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Sample records for nonlinear semiconducting devices

  1. Evidence for bifurcation and universal chaotic behavior in nonlinear semiconducting devices

    SciTech Connect

    Testa, J.; Perez, J.; Jeffries, C.

    1982-01-01

    Bifurcations, chaos, and extensive periodic windows in the chaotic regime are observed for a driven LRC circuit, the capacitive element being a nonlinear varactor diode. Measurements include power spectral analysis; real time amplitude data; phase portraits; and a bifurcation diagram, obtained by sampling methods. The effects of added external noise are studied. These data yield experimental determinations of several of the universal numbers predicted to characterize nonlinear systems having this route to chaos.

  2. Semiconducting compounds and devices incorporating same

    SciTech Connect

    Marks, Tobin J; Facchetti, Antonio; Boudreault, Pierre-Luc; Miyauchi, Hiroyuki

    2014-06-17

    Disclosed are molecular and polymeric compounds having desirable properties as semiconducting materials. Such compounds can exhibit desirable electronic properties and possess processing advantages including solution-processability and/or good stability. Organic transistor and photovoltaic devices incorporating the present compounds as the active layer exhibit good device performance.

  3. Semiconducting compounds and devices incorporating same

    DOEpatents

    Marks, Tobin J.; Facchetti, Antonio; Boudreault, Pierre-Luc; Miyauchi, Hiroyuki

    2016-01-19

    Disclosed are molecular and polymeric compounds having desirable properties as semiconducting materials. Such compounds can exhibit desirable electronic properties and possess processing advantages including solution-processability and/or good stability. Organic transistor and photovoltaic devices incorporating the present compounds as the active layer exhibit good device performance.

  4. Bulk semiconducting scintillator device for radiation detection

    DOEpatents

    Stowe, Ashley C.; Burger, Arnold; Groza, Michael

    2016-08-30

    A bulk semiconducting scintillator device, including: a Li-containing semiconductor compound of general composition Li-III-VI.sub.2, wherein III is a Group III element and VI is a Group VI element; wherein the Li-containing semiconductor compound is used in one or more of a first mode and a second mode, wherein: in the first mode, the Li-containing semiconductor compound is coupled to an electrical circuit under bias operable for measuring electron-hole pairs in the Li-containing semiconductor compound in the presence of neutrons and the Li-containing semiconductor compound is also coupled to current detection electronics operable for detecting a corresponding current in the Li-containing semiconductor compound; and, in the second mode, the Li-containing semiconductor compound is coupled to a photodetector operable for detecting photons generated in the Li-containing semiconductor compound in the presence of the neutrons.

  5. Semiconducting ferroelectric SbSI quantum dots in amorphous matrix: preparation and nonlinear optical properties

    NASA Astrophysics Data System (ADS)

    Ye, Hui; Yang, Ligong; Gu, Peifu

    2002-09-01

    Semiconducting ferroelectric antimony sulphoiodide (SbSI) microcrystallite doped organically modified TiO2 thin films were successfully fabricated with the sol-gel process. Ferroelectric SbSI crystallites have some attractive properties, including high dielectric permittivity, high electro-optical coefficient and high photoconductivity. SbSI is also an intrinsic semiconductor with a relatively narrow eneryg gap. The Bohr radius of the SbSI crystal was calculated larger than other semiconductors due to its large dielectric constant. If the crystal size is smaller than its Bohr radius and the microcrystallite are dispersed in a suitable matrix, a dramatic improvement of the nonlinear three-order nonlinearity will be achieved due to the quantum confinement effect. The SbSI quantum dot composites were proved to be good candidates for nonlinear and electro-optical devices. Glycidopropyltrimetroxysilane modified TiO2 was chosen as the matrix and SbSI was synthesized in situ by using SbI3, SC(NH2)2. The materials in thin film were heat-treated in different conditions and the size of the microcrystallite was characterized by the XRD. A value of 3.5pm/V of effective transverse electro-optical coefficient reff for the nano-composite containing 8 wt percent of antimony sulfide iodide was measured. The third-order nonlinear optical susceptibility of the SbSI quantum dot thin film was measured by degenerate four-wave mixing at 532nm using a frequency double Nd:YAG laser beams with a pulse width of around 10ns, the x(3) value of 3 μm sample was measured to be 6 × 10-11 esu.

  6. Exciton Dynamics and Many Body Interactions in Layered Semiconducting Materials Revealed with Non-linear Coherent Spectroscopy

    NASA Astrophysics Data System (ADS)

    Dey, Prasenjit

    Atomically thin, semiconducting transition metal dichalogenides (TMDs), a special class of layered semiconductors, that can be shaped as a perfect two dimensional material, have garnered a lot of attention owing to their fascinating electronic properties which are achievable at the extreme nanoscale. In contrast to graphene, the most celebrated two-dimensional (2D) material thus far; TMDs exhibit a direct band gap in the monolayer regime. The presence of a non-zero bandgap along with the broken inversion symmetry in the monolayer limit brands semiconducting TMDs as the perfect candidate for future optoelectronic and valleytronics-based device application. These remarkable discoveries demand exploration of different materials that possess similar properties alike TMDs. Recently, III-VI layered semiconducting materials (example: InSe, GaSe etc.) have also emerged as potential materials for optical device based applications as, similar to TMDs, they can be shaped into a perfect two-dimensional form as well as possess a sizable band gap in their nano-regime. The perfect 2D character in layered materials cause enhancement of strong Coulomb interaction. As a result, excitons, a coulomb bound quasiparticle made of electron-hole pair, dominate the optical properties near the bandgap. The basis of development for future optoelectronic-based devices requires accurate characterization of the essential properties of excitons. Two fundamental parameters that characterize the quantum dynamics of excitons are: a) the dephasing rate, gamma, which represents the coherence loss due to the interaction of the excitons with their environment (for example- phonons, impurities, other excitons, etc.) and b) excited state population decay rate arising from radiative and non-radiative relaxation processes. The dephasing rate is representative of the time scale over which excitons can be coherently manipulated, therefore accurately probing the source of exciton decoherence is crucial for

  7. Detection of a biexciton in semiconducting carbon nanotubes using nonlinear optical spectroscopy.

    PubMed

    Colombier, L; Selles, J; Rousseau, E; Lauret, J S; Vialla, F; Voisin, C; Cassabois, G

    2012-11-01

    We report the observation of the biexciton in semiconducting single-wall carbon nanotubes by means of nonlinear optical spectroscopy. Our measurements reveal the universal asymmetric line shape of the Fano resonance intrinsic to the biexciton transition. For nanotubes of the (9,7) chirality, we find a biexciton binding energy of 106 meV. From the calculation of the χ((3)) nonlinear response, we provide a quantitative interpretation of our measurements, leading to an estimation of the characteristic Fano factor q of 7 ± 3. This value allows us to extract the first experimental information on the biexciton stability and we obtain a biexciton annihilation rate comparable to the exciton-exciton annihilation one. PMID:23215424

  8. Diphenylpolyynes For Nonlinear Optical Devices

    NASA Technical Reports Server (NTRS)

    Stiegman, Albert E.; Perry, Joseph W.; Coulter, Daniel R.

    1989-01-01

    Several diphenylpolyyne compounds found to exhibit second-order nonlinear electric susceptibilities and chemical structures conducive to orientation in appropriate chemical environments. These features make new materials suitable for use in optical devices. Diphenylacetylene links give molecules rodlike characteristics making them amenable to orientation by suspension in liquid crystals. New molecules also have inherent liquid-crystalline properties enabling them to be oriented directly.

  9. High Efficiency Alternating Current Driven Organic Light Emitting Devices Employing Active Semiconducting Gate Layers

    NASA Astrophysics Data System (ADS)

    Smith, Gregory; Xu, Junwei; Carroll, David

    2015-03-01

    In this work, we describe the role of semiconductor-polymer interfaces in alternating current (AC) driven organic electroluminescent (EL) devices. We implement inorganic semiconducting materials between the external contact and the active layers in organic light EL devices. Precise control of capacitance and charge injection is required to realize bright and efficient large area AC driven devices. We show how this architecture results in active gating to the polymer layers, resulting in the novel ability to control the capacitance and charge injection characteristics. We propose a model based on band bending at the semiconductor-polymer interface. Furthermore, we elucidate the influence of the semiconductor-polymer interface on the internally coupled magnetic field generated in an alternating current driven organic light emitting device configuration. Magnetic fields can alter the ratios of singlet and triplet populations, and we show that internal generation of a magnetic field can dramatically alter the efficiency of light emission in organic EL devices.

  10. Emerging device applications for semiconducting two-dimensional transition metal dichalcogenides.

    PubMed

    Jariwala, Deep; Sangwan, Vinod K; Lauhon, Lincoln J; Marks, Tobin J; Hersam, Mark C

    2014-02-25

    With advances in exfoliation and synthetic techniques, atomically thin films of semiconducting transition metal dichalcogenides have recently been isolated and characterized. Their two-dimensional structure, coupled with a direct band gap in the visible portion of the electromagnetic spectrum, suggests suitability for digital electronics and optoelectronics. Toward that end, several classes of high-performance devices have been reported along with significant progress in understanding their physical properties. Here, we present a review of the architecture, operating principles, and physics of electronic and optoelectronic devices based on ultrathin transition metal dichalcogenide semiconductors. By critically assessing and comparing the performance of these devices with competing technologies, the merits and shortcomings of this emerging class of electronic materials are identified, thereby providing a roadmap for future development. PMID:24476095

  11. Nonvolatile organic thin film transistor memory devices based on hybrid nanocomposites of semiconducting polymers: gold nanoparticles.

    PubMed

    Chang, Hsuan-Chun; Liu, Cheng-Liang; Chen, Wen-Chang

    2013-12-26

    We report the facile fabrication and characteristics of organic thin film transistor (OTFT)-based nonvolatile memory devices using the hybrid nanocomposites of semiconducting poly(9,9-dioctylfluorene-alt-bithiophene) (F8T2) and ligand-capped Au nanoparticles (NPs), thereby serving as a charge storage medium. Electrical bias sweep/excitation effectively modulates the current response of hybrid memory devices through the charge transfer between F8T2 channel and functionalized Au NPs trapping sites. The electrical performance of the hybrid memory devices can be effectively controlled though the loading concentrations (0-9 %) of Au NPs and organic thiolate ligands on Au NP surfaces with different carbon chain lengths (Au-L6, Au-L10, and Au-L18). The memory window induced by voltage sweep is considerably increased by the high content of Au NPs or short carbon chain on the ligand. The hybrid nanocomposite of F8T2:9% Au-L6 provides the OTFT memories with a memory window of ~41 V operated at ± 30 V and memory ratio of ~1 × 10(3) maintained for 1 × 10(4) s. The experimental results suggest that the hybrid materials of the functionalized Au NPs in F8T2 matrix have the potential applications for low voltage-driven high performance nonvolatile memory devices. PMID:24224739

  12. Advances in nonlinear optical materials and devices

    NASA Technical Reports Server (NTRS)

    Byer, Robert L.

    1991-01-01

    The recent progress in the application of nonlinear techniques to extend the frequency of laser sources has come from the joint progress in laser sources and in nonlinear materials. A brief summary of the progress in diode pumped solid state lasers is followed by an overview of progress in nonlinear frequency extension by harmonic generation and parametric processes. Improved nonlinear materials including bulk crystals, quasiphasematched interactions, guided wave devices, and quantum well intersubband studies are discussed with the idea of identifying areas of future progress in nonlinear materials and devices.

  13. Reversible Semiconducting-to-Metallic Phase Transition in Chemical Vapor Deposition Grown Monolayer WSe2 and Applications for Devices

    NASA Astrophysics Data System (ADS)

    Ma, Yuqiang; Liu, Bilu; Zhang, Anyi; Chen, Liang; Fathi, Mohammad; Shen, Chenfei; Abbas, Ahmad; Ge, Mingyuan; Mecklenburg, Matthew; Zhou, Chongwu; Usc Nanolab Team

    Two-dimensional (2D) semiconducting monolayer transition metal dichalcogenides (TMDCs) have stimulated lots of interest because they are direct bandgap materials that have reasonably good mobility values. However, contact between most metals and semiconducting TMDCs like 2H phase WSe2 is highly resistive, thus degrading the performance of field effect transistors (FETs) fabricated with WSe2 as active channel materials. We applied a phase engineering method to chemical vapor deposition (CVD) grown monolayer 2H-WSe2 and demonstrated semiconducting-to-metallic phase transition in atomically thin WSe2. We have also shown that metallic phase WSe2 can be converted back to semiconducting phase, demonstrating the reversibility of this phase transition. In addition, we fabricated FETs based on these CVD-grown WSe2 flakes with phase-engineered metallic 1T-WSe2 as contact regions and intact semiconducting 2H-WSe2 as active channel materials. The device performance is substantially improved with metallic phase source/drain electrodes, showing on/off current ratios of 107 and mobilities up to 66 cm2/Vs for monolayer WSe2. PI name: Chongwu Zhou.

  14. Printed thin film transistors and CMOS inverters based on semiconducting carbon nanotube ink purified by a nonlinear conjugated copolymer

    NASA Astrophysics Data System (ADS)

    Xu, Wenya; Dou, Junyan; Zhao, Jianwen; Tan, Hongwei; Ye, Jun; Tange, Masayoshi; Gao, Wei; Xu, Weiwei; Zhang, Xiang; Guo, Wenrui; Ma, Changqi; Okazaki, Toshiya; Zhang, Kai; Cui, Zheng

    2016-02-01

    Two innovative research studies are reported in this paper. One is the sorting of semiconducting carbon nanotubes and ink formulation by a novel semiconductor copolymer and second is the development of CMOS inverters using not the p-type and n-type transistors but a printed p-type transistor and a printed ambipolar transistor. A new semiconducting copolymer (named P-DPPb5T) was designed and synthesized with a special nonlinear structure and more condensed conjugation surfaces, which can separate large diameter semiconducting single-walled carbon nanotubes (sc-SWCNTs) from arc discharge SWCNTs according to their chiralities with high selectivity. With the sorted sc-SWCNTs ink, thin film transistors (TFTs) have been fabricated by aerosol jet printing. The TFTs displayed good uniformity, low operating voltage (+/-2 V) and subthreshold swing (SS) (122-161 mV dec-1), high effective mobility (up to 17.6-37.7 cm2 V-1 s-1) and high on/off ratio (104-107). With the printed TFTs, a CMOS inverter was constructed, which is based on the p-type TFT and ambipolar TFT instead of the conventional p-type and n-type TFTs. Compared with other recently reported inverters fabricated by printing, the printed CMOS inverters demonstrated a better noise margin (74% 1/2 Vdd) and was hysteresis free. The inverter has a voltage gain of up to 16 at an applied voltage of only 1 V and low static power consumption.Two innovative research studies are reported in this paper. One is the sorting of semiconducting carbon nanotubes and ink formulation by a novel semiconductor copolymer and second is the development of CMOS inverters using not the p-type and n-type transistors but a printed p-type transistor and a printed ambipolar transistor. A new semiconducting copolymer (named P-DPPb5T) was designed and synthesized with a special nonlinear structure and more condensed conjugation surfaces, which can separate large diameter semiconducting single-walled carbon nanotubes (sc-SWCNTs) from arc discharge

  15. Printed thin film transistors and CMOS inverters based on semiconducting carbon nanotube ink purified by a nonlinear conjugated copolymer.

    PubMed

    Xu, Wenya; Dou, Junyan; Zhao, Jianwen; Tan, Hongwei; Ye, Jun; Tange, Masayoshi; Gao, Wei; Xu, Weiwei; Zhang, Xiang; Guo, Wenrui; Ma, Changqi; Okazaki, Toshiya; Zhang, Kai; Cui, Zheng

    2016-02-28

    Two innovative research studies are reported in this paper. One is the sorting of semiconducting carbon nanotubes and ink formulation by a novel semiconductor copolymer and second is the development of CMOS inverters using not the p-type and n-type transistors but a printed p-type transistor and a printed ambipolar transistor. A new semiconducting copolymer (named P-DPPb5T) was designed and synthesized with a special nonlinear structure and more condensed conjugation surfaces, which can separate large diameter semiconducting single-walled carbon nanotubes (sc-SWCNTs) from arc discharge SWCNTs according to their chiralities with high selectivity. With the sorted sc-SWCNTs ink, thin film transistors (TFTs) have been fabricated by aerosol jet printing. The TFTs displayed good uniformity, low operating voltage (±2 V) and subthreshold swing (SS) (122-161 mV dec(-1)), high effective mobility (up to 17.6-37.7 cm(2) V(-1) s(-1)) and high on/off ratio (10(4)-10(7)). With the printed TFTs, a CMOS inverter was constructed, which is based on the p-type TFT and ambipolar TFT instead of the conventional p-type and n-type TFTs. Compared with other recently reported inverters fabricated by printing, the printed CMOS inverters demonstrated a better noise margin (74% 1/2 Vdd) and was hysteresis free. The inverter has a voltage gain of up to 16 at an applied voltage of only 1 V and low static power consumption. PMID:26847814

  16. Thermodynamically valid noise models for nonlinear devices

    NASA Astrophysics Data System (ADS)

    Coram, Geoffrey J.

    2000-11-01

    Noise has been a concern from the very beginning of signal processing and electrical engineering in general, although it was perhaps of less interest until vacuum- tube amplifiers made it audible just after 1900. Rigorous noise models for linear resistors were developed in 1927 by Nyquist and Johnson [1, 2]. However, the intervening years have not brought similarly well-established models for noise in nonlinear devices. This thesis proposes using thermodynamic principles to determine whether a given nonlinear device noise model is physically valid. These tests are applied to several models. One conclusion is that the standard Gaussian noise models for nonlinear devices predict thermodynamically impossible circuit behavior: these models should be abandoned. But the nonlinear shot-noise model predicts thermodynamically acceptable behavior under a constraint derived here. This thesis shows how the thermodynamic requirements can be reduced to concise mathematical tests, involving no approximations, for the Gaussian and shot-noise models. When the above-mentioned constraint is satisfied, the nonlinear shot-noise model specifies the current noise amplitude at each operating point from knowledge of the device v - i curve alone. This relation between the dissipative behavior and the noise fluctuations is called, naturally enough, a fluctuation- dissipation relation. This thesis further investigates such FDRs, including one for linear resistors in nonlinear circuits that was previously unexplored. The aim of this thesis is to provide thermodynamically solid foundations for noise models. It is hoped that hypothesized noise models developed to match experiment will be validated against the concise mathematical tests of this thesis. Finding a correct noise model will help circuit designers and physicists understand the actual processes causing the noise, and perhaps help them minimize the noise or its effect in the circuit. (Copies available exclusively from MIT Libraries, Rm

  17. Vacuum filtration based formation of liquid crystal films of semiconducting carbon nanotubes and high performance transistor devices

    NASA Astrophysics Data System (ADS)

    King, Benjamin; Panchapakesan, Balaji

    2014-05-01

    In this paper, we report ultra-thin liquid crystal films of semiconducting carbon nanotubes using a simple vacuum filtration process. Vacuum filtration of nanotubes in aqueous surfactant solution formed nematic domains on the filter membrane surface and exhibited local ordering. A 2D fast Fourier transform was used to calculate the order parameters from scanning electron microscopy images. The order parameter was observed to be sensitive to the filtration time demonstrating different regions of transformation namely nucleation of nematic domains, nanotube accumulation and large domain growth.Transmittance versus sheet resistance measurements of such films resulted in optical to dc conductivity of σ opt/σ dc = 9.01 indicative of purely semiconducting nanotube liquid crystal network.Thin films of nanotube liquid crystals with order parameters ranging from S = 0.1-0.5 were patterned into conducting channels of transistor devices which showed high I on/I off ratios from 10-19 800 and electron mobility values μ e = 0.3-78.8 cm2 (V-s)-1, hole mobility values μ h = 0.4-287 cm2 (V-s)-1. High I on/I off ratios were observed at low order parameters and film mass. A Schottky barrier transistor model is consistent with the observed transistor characteristics. Electron and hole mobilities were seen to increase with order parameters and carbon nanotube mass fractions. A fundamental tradeoff between decreasing on/off ratio and increasing mobility with increasing nanotube film mass and order parameter is therefore concluded. Increase in order parameters of nanotubes liquid crystals improved the electronic transport properties as witnessed by the increase in σ dc/σ opt values on macroscopic films and high mobilities in microscopic transistors. Liquid crystal networks of semiconducting nanotubes as demonstrated here are simple to fabricate, transparent, scalable and could find wide ranging device applications.

  18. Nonlinear Ballistic Transport in Graphene Devices

    NASA Astrophysics Data System (ADS)

    Farrokhi, M. Javad; Boland, Mathias; Nasseri, Mohsen; Strachan, Douglas

    Through the extreme size scaling of electronic devices, there is great potential to achieve highly efficient and ultrafast electronics. By scaling down the channel length in graphene transistors to the point where the mean free path exceeds the relevant channel length, the electron transport can transition from a diffusive regime to an intrinsic ballistic regime. In such a regime, both quantum tunneling at the electrode-channel interface and the screening length, as determined by electrode-channel barrier width, can have a strong effect on current nonlinearity and asymmetric gate response. Here we discuss our experimental results on nangap electrodes to graphene channels that show quantitative agreement with an intrinsic ballistic model. Moreover, this behavior persists to room temperature and on standard oxide substrates, providing strong evidence for a new regime of nonlinearity in graphene devices that could be of potential use for electronic applications.

  19. Non-Linear Raman Scattering from Semiconducting GaP Nanowires

    NASA Astrophysics Data System (ADS)

    Gupta, A.; Wu, Jian; Eklund, P. C.

    2008-03-01

    Results of polarized micro-Raman scattering from LO and TO phonons in individual GaP nanowires (NWs) with different diameter and length are reported. The NW diameters were determined by Atomic Force Microscope (AFM) and length was measured by Scanning Electron Microscope (SEM). NWs with the same growth direction but variable length were prepared by cutting ˜40 μm long wires into segments using a Focused Ion Beam. The polar plots of the back scattered intensity ITO,LO(θ) from these segments were collected, where θ is the angle between the incident electric field and the NW axis. Interestingly, the shapes of these polar patterns depend on both the length and diameter of the NWs. The Raman scattering intensities for short wires (i.e., L<1μm) also exhibit a non-linear dependence on the incident laser power I0. The non-linearity increases with decreasing NW length and behaves as ˜I0^1.5 for the shortest wires measured so far (i.e., L˜500 nm). Our results strong suggest strong enhancement in the internal electric field via antenna effects. This work is supported by NSF NIRT, grant DMR-0304178.

  20. Non-linear electrohydrodynamics in microfluidic devices.

    PubMed

    Zeng, Jun

    2011-01-01

    Since the inception of microfluidics, the electric force has been exploited as one of the leading mechanisms for driving and controlling the movement of the operating fluid and the charged suspensions. Electric force has an intrinsic advantage in miniaturized devices. Because the electrodes are placed over a small distance, from sub-millimeter to a few microns, a very high electric field is easy to obtain. The electric force can be highly localized as its strength rapidly decays away from the peak. This makes the electric force an ideal candidate for precise spatial control. The geometry and placement of the electrodes can be used to design electric fields of varying distributions, which can be readily realized by Micro-Electro-Mechanical Systems (MEMS) fabrication methods. In this paper, we examine several electrically driven liquid handling operations. The emphasis is given to non-linear electrohydrodynamic effects. We discuss the theoretical treatment and related numerical methods. Modeling and simulations are used to unveil the associated electrohydrodynamic phenomena. The modeling based investigation is interwoven with examples of microfluidic devices to illustrate the applications. PMID:21673912

  1. Non-Linear Electrohydrodynamics in Microfluidic Devices

    PubMed Central

    Zeng, Jun

    2011-01-01

    Since the inception of microfluidics, the electric force has been exploited as one of the leading mechanisms for driving and controlling the movement of the operating fluid and the charged suspensions. Electric force has an intrinsic advantage in miniaturized devices. Because the electrodes are placed over a small distance, from sub-millimeter to a few microns, a very high electric field is easy to obtain. The electric force can be highly localized as its strength rapidly decays away from the peak. This makes the electric force an ideal candidate for precise spatial control. The geometry and placement of the electrodes can be used to design electric fields of varying distributions, which can be readily realized by Micro-Electro-Mechanical Systems (MEMS) fabrication methods. In this paper, we examine several electrically driven liquid handling operations. The emphasis is given to non-linear electrohydrodynamic effects. We discuss the theoretical treatment and related numerical methods. Modeling and simulations are used to unveil the associated electrohydrodynamic phenomena. The modeling based investigation is interwoven with examples of microfluidic devices to illustrate the applications. PMID:21673912

  2. Spin-cast thin semiconducting polymer interlayer for improving device efficiency of polymer light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Kim, Ji-Seon; Friend, Richard H.; Grizzi, Ilaria; Burroughes, Jeremy H.

    2005-07-01

    We report that adding a thin (˜10nm) semiconducting polymer interlayer between apoly(styrenesulphonate)-doped poly(3,4-ethylenedioxythiophene) (PEDT:PSS) hole transporter and an emissive semiconductor significantly improves the device efficiency of polymer light-emitting diodes (LEDs). With the interlayer, the external quantum efficiency (EQE) increases from 0.7%(0.4cd/A at 3.7V) to 1.9% (1.0cd/A at 3.3V) at 100cd/m2 for red LEDs and from 1.9%(6.2cd/A at 3.4V) to 3.0% (10.1cd/A at 3.0V) at 1000cd/m2 for green LEDs. An EQE of 4.0% is also observed in blue LEDs (35% increase). The interlayer is spin-coated directly on top of the PEDT:PSS layer from a poly(2,7-(9,9-di-n-octylfluorene)-alt-(1,4-phenylene-((4-sec-butylphenyl)imino)-1,4-phenylene)) (TFB) solution. This interlayer prevents significant quenching of radiative excitons at the PEDT:PSS interface by acting as an efficient exciton blocking layer.

  3. Final Report for DE-FG36-08GO18007 "All-Inorganic, Efficient Photovoltaic Solid State Devices Utilizing Semiconducting Colloidal Nanocrystal Quantum Dots"

    SciTech Connect

    Vladimir Bulovic and Moungi Bawendi

    2011-09-30

    We demonstrated robust colloidal quantum dot (QD) photovoltaics with high internal quantum efficiencies. In our structures, device durability is derived from use of all-inorganic atmospherically-stable semiconducting metal-oxide films together with QD photoreceptors. We have shown that both QD and metal-oxide semiconducting films and contacts are amenable to room temperature processing under minimal vacuum conditions, enabling large area processing of PV structures of high internal efficiency. We generated the state of the art devices with power conversion efficiency of more than 4%, and have shown that efficiencies as high as 9% are achievable in the near-term, and as high as 17% in the long-term.

  4. High-performance polymer semiconducting heterostructure devices by nitrene-mediated photocrosslinking of alkyl side chains.

    PubMed

    Png, Rui-Qi; Chia, Perq-Jon; Tang, Jie-Cong; Liu, Bo; Sivaramakrishnan, Sankaran; Zhou, Mi; Khong, Siong-Hee; Chan, Hardy S O; Burroughes, Jeremy H; Chua, Lay-Lay; Friend, Richard H; Ho, Peter K H

    2010-02-01

    Heterostructures are central to the efficient manipulation of charge carriers, excitons and photons for high-performance semiconductor devices. Although these can be formed by stepwise evaporation of molecular semiconductors, they are a considerable challenge for polymers owing to re-dissolution of the underlying layers. Here we demonstrate a simple and versatile photocrosslinking methodology based on sterically hindered bis(fluorophenyl azide)s. The photocrosslinking efficiency is high and dominated by alkyl side-chain insertion reactions, which do not degrade semiconductor properties. We demonstrate two new back-infiltrated and contiguous interpenetrating donor-acceptor heterostructures for photovoltaic applications that inherently overcome internal recombination losses by ensuring path continuity to give high carrier-collection efficiency. This provides the appropriate morphology for high-efficiency polymer-based photovoltaics. We also demonstrate photopatternable polymer-based field-effect transistors and light-emitting diodes, and highly efficient separate-confinement-heterostructure light-emitting diodes. These results open the way to the general development of high-performance polymer semiconductor heterostructures that have not previously been thought possible. PMID:19966791

  5. PREFACE: Semiconducting oxides Semiconducting oxides

    NASA Astrophysics Data System (ADS)

    Catlow, Richard; Walsh, Aron

    2011-08-01

    Semiconducting oxides are amongst the most widely studied and topical materials in contemporary condensed matter science, with interest being driven both by the fundamental challenges posed by their electronic and magnetic structures and properties, and by the wide range of applications, including those in catalysis and electronic devices. This special section aims to highlight recent developments in the physics of these materials, and to show the link between developing fundamental understanding and key application areas of oxide semiconductors. Several aspects of the physics of this wide and expanding range of materials are explored in this special section. Transparent semiconducting oxides have a growing role in several technologies, but challenges remain in understanding their electronic structure and the physics of charge carriers. A related problem concerns the nature of redox processes and the reactions which interconvert defects and charge carriers—a key issue which may limit the extent to which doping strategies may be used to alter electronic properties. The magnetic structures of the materials pose several challenges, while surface structures and properties are vital in controlling catalytic properties, including photochemical processes. The field profits from and exploits a wide range of contemporary physical techniques—both experimental and theoretical. Indeed, the interplay between experiment and computation is a key aspect of contemporary work. A number of articles describe applications of computational methods whose use, especially in modelling properties of defects in these materials, has a long and successful history. Several papers in this special section relate to work presented at a symposium within the European Materials Research Society (EMRS) meeting held in Warsaw in September 2010, and we are grateful to the EMRS for supporting this symposium. We would also like to thank the editorial staff of Journal of Physics: Condensed Matter for

  6. PREFACE: Semiconducting oxides Semiconducting oxides

    NASA Astrophysics Data System (ADS)

    Catlow, Richard; Walsh, Aron

    2011-08-01

    Semiconducting oxides are amongst the most widely studied and topical materials in contemporary condensed matter science, with interest being driven both by the fundamental challenges posed by their electronic and magnetic structures and properties, and by the wide range of applications, including those in catalysis and electronic devices. This special section aims to highlight recent developments in the physics of these materials, and to show the link between developing fundamental understanding and key application areas of oxide semiconductors. Several aspects of the physics of this wide and expanding range of materials are explored in this special section. Transparent semiconducting oxides have a growing role in several technologies, but challenges remain in understanding their electronic structure and the physics of charge carriers. A related problem concerns the nature of redox processes and the reactions which interconvert defects and charge carriers—a key issue which may limit the extent to which doping strategies may be used to alter electronic properties. The magnetic structures of the materials pose several challenges, while surface structures and properties are vital in controlling catalytic properties, including photochemical processes. The field profits from and exploits a wide range of contemporary physical techniques—both experimental and theoretical. Indeed, the interplay between experiment and computation is a key aspect of contemporary work. A number of articles describe applications of computational methods whose use, especially in modelling properties of defects in these materials, has a long and successful history. Several papers in this special section relate to work presented at a symposium within the European Materials Research Society (EMRS) meeting held in Warsaw in September 2010, and we are grateful to the EMRS for supporting this symposium. We would also like to thank the editorial staff of Journal of Physics: Condensed Matter for

  7. Nonlinear electrical properties of Si three-terminal junction devices

    NASA Astrophysics Data System (ADS)

    Meng, Fantao; Sun, Jie; Graczyk, Mariusz; Zhang, Kailiang; Prunnila, Mika; Ahopelto, Jouni; Shi, Peixiong; Chu, Jinkui; Maximov, Ivan; Xu, H. Q.

    2010-12-01

    This letter reports on the realization and characterization of silicon three-terminal junction devices made in a silicon-on-insulator wafer. Room temperature electrical measurements show that the fabricated devices exhibit pronounced nonlinear electrical properties inherent to ballistic electron transport in a three-terminal ballistic junction (TBJ) device. The results show that room temperature functional TBJ devices can be realized in a semiconductor material other than high-mobility III-V semiconductor heterostructures and provide a simple design principle for compact silicon devices in nanoelectronics.

  8. Stability, Nonlinearity and Reliability of Electrostatically Actuated MEMS Devices

    PubMed Central

    Zhang, Wen-Ming; Meng, Guang; Chen, Di

    2007-01-01

    Electrostatic micro-electro-mechanical system (MEMS) is a special branch with a wide range of applications in sensing and actuating devices in MEMS. This paper provides a survey and analysis of the electrostatic force of importance in MEMS, its physical model, scaling effect, stability, nonlinearity and reliability in detail. It is necessary to understand the effects of electrostatic forces in MEMS and then many phenomena of practical importance, such as pull-in instability and the effects of effective stiffness, dielectric charging, stress gradient, temperature on the pull-in voltage, nonlinear dynamic effects and reliability due to electrostatic forces occurred in MEMS can be explained scientifically, and consequently the great potential of MEMS technology could be explored effectively and utilized optimally. A simplified parallel-plate capacitor model is proposed to investigate the resonance response, inherent nonlinearity, stiffness softened effect and coupled nonlinear effect of the typical electrostatically actuated MEMS devices. Many failure modes and mechanisms and various methods and techniques, including materials selection, reasonable design and extending the controllable travel range used to analyze and reduce the failures are discussed in the electrostatically actuated MEMS devices. Numerical simulations and discussions indicate that the effects of instability, nonlinear characteristics and reliability subjected to electrostatic forces cannot be ignored and are in need of further investigation.

  9. Hole-selective and impedance characteristics of an aqueous solution-processable MoO3 layer for solution-processable organic semiconducting devices

    NASA Astrophysics Data System (ADS)

    Moon, Byung Seuk; Lee, Soo-Hyoung; Huh, Yoon Ho; Park, Byoungchoo

    2015-02-01

    We herein report an investigation of aqueous solution-processable molybdenum-oxide (MoO3) hole-selective layers fabricated for solution-processable organic semiconducting devices. A homogeneous MoO3 layer was successfully deposited via spin-coating using aqueous solutions of ammonium heptamolybdate as a MoO3 precursor. The use of the solution-processable MoO3 layer as a hole-injecting layer (HIL) on an indium-tin-oxide (ITO) anode in solution-processable organic light-emitting diodes (OLEDs) resulted in excellent device performance in terms of the brightness (maximum brightness of 37,000 cd m-2) and the efficiency (peak efficiency of 25.2 cd A-1), comparable to or better than those of a reference OLED with a conventional poly(ethylenedioxy thiophene):poly(styrene sulfonate) (PEDOT:PSS) HIL. Such good device performance is attributed to the water-processable MoO3 hole-selective layers, which allowed the formation of a high-quality film and provided good matching of the energy levels between adjacent layers with improved hole-injecting properties, impedance characteristics, and stability. Furthermore, polymer solar cells (PSCs) with a MoO3 layer used as a hole-collecting layer (HCL) showed improved power conversion efficiency (3.81%), which was higher than that obtained using the PEDOT:PSS HCL. These results clearly indicate the benefits of using a water-processable MoO3 layer, which effectively acts as a hole-selective layer on an ITO anode and provides good hole-injection/collection, electron-blocking and energy-level-matching properties, and improved stability. They, therefore, offer considerable promise as an alternative to a conventional PEDOT:PSS layer in the production of high-performance solution-processable organic semiconducting devices.

  10. Semiconductor Nonlinear Waveguide Devices and Integrated-Mirror Etalons

    NASA Astrophysics Data System (ADS)

    Chuang, Chih-Li.

    This dissertation investigates different III-V semiconductor devices for applications in nonlinear photonics. These include passive and active nonlinear directional couplers, current-controlled optical phase shifter, and integrated -mirror etalons. A novel method to find the propagation constants of an optical waveguide is introduced. The same method is applied, with minor modifications, to find the coupling length of a directional coupler. The method presented provides a tool for the design of optical waveguide devices. The design, fabrication, and performance of a nonlinear directional coupler are presented. This device uses light intensity to control the direction of light coming out. This is achieved through photo-generated-carriers mechanism in the picosecond regime and through the optical Stark effect in the femtosecond regime. A two-transverse -dimensions beam-propagation computation is used to model the switching behavior in the nonlinear directional coupler. It is found that, by considering the pulse degradation effect, the computation agrees well with experiments. The possibility of operating a nonlinear directional coupler with gain is investigated. It is concluded that by injecting current into the nonlinear directional coupler does not provide the advantages hoped for and the modelling using 2-D beam -propagation methods verifies that. Using current injection to change the refractive index of a waveguide, an optical phase shifter is constructed. This device has the merit of delivering large phase shift with almost no intensity modulation. A phase shift as large as 3pi is produced in a waveguide 400 μm in length. Finally, a new structure, grown by the molecular beam epitaxy machine, is described. The structure consists of two quarter-wave stacks and a spacer layer to form an integrated-mirror etalon. The theory, design principles, spectral analyses are discussed with design examples to clarify the ideas. Emphasis is given to the vertical-cavity surface

  11. Nonlinear optimization of acoustic energy harvesting using piezoelectric devices.

    PubMed

    Lallart, Mickaeël; Guyomar, Daniel; Richard, Claude; Petit, Lionel

    2010-11-01

    In the first part of the paper, a single degree-of-freedom model of a vibrating membrane with piezoelectric inserts is introduced and is initially applied to the case when a plane wave is incident with frequency close to one of the resonance frequencies. The model is a prototype of a device which converts ambient acoustical energy to electrical energy with the use of piezoelectric devices. The paper then proposes an enhancement of the energy harvesting process using a nonlinear processing of the output voltage of piezoelectric actuators, and suggests that this improves the energy conversion and reduces the sensitivity to frequency drifts. A theoretical discussion is given for the electrical power that can be expected making use of various models. This and supporting experimental results suggest that a nonlinear optimization approach allows a gain of up to 10 in harvested energy and a doubling of the bandwidth. A model is introduced in the latter part of the paper for predicting the behavior of the energy-harvesting device with changes in acoustic frequency, this model taking into account the damping effect and the frequency changes introduced by the nonlinear processes in the device. PMID:21110569

  12. Carbon Nanotube Passive Intermodulation Device for Nonlinear Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Lerner, Mitchell; Perez, Israel; Rockway, John

    2014-03-01

    The navy is interested in designing RF front-ends for receivers to handle high power jammers and other strong interferers. Instead of blocking that energy or dissipating it as heat in filters or amplifiers, this project investigates re-directing that energy for harvesting and storage. The approach is based on channelizing a high power jamming signal into a passive intermodulation device to create intermodulation products in sub-band frequencies, which could then be harvested for energy. The intermodulation device is fabricated using carbon nanotube transistors and such devices can be modified by creating chemical defects in the sidewalls of the nanotubes and locally gating the devices with a slowly varying electric field. These effects controllably enhance the hysteretic non-linearity in the transistors IV behavior. Combining these components with a RF energy harvester on the back-end should optimize the re-use of inbound jamming energy while maximizing the utility of standard back end radio components.

  13. Nanostructured p-type semiconducting transparent oxides: promising materials for nano-active devices and the emerging field of "transparent nanoelectronics".

    PubMed

    Banerjee, Arghya; Chattopadhyay, Kalyan K

    2008-01-01

    Transparent conducting oxides (TCO) with p-type semiconductivity have recently gained renewed interest for the fabrication of all-oxide transparent junctions, having potential applications in the emerging field of 'Transparent' or 'Invisible Electronics'. This kind of transparent junctions can be used as a "functional" window, which will transmit visible portion of solar radiation, but generates electricity by the absorption of the UV part. Therefore, these devices can be used as UV shield as well as UV cells. In this report, a brief review on the research activities on various p-TCO materials is furnished along-with the fabrication of different transparent p-n homojunction, heterojunction and field-effect transistors. Also the reason behind the difficulties in obtaining p-TCO materials and possible solutions are discussed in details. Considerable attention is given in describing the various patent generations on the field of p-TCO materials as well as transparent p-n junction diodes and light emitting devices. Also, most importantly, a detailed review and patenting activities on the nanocrystalline p-TCO materials and transparent nano-active device fabrication are furnished with considerable attention. And finally, a systematic description on the fabrication and characterization of nanocrystalline, p-type transparent conducting CuAlO(2) thin film, deposited by cost-effective low-temperature DC sputtering technique, by our group, is furnished in details. These p-TCO micro/nano-materials have wide range of applications in the field of optoelectronics, nanoelectronics, space sciences, field-emission displays, thermoelectric converters and sensing devices. PMID:19076042

  14. Integrated optical devices using bacteriorhodopsin as active nonlinear optical material

    NASA Astrophysics Data System (ADS)

    Dér, András; Fábián, László; Valkai, Sándor; Wolff, Elmar; Ramsden, Jeremy; Ormos, Pál

    2006-08-01

    Coupling of optical data-processing devices with microelectronics, telecocommunication and sensory functions, is among the biggest challenges in molecular electronics. Intensive research is going on to find suitable nonlinear optical materials that could meet the demanding requirements of optoelectronic applications, especially regarding high sensitivity and stability. In addition to inorganic and organic crystals, biological molecules have also been considered for use in integrated optics, among which the bacterial chromoprotein, bacteriorhodopsin (bR) generated the most interest. bR undergoes enormous absorption and concomitant refractive index changes upon initiation of a cyclic series of photoreactions by a burst of actinic light. This effect can be exploited to create highly versatile all-optical logical elements. We demonstrate the potential of this approach by investigating the static and dynamic response of several basic elements of integrated optical devices. Our results show that, due to its relatively high refractive index changes, bR can be used as an active nonlinear optical material to produce a variety of integrated optical switching and modulation effects.

  15. Electronically Pure Single-Chirality Semiconducting Single-Walled Carbon Nanotube for Large-Scale Electronic Devices.

    PubMed

    Li, Huaping; Liu, Hongyu; Tang, Yifan; Guo, Wenmin; Zhou, Lili; Smolinski, Nina

    2016-08-17

    Single-walled carbon nanotube (SWCNT) networks deposited from a purple single chirality (6,5) SWCNT aqueous solution were electrically characterized as pure semiconductors based on metal/semiconductor/metal Schottky contacts using both complex instruments and a portable device. Both air-stable PMOS (p-type metal-oxide-semiconductor) and NMOS (n-type metal-oxide-semiconductor, resembling amorphous silicon) thin film transistors were fabricated on (6,5) SWCNT in large scale showing the characteristics of fA off current and ION/IOFF ratio of >1 × 10(8). CMOS (complementary metal-oxide-semiconductor) SWCNT inverter was demonstrated by wire-bonding PMOS (6,5) SWCNT TFT and NMOS (6,5) SWCNT TFT together to achieve the voltage gain as large as 52. PMID:27487382

  16. Non-linear optical crystal vibration sensing device

    DOEpatents

    Kalibjian, R.

    1994-08-09

    A non-linear optical crystal vibration sensing device including a photorefractive crystal and a laser is disclosed. The laser produces a coherent light beam which is split by a beam splitter into a first laser beam and a second laser beam. After passing through the crystal the first laser beam is counter-propagated back upon itself by a retro-mirror, creating a third laser beam. The laser beams are modulated, due to the mixing effect within the crystal by vibration of the crystal. In the third laser beam, modulation is stable and such modulation is converted by a photodetector into a usable electrical output, intensity modulated in accordance with vibration applied to the crystal. 3 figs.

  17. Non-linear optical crystal vibration sensing device

    DOEpatents

    Kalibjian, Ralph

    1994-01-11

    A non-linear optical crystal vibration sensing device (10) including a photorefractive crystal (26) and a laser (12). The laser (12 ) produces a coherent light beam (14) which is split by a beam splitter (18) into a first laser beam (20) and a second laser beam (22). After passing through the crystal (26) the first laser beam (20) is counter-propagated back upon itself by a retro-mirror (32), creating a third laser beam (30). The laser beams (20, 22, 30) are modulated, due to the mixing effect within the crystal (26) by vibration of the crystal (30). In the third laser beam (30), modulation is stable and such modulation is converted by a photodetector (34) into a usable electrical output, intensity modulated in accordance with vibration applied to the crystal (26).

  18. Nonlinear dynamics in a microfluidic loop device: Chaos and Fractals

    NASA Astrophysics Data System (ADS)

    Maddala, Jeevan; Rengaswamy, Raghunathan

    2012-11-01

    Discrete decision making and resistive interactions between droplets in a microfluidic loop device induces fascinating nonlinear dynamics such as multi-stability and period doubling. Droplets entering the device at fixed time intervals can exit at different periods or chaotically. One of the periodic behaviors that is observed in a loop is the three-period behavior; this is consistent with the notion that three period behavior implies chaos. Switching between these different dynamical regimes is achieved by changing the inlet droplet feeding frequency. Chaotic behavior is observed between islands of periodic behavior. We show through simulations and experimental observations that the transitions between periods are indeed chaotic. Network model is used to study the dynamic behavior for different inlet feeding frequencies resulting in the development of a bifurcation map. The bifurcation map shows that the three period dynamics is preceded by chaos. A Lyapunov exponent is used to further validate these results. The exit droplet spacing shows several fascinating patterns when the model is simulated for a large number of droplets in the chaotic regime. One such chaotic regime produces a fractal that has a boundary of cardioid. The correlation dimension for a fractal pattern produced by this particular loop system is calculated to be 0.7.

  19. Nonlinear parametric amplification in a triport nanoelectromechanical device

    NASA Astrophysics Data System (ADS)

    Collin, E.; Moutonet, T.; Heron, J.-S.; Bourgeois, O.; Bunkov, Yu. M.; Godfrin, H.

    2011-08-01

    We report on measurements performed at low temperatures on a nanoelectromechanical system (NEMS) under (capacitive) parametric pumping. The excitations and detection schemes are purely electrical and, in the present experiment, enable the straightforward measurement of forces down to about a femtonewton, for displacements of an angström, using standard room-temperature electronics. We demonstrate that a small (linear) force applied on the device can be amplified up to more than a 100 times, while the system is truly moving. We explore the dynamics up to about 50-nm deflections for cantilevers about 200 nm thick and 3 μm long, oscillating at a frequency of 7 MHz. We present a generic modeling of nonlinear parametric amplification and give analytic theoretical solutions enabling the fit of experimental results. We finally discuss the practical limits of the technique, with a particular application: the measurement of anelastic damping in the metallic coating of the device, with an exceptional resolution of about 0.5%.

  20. Surface physics of semiconducting nanowires

    NASA Astrophysics Data System (ADS)

    Amato, Michele; Rurali, Riccardo

    2016-02-01

    Semiconducting nanowires (NWs) are firm candidates for novel nanoelectronic devices and a fruitful playground for fundamental physics. Ultra-thin nanowires, with diameters below 10 nm, present exotic quantum effects due to the confinement of the wave functions, e.g. widening of the electronic band-gap, deepening of the dopant states. However, although several reports of sub-10 nm wires exist to date, the most common NWs have diameters that range from 20 to 200 nm, where these quantum effects are absent or play a very minor role. Yet, the research activity on this field is very intense and these materials still promise to provide an important paradigm shift for the design of emerging electronic devices and different kinds of applications. A legitimate question is then: what makes a nanowire different from bulk systems? The answer is certainly the large surface-to-volume ratio. In this article we discuss the most salient features of surface physics and chemistry in group-IV semiconducting nanowires, focusing mostly on Si NWs. First we review the state-of-the-art of NW growth to achieve a smooth and controlled surface morphology. Next we discuss the importance of a proper surface passivation and its role on the NW electronic properties. Finally, stressing the importance of a large surface-to-volume ratio and emphasizing the fact that in a NW the surface is where most of the action takes place, we discuss molecular sensing and molecular doping.

  1. An experimental nonlinear low dynamic stiffness device for shock isolation

    NASA Astrophysics Data System (ADS)

    Francisco Ledezma-Ramirez, Diego; Ferguson, Neil S.; Brennan, Michael J.; Tang, Bin

    2015-07-01

    The problem of shock generated vibration is very common in practice and difficult to isolate due to the high levels of excitation involved and its transient nature. If not properly isolated it could lead to large transmitted forces and displacements. Typically, classical shock isolation relies on the use of passive stiffness elements to absorb energy by deformation and some damping mechanism to dissipate residual vibration. The approach of using nonlinear stiffness elements is explored in this paper, focusing in providing an isolation system with low dynamic stiffness. The possibilities of using such a configuration for a shock mount are studied experimentally following previous theoretical models. The model studied considers electromagnets and permanent magnets in order to obtain nonlinear stiffness forces using different voltage configurations. It is found that the stiffness nonlinearities could be advantageous in improving shock isolation in terms of absolute displacement and acceleration response when compared with linear elastic elements.

  2. All-optical logic devices with cascaded nonlinear couplers.

    PubMed

    Wang, Y; Wang, Z H; Bialkowski, M E

    2000-08-10

    The switching behaviors of cascaded nonlinear couplers were investigated. They have nearly ideal digital-switching characteristics, and their output power levels can be adjusted by means of varying the nonlinear coupling coefficient of the final coupler. The two-input excitation nonlinear cascaded couplers can perform not only switching operations but also a series of logic operations. The logic operations depend mainly on the coupling length of the two-input coupler and its initial inputs. The power corresponding to the rising and falling ridge of the logic operating waveforms can be shifted effectively by means of varying the switching power of the reshaper. Allowable ranges of three important parameters--coupling length of the two-input coupler L(1), bias optical power P(bia), and phase difference psi between the signal and bias beams for six fundamental logic operations--were calculated. Curves for design considerations and suggestions for the best choice of parameters for stable and reliable logic operations and, or, xor, nand, nor, and nxor are also presented individually. PMID:18349996

  3. TEM-nanoindentation studies of semiconducting structures.

    PubMed

    Le Bourhis, E; Patriarche, G

    2007-01-01

    This paper reviews the application of nanoindentation coupled with transmission electron microscopy (TEM) to investigations of the plastic behaviour of semiconducting structures and its implication for device design. Instrumented nanoindentation has been developed to extract the mechanical behaviour of small volumes scaled to those encountered in semiconductor heterostructures. We illustrate that TEM is a powerful complementary tool for the study of local plasticity induced by nanoindentation. TEM-nanoindentation allows for detailed understanding of the plastic deformation in semiconducting structures and opens practical routes for improvement of devices. Performances of heterostructures are deteriously affected by dislocations that relax the lattice mismatched layers. Different ways to obtain compliant substructures are being developed in order to concentrate the plastic relaxation underneath the heterostructure. Such approaches allow for mechanical design of micro- and opto-electronic devices to be considered throughout the fabrication process. PMID:16901706

  4. High power pumped MID-IR wavelength devices using nonlinear frequency mixing (NFM)

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Lang, Robert J. (Inventor); Waarts, Robert G. (Inventor)

    2001-01-01

    Laser diode pumped mid-IR wavelength sources include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

  5. High power pumped mid-IR wavelength systems using nonlinear frequency mixing (NFM) devices

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Lang, Robert J. (Inventor); Waarts, Robert G. (Inventor)

    1999-01-01

    Laser diode pumped mid-IR wavelength systems include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

  6. Understanding nonlinear vibration behaviours in high-power ultrasonic surgical devices

    PubMed Central

    Mathieson, Andrew; Cardoni, Andrea; Cerisola, Niccolò; Lucas, Margaret

    2015-01-01

    Ultrasonic surgical devices are increasingly used in oral, craniofacial and maxillofacial surgery to cut mineralized tissue, offering the surgeon high accuracy with minimal risk to nerve and vessel tissue. Power ultrasonic devices operate in resonance, requiring their length to be a half-wavelength or multiple-half-wavelength. For bone surgery, devices based on a half-wavelength have seen considerable success, but longer multiple-half-wavelength endoscopic devices have recently been proposed to widen the range of surgeries. To provide context for these developments, some examples of surgical procedures and the associated designs of ultrasonic cutting tips are presented. However, multiple-half-wavelength components, typical of endoscopic devices, have greater potential to exhibit nonlinear dynamic behaviours that have a highly detrimental effect on device performance. Through experimental characterization of the dynamic behaviour of endoscopic devices, it is demonstrated how geometrical features influence nonlinear dynamic responses. Period doubling, a known route to chaotic behaviour, is shown to be significantly influenced by the cutting tip shape, whereas the cutting tip has only a limited effect on Duffing-like responses, particularly the shape of the hysteresis curve, which is important for device stability. These findings underpin design, aiming to pave the way for a new generation of ultrasonic endoscopic surgical devices. PMID:27547081

  7. Nanogenerator comprising piezoelectric semiconducting nanostructures and Schottky conductive contacts

    NASA Technical Reports Server (NTRS)

    Wang, Zhong L. (Inventor); Wang, Xudong (Inventor); Song, Jinhui (Inventor); Zhou, Jun (Inventor); He, Jr-Hau (Inventor)

    2011-01-01

    A semiconducting device includes a substrate, a piezoelectric wire, a structure, a first electrode and a second electrode. The piezoelectric wire has a first end and an opposite second end and is disposed on the substrate. The structure causes the piezoelectric wire to bend in a predetermined manner between the first end and the second end so that the piezoelectric wire enters a first semiconducting state. The first electrode is coupled to the first end and the second electrode is coupled to the second end so that when the piezoelectric wire is in the first semiconducting state, an electrical characteristic will be exhibited between the first electrode and the second electrode.

  8. Silicon Photonics Research in Hong Kong: Microresonator Devices and Optical Nonlinearities

    NASA Astrophysics Data System (ADS)

    Poon, Andrew W.; Zhou, Linjie; Xu, Fang; Li, Chao; Chen, Hui; Liang, Tak-Keung; Liu, Yang; Tsang, Hon K.

    In this review paper we showcase recent activities on silicon photonics science and technology research in Hong Kong regarding two important topical areas-microresonator devices and optical nonlinearities. Our work on silicon microresonator filters, switches and modulators have shown promise for the nascent development of on-chip optoelectronic signal processing systems, while our studies on optical nonlinearities have contributed to basic understanding of silicon-based optically-pumped light sources and helium-implanted detectors. Here, we review our various passive and electro-optic active microresonator devices including (i) cascaded microring resonator cross-connect filters, (ii) NRZ-to-PRZ data format converters using a microring resonator notch filter, (iii) GHz-speed carrier-injection-based microring resonator modulators and 0.5-GHz-speed carrier-injection-based microdisk resonator modulators, and (iv) electrically reconfigurable microring resonator add-drop filters and electro-optic logic switches using interferometric resonance control. On the nonlinear waveguide front, we review the main nonlinear optical effects in silicon, and show that even at fairly modest average powers two-photon absorption and the accompanied free-carrier linear absorption could lead to optical limiting and a dramatic reduction in the effective lengths of nonlinear devices.

  9. Solar cells composed of semiconductive materials

    SciTech Connect

    Hezel, R.

    1981-03-03

    A solar cell is composed of a semiconductive material having an active zone in which charge carriers are produced by photons which strike and penetrate into the solar cell. The cell is comprised of a semiconductive body having an electrically insulating laminate with metal contacts therein positioned on the semiconductor body in the active zone thereof. The insulating laminate is composed of a double layer of insulating material, with the layer in direct contact with the semiconductive surface being composed of SiO2 which is either natural or is produced at temperatures below 800/sup 0/ C. And the layer superimposed above the SiO2 layer being composed of a different insulating material, such as plasma-produced Si3N4. In certain embodiments of the invention, a whole-area pn-junction is provided parallel to the semiconductive surface. The solar cells of the invention exhibit a higher degree of efficiency due to a higher fixed interface charged density, and low surface recombination velocity, an increased UV sensitivity, improved surface protection and passivation and improved anti-reflection characteristics relative to prior art solar cell devices.

  10. Growth of bulk single crystals of organic materials for nonlinear optical devices - An overview

    NASA Technical Reports Server (NTRS)

    Penn, Benjamin G.; Cardelino, Beatriz H.; Moore, Craig E.; Shields, Angela W.; Frazier, D. O.

    1991-01-01

    Highly perfect single crystals of nonlinear optical organic materials are required for use in optical devices. An overview of the bulk crystal growth of these materials by melt, vapor, and solution processes is presented. Additionally, methods that may be used to purify starting materials, detect impurities at low levels, screen materials for crystal growth, and process grown crystals are discussed.

  11. Non-linear control of the ''clam'' wave energy device. Final report

    SciTech Connect

    Not Available

    1983-09-01

    A promising wave energy device being currently investigated is the ''clam'' device. The clam extracts energy by pumping air through a specially designed (Wells) turbine. Although operation of the Wells turbine does not require a rectified air flow, some additional control will be necessary to optimize the phase of the clam motion for good efficiencies. An examination of the equation of motion in the time domain suggests the possibility of non-linear phase control by mechanical, power take-off, or pneumatic latching. Latching can be shown to increase the efficiency of the device in the longer wavelengths of the wave spectrum, i.e. those of high incident wave power.

  12. Organic ferroelectric/semiconducting nanowire hybrid layer for memory storage.

    PubMed

    Cai, Ronggang; Kassa, Hailu G; Haouari, Rachid; Marrani, Alessio; Geerts, Yves H; Ruzié, Christian; van Breemen, Albert J J M; Gelinck, Gerwin H; Nysten, Bernard; Hu, Zhijun; Jonas, Alain M

    2016-03-21

    Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires. This lateral electrostatic coupling between ferroelectric and semiconducting nanowires offers new opportunities to design new device architectures. As an example, we demonstrate the fabrication of an elementary non-volatile memory device in a transistor-like configuration, of which the source-drain current exhibits a typical hysteretic behavior with respect to the poling voltage. The potential for size reduction intrinsic to the nanostructured hybrid layer offers opportunities for the development of strongly miniaturized ferroelectric and piezoelectric devices. PMID:26927694

  13. Nonlinear time dependence of dark current in charge-coupled devices

    NASA Astrophysics Data System (ADS)

    Dunlap, Justin C.; Bodegom, Erik; Widenhorn, Ralf

    2011-03-01

    It is generally assumed that charge-coupled device (CCD) imagers produce a linear response of dark current versus exposure time except near saturation. We found a large number of pixels with nonlinear dark current response to exposure time to be present in two scientific CCD imagers. These pixels are found to exhibit distinguishable behavior with other analogous pixels and therefore can be characterized in groupings. Data from two Kodak CCD sensors are presented for exposure times from a few seconds up to two hours. Linear behavior is traditionally taken for granted when carrying out dark current correction and as a result, pixels with nonlinear behavior will be corrected inaccurately.

  14. Organic ferroelectric/semiconducting nanowire hybrid layer for memory storage

    NASA Astrophysics Data System (ADS)

    Cai, Ronggang; Kassa, Hailu G.; Haouari, Rachid; Marrani, Alessio; Geerts, Yves H.; Ruzié, Christian; van Breemen, Albert J. J. M.; Gelinck, Gerwin H.; Nysten, Bernard; Hu, Zhijun; Jonas, Alain M.

    2016-03-01

    Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires. This lateral electrostatic coupling between ferroelectric and semiconducting nanowires offers new opportunities to design new device architectures. As an example, we demonstrate the fabrication of an elementary non-volatile memory device in a transistor-like configuration, of which the source-drain current exhibits a typical hysteretic behavior with respect to the poling voltage. The potential for size reduction intrinsic to the nanostructured hybrid layer offers opportunities for the development of strongly miniaturized ferroelectric and piezoelectric devices.Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires. This lateral electrostatic coupling between ferroelectric and semiconducting nanowires offers new opportunities to design new device architectures. As an example, we demonstrate the fabrication of an elementary non-volatile memory device in a transistor-like configuration, of which the source-drain current exhibits a typical hysteretic behavior with respect to the poling voltage. The potential for size reduction

  15. Simultaneous correction of flat field and nonlinearity response of intensified charge-coupled devices

    NASA Astrophysics Data System (ADS)

    Williams, Timothy C.; Shaddix, Christopher R.

    2007-12-01

    Intensified charge-coupled devices (ICCDs) are used extensively in many scientific and engineering environments to image weak or temporally short optical events. Care has to be taken in interpreting the images from ICCDs if quantitative results are required. In particular, nonuniform gain (flat field) and nonlinear response effects must be properly accounted for. Traditional flat-field corrections can only be applied in the linear regime of the ICCD camera, which limits the usable dynamic range. This paper reports a more general approach to image correction whereby the nonlinear gain response of each pixel of the ICCD is characterized over the full dynamic range of the camera. Image data can then be corrected for the combined effects of nonuniform gain and nonlinearity. The results from a two-color pyrometry measurement of soot field temperature are used to illustrate the capabilities of the new correction approach.

  16. Nonlinear electronic transport in nanoscopic devices: nonequilibrium Green's functions versus scattering approach

    NASA Astrophysics Data System (ADS)

    Hernández, Alexis R.; Lewenkopf, Caio H.

    2013-04-01

    We study the nonlinear elastic quantum electronic transport properties of nanoscopic devices using the nonequilibrium Green's function (NEGF) method. The Green's function method allows us to expand the I- V characteristics of a given device to arbitrary powers of the applied voltages. By doing so, we are able to relate the NEGF method to the scattering approach, showing their similarities and differences and calculate the conductance coefficients to arbitrary order. We demonstrate that the electronic current given by NEGF is gauge invariant to all orders in powers of V, and discuss the requirements for gauge invariance in the standard density functional theory (DFT) implementations in molecular electronics. We also analyze the symmetries of the nonlinear conductance coefficients with respect to a magnetic field inversion and the violation of the Onsager reciprocity relations with increasing source-drain bias.

  17. Modified hyperspheres algorithm to trace homotopy curves of nonlinear circuits composed by piecewise linear modelled devices.

    PubMed

    Vazquez-Leal, H; Jimenez-Fernandez, V M; Benhammouda, B; Filobello-Nino, U; Sarmiento-Reyes, A; Ramirez-Pinero, A; Marin-Hernandez, A; Huerta-Chua, J

    2014-01-01

    We present a homotopy continuation method (HCM) for finding multiple operating points of nonlinear circuits composed of devices modelled by using piecewise linear (PWL) representations. We propose an adaptation of the modified spheres path tracking algorithm to trace the homotopy trajectories of PWL circuits. In order to assess the benefits of this proposal, four nonlinear circuits composed of piecewise linear modelled devices are analysed to determine their multiple operating points. The results show that HCM can find multiple solutions within a single homotopy trajectory. Furthermore, we take advantage of the fact that homotopy trajectories are PWL curves meant to replace the multidimensional interpolation and fine tuning stages of the path tracking algorithm with a simple and highly accurate procedure based on the parametric straight line equation. PMID:25184157

  18. Modified Hyperspheres Algorithm to Trace Homotopy Curves of Nonlinear Circuits Composed by Piecewise Linear Modelled Devices

    PubMed Central

    Vazquez-Leal, H.; Jimenez-Fernandez, V. M.; Benhammouda, B.; Filobello-Nino, U.; Sarmiento-Reyes, A.; Ramirez-Pinero, A.; Marin-Hernandez, A.; Huerta-Chua, J.

    2014-01-01

    We present a homotopy continuation method (HCM) for finding multiple operating points of nonlinear circuits composed of devices modelled by using piecewise linear (PWL) representations. We propose an adaptation of the modified spheres path tracking algorithm to trace the homotopy trajectories of PWL circuits. In order to assess the benefits of this proposal, four nonlinear circuits composed of piecewise linear modelled devices are analysed to determine their multiple operating points. The results show that HCM can find multiple solutions within a single homotopy trajectory. Furthermore, we take advantage of the fact that homotopy trajectories are PWL curves meant to replace the multidimensional interpolation and fine tuning stages of the path tracking algorithm with a simple and highly accurate procedure based on the parametric straight line equation. PMID:25184157

  19. Preferential syntheses of semiconducting vertically aligned single-walled carbon nanotubes for direct use in FETs.

    PubMed

    Qu, Liangti; Du, Feng; Dai, Liming

    2008-09-01

    We have combined fast heating with plasma enhanced chemical vapor deposition (PECVD) for preferential growth of semiconducting vertically aligned single-walled carbon nanotubes (VA-SWNTs). Raman spectroscopic estimation indicated a high yield of up to 96% semiconducting SWNTs in the VA-SWNT array. The as-synthesized semiconducting SWNTs can be used directly for fabricating FET devices without the need for any postsynthesis purification or separation. PMID:18665651

  20. Tunable strong nonlinearity of a micromechanical beam embedded in a dc-superconducting quantum interference device

    SciTech Connect

    Ella, Lior Yuvaraj, D.; Suchoi, Oren; Shtempluk, Oleg; Buks, Eyal

    2015-01-07

    We present a study of the controllable nonlinear dynamics of a micromechanical beam coupled to a dc-SQUID (superconducting quantum interference device). The coupling between these systems places the modes of the beam in a highly nonlinear potential, whose shape can be altered by varying the bias current and applied flux of the SQUID. We detect the position of the beam by placing it in an optical cavity, which sets free the SQUID to be used solely for actuation. This enables us to probe the previously unexplored full parameter space of this device. We measure the frequency response of the beam and find that it displays a Duffing oscillator behavior which is periodic in the applied magnetic flux. To account for this, we develop a model based on the standard theory for SQUID dynamics. In addition, with the aim of understanding if the device can reach nonlinearity at the single phonon level, we use this model to show that the responsivity of the current circulating in the SQUID to the position of the beam can become divergent, with its magnitude limited only by noise. This suggests a direction for the generation of macroscopically distinguishable superposition states of the beam.

  1. Tunable strong nonlinearity of a micromechanical beam embedded in a dc-superconducting quantum interference device

    NASA Astrophysics Data System (ADS)

    Ella, Lior; Yuvaraj, D.; Suchoi, Oren; Shtempluk, Oleg; Buks, Eyal

    2015-01-01

    We present a study of the controllable nonlinear dynamics of a micromechanical beam coupled to a dc-SQUID (superconducting quantum interference device). The coupling between these systems places the modes of the beam in a highly nonlinear potential, whose shape can be altered by varying the bias current and applied flux of the SQUID. We detect the position of the beam by placing it in an optical cavity, which sets free the SQUID to be used solely for actuation. This enables us to probe the previously unexplored full parameter space of this device. We measure the frequency response of the beam and find that it displays a Duffing oscillator behavior which is periodic in the applied magnetic flux. To account for this, we develop a model based on the standard theory for SQUID dynamics. In addition, with the aim of understanding if the device can reach nonlinearity at the single phonon level, we use this model to show that the responsivity of the current circulating in the SQUID to the position of the beam can become divergent, with its magnitude limited only by noise. This suggests a direction for the generation of macroscopically distinguishable superposition states of the beam.

  2. All-optical devices based on carrier nonlinearities for optical filtering and spectral equalization

    NASA Astrophysics Data System (ADS)

    Burger, Johan Petrus

    InGaAsP-based quantum wells can display nonlinear refractive index changes of ~0.1 near the band-edge for intrawell carrier density changes of 1 × 1018cm-3, due to effects like bandfilling and the plasma effect, which make these materials promising for the realization of all-optical signal processing devices, as demonstrated here. A novel single passband filter with sub-gigahertz bandwidth and greater than 40nm of tunability was experimentally demonstrated. The filter uses the detuning characteristics of nearly degenerate four-wave mixing in a broad area semiconductor optical amplifier to obtain frequency selectivity. The key to this demonstration was the spatial separation of the filtered signal from the input signal, based on their different propagation directions. An analysis of an analogous integrated optic dual-order mode nonlinear mode-converter, with integrated mode sorters which separate the signal from the interacting modes, was also undertaken. This device is promising as a filter, a wavelength converter, notch filter, and a wavelength recognizing switch. Novel ways to prevent carrier diffusion, which washes out the nonlinear grating, were suggested. It is important to have a large mutual overlap to modal overlap ratio of the two interacting modes on the nonlinear medium, because the mixing efficiency scales as the fourth power of this number. Three types of integrated optic limiters (based on Kerr- like nonlinearities) namely an all-optical cutoff modulator, a nonlinear Y-branch and an interferometer with an internal Kerr element, were theoretically investigated. A beam propagation program, which can solve the propagation of an optical field in a semiconductor in the presence of carrier diffusion, was developed for the numerical analysis of these structures. A negative feedback mechanism was identified in the Y-branch devices and a new limiting configuration was discovered in a Y- branch with a selectively placed defocusing nonlinearity. Dichroic

  3. A Compact Combinatorial Device for Measurement of Nonlinearity of Radiation Detectors

    NASA Astrophysics Data System (ADS)

    Saunders, P.; White, D. R.; Edgar, H.

    2015-03-01

    A new compact computer-controlled device using a combinatorial technique for measuring the nonlinearity of radiation detectors is described. The device consists of two sets of four beam-splitter cubes optically cemented together and arranged so that radiation from a single source is split into four separate paths, then recombined after passing through one of five neutral density filters placed in each path. This allows for the measurement of 625 approximately equi-spaced inter-related flux levels based on only 16 unknown transmittance values. These can be solved for by least-squares fitting, leaving 609 degrees of freedom remaining to determine the nonlinearity of the detector. A novel aspect of the design is the use of neutral density glass plates optically cemented along all the external faces of the beam-splitter cubes, which act as beam dumps for any reflected or scattered radiation. The cube faces in the desired beam paths have clear glass plates with an anti-reflection coating applied at the wavelength of interest optically cemented to them. Operation at other wavelengths is achieved by simply replacing these plates with plates coated for the new wavelength. The performance of the device has been tested using a silicon photodiode with a collimated 650 nm LED as the source. The results demonstrate that the device is able to measure linearity to better than 1 part in.

  4. Electronic structure and optical property of boron doped semiconducting graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Chen, Aqing; Shao, Qingyi; Wang, Li; Deng, Feng

    2011-08-01

    We present a system study on the electronic structure and optical property of boron doped semiconducting graphene nanoribbons using the density functional theory. Energy band structure, density of states, deformation density, Mulliken popular and optical spectra are considered to show the special electronic structure of boron doped semiconducting graphene nanoribbons. The C-B bond form is discussed in detail. From our analysis it is concluded that the Fermi energy of boron doped semiconducting graphene nanoribbons gets lower than that of intrinsic semiconducting graphene nanoribbons. Our results also show that the boron doped semiconducting graphene nanoribbons behave as p-type semiconducting and that the absorption coefficient of boron doped armchair graphene nanoribbons is generally enhanced between 2.0 eV and 3.3 eV. Therefore, our results have a great significance in developing nano-material for fabricating the nano-photovoltaic devices.

