranging applications such as solid state lighting, displays, plastic fiber communication, medical diagnostics, and silicon photonics. PMID:24971807

  13. Optical assessment of silicon nanowire arrays fabricated by metal-assisted chemical etching

    PubMed Central

    2013-01-01

    Silicon nanowire (SiNW) arrays were prepared on silicon substrates by metal-assisted chemical etching and peeled from the substrates, and their optical properties were measured. The absorption coefficient of the SiNW arrays was higher than that for the bulk silicon over the entire region. The absorption coefficient of a SiNW array composed of 10-μm-long nanowires was much higher than the theoretical absorptance of a 10-μm-thick flat Si wafer, suggesting that SiNW arrays exhibit strong optical confinement. To reveal the reason for this strong optical confinement demonstrated by SiNW arrays, angular distribution functions of their transmittance were experimentally determined. The results suggest that Mie-related scattering plays a significant role in the strong optical confinement of SiNW arrays. PMID:23651912

  14. Hydrophobic recovery in ultrathin PDMS-coated long and short silicon nanowires

    NASA Astrophysics Data System (ADS)

    Ganta, D.; Marry, C.; Ma, J.; Sinha, S.

    2016-03-01

    The ability to modify the contact angle (CA) of water on silicon has applications ranging from thermal management of electronics to miniaturized biomedical devices. Here, we report ∼30 ± 1° variation in superhydrophobic CA on silicon nanowires (NWs) coated with few nm of polydimethylsiloxane (PDMS), using a simple and stable plasma treatment. The variation in CA arises from choosing NWs of different lengths. We characterize the surfaces using a combination of X-ray photoelectron spectroscopy and other techniques. Together with CA available from similar treatment on bulk silicon, it is possible to non-lithographically create regions of diverse CA, from ∼5 to 149 ± 1°.

  15. Effect of biointerfacing linker chemistries on the sensitivity of silicon nanowires for protein detection.

    PubMed

    Dorvel, Brian; Reddy, Bobby; Bashir, Rashid

    2013-10-15

    Point-of-care diagnostics show promise in removing reliance on centralized lab testing facilities and may help increase both the survival rate for infectious diseases as well as monitoring of chronic illnesses. CMOS compatible diagnostic platforms are currently being considered as possible solutions as they can be easily miniaturized and can be cost-effective. Top-down fabricated silicon nanowires are a CMOS-compatible technology which have demonstrated high sensitivities in detecting biological analytes, such as proteins, DNA, and RNA. However, the reported response of nanowires to these analytes has varied widely since several different functionalization protocols have been attempted with little characterization and comparison. Here we report protocols for fabrication and functionalization of silicon nanowires which yield highly stable nanowires in aqueous solutions and limits of detection to ∼1 pg/mL of the model protein used in the study. A thorough characterization was done into optimizing the release of the silicon nanowires using combined dry and wet etch techniques, which yielded nanowires that could be directly compared to increase output statistics. Moreover, a range of different linker chemistries were tried for reacting the primary antibody, and its response to target and nonspecific antigens, with polyethylene glycol based linker BS(PEG)5 providing the best response. Consequently, this chemistry was used to characterize different oxide thicknesses and their responses to the mouse IgG antigen, which with the smallest oxide thickness yielded 0.1-1 pg/mL limits of detection and a dynamic range over 3 orders of magnitude. PMID:24040958

  16. Enhanced lithium ion battery cycling of silicon nanowire anodes by template growth to eliminate silicon underlayer islands.

    PubMed

    Cho, Jeong-Hyun; Picraux, S Tom

    2013-01-01

    It is well-known that one-dimensional nanostructures reduce pulverization of silicon (Si)-based anode materials during Li ion cycling because they allow lateral relaxation. However, even with improved designs, Si nanowire-based structures still exhibit limited cycling stability for extended numbers of cycles, with the specific capacity retention with cycling not showing significant improvements over commercial carbon-based anode materials. We have found that one important reason for the lack of long cycling stability can be the presence of milli- and microscale Si islands which typically form under nanowire arrays during their growth. Stress buildup in these Si island underlayers with cycling results in cracking, and the loss of specific capacity for Si nanowire anodes, due to progressive loss of contact with current collectors. We show that the formation of these parasitic Si islands for Si nanowires grown directly on metal current collectors can be avoided by growth through anodized aluminum oxide templates containing a high density of sub-100 nm nanopores. Using this template approach we demonstrate significantly enhanced cycling stability for Si nanowire-based lithium-ion battery anodes, with retentions of more than ~1000 mA·h/g discharge capacity over 1100 cycles. PMID:24144166

  17. Novel junctionless silicon-oxide-nitride-oxide-silicon memory devices with field-enhanced poly-Si nanowire structure

    NASA Astrophysics Data System (ADS)

    Chou, Chia-Hsin; Chan, Wei-Sheng; Wu, Chun-Yu; Lee, I.-Che; Liao, Ta-Chuan; Wang, Chao-Lung; Wang, Kuang-Yu; Cheng, Huang-Chung

    2015-08-01

    In this work, a novel gate-all-around (GAA) low-temperature poly-Si (LTPS) junctionless (JL) silicon-oxide-nitride-oxide-silicon (SONOS) nonvolatile memory device with a field-enhanced nanowire (NW) structure has been proposed to improve the programing/erasing (P/E) performance. Each nanowire has three sharp corners fabricated by a sidewall spacer formation technique to obtain high local electrical fields. Owing to the higher carrier concentration in the channel and the high local electrical field from the three sharp corners, such a JL SONOS memory device exhibits a significantly enhanced P/E speed, a larger memory window, and better data retention properties than a conventional inversion mode NW-channel memory device.

  18. A comparison of light-harvesting performance of silicon nanocones and nanowires for radial-junction solar cells

    PubMed Central

    Li, Yingfeng; Li, Meicheng; Fu, Pengfei; Li, Ruike; Song, Dandan; Shen, Chao; Zhao, Yan

    2015-01-01

    Silicon nanorod based radial-junction solar cells are competitive alternatives to traditional planar silicon solar cells. In various silicon nanorods, nanocone is always considered to be better than nanowire in light-absorption. Nevertheless, we find that this notion isn’t absolutely correct. Silicon nanocone is indeed significantly superior over nanowire in light-concentration due to its continuous diameters, and thus resonant wavelengths excited. However, the concentrated light can’t be effectively absorbed and converted to photogenerated carriers, since its propagation path in silicon nanocone is shorter than that in nanowire. The results provide critical clues for the design of silicon nanorod based radial-junction solar cells. PMID:26113194

  19. A comparison of light-harvesting performance of silicon nanocones and nanowires for radial-junction solar cells.

    PubMed

    Li, Yingfeng; Li, Meicheng; Fu, Pengfei; Li, Ruike; Song, Dandan; Shen, Chao; Zhao, Yan

    2015-01-01

    Silicon nanorod based radial-junction solar cells are competitive alternatives to traditional planar silicon solar cells. In various silicon nanorods, nanocone is always considered to be better than nanowire in light-absorption. Nevertheless, we find that this notion isn't absolutely correct. Silicon nanocone is indeed significantly superior over nanowire in light-concentration due to its continuous diameters, and thus resonant wavelengths excited. However, the concentrated light can't be effectively absorbed and converted to photogenerated carriers, since its propagation path in silicon nanocone is shorter than that in nanowire. The results provide critical clues for the design of silicon nanorod based radial-junction solar cells. PMID:26113194

  20. Adjustable optical response of amorphous silicon nanowires integrated with thin films.

    PubMed

    Dhindsa, Navneet; Walia, Jaspreet; Pathirane, Minoli; Khodadad, Iman; Wong, William S; Saini, Simarjeet Singh

    2016-04-01

    We experimentally demonstrate a new optical platform by integrating hydrogenated amorphous silicon nanowire arrays with thin films deposited on transparent substrates like glass. A 535 nm thick thin film is anisotropically etched to fabricate vertical nanowire arrays of 100 nm diameter arranged in a square lattice. Adjusting the nanowire length, and consequently the thin film thickness permits the optical properties of this configuration to be tuned for either transmission filter response or enhanced broadband absorption. Vivid structural colors are also achieved in reflection and transmission. The optical properties of the platform are investigated for three different etch depths. Transmission filter response is achieved for a configuration with nanowires on glass without any thin film. Alternatively, integrating thin film with nanowires increases the absorption efficiency by ∼97% compared to the thin film starting layer and by ∼78% over nanowires on glass. The ability to tune the optical response of this material in this fashion makes it a promising platform for high performance photovoltaics, photodetectors and sensors. PMID:26906427

  1. Effect of diborane on the microstructure of boron-doped silicon nanowires

    NASA Astrophysics Data System (ADS)

    Pan, Ling; Lew, Kok-Keong; Redwing, Joan M.; Dickey, Elizabeth C.

    2005-04-01

    Boron-doped silicon (Si) nanowires, with nominal diameters of 80 nm, were grown via the vapor-liquid-solid (VLS) mechanism using gold (Au) as a catalyst and silane (SiH 4) and diborane (B 2H 6) as precursors. The microstructure of the nanowires was studied by scanning electron microscopy, transmission electron microscopy and electron energy-loss spectroscopy. At lower B 2H 6 partial pressure and thus lower doping levels (⩽1×10 18 cm -3), most of the boron-doped Si nanowires exhibited high crystallinity. At higher B 2H 6 partial pressure (˜2×10 19 cm -3 doping level), the majority of the wires exhibited a core-shell structure with an amorphous Si shell (20-30 nm thick) surrounding a crystalline Si core. Au nanoparticles on the outer surface of the nanowires were also observed in structures grown with high B/Si gas ratios. The structural changes are believed to result from an increase in the rate of Si thin-film deposition on the outer surface of the nanowire at high B 2H 6 partial pressure, which produces the amorphous coating and also causes an instability at the liquid/solid interface resulting in a loss of Au during nanowire growth.

  2. Single p-type/intrinsic/n-type silicon nanowires as nanoscale avalanche photodetectors.

    PubMed

    Yang, Chen; Barrelet, Carl J; Capasso, Federico; Lieber, Charles M

    2006-12-01

    We report the controlled synthesis of axial modulation-doped p-type/intrinsic/n-type (p-i-n) silicon nanowires with uniform diameters and single-crystal structures. The p-i-n nanowires were grown in three sequential steps: in the presence of diborane for the p-type region, in the absence of chemical dopant sources for the middle segment, and in the presence of phosphine for the n-type region. The p-i-n nanowires were structurally characterized by transmission electron microscopy, and the spatially resolved electrical properties of individual nanowires were determined by electrostatic force and scanning gate microscopies. Temperature-dependent current-voltage measurements recorded from individual p-i-n devices show an increase in the breakdown voltage with temperature, characteristic of band-to-band impact ionization, or avalanche breakdown. Spatially resolved photocurrent measurements show that the largest photocurrent is generated at the intrinsic region located between the electrode contacts, with multiplication factors in excess of ca. 30, and demonstrate that single p-i-n nanowires function as avalanche photodiodes. Electron- and hole-initiated avalanche gain measurements performed by localized photoexcitation of the p-type and n-type regions yield multiplication factors of ca. 100 and 20, respectively. These results demonstrate the significant potential of single p-i-n nanowires as nanoscale avalanche photodetectors and open possible opportunities for studying impact ionization of electrons and holes within quasi-one-dimensional semiconductor systems. PMID:17163733

  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. 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.

  5. CMOS-Compatible Silicon-Nanowire-Based Coulter Counter for Cell Enumeration.

    PubMed

    Chen, Yu; Guo, Jinhong; Muhammad, Hamidullah; Kang, Yuejun; Ary, Sunil K

    2016-02-01

    A silicon-nanowire-based Coulter counter has been designed and fabricated for particle/cell enumeration. The silicon nanowire was fabricated in a fully complementary metal-oxide-semiconductor (CMOS)-compatible process and used as a field effect transistor (FET) device. The Coulter counter device worked on the principle of potential change detection introduced by the passing of microparticles/cells through a sensing channel. Device uniformity was confirmed by scanning electron microscopy and transmission electron microscopy. Current-voltage measurement showed the high sensitivity of the nanowire FET device to the surface potential change. The results revealed that the silicon-nanowire-based Coulter counter can differentiate polystyrene beads with diameters of 8 and 15 μm. Michigan Cancer Foundation-7 (MCF-7) cells have been successfully counted to validate the device. A fully CMOS-compatible fabrication process can help the device integration and facilitate the development of sensor arrays for high throughput application. With appropriate sample preparation steps, it is also possible to expand the work to applications such as rare-cells detection. PMID:26799578

  6. Exploring Direct to Indirect Bandgap Transition in Silicon Nanowires: Size Effect

    NASA Astrophysics Data System (ADS)

    Shi, Lihong; Zhang, Gang

    2016-06-01

    We have investigated the electronic band structure of [110] silicon nanowires (SiNWs) using first-principles calculations. We find that, in the ultrathin diameter regime, SiNWs have a direct bandgap, but the energy difference between the indirect and direct fundamental bandgaps decreases as the nanowire diameter increases. This indicates that larger [110] SiNWs could have an indirect bandgap. Fundamentally, a series of quantitative direct-indirect bandgap transitional diameters are obtained for different cross-sectional geometries, with the largest values for SiNWs with triangular cross section.

  7. Tailoring thermal conductivity of silicon/germanium nanowires utilizing core-shell architecture

    NASA Astrophysics Data System (ADS)

    Sarikurt, S.; Ozden, A.; Kandemir, A.; Sevik, C.; Kinaci, A.; Haskins, J. B.; Cagin, T.

    2016-04-01

    Low-dimensional nanostructured materials show large variations in their thermal transport properties. In this work, we investigate the influence of the core-shell architecture on nanowire (1D) thermal conductivity and evaluate its validity as a strategy to achieve a better thermoelectric performance. To obtain the thermal conductivity values, equilibrium molecular dynamics simulations are conducted for core-shell nanowires of silicon and germanium. To explore the parameter space, we have calculated thermal conductivity values of the Si-core/Ge-shell and Ge-core/Si-shell nanowires having different cross-sectional sizes and core contents at several temperatures. Our results indicate that (1) increasing the cross-sectional area of pristine Si and pristine Ge nanowires increases the thermal conductivity, (2) increasing the Ge core size in the Ge-core/Si-shell structure results in a decrease in the thermal conductivity at 300 K, (3) the thermal conductivity of the Si-core/Ge-shell nanowires demonstrates a minima at a specific core size, (4) no significant variation in the thermal conductivity is observed in nanowires for temperatures larger than 300 K, and (5) the predicted thermal conductivity within the frame of applied geometrical constraints is found to be around 10 W/(mK) for the Si and Ge core-shell architecture with a smooth interface. The value is still higher than the amorphous limit (1 W/(mK)). This represents a significant reduction in thermal conductivity with respect to their bulk crystalline and pristine nanowire forms. Furthermore, we observed additional suppression of thermal conductivity through the introduction of interface roughness to Si/Ge core-shell nanowires.

  8. Hybrid core-shell nanowire electrodes utilizing vertically aligned carbon nanofiber arrays for high-performance energy storage

    NASA Astrophysics Data System (ADS)

    Klankowski, Steven Arnold

    Nanostructured electrode materials for electrochemical energy storage systems have been shown to improve both rate performance and capacity retention, while allowing considerably longer cycling lifetime. The nano-architectures provide enhanced kinetics by means of larger surface area, higher porosity, better material interconnectivity, shorter diffusion lengths, and overall mechanical stability. Meanwhile, active materials that once were excluded from use due to bulk property issues are now being examined in new nanoarchitecture. Silicon was such a material, desired for its large lithium-ion storage capacity of 4,200 mAh g-1 and low redox potential of 0.4 V vs. Li/Li+; however, a ˜300% volume expansion and increased resistivity upon lithiation limited its broader applications. In the first study, the silicon-coated vertically aligned carbon nanofiber (VACNF) array presents a unique core-shell nanowire (NW) architecture that demonstrates both good capacity and high rate performance. In follow-up, the Si-VACNFs NW electrode demonstrates enhanced power rate capabilities as it shows excellent storage capacity at high rates, attributed to the unique nanoneedle structure that high vacuum sputtering produces on the three-dimensional array. Following silicon's success, titanium dioxide has been explored as an alternative high-rate electrode material by utilizing the dual storage mechanisms of Li+ insertion and pseudocapacitance. The TiO 2-coated VACNFs shows improved electrochemical activity that delivers near theoretical capacity at larger currents due to shorter Li+ diffusion lengths and highly effective electron transport. A unique cell is formed with the Si-coated and TiO2-coated electrodes place counter to one another, creating the hybrid of lithium ion battery-pseudocapacitor that demonstrated both high power and high energy densities. The hybrid cell operates like a battery at lower current rates, achieving larger discharge capacity, while retaining one-third of

  9. Silicon carbide nanowires: Elastic properties, defects, and surface formations

    NASA Astrophysics Data System (ADS)

    Rich, Ryan Michael

    A highly reproducible method of producing SiC nanowires on a large scale is presented, and the average size of SiC nanowires was 30 nm. XRD revealed that the molar yield increased linearly with time. TEM showed a distribution of nanowire sizes that shifted towards larger diameters as sintering time increased. It is known that vapor-liquid-solid reactions involving a metal catalyst play a role in their formation, and there is further evidence that a vapor-solid mechanism contributes as well. The elastic properties of the following SiC morphologies were explored with pressure applied via a diamond anvil cell: 20 nm grains, 50 nm grains, 130 nm grains, and 30 nm nanowires The bulk modulus of nanowires increased by 8%, while that of 20 nm grains increased 30% in comparison to bulk material. The increased bulk modulus is explained by the core-shell model, where nanoparticles possess one or more distinct regions near the surface with identical crystal symmetry but different interatomic distances. Defects may also affect the bulk modulus, especially in the heavily faulted nanowires. As seen by TEM, planar faults were abundant, and their quantity decreased with decreasing diameter. The extended Convolutional Multiple Whole Profile (eCMWP) analysis was employed to quantitate the defects by XRD. This analysis concluded that twins are the most frequently occurring planar fault with a 2.20% probability of formation, which corresponds to a defect spacing of 38 nm. SiC nanowires are formed with an amorphous outer layer a few nanometers deep. It was concluded that the layer consisted mainly of amorphous SiC, but EDS confirmed that this structure was rich in oxygen. FTIR confirmed the presence of Si-O bands which increased in population with thermal treatment. The surface of SiC nanowires was modified by etching in HF and HNO3 acids. Silica bands were reduced and functional groups appeared after treatment. XRD found that grain size increased by 186% and dislocations decreased by

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

    PubMed Central

    2012-01-01

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

  11. Absorption enhancement in silicon nanowire-optical nanoantenna system for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Robak, Elżbieta; Grześkiewicz, Bartłomiej; Kotkowiak, Michał

    2014-11-01

    The rapidly growing green energy sector has prompted the search for new solutions to increase the performance of solar cells. In this area there is still room for the silicon-based photovoltaic, although the main problem is to find a way to increase the efficiency of the silicon solar cells, at the lowest possible cost. In this work we investigate the influence of a gold bowtie nanoantenna on the absorption profile of silicon nanowire. Because of the energy band gap and low effective absorption cross section, bulk silicon absorbs rather poorly in longer wavelengths of visible light and near-infrared range. Our calculations with frequency domain solver show the absorption boost in nanowire at long-wavelengths due to the coupling of the large local near-field of metallic bowtie nanoantenna to the semiconductor layer. The enhancement was observed at various levels although it was correlated with the shift of localized surface plasmon resonance thus making it dependent on the bowtie geometry. The results suggest that by incorporating metallic nanostructures as well as nanoparticles to the nanowire system, the performance of photovoltaic device can be improved thanks to greater generation of a electron-hole pairs.

  12. Enhanced photocatalytic degradation of methylene blue by metal-modified silicon nanowires

    SciTech Connect

    Brahiti, N.; Hadjersi, T.; Menari, H.; Amirouche, S.; El Kechai, O.

    2015-02-15

    Highlights: • SiNWs modified with Pd, Au and Pt were used as photocatalysts to degrade MB. • Yield of photodegardation increases with UV irradiation time. • SiNWs modified with Pd nanoparticles show the best photocatalytic activity. • A degradation of 97% was obtained after 200 min of UV irradiation. - Abstract: Silicon nanowires (SiNWs) modified with Au, Pt and Pd nanoparticles were used as heterogeneous photocatalysts for the photodegradation of methylene blue in water under UV light irradiation. The modification of SiNWs was carried out by deposition of metal nanoparticles using the electroless metal deposition (EMD) technique. The effect of metal nanoparticles deposition time on the photocatalytic activity was studied. It was found that the photocatalytic activity of modified SiNWs was enhanced when the deposition time of metal nanoparticles was increased. In addition of modified SiNWs with Pt, Au and Pd nanoparticles, oxidized silicon substrate (Ox-Si), oxidized silicon nanowires (Ox-SiNWs) and hydrogen-terminated silicon nanowires (H-SiNWs) were also evaluated for the photodegradation of methylene blue.

  13. Resonant tunnelling features in a suspended silicon nanowire single-hole transistor

    SciTech Connect

    Llobet, Jordi; Pérez-Murano, Francesc E-mail: z.durrani@imperial.ac.uk; Krali, Emiljana; Wang, Chen; Jones, Mervyn E.; Durrani, Zahid A. K. E-mail: z.durrani@imperial.ac.uk; Arbiol, Jordi

    2015-11-30

    Suspended silicon nanowires have significant potential for a broad spectrum of device applications. A suspended p-type Si nanowire incorporating Si nanocrystal quantum dots has been used to form a single-hole transistor. Transistor fabrication uses a novel and rapid process, based on focused gallium ion beam exposure and anisotropic wet etching, generating <10 nm nanocrystals inside suspended Si nanowires. Electrical characteristics at 10 K show Coulomb diamonds with charging energy ∼27 meV, associated with a single dominant nanocrystal. Resonant tunnelling features with energy spacing ∼10 meV are observed, parallel to both diamond edges. These may be associated either with excited states or hole–acoustic phonon interactions, in the nanocrystal. In the latter case, the energy spacing corresponds well with reported Raman spectroscopy results and phonon spectra calculations.

  14. Fabrication and evaluation of series-triple quantum dots by thermal oxidation of silicon nanowire

    SciTech Connect

    Uchida, Takafumi Jo, Mingyu; Tsurumaki-Fukuchi, Atsushi; Arita, Masashi; Takahashi, Yasuo; Fujiwara, Akira

    2015-11-15

    Series-connected triple quantum dots were fabricated by a simple two-step oxidation technique using the pattern-dependent oxidation of a silicon nanowire and an additional oxidation of the nanowire through the gap of the fine gates attached to the nanowire. The characteristics of multi-dot single-electron devices are obtained. The formation of each quantum dot beneath an attached gate is confirmed by analyzing the electrical characteristics and by evaluating the gate capacitances between all pairings of gates and quantum dots. Because the gate electrode is automatically attached to each dot, the device structure benefits from scalability. This technique promises integrability of multiple quantum dots with individual control gates.

  15. Needle-shaped silicon carbide nanowires: Synthesis and field electron emission properties

    NASA Astrophysics Data System (ADS)

    Wu, Z. S.; Deng, S. Z.; Xu, N. S.; Chen, Jian; Zhou, J.; Chen, Jun

    2002-05-01

    Bunches of needle-shaped silicon carbide (SiC) nanowires were grown from commercially available SiC powders in thermal evaporation process and using iron as catalyst. Their structure and chemical composition were studied by Raman spectroscopy and high-resolution transmission electron microscopy. The powder of these nanowires may be easily dispersed, and was used to form samples of field electron emitters. The needle shape of individual nanowires is well-suited to field electron emission. Stable emission with current density of 30.8 mA/cm2 was observed at fields as low as 9.6 V/μm, and current density of up to 83 mA/cm2 was recorded.

  16. Fabrication and evaluation of series-triple quantum dots by thermal oxidation of silicon nanowire

    NASA Astrophysics Data System (ADS)

    Uchida, Takafumi; Jo, Mingyu; Tsurumaki-Fukuchi, Atsushi; Arita, Masashi; Fujiwara, Akira; Takahashi, Yasuo

    2015-11-01

    Series-connected triple quantum dots were fabricated by a simple two-step oxidation technique using the pattern-dependent oxidation of a silicon nanowire and an additional oxidation of the nanowire through the gap of the fine gates attached to the nanowire. The characteristics of multi-dot single-electron devices are obtained. The formation of each quantum dot beneath an attached gate is confirmed by analyzing the electrical characteristics and by evaluating the gate capacitances between all pairings of gates and quantum dots. Because the gate electrode is automatically attached to each dot, the device structure benefits from scalability. This technique promises integrability of multiple quantum dots with individual control gates.

