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Sample records for single crystalline silicon

  1. Single crystalline mesoporous silicon nanowires

    SciTech Connect

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

    2009-08-18

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

  2. Single crystalline mesoporous silicon nanowires

    SciTech Connect

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

    2009-08-04

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

  3. Subsurface damage of single crystalline silicon carbide in nanoindentation tests.

    PubMed

    Yan, Jiwang; Gai, Xiaohui; Harada, Hirofumi

    2010-11-01

    The response of single crystalline silicon carbide (SiC) to a Berkovich nanoindenter was investigated by examining the indents using a transmission electron microscope and the selected area electron diffraction technique. It was found that the depth of indentation-induced subsurface damage was far larger than the indentation depth, and the damaging mechanism of SiC was distinctly different from that of single crystalline silicon. For silicon, a broad amorphous region is formed underneath the indenter after unloading; for SiC, however, no amorphous phase was detected. Instead, a polycrystalline structure with a grain size of ten nanometer level was identified directly under the indenter tip. Micro cracks, basal plane dislocations and possible cross slips were also found around the indent. These finding provide useful information for ultraprecision manufacturing of SiC wafers. PMID:21138038

  4. Dynamic crack propagation in single-crystalline silicon

    SciTech Connect

    Cramer, T.; Gumbsch, P.; Wanner, A.

    1999-08-01

    Tensile tests on notched plates of single-crystalline silicon were carried out at high overloads. Cracks were forced to propagate on {l_brace}110{r_brace} planes in a {l_angle}1{bar 1}0{r_angle} direction. The dynamics of the fracture process was measured using the potential drop technique and correlated with the fracture surface morphology. Crack propagation velocity did not exceed a terminal velocity of v{sub c} = 3,800 m/s, which corresponds to 83% of the Rayleigh wave velocity v{sub R}. Specimens fractured at low stresses exhibited crystallographic cleavage whereas a transition from mirror-like smooth regions to rougher hackle zones was observed in case of the specimens fractured at high stresses. Inspection of the mirror zone at high magnification revealed a deviation of the {l_brace}110{r_brace} plane onto {l_brace}111{r_brace}crystallographic facets.

  5. Laser ablation of single-crystalline silicon by radiation of pulsed frequency-selective fiber laser

    NASA Astrophysics Data System (ADS)

    Veiko, V. P.; Skvortsov, A. M.; Huynh, C. T.; Petrov, A. A.

    2015-07-01

    We have studied the process of destruction of the surface of a single-crystalline silicon wafer scanned by the beam of a pulsed ytterbium-doped fiber laser radiation with a wavelength of λ = 1062 nm. It is established that the laser ablation can proceed without melting of silicon and the formation of a plasma plume. Under certain parameters of the process (radiation power, beam scan velocity, and beam overlap density), pronounced oxidation of silicon microparticles with the formation of a characteristic loose layer of fine powdered silicon dioxide has been observed for the first time. The range of lasing and beam scanning regimes in which the growth of SiO2 layer takes place is determined.

  6. Surface modification via wet chemical etching of single-crystalline silicon for photovoltaic application.

    PubMed

    Reshak, A H; Shahimin, M M; Shaari, S; Johan, N

    2013-11-01

    The potential of solar cells have not been fully tapped due to the lack of energy conversion efficiency. There are three important mechanisms in producing high efficiency cells to harvest solar energy; reduction of light reflectance, enhancement of light trapping in the cell and increment of light absorption. The current work represent studies conducted in surface modification of single-crystalline silicon solar cells using wet chemical etching techniques. Two etching types are applied; alkaline etching (KOH:IPA:DI) and acidic etching (HF:HNO3:DI). The alkaline solution resulted in anisotropic profile that leads to the formation of inverted pyramids. While acidic solution formed circular craters along the front surface of silicon wafer. This surface modification will leads to the reduction of light reflectance via texturizing the surface and thereby increases the short circuit current and conversion rate of the solar cells. PMID:24139943

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

    SciTech Connect

    Wang, X.; Han, W.

    2010-12-01

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

  8. Oxygen recoil implant from SiO{sub 2} layers into single-crystalline silicon

    SciTech Connect

    Wang, G.; Chen, Y.; Li, D.; Oak, S.; Srivastav, G.; Banerjee, S.; Tasch, A.; Merrill, P.; Bleiler, R.

    2001-06-01

    It is important to understand the distribution of recoil-implanted atoms and the impact on device performance when ion implantation is performed at a high dose through surface materials into single crystalline silicon. For example, in ultralarge scale integration impurity ions are often implanted through a thin layer of screen oxide and some of the oxygen atoms are inevitably recoil implanted into single-crystalline silicon. Theoretical and experimental studies have been performed to investigate this phenomenon. We have modified the Monte Carlo ion implant simulator, UT-Marlowe (B. Obradovic, G. Wang, Y. Chen, D. Li, C. Snell, and A. F. Tasch, UT-MARLOWE Manual, 1999), which is based on the binary collision approximation, to follow the full cascade and to dynamically modify the stoichiometry of the Si layer as oxygen atoms are knocked into it. CPU reduction techniques are used to relieve the demand on computational power when such a full cascade simulation is involved. Secondary ion mass spectrometry (SIMS) profiles of oxygen have been carefully obtained for high dose As and BF{sub 2} implants at different energies through oxide layers of various thicknesses, and the simulated oxygen profiles are found to agree very well with the SIMS data. {copyright} 2001 American Institute of Physics.

  9. Dependence of Fracture Toughness on Crystallographic Orientation in Single-Crystalline Cubic (β) Silicon Carbide

    SciTech Connect

    Pharr, M.; Katoh, Y.; Bei, H.

    2006-01-01

    Along with other desirable properties, the ability of silicon carbide (SiC) to retain high strength after elevated temperature exposures to neutron irradiation renders it potentially applicable in fusion and advanced fission reactors. However, properties of the material such as room temperature fracture toughness must be thoroughly characterized prior to such practical applications. The objective of this work is to investigate the dependence of fracture toughness on crystallographic orientation for single-crystalline β-SiC. X-ray diffraction was first performed on the samples to determine the orientation of the crystal. Nanoindentation was used to determine a hardness of 39.1 and 35.2 GPa and elastic modulus of 474 and 446 GPa for the single-crystalline and polycrystalline samples, respectively. Additionally, crack lengths and indentation diagonals were measured via a Vickers micro-hardness indenter under a load of 100 gf for different crystallographic orientations with indentation diagonals aligned along fundamental cleavage planes. Upon examination of propagation direction of cracks, the cracks usually did not initiate and propagate from the corners of the indentation where the stresses are concentrated but instead from the indentation sides. Such cracks clearly moved along the {1 1 0} family of planes (previously determined to be preferred cleavage plane), demonstrating that the fracture toughness of SiC is comparatively so much lower along this set of planes that the lower energy required to cleave along this plane overpowers the stress-concentration at indentation corners. Additionally, fracture toughness in the <1 1 0> direction was 1.84 MPa·m1/2, lower than the 3.46 MPa·m1/2 measured for polycrystalline SiC (which can serve as an average of a spectrum of orientations), further demonstrating that single-crystalline β-SiC has a strong fracture toughness anisotropy.

  10. Fabrication of 3D fractal structures using nanoscale anisotropic etching of single crystalline silicon

    NASA Astrophysics Data System (ADS)

    Berenschot, Erwin J. W.; Jansen, Henri V.; Tas, Niels R.

    2013-05-01

    When it comes to high-performance filtration, separation, sunlight collection, surface charge storage or catalysis, the effective surface area is what counts. Highly regular fractal structures seem to be the perfect candidates, but manufacturing can be quite cumbersome. Here it is shown--for the first time—that complex 3D fractals can be engineered using a recursive operation in conventional micromachining of single crystalline silicon. The procedure uses the built-in capability of the crystal lattice to form self-similar octahedral structures with minimal interference of the constructor. The silicon fractal can be used directly or as a mold to transfer the shape into another material. Moreover, they can be dense, porous, or like a wireframe. We demonstrate, after four levels of processing, that the initial number of octahedral structures is increased by a factor of 625. Meanwhile the size decreases 16 times down to 300 nm. At any level, pores of less than 100 nm can be fabricated at the octahedral vertices of the fractal. The presented technique supports the design of fractals with Hausdorff dimension D free of choice and up to D = 2.322.

  11. Optical phased array using single crystalline silicon high-contrast-gratings for beamsteering

    NASA Astrophysics Data System (ADS)

    Yoo, Byung-Wook; Chan, Trevor; Megens, Mischa; Sun, Tianbo; Yang, Weijian; Rao, Yi; Horsley, David A.; Chang-Hasnain, Connie J.; Wu, Ming C.

    2013-03-01

    We present a single crystalline silicon optical phased array using high-contrast-gratings (HCG) for fast two dimensional beamforming and beamsteering at 0.5 MHz. Since there are various applications for beamforming and beamsteering such as 3D imaging, optical communications, and light detection and ranging (LIDAR), it is great interest to develop ultrafast optical phased arrays. However, the beamsteering speed of optical phased arrays using liquid crystal and electro-wetting are typically limited to tens of milliseconds. Optical phased arrays using micro-electro-mechanical systems (MEMS) technologies can operate in the submegahertz range, but generally require metal coatings. The metal coating unfortunately cause bending of mirrors due to thermally induced stress. The novel MEMS-based optical phased array presented here consists of electrostatically driven 8 × 8 HCG pixels fabricated on a silicon-on-insulator (SOI) wafer. The HCG mirror is designed to have 99.9% reflectivity at 1550 nm wavelength without any reflective coating. The size of the HCG mirror is 20 × 20 μm2 and the mass is only 140 pg, much lighter than traditional MEMS mirrors. Our 8 × 8 optical phased array has a total field of view of +/-10° × 10° and a beam width of 2°. The maximum phase shift regarding the actuation gap defined by a 2 μm buried oxide layer of a SOI wafer is 1.7π at 20 V.

  12. Generation of single-crystalline domain in nano-scale silicon pillars by near-field short pulsed laser

    NASA Astrophysics Data System (ADS)

    In, Jung Bin; Xiang, Bin; Hwang, David J.; Ryu, Sang-Gil; Kim, Eunpa; Yoo, Jae-Hyuck; Dubon, Oscar; Minor, Andrew M.; Grigoropoulos, Costas P.

    2014-01-01

    We observe laser-induced grain morphology change in silicon nanopillars under a transmission electron microscopy (TEM) environment. We couple the TEM with a near-field scanning optical microscopy pulsed laser processing system. This novel combination enables immediate scrutiny on the grain morphologies that the pulsed laser irradiation produces. We find unusual transformation of the tip of the amorphous or polycrystalline silicon pillar into a single crystalline domain via melt-mediated crystallization. On the basis of the three-dimensional finite difference simulation result and the dark field TEM data, we propose that the creation of the distinct single crystalline tip originates from the dominant grain growth initiated at the apex of the non-planar liquid-solid interface. Our microscopic observation provides a fundamental basis for laser-induced conversion of amorphous nanostructures into coarse-grained crystals.

  13. Fluorescence signals of core-shell quantum dots enhanced by single crystalline gold caps on silicon nanowires

    NASA Astrophysics Data System (ADS)

    Christiansen, S. H.; Chou, J. W.; Becker, M.; Sivakov, V.; Ehrhold, K.; Berger, A.; Chou, W. C.; Chuu, D. S.; Gösele, U.

    2009-04-01

    We use nanoscale (20-300 nm in diameter) single crystalline gold (Au)-caps on silicon nanowires (NWs) grown by the vapor-liquid-solid (VLS) growth mechanism to enhance the fluorescence photoluminescence (PL) signals of highly dilute core/shell CdSeTe/ZnS quantum dots (QDs) in aqueous solution (10-5 M). For NWs without Au-caps, as they appear, for example, after Au etching in aqua regia or buffered KI/I2-solution, essentially no fluorescence signal of the same diluted QDs could be observed. Fluorescence PL signals were measured using excitation with a laser wavelength of 633 nm. The signal enhancement by single crystalline, nanoscale Au-caps is discussed and interpreted based on finite element modeling (FEM).

  14. Graphene-silicon layered structures on single-crystalline Ir(111) thin films

    SciTech Connect

    Que, Yande D.; Tao, Jing; Zhang, Yong; Wang, Yeliang L.; Wu, Lijun J.; Zhu, Yimei M.; Kim, Kisslinger; Weinl, Michael; Schreck, Matthias; Shen, Chengmin M.; Du, Shixuan X.; Liu, Yunqi Q.; Gao, H. -J.; Huang, Li; Xu, Wenyan Y.

    2015-01-20

    Epitaxial growth of graphene on transition metal crystals, such as Ru,⁽¹⁻³⁾ Ir,⁽⁴⁻⁶⁾ and Ni,⁽⁷⁾ provides large-area, uniform graphene layers with controllable defect density, which is crucial for practical applications in future devices. To decrease the high cost of single-crystalline metal bulks, single-crystalline metal films are strongly suggested as the substrates for epitaxial growth large-scale high-quality graphene.⁽⁸⁻¹⁰⁾ Moreover, in order to weaken the interactions of graphene with its metal host, which may result in a suppression of the intrinsic properties of graphene,⁽¹¹ ¹²⁾ the method of element intercalation of semiconductors at the interface between an epitaxial graphene layer and a transition metal substrate has been successfully realized.⁽¹³⁻¹⁶⁾

  15. Graphene-silicon layered structures on single-crystalline Ir(111) thin films

    DOE PAGESBeta

    Que, Yande D.; Tao, Jing; Zhang, Yong; Wang, Yeliang L.; Wu, Lijun J.; Zhu, Yimei M.; Kim, Kisslinger; Weinl, Michael; Schreck, Matthias; Shen, Chengmin M.; et al

    2015-01-20

    Epitaxial growth of graphene on transition metal crystals, such as Ru,⁽¹⁻³⁾ Ir,⁽⁴⁻⁶⁾ and Ni,⁽⁷⁾ provides large-area, uniform graphene layers with controllable defect density, which is crucial for practical applications in future devices. To decrease the high cost of single-crystalline metal bulks, single-crystalline metal films are strongly suggested as the substrates for epitaxial growth large-scale high-quality graphene.⁽⁸⁻¹⁰⁾ Moreover, in order to weaken the interactions of graphene with its metal host, which may result in a suppression of the intrinsic properties of graphene,⁽¹¹ ¹²⁾ the method of element intercalation of semiconductors at the interface between an epitaxial graphene layer and a transitionmore » metal substrate has been successfully realized.⁽¹³⁻¹⁶⁾« less

  16. Crystalline Silicon Solar Cells

    NASA Astrophysics Data System (ADS)

    Green, Martin A.

    2015-10-01

    The following sections are included: * Overview * Silicon cell development * Substrate production * Cell processing * Cell costs * Opportunities for improvement * Silicon-supported thin films * Summary * Acknowledgement * References

  17. Structural defects in crystalline silicon

    NASA Technical Reports Server (NTRS)

    Sirtl, E.

    1985-01-01

    The basic photovoltaic properties of a given crystalline silicon specimen seem to be governed by density and nature of two to three dimensional lattice defects. These are mainly generated by primary growth conditions as grain boundaries of more or less intrinsic character or second phase precipitates from supersaturated solutions of carbon or oxygen. Considerably high values of both solubility and diffusivity in connection with their abundance in common refractory material systems account for the predominance of the two particular elements. Unsaturated dislocations of different types very often can be seen as a consequence of the existence of more dimensional defects as described initially. The final performance of a solar cell is dependent of the concentration and distribution of recombination active centers in the different regions of this device. Typical representatives are fast diffusing transition metals in form of either single atoms or simple complexes. Their avoidance, annihilation, or removal is of great concern in different fields of electronic materials development.

  18. Direct writing of continuous and discontinuous sub-wavelength periodic surface structures on single-crystalline silicon using femtosecond laser

    SciTech Connect

    Kuladeep, Rajamudili; Sahoo, Chakradhar; Narayana Rao, Desai E-mail: dnr-laserlab@yahoo.com

    2014-06-02

    Laser-induced ripples or uniform arrays of continuous near sub-wavelength or discontinuous deep sub-wavelength structures are formed on single-crystalline silicon (Si) by femtosecond (fs) laser direct writing technique. Laser irradiation was performed on Si wafers at normal incidence in air and by immersing them in dimethyl sulfoxide using linearly polarized Ti:sapphire fs laser pulses of ∼110 fs pulse duration and ∼800 nm wavelength. Morphology studies of laser written surfaces reveal that sub-wavelength features are oriented perpendicular to laser polarization, while their morphology and spatial periodicity depend on the surrounding dielectric medium. The formation mechanism of the sub-wavelength features is explained by interference of incident laser with surface plasmon polaritons. This work proves the feasibility of fs laser direct writing technique for the fabrication of sub-wavelength features, which could help in fabrication of advanced electro-optic devices.

  19. Shape- and dimension-controlled single-crystalline silicon and SiGe nanotubes: toward nanofluidic FET devices.

    PubMed

    Ben Ishai, Moshit; Patolsky, Fernando

    2009-03-18

    We report here on the formation of robust and entirely hollow single-crystalline silicon nanotubes, from various tubular to conical structures, with uniform and well-controlled inner diameter, ranging from as small as 1.5 up to 500 nm, and controllable wall thickness. Second, and most important, these nanotubes can be doped in situ with different concentrations of boron and phosphine to give p/n-type semiconductor nanotubes. Si(x)Ge(1-x)-alloy nanotubes can also be prepared. This synthetic approach enables independent and precise control of diameter, wall thickness, shape, taper angle, crystallinity, and chemical/electrical characteristics of the nanotubular structures obtained. Notably, diameter and wall thickness of nearly any size can be obtained. This unique advantage allows the achievement of novel and perfectly controlled high-quality electronic materials and the tailoring of the tube properties to better fit many biological, chemical, and electrical applications. Electrical devices based on this new family of electrically active nanotubular building-block structures are also described with a view toward the future realization of nanofluidic FET devices. PMID:19226180

  20. Method of making selective crystalline silicon regions containing entrapped hydrogen by laser treatment

    DOEpatents

    Pankove, Jacques I.; Wu, Chung P.

    1982-01-01

    A novel hydrogen rich single crystalline silicon material having a band gap energy greater than 1.1 eV can be fabricated by forming an amorphous region of graded crystallinity in a body of single crystalline silicon and thereafter contacting the region with atomic hydrogen followed by pulsed laser annealing at a sufficient power and for a sufficient duration to recrystallize the region into single crystalline silicon without out-gasing the hydrogen. The new material can be used to fabricate semi-conductor devices such as single crystalline silicon solar cells with surface window regions having a greater band gap energy than that of single crystalline silicon without hydrogen.

  1. Interfacial Layer Control by Dry Cleaning Technology for Polycrystalline and Single Crystalline Silicon Growth.

    PubMed

    Im, Dong-Hyun; Kong-Soo Lee; Kang, Yoongoo; Jeong, Myoungho; Park, Kwang Wuk; Lee, Soon-Gun; Ma, Jin-Won; Kim, Youngseok; Kim, Bonghyun; Im, Ki-Vin; Lim, Hanjin; Lee, Jeong Yong

    2016-05-01

    Native oxide removal prior to poly-Si contact and epitaxial growth of Si is the most critical technology to ensure process and device performances of poly-Si plugs and selective epitaxial growth (SEG) layers for DRAM, flash memory, and logic device. Recently, dry cleaning process for interfacial oxide removal has attracted a world-wide attention due to its superior passivation properties to conventional wet cleaning processes. In this study, we investigated the surface states of Si substrate during and after dry cleaning process, and the role of atomic elements including fluorine and hydrogen on the properties of subsequent deposited silicon layer using SIMS, XPS, and TEM analysis. The controlling of residual fluorine on the Si surface after dry cleaning is a key factor for clean interface. The mechanism of native oxide re-growth caused by residual fluorine after dry cleaning is proposed based on analytical results. PMID:27483844

  2. Birefringence measurements on crystalline silicon

    NASA Astrophysics Data System (ADS)

    Krüger, Christoph; Heinert, Daniel; Khalaidovski, Alexander; Steinlechner, Jessica; Nawrodt, Ronny; Schnabel, Roman; Lück, Harald

    2016-01-01

    Crystalline silicon has been proposed as a new test mass material in third generation gravitational wave detectors such as the Einstein telescope (ET). Birefringence can reduce the interferometric contrast and can produce dynamical disturbances in interferometers. In this work we use the method of polarization-dependent resonance-frequency analysis of Fabry-Perot-cavities containing silicon as a birefringent medium. Our measurements show a birefringence of silicon along the (111) axis of the order of {{Δ }} n≈ {10}-7 at a laser wavelength of 1550 nm and room temperature. A model is presented that explains the results of different settings of our measurements as a superposition of elastic strains caused by external stresses in the sample and plastic strains possibly generated during the production process. An application of our theory on the proposed ET test mass geometry suggests no critical effect on birefringence due to elastic strains.

  3. Strain Anisotropies and Self-limiting Capacities in Single-crystalline 3D Silicon Microstructures: Models for High Energy Denisty Lithium-Ion Battery Anodes

    SciTech Connect

    Goldman, Jason L.; Long, Brandon R.; Gewirth, Andrew A.; Nuzzo, Ralph G

    2011-01-01

    This study examines the crystallographic anisotropy of strain evolution in model, single-crystalline silicon anode microstructures on electrochemical intercalation of lithium atoms. The 3D hierarchically patterned single- crystalline silicon microstructures used as model anodes were prepared using combined methods of photolithography and anisotropic dry and wet chemical etching. Silicon anodes, which possesses theoretically ten times the energy density by weight compared to conventional carbon anodes, reveal highly anisotropic but more importantly, variably recoverable crystallographic strains during cycling. Model strain-limiting silicon anode architectures that mitigate these impacts are highlighted. By selecting a specific design for the silicon anode microstructure, and exploiting the crystallographic anisotropy of strain evolution upon lithium intercalation to control the direction of volumetric expansion, the volume available for expansion and thus the charging capacity of these structures can be broadly varied. We highlight exemplary design rules for this self-strain-limited charging in which an anode can be variably optimized between capacity and stability. Strain-limited capacities ranging from 677 mAhg-1 to 2833 mAhg-1 were achieved by constraining the area available for volumetric expansion via the design rules of the microstructures.

  4. Basic research challenges in crystalline silicon photovoltaics

    SciTech Connect

    Werner, J.H.

    1995-08-01

    Silicon is abundant, non-toxic and has an ideal band gap for photovoltaic energy conversion. Experimental world record cells of 24 % conversion efficiency with around 300 {mu}m thickness are only 4 % (absolute) efficiency points below the theoretical Auger recombination-limit of around 28 %. Compared with other photovoltaic materials, crystalline silicon has only very few disadvantages. The handicap of weak light absorbance may be mastered by clever optical designs. Single crystalline cells of only 48 {mu}m thickness showed 17.3 % efficiency even without backside reflectors. A technology of solar cells from polycrystalline Si films on foreign substrates arises at the horizon. However, the disadvantageous, strong activity of grain boundaries in Si could be an insurmountable hurdle for a cost-effective, terrestrial photovoltaics based on polycrystalline Si on foreign substrates. This talk discusses some basic research challenges related to a Si based photovoltaics.

  5. Single crystalline magnetite nanotubes.

    PubMed

    Liu, Zuqin; Zhang, Daihua; Han, Song; Li, Chao; Lei, Bo; Lu, Weigang; Fang, Jiye; Zhou, Chongwu

    2005-01-12

    We descried a method to synthesize single crystalline Fe3O4 nanotubes by wet-etching the MgO inner cores of MgO/Fe3O4 core-shell nanowires. Homogeneous Fe3O4 nanotubes with controllable length, diameter, and wall thickness have been obtained. Resistivity of the Fe3O4 nanotubes was estimated to be approximately 4 x 10-2 Omega cm at room temperature. Magnetoresistance of approximately 1% was observed at T = 77 K when a magnetic field of B = 0.7 T was applied. The synthetic strategy presented here may be extended to a variety of materials such as YBCO, PZT, and LCMO which should provide ideal candidates for fundamental studies of superconductivity, piezoelectricity, and ferromagnetism in nanoscale structures. PMID:15631421

  6. Zero lattice mismatch and twin-free single crystalline ScN buffer layers for GaN growth on silicon

    NASA Astrophysics Data System (ADS)

    Lupina, L.; Zoellner, M. H.; Niermann, T.; Dietrich, B.; Capellini, G.; Thapa, S. B.; Haeberlen, M.; Lehmann, M.; Storck, P.; Schroeder, T.

    2015-11-01

    We report the growth of thin ScN layers deposited by plasma-assisted molecular beam epitaxy on Sc2O3/Y2O3/Si(111) substrates. Using x-ray diffraction, Raman spectroscopy, and transmission electron microscopy, we find that ScN films grown at 600 °C are single crystalline, twin-free with rock-salt crystal structure, and exhibit a direct optical band gap of 2.2 eV. A high degree of crystalline perfection and a very good lattice matching between ScN and GaN (misfit < 0.1%) makes the ScN/Sc2O3/Y2O3 buffer system a very promising template for the growth of high quality GaN layers on silicon.

  7. Zero lattice mismatch and twin-free single crystalline ScN buffer layers for GaN growth on silicon

    SciTech Connect

    Lupina, L.; Zoellner, M. H.; Dietrich, B.; Capellini, G.; Niermann, T.; Lehmann, M.; Thapa, S. B.; Haeberlen, M.; Storck, P.; Schroeder, T.

    2015-11-16

    We report the growth of thin ScN layers deposited by plasma-assisted molecular beam epitaxy on Sc{sub 2}O{sub 3}/Y{sub 2}O{sub 3}/Si(111) substrates. Using x-ray diffraction, Raman spectroscopy, and transmission electron microscopy, we find that ScN films grown at 600 °C are single crystalline, twin-free with rock-salt crystal structure, and exhibit a direct optical band gap of 2.2 eV. A high degree of crystalline perfection and a very good lattice matching between ScN and GaN (misfit < 0.1%) makes the ScN/Sc{sub 2}O{sub 3}/Y{sub 2}O{sub 3} buffer system a very promising template for the growth of high quality GaN layers on silicon.

  8. High efficiency crystalline silicon solar cells

    NASA Technical Reports Server (NTRS)

    Sah, C. Tang

    1986-01-01

    A review of the entire research program since its inception ten years ago is given. The initial effort focused on the effects of impurities on the efficiency of silicon solar cells to provide figures of maximum allowable impurity density for efficiencies up to about 16 to 17%. Highly accurate experimental techniques were extended to characterize the recombination properties of the residual imputities in the silicon solar cell. A numerical simulator of the solar cell was also developed, using the Circuit Technique for Semiconductor Analysis. Recent effort focused on the delineation of the material and device parameters which limited the silicon efficiency to below 20% and on an investigation of cell designs to break the 20% barrier. Designs of the cell device structure and geometry can further reduce recombination losses as well as the sensitivity and criticalness of the fabrication technology required to exceed 20%. Further research is needed on the fundamental characterization of the carrier recombination properties at the chemical impurity and physical defect centers. It is shown that only single crystalline silicon cell technology can be successful in attaining efficiencies greater than 20%.

  9. High-efficiency crystalline silicon technology development

    NASA Technical Reports Server (NTRS)

    Prince, M. B.

    1984-01-01

    The rationale for pursuing high efficiency crystalline silicon technology research is discussed. Photovoltaic energy systems are reviewed as to their cost effectiveness and their competitiveness with other energy systems. The parameters of energy system life are listed and briefly reviewed.

  10. Porous silicon Bragg reflectors on multi-crystalline silicon wafer with p-n junction

    NASA Astrophysics Data System (ADS)

    Ivanov, I. I.; Skryshevsky, V. A.; Kyslovets, O. S.; Nychyporuk, T.; Lemiti, M.

    2016-04-01

    Bragg reflectors consisting of the sequence of dielectric layers are considered to create p-n junction solar cells (SC) with improved efficiency in the longwave spectral range. Bragg mirrors (BM) based on porous silicon (PS) mutilayers at the backside of single crystalline and multicrystalline silicon wafer were formed by electrochemically etching. Maximal experimental reflectivity for BM on multicrystalline substrate achieves 62% due to the natural crystallites disorientation of multicrystalline substrate, whereas for single crystalline silicon the reflectivity in maximum is 87%. BM was formed also on rear side of multicrystalline silicon wafer with p-n junction.

  11. Laser recrystallization for efficient multi-crystalline silicon solar cell

    NASA Astrophysics Data System (ADS)

    Song, Lihui; Wilson, John; Lee, James

    2016-08-01

    A multi-crystalline silicon wafer contains dislocations and grain boundaries, which are detrimental to the performance of the multi-crystalline silicon solar cell. The dislocations and grain boundaries extend across the junction and dramatically degrade the ideality and fill factor of the cell. In this paper, a laser is used to recrystallize the emitter region of a multi-crystalline silicon wafer to remove crystallographic defects present in the junction. It was demonstrated that, with an appropriate laser power and scan speed, laser recrystallized patterns can have an enhanced photoluminescence response and internal quantum efficiency. Backscattered electron image and x-ray diffraction analyses also revealed that the laser recrystallized layer resembles a single crystalline like layer. Introducing a full area laser recrystallized layer may improve the open circuit voltage and fill factor of the cell, which significantly improved cell efficiency. External quantum efficiency and dark I–V measurements consistently supported this result.

  12. Method of making selective crystalline silicon regions containing entrapped hydrogen by laser treatment

    DOEpatents

    Pankove, J.I.; Wu, C.P.

    1982-03-30

    A novel hydrogen rich single crystalline silicon material having a band gap energy greater than 1.1 eV can be fabricated by forming an amorphous region of graded crystallinity in a body of single crystalline silicon and thereafter contacting the region with atomic hydrogen followed by pulsed laser annealing at a sufficient power and for a sufficient duration to recrystallize the region into single crystalline silicon without out-gassing the hydrogen. The new material can be used to fabricate semi-conductor devices such as single crystalline silicon solar cells with surface window regions having a greater band gap energy than that of single crystalline silicon without hydrogen. 2 figs.

  13. University Crystalline Silicon Photovoltaics Research and Development

    SciTech Connect

    Ajeet Rohatgi; Vijay Yelundur; Abasifreke Ebong; Dong Seop Kim

    2008-08-18

    The overall goal of the program is to advance the current state of crystalline silicon solar cell technology to make photovoltaics more competitive with conventional energy sources. This program emphasizes fundamental and applied research that results in low-cost, high-efficiency cells on commercial silicon substrates with strong involvement of the PV industry, and support a very strong photovoltaics education program in the US based on classroom education and hands-on training in the laboratory.

  14. Crystalline silicon growth in nickel/a-silicon bilayer

    SciTech Connect

    Mohiddon, Md Ahamad; Naidu, K. Lakshun; Dalba, G.; Rocca, F.; Krishna, M. Ghanashyam

    2013-02-05

    The effect of substrate temperature on amorphous Silicon crystallization, mediated by metal impurity is reported. Bilayers of Ni(200nm)/Si(400nm) are deposited on fused silica substrate by electron beam evaporator at 200 and 500 Degree-Sign C. Raman mapping shows that, 2 to 5 micron size crystalline silicon clusters are distributed over the entire surface of the sample. X-ray diffraction and X-ray absorption spectroscopy studies demonstrate silicon crystallizes over the metal silicide seeds and grow with the annealing temperature.

  15. Meniscus-force-mediated layer transfer technique using single-crystalline silicon films with midair cavity: Application to fabrication of CMOS transistors on plastic substrates

    NASA Astrophysics Data System (ADS)

    Sakaike, Kohei; Akazawa, Muneki; Nakagawa, Akitoshi; Higashi, Seiichiro

    2015-04-01

    A novel low-temperature technique for transferring a silicon-on-insulator (SOI) layer with a midair cavity (supported by narrow SiO2 columns) by meniscus force has been proposed, and a single-crystalline Si (c-Si) film with a midair cavity formed in dog-bone shape was successfully transferred to a poly(ethylene terephthalate) (PET) substrate at its heatproof temperature or lower. By applying this proposed transfer technique, high-performance c-Si-based complementary metal-oxide-semiconductor (CMOS) transistors were successfully fabricated on the PET substrate. The key processes are the thermal oxidation and subsequent hydrogen annealing of the SOI layer on the midair cavity. These processes ensure a good MOS interface, and the SiO2 layer works as a “blocking” layer that blocks contamination from PET. The fabricated n- and p-channel c-Si thin-film transistors (TFTs) on the PET substrate showed field-effect mobilities of 568 and 103 cm2 V-1 s-1, respectively.

  16. Oxygen, carbon, hydrogen and nitrogen in crystalline silicon

    SciTech Connect

    Mikkelsen, J.C.; Pearton, S.J.; Corbett, J.W.; Pennycook, S.J

    1986-01-01

    These proceedings collect papers on interstitial material in silicon. Topics include: hydrogen in crystalline silicon, low energy hydrogen ion bombarded silicon, oxygen in silicon, oxygen thermal donor formation, thermal donor generation and annihilation effects on oxygen precipitation oxygen effects on plastic flow during growth of dendrixic web silicon, nitrogen in silicon, off-center nitrogen and oxygen in silicon, and thermal donor hierarchies in silicon and germanium.

  17. Transistors using crystalline silicon devices on glass

    DOEpatents

    McCarthy, Anthony M.

    1995-01-01

    A method for fabricating transistors using single-crystal silicon devices on glass. This method overcomes the potential damage that may be caused to the device during high voltage bonding and employs a metal layer which may be incorporated as part of the transistor. This is accomplished such that when the bonding of the silicon wafer or substrate to the glass substrate is performed, the voltage and current pass through areas where transistors will not be fabricated. After removal of the silicon substrate, further metal may be deposited to form electrical contact or add functionality to the devices. By this method both single and gate-all-around devices may be formed.

  18. Two- and three-dimensional folding of thin film single-crystalline silicon for photovoltaic power applications

    PubMed Central

    Guo, Xiaoying; Li, Huan; Yeop Ahn, Bok; Duoss, Eric B.; Hsia, K. Jimmy; Lewis, Jennifer A.; Nuzzo, Ralph G.

    2009-01-01

    Fabrication of 3D electronic structures in the micrometer-to-millimeter range is extremely challenging due to the inherently 2D nature of most conventional wafer-based fabrication methods. Self-assembly, and the related method of self-folding of planar patterned membranes, provide a promising means to solve this problem. Here, we investigate self-assembly processes driven by wetting interactions to shape the contour of a functional, nonplanar photovoltaic (PV) device. A mechanics model based on the theory of thin plates is developed to identify the critical conditions for self-folding of different 2D geometrical shapes. This strategy is demonstrated for specifically designed millimeter-scale silicon objects, which are self-assembled into spherical, and other 3D shapes and integrated into fully functional light-trapping PV devices. The resulting 3D devices offer a promising way to efficiently harvest solar energy in thin cells using concentrator microarrays that function without active light tracking systems. PMID:19934059

  19. The microstructure matters: breaking down the barriers with single crystalline silicon as negative electrode in Li-ion batteries.

    PubMed

    Sternad, M; Forster, M; Wilkening, M

    2016-01-01

    Silicon-based microelectronics forms a major foundation of our modern society. Small lithium-ion batteries act as the key enablers of its success and have revolutionised portable electronics used in our all everyday's life. While large-scale LIBs are expected to help establish electric vehicles, on the other end of device size chip-integrated Si-based μ-batteries may revolutionise microelectronics once more. In general, Si is regarded as one of the white hopes since it offers energy densities being ten times higher than conventional anode materials. The use of monocrystalline, wafer-grade Si, however, requires several hurdles to be overcome since it its volume largely expands during lithiation. Here, we will show how 3D patterned Si wafers, prepared by the sophisticated techniques from semiconductor industry, are to be electrochemically activated to overcome these limitations and to leverage their full potential being reflected in stable charge capacities (>1000 mAhg(-1)) and high Coulomb efficiencies (98.8%). PMID:27531589

  20. The microstructure matters: breaking down the barriers with single crystalline silicon as negative electrode in Li-ion batteries

    PubMed Central

    Sternad, M.; Forster, M.; Wilkening, M.

    2016-01-01

    Silicon-based microelectronics forms a major foundation of our modern society. Small lithium-ion batteries act as the key enablers of its success and have revolutionised portable electronics used in our all everyday’s life. While large-scale LIBs are expected to help establish electric vehicles, on the other end of device size chip-integrated Si-based μ-batteries may revolutionise microelectronics once more. In general, Si is regarded as one of the white hopes since it offers energy densities being ten times higher than conventional anode materials. The use of monocrystalline, wafer-grade Si, however, requires several hurdles to be overcome since it its volume largely expands during lithiation. Here, we will show how 3D patterned Si wafers, prepared by the sophisticated techniques from semiconductor industry, are to be electrochemically activated to overcome these limitations and to leverage their full potential being reflected in stable charge capacities (>1000 mAhg–1) and high Coulomb efficiencies (98.8%). PMID:27531589

  1. Research on crystalline silicon solar cells

    SciTech Connect

    Milstein, J.B.; Tsuo, Y.S.

    1984-06-01

    Since the 16th IEEE Photovoltaic Specialists Conference, the focus of the Crystalline Silicon Solar Cell Task at the Solar Energy Research Institute (SERI) has narrowed somewhat. Responsibility for silicon material preparation and ribbon growth were consolidated at the Jet Propulsion Laboratory (JPL) at the end of FY 1983. Five subcontracts were awarded under RFP No. RB-2-02090, Research on Basic Understanding of High Efficiency in Silicon Solar Cells. JPL and Oak Ridge National Laboratory are also working on high-efficiency solar cell research under SERI subcontract. Reports of past solar cell improvements have prompted appreciable interest in the physical, chemical, and electrical transport properties of grain boundaries and other electrically active defects. Studies to achieve better understanding of the hydrogen passivation process are being conducted at various subcontractors, and our in-house research continues. This paper presents the results of these efforts as well as future directions.

  2. A holistic view of crystalline silicon module reliability

    SciTech Connect

    Hanoka, J.I.

    1995-11-01

    Several aspects of module reliability are discussed, particularly with reference to the encapsulant and its interaction with the metallization and interconnection of a module. A need to look at the module as a whole single unit is stressed. Also, the issue of a slight light degradation effect in crystalline silicon cells is discussed. A model for this is mentioned and it may well be that polycrystalline cells with dislocations may have an advantage.

  3. Solar cell structure incorporating a novel single crystal silicon material

    DOEpatents

    Pankove, Jacques I.; Wu, Chung P.

    1983-01-01

    A novel hydrogen rich single crystal silicon material having a band gap energy greater than 1.1 eV can be fabricated by forming an amorphous region of graded crystallinity in a body of single crystalline silicon and thereafter contacting the region with atomic hydrogen followed by pulsed laser annealing at a sufficient power and for a sufficient duration to recrystallize the region into single crystal silicon without out-gassing the hydrogen. The new material can be used to fabricate semiconductor devices such as single crystal silicon solar cells with surface window regions having a greater band gap energy than that of single crystal silicon without hydrogen.

  4. Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

    SciTech Connect

    Lowden, Richard A.

    1994-01-01

    A process for chemical vapor deposition of crystalline silicon nitride which comprises the steps of: introducing a mixture of a silicon source, a molybdenum source, a nitrogen source, and a hydrogen source into a vessel containing a suitable substrate; and thermally decomposing the mixture to deposit onto the substrate a coating comprising crystalline silicon nitride containing a dispersion of molybdenum silicide.

  5. (Preoxidation cleaning optimization for crystalline silicon)

    SciTech Connect

    Not Available

    1991-01-01

    A series of controlled experiments has been performed in Sandia's Photovoltaic Device Fabrication Laboratory to evaluate the effect of various chemical surface treatments on the recombination lifetime of crystalline silicon wafers subjected to a high-temperature dry oxidation. From this series of experiments we have deduced a relatively simple yet effective cleaning sequence. We have also evaluated the effect of different chemical damage-removal etches for improving the recombination lifetime and surface smoothness of mechanically lapped wafers. This paper presents the methodology used, the experimental results obtained, and our experience with using this process on a continuing basis over a period of many months. 7 refs., 4 figs., 1 tab.

  6. Effect of nitridation surface treatment on silicon (1 1 1) substrate for the growth of high quality single-crystalline GaN hetero-epitaxy layer by MOCVD

    NASA Astrophysics Data System (ADS)

    Rahman, Mohd Nazri Abd.; Yusuf, Yusnizam; Mansor, Mazwan; Shuhaimi, Ahmad

    2016-01-01

    A single-crystalline with high quality of gallium nitride epilayers was grown on silicon (1 1 1) substrate by metal organic chemical vapor deposition. The process of nitridation surface treatment was accomplished on silicon (1 1 1) substrate by flowing the ammonia gaseous. Then, it was followed by a thin aluminum nitride nucleation layer, aluminum nitride/gallium nitride multi-layer and a thick gallium nitride epilayer. The influence of in situ nitridation surface treatment on the crystallinity quality of gallium nitride epilayers was studied by varying the nitridation times at 40, 220 and 400 s, respectively. It was shown that the nitridation times greatly affect the structural properties of the grown top gallium nitride epilayer on silicon (1 1 1) substrate. In the (0 0 0 2) and (1 0 1 bar 2) X-ray rocking curve analysis, a narrower value of full width at half-maximum has been obtained as the nitridation time increased. This is signifying the reduction of dislocation density in the gallium nitride epilayer. This result was supported by the value of bowing and root mean square roughness measured by surface profilometer and atomic force microscopy. Furthermore, a crack-free gallium nitride surface with an abrupt cross-sectional structure that observed using field effect scanning electron microscopy was also been obtained. The phi-scan curve of asymmetric gallium nitride proved the top gallium nitride epilayer exhibited a single-crystalline structure.

  7. Transistors using crystalline silicon devices on glass

    DOEpatents

    McCarthy, A.M.

    1995-05-09

    A method is disclosed for fabricating transistors using single-crystal silicon devices on glass. This method overcomes the potential damage that may be caused to the device during high voltage bonding and employs a metal layer which may be incorporated as part of the transistor. This is accomplished such that when the bonding of the silicon wafer or substrate to the glass substrate is performed, the voltage and current pass through areas where transistors will not be fabricated. After removal of the silicon substrate, further metal may be deposited to form electrical contact or add functionality to the devices. By this method both single and gate-all-around devices may be formed. 13 figs.

  8. Crystalline-silicon photovoltaics: Necessary and sufficient

    SciTech Connect

    Basore, P.A.; Gee, J.M.

    1995-01-01

    Photovoltaic (PV) energy systems have always been dominated by crystalline-silicon (c-Si) technology, and recent developments persuasively suggest that c-Si will continue to be the dominant technology well into the next century. The authors explain why c-Si technology is fairing much better than previously expected, and discuss the impact of improvements currently under development. They use a ground-up, engineering-based approach to predict the expected evolution of this type of PV system, and argue that c-Si PV will be in a position to compete for the US residential power market starting in about the year 2010. This market alone will provide the opportunity for PV to supply several percent of the electrical energy used in the United States. Crystalline-silicon technology is therefore not just necessary for building a near-term PV industry; it also offers a low-risk approach to meeting long-term goals for PV energy systems.

  9. Crystalline to amorphous transformation in silicon

    SciTech Connect

    Cheruvu, S.M.

    1982-09-01

    In the present investigation, an attempt was made to understand the fundamental mechanism of crystalline-to-amorphous transformation in arsenic implanted silicon using high resolution electron microscopy. A comparison of the gradual disappearance of simulated lattice fringes with increasing Frenkel pair concentration with the experimental observation of sharp interfaces between crystalline and amorphous regions was carried out leading to the conclusion that when the defect concentration reaches a critical value, the crystal does relax to an amorphous state. Optical diffraction experiments using atomic models also supported this hypothesis. Both crystalline and amorphous zones were found to co-exist with sharp interfaces at the atomic level. Growth of the amorphous fraction depends on the temperature, dose rate and the mass of the implanted ion. Preliminary results of high energy electron irradiation experiments at 1.2 MeV also suggested that clustering of point defects occurs near room temperature. An observation in a high resolution image of a small amorphous zone centered at the core of a dislocation is presented as evidence that the nucleation of an amorphous phase is heterogeneous in nature involving clustering or segregation of point defects near existing defects.

  10. Deuterium in crystalline and amorphous silicon

    SciTech Connect

    Borzi, R.; Ma, H.; Fedders, P.A.; Leopold, D.J.; Norberg, R.E.; Boyce, J.B.; Johnson, N.M.; Ready, S.E.; Walker, J.

    1997-07-01

    The authors report deuteron magnetic resonance (DMR) measurements on aged deuterium-implanted single crystal n-type silicon and comparisons with amorphous silicon spectra. The sample film was prepared six years ago by deuteration from a-D{sub 2} plasma and evaluated by a variety of experimental methods. Deuterium has been evolving with time and the present DMR signal shows a smaller deuteron population. A doublet from Si-D configurations along (111) has decreased more than have central molecular DMR components, which include 47 and 12 kHz FWHM gaussians. Transient DMR magnetization recoveries indicate spin lattice relaxation to para-D{sub 2} relaxation centers.

  11. Ionization induced damage in crystalline silicon

    NASA Technical Reports Server (NTRS)

    Meulenberg, A., Jr.

    1977-01-01

    Close examination of the interaction of the energetic knock-on atoms with the local lattice environment reveals a damage mechanism which does satisfy the experimental data on proton irradiation of silicon. A proton-atom interaction with high energy transfer is considered where the proton path is delineated by a trail of ionization, and the silicon ion path is characterized by much heavier ionization terminating in a dense displacement cluster. At collision, many of the silicon electrons are stripped off, and the resulting energetic ion subsequently loses energy rapidly by Coulomb interaction with bound electrons. The rate of energy loss depends on the charge state and velocity of the knock-on ion. For ion energies in excess of 1 MeV, the intensity of ionization is sufficient to permit lattice atoms, stripped of their binding electrons, to reorient randomly before having an opportunity to recombine with electrons and re-establish the lattice. The path of a knock-on ion thus becomes a thin cylinder of amorphous material within the crystal. Amorphous silicon has a Fermi level closer to mid-band than does single crystal silicon, and a strong field therefore, results around this damaged region. The field produces a large depletion region, representing a very large capture cross section for minority carriers.

  12. Single crystal functional oxides on silicon

    PubMed Central

    Bakaul, Saidur Rahman; Serrao, Claudy Rayan; Lee, Michelle; Yeung, Chun Wing; Sarker, Asis; Hsu, Shang-Lin; Yadav, Ajay Kumar; Dedon, Liv; You, Long; Khan, Asif Islam; Clarkson, James David; Hu, Chenming; Ramesh, Ramamoorthy; Salahuddin, Sayeef

    2016-01-01

    Single-crystalline thin films of complex oxides show a rich variety of functional properties such as ferroelectricity, piezoelectricity, ferro and antiferromagnetism and so on that have the potential for completely new electronic applications. Direct synthesis of such oxides on silicon remains challenging because of the fundamental crystal chemistry and mechanical incompatibility of dissimilar interfaces. Here we report integration of thin (down to one unit cell) single crystalline, complex oxide films onto silicon substrates, by epitaxial transfer at room temperature. In a field-effect transistor using a transferred lead zirconate titanate layer as the gate insulator, we demonstrate direct reversible control of the semiconductor channel charge with polarization state. These results represent the realization of long pursued but yet to be demonstrated single-crystal functional oxides on-demand on silicon. PMID:26853112

  13. Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

    DOEpatents

    Lowden, R.A.

    1994-04-05

    A process for chemical vapor deposition of crystalline silicon nitride is described which comprises the steps of: introducing a mixture of a silicon source, a molybdenum source, a nitrogen source, and a hydrogen source into a vessel containing a suitable substrate; and thermally decomposing the mixture to deposit onto the substrate a coating comprising crystalline silicon nitride containing a dispersion of molybdenum silicide. 5 figures.

  14. Process for producing amorphous and crystalline silicon nitride

    DOEpatents

    Morgan, P.E.D.; Pugar, E.A.

    1985-11-12

    A process for producing amorphous or crystalline silicon nitride is disclosed which comprises reacting silicon disulfide ammonia gas at elevated temperature. In a preferred embodiment silicon disulfide in the form of whiskers'' or needles is heated at temperature ranging from about 900 C to about 1,200 C to produce silicon nitride which retains the whisker or needle morphological characteristics of the silicon disulfide. Silicon carbide, e.g. in the form of whiskers, also can be prepared by reacting substituted ammonia, e.g. methylamine, or a hydrocarbon containing active hydrogen-containing groups, such as ethylene, with silicon disulfide, at elevated temperature, e.g. 900 C. 6 figs.

  15. Process for producing amorphous and crystalline silicon nitride

    DOEpatents

    Morgan, Peter E. D.; Pugar, Eloise A.

    1985-01-01

    A process for producing amorphous or crystalline silicon nitride is disclosed which comprises reacting silicon disulfide ammonia gas at elevated temperature. In a preferred embodiment silicon disulfide in the form of "whiskers" or needles is heated at temperature ranging from about 900.degree. C. to about 1200.degree. C. to produce silicon nitride which retains the whisker or needle morphological characteristics of the silicon disulfide. Silicon carbide, e.g. in the form of whiskers, also can be prepared by reacting substituted ammonia, e.g. methylamine, or a hydrocarbon containing active hydrogen-containing groups, such as ethylene, with silicon disulfide, at elevated temperature, e.g. 900.degree. C.

  16. Crystalline silicon germanium films grown on crystalline silicon substrates by solid phase crystallization

    NASA Astrophysics Data System (ADS)

    Kojima, Yuji; Isomura, Masao

    2015-08-01

    We researched on crystalline silicon-germanium films (c-SiGe) for bottom cells of silicon-based multijunction solar cells. We conducted the epitaxial crystal growth of SiGe with approximately 75% Ge fraction due to solid phase crystallization (SPC) from amorphous silicon-germanium (a-SiGe) precursors on n-type (100) Si substrates. We evaluated the preparation conditions of a-SiGe precursors for the SPC epitaxial growth. The epitaxial growth was successfully conducted and (100)-oriented c-SiGe films were formed. The epitaxial growth was effectively promoted in the a-SiGe precursors prepared at the substrate temperature from 250 to 300 °C, but is not sufficiently promoted in the a-SiGe precursors prepared below 250 °C. The density of a-SiGe precursors is relatively low at the substrate temperature below 250 °C, and the low-density structures cause the impurity incorporation from the air-exposed surface. The impurities are probably the main cause of disturbance of the epitaxial growth. On the other hand, the random crystallization occurred in the SPC of the a-SiGe precursors prepared at 350 °C. The precursors have the slightly crystallized structure and are not suitable for the SPC.

  17. Lithiation of Crystalline Silicon As Analyzed by Operando Neutron Reflectivity.

    PubMed

    Seidlhofer, Beatrix-Kamelia; Jerliu, Bujar; Trapp, Marcus; Hüger, Erwin; Risse, Sebastian; Cubitt, Robert; Schmidt, Harald; Steitz, Roland; Ballauff, Matthias

    2016-08-23

    We present an operando neutron reflectometry study on the electrochemical incorporation of lithium into crystalline silicon for battery applications. Neutron reflectivity is measured from the ⟨100⟩ surface of a silicon single crystal which is used as a negative electrode in an electrochemical cell. The strong scattering contrast between Si and Li due to the negative scattering length of Li leads to a precise depth profile of Li within the Si anode as a function of time. The operando cell can be used to study the uptake and the release of Li over several cycles. Lithiation starts with the formation of a lithium enrichment zone during the first charge step. The uptake of Li can be divided into a highly lithiated zone at the surface (skin region) (x ∼ 2.5 in LixSi) and a much less lithiated zone deep into the crystal (growth region) (x ∼ 0.1 in LixSi). The total depth of penetration was less than 100 nm in all experiments. The thickness of the highly lithiated zone is the same for the first and second cycle, whereas the thickness of the less lithiated zone is larger for the second lithiation. A surface layer of lithium (x ∼ 1.1) remains in the silicon electrode after delithiation. Moreover, a solid electrolyte interface is formed and dissolved during the entire cycling. The operando analysis presented here demonstrates that neutron reflectivity allows the tracking of the kinetics of lithiation and delithiation of silicon with high spatial and temporal resolution. PMID:27447734

  18. Laterally inherently thin amorphous-crystalline silicon heterojunction photovoltaic cell

    SciTech Connect

    Chowdhury, Zahidur R. Kherani, Nazir P.

    2014-12-29

    This article reports on an amorphous-crystalline silicon heterojunction photovoltaic cell concept wherein the heterojunction regions are laterally narrow and distributed amidst a backdrop of well-passivated crystalline silicon surface. The localized amorphous-crystalline silicon heterojunctions consisting of the laterally thin emitter and back-surface field regions are precisely aligned under the metal grid-lines and bus-bars while the remaining crystalline silicon surface is passivated using the recently proposed facile grown native oxide–plasma enhanced chemical vapour deposited silicon nitride passivation scheme. The proposed cell concept mitigates parasitic optical absorption losses by relegating amorphous silicon to beneath the shadowed metallized regions and by using optically transparent passivation layer. A photovoltaic conversion efficiency of 13.6% is obtained for an untextured proof-of-concept cell illuminated under AM 1.5 global spectrum; the specific cell performance parameters are V{sub OC} of 666 mV, J{sub SC} of 29.5 mA-cm{sup −2}, and fill-factor of 69.3%. Reduced parasitic absorption, predominantly in the shorter wavelength range, is confirmed with external quantum efficiency measurement.

  19. Laterally inherently thin amorphous-crystalline silicon heterojunction photovoltaic cell

    NASA Astrophysics Data System (ADS)

    Chowdhury, Zahidur R.; Kherani, Nazir P.

    2014-12-01

    This article reports on an amorphous-crystalline silicon heterojunction photovoltaic cell concept wherein the heterojunction regions are laterally narrow and distributed amidst a backdrop of well-passivated crystalline silicon surface. The localized amorphous-crystalline silicon heterojunctions consisting of the laterally thin emitter and back-surface field regions are precisely aligned under the metal grid-lines and bus-bars while the remaining crystalline silicon surface is passivated using the recently proposed facile grown native oxide-plasma enhanced chemical vapour deposited silicon nitride passivation scheme. The proposed cell concept mitigates parasitic optical absorption losses by relegating amorphous silicon to beneath the shadowed metallized regions and by using optically transparent passivation layer. A photovoltaic conversion efficiency of 13.6% is obtained for an untextured proof-of-concept cell illuminated under AM 1.5 global spectrum; the specific cell performance parameters are VOC of 666 mV, JSC of 29.5 mA-cm-2, and fill-factor of 69.3%. Reduced parasitic absorption, predominantly in the shorter wavelength range, is confirmed with external quantum efficiency measurement.

  20. Fabricating metal-oxide-semiconductor field-effect transistors on a polyethylene terephthalate substrate by applying low-temperature layer transfer of a single-crystalline silicon layer by meniscus force

    SciTech Connect

    Sakaike, Kohei; Akazawa, Muneki; Nakamura, Shogo; Higashi, Seiichiro

    2013-12-02

    A low-temperature local-layer technique for transferring a single-crystalline silicon (c-Si) film by using a meniscus force was proposed, and an n-channel metal-oxide-semiconductor field-effect transistor (MOSFET) was fabricated on polyethylene terephthalate (PET) substrate. It was demonstrated that it is possible to transfer and form c-Si films in the required shape at the required position on PET substrates at extremely low temperatures by utilizing a meniscus force. The proposed technique for layer transfer was applied for fabricating high-performance c-Si MOSFETs on a PET substrate. The fabricated MOSFET showed a high on/off ratio of more than 10{sup 8} and a high field-effect mobility of 609 cm{sup 2} V{sup −1} s{sup −1}.

  1. Magnetotransport of single crystalline YSb.

    PubMed

    Ghimire, N J; Botana, A S; Phelan, D; Zheng, H; Mitchell, J F

    2016-06-15

    We report magnetic field dependent transport measurements on a single crystal of cubic YSb together with first principles calculations of its electronic structure. The transverse magnetoresistance does not saturate up to 9 T and attains a value of 75 000% at 1.8 K. The Hall coefficient is electron-like at high temperature, changes sign to hole-like between 110 and 50 K, and again becomes electron-like below 50 K. First principles calculations show that YSb is a compensated semimetal with a qualitatively similar electronic structure to that of isostructural LaSb and LaBi, but with larger Fermi surface volume. The measured electron carrier density and Hall mobility calculated at 1.8 K, based on a single band approximation, are [Formula: see text] cm(-3) and [Formula: see text] cm(2) Vs(-1), respectively. These values are comparable with those reported for LaBi and LaSb. Like LaBi and LaSb, YSb undergoes a magnetic field-induced metal-insulator-like transition below a characteristic temperature T m, with resistivity saturation below 13 K. Thickness dependent electrical resistance measurements show a deviation of the resistance behavior from that expected for a normal metal; however, they do not unambiguously establish surface conduction as the mechanism for the resistivity plateau. PMID:27160492

  2. Magnetotransport of single crystalline YSb

    NASA Astrophysics Data System (ADS)

    Ghimire, N. J.; Botana, A. S.; Phelan, D.; Zheng, H.; Mitchell, J. F.

    2016-06-01

    We report magnetic field dependent transport measurements on a single crystal of cubic YSb together with first principles calculations of its electronic structure. The transverse magnetoresistance does not saturate up to 9 T and attains a value of 75 000% at 1.8 K. The Hall coefficient is electron-like at high temperature, changes sign to hole-like between 110 and 50 K, and again becomes electron-like below 50 K. First principles calculations show that YSb is a compensated semimetal with a qualitatively similar electronic structure to that of isostructural LaSb and LaBi, but with larger Fermi surface volume. The measured electron carrier density and Hall mobility calculated at 1.8 K, based on a single band approximation, are 6.5× {{10}20} cm‑3 and 6.2× {{10}4} cm2 Vs‑1, respectively. These values are comparable with those reported for LaBi and LaSb. Like LaBi and LaSb, YSb undergoes a magnetic field-induced metal-insulator-like transition below a characteristic temperature T m, with resistivity saturation below 13 K. Thickness dependent electrical resistance measurements show a deviation of the resistance behavior from that expected for a normal metal; however, they do not unambiguously establish surface conduction as the mechanism for the resistivity plateau.

  3. Thermal properties of amorphous/crystalline silicon superlattices.

    PubMed

    France-Lanord, Arthur; Merabia, Samy; Albaret, Tristan; Lacroix, David; Termentzidis, Konstantinos

    2014-09-01

    Thermal transport properties of crystalline/amorphous silicon superlattices using molecular dynamics are investigated. We show that the cross-plane conductivity of the superlattices is very low and close to the conductivity of bulk amorphous silicon even for amorphous layers as thin as ≃ 6 Å. The cross-plane thermal conductivity weakly increases with temperature which is associated with a decrease of the Kapitza resistance with temperature at the crystalline/amorphous interface. This property is further investigated considering the spatial analysis of the phonon density of states in domains close to the interface. Interestingly, the crystalline/amorphous superlattices are shown to display large thermal anisotropy, according to the characteristic sizes of elaborated structures. These last results suggest that the thermal conductivity of crystalline/amorphous superlattices can be phonon engineered, providing new directions for nanostructured thermoelectrics and anisotropic materials in thermal transport. PMID:25105883

  4. New opportunities in crystalline silicon R D

    SciTech Connect

    Menna, P. )

    1999-03-01

    To support the expected growth of the silicon solar cell industry, we believe that research and development (R D) activities should be carried out in the following areas: [ital polysilicon feedstock] for the PV industry; [ital thin-layer silicon] deposition methods, and more [ital environmentally benign] cell and module manufacturing processes. For each of these activities, we identify the main issues that needed to be addressed. [copyright] [ital 1999 American Institute of Physics.

  5. A Single-Crystalline Mesoporous Quartz Superlattice.

    PubMed

    Matsuno, Takamichi; Kuroda, Yoshiyuki; Kitahara, Masaki; Shimojima, Atsushi; Wada, Hiroaki; Kuroda, Kazuyuki

    2016-05-10

    There has been significant interest in the crystallization of nanostructured silica into α-quartz because of its physicochemical properties. We demonstrate a single-crystalline mesoporous quartz superlattice, a silica polymorph with unprecedentedly ordered hierarchical structures on both the several tens of nanometers scale and the atomic one. The mesoporous quartz superlattice consists of periodically arranged α-quartz nanospheres whose crystalline axes are mostly oriented in an assembly. The superlattice is prepared by thermal crystallization of amorphous silica nanospheres constituting a colloidal crystal. We found that the deposition of a strong flux of Li(+) only on the surface of silica nanospheres is effective for crystallization. PMID:27060365

  6. Surface passivation of heavily boron or phosphorus doped crystalline silicon utilizing amorphous silicon

    NASA Astrophysics Data System (ADS)

    Carstens, K.; Dahlinger, M.

    2016-05-01

    Excellent surface passivation of heavily boron or phosphorus doped crystalline silicon is presented utilizing undoped hydrogenated amorphous silicon (a-Si:H). For passivating boron doped crystalline silicon surfaces, amorphous silicon needs to be deposited at low temperatures 150°C ≤Tdep≤200°C , leading to a high bandgap. In contrast, low bandgap amorphous silicon causes an inferior surface passivation of highly boron doped crystalline silicon. Boron doping in crystalline silicon leads to a shift of the Fermi energy towards the valence band maximum in the undoped a-Si:H. A simulation, implementing dangling bond defects according to the defect pool model, shows this shift in the undoped a-Si:H passivation to be more pronounced if the a-Si:H has a lower bandgap. Hence, the inferior passivation of boron doped surfaces with low bandgap amorphous silicon stems from a lower silicon-hydrogen bond energy due to this shift of the Fermi energy. Hydrogen effusion and ellipsometry measurements support our interpretation.

  7. 77 FR 4764 - Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules, From the People's...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-31

    ... Preliminary Determination in the Countervailing Duty Investigation, 76 FR 81914 (December 29, 2011... International Trade Administration Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules... duty investigation of crystalline silicon photovoltaic cells, whether or not assembled into...

  8. 77 FR 73017 - Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules, From the People's...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-07

    ... Determination and Final Affirmative Critical Circumstances Determination, 77 FR 63788 (October 17, 2012). Scope... International Trade Administration Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules... issuing a countervailing duty order on crystalline silicon photovoltaic cells, whether or not...

  9. High Efficiency, Low Cost Solar Cells Manufactured Using 'Silicon Ink' on Thin Crystalline Silicon Wafers

    SciTech Connect

    Antoniadis, H.

    2011-03-01

    Reported are the development and demonstration of a 17% efficient 25mm x 25mm crystalline Silicon solar cell and a 16% efficient 125mm x 125mm crystalline Silicon solar cell, both produced by Ink-jet printing Silicon Ink on a thin crystalline Silicon wafer. To achieve these objectives, processing approaches were developed to print the Silicon Ink in a predetermined pattern to form a high efficiency selective emitter, remove the solvents in the Silicon Ink and fuse the deposited particle Silicon films. Additionally, standard solar cell manufacturing equipment with slightly modified processes were used to complete the fabrication of the Silicon Ink high efficiency solar cells. Also reported are the development and demonstration of a 18.5% efficient 125mm x 125mm monocrystalline Silicon cell, and a 17% efficient 125mm x 125mm multicrystalline Silicon cell, by utilizing high throughput Ink-jet and screen printing technologies. To achieve these objectives, Innovalight developed new high throughput processing tools to print and fuse both p and n type particle Silicon Inks in a predetermined pat-tern applied either on the front or the back of the cell. Additionally, a customized Ink-jet and screen printing systems, coupled with customized substrate handling solution, customized printing algorithms, and a customized ink drying process, in combination with a purchased turn-key line, were used to complete the high efficiency solar cells. This development work delivered a process capable of high volume producing 18.5% efficient crystalline Silicon solar cells and enabled the Innovalight to commercialize its technology by the summer of 2010.