  5. Nonlinear Optimization-Based Device-Free Localization with Outlier Link Rejection

    PubMed Central

    Xiao, Wendong; Song, Biao; Yu, Xiting; Chen, Peiyuan

    2015-01-01

    Device-free localization (DFL) is an emerging wireless technique for estimating the location of target that does not have any attached electronic device. It has found extensive use in Smart City applications such as healthcare at home and hospitals, location-based services at smart spaces, city emergency response and infrastructure security. In DFL, wireless devices are used as sensors that can sense the target by transmitting and receiving wireless signals collaboratively. Many DFL systems are implemented based on received signal strength (RSS) measurements and the location of the target is estimated by detecting the changes of the RSS measurements of the wireless links. Due to the uncertainty of the wireless channel, certain links may be seriously polluted and result in erroneous detection. In this paper, we propose a novel nonlinear optimization approach with outlier link rejection (NOOLR) for RSS-based DFL. It consists of three key strategies, including: (1) affected link identification by differential RSS detection; (2) outlier link rejection via geometrical positional relationship among links; (3) target location estimation by formulating and solving a nonlinear optimization problem. Experimental results demonstrate that NOOLR is robust to the fluctuation of the wireless signals with superior localization accuracy compared with the existing Radio Tomographic Imaging (RTI) approach. PMID:25853406

  6. Nonlinear optimization-based device-free localization with outlier link rejection.

    PubMed

    Xiao, Wendong; Song, Biao; Yu, Xiting; Chen, Peiyuan

    2015-01-01

    Device-free localization (DFL) is an emerging wireless technique for estimating the location of target that does not have any attached electronic device. It has found extensive use in Smart City applications such as healthcare at home and hospitals, location-based services at smart spaces, city emergency response and infrastructure security. In DFL, wireless devices are used as sensors that can sense the target by transmitting and receiving wireless signals collaboratively. Many DFL systems are implemented based on received signal strength (RSS) measurements and the location of the target is estimated by detecting the changes of the RSS measurements of the wireless links. Due to the uncertainty of the wireless channel, certain links may be seriously polluted and result in erroneous detection. In this paper, we propose a novel nonlinear optimization approach with outlier link rejection (NOOLR) for RSS-based DFL. It consists of three key strategies, including: (1) affected link identification by differential RSS detection; (2) outlier link rejection via geometrical positional relationship among links; (3) target location estimation by formulating and solving a nonlinear optimization problem. Experimental results demonstrate that NOOLR is robust to the fluctuation of the wireless signals with superior localization accuracy compared with the existing Radio Tomographic Imaging (RTI) approach. PMID:25853406

  7. Nonlinear current-voltage characteristics based on semiconductor nanowire networks enable a new concept in thermoelectric device optimization

    NASA Astrophysics Data System (ADS)

    Diaz Leon, Juan J.; Norris, Kate J.; Hartnett, Ryan J.; Garrett, Matthew P.; Tompa, Gary S.; Kobayashi, Nobuhiko P.

    2016-08-01

    Thermoelectric (TE) devices that produce electric power from heat are driven by a temperature gradient (Δ T = T_{{hot}} - T_{{cold}}, T hot: hot side temperature, T cold: cold side temperature) with respect to the average temperature ( T). While the resistance of TE devices changes as Δ T and/or T change, the current-voltage ( I- V) characteristics have consistently been shown to remain linear, which clips generated electric power ( P gen) within the given open-circuit voltage ( V OC) and short-circuit current ( I SC). This P gen clipping is altered when an appropriate nonlinearity is introduced to the I- V characteristics—increasing P gen. By analogy, photovoltaic cells with a large fill factor exhibit nonlinear I- V characteristics. In this paper, the concept of a unique TE device with nonlinear I- V characteristics is proposed and experimentally demonstrated. A single TE device with nonlinear I- V characteristics is fabricated by combining indium phosphide (InP) and silicon (Si) semiconductor nanowire networks. These TE devices show P gen that is more than 25 times larger than those of comparable devices with linear I- V characteristics. The plausible causes of the nonlinear I- V characteristics are discussed. The demonstrated concept suggests that there exists a new pathway to increase P gen of TE devices made of semiconductors.

  8. Silicon Photonics: All-Optical Devices for Linear and Nonlinear Applications

    NASA Astrophysics Data System (ADS)

    Driscoll, Jeffrey B.

    Silicon photonics has grown rapidly since the first Si electro-optic switch was demonstrated in 1987, and the field has never grown more quickly than it has over the past decade, fueled by milestone achievements in semiconductor processing technologies for low loss waveguides, high-speed Si modulators, Si lasers, Si detectors, and an enormous toolbox of passive and active integrated devices. Silicon photonics is now on the verge of major commercialization breakthroughs, and optical communication links remain the force driving integrated and Si photonics towards the first commercial telecom and datacom transceivers; however other potential and future applications are becoming uncovered and refined as researchers reveal the benefits of manipulating photons on the nanoscale. This thesis documents an exploration into the unique guided-wave and nonlinear properties of deeply-scaled high-index-contrast sub-wavelength Si waveguides. It is found that the tight confinement inherent to single-mode channel waveguides on the silicon-on-insulator platform lead to a rich physics, which can be leveraged for new devices extending well beyond simple passive interconnects and electro-optic devices. The following chapters will concentrate, in detail, on a number of unique physical features of Si waveguides and extend these attributes towards new and interesting devices. Linear optical properties and nonlinear optical properties are investigated, both of which are strongly affected by tight optical confinement of the guided waveguide modes. As will be shown, tight optical confinement directly results in strongly vectoral modal components, where the electric and magnetic fields of the guided modes extend into all spatial dimensions, even along the axis of propagation. In fact, the longitudinal electric and magnetic field components can be just as strong as the transverse fields, directly affecting the modal group velocity and energy transport properties since the longitudinal fields

  9. Step-response of a torsional device with multiple discontinuous non-linearities: Formulation of a vibratory experiment

    NASA Astrophysics Data System (ADS)

    Krak, Michael D.; Dreyer, Jason T.; Singh, Rajendra

    2016-03-01

    A vehicle clutch damper is intentionally designed to contain multiple discontinuous non-linearities, such as multi-staged springs, clearances, pre-loads, and multi-staged friction elements. The main purpose of this practical torsional device is to transmit a wide range of torque while isolating torsional vibration between an engine and transmission. Improved understanding of the dynamic behavior of the device could be facilitated by laboratory measurement, and thus a refined vibratory experiment is proposed. The experiment is conceptually described as a single degree of freedom non-linear torsional system that is excited by an external step torque. The single torsional inertia (consisting of a shaft and torsion arm) is coupled to ground through parallel production clutch dampers, which are characterized by quasi-static measurements provided by the manufacturer. Other experimental objectives address physical dimensions, system actuation, flexural modes, instrumentation, and signal processing issues. Typical measurements show that the step response of the device is characterized by three distinct non-linear regimes (double-sided impact, single-sided impact, and no-impact). Each regime is directly related to the non-linear features of the device and can be described by peak angular acceleration values. Predictions of a simplified single degree of freedom non-linear model verify that the experiment performs well and as designed. Accordingly, the benchmark measurements could be utilized to validate non-linear models and simulation codes, as well as characterize dynamic parameters of the device including its dissipative properties.

  10. Nonlinear modeling of a long flexible manipulator and control by inertial devices

    NASA Technical Reports Server (NTRS)

    Barbieri, Enrique; Kenny, Sean P.; Montgomery, Raymond C.

    1992-01-01

    The authors consider the modeling and control of a planar, long flexible manipulator that is representative of current space-based robotic arms. The arm is equipped with three actuators: 1) a shoulder motor; 2) a torque wheel at the tip; and 3) a proof-mass actuator at the tip. The goal is to investigate the potential use of inertial devices as control inputs for maneuvering tasks and vibration suppression. The parameters used for the inertial devices at the tip are comparable to those specified for the Mini-Mast facility at the Langley Research Center. A nonlinear distributed parameter model is obtained by the extended Hamilton principle. The associated eigenvalue/eigenfunction problem is solved and a finite-dimensional state space model is assembled. A preliminary design of a linear quadratic regulator is used, and computer simulation results illustrate the benefits of using the proposed actuators.

  11. Fabrication and Characterization of Thin Film Ion Implanted Composite Materials for Integrated Nonlinear Optical Devices

    NASA Technical Reports Server (NTRS)

    Sarkisov, S.; Curley, M.; Williams, E. K.; Wilkosz, A.; Ila, D.; Poker, D. B.; Hensley, D. K.; Smith, C.; Banks, C.; Penn, B.; Clark, R.

    1998-01-01

    Ion implantation has been shown to produce a high density of metal colloids within the layer regions of glasses and crystalline materials. The high-precipitate volume fraction and small size of metal nanoclusters formed leads to values for the third-order susceptibility much greater than those for metal doped solids. This has stimulated interest in use of ion implantation to make nonlinear optical materials. On the other side, LiNbO3 has proved to be a good material for optical waveguides produced by MeV ion implantation. Light confinement in these waveguides is produced by refractive index step difference between the implanted region and the bulk material. Implantation of LiNbO3 with MeV metal ions can therefore result into nonlinear optical waveguide structures with great potential in a variety of device applications. We describe linear and nonlinear optical properties of a waveguide structure in LiNbO3-based composite material produced by silver ion implantation in connection with mechanisms of its formation.

  12. Loss of energy dissipation capacity from the deadzone in linear and nonlinear viscous damping devices

    NASA Astrophysics Data System (ADS)

    Tong, Mai; Liebner, Thomas

    2007-03-01

    In a viscous damping device under cyclic loading, after the piston reaches a peak stroke, the reserve movement that follows may sometimes experience a short period of delayed or significantly reduced device force output. A similar delay or reduced device force output may also occur at the damper’s initial stroke as it moves away from its neutral position. This phenomenon is referred to as the effect of “deadzone”. The deadzone can cause a loss of energy dissipation capacity and less efficient vibration control. It is prominent in small amplitude vibrations. Although there are many potential causes of deadzone such as environmental factors, construction, material aging, and manufacture quality, in this paper, its general effect in linear and nonlinear viscous damping devices is analyzed. Based on classical dynamics and damping theory, a simple model is developed to capture the effect of deadzone in terms of the loss of energy dissipation capacity. The model provides several methods to estimate the loss of energy dissipation within the deadzone in linear and sublinear viscous fluid dampers. An empirical equation of loss of energy dissipation capacity versus deadzone size is formulated, and the equivalent reduction of effective damping in SDOF systems has been obtained. A laboratory experimental evaluation is carried out to verify the effect of deadzone and its numerical approximation. Based on the analysis, a modification is suggested to the corresponding formulas in FEMA 356 for calculation of equivalent damping if a deadzone is to be considered.

  13. Ultrafast nonlinear photoresponse of single-wall carbon nanotubes: a broadband degenerate investigation.

    PubMed

    Xu, Shuo; Wang, Fengqiu; Zhu, Chunhui; Meng, Yafei; Liu, Yujie; Liu, Wenqing; Tang, Jingyi; Liu, Kaihui; Hu, Guohua; Howe, Richard C T; Hasan, Tawfique; Zhang, Rong; Shi, Yi; Xu, Yongbing

    2016-04-28

    Understanding of the fundamental photoresponse of carbon nanotubes has broad implications for various photonic and optoelectronic devices. Here, Z-scan and pump-probe spectroscopy performed across 600-2400 nm were combined to give a broadband 'degenerate' mapping of the nonlinear absorption properties of single-wall carbon nanotubes (SWNTs). In contrast to the views obtained from non-degenerate techniques, sizable saturable absorption is observed from the visible to the near-infrared range, including the spectral regions between semiconducting excitonic peaks and metallic tube transitions. In addition, the broadband mapping unambiguously reveals a photobleaching to photoinduced absorption transition feature within the first semiconducting excitonic band ∼2100 nm, quantitatively marking the long-wavelength cut-off for saturable absorption of the SWNTs investigated. Our findings present a much clearer physical picture of SWNTs' nonlinear absorption characteristics, and help provide updated design guidelines for SWNT based nonlinear optical devices. PMID:27088630

  14. Ultrafast nonlinear photoresponse of single-wall carbon nanotubes: a broadband degenerate investigation

    NASA Astrophysics Data System (ADS)

    Xu, Shuo; Wang, Fengqiu; Zhu, Chunhui; Meng, Yafei; Liu, Yujie; Liu, Wenqing; Tang, Jingyi; Liu, Kaihui; Hu, Guohua; Howe, Richard C. T.; Hasan, Tawfique; Zhang, Rong; Shi, Yi; Xu, Yongbing

    2016-04-01

    Understanding of the fundamental photoresponse of carbon nanotubes has broad implications for various photonic and optoelectronic devices. Here, Z-scan and pump-probe spectroscopy performed across 600-2400 nm were combined to give a broadband `degenerate' mapping of the nonlinear absorption properties of single-wall carbon nanotubes (SWNTs). In contrast to the views obtained from non-degenerate techniques, sizable saturable absorption is observed from the visible to the near-infrared range, including the spectral regions between semiconducting excitonic peaks and metallic tube transitions. In addition, the broadband mapping unambiguously reveals a photobleaching to photoinduced absorption transition feature within the first semiconducting excitonic band ~2100 nm, quantitatively marking the long-wavelength cut-off for saturable absorption of the SWNTs investigated. Our findings present a much clearer physical picture of SWNTs' nonlinear absorption characteristics, and help provide updated design guidelines for SWNT based nonlinear optical devices.Understanding of the fundamental photoresponse of carbon nanotubes has broad implications for various photonic and optoelectronic devices. Here, Z-scan and pump-probe spectroscopy performed across 600-2400 nm were combined to give a broadband `degenerate' mapping of the nonlinear absorption properties of single-wall carbon nanotubes (SWNTs). In contrast to the views obtained from non-degenerate techniques, sizable saturable absorption is observed from the visible to the near-infrared range, including the spectral regions between semiconducting excitonic peaks and metallic tube transitions. In addition, the broadband mapping unambiguously reveals a photobleaching to photoinduced absorption transition feature within the first semiconducting excitonic band ~2100 nm, quantitatively marking the long-wavelength cut-off for saturable absorption of the SWNTs investigated. Our findings present a much clearer physical picture of

  15. Superconducting-semiconducting nanowire hybrid microwave circuits

    NASA Astrophysics Data System (ADS)

    de Lange, G.; van Heck, B.; Bruno, A.; van Woerkom, D.; Geresdi, A.; Plissard, S. R.; Bakkers, E. P. A. M.; Akhmerov, A. R.; Dicarlo, L.

    2015-03-01

    Hybrid superconducting-semiconducting circuits offer a versatile platform for studying quantum effects in mesoscopic solid-state systems. We report the realization of hybrid artificial atoms based on Indium-Arsenide nanowire Josephson elements in a circuit quantum electrodynamics architecture. Transmon-like single-junction devices have gate-tunable transition frequencies. Split-junction devices behave as transmons near zero applied flux and as flux qubits near half flux quantum, wherein states with oppositely flowing persistent current can be driven by microwaves. This flux-qubit like behaviour results from non-sinusoidal current-phase relations in the nanowire Josephson elements. These hybrid microwave circuits are made entirely of magnetic-field compatible materials, offering new opportunities for hybrid experiments combining microwave circuits with polarized spin ensembles and Majorana bound states. We acknowledge funding from Microsoft Research and the Dutch Organization for Fundamental Research on Matter (FOM).

  16. Broadband high-sensitivity current-sensing device utilizing nonlinear magnetoelectric medium and nanocrystalline flux concentrator.

    PubMed

    Zhang, Jitao; He, Wei; Zhang, Ming; Zhao, Hongmei; Yang, Qian; Guo, Shuting; Wang, Xiaolei; Zheng, Xiaowan; Cao, Lingzhi

    2015-09-01

    A broadband current-sensing device with frequency-conversion mechanism consisting of Terfenol-D/Pb(Zr.Ti)O3 (PZT)/Terfenol-D magnetoelectric laminate and Fe73.5Cu1Nb3Si13.5B9 nanocrystalline flux concentrator is fabricated and characterized. For the purpose of acquiring resonance-enhanced sensitivity within broad bandwidth, a frequency-modulation mechanism is introduced into the presented device through the nonlinearity of field-dependence giant magnetostrictive materials. The presented configuration provides a solution to monitor the weak currents and achieves resonance-enhanced sensitivity of 178.4 mV/A at power-line frequency, which exhibits ∼3.86 times higher than that of direct output at power-line frequency of 50 Hz. Experimental results demonstrate that a weak step-change input current of 1 mA can be clearly distinguished by the output amplitude or phase. This miniature current-sensing device provides a promising application in power-line weak current measurement. PMID:26429473

  17. Spin Dependent Transport Properties of Metallic and Semiconducting Nanostructures

    NASA Astrophysics Data System (ADS)

    Sapkota, Keshab R.

    Present computing and communication devices rely on two different classes of technologies; information processing devices are based on electrical charge transport in semiconducting materials while information storage devices are based on orientation of electron spins in magnetic materials. A realization of a hybrid-type device that is based on charge as well as spin properties of electrons would perform both of these actions thereby enhancing computation power to many folds and reducing power consumptions. This dissertation focuses on the fabrication of such spin-devices based on metallic and semiconducting nanostructures which can utilize spin as well as charge properties of electrons. A simplified design of the spin-device consists of a spin injector, a semiconducting or metallic channel, and a spin detector. The channel is the carrier of the spin signal from the injector to the detector and therefore plays a crucial role in the manipulation of spin properties in the device. In this work, nanostructures like nanowires and nanostripes are used to function the channel in the spin-device. Methods like electrospinning, hydrothermal, and wet chemical were used to synthesize nanowires while physical vapor deposition followed by heat treatment in controlled environment was used to synthesis nanostripes. Spin-devices fabrication of the synthesized nanostructures were carried out by electron beam lithography process. The details of synthesis of nanostructures, device fabrication procedures and measurement techniques will be discussed in the thesis. We have successfully fabricated the spin-devices of tellurium nanowire, indium nanostripe, and indium oxide nanostripe and studied their spin transport properties for the first time. These spin-devices show large spin relaxation length compared to normal metals like copper and offer potentials for the future technologies. Further, Heusler alloys nanowires like nanowires of Co 2FeAl were synthesized and studied for electrical

  18. Highly nonlinear chalcogenide glass micro/nanofiber devices: Design, theory, and octave-spanning spectral generation

    NASA Astrophysics Data System (ADS)

    Hudson, Darren D.; Mägi, Eric C.; Judge, Alexander C.; Dekker, Stephen A.; Eggleton, Benjamin J.

    2012-10-01

    In this review we consider the basic elements of tapering chalcogenide optical fibers for the generation of extreme spectral broadening through supercontinuum generation. Creating tapered nanofiber devices in chalcogenide fiber, which has an intrinsic nonlinearity that is two orders of magnitude higher than silica, has resulted in the demonstration of octave-spanning spectra using record low power. We first present a brief theoretical understanding of the tapering process that follows from the basic principle of mass conservation, and a geometric construction tool for the visualization of the shape of tapered fibers. This is followed by a theoretical treatment of dispersion engineering and supercontinuum generation in a chalcogenide nanofiber. In the final section, we cover the experimental implementation of the chalcogenide nanofiber and demonstrate an octave-spanning spectrum created with 150 W of peak power.

  19. CONTROL OF NONLINEAR DYNAMICS BY ACTIVE AND PASSIVE METHODS FOR THE NSLS-II INSERTION DEVICES

    SciTech Connect

    Bengtsson J.; Chubar, O.; Kitegi, C.; Tanabe, T.

    2012-05-20

    Nonlinear effects from insertion devices are potentially a limiting factor for the electron beam quality of modern ring-based light sources, i.e., the on and off-dynamical aperture, leading to reduced injection efficiency and beam lifetime. These effects can be modelled by e.g. kick maps ({approx}1/{gamma}{sup 2}) and controlled by e.g. first-order thin or thick magnetic kicks introduced by 'magic fingers,' 'L-shims,' or 'current strips'. However, due to physical or technological constraints, these corrections are typically only partial. Therefore, a precise model is needed to correctly minimize the residual nonlinear effects for the entire system. We outline a systematic method for integrated design and rapid prototyping based on evaluation of the 3D magnetic field and control of the local trajectory with RADIA, and particle tracking with Tracy-3 for validation. The optimal geometry for the compensating magnetic fields is determined from the results of these simulations using a combination of linear algebra and genetic optimization.

  20. Ni doping of semiconducting boron carbide

    SciTech Connect

    Hong, Nina; Liu Jing; Adenwalla, S.; Langell, M. A.; Kizilkaya, Orhan

    2010-01-15

    The wide band gap, temperature stability, high resistivity, and robustness of semiconducting boron carbide make it an attractive material for device applications. Undoped boron carbide is p type; Ni acts as a n-type dopant. Here we present the results of controlled doping of boron carbide with Ni on thin film samples grown using plasma enhanced chemical vapor deposition. The change in the dopant concentration within the thin film as a function of the dopant flow rate in the precursor gas mixture was confirmed by x-ray photoelectron spectroscopy measurements; with increasing dopant concentration, current-voltage (I-V) curves clearly establish the trend from p-type to n-type boron carbide.

  1. Nonlinear vibration control and energy harvesting of a beam using a nonlinear energy sink and a piezoelectric device

    NASA Astrophysics Data System (ADS)

    Nili Ahmadabadi, Z.; Khadem, S. E.

    2014-09-01

    This paper presents an optimal design for a system comprising a nonlinear energy sink (NES) and a piezoelectric-based vibration energy harvester attached to a free-free beam under shock excitation. The energy harvester is used for scavenging vibration energy dissipated by the NES. Grounded and ungrounded configurations are examined and the systems parameters are optimized globally to both maximize the dissipated energy by the NES and increase the harvested energy by piezoelectric element. A satisfactory amount of energy has been harvested as electric power in both configurations. The realization of nonlinear vibration control through one-way irreversible nonlinear energy pumping and optimizing the system parameters result in acquiring up to 78 percent dissipation of the grounded system energy.

  2. Frequency-Domain Models for Nonlinear Microwave Devices Based on Large-Signal Measurements

    PubMed Central

    Jargon, Jeffrey A.; DeGroot, Donald C.; Gupta, K. C.

    2004-01-01

    In this paper, we introduce nonlinear large-signal scattering ( S) parameters, a new type of frequency-domain mapping that relates incident and reflected signals. We present a general form of nonlinear large-signal S-parameters and show that they reduce to classic S-parameters in the absence of nonlinearities. Nonlinear large-signal impedance ( Z) and admittance ( D) parameters are also introduced, and equations relating the different representations are derived. We illustrate how nonlinear large-signal S-parameters can be used as a tool in the design process of a nonlinear circuit, specifically a single-diode 1 GHz frequency-doubler. For the case where a nonlinear model is not readily available, we developed a method of extracting nonlinear large-signal S-parameters obtained with artificial neural network models trained with multiple measurements made by a nonlinear vector network analyzer equipped with two sources. Finally, nonlinear large-signal S-parameters are compared to another form of nonlinear mapping, known as nonlinear scattering functions. The nonlinear large-signal S-parameters are shown to be more general. PMID:27366621

  3. Acceleration Sensing, Feedback Cooling, and Nonlinear Dynamics with Nanoscale Cavity-Optomechanical Devices

    NASA Astrophysics Data System (ADS)

    Krause, Alexander Grey

    Light has long been used for the precise measurement of moving bodies, but the burgeoning field of optomechanics is concerned with the interaction of light and matter in a regime where the typically weak radiation pressure force of light is able to push back on the moving object. This field began with the realization in the late 1960's that the momentum imparted by a recoiling photon on a mirror would place fundamental limits on the smallest measurable displacement of that mirror. This coupling between the frequency of light and the motion of a mechanical object does much more than simply add noise, however. It has been used to cool objects to their quantum ground state, demonstrate electromagnetically-induced-transparency, and modify the damping and spring constant of the resonator. Amazingly, these radiation pressure effects have now been demonstrated in systems ranging 18 orders of magnitude in mass (kg to fg). In this work we will focus on three diverse experiments in three different optomechanical devices which span the fields of inertial sensors, closed-loop feedback, and nonlinear dynamics. The mechanical elements presented cover 6 orders of magnitude in mass (ng to fg), but they all employ nano-scale photonic crystals to trap light and resonantly enhance the light-matter interaction. In the first experiment we take advantage of the sub-femtometer displacement resolution of our photonic crystals to demonstrate a sensitive chip-scale optical accelerometer with a kHz-frequency mechanical resonator. This sensor has a noise density of approximately 10 micro-g/rt-Hz over a useable bandwidth of approximately 20 kHz and we demonstrate at least 50 dB of linear dynamic sensor range. We also discuss methods to further improve performance of this device by a factor of 10. In the second experiment, we used a closed-loop measurement and feedback system to damp and cool a room-temperature MHz-frequency mechanical oscillator from a phonon occupation of 6.5 million down to

  4. A nonlinear MEMS electrostatic kinetic energy harvester for human-powered biomedical devices

    NASA Astrophysics Data System (ADS)

    Lu, Y.; Cottone, F.; Boisseau, S.; Marty, F.; Galayko, D.; Basset, P.

    2015-12-01

    This article proposes a silicon-based electrostatic kinetic energy harvester with an ultra-wide operating frequency bandwidth from 1 Hz to 160 Hz. This large bandwidth is obtained, thanks to a miniature tungsten ball impacting with a movable proof mass of silicon. The motion of the silicon proof mass is confined by nonlinear elastic stoppers on the fixed part standing against two protrusions of the proof mass. The electrostatic transducer is made of interdigited-combs with a gap-closing variable capacitance that includes vertical electrets obtained by corona discharge. Below 10 Hz, the e-KEH offers 30.6 nJ per mechanical oscillation at 2 grms, which makes it suitable for powering biomedical devices from human motion. Above 10 Hz and up to 162 Hz, the harvested power is more than 0.5 μW with a maximum of 4.5 μW at 160 Hz. The highest power of 6.6 μW is obtained without the ball at 432 Hz, in accordance with a power density of 142 μW/cm3. We also demonstrate the charging of a 47-μF capacitor to 3.5 V used to power a battery-less wireless temperature sensor node.

  5. Sensorless cardiac phase detection for synchronized control of ventricular assist devices using nonlinear kernel regression model.

    PubMed

    Hirohashi, Yoshihiro; Tanaka, Akira; Yoshizawa, Makoto; Sugita, Norihiro; Abe, Makoto; Kato, Tsuyoshi; Shiraishi, Yasuyuki; Miura, Hidekazu; Yambe, Tomoyuki

    2016-06-01

    Recently, driving methods for synchronizing ventricular assist devices (VADs) with heart rhythm of patients suffering from severe heart failure have been receiving attention. Most of the conventional methods require implanting a sensor for measurement of a signal, such as electrocardiogram, to achieve synchronization. In general, implanting sensors into the cardiovascular system of the patients is undesirable in clinical situations. The objective of this study was to extract the heartbeat component without any additional sensors, and to synchronize the rotational speed of the VAD with this component. Although signals from the VAD such as the consumption current and the rotational speed are affected by heartbeat, these raw signals cannot be utilized directly in the heartbeat synchronization control methods because they are changed by not only the effect of heartbeat but also the change in the rotational speed itself. In this study, a nonlinear kernel regression model was adopted to estimate the instantaneous rotational speed from the raw signals. The heartbeat component was extracted by computing the estimation error of the model with parameters determined by using the signals when there was no effect of heartbeat. Validations were conducted on a mock circulatory system, and the heartbeat component was extracted well by the proposed method. Also, heartbeat synchronization control was achieved without any additional sensors in the test environment. PMID:26758256

  6. A nonlinear MEMS electrostatic kinetic energy harvester for human-powered biomedical devices

    SciTech Connect

    Lu, Y.; Cottone, F.; Marty, F.; Basset, P.; Galayko, D.

    2015-12-21

    This article proposes a silicon-based electrostatic kinetic energy harvester with an ultra-wide operating frequency bandwidth from 1 Hz to 160 Hz. This large bandwidth is obtained, thanks to a miniature tungsten ball impacting with a movable proof mass of silicon. The motion of the silicon proof mass is confined by nonlinear elastic stoppers on the fixed part standing against two protrusions of the proof mass. The electrostatic transducer is made of interdigited-combs with a gap-closing variable capacitance that includes vertical electrets obtained by corona discharge. Below 10 Hz, the e-KEH offers 30.6 nJ per mechanical oscillation at 2 g{sub rms}, which makes it suitable for powering biomedical devices from human motion. Above 10 Hz and up to 162 Hz, the harvested power is more than 0.5 μW with a maximum of 4.5 μW at 160 Hz. The highest power of 6.6 μW is obtained without the ball at 432 Hz, in accordance with a power density of 142 μW/cm{sup 3}. We also demonstrate the charging of a 47-μF capacitor to 3.5 V used to power a battery-less wireless temperature sensor node.

  7. Considerations on nonlinearity measurement with high signal-to-noise ratio for RF surface and bulk acoustic wave devices

    NASA Astrophysics Data System (ADS)

    Kodaira, Ryosuke; Omori, Tatsuya; Hashimoto, Ken-ya; Kyoya, Haruki; Nakagawa, Ryo

    2015-07-01

    This paper discusses the measurement setup of non-linearity caused in radio frequency (RF) surface and bulk acoustic wave (SAW/BAW) devices with high signal-to-noise ratio (SNR). It is shown that when some important points are considered, the background level can be suppressed better than -135 dBm, and the non-linearity signals can be measured in high SNR. Finally, measured results are compared with those measured independently by Murata Manufacturing, and validity of the measurement is cross-checked.

  8. Strategies on improving the micro-fluidic devices using the nonlinear electro- and thermo-kinetic phenomena.

    PubMed

    Sugioka, Hideyuki

    2015-12-01

    Surface science is key to innovations on microfluidics, smart materials, and future non-equilibrium systems. However, challenging issues still exist in this field. In this article, from the viewpoint of the fundamental design, we will briefly review our strategies on improving the micro-fluidic devices using the nonlinear electro- and thermo-kinetic phenomena. In particular, we will review the microfluidic applications using ICEO, the correction based on the ion-conserving Poisson-Boltzmann theory, the direct simulation on ICEO, and the new horizon such as nonlinear thermo-kinetic phenomena and the artificial cilia. PMID:26482087

  9. Graphene-assisted nonlinear optical device for four-wave mixing based tunable wavelength conversion of QPSK signal.

    PubMed

    Hu, Xiao; Zeng, Mengqi; Wang, Andong; Zhu, Long; Fu, Lei; Wang, Jian

    2015-10-01

    We fabricate a nonlinear optical device based on a fiber pigtail cross-section coated with a single-layer graphene grown by chemical vapor deposition (CVD) method. Using such graphene-assisted nonlinear optical device, we experimentally demonstrate tunable wavelength conversion of a 10 Gbaud quadrature phase-shift keying (QPSK) signal by exploiting degenerate four-wave mixing (FWM) progress in graphene. We study the conversion efficiency as functions of the pump power and pump wavelength and evaluate the bit-error rate (BER) performance. The observed optical signal-to-noise ratio (OSNR) penalties for tunable QPSK wavelength conversion are less than 2.2 dB at a BER of 1 × 10(-3). PMID:26480130

  10. Atomistic study on dithiolated oligo-phenylenevinylene gated device

    SciTech Connect

    Mahmoud, Ahmed Lugli, Paolo

    2014-11-28

    Thanks to their semiconducting behavior, conjugated molecules are considered as an attractive candidate for future electronic devices. Understanding the charge transport characteristics through such molecules for different device applications would accelerate the progress in the field of molecular electronics. In addition, it would become more feasible to introduce/enhance specific properties of molecular devices. This theoretical paper focuses on atomistic simulation and characterization of novel molecular FET employing dithiolated oligo-phenylenevinylene molecules. The simulation is validated by its agreement with the experimental measurements conducted on the same molecules. The employed molecule has oxygen linkers, which are responsible for the strongly nonlinear current characteristics on the molecular device. We perform a thorough atomistic device analysis to illustrate the principles behind the nonlinear current characteristics and the gating effect.

  11. Doping of Semiconducting Atomic Chains

    NASA Technical Reports Server (NTRS)

    Toshishige, Yamada; Kutler, Paul (Technical Monitor)

    1997-01-01

    Due to the rapid progress in atom manipulation technology, atomic chain electronics would not be a dream, where foreign atoms are placed on a substrate to form a chain, and its electronic properties are designed by controlling the lattice constant d. It has been shown theoretically that a Si atomic chain is metallic regardless of d and that a Mg atomic chain is semiconducting or insulating with a band gap modified with d. For electronic applications, it is essential to establish a method to dope a semiconducting chain, which is to control the Fermi energy position without altering the original band structure. If we replace some of the chain atoms with dopant atoms randomly, the electrons will see random potential along the chain and will be localized strongly in space (Anderson localization). However, if we replace periodically, although the electrons can spread over the chain, there will generally appear new bands and band gaps reflecting the new periodicity of dopant atoms. This will change the original band structure significantly. In order to overcome this dilemma, we may place a dopant atom beside the chain at every N lattice periods (N > 1). Because of the periodic arrangement of dopant atoms, we can avoid the unwanted Anderson localization. Moreover, since the dopant atoms do not constitute the chain, the overlap interaction between them is minimized, and the band structure modification can be made smallest. Some tight-binding results will be discussed to demonstrate the present idea.

  12. Uncovering location-specific ultrafast exciton dynamics in organic semiconducting thin films

    NASA Astrophysics Data System (ADS)

    Ginsberg, Naomi

    2014-03-01

    In solid state semiconducting molecular materials used in electro-optical applications, relatively long exciton diffusion lengths hold the promise to boost device performance by relaxing proximity constraints on the locations for light absorption and interfacial charge separation. The architecture of such materials determines their optical and electronic properties as a result of spacing- and orientation-dependent Coulomb couplings between adjacent molecules. Exciton character and dynamics are generally inferred from bulk optical measurements, which can present a severe limitation on our understanding of these films because their constituent molecules are neither perfectly ordered nor perfectly disordered. Nevertheless, such microstructure can have profound impacts on transport properties. The ultrafast spectroscopy of single domains of polycrystalline films of TIPS-pentacene, a small-molecule organic semiconductor of interest in electronic and photovoltaic applications, is investigated using transient absorption microscopy. Individual domains are distinguished by their different polarization-dependent linear and nonlinear optical responses. As compared to bulk measurements, we show that the nonlinear response within a given domain can be tied more concretely to specific physical processes that transfer exciton populations between specified electronic states. By use of this approach and a simple kinetic model, the signatures of singlet fission as well as vibrational relaxation of the initially excited singlet state are identified. As such, observing exciton dynamics within and comparing exciton dynamics between different TIPS-pentacene domains reveal the relationship between photophysics and film morphology and the potential to resolve unique signatures at interfaces between different regions of the film.

  13. Recent Advances in Photonic Devices for Optical Computing and the Role of Nonlinear Optics-Part II

    NASA Technical Reports Server (NTRS)

    Abdeldayem, Hossin; Frazier, Donald O.; Witherow, William K.; Banks, Curtis E.; Paley, Mark S.

    2007-01-01

    The twentieth century has been the era of semiconductor materials and electronic technology while this millennium is expected to be the age of photonic materials and all-optical technology. Optical technology has led to countless optical devices that have become indispensable in our daily lives in storage area networks, parallel processing, optical switches, all-optical data networks, holographic storage devices, and biometric devices at airports. This chapters intends to bring some awareness to the state-of-the-art of optical technologies, which have potential for optical computing and demonstrate the role of nonlinear optics in many of these components. Our intent, in this Chapter, is to present an overview of the current status of optical computing, and a brief evaluation of the recent advances and performance of the following key components necessary to build an optical computing system: all-optical logic gates, adders, optical processors, optical storage, holographic storage, optical interconnects, spatial light modulators and optical materials.

  14. Correlation between quasi-static and dynamic experiments for a practical torsional device with multiple discontinuous nonlinearities

    NASA Astrophysics Data System (ADS)

    Krak, Michael D.; Singh, Rajendra

    2016-09-01

    Vehicle clutch dampers belong to a family of torsional devices or isolators that contain multi-staged torsional springs, pre-load features, clearances, and multi-staged dry friction elements. Estimation of elastic and dissipative parameters is usually carried out under quasi-static loading and then these static parameters are often assumed when predicting dynamic responses. For the purpose of comparison, this article proposes a new time domain parameter estimation method under dynamic, transient loading conditions. The proposed method assumes a priori knowledge of few nonlinear features based on the design and quasi-static characterization. Angular motion measurements from a component-level laboratory experiment under dynamic loading are utilized. Elastic parameters are first estimated through an instantaneous stochastic linearization technique. A model-based approach and energy balance principle are employed to estimate a combination of viscous and Coulomb damping parameters for seven local (stage-dependent) and global damping formulations for a practical device. The proposed method is validated by comparing time domain predictions from nonlinear models to dynamic measurements. Nonlinear models that utilize the proposed damping formulations are found to be superior to those that solely rely on parameters from a quasi-static experiment.

  15. Dynamic manipulation and separation of individual semiconducting and metallic nanowires

    PubMed Central

    Jamshidi, Arash; Pauzauskie, Peter J.; Schuck, P. James; Ohta, Aaron T.; Chiou, Pei-Yu; Chou, Jeffrey; Yang, Peidong; Wu, Ming C.

    2009-01-01

    The synthesis of nanowires has advanced in the last decade to a point where a vast range of insulating, semiconducting, and metallic materials1 are available for use in integrated, heterogeneous optoelectronic devices at nanometer scales 2. However, a persistent challenge has been the development of a general strategy for the manipulation of individual nanowires with arbitrary composition. Here we report that individual semiconducting and metallic nanowires with diameters below 20 nm, are addressable with forces generated by optoelectronic tweezers (OET) 3. Using 100,000× less optical power density than optical tweezers, OET is capable of transporting individual nanowires with speeds 4× larger than maximum speeds achieved by optical tweezers. A real-time array of silver nanowires is formed using photopatterned virtual-electrodes, demonstrating the potential for massively parallel assemblies. Furthermore, OET enables the separation of semiconducting and metallic nanowires, suggesting a broad range of applications for the separation and heterogenous integration of one-dimensional nanoscale materials. PMID:19789729

  16. Electrospun Composite Nanofibers of Semiconductive Polymers for Coaxial PN Junctions

    NASA Astrophysics Data System (ADS)

    Serrano, William; Thomas, Sylvia

    The objective of this research is to investigate the conditions under P3HT and Activink, semiconducting polymers, form 1 dimension (1D) coaxial p-n junctions and to characterize their behavior in the presence of UV radiation and organic gases. For the first time, fabrication and characterization of semiconductor polymeric single fiber coaxial arrangements will be studied. Electrospinning, a low cost, fast and reliable method, with a coaxial syringe arrangement will be used to fabricate these fibers. With the formation of fiber coaxial arrangements, there will be investigations of dimensionality crossovers e.g., from one-dimensional (1D) to two-dimensional (2D). Coaxial core/shell fibers have been realized as seen in a recent publication on an electrospun nanofiber p-n heterojunction of oxides (BiFeO3 and TiO2, respectively) using the electrospinning technique with hydrothermal method. In regards to organic semiconducting coaxial p-n junction nanofibers, no reported studies have been conducted, making this study fundamental and essential for organic semiconducting nano devices for flexible electronics and multi-dimensional integrated circuits.

  17. A non-device-specific approach to display characterization based on linear, nonlinear, and hybrid search algorithms.

    PubMed

    Ban, Hiroshi; Yamamoto, Hiroki

    2013-01-01

    In almost all of the recent vision experiments, stimuli are controlled via computers and presented on display devices such as cathode ray tubes (CRTs). Display characterization is a necessary procedure for such computer-aided vision experiments. The standard display characterization called "gamma correction" and the following linear color transformation procedure are established for CRT displays and widely used in the current vision science field. However, the standard two-step procedure is based on the internal model of CRT display devices, and there is no guarantee as to whether the method is applicable to the other types of display devices such as liquid crystal display and digital light processing. We therefore tested the applicability of the standard method to these kinds of new devices and found that the standard method was not valid for these new devices. To overcome this problem, we provide several novel approaches for vision experiments to characterize display devices, based on linear, nonlinear, and hybrid search algorithms. These approaches never assume any internal models of display devices and will therefore be applicable to any display type. The evaluations and comparisons of chromaticity estimation accuracies based on these new methods with those of the standard procedure proved that our proposed methods largely improved the calibration efficiencies for non-CRT devices. Our proposed methods, together with the standard one, have been implemented in a MATLAB-based integrated graphical user interface software named Mcalibrator2. This software can enhance the accuracy of vision experiments and enable more efficient display characterization procedures. The software is now available publicly for free. PMID:23729771

  18. Spatial confinement effects on ultrathin semiconducting polymer heterojunction thin films

    SciTech Connect

    Xuejun Zhang; Jenekhe, S.A.

    1996-12-31

    Thin and ultrathin films of electroactive and photoactive polymers are of growing interest for applications in electronic and optoelectronic devices such as thin film transistors, light emitting diodes, solar cells, and xerographic photoreceptors. Although spatial confinement effects on the electronic, optical, optoelectronic, magnetic, and mechanical properties of inorganic semiconductors, metals, oxides, and ceramics are well known and understood, very little is currently known about nanoscale size effects in electroactive and photoactive polymers. Therefore, we recently initiated studies aimed at the understanding of spatial confinement effects on electroactive and photoactive nanostructured polymers and related thin film devices. We have extensively investigated layered nanoscale semiconducting polymer heterojunctions by applying several experimental techniques including photoluminescence, optical absorption, transient absorption, electroluminescence, cyclic voltammetry, and current-voltage measurements. Our findings reveal clear evidence of spatial confinement effects, including: dramatic enhancement of photoconductivity in ultrathin films; enhancement of electroluminescence efficiency and performance characteristics in nanoscale heterojunction devices; observation of novel phenomena in nanoscale devices. These spatial confinement effects in nanostructured semiconducting polymers can be understood in terms of classical charge transport and interfacial processes without invoking quantum size effects.

  19. Semiconducting nanowire field effect transistor for nanoelectronics and nanomechanics

    NASA Astrophysics Data System (ADS)

    Deshmukh, Mandar

    2013-02-01

    Semiconducting nanowire transistors offer an interesting avenue to make fundamentally new device architecture for future switching devices. I will our work to develop a simple fabrication technique for lateral nanowire wrap-gate devices with high capacitive coupling and field-effect mobility using InAs nanowires and also discuss electrical characterization of these devices. Our process uses e-beam lithography with a single resist-spinning step and does not require chemical etching. We measure significantly larger mobility and good sub-threshold characteristics [1]. I will also discuss the applications of using suspended nanowire transistors in studying mechanics and thermal properties of nanostructures as they can be useful in studying a wide variety of physics at the nanoscale. This work is supported by Government of India and partially supported by IBM India.

  20. A simple and reliable technique to characterize amplitude to phase modulation distortion for high-frequency amplifiers and nonlinear devices

    NASA Astrophysics Data System (ADS)

    Jauregui, Rigoberto; Portilla, Joaquin; Reynoso-Hernández, J. A.; Hirata-Flores, F. I.

    2013-08-01

    This paper presents a simple and reliable measurement system for characterizing the amplitude to phase modulation (AM-PM) characteristics of high frequency amplifiers and nonlinear devices. The AM-PM measurement system is based on a null detector implemented with a double balanced mixer, and requires a voltmeter and a calibrated phase shifter. A 12 W class A radio frequency power amplifier has been designed using a GaN transistor, and the AM-PM has been measured using both the method proposed in this work and the classical method with a calibrated vector network analyzer. A good correlation between both methods is observed, which validates the proposed method.

  1. Assembly of ordered carbon shells on semiconducting nanomaterials

    DOEpatents

    Sutter, Eli Anguelova; Sutter, Peter Werner

    2012-10-02

    In some embodiments of the invention, encapsulated semiconducting nanomaterials are described. In certain embodiments the nanostructures described are semiconducting nanomaterials encapsulated with ordered carbon shells. In some aspects a method for producing encapsulated semiconducting nanomaterials is disclosed. In some embodiments applications of encapsulated semiconducting nanomaterials are described.

  2. Assembly of ordered carbon shells on semiconducting nanomaterials

    DOEpatents

    Sutter, Eli Anguelova; Sutter, Peter Werner

    2010-05-11

    In some embodiments of the invention, encapsulated semiconducting nanomaterials are described. In certain embodiments the nanostructures described are semiconducting nanomaterials encapsulated with ordered carbon shells. In some aspects a method for producing encapsulated semiconducting nanomaterials is disclosed. In some embodiments applications of encapsulated semiconducting nanomaterials are described.

  3. High-mobility ultrathin semiconducting films prepared by spin coating

    NASA Astrophysics Data System (ADS)

    Mitzi, David B.; Kosbar, Laura L.; Murray, Conal E.; Copel, Matthew; Afzali, Ali

    2004-03-01

    The ability to deposit and tailor reliable semiconducting films (with a particular recent emphasis on ultrathin systems) is indispensable for contemporary solid-state electronics. The search for thin-film semiconductors that provide simultaneously high carrier mobility and convenient solution-based deposition is also an important research direction, with the resulting expectations of new technologies (such as flexible or wearable computers, large-area high-resolution displays and electronic paper) and lower-cost device fabrication. Here we demonstrate a technique for spin coating ultrathin (~50Å), crystalline and continuous metal chalcogenide films, based on the low-temperature decomposition of highly soluble hydrazinium precursors. We fabricate thin-film field-effect transistors (TFTs) based on semiconducting SnS2-xSex films, which exhibit n-type transport, large current densities (>105Acm-2) and mobilities greater than 10cm2V-1s-1-an order of magnitude higher than previously reported values for spin-coated semiconductors. The spin-coating technique is expected to be applicable to a range of metal chalcogenides, particularly those based on main group metals, as well as for the fabrication of a variety of thin-film-based devices (for example, solar cells, thermoelectrics and memory devices).

  4. Nonlinear dynamics of a rack-pinion-rack device powered by the Casimir force.

    PubMed

    Miri, MirFaez; Nekouie, Vahid; Golestanian, Ramin

    2010-01-01

    Using the lateral Casimir force-a manifestation of the quantum fluctuations of the electromagnetic field between objects with corrugated surfaces-as the main force transduction mechanism, a nanomechanical device with rich dynamical behaviors is proposed. The device is made of two parallel racks that are moving in the same direction and a pinion in the middle that couples with both racks via the noncontact lateral Casimir force. The built-in frustration in the device causes it to be very sensitive and react dramatically to minute changes in the geometrical parameters and initial conditions of the system. The noncontact nature of the proposed device could help with the ubiquitous wear problem in nanoscale mechanical systems. PMID:20365429

  5. Coexistence of negative photoconductivity and hysteresis in semiconducting graphene

    NASA Astrophysics Data System (ADS)

    Zhuang, Shendong; Chen, Yan; Xia, Yidong; Tang, Nujiang; Xu, Xiaoyong; Hu, Jingguo; Chen, Zhuo

    2016-04-01

    Solution-processed graphene quantum dots (GQDs) possess a moderate bandgap, which make them a promising candidate for optoelectronics devices. However, negative photoconductivity (NPC) and hysteresis that happen in the photoelectric conversion process could be harmful to performance of the GQDs-based devices. So far, their origins and relations have remained elusive. Here, we investigate experimentally the origins of the NPC and hysteresis in GQDs. By comparing the hysteresis and photoconductance of GQDs under different relative humidity conditions, we are able to demonstrate that NPC and hysteresis coexist in GQDs and both are attributed to the carrier trapping effect of surface adsorbed moisture. We also demonstrate that GQDs could exhibit positive photoconductivity with three-order-of-magnitude reduction of hysteresis after a drying process and a subsequent encapsulation. Considering the pervasive moisture adsorption, our results may pave the way for a commercialization of semiconducting graphene-based and diverse solution-based optoelectronic devices.

  6. An Exploration of Neutron Detection in Semiconducting Boron Carbide

    NASA Astrophysics Data System (ADS)

    Hong, Nina

    The 3He supply problem in the U.S. has necessitated the search for alternatives for neutron detection. The neutron detection efficiency is a function of density, atomic composition, neutron absorption cross section, and thickness of the neutron capture material. The isotope 10B is one of only a handful of isotopes with a high neutron absorption cross section---3840 barns for thermal neutrons. So a boron carbide semiconductor represents a viable alternative to 3He. This dissertation provides an evaluation of the performance of semiconducting boron carbide neutron detectors grown by plasma enhance chemical vapor deposition (PECVD) in order to determine the advantages and drawbacks of these devices for neutron detection. Improved handling of the PECVD system has resulted in an extremely stable plasma, enabling deposition of thick films of semiconducting boron carbide. A variety of material and semiconducting characterization tools have been used to investigate the structure and electronic properties of boron carbide thin films, including X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, infrared/Raman spectroscopy, current-voltage measurements and capacitance-voltage measurements. Elemental concentrations in the boron carbide films have been obtained from Rutherford backscattering and elastic recoil detection analysis. Solid state neutron detection devices have been fabricated in the form of heterostructured p-n diodes, p-type boron carbide/n-type Si. Operating conditions, including applied bias voltage, and time constants, have been optimized for maximum detection efficiency and correlated to the semiconducting properties investigated in separate electronic measurements. Accurate measurements of the neutron detection efficiency and the response of the detector to a wide range of neutron wavelengths have been performed at a well calibrated, tightly collimated, "white" cold neutron beam source using time-of-flight neutron detection technique

  7. Short Channel Field-Effect-Transistors with Inkjet-Printed Semiconducting Carbon Nanotubes.

    PubMed

    Jang, Seonpil; Kim, Bongjun; Geier, Michael L; Hersam, Mark C; Dodabalapur, Ananth

    2015-11-01

    Short channel field-effect-transistors with inkjet-printed semiconducting carbon nanotubes are fabricated using a novel strategy to minimize material consumption, confining the inkjet droplet into the active channel area. This fabrication approach is compatible with roll-to-roll processing and enables the formation of high-performance short channel device arrays based on inkjet printing. PMID:26312458

  8. Method of forming semiconducting amorphous silicon films from the thermal decomposition of fluorohydridodisilanes

    DOEpatents

    Sharp, Kenneth G.; D'Errico, John J.

    1988-01-01

    The invention relates to a method of forming amorphous, photoconductive, and semiconductive silicon films on a substrate by the vapor phase thermal decomposition of a fluorohydridodisilane or a mixture of fluorohydridodisilanes. The invention is useful for the protection of surfaces including electronic devices.

  9. High-performing nonlinear visualization of terahertz radiation on a silicon charge-coupled device

    PubMed Central

    Shalaby, Mostafa; Vicario, Carlo; Hauri, Christoph P.

    2015-01-01

    Photoinduced electron transitions can lead to significant changes of the macroscopic electronic properties in semiconductors. This principle is responsible for the detection of light with charge-coupled devices. Their spectral sensitivity is limited by the semiconductor bandgap which has restricted their visualization capabilities to the optical, ultraviolet, and X-ray regimes. The absence of an imaging device in the low frequency terahertz range has severely hampered the advance of terahertz imaging applications in the past. Here we introduce a high-performing imaging concept to the terahertz range. On the basis of a silicon charge-coupled device we visualize 5–13 THz radiation with photon energy under 2% of the sensor's band-gap energy. The unprecedented small pitch and large number of pixels allow the visualization of complex terahertz radiation patterns in real time and with high spatial detail. This advance will have a great impact on a wide range of terahertz imaging disciplines. PMID:26496973

  10. Wafer-scale arrays of nonvolatile polymer memories with microprinted semiconducting small molecule/polymer blends.

    PubMed

    Bae, Insung; Hwang, Sun Kak; Kim, Richard Hahnkee; Kang, Seok Ju; Park, Cheolmin

    2013-11-13

    Nonvolatile ferroelectric-gate field-effect transistors (Fe-FETs) memories with solution-processed ferroelectric polymers are of great interest because of their potential for use in low-cost flexible devices. In particular, the development of a process for patterning high-performance semiconducting channel layers with mechanical flexibility is essential not only for proper cell-to-cell isolation but also for arrays of flexible nonvolatile memories. We demonstrate a robust route for printing large-scale micropatterns of solution-processed semiconducting small molecules/insulating polymer blends for high performance arrays of nonvolatile ferroelectric polymer memory. The nonvolatile memory devices are based on top-gate/bottom-contact Fe-FET with ferroelectric polymer insulator and micropatterned semiconducting blend channels. Printed micropatterns of a thin blended semiconducting film were achieved by our selective contact evaporation printing, with which semiconducting small molecules in contact with a micropatterned elastomeric poly(dimethylsiloxane) (PDMS) mold were preferentially evaporated and absorbed into the PDMS mold while insulating polymer remained intact. Well-defined micrometer-scale patterns with various shapes and dimensions were readily developed over a very large area on a 4 in. wafer, allowing for fabrication of large-scale printed arrays of Fe-FETs with highly uniform device performance. We statistically analyzed the memory properties of Fe-FETs, including ON/OFF ratio, operation voltage, retention, and endurance, as a function of the micropattern dimensions of the semiconducting films. Furthermore, roll-up memory arrays were produced by successfully detaching large-area Fe-FETs printed on a flexible substrate with a transient adhesive layer from a hard substrate and subsequently transferring them to a nonplanar surface. PMID:24070419

  11. Large-Area Semiconducting Graphene Nanomesh Tailored by Interferometric Lithography

    PubMed Central

    Kazemi, Alireza; He, Xiang; Alaie, Seyedhamidreza; Ghasemi, Javad; Dawson, Noel Mayur; Cavallo, Francesca; Habteyes, Terefe G.; Brueck, Steven R. J.; Krishna, Sanjay

    2015-01-01

    Graphene nanostructures are attracting a great deal of interest because of newly emerging properties originating from quantum confinement effects. We report on using interferometric lithography to fabricate uniform, chip-scale, semiconducting graphene nanomesh (GNM) with sub-10 nm neck widths (smallest edge-to-edge distance between two nanoholes). This approach is based on fast, low-cost, and high-yield lithographic technologies and demonstrates the feasibility of cost-effective development of large-scale semiconducting graphene sheets and devices. The GNM is estimated to have a room temperature energy bandgap of ~30 meV. Raman studies showed that the G band of the GNM experiences a blue shift and broadening compared to pristine graphene, a change which was attributed to quantum confinement and localization effects. A single-layer GNM field effect transistor exhibited promising drive current of ~3.9 μA/μm and ON/OFF current ratios of ~35 at room temperature. The ON/OFF current ratio of the GNM-device displayed distinct temperature dependence with about 24-fold enhancement at 77 K. PMID:26126936

  12. Large-Area Semiconducting Graphene Nanomesh Tailored by Interferometric Lithography

    NASA Astrophysics Data System (ADS)

    Kazemi, Alireza; He, Xiang; Alaie, Seyedhamidreza; Ghasemi, Javad; Dawson, Noel Mayur; Cavallo, Francesca; Habteyes, Terefe G.; Brueck, Steven R. J.; Krishna, Sanjay

    2015-07-01

    Graphene nanostructures are attracting a great deal of interest because of newly emerging properties originating from quantum confinement effects. We report on using interferometric lithography to fabricate uniform, chip-scale, semiconducting graphene nanomesh (GNM) with sub-10 nm neck widths (smallest edge-to-edge distance between two nanoholes). This approach is based on fast, low-cost, and high-yield lithographic technologies and demonstrates the feasibility of cost-effective development of large-scale semiconducting graphene sheets and devices. The GNM is estimated to have a room temperature energy bandgap of ~30 meV. Raman studies showed that the G band of the GNM experiences a blue shift and broadening compared to pristine graphene, a change which was attributed to quantum confinement and localization effects. A single-layer GNM field effect transistor exhibited promising drive current of ~3.9 μA/μm and ON/OFF current ratios of ~35 at room temperature. The ON/OFF current ratio of the GNM-device displayed distinct temperature dependence with about 24-fold enhancement at 77 K.

  13. Nonlinear saturation of the ion-electron Buneman instability in a spherical positively pulsed gridded inertial electrostatic confinement device

    SciTech Connect

    Bandara, R.; Khachan, J.

    2015-08-15

    A pulsed, positively biased gridded inertial electrostatic confinement device has been investigated experimentally, using Doppler broadened spectra and current and voltage traces as primary diagnostics. In the high current and energy regime explored in this paper resulting from the removal of the series ballast resistance from the external biasing circuit, large amplitude oscillations in the plasma current and potential were observed within 100 ns of the discharge onset. These oscillations are attributed to the nonlinear and saturated Buneman instability, characterised by a locked oscillation frequency as a function of increasing anode potential. The saturated Buneman instability is known to exhibit ion mass independent behaviour and cause electron trapping, resulting in a transient spatio-temporal virtual cathode and ponderomotive ion confinement, as evidenced by broadened spectra when operated at high currents.

  14. Further improved algorithm for the solution of the nonlinear Poisson equation in semiconductor devices

    NASA Astrophysics Data System (ADS)

    Ouwerling, G. J. L.

    1989-12-01

    This paper gives a concise overview of some existing methods for the solution of the nonlinear Poisson equation in semiconductors. A method for the solution of this equation was recently proposed in this journal by I. D. Mayergoyz [J. Appl. Phys. 59, 195 (1986)]. Soon afterwards, an improved version was described by W. Keller [J. Appl. Phys. 61, 5189 (1987)]. Both methods are classified within the perspective of the existing methods. Moreover, Keller's method is further improved by the introduction of scaled variables and by using red-black ordening to allow for overrelaxation. All advantages of the two methods are maintained. An illustrative example shows an improvement in solution speed of at least a factor of 5.6.

  15. Photoexcitation dynamics of coupled semiconducting carbon nanotube thin films.

    PubMed

    Mehlenbacher, Randy D; Wu, Meng-Yin; Grechko, Maksim; Laaser, Jennifer E; Arnold, Michael S; Zanni, Martin T

    2013-04-10

    Carbon nanotubes are a promising means of capturing photons for use in solar cell devices. We time-resolved the photoexcitation dynamics of coupled, bandgap-selected, semiconducting carbon nanotubes in thin films tailored for photovoltaics. Using transient absorption spectroscopy and anisotropy measurements, we found that the photoexcitation evolves by two mechanisms with a fast and long-range component followed by a slow and short-range component. Within 300 fs of optical excitation, 20% of nanotubes transfer their photoexcitation over 5-10 nm into nearby nanotube fibers. After 3 ps, 70% of the photoexcitation resides on the smallest bandgap nanotubes. After this ultrafast process, the photoexcitation continues to transfer on a ~10 ps time scale but to predominantly aligned tubes. Ultimately the photoexcitation hops twice on average between fibers. These results are important for understanding the flow of energy and charge in coupled nanotube materials and light-harvesting devices. PMID:23464618

  16. Semiconducting single-walled carbon nanotubes sorting with a removable solubilizer based on dynamic supramolecular coordination chemistry

    NASA Astrophysics Data System (ADS)

    Toshimitsu, Fumiyuki; Nakashima, Naotoshi

    2014-10-01

    Highly pure semiconducting single-walled carbon nanotubes (SWNTs) are essential for the next generation of electronic devices, such as field-effect transistors and photovoltaic applications; however, contamination by metallic SWNTs reduces the efficiency of their associated devices. Here we report a simple and efficient method for the separation of semiconducting- and metallic SWNTs based on supramolecular complex chemistry. We here describe the synthesis of metal-coordination polymers (CP-Ms) composed of a fluorene-bridged bis-phenanthroline ligand and metal ions. On the basis of a difference in the ‘solubility product’ of CP-M-solubilized semiconducting SWNTs and metallic SWNTs, we readily separated semiconducting SWNTs. Furthermore, the CP-M polymers on the SWNTs were simply removed by adding a protic acid and inducing depolymerization to the monomer components. We also describe molecular mechanics calculations to reveal the difference of binding and wrapping mode between CP-M/semiconducting SWNTs and CP-M/metallic SWNTs. This study opens a new stage for the use of such highly pure semiconducting SWNTs in many possible applications.

  17. Gallium Arsenide Quantum Well Devices for Detection and Nonlinear Optics in the Mid-Infrared

    NASA Astrophysics Data System (ADS)

    Grave, Ilan

    observation of enhanced nonlinear optical effects at the mid infrared, close to intersubband resonances. Second harmonic generation is obtained around 5 mu m. Third-order effects are then investigated in different experimental configurations, including the first observation of phase conjugation based on these nonlinearities. Very large third-order susceptibilities and intensity-dependent refractive indices are deduced from the experimental results.

  18. A concept for a magnetic field detector underpinned by the nonlinear dynamics of coupled multiferroic devices

    SciTech Connect

    Beninato, A.; Baglio, S.; Andò, B.; Emery, T.; Bulsara, A. R.; Jenkins, C.; Palkar, V.

    2013-12-09

    Multiferroic (MF) composites, in which magnetic and ferroelectric orders coexist, represent a very attractive class of materials with promising applications in areas, such as spintronics, memories, and sensors. One of the most important multiferroics is the perovskite phase of bismuth ferrite, which exhibits weak magnetoelectric properties at room temperature; its properties can be enhanced by doping with other elements such as dysprosium. A recent paper has demonstrated that a thin film of Bi{sub 0.7}Dy{sub 0.3}FeO{sub 3} shows good magnetoelectric coupling. In separate work it has been shown that a carefully crafted ring connection of N (N odd and N ≥ 3) ferroelectric capacitors yields, past a critical point, nonlinear oscillations that can be exploited for electric (E) field sensing. These two results represent the starting point of our work. In this paper the (electrical) hysteresis, experimentally measured in the MF material Bi{sub 0.7}Dy{sub 0.3}FeO{sub 3}, is characterized with the applied magnetic field (B) taken as a control parameter. This yields a “blueprint” for a magnetic (B) field sensor: a ring-oscillator coupling of N = 3 Sawyer-Tower circuits each underpinned by a mutliferroic element. In this configuration, the changes induced in the ferroelectric behavior by the external or “target” B-field are quantified, thus providing a pathway for very low power and high sensitivity B-field sensing.

  19. A concept for a magnetic field detector underpinned by the nonlinear dynamics of coupled multiferroic devices

    NASA Astrophysics Data System (ADS)

    Beninato, A.; Emery, T.; Baglio, S.; Andò, B.; Bulsara, A. R.; Jenkins, C.; Palkar, V.

    2013-12-01

    Multiferroic (MF) composites, in which magnetic and ferroelectric orders coexist, represent a very attractive class of materials with promising applications in areas, such as spintronics, memories, and sensors. One of the most important multiferroics is the perovskite phase of bismuth ferrite, which exhibits weak magnetoelectric properties at room temperature; its properties can be enhanced by doping with other elements such as dysprosium. A recent paper has demonstrated that a thin film of Bi0.7Dy0.3FeO3 shows good magnetoelectric coupling. In separate work it has been shown that a carefully crafted ring connection of N (N odd and N ≥ 3) ferroelectric capacitors yields, past a critical point, nonlinear oscillations that can be exploited for electric (E) field sensing. These two results represent the starting point of our work. In this paper the (electrical) hysteresis, experimentally measured in the MF material Bi0.7Dy0.3FeO3, is characterized with the applied magnetic field (B) taken as a control parameter. This yields a "blueprint" for a magnetic (B) field sensor: a ring-oscillator coupling of N = 3 Sawyer-Tower circuits each underpinned by a mutliferroic element. In this configuration, the changes induced in the ferroelectric behavior by the external or "target" B-field are quantified, thus providing a pathway for very low power and high sensitivity B-field sensing.

  20. Nonlinear fluid/structure interaction relating a rupture-disc pressure-relief device. [LMFBR

    SciTech Connect

    Hsieh, B.J.; Kot, C.A.; Shin, Y.W.; Youngdahl, C.K.

    1983-01-01

    Rupture disc assemblies are used in piping network systems as a pressure-relief device. The reverse-buckling type is chosen for application in a liquid metal fast breeder reactor. This assembly is used successfully in systems in which the fluid is highly compressible, such as air; the opening up of the disc by the knife setup is complete. However, this is not true for a liquid system; it had been observed experimentally that the disc may open up only partially or not at all. Therefore, to realistically understand and represent a rupture disc assembly in a liquid environment, the fluid-structure interactions between the liquid medium and the disc assembly must be considered. The methods for analyzing the fluid and the disc and the mechanism interconnecting them are presented. The fluid is allowed to cavitate through a column-cavitation model and the disc is allowed to become plastically deformed through the classic Von Mises' yield criteria, when necessary.

  1. Single-Crystalline Aluminum Nanostructures on a Semiconducting GaAs Substrate for Ultraviolet to Near-Infrared Plasmonics.

    PubMed

    Liu, Hsuan-Wei; Lin, Fan-Cheng; Lin, Shi-Wei; Wu, Jau-Yang; Chou, Bo-Tsun; Lai, Kuang-Jen; Lin, Sheng-Di; Huang, Jer-Shing

    2015-04-28

    Aluminum, as a metallic material for plasmonics, is of great interest because it extends the applications of surface plasmon resonance into the ultraviolet (UV) region and is superior to noble metals in natural abundance, cost, and compatibility with modern semiconductor fabrication processes. Ultrasmooth single-crystalline metallic films are beneficial for the fabrication of high-definition plasmonic nanostructures, especially complex integrated nanocircuits. The absence of surface corrugation and crystal boundaries also guarantees superior optical properties and applications in nanolasers. Here, we present UV to near-infrared plasmonic resonance of single-crystalline aluminum nanoslits and nanoholes. The high-definition nanostructures are fabricated with focused ion-beam milling into an ultrasmooth single-crystalline aluminum film grown on a semiconducting GaAs substrate with a molecular beam epitaxy method. The single-crystalline aluminum film shows improved reflectivity and reduced two-photon photoluminescence (TPPL) due to the ultrasmooth surface. Both linear scattering and nonlinear TPPL are studied in detail. The nanoslit arrays show clear Fano-like resonance, and the nanoholes are found to support both photonic modes and localized surface plasmon resonance. We also found that TPPL generation is more efficient when the excitation polarization is parallel rather than perpendicular to the edge of the aluminum film. Such a counterintuitive phenomenon is attributed to the high refractive index of the GaAs substrate. We show that the polarization of TPPL from aluminum preserves the excitation polarization and is independent of the crystal orientation of the film or substrate. Our study gains insight into the optical property of aluminum nanostructures on a high-index semiconducting GaAs substrate and illustrates a practical route to implement plasmonic devices onto semiconductors for future hybrid nanodevices. PMID:25848830

  2. Annealing Effect of Al2O3 Tunnel Barriers in HfO2-Based ReRAM Devices on Nonlinear Resistive Switching Characteristics.

    PubMed

    Park, Sukhyung; Cho, Kyoungah; Jung, Jungwoo; Kim, Sangsig

    2015-10-01

    In this study, we demonstrate the enhancement of the nonlinear resistive switching characteristics of HfO2-based resistive random access memory (ReRAM) devices by carrying out thermal annealing of Al2O3 tunnel barriers. The nonlinearity of ReRAM device with an annealed Al2O3 tunnel barrier is determined to be 10.1, which is larger than that of the ReRAM device with an as-deposited Al2O3 tunnel barrier. From the electrical characteristics of the ReRAM devices with as-deposited and annealed Al2O3 tunnel barriers, it reveals that there is a trade-off relationship between nonlinearity in low-resistance state (LRS) current and the ratio of the high-resistance state (HRS) and the LRS. The enhancement of nonlinearity is attributed to a change in the conduction mechanism in the LRS of the ReRAM after the annealing. While the conduction mechanism before the annealing follows Ohmic conduction, the conduction of the ReRAM after the annealing is controlled by a trap-controlled space charge limited conduction mechanism. Additionally, the annealing of the Al2O3 tunnel barriers is also shown to improve the endurance and retention characteristics. PMID:26726373

  3. Surface passivation of semiconducting oxides by self-assembled nanoparticles

    PubMed Central

    Park, Dae-Sung; Wang, Haiyuan; Vasheghani Farahani, Sepehr K.; Walker, Marc; Bhatnagar, Akash; Seghier, Djelloul; Choi, Chel-Jong; Kang, Jie-Hun; McConville, Chris F.

    2016-01-01

    Physiochemical interactions which occur at the surfaces of oxide materials can significantly impair their performance in many device applications. As a result, surface passivation of oxide materials has been attempted via several deposition methods and with a number of different inert materials. Here, we demonstrate a novel approach to passivate the surface of a versatile semiconducting oxide, zinc oxide (ZnO), evoking a self-assembly methodology. This is achieved via thermodynamic phase transformation, to passivate the surface of ZnO thin films with BeO nanoparticles. Our unique approach involves the use of BexZn1-xO (BZO) alloy as a starting material that ultimately yields the required coverage of secondary phase BeO nanoparticles, and prevents thermally-induced lattice dissociation and defect-mediated chemisorption, which are undesirable features observed at the surface of undoped ZnO. This approach to surface passivation will allow the use of semiconducting oxides in a variety of different electronic applications, while maintaining the inherent properties of the materials. PMID:26757827

  4. Surface passivation of semiconducting oxides by self-assembled nanoparticles

    NASA Astrophysics Data System (ADS)

    Park, Dae-Sung; Wang, Haiyuan; Vasheghani Farahani, Sepehr K.; Walker, Marc; Bhatnagar, Akash; Seghier, Djelloul; Choi, Chel-Jong; Kang, Jie-Hun; McConville, Chris F.

    2016-01-01

    Physiochemical interactions which occur at the surfaces of oxide materials can significantly impair their performance in many device applications. As a result, surface passivation of oxide materials has been attempted via several deposition methods and with a number of different inert materials. Here, we demonstrate a novel approach to passivate the surface of a versatile semiconducting oxide, zinc oxide (ZnO), evoking a self-assembly methodology. This is achieved via thermodynamic phase transformation, to passivate the surface of ZnO thin films with BeO nanoparticles. Our unique approach involves the use of BexZn1-xO (BZO) alloy as a starting material that ultimately yields the required coverage of secondary phase BeO nanoparticles, and prevents thermally-induced lattice dissociation and defect-mediated chemisorption, which are undesirable features observed at the surface of undoped ZnO. This approach to surface passivation will allow the use of semiconducting oxides in a variety of different electronic applications, while maintaining the inherent properties of the materials.