  17. Self-Aligned Cu-Si Core-Shell Nanowire Array as a High-Performance Anode for Li-Ion Batteries

    SciTech Connect

    Qu, Jun; Li, Huaqing; Henry Jr, John James; Martha, Surendra K; Dudney, Nancy J; Lance, Michael J; Mahurin, Shannon Mark; Besmann, Theodore M; Dai, Sheng

    2012-01-01

    Silicon nanowires (NWs) have been reported as a promising anode that demonstrated high capacity without pulverization during cycling, however, they present some technical issues that remain to be solved. The high aspect ratio of the NWs and their small contact areas with the current collector cause high electrical resistance, which results in inefficient electron transport. The nano-size interface between a NW and the substrate experiences high shear stress during lithiation, causing the wire to separate from the current collector. In addition, most reported methods for producing silicon NWs involve high-temperature processing and require catalysts that later become contaminants. This study developed a new self-aligned Cu-Si core-shell NW array using a low-temperature, catalyst-free process to address the issues described. The silicon shell is amorphous as synthesized and accommodates Li-ions without phase transformation. The copper core functions as a built-in current collector to provide very short (nm) electron transport pathways as well as backbone to improve mechanical strength. Initial electrochemical evaluation has demonstrated good capacity retention and high Coulombic efficiency for this new anode material in a half-cell configuration. No wire fracture or core-shell separation was observed after cycling. However, electrolyte decomposition products largely covered the top surface of the NW array, restricting electrolyte access and causing capacity reduction at high charging rates.

  18. Electrocatalytic activity of NiO on silicon nanowires with a carbon shell and its application in dye-sensitized solar cell counter electrodes.

    PubMed

    Kim, Junhee; Jung, Cho-long; Kim, Minsoo; Kim, Soomin; Kang, Yoonmook; Lee, Hae-seok; Park, Jeounghee; Jun, Yongseok; Kim, Donghwan

    2016-04-14

    To improve the catalytic activity of a material, it is critical to maximize the effective surface area by directly contacting the electrolyte. Nanowires are a promising building block for catalysts in electrochemical applications because of their large surface area. Nickel oxide (NiO) decoration was achieved by drop-casting a nickel-dissolved solution onto vertically aligned silicon nanowire arrays with a carbon shell (SiNW/C). Based on the hybridization of the NiO and silicon nanowire arrays with a carbon shell this study aimed to achieve a synergic effect for the catalytic activity performance. This study demonstrated that the resulting nanomaterial exhibits excellent electrocatalytic activity and performs well as a counter electrode for dye-sensitized solar cells (DSSCs). The compositions of the materials were examined using X-ray diffraction, X-ray photoelectron spectroscopy, and energy dispersive spectroscopy. Their micro- and nano-structures were investigated using scanning electron microscopy and transmission electron microscopy. The electrochemical activity toward I(-)/I3(-) was examined using cyclic voltammetry and electrochemical impedance spectroscopy. The obtained peak power conversion efficiency of the DSSC based on the NiO@SiNW/C counter electrode was 9.49%, which was greater than that of the DSSC based on the Pt counter electrode. PMID:27001286

  19. Study of Ac Dielectrophoretic Process of SiC Nanowires: A Universal Method for Alignment of Semiconductor Nanowires.

    PubMed

    Yao, Limei; Cui, Yan; Cong, Haining; Zheng, Jinju; Shang, Minghui; Yang, Zuobao; Yang, Weiyou; Wei, Guodong; Gao, Fengmei

    2016-04-01

    In this study, the dielectrophoretic processes of SiC nanowires suspended in three typical solvents, (highly purified water, ethanol and isopropanol) were systematically investigated. Optical microscope and SEM characterizations were used to observe the order of SiC nanowires on the surface of gold microchannels. The gold microchannels were induced by Ac dielectrophoresis of the corresponding dispersion solutions of SiC nanowires, with a concentration of 0.1 mg/mL. The study shows that the dielectrophoresis process is an effective way of synthesizing highly oriented SiC nanoarrays using isopropanol solution. The results also show that the arrangement of SiC nanowires on the interdigital electrode configuration not only depend on the kind of solvent used, but also on the applied frequency (1000 Hz~1 MHz) and voltage (1 V~20 V). PMID:27451739

  20. Characteristics of Al substituted nanowires fabricated by self-aligned growth for future large scale integration interconnects

    NASA Astrophysics Data System (ADS)

    Kudo, Hiroshi; Kurahashi, Teruo

    2011-06-01

    Substituted Al nanowires for use in future large scale integration interconnects were fabricated by self-aligned growth. The resistivity of an Al substituted nanowire 80 nm in width, 100 nm in height, and 20 μm in length was 4.7 μΩ cm, which is 48% lower than that of an Al nanowire with the same dimensions fabricated using a bottom-up approach. The variation in the resistivity was in a narrow range (14%) over a Si wafer. The TEM imaging revealed that the Al substituted nanowire had a bamboo-like structure with grains larger than 1.6 μm. The electromigration activation energy was 0.72 eV, which is comparable to that of a pure Al wire with a bamboo-like structure. The product of the critical current density and wire length was 1.3 × 103 A/cm at 250 °C; 2.1 times higher than that of a pure Al wire with a polycrystalline structure. The acceleration of electromigration due to current density was 2.0, indicating that incubation time dominates electromigration lifetime. The prolonged incubation time observed in the electromigration test is attributed to the reduction in electromigration-induced mass transport due to the microstructure of the Al substituted nanowire. Even the formation of a small void immediately after incubation may be a fatal defect for nanoscale Al wires.

  1. Subsurface imaging of silicon nanowire circuits and iron oxide nanoparticles with sub-10 nm spatial resolution.

    PubMed

    Perrino, A P; Ryu, Y K; Amo, C A; Morales, M P; Garcia, R

    2016-07-01

    Non-destructive subsurface characterization of nanoscale structures and devices is of significant interest in nanolithography and nanomanufacturing. In those areas, the accurate location of the buried structures and their nanomechanical properties are relevant for optimization of the nanofabrication process and the functionality of the system. Here we demonstrate the capabilities of bimodal and trimodal force microscopy for imaging silicon nanowire devices buried under an ultrathin polymer film. We resolve the morphology and periodicities of silicon nanowire pairs. We report a spatial resolution in the sub-10 nm range for nanostructures buried under a 70 nm thick polymer film. By using numerical simulations we explain the role of the excited modes in the subsurface imaging process. Independent of the bimodal or trimodal atomic force microscopy approach, the fundamental mode is the most suitable for tracking the topography while the higher modes modulate the interaction of the tip with the buried nanostructures and provide subsurface contrast. PMID:27232523

  2. Subsurface imaging of silicon nanowire circuits and iron oxide nanoparticles with sub-10 nm spatial resolution

    NASA Astrophysics Data System (ADS)

    Perrino, A. P.; Ryu, Y. K.; Amo, C. A.; Morales, M. P.; Garcia, R.

    2016-07-01

    Non-destructive subsurface characterization of nanoscale structures and devices is of significant interest in nanolithography and nanomanufacturing. In those areas, the accurate location of the buried structures and their nanomechanical properties are relevant for optimization of the nanofabrication process and the functionality of the system. Here we demonstrate the capabilities of bimodal and trimodal force microscopy for imaging silicon nanowire devices buried under an ultrathin polymer film. We resolve the morphology and periodicities of silicon nanowire pairs. We report a spatial resolution in the sub-10 nm range for nanostructures buried under a 70 nm thick polymer film. By using numerical simulations we explain the role of the excited modes in the subsurface imaging process. Independent of the bimodal or trimodal atomic force microscopy approach, the fundamental mode is the most suitable for tracking the topography while the higher modes modulate the interaction of the tip with the buried nanostructures and provide subsurface contrast.

  3. The Analysis of Characteristics in Dry and Wet Environments of Silicon Nanowire-Biosensor.

    PubMed

    Choi, Hyoun Mo; Shin, Dong Jae; Lee, Jung Han; Mo, Hyun-Sun; Park, Tae Jung; Park, Byung-Gook; Kim, Dong Myong; Choi, Sung-Jin; Kim, Dae Hwan; Park, Jisun

    2016-05-01

    Our study investigates differences in sensitivity of dry and wet environment in the field of biosensing experiment in detail and depth. The sensitivity of biosensing varies by means of surrounding conditions of silicon nanowire field effect transistor (SiNW FET). By examining charged polymer reaction in the silicon nanowire transistor (SiNW), we have discovered that the threshold voltage (V(T)) shift and change of subthreshold slope (SS) in wet environment are smaller than that of the air. Furthermore, we analyzed the sensitivity through modifying electrolyte concentration in the wet condition, and confirmed that V(T) shift increases in low concentration condition of phosphate buffered saline (PBS) due to the Debye length. We believe that the results we have found in this study would be the cornerstone in contributing to advanced biosensing experiment in the future. PMID:27483843

  4. The piezoresistive effect in n-type junctionless silicon nanowire transistors.

    PubMed

    Kang, Ting-Kuo

    2012-11-30

    The piezoresistive effect in n-type silicon nanowires on silicon-on-insulator wafers, also called junctionless nanowire transistors (JNTs), is investigated. A marked change in the subthreshold drain current for strained JNTs is observed. This change can be attributed to strain-induced interface state modification, due to an increase in the interface state for tensile strain or a decrease in the trap activation energy for compressive strain. Through many long-time cycles of compressive and released strain, the electromechanical response of subthreshold I(DS) with time is found, thus supporting the widely reported giant piezoresistance effect. In addition, JNTs involving a back-gate and an additional top-gate electrode may become a new prospect for high-precision sensor applications and next-generation multigate transistors. PMID:23111286

  5. Room temperature NO2 gas sensing of Au-loaded tungsten oxide nanowires/porous silicon hybrid structure

    NASA Astrophysics Data System (ADS)

    Deng-Feng, Wang; Ji-Ran, Liang; Chang-Qing, Li; Wen-Jun, Yan; Ming, Hu

    2016-02-01

    In this work, we report an enhanced nitrogen dioxide (NO2) gas sensor based on tungsten oxide (WO3) nanowires/porous silicon (PS) decorated with gold (Au) nanoparticles. Au-loaded WO3 nanowires with diameters of 10 nm-25 nm and lengths of 300 nm-500 nm are fabricated by the sputtering method on a porous silicon substrate. The high-resolution transmission electron microscopy (HRTEM) micrographs show that Au nanoparticles are uniformly distributed on the surfaces of WO3 nanowires. The effect of the Au nanoparticles on the NO2-sensing performance of WO3 nanowires/porous silicon is investigated over a low concentration range of 0.2 ppm-5 ppm of NO2 at room temperature (25 °C). It is found that the 10-Å Au-loaded WO3 nanowires/porous silicon-based sensor possesses the highest gas response characteristic. The underlying mechanism of the enhanced sensing properties of the Au-loaded WO3 nanowires/porous silicon is also discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 61274074 and 61271070) and the Key Research Program of Application Foundation and Advanced Technology of Tianjin, China (Grant No. 11JCZDJC15300).

  6. Potential barrier height at the grain boundaries of a poly-silicon nanowire.

    PubMed

    Shamir, Assaf; Amit, Iddo; Englander, Danny; Horvitz, Dror; Rosenwaks, Yossi

    2015-09-01

    We present measurements of the potential barrier height and its dependence on grain size in poly-silicon nanowire (P-SiNW) arrays. Measurements conducted using Kelvin probe force microscopy coupled with electrostatic simulations, enabled us also to extract the density of the grain boundary interface states and their energy distribution. In addition it was shown that the barrier height scales with the grain size as the square of the grain radius. PMID:26245190

  7. Tunable narrowband microwave photonic filter created by stimulated Brillouin scattering from a silicon nanowire

    NASA Astrophysics Data System (ADS)

    Casas-Bedoya, Alvaro; Morrison, Blair; Pagani, Mattia; Marpaung, David; Eggleton, Benjamin J.

    2015-09-01

    We demonstrate the first functional signal processing device based on stimulated Brillouin scattering in a silicon nanowire. We use only 1 dB of on-chip SBS gain to create an RF photonic notch filter with 48 dB of suppression, 98 MHz linewidth, and 6 GHz frequency tuning. This device has potential applications in on-chip microwave signal processing and establishes the foundation for the first CMOS-compatible high performance RF photonic filter.

  8. Tunable electronic properties of silicon nanowires under strain and electric bias

    SciTech Connect

    Nduwimana, Alexis; Wang, Xiao-Qian

    2014-07-15

    The electronic structure characteristics of silicon nanowires under strain and electric bias are studied using first-principles density functional theory. The unique wire-like structure leads to distinct spatial distribution of carriers, which can be tailored by applying tensile and compressive strains, as well as by an electric bias. Our results indicate that the combined effect of strain and electric bias leads to tunable electronic structures that can be used for piezo-electric devices.

  9. Growth, patterning and alignment of organolead iodide perovskite nanowires for optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Deng, Hui; Dong, Dongdong; Qiao, Keke; Bu, Lingling; Li, Bing; Yang, Dun; Wang, Hong-En; Cheng, Yibing; Zhao, Zhixin; Tang, Jiang; Song, Haisheng

    2015-02-01

    Organolead halide perovskites are becoming intriguing materials applied in optoelectronics. In the present work, organolead iodide perovskite (OIP) nanowires (NWs) have been fabricated by a one step self-assembly method. The controllable NW distributions were implemented by a series of facile techniques: monolayer and small diameter NWs were prepared by precursor concentration tuning; NW patterning was achieved via selected area treatment assisted by a mask; NW alignment was implemented by modified evaporation-induced self-assembly (EISA). The synthesized multifunctional NWs were further applied in photodetectors (PDs) and solar cells as application demos. The PD performances have reached 1.32 AW-1 for responsivity, 2.5 × 1012 Jones for detectivity and 0.3 ms for response speed, superior to OIP films and other typical inorganic NW based PD performances. An energy conversion efficiency of ~2.5% has been obtained for NW film based solar cells. The facile fabrication process, controllable distribution and optoelectronic applications make the OIP NWs promising building blocks for future optoelectronics, especially for low dimensional devices.Organolead halide perovskites are becoming intriguing materials applied in optoelectronics. In the present work, organolead iodide perovskite (OIP) nanowires (NWs) have been fabricated by a one step self-assembly method. The controllable NW distributions were implemented by a series of facile techniques: monolayer and small diameter NWs were prepared by precursor concentration tuning; NW patterning was achieved via selected area treatment assisted by a mask; NW alignment was implemented by modified evaporation-induced self-assembly (EISA). The synthesized multifunctional NWs were further applied in photodetectors (PDs) and solar cells as application demos. The PD performances have reached 1.32 AW-1 for responsivity, 2.5 × 1012 Jones for detectivity and 0.3 ms for response speed, superior to OIP films and other typical inorganic

  10. Critical Role of Diels–Adler Adducts to Realise Stretchable Transparent Electrodes Based on Silver Nanowires and Silicone Elastomer

    NASA Astrophysics Data System (ADS)

    Heo, Gaeun; Pyo, Kyoung-Hee; Lee, Da Hee; Kim, Youngmin; Kim, Jong-Woong

    2016-05-01

    This paper presents the successful fabrication of a transparent electrode comprising a sandwich structure of silicone/Ag nanowires (AgNWs)/silicone equipped with Diels–Alder (DA) adducts as crosslinkers to realise highly stable stretchability. Because of the reversible DA reaction, the crosslinked silicone successfully bonds with the silicone overcoat, which should completely seal the electrode. Thus, any surrounding liquid cannot leak through the interfaces among the constituents. Furthermore, the nanowires are protected by the silicone cover when they are stressed by mechanical loads such as bending, folding, and stretching. After delicate optimisation of the layered silicone/AgNW/silicone sandwich structure, a stretchable transparent electrode which can withstand 1000 cycles of 50% stretching–releasing with an exceptionally high stability and reversibility was fabricated. This structure can be used as a transparent strain sensor; it possesses a strong piezoresistivity with a gauge factor greater than 11.

  11. Critical Role of Diels-Adler Adducts to Realise Stretchable Transparent Electrodes Based on Silver Nanowires and Silicone Elastomer.

    PubMed

    Heo, Gaeun; Pyo, Kyoung-Hee; Lee, Da Hee; Kim, Youngmin; Kim, Jong-Woong

    2016-01-01

    This paper presents the successful fabrication of a transparent electrode comprising a sandwich structure of silicone/Ag nanowires (AgNWs)/silicone equipped with Diels-Alder (DA) adducts as crosslinkers to realise highly stable stretchability. Because of the reversible DA reaction, the crosslinked silicone successfully bonds with the silicone overcoat, which should completely seal the electrode. Thus, any surrounding liquid cannot leak through the interfaces among the constituents. Furthermore, the nanowires are protected by the silicone cover when they are stressed by mechanical loads such as bending, folding, and stretching. After delicate optimisation of the layered silicone/AgNW/silicone sandwich structure, a stretchable transparent electrode which can withstand 1000 cycles of 50% stretching-releasing with an exceptionally high stability and reversibility was fabricated. This structure can be used as a transparent strain sensor; it possesses a strong piezoresistivity with a gauge factor greater than 11. PMID:27140436

  12. Critical Role of Diels–Adler Adducts to Realise Stretchable Transparent Electrodes Based on Silver Nanowires and Silicone Elastomer

    PubMed Central

    Heo, Gaeun; Pyo, Kyoung-hee; Lee, Da Hee; Kim, Youngmin; Kim, Jong-Woong

    2016-01-01

    This paper presents the successful fabrication of a transparent electrode comprising a sandwich structure of silicone/Ag nanowires (AgNWs)/silicone equipped with Diels–Alder (DA) adducts as crosslinkers to realise highly stable stretchability. Because of the reversible DA reaction, the crosslinked silicone successfully bonds with the silicone overcoat, which should completely seal the electrode. Thus, any surrounding liquid cannot leak through the interfaces among the constituents. Furthermore, the nanowires are protected by the silicone cover when they are stressed by mechanical loads such as bending, folding, and stretching. After delicate optimisation of the layered silicone/AgNW/silicone sandwich structure, a stretchable transparent electrode which can withstand 1000 cycles of 50% stretching–releasing with an exceptionally high stability and reversibility was fabricated. This structure can be used as a transparent strain sensor; it possesses a strong piezoresistivity with a gauge factor greater than 11. PMID:27140436

  13. Thermal Conductivity Suppression in Nanostructured Silicon and Germanium Nanowires

    NASA Astrophysics Data System (ADS)

    Özden, Ayberk; Kandemir, Ali; Ay, Feridun; Perkgöz, Nihan Kosku; Sevik, Cem

    2016-03-01

    The inherent low lattice thermal conductivity (TC) of semiconductor nanowires (s-NW) due to one-dimensional phonon confinement might provide a solution for the long-lasting figure-of-merit problem for highly efficient thermoelectric (TE) applications. Standalone diameter modulation or alloying of s-NW serve as a toolkit for TC control, but realizing the full potential of nanowires requires new atomic-scale designs, growth, characterization, and understanding of the physical mechanisms behind the structure-property (TC) relationship. Before undertaking time-consuming and expensive experimental work, molecular dynamics (MD) simulations serve as an excellent probe to investigate new designs and understand how nanostructures affect thermal transport properties through their capability to capture various phenomena such as phonon boundary scattering, phonon coherence resonance, and phonon backscattering. On the other hand, because different research groups use different structural and MD parameters in their simulations, it is rather difficult to make comparisons between different nanostructures and select appropriate ones for potential TE applications. Therefore, in this work, we systematically investigated pristine, core-shell (C-S), holey (H-N), superlattice (SL), sawtooth (ST), and superlattice sawtooth (SL-ST) nanowires with identical structural parameters. Specifically, we aim to compare the relative TC reduction achieved by these nanostructures with respect to pristine nanowires in order to propose the best structural design with the lowest lattice TC, using Green-Kubo method-based equilibrium molecular dynamics simulations at 300 K. Our results show that the TC can be minimized by changing specific parameters such as the core diameter and monolayer separation for C-S, H-N, and ST structures. In the case of SL structures, the TC is found to be independent of these parameters. However, surface roughness in the form of a ST morphology provides a TC value below 2 W

  14. Low-power microsensors for explosives and nerve warfare agents using silicon nanodots and nanowires

    NASA Astrophysics Data System (ADS)

    Sailor, Michael J.; Trogler, William C.; Letant, Sonia; Sohn, Honglae; Content, Stephane; Schmedake, Thomas A.; Gao, Jun; Zmolek, Peter; Link, Jamie R.; Fainman, Yeshaiahu; Xu, Fang; Shames, Paul E.

    2001-09-01

    Nanocrystalline porous silicon films (nanodots) and polymeric silicon wires (nanowires) have been used to detect chemicals in gas and liquid phase. Transduction mechanisms using quantum confinement derived photoluminescence and optical reflectivity have been used. Photoluminescence intensity is modulated by energy or electron transfer induced quenching, and a shift of the Fabry-Perot reflectivity fringes from thin nanocrystalline films occurs upon molecular absorption. Examples of irreversible detection and reversible sensing modes for explosives, nerve warfare agents, and various odors of commercial interest will be provided. A catalyst can be incorporated into the nanomaterials to provide specificity for the analyte of interest.

  15. Hydrogen-terminated silicon nanowire photocatalysis: Benzene oxidation and methyl red decomposition

    SciTech Connect

    Lian, Suoyuan; Tsang, Chi Him A.; Kang, Zhenhui; Liu, Yang; Wong, Ningbew; Lee, Shuit-Tong

    2011-12-15

    Graphical abstract: H-SiNWs can catalyze hydroxylation of benzene and degradation of methyl red under visible light irradiation. Highlights: Black-Right-Pointing-Pointer Hydrogen-terminated silicon nanowires were active photocatalyst in the hydroxylation of benzene under light. Black-Right-Pointing-Pointer Hydrogen-terminated silicon nanowires were also effective in the decomposition of methyl red dye. Black-Right-Pointing-Pointer The Si/SiO{sub x} core-shell structure is the main reason of the obtained high selectivity during the hydroxylation. -- Abstract: Hydrogen-terminated silicon nanowires (H-SiNWs) were used as heterogeneous photocatalysts for the hydroxylation of benzene and for the decomposition of methyl red under visible light irradiation. The above reactions were monitored by GC-MS and UV-Vis spectrophotometry, respectively, which shows 100% selectivity for the transformation of benzene to phenol. A complete decomposition of a 2 Multiplication-Sign 10{sup -4} M methyl red solution was achieved within 30 min. The high selectivity for the hydroxylation of benzene and the photodecomposition demonstrate the catalytic activity of ultrafine H-SiNWs during nanocatalysis.

  16. Sensing properties of assembled Bi2S3 nanowire arrays

    NASA Astrophysics Data System (ADS)

    Kunakova, G.; Meija, R.; Bite, I.; Prikulis, J.; Kosmaca, J.; Varghese, J.; Holmes, J. D.; Erts, Donats

    2015-09-01

    Bismuth sulfide (Bi2S3) nanowires were grown in porous aluminium oxide template and a selective chemical etching was applied to transfer the nanowires to a solution. Well aligned nanowire arrays were assembled on pre-patterned silicon substrates employing dielectrophoresis. Electron beam lithography was used to connect aligned individual nanowires to the common macroelectrode. In order to evaluate the conductometric sensing performance of the Bi2S3 nanowires, current-voltage characteristics were measured at different relative humidity (RH) levels (5-80%) / argon medium. The response of the Bi2S3 nanowires depending of RH is found to be considerably different from those reported for other types of nanowire RH sensor devices.

  17. Electrical detection of dengue virus (DENV) DNA oligomer using silicon nanowire biosensor with novel molecular gate control.