  10. Molecular dynamics studies of the bonding properties of amorphous silicon nitride coatings on crystalline silicon

    NASA Astrophysics Data System (ADS)

    Butler, Keith T.; Lamers, Machteld P. W. E.; Weeber, Arthur W.; Harding, John H.

    2011-12-01

    In this paper we present molecular dynamics simulations of silicon nitride, both in bulk and as an interface to crystalline silicon. We investigate, in particular, the bonding structure of the silicon nitride and analyze the simulations to search for defective geometries which have been identified as potential charge carrier traps when silicon nitride forms an interface with silicon semiconductors. The simulations reveal how the bonding patterns in silicon nitride are dependent upon the stoichiometry of the system. Furthermore we demonstrate how having an "interphase", where the nitrogen content in silicon gradually reduces toward pure silicon across a boundary region, as opposed to an interface where there is an abrupt drop in nitrogen concentration at the boundary, can result in significantly different numbers of certain important carrier trap.

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

    PubMed

    Kohno; Takeda; Tanaka

    2000-01-01

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

  12. Femtosecond studies of plasma formation in crystalline and amorphous silicon

    NASA Astrophysics Data System (ADS)

    Kuett, Waldemar; Esser, Anton; Seibert, Klaus; Lemmer, Uli; Kurz, Heinrich

    1990-08-01

    Transient pump-probe reflectivity measurements are performed on crystalline and amorphous Silicon samples with 50 fs optical pulses at 2 eV. The excited carrier densities range from 1017cm3 up to a few 1021cm3. In both cases the reflectivity signal is dominated by a Drude-like carrier response. Crystalline Silicon shows a distinct subpicosecond feature due to the cooling of the optically excited hot carriers with a time constant of 200-300 fs. Diffusion and Auger-recombination come into play at higher carrier densities. A superlinear increase of instant reflectivity signal with excitation fluence is due to two-photon absorption (TPA) with a TPA-coeffiecient f:37+-5 cm/GW. In amorphous Silicon the TPA process is not observable. The recovery of the induced negative reflectivity changes is dominated by trapping into bandtail and defect states at lower carrier densities. At higher densities a non-radiative recombination process dominates the relaxation of free carriers in both materials. Comparison with crystalline Silicon clearly demonstrates the enhancement of the Auger-recombination process in disordered materials by more than an order of magnitude.

  13. Method of forming crystalline silicon devices on glass

    DOEpatents

    McCarthy, A.M.

    1995-03-21

    A method is disclosed for fabricating single-crystal silicon microelectronic components on a silicon substrate and transferring same to a glass substrate. This is achieved by utilizing conventional silicon processing techniques for fabricating components of electronic circuits and devices on bulk silicon, wherein a bulk silicon surface is prepared with epitaxial layers prior to the conventional processing. The silicon substrate is bonded to a glass substrate and the bulk silicon is removed leaving the components intact on the glass substrate surface. Subsequent standard processing completes the device and circuit manufacturing. This invention is useful in applications requiring a transparent or insulating substrate, particularly for display manufacturing. Other applications include sensors, actuators, optoelectronics, radiation hard electronics, and high temperature electronics. 7 figures.

  14. Method of forming crystalline silicon devices on glass

    DOEpatents

    McCarthy, Anthony M.

    1995-01-01

    A method for fabricating single-crystal silicon microelectronic components on a silicon substrate and transferring same to a glass substrate. This is achieved by utilizing conventional silicon processing techniques for fabricating components of electronic circuits and devices on bulk silicon, wherein a bulk silicon surface is prepared with epitaxial layers prior to the conventional processing. The silicon substrate is bonded to a glass substrate and the bulk silicon is removed leaving the components intact on the glass substrate surface. Subsequent standard processing completes the device and circuit manufacturing. This invention is useful in applications requiring a transparent or insulating substrate, particularly for display manufacturing. Other applications include sensors, actuators, optoelectronics, radiation hard electronics, and high temperature electronics.

  15. Amorphous silicon carbide passivating layers for crystalline-silicon-based heterojunction solar cells

    SciTech Connect

    Boccard, Mathieu; Holman, Zachary C.

    2015-08-14

    Amorphous silicon enables the fabrication of very high-efficiency crystalline-silicon-based solar cells due to its combination of excellent passivation of the crystalline silicon surface and permeability to electrical charges. Yet, amongst other limitations, the passivation it provides degrades upon high-temperature processes, limiting possible post-deposition fabrication possibilities (e.g., forcing the use of low-temperature silver pastes). We investigate the potential use of intrinsic amorphous silicon carbide passivating layers to sidestep this issue. The passivation obtained using device-relevant stacks of intrinsic amorphous silicon carbide with various carbon contents and doped amorphous silicon are evaluated, and their stability upon annealing assessed, amorphous silicon carbide being shown to surpass amorphous silicon for temperatures above 300 °C. We demonstrate open-circuit voltage values over 700 mV for complete cells, and an improved temperature stability for the open-circuit voltage. Transport of electrons and holes across the hetero-interface is studied with complete cells having amorphous silicon carbide either on the hole-extracting side or on the electron-extracting side, and a better transport of holes than of electrons is shown. Also, due to slightly improved transparency, complete solar cells using an amorphous silicon carbide passivation layer on the hole-collecting side are demonstrated to show slightly better performances even prior to annealing than obtained with a standard amorphous silicon layer.

  16. Amorphous silicon carbide passivating layers for crystalline-silicon-based heterojunction solar cells

    DOE PAGESBeta

    Boccard, Mathieu; Holman, Zachary C.

    2015-08-14

    With this study, amorphous silicon enables the fabrication of very high-efficiency crystalline-silicon-based solar cells due to its combination of excellent passivation of the crystalline silicon surface and permeability to electrical charges. Yet, amongst other limitations, the passivation it provides degrades upon high-temperature processes, limiting possible post-deposition fabrication possibilities (e.g., forcing the use of low-temperature silver pastes). We investigate the potential use of intrinsic amorphous silicon carbide passivating layers to sidestep this issue. The passivation obtained using device-relevant stacks of intrinsic amorphous silicon carbide with various carbon contents and doped amorphous silicon are evaluated, and their stability upon annealing assessed, amorphousmore » silicon carbide being shown to surpass amorphous silicon for temperatures above 300°C. We demonstrate open-circuit voltage values over 700 mV for complete cells, and an improved temperature stability for the open-circuit voltage. Transport of electrons and holes across the hetero-interface is studied with complete cells having amorphous silicon carbide either on the hole-extracting side or on the electron-extracting side, and a better transport of holes than of electrons is shown. Also, due to slightly improved transparency, complete solar cells using an amorphous silicon carbide passivation layer on the hole-collecting side are demonstrated to show slightly better performances even prior to annealing than obtained with a standard amorphous silicon layer.« less

  17. Amorphous silicon carbide passivating layers for crystalline-silicon-based heterojunction solar cells

    SciTech Connect

    Boccard, Mathieu; Holman, Zachary C.

    2015-08-14

    With this study, amorphous silicon enables the fabrication of very high-efficiency crystalline-silicon-based solar cells due to its combination of excellent passivation of the crystalline silicon surface and permeability to electrical charges. Yet, amongst other limitations, the passivation it provides degrades upon high-temperature processes, limiting possible post-deposition fabrication possibilities (e.g., forcing the use of low-temperature silver pastes). We investigate the potential use of intrinsic amorphous silicon carbide passivating layers to sidestep this issue. The passivation obtained using device-relevant stacks of intrinsic amorphous silicon carbide with various carbon contents and doped amorphous silicon are evaluated, and their stability upon annealing assessed, amorphous silicon carbide being shown to surpass amorphous silicon for temperatures above 300°C. We demonstrate open-circuit voltage values over 700 mV for complete cells, and an improved temperature stability for the open-circuit voltage. Transport of electrons and holes across the hetero-interface is studied with complete cells having amorphous silicon carbide either on the hole-extracting side or on the electron-extracting side, and a better transport of holes than of electrons is shown. Also, due to slightly improved transparency, complete solar cells using an amorphous silicon carbide passivation layer on the hole-collecting side are demonstrated to show slightly better performances even prior to annealing than obtained with a standard amorphous silicon layer.

  18. Amorphous silicon carbide passivating layers for crystalline-silicon-based heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Boccard, Mathieu; Holman, Zachary C.

    2015-08-01

    Amorphous silicon enables the fabrication of very high-efficiency crystalline-silicon-based solar cells due to its combination of excellent passivation of the crystalline silicon surface and permeability to electrical charges. Yet, amongst other limitations, the passivation it provides degrades upon high-temperature processes, limiting possible post-deposition fabrication possibilities (e.g., forcing the use of low-temperature silver pastes). We investigate the potential use of intrinsic amorphous silicon carbide passivating layers to sidestep this issue. The passivation obtained using device-relevant stacks of intrinsic amorphous silicon carbide with various carbon contents and doped amorphous silicon are evaluated, and their stability upon annealing assessed, amorphous silicon carbide being shown to surpass amorphous silicon for temperatures above 300 °C. We demonstrate open-circuit voltage values over 700 mV for complete cells, and an improved temperature stability for the open-circuit voltage. Transport of electrons and holes across the hetero-interface is studied with complete cells having amorphous silicon carbide either on the hole-extracting side or on the electron-extracting side, and a better transport of holes than of electrons is shown. Also, due to slightly improved transparency, complete solar cells using an amorphous silicon carbide passivation layer on the hole-collecting side are demonstrated to show slightly better performances even prior to annealing than obtained with a standard amorphous silicon layer.

  19. Method for fabricating an ultra-low expansion mask blank having a crystalline silicon layer

    DOEpatents

    Cardinale, Gregory F.

    2002-01-01

    A method for fabricating masks for extreme ultraviolet lithography (EUVL) using Ultra-Low Expansion (ULE) substrates and crystalline silicon. ULE substrates are required for the necessary thermal management in EUVL mask blanks, and defect detection and classification have been obtained using crystalline silicon substrate materials. Thus, this method provides the advantages for both the ULE substrate and the crystalline silicon in an Extreme Ultra-Violet (EUV) mask blank. The method is carried out by bonding a crystalline silicon wafer or member to a ULE wafer or substrate and thinning the silicon to produce a 5-10 .mu.m thick crystalline silicon layer on the surface of the ULE substrate. The thinning of the crystalline silicon may be carried out, for example, by chemical mechanical polishing and if necessary or desired, oxidizing the silicon followed by etching to the desired thickness of the silicon.

  20. Low-cost industrial technologies of crystalline silicon solar cells

    SciTech Connect

    Szlufcik, J.; Sivoththaman, S.; Nijs, J.F.; Mertens, R.P.; Overstraeten, R. van

    1997-05-01

    Approximately 2 billion people, mainly in Third World countries, are not connected to an electric grid. The standard, centralized grid development is too expensive and time consuming to solve the energy demand problem. Therefore, there is a need for decentralized renewable energy sources. The main attractiveness of solar cells is that they generate electricity directly from sunlight and can be mounted in modular, stand-alone photovoltaic (PV) systems. Particular attention is paid in this paper to crystalline silicon solar cells, since bulk silicon solar-cell (mono and multi) modules comprise approximately 85% of all worldwide PV module shipments. Energy conversion efficiency as high as 24% has been achieved on laboratory, small-area monocrystalline silicon cells, whereas the typical efficiency of industrial crystalline silicon solar cells is in the range of 13--16%. The market price of PV modules has remained for the last few years in the range of $3.5--4.5/watt peak (Wp). For the photovoltaic industry, the biggest concern is to improve the efficiency and decrease the price of the commercial PV modules. Efficiency-enhancement techniques of commercial cells are described in detail. Adaptation of many high-efficiency features to industrially fabricated solar cells resulted in efficiencies above 17% for multicrystalline and above 18% for monocrystalline silicon solar cells. The latest study shows that increasing the PV market size toward 500 MWp/y and accounting for realistic industrial improvements can lead to a drastic PV module price reduction down to $1/Wp. 120 refs.

  1. MeV-ion beam analysis of the interface between filtered cathodic arc-deposited a-carbon and single crystalline silicon

    SciTech Connect

    Kamwanna, T.; Pasaja, N.; Yu, L.D.; Vilaithong, T.; Anders, A.; Singkarat, S.

    2008-08-01

    Amorphous carbon (a-C) films were deposited on Si(100) wafers by a filtered cathodicvacuum arc (FCVA) plasma source. A negative electrical bias was applied tothe silicon substrate in order to control the incident energy of carbon ions. Effects ofthe electrical bias on the a-C/Si interface characteristics were investigated by usingstandard Rutherford backscattering spectrometry (RBS) in the channeling modewith 2.1-MeV He2+ ions. The shape of the Si surface peaks of the RBS/channelingspectra reflects the degree of interface disorder due to atomic displacement fromthe bulk position of the Si crystal. Details of the analysis method developed aredescribed. It was found that the width of the a-C/Si interface increases linearlywith the substrate bias voltage but not the thickness of the a-C film.

  2. Controlled synthesis of single-crystalline graphene

    SciTech Connect

    Xueshen, Wang Jinjin, Li Qing, Zhong; Yuan, Zhong; Mengke, Zhao; Yonggang, Liu

    2014-03-15

    This paper reports the controlled synthesis of single-crystalline graphene on the back side of copper foil using CH{sub 4} as the precursor. The influence of growth time and the pressure ratio of CH{sub 4}/H{sub 2} on the structure of graphene are examined. An optimized polymer-assisted method is used to transfer the synthesized graphene onto a SiO{sub 2}/Si substrate. Scanning electron microscopy and Raman spectroscopy are used to characterize the graphene.

  3. Crystalline-silicon reliability lessons for thin-film modules

    NASA Technical Reports Server (NTRS)

    Ross, R. G., Jr.

    1985-01-01

    The reliability of crystalline silicon modules has been brought to a high level with lifetimes approaching 20 years, and excellent industry credibility and user satisfaction. The transition from crystalline modules to thin film modules is comparable to the transition from discrete transistors to integrated circuits. New cell materials and monolithic structures will require new device processing techniques, but the package function and design will evolve to a lesser extent. Although there will be new encapsulants optimized to take advantage of the mechanical flexibility and low temperature processing features of thin films, the reliability and life degradation stresses and mechanisms will remain mostly unchanged. Key reliability technologies in common between crystalline and thin film modules include hot spot heating, galvanic and electrochemical corrosion, hail impact stresses, glass breakage, mechanical fatigue, photothermal degradation of encapsulants, operating temperature, moisture sorption, circuit design strategies, product safety issues, and the process required to achieve a reliable product from a laboratory prototype.

  4. Crystalline micro/nanostructures fabrication on silicon using femtosecond laser

    NASA Astrophysics Data System (ADS)

    Deng, Guoliang; Yang, Xianheng; Feng, Guoying; Zhou, Shouhuan

    2015-02-01

    The laser induced micro/ nano-meter size surface structures are fabricated by multi linear polarized femtosecond laser pulses (pulse duration τ=35 fs, wavelength λ=800 nm) irradiation at room temperature(25 ° ) and 400 °. The structures fabricated at these two temperatures show distinct temperature dependence. The grooves, which are parallel to the polarization of the laser light, can be clearly observed at almost all the structured area formed at 400 ° while laser induced period structures(ripples) are the most pronounced surface structure in the crater formed at room temperature. The crystallinity of these surface structures are investigated by using Raman spectroscopy. The Raman spectrum shows that all the structured area formed at 400 ° is crystalline(or poly-crystalline) while amorphous silicon can be observed within the structures formed at room temperature (25 °). These results indicate that temperature is an important parameter to be tuned to tailor the micro/nano-structure fabrication.

  5. Efficient Crystalline Si Solar Cell with Amorphous/Crystalline Silicon Heterojunction as Back Contact: Preprint

    SciTech Connect

    Nemeth, B.; Wang, Q.; Shan, W.

    2012-06-01

    We study an amorphous/crystalline silicon heterojunction (Si HJ) as a back contact in industrial standard p-type five-inch pseudo-square wafer to replace Al back surface field (BSF) contact. The best efficiency in this study is over 17% with open-circuit (Voc) of 0.623 V, which is very similar to the control cell with Al BSF. We found that Voc has not been improved with the heterojunction structure in the back. The typical minority carrier lifetime of these wafers is on the order of 10 us. We also found that the doping levels of p-layer affect the FF due to conductivity and band gap shifting, and an optimized layer is identified. We conclude that an amorphous/crystalline silicon heterojunction can be a very promising structure to replace Al BSF back contact.

  6. Method for fabricating transistors using crystalline silicon devices on glass

    DOEpatents

    McCarthy, Anthony M.

    1997-01-01

    A method for fabricating transistors using single-crystal silicon devices on glass. This method overcomes the potential damage that may be caused to the device during high voltage bonding and employs a metal layer which may be incorporated as part of the transistor. This is accomplished such that when the bonding of the silicon wafer or substrate to the glass substrate is performed, the voltage and current pass through areas where transistors will not be fabricated. After removal of the silicon substrate, further metal may be deposited to form electrical contact or add functionality to the devices. By this method both single and gate-all-around devices may be formed.

  7. Enhanced crystallinity of low temperature deposited silicon films on graphite subtrates

    NASA Technical Reports Server (NTRS)

    Chang, C. A.

    1975-01-01

    The previously developed technique of a sandwich coating for silicon crystallinity enhancement in silicon films deposited at low temperature is applied to graphite substrates. The measured increase in silicon crystallinity is comparable to that observed earlier using a quartz substrate. The distribution of aluminum in the silicon films is determined using Auger spectroscopic depth profiling. Carbon diffusion from the substrate into the silicon film is shown to be negligible at a substrate temperature of 600 C.

  8. Direct electrodeposition of crystalline silicon at low temperatures.

    PubMed

    Gu, Junsi; Fahrenkrug, Eli; Maldonado, Stephen

    2013-02-01

    An electrochemical liquid-liquid-solid (ec-LLS) process that yields crystalline silicon at low temperature (80 °C) without any physical or chemical templating agent has been demonstrated. Electroreduction of dissolved SiCl(4) in propylene carbonate using a liquid gallium [Ga(l)] pool as the working electrode consistently yielded crystalline Si. X-ray diffraction and electron diffraction data separately indicated that the as-deposited materials were crystalline with the expected patterns for a diamond cubic crystal structure. Scanning and transmission electron microscopies further revealed the as-deposited materials (i.e., with no annealing) to be faceted nanocrystals with diameters in excess of 500 nm. Energy-dispersive X-ray spectra further showed no evidence of any other species within the electrodeposited crystalline Si. Raman spectra separately showed that the electrodeposited films on the Ga(l) electrodes were not composed of amorphous carbon from solvent decomposition. The cumulative data support two primary contentions. First, a liquid-metal electrode can serve simultaneously as both a source of electrons for the heterogeneous reduction of dissolved Si precursor in the electrolyte (i.e., a conventional electrode) and a separate phase (i.e., a solvent) that promotes Si crystal growth. Second, ec-LLS is a process that can be exploited for direct production of crystalline Si at much lower temperatures than ever reported previously. The further prospect of ec-LLS as an electrochemical and non-energy-intensive route for preparing crystalline Si is discussed. PMID:23347180

  9. Growth Of Single Crystalline Copper Nanowhiskers

    SciTech Connect

    Kolb, Matthias; Richter, Gunther

    2010-11-24

    Nanowhiskers are defect free single crystals with high aspect ratios and as result exhibit superior physical, e.g. mechanical properties. This paper sheds light on the kinetics of copper nanowhisker growth and thickening. Whisker growth was provoked by covering silicon wafers with a thin carbon film and subsequently coating them with copper by molecular beam epitaxy. The whiskers grown were examined by scanning electron microscopy and the length and diameter were measured as a function of the amount of copper deposited. The experiments show that nanowhisker growth follows Ruth and Hirth's growth model. A fit of the model parameters to the acquired data shows that adsorption of atoms on the substrate and on the whisker surface, with subsequent surface diffusion to the whisker tip, delivers by far the greatest portion of material for whisker growth. Additionally, the experiments demonstrate that the crystallographic orientation of the substrate surface greatly influences the growth rate in the early stage of whisker growth.

  10. Thermal conductivity reduction of crystalline silicon by high-pressure torsion

    NASA Astrophysics Data System (ADS)

    Harish, Sivasankaran; Tabara, Mitsuru; Ikoma, Yoshifumi; Horita, Zenji; Takata, Yasuyuki; Cahill, David G.; Kohno, Masamichi

    2014-06-01

    We report a dramatic and irreversible reduction in the lattice thermal conductivity of bulk crystalline silicon when subjected to intense plastic strain under a pressure of 24 GPa using high-pressure torsion (HPT). Thermal conductivity of the HPT-processed samples were measured using picosecond time domain thermoreflectance. Thermal conductivity measurements show that the HPT-processed samples have a lattice thermal conductivity reduction by a factor of approximately 20 (from intrinsic single crystalline value of 142 Wm-1 K-1 to approximately 7.6 Wm-1 K-1). Thermal conductivity reduction in HPT-processed silicon is attributed to the formation of nanograin boundaries and metastable Si-III/XII phases which act as phonon scattering sites, and because of a large density of lattice defects introduced by HPT processing. Annealing the samples at 873 K increases the thermal conductivity due to the reduction in the density of secondary phases and lattice defects.

  11. Back-Contact Crystalline-Silicon Solar Cells and Modules

    SciTech Connect

    Bode, M.D.; Garrett, S.E.; Gee, J.M.; Jimeno, J.C.; Smith, D.D.

    1999-03-10

    This paper summarizes recent progress in the development of back-contact crystalline-silicon (c-Si) solar cells and modules at Sandia National Laboratories. Back-contact cells have potentially improved efficiencies through the elimination of grid obscuration and allow for significant simplifications in the module assembly process. Optimization of the process sequence has improved the efficiency of our back-contact cell (emitter wrap through) from around 12% to near 17% in the past 12 months. In addition, recent theoretical work has elucidated the device physics of emitter wrap-through cells. Finally, improvements in the assembly processing back-contact cells are described.

  12. Solution-processed crystalline silicon double-heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Devkota, Ramesh; Liu, Qiming; Ohki, Tatsuya; Hossain, Jaker; Ueno, Keiji; Shirai, Hajime

    2016-02-01

    Crystalline silicon double-heterojunction solar cells were fabricated using Si/organic and Si/Cs2CO3 heterojunctions. The front heterojunction is formed by spin-coating conductive polymer poly(3,4-ethyenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) on n-type Czochralski (CZ) (100) silicon, which separates the photogenerated carriers and blocks the electron dark current while allowing the photocurrent to pass through. The rear heterojunction, formed by spin-coating Cs2CO3 and polyethylenimine (PEI) dissolved in 2-ethoxyethanol and Al metal evaporation, functions as a back surface field that reduces the hole dark current while allowing the electron photocurrent to pass through. The double-heterojunction device showed a power conversion efficiency of 12.7% under AM1.5G simulated solar light exposure.

  13. Inexpensive transparent nanoelectrode for crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Peng, Qiang; Pei, Ke; Han, Bing; Li, Ruopeng; Zhou, Guofu; Liu, Jun-Ming; Kempa, Krzysztof; Gao, Jinwei

    2016-06-01

    We report an easily manufacturable and inexpensive transparent conductive electrode for crystalline silicon (c-Si) solar cells. It is based on a silver nanoparticle network self-forming in the valleys between the pyramids of a textured solar cell surface, transformed into a nanowire network by sintering, and subsequently "buried" under the silicon surface by a metal-assisted chemical etching. We have successfully incorporated these steps into the conventional c-Si solar cell manufacturing process, from which we have eliminated the expensive screen printing and firing steps, typically used to make the macro-electrode of conducting silver fingers. The resulting, preliminary solar cell achieved power conversion efficiency only 14 % less than the conventionally processed c-Si control cell. We expect that a cell with an optimized processing will achieve at least efficiency of the conventional commercial cell, but at significantly reduced manufacturing cost.

  14. Inexpensive transparent nanoelectrode for crystalline silicon solar cells.

    PubMed

    Peng, Qiang; Pei, Ke; Han, Bing; Li, Ruopeng; Zhou, Guofu; Liu, Jun-Ming; Kempa, Krzysztof; Gao, Jinwei

    2016-12-01

    We report an easily manufacturable and inexpensive transparent conductive electrode for crystalline silicon (c-Si) solar cells. It is based on a silver nanoparticle network self-forming in the valleys between the pyramids of a textured solar cell surface, transformed into a nanowire network by sintering, and subsequently "buried" under the silicon surface by a metal-assisted chemical etching. We have successfully incorporated these steps into the conventional c-Si solar cell manufacturing process, from which we have eliminated the expensive screen printing and firing steps, typically used to make the macro-electrode of conducting silver fingers. The resulting, preliminary solar cell achieved power conversion efficiency only 14 % less than the conventionally processed c-Si control cell. We expect that a cell with an optimized processing will achieve at least efficiency of the conventional commercial cell, but at significantly reduced manufacturing cost. PMID:27356559

  15. Crystalline silicon solar cells with micro/nano texture

    NASA Astrophysics Data System (ADS)

    Dimitrov, Dimitre Z.; Du, Chen-Hsun

    2013-02-01

    Crystalline silicon solar cells with two-scale texture consisting of random upright pyramids and surface nanotextured layer directly onto the pyramids are prepared and reflectance properties and I-V characteristics measured. Random pyramids texture is produced by etching in an alkaline solution. On top of the pyramids texture, a nanotexture is developed using an electroless oxidation/etching process. Solar cells with two-scale surface texturization are prepared following the standard screen-printing technology sequence. The micro/nano surface is found to lower considerably the light reflectance of silicon. The short wavelengths spectral response (blue response) improvement is observed in micro/nano textured solar cells compared to standard upright pyramids textured cells. An efficiency of 17.5% is measured for the best micro/nano textured c-Si solar cell. The efficiency improvement is found to be due to the gain in both Jsc and Voc.

  16. Method for fabricating transistors using crystalline silicon devices on glass

    DOEpatents

    McCarthy, A.M.

    1997-09-02

    A method for fabricating transistors using single-crystal silicon devices on glass. This method overcomes the potential damage that may be caused to the device during high voltage bonding and employs a metal layer which may be incorporated as part of the transistor. This is accomplished such that when the bonding of the silicon wafer or substrate to the glass substrate is performed, the voltage and current pass through areas where transistors will not be fabricated. After removal of the silicon substrate, further metal may be deposited to form electrical contact or add functionality to the devices. By this method both single and gate-all-around devices may be formed. 13 figs.

  17. Multi-crystalline silicon solidification under controlled forced convection

    NASA Astrophysics Data System (ADS)

    Cablea, M.; Zaidat, K.; Gagnoud, A.; Nouri, A.; Chichignoud, G.; Delannoy, Y.

    2015-05-01

    Multi-crystalline silicon wafers have a lower production cost compared to mono-crystalline wafers. This comes at the price of reduced quality in terms of electrical properties and as a result the solar cells made from such materials have a reduced efficiency. The presence of different impurities in the bulk material plays an important role during the solidification process. The impurities are related to different defects (dislocations, grain boundaries) encountered in multi-crystalline wafers. Applying an alternative magnetic field during the solidification process has various benefits. Impurities concentration in the final ingot could be reduced, especially metallic species, due to a convective term added in the liquid that reduces the concentration of impurities in the solute boundary layer. Another aspect is the solidification interface shape that is influenced by the electromagnetic stirring. A vertical Bridgman type furnace was used in order to study the solidification process of Si under the influence of a travelling magnetic field able to induce a convective flow in the liquid. The furnace was equipped with a Bitter type three-phase electromagnet that provides the required magnetic field. A numerical model of the furnace was developed in ANSYS Fluent commercial software. This paper presents experimental and numerical results of this approach, where interface markings were performed.

  18. Test-to-Failure of Crystalline Silicon Modules: Preprint

    SciTech Connect

    Hacke, P.; Terwilliger, K.; Glick, S.; Trudell, D.; Bosco, N.; Johnston, S.; Kurtz, S. R.

    2010-10-01

    Accelerated lifetime testing of five crystalline silicon module designs was carried out according to the Terrestrial Photovoltaic Module Accelerated Test-to-Failure Protocol. This protocol compares the reliability of various module constructions on a quantitative basis. The modules under test are subdivided into three accelerated lifetime testing paths: 85..deg..C/85% relative humidity with system bias, thermal cycling between ?40..deg..C and 85..deg..C, and a path that alternates between damp heat and thermal cycling. The most severe stressor is damp heat with system bias applied to simulate the voltages that modules experience when connected in an array. Positive 600 V applied to the active layer with respect to the grounded module frame accelerates corrosion of the silver grid fingers and degrades the silicon nitride antireflective coating on the cells. Dark I-V curve fitting indicates increased series resistance and saturation current around the maximum power point; however, an improvement in junction recombination characteristics is obtained. Shunt paths and cell-metallization interface failures are seen developing in the silicon cells as determined by electroluminescence, thermal imaging, and I-V curves in the case of negative 600 V bias applied to the active layer. Ability to withstand electrolytic corrosion, moisture ingress, and ion drift under system voltage bias are differentiated.

  19. Selective-emitter crystalline silicon solar cells using phosphorus paste

    NASA Astrophysics Data System (ADS)

    Jeong, Kyung Taek; Kang, Min Gu; Song, Hee-eun

    2014-11-01

    Selective-emitter structures have been studied to improve the conversion efficiency of crystalline silicon solar cells. However, such structures require additional complicated processes and incur extra cost. In this work, we used phosphorus paste (P-paste) to form a heavily-doped region beneath the grid and POCl3 to create a shallow emitter area. This method should be convenient to use in the solar-cell industry because it requires only additional P paste printing, compared to the case of homogeneous solar cells. Diffusion parameters including the temperature, diffusion time, and ambient gases were optimized. We observed that the spreading of the P paste was affected by the pyramidal size of the textured wafer due to the low viscosity of the P paste. The pyramidal height of the textured silicon surface was optimized at 3 μm to counterbalance the surface reflectance and the spreading of the P paste. The short-circuit current density of the completed selective emitter solar cell was increased, and an improvement of blue response in the internal quantum efficiency was seen while contact properties such as the fill factor deteriorated due to the spreading of the P paste and the thin emitter on top of the pyramid of the textured silicon surface. Double printing of the P paste was applied to solve this contact problem; a fill factor improvement of 2.4% was obtained.

  20. 77 FR 37877 - Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules, From the People's...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-25

    ... Determination of Critical Circumstances, 77 FR 31309 (May 25, 2012), under the section entitled ``Preliminary... International Trade Administration Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules... determination in the antidumping duty investigation of crystalline silicon photovoltaic cells, whether or...

  1. 77 FR 72884 - Crystalline Silicon Photovoltaic Cells and Modules From China

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-06

    ... in the Federal Register on June 13, 2012 (77 FR 35425). The hearing was held in Washington, DC, on... COMMISSION Crystalline Silicon Photovoltaic Cells and Modules From China Determinations On the basis of the... reason of imports of crystalline silicon photovoltaic cells and modules from China, provided for...

  2. 76 FR 78313 - Crystalline Silicon Photovoltaic Cells and Modules From China

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-16

    ... notice in the Federal Register of October 27, 2011 (76 FR 66748). The conference was held in Washington... COMMISSION Crystalline Silicon Photovoltaic Cells and Modules From China Determinations On the basis of the... is materially injured by reason of imports from China of crystalline silicon photovoltaic cells...

  3. 77 FR 14732 - Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules, From the People's...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-13

    ... People's Republic of China: Initiation of Antidumping Duty Investigation, 76 FR 70960 (November 16, 2011... International Trade Administration Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules... of crystalline silicon photovoltaic cells, whether or not assembled into modules, from the...

  4. Multilayer structures of silicon-suboxide embedded in single crystal silicon

    NASA Astrophysics Data System (ADS)

    Pohl, Christoph; Raab, Nicolas; Mitterer, Martin; Tarakina, Nadezda; Breuer, Uwe; Brunner, Karl

    2014-03-01

    Si/SiOx multilayer structures with ultra-thin silicon-suboxide layers are fabricated with molecular beam epitaxy. The silicon surface is oxidized during growth interruptions at an oxygen pressure between 1.0×10-7 mbar and 8.0×10-7 mbar. Overgrowth with Si of the oxidized surface is possible for coverages of a few monolayers of O and improves with increasing substrate temperature. X-ray diffraction shows that the silicon layers are single crystalline. Transmission electron microscopy measurements show that the suboxide layers are ~1 nm thick, pseudomorph, and exhibit crystalline order throughout the layer. In addition, transmission electron microscopy shows that the oxygen concentration is laterally inhomogeneous. The multilayer structures are thermally very stable, as rapid thermal annealing up to 1000 °C shows no influence on the X-ray diffraction patterns.

  5. Crystalline Silicon Short-Circuit Current Degradation Study: Initial Results

    SciTech Connect

    Osterwald, C. R.; Pruett, J.; Moriarty, T.

    2005-02-01

    Following our observation of slow degradation of short-circuit current (Isc) in crystalline silicon (x-Si) modules that was correlated with ultraviolet (UV) exposure dose, we initiated a new study of individual x-Si cells designed to determine the degradation cause. In this paper, we report the initial results of this study, which has accumulated 1056 MJ/m2 of UV dose from 1-sun metal-halide irradiance, equivalent to 3.8 years at our test site. At this time, the control samples are unchanged, the unencapsulated samples have lost about 2% of Isc, and the samples encapsulated in module-style packages have declined from 1% to 3%, depending on the cell technology.

  6. Hydrogen platelets in crystalline silicon - Precursors for the "smart cut"

    SciTech Connect

    Reboredo, Fernando A; Pantelides, Sokrates T

    1999-01-01

    High concentrations of H in crystalline Si are known to induce planar defects (platelets), primarily in the (100) and the (Ill)planes. These platelets are precursors for the so-called "smart cut" technique for fabricating Silicon-On-insulator (SOI) structures. The atomic-scale mechanisms for the nucleation and growth of the H-induced platelets and many other experimental observations have remained elusive. We review recent extensive first-principles calculations in terms of which a comprehensive picture of platelet nucleation and growth has emerged. The theory naturally accounts for the observed preference for (111) and (100) planes, for H release and trapping of H-2 molecules, and other observations. The platelets are arrays of second-neighbor hydrogenated vacancies that do not bind to each other, but their formation is due to energetically preferred reaction pathways.

  7. Optical bandgap of ultra-thin amorphous silicon films deposited on crystalline silicon by PECVD

    NASA Astrophysics Data System (ADS)

    Abdulraheem, Yaser; Gordon, Ivan; Bearda, Twan; Meddeb, Hosny; Poortmans, Jozef

    2014-05-01

    An optical study based on spectroscopic ellipsometry, performed on ultrathin hydrogenated amorphous silicon (a-Si:H) layers, is presented in this work. Ultrathin layers of intrinsic amorphous silicon have been deposited on n-type mono-crystalline silicon (c-Si) wafers by plasma enhanced chemical vapor deposition (PECVD). The layer thicknesses along with their optical properties -including their refractive index and optical loss- were characterized by spectroscopic ellipsometry (SE) in a wavelength range from 250 nm to 850 nm. The data was fitted to a Tauc-Lorentz optical model and the fitting parameters were extracted and used to compute the refractive index, extinction coefficient and optical bandgap. Furthermore, the a-Si:H film grown on silicon was etched at a controlled rate using a TMAH solution prepared at room temperature. The optical properties along with the Tauc-Lorentz fitting parameters were extracted from the model as the film thickness was reduced. The etch rate for ultrathin a-Si:H layers in TMAH at room temperature was found to slow down drastically as the c-Si interface is approached. From the Tauc-Lorentz parameters obtained from SE, it was found that the a-Si film exhibited properties that evolved with thickness suggesting that the deposited film is non-homogeneous across its depth. It was also found that the degree of crystallinity and optical (Tauc) bandgap increased as the layers were reduced in thickness and coming closer to the c-Si substrate interface, suggesting the presence of nano-structured clusters mixed into the amorphous phase for the region close to the crystalline silicon substrate. Further results from Atomic Force Microscopy and Transmission Electron Microscopy confirmed the presence of an interfacial transitional layer between the amorphous film and the underlying substrate showing silicon nano-crystalline enclosures that can lead to quantum confinement effects. Quantum confinement is suggested to be the cause of the observed

  8. Optical bandgap of ultra-thin amorphous silicon films deposited on crystalline silicon by PECVD

    SciTech Connect

    Abdulraheem, Yaser; Gordon, Ivan; Bearda, Twan; Meddeb, Hosny; Poortmans, Jozef

    2014-05-15

    An optical study based on spectroscopic ellipsometry, performed on ultrathin hydrogenated amorphous silicon (a-Si:H) layers, is presented in this work. Ultrathin layers of intrinsic amorphous silicon have been deposited on n-type mono-crystalline silicon (c-Si) wafers by plasma enhanced chemical vapor deposition (PECVD). The layer thicknesses along with their optical properties –including their refractive index and optical loss- were characterized by spectroscopic ellipsometry (SE) in a wavelength range from 250 nm to 850 nm. The data was fitted to a Tauc-Lorentz optical model and the fitting parameters were extracted and used to compute the refractive index, extinction coefficient and optical bandgap. Furthermore, the a-Si:H film grown on silicon was etched at a controlled rate using a TMAH solution prepared at room temperature. The optical properties along with the Tauc-Lorentz fitting parameters were extracted from the model as the film thickness was reduced. The etch rate for ultrathin a-Si:H layers in TMAH at room temperature was found to slow down drastically as the c-Si interface is approached. From the Tauc-Lorentz parameters obtained from SE, it was found that the a-Si film exhibited properties that evolved with thickness suggesting that the deposited film is non-homogeneous across its depth. It was also found that the degree of crystallinity and optical (Tauc) bandgap increased as the layers were reduced in thickness and coming closer to the c-Si substrate interface, suggesting the presence of nano-structured clusters mixed into the amorphous phase for the region close to the crystalline silicon substrate. Further results from Atomic Force Microscopy and Transmission Electron Microscopy confirmed the presence of an interfacial transitional layer between the amorphous film and the underlying substrate showing silicon nano-crystalline enclosures that can lead to quantum confinement effects. Quantum confinement is suggested to be the cause of the observed

  9. Research Opportunities in Crystalline Silicon Photovoltaics for the 21st Century

    SciTech Connect

    Atwater, Harry A.; Ciszek, Ted; Feldman, Leonard C.; Gee, James; Rohatgi, Ajeet; Sopori, Bhushan

    1999-07-28

    Crystalline silicon continues to be the dominant semiconductor material used for terrestrial photovoltaics. This paper discusses the scientific issues associated with silicon photovoltaics processing, and cell design that may yield cell and module performance improvements that are both evolutionary and revolutionary in nature. We first survey critical issues in ''thick'' crystalline silicon photovoltaics, including novel separations processes for impurity removal, impurity and defect fundamentals, interface passivation, the role of hydrogen. Second, we outline emerging opportunities for creation of a very different ''thin-layer'' silicon cell structure, including the scientific issues and engineering challenges associated with thin-layer silicon processing and cell design.

  10. Single Molecule Study of Cellulase Hydrolysis of Crystalline Cellulose

    SciTech Connect

    Liu, Y.-S.; Luo, Y.; Baker, J. O.; Zeng, Y.; Himmel, M. E.; Smith, S.; Ding, S.-Y.

    2009-12-01

    This report seeks to elucidate the role of cellobiohydrolase-I (CBH I) in the hydrolysis of crystalline cellulose. A single-molecule approach uses various imaging techniques to investigate the surface structure of crystalline cellulose and changes made in the structure by CBH I.

  11. LiBr treated porous silicon used for efficient surface passivation of crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Zarroug, Ahmed; Haddadi, Ikbel; Derbali, Lotfi; Ezzaouia, Hatem

    2015-04-01

    A simple but effective passivation method of both front and rear surfaces using porous silicon (PS) has been developed. This paper investigates the effect of LiBr on the passivation of PS. The immersion of as-etched PS in dilute LiBr solution followed by an annealing in an infrared furnace, under a controlled atmosphere at different temperatures, led to the passivation of the PS layer and the improvement of the electronic properties of the crystalline silicon substrates. The influence of substrate temperature was investigated, since the processed wafers were found to be sensitive to heat, which in turn was optimized to have a gettering effect. The bromide of lithium can effectively saturate dangling bonds and hence contributed to the formation of a stable passivation film, at both front and back surfaces. Such a reaction was found to have a beneficial effect on the passivation process of the PS layer grown on both sides. The obtained results exhibited a significant improvement of the minority carrier lifetime, which is an important parameter that defines the quality of crystalline silicon substrates, and an apparent enhancement of its photoluminescence (PL). The internal quantum efficiency was investigated and found to be significantly improved. The qualitative effect of the above-mentioned procedure proved a significant enhancement of the electronic quality of the treated substrates.

  12. The crystalline-silicon photovoltaic R&D project at NREL and SNL

    SciTech Connect

    Gee, J.M.; Ciszek, T.F.

    1996-12-31

    This paper summarizes the U.S. Department of Energy R&D program in crystalline-silicon photovoltaic technology, which is jointly managed by Sandia National Laboratories and National Renewable Energy Laboratory. This program features a balance of basic an d applied R&D, and of university, industry, and national laboratory R&D. The goal of the crystalline-silicon R&D program is to accelerate the commercial growth of crystalline-silicon photovoltaic technology, and four strategic objectives were identified to address this program goal. Technical progress towards meeting these objectives is reviewed.

  13. Temperature-dependent minority carrier lifetime of crystalline silicon wafers passivated by high quality amorphous silicon oxide

    NASA Astrophysics Data System (ADS)

    Inaba, Masahiro; Todoroki, Soichiro; Nakada, Kazuyoshi; Miyajima, Shinsuke

    2016-04-01

    We investigated the effects of annealing on the temperature-dependent minority carrier lifetime of a crystalline silicon wafer passivated by hydrogenated amorphous silicon oxide. The annealing significantly affects the lifetime and its temperature dependence. Our device simulations clearly indicate that valence band offset significantly affects the temperature dependence. We also found a slight increase in the interface defect density after annealing.

  14. Crystalline Silicon/Graphene Oxide Hybrid Junction Solar Cells

    NASA Astrophysics Data System (ADS)

    Liu, Qiming; Wanatabe, Fumiya; Hoshino, Aya; Ishikawa, Ryo; Gotou, Takuya; Ueno, Keiji; Shirai, Hajime

    2012-10-01

    Soluble graphene oxide (GO) and plasma-reduced (pr-) GO were investigated using crystalline silicon (c-Si) (100)/GO/pr-GO hybrid junction solar cells. Their photovoltaic performances were compared with those of c-Si/GO/pristine conductive poly(ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) heterojunction and c-Si/PEDOT:PSS:GO composite devices. The c-Si/GO/pr-GO and conductive PEDOT:PSS/Al heterojunction solar cells showed power conversion efficiencies of 6.5 and 8.2%, respectively, under illumination with AM 1.5 G 100 mW/cm2 simulated solar light. A higher performance of 10.7% was achieved using the PEDOT:PSS:GO (12.5 wt %) composite device. These findings imply that soluble GO, pr-GO, and the PEDOT:PSS:GO composite are promising materials as hole transport and transparent conductive layers for c-Si/organic hybrid junction solar cells.

  15. A vacancy-related muon species in crystalline silicon

    NASA Astrophysics Data System (ADS)

    Schefzik, M.; Scheuermann1, R.; Schimmele, L.; Seeger, A.; Herlach, D.; Kormann, O.; Major, J.; Röck, A.

    2000-08-01

    A new muonium centre, termed Mu V, with weak hyperfine interaction has been discovered recently in crystalline silicon in longitudinal field quenching μSR (LFQ) experiments (Schefzik et al., Solid State Commun. 107 (1998) 395). The signatures of this species were found in intrinsic, but not in doped samples (dopant concentration larger than 10 16 cm-3). The centre is not formed promptly but results from a reaction in which normal muonium transforms into the novel species. Since from LFQ experiments one can obtain only a rough estimate of the hyperfine tensor of Mu V it is now determined from zero-field (ZF) μSR experiments. The hyperfine interaction is found to be axially symmetric around the <1 1 0> crystallographic axis with small hyperfine parameters. Properly rescaled it essentially agrees with the hyperfine tensor of the hydrogen centre VH, which has been discovered recently by Bech Nielsen et al. (Phys. Rev. Lett. 79 (1997) 1507) and which has been attributed to hydrogen trapped in vacancies. Accordingly Mu V is interpreted as muonium trapped in a vacancy, in agreement with the interpretation given on the basis of the earlier LFQ data.

  16. Evidence for a novel muon species in crystalline silicon

    NASA Astrophysics Data System (ADS)

    Schefzik, M.; Scheuermann, R.; Schimmele, L.; Schmidl, J.; Seeger, A.; Herlach, D.; Kormann, O.; Major, J.; Röck, A.

    1998-07-01

    Investigations of positive muons ( μ+) in crystalline silicon employing the longitudinal field-quenching (LFQ) technique give strong evidence for the existence of a novel paramagnetic muon species with a small anisotropic hyperfine interaction. It adds to the list of known muon species, i.e., normal and anomalous muonium and the diamagnetic muon species. The signatures of the novel species are found in intrinsic but not in doped samples (dopant concentration about 10 16 cm -3). The novel species is not formed promptly but results from a reaction in which normal muonium transforms into the novel species. The reaction rate constant at 10 K was found to be about 10 6 s -1. The hyperfine coupling of the novel paramagnetic muon species corresponds, after rescaling, to that of a hydrogen center termed VH, which has been discovered recently by Bech Nielsen et al. ( Phys. Rev. Lett., 79, 1997, 1507) and which has been attributed to hydrogen trapped in vacancies. The LFQ data are tentatively interpreted in terms of trapping of normal muonium in vacancies that are created during the slowing-down of implanted muons close to the end of their stopping tracks.

  17. Aluminum gettering in single and multicrystalline silicon

    SciTech Connect

    McHugo, S.A.; Hieslmair, H.; Weber, E.R.

    1995-08-01

    Al gettering has been performed on integrated circuit (I.C.) quality silicon and a variety of single and multicrystalline silicon solar cell materials. The minority carrier diffusion length, Ln, has been used to quantify the gettering response. Vast differences in response to the Al gettering treatment are observed between the I.C. quality silicon and the solar cell materials. The I.C. silicon generally responds well while the solar cell silicon performance progressively degrades with increasing gettering temperature. Preliminary data shows that by performing a Rapid Thermal Annealing treatment prior to the Al gettering, an improved or further degraded Ln emerges in solar cell material depending on the material`s manufacturer. We explain these observed phenomena by suggesting that Al gettering in solar cell silicon is an impurity emission-limited process while for I.C. quality silicon it is diffusion limited.

  18. Crack Growth in Single-Crystal Silicon

    NASA Technical Reports Server (NTRS)

    Chen, C. P.; Leipold, M. H.

    1986-01-01

    Report describes experiments on crack growth in single-crystal silicon at room temperature in air. Crack growth in (111) cleavage plane of wafers, 50 by 100 by 0.76 mm in dimension, cut from Czochralski singlecrystal silicon studied by double-torsion load-relaxation method and by acoustic-emission measurements. Scanning electron microscopy and X-ray topography also employed. Results aid in design and fabrication of silicon photovoltaic and microelectronic devices.

  19. 77 FR 63788 - Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules, From the People's...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-17

    ... the People's Republic of China: Preliminary Affirmative Countervailing Duty Determination, 77 FR 17439... Critical Circumstances, 77 FR 5487 (February 3, 2012) (Preliminary Critical Circumstances Determination... International Trade Administration Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into...

  20. A pseudo-single-crystalline germanium film for flexible electronics

    SciTech Connect

    Higashi, H.; Yamada, S.; Kanashima, T.; Hamaya, K.; Kasahara, K.; Park, J.-H.; Miyao, M.; Kudo, K.; Okamoto, H.; Moto, K.; Tsunoda, I.

    2015-01-26

    We demonstrate large-area (∼600 μm), (111)-oriented, and high-crystallinity, i.e., pseudo-single-crystalline, germanium (Ge) films at 275 °C, where the temperature is lower than the softening temperature of a flexible substrate. A modulated gold-induced layer exchange crystallization method with an atomic-layer deposited Al{sub 2}O{sub 3} barrier and amorphous-Ge/Au multilayers is established. From the Raman measurements, we can judge that the crystallinity of the obtained Ge films is higher than those grown by aluminum-induced-crystallization methods. Even on a flexible substrate, the pseudo-single-crystalline Ge films for the circuit with thin-film transistor arrays can be achieved, leading to high-performance flexible electronics based on an inorganic-semiconductor channel.

  1. Scalable High-Efficiency Thin Crystalline Silicon Photovoltaic Cells Enabled by Light-Trapping Nanostructures

    SciTech Connect

    Chen, Gang; Branham, Matthew S.; Hsu, Wei-Chun; Yerci, Selcuk

    2014-09-02

    This report summarizes the research activities of the Chen group at MIT over the last two years pertaining to our research effort developing and proving light-trapping designs for ultrathin crystalline silicon solar cells. We present a new world record efficiency for a sub-20-micron crystalline silicon device, as well as details on the combined photonic/electronic transport simulation we developed for photovoltaic applications.

  2. Thermal conductivity reduction of crystalline silicon by high-pressure torsion

    PubMed Central

    2014-01-01

    We report a dramatic and irreversible reduction in the lattice thermal conductivity of bulk crystalline silicon when subjected to intense plastic strain under a pressure of 24 GPa using high-pressure torsion (HPT). Thermal conductivity of the HPT-processed samples were measured using picosecond time domain thermoreflectance. Thermal conductivity measurements show that the HPT-processed samples have a lattice thermal conductivity reduction by a factor of approximately 20 (from intrinsic single crystalline value of 142 Wm−1 K−1 to approximately 7.6 Wm−1 K−1). Thermal conductivity reduction in HPT-processed silicon is attributed to the formation of nanograin boundaries and metastable Si-III/XII phases which act as phonon scattering sites, and because of a large density of lattice defects introduced by HPT processing. Annealing the samples at 873 K increases the thermal conductivity due to the reduction in the density of secondary phases and lattice defects. PMID:25024687

  3. Probing the low thermal conductivity of single-crystalline porous Si nanowires

    NASA Astrophysics Data System (ADS)

    Zhao, Yunshan; Lina Yang Collaboration; Lingyu Kong Collaboration; Baowen Li Collaboration; John T L Thong Collaboration; Kedar Hippalgaonkar Collaboration

    Pore-like structures provide a novel way to reduce the thermal conductivity of silicon nanowires, compared to both smooth-surface VLS nanowires and rough EE nanowires. Because of enhanced phonon scattering with interface and decrease in phonon transport path, the porous nanostructures show reduction in thermal conductance by few orders of magnitude. It proves to be extremely challenging to evaluate porosity accurately in an experimental manner and further understand its effect on thermal transport. In this study, we use the newly developed electron-beam based micro-electrothermal device technique to study the porosity dependent thermal conductivity of mesoporous silicon nanowires that have single-crystalline scaffolding. Based on the Casino simulation, the power absorbed by the nanowire, coming from the loss of travelling electron energy, has a linear relationship with it cross section. The relationship has been verified experimentally as well. Monte Carlo simulation is carried out to theoretically predict the thermal conductivity of silicon nanowires with a specific value of porosity. These single-crystalline porous silicon nanowires show extremely low thermal conductivity, even below the amorphous limit. These structures together with our experimental techniques provide a particularly intriguing platform to understand the phonon transport in nanoscale and aid the performance improvement in future nanowires-based devices.

  4. A single crystalline InP nanowire photodetector

    NASA Astrophysics Data System (ADS)

    Yan, Xin; Li, Bang; Wu, Yao; Zhang, Xia; Ren, Xiaomin

    2016-08-01

    Single crystalline nanowires are critical for achieving high-responsivity, high-speed, and low-noise nanoscale photodetectors. Here, we report a metal-semiconductor-metal photodetector based on a single crystalline InP nanowire. The nanowires are grown by a self-catalyzed method and exhibit stacking-fault-free zinc blende crystal structure. The nanowire exhibits a typical n-type semiconductor property and shows a low room temperature dark current of several hundred pA at moderate biases. A photoresponsivity of 6.8 A/W is obtained at a laser power density of 0.2 mW/cm2. This work demonstrates that single crystalline InP nanowires are good candidates for future optoelectronic device applications.

  5. Magnetotransport of single crystalline NbAs

    DOE PAGESBeta

    Ghimire, N. J.; Luo, Yongkang; Neupane, M.; Williams, D. J.; Bauer, E. D.; Ronning, F.

    2015-03-27

    We report transport measurement in zero and applied magnetic field on a single crystal of NbAs. Transverse and longitudinal magnetoresistance in the plane of this tetragonal structure does not saturate up to 9 T. In the transverse configuration (H ∥ c, I ⊥ c) it is 230,000% at 2 K. The Hall coefficient changes sign from hole-like at room temperature to electron-like below ~150 K. The electron carrier density and mobility calculated at 2 K based on a single band approximation are 1.8 × 1019 cm-3 and 3.5 × 105 cm2/Vs, respectively. These values are similar to reported values formore » TaAs and NbP, and further emphasize that this class of noncentrosymmetric, transition-metal monopnictides is a promising family to explore the properties of Weyl semimetals and the consequences of their novel electronic structure.« less

  6. Damage at hydrogenated amorphous/crystalline silicon interfaces by indium tin oxide overlayer sputtering

    NASA Astrophysics Data System (ADS)

    Demaurex, Bénédicte; De Wolf, Stefaan; Descoeudres, Antoine; Charles Holman, Zachary; Ballif, Christophe

    2012-10-01

    Damage of the hydrogenated amorphous/crystalline silicon interface passivation during transparent conductive oxide sputtering is reported. This occurs in the fabrication process of silicon heterojunction solar cells. We observe that this damage is at least partially caused by luminescence of the sputter plasma. Following low-temperature annealing, the electronic interface properties are recovered. However, the silicon-hydrogen configuration of the amorphous silicon film is permanently changed, as observed from infra-red absorbance spectra. In silicon heterojunction solar cells, although the as-deposited film's microstructure cannot be restored after sputtering, no significant losses are observed in their open-circuit voltage.

  7. Polycrystalline graphene with single crystalline electronic structure.

    PubMed

    Brown, Lola; Lochocki, Edward B; Avila, José; Kim, Cheol-Joo; Ogawa, Yui; Havener, Robin W; Kim, Dong-Ki; Monkman, Eric J; Shai, Daniel E; Wei, Haofei I; Levendorf, Mark P; Asensio, María; Shen, Kyle M; Park, Jiwoong

    2014-10-01

    We report the scalable growth of aligned graphene and hexagonal boron nitride on commercial copper foils, where each film originates from multiple nucleations yet exhibits a single orientation. Thorough characterization of our graphene reveals uniform crystallographic and electronic structures on length scales ranging from nanometers to tens of centimeters. As we demonstrate with artificial twisted graphene bilayers, these inexpensive and versatile films are ideal building blocks for large-scale layered heterostructures with angle-tunable optoelectronic properties. PMID:25207847

  8. Single-crystalline monolayer and multilayer graphene nano switches

    SciTech Connect

    Li, Peng; Cui, Tianhong; Jing, Gaoshan; Zhang, Bo; Sando, Shota

    2014-03-17

    Growth of monolayer, bi-layer, and tri-layer single-crystalline graphene (SCG) using chemical vapor deposition method is reported. SCG's mechanical properties and single-crystalline nature were characterized and verified by atomic force microscope and Raman spectroscopy. Electro-mechanical switches based on mono- and bi-layer SCG were fabricated, and the superb properties of SCG enable the switches to operate at pull-in voltage as low as 1 V, and high switching speed about 100 ns. These devices exhibit lifetime without a breakdown of over 5000 cycles, far more durable than any other graphene nanoelectromechanical system switches reported.

  9. Nonvolatile resistive switching in single crystalline ZnO nanowires.

    PubMed

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

    2011-04-01

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

  10. Magnetoresistance in single crystalline chromium sulfides

    NASA Astrophysics Data System (ADS)

    Lee, K. D.; Won, C. J.; Song, K. M.; Hur, N.

    2011-03-01

    We studied the anisotropic magnetic and magnetotransport properties of Cr2S3 single crystals grown by using the vapor transport method. Large magnetoresistance of ˜ 46% was observed in 9 T magnetic field applied perpendicular to the c axis near the Néel temperature TN ≈ 118 K. Comparison of electric and magnetic properties of Cr2S3 crystals with different sulfur deficiencies suggested that the electron doping by the sulfur deficiency does not contribute to weak ferromagnetism. The correlation between the field-dependent magnetization and resistivity was analyzed by the polaron hopping model of magnetotransport in Cr2S3.

  11. Magnetotransport of single crystalline NbAs

    SciTech Connect

    Ghimire, N. J.; Luo, Yongkang; Neupane, M.; Williams, D. J.; Bauer, E. D.; Ronning, F.

    2015-03-27

    We report transport measurement in zero and applied magnetic field on a single crystal of NbAs. Transverse and longitudinal magnetoresistance in the plane of this tetragonal structure does not saturate up to 9 T. In the transverse configuration (H ∥ c, I ⊥ c) it is 230,000% at 2 K. The Hall coefficient changes sign from hole-like at room temperature to electron-like below ~150 K. The electron carrier density and mobility calculated at 2 K based on a single band approximation are 1.8 × 1019 cm-3 and 3.5 × 105 cm2/Vs, respectively. These values are similar to reported values for TaAs and NbP, and further emphasize that this class of noncentrosymmetric, transition-metal monopnictides is a promising family to explore the properties of Weyl semimetals and the consequences of their novel electronic structure.

  12. Synthesis of single-crystalline anisotropic gold nano-crystals via chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Manna, Sohini; Kim, Jong Woo; Takahashi, Yukiko; Shpyrko, Oleg G.; Fullerton, Eric E.

    2016-05-01

    We report on a novel one-step catalyst-free, thermal chemical vapor deposition procedure to synthesize gold nanocrystals on silicon substrates. This approach yields single-crystal nanocrystals with various morphologies, such as prisms, icosahedrons, and five-fold twinned decahedrons. Our approach demonstrates that high-quality anisotropic crystals composed of fcc metals can be produced without the need for surfactants or templates. Compared with the traditional wet chemical synthesis processes, our method enables direct formation of highly pure and single crystalline nanocrystals on solid substrates which have applications in catalysis. We investigated the evolution of gold nanocrystals and established their formation mechanism.

  13. Low temperature growth of crystalline magnesium oxide on hexagonal silicon carbide (0001) by molecular beam epitaxy

    SciTech Connect

    Goodrich, T. L.; Parisi, J.; Cai, Z.; Ziemer, K. S.

    2007-01-22

    Magnesium oxide (111) was grown epitaxially on hexagonal silicon carbide (6H-SiC) (0001) substrates at low temperatures by molecular beam epitaxy and a remote oxygen plasma source. The films were characterized by reflection high-energy electron diffraction, Auger electron spectroscopy, x-ray photoelectron spectroscopy, and atomic force microscopy. Crystal structure, morphology, and growth rate of the magnesium oxide (MgO) films were found to be dependent on the magnesium flux, indicating a magnesium adsorption controlled growth mechanism. The single crystalline MgO thin films had an epitaxial relationship where MgO (111) parallel 6H-SiC (0001) and were stable in both air and 10{sup -9} Torr up to 1023 K.

  14. Wet-texturing process for a thin crystalline silicon solar cell at low cost with high efficiency

    NASA Astrophysics Data System (ADS)

    Han, Kyu-Min; Yoo, Jin-Su

    2014-04-01

    In the wet-texturing process, a smaller etch depth of 8 µm was established on each side of the thin silicon wafer. Formation of a very small size (1-3 µm) pyramidal structure was confirmed on a thin c-Si surface through the use of SEM micrographs. For this silicon surface with small pyramidal structures, a surface reflectance of 15.14% was observed. Saw damage removal was employed for the second and the third sets of silicon wafers in a NaOH (8 wt%) solution, and the wafers were then textured in a mixture of NaOH (1.5 wt%), de-ionized water and Isopropyl alcohol (IPA, 6-8 wt%) at 80 °C for 18 min and 24 min, respectively. In this process, the scraped depths were 16 and 26 µm on each side of the second and the third sets of silicon wafers, and the pyramidal sizes were 4-9 µm and 9-12 µm respectively. We found that the reflectances of these sets of wafers were 14.98% and 14.78%, respectively. Our novel approach of ultrasonic cleaning, hot de-ionized water treatment, and texturing for thin c-Si wafers yielded small-sized (1-3 µm) uniform pyramidal structure that were stable and suitable for metalized screen printing. Even though the reflectance was high for the first set of wafers the illuminated current-voltage (LIV) measurements confirmed the wafers' superiority over the conventional textured c-Si solar cells in terms of the open-circuit voltage and the fill factor. The small-size pyramidal-structured thin single-crystalline silicon solar cells showed a 17.9% efficiency. Since no NaOH solution was used for saw damage removal in the first set of silicon wafers, the production cost for commercial production of large-area single-crystalline silicon solar cells was reduced by nearly 20%.

  15. Effect of scandium on the optical properties of crystalline silicon material.

    PubMed

    Dong, Xiao; Wang, Yongyong; Li, Xueping; Li, Yingying

    2016-09-01

    We have studied the optical properties of Sc-hyperdoped crystalline silicon based on quantum calculations. We have designed several probable configurations and found that the interstitial atomic positions of Sc (ScI, ScSI, ScTI, ScHI) are stable in the silicon matrix and can largely extend the absorption range of silicon from visible to infrared. The sub-band gap light absorption is attributed to the change of band structures of silicon and its intensity depends on the atomic concentration of Sc in silicon. The special effect of Sc on the properties of silicon will extend the sensitivity of silicon-based photodetectors to near infrared wavelength range. PMID:27607729

  16. Process optimization for lattice-selective wet etching of crystalline silicon structures

    NASA Astrophysics Data System (ADS)

    Dixson, Ronald G.; Guthrie, William F.; Allen, Richard A.; Orji, Ndubuisi G.; Cresswell, Michael W.; Murabito, Christine E.

    2016-01-01

    Lattice-selective etching of silicon is used in a number of applications, but it is particularly valuable in those for which the lattice-defined sidewall angle can be beneficial to the functional goals. A relatively small but important niche application is the fabrication of tip characterization standards for critical dimension atomic force microscopes (CD-AFMs). CD-AFMs are commonly used as reference tools for linewidth metrology in semiconductor manufacturing. Accurate linewidth metrology using CD-AFM, however, is critically dependent upon calibration of the tip width. Two national metrology institutes and at least two commercial vendors have explored the development of tip calibration standards using lattice-selective etching of crystalline silicon. The National Institute of Standards and Technology standard of this type is called the single crystal critical dimension reference material. These specimens, which are fabricated using a lattice-plane-selective etch on (110) silicon, exhibit near vertical sidewalls and high uniformity and can be used to calibrate CD-AFM tip width to a standard uncertainty of less than 1 nm. During the different generations of this project, we evaluated variations of the starting material and process conditions. Some of our starting materials required a large etch bias to achieve the desired linewidths. During the optimization experiment described in this paper, we found that for potassium hydroxide etching of the silicon features, it was possible to independently tune the target linewidth and minimize the linewidth nonuniformity. Consequently, this process is particularly well suited for small-batch fabrication of CD-AFM linewidth standards.

  17. Novel low cost chemical texturing for very large area industrial multi-crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Gangopadhyay, U.; Dhungel, S. K.; Kim, K.; Manna, U.; Basu, P. K.; Kim, H. J.; Karunagaran, B.; Lee, K. S.; Yoo, J. S.; Yi, J.