  5. Piezo-phototronic effect devices

    DOEpatents

    Wang, Zhong L.; Yang, Qing

    2013-09-10

    A semiconducting device includes a piezoelectric structure that has a first end and an opposite second end. A first conductor is in electrical communication with the first end and a second conductor is in electrical communication with the second end so as to form an interface therebetween. A force applying structure is configured to maintain an amount of strain in the piezoelectric member sufficient to generate a desired electrical characteristic in the semiconducting device.

  6. Nonlinear Magnetic Dynamics and The Switching Phase Diagrams in Spintronic Devices

    NASA Astrophysics Data System (ADS)

    Yan, Shu

    Spin-transfer torque induced magnetic switching, by which the spin-polarized current transfers its magnetic moment to the ferromagnetic layer and changes its magnetization, holds great promise towards faster and smaller magnetic bits in data-storage applications due to the lower power consumption and better scalability. We propose an analytic approach which can be used to calculate the switching phase diagram of a nanomagnetic system in the presence of both magnetic field and spin-transfer torque in an exact fashion. This method is applied to the study of switching conditions for the uniaxial, single domain magnetic layers in different spin-transfer devices. In a spin valve with spin polarization collinear with the easy axis, we get a modified Stoner-Wohlfarth astroid which represents many of the features that have been found in experiment. It also shows a self-crossing boundary and demonstrates a region with three stable equilibria. We demonstrate that the region of stable equilibria with energy near the maximum can be reached only through a narrow bottleneck in the field space, which sets a stringent requirement for magnetic field alignment in the experiments. Switching diagrams are then calculated for the setups with magnetic field not perfectly aligned with the easy axis. In a ferromagnet-heavy-metal bilayer device with strong spin Hall effect, the in plane current becomes spin-polarized and transfers its magnetic moment to the ferromagnetic layer by diffusion. The three-dimensional asymmetric phase diagram is calculated. In the case that the external field is confined in the vertical plane defined by the direction of the current and the easy axis, the spin-transfer torque shifts the conventional in-plane (IP) equilibria within the same plane, and also creates two out-of-plane (OOP) equilibria, one of which can be stable. The threshold switching currents for IP switching and OOP switching are discussed. We also address the magnetic switching processes. Damping

  7. Organic field-effect transistors based on a crosslinkable polymer blend as the semiconducting layer

    NASA Astrophysics Data System (ADS)

    Yan, He; Yoon, Myung-Han; Facchetti, Antonio; Marks, Tobin J.

    2005-10-01

    For fabrication of top-gate polymer-based organic field-effect transistors (OFETs), it is essential that the semiconducting layer remain intact during spin coating of the overlying dielectric layer. This requirement severely limits the applicable solvent and materials combinations. We show here that a crosslinkable polymer blend consisting of a p-type semiconducting polymer {e.g., TFB; poly[9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine]} and an electroactive crosslinkable silyl reagent {e.g., TPDSi2; 4,4'-bis[(p-trichloro-silylpropylphenyl)phenylamino]biphenyl} is effective as the semiconducting layer in a top-gate bottom-contact OFET device. The TFB +TPDSi2 semiconducting blend is prepared by spin-coating in ambient. The crosslinking process occurs during spin-coating in air and is completed by curing at 90 °C, which renders the resulting film insoluble in common organic solvents and allows subsequent deposition of dielectric layers from a wide range of organic solvents. We also show that the presence of TPDSi2 in the semiconductor layer significantly reduces typical TFB-source-drain threshold voltages in bottom-contact devices, likely due to favorable interfacial TPDSi2-gold electrode interactions.

  8. Nonlinear fluid/structure interaction relating a rupture-disc pressure-relief device

    SciTech Connect

    Hsieh, B.J.; Kot, C.A.; Shin, Y.W.; Youngdahi, C.K.

    1983-01-01

    Rupture disc assemblies are used in piping network systems as pressure-relief devices. The reverse-buckling type discs are chosen for application in heat transport systems of liquid metal fast breeder reactors. When the pressure on the disc is of sufficient magnitude and duration, the disc develops large displacement, is consequently torn open by a cutting-knife setup and thus relieves the excess pressure. Such disc assemblies are used very successfully in systems in which the fluid is highly compressible, e.g., air; the opening of the disc by the knife setup is complete. However, this is not true for a liquid system; in this case it has been observed experimentally that the disc may open up only partially or not at all. Therefore, to understand and realistically represent a rupture disc assembly in a liquid environment, the fluid-structure interactions between the liquid medium and the disc assembly must be considered. In this paper, methods for analyzing the fluid and the disc and the mechanism interconnecting them are presented. When necessary the fluid is allowed to cavitate through a column separation model and the disc can become plastically deformed using the classic Von Mises' yield criteria.

  9. Investigation of charge injection characteristics in diketopyrrolopyrrole ambipolar semiconducting polymers

    NASA Astrophysics Data System (ADS)

    Lee, Seon Jeng; Jung, Seok Heon; Lee, Jin-Kyun; Kim, Cheawon; Lee, Mi Jung

    2014-10-01

    A semiconducting polymers with conjugated diketopyrrolopyrrole (DPP) unit was developed for high performance ambipolar organic field-effect transistors (OFETs). We report electrical characteristics of DPP OFETs in various ways which measured transistor and inverter performance with various bias conditions and self-assembled monolayers (SAMs) treatment. Ambipolar DPP conjugated polymer OFETs showed high hole and electron mobility of μh=0.57 cm2V-1s-1 and μe=0.51 cm2V-1s-1 with O2 plasma treatment and 1-decanethiol SAMs treatment, respectively with annealing at 100°C. Contact resistance effect on mobilities was investigated by measuring contact resistance during device operation through gated four-point probe (gFPP) and simultaneous contact resistance extraction model directly from current voltage characteristics.

  10. Semiconducting Ge clathrates: Promising candidates for thermoelectric applications

    NASA Astrophysics Data System (ADS)

    Nolas, G. S.; Cohn, J. L.; Slack, G. A.; Schujman, S. B.

    1998-07-01

    Transport properties of polycrystalline Ge clathrates with general composition Sr8Ga16Ge30 are reported in the temperature range 5 K⩽T⩽300 K. These compounds exhibit N-type semiconducting behavior with relatively high Seebeck coefficients and electrical conductivity, and room temperature carrier concentrations in the range of 1017-1018cm-3. The thermal conductivity is more than an order of magnitude smaller than that of crystalline germanium and has a glasslike temperature dependence. The resulting thermoelectric figure of merit, ZT, at room temperature for the present samples is 1/4 that of Bi2Te3 alloys currently used in devices for thermoelectric cooling. Extrapolating our measurements to above room temperature, we estimate that ZT>1 at T>700 K, thus exceeding that of most known materials.

  11. Metal Contacts on Semiconducting Two-Dimension Crystals

    NASA Astrophysics Data System (ADS)

    Liu, Han; Neal, Adam; Du, Yuchen; Ye, Peide

    2013-03-01

    Semiconducting 2-D crystals, such as MoS2, WSe2, are viewed as promising candidates for electronic applications for their high carrier mobility, thermal stability, compatibility to CMOS process, and superior immunity to short channel effects. However, with the difficulty in ion implantation, the metal contacts on 2-D crystals are yet with large contact resistance, thus eliminates further device performance. We study different metal contacts from low work function to high work function metals on MoS2 and WSe2 crystals with various thicknesses and discuss the Fermi level pinning at the metal/semiconductor interface. Effective Schottky Barrier Heights (SBHs) are also measured. Molecular doping and dual-side contacts metals are performed as two tentative solutions to reduce the effective SBHs, and high-performance of field effect transistors are achieved by reduced contact resistance.

  12. Growth of single crystals of organic salts with large second-order optical nonlinearities by solution processes for devices

    NASA Technical Reports Server (NTRS)

    Leslie, Thomas M.

    1995-01-01

    Data obtained from the electric field induced second harmonic generation (EFISH) and Kurtz Powder Methods will be provided to MSFC for further refinement of their method. A theoretical model for predicting the second-order nonlinearities of organic salts is being worked on. Another task is the synthesis of a number of salts with various counterions. Several salts with promising SHG activities and new salts will be tested for the presence of two crystalline forms. The materials will be recrystallized from dry and wet solvents and compared for SHG efficiency. Salts that have a high SHG efficiency and no tendency to form hydrates will be documented. The synthesis of these materials are included in this report. A third task involves method to aid in the growth of large, high quality single crystals by solution processes. These crystals will be characterized for their applicability in the fabrication of devices that will be incorporated into optical computers in future programs. Single crystals of optimum quality may be obtained by crystal growth in low-gravity. The final task is the design of a temperature lowering single crystal growth apparatus for ground based work. At least one prototype will be built.

  13. Single-Chain Semiconducting Polymer Dots

    PubMed Central

    2015-01-01

    This work describes the preparation and validation of single-chain semiconducting polymer dots (sPdots), which were generated using a method based on surface immobilization, washing, and cleavage. The sPdots have an ultrasmall size of ∼3.0 nm as determined by atomic force microscopy, a size that is consistent with the anticipated diameter calculated from the molecular weight of the single-chain semiconducting polymer. sPdots should find use in biology and medicine as a new class of fluorescent probes. The FRET assay this work presents is a simple and rapid test to ensure methods developed for preparing sPdot indeed produced single-chain Pdots as designed. PMID:25521606

  14. Low bandgap semiconducting polymers for polymeric photovoltaics.

    PubMed

    Liu, Chang; Wang, Kai; Gong, Xiong; Heeger, Alan J

    2016-08-22

    In order to develop high performance polymer solar cells (PSCs), full exploitation of the sun-irradiation from ultraviolet (UV) to near infrared (NIR) is one of the key factors to ensure high photocurrents and thus high efficiency. In this review, five of the effective design rules for approaching LBG semiconducting polymers with high molar absorptivity, suitable energy levels, high charge carrier mobility and high solubility in organic solvents are overviewed. These design stratagems include fused heterocycles for facilitating π-electron flowing along the polymer backbone, groups/atoms bridging adjacent rings for maintaining a high planarity, introduction of electron-withdrawing units for lowering the bandgap (Eg), donor-acceptor (D-A) copolymerization for narrowing Eg and 2-dimensional conjugation for broadened absorption and enhanced hole mobility. It has been demonstrated that LBG semiconducting polymers based on electron-donor units combined with strong electron-withdrawing units possess excellent electronic and optic properties, emerging as excellent candidates for efficient PSCs. While for ultrasensitive photodetectors (PDs), which have intensive applications in both scientific and industrial sectors, sensing from the UV to the NIR region is of critical importance. For polymer PDs, Eg as low as 0.8 eV has been obtained through a rational design stratagem, covering a broad wavelength range from the UV to the NIR region (1450 nm). However, the response time of the polymer PDs are severely limited by the hole mobility of LBG semiconducting polymers, which is significantly lower than those of the inorganic materials. Thus, further advancing the hole mobility of LBG semiconducting polymers is of equal importance as broadening the spectral response for approaching uncooled ultrasensitive broadband polymer PDs in the future study. PMID:26548402

  15. Predicting X-ray absorption spectra of semiconducting polymers for electronic structure and morphology characterization

    NASA Astrophysics Data System (ADS)

    Su, Gregory; Patel, Shrayesh; Pemmaraju, C. Das; Kramer, Edward; Prendergast, David; Chabinyc, Michael

    2015-03-01

    Core-level X-ray absorption spectroscopy (XAS) reveals important information on the electronic structure of materials and plays a key role in morphology characterization. Semiconducting polymers are the active component in many organic electronics. Their electronic properties are critically linked to device performance, and a proper understanding of semiconducting polymer XAS is crucial. Techniques such as resonant X-ray scattering rely on core-level transitions to gain materials contrast and probe orientational order. However, it is difficult to identify these transitions based on experiments alone, and complementary simulations are required. We show that first-principles calculations can capture the essential features of experimental XAS of semiconducting polymers, and provide insight into which molecular model, such as oligomers or periodic boundary conditions, are best suited for XAS calculations. Simulated XAS can reveal contributions from individual atoms and be used to visualize molecular orbitals. This allows for improved characterization of molecular orientation and scattering analysis. These predictions lay the groundwork for understanding how chemical makeup is linked to electronic structure, and to properly utilize experiments to characterize semiconducting polymers.

  16. High purity isolation and quantification of semiconducting carbon nanotubes via column chromatography.

    PubMed

    Tulevski, George S; Franklin, Aaron D; Afzali, Ali

    2013-04-23

    The isolation of semiconducting carbon nanotubes (CNTs) to ultrahigh (ppb) purity is a prerequisite for their integration into high-performance electronic devices. Here, a method employing column chromatography is used to isolate semiconducting nanotubes to 99.9% purity. The study finds that by modifying the solution preparation step, both the metallic and semiconducting fraction are resolved and elute using a single surfactant system, allowing for multiple iterations. Iterative processing enables a far more rapid path to achieving the level of purities needed for high performance computing. After a single iteration, the metallic peak in the absorption spectra is completely attenuated. Although absorption spectroscopy is typically used to characterize CNT purity, it is found to be insufficient in quantifying solutions of high purity (>98 to 99%) due to low signal-to-noise in the metallic region of ultrahigh purity solutions. Therefore, a high throughput electrical testing method was developed to quantify the degree of separation by characterizing ∼4000 field-effect transistors fabricated from the separated nanotubes after multiple iterations of the process. The separation and characterization methods described here provide a path to produce the ultrahigh purity semiconducting CNT solutions needed for high performance electronics. PMID:23484490

  17. Semiconducting polymers with nanocrystallites interconnected via boron-doped carbon nanotubes.

    PubMed

    Yu, Kilho; Lee, Ju Min; Kim, Junghwan; Kim, Geunjin; Kang, Hongkyu; Park, Byoungwook; Ho Kahng, Yung; Kwon, Sooncheol; Lee, Sangchul; Lee, Byoung Hun; Kim, Jehan; Park, Hyung Il; Kim, Sang Ouk; Lee, Kwanghee

    2014-12-10

    Organic semiconductors are key building blocks for future electronic devices that require unprecedented properties of low-weight, flexibility, and portability. However, the low charge-carrier mobility and undesirable processing conditions limit their compatibility with low-cost, flexible, and printable electronics. Here, we present significantly enhanced field-effect mobility (μ(FET)) in semiconducting polymers mixed with boron-doped carbon nanotubes (B-CNTs). In contrast to undoped CNTs, which tend to form undesired aggregates, the B-CNTs exhibit an excellent dispersion in conjugated polymer matrices and improve the charge transport between polymer chains. Consequently, the B-CNT-mixed semiconducting polymers enable the fabrication of high-performance FETs on plastic substrates via a solution process; the μFET of the resulting FETs reaches 7.2 cm(2) V(-1) s(-1), which is the highest value reported for a flexible FET based on a semiconducting polymer. Our approach is applicable to various semiconducting polymers without any additional undesirable processing treatments, indicating its versatility, universality, and potential for high-performance printable electronics. PMID:25372930

  18. Suppression of Nonlinear Interactions in Resonant Macroscopic Quantum Devices: The Example of the Solid-State Ring Laser Gyroscope

    SciTech Connect

    Schwartz, Sylvain; Feugnet, Gilles; Pocholle, Jean-Paul; Gutty, Francois; Bouyer, Philippe

    2008-05-09

    We report fine-tuning of nonlinear interactions in a solid-state ring laser gyroscope by vibrating the gain medium along the cavity axis. We demonstrate both experimentally and theoretically that nonlinear interactions vanish for some values of the vibration parameters, leading to quasi-ideal rotation sensing. We eventually point out that our conclusions can be mapped onto other subfields of physics such as ring-shaped superfluid configurations, where nonlinear interactions could be tuned by using Feshbach resonance.

  19. Efficient photovoltaic cells from semiconducting polymer heterojunctions

    NASA Astrophysics Data System (ADS)

    Jenekhe, Samson A.; Yi, Shujian

    2000-10-01

    Solar cells made from spin-coated bilayer thin-film heterojunctions of poly(p-phenylene vinylene) and poly(benzimidazobenzophenanthroline ladder) were found to have photovoltaic charge collection efficiency as high as 49%. The power conversion efficiency varied from 1.4% under sunlight illumination to 2.0% at the peak wavelength. A space-charge region around the polymer/polymer interface, Ohmic contacts at the electrodes, and complementary absorption bands of the semiconducting polymers, play important roles in the efficient charge collection in the photocells.

  20. Semiconducting conjugated polymer-inorganic tetrapod nanocomposites.

    PubMed

    Jung, Jaehan; Pang, Xinchang; Feng, Chaowei; Lin, Zhiqun

    2013-06-25

    Cadmium telluride (CdTe) tetrapods were synthesized via multiple injections of the Te precursor by utilizing bifunctional ligands. Subsequently, tetrapod-shaped semiconducting inorganic-organic nanocomposites (i.e., P3HT-CdTe tetrapod nanocomposites) were produced by directly grafting conjugated polymer ethynyl-terminated poly(3-hexylthiophene) (i.e., P3HT-≡) onto azide-functionalized CdTe tetrapods (i.e., CdTe-N3) via a catalyst-free click chemistry. The intimate contact between P3HT and CdTe tetrapod rendered the effective dispersion of CdTe tetrapods in nanocomposites and facilitated their efficient electronic interaction. The success of coupling reaction was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The grafting density of P3HT chains on the CdTe tetrapods was estimated by thermogravimetric analysis. The photophysical properties of P3HT-CdTe tetrapod nanocomposites were studied using UV-vis and photoluminescence spectroscopies. These intimate semiconducting conjugated polymer-tetrapod nanocomposites may offer a maximized interface between conjugated polymers and tetrapods for efficient charge separation and enhanced charge transport regardless of their orientation for potential application in hybrid solar cells with improved power conversion efficiency. PMID:23600796

  1. Label-free immunodetection with CMOS-compatible semiconducting nanowires.

    PubMed

    Stern, Eric; Klemic, James F; Routenberg, David A; Wyrembak, Pauline N; Turner-Evans, Daniel B; Hamilton, Andrew D; LaVan, David A; Fahmy, Tarek M; Reed, Mark A

    2007-02-01

    Semiconducting nanowires have the potential to function as highly sensitive and selective sensors for the label-free detection of low concentrations of pathogenic microorganisms. Successful solution-phase nanowire sensing has been demonstrated for ions, small molecules, proteins, DNA and viruses; however, 'bottom-up' nanowires (or similarly configured carbon nanotubes) used for these demonstrations require hybrid fabrication schemes, which result in severe integration issues that have hindered widespread application. Alternative 'top-down' fabrication methods of nanowire-like devices produce disappointing performance because of process-induced material and device degradation. Here we report an approach that uses complementary metal oxide semiconductor (CMOS) field effect transistor compatible technology and hence demonstrate the specific label-free detection of below 100 femtomolar concentrations of antibodies as well as real-time monitoring of the cellular immune response. This approach eliminates the need for hybrid methods and enables system-scale integration of these sensors with signal processing and information systems. Additionally, the ability to monitor antibody binding and sense the cellular immune response in real time with readily available technology should facilitate widespread diagnostic applications. PMID:17268465

  2. Room temperature infrared imaging sensors based on highly purified semiconducting carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Wei, Nan; Zhao, Qingliang; Zhang, Dehui; Wang, Sheng; Peng, Lian-Mao

    2015-04-01

    High performance infrared (IR) imaging systems usually require expensive cooling systems, which are highly undesirable. Here we report the fabrication and performance characteristics of room temperature carbon nanotube (CNT) IR imaging sensors. The CNT IR imaging sensor is based on aligned semiconducting CNT films with 99% purity, and each pixel or device of the imaging sensor consists of aligned strips of CNT asymmetrically contacted by Sc and Pd. We found that the performance of the device is dependent on the CNT channel length. While short channel devices provide a large photocurrent and a rapid response of about 110 μs, long channel length devices exhibit a low dark current and a high signal-to-noise ratio which are critical for obtaining high detectivity. In total, 36 CNT IR imagers are constructed on a single chip, each consists of 3 × 3 pixel arrays. The demonstrated advantages of constructing a high performance IR system using purified semiconducting CNT aligned films include, among other things, fast response, excellent stability and uniformity, ideal linear photocurrent response, high imaging polarization sensitivity and low power consumption.High performance infrared (IR) imaging systems usually require expensive cooling systems, which are highly undesirable. Here we report the fabrication and performance characteristics of room temperature carbon nanotube (CNT) IR imaging sensors. The CNT IR imaging sensor is based on aligned semiconducting CNT films with 99% purity, and each pixel or device of the imaging sensor consists of aligned strips of CNT asymmetrically contacted by Sc and Pd. We found that the performance of the device is dependent on the CNT channel length. While short channel devices provide a large photocurrent and a rapid response of about 110 μs, long channel length devices exhibit a low dark current and a high signal-to-noise ratio which are critical for obtaining high detectivity. In total, 36 CNT IR imagers are constructed on a

  3. Doping Scheme of Semiconducting Atomic Chains

    NASA Technical Reports Server (NTRS)

    Toshishige, Yamada; Saini, Subhash (Technical Monitor)

    1998-01-01

    Atomic chains, precise structures of atomic scale created on an atomically regulated substrate surface, are candidates for future electronics. A doping scheme for intrinsic semiconducting Mg chains is considered. In order to suppress the unwanted Anderson localization and minimize the deformation of the original band shape, atomic modulation doping is considered, which is to place dopant atoms beside the chain periodically. Group I atoms are donors, and group VI or VII atoms are acceptors. As long as the lattice constant is long so that the s-p band crossing has not occurred, whether dopant atoms behave as donors or acceptors is closely related to the energy level alignment of isolated atomic levels. Band structures are calculated for Br-doped (p-type) and Cs-doped (n-type) Mg chains using the tight-binding theory with universal parameters, and it is shown that the band deformation is minimized and only the Fermi energy position is modified.

  4. Response functions of semiconducting lithium indium diselenide

    NASA Astrophysics Data System (ADS)

    Lukosi, Eric; Chvala, Ondrej; Stowe, Ashley

    2016-06-01

    This paper presents the results of a computational investigation that determined the gamma-ray and neutron response functions of a new semiconducting material, 6LiInSe2, which is very sensitive to thermal neutrons. Both MCNP6 simulations and custom post-processing/simulation techniques were used to determine various detection properties of LISe. The computational study included consideration of energetic electron escape, the contribution from the activation of 115In and subsequent decay of 116In, triton and alpha particle escape from the 6Li reaction pathway, and the effect of incomplete charge collection when detecting neutrons via the 6Li reaction pathway. The result of neutron detection with incomplete charge collection was compared to experimental results and showed general agreement, where holes exhibit a lower mobility-lifetime product than electrons, as expected for compound semiconductors.

  5. semiconducting nanostructures: morphology and thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Culebras, Mario; Torán, Raquel; Gómez, Clara M.; Cantarero, Andrés

    2014-08-01

    Semiconducting metallic oxides, especially perosvkite materials, are great candidates for thermoelectric applications due to several advantages over traditionally metallic alloys such as low production costs and high chemical stability at high temperatures. Nanostructuration can be the key to develop highly efficient thermoelectric materials. In this work, La 1- x Ca x MnO 3 perosvkite nanostructures with Ca as a dopant have been synthesized by the hydrothermal method to be used in thermoelectric applications at room temperature. Several heat treatments have been made in all samples, leading to a change in their morphology and thermoelectric properties. The best thermoelectric efficiency has been obtained for a Ca content of x=0.5. The electrical conductivity and Seebeck coefficient are strongly related to the calcium content.

  6. Ordered Semiconducting Nitrogen-Graphene Alloys

    SciTech Connect

    Xiang, H. J.; Huang, B.; Li, Z. Y.; Wei, S. H.; Yang, J. L.; Gong, X. G.

    2012-01-01

    The interaction between substitutional nitrogen atoms in graphene is studied by performing first-principles calculations. The effective nearest-neighbor interaction between nitrogen dopants is found to be highly repulsive because of the strong electrostatic repulsion between nitrogen atoms. This interaction prevents the full nitrogen-carbon phase separation in nitrogen-doped graphene. Interestingly, there are two relatively stable nitrogen-nitrogen pair configurations, whose stability can be attributed to the anisotropy in the charge redistribution induced by nitrogen doping. We reveal two stable, ordered, semiconducting N-doped graphene structures, C{sub 3}N and C{sub 12}N, through the cluster-expansion technique and particle-swarm optimization method. In particular, we show that C{sub 12}N has a direct band gap of 0.98 eV. The heterojunctions between C{sub 12}N and graphene nanoribbons might be a promising basis for organic solar cells.

  7. Ferromagnetism and semiconducting of boron nanowires

    PubMed Central

    2012-01-01

    More recently, motivated by extensively technical applications of carbon nanostructures, there is a growing interest in exploring novel non-carbon nanostructures. As the nearest neighbor of carbon in the periodic table, boron has exceptional properties of low volatility and high melting point and is stronger than steel, harder than corundum, and lighter than aluminum. Boron nanostructures thus are expected to have broad applications in various circumstances. In this contribution, we have performed a systematical study of the stability and electronic and magnetic properties of boron nanowires using the spin-polarized density functional calculations. Our calculations have revealed that there are six stable configurations of boron nanowires obtained by growing along different base vectors from the unit cell of the bulk α-rhombohedral boron (α-B) and β-rhombohedral boron (β-B). Well known, the boron bulk is usually metallic without magnetism. However, theoretical results about the magnetic and electronic properties showed that, whether for the α-B-based or the β-B-based nanowires, their magnetism is dependent on the growing direction. When the boron nanowires grow along the base vector [001], they exhibit ferromagnetism and have the magnetic moments of 1.98 and 2.62 μB, respectively, for the α-c [001] and β-c [001] directions. Electronically, when the boron nanowire grows along the α-c [001] direction, it shows semiconducting and has the direct bandgap of 0.19 eV. These results showed that boron nanowires possess the unique direction dependence of the magnetic and semiconducting behaviors, which are distinctly different from that of the bulk boron. Therefore, these theoretical findings would bring boron nanowires to have many promising applications that are novel for the boron bulk. PMID:23244063

  8. Nonlinear glass waveguide devices fabricated by femtosecond laser writing with thermal poling and waveguide modeling for silver ion exchange in glass

    NASA Astrophysics Data System (ADS)

    Li, Guangyu

    Integrated optics technology has led to the development of miniaturized optical devices that can offer high functionality on a single chip. This technology has proven useful for a host of applications, including telecommunications, sensing, navigation, quantum optics and astronomy. Complex integrated optical devices, such as lasers, frequency converters, filters and demultiplexers, have been developed in a variety of substrate materials, including crystals, glasses, polymers and semiconductors. This thesis contributes to the field of glass integrated optics with two primary additions: Direct waveguide writing, using femtosecond lasers, is combined with thermal poling to demonstrate electro-optic (EO) and quasi-phase matched (QPM), second-order, nonlinear, parametric waveguide devices in bulk fused silica for the first time. In particular, a 25.6 mm long waveguide EO modulator in bulk glass is reported that has an effective EO coefficient of 0.17 pm/V, which is the highest value obtained to date for a planar, glass, waveguide device. Frequency doubling (SHG) is also demonstrated in a QPM, glass, waveguide device where the chi(2) grating is produced using a new method for the selective erasure of a uniformly poled region. A 1064 nm to 532 nm conversion efficiency of approximately 8 x 10-6%W-1cm-2 is obtained for this device, and it is predicted that values several hundred times larger should be achievable through careful device optimization. The second contribution of this thesis is a systematic modeling study of the silver ion exchange process in a single-alkali (Na) glass based on first principles. It is shown for the first time that a Fickian diffusion analysis, combined with a concentration-dependent diffusion coefficient in the absence of free parameters, is able to predict 2-D refractive index waveguide profiles that are in relatively good agreement with measured results. Low loss, large diameter, ring resonators are also fabricated by silver ion exchange in

  9. Tunable surface plasmon devices

    DOEpatents

    Shaner, Eric A.; Wasserman, Daniel

    2011-08-30

    A tunable extraordinary optical transmission (EOT) device wherein the tunability derives from controlled variation of the dielectric constant of a semiconducting material (semiconductor) in evanescent-field contact with a metallic array of sub-wavelength apertures. The surface plasmon resonance wavelength can be changed by changing the dielectric constant of the dielectric material. In embodiments of this invention, the dielectric material is a semiconducting material. The dielectric constant of the semiconducting material in the metal/semiconductor interfacial region is controllably adjusted by adjusting one or more of the semiconductor plasma frequency, the concentration and effective mass of free carriers, and the background high-frequency dielectric constant in the interfacial region. Thermal heating and/or voltage-gated carrier-concentration changes may be used to variably adjust the value of the semiconductor dielectric constant.

  10. Two-dminensional exciton states in monolayer semiconducting phosphorus alotropes

    NASA Astrophysics Data System (ADS)

    Rocha, Alexandre R.; Villegas, Cesar E. P.

    During the last decade, novel two-dimensional (2D) semiconducting materials have been synthesized and characterised. As a result, there have been several theoretical and experimental proposals to incorporate 2D materials for designing next generation electronic and optoelectronics devices. In particular, it has been demonstrated that light absorption in phosphorus-based monolayers can span the whole visible spectrum, suggesting they could be used for optolectronic applications. A key ingredient for optolectronic applications is the presence of excitons and their subsequent diffusion along a donor material. This is influenced by the character of the different excitations taking place, as well as, the exciton binding energy. Therefore, In this work we use accurate many-body corrected density functional theory by means of GW-BSE methodology to elucidate the most important optical transitions, exciton energy spectrum as well as exciton extension in different types of phosphorene materials. In addition, we solve the Schrodinger equation for different 2D screened potentials and estimate the 2D exciton energy levels and radius extension. Finally, in order to assess further studies based on these systems, we provide a simple analityc expression for estimating 2D exciton energy levels. Research funded by FAPESP-Brazil.

  11. High temperature photoelectron emission and surface photovoltage in semiconducting diamond

    SciTech Connect

    Williams, G. T.; Cooil, S. P.; Roberts, O. R.; Evans, S.; Langstaff, D. P.; Evans, D. A.

    2014-08-11

    A non-equilibrium photovoltage is generated in semiconducting diamond at above-ambient temperatures during x-ray and UV illumination that is sensitive to surface conductivity. The H-termination of a moderately doped p-type diamond (111) surface sustains a surface photovoltage up to 700 K, while the clean (2 × 1) reconstructed surface is not as severely affected. The flat-band C 1s binding energy is determined from 300 K measurement to be 283.87 eV. The true value for the H-terminated surface, determined from high temperature measurement, is (285.2 ± 0.1) eV, corresponding to a valence band maximum lying 1.6 eV below the Fermi level. This is similar to that of the reconstructed (2 × 1) surface, although this surface shows a wider spread of binding energy between 285.2 and 285.4 eV. Photovoltage quantification and correction are enabled by real-time photoelectron spectroscopy applied during annealing cycles between 300 K and 1200 K. A model is presented that accounts for the measured surface photovoltage in terms of a temperature-dependent resistance. A large, high-temperature photovoltage that is sensitive to surface conductivity and photon flux suggests a new way to use moderately B-doped diamond in voltage-based sensing devices.

  12. Uniformly spaced arrays of purely semiconducting carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Falk, Abram; Kumar, Bharat; Tulevski, George; Farmer, Damon; Hannon, James; Han, Shu-Jen

    Patterning uniformly spaced arrays of carbon nanotubes (CNTs) is a key challenge for carbon electronics. Our group adopts a hybrid approach to meeting this goal. We use top-down lithography to pattern trenches on chips. We then use surface-selective chemical monolayers to facilitate the bottom-up assembly of solution-processed CNTs into these trenches. Previously, we showed large-scale integration of CNTs based on this approach, but modifications to this process have been needed in order to improve the yield and decrease the fraction of non-switching devices. Our latest results show a high degree of selectivity, alignment and yield of successfully placed CNTs at a 100 nm pitch. Electrical measurements confirm that these chemically placed CNTs are nearly 100% semiconducting and of similar quality to randomly dispersed ones. I will then discuss our strategies for increasing the CNT density and extending these results from chip- to wafer-scale electronics. email: alfalk@us.ibm.com.

  13. Intrinsic nature of visible-light absorption in amorphous semiconducting oxides

    SciTech Connect

    Kang, Youngho; Song, Hochul; Han, Seungwu; Nahm, Ho-Hyun; Jeon, Sang Ho; Cho, Youngmi

    2014-03-01

    To enlighten microscopic origin of visible-light absorption in transparent amorphous semiconducting oxides, the intrinsic optical property of amorphous InGaZnO{sub 4} is investigated by considering dipole transitions within the quasiparticle band structure. In comparison with the crystalline InGaZnO{sub 4} with the optical gap of 3.6 eV, the amorphous InGaZnO{sub 4} has two distinct features developed in the band structure that contribute to significant visible-light absorption. First, the conduction bands are down-shifted by 0.55 eV mainly due to the undercoordinated In atoms, reducing the optical gap between extended states to 2.8 eV. Second, tail states formed by localized oxygen p orbitals are distributed over ∼0.5 eV near the valence edge, which give rise to substantial subgap absorption. The fundamental understanding on the optical property of amorphous semiconducting oxides based on underlying electronic structure will pave the way for resolving instability issues in recent display devices incorporating the semiconducting oxides.

  14. Growth of semiconducting single-wall carbon nanotubes with a narrow band-gap distribution

    PubMed Central

    Zhang, Feng; Hou, Peng-Xiang; Liu, Chang; Wang, Bing-Wei; Jiang, Hua; Chen, Mao-Lin; Sun, Dong-Ming; Li, Jin-Cheng; Cong, Hong-Tao; Kauppinen, Esko I.; Cheng, Hui-Ming

    2016-01-01

    The growth of high-quality semiconducting single-wall carbon nanotubes with a narrow band-gap distribution is crucial for the fabrication of high-performance electronic devices. However, the single-wall carbon nanotubes grown from traditional metal catalysts usually have diversified structures and properties. Here we design and prepare an acorn-like, partially carbon-coated cobalt nanoparticle catalyst with a uniform size and structure by the thermal reduction of a [Co(CN)6]3− precursor adsorbed on a self-assembled block copolymer nanodomain. The inner cobalt nanoparticle functions as active catalytic phase for carbon nanotube growth, whereas the outer carbon layer prevents the aggregation of cobalt nanoparticles and ensures a perpendicular growth mode. The grown single-wall carbon nanotubes have a very narrow diameter distribution centred at 1.7 nm and a high semiconducting content of >95%. These semiconducting single-wall carbon nanotubes have a very small band-gap difference of ∼0.08 eV and show excellent thin-film transistor performance. PMID:27025784

  15. Enhanced x-ray detection sensitivity in semiconducting polymer diodes containing metallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Mills, Christopher A.; Al-Otaibi, Hulayel; Intaniwet, Akarin; Shkunov, Maxim; Pani, Silvia; Keddie, Joseph L.; Sellin, Paul J.

    2013-07-01

    Semiconducting polymer X-radiation detectors are a completely new family of low-cost radiation detectors with potential application as beam monitors or dosimeters. These detectors are easy to process, mechanically flexible, relatively inexpensive, and able to cover large areas. However, their x-ray photocurrents are typically low as, being composed of elements of low atomic number (Z), they attenuate x-rays weakly. Here, the addition of high-Z nanoparticles is used to increase the x-ray attenuation without sacrificing the attractive properties of the host polymer. Two types of nanoparticles (NPs) are compared: metallic tantalum and electrically insulating bismuth oxide. The detection sensitivity of 5 µm thick semiconducting poly([9,9-dioctylfluorenyl-2,7-diyl]-co-bithiophene) diodes containing tantalum NPs is four times greater than that for the analogous NP-free devices; it is approximately double that of diodes containing an equal volume of bismuth oxide NPs. The x-ray induced photocurrent output of the diodes increases with an increased concentration of NPs. However, contrary to the results of theoretical x-ray attenuation calculations, the experimental current output is higher for the lower-Z tantalum diodes than the bismuth oxide diodes, at the same concentration of NP loading. This result is likely due to the higher tantalum NP electrical conductivity, which increases charge transport through the semiconducting polymer, leading to increased diode conductivity.

  16. Room temperature infrared imaging sensors based on highly purified semiconducting carbon nanotubes.

    PubMed

    Liu, Yang; Wei, Nan; Zhao, Qingliang; Zhang, Dehui; Wang, Sheng; Peng, Lian-Mao

    2015-04-21

    High performance infrared (IR) imaging systems usually require expensive cooling systems, which are highly undesirable. Here we report the fabrication and performance characteristics of room temperature carbon nanotube (CNT) IR imaging sensors. The CNT IR imaging sensor is based on aligned semiconducting CNT films with 99% purity, and each pixel or device of the imaging sensor consists of aligned strips of CNT asymmetrically contacted by Sc and Pd. We found that the performance of the device is dependent on the CNT channel length. While short channel devices provide a large photocurrent and a rapid response of about 110 μs, long channel length devices exhibit a low dark current and a high signal-to-noise ratio which are critical for obtaining high detectivity. In total, 36 CNT IR imagers are constructed on a single chip, each consists of 3 × 3 pixel arrays. The demonstrated advantages of constructing a high performance IR system using purified semiconducting CNT aligned films include, among other things, fast response, excellent stability and uniformity, ideal linear photocurrent response, high imaging polarization sensitivity and low power consumption. PMID:25807291

  17. Device and method for imaging of non-linear and linear properties of formations surrounding a borehole

    DOEpatents

    Johnson, Paul A; Tencate, James A; Le Bas, Pierre-Yves; Guyer, Robert; Vu, Cung Khac; Skelt, Christopher

    2013-11-05

    In some aspects of the disclosure, a method and an apparatus is disclosed for investigating material surrounding the borehole. The method includes generating a first low frequency acoustic wave within the borehole, wherein the first low frequency acoustic wave induces a linear and a nonlinear response in one or more features in the material that are substantially perpendicular to a radius of the borehole; directing a first sequence of high frequency pulses in a direction perpendicularly with respect to the longitudinal axis of the borehole into the material contemporaneously with the first acoustic wave; and receiving one or more second high frequency pulses at one or more receivers positionable in the borehole produced by an interaction between the first sequence of high frequency pulses and the one or more features undergoing linear and nonlinear elastic distortion due to the first low frequency acoustic wave to investigate the material surrounding the borehole.

  18. Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection

    PubMed Central

    Kanan, Sofian M.; El-Kadri, Oussama M.; Abu-Yousef, Imad A.; Kanan, Marsha C.

    2009-01-01

    A review of some papers published in the last fifty years that focus on the semiconducting metal oxide (SMO) based sensors for the selective and sensitive detection of various environmental pollutants is presented. PMID:22408500

  19. Trion electroluminescence from semiconducting carbon nanotubes.

    PubMed

    Jakubka, Florian; Grimm, Stefan B; Zakharko, Yuriy; Gannott, Florentina; Zaumseil, Jana

    2014-08-26

    Near-infrared emission from semiconducting single-walled carbon nanotubes (SWNTs) usually results from radiative relaxation of excitons. By binding an additional electron or hole through chemical or electrochemical doping, charged three-body excitons, so-called trions, are created that emit light at lower energies. The energy difference is large enough to observe weak trion photoluminescence from doped SWNTs even at room temperature. Here, we demonstrate strong trion electroluminescence from electrolyte-gated, light-emitting SWNT transistors with three different polymer-sorted carbon nanotube species, namely, (6,5), (7,5) and (10,5). The red-shifted trion emission is equal to or even stronger than the exciton emission, which is attributed to the high charge carrier density in the transistor channel. The possibility of trions as a radiative relaxation pathway for triplets and dark excitons that are formed in large numbers by electron-hole recombination is discussed. The ratio of trion to exciton emission can be tuned by the applied voltages, enabling voltage-controlled near-infrared light sources with narrow line widths that are solution-processable and operate at low voltages (<3 V). PMID:25029479

  20. Innate cation sensitivity in a semiconducting polymer.

    PubMed

    Althagafi, Talal M; Algarni, Saud A; Grell, Martin

    2016-09-01

    Water-gated organic thin film transistors (OTFTs) using the hole transporting semiconducting polymer, poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT), show an innate response of their threshold voltage to the addition of divalent metal cations to the gating water, without deliberately introducing an ion-sensitive component. A similar threshold response is shown for several divalent cations, but is absent for monovalent cations. Response is absent for transistors using the inorganic semiconductor ZnO, or the similar organic semiconductor poly(3-hexylthiophene) (rrP3HT), instead of PBTTT. We assign innate cation sensitivity to residues of the organometallic Pd(0) complex used as catalyst in PBTTT synthesis which bears strong resemblance to typical metal chelating agents. Organometallic Pd(0) residues are absent from ZnO, and also from rrP3HT which is polymerised with a different type of catalyst. However, when Pd(0) complex is deliberately added to rrP3HT casting solutions, resulting OTFTs also display threshold response to a divalent cation. PMID:27343580

  1. Growth of semiconducting single-walled carbon nanotubes by using ceria as catalyst supports.

    PubMed

    Qin, Xiaojun; Peng, Fei; Yang, Feng; He, Xiaohui; Huang, Huixin; Luo, Da; Yang, Juan; Wang, Sheng; Liu, Haichao; Peng, Lianmao; Li, Yan

    2014-02-12

    The growth of semiconducting single-walled carbon nanotubes (s-SWNTs) on flat substrates is essential for the application of SWNTs in electronic and optoelectronic devices. We developed a flexible strategy to selectively grow s-SWNTs on silicon substrates using a ceria-supported iron or cobalt catalysts. Ceria, which stores active oxygen, plays a crucial role in the selective growth process by inhibiting the formation of metallic SWNTs via oxidation. The so-produced ultralong s-SWNT arrays are immediately ready for building field effect transistors. PMID:24392872

  2. Using nonlinear ac electrokinetics vortex flow to enhance catalytic activities of sol-gel encapsulated trypsin in microfluidic devices

    PubMed Central

    Wang, Shau-Chun; Chen, Hsiao-Ping; Lai, Yi-Wen; Chau, Lai-Kwan; Chuang, Yu-Chun; Chen, Yi-Jie

    2007-01-01

    A novel microstirring strategy is applied to accelerate the digestion rate of the substrate Nα-benzoyl-L-arginine-4-nitroanilide (L-BAPA) catalyzed by sol-gel encapsulated trypsin. We use an ac nonlinear electrokinetic vortex flow to stir the solution in a microfluidic reaction chamber to reduce the diffusion length between the immobilized enzyme and substrate in the solution. High-intensity nonlinear electroosmotic microvortices, with angular speeds in excess of 1 cm∕s, are generated around a small (∼1.2 mm) conductive ion exchange granule when ac electric fields (133 V∕cm) are applied across a miniature chamber smaller than 10 μl. Coupling between these microvortices and the on-and-off electrophoretic motion of the granule in low frequency (0.1 Hz) ac fields produces chaotic stream lines to stir substrate molecules sufficiently. We demonstrate that, within a 5-min digestion period, the catalytic reaction rate of immobilized trypsin increases almost 30-fold with adequate reproducibility (15%) due to sufficient stirring action through the introduction of the nonlinear electrokinetic vortices. In contrast, low-frequency ac electroosmotic flow without the granule, provides limited stirring action and increases the reaction rate approximately ninefold with barely acceptable reproducibility (30%). Dye molecules are used to characterize the increases in solute diffusivity in the reaction reservoir in which sol-gel particles are placed, with and without the presence of granule, and compared with the static case. The solute diffusivity enhancement data show respective increases of ∼30 and ∼8 times, with and without the presence of granule. These numbers are consistent with the ratios of the enhanced reaction rate. PMID:19693360

  3. Light-emitting diodes made from cadmium selenide nanocrystals and a semiconducting polymer

    NASA Astrophysics Data System (ADS)

    Colvin, V. L.; Schlamp, M. C.; Alivisatos, A. P.

    1994-08-01

    ELECTROLUMINESCENT devices have been developed recently that are based on new materials such as porous silicon1 and semiconducting polymers2,3. By taking advantage of developments in the preparation and characterization of direct-gap semiconductor nanocrystals4-6, and of electroluminescent polymers7, we have now constructed a hybrid organic/inorganic electroluminescent device. Light emission arises from the recombination of holes injected into a layer of semiconducting p-paraphenylene vinylene (PPV)8-10 with electrons injected into a multilayer film of cadmium selenide nanocrystals. Close matching of the emitting layer of nanocrystals with the work function of the metal contact leads to an operating voltage11 of only 4V. At low voltages emission from the CdSe layer occurs. Because of the quantum size effect19-24 the colour of this emission can be varied from red to yellow by changing the nanocrystal size. At higher voltages green emission from the polymer layer predominates. Thus this device has a degree of voltage tunability of colour.

  4. PREFACE: 16th International Conference on Microscopy of Semiconducting Materials

    NASA Astrophysics Data System (ADS)

    Walther, T.; Nellist, P. D.; Hutchison, J. L.; Cullis, A. G.

    2010-01-01

    This volume contains invited and contributed papers from the 16th international conference on 'Microscopy of Semiconducting Materials' held at the University of Oxford on 17-20 March 2009. The meeting was organised under the auspices of the Royal Microscopical Society with support by the Electron Microscopy and Analysis Group of the Institute of Physics and the Materials Research Society. This conference series focuses on the most recent advances in semiconductor studies carried out by all forms of microscopy, with an emphasis on electron microscopy and related techniques with high spatial resolution. It was attended by 139 delegates from 18 countries world-wide. As semiconductor devices shrink further both new routes of device processing and device characterisation need to be developed, and for the latter methods that offer subnanometre spatial resolution are particularly valuable. Electron microscopy in its various forms of imaging, diffraction and spectroscopy provides indispensable information on both microstructure and chemistry. Recent advances in instrumentation, from lens aberration correction in both TEM and STEM instruments, to the development of a wide range of scanning probe techniques, as well as new methods of quantification of the various signals recorded have been presented at this conference. Two examples of topics that have attracted a number of interesting studies at this meeting are the contrast interpretation in secondary electron images of cleaved semiconductor surfaces and the measurement of chemical composition on the nano-scale of quantum domain structures and devices investigated in cross-section. Each manuscript submitted for publication in this proceedings volume has been reviewed by at least two referees and was modified accordingly. Finally, 70 manuscripts were accepted for publication. The editors are very grateful to the following colleagues for their rapid and careful reviewing of the papers: M al Jassim, J Barnard, R Beanland, H

  5. Physical Properties of Thin Film Semiconducting Materials

    NASA Astrophysics Data System (ADS)

    Bouras, N.; Djebbouri, M.; Outemzabet, R.; Sali, S.; Zerrouki, H.; Zouaoui, A.; Kesri, N.

    2005-10-01

    The physics and chemistry of semiconducting materials is a continuous question of debate. We can find a large stock of well-known properties but at the same time, many things are not understood. In recent years, porous silicon (PS-Si), diselenide of copper and indium (CuInSe2 or CIS) and metal oxide semiconductors like tin oxide (SnO2) and zinc oxide (ZnO) have been subjected to extensive studies because of the rising interest their potential applications in fields such as electronic components, solar panels, catalysis, gas sensors, in biocompatible materials, in Li-based batteries, in new generation of MOSFETS. Bulk structure and surface and interface properties play important roles in all of these applications. A deeper understanding of these fundamental properties would impact largely on technological application performances. In our laboratory, thin films of undoped and antimony-doped films of tin oxide have been deposited by chemical vapor deposition. Spray pyrolysis was used for ZnO. CIS was prepared by flash evaporation or close-space vapor transport. Some of the deposition parameters have been varied, such as substrate temperature, time of deposition (or anodization), and molar concentration of bath preparation. For some samples, thermal annealing was carried out under oxygen (or air), under nitrogen gas and under vacuum. Deposition and post-deposition parameters are known to strongly influence film structure and electrical resistivity. We investigated the influence of film thickness and thermal annealing on structural optical and electrical properties of the films. Examination of SnO2 by x-ray diffraction showed that the main films are polycrystalline with rutile structure. The x-ray spectra of ZnO indicated a hexagonal wurtzite structure. Characterizations of CIS films with compositional analysis, x-ray diffraction, scanning microscopy, spectrophotometry, and photoluminescence were carried out.

  6. Device and method for imaging of non-linear and linear properties of formations surrounding a borehole

    SciTech Connect

    Johnson, Paul A; Tencate, James A; Le Bas, Pierre-Yves; Guyer, Robert; Vu, Cung Khac; Skelt, Christopher

    2013-10-08

    In some aspects of the disclosure, a method and an apparatus is disclosed for investigating material surrounding the borehole. The method includes generating within a borehole an intermittent low frequency vibration that propagates as a tube wave longitudinally to the borehole and induces a nonlinear response in one or more features in the material that are substantially perpendicular to a longitudinal axis of the borehole; generating within the borehole a sequence of high frequency pulses directed such that they travel longitudinally to the borehole within the surrounding material; and receiving, at one or more receivers positionable in the borehole, a signal that includes components from the low frequency vibration and the sequence of high frequency pulses during intermittent generation of the low frequency vibration, to investigate the material surrounding the borehole.

  7. Homo and heteroepitaxial growth and study of orientation-patterned GaP for nonlinear frequency conversion devices

    NASA Astrophysics Data System (ADS)

    Tassev, V. L.; Vangala, S.; Peterson, R.; Kimani, M.; Snure, M.; Markov, I.

    2016-03-01

    Frequency conversion in orientation-patterned quasi-phase matched materials is a leading approach for generating tunable mid- and long-wave coherent IR radiation for a wide variety of applications. A number of nonlinear optical materials are currently under intensive investigation. Due to their unique properties, chiefly wide IR transparency and high nonlinear susceptibility, GaAs and GaP are among the most promising. Compared to GaAs, GaP has the advantage of having higher thermal conductivity and significantly lower 2PA in the convenient pumping range of 1- 1.7 μm. HVPE growth of OPGaP, however, has encountered certain challenges: low quality and high price of commercially available GaP wafers; and strong parasitic nucleation during HVPE growth that reduces growth rate and aggravates layer quality, often leading to pattern overgrowth. Lessons learned from growing OPGaAs were not entirely helpful, leaving us to alternative solutions for both homoepitaxial growth and template preparation. We report repeatable one-step HVPE growth of up to 400 μm thick OPGaP with excellent domain fidelity deposited for first time on OPGaAs templates. The templates were prepared by wafer fusion bonding or MBE assisted polarity inversion technique. A close to equilibrium growth at such a large lattice mismatch (-3.6%) is itself noteworthy, especially when previously reported attempts (growth of OPZnSe on OPGaAs templates) at much smaller mismatch (+0.3%) have produced limited results. Combining the advantages of the two most promising materials, GaAs and GaP, is a solution that will accelerate the development of high power, tunable laser sources for the mid- and long-wave IR, and THz region.

  8. PREFACE: 18th Microscopy of Semiconducting Materials Conference (MSM XVIII)

    NASA Astrophysics Data System (ADS)

    Walther, T.; Hutchison, John L.

    2013-11-01

    YRM logo This volume contains invited and contributed papers from the 18th international conference on 'Microscopy of Semiconducting Materials' held at St Catherine's College, University of Oxford, on 7-11 April 2013. The meeting was organised under the auspices of the Royal Microscopical Society and supported by the Institute of Physics as well as the Materials Research Society of the USA. This conference series deals with recent advances in semiconductor studies carried out by all forms of microscopy, with an emphasis on electron microscopy and scanning probe microscopy with high spatial resolution. This time the meeting was attended by 109 delegates from 17 countries world-wide. We were welcomed by Professor Sir Peter Hirsch, who noted that this was the first of these conferences where Professor Tony Cullis was unable to attend, owing to ill-health. During the meeting a card containing greetings from many of Tony's friends and colleagues was signed, and duly sent to Tony afterwards. As semiconductor devices shrink further new routes for device processing and characterisation need to be developed, and, for the latter, methods that offer sub-nanometre spatial resolution are particularly valuable. The various forms of imaging, diffraction and spectroscopy available in modern microscopes are powerful tools for studying the microstructure, electronic structure, chemistry and also electric fields in semiconducting materials. Recent advances in instrumentation, from lens aberration correction in both TEM and STEM instruments, to the development of a wide range of scanning probe techniques, as well as new methods of signal quantification have been presented at this conference. Two topics that have at this meeting again highlighted the interesting contributions of aberration corrected transmission electron microscopy were: contrast quantification of annular dark-field STEM images in terms of chemical composition (Z-contrast), sample thickness and strain, and the study of

  9. Pi-Stack Engineering of Semiconducting Perylene Tetracarboxylic Derivatives

    NASA Astrophysics Data System (ADS)

    Xue, Chenming

    D crystalline intra-layer order. Chapter 4, PDI pi-stacking order has been engineered in the crystalline phase. By introducing two structuring factors, a series of crystalline PDIs with finely tunable PDI pi-stacking order was obtained. The crystalline PDIs with exceptionally red-shifted lambda max were obtained. Several PDIs possess lambdamax values greater than any literature-reported ones. These materials can be excellent candidates in solar cell devices. In Chapter 5, new chiral main-chain PDI containing polymers were synthesized. These polymers can form intramolecular helical pi-stacks in diluted solutions. In Chapter 6, a novel synthetic route leading to unsymmetrical perylene tetracarboxylic derivatives has been developed. Based on this synthetic method, more perylene tetracarboxylic derivatives can be generated. In my research in this thesis, not only synthesis is an important part because it provides novel materials, but the characterization is critical as well. Infrared spectroscopy, Ultra-violet, fluorescence, differential scanning calorimetry, circular dichroism, polarized light microscopy, gel permeation chromatography, X-ray diffraction including both small angle and wide angle have been used. Additionally, molecular simulation is also very useful in design and obtaining details in molecular packing. Overall, the achievements in this research contribute a considerable advance in the field of generating semiconducting perylene tetracarboxylic derivatives which have versatile potential applications such as in solar cell devices, organic field effect transistors and light emitting diodes.

  10. Mechanical and Electromechanical Properties of Semiconducting and Metallic Nanowires

    NASA Astrophysics Data System (ADS)

    Bernal Montoya, Rodrigo A.

    Nanowires are envisioned as the building blocks of future electronics, sensing and actuation devices, nanostructured materials, among many applications. This technological potential arises because the properties of nanowires tend to be superior to those of bulk structures. However, unambiguous characterization of these properties has not been yet achieved, due to the challenging nature of nanoscale experimentation. In this thesis, we aimed at advancing the unambiguous characterization of mechanical and electromechanical properties of nanowires, by employing and improving MEMS-based (Microelectromechanical Systems) characterization technologies, which allow in-situ electron microscopy testing. Furthermore, we coupled the experimental results with atomistic simulations in order to attain fundamental understanding, and allow the determination of structure-property relations. This synergy between experiments and simulations also provides guidelines for improvements in both the experimental and computational techniques. In the context of semiconducting specimens, we characterized the elastic modulus of GaN nanowires. We find that below 20 nm in diameter, the nanowires display enhanced elastic moduli. Above this size, nanowires show bulk behavior. The measured trends are consistent both in experiments and simulations. The modulus enhancement is caused by local contraction of the atomic bonds near the surface of the nanowires, which leads to a locally higher modulus at the surface. For metallic specimens, we characterized the mechanical behavior of fivefold-twinned silver nanowires below 120 nm in diameter. To better match the loading condition between experiments and simulations, we implement a MEMS device for displacement-controlled testing, and subsequently employ it to characterize the cyclic plastic behavior of the nanowires. Experimentally, Bauschinger effect and partial recovery of the plastic deformation are observed. In-situ TEM experiments and atomistic

  11. Excitons in semiconducting superlattices, quantum wells, and ternary alloys

    SciTech Connect

    Sturge, M.D. . Dept. of Physics); Nahory, R.E.; Tamargo, M.C. )

    1992-06-01

    Semiconducting layered structures can now be fabricated with precisely defined layer thicknesses down to one monolayer. An example is the superlattice'' (SL) structure, in which to semiconductors with different band gaps are interleaved. The electronic and optical properties of the SL are quite different from those of the constitutents and offer interesting new possibilities both in device design and in basic physics. This proposal aims to improve our understanding of optically excited states in SL's, particularly in the so-called Type 2 indirect'' SL's in which in electron and hole created by optical excitation are separated both in real and in momentum space. We study these structures by time-resolved tunable laser spectroscopy, with and without external perturbations such as magnetic field, electric field, and uniaxial stress. In SLs with only a few atomic layers per period the familiar effective mass model'' of semiconductor states breaks down. We have made precise optical experiments on well-characterized material to test current first principles'' calculations of the band structure. Our work under this grant has shown that the material we are using is of sufficiently high quality to test the theoretical predictions. Comparison of theory and experiment provides a new and sensitive probe of the interface quality on a fine scale. Statistical analysis of the temperature dependence of the exciton decay dynamics provides complementary information. From a careful study of the exciton spectra of the recently discovered mixed type 1- type 2 CdTe/CdZnTe SLs we have obtained the band offset at the CdTe/CdZnTe interface to unprecedented accuracy.

  12. Coherent tools for physics-based simulation and characterization of noise in semiconductor devices oriented to nonlinear microwave circuit CAD

    NASA Astrophysics Data System (ADS)

    Riah, Zoheir; Sommet, Raphael; Nallatamby, Jean C.; Prigent, Michel; Obregon, Juan

    2004-05-01

    We present in this paper a set of coherent tools for noise characterization and physics-based analysis of noise in semiconductor devices. This noise toolbox relies on a low frequency noise measurement setup with special high current capabilities thanks to an accurate and original calibration. It relies also on a simulation tool based on the drift diffusion equations and the linear perturbation theory, associated with the Green's function technique. This physics-based noise simulator has been implemented successfully in the Scilab environment and is specifically dedicated to HBTs. Some results are given and compared to those existing in the literature.

  13. Room-temperature nonlinear transport phenomena in low-dimensional Ni-Nb-Zr-H glassy alloys and its device

    SciTech Connect

    Fukuhara, Mikio; Yoshida, Hajime

    2014-05-15

    We report the room-temperature switching and Coulomb blockade effects in three–terminal glassy alloy field effect transistor (GAFET), using the millimeter sized glassy alloy. By applying dc and ac voltages to a gate electrode, GAFET can be switched from a metallic conducting state to an insulating state with Coulomb oscillation at a period of 14 μV at room temperature. The transistor showed the three-dimensional Coulomb diamond structure. The fabrication of a low-energy controllable device throws a new light on cluster electronics without wiring.

  14. Optimization of thermoelectric performance in semiconducting polymers for understanding charge transport and flexible thermoelectric applications

    NASA Astrophysics Data System (ADS)

    Glaudell, Anne; Chabinyc, Michael

    2014-03-01

    Organic electronic materials have been widely considered for a variety of energy conversion applications, from photovoltaics to LEDs. Only very recently have organic materials been considered for thermoelectric applications - converting between temperature gradients and electrical potential. The intrinsic disorder in semiconducting polymers leads to an inherently low thermal conductivity, a key parameter in thermoelectric performance. The ability to solution deposit on flexible substrates opens up niche applications including personal cooling and conformal devices. Here work is presented on the electrical conductivity and thermopower of thin film semiconducting polymers, including P3HT and PBTTT-C14. Thermoelectric properties are explored over a wide range of conductivities, from nearly insulating to beyond 100 S/cm, enabled by employing different doping mechanisms, including molecular charge-transfer doping with F4TCNQ and vapor doping with a fluoroalkyl trichlorosilane (FTS). Temperature-dependent measurements suggest competing charge transport mechanisms, likely due to the mixed ordered/disordered character of these polymers. These results show promise for organic materials for thermoelectric applications, and recent results on thin film devices will also be presented.

  15. Graphene Based Reversible Nano-Switch/Sensor Schottky Diode (NANOSSSD) Device

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A. (Inventor); Theofylaktos, Onoufrios (Inventor); Pinto, Nicholas J. (Inventor); Mueller, Carl H. (Inventor); Santos, Javier (Inventor); Meador, Michael A. (Inventor)

    2015-01-01

    A nanostructure device is provided and performs dual functions as a nano-switching/sensing device. The nanostructure device includes a doped semiconducting substrate, an insulating layer disposed on the doped semiconducting substrate, an electrode formed on the insulating layer, and at least one layer of graphene formed on the electrode. The at least one layer of graphene provides an electrical connection between the electrode and the substrate and is the electroactive element in the device.

  16. Nonlinear diffraction in orientation-patterned semiconductors.

    PubMed

    Karpinski, Pawel; Chen, Xin; Shvedov, Vladlen; Hnatovsky, Cyril; Grisard, Arnaud; Lallier, Eric; Luther-Davies, Barry; Krolikowski, Wieslaw; Sheng, Yan

    2015-06-01

    This work represents experimental demonstration of nonlinear diffraction in an orientation-patterned semiconducting material. By employing a new transverse geometry of interaction, three types of second-order nonlinear diffraction have been identified according to different configurations of quasi-phase matching conditions. Specifically, nonlinear Čerenkov diffraction is defined by the longitudinal quasi-phase matching condition, nonlinear Raman-Nath diffraction satisfies only the transverse quasi-phase matching condition, and nonlinear Bragg diffraction fulfils the full vectorial quasi-phase matching conditions. The study extends the concept of transverse nonlinear parametric interaction toward infrared frequency conversion in semiconductors. It also offers an effective nondestructive method to visualise and diagnose variations of second-order nonlinear coefficients inside semiconductors. PMID:26072847

  17. Hybrid semiconducting polymer nanoparticles as polarization-sensitive fluorescent probes

    PubMed Central

    Zeigler, Maxwell B.; Sun, Wei; Rong, Yu; Chiu, Daniel T.

    2013-01-01

    Much work has been done on collapsed chains of conjugated semiconducting polymers and their applications as fluorescent probes or sensors. On surfaces spin-coated with semiconducting polymers, excitation energy transfer along the polymer backbone can be used to quickly and efficiently funnel energy to chromophores with localized energy minima. If each chromophore is immobilized within its matrix, this can result in large fluorescence anisotropy. Through nanoprecipitation of a matrix polymer blended at low mass ratios with short-chain, hydrophobic, fluorescent semiconducting polymers, we take advantage of this large fluorescence anisotropy to make polarization-sensitive nanoparticles. These nanoparticles are small at approximately 7 nm in diameter; exhibit a high quantum yield of 0.75; and are easily functionalized to bind to protein targets. By exciting the nanoparticles with polarized light on a wide-field fluorescence microscope, we are able to monitor not only protein location, but also changes in their orientation. PMID:23895535

  18. Semiconducting glasses: A new class of thermoelectric materials?

    SciTech Connect

    Goncalves, A.P.; Vaney, J.B.; Lenoir, B.; Piarristeguy, A.; Pradel, A.; Monnier, J.; Ochin, P.; Godart, C.

    2012-09-15

    The deeper understanding of the factors that affect the dimensionless figure of merit, ZT, and the use of new synthetic methods has recently led to the development of novel systems with improved thermoelectric performances. Albeit up to now with ZT values lower than the conventional bulk materials, semiconducting glasses have also emerged as a new family of potential thermoelectric materials. This paper reviews the latest advances on semiconducting glasses for thermoelectric applications. Key examples of tellurium-based glasses, with high Seebeck coefficients, very low thermal conductivities and tunable electrical conductivities, are presented. ZT values as high as 0.2 were obtained at room temperature for several tellurium-based glasses with high copper concentrations, confirming chalcogenide semiconducting glasses as good candidates for high-performance thermoelectric materials. However, the temperature stability and electrical conductivity of the reported glasses are still not good enough for practical applications and further studies are still needed to enhance them. - Graphical abstract: Power factor as a function of the temperature for the Cu{sub 27.5}Ge{sub 2.5}Te{sub 70} and Cu{sub 30}As{sub 15}Te{sub 55} seniconducting glasses. Highlights: Black-Right-Pointing-Pointer A review of semiconducting glasses for thermoelectrics applications is presented. Black-Right-Pointing-Pointer The studied semiconducting glasses present very low thermal conductivities. Black-Right-Pointing-Pointer Composition can tune electrical conductivity and Seebeck coefficient. Black-Right-Pointing-Pointer ZT=0.2 is obtained at 300 K for different semiconducting glasses.

  19. Recent advances in organic semiconducting materials

    NASA Astrophysics Data System (ADS)

    Ostroverkhova, Oksana

    2011-10-01

    Organic semiconductors have attracted attention due to their low cost, easy fabrication, and tunable properties. Applications of organic materials in thin-film transistors, solar cells, light-emitting diodes, sensors, and many other devices have been actively explored. Recent advances in organic synthesis, material processing, and device fabrication led to significant improvements in (opto)electronic device performance. However, a number of challenges remain. These range from lack of understanding of basic physics of intermolecular interactions that determine optical and electronic properties of organic materials to difficulties in controlling film morphology and stability. In this presentation, current state of the field will be reviewed and recent results related to charge carrier and exciton dynamics in organic thin films will be presented.[4pt] In collaboration with Whitney Shepherd, Mark Kendrick, Andrew Platt, Oregon State University; Marsha Loth and John Anthony, University of Kentucky.

  20. Molecular Design of Semiconducting Polymers for High-Performance Organic Electrochemical Transistors.

    PubMed

    Nielsen, Christian B; Giovannitti, Alexander; Sbircea, Dan-Tiberiu; Bandiello, Enrico; Niazi, Muhammad R; Hanifi, David A; Sessolo, Michele; Amassian, Aram; Malliaras, George G; Rivnay, Jonathan; McCulloch, Iain

    2016-08-17

    The organic electrochemical transistor (OECT), capable of transducing small ionic fluxes into electronic signals in an aqueous environment, is an ideal device to utilize in bioelectronic applications. Currently, most OECTs are fabricated with commercially available conducting poly(3,4-ethylenedioxythiophene) (PEDOT)-based suspensions and are therefore operated in depletion mode. Here, we present a series of semiconducting polymers designed to elucidate important structure-property guidelines required for accumulation mode OECT operation. We discuss key aspects relating to OECT performance such as ion and hole transport, electrochromic properties, operational voltage, and stability. The demonstration of our molecular design strategy is the fabrication of accumulation mode OECTs that clearly outperform state-of-the-art PEDOT-based devices, and show stability under aqueous operation without the need for formulation additives and cross-linkers. PMID:27444189

  1. Semiconducting monolayer materials as a tunable platform for excitonic solar cells.

    PubMed

    Bernardi, Marco; Palummo, Maurizia; Grossman, Jeffrey C

    2012-11-27

    The recent advent of two-dimensional monolayer materials with tunable optical properties and high carrier mobility offers renewed opportunities for efficient, ultrathin excitonic solar cells alternative to those based on conjugated polymer and small molecule donors. Using first-principles density functional theory and many-body calculations, we demonstrate that monolayers of hexagonal BN and graphene (CBN) combined with commonly used acceptors such as PCBM fullerene or semiconducting carbon nanotubes can provide excitonic solar cells with tunable absorber gap, donor-acceptor interface band alignment, and power conversion efficiency, as well as novel device architectures. For the case of CBN-PCBM devices, we predict power conversion efficiency limits in the 10-20% range depending on the CBN monolayer structure. Our results demonstrate the possibility of using monolayer materials in tunable, efficient, ultrathin solar cells in which unexplored exciton and carrier transport regimes are at play. PMID:23062107

  2. Three dimensional architectures of ultra-high density semiconducting nanowires deposited on chip.

    PubMed

    Ryan, Kevin M; Erts, Donats; Olin, Hakan; Morris, Michael A; Holmes, Justin D

    2003-05-21

    We report a "clean" and fast process, utilizing supercritical carbon dioxide, for producing ultrahigh densities, up to 10(12) nanowires per square centimeter, of ordered germanium nanowires on silicon and quartz substrates. Uniform mesoporous thin films were employed as templates for the nucleation and growth of unidirectional nanowire arrays orientated almost perpendicular to a substrate surface. Additionally, these nanocomposite materials display room-temperature photoluminescence (PL), the energy of which is dependent on the diameter of the encased nanowires. The ability to synthesis ultrahigh-density arrays of semiconducting nanowires on-chip is a key step in future "bottom-up" fabrication of multilayered device architectures for nanoelectronic and optoelectronic devices. PMID:12785861

  3. Large Bandgap Shrinkage from Doping and Dielectric Interface in Semiconducting Carbon Nanotubes.

    PubMed

    Comfort, Everett; Lee, Ji Ung

    2016-01-01

    The bandgap of a semiconductor is one of its most important electronic properties. It is often considered to be a fixed property of the semiconductor. As the dimensions of semiconductors reduce, however, many-body effects become dominant. Here, we show that doping and dielectric, two critical features of semiconductor device manufacturing, can dramatically shrink (renormalize) the bandgap. We demonstrate this in quasi-one-dimensional semiconducting carbon nanotubes. Specifically, we use a four-gated device, configured as a p-n diode, to investigate the fundamental electronic structure of individual, partially supported nanotubes of varying diameter. The four-gated construction allows us to combine both electrical and optical spectroscopic techniques to measure the bandgap over a wide doping range. PMID:27339272

  4. Identifying [corrected] signatures of photothermal current in a double-gated semiconducting nanotube.

    PubMed

    Buchs, G; Bagiante, S; Steele, G A

    2014-01-01

    The remarkable electrical and optical properties of single-walled carbon nanotubes have allowed for engineering device prototypes showing great potential for applications such as photodectors and solar cells. However, any path towards industrial maturity requires a detailed understanding of the fundamental mechanisms governing the process of photocurrent generation. Here we present scanning photocurrent microscopy measurements on a double-gated suspended semiconducting single-walled carbon nanotube and show that both photovoltaic and photothermal mechanisms are relevant for the interpretation of the photocurrent. We find that the dominant or non-dominant character of one or the other processes depends on the doping profile, and that the magnitude of each contribution is strongly influenced by the series resistance from the band alignment with the metal contacts. These results provide new insight into the interpretation of features in scanning photocurrent microscopy and lay the foundation for the understanding of optoelectronic devices made from single-walled carbon nanotubes. PMID:25236955

  5. Large Bandgap Shrinkage from Doping and Dielectric Interface in Semiconducting Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Comfort, Everett; Lee, Ji Ung

    2016-06-01

    The bandgap of a semiconductor is one of its most important electronic properties. It is often considered to be a fixed property of the semiconductor. As the dimensions of semiconductors reduce, however, many-body effects become dominant. Here, we show that doping and dielectric, two critical features of semiconductor device manufacturing, can dramatically shrink (renormalize) the bandgap. We demonstrate this in quasi-one-dimensional semiconducting carbon nanotubes. Specifically, we use a four-gated device, configured as a p-n diode, to investigate the fundamental electronic structure of individual, partially supported nanotubes of varying diameter. The four-gated construction allows us to combine both electrical and optical spectroscopic techniques to measure the bandgap over a wide doping range.