    PubMed

    Nuzaihan M N, M; Hashim, U; Md Arshad, M K; Kasjoo, S R; Rahman, S F A; Ruslinda, A R; Fathil, M F M; Adzhri, R; Shahimin, M M

    2016-09-15

    In this paper, a silicon nanowire biosensor with novel molecular gate control has been demonstrated for Deoxyribonucleic acid (DNA) detection related to dengue virus (DENV). The silicon nanowire was fabricated using the top-down nanolithography approach, through nanostructuring of silicon-on-insulator (SOI) layers achieved by combination of the electron-beam lithography (EBL), plasma dry etching and size reduction processes. The surface of the fabricated silicon nanowire was functionalized by means of a three-step procedure involving surface modification, DNA immobilization and hybridization. This procedure acts as a molecular gate control to establish the electrical detection for 27-mers base targets DENV DNA oligomer. The electrical detection is based on the changes in current, resistance and conductance of the sensor due to accumulation of negative charges added by the immobilized probe DNA and hybridized target DNA. The sensitivity of the silicon nanowire biosensors attained was 45.0µAM(-1), which shows a wide-range detection capability of the sensor with respect to DNA. The limit of detection (LOD) achieved was approximately 2.0fM. The demonstrated results show that the silicon nanowire has excellent properties for detection of DENV with outstanding repeatability and reproducibility performances. PMID:27107147

  18. 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.

  19. Formation of a Top Electrode on Vertical Si Nanowire Devices Using Graphene as a Supporting Layer

    NASA Astrophysics Data System (ADS)

    Jeong, Hyeon Ho; Kim, Jungkil; Lee, Jinsup; Jeon, Seokwoo; Lee, Woo; Lee, Seok-Hee

    2012-10-01

    This letter presents a method of forming a top electrode on vertical silicon nanowires by using multilayer graphene as a supporting layer during metal deposition. We exploit graphene's unique material properties such as its impermeability to various gases and ions. An improved shallow trench isolation process is also presented to fabricate self-aligned silicon nanowire arrays for device integration. By this method, silicon nanowire bundle arrays with air gap structures are successfully fabricated using a top-down approach. This technique is expected to find use in many nanowire device applications.

  20. Low-temperature study of array of dopant atoms on transport behaviors in silicon junctionless nanowire transistor

    SciTech Connect

    Wang, Hao; Han, Weihua Li, Xiaoming; Zhang, Yanbo; Yang, Fuhua

    2014-09-28

    We demonstrate temperature-dependent quantum transport characteristics in silicon junctionless nanowire transistor fabricated on Silicon-on-Insulator substrate by the femtosecond laser lithography. Clear drain-current oscillations originated from dopant-induced quantum dots are observed in the initial stage of the conduction for the silicon nanowire channel at low temperatures. Arrhenius plot of the conductance indicates the transition temperature of 30 K from variable-range hopping to nearest-neighbor hopping, which can be well explained under Mott formalism. The transition of electron hopping behavior is the interplay result between the thermal activation and the Coulomb interaction.

  1. Thermal Test of an Improved Platform for Silicon Nanowire-Based Thermoelectric Micro-generators

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    This work reports on an improved design intended to enhance the thermal isolation between the hot and cold parts of a silicon-based thermoelectric microgenerator. Micromachining techniques and silicon on insulator substrates are used to obtain a suspended silicon platform surrounded by a bulk silicon rim, in which arrays of bottom-up silicon nanowires are integrated later on to join both parts with a thermoelectric active material. In previous designs the platform was linked to the rim by means of bulk silicon bridges, used as mechanical support and holder for the electrical connections. Such supports severely reduce platform thermal isolation and penalise the functional area due to the need of longer supports. A new technological route is planned to obtain low thermal conductance supports, making use of a particular geometrical design and a wet bulk micromachining process to selectively remove silicon shaping a thin dielectric membrane. Thermal conductance measurements have been performed to analyse the influence of the different design parameters of the suspended platform (support type, bridge/membrane length, separation between platform and silicon rim,) on overall thermal isolation. A thermal conductance reduction from 1.82 mW/K to 1.03 mW/K, has been obtained on tested devices by changing the support type, even though its length has been halved.

  2. Electrowetting properties of atomic layer deposited Al{sub 2}O{sub 3} decorated silicon nanowires

    SciTech Connect

    Rajkumar, K.; Rajavel, K.; Cameron, D. C.; Mangalaraj, D.; Rajendrakumar, R. T.

    2015-06-24

    This paper reports the electrowetting properties of liquid droplet on superhydrophobic silicon nanowires with Atomic layer deposited (ALD) Al{sub 2}O{sub 3} as dielectric layer. Silicon wafer were etched by metal assisted wet chemical etching with silver as catalyst. ALD Al{sub 2}O{sub 3} films of 10nm thickness were conformally deposited over silicon nanowires. Al{sub 2}O{sub 3} dielectric film coated silicon nanowires was chemically modified with Trichloro (1H, 1H, 2H, 2H-perfluorooctyl) silane to make it superhydrophobic(SHP). The contact angle was measured and all the samples exhibited superhydrophobic nature with maximum contact angles of 163° and a minimum contact angle hysteresis of 6°. Electrowetting induced a maximum reversible decrease of the contact angle of 20°at 150V in air.

  3. Insertion of Vertically Aligned Nanowires into Living Cells by Inkjet Printing of Cells.

    PubMed

    Lee, Donggyu; Lee, Daehee; Won, Yulim; Hong, Hyeonaug; Kim, Yongjae; Song, Hyunwoo; Pyun, Jae-Chul; Cho, Yong Soo; Ryu, Wonhyoung; Moon, Jooho

    2016-03-01

    Effective insertion of vertically aligned nanowires (NWs) into cells is critical for bioelectrical and biochemical devices, biological delivery systems, and photosynthetic bioenergy harvesting. However, accurate insertion of NWs into living cells using scalable processes has not yet been achieved. Here, NWs are inserted into living Chlamydomonas reinhardtii cells (Chlamy cells) via inkjet printing of the Chlamy cells, representing a low-cost and large-scale method for inserting NWs into living cells. Jetting conditions and printable bioink composed of living Chlamy cells are optimized to achieve stable jetting and precise ink deposition of bioink for indentation of NWs into Chlamy cells. Fluorescence confocal microscopy is used to verify the viability of Chlamy cells after inkjet printing. Simple mechanical considerations of the cell membrane and droplet kinetics are developed to control the jetting force to allow penetration of the NWs into cells. The results suggest that inkjet printing is an effective, controllable tool for stable insertion of NWs into cells with economic and scale-related advantages. PMID:26800021

  4. 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.

  5. Aligned silver nanowire-based transparent electrodes for engineering polarisation-selective optoelectronics.

    PubMed

    Park, Byoungchoo; Bae, In-Gon; Huh, Yoon Ho

    2016-01-01

    We herein report on a remarkably simple, fast, and economic way of fabricating homogeneous and well oriented silver nanowires (AgNWs) that exhibit strong in-plane electrical and optical anisotropies. Using a small quantity of AgNW suspension, the horizontal-dip (H-dip) coating method was applied, in which highly oriented AgNWs were deposited unidirectionally along the direction of coating over centimetre-scale lengths very rapidly. In applying the H-dip-coating method, we adjusted the shear strain rate of the capillary flow in the Landau-Levich meniscus of the AgNW suspension, which induced a high degree of uniaxial orientational ordering (0.37-0.43) of the AgNWs, comparable with the ordering seen in archetypal nematic liquid crystal (LC) materials. These AgNWs could be used to fabricate not only transparent electrodes, but also LC-alignment electrodes for LC devices and/or polarising electrodes for organic photovoltaic devices, having the potential to revolutionise the architectures of a number of polarisation-selective opto-electronic devices for use in printed/organic electronics. PMID:26778621

  6. Massive transfer of vertically aligned Si nanowire array onto alien substrates and their characteristics

    NASA Astrophysics Data System (ADS)

    Shiu, Shu-Chia; Hung, Shih-Che; Chao, Jiun-Jie; Lin, Ching-Fuh

    2009-07-01

    Si nanowires (NWs) are promising materials for future electronic, photovoltaic, and sensor applications. So far the Si NWs are mainly formed on particular substrates or at high temperatures, greatly limiting their application flexibility. Here we report a low temperature process for forming and massively transferring vertically aligned Si NWs on alien substrates with a large density of about (3-5) × 10 7 NWs/mm 2. The X-ray diffraction spectrum reveals that the transferred NWs exhibit almost the same crystal property as the bulk Si. Our investigation further shows that the transferred NWs have exceptional optical characteristics. The transferred Si NWs of 12.14 μm exhibit the transmittance as low as 0.3% in the near infrared region and 0.07% in the visible region. The extracted absorption coefficient of Si NWs in the near infrared region is about 3 × 10 3 cm -1, over 30 times larger than that of the bulk Si. Because of the low temperature process, it enables a large variety of alien substrates such as glass and plastics to be used. In addition, the exceptional properties of the transferred NWs offer potential applications for photovoltaic, photo-detectors, sensors, and flexible electronics.

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

    PubMed Central

    2011-01-01

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

  8. Wet etch methods for InAs nanowire patterning and self-aligned electrical contacts.

    PubMed

    Fülöp, G; d'Hollosy, S; Hofstetter, L; Baumgartner, A; Nygård, J; Schönenberger, C; Csonka, S

    2016-05-13

    Advanced synthesis of semiconductor nanowires (NWs) enables their application in diverse fields, notably in chemical and electrical sensing, photovoltaics, or quantum electronic devices. In particular, indium arsenide (InAs) NWs are an ideal platform for quantum devices, e.g. they may host topological Majorana states. While the synthesis has been continously perfected, only a few techniques have been developed to tailor individual NWs after growth. Here we present three wet chemical etch methods for the post-growth morphological engineering of InAs NWs on the sub-100 nm scale. The first two methods allow the formation of self-aligned electrical contacts to etched NWs, while the third method results in conical shaped NW profiles ideal for creating smooth electrical potential gradients and shallow barriers. Low temperature experiments show that NWs with etched segments have stable transport characteristics and can serve as building blocks of quantum electronic devices. As an example we report the formation of a single electrically stable quantum dot between two etched NW segments. PMID:27040175

  9. Aligned silver nanowire-based transparent electrodes for engineering polarisation-selective optoelectronics

    NASA Astrophysics Data System (ADS)

    Park, Byoungchoo; Bae, In-Gon; Huh, Yoon Ho

    2016-01-01

    We herein report on a remarkably simple, fast, and economic way of fabricating homogeneous and well oriented silver nanowires (AgNWs) that exhibit strong in-plane electrical and optical anisotropies. Using a small quantity of AgNW suspension, the horizontal-dip (H-dip) coating method was applied, in which highly oriented AgNWs were deposited unidirectionally along the direction of coating over centimetre-scale lengths very rapidly. In applying the H-dip-coating method, we adjusted the shear strain rate of the capillary flow in the Landau-Levich meniscus of the AgNW suspension, which induced a high degree of uniaxial orientational ordering (0.37-0.43) of the AgNWs, comparable with the ordering seen in archetypal nematic liquid crystal (LC) materials. These AgNWs could be used to fabricate not only transparent electrodes, but also LC-alignment electrodes for LC devices and/or polarising electrodes for organic photovoltaic devices, having the potential to revolutionise the architectures of a number of polarisation-selective opto-electronic devices for use in printed/organic electronics.

  10. Aligned silver nanowire-based transparent electrodes for engineering polarisation-selective optoelectronics

    PubMed Central

    Park, Byoungchoo; Bae, In-Gon; Huh, Yoon Ho

    2016-01-01

    We herein report on a remarkably simple, fast, and economic way of fabricating homogeneous and well oriented silver nanowires (AgNWs) that exhibit strong in-plane electrical and optical anisotropies. Using a small quantity of AgNW suspension, the horizontal-dip (H-dip) coating method was applied, in which highly oriented AgNWs were deposited unidirectionally along the direction of coating over centimetre-scale lengths very rapidly. In applying the H-dip-coating method, we adjusted the shear strain rate of the capillary flow in the Landau-Levich meniscus of the AgNW suspension, which induced a high degree of uniaxial orientational ordering (0.37–0.43) of the AgNWs, comparable with the ordering seen in archetypal nematic liquid crystal (LC) materials. These AgNWs could be used to fabricate not only transparent electrodes, but also LC-alignment electrodes for LC devices and/or polarising electrodes for organic photovoltaic devices, having the potential to revolutionise the architectures of a number of polarisation-selective opto-electronic devices for use in printed/organic electronics. PMID:26778621

  11. 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

  12. Silicon oxides as alignment surfaces for vertically-aligned nematics in photonic devices

    NASA Astrophysics Data System (ADS)

    Oton, E.; López-Andrés, S.; Bennis, N.; Otón, J. M.; Geday, M. A.

    2014-06-01

    A comparative study on alignment performance and microstructure of inorganic layers used for liquid crystal cell conditioning has been carried out. The study has focused on two specific materials, SiOx and SiO2, deposited under different conditions. The purpose was to establish a relationship between layer microstructure and liquid crystal alignment. The surface morphology has been studied by FESEM and AFM. An analysis on liquid crystal alignment, pretilt angle, response time, contrast ratio and the conditions to develop backflow effect (significant rise time increase due to pure homeotropic alignment) on vertically-aligned nematic cells has been carried out. A technique to overcome the presence of backflow has been identified. The full comparative study of SiOx and SiO2 layer properties and their influence over liquid crystal alignment and electrooptic response is presented.

  13. Effects of silver and gold catalytic activities on the structural and optical properties of silicon nanowires

    NASA Astrophysics Data System (ADS)

    Lajvardi, M.; Eshghi, H.; Izadifard, M.; Ghazi, M. E.; Goodarzi, A.

    2016-01-01

    The metal-assisted chemical etching of silicon in an aqueous solution of hydrofluoric acid and hydrogen peroxide is established for the fabrication of large area, uniform silicon nanowire (SiNW) arrays. In this study, silver (Ag) and gold (Au) are considered as catalysts and the effect of different catalysts with various thicknesses on the structural and optical properties of the fabricated SiNWs is investigated. The morphology of deposited catalysts on the silicon wafer is characterized by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). It is shown that the morphology of the fabricated silicon nanostructures remarkably depends upon the catalyst layer thickness, and the catalyst etching time directly affects the structural and optical properties of the synthesized SiNWs. FESEM images show a linear increment of the nanowire length versus time, whereas the etching rate for the Au-etched SiNWs was lower than the Ag-etched ones. Strong light scattering in SiNWs caused the total reflection to decrease in the range of visible light, and this decrement was higher for the Ag-etched SiNW sample, with a longer length than the Au-etched one. A broadband visible photoluminescence (PL) with different peak positions is observed for the Au- and Ag-etched samples. The synthesized optically active SiNWs can be considered as a promising candidate for a new generation of nano-scale opto-electronic devices.

  14. Novel Iron-oxide Catalyzed CNT Formation on Semiconductor Silicon Nanowire

    PubMed Central

    Adam, Tijjani; U, Hashim

    2014-01-01

    An aqueous ferric nitrate nonahydrate (Fe(NO3)3.9H2O) and magnesium oxide (MgO) were mixed and deposited on silicon nanowires (SiNWs), the carbon nanotubes (CNTs) formed by the concentration of Fe3O4/MgO catalysts with the mole ratio set at 0.15:9.85 and 600°C had diameter between 15.23 to 90nm with high-density distribution of CNT while those with the mole ratio set at 0.45:9.55 and 730°C had diameter of 100 to 230nm. The UV/Vis/NIR and FT-IR spectroscopes clearly confirmed the presence of the silicon-CNTs hybrid structure. UV/Vis/NIR, FT-IR spectra and FESEM images confirmed the silicon-CNT structure exists with diameters ranging between 15-230nm. Thus, the study demonstrated cost effective method of silicon-CNT composite nanowire formation via Iron-oxide Catalyze synthesis. PMID:25237290

  15. 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. PMID:24323873

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

    NASA Astrophysics Data System (ADS)

    Shen, Gang

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

  17. 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.

  18. Vapor-liquid-solid growth of silicon and silicon germanium nanowires

    NASA Astrophysics Data System (ADS)

    Nimmatoori, Pramod

    2009-12-01

    Si and Si1-xGex nanowires are promising materials with potential applications in various disciplines of science and technology. Small diameter nanowires can act as model systems to study interesting phenomena such as tunneling that occur in the nanometer regime. Furthermore, technical challenges in fabricating nanoscale size devices from thin films have resulted in interest and research on nanowires. In this perspective, vertical integrated nanowire field effect transistors (VINFETs) fabricated from Si nanowires are promising devices that offer better control on device properties and push the transistor architecture into the third dimension potentially enabling ultra-high transistor density circuits. Transistors fabricated from Si/Si 1-xGex nanowires have also been proposed that can have high carrier mobility. In addition, the Si and Si1-xGe x nanowires have potential to be used in various applications such as sensing, thermoelectrics and solar cells. Despite having considerable potential, the understanding of the vapor-liquid-solid (VLS) mechanism utilized to fabricate these wires is still rudimentary. Hence, the objective of this thesis is to understand the effects of nanoscale size and the role of catalyst that mediates the wire growth on the growth rate of Si and Si1-xGe x nanowires and interfacial abruptness in Si/Si1-xGe x axial heterostructure nanowires. Initially, the growth and structural properties of Si nanowires with tight diameter distribution grown from 10, 20 and 50 nm Au particles dispersed on a polymer-modified substrate was studied. A nanoparticle application process was developed to disperse Au particles on the substrate surface with negligible agglomeration and sufficient density. The growth temperature and SiH4 partial pressure were varied to optimize the growth conditions amenable to VLS growth with smooth wire morphology and negligible Si thin film deposition on wire sidewalls. The Si nanowire growth rate was studied as a function of growth

  19. Position-sensitive spectral splitting with a plasmonic nanowire on silicon chip

    PubMed Central

    Hu, Qing; Xu, Di-Hu; Zhou, Yu; Peng, Ru-Wen; Fan, Ren-Hao; Fang, Nicholas X.; Wang, Qian-Jin; Huang, Xian-Rong; Wang, Mu

    2013-01-01

    On-chip nanophotonics serves as the foundation for the new generation of information technology, but it is challenged by the diffraction limit of light. With the capabilities of confining light into (deep) subwavelength volumes, plasmonics makes it possible to dramatically miniaturize optical devices so as to integrate them into silicon chips. Here we demonstrate that by cascading nano-corrugation gratings with different periodicities on silver nanowires atop silicon, different colors can be spatially separated and chronologically released at different grating junctions. The released light frequency depends on the grating arrangement and corrugation periodicities. Hence the nanowire acts as a spectral splitter for sorting/demultiplexing photons at different nano-scale positions with a ten-femtosecond-level interval. Such nanowires can be constructed further into compact 2D networks or circuits. We believe that this study provides a new and promising approach for realizing spatiotemporal-sensitive spectral splitting and optical signal processing on nanoscales, and for general integration of nanophotonics with microelectronics. PMID:24172838

  20. Label-free biosensing of a gene mutation using a silicon nanowire field-effect transistor.

    PubMed

    Wu, Chi-Chang; Ko, Fu-Hsiang; Yang, Yuh-Shyong; Hsia, Der-Ling; Lee, Bo-Syuan; Su, Ting-Siang

    2009-12-15

    We have developed a silicon nanowire field-effect transistor (NWFET) that allows deoxyribonucleic acid (DNA) biosensing. The nanowire (NW) was fabricated on a silicon-on-insulator wafer to provide effective ohmic contact. The NWFET sensor displayed n-channel depletion characteristics. To demonstrate the sensing capacity of the NWFET, we employed the BRAF(V599E) mutation gene, which correlates to the occurrence of cancers, as the target DNA sequence. The threshold voltage of the NWFET increased when the mutation gene was hybridized with the capture DNA strands on the nanowire, and decreased to the original level after de-hybridization of the gene. The shift in the drain current-gate voltage (I(D)-V(G)) curves revealed that the electrical signal had a logarithmic relationship with respect to the concentration of the mutation gene of up to six orders of magnitude, with the detection limit in the sub-femtomolar level. The detection results of mismatched DNA sequences, including one- and five-base-mismatched DNA strands, could be distinguished from complementary DNA gene by this sensor. The excellent electrical results obtained using this label-free NWFET sensor suggest that such devices might be potentially useful tools for biological research and oncogene screening. PMID:19765969

  1. 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.

  2. Electronic transport properties of silicon junctionless nanowire transistors fabricated by femtosecond laser direct writing

    NASA Astrophysics Data System (ADS)

    Liu-Hong, Ma; Wei-Hua, Han; Hao, Wang; Qi-feng, Lyu; Wang, Zhang; Xiang, Yang; Fu-Hua, Yang

    2016-06-01

    Silicon junctionless nanowire transistor (JNT) is fabricated by femtosecond laser direct writing on a heavily n-doped SOI substrate. The performances of the transistor, i.e., current drive, threshold voltage, subthreshold swing (SS), and electron mobility are evaluated. The device shows good gate control ability and low-temperature instability in a temperature range from 10 K to 300 K. The drain currents increasing by steps with the gate voltage are clearly observed from 10 K to 50 K, which is attributed to the electron transport through one-dimensional (1D) subbands formed in the nanowire. Besides, the device exhibits a better low-field electron mobility of 290 cm2·V‑1·s‑1, implying that the silicon nanowires fabricated by femtosecond laser have good electrical properties. This approach provides a potential application for nanoscale device patterning. Project supported by the National Natural Science Foundation of China (Grant Nos. 61376096, 61327813, and 61404126) and the National Basic Research Program of China (Grant No. 2010CB934104).

  3. Elastic Properties of Silicon Carbide Nanowires and Nanosize Grains up to 75 GPa

    NASA Astrophysics Data System (ADS)

    Zerda, T. W.

    2010-03-01

    Silicon carbide nanowires of average diameter of 30 nm and narrow size distribution were sintered from carbon nanotubes and silicon at 1200^oC. X-ray diffraction measurements of those SiC nanowires were conducted in a diamond anvil cell at room temperature and pressures up to 55 GPa applied by an alcohol medium. We used the same technique to study SiC grains of various sizes. The pressure-dependent volumes of the respective unit cells were calculated from the diffraction data, and the bulk moduli extracted from these studies depended on the particle size: 260 GPa for the 20 nm grains, 198 GPa for the 50 nm grains, and 193 GPa for the 130 nm grains. The bulk modulus of the 30 nm SiC nanowire was found to be 240 GPa. The bulk modulus study was extended to 75 GPa of pressure by use of a diamond anvil cell cryogenically loaded with an argon pressure medium. The bulk modulus was unchanged in this extended pressure range. The elevated bulk modulus of 20 nm grains is explained by the core-shell model developed by Palosz, et al. The core atoms exhibit all the properties associated with the bulk material, but the interatomic distances of shell atoms may differ. With nano-sized materials, a much larger percentage of the constituent atoms belong to the shell.

  4. Visible and Infra-red Light Emission in Boron-Doped Wurtzite Silicon Nanowires

    PubMed Central

    Fabbri, Filippo; Rotunno, Enzo; Lazzarini, Laura; Fukata, Naoki; Salviati, Giancarlo

    2014-01-01

    Silicon, the mainstay semiconductor in microelectronic circuitry, is considered unsuitable for optoelectronic applications owing to its indirect electronic band gap, which limits its efficiency as a light emitter. Here we show the light emission properties of boron-doped wurtzite silicon nanowires measured by cathodoluminescence spectroscopy at room temperature. A visible emission, peaked above 1.5 eV, and a near infra-red emission at 0.8 eV correlate respectively to the direct transition at the Γ point and to the indirect band-gap of wurtzite silicon. We find additional intense emissions due to boron intra-gap states in the short wavelength infra-red range. We present the evolution of the light emission properties as function of the boron doping concentration and the growth temperature. PMID:24398782

  5. Electrical Control of g-Factor in a Few-Hole Silicon Nanowire MOSFET.

    PubMed

    Voisin, B; Maurand, R; Barraud, S; Vinet, M; Jehl, X; Sanquer, M; Renard, J; De Franceschi, S

    2016-01-13

    Hole spins in silicon represent a promising yet barely explored direction for solid-state quantum computation, possibly combining long spin coherence, resulting from a reduced hyperfine interaction, and fast electrically driven qubit manipulation. Here we show that a silicon-nanowire field-effect transistor based on state-of-the-art silicon-on-insulator technology can be operated as a few-hole quantum dot. A detailed magnetotransport study of the first accessible hole reveals a g-factor with unexpectedly strong anisotropy and gate dependence. We infer that these two characteristics could enable an electrically driven g-tensor-modulation spin resonance with Rabi frequencies exceeding several hundred mega-Hertz. PMID:26599868

  6. Enhanced light trapping in periodically truncated cone silicon nanowire structure

    NASA Astrophysics Data System (ADS)

    Kai, Qiu; Yuhua, Zuo; Tianwei, Zhou; Zhi, Liu; Jun, Zheng; Chuanbo, Li; Buwen, Cheng

    2015-10-01

    Light trapping plays an important role in improving the conversion efficiency of thin-film solar cells. The good wideband light trapping is achieved using our periodically truncated cone Si nanowire (NW) structures, and their inherent mechanism is analyzed and simulated by FDTD solution software. Ordered cylinder Si NW structure with initial size of 80 nm and length of 200 nm is grown by pattern transfer and selective epitaxial growth. Truncated cone Si NW array is then obtained by thermal oxidation treatment. Its mean reflection in the range of 300-900 nm is lowered to be 5% using 140 nm long truncated cone Si NW structure, compared with that of 20% using cylinder counterparts. It indicates that periodically truncated Si cone structures trap the light efficiently to enhance the light harvesting in a wide spectral range and have the potential application in highly efficient NW solar cells. Project supported by the National Natural Science Foundation of China (Nos. 51072194, 61021003, 61036001, 61376057).