    2005-09-01

    Multi-crystalline silicon surface etching without grain-boundary delineation is a challenging task for the fabrication of high efficiency solar cells. The use of sodium hydroxide-sodium hypochlorite (NaOH-NaOCl) solution for texturing a multi-crystalline silicon wafer surface in a solar cell fabrication line is reported in this paper. The optimized etching solution of NaOH-NaOCl does not have any effect on multi-crystalline silicon grain boundaries and it also has excellent isotropic etch characteristics, which ultimately helps to achieve higher values of performance parameters, especially the open circuit voltage (Voc) and fill factor (FF), than those in the case of conventional silicon texturing. Easy control over the reaction of the NaOH-NaOCl solution is also one of the major advantages due to which sophistication in controlling the temperature of the etching bath is not required for the industrial batch process. The FTIR analysis of the silicon surface after etching with the current approach shows the formation of Si-Cl bonds, which improves the quality of the diffused junction due to chlorine gettering during diffusion. We are the first to report 14-14.5% efficiency of very large area (150 mm × 150 mm) multi-crystalline silicon solar cells using a NaOH-NaOCl texturing approach in an industrial production line with a yield greater than 95%.

  18. Influence of different seed materials on multi-crystalline silicon ingot properties

    NASA Astrophysics Data System (ADS)

    Reimann, C.; Trempa, M.; Lehmann, T.; Rosshirt, K.; Stenzenberger, J.; Friedrich, J.; Hesse, K.; Dornberger, E.

    2016-01-01

    Different silicon feedstock materials, Single Crystalline Crushed (SCS), Fluidized-Bed-Reactor (FBR) and Siemens (SIE) feedstock, were used as seeding layer for growing cylindrical shaped, high performance multi-crystalline ingots with a weight of 1.2 kg. Within the investigations a systematic variation of the particle size of the seeding material in the range of <1 mm up to 15 mm was performed. Grain size, grain orientation, and grain boundary type were evaluated at different ingot heights. These results show clearly, that the microstructure size, respectively the particle size for the crushed single crystalline material, determines the resulting grain structure in the ingot near the seeding position. If the microstructure size is equal to the particle size, as it is the case for the SCS material, the particle size has a significant influence on grain size, grain orientation, and grain boundary distribution. With increasing average particle size of the SCS seed material the grain size increases, the grain orientation distribution becomes less uniform, and the random grain boundary length fraction decreases. If the microstructure size is smaller than the particle size, as it is the case for FBR and SIE feedstock materials, the particle size has no influence on the initial grain structure of the ingot. For FBR and SIE seeding material, small grains, with a homogeneous orientation distribution and a high random grain boundary length fraction are obtained. Therefore, all FBR and all SIE seeding materials, as well as the SCS with particle size <1 mm, show lowest fractions of defected areas at about the same level which were determined by etch pit analysis.

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

    SciTech Connect

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

    2014-05-21

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

  20. Modeling of optical spectroscopy for the crystalline silicon

    NASA Astrophysics Data System (ADS)

    Liu, Changshi

    2014-03-01

    The paper is aimed at modeling optical spectra of silicon. Optical spectra of silicon are described with the Logistic function. A satisfactory agreement between the measured and the modeled optical spectra are obtained. The minimum magnitude of the correlation coefficient between experiment and theoretical results is 0.994, and the maximum average relative error is 4.21%. Meanwhile, it is found that the band gap of semiconductor may be determined by fitting absorption coefficient as a function of wavelength. Lastly, the mathematical relationships between the parameters, which are used to link the reflectance of silicon and wavelength, and radiation fluency, are obtained. Consequently, the change of reflectance for silicon can be predicted by both wavelength and dose radiation fluency only one function. All results in this paper are of interest from both optics and materials point of view.

  1. New Opportunities in Crystalline Silicon R&D

    SciTech Connect

    Tsuo, Y. S.; Wang, T. H.; Ciszek, T. F.; Menna, P.

    1998-10-06

    To support the expected growth of the silicon solar cell industry, we believe that research and development (R&D) activities should be carried out in the following areas: polysilicon feedstock for the PV industry; thin-layer silicon deposition methods, and more environmentally benign cell and module manufacturing processes. For each of these activities, we identify the main issues that needed to be addressed.

  2. Multiscaled hierarchical nanostructures for enhancing the conversion efficiency of crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Bingfa; Qiu, Shenyu; Hu, Ruiyi; Liao, Yuanbin; Chen, Nan; Du, Guoping

    2012-10-01

    High-performance antireflection structure is critical for enhancing the conversion efficiency of solar cells. One of the most effective antireflection techniques for solar cells is the introduction of nanostructures to the cells. In this work, we prepared multiscaled hierarchical Er-doped ZnO nanostructures on the plasma enhanced chemical vapor deposited silicon nitride-coated texturized single crystalline silicon solar cells for antireflection. The multiscaled hierarchical Er-doped ZnO nanostructures were needle-like nanotip arrays, and they were grown using the hydrothermal method. The dependence of microstructure and antireflection performance of the multiscaled hierarchical Er-doped ZnO nanostructures on the growth time were studied. It was shown that longer growth time resulted in greater length and diameter for the Er-doped ZnO nanostructures. For longer growth time, the needle-like tips of the multiscaled hierarchical Er-doped ZnO nanostructures were found to transform to flat tops, which greatly degraded their antireflection performance. An optimal growth time for the multiscaled hierarchical Er-doped ZnO nanostructures was determined, and a large enhancement in the photovoltaic performance of sc-Si solar cells was resulted.

  3. Solution-based synthesis of crystalline silicon from liquid silane through laser and chemical annealing.

    PubMed

    Iyer, Ganjigunte R S; Hobbie, Erik K; Guruvenket, Srinivasan; Hoey, Justin M; Anderson, Kenneth J; Lovaasen, John; Gette, Cody; Schulz, Douglas L; Swenson, Orven F; Elangovan, Arumugasamy; Boudjouk, P

    2012-05-01

    We report a solution process for the synthesis of crystalline silicon from the liquid silane precursor cyclohexasilane (Si(6)H(12)). Polysilane films were crystallized through thermal and laser annealing, with plasma hydrogenation at atmospheric pressure generating further structural changes in the films. The evolution from amorphous to microcrystalline is characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and impedance spectroscopy. A four-decade enhancement in the electrical conductivity is attributed to a disorder-order transition in a bonded Si network. Our results demonstrate a potentially attractive approach that employs a solution process coupled with ambient postprocessing to produce crystalline silicon thin films. PMID:22545711

  4. Single-crystalline nanoporous Nb2O5 nanotubes

    PubMed Central

    2011-01-01

    Single-crystalline nanoporous Nb2O5 nanotubes were fabricated by a two-step solution route, the growth of uniform single-crystalline Nb2O5 nanorods and the following ion-assisted selective dissolution along the [001] direction. Nb2O5 tubular structure was created by preferentially etching (001) crystallographic planes, which has a nearly homogeneous diameter and length. Dense nanopores with the diameters of several nanometers were created on the shell of Nb2O5 tubular structures, which can also retain the crystallographic orientation of Nb2O5 precursor nanorods. The present chemical etching strategy is versatile and can be extended to different-sized nanorod precursors. Furthermore, these as-obtained nanorod precursors and nanotube products can also be used as template for the fabrication of 1 D nanostructured niobates, such as LiNbO3, NaNbO3, and KNbO3. PMID:21711650

  5. Single-crystalline nanoporous Nb2O5 nanotubes.

    PubMed

    Liu, Jun; Xue, Dongfeng; Li, Keyan

    2011-01-01

    Single-crystalline nanoporous Nb2O5 nanotubes were fabricated by a two-step solution route, the growth of uniform single-crystalline Nb2O5 nanorods and the following ion-assisted selective dissolution along the [001] direction. Nb2O5 tubular structure was created by preferentially etching (001) crystallographic planes, which has a nearly homogeneous diameter and length. Dense nanopores with the diameters of several nanometers were created on the shell of Nb2O5 tubular structures, which can also retain the crystallographic orientation of Nb2O5 precursor nanorods. The present chemical etching strategy is versatile and can be extended to different-sized nanorod precursors. Furthermore, these as-obtained nanorod precursors and nanotube products can also be used as template for the fabrication of 1 D nanostructured niobates, such as LiNbO3, NaNbO3, and KNbO3. PMID:21711650

  6. The future of crystalline silicon technology in the US Department of Energy program

    NASA Technical Reports Server (NTRS)

    Scolaro, A. F.

    1984-01-01

    Two basic findings were presented in the outlined report. The first is that silicon has a very high potential efficiency, demonstrated improvement in reliability and a significant potential for cost reductions. The second is that the photovoltaic technology development process is highly uncertain, but crystalline silicon technology has a substantial knowledge base to draw from, improving its chances of success. Several issues to be addressed are outlined.

  7. Crack growth in single-crystal silicon

    NASA Technical Reports Server (NTRS)

    Chen, C. P.; Leipold, M. H.

    1986-01-01

    Crack growth in single-crystal silicon at room temperature in air was evaluated by double torsion (DT) load-relaxation method and monitored by acoustic emission (AE) technique. Both DT and AE methods indicated lack of subcritical crack growth in silicon. At the critical stress intensity factor, the crack front was found to be jumping several times in a 'mirror' region and then followed by fast crack growth in a 'hackle' region. Hackle marks were found to be associated with plastic deformation at the tip of the fast moving crack. No dislocation etch pits were found in the 'mirror' region, in which crack growth may result from interatomic bonds broken at the crack tip under stress without any plastic deformation. Acoustic emission appears to be spontaneously generated from both interatomic bonds broken and dislocation generation at the moving crack tip during the crack growth in single-crystal silicon.

  8. Freestanding single-crystalline magnetic structures fabricated by ion bombardment

    NASA Astrophysics Data System (ADS)

    Schoenherr, P.; Bischof, A.; Boehm, B.; Eib, P.; Grimm, S.; Alvarado, S. F.; Gross, L.; Allenspach, R.

    2015-01-01

    Starting from an ultrathin Fe film grown epitaxially on top of a GaAs(001) substrate, we show that freestanding structures can be created by ion-beam treatment. These structures are single-crystalline blisters and only a few nanometers thick. Anisotropic stress in the rim of a blister induces magnetic domain states magnetized in the direction normal to the blister edge. Experimental evidence is provided that the lateral size can be confined by starting from a nanostructured template.

  9. Growth of one-dimensional single-crystalline hydroxyapatite nanorods

    NASA Astrophysics Data System (ADS)

    Ren, Fuzeng; Ding, Yonghui; Ge, Xiang; Lu, Xiong; Wang, Kefeng; Leng, Yang

    2012-06-01

    A facile, effective and template/surfactant-free hydrothermal route in the presence of sodium bicarbonate was developed to synthesize highly uniform single-crystalline hydroxyapatite (HA) nanorods with the lengths of several hundred nanometers and aspect ratio up to ˜20. One dimensional (1-D) growth and aspect ratio could be controlled by hydrothermal reaction time and temperature. The longitudinal axis, also the growth direction of the nanorods, is parallel to the [001] direction of HA hexagonal crystal structure.

  10. Synthesis and characterization of single crystalline selenium nanowire arrays

    SciTech Connect

    Zhang, X.Y. . E-mail: apzhxy@polyu.edu.hk; Xu, L.H.; Dai, J.Y.; Cai, Y.; Wang, N.

    2006-09-14

    Ordered selenium nanowire arrays with diameters about 40 nm have been fabricated by electrodeposition using anodic porous alumina templates. As determined by X-ray diffraction, Raman spectra, electron diffraction and high-resolution transmission electron microscopy, selenium nanowires have uniform diameters, which are fully controllable. Single crystalline trigonal selenium nanowires have been obtained after postannealing at 180 deg. C. These nanowires are perfect with a c-axis growth orientation. The optical absorption spectra reveal two types of electron transition activity.

  11. Freestanding single-crystalline magnetic structures fabricated by ion bombardment

    SciTech Connect

    Schoenherr, P.; Bischof, A.; Boehm, B.; Eib, P.; Grimm, S.; Gross, L.; Allenspach, R.; Alvarado, S. F.

    2015-01-19

    Starting from an ultrathin Fe film grown epitaxially on top of a GaAs(001) substrate, we show that freestanding structures can be created by ion-beam treatment. These structures are single-crystalline blisters and only a few nanometers thick. Anisotropic stress in the rim of a blister induces magnetic domain states magnetized in the direction normal to the blister edge. Experimental evidence is provided that the lateral size can be confined by starting from a nanostructured template.

  12. A single crystalline porphyrinic titanium metal–organic framework

    SciTech Connect

    Yuan, Shuai; Liu, Tian -Fu; Feng, Dawei; Tian, Jian; Wang, Kecheng; Qin, Junsheng; Zhang, Qiang; Chen, Ying -Pin; Bosch, Mathieu; Zou, Lanfang; Teat, Simon J.; Dalgarno, Scott J.; Zhou, Hong -Cai

    2015-04-28

    We successfully assembled the photocatalytic titanium-oxo cluster and photosensitizing porphyrinic linker into a metal–organic framework (MOF), namely PCN-22. A preformed titanium-oxo carboxylate cluster is adopted as the starting material to judiciously control the MOF growth process to afford single crystals. This synthetic method is useful to obtain highly crystalline titanium MOFs, which has been a daunting challenge in this field. Moreover, PCN-22 demonstrated permanent porosity and photocatalytic activities toward alcohol oxidation.

  13. Epitaxial single crystalline ferrite films for high frequency applications

    SciTech Connect

    Suzuki, Y.; Dover, R.B. van; Korenivski, V.; Werder, D.; Chen, C.H.; Felder, R.J.; Phillips, J.M.

    1996-11-01

    The successful growth of single crystal ferrites in thin film form is an important step towards their future incorporation into integrated circuits operating at microwave frequencies. The authors have successfully grown high quality single crystalline spinel ferrite thin films of (Mn,Zn)Fe{sub 2}O{sub 4} and CoFe{sub 2}O{sub 4} on (100) and (110) SrTiO{sub 3} and MgAl{sub 2}O{sub 4} at low temperature. These ferrite films are buffered with spinel structure layers that are paramagnetic at room temperature. In contrast to ferrite films grown directly on the substrates, ferrite films grown on buffered substrates exhibit excellent crystallinity and bulk saturation magnetization values, thus indicating the importance of lattice match and structural similarity between the film and the immediately underlying layer. X-ray, RBS, AFM and TEM analysis provide a consistent picture of the structural properties of these ferrite films. The authors then use this technique to grow exchange-coupled bilayers of single crystalline CoFe{sub 2}O{sub 4} and (Mn,Zn)Fe{sub 2}O{sub 4}. In these bilayers, they observe strong exchange coupling across the interface that is similar in strength to the exchange coupling in the individual layers.

  14. Sub-amorphous thermal conductivity in ultrathin crystalline silicon nanotubes.

    PubMed

    Wingert, Matthew C; Kwon, Soonshin; Hu, Ming; Poulikakos, Dimos; Xiang, Jie; Chen, Renkun

    2015-04-01

    Thermal transport behavior in nanostructures has become increasingly important for understanding and designing next generation electronic and energy devices. This has fueled vibrant research targeting both the causes and ability to induce extraordinary reductions of thermal conductivity in crystalline materials, which has predominantly been achieved by understanding that the phonon mean free path (MFP) is limited by the characteristic size of crystalline nanostructures, known as the boundary scattering or Casimir limit. Herein, by using a highly sensitive measurement system, we show that crystalline Si (c-Si) nanotubes (NTs) with shell thickness as thin as ∼5 nm exhibit a low thermal conductivity of ∼1.1 W m(-1) K(-1). Importantly, this value is lower than the apparent boundary scattering limit and is even about 30% lower than the measured value for amorphous Si (a-Si) NTs with similar geometries. This finding diverges from the prevailing general notion that amorphous materials represent the lower limit of thermal transport but can be explained by the strong elastic softening effect observed in the c-Si NTs, measured as a 6-fold reduction in Young's modulus compared to bulk Si and nearly half that of the a-Si NTs. These results illustrate the potent prospect of employing the elastic softening effect to engineer lower than amorphous, or subamorphous, thermal conductivity in ultrathin crystalline nanostructures. PMID:25758163

  15. Simplified module assembly using back-contact crystalline-silicon solar cells

    SciTech Connect

    Gee, J.M.; Garrett, S.E.; Morgan, W.P.

    1997-11-01

    The authors are developing new module concepts that encapsulate and electrically connect all the crystalline-silicon (c-Si) photovoltaic (PV) cells in a module in a single step. The new assembly process (1) uses back-contact c-Si cells, (2) uses a module backplane that has both the electrical circuit, encapsulant, and backsheet in a single piece, and (3) uses a single-step process for assembly of these components into a module. This new process reduces module assembly cost by using planar processes that are easy to automate, by reducing the number of steps, and by eliminating low-throughput (e.g., individual cell tabbing, cell stringing, etc.) steps. The authors refer to this process as monolithic module assembly since it translates many of the advantages of monolithic module construction of thin-film PV modules to wafered c-Si PV modules. Preliminary development of the new module assembly process, and some estimations of the cost potential of the new process, are presented.

  16. High-Performance TiO2 -Based Electron-Selective Contacts for Crystalline Silicon Solar Cells.

    PubMed

    Yang, Xinbo; Bi, Qunyu; Ali, Haider; Davis, Kristopher; Schoenfeld, Winston V; Weber, Klaus

    2016-07-01

    Thin TiO2 films are demonstrated to be an excellent electron-selective contact for crystalline silicon solar cells. An efficiency of 21.6% is achieved for crystalline silicon solar cells featuring a full-area TiO2 -based electron-selective contact. PMID:27159874

  17. 77 FR 35425 - Crystalline Silicon Photovoltaic Cells and Modules From China; Scheduling of the Final Phase of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-13

    ... 7, 2011. See 76 FR 61937 (Oct. 6, 2011) and the newly revised Commission's Handbook on E-Filing... COMMISSION Crystalline Silicon Photovoltaic Cells and Modules From China; Scheduling of the Final Phase of... crystalline silicon photovoltaic cells and modules, provided for in subheadings 8501.31.80, 8501.61.00,...

  18. Single Shot Measurement of a Silicon Single Electron Transistor

    NASA Astrophysics Data System (ADS)

    Ferrus, T.; Hasko, D. G.; Morrissey, Q. R.; Burge, S. R.; Freeman, E. J.; French, M. J.; Lam, A.; Creswell, L.; Collier, R. J.; Williams, D. A.; Briggs, G. A. D.

    2009-06-01

    We describe measurements on a silicon single electron transistor (SET) carried out using a custom cryogenic CMOS measurement circuit (LTCMOS) in close proximity to the device. Quantum mechanical states in the SET were mapped by continuous microwave spectroscopy. The real time evolution of a particularly long lived quantum mechanical state was observed in a single shot measurement, made possible by the much faster measurement rate (50kHz bandwidth). This technique is intended to be applied to the measurement of coherent states in a charge qubit device made of a silicon double dot.

  19. Si + ion beam mixing of tin layers on crystalline silicon

    NASA Astrophysics Data System (ADS)

    Massouras, G.; Roger, J. A.; Romana, L.; Fuchs, G.

    1989-02-01

    Sn layers 64 nm thick deposited onto crystalline Si were irradiated at room temperature using 100 keV Si + ions, with fluences φ ranging from 1 × 10 15 to 9 × 10 16 ions cm -2. RBS analyses show that Si atoms move from the bulk towards the surface as the fluence increases, and are found at the very surface for φ = 4 × 10 16 Si + cm -2. Then a saturation is reached. Sn and Si profiles determined using a Fortran programme, and the calibration of depth scale is obtained from cross-sectional TEM observations. The average composition of the intermixed layer is given as a function of φ. Different layers of various crystallinity are found below the surface and their nature is discussed.

  20. 77 FR 73018 - Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules, From the People's...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-07

    ... FR 63791 (October 17, 2012) (``Final Determination''). \\2\\ See Crystalline Silicon Photovoltaic Cells... and Affirmative Preliminary Determination of Critical Circumstances,77 FR 31309 (May 25, 2012...., Ltd HC Solar Power Co., Ltd. 24.48 Zhiheng Solar Inc....... 24.48 Zhejiang Leye 24.48...

  1. 77 FR 25400 - Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules, From the People's...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-30

    ..., 76 FR 70966 (November 16, 2011), and Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules, From the People's Republic of China: Initiation of Antidumping Duty Investigation, 76 FR..., 77 FR 17439 (March 26, 2012). Because the AD and CVD investigations were initiated simultaneously...

  2. 76 FR 81914 - Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules, From the People's...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-29

    ... Countervailing Duty Investigation, 76 FR 70966 (November 16, 2011). Postponement of Due Date for the Preliminary... Amended, 70 FR 24533 (May 10, 2005). This notice is issued and published pursuant to section 703(c)(2) of... International Trade Administration Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into...

  3. 77 FR 10478 - Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules, From the People's...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-22

    ... the Countervailing Duty Investigation, 76 FR 81914 (December 29, 2011). \\2\\ See Crystalline Silicon... Postponement of Preliminary Determination in the Countervailing Duty Investigation, 77 FR 4764 (January 31... Determination Deadlines Pursuant to the Tariff Act of 1930, As Amended, 70 FR 24533 (May 10, 2005). This...

  4. Planar-integrated single-crystalline perovskite photodetectors

    PubMed Central

    Saidaminov, Makhsud I.; Adinolfi, Valerio; Comin, Riccardo; Abdelhady, Ahmed L.; Peng, Wei; Dursun, Ibrahim; Yuan, Mingjian; Hoogland, Sjoerd; Sargent, Edward H.; Bakr, Osman M.

    2015-01-01

    Hybrid perovskites are promising semiconductors for optoelectronic applications. However, they suffer from morphological disorder that limits their optoelectronic properties and, ultimately, device performance. Recently, perovskite single crystals have been shown to overcome this problem and exhibit impressive improvements: low trap density, low intrinsic carrier concentration, high mobility, and long diffusion length that outperform perovskite-based thin films. These characteristics make the material ideal for realizing photodetection that is simultaneously fast and sensitive; unfortunately, these macroscopic single crystals cannot be grown on a planar substrate, curtailing their potential for optoelectronic integration. Here we produce large-area planar-integrated films made up of large perovskite single crystals. These crystalline films exhibit mobility and diffusion length comparable with those of single crystals. Using this technique, we produced a high-performance light detector showing high gain (above 104 electrons per photon) and high gain-bandwidth product (above 108 Hz) relative to other perovskite-based optical sensors. PMID:26548941

  5. Use of low energy hydrogen ion implants in high efficiency crystalline silicon solar cells

    NASA Technical Reports Server (NTRS)

    Fonash, S. J.; Singh, R.

    1985-01-01

    This program is a study of the use of low energy hydrogen ion implantation for high efficiency crystalline silicon solar cells. The first quarterly report focuses on two tasks of this program: (1) an examination of the effects of low energy hydrogen implants on surface recombination speed; and (2) an examination of the effects of hydrogen on silicon regrowth and diffusion in silicon. The first part of the project focussed on the measurement of surface properties of hydrogen implanted silicon. Low energy hydrogen ions when bombarded on the silicon surface will create structural damage at the surface, deactivate dopants and introduce recombination centers. At the same time the electrically active centers such as dangling bonds will be passivated by these hydrogen ions. Thus hydrogen is expected to alter properties such as the surface recombination velocity, dopant profiles on the emitter, etc. In this report the surface recombination velocity of a hydrogen emplanted emitter was measured.

  6. Exposure to Fibres, Crystalline Silica, Silicon Carbide and Sulphur Dioxide in the Norwegian Silicon Carbide Industry

    PubMed Central

    Føreland, S.; Bye, E.; Bakke, B.; Eduard, W.

    2008-01-01

    Objectives: The aim of this study was to assess personal exposure to fibres, crystalline silica, silicon carbide (SiC) and sulphur dioxide in the Norwegian SiC industry. Methods: Approximately 720 fibre samples, 720 respirable dust samples and 1400 total dust samples were collected from randomly chosen workers from the furnace, processing and maintenance departments in all three Norwegian SiC plants. The respirable dust samples were analysed for quartz, cristobalite and non-fibrous SiC content. Approximately 240 sulphur dioxide samples were collected from workers in the furnace department. Results: The sorting operators from all plants, control room and cleaning operators in Plant A and charger, charger/mix and payloader operators in Plant C had a geometric mean (GM) of fibre exposure above the Norwegian occupational exposure limit (OEL) (0.1 fibre cm−3). The cleaner operators in Plant A had the highest GM exposure to respirable quartz (20 μg m−3). The charger/mix operators in Plant C had the highest GM exposure to respirable cristobalite (38 μg m−3) and the refinery crusher operators in Plant A had the highest GM exposure to non-fibrous SiC (0.65 mg m−3). Exposure to the crystalline silica and non-fibrous SiC was generally low and between 0.4 and 2.1% of the measurements exceeded the OELs. The cleaner operators in Plant A had the highest GM exposure to respirable dust (1.3 mg m−3) and total dust (21 mg m−3). GM exposures for respirable dust above the Norwegian SiC industry-specific OEL of 0.5 mg m−3 were also found for refinery crusher operators in all plants and mix, charger, charger/mix and sorting operators in Plant C. Only 4% of the total dust measurements exceeded the OEL for nuisance dust of (10 mg m−3). Exposure to sulphur dioxide was generally low. However, peaks in the range of 10–100 p.p.m. were observed for control room and crane operators in Plants A and B and for charger and charger/mix operators in Plant C. Conclusion: Workers in

  7. Graphene Quantum Dot Layers with Energy-Down-Shift Effect on Crystalline-Silicon Solar Cells.

    PubMed

    Lee, Kyung D; Park, Myung J; Kim, Do-Yeon; Kim, Soo M; Kang, Byungjun; Kim, Seongtak; Kim, Hyunho; Lee, Hae-Seok; Kang, Yoonmook; Yoon, Sam S; Hong, Byung H; Kim, Donghwan

    2015-09-01

    Graphene quantum dot (GQD) layers were deposited as an energy-down-shift layer on crystalline-silicon solar cell surfaces by kinetic spraying of GQD suspensions. A supersonic air jet was used to accelerate the GQDs onto the surfaces. Here, we report the coating results on a silicon substrate and the GQDs' application as an energy-down-shift layer in crystalline-silicon solar cells, which enhanced the power conversion efficiency (PCE). GQD layers deposited at nozzle scan speeds of 40, 30, 20, and 10 mm/s were evaluated after they were used to fabricate crystalline-silicon solar cells; the results indicate that GQDs play an important role in increasing the optical absorptivity of the cells. The short-circuit current density was enhanced by about 2.94% (0.9 mA/cm(2)) at 30 mm/s. Compared to a reference device without a GQD energy-down-shift layer, the PCE of p-type silicon solar cells was improved by 2.7% (0.4 percentage points). PMID:26264738

  8. Laser induced lifetime degradation in p-type crystalline silicon

    SciTech Connect

    Ametowobla, M.; Bilger, G.; Koehler, J. R.; Werner, J. H.

    2012-06-01

    Pulsed, green laser irradiation of uncoated p-type silicon leads to a significant reduction of the effective minority carrier lifetime. The reason for the lifetime drop lies in the introduction of recombination centres into the laser melted and recrystallized surface layer, leading to a low local minority carrier lifetime {tau} Almost-Equal-To 10 ns inside this surface layer. The laser treatment introduces the impurities oxygen, carbon and nitrogen into the silicon and further leads to an n-type doping of the surface layer. There are strong indications that these impurities are responsible for the observed n-type doping, as well as the lifetime reduction after irradiation. Both effects are removed by thermal annealing. An estimate shows that the low local lifetime does nevertheless not affect the performance of industrial or contacted selective solar cell emitter structures.

  9. Laser induced lifetime degradation in p-type crystalline silicon

    NASA Astrophysics Data System (ADS)

    Ametowobla, M.; Bilger, G.; Köhler, J. R.; Werner, J. H.

    2012-06-01

    Pulsed, green laser irradiation of uncoated p-type silicon leads to a significant reduction of the effective minority carrier lifetime. The reason for the lifetime drop lies in the introduction of recombination centres into the laser melted and recrystallized surface layer, leading to a low local minority carrier lifetime τ ≈ 10 ns inside this surface layer. The laser treatment introduces the impurities oxygen, carbon and nitrogen into the silicon and further leads to an n-type doping of the surface layer. There are strong indications that these impurities are responsible for the observed n-type doping, as well as the lifetime reduction after irradiation. Both effects are removed by thermal annealing. An estimate shows that the low local lifetime does nevertheless not affect the performance of industrial or contacted selective solar cell emitter structures.

  10. Al-O interactions in ion-implanted crystalline silicon

    NASA Astrophysics Data System (ADS)

    Galvagno, G.; La Ferla, A.; Spinella, C.; Priolo, F.; Raineri, V.; Torrisi, Lucio; Rimini, E.; Carnera, A.; Gasparotto, A.

    1994-08-01

    The formation and dissolution of Si-O-Al precipitates have been investigated in Czochralski silicon wafers implanted with 6 MeV Al ions and thermally processed. The data have been compared to the O precipitation in samples implanted with 6 MeV Si or P ions. The amount of precipitated O atoms is about one order of magnitude higher for Al than for Si or P implanted samples. Moreover, a strong gettering of the Al atoms by the silicon dioxide precipitates has been observed. The precipitate evolution has been studied for different annealing times and temperatures. The oxygen precipitation has been simulated by the classical theory of nucleation and growth, with the introduction of new factors that take into account the implant damage distribution, the agglomeration of point defects during the initial stages of the annealing and the oxygen outdiffusion from the sample surface.

  11. Simultaneous broadband light trapping and fill factor enhancement in crystalline silicon solar cells induced by Ag nanoparticles and nanoshells.

    PubMed

    Fahim, Narges F; Jia, Baohua; Shi, Zhengrong; Gu, Min

    2012-09-10

    Crystalline silicon solar cells are predominant and occupying more than 89% of the global solar photovoltaic market. Despite the boom of the innovative solar technologies, few can provide a low-cost radical solution to dramatically boost the efficiency of crystalline silicon solar cells, which has reached plateau in the past ten years. Here, we present a novel strategy to simultaneously achieve dramatic enhancement in the short-circuit current and the fill factor through the integration of Ag plasmonic nanoparticles and nanoshells on the antireflection coating and the screen-printed fingers of monocrystalline silicon solar cells, respectively, by a single step and scalable modified electroless displacement method. As a consequence, up to 35.2% enhancement in the energy conversion efficiency has been achieved due to the plasmonic broadband light trapping and the significant reduction in the series resistance. More importantly, this method can further increase the efficiency of the best performing textured solar cells from 18.3% to 19.2%, producing the highest efficiency cells exceeding the state-of-the-art efficiency of the standard screen-printed solar cells. The dual functions of the Ag nanostructures, reported for the first time here, present a clear contrast to the previous works, where plasmonic nanostructures were integrated into solar cells to achieve the short-circuit current enhancement predominately. Our method offers a facile, cost-effective and scalable pathway for metallic nanostructures to be used to dramatically boost the overall efficiency of the optically thick crystalline silicon solar cells. PMID:23037536

  12. The Effect of Metallic Coatings and Crystallinity on the Volume Expansion of Silicon during Electrochemical Lithiation and Delithiation

    SciTech Connect

    Mcdowell, Matthew T.; Woo Lee, Seok; Wang, Chong M.; Cui, Yi

    2012-05-01

    Applying surface coatings to alloying anodes for Li-ion batteries can improve rate capability and cycle life, but it is unclear how this second phase affects mechanical deformation during electrochemical reaction. Here, in-situ transmission electron microscopy is employed to investigate the electrochemical lithiation and delithiation of silicon nanowires (NWs) with copper coatings. When copper is coated on one sidewall, the NW bilayer structure bends due to length changes in the silicon during delithiation. Tensile hoop stress causes conformal copper coatings to fracture during lithiation without undergoing bending deformation. In addition, in-situ and ex-situ observations indicate that a copper coating plays a role in suppressing volume expansion during lithiation. Finally, the deformation characteristics and dimensional changes of amorphous, polycrystalline, and single-crystalline silicon are compared and related to observed electrochemical behavior. This study reveals important aspects of the deformation process of silicon anodes, and the results suggest that metallic coatings can be used to improve rate behavior and to manage or direct volume expansion in optimized silicon anode frameworks.

  13. A single molecule study of cellulase hydrolysis of crystalline cellulose

    NASA Astrophysics Data System (ADS)

    Liu, Yu-San; Luo, Yonghua; Baker, John O.; Zeng, Yining; Himmel, Michael E.; Smith, Steve; Ding, Shi-You

    2010-02-01

    Cellobiohydrolase-I (CBH I), a processive exoglucanase secreted by Trichoderma reesei, is one of the key enzyme components in a commercial cellulase mixture currently used for processing biomass to biofuels. CBH I contains a family 7 glycoside hydrolase catalytic module, a family 1 carbohydrate-binding module (CBM), and a highlyglycosylated linker peptide. It has been proposed that the CBH I cellulase initiates the hydrolysis from the reducing end of one cellulose chain and successively cleaves alternate β-1,4-glycosidic bonds to release cellobiose as its principal end product. The role each module of CBH I plays in the processive hydrolysis of crystalline cellulose has yet to be convincingly elucidated. In this report, we use a single-molecule approach that combines optical (Total Internal Reflection Fluorescence microscopy, or TIRF-M) and non-optical (Atomic Force Microscopy, or AFM) imaging techniques to analyze the molecular motion of CBM tagged with green fluorescence protein (GFP), and to investigate the surface structure of crystalline cellulose and changes made in the structure by CBM and CBH I. The preliminary results have revealed a confined nanometer-scale movement of the TrCBM1-GFP bound to cellulose, and decreases in cellulose crystal size as well as increases in surface roughness during CBH I hydrolysis of crystalline cellulose.

  14. Amorphous Silicon Carbide Passivating Layers to Enable Higher Processing Temperature in Crystalline Silicon Heterojunction Solar Cells

    SciTech Connect

    Boccard, Mathieu; Holman, Zachary

    2015-04-06

    "Very efficient crystalline silicon (c-Si) solar cells have been demonstrated when thin layers of intrinsic and doped hydrogenated amorphous silicon (a-Si:H) are used for passivation and carrier selectivity in a heterojunction device. One limitation of this device structure is the (parasitic) absorption in the front passivation/collection a-Si:H layers; another is the degradation of the a-Si:H-based passivation upon temperature, limiting the post-processes to approximately 200°C thus restricting the contacting possibilities and potential tandem device fabrication. To alleviate these two limitations, we explore the potential of amorphous silicon carbide (a-SiC:H), a widely studied material in use in standard a-Si:H thin-film solar cells, which is known for its wider bandgap, increased hydrogen content and stronger hydrogen bonding compared to a-Si:H. We study the surface passivation of solar-grade textured n-type c-Si wafers for symmetrical stacks of 10-nm-thick intrinsic a-SiC:H with various carbon content followed by either p-doped or n-doped a-Si:H (referred to as i/p or i/n stacks). For both doping types, passivation (assessed through carrier lifetime measurements) is degraded by increasing the carbon content in the intrinsic a-SiC:H layer. Yet, this hierarchy is reversed after annealing at 350°C or more due to drastic passivation improvements upon annealing when an a-SiC:H layer is used. After annealing at 350°C, lifetimes of 0.4 ms and 2.0 ms are reported for i/p and i/n stacks, respectively, when using an intrinsic a-SiC:H layer with approximately 10% of carbon (initial lifetimes of 0.3 ms and 0.1 ms, respectively, corresponding to a 30% and 20-fold increase, respectively). For stacks of pure a-Si:H material the lifetimes degrade from 1.2 ms and 2.0 ms for i/p and i/n stacks, respectively, to less than 0.1 ms and 1.1 ms (12-fold and 2-fold decrease, respectively). For complete solar cells using pure a-Si:H i/p and i/n stacks, the open-circuit voltage (Voc

  15. Cutting fluid study for single crystal silicon

    SciTech Connect

    Chargin, D.

    1998-05-05

    An empirical study was conducted to evaluate cutting fluids for Single Point Diamond Turning (SPDT) of single crystal silicon. The pH of distilled waster was adjusted with various additives the examine the effect of pH on cutting operations. Fluids which seemed to promote ductile cutting appeared to increase tool wear as well, an undesirable tradeoff. High Ph sodium hydroxide solutions showed promise for further research, as they yielded the best combination of reduced tool wear and good surface finish in the ductile regime. Negative rake tools were verified to improve the surface finish, but the negative rake tools used in the experiments also showed much higher wear than conventional 0{degree} rake tools. Effects of crystallographic orientation on SPDT, such as star patterns of fracture damage forming near the center of the samples, were observed to decrease with lower feedrates. Silicon chips were observed and photographed, indicative of a ductile materials removal process.

  16. Advantages of gated silicon single photon detectors

    NASA Astrophysics Data System (ADS)

    Legré, Matthieu; Lunghi, Tommaso; Stucki, Damien; Zbinden, Hugo

    2013-05-01

    We present gated silicon single photon detectors based on two commercially available avalanche photodiodes (APDs) and one customised APD from ID Quantique SA. This customised APD is used in a commercially available device called id110. A brief comparison of the two commercial APDs is presented. Then, the charge persistence effect of all of those detectors that occurs just after a strong illumination is shown and discussed.

  17. Hydrogen structures in heavily hydrogenated crystalline and amorphous silicon

    SciTech Connect

    Jackson, W.G.; Franz, A.; Chabal, Y.; Weldon, M.K.; Jin, H.C.; Abelson, J.R.

    1998-12-31

    The hydrogen binding energy distribution and IR spectra of hydrogen platelets in c-Si have been measured and compared to H in other forms of silicon including hydrogenated polycrystalline and amorphous Si. The binding distribution for platelet containing samples, determined using H evolution, exhibits two peaks: a bulk peak at 1.8--1.9 eV below the transport barrier, and a second possibly surface related peak 1.8--1.9 eV below the surface evolution barrier. The bulk peak grows at 250 C and is consistent with calculated energies for platelet structures. The same two evolution peaks are found in hydrogenated polycrystalline Si and amorphous silicon. The IR spectra for heavily hydrogenated c-Si are dominated by the stretching modes at 2076 and 2128 cm{sup {minus}1}. Most surprisingly there appears to be a strong mode at 856 cm{sup {minus}1} which is associated with a deformation mode of SiH{sub 3}. Even more surprising, this SiH{sub 3} 856 cm{sup {minus}1} mode remains until 550 C indicating that the SiH{sub 3} containing structures are rather stable.

  18. Synthesis and Characterization of Crystalline Silicon Carbide Nanoribbons

    PubMed Central

    2010-01-01

    In this paper, a simple method to synthesize silicon carbide (SiC) nanoribbons is presented. Silicon powder and carbon black powder placed in a horizontal tube furnace were exposed to temperatures ranging from 1,250 to 1,500°C for 5–12 h in an argon atmosphere at atmospheric pressure. The resulting SiC nanoribbons were tens to hundreds of microns in length, a few microns in width and tens of nanometers in thickness. The nanoribbons were characterized with electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy, and were found to be hexagonal wurtzite–type SiC (2H-SiC) with a growth direction of . The influence of the synthesis conditions such as the reaction temperature, reaction duration and chamber pressure on the growth of the SiC nanomaterial was investigated. A vapor–solid reaction dominated nanoribbon growth mechanism was discussed. PMID:20676202

  19. Synthesis and Characterization of Crystalline Silicon Carbide Nanoribbons

    NASA Astrophysics Data System (ADS)

    Zhang, Huan; Ding, Weiqiang; He, Kai; Li, Ming

    2010-08-01

    In this paper, a simple method to synthesize silicon carbide (SiC) nanoribbons is presented. Silicon powder and carbon black powder placed in a horizontal tube furnace were exposed to temperatures ranging from 1,250 to 1,500°C for 5-12 h in an argon atmosphere at atmospheric pressure. The resulting SiC nanoribbons were tens to hundreds of microns in length, a few microns in width and tens of nanometers in thickness. The nanoribbons were characterized with electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy, and were found to be hexagonal wurtzite-type SiC (2H-SiC) with a growth direction of [10bar{1}0] . The influence of the synthesis conditions such as the reaction temperature, reaction duration and chamber pressure on the growth of the SiC nanomaterial was investigated. A vapor-solid reaction dominated nanoribbon growth mechanism was discussed.

  20. Photovoltaic solar panels of crystalline silicon: Characterization and separation.

    PubMed

    Dias, Pablo Ribeiro; Benevit, Mariana Gonçalves; Veit, Hugo Marcelo

    2016-03-01

    Photovoltaic panels have a limited lifespan and estimates show large amounts of solar modules will be discarded as electronic waste in a near future. In order to retrieve important raw materials, reduce production costs and environmental impacts, recycling such devices is important. Initially, this article investigates which silicon photovoltaic module's components are recyclable through their characterization using X-ray fluorescence, X-ray diffraction, energy dispersion spectroscopy and atomic absorption spectroscopy. Next, different separation methods are tested to favour further recycling processes. The glass was identified as soda-lime glass, the metallic filaments were identified as tin-lead coated copper, the panel cells were made of silicon and had silver filaments attached to it and the modules' frames were identified as aluminium, all of which are recyclable. Moreover, three different components segregation methods have been studied. Mechanical milling followed by sieving was able to separate silver from copper while chemical separation using sulphuric acid was able to detach the semiconductor material. A thermo gravimetric analysis was performed to evaluate the use of a pyrolysis step prior to the component's removal. The analysis showed all polymeric fractions present degrade at 500 °C. PMID:26787682

  1. Maskless implants of 20 keV Ga{sup +} in thin crystalline silicon on insulator

    SciTech Connect

    Mio, A. M.; D'Arrigo, G.; Rimini, E.; Spinella, C.; Milazzo, R. G.; Peto, L.; Nadzeyka, A.; Bauerdick, S.

    2013-01-28

    A nano-sized ion beam apparatus has been used as maskless lithography to implant 20 keV Ga{sup +} ions into a 26 nm thick silicon crystalline film on insulator. The ion beam, with about 5 nm standard deviation, delivered few hundred ions during a single shot. Circular areas with nominal diameter of 20 or 50 nm were irradiated to a fluence of 5 Multiplication-Sign 10{sup 14}/cm{sup 2}. Transmission electron microscopy evidenced that the damaged regions are characterized by an irregular contour with many disordered filaments. Damage extends across the layer thickness and fast Fourier transform analysis indicates that implantation causes the amorphization of a region which extends beyond the nominal diameter. In situ annealing experiments demonstrated that the disordered filamentary regions disappear in the 250-450 Degree-Sign C temperature range and the interfaces with the surrounding crystalline regions sharpen. A temperature as high as 600 Degree-Sign C is required to fully re-crystallize the amorphous core of the implanted dots. Reordering occurs by multi-orientation lateral solid-phase epitaxial growth and the breaking of (111) and (101) interfaces, due to the formation of twins, triggers a fast crystallization kinetics. Rapid thermal annealing (890 Degree-Sign C-10 s) completely crystallizes the amorphous regions, twins are absent and small cluster of defects remains instead. Preliminary scanning capacitance measurements indicate that the implanted atoms, after crystallization, are electrically active. The implant method is then a viable processing step for the doping of non-bulk fully depleted ultra-thin-body MOSFET.

  2. Advancements in n-Type Base Crystalline Silicon Solar Cells and Their Emergence in the Photovoltaic Industry

    PubMed Central

    ur Rehman, Atteq; Lee, Soo Hong

    2013-01-01

    The p-type crystalline silicon wafers have occupied most of the solar cell market today. However, modules made with n-type crystalline silicon wafers are actually the most efficient modules up to date. This is because the material properties offered by n-type crystalline silicon substrates are suitable for higher efficiencies. Properties such as the absence of boron-oxygen related defects and a greater tolerance to key metal impurities by n-type crystalline silicon substrates are major factors that underline the efficiency of n-type crystalline silicon wafer modules. The bi-facial design of n-type cells with good rear-side electronic and optical properties on an industrial scale can be shaped as well. Furthermore, the development in the industrialization of solar cell designs based on n-type crystalline silicon substrates also highlights its boost in the contributions to the photovoltaic industry. In this paper, a review of various solar cell structures that can be realized on n-type crystalline silicon substrates will be given. Moreover, the current standing of solar cell technology based on n-type substrates and its contribution in photovoltaic industry will also be discussed. PMID:24459433

  3. Vibrational Lifetime of Interstitial Oxygen in Crystalline Silicon

    NASA Astrophysics Data System (ADS)

    Sun, Baozhou; Fraser, Andrew; Lüpke, Gunter

    2003-03-01

    - The lifetime of the asymmetric stretch mode of interstitial oxygen in crystalline Si is measured directly by transient bleaching spectroscopy. The 1136-cm-1 mode has an extremely long lifetime, T1 = 229 ps at 10 K. The lifetime shows surprisingly strong temperature dependence, decreasing by more than two orders in magnitude between 50 and 180 K. The dominating decay channel involves a high number of low-frequency modes of 142 +/- 20 cm-1 corresponding to transverse acoustic phonons or pseudolocalized modes of Oi. This work was supported in part by NSF through grant DMR-00-76027, ONR through grant N00014-01-1-0770, and the Thomas F. and Kate Miller Jeffress Memorial Trust through grant J-545.

  4. Epitaxial growth of homogeneous single-crystalline AlN films on single-crystalline Cu (1 1 1) substrates

    NASA Astrophysics Data System (ADS)

    Wang, Wenliang; Yang, Weijia; Liu, Zuolian; Lin, Yunhao; Zhou, Shizhong; Qian, Huirong; Gao, Fangliang; Yang, Hui; Li, Guoqiang

    2014-03-01

    The homogeneous and crack free single-crystalline AlN thin films have been epitaxially grown on single-crystalline Cu (1 1 1) substrates with an in-plane alignment of AlN [11-20]//Cu [1-10] by pulsed laser deposition (PLD) technology with an integrated laser rastering program. The as-grown AlN films are studied by spectroscopic ellipsometry, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), polarized light microscopy, high-resolution X-ray diffraction, and high-resolution transmission electron microscopy (HRTEM). The spectroscopic ellipsometry reveals the excellent thickness uniformity of as-grown AlN films on the Cu (1 1 1) substrates with a root-mean-square (RMS) thickness inhomogeneity less than 2.6%. AFM and FESEM measurements indicate that very smooth and flat surface AlN films are obtained with a surface RMS roughness of 2.3 nm. The X-ray reflectivity image illustrates that there is a maximum of 1.2 nm thick interfacial layer existing between the as-grown AlN and Cu (1 1 1) substrates and is confirmed by HRTEM measurement, and reciprocal space mapping shows that almost fully relaxed AlN films are achieved only with a compressive strain of 0.48% within ˜321 nm thick films. This work demonstrates a possibility to obtain homogeneous and crack free single-crystalline AlN films on metallic substrates by PLD with optimized laser rastering program, and brings up a broad prospect for the application of acoustic filters that require abrupt hetero-interfaces between the AlN films and the metallic electrodes.

  5. Variations in Crystalline Structures and Electrical Properties of Single Crystalline Boron Nitride Nanosheets

    PubMed Central

    Aldalbahi, Ali; Zhou, Andrew Feng; Feng, Peter

    2015-01-01

    We report the studies of (1) the basic mechanism underlying the formation of defect-free, single crystalline boron nitride nanosheets (BNNSs) synthesized using pulsed laser plasma deposition (PLPD) technique, (2) the variation in the crystalline structure at the edges of the hexagonal boron nitride (h-BN) nanosheets, and (3) the basic electrical properties related to the BNNSs tunneling effect and electrical breakdown voltage. The nanoscale morphologies of BNNSs are characterized using scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM). The results show that each sample consisted of a number of transparent BNNSs that partially overlapped one another. Varying the deposition duration yielded different thicknesses of sample but did not affect the morphology, structure, and thickness of individual BNNSs pieces. Analysis of the SEM and HRTEM data revealed changes in the spatial period of the B3–N3 hexagonal structures and the interlayer distance at the edge of the BNNSs, which occurred due to the limited number of atomic layers and was confirmed further by x-ray diffraction (XRD) study. The experimental results clearly indicate that the values of the electrical conductivities of the super-thin BNNSs and the effect of temperature relied strongly on the direction of observation. PMID:26563901

  6. Variations in Crystalline Structures and Electrical Properties of Single Crystalline Boron Nitride Nanosheets.

    PubMed

    Aldalbahi, Ali; Zhou, Andrew Feng; Feng, Peter

    2015-01-01

    We report the studies of (1) the basic mechanism underlying the formation of defect-free, single crystalline boron nitride nanosheets (BNNSs) synthesized using pulsed laser plasma deposition (PLPD) technique, (2) the variation in the crystalline structure at the edges of the hexagonal boron nitride (h-BN) nanosheets, and (3) the basic electrical properties related to the BNNSs tunneling effect and electrical breakdown voltage. The nanoscale morphologies of BNNSs are characterized using scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM). The results show that each sample consisted of a number of transparent BNNSs that partially overlapped one another. Varying the deposition duration yielded different thicknesses of sample but did not affect the morphology, structure, and thickness of individual BNNSs pieces. Analysis of the SEM and HRTEM data revealed changes in the spatial period of the B3-N3 hexagonal structures and the interlayer distance at the edge of the BNNSs, which occurred due to the limited number of atomic layers and was confirmed further by x-ray diffraction (XRD) study. The experimental results clearly indicate that the values of the electrical conductivities of the super-thin BNNSs and the effect of temperature relied strongly on the direction of observation. PMID:26563901

  7. Stable porous crystalline silicon with nanotubular structure: A predicted allotrope with direct band gap

    NASA Astrophysics Data System (ADS)

    Tang, Chi-Pui; Cao, Jie; Xiong, Shi-Jie

    2015-06-01

    On basis of the first principle calculation we show that a crystalline structure of silicon, as a novel allotrope with nanotubular holes along two perpendicular directions, is stable. The calculations on geometrical and electronic properties reveal that this allotrope possesses a direct band gap wider by 0.5 eV than the indirect one of silicon with diamond structure. The crystal belongs to I41/AMD space group, showing anisotropic optical properties and Young modulus. The bulk modulus is 64.4 GPa and the density is 1.9 g/cm3, lower than that of the diamond silicon due to the presence of nanotubular holes. It is hopeful that the allotrope may widely expand applications of silicon in many fields due to its direct band gap and specific nanotubular structure.

  8. Optimization of textured-dielectric coatings for crystalline-silicon solar cells

    SciTech Connect

    Gee, J.M.; Gordon, R.; Liang, H.

    1996-07-01

    The authors report on the optimization of textured-dielectric coatings for reflectance control in crystalline-silicon (c-Si) photovoltaic modules. Textured-dielectric coatings reduce encapsulated-cell reflectance by promoting optical confinement in the module encapsulation; i.e., the textured-dielectric coating randomizes the direction of rays reflected from the dielectric and from the c-Si cell so that many of these reflected rays experience total internal reflection at the glass-air interface. Some important results of this work include the following: the authors demonstrated textured-dielectric coatings (ZnO) deposited by a high-throughput low-cost deposition process; they identified factors important for achieving necessary texture dimensions; they achieved solar-weighted extrinsic reflectances as low as 6% for encapsulated c-Si wafers with optimized textured-ZnO coatings; and they demonstrated improvements in encapsulated cell performance of up to 0.5% absolute compared to encapsulated planar cells with single-layer antireflection coatings.

  9. Camera-Based Lock-in and Heterodyne Carrierographic Photoluminescence Imaging of Crystalline Silicon Wafers

    NASA Astrophysics Data System (ADS)

    Sun, Q. M.; Melnikov, A.; Mandelis, A.

    2015-06-01

    Carrierographic (spectrally gated photoluminescence) imaging of a crystalline silicon wafer using an InGaAs camera and two spread super-bandgap illumination laser beams is introduced in both low-frequency lock-in and high-frequency heterodyne modes. Lock-in carrierographic images of the wafer up to 400 Hz modulation frequency are presented. To overcome the frame rate and exposure time limitations of the camera, a heterodyne method is employed for high-frequency carrierographic imaging which results in high-resolution near-subsurface information. The feasibility of the method is guaranteed by the typical superlinearity behavior of photoluminescence, which allows one to construct a slow enough beat frequency component from nonlinear mixing of two high frequencies. Intensity-scan measurements were carried out with a conventional single-element InGaAs detector photocarrier radiometry system, and the nonlinearity exponent of the wafer was found to be around 1.7. Heterodyne images of the wafer up to 4 kHz have been obtained and qualitatively analyzed. With the help of the complementary lock-in and heterodyne modes, camera-based carrierographic imaging in a wide frequency range has been realized for fundamental research and industrial applications toward in-line nondestructive testing of semiconductor materials and devices.

  10. On the generation of grooves on crystalline silicon irradiated by femtosecond laser pulses.

    PubMed

    He, Shutong; Nivas, Jijil J J; Vecchione, Antonio; Hu, Minglie; Amoruso, Salvatore

    2016-02-22

    Irradiation of crystalline silicon with femtosecond laser pulses produces a variety of quasi-periodic surface structures, among which sub-wavelength ripples creation is largely studied. Here we report an experimental investigation and a theoretical interpretation focusing on the seldom considered issue of quasi-periodic, micron spaced grooves formation. We characterize the morphological evolution of the grooves generation and experimentally single out the variation of the threshold fluence for their formation with the number of pulses N, while typical ripples simultaneously produced in the irradiated area are always considered for comparison. Our experimental findings evidence a power law dependence of the threshold fluence on the number of pulses both for ripples and grooves formation, typical of an incubation behavior. The incubation factor and single pulse threshold are (0.76 ± 0.04) and (0.20 ± 0.04) J/cm2 for ripples and (0.84 ± 0.03) and (0.54 ± 0.08) J/cm2 for grooves, respectively. Surface-scattered wave theory, which allows modeling irradiation with a single pulse on a rough surface, is exploited to interpret the observed structural modification of the surface textures. A simple, empirical scaling approach is proposed associating the surface structures generated in multiple-pulse experiments with the predictions of the surface-scattered wave theory, at laser fluencies around the grooves formation threshold. This, in turn, allows proposing a physical mechanism interpreting the grooves generation as well as the coexistence and relative prominence of grooves and ripples in the irradiated area. PMID:26906987

  11. Influence of Chemical Composition and Structure in Silicon Dielectric Materials on Passivation of Thin Crystalline Silicon on Glass.

    PubMed

    Calnan, Sonya; Gabriel, Onno; Rothert, Inga; Werth, Matteo; Ring, Sven; Stannowski, Bernd; Schlatmann, Rutger

    2015-09-01

    In this study, various silicon dielectric films, namely, a-SiOx:H, a-SiNx:H, and a-SiOxNy:H, grown by plasma enhanced chemical vapor deposition (PECVD) were evaluated for use as interlayers (ILs) between crystalline silicon and glass. Chemical bonding analysis using Fourier transform infrared spectroscopy showed that high values of oxidant gases (CO2 and/or N2), added to SiH4 during PECVD, reduced the Si-H and N-H bond density in the silicon dielectrics. Various three layer stacks combining the silicon dielectric materials were designed to minimize optical losses between silicon and glass in rear side contacted heterojunction pn test cells. The PECVD grown silicon dielectrics retained their functionality despite being subjected to harsh subsequent processing such as crystallization of the silicon at 1414 °C or above. High values of short circuit current density (Jsc; without additional hydrogen passivation) required a high density of Si-H bonds and for the nitrogen containing films, additionally, a high N-H bond density. Concurrently high values of both Jsc and open circuit voltage Voc were only observed when [Si-H] was equal to or exceeded [N-H]. Generally, Voc correlated with a high density of [Si-H] bonds in the silicon dielectric; otherwise, additional hydrogen passivation using an active plasma process was required. The highest Voc ∼ 560 mV, for a silicon acceptor concentration of about 10(16) cm(-3), was observed for stacks where an a-SiOxNy:H film was adjacent to the silicon. Regardless of the cell absorber thickness, field effect passivation of the buried silicon surface by the silicon dielectric was mandatory for efficient collection of carriers generated from short wavelength light (in the vicinity of the glass-Si interface). However, additional hydrogen passivation was obligatory for an increased diffusion length of the photogenerated carriers and thus Jsc in solar cells with thicker absorbers. PMID:26281016

  12. Solution-Based Synthesis of Crystalline Silicon from Liquid Silane through Laser and Chemical Annealing

    SciTech Connect

    Iyer, Ganjigunte R. S.; Hobbie, Erik K.; Guruvenket, Srinivasan; Hoey, Justin M.; Anderson, Kenneth J.; Lovaasen, John; Gette, Cody; Schulz, Douglas L.; Swenson, Orven F.; Elangovan, Arumugasamy; Boudjouk, P.

    2012-05-23

    We report a solution process for the synthesis of crystalline silicon from the liquid silane precursor cyclohexasilane (Si6H12). Polysilane films were crystallized through thermal and laser annealing, with plasma hydrogenation at atmospheric pressure generating further structural changes in the films. The evolution from amorphous to microcrystalline is characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and impedance spectroscopy. A four-decade enhancement in the electrical conductivity is attributed to a disorder-order transition in a bonded Si network. Lastly, our results demonstrate a potentially attractive approach that employs a solution process coupled with ambient post-processing to produce crystalline silicon thin films.

  13. Planar-integrated single-crystalline perovskite photodetectors.

    PubMed

    Saidaminov, Makhsud I; Adinolfi, Valerio; Comin, Riccardo; Abdelhady, Ahmed L; Peng, Wei; Dursun, Ibrahim; Yuan, Mingjian; Hoogland, Sjoerd; Sargent, Edward H; Bakr, Osman M

    2015-01-01

    Hybrid perovskites are promising semiconductors for optoelectronic applications. However, they suffer from morphological disorder that limits their optoelectronic properties and, ultimately, device performance. Recently, perovskite single crystals have been shown to overcome this problem and exhibit impressive improvements: low trap density, low intrinsic carrier concentration, high mobility, and long diffusion length that outperform perovskite-based thin films. These characteristics make the material ideal for realizing photodetection that is simultaneously fast and sensitive; unfortunately, these macroscopic single crystals cannot be grown on a planar substrate, curtailing their potential for optoelectronic integration. Here we produce large-area planar-integrated films made up of large perovskite single crystals. These crystalline films exhibit mobility and diffusion length comparable with those of single crystals. Using this technique, we produced a high-performance light detector showing high gain (above 10(4) electrons per photon) and high gain-bandwidth product (above 10(8) Hz) relative to other perovskite-based optical sensors. PMID:26548941

  14. Atomically flat single-crystalline gold nanostructures for plasmonic nanocircuitry.

    PubMed

    Huang, Jer-Shing; Callegari, Victor; Geisler, Peter; Brüning, Christoph; Kern, Johannes; Prangsma, Jord C; Wu, Xiaofei; Feichtner, Thorsten; Ziegler, Johannes; Weinmann, Pia; Kamp, Martin; Forchel, Alfred; Biagioni, Paolo; Sennhauser, Urs; Hecht, Bert

    2010-01-01

    Deep subwavelength integration of high-definition plasmonic nanostructures is of key importance in the development of future optical nanocircuitry for high-speed communication, quantum computation and lab-on-a-chip applications. To date, the experimental realization of proposed extended plasmonic networks consisting of multiple functional elements remains challenging, mainly because of the multi-crystallinity of commonly used thermally evaporated gold layers. This can produce structural imperfections in individual circuit elements that drastically reduce the yield of functional integrated nanocircuits. In this paper we demonstrate the use of large (>100 μm(2)) but thin (<80 nm) chemically grown single-crystalline gold flakes that, after immobilization, serve as an ideal basis for focused ion beam milling and other top-down nanofabrication techniques on any desired substrate. Using this methodology we obtain high-definition ultrasmooth gold nanostructures with superior optical properties and reproducible nano-sized features over micrometre-length scales. Our approach provides a possible solution to overcome the current fabrication bottleneck and realize high-definition plasmonic nanocircuitry. PMID:21267000

  15. Method for forming single phase, single crystalline 2122 BCSCO superconductor thin films by liquid phase epitaxy

    NASA Technical Reports Server (NTRS)

    Pandey, Raghvendra K. (Inventor); Raina, Kanwal (Inventor); Solayappan, Narayanan (Inventor)

    1994-01-01

    A substantially single phase, single crystalline, highly epitaxial film of Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor which has a T.sub.c (zero resistance) of 83 K is provided on a lattice-matched substrate with no intergrowth. This film is produced by a Liquid Phase Epitaxy method which includes the steps of forming a dilute supercooled molten solution of a single phase superconducting mixture of oxides of Bi, Ca, Sr, and Cu having an atomic ratio of about 2:1:2:2 in a nonreactive flux such as KCl, introducing the substrate, e.g., NdGaO.sub.3, into the molten solution at 850.degree. C., cooling the solution from 850.degree. C. to 830.degree. C. to grow the film and rapidly cooling the substrate to room temperature to maintain the desired single phase, single crystalline film structure.

  16. Microdefects and self-interstitial diffusion in crystalline silicon

    SciTech Connect

    Knowlton, W.B.

    1998-05-01

    In this thesis, a study is presented of D-defects and self-interstitial diffusion in silicon using Li ion (Li{sup +}) drifting in an electric field and transmission electron microscopy (TEM). Obstruction of Li{sup +} drifting has been found in wafers from certain but not all FZ p-type Si. Incomplete Li{sup +} drifting always occurs in the central region of the wafers. This work established that interstitial oxygen is not responsible for hindering Li{sup +} drifting. TEM was performed on a samples from the partially Li{sup +} drifted area and compared to regions without D-defects. Precipitates were found only in the region containing D-defects that had partially Li{sup +} drifted. This result indicates D-defects are responsible for the precipitation that halts the Li{sup +} drift process. Nitrogen (N) doping has been shown to eliminate D-defects as measured by conventional techniques. Li{sup +} drifting and D-defects provide a useful means to study Si self-interstitial diffusion. The process modeling program SUPREM-IV was used to simulate the results of Si self-interstitial diffusion obtained from Li{sup +} drifting experiments. Anomalous results from the Si self-interstitial diffusion experiments forced a re-examination of the possibility of thermal dissociation of D-defects. Thermal annealing experiments that were performed support this possibility. A review of the current literature illustrates the need for more research on the effects of thermal processing on FZ Si to understand the dissolution kinetics of D-defects.

  17. 17th Workshop on Crystalline Silicon Solar Cells and Modules: Materials and Processes; Workshop Proceedings

    SciTech Connect

    Sopori, B. L.

    2007-08-01

    The National Center for Photovoltaics sponsored the 17th Workshop on Crystalline Silicon Solar Cells & Modules: Materials and Processes, held in Vail, CO, August 5-8, 2007. This meeting provided a forum for an informal exchange of technical and scientific information between international researchers in the photovoltaic and relevant non-photovoltaic fields. The theme of this year's meeting was 'Expanding Technology for a Future Powered by Si Photovoltaics.'

  18. Studies of the nature of interfacial barriers in high efficiency crystalline silicon solar cells

    NASA Technical Reports Server (NTRS)

    Bates, Clayton W., Jr.

    1985-01-01

    The effects of interfacial barriers in crystalline silicon solar cells were studied. The effort was directed toward the investigation and use of such techniques as Angular Resolved Parameter Spectroscopy (ARAPS) and Impedance Spectroscopy in initially characterizing n-type Si doped to levels commonly used for n+p solar cells, and eventually Si solar cells. The objectives of the research are given. Those accomplished are detailed, as are recommendations for future work.

  19. Phase transformation as the single-mode mechanical deformation of silicon

    SciTech Connect

    Wong, S. Williams, J. S.; Bradby, J. E.; Haberl, B.

    2015-06-22

    The metastable body-centered cubic (bc8) and rhombohedral (r8) phases of silicon that are formed after the nanoindentation of diamond cubic silicon exhibit properties that are of both scientific and technological interest. This letter demonstrates that large regions of these phases can be readily formed from crystalline silicon via nanoindentation with minimal damage to the surrounding crystal. Cross-sectional transmission electron microscopy is used to show that volumes of these phases 6 μm wide and up to 650 nm deep can be generated using a symmetrical spherical tip of ∼21.5 μm diameter. This result indicates that the use of large symmetrical spherical tips result in highly hydrostatic conditions that can favor the single phase transformation mode without extensive damage to the surrounding crystalline regions that are observed in previous studies.