  6. Organic semiconducting single crystals as solid-state sensors for ionizing radiation.

    PubMed

    Fraboni, Beatrice; Ciavatti, Andrea; Basiricò, Laura; Fraleoni-Morgera, Alessandro

    2014-01-01

    So far, organic semiconductors have been mainly proposed as detectors for ionizing radiation in the indirect conversion approach, i.e. as scintillators, which convert ionizing radiation into visible photons, or as photodiodes, which detect visible photons coming from a scintillator and convert them into an electrical signal. The direct conversion of ionizing radiation into an electrical signal within the same device is a more effective process than indirect conversion, since it improves the signal-to-noise ratio and it reduces the device response time. We report here the use of Organic Semiconducting Single Crystals (OSSCs) as intrinsic direct ionizing radiation detectors, thanks to their stability, good transport properties and large interaction volume. Ionizing radiation X-ray detectors, based on low-cost solution-grown OSSCs, are here shown to operate at room temperature, providing a stable linear response with increasing dose rate in the ambient atmosphere and in high radiation environments. PMID:25485676

  7. Molecular Design of Semiconducting Polymers for High-Performance Organic Electrochemical Transistors

    PubMed Central

    2016-01-01

    The organic electrochemical transistor (OECT), capable of transducing small ionic fluxes into electronic signals in an aqueous environment, is an ideal device to utilize in bioelectronic applications. Currently, most OECTs are fabricated with commercially available conducting poly(3,4-ethylenedioxythiophene) (PEDOT)-based suspensions and are therefore operated in depletion mode. Here, we present a series of semiconducting polymers designed to elucidate important structure–property guidelines required for accumulation mode OECT operation. We discuss key aspects relating to OECT performance such as ion and hole transport, electrochromic properties, operational voltage, and stability. The demonstration of our molecular design strategy is the fabrication of accumulation mode OECTs that clearly outperform state-of-the-art PEDOT-based devices, and show stability under aqueous operation without the need for formulation additives and cross-linkers. PMID:27444189

  8. Identifiying signatures of photothermal current in a double-gated semiconducting nanotube

    NASA Astrophysics Data System (ADS)

    Buchs, G.; Bagiante, S.; Steele, G. A.

    2014-09-01

    The remarkable electrical and optical properties of single-walled carbon nanotubes have allowed for engineering device prototypes showing great potential for applications such as photodectors and solar cells. However, any path towards industrial maturity requires a detailed understanding of the fundamental mechanisms governing the process of photocurrent generation. Here we present scanning photocurrent microscopy measurements on a double-gated suspended semiconducting single-walled carbon nanotube and show that both photovoltaic and photothermal mechanisms are relevant for the interpretation of the photocurrent. We find that the dominant or non-dominant character of one or the other processes depends on the doping profile, and that the magnitude of each contribution is strongly influenced by the series resistance from the band alignment with the metal contacts. These results provide new insight into the interpretation of features in scanning photocurrent microscopy and lay the foundation for the understanding of optoelectronic devices made from single-walled carbon nanotubes.

  9. Large Bandgap Shrinkage from Doping and Dielectric Interface in Semiconducting Carbon Nanotubes

    PubMed Central

    Comfort, Everett; Lee, Ji Ung

    2016-01-01

    The bandgap of a semiconductor is one of its most important electronic properties. It is often considered to be a fixed property of the semiconductor. As the dimensions of semiconductors reduce, however, many-body effects become dominant. Here, we show that doping and dielectric, two critical features of semiconductor device manufacturing, can dramatically shrink (renormalize) the bandgap. We demonstrate this in quasi-one-dimensional semiconducting carbon nanotubes. Specifically, we use a four-gated device, configured as a p-n diode, to investigate the fundamental electronic structure of individual, partially supported nanotubes of varying diameter. The four-gated construction allows us to combine both electrical and optical spectroscopic techniques to measure the bandgap over a wide doping range. PMID:27339272

  10. Exciton-exciton annihilation and relaxation pathways in semiconducting carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Chmeliov, Jevgenij; Narkeliunas, Jonas; Graham, Matt W.; Fleming, Graham R.; Valkunas, Leonas

    2016-01-01

    We present a thorough analysis of one- and two-color transient absorption measurements performed on single- and double-walled semiconducting carbon nanotubes. By combining the currently existing models describing exciton-exciton annihilation--the coherent and the diffusion-limited ones--we are able to simultaneously reproduce excitation kinetics following both E11 and E22 pump conditions. Our simulations revealed the fundamental photophysical behavior of one-dimensional coherent excitons and non-trivial excitation relaxation pathways. In particular, we found that after non-linear annihilation a doubly-excited exciton relaxes directly to its E11 state bypassing the intermediate E22 manifold, so that after excitation resonant with the E11 transition, the E22 state remains unpopulated. A quantitative explanation for the observed much faster excitation kinetics probed at E22 manifold, comparing to those probed at the E11 band, is also provided.

  11. Scattering attributes of one-dimensional semiconducting oxide nanomaterials individually probed for varying light-matter interaction angles

    SciTech Connect

    Choi, Daniel S.; Singh, Manpreet; Zhou, Hebing; Milchak, Marissa; Hahm, Jong-in

    2015-10-12

    We report the characteristic optical responses of one-dimensional semiconducting oxide nanomaterials by examining the individual nanorods (NRs) of ZnO, SnO{sub 2}, indium tin oxide, and zinc tin oxide under precisely controlled, light-matter interaction geometry. Scattering signals from a large set of NRs of the different types are evaluated spatially along the NR length while varying the NR tilt angle, incident light polarization, and analyzer rotation. Subsequently, we identify material-indiscriminate, NR tilt angle- and incident polarization-dependent scattering behaviors exhibiting continuous, intermittent, and discrete responses. The insight gained from this study can advance our fundamental understanding of the optical behaviors of the technologically useful nanomaterials and, at the same time, promote the development of highly miniaturized, photonic and bio-optical devices utilizing the spatially controllable, optical responses of the individual semiconducting oxide NRs.

  12. Nonlinear Hysteretic Torsional Waves.

    PubMed

    Cabaret, J; Béquin, P; Theocharis, G; Andreev, V; Gusev, V E; Tournat, V

    2015-07-31

    We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found to be nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other types of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short-term memory, as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control devices such as strong amplitude-dependent filters. PMID:26274421

  13. Nonlinear Hysteretic Torsional Waves

    NASA Astrophysics Data System (ADS)

    Cabaret, J.; Béquin, P.; Theocharis, G.; Andreev, V.; Gusev, V. E.; Tournat, V.

    2015-07-01

    We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found to be nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other types of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short-term memory, as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control devices such as strong amplitude-dependent filters.

  14. Semiconducting materials for photoelectrochemical energy conversion

    NASA Astrophysics Data System (ADS)

    Sivula, Kevin; van de Krol, Roel

    2016-02-01

    To achieve a sustainable society with an energy mix primarily based on solar energy, we need methods of storing energy from sunlight as chemical fuels. Photoelectrochemical (PEC) devices offer the promise of solar fuel production through artificial photosynthesis. Although the idea of a carbon-neutral energy economy powered by such ‘artificial leaves’ is intriguing, viable PEC energy conversion on a global scale requires the development of devices that are highly efficient, stable and simple in design. In this Review, recently developed semiconductor materials for the direct conversion of light into fuels are scrutinized with respect to their atomic constitution, electronic structure and potential for practical performance as photoelectrodes in PEC cells. The processes of light absorption, charge separation and transport, and suitable energetics for energy conversion in PEC devices are emphasized. Both the advantageous and unfavourable aspects of multinary oxides, oxynitrides, chalcogenides, classic semiconductors and carbon-based semiconductors are critically considered on the basis of their experimentally demonstrated performance and predicted properties.

  15. Semiconducting boron carbide thin films: Structure, processing, and diode applications

    NASA Astrophysics Data System (ADS)

    Bao, Ruqiang

    The high energy density and long lifetime of betavoltaic devices make them very useful to provide the power for applications ranging from implantable cardiac pacemakers to deep space satellites and remote sensors. However, when made with conventional semiconductors, betavoltaic devices tend to suffer rapid degradation as a result of radiation damage. It has been suggested that the degradation problem could potentially be alleviated by replacing conventional semiconductors with a radiation hard semiconducting material like icosahedral boron carbide. The goal of my dissertation was to better understand the fundamental properties and structure of boron carbide thin films and to explore the processes to fabricate boron carbide based devices for voltaic applications. A pulsed laser deposition system and a radio frequency (RF) magnetron sputtering deposition system were designed and built to achieve the goals. After comparing the experimental results obtained using these two techniques, it was concluded that RF magnetron sputtering deposition technique is a good method to make B4C boron carbide thin films to fabricate repeatable and reproducible voltaic devices. The B4C thin films deposited by RF magnetron sputtering require in situ dry pre-cleaning to make ohmic contacts for B4C thin films to fabricate the devices. By adding another RF sputtering to pre-clean the substrate and thin films, a process to fabricate B4C / n-Si heterojunctions has been established. In addition, a low energy electron accelerator (LEEA) was built to mimic beta particles emitted from Pm147 and used to characterize the betavoltaic performance of betavoltaic devices as a function of beta energy and beta flux as well as do accelerated lifetime testing for betavoltaic devices. The energy range of LEEA is 20 - 250 keV with the current from several nA to 50 muA. High efficiency Si solar cells were used to demonstrate the powerful capabilities of LEEA, i.e., the characterization of betavoltaic

  16. Evaluation of polarization rotation in the scattering responses from individual semiconducting oxide nanorods

    PubMed Central

    Choi, Daniel S.; Singh, Manpreet; Zhou, Hebing; Milchak, Marissa; Monahan, Brian; Hahm, Jong-in

    2016-01-01

    We investigate the interaction of visible light with the solid matters of semiconducting oxide nanorods (NRs) of zinc oxide (ZnO), indium tin oxide (ITO), and zinc tin oxide (ZTO) at the single nanomaterial level. We subsequently identify an intriguing, material-dependent phenomenon of optical rotation in the electric field oscillation direction of the scattered light by systematically controlling the wavelength and polarization direction of the incident light, the NR tilt angle, and the analyzer angle. This polarization rotation effect in the scattered light is repeatedly observed from the chemically pure and highly crystalline ZnO NRs, but absent on the chemically doped NR variants of ITO and ZTO under all measurement circumstances. We further elucidate that the phenomenon of polarization rotation detected from single ZnO NRs is affected by the NR tilt angle, while the phenomenon itself occurs irrespective of the wavelength and incident polarization direction of the visible light. Combined with the widespread optical and optoelectronic use of the semiconducting oxide nanomaterials, these efforts may provide much warranted fundamental bases to tailor material-specific, single nanomaterial-driven, optically modulating functionalities which, in turn, can be beneficial for the realization of high-performance integrated photonic circuits and miniaturized bio-optical sensing devices. PMID:27158560

  17. Evaluation of polarization rotation in the scattering responses from individual semiconducting oxide nanorods

    NASA Astrophysics Data System (ADS)

    Choi, Daniel S.; Singh, Manpreet; Zhou, Hebing; Milchak, Marissa; Monahan, Brian; Hahm, Jong-in

    2016-04-01

    We investigate the interaction of visible light with the solid matters of semiconducting oxide nanorods (NRs) of zinc oxide (ZnO), indium tin oxide (ITO), and zinc tin oxide (ZTO) at the single nanomaterial level. We subsequently identify an intriguing, material-dependent phenomenon of optical rotation in the electric field oscillation direction of the scattered light by systematically controlling the wavelength and polarization direction of the incident light, the NR tilt angle, and the analyzer angle. This polarization rotation effect in the scattered light is repeatedly observed from the chemically pure and highly crystalline ZnO NRs, but absent on the chemically doped NR variants of ITO and ZTO under all measurement circumstances. We further elucidate that the phenomenon of polarization rotation detected from single ZnO NRs is affected by the NR tilt angle, while the phenomenon itself occurs irrespective of the wavelength and incident polarization direction of the visible light. Combined with the widespread optical and optoelectronic use of the semiconducting oxide nanomaterials, these efforts may provide much warranted fundamental bases to tailor material-specific, single nanomaterial-driven, optically modulating functionalities which, in turn, can be beneficial for the realization of high-performance integrated photonic circuits and miniaturized bio-optical sensing devices.

  18. Optimal wide-area monitoring and nonlinear adaptive coordinating neurocontrol of a power system with wind power integration and multiple FACTS devices.

    PubMed

    Qiao, Wei; Venayagamoorthy, Ganesh K; Harley, Ronald G

    2008-01-01

    Wide-area coordinating control is becoming an important issue and a challenging problem in the power industry. This paper proposes a novel optimal wide-area coordinating neurocontrol (WACNC), based on wide-area measurements, for a power system with power system stabilizers, a large wind farm and multiple flexible ac transmission system (FACTS) devices. An optimal wide-area monitor (OWAM), which is a radial basis function neural network (RBFNN), is designed to identify the input-output dynamics of the nonlinear power system. Its parameters are optimized through particle swarm optimization (PSO). Based on the OWAM, the WACNC is then designed by using the dual heuristic programming (DHP) method and RBFNNs, while considering the effect of signal transmission delays. The WACNC operates at a global level to coordinate the actions of local power system controllers. Each local controller communicates with the WACNC, receives remote control signals from the WACNC to enhance its dynamic performance and therefore helps improve system-wide dynamic and transient performance. The proposed control is verified by simulation studies on a multimachine power system. PMID:18206349

  19. The detection of terahertz waves by semimetallic and by semiconducting materials

    NASA Astrophysics Data System (ADS)

    Gouider, F.; Nachtwei, G.; Brüne, C.; Buhmann, H.; Vasilyev, Yu. B.; Salman, M.; Könemann, J.; Buckle, P. D.

    2011-01-01

    We present a survey of photoresponse (PR) measurements of various devices containing quantum wells (QWs) of HgTe of various widths dQW and of InSb. By varying dQW for HgTe, the material properties of the QW material change from semiconducting to semimetallic as dQW is increased above a value of about 6nm. We have studied the PR of devices made from CdxHg1-xTe/HgTe/CdxHg1-xTe wafers with values of the QW width in the range of 6 nm≤dQW≤21 nm. Only for samples with semimetallic HgTe QWs, a measurable PR could be detected. However, our investigations of samples made from AlxIn1-xSb/InSb/AlxIn1-xSb wafers gave evidence that a measurable PR also can appear from devices with a semiconducting QW. Both cyclotron-resonant (CR) and nonresonant (bolometric, BO) interaction mechanisms can contribute to the PR signal. Whereas the CR contribution is dominant in AlxIn1-xSb/InSb/AlxIn1-xSb samples, in CdxHg1-xTe/HgTe/CdxHg1-xTe samples the behavior is more complex. In a sample with dQW=8 nm, the PR is clearly dominated by the BO contribution. In the PR of another sample of dQW=12 nm, both contributions (BO and CR) are present. The sample of dQW=21 nm shows a PR with not clearly separable BO and CR contributions.

  20. Semiconducting organic-inorganic nanocomposites by intimately tethering conjugated polymers to inorganic tetrapods.

    PubMed

    Jung, Jaehan; Yoon, Young Jun; Lin, Zhiqun

    2016-04-28

    Semiconducting organic-inorganic nanocomposites were judiciously crafted by placing conjugated polymers in intimate contact with inorganic tetrapods via click reaction. CdSe tetrapods were first synthesized by inducing elongated arms from CdSe zincblende seeds through seed-mediated growth. The subsequent effective inorganic ligand treatment, followed by reacting with short bifunctional ligands, yielded azide-functionalized CdSe tetrapods (i.e., CdSe-N3). Finally, the ethynyl-terminated conjugated polymer poly(3-hexylthiophene) (i.e., P3HT-[triple bond, length as m-dash]) was tethered to CdSe-N3 tetrapods via a catalyst-free alkyne-azide cycloaddition, forming intimate semiconducting P3HT-CdSe tetrapod nanocomposites. Intriguingly, the intimate contact between P3HT and CdSe tetrapod was found to not only render the effective dispersion of CdSe tetrapods in the P3HT matrix, but also facilitate the efficient electronic interaction between these two semiconducting constituents. The successful anchoring of P3HT chains onto CdSe tetrapods was substantiated through Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy measurements. Moreover, the absorption and photoluminescence studies further corroborated the intimate tethering between P3HT and CdSe tetrapods. The effect of the type of bifunctional ligands (i.e., aryl vs. aliphatic ligands) and the size of tetrapods on the device performance of hybrid organic-inorganic solar cells was also scrutinized. Interestingly, P3HT-CdSe tetrapod nanocomposites produced via the use of an aryl bifunctional ligand (i.e., 4-azidobenzoic acid) exhibited an improved photovoltaic performance compared to that synthesized with their aliphatic ligand counterpart (i.e., 5-bromovaleric acid). Clearly, the optimal size of CdSe tetrapods ensuring the effective charge transport in conjunction with the good dispersion of CdSe tetrapods rendered an improved device performance. We envision that the click

  1. Implication of Fluorine Atom on Electronic Properties, Ordering Structures, and Photovoltaic Performance in Naphthobisthiadiazole-Based Semiconducting Polymers.

    PubMed

    Kawashima, Kazuaki; Fukuhara, Tomohiro; Suda, Yousuke; Suzuki, Yasuhito; Koganezawa, Tomoyuki; Yoshida, Hiroyuki; Ohkita, Hideo; Osaka, Itaru; Takimiya, Kazuo

    2016-08-17

    The development of semiconducting polymers is imperative to improve the performance of polymer-based solar cells (PSCs). In this study, new semiconducting polymers based on naphtho[1,2-c:5,6-c']bis[1,2,5]thiadiazole (NTz), PNTz4TF2 and PNTz4TF4, having 3,3'-difluoro-2,2'-bithiophene and 3,3',4,4'-tetrafluoro-2,2'-bithiophene, respectively, are designed and synthesized. These polymers possess a deeper HOMO energy level than their counterpart, PNTz4T, which results in higher open-circuit voltages in solar cells. This concequently reduces the photon energy loss that is one of the most important issues surrounding PSCs. The PNTz4TF4 cell exhibits up to 6.5% power conversion efficiency (PCE), whereas the PNTz4TF2 cell demonstrates outstanding device performance with as high as 10.5% PCE, which is quite high for PSCs. We further discuss the performances of the PSCs based on these polymers by correlating the charge generation and recombination dynamics with the polymer structure and ordering structure. We believe that the results provide new insights into the design of semiconducting polymers and that there is still much room for improvement of PSC efficiency. PMID:27448181

  2. Light emitting ceramic device

    DOEpatents

    Valentine, Paul; Edwards, Doreen D.; Walker, Jr., William John; Slack, Lyle H.; Brown, Wayne Douglas; Osborne, Cathy; Norton, Michael; Begley, Richard

    2010-05-18

    A light-emitting ceramic based panel, hereafter termed "electroceramescent" panel, is herein claimed. The electroceramescent panel is formed on a substrate providing mechanical support as well as serving as the base electrode for the device. One or more semiconductive ceramic layers directly overlay the substrate, and electrical conductivity and ionic diffusion are controlled. Light emitting regions overlay the semiconductive ceramic layers, and said regions consist sequentially of a layer of a ceramic insulation layer and an electroluminescent layer, comprised of doped phosphors or the equivalent. One or more conductive top electrode layers having optically transmissive areas overlay the light emitting regions, and a multi-layered top barrier cover comprising one or more optically transmissive non-combustible insulation layers overlay said top electrode regions.

  3. Superconducting proximity effect in superconductor / semiconducting-carbon-nanotube / superconductor junctions.

    NASA Astrophysics Data System (ADS)

    Barbara, Paola

    2005-03-01

    We measure the proximity effect in devices made of two superconducting electrodes bridged by a 3-micrometer long semiconducting carbon nanotube. The electrodes are made of a Pd/Nb bilayer and the junctions are fabricated by using standard photolithography [1]. The superconducting proximity effect manifests itself with a peak in the low-bias differential conductance due to Andreev reflection at the superconductor/carbon nanotube interfaces. Application of a gate voltage allows the transparency of the junction to be tuned from high (Andreev reflection) to low (tunneling) [2]. We have studied the temperature dependence of the features in each regime. This work is supported by the NSF (DMR-0239721) and by the Research Corporation. [1] A. Tselev, K. Hatton, M. S. Fuhrer, M. Paranjape and P. Barbara, Nanotechnology 15, 1475 (2004). [2] A. F. Morpurgo, J. Kong, C. M. Marcus, and H. Dai, Science 286, 263 (1999).

  4. Molecular dynamics simulations for the study of optical properties in conjugated semiconducting molecules

    NASA Astrophysics Data System (ADS)

    Wildman, Jack; Denis, Jean-Christophe; Repiščák, Peter; Paterson, Martin J.; Galbraith, Ian

    Conformational disorder of conjugated polymers strongly influences their optical and electronic properties. Molecular Dynamics (MD) simulations can provide a quantitative understanding of these effects. Given the ever-expanding range of molecules with potential for device applications, it is critical to systematically establish accurate MD parameters for such simulations. We present an experimentally verified, general and optimised procedure, based on a computationally inexpensive methodology for generating the required MD parameters for conjugated molecules. By combining a large sample (~1000) of MD generated conformations with DFT calculations for the resulting electronic states we can explore the influence of conformational disorder on the optical properties. Using this scheme, we determine the effect of conformational variation on both linear and two-photon absorption spectra in a number of different conjugated semiconducting oligomers. Our results indicate that, while there exists significant inhomogeneous broadening in the linear absorption, there is only a weak conformational influence on the two-photon absorption spectrum.

  5. Color tunable light-emitting diodes based on copper doped semiconducting nanocrystals

    NASA Astrophysics Data System (ADS)

    Bhaumik, Saikat; Ghosh, Batu; Pal, Amlan J.

    2011-08-01

    We have introduced copper-doped semiconducting nanocrystals in light-emitting diodes (LEDs). Characteristics of the devices show that electroluminescence (EL) emission in these LEDs is color tunable. In copper-doped ZnS nanocrystals in the core and Zn1-xCdxS host as a shell-layer, photoluminescence (PL) arises from a transition from conduction band-edge of the host to 3d-levels of copper-ions. The PL of the nanocrystals and hence the EL of LEDs based on such nanostructures become tunable by varying the Cd-content in Zn-Cd-S alloys, that is, Zn1-xCdxS with different values of x, which changes the conduction band-edge of the host.

  6. Studies of ferromagnetic semiconducting hybrid structures

    NASA Astrophysics Data System (ADS)

    Cheon, Miyeon

    2006-04-01

    spintronic devices. The exchange bias effect with antiferromagnetic Cr cap layers on small size mesas resulted in significant enhancement of ferromagnetism and the effect was more clear in samples where significant demagnetizing effect is expected. We have studied also several different spintronic device structures. We have grown epitaxial MnAs/GaAs/MnAs ferromagnet/semiconductor trilayer heterostructures, spin Bragg reflectors with a periodic magnetic bars and FRITD structures with different conditions and studied their properties.

  7. Characteristic features of an ionization system with semiconducting cathode

    NASA Astrophysics Data System (ADS)

    Salamov, B. G.; Altındal, Ş.; Özer, M.; Çolakoğlu, K.; Bulur, E.

    1998-06-01

    The characteristic features of a dc discharge generated between parallel plate electrodes and especially the discharge stabilization by the GaAs semiconducting cathode in such a system are studied. The cathode was irradiated on the back-side with IR light in a particular wavelength range that was used to control the photoconductivity of the material. The semiconductor material was found to stabilize the discharge. The current-voltage and radiation-voltage characteristics of the gas discharge cell with a semiconducting cathode were obtained experimentally. An investigation of the effect of the voltage amplitude on the dynamics of transient processes in the plane semiconductor-discharge gap structure was made for explanation of the light intensity and current decay. Expressions are obtained for the photoelectric gain.

  8. Morphology control in biphasic hybrid systems of semiconducting materials.

    PubMed

    Mathias, Florian; Fokina, Ana; Landfester, Katharina; Tremel, Wolfgang; Schmid, Friederike; Char, Kookheon; Zentel, Rudolf

    2015-06-01

    Simple blends of inorganic nanocrystals and organic (semiconducting) polymers usually lead to macroscopic segregation. Thus, such blends typically exhibit inferior properties than expected. To overcome the problem of segregation, polymer coated nanocrystals (nanocomposites) have been developed. Such nanocomposites are highly miscible within the polymer matrix. In this Review, a summary of synthetic approaches to achieve stable nanocomposites in a semiconducting polymer matrix is presented. Furthermore, a theoretical background as well as an overview concerning morphology control of inorganic NCs in polymer matrices are provided. In addition, the morphologic behavior of highly anisotropic nanoparticles (i.e. liquid crystalline phase formation of nanorod-composites) and branched nanoparticles (spatial orientation of tetrapods) is described. Finally, the morphology requirements for the application of inorganic/organic hybrid systems in light emitting diodes and solar cells are discussed, and potential solutions to achieve the required morphologies are provided. PMID:25737161

  9. An alternative approach to charge transport in semiconducting electrodes

    NASA Technical Reports Server (NTRS)

    Thomchick, J.; Buoncristiani, A. M.

    1980-01-01

    The excess-carrier charge transport through the space-charge region of a semiconducting electrode is analyzed by a technique known as the flux method. In this approach reflection and transmission coefficients appropriate for a sheet of uniform semiconducting material describe its transport properties. A review is presented of the flux method showing that the results for a semiconductor electrode reduce in a limiting case to those previously found by Gaertner if the depletion layer is treated as a perfectly transmitting medium in which scattering and recombination are ignored. Then, in the framework of the flux method the depletion layer is considered more realistically by explicitly taking into account scattering and recombination processes which occur in this region.

  10. Transport properties in semiconducting NbS{sub 2} nanoflakes

    SciTech Connect

    Huang, Y. H.; Chen, R. S. Ho, C. H.; Peng, C. C.; Huang, Y. S.

    2014-09-01

    The electronic transport properties in individual niobium disulphide (NbS{sub 2}) nanoflakes mechanically exfoliated from the bulk crystal with three rhombohedral (3R) structure grown by chemical vapor transport were investigated. It is found that the conductivity values of the single-crystalline nanoflakes are approximately two orders of magnitude lower than that of their bulk counterparts. Temperature-dependent conductivity measurements show that the 3R-NbS{sub 2} nanoflakes exhibit semiconducting transport behavior, which is also different from the metallic character in the bulk crystals. In addition, the noncontinuous conductivity variations were observed at the temperature below 180 K for both the nanoflakes and the bulks, which is attributed to the probable charge density wave transition. The photoconductivities in the semiconducting nanoflakes were also observed under the excitation at 532 nm wavelength. The probable mechanisms resulting in the different transport behaviors between the NbS{sub 2} nanostructure and bulk were discussed.

  11. The high-pressure semiconducting phase of LiBC

    NASA Astrophysics Data System (ADS)

    Zhang, Meiguang

    2016-04-01

    A high-pressure hexagonal semiconducting phase (space group P63mc , 2f.u./cell) of LiBC stable above 108 GPa was predicted through first-principles calculations combined with unbiased swarm structure searching techniques. This new phase consisted of three-dimensional B-C networks which originate from the dramatic out-of-plane distortions of the graphene-like B-C sublattice in the low-pressure P63/mmc phase under compression. Contrary to the metallizations of LiBC under high pressure previously proposed, the resulting three-dimensional B-C framework lacks the system of π bonds with mobile electrons and has more localized electrons, as a result of the semiconducting nature of this high-pressure LiBC phase.

  12. Current-voltage characteristics and parameter retrieval of semiconducting nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, Z. Y.; Jin, C. H.; Liang, X. L.; Chen, Q.; Peng, L.-M.

    2006-02-01

    Electrical transport measurements were conducted on semiconducting nanowires and three distinct current-voltage (I-V) characteristics were observed, i.e., almost symmetric, almost rectifying, and almost linear. These I-V characteristics were modeled by treating the transport in the nanowire as in a metal-semiconductor-metal structure involving two Schottky barriers and a resistor in between these barriers, and the transport is shown to be dominated by the reverse-biased Schottky barrier under low bias and by the semiconducting nanowire at large bias. In contrast to the conventional Schottky diode, the reverse current in the nano-Schottky barrier structure is not negligible and the current is largely tunneling rather than thermionic. Experimental I-V curves are reproduced very well using our model, and a method for extracting nanowire resistance, electron density, and mobility is proposed and applied to ZnO, CdS, and Bi2S3 nanowires.

  13. Thiofluorographene-hydrophilic graphene derivative with semiconducting and genosensing properties.

    PubMed

    Urbanová, Veronika; Holá, Kateřina; Bourlinos, Athanasios B; Čépe, Klára; Ambrosi, Adriano; Loo, Adeline Huiling; Pumera, Martin; Karlický, František; Otyepka, Michal; Zbořil, Radek

    2015-04-01

    We present the first example of covalent chemistry on fluorographene, enabling the attachment of -SH groups through nucleophilic substitution of fluorine in a polar solvent. The resulting thiographene-like, 2D derivative is hydrophilic with semiconducting properties and bandgap between 1 and 2 eV depending on F/SH ratio. Thiofluorographene is applied in DNA biosensing by electrochemical impedance spectroscopy. PMID:25692678

  14. Semiconducting organic-inorganic nanocomposites by intimately tethering conjugated polymers to inorganic tetrapods

    NASA Astrophysics Data System (ADS)

    Jung, Jaehan; Yoon, Young Jun; Lin, Zhiqun

    2016-04-01

    Semiconducting organic-inorganic nanocomposites were judiciously crafted by placing conjugated polymers in intimate contact with inorganic tetrapods via click reaction. CdSe tetrapods were first synthesized by inducing elongated arms from CdSe zincblende seeds through seed-mediated growth. The subsequent effective inorganic ligand treatment, followed by reacting with short bifunctional ligands, yielded azide-functionalized CdSe tetrapods (i.e., CdSe-N3). Finally, the ethynyl-terminated conjugated polymer poly(3-hexylthiophene) (i.e., P3HT-&z.tbd;) was tethered to CdSe-N3 tetrapods via a catalyst-free alkyne-azide cycloaddition, forming intimate semiconducting P3HT-CdSe tetrapod nanocomposites. Intriguingly, the intimate contact between P3HT and CdSe tetrapod was found to not only render the effective dispersion of CdSe tetrapods in the P3HT matrix, but also facilitate the efficient electronic interaction between these two semiconducting constituents. The successful anchoring of P3HT chains onto CdSe tetrapods was substantiated through Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy measurements. Moreover, the absorption and photoluminescence studies further corroborated the intimate tethering between P3HT and CdSe tetrapods. The effect of the type of bifunctional ligands (i.e., aryl vs. aliphatic ligands) and the size of tetrapods on the device performance of hybrid organic-inorganic solar cells was also scrutinized. Interestingly, P3HT-CdSe tetrapod nanocomposites produced via the use of an aryl bifunctional ligand (i.e., 4-azidobenzoic acid) exhibited an improved photovoltaic performance compared to that synthesized with their aliphatic ligand counterpart (i.e., 5-bromovaleric acid). Clearly, the optimal size of CdSe tetrapods ensuring the effective charge transport in conjunction with the good dispersion of CdSe tetrapods rendered an improved device performance. We envision that the click-reaction strategy enabled by

  15. Understanding Charge Transport in Mixed Networks of Semiconducting Carbon Nanotubes.

    PubMed

    Rother, Marcel; Schießl, Stefan P; Zakharko, Yuriy; Gannott, Florentina; Zaumseil, Jana

    2016-03-01

    The ability to select and enrich semiconducting single-walled carbon nanotubes (SWNT) with high purity has led to a fast rise of solution-processed nanotube network field-effect transistors (FETs) with high carrier mobilities and on/off current ratios. However, it remains an open question whether it is best to use a network of only one nanotube species (monochiral) or whether a mix of purely semiconducting nanotubes but with different bandgaps is sufficient for high performance FETs. For a range of different polymer-sorted semiconducting SWNT networks, we demonstrate that a very small amount of narrow bandgap nanotubes within a dense network of large bandgap nanotubes can dominate the transport and thus severely limit on-currents and effective carrier mobility. Using gate-voltage-dependent electroluminescence, we spatially and spectrally reveal preferential charge transport that does not depend on nominal network density but on the energy level distribution within the network and carrier density. On the basis of these results, we outline rational guidelines for the use of mixed SWNT networks to obtain high performance FETs while reducing the cost for purification. PMID:26867006

  16. Understanding Charge Transport in Mixed Networks of Semiconducting Carbon Nanotubes

    PubMed Central

    2016-01-01

    The ability to select and enrich semiconducting single-walled carbon nanotubes (SWNT) with high purity has led to a fast rise of solution-processed nanotube network field-effect transistors (FETs) with high carrier mobilities and on/off current ratios. However, it remains an open question whether it is best to use a network of only one nanotube species (monochiral) or whether a mix of purely semiconducting nanotubes but with different bandgaps is sufficient for high performance FETs. For a range of different polymer-sorted semiconducting SWNT networks, we demonstrate that a very small amount of narrow bandgap nanotubes within a dense network of large bandgap nanotubes can dominate the transport and thus severely limit on-currents and effective carrier mobility. Using gate-voltage-dependent electroluminescence, we spatially and spectrally reveal preferential charge transport that does not depend on nominal network density but on the energy level distribution within the network and carrier density. On the basis of these results, we outline rational guidelines for the use of mixed SWNT networks to obtain high performance FETs while reducing the cost for purification. PMID:26867006

  17. Wafer-Scale Monolayer Films of Semiconducting Metal Dichalcogenides for High-Performance Electronics

    NASA Astrophysics Data System (ADS)

    Xie, Saien; Kang, Kibum; Huang, Lujie; Han, Yimo; Huang, Pinshane; Mak, Kin Fai; Kim, Cheol-Joo; Muller, David; Park, Jiwoong

    2015-03-01

    Two-dimensional semiconducting transition metal dichalcogenides (TMDs) have shown their potential in electronics, optoelectronic and valleytronis. However, large-scale growth methods reported to date have only produced materials with limited structural and electrical uniformity, hindering further technological applications. Here we present a 4-inch scale growth of continuous monolayer molybdenum disulfide (MoS2) and tungsten disulfide (WS2) films that show excellent structural and electrical uniformity over the entire wafer using metal-organic chemical vapor deposition. The resulting monolayer films show high mobility of 30 cm2/Vs at room temperature, as well as the phonon-limited transport for MoS2, regardless of the channel length and device location. They allow for the batch fabrication of monolayer MoS2 field effect transistors with a 99% yield, which display spatially-uniform n-type transistor operation with a high on/off ratio. We further demonstrate the multi-level growth and fabrication of vertically-stacked monolayer MoS2 films and devices, which could enable the development of novel three-dimensional circuitry and device integration.

  18. Electronic structure and quantum transport properties of metallic and semiconducting nanowires

    NASA Astrophysics Data System (ADS)

    Simbeck, Adam J.

    The future of the semiconductor industry hinges upon new developments to combat the scaling issues that currently afflict two main chip components: transistors and interconnects. For transistors this means investigating suitable materials to replace silicon for both the insulating gate and the semiconducting channel in order to maintain device performance with decreasing size. For interconnects this equates to overcoming the challenges associated with copper when the wire dimensions approach the confinement limit, as well as continuing to develop low-k dielectric materials that can assure minimal cross-talk between lines. In addition, such challenges make it increasingly clear that device design must move from a top-down to a bottom-up approach in which the desired electronic characteristics are tailored from first-principles. It is with such fundamental hurdles in mind that ab initio calculations on the electronic and quantum transport properties of nanoscale metallic and semiconducting wires have been performed. More specifically, this study seeks to elaborate on the role played by confinement, contacts, dielectric environment, edge decoration, and defects in altering the electronic and transport characteristics of such systems. As experiments continue to achieve better control over the synthesis and design of nanowires, these results are expected to become increasingly more important for not only the interpretation of electronic and transport trends, but also in engineering the electronic structure of nanowires for the needs of the devices of the future. For the metallic atomic wires, the quantum transport properties are first investigated by considering finite, single-atom chains of aluminum, copper, gold, and silver sandwiched between gold contacts. Non-equilibrium Green's function based transport calculations reveal that even in the presence of the contact the conductivity of atomic-scale aluminum is greater than that of the other metals considered. This is

  19. Spin glass in semiconducting KFe1.05Ag0.88Te2 single crystals

    DOE PAGESBeta

    Ryu, H.; Lei, H.; Klobes, B.; Warren, J. B.; Hermann, R. P.; Petrovic, C.

    2015-05-26

    We report discovery of KFe1.05Ag0.88Te2 single crystals with semiconducting spin glass ground state. Composition and structure analysis suggest nearly stoichiometric I4/mmm space group but allow for the existence of vacancies, absent in long range semiconducting antiferromagnet KFe1.05Ag0.88Te2. The subtle change in stoichometry in Fe/Ag sublattice changes magnetic ground state but not conductivity, giving further insight into the semiconducting gap mechanism.

  20. Unsymmetrical squaraines for nonlinear optical materials

    NASA Technical Reports Server (NTRS)

    Marder, Seth R. (Inventor); Chen, Chin-Ti (Inventor); Cheng, Lap-Tak (Inventor)

    1996-01-01

    Compositions for use in non-linear optical devices. The compositions have first molecular electronic hyperpolarizability (.beta.) either positive or negative in sign and therefore display second order non-linear optical properties when incorporated into non-linear optical devices.

  1. Design of semiconducting indacenodithiophene polymers for high performance transistors and solar cells.

    PubMed

    McCulloch, Iain; Ashraf, Raja Shahid; Biniek, Laure; Bronstein, Hugo; Combe, Craig; Donaghey, Jenny E; James, David I; Nielsen, Christian B; Schroeder, Bob C; Zhang, Weimin

    2012-05-15

    The prospect of using low cost, high throughput material deposition processes to fabricate organic circuitry and solar cells continues to drive research towards improving the performance of the semiconducting materials utilized in these devices. Conjugated aromatic polymers have emerged as a leading candidate semiconductor material class, due to their combination of their amenability to processing and reasonable electrical and optical performance. Challenges remain, however, to further improve the charge carrier mobility of the polymers for transistor applications and the power conversion efficiency for solar cells. This optimization requires a clear understanding of the relationship between molecular structure and both electronic properties and thin film morphology. In this Account, we describe an optimization process for a series of semiconducting polymers based on an electron rich indacenodithiophene aromatic backbone skeleton. We demonstrate the effect of bridging atoms, alkyl chain functionalization, and co-repeating units on the morphology, molecular orbital energy levels, charge carrier mobility, and solar cell efficiencies. This conjugated unit is extremely versatile with a coplanar aromatic ring structure, and the electron density can be manipulated by the choice of bridging group between the rings. The functionality of the bridging group also plays an important role in the polymer solubility, and out of plane aliphatic chains present in both the carbon and silicon bridge promote solubility. This particular polymer conformation, however, typically suppresses long range organization and crystallinity, which had been shown to strongly influence charge transport. In many cases, polymers exhibited both high solubility and excellent charge transport properties, even where there was no observable evidence of polymer crystallinity. The optical bandgap of the polymers can be tuned by the combination of the donating power of the bridging unit and the electron

  2. Nuclear relaxation measurements in organic semiconducting polymers for application to organic spintronics

    NASA Astrophysics Data System (ADS)

    Thenell, E. F.; Limes, M. E.; Sorte, E. G.; Vardeny, Z. V.; Saam, B.

    2015-01-01

    NMR measurements of spin-lattice relaxation of hydrogen nuclei in two prototype organic semiconducting solids, MEH-PPV and DOO-PPV, were carried out for temperatures between 4.2 K and room temperature, and for applied magnetic fields between 1.25 and 4.7 T. These π -conjugated polymers are of interest for use as the active semiconducting layer in spintronic devices. They typically exhibit weak spin-orbit coupling, and the interaction with inhomogeneous hyperfine fields generated by the nuclear spins plays a significant, if not dominant, role in the spin coherence and spin relaxation of electronic charge carriers. Our studies were conducted on unbiased bulk material with no photo-illumination. The characteristic 1H longitudinal relaxation times in these materials ranges from hundreds of milliseconds to >1000 s, and are predominantly nonmonoexponential. We present the data both in terms of a recovery time, T1 /2, corresponding to 50% recovery of thermal magnetization from saturation and in terms of a "T1 spectrum" produced via a numerical Laplace transform of the time-domain data. The evidence best supports relaxation to paramagnetic centers (radicals) mediated by nuclear spin diffusion as the primary mechanism: the observed relaxation is predominantly nonmonoexponential, and a characteristic T1 minimum as a function of temperature is apparent for both materials somewhere between 77 K and room temperature. The paramagnetic centers may be somewhat-delocalized charge-carrier pairs (i.e., polarons) along the polymer backbone, although the concentration in an unbiased sample (no carrier injection) should be very low. Alternatively, the centers may be localized defects, vacancies, or impurities. Our results may also be used to judge the feasibility of Overhauser-type dynamic nuclear polarization from polarized charge carriers or optically pumped exciton states.

  3. Crystal Growth of II-VI Semiconducting Alloys by Directional Solidification

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, Frank R.; Su, Ching-Hua; Cobb, Sharon D.; Scripa, Rosalia A.; Sha, Yi-Gao

    1999-01-01

    This research study is investigating the effects of a microgravity environment during the crystal growth of selected II-VI semiconducting alloys on their compositional, metallurgical, electrical and optical properties. The on-going work includes both Bridgman-Stockbarger and solvent growth methods, as well as growth in a magnetic field. The materials investigated are II-VI, Hg(1-x)Zn(x)Te, and Hg(1-x)Zn(x)Se, where x is between 0 and 1 inclusive, with particular emphasis on x-values appropriate for infrared detection and imaging in the 5 to 30 micron wavelength region. Wide separation between the liquidus and solidus of the phase diagrams with consequent segregation during solidification and problems associated with the high volatility of one of the components (Hg), make the preparation of homogeneous, high-quality, bulk crystals of the alloys an extremely difficult nearly an impossible task in a gravitational environment. The three-fold objectives of the on-going investigation are as follows: (1) To determine the relative contributions of gravitationally-driven fluid flows to the compositional redistribution observed during the unidirectional crystal growth of selected semiconducting solid solution alloys having large separation between the liquidus and solidus of the constitutional phase diagram; (2) To ascertain the potential role of irregular fluid flows and hydrostatic pressure effects in generation of extended crystal defects and second-phase inclusions in the crystals; and, (3) To obtain a limited amount of "high quality" materials needed for bulk crystal property characterizations and for the fabrication of various device structures needed to establish ultimate material performance limits. The flight portion of the study was to be accomplished by performing growth experiments using the Crystal Growth Furnace (CGF) manifested to fly on various Spacelab missions.

  4. P-type Semiconducting Behavior of BaSn1-xRuxO3 system

    NASA Astrophysics Data System (ADS)

    Kwon, Hyukwoo; Shin, Juyeon; Char, Kookrin

    2015-03-01

    BaSnO3 is a promising transparent perovskite oxide semiconductor due to its high mobility and chemical stability. Exploiting such properties, we have applied BaSnO3 to the field effect, the 2-dimensional electron gas, and the pn-junction devices. In spite of the success of the K-doped BaSnO3 as a p-type doped, its carrier density at room temperature is rather small due to its high activation energy of about 0.5 eV. In continuation of our previous study on SrSn1-xRuxO3 system, we studied the p-type semiconducting behavior of BaSn1-xRuxO3 system. We have epitaxially grown the BaSn1-xRuxO3 (0 <=x <=0.12) thin films by pulsed laser deposition. X-ray diffraction measurements show that the films maintain a single phase over the entire doping range and the lattice constants of the system decrease monotonously as the doping increases. Transport measurements show that the films are semiconducting and their resistivities dramatically decrease as the Ru doping increases. Hall measurement data show that the charge carriers are p-type and its corresponding mobility values vary from 0.3 ~ 0.04 cm2/V .s, depending on the doping rate. The hole carrier densities, measured to be 1017 ~ 1019 /cm3, are larger than those of K-doped BaSnO3. Using BaSn1-xRuxO3 and Ba1-xLaxSnO3 as p-type and n-type semiconductors, we will fabricate pn-junctions and report its performance.

  5. Electroexplosive device

    NASA Technical Reports Server (NTRS)

    Menichelli, V. J. (Inventor)

    1978-01-01

    An electroexplosive device is presented which employs a header having contact pins hermetically sealed with glass passing through from a connector end of the header to a cavity filled with a shunt layer of a new nonlinear resistive composition and a heat-sink layer of a new dielectric composition having good thermal conductivity and capacity. The nonlinear resistive layer and the heat-sink layer are prepared from materials by mixing with a low temperature polymerizing resin. The resin is dissolved in a suitable solvent and later evaporated. The resultant solid composite is ground into a powder, press formed into the header and cured (polymerized) at about 250 to 300 F.

  6. Process for separating metallic from semiconducting single-walled carbon nanotubes

    NASA Technical Reports Server (NTRS)

    Sun, Ya-Ping (Inventor)

    2008-01-01

    A method for separating semiconducting single-walled carbon nanotubes from metallic single-walled carbon nanotubes is disclosed. The method utilizes separation agents that preferentially associate with semiconducting nanotubes due to the electrical nature of the nanotubes. The separation agents are those that have a planar orientation, .pi.-electrons available for association with the surface of the nanotubes, and also include a soluble portion of the molecule. Following preferential association of the separation agent with the semiconducting nanotubes, the agent/nanotubes complex is soluble and can be solubilized with the solution enriched in semiconducting nanotubes while the residual solid is enriched in metallic nanotubes.

  7. Enhanced ambipolar charge injection with semiconducting polymer/carbon nanotube thin films for light-emitting transistors.

    PubMed

    Gwinner, Michael C; Jakubka, Florian; Gannott, Florentina; Sirringhaus, Henning; Zaumseil, Jana

    2012-01-24

    We investigate the influence of small amounts of semiconducting single-walled carbon nanotubes (SWNTs) dispersed in polyfluorenes such as poly(9,9-di-n-octylfluorene-alt-benzothiadiazole (F8BT) and poly(9,9-dioctylfluorene) (F8) on device characteristics of bottom contact/top gate ambipolar light-emitting field-effect transistors (LEFETs) based on these conjugated polymers. We find that the presence of SWNTs within the semiconducting layer at concentrations below the percolation limit significantly increases both hole and electron injection, even for a large band gap semiconductor like F8, without leading to significant luminescence quenching of the conjugated polymer. As a result of the reduced contact resistance and lower threshold voltages, larger ambipolar currents and thus brighter light emission are observed. We examine possible mechanisms of this effect such as energy level alignment, reduced bulk resistance above the contacts, and field-enhanced injection at the nanotube tips. The observed ambipolar injection improvement is applicable to most conjugated polymers in staggered transistor configurations or similar organic electronic devices where injection barriers are an issue. PMID:22142143

  8. Encapsulation of Semiconducting Polymers in Vault Protein Cages

    SciTech Connect

    Ng, B.C.; Yu, M.; Gopal, A.; Rome, L.H.; Monbouquette, H.G.; Tolbert, S.H.

    2009-05-22

    We demonstrate that a semiconducting polymer [poly(2-methoxy-5-propyloxy sulfonate phenylene vinylene), MPS-PPV] can be encapsulated inside recombinant, self-assembling protein nanocapsules called 'vaults'. Polymer incorporation into these nanosized protein cages, found naturally at {approx}10,000 copies per human cell, was confirmed by fluorescence spectroscopy and small-angle X-ray scattering. Although vault cellular functions and gating mechanisms remain unknown, their large internal volume and natural prevalence within the human body suggests they could be used as carriers for therapeutics and medical imaging reagents. This study provides the groundwork for the use of vaults in encapsulation and delivery applications.

  9. Annealing effects on the optical properties of semiconducting boron carbide

    SciTech Connect

    Billa, R. B.; Robertson, B. W.; Hofmann, T.; Schubert, M.

    2009-08-01

    Infrared vibrations of as-deposited and annealed semiconducting boron carbide thin films were investigated by midinfrared spectroscopic ellipsometry. The strong boron-hydrogen resonance at approx2560 cm{sup -1} in as-deposited films reveals considerable hydrogen incorporation during plasma-enhanced chemical vapor deposition. Extended annealing at 600 deg. C caused significant reduction in film thickness, substantial reduction of boron-hydrogen bond resonance absorption, and development of distinct blue-shifted boron-carbon and icosahedral vibration mode resonances. Our findings suggest that annealing results in substantial loss of hydrogen and in development of icosahedral structure, accompanied by strain relaxation and densification.

  10. Silicon germanium semiconductive alloy and method of fabricating same

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor)

    2008-01-01

    A silicon germanium (SiGe) semiconductive alloy is grown on a substrate of single crystalline Al.sub.2O.sub.3. A {111} crystal plane of a cubic diamond structure SiGe is grown on the substrate's {0001} C-plane such that a <110> orientation of the cubic diamond structure SiGe is aligned with a <1,0,-1,0> orientation of the {0001} C-plane. A lattice match between the substrate and the SiGe is achieved by using a SiGe composition that is 0.7223 atomic percent silicon and 0.2777 atomic percent germanium.

  11. Ultraviolet optical absorptions of semiconducting copper phosphate glasses

    NASA Technical Reports Server (NTRS)

    Bae, Byeong-Soo; Weinberg, Michael C.

    1993-01-01

    Results are presented of a quantitative investigation of the change in UV optical absorption in semiconducting copper phosphate glasses with batch compositions of 40, 50, and 55 percent CuO, as a function of the Cu(2+)/Cu(total) ratio in the glasses for each glass composition. It was found that optical energy gap, E(opt), of copper phosphate glass is a function of both glass composition and Cu(2+)/Cu(total) ratio in the glass. E(opt) increases as the CuO content for fixed Cu(2+)/Cu(total) ratio and the Cu(2+)/Cu(total) ratio for fixed glass composition are reduced.

  12. High-mobility three-atom-thick semiconducting films with wafer-scale homogeneity.

    PubMed

    Kang, Kibum; Xie, Saien; Huang, Lujie; Han, Yimo; Huang, Pinshane Y; Mak, Kin Fai; Kim, Cheol-Joo; Muller, David; Park, Jiwoong

    2015-04-30

    The large-scale growth of semiconducting thin films forms the basis of modern electronics and optoelectronics. A decrease in film thickness to the ultimate limit of the atomic, sub-nanometre length scale, a difficult limit for traditional semiconductors (such as Si and GaAs), would bring wide benefits for applications in ultrathin and flexible electronics, photovoltaics and display technology. For this, transition-metal dichalcogenides (TMDs), which can form stable three-atom-thick monolayers, provide ideal semiconducting materials with high electrical carrier mobility, and their large-scale growth on insulating substrates would enable the batch fabrication of atomically thin high-performance transistors and photodetectors on a technologically relevant scale without film transfer. In addition, their unique electronic band structures provide novel ways of enhancing the functionalities of such devices, including the large excitonic effect, bandgap modulation, indirect-to-direct bandgap transition, piezoelectricity and valleytronics. However, the large-scale growth of monolayer TMD films with spatial homogeneity and high electrical performance remains an unsolved challenge. Here we report the preparation of high-mobility 4-inch wafer-scale films of monolayer molybdenum disulphide (MoS2) and tungsten disulphide, grown directly on insulating SiO2 substrates, with excellent spatial homogeneity over the entire films. They are grown with a newly developed, metal-organic chemical vapour deposition technique, and show high electrical performance, including an electron mobility of 30 cm(2) V(-1) s(-1) at room temperature and 114 cm(2) V(-1) s(-1) at 90 K for MoS2, with little dependence on position or channel length. With the use of these films we successfully demonstrate the wafer-scale batch fabrication of high-performance monolayer MoS2 field-effect transistors with a 99% device yield and the multi-level fabrication of vertically stacked transistor devices for three

  13. Networks of semiconducting SWNTs: contribution of midgap electronic states to the electrical transport.

    PubMed

    Itkis, Mikhail E; Pekker, Aron; Tian, Xiaojuan; Bekyarova, Elena; Haddon, Robert C

    2015-08-18

    Single-walled carbon nanotube (SWNT) thin films provide a unique platform for the development of electronic and photonic devices because they combine the advantages of the outstanding physical properties of individual SWNTs with the capabilities of large area thin film manufacturing and patterning technologies. Flexible SWNT thin film based field-effect transistors, sensors, detectors, photovoltaic cells, and light emitting diodes have been already demonstrated, and SWNT thin film transparent, conductive coatings for large area displays and smart windows are under development. While chirally pure SWNTs are not yet commercially available, the marketing of semiconducting (SC) and metallic (MT) SWNTs has facilitated progress toward applications by making available materials of consistent electronic structure. Nevertheless the electrical transport properties of networks of separated SWNTs are inferior to those of individual SWNTs. In particular, for semiconducting SWNTs, which are the subject of this Account, the electrical transport drastically differs from the behavior of traditional semiconductors: for example, the bandgap of germanium (E = 0.66 eV) roughly matches that of individual SC-SWNTs of diameter 1.5 nm, but in the range 300-100 K, the intrinsic carrier concentration in Ge decreases by more than 10 orders of magnitude while the conductivity of a typical SC-SWNT network decreases by less than a factor of 4. Clearly this weak modulation of the conductivity hinders the application of SC-SWNT films as field effect transistors and photodetectors, and it is the purpose of this Account to analyze the mechanism of the electrical transport leading to the unusually weak temperature dependence of the electrical conductivity of such networks. Extrinsic factors such as the contribution of residual amounts of MT-SWNTs arising from incomplete separation and doping of SWNTs are evaluated. However, the observed temperature dependence of the conductivity indicates the

  14. Electrical device fabrication from nanotube formations

    DOEpatents

    Nicholas, Nolan Walker; Kittrell, W. Carter; Kim, Myung Jong; Schmidt, Howard K.

    2013-03-12

    A method for forming nanotube electrical devices, arrays of nanotube electrical devices, and device structures and arrays of device structures formed by the methods. Various methods of the present invention allow creation of semiconducting and/or conducting devices from readily grown SWNT carpets rather than requiring the preparation of a patterned growth channel and takes advantage of the self-controlling nature of these carpet heights to ensure a known and controlled channel length for reliable electronic properties as compared to the prior methods.

  15. Ultrahigh responsivity of optically active, semiconducting asymmetric nano-channel diodes

    NASA Astrophysics Data System (ADS)

    Akbas, Y.; Stern, A.; Zhang, L. Q.; Alimi, Y.; Song, A. M.; Iñiguez-de-la-Torre, I.; Mateos, J.; González, T.; Wicks, G. W.; Sobolewski, Roman

    2015-10-01

    We present our research on the fabrication and optical characterization of novel semiconducting asymmetric nano-channel diodes (ANCDs). We focus on optical properties of ANCDs and demonstrate that they can be operated as very sensitive, single-photon-level, visible-light photodetectors. Our test devices consisted of 1.2-μm-long, ∼200- to 300-nm-wide channels that were etched in an InGaAs/InAlAs quantum-well hetero structure with a twodimensional electron gas layer. The ANCD I-V curves were collected by measuring the transport current both in the dark and under 800-nm-wavelength, continuous-wave-light laser illumination. In all of our devices, the impact of the light illumination was very clear, and there was a substantial photocurrent, even for incident optical power as low as 1 nW. The magnitude of the optical responsivity in ANCDs with the conducting nano-channel increased linearly with a decrease in optical power over many orders of magnitude, reaching a value of almost 10,000 A/W at 1-nW excitation.

  16. Chemically Tailoring Semiconducting Two-Dimensional Transition Metal Dichalcogenides and Black Phosphorus.

    PubMed

    Ryder, Christopher R; Wood, Joshua D; Wells, Spencer A; Hersam, Mark C

    2016-04-26

    Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDCs) and black phosphorus (BP) have beneficial electronic, optical, and physical properties at the few-layer limit. As atomically thin materials, 2D TMDCs and BP are highly sensitive to their environment and chemical modification, resulting in a strong dependence of their properties on substrate effects, intrinsic defects, and extrinsic adsorbates. Furthermore, the integration of 2D semiconductors into electronic and optoelectronic devices introduces unique challenges at metal-semiconductor and dielectric-semiconductor interfaces. Here, we review emerging efforts to understand and exploit chemical effects to influence the properties of 2D TMDCs and BP. In some cases, surface chemistry leads to significant degradation, thus necessitating the development of robust passivation schemes. On the other hand, appropriately designed chemical modification can be used to beneficially tailor electronic properties, such as controlling doping levels and charge carrier concentrations. Overall, chemical methods allow substantial tunability of the properties of 2D TMDCs and BP, thereby enabling significant future opportunities to optimize performance for device applications. PMID:27018800

  17. Q-switched waveguide laser based on two-dimensional semiconducting materials: tungsten disulfide and black phosphorous.

    PubMed

    Tan, Yang; Guo, Zhinan; Ma, Linan; Zhang, Han; Akhmadaliev, Shavkat; Zhou, Shengqiang; Chen, Feng

    2016-02-01

    Owing to their unique properties, graphene-like two dimensional semiconducting materials, including Tungsten Disulfide (WS2) and Black Phosphorous (BP), have attracted increasing interest from basic research to practical applications. Herein, we demonstrated the ultrafast nonlinear saturable absorption response of WS2 and BP films in the waveguide structure. Through fabricating WS2 and BP films by evaporating the solutions on glass wafers. Saturable absorber films were attached onto the end-facet of the waveguide, which therefore constitutes a resonant cavity for the waveguide laser. Under a pump laser at 810 nm, we could obtain a stable Q-switched operation in the waveguide structure. This work indicated the significant potential of WS2 and BP for the ultrafast waveguide laser. PMID:26906854

  18. Excellent nonlinearity of a selection device based on anti-series connected Zener diodes for ultrahigh-density bipolar RRAM arrays.

    PubMed

    Li, Yingtao; Li, Rongrong; Fu, Liping; Gao, Xiaoping; Wang, Yang; Tao, Chunlan

    2015-10-23

    A crossbar array is usually used for the high-density application of a resistive random access memory (RRAM) device. However, the cross-talk interference limits the increase in the integration density. In this paper, anti-series connected Zener diodes as a selection device are proposed for bipolar RRAM arrays. Simulation results show that, by using the anti-series connected Zener diodes as a selection device, the readout margin is sufficiently improved compared to that obtained without a selection device or with anti-parallel connected diodes as the selection device. The maximum size of the crossbar arrays with anti-series connected Zener diodes as a selection device over 1 TB is estimated by theoretical simulation. In addition, the feasibility of using the anti-series connected Zener diodes as a selection device for bipolar RRAM is demonstrated experimentally. These results indicate that anti-series connected Zener diodes as a selection device opens up great opportunities to realize ultrahigh-density bipolar RRAM arrays. PMID:26422279

  19. Exploring the influence of carboxylic acids on nonlinear optical (NLO) and dielectric properties of KDP crystal for applications of NLO facilitated photonic devices

    NASA Astrophysics Data System (ADS)

    Anis, Mohd; Muley, G. G.; Hakeem, A.; Shirsat, M. D.; Hussaini, S. S.

    2015-08-01

    The aim of present investigation is to assess the impact of oxalic acid (OA) and maleic acid (MA) on nonlinearity (second and third order) and dielectric behavior of potassium dihydrogen phosphate (KDP) crystal by means of SHG efficiency test, Z-scan analysis and dielectric studies respectively. The enhancement in SHG efficiency of OA and MA doped KDP crystal has been confirmed by means of Kurtz-Perry powder test technique. The close and open aperture Z-scan technique has been employed to study the nature and origin of improved third order NLO behavior of doped KDP crystals at 632.8 nm. The magnitude of third order nonlinear susceptibility (χ3), nonlinear refraction (n2), nonlinear absorption coefficient (β) and figure of merit (FOM) of doped KDP crystals has been calculated using the Z-scan transmittance data to explore the suitability of crystals for distinct laser assisted applications. The dielectric constant and dielectric loss of pure, OA and MA doped KDP crystals were measured at different temperatures by means of dielectric studies.

  20. Stacked mechanical nanogenerator comprising piezoelectric semiconducting nanostructures and Schottky conductive contacts

    DOEpatents

    Wang, Zhong L.; Xu, Sheng

    2011-08-23

    An electric power generator includes a first conductive layer, a plurality of semiconducting piezoelectric nanostructures, a second conductive layer and a plurality of conductive nanostructures. The first conductive layer has a first surface from which the semiconducting piezoelectric nanostructures extend. The second conductive layer has a second surface and is parallel to the first conductive layer so that the second surface faces the first surface of the first conductive layer. The conductive nanostructures depend downwardly therefrom. The second conductive layer is spaced apart from the first conductive layer at a distance so that when a force is applied, the semiconducting piezoelectric nanostructures engage the conductive nanostructures so that the piezoelectric nanostructures bend, thereby generating a potential difference across the at semiconducting piezoelectric nanostructures and also thereby forming a Schottky barrier between the semiconducting piezoelectric nanostructures and the conductive nanostructures.

  1. Charge-carrier injection via semiconducting electrodes into semiconducting/electroluminescent polymers

    NASA Astrophysics Data System (ADS)

    Wünsch, F.; Chazalviel, J.-N.; Ozanam, F.; Sigaud, P.; Stéphan, O.

    2001-08-01

    The indium-tin-oxide (ITO) electrode commonly used for hole injection in organic electroluminescent devices is replaced by a crystalline p-type Si electrode in order to improve the injection efficiency. Several conducting/electroluminescent polymers such as poly(9-vinylcarbazole), poly(9,9-dihexylfluorene) and polyhexylcarbazole are deposited via spin-coating onto the Si electrode, and an Al contact is evaporated on top. Current-voltage characteristics indicate that hole injection into these polymers is easier from p-Si than from ITO or Au. Surface effects hinder an even better performance, expected from naive energetics considerations. This major role of the surface is demonstrated by comparing the average photoconductivity decay time at the Si/polymer-interface with that at an Si surface, using spatially resolved microwave reflection. Also, various surface treatments such as hydrogenation, oxidation and methylation are applied to the Si substrate before polymer deposition. The results highlight the key role of the interface state density at the semiconductor/polymer interface, and the need for a surface state density as low as possible in order to minimise the operating voltage.

  2. Nonlinear Optics and Applications

    NASA Technical Reports Server (NTRS)

    Abdeldayem, Hossin A. (Editor); Frazier, Donald O. (Editor)

    2007-01-01

    Nonlinear optics is the result of laser beam interaction with materials and started with the advent of lasers in the early 1960s. The field is growing daily and plays a major role in emerging photonic technology. Nonlinear optics play a major role in many of the optical applications such as optical signal processing, optical computers, ultrafast switches, ultra-short pulsed lasers, sensors, laser amplifiers, and many others. This special review volume on Nonlinear Optics and Applications is intended for those who want to be aware of the most recent technology. This book presents a survey of the recent advances of nonlinear optical applications. Emphasis will be on novel devices and materials, switching technology, optical computing, and important experimental results. Recent developments in topics which are of historical interest to researchers, and in the same time of potential use in the fields of all-optical communication and computing technologies, are also included. Additionally, a few new related topics which might provoke discussion are presented. The book includes chapters on nonlinear optics and applications; the nonlinear Schrodinger and associated equations that model spatio-temporal propagation; the supercontinuum light source; wideband ultrashort pulse fiber laser sources; lattice fabrication as well as their linear and nonlinear light guiding properties; the second-order EO effect (Pockels), the third-order (Kerr) and thermo-optical effects in optical waveguides and their applications in optical communication; and, the effect of magnetic field and its role in nonlinear optics, among other chapters.

  3. Tailored semiconducting carbon nanotube networks with enhanced thermoelectric properties

    DOE PAGESBeta

    Avery, Azure D.; Zhou, Ben H.; Lee, Jounghee; Lee, Eui -Sup; Miller, Elisa M.; Ihly, Rachelle; Wesenberg, Devin; Mistry, Kevin S.; Guillot, Sarah L.; Zink, Barry L.; et al

    2016-04-04

    Thermoelectric power generation, allowing recovery of part of the energy wasted as heat, is emerging as an important component of renewable energy and energy efficiency portfolios. Although inorganic semiconductors have traditionally been employed in thermoelectric applications, organic semiconductors garner increasing attention as versatile thermoelectric materials. Here we present a combined theoretical and experimental study suggesting that semiconducting single-walled carbon nanotubes with carefully controlled chirality distribution and carrier density are capable of large thermoelectric power factors, higher than 340 μW m-1 K-2, comparable to the best-performing conducting polymers and larger than previously observed for carbon nanotube films. Furthermore, we demonstrate thatmore » phonons are the dominant source of thermal conductivity in the networks, and that our carrier doping process significantly reduces the thermal conductivity relative to undoped networks. As a result, these findings provide the scientific underpinning for improved functional organic thermoelectric composites with carbon nanotube inclusions.« less

  4. BaMn2Sb2: A New Semiconducting Ferromagnet

    NASA Astrophysics Data System (ADS)

    Li, Jianneng; Stadler, S.; Karki, A.; Xiong, Y.; Jin, R.

    2012-02-01

    We have grown high-quality single crystals of BaMn2Sb2, which possesses the ThCr2Si2 structure as determined by X-ray powder diffraction technique. Magnetization measurements indicate that BaMn2Fe2 is ferromagnetic below TC = 580K. On the other hand, the temperature dependence of electrical resistivity shows semiconducting behavior, which can be described by thermally-activated resistivity formula with thermal activation energy about 0.25 eV . While the Hall coefficient has positive sign between 2 and 300 K, the Seebeck Coefficient undergoes sign change from positive at high temperatures to negative at low temperatures, reaching -260 μV/K at 70 K. The implication will be discussed.

  5. Nanoscale semiconducting silicon as a nutritional food additive

    NASA Astrophysics Data System (ADS)

    Canham, L. T.

    2007-05-01

    Very high surface area silicon powders can be realized by high energy milling or electrochemical etching techniques. Such nanoscale silicon structures, whilst biodegradable in the human gastrointestinal tract, are shown to be remarkably stable in most foodstuffs and beverages. The potential for using silicon to improve the shelf life and bioavailability of specific nutrients in functional foods is highlighted. Published drug delivery data implies that the nanoentrapment of hydrophobic nutrients will significantly improve their dissolution kinetics, through a combined effect of nanostructuring and solid state modification. Nutrients loaded to date include vitamins, fish oils, lycopene and coenzyme Q10. In addition, there is growing published evidence that optimized release of orthosilicic acid, the biodegradation product of semiconducting silicon in the gut, offers beneficial effects with regard bone health. The utility of nanoscale silicon in the nutritional field shows early promise and is worthy of much further study.

  6. Tailored semiconducting carbon nanotube networks with enhanced thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Avery, Azure D.; Zhou, Ben H.; Lee, Jounghee; Lee, Eui-Sup; Miller, Elisa M.; Ihly, Rachelle; Wesenberg, Devin; Mistry, Kevin S.; Guillot, Sarah L.; Zink, Barry L.; Kim, Yong-Hyun; Blackburn, Jeffrey L.; Ferguson, Andrew J.

    2016-04-01

    Thermoelectric power generation, allowing recovery of part of the energy wasted as heat, is emerging as an important component of renewable energy and energy efficiency portfolios. Although inorganic semiconductors have traditionally been employed in thermoelectric applications, organic semiconductors garner increasing attention as versatile thermoelectric materials. Here we present a combined theoretical and experimental study suggesting that semiconducting single-walled carbon nanotubes with carefully controlled chirality distribution and carrier density are capable of large thermoelectric power factors, higher than 340 μW m‑1 K‑2, comparable to the best-performing conducting polymers and larger than previously observed for carbon nanotube films. Furthermore, we demonstrate that phonons are the dominant source of thermal conductivity in the networks, and that our carrier doping process significantly reduces the thermal conductivity relative to undoped networks. These findings provide the scientific underpinning for improved functional organic thermoelectric composites with carbon nanotube inclusions.

  7. Amplified Spontaneous Emission Properties of Semiconducting Organic Materials

    PubMed Central

    Calzado, Eva M.; Boj, Pedro G.; Díaz-García, María A.

    2010-01-01

    This paper aims to review the recent advances achieved in the field of organic solid-state lasers with respect to the usage of semiconducting organic molecules and oligomers in the form of thin films as active laser media. We mainly focus on the work performed in the last few years by our research group. The amplified spontaneous emission (ASE) properties, by optical pump, of various types of molecules doped into polystyrene films in waveguide configuration, are described. The various systems investigated include N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD), several perilenediimide derivatives (PDIs), as well as two oligo-phenylenevinylene derivatives. The ASE characteristics, i.e., threshold, emission wavelength, linewidth, and photostability are compared with that of other molecular materials investigated in the literature. PMID:20640167

  8. Design of Semiconducting Tetrahedral Mn 1 ₋ x Zn x O Alloys and Their Application to Solar Water Splitting

    DOE PAGESBeta

    Peng, Haowei; Ndione, Paul F.; Ginley, David S.; Zakutayev, Andriy; Lany, Stephan

    2015-05-18

    Transition metal oxides play important roles as contact and electrode materials, but their use as active layers in solar energy conversion requires achieving semiconducting properties akin to those of conventional semiconductors like Si or GaAs. In particular, efficient bipolar carrier transport is a challenge in these materials. Based on the prediction that a tetrahedral polymorph of MnO should have such desirable semiconducting properties, and the possibility to overcome thermodynamic solubility limits by nonequilibrium thin-film growth, we exploit both structure-property and composition-structure relationships to design and realize novel wurtzite-structure Mn₁₋xZnxO alloys. At Zn compositions above x ≈ 0.3, thin films ofmore » these alloys assume the tetrahedral wurtzite structure instead of the octahedral rocksalt structure of MnO, thereby enabling semiconductor properties that are unique among transition metal oxides, i.e., a band gap within the visible spectrum, a band-transport mechanism for both electron and hole carriers, electron doping, and a band lineup suitable for solar hydrogen generation. A proof of principle is provided by initial photo-electrocatalytic device measurements, corroborating, in particular, the predicted favorable hole-transport properties of these alloys.« less

  9. ``Once Nonlinear, Always Nonlinear''

    NASA Astrophysics Data System (ADS)

    Blackstock, David T.