  7. Crystallinity, Surface Morphology, and Photoelectrochemical Effects in Conical InP and InN Nanowires Grown on Silicon.

    PubMed

    Parameshwaran, Vijay; Xu, Xiaoqing; Clemens, Bruce

    2016-08-24

    The growth conditions of two types of indium-based III-V nanowires, InP and InN, are tailored such that instead of yielding conventional wire-type morphologies, single-crystal conical structures are formed with an enlarged diameter either near the base or near the tip. By using indium droplets as a growth catalyst, combined with an excess indium supply during growth, "ice cream cone" type structures are formed with a nanowire "cone" and an indium-based "ice cream" droplet on top for both InP and InN. Surface polycrystallinity and annihilation of the catalyst tip of the conical InP nanowires are observed when the indium supply is turned off during the growth process. This growth design technique is extended to create single-crystal InN nanowires with the same morphology. Conical InN nanowires with an enlarged base are obtained through the use of an excess combined Au-In growth catalyst. Electrochemical studies of the InP nanowires on silicon demonstrate a reduction photocurrent as a proof of photovolatic behavior and provide insight as to how the observed surface polycrystallinity and the resulting interface affect these device-level properties. Additionally, a photovoltage is induced in both types of conical InN nanowires on silicon, which is not replicated in epitaxial InN thin films. PMID:27455379

  8. 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. PMID:27448026

  9. 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.

  10. Controllable electrical and physical breakdown of poly-crystalline silicon nanowires by thermally assisted electromigration

    NASA Astrophysics Data System (ADS)

    Park, Jun-Young; Moon, Dong-Il; Seol, Myeong-Lok; Jeon, Chang-Hoon; Jeon, Gwang-Jae; Han, Jin-Woo; Kim, Choong-Ki; Park, Sang-Jae; Lee, Hee Chul; Choi, Yang-Kyu

    2016-01-01

    The importance of poly-crystalline silicon (poly-Si) in semiconductor manufacturing is rapidly increasing due to its highly controllable conductivity and excellent, uniform deposition quality. With the continuing miniaturization of electronic components, low dimensional structures such as 1-dimensional nanowires (NWs) have attracted a great deal of attention. But such components have a much higher current density than 2- or 3- dimensional films, and high current can degrade device lifetime and lead to breakdown problems. Here, we report on the electrical and thermal characteristics of poly-Si NWs, which can also be used to control electrical and physical breakdown under high current density. This work reports a controllable catastrophic change of poly-Si NWs by thermally-assisted electromigration and underlying mechanisms. It also reports the direct and real time observation of these catastrophic changes of poly-Si nanowires for the first time, using scanning electron microscopy.

  11. Controllable electrical and physical breakdown of poly-crystalline silicon nanowires by thermally assisted electromigration

    PubMed Central

    Park, Jun-Young; Moon, Dong-Il; Seol, Myeong-Lok; Jeon, Chang-Hoon; Jeon, Gwang-Jae; Han, Jin-Woo; Kim, Choong-Ki; Park, Sang-Jae; Lee, Hee Chul; Choi, Yang-Kyu

    2016-01-01

    The importance of poly-crystalline silicon (poly-Si) in semiconductor manufacturing is rapidly increasing due to its highly controllable conductivity and excellent, uniform deposition quality. With the continuing miniaturization of electronic components, low dimensional structures such as 1-dimensional nanowires (NWs) have attracted a great deal of attention. But such components have a much higher current density than 2- or 3- dimensional films, and high current can degrade device lifetime and lead to breakdown problems. Here, we report on the electrical and thermal characteristics of poly-Si NWs, which can also be used to control electrical and physical breakdown under high current density. This work reports a controllable catastrophic change of poly-Si NWs by thermally-assisted electromigration and underlying mechanisms. It also reports the direct and real time observation of these catastrophic changes of poly-Si nanowires for the first time, using scanning electron microscopy. PMID:26782708

  12. Photocurrents in a Single InAs Nanowire/Silicon Heterojunction.

    PubMed

    Brenneis, Andreas; Overbeck, Jan; Treu, Julian; Hertenberger, Simon; Morkötter, Stefanie; Döblinger, Markus; Finley, Jonathan J; Abstreiter, Gerhard; Koblmüller, Gregor; Holleitner, Alexander W

    2015-10-27

    We investigate the optoelectronic properties of single indium arsenide nanowires, which are grown vertically on p-doped silicon substrates. We apply a scanning photocurrent microscopy to study the optoelectronic properties of the single heterojunctions. The measured photocurrent characteristics are consistent with an excess charge carrier transport through midgap trap states, which form at the Si/InAs heterojunctions. Namely, the trap states add an additional transport path across a heterojunction, and the charge of the defects changes the band bending at the junction. The bending gives rise to a photovoltaic effect at a small bias voltage. In addition, we observe a photoconductance effect within the InAs nanowires at large biases. PMID:26348461

  13. Formation of compositionally abrupt axial heterojunctions in silicon-germanium nanowires.

    PubMed

    Wen, C-Y; Reuter, M C; Bruley, J; Tersoff, J; Kodambaka, S; Stach, E A; Ross, F M

    2009-11-27

    We have formed compositionally abrupt interfaces in silicon-germanium (Si-Ge) and Si-SiGe heterostructure nanowires by using solid aluminum-gold alloy catalyst particles rather than the conventional liquid semiconductor-metal eutectic droplets. We demonstrated single interfaces that are defect-free and close to atomically abrupt, as well as quantum dots (i.e., Ge layers tens of atomic planes thick) embedded within Si wires. Real-time imaging of growth kinetics reveals that a low solubility of Si and Ge in the solid particle accounts for the interfacial abruptness. Solid catalysts that can form functional group IV nanowire-based structures may yield an extended range of electronic applications. PMID:19965471

  14. Controllable electrical and physical breakdown of poly-crystalline silicon nanowires by thermally assisted electromigration.

    PubMed

    Park, Jun-Young; Moon, Dong-Il; Seol, Myeong-Lok; Jeon, Chang-Hoon; Jeon, Gwang-Jae; Han, Jin-Woo; Kim, Choong-Ki; Park, Sang-Jae; Lee, Hee Chul; Choi, Yang-Kyu

    2016-01-01

    The importance of poly-crystalline silicon (poly-Si) in semiconductor manufacturing is rapidly increasing due to its highly controllable conductivity and excellent, uniform deposition quality. With the continuing miniaturization of electronic components, low dimensional structures such as 1-dimensional nanowires (NWs) have attracted a great deal of attention. But such components have a much higher current density than 2- or 3-dimensional films, and high current can degrade device lifetime and lead to breakdown problems. Here, we report on the electrical and thermal characteristics of poly-Si NWs, which can also be used to control electrical and physical breakdown under high current density. This work reports a controllable catastrophic change of poly-Si NWs by thermally-assisted electromigration and underlying mechanisms. It also reports the direct and real time observation of these catastrophic changes of poly-Si nanowires for the first time, using scanning electron microscopy. PMID:26782708

  15. Silicon nanowires used as the anode of a lithium-ion battery

    SciTech Connect

    Prosini, Pier Paolo; Rufoloni, Alessandro; Rondino, Flaminia; Santoni, Antonino

    2015-06-23

    In this paper the synthesis and characterization of silicon nanowires to be used as the anode of a lithium-ion battery cell are reported. The nanowires were synthesized by CVD and characterized by SEM. The nanostructured material was used as an electrode in a lithium cell and its electrochemical properties were investigated by galvanostatic charge/discharge cycles at C/10 rate as a function of the cycle number and at various rates as a function of the charge current. The electrode was then coupled with a LiFePO{sub 4} cathode to fabricate a lithium-ion battery cell and the cell performance evaluated by galvanostatic charge/discharge cycles.

  16. EDITORIAL: Nanowires Nanowires

    NASA Astrophysics Data System (ADS)

    Jagadish, Chennupati

    2010-02-01

    Nanowires are considered as building blocks for the next generation of electronics, photonics, sensors and energy applications. One-dimensional nanostructures offer unique opportunities to control the density of states of semiconductors, and in turn their electronic and optical properties. Nanowires allow the growth of axial heterostructures without the constraints of lattice mismatch. This provides flexibility to create heterostructures of a broad range of materials and allows integration of compound semiconductor based optoelectronic devices with silicon based microelectronics. Nanowires are widely studied and the number of papers published in the field is growing exponentially with time. Already nanowire lasers, nanowire transistors, nanowire light emitting diodes, nanowire sensors and nanowire solar cells have been demonstrated. This special issue on semiconductor nanowires features 17 invited papers from leading experts in the field. In this special issue, the synthesis and growth of semiconductor nanowires of a broad range of materials have been addressed. Both axial and radial heterostructures and their structural properties have been discussed. Electrical transport properties of nanowires have been presented, as well as optical properties and carrier dynamics in a range of nanowires and nanowire heterostructures. Devices such as nanowire lasers and nanowire sensors have also been discussed. I would like to thank the Editorial Board of the journal for suggesting this special issue and inviting me to serve as the Guest Editor. Sincere thanks are due to all the authors for their contributions to this special issue. I am grateful to the reviewers and editorial staff at Semiconductor Science and Technology and the Institute of Physics Publishing for their excellent efforts. Special thanks are due to Dr Claire Bedrock for coordinating this special issue.

  17. Metal-catalyzed electroless etching and nanoimprinting silicon nanowire-based solar cells: Silicon nanowire defect reduction and efficiency enhancement by two-step H2 annealing

    NASA Astrophysics Data System (ADS)

    Jevasuwan, Wipakorn; Nakajima, Kiyomi; Sugimoto, Yoshimasa; Fukata, Naoki

    2016-06-01

    The effects of H2 annealing on material properties including defects of silicon nanowire (SiNW) surface and Si film layer for solar cell application were investigated. Single-junction solar cells consisting of n-SiNWs and chemical vapor deposition grown p-Si matrix were demonstrated using two-step H2 annealing. n-SiNWs formed by two different methods of metal-catalyzed electroless etching and nanoimprinting followed by the Bosch process were compared. Two-step H2 annealing at 900 °C for 10 min after both n-SiNW formations and subsequent p-Si matrix deposition effectively improved SiNW surface and p-Si crystallinity, resulting in higher solar cell efficiency.

  18. EFFECT OF PRE-ANNEALING TEMPERATURE ON THE GROWTH OF ALIGNED α-Fe2O3 NANOWIRES VIA A TWO-STEP THERMAL OXIDATION

    NASA Astrophysics Data System (ADS)

    Rashid, Norhana Mohamed; Kishi, Naoki; Soga, Tetsuo

    2016-03-01

    Pre-annealing as part of a two-step thermal oxidation process has a significant effect on the growth of hematite (α-Fe2O3) nanowires on Fe foil. High-density aligned nanowires were obtained on iron foils pre-annealed at 300∘C under a dry air flow for 30min. The X-ray diffraction (XRD) patterns indicate that the nanowires are transformed from the small α-Fe2O3 grains and uniquely grow in the (110) direction. The formation of a high-density of small grains by pre-annealing improved the alignment and density of the α-Fe2O3 nanowires.

  19. Optical biosensor based on a silicon nanowire ridge waveguide for lab on chip applications

    NASA Astrophysics Data System (ADS)

    Gamal, Rania; Ismail, Yehea; Swillam, Mohamed A.

    2015-04-01

    We propose a novel sensor using a silicon nanowire ridge waveguide (SNRW). This waveguide is comprised of an array of silicon nanowires on an insulator substrate that has the envelope of a ridge waveguide. The SNRW inherently maximizes the overlap between the material-under-test and the incident light wave by introducing voids to the otherwise bulk structure. When a sensing sample is injected, the voids within the SNRW adopt the refractive index of the material-under-test. Hence, the strong contribution of the material-under-test to the overall modal effective index will greatly augment the sensitivity. Additionally, the ridge structure provides a fabrication convenience as it covers the entire substrate, ensuring that the etching process would not damage the substrate. Finite-difference time-domain simulations are conducted and showed that the percentage change in the effective index due to a 1% change in the surrounding environment is more than 170 times the change perceived in an evanescent-detection based bulk silicon ridge waveguide. Moreover, the SNRW proves to be more sensitive than recent other, non-evanescent sensors. In addition, the detection limit for this structure was revealed to be as small as 10-8. A compact bimodal waveguide based on SNRW is designed and tested. It delivers high sensitivity values that offer comparable performance to similar low-index light-guiding sensing configurations; however, our proposed structure has much smaller footprints and allows high dense integration for lab-on-chip applications.

  20. High efficiency silicon nanowire/organic hybrid solar cells with two-step surface treatment.

    PubMed

    Wang, Jianxiong; Wang, Hao; Prakoso, Ari Bimo; Togonal, Alienor Svietlana; Hong, Lei; Jiang, Changyun; Rusli

    2015-03-14

    A simple two-step surface treatment process is proposed to boost the efficiency of silicon nanowire/PEDOT:PSS hybrid solar cells. The Si nanowires (SiNWs) are first subjected to a low temperature ozone treatment to form a surface sacrificial oxide, followed by a HF etching process to partially remove the oxide. TEM investigation demonstrates that a clean SiNW surface is achieved after the treatment, in contrast to untreated SiNWs that have Ag nanoparticles left on the surface from the metal-catalyzed etching process that is used to form the SiNWs. The cleaner SiNW surface achieved and the thin layer of residual SiO2 on the SiNWs have been found to improve the performance of the hybrid solar cells. Overall, the surface recombination of the hybrid SiNW solar cells is greatly suppressed, resulting in a remarkably improved open circuit voltage of 0.58 V. The power conversion efficiency has also increased from about 10% to 12.4%. The two-step surface treatment method is promising in enhancing the photovoltaic performance of the hybrid silicon solar cells, and can also be applied to other silicon nanostructure based solar cells. PMID:25686737

  1. Silicon Nanowires for Solar Thermal Energy Harvesting: an Experimental Evaluation on the Trade-off Effects of the Spectral Optical Properties.

    PubMed

    Sekone, Abdoul Karim; Chen, Yu-Bin; Lu, Ming-Chang; Chen, Wen-Kai; Liu, Chia-An; Lee, Ming-Tsang

    2016-12-01

    Silicon nanowire possesses great potential as the material for renewable energy harvesting and conversion. The significantly reduced spectral reflectivity of silicon nanowire to visible light makes it even more attractive in solar energy applications. However, the benefit of its use for solar thermal energy harvesting remains to be investigated and has so far not been clearly reported. The purpose of this study is to provide practical information and insight into the performance of silicon nanowires in solar thermal energy conversion systems. Spectral hemispherical reflectivity and transmissivity of the black silicon nanowire array on silicon wafer substrate were measured. It was observed that the reflectivity is lower in the visible range but higher in the infrared range compared to the plain silicon wafer. A drying experiment and a theoretical calculation were carried out to directly evaluate the effects of the trade-off between scattering properties at different wavelengths. It is clearly seen that silicon nanowires can improve the solar thermal energy harnessing. The results showed that a 17.8 % increase in the harvest and utilization of solar thermal energy could be achieved using a silicon nanowire array on silicon substrate as compared to that obtained with a plain silicon wafer. PMID:26729219

  2. Silicon Nanowires for Solar Thermal Energy Harvesting: an Experimental Evaluation on the Trade-off Effects of the Spectral Optical Properties

    NASA Astrophysics Data System (ADS)

    Sekone, Abdoul Karim; Chen, Yu-Bin; Lu, Ming-Chang; Chen, Wen-Kai; Liu, Chia-An; Lee, Ming-Tsang

    2016-01-01

    Silicon nanowire possesses great potential as the material for renewable energy harvesting and conversion. The significantly reduced spectral reflectivity of silicon nanowire to visible light makes it even more attractive in solar energy applications. However, the benefit of its use for solar thermal energy harvesting remains to be investigated and has so far not been clearly reported. The purpose of this study is to provide practical information and insight into the performance of silicon nanowires in solar thermal energy conversion systems. Spectral hemispherical reflectivity and transmissivity of the black silicon nanowire array on silicon wafer substrate were measured. It was observed that the reflectivity is lower in the visible range but higher in the infrared range compared to the plain silicon wafer. A drying experiment and a theoretical calculation were carried out to directly evaluate the effects of the trade-off between scattering properties at different wavelengths. It is clearly seen that silicon nanowires can improve the solar thermal energy harnessing. The results showed that a 17.8 % increase in the harvest and utilization of solar thermal energy could be achieved using a silicon nanowire array on silicon substrate as compared to that obtained with a plain silicon wafer.

  3. Lipid bilayer supported on silicon nanowire sensors with functional ion channels

    NASA Astrophysics Data System (ADS)

    Matinez, Julio Alberto

    The next generation of silicon nanowire (SiNW) based sensors will benefit from a possibility of using biological molecules embedded in biomimetic matrices such as lipid membranes. We demonstrate the integration of a 1,2-Dioleoyl-sn-Glycero-3-Phosphocholine (DOPC) lipid bilayer with SiNW substrates. Fluidity measurements for supported DOPC bilayer on SiNWs show that they fully recover after photobleaching with diffusion coefficients comparable to flat membranes. Electrochemical characterization of DOPC bilayer supported onto highly-doped SiNW electrodes indicates the formation of a highly insulating membrane that blocks the transport of solution redox species to the SiNW surface. We also observe that the reaction efficiency of electroactive species on the electrodes constructed of highly-doped silicon nanowires greatly exceeds the efficiency of flat Si electrodes at similar doping level. Incorporating a functional pore forming protein, alpha-hemolysin, in the lipid bilayer results in a partial recovery of the Faradic current due to the specific transport of electroactive species through the protein pore. We also engineer a highly organized biosurface for cell deposition and subsequent growth by the chemical modification of a surface with electrostatically adsorbed peptide, poly L-arginine, adsorbs onto surface hemi-micelles of sodium dodecyl sulfate on a hydrophobic self-assembled monolayer. Finally, we incorporate these assemblies into functional semiconducting silicon nanowire transistors and show that these devices could detect the binding events to ligand-gated ion channel. We particularly study the binding of calcium ions in solution to Gramidicin-A. Ion transport trough the voltage-gated ion channel, Alamethicin, is also observed for the proposed detection platform. These assemblies represent a robust and versatile platform for building a new generation of specific electrically based biosensors and nanobioelectronic devices.

  4. Ab initio quantum mechanical studies in electronic and structural properties of carbon nanotubes and silicon nanowires

    NASA Astrophysics Data System (ADS)

    Matsuda, Yuki

    This dissertation focuses on ab-initio quantum mechanical calculations of nanoelectronics in three research topics: contact resistance properties of carbon nanotubes and graphenes (Chapters 1 through 3), electrical properties of carbon nanotubes (Chapter 4) and silicon nanowires (Chapter 5). Through all the chapters, the aim of the research is to provide useful guidelines for experimentalists. Chapter 1 presents the contact resistance of metal electrode-carbon nanotube and metal electrode-graphene interfaces for various deposited metals, based on first-principles quantum mechanical density functional and matrix Green's function methods. Chapters 2 and 3 describe inventive ways to enhance contact resistance properties as well as mechanical stabilities using "molecular anchors" (Chapter 2) or using "end-contacted" (or end-on) electrodes (Chapter 3). Chapters 1 through 3 also provide useful guidelines for nanotube assembly process which is one of the main obstacles in nanoelectronics. Chapter 4 shows accurate and detailed band structure properties of single-walled carbon nanotubes using B3LYP hybrid functional, which are critical parameters in determining the electronic properties such as small band gaps (˜0.1 eV) and effective masses. Chapter 5 details both structural and electronic properties of silicon nanowires. These results lead to the findings controlling the diameter and surface coverage by adsorbates (e.g., hydrogen) of silicon nanowires can be effectively used to optimize their properties for various applications. All the theoretical results are compared with other theoretical studies and experimental data. Notably, electronic studies using B3LYP show excellent agreement with experimental studies quantitatively, which previous quantum mechanical calculations had failed. These studies show how quantum mechanical predictions of complex phenomena can be effectively investigated computationally in nanomaterials and nanodevices. Given the difficulty, expense

  5. Theory of Corner States in Silicon Nanowire Devices

    NASA Astrophysics Data System (ADS)

    Saraiva, Andre; Koiller, Belita; Gonzalez-Zalba, M. Fernando

    Nanowire-based transistors, such as FinFETs and Tri-gate FETs, form one and zero dimensional states at the corners. These corner states may be manipulated for quantum electronic applications, such as tunable quantum dot-based spin qubits. We discuss the electronic structure of the electrons bound at the corner, considering the effects due to the anisotropy of the effective mass, the splitting of valleys due to the confinement and the scattering at the interface, generalizing our results to corners of arbitrary angle. Our results indicate the optimal conditions for lifting the valley degeneracy, known to impact quantum coherence and control. We finally mention the expected impacts of this geometry on the tunnel and exchange coupling between dots at opposite corners of a wire. As and BK performed this work as part of the Brazilian National Institute for Science and Technology on Quantum Information and acknowledge support from the Brazilian agencies FAPERJ, CNPq, CAPES. MFG-Z is funded by the FP7/318397-TOLOP project.

  6. Self-transducing silicon nanowire electromechanical systems at room temperature.

    PubMed

    He, Rongrui; Feng, X L; Roukes, M L; Yang, Peidong

    2008-06-01

    Electronic readout of the motions of genuinely nanoscale mechanical devices at room temperature imposes an important challenge for the integration and application of nanoelectromechanical systems (NEMS). Here, we report the first experiments on piezoresistively transduced very high frequency Si nanowire (SiNW) resonators with on-chip electronic actuation at room temperature. We have demonstrated that, for very thin (~90 nm down to ~30 nm) SiNWs, their time-varying strain can be exploited for self-transducing the devices' resonant motions at frequencies as high as approximately 100 MHz. The strain of wire elongation, which is only second-order in doubly clamped structures, enables efficient displacement transducer because of the enhanced piezoresistance effect in these SiNWs. This intrinsically integrated transducer is uniquely suited for a class of very thin wires and beams where metallization and multilayer complex patterning on devices become impractical. The 30 nm thin SiNW NEMS offer exceptional mass sensitivities in the subzeptogram range. This demonstration makes it promising to advance toward NEMS sensors based on ultrathin and even molecular-scale SiNWs, and their monolithic integration with microelectronics on the same chip. PMID:18481896

  7. Characterization of functional biointerface on silicon nanowire MOSFET.

    PubMed

    Lin, Shu-Ping; Liu, Mao-Chen; Chi, Tien-Yin; Kang, Yu-Shan

    2011-01-01

    Biointerface between biological organisms and electronic devices has attracted a lot of attention since a biocompatible and functional interface can revolutionize medical applications of bioelectronics. Here, we used 3-aminopropyl trimethoxysilane (APTMS) self-assembled monolayer (SAM) to modify the surface of nanowire-based metal-oxide-semiconductor field-effect transistors (NW-MOSFETs) for pH sensing and later creation of biointerface. Electrical measurement was utilized to first verify the sensing response of unmodified NW-MOSFETs and then examine pH sensing on APTMS modified NW-MOSFETs. A biointerface was then created by immobilizing polylysine, either poly-D-lysine (PDL) or poly-L-lysine (PLL), on APTMS modified NW-MOSFETs. This biointerface was characterized by electron spectroscopy for chemical analysis (ESCA), cell biocompatibility, and fluorescent images. The results of ESCA verified the amide bonding (CONH) between polylysine and APTMS modified surface. After PC12 cultured on polylysine-APTMS modified area, highly selective areas for cell growth were observed by fluorescent microscope. Analysis and improvement of selectively cell-growth biointerface on the NW-MOSFETs gave us an insight into future development of neuronal biosensors. PMID:22255403

  8. Scalable synthesis of vertically aligned, catalyst-free gallium arsenide nanowire arrays: towards optimized optical absorption

    NASA Astrophysics Data System (ADS)

    Yao, Maoqing; Madaria, Anuj R.; Chi, ChunYung; Huang, Ningfeng; Lin, Chenxi; Povinelli, Michelle L.; Dapkus, P. Daniel; Zhou, Chongwu

    2012-06-01

    Recently nanostructure materials have emerged as a building block for constructing next generation of photovoltaic devices. Nanowire based semiconductor solar cells, among other candidates, have shown potential to produce high efficiency. In a radial pn junction light absorption and carrier collection can be decoupled. Also nanowires can increase choice of materials one can use to fabricate high efficiency tandem solar cells by relaxing the lattice-match constraint. Here we report synthesis of vertical III-V semiconducting nanowire arrays using Selective-Area Metal Organic Chemical Vapor Deposition (SA-MOCVD) technique, which can find application in various optoelectronic devices. We also demonstrate nanosphere lithography (NSL) patterning techniques to obtain ordered pattern for SAMOCVD. Reflection spectrum of nanowires array made by this technique shows excellent light absorption performance without additional anti-reflection coating layer. Thus, we show that highly ordered nanowire structure is 'not needed' to maximize the absorption in vertical nanowire array. Our scalable approach for synthesis of vertical semiconducting nanowire can have application in high throughput and low cost optoelectronic devices including photovoltaic devices.