  20. Nanophotonics-based low-temperature PECVD epitaxial crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Chen, Wanghua; Cariou, Romain; Foldyna, Martin; Depauw, Valerie; Trompoukis, Christos; Drouard, Emmanuel; Lalouat, Loic; Harouri, Abdelmounaim; Liu, Jia; Fave, Alain; Orobtchouk, Régis; Mandorlo, Fabien; Seassal, Christian; Massiot, Inès; Dmitriev, Alexandre; Lee, Ki-Dong; Cabarrocas, Pere Roca i.

    2016-03-01

    The enhancement of light absorption via nanopatterning in crystalline silicon solar cells is becoming extremely important with the decrease of wafer thickness for the further reduction of solar cell fabrication cost. In order to study the influence of nanopatterning on crystalline silicon thin-film solar cells, we applied two lithography techniques (laser interference lithography and nanoimprint lithography) combined with two etching techniques (dry and wet) to epitaxial crystalline silicon thin films deposited via plasma-enhanced chemical vapor deposition at 175 °C. The influence of nanopatterning with different etching profiles on solar cell performance is studied. We found that the etching profiles (pitch, depth and diameter) have a stronger impact on the passivation quality (open circuit voltage and fill factor) than on the optical performance (short circuit current density) of the solar cells. We also show that nanopatterns obtained via wet-etching can improve solar cell performance; and in contrast, dry-etching leads to poor passivation related to the etching profile, surface damage, and/or contamination introduced during the etching process.

  1. Fatigue crack propagation behavior of a single crystalline superalloy

    NASA Technical Reports Server (NTRS)

    Lerch, B. A.; Antolovich, Stephen D.

    1990-01-01

    Crack propagation mechanisms occurring at various temperatures in a single crystalline Ni-base alloy, Rene N4, were investigated. The rates of crack growth at 21, 704, 927, 1038, and 1093 C were measured in specimens with 001-line and 110-line directions parallel to the load axis and the machined notch, respectively, using a pulsed dc potential drop apparatus, and the fracture surfaces at each temperature were examined using SEM. Crack growth rates (CGRs) for specimens tested at or below 927 C were similar, while at two higher temperatures, the CGRs were about an order of magnitude higher than at the lower temperatures. Results of SEM observations showed that surface morphologies depended on temperature.

  2. Periodic magnetic domains in single-crystalline cobalt filament arrays

    NASA Astrophysics Data System (ADS)

    Chen, Fei; Wang, Fan; Jia, Fei; Li, Jingning; Liu, Kai; Huang, Sunxiang; Luan, Zhongzhi; Wu, Di; Chen, Yanbin; Zhu, Jianmin; Peng, Ru-Wen; Wang, Mu

    2016-02-01

    Magnetic structures with controlled domain wall pattern may be applied as potential building blocks for three-dimensional magnetic memory and logic devices. Using a unique electrochemical self-assembly method, we achieve regular single-crystalline cobalt filament arrays with specific geometric profile and crystallographic orientation, and the magnetic domain configuration can be conveniently tailored. We report the transition of periodic antiparallel magnetic domains to compressed vortex magnetic domains depending on the ratio of height to width of the wires. A "phase diagram" is obtained to describe the dependence of the type of magnetic domain and the geometrical profiles of the wires. Magnetoresistance of the filaments demonstrates that the contribution of a series of 180∘ domain walls is over 0.15 % of the zero-field resistance ρ (H =0 ) . These self-assembled magnetic nanofilaments, with controlled periodic domain patterns, offer an interesting platform to explore domain-wall-based memory and logic devices.

  3. Optical and electrical properties of single-crystalline zirconium carbide

    SciTech Connect

    Modine, F.A.; Haywood, T.W.; Allison, C.Y.

    1985-12-15

    Optical and electrical properties are reported for single-crystalline ZrC/sub 0.89/. The specular reflectance was measured between 0.025 and 6.5 eV, and ellipsometry measurements were made between 1.2 and 4.5 eV. The combination of ellipsometry with reflectance allows optical functions to be computed reliably between 0 and 6.5 eV and also provides a check on the consistency of the measurements. The van der Pauw technique was used to measure the electrical resistivity of the samples at temperatures between 4.2 and 300 K and the Hall coefficient at room temperature. Drude parameters obtained from the electrical measurements are in good agreement with those obtained from the optical data. Both the optical and electrical results are compared to other experimental results and to theory.

  4. Physical properties of single crystalline BaSn{sub 5}

    SciTech Connect

    Lin, Xiao; Budko, Sergey; Canfield, Paul

    2012-01-30

    We present a comprehensive study of the binary intermetallic superconductor, BaSn{sub 5}. High-quality single crystalline BaSn{sub 5} was grown out of a Sn flux. Detailed thermodynamic and transport measurements were performed to study BaSn{sub 5}'s normal and superconducting state properties. This material appears to be a strongly coupled, multiband superconductor. H{sub c2}(T) is almost isotropic. De Haas–van Alphen oscillations were observed and two effective masses were estimated from the FFT spectra. Hydrostatic pressure causes a decrease in the superconducting transition temperature at the rate of ≈−0.053 ± 0.001 K/kbar.

  5. Femtosecond laser-controlled self-assembly of amorphous-crystalline nanogratings in silicon.

    PubMed

    Puerto, Daniel; Garcia-Lechuga, Mario; Hernandez-Rueda, Javier; Garcia-Leis, Adianez; Sanchez-Cortes, Santiago; Solis, Javier; Siegel, Jan

    2016-07-01

    Self-assembly (SA) of molecular units to form regular, periodic extended structures is a powerful bottom-up technique for nanopatterning, inspired by nature. SA can be triggered in all classes of solid materials, for instance, by femtosecond laser pulses leading to the formation of laser-induced periodic surface structures (LIPSS) with a period slightly shorter than the laser wavelength. This approach, though, typically involves considerable material ablation, which leads to an unwanted increase of the surface roughness. We present a new strategy to fabricate high-precision nanograting structures in silicon, consisting of alternating amorphous and crystalline lines, with almost no material removal. The strategy can be applied to static irradiation experiments and can be extended into one and two dimensions by scanning the laser beam over the sample surface. We demonstrate that lines and areas with parallel nanofringe patterns can be written by an adequate choice of spot size, repetition rate and scan velocity, keeping a constant effective pulse number (N eff) per area for a given laser wavelength. A deviation from this pulse number leads either to inhomogeneous or ablative structures. Furthermore, we demonstrate that this approach can be used with different laser systems having widely different wavelengths (1030 nm, 800 nm, 400 nm), pulse durations (370 fs, 100 fs) and repetition rates (500 kHz, 100 Hz, single pulse) and that the grating period can also be tuned by changing the angle of laser beam incidence. The grating structures can be erased by irradiation with a single nanosecond laser pulse, triggering recrystallization of the amorphous stripes. Given the large differences in electrical conductivity between the two phases, our structures could find new applications in nanoelectronics. PMID:27199344

  6. Femtosecond laser-controlled self-assembly of amorphous-crystalline nanogratings in silicon

    NASA Astrophysics Data System (ADS)

    Puerto, Daniel; Garcia-Lechuga, Mario; Hernandez-Rueda, Javier; Garcia-Leis, Adianez; Sanchez-Cortes, Santiago; Solis, Javier; Siegel, Jan

    2016-07-01

    Self-assembly (SA) of molecular units to form regular, periodic extended structures is a powerful bottom-up technique for nanopatterning, inspired by nature. SA can be triggered in all classes of solid materials, for instance, by femtosecond laser pulses leading to the formation of laser-induced periodic surface structures (LIPSS) with a period slightly shorter than the laser wavelength. This approach, though, typically involves considerable material ablation, which leads to an unwanted increase of the surface roughness. We present a new strategy to fabricate high-precision nanograting structures in silicon, consisting of alternating amorphous and crystalline lines, with almost no material removal. The strategy can be applied to static irradiation experiments and can be extended into one and two dimensions by scanning the laser beam over the sample surface. We demonstrate that lines and areas with parallel nanofringe patterns can be written by an adequate choice of spot size, repetition rate and scan velocity, keeping a constant effective pulse number (N eff) per area for a given laser wavelength. A deviation from this pulse number leads either to inhomogeneous or ablative structures. Furthermore, we demonstrate that this approach can be used with different laser systems having widely different wavelengths (1030 nm, 800 nm, 400 nm), pulse durations (370 fs, 100 fs) and repetition rates (500 kHz, 100 Hz, single pulse) and that the grating period can also be tuned by changing the angle of laser beam incidence. The grating structures can be erased by irradiation with a single nanosecond laser pulse, triggering recrystallization of the amorphous stripes. Given the large differences in electrical conductivity between the two phases, our structures could find new applications in nanoelectronics.

  7. Selective functionalization and loading of biomolecules in crystalline silicon nanotube field-effect-transistors

    NASA Astrophysics Data System (ADS)

    Kwon, Soonshin; Chen, Zack C. Y.; Noh, Hyunwoo; Lee, Ju Hun; Liu, Hang; Cha, Jennifer N.; Xiang, Jie

    2014-06-01

    Crystalline silicon nanotubes (Si NTs) provide distinctive advantages as electrical and biochemical analysis scaffolds through their unique morphology and electrical tunability compared to solid nanowires or amorphous/non-conductive nanotubes. Such potential is investigated in this report. Gate-dependent four-probe current-voltage analysis reveals electrical properties such as resistivity to differ by nearly 3 orders of magnitude between crystalline and amorphous Si NTs. Analysis of transistor transfer characteristics yields a field effect mobility of 40.0 cm2 V-1 s-1 in crystalline Si NTs. The hollow morphology also allows selective inner/outer surface functionalization and loading capability either as a carrier for molecular targets or as a nanofluidic channel for biomolecular assays. We present for the first time a demonstration of internalization of fluorescent dyes (rhodamine) and biomolecules (BSA) in Si NTs as long as 22 μm in length.Crystalline silicon nanotubes (Si NTs) provide distinctive advantages as electrical and biochemical analysis scaffolds through their unique morphology and electrical tunability compared to solid nanowires or amorphous/non-conductive nanotubes. Such potential is investigated in this report. Gate-dependent four-probe current-voltage analysis reveals electrical properties such as resistivity to differ by nearly 3 orders of magnitude between crystalline and amorphous Si NTs. Analysis of transistor transfer characteristics yields a field effect mobility of 40.0 cm2 V-1 s-1 in crystalline Si NTs. The hollow morphology also allows selective inner/outer surface functionalization and loading capability either as a carrier for molecular targets or as a nanofluidic channel for biomolecular assays. We present for the first time a demonstration of internalization of fluorescent dyes (rhodamine) and biomolecules (BSA) in Si NTs as long as 22 μm in length. Electronic supplementary information (ESI) available: Modelling (Fig. S1) and

  8. Determining the crystalline degree of silicon nanoclusters/SiO{sub 2} multilayers by Raman scattering

    SciTech Connect

    Hernández, S.; López-Vidrier, J.; López-Conesa, L.; Peiró, F.; Garrido, B.; Hiller, D.; Gutsch, S.; Zacharias, M.; Ibáñez, J.

    2014-05-28

    We use Raman scattering to investigate the size distribution, built-in strains and the crystalline degree of Si-nanoclusters (Si-nc) in high-quality Si-rich oxynitride/SiO{sub 2} multilayered samples obtained by plasma enhanced chemical vapor deposition and subsequent annealing at 1150 °C. An initial structural characterization of the samples was performed by means of energy-filtered transmission electron microscopy (EFTEM) and X-ray diffraction (XRD) to obtain information about the cluster size and the presence of significant amounts of crystalline phase. The contributions to the Raman spectra from crystalline and amorphous Si were analyzed by using a phonon confinement model that includes the Si-nc size distribution, the influence of the matrix compressive stress on the clusters, and the presence of amorphous Si domains. Our lineshape analysis confirms the existence of silicon precipitates in crystalline state, in good agreement with XRD results, and provides also information about the presence of a large compressive stress over the Si-nc induced by the SiO{sub 2} matrix. By using the Raman spectra from low temperature annealed samples (i.e., before the crystallization of the Si-nc), the relative scattering cross-section between crystalline and amorphous Si was evaluated as a function of the crystalline Si size. Taking into account this parameter and the integrated intensities for each phase as extracted from the Raman spectra, we were able to evaluate the degree of crystallization of the precipitated Si-nc. Our data suggest that all samples exhibit high crystalline fractions, with values up to 89% for the biggest Si-nc. The Raman study, supported by the EFTEM characterization, indicates that this system undergoes a practically abrupt phase separation, in which the precipitated Si-nanoclusters are formed by a crystalline inner part surrounded by a thin amorphous shell of approximately 1–2 atomic layers.

  9. Single-layer crystalline phases of antimony: Antimonenes

    NASA Astrophysics Data System (ADS)

    Aktürk, O. Üzengi; Ã-zçelik, V. Ongun; Ciraci, S.

    2015-06-01

    The pseudolayered character of 3D bulk crystals of antimony has led us to predict its 2D single-layer crystalline phase named antimonene in a buckled honeycomb structure like silicene. Sb atoms also form an asymmetric washboard structure like black phospherene. Based on an extensive analysis comprising ab initio phonon and finite-temperature molecular dynamics calculations, we show that these two single-layer phases are robust and can remain stable at high temperatures. They are nonmagnetic semiconductors with band gaps ranging from 0.3 eV to 1.5 eV, and are suitable for 2D electronic applications. The washboard antimonene displays strongly directional mechanical properties, which may give rise to a strong influence of strain on the electronic properties. Single-layer antimonene phases form bilayer and trilayer structures with wide interlayer spacings. In multilayers, this spacing is reduced and eventually the structure changes to 3D pseudolayered bulk crystals. The zigzag and armchair nanoribbons of the antimonene phases have fundamental band gaps derived from reconstructed edge states and display a diversity of magnetic and electronic properties depending on their width and edge geometry. Their band gaps are tunable with the widths of the nanoribbons. When grown on substrates, such as germanene or Ge(111), the buckled antimonene attains a significant influence of substrates.

  10. High energy picosecond laser for applications in microstructuring of crystalline silicon

    NASA Astrophysics Data System (ADS)

    Lin, Xuechun; Yu, Haijuan; Huang, Yongguang; Zhang, Ling; Zhu, Hongliang

    2012-10-01

    Black silicon is very promising for the third generation Solar Cells, because of its fascinating light absorption of above 98% in visible spectrum and more than 90% in 800-2500 nm, and its surface micro-nano structures enlarge light trapping intermediate impurities levels caused by supersaturated doping expand absorptive limitation of crystalline Si. In recent years femtosecond laser pulses were widely used in the process of improving the absorptance by irradiating silicon surfaces with in the presence of different gases. Nevertheless, picosecond laser used to fabricate large-area black silicon is seldom reported. A diode-pumped picosecond Nd:YAG regenerative amplifier laser system designed for microstructuring the crystalline silicon was reported in this paper. At the repetition of 1 kHz, the system generated 1 W average-power, 26-ps-long pulses with a pulse energy of 1 mJ at 1064 nm, which corresponds the peak power of 38.5 MW. A 0.5 W second-harmonic 532 nm laser is achieved with a 20 mm long noncritically phase-matched lithium triborate (LBO) crystal from the 1W 1064 nm laser. igh optical absorption black Si irradiated with 1064 nm and 532 nm picosecond pulses in SF6 at different laser fluence. And the relationship between the surface morphology and the wavelength or the laser fluence was researched.

  11. Tribological properties of sintered polycrystalline and single crystal silicon carbide

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.; Srinivasan, M.

    1982-01-01

    Tribological studies and X-ray photoelectron spectroscopy analyses were conducted with sintered polycrystalline and single crystal silicon carbide surfaces in sliding contact with iron at various temperatures to 1500 C in a vacuum of 30 nPa. The results indicate that there is a significant temperature influence on both the friction properties and the surface chemistry of silicon carbide. The main contaminants on the as received sintered polycrystalline silicon carbide surfaces are adsorbed carbon, oxygen, graphite, and silicon dioxide. The surface revealed a low coefficient of friction. This is due to the presence of the graphite on the surface. At temperatures of 400 to 600 C graphite and copious amount of silicon dioxide were observed on the polycrystalline silicon carbide surface in addition to silicon carbide. At 800 C, the amount of the silicon dioxide decreased rapidly and the silicon carbide type silicon and carbon peaks were at a maximum intensity in the XPS spectra. The coefficients of friction were high in the temperature range 400 to 800 C. Small amounts of carbon and oxygen contaminants were observed on the as received single crystal silicon carbide surface below 250 C. Silicon carbide type silicon and carbon peaks were seen on the silicon carbide in addition to very small amount of graphite and silicon dioxide at temperatures of 450 to 800 C.

  12. Nanopatterning of Crystalline Silicon Using Anodized Aluminum Oxide Templates for Photovoltaics

    NASA Astrophysics Data System (ADS)

    Chao, Tsu-An

    A novel thin film anodized aluminum oxide templating process was developed and applied to make nanopatterns on crystalline silicon to enhance the optical properties of silicon. The thin film anodized aluminum oxide was created to improve the conventional thick aluminum templating method with the aim for potential large scale fabrication. A unique two-step anodizing method was introduced to create high quality nanopatterns and it was demonstrated that this process is superior over the original one-step approach. Optical characterization of the nanopatterned silicon showed up to 10% reduction in reflection in the short wavelength range. Scanning electron microscopy was also used to analyze the nanopatterned surface structure and it was found that interpore spacing and pore density can be tuned by changing the anodizing potential.

  13. Impact of dislocations and dangling bond defects on the electrical performance of crystalline silicon thin films

    SciTech Connect

    Steffens, S.; Becker, C. Amkreutz, D.; Schnegg, A.; Abou-Ras, D.; Lips, K.; Rech, B.; Klossek, A.; Kittler, M.; Chen, Y.-Y.; Klingsporn, M.

    2014-07-14

    A wide variety of liquid and solid phase crystallized silicon films are investigated in order to determine the performance limiting defect types in crystalline silicon thin-film solar cells. Complementary characterization methods, such as electron spin resonance, photoluminescence, and electron microscopy, yield the densities of dangling bond defects and dislocations which are correlated with the electronic material quality in terms of solar cell open circuit voltage. The results indicate that the strongly differing performance of small-grained solid and large-grain liquid phase crystallized silicon can be explained by intra-grain defects like dislocations rather than grain boundary dangling bonds. A numerical model is developed containing both defect types, dislocations and dangling bonds, describing the experimental results.

  14. Process for forming a porous silicon member in a crystalline silicon member

    DOEpatents

    Northrup, M. Allen; Yu, Conrad M.; Raley, Norman F.

    1999-01-01

    Fabrication and use of porous silicon structures to increase surface area of heated reaction chambers, electrophoresis devices, and thermopneumatic sensor-actuators, chemical preconcentrates, and filtering or control flow devices. In particular, such high surface area or specific pore size porous silicon structures will be useful in significantly augmenting the adsorption, vaporization, desorption, condensation and flow of liquids and gasses in applications that use such processes on a miniature scale. Examples that will benefit from a high surface area, porous silicon structure include sample preconcentrators that are designed to adsorb and subsequently desorb specific chemical species from a sample background; chemical reaction chambers with enhanced surface reaction rates; and sensor-actuator chamber devices with increased pressure for thermopneumatic actuation of integrated membranes. Examples that benefit from specific pore sized porous silicon are chemical/biological filters and thermally-activated flow devices with active or adjacent surfaces such as electrodes or heaters.

  15. Fiber Optic Excitation of Silicon Microspheres in Amorphous and Crystalline Fluids

    NASA Astrophysics Data System (ADS)

    Yılmaz, Huzeyfe; Yılmaz, Hasan; Sharif Murib, Mohammed; Serpengüzel, Ali

    2016-03-01

    This study investigates the optical resonance spectra of free-standing monolithic single crystal silicon microspheres immersed in various amorphous fluids, such as air, water, ethylene glycol, and 4-Cyano-4'-pentylbiphenyl nematic liquid crystal. For the various amorphous fluids, morphology-dependent resonances with quality factors on the order of 105 are observed at 1428 nm. The mode spacing is always on the order of 0.23 nm. The immersion in various amorphous fluids affects the spectral response of the silicon microsphere and heralds this technique for use in novel optofluidics applications. Even though the nematic liquid crystal is a highly birefringent, scattering, and high-index optical medium, morphology-dependent resonances with quality factors on the order of 105 are observed at 1300 nm in the elastic scattering spectra of the silicon microsphere, realizing a liquid-crystal-on-silicon geometry. The relative refractive index and the size parameter of the silicon microsphere are the parameters that affect the resonance structure. The more 4-Cyano-4'-pentylbiphenyl interacting with the silicon microsphere, the lower the quality factor of the resonances is. The more 4-Cyano-4'-pentylbiphenyl is interacting with the silicon microsphere, the lower the mode spacing Δλ of the resonances is. The silicon microspheres wetted with nematic liquid crystal can be used for optically addressed liquid-crystal-on-silicon displays, light valve applications, or reconfigurable optical networks.

  16. Formation of quasi-single crystalline porous ZnO nanostructures with a single large cavity

    NASA Astrophysics Data System (ADS)

    Cho, Seungho; Kim, Semi; Jung, Dae-Won; Lee, Kun-Hong

    2011-09-01

    We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 °C) and a stage in which the temperature is maintained at 120 °C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space.We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 °C) and a stage in which the temperature is maintained at 120 °C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space. Electronic supplementary information (ESI) available: TEM images and the corresponding SAED image of a Zn

  17. Bright Single Photon Emitter in Silicon Carbide

    NASA Astrophysics Data System (ADS)

    Lienhard, Benjamin; Schroeder, Tim; Mouradian, Sara; Dolde, Florian; Trong Tran, Toan; Aharonovich, Igor; Englund, Dirk

    Efficient, on-demand, and robust single photon emitters are of central importance to many areas of quantum information processing. Over the past 10 years, color centers in solids have emerged as excellent single photon emitters. Color centers in diamond are among the most intensively studied single photon emitters, but recently silicon carbide (SiC) has also been demonstrated to be an excellent host material. In contrast to diamond, SiC is a technologically important material that is widely used in optoelectronics, high power electronics, and microelectromechanical systems. It is commercially available in sizes up to 6 inches and processes for device engineering are well developed. We report on a visible-spectrum single photon emitter in 4H-SiC. The emitter is photostable at both room and low temperatures, and it enables 2 million photons/second from unpatterned bulk SiC. We observe two classes of orthogonally polarized emitters, each of which has parallel absorption and emission dipole orientations. Low temperature measurements reveal a narrow zero phonon line with linewidth < 0.1 nm that accounts for more than 30% of the total photoluminescence spectrum. To our knowledge, this SiC color emitter is the brightest stable room-temperature single photon emitter ever observed.

  18. Deformation mechanisms in nanoscale single crystalline electroplated copper pillars

    NASA Astrophysics Data System (ADS)

    Jennings, Andrew T.

    Scientific research in nanotechnology has enabled advances in a diverse range of applications, such as: electronics, chemical sensing, and cancer treatment. In order to transition these nanotechnology-driven innovations out of the laboratory and into real-world applications, the resilience and mechanical reliability of nanoscale structures must be well understood in order to preserve functionality under real-world operating environments. Understanding the mechanical properties of nanoscale materials is especially important because several authors have shown that single crystalline metal pillars produced through focused-ion-beam milling have unique properties when the pillar diameter, D, approaches nanotechnology-relevant dimensions. The strength, sigma, of these pillars is size-dependent and is well described through a power-law relation showing that smaller is stronger: sigma∝D-n , where n is the exponent and is found to be 0.5≤n≤1.0 in face-centered-cubic metals. In this work, the fundamental deformation mechanisms governing the size-dependent mechanical properties are investigated through uniaxial compression and tension tests of electroplated single crystalline copper pillars with diameters between 75 nm and 1000 nm. At larger pillar diameters, D >125 nm, these copper pillars are shown to obey a similar size-dependent regime, demonstrating that the "smaller is stronger" phenomenon is a function of the pillar microstructure, as opposed to the fabrication route. Furthermore, the dominant dislocation mechanism in this size-dependent regime is shown to be the result of single-arm, or spiral, sources. At smaller pillar diameters, D≤125 nm, a strain-rate-dependent mechanism transition is observed through both the size-strength relation and also quantitative, experimental measures of the activation volume. This new deformation regime is characterized by a size-independent strength and is governed by surface dislocation nucleation, a thermally activated

  19. Combined single-crystalline and polycrystalline CVD diamond substrates for diamond electronics

    SciTech Connect

    Vikharev, A. L. Gorbachev, A. M.; Dukhnovsky, M. P.; Muchnikov, A. B.; Ratnikova, A. K.; Fedorov, Yu. Yu.

    2012-02-15

    The fabrication of diamond substrates in which single-crystalline and polycrystalline CVD diamond form a single wafer, and the epitaxial growth of diamond films on such combined substrates containing polycrystalline and (100) single-crystalline CVD diamond regions are studied.

  20. Novel Approach for Selective Emitter Formation and Front Side Metallization of Crystalline Silicon Solar Cells

    SciTech Connect

    Xu, Baomin

    2010-07-26

    In this project we will explore the possibility of forming the front side metallization and selective emitter layer for the crystalline silicon solar cells through using selective laser ablation to create contact openings on the front surface and a screen printer to make connections with conductive paste. Using this novel approach we expect to reduce the specific contact resistance of the silver gridlines by about one order of magnitude compared to the state-of-art industrial crystalline silicon solar cells to below 1 mΩ∙cm2, and use lightly doped n+ emitter layer with sheet resistance of not smaller than 100 Ω. This represents an enabling improvement on crystalline silicon solar cell performance and can increase the absolute efficiency of the solar cell by about 1%. In this scientific report we first present our result on the selective laser ablation of the nitride layer to make contact openings. Then we report our work on the solar cell fabrication by using the laser ablated contact openings with self-doping paste. Through various electrical property characterization and SIMS analysis, the factors limiting the cell performance have been discussed. While through this proof-of-concept project we could not reach the target on cell efficiency improvement, the process to fabricate 125mm full-sized silicon solar cells using laser ablation and self-doping paste has been developed, and a much better understanding of technical challenges has been achieved. Future direction to realize the potential of the new technology has been clearly defined.

  1. Electrical characterization of 6H crystalline silicon carbide. M.S. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Lempner, Stephen E.

    1994-01-01

    Crystalline silicon carbide (SiC) substrates and epilayers, undoped as well as n- and p-doped, have been electrically characterized by performing Hall effect and resistivity measurements (van der Pauw) over the temperature range of approximately 85 K to 650 K (200 K to 500 K for p-type sample). By fitting the measured temperature dependent carrier concentration data to the single activation energy theoretical model: (1) the activation energy for the nitrogen donor ranged from 0.078 eV to 0.101 eV for a doping concentration range of 10(exp 17) cm(exp -3) to 10(exp 18) cm(exp -3) and (2) the activation energy for the aluminum acceptor was 0.252 eV for a doping concentration of 4.6 x 10(exp 18) cm(exp -3). By fitting the measured temperature dependent carrier concentration data to the double activation energy level theoretical model for the nitrogen donor: (1) the activation energy for the hexagonal site was 0.056 eV and 0.093 eV corresponding to doping concentrations of 3.33 x 10 (exp 17) cm(exp -3) and 1.6 x 10(exp 18) cm(exp -3) and (2) the activation energy for the cubic site was 0.113 and 0.126 eV corresponding to doping concentrations of 4.2 x 10(exp 17) cm(exp -3) and 5.4 x 10(exp 18) cm(exp -3).

  2. Influence of the surface termination on the light emission of crystalline silicon nanoparticles

    NASA Astrophysics Data System (ADS)

    Botas, Alexandre M. P.; Anthony, Rebecca J.; Wu, Jeslin; Rowe, David J.; Silva, Nuno J. O.; Kortshagen, Uwe; Pereira, Rui N.; Ferreira, Rute A. S.

    2016-08-01

    The light emission properties of silicon crystalline nanoparticles (SiNPs) have been investigated using steady-state and time-resolved photoluminescence measurements carried out at 12 K and at room temperature. To enable a comparative study of the role of surface terminal groups on the optical properties, we investigated SiNPs-H ensembles with the same mean NP diameter but differing on the surface termination, namely organic-functionalized with 1-dodecene (SiNPs-C12) and H-terminated (SiNPs-H). We show that although the spectral dependence of the light emission is rather unaffected by surface termination, characterized by a single broad band peaking at ∼1.64 eV, both the exciton recombination lifetimes and quantum yields display a pronounced dependence on the surface termination. Exciton lifetimes and quantum yields are found to be significantly lower in SiNPs-H compared SiNPs-C12. This difference is due to distinct non-radiative recombination probabilities resulting from inter-NP exciton migration, which in SiNPs-C12 is inhibited by the energy barriers imposed by the bulky surface groups. The surface groups of organic-terminated SiPs are responsible for the inhibition of inter-NP exciton transfer, yielding a higher quantum yield compared to SiNPs-H. The surface oxidation of SiNPs-C12 leads to the appearance of a phenomenon of an exciton transference from to the Si core to oxide-related states that contribute to light emission. These excitons recombine radiatively, explaining why the emission quantum of the organic-terminated SiNPs is the same after surface oxidation of SiNPs-C12.

  3. Influence of the surface termination on the light emission of crystalline silicon nanoparticles.

    PubMed

    Botas, Alexandre M P; Anthony, Rebecca J; Wu, Jeslin; Rowe, David J; Silva, Nuno J O; Kortshagen, Uwe; Pereira, Rui N; Ferreira, Rute A S

    2016-08-12

    The light emission properties of silicon crystalline nanoparticles (SiNPs) have been investigated using steady-state and time-resolved photoluminescence measurements carried out at 12 K and at room temperature. To enable a comparative study of the role of surface terminal groups on the optical properties, we investigated SiNPs-H ensembles with the same mean NP diameter but differing on the surface termination, namely organic-functionalized with 1-dodecene (SiNPs-C12) and H-terminated (SiNPs-H). We show that although the spectral dependence of the light emission is rather unaffected by surface termination, characterized by a single broad band peaking at ∼1.64 eV, both the exciton recombination lifetimes and quantum yields display a pronounced dependence on the surface termination. Exciton lifetimes and quantum yields are found to be significantly lower in SiNPs-H compared SiNPs-C12. This difference is due to distinct non-radiative recombination probabilities resulting from inter-NP exciton migration, which in SiNPs-C12 is inhibited by the energy barriers imposed by the bulky surface groups. The surface groups of organic-terminated SiPs are responsible for the inhibition of inter-NP exciton transfer, yielding a higher quantum yield compared to SiNPs-H. The surface oxidation of SiNPs-C12 leads to the appearance of a phenomenon of an exciton transference from to the Si core to oxide-related states that contribute to light emission. These excitons recombine radiatively, explaining why the emission quantum of the organic-terminated SiNPs is the same after surface oxidation of SiNPs-C12. PMID:27348305

  4. Orientation-dependent mechanical behavior and phase transformation of mono-crystalline silicon

    NASA Astrophysics Data System (ADS)

    Sun, Jiapeng; Ma, Aibin; Jiang, Jinghua; Han, Jing; Han, Ying

    2016-03-01

    We perform a large-scale molecular dynamics simulation of nanoindentation on the (100), (110), and (111) oriented silicon surface to investigate the orientation-dependent mechanical behavior and phase transformation of monocrystalline silicon. The results show both the remarkable anisotropic mechanical behavior and structure phase transformation of monocrystalline silicon. The mechanical behavior of the (110) and (111) oriented surfaces are similar (has a high indentation modulus, low critical indentation depth for the onset of plastic deformation) but quite different from the (100) oriented surface. The mechanical behavior is carefully linked to the phase transformation. The formation of crystalline bct5 phase and β-Si phase is the fundamental phase transformation mechanism for (100) oriented surface. But, a large number of amorphous silicon can be found beneath the indenter for (110) and (111) oriented surface beside the bct5 phase and β-Si phase. The β-Si phase region is relatively small for (110) and (111) oriented surface, even cannot be detected for (111) oriented surface. This result highlights the dominating role of the amorphous transformation in the mechanical behavior of monocrystalline silicon. Additionally, our results indicate that the high pressure phases form a symmetrical, anisotropic pattern on the indented surface for all three oriented surface which is linked to the active {111}<110> slip systems.

  5. 14th Workshop on Crystalline Silicon Solar Cells& Modules: Materials and Processes; Summary of Discussion Sessions

    SciTech Connect

    Sopori, B.; Tan, T.; Sinton, R.; Swanson, D.

    2004-10-01

    The 14th Workshop discussion sessions addressed funding needs for Si research and for R&D to enhance U.S. PV manufacturing. The wrap-up session specifically addressed topics for the new university silicon program. The theme of the workshop, Crystalline Silicon Solar Cells: Leapfrogging the Barriers, was selected to reflect the astounding progress in Si PV technology during last three decades, despite a host of barriers and bottlenecks. A combination of oral, poster, and discussion sessions addressed recent advances in crystal growth technology, new cell structures and doping methods, silicon feedstock issues, hydrogen passivation and fire through metallization, and module issues/reliability. The following oral/discussion sessions were conducted: (1) Technology Update; (2) Defects and Impurities in Si/Discussion; (3) Rump Session; (4) Module Issues and Reliability/Discussion; (5) Silicon Feedstock/Discussion; (6) Novel Doping, Cells, and Hetero-Structure Designs/Discussion; (7) Metallization/Silicon Nitride Processing/Discussion; (8) Hydrogen Passivation/Discussion; (9) Characterization/Discussion; and (10) Wrap-Up. This year's workshop lasted three and a half days and, for the first time, included a session on Si modules. A rump session was held on the evening of August 8, which addressed efficiency expectations and challenges of c Si solar cells/modules. Richard King of DOE and Daren Dance of Wright Williams& Kelly (formerly of Sematech) spoke at two of the luncheon sessions. Eleven students received Graduate Student Awards from funds contributed by the PV industry.

  6. Single-charge transport in ambipolar silicon nanoscale field-effect transistors

    SciTech Connect

    Mueller, Filipp; Konstantaras, Georgios; Wiel, Wilfred G. van der; Zwanenburg, Floris A.

    2015-04-27

    We report single-charge transport in ambipolar nanoscale MOSFETs, electrostatically defined in near-intrinsic silicon. We use the ambipolarity to demonstrate the confinement of either a few electrons or a few holes in exactly the same crystalline environment underneath a gate electrode. We find similar electron and hole quantum dot properties while the mobilities differ quantitatively like in microscale devices. The understanding and control of individual electrons and holes are essential for spin-based quantum information processing.

  7. First Principles Simulations of the Electrochemical Lithiation and Delithiation of Faceted Crystalline Silicon

    SciTech Connect

    Chan, Maria K.; Wolverton, Christopher M.; Greeley, Jeffrey P.

    2012-09-05

    Silicon is of significant interest as a next-generation anode material for lithium-ion batteries due to its extremely high capacity. The reaction of lithium with crystalline silicon is known to present a rich range of phenomena, including electrochemical solid state amorphization, crystallization at full lithiation of a Li15Si4 phase, hysteresis in the first lithiation–delithiation cycle, and highly anisotropic lithiation in crystalline samples. Very little is known about these processes at an atomistic level, however. To provide fundamental insights into these issues, we develop and apply a first principles, history-dependent, lithium insertion and removal algorithm to model the process of lithiation and subsequent delithiation of crystalline Si. The simulations give a realistic atomistic picture of lithiation demonstrating, for the first time, the amorphization process and hinting at the formation of the Li15Si4 phase. Voltages obtained from the simulations show that lithiation of the (110) surface is thermodynamically more favorable than lithiation of the (100) or (111) surfaces, providing an explanation for the drastic lithiation anisotropy seen in experiments on Si micro- and nanostructures. Analysis of the delithiation and relithiation processes also provides insights into the underlying physics of the lithiation–delithiation hysteresis, thus providing firm conceptual foundations for future design of improved Si-based anodes for Li ion battery applications.

  8. Programmable SERS active substrates for chemical and biosensing applications using amorphous/crystalline hybrid silicon nanomaterial

    NASA Astrophysics Data System (ADS)

    Powell, Jeffery Alexander; Venkatakrishnan, Krishnan; Tan, Bo

    2016-01-01

    We present the creation of a unique nanostructured amorphous/crystalline hybrid silicon material that exhibits surface enhanced Raman scattering (SERS) activity. This nanomaterial is an interconnected network of amorphous/crystalline nanospheroids which form a nanoweb structure; to our knowledge this material has not been previously observed nor has it been applied for use as a SERS sensing material. This material is formed using a femtosecond synthesis technique which facilitates a laser plume ion condensation formation mechanism. By fine-tuning the laser plume temperature and ion interaction mechanisms within the plume, we are able to precisely program the relative proportion of crystalline Si to amorphous Si content in the nanospheroids as well as the size distribution of individual nanospheroids and the size of Raman hotspot nanogaps. With the use of Rhodamine 6G (R6G) and Crystal Violet (CV) chemical dyes, we have been able to observe a maximum enhancement factor of 5.38 × 106 and 3.72 × 106 respectively, for the hybrid nanomaterial compared to a bulk Si wafer substrate. With the creation of a silicon-based nanomaterial capable of SERS detection of analytes, this work demonstrates a redefinition of the role of nanostructured Si from an inactive to SERS active role in nano-Raman sensing applications.

  9. Programmable SERS active substrates for chemical and biosensing applications using amorphous/crystalline hybrid silicon nanomaterial

    PubMed Central

    Powell, Jeffery Alexander; Venkatakrishnan, Krishnan; Tan, Bo

    2016-01-01

    We present the creation of a unique nanostructured amorphous/crystalline hybrid silicon material that exhibits surface enhanced Raman scattering (SERS) activity. This nanomaterial is an interconnected network of amorphous/crystalline nanospheroids which form a nanoweb structure; to our knowledge this material has not been previously observed nor has it been applied for use as a SERS sensing material. This material is formed using a femtosecond synthesis technique which facilitates a laser plume ion condensation formation mechanism. By fine-tuning the laser plume temperature and ion interaction mechanisms within the plume, we are able to precisely program the relative proportion of crystalline Si to amorphous Si content in the nanospheroids as well as the size distribution of individual nanospheroids and the size of Raman hotspot nanogaps. With the use of Rhodamine 6G (R6G) and Crystal Violet (CV) chemical dyes, we have been able to observe a maximum enhancement factor of 5.38 × 106 and 3.72 × 106 respectively, for the hybrid nanomaterial compared to a bulk Si wafer substrate. With the creation of a silicon-based nanomaterial capable of SERS detection of analytes, this work demonstrates a redefinition of the role of nanostructured Si from an inactive to SERS active role in nano-Raman sensing applications. PMID:26785682

  10. Programmable SERS active substrates for chemical and biosensing applications using amorphous/crystalline hybrid silicon nanomaterial.

    PubMed

    Powell, Jeffery Alexander; Venkatakrishnan, Krishnan; Tan, Bo

    2016-01-01

    We present the creation of a unique nanostructured amorphous/crystalline hybrid silicon material that exhibits surface enhanced Raman scattering (SERS) activity. This nanomaterial is an interconnected network of amorphous/crystalline nanospheroids which form a nanoweb structure; to our knowledge this material has not been previously observed nor has it been applied for use as a SERS sensing material. This material is formed using a femtosecond synthesis technique which facilitates a laser plume ion condensation formation mechanism. By fine-tuning the laser plume temperature and ion interaction mechanisms within the plume, we are able to precisely program the relative proportion of crystalline Si to amorphous Si content in the nanospheroids as well as the size distribution of individual nanospheroids and the size of Raman hotspot nanogaps. With the use of Rhodamine 6G (R6G) and Crystal Violet (CV) chemical dyes, we have been able to observe a maximum enhancement factor of 5.38 × 10(6) and 3.72 × 10(6) respectively, for the hybrid nanomaterial compared to a bulk Si wafer substrate. With the creation of a silicon-based nanomaterial capable of SERS detection of analytes, this work demonstrates a redefinition of the role of nanostructured Si from an inactive to SERS active role in nano-Raman sensing applications. PMID:26785682

  11. Evolutionary process development towards next generation crystalline silicon solar cells : a semiconductor process toolbox application

    NASA Astrophysics Data System (ADS)

    John, J.; Prajapati, V.; Vermang, B.; Lorenz, A.; Allebe, C.; Rothschild, A.; Tous, L.; Uruena, A.; Baert, K.; Poortmans, J.

    2012-08-01

    Bulk crystalline Silicon solar cells are covering more than 85% of the world's roof top module installation in 2010. With a growth rate of over 30% in the last 10 years this technology remains the working horse of solar cell industry. The full Aluminum back-side field (Al BSF) technology has been developed in the 90's and provides a production learning curve on module price of constant 20% in average. The main reason for the decrease of module prices with increasing production capacity is due to the effect of up scaling industrial production. For further decreasing of the price per wattpeak silicon consumption has to be reduced and efficiency has to be improved. In this paper we describe a successive efficiency improving process development starting from the existing full Al BSF cell concept. We propose an evolutionary development includes all parts of the solar cell process: optical enhancement (texturing, polishing, anti-reflection coating), junction formation and contacting. Novel processes are benchmarked on industrial like baseline flows using high-efficiency cell concepts like i-PERC (Passivated Emitter and Rear Cell). While the full Al BSF crystalline silicon solar cell technology provides efficiencies of up to 18% (on cz-Si) in production, we are achieving up to 19.4% conversion efficiency for industrial fabricated, large area solar cells with copper based front side metallization and local Al BSF applying the semiconductor toolbox.

  12. Enhanced cooling in mono-crystalline ultra-thin silicon by embedded micro-air channels

    NASA Astrophysics Data System (ADS)

    Ghoneim, Mohamed T.; Fahad, Hossain M.; Hussain, Aftab M.; Rojas, Jhonathan P.; Torres Sevilla, Galo A.; Alfaraj, Nasir; Lizardo, Ernesto B.; Hussain, Muhammad M.

    2015-12-01

    In today's digital world, complementary metal oxide semiconductor (CMOS) technology enabled scaling of bulk mono-crystalline silicon (100) based electronics has resulted in their higher performance but with increased dynamic and off-state power consumption. Such trade-off has caused excessive heat generation which eventually drains the charge of battery in portable devices. The traditional solution utilizing off-chip fans and heat sinks used for heat management make the whole system bulky and less mobile. Here we show, an enhanced cooling phenomenon in ultra-thin (>10 μm) mono-crystalline (100) silicon (detached from bulk substrate) by utilizing deterministic pattern of porous network of vertical "through silicon" micro-air channels that offer remarkable heat and weight management for ultra-mobile electronics, in a cost effective way with 20× reduction in substrate weight and a 12% lower maximum temperature at sustained loads. We also show the effectiveness of this event in functional MOS field effect transistors (MOSFETs) with high-κ/metal gate stacks.

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

    SciTech Connect

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

    2014-03-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  15. Effective surface passivation of p-type crystalline silicon with silicon oxides formed by light-induced anodisation

    NASA Astrophysics Data System (ADS)

    Cui, Jie; Grant, Nicholas; Lennon, Alison

    2014-12-01

    Electronic surface passivation of p-type crystalline silicon by anodic silicon dioxide (SiO2) was investigated. The anodic SiO2 was grown by light-induced anodisation (LIA) in diluted sulphuric acid at room temperature, a process that is significantly less-expensive than thermal oxidation which is widely-used in silicon solar cell fabrication. After annealing in oxygen and then forming gas at 400 °C for 30 min, the effective minority carrier lifetime of 3-5 Ω cm, boron-doped Czochralski silicon wafers with a phosphorus-doped 80 Ω/□ emitter and a LIA anodic SiO2 formed on the p-type surface was increased by two orders of magnitude to 150 μs. Capacitance-voltage measurements demonstrated a very low positive charge density of 3.4 × 1011 cm-2 and a moderate density of interface states of 6 × 1011 eV-1 cm-2. This corresponded to a silicon surface recombination velocity of 62 cm s-1, which is comparable with values reported for other anodic SiO2 films, which required higher temperatures and longer growth times, and significantly lower than oxides grown by chemical vapour deposition techniques. Additionally, a very low leakage current density of 3.5 × 10-10 and 1.6 × 10-9 A cm-2 at 1 and -1 V, respectively, was measured for LIA SiO2 suggesting its potential application as insulation layer in IBC solar cells and a barrier for potential induced degradation.

  16. Single-crystalline aluminum film for ultraviolet plasmonic nanolasers.

    PubMed

    Chou, Bo-Tsun; Chou, Yu-Hsun; Wu, Yen-Mo; Chung, Yi-Cheng; Hsueh, Wei-Jen; Lin, Shih-Wei; Lu, Tien-Chang; Lin, Tzy-Rong; Lin, Sheng-Di

    2016-01-01

    Significant advances have been made in the development of plasmonic devices in the past decade. Plasmonic nanolasers, which display interesting properties, have come to play an important role in biomedicine, chemical sensors, information technology, and optical integrated circuits. However, nanoscale plasmonic devices, particularly those operating in the ultraviolet regime, are extremely sensitive to the metal and interface quality. Thus, these factors have a significant bearing on the development of ultraviolet plasmonic devices. Here, by addressing these material-related issues, we demonstrate a low-threshold, high-characteristic-temperature metal-oxide-semiconductor ZnO nanolaser that operates at room temperature. The template for the ZnO nanowires consists of a flat single-crystalline Al film grown by molecular beam epitaxy and an ultrasmooth Al2O3 spacer layer synthesized by atomic layer deposition. By effectively reducing the surface plasmon scattering and metal intrinsic absorption losses, the high-quality metal film and the sharp interfaces formed between the layers boost the device performance. This work should pave the way for the use of ultraviolet plasmonic nanolasers and related devices in a wider range of applications. PMID:26814581

  17. Single-crystalline aluminum film for ultraviolet plasmonic nanolasers

    NASA Astrophysics Data System (ADS)

    Chou, Bo-Tsun; Chou, Yu-Hsun; Wu, Yen-Mo; Chung, Yi-Cheng; Hsueh, Wei-Jen; Lin, Shih-Wei; Lu, Tien-Chang; Lin, Tzy-Rong; Lin, Sheng-Di

    2016-01-01

    Significant advances have been made in the development of plasmonic devices in the past decade. Plasmonic nanolasers, which display interesting properties, have come to play an important role in biomedicine, chemical sensors, information technology, and optical integrated circuits. However, nanoscale plasmonic devices, particularly those operating in the ultraviolet regime, are extremely sensitive to the metal and interface quality. Thus, these factors have a significant bearing on the development of ultraviolet plasmonic devices. Here, by addressing these material-related issues, we demonstrate a low-threshold, high-characteristic-temperature metal-oxide-semiconductor ZnO nanolaser that operates at room temperature. The template for the ZnO nanowires consists of a flat single-crystalline Al film grown by molecular beam epitaxy and an ultrasmooth Al2O3 spacer layer synthesized by atomic layer deposition. By effectively reducing the surface plasmon scattering and metal intrinsic absorption losses, the high-quality metal film and the sharp interfaces formed between the layers boost the device performance. This work should pave the way for the use of ultraviolet plasmonic nanolasers and related devices in a wider range of applications.

  18. Single-crystalline aluminum film for ultraviolet plasmonic nanolasers

    PubMed Central

    Chou, Bo-Tsun; Chou, Yu-Hsun; Wu, Yen-Mo; Chung, Yi-Cheng; Hsueh, Wei-Jen; Lin, Shih-Wei; Lu, Tien-Chang; Lin, Tzy-Rong; Lin, Sheng-Di

    2016-01-01

    Significant advances have been made in the development of plasmonic devices in the past decade. Plasmonic nanolasers, which display interesting properties, have come to play an important role in biomedicine, chemical sensors, information technology, and optical integrated circuits. However, nanoscale plasmonic devices, particularly those operating in the ultraviolet regime, are extremely sensitive to the metal and interface quality. Thus, these factors have a significant bearing on the development of ultraviolet plasmonic devices. Here, by addressing these material-related issues, we demonstrate a low-threshold, high-characteristic-temperature metal-oxide-semiconductor ZnO nanolaser that operates at room temperature. The template for the ZnO nanowires consists of a flat single-crystalline Al film grown by molecular beam epitaxy and an ultrasmooth Al2O3 spacer layer synthesized by atomic layer deposition. By effectively reducing the surface plasmon scattering and metal intrinsic absorption losses, the high-quality metal film and the sharp interfaces formed between the layers boost the device performance. This work should pave the way for the use of ultraviolet plasmonic nanolasers and related devices in a wider range of applications. PMID:26814581

  19. Crystalline silicon photovoltaics via low-temperature TiO 2/Si and PEDOT/Si heterojunctions

    NASA Astrophysics Data System (ADS)

    Nagamatsu, Ken Alfred

    The most important goals in developing solar cell technology are to achieve high power conversion efficiencies and lower costs of manufacturing. Solar cells based on crystalline silicon currently dominate the market because they can achieve high efficiency. However, conventional p-n junction solar cells require high-temperature diffusions of dopants, and conventional heterojunction cells based on amorphous silicon require plasma-enhanced deposition, both of which can add manufacturing costs. This dissertation investigates an alternative approach, which is to form crystalline-silicon-based solar cells using heterojunctions with materials that are easily deposited at low temperatures and without plasma enhancement, such as organic semiconductors and metal oxides. We demonstrate a heterojunction between the organic polymer, poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT), and crystalline silicon, which acts as a hole-selective contact and an alternative to a diffused p-n junction. We also present the use of a heterojunction between titanium dioxide and crystalline silicon as a passivating electron-selective contact. The Si/TiO2 heterojunction is demonstrated for the first time as a back-surface field in a crystalline silicon solar cell, and is incorporated into a PEDOT/Si device. The resulting PEDOT/Si/TiO2 solar cell represents an alternative to conventional silicon solar cells that rely on thermally-diffused junctions or plasma-deposited heterojunctions. Finally, we investigate the merits of using conductive networks of silver nanowires to enhance the photovoltaic performance of PEDOT/Si solar cells. The investigation of these materials and devices contributes to the growing body of work regarding crystalline silicon solar cells made with selective contacts.

  20. Vertically Integrated MEMS SOI Composite Porous Silicon-Crystalline Silicon Cantilever-Array Sensors: Concept for Continuous Sensing of Explosives and Warfare Agents

    NASA Astrophysics Data System (ADS)

    Stolyarova, Sara; Shemesh, Ariel; Aharon, Oren; Cohen, Omer; Gal, Lior; Eichen, Yoav; Nemirovsky, Yael

    This study focuses on arrays of cantilevers made of crystalline silicon (c-Si), using SOI wafers as the starting material and using bulk micromachining. The arrays are subsequently transformed into composite porous silicon-crystalline silicon cantilevers, using a unique vapor phase process tailored for providing a thin surface layer of porous silicon on one side only. This results in asymmetric cantilever arrays, with one side providing nano-structured porous large surface, which can be further coated with polymers, thus providing additional sensing capabilities and enhanced sensing. The c-Si cantilevers are vertically integrated with a bottom silicon die with electrodes allowing electrostatic actuation. Flip Chip bonding is used for the vertical integration. The readout is provided by a sensitive Capacitance to Digital Converter. The fabrication, processing and characterization results are reported. The reported study is aimed towards achieving miniature cantilever chips with integrated readout for sensing explosives and chemical warfare agents in the field.

  1. Surface finish in ultra-precision diamond turning of single-crystal silicon

    NASA Astrophysics Data System (ADS)

    Ayomoh, M.; Abou-El-Hossein, K.

    2015-10-01

    Silicon is an optical material widely used in the production of infrared optics. However, silicon as a brittle material exhibits some difficulties when ultra-precision machined by mono-crystalline single point diamond. Finish turning of silicon with mono- crystalline diamond inserts results in accelerated tool wear rates if the right combination of the machining parameters is not properly selected. In this study, we conducted a series of machining tests on an ultra-high precision machine tool using finish turning conditions when using mono-crystalline diamond inserts with negative rake angle and relatively big nose radius. The study yields some recommendations on the best combination of machining parameters that will result in maximum material removal rates with smallest possible surface finish. In this work, standard non-controlled waviness diamond inserts having nose radius of about 1.5 mm, rake angle of negative 25°, and clearance angle of 5° were used to produce flat surfaces on silicon disk. From the results, it has been established that feed rate has the most influential effect followed by the depth of cut and cutting speed.

  2. The radiation damage of crystalline silicon PN diode in tritium beta-voltaic battery.

    PubMed

    Lei, Yisong; Yang, Yuqing; Liu, Yebing; Li, Hao; Wang, Guanquan; Hu, Rui; Xiong, Xiaoling; Luo, Shunzhong

    2014-08-01

    A tritium beta-voltaic battery using a crystalline silicon convertor composed of (100)Si/SiO2/Si3N4 film degrades remarkably with radiation from a high intensity titanium tritide film. Simulation and experiments were carried out to investigate the main factor causing the degradation. The radiation damages mainly comes from the x-ray emitted from the titanium tritide film and beta particle can relieve the damages. The x-ray radiation induced positive charges in the SiO2 film destroying the output property of the PN diode with the induction of an electric field. PMID:24751350

  3. Studying The Kinetics Of Crystalline Silicon Nanoparticle Lithiation With In-Situ Transmission Electron Microscopy

    SciTech Connect

    Mcdowell, Matthew T.; Ryu, Ill; Lee, Seokwoo; Wang, Chong M.; Nix, William D.; Cui, Yi

    2012-11-27

    Silicon is an attractive high-capacity anode material for Li-ion batteries, but a comprehensive understanding of the massive ~300% volume change and fracture during lithiation/delithiation is necessary to reliably employ Si anodes. Here, in-situ transmission electron microscopy (TEM) of the lithiation of crystalline Si nanoparticles reveals that the reaction slows down as it progresses into the particle interior. Analysis suggests that this behavior is due to the influence of mechanical stress at the reaction front on the driving force for the reaction. These experiments give insight into the factors controlling the kinetics of this unique reaction.

  4. Computation modelling on von Mises stress in multi-crystalline silicon ingot for PV application

    NASA Astrophysics Data System (ADS)

    Aravindan, G.; Srinivasan, M.; Aravinth, K.; Ramasamy, P.

    2016-05-01

    Numerical simulation studies have been made on multi crystalline-Silicon (mc-Si) growth by directional solidification (DS) process for Photovoltaic (PV) application. Heat transfer plays an important role in the DS process as dislocation density and growth rate are controlled by temperature gradient of the DS furnace. The heat transfer in the DS furnace is controlled by movement of side wall insulation at different velocity upto 200 mm from the bottom insulation. The simulation results show that the thermal stress in the mc-si ingot for 0.2 mm/min velocity is minimum.

  5. Formation kinetics of copper-related light-induced degradation in crystalline silicon

    SciTech Connect

    Lindroos, J. Savin, H.

    2014-12-21

    Light-induced degradation (LID) is a deleterious effect in crystalline silicon, which is considered to originate from recombination-active boron-oxygen complexes and/or copper-related defects. Although LID in both cases appears as a fast initial decay followed by a second slower degradation, we show that the time constant of copper-related degradation increases with increasing boron concentration in contrast to boron-oxygen LID. Temperature-dependent analysis reveals that the defect formation is limited by copper diffusion. Finally, interface defect density measurements confirm that copper-related LID is dominated by recombination in the wafer bulk.

  6. Method using laser irradiation for the production of atomically clean crystalline silicon and germanium surfaces

    DOEpatents

    Ownby, Gary W.; White, Clark W.; Zehner, David M.

    1981-01-01

    This invention relates to a new method for removing surface impurities from crystalline silicon or germanium articles, such as off-the-shelf p- or n-type wafers to be doped for use as junction devices. The principal contaminants on such wafers are oxygen and carbon. The new method comprises laser-irradiating the contaminated surface in a non-reactive atmosphere, using one or more of Q-switched laser pulses whose parameters are selected to effect melting of the surface without substantial vaporization thereof. In a typical application, a plurality of pulses is used to convert a surface region of an off-the-shelf silicon wafer to an automatically clean region. This can be accomplished in a system at a pressure below 10.sup.-8 Torr, using Q-switched ruby-laser pulses having an energy density in the range of from about 60 to 190 MW/cm.sup.2.

  7. Solution-Based Synthesis of Crystalline Silicon from Liquid Silane through Laser and Chemical Annealing

    DOE PAGESBeta

    Iyer, Ganjigunte R. S.; Hobbie, Erik K.; Guruvenket, Srinivasan; Hoey, Justin M.; Anderson, Kenneth J.; Lovaasen, John; Gette, Cody; Schulz, Douglas L.; Swenson, Orven F.; Elangovan, Arumugasamy; et al

    2012-05-23

    We report a solution process for the synthesis of crystalline silicon from the liquid silane precursor cyclohexasilane (Si6H12). Polysilane films were crystallized through thermal and laser annealing, with plasma hydrogenation at atmospheric pressure generating further structural changes in the films. The evolution from amorphous to microcrystalline is characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and impedance spectroscopy. A four-decade enhancement in the electrical conductivity is attributed to a disorder-order transition in a bonded Si network. Lastly, our results demonstrate a potentially attractive approach that employs a solution process coupled with ambient post-processing to produce crystallinemore » silicon thin films.« less

  8. Temperature dependence of the radiative recombination coefficient in crystalline silicon from spectral photoluminescence

    SciTech Connect

    Nguyen, Hieu T. Macdonald, Daniel; Baker-Finch, Simeon C.

    2014-03-17

    The radiative recombination coefficient B(T) in crystalline silicon is determined for the temperature range 90–363 K, and in particular from 270 to 350 K with an interval of 10 K, where only sparse data are available at present. The band-band absorption coefficient established recently by Nguyen et al. [J. Appl. Phys. 115, 043710 (2014)] via photoluminescence spectrum measurements is employed to compute the values of B(T) at various temperatures. The results agree very well with literature data from Trupke et al. [J. Appl. Phys. 94, 4930 (2003).] We present a polynomial parameterization describing the temperature dependence of the product of B(T) and the square of the intrinsic carrier density. We also find that B(T) saturates at a near constant value at room temperature and above for silicon samples with relatively low free carrier densities.

  9. Method using laser irradiation for the production of atomically clean crystalline silicon and germanium surfaces

    DOEpatents

    Ownby, G.W.; White, C.W.; Zehner, D.M.

    1979-12-28

    This invention relates to a new method for removing surface impurities from crystalline silicon or germanium articles, such as off-the-shelf p- or n-type wafers to be doped for use as junction devices. The principal contaminants on such wafers are oxygen and carbon. The new method comprises laser-irradiating the contaminated surface in a non-reactive atmosphere, using one or more of Q-switched laser pulses whose parameters are selected to effect melting of the surface without substantial vaporization thereof. In a typical application, a plurality of pulses is used to convert a surface region of an off-the-shelf silicon wafer to an atomically clean region. This can be accomplished in a system at a pressure below 10-/sup 8/ Torr, using Q-switched ruber-laser pulses having an energy density in the range of from about 60 to 190 MW/cm/sup 2/.

  10. "Liquid Knife" to Fabricate Patterning Single-Crystalline Perovskite Microplates toward High-Performance Laser Arrays.

    PubMed

    Feng, Jiangang; Yan, Xiaoxu; Zhang, Yifan; Wang, Xuedong; Wu, Yuchen; Su, Bin; Fu, Hongbin; Jiang, Lei

    2016-05-01

    A facile and effective "liquid knife" is created by controlling the dewetting process of the liquid precursor, yielding patterning single-crystalline perovskite microplates with uniform size, precise positioning, high quality, and low lasing thresholds. The sizes and location of single-crystalline perovskite are controllable, leading to mode-tunable lasing emission and patterned lasers. PMID:27000628

  11. Optical properties and surface damage studies of crystalline silicon caused by swift iron ions

    NASA Astrophysics Data System (ADS)

    Dubey, S. K.

    2016-05-01

    p-Type silicon samples irradiated with 70 MeV 56Fe5+ ions for various fluences varying between 5 × 1012 and 4 × 1014 ions cm-2 have been studied using spectroscopic ellipsometry and Fourier transform infrared spectroscopy. The microstructure of the irradiated samples was modeled from ellipsometric data, using a multilayer optical model and Bruggeman effective medium approximation. The values of pseudodielectric function, absorption coefficient and Penn gap energy were determined with respect to ion fluence. The effective medium analysis suggests that the superficial silicon layer can be explained as a mixture of crystalline and damaged silicon. The thickness of the damaged layer and percentage of voids present in the layer were found to increase with increase in the ion fluence. The effect of disorder on the interband optical spectra, especially on the critical point E1 at 3.4 eV was found to vary with ion fluence. A red shift in the critical point E1 with increasing ion fluence was observed. FTIR study showed of silicon samples irradiated with 70 MeV 56Fe5+ ions produced the oscillations in the spectral region 1000-400 cm-1. As irradiated sample showed more pronounced fringes, while contrast of the fringes and amplitude both were found to decrease with increase in depth.

  12. Electrical detection and imaging of individual phosphorus and silicon-dangling bonds states at the crystalline silicon to silicon dioxide interface

    NASA Astrophysics Data System (ADS)

    Ambal, Kapildeb; Rahe, Philipp; Payne, Adam; Slinkman, James; Williams, Clayton C.; Boehme, Christoph

    Nuclear spins of phosphorus [P] donor atoms in crystalline silicon are promising qubit candidates, but utilizing these systems for scalable quantum devices will require the ability to probe individual donors on atomic length scales and address these systems by application of well-controlled electric fields1. In this talk we focus on identifying individual P donor and Pb (dangling bond) states by measuring electric current through a crystalline silicon (100) - SiO2 interface, observing charge flow through individual pairs of P donors and highly localized (Å-range) silicon dangling bond states. The experiments were conducted with neutral P donor states using a low-temperature (T = 4.3K) ultra-high vacuum scanning probe microscope with a quartz tuning fork sensor that allows simultaneous AFM and local current measurements in complete darkness. This so called conduction-atomic force microscopy experiment2 yields images of the dangling bond states coupled to individual phosphorus donors. I-V responses on these isolated highly localized charge percolation paths further support the hypothesis that individual P-donor - Pb states are being addressed, and that spin-states may be probed using spin-dependent charge-carrier recombination current between 31P and the interface defects.

  13. Optimization of oxidation processes to improve crystalline silicon solar cell emitters

    SciTech Connect

    Shen, L.; Liang, Z. C. Liu, C. F.; Long, T. J.; Wang, D. L.

    2014-02-15

    Control of the oxidation process is one key issue in producing high-quality emitters for crystalline silicon solar cells. In this paper, the oxidation parameters of pre-oxidation time, oxygen concentration during pre-oxidation and pre-deposition and drive-in time were optimized by using orthogonal experiments. By analyzing experimental measurements of short-circuit current, open circuit voltage, series resistance and solar cell efficiency in solar cells with different sheet resistances which were produced by using different diffusion processes, we inferred that an emitter with a sheet resistance of approximately 70 Ω/□ performed best under the existing standard solar cell process. Further investigations were conducted on emitters with sheet resistances of approximately 70 Ω/□ that were obtained from different preparation processes. The results indicate that emitters with surface phosphorus concentrations between 4.96 × 10{sup 20} cm{sup −3} and 7.78 × 10{sup 20} cm{sup −3} and with junction depths between 0.46 μm and 0.55 μm possessed the best quality. With no extra processing, the final preparation of the crystalline silicon solar cell efficiency can reach 18.41%, which is an increase of 0.4%{sub abs} compared to conventional emitters with 50 Ω/□ sheet resistance.