    2006-05-01

    The phrase "Once nonlinear, always nonlinear" is attributed to David F. Pernet. In the 1970s he noticed that nonlinearly generated higher harmonic components (both tones and noise) don't decay as small signals, no matter how far the wave propagates. Despite being out of step with the then widespread notion that small-signal behavior is restored in "old age," Pernet's view is supported by the Burgers-equation solutions of the early 1960s. For a plane wave from a sinusoidally vibrating source in a thermoviscous fluid, the old-age decay of the nth harmonic is e-nαx, not e-n2αx (small-signal expectation), where α is the absorption coefficient at the fundamental frequency f and x is propagation distance. Moreover, for spherical waves (r the distance) the harmonic diminishes as e-nαx/rn, not e-n2αx/r. While not new, these results have special application to aircraft noise propagation, since the large propagation distances of interest imply old age. The virtual source model may be used to explain the "anomalous" decay rates. In old age most of the nth harmonic sound comes from virtual sources close to the receiver. Their strength is proportional to the nth power of the local fundamental amplitude, and that sets the decay law for the nth harmonic.

  10. Emissivity and electrooptical properties of semiconducting quantum dots/rods and liquid crystal composites: a review.

    PubMed

    Singh, Gautam; Fisch, Michael; Kumar, Satyendra

    2016-05-01

    Investigations of the mixtures of semiconducting quantum scale particles in anisotropic liquid crystal (LC) medium have become a vibrant area of research primarily due to their very interesting phenomenology. The results of these investigations fall into four groups: (i) Photoluminescent emissive properties of the quantum particles ordinarily depend on the size, shape, and chemical nature of the particles. These undergo important changes in their spectrum, polarization, and isotropy of emission when dissolved in an anisotropic LC phase. Moreover, their response to external stimuli such as mechanical, optical, or electric fields is altered in important ways; (ii) physical properties of LCs such as viscosity, dielectric relaxation, etc are modified by the addition of quantum particles. Their presence in ferroelectric smectic LC is known to give rise to an antiferro- to ferri-electric phase transition and suppresses the paraelectric phase; (iii) switching characteristics of LC devices are altered in important ways by the addition of quantum particles. Their threshold voltage is usually lowered, contrast ratio, and switching speed of nematic, ferroelectric, and cholesteric devices may increase or decrease depending on the concentration, applied field, and particle anisotropy; and (iv) controlled aggregation of quantum particles at the interface between isotropic and LC domains, near added polystyrene beads, and in the vicinity of point defects gives rise to interesting photonic structures, enables studies of photon antibunching and single photon sources. Clearly, there is a need to understand the basic and applied aspects of these systems and find routes to their technological applications including sensors, electrooptical devices, and solar energy harvesting. This review provides an overview of recent work involving liquid crystals and a variety of quantum particles. PMID:27088655

  11. Emissivity and electrooptical properties of semiconducting quantum dots/rods and liquid crystal composites: a review

    NASA Astrophysics Data System (ADS)

    Singh, Gautam; Fisch, Michael; Kumar, Satyendra

    2016-05-01

    Investigations of the mixtures of semiconducting quantum scale particles in anisotropic liquid crystal (LC) medium have become a vibrant area of research primarily due to their very interesting phenomenology. The results of these investigations fall into four groups: (i) Photoluminescent emissive properties of the quantum particles ordinarily depend on the size, shape, and chemical nature of the particles. These undergo important changes in their spectrum, polarization, and isotropy of emission when dissolved in an anisotropic LC phase. Moreover, their response to external stimuli such as mechanical, optical, or electric fields is altered in important ways; (ii) physical properties of LCs such as viscosity, dielectric relaxation, etc are modified by the addition of quantum particles. Their presence in ferroelectric smectic LC is known to give rise to an antiferro- to ferri-electric phase transition and suppresses the paraelectric phase; (iii) switching characteristics of LC devices are altered in important ways by the addition of quantum particles. Their threshold voltage is usually lowered, contrast ratio, and switching speed of nematic, ferroelectric, and cholesteric devices may increase or decrease depending on the concentration, applied field, and particle anisotropy; and (iv) controlled aggregation of quantum particles at the interface between isotropic and LC domains, near added polystyrene beads, and in the vicinity of point defects gives rise to interesting photonic structures, enables studies of photon antibunching and single photon sources. Clearly, there is a need to understand the basic and applied aspects of these systems and find routes to their technological applications including sensors, electrooptical devices, and solar energy harvesting. This review provides an overview of recent work involving liquid crystals and a variety of quantum particles.

  12. Recent advances in large-scale assembly of semiconducting inorganic nanowires and nanofibers for electronics, sensors and photovoltaics.

    PubMed

    Long, Yun-Ze; Yu, Miao; Sun, Bin; Gu, Chang-Zhi; Fan, Zhiyong

    2012-06-21

    Semiconducting inorganic nanowires (NWs), nanotubes and nanofibers have been extensively explored in recent years as potential building blocks for nanoscale electronics, optoelectronics, chemical/biological/optical sensing, and energy harvesting, storage and conversion, etc. Besides the top-down approaches such as conventional lithography technologies, nanowires are commonly grown by the bottom-up approaches such as solution growth, template-guided synthesis, and vapor-liquid-solid process at a relatively low cost. Superior performance has been demonstrated using nanowires devices. However, most of the nanowire devices are limited to the demonstration of single devices, an initial step toward nanoelectronic circuits, not adequate for production on a large scale at low cost. Controlled and uniform assembly of nanowires with high scalability is still one of the major bottleneck challenges towards the materials and device integration for electronics. In this review, we aim to present recent progress toward nanowire device assembly technologies, including flow-assisted alignment, Langmuir-Blodgett assembly, bubble-blown technique, electric/magnetic- field-directed assembly, contact/roll printing, planar growth, bridging method, and electrospinning, etc. And their applications in high-performance, flexible electronics, sensors, photovoltaics, bioelectronic interfaces and nano-resonators are also presented. PMID:22573265

  13. Semiconducting boron carbides with better charge extraction through the addition of pyridine moieties

    NASA Astrophysics Data System (ADS)

    Echeverria, Elena; Dong, Bin; Peterson, George; Silva, Joseph P.; Wilson, Ethiyal R.; Sky Driver, M.; Jun, Young-Si; Stucky, Galen D.; Knight, Sean; Hofmann, Tino; Han, Zhong-Kang; Shao, Nan; Gao, Yi; Mei, Wai-Ning; Nastasi, Michael; Dowben, Peter A.; Kelber, Jeffry A.

    2016-09-01

    The plasma-enhanced chemical vapor (PECVD) co-deposition of pyridine and 1,2 dicarbadodecaborane, 1,2-B10C2H12 (orthocarborane) results in semiconducting boron carbide composite films with a significantly better charge extraction than plasma-enhanced chemical vapor deposited semiconducting boron carbide synthesized from orthocarborane alone. The PECVD pyridine/orthocarborane based semiconducting boron carbide composites, with pyridine/orthocarborane ratios ~3:1 or 9:1 exhibit indirect band gaps of 1.8 eV or 1.6 eV, respectively. These energies are less than the corresponding exciton energies of 2.0 eV–2.1 eV. The capacitance/voltage and current/voltage measurements indicate the hole carrier lifetimes for PECVD pyridine/orthocarborane based semiconducting boron carbide composites (3:1) films of ~350 µs compared to values of  ⩽35 µs for the PECVD semiconducting boron carbide films fabricated without pyridine. The hole carrier lifetime values are significantly longer than the initial exciton decay times in the region of ~0.05 ns and 0.27 ns for PECVD semiconducting boron carbide films with and without pyridine, respectively, as suggested by the time-resolved photoluminescence. These data indicate enhanced electron–hole separation and charge carrier lifetimes in PECVD pyridine/orthocarborane based semiconducting boron carbide and are consistent with the results of zero bias neutron voltaic measurements indicating significantly enhanced charge collection efficiency.

  14. Semiconducting ferroelectric SbSI quantum dots in organically modified TiO2 matrix

    NASA Astrophysics Data System (ADS)

    Ye, Hui; Xu, Yuhuan; Mackenzie, John D.

    2000-05-01

    Semiconducting ferro electric antimony sulphoiodide (SbSI) microcrystallite doped organically modified TiO2 thin film and bulk solids are successfully fabricated by the sol- gel process. Ferro electric SbSI crystallites have some attractive properties, including high dielectric permittivity, high electro-optical coefficient and high photoconductivity. SbSI is also an intrinsic semiconductor with a relatively narrow energy gap. If the crystal size is near its Bohr radius and the microcrystallites are dispersed in a suitable matrix, a dramatic improvement of the third order non linearity will be achieved due to the quantum confinement effect. It is clear that the SbSI quantum dot composites are good candidates for electro-optical devices. Glycidoxypropyltrimetroxysilane modified TiO2 is used as the matrix and SbSI is synthesized in situ by using SbI3 SC9NH2)2 and H2S gas. The size is controlled by the heat-treatment conditions and is characterized by the XRD and HRTEM measurements. The optical absorption spectrum gives evidence of the quantum confinement effect. The third order susceptibility of the SbSI quantum dot is measured by the degenerate four wave mixing method.

  15. Thermal conductivity of organic semi-conducting materials using 3omega and photothermal radiometry techniques

    NASA Astrophysics Data System (ADS)

    Reisdorffer, Frederic; Garnier, Bertrand; Horny, Nicolas; Renaud, Cedric; Chirtoc, Mihai; Nguyen, Thien-Phap

    2014-12-01

    Organic semiconductors for opto-electronic devices show several defects which can be enhanced while increasing the operating temperature. Their thermal management and especially the reduction of their temperature are of great interest. For the heat transfer study, one has to measure the thermal conductivity of thin film organic materials. However the major difficulty for this measurement is the very low thickness of the films which needs the use of very specific techniques. In our work, the 3-omega and photothermal radiometric methods were used to measure the thermal conductivity of thin film organic semiconducting material (Alq3). The measurements were performed as function of the thin film thickness from 45 to 785 nm and also of its temperature from 80 to 350 K. With the 3 omega method, a thermal conductivity value of 0.066 W.m-1K-1 was obtained for Alq3 thin film of 200 nm at room temperature, in close agreement with the photothermal value. Both techniques appear to be complementary: the 3 omega method is easier to implement for large temperature range and small thicknesses down to a few tens of nanometers whereas the photothermal method is more suitable for thicknesses over 200nm since it provides additional information such as the thin film volumetric heat capacity.

  16. Transparent ferromagnetic and semiconducting behavior in Fe-Dy-Tb based amorphous oxide films

    PubMed Central

    Taz, H.; Sakthivel, T.; Yamoah, N. K.; Carr, C.; Kumar, D.; Seal, S.; Kalyanaraman, R.

    2016-01-01

    We report a class of amorphous thin film material comprising of transition (Fe) and Lanthanide metals (Dy and Tb) that show unique combination of functional properties. Films were deposited with different atomic weight ratio (R) of Fe to Lanthanide (Dy + Tb) using electron beam co-evaporation at room temperature. The films were found to be amorphous, with grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy studies indicating that the films were largely oxidized with a majority of the metal being in higher oxidation states. Films with R = 0.6 were semiconducting with visible light transmission due to a direct optical band-gap (2.49 eV), had low resistivity and sheet resistance (7.15 × 10−4 Ω-cm and ~200 Ω/sq respectively), and showed room temperature ferromagnetism. A metal to semiconductor transition with composition (for R < 11.9) also correlated well with the absence of any metallic Fe0 oxidation state in the R = 0.6 case as well as a significantly higher fraction of oxidized Dy. The combination of amorphous microstructure and room temperature electronic and magnetic properties could lead to the use of the material in multiple applications, including as a transparent conductor, active material in thin film transistors for display devices, and in spin-dependent electronics. PMID:27298196

  17. Universal helimagnon and skyrmion excitations in metallic, semiconducting and insulating chiral magnets

    NASA Astrophysics Data System (ADS)

    Schwarze, T.; Waizner, J.; Garst, M.; Bauer, A.; Stasinopoulos, I.; Berger, H.; Pfleiderer, C.; Grundler, D.

    2015-05-01

    Nearly seven decades of research on microwave excitations of magnetic materials have led to a wide range of applications in electronics. The recent discovery of topological spin solitons in chiral magnets, so-called skyrmions, promises high-frequency devices that exploit the exceptional emergent electrodynamics of these compounds. Therefore, an accurate and unified quantitative account of their resonant response is key. Here, we report all-electrical spectroscopy of the collective spin excitations in the metallic, semiconducting and insulating chiral magnets MnSi, Fe1-xCoxSi and Cu2OSeO3, respectively, using broadband coplanar waveguides. By taking into account dipolar interactions, we achieve a precise quantitative modelling across the entire magnetic phase diagrams using two material-specific parameters that quantify the chiral and the critical field energy. The universal behaviour sets the stage for purpose-designed applications based on the resonant response of chiral magnets with tailored electric conductivity and an unprecedented freedom for an integration with electronics.

  18. Biotin-Functionalized Semiconducting Polymer in an Organic Field Effect Transistor and Application as a Biosensor

    PubMed Central

    Kim, Zin-Sig; Lim, Sang Chul; Kim, Seong Hyun; Yang, Yong Suk; Hwang, Do-Hoon

    2012-01-01

    This report presents biotin-functionalized semiconducting polymers that are based on fluorene and bithiophene co-polymers (F8T2). Also presented is the application of these polymers to an organic thin film transistor used as a biosensor. The side chains of fluorene were partially biotinylated after the esterification of the biotin with corresponding alcohol-groups at the side chain in F8T2. Their properties as an organic semiconductor were tested using an organic thin film transistor (OTFT) and were found to show typical p-type semiconductor curves. The functionality of this biosensor in the sensing of biologically active molecules such as avidin in comparison with bovine serum albumin (BSA) was established through a selective decrease in the conductivity of the transistor, as measured with a device that was developed by the authors. Changes to the optical properties of this polymer were also measured through the change in the color of the UV-fluorescence before and after a reaction with avidin or BSA. PMID:23112654

  19. Direct observation of hole transfer from semiconducting polymer to carbon nanotubes.

    PubMed

    Lan, Fei; Li, Guangyong

    2013-05-01

    Carbon nanotubes have been proven to play significant roles in polymer-based solar cells. However, there is intensive debate on whether carbon nanotube behaves as a donor or acceptor in the semiconducting polymer:carbon nanotube composite. In this paper, we report a direct observation via Kelvin probe force microscopy (KPFM) that single walled carbon nanotubes (SWNTs) behave as hole transporting channels in poly(3-hexylthiophene-2,5-diyl) (P3HT)/SWNT heterojunctions. By comparing the surface potential (SP) change of SWNT in dark and under illumination, we observed that electrons are blocked from SWNT while holes are transferred to SWNT. This observation can be well-explained by our proposed band alignment model of P3HT/SWNT heterojunction. The finding is further verified by hole mobility measurement using the space charge limited current (SCLC) method. SCLC results indicate that the existence of small amount of SWNT (wt 0.5%) promotes device hole mobility to around 15-fold, indicating SWNT act as hole transfer channel. Our finding of hole transporting behavior of SWNT in P3HT/SWNT blend will provide a useful guidance for enhancing the performance of polymer solar cells by carbon nanotubes. PMID:23574570

  20. Transparent ferromagnetic and semiconducting behavior in Fe-Dy-Tb based amorphous oxide films

    NASA Astrophysics Data System (ADS)

    Taz, H.; Sakthivel, T.; Yamoah, N. K.; Carr, C.; Kumar, D.; Seal, S.; Kalyanaraman, R.

    2016-06-01

    We report a class of amorphous thin film material comprising of transition (Fe) and Lanthanide metals (Dy and Tb) that show unique combination of functional properties. Films were deposited with different atomic weight ratio (R) of Fe to Lanthanide (Dy + Tb) using electron beam co-evaporation at room temperature. The films were found to be amorphous, with grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy studies indicating that the films were largely oxidized with a majority of the metal being in higher oxidation states. Films with R = 0.6 were semiconducting with visible light transmission due to a direct optical band-gap (2.49 eV), had low resistivity and sheet resistance (7.15 × 10‑4 Ω-cm and ~200 Ω/sq respectively), and showed room temperature ferromagnetism. A metal to semiconductor transition with composition (for R < 11.9) also correlated well with the absence of any metallic Fe0 oxidation state in the R = 0.6 case as well as a significantly higher fraction of oxidized Dy. The combination of amorphous microstructure and room temperature electronic and magnetic properties could lead to the use of the material in multiple applications, including as a transparent conductor, active material in thin film transistors for display devices, and in spin-dependent electronics.

  1. Transparent ferromagnetic and semiconducting behavior in Fe-Dy-Tb based amorphous oxide films.

    PubMed

    Taz, H; Sakthivel, T; Yamoah, N K; Carr, C; Kumar, D; Seal, S; Kalyanaraman, R

    2016-01-01

    We report a class of amorphous thin film material comprising of transition (Fe) and Lanthanide metals (Dy and Tb) that show unique combination of functional properties. Films were deposited with different atomic weight ratio (R) of Fe to Lanthanide (Dy + Tb) using electron beam co-evaporation at room temperature. The films were found to be amorphous, with grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy studies indicating that the films were largely oxidized with a majority of the metal being in higher oxidation states. Films with R = 0.6 were semiconducting with visible light transmission due to a direct optical band-gap (2.49 eV), had low resistivity and sheet resistance (7.15 × 10(-4) Ω-cm and ~200 Ω/sq respectively), and showed room temperature ferromagnetism. A metal to semiconductor transition with composition (for R < 11.9) also correlated well with the absence of any metallic Fe(0) oxidation state in the R = 0.6 case as well as a significantly higher fraction of oxidized Dy. The combination of amorphous microstructure and room temperature electronic and magnetic properties could lead to the use of the material in multiple applications, including as a transparent conductor, active material in thin film transistors for display devices, and in spin-dependent electronics. PMID:27298196

  2. Progression in sensing cardiac troponin biomarker charge transductions on semiconducting nanomaterials.

    PubMed

    Fathil, M F M; Md Arshad, M K; Ruslinda, A R; Nuzaihan M N, M; Gopinath, Subash C B; Adzhri, R; Hashim, U

    2016-09-01

    A real-time ability to interpret the interaction between targeted biomolecules and the surface of semiconductors (metal transducers) into readable electrical signals, without biomolecular modification involving fluorescence dyes, redox enzymes, and radioactive labels, created by label-free biosensors has been extensively researched. Field-effect transistor (FET)- and capacitor-based biosensors are among the diverse electrical charge biosensing architectures that have drawn much attention for having charge transduction; thus, enabling the early and rapid diagnosis of the appropriate cardiac biomarkers at lower concentrations. These semiconducting material-based transducers are very suitable to be integrated with portable electronic devices for future online collection, transmission, reception, analysis, and reporting. This overview elucidates and clarifies two major electrical label-free systems (FET- and capacitor-based biosensors) with cardiac troponin (cTn) biomarker-mediated charge transduction for acute myocardial infarction (AMI) diagnosis. Advances in these systems are highlighted by their progression in bridging the laboratory and industry; the foremost technologies have made the transition from benchtop to bedside and beyond. PMID:27543013

  3. Universal helimagnon and skyrmion excitations in metallic, semiconducting and insulating chiral magnets.

    PubMed

    Schwarze, T; Waizner, J; Garst, M; Bauer, A; Stasinopoulos, I; Berger, H; Pfleiderer, C; Grundler, D

    2015-05-01

    Nearly seven decades of research on microwave excitations of magnetic materials have led to a wide range of applications in electronics. The recent discovery of topological spin solitons in chiral magnets, so-called skyrmions, promises high-frequency devices that exploit the exceptional emergent electrodynamics of these compounds. Therefore, an accurate and unified quantitative account of their resonant response is key. Here, we report all-electrical spectroscopy of the collective spin excitations in the metallic, semiconducting and insulating chiral magnets MnSi, Fe1-xCoxSi and Cu2OSeO3, respectively, using broadband coplanar waveguides. By taking into account dipolar interactions, we achieve a precise quantitative modelling across the entire magnetic phase diagrams using two material-specific parameters that quantify the chiral and the critical field energy. The universal behaviour sets the stage for purpose-designed applications based on the resonant response of chiral magnets with tailored electric conductivity and an unprecedented freedom for an integration with electronics. PMID:25730395

  4. Critical Role of Processing on the Thermoelectric Performance of Doped Semiconducting Polymers

    NASA Astrophysics Data System (ADS)

    Patel, Shrayesh; Glaudell, Anne; Chabinyc, Michael

    The ability to convert excess waste heat into useable energy can significantly help meet the global energy demands. One may capture this waste heat through thermoelectrics devices. In a thermoelectric material, the charge carriers transport both electrical current and heat. Consequently, under a temperature difference (ΔT), a carrier concentration gradient results in a voltage (ΔV), which is related to the Seebeck coefficient, α = - Δ V/ ΔT. One of the challenges lies in finding materials that simultaneously have low thermal conductivity (κ) , high electrical conductivity (σ) , and high Seebeck coefficient (α) . Conjugated semiconducting polymers can potentially meet this demand due to their inherent low thermal conductivity and high electrical conductivity through sufficient doping. Here, we report on the critical role of thermal processing on the enhancement of thermoelectric properties of conjugated polymer thin films. These films were doping using three different mechanisms: acid (toluene sulfonic acid), charge transfer (F4TCNQ), and vapor (fluorinated-alkyl trichlorosilane). These thermoelectrics properties will be correlated to the structural and morphological properties of the doped thin-films through various synchrotron X-ray scattering techniques. Lastly, to further elucidate the charge transport mechanism driving the thermoelectric performance, we report on the temperature-dependent measurements of both the Seebeck coefficient and electrical conductivity.

  5. Diffusion-assisted photoexcitation transfer in coupled semiconducting carbon nanotube thin films.

    PubMed

    Grechko, Maksim; Ye, Yumin; Mehlenbacher, Randy D; McDonough, Thomas J; Wu, Meng-Yin; Jacobberger, Robert M; Arnold, Michael S; Zanni, Martin T

    2014-06-24

    We utilize femtosecond transient absorption spectroscopy to study dynamics of photoexcitation migration in films of semiconducting single-wall carbon nanotubes. Films of nanotubes in close contact enable energy migration such as needed in photovoltaic and electroluminescent devices. Two types of films composed of nanotube fibers are utilized in this study: densely packed and very porous. By comparing exciton kinetics in these films, we characterize excitation transfer between carbon nanotubes inside fibers versus between fibers. We find that intrafiber transfer takes place in both types of films, whereas interfiber transfer is greatly suppressed in the porous one. Using films with different nanotube composition, we are able to test several models of exciton transfer. The data are inconsistent with models that rely on through-space interfiber energy transfer. A model that fits the experimental results postulates that interfiber transfer occurs only at intersections between fibers, and the excitons reach the intersections by diffusing along the long-axis of the tubes. We find that time constants for the inter- and intrafiber transfers are 0.2-0.4 and 7 ps, respectively. In total, hopping between fibers accounts for about 60% of all exciton downhill transfer prior to 4 ps in the dense film. The results are discussed with regards to transmission electron micrographs of the films. This study provides a rigorous analysis of the photophysics in this new class of promising materials for photovoltaics and other technologies. PMID:24806792

  6. Universal empirical formula for optical transition energies of semiconducting single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Jamal, G. R. Ahmed; Mominuzzaman, S. M.

    2016-01-01

    A general empirical relation for calculating first seven optical transition energies of semiconducting single wall carbon nanotubes (SWCNTs) is proposed here for the first time. The proposed formula effectively relates first seven optical transition energies of semiconducting SWCNTs with their chiral indices (n, m) through exponential form containing two specific terms (n+2m) and (2n-m). Both mod 1 and mod 2 types of semiconducting tubes are considered here over a wide diameter range from 0.4 nm to 4.75 nm. It was observed that the proposed empirical relations can predict the recent experimental data of those optical transitions with high accuracy.

  7. Aligned crystalline semiconducting film on a glass substrate and method of making

    DOEpatents

    Findikoglu, Alp T.

    2010-08-24

    A semiconducting structure having a glass substrate. In one embodiment, the glass substrate has a softening temperature of at least about 750.degree. C. The structure includes a nucleation layer formed on a surface of the substrate, a template layer deposited on the nucleation layer by one of ion assisted beam deposition and reactive ion beam deposition, at least on biaxially oriented buffer layer epitaxially deposited on the template layer, and a biaxially oriented semiconducting layer epitaxially deposited on the buffer layer. A method of making the semiconducting structure is also described.

  8. Long term experience with semi-conductive glaze high voltage post insulators

    SciTech Connect

    Baker, A.C.; Maney, J.W.; Szilagyi, Z. )

    1990-01-01

    Insulators using semi-conductive glaze have long been known for their superior contamination performance. Early glazes for this type however were not stable and successful use of semi-conductive glazed porcelain insulators was delayed many years until tin-antimony oxide glazes were developed. Service experience of eighteen years is now available for line and station post insulators with this type of glaze. Based on this experience, the aging characteristics of tin-antimony oxide semi-conductive glazes are described and quantified. Several different applications of these insulators are also described.

  9. Control of transport and magnetism in ferromagnetic semiconducting superlattices through growth conditions and chemical surface effects

    NASA Astrophysics Data System (ADS)

    Kreutz, Theodore Carlton

    2003-10-01

    Within the emerging area of spintronics, magnetic semiconductors have been the subject of many recent studies. Advances in magnetizing traditional semiconductors like GaAs, through the introduction of Mn, have been the focus of many experiments. Recently, studies have focused on ferromagnetic semiconducting superlattices, where half-monolayer MnAs planes are separated by GaAs spacers. These structures have only recently been grown, and it is of particular interest to discover the properties of this material, and if it can be used in future spintronic devices. We have studied changes in the magnetic and transport properties of ferromagnetic semiconducting superlattices as a function of temperature, superlattice period and substrate growth temperature. We have measured the resistance, Hall resistance and magnetoresistance over a wide range of temperatures. We see that as the period of the superlattice increases, the per-layer resistance and the Curie temperature reach saturation values at approximately the same value. We also find that electrical transport is predominantly through hopping conduction. The anomalous Hall effect dominates the Hall resistance. With the period fixed, we vary the substrate temperature during growth and observe that higher substrate temperatures lead to less resistive samples. Also, for samples with high substrate temperatures, we find that the anomalous Hall coefficient can flip in sign. We also observe changes in the magnetic anisotropy as we vary the period of the superlattice and the substrate temperature. We observe this change with planar Hall effect as well as SQUID magnetometry measurements. Samples with short periods show cubic magnetic anisotropy whereas samples with larger period show uniaxial anisotropy. We then determine the anisotropy constants for this material. We also see that the switching is dominated by domain pinning processes. Finally, we are able to change the Curie temperature of ½ ML MnAs planes in GaAs through the

  10. Ultrafast Exciton Hopping Observed in Bare Semiconducting Carbon Nanotube Thin Films with Two-Dimensional White-Light Spectroscopy.

    PubMed

    Mehlenbacher, Randy D; Wang, Jialiang; Kearns, Nicholas M; Shea, Matthew J; Flach, Jessica T; McDonough, Thomas J; Wu, Meng-Yin; Arnold, Michael S; Zanni, Martin T

    2016-06-01

    We observe ultrafast energy transfer between bare carbon nanotubes in a thin film using two-dimensional (2D) white-light spectroscopy. Using aqueous two-phase separation, semiconducting carbon nanotubes are purified from their metallic counterparts and condensed into a 10 nm thin film with no residual surfactant. Cross peak intensities put the time scale for energy transfer at <60 fs, and 2D anisotropy measurements determine that energy transfer is most efficient between parallel nanotubes, thus favoring directional energy flow. Lifetimes are about 300 fs. Thus, these results are in sharp contrast to thin films prepared from nanotubes that are wrapped by polymers, which exhibit picosecond energy transfer and randomize the direction of energy flow. Ultrafast energy flow and directionality are exciting properties for next-generation photovoltaics, photodetectors, and other devices. PMID:27182690

  11. Novel Electrical and Optoelectronic Characterization Methods for Semiconducting Nanowires and Nanotubes

    NASA Astrophysics Data System (ADS)

    Katzenmeyer, Aaron Michael

    As technology journalist David Pogue recounted, "If everything we own had improved over the last 25 years as much as electronics have, the average family car would travel four times faster than the space shuttle; houses would cost 200 bucks." The electronics industry is one which, through Moore's Law, created a self-fulfilling prophecy of exponential advancement. This progress has made unforeseen technologies commonplace and revealed new physical understanding of the world in which we live. It is in keeping with these trends that the current work is motivated. This dissertation focuses on the advancement of electrical and optoelectronic characterization techniques suitable for understanding the underlying physics and applications of nanoscopic devices, in particular semiconducting nanowires and nanotubes. In this work an in situ measurement platform based on a field-emission scanning electron microscope fitted with an electrical nanoprobe is shown to be a robust instrument for determining fundamental aspects of nanowire systems (i.e. the dominant mode of carrier transport and the nature of the electrical contacts to the nanowire). The platform is used to fully classify two distinct systems. In one instance it is found that indium arsenide nanowires display space-charge-limited transport and are contacted Ohmically. In the other, gallium arsenide nanowires are found to sequentially show the trap-mediated transport regimes of Poole-Frenkel effect and phonon-assisted tunneling. The contacts in this system are resolved to be asymmetric -- one is Ohmic while the other is a Schottky barrier. Additionally scanning photocurrent microscopy is used to spatially resolve optoelectronic nanowire and nanotube devices. In core/shell gallium arsenide nanowire solar cell arrays it is shown that each individual nanowire functions as a standalone solar cell. Nanotube photodiodes are mapped by scanning photocurrent microscopy to confirm an optimal current collection scheme has been

  12. Semiconducting YBaCuO microbolometers for uncooled broadband IR sensing

    NASA Astrophysics Data System (ADS)

    Almasri, Mahmoud F.; Celik-Butler, Zeynep; Butler, Donald P.; Yaradanakul, Alp; Yildiz, Ali

    2001-10-01

    This paper describes the modeling, design, fabrication and testing of advanced uncooled thermal detectors, based on semiconducting YBaCuO. The aim is to provide NASA with advanced broad-band infrared (IR) detectors to replace the current CERES (Clouds and the Earth's Radiant Energy System) hardware that utilizes three channels, each housing a 1.5 mm X 1.5 mm thermister bolometer with 1 X 4 array of detectors in each of the three channels, thus yielding a total of 12 channels. A double mirror structure is used to obtain uniform spectral response from 0.3-100 μm wavelength. Double absorbers are utilized to further flatten the spectral response and to enhance the absorption of infrared radiation. The devices were fabricated using a polyimide sacrificial layer to achieve thermal isolation of the detector. A low thermal conductivity to the substrate enables the detector to integrate the energy from the incident radiation. An air gap was created by ashing the polyimide sacrificial layer from underneath the thermometer. A passivation layer was used to protect YBaCuO during ashing process and maintain a relatively high temperature coefficient of resistance of around 2.8%. These devices have successfully demonstrated voltage responsivities over 103 V/W, detectivities above 108 cm Hz1/2/W, NEP per root Hertz bandwidth less than 4 X 10-10 W/Hz1/2 and thermal time constant less than 15 ms. Several specific designs were fabricated and tested. Relatively uniform response in the wavelength range of 0.6 to 15 μm was measured.

  13. The quantum pinch effect in semiconducting quantum wires: A bird’s-eye view

    NASA Astrophysics Data System (ADS)

    Kushwaha, Manvir S.

    2016-01-01

    Those who measure success with culmination do not seem to be aware that life is a journey not a destination. This spirit is best reflected in the unceasing failures in efforts for solving the problem of controlled thermonuclear fusion for even the simplest pinches for over decades; and the nature keeps us challenging with examples. However, these efforts have permitted researchers the obtention of a dense plasma with a lifetime that, albeit short, is sufficient to study the physics of the pinch effect, to create methods of plasma diagnostics, and to develop a modern theory of plasma processes. Most importantly, they have impregnated the solid state plasmas, particularly the electron-hole plasmas in semiconductors, which do not suffer from the issues related with the confinement and which have demonstrated their potential not only for the fundamental physics but also for the device physics. Here, we report on a two-component, cylindrical, quasi-one-dimensional quantum plasma subjected to a radial confining harmonic potential and an applied magnetic field in the symmetric gauge. It is demonstrated that such a system, as can be realized in semiconducting quantum wires, offers an excellent medium for observing the quantum pinch effect at low temperatures. An exact analytical solution of the problem allows us to make significant observations: Surprisingly, in contrast to the classical pinch effect, the particle density as well as the current density display a determinable maximum before attaining a minimum at the surface of the quantum wire. The effect will persist as long as the equilibrium pair density is sustained. Therefore, the technological promise that emerges is the route to the precise electronic devices that will control the particle beams at the nanoscale.

  14. Below-gap excitation of semiconducting single-wall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Soavi, G.; Grupp, A.; Budweg, A.; Scotognella, F.; Hefner, T.; Hertel, T.; Lanzani, G.; Leitenstorfer, A.; Cerullo, G.; Brida, D.

    2015-10-01

    We investigate the optoelectronic properties of the semiconducting (6,5) species of single-walled carbon nanotubes by measuring ultrafast transient transmission changes with 20 fs time resolution. We demonstrate that photons with energy below the lowest exciton resonance efficiently lead to linear excitation of electronic states. This finding challenges the established picture of a vanishing optical absorption below the fundamental excitonic resonance. Our result points towards below-gap electronic states as an intrinsic property of semiconducting nanotubes.

  15. Topological end states due to inhomogeneous strains in wrinkled semiconducting ribbons

    NASA Astrophysics Data System (ADS)

    Pandey, Sudhakar; Ortix, Carmine

    2016-05-01

    We show that curvature-induced inhomogeneous strain distributions in nanoscale buckled semiconducting ribbons lead to the existence of end states which are topologically protected by inversion symmetry. These end-state doublets, corresponding to the so-called Maue-Shockley states, are robust against weak disorder. By identifying and calculating the corresponding topological invariants, we further show that a buckled semiconducting ribbon undergoes topological phase transitions between trivial and nontrivial insulating phases by varying its real-space geometry.

  16. Tunable Percolation in Semiconducting Binary Polymer Nanoparticle Glasses.

    PubMed

    Renna, Lawrence A; Bag, Monojit; Gehan, Timothy S; Han, Xu; Lahti, Paul M; Maroudas, Dimitrios; Venkataraman, D

    2016-03-10

    Binary polymer nanoparticle glasses provide opportunities to realize the facile assembly of disparate components, with control over nanoscale and mesoscale domains, for the development of functional materials. This work demonstrates that tunable electrical percolation can be achieved through semiconducting/insulating polymer nanoparticle glasses by varying the relative percentages of equal-sized nanoparticle constituents of the binary assembly. Using time-of-flight charge carrier mobility measurements and conducting atomic force microscopy, we show that these systems exhibit power law scaling percolation behavior with percolation thresholds of ∼24-30%. We develop a simple resistor network model, which can reproduce the experimental data, and can be used to predict percolation trends in binary polymer nanoparticle glasses. Finally, we analyze the cluster statistics of simulated binary nanoparticle glasses, and characterize them according to their predominant local motifs as (p(i), p(1-i))-connected networks that can be used as a supramolecular toolbox for rational material design based on polymer nanoparticles. PMID:26854924

  17. Magnetic ground state of semiconducting transition-metal trichalcogenide monolayers

    SciTech Connect

    Sivadas, Nikhil; Daniels, Matthew W.; Swendsen, Robert H.; Okamoto, Satoshi; Xiao, Di

    2015-06-16

    Layered transition-metal trichalcogenides with the chemical formula ABX3 have attracted recent interest as potential candidates for two-dimensional magnets. Using first-principles calculations within density functional theory, we investigate the magnetic ground states of monolayers of Mn- and Cr-based semiconducting trichalcogenides.We show that the second and third nearest-neighbor exchange interactions (J2 and J3) between magnetic ions, which have been largely overlooked in previous theoretical studies, are crucial in determining the magnetic ground state. Specifically, we find that monolayer CrSiTe3 is an antiferromagnet with a zigzag spin texture due to significant contribution from J3, whereas CrGeTe3 is a ferromagnet with a Curie temperature of 106 K. Monolayers of Mn compounds (MnPS3 and MnPSe3) always show antiferromagnetic N eel order. We identify the physical origin of various exchange interactions, and demonstrate that strain can be an effective knob for tuning the magnetic properties. Possible magnetic ordering in the bulk is also discussed. In conclusion, our study suggests that ABX3 can be a promising platform to explore two-dimensional magnetic phenomena.

  18. Magnetic ground state of semiconducting transition-metal trichalcogenide monolayers

    DOE PAGESBeta

    Sivadas, Nikhil; Daniels, Matthew W.; Swendsen, Robert H.; Okamoto, Satoshi; Xiao, Di

    2015-06-16

    Layered transition-metal trichalcogenides with the chemical formula ABX3 have attracted recent interest as potential candidates for two-dimensional magnets. Using first-principles calculations within density functional theory, we investigate the magnetic ground states of monolayers of Mn- and Cr-based semiconducting trichalcogenides.We show that the second and third nearest-neighbor exchange interactions (J2 and J3) between magnetic ions, which have been largely overlooked in previous theoretical studies, are crucial in determining the magnetic ground state. Specifically, we find that monolayer CrSiTe3 is an antiferromagnet with a zigzag spin texture due to significant contribution from J3, whereas CrGeTe3 is a ferromagnet with a Curie temperaturemore » of 106 K. Monolayers of Mn compounds (MnPS3 and MnPSe3) always show antiferromagnetic N eel order. We identify the physical origin of various exchange interactions, and demonstrate that strain can be an effective knob for tuning the magnetic properties. Possible magnetic ordering in the bulk is also discussed. In conclusion, our study suggests that ABX3 can be a promising platform to explore two-dimensional magnetic phenomena.« less

  19. Gas sensors based on semiconducting nanowire field-effect transistors.

    PubMed

    Feng, Ping; Shao, Feng; Shi, Yi; Wan, Qing

    2014-01-01

    One-dimensional semiconductor nanostructures are unique sensing materials for the fabrication of gas sensors. In this article, gas sensors based on semiconducting nanowire field-effect transistors (FETs) are comprehensively reviewed. Individual nanowires or nanowire network films are usually used as the active detecting channels. In these sensors, a third electrode, which serves as the gate, is used to tune the carrier concentration of the nanowires to realize better sensing performance, including sensitivity, selectivity and response time, etc. The FET parameters can be modulated by the presence of the target gases and their change relate closely to the type and concentration of the gas molecules. In addition, extra controls such as metal decoration, local heating and light irradiation can be combined with the gate electrode to tune the nanowire channel and realize more effective gas sensing. With the help of micro-fabrication techniques, these sensors can be integrated into smart systems. Finally, some challenges for the future investigation and application of nanowire field-effect gas sensors are discussed. PMID:25232915

  20. Information-based screens for deep traps in semiconducting materials

    NASA Astrophysics Data System (ADS)

    Ferris, Kim; Shah, Kunal; Jones, Dumont

    2011-03-01

    The key to a successful materials search is the ability to suggest promising materials and a priori eliminate unfruitful inquiry. For semiconducting radiation detection materials, performance is characterized by several key properties; band gap, density, electron mobility, and carrier lifetime. The material's proclivity to form defects is critical, as even simple antisite and vacancy defects can be sufficiently deep to affect effective carrier lifetime and mobility. We have developed a new model for defect formation proclivity, leveraging prior defect models (van Vechten and Feichter) and our information-based work. Our approach is based upon classification of materials chemistry and properties consistent with high concentrations of particular defects (e.g. antisites and vacancies). One issue is that nearly any charged local defect can potentially form a deep trap, so the screen must cover different defect types. Second, the screening model for new materials cannot rely on generally unknown factors such as 3D crystal geometry. The resulting model is intended to provide design guidance on expected defect behavior for candidate detection materials for which there is little or no prior information. The authors gratefully acknowledge financial support from U.S. Department of Homeland Security under Contract No. HSHQDC-08-X-00872.

  1. Advanced Branching Control and Characterization of Inorganic Semiconducting Nanocrystals

    SciTech Connect

    Hughes, Steven Michael

    2007-01-01

    The ability to finely tune the size and shape of inorganic semiconducting nanocrystals is an area of great interest, as the more control one has, the more applications will be possible for their use. The first two basic shapes develped in nanocrystals were the sphere and the anistropic nanorod. the II_VI materials being used such as Cadmium Selenide (CdSe) and Cadmium Telluride (CdTe), exhibit polytypism, which allows them to form in either the hexagonally packed wurtzite or cubically packed zinc blende crystalline phase. The nanorods are wurtzite with the length of the rod growing along the c-axis. As this grows, stacking faults may form, which are layers of zinc blende in the otherwise wurtzite crystal. Using this polytypism, though, the first generation of branched crystals were developed in the form of the CdTe tetrapod. This is a nanocrystal that nucleates in the zincblend form, creating a tetrahedral core, on which four wurtzite arms are grown. This structure opened up the possibility of even more complex shapes and applications. This disseration investigates the advancement of branching control and further understanding the materials polytypism in the form of the stacking faults in nanorods.

  2. Reversible Photoswitching of Spiropyran-Conjugated Semiconducting Polymer Dots

    PubMed Central

    Chan, Yang-Hsiang; Gallina, Maria Elena; Zhang, Xuanjun; Wu, I-Che; Jin, Yuhui; Sun, Wei; Chiu, Daniel T.

    2012-01-01

    Semiconducting polymer dots (Pdots) recently have emerged as a new class of ultrabright fluorescent probes with promising applications in biological detection and imaging. We developed photoswitchable Pdots by conjugating photochromic spiropyran molecules onto poly[9,9-dioctylfluorenyl-2,7-diyl)-co-1,4-benzo-{2,1′-3}-thiadiazole)] (PFBT). The modulation of fluorescence was achieved by ultraviolet irradiation, which converted spiropyran into its visible-absorbing merocyanine form. The merocyanine efficiently quenched the fluorescence of PFBT via Förster resonance energy transfer (FRET). We then reversed the quenching by subsequent irradiation with visible light to get back the fluorescence of PFBT. This FRET-based photomodulation of Pdot fluorescence could be repeated multiple times. We next conjugated biomolecules onto the surface of these photoswitchable Pdots and demonstrated their specific cellular and subcellular labeling to different types of cells without any noticeable nonspecific binding. We anticipate these photoswitchable and biocompatible Pdots will be useful in developing bio-imaging techniques in the future. PMID:23033991

  3. Substrate effect on the band gap of semiconducting atomic wires

    NASA Astrophysics Data System (ADS)

    Simbeck, Adam J.; Nayak, Saroj K.

    2014-03-01

    The electronic structure of free-standing and supported semiconducting atomic wires is investigated using a combination of first-principles density functional theory (DFT) and many-body perturbation theory (MBPT). The band gaps predicted from DFT for SiH2 and GeH2 atomic wires are unaffected by the presence of the substrate, whereas the gaps calculated using MBPT under the GW approximation are reduced by about 1eV when the wires are supported. The reduction in the band gap is attributed to a change in the electronic correlation energy, which can be understood as a screened Coulomb interaction. These results highlight the importance of the role played by the substrate in manipulating the electronic and optical properties of quantum confined Si and Ge systems. Work supported by the Interconnect Focus Center (MARCO program), State of New York, NSF IGERT Program, Grant no. 0333314, NSF Petascale Simulations and Analysis (PetaApps) program, Grant No. 0749140, and computing resources of the CCNI at RPI.

  4. Semiconducting nanowires from hairpin-shaped self-assembling sexithiophenes.

    PubMed

    Tsai, Wei-Wen; Tevis, Ian D; Tayi, Alok S; Cui, Honggang; Stupp, Samuel I

    2010-11-18

    Conjugated organic molecules can be designed to self-assemble from solution into nanostructures for functions such as charge transport, light emission, or light harvesting. We report here the design and synthesis of a novel hairpin-shaped self-assembling molecule containing electronically active sexithiophene moieties. In several nonpolar organic solvents, such as toluene or chlorocyclohexane, this compound was found to form organogels composed of nanofibers with uniform diameters of 3.0 (±0.3) nm. NMR analysis and spectroscopic measurements revealed that the self-assembly is driven by π-π interactions of the sexithiophene moieties and hydrogen bonding among the amide groups at the head of the hairpin. Field effect transistors built with this molecule revealed p-type semiconducting behavior and higher hole mobilities when films were cast from solvents that promote self-assembly. We propose that hydrogen bonding and π-π stacking act synergistically to create ordered stacking of sexithiophene moieties, thus providing an efficient pathway for charge carriers within the nanowires. The nanostructures formed exhibit unusually broad absorbance in their UV-vis spectrum, which we attribute to the coexistence of both H and J aggregates from face-to-face π-π stacking of sexithiophene moieties and hierarchical bundling of the nanowires. The large absorption range associated with self-assembly of the hairpin molecules makes them potentially useful in light harvesting for energy applications. PMID:20698523

  5. Damage Diagnosis in Semiconductive Materials Using Electrical Impedance Measurements

    NASA Technical Reports Server (NTRS)

    Ross, Richard W.; Hinton, Yolanda L.

    2008-01-01

    Recent aerospace industry trends have resulted in an increased demand for real-time, effective techniques for in-flight structural health monitoring. A promising technique for damage diagnosis uses electrical impedance measurements of semiconductive materials. By applying a small electrical current into a material specimen and measuring the corresponding voltages at various locations on the specimen, changes in the electrical characteristics due to the presence of damage can be assessed. An artificial neural network uses these changes in electrical properties to provide an inverse solution that estimates the location and magnitude of the damage. The advantage of the electrical impedance method over other damage diagnosis techniques is that it uses the material as the sensor. Simple voltage measurements can be used instead of discrete sensors, resulting in a reduction in weight and system complexity. This research effort extends previous work by employing finite element method models to improve accuracy of complex models with anisotropic conductivities and by enhancing the computational efficiency of the inverse techniques. The paper demonstrates a proof of concept of a damage diagnosis approach using electrical impedance methods and a neural network as an effective tool for in-flight diagnosis of structural damage to aircraft components.

  6. Semiconducting polyacetylene materials for energy-conversion applications

    NASA Astrophysics Data System (ADS)

    Kiss, Z.; Weinberger, B.

    1982-03-01

    Well controlled growth of semiconducting polyacetylene films by the Ziegler catalyst method was achieved. Thermal isomerization to the trans-(CH)/sub x/stage has yielded (CH)/sub x/films of p-type doping with an acceptor concentration of 10 to the sixteenth to 10 to the 17th power cu cm. Initial proof of concept experiments were also performed to grow polyacetylene by a plasma assisted process. The band edge of (CH)/sub x/ was measured. The technique consisted of measuring the photoresponse of a reverse biased (CH)/sub x/ solar cell, and studying the cut off in the response. The (CH)/sub x/ films had a band gap in the range of 1.4 to 1.5 eV, in good agreement with the measurement of absorption. A very important result of the successful demonstration of this technique is that very low absorption coefficients can be measured quite easily, yielding invaluable data on band tails in (CH)/sub x/.

  7. Gas Sensors Based on Semiconducting Nanowire Field-Effect Transistors

    PubMed Central

    Feng, Ping; Shao, Feng; Shi, Yi; Wan, Qing

    2014-01-01

    One-dimensional semiconductor nanostructures are unique sensing materials for the fabrication of gas sensors. In this article, gas sensors based on semiconducting nanowire field-effect transistors (FETs) are comprehensively reviewed. Individual nanowires or nanowire network films are usually used as the active detecting channels. In these sensors, a third electrode, which serves as the gate, is used to tune the carrier concentration of the nanowires to realize better sensing performance, including sensitivity, selectivity and response time, etc. The FET parameters can be modulated by the presence of the target gases and their change relate closely to the type and concentration of the gas molecules. In addition, extra controls such as metal decoration, local heating and light irradiation can be combined with the gate electrode to tune the nanowire channel and realize more effective gas sensing. With the help of micro-fabrication techniques, these sensors can be integrated into smart systems. Finally, some challenges for the future investigation and application of nanowire field-effect gas sensors are discussed. PMID:25232915

  8. Solidification and crystal growth of solid solution semiconducting alloys

    NASA Technical Reports Server (NTRS)

    Lehoczky, S. L.; Szofran, F. R.

    1984-01-01

    Problems associated with the solidification and crytal growth of solid-solution semiconducting alloy crystals in a terrestrial environment are described. A detailed description is given of the results for the growth of mercury cadmium telluride (HgCdTe) alloy crystals by directional solidification, because of their considerable technological importance. A series of HgCdTe alloy crystals are grown from pseudobinary melts by a vertical Bridgman method using a wide range of growth rates and thermal conditions. Precision measurements are performed to establish compositional profiles for the crystals. The compositional variations are related to compositional variations in the melts that can result from two-dimensional diffusion or density gradient driven flow effects ahead of the growth interface. These effects are discussed in terms of the alloy phase equilibrium properties, the recent high temperature thermophysical data for the alloys and the highly unusual heat transfer characteristics of the alloy/ampule/furnace system that may readily lead to double diffusive convective flows in a gravitational environment.

  9. Air cushion vehicle conductive/semiconductive flexible skirt, and method

    NASA Astrophysics Data System (ADS)

    Cavenagh, Richard A.; Dyke, Raymond W.

    1990-03-01

    Discussed here is a method for dissipating static electrical energy from air cushion vehicles when operating more particularly in cold, low humidity environments, which method involves fabricating the skirt assembly from a flexible sheet material of at least semiconductive character, which will provide a suitable dissipating grounding pathway to discharge potential static electrical energy generated during the aforesaid operation. The method includes using a coated flexible fabric material having at least one of its opposite surfaces coated with an elastomeric abrasion-resistant material, and embedding a plurality of electrically conductive flexible strands at least partially within said flexible fabric material, or alternatively embedding electrically conductive particles or fibers in a generally uniformly manner throughout a forming of its elastomeric composition. The invention also is directed specifically to/on an air cushion vehicle skirt component comprised of electrically conductive composite flexible sheet material having sufficient conductive characteristics to provide a near constant dissipation grounding pathway from said vehicle for any substantial build up of generated static electrical energy, more particularly when the air cushion vehicle is operating in cold, low humidity environments.

  10. Transport and dielectric studies of metallic, semiconducting, and magnetic materials and devices

    NASA Astrophysics Data System (ADS)

    Vasic, Relja

    Several organic and inorganic systems of importance for fundamental physics and applications have been studied by magnetotransport, dielectric constant, and Raman spectroscopy techniques. At the beginning of my thesis work, I investigated three carbon based organic systems: carbon fibers, pentacene derivatives, and a nanomagnetic material ("V15"). In the latter stages of my dissertation, I used the techniques I had developed to explore the properties of two inorganic systems: NiFe nanopillars in a silicon matrix, and spin systems in multiferroic rare earth-transition metal oxides. The main activities and achievements of my thesis work are as follows: The carbon fibers were characterized by magnetotransport and Raman spectroscopy studies. I found that carbon fibers are promising as wires in molecular electronics and compatible with organic films. Preliminary results on simple films of melted pentacene derivatives connected with carbon fiber wires were a first step in the fabrication and characterization of pentacene field effect transistors (FET's). The work on the pentacene system resulted in a series of successful logic circuits based on field-effect transistors such as NOT (inverter), NOR, and NAND. The temperature-dependent mobility was described as thermally activated at low gate voltages, but at high gate voltages the mobility was enhanced due to shallow traps. The second system investigated was the organic nanomagnetic material, polyoxovanadate, K6[V15As6O42(H 2O)]˙8H2O (i.e. V15). The conductivity and the dielectric measurements at high and low temperatures respectively were used to determine electrical properties of this single magnet molecule system. The main accomplishments were the determination of the energy gap (0.2eV) and the identification of multiple dipole relaxation modes. Raman vibrational spectroscopy was used to correlate dielectric relaxation with the Raman intramolecular vibrations. An investigation was then carried out on NiFe nanopillars electrodeposited in nanoporous silicon templates (Si:P), studied with transport and dielectric methods in high magnetic fields. This system exhibited a frequency and temperature dependent dielectric response which followed a Debye relaxation mechanism. It was discovered that in high magnetic fields greater than 10 T, multiple relaxation structures emerged that were magnetic field direction dependent. It was realized that such a phenomena occurs in Si:P, and is not directly related to the NiFe nanostructure. Hence, a new magnetic field induced phenomenon in the dielectric response in Si was observed, which involves the effects of a magnetic field on an electric dipole. Here, the field induces a harmonic oscillator state from the zero field Debye-like relaxation behavior. The final work in the thesis project focused on the inorganic rare-earth transition metal oxide system HoMnO3 and related compounds. Dielectric measurements were used to characterize and map out the magnetic phase transitions in the doped ferroelectric series Ho1-xY xMnO3. The phase transitions involved complex rotations of the Mn spins. I found that the behavior of these spin rotations were highly dependent on magnetic field, magnetic field direction, and the degree of doping with the non-magnetic Y ion. Hence the magnetic field anisotropy study is an important step towards the understanding of magnetic and electric phase competition in the diluted 4 f system by the non-magnetic ion Yttrium (Y). From highly systematic measurements involving these parameters, I mapped out detailed phase diagrams for the Ho1-x YxMnO3 system which will be very useful for future theoretical work to describe the complex spin interactions involved.

  11. PREFACE: 17th International Conference on Microscopy of Semiconducting Materials 2011

    NASA Astrophysics Data System (ADS)

    Walther, T.; Midgley, P. A.

    2011-11-01

    This volume contains invited and contributed papers from the 17th international conference on 'Microscopy of Semiconducting Materials' held at Churchill College, University of Cambridge, on 4-7 April 2011. The meeting was organised under the auspices of the Institute of Physics and supported by the Royal Microscopical Society as well as the Materials Research Society of the USA. This conference series deals with recent advances in semiconductor studies carried out by all forms of microscopy, with an emphasis on electron microscopy and related techniques with high spatial resolution. This time the meeting was attended by 131 delegates from 25 countries world-wide, a record in terms of internationality. As semiconductor devices shrink further new routes of device processing and characterisation need to be developed, and, for the latter, methods that offer sub-nanometre spatial resolution are particularly valuable. The various forms of imaging, diffraction and spectroscopy available in modern microscopes are powerful tools for studying the microstructure, the electronic structure, the chemistry and also electric fields in semiconducting materials. Recent advances in instrumentation, from lens aberration correction in both TEM and STEM instruments, to the development of a wide range of scanning probe techniques, as well as new methods of signal quantification have been presented at this conference. Two examples of topics at this meeting that have attracted a number of interesting studies were: the correlation of microstructural, optical and chemical information at atomic resolution with nanometre-scale resolved maps of the local electrical fields in (In,Al)GaN based semiconductors and tomographic approaches to characterise ensembles of nanowires and stacks of processed layers in devices Figure 1 Figure 1. Opening lecture by Professor Sir Colin J Humphreys. Each manuscript submitted for publication in this proceedings volume has been independently reviewed and revised

  12. Highly transparent bipolar resistive switching memory with In-Ga-Zn-O semiconducting electrode in In-Ga-Zn-O/Ga2O3/In-Ga-Zn-O structure

    NASA Astrophysics Data System (ADS)

    Yan, X. B.; Hao, H.; Chen, Y. F.; Li, Y. C.; Banerjee, W.

    2014-09-01

    In this work, based on wide bandgap Ga2O3 films, we demonstrated a fully transparent bipolar resistive random access memory (RRAM) device with very high average transmittance of 91.7% in the visible region. The semiconducting In-Ga-Zn-O (IGZO) films were used as symmetric electrodes to reduce sneak current. Different I-V performance will introduce a change in the overall oxygen vacancy distribution by an opposite polarity of electroforming voltage. The temperature dependent of I-V characteristics will be fitted to the hopping conduction mechanism for both of the high-resistance states (HRS) and low-resistance states (LRS) with semiconducting nature. The activation energy and trap spacing of LRS were lower and shorter than that of HRS. A model of resistive switching mechanism related to correlated barrier hopping theory has been proposed for the fully transparent IGZO/Ga2O3/IGZO RRAM device.

  13. Synthesis and characterization of transition metal doped semiconducting nanowires

    NASA Astrophysics Data System (ADS)

    Kaszpurenko, Jason Michael

    The abundance of semiconductors in everyday life has exploded because of their cheapness, ability to do massive calculations, harvest energy and more. For all their utility semiconductors used in calculations suffer because they need an auxiliary way to store the data they've calculated. Magnetic storage has traditionally been the answer to this problem but suffers from slower speeds. Since the 1960's a class of materials known as dilute magnetic semiconductors has tried to combine the advantages of semiconductors with the non-volatile storage properties found in magnets. Often the easiest way to make these materials is by doping semiconductors with transition metal ions. In this study I worked with PbS and ZnSe to create transition metal doped semiconducting nanostructures. The initial studies focus on the synthesis and characterization of PbS nanowires doped with Mn. The wires revealed high quality nanowires with uniform doping concentrations, both axially and radially, with atomic concentrations of 0.18 and 0.01 atomic %. The Mn didn't create any secondary phases and was substitutionally introduced. Zn1-xMn xSe nanostructures were grown with the hopes of achieving a higher Mn doping concentration where we succeeded in achieving dopant levels of x~0.3. To increase carrier concentrations, estimated to be~1016cm -3 for pure ZnSe samples, Al was doped with ZnSe and co-doped with Mn. ZnAlSe nanowires showed carrier concentration ~1019cm -3. Optical studies revealed hole traps with a characteristic time on the order of 1ms in ZnAlSe nanowire samples

  14. Semiconducting and piezoelectric nanoarchitectures of ZnO

    NASA Astrophysics Data System (ADS)

    Wang, Zhong Lin

    2005-03-01

    ZnO is a semiconducting and piezoelectric material. The structure of ZnO can be described as a number of alternating planes composed of tetrahedrally coordinated O^2- and Zn^2+ ions, stacked alternatively along the c-axis. The oppositely charged ions produce positively charged (0001)-Zn and negatively charged (000-1)-O polar surfaces, resulting in a normal dipole moment and spontaneous polarization along the c-axis. We have synthesized a series of novel nanostructures of ZnO utilizing the effect from the polar surface [1-4]e. The piezoelectric coefficient of a piezoelectric nanobelt has been found to be almost tripled compared to the value of the bulk [5], clearly indicating the exciting applications of piezoelectric ZnO nanobelts for nano-scale electromechanical coupled sensors, transducers, switches and resonators. This presentation will focus on the growth mechanisms and potential applications of piezoelectric nanobelts, nanorings and nanosprings. [1] Z.W. Pan, Z.R. Dai and Z.L. Wang, Science, 209 (2001) 1947. [2] X.Y. Kong and Z.L. Wang, Nano Letters, 2 (2003) 1625 + cover. [3] Z.L. Wang, X.Y. Kong and J.M. Zuo, Phys. Rev. Letts. 91 (2003) 185502. [4] X.Y. Kong, Y. Ding, R.S. Yang, Z.L. Wang, Science, 303 (2004) 1348. [5] M. Zhao, Z.L. Wang^, S. X.Mao, Nano Letters, 4 (2004) 587. [6] For details please visit http://www.nanoscience.gatech.edu/zlwang/

  15. Charged-particle spectroscopy in organic semiconducting single crystals

    NASA Astrophysics Data System (ADS)

    Ciavatti, A.; Sellin, P. J.; Basiricò, L.; Fraleoni-Morgera, A.; Fraboni, B.

    2016-04-01

    The use of organic materials as radiation detectors has grown, due to the easy processability in liquid phase at room temperature and the possibility to cover large areas by means of low cost deposition techniques. Direct charged-particle detectors based on solution-grown Organic Semiconducting Single Crystals (OSSCs) are shown to be capable to detect charged particles in pulse mode, with very good peak discrimination. The direct charged-particle detection in OSSCs has been assessed both in the planar and in the vertical axes, and a digital pulse processing algorithm has been used to perform pulse height spectroscopy and to study the charge collection efficiency as a function of the applied bias voltage. Taking advantage of the charge spectroscopy and the good peak discrimination of pulse height spectra, an Hecht-like behavior of OSSCs radiation detectors is demonstrated. It has been possible to estimate the mobility-lifetime value in organic materials, a fundamental parameter for the characterization of radiation detectors, whose results are equal to μτcoplanar = (5 .5 ± 0.6 ) × 10-6 cm2/V and μτsandwich = (1 .9 ± 0.2 ) × 10-6 cm2/V, values comparable to those of polycrystalline inorganic detectors. Moreover, alpha particles Time-of-Flight experiments have been carried out to estimate the drift mobility value. The results reported here indicate how charged-particle detectors based on OSSCs possess a great potential as low-cost, large area, solid-state direct detectors operating at room temperature. More interestingly, the good detection efficiency and peak discrimination observed for charged-particle detection in organic materials (hydrogen-rich molecules) are encouraging for their further exploitation in the detection of thermal and high-energy neutrons.

  16. Numerical Analysis of Dynamic Effects of a Nonlinear Vibro-Impact Process for Enhancing the Reliability of Contact-Type MEMS Devices

    PubMed Central

    Ostasevicius, Vytautas; Gaidys, Rimvydas; Dauksevicius, Rolanas

    2009-01-01

    This paper reports on numerical modeling and simulation of a generalized contact-type MEMS device having large potential in various micro-sensor/actuator applications, which are currently limited because of detrimental effects of the contact bounce phenomenon that is still not fully explained and requires comprehensive treatment. The proposed 2-D finite element model encompasses cantilever microstructures operating in a vacuum and impacting on a viscoelastic support. The presented numerical analysis focuses on the first three flexural vibration modes and their influence on dynamic characteristics. Simulation results demonstrate the possibility to use higher modes and their particular points for enhancing MEMS performance and reliability through reduction of vibro-impact process duration. PMID:22303170

  17. Mesoporous semiconducting oxide thin films with nanocrystalline walls: Synthesis, characterization, and applications

    NASA Astrophysics Data System (ADS)

    Frindell, Karen Lynne

    Mesoporous titania thin films were synthesized using a novel modified sol-gel method, which involves the inhibition of rapid condensative polymerization of hydrolyzed titanium alkoxide using concentrated acid solutions. Lamellar, 2D-hexagonal, and cubic mesostructures were created by varying the volume fraction of the structure-directing block copolymer in the precursor solution. A mesostructured cubic semiconducting framework made up of three-dimensionally arranged anatase nanocrystallites embedded in an amorphous titania matrix was obtained by heat treating the films. Interesting absorbance and photoluminescence properties were observed including a blue shifted band gap and well-defined photoluminescence peaks owing to the high surface area and unusual surface environment of the nanocrystallites present in the framework. Selected rare earth ions were included into the walls of the mesoporous titania thin films and excitation of the mesoporous titania in its band gap resulted in sensitized photoluminescence in the visible and near infrared regions of the spectrum. The energy transfer mechanism was determined in part by evaluating which rare earth ions exhibited photoluminescence via energy transfer. Mesoporous titania thin films were incorporated into several devices including a dye sensitized solar cell. The photocurrent, photovoltage and power conversion efficiency of several iterations of solar cell devices were tested. Electrochromic devices were also fabricated and tested using pure mesoporous titania films and those doped with cerium ions. Contrary to the behavior of non-porous Ce-TiO2 thin films, the addition of cerium to mesoporous titania films caused an increased electrochromic effect. The calcination temperature was varied to correlate the evolution of the structure of the titania thin films with optical and electrochemical properties. Electron microscopy, optical absorbance, photoluminescence, lithium insertion, chronoamperometry, and

  18. Generalized chemical route to develop fatty acid capped highly dispersed semiconducting metal sulphide nanocrystals

    SciTech Connect

    Patel, Jayesh D.; Mighri, Frej; Ajji, Abdellah

    2012-08-15

    Highlights: ► Chemical route for the synthesis of OA-capped CdS, ZnS and PbS at low temperature. ► Synthesized nanocrystals via thermolysis of their metal–oleate complexes. ► Size quantized nanocrystals were highly dispersed and stable at room temperature. -- Abstract: This work deals with the synthesis of highly dispersed semiconducting nanocrystals (NCs) of cadmium sulphide (CdS), zinc sulphide (ZnS) and lead sulphide (PbS) through a simple and generalized process using oleic acid (OA) as surfactant. To synthesize these NCs, metal–oleate (M–O) complexes were obtained from the reaction at 140 °C between metal acetates and OA in hexanes media. Subsequently, M–O complexes were sulphurized using thioacetamide at the same temperature. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) characterizations show that the synthesized products are of nanoscale-size with highly crystalline cubic phase. The optical absorption of OA-capped metal sulphide NCs confirms that their size quantization induced a large shift towards visible region. Photoluminescence (PL) spectrum of CdS NCs shows a broad band-edge emission with shallow and deep-trap emissions, while PL spectrum of ZnS NCs reveals a broad emission due to defects states on the surface. The thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy indicate that fatty acid monolayers were bound strongly on the nanocrystal surface as a carboxylate and the two oxygen atoms of the carboxylate were coordinated symmetrically to the surface of the NCs. The strong binding between the fatty acid and the NCs surface enhances the stability of NCs colloids. In general, this generalized route has a great potential in developing nanoscale metal sulphides for opto-electronic devices.

  19. Porous silicon carbide (SiC) semiconductor device

    NASA Technical Reports Server (NTRS)

    Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

    1994-01-01

    A semiconductor device employs at least one layer of semiconducting porous silicon carbide (SiC). The porous SiC layer has a monocrystalline structure wherein the pore sizes, shapes, and spacing are determined by the processing conditions. In one embodiment, the semiconductor device is a p-n junction diode in which a layer of n-type SiC is positioned on a p-type layer of SiC, with the p-type layer positioned on a layer of silicon dioxide. Because of the UV luminescent properties of the semiconducting porous SiC layer, it may also be utilized for other devices such as LEDs and optoelectronic devices.

  20. High-Yield Separation of Metallic and Semiconducting Single-Wall Carbon Nanotubes by Agarose Gel Electrophoresis

    NASA Astrophysics Data System (ADS)

    Tanaka, Takeshi; Jin, Hehua; Miyata, Yasumitsu; Kataura, Hiromichi

    2008-11-01

    We have developed a novel separation method of metallic and semiconducting single-wall carbon nanotubes (SWCNTs) using agarose gel electrophoresis. When the SWCNTs were isolated with sodium dodecyl sulfate (SDS) and embedded in agarose gel, only the metallic SWCNTs separated from the starting gel by an electric field. After 20 min, almost all SWCNTs applied to gel electrophoresis were separated into two fractions, containing ˜95% semiconducting and ˜70% metallic nanotubes. The difference in the response to the electric field between metallic and semiconducting SWCNTs can be explained by the higher affinity of semiconducting SWCNTs to agarose than to SDS.

  1. Nonlinear interaction between single photons.

    PubMed

    Guerreiro, T; Martin, A; Sanguinetti, B; Pelc, J S; Langrock, C; Fejer, M M; Gisin, N; Zbinden, H; Sangouard, N; Thew, R T

    2014-10-24

    Harnessing nonlinearities strong enough to allow single photons to interact with one another is not only a fascinating challenge but also central to numerous advanced applications in quantum information science. Here we report the nonlinear interaction between two single photons. Each photon is generated in independent parametric down-conversion sources. They are subsequently combined in a nonlinear waveguide where they are converted into a single photon of higher energy by the process of sum-frequency generation. Our approach results in the direct generation of photon triplets. More generally, it highlights the potential for quantum nonlinear optics with integrated devices and, as the photons are at telecom wavelengths, it opens the way towards novel applications in quantum communication such as device-independent quantum key distribution. PMID:25379916

  2. A Study of Tunable Metamaterial Devices for the THz Region

    NASA Astrophysics Data System (ADS)

    Chikhi, N.; Di Gennaro, E.; Esposito, E.; Andreone, A.

    In order to cope with the "THz Gap", metamaterial based devices operating at about 1 THz have been designed to have a tunable response. We studied the electromagnetic behaviour of periodic structures consisting of different "unit cells" based on the concept of Split Ring Resonator (SRR). The devices response in the required frequency region is simulated using a commercial electromagnetic code. Different modulation mechanisms have been investigated, including the use of liquid crystals, MEMS, semiconducting substrates.

  3. Nonlinear optical protection against frequency agile lasers

    SciTech Connect

    McDowell, V.P.

    1988-08-04

    An eye-protection or equipment-filter device for protection from laser energy is disclosed. The device may be in the form of a telescope, binoculars, goggles, constructed as part of equipment such as image intensifiers or range designators. Optical elements focus the waist of the beam within a nonlinear frequency-doubling crystal or nonlinear optical element or fiber. The nonlinear elements produce a harmonic outside the visible spectrum in the case of crystals, or absorb the laser energy in the case of nonlinear fibers. Embodiments include protectors for the human eye as well as filters for sensitive machinery such as TV cameras, FLIR systems or other imaging equipment.

  4. Controlled Growth of Semiconducting and Metallic Single-Wall Carbon Nanotubes.

    PubMed

    Liu, Chang; Cheng, Hui-Ming

    2016-06-01

    Single-wall carbon nanotubes (SWCNTs) can be either semiconducting or metallic depending on their chiral angles and diameters. The use of SWCNTs in electronics has long been hindered by the fact that the as-prepared SWCNTs are usually a mixture of semiconducting and metallic ones. Therefore, controlled synthesis of SWCNTs with a uniform electrical type or even predefined chirality has been a focus of carbon nanotube research in recent years. In this Perspective, we summarize recent progress on the controlled growth of semiconducting and metallic SWCNTs by in situ selective etching and by novel catalyst design. The advantages and mechanisms of these approaches are analyzed, and the challenges are discussed. Finally, we predict possible breakthroughs and future trends in the controlled synthesis and applications of SWCNTs. PMID:27149629

  5. The use of lasers for semiconducter scribing/singulation applications

    NASA Astrophysics Data System (ADS)

    Venkat, Sri; Dunsky, Corey

    2006-02-01

    Semiconductor manufacturing, is dominated by the relentless demand for electronic products with greater performance, minimized dimensions, increased sophistication, and higher speed, all at reduced process cost. Logic device manufacturers need to satisfy this demand by producing integrated circuits that meet the predicted density increase encapsulated in Moore's law. This has led to the use of low-κ dielectrics. For memory devices, thinner wafers are used to enable close stacking of multiple dies in a single low-profile package. And in a third market segment, newer photonic devices are using novel materials such as GaAs, SiC, GaN and sapphire. Traditional mechanical methods are struggling to meet the singulation needs in all three of these device types. Yet at the same time, market realities dictate that the effective cost for increased processing power, novel photonic performance, and higher memory density all continue to fall. As a result, laser-based methods are being adopted in all three areas. In this overview paper, we examine the drivers for each of these market segments and see how laser technology is meeting the singulation demands of current and future devices.