  9. Influence of nanowires length on performance of crystalline silicon solar cell

    NASA Astrophysics Data System (ADS)

    Li, Haofeng; Jia, Rui; Chen, Chen; Xing, Zhao; Ding, Wuchang; Meng, Yanlong; Wu, Deqi; Liu, Xinyu; Ye, Tianchun

    2011-04-01

    Silicon-nanowire (Si-NW) array, prepared by an electroless chemical-etching method, shows excellent optical antireflection property over a wide spectral bandwidth. The influence of the wire length on the optical antireflection property and the solar cell performance were studied for both the Si-NW array solar cells and the planar solar cells. The reflectance of NWs solar cells is almost invariable and much lower than that of the planar solar cells but the performance of planar solar cells is the best. Results show the performance of NWs solar cells is strongly affected by some other factors such as surface passivation and electrode-contact property.

  10. Tunable narrowband microwave photonic filter created by stimulated Brillouin scattering from a silicon nanowire.

    PubMed

    Casas-Bedoya, Alvaro; Morrison, Blair; Pagani, Mattia; Marpaung, David; Eggleton, Benjamin J

    2015-09-01

    We demonstrate the first, to the best of our knowledge, functional signal processing device based on stimulated Brillouin scattering in a silicon nanowire. We use only 1 dB of on-chip stimulated Brillouin scattering gain to create an RF photonic notch filter with 48 dB of suppression, 98 MHz linewidth, and 6 GHz frequency tuning. This device has potential applications in on-chip microwave signal processing and establishes the foundation for the first CMOS-compatible high-performance RF photonic filter. PMID:26368735

  11. Improved photovoltaic performance of silicon nanowire/organic hybrid solar cells by incorporating silver nanoparticles

    PubMed Central

    2013-01-01

    Silicon nanowire (SiNW) arrays show an excellent light-trapping characteristic and high mobility for carriers. Surface plasmon resonance of silver nanoparticles (AgNPs) can be used to increase light scattering and absorption in solar cells. We fabricated a new kind of SiNW/organic hybrid solar cell by introducing AgNPs. Reflection spectra confirm the improved light scattering of AgNP-decorated SiNW arrays. A double-junction tandem structure was designed to manufacture our hybrid cells. Both short-circuit current and external quantum efficiency measurements show an enhancement in optical absorption of organic layer, especially at lower wavelengths. PMID:23418988

  12. Probing protein complexes inside living cells using a silicon nanowire-based pull-down assay.

    PubMed

    Choi, Sojoong; Kim, Hyunju; Kim, So Yeon; Yang, Eun Gyeong

    2016-06-01

    Most proteins perform their functions as interacting complexes. Here we propose a novel method for capturing an intracellular protein and its interacting partner out of living cells by utilizing intracellular access of antibody modified vertical silicon nanowire arrays whose surface is covered with a polyethylene glycol layer to prevent strong cell adhesion. Such a feature facilitates the removal of cells by simple washing, enabling subsequent detection of a pulled-down protein and its interacting partner, and further assessment of a drug-induced change in the interacting complex. Our new SiNW-based tool is thus suitable for authentication of protein networks inside living cells. PMID:27198202

  13. Polycrystalline nanowires of gadolinium-doped ceria via random alignment mediated by supercritical carbon dioxide

    PubMed Central

    Kim, Sang Woo; Ahn, Jae-Pyoung

    2013-01-01

    This study proposes a seed/template-free method that affords high-purity semiconducting nanowires from nanoclusters, which act as basic building blocks for nanomaterials, under supercritical CO2 fluid. Polycrystalline nanowires of Gd-doped ceria (Gd-CeO2) were formed by CO2-mediated non-oriented attachment of the nanoclusters resulting from the dissociation of single-crystalline aggregates. The unique formation mechanism underlying this morphological transition may be exploited for the facile growth of high-purity polycrystalline nanowires. PMID:23572061

  14. Alignment of the CMS silicon strip tracker during stand-alone commissioning

    SciTech Connect

    Adam, W.; et al.

    2009-07-01

    The results of the CMS tracker alignment analysis are presented using the data from cosmic tracks, optical survey information, and the laser alignment system at the Tracker Integration Facility at CERN. During several months of operation in the spring and summer of 2007, about five million cosmic track events were collected with a partially active CMS Tracker. This allowed us to perform first alignment of the active silicon modules with the cosmic tracks using three different statistical approaches; validate the survey and laser alignment system performance; and test the stability of Tracker structures under various stresses and temperatures ranging from +15C to -15C. Comparison with simulation shows that the achieved alignment precision in the barrel part of the tracker leads to residual distributions similar to those obtained with a random misalignment of 50 (80) microns in the outer (inner) part of the barrel.

  15. Balanced ternary addition using a gated silicon nanowire

    NASA Astrophysics Data System (ADS)

    Mol, J. A.; van der Heijden, J.; Verduijn, J.; Klein, M.; Remacle, F.; Rogge, S.

    2011-12-01

    Ternary logic has the lowest cost of complexity, here, we demonstrate a CMOS hardware implementation of a ternary adder using a silicon metal-on-insulator single electron transistor. Gate dependent rectifying behavior of a single electron transistor (SET) results in a robust three-valued output as a function of the potential of the single electron transistor island. Mapping logical, ternary inputs to the three gates controlling the potential of the single electron transistor island allows us to perform complex, inherently ternary operations, on a single transistor.

  16. Direct electrical contact of slanted ITO film on axial p-n junction silicon nanowire solar cells.

    PubMed

    Lee, Ya-Ju; Yao, Yung-Chi; Yang, Chia-Hao

    2013-01-14

    A novel scheme of direct electrical contact on vertically aligned silicon nanowire (SiNW) axial p-n junction is demonstrated by means of oblique-angle deposition of slanted indium-tin-oxide (ITO) film for photovoltaic applications. The slanted ITO film exhibits an acceptable resistivity of 1.07 x 10⁻³Ω-cm underwent RTA treatment of T = 450°C, and the doping concentration and carrier mobility by Hall measurement amount to 3.7 x 10²⁰ cm⁻³ and 15.8 cm²/V-s, respectively, with an n-type doping polarity. Because of the shadowing effect provided by the SiNWs, the incident ITO vapor-flow is deposited preferentially on the top of SiNWs, which coalesces and eventually forms a nearly continuous film for the subsequent fabrication of grid electrode. Under AM 1.5 G normal illumination, our axial p-n junction SiNW solar cell exhibits an open circuit voltage of VOC = 0.56 V, and a short circuit current of JSC = 1.54 mA/cm² with a fill factor of FF = 30%, resulting in a total power conversion efficiency of PEC = 0.26%. PMID:23389277

  17. Top-down fabrication of fully CMOS-compatible silicon nanowire arrays and their integration into CMOS Inverters on plastic.

    PubMed

    Lee, Myeongwon; Jeon, Youngin; Moon, Taeho; Kim, Sangsig

    2011-04-26

    A route to the top-down fabrication of highly ordered and aligned silicon nanowire (SiNW) arrays with degenerately doped source/drain regions from a bulk Si wafer is presented. In this approach, freestanding n- and p-SiNWs with an inverted triangular cross section are obtained using conventional photolithography, crystal orientation dependent wet etching, size reduction oxidation, and ion implantation doping. Based on these n- and p-SiNWs transferred onto a plastic substrate, simple SiNW-based complementary metal-oxide-semiconductor (CMOS) inverters are constructed for the possible applications of these SiNW arrays in integrated circuits on plastic. The static voltage transfer characteristic of the SiNW-based CMOS inverter exhibits a voltage gain of ∼9 V/V and a transition of 0.32 V at an operating voltage of 1.5 V with a full output voltage swing between 0 V and V(DD), and its mechnical bendability indicates good fatigue properties for potential applications of flexible electronics. This novel top-down approach is fully compatible with the current state-of-the-art Si-based CMOS technologies and, therefore, offers greater flexibility in device design for both high-performance and low-power functionality. PMID:21355599

  18. Structure and field emission of graphene layers on top of silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Huang, Bohr-Ran; Chan, Hui-Wen; Jou, Shyankay; Chen, Guan-Yu; Kuo, Hsiu-An; Song, Wan-Jhen

    2016-01-01

    Monolayer graphene was grown on copper foils and then transferred on planar silicon substrates and on top of silicon nanowire (SiNW) arrays to form single- to quadruple-layer graphene films. The morphology, structure, and electron field emission (FE) of these graphene films were investigated. The graphene films on the planar silicon substrates were continuous. The single- to triple-layer graphene films on the SiNW arrays were discontinuous and while the quadruple-layer graphene film featured a mostly continuous area. The Raman spectra of the graphene films on the SiNW arrays showed G and Gʹ bands with a singular-Lorentzian shape together with a weak D band. The D band intensity decreased as the number of graphene layers increased. The FE efficiency of the graphene films on the planar silicon substrates and the SiNW arrays varied with the number of graphene layers. The turn-on field for the single- to quadruple-layer graphene films on planar silicon substrates were 4.3, 3.7, 3.5 and 3.4 V/μm, respectively. The turn-on field for the single- to quadruple-layer graphene films on SiNW arrays decreased to 3.9, 3.3, 3.0 and 3.3 V/μm, respectively. Correlation of the FE with structure and morphology of the graphene films is discussed.

  19. Self-bridging of vertical silicon nanowires and a universal capacitive force model for spontaneous attraction in nanostructures.

    PubMed

    Sun, Zhelin; Wang, Deli; Xiang, Jie

    2014-11-25

    Spontaneous attractions between free-standing nanostructures have often caused adhesion or stiction that affects a wide range of nanoscale devices, particularly nano/microelectromechanical systems. Previous understandings of the attraction mechanisms have included capillary force, van der Waals/Casimir forces, and surface polar charges. However, none of these mechanisms universally applies to simple semiconductor structures such as silicon nanowire arrays that often exhibit bunching or adhesions. Here we propose a simple capacitive force model to quantitatively study the universal spontaneous attraction that often causes stiction among semiconductor or metallic nanostructures such as vertical nanowire arrays with inevitably nonuniform size variations due to fabrication. When nanostructures are uniform in size, they share the same substrate potential. The presence of slight size differences will break the symmetry in the capacitive network formed between the nanowires, substrate, and their environment, giving rise to electrostatic attraction forces due to the relative potential difference between neighboring wires. Our model is experimentally verified using arrays of vertical silicon nanowire pairs with varied spacing, diameter, and size differences. Threshold nanowire spacing, diameter, or size difference between the nearest neighbors has been identified beyond which the nanowires start to exhibit spontaneous attraction that leads to bridging when electrostatic forces overcome elastic restoration forces. This work illustrates a universal understanding of spontaneous attraction that will impact the design, fabrication, and reliable operation of nanoscale devices and systems. PMID:25329454

  20. Silicon nanowire biosensors for detection of cardiac troponin I (cTnI) with high sensitivity.

    PubMed

    Kim, Kihyun; Park, Chanoh; Kwon, Donghoon; Kim, Donghoon; Meyyappan, M; Jeon, Sangmin; Lee, Jeong-Soo

    2016-03-15

    We have demonstrated highly sensitive and label-free detection of cardiac troponin I (cTnI), a biomarker for diagnosis of acute myocardial infarction, using silicon nanowire field-effect transistors. A honeycomb-like structure is utilized for nanowire configuration to offer improved electrical performance and increased sensing area. The fabricated devices show n-type behavior with a relatively high ON-OFF current ratio, small sub-threshold swing and low gate leakage current. Monoclonal antibodies for cTnI were covalently immobilized on the nanowire surface and the attachment of antibodies is clearly visualized by atomic force microscope. The sensitivity with various concentrations of buffer solution was also investigated in order to determine the optimal buffer condition. The devices exhibit highest sensitivity under buffer solutions with low ion concentration. In addition, the detection limit of the sensor is as low as ~5 pg/mL, the lowest reported in the literature to date and nearly an order of magnitude smaller than the suggested threshold limit. The fabricated devices demonstrate a good selectivity for detecting cTnI. PMID:26496224

  1. Modeling and theoretical efficiency of a silicon nanowire based thermoelectric junction with area enhancement

    SciTech Connect

    Seong, M; Sadhu, JS; Ma, J; Ghossoub, MG; Sinha, S

    2012-06-15

    Recent experimental work suggests that individual silicon nanowires with rough surfaces possess a thermoelectric figure of merit as high as 0.6 near room temperature. This paper addresses the possibility of using an array of such nanowires in a thermoelectric junction for generation. Employing a model of frequency dependent phonon boundary scattering, we estimate the effective thermal conductivity of the array and investigate heat flow through the junction. We show that charge transport is largely unaffected by the roughness scales considered. Enhancing the area for heat exchange at an individual 200 mu m x 200 mu m p-n junction yields significant temperature differences across the junction leading to power >0.6 mW and efficiency >1.5% for a junction with effective thermal conductivity <5 W/mK, when the source and sink are at 450 K and 300 K, respectively. We show that relatively short nanowires of similar to 50 mu m length are sufficient for obtaining peak power and reasonable efficiency. This substantially reduces the challenge of engineering low resistivity electrical contacts that critically affect power and efficiency. This paper provides insight into how fundamental transport in relation to bulk heat transfer and charge transport, affects the performance of thermoelectric junctions based on nanostructured materials. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4728189

  2. Spin transport and Hanle effect in silicon nanowires using graphene tunnel barriers.

    PubMed

    van 't Erve, O M J; Friedman, A L; Li, C H; Robinson, J T; Connell, J; Lauhon, L J; Jonker, B T

    2015-01-01

    Spin-based devices offer non-volatile, scalable, low power and reprogrammable functionality for emerging device technologies. Here we fabricate nanoscale spintronic devices with ferromagnetic metal/single-layer graphene tunnel barriers used to generate spin accumulation and spin currents in a silicon nanowire transport channel. We report the first observation of spin precession via the Hanle effect in both local three-terminal and non-local spin-valve geometries, providing a direct measure of spin lifetimes and confirmation of spin accumulation and pure spin transport. The use of graphene as the tunnel barrier provides a low-resistance area product contact and clean magnetic switching characteristics, because it smoothly bridges the nanowire and minimizes complicated magnetic domains that otherwise compromise the magnetic behaviour. Utilizing intrinsic two-dimensional layers such as graphene or hexagonal boron nitride as tunnel contacts on nanowires offers many advantages over conventional materials deposited by vapour deposition, enabling a path to highly scaled electronic and spintronic devices. PMID:26089110

  3. Vertical Silicon Nanowire Field Effect Transistors with Nanoscale Gate-All-Around

    NASA Astrophysics Data System (ADS)

    Guerfi, Youssouf; Larrieu, Guilhem

    2016-04-01

    Nanowires are considered building blocks for the ultimate scaling of MOS transistors, capable of pushing devices until the most extreme boundaries of miniaturization thanks to their physical and geometrical properties. In particular, nanowires' suitability for forming a gate-all-around (GAA) configuration confers to the device an optimum electrostatic control of the gate over the conduction channel and then a better immunity against the short channel effects (SCE). In this letter, a large-scale process of GAA vertical silicon nanowire (VNW) MOSFETs is presented. A top-down approach is adopted for the realization of VNWs with an optimum reproducibility followed by thin layer engineering at nanoscale. Good overall electrical performances were obtained, with excellent electrostatic behavior (a subthreshold slope (SS) of 95 mV/dec and a drain induced barrier lowering (DIBL) of 25 mV/V) for a 15-nm gate length. Finally, a first demonstration of dual integration of n-type and p-type VNW transistors for the realization of CMOS inverter is proposed.

  4. Vertical Silicon Nanowire Field Effect Transistors with Nanoscale Gate-All-Around.

    PubMed

    Guerfi, Youssouf; Larrieu, Guilhem

    2016-12-01

    Nanowires are considered building blocks for the ultimate scaling of MOS transistors, capable of pushing devices until the most extreme boundaries of miniaturization thanks to their physical and geometrical properties. In particular, nanowires' suitability for forming a gate-all-around (GAA) configuration confers to the device an optimum electrostatic control of the gate over the conduction channel and then a better immunity against the short channel effects (SCE). In this letter, a large-scale process of GAA vertical silicon nanowire (VNW) MOSFETs is presented. A top-down approach is adopted for the realization of VNWs with an optimum reproducibility followed by thin layer engineering at nanoscale. Good overall electrical performances were obtained, with excellent electrostatic behavior (a subthreshold slope (SS) of 95 mV/dec and a drain induced barrier lowering (DIBL) of 25 mV/V) for a 15-nm gate length. Finally, a first demonstration of dual integration of n-type and p-type VNW transistors for the realization of CMOS inverter is proposed. PMID:27094824

  5. Young's Modulus, Residual Stress, and Crystal Orientation of Doubly Clamped Silicon Nanowire Beams.

    PubMed

    Calahorra, Y; Shtempluck, O; Kotchetkov, V; Yaish, Y E

    2015-05-13

    Initial or residual stress plays an important role in nanoelectronics. Valley degeneracy in silicon nanowires (SiNWs) is partially lifted due to built-in stresses, and consequently, electron-phonon scattering rate is reduced and device mobility and performance are improved. In this study we use a nonlinear model describing the force-deflection relationship to extract the Young's modulus, the residual stress, and the crystallographic growth orientation of SiNW beams. Measurements were performed on suspended doubly clamped SiNWs subjected to atomic force microscopy (AFM) three-point bending constraints. The nanowires comprised different growth directions and two SiO2 sheath thicknesses, and underwent different rapid thermal annealing processes. Analysis showed that rapid thermal annealing introduces compressive strains into the SiNWs and may result in buckling of the SiNWs. Furthermore, the core-shell model together with the residual stress analysis accurately describe the Young's modulus of oxide covered SiNWs and the crystal orientation of the measured nanowires. PMID:25826449

  6. Spin transport and Hanle effect in silicon nanowires using graphene tunnel barriers

    NASA Astrophysics Data System (ADS)

    van't Erve, O. M. J.; Friedman, A. L.; Li, C. H.; Robinson, J. T.; Connell, J.; Lauhon, L. J.; Jonker, B. T.

    2015-06-01

    Spin-based devices offer non-volatile, scalable, low power and reprogrammable functionality for emerging device technologies. Here we fabricate nanoscale spintronic devices with ferromagnetic metal/single-layer graphene tunnel barriers used to generate spin accumulation and spin currents in a silicon nanowire transport channel. We report the first observation of spin precession via the Hanle effect in both local three-terminal and non-local spin-valve geometries, providing a direct measure of spin lifetimes and confirmation of spin accumulation and pure spin transport. The use of graphene as the tunnel barrier provides a low-resistance area product contact and clean magnetic switching characteristics, because it smoothly bridges the nanowire and minimizes complicated magnetic domains that otherwise compromise the magnetic behaviour. Utilizing intrinsic two-dimensional layers such as graphene or hexagonal boron nitride as tunnel contacts on nanowires offers many advantages over conventional materials deposited by vapour deposition, enabling a path to highly scaled electronic and spintronic devices.

  7. Tuning the electronic band-gap of fluorinated 3C-silicon carbide nanowires

    NASA Astrophysics Data System (ADS)

    Miranda Durán, Álvaro; Trejo Baños, Alejandro; Pérez, Luis Antonio; Cruz Irisson, Miguel

    The possibility of control and modulation of the electronic properties of silicon carbide nanowires (SiCNWs) by varying the wire diameter is well known. SiCNWs are particularly interesting and technologically important, due to its electrical and mechanical properties, allowing the development of materials with specific electronic features for the design of stable and robust electronic devices. Tuning the band gap by chemical surface passivation constitutes a way for the modification of the electronic band gap of these nanowires. We present, the structural and electronic properties of fluorinated SiCNWs, grown along the [111] crystallographic direction, which are investigated by first principles. We consider nanowires with six diameters, varying from 0.35 nm to 2.13 nm, and eight random covering schemes including fully hydrogen- and fluorine terminated ones. Gibbs free energy of formation and electronic properties were calculated for the different surface functionalization schemes and diameters considered. The results indicate that the stability and band gap of SiCNWs can be tuned by surface passivation with fluorine atoms This work was supported by CONACYT infrastructure project 252749 and UNAM-DGAPA-PAPIIT IN106714. A.M. would like to thank for financial support from CONACyT-Retención. Computing resources from proyect SC15-1-IR-27 of DGTIC-UNAM are acknowledged.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  10. Stable field emission from arrays of vertically aligned free-standing metallic nanowires

    NASA Astrophysics Data System (ADS)

    Xavier, Stephane; Mátéfi-Tempfli, Stefan; Ferain, Etienne; Purcell, Stephen; Enouz-Védrenne, Shaïma; Gangloff, Laurent; Minoux, Eric; Hudanski, Ludovic; Vincent, Pascal; Schnell, Jean-Philippe; Pribat, Didier; Piraux, Luc; Legagneux, Pierre

    2008-05-01

    We present a fully elaborated process to grow arrays of metallic nanowires with controlled geometry and density, based on electrochemical filling of nanopores in track-etched templates. Nanowire growth is performed at room temperature, atmospheric pressure and is compatible with low cost fabrication and large surfaces. This technique offers an excellent control of the orientation, shape and nanowires density. It is applied to fabricate field emission arrays with a good control of the emission site density. We have prepared Co, Ni, Cu and Rh nanowires with a height of 3 µm, a diameter of 80 nm and a density of ~107 cm-2. The electron field emission measurements and total energy distributions show that the as-grown nanowires exhibit a complex behaviour, first with emission activation under high field, followed by unstable emission. A model taking into account the effect of an oxide layer covering the nanowire surface is developed to explain this particular field emission behaviour. Finally, we present an in situ cleaning procedure by ion bombardment that collectively removes this oxide layer, leading to a stable and reproducible emission behaviour. After treatment, the emission current density is ~1 mA cm-2 for a 30 V µm-1 applied electric field.

  11. Effect of etching time on morphological, optical, and electronic properties of silicon nanowires

    PubMed Central

    2012-01-01

    Owing to their interesting electronic, mechanical, optical, and transport properties, silicon nanowires (SiNWs) have attracted much attention, giving opportunities to several potential applications in nanoscale electronic, optoelectronic devices, and silicon solar cells. For photovoltaic application, a superficial film of SiNWs could be used as an efficient antireflection coating. In this work we investigate the morphological, optical, and electronic properties of SiNWs fabricated at different etching times. Characterizations of the formed SiNWs films were performed using a scanning electron microscope, ultraviolet–visible-near-infrared spectroscopy, and light-beam-induced-current technique. The latter technique was used to determine the effective diffusion length in SiNWs films. From these investigations, we deduce that the homogeneity of the SiNWs film plays a key role on the electronic properties. PMID:22799265

  12. Effect of etching time on morphological, optical, and electronic properties of silicon nanowires.

    PubMed

    Nafie, Nesma; Lachiheb, Manel Abouda; Bouaicha, Mongi

    2012-01-01

    Owing to their interesting electronic, mechanical, optical, and transport properties, silicon nanowires (SiNWs) have attracted much attention, giving opportunities to several potential applications in nanoscale electronic, optoelectronic devices, and silicon solar cells. For photovoltaic application, a superficial film of SiNWs could be used as an efficient antireflection coating. In this work we investigate the morphological, optical, and electronic properties of SiNWs fabricated at different etching times. Characterizations of the formed SiNWs films were performed using a scanning electron microscope, ultraviolet-visible-near-infrared spectroscopy, and light-beam-induced-current technique. The latter technique was used to determine the effective diffusion length in SiNWs films. From these investigations, we deduce that the homogeneity of the SiNWs film plays a key role on the electronic properties. PMID:22799265

  13. 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.