  14. Optimization of the antireflection coating of thin epitaxial crystalline silicon solar cells

    DOE PAGESBeta

    Selj, Josefine K.; Young, David; Grover, Sachit

    2015-08-28

    In this study we use an effective weighting function to include the internal quantum efficiency (IQE) and the effective thickness, Te, of the active cell layer in the optical modeling of the antireflection coating (ARC) of very thin crystalline silicon solar cells. The spectrum transmitted through the ARC is hence optimized for efficient use in the given cell structure and the solar cell performance can be improved. For a 2-μm thick crystalline silicon heterojunction solar cell the optimal thickness of the Indium Tin Oxide (ITO) ARC is reduced by ~8 nm when IQE data and effective thickness are taken intomore » account compared to the standard ARC optimization, using the AM1.5 spectrum only. The reduced ARC thickness will shift the reflectance minima towards shorter wavelengths and hence better match the absorption of very thin cells, where the short wavelength range of the spectrum is relatively more important than the long, weakly absorbed wavelengths. For this cell, we find that the optimal thickness of the ITO starts at 63 nm for very thin (1 μm) active Si layer and then increase with increasing Te until it saturates at 71 nm for Te > 30 μm.« less

  15. Optimization of the antireflection coating of thin epitaxial crystalline silicon solar cells

    SciTech Connect

    Selj, Josefine K.; Young, David; Grover, Sachit

    2015-08-28

    In this study we use an effective weighting function to include the internal quantum efficiency (IQE) and the effective thickness, Te, of the active cell layer in the optical modeling of the antireflection coating (ARC) of very thin crystalline silicon solar cells. The spectrum transmitted through the ARC is hence optimized for efficient use in the given cell structure and the solar cell performance can be improved. For a 2-μm thick crystalline silicon heterojunction solar cell the optimal thickness of the Indium Tin Oxide (ITO) ARC is reduced by ~8 nm when IQE data and effective thickness are taken into account compared to the standard ARC optimization, using the AM1.5 spectrum only. The reduced ARC thickness will shift the reflectance minima towards shorter wavelengths and hence better match the absorption of very thin cells, where the short wavelength range of the spectrum is relatively more important than the long, weakly absorbed wavelengths. For this cell, we find that the optimal thickness of the ITO starts at 63 nm for very thin (1 μm) active Si layer and then increase with increasing Te until it saturates at 71 nm for Te > 30 μm.

  16. Electron microscopy analysis of crystalline silicon islands formed on screen-printed aluminum-doped p-type silicon surfaces

    SciTech Connect

    Bock, Robert; Schmidt, Jan; Brendel, Rolf

    2008-08-15

    The origin of a not yet understood concentration peak, which is generally measured at the surface of aluminum-doped p{sup +} regions produced in a conventional screen-printing process is investigated. Our findings provide clear experimental evidence that the concentration peak is due to the microscopic structures formed at the silicon surface during the firing process. To characterize the microscopic nature of the islands (lateral dimensions of 1-3 {mu}m) and line networks of self-assembled nanostructures (lateral dimension of {<=}50 nm), transmission electron microscopy, scanning electron microscopy, scanning transmission electron microscopy, and energy dispersive x-ray analysis are combined. Aluminum inclusions are detected 50 nm below the surface of the islands and crystalline aluminum precipitates of {<=}7 nm in diameter are found within the bulk of the islands. In addition, aluminum inclusions (lateral dimension of {approx}30 nm) are found within the bulk of the self-assembled line networks.

  17. Tailoring the surface density of silicon nanocrystals embedded in SiO{sub x} single layers

    SciTech Connect

    Hernández, S.; Peiró, F.; Garrido, B.; Pellegrino, P.; Miska, P.; Grün, M.; Vergnat, M.; Estradé, S.

    2013-12-21

    In this article, we explore the possibility of modifying the silicon nanocrystal areal density in SiO{sub x} single layers, while keeping constant their size. For this purpose, a set of SiO{sub x} monolayers with controlled thickness between two thick SiO{sub 2} layers has been fabricated, for four different compositions (x = 1, 1.25, 1.5, or 1.75). The structural properties of the SiO{sub x} single layers have been analyzed by transmission electron microscopy (TEM) in planar view geometry. Energy-filtered TEM images revealed an almost constant Si-cluster size and a slight increase in the cluster areal density as the silicon content increases in the layers, while high resolution TEM images show that the size of the Si crystalline precipitates largely decreases as the SiO{sub x} stoichiometry approaches that of SiO{sub 2}. The crystalline fraction was evaluated by combining the results from both techniques, finding a crystallinity reduction from 75% to 40%, for x = 1 and 1.75, respectively. Complementary photoluminescence measurements corroborate the precipitation of Si-nanocrystals with excellent emission properties for layers with the largest amount of excess silicon. The integrated emission from the nanoaggregates perfectly scales with their crystalline state, with no detectable emission for crystalline fractions below 40%. The combination of the structural and luminescence observations suggests that small Si precipitates are submitted to a higher compressive local stress applied by the SiO{sub 2} matrix that could inhibit the phase separation and, in turn, promotes the creation of nonradiative paths.

  18. Tailoring the surface density of silicon nanocrystals embedded in SiOx single layers

    NASA Astrophysics Data System (ADS)

    Hernández, S.; Miska, P.; Grün, M.; Estradé, S.; Peiró, F.; Garrido, B.; Vergnat, M.; Pellegrino, P.

    2013-12-01

    In this article, we explore the possibility of modifying the silicon nanocrystal areal density in SiOx single layers, while keeping constant their size. For this purpose, a set of SiOx monolayers with controlled thickness between two thick SiO2 layers has been fabricated, for four different compositions (x = 1, 1.25, 1.5, or 1.75). The structural properties of the SiOx single layers have been analyzed by transmission electron microscopy (TEM) in planar view geometry. Energy-filtered TEM images revealed an almost constant Si-cluster size and a slight increase in the cluster areal density as the silicon content increases in the layers, while high resolution TEM images show that the size of the Si crystalline precipitates largely decreases as the SiOx stoichiometry approaches that of SiO2. The crystalline fraction was evaluated by combining the results from both techniques, finding a crystallinity reduction from 75% to 40%, for x = 1 and 1.75, respectively. Complementary photoluminescence measurements corroborate the precipitation of Si-nanocrystals with excellent emission properties for layers with the largest amount of excess silicon. The integrated emission from the nanoaggregates perfectly scales with their crystalline state, with no detectable emission for crystalline fractions below 40%. The combination of the structural and luminescence observations suggests that small Si precipitates are submitted to a higher compressive local stress applied by the SiO2 matrix that could inhibit the phase separation and, in turn, promotes the creation of nonradiative paths.

  19. Simultaneous high crystallinity and sub-bandgap optical absorptance in hyperdoped black silicon using nanosecond laser annealing

    SciTech Connect

    Franta, Benjamin Pastor, David; Gandhi, Hemi H.; Aziz, Michael J.; Mazur, Eric; Rekemeyer, Paul H.; Gradečak, Silvija

    2015-12-14

    Hyperdoped black silicon fabricated with femtosecond laser irradiation has attracted interest for applications in infrared photodetectors and intermediate band photovoltaics due to its sub-bandgap optical absorptance and light-trapping surface. However, hyperdoped black silicon typically has an amorphous and polyphasic polycrystalline surface that can interfere with carrier transport, electrical rectification, and intermediate band formation. Past studies have used thermal annealing to obtain high crystallinity in hyperdoped black silicon, but thermal annealing causes a deactivation of the sub-bandgap optical absorptance. In this study, nanosecond laser annealing is used to obtain high crystallinity and remove pressure-induced phases in hyperdoped black silicon while maintaining high sub-bandgap optical absorptance and a light-trapping surface morphology. Furthermore, it is shown that nanosecond laser annealing reactivates the sub-bandgap optical absorptance of hyperdoped black silicon after deactivation by thermal annealing. Thermal annealing and nanosecond laser annealing can be combined in sequence to fabricate hyperdoped black silicon that simultaneously shows high crystallinity, high above-bandgap and sub-bandgap absorptance, and a rectifying electrical homojunction. Such nanosecond laser annealing could potentially be applied to non-equilibrium material systems beyond hyperdoped black silicon.

  20. Simultaneous high crystallinity and sub-bandgap optical absorptance in hyperdoped black silicon using nanosecond laser annealing

    NASA Astrophysics Data System (ADS)

    Franta, Benjamin; Pastor, David; Gandhi, Hemi H.; Rekemeyer, Paul H.; Gradečak, Silvija; Aziz, Michael J.; Mazur, Eric

    2015-12-01

    Hyperdoped black silicon fabricated with femtosecond laser irradiation has attracted interest for applications in infrared photodetectors and intermediate band photovoltaics due to its sub-bandgap optical absorptance and light-trapping surface. However, hyperdoped black silicon typically has an amorphous and polyphasic polycrystalline surface that can interfere with carrier transport, electrical rectification, and intermediate band formation. Past studies have used thermal annealing to obtain high crystallinity in hyperdoped black silicon, but thermal annealing causes a deactivation of the sub-bandgap optical absorptance. In this study, nanosecond laser annealing is used to obtain high crystallinity and remove pressure-induced phases in hyperdoped black silicon while maintaining high sub-bandgap optical absorptance and a light-trapping surface morphology. Furthermore, it is shown that nanosecond laser annealing reactivates the sub-bandgap optical absorptance of hyperdoped black silicon after deactivation by thermal annealing. Thermal annealing and nanosecond laser annealing can be combined in sequence to fabricate hyperdoped black silicon that simultaneously shows high crystallinity, high above-bandgap and sub-bandgap absorptance, and a rectifying electrical homojunction. Such nanosecond laser annealing could potentially be applied to non-equilibrium material systems beyond hyperdoped black silicon.

  1. Amorphous silicon/crystalline silicon heterojunctions for nuclear radiation detector applications

    SciTech Connect

    Walton, J.T.; Hong, W.S.; Luke, P.N.; Wang, N.W.; Ziemba, F.P.

    1996-10-01

    Results on characterization of electrical properties of amorphous Si films for the 3 different growth methods (RF sputtering, PECVD [plasma enhanced], LPCVD [low pressure]) are reported. Performance of these a-Si films as heterojunctions on high resistivity p-type and n- type crystalline Si is examined by measuring the noise, leakage current, and the alpha particle response of 5mm dia detector structures. It is demonstrated that heterojunction detectors formed by RF sputtered films and PECVD films are comparable in performance with conventional surface barrier detectors. Results indicate that the a-Si/c-Si heterojunctions have the potential to greatly simplify detector fabrication. Directions for future avenues of nuclear particle detector development are indicated.

  2. Laser fabrication of crystalline silicon nanoresonators from an amorphous film for low-loss all-dielectric nanophotonics.

    PubMed

    Dmitriev, P A; Makarov, S V; Milichko, V A; Mukhin, I S; Gudovskikh, A S; Sitnikova, A A; Samusev, A K; Krasnok, A E; Belov, P A

    2016-03-01

    The concept of high refractive index subwavelength dielectric nanoresonators, supporting electric and magnetic optical resonance, is a promising platform for waveguiding, sensing, and nonlinear nanophotonic devices. However, high concentration of defects in the nanoresonators diminishes their resonant properties, which are crucially dependent on their internal losses. Therefore, it seems to be inevitable to use initially crystalline materials for fabrication of the nanoresonators. Here, we show that the fabrication of crystalline (low-loss) resonant silicon nanoparticles by femtosecond laser ablation of amorphous (high-loss) silicon thin films is possible. We apply two conceptually different approaches: recently proposed laser-induced transfer and a novel laser writing technique for large-scale fabrication of the crystalline nanoparticles. The crystallinity of the fabricated nanoparticles is proven by Raman spectroscopy and electron transmission microscopy, whereas optical resonant properties of the nanoparticles are studied using dark-field optical spectroscopy and full-wave electromagnetic simulations. PMID:26864805

  3. Laser fabrication of crystalline silicon nanoresonators from an amorphous film for low-loss all-dielectric nanophotonics

    NASA Astrophysics Data System (ADS)

    Dmitriev, P. A.; Makarov, S. V.; Milichko, V. A.; Mukhin, I. S.; Gudovskikh, A. S.; Sitnikova, A. A.; Samusev, A. K.; Krasnok, A. E.; Belov, P. A.

    2016-02-01

    The concept of high refractive index subwavelength dielectric nanoresonators, supporting electric and magnetic optical resonance, is a promising platform for waveguiding, sensing, and nonlinear nanophotonic devices. However, high concentration of defects in the nanoresonators diminishes their resonant properties, which are crucially dependent on their internal losses. Therefore, it seems to be inevitable to use initially crystalline materials for fabrication of the nanoresonators. Here, we show that the fabrication of crystalline (low-loss) resonant silicon nanoparticles by femtosecond laser ablation of amorphous (high-loss) silicon thin films is possible. We apply two conceptually different approaches: recently proposed laser-induced transfer and a novel laser writing technique for large-scale fabrication of the crystalline nanoparticles. The crystallinity of the fabricated nanoparticles is proven by Raman spectroscopy and electron transmission microscopy, whereas optical resonant properties of the nanoparticles are studied using dark-field optical spectroscopy and full-wave electromagnetic simulations.

  4. Crystalline-amorphous silicon nano-composites: Nano-pores and nano-inclusions impact on the thermal conductivity

    NASA Astrophysics Data System (ADS)

    Verdier, M.; Termentzidis, K.; Lacroix, D.

    2016-05-01

    The thermal conductivities of nanoporous and nanocomposite silicon with incorporated amorphous phases have been computed by molecular dynamics simulations. A systematic investigation of the porosity and the width of the amorphous shell contouring a spherical pore has been made. The impact of amorphous phase nanoinclusions in a crystalline matrix has also been studied with the same amorphous fraction as the porosity of nanoporous silicon to achieve comparison. The key parameter for all configurations with or without the amorphous phase is proved to be the interface (between the crystalline and amorphous phases or crystalline and void) to volume ratio. We obtain the sub-amorphous thermal conductivity for several configurations by combining pores, amorphous shell, and crystalline phase. These configurations are promising candidates for low cost and not toxic thermoelectric devices based on abundant semiconductors.

  5. Single Walled Carbon Nanotube/Silicon Heterojunctions

    NASA Astrophysics Data System (ADS)

    Wu, Zhuangchun

    2005-11-01

    Characterization of the electrical heterojunction between single walled carbon nanotubes (SWNTs) and semiconductors is important for an array of potential applications. Thin, homogeneous, transparent, films of 100% SWNTs exhibiting good electrical conductivity [1] have already been demonstrated as the hole injection electrode in GaN light emitting diodes [2]. The simultaneous transparency and high electrical conductivity of these films makes them similarly promising for the light transmissive electrode in photovoltaic devices. SWNTs have moreover long been proposed as on-chip, device interconnects. To understand the electrical coupling between the nanotubes and semiconductors, likely to have relevance in such devices, we have begun a systematic exploration of the electrical properties of SWNT/silicon hetrojunctions. We will discuss findings as well as a novel test method made possible by the unique morphology of the nanotubes. 1. Z. Wu, Z. Chen, X. Du, J. M. Logan, J. Sippel, M. Nikolou, K. Kamaras, J. R. Reynolds, D. B. Tanner, A. F. Hebard, A. G. Rinzler, Science 305, 1273 (2004) 2. K. Lee, Z. Wu, Z. Chen, F. Ren, S. J. Pearton, A. G. Rinzler, Nano Lett. 4, 911 (2004)

  6. Magnesium Fluoride Electron-Selective Contacts for Crystalline Silicon Solar Cells.

    PubMed

    Wan, Yimao; Samundsett, Chris; Bullock, James; Allen, Thomas; Hettick, Mark; Yan, Di; Zheng, Peiting; Zhang, Xinyu; Cui, Jie; McKeon, Josephine; Javey, Ali; Cuevas, Andres

    2016-06-15

    In this study, we present a novel application of thin magnesium fluoride films to form electron-selective contacts to n-type crystalline silicon (c-Si). This allows the demonstration of a 20.1%-efficient c-Si solar cell. The electron-selective contact is composed of deposited layers of amorphous silicon (∼6.5 nm), magnesium fluoride (∼1 nm), and aluminum (∼300 nm). X-ray photoelectron spectroscopy reveals a work function of 3.5 eV at the MgF2/Al interface, significantly lower than that of aluminum itself (∼4.2 eV), enabling an Ohmic contact between the aluminum electrode and n-type c-Si. The optimized contact structure exhibits a contact resistivity of ∼76 mΩ·cm(2), sufficiently low for a full-area contact to solar cells, together with a very low contact recombination current density of ∼10 fA/cm(2). We demonstrate that electrodes functionalized with thin magnesium fluoride films significantly improve the performance of silicon solar cells. The novel contacts can potentially be implemented also in organic optoelectronic devices, including photovoltaics, thin film transistors, or light emitting diodes. PMID:27219911

  7. A hybrid life-cycle inventory for multi-crystalline silicon PV module manufacturing in China

    NASA Astrophysics Data System (ADS)

    Yao, Yuan; Chang, Yuan; Masanet, Eric

    2014-11-01

    China is the world’s largest manufacturer of multi-crystalline silicon photovoltaic (mc-Si PV) modules, which is a key enabling technology in the global transition to renewable electric power systems. This study presents a hybrid life-cycle inventory (LCI) of Chinese mc-Si PV modules, which fills a critical knowledge gap on the environmental implications of mc-Si PV module manufacturing in China. The hybrid LCI approach combines process-based LCI data for module and poly-silicon manufacturing plants with a 2007 China IO-LCI model for production of raw material and fuel inputs to estimate ‘cradle to gate’ primary energy use, water consumption, and major air pollutant emissions (carbon dioxide, methane, sulfur dioxide, nitrous oxide, and nitrogen oxides). Results suggest that mc-Si PV modules from China may come with higher environmental burdens that one might estimate if one were using LCI results for mc-Si PV modules manufactured elsewhere. These higher burdens can be reasonably explained by the efficiency differences in China’s poly-silicon manufacturing processes, the country’s dependence on highly polluting coal-fired electricity, and the expanded system boundaries associated with the hybrid LCI modeling framework. The results should be useful for establishing more conservative ranges on the potential ‘cradle to gate’ impacts of mc-Si PV module manufacturing for more robust LCAs of PV deployment scenarios.

  8. Nickel Electroless Plating: Adhesion Analysis for Mono-Type Crystalline Silicon Solar Cells.

    PubMed

    Shin, Eun Gu; Rehman, Atteq ur; Lee, Sang Hee; Lee, Soo Hong

    2015-10-01

    The adhesion of the front electrodes to silicon substrate is the most important parameters to be optimized. Nickel silicide which is formed by sintering process using a silicon substrate improves the mechanical and electrical properties as well as act as diffusion barrier for copper. In this experiment p-type mono-crystalline czochralski (CZ) silicon wafers having resistivity of 1.5 Ω·cm were used to study one step and two step nickel electroless plating process. POCl3 diffusion process was performed to form the emitter with the sheet resistance of 70 ohm/sq. The Six, layer was set down as an antireflection coating (ARC) layer at emitter surface by plasma enhanced chemical vapor deposition (PECVD) process. Laser ablation process was used to open SiNx passivation layer locally for the formation of the front electrodes. Nickel was deposited by electroless plating process by one step and two step nickel electroless deposition process. The two step nickel plating was performed by applying a second nickel deposition step subsequent to the first sintering process. Furthermore, the adhesion analysis for both one step and two steps process was conducted using peel force tester (universal testing machine, H5KT) after depositing Cu contact by light induced plating (LIP). PMID:26726421

  9. The Synthesis and Structural Properties of Crystalline Silicon Quantum Dots upon Thermal Annealing of Hydrogenated Amorphous Si-Rich Silicon Carbide Films

    NASA Astrophysics Data System (ADS)

    Wen, Guozhi; Zeng, Xiangbin; Li, Xianghu

    2016-05-01

    Silicon quantum dots (QDs) embedded in non-stoichiometric hydrogenated silicon carbide (SiC:H) thin films have been successfully synthesized by plasma-enhanced chemical vapor deposition and post-annealing. The chemical composition analyses have been carried out by x-ray photoelectron spectroscopy (XPS). The bonding configurations have been deduced from Fourier transform infrared absorption measurements (FTIR). The evolution of microstructure with temperature has been characterized by glancing incident x-ray diffraction (XRD) and Raman diffraction spectroscopy. XPS and FTIR show that it is in Si-rich feature and there are a few hydrogenated silicon clusters in the as-grown sample. XRD and Raman diffraction spectroscopy show that it is in amorphous for the as-grown sample, while crystalline silicon QDs have been synthesized in the 900°C annealed sample. Silicon atoms precipitation from the SiC matrix or silicon phase transition from amorphous SiC is enhanced with annealing temperature increase. The average sizes of silicon QDs are about 5.1 nm and 5.6 nm, the number densities are as high as 1.7 × 1012 cm-2 and 3.2 × 1012 cm-2, and the crystalline volume fractions are about 58.3% and 61.3% for the 900°C and 1050°C annealed samples, respectively. These structural properties analyses provide an understanding about the synthesis of silicon QDs upon thermal annealing for applications in next generation optoelectronic and photovoltaic devices.

  10. The Synthesis and Structural Properties of Crystalline Silicon Quantum Dots upon Thermal Annealing of Hydrogenated Amorphous Si-Rich Silicon Carbide Films

    NASA Astrophysics Data System (ADS)

    Wen, Guozhi; Zeng, Xiangbin; Li, Xianghu

    2016-08-01

    Silicon quantum dots (QDs) embedded in non-stoichiometric hydrogenated silicon carbide (SiC:H) thin films have been successfully synthesized by plasma-enhanced chemical vapor deposition and post-annealing. The chemical composition analyses have been carried out by x-ray photoelectron spectroscopy (XPS). The bonding configurations have been deduced from Fourier transform infrared absorption measurements (FTIR). The evolution of microstructure with temperature has been characterized by glancing incident x-ray diffraction (XRD) and Raman diffraction spectroscopy. XPS and FTIR show that it is in Si-rich feature and there are a few hydrogenated silicon clusters in the as-grown sample. XRD and Raman diffraction spectroscopy show that it is in amorphous for the as-grown sample, while crystalline silicon QDs have been synthesized in the 900°C annealed sample. Silicon atoms precipitation from the SiC matrix or silicon phase transition from amorphous SiC is enhanced with annealing temperature increase. The average sizes of silicon QDs are about 5.1 nm and 5.6 nm, the number densities are as high as 1.7 × 1012 cm-2 and 3.2 × 1012 cm-2, and the crystalline volume fractions are about 58.3% and 61.3% for the 900°C and 1050°C annealed samples, respectively. These structural properties analyses provide an understanding about the synthesis of silicon QDs upon thermal annealing for applications in next generation optoelectronic and photovoltaic devices.

  11. Lattice-Matched Semiconductor Layers on Single Crystalline Sapphire Substrate

    NASA Technical Reports Server (NTRS)

    Choi, Sang; King, Glen; Park, Yeonjoon

    2009-01-01

    SiGe is an important semiconductor alloy for high-speed field effect transistors (FETs), high-temperature thermoelectric devices, photovoltaic solar cells, and photon detectors. The growth of SiGe layer is difficult because SiGe alloys have different lattice constants from those of the common Si wafers, which leads to a high density of defects, including dislocations, micro-twins, cracks, and delaminations. This innovation utilizes newly developed rhombohedral epitaxy of cubic semiconductors on trigonal substrates in order to solve the lattice mismatch problem of SiGe by using trigonal single crystals like sapphire (Al2O3) as substrate to give a unique growth-orientation to the SiGe layer, which is automatically controlled at the interface upon sapphire (0001). This technology is different from previous silicon on insulator (SOI) or SGOI (SiGe on insulator) technologies that use amorphous SiO2 as the growth plane. A cubic semiconductor crystal is a special case of a rhombohedron with the inter-planar angle, alpha = 90 deg. With a mathematical transformation, all rhombohedrons can be described by trigonal crystal lattice structures. Therefore, all cubic lattice constants and crystal planes (hkl) s can be transformed into those of trigonal crystal parameters. These unique alignments enable a new opportunity of perfect lattice matching conditions, which can eliminate misfit dislocations. Previously, these atomic alignments were thought to be impossible or very difficult. With the invention of a new x-ray diffraction measurement method here, growth of cubic semiconductors on trigonal crystals became possible. This epitaxy and lattice-matching condition can be applied not only to SiGe (111)/sapphire (0001) substrate relations, but also to other crystal structures and other materials, including similar crystal structures which have pointgroup rotational symmetries by 120 because the cubic (111) direction has 120 rotational symmetry. The use of slightly miscut (less than

  12. Gallium Arsenide Layers Grown by Molecular Beam Epitaxy on Single Crystalline Germanium Islands on Insulator

    NASA Astrophysics Data System (ADS)

    Takai, Mikio; Tanigawa, Takaho; Minamisono, Tadanori; Gamo, Kenji; Namba, Susumu

    1984-05-01

    Gallium arsenide (GaAs) layers have successfully been grown by molecular beam epitaxy on single crystalline germanium (Ge) islands, recrystallized by zone melting with SiO2 capping layers, on thermally-oxidized Si-wafers. The GaAs layers, grown on the single crystalline Ge islands, show smooth surfaces without any grain-boundaries, while those, grown on the Ge islands with grain-boundaries and on the SiO2, have grain-boundaries. The GaAs layers on the single crystalline Ge islands emit photoluminescence, the intensity of which is almost comparable to that of GaAs layers on bulk Ge crystals.

  13. Depth-dependent crystallinity of nano-crystalline silicon induced by step-wise variation of hydrogen dilution during hot-wire CVD

    NASA Astrophysics Data System (ADS)

    Arendse, C. J.; van Heerden, B. A.; Muller, T. F. G.; Cummings, F. R.; Oliphant, C. J.; Malgas, G. F.; Motaung, D. E.

    2015-06-01

    To induce an amorphous surface in a nano-crystalline silicon (nc-Si:H) thin film, the hydrogen dilution was reduced step-wise at fixed time intervals from 90 - 50% during the hotwire chemical vapour deposition process. This contribution reports on the structural properties of the resultant nc-Si:H thin film as a function of the deposition time. Raman spectroscopy, confirmed by high resolution transmission spectroscopy, indicates crystalline uniformity in the growth direction, accompanied by the progression of an amorphous surface layer as the deposition time is increased. The silicon- and oxygen bonding configurations were probed using infrared spectroscopy and electron energy loss spectroscopy. The growth mechanism is ascribed to the improved etching rate by atomic hydrogen in nano-crystalline silicon towards the film/substrate interface region. The optical properties were calculated by applying the effective medium approximation theory, where the existence of bulk and interfacial layers, as inferred from cross-sectional microscopy, were taken into account.

  14. The ``Micromorph'' cell: a new way to high-efficiency-low-temperature crystalline silicon thin-film cell manufacturing?

    NASA Astrophysics Data System (ADS)

    Keppner, H.; Kroll, U.; Torres, P.; Meier, J.; Platz, R.; Fischer, D.; Beck, N.; Dubail, S.; Anna Selvan, J. A.; Pellaton Vaucher, N.; Goerlitzer, M.; Ziegler, Y.; Tscharner, R.; Hof, Ch.; Goetz, M.; Pernet, P.; Wyrsch, N.; Vuille, J.; Cuperus, J.; Shah, A.; Pohl, J.

    1997-02-01

    Hydrogenated microcrystalline Silicon (μc-Si:H) produced by the VHF-GD (Very High Frequency Glow Discharge) process can be considered to be a new base material for thin-film crystalline silicon solar cells. The most striking feature of such cells, in contrast to conventional amorphous silicon technology, is their stability under light-soaking. With respect to crystalline silicon technology, their most striking advantage is their low process temperature (220 °C). The so called "micromorph" cell contains such a μc-Si:H based cell as bottom cell, whereas the top-cell consists of amorphous silicon. A stable efficiency of 10.7% (confirmed by ISE Freiburg) is reported in this paper. At present, all solar cell concepts based on thin-film crystalline silicon have a common problem to overcome: namely, too long manufacturing times. In order to help in solving this problem for the particular case of plasma-deposited μc-Si:H, results on combined argon/hydrogen dilution of the feedgas (silane) are presented. It is shown that rates as high as 9.4 Å/s can be obtained: furthermore, a first solar cell deposited with 8.7 Å/s resulted in an efficiency of 3.1%.

  15. Fluidized-Bed Deposition Of Single-Crystal Silicon

    NASA Technical Reports Server (NTRS)

    Hsu, George C.; Rohatgi, Naresh K.

    1988-01-01

    Uniformly thin single-crystal films of silicon produced by modification of fluidized-bed-reactor technique producing polysilicon by chemical vapor deposition. Proposed for silicon wafers for flat-plate solar arrays and results in different structural and electronic properties in deposition layer desirable for specific microelectronic or solar-cell processing. In process deposition occurs on silicon wafers, kept individually at temperatures above 1,000 degree C. Heated wafers held in unheated and minimally-agitated-fluidized bed of silicon particles and in low concentration of silane.

  16. Friction and deformation behavior of single-crystal silicon carbide

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1977-01-01

    Friction and deformation studies were conducted with single-crystal silicon carbide in sliding contact with diamond. When the radius of curvature of the spherical diamond rider was large (0.3), deformation of silicon carbide was primarily elastic. Under these conditions the friction coefficient was low and did not show a dependence on the silicon carbide orientation. Further, there was no detectable cracking of the silicon carbide surfaces. When smaller radii of curvature of the spherical diamond riders (0.15 and 0.02 mm) or a conical diamond rider was used, plastic grooving occured and the silicon carbide exhibited anisotropic friction and deformation behavior. Under these conditions the friction coefficient depended on load. Anisotropic friction and deformation of the basal plane of silicon carbide was controlled by the slip system. 10101120and cleavage of1010.

  17. Imaging Study of Multi-Crystalline Silicon Wafers Throughout the Manufacturing Process: Preprint

    SciTech Connect

    Johnston, S.; Yan, F.; Zaunbracher, K.; Al-Jassim, M.; Sidelkheir, O.; Blosse, A.

    2011-07-01

    Imaging techniques are applied to multi-crystalline silicon bricks, wafers at various process steps, and finished solar cells. Photoluminescence (PL) imaging is used to characterize defects and material quality on bricks and wafers. Defect regions within the wafers are influenced by brick position within an ingot and height within the brick. The defect areas in as-cut wafers are compared to imaging results from reverse-bias electroluminescence and dark lock-in thermography and cell parameters of near-neighbor finished cells. Defect areas are also characterized by defect band emissions. The defect areas measured by these techniques on as-cut wafers are shown to correlate to finished cell performance.

  18. Imaging Study of Multi-Crystalline Silicon Wafers Throughout the Manufacturing Process

    SciTech Connect

    Johnston, S.; Yan, F.; Zaunbrecher, K.; Al-Jassim, M.; Sidelkheir, O.; Blosse, A.

    2011-01-01

    Imaging techniques are applied to multi-crystalline silicon bricks, wafers at various process steps, and finished solar cells. Photoluminescence (PL) imaging is used to characterize defects and material quality on bricks and wafers. Defect regions within the wafers are influenced by brick position within an ingot and height within the brick. The defect areas in as-cut wafers are compared to imaging results from reverse-bias electroluminescence and dark lock-in thermography and cell parameters of near-neighbor finished cells. Defect areas are also characterized by defect band emissions. The defect areas measured by these techniques on as-cut wafers are shown to correlate to finished cell performance.

  19. Ge growth on porous silicon: The effect of buffer porosity on the epilayer crystalline quality

    NASA Astrophysics Data System (ADS)

    Calabrese, G.; Baricordi, S.; Bernardoni, P.; De Salvador, D.; Ferroni, M.; Guidi, V.; Morandi, V.; Vincenzi, D.

    2014-09-01

    We report on the epitaxial growth of Ge virtual substrates directly on Si (001) and on different porosity porous silicon (pSi) buffers. Obtained results indicate that Ge grown on low porosity (22%) pSi buffer has a better crystalline quality compared to Ge grown on bulk Si and on higher porosity buffers. This result is attributed to the compliant nature of pSi and to its reduced Young's modulus, which leads to plastic tensile deformation of the 22% porosity buffer under the in-plane tensile stress introduced by Ge lattice. The same result is not observed for higher porosity buffers, this effect being attributed to the higher buffer fragility. A low porosity pSi layer can hence be used as buffer for the growth of Ge on Si virtual substrates with reduced dislocation content and for the growth of Ge based devices or the successive integration of III-V semiconductors on Si.

  20. Hydrogen plasma treatments for passivation of amorphous-crystalline silicon-heterojunctions on surfaces promoting epitaxy

    SciTech Connect

    Mews, Mathias; Mingirulli, Nicola; Korte, Lars; Schulze, Tim F.

    2013-03-25

    The impact of post-deposition hydrogen plasma treatment (HPT) on passivation in amorphous/crystalline silicon (a-Si:H/c-Si) interfaces is investigated. Combining low temperature a-Si:H deposition and successive HPT, a high minority carrier lifetime >8 ms is achieved on c-Si <100>, which is otherwise prone to epitaxial growth and thus inferior passivation. It is shown that the passivation improvement stems from diffusion of hydrogen atoms to the heterointerface and subsequent dangling bond passivation. Concomitantly, the a-Si:H hydrogen density increases, leading to band gap widening and void formation, while the film disorder is not increased. Thus, HPT allows for a-Si:H band gap and a-Si:H/c-Si band offset engineering.

  1. Conventional and 360 degree electron tomography of a micro-crystalline silicon solar cell

    NASA Astrophysics Data System (ADS)

    Duchamp, M.; Ramar, A.; Kovács, A.; Kasama, T.; Haug, F.-J.; Newcomb, S. B.; Ballif, C.; Dunin-Borkowski, R. E.

    2011-11-01

    Bright-field (BF) and annular dark-field (ADF) electron tomography in the transmission electron microscope (TEM) are used to characterize elongated porous regions or cracks (simply referred to as cracks thereafter) in micro-crystalline silicon (μc-Si:H) solar cell. The limitations of inferring the 3D geometry of a crack from a tilt series of images acquired from 100-nm-thick focused ion beam (FTB) milled TEM specimen are discussed. In an attempt to maximize the specimen tilt range and to reduce the effects of diffraction and phase contrast on the reconstruction, both BF and ADF electron tomography are used to acquire 360° tilt series of images from a FIB-prepared needle-shaped μc-Si:H specimen.

  2. Light-induced point defect reactions of residual iron in crystalline silicon after aluminum gettering

    SciTech Connect

    Abdelbarey, D.; Kveder, V.; Schroeter, W.; Seibt, M.

    2010-08-15

    Deep level transient spectroscopy is used to study light-induced reactions of residual iron impurities after aluminum gettering (AlG) in crystalline silicon. White-light illumination at room temperature leads to the formation of a defect which is associated with a donor level at 0.33 eV above the valence band. This defect is stable up to about 175 deg. C where it dissociates reversibly in case of small iron concentrations and irreversibly for high iron concentrations. Since marker experiments using gold and platinum diffusion show a high vacancy concentration after AlG a tentative identification of the new defect as the metastable iron-vacancy pair is proposed.

  3. Controllable electrical and physical breakdown of poly-crystalline silicon nanowires by thermally assisted electromigration

    NASA Astrophysics Data System (ADS)

    Park, Jun-Young; Moon, Dong-Il; Seol, Myeong-Lok; Jeon, Chang-Hoon; Jeon, Gwang-Jae; Han, Jin-Woo; Kim, Choong-Ki; Park, Sang-Jae; Lee, Hee Chul; Choi, Yang-Kyu

    2016-01-01

    The importance of poly-crystalline silicon (poly-Si) in semiconductor manufacturing is rapidly increasing due to its highly controllable conductivity and excellent, uniform deposition quality. With the continuing miniaturization of electronic components, low dimensional structures such as 1-dimensional nanowires (NWs) have attracted a great deal of attention. But such components have a much higher current density than 2- or 3- dimensional films, and high current can degrade device lifetime and lead to breakdown problems. Here, we report on the electrical and thermal characteristics of poly-Si NWs, which can also be used to control electrical and physical breakdown under high current density. This work reports a controllable catastrophic change of poly-Si NWs by thermally-assisted electromigration and underlying mechanisms. It also reports the direct and real time observation of these catastrophic changes of poly-Si nanowires for the first time, using scanning electron microscopy.

  4. Controllable electrical and physical breakdown of poly-crystalline silicon nanowires by thermally assisted electromigration

    PubMed Central

    Park, Jun-Young; Moon, Dong-Il; Seol, Myeong-Lok; Jeon, Chang-Hoon; Jeon, Gwang-Jae; Han, Jin-Woo; Kim, Choong-Ki; Park, Sang-Jae; Lee, Hee Chul; Choi, Yang-Kyu

    2016-01-01

    The importance of poly-crystalline silicon (poly-Si) in semiconductor manufacturing is rapidly increasing due to its highly controllable conductivity and excellent, uniform deposition quality. With the continuing miniaturization of electronic components, low dimensional structures such as 1-dimensional nanowires (NWs) have attracted a great deal of attention. But such components have a much higher current density than 2- or 3- dimensional films, and high current can degrade device lifetime and lead to breakdown problems. Here, we report on the electrical and thermal characteristics of poly-Si NWs, which can also be used to control electrical and physical breakdown under high current density. This work reports a controllable catastrophic change of poly-Si NWs by thermally-assisted electromigration and underlying mechanisms. It also reports the direct and real time observation of these catastrophic changes of poly-Si nanowires for the first time, using scanning electron microscopy. PMID:26782708

  5. Controllable electrical and physical breakdown of poly-crystalline silicon nanowires by thermally assisted electromigration.

    PubMed

    Park, Jun-Young; Moon, Dong-Il; Seol, Myeong-Lok; Jeon, Chang-Hoon; Jeon, Gwang-Jae; Han, Jin-Woo; Kim, Choong-Ki; Park, Sang-Jae; Lee, Hee Chul; Choi, Yang-Kyu

    2016-01-01

    The importance of poly-crystalline silicon (poly-Si) in semiconductor manufacturing is rapidly increasing due to its highly controllable conductivity and excellent, uniform deposition quality. With the continuing miniaturization of electronic components, low dimensional structures such as 1-dimensional nanowires (NWs) have attracted a great deal of attention. But such components have a much higher current density than 2- or 3-dimensional films, and high current can degrade device lifetime and lead to breakdown problems. Here, we report on the electrical and thermal characteristics of poly-Si NWs, which can also be used to control electrical and physical breakdown under high current density. This work reports a controllable catastrophic change of poly-Si NWs by thermally-assisted electromigration and underlying mechanisms. It also reports the direct and real time observation of these catastrophic changes of poly-Si nanowires for the first time, using scanning electron microscopy. PMID:26782708

  6. Transport through a single donor in p-type silicon

    NASA Astrophysics Data System (ADS)

    Miwa, J. A.; Mol, J. A.; Salfi, J.; Rogge, S.; Simmons, M. Y.

    2013-07-01

    Single phosphorus donors in silicon are promising candidates as qubits in the solid state. Here, we present low temperature scanning probe microscopy and spectroscopy measurements of individual phosphorus dopants deliberately placed in p-type silicon ˜1 nm below the surface. The ability to image individual dopants combined with scanning tunnelling spectroscopy allows us to directly study the transport mechanism through the donor. We show that for a single P donor, transport is dominated by a minority carrier recombination process with the surrounding p-type matrix. The understanding gained will underpin future studies of atomically precise mapping of donor-donor interactions in silicon.

  7. Single-crystalline ZnO sheet Source-Gated Transistors

    PubMed Central

    Dahiya, A. S.; Opoku, C.; Sporea, R. A.; Sarvankumar, B.; Poulin-Vittrant, G.; Cayrel, F.; Camara, N.; Alquier, D.

    2016-01-01

    Due to their fabrication simplicity, fully compatible with low-cost large-area device assembly strategies, source-gated transistors (SGTs) have received significant research attention in the area of high-performance electronics over large area low-cost substrates. While usually based on either amorphous or polycrystalline silicon (α-Si and poly-Si, respectively) thin-film technologies, the present work demonstrate the assembly of SGTs based on single-crystalline ZnO sheet (ZS) with asymmetric ohmic drain and Schottky source contacts. Electrical transport studies of the fabricated devices show excellent field-effect transport behaviour with abrupt drain current saturation (IDSSAT) at low drain voltages well below 2 V, even at very large gate voltages. The performance of a ZS based SGT is compared with a similar device with ohmic source contacts. The ZS SGT is found to exhibit much higher intrinsic gain, comparable on/off ratio and low off currents in the sub-picoamp range. This approach of device assembly may form the technological basis for highly efficient low-power analog and digital electronics using ZnO and/or other semiconducting nanomaterial. PMID:26757945

  8. Single-crystalline ZnO sheet Source-Gated Transistors.

    PubMed

    Dahiya, A S; Opoku, C; Sporea, R A; Sarvankumar, B; Poulin-Vittrant, G; Cayrel, F; Camara, N; Alquier, D

    2016-01-01

    Due to their fabrication simplicity, fully compatible with low-cost large-area device assembly strategies, source-gated transistors (SGTs) have received significant research attention in the area of high-performance electronics over large area low-cost substrates. While usually based on either amorphous or polycrystalline silicon (α-Si and poly-Si, respectively) thin-film technologies, the present work demonstrate the assembly of SGTs based on single-crystalline ZnO sheet (ZS) with asymmetric ohmic drain and Schottky source contacts. Electrical transport studies of the fabricated devices show excellent field-effect transport behaviour with abrupt drain current saturation (IDS(SAT)) at low drain voltages well below 2 V, even at very large gate voltages. The performance of a ZS based SGT is compared with a similar device with ohmic source contacts. The ZS SGT is found to exhibit much higher intrinsic gain, comparable on/off ratio and low off currents in the sub-picoamp range. This approach of device assembly may form the technological basis for highly efficient low-power analog and digital electronics using ZnO and/or other semiconducting nanomaterial. PMID:26757945

  9. Single-crystalline ZnO sheet Source-Gated Transistors

    NASA Astrophysics Data System (ADS)

    Dahiya, A. S.; Opoku, C.; Sporea, R. A.; Sarvankumar, B.; Poulin-Vittrant, G.; Cayrel, F.; Camara, N.; Alquier, D.

    2016-01-01

    Due to their fabrication simplicity, fully compatible with low-cost large-area device assembly strategies, source-gated transistors (SGTs) have received significant research attention in the area of high-performance electronics over large area low-cost substrates. While usually based on either amorphous or polycrystalline silicon (α-Si and poly-Si, respectively) thin-film technologies, the present work demonstrate the assembly of SGTs based on single-crystalline ZnO sheet (ZS) with asymmetric ohmic drain and Schottky source contacts. Electrical transport studies of the fabricated devices show excellent field-effect transport behaviour with abrupt drain current saturation (IDSSAT) at low drain voltages well below 2 V, even at very large gate voltages. The performance of a ZS based SGT is compared with a similar device with ohmic source contacts. The ZS SGT is found to exhibit much higher intrinsic gain, comparable on/off ratio and low off currents in the sub-picoamp range. This approach of device assembly may form the technological basis for highly efficient low-power analog and digital electronics using ZnO and/or other semiconducting nanomaterial.

  10. A route to fabricate single crystalline bismuth nanowire arrays with different diameters

    NASA Astrophysics Data System (ADS)

    Li, Liang; Zhang, Yong; Li, Guanghai; Zhang, Lide

    2003-09-01

    Single crystalline bismuth nanowire arrays in anodic alumina membrane have been fabricated by pulsed electrodeposition. The nanowires of different diameters were obtained by changing the electrical parameter of the pulsed electrodeposition using anodic alumina membrane as template with the same pore size. X-ray diffraction and TEM analysis show that the bismuth nanowires are single crystalline with highly preferential orientation, and the diameter of nanowires increases with increasing the relaxation time of pulse. The growth mechanism of nanowires was discussed.

  11. Proceedings of the Flat-plate Solar Array Project Research Forum on High-efficiency Crystalline Silicon Solar Cells

    NASA Technical Reports Server (NTRS)

    Kachare, R.

    1985-01-01

    The high-efficiency crystalline silicon solar cells research forum addressed high-efficiency concepts, surface-interface effects, bulk effects, modeling and device processing. The topics were arranged into six interactive sessions, which focused on the state-of-the-art of device structures, identification of barriers to achieve high-efficiency cells and potential ways to overcome these barriers.

  12. Symmetry, strain, defects, and the nonlinear optical response of crystalline BaTiO3/silicon

    NASA Astrophysics Data System (ADS)

    Kormondy, Kristy; Abel, Stefan; Popoff, Youri; Sousa, Marilyne; Caimi, Daniele; Siegwart, Heinz; Marchiori, Chiara; Rossell, Marta; Demkov, Alex; Fompeyrine, Jean

    Recent progress has been made towards exploiting the linear electro-optic or Pockels effect in ferroelectric BaTiO3 (BTO) for novel integrated silicon photonics devices. In such structures, the crystalline symmetry and domain structure of BTO determine which electro-optic tensor elements are accessible under application of an external electric field. For epitaxial thin films of BTO on Si (001), the role of defects in strain relaxation can lead to very different crystalline symmetry even for films of identical thickness. Indeed, through geometric phase analysis of high-resolution scanning transmission electron microscopy images, we map changes of the in-plane and out-of-plane lattice parameters across two 80-nm-thick BTO films. A corresponding 20% difference in the effective electro-optic response was measured by analyzing induced rotation of the polarization of a laser beam (λ = 1550 nm) transmitted through lithographically defined electrodes. Understanding, controlling, and modelling the role of BTO symmetry in nonlinear optics is of fundamental importance for the development of a hybrid BTO/Si photonics platform.. Work supported by the NSF (IRES-1358111), AFOSR (FA9550-12-10494), and European Commission (FP7-ICT-2013-11-619456-SITOGA).

  13. Diffusion of point defects in crystalline silicon using the kinetic activation-relaxation technique method

    NASA Astrophysics Data System (ADS)

    Trochet, Mickaël; Béland, Laurent Karim; Joly, Jean-François; Brommer, Peter; Mousseau, Normand

    2015-06-01

    We study point-defect diffusion in crystalline silicon using the kinetic activation-relaxation technique (k-ART), an off-lattice kinetic Monte Carlo method with on-the-fly catalog building capabilities based on the activation-relaxation technique (ART nouveau), coupled to the standard Stillinger-Weber potential. We focus more particularly on the evolution of crystalline cells with one to four vacancies and one to four interstitials in order to provide a detailed picture of both the atomistic diffusion mechanisms and overall kinetics. We show formation energies, activation barriers for the ground state of all eight systems, and migration barriers for those systems that diffuse. Additionally, we characterize diffusion paths and special configurations such as dumbbell complex, di-interstitial (IV-pair+2I) superdiffuser, tetrahedral vacancy complex, and more. This study points to an unsuspected dynamical richness even for this apparently simple system that can only be uncovered by exhaustive and systematic approaches such as the kinetic activation-relaxation technique.

  14. Atomic-Resolution Observations of Semi-Crystalline IntegranularThin Films in Silicon Nitride

    SciTech Connect

    Ziegler, Alexander; Idrobo, Juan C.; Cinibulk, Michael K.; Kisielowski, Christian; Browning, Nigel D.; Ritchie, Robert O.

    2005-08-01

    The thin intergranular phase in a silicon nitride (Si3N4)ceramic, which has been regarded for decades as having an entirely amorphous morphology, is shown to have a semi-crystalline structure. Using two different but complementary high-resolution electron microscopy methods, the intergranular atomic structure was directly imaged at the atomic level. These high-resolution images show that the atomic arrangement of the dopand element cerium takes very periodic positions not only along the interface between the intergranular phase and the Si3N4 matrix grains, but it arranges in a semi-crystalline structure that spans the entire width of the intergranular phase between two adjacent matrix grains, in principle connecting the two separate matrix grains. The result will have implications on the approach of understanding the materials properties of ceramics, most significantly on the mechanical properties and the associated computational modeling of the atomic structure of the thin intergranular phase in Si3N4 ceramics.

  15. Mitigating mechanical failure of crystalline silicon electrodes for lithium batteries by morphological design.

    PubMed

    An, Yonghao; Wood, Brandon C; Ye, Jianchao; Chiang, Yet-Ming; Wang, Y Morris; Tang, Ming; Jiang, Hanqing

    2015-07-21

    Although crystalline silicon (c-Si) anodes promise very high energy densities in Li-ion batteries, their practical use is complicated by amorphization, large volume expansion and severe plastic deformation upon lithium insertion. Recent experiments have revealed the existence of a sharp interface between crystalline Si (c-Si) and the amorphous LixSi alloy during lithiation, which propagates with a velocity that is orientation dependent; the resulting anisotropic swelling generates substantial strain concentrations that initiate cracks even in nanostructured Si. Here we describe a novel strategy to mitigate lithiation-induced fracture by using pristine c-Si structures with engineered anisometric morphologies that are deliberately designed to counteract the anisotropy in the crystalline/amorphous interface velocity. This produces a much more uniform volume expansion, significantly reducing strain concentration. Based on a new, validated methodology that improves previous models of anisotropic swelling of c-Si, we propose optimal morphological designs for c-Si pillars and particles. The advantages of the new morphologies are clearly demonstrated by mesoscale simulations and verified by experiments on engineered c-Si micropillars. The results of this study illustrate that morphological design is effective in improving the fracture resistance of micron-sized Si electrodes, which will facilitate their practical application in next-generation Li-ion batteries. The model and design approach present in this paper also have general implications for the study and mitigation of mechanical failure of electrode materials that undergo large anisotropic volume change upon ion insertion and extraction. PMID:26082019

  16. Ga-doped ZnO conducting antireflection coatings for crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Estrich, N. A.; Hook, D. H.; Smith, A. N.; Leonard, J. T.; Laughlin, B.; Maria, J.-P.

    2013-06-01

    Transparent, conductive gallium-doped ZnO thin films are evaluated for application as conducting antireflection coatings (ARC) for crystalline silicon solar cells as a means to enhance efficiency by reducing the overall resistivity of the photovoltaic circuit. All Ga-doped ZnO thin films in this study were deposited using pulsed laser deposition. Synthesis conditions were first optimized for maximum electrical resistivity and minimal visible light absorption. The ideal combination contained 1 mol. % Ga doping and exhibited ˜90% transmission, with resistivity in the 1 × 10-3 ohm-cm range. Optimized films were prepared on reference flat silicon wafers with known dopant densities and on commercially obtained solar cell emitters without ARCs. Circular transmission line method measurements were used to measure specific contact resistivity (ρc). For n-type doped solar cell emitters, contact resistivity values of 0.1 mΩ cm2 were observed repeatedly. These values are consistent with, or lower than, contact resistivities associated with conventional silver paste metallization.

  17. Study of Photoluminescence from Amorphous and Crystalline Silicon Nanoparticles Synthesized using a Non-Thermal Plasma

    NASA Astrophysics Data System (ADS)

    Garg, Prateek

    High photoluminescence (PL) quantum yields reported from amorphous (a-Si) and crystalline (c-Si) nanoparticles have opened up lots of possibilities for use of silicon in optical applications such as light emitting diodes (LEDs), photonics and solar cells with added processing and cost benefits. However, the PL response and the mechanisms behind it are highly dependent on the matrix in which the nanoparticles are grown and on the growth method. While, the bottom-up approach for deposition of free standing nanoparticles seem to be perfectly suited for large area deposition for LED and solar cell applications, the dominant growth techniques (laser ablation and pyrolysis) have been shown to suffer from limitations in control over size distribution of nanoparticles and the requirement of equipment capable of withstanding high temperature. This led to the exploration of plasma based synthesis methods in this work. Towards this effort, the development and automation of a novel tool "Anny" for synthesis of silicon nanoparticles using non-thermal plasma chamber is reported. These nanoparticles are then accelerated due to choked flow through a nozzle leading to substrate independent deposition. The nanoparticle properties are characterized against precursor gas flow rates and RF power to identify the optimum growth conditions for a stable, continuous deposition. It is found that amorphous nanoparticles offer a wide variety of chamber conditions for growth with a high throughput, stable plasma for continuous, long term operations. The quantum confinement model for crystalline and spatial confinement models for amorphous nanoparticles in our size regime (6-8nm) are suggested for free standing nanoparticles and we report a high PL output from well passivated amorphous nanoparticles. The PL output and its dependence on stability of surface hydrogen passivation is explored using Fourier Transform Infrared spectroscopy (FTIR). It is shown that the amorphous nanoparticles have a

  18. Novel light trapping concepts for crystalline silicon solar cells using diffractive rear side structures

    NASA Astrophysics Data System (ADS)

    Eisenlohr, J.; Tucher, N.; Bett, Alexander; Hauser, H.; Graf, M.; Benick, J.; Goldschmidt, J. C.; Bläsi, B.; Hermle, M.

    2014-05-01

    Crystalline silicon solar cells absorb light in the near infrared only weakly. To utilize also the infrared light of the solar spectrum with energies still greater than the band gap of silicon, the effective path of the light inside the solar cell has to be enhanced. Light paths can be manipulated at the front side as well as at the rear side of a solar cell. For the front side, pyramidal textures that also show anti-reflection properties are widely used. These anti-reflection properties, however, can also be achieved with planar dielectric coatings or nanostructured surfaces. In this case, the path length enhancement can be achieved with rear side structures that are especially optimized for this purpose, thus de-coupling anti-reflection and path-length enhancement functionalities. This de-coupling creates leeway to optimize not only the optical properties but also the electrical properties of the optically active structures, and to realize structures that are compatible with very thin silicon wafers. To this end, this paper investigates two kinds of diffractive rear side structures, both, theoretically and experimentally. First, hexagonal sphere gratings that are produced by a self-organized growth process using spin coating, and second, binary gratings produced via nano-imprint lithography. Both process chains are potentially scalable to large areas. In optical measurements we determined potential photocurrent density gains of over 1 mA/cm2 for 250 μm thick wafers for both structures. Furthermore, we developed a process for contact formation as one key step to fully processed solar cells with diffractive rear side structures.

  19. Single-crystal silicon beams formed by merged epitaxial lateral overgrowth (MELO) for optical reflectors

    NASA Astrophysics Data System (ADS)

    Neudeck, Gerold W.; Kabir, Abul E.

    1995-05-01

    Single crystalline silicon has very well known and predictable mechanical, optical, and electrical properties and is easily manufactured with consistent results. It is also integrated circuit compatible and leads to incorporation of circuits and high quality piezoresistors which are available to monitor motion for self-testing. We present for the first time a novel surface micro-machining process using merged epitaxial lateral overgrowth (MELO) silicon to demonstrate the fabrication of single crystal silicon, free standing cantilever beams 1 mm long and 5 micrometers X 10 micrometers in cross section. These beams had no evidence of stress related bending and were free from the substrate, returning to its original position after numerous electrostatic deflections. MELO has also shown great potential for advanced BJT and MOSFET device applications, hence active devices can be incorporated into the deflecting beam arrays. Diodes fabricated in the beams show excellent characteristics with average ideality factors of 1.01. Note that the technology permits adding of single crystal silicon to selected areas, hence it is an additive process as compared to traditional subtractive methods that deposit films over the entire wafer.

  20. Micro-organic single crystalline phototransistors of 7,7,8,8-tetracyanoquinodimethane and tetrathiafulvalene

    NASA Astrophysics Data System (ADS)

    Jiang, Hui; Yang, Xianjin; Cui, Zhenduo; Liu, Yongchang; Li, Hongxiang; Hu, Wenping

    2009-03-01

    Classical p-type and n-type organic single crystals, tetrathiafulvalene (TTF) and 7,7,8,8-tetracyanoquinodimethane (TCNQ), are introduced to investigate photoswitch and phototransistor. High photoresponsivity, low persistent conductivity, and response reversibility can be found in single crystalline TCNQ, while TTF has large persistent conductivity when the light is switched on and off. It is probably attributed to different band gaps and the compactness of molecular packing. Single crystalline TCNQ combines light detection, switching, signal amplification in a single device and realization of multiple functions which exhibit a very promising potential for the fabrication of organic photoelectric devices.

  1. Crystalline SiCO: Implication on structure and thermochemistry of ternary silicon oxycarbide ceramics

    NASA Astrophysics Data System (ADS)

    Bodiford, Nelli

    The need for innovative refractory materials---materials that can sustain extreme temperatures---has been constantly growing within the modern industries. Basic requirements for usage at ultra-high-temperatures have been considered such as high melting point, high structural strength, exceptional resistance to oxidation, zero or almost zero creep. Monolithic ceramics alone cannot provide these properties, therefore, composite materials are sought to fulfill the demand. For example, silicon nitride and silicon carbide based ceramics have long been leading contenders for structural use in gas turbine engines. In the course of this work we are investigating amorphous SiCO formed via polymer-to-ceramic route. Previously a considerable amount of work has been done on structures of stoichiometric amorphous SiCO and a "perfect" random network was obtained (experimentally as well as supported by computational work) up to the phase content of 33 mol-% SiC. By "perfect" one assumes to have four fold coordinated Si atoms bonded to C and O; C atoms bond to Si atoms only and O is two fold connected to Si. Beyond 33 mol-% SiC within SiCO phase the structural imperfections and defects start to develop. Aside from the stoichiometric form of SiCO, the polymer-to-ceramic route allows for the incorporation of high molar amounts of carbon to create SiCO ceramic with excess carbon. The incorporation of carbon into silica glass improves high-temperature mechanical properties and increases resistance to crystallization of the amorphous material. The amount of 'free carbon' can be controlled through the choice of precursors used during synthesis. There were no ternary crystalline phases of SiCO observed. However, in systems such as MgO-SiO2, Na2O-Al2O 3-SiO2 there are ternary crystalline compounds (MgSiO 3, Mg2SiO4, NaAlSiO4, NaAlSi3 O8) that are of a greater energetic stability than glasses of the same composition. What makes the SiCO system different? In the approach proposed in this

  2. Ultra-thin single crystal perovskite ferroelectric on Silicon

    NASA Astrophysics Data System (ADS)

    Bakaul, Saidur; Serrao, Claudy; Ramamoorthy, Ramesh; Salahuddin, Sayeef

    Single crystalline ultra-thin films (sub-10 nm) of ferroelectric complex oxides are important for tunnelling memory devices. Commercially viable realization of such devices requires their integration with the peripheral Si-based input-output electronics. Integration of single crystalline films of such oxides using direct synthesis remains challenging due to the fundamental crystal chemistry and mechanical incompatibility of dissimilar interfaces. In this work we report epitaxial transfer of ultra-thin single crystalline, oxide films (down to 1 unit cell) onto Si substrates, at room temperature. The thickness of the transferred films has been confirmed by atomic force microscopy. Piezoelectric force microscopy shows ferroelectric property is retained in the transferred film. Electrical transport studies on these transferred ultra-thin films are ongoing.

  3. Reaching Grid Parity Using BP Solar Crystalline Silicon Technology: A Systems Class Application

    SciTech Connect

    Cunningham, Daniel W; Wohlgemuth, John; Carlson, David E; Clark, Roger F; Gleaton, Mark; Posbic, John P; Zahler, James

    2010-12-06

    The primary target market for this program was the residential and commercial PV markets, drawing on BP Solar's premium product and service offerings, brand and marketing strength, and unique routes to market. These two markets were chosen because: (1) in 2005 they represented more than 50% of the overall US PV market; (2) they are the two markets that will likely meet grid parity first; and (3) they are the two market segments in which product development can lead to the added value necessary to generate market growth before reaching grid parity. Federal investment in this program resulted in substantial progress toward the DOE TPP target, providing significant advancements in the following areas: (1) Lower component costs particularly the modules and inverters. (2) Increased availability and lower cost of silicon feedstock. (3) Product specifically developed for residential and commercial applications. (4) Reducing the cost of installation through optimization of the products. (5) Increased value of electricity in mid-term to drive volume increases, via the green grid technology. (6) Large scale manufacture of PV products in the US, generating increased US employment in manufacturing and installation. To achieve these goals BP Solar assembled a team that included suppliers of critical materials, automated equipment developers/manufacturers, inverter and other BOS manufacturers, a utility company, and University research groups. The program addressed all aspects of the crystalline silicon PV business from raw materials (particularly silicon feedstock) through installation of the system on the customers site. By involving the material and equipment vendors, we ensured that supplies of silicon feedstock and other PV specific materials like encapsulation materials (EVA and cover glass) will be available in the quantities required to meet the DOE goals of 5 to 10 GW of installed US PV by 2015 and at the prices necessary for PV systems to reach grid parity in 2015

  4. High sensitivity silicon single nanowire junctionless phototransistor

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  5. Single-Event Effects in Silicon Carbide Power Devices

    NASA Technical Reports Server (NTRS)

    Lauenstein, Jean-Marie; Casey, Megan C.; LaBel, Kenneth A.; Ikpe, Stanley; Topper, Alyson D.; Wilcox, Edward P.; Kim, Hak; Phan, Anthony M.

    2015-01-01

    This report summarizes the NASA Electronic Parts and Packaging Program Silicon Carbide Power Device Subtask efforts in FY15. Benefits of SiC are described and example NASA Programs and Projects desiring this technology are given. The current status of the radiation tolerance of silicon carbide power devices is given and paths forward in the effort to develop heavy-ion single-event effect hardened devices indicated.

  6. Positioning and joining of organic single-crystalline wires

    NASA Astrophysics Data System (ADS)

    Wu, Yuchen; Feng, Jiangang; Jiang, Xiangyu; Zhang, Zhen; Wang, Xuedong; Su, Bin; Jiang, Lei

    2015-03-01

    Organic single-crystal, one-dimensional materials can effectively carry charges and/or excitons due to their highly ordered molecule packing, minimized defects and eliminated grain boundaries. Controlling the alignment/position of organic single-crystal one-dimensional architectures would allow on-demand photon/electron transport, which is a prerequisite in waveguides and other optoelectronic applications. Here we report a guided physical vapour transport technique to control the growth, alignment and positioning of organic single-crystal wires with the guidance of pillar-structured substrates. Submicrometre-wide, hundreds of micrometres long, highly aligned, organic single-crystal wire arrays are generated. Furthermore, these organic single-crystal wires can be joined within controlled angles by varying the pillar geometries. Owing to the controllable growth of organic single-crystal one-dimensional architectures, we can present proof-of-principle demonstrations utilizing joined wires to allow optical waveguide through small radii of curvature (internal angles of ~90-120°). Our methodology may open a route to control the growth of organic single-crystal one-dimensional materials with potential applications in optoelectronics.

  7. Positioning and joining of organic single-crystalline wires

    PubMed Central

    Wu, Yuchen; Feng, Jiangang; Jiang, Xiangyu; Zhang, Zhen; Wang, Xuedong; Su, Bin; Jiang, Lei

    2015-01-01

    Organic single-crystal, one-dimensional materials can effectively carry charges and/or excitons due to their highly ordered molecule packing, minimized defects and eliminated grain boundaries. Controlling the alignment/position of organic single-crystal one-dimensional architectures would allow on-demand photon/electron transport, which is a prerequisite in waveguides and other optoelectronic applications. Here we report a guided physical vapour transport technique to control the growth, alignment and positioning of organic single-crystal wires with the guidance of pillar-structured substrates. Submicrometre-wide, hundreds of micrometres long, highly aligned, organic single-crystal wire arrays are generated. Furthermore, these organic single-crystal wires can be joined within controlled angles by varying the pillar geometries. Owing to the controllable growth of organic single-crystal one-dimensional architectures, we can present proof-of-principle demonstrations utilizing joined wires to allow optical waveguide through small radii of curvature (internal angles of ~90–120°). Our methodology may open a route to control the growth of organic single-crystal one-dimensional materials with potential applications in optoelectronics. PMID:25814032

  8. Positioning and joining of organic single-crystalline wires.

    PubMed

    Wu, Yuchen; Feng, Jiangang; Jiang, Xiangyu; Zhang, Zhen; Wang, Xuedong; Su, Bin; Jiang, Lei

    2015-01-01

    Organic single-crystal, one-dimensional materials can effectively carry charges and/or excitons due to their highly ordered molecule packing, minimized defects and eliminated grain boundaries. Controlling the alignment/position of organic single-crystal one-dimensional architectures would allow on-demand photon/electron transport, which is a prerequisite in waveguides and other optoelectronic applications. Here we report a guided physical vapour transport technique to control the growth, alignment and positioning of organic single-crystal wires with the guidance of pillar-structured substrates. Submicrometre-wide, hundreds of micrometres long, highly aligned, organic single-crystal wire arrays are generated. Furthermore, these organic single-crystal wires can be joined within controlled angles by varying the pillar geometries. Owing to the controllable growth of organic single-crystal one-dimensional architectures, we can present proof-of-principle demonstrations utilizing joined wires to allow optical waveguide through small radii of curvature (internal angles of ~90-120°). Our methodology may open a route to control the growth of organic single-crystal one-dimensional materials with potential applications in optoelectronics. PMID:25814032

  9. Artificial neural systems using memristive synapses and nano-crystalline silicon thin-film transistors

    NASA Astrophysics Data System (ADS)

    Cantley, Kurtis D.