  6. Understanding and improving the mechanical stability of semiconducting polymers for flexible and stretchable electronics

    NASA Astrophysics Data System (ADS)

    Printz, Adam David

    Polymeric semiconductors offer the promise of low-cost, printable, and mechanically robust electronic devices for use in outdoor, portable, and wearable applications such as organic photovoltaics, biosensors, and electronic skins. However, many organic semiconductors are unable to accommodate the mechanical stresses these applications require, and it is therefore important to understand the factors and parameters that govern the mechanical stability of these materials. Chapter 1 provides a gentle introduction to the electronic and mechanical properties relevant to flexible and stretchable organic semiconductor devices. The idea of inherent competition between electronic performance and mechanical robustness is explored. Chapter 2 investigates the inherent competition between good electronic performance and mechanical robustness in poly(3-alkylthiophene)s. A key finding is a critical alkyl side-chain length that allows for good electronic performance and mechanical compliance. Chapter 3 and Appendix A are further studies on the properties of poly(3-alkylthiophene)s with side-chains close to the critical length to gain better understanding of the transition from good electronic properties and poor mechanical properties to poor electronic properties and good mechanical properties. Chapter 4 and Appendix B detail the effects on mechanical and electronic properties of statistical incorporation of unlike monomer into a low-bandgap polymer backbone in an effort to disrupt aggregation and improve mechanical compliance. Chapter 5 explores how the extent of molecular mixing of polythiophenes and fullerenes---materials common in organic photovoltaics---affects their mechanical properties. Chapter 6 describes the invention of a new technique to determine the yield point of thin films. A dependence on the alkyl-side chain length is observed, as well as a critical film thickness below which the yield point increases substantially. In Chapter 7, the weakly interacting H

  7. Spectroscopic properties of doped and defective semiconducting oxides from hybrid density functional calculations.

    PubMed

    Di Valentin, Cristiana; Pacchioni, Gianfranco

    2014-11-18

    CONSPECTUS: Very rarely do researchers use metal oxides in their pure and fully stoichiometric form. In most of the countless applications of these compounds, ranging from catalysis to electronic devices, metal oxides are either doped or defective because the most interesting chemical, electronic, optical, and magnetic properties arise when foreign components or defects are introduced in the lattice. Similarly, many metal oxides are diamagnetic materials and do not show a response to specific spectroscopies such as electron paramagnetic resonance (EPR) spectroscopy. However, doped or defective oxides may exhibit an interesting and informative paramagnetic behavior. Doped and defective metal oxides offer an expanding range of applications in contemporary condensed matter science; therefore researchers have devoted enormous effort to the understanding their physical and chemical properties. The interplay between experiment and computation is particularly useful in this field, and contemporary simulation techniques have achieved high accuracies with these materials. In this Account, we show how the direct comparison between spectroscopic experimental and computational data for some selected and relevant materials provides ways to understand and control these complex systems. We focus on the EPR properties and electronic transitions that arise from the presence of dopants and defects in bulk metal oxide materials. We analyze and compare the effect of nitrogen doping in TiO2 and ZnO (two semiconducting oxides) and MgO (a wide gap insulator) and examine the effect of oxygen deficiency in the semiconducting properties of TiO2-x, ZnO1-x, and WO3-x materials. We chose these systems because of their relevance in applications including photocatalysis, touch screens, electrodes in magnetic random access memories, and smart glasses. Density functional theory (DFT) provides the general computational framework used to illustrate the electronic structure of these systems. However

  8. Electroluminescence of colloidal quasi-two-dimensional semiconducting CdSe nanostructures in a hybrid light-emitting diode

    SciTech Connect

    Selyukov, A. S. Vitukhnovskii, A. G.; Lebedev, V. S.; Vashchenko, A. A.; Vasiliev, R. B.; Sokolikova, M. S.

    2015-04-15

    We report on the results of studying quasi-two-dimensional nanostructures synthesized here in the form of semiconducting CdSe nanoplatelets with a characteristic longitudinal size of 20–70 nm and a thick-ness of a few atomic layers. Their morphology is studied using TEM and AFM and X-ray diffraction analysis; the crystal structure and sizes are determined. At room and cryogenic temperatures, the spectra and kinetics of the photoluminescence of such structures (quantum wells) are investigated. A hybrid light-emitting diode operating on the basis of CdSe nanoplatelets as a plane active element (emitter) is developed using the organic materials TAZ and TPD to form electron and hole transport layers, respectively. The spectral and current-voltage characteristics of the constructed device with a radiation wavelength λ = 515 nm are obtained. The device triggering voltage is 5.5 V (visible glow). The use of quasi-two-dimensional structures of this type is promising for hybrid light-emitting diodes with pure color and low operating voltages.

  9. Nonlinear optical thin films

    NASA Technical Reports Server (NTRS)

    Leslie, Thomas M.

    1993-01-01

    A focused approach to development and evaluation of organic polymer films for use in optoelectronics is presented. The issues and challenges that are addressed include: (1) material synthesis, purification, and the tailoring of the material properties; (2) deposition of uniform thin films by a variety of methods; (3) characterization of material physical properties (thermal, electrical, optical, and electro-optical); and (4) device fabrication and testing. Photonic materials, devices, and systems were identified as critical technology areas by the Department of Commerce and the Department of Defense. This approach offers strong integration of basic material issues through engineering applications by the development of materials that can be exploited as the active unit in a variety of polymeric thin film devices. Improved materials were developed with unprecedented purity and stability. The absorptive properties can be tailored and controlled to provide significant improvement in propagation losses and nonlinear performance. Furthermore, the materials were incorporated into polymers that are highly compatible with fabrication and patterning processes for integrated optical devices and circuits. By simultaneously addressing the issues of materials development and characterization, keeping device design and fabrication in mind, many obstacles were overcome for implementation of these polymeric materials and devices into systems. We intend to considerably improve the upper use temperature, poling stability, and compatibility with silicon based devices. The principal device application that was targeted is a linear electro-optic modulation etalon. Organic polymers need to be properly designed and coupled with existing integrated circuit technology to create new photonic devices for optical communication, image processing, other laser applications such as harmonic generation, and eventually optical computing. The progression from microscopic sample to a suitable film

  10. Photothermal Investigation of Surface Defects of Pure Semiconducting A2B6 Materials

    NASA Astrophysics Data System (ADS)

    Zakrzewski, J.; Maliński, M.; Strzałkowski, K.; Madaj, D.; Firszt, F.; Łęgowski, S.; Męczyńska, H.

    2012-04-01

    Photoacoustic spectroscopy is a sensitive and useful method to investigate the quality of semiconducting A2B6 crystals. An imperfection of surface quality can strongly influence photoacoustic spectra but it shows the different character for the different kinds of semiconducting materials. To properly interpret the amplitude and phase spectra, the temperature distribution and its modifications, due to the surface defects, are needed. The Blonskij model of the temperature distribution was used to investigate the influence of the defect on the amplitude and phase spectra.

  11. Zinc oxide nanowire networks for macroelectronic devices

    NASA Astrophysics Data System (ADS)

    Unalan, Husnu Emrah; Zhang, Yan; Hiralal, Pritesh; Dalal, Sharvari; Chu, Daping; Eda, Goki; Teo, K. B. K.; Chhowalla, Manish; Milne, William I.; Amaratunga, Gehan A. J.

    2009-04-01

    Highly transparent zinc oxide (ZnO) nanowire networks have been used as the active material in thin film transistors (TFTs) and complementary inverter devices. A systematic study on a range of networks of variable density and TFT channel length was performed. ZnO nanowire networks provide a less lithographically intense alternative to individual nanowire devices, are always semiconducting, and yield significantly higher mobilites than those achieved from currently used amorphous Si and organic TFTs. These results suggest that ZnO nanowire networks could be ideal for inexpensive large area electronics.

  12. CoPt/CeO2 catalysts for the growth of narrow diameter semiconducting single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Tang, Lei; Li, Taotao; Li, Chaowei; Ling, Lin; Zhang, Kai; Yao, Yagang

    2015-11-01

    For the application of single-walled carbon nanotubes (SWNTs) in nanoelectronic devices, effective techniques for the growth of semiconducting SWNTs (s-SWNTs) with a specific diameter are still a great challenge. Herein, we report a facile strategy for the selective growth of narrow diameter distributed s-SWNTs using CoPt/CeO2 catalysts. The addition of Pt into a Co catalyst dramatically reduces the diameter distributions and even the chirality distributions of the as-grown SWNTs. Oxygen vacancies that are provided by mesoporous CeO2 are responsible for creating an oxidative environment to in situ etch metallic SWNTs (m-SWNTs). Atomic force microscope (AFM) and Raman spectroscopy characterizations indicate a narrow diameter distribution of 1.32 +/- 0.03 nm and the selective growth of s-SWNTs to 93%, respectively. In addition, electronic transport measurements also confirm that the Ion/Ioff ratio is mainly in the order of ~103. This work provides an effective strategy for the facile fabrication of narrow diameter distributed s-SWNTs, which will be beneficial to fundamental research and the broad application of SWNTs for future nanoelectronics.For the application of single-walled carbon nanotubes (SWNTs) in nanoelectronic devices, effective techniques for the growth of semiconducting SWNTs (s-SWNTs) with a specific diameter are still a great challenge. Herein, we report a facile strategy for the selective growth of narrow diameter distributed s-SWNTs using CoPt/CeO2 catalysts. The addition of Pt into a Co catalyst dramatically reduces the diameter distributions and even the chirality distributions of the as-grown SWNTs. Oxygen vacancies that are provided by mesoporous CeO2 are responsible for creating an oxidative environment to in situ etch metallic SWNTs (m-SWNTs). Atomic force microscope (AFM) and Raman spectroscopy characterizations indicate a narrow diameter distribution of 1.32 +/- 0.03 nm and the selective growth of s-SWNTs to 93%, respectively. In addition

  13. A rational design for the separation of metallic and semiconducting single-walled carbon nanotubes using a magnetic field

    NASA Astrophysics Data System (ADS)

    Luo, Chengzhi; Wan, Da; Jia, Junji; Li, Delong; Pan, Chunxu; Liao, Lei

    2016-06-01

    The separation of metallic (m-) and semiconducting (s-) single-walled carbon nanotubes (SWNTs) without causing contamination and damage is a major challenge for SWNT-based devices. As a facile and nondestructive tool, the use of a magnetic field could be an ideal strategy to separate m-/s-SWNTs, based on the difference of magnetic susceptibilities. Here, we designed a novel magnetic field-assisted floating catalyst chemical vapor deposition system to separate m-/s-SWNTs. Briefly, m-SWNTs are attracted toward the magnetic pole, leaving s-SWNTs on the substrate. By using this strategy, s-SWNTs with a purity of 99% could be obtained, which is enough to construct high-performance transistors with a mobility of 230 cm2 V-1 s-1 and an on/off ratio of 106. We also established a model to quantitatively calculate the percentage of m-SWNTs on the substrate and this model shows a good match with the experimental data. Furthermore, our rational design also provides a new avenue for the growth of SWNTs with specific chirality and manipulated arrangement due to the difference of magnetic susceptibilities between different diameters, chiralities, and types.The separation of metallic (m-) and semiconducting (s-) single-walled carbon nanotubes (SWNTs) without causing contamination and damage is a major challenge for SWNT-based devices. As a facile and nondestructive tool, the use of a magnetic field could be an ideal strategy to separate m-/s-SWNTs, based on the difference of magnetic susceptibilities. Here, we designed a novel magnetic field-assisted floating catalyst chemical vapor deposition system to separate m-/s-SWNTs. Briefly, m-SWNTs are attracted toward the magnetic pole, leaving s-SWNTs on the substrate. By using this strategy, s-SWNTs with a purity of 99% could be obtained, which is enough to construct high-performance transistors with a mobility of 230 cm2 V-1 s-1 and an on/off ratio of 106. We also established a model to quantitatively calculate the percentage of m

  14. Networks of nonlinear superconducting transmission line resonators

    NASA Astrophysics Data System (ADS)

    Leib, M.; Deppe, F.; Marx, A.; Gross, R.; Hartmann, M. J.

    2012-07-01

    We investigate a network of coupled superconducting transmission line resonators, each of them made nonlinear with a capacitively shunted Josephson junction coupling to the odd flux modes of the resonator. The resulting eigenmode spectrum shows anticrossings between the plasma mode of the shunted junction and the odd resonator modes. Notably, we find that the combined device can inherit the complete nonlinearity of the junction, allowing for a description as a harmonic oscillator with a Kerr nonlinearity. Using a dc SQUID instead of a single junction, the nonlinearity can be tuned between 10 kHz and 4 MHz while maintaining resonance frequencies of a few gigahertz for realistic device parameters. An array of such nonlinear resonators can be considered a scalable superconducting quantum simulator for a Bose-Hubbard Hamiltonian. The device would be capable of accessing the strongly correlated regime and be particularly well suited for investigating quantum many-body dynamics of interacting particles under the influence of drive and dissipation.

  15. Study of organic-inorganic hetero-interfaces and electrical transport in semiconducting nanostructures

    NASA Astrophysics Data System (ADS)

    Wagner, Sean Robert

    As the electronics industry continues to evolve and move towards functional electronic devices with increasing complexity and functionality, it becomes important to explore materials outside the regime of conventional semiconductors. Organic semiconducting small molecules have received a large amount of attention due to their high degree of flexibility, the option to perform molecular synthesis to modify their electronic and magnetic properties, and their ability to organize into highly-ordered functionalized nanostructures and thin films. Being able to form complex nanostructures and thin films with molecular precision, while maintaining the ability to tune properties through modifications in the molecular chemistry could result in vast improvements in conventional device architectures. However, before this is realized, there still remains a significant lack of understanding regarding how these molecules interact with various substrate surfaces as well as their intermolecular interactions. The interplay between these interactions can produce drastic changes in the molecular orientation and ordering at the hetero-interface, which can affect the transport properties of the molecular thin film and ultimately modify the performance of the organic electronic device. This study first focuses on the growth dynamics, molecular ordering, and molecular orientation of metal phthalocyanine (MPc) molecules, particularly on Si, a substrate which is notoriously difficult to form an organized organic thin film on due to the surface dangling bonds. By deactivating these bonds, the formation of a highly ordered organic molecular thin film becomes possible. Combining scanning tunneling microscopy, scanning tunneling spectroscopy, low-energy electron diffraction, and density functional theory calculations, the growth evolution of MPc molecules ( M = Zn, Cu, Co) from the single molecule level to multilayered films on the deactivated Si(111)-B surface is investigated. Initial tests are

  16. Spin transport in lateral structures with semiconducting channel

    NASA Astrophysics Data System (ADS)

    Zainuddin, Abu Naser

    Spintronics is an emerging field of electronics with the potential to be used in future integrated circuits. Spintronic devices are already making their mark in storage technologies in recent times and there are proposals for using spintronic effects in logic technologies as well. So far, major improvement in spintronic effects, for example, the `spin-valve' effect, is being achieved in metals or insulators as channel materials. But not much progress is made in semiconductors owing to the difficulty in injecting spins into them, which has only very recently been overcome with the combined efforts of many research groups around the world. The key motivations for semiconductor spintronics are their ease in integration with the existing semiconductor technology along with the gate controllability. At present semiconductor based spintronic devices are mostly lateral and are showing a very poor performance compared to their metal or insulator based vertical counterparts. The objective of this thesis is to analyze these devices based on spin-transport models and simulations. At first a lateral spin-valve device is modeled with the spin-diffusion equation based semiclassical approach. Identifying the important issues regarding the device performance, a compact circuit equivalent model is presented which would help to improve the device design. It is found that the regions outside the current path also have a significant influence on the device performance under certain conditions, which is ordinarily neglected when only charge transport is considered. Next, a modified spin-valve structure is studied where the spin signal is controlled with a gate in between the injecting and detecting contacts. The gate is used to modulate the rashba spin-orbit coupling of the channel which, in turn, modulates the spin-valve signal. The idea of gate controlled spin manipulation was originally proposed by Datta and Das back in 1990 and is called 'Datta-Das' effect. In this thesis, we have

  17. Direct attachment of DNA to semiconducting surfaces for biosensor applications.

    PubMed

    Fahrenkopf, Nicholas M; Shahedipour-Sandvik, Fatemeh; Tokranova, Natalya; Bergkvist, Magnus; Cady, Nathaniel C

    2010-11-01

    In this work we propose a novel method of immobilizing nucleic acids for field effect or high electron mobility transistor-based biosensors. The naturally occurring 5' terminal phosphate group on nucleic acids was used to coordinate with semiconductor and metal oxide surfaces. We demonstrate that DNA can be directly immobilized onto ZrO(2), AlGaN, GaN, and HfO(2) while retaining its ability to hybridize to target sequences with high specificity. By directly immobilizing the probe molecule to the sensor surface, as opposed to conventional crosslinking strategies, the number of steps in device fabrication is reduced. Furthermore, hybridization to target strands occurs closer to the sensor surface, which has the potential to increase device sensitivity by reducing the impact of the Debye screening length. PMID:20869405

  18. Nanowire structures and electrical devices

    DOEpatents

    Bezryadin, Alexey; Remeika, Mikas

    2010-07-06

    The present invention provides structures and devices comprising conductive segments and conductance constricting segments of a nanowire, such as metallic, superconducting or semiconducting nanowire. The present invention provides structures and devices comprising conductive nanowire segments and conductance constricting nanowire segments having accurately selected phases including crystalline and amorphous states, compositions, morphologies and physical dimensions, including selected cross sectional dimensions, shapes and lengths along the length of a nanowire. Further, the present invention provides methods of processing nanowires capable of patterning a nanowire to form a plurality of conductance constricting segments having selected positions along the length of a nanowire, including conductance constricting segments having reduced cross sectional dimensions and conductance constricting segments comprising one or more insulating materials such as metal oxides.

  19. Forward model nonlinearity versus inverse model nonlinearity

    USGS Publications Warehouse

    Mehl, S.

    2007-01-01

    The issue of concern is the impact of forward model nonlinearity on the nonlinearity of the inverse model. The question posed is, "Does increased nonlinearity in the head solution (forward model) always result in increased nonlinearity in the inverse solution (estimation of hydraulic conductivity)?" It is shown that the two nonlinearities are separate, and it is not universally true that increased forward model nonlinearity increases inverse model nonlinearity. ?? 2007 National Ground Water Association.

  20. Biomedical Detection via Macro- and Nano-Sensors Fabricated with Metallic and Semiconducting Oxides

    PubMed Central

    Hahm, Jong-In

    2013-01-01

    Originally developed as gas sensors, the benefits of metallic and semiconducting oxide materials are now being realized in other areas of sensing, such as chemical, environmental, and biomedical monitoring and detection. Metallic and semiconducting oxides have continuously expanded their roles to date, and have also established their significance in biosensing by utilizing a variety of modes for signal generation and detection mechanism. These sensors are typically based either on their optical, electrochemical, electrical, gravimetric, acoustic, and magnetic properties for signal transduction. This article reviews such biosensors that employ metallic and semiconducting oxides as active sensing elements to detect nucleic acids, proteins, cells, and a variety of important biomarkers, both in thin film and one-dimensional forms. Specific oxide materials (Mx Oy ) examined comprehensively in this article include M = Fe, Cu, Si, Zn, Sn, In. The derivatives of these oxide materials resulting from incorporation of dopants are examined as well. The crystalline structures and unique properties that may be exploited for various biosensing applications are discussed, and recent efforts investigating the feasibility of using these oxide materials in biosensor technology are described. Key biosensor characteristics resulting from reduced dimensionality are overviewed under the motif of planar and one-dimensional sensors. This article also provides insight into current challenges facing biosensor applications for metallic and semiconducting oxides. In addition, future outlook in this particular field as well as different impacts on biology and medicine are addressed. PMID:23627064

  1. Highly Efficient and Scalable Separation of Semiconducting Carbon Nanotubes via Weak Field Centrifugation.

    PubMed

    Reis, Wieland G; Weitz, R Thomas; Kettner, Michel; Kraus, Alexander; Schwab, Matthias Georg; Tomović, Željko; Krupke, Ralph; Mikhael, Jules

    2016-01-01

    The identification of scalable processes that transfer random mixtures of single-walled carbon nanotubes (SWCNTs) into fractions featuring a high content of semiconducting species is crucial for future application of SWCNTs in high-performance electronics. Herein we demonstrate a highly efficient and simple separation method that relies on selective interactions between tailor-made amphiphilic polymers and semiconducting SWCNTs in the presence of low viscosity separation media. High purity individualized semiconducting SWCNTs or even self-organized semiconducting sheets are separated from an as-produced SWCNT dispersion via a single weak field centrifugation run. Absorption and Raman spectroscopy are applied to verify the high purity of the obtained SWCNTs. Furthermore SWCNT - network field-effect transistors were fabricated, which exhibit high ON/OFF ratios (10(5)) and field-effect mobilities (17 cm(2)/Vs). In addition to demonstrating the feasibility of high purity separation by a novel low complexity process, our method can be readily transferred to large scale production. PMID:27188435

  2. Highly Efficient and Scalable Separation of Semiconducting Carbon Nanotubes via Weak Field Centrifugation

    NASA Astrophysics Data System (ADS)

    Reis, Wieland G.; Weitz, R. Thomas; Kettner, Michel; Kraus, Alexander; Schwab, Matthias Georg; Tomović, Željko; Krupke, Ralph; Mikhael, Jules

    2016-05-01

    The identification of scalable processes that transfer random mixtures of single-walled carbon nanotubes (SWCNTs) into fractions featuring a high content of semiconducting species is crucial for future application of SWCNTs in high-performance electronics. Herein we demonstrate a highly efficient and simple separation method that relies on selective interactions between tailor-made amphiphilic polymers and semiconducting SWCNTs in the presence of low viscosity separation media. High purity individualized semiconducting SWCNTs or even self-organized semiconducting sheets are separated from an as-produced SWCNT dispersion via a single weak field centrifugation run. Absorption and Raman spectroscopy are applied to verify the high purity of the obtained SWCNTs. Furthermore SWCNT - network field-effect transistors were fabricated, which exhibit high ON/OFF ratios (105) and field-effect mobilities (17 cm2/Vs). In addition to demonstrating the feasibility of high purity separation by a novel low complexity process, our method can be readily transferred to large scale production.

  3. Highly Efficient and Scalable Separation of Semiconducting Carbon Nanotubes via Weak Field Centrifugation

    PubMed Central

    Reis, Wieland G.; Weitz, R. Thomas; Kettner, Michel; Kraus, Alexander; Schwab, Matthias Georg; Tomović, Željko; Krupke, Ralph; Mikhael, Jules

    2016-01-01

    The identification of scalable processes that transfer random mixtures of single-walled carbon nanotubes (SWCNTs) into fractions featuring a high content of semiconducting species is crucial for future application of SWCNTs in high-performance electronics. Herein we demonstrate a highly efficient and simple separation method that relies on selective interactions between tailor-made amphiphilic polymers and semiconducting SWCNTs in the presence of low viscosity separation media. High purity individualized semiconducting SWCNTs or even self-organized semiconducting sheets are separated from an as-produced SWCNT dispersion via a single weak field centrifugation run. Absorption and Raman spectroscopy are applied to verify the high purity of the obtained SWCNTs. Furthermore SWCNT - network field-effect transistors were fabricated, which exhibit high ON/OFF ratios (105) and field-effect mobilities (17 cm2/Vs). In addition to demonstrating the feasibility of high purity separation by a novel low complexity process, our method can be readily transferred to large scale production. PMID:27188435

  4. Growth of Horizontal Semiconducting SWNT Arrays with Density Higher than 100 tubes/μm using Ethanol/Methane Chemical Vapor Deposition.

    PubMed

    Kang, Lixing; Zhang, Shuchen; Li, Qingwen; Zhang, Jin

    2016-06-01

    Horizontally aligned semiconducting single-walled carbon nanotube (s-SWNT) arrays with a certain density are highly desirable for future electronic devices. However, obtaining s-SWNT arrays with simultaneously high purity and high density is extremely challenging. We report herein a rational approach, using ethanol/methane chemical vapor deposition, to grow SWNT arrays with a s-SWNT ratio over 91% and a density higher than 100 tubes/μm. In this approach, at a certain temperature, ethanol was fully thermally decomposed to feed carbon atoms for Trojan-Mo catalysts growing high density SWNT arrays, while the incomplete pyrolysis of methane provided appropriate active H radicals with the help of catalytic sapphire surface to inhibit metallic SWNT (m-SWNT) growth. The synergistic effect of ethanol/methane mixtures resulted in enriched semiconducting SWNTs and no obvious decrease in nanotube density due to their milder reactivity and higher controllability at suitable growth conditions. This work represents a step forward in large-area synthesis of high density s-SWNT arrays on substrates and demonstrates potential applications in scalable carbon nanotube electronics. PMID:27177360

  5. Nonlinear metamaterials for holography

    PubMed Central

    Almeida, Euclides; Bitton, Ora

    2016-01-01

    A hologram is an optical element storing phase and possibly amplitude information enabling the reconstruction of a three-dimensional image of an object by illumination and scattering of a coherent beam of light, and the image is generated at the same wavelength as the input laser beam. In recent years, it was shown that information can be stored in nanometric antennas giving rise to ultrathin components. Here we demonstrate nonlinear multilayer metamaterial holograms. A background free image is formed at a new frequency—the third harmonic of the illuminating beam. Using e-beam lithography of multilayer plasmonic nanoantennas, we fabricate polarization-sensitive nonlinear elements such as blazed gratings, lenses and other computer-generated holograms. These holograms are analysed and prospects for future device applications are discussed. PMID:27545581

  6. Nonlinear metamaterials for holography.

    PubMed

    Almeida, Euclides; Bitton, Ora; Prior, Yehiam

    2016-01-01

    A hologram is an optical element storing phase and possibly amplitude information enabling the reconstruction of a three-dimensional image of an object by illumination and scattering of a coherent beam of light, and the image is generated at the same wavelength as the input laser beam. In recent years, it was shown that information can be stored in nanometric antennas giving rise to ultrathin components. Here we demonstrate nonlinear multilayer metamaterial holograms. A background free image is formed at a new frequency-the third harmonic of the illuminating beam. Using e-beam lithography of multilayer plasmonic nanoantennas, we fabricate polarization-sensitive nonlinear elements such as blazed gratings, lenses and other computer-generated holograms. These holograms are analysed and prospects for future device applications are discussed. PMID:27545581

  7. Femtosecond electronic dephasing and population relaxation of some novel semiconducting materials

    NASA Astrophysics Data System (ADS)

    Schneck, Jude Robert

    The dissipation of energy by excited carriers in semiconductors is crucial to device development. In particular, the carrier relaxation mechanisms are strongly modified by the degree of disorder introduced into the lattice via the growth process. The pump probe spectroscopic technique is ideally suited to monitor the energy dissipation process and elucidate the relaxation mechanisms contributing to the carrier decay. Additionally, phase breaking interactions of optical transitions, as measured via the photon echo spectroscopic technique, provides insight into the different homogeneous relaxation mechanisms contributing to the optical resonance. When compared to high quality semiconducting materials, the fundamental homogeneous relaxation mechanisms depend strongly on the disorder inherent in the material. The photon echo technique is ideal for quantifying the strength of these interactions. Femtosecond pump-probe responses of a GaN thin film excited above and below the UV band gap were measured to determine the kinetic relaxation pathways of carriers. A number of fluence dependent decay processes were identified, including carrier-carrier scattering, exciton decay, trapping to defect states, and hole state recovery. The characteristic timescales of these mechanisms ranged from <50 fs to >600 ps. In other measurements on GaN, two-pulse photon echoes due to the strongly dipole coupled excitons were observed as a function of temperature (10 -- 295K). A biexponential decay of the dephasing rate was found from these measurements and attributed to free and bound excitons. The dynamics of the E22 transition of (6,5) single walled carbon nanotubes was studied over a range of fluences via pump-probe spectroscopy. A fluence dependent dephasing rate was deduced from an analysis of the pump-probe signal intensity at a fixed short delay time allowing an effective cross section for exciton-exciton interactions to be determined. The relaxation kinetics of optically excited E22

  8. Nonlinear waveguides

    NASA Astrophysics Data System (ADS)

    SjöBerg, Daniel

    2003-04-01

    We investigate the propagation of electromagnetic waves in a cylindrical waveguide with an arbitrary cross section filled with a nonlinear material. The electromagnetic field is expanded in the usual eigenmodes of the waveguide, and the coupling between the modes is quantified. We derive the wave equations governing each mode with special emphasis on the situation with a dominant TE mode. The result is a strictly hyperbolic system of nonlinear partial differential equations for the dominating mode, whereas the minor modes satisfy hyperbolic systems of linear, nonstationary, and partial differential equations. A growth estimate is given for the minor modes.

  9. Continuous control of the nonlinearity phase for harmonic generations.

    PubMed

    Li, Guixin; Chen, Shumei; Pholchai, Nitipat; Reineke, Bernhard; Wong, Polis Wing Han; Pun, Edwin Yue Bun; Cheah, Kok Wai; Zentgraf, Thomas; Zhang, Shuang

    2015-06-01

    The capability of locally engineering the nonlinear optical properties of media is crucial in nonlinear optics. Although poling is the most widely employed technique for achieving locally controlled nonlinearity, it leads only to a binary nonlinear state, which is equivalent to a discrete phase change of π in the nonlinear polarizability. Here, inspired by the concept of spin-rotation coupling, we experimentally demonstrate nonlinear metasurfaces with homogeneous linear optical properties but spatially varying effective nonlinear polarizability with continuously controllable phase. The continuous phase control over the local nonlinearity is demonstrated for second and third harmonic generation by using nonlinear metasurfaces consisting of nanoantennas of C3 and C4 rotational symmetries, respectively. The continuous phase engineering of the effective nonlinear polarizability enables complete control over the propagation of harmonic generation signals. Therefore, this method seamlessly combines the generation and manipulation of harmonic waves, paving the way for highly compact nonlinear nanophotonic devices. PMID:25849530

  10. Nonlinear dynamics and plasma transport

    SciTech Connect

    Antonsen, T.M. Jr.; Drake, J.F.; Finn, J.M.; Guzdar, P.N.; Hassam, A.B.; Sageev, R.Z.

    1993-01-01

    This progress report details work done on a program in nonlinear dynamical aspects of plasma turbulence and transport funded by DOE since 1989. This program has been in cooperation with laboratories in theUSSR [now Russia and the Confederation of Independent States (CIS)]. The purpose of this program has been: To promote the utilization of recent pathbreaking developments in nonlinear science in plasma turbulence and transport. To promote cooperative scientific investigations between the US and CIS in the related areas of nonlinear science and plasma turbulence and transport. In the work reported in our progress report, we have studied simple models which are motivated by observation on actual fusion devices. The models focus on the important physical processes without incorporating the complexity of the geometry of real devices. This allows for a deeper analysis and understanding of the system both analytically and numerically.

  11. Theoretical tools for semiconductors devices

    SciTech Connect

    Hagan, P.; Cox, R.; Randall, E.; Reyna, L.

    1996-10-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Future generations of Very Large Scale Integrated (VLSI) circuits require semiconducting devices that are much faster and smaller than current devices. Three-dimensional and transient effects are critical to the performance of these devices. Yet using Monte Carlo (MC) codes to perform time-dependent, three-dimensional simulations will not be feasible in the foreseeable future. Here we re-analyze the physics of semiconductors; use singular perturbation techniques to derive the reduced-dimensionality equations that accurately describe the semiconductor in the regimes corresponding to ultra-small ultra-fast devices; and validate the resulting theoretical models against MC simulations and experimental data. The objective of this project was to gain the capability of accurately simulating ultra-small ultra-fast devices in three spatial dimensions with the ultimate goal of transforming the design of advanced devices.

  12. Nanoimprint-Induced Molecular Orientation in Semiconducting Polymer Nanostructures

    SciTech Connect

    Hlaing, H.; Ocko, B.; Lu, X.; Hofmann, T.; Yager, K.G.; Black, C.T.

    2011-09-01

    The morphology and orientation of thin films of the polymer poly-3(hexylthiophene) - important parameters influencing electronic and photovoltaic device performance - have been significantly altered through nanoimprinting with 100 nm spaced grooves. Grazing-incidence small-angle X-ray scattering studies demonstrate the excellent fidelity of the pattern transfer, while wide-angle scattering convincingly shows an imprinting-induced {pi}-{pi} reorientation and polymer backbone alignment along the imprinted grooves. Surprisingly, temperature-dependent scattering measurements indicate that the imprinted induced orientation and alignment remain intact even at temperatures where the imprinted topographical features nearly vanish.

  13. Growth of Homoepitaxial ZnO Semiconducting Films

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, Ching-Hua; Lehoczky, S. L.; Harris, M. T.; George, Michael A.; McCarty, P.

    1999-01-01

    As a high temperature semiconductor, ZnO has been used for many applications such as wave-guide, solar cells, and surface acoustic wave devices. Since the ZnO material has an energy gap of 3.3 eV at room temperature and an excitonic binding energy (60 meV) that is possible to make excitonic lasering at room temperature a recent surge of interest is to synthesize ZnO films for electro-optical devices. These applications require films with a smooth surface, good crystal quality, and low defect density. Homoepitaxial films have been studied in terms of morphology, crystal structure, and electrical and optical properties. ZnO single crystals are grown by the hydrothermal method. Substrates are mechanically polished and annealed in air for four hours before deposited films. The annealing temperature-dependence of ZnO substrates is studied. Films are synthesized by the off-axis reactive sputtering deposition. The films have very smooth surface with a roughness

  14. Semiconducting properties of layered cadmium sulphide-based hybrid nanocomposites

    PubMed Central

    2011-01-01

    A series of hybrid cadmium salt/cationic surfactant layered nanocomposites containing different concentrations of cadmium sulphide was prepared by exchanging chloride by sulphide ions in the layered precursor CdXx(OH)y(CnTA)z in a solid phase/gas reaction, resulting in a series of layered species exhibiting stoichiometries corresponding to CdSvXx(OH)y(CnTA)z, constituted by two-dimensional CdCl2/CdS ultra-thin sheets sandwiched between two self-assembled surfactant layers. The electronic structure of CdS in the nanocomposite is similar to that of bulk, but showing the expected features of two-dimensional confinement of the semiconductor. The nanocomposite band gap is found to depend in a non-linear manner on both the length of the hydrocarbon chain of the surfactant and the concentration of the sulphide in the inorganic sheet. The products show photocatalytic activity at least similar and usually better than that of "bulk" CdS in a factor of two. PMID:21896162

  15. Semiconducting ZnSnN2 thin films for Si/ZnSnN2 p-n junctions

    NASA Astrophysics Data System (ADS)

    Qin, Ruifeng; Cao, Hongtao; Liang, Lingyan; Xie, Yufang; Zhuge, Fei; Zhang, Hongliang; Gao, Junhua; Javaid, Kashif; Liu, Caichi; Sun, Weizhong

    2016-04-01

    ZnSnN2 is regarded as a promising photovoltaic absorber candidate due to earth-abundance, non-toxicity, and high absorption coefficient. However, it is still a great challenge to synthesize ZnSnN2 films with a low electron concentration, in order to promote the applications of ZnSnN2 as the core active layer in optoelectronic devices. In this work, polycrystalline and high resistance ZnSnN2 films were fabricated by magnetron sputtering technique, then semiconducting films were achieved after post-annealing, and finally Si/ZnSnN2 p-n junctions were constructed. The electron concentration and Hall mobility were enhanced from 2.77 × 1017 to 6.78 × 1017 cm-3 and from 0.37 to 2.07 cm2 V-1 s-1, corresponding to the annealing temperature from 200 to 350 °C. After annealing at 300 °C, the p-n junction exhibited the optimum rectifying characteristics, with a forward-to-reverse ratio over 103. The achievement of this ZnSnN2-based p-n junction makes an opening step forward to realize the practical application of the ZnSnN2 material. In addition, the nonideal behaviors of the p-n junctions under both positive and negative voltages are discussed, in hope of suggesting some ideas to further improve the rectifying characteristics.

  16. CoPt/CeO2 catalysts for the growth of narrow diameter semiconducting single-walled carbon nanotubes.

    PubMed

    Tang, Lei; Li, Taotao; Li, Chaowei; Ling, Lin; Zhang, Kai; Yao, Yagang

    2015-12-14

    For the application of single-walled carbon nanotubes (SWNTs) in nanoelectronic devices, effective techniques for the growth of semiconducting SWNTs (s-SWNTs) with a specific diameter are still a great challenge. Herein, we report a facile strategy for the selective growth of narrow diameter distributed s-SWNTs using CoPt/CeO2 catalysts. The addition of Pt into a Co catalyst dramatically reduces the diameter distributions and even the chirality distributions of the as-grown SWNTs. Oxygen vacancies that are provided by mesoporous CeO2 are responsible for creating an oxidative environment to in situ etch metallic SWNTs (m-SWNTs). Atomic force microscope (AFM) and Raman spectroscopy characterizations indicate a narrow diameter distribution of 1.32 ± 0.03 nm and the selective growth of s-SWNTs to 93%, respectively. In addition, electronic transport measurements also confirm that the Ion/Ioff ratio is mainly in the order of ∼10(3). This work provides an effective strategy for the facile fabrication of narrow diameter distributed s-SWNTs, which will be beneficial to fundamental research and the broad application of SWNTs for future nanoelectronics. PMID:26553394

  17. Effect of ozone exposure on the electrical characteristics of high-purity, large-diameter semiconducting carbon nanotubes.

    PubMed

    Gao, Jia; Loo, Yueh-Lin

    2014-06-14

    In this study, we have elucidated the interactions between ozone and carbon nanotubes by monitoring the characteristics of field-effect transistors based on polymer-sorted, large-diameter semiconducting carbon nanotubes. The drain-source current of these transistors initially increases with ozone exposure and then it progressively decreases with increasing exposure beyond 3 min. This non-monotonic dependence of the drain-source current can be ascribed to two competing processes. At short ozone exposure, p-doping of carbon nanotubes dominates; the drain-source current thus increases as a result of increasing hole concentration. This effect is most evidenced in a progressive threshold voltage shift towards positive voltages with increasing exposure to ozone. At extended ozone exposure, chemical oxidation of carbon nanotubes instead dominates. The drain-source current decreases as a result of decreasing hole mobility. This effect manifests itself in a monotonic decrease in the mobility of these devices as a function of ozone exposure. PMID:24760174

  18. Magnetic and electron-transport properties of spin-gapless semiconducting CoFeCrAl films

    NASA Astrophysics Data System (ADS)

    Sellmyer, David; Jin, Yunlong; Kharel, Parashu; Valloppilly, Shah; George, Tom; Balasubramanian, Balamurugan; Skomski, Ralph

    Recently, spin-gapless semiconductors (SGS) with a semiconducting or insulating gap in one spin channel and zero gap in the other at the Fermi level have attracted much attention due to their new functionalities such as voltage-tunable spin polarization, the ability to switch between spin-polarized n-type and p-type conduction, high spin polarization and carrier mobility. For the development of spintronic devices utilizing SGS, it is necessary to have a better understanding of the magnetic and transport properties of the thin films of these materials. In this study, the structural, magnetic, and electron-transport properties of a SGS material CoFeCrAl in the thin film geometry have been investigated. CoFeCrAl films were grown on atomically flat SiO2 substrates using magnetron sputtering. The Curie temperature was measured to be 550 K very close to the value reported for bulk CoFeCrAl. Electron-transport measurements on the oriented films revealed a negative temperature coefficient of resistivity, small anomalous Hall conductivity and linear field dependence of magnetoresistance, which are transport signatures of SGS. The effect of elemental compositions and structural ordering on the SGS properties of the CoFeCrAl films will be discussed. Research supported by NSF (Y. J.), DoE (B. B., D. J. S), ARO (T. A. G., S. R. V.), SDSU (P. K.), and NRI (Facilities).

  19. Multimodal probing of oxygen and water interaction with metallic and semiconducting carbon nanotube networks under ultraviolet irradiation

    NASA Astrophysics Data System (ADS)

    Muckley, Eric S.; Nelson, Anthony J.; Jacobs, Christopher B.; Ivanov, Ilia N.

    2016-04-01

    Interaction between ultraviolet (UV) light and carbon nanotube (CNT) networks plays a central role in gas adsorption, sensor sensitivity, and stability of CNT-based electronic devices. To determine the effect of UV light on sorption kinetics and resistive gas/vapor response of different CNT networks, films of semiconducting single-wall nanotubes (s-SWNTs), metallic single-wall nanotubes, and multiwall nanotubes were exposed to O2 and H2O vapor in the dark and under UV irradiation. Changes in film resistance and mass were measured in situ. In the dark, resistance of metallic nanotube networks increases in the presence of O2 and H2O, whereas resistance of s-SWNT networks decreases. UV irradiation decreases the resistance of metallic nanotube networks in the presence of O2 and H2O and increases the gas/vapor sensitivity of s-SWNT networks by nearly a factor of 2 compared to metallic nanotube networks. s-SWNT networks show evidence of delamination from the gold-plated quartz crystal microbalance crystal, possibly due to preferential adsorption of O2 and H2O on gold. UV irradiation increases the sensitivity of all CNT networks to O2 and H2O by an order of magnitude, which demonstrates the importance of UV light for enhancing response and lowering detection limits in CNT-based gas/vapor sensors.

  20. A rational design for the separation of metallic and semiconducting single-walled carbon nanotubes using a magnetic field.

    PubMed

    Luo, Chengzhi; Wan, Da; Jia, Junji; Li, Delong; Pan, Chunxu; Liao, Lei

    2016-07-14

    The separation of metallic (m-) and semiconducting (s-) single-walled carbon nanotubes (SWNTs) without causing contamination and damage is a major challenge for SWNT-based devices. As a facile and nondestructive tool, the use of a magnetic field could be an ideal strategy to separate m-/s-SWNTs, based on the difference of magnetic susceptibilities. Here, we designed a novel magnetic field-assisted floating catalyst chemical vapor deposition system to separate m-/s-SWNTs. Briefly, m-SWNTs are attracted toward the magnetic pole, leaving s-SWNTs on the substrate. By using this strategy, s-SWNTs with a purity of 99% could be obtained, which is enough to construct high-performance transistors with a mobility of 230 cm(2) V(-1) s(-1) and an on/off ratio of 10(6). We also established a model to quantitatively calculate the percentage of m-SWNTs on the substrate and this model shows a good match with the experimental data. Furthermore, our rational design also provides a new avenue for the growth of SWNTs with specific chirality and manipulated arrangement due to the difference of magnetic susceptibilities between different diameters, chiralities, and types. PMID:27315328

  1. Magneto-optical absorption in semiconducting spherical quantum dots: Influence of the dot-size, confining potential, and magnetic field

    SciTech Connect

    Kushwaha, Manvir S.

    2014-12-15

    Semiconducting quantum dots – more fancifully dubbed artificial atoms – are quasi-zero dimensional, tiny, man-made systems with charge carriers completely confined in all three dimensions. The scientific quest behind the synthesis of quantum dots is to create and control future electronic and optical nanostructures engineered through tailoring size, shape, and composition. The complete confinement – or the lack of any degree of freedom for the electrons (and/or holes) – in quantum dots limits the exploration of spatially localized elementary excitations such as plasmons to direct rather than reciprocal space. Here we embark on a thorough investigation of the magneto-optical absorption in semiconducting spherical quantum dots characterized by a confining harmonic potential and an applied magnetic field in the symmetric gauge. This is done within the framework of Bohm-Pines’ random-phase approximation that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. As an application of our theoretical strategy, we compute various single-particle and many-particle phenomena such as the Fock-Darwin spectrum; Fermi energy; magneto-optical transitions; probability distribution; and the magneto-optical absorption in the quantum dots. It is observed that the role of an applied magnetic field on the absorption spectrum is comparable to that of a confining potential. Increasing (decreasing) the strength of the magnetic field or the confining potential is found to be analogous to shrinking (expanding) the size of the quantum dots: resulting into a blue (red) shift in the absorption spectrum. The Fermi energy diminishes with both increasing magnetic-field and dot-size; and exhibits saw-tooth-like oscillations at large values of field or dot-size. Unlike laterally confined quantum dots, both (upper and lower) magneto-optical transitions survive even in the extreme instances. However, the intra-Landau level

  2. Magneto-optical absorption in semiconducting spherical quantum dots: Influence of the dot-size, confining potential, and magnetic field

    NASA Astrophysics Data System (ADS)

    Kushwaha, Manvir S.

    2014-12-01

    Semiconducting quantum dots - more fancifully dubbed artificial atoms - are quasi-zero dimensional, tiny, man-made systems with charge carriers completely confined in all three dimensions. The scientific quest behind the synthesis of quantum dots is to create and control future electronic and optical nanostructures engineered through tailoring size, shape, and composition. The complete confinement - or the lack of any degree of freedom for the electrons (and/or holes) - in quantum dots limits the exploration of spatially localized elementary excitations such as plasmons to direct rather than reciprocal space. Here we embark on a thorough investigation of the magneto-optical absorption in semiconducting spherical quantum dots characterized by a confining harmonic potential and an applied magnetic field in the symmetric gauge. This is done within the framework of Bohm-Pines' random-phase approximation that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. As an application of our theoretical strategy, we compute various single-particle and many-particle phenomena such as the Fock-Darwin spectrum; Fermi energy; magneto-optical transitions; probability distribution; and the magneto-optical absorption in the quantum dots. It is observed that the role of an applied magnetic field on the absorption spectrum is comparable to that of a confining potential. Increasing (decreasing) the strength of the magnetic field or the confining potential is found to be analogous to shrinking (expanding) the size of the quantum dots: resulting into a blue (red) shift in the absorption spectrum. The Fermi energy diminishes with both increasing magnetic-field and dot-size; and exhibits saw-tooth-like oscillations at large values of field or dot-size. Unlike laterally confined quantum dots, both (upper and lower) magneto-optical transitions survive even in the extreme instances. However, the intra-Landau level transitions are seen

  3. [Nonlinear magnetohydrodynamics

    SciTech Connect

    Not Available

    1992-11-01

    Theoretical predictions were compared with available data from JET on the threshold unstable MHD activity in toroidal confinement devices. In particular, questions arising as to Hartmans number and the selection of a kinematic viscosity are discussed.

  4. Synchrotron-based soft X-ray spectroscopic studies of the electronic structure of organic semiconducting molecules

    NASA Astrophysics Data System (ADS)

    Demasi, Alexander

    Organic molecules have been the subject of many scientific studies due to their potential for use in a new generation of optoelectronic and semiconducting devices, such as organic photovoltaics and organic light emitting diodes. These studies are motivated by the fact that organic semiconductor devices have several advantages over traditional inorganic semiconductor devices. Unlike inorganic semiconductors, where the electronic properties are a result of the deliberate introduction of dopants to the material, the properties of organic semiconductors are often intrinsic to the molecules themselves. As a result, organic semiconductor devices are frequently less susceptible to contamination by impurities than their inorganic counterparts, which results in the relatively lower cost of producing such devices. Accurate experimental determination of the bulk and surface electronic structure of organic semiconductors is a prerequisite in developing a comprehensive understanding of such materials. The organic materials studied in this thesis were N,N-Ethylene-bis(1,1,1trifluoropentane-2,4-dioneiminato)-copper(ii) (abbreviated Cu-TFAC), aluminum tris-8hydroxyquinoline (A1g3), lithium quinolate (Liq), tetracyanoquinodimethane (TCNQ), and tetrafluorotetracyanoquinodimethane (F4TCNQ). The electronic structures of these materials were measured with several synchrotron-based x-ray spectroscopies. X-ray photoemission spectroscopy was used to measure the occupied total density of states and the core-level states of the aforementioned materials. X-ray absorption spectroscopy (XAS) was used to probe the element-specific unoccupied partial density of states (PDOS); its angle-resolved variant was used to measure the orientation of the molecules in a film and, in some circumstances, to gauge the extent of an organic film's crystallinity. Most notably, x-ray emission spectroscopy (XES) measures the element- specific occupied PDOS and, when aided by XAS, resonant XES can additionally be

  5. Radio Frequency Tunable Oscillator Device Based on a SmB6 Microcrystal

    NASA Astrophysics Data System (ADS)

    Stern, Alex; Efimkin, Dmitry K.; Galitski, Victor; Fisk, Zachary; Xia, Jing

    2016-04-01

    Radio frequency tunable oscillators are vital electronic components for signal generation, characterization, and processing. They are often constructed with a resonant circuit and a "negative" resistor, such as a Gunn diode, involving complex structure and large footprints. Here we report that a piece of SmB6 , 100 μ m in size, works as a current-controlled oscillator in the 30 MHz frequency range. SmB6 is a strongly correlated Kondo insulator that was recently found to have a robust surface state likely to be protected by the topology of its electronics structure. We exploit its nonlinear dynamics, and demonstrate large ac voltage outputs with frequencies from 20 Hz to 30 MHz by adjusting a small dc bias current. The behaviors of these oscillators agree well with a theoretical model describing the thermal and electronic dynamics of coupled surface and bulk states. With reduced crystal size we anticipate the device to work at higher frequencies, even in the THz regime. This type of oscillator might be realized in other materials with a metallic surface and a semiconducting bulk.

  6. Radio Frequency Tunable Oscillator Device Based on a SmB_{6} Microcrystal.

    PubMed

    Stern, Alex; Efimkin, Dmitry K; Galitski, Victor; Fisk, Zachary; Xia, Jing

    2016-04-22

    Radio frequency tunable oscillators are vital electronic components for signal generation, characterization, and processing. They are often constructed with a resonant circuit and a "negative" resistor, such as a Gunn diode, involving complex structure and large footprints. Here we report that a piece of SmB_{6}, 100  μm in size, works as a current-controlled oscillator in the 30 MHz frequency range. SmB_{6} is a strongly correlated Kondo insulator that was recently found to have a robust surface state likely to be protected by the topology of its electronics structure. We exploit its nonlinear dynamics, and demonstrate large ac voltage outputs with frequencies from 20 Hz to 30 MHz by adjusting a small dc bias current. The behaviors of these oscillators agree well with a theoretical model describing the thermal and electronic dynamics of coupled surface and bulk states. With reduced crystal size we anticipate the device to work at higher frequencies, even in the THz regime. This type of oscillator might be realized in other materials with a metallic surface and a semiconducting bulk. PMID:27152816

  7. Polariton spectrum in nonlinear dielectric medium.

    PubMed

    Dzedolik, Igor V; Karakchieva, Olga

    2013-05-01

    We obtain theoretically the phonon-polariton spectrum in nonlinear dielectric medium with the third-order Kerr-type nonlinearity. We investigate the dependence of number of the polariton spectrum branches on the intensity of electromagnetic field and demonstrate that the appearance of new branches located in the polariton spectrum gap is caused by the influence of dispersion of the third-order dielectric susceptibility at the intensive electromagnetic field in the medium. The modulation instability of new spectrum branch waves leads to the appearance of the cnoidal waves or solitons. These new nonlinear waves one can use for designing optical devices such as the nonlinear optical filter converter. PMID:23669776

  8. Optical and electronic properties of semiconducting Sn2S3

    NASA Astrophysics Data System (ADS)

    Singh, David J.

    2016-07-01

    We report the electronic and optical properties of Sn2S3 as obtained from first principles calculations with the modified Becke-Johnson potential. The electronic structure shows that Sn occurs in both divalent and tetravalent forms. The fundamental band gap of 0.82 eV is indirect. The direct gap is 0.97 eV, but the onset of strong optical absorption is much higher at ˜1.75 eV. This is as a consequence of the Sn2+ s and Sn4+ s characters of the valence and conduction band extrema, respectively. We also find strong and different anisotropies for conduction in p- and n-type Sn2S3. This should be taken into account in device structures in order to obtain efficient charge collection. The thermopowers are reasonably high for both p- and n-type materials. p-type Sn2S3 shows complex corrugated isosurface sections, while the n-type material shows multiple band extrema.

  9. Topological Crystalline Insulator in a New Bi Semiconducting Phase

    PubMed Central

    Munoz, F.; Vergniory, M. G.; Rauch, T.; Henk, J.; Chulkov, E. V.; Mertig, I.; Botti, S.; Marques, M. A. L.; Romero, A. H.

    2016-01-01

    Topological crystalline insulators are a type of topological insulators whose topological surface states are protected by a crystal symmetry, thus the surface gap can be tuned by applying strain or an electric field. In this paper we predict by means of ab initio calculations a new phase of Bi which is a topological crystalline insulator characterized by a mirror Chern number nM = −2, but not a strong topological insulator. This system presents an exceptional property: at the (001) surface its Dirac cones are pinned at the surface high-symmetry points. As a consequence they are also protected by time-reversal symmetry and can survive against weak disorder even if in-plane mirror symmetry is broken at the surface. Taking advantage of this dual protection, we present a strategy to tune the band-gap based on a topological phase transition unique to this system. Since the spin-texture of these topological surface states reduces the back-scattering in carrier transport, this effective band-engineering is expected to be suitable for electronic and optoelectronic devices with reduced dissipation. PMID:26905601

  10. Topological Crystalline Insulator in a New Bi Semiconducting Phase.

    PubMed

    Munoz, F; Vergniory, M G; Rauch, T; Henk, J; Chulkov, E V; Mertig, I; Botti, S; Marques, M A L; Romero, A H

    2016-01-01

    Topological crystalline insulators are a type of topological insulators whose topological surface states are protected by a crystal symmetry, thus the surface gap can be tuned by applying strain or an electric field. In this paper we predict by means of ab initio calculations a new phase of Bi which is a topological crystalline insulator characterized by a mirror Chern number nM = -2, but not a strong topological insulator. This system presents an exceptional property: at the (001) surface its Dirac cones are pinned at the surface high-symmetry points. As a consequence they are also protected by time-reversal symmetry and can survive against weak disorder even if in-plane mirror symmetry is broken at the surface. Taking advantage of this dual protection, we present a strategy to tune the band-gap based on a topological phase transition unique to this system. Since the spin-texture of these topological surface states reduces the back-scattering in carrier transport, this effective band-engineering is expected to be suitable for electronic and optoelectronic devices with reduced dissipation. PMID:26905601

  11. Topological Crystalline Insulator in a New Bi Semiconducting Phase

    NASA Astrophysics Data System (ADS)

    Munoz, F.; Vergniory, M. G.; Rauch, T.; Henk, J.; Chulkov, E. V.; Mertig, I.; Botti, S.; Marques, M. A. L.; Romero, A. H.

    2016-02-01

    Topological crystalline insulators are a type of topological insulators whose topological surface states are protected by a crystal symmetry, thus the surface gap can be tuned by applying strain or an electric field. In this paper we predict by means of ab initio calculations a new phase of Bi which is a topological crystalline insulator characterized by a mirror Chern number nM = -2, but not a strong topological insulator. This system presents an exceptional property: at the (001) surface its Dirac cones are pinned at the surface high-symmetry points. As a consequence they are also protected by time-reversal symmetry and can survive against weak disorder even if in-plane mirror symmetry is broken at the surface. Taking advantage of this dual protection, we present a strategy to tune the band-gap based on a topological phase transition unique to this system. Since the spin-texture of these topological surface states reduces the back-scattering in carrier transport, this effective band-engineering is expected to be suitable for electronic and optoelectronic devices with reduced dissipation.

  12. Semiconducting properties of Al doped ZnO thin films.

    PubMed

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

    2014-10-15

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

  13. Semiconducting Graphene on Silicon from First-Principles Calculations.

    PubMed

    Dang, Xuejie; Dong, Huilong; Wang, Lu; Zhao, Yanfei; Guo, Zhenyu; Hou, Tingjun; Li, Youyong; Lee, Shuit-Tong

    2015-08-25

    Graphene is a semimetal with zero band gap, which makes it impossible to turn electric conduction off below a certain limit. Transformation of graphene into a semiconductor has attracted wide attention. Owing to compatibility with Si technology, graphene adsorbed on a Si substrate is particularly attractive for future applications. However, to date there is little theoretical work on band gap engineering in graphene and its integration with Si technology. Employing first-principles calculations, we study the electronic properties of monolayer and bilayer graphene adsorbed on clean and hydrogen (H)-passivated Si (111)/Si (100) surfaces. Our calculation shows that the interaction between monolayer graphene and a H-passivated Si surface is weak, with the band gap remaining negligible. For bilayer graphene adsorbed onto a H-passivated Si surface, the band gap opens up to 108 meV owing to asymmetry introduction. In contrast, the interaction between graphene and a clean Si surface is strong, leading to formation of chemical bonds and a large band gap of 272 meV. Our results provide guidance for device designs based on integrating graphene with Si technology. PMID:26213346

  14. Fabrication of bright and small size semiconducting polymer nanoparticles for cellular labelling and single particle tracking.

    PubMed

    Wei, Lin; Zhou, Peng; Yang, Qingxiu; Yang, Qiaoyu; Ma, Ming; Chen, Bo; Xiao, Lehui

    2014-10-01

    In this work, we demonstrate a convenient and robust strategy for efficient fabrication of high fluorescence quantum yield (QY, 49.8 ± 3%) semiconducting polymer nanoparticles (SPNs), with size comparable with semiconductor quantum dots (Qdots). The SPNs were synthesized by co-precipitation of hydrophobic semiconducting polymer together with amphiphilic multidentate polymer. Comprehensive spectroscopic and microscopic characterizations showed that the SPNs possess superior photophysical performance, with excellent fluorescence brightness and reduced photoblinking in contrast with Qdots, as well as good photostability compared to a fluorescent protein of a similar size, phycoerythrin. More importantly, by conjugating membrane biomarkers onto the surface of SPNs, it was found that they were not only suitable for specific cellular labelling but also for single particle tracking because of the improved optical performance. PMID:25141182

  15. Two-semiconductive-component hybrid coordination polymers with controllable photo-induced electron-transfer properties.

    PubMed

    Liu, Jian-Jun; Chen, Yong; Lin, Mei-Jin; Huang, Chang-Cang; Dai, Wen-Xin

    2016-04-12

    Two semiconductive inorganic-organic hybrid coordination polymers constructed from metal iodide clusters and naphthalene diimide semiconductive components, [Cu2I2(DPNDI)]n () and [PbI2(DPNDI)]n () (DPNDI = N,N'-di-(4-pyridyl)-1,4,5,8-naphthalene diimide), have been synthesized and characterized. Although possessing similar 2D heterostructures, hybrids exhibited different photo-induced electron-transfer properties. Due to the higher HOMO energy level of the [Cu2I2]n chain than that of the [PbI2]n cluster, only hybrid can easily undergo intramolecular electron transfer to form a long-lived charge separated state, which may be applied in artificial photosynthesis. PMID:26985714

  16. Characterisation of nanohybrids of porphyrins with metallic and semiconducting carbon nanotubes by EPR and optical spectroscopy.

    PubMed

    Cambré, Sofie; Wenseleers, Wim; Culin, Jelena; Van Doorslaer, Sabine; Fonseca, Antonio; Nagy, Janos B; Goovaerts, Etienne

    2008-09-15

    Single-walled carbon nanotubes (SWCNTs) are noncovalently functionalised with octaethylporphyrins (OEPs) and the resulting nanohybrids are isolated from the free OEPs. Electron paramagnetic resonance (EPR) spectroscopy of cobalt(II)OEP, adsorbed on the nanotube walls by pi-pi-stacking, demonstrates that the CNTs act as electron acceptors. EPR is shown to be very effective in resolving the different interactions for metallic and semiconducting tubes. Moreover, molecular oxygen is shown to bind selectively to nanohybrids with semiconducting tubes. Water solubilisation of the porphyrin/CNT nanohybrids using bile salts, after applying a thorough washing procedure, yields solutions in which at least 99% of the porphyrins are interacting with the CNTs. Due to this purification, we observe, for the first time, the isolated absorption spectrum of the interacting porphyrins, which is strongly red-shifted compared to the free porphyrin absorption. In addition a quasi-complete quenching of the porphyrin fluorescence is also observed. PMID:18712730

  17. Technique for Determining the Viscosity and Electrical Conductivity of Semiconducting Liquids

    NASA Technical Reports Server (NTRS)

    Li, C.; Scripa, R. N.; Ban, H.; Lin, B.; Su, C. H.; Lehoczky, S. L.; Feth, S.; Zhu, S.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    A novel apparatus for determining the viscosity and electrical conductivity of semiconducting liquids has been developed at NASA/MSFC. The apparatus is based on the transient torque technique and utilizes a 125 micrometer diameter quartz fiber as a torsion wire and a sensitive angular detector to measure the deflection angle of the crucible containing the liquid. A rotating flow is induced in the semiconducting melt by the application of a rotating magnetic field and measurement of the magnitude and transient behavior of the induced deflection angle allows the simultaneous determination of the viscosity and electrical conductivity of the melt. Measurements at room temperature and up to 900 C were made on high purity melts.

  18. Photoelectric Property Modulation by Nanoconfinement in the Longitude Direction of Short Semiconducting Nanorods.

    PubMed

    Tang, Chaolong; Jiang, Chengming; Bi, Sheng; Song, Jinhui

    2016-05-01

    Photoelectric property change in half-dimensional (0.5D) semiconducting nanomaterials as a function of illumination light intensity and materials geometry has been systematically studied. Through two independent methods, conductive atomic force microscopy (C-AFM) direct current-voltage acquisition and scanning kelvin probe microscopy (SKPM) surface potential mapping, photoelectric property of 0.5D ZnO nanomaterial has been characterized with exceptional behaviors compared with bulk/micro/one-dimensional (1D) nanomaterial. A new model by considering surface effect, quantum effect, and illumination effect has been successfully built, which could more accurately predict the photoelectric characteristics of 0.5D semiconducting nanomaterials. The findings reported in this study could potentially impact three-dimensional (3D) photoelectronics. PMID:27057764

  19. Linear ac transport in graphene semiconducting nanosystem with normal-metal electrodes

    NASA Astrophysics Data System (ADS)

    Ye, En-Jia; Sun, Yun-Lei; Lan, Jin; Shi, Yi-Jian

    2016-03-01

    Linear ac transport properties are investigated in a graphene semiconducting nanosystem, with the effect of normal-metal electrodes taken into account. We use a tight-binding approach and ac transport theory to study the dc conductance and ac emittance in normal-metal/graphene (NG) and normal-metal/graphene/normal-metal (NGN) systems with armchair-edge graphene. We find that the resonant and semiconducting behaviors in NG and NGN systems are closely related to the spatial-resolved local density of states. Furthermore, features of the size-dependent emittances in the NGN system are investigated. The results suggest a positive correlation between the width and capacitive response, and the capacitive response is robust as the size of the system increases proportionally.

  20. Structural Evolution of an Organic Semiconducting Molecule onto a Soft Substrate.

    PubMed

    Martínez-Tong, Daniel E; Ruzié, Christian; Geerts, Yves H; Sferrazza, Michele

    2016-04-18

    The structural organization and evolution of the organic semiconducting molecule 2,7-dioctyloxy[1]benzothieno[3,2-b]-benzothiophene on a soft matrix is studied. Thin films of a blend formed from polystyrene and the molecule were prepared by spin-coating onto silicon substrates, which were subsequently studied by using a combination of microscopy and scattering techniques. The organic semiconducting molecule segregated to the surface and developed a phase with a different structure to the bulk, as in the case of a substrate induced phase observed previously. Under a solvent vapor annealing procedure, the growth of micrometer-sized tetragonal crystals onto the polymer surface was observed, which was not evidenced for the silicon substrates. PMID:26853087

  1. Dielectrophoretic Assembly of Semiconducting Carbon Nanotubes Separated and Enriched by Spin Column Chromatography and Its Application to Gas Sensing

    NASA Astrophysics Data System (ADS)

    Nakano, Michihiko; Fujioka, Masahiro; Mai, Kaori; Watanabe, Hideaki; Martin, Yul; Suehiro, Junya

    2012-04-01

    The present authors have previously demonstrated the electrokinetic fabrication of a single-walled carbon nanotube (SWCNT) gas sensor by employing dielectrophoresis. Because this method employs mass-produced SWCNTs, it can realize cheaper and more flexible SWCNT gas sensor fabrication than that based on the on-site synthesis of SWCNTs. In this study, a new protocol was proposed and tested for the separation and enrichment of semiconducting SWCNTs, aiming to improve the SWCNT gas sensor sensitivity. The protocol employed a spin column filled with size-exclusion dextran-based gel beads as well as two surfactants (sodium dodecyl sulfate and sodium deoxycholate), which had different affinities to metallic and semiconducting SWCNTs. The separation and enrichment of the semiconducting SWCNTs were confirmed by measuring their optical and electrical properties. The CNT gas sensor fabricated using enriched semiconducting SWCNTs was highly sensitive to nitrogen dioxide (NO2) gas, - more sensitive by 10 times than that fabricated using the pristine SWCNT mixture.

  2. Wide-band-gap, alkaline-earth-oxide semiconductor and devices utilizing same

    DOEpatents

    Abraham, Marvin M.; Chen, Yok; Kernohan, Robert H.

    1981-01-01

    This invention relates to novel and comparatively inexpensive semiconductor devices utilizing semiconducting alkaline-earth-oxide crystals doped with alkali metal. The semiconducting crystals are produced by a simple and relatively inexpensive process. As a specific example, a high-purity lithium-doped MgO crystal is grown by conventional techniques. The crystal then is heated in an oxygen-containing atmosphere to form many [Li].degree. defects therein, and the resulting defect-rich hot crystal is promptly quenched to render the defects stable at room temperature and temperatures well above the same. Quenching can be effected conveniently by contacting the hot crystal with room-temperature air.

  3. Hydrogen-bonded semiconducting pigments for air-stable field-effect transistors.

    PubMed

    Głowacki, Eric Daniel; Irimia-Vladu, Mihai; Kaltenbrunner, Martin; Gsiorowski, Jacek; White, Matthew S; Monkowius, Uwe; Romanazzi, Giuseppe; Suranna, Gian Paolo; Mastrorilli, Piero; Sekitani, Tsuyoshi; Bauer, Siegfried; Someya, Takao; Torsi, Luisa; Sariciftci, Niyazi Serdar

    2013-03-20

    Extensive intramolecular π-conjugation is considered to be requisite in the design of organic semiconductors. Here, two inkjet pigments, epindolidione and quinacridone, that break this design rule are explored. These molecules afford intermolecular π-stacking reinforced by hydrogen-bonding bridges. Air-stable organic field effect transistors are reported that support mobilities up to 1.5 cm(2)/Vs with T80 lifetimes comparable with the most stable reported organic semiconducting materials. PMID:23239229

  4. Fabrication of bright and small size semiconducting polymer nanoparticles for cellular labelling and single particle tracking

    NASA Astrophysics Data System (ADS)

    Wei, Lin; Zhou, Peng; Yang, Qingxiu; Yang, Qiaoyu; Ma, Ming; Chen, Bo; Xiao, Lehui

    2014-09-01

    In this work, we demonstrate a convenient and robust strategy for efficient fabrication of high fluorescence quantum yield (QY, 49.8 +/- 3%) semiconducting polymer nanoparticles (SPNs), with size comparable with semiconductor quantum dots (Qdots). The SPNs were synthesized by co-precipitation of hydrophobic semiconducting polymer together with amphiphilic multidentate polymer. Comprehensive spectroscopic and microscopic characterizations showed that the SPNs possess superior photophysical performance, with excellent fluorescence brightness and reduced photoblinking in contrast with Qdots, as well as good photostability compared to a fluorescent protein of a similar size, phycoerythrin. More importantly, by conjugating membrane biomarkers onto the surface of SPNs, it was found that they were not only suitable for specific cellular labelling but also for single particle tracking because of the improved optical performance.In this work, we demonstrate a convenient and robust strategy for efficient fabrication of high fluorescence quantum yield (QY, 49.8 +/- 3%) semiconducting polymer nanoparticles (SPNs), with size comparable with semiconductor quantum dots (Qdots). The SPNs were synthesized by co-precipitation of hydrophobic semiconducting polymer together with amphiphilic multidentate polymer. Comprehensive spectroscopic and microscopic characterizations showed that the SPNs possess superior photophysical performance, with excellent fluorescence brightness and reduced photoblinking in contrast with Qdots, as well as good photostability compared to a fluorescent protein of a similar size, phycoerythrin. More importantly, by conjugating membrane biomarkers onto the surface of SPNs, it was found that they were not only suitable for specific cellular labelling but also for single particle tracking because of the improved optical performance. Electronic supplementary information (ESI) available: Experimental section and additional supporting results as noted in the text

  5. Growth of Homoepitaxial ZnO Semiconducting Films

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, C.-H.; Lehoczky, S. L.; Harris, M. T.; George, M. A.; McCarty, P.

    1999-01-01

    As a high temperature wide-band-gap (3.3 eV at room temperature) semiconductor, ZnO has been used for many applications such as wave-guides, solar cells, and surface acoustic wave devices, Since ZnO has a 60 meV excitonic binding energy that makes it possible to produce excitonic lasing at room temperature, a recent surge of interest is to synthesize ZnO films for UV/blue/green laser diodes. These applications require films with a smooth surface, good crystal quality, and low defect density. Thus, homoepitaxial film growth is the best choice. Homoepitaxial films have been studied in terms of morphology, crystal structure, and electrical and optical properties. ZnO single crystal substrates grown by the hydrothermal method are mechanically polished and annealed in air for four hours before the films are deposited. The annealing temperature-dependence on ZnO substrate morphology and electrical properties is investigated. Films are synthesized by off-axis reactive sputtering deposition. This produces films that have very smooth surfaces with roughness less than or equal to 5 nm on a 5 microns x 5 microns area. The full width at half maximum of film theta rocking curves measured by the x-ray diffraction is slightly larger than that of the crystal substrate. Films are also characterized by measuring resistivity, optical transmittance, and photoluminescence. The properties of ZnO films grown on (0001) ZnO and (0001) sapphire substrates will also be compared and discussed.