  14. 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

  15. High-sensitivity pesticide detection via silicon nanowires-supported acetylcholinesterase-based electrochemical sensors

    NASA Astrophysics Data System (ADS)

    Su, Shao; He, Yao; Zhang, Mingliang; Yang, Kun; Song, Shiping; Zhang, Xiaohong; Fan, Chunhai; Lee, Shuit-Tong

    2008-07-01

    We report the use of a silicon-based nanocomplex, i.e., gold nanoparticles-coated silicon nanowires, for the improvement of acetylcholinesterase (AChE)-based electrochemical sensors for pesticide detection. Owing to the high electrical conductivity of the nanocomplex and its compatibility with the enzyme, the sensor exhibited significantly enhanced performance. The AChE enzyme bound to the surface possessed Michaelis-Menton constant of 81μM, resembling that in its free form. The sensor showed rapid response toward substrate acetylcholine in the concentration range of 1.0μM-1.0mM. This AChE nanosensor could detect as low as 8ng/L dichlorvos, an organophosphate pesticide.

  16. Thermally activated tunneling in porous silicon nanowires with embedded Si quantum dots

    NASA Astrophysics Data System (ADS)

    Rezvani, S. J.; Pinto, N.; Enrico, E.; D'Ortenzi, L.; Chiodoni, A.; Boarino, L.

    2016-03-01

    Electronic transport properties of porous Si nanowires either with embedded Si quantum dots or with a percolative crystalline path are studied as a function of the temperature for the first time. We show that unlike bulk porous Si, the predesigned structure of the wires results in a single distinct conduction mechanism such as tunneling in the former case and variable range hopping in the latter case. We demonstrate that the geometry of the systems with a large internal surface area and high density of the Si quantum dots have a significant conduction enhancement compared to bulk porous silicon. These results can also improve the understanding of the basis of the different electronic transport mechanisms reported in bulk porous silicon.

  17. Disorder-free localization around the conduction band edge of crossing and kinked silicon nanowires

    SciTech Connect

    Keleş, Ümit; Çakan, Aslı; Bulutay, Ceyhun

    2015-02-14

    We explore ballistic regime quantum transport characteristics of oxide-embedded crossing and kinked silicon nanowires (NWs) within a large-scale empirical pseudopotential electronic structure framework, coupled to the Kubo-Greenwood transport analysis. A real-space wave function study is undertaken and the outcomes are interpreted together with the findings of ballistic transport calculations. This reveals that ballistic transport edge lies tens to hundreds of millielectron volts above the lowest unoccupied molecular orbital, with a substantial number of localized states appearing in between, as well as above the former. We show that these localized states are not due to the oxide interface, but rather core silicon-derived. They manifest the wave nature of electrons brought to foreground by the reflections originating from NW junctions and bends. Hence, we show that the crossings and kinks of even ultraclean Si NWs possess a conduction band tail without a recourse to atomistic disorder.

  18. Broadband absorptance enhancement of silicon nanowire arrays with germanium as the substrate

    NASA Astrophysics Data System (ADS)

    Wang, Han; Xia, Xin-Lin

    2013-08-01

    A composite structure with silicon nanowire arrays on germanium substrate is proposed as a good candidate for highly efficient solar cells. The Bruggeman approximation considering anisotropic wave propagating in uniaxial media is employed to calculate the radiative properties. Meantime, finite-difference time-domain (FDTD) method is used to verify for both normal and oblique incidence. It is found that the composite structure has superior absorption characteristics over thin Si film, particularly near the bandgap. With a thickness only of 4 μm, the composite structure improved the absorptance to above 0.6 across the whole wavelength band with the lattice constant of 100 nm, and the ultimate efficiency about 10% is higher than that of infinite bulk silicon, owing to the combined effects of suppressed reflection and high light trapping capability. To better understand the absorption enhancement process in the composite structure, the photogeneration profiles are provided by using FDTD method.

  19. High Efficiency Organic/Silicon-Nanowire Hybrid Solar Cells: Significance of Strong Inversion Layer

    PubMed Central

    Yu, Xuegong; Shen, Xinlei; Mu, Xinhui; Zhang, Jie; Sun, Baoquan; Zeng, Lingsheng; Yang, Lifei; Wu, Yichao; He, Hang; Yang, Deren

    2015-01-01

    Organic/silicon nanowires (SiNWs) hybrid solar cells have recently been recognized as one of potentially low-cost candidates for photovoltaic application. Here, we have controllably prepared a series of uniform silicon nanowires (SiNWs) with various diameters on silicon substrate by metal-assisted chemical etching followed by thermal oxidization, and then fabricated the organic/SiNWs hybrid solar cells with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS). It is found that the reflective index of SiNWs layer for sunlight depends on the filling ratio of SiNWs. Compared to the SiNWs with the lowest reflectivity (LR-SiNWs), the solar cell based on the SiNWs with low filling ratio (LF-SiNWs) has a higher open-circuit voltage and fill factor. The capacitance-voltage measurements have clarified that the built-in potential barrier at the LF-SiNWs/PEDOT:PSS interface is much larger than that at the LR-SiNWs/PEDOT one, which yields a strong inversion layer generating near the silicon surface. The formation of inversion layer can effectively suppress the carrier recombination, reducing the leakage current of solar cell, and meanwhile transfer the LF-SiNWs/PEDOT:PSS device into a p-n junction. As a result, a highest efficiency of 13.11% is achieved for the LF-SiNWs/PEDOT:PSS solar cell. These results pave a way to the fabrication of high efficiency organic/SiNWs hybrid solar cells. PMID:26610848

  20. Controlled Synthesis of Millimeter-Long Silicon Nanowires with Uniform Electronic Properties

    PubMed Central

    Park, Won Il; Zheng, Gengfeng; Jiang, Xiaocheng; Tian, Bozhi; Lieber, Charles M.

    2009-01-01

    We report the nanocluster-catalyzed growth of ultra-long and highly-uniform single-crystalline silicon nanowires (SiNWs) with millimeter-scale lengths and aspect ratios up to ca. 100,000. The average SiNW growth rate using disilane (Si2H6) at 400 °C was 31 µm/min, while the growth rate determined for silane (SiH4) reactant under similar growth conditions was 130 times lower. Transmission electron microscopy studies of millimeter-long SiNWs with diameters of 20–80 nm show that the nanowires grow preferentially along the <110> direction independent of diameter. In addition, ultra-long SiNWs were used as building blocks to fabricate one-dimensional arrays of field-effect transistors (FETs) consisting of ca. 100 independent devices per nanowire. Significantly, electrical transport measurements demonstrated that the millimeter-long SiNWs had uniform electrical properties along the entire length of wires, and each device can behave as a reliable FET with an on-state current, threshold voltage, and transconductance values (average ± 1 standard deviation) of 1.8 ± 0.3 µA, 6.0 ± 1.1 V, 210 ± 60 nS, respectively. Electronically-uniform millimeter-long SiNWs were also functionalized with monoclonal antibody receptors, and used to demonstrate multiplexed detection of cancer marker proteins with a single nanowire. The synthesis of structurally- and electronically-uniform ultra-long SiNWs may open up new opportunities for integrated nanoelectronics, and could serve as unique building blocks linking integrated structures from the nanometer through millimeter length scales. PMID:18710294

  1. Controlled synthesis of millimeter-long silicon nanowires with uniform electronic properties.

    PubMed

    Park, Won Il; Zheng, Gengfeng; Jiang, Xiaocheng; Tian, Bozhi; Lieber, Charles M

    2008-09-01

    We report the nanocluster-catalyzed growth of ultralong and highly uniform single-crystalline silicon nanowires (SiNWs) with millimeter-scale lengths and aspect ratios up to approximately 100,000. The average SiNW growth rate using disilane (Si 2H 6) at 400 degrees C was 31 microm/min, while the growth rate determined for silane (SiH 4) reactant under similar growth conditions was 130 times lower. Transmission electron microscopy studies of millimeter-long SiNWs with diameters of 20-80 nm show that the nanowires grow preferentially along the 110 direction independent of diameter. In addition, ultralong SiNWs were used as building blocks to fabricate one-dimensional arrays of field-effect transistors (FETs) consisting of approximately 100 independent devices per nanowire. Significantly, electrical transport measurements demonstrated that the millimeter-long SiNWs had uniform electrical properties along the entire length of wires, and each device can behave as a reliable FET with an on-state current, threshold voltage, and transconductance values (average +/-1 standard deviation) of 1.8 +/- 0.3 microA, 6.0 +/- 1.1 V, 210 +/- 60 nS, respectively. Electronically uniform millimeter-long SiNWs were also functionalized with monoclonal antibody receptors and used to demonstrate multiplexed detection of cancer marker proteins with a single nanowire. The synthesis of structurally and electronically uniform ultralong SiNWs may open up new opportunities for integrated nanoelectronics and could serve as unique building blocks linking integrated structures from the nanometer through millimeter length scales. PMID:18710294

  2. Thickness effect of catalyst layer on silicon nanowires morphology and features

    NASA Astrophysics Data System (ADS)

    Hamidinezhad, Habib

    2016-02-01

    Silicon nanowires (SiNWs) have been synthesized on gold layer-coated silicon substrates via plasma enhanced chemical vapor deposition method (PECVD). Various thicknesses of Au layers were coated on Si (111) substrates using radio frequency magnetron sputtering. Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) were used to characterize the morphology, compositions, and structures of the samples. The results show that the sample consisted of single-crystalline SiNWs with the diameters ranging from 40 to 160 nm and length up to 3 μm. It was observed that the diameter of SiNWs increases with increasing of Au catalyst layers thickness. Raman spectra display peaks with narrow and asymmetric shape at 518 cm-1 for the SiNWs, indicating the high crystalline nature of the samples. A possible growth mechanism is proposed for the formation of nanowires (NWs). It has been found that the features of SiNWs depend on the thickness of Au layers.

  3. Optical Properties of Silicon Nanowires Fabricated by Environment-Friendly Chemistry

    NASA Astrophysics Data System (ADS)

    Gonchar, Kirill A.; Zubairova, Alsu A.; Schleusener, Alexander; Osminkina, Liubov A.; Sivakov, Vladimir

    2016-08-01

    Silicon nanowires (SiNWs) were fabricated by metal-assisted chemical etching (MACE) where hydrofluoric acid (HF), which is typically used in this method, was changed into ammonium fluoride (NH4F). The structure and optical properties of the obtained SiNWs were investigated in details. The length of the SiNW arrays is about 2 μm for 5 min of etching, and the mean diameter of the SiNWs is between 50 and 200 nm. The formed SiNWs demonstrate a strong decrease of the total reflectance near 5-15 % in the spectral region λ < 1 μm in comparison to crystalline silicon (c-Si) substrate. The interband photoluminescence (PL) and Raman scattering intensities increase strongly for SiNWs in comparison with the corresponding values of the c-Si substrate. These effects can be interpreted as an increase of the excitation intensity of SiNWs due to the strong light scattering and the partial light localization in an inhomogeneous optical medium. Along with the interband PL was also detected the PL of SiNWs in the spectral region of 500-1100 nm with a maximum at 750 nm, which can be explained by the radiative recombination of excitons in small Si nanocrystals at nanowire sidewalls in terms of a quantum confinement model. So SiNWs, which are fabricated by environment-friendly chemistry, have a great potential for use in photovoltaic and photonics applications.

  4. High frequency top-down junction-less silicon nanowire resonators

    NASA Astrophysics Data System (ADS)

    Koumela, Alexandra; Hentz, Sébastien; Mercier, Denis; Dupré, Cécilia; Ollier, Eric; X-L Feng, Philip; Purcell, Stephen T.; Duraffourg, Laurent

    2013-11-01

    We report here the first realization of top-down silicon nanowires (SiNW) transduced by both junction-less field-effect transistor (FET) and the piezoresistive (PZR) effect. The suspended SiNWs are among the smallest top-down SiNWs reported to date, featuring widths down to ˜20 nm. This has been achieved thanks to a 200 mm-wafer-scale, VLSI process fully amenable to monolithic CMOS co-integration. Thanks to the very small dimensions, the conductance of the silicon nanowire can be controlled by a nearby electrostatic gate. Both the junction-less FET and the previously demonstrated PZR transduction have been performed with the same SiNW. These self-transducing schemes have shown similar signal-to-background ratios, and the PZR transduction has exhibited a relatively higher output signal. Allan deviation (σA) of the same SiNW has been measured with both schemes, and we obtain σA ˜ 20 ppm for the FET detection and σA ˜ 3 ppm for the PZR detection at room temperature and low pressure. Orders of magnitude improvements are expected from tighter electrostatic control via changes in geometry and doping level, as well as from CMOS integration. The compact, simple topology of these elementary SiNW resonators opens up new paths towards ultra-dense arrays for gas and mass sensing, time keeping or logic switching systems on the SiNW-CMOS platform.

  5. Reducing the porosity and reflection loss of silicon nanowires by a sticky tape

    NASA Astrophysics Data System (ADS)

    Liu, Junjun; Huang, Zhifeng

    2015-05-01

    Engineering the porosity of silicon nanowires (SiNWs) is of fundamental importance, and this work introduces a new method for doing so. Metal-assisted chemical etching (MACE) of heavily doped Si(100) creates mesoporous silicon nanowires (mp-SiNWs). mp-SiNWs are transferred from the MACE-treated wafer to a sticky tape, leaving residues composed of broken mp-SiNWs and a mesoporous Si layer on the wafer. Then the taped wafer is re-treated by MACE, without changing the etching conditions. The second MACE treatment generates mp-SiNWs that are less porous and longer than those generated by the first MACE treatment, which can be attributed to the difference in the surface topography at the beginning of the etching process. Less porous mp-SiNWs reduce optical scattering from the porous Si skeletons, and vertically protrude on the wafer without aggregation to facilitate optical trapping. Consequently, less porous mp-SiNWs effectively reduce ultraviolet-visible reflection loss.

  6. Dispersively Detected Pauli Spin-Blockade in a Silicon Nanowire Field-Effect Transistor

    NASA Astrophysics Data System (ADS)

    Betz, Andreas; Wacquez, R.; Vinet, M.; Jehl, X.; Saraiva, A. L.; Sanquer, M.; Ferguson, A. J.; Gonzalez-Zalba, M. F.

    We report the dispersive readout of the spin state of a double quantum dot (DQD) formed at the corner states of a silicon nanowire FET. Two face-to-face topgate electrodes allow us to independently tune the charge occupation of the quantum dot system down to the few-electron limit. We measure the charge stability of the DQD in DC transport as well as dispersively via in situ gate-based radio frequency (rf) reflectometry, where one top-gate electrode is connected to a resonator. The latter removes the need for external charge sensors in quantum computing architectures and provides a compact way to readout the dispersive shift caused by changes in the quantum capacitance during inter-dot charge transitions. Here, we observe Pauli spin-blockade in the rf response of the circuit at finite magnetic fields between singlet and triplet states. The blockade is lifted at higher magnetic fields when intra-dot triplet states become the ground state configuration. A line shape analysis of the dispersive signal reveals furthermore an intra-dot valley-orbit splitting Δvo ~= 145 μ eV. Our results open up the possibility to operate compact CMOS technology as a singlet-triplet qubit and make split-gate silicon nanowire architectures an ideal candidate for the study of spin dynamics.

  7. Preparation of Silicon Nanowire Field-effect Transistor for Chemical and Biosensing Applications.

    PubMed

    Wu, Jennifer Yun-Shin; Lin, Chih-Heng; Feng, Mei-Huei; Chen, Chien-Hung; Su, Ping-Chia; Yang, Po-Wen; Zheng, Jian-Ming; Fu, Chang-Wei; Yang, Yuh-Shyong

    2016-01-01

    Surveillance using biomarkers is critical for the early detection, rapid intervention, and reduction in the incidence of diseases. In this study, we describe the preparation of polycrystalline silicon nanowire field-effect transistors (pSNWFETs) that serve as biosensing devices for biomarker detection. A protocol for chemical and biomolecular sensing by using pSNWFETs is presented. The pSNWFET device was demonstrated to be a promising transducer for real-time, label-free, and ultra-high-sensitivity biosensing applications. The source/drain channel conductivity of a pSNWFET is sensitive to changes in the environment around its silicon nanowire (SNW) surface. Thus, by immobilizing probes on the SNW surface, the pSNWFET can be used to detect various biotargets ranging from small molecules (dopamine) to macromolecules (DNA and proteins). Immobilizing a bioprobe on the SNW surface, which is a multistep procedure, is vital for determining the specificity of the biosensor. It is essential that every step of the immobilization procedure is correctly performed. We verified surface modifications by directly observing the shift in the electric properties of the pSNWFET following each modification step. Additionally, X-ray photoelectron spectroscopy was used to examine the surface composition following each modification. Finally, we demonstrated DNA sensing on the pSNWFET. This protocol provides step-by-step procedures for verifying bioprobe immobilization and subsequent DNA biosensing application. PMID:27167162

  8. Selectively deposited silver coatings on gold-capped silicon nanowires for surface-enhanced Raman spectroscopy.

    PubMed

    Becker, M; Stelzner, Th; Steinbrück, A; Berger, A; Liu, J; Lerose, D; Gösele, U; Christiansen, S

    2009-06-01

    Gold caps on silicon nanowires are selectively coated with silver by autometallography (electroless deposition). Changing the conditions of silver deposition, a variety of different coating morphologies can be produced [figure: see text]. The different silver coating morphologies are investigated in terms of their capabilities for surface enhanced Raman scattering (SERS) experiments.Gold caps on silicon nanowires are hemispherical and only a few tens of nanometers in diameter when grown from metal catalysts by the vapor-liquid-solid growth mechanism using chemical vapor deposition. These gold caps are capable of enhancing Raman signals based on the surface-enhanced Raman scattering effect. The Raman signal can be enhanced even further (by at least one order of magnitude) when silver is selectively deposited onto these gold caps by autometallography (electroless deposition). By changing the silver deposition conditions, different coating morphologies can be realized on the gold caps that range from very thin, smooth layers to uneven and extremely rough coatings. The SERS signal enhancement and the spatial homogeneity of the achievable enhancement are compared for the different silver coatings using a model dye molecule. PMID:19399821

  9. Dispersively Detected Pauli Spin-Blockade in a Silicon Nanowire Field-Effect Transistor.

    PubMed

    Betz, A C; Wacquez, R; Vinet, M; Jehl, X; Saraiva, A L; Sanquer, M; Ferguson, A J; Gonzalez-Zalba, M F

    2015-07-01

    We report the dispersive readout of the spin state of a double quantum dot formed at the corner states of a silicon nanowire field-effect transistor. Two face-to-face top-gate electrodes allow us to independently tune the charge occupation of the quantum dot system down to the few-electron limit. We measure the charge stability of the double quantum dot in DC transport as well as dispersively via in situ gate-based radio frequency reflectometry, where one top-gate electrode is connected to a resonator. The latter removes the need for external charge sensors in quantum computing architectures and provides a compact way to readout the dispersive shift caused by changes in the quantum capacitance during inter-dot charge transitions. Here, we observe Pauli spin-blockade in the high-frequency response of the circuit at finite magnetic fields between singlet and triplet states. The blockade is lifted at higher magnetic fields when intra-dot triplet states become the ground state configuration. A line shape analysis of the dispersive phase shift reveals furthermore an intra-dot valley-orbit splitting Δvo of 145 μeV. Our results open up the possibility to operate compact complementary metal-oxide semiconductor (CMOS) technology as a singlet-triplet qubit and make split-gate silicon nanowire architectures an ideal candidate for the study of spin dynamics. PMID:26047255

  10. Laser-induced Greenish-Blue Photoluminescence of Mesoporous Silicon Nanowires

    NASA Astrophysics Data System (ADS)

    Choi, Yan-Ru; Zheng, Minrui; Bai, Fan; Liu, Junjun; Tok, Eng-Soon; Huang, Zhifeng; Sow, Chorng-Haur

    2014-05-01

    Solid silicon nanowires and their luminescent properties have been widely studied, but lesser is known about the optical properties of mesoporous silicon nanowires (mp-SiNWs). In this work, we present a facile method to generate greenish-blue photoluminescence (GB-PL) by fast scanning a focused green laser beam (wavelength of 532 nm) on a close-packed array of mp-SiNWs to carry out photo-induced chemical modification. The threshold of laser power is 5 mW to excite the GB-PL, whose intensity increases with laser power in the range of 5-105 mW. The quenching of GB-PL comes to occur beyond 105 mW. The in-vacuum annealing effectively excites the GB-PL in the pristine mp-SiNWs and enhances the GB-PL of the laser-modified mp-SiNWs. A complex model of the laser-induced surface modification is proposed to account for the laser-power and post-annealing effect. Moreover, the fast scanning of focused laser beam enables us to locally tailor mp-SiNWs en route to a wide variety of micropatterns with different optical functionality, and we demonstrate the feasibility in the application of creating hidden images.

  11. Probing protein complexes inside living cells using a silicon nanowire-based pull-down assay

    NASA Astrophysics Data System (ADS)

    Choi, Sojoong; Kim, Hyunju; Kim, So Yeon; Yang, Eun Gyeong

    2016-06-01

    Most proteins perform their functions as interacting complexes. Here we propose a novel method for capturing an intracellular protein and its interacting partner out of living cells by utilizing intracellular access of antibody modified vertical silicon nanowire arrays whose surface is covered with a polyethylene glycol layer to prevent strong cell adhesion. Such a feature facilitates the removal of cells by simple washing, enabling subsequent detection of a pulled-down protein and its interacting partner, and further assessment of a drug-induced change in the interacting complex. Our new SiNW-based tool is thus suitable for authentication of protein networks inside living cells.Most proteins perform their functions as interacting complexes. Here we propose a novel method for capturing an intracellular protein and its interacting partner out of living cells by utilizing intracellular access of antibody modified vertical silicon nanowire arrays whose surface is covered with a polyethylene glycol layer to prevent strong cell adhesion. Such a feature facilitates the removal of cells by simple washing, enabling subsequent detection of a pulled-down protein and its interacting partner, and further assessment of a drug-induced change in the interacting complex. Our new SiNW-based tool is thus suitable for authentication of protein networks inside living cells. Electronic supplementary information (ESI) available: Materials, experimental methods and Fig. S1-S8. See DOI: 10.1039/c6nr00171h

  12. Solid-state diffusion as an efficient doping method for silicon nanowires and nanowire field effect transistors.

    PubMed

    Moselund, K E; Ghoneim, H; Schmid, H; Björk, M T; Lörtscher, E; Karg, S; Signorello, G; Webb, D; Tschudy, M; Beyeler, R; Riel, H

    2010-10-29

    In this work we investigate doping by solid-state diffusion from a doped oxide layer, obtained by plasma-enhanced chemical vapor deposition (PECVD), as a means for selectively doping silicon nanowires (NWs). We demonstrate both n-type (phosphorous) and p-type (boron) doping up to concentrations of 10(20) cm(-3), and find that this doping mechanism is more efficient for NWs as opposed to planar substrates. We observe no diameter dependence in the range of 25 to 80 nm, which signifies that the NWs are uniformly doped. The drive-in temperature (800-950 °C) can be used to adjust the actual doping concentration in the range 2 × 10(18) to 10(20) cm(-3). Furthermore, we have fabricated NMOS and PMOS devices to show the versatility of this approach and the possibility of achieving segmented doping of NWs. The devices show high I(on)/I(off) ratios of around 10(7) and, especially for the PMOS, good saturation behavior and low hysteresis. PMID:20890021

  13. High Density of Aligned Nanowire Treated with Polydopamine for Efficient Gene Silencing by siRNA According to Cell Membrane Perturbation.