    Future computer systems will not rely solely on digital processing of inputs from well-defined data sets. They will also be required to perform various computational tasks using large sets of ill-defined information from the complex environment around them. The most efficient processor of this type of information known today is the human brain. Using a large number of primitive elements (˜1010 neurons in the neocortex) with high parallel connectivity (each neuron has ˜104 synapses), brains have the remarkable ability to recognize and classify patterns, predict outcomes, and learn from and adapt to incredibly diverse sets of problems. A reasonable goal in the push to increase processing power of electronic systems would thus be to implement artificial neural networks in hardware that are compatible with today's digital processors. This work focuses on the feasibility of utilizing non-crystalline silicon devices in neuromorphic electronics. Hydrogenated amorphous silicon (a-Si:H) nanowire transistors with Schottky barrier source/drain junctions, as well as a-Si:H/Ag resistive switches are fabricated and characterized. In the transistors, it is found that the on-current scales linearly with the effective width W eff of the channel nanowire array down to at least 20 nm. The solid-state electrolyte resistive switches (memristors) are shown to exhibit the proper current-voltage hysteresis. SPICE models of similar devices are subsequently developed to investigate their performance in neural circuits. The resulting SPICE simulations demonstrate spiking properties and synaptic learning rules that are incredibly similar to those in biology. Specifically, the neuron circuits can be designed to mimic the firing characteristics of real neurons, and Hebbian learning rules are investigated. Finally, some applications are presented, including associative learning analogous to the classical conditioning experiments originally performed by Pavlov, and frequency and pattern

  10. Microwave Induced Direct Bonding of Single Crystal Silicon Wafers

    NASA Technical Reports Server (NTRS)

    Budraa, N. K.; Jackson, H. W.; Barmatz, M.

    1999-01-01

    We have heated polished doped single-crystal silicon wafers in a single mode microwave cavity to temperatures where surface to surface bonding occurred. The absorption of microwaves and heating of the wafers is attributed to the inclusion of n-type or p-type impurities into these substrates. A cylindrical cavity TM (sub 010) standing wave mode was used to irradiate samples of various geometry's at positions of high magnetic field. This process was conducted in vacuum to exclude plasma effects. This initial study suggests that the inclusion of impurities in single crystal silicon significantly improved its microwave absorption (loss factor) to a point where heating silicon wafers directly can be accomplished in minimal time. Bonding of these substrates, however, occurs only at points of intimate surface to surface contact. The inclusion of a thin metallic layer on the surfaces enhances the bonding process.

  11. Silicon dioxide thin film mediated single cell nucleic acid isolation.

    PubMed

    Bogdanov, Evgeny; Dominova, Irina; Shusharina, Natalia; Botman, Stepan; Kasymov, Vitaliy; Patrushev, Maksim

    2013-01-01

    A limited amount of DNA extracted from single cells, and the development of single cell diagnostics make it necessary to create a new highly effective method for the single cells nucleic acids isolation. In this paper, we propose the DNA isolation method from biomaterials with limited DNA quantity in sample, and from samples with degradable DNA based on the use of solid-phase adsorbent silicon dioxide nanofilm deposited on the inner surface of PCR tube. PMID:23874571

  12. Silicon Dioxide Thin Film Mediated Single Cell Nucleic Acid Isolation

    PubMed Central

    Bogdanov, Evgeny; Dominova, Irina; Shusharina, Natalia; Botman, Stepan; Kasymov, Vitaliy; Patrushev, Maksim

    2013-01-01

    A limited amount of DNA extracted from single cells, and the development of single cell diagnostics make it necessary to create a new highly effective method for the single cells nucleic acids isolation. In this paper, we propose the DNA isolation method from biomaterials with limited DNA quantity in sample, and from samples with degradable DNA based on the use of solid-phase adsorbent silicon dioxide nanofilm deposited on the inner surface of PCR tube. PMID:23874571

  13. Use of low-energy hydrogen ion implants in high-efficiency crystalline-silicon solar cells

    NASA Technical Reports Server (NTRS)

    Fonash, S. J.; Sigh, R.; Mu, H. C.

    1986-01-01

    The use of low-energy hydrogen implants in the fabrication of high-efficiency crystalline silicon solar cells was investigated. Low-energy hydrogen implants result in hydrogen-caused effects in all three regions of a solar cell: emitter, space charge region, and base. In web, Czochralski (Cz), and floating zone (Fz) material, low-energy hydrogen implants reduced surface recombination velocity. In all three, the implants passivated the space charge region recombination centers. It was established that hydrogen implants can alter the diffusion properties of ion-implanted boron in silicon, but not ion-implated arsenic.

  14. Shock compression of [001] single crystal silicon

    NASA Astrophysics Data System (ADS)

    Zhao, S.; Hahn, E. N.; Kad, B.; Remington, B. A.; Bringa, E. M.; Meyers, M. A.

    2016-05-01

    Silicon is ubiquitous in our advanced technological society, yet our current understanding of change to its mechanical response at extreme pressures and strain-rates is far from complete. This is due to its brittleness, making recovery experiments difficult. High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon (using impedance-matched momentum traps) unveiled remarkable structural changes observed by transmission electron microscopy. As laser energy increases, corresponding to an increase in peak shock pressure, the following plastic responses are are observed: surface cleavage along {111} planes, dislocations and stacking faults; bands of amorphized material initially forming on crystallographic orientations consistent with dislocation slip; and coarse regions of amorphized material. Molecular dynamics simulations approach equivalent length and time scales to laser experiments and reveal the evolution of shock-induced partial dislocations and their crucial role in the preliminary stages of amorphization. Application of coupled hydrostatic and shear stresses produce amorphization below the hydrostatically determined critical melting pressure under dynamic shock compression.

  15. Shock compression of [001] single crystal silicon

    DOE PAGESBeta

    Zhao, S.; Remington, B.; Hahn, E. N.; Kad, B.; Bringa, E. M.; Meyers, M. A.

    2016-03-14

    Silicon is ubiquitous in our advanced technological society, yet our current understanding of change to its mechanical response at extreme pressures and strain-rates is far from complete. This is due to its brittleness, making recovery experiments difficult. High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon (using impedance-matched momentum traps) unveiled remarkable structural changes observed by transmission electron microscopy. As laser energy increases, corresponding to an increase in peak shock pressure, the following plastic responses are are observed: surface cleavage along {111} planes, dislocations and stacking faults; bands of amorphized material initially forming on crystallographic orientations consistent withmore » dislocation slip; and coarse regions of amorphized material. Molecular dynamics simulations approach equivalent length and time scales to laser experiments and reveal the evolution of shock-induced partial dislocations and their crucial role in the preliminary stages of amorphization. Furthermore, application of coupled hydrostatic and shear stresses produce amorphization below the hydrostatically determined critical melting pressure under dynamic shock compression.« less

  16. An amorphous-to-crystalline phase transition within thin silicon films grown by ultra-high-vacuum evaporation and its impact on the optical response

    NASA Astrophysics Data System (ADS)

    Orapunt, Farida; Tay, Li-Lin; Lockwood, David J.; Baribeau, Jean-Marc; Noël, Mario; Zwinkels, Joanne C.; O'Leary, Stephen K.

    2016-02-01

    A number of thin silicon films are deposited on crystalline silicon, native oxidized crystalline silicon, and optical quality fused quartz substrates through the use of ultra-high-vacuum evaporation at growth temperatures ranging from 98 to 572 °C. An analysis of their grazing incidence X-ray diffraction and Raman spectra indicates that a phase transition, from amorphous-to-crystalline, occurs as the growth temperature is increased. Through a peak decomposition process, applied to the Raman spectroscopy results, the crystalline volume fractions associated with these samples are plotted as a function of the growth temperature for the different substrates considered. It is noted that the samples grown on the crystalline silicon substrates have the lowest crystallanity onset temperature, whereas those grown on the optical quality fused quartz substrates have the highest crystallanity onset temperature; the samples grown on the native oxidized crystalline silicon substrates have a crystallanity onset temperature between these two limits. These resultant dependencies on the growth temperature provide a quantitative means of characterizing the amorphous-to-crystalline phase transition within these thin silicon films. It is noted that the thin silicon film grown on an optical quality fused quartz substrate at 572 °C, possessing an 83% crystalline volume fraction, exhibits an optical absorption spectrum which is quite distinct from that associated with the other thin silicon films. We suggest that this is due to the onset of sufficient long-range order in the film for wave-vector conservation to apply, at least partially. Finally, we use a semi-classical optical absorption analysis to study how this phase transition, from amorphous-to-crystalline, impacts the spectral dependence of the optical absorption coefficient.

  17. Experimental and Theoretical Investigation of Crystallographic Orientation Dependence of Nanoscratching of Single Crystalline Copper.

    PubMed

    Geng, Yanquan; Zhang, Junjie; Yan, Yongda; Yu, Bowen; Geng, Lin; Sun, Tao

    2015-01-01

    In the present work, we perform experiments and molecular dynamics simulations to elucidate the underlying deformation mechanisms of single crystalline copper under the load-controlled multi-passes nanoscratching using a triangular pyramidal probe. The correlation of microscopic deformation behavior of the material with macroscopically-observed machining results is revealed. Moreover, the influence of crystallographic orientation on the nanoscratching of single crystalline copper is examined. Our simulation results indicate that the plastic deformation of single crystalline Cu under the nanoscratching is exclusively governed by dislocation mechanisms. However, there is no glissile dislocation structure formed due to the probe oscillation under the load-controlled mode. Both experiments and MD simulations demonstrate that the machined surface morphologies in terms of groove depth and surface pile-up exhibit strong crystallographic orientation dependence, because of different geometries of activated slip planes cutting with free surfaces and strain hardening abilities associated with different crystallographic orientations. PMID:26147506

  18. Experimental and Theoretical Investigation of Crystallographic Orientation Dependence of Nanoscratching of Single Crystalline Copper

    PubMed Central

    Geng, Yanquan; Zhang, Junjie; Yan, Yongda; Yu, Bowen; Geng, Lin; Sun, Tao

    2015-01-01

    In the present work, we perform experiments and molecular dynamics simulations to elucidate the underlying deformation mechanisms of single crystalline copper under the load-controlled multi-passes nanoscratching using a triangular pyramidal probe. The correlation of microscopic deformation behavior of the material with macroscopically-observed machining results is revealed. Moreover, the influence of crystallographic orientation on the nanoscratching of single crystalline copper is examined. Our simulation results indicate that the plastic deformation of single crystalline Cu under the nanoscratching is exclusively governed by dislocation mechanisms. However, there is no glissile dislocation structure formed due to the probe oscillation under the load-controlled mode. Both experiments and MD simulations demonstrate that the machined surface morphologies in terms of groove depth and surface pile-up exhibit strong crystallographic orientation dependence, because of different geometries of activated slip planes cutting with free surfaces and strain hardening abilities associated with different crystallographic orientations. PMID:26147506

  19. Fast growth of inch-sized single-crystalline graphene from a controlled single nucleus on Cu-Ni alloys

    NASA Astrophysics Data System (ADS)

    Wu, Tianru; Zhang, Xuefu; Yuan, Qinghong; Xue, Jiachen; Lu, Guangyuan; Liu, Zhihong; Wang, Huishan; Wang, Haomin; Ding, Feng; Yu, Qingkai; Xie, Xiaoming; Jiang, Mianheng

    2016-01-01

    Wafer-scale single-crystalline graphene monolayers are highly sought after as an ideal platform for electronic and other applications. At present, state-of-the-art growth methods based on chemical vapour deposition allow the synthesis of one-centimetre-sized single-crystalline graphene domains in ~12 h, by suppressing nucleation events on the growth substrate. Here we demonstrate an efficient strategy for achieving large-area single-crystalline graphene by letting a single nucleus evolve into a monolayer at a fast rate. By locally feeding carbon precursors to a desired position of a substrate composed of an optimized Cu-Ni alloy, we synthesized an ~1.5-inch-large graphene monolayer in 2.5 h. Localized feeding induces the formation of a single nucleus on the entire substrate, and the optimized alloy activates an isothermal segregation mechanism that greatly expedites the growth rate. This approach may also prove effective for the synthesis of wafer-scale single-crystalline monolayers of other two-dimensional materials.

  20. Fast growth of inch-sized single-crystalline graphene from a controlled single nucleus on Cu-Ni alloys.

    PubMed

    Wu, Tianru; Zhang, Xuefu; Yuan, Qinghong; Xue, Jiachen; Lu, Guangyuan; Liu, Zhihong; Wang, Huishan; Wang, Haomin; Ding, Feng; Yu, Qingkai; Xie, Xiaoming; Jiang, Mianheng

    2016-01-01

    Wafer-scale single-crystalline graphene monolayers are highly sought after as an ideal platform for electronic and other applications. At present, state-of-the-art growth methods based on chemical vapour deposition allow the synthesis of one-centimetre-sized single-crystalline graphene domains in ∼12 h, by suppressing nucleation events on the growth substrate. Here we demonstrate an efficient strategy for achieving large-area single-crystalline graphene by letting a single nucleus evolve into a monolayer at a fast rate. By locally feeding carbon precursors to a desired position of a substrate composed of an optimized Cu-Ni alloy, we synthesized an ∼1.5-inch-large graphene monolayer in 2.5 h. Localized feeding induces the formation of a single nucleus on the entire substrate, and the optimized alloy activates an isothermal segregation mechanism that greatly expedites the growth rate. This approach may also prove effective for the synthesis of wafer-scale single-crystalline monolayers of other two-dimensional materials. PMID:26595118

  1. Nanosphere lithography for improved absorption in thin crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Chang, Yuanchih; Payne, David N. R.; Pollard, Michael E.; Pillai, Supriya; Bagnall, Darren M.

    2015-12-01

    Over the last decade, plasmonic nanoparticle arrays have been extensively studied for their light trapping potential in thin film solar cells. However, the commercial use of such arrays has been limited by complex and expensive fabrication techniques such as e-beam lithography. Nanosphere lithography (NSL) is a promising low-cost alternative for forming regular arrays of nanoscale features. Here, we use finite-difference time-domain (FDTD) simulations to determine the optical enhancement due to nanosphere arrays embedded at the rear of a complete thin film device. Array parameters including the nanosphere pitch and diameter are explored, with the FDTD model itself first validated by comparing simulations of Ag nanodisc arrays with optical measurements of pre-existing e-beam fabricated test structures. These results are used to guide the development of a nanosphere back-reflector for 20 μm thin crystalline silicon cells. The deposition of polystyrene nanosphere monolayers is optimized to provide uniform arrays, which are subsequently incorporated into preliminary, proof of concept device structures. Absorption and photoluminescence measurements clearly demonstrate the potential of nanosphere arrays for improving the optical response of a solar cell using economical and scalable methods.

  2. Electric properties and carrier multiplication in breakdown sites in multi-crystalline silicon solar cells

    SciTech Connect

    Schneemann, Matthias; Carius, Reinhard; Rau, Uwe; Kirchartz, Thomas

    2015-05-28

    This paper studies the effective electrical size and carrier multiplication of breakdown sites in multi-crystalline silicon solar cells. The local series resistance limits the current of each breakdown site and is thereby linearizing the current-voltage characteristic. This fact allows the estimation of the effective electrical diameters to be as low as 100 nm. Using a laser beam induced current (LBIC) measurement with a high spatial resolution, we find carrier multiplication factors on the order of 30 (Zener-type breakdown) and 100 (avalanche breakdown) as new lower limits. Hence, we prove that also the so-called Zener-type breakdown is followed by avalanche multiplication. We explain that previous measurements of the carrier multiplication using thermography yield results higher than unity, only if the spatial defect density is high enough, and the illumination intensity is lower than what was used for the LBIC method. The individual series resistances of the breakdown sites limit the current through these breakdown sites. Therefore, the measured multiplication factors depend on the applied voltage as well as on the injected photocurrent. Both dependencies are successfully simulated using a series-resistance-limited diode model.

  3. Interlaced semi-ellipsoid nanostructures for improving light trapping of ultrathin crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Gao, Ge; Li, Juntao; Wang, Xuehua

    2015-10-01

    Ultrathin crystalline silicon (c-Si) solar cells, which are of several micrometers thick, have attracted much attention in recent years, since it can greatly save raw materials than the traditional ones. To enhance the absorption, as well as to improve the cell efficiency, of the ultrathin c-Si, light trapping nanostructures are used to increase the effective absorption length to close to the 4n2 of the materials thickness, which is determined by the Lambertian limit. Here, we propose a novel interlaced semi-ellipsoid nanostructures (ISENs) to improve the performance of ultrathin c-Si solar cells. In this structure, the large and small periods in x and y direction can improve the light trapping capability at long and short wavelengths respectively. Meanwhile, the graded refractive index of the surface can act as the antireflection coating. By optimizing the ISENs, the short circuit current density of 30.15mA/cm2 was achieved by simulations for a 2 μm thick c-Si solar cell with rx = 500 nm, ry = 200 nm, rz= 550 nm and without antireflection coating and metal back reflector. The absorption is close to 87% of the Lambertian limit with equivalent thickness. We expect this structure can be fabricated by low cost nanosphere lithography technology and used to improve the efficiency of the ultrathin c-Si solar cells.

  4. Acceleration of potential-induced degradation by salt-mist preconditioning in crystalline silicon photovoltaic modules

    NASA Astrophysics Data System (ADS)

    Suzuki, Soh; Nishiyama, Naoki; Yoshino, Seiji; Ujiro, Takumi; Watanabe, Shin; Doi, Takuya; Masuda, Atsushi; Tanahashi, Tadanori

    2015-08-01

    We examined the sequential effects of salt-mist stress followed by high-system-voltage stress on the power loss of crystalline silicon photovoltaic (PV) modules to determine whether a crucial failure as potential-induced degradation (PID) is accelerated by material-property changes caused by the long-term effects of a less harmful stress such as salt-mist spraying. Degradation profiles confirmed in this study show that PID is accelerated by certain types of salt-mist preconditioning. For the acceleration of PID, the contribution of sodium ions liberated from the front glass of the PV module seems to be excluded. Therefore, we consider that the sodium ions penetrating into the PV modules from the ambient environment may also cause degradation according to the proposed mechanisms of PID, as the sodium ions existing in the front glass cause PID. Furthermore, this type of degradation may indicate the wear-out phenomenon after a long-term exposure in the field (especially near the coast).

  5. Effects of vacancy defects on thermal conductivity in crystalline silicon: A nonequilibrium molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Lee, Yongjin; Lee, Sangheon; Hwang, Gyeong S.

    2011-03-01

    We examine the effects of vacancy defects on thermal conductivity in bulk crystalline silicon (c-Si) using nonequilibrium molecular dynamics simulations. While most vacancies are thought to remain in the form of clusters in bulk c-Si, recent theoretical studies have predicted that small vacancy clusters energetically prefer to be fourfold coordinated by nullifying dangling bonds. Hence, in this work, we consider three different-sized fourfold vacancy clusters, tetra- (V4), hexa- (V6), and dodeca-vacancy (V12), with particular interest in studying how phonon transport is affected by vacancy concentration and cluster size in association with fourfold coordination-induced lattice distortions. Our simulations show that thermal conductivity (κ) rapidly drops with vacancy concentration (nv) with an inverse power-law relation (κ∝nv-α, with α ≈ 0.7-1.1 depending on cluster size); the presence of 1.5% vacancies leads to a 95% reduction in κ as compared to the defect free c-Si. When nv is low (<1%), the reduction of κ with nv appears to be a function of cluster size, and the size effect becomes unimportant as nv increases above 1%. We discuss the correlation between phone scattering and cluster size, based on the relative rates of phonon-vacancy scattering associated with defect-induced strain fields. We also estimate the dependence of phonon mean free path on vacancy concentration and cluster size.

  6. A method for determining average damage depth of sawn crystalline silicon wafers

    NASA Astrophysics Data System (ADS)

    Sopori, B.; Devayajanam, S.; Basnyat, P.

    2016-04-01

    The depth of surface damage (or simply, damage) in crystalline silicon wafers, caused by wire sawing of ingots, is determined by performing a series of minority carrier lifetime (MCLT) measurements. Samples are sequentially etched to remove thin layers from each surface and MCLT is measured after each etch step. The thickness-removed (δt) at which the lifetime reaches a peak value corresponds to the damage depth. This technique also allows the damage to be quantified in terms of effective surface recombination velocity (Seff). To accomplish this, the MCLT data are converted into an Seff vs δt plot, which represents a quantitative distribution of the degree of damage within the surface layer. We describe a wafer preparation procedure to attain reproducible etching and MCLT measurement results. We also describe important characteristics of an etchant used for controllably removing thin layers from the wafer surfaces. Some typical results showing changes in the MCLT vs δt plots for different cutting parameters are given.

  7. Silicon based near infrared photodetector using self-assembled organic crystalline nano-pillars

    NASA Astrophysics Data System (ADS)

    Ajiki, Yoshiharu; Kan, Tetsuo; Yahiro, Masayuki; Hamada, Akiko; Adachi, Junji; Adachi, Chihaya; Matsumoto, Kiyoshi; Shimoyama, Isao

    2016-04-01

    We propose a silicon (Si) based near-infrared photodetector using self-assembled organic crystalline nano-pillars, which were formed on an n-type Si substrate and were covered with an Au thin-film. These structures act as antennas for near-infrared light, resulting in an enhancement of the light absorption on the Au film. Because the Schottky junction is formed between the Au/n-type Si, the electron excited by the absorbed light can be detected as photocurrent. The optical measurement revealed that the nano-pillar structures enhanced the responsivity for the near-infrared light by 89 (14.5 mA/W) and 16 (0.433 mA/W) times compared with those of the photodetector without nano-pillars at the wavelengths of 1.2 and 1.3 μm, respectively. Moreover, no polarization dependency of the responsivity was observed, and the acceptable incident angle ranged from 0° to 30°. These broad responses were likely to be due to the organic nano-pillar structures' having variation in their orientation, which is advantageous for near-infrared detector uses.

  8. George E. Pake Prize Lecture: Crystalline Silicon Photovoltaics: Accelerating to Grid Parity

    NASA Astrophysics Data System (ADS)

    Pinto, Mark

    2013-03-01

    Lost in recent headlines about solar company failures, reduced government support and depressed stock valuations is the fact that photovoltaic (PV) systems continue to be installed at an extremely healthy rate - a ten-fold increase between 2007 and 2012, to a cumulative 100GWp of installations worldwide. The primary factor behind this remarkable growth has been cost reduction at the installed system level afforded by manufacturing and technology improvements to the crystalline silicon (c-Si) PV cell. In fact in the past 2 years, c-Si module cost learning curves have accelerated over their historical norms as a function of both volume and time, and as a result c-Si PV has reached parity with conventional forms of electricity in 20 + countries worldwide. In this presentation future c-Si technology paths will be reviewed along with market implications, leading to the projection that between 2015 and 2020, c-Si based PV electricity will be cost-effectively delivered to >95% of the world's population.

  9. Neural learning circuits utilizing nano-crystalline silicon transistors and memristors.

    PubMed

    Cantley, Kurtis D; Subramaniam, Anand; Stiegler, Harvey J; Chapman, Richard A; Vogel, Eric M

    2012-04-01

    Properties of neural circuits are demonstrated via SPICE simulations and their applications are discussed. The neuron and synapse subcircuits include ambipolar nano-crystalline silicon transistor and memristor device models based on measured data. Neuron circuit characteristics and the Hebbian synaptic learning rule are shown to be similar to biology. Changes in the average firing rate learning rule depending on various circuit parameters are also presented. The subcircuits are then connected into larger neural networks that demonstrate fundamental properties including associative learning and pulse coincidence detection. Learned extraction of a fundamental frequency component from noisy inputs is demonstrated. It is then shown that if the fundamental sinusoid of one neuron input is out of phase with the rest, its synaptic connection changes differently than the others. Such behavior indicates that the system can learn to detect which signals are important in the general population, and that there is a spike-timing-dependent component of the learning mechanism. Finally, future circuit design and considerations are discussed, including requirements for the memristive device. PMID:24805040

  10. Nano-crystalline silicon solar cell architecture with absorption at the classical 4n2 limit

    SciTech Connect

    Biswas, Rana; Xu, Chun

    2011-07-04

    We develop a periodically patterned conformal photonic-plasmonic crystal based solar architecture for a nano-crystalline silicon solar cell, through rigorous scattering matrix simulations. The solar cell architecture has a periodic array of tapered silver nano-pillars as the back-reflector coupled with a conformal periodic structure at the top of the cell. The absorption and maximal current, averaged over the entire range of wavelengths, for this solar cell architecture is at the semi-classical 4n{sup 2} limit over a range of common thicknesses (500-1500 nm) and slightly above the 4n{sup 2} limit for a 500 nm nc-Si cell. The absorption exceeds the 4n{sup 2} limit, corrected for reflection loss at the top surface. The photonic crystal cell current is enhanced over the flat Ag back-reflector by 60%, for a thick 1000 nm nc-Si layer, where predicted currents exceed 31 mA/cm{sup 2}. The conformal structure at the top surface focuses light within the absorber layer. There is plasmonic concentration of light, with intensity enhancements exceeding 7, near the back reflector that substantially enhances absorption.

  11. Low resistance Ohmic contact to p-type crystalline silicon via nitrogen-doped copper oxide films

    NASA Astrophysics Data System (ADS)

    Zhang, Xinyu; Wan, Yimao; Bullock, James; Allen, Thomas; Cuevas, Andres

    2016-08-01

    This work explores the application of transparent nitrogen doped copper oxide (CuOx:N) films deposited by reactive sputtering to create hole-selective contacts for p-type crystalline silicon (c-Si) solar cells. It is found that CuOx:N sputtered directly onto crystalline silicon is able to form an Ohmic contact. X-ray photoelectron spectroscopy and Raman spectroscopy measurements are used to characterise the structural and physical properties of the CuOx:N films. Both the oxygen flow rate and the substrate temperature during deposition have a significant impact on the film composition, as well as on the resulting contact resistivity. After optimization, a low contact resistivity of ˜10 mΩ cm2 has been established. This result offers significant advantages over conventional contact structures in terms of carrier transport and device fabrication.

  12. Evaluation of defects generation in crystalline silicon ingot grown by cast technique with seed crystal for solar cells.

    PubMed

    Tachibana, Tomihisa; Sameshima, Takashi; Kojima, Takuto; Arafune, Koji; Kakimoto, Koichi; Miyamura, Yoshiji; Harada, Hirofumi; Sekiguchi, Takashi; Ohshita, Yoshio; Ogura, Atsushi

    2012-04-01

    Although crystalline silicon is widely used as substrate material for solar cell, many defects occur during crystal growth. In this study, the generation of crystalline defects in silicon substrates was evaluated. The distributions of small-angle grain boundaries were observed in substrates sliced parallel to the growth direction. Many precipitates consisting of light elemental impurities and small-angle grain boundaries were confirmed to propagate. The precipitates mainly consisted of Si, C, and N atoms. The small-angle grain boundaries were distributed after the precipitation density increased. Then, precipitates appeared at the small-angle grain boundaries. We consider that the origin of the small-angle grain boundaries was lattice mismatch and/or strain caused by the high-density precipitation. PMID:22536006

  13. One-step synthesis of hybrid silver particles for front contact paste for crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Che, Quande; Yang, Hongxing; Lu, Lin; Wang, Yuanhao; Wang, Hai

    2013-05-01

    This paper reports a one-step synthesis of hybrid rod-like and spherical silver particles and its application in the silver front contact paste for crystalline silicon solar cells. The hybrid silver particles were synthesized by reducing silver nitrate in ethylene glycol. X-ray diffraction indicated that the hybrid silver particles were well crystallized with no crystallographic impurities. Scanning electron microscopy showed that the rod-like particles in the hybrid particles were 0.2 µm to 0.5 µm in width and 1 µm to 4 µm in length, and that the average size of the spherical particles was 0.5 µm. The fabricated crystalline silicon solar cell based on the as-prepared hybrid silver particles showed good photovoltaic performance.

  14. Ultra-thin crystalline silicon films produced by plasma assisted epitaxial growth on silicon wafers and their transfer to foreign substrates

    NASA Astrophysics Data System (ADS)

    Moreno, M.; Cabarrocas, P. Roca I.

    2010-07-01

    We have developed a new process to produce ultra-thin crystalline silicon films with thicknesses in the range of 0.1 - 1 μm on flexible substrates. A crystalline silicon wafer was cleaned by SiF4 plasma exposure and without breaking vacuum, an epitaxial film was grown from SiF4, H2 and Ar gas mixtures at low substrate temperature (Tsub ≈ 200 °C) in a standard RF PECVD reactor. We found that H2 dilution is a key parameter for the growth of high quality epitaxial films and modification of the structural composition of the interface with the c-Si wafer, allowing one to switch from a smooth interface at low hydrogen flow rates to a fragile one, composed of hydrogen-rich micro-cavities, at high hydrogen flow rates. This feature can be advantageously used to separate the epitaxial film from the crystalline Si wafer. As a example demonstration, we show that by depositing a metal film followed by a spin-coated polyimide layer and applying a moderate thermal treatment to the stack, the fragile interface breaks down and allows one to obtain an ultrathin crystalline wafer on the flexible polyimide support. This article has been previously published in PV Direct, the former name of EPJ Photovoltaics.

  15. Controlled spatial switching and routing of surface plasmons in designed single-crystalline gold nanostructures

    NASA Astrophysics Data System (ADS)

    Könenkamp, R.; Word, R. C.; Fitzgerald, J. P. S.; Nadarajah, Athavan; Saliba, S. D.

    2012-10-01

    Electron emission microscopy is used to visualize plasmonic routing in gold nano-structures. We show that in single-crystalline gold structures reliable routing can be achieved with polarization switching. The routing is due to the polarization dependence of the photon-to-plasmon coupling, which controls the mode distribution in the plasmonic gold film. We use specifically designed, single-crystalline planar structures. In these structures, the plasmon propagation length is sufficiently large such that significant plasmon power can be delivered to the near-field region around the end tips of the router. Solid state devices based on internal electron excitation and emission processes appear feasible.

  16. Wurtzite-type faceted single-crystalline GaN nanotubes

    NASA Astrophysics Data System (ADS)

    Liu, Baodan; Bando, Yoshio; Tang, Chengchun; Shen, Guozhen; Golberg, Dmitri; Xu, Fangfang

    2006-02-01

    We report on the direct fabrication of single-crystalline wurtzite-type hexagonal GaN nanotubes via a newly designed, controllable, and reproducible chemical thermal-evaporation process. The nanotubes are single crystalline, have one end closed, an average outer diameter of ˜300nm, an inner diameter of ˜100nm, and a wall thickness of ˜100nm. The structure and morphology of the tubes are characterized using a scanning electron microscope and a transmission electron microscope. The cathodoluminescence of individual nanotubes is also investigated. The growth mechanism, formation kinetics, and crystallography of GaN nanotubes are finally discussed.

  17. Prototyping and Development of Commercial Nano Crystalline and Thin Film Silicon for Photovoltaic Manufacturing

    SciTech Connect

    Haldar, Pradeep, Ph.D.; Pethuraja, Gopal, Ph.D.; Efstathiadis, Haralabos, Ph.D.

    2011-12-02

    The College of Nanoscale Science and Engineering (CNSE) at the University at Albany received funding from the Department of Energy for its proposal Prototyping and Development of Commercial Nanocrystalline and Thin Film Si for Photovoltaic Manufacturing. This project was created to identify growth rate, texture uniformity, process window, economics, composition and thickness uniformity solutions related to fabricating large area, high efficiency thin film silicon based solar cells. This document serves as a final report for the closure of this program and details the deliverables from CNSE against its original scope of work. Thin-film silicon solar cells are a promising candidate for electricity generation applications because of a combination of advantages. Nanocrystalline and poly-Si based thin films, reduces the use of expensive semiconductor material content, can be deposited onto a foreign substrate (e.g. glass or flexible stainless steel) and enables use of the cells in wide variety of applications. In addition, nano and poly-Si films have higher carrier mobility as well as reduce recombination effects, relative to traditional amorphous-silicon films. They can be mass-produced at low cost, and expected to have a strong position in the international photovoltaic industry, which is experiencing a compounded annual growth of 25%. The objectives included: • Demonstration of high rate VHF (Very High Frequency) growth of nc-Si over large areas with uniform thickness. • Demonstration of single chamber device growth that allows mass production processing. • Demonstration of uniform segmented electrodes. • Development of computer models to accelerate efforts. • Demonstration of large grain thin film polycrystalline silicon films fabrication. • Utilizing the AIC (Aluminum Induced Crystallization) process for large grain silicon film

  18. Single-crystalline InI—Material for infrared optics

    NASA Astrophysics Data System (ADS)

    Fedorov, P. P.; Kuznetsov, S. V.; Chuvilina, E. L.; Gasanov, A. A.; Plotnichenko, V. G.; Popov, P. A.; Matovnikov, A. V.; Osiko, V. V.

    2016-06-01

    The Bridgman-Stockbarger method is used for growing InI single crystals. The crystals are characterized by a perfect cleavage along (0k0). The long-wave IR transmission boundary amounts to 51 µm. For the first time, the thermal capacity and thermal conductivity are measured in the intervals of 80-300 and 50-300 K, respectively. The crystals have a high thermal capacity and a low thermal conductivity ( C = 52.7 J/(mol K) and k = 0.58 W/(m K) at 300 K).

  19. Evaluation of repeated single-point diamond turning on the deformation behavior of monocrystalline silicon via molecular dynamic simulations

    NASA Astrophysics Data System (ADS)

    Zhang, Lin; Zhao, Hongwei; Yang, Yihan; Huang, Hu; Ma, Zhichao; Shao, Mingkun

    2014-07-01

    A three-dimensional molecular dynamics simulation study is conducted to investigate repeated single-point turnings of a monocrystalline silicon specimen with diamond tools at nanometric scale. Morse potential energy function and Tersoff potential energy function are applied to model the silicon/diamond and silicon/silicon interactions, respectively. As repeated nano-cutting process on surfaces often involve the interactions between the consequent machining processes, repeated single-point diamond turnings are employed to investigate the phase transformation in the successive nano-cutting processes. The simulation results show that a layer of the damaged residual amorphous silicon remained beneath the surface after the first-time nano-cutting process. The amorphous phase silicon deforms and removes differently in the second nano-cutting process. By considering the coordination number (CN) of silicon atoms in the specimen, it is observed that there is an increase of atoms with six nearest neighbors during the second nano-cutting process. It suggests that the recovery of the crystalline phase from the amorphous phase occurred. Moreover, the instantaneous temperature distributions in the specimen are analyzed. Although the tangential force ( F X ) and the thrust force ( F Y ) become much smaller in the second cutting process, the material resistance rate is larger than the first cutting process. The larger resistance also induces the increase of local temperature between the cutting tool and the amorphous layer in the second cutting process.

  20. Numerical modelling on stress and dislocation generation in multi-crystalline silicon during directional solidification for PV applications

    NASA Astrophysics Data System (ADS)

    Srinivasan, M.; Karuppasamy, P.; Ramasamy, P.; Barua, A. K.

    2016-07-01

    Numerical modelling has emerged as a powerful tool for the development and optimization of directional solidification process for mass production of multicrystalline silicon. A transient global heat transfer model is performed to investigate the effect of bottom grooved furnace upon the directional solidification (DS) process of multi-crystalline silicon (mc-Si). The temperature distribution, von Mises stress, residual stress and dislocation density rate in multi-crystalline silicon ingots grown by modified directional solidification method have been investigated for five growth stages using finite volume method at the critical Prandtl number, Pr = 0.01. This paper discusses bottom groove furnace instead of seed crystal DS method. It achieves an advanced understanding of the thermal and mechanical behaviour in grown multi-crystalline ingot by bottom grooved directional solidification method. The von Mises stress and dislocation density were reduced while using the bottom grooved furnace. This work was carried out in the different grooves of radius 30 mm, 60 mm and 90 mm of the heat exchanger block of the DS furnace. In this paper, the results are presented for 60 mm radius groove only because it has got better results compared to the other grooves. Also, the computational results of bottom grooved DS method show better performance compared the conventional DS method for stress and dislocation density in grown ingot. [Figure not available: see fulltext.

  1. Use of antireflection layers to avoid ghost plating on Ni/Cu plated crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Jeong, Myeong Sang; Choi, Sung Jin; Chang, Hyo Sik; In Lee, Jeong; Kang, Min Gu; Kim, Donghwan; Song, Hee-eun

    2016-03-01

    Screen printing is a method commonly used for making electrodes for crystalline silicon solar cells. Although the screen-printing method is fast and easy, screen-printed electrodes have a porous structure, high contact resistance, and low aspect ratio. On the other hand, plated electrodes have low contact resistance and narrow electrode width. Therefore, the plating method could be substituted for the screen-printing method in crystalline silicon solar cells. During the plating process, ghost plating can appear at the surface when the quality of the passivation layer is poor, causing an increase in the recombination rate. In this paper, light-induced plating was applied to the fabrication of electrodes, and various passivation layers were investigated to remove ghost plating in crystalline silicon solar cells. These included, (1) SiNx deposited by plasma-enhanced chemical vapor deposition (PECVD), (2) a double SiNx layer formed by PECVD, (3) a double layer with thermal silicon oxide and SiNx deposited by PECVD, and (4) a double layer comprising SiNx and SiOx formed by PECVD. For the plated solar cells, a laser was used to remove various antireflection coating (ARC) layers and phosphoric acid was spin-coated onto the doped silicon wafer prior to laser ablation. Also, a screen-printed solar cell was fabricated to compare plated solar cells with screen-printed solar cells. As a result, we found that a thermal SiO2/PECVD SiNx layer showed the lowest pinhole density and its wet vapor transmission rate was characterized. The solar cell with the thermal SiO2/PECVD SiNx layer showed the lowest J02 value, as well as improved Voc and Jsc.

  2. Field emission from single-crystalline HfC nanowires

    SciTech Connect

    Yuan, Jinshi; Tang, Jie; Zhang Han; Shinya, Norio; Nakajima, Kiyomi; Qin, Lu-Chang

    2012-03-12

    Single HfC nanowire field emitter/electrode structures have been fabricated using nano-assembling and electron beam induced deposition. Field ion microscopy has been applied to study the atomic arrangement of facets formed on a field evaporation-modified HfC nanowire tip. Field evaporation and crystal form studies suggest that the {l_brace}111{r_brace} and {l_brace}110{r_brace} crystal planes have lower work functions, while the {l_brace}100{r_brace}, {l_brace}210{r_brace}, and {l_brace}311{r_brace} planes have higher work functions. Field emission measurement permits us to obtain that the work function of the {l_brace}111{r_brace} crystal plane is about 3.4 eV.

  3. Epitaxial layers of 2122 BCSCO superconductor thin films having single crystalline structure

    NASA Technical Reports Server (NTRS)

    Pandey, Raghvendra K. (Inventor); Raina, Kanwal K. (Inventor); Solayappan, Narayanan (Inventor)

    1995-01-01

    A substantially single phase, single crystalline, highly epitaxial film of Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor which has a T.sub.c (zero resistance) of 83K is provided on a lattice-matched substrate with no intergrowth. This film is produced by a Liquid Phase Epitaxy method which includes the steps of forming a dilute supercooled molten solution of a single phase superconducting mixture of oxides of Bi, Ca, Sr, and Cu having an atomic ratio of about 2:1:2:2 in a nonreactive flux such as KCl, introducing the substrate, e.g., NdGaO.sub.3, into the molten solution at 850.degree. C., cooling the solution from 850.degree. C. to 830.degree. C. to grow the film and rapidly cooling the substrate to room temperature to maintain the desired single phase, single crystalline film structure.

  4. Improved cure method for single component silicone rubber

    NASA Technical Reports Server (NTRS)

    Lippitt, M. W.

    1969-01-01

    Water is incorporated in a carrier and then thoroughly mixed with the single component silicone rubber containing acetic anhydride as a curing agent. Because curing occurs with the water supplied internally, controlled curing is possible within a reasonable period of time, regardless of the thickness of the material.

  5. Atom devices based on single dopants in silicon nanostructures

    PubMed Central

    2011-01-01

    Silicon field-effect transistors have now reached gate lengths of only a few tens of nanometers, containing a countable number of dopants in the channel. Such technological trend brought us to a research stage on devices working with one or a few dopant atoms. In this work, we review our most recent studies on key atom devices with fundamental structures of silicon-on-insulator MOSFETs, such as single-dopant transistors, preliminary memory devices, single-electron turnstile devices and photonic devices, in which electron tunneling mediated by single dopant atoms is the essential transport mechanism. Furthermore, observation of individual dopant potential in the channel by Kelvin probe force microscopy is also presented. These results may pave the way for the development of a new device technology, i.e., single-dopant atom electronics. PMID:21801408

  6. Upgrade of the hot zone for large-size high-performance multi-crystalline silicon ingot casting

    NASA Astrophysics Data System (ADS)

    Wu, Zhiyong; Zhong, Genxiang; Zhou, Xucheng; Zhang, Zhaoyu; Wang, Zixu; Chen, Wenliang; Huang, Xinming

    2016-05-01

    Casting larger silicon ingots by upgrading the hot zone is one of the main methods used to reduce the cost of multi-crystalline silicon wafers. In this paper, a new hot zone is designed and a transient global model is applied to investigate the effects of the new hot zone on the electricity consumption, the crystal growth rate, and the shape of the C-M interface during the solidification process. Based on the simulation results, a generation-five, directional-solidification furnace was upgraded and implemented in casting experiments. The experimental results show that the feedstock capacity increased by 77.8%, the crystal growth efficiency increased by 53.8%, and the average yield rate of the silicon ingots increased by 9%. The crystal-melt interface was flatter and the growth direction of the grains was almost straight upward.

  7. Catalytic Growth of Graphene: Toward Large-Area Single-Crystalline Graphene.

    PubMed

    Ago, Hiroki; Ogawa, Yui; Tsuji, Masaharu; Mizuno, Seigi; Hibino, Hiroki

    2012-08-16

    For electronic applications, synthesis of large-area, single-layer graphene with high crystallinity is required. One of the most promising and widely employed methods is chemical vapor deposition (CVD) using Cu foil/film as the catalyst. However, the CVD graphene is generally polycrystalline and contains a significant amount of domain boundaries that limit intrinsic physical properties of graphene. In this Perspective, we discuss the growth mechanism of graphene on a Cu catalyst and review recent development in the observation and control of the domain structure of graphene. We emphasize the importance of the growth condition and crystallinity of the Cu catalyst for the realization of large-area, single-crystalline graphene. PMID:26295775

  8. Silicon single-crystal cryogenic optical resonator.

    PubMed

    Wiens, Eugen; Chen, Qun-Feng; Ernsting, Ingo; Luckmann, Heiko; Rosowski, Ulrich; Nevsky, Alexander; Schiller, Stephan

    2014-06-01

    We report on the demonstration and characterization of a silicon optical resonator for laser frequency stabilization, operating in the deep cryogenic regime at temperatures as low as 1.5 K. Robust operation was achieved, with absolute frequency drift less than 20 Hz over 1 h. This stability allowed sensitive measurements of the resonator thermal expansion coefficient (α). We found that α=4.6×10(-13)  K(-1) at 1.6 K. At 16.8 K α vanishes, with a derivative equal to -6×10(-10)  K(-2). The temperature of the resonator was stabilized to a level below 10 μK for averaging times longer than 20 s. The sensitivity of the resonator frequency to a variation of the laser power was also studied. The corresponding sensitivities and the expected Brownian noise indicate that this system should enable frequency stabilization of lasers at the low-10(-17) level. PMID:24876023

  9. Preparation of C 60 single crystalline thin film by ionized cluster beam deposition and ion implantation into single crystalline C 60 thin film

    NASA Astrophysics Data System (ADS)

    Isoda, Satoru; Kawakubo, Hiroaki; Nishikawa, Satoshi; Wada, Osamu

    1996-05-01

    We have succeeded in preparing single crystalline C 60 thin film of a lateral extension in the order of several millimeters on mica by ionized cluster beam (ICB) deposition. During the growth process, planar dendrite-like single crystalline islands were observed by an atomic force microscope (AFM). It was concluded from reflection high-energy electron diffraction (RHEED) and transmission electron diffraction (TED) analyses that these islands grow hetero-epitaxially on mica. As the deposition process continues, the single crystalline islands coalesce and finally form a giant single crystal without grain boundaries between the former islands. This layered dendrite-like crystal growth is considered to be due to the ICB process, namely, ionizing molecules and accelerating them. Furthermore, the effect of ion (P +, B +, Ar +) implantation into C 60 thin films on the molecular structure and the conductivity has been studied under various implantation conditions. It was found from the analyses of FT-IR and Raman spectroscopies that the soccer-ball-like structure of C 60 changes into a diamond-like carbon (DLC) structure with an implantation energy higher than 40 keV, whereas the structure undergoes virtually no change with 10 keV implantation. As for conductivity changes under the lower implantation energy condition, the minimum dose of P + ions required to increase the conductivity from the non-doped value (10 12 cm -2) is 10 times lower than in the case of Ar + implantation. The conductivity change for the P + implantation could be explained satisfactorily not only by the effect of chemically-modified C 60 but also by the effect of a charge-transfer state between C 60 and implanted ions. It was concluded from these results that the conductivity of the C 60 film can be controlled over a wide range based on the carrier generation mechanism, which depends on the implantation conditions.

  10. Magnetic properties of single-crystalline UCu3Al2

    NASA Astrophysics Data System (ADS)

    Nakotte, H.; Brueck, E.; Brabers, J. H. V. J.; Prokes, K.; Deboer, F. R.; Sechovsky, V.; Buschow, K. H. J.; Andreev, A. V.; Robinson, R. A.; Puranto, A.

    UCu3Al2 crystallizes in an ordered variant of the hexagonal CaCu5 structure. By neutron powder-diffraction, the U atoms were found to occupy the 1a sites, while the 2c sites are occupied by Cu atoms only and a random occupation of the 3g sites by the remaining Cu and Al is found. The magnetic susceptibility, measured on a single crystal grown by the Czochralski tri-arc technique, is found to be maximal within the hexagonal basal plane with a maximum at about 10 K. For fields applied within the basal plane, the magnetization at 4.2 K exhibits a slight S-shape starting slightly below 15 T. No such anomalies are found for fields applied along the c-axis where the magnetic response is found to be much lower. No additional magnetic peaks, which could be related with long-range antiferromagnetic ordering, were detected in the neutron powder-patterns at low temperatures.

  11. Deformation compatibility in a single crystalline Ni superalloy

    PubMed Central

    Zhang, Tiantian; Dunne, Fionn P. E.

    2016-01-01

    Deformation in materials is often complex and requires rigorous understanding to predict engineering component lifetime. Experimental understanding of deformation requires utilization of advanced characterization techniques, such as high spatial resolution digital image correlation (HR-DIC) and high angular resolution electron backscatter diffraction (HR-EBSD), combined with clear interpretation of their results to understand how a material has deformed. In this study, we use HR-DIC and HR-EBSD to explore the mechanical behaviour of a single-crystal nickel alloy and to highlight opportunities to understand the complete deformations state in materials. Coupling of HR-DIC and HR-EBSD enables us to precisely focus on the extent which we can access the deformation gradient, F, in its entirety and uncouple contributions from elastic deformation gradients, slip and rigid body rotations. Our results show a clear demonstration of the capabilities of these techniques, found within our experimental toolbox, to underpin fundamental mechanistic studies of deformation in polycrystalline materials and the role of microstructure. PMID:26997901

  12. Single crystalline tantalum oxychloride microcubes: controllable synthesis, formation mechanism and enhanced photocatalytic hydrogen production activity.

    PubMed

    Tu, Hao; Xu, Leilei; Mou, Fangzhi; Guan, Jianguo

    2015-08-11

    Single crystalline microcubes of a new tantalum compound, tantalum oxychloride (TaO2.18Cl0.64), have been fabricated hydrothermally in a concentrated aqueous solution of hydrochloric acid and acetic acid. They contain a superstructure and exhibit remarkably enhanced photocatalytic activities for hydrogen production due to the improved light harvest and facilitated charge transport. PMID:26143863

  13. 3D Dewetting for Crystal Patterning: Toward Regular Single-Crystalline Belt Arrays and Their Functionality.

    PubMed

    Wu, Yuchen; Feng, Jiangang; Su, Bin; Jiang, Lei

    2016-03-01

    Arrays of unidirectional dewetting behaviors can be generated by using 3D-wettability-difference micropillars, yielding highly ordered organic single-crystalline belt arrays. These patterned organic belts show an improved mobility record and can be used as flexible pressure sensors with high sensitivity. PMID:26823061

  14. A positron beam study of hydrogen confined in nano-cavities in crystalline silicon

    NASA Astrophysics Data System (ADS)

    Schut, H.; van Gog, H.; van Veen, A.; van Huis, M. A.; Eijt, S. W. H.

    2004-02-01

    The Positron Beam Doppler Broadening (DB) and Two Dimensional Angular Correlation of Annihilation Radiation (2D-ACAR) techniques have been applied to study the behavior of hydrogen confined in nanometer size cavities in crystalline silicon. A layer of subsurface cavities was successfully created by He + ion implantation at 33 keV to a dose of 3 × 10 16 cm -2 followed by an annealing in vacuum at 800 °C for 30 min. Hydrogen was introduced by implanting 28 keV hydrogen ions to doses of 1, 3 and 6 × 10 16 cm -2, respectively, followed by annealing from 200 to 900 °C. Results for the low dose H implantation show two main features. Below 400 °C the hydrogen dissociates from the small defects and re-trapping of hydrogen in the pre-existing cavities takes place. It is not until about 700 °C that the hydrogen is released from the cavities. For the higher dose a similar behavior is observed although the defects created by the H implantation itself start to play a role in the initial redistribution of the hydrogen. A novel method to fill the cavities by in-diffusion from a deuterium ambient (16 h at 550 °C in 10 bar) was successfully tested. In this case, the release of deuterium was found to occur in a narrower temperature interval starting at 600 °C. The gas release from the cavities is quantitatively understood using literature data for the of heat of solution and migration- and adsorption enthalpies of H in Si.

  15. Life Cycle Greenhouse Gas Emissions of Crystalline Silicon Photovoltaic Electricity Generation: Systematic Review and Harmonization

    SciTech Connect

    Hsu, D. D.; O'Donoughue, P.; Fthenakis, V.; Heath, G. A.; Kim, H. C.; Sawyer, P.; Choi, J. K.; Turney, D. E.

    2012-04-01

    Published scientific literature contains many studies estimating life cycle greenhouse gas (GHG) emissions of residential and utility-scale solar photovoltaics (PVs). Despite the volume of published work, variability in results hinders generalized conclusions. Most variance between studies can be attributed to differences in methods and assumptions. To clarify the published results for use in decision making and other analyses, we conduct a meta-analysis of existing studies, harmonizing key performance characteristics to produce more comparable and consistently derived results. Screening 397 life cycle assessments (LCAs) relevant to PVs yielded 13 studies on crystalline silicon (c-Si) that met minimum standards of quality, transparency, and relevance. Prior to harmonization, the median of 42 estimates of life cycle GHG emissions from those 13 LCAs was 57 grams carbon dioxide equivalent per kilowatt-hour (g CO{sub 2}-eq/kWh), with an interquartile range (IQR) of 44 to 73. After harmonizing key performance characteristics, irradiation of 1,700 kilowatt-hours per square meter per year (kWh/m{sup 2}/yr); system lifetime of 30 years; module efficiency of 13.2% or 14.0%, depending on module type; and a performance ratio of 0.75 or 0.80, depending on installation, the median estimate decreased to 45 and the IQR tightened to 39 to 49. The median estimate and variability were reduced compared to published estimates mainly because of higher average assumptions for irradiation and system lifetime. For the sample of studies evaluated, harmonization effectively reduced variability, providing a clearer synopsis of the life cycle GHG emissions from c-Si PVs. The literature used in this harmonization neither covers all possible c-Si installations nor represents the distribution of deployed or manufactured c-Si PVs.

  16. Crystalline silicon growth in the aluminium-induced glass texturing process

    NASA Astrophysics Data System (ADS)

    Huang, Ying; Law, Felix; Widenborg, Per I.; Aberle, Armin G.

    2012-12-01

    Aluminium-induced texturing (AIT) is a method to texture glass surfaces by utilising the reaction between aluminium (Al) and glass at high temperature (above 500 °C) and a subsequent wet-chemical treatment that removes the reaction products. In this work, we studied the solid state reaction between a sputtered Al layer and a borosilicate glass sheet during AIT annealing. Raman spectroscopy showed that crystalline silicon (c-Si) is formed during the AIT process. An optical microscope was used to visualise the evolution of the c-Si growth. Plan-view scanning electron microscopy (SEM) investigations performed on samples after completed AIT reaction showed that separate c-Si clusters formed at the glass surface. Atomic force microscopy revealed that the c-Si clusters grew upwards and were on top of the glass surface. Cross-sectional SEM examination showed that the c-Si layer is not uniform and that crater-shaped nodules are embedded into the glass. The widths and depths of the nodules are in the micrometre range. Energy-dispersive X-ray spectroscopy showed that the nodules consist mainly of aluminium oxide (Al2O3). X-ray diffraction analysis showed that the c-Si grains are preferentially (111) oriented. The activation energy of the reaction between Al and borosilicate glass is 3.0±0.2 eV based on in-situ XRD analysis of the c-Si growth. Finally, a phenomenological model of the AIT process is proposed and we suggest that the topology of the glass texture strongly depends on the size, depth and lateral separation of the Al2O3 nodules embedded in the glass.

  17. Reassessment of the recombination parameters of chromium in n- and p-type crystalline silicon and chromium-boron pairs in p-type crystalline silicon

    SciTech Connect

    Sun, Chang Rougieux, Fiacre E.; Macdonald, Daniel

    2014-06-07

    Injection-dependent lifetime spectroscopy of both n- and p-type, Cr-doped silicon wafers with different doping levels is used to determine the defect parameters of Cr{sub i} and CrB pairs, by simultaneously fitting the measured lifetimes with the Shockley-Read-Hall model. A combined analysis of the two defects with the lifetime data measured on both n- and p-type samples enables a significant tightening of the uncertainty ranges of the parameters. The capture cross section ratios k = σ{sub n}/σ{sub p} of Cr{sub i} and CrB are determined as 3.2 (−0.6, +0) and 5.8 (−3.4, +0.6), respectively. Courtesy of a direct experimental comparison of the recombination activity of chromium in n- and p-type silicon, and as also suggested by modelling results, we conclude that chromium has a greater negative impact on carrier lifetimes in p-type silicon than n-type silicon with similar doping levels.

  18. Ultrathin flexible planar crystalline-silicon/polymer hybrid solar cell with 5.68% efficiency by effective passivation

    NASA Astrophysics Data System (ADS)

    Li, Yingfeng; Fu, Pengfei; Li, Ruike; Li, Meicheng; Luo, Younan; Song, Dandan

    2016-03-01

    Ultrathin silicon based solar cells provide a viable way to reduce the material usage and diversify their applications. However, complex light-trapping structures are always needed to be fabricated to enhance light absorption, which will lead to exacerbation of carrier collection and expensive fabrication cost. Here, we report very simple planar flexible crystalline silicon-polymer hybrid solar cell with thickness about 18 μm, whose power conversion efficiency (PCE) reaches 5.68%. By introducing the amorphous silicon layer to passivate the Silicon/Polymer interface in our device, with accuracy control of the thickness of 2 nm to balance the passivation effect and the deterioration of internal electric field, the short current density reaches 83.0% of the theoretical limit. Additionally, we found that the average PCE of solar cells passivated by such technology is 5.8% and 7.1% enhanced compared with those without passivation (H-terminated) and passivated by native oxide approaches. The simple device structure provided in this study has great practicability, and the passivation processes can be duplicated for other silicon based photovoltaic devices.

  19. GAGG:ce single crystalline films: New perspective scintillators for electron detection in SEM.

    PubMed

    Bok, Jan; Lalinský, Ondřej; Hanuš, Martin; Onderišinová, Zuzana; Kelar, Jakub; Kučera, Miroslav

    2016-04-01

    Single crystal scintillators are frequently used for electron detection in scanning electron microscopy (SEM). We report gadolinium aluminum gallium garnet (GAGG:Ce) single crystalline films as a new perspective scintillators for the SEM. For the first time, the epitaxial garnet films were used in a practical application: the GAGG:Ce scintillator was incorporated into a SEM scintillation electron detector and it showed improved image quality. In order to prove the GAGG:Ce quality accurately, the scintillation properties were examined using electron beam excitation and compared with frequently used scintillators in the SEM. The results demonstrate excellent emission efficiency of the GAGG:Ce single crystalline films together with their very fast scintillation decay useful for demanding SEM applications. PMID:26855204

  20. Single-Crystalline SrRuO3 Nanomembranes: A Platform for Flexible Oxide Electronics

    SciTech Connect

    Fong, Dillon D.; Paskiewicz, Deborah M.; Sichel-Tissot, Rebecca; Stan, Liliana; Karapetrova, Evguenia

    2016-01-01

    The field of oxide electronics has benefited from the wide spectrum of functionalities available to the ABO3 perovskites, and researchers are now employing defect engineering in single crystalline heterostructures to tailor properties. However, bulk oxide single crystals are not conducive to many types of applications, particularly those requiring mechanical flexibility. Here, we demonstrate the realization of an all-oxide, single-crystalline nanomembrane heterostructure. With a surface-to-volume ratio of 2 × 107 , the nanomembranes are fully flexible and can be readily transferred to other materials for handling purposes or for new materials integration schemes. Using in situ synchrotron X-ray scattering, we find that the nanomembranes can bond to other host substrates near room temperature and demonstrate coupling between surface reactivity and electromechanical properties in ferroelectric nanomembrane systems. The synthesis technique described here represents a significant advancement in materials integration and provides a new platform for the development of flexible oxide electronics.

  1. Single-crystalline polytetrafluoroethylene-like nanotubes prepared from atmospheric plasma discharge

    SciTech Connect

    Zhang, J.; Guo, Y.; Xu, J.Z.; Fang, X.S.; Xie, H.K.; Shi, D.L.; He, P.; Ooij, W.J. van

    2005-03-28

    Atmospheric plasma polymerization of perfluorohexane was investigated in this letter. A large quantity of single-crystalline polytetrafluoroethylene (PTFE)-like nanotubes were formed on a simultaneously deposited film at room temperature without any catalysts or templates. The outer diameter of the nanotubes varied from 60 to 1200 nm with a maximum aspect ratio up to 100:1. Transmission electron microscopy and x-ray diffraction results indicated a single crystal close-packed hexagonal (cph) structure in the nanotubes. Polarization optical micrographs of the nanotubes showed their thermal stability comparable to PTFE. It is suggested that the plasma filament played a key role in the rapid formation of the nanotubes. This atmospheric plasma discharge synthesis can serve as a common method for nanofabrication of many other single-crystalline polymer systems.

  2. Single-photon emitting diode in silicon carbide.

    PubMed

    Lohrmann, A; Iwamoto, N; Bodrog, Z; Castelletto, S; Ohshima, T; Karle, T J; Gali, A; Prawer, S; McCallum, J C; Johnson, B C

    2015-01-01

    Electrically driven single-photon emitting devices have immediate applications in quantum cryptography, quantum computation and single-photon metrology. Mature device fabrication protocols and the recent observations of single defect systems with quantum functionalities make silicon carbide an ideal material to build such devices. Here, we demonstrate the fabrication of bright single-photon emitting diodes. The electrically driven emitters display fully polarized output, superior photon statistics (with a count rate of >300 kHz) and stability in both continuous and pulsed modes, all at room temperature. The atomic origin of the single-photon source is proposed. These results provide a foundation for the large scale integration of single-photon sources into a broad range of applications, such as quantum cryptography or linear optics quantum computing. PMID:26205309

  3. Single-crystalline Ni(OH)2 and NiO nanoplatelet arrays as supercapacitor electrodes

    NASA Astrophysics Data System (ADS)

    Li, Jiangtian; Zhao, Wei; Huang, Fuqiang; Manivannan, Ayyakkannu; Wu, Nianqiang

    2011-12-01

    Vertically aligned Ni(OH)2 and NiO single-crystalline nanoplatelet arrays were directly grown on the fluorine-doped tin oxide (FTO) substrate by a simple hydrothermal method. The effects of the hydrothermal parameters on the morphology and crystal structure of the nanoarray film were investigated. Controlling the ammonia and persulfate concentrations was the key to controlling the morphology of the nanoarray film. The experimental results showed that the single-crystalline NiO nanoplatelet array was a promising candidate for the supercapacitor electrode. It exhibited a high specific capacitance, prompt charge/discharge rate, and good stability of cycling performance. It is believed that the vertically oriented aligned single-crystalline NiO nanoplatelet array is beneficial to the charge transfer in the electrode and to the ion transport in the solution during redox reaction.Vertically aligned Ni(OH)2 and NiO single-crystalline nanoplatelet arrays were directly grown on the fluorine-doped tin oxide (FTO) substrate by a simple hydrothermal method. The effects of the hydrothermal parameters on the morphology and crystal structure of the nanoarray film were investigated. Controlling the ammonia and persulfate concentrations was the key to controlling the morphology of the nanoarray film. The experimental results showed that the single-crystalline NiO nanoplatelet array was a promising candidate for the supercapacitor electrode. It exhibited a high specific capacitance, prompt charge/discharge rate, and good stability of cycling performance. It is believed that the vertically oriented aligned single-crystalline NiO nanoplatelet array is beneficial to the charge transfer in the electrode and to the ion transport in the solution during redox reaction. Electronic supplementary information (ESI) available: XRD patterns of Ni(OH)2 and NiO powders; SEM and TEM images of Ni(OH)2 and NiO nanoplatelet arrays; and electrochemical performances for NiO nanoarrays and powders. See

  4. PMN-PT single crystal thick films on silicon substrate for high-frequency micromachined ultrasonic transducers

    NASA Astrophysics Data System (ADS)

    Peng, J.; Lau, S. T.; Chao, C.; Dai, J. Y.; Chan, H. L. W.; Luo, H. S.; Zhu, B. P.; Zhou, Q. F.; Shung, K. K.

    2010-01-01

    In this work, a novel high-frequency ultrasonic transducer structure is realized by using PMNPT-on-silicon technology and silicon micromachining. To prepare the single crystalline PMNPT-on-silicon wafers, a hybrid processing method involving wafer bonding, mechanical lapping and wet chemical thinning is successfully developed. In the transducer structure, the active element is fixed within the stainless steel needle housing. The measured center frequency and -6 dB bandwidth of the transducer are 35 MHz and 34%, respectively. Owing to the superior electromechanical coupling coefficient ( k t ) and high piezoelectric constant ( d 33) of PMNPT film, the transducer shows a good energy conversion performance with a very low insertion loss down to 8.3 dB at the center frequency.

  5. Ultimate efficiency limit of single-junction perovskite and dual-junction perovskite/silicon two-terminal devices

    NASA Astrophysics Data System (ADS)

    Almansouri, Ibraheem; Ho-Baillie, Anita; Green, Martin A.