  6. Semiconducting polymer nanoparticles as photoacoustic molecular imaging probes in living mice

    NASA Astrophysics Data System (ADS)

    Pu, Kanyi; Shuhendler, Adam J.; Jokerst, Jesse V.; Mei, Jianguo; Gambhir, Sanjiv S.; Bao, Zhenan; Rao, Jianghong

    2014-03-01

    Photoacoustic imaging holds great promise for the visualization of physiology and pathology at the molecular level with deep tissue penetration and fine spatial resolution. To fully utilize this potential, photoacoustic molecular imaging probes have to be developed. Here, we introduce near-infrared light absorbing semiconducting polymer nanoparticles as a new class of contrast agents for photoacoustic molecular imaging. These nanoparticles can produce a stronger signal than the commonly used single-walled carbon nanotubes and gold nanorods on a per mass basis, permitting whole-body lymph-node photoacoustic mapping in living mice at a low systemic injection mass. Furthermore, the semiconducting polymer nanoparticles possess high structural flexibility, narrow photoacoustic spectral profiles and strong resistance to photodegradation and oxidation, enabling the development of the first near-infrared ratiometric photoacoustic probe for in vivo real-time imaging of reactive oxygen species--vital chemical mediators of many diseases. These results demonstrate semiconducting polymer nanoparticles to be an ideal nanoplatform for developing photoacoustic molecular probes.

  7. Polymer-Sorted Semiconducting Carbon Nanotube Networks for High-Performance Ambipolar Field-Effect Transistors

    PubMed Central

    2014-01-01

    Efficient selection of semiconducting single-walled carbon nanotubes (SWNTs) from as-grown nanotube samples is crucial for their application as printable and flexible semiconductors in field-effect transistors (FETs). In this study, we use atactic poly(9-dodecyl-9-methyl-fluorene) (a-PF-1-12), a polyfluorene derivative with asymmetric side-chains, for the selective dispersion of semiconducting SWNTs with large diameters (>1 nm) from plasma torch-grown SWNTs. Lowering the molecular weight of the dispersing polymer leads to a significant improvement of selectivity. Combining dense semiconducting SWNT networks deposited from an enriched SWNT dispersion with a polymer/metal-oxide hybrid dielectric enables transistors with balanced ambipolar, contact resistance-corrected mobilities of up to 50 cm2·V–1·s–1, low ohmic contact resistance, steep subthreshold swings (0.12–0.14 V/dec) and high on/off ratios (106) even for short channel lengths (<10 μm). These FETs operate at low voltages (<3 V) and show almost no current hysteresis. The resulting ambipolar complementary-like inverters exhibit gains up to 61. PMID:25493421

  8. Tailoring (bio)chemical activity of semiconducting nanoparticles: critical role of deposition and aggregation.

    PubMed

    Chernyshova, Irina V; Ponnurangam, Sathish; Somasundaran, Ponisseril

    2011-06-22

    The impact of deposition and aggregation on (bio)chemical properties of semiconducting nanoparticles (NPs) is perhaps among the least studied aspects of aquatic chemistry of solids. Employing a combination of in situ FTIR and ex situ X-ray photoelectron spectroscopy (XPS) and using the Mn(II) oxygenation on hematite (α-Fe(2)O(3)) and anatase (TiO(2)) NPs as a model catalytic reaction, we discovered that the catalytic and sorption performance of the semiconducting NPs in the dark can be manipulated by depositing them on different supports or mixing them with other NPs. We introduce the electrochemical concept of the catalytic redox activity to explain the findings and to predict the effects of (co)aggregation and deposition on the catalytic and corrosion properties of ferric (hydr)oxides. These results offer new possibilities for rationally tailoring the technological performance of semiconducting metal oxide NPs, provide a new framework for modeling their fate and transport in the environment and living organisms, and can be helpful in discriminating between weakly and strongly adsorbed species in spectra. PMID:21557599

  9. Assembling semiconducting molecules by covalent attachment to a lamellar crystalline polymer substrate

    PubMed Central

    Machatschek, Rainhard; Ortmann, Patrick; Reiter, Renate; Mecking, Stefan

    2016-01-01

    Summary We have investigated the potential of polymers containing precisely spaced side-branches for thin film applications, particularly in the context of organic electronics. Upon crystallization, the side-branches were excluded from the crystalline core of a lamellar crystal. Thus, the surfaces of these crystals were covered by side-branches. By using carboxyl groups as side-branches, which allow for chemical reactions, we could functionalize the crystal with semiconducting molecules. Here, we compare properties of crystals differing in size: small nanocrystals and large single crystals. By assembling nanocrystals on a Langmuir trough, large areas could be covered by monolayers consisting of randomly arranged nanocrystals. Alternatively, we used a method based on local supersaturation to grow large area single crystals of the precisely side-branched polymer from solution. Attachment of the semiconducting molecules to the lamellar surface of large single crystals was possible, however, only after an appropriate annealing procedure. As a function of the duration of the grafting process, the morphology of the resulting layer of semiconducting molecules changed from patchy to compact. PMID:27335767

  10. Semiconducting polymer nanoparticles as photoacoustic molecular imaging probes in living mice.

    PubMed

    Pu, Kanyi; Shuhendler, Adam J; Jokerst, Jesse V; Mei, Jianguo; Gambhir, Sanjiv S; Bao, Zhenan; Rao, Jianghong

    2014-03-01

    Photoacoustic imaging holds great promise for the visualization of physiology and pathology at the molecular level with deep tissue penetration and fine spatial resolution. To fully utilize this potential, photoacoustic molecular imaging probes have to be developed. Here, we introduce near-infrared light absorbing semiconducting polymer nanoparticles as a new class of contrast agents for photoacoustic molecular imaging. These nanoparticles can produce a stronger signal than the commonly used single-walled carbon nanotubes and gold nanorods on a per mass basis, permitting whole-body lymph-node photoacoustic mapping in living mice at a low systemic injection mass. Furthermore, the semiconducting polymer nanoparticles possess high structural flexibility, narrow photoacoustic spectral profiles and strong resistance to photodegradation and oxidation, enabling the development of the first near-infrared ratiometric photoacoustic probe for in vivo real-time imaging of reactive oxygen species--vital chemical mediators of many diseases. These results demonstrate semiconducting polymer nanoparticles to be an ideal nanoplatform for developing photoacoustic molecular probes. PMID:24463363

  11. Polymer-sorted semiconducting carbon nanotube networks for high-performance ambipolar field-effect transistors.

    PubMed

    Schiessl, Stefan P; Fröhlich, Nils; Held, Martin; Gannott, Florentina; Schweiger, Manuel; Forster, Michael; Scherf, Ullrich; Zaumseil, Jana

    2015-01-14

    Efficient selection of semiconducting single-walled carbon nanotubes (SWNTs) from as-grown nanotube samples is crucial for their application as printable and flexible semiconductors in field-effect transistors (FETs). In this study, we use atactic poly(9-dodecyl-9-methyl-fluorene) (a-PF-1-12), a polyfluorene derivative with asymmetric side-chains, for the selective dispersion of semiconducting SWNTs with large diameters (>1 nm) from plasma torch-grown SWNTs. Lowering the molecular weight of the dispersing polymer leads to a significant improvement of selectivity. Combining dense semiconducting SWNT networks deposited from an enriched SWNT dispersion with a polymer/metal-oxide hybrid dielectric enables transistors with balanced ambipolar, contact resistance-corrected mobilities of up to 50 cm(2)·V(-1)·s(-1), low ohmic contact resistance, steep subthreshold swings (0.12-0.14 V/dec) and high on/off ratios (10(6)) even for short channel lengths (<10 μm). These FETs operate at low voltages (<3 V) and show almost no current hysteresis. The resulting ambipolar complementary-like inverters exhibit gains up to 61. PMID:25493421

  12. Strong nonlinear focusing of light in nonlinearly controlled electromagnetic active metamaterial field concentrators

    NASA Astrophysics Data System (ADS)

    Rapoport, Yu G.; Boardman, A. D.; Grimalsky, V. V.; Ivchenko, V. M.; Kalinich, N.

    2014-05-01

    The idea of nonlinear ‘transformation optics-inspired’ [1-6] electromagnetic cylindrical field concentrators has been taken up in a preliminary manner in a number of conference reports [7-9]. Such a concentrator includes both external linear region with a dielectric constant increased towards the centre and internal region with nonlinearity characterized by constant coefficients. Then, in the process of farther investigations we realized the following factors considered neither in [7-9] nor in the recent paper [10]: saturation of nonlinearity, nonlinear losses, linear gain, numerical convergence, when nonlinear effect becomes very strong and formation of ‘hotspots’ starts. It is clearly demonstrated here that such a strongly nonlinear process starts when the nonlinear amplitude of any incident beam(s) exceeds some ‘threshold’ value. Moreover, it is shown that the formation of hotspots may start as the result of any of the following processes: an increase of the input amplitude, increasing the linear amplification in the central nonlinear region, decreasing the nonlinear losses, a decrease in the saturation of the nonlinearity. Therefore, a tendency to a formation of ‘hotspots’ is a rather universal feature of the strongly nonlinear behaviour of the ‘nonlinear resonator’ system, while at the same time the system is not sensitive to the ‘prehistory’ of approaching nonlinear threshold intensity (amplitude). The new proposed method includes a full-wave nonlinear solution analysis (in the nonlinear region), a new form of complex geometric optics (in the linear inhomogeneous external cylinder), and new boundary conditions, matching both solutions. The observed nonlinear phenomena will have a positive impact upon socially and environmentally important devices of the future. Although a graded-index concentrator is used here, it is a direct outcome of transformation optics. Numerical evaluations show that for known materials these nonlinear effects

  13. Single-Photon Nonlinear Optics with Graphene Plasmons

    NASA Astrophysics Data System (ADS)

    Gullans, M.; Chang, D. E.; Koppens, F. H. L.; de Abajo, F. J. García; Lukin, M. D.

    2013-12-01

    We show that it is possible to realize significant nonlinear optical interactions at the few photon level in graphene nanostructures. Our approach takes advantage of the electric field enhancement associated with the strong confinement of graphene plasmons and the large intrinsic nonlinearity of graphene. Such a system could provide a powerful platform for quantum nonlinear optical control of light. As an example, we consider an integrated optical device that exploits this large nonlinearity to realize a single photon switch.

  14. Photochromic, electrochromic, photoelectrochromic and photovoltaic devices

    DOEpatents

    Kostecki, Robert; McLarnon, Frank R.

    2000-01-01

    A light activated photoelectrochromic device is formed of a two-component system formed of a photoactive charge carrier generating material and electrochromic material (plus an elecrolyte). Light interacts with a semiconductive material to generate hole-electron charge carriers which cause a redox reaction in the electrochromic material. One device is formed of hydrated nickel oxide as the electrochromic layer and polycrystalline titanium dioxide as the charge generating material. The materials may be formed as discrete layers or mixed together. Because of the direct charge transfer between the layers, a circuit to apply a voltage to drive the electrochromic reaction is not required, although one can be used to enhance the reaction. The hydrated nickel oxide-titanium dioxide materials can also be used to form a photovoltaic device for generating electricity.

  15. Understanding degradation phenomena in organic electronic devices

    NASA Astrophysics Data System (ADS)

    A. K., Jagdish; Pavankumar, G.; Ramamurthy, Praveen C.; Roy Mahapatra, D.; Hegde, Gopalkrishna

    2015-03-01

    This study addresses a unique degradation mechanism in organic electronic devices occurring due to combined effects of electric field and temperature. A simple polymer diode structure consisting of a semiconducting polymer sandwiched between two electrodes (ITO and Al) is considered for degradation studies. It is observed that voltages beyond a certain value lead to fracture of polymer and aluminium films. As characterized, these defects show that the degradation nucleates in the form of a chain-like pattern consisting of alternating polymer fracture sites (hinges) and aluminium rupture sites (links). A mechanism is hypothesized based on experimental observations to explain the phenomenon. This is further validated by an analytical model for stress at degradation sites due to electric field and temperature. The model is used to develop a failure criteria based on device geometry, operating voltage and temperature. Experiments and modelling predict that this mechanism might be unique to soft thin film electronic devices.

  16. Carbon Based Transistors and Nanoelectronic Devices

    NASA Astrophysics Data System (ADS)

    Rouhi, Nima

    Carbon based materials (carbon nanotube and graphene) has been extensively researched during the past decade as one of the promising materials to be used in high performance device technology. In long term it is thought that they may replace digital and/or analog electronic devices, due to their size, near-ballistic transport, and high stability. However, a more realistic point of insertion into market may be the printed nanoelectronic circuits and sensors. These applications include printed circuits for flexible electronics and displays, large-scale bendable electrical contacts, bio-membranes and bio sensors, RFID tags, etc. In order to obtain high performance thin film transistors (as the basic building block of electronic circuits) one should be able to manufacture dense arrays of all semiconducting nanotubes. Besides, graphene synthesize and transfer technology is in its infancy and there is plenty of room to improve the current techniques. To realize the performance of nanotube and graphene films in such systems, we need to economically fabricate large-scale devices based on these materials. Following that the performance control over such devices should also be considered for future design variations for broad range of applications. Here we have first investigated carbon nanotube ink as the base material for our devices. The primary ink used consisted of both metallic and semiconducting nanotubes which resulted in networks suitable for moderate-resistivity electrical connections (such as interconnects) and rfmatching circuits. Next, purified all-semiconducting nanotube ink was used to fabricate waferscale, high performance (high mobility, and high on/off ratio) thin film transistors for printed electronic applications. The parameters affecting device performance were studied in detail to establish a roadmap for the future of purified nanotube ink printed thin film transistors. The trade of between mobility and on/off ratio of such devices was studied and the

  17. Cognitive processing for nonlinear radar

    NASA Astrophysics Data System (ADS)

    Martone, Anthony; Ranney, Kenneth; Hedden, Abigail; Mazzaro, Gregory; McNamara, David

    2013-05-01

    An increasingly cluttered electromagnetic environment (EME) is a growing problem for radar systems. This problem is becoming critical as the available frequency spectrum shrinks due to growing wireless communication device usage and changing regulations. A possible solution to these problems is cognitive radar, where the cognitive radar learns from the environment and intelligently modifies the transmit waveform. In this paper, a cognitive nonlinear radar processing framework is introduced where the main components of this framework consist of spectrum sensing processing, target detection and classification, and decision making. The emphasis of this paper is to introduce a spectrum sensing processing technique that identifies a transmit-receive frequency pair for nonlinear radar. It will be shown that the proposed technique successfully identifies a transmit-receive frequency pair for nonlinear radar from data collected from the EME.

  18. Nonlinear Terahertz Absorption of Graphene Plasmons.

    PubMed

    Jadidi, Mohammad M; König-Otto, Jacob C; Winnerl, Stephan; Sushkov, Andrei B; Drew, H Dennis; Murphy, Thomas E; Mittendorff, Martin

    2016-04-13

    Subwavelength graphene structures support localized plasmonic resonances in the terahertz and mid-infrared spectral regimes. The strong field confinement at the resonant frequency is predicted to significantly enhance the light-graphene interaction, which could enable nonlinear optics at low intensity in atomically thin, subwavelength devices. To date, the nonlinear response of graphene plasmons and their energy loss dynamics have not been experimentally studied. We measure and theoretically model the terahertz nonlinear response and energy relaxation dynamics of plasmons in graphene nanoribbons. We employ a terahertz pump-terahertz probe technique at the plasmon frequency and observe a strong saturation of plasmon absorption followed by a 10 ps relaxation time. The observed nonlinearity is enhanced by 2 orders of magnitude compared to unpatterned graphene with no plasmon resonance. We further present a thermal model for the nonlinear plasmonic absorption that supports the experimental results. The model shows that the observed strong linearity is caused by an unexpected red shift of plasmon resonance together with a broadening and weakening of the resonance caused by the transient increase in electron temperature. The model further predicts that even greater resonant enhancement of the nonlinear response can be expected in high-mobility graphene, suggesting that nonlinear graphene plasmonic devices could be promising candidates for nonlinear optical processing. PMID:26978242

  19. H-bonded supramolecular polymer for the selective dispersion and subsequent release of large-diameter semiconducting single-walled carbon nanotubes.

    PubMed

    Pochorovski, Igor; Wang, Huiliang; Feldblyum, Jeremy I; Zhang, Xiaodong; Antaris, Alexander L; Bao, Zhenan

    2015-04-01

    Semiconducting, single-walled carbon nanotubes (SWNTs) are promising candidates for applications in thin-film transistors, solar cells, and biological imaging. To harness their full potential, however, it is necessary to separate the semiconducting from the metallic SWNTs present in the as-synthesized SWNT mixture. While various polymers are able to selectively disperse semiconducting SWNTs, the subsequent removal of the polymer is challenging. However, many applications require semiconducting SWNTs in their pure form. Toward this goal, we have designed a 2-ureido-6[1H]-pyrimidinone (UPy)-based H-bonded supramolecular polymer that can selectively disperse semiconducting SWNTs. The dispersion purity is inversely related to the dispersion yield. In contrast to conventional polymers, the polymer described herein was shown to disassemble into monomeric units upon addition of an H-bond-disrupting agent, enabling isolation of dispersant-free, semiconducting SWNTs. PMID:25815604

  20. Nonlinear optical properties and nonlinear optical probes of organic materials

    NASA Astrophysics Data System (ADS)

    Meredith, Gerald R.

    1992-02-01

    Nonlinear optical processes and electro-optical effects are expected to have increasing importance as the information age matures and photonics augment electronics in various high density and high bandwidth technologies. Whereas for electronics the emphasis is in construction of smaller device structures from a few parent materials, for organic materials the direction of materials research has been reversed. For some time it's been known that some molecular structures engender exceptionally large molecular nonlinear-polarization responses. If such molecules could be assembled in convenient, versatile, and reliable ways, the resulting materials would be very useful or even enabling in various photonics applications. The mature science and art of chemistry allows very good control over molecular composition and structure and, as will be illustrated in this talk, our knowledge of hyperpolarizability structure- property relationships is advancing rapidly. However, the science of fabrication and arrangement in molecular ensembles and polymers is rather primitive. Thus the goal to develop the appropriately structured materials for utilization in nonlinear and electro-optics has fostered the widespread use of nonlinear optical processes to probe the nature of supramolecular order and assembly. Examples of intrinsic and artificially assembled structures of crystals, molecular aggregates, polymeric orientational electrets and molecular mono- and multi-layer thin films will be shown. Nonlinear optical processes, primarily second-harmonic generation, provide unique probes of these structures, their assembly, and evolution.

  1. Integration of High-Purity Carbon Nanotube Solution into Electronic Devices

    NASA Astrophysics Data System (ADS)

    Tulevski, George; IBM TJ Watson Reserach Center Team

    Due to their exceptional electronic properties, carbon nanotubes (cnt) are leading candidates to be employed as channel materials in future nanoelectronic devices. A key bottleneck to realizing device integration is the sorting of carbon nanotubes, namely the isolation of high-purity, semiconducting cnt solutions. This talk will describe our efforts in using polymer-based sorting methods to isolate high-density and high-purity semiconducting cnt solutions. We explore the dependence of starting material and polymer to cnt ratio on the effectiveness of the separation. We confirm optically and electrically that the semiconducting purity is >99.99% through several thousand individual device measurements. In addition to single-cnt devices, thin-film transistors were also fabricated and tested. Due to the high purity of the solutions, device switching (~105 ION/IOFF) was observed at channel lengths below the percolation threshold (<500 nm). Operating below the percolation threshold allows for devices with much higher current densities and effective mobilities as transport is now the result of direct transport as opposed to hopping between cnts.

  2. Excitons in semiconducting superlattices, quantum wells, and ternary alloys. Progress report, September 15, 1991--May 31, 1992

    SciTech Connect

    Sturge, M.D.; Nahory, R.E.; Tamargo, M.C.

    1992-06-01

    Semiconducting layered structures can now be fabricated with precisely defined layer thicknesses down to one monolayer. An example is the ``superlattice`` (SL) structure, in which to semiconductors with different band gaps are interleaved. The electronic and optical properties of the SL are quite different from those of the constitutents and offer interesting new possibilities both in device design and in basic physics. This proposal aims to improve our understanding of optically excited states in SL`s, particularly in the so-called ``Type 2 indirect`` SL`s in which in electron and hole created by optical excitation are separated both in real and in momentum space. We study these structures by time-resolved tunable laser spectroscopy, with and without external perturbations such as magnetic field, electric field, and uniaxial stress. In SLs with only a few atomic layers per period the familiar ``effective mass model`` of semiconductor states breaks down. We have made precise optical experiments on well-characterized material to test current ``first principles`` calculations of the band structure. Our work under this grant has shown that the material we are using is of sufficiently high quality to test the theoretical predictions. Comparison of theory and experiment provides a new and sensitive probe of the interface quality on a fine scale. Statistical analysis of the temperature dependence of the exciton decay dynamics provides complementary information. From a careful study of the exciton spectra of the recently discovered mixed type 1- type 2 CdTe/CdZnTe SLs we have obtained the band offset at the CdTe/CdZnTe interface to unprecedented accuracy.

  3. A simple equivalent circuit model to represent microstructure effects on the response of semiconducting oxide-based gas sensors

    NASA Astrophysics Data System (ADS)

    Chabanis, Gilles; Parkin, Ivan P.; Williams, David E.

    2003-01-01

    We show that the effects of microstructure on the response of gas-sensitive resistors based on semiconducting oxides can be understood in a pragmatic and practically useful way using a simple three-element resistance network, in which only one of the elements is gas-sensitive. This model, with the gas-sensitive resistance showing a simple form of response consistent with surface reaction models, displays the power-law response to variation of gas concentration (Pg) shown by practical devices: G = Ag Pgbeta, where G is (R - R0)/R0 for resistance increase or (sigma - sigma0)/sigma0 for conductance increase. The observations that beta varies widely between preparations, is different for different gases on the same sensor, and changes with change of the relative humidity of the gas, are simply explained as being due to changes in the relative values of the resistors in the network, related to the microstructure. The model predicts that, for a range of sensor preparations responding to a given gas, Ag and beta should be correlated. The predictions are confirmed by measurements of the response of a wide range of microstructures of sensors of both tin dioxide and chromium titanium oxide to toluene, ethanol and carbon monoxide in atmospheres of varying relative humidity. We show that the correlation of Ag and beta is a powerful tool for discovering subtle effects on the sensor response. These include: effects due to gas concentration gradients within the sensing layer, effects of variation in microstructure throughout the sensing layer, the extent of sintering of the material in the finished sensor, and whether water vapour acts on the sensor surface synergistically or independently of the reactive gas being measured.

  4. Piezoelectric monolayers as nonlinear energy harvesters.

    PubMed

    López-Suárez, Miquel; Pruneda, Miguel; Abadal, Gabriel; Rurali, Riccardo

    2014-05-01

    We study the dynamics of h-BN monolayers by first performing ab-initio calculations of the deformation potential energy and then solving numerically a Langevine-type equation to explore their use in nonlinear vibration energy harvesting devices. An applied compressive strain is used to drive the system into a nonlinear bistable regime, where quasi-harmonic vibrations are combined with low-frequency swings between the minima of a double-well potential. Due to its intrinsic piezoelectric response, the nonlinear mechanical harvester naturally provides an electrical power that is readily available or can be stored by simply contacting the monolayer at its ends. Engineering the induced nonlinearity, a 20 nm2 device is predicted to harvest an electrical power of up to 0.18 pW for a noisy vibration of 5 pN. PMID:24722065

  5. Nonlinear multiferroic phase shifters for microwave frequencies

    SciTech Connect

    Ustinov, Alexey B.; Kalinikos, Boris A.; Srinivasan, G.

    2014-02-03

    A nonlinear microwave phase shifter based on a planar multiferroic composite has been studied. The multiferroic structure is fabricated in the form of a bilayer consisting of yttrium iron garnet and barium strontium titanate. The principle of operation of the device is based on the linear and nonlinear control of the phase shift of the hybrid spin-electromagnetic waves propagating in the bilayer. The linear control is realized with magnetic and electric fields. The nonlinear control is provided by the input power of microwave signal. The device showed a nonlinear phase shift up to 250°, electric field induced phase shift up to 330°, and magnetic field induced phase shift of more than 180°.

  6. New Nonlinear Multigrid Analysis

    NASA Technical Reports Server (NTRS)

    Xie, Dexuan

    1996-01-01

    The nonlinear multigrid is an efficient algorithm for solving the system of nonlinear equations arising from the numerical discretization of nonlinear elliptic boundary problems. In this paper, we present a new nonlinear multigrid analysis as an extension of the linear multigrid theory presented by Bramble. In particular, we prove the convergence of the nonlinear V-cycle method for a class of mildly nonlinear second order elliptic boundary value problems which do not have full elliptic regularity.

  7. Two spatially separated phases in semiconducting Rb0.8Fe1.5S2

    DOE PAGESBeta

    Wang, Meng; Tian, Wei; Valdivia, P.; Chi, Songxue; Bourret-Courchesne, E.; Dai, Pengcheng; Birgeneau, R. J.

    2014-09-26

    We report neutron scattering and transport measurements on semiconducting Rb0.8Fe1.5S2, a compound isostructural and isoelectronic to the well-studied A0.8FeySe2(A = K, Rb, Cs, Tl/K) superconducting systems. Both resistivity and DC susceptibility measurements reveal a magnetic phase transition at T = 275 K. Neutron diffraction studies show that the 275 K transition originates from a phase with rhombic iron vacancy order which exhibits an in-plane stripe antiferromagnetic ordering below 275 K. In addition, the stripe antiferromagnetic phase interdigitates mesoscopically with an ubiquitous phase with √5 x√5 iron vacancy order. This phase has a magnetic transition at TN = 425 K andmore » an iron vacancy order-disorder transition at TS = 600 K. These two different structural phases are closely similar to those observed in the isomorphous Se materials. Based on the close similarities of the in-plane antiferromagnetic structures, moments sizes, and ordering temperatures in semiconducting Rb0.8Fe1.5S2 and K0.81Fe1.58Se2, we argue that the in-plane antiferromagnetic order arises from strong coupling between local moments. Superconductivity, previously observed in the A0.8FeySe2₋ zSz system, is absent in A0.8Fe1.5S2, which has a semiconducting ground state. We discuss the implied relationship between stripe and block antiferromagnetism and superconductivity in these materials as well as a strategy for further investigation.« less

  8. Chaotic dynamics of weakly nonlinear systems

    SciTech Connect

    Vavriv, D.M.

    1996-06-01

    A review is given on the recent results in studying chaotic phenomena in weakly nonlinear systems. We are concerned with the class of chaotic states that can arise in physical systems with any degree of nonlinearity however small. The conditions for, and the mechanisms of, the transitions to chaos are discussed. These findings are illustrated by the results of the stability analysis of practical microwave and optical devices. {copyright} {ital 1996 American Institute of Physics.}

  9. Structural and transport properties of metallic and semiconducting Sb{sub 2}Te{sub 3} alloy

    SciTech Connect

    Das, Diptasikha; Malik, K.; Bandyopadhyay, S.; Banerjee, S.; Banerjee, Aritra; Dhara, S.

    2015-06-24

    Metallic and semiconducting Sb{sub 2}Te{sub 3} alloys have been synthesized by controlling the cooling rate in the solid state reaction method. Temperature dependent resistivity is measured down to 10 K for the identification of metallic and semiconducting phases. Structural studies are performed by both X-ray diffraction (XRD) and Raman spectroscopic analyses. XRD study confirms single phase nature of polycrystalline alloys in the detectable limit. Raman spectroscopy is used to understand the vibration properties of Sb{sub 2}Te{sub 3} crystals. Widening of full width at half maxima of the highest intense peak in the XRD analysis indicates higher amount of defects in the semiconducting phase than that in the metallic one. Raman study indicates presence of impurity phases in the semiconducting Sb{sub 2}Te{sub 3}. The resistivity of semiconducting Sb{sub 2}Te{sub 3} sample is higher than that of metallic one, which corroborates with the XRD and Raman analyses.

  10. Light emitting ceramic device and method for fabricating the same

    DOEpatents

    Valentine, Paul; Edwards, Doreen D.; Walker Jr., William John; Slack, Lyle H.; Brown, Wayne Douglas; Osborne, Cathy; Norton, Michael; Begley, Richard

    2004-11-30

    A light-emitting ceramic based panel, hereafter termed "electroceramescent" panel, and alternative methods of fabrication for the same are claimed. The electroceramescent panel is formed on a substrate providing mechanical support as well as serving as the base electrode for the device. One or more semiconductive ceramic layers directly overlay the substrate, and electrical conductivity and ionic diffusion are controlled. Light emitting regions overlay the semiconductive ceramic layers, and said regions consist sequentially of a layer of a ceramic insulation layer and an electroluminescent layer, comprised of doped phosphors or the equivalent. One or more conductive top electrode layers having optically transmissive areas overlay the light emitting regions, and a multi-layered top barrier cover comprising one or more optically transmissive non-combustible insulation layers overlay said top electrode regions.

  11. Influence of cysteine doping on photoluminescence intensity from semiconducting single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Kurnosov, N. V.; Leontiev, V. S.; Linnik, A. S.; Karachevtsev, V. A.

    2015-03-01

    Photoluminescence (PL) from semiconducting single-walled carbon nanotubes can be applied for detection of cysteine. It is shown that cysteine doping (from 10-8 to 10-3 M) into aqueous suspension of nanotubes with adsorbed DNA leads to increase of PL intensity. The PL intensity was enhanced by 27% at 10-3 M cysteine concentration in suspension. Most likely, the PL intensity increases due to the passivation of p-defects on the nanotube by the cysteine containing reactive thiol group. The effect of doping with other amino acids without this group (methionine, serine, aspartic acid, lysine, proline) on the PL intensity is essentially weaker.

  12. Modeling of Schottky Barrier Modulation due to Oxidation at Metallic Electrode and Semiconducting Carbon Nanotube Junction

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Biegel, Bryan (Technical Monitor)

    2003-01-01

    A model is proposed for the previously reported lower Schottky barrier for holes PHI (sub bH) in air than in vacuum at a metallic electrode - semiconducting carbon nanotube (CNT) junction. We assume that there is a transition region between the electrode and the CNT, and an appreciable potential can drop there. The role of the oxidation is to increase this potential drop with negatively charged oxygen molecules on the CNT, leading to lower PHI(sub Bh) after oxidation. The mechanism prevails in both p- and n-CNTs, and the model consistently explains the key experimental findings.

  13. Anomalous Josephson effect in semiconducting nanowires as a signature of the topologically nontrivial phase

    NASA Astrophysics Data System (ADS)

    Nesterov, Konstantin N.; Houzet, Manuel; Meyer, Julia S.

    2016-05-01

    We study Josephson junctions made of semiconducting nanowires with Rashba spin-orbit coupling, where superconducting correlations are induced by the proximity effect. In the presence of a suitably directed magnetic field, the system displays the anomalous Josephson effect: a nonzero supercurrent in the absence of a phase bias between two superconductors. We show that this anomalous current can be increased significantly by tuning the nanowire into the helical regime. In particular, in a short junction, a large anomalous current is a signature for topologically nontrivial superconductivity in the nanowire.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  15. Transient Torque Technique for Viscosity and Electrical Conductivity Determination of Semiconducting Liquids

    NASA Technical Reports Server (NTRS)

    Li, C.; Scripa, R. N.; Ban, H.; Lin, B.; Su, C.-H.; Lehoczky, S. L.; Feth, S.; Zhu, S.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    A novel apparatus based on transient torque technique is constructed in MSFC/NASA. The apparatus uses a 125um diameter quartz fiber as torsion wire. A high sensitive angular detector is implemented to measure the deflection angle of the crucible containing the liquid. A rotating magnetic field (RMF) is used to induce a rotating flow of a conducting or semiconducting melts. By measuring the magnitude and transient behavior of the induced deflection angle, the electrical conductivity and viscosity of the melt can be measured simultaneously. High purity elements namely Hg, Ga, Zn and Te are tested at room temperature and high temperature up to 900 C.

  16. Step-edge faceting and local metallization of a single-wall semiconducting carbon nanotube

    NASA Astrophysics Data System (ADS)

    Clair, Sylvain; Kim, Yousoo; Kawai, Maki

    2011-10-01

    The adsorption of a single-wall carbon nanotube on a well-defined metal surface produces substantial mutual interaction that can lead to strong effects both on the nanotube and on the substrate side. We report two kinds of step faceting on Au(111) and Cu(111). We observed local metallization of a semiconducting nanotube induced by the deformation pressure of crossing a step edge on Cu(111). The origin of this effect is discussed. Our results illustrate the complexity and the large number of situations encountered for the nanotube-on-metal system.

  17. Deterministic radiative coupling between plasmonic nanoantennas and semiconducting nanowire quantum dots

    NASA Astrophysics Data System (ADS)

    Jeannin, Mathieu; Rueda-Fonseca, Pamela; Bellet-Amalric, Edith; Kheng, Kuntheak; Nogues, Gilles

    2016-05-01

    We report on the deterministic coupling between single semiconducting nanowire quantum dots emitting in visible and plasmonic Au nanoantennas. Both systems are separately and carefully characterized through micro-photoluminescence and cathodoluminescence. A two-step realignment process using cathodoluminescence allows for electron-beam lithography of Au antennas near individual nanowire quantum dots with a precision of 50 nm. A complete set of optical properties was measured before and after antenna fabrication. They evidence both an increase of the nanowire absorption, and an improvement of the quantum dot emission rate up to a factor of two in presence of the antenna.

  18. Semiconducting Polymer Photodetectors with Electron and Hole Blocking Layers: High Detectivity in the Near-Infrared

    PubMed Central

    Gong, Xiong; Tong, Ming-Hong; Park, Sung Heum; Liu, Michelle; Jen, Alex; Heeger, Alan J.

    2010-01-01

    Sensing from the ultraviolet-visible to the infrared is critical for a variety of industrial and scientific applications. Photodetectors with broad spectral response, from 300 nm to 1,100 nm, were fabricated using a narrow-band gap semiconducting polymer blended with a fullerene derivative. By using both an electron-blocking layer and a hole-blocking layer, the polymer photodetectors, operating at room temperature, exhibited calculated detectivities greater than 1013 cm Hz1/2/W over entire spectral range with linear dynamic range approximately 130 dB. The performance is comparable to or even better than Si photodetectors. PMID:22163562

  19. Demonstration of molecular beam epitaxy and a semiconducting band structure for I-Mn-V compounds

    SciTech Connect

    Jungwirth, T.; Novak, V.; Cukr, M.; Zemek, J.; Marti, X.; Horodyska, P.; Nemec, P.; Holy, V.; Maca, F.; Shick, A. B.; Masek, J.; Kuzel, P.; Nemec, I.; Gallagher, B. L.; Campion, R. P.; Foxon, C. T.; Wunderlich, J.

    2011-01-15

    Our ab initio theory calculations predict a semiconducting band structure of I-Mn-V compounds. We demonstrate on LiMnAs that high-quality materials with group-I alkali metals in the crystal structure can be grown by molecular beam epitaxy. Optical measurements on the LiMnAs epilayers are consistent with the theoretical electronic structure. Our calculations also reproduce earlier reports of high antiferromagnetic ordering temperature and predict large, spin-orbit-coupling-induced magnetic anisotropy effects. We propose a strategy for employing antiferromagnetic semiconductors in high-temperature semiconductor spintronics.

  20. Deterministic radiative coupling between plasmonic nanoantennas and semiconducting nanowire quantum dots.

    PubMed

    Jeannin, Mathieu; Rueda-Fonseca, Pamela; Bellet-Amalric, Edith; Kheng, Kuntheak; Nogues, Gilles

    2016-05-01

    We report on the deterministic coupling between single semiconducting nanowire quantum dots emitting in visible and plasmonic Au nanoantennas. Both systems are separately and carefully characterized through micro-photoluminescence and cathodoluminescence. A two-step realignment process using cathodoluminescence allows for electron-beam lithography of Au antennas near individual nanowire quantum dots with a precision of 50 nm. A complete set of optical properties was measured before and after antenna fabrication. They evidence both an increase of the nanowire absorption, and an improvement of the quantum dot emission rate up to a factor of two in presence of the antenna. PMID:27001959

  1. The effect of induced charges on low-energy particle trajectories near conducting and semiconducting plates

    NASA Technical Reports Server (NTRS)

    Coffey, Victoria N.; Moore, Thomas E.

    1992-01-01

    The effect of the induced charge was found on particles less than 1 eV as they passed through simulated parallel, grounded channels that are comparable in dimension to those that are presently in space plasma instruments which measure the flux of low-energy ions. Applications were made to both conducting and semiconducting channels that ranged in length from 0.1 to 50 mm and in aspect ratio from 1 to 100. The effect of the induced charge on particle trajectories from simple straight lines. Several configurations of channel aspect ratio and detector locations are considered. The effect is important only at very low energies with small dimensions.

  2. Temperature-dependent thermoelectric power of semiconducting bismuth-vanadate glass

    NASA Astrophysics Data System (ADS)

    Ghosh, Aswini

    1989-01-01

    The temperature dependence of the thermoelectric power of the semiconducting bismuth-vanadate glasses was presented in a range of compositions. The high-temperature thermoelectric power was satisfactorily explained by Heikes' relation [R. R. Heikes and R. W. Ure, Eds., Thermoelectricity (Interscience, New York, 1961), p. 81]. The thermoelectric power data also showed evidence of small polaron formation in the glass and revealed that the disorder energy happened to increase with the increase of V2O5 content in the glass. An estimate of the disorder energy was made from the low-temperature thermoelectric power data.

  3. [Nonlinear magnetohydrodynamics

    SciTech Connect

    Not Available

    1994-01-01

    Resistive MHD equilibrium, even for small resistivity, differs greatly from ideal equilibrium, as do the dynamical consequences of its instabilities. The requirement, imposed by Faraday`s law, that time independent magnetic fields imply curl-free electric fields, greatly restricts the electric fields allowed inside a finite-resistivity plasma. If there is no flow and the implications of the Ohm`s law are taken into account (and they need not be, for ideal equilibria), the electric field must equal the resistivity times the current density. The vanishing of the divergence of the current density then provides a partial differential equation which, together with boundary conditions, uniquely determines the scalar potential, the electric field, and the current density, for any given resistivity profile. The situation parallels closely that of driven shear flows in hydrodynamics, in that while dissipative steady states are somewhat more complex than ideal ones, there are vastly fewer of them to consider. Seen in this light, the vast majority of ideal MHD equilibria are just irrelevant, incapable of being set up in the first place. The steady state whose stability thresholds and nonlinear behavior needs to be investigated ceases to be an arbitrary ad hoc exercise dependent upon the whim of the investigator, but is determined by boundary conditions and choice of resistivity profile.

  4. Defect characterization and stress analysis by white beam synchrotron X-ray topography in single crystal semiconducting materials

    NASA Astrophysics Data System (ADS)

    Sarkar, Vishwanath

    Semiconductor devices are becoming increasingly more complex as the number of transistors increases in the same Integrated Circuit (IC) area. Due to the complexity in design; processing and packaging of the device plays a crucial role in the IC fabrication. Package induced residual stress are not only detrimental to device performance but can also lead to device failure. We propose a non-destructive method to determine the complete stress state at each point on a packaged Silicon device. Surface and edge defect created as a result of various manufacturing steps were characterized using different techniques, primarily X-ray diffraction topography, optical microscopy, SEM and TEM. Residual stress plays an important role in the performance and lifetime of single crystal device material. Here we present a novel technique using white beam synchrotron X-ray diffraction reticulography, Stress Mapping and Analysis via Ray Tracing (SMART) in order to determine residual stress level at an array of points over the entire crystal area. This method has a unique advantage compared with other stress measurement technique in that it can evaluate all six components of the stress tensor. The underlying experimental technique is based on white beam synchrotron X-ray diffraction topography and ray tracing. An array of X-ray micro-beam is illuminated on the single crystal sample and multiple reflections (reticulographs) are recorded simultaneously on a photographic film. Crystallographic plane normal vector at the location of each micro-beam in the crystal is calculated. The variation of the plane normal vector direction is due to residual strain (both sheer and dilatational) present in the crystal. By considering three different diffracting planes and corresponding reticulograph a complete state of stress is calculated. Principle, applications and limitations are discussed. White beam synchrotron reticulography is used in reflection geometry to evaluate complete residual stress tensor

  5. Spectral Hole Burning via Kerr Nonlinearity

    NASA Astrophysics Data System (ADS)

    Khan, Anwar Ali; Abdul Jabar, M. S.; Jalaluddin, M.; Bacha, Bakht Amin; Iftikhar, Ahmad

    2015-10-01

    Spectral hole burning is investigated in an optical medium in the presence of Doppler broadening and Kerr nonlinearity. The Kerr nonlinearity generates coherent hole burning in the absorption spectrum. The higher order Kerr nonlinearity enhances the typical lamb dip of the hole. Normal dispersion in the hole burning region while Steep anomalous dispersion between the two hole burning regions also enhances with higher order Kerr effect. A large phase shift creates large delay or advancement in the pulse propagation while no distortion is observed in the pulse. These results provide significant steps to improve optical memory, telecom devices, preservation of information and image quality. Supported by Higher Education Commission (HEC) of Pakistan

  6. Optical nonlinearity of HBI in different solvents

    NASA Astrophysics Data System (ADS)

    Wu, Feng; Ma, Lina; Geng, Yaohui; Zhang, Siwen; Wang, Zhe; Cheng, Xiaoman

    2014-04-01

    2-(2'-Hydroxyphenyl) benzimidazole (HBI) is one kind of organic molecules featuring excited-state proton transfer (ESPT). The nonlinear optical properties of 2-(2'-hydroxyphenyl) benzimidazole (HBI) in different polar solvents were investigated by means of Z-scan technique under the excitation of the 1064 nm picoseconds laser pulse. The experimental results show that the nonlinear refractive indices decrease with the enhancement of the polarity of the solvent. The nonlinear refractive indices sensitive to the solvent polarity allow them to be widely used for the optoelectronic devices.

  7. NOVEL SIGNAL PROCESSING WITH NONLINEAR TRANSMISSION LINES

    SciTech Connect

    D. REAGOR; ET AL

    2000-08-01

    Nonlinear dielectrics offer uniquely strong and tunable nonlinearities that make them attractive for current devices (for example, frequency-agile microwave filters) and for future signal-processing technologies. The goal of this project is to understand pulse propagation on nonlinear coplanar waveguide prototype devices. We have performed time-domain and frequency-domain experimental studies of simple waveguide structures and pursued a theoretical understanding of the propagation of signals on these nonlinear waveguides. To realistically assess the potential applications, we used a time-domain measurement and analysis technique developed during this project to perform a broadband electrodynamics characterization in terms of nonlinear, dispersive, and dissipative effects. We completed a comprehensive study of coplanar waveguides made from high-temperature superconducting thin-film YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} electrodes on nonlinear dielectric single-crystal SrTiO{sub 3} substrates. By using parameters determined from small-signal (linear) transmission characteristics of the waveguides, we develop a model equation that successfully predicts and describes large-signal (nonlinear) behavior.

  8. Application and deterioration of thin films used for microelectronic devices

    SciTech Connect

    Hummel, R.E.

    1987-01-01

    Microelectronic technology makes use of the knowledge and characterization methods of thin films and of our understanding of interfaces between thin films or between films and substrates. (See in this context some of the other papers in this book). The present contribution deals accordingly with thin films utilized in microelectronic devices. It needs to be realized that computers and other related devices depend heavily on metallic or semiconducting layers that often have only the size of one-tenth of the thickness of a human hair. As the electronic devices shrink, these layers represent an ever-greater fraction of the total device volume. These very films actually determine the electrical characteristics and also the stability (reliability) of the devices.

  9. A piezoelectric bistable plate for nonlinear broadband energy harvesting

    NASA Astrophysics Data System (ADS)

    Arrieta, A. F.; Hagedorn, P.; Erturk, A.; Inman, D. J.

    2010-09-01

    Recently, the idea of using nonlinearity to enhance the performance of vibration-based energy harvesters has been investigated. Nonlinear energy harvesting devices have been shown to be capable of operating over wider frequency ranges delivering more power than their linear counterparts, rendering them more suitable for real applications. In this paper, we propose to exploit the rich nonlinear behavior of a bistable composite plate with bonded piezoelectric patches for broadband nonlinear energy harvesting. The response of the structure is experimentally investigated revealing different large amplitude oscillations. Substantially large power is extracted over a wide frequency range achieving broadband nonlinear energy harvesting.

  10. Nonlinear synthetic aperture radar imaging using a harmonic radar

    NASA Astrophysics Data System (ADS)

    Gallagher, Kyle A.; Mazzaro, Gregory J.; Ranney, Kenneth I.; Nguyen, Lam H.; Martone, Anthony F.; Sherbondy, Kelly D.; Narayanan, Ram M.

    2015-05-01

    This paper presents synthetic aperture radar (SAR) images of linear and nonlinear targets. Data are collected using a linear/nonlinear step frequency radar. We show that it is indeed possible to produce SAR images using a nonlinear radar. Furthermore, it is shown that the nonlinear radar is able to reduce linear clutter by at least 80 dB compared to a linear radar. The nonlinear SAR images also show the system's ability to detect small electronic devices in the presence of large linear clutter. The system presented here has the ability to completely ignore a 20-inch trihedral corner reflector while detecting a RF mixer with a dipole antenna attached.

  11. The interaction of selected semiconducting biomaterials with platelet-rich plasma and whole blood.

    PubMed

    Shih, Chun-Che; Shih, Chun-Ming; Su, Yea-Yang; Gerhardt, Rosario A; Lin, Shing-Jong

    2005-09-01

    Copper and silicon are used as biomaterials in various forms. Silicon is a well-known semiconductor and has two distinct types (n-type and p-type), depending on the dopants used. The oxides (e.g., CuO and Cu2O) on the copper surface also behave as semiconductors. The electrochemical properties of these two selected semiconducting biomaterials were investigated by cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and open-circuit potential (OCP) in an aerated Ringer's solution at 37 degrees C. Platelet-rich plasma (PRP) and whole blood from a healthy human donor were used to determine the degree of interaction with the selected semiconducting materials in vitro. Morphologies of adherent platelets and blood on these two biomaterials were examined by scanning electron microscopy (SEM). Experimental results indicated that the degree of interaction is a function of the electrochemical properties of these two biomaterials. Platelets and blood were found to react strongly with p-type biomaterials while little or no sign of interaction with n-type biomaterials was demonstrated. The difference in PRP and whole blood reactions between p-type and n-type semiconductors was quantified to be significant as p<0.05. PMID:16010666

  12. Self-Trapping of Charge Carriers in Semiconducting Carbon Nanotubes: Structural Analysis.

    PubMed

    Adamska, Lyudmyla; Nazin, George V; Doorn, Stephen K; Tretiak, Sergei

    2015-10-01

    The spatial extent of charged electronic states in semiconducting carbon nanotubes with indices (6,5) and (7,6) was evaluated using density functional theory. It was observed that electrons and holes self-trap along the nanotube axis on length scales of about 4 and 8 nm, respectively, which localize cations and anions on comparable length scales. Self-trapping is accompanied by local structural distortions showing periodic bond-length alternation. The average lengthening (shortening) of the bonds for anions (cations) is expected to shift the G-mode frequency to lower (higher) values. The smaller-diameter nanotube has reduced structural relaxation due to higher carbon-carbon bond strain. The reorganization energy due to charge-induced deformations in both nanotubes is found to be in the 30-60 meV range. Our results represent the first theoretical simulation of self-trapping of charge carriers in semiconducting nanotubes, and agree with available experimental data. PMID:26722885

  13. Mechanical and electronic properties at the interface between the Si(100) surface and semiconducting carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Barraza-Lopez, Salvador

    2007-03-01

    I discuss the ab initio mechanical and electronic properties of semiconducting carbon nanotubes adsorbed on the Si(100) surface. After revising results from nanotubes on the fully unpassivated surface[1], the interaction between a semiconducting nanotube and a fully H-passivated Si(100) surface with dopants is examined[2]. As silicon wafers are ordinarily doped, the model closely resembles experimental onditions[2,3,4], allowing for qualitative comparison. The single H-monolayer prevents electronic states in nanotubes from energetically shifting along with those of the doped supporting substrate, permitting the engineering of the relative positions of the slab and nanotube band edges. Finally, and following experimental work, we study adsorption characteristics of nanotubes on partially passivated surfaces. Surface states in the unpassivated regions modify the electronic structure of the interface and provide for the anchoring of nanotubes, deforming them in some cases. Results with and without dopants will be given[2].1 S. Barraza-Lopez et al. J. Appl. Phys. (in press). 2 Submitted. 3 Appl. Phys. Lett 83, 5029 (2003). 4 P. M. Albrecht and J. W. Lyding, Small (in press).

  14. Size-dependent property and cell labeling of semiconducting polymer dots.

    PubMed

    Sun, Kai; Chen, Haobin; Wang, Lei; Yin, Shengyan; Wang, Haiyu; Xu, Gaixia; Chen, Danni; Zhang, Xuanjun; Wu, Changfeng; Qin, Weiping

    2014-07-01

    Semiconducting polymer dots (Pdots) represent a new class of fluorescent nanoparticles for biological applications. In this study, we investigated their size-dependent fluorescence and cellular labeling properties. We demonstrate that the polymer conformation in solution phase largely affects the polymer folding and packing during the nanoparticle preparation process, resulting in solution-phase control over the fluorescence properties of semiconducting polymer nanoparticles. The resulting Pdots exhibit apparent size dependent absorption and emission, a characteristic feature of different chain packing behaviors due to the preparation conditions. Single-particle fluorescence imaging was employed to perform a side-by-side comparison on the Pdot brightness, indicating a quadratic dependence of single-particle brightness on particle size. Upon introducing a positively charged dye Nile blue, all the three type of Pdots were quenched very efficiently (Ksv > 1 × 10(7) M(-1)) in an applied quenching process at low dye concentrations, but exhibit apparent difference in quenching efficiency with increasing dye concentration. Furthermore, Pdots of different sizes were used for cell uptake and cellular labeling involving biotin-streptavidin interactions. Fluorescence imaging together with flow cytometry studies clearly showed size dependent labeling brightness. Small-sized Pdots appear to be more effective for immunolabeling of cell surface, whereas medium-sized Pdots exhibit the highest uptake efficiency. This study provides a concrete guidance for selecting appropriate particle size for biological imaging and sensing applications. PMID:24930393

  15. Effect of fractal silver electrodes on charge collection and light distribution in semiconducting organic polymer films

    SciTech Connect

    Chamousis, RL; Chang, LL; Watterson, WJ; Montgomery, RD; Taylor, RP; Moule, AJ; Shaheen, SE; Ilan, B; van de Lagemaat, J; Osterloh, FE

    2014-08-21

    Living organisms use fractal structures to optimize material and energy transport across regions of differing size scales. Here we test the effect of fractal silver electrodes on light distribution and charge collection in organic semiconducting polymer films made of P3HT and PCBM. The semiconducting polymers were deposited onto electrochemically grown fractal silver structures (5000 nm x 500 nm; fractal dimension of 1.71) with PEDOT:PSS as hole-selective interlayer. The fractal silver electrodes appear black due to increased horizontal light scattering, which is shown to improve light absorption in the polymer. According to surface photovoltage spectroscopy, fractal silver electrodes outperform the flat electrodes when the BHJ film thickness is large (>400 nm, 0.4 V photovoltage). Photocurrents of up to 200 microamperes cm(-2) are generated from the bulk heterojunction (BHJ) photoelectrodes under 435 nm LED (10-20 mW cm(-2)) illumination in acetonitrile solution containing 0.005 M ferrocenium hexafluorophosphate as the electron acceptor. The low IPCE values (0.3-0.7%) are due to slow electron transfer to ferrocenium ion and due to shunting along the large metal-polymer interface. Overall, this work provides an initial assessment of the potential of fractal electrodes for organic photovoltaic cells.

  16. Importance of Having Low-Density Functional Groups for Generating High-Performance Semiconducting Polymer Dots

    PubMed Central

    Zhang, Xuanjun; Yu, Jiangbo; Wu, Changfeng; Jin, Yuhui; Rong, Yu; Ye, Fangmao

    2012-01-01

    Semiconducting polymers with low-density side-chain carboxylic acid groups were synthesized to form stable, functionalized, and highly fluorescent polymer dots (Pdots). The influence of the molar fraction of hydrophilic side-chains on Pdot properties and performance was systematically investigated. Our results show that the density of side-chain carboxylic acid groups significantly affects Pdot stability, internal structure, fluorescence brightness, and nonspecific binding in cellular labeling. Fluorescence spectroscopy, single-particle imaging, and a dye-doping method were employed to investigate the fluorescence brightness and the internal structure of the Pdots. The results of these experiments indicate that semiconducting polymers with low density of side-chain functional groups can form stable, compact, and highly bright Pdots as compared to those with high density of hydrophilic side-chains. The functionalized polymer dots were conjugated to streptavidin (SA) by carbodiimide-catalyzed coupling and the Pdot-SA probes effectively and specifically labeled the cancer cell-surface marker Her2 in human breast cancer cells. The carboxylate-functionalized polymer could also be covalently modified with small functional molecules to generate Pdot probes for click chemistry-based bioorthogonal labeling. This study presents a promising approach for further developing functional Pdot probes for biological applications. PMID:22607220

  17. Strain induced effects on electronic structure of semi-metallic and semiconducting tin nanowires

    NASA Astrophysics Data System (ADS)

    Ansari, Lida; Fagas, Giorgos; Greer, James C.

    2014-09-01

    Semimetal nanowires are known to undergo a semimetal to semiconductor transition as a consequence of quantum confinement as their diameters are decreased. Using density functional theory calculations, the electronic structure of tin nanowires (SnNWs) under uniaxial strain within a range of -4% to +4% is investigated. It is demonstrated that a [110]-oriented semi-metallic SnNW with a diameter of ˜4.2 nm can be made either more metallic or semiconducting by the application of tensile or compressive strain, respectively. On the contrary, a [100]-oriented semi-metallic SnNW with a slightly larger diameter of ˜4.5 nm remains semiconducting with the application of either compressive or tensile strain. Carrier effective masses are calculated from the band structures; it is shown that for semimetal SnNW along [110] orientation the conduction and valence bands display near linear dispersion under both compressive and tensile strains (<3%) which leads to very small effective masses of ˜0.007m0. We also show that strain energies and Young modulus vary with nanowire diameter and crystal orientation. The effect of alloying on the generation of tensile and compressive strains in SnNWs is also investigated.

  18. Atomistic modeling of the metallic-to-semiconducting phase boundaries in monolayer MoS2

    NASA Astrophysics Data System (ADS)

    Saha, Dipankar; Mahapatra, Santanu

    2016-06-01

    Recent experimental demonstration on the coexistence of metallic and semiconducting phases in the same monolayer MoS2 crystal has attracted much attention for its use in ultra-low contact resistance-MoS2 transistors. However, the electronic structures of the metallic-to-semiconducting phase boundaries, which appear to dictate the carrier injection in such transistors, are not yet well understood. In this letter, interfacing the 2H and 1T' polytypes appropriately, we first model the "beta" (β) and the "gamma" (γ) phase boundaries, and demonstrate good agreement with experiential results. We then apply first-principles based density functional theory to calculate the electronic structures for those optimized geometries. We further employ non equilibrium Green's function formalism to evaluate the transmission spectra and the local density of states (LDOS) in order to assess the Schottky barrier nature of the phase boundaries. Our study reveals that while the γ boundary yields p-type Schottky barrier, the β boundary leads to the distinct symmetric Schottky barrier with an atomically sharp transition region. This understanding could be useful for designing high performance transistors using phase-engineered MoS2 crystals.

  19. Effect of fractal silver electrodes on charge collection and light distribution in semiconducting organic polymer films

    SciTech Connect

    Chamousis, RL; Chang, LL; Watterson, WJ; Montgomery, RD; Taylor, RP; Moule, AJ; Shaheen, SE; Ilan, B; van de Lagemaat, J; Osterloh, FE

    2014-10-21

    Living organisms use fractal structures to optimize material and energy transport across regions of differing size scales. Here we test the effect of fractal silver electrodes on light distribution and charge collection in organic semiconducting polymer films made of P3HT and PCBM. The semiconducting polymers were deposited onto electrochemically grown fractal silver structures (5000 nm x 500 nm; fractal dimension of 1.71) with PEDOT:PSS as hole-selective interlayer. The fractal silver electrodes appear black due to increased horizontal light scattering, which is shown to improve light absorption in the polymer. According to surface photovoltage spectroscopy, fractal silver electrodes outperform the flat electrodes when the BHJ film thickness is large (>400 nm, 0.4 V photovoltage). Photocurrents of up to 200 microamperes cm(-2) are generated from the bulk heterojunction (BHJ) photoelectrodes under 435 nm LED (10-20 mW cm(-2)) illumination in acetonitrile solution containing 0.005 M ferrocenium hexafluorophosphate as the electron acceptor. The low IPCE values (0.3-0.7%) are due to slow electron transfer to ferrocenium ion and due to shunting along the large metal-polymer interface. Overall, this work provides an initial assessment of the potential of fractal electrodes for organic photovoltaic cells.

  20. In situ electron microscopy four-point electromechanical characterization of freestanding metallic and semiconducting nanowires.

    PubMed

    Bernal, Rodrigo A; Filleter, Tobin; Connell, Justin G; Sohn, Kwonnam; Huang, Jiaxing; Lauhon, Lincoln J; Espinosa, Horacio D

    2014-02-26

    Electromechanical coupling is a topic of current interest in nanostructures, such as metallic and semiconducting nanowires, for a variety of electronic and energy applications. As a result, the determination of structure-property relations that dictate the electromechanical coupling requires the development of experimental tools to perform accurate metrology. Here, a novel micro-electro-mechanical system (MEMS) that allows integrated four-point, uniaxial, electromechanical measurements of freestanding nanostructures in-situ electron microscopy, is reported. Coupled mechanical and electrical measurements are carried out for penta-twinned silver nanowires, their resistance is identified as a function of strain, and it is shown that resistance variations are the result of nanowire dimensional changes. Furthermore, in situ SEM piezoresistive measurements on n-type, [111]-oriented silicon nanowires up to unprecedented levels of ∼7% strain are demonstrated. The piezoresistance coefficients are found to be similar to bulk values. For both metallic and semiconducting nanowires, variations of the contact resistance as strain is applied are observed. These variations must be considered in the interpretation of future two-point electromechanical measurements. PMID:24115555

  1. Frequency-dependent learning achieved using semiconducting polymer/electrolyte composite cells

    NASA Astrophysics Data System (ADS)

    Dong, W. S.; Zeng, F.; Lu, S. H.; Liu, A.; Li, X. J.; Pan, F.

    2015-10-01

    Frequency-dependent learning has been achieved using semiconducting polymer/electrolyte composite cells. The cells composed of polymer/electrolyte double layers realized the conventional spike-rate-dependent plasticity (SRDP) learning model. These cells responded to depression upon low-frequency stimulation and to potentiation upon high-frequency stimulation and presented long-term memory. The transition threshold θm from depression to potentiation varied depending on the previous stimulations. A nanostructure resembling a bio-synapse in its transport passages was demonstrated and a random channel model was proposed to describe the ionic kinetics at the polymer/electrolyte interface during and after stimulations with various frequencies, accounting for the observed SRDP.Frequency-dependent learning has been achieved using semiconducting polymer/electrolyte composite cells. The cells composed of polymer/electrolyte double layers realized the conventional spike-rate-dependent plasticity (SRDP) learning model. These cells responded to depression upon low-frequency stimulation and to potentiation upon high-frequency stimulation and presented long-term memory. The transition threshold θm from depression to potentiation varied depending on the previous stimulations. A nanostructure resembling a bio-synapse in its transport passages was demonstrated and a random channel model was proposed to describe the ionic kinetics at the polymer/electrolyte interface during and after stimulations with various frequencies, accounting for the observed SRDP. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02891d

  2. Active Control of Protein and Ionic Transport through Semiconducting Conical Nanopores

    NASA Astrophysics Data System (ADS)

    James, Teena; Kalinin, Yevgeniy; Chan, Chih-Chieh; Randhawa, Jatinder; Gaevski, Mikhail; Gracias, David

    2013-03-01

    Nanopores with conical geometries have been found to rectify ionic current in electrolytes. While nanopores in semiconducting membranes offer the ability to modulate ionic transport, the fabrication of conical nanopores in silicon has proven challenging. Here, we report the discovery that Au nanoparticle-assisted plasma etching results in the formation of conical etch profiles in Si. We show that this process provides a versatile means to fabricate nanopores on Si substrates with variable pore-diameters and cone-angles. When in contact with aqueous electrolyte solution (pH>3), the nanopore was found to exhibit negative surface charge due to de-protonation of the Si-OH surface groups. The rectification ratio of ionic current through the pore was thus found to be variable by altering the pH, owing to the amphoteric nature of Si-OH surface groups (pKa 6.9) and was also dependent on the ionic strengths, agreeing with the theoretical predictions based on Poisson -Nernst -Planck equation. We demonstrate that these semiconducting conical nanopores can function as ionic switches with high on-off ratios, by varying Si surface charge through voltage gating. Further, we demonstrate voltage gated control over protein translocation through these pores.

  3. Nonlinear modelling of polymer electrolyte membrane fuel cell stack using nonlinear cancellation technique

    NASA Astrophysics Data System (ADS)

    Barus, R. P. P.; Tjokronegoro, H. A.; Leksono, E.; Ismunandar

    2014-09-01

    Fuel cells are promising new energy conversion devices that are friendly to the environment. A set of control systems are required in order to operate a fuel cell based power plant system optimally. For the purpose of control system design, an accurate fuel cell stack model in describing the dynamics of the real system is needed. Currently, linear model are widely used for fuel cell stack control purposes, but it has limitations in narrow operation range. While nonlinear models lead to nonlinear control implemnetation whos more complex and hard computing. In this research, nonlinear cancellation technique will be used to transform a nonlinear model into a linear form while maintaining the nonlinear characteristics. The transformation is done by replacing the input of the original model by a certain virtual input that has nonlinear relationship with the original input. Then the equality of the two models is tested by running a series of simulation. Input variation of H2, O2 and H2O as well as disturbance input I (current load) are studied by simulation. The error of comparison between the proposed model and the original nonlinear model are less than 1 %. Thus we can conclude that nonlinear cancellation technique can be used to represent fuel cell nonlinear model in a simple linear form while maintaining the nonlinear characteristics and therefore retain the wide operation range.

  4. Nonlinear modelling of polymer electrolyte membrane fuel cell stack using nonlinear cancellation technique

    SciTech Connect

    Barus, R. P. P.; Tjokronegoro, H. A.; Leksono, E.; Ismunandar

    2014-09-25

    Fuel cells are promising new energy conversion devices that are friendly to the environment. A set of control systems are required in order to operate a fuel cell based power plant system optimally. For the purpose of control system design, an accurate fuel cell stack model in describing the dynamics of the real system is needed. Currently, linear model are widely used for fuel cell stack control purposes, but it has limitations in narrow operation range. While nonlinear models lead to nonlinear control implemnetation whos more complex and hard computing. In this research, nonlinear cancellation technique will be used to transform a nonlinear model into a linear form while maintaining the nonlinear characteristics. The transformation is done by replacing the input of the original model by a certain virtual input that has nonlinear relationship with the original input. Then the equality of the two models is tested by running a series of simulation. Input variation of H2, O2 and H2O as well as disturbance input I (current load) are studied by simulation. The error of comparison between the proposed model and the original nonlinear model are less than 1 %. Thus we can conclude that nonlinear cancellation technique can be used to represent fuel cell nonlinear model in a simple linear form while maintaining the nonlinear characteristics and therefore retain the wide operation range.

  5. Theory and design of nonlinear metamaterials

    NASA Astrophysics Data System (ADS)

    Rose, Alec Daniel

    If electronics are ever to be completely replaced by optics, a significant possibility in the wake of the fiber revolution, it is likely that nonlinear materials will play a central and enabling role. Indeed, nonlinear optics is the study of the mechanisms through which light can change the nature and properties of matter and, as a corollary, how one beam or color of light can manipulate another or even itself within such a material. However, of the many barriers preventing such a lofty goal, the narrow and limited range of properties supported by nonlinear materials, and natural materials in general, stands at the forefront. Many industries have turned instead to artificial and composite materials, with homogenizable metamaterials representing a recent extension of such composites into the electromagnetic domain. In particular, the inclusion of nonlinear elements has caused metamaterials research to spill over into the field of nonlinear optics. Through careful design of their constituent elements, nonlinear metamaterials are capable of supporting an unprecedented range of interactions, promising nonlinear devices of novel design and scale. In this context, I cast the basic properties of nonlinear metamaterials in the conventional formalism of nonlinear optics. Using alternately transfer matrices and coupled mode theory, I develop two complementary methods for characterizing and designing metamaterials with arbitrary nonlinear properties. Subsequently, I apply these methods in numerical studies of several canonical metamaterials, demonstrating enhanced electric and magnetic nonlinearities, as well as predicting the existence of nonlinear magnetoelectric and off-diagonal nonlinear tensors. I then introduce simultaneous design of the linear and nonlinear properties in the context of phase matching, outlining five different metamaterial phase matching methods, with special emphasis on the phase matching of counter propagating waves in mirrorless parametric amplifiers

  6. Photovoltaic device

    DOEpatents

    Reese, Jason A.; Keenihan, James R.; Gaston, Ryan S.; Kauffmann, Keith L.; Langmaid, Joseph A.; Lopez, Leonardo C.; Maak, Kevin D.; Mills, Michael E.; Ramesh, Narayan; Teli, Samar R.

    2015-06-02

    The present invention is premised upon an improved photovoltaic device ("PV device"), more particularly to an improved photovoltaic device with a multilayered photovoltaic cell assembly and a body portion joined at an interface region and including an intermediate layer, at least one interconnecting structural member, relieving feature, unique component geometry, or any combination thereof.

  7. Photovoltaic device

    SciTech Connect

    Reese, Jason A.; Keenihan, James R.; Gaston, Ryan S.; Kauffmann, Keith L.; Langmaid, Joseph A.; Lopez, Leonardo C.; Maak, Kevin D.; Mills, Michael E.; Ramesh, Narayan; Teli, Samar R.

    2015-09-01

    The present invention is premised upon an improved photovoltaic device ("PV device"), more particularly to an improved photovoltaic device (10) with a multilayered photovoltaic cell assembly (100) and a body portion (200) joined at an interface region (410) and including an intermediate layer (500), at least one interconnecting structural member (1500), relieving feature (2500), unique component geometry, or any combination thereof.

  8. Materials growth and characterization of thermoelectric and resistive switching devices

    NASA Astrophysics Data System (ADS)

    Norris, Kate J.

    In the 74 years since diode rectifier based radar technology helped the allied forces win WWII, semiconductors have transformed the world we live in. From our smart phones to semiconductor-based energy conversion, semiconductors touch every aspect of our lives. With this thesis I hope to expand human knowledge of semiconductor thermoelectric devices and resistive switching devices through experimentation with materials growth and subsequent materials characterization. Metal organic chemical vapor deposition (MOCVD) was the primary method of materials growth utilized in these studies. Additionally, plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD),ion beam sputter deposition, reactive sputter deposition and electron-beam (e-beam) evaporation were also used in this research for device fabrication. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Electron energy loss spectroscopy (EELS) were the primary characterization methods utilized for this research. Additional device and materials characterization techniques employed include: current-voltage measurements, thermoelectric measurements, x-ray diffraction (XRD), reflection absorption infra-red spectroscopy (RAIRS), atomic force microscopy (AFM), photoluminescence (PL), and raman spectroscopy. As society has become more aware of its impact on the planet and its limited resources, there has been a push toward developing technologies to sustainably produce the energy we need. Thermoelectric devices convert heat directly into electricity. Thermoelectric devices have the potential to save huge amounts of energy that we currently waste as heat, if we can make them cost-effective. Semiconducting thin films and nanowires appear to be promising avenues of research to attain this goal. Specifically, in this work we will explore the use of ErSb thin films as well as Si and InP nanowire networks for thermoelectric applications. First we will discuss the growth of

  9. High performance thin film transistors based on regioregular poly(3-dodecylthiophene)-sorted large diameter semiconducting single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Qian, Long; Xu, Wenya; Nie, Shuhong; Gu, Weibing; Zhang, Jianhui; Zhao, Jianwen; Lin, Jian; Chen, Zheng; Cui, Zheng

    2013-05-01

    In this work, a simple and rapid method to selectively sort semiconducting-SWCNTs (sc-SWCNTs) with large diameters using regioregular poly(3-dodecylthiophene) (rr-P3DDT) is presented. The absorption spectra and Raman spectra demonstrated that metallic species of arc discharge SWCNTs were effectively removed after interaction with rr-P3DDT in toluene with the aid of sonication and centrifugation. The sorted sc-SWCNT inks have been directly used to fabricate thin film transistors (TFTs) by dip-coating, drop-casting and inkjet printing. TFTs with an effective mobility of ~34 cm2 V-1 s-1 and on-off ratios of ~107 have been achieved by dip coating and drop casting the ink on SiO2/Si substrates with pre-patterned interdigitated gold electrode arrays. The printed devices also showed excellent electrical properties with a mobility of up to 6.6 cm2 V-1 s-1 and on-off ratios of up to 105. Printed inverters based on the TFTs have been constructed on glass substrates, showing a maximum voltage gain of 112 at a Vdd of -5 V. This work paves the way for making printable logic circuits for real applications.In this work, a simple and rapid method to selectively sort semiconducting-SWCNTs (sc-SWCNTs) with large diameters using regioregular poly(3-dodecylthiophene) (rr-P3DDT) is presented. The absorption spectra and Raman spectra demonstrated that metallic species of arc discharge SWCNTs were effectively removed after interaction with rr-P3DDT in toluene with the aid of sonication and centrifugation. The sorted sc-SWCNT inks have been directly used to fabricate thin film transistors (TFTs) by dip-coating, drop-casting and inkjet printing. TFTs with an effective mobility of ~34 cm2 V-1 s-1 and on-off ratios of ~107 have been achieved by dip coating and drop casting the ink on SiO2/Si substrates with pre-patterned interdigitated gold electrode arrays. The printed devices also showed excellent electrical properties with a mobility of up to 6.6 cm2 V-1 s-1 and on-off ratios of up to 105

  10. Photoinduced Nonlinear Mixing of Terahertz Dipole Resonances in Graphene Metadevices.

    PubMed

    In, Chihun; Kim, Hyeon-Don; Min, Bumki; Choi, Hyunyong

    2016-02-17

    The first experimental demonstration of nonlinear terahertz difference-frequency generation in a hybrid graphene metadevice is reported. Decades of research have revealed that terahertz-wave generation is impossible in single-layer graphene. This limitation is overcome and nonlinear terahertz generation by ultra-short optical pulse injection is demonstrated. This device is an essential step toward atomically thin, nonlinear terahertz optoelectronic components. PMID:26639550

  11. Laser And Nonlinear Optical Materials For Laser Remote Sensing

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.