    PubMed

    Nair, Baiju G; Hagiwara, Kyoji; Ueda, Motoki; Yu, Hsiao-Hua; Tseng, Hsian-Rong; Ito, Yoshihiro

    2016-07-27

    High aspect ratio nanomaterials, such as vertically aligned silicon nanowire (SiNW) substrates, are three-dimensional topological features for cell manipulations. A high density of SiNWs significantly affects not only cell adhesion and proliferation but also the delivery of biomolecules to cells. Here, we used polydopamine (PD) that simply formed a thin coating on various material surfaces by the action of dopamine as a bioinspired approach. The PD coating not only enhanced cell adhesion, spreading, and growth but also anchored more siRNA by adsorption and provided more surface concentration for substrate-mediated delivery. By comparing plain and SiNW surfaces with the same amount of loaded siRNA, we quantitatively found that PD coating efficiently anchored siRNA on the surface, which knocked down the expression of a specific gene by RNA interference. It was also found that the interaction of SiNWs with the cell membrane perturbed the lateral diffusion of lipids in the membrane by fluorescence recovery after photobleaching. The perturbation was considered to induce the effective delivery of siRNA into cells and allow the cells to carry out their biological functions. These results suggest promising applications of PD-coated, high-density SiNWs as simple, fast, and versatile platforms for transmembrane delivery of biomolecules. PMID:27420034

  14. Kinetic study of the oxide-assisted catalyst-free synthesis of silicon nitride nanowires

    NASA Astrophysics Data System (ADS)

    Farjas, J.; Pinyol, A.; Rath, Chandana; Roura, P.; Bertran, E.

    2006-05-01

    The synthesis of Si3N4 nanowires from the reaction of silicon nanoparticles with N2 in the 1200-1440 °C temperature range is reported. The nitridation conditions are such that the reaction with nitrogen is favoured by the presence of silicon oxide in the particles and by the active oxidation of silicon without a catalyst. It is shown that the Si to Si3N4 conversion rate depends on the amount of silicon particles used in the experiments and that, in general, the reaction slows down for greater amounts. This trend is explained by particle stacking, which restricts the exchange of gases between the furnace atmosphere and the atmosphere around the inner particles. In a first stage, local oxygen partial pressure increases around the inner particles and inhibits nitridation locally. If the amount of reactant Si nanoparticles is small enough, this extrinsic effect is avoided and the intrinsic nitridation kinetics can be measured. Experiments show that intrinsic kinetics does not depend on temperature.

  15. Nanoparticles prepared from porous silicon nanowires for bio-imaging and sonodynamic therapy

    PubMed Central

    2014-01-01

    Evaluation of cytotoxicity, photoluminescence, bio-imaging, and sonosensitizing properties of silicon nanoparticles (SiNPs) prepared by ultrasound grinding of porous silicon nanowires (SiNWs) have been investigated. SiNWs were formed by metal (silver)-assisted wet chemical etching of heavily boron-doped (100)-oriented single crystalline silicon wafers. The prepared SiNWs and aqueous suspensions of SiNPs exhibit efficient room temperature photoluminescence (PL) in the spectral region of 600 to 1,000 nm that is explained by the radiative recombination of excitons confined in small silicon nanocrystals, from which SiNWs and SiNPs consist of. On the one hand, in vitro studies have demonstrated low cytotoxicity of SiNPs and possibilities of their bio-imaging applications. On the other hand, it has been found that SiNPs can act as efficient sensitizers of ultrasound-induced suppression of the viability of Hep-2 cancer cells. PMID:25288909

  16. Method for making alignment-enhancing feed-through conductors for stackable silicon-on-sapphire

    NASA Technical Reports Server (NTRS)

    Anthony, Thomas R. (Inventor)

    1985-01-01

    Alignment-enhancing electrically conductive feed-through paths are provided for the high-speed low-loss transfer of electrical signals between integrated circuits of a plurality of silicon-on-sapphire bodies arrayed in a stack. The alignment-enhancing feed-throughs are made by a process of this invention involving the drilling of holes through the body, double-sided sputtering, electroplating, and the filling of the holes with solder by capillary action. The alignment-enhancing feed-throughs are activated by forming a stack of wafers and remelting the solder whereupon the wafers, and the feed-through paths, are pulled into alignment by surface tension forces.

  17. Highly robust silicon nanowire/graphene core-shell electrodes without polymeric binders

    NASA Astrophysics Data System (ADS)

    Lee, Sang Eon; Kim, Han-Jung; Kim, Hwanjin; Park, Jong Hyeok; Choi, Dae-Geun

    2013-09-01

    A large theoretical charge storage capacity along with a low discharge working potential renders silicon a promising anode material for high energy density lithium ion batteries. However, up to 400% volume expansion during charge-discharge cycling coupled with a low intrinsic electronic conductivity causes pulverization and fracture, thus inhibiting silicon's widespread use in practical applications. We report herein on a low cost approach to fabricate hybrid silicon nanowire (SiNW)/graphene nanostructures that exhibit enhanced cycle performance with the capability of retaining more than 90% of their initial capacity after 50 cycles. We also demonstrate the use of hot-pressing in the absence of any common polymer binder such as PVDF to bind the hybrid structure to the current collector. The applied heat and pressure ensure strong adhesion between the SiNW/graphene nano-composite and current collector. This facile yet strong binding method is expected to find use in the further development of polymer-binder free anodes for lithium ion batteries.A large theoretical charge storage capacity along with a low discharge working potential renders silicon a promising anode material for high energy density lithium ion batteries. However, up to 400% volume expansion during charge-discharge cycling coupled with a low intrinsic electronic conductivity causes pulverization and fracture, thus inhibiting silicon's widespread use in practical applications. We report herein on a low cost approach to fabricate hybrid silicon nanowire (SiNW)/graphene nanostructures that exhibit enhanced cycle performance with the capability of retaining more than 90% of their initial capacity after 50 cycles. We also demonstrate the use of hot-pressing in the absence of any common polymer binder such as PVDF to bind the hybrid structure to the current collector. The applied heat and pressure ensure strong adhesion between the SiNW/graphene nano-composite and current collector. This facile yet strong

  18. An in-situ hard mask block copolymer approach for the fabrication of ordered, large scale, horizontally aligned, Si nanowire arrays on Si substrate

    NASA Astrophysics Data System (ADS)

    Ghoshal, Tandra; Senthamaraikannan, Ramsankar; Shaw, Matthew T.; Holmes, Justin D.; Morris, Michael A.

    2014-03-01

    We report a simple technique to fabricate horizontal, uniform Si nanowire arrays with controlled orientation and density at spatially well defined locations on substrate based on insitu hard mask pattern formation approach by microphase separated polystyrene-b-poly(ethylene oxide) (PS-b-PEO) block copolymer (BCP) thin films. The methodology may be applicable to large scale production. Ordered microphase separated patterns of the BCP were defined by solvent annealing and the orientation was controlled by film thickness and annealing time. Films of PEO cylinders with parallel orientation (to the surface plane) were applied to create `frames' for the generation of inorganic oxide nanowire arrays. These PEO cylinders were subject to selective metal ion inclusion and subsequent processing was used to create iron oxide nanowire arrays. The oxide nanowires were isolated, of uniform diameter and their structure a mimic of the original BCP nanopatterns. The phase purity, crystallinity and thermal stability of the nanowires coupled to the ease of large scale production may make them useful in technological applications. Here, we demonstrate that the oxide nanowire arrays could be used as a resist mask to fabricate densely packed, identical ordered, good fidelity silicon nanowire arrays on the substrate. The techniques may have significant application in the manufacture of transistor circuitry.

  19. Mg-catalyzed autoclave synthesis of aligned silicon carbide nanostructures.

    PubMed

    Xi, Guangcheng; Liu, Yankuan; Liu, Xiaoyan; Wang, Xiaoqing; Qian, Yitai

    2006-07-27

    In this article, a novel magnesium-catalyzed co-reduction route was developed for the large-scale synthesis of aligned beta-SiC one-dimensional (1D) nanostructures at relative lower temperature (600 degrees C). By carefully controlling the reagent concentrations, we could synthesize beta-SiC rodlike and needlelike nanostructures. The possible growth mechanism of the as-synthesized beta-SiC 1D nanostructures has been investigated. The structure and morphology of the as-synthesized beta-SiC nanostructures are characterized using X-ray diffraction, Fourier transform infrared absorption, and scanning and transmission electron microscopes. Raman and photoluminescence properties are also investigated at room temperature. The as-synthesized beta-SiC nanostructures exhibit strong shape-dependent field emission properties. Corresponding to their shapes, the as-synthesized nanorods and nanoneedles display the turn-on fields of 12, 8.4, and 1.8 V/microm, respectively. PMID:16854116

  20. In Situ TEM Observations of Sn-Containing Silicon Nanowires Undergoing Reversible Pore Formation Due to Fast Lithiation/Delithiation Kinetics

    SciTech Connect

    Lu, Xiaotang; Bogart, Timothy D.; Gu, Meng; Wang, Chong M.; Korgel, Brian

    2015-09-03

    In situ transmission electron microscopy (TEM) studies were carried out to observe directly in real time the lithiation and delithiation of silicon (Si) nanowires with significant amounts of tin (Sn). The incorporation of Sn significantly enhances the lithiation rate compared to typical Si nanowires. For instance, surface diffusion is enhanced by two orders of magnitude and the bulk lithiation rate by one order of magnitude, resulting in a sequential surface-then-core lithiation mechanism. Pore formation was observed in the nanowires during delithiation, most likely as a result of the fast delithiation kinetics of the nanowires. Pore formation was reversible and the pores disappeared during subsequent lithiation. When an amorphous Si shell was applied to the nanowires, pore formation was not observed during the in situ TEM experimences. Ex situ TEM analysis of Sn-containing Si nanowires cycled in coin cell batteries also showed that the application of an a-Si shell significantly retards pore formation in these nanowires.

  1. Fabrication and photocatalytic properties of silicon nanowires by metal-assisted chemical etching: effect of H2O2 concentration

    PubMed Central

    2012-01-01

    In the current study, monocrystalline silicon nanowire arrays (SiNWs) were prepared through a metal-assisted chemical etching method of silicon wafers in an etching solution composed of HF and H2O2. Photoelectric properties of the monocrystalline SiNWs are improved greatly with the formation of the nanostructure on the silicon wafers. By controlling the hydrogen peroxide concentration in the etching solution, SiNWs with different morphologies and surface characteristics are obtained. A reasonable mechanism of the etching process was proposed. Photocatalytic experiment shows that SiNWs prepared by 20% H2O2 etching solution exhibit the best activity in the decomposition of the target organic pollutant, Rhodamine B (RhB), under Xe arc lamp irradiation for its appropriate Si nanowire density with the effect of Si content and contact area of photocatalyst and RhB optimized. PMID:23217211

  2. Rapid Charge Transport in Dye-Sensitized Solar Cells Made from Vertically Aligned Single-Crystal Rutile TiO2 Nanowires

    SciTech Connect

    Feng, X.; Zhu, K.; Frank, A. J.; Grimes, C. A.; Mallouk, T. E.

    2012-03-12

    A rapid solvothermal approach was used to synthesize aligned 1D single-crystal rutile TiO2 nanowire (NW) arrays on transparent conducting substrates as electrodes for dye-sensitized solar cells. The NW arrays showed a more than 200 times faster charge transport (see picture) and a factor four lower defect state density than conventional rutile nanoparticle films.

  3. Fabrication of CoFe2O4 ferrite nanowire arrays in porous silicon template and their local magnetic properties

    NASA Astrophysics Data System (ADS)

    Hui, Zheng; Man-Gui, Han; Long-Jiang, Deng

    2016-02-01

    CoFe2O4 ferrite nanowire arrays are fabricated in porous silicon templates. The porous silicon templates are prepared via metal-assisted chemical etching with gold (Au) nanoparticles as the catalyst. Subsequently, CoFe2O4 ferrite nanowires are successfully synthesized into porous silicon templates by the sol-gel method. The magnetic hysteresis loop of nanowire array shows an isotropic feature of magnetic properties. The coercivity and squareness ratio (Mr/Ms) of ensemble nanowires are found to be 630 Oe (1 Oe, = 79.5775 A·m-1 and 0.4 respectively. However, the first-order reversal curve (FORC) is adopted to reveal the probability density function of local magnetostatic properties (i.e., interwire interaction field and coercivity). The FORC diagram shows an obvious distribution feature for interaction field and coercivity. The local coercivity with a value of about 1000 Oe is found to have the highest probability. Project supported by the National Natural Science Foundation of China (Grant No. 61271039), the Scientific Projects of Sichuan Province, China (Grant No. 2015HH0016), and the Natural Science Foundations of Zhejiang Province, China (Grant Nos. LQ12E02001 and Y107255).

  4. A Monolithically Integrated Gallium Nitride Nanowire/Silicon Solar Cell Photocathode for Selective Carbon Dioxide Reduction to Methane.

    PubMed

    Wang, Yichen; Fan, Shizhao; AlOtaibi, Bandar; Wang, Yongjie; Li, Lu; Mi, Zetian

    2016-06-20

    A gallium nitride nanowire/silicon solar cell photocathode for the photoreduction of carbon dioxide (CO2 ) is demonstrated. Such a monolithically integrated nanowire/solar cell photocathode offers several unique advantages, including the absorption of a large part of the solar spectrum and highly efficient carrier extraction. With the incorporation of copper as the co-catalyst, the devices exhibit a Faradaic efficiency of about 19 % for the 8e(-) photoreduction to CH4 at -1.4 V vs Ag/AgCl, a value that is more than thirty times higher than that for the 2e(-) reduced CO (ca. 0.6 %). PMID:27128407

  5. Highly robust silicon nanowire/graphene core-shell electrodes without polymeric binders.

    PubMed

    Lee, Sang Eon; Kim, Han-Jung; Kim, Hwanjin; Park, Jong Hyeok; Choi, Dae-Geun

    2013-10-01

    A large theoretical charge storage capacity along with a low discharge working potential renders silicon a promising anode material for high energy density lithium ion batteries. However, up to 400% volume expansion during charge-discharge cycling coupled with a low intrinsic electronic conductivity causes pulverization and fracture, thus inhibiting silicon's widespread use in practical applications. We report herein on a low cost approach to fabricate hybrid silicon nanowire (SiNW)/graphene nanostructures that exhibit enhanced cycle performance with the capability of retaining more than 90% of their initial capacity after 50 cycles. We also demonstrate the use of hot-pressing in the absence of any common polymer binder such as PVDF to bind the hybrid structure to the current collector. The applied heat and pressure ensure strong adhesion between the SiNW/graphene nano-composite and current collector. This facile yet strong binding method is expected to find use in the further development of polymer-binder free anodes for lithium ion batteries. PMID:23760363

  6. Probing contact-mode characteristics of silicon nanowire electromechanical systems with embedded piezoresistive transducers

    NASA Astrophysics Data System (ADS)

    Yang, Rui; He, Tina; Tupta, Mary Anne; Marcoux, Carine; Andreucci, Philippe; Duraffourg, Laurent; X-L Feng, Philip

    2015-09-01

    This article reports on a new method of monitoring nanoscale contacts in switches based on nanoelectromechanical systems, where the contact-mode switching characteristics can be recorded with the sensitive embedded piezoresistive (PZR) strain transducers. The devices are manufactured using state-of-the-art wafer-scale silicon-on-insulator technology featuring suspended silicon cantilevers and beams as switching elements and sub-100 nm thin silicon nanowires (SiNWs) as PZR transducers. Several different device configurations are studied, including mechanically ‘cross’-shaped (‘+’), coupled cantilever-SiNW structures, with and without local drain electrodes, and doubly clamped SiNW beams. Through detailed measurement and analysis, we demonstrate that the PZR transducers can enable detection of both mechanical and tunneling switching with multiple repeatable cycles. With the strong PZR effects in thin SiNWs, this type of device could be valuable especially for monitoring cold switching events, and when conventional direct readout of the switching events from the local gate or drain electrodes would not be efficient or sensitive, as nanoscale contacts may not be highly conductive, or may be degrading over time.

  7. 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

  8. Inuence of Gold-Copper Alloy Catalyst Composition on Crystal Growth and Dopant Distribution in Silicon and Germanium Nanowires

    NASA Astrophysics Data System (ADS)

    Connell, Justin G.

    A combination of local electrode atom probe tomography (LEAP) and transmission electron microscopy characterization were used to investigate growth of and dopant incorporation in silicon and germanium nanowires (Si and GeNWs) via the vapor-liquid- solid (VLS) mechanism. A sample structure was developed that enabled isolation of the catalyst-mediated contribution to doping in individual nanowires during LEAP analysis. As a result, the distribution coefficient - a thermodynamic quantity describing axial junction abruptness - was measured in nanowires for the first time, providing a fundamental framework for comparison of junction abruptness in nanowires. These investigations also enabled the identification of a previously unknown radial anisotropy in dopant incorporation through the catalyst, with variations in dopant concentration across the VLS-defined diameter of the nanowire as large as two orders of magnitude. Finite element modeling of the doping process, coupled with in situ TEM observations reported in the literature, suggests that this radially inhomogeneous dopant distribution is a direct consequence of growth from a faceted liquid-solid interface, rather than the commonly assumed planar interface. Au-Cu alloy catalysts were explored as alternatives to Au-catalyzed VLS nanowire growth as a means to alleviate or eliminate axial and radial doping gradients in nanowires. Both an aqueous solution and electron beam lithographic method for creating Au-Cu alloy catalysts of controlled composition were developed, and GeNW growth was demonstrated from both types of catalyst. LEAP characterization of Au-Cu alloy catalyzed P-doped GeNWs revealed that alloying with Cu results in more abrupt axial doping junctions, as well as a more homogeneous radial distribution of dopants within the VLS-defined diameter of the nanowire.

  9. Morphology-tunable assembly of periodically aligned Si nanowire and radial pn junction arrays for solar cell applications

    NASA Astrophysics Data System (ADS)

    Li, Xiaocheng; Liang, Kun; Tay, Beng Kang; Teo, Edwin H. T.

    2012-06-01

    Large-area periodically aligned Si nanowire (PASiNW) arrays have been fabricated on Si substrates via a templated catalytic chemical etching process. The diameter, length, packing density, and even the shape of Si nanowires (SiNWs) could be precisely controlled and tuned. A local coupling redox mechanism involving the reduction of H2O2 on silver particles and the dissolution of Si is responsible for formation of SiNWs. With the as-prepared SiNWs as templates, three kinds of PASiNW radial pn junction structures were fabricated on Si substrates via a solid-state phosphorous diffusion strategy and their applications in solar cells were also explored. The PASiNW radial pn junction-based solar cell with big diameter and interspace shows the highest power conversion efficiency (PCE) of 4.10% among the three kinds of devices. Further optimization, including surface passivation and electrode contact, is still needed for the higher efficiency PASiNW radial pn junction-based solar cells in the future.

  10. TiO2/BiVO4 Nanowire Heterostructure Photoanodes Based on Type II Band Alignment

    PubMed Central

    2016-01-01

    Metal oxides that absorb visible light are attractive for use as photoanodes in photoelectrosynthetic cells. However, their performance is often limited by poor charge carrier transport. We show that this problem can be addressed by using separate materials for light absorption and carrier transport. Here, we report a Ta:TiO2|BiVO4 nanowire photoanode, in which BiVO4 acts as a visible light-absorber and Ta:TiO2 acts as a high surface area electron conductor. Electrochemical and spectroscopic measurements provide experimental evidence for the type II band alignment necessary for favorable electron transfer from BiVO4 to TiO2. The host–guest nanowire architecture presented here allows for simultaneously high light absorption and carrier collection efficiency, with an onset of anodic photocurrent near 0.2 V vs RHE, and a photocurrent density of 2.1 mA/cm2 at 1.23 V vs RHE. PMID:27163032

  11. Temperature dependent resistance and cryogenic microwave spectroscopy of Au decorated silicon nanowires

    NASA Astrophysics Data System (ADS)

    Zhu, Xueni; Hasko, David G.; Hofmann, Stephan; Milne, William I.

    2011-06-01

    We investigate the electrical transport properties of silicon nanowire arrays grown by Au catalyzed chemical vapor deposition, resulting in prominent Au nanoparticle sidewall decoration. dc electrical measurements show symmetric nonlinear I-V characteristics with a zero field conductivity temperature dependence consistent with nearest neighbor hopping. The characteristic energy for this temperature dependence is similar to the expected charging energy of the Au nanoparticles. The measured resistance is also dependent on the bias voltage history if large electric fields are applied. Random telegraph noise events at low temperature indicate that the measured resistance is dominated by a small number of electrons confined to a single nanowire in the array. With a fixed bias, the resistance can be influenced by indirectly coupled microwave radiation at low temperature. This results in a large number of high quality factor resonant features, indicating significant excitation lifetimes. The origin of these resonances is thought to be due to spatial Rabi oscillations of trapped electrons between pairs of trap sites located close to the channel. Such systems are promising for charge qubit-based quantum information processing.

  12. Electron-acoustic phonon interaction and mobility in stressed rectangular silicon nanowires

    NASA Astrophysics Data System (ADS)

    Zhu, Lin-Li

    2015-01-01

    We investigate the effects of pre-stress and surface tension on the electron-acoustic phonon scattering rate and the mobility of rectangular silicon nanowires. With the elastic theory and the interaction Hamiltonian for the deformation potential, which considers both the surface energy and the acoustoelastic effects, the phonon dispersion relation for a stressed nanowire under spatial confinement is derived. The subsequent analysis indicates that both surface tension and pre-stress can dramatically change the electron-acoustic phonon interaction. Under a negative (positive) surface tension and a tensile (compressive) pre-stress, the electron mobility is reduced (enhanced) due to the decrease (increase) of the phonon energy as well as the deformation-potential scattering rate. This study suggests an alternative approach based on the strain engineering to tune the speed and the drive current of low-dimensional electronic devices. Project supported by the National Natural Science Foundation of China (Grant Nos. 11472243, 11302189, and 11321202), the Doctoral Fund of Ministry of Education of China (Grant No. 20130101120175), the Zhejiang Provincial Qianjiang Talent Program, China (Grant No. QJD1202012), and the Educational Commission of Zhejiang Province, China (Grant No. Y201223476).

  13. Exact comprehensive equations for the photon management properties of silicon nanowire

    PubMed Central

    Li, Yingfeng; Li, Meicheng; Li, Ruike; Fu, Pengfei; Wang, Tai; Luo, Younan; Mbengue, Joseph Michel; Trevor, Mwenya

    2016-01-01

    Unique photon management (PM) properties of silicon nanowire (SiNW) make it an attractive building block for a host of nanowire photonic devices including photodetectors, chemical and gas sensors, waveguides, optical switches, solar cells, and lasers. However, the lack of efficient equations for the quantitative estimation of the SiNW’s PM properties limits the rational design of such devices. Herein, we establish comprehensive equations to evaluate several important performance features for the PM properties of SiNW, based on theoretical simulations. Firstly, the relationships between the resonant wavelengths (RW), where SiNW can harvest light most effectively, and the size of SiNW are formulized. Then, equations for the light-harvesting efficiency at RW, which determines the single-frequency performance limit of SiNW-based photonic devices, are established. Finally, equations for the light-harvesting efficiency of SiNW in full-spectrum, which are of great significance in photovoltaics, are established. Furthermore, using these equations, we have derived four extra formulas to estimate the optimal size of SiNW in light-harvesting. These equations can reproduce majority of the reported experimental and theoretical results with only ~5% error deviations. Our study fills up a gap in quantitatively predicting the SiNW’s PM properties, which will contribute significantly to its practical applications. PMID:27103087

  14. Universal disorder in the microwave conductance spectra of doped silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Highstrete, Clark; Lee, Mark; Vallett, Aaron; Eichfeld, Sarah; Redwing, Joan; Mayer, Theresa

    2008-03-01

    Microwave conductance spectra of doped silicon nanowire (SiNW) arrays were measured from 0.1 to 50 GHz at temperatures between 4 K and 293 K. SiNWs were synthesized by VLS growth, assembled into arrays on co-planar waveguides and measured using microwave vector network analysis. The complex conductance of the arrays was found to increase with frequency at all temperatures as f^s, with 0.25 < s < 0.4, and to agree with the expected Kramers-Kronig relations. This AC conductance is consistent with behavior found universally in disordered systems. The likely cause is disorder from Si/SiOx interface states dominating the conduction due to the high surface-to-volume ratio of the nanowires. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. Penn State authors acknowledge partial support from NSF DMR-0213623 and NSF NIRT ECCS-0609282.