    2015-08-01

    Theoretical calculation based on detailed balance and incorporating different realistic optical and electrical losses predicts conversion efficiency beyond 22% for single-junction perovskite devices. In dual-junction perovskite/silicon devices, theoretical conversion efficiency around 40% is been determined. However, dramatic drop in the conversion efficiency is shown to be due to the glass reflection and FTO parasitic absorption losses. Additionally, practical conversion efficiency limits of dual-junction two-terminal perovskite/silicon tandem solar cell of 30% are achievable as reported in this work using state-of-the-art demonstrated devices. Additionally, various crystalline silicon (industry and laboratory demonstrated) technologies are used as the bottom cell for the current matched tandem cell stacks with higher relative improvements when using commercial c-Si solar cells. Moreover, the effect of eliminating the parasitic resistances and enhancing the external radiative efficiency (ERE) in the perovskite junction on tandem performance are also investigated enhancing the stack efficiencies.

  6. Valence band offset in heterojunctions between crystalline silicon and amorphous silicon (sub)oxides (a-SiO{sub x}:H, 0 < x < 2)

    SciTech Connect

    Liebhaber, M.; Mews, M.; Schulze, T. F.; Korte, L. Rech, B.; Lips, K.

    2015-01-19

    The heterojunction between amorphous silicon (sub)oxides (a-SiO{sub x}:H, 0 < x < 2) and crystalline silicon (c-Si) is investigated. We combine chemical vapor deposition with in-system photoelectron spectroscopy in order to determine the valence band offset ΔE{sub V} and the interface defect density, being technologically important junction parameters. ΔE{sub V} increases from ≈0.3 eV for the a-Si:H/c-Si interface to >4 eV for the a-SiO{sub 2}/c-Si interface, while the electronic quality of the heterointerface deteriorates. High-bandgap a-SiO{sub x}:H is therefore unsuitable for the hole contact in heterojunction solar cells, due to electronic transport hindrance resulting from the large ΔE{sub V}. Our method is readily applicable to other heterojunctions.

  7. Performance characterization of thin-film-silicon based solar modules under clouded and clear sky conditions in comparison to crystalline silicon modules

    NASA Astrophysics Data System (ADS)

    Weicht, J. A.; Rasch, R.; Behrens, G.; Hamelmann, F. U.

    2016-07-01

    For a precise prediction of the energy yield of amorphous ( a-Si) and amorphous-microcrystalline tandem ( a-Si/ μc-Si) thinfilm-silicon photovoltaic (PV) modules it is important to know their performance ratio under different light conditions. The efficiency of solar modules is an important value for the monitoring and planning of PV-systems. The efficiency of a-Si solar modules shows no significant changes in the performance ratio at clouded or clear sky conditions. The efficiency of crystalline silicon-based ( c-Si) and a-Si/ μc-Si solar modules shows a lower efficiency for fully clouded conditions without direct irradiation compared to conditions with direct irradiation (clear sky). [Figure not available: see fulltext.

  8. Single Crystalline Film of Hexagonal Boron Nitride Atomic Monolayer by Controlling Nucleation Seeds and Domains

    PubMed Central

    Wu, Qinke; Park, Ji-Hoon; Park, Sangwoo; Jung, Seong Jun; Suh, Hwansoo; Park, Noejung; Wongwiriyapan, Winadda; Lee, Sungjoo; Lee, Young Hee; Song, Young Jae

    2015-01-01

    A monolayer hexagonal boron nitride (h-BN) film with controllable domain morphology and domain size (varying from less than 1 μm to more than 100 μm) with uniform crystalline orientation was successfully synthesized by chemical vapor deposition (CVD). The key for this extremely large single crystalline domain size of a h-BN monolayer is a decrease in the density of nucleation seeds by increasing the hydrogen gas flow during the h-BN growth. Moreover, the well-defined shape of h-BN flakes can be selectively grown by controlling Cu-annealing time under argon atmosphere prior to h-BN growth, which provides the h-BN shape varies in triangular, trapezoidal, hexagonal and complex shapes. The uniform crystalline orientation of h-BN from different nucleation seeds can be easily confirmed by polarized optical microscopy (POM) with a liquid crystal coating. Furthermore, seamlessly merged h-BN flakes without structural domain boundaries were evidence by a selective hydrogen etching after a full coverage of a h-BN film was achieved. This seamless large-area and atomic monolayer of single crystalline h-BN film can offer as an ideal and practical template of graphene-based devices or alternative two-dimensional materials for industrial applications with scalability. PMID:26537788

  9. Single Crystalline Film of Hexagonal Boron Nitride Atomic Monolayer by Controlling Nucleation Seeds and Domains

    NASA Astrophysics Data System (ADS)

    Wu, Qinke; Park, Ji-Hoon; Park, Sangwoo; Jung, Seong Jun; Suh, Hwansoo; Park, Noejung; Wongwiriyapan, Winadda; Lee, Sungjoo; Lee, Young Hee; Song, Young Jae

    2015-11-01

    A monolayer hexagonal boron nitride (h-BN) film with controllable domain morphology and domain size (varying from less than 1 μm to more than 100 μm) with uniform crystalline orientation was successfully synthesized by chemical vapor deposition (CVD). The key for this extremely large single crystalline domain size of a h-BN monolayer is a decrease in the density of nucleation seeds by increasing the hydrogen gas flow during the h-BN growth. Moreover, the well-defined shape of h-BN flakes can be selectively grown by controlling Cu-annealing time under argon atmosphere prior to h-BN growth, which provides the h-BN shape varies in triangular, trapezoidal, hexagonal and complex shapes. The uniform crystalline orientation of h-BN from different nucleation seeds can be easily confirmed by polarized optical microscopy (POM) with a liquid crystal coating. Furthermore, seamlessly merged h-BN flakes without structural domain boundaries were evidence by a selective hydrogen etching after a full coverage of a h-BN film was achieved. This seamless large-area and atomic monolayer of single crystalline h-BN film can offer as an ideal and practical template of graphene-based devices or alternative two-dimensional materials for industrial applications with scalability.

  10. Single Crystalline Film of Hexagonal Boron Nitride Atomic Monolayer by Controlling Nucleation Seeds and Domains.

    PubMed

    Wu, Qinke; Park, Ji-Hoon; Park, Sangwoo; Jung, Seong Jun; Suh, Hwansoo; Park, Noejung; Wongwiriyapan, Winadda; Lee, Sungjoo; Lee, Young Hee; Song, Young Jae

    2015-01-01

    A monolayer hexagonal boron nitride (h-BN) film with controllable domain morphology and domain size (varying from less than 1 μm to more than 100 μm) with uniform crystalline orientation was successfully synthesized by chemical vapor deposition (CVD). The key for this extremely large single crystalline domain size of a h-BN monolayer is a decrease in the density of nucleation seeds by increasing the hydrogen gas flow during the h-BN growth. Moreover, the well-defined shape of h-BN flakes can be selectively grown by controlling Cu-annealing time under argon atmosphere prior to h-BN growth, which provides the h-BN shape varies in triangular, trapezoidal, hexagonal and complex shapes. The uniform crystalline orientation of h-BN from different nucleation seeds can be easily confirmed by polarized optical microscopy (POM) with a liquid crystal coating. Furthermore, seamlessly merged h-BN flakes without structural domain boundaries were evidence by a selective hydrogen etching after a full coverage of a h-BN film was achieved. This seamless large-area and atomic monolayer of single crystalline h-BN film can offer as an ideal and practical template of graphene-based devices or alternative two-dimensional materials for industrial applications with scalability. PMID:26537788

  11. Titanium dioxide/silicon hole-blocking selective contact to enable double-heterojunction crystalline silicon-based solar cell

    NASA Astrophysics Data System (ADS)

    Nagamatsu, Ken A.; Avasthi, Sushobhan; Sahasrabudhe, Girija; Man, Gabriel; Jhaveri, Janam; Berg, Alexander H.; Schwartz, Jeffrey; Kahn, Antoine; Wagner, Sigurd; Sturm, James C.

    2015-03-01

    In this work, we use an electron-selective titanium dioxide (TiO2) heterojunction contact to silicon to block minority carrier holes in the silicon from recombining at the cathode contact of a silicon-based photovoltaic device. We present four pieces of evidence demonstrating the beneficial effect of adding the TiO2 hole-blocking layer: reduced dark current, increased open circuit voltage (VOC), increased quantum efficiency at longer wavelengths, and increased stored minority carrier charge under forward bias. The importance of a low rate of recombination of minority carriers at the Si/TiO2 interface for effective blocking of minority carriers is quantitatively described. The anode is made of a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) heterojunction to silicon which forms a hole selective contact, so that the entire device is made at a maximum temperature of 100 °C, with no doping gradients or junctions in the silicon. A low rate of recombination of minority carriers at the Si/TiO2 interface is crucial for effective blocking of minority carriers. Such a pair of complementary carrier-selective heterojunctions offers a path towards high-efficiency silicon solar cells using relatively simple and near-room temperature fabrication techniques.

  12. Titanium dioxide/silicon hole-blocking selective contact to enable double-heterojunction crystalline silicon-based solar cell

    SciTech Connect

    Nagamatsu, Ken A. Man, Gabriel; Jhaveri, Janam; Berg, Alexander H.; Kahn, Antoine; Wagner, Sigurd; Sturm, James C.; Avasthi, Sushobhan; Sahasrabudhe, Girija; Schwartz, Jeffrey

    2015-03-23

    In this work, we use an electron-selective titanium dioxide (TiO{sub 2}) heterojunction contact to silicon to block minority carrier holes in the silicon from recombining at the cathode contact of a silicon-based photovoltaic device. We present four pieces of evidence demonstrating the beneficial effect of adding the TiO{sub 2} hole-blocking layer: reduced dark current, increased open circuit voltage (V{sub OC}), increased quantum efficiency at longer wavelengths, and increased stored minority carrier charge under forward bias. The importance of a low rate of recombination of minority carriers at the Si/TiO{sub 2} interface for effective blocking of minority carriers is quantitatively described. The anode is made of a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) heterojunction to silicon which forms a hole selective contact, so that the entire device is made at a maximum temperature of 100 °C, with no doping gradients or junctions in the silicon. A low rate of recombination of minority carriers at the Si/TiO{sub 2} interface is crucial for effective blocking of minority carriers. Such a pair of complementary carrier-selective heterojunctions offers a path towards high-efficiency silicon solar cells using relatively simple and near-room temperature fabrication techniques.

  13. Structure-Property Relationships in Polymer Derived Amorphous/Nano-Crystalline Silicon Carbide for Nuclear Applications

    SciTech Connect

    Zunjarrao, Suraj C.; Singh, Abhishek K.; Singh, Raman P.

    2006-07-01

    Silicon carbide (SiC) is a promising candidate for several applications in nuclear reactors owing to its high thermal conductivity, high melting temperature, good chemical stability, and resistance to swelling under heavy ion bombardment. However, fabricating SiC by traditional powder processing route generally requires very high temperatures for pressureless sintering. Polymer derived ceramic materials offer unique advantages such as ability to fabricate net shaped components, incorporate reinforcements and relatively low processing temperatures. Furthermore, for SiC based ceramics fabricated using polymer infiltration process (PIP), the microstructure can be tailored by controlling the processing parameters, to get an amorphous, nanocrystalline or crystalline SiC. In this work, fabrication of polymer derived amorphous and nano-grained SiC is presented and its application as an in-core material is explored. Monolithic SiC samples are fabricated by controlled pyrolysis of allyl-hydrido-poly-carbo-silane (AHPCS) under inert atmosphere. Chemical changes, phase transformations and microstructural changes occurring during the pyrolysis process are studied as a function of the processing temperature. Polymer cross-linking and polymer to ceramic conversion is studied using infrared spectroscopy (FTIR). Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) are performed to monitor the mass loss and phase change as a function of temperature. X-ray diffraction studies are done to study the intermediate phases and microstructural changes. Variation in density is carefully monitored as a function of processing temperature. Owing to shrinkage and gas evolution during pyrolysis, precursor derived ceramics are inherently porous and composite fabrication typically involves repeated cycles of polymer re-infiltration and pyrolysis. However, there is a limit to the densification that can be achieved by this method and porosity in the final materials presents

  14. Single crystalline nature of para-sexiphenyl crystallites grown on KCl(100).

    PubMed

    Haber, T; Oehzelt, M; Resel, R; Andreev, A; Thierry, A; Sitter, H; Smilgies, D M; Schaffer, B; Grogger, W; Resel, R

    2006-03-01

    This work focuses on studies of the single crystal nature of para-sexiphenyl structures grown on freshly cleaved KCl(100) surfaces. Two different kinds of morphologies, namely terrace like structures and needle like structures, are found by atomic force microscopy as well as by electron microscopy. Regardless of the morphology the individual crystallites show highly regular shapes. The crystalline alignment and the degree of order of the crystallites on the surface are determined by X-ray diffraction. Several epitaxial alignments of para-sexiphenyl on KCl(100) are observed and all of them are perfectly aligned on the surface. The rocking curve widths of the organic crystallites do not exceed 800" which is approximately only the four fold of the substrates' ones. The single crystalline nature of para-sexiphenyl crystallites is proven by transmission electron microscopy, diffraction patterns, dark field imaging and high resolution techniques. Single crystalline terraced mounds reach diameters of several microns and heights of 50 nm. Single crystal needles show heights and breadths of more than 100 nm and lengths of several microns. PMID:16573123

  15. Electrolytic Formation of Crystalline Silicon/Germanium Alloy Nanotubes and Hollow Particles with Enhanced Lithium-Storage Properties.

    PubMed

    Xiao, Wei; Zhou, Jing; Yu, Le; Wang, Dihua; Lou, Xiong Wen David

    2016-06-20

    Crystalline silicon(Si)/germanium(Ge) alloy nanotubes and hollow particles are synthesized for the first time through a one-pot electrolytic process. The morphology of these alloy structures can be easily tailored from nanotubes to hollow particles by varying the overpotential during the electro-reduction reaction. The continuous solid diffusion governed by the nanoscale Kirkendall effect results in the formation of inner void in the alloy particles. Benefitting from the compositional and structural advantages, these SiGe alloy nanotubes exhibit much enhanced lithium-storage performance compared with the individual solid Si and Ge nanowires as the anode material for lithium-ion batteries. PMID:27159140

  16. Technology and design of an active-matrix OLED on crystalline silicon direct-view display for a wristwatch computer

    NASA Astrophysics Data System (ADS)

    Sanford, James L.; Schlig, Eugene S.; Prache, Olivier; Dove, Derek B.; Ali, Tariq A.; Howard, Webster E.

    2002-02-01

    The IBM Research Division and eMagin Corp. jointly have developed a low-power VGA direct view active matrix OLED display, fabricated on a crystalline silicon CMOS chip. The display is incorporated in IBM prototype wristwatch computers running the Linus operating system. IBM designed the silicon chip and eMagin developed the organic stack and performed the back-end-of line processing and packaging. Each pixel is driven by a constant current source controlled by a CMOS RAM cell, and the display receives its data from the processor memory bus. This paper describes the OLED technology and packaging, and outlines the design of the pixel and display electronics and the processor interface. Experimental results are presented.

  17. Controlling wave-vector of propagating surface plasmon polaritons on single-crystalline gold nanoplates

    PubMed Central

    Luo, Si; Yang, Hangbo; Yang, Yuanqing; Zhao, Ding; Chen, Xingxing; Qiu, Min; Li, Qiang

    2015-01-01

    Surface plasmon polaritons (SPPs) propagating at metal nanostructures play an important role in breaking the diffraction limit. Chemically synthesized single-crystalline metal nanoplates with atomically flat surfaces provide favorable features compared with traditional polycrystalline metal films. The excitation and propagation of leaky SPPs on micrometer sized (10–20 μm) and thin (30 nm) gold nanoplates are investigated utilizing leakage radiation microscopy. By varying polarization and excitation positions of incident light on apexes of nanoplates, wave-vector (including propagation constant and propagation direction) distributions of leaky SPPs in Fourier planes can be controlled, indicating tunable SPP propagation. These results hold promise for potential development of chemically synthesized single-crystalline metal nanoplates as plasmonic platforms in future applications. PMID:26302955

  18. Single crystalline graphene synthesized by thermal annealing of humic acid over copper foils

    NASA Astrophysics Data System (ADS)

    Beall, Gary W.; Duraia, El-Shazly M.; Yu, Q.; Liu, Z.

    2014-02-01

    Production of graphene by thermal annealing on copper foil substrates has been studied with different sources of carbon. The three carbon sources include humic acid derived from leonardite, graphenol, and activated charcoal. Hexagonal single crystalline graphene has been synthesized over the copper foil substrates by thermal annealing of humic acid, derived from leonardite, in argon and hydrogen atmosphere (Ar/H2=20). The annealing temperature was varied between 1050 °C and 1100 °C at atmospheric pressure. Samples have been investigated using scanning electron microscope (SEM) and Raman spectroscopy. At lower temperatures the thermal annealing of the three carbon sources used in this study produces pristine graphene nanosheets which cover almost the whole substrate. However when the annealing temperature has been increased up to 1100 °C, hexagonal single crystalline graphene have been observed only in the case of the humic acid. Raman analysis showed the existence of 2D band around 2690 cm-1.

  19. Optoelectronic properties of Black-Silicon generated through inductively coupled plasma (ICP) processing for crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Hirsch, Jens; Gaudig, Maria; Bernhard, Norbert; Lausch, Dominik

    2016-06-01

    The optoelectronic properties of maskless inductively coupled plasma (ICP) generated black silicon through SF6 and O2 are analyzed by using reflection measurements, scanning electron microscopy (SEM) and quasi steady state photoconductivity (QSSPC). The results are discussed and compared to capacitively coupled plasma (CCP) and industrial standard wet chemical textures. The ICP process forms parabolic like surface structures in a scale of 500 nm. This surface structure reduces the average hemispherical reflection between 300 and 1120 nm up to 8%. Additionally, the ICP texture shows a weak increase of the hemispherical reflection under tilted angles of incidence up to 60°. Furthermore, we report that the ICP process is independent of the crystal orientation and the surface roughness. This allows the texturing of monocrystalline, multicrystalline and kerf-less wafers using the same parameter set. The ICP generation of black silicon does not apply a self-bias on the silicon sample. Therefore, the silicon sample is exposed to a reduced ion bombardment, which reduces the plasma induced surface damage. This leads to an enhancement of the effective charge carrier lifetime up to 2.5 ms at 1015 cm-3 minority carrier density (MCD) after an atomic layer deposition (ALD) with Al2O3. Since excellent etch results were obtained already after 4 min process time, we conclude that the ICP generation of black silicon is a promising technique to substitute the industrial state of the art wet chemical textures in the solar cell mass production.

  20. Highly Polarized and Self-Waveguided Emission from Single-Crystalline Organic Nanobelts

    SciTech Connect

    Che, Yanke; Yang, Xiaomei; Balakrishnan, Kaushik; Zuo, Jianmin; Zang, Ling

    2009-09-15

    Well-defined single-crystalline nanobelts with strong fluorescence were fabricated from a perylene tetracarboxylic diimide molecule modified with specific side-chains that afford flip-flap stacking, rather than the common translated stacking, between the molecules along the long axis of the nanobelt. The nanobelts thus fabricated possess highly polarized, self-waveguided emission, making them ideal candidates for application in nanolasers and other angle-dependent optical nanodevices.

  1. Self-powered cardiac pacemaker enabled by flexible single crystalline PMN-PT piezoelectric energy harvester.

    PubMed

    Hwang, Geon-Tae; Park, Hyewon; Lee, Jeong-Ho; Oh, SeKwon; Park, Kwi-Il; Byun, Myunghwan; Park, Hyelim; Ahn, Gun; Jeong, Chang Kyu; No, Kwangsoo; Kwon, HyukSang; Lee, Sang-Goo; Joung, Boyoung; Lee, Keon Jae

    2014-07-23

    A flexible single-crystalline PMN-PT piezoelectric energy harvester is demonstrated to achieve a self-powered artificial cardiac pacemaker. The energy-harvesting device generates a short-circuit current of 0.223 mA and an open-circuit voltage of 8.2 V, which are enough not only to meet the standard for charging commercial batteries but also for stimulating the heart without an external power source. PMID:24740465

  2. Accumulation and diffusion of crystallin inside single fiber cells in intact chicken embryo lenses.

    PubMed Central

    Peetermans, J A; Foy, B D; Tanaka, T

    1987-01-01

    The use of microscope laser light-scattering spectroscopy allows for the measurement of dynamic properties of intracellular particles inside single fiber cells at different locations in the intact chicken embryo lens. Profiles of the diffusive properties of the delta-crystallin proteins across the lens are reported for developing chickens from day 5 to day 37. A clear decrease of the diffusion is observed in the lens nucleus relative to the cortex beginning with day 10. Images PMID:3470754

  3. Design of intrinsically single-mode double clad crystalline fiber waveguides for high power lasers

    NASA Astrophysics Data System (ADS)

    Li, Da; Hong, Pengda; Meissner, Stephanie K.; Meissner, Helmuth E.

    2016-03-01

    Recently, double-clad crystalline fiber waveguides (CFWs), consisting of single crystalline or ceramic RE3+:YAG cores of square cross section and inner claddings of either undoped or laser-inactive-ion-doped YAG and outer claddings of sapphire, have been successfully demonstrated. These waveguides, manufactured by an Adhesive-Free Bonding (AFB®) technique, can be precisely engineered and fabricated with predictable beam propagation behavior. In this work, with high power laser designs in mind, minimum thicknesses for inner cladding are derived for different core cross sections and refractive index differences between the core and inner cladding and sapphire as outer cladding material for common laser core dopants such as Nd3+, Yb3+, Er3+, Tm3+ and Ho3+. All designs are intended to use high NA high power laser diode pumping to obtain high power intrinsically single transverse mode laser output. The obtained data are applicable to any crystalline fiber waveguide design, regardless of fabrication technique. As an example, a CFW with 40 μm × 40 μm 4% Tm:YAG core, 5% Yb:YAG inner cladding, and sapphire outer cladding was calculated to be intrinsically single transverse mode, with the minimum inner cladding width of 21.7 μm determined by the effective index technique [1].

  4. Isolating and moving single atoms using silicon nanocrystals

    DOEpatents

    Carroll, Malcolm S.

    2010-09-07

    A method is disclosed for isolating single atoms of an atomic species of interest by locating the atoms within silicon nanocrystals. This can be done by implanting, on the average, a single atom of the atomic species of interest into each nanocrystal, and then measuring an electrical charge distribution on the nanocrystals with scanning capacitance microscopy (SCM) or electrostatic force microscopy (EFM) to identify and select those nanocrystals having exactly one atom of the atomic species of interest therein. The nanocrystals with the single atom of the atomic species of interest therein can be sorted and moved using an atomic force microscope (AFM) tip. The method is useful for forming nanoscale electronic and optical devices including quantum computers and single-photon light sources.

  5. Improved multicrystalline silicon ingot quality using single layer silicon beads coated with silicon nitride as seed layer

    NASA Astrophysics Data System (ADS)

    babu, G. Anandha; Takahashi, Isao; Matsushima, Satoru; Usami, Noritaka

    2016-05-01

    We propose to utilize single layer silicon beads (SLSB) coated with silicon nitride as cost-effective seed layer to grow high-quality multicrystalline silicon (mc-Si) ingot. The texture structure of silicon nitride provides a large number of nucleation sites for the fine grain formation at the bottom of the crucible. No special care is needed to prevent seed melting, which would lead to decrease of red zone owing to decrease of feedstock melting time. As we expected, mc-Si ingot seeded with SLSB was found to consist of small, different grain orientations, more uniform grain distribution, high percentage of random grain boundaries, less twin boundaries, and low density of dislocation clusters compared with conventional mc-Si ingot grown under identical growth conditions. These results show that the SLSB seeded mc-Si ingot has enhanced ingot quality. The correlation between grain boundary structure and defect structure as well as the reason responsible for dislocation clusters reduction in SLSB seeded mc-Si wafer are also discussed.

  6. Test procedures and instructions for single shell tank saltcake cesium removal with crystalline silicotitanate

    SciTech Connect

    Duncan, J.B.

    1997-01-07

    This document provides specific test procedures and instructions to implement the test plan for the preparation and conduct of a cesium removal test, using Hanford Single Shell Tank Saltcake from tanks 24 t -BY- I 10, 24 1 -U- 108, 24 1 -U- 109, 24 1 -A- I 0 1, and 24 t - S-102, in a bench-scale column. The cesium sorbent to be tested is crystalline siticotitanate. The test plan for which this provides instructions is WHC-SD-RE-TP-024, Hanford Single Shell Tank Saltcake Cesium Removal Test Plan.

  7. Single crystal ternary oxide ferroelectric integration with Silicon

    NASA Astrophysics Data System (ADS)

    Bakaul, Saidur; Serrao, Claudy; Youun, Long; Khan, Asif; Salahuddin, Sayeef

    2015-03-01

    Integrating single crystal, ternary oxide ferroelectric thin film with Silicon or other arbitrary substrates has been a holy grail for the researchers since the inception of microelectronics industry. The key motivation is that adding ferroelectric materials to existing electronic devices could bring into new functionality, physics and performance improvement such as non-volatility of information, negative capacitance effect and lowering sub-threshold swing of field effect transistor (FET) below 60 mV/decade in FET [Salahuddin, S, Datta, S. Nano Lett. 8, 405(2008)]. However, fabrication of single crystal ferroelectric thin film demands stringent conditions such as lattice matched single crystal substrate and high processing temperature which are incompatible with Silicon. Here we report on successful integration of PbZr0.2Ti0.8O3 in single crystal form with by using a layer transfer method. The lattice structure, surface morphology, piezoelectric coefficient d33, dielectric constant, ferroelectric domain switching and spontaneous and remnant polarization of the transferred PZT are as good as these characteristics of the best PZT films grown by pulsed laser deposition on lattice matched oxide substrates. We also demonstrate Si based, FE gate controlled FET devices.

  8. Ink jet printable silver metallization with zinc oxide for front side metallization for micro crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Jurk, Robert; Fritsch, Marco; Eberstein, Markus; Schilm, Jochen; Uhlig, Florian; Waltinger, Andreas; Michaelis, Alexander

    2015-12-01

    Ink jet printable water based inks are prepared by a new silver nanoparticle synthesis and the addition of nanoscaled ZnO particles. For the formation of front side contacts the inks are ink jet printed on the front side of micro crystalline silicon solar cells, and contact the cell directly during the firing step by etching through the wafers’ anti-reflection coating (ARC). In terms of Ag dissolution and precipitation the mechanism of contact formation can be compared to commercial glass containing thick film pastes. This avoids additional processing steps, like laser ablation, which are usually necessary to open the ARC prior to ink jet printing. As a consequence process costs can be reduced. In order to optimize the ARC etching and contact formation during firing, zinc oxide nanoparticles are investigated as an ink additive. By utilization of in situ contact resistivity measurements the mechanism of contacting was explored. Our results show that silver inks containing ZnO particles realize a specific contact resistance below 10 mΩṡcm2. By using a multi-pass ink jet printing and plating process a front side metallization of commercial 6  ×  6 inch2 standard micro crystalline silicone solar cells with emitter resistance of 60 Ω/◽ was achieved and showed an efficiency of 15.7%.

  9. Temperature-Dependent Photoluminescence Imaging and Characterization of a Multi-Crystalline Silicon Solar Cell Defect Area: Preprint

    SciTech Connect

    Johnston, S.; Yan, F.; Li, J.; Romero, M. J.; Al-Jassim, M.; Zaunbrecher, K.; Sidelkheir, O.; Blosse, A.

    2011-07-01

    Photoluminescence (PL) imaging is used to detect areas in multi-crystalline silicon that appear dark in band-to-band imaging due to high recombination. Steady-state PL intensity can be correlated to effective minority-carrier lifetime, and its temperature dependence can provide additional lifetime-limiting defect information. An area of high defect density has been laser cut from a multi-crystalline silicon solar cell. Both band-to-band and defect-band PL imaging have been collected as a function of temperature from ~85 to 350 K. Band-to-band luminescence is collected by an InGaAs camera using a 1200-nm short-pass filter, while defect band luminescence is collected using a 1350-nm long pass filter. The defect band luminescence is characterized by cathodo-luminescence. Small pieces from adjacent areas within the same wafer are measured by deep-level transient spectroscopy (DLTS). DLTS detects a minority-carrier electron trap level with an activation energy of 0.45 eV on the sample that contained defects as seen by imaging.

  10. Specific features of erbium ion photoluminescence in structures with amorphous and crystalline silicon nanoclusters in silica matrix

    SciTech Connect

    Dyakov, S. A. Zhigunov, D. M.; Timoshenko, V. Yu.

    2010-04-15

    Photoluminescence properties of the structures of amorphous and crystalline silicon nanoclusters with average sizes no larger than 4 nm in an erbium-doped silicon dioxide matrix were studied. It was found that the photoluminescence lifetime of Er{sup 3+} ions at a wavelength of 1.5 {mu}m decreases from 5.7 to 2.0 ms and from 3.5 to 1.5 ms in samples with amorphous nanoclusters and with nanocrystals, respectively, as the Er{sup 3+} concentration increases from 10{sup 19} to 10{sup 21} cm{sup -3}. The decrease in the erbium photoluminescence lifetime with the ion concentration is attributed to the effects of concentration-related quenching and residual implantation-induced defects. The difference between lifetimes for samples with amorphous and crystalline nanoclusters is interpreted as the effect of different probabilities of energy back transfer from Er{sup 3+} ions to the solid-state matrix in the structures under consideration.

  11. Thin film PV standing tall side-by-side with multi-crystalline silicon: also in terms of reliability

    NASA Astrophysics Data System (ADS)

    Dhere, Neelkanth G.; Ward, Allan; Wieting, Robert; Guha, Subhendu; Dhere, Ramesh G.

    2015-09-01

    Triple junction hydrogenated amorphous silicon (a-Si:H) have shown exceptionally good reliability and durability. Cadmium telluride, CdTe PV modules have shown the lowest production cost without subsidies. Copper-indium gallium selenide sulfide (CIGS) and cadmium telluride (CdTe) cells and modules have been showing efficiencies equal or greater than those of multi-crystalline, (mx-Si), PV modules. Early generation CIGS and CdTe PV modules had a different qualification standard 61646 as compared to 61215 for crystalline silicon, (c-Si), PV modules. This, together with small vulnerability in harsh climates, was used to create doubts about their reliability. Recently CdTe and CIGS glass-to-glass modules have passed the rigorous accelerated tests, especially as long as the edge seals are not compromised. Moreover, the cumulative shipment of these modules is more than 12 GW demonstrating the customer confidence in these products. Hence it can be stated that also in terms of the reliability and durability all the thin film PV modules stand tall and compare favorably with mx-Si.

  12. Single-crystalline nanogap electrodes: enhancing the nanowire-breakdown process with a gaseous environment.

    PubMed

    Suga, Hiroshi; Sumiya, Touru; Furuta, Shigeo; Ueki, Ryuichi; Miyazawa, Yosuke; Nishijima, Takuya; Fujita, Jun-ichi; Tsukagoshi, Kazuhito; Shimizu, Tetsuo; Naitoh, Yasuhisa

    2012-10-24

    A method for fabricating single-crystalline nanogaps on Si substrates was developed. Polycrystalline Pt nanowires on Si substrates were broken down by current flow under various gaseous environments. The crystal structure of the nanogap electrode was evaluated using scanning electron microscopy and transmission electron microscopy. Nanogap electrodes sandwiched between Pt-large-crystal-grains were obtained by the breakdown of the wire in an O(2) or H(2) atmosphere. These nanogap electrodes show intense spots in the electron diffraction pattern. The diffraction pattern corresponds to Pt (111), indicating that single-crystal grains are grown by the electrical wire breakdown process in an O(2) or H(2) atmosphere. The Pt wires that have (111)-texture and coherent boundaries can be considered ideal as interconnectors for single molecular electronics. The simple method for fabrication of a single-crystalline nanogap is one of the first steps toward standard nanogap electrodes for single molecular instruments and opens the door to future research on physical phenomena in nanospaces. PMID:23054205

  13. Topological surface transport properties of single-crystalline SnTe nanowire.

    PubMed

    Safdar, Muhammad; Wang, Qisheng; Mirza, Misbah; Wang, Zhenxing; Xu, Kai; He, Jun

    2013-01-01

    SnTe has attracted worldwide interest since its theoretical predication as topological crystalline insulator. Because of promising applications of one-dimensional topological insulator in nanoscale electronics and spintronics device, it is very important to realize the observation of topological surface states in one-dimensional SnTe. In this work, for the first time we successfully synthesized high-quality single crystalline SnTe nanowire via gold-catalyst chemical vapor deposition method. Systematical investigation of Aharonov-Bohm and Shubnikov-de Haas oscillations in single SnTe nanowire prove the existence of Dirac electrons. Further analysis of temperature-dependent Shubnikov-de Haas oscillations gives valuable information of cyclotron mass, mean-free path, and mobility of Dirac electrons in SnTe nanowire. Our study provides the experimental groundwork for research in low-dimensional topological crystalline insulator materials and paves the way for the application of SnTe nanowire in nanoelectronics and spintronics device. PMID:24175637

  14. Hydrogen passivation of electrically active defects in crystalline silicon solar cells

    SciTech Connect

    Milstein, J B; Tsuo, Y S; Osterwald, C R; White, C W

    1984-06-01

    We have observed significant improvements in the efficiencies of dendritic web and edge-supported-pulling (ESP) silicon sheet solar cells after hydrogen ion beam passivation for a period of ten minutes or less. We have studied the effects of the hydrogen ion beam treatment with respect to silicon material damage, silicon sputter rate, introduction of impurities, and changes in reflectance. We have determined that the silicon sputter rate for a constant ion beam flux of 0.60 +- 0.05 mA/cm/sup 2/ exhibits a maximum at approximately 1400 eV ion beam energy. We have observed that hydrogen ion beam treatment can result in a reduced fill factor, which is caused by damage to the front metallization of the cell rather than by damage to the p-n junction.

  15. Formation of carbon nanostructures containing single-crystalline cobalt carbides by ion irradiation method

    NASA Astrophysics Data System (ADS)

    Wang, Zhipeng; Yusop, Zamri; Ghosh, Pradip; Hayashi, Yasuhiko; Tanemura, Masaki

    2011-02-01

    Carbon nanofibers (CNFs) with a diameter of 17 nm, and carbon nanoneedles (CNNs) with sharp tips have been synthesized on graphite substrates by ion irradiation of argon ions with the Co supplies rate of 1 and 3.4 nm/min, respectively. Energy dispersive X-ray spectrometry, combined with selected area electron diffraction patterns has been used to identify the chemical composition and crystallinity of these carbon nanostructures. The CNFs were found to be amorphous in nature, while the structures of the CNNs consisted of cubic CoCx, orthorhombic Co2C and Co3C depending on the cobalt content in the CNNs. The diameter of the carbide crystals was almost as large as the diameter of the CNN. Compared to the ion-induced nickel carbides and iron carbides, the formation of single-crystalline cobalt carbides might be due to the high temperature produced by the irradiation.

  16. Development of Novel Front Contract Pastes for Crystalline Silicon Solar Cells

    SciTech Connect

    Duty, C.; Jellison, D. G.E. P.; Joshi, P.

    2012-04-05

    In order to improve the efficiencies of silicon solar cells, paste to silicon contact formation mechanisms must be more thoroughly understood as a function of paste chemistry, wafer properties and firing conditions. Ferro Corporation has been involved in paste development for over 30 years and has extensive expertise in glass and paste formulations. This project has focused on the characterization of the interface between the top contact material (silver paste) and the underlying silicon wafer. It is believed that the interface between the front contact silver and the silicon wafer plays a dominant role in the electrical performance of the solar cell. Development of an improved front contact microstructure depends on the paste chemistry, paste interaction with the SiNx, and silicon (“Si”) substrate, silicon sheet resistivity, and the firing profile. Typical front contact ink contains silver metal powders and flakes, glass powder and other inorganic additives suspended in an organic medium of resin and solvent. During fast firing cycles glass melts, wets, corrodes the SiNx layer, and then interacts with underlying Si. Glass chemistry is also a critical factor in the development of an optimum front contact microstructure. Over the course of this project, several fundamental characteristics of the Ag/Si interface were documented, including a higher-than-expected distribution of voids along the interface, which could significantly impact electrical conductivity. Several techniques were also investigated for the interfacial analysis, including STEM, EDS, FIB, EBSD, and ellipsometry.

  17. Formation of shallow boron emitters in crystalline silicon using flash lamp annealing: Role of excess silicon interstitials

    SciTech Connect

    Riise, Heine Nygard Azarov, Alexander; Svensson, Bengt G.; Monakhov, Edouard

    2015-07-13

    Shallow, Boron (B)-doped p{sup +} emitters have been realized using spin-on deposition and Flash Lamp Annealing (FLA) to diffuse B into monocrystalline float zone Silicon (Si). The emitters extend between 50 and 140 nm in depth below the surface, have peak concentrations between 9 × 10{sup 19 }cm{sup –3} and 3 × 10{sup 20 }cm{sup –3}, and exhibit sheet resistances between 70 and 3000 Ω/□. An exceptionally large increase in B diffusion occurs for FLA energy densities exceeding ∼93 J/cm{sup 2} irrespective of 10 or 20 ms pulse duration. The effect is attributed to enhanced diffusion of B caused by Si interstitial injection following a thermally activated reaction between the spin-on diffusant film and the silicon wafer.

  18. A single-atom electron spin qubit in silicon.

    PubMed

    Pla, Jarryd J; Tan, Kuan Y; Dehollain, Juan P; Lim, Wee H; Morton, John J L; Jamieson, David N; Dzurak, Andrew S; Morello, Andrea

    2012-09-27

    A single atom is the prototypical quantum system, and a natural candidate for a quantum bit, or qubit--the elementary unit of a quantum computer. Atoms have been successfully used to store and process quantum information in electromagnetic traps, as well as in diamond through the use of the nitrogen-vacancy-centre point defect. Solid-state electrical devices possess great potential to scale up such demonstrations from few-qubit control to larger-scale quantum processors. Coherent control of spin qubits has been achieved in lithographically defined double quantum dots in both GaAs (refs 3-5) and Si (ref. 6). However, it is a formidable challenge to combine the electrical measurement capabilities of engineered nanostructures with the benefits inherent in atomic spin qubits. Here we demonstrate the coherent manipulation of an individual electron spin qubit bound to a phosphorus donor atom in natural silicon, measured electrically via single-shot read-out. We use electron spin resonance to drive Rabi oscillations, and a Hahn echo pulse sequence reveals a spin coherence time exceeding 200 µs. This time should be even longer in isotopically enriched (28)Si samples. Combined with a device architecture that is compatible with modern integrated circuit technology, the electron spin of a single phosphorus atom in silicon should be an excellent platform on which to build a scalable quantum computer. PMID:22992519

  19. Towards high efficiency thin-film crystalline silicon solar cells: The roles of light trapping and non-radiative recombinations

    SciTech Connect

    Bozzola, A. Kowalczewski, P.; Andreani, L. C.

    2014-03-07

    Thin-film solar cells based on silicon have emerged as an alternative to standard thick wafers technology, but they are less efficient, because of incomplete absorption of sunlight, and non-radiative recombinations. In this paper, we focus on the case of crystalline silicon (c-Si) devices, and we present a full analytic electro-optical model for p-n junction solar cells with Lambertian light trapping. This model is validated against numerical solutions of the drift-diffusion equations. We use this model to investigate the interplay between light trapping, and bulk and surface recombination. Special attention is paid to surface recombination processes, which become more important in thinner devices. These effects are further amplified due to the textures required for light trapping, which lead to increased surface area. We show that c-Si solar cells with thickness of a few microns can overcome 20% efficiency and outperform bulk ones when light trapping is implemented. The optimal device thickness in presence of light trapping, bulk and surface recombination, is quantified to be in the range of 10–80 μm, depending on the bulk quality. These results hold, provided the effective surface recombination is kept below a critical level of the order of 100 cm/s. We discuss the possibility of meeting this requirement, in the context of state-of-the-art techniques for light trapping and surface passivation. We show that our predictions are within the capability of present day silicon technologies.

  20. Towards high efficiency thin-film crystalline silicon solar cells: The roles of light trapping and non-radiative recombinations

    NASA Astrophysics Data System (ADS)

    Bozzola, A.; Kowalczewski, P.; Andreani, L. C.

    2014-03-01

    Thin-film solar cells based on silicon have emerged as an alternative to standard thick wafers technology, but they are less efficient, because of incomplete absorption of sunlight, and non-radiative recombinations. In this paper, we focus on the case of crystalline silicon (c-Si) devices, and we present a full analytic electro-optical model for p-n junction solar cells with Lambertian light trapping. This model is validated against numerical solutions of the drift-diffusion equations. We use this model to investigate the interplay between light trapping, and bulk and surface recombination. Special attention is paid to surface recombination processes, which become more important in thinner devices. These effects are further amplified due to the textures required for light trapping, which lead to increased surface area. We show that c-Si solar cells with thickness of a few microns can overcome 20% efficiency and outperform bulk ones when light trapping is implemented. The optimal device thickness in presence of light trapping, bulk and surface recombination, is quantified to be in the range of 10-80 μm, depending on the bulk quality. These results hold, provided the effective surface recombination is kept below a critical level of the order of 100 cm/s. We discuss the possibility of meeting this requirement, in the context of state-of-the-art techniques for light trapping and surface passivation. We show that our predictions are within the capability of present day silicon technologies.

  1. Numerical investigation of thermal history and residual stress of grown multi-crystalline silicon at the various growth stages for PV applications

    NASA Astrophysics Data System (ADS)

    Srinivasan, M.; Ramasamy, P.

    2016-05-01

    The directional solidification is a very important technique for growing high quality multi-crystalline silicon at large scale for PV solar cells. Time dependent numerical modelling of the temperature distribution, residual stress in multi-crystalline silicon ingots grown by directional solidification has been investigated for five growth stage. The computation was carried in a 2D axis symmetric model by the finite volume method. The history of temperature distribution, stress generation, are tracked in our modelling continuously to consider the growth process from the beginning to the end of solidification process. This paper is aimed to achieve an advanced understanding of the thermal and mechanical behavior of grown crystal.

  2. Direct growth of single-crystalline III–V semiconductors on amorphous substrates

    DOE PAGESBeta

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M.; Tsang, Michael; Zeng, Yuping; et al

    2016-01-27

    The III–V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III–V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III–V’s on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III–V’s of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. Themore » patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. In conclusion, the work presents an important advance towards universal integration of III–V’s on application-specific substrates by direct growth.« less

  3. Direct growth of single-crystalline III-V semiconductors on amorphous substrates

    NASA Astrophysics Data System (ADS)

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M.; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager, Joel W., III; Chrzan, Daryl C.; Javey, Ali

    2016-01-01

    The III-V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III-V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III-V's on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III-V's of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. The work presents an important advance towards universal integration of III-V's on application-specific substrates by direct growth.

  4. Direct growth of single-crystalline III–V semiconductors on amorphous substrates

    PubMed Central

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M.; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager III, Joel W.; Chrzan, Daryl C.; Javey, Ali

    2016-01-01

    The III–V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III–V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III–V's on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III–V's of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. The work presents an important advance towards universal integration of III–V's on application-specific substrates by direct growth. PMID:26813257

  5. Direct growth of single-crystalline III-V semiconductors on amorphous substrates.

    PubMed

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager Iii, Joel W; Chrzan, Daryl C; Javey, Ali

    2016-01-01

    The III-V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III-V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III-V's on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III-V's of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. The work presents an important advance towards universal integration of III-V's on application-specific substrates by direct growth. PMID:26813257

  6. Single impact crater functions for ion bombardment of silicon

    SciTech Connect

    Kalyanasundaram, N.; Ghazisaeidi, M.; Freund, J. B.; Johnson, H. T.

    2008-03-31

    The average effect of a single 500 eV incident argon ion on a silicon surface is studied using molecular dynamics simulations. More than 10{sup 3} ion impacts at random surface points are averaged for each of seven incidence angles, from 0 deg. to 28 deg. off normal, to determine a local surface height change function, or a crater function. The crater shapes are mostly determined by mass rearrangement; sputtering has a relatively small effect. Analytical fitting functions are provided for several cases, and may serve as input into kinetic Monte Carlo calculations or stability analyses for surfaces subjected to ion bombardment.

  7. Stress effects on the initial lithiation of crystalline silicon nanowires: reactive molecular dynamics simulations using ReaxFF.

    PubMed

    Ostadhossein, Alireza; Cubuk, Ekin D; Tritsaris, Georgios A; Kaxiras, Efthimios; Zhang, Sulin; van Duin, Adri C T

    2015-02-01

    Silicon (Si) has been recognized as a promising anode material for the next-generation high-capacity lithium (Li)-ion batteries because of its high theoretical energy density. Recent in situ transmission electron microscopy (TEM) revealed that the electrochemical lithiation of crystalline Si nanowires (c-SiNWs) proceeds by the migration of the interface between the lithiated Si (LixSi) shell and the pristine unlithiated core, accompanied by solid-state amorphization. The underlying atomic mechanisms of Li insertion into c-Si remain poorly understood. Herein, we perform molecular dynamics (MD) simulations using the reactive force field (ReaxFF) to characterize the lithiation process of c-SiNWs. Our calculations show that ReaxFF can accurately reproduce the energy barriers of Li migration from DFT calculations in both crystalline (c-Si) and amorphous Si (a-Si). The ReaxFF-based MD simulations reveal that Li insertion into interlayer spacing between two adjacent (111) planes results in the peeling-off of the (111) facets and subsequent amorphization, in agreement with experimental observations. We find that breaking of the Si-Si bonds between (111)-bilayers requires a rather high local Li concentration, which explains the atomically sharp amorphous-crystalline interface (ACI). Our stress analysis shows that lithiation induces compressive stress at the ACI layer, causing retardation or even the stagnation of the reaction front, also in good agreement with TEM observations. Lithiation at high temperatures (e.g. 1200 K) shows that Li insertion into c-SiNW results in an amorphous to crystalline phase transformation at Li : Si composition of ∼4.2 : 1. Our modeling results provide a comprehensive picture of the effects of reaction and diffusion-induced stress on the interfacial dynamics and mechanical degradation of SiNW anodes under chemo-mechanical lithiation. PMID:25559797

  8. Stress effects on the initial lithiation of crystalline silicon nanowires: Reactive molecular dynamics simulations using ReaxFF

    DOE PAGESBeta

    Ostadhossein, Alireza; Cubuk, Ekin D.; Tritsaris, Georgios A.; Kaxiras, Efthimios; Zhang, Sulin; Adri C. T. van Duin

    2014-12-18

    Silicon (Si) has been recognized as a promising anode material for the next-generation high-capacity lithium (Li)-ion batteries because of its high theoretical energy density. Recent in situ transmission electron microscopy (TEM) revealed that the electrochemical lithiation of crystalline Si nanowires (c-SiNWs) proceeds by the migration of the interface between the lithiated Si (LixSi) shell and the pristine unlithiated core, accompanied by solid-state amorphization. The underlying atomic mechanisms of Li insertion into c-Si remain poorly understood. In this research, we perform molecular dynamics (MD) simulations using the reactive force field (ReaxFF) to characterize the lithiation process of c-SiNWs. Our calculations showmore » that ReaxFF can accurately reproduce the energy barriers of Li migration from DFT calculations in both crystalline (c-Si) and amorphous Si (a-Si). The ReaxFF-based MD simulations reveal that Li insertion into interlayer spacing between two adjacent (111) planes results in the peeling-off of the (111) facets and subsequent amorphization, in agreement with experimental observations. We find that breaking of the Si–Si bonds between (111)-bilayers requires a rather high local Li concentration, which explains the atomically sharp amorphous–crystalline interface (ACI). Our stress analysis shows that lithiation induces compressive stress at the ACI layer, causing retardation or even the stagnation of the reaction front, also in good agreement with TEM observations. Lithiation at high temperatures (e.g. 1200 K) shows that Li insertion into c-SiNW results in an amorphous to crystalline phase transformation at Li : Si composition of ~4.2:1. In conclusion, our modeling results provide a comprehensive picture of the effects of reaction and diffusion-induced stress on the interfacial dynamics and mechanical degradation of SiNW anodes under chemo-mechanical lithiation.« less

  9. Stress effects on the initial lithiation of crystalline silicon nanowires: Reactive molecular dynamics simulations using ReaxFF

    SciTech Connect

    Ostadhossein, Alireza; Cubuk, Ekin D.; Tritsaris, Georgios A.; Kaxiras, Efthimios; Zhang, Sulin; Adri C. T. van Duin

    2014-12-18

    Silicon (Si) has been recognized as a promising anode material for the next-generation high-capacity lithium (Li)-ion batteries because of its high theoretical energy density. Recent in situ transmission electron microscopy (TEM) revealed that the electrochemical lithiation of crystalline Si nanowires (c-SiNWs) proceeds by the migration of the interface between the lithiated Si (LixSi) shell and the pristine unlithiated core, accompanied by solid-state amorphization. The underlying atomic mechanisms of Li insertion into c-Si remain poorly understood. In this research, we perform molecular dynamics (MD) simulations using the reactive force field (ReaxFF) to characterize the lithiation process of c-SiNWs. Our calculations show that ReaxFF can accurately reproduce the energy barriers of Li migration from DFT calculations in both crystalline (c-Si) and amorphous Si (a-Si). The ReaxFF-based MD simulations reveal that Li insertion into interlayer spacing between two adjacent (111) planes results in the peeling-off of the (111) facets and subsequent amorphization, in agreement with experimental observations. We find that breaking of the Si–Si bonds between (111)-bilayers requires a rather high local Li concentration, which explains the atomically sharp amorphous–crystalline interface (ACI). Our stress analysis shows that lithiation induces compressive stress at the ACI layer, causing retardation or even the stagnation of the reaction front, also in good agreement with TEM observations. Lithiation at high temperatures (e.g. 1200 K) shows that Li insertion into c-SiNW results in an amorphous to crystalline phase transformation at Li : Si composition of ~4.2:1. In conclusion, our modeling results provide a comprehensive picture of the effects of reaction and diffusion-induced stress on the interfacial dynamics and mechanical degradation of SiNW anodes under chemo-mechanical lithiation.

  10. 18th Workshop on Crystalline Silicon Solar Cells and Modules: Materials and Processes; Workshop Proceedings, 3-6 August 2008, Vail, Colorado

    SciTech Connect

    Sopori, B. L.

    2008-09-01

    The National Center for Photovoltaics sponsored the 18th Workshop on Crystalline Silicon Solar Cells & Modules: Materials and Processes, held in Vail, CO, August 3-6, 2008. This meeting provided a forum for an informal exchange of technical and scientific information between international researchers in the photovoltaic and relevant non-photovoltaic fields. The theme of this year's meeting was 'New Directions for Rapidly Growing Silicon Technologies.'

  11. New Approaches for Passivation of Crystalline and Amorphous Silicon: Cooperative Research and Development Final Report, CRADA Number CRD-09-351

    SciTech Connect

    Sopori, B.

    2012-09-01

    New approaches of passivating crystalline, multicrystalline, and amorphous silicon will be explored. These will include the use of aqueous solution of KCN and a proprietary composition formulated by Mallinckrodt Baker, Inc. The surface passivation will be compared with that provided by an iodine-ethanol solution, and bulk passivation will be compared with that of H-passivation obtained by silicon nitride, in a fire-through process.

  12. Magnetic properties of single crystalline expanded austenite obtained by plasma nitriding of austenitic stainless steel single crystals.

    PubMed

    Menéndez, Enric; Templier, Claude; Garcia-Ramirez, Pablo; Santiso, José; Vantomme, André; Temst, Kristiaan; Nogués, Josep

    2013-10-23

    Ferromagnetic single crystalline [100], [110], and [111]-oriented expanded austenite is obtained by plasma nitriding of paramagnetic 316L austenitic stainless steel single crystals at either 300 or 400 °C. After nitriding at 400 °C, the [100] direction appears to constitute the magnetic easy axis due to the interplay between a large lattice expansion and the expected decomposition of the expanded austenite, which results in Fe- and Ni-enriched areas. However, a complex combination of uniaxial (i.e., twofold) and biaxial (i.e., fourfold) in-plane magnetic anisotropies is encountered. It is suggested that the former is related to residual stress-induced effects while the latter is associated to the in-plane projections of the cubic lattice symmetry. Increasing the processing temperature strengthens the biaxial in-plane anisotropy in detriment of the uniaxial contribution, in agreement with a more homogeneous structure of expanded austenite with lower residual stresses. In contrast to polycrystalline expanded austenite, single crystalline expanded austenite exhibits its magnetic easy axes along basic directions. PMID:24028676

  13. Electrochemical preparation of single-crystalline Cr 2O 3 from molten salts

    NASA Astrophysics Data System (ADS)

    Abe, Hideki; Nishida, Kenji; Imai, Motoharu; Kitazawa, Hideaki

    2004-06-01

    Single crystals of Cr 2O 3 have been grown by means of electrolysis on a 1:100 stoichiometric mixture of CrO 3 and cesium molybdate, Cs 2MoO 4, fused at 1000°C in an ambient atmosphere. Potentiometric measurements on the molten salts have shown the existence of a critical voltage of -320 mV below which hexagonal platelets-shaped single-crystalline Cr 2O 3 is grown on the surface of the working electrode. Coulometry measurements have revealed that the Cr ions are at their highest oxidation state of Cr +6 in the molten electrolyte, which suggests that the electric reduction of Cr +6 to Cr +3 drives the single-crystal growth of Cr 2O 3.

  14. Reversible Sodium Ion Insertion in Single Crystalline Manganese Oxide Nanowires with Long Cycle Life

    SciTech Connect

    Cao, Yuliang; Xiao, Lifen; Wang, Wei; Choi, Daiwon; Nie, Zimin; Yu, Jianguo; Saraf, Laxmikant V.; Yang, Zhenguo; Liu, Jun

    2011-07-26

    Single crystalline Na4Mn9O18 nanowires were synthesized via pyrolysis of polyacrylate salt precursors prepared by in-situ polymerization of the metal salts and acrylate acid, followed by calcinations at an appropriate temperature to achieve good crystalline structure and uniform nanowire morphology with an average diameter of 50 nm. The Na4Mn9O18 nanowires have shown a high, reversible, and near theoretical sodium ion insertion capacity (128 mA h g-1 at 0.1C), excellent long cyclability (77% capacity retention for 1000 cycles at 0.5 C), along with good rate capability. Good capacity and charge-discharge stability are also observed for full cell experiments using a pyrolyzed carbon as the anode, therefore demonstrating the potential of these materials for sodium-ion batteries for large scale energy storage. Furthermore, this research shows that a good crystallinity and small particles are required to enhance the Na-ion diffusion and increase the stability of the electrode materials for long charge-discharge cycles.

  15. Large-scale growth of millimeter-long single-crystalline ZnS nanobelts

    SciTech Connect

    Li Jianye Zhang Qi; An Lei; Qin Luchang; Liu Jie

    2008-11-15

    Millimeter-long single-crystalline hexagonal ZnS nanobelts were grown on specific locations on a wafer scale. This is the first time that the millimeter-scale ZnS nanobelt has been synthesized. The longest nanobelts are about 3 mm. The as-grown nanobelts were characterized by means of field emission scanning electron microscopy, X-ray powder diffraction, high-resolution transmission electron microscopy, and selected area electron diffraction. The results indicate that the ultra-long nanobelts are pure single-crystalline hexagonal ZnS. There are two kinds of ZnS nanobelts existing in the products. One is the nanobelts that have two smooth sides and grow along the [0 0 1] longitudinal direction, and the other is the nanobelts that have one smooth side and one saw-teeth-like side, namely nanosaws, and grow along the [2 1 0] longitudinal direction. A vapor-liquid-solid mechanism is suggested for the lengthwise growth of the ZnS nanobelts (nanosaws) and a vapor-solid mechanism for the side direction growth of the saw-teeth of the nanosaws. - Graphical Abstract: Millimeter-long single-crystalline ZnS nanobelts were grown on specific locations on a large scale. There are two kinds of nanobelts in the products-one has two smooth sides, and the other has one smooth side and one saw-teeth-like side, namely nanosaws. Mechanisms for the longitudinal direction growth of the nanobelts/nanosaws and the side saw-teeth direction growth of the nanosaws are discussed.

  16. Investigation of the nonlinear refractive index of single-crystalline thin gold films and plasmonic nanostructures

    NASA Astrophysics Data System (ADS)

    Goetz, Sebastian; Razinskas, Gary; Krauss, Enno; Dreher, Christian; Wurdack, Matthias; Geisler, Peter; Pawłowska, Monika; Hecht, Bert; Brixner, Tobias

    2016-04-01

    The nonlinear refractive index of plasmonic materials may be used to obtain nonlinear functionality, e.g., power-dependent switching. Here, we investigate the nonlinear refractive index of single-crystalline gold in thin layers and nanostructures on dielectric substrates. In a first step, we implement a z-scan setup to investigate ~100-µm-sized thin-film samples. We determine the nonlinear refractive index of fused silica, n 2(SiO2) = 2.9 × 10-20 m2/W, in agreement with literature values. Subsequent z-scan measurements of single-crystalline gold films reveal a damage threshold of 0.22 TW/cm2 and approximate upper limits of the real and imaginary parts of the nonlinear refractive index, | n 2'(Au)| < 1.2 × 10-16 m2/W and | n 2″(Au)| < 0.6 × 10-16 m2/W, respectively. To further determine possible effects of a nonlinear refractive index in plasmonic circuitry, interferometry is proposed as a phase-sensitive probe. In corresponding nanostructures, relative phase changes between two propagating near-field modes are converted to amplitude changes by mode interference. Power-dependent experiments using sub-10-fs near-infrared pulses and diffraction-limited resolution (NA = 1.4) reveal linear behavior up to the damage threshold (0.23 times relative to that of a solid single-crystalline gold film). An upper limit for the nonlinear power-dependent phase change between two propagating near-field modes is determined to Δ φ < 0.07 rad.

  17. Amorphous/crystalline silicon interface passivation: Ambient-temperature dependence and implications for solar cell performance

    DOE PAGESBeta

    Seif, Johannes P.; Krishnamani, Gopal; Demaurex, Benedicte; Ballif, Christophe; Wolf, Stefaan De

    2015-03-02

    Silicon heterojunction (SHJ) solar cells feature amorphous silicon passivation films, which enable very high voltages. We report how such passivation increases with operating temperature for amorphous silicon stacks involving doped layers and decreases for intrinsic-layer-only passivation. We discuss the implications of this phenomenon on the solar cell's temperature coefficient, which represents an important figure-of-merit for the energy yield of devices deployed in the field. We show evidence that both open-circuit voltage (Voc) and fill factor (FF) are affected by these variations in passivation and quantify these temperature-mediated effects, compared with those expected from standard diode equations. We confirm that devicesmore » with high Voc values at 25°C show better high-temperature performance. Thus, we also argue that the precise device architecture, such as the presence of charge-transport barriers, may affect the temperature-dependent device performance as well.« less

  18. Amorphous/crystalline silicon interface passivation: Ambient-temperature dependence and implications for solar cell performance

    SciTech Connect

    Seif, Johannes P.; Krishnamani, Gopal; Demaurex, Benedicte; Ballif, Christophe; Wolf, Stefaan De

    2015-03-02

    Silicon heterojunction (SHJ) solar cells feature amorphous silicon passivation films, which enable very high voltages. We report how such passivation increases with operating temperature for amorphous silicon stacks involving doped layers and decreases for intrinsic-layer-only passivation. We discuss the implications of this phenomenon on the solar cell's temperature coefficient, which represents an important figure-of-merit for the energy yield of devices deployed in the field. We show evidence that both open-circuit voltage (Voc) and fill factor (FF) are affected by these variations in passivation and quantify these temperature-mediated effects, compared with those expected from standard diode equations. We confirm that devices with high Voc values at 25°C show better high-temperature performance. Thus, we also argue that the precise device architecture, such as the presence of charge-transport barriers, may affect the temperature-dependent device performance as well.

  19. Free-Standing Two-Dimensional Single-Crystalline InSb Nanosheets.

    PubMed

    Pan, D; Fan, D X; Kang, N; Zhi, J H; Yu, X Z; Xu, H Q; Zhao, J H

    2016-02-10

    Growth of high-quality single-crystalline InSb layers remains challenging in material science. Such layered InSb materials are highly desired for searching for and manipulation of Majorana Fermions in solid state, a fundamental research task in physics today, and for development of novel high-speed nanoelectronic and infrared optoelectronic devices. Here, we report on a new route toward growth of single-crystalline, layered InSb materials. We demonstrate the successful growth of free-standing, two-dimensional InSb nanosheets on one-dimensional InAs nanowires by molecular-beam epitaxy. The grown InSb nanosheets are pure zinc-blende single crystals. The length and width of the InSb nanosheets are up to several micrometers and the thickness is down to ∼10 nm. The InSb nanosheets show a clear ambipolar behavior and a high electron mobility. Our work will open up new technology routes toward the development of InSb-based devices for applications in nanoelectronics, optoelectronics, and quantum electronics and for the study of fundamental physical phenomena. PMID:26788662

  20. PbO networks composed of single crystalline nanosheets synthesized by a facile chemical precipitation method

    SciTech Connect

    Samberg, Joshua P.; Kajbafvala, Amir; Koolivand, Amir

    2014-03-01

    Graphical abstract: - Highlights: • Synthesis of PbO networks through a simple chemical precipitation route. • The synthesis method is rapid and low-cost. • Each network is composed of single crystalline PbO nanosheets. • A possible growth mechanism is proposed for synthesized PbO networks. - Abstract: For the field of energy storage, nanostructured lead oxide (PbO) shows immense potential for increased specific energy and deep discharge for lead acid battery technologies. In this work, PbO networks composed of single crystalline nanosheets were synthesized utilizing a simple, low cost and rapid chemical precipitation method. The PbO networks were prepared in a single reaction vessel from starting reagents of lead acetate dehydrate, ammonium hydroxide and deionized water. Lead acetate dehydrate was chosen as a reagent, as opposed to lead nitrate, to eliminate the possibility of nitrate contamination of the final product. X-ray diffraction (XRD) analysis, high resolution scanning electron microscopy (HRSEM) and high resolution transmission electron microscopy (HRTEM) analysis were used to characterize the synthesized PbO networks. The reproducible method described herein synthesized pure β-PbO (massicot) powders, with no byproducts. A possible formation mechanism for these PbO networks is proposed. The growth is found to proceed predominately in the 〈1 1 1〉 and 〈2 0 0〉 directions while being limited in the 〈0 1 1〉 direction.

  1. Self-assembled single-crystal silicon circuits on plastic

    PubMed Central

    Stauth, Sean A.; Parviz, Babak A.

    2006-01-01

    We demonstrate the use of self-assembly for the integration of freestanding micrometer-scale components, including single-crystal, silicon field-effect transistors (FETs) and diffusion resistors, onto flexible plastic substrates. Preferential self-assembly of multiple microcomponent types onto a common platform is achieved through complementary shape recognition and aided by capillary, fluidic, and gravitational forces. We outline a microfabrication process that yields single-crystal, silicon FETs in a freestanding, powder-like collection for use with self-assembly. Demonstrations of self-assembled FETs on plastic include logic inverters and measured electron mobility of 592 cm2/V-s. Finally, we extend the self-assembly process to substrates each containing 10,000 binding sites and realize 97% self-assembly yield within 25 min for 100-μm-sized elements. High-yield self-assembly of micrometer-scale functional devices as outlined here provides a powerful approach for production of macroelectronic systems. PMID:16968780

  2. Mutiple Czochralski growth of silicon crystals from a single crucible

    NASA Technical Reports Server (NTRS)

    Lane, R. L.; Kachare, A. H.