    2005-01-01

    NASA remote sensing missions involving laser systems and their economic impact are outlined. Potential remote sensing missions include: green house gasses, tropospheric winds, ozone, water vapor, and ice cap thickness. Systems to perform these measurements use lanthanide series lasers and nonlinear devices including second harmonic generators and parametric oscillators. Demands these missions place on the laser and nonlinear optical materials are discussed from a materials point of view. Methods of designing new laser and nonlinear optical materials to meet these demands are presented.

  12. The effect of system nonlinearities on system noise statistics

    NASA Technical Reports Server (NTRS)

    Robinson, L. H., Jr.

    1971-01-01

    The effects are studied of nonlinearities in a baseline communications system on the system noise amplitude statistics. So that a meaningful identification of system nonlinearities can be made, the baseline system is assumed to transmit a single biphase-modulated signal through a relay satellite to the receiving equipment. The significant nonlinearities thus identified include square-law or product devices (e.g., in the carrier reference recovery loops in the receivers), bandpass limiters, and traveling wave tube amplifiers.

  13. Materials For Improved Josephson-Junction Devices

    NASA Technical Reports Server (NTRS)

    Vasquez, Richard P.; Barner, Jeffrey B.

    1996-01-01

    Number of superconductive, normally conductive, and insulating materials proposed for use in fabricating improved superconductor/insulator/superconductor (SIS) and superconductor/normal conductor/superconductor (SNS) electronic devices capable of operation at frequencies up into terahertz range. Such devices particularly useful as electrically nonlinear circuit elements of mixers and local oscillators in heterodyne receivers.

  14. Nonlinear Acoustics in Fluids

    NASA Astrophysics Data System (ADS)

    Lauterborn, Werner; Kurz, Thomas; Akhatov, Iskander

    At high sound intensities or long propagation distances at in fluids sufficiently low damping acoustic phenomena become nonlinear. This chapter focuses on nonlinear acoustic wave properties in gases and liquids. The origin of nonlinearity, equations of state, simple nonlinear waves, nonlinear acoustic wave equations, shock-wave formation, and interaction of waves are presented and discussed. Tables are given for the nonlinearity parameter B/A for water and a range of organic liquids, liquid metals and gases. Acoustic cavitation with its nonlinear bubble oscillations, pattern formation and sonoluminescence (light from sound) are modern examples of nonlinear acoustics. The language of nonlinear dynamics needed for understanding chaotic dynamics and acoustic chaotic systems is introduced.

  15. Noise in Nonlinear Dynamical Systems

    NASA Astrophysics Data System (ADS)

    Moss, Frank; McClintock, P. V. E.

    2009-08-01

    List of contributors; Preface; Introduction to volume three; 1. The effects of coloured quadratic noise on a turbulent transition in liquid He II J. T. Tough; 2. Electrohydrodynamic instability of nematic liquid crystals: growth process and influence of noise S. Kai; 3. Suppression of electrohydrodynamic instabilities by external noise Helmut R. Brand; 4. Coloured noise in dye laser fluctuations R. Roy, A. W. Yu and S. Zhu; 5. Noisy dynamics in optically bistable systems E. Arimondo, D. Hennequin and P. Glorieux; 6. Use of an electronic model as a guideline in experiments on transient optical bistability W. Lange; 7. Computer experiments in nonlinear stochastic physics Riccardo Mannella; 8. Analogue simulations of stochastic processes by means of minimum component electronic devices Leone Fronzoni; 9. Analogue techniques for the study of problems in stochastic nonlinear dynamics P. V. E. McClintock and Frank Moss; Index.

  16. Separation of single-walled carbon nanotubes into metallic and semiconducting groups: a simple and large-scale method

    NASA Astrophysics Data System (ADS)

    Lu, Jing; Maeda, Y.

    2006-03-01

    Separation of a large number of single-walled carbon nanotubes (SWNTs) into groups each with specifically metallic and semiconducting properties is an extremely important task for technology application. Even though effective methods (1, 2) have been devised, they suffer from drawbacks such as either the yield is low (3) or expense is high (4). In this work, we study the problem from a theoretical approach, we notice that based on the first principles calculations the binding strengths of methylamine to the semiconducting [13, 0] SWNT are only 36˜61% of that to the metallic [7, 7] SWNT, which suggests that the amines is much more attractive toward the pure metallic than the semiconducting SWNTs. Therefore starting from as-prepared SWNTs and with the assistance of amines, we achieved SWNTs with enriched metallic properties over semiconducting in a convenient and large-scale manner. References: (1) D. Chattopadhyay, L. Galeska, F. Papadimitrakopoulos, Journal of the American Chemical Society 125, 3370 (MAR 19, 2003). (2) H. P. Li et al., Journal of the American Chemical Society 126, 1014 (FEB 4, 2004). (3) R. Krupke, F. Hennrich, H. von Lohneysen, M. Kappes, SCIENCE 301, 344 (JUL 18, 2003). (4) M. Zheng et al., Science 302, 1545 (NOV 28, 2003).

  17. Nonlinear Submodels Of Orthogonal Linear Models

    ERIC Educational Resources Information Center

    Bechtel, Gordon G.

    1973-01-01

    It is the purpose of this paper to suggest the orthogonal analysis of variance as a device for simplifying either the analytic or iterative problem of finding LS (least squares) estimates for the parameters of particular nonlinear models. (Author/RK)

  18. Method for forming low-resistance ohmic contacts on semiconducting oxides

    DOEpatents

    Narayan, J.

    1979-10-01

    The invention provides a new method for the formation of high-quality ohmic contacts on wide-band-gap semiconducting oxides. As exemplified by the formation of an ohmic contact on n-type BaTiO/sub 3/ containing a p-n junction, the invention entails depositing a film of a metallic electroding material on the BaTiO/sub 3/ surface and irradiating the film with a Q-switched laser pulse effecting complete melting of the film and localized melting of the surface layer of oxide immediately underlying the film. The resulting solidified metallic contact is ohmic, has unusually low contact resistance, and is thermally stable, even at elevated temmperatures. The contact does not require cleaning before attachment of any suitable electrical lead. This method is safe, rapid, reproducible, and relatively inexpensive.

  19. Tunable spin-polaron state in a singly clamped semiconducting carbon nanotube

    NASA Astrophysics Data System (ADS)

    Pistolesi, F.; Shekhter, R.

    2015-07-01

    We consider a semiconducting carbon nanotube (CNT) lying on a ferromagnetic insulating substrate with one end passing the substrate and suspended over a metallic gate. We assume that the polarized substrate induces an exchange interaction acting as a local magnetic field for the electrons in the nonsuspended CNT side. Generalizing the approach of I. Snyman and Yu.V. Nazarov [Phys. Rev. Lett. 108, 076805 (2012), 10.1103/PhysRevLett.108.076805], we show that one can generate electrostatically a tunable spin-polarized polaronic state localized at the bending end of the CNT. We argue that at low temperatures manipulation and detection of the localized quantum spin state are possible.

  20. A photodegradable hexaaza-pentacene molecule for selective dispersion of large-diameter semiconducting carbon nanotubes.

    PubMed

    Han, Jie; Ji, Qiyan; Li, Hongbo; Li, Gang; Qiu, Song; Li, Hai-Bei; Zhang, Qichun; Jin, Hehua; Li, Qingwen; Zhang, Jin

    2016-06-01

    Harvesting high-purity semiconducting single-walled carbon nanotubes (s-SWCNTs) with removable dispersants remains a challenge. In this work, we demonstrate that small heteroacene derivatives may serve as promising selective dispersants for sorting s-SWCNTs. A rich N "doped" and thiophene-substituted hexaazapentacene molecule, denoted as 4HP, was found to be more favorable for high-purity s-SWCNTs with large diameters. Importantly, 4HP is photodegradable under 365 nm or blue light, which enables a simple deposition approach for the formation of clean s-SWCNT networks. The as-fabricated thin film transistors show excellent performance with a charge-mobility of 30-80 cm(2) V(-1) s(-1) and an on-off ratio of 10(4)-10(6). PMID:27230421

  1. First-principles calculations of semiconducting TiMgN2

    NASA Astrophysics Data System (ADS)

    Irokawa, Yoshihiro; Usami, Mamoru

    2016-09-01

    We investigated semiconducting TiMgN2 by a density functional approach. As a result, we found that the L11 structure was more stable than the L10 and CH structures. The band gap of L11 TiMgN2 calculated using the generalized gradient approximation was 0.27 eV, indicating an indirect band gap. Here, we show that a N vacancy introduces a donor level, but Ti and Mg vacancies introduce an acceptor level, suggesting the possibility of obtaining either n- or p-type semiconductors by introducing a specific vacancy. Since L11 TiMgN2 is a layered structure, it could be epitaxially grown by layer-by-layer deposition.

  2. Laser method for forming low-resistance ohmic contacts on semiconducting oxides

    DOEpatents

    Narayan, Jagdish

    1981-01-01

    This invention is a new method for the formation of high-quality ohmic contacts on wide-band-gap semiconducting oxides. As exemplified by the formation of an ohmic contact on n-type BaTiO.sub.3 containing a p-n junction, the invention entails depositing a film of a metallic electroding material on the BaTiO.sub.3 surface and irradiating the film with a Q-switched laser pulse effecting complete melting of the film and localized melting of the surface layer of oxide immediately underlying the film. The resulting solidified metallic contact is ohmic, has unusually low contact resistance, and is thermally stable, even at elevated temperatures. The contact does not require cleaning before attachment of any suitable electrical lead. This method is safe, rapid, reproducible, and relatively inexpensive.

  3. Atomic-scale studies of nanometer-sized graphene on semiconducting surfaces.

    NASA Astrophysics Data System (ADS)

    Koepke, Justin; Ritter, Kyle; He, Kevin; Lyding, Joseph

    2008-03-01

    We have performed atomic level studies of graphene on semiconducting surfaces using ultrahigh vacuum scanning tunneling microscopy (UHV-STM) [1]. By mechanically exfoliating graphite and using an in-situ dry contact transfer technique [2], we observe predominantly single and double layers of atomically clean graphene with lateral dimensions of 2-20 nm. Room temperature scanning tunneling spectroscopy measurements of the 2-10 nm monolayer pieces display a size-dependent energy gap ranging from 0.1-1 eV, while monolayers with lateral dimensions of 20 nm exhibit a finite density of states at the Fermi level. [1] K.A. Ritter and J.W. Lyding, Nanotechnology, in press (http://arxiv.org/pdf/0711.0050). [2] P.M. Albrecht and J.W. Lyding, APL 83, 5029 (2003).

  4. Controlled defects in semiconducting carbon nanotubes promote efficient generation and luminescence of trions.

    PubMed

    Brozena, Alexandra H; Leeds, Jarrett D; Zhang, Yin; Fourkas, John T; Wang, YuHuang

    2014-05-27

    We demonstrate efficient creation of defect-bound trions through chemical doping of controlled sp(3) defect sites in semiconducting, single-walled carbon nanotubes. These tricarrier quasi-particles luminesce almost as brightly as their parent excitons, indicating a remarkably efficient conversion of excitons into trions. Substantial populations of trions can be generated at low excitation intensities, even months after a sample has been prepared. Photoluminescence spectroscopy reveals a trion binding energy as high as 262 meV, which is substantially larger than any previously reported values. This discovery may have important ramifications not only for studying the basic physics of trions but also for the application of these species in fields such as photonics, electronics, and bioimaging. PMID:24669843

  5. Strong carrier lifetime enhancement in GaAs nanowires coated with semiconducting polymer.

    PubMed

    Yong, Chaw Keong; Noori, Keian; Gao, Qiang; Joyce, Hannah J; Tan, H Hoe; Jagadish, Chennupati; Giustino, Feliciano; Johnston, Michael B; Herz, Laura M

    2012-12-12

    The ultrafast charge carrier dynamics in GaAs/conjugated polymer type II heterojunctions are investigated using time-resolved photoluminescence spectroscopy at 10 K. By probing the photoluminescence at the band edge of GaAs, we observe strong carrier lifetime enhancement for nanowires blended with semiconducting polymers. The enhancement is found to depend crucially on the ionization potential of the polymers with respect to the Fermi energy level at the surface of the GaAs nanowires. We attribute these effects to electron doping by the polymer which reduces the unsaturated surface-state density in GaAs. We find that when the surface of nanowires is terminated by native oxide, the electron injection across the interface is greatly reduced and such surface doping is absent. Our results suggest that surface engineering via π-conjugated polymers can substantially improve the carrier lifetime in nanowire hybrid heterojunctions with applications in photovoltaics and nanoscale photodetectors. PMID:23171081

  6. Investigation of compositional segregation during unidirectional solidification of solid solution semiconducting alloys

    NASA Technical Reports Server (NTRS)

    Wang, J. C.

    1982-01-01

    Compositional segregation of solid solution semiconducting alloys in the radial direction during unidirectional solidification was investigated by calculating the effect of a curved solid liquid interface on solute concentration at the interface on the solid. The formulation is similar to that given by Coriell, Boisvert, Rehm, and Sekerka except that a more realistic cylindrical coordinate system which is moving with the interface is used. Analytical results were obtained for very small and very large values of beta with beta = VR/D, where V is the velocity of solidification, R the radius of the specimen, and D the diffusivity of solute in the liquid. For both very small and very large beta, the solute concentration at the interface in the solid C(si) approaches C(o) (original solute concentration) i.e., the deviation is minimal. The maximum deviation of C(si) from C(o) occurs for some intermediate value of beta.

  7. Transparent ferrimagnetic semiconducting CuCr2O4 thin films by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Tripathi, T. S.; Yadav, C. S.; Karppinen, M.

    2016-04-01

    We report the magnetic and optical properties of CuCr2O4 thin films fabricated by atomic layer deposition (ALD) from Cu(thd)2, Cr(acac)3, and ozone; we deposit 200 nm thick films and anneal them at 700 °C in oxygen atmosphere to crystallize the spinel phase. A ferrimagnetic transition at 140 K and a direct bandgap of 1.36 eV are determined for the films from magnetic and UV-vis spectrophotometric measurements. Electrical transport measurements confirm the p-type semiconducting behavior of the films. As the ALD technique allows the deposition of conformal pin-hole-free coatings on complex 3D surfaces, our CuCr2O4 films are interesting material candidates for various frontier applications.

  8. Semiconducting properties of amorphous GaZnSnO thin film based on combinatorial electronic structures

    SciTech Connect

    Kim, B. K.; Park, J. S.; Kim, D. H.; Chung, K. B.

    2014-05-05

    Semiconducting properties and electronic structures of amorphous GaZnSnO (GZTO) thin films are investigated with respect to metal cationic composition. An increase of the cationic Sn ratio resulted in an increase of the carrier concentration and a decrease of the mobility of the films. Combinatorial analysis revealed that the electrical characteristics of GZTO films are strongly correlated to changes in electronic structure. The increase in carrier concentration is related to the generation of vacancies by the changes of oxygen coordination around the cationic metal and the shallow band edge state below the conduction band. On the other hand, the decrease of mobility can be explained by the deep band edge state, and the difference between the experimental conduction band and simulated conduction band by the combinatorial electronic structure based on the chemical composition.

  9. Near valence-band electronic properties of semiconducting β -Ga2O3 (100) single crystals

    NASA Astrophysics Data System (ADS)

    Navarro-Quezada, A.; Alamé, S.; Esser, N.; Furthmüller, J.; Bechstedt, F.; Galazka, Z.; Skuridina, D.; Vogt, P.

    2015-11-01

    β -Ga2O3 is a transparent wide-band-gap semiconductor that has attracted considerable interest in recent years due to its suitable electrical conductivity and transparency in the ultraviolet spectral region. In this work we investigate the electronic properties of the near valence-band-edge region for semiconducting β -Ga2O3 (100) bulk single crystals using core-level photoelectron spectroscopy and ab initio theory within the framework of density functional theory and the GW approach. We find good agreement between the experimental results and the theoretical calculations. This is explained by the hybridization of the Ga 3 d and O 2 s states, similar as for In2O3 .

  10. Integration of Semiconducting Sulfides for Full-Spectrum Solar Energy Absorption and Efficient Charge Separation.

    PubMed

    Zhuang, Tao-Tao; Liu, Yan; Li, Yi; Zhao, Yuan; Wu, Liang; Jiang, Jun; Yu, Shu-Hong

    2016-05-23

    The full harvest of solar energy by semiconductors requires a material that simultaneously absorbs across the whole solar spectrum and collects photogenerated electrons and holes separately. The stepwise integration of three semiconducting sulfides, namely ZnS, CdS, and Cu2-x S, into a single nanocrystal, led to a unique ternary multi-node sheath ZnS-CdS-Cu2-x S heteronanorod for full-spectrum solar energy absorption. Localized surface plasmon resonance (LSPR) in the nonstoichiometric copper sulfide nanostructures enables effective NIR absorption. More significantly, the construction of pn heterojunctions between Cu2-x S and CdS leads to staggered gaps, as confirmed by first-principles simulations. This band alignment causes effective electron-hole separation in the ternary system and hence enables efficient solar energy conversion. PMID:27062543

  11. High-performance radio frequency transistors based on diameter-separated semiconducting carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Cao, Yu; Che, Yuchi; Seo, Jung-Woo T.; Gui, Hui; Hersam, Mark C.; Zhou, Chongwu

    2016-06-01

    In this paper, we report the high-performance radio-frequency transistors based on the single-walled semiconducting carbon nanotubes with a refined average diameter of ˜1.6 nm. These diameter-separated carbon nanotube transistors show excellent transconductance of 55 μS/μm and desirable drain current saturation with an output resistance of ˜100 KΩ μm. An exceptional radio-frequency performance is also achieved with current gain and power gain cut-off frequencies of 23 GHz and 20 GHz (extrinsic) and 65 GHz and 35 GHz (intrinsic), respectively. These radio-frequency metrics are among the highest reported for the carbon nanotube thin-film transistors. This study provides demonstration of radio frequency transistors based on carbon nanotubes with tailored diameter distributions, which will guide the future application of carbon nanotubes in radio-frequency electronics.

  12. Recent Progress in Obtaining Semiconducting Single-Walled Carbon Nanotubes for Transistor Applications.

    PubMed

    Islam, Ahmad E; Rogers, John A; Alam, Muhammad A

    2015-12-22

    High purity semiconducting single-walled carbon nanotubes (s-SWCNTs) with a narrow diameter distribution are required for high-performance transistors. Achieving this goal is extremely challenging because the as-grown material contains mixtures of s-SWCNTs and metallic- (m-) SWCNTs with wide diameter distributions, typically inadequate for integrated circuits. Since 2000, numerous ex situ methods have been proposed to improve the purity of the s-SWCNTs. The majority of these techniques fail to maintain the quality and integrity of the s-SWCNTs with a few notable exceptions. Here, the progress in realizing high purity s-SWCNTs in as-grown and post-processed materials is highlighted. A comparison of transistor parameters (such as on/off ratio and field-effect mobility) obtained from test structures establishes the effectiveness of various methods and suggests opportunities for future improvements. PMID:26540144

  13. La 1-x Ca x MnO 3 semiconducting nanostructures: morphology and thermoelectric properties.

    PubMed

    Culebras, Mario; Torán, Raquel; Gómez, Clara M; Cantarero, Andrés

    2014-01-01

    Semiconducting metallic oxides, especially perosvkite materials, are great candidates for thermoelectric applications due to several advantages over traditionally metallic alloys such as low production costs and high chemical stability at high temperatures. Nanostructuration can be the key to develop highly efficient thermoelectric materials. In this work, La 1-x Ca x MnO 3 perosvkite nanostructures with Ca as a dopant have been synthesized by the hydrothermal method to be used in thermoelectric applications at room temperature. Several heat treatments have been made in all samples, leading to a change in their morphology and thermoelectric properties. The best thermoelectric efficiency has been obtained for a Ca content of x=0.5. The electrical conductivity and Seebeck coefficient are strongly related to the calcium content. PMID:25206315

  14. Host guest coupling in semiconducting Ba8Zn8Ge38

    NASA Astrophysics Data System (ADS)

    Christensen, M.; Iversen, B. B.

    2008-03-01

    Two samples of the type I clathrate Ba8Zn8Ge38 have been prepared by a self-flux method with different cooling rates. Transport properties have been measured for a large single crystal of Ba8Zn8Ge38 from the slow cooled batch, and they reveal the sample to be semiconducting. A high Seebeck coefficient of -175 µV K-1 was observed at 400 K. High resolution single crystal neutron diffraction data measured for both slow cooled and fast cooled samples reveal significant differences in the guest atom nuclear density, which can be related to the occupancies of Zn in the host structure framework. Analysis of the atomic displacement parameters shows that the Einstein temperatures of the barium guest atoms are of comparable size at 62 and 67 K for the slow and fast cooled samples, respectively. The Debye temperature for the host framework was in both cases found to be ~280 K.

  15. Domain wall conductivity in semiconducting hexagonal ferroelectric TbMnO3 thin films.

    PubMed

    Kim, D J; Connell, J G; Seo, S S A; Gruverman, A

    2016-04-15

    Although enhanced conductivity of ferroelectric domain boundaries has been found in BiFeO3 and Pb(Zr,Ti)O3 films as well as hexagonal rare-earth manganite single crystals, the mechanism of the domain wall conductivity is still under debate. Using conductive atomic force microscopy, we observe enhanced conductance at the electrically-neutral domain walls in semiconducting hexagonal ferroelectric TbMnO3 thin films where the structure and polarization direction are strongly constrained along the c-axis. This result indicates that domain wall conductivity in ferroelectric rare-earth manganites is not limited to charged domain walls. We show that the observed conductivity in the TbMnO3 films is governed by a single conduction mechanism, namely, the back-to-back Schottky diodes tuned by the segregation of defects. PMID:26933770

  16. Energy Band Gap Study of Semiconducting Single Walled Carbon Nanotube Bundle

    NASA Technical Reports Server (NTRS)

    Elkadi, Asmaa; Decrossas, Emmanuel; El-Ghazaly, Samir

    2013-01-01

    The electronic properties of multiple semiconducting single walled carbon nanotubes (s-SWCNTs) considering various distribution inside a bundle are studied. The model derived from the proposed analytical potential function of electron density for na individual s-SWCNT is general and can be easily applied to multiple nanotubes. This work demonstrates that regardless the number of carbon nanotubes, the strong coupling occurring between the closet neighbors reduces the energy band gap of the bundle by 10%. As expected, the coupling is strongly dependent on the distance separating the s-SWCNTs. In addition, based on the developed model, it is proposed to enhance this coupling effect by applying an electric field across the bundle to significantly reduce the energy band gap of the bundle by 20%.

  17. Energy Band Gap Study of Semiconducting Single Walled Carbon Nanotube Bundle

    NASA Technical Reports Server (NTRS)

    Elkadi, Asmaa; Decrossas, Emmanuel; El-Ghazaly, Samir

    2013-01-01

    The electronic properties of multiple semiconducting single walled carbon nanotubes (s-SWCNTs) considering various distribution inside a bundle are studied. The model derived from the proposed analytical potential function of the electron density for an individual s-SWCNT is general and can be easily applied to multiple nanotubes. This work demonstrates that regardless the number of carbon nanotubes, the strong coupling occurring between the closest neighbours reduces the energy band gap of the bundle by 10%. As expected, the coupling is strongly dependent on the distance separating the s-SWCNTs. In addition, based on the developed model, it is proposed to enhance this coupling effect by applying an electric field across the bundle to significantly reduce the energy band gap of the bundle by 20%.

  18. Domain wall conductivity in semiconducting hexagonal ferroelectric TbMnO3 thin films

    NASA Astrophysics Data System (ADS)

    Kim, D. J.; Connell, J. G.; Seo, S. S. A.; Gruverman, A.

    2016-04-01

    Although enhanced conductivity of ferroelectric domain boundaries has been found in BiFeO3 and Pb(Zr,Ti)O3 films as well as hexagonal rare-earth manganite single crystals, the mechanism of the domain wall conductivity is still under debate. Using conductive atomic force microscopy, we observe enhanced conductance at the electrically-neutral domain walls in semiconducting hexagonal ferroelectric TbMnO3 thin films where the structure and polarization direction are strongly constrained along the c-axis. This result indicates that domain wall conductivity in ferroelectric rare-earth manganites is not limited to charged domain walls. We show that the observed conductivity in the TbMnO3 films is governed by a single conduction mechanism, namely, the back-to-back Schottky diodes tuned by the segregation of defects.

  19. Itinerant magnetism in doped semiconducting β-FeSi2 and CrSi2

    PubMed Central

    Singh, David J.; Parker, David

    2013-01-01

    Novel or unusual magnetism is a subject of considerable interest, particularly in metals and degenerate semiconductors. In such materials the interplay of magnetism, transport and other Fermi liquid properties can lead to fascinating physical behavior. One example is in magnetic semiconductors, where spin polarized currents may be controlled and used. We report density functional calculations predicting magnetism in doped semiconducting β-FeSi2 and CrSi2 at relatively low doping levels particularly for n-type. In this case, there is a rapid cross-over to a half-metallic state as a function of doping level. The results are discussed in relation to the electronic structure and other properties of these compounds. PMID:24343332

  20. Evaluation Methods of Contamination Flashover Voltage Performance of Cylindrical Type Semi-conducting Glaze Porcelain Insulators

    NASA Astrophysics Data System (ADS)

    Yamada, Kazuma; Hayashi, Akio; Saka, Chiharu; Sakanishi, Kenji; Matsuoka, Ryosuke; Ito, Susumu; Fujii, Osamu

    Higher contamination flashover voltage of a semi-conducting glaze (SG) insulator owes primarily to the drying effect by leakage current flowing in the glaze. Significant reduction in contamination flashover voltage was confirmed on a cylindrical SG insulator when fog density was increased from 0.5g/m3 to 13g/m3 in clean fog test. The effect of de-energized duration between trip-out and re-energization on the contamination flashover voltage of a cylindrical SG insulator under cold-wet switch-on conditions was investigated. As the de-energized duration becomes shorter, the flashover voltage of a cylindrical SG insulator becomes higher. Higher contamination design voltages may be adopted even under cold-wet switch-on conditions.

  1. Semiconducting Polymer Nanoparticles as Photoacoustic Molecular Imaging Probes in Living Mice

    PubMed Central

    Pu, Kanyi; Shuhendler, Adam J.; Jokerst, Jesse V.; Mei, Jianguo; Gambhir, Sanjiv S.; Bao, Zhenan; Rao, Jianghong

    2014-01-01

    Photoacoustic (PA) imaging holds great promise for the visualization of physiology and pathology at the molecular level with deep tissue penetration and fine spatial resolution. To fully utilize this potential, PA molecular imaging probes have to be developed. Herein we introduce near infrared (NIR) light absorbing semiconducting polymer nanoparticles (SPNs) as a new class of contrast agents for PA molecular imaging. SPNs can produce stronger signal than commonly used single-wall carbon nanotubes and gold nanorods on a per mass basis, permitting whole-body lymph node PA mapping in living mice at a low systematic injection mass. Furthermore, SPNs possess high structural flexibility, narrow PA spectral profiles, and strong resistance to photodegradation and oxidation, which enables development of the first NIR ratiometric PA probe for in vivo real-time imaging of reactive oxygen species—vital chemical mediators of many diseases. These results demonstrate SPNs an ideal nanoplatform for developing PA molecular probes. PMID:24463363

  2. Selective Growth of Metallic and Semiconducting Single Walled Carbon Nanotubes on Textured Silicon.

    PubMed

    Jang, Mira; Lee, Jongtaek; Park, Teahee; Lee, Junyoung; Yang, Jonghee; Yi, Whikun

    2016-03-01

    We fabricated the etched Si substrate having the pyramidal pattern size from 0.5 to 4.2 μm by changing the texturing process parameters, i.e., KOH concentration, etching time, and temperature. Single walled carbon nanotubes (SWNTs) were then synthesized on the etched Si substrates with different pyramidal pattern by chemical vapor deposition. We investigated the optical and electronic properties of SWNT film grown on the etched Si substrates of different morphology by using scanning electron microscopy, Raman spectroscopy and conducting probe atomic force microscopy. We confirmed that the morphology of substrate strongly affected the selective growth of the SWNT film. Semiconducting SWNTs were formed on larger pyramidal sized Si wafer with higher ratio compared with SWNTs on smaller pyramidal sized Si. PMID:27455748

  3. The biostimulation of anaerobic digestion with (semi)conductive ferric oxides: their potential for enhanced biomethanation.

    PubMed

    Baek, Gahyun; Kim, Jaai; Cho, Kyungjin; Bae, Hyokwan; Lee, Changsoo

    2015-12-01

    The effect of biostimulation with ferric oxides, semiconductive ferric oxyhydroxide, and conductive magnetite on the anaerobic digestion of dairy wastewater was examined in a batch mode. The reactors supplemented with ferric oxyhydroxide (R2) and magnetite (R3) showed significantly enhanced biomethanation performance compared with the control (R1). The removal of chemical oxygen demand (COD) after 30 days was 31.9, 59.3, and 82.5% in R1, R2, and R3, respectively. The consumed COD was almost fully recovered as biogas in R2 and R3, while only 79% was recovered in R1. The total energy production as biogas was accordingly 32.2, 71.0, and 97.7 kJ in R1, R2, and R3, respectively. The reactors also differed in the acid formation profile with more propionate and butyrate found in R1 and more acetate found in R3. The enhanced biomethanation seems to be associated with variations in the bacterial community structure supposedly induced by the ferric oxides added. In contrast, no evident variation was observed in the archaeal community structure among the reactors. The potential electric syntrophy formed between Methanosaeta concilii-like methanogens and electroactive iron-reducing bacteria, particularly Trichococcus, was likely responsible for the enhanced performance. The stimulated growth of fermentative iron reducers may also have contributed by altering the metabolic characteristics of the bacterial communities to produce more favorable acidogenic products for methanogenesis. The overall results suggest the potential of biostimulation with (semi)conductive ferric oxides to enhance the rate and efficiency of the biomethanation of organic wastes. This seems to be potentially attractive, as increasing attention is being paid to the energy self-sufficiency of waste/wastewater treatment processes today. PMID:26272096

  4. General strategy for self-assembly of highly oriented nanocrystalline semiconducting polymers with high mobility.

    PubMed

    Luo, Chan; Kyaw, Aung Ko Ko; Perez, Louis A; Patel, Shrayesh; Wang, Ming; Grimm, Bruno; Bazan, Guillermo C; Kramer, Edward J; Heeger, Alan J

    2014-05-14

    Solution processable semiconducting polymers with excellent film forming capacity and mechanical flexibility are considered among the most progressive alternatives to conventional inorganic semiconductors. However, the random packing of polymer chains and the disorder of the polymer matrix typically result in low charge transport mobilities (10(-5)-10(-2) cm(2) V(-1) s(-1)). These low mobilities compromise their performance and development. Here, we present a strategy, by utilizing capillary action, to mediate polymer chain self-assembly and unidirectional alignment on nanogrooved substrates. We designed a sandwich tunnel system separated by functionalized glass spacers to induce capillary action for controlling the polymer nanostructure, crystallinity, and charge transport. Using capillary action, we demonstrate saturation mobilities with average values of 21.3 and 18.5 cm(2) V(-1 )s(-1) on two different semiconducting polymers at a transistor channel length of 80 μm. These values are limited by the source-drain contact resistance, Rc. Using a longer channel length of 140 μm where the contact resistance is less important, we measured μh = 36.3 cm(2) v(-1) s(-1). Extrapolating to infinite channel length where Rc is unimportant, the intrinsic mobility for poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)-alt-[1,2,5]thiadiazolo[3,4-c]pyridine] (Mn = 140 kDa) at this degree of chain alignment and structural order is μh ≈ 47 cm(2 )v(-1) s(-1). Our results create a promising pathway toward high performance, solution processable, and low-cost organic electronics. PMID:24712578

  5. Comparative study of the semiconducting properties of benzothiadiazole and benzobis(thiadiazole) derivatives using computational techniques.

    PubMed

    Thomas, Anup; Bhanuprakash, Kotamarthi

    2012-02-01

    Recent literature reports indicate that derivatives of benzothiadiazole (BT) and benzobis(thiadiazole) (BBT), which differs from BT by an extra thiadiazole ring, exhibit good semiconducting properties, such as high electron mobility and low-lying lowest unoccupied molecular-orbital (LUMO) levels. In this study herein, computational techniques like density functional theory (DFT), spin-flip DFT and valence-bond methods are used to analyze the semiconducting properties of these molecules. Calculations at the B3LYP/cc-pVTZ level reveal that all the BBT molecules, including the bare BBT ring, have lower lying LUMO energies (3.70-4.11 eV) compared to the BT derivatives (2.56-3.41 eV) with similar substitution. The reorganization energies (λ(+)/λ(-)) obtained at this level of theory of the BT derivatives are around (225-333)/(246-315) meV, while BBT derivatives have much smaller reorganization energies and these are in the range of (129-259)/(150-230) meV. We observe that the different behavior of BBT is due to the inherited biradicaloid character from the parent molecule tetramethylenebenzene (TMB), a disjoint non-Kekule biradical having non-bonding molecular orbitals (NBMOs) as the highest occupied molecular orbital (HOMO) and LUMO. Additionally, the perturbation of the orbitals of the biradical TMB to obtain BBT is the major cause for the BBT derivatives to have a larger electron affinity (EA) and a smaller HOMO-LUMO gap (HLG) compared to BT derivatives. PMID:22238180

  6. Scalable and selective dispersion of semiconducting arc-discharged carbon nanotubes by dithiafulvalene/thiophene copolymers for thin film transistors.

    PubMed

    Wang, Huiliang; Mei, Jianguo; Liu, Peng; Schmidt, Kristin; Jiménez-Osés, Gonzalo; Osuna, Sílvia; Fang, Lei; Tassone, Christopher J; Zoombelt, Arjan Pieter; Sokolov, Anatoliy N; Houk, Kendall N; Toney, Michael F; Bao, Zhenan

    2013-03-26

    We report a simple and scalable method to enrich large quantities of semiconducting arc-discharged single-walled carbon nanotubes (SWNTs) with diameters of 1.1-1.8 nm using dithiafulvalene/thiophene copolymers. Stable solutions of highly individualized and highly enriched semiconducting SWNTs were obtained after a simple sonication and centrifuge process. Molecular dynamics (MD) simulations of polymer backbone interactions with and without side chains indicated that the presence of long alkyl side chains gave rise to the selectivity toward semiconducting tubes, indicating the importance of the roles of the side chains to both solubilize and confer selectivity to the polymers. We found that, by increasing the ratio of thiophene to dithiafulvalene units in the polymer backbone (from pDTFF-1T to pDTFF-3T), we can slightly improve the selectivity toward semiconducting SWNTs. This is likely due to the more flexible backbone of pDTFF-3T that allows the favorable wrapping of SWNTs with certain chirality as characterized by small-angle X-ray scattering. However, the dispersion yield was reduced from pDTFF-1T to pDTFF-3T. MD simulations showed that the reduction is due to the smaller polymer/SWNT contact area, which reduces the dispersion ability of pDTFF-3T. These experimental and modeling results provide a better understanding for future rational design of polymers for sorting SWNTs. Finally, high on/off ratio solution-processed thin film transistors were fabricated from the sorted SWNTs to confirm the selective dispersion of semiconducting arc-discharge SWNTs. PMID:23402644

  7. Nonlinear optical propagation in a tandem structure comprising nonlinear absorption and scattering materials

    SciTech Connect

    Wang, Kangpeng; Ju, Yongfeng; He, Jin; Zhang, Long E-mail: lzhang@siom.ac.cn; Wang, Jun E-mail: lzhang@siom.ac.cn; Chen, Yu; Blau, Werner J.

    2014-01-13

    Laser propagation in a tandem structure comprising carbon nanotubes and phthalocyanines is studied by Z-scan method. Due to the different mechanisms of the two materials, the laser beam can be attenuated with different absorptivities, by changing the sequence of light passing through each material. Numerical simulations considering the effect of path length and the change of nonlinear coefficient within each material are conducted for understanding the distribution of laser intensity in the tandem system and hence, fitting of the asymmetric Z-scan curves. The results are helpful for the design of nonlinear optical devices comprising multiple nonlinear materials and mechanisms.

  8. Development of Inorganic Precursors for Manufacturing of Photovoltaic Devices: Cooperative Research and Development Final Report, CRADA Number CRD-08-308

    SciTech Connect

    van Hest, M.; Ginley, D.

    2013-06-01

    Both NREL and Rohm and Haas Electronic Materials are interested in the development of solution phase metal and semiconductive precursors for the manufacturing of photovoltaic devices. In particular, we intend to develop material sets for atmospheric deposition processes. The cooperation between these two parties will enable high value materials and processing solutions for the manufacturing of low cost, roll-to-roll photovoltaics.

  9. Deflectometry using portable devices

    NASA Astrophysics Data System (ADS)

    Butel, Guillaume P.; Smith, Greg A.; Burge, James H.

    2015-02-01

    Deflectometry is a powerful metrology technique that uses off-the-shelf equipment to achieve nanometer-level accuracy surface measurements. However, there is no portable device to quickly measure eyeglasses, lenses, or mirrors. We present an entirely portable new deflectometry technique that runs on any Android™ smartphone with a front-facing camera. Our technique overcomes some specific issues of portable devices like screen nonlinearity and automatic gain control. We demonstrate our application by measuring an amateur telescope mirror and simulating a measurement of the faulty Hubble Space Telescope primary mirror. Our technique can, in less than 1 min, measure surface errors with accuracy up to 50 nm RMS, simply using a smartphone.

  10. Microfluidic Device

    NASA Technical Reports Server (NTRS)

    Tai, Yu-Chong (Inventor); Zheng, Siyang (Inventor); Lin, Jeffrey Chun-Hui (Inventor); Kasdan, Harvey (Inventor)

    2015-01-01

    Described herein are particular embodiments relating to a microfluidic device that may be utilized for cell sensing, counting, and/or sorting. Particular aspects relate to a microfabricated device that is capable of differentiating single cell types from dense cell populations. One particular embodiment relates a device and methods of using the same for sensing, counting, and/or sorting leukocytes from whole, undiluted blood samples.

  11. Microfluidic Device

    NASA Technical Reports Server (NTRS)

    Tai, Yu-Chong (Inventor); Zheng, Siyang (Inventor); Lin, Jeffrey Chun-Hui (Inventor); Kasdan, Harvey L. (Inventor)

    2016-01-01

    Described herein are particular embodiments relating to a microfluidic device that may be utilized for cell sensing, counting, and/or sorting. Particular aspects relate to a microfabricated device that is capable of differentiating single cell types from dense cell populations. One particular embodiment relates a device and methods of using the same for sensing, counting, and/or sorting leukocytes from whole, undiluted blood samples.

  12. Sealing device

    SciTech Connect

    Garcia-Crespo, Andres Jose

    2013-12-10

    A sealing device for sealing a gap between a dovetail of a bucket assembly and a rotor wheel is disclosed. The sealing device includes a cover plate configured to cover the gap and a retention member protruding from the cover plate and configured to engage the dovetail. The sealing device provides a seal against the gap when the bucket assemply is subjected to a centrifugal force.

  13. Blending of n-type Semiconducting Polymer and PC61BM for an Efficient Electron-Selective Material to Boost the Performance of the Planar Perovskite Solar Cell.

    PubMed

    Seo, You-Hyun; Yeo, Jun-Seok; Myoung, NoSoung; Yim, Sang-Youp; Kang, Minji; Kim, Dong-Yu; Na, Seok-In

    2016-05-25

    The highly efficient CH3NH3PbI3 perovskite solar cell (PeSC) is simply achieved by employing a blended electron-transport layer (ETL) consisting of PC61BM and P(NDI2OD-T2). The high molecular weight of P(NDI2OD-T2) allows for a thinned ETL with a uniform morphology that optimizes the PC61BM ETL more effectively. As a result of this enhancement, the power conversion efficiency of a PC61BM:P(NDI2OD-T2)-based PeSC is 25% greater than that of the conventional PC61BM based-PeSC; additionally, the incorporation of P(NDI2OD-T2) into PC61BM attenuates the dependence of the PeSC on the ETL-processing conditions regarding its performance. It is revealed that, in addition to the desirable n-type semiconducting characteristics of PC61BM:P(NDI2OD-T2)-including a higher electron-mobility and a more-effective electron selectivity of a blended ETL for an efficient electron extraction-the superior performance of a PC61BM:P(NDI2OD-T2) device is the result of a thinned and uniformly covered ETL on the perovskite layer. PMID:27160866

  14. Growth of close-packed semiconducting single-walled carbon nanotube arrays using oxygen-deficient TiO2 nanoparticles as catalysts.

    PubMed

    Kang, Lixing; Hu, Yue; Liu, Lili; Wu, Juanxia; Zhang, Shuchen; Zhao, Qiuchen; Ding, Feng; Li, Qingwen; Zhang, Jin

    2015-01-14

    For the application of single-walled carbon nanotubes (SWNTs) in nanoelectronic devices, techniques to obtain horizontally aligned semiconducting SWNTs (s-SWNTs) with higher densities are still in their infancy. We reported herein a rational approach for the preferential growth of densely packed and well-aligned s-SWNTs arrays using oxygen-deficient TiO2 nanoparticles as catalysts. Using this approach, a suitable concentration of oxygen vacancies in TiO2 nanoparticles could form by optimizing the flow rate of hydrogen and carbon sources during the process of SWNT growth, and then horizontally aligned SWNTs with the density of ∼ 10 tubes/μm and the s-SWNT percentage above 95% were successfully obtained on ST-cut quartz substrates. Theoretical calculations indicated that TiO2 nanoparticles with a certain concentration of oxygen vacancies have a lower formation energy between s-SWNT than metallic SWNT (m-SWNT), thus realizing the preferential growth of s-SWNT arrays. Furthermore, this method can also be extended to other semiconductor oxide nanoparticles (i.e., ZnO, ZrO2 and Cr2O3) for the selective growth of s-SWNTs, showing clear potential to the future applications in nanoelectronics. PMID:25539021

  15. Near-infrared photoconductive and photovoltaic devices using single-wall carbon nanotubes in conductive polymer films

    NASA Astrophysics Data System (ADS)

    Kazaoui, S.; Minami, N.; Nalini, B.; Kim, Y.; Hara, K.

    2005-10-01

    We have fabricated prototypical Al/single-wall carbon nanotube (SWNT)-polymer/indium tin oxide thin-film devices that exhibit promising photoconductive and photovoltaic responses in a broad spectral range, typically from 300 to 1600 nm. This achievement was made possible by finely dispersed SWNT powders in polymer matrices such as poly-phenylene-vinylene and poly-thiophene. These devices utilize (i) the intrinsic near-infrared light harvesting properties of semiconducting SWNTs, (ii) the electronic transport properties of both semiconducting and metallic SWNTs in combination with those of the polymer matrices, and (iii) probably charge/energy transfer processes between SWNTs and the polymers. By selecting different sources of SWNTs and polymers, we have shown that the optoelectronic properties of these devices are potentially tunable. To support our investigation, several techniques including spectrally resolved photoconductivity, optical absorption, and photoluminescence spectroscopy were utilized.

  16. A mechanical memory with a dc modulation of nonlinear resonance

    NASA Astrophysics Data System (ADS)

    Noh, Hyunho; Shim, Seung-Bo; Jung, Minkyung; Khim, Zheong G.; Kim, Jinhee

    2010-07-01

    We present a mechanical memory device based on dynamic motion of a nanoelectromechanical (NEM) resonator. The NEM resonator exhibits clear nonlinear resonance characteristics which can be controlled by the dc bias voltage. For memory operations, the NEM resonator is driven to the nonlinear resonance region, and binary values are assigned to the two allowed states on the bifurcation branch. The transition between memory states is achieved by modulating the nonlinear resonance characteristics with dc bias voltage. Our device works at room temperature and modest vacuum conditions with a maximum operation frequency of about 5 kHz.

  17. Spin glass in semiconducting KFe1.05Ag0.88Te2 single crystals

    SciTech Connect

    Ryu, H.; Lei, H.; Klobes, B.; Warren, J. B.; Hermann, R. P.; Petrovic, C.

    2015-05-26

    We report discovery of KFe1.05Ag0.88Te2 single crystals with semiconducting spin glass ground state. Composition and structure analysis suggest nearly stoichiometric I4/mmm space group but allow for the existence of vacancies, absent in long range semiconducting antiferromagnet KFe1.05Ag0.88Te2. The subtle change in stoichometry in Fe/Ag sublattice changes magnetic ground state but not conductivity, giving further insight into the semiconducting gap mechanism.

  18. Electrochromic devices

    DOEpatents

    Allemand, Pierre M.; Grimes, Randall F.; Ingle, Andrew R.; Cronin, John P.; Kennedy, Steve R.; Agrawal, Anoop; Boulton, Jonathan M.

    2001-01-01

    An electrochromic device is disclosed having a selective ion transport layer which separates an electrochemically active material from an electrolyte containing a redox active material. The devices are particularly useful as large area architectural and automotive glazings due to there reduced back reaction.

  19. BRAKE DEVICE

    DOEpatents

    O'Donnell, T.J.

    1959-03-10

    A brake device is described for utilization in connection with a control rod. The device comprises a pair of parallelogram link mechanisms, a control rod moveable rectilinearly therebetween in opposite directions, and shoes resiliently supported by the mechanism for frictional engagement with the control rod.

  20. Enrichment of large-diameter semiconducting SWCNTs by polyfluorene extraction for high network density thin film transistors

    NASA Astrophysics Data System (ADS)

    Ding, Jianfu; Li, Zhao; Lefebvre, Jacques; Cheng, Fuyong; Dubey, Girjesh; Zou, Shan; Finnie, Paul; Hrdina, Amy; Scoles, Ludmila; Lopinski, Gregory P.; Kingston, Christopher T.; Simard, Benoit; Malenfant, Patrick R. L.

    2014-01-01

    a narrow chirality and diameter distribution dominated by the (10,9) species with d = 1.29 nm. The enriched sc-SWCNTs allow a simple drop-casting method to form a dense nanotube network on SiO2/Si substrates, leading to thin film transistors (TFTs) with an average mobility of 27 cm2 V-1 s-1 and an average on/off current ratio of 1.8 × 106 when considering all 25 devices having 25 μm channel length prepared on a single chip. The results presented herein demonstrate how an easily scalable technique provides large-diameter sc-SWCNTs with high purity, further enabling the best TFT performance reported to date for conjugated polymer enriched sc-SWCNTs.A systematic study on the use of 9,9-dialkylfluorene homopolymers (PFs) for large-diameter semiconducting (sc-) single-walled carbon nanotube (SWCNT) enrichment is the focus of this report. The enrichment is based on a simple three-step extraction process: (1) dispersion of as-produced SWCNTs in a PF solution; (2) centrifugation at a low speed to separate the enriched sc-tubes; (3) filtration to collect the enriched sc-SWCNTs and remove excess polymer. The effect of the extraction conditions on the purity and yield including molecular weight and alkyl side-chain length of the polymers, SWCNT concentration, and polymer/SWCNT ratio have been examined. It was observed that PFs with alkyl chain lengths of C10, C12, C14, and C18, all have an excellent capability to enrich laser-ablation sc-SWCNTs when their molecular weight is larger than ~10 000 Da. More detailed studies were therefore carried out with the C12 polymer, poly(9,9-di-n-dodecylfluorene), PFDD. It was found that a high polymer/SWCNT ratio leads to an enhanced yield but a reduced sc-purity. A ratio of 0.5-1.0 gives an excellent sc-purity and a yield of 5-10% in a single extraction as assessed by UV-vis-NIR absorption spectra. The yield can also be promoted by multiple extractions while maintaining high sc-purity. Mechanistic experiments involving time

  1. PLASMA DEVICE

    DOEpatents

    Gow, J.D.; Wilcox, J.M.

    1961-12-26

    A device is designed for producing and confining highenergy plasma from which neutrons are generated in copious quantities. A rotating sheath of electrons is established in a radial electric field and axial magnetic field produced within the device. The electron sheath serves as a strong ionizing medium to gas introdueed thereto and also functions as an extremely effective heating mechanism to the resulting plasma. In addition, improved confinement of the plasma is obtained by ring magnetic mirror fields produced at the ends of the device. Such ring mirror fields are defined by the magnetic field lines at the ends of the device diverging radially outward from the axis of the device and thereafter converging at spatial annular surfaces disposed concentrically thereabout. (AFC)

  2. Applied Nonlinear Dynamics and Stochastic Systems Near The Millenium. Proceedings

    SciTech Connect

    Kadtke, J.B.; Bulsara, A.

    1997-12-01

    These proceedings represent papers presented at the Applied Nonlinear Dynamics and Stochastic Systems conference held in San Diego, California in July 1997. The conference emphasized the applications of nonlinear dynamical systems theory in fields as diverse as neuroscience and biomedical engineering, fluid dynamics, chaos control, nonlinear signal/image processing, stochastic resonance, devices and nonlinear dynamics in socio{minus}economic systems. There were 56 papers presented at the conference and 5 have been abstracted for the Energy Science and Technology database.(AIP)

  3. A Novel Effective Approach for Solving Fractional Nonlinear PDEs

    PubMed Central

    Aminikhah, Hossein; Malekzadeh, Nasrin; Rezazadeh, Hadi

    2014-01-01

    The present work introduces an effective modification of homotopy perturbation method for the solution of nonlinear time-fractional biological population model and a system of three nonlinear time-fractional partial differential equations. In this approach, the solution is considered a series expansion that converges to the nonlinear problem. The new approximate analytical procedure depends only on two iteratives. The analytical approximations to the solution are reliable and confirm the ability of the new homotopy perturbation method as an easy device for computing the solution of nonlinear equations.

  4. Hotspot-mediated ultrafast nonlinear control of multifrequency plasmonic nanoantennas

    NASA Astrophysics Data System (ADS)

    Abb, Martina; Wang, Yudong; de Groot, C. H.; Muskens, Otto L.

    2014-09-01

    Plasmonic devices have a unique ability to concentrate and convert optical energy into a small volume. There is a tremendous interest in achieving active control of plasmon resonances, which would enable switchable hotspots for applications such as surface-enhanced spectroscopy and single molecule emission. The small footprint and strong-field confinement of plasmonic nanoantennas also holds great potential for achieving transistor-type devices for nanoscale-integrated circuits. To achieve such a functionality, new methods for nonlinear modulation are required, which are able to precisely tune the nonlinear interactions between resonant antenna elements. Here we demonstrate that resonant pumping of a nonlinear medium in a plasmonic hotspot produces an efficient transfer of optical Kerr nonlinearity between different elements of a multifrequency antenna. By spatially and spectrally separating excitation and readout, isolation of the hotspot-mediated ultrafast Kerr nonlinearity from slower, thermal effects is achieved.

  5. Nonlinear Ballistic Transport in an Atomically Thin Material.

    PubMed

    Boland, Mathias J; Sundararajan, Abhishek; Farrokhi, M Javad; Strachan, Douglas R

    2016-01-26

    Ultrashort devices that incorporate atomically thin components have the potential to be the smallest electronics. Such extremely scaled atomically thin devices are expected to show ballistic nonlinear behavior that could make them tremendously useful for ultrafast applications. While nonlinear diffusive electron transport has been widely reported, clear evidence for intrinsic nonlinear ballistic transport in the growing array of atomically thin conductors has so far been elusive. Here we report nonlinear electron transport of an ultrashort single-layer graphene channel that shows quantitative agreement with intrinsic ballistic transport. This behavior is shown to be distinctly different than that observed in similarly prepared ultrashort devices consisting, instead, of bilayer graphene channels. These results suggest that the addition of only one extra layer of an atomically thin material can make a significant impact on the nonlinear ballistic behavior of ultrashort devices, which is possibly due to the very different chiral tunneling of their charge carriers. The fact that we observe the nonlinear ballistic response at room temperature, with zero applied magnetic field, in non-ultrahigh vacuum conditions and directly on a readily accessible oxide substrate makes the nanogap technology we utilize of great potential for achieving extremely scaled high-speed atomically thin devices. PMID:26630250

  6. Strong electron correlation and nonlinear optics

    NASA Astrophysics Data System (ADS)

    Ghosh, Haranath

    2012-07-01

    Based on experimental and theoretical research during the last decade, giant optical nonlinearities found in Mott-Hubbard insulators like Sr2CuO3,Ca2CuO3, Nickel halides ([Ni(chxn)2X]X2 where X = Br, Cl and `chxn' refers to cyclohexanediamine) are presented. These materials are reported to be potential materials for all optical switching devices. The occurrence of nearly degenerate lowest one- and two-photon states, strong Coulomb correlation and strong dipole coupling between the one- and two-photon states are believed to be the reason for such colossal optical nonlinearities in these systems. In some of these materials (at least), the two photon state is below the one-photon state. This leads to the possibility that such material can be excited to the lowest optical state by shinning laser of suitable wavelength, the populations thus generated decays to the two-photon state at ultrafast short time. Thus nonlinear measurements can be made from an excited state (we call as excited state nonlinear optical properties). One dimensional strongly correlated materials are predicted to have several orders-of-magnitude larger excited state optical non-linearities in comparison to that from the ground state, in the wavelength region suitable for terahertz communications. A large number of measurable nonlinear optical properties like Two Photon absorption, Photo induced absorption, Third Harmonic generation, Stimulated Raman Scattering are obtained theoretically and compared with available experimental observations. Then a large number excited state nonlinear optical properties are predicted which are experimentally measurable. We emphasize that the mechanism of nonlinear optics in one dimensional Mott-Hubbard insulators is different from that of the π-conjugated polymers — in the former spin excitation play an important role. We argue from detailed understanding of nonlinear optics of π-conjugated systems that some features in the Third Harmonic Generation

  7. Synthesis and device applications of graphitic nanomaterials

    NASA Astrophysics Data System (ADS)

    Umair, Ahmad

    This thesis is focused on two topics: (i) synthesis and characterization of bilayer graphene and pyrolytic carbon by atmospheric pressure chemical vapor deposition, and (ii) application of graphene in the fabrication of a buckyball memory device. Monolayer and bilayer graphene are semi-metal with zero bandgap. One can induce a bandgap in bilayer graphene by applying a gate voltage in the stacking direction. Thus, bandgap and Fermi level in bilayer graphene can be controlled simultaneously with a double-gate device, making it a useful material for future semiconducting applications. Controlled synthesis of bilayer graphene would be the first step to fabricate bilayer graphene based devices. In this context, we report a uniform and low-defect synthesis of bilayer graphene on evaporated nickel films. Ultra-fast cooling is employed to control the number of layers and sample uniformity. The process is self-limiting, which leads to bilayer graphene synthesis over a wide range of growth-time and precursor flow-rate. Pryolytic carbon is another important carbon nanomaterial, due to its diverse applications in electronic and biomedicalengineering. We employ chemical vapor deposition with ultra-fast cooling technique to synthesize pyrolytic carbon. Furthermore, we elucidate a method to calculate the in-plane crystal size by using Raman spectroscopy. Finally, the use of bilayer graphene in a write-once read-many memory device has been demonstrated. The device showed irreversible switching from low-resistance to high-resistance state, with hysteresis in the transport characteristics. The control sample showed random switching and hysteresis due to electromigration of metal atoms into the active material of the device. We attribute the reliability and performance of the reported device to the ultra-smooth graphene contacts, which additionally inhibits electromigration from the underlying metallic film. Moreover, the memory device showed excellent endurance and retention

  8. Carbon nanotube devices: Sorting, Assembling, Characterizing

    NASA Astrophysics Data System (ADS)

    Krupke, Ralph

    2009-03-01

    Carbon nanotubes have been studied extensively over the last decade. Various exceptional properties have been revealed which still drive the vision about using carbon nanotube in future electronics, for instance as molecular nanoscale transistors or electromigration resistant interconnects. For many years a major obstacle was the inability to grow nanotubes with defined dimensions (length, diameter) and electronic properties (metallic,semiconducting). Recently those problems have been solved to a large extent by advanced sorting techniques. Today the challenge is to assemble nanotubes devices with defined properties to form a complex circuitry. As progress is made in making highly-integrated nanotube device arrays new characterization techniques have to be developed which allow testing large number of devices within an acceptable time. Along this line I will report on the state-of-the-art of sorting of carbon nanotube, as a base for nanotube device fabrication [1]. I will then explain our strategy to assemble high-density arrays of nanotube devices [2] and discuss a new characterization technique for nanotube devices [3]. Finally I will introduce a novel device engineering tool [4]. [4pt] [1] R. Krupke et al., ``Separation techniques for carbon nanotubes'' in Chemistry of Carbon Nanotubes, p.129-139, American Scientific Publishers 2008[0pt] [2] A. Vijayaraghavan et al., ``Ultra-Large-Scale Directed Assembly of Single-Walled Carbon Nanotube Devices'', Nano Lett. 7 (2007) 1556-1560[0pt] [3] A. Vijayaraghavan et al., ``Imaging Electronic Structure of Carbon Nanotubes by Voltage-Contrast Scanning Electron Microscopy'', Nano Resarch 1 (2008) 321-332[0pt] [4] C. W. Marquardt et al., ``Reversible metal-insulator transitions in metallic single-walled carbon nanotubes'', Nano Lett. 9 (2008) 2767-2772

  9. Skutterudite Compounds For Power Semiconductor Devices

    NASA Technical Reports Server (NTRS)

    Fleurial, Jean-Pierre; Caillat, Thierry; Borshchevsky, Alexander; Vandersande, Jan

    1996-01-01

    New semiconducting materials with p-type carrier mobility values much higher than state-of-art semiconductors discovered. Nine compounds, antimonides CoSb(sub3), RhSb(sub3), IrSb(sub3), arsenides CoAs(sub3), RhAs(sub3), IrAs(sub3), and phosphides CoP(sub3), RhP(sub3) and IrP(sub3), exhibit same skutterudite crystallographic structure and form solid solutions of general composition Co(1-x-y)RH(x)Ir(y)P(1-w-z)As(w)Sb(z). Materials exhibit high hole mobilities, high doping levels, and high electronic figures of merit. Some compositions show great potential for application to thermoelectric devices.

  10. Nonlinear dynamics and plasma transport

    SciTech Connect

    Liu, C.S.; Sagdeev, R.; Antonsen, T.; Drake, J.; Hassma, A.; Guzdar, P.N.

    1995-12-01

    This progress report reports work done on a program in nonlinear dynamical aspects of plasma turbulence and transport funded by DOE from 1992-1995. The purpose of this program has been to promote the utilization of recent pathbreaking developments in nonlinear science in plasma turbulence and transport and to fully utilize the scientific expertise of Russian fusion and plasma community in collaboration with our group to address outstanding fusion theory problems. In the work reported in our progress report, we have studied simple models which are motivated by observation on actual fusion devices. The models focus on the important physical processes without incorporating the complexity of the geometry of real devices. We have also studied linear stability problems which incorporated important physics issues related to geometry involving closed field lines and open field lines. This allows for a deeper analysis and understanding of the system both analytically and numerically. The strong collaboration between the Russian visitors and the US participants has led to a fruitful and strong research program that taps the complementary analytic and numerical capabilities of the two groups. Over the years several distinguished Russian visitors have interacted with various members of the group and set up collaborative work which forms a significant part of proposed research. Dr. Galeev, Director of the Space Research Institute of Moscow and Dr. Novakovskii from the Kurchatov Institute are two such ongoing collaborations. 21 refs.

  11. Narrow bandgap semiconducting silicides: Intrinsic infrared detectors on a silicon chip

    NASA Technical Reports Server (NTRS)

    Mahan, John E.

    1990-01-01

    Work done during the final report period is presented. The main technical objective was to achieve epitaxial growth on silicon of two semiconducting silicides, ReSi2 and CrSi2. ReSi2 thin films were grown on (001) silicon wafers by vacuum evaporation of rhenium onto hot substrates in ultrahigh vacuum. The preferred epitaxial relationship was found to be ReSi2(100)/Si(001) with ReSi2(010) parallel to Si(110). The lattice matching consists of a common unit mesh of 120 A(sup 2) area, and a mismatch of 1.8 percent. Transmission electron microscopy revealed the existence of rotation twins corresponding to two distinct but equivalent azimuthal orientations of the common unit mesh. MeV He(+) backscattering spectrometry revealed a minimum channeling yield of 2 percent for an approximately 1,500 A thick film grown at 650 C. Although the lateral dimension of the twins is on the order of 100 A, there is a very high degree of alignment between the ReSi2(100) and the Si(001) planes. Highly oriented films of CrSi2 were grown on (111) silicon substrates, with the matching crystallographic faces being CrSi2(001)/Si(111). The reflection high-energy electron diffraction (RHEED) patterns of the films consist of sharp streaks, symmetrically arranged. The predominant azimuthal orientation of the films was determined to be CrSi2(210) parallel to Si(110). This highly desirable heteroepitaxial relationship has been obtained previously by others; it may be described with a common unit mesh of 51 A(sup 2) and mismatch of 0.3 percent. RHEED also revealed the presence of limited film regions of a competing azimuthal orientation, CrSi2(110) parallel to Si(110). A channeling effect for MeV He(+) ions was not found for this material. Potential commercial applications of this research may be found in silicon-integrated infrared detector arrays. Optical characterizations showed that semiconducting ReSi2 is a strong absorber of infrared radiation, with the adsorption constant increasing above 2 x

  12. Polydiacetylene thin films for nonlinear optical applications

    NASA Technical Reports Server (NTRS)

    Paley, Mark S.

    1993-01-01

    One very promising class of organic compounds for nonlinear optical (NLO) applications are polydiacetylenes, which are novel in that they are highly conjugated polymers which can also be crystalline. Polydiacetylenes offer several advantages over other organic materials: because of their highly conjugated electronic structures, they are capable of possessing large optical nonlinearities with fast response times; because they are crystalline, they can be highly ordered, which is essential for optimizing their NLO properties; and, last, because they are polymeric, they can be formed as thin films, which are useful for device fabrication. We have actively been carrying out ground-based research on several compounds of interest.

  13. Photonic Nonlinearities via Quantum Zeno Blockade

    NASA Astrophysics Data System (ADS)

    Sun, Yu-Zhu; Huang, Yu-Ping; Kumar, Prem

    2013-05-01

    Realizing optical-nonlinear effects at a single-photon level is a highly desirable but also extremely challenging task, because of both fundamental and practical difficulties. We present an avenue to surmounting these difficulties by exploiting quantum Zeno blockade in nonlinear optical systems. Considering specifically a lithium-niobate microresonator, we find that a deterministic phase gate can be realized between single photons with near-unity fidelity. Supported by established techniques for fabricating and operating such devices, our approach can provide an enabling tool for all-optical applications in both classical and quantum domains.

  14. Hierarchical Nanocomposites for Device Applications

    NASA Astrophysics Data System (ADS)

    Watkins, James

    We have outlined templating strategies for electronic and optical device fabrication that include self-assembly of well-ordered polymer/nanoparticle hybrids and nanoimprint lithography using novel materials sets. Using additive-driven self-assembly, for example, we demonstrate the formation of periodic nanocomposites with tunable magnetic and optical characteristics containing up to 70 wt. % of metal, metal oxide and/or semiconducting nanoparticles through phase specific interactions of the particles with either linear block copolymer or brush block copolymer (BBCP) templates. The BBCP templates provide direct access to large domain spacings for optical applications and spontaneous alignment within large volume elements. We have further developed highly filled nanoparticle/polymer hybrids for applications that require tailored dielectric constant or refractive index and a new imprinting process that allows direct printing of patterned 2-D and 3-D crystalline metal oxide films and composites with feature sizes of less than 100 nm. Applications in flexible electronics, light and energy management, and sensors and will be discussed.

  15. Polymer Thermoelectric Generators: Device Considerations

    NASA Astrophysics Data System (ADS)

    Yee, Shannon

    2014-03-01

    Recent control of the transport properties in polymers has encouraged the development of polymer thermoelectric (TE) devices. Polymer TEs are thought to be less expensive and more scalable than their inorganic counterparts. The cost of the raw material is less and polymer TEs can leverage the large areal manufacturing technique established by the plastics industry. Additionally, while the overall ZT of polymer TEs appears attractive, individual polymer properties have a very different scale than their inorganic counterparts (i.e., the thermal conductivity and electrical conductivity are approximately one and two orders of magnitude smaller, respectively). Furthermore, the majority of TE measurements on polymers have been limited to thin-films where traditional TE materials are measured in bulk. So why should it be expected that polymer TE devices resemble traditional TE devices? Given the uniqueness of polymers, different device architectures are proposed that can leverage the unique strengths of polymer films. It will be shown that by logically considering device requirements, new polymer TE devices have non-linear features that are more attractive than linear inorganic TE devices. This leads to very different device optimizations that favor polymer TEs.

  16. Stable solar-driven oxidation of water by semiconducting photoanodes protected by transparent catalytic nickel oxide films.

    PubMed

    Sun, Ke; Saadi, Fadl H; Lichterman, Michael F; Hale, William G; Wang, Hsin-Ping; Zhou, Xinghao; Plymale, Noah T; Omelchenko, Stefan T; He, Jr-Hau; Papadantonakis, Kimberly M; Brunschwig, Bruce S; Lewis, Nathan S

    2015-03-24

    Reactively sputtered nickel oxide (NiOx) films provide transparent, antireflective, electrically conductive, chemically stable coatings that also are highly active electrocatalysts for the oxidation of water to O2(g). These NiOx coatings provide protective layers on a variety of technologically important semiconducting photoanodes, including textured crystalline Si passivated by amorphous silicon, crystalline n-type cadmium telluride, and hydrogenated amorphous silicon. Under anodic operation in 1.0 M aqueous potassium hydroxide (pH 14) in the presence of simulated sunlight, the NiOx films stabilized all of these self-passivating, high-efficiency semiconducting photoelectrodes for >100 h of sustained, quantitative solar-driven oxidation of water to O2(g). PMID:25762067

  17. First-principles study of direct and narrow band gap semiconducting β-CuGaO2

    NASA Astrophysics Data System (ADS)

    Nguyen, Manh Cuong; Zhao, Xin; Wang, Cai-Zhuang; Ho, Kai-Ming

    2015-04-01

    Semiconducting oxides have attracted much attention due to their great stability in air or water and the abundance of oxygen. Recent success in synthesizing a metastable phase of CuGaO2 with direct narrow band gap opens up new applications of semiconducting oxides as absorber layer for photovoltaics. Using first-principles density functional theory calculations, we investigate the thermodynamic and mechanical stabilities as well as the structural and electronic properties of the β-CuGaO2 phase. Our calculations show that the β-CuGaO2 structure is dynamically and mechanically stable. The energy band gap is confirmed to be direct at the Γ point of Brillouin zone. The optical absorption occurs right at the band gap edge and the density of states near the valance band maximum is large, inducing an intense absorption of light as observed in experiment.

  18. First-principles study of direct and narrow band gap semiconducting β -CuGaO2

    DOE PAGESBeta

    Nguyen, Manh Cuong; Zhao, Xin; Wang, Cai-Zhuang; Ho, Kai-Ming

    2015-04-16

    Semiconducting oxides have attracted much attention due to their great stability in air or water and the abundance of oxygen. Recent success in synthesizing a metastable phase of CuGaO2 with direct narrow band gap opens up new applications of semiconducting oxides as absorber layer for photovoltaics. Using first-principles density functional theory calculations, we investigate the thermodynamic and mechanical stabilities as well as the structural and electronic properties of the β-CuGaO2 phase. Our calculations show that the β-CuGaO2 structure is dynamically and mechanically stable. The energy band gap is confirmed to be direct at the Γ point of Brillouin zone. Inmore » conclusion, the optical absorption occurs right at the band gap edge and the density of states near the valance band maximum is large, inducing an intense absorption of light as observed in experiment.« less

  19. Stable solar-driven oxidation of water by semiconducting photoanodes protected by transparent catalytic nickel oxide films

    PubMed Central

    Sun, Ke; Saadi, Fadl H.; Lichterman, Michael F.; Hale, William G.; Wang, Hsin-Ping; Zhou, Xinghao; Plymale, Noah T.; Omelchenko, Stefan T.; He, Jr-Hau; Papadantonakis, Kimberly M.; Brunschwig, Bruce S.; Lewis, Nathan S.

    2015-01-01

    Reactively sputtered nickel oxide (NiOx) films provide transparent, antireflective, electrically conductive, chemically stable coatings that also are highly active electrocatalysts for the oxidation of water to O2(g). These NiOx coatings provide protective layers on a variety of technologically important semiconducting photoanodes, including textured crystalline Si passivated by amorphous silicon, crystalline n-type cadmium telluride, and hydrogenated amorphous silicon. Under anodic operation in 1.0 M aqueous potassium hydroxide (pH 14) in the presence of simulated sunlight, the NiOx films stabilized all of these self-passivating, high-efficiency semiconducting photoelectrodes for >100 h of sustained, quantitative solar-driven oxidation of water to O2(g). PMID:25762067

  20. Gripping device

    NASA Technical Reports Server (NTRS)

    Parma, George F. (Inventor)

    1989-01-01

    This invention relates to a gripping device, and more particularly to one with a large moment carrying capability for handling long workpieces of various diameters and which can be particularly used as an end effector on a robotic arm.