  15. Ultra-thin superconducting film coated silicon nitride nanowire resonators for low-temperature applications

    NASA Astrophysics Data System (ADS)

    Sebastian, Abhilash; Zhelev, Nikolay; de Alba, Roberto; Parpia, Jeevak

    We demonstrate fabrication of high stress silicon nitride nanowire resonators with a thickness and width of less than 50 nm intended to be used as probes for the study of superfluid 3He. The resonators are fabricated as doubly-clamped wires/beams using a combination of electron-beam lithography and wet/dry etching techniques. We demonstrate the ability to suspend (over a trench of depth ~8 µm) wires with a cross section as small as 30 nm, covered with a 20 nm superconducting film, and having lengths up to 50 µm. Room temperature resonance measurements were carried out by driving the devices using a piezo stage and detecting the motion using an optical interferometer. The results show that metalizing nano-mechanical resonators not only affects their resonant frequencies but significantly reduce their quality factor (Q). The devices are parametrically pumped by modulating the system at twice its fundamental resonant frequency, which results in observed amplification of the signal. The wires show self-oscillation with increasing modulation strength. The fabricated nanowire resonators are intended to be immersed in the superfluid 3He. By tracking the resonant frequency and the Q of the various modes of the wire versus temperature, we aim to probe the superfluid gap structure.

  16. Surface-Coating Regulated Lithiation Kinetics and Degradation in Silicon Nanowires for Lithium Ion Battery

    SciTech Connect

    Luo, Langli; Yang, Hui; Yan, Pengfei; Travis, Jonathan J.; Lee, Younghee; Liu, Nian; Piper, Daniela M.; Lee, Se-Hee; Zhao, Peng; George, Steven M.; Zhang, Jiguang; Cui, Yi; Zhang, Sulin; Ban, Chunmei; Wang, Chong M.

    2015-05-26

    Silicon (Si)-based materials hold promise as the next-generation anodes for high-energy lithium (Li)-ion batteries. Enormous research efforts have been undertaken to mitigate the chemo-mechanical failure due to the large volume changes of Si during lithiation and delithiation cycles. It has been found nanostructured Si coated with carbon or other functional materials can lead to significantly improved cyclability. However, the underlying mechanism and comparative performance of different coatings remain poorly understood. Herein, using in situ transmission electron microscopy (TEM) through a nanoscale half-cell battery, in combination with chemo-mechanical simulation, we explored the effect of thin (~5 nm) alucone and Al2O3 coatings on the lithiation kinetics of Si nanowires (SiNWs). We observed that the alucone coating leads to a “V-shaped” lithiation front of the SiNWs , while the Al2O3 coating yields an “H-shaped” lithiation front. These observations indicate that the difference between the Li surface diffusivity and bulk diffusivity of the coatings dictates lithiation induced morphological evolution in the nanowires. Our experiments also indicate that the reaction rate in the coating layer can be the limiting step for lithiation and therefore critically influences the rate performance of the battery. Further, the failure mechanism of the Al2O3 coated SiNWs was also explored. Our studies shed light on the design of high capacity, high rate and long cycle life Li-ion batteries.

  17. Lateral heat flow distribution and defect-dependent thermal resistance in an individual silicon nanowire

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Yong; Lee, Won-Yong; Thong, John T. L.; Kim, Gil-Sung; Lee, Sang-Kwon

    2016-03-01

    Studies aiming to significantly improve thermal properties, such as figure-of-merit, of silicon nanowires (SiNW) have focused on diameter reduction and surface or interface roughness control. However, the mechanism underlying thermal conductivity enhancement of roughness controlled NWs remains unclear. Here, we report a significant influence of stacking faults (SFs) on the lateral thermal conductivity of a single SiNW, using a combination of newly developed in situ spatially-resolved thermal resistance experiments and high-resolution transmission electron microscopy measurements. We used as-grown SiNWs tapered along the growth direction with progressively lower roughness and SFs density. The results clearly confirmed that both surface roughness and twins or SFs densities suppress the thermal conductivity of an individual SiNW. The results and measurement techniques presented here hold great potential for inspecting minute changes in thermal resistance along an individual SiNW, caused by induced SFs on the nanostructure, and for improving one-dimensional nanowire-based thermoelectric device performance.

  18. Exact comprehensive equations for the photon management properties of silicon nanowire.

    PubMed

    Li, Yingfeng; Li, Meicheng; Li, Ruike; Fu, Pengfei; Wang, Tai; Luo, Younan; Mbengue, Joseph Michel; Trevor, Mwenya

    2016-01-01

    Unique photon management (PM) properties of silicon nanowire (SiNW) make it an attractive building block for a host of nanowire photonic devices including photodetectors, chemical and gas sensors, waveguides, optical switches, solar cells, and lasers. However, the lack of efficient equations for the quantitative estimation of the SiNW's PM properties limits the rational design of such devices. Herein, we establish comprehensive equations to evaluate several important performance features for the PM properties of SiNW, based on theoretical simulations. Firstly, the relationships between the resonant wavelengths (RW), where SiNW can harvest light most effectively, and the size of SiNW are formulized. Then, equations for the light-harvesting efficiency at RW, which determines the single-frequency performance limit of SiNW-based photonic devices, are established. Finally, equations for the light-harvesting efficiency of SiNW in full-spectrum, which are of great significance in photovoltaics, are established. Furthermore, using these equations, we have derived four extra formulas to estimate the optimal size of SiNW in light-harvesting. These equations can reproduce majority of the reported experimental and theoretical results with only ~5% error deviations. Our study fills up a gap in quantitatively predicting the SiNW's PM properties, which will contribute significantly to its practical applications. PMID:27103087

  19. Geometric and chemical components of the giant piezoresistance in silicon nanowires

    NASA Astrophysics Data System (ADS)

    McClarty, M. M.; Jegenyes, N.; Gaudet, M.; Toccafondi, C.; Ossikovski, R.; Vaurette, F.; Arscott, S.; Rowe, A. C. H.

    2016-07-01

    A wide variety of apparently contradictory piezoresistance (PZR) behaviors have been reported in p-type silicon nanowires (SiNW), from the usual positive bulk effect to anomalous (negative) PZR and giant PZR. The origin of such a range of diverse phenomena is unclear, and consequently so too is the importance of a number of parameters including SiNW type (top down or bottom up), stress concentration, electrostatic field effects, or surface chemistry. Here, we observe all these PZR behaviors in a single set of nominally p-type, <110 > oriented, top-down SiNWs at uniaxial tensile stresses up to 0.5 MPa. Longitudinal π-coefficients varying from -800 × 10-11 Pa-1 to 3000 × 10-11 Pa-1 are measured. Micro-Raman spectroscopy on chemically treated nanowires reveals that stress concentration is the principal source of giant PZR. The sign and an excess PZR similar in magnitude to the bulk effect are related to the chemical treatment of the SiNW.

  20. Enhanced sensing of nucleic acids with silicon nanowire field effect transistor biosensors.

    PubMed

    Gao, Anran; Lu, Na; Wang, Yuchen; Dai, Pengfei; Li, Tie; Gao, Xiuli; Wang, Yuelin; Fan, Chunhai

    2012-10-10

    Silicon nanowire (SiNW) field effect transistors (FETs) have emerged as powerful sensors for ultrasensitive, direct electrical readout, and label-free biological/chemical detection. The sensing mechanism of SiNW-FET can be understood in terms of the change in charge density at the SiNW surface after hybridization. So far, there have been limited systematic studies on fundamental factors related to device sensitivity to further make clear the overall effect on sensing sensitivity. Here, we present an analytical result for our triangle cross-section wire for predicting the sensitivity of nanowire surface-charge sensors. It was confirmed through sensing experiments that the back-gated SiNW-FET sensor had the highest percentage current response in the subthreshold regime and the sensor performance could be optimized in low buffer ionic strength and at moderate probe concentration. The optimized SiNW-FET nanosensor revealed ultrahigh sensitivity for rapid and reliable detection of target DNA with a detection limit of 0.1 fM and high specificity for single-nucleotide polymorphism discrimination. In our work, enhanced sensing of biological species by optimization of operating parameters and fundamental understanding for SiNW FET detection limit was obtained. PMID:22985088

  1. Exact comprehensive equations for the photon management properties of silicon nanowire

    NASA Astrophysics Data System (ADS)

    Li, Yingfeng; Li, Meicheng; Li, Ruike; Fu, Pengfei; Wang, Tai; Luo, Younan; Mbengue, Joseph Michel; Trevor, Mwenya

    2016-04-01

    Unique photon management (PM) properties of silicon nanowire (SiNW) make it an attractive building block for a host of nanowire photonic devices including photodetectors, chemical and gas sensors, waveguides, optical switches, solar cells, and lasers. However, the lack of efficient equations for the quantitative estimation of the SiNW’s PM properties limits the rational design of such devices. Herein, we establish comprehensive equations to evaluate several important performance features for the PM properties of SiNW, based on theoretical simulations. Firstly, the relationships between the resonant wavelengths (RW), where SiNW can harvest light most effectively, and the size of SiNW are formulized. Then, equations for the light-harvesting efficiency at RW, which determines the single-frequency performance limit of SiNW-based photonic devices, are established. Finally, equations for the light-harvesting efficiency of SiNW in full-spectrum, which are of great significance in photovoltaics, are established. Furthermore, using these equations, we have derived four extra formulas to estimate the optimal size of SiNW in light-harvesting. These equations can reproduce majority of the reported experimental and theoretical results with only ~5% error deviations. Our study fills up a gap in quantitatively predicting the SiNW’s PM properties, which will contribute significantly to its practical applications.

  2. Vertically Aligned Ge Nanowires on Flexible Plastic Films Synthesized by (111)-Oriented Ge Seeded Vapor-Liquid-Solid Growth.

    PubMed

    Toko, Kaoru; Nakata, Mitsuki; Jevasuwan, Wipakorn; Fukata, Naoki; Suemasu, Takashi

    2015-08-19

    Transfer-free fabrication of vertical Ge nanowires (NWs) on a plastic substrate is demonstrated using a vapor-liquid-solid (VLS) method. The crystal quality of Ge seed layers (50 nm thickness) prepared on plastic substrates strongly influenced the VLS growth morphology, i.e., the density, uniformity, and crystal quality of Ge NWs. The metal-induced layer exchange yielded a (111)-oriented Ge seed layer at 325 °C, which allowed for the VLS growth of vertically aligned Ge NWs. The Ge NW array had almost the same quality as that formed on a bulk Ge(111) substrate. Transmission electron microscopy demonstrated that the Ge NWs were defect-free single crystals. The present investigation paves the way for advanced electronic optical devices integrated on a low-cost flexible substrate. PMID:26230716

  3. Investigation of drift effect on silicon nanowire field effect transistor based pH sensor

    NASA Astrophysics Data System (ADS)

    Kim, Sihyun; Kwon, Dae Woong; Lee, Ryoongbin; Kim, Dae Hwan; Park, Byung-Gook

    2016-06-01

    It is widely accepted that the operation mechanism of pH-sensitive ion sensitive field effect transistor (ISFET) can be divided into three categories; reaction of surface sites, chemical modification of insulator surface, and ionic diffusion into the bulk of insulator. The first mechanism is considered as the main operation mechanism of pH sensors due to fast response, while the others with relatively slow responses disturb accurate pH detection. In this study, the slow responses (often called drift effects) are investigated in silicon nanowire (SiNW) pH-sensitive ISFETs. Based on the dependence on the channel type of SiNW, liquid gate bias, and pH, it is clearly revealed that the drift of n-type SiNW results from H+ diffusion into the insulator whereas that of p-type SiNW is caused by chemical modification (hydration) of the insulator.

  4. 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.

  5. Origin of photoluminescence from silicon nanowires prepared by metal induced etching (MIE)

    SciTech Connect

    Saxena, Shailendra K. Rai, Hari. M.; Late, Ravikiran; Sagdeo, Pankaj R.; Kumar, Rajesh

    2015-05-15

    In this present study the origin of luminescence from silicon nanowires (SiNws) has been studied. SiNWs are fabricated on Si substrate by metal induced chemical etching (MIE). Here it is found that the band gap of SiNWs is higher than the gap of luminescent states in SiNWs which leads to the effect of Si=O bond. The band gap is estimated from diffuse reflectance analysis. Here we observe that band gap can be tailored depending on size (quantum confinement) but photoluminescence (PL) from all the sample is found to be fixed at 1.91 eV. This study is important for the understanding of origin of photoluminescence.

  6. Nanotubes, nanobelts, nanowires, and nanorods of silicon carbide from the wheat husks

    SciTech Connect

    Qadri, S. B.; Rath, B. B.; Gorzkowski, E. P.; Feng, J.; Qadri, S. N.; Caldwell, J. D.

    2015-09-14

    Nanotubes, nanowires, nanobelts, and nanorods of SiC were synthesized from the thermal treatment of wheat husks at temperatures in excess of 1450 °C. From the analysis based on x-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy, it has been found that the processed samples of wheat husk consisted of 2H and 3C polytypes of SiC exhibiting the nanostructure shapes. These nanostructures of silicon carbide formed from wheat husks are of technological importance for designing advance composites, applications in biotechnology, and electro-optics. The thermodynamics of the formation of SiC is discussed in terms of the rapid solid state reaction between hydrocarbons and silica on the molecular scale, which is inherently present in the wheat husks.

  7. Near-theoretical fracture strengths in native and oxidized silicon nanowires

    NASA Astrophysics Data System (ADS)

    DelRio, Frank W.; White, Ryan M.; Krylyuk, Sergiy; Davydov, Albert V.; Friedman, Lawrence H.; Cook, Robert F.

    2016-08-01

    In this letter, fracture strengths σ f of native and oxidized silicon nanowires (SiNWs) were determined via atomic force microscopy bending experiments and nonlinear finite element analysis. In the native SiNWs, σ f in the Si was comparable to the theoretical strength of Si<111>, ≈22 GPa. In the oxidized SiNWs, σ f in the SiO2 was comparable to the theoretical strength of SiO2, ≈6 to 12 GPa. The results indicate a change in the failure mechanism between native SiNWs, in which fracture originated via inter-atomic bond breaking or atomic-scale defects in the Si, and oxidized SiNWs, in which fracture initiated from surface roughness or nano-scale defects in the SiO2.

  8. Highly end-doped silicon nanowires for field-effect transistors on flexible substrates

    NASA Astrophysics Data System (ADS)

    Celle, Caroline; Carella, Alexandre; Mariolle, Denis; Chevalier, Nicolas; Rouvière, Emmanuelle; Simonato, Jean-Pierre

    2010-05-01

    We report on the VLS (vapour-liquid-solid) fabrication and characterization of in situ axially doped silicon nanowires (SiNWs) at both ends, and on their integration into a bottom gate-top contact geometry on both rigid and flexible substrates to realize field-effect transistors (FETs). To improve contact resistance between SiNWs and source/drain electrodes, we axially tuned the level of doping at both ends of the SiNWs by sequential in situ addition of PH3. Characterisation of SiNWs by scanning spreading resistance microscopy in the device configuration allowed us to determine precisely the different sections of the SiNWs. The transfer to flexible substrates still allowed for workable FET structures. Transistors with electron mobilities exceeding 120 cm2 V-1 s-1, Ion/Ioff ratios greater than 107 and ambipolar behaviour were achieved.

  9. Nanoelectronic detection of triggered secretion of pro-inflammatory cytokines using CMOS compatible silicon nanowires.

    PubMed

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

    2011-01-15

    Nanotechnology, such as nanoelectronic biosensors, is bringing new opportunities and tools to the studies of cell biology, clinical applications, and drug discovery. In this study, crystalline silicon nanowire based field-effect transistors fabricated using top-down approach were employed to parallelly detect pro-inflammatory cytokines in the complex biological fluids (cell culture medium and blood samples) with high specificity and femtomolar sensitivity. Using this technique, the dynamic secretion of TNF-alpha and IL6 was revealed during the immune response of macrophages and rats to the stimulation of bacteria endotoxin. This technique could provide a unique platform to examine the profile of complex immune responses for fundamental studies and diagnosis. PMID:20977978

  10. Rhodium Nanoparticle-mesoporous Silicon Nanowire Nanohybrids for Hydrogen Peroxide Detection with High Selectivity

    NASA Astrophysics Data System (ADS)

    Song, Zhiqian; Chang, Hucheng; Zhu, Weiqin; Xu, Chenlong; Feng, Xinjian

    2015-01-01

    Developing nanostructured electrocatalysts, with low overpotential, high selectivity and activity has fundamental and technical importance in many fields. We report here rhodium nanoparticle and mesoporous silicon nanowire (RhNP@mSiNW) hybrids for hydrogen peroxide (H2O2) detection with high electrocatalytic activity and selectivity. By employing electrodes that loaded with RhNP@mSiNW nanohybrids, interference caused from both many electroactive substances and dissolved oxygen were eliminated by electrochemical assaying at an optimal potential of +75 mV. Furthermore, the electrodes exhibited a high detection sensitivity of 0.53 μA/mM and fast response (< 5 s). This high-performance nanohybrid electrocatalyst has great potential for future practical application in various oxidase-base biosensors.

  11. A silicon nanowire-based electrochemical glucose biosensor with high electrocatalytic activity and sensitivity

    NASA Astrophysics Data System (ADS)

    Su, Shao; He, Yao; Song, Shiping; Li, Di; Wang, Lihua; Fan, Chunhai; Lee, Shuit-Tong

    2010-09-01

    An electrochemical glucose biosensor was developed by immobilizing glucose oxidase (GOx) on an electrode decorated with a novel nanostructure, silicon nanowires (SiNWs) with in situ grown gold nanoparticles (AuNPs). The immobilized GOx displayed a pair of well-defined and quasi-reversible redox peaks with a formal potential (E°') of -0.376 V in a phosphate buffer solution. The fabricated glucose biosensor has good electrocatalytic activity toward oxidation of glucose. In addition, such resultant SiNWs-based glucose biosensor possesses high biological affinity. Particularly, the apparent Michaelis-Mentan constant was estimated to be 0.902 mM, which is much smaller than the reported values for GOx at a range of nanomaterials-incorporated electrodes. Consequently, this novel SiNWs-based biosensor is expected to be a promising tool for biological assays (e.g., monitoring blood glucose).

  12. Controlled in situ boron doping of short silicon nanowires grown by molecular beam epitaxy

    SciTech Connect

    Das Kanungo, Pratyush; Zakharov, Nikolai; Bauer, Jan; Breitenstein, Otwin; Werner, Peter; Goesele, Ulrich

    2008-06-30

    Epitaxial silicon nanowires (NWs) of short heights ({approx}280 nm) on Si <111> substrate were grown and doped in situ with boron on a concentration range of 10{sup 15}-10{sup 19} cm{sup -3} by coevaporation of atomic Si and B by molecular beam epitaxy. Transmission electron microscopy revealed a single-crystalline structure of the NWs. Electrical measurements of the individual NWs confirmed the doping. However, the low doped (10{sup 15} cm{sup -3}) and medium doped (3x10{sup 16} and 1x10{sup 17} cm{sup -3}) NWs were heavily depleted by the surface states while the high doped (10{sup 18} and 10{sup 19} cm{sup -3}) ones showed volume conductivities expected for the corresponding intended doping levels.

  13. Near-theoretical fracture strengths in native and oxidized silicon nanowires.

    PubMed

    DelRio, Frank W; White, Ryan M; Krylyuk, Sergiy; Davydov, Albert V; Friedman, Lawrence H; Cook, Robert F

    2016-08-01

    In this letter, fracture strengths σ f of native and oxidized silicon nanowires (SiNWs) were determined via atomic force microscopy bending experiments and nonlinear finite element analysis. In the native SiNWs, σ f in the Si was comparable to the theoretical strength of Si〈111〉, ≈22 GPa. In the oxidized SiNWs, σ f in the SiO2 was comparable to the theoretical strength of SiO2, ≈6 to 12 GPa. The results indicate a change in the failure mechanism between native SiNWs, in which fracture originated via inter-atomic bond breaking or atomic-scale defects in the Si, and oxidized SiNWs, in which fracture initiated from surface roughness or nano-scale defects in the SiO2. PMID:27325151

  14. Ag-modified silicon nanowires substrate for ultrasensitive surface-enhanced raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Shao, Ming-Wang; Zhang, Ming-Liang; Wong, Ning-Bew; Ma, Dorothy Duo-duo; Wang, Hui; Chen, Weiwei; Lee, Shuit-Tong

    2008-12-01

    We report a unique substrate for surface-enhanced raman spectroscopy (SERS) based on silver nanoparticles-embedded silicon nanowires (SiNWs). The SiNWs were prepared by thermal evaporation of SiO powder via oxide-assisted growth, oxide removed with HF, and then used to reduce silver ions to form a highly decorated Ag-embedded surface. Such modified SiNWs substrates yielded ultrahigh SERS sensitivity, which could detect 25μl of 1×10-16M Rhodamine 6G, 1×10-16M crystal violet, and 1×10-14M nicotine in methanol solutions. An Ag-modified SiNW strand could also enable SERS detection of 25μl of 1×10-8mg/ml calf thymus DNA. The possible mechanisms for the ultrahigh SERS sensitivity were discussed.

  15. Stability and evolution of low-surface-tension metal catalyzed growth of silicon nanowires

    NASA Astrophysics Data System (ADS)

    Yu, Linwei; Fortuna, Franck; O'Donnell, Benedict; Patriache, Gilles; Roca i Cabarrocas, Pere

    2011-03-01

    Low-surface-tension metals were predicted to be insufficient to catalyze the growth of silicon nanowires (SiNWs) in vapor-liquid-solid (VLS) mode while counter examples do exist, for example, in the tin- or indium-catalyzed SiNWs. This puzzle remains largely unresolved. We first examine the local tension-force-balance in a tin-catalyzed SiNW by using a cross-section analysis. We found that the existence of an ultrathin sidewall-spreading catalyst layer helps to stabilize the catalyst drop during growth. The predicted contact-angle evolution, by an energetic balance model, is also supported by the experimental data. These results bring critical understanding on the low-surface-tension catalyzed VLS process.

  16. Nanotubes, nanobelts, nanowires, and nanorods of silicon carbide from the wheat husks

    NASA Astrophysics Data System (ADS)

    Qadri, S. B.; Rath, B. B.; Gorzkowski, E. P.; Feng, J.; Qadri, S. N.; Caldwell, J. D.

    2015-09-01

    Nanotubes, nanowires, nanobelts, and nanorods of SiC were synthesized from the thermal treatment of wheat husks at temperatures in excess of 1450 °C. From the analysis based on x-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy, it has been found that the processed samples of wheat husk consisted of 2H and 3C polytypes of SiC exhibiting the nanostructure shapes. These nanostructures of silicon carbide formed from wheat husks are of technological importance for designing advance composites, applications in biotechnology, and electro-optics. The thermodynamics of the formation of SiC is discussed in terms of the rapid solid state reaction between hydrocarbons and silica on the molecular scale, which is inherently present in the wheat husks.

  17. Rhodium Nanoparticle-mesoporous Silicon Nanowire Nanohybrids for Hydrogen Peroxide Detection with High Selectivity

    PubMed Central

    Song, Zhiqian; Chang, Hucheng; Zhu, Weiqin; Xu, Chenlong; Feng, Xinjian

    2015-01-01

    Developing nanostructured electrocatalysts, with low overpotential, high selectivity and activity has fundamental and technical importance in many fields. We report here rhodium nanoparticle and mesoporous silicon nanowire (RhNP@mSiNW) hybrids for hydrogen peroxide (H2O2) detection with high electrocatalytic activity and selectivity. By employing electrodes that loaded with RhNP@mSiNW nanohybrids, interference caused from both many electroactive substances and dissolved oxygen were eliminated by electrochemical assaying at an optimal potential of +75 mV. Furthermore, the electrodes exhibited a high detection sensitivity of 0.53 μA/mM and fast response (< 5 s). This high-performance nanohybrid electrocatalyst has great potential for future practical application in various oxidase-base biosensors. PMID:25588953

  18. A study of the self-aligned nanometre scale palladium clusters on silicon formation process

    NASA Astrophysics Data System (ADS)

    Gavrilov, S.; Lemeshko, S.; Shevyakov, V.; Roschin, V.

    1999-06-01

    The possibility of the self-aligned formation of Pd/Pd2Si/Si nanostructures on a single-crystal silicon substrate is shown. A porous anodic oxide film of Al was used as a mask which determines the size and shape of the nanostructures. A thin Al film was first deposited on the silicon substrate and then transformed in a nanoporous oxide by the well known anodic treatment procedure in a sulfuric acid and water solution. It is shown by atomic force microscopy that nanoscale Pd clusters with diameters equal to the size of pores in anodic Al remain at the surface of silicon substrate after cathode deposition of Pd into the pores, vacuum thermal annealing and chemical etching of the Al2O3 mask. In addition, we determine the dependencies of the size and shape of the nanoclusters on the mask formation regimes and the Pd deposition conditions.

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

    NASA Astrophysics Data System (ADS)

    Kitazawa, Nobuaki; Aono, Masami; Watanabe, Yoshihisa

    2014-11-01

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

  20. 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