    1980-01-01

    An apparatus for the Czochralski growth of silicon crystals is presented which is capable of producing multiple ingots from a single crucible. The growth chamber features a refillable crucible with a water-cooled, vacuum-tight isolation valve located between the pull chamber and the growth furnace tank which allows the melt crucible to always be at vacuum or low argon pressure when retrieving crystal or introducing recharge polysilicon feed stock. The grower can thus be recharged to obtain 100 kg of silicon crystal ingots from one crucible, and may accommodate crucibles up to 35 cm in diameter. Evaluation of the impurity contents and I-V characteristics of solar cells fabricated from seven ingots grown from two crucibles reveals a small but consistent decrease in cell efficiency from 10.4% to 9.6% from the first to the fourth ingot made in a single run, which is explained by impurity build-up in the residual melt. The crystal grower thus may offer economic benefits through the extension of crucible lifetime and the reduction of furnace downtime.

  3. Silicon technologies for arrays of Single Photon Avalanche Diodes

    NASA Astrophysics Data System (ADS)

    Gulinatti, Angelo; Ceccarelli, Francesco; Rech, Ivan; Ghioni, Massimo

    2016-05-01

    In order to fulfill the requirements of many applications, we recently developed a new technology aimed at combining the advantages of traditional thin and thick silicon Single Photon Avalanche Diodes (SPAD). In particular we demonstrated single-pixel detectors with a remarkable improvement in the Photon Detection Efficiency in the red/nearinfrared spectrum (e.g. 40% at 800nm) while maintaining a timing jitter better than 100ps. In this paper we discuss the limitations of such Red-Enhanced (RE) technology from the point of view of the fabrication of small arrays of SPAD and we propose modifications to the structure aimed at overcoming these issues. We also report the first preliminary experimental results attained on devices fabricated adopting the improved structure.

  4. Characterization of oxide scales thermally formed on single-crystal silicon carbide.

    PubMed

    Chayasombat, B; Kato, T; Hirayama, T; Tokunaga, T; Sasaki, K; Kuroda, K

    2010-08-01

    Microstructures of oxide scales thermally formed on single-crystal silicon carbide were investigated using transmission electron microscopy. The oxide scales were formed on the Si-face of 6H-SiC at 1273-1473 K in dry oxygen. Spherical patterns were observed on the surfaces of the oxidized samples by an optical microscope in some regions. In these regions, cross-sectional transmission electron microscopy (TEM) observations show that the oxide scale was divided into two layers; the upper layer (surface side) was composed of crystalline silica, and the lower layer on the silicon carbide substrate was amorphous silica, while the oxide scales in the surroundings of the patterns were composed of only amorphous silica. The oxidation activation energy in the amorphous silica layer of the Si-face of 6H-SiC was found to be 408 kJ/mol by the evolution of thickness directly measured from the cross-sectional scanning electron microscopy and TEM images. PMID:20554755

  5. Plasma-assisted self-sharpening of platelet-structured single-crystalline carbon nanocones

    SciTech Connect

    Levchenko, I.; Ostrikov, K.; Long, J. D.; Xu, S.

    2007-09-10

    A mechanism and model for the vertical growth of platelet-structured vertically aligned single-crystalline carbon nanostructures by the formation of graphene layers on a flat top surface are proposed and verified experimentally. It is demonstrated that plasma-related effects lead to self-sharpening of tapered nanocones to form needlelike nanostructures, in a good agreement with the predicted dependence of the radius of a nanocone's flat top on the incoming ion flux and surface temperature. The growth mechanism is relevant to a broad class of nanostructures including nanotips, nanoneedles, and nanowires and can be used to improve the predictability of nanofabrication processes.

  6. Multiple charge-density-wave transitions in single-crystalline Lu2Ir3Si5

    NASA Astrophysics Data System (ADS)

    Sangeetha, N. S.; Thamizhavel, A.; Tomy, C. V.; Basu, Saurabh; Awasthi, A. M.; Rajak, Piu; Bhattacharyya, Somnath; Ramakrishnan, S.; Pal, D.

    2015-05-01

    The physical properties of the single-crystalline samples of Lu2Ir3Si5 have been investigated by magnetic susceptibility, resistivity, and heat capacity studies. We observed multiple charge-density-wave (CDW) transitions in all the measurements. A strong thermal hysteresis at these transitions suggests a possible first order CDW ordering. In addition, the first order nature is ascertained by a very narrow and a huge cusp (62 J/mol K) in the zero field specific heat data which also suggests strong electron-phonon interchain coupling.

  7. Electric dipolar interaction assisted growth of single crystalline organic thin films

    SciTech Connect

    Jin-ming, Cai; Yu-Yang, Zhang; Hao, Hu; Li-Hong, Bao; Li-Da, Pan; Wei, Tang; Guo, Li; Shi-Xuan, Du; Jian, Shen; Hong-Jun, Gao

    2010-01-01

    We report on a forest-like-to-desert-like pattern evolution in the growth of an organic thin film observed by using an atomic force microscope. We use a modified diffusion limited aggregation model to simulate the growth process and are able to reproduce the experimental patterns. The energy of electric dipole interaction is calculated and determined to be the driving force for the pattern formation and evolution. Based on these results, single crystalline films are obtained by enhancing the electric dipole interaction while limiting effects of other growth parameters.

  8. Proton irradiation effects on the thermoelectric properties in single-crystalline Bi nanowires

    SciTech Connect

    Chang, Taehoo; Kim, Jeongmin; Song, Min-Jung; Lee, Wooyoung

    2015-05-15

    The effects of proton irradiation on the thermoelectric properties of Bi nanowires (Bi-NWs) were investigated. Single crystalline Bi-NWs were grown by the on-film formation of nanowires method. The devices based on individual Bi-NWs were irradiated with protons at different energies. The total number of displaced atoms was estimated using the Kinchin-Pease displacement model. The electric conductivity and Seebeck coefficient in the Bi-NW devices were investigated before and after proton irradiation at different temperatures. Although the Seebeck coefficient remained stable at various irradiation energies, the electrical conductivity significantly declined with increasing proton energy up to 40 MeV.

  9. Self-assembly of gold nanoparticles on a single crystalline sapphire substrate

    NASA Astrophysics Data System (ADS)

    Takahashi, Hiroyuki; Shirahata, Naoto; Narushima, Takashi; Yonezawa, Tetsu

    2012-12-01

    Single crystalline sapphire is an atomically flat substrate with a high transparency in a wide wavelength region. However, its surface is chemically stable so that the modification by a self-assembled monolayer is somewhat difficult. We have used a H2O2 treatment at 70 °C to activate the surface and modified with a silan coupling reagent. The modification of the surface is discussed with the water contact angle. Immobilization of citrate-stabilized anionic gold nanoparticles on a cationically modified sapphire surface was carried out.

  10. Versatile method for template-free synthesis of single crystalline metal and metal alloy nanowires

    NASA Astrophysics Data System (ADS)

    Scott, John A.; Totonjian, Daniel; Martin, Aiden A.; Tran, Toan Trong; Fang, Jinghua; Toth, Milos; McDonagh, Andrew M.; Aharonovich, Igor; Lobo, Charlene J.

    2016-01-01

    Metal and metal alloy nanowires have applications ranging from spintronics to drug delivery, but high quality, high density single crystalline materials have been surprisingly difficult to fabricate. Here we report a versatile, template-free, self-assembly method for fabrication of single crystalline metal and metal alloy nanowires (Co, Ni, NiCo, CoFe, and NiFe) by reduction of metal nitride precursors formed in situ by reaction of metal salts with a nitrogen source. Thiol reduction of the metal nitrides to the metallic phase at 550-600 °C results in nanowire growth. In this process, sulfur acts as a uniaxial structure-directing agent, passivating the surface of the growing nanowires and preventing radial growth. The versatility of the method is demonstrated by achieving nanowire growth from gas-phase, solution-phase or a combination of gas- and solution-phase precursors. The fabrication method is suited to large-area CVD on a wide range of solid substrates.Metal and metal alloy nanowires have applications ranging from spintronics to drug delivery, but high quality, high density single crystalline materials have been surprisingly difficult to fabricate. Here we report a versatile, template-free, self-assembly method for fabrication of single crystalline metal and metal alloy nanowires (Co, Ni, NiCo, CoFe, and NiFe) by reduction of metal nitride precursors formed in situ by reaction of metal salts with a nitrogen source. Thiol reduction of the metal nitrides to the metallic phase at 550-600 °C results in nanowire growth. In this process, sulfur acts as a uniaxial structure-directing agent, passivating the surface of the growing nanowires and preventing radial growth. The versatility of the method is demonstrated by achieving nanowire growth from gas-phase, solution-phase or a combination of gas- and solution-phase precursors. The fabrication method is suited to large-area CVD on a wide range of solid substrates. Electronic supplementary information (ESI) available

  11. Synthesis and ethanol sensing characteristics of single crystalline SnO2 nanorods

    NASA Astrophysics Data System (ADS)

    Chen, Y. J.; Xue, X. Y.; Wang, Y. G.; Wang, T. H.

    2005-12-01

    In a basic water-alcohol mixing solution without any other toxically organic solvents, the single crystalline SnO2 nanorods with diameters of 4-15 nm and lengths of 100-200 nm were synthesized using SnCl4 as a precursor. The sensors fabricated from the nanorods exhibited the sensitivity of 31.4 for 300 ppm of ethanol. Both the response and recovery time are short, around 1 s. Moreover, a linear dependence of the sensitivity on the ethanol concentration was observed. These behaviors were well explained by considering the high surface-to-volume ratio of the nanorods.

  12. Thin-film transistor fabricated in single-crystalline transparent oxide semiconductor.

    PubMed

    Nomura, Kenji; Ohta, Hiromichi; Ueda, Kazushige; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

    2003-05-23

    We report the fabrication of transparent field-effect transistors using a single-crystalline thin-film transparent oxide semiconductor, InGaO3(ZnO)5, as an electron channel and amorphous hafnium oxide as a gate insulator. The device exhibits an on-to-off current ratio of approximately 106 and a field-effect mobility of approximately 80 square centimeters per volt per second at room temperature, with operation insensitive to visible light irradiation. The result provides a step toward the realization of transparent electronics for next-generation optoelectronics. PMID:12764192

  13. Silicon nitride/silicon carbide composite powders

    DOEpatents

    Dunmead, Stephen D.; Weimer, Alan W.; Carroll, Daniel F.; Eisman, Glenn A.; Cochran, Gene A.; Susnitzky, David W.; Beaman, Donald R.; Nilsen, Kevin J.

    1996-06-11

    Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

  14. Antifuse with a single silicon-rich silicon nitride insulating layer

    DOEpatents

    Habermehl, Scott D.; Apodaca, Roger T.

    2013-01-22

    An antifuse is disclosed which has an electrically-insulating region sandwiched between two electrodes. The electrically-insulating region has a single layer of a non-hydrogenated silicon-rich (i.e. non-stoichiometric) silicon nitride SiN.sub.X with a nitrogen content X which is generally in the range of 0silicon. Arrays of antifuses can also be formed.

  15. A silicon carbide room-temperature single-photon source.

    PubMed

    Castelletto, S; Johnson, B C; Ivády, V; Stavrias, N; Umeda, T; Gali, A; Ohshima, T

    2014-02-01

    Over the past few years, single-photon generation has been realized in numerous systems: single molecules, quantum dots, diamond colour centres and others. The generation and detection of single photons play a central role in the experimental foundation of quantum mechanics and measurement theory. An efficient and high-quality single-photon source is needed to implement quantum key distribution, quantum repeaters and photonic quantum information processing. Here we report the identification and formation of ultrabright, room-temperature, photostable single-photon sources in a device-friendly material, silicon carbide (SiC). The source is composed of an intrinsic defect, known as the carbon antisite-vacancy pair, created by carefully optimized electron irradiation and annealing of ultrapure SiC. An extreme brightness (2×10(6) counts s(-1)) resulting from polarization rules and a high quantum efficiency is obtained in the bulk without resorting to the use of a cavity or plasmonic structure. This may benefit future integrated quantum photonic devices. PMID:24240243

  16. Crystalline-silicon solar cell development sponsored by the US Department of Energy

    NASA Astrophysics Data System (ADS)

    Basore, P. A.

    Activities planned for the current fiscal year at Sandia National Laboratories include investigation of specific industrial cell processing issues using Sandia's Photovoltaic Device Processing Laboratory (PDFL), as well as several processing issues of general interest to companies using multicrystalline silicon. A significant and difficult goal for Sandia this year will be the fabrication of a 15% efficient prototype module using large-area multicrystalline cells. Sandia also provides primary funding for the University Center of Excellence in Photovoltaic Research and Education at the Georgia Institute of Technology. The National Renewable Energy Laboratory's (NREL's) plans for c-Si this fiscal year include continuation of the University Silicon Materials Research Program, which funds research at six universities to study the effect of cell processing on the properties of silicon materials. As the lead DOS laboratory for thin film technologies, NREL supports the development of thin film silicon cells by providing both funding and expertise. NREL also provides substantial funding to the PV industry through the PV Manufacturing Technology (PVMaT) initiative, some of which supports the development of c-Si cell technology either directly or indirectly.

  17. Fundamental Research and Development for Improved Crystalline Silicon Solar Cells: Final Subcontract Report, March 2002 - July 2006

    SciTech Connect

    Rohatgi, A.

    2007-11-01

    This report summarizes the progress made by Georgia Tech in the 2002-2006 period toward high-efficiency, low-cost crystalline silicon solar cells. This program emphasize fundamental and applied research on commercial substrates and manufacturable technologies. A combination of material characterization, device modeling, technology development, and complete cell fabrication were used to accomplish the goals of this program. This report is divided into five sections that summarize our work on i) PECVD SiN-induced defect passivation (Sections 1 and 2); ii) the effect of material inhomogeneity on the performance of mc-Si solar cells (Section 3); iii) a comparison of light-induced degradation in commercially grown Ga- and B-doped Czochralski Si ingots (Section 4); and iv) the understanding of the formation of high-quality thick-film Ag contacts on high sheet-resistance emitters (Section 5).

  18. In-Situ Measurement of Power Loss for Crystalline Silicon Modules Undergoing Thermal Cycling and Mechanical Loading Stress Testing: Preprint

    SciTech Connect

    Spataru, Sergiu; Hacke, Pater; Sera, Dezso

    2015-09-15

    We analyze the degradation of multi-crystalline silicon photovoltaic modules undergoing simultaneous thermal, mechanical, and humidity stress testing to develop a dark environmental chamber in-situ measurement procedure for determining module power loss. From the analysis we determine three main categories of failure modes associated with the module degradation consisting of: shunting, recombination losses, increased series resistance losses, and current mismatch losses associated with a decrease in photo-current generation by removal of some cell areas due to cell fractures. Based on the analysis, we propose an in-situ module power loss monitoring procedure that relies on dark current-voltage measurements taken during the stress test, and initial and final module flash testing, to determine the power degradation characteristic of the module.

  19. Dynamic simulation of impurity transport and chemical reactions in a Bridgman furnace for directional solidification of multi-crystalline silicon

    NASA Astrophysics Data System (ADS)

    Bellmann, M. P.; Panjwani, B.; Syvertsen, M.; Meese, E. A.

    2013-04-01

    Numerical results from a dynamic simulation of impurity transport and reactions in a Bridgman furnace for directional solidification of multi-crystalline silicon are presented and compared to experimental results. The simulation includes the calculation of the thermal field, melt and gas flow velocity field, transport and chemical reactions of oxygen and carbon impurities for the entire process based on heating, melting and solidification phases. Carbon and oxygen distribution in the ingot is analyzed experimentally by means of FT-IR spectroscopy and LECO combustion method, the CO development by means of an μ-GC gas analyzer. The simulated impurity distribution in the ingot and the CO development above the free melt surface are in good agreement with the experimental results. Furthermore the results indicate that the carbon solubility limit is already reached at the stage of melting and SiC precipitates are likely to form at the early stage of growth.

  20. 16th Workshop on Crystalline Silicon Solar Cells and Modules: Materials and Processes; Program, Extended Abstracts, and Papers

    SciTech Connect

    Sopori, B. L.

    2006-08-01

    The National Center for Photovoltaics sponsored the 16th Workshop on Crystalline Silicon Solar Cells and Modules: Materials and Processes held August 6-9, 2006 in Denver, Colorado. The workshop addressed the fundamental properties of PV-Si, new solar cell designs, and advanced solar cell processing techniques. It provided a forum for an informal exchange of technical and scientific information between international researchers in the photovoltaic and relevant non-photovoltaic fields. The Workshop Theme was: "Getting more (Watts) for Less ($i)". A combination of oral presentations by invited speakers, poster sessions, and discussion sessions reviewed recent advances in crystal growth, new cell structures, new processes and process characterization techniques, and cell fabrication approaches suitable for future manufacturing demands. The special sessions included: Feedstock Issues: Si Refining and Purification; Metal-impurity Engineering; Thin Film Si; and Diagnostic Techniques.

  1. Friction and wear behavior of single-crystal silicon carbide in contact with titanium

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1977-01-01

    Sliding friction experiments were conducted with single crystal silicon carbide in sliding contact with titanium. Results indicate that the friction coefficient is greater in vacuum than in argon and that this is due to the greater adhesion or adhesive transfer in vacuum. Thin films of silicon carbide transferred to titanium also adhered to silicon carbide both in argon at atmospheric pressure and in high vacuum. Cohesive bonds fractured on both the silicon carbide and titanium surfaces. The wear debris of silicon carbide created by fracture plowed the silicon carbide surface in a plastic manner. The friction characteristics of titanium in contact with silicon carbide were sensitive to the surface roughness of silicon carbide, and the friction coefficients were higher for a rough surface of silicon carbide than for a smooth one. The difference in friction results was due to plastic deformation (plowing of titanium).

  2. A simple method to synthesize single-crystalline lanthanide orthovanadate nanorods

    NASA Astrophysics Data System (ADS)

    Fan, Weiliu; Zhao, Wei; You, Liping; Song, Xinyu; Zhang, Weimin; Yu, Haiyun; Sun, Sixiu

    2004-12-01

    Single-crystalline tetragonal LnVO 4 ( Ln=La, Nd, Sm, Eu, Dy) nanorods were prepared via a simple hydrothermal method, in the absence of any surfactant or template using cheap and simple inorganic salts as raw materials. The products were characterized by XRD, TEM, HRTEM, and PL. It has been shown that after the hydrothermal process, LaVO 4 transformed its crystal structure from monoclinic to tetragonal phase, but LnVO 4 ( Ln=Nd, Sm, Eu, Dy) have not exhibited the structural change. This could be associated with the change of lanthanide ion radius. TEM and HRTEM results show that the nanorods are pure, structurally uniform, single crystalline, and most of them are free from dislocations. Further study reveals the nanorods grow along the [001] direction. A possible growth mechanism of lanthanide orthovanadate nanorods was also proposed. The advantages of our method for the nanorods synthesis lie in the high yield and the low temperature and mild reaction conditions, which permit large scale production at low cost.

  3. Interdiffusion and stress development in single-crystalline Pd/Ag bilayers

    NASA Astrophysics Data System (ADS)

    Noah, Martin A.; Flötotto, David; Wang, Zumin; Mittemeijer, Eric J.

    2016-04-01

    Interdiffusion and stress evolution in single-crystalline Pd/single-crystalline Ag thin films were investigated by Auger electron spectroscopy sputter-depth profiling and in-situ X-ray diffraction, respectively. The concentration-dependent chemical diffusion coefficient, as well as the impurity diffusion coefficient of Ag in Pd could be determined in the low temperature range of 356 °C-455 °C. As a consequence of the similarity of the strong concentration-dependences of the intrinsic diffusion coefficients, the chemical diffusion coefficient varies only over three orders of magnitude over the whole composition range, despite the large difference of six orders of magnitude of the self-diffusion coefficients of Ag in Ag and Pd in Pd. It is shown that the Darken-Manning treatment should be adopted for interpretation of the experimental data; the Nernst-Planck treatment yielded physically unreasonable results. Apart from the development of compressive thermal stress, the development of stress in both sublayers separately could be ascribed to compositional stress (tensile in the Ag sublayer and compressive in the Pd sublayer) and dominant relaxation processes, especially in the Ag sublayer. The effect of these internal stresses on the values determined for the diffusion coefficients is shown to be negligible.

  4. Single crystalline molybdenum nanowires, nanowire arrays and nanopore arrays in nickel-aluminium.

    PubMed

    Milenkovic, Srdjan; Smith, Andrew Jonathan; Hassel, Achim Walter

    2009-06-01

    This work describes a novel fabrication method of single crystalline Mo nanowires and nanowire arrays. The method utilizes directional solidification (ds) of a NiAl-Mo eutectic alloy and its subsequent electrochemical processing. In the first step, a self-organized array of Mo nanowires embedded in a NiAl matrix is obtained. By combining the Pourbaix diagrams of the three elements involved, a strategy for selective removal of either of the two phases is derived. An oxidizing acidic solution of pH 0.2 dissolved the matrix and released an array of long and uniform Mo wires. Even a complete extraction of the wires is possible through entire dissolution of the matrix. On the other hand, electrodissolution of the Mo with a simultaneous passivation of the NiAl matrix at the pH 6 and the potential of 200 mV SHE yielded nanopore arrays with rectangular pores. This method has several advantages. First of all, it is one of the few top-down methods that allow the production of large amounts of nanostructures. In addition, both the wires and the matrix are single crystalline which makes them favorable for various applications. Further, the obtained nanostructures exhibit extremely high aspect ratios (> 1000), unreachable by most other techniques. This technique has the potential for the production of nanowire arrays either for employment in sensors or in field emission. PMID:19504862

  5. Versatile method for template-free synthesis of single crystalline metal and metal alloy nanowires.

    PubMed

    Scott, John A; Totonjian, Daniel; Martin, Aiden A; Tran, Toan Trong; Fang, Jinghua; Toth, Milos; McDonagh, Andrew M; Aharonovich, Igor; Lobo, Charlene J

    2016-02-01

    Metal and metal alloy nanowires have applications ranging from spintronics to drug delivery, but high quality, high density single crystalline materials have been surprisingly difficult to fabricate. Here we report a versatile, template-free, self-assembly method for fabrication of single crystalline metal and metal alloy nanowires (Co, Ni, NiCo, CoFe, and NiFe) by reduction of metal nitride precursors formed in situ by reaction of metal salts with a nitrogen source. Thiol reduction of the metal nitrides to the metallic phase at 550-600 °C results in nanowire growth. In this process, sulfur acts as a uniaxial structure-directing agent, passivating the surface of the growing nanowires and preventing radial growth. The versatility of the method is demonstrated by achieving nanowire growth from gas-phase, solution-phase or a combination of gas- and solution-phase precursors. The fabrication method is suited to large-area CVD on a wide range of solid substrates. PMID:26763153

  6. Gettering effects in Si{sub x}Ge{sub 1-x} single crystalline wafers

    SciTech Connect

    Wollweber, J.; Schulz, D.; Schroeder, W.

    1995-08-01

    The new interest in single crystal growth of SiGe solid solutions is caused by the development of advanced electronics. The SiGe alloys are mostly used in the form of Si/Si{sub x}Ge{sub 1-x} epitaxial layers in heterostructures, the perfect bulk crystals are required to study fundamental properties. Furthermore, Si{sub x}Ge{sub 1-x} crystals can be used as a substrate material instead of Silicon in order to avoid the buffer layers between the Silicon substrate and strained Si{sub x}Ge{sub 1-x}. Monocrystalline SiGe alloys may be a potential candidate as a base material for infrared solar cells too because of an enhanced IR-sensitivity. In this paper we report a new approach to the growth of Si{sub x}Ge{sub 1-x} single crystals (up to 2{double_prime} in diameter) using the crucible free rf-heated float zone technique as well as the Czochralski-technique for solar cells. The goal is to produce solar cells with an increased photo current in comparison to Silicon cells. based on the lower bandgap of the alloyed crystal. In order to be able to use the Si cells technology (a matter still pending to be proven), low contents of Ge are intended, desirably in the range of about x=0.2. It is worth to mention, that in the conventional Silicon cell processes which give efficiencies up to 18-19%, this efficiency is not limited by the bulk base recombination in the lifetime is above 200 {mu}s there. We can conclude, that there is no basic limitation did prevents Si{sub x}Ge{sub 1-x} wafers to present high lifetimes, above 200{mu}s, at least if the Ge content is below 5%. We can also conclude that the phosphorous gettering from a POCl{sub 3} source, used in silicon, can be successfully used to enhance lifetimes in Si{sub x}Ge{sub 1-x}, at least for the Ge concentration used here.

  7. Transport properties in single-crystalline rutile TiO2 nanorods

    NASA Astrophysics Data System (ADS)

    Chen, R. S.; Chen, C. A.; Wang, W. C.; Tsai, H. Y.; Huang, Y. S.

    2011-11-01

    Electronic transport properties of the single-crystalline titanium dioxide (TiO2) nanorods (NRs) with single rutile phase have been investigated. The conductivity values for the individual TiO2 NRs grown by metal-organic chemical vapor deposition are in the range of 1-10 Ω-1 cm-1. The temperature-dependent measurement shows the presence of two shallow donor levels/bands with activation energies at 8 and 28 meV, respectively. On the photoconductivity (PC), the TiO2 NRs exhibit the much higher normalized PC gain and sensitive excitation-power dependence than the polycrystalline nanotubes. The results demonstrate the superior photoconduction efficiency and distinct mechanism in the monocrystalline one-dimensional TiO2 nanostructures in comparison to the polycrystalline or nanoporous counterparts.

  8. High pressure nano-crystalline microstructure of shock compressed single crystal iron

    SciTech Connect

    Hawreliak, J; Kalantar, D; Stolken, J; Remington, B; Lorenzana, H; Wark, J

    2007-12-11

    We discuss the first grain size measurements made during shock compression using in situ x-ray diffraction. Our experiments have shown unambiguously that single crystal iron shock loaded above 13 GPa along the [100] direction will transform from the ambient {alpha}-phase (BCC) to a highly ordered polycrystalline {epsilon}-phase (HCP). Here, we present a detailed shape analysis of the diffraction peaks using a modified Warren-Averbach method to quantify the microstructure of shock compressed high pressure iron. The {epsilon}-phase was determined through this method to have grain sizes between of 2 and 15 nm, in reasonable agreement with results from large scale MD simulations. We conclude that single crystal iron becomes nano-crystalline in shock transforming from the {alpha} to {epsilon} phase.

  9. Investigation on crystalline perfection, mechanical, piezoelectric and ferroelectric properties of L-tartaric acid single crystal

    SciTech Connect

    Murugan, G. Senthil Ramasamy, P.

    2014-04-24

    Polar organic nonlinear optical material, L-tartaric acid single crystals have been grown from slow evaporation solution growth technique. Single crystal X-ray diffraction study indicates that the grown crystal crystallized in monoclinic system with space group P2{sub 1}. Crystalline perfection of the crystal has been evaluated by high resolution X-ray diffraction technique and it reveals that the crystal quality is good and free from structural grain boundaries. Mechanical stability of the crystal has been analyzed by Vickers microhardness measurement and it exhibits reverse indentation size effect. Piezoelectric d{sub 33} co-efficient for the crystal has been examined and its value is 47 pC/N. The ferroelectric behaviour of the crystal was analyzed by polarization-electric field hysteresis loop measurement.

  10. Single-crystalline δ-Ni2Si nanowires with excellent physical properties.

    PubMed

    Chiu, Wen-Li; Chiu, Chung-Hua; Chen, Jui-Yuan; Huang, Chun-Wei; Huang, Yu-Ting; Lu, Kuo-Chang; Hsin, Cheng-Lun; Yeh, Ping-Hung; Wu, Wen-Wei

    2013-01-01

    In this article, we report the synthesis of single-crystalline nickel silicide nanowires (NWs) via chemical vapor deposition method using NiCl2·6H2O as a single-source precursor. Various morphologies of δ-Ni2Si NWs were successfully acquired by controlling the growth conditions. The growth mechanism of the δ-Ni2Si NWs was thoroughly discussed and identified with microscopy studies. Field emission measurements show a low turn-on field (4.12 V/μm), and magnetic property measurements show a classic ferromagnetic characteristic, which demonstrates promising potential applications for field emitters, magnetic storage, and biological cell separation. PMID:23782805

  11. Single-crystalline δ-Ni2Si nanowires with excellent physical properties

    PubMed Central

    2013-01-01

    In this article, we report the synthesis of single-crystalline nickel silicide nanowires (NWs) via chemical vapor deposition method using NiCl2·6H2O as a single-source precursor. Various morphologies of δ-Ni2Si NWs were successfully acquired by controlling the growth conditions. The growth mechanism of the δ-Ni2Si NWs was thoroughly discussed and identified with microscopy studies. Field emission measurements show a low turn-on field (4.12 V/μm), and magnetic property measurements show a classic ferromagnetic characteristic, which demonstrates promising potential applications for field emitters, magnetic storage, and biological cell separation. PMID:23782805

  12. 15th Workshop on Crystalline Silicon Solar Cells and Modules: Materials and Processes; Extended Abstracts and Papers

    SciTech Connect

    Sopori, B. L.

    2005-11-01

    The National Center for Photovoltaics sponsored the 15th Workshop on Crystalline Silicon Solar Cells & Modules: Materials and Processes, held in Vail, CO, August 7-10, 2005. This meeting provided a forum for an informal exchange of technical and scientific information between international researchers in the photovoltaic and relevant non-photovoltaic fields. The workshop addressed the fundamental properties of PV silicon, new solar cell designs, and advanced solar cell processing techniques. A combination of oral presentations by invited speakers, poster sessions, and discussion sessions reviewed recent advances in crystal growth, new cell designs, new processes and process characterization techniques, and cell fabrication approaches suitable for future manufacturing demands. The theme of this year's meeting was 'Providing the Scientific Basis for Industrial Success.' Specific sessions during the workshop included: Advances in crystal growth and material issues; Impurities and defects in Si; Advanced processing; High-efficiency Si solar cells; Thin Si solar cells; and Cell design for efficiency and reliability module operation. The topic for the Rump Session was ''Si Feedstock: The Show Stopper'' and featured a panel discussion by representatives from various PV companies.

  13. A fair comparison between ultrathin crystalline-silicon solar cells with either periodic or correlated disorder inverted pyramid textures.

    PubMed

    Muller, Jérôme; Herman, Aline; Mayer, Alexandre; Deparis, Olivier

    2015-06-01

    Fabrication of competitive solar cells based on nano-textured ultrathin silicon technology is challenging nowadays. Attention is paid to the optimization of this type of texture, with a lot of simulation and experimental results published in the last few years. While previous studies discussed mainly the local features of the surface texture, we highlight here the importance of their filling fraction. In this work, we focus on a fair comparison between a technologically realizable correlated disorder pattern of inverted nano-pyramids on an ultrathin crystalline-silicon layer, and its periodically patterned counterpart. A fair comparison is made possible by defining an equivalent periodic structure for each hole filling fraction. Moreover, in order to be as realistic as possible, we consider patterns that could be fabricated by standard patterning techniques: hole-mask colloidal lithography, nanoimprint lithography and wet chemical etching. Based on numerical simulations, we show that inverted nano-pyramid patterns with correlated disorder provide typically greater efficiency than their periodic counterparts. However, the hole filling fraction of the etched pattern plays a crucial role and may limit the benefits of the correlated disorder due to experimental restrictions on pattern fabrication. PMID:26072890

  14. Blistering of implanted crystalline silicon by plasma hydrogenation investigated by Raman scattering spectroscopy

    SciTech Connect

    Duengen, W.; Job, R.; Mueller, T.; Ma, Y.; Fahrner, W. R.; Keller, L. O.; Horstmann, J. T.; Fiedler, H.

    2006-12-15

    Czochralski silicon wafers were implanted with H{sup +} ions at a dose of 1x10{sup 16} cm{sup -2} followed by hydrogen plasma treatments at different temperatures. The minimum hydrogen implantation dose required for silicon surface exfoliation of 3x10{sup 16} H{sup +}/cm{sup 2} without further hydrogen incorporation was reduced to one-third by subsequent plasma hydrogenation. The corresponding local vibrational modes of hydrogen molecules, vacancy-hydrogen complexes, and Si-H bonds on surfaces have been analyzed by micro-Raman scattering spectroscopy to investigate blistering and platelet formation. The surface profile has been studied by atomic force microscopy and scanning electron microscopy. The plasma treated samples were annealed to investigate the mechanism and applicability of the induced exfoliation. <111>-platelet formation occurred below plasma hydrogenation temperatures of 350 deg. C. At temperatures above 450 deg. C, <100>-platelet nucleation induced blistering.

  15. Direct Observation of the Collision of Single Pt Nanoparticles onto Single-Crystalline Gold Nanowire Electrodes.

    PubMed

    Shin, Changhwan; Bae, Hyeonhu; Kang, Mijeong; Kim, Bongsoo; Kwon, Seong Jung

    2016-08-01

    We observed the collision of single Pt nanoparticles (NPs) onto an Au nanowire (NW) electrode by using electrocatalytic amplification. Previously, such observations had typically been performed by using a microscale disk-type ultramicroelectrode (UME). The use of a NW electrode decreased the background noise current and provided a shielding effect, owing to adsorption of the NPs onto the insulating sheath. Therefore, the transient current signal that was caused by the collision of single NPs could be more clearly distinguished from the background current by using a NW electrode instead of a UME. Furthermore, the use of a NW electrode increased the collisional frequency and the magnitude of the transient current signal. The experimental data were analyzed by using a theoretical model and a random walk simulation model. PMID:27305586

  16. Defect Engineering, Cell Processing, and Modeling for High-Performance, Low-Cost Crystalline Silicon Photovoltaics

    SciTech Connect

    Buonassisi, Tonio

    2013-02-26

    The objective of this project is to close the efficiency gap between industrial multicrystalline silicon (mc-Si) and monocrystalline silicon solar cells, while preserving the economic advantage of low-cost, high-volume substrates inherent to mc-Si. Over the course of this project, we made significant progress toward this goal, as evidenced by the evolution in solar-cell efficiencies. While most of the benefits of university projects are diffuse in nature, several unique contributions can be traced to this project, including the development of novel characterization methods, defect-simulation tools, and novel solar-cell processing approaches mitigate the effects of iron impurities ("Impurities to Efficiency" simulator) and dislocations. In collaboration with our industrial partners, this project contributed to the development of cell processing recipes, specialty materials, and equipment that increased cell efficiencies overall (not just multicrystalline silicon). Additionally, several students and postdocs who were either partially or fully engaged in this project (as evidenced by the publication record) are currently in the PV industry, with others to follow.

  17. Surface Engineering of Copper Foils for Growing Centimeter-Sized Single-Crystalline Graphene.

    PubMed

    Lin, Li; Li, Jiayu; Ren, Huaying; Koh, Ai Leen; Kang, Ning; Peng, Hailin; Xu, H Q; Liu, Zhongfan

    2016-02-23

    The controlled growth of high-quality graphene on a large scale is of central importance for applications in electronics and optoelectronics. To minimize the adverse impacts of grain boundaries in large-area polycrystalline graphene, the synthesis of large single crystals of monolayer graphene is one of the key challenges for graphene production. Here, we develop a facile surface-engineering method to grow large single-crystalline monolayer graphene by the passivation of the active sites and the control of graphene nucleation on copper surface using the melamine pretreatment. Centimeter-sized hexagonal single-crystal graphene domains were successfully grown, which exhibit ultrahigh carrier mobilities exceeding 25,000 cm(2) V(-1) s(-1) and quantum Hall effects on SiO2 substrates. The underlying mechanism of melamine pretreatments were systematically investigated through elemental analyses of copper surface in the growth process of large single-crystals. This present work provides a surface design of a catalytic substrate for the controlled growth of large-area graphene single crystals. PMID:26832229

  18. Path to meter class single crystal silicon (SCSi) space optics

    NASA Astrophysics Data System (ADS)

    McCarter, Douglas R.

    2012-03-01

    With the global financial crisis affecting funding for space systems development, customers are calling for lower cost systems. Yet, at the same time, these lower cost systems must have increased thermal response to operational environments and load survivability. We submit that single crystal silicon (SCSi) meets both of these requirements. This paper will highlight some key SCSi material properties, discuss the opportunities that led to the development of McCarter processing methods, and present the latest steps in the manufacturing path of McCarter Mirrors using SCSi, GFB (glass frit bonding) and MSF (McCarter super finish), including the concept drawing of a one meter SCSi lightweight mirror, which together sets up the last step toward a lower cost, high performing one meter SCSi space optic.

  19. Single-layer graphene on silicon nitride micromembrane resonators

    SciTech Connect

    Schmid, Silvan; Guillermo Villanueva, Luis; Amato, Bartolo; Boisen, Anja; Bagci, Tolga; Zeuthen, Emil; Sørensen, Anders S.; Usami, Koji; Polzik, Eugene S.; Taylor, Jacob M.; Marcus, Charles M.; Cheol Shin, Yong; Kong, Jing

    2014-02-07

    Due to their low mass, high quality factor, and good optical properties, silicon nitride (SiN) micromembrane resonators are widely used in force and mass sensing applications, particularly in optomechanics. The metallization of such membranes would enable an electronic integration with the prospect for exciting new devices, such as optoelectromechanical transducers. Here, we add a single-layer graphene on SiN micromembranes and compare electromechanical coupling and mechanical properties to bare dielectric membranes and to membranes metallized with an aluminium layer. The electrostatic coupling of graphene covered membranes is found to be equal to a perfectly conductive membrane, without significantly adding mass, decreasing the superior mechanical quality factor or affecting the optical properties of pure SiN micromembranes. The concept of graphene-SiN resonators allows a broad range of new experiments both in applied physics and fundamental basic research, e.g., for the mechanical, electrical, or optical characterization of graphene.

  20. Process development for single-crystal silicon solar cells

    NASA Astrophysics Data System (ADS)

    Bohra, Mihir H.

    Solar energy is a viable, rapidly growing and an important renewable alternative to other sources of energy generation because of its abundant supply and low manufacturing cost. Silicon still remains the major contributor for manufacturing solar cells accounting for 80% of the market share. Of this, single-crystal solar cells account for half of the share. Laboratory cells have demonstrated 25% efficiency; however, commercial cells have efficiencies of 16% - 20% resulting from a focus on implementation processes geared to rapid throughput and low cost, thereby reducing the energy pay-back time. An example would be the use of metal pastes which dissolve the dielectric during the firing process as opposed to lithographically defined contacts. With current trends of single-crystal silicon photovoltaic (PV) module prices down to 0.60/W, almost all other PV technologies are challenged to remain cost competitive. This presents a unique opportunity in revisiting the PV cell fabrication process and incorporating moderately more expensive IC process practices into PV manufacturing. While they may drive the cost toward a 1/W benchmark, there is substantial room to "experiment", leading to higher efficiencies which will help maintain the overall system cost. This work entails a turn-key process designed to provide a platform for rapid evaluation of novel materials and processes. A two-step lithographic process yielding a baseline 11% - 13% efficient cell is described. Results of three studies have shown improvements in solar cell output parameters due to the inclusion of a back-surface field implant, a higher emitter doping and also an additional RCA Clean.

  1. Spatially resolved resonant tunneling on single atoms in silicon.

    PubMed

    Voisin, B; Salfi, J; Bocquel, J; Rahman, R; Rogge, S

    2015-04-22

    The ability to control single dopants in solid-state devices has opened the way towards reliable quantum computation schemes. In this perspective it is essential to understand the impact of interfaces and electric fields, inherent to address coherent electronic manipulation, on the dopants atomic scale properties. This requires both fine energetic and spatial resolution of the energy spectrum and wave-function, respectively. Here we present an experiment fulfilling both conditions: we perform transport on single donors in silicon close to a vacuum interface using a scanning tunneling microscope (STM) in the single electron tunneling regime. The spatial degrees of freedom of the STM tip provide a versatility allowing a unique understanding of electrostatics. We obtain the absolute energy scale from the thermal broadening of the resonant peaks, allowing us to deduce the charging energies of the donors. Finally we use a rate equations model to derive the current in presence of an excited state, highlighting the benefits of the highly tunable vacuum tunnel rates which should be exploited in further experiments. This work provides a general framework to investigate dopant-based systems at the atomic scale. PMID:25782866

  2. Quantum memory in a single nucleus in silicon

    NASA Astrophysics Data System (ADS)

    Freer, Solomon; Simmons, Stephanie; Laucht, Arne; Muhonen, Juha; Dehollain, Juan Pablo; Kalra, Rachpon; Hudson, Fay; Dzurak, Andrew; Itoh, Kohei; McCallum, Jeffrey; Jamieson, David; Morello, Andrea

    2015-03-01

    Long coherence times and fast manipulation are two desirable qualities of a qubit that for many systems are mutually incompatible. Storing quantum information in an ancillary qubit, i.e. a `quantum memory', is a strategy to address this issue. It is a advantageous property of donor impurities in silicon to have qubits of both qualities in a single lattice site. Here we demonstrate storage and retrieval of quantum information from a single donor electron spin to its host phosphorus nucleus in isotopically-enriched 28Si. We demonstrate a high fidelity memory process characterised via both state and process tomography. We use dynamical decoupling sequences during the nuclear storage to extend the memory time, and demonstrate storage and retrieval of a single qubit of information multiple times before decay. These results underline the inherent versatility and high fidelity of our two qubit system. Funded by the Australian Research Council (CE11E000127) and the U.S. Army Research Office (W911NF-13-1-0024).

  3. Effects of 22 MeV protons on single junction and silicon controlled rectifiers

    NASA Technical Reports Server (NTRS)

    Beatty, M. E., III

    1972-01-01

    The effects of 22-MeV protons on various types of silicon single junction and silicon controlled rectifiers were investigated. The results show that low-leakage devices and silicon controlled rectifiers are the most susceptable to radiation damage. There are also differences noted between single junction rectifiers of the same type made by different manufacturers, which emphasizes the need for better selection of devices used in spacecraft.

  4. Amorphous to crystalline phase transition in pulsed laser deposited silicon carbide

    NASA Astrophysics Data System (ADS)

    Tabbal, M.; Said, A.; Hannoun, E.; Christidis, T.

    2007-06-01

    SiC thin films were grown on Si (1 0 0) substrates by excimer laser ablation of a SiC target in vacuum. The effect of deposition temperature (up to 950 °C), post-deposition annealing and laser energy on the nanostructure, bonding and crystalline properties of the films was studied, in order to elucidate their transition from an amorphous to a crystalline phase. Infra-red spectroscopy shows that growth at temperatures greater than 600 °C produces layers with increasingly uniform environment of the Si-C bonds, while the appearance of large crystallites is detected, by X-ray diffraction, at 800 °C. Electron paramagnetic resonance confirms the presence of clustered paramagnetic centers within the sp 2 carbon domains. Increasing deposition temperature leads to a decrease of the spin density and to a temperature-dependent component of the EPR linewidth induced by spin hopping. For films grown below 650 °C, post-deposition annealing at 1100 °C reduces the spin density as a result of a more uniform Si-C nanostructure, though large scale crystallization is not observed. For greater deposition temperatures, annealing leads to little changes in the bonding properties, but suppresses the temperature dependent component of the EPR linewidth. These findings are explained by a relaxation of the stress in the layers, through the annealing of the bond angle disorder that inhibits spin hopping processes.

  5. Micromachined anti-scatter grid fabricated using crystalline wet etching of (1 1 0) silicon and metal electroplating for X-ray imaging

    NASA Astrophysics Data System (ADS)

    Jeong, Dae-Hun; Myung Kim, Jae; Noh, Do Young; Hyun Kim, Kwang; Lee, Jong-Hyun

    2011-10-01

    Two-dimensional micromachined anti-scatter grids were fabricated using MEMS technology, including crystalline wet etching of (1 1 0) silicon and metal electroplating for X-ray imaging. The core sizes of the square grids were 100, 200, and 300 μm with 2.2 mm height and 50 μm septa thickness. To prepare the etch mask for crystalline wet etching, silicon nitride was deposited using low pressure chemical vapor deposition (LPCVD). The grid patterns, which are aligned parallel to the vertical (1 1 1) plane of the (1 1 0) silicon, were transferred from the photomask onto the photoresist using deep ultraviolet (DUV) photolithography, and consecutively onto the silicon nitride using reactive ion etching (RIE). A (1 1 0) silicon substrate was then etched in a tetramethyl ammonium hydroxide (TMAH) solution to form a skeleton for the septa structure. Chrome was sputtered to provide a seed layer for nickel electroplating, where nickel grows on the sidewalls of the skeleton of the septa structure. Finally, two-dimensional septa with various grid ratios were constructed by cross-stacking several layers of the patterned (1 1 0) silicon wafer. Anti-scattering ability was experimentally characterized in terms of X-ray transmission by one-dimensional scanning of incident angle.

  6. Synthesis and characterization of single-crystalline zinc tin oxide nanowires.

    PubMed

    Shi, Jen-Bin; Wu, Po-Feng; Lin, Hsien-Sheng; Lin, Ya-Ting; Lee, Hsuan-Wei; Kao, Chia-Tze; Liao, Wei-Hsiang; Young, San-Lin

    2014-01-01

    Crystalline zinc tin oxide (ZTO; zinc oxide with heavy tin doping of 33 at.%) nanowires were first synthesized using the electrodeposition and heat treatment method based on an anodic aluminum oxide (AAO) membrane, which has an average diameter of about 60 nm. According to the field emission scanning electron microscopy (FE-SEM) results, the synthesized ZTO nanowires are highly ordered and have high wire packing densities. The length of ZTO nanowires is about 4 μm, and the aspect ratio is around 67. ZTO nanowires with a Zn/(Zn + Sn) atomic ratio of 0.67 (approximately 2/3) were observed from an energy dispersive spectrometer (EDS). X-ray diffraction (XRD) and corresponding selected area electron diffraction (SAED) patterns demonstrated that the ZTO nanowire is hexagonal single-crystalline. The study of ultraviolet/visible/near-infrared (UV/Vis/NIR) absorption showed that the ZTO nanowire is a wide-band semiconductor with a band gap energy of 3.7 eV. PMID:24872800

  7. Influence of nanowires length on performance of crystalline silicon solar cell

    NASA Astrophysics Data System (ADS)

    Li, Haofeng; Jia, Rui; Chen, Chen; Xing, Zhao; Ding, Wuchang; Meng, Yanlong; Wu, Deqi; Liu, Xinyu; Ye, Tianchun

    2011-04-01

    Silicon-nanowire (Si-NW) array, prepared by an electroless chemical-etching method, shows excellent optical antireflection property over a wide spectral bandwidth. The influence of the wire length on the optical antireflection property and the solar cell performance were studied for both the Si-NW array solar cells and the planar solar cells. The reflectance of NWs solar cells is almost invariable and much lower than that of the planar solar cells but the performance of planar solar cells is the best. Results show the performance of NWs solar cells is strongly affected by some other factors such as surface passivation and electrode-contact property.

  8. Planar polar liquid crystalline alignment in nanostructured porous silicon one-dimensional photonic crystals

    NASA Astrophysics Data System (ADS)

    Mor, Shahar; Torres-Costa, Vicente; Martín-Palma, Raúl J.; Abdulhalim, I.

    2010-09-01

    The ability of liquid crystals (LCs) to flow and fill nanopores assists in using them for infiltration into porous nanophotonic structures such as nanostructured porous silicon (nanoPS). The reflectivity spectra at normal incidence from periodic nanostructured nanoPS filters infiltrated with nematic LC is found to exhibit polarization dependence. This is experimental evidence that the LC molecules in the nanoPS matrix are aligned such that an effective anisotropy exists parallel to the substrate plane. From the theoretical fit the preferred configuration was found to be the planar-polar geometry which is shown to be biaxial.

  9. Isotropic behavior of an anisotropic material: single crystal silicon

    NASA Astrophysics Data System (ADS)

    McCarter, Douglas R.; Paquin, Roger A.

    2013-09-01

    Zero defect single crystal silicon (Single-Crystal Si), with its diamond cubic crystal structure, is completely isotropic in most properties important for advanced aerospace systems. This paper will identify behavior of the three most dominant planes of the Single-Crystal Si cube (110), (100) and (111). For example, thermal and optical properties are completely isotropic for any given plane. The elastic and mechanical properties however are direction dependent. But we show through finite element analysis that in spite of this, near-isotropic behavior can be achieved with component designs that utilize the optimum elastic modulus in directions with the highest loads. Using glass frit bonding to assemble these planes is the only bonding agent that doesn't degrade the performance of Single-Crystal Si. The most significant anisotropic property of Single-Crystal Si is the Young's modulus of elasticity. Literature values vary substantially around a value of 145 GPa. The truth is that while the maximum modulus is 185 GPa, the most useful <110< crystallographic direction has a high 169 GPa, still higher than that of many materials such as aluminum and invar. And since Poisson's ratio in this direction is an extremely low 0.064, distortion in the plane normal to the load is insignificant. While the minimum modulus is 130 GPa, a calculated average value is close to the optimum at approximately 160 GPa. The minimum modulus is therefore almost irrelevant. The (111) plane, referred to as the natural cleave plane survives impact that would overload the (110) and/or (100) plane due to its superior density. While mechanical properties vary from plane to plane each plane is uniform and response is predictable. Understanding the Single-Crystal Si diamond cube provides a design and manufacture path for building lightweight Single-Crystal Si systems with near-isotropic response to loads. It is clear then that near-isotropic elastic behavior is achievable in Single-Crystal Si

  10. Comparison of Photoluminescence Imaging on Starting Multi-Crystalline Silicon Wafers to Finished Cell Performance: Preprint

    SciTech Connect

    Johnston, S.; Yan, F.; Dorn, D.; Zaunbrecher, K.; Al-Jassim, M.; Sidelkheir, O.; Ounadjela, K.

    2012-06-01

    Photoluminescence (PL) imaging techniques can be applied to multicrystalline silicon wafers throughout the manufacturing process. Both band-to-band PL and defect-band emissions, which are longer-wavelength emissions from sub-bandgap transitions, are used to characterize wafer quality and defect content on starting multicrystalline silicon wafers and neighboring wafers processed at each step through completion of finished cells. Both PL imaging techniques spatially highlight defect regions that represent dislocations and defect clusters. The relative intensities of these imaged defect regions change with processing. Band-to-band PL on wafers in the later steps of processing shows good correlation to cell quality and performance. The defect band images show regions that change relative intensity through processing, and better correlation to cell efficiency and reverse-bias breakdown is more evident at the starting wafer stage as opposed to later process steps. We show that thermal processing in the 200 degrees - 400 degrees C range causes impurities to diffuse to different defect regions, changing their relative defect band emissions.

  11. Tailoring the optical constants in single-crystal silicon with embedded silver nanostructures for advanced silicon photonics applications

    SciTech Connect

    Akhter, Perveen; Huang, Mengbing Spratt, William; Kadakia, Nirag; Amir, Faisal

    2015-03-28

    Plasmonic effects associated with metal nanostructures are expected to hold the key to tailoring light emission/propagation and harvesting solar energy in materials including single crystal silicon which remains the backbone in the microelectronics and photovoltaics industries but unfortunately, lacks many functionalities needed for construction of advanced photonic and optoelectronics devices. Currently, silicon plasmonic structures are practically possible only in the configuration with metal nanoparticles or thin film arrays on a silicon surface. This does not enable one to exploit the full potential of plasmonics for optical engineering in silicon, because the plasmonic effects are dominant over a length of ∼50 nm, and the active device region typically lies below the surface much beyond this range. Here, we report on a novel method for the formation of silver nanoparticles embedded within a silicon crystal through metal gettering from a silver thin film deposited at the surface to nanocavities within the Si created by hydrogen ion implantation. The refractive index of the Ag-nanostructured layer is found to be 3–10% lower or higher than that of silicon for wavelengths below or beyond ∼815–900 nm, respectively. Around this wavelength range, the optical extinction values increase by a factor of 10–100 as opposed to the pure silicon case. Increasing the amount of gettered silver leads to an increased extinction as well as a redshift in wavelength position for the resonance. This resonance is attributed to the surface plasmon excitation of the resultant silver nanoparticles in silicon. Additionally, we show that the profiles for optical constants in silicon can be tailored by varying the position and number of nanocavity layers. Such silicon crystals with embedded metal nanostructures would offer novel functional base structures for applications in silicon photonics, optoelectronics, photovoltaics, and plasmonics.

  12. Tailoring the optical constants in single-crystal silicon with embedded silver nanostructures for advanced silicon photonics applications

    NASA Astrophysics Data System (ADS)

    Akhter, Perveen; Huang, Mengbing; Spratt, William; Kadakia, Nirag; Amir, Faisal

    2015-03-01

    Plasmonic effects associated with metal nanostructures are expected to hold the key to tailoring light emission/propagation and harvesting solar energy in materials including single crystal silicon which remains the backbone in the microelectronics and photovoltaics industries but unfortunately, lacks many functionalities needed for construction of advanced photonic and optoelectronics devices. Currently, silicon plasmonic structures are practically possible only in the configuration with metal nanoparticles or thin film arrays on a silicon surface. This does not enable one to exploit the full potential of plasmonics for optical engineering in silicon, because the plasmonic effects are dominant over a length of ˜50 nm, and the active device region typically lies below the surface much beyond this range. Here, we report on a novel method for the formation of silver nanoparticles embedded within a silicon crystal through metal gettering from a silver thin film deposited at the surface to nanocavities within the Si created by hydrogen ion implantation. The refractive index of the Ag-nanostructured layer is found to be 3-10% lower or higher than that of silicon for wavelengths below or beyond ˜815-900 nm, respectively. Around this wavelength range, the optical extinction values increase by a factor of 10-100 as opposed to the pure silicon case. Increasing the amount of gettered silver leads to an increased extinction as well as a redshift in wavelength position for the resonance. This resonance is attributed to the surface plasmon excitation of the resultant silver nanoparticles in silicon. Additionally, we show that the profiles for optical constants in silicon can be tailored by varying the position and number of nanocavity layers. Such silicon crystals with embedded metal nanostructures would offer novel functional base structures for applications in silicon photonics, optoelectronics, photovoltaics, and plasmonics.

  13. Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe3O4 nanoparticle rings

    PubMed Central

    Takeno, Yumu; Murakami, Yasukazu; Sato, Takeshi; Tanigaki, Toshiaki; Park, Hyun Soon; Shindo, Daisuke; Ferguson, R. Matthew

    2014-01-01

    This study reports on the correlation between crystal orientation and magnetic flux distribution of Fe3O4 nanoparticles in the form of self-assembled rings. High-resolution transmission electron microscopy demonstrated that the nanoparticles were single-crystalline, highly monodispersed, (25 nm average diameter), and showed no appreciable lattice imperfections such as twins or stacking faults. Electron holography studies of these superparamagnetic nanoparticle rings indicated significant fluctuations in the magnetic flux lines, consistent with variations in the magnetocrystalline anisotropy of the nanoparticles. The observations provide useful information for a deeper understanding of the micromagnetics of ultrasmall nanoparticles, where the magnetic dipolar interaction competes with the magnetic anisotropy. PMID:25422526

  14. Interfacial electronic transport phenomena in single crystalline Fe-MgO-Fe thin barrier junctions

    SciTech Connect

    Gangineni, R. B.; Negulescu, B.; Baraduc, C.; Gaudin, G.

    2014-05-05

    Spin filtering effects in nano-pillars of Fe-MgO-Fe single crystalline magnetic tunnel junctions are explored with two different sample architectures and thin MgO barriers (thickness: 3–8 monolayers). The two architectures, with different growth and annealing conditions of the bottom electrode, allow tuning the quality of the bottom Fe/MgO interface. As a result, an interfacial resonance states (IRS) is observed or not depending on this interface quality. The IRS contribution, observed by spin polarized tunnel spectroscopy, is analyzed as a function of the MgO barrier thickness. Our experimental findings agree with theoretical predictions concerning the symmetry of the low energy (0.2 eV) interfacial resonance states: a mixture of Δ{sub 1}-like and Δ{sub 5}-like symmetries.

  15. Unusual angular dependent magnetoresistance in single-crystalline Co/Pt bilayers

    NASA Astrophysics Data System (ADS)

    Xiao, X.; Li, J. X.; Ding, Z.; Liang, J. H.; Sun, L.; Wu, Y. Z.

    2016-05-01

    The magnetoresistance (MR) of the single-crystalline Co/Pt(111) bilayers was studied systematically as a function of Co or Pt thickness at room temperature. For Co thickness dCo < 6 nm, the resistances with in-plane magnetization M parallel ( R∥ ) and transverse ( R⊥ ) to current and with a perpendicular M normal ( RP ) to film show the unconventional behavior of RP>R∥>R⊥ . This MR behavior can be attributed to the combination effect of spin Hall MR with RP≈R∥>R⊥ and the geometrical size effect. In addition, the angular dependent magnetoresistance behavior of the (111)-oriented Co/Pt bilayer shows striking difference with that of the (001)-oriented Co/Pt bilayer.

  16. Cold welding of copper nanowires with single-crystalline and twinned structures: A comparison study

    NASA Astrophysics Data System (ADS)

    Huang, Rao; Shao, Gui-Fang; Wen, Yu-Hua

    2016-09-01

    In this article, molecular simulations were adopted to explore the cold welding processes of copper nanowires with both single-crystalline and fivefold twinned structures. It was verified that the twinned nanowires exhibited enhanced strength but lowered elastic limit and ductility. Both nanowires could be successfully welded through rather small loadings, although their stress-strain responses toward compression were different. Meanwhile, more stress was accumulated in the twinned nanowire due to repulsive force of the twin boundaries against the nucleation and motions of dislocations. Moreover, by characterizing the structure evolutions in the welding process, it can be ascertained that perfect atomic order was finally built at the weld region in both nanowires. This comparison study will be of great importance to future mechanical processing of metallic nanowires.

  17. Formation and Stabilization of Single-Crystalline Metastable AuGe Phases in Ge Nanowires

    SciTech Connect

    Sutter, E.; Sutter, P.

    2011-07-22

    We use in situ observations by variable temperature transmission electron microscopy on AuGe alloy drops at the tips of Ge nanowires (NWs) with systematically varying composition to demonstrate the controlled formation of metastable solid phases integrated in NWs. The process, which operates in the regime of vapor-liquid-solid growth, involves a size-dependent depression of the alloy liquidus at the nanoscale that leads to extremely Ge-rich AuGe melts at low temperatures. During slow cooling, these liquid AuGe alloy drops show pronounced departures from equilibrium, i.e., a frustrated phase separation of Ge into the adjacent solid NW, and ultimately crystallize as single-crystalline segments of metastable {gamma}-AuGe. Our findings demonstrate a general avenue for synthesizing NW heterostructures containing stable and metastable solid phases, applicable to a wide range of materials of which NWs form by the vapor-liquid-solid method.

  18. Nanomechanical Behavior of Single Crystalline SiC Nanotubes Revealed by Molecular Dynamics Simulations

    SciTech Connect

    Wang, Zhiguo; Zu, Xiaotao T.; Gao, Fei; Weber, William J.

    2008-11-01

    Molecular dynamics simulations with Tersoff potentials were used to study the response of single crystalline SiC nanotubes under tensile, compressive, torsional, combined tension-torsional and combined compression-torsional strains. The simulation results reveal that the nanotubes deform through bond-stretching and breaking and exhibit brittle properties under uniaxial tensile strain, except for the thinnest nanotube at high temperatures, which fails in a ductile manner. Under uniaxial compressive strain, the SiC nanotubes buckle with two modes, i.e. shell buckling and column buckling, depending on the length of the nanotubes. Under torsional strain, the nanotubes buckle either collapse in the middle region into a dumbbell-like structure for thinner wall thicknesses or fail by bond breakage for the largest wall thickness. Both the tensile failure stress and buckling stress decrease under combined tension-torsional and combined compression-torsional strain, and they decrease with increasing torsional rate under combined loading.

  19. Synthesis and nonlinear optical properties of single-crystalline KNb3O8 nanowires

    NASA Astrophysics Data System (ADS)

    Yu, Bin; Cao, Bo; Cao, Huiqun; Zhang, Xinpeng; Chen, Danni; Qu, Junle; Niu, Hanben

    2013-03-01

    Single-crystalline KNb3O8 nanowires with widths of 100-300 nm and lengths up to tens of microns were synthesized by calcining Nb2O5 powders in molten KCl and K2SO4. The phase of the products was determined by means of x-ray diffraction, and the morphology and structure were characterized by using scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy and selected area electron diffraction techniques. The growth direction of the KNb3O8 obtained was determined to be the [001] crystallographic direction. Meanwhile, the polarization response of the second-harmonic generation (SHG) response was investigated. The as-synthesized nanowires clearly exhibited a SHG response, which means that the nanowires were an efficient nanoscale second-harmonic light source. The excellent nonlinear optical property of KNb3O8 shows potential for application in nano-optical devices.

  20. Synthesis and nonlinear optical properties of single-crystalline KNb3O8 nanowires.

    PubMed

    Yu, Bin; Cao, Bo; Cao, Huiqun; Zhang, Xinpeng; Chen, Danni; Qu, Junle; Niu, Hanben

    2013-03-01

    Single-crystalline KNb(3)O(8) nanowires with widths of 100-300 nm and lengths up to tens of microns were synthesized by calcining Nb(2)O(5) powders in molten KCl and K(2)SO(4). The phase of the products was determined by means of x-ray diffraction, and the morphology and structure were characterized by using scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy and selected area electron diffraction techniques. The growth direction of the KNb(3)O(8) obtained was determined to be the [001] crystallographic direction. Meanwhile, the polarization response of the second-harmonic generation (SHG) response was investigated. The as-synthesized nanowires clearly exhibited a SHG response, which means that the nanowires were an efficient nanoscale second-harmonic light source. The excellent nonlinear optical property of KNb(3)O(8) shows potential for application in nano-optical devices. PMID:23377103

  1. Mask-free fabrication of inverted-pyramid texture on single-crystalline Si wafer

    NASA Astrophysics Data System (ADS)

    Yang, Bogeum; Lee, Myeongkyu

    2014-11-01

    We here show that inverted-pyramid (IP) textures can be fabricated on single-crystalline Si wafer by simply irradiating the surface with a nanosecond pulsed laser at 532 nm, followed by alkali etching. This process is fundamentally based on the laser-induced melting of material. When exposed to three interfering laser beams, the surface was locally melted in a periodic fashion in accordance with the interference pattern. This generated concave holes on the surface because the melted material overflowed and condensed at the periphery. When subsequently etched by KOH, the internal morphology of the concave holes changed into an IP shape as a result of the position-dependent different etching rates. Uniform IP structures could be obtained with a minimum reflectance of 15.8%.

  2. Synthesis and size-dependent magnetic properties of single-crystalline hematite nanodiscs

    NASA Astrophysics Data System (ADS)

    Bao, Liu; Yang, Heqing; Wang, Xuewen; Zhang, Fenghua; Shi, Ruyu; Liu, Bin; Wang, Lin; Zhao, Hua

    2011-08-01

    Single-crystalline α-Fe 2O 3 nanodiscs with diameters of 132-150 nm were synthesized by a facile and efficient hydrothermal reaction of FeCl 3 with NaH 2PO 4 and H 2O at 200 °C for 12 h. The diameters of the nanodiscs can be decreased to 91-112 and 78-92 nm by adding ethanol glycol into the hydrothermal system. The α-Fe 2O 3 nanodiscs are formed by the cooperative action of selective adsorption and etching of the phosphate ions. The as-synthesized α-Fe 2O 3 nanodiscs exhibit weak ferromagnetic behaviours. The remanent magnetization and coercivity of the nanodiscs with the diameters of 132-150 nm are 0.01743 emu g -1 and 214.8 Oe, respectively, and the remanent magnetization and coercivity decrease with deceasing the nanodisc size.

  3. Finite-size scaling law in single-crystalline Fe3O4 hollow nanostructures

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoping; Wang, Jun; Gao, Miao

    2016-07-01

    Single-crystalline Fe3O4 hollow nanostructures (nanoring and nanotube) have been successfully synthesized by a hydrothermal method along with a heat treatment process. The temperature dependences of the magnetization of the hollow nanostructures were measured under a high vacuum ( < 9.5 × 10‑6 Torr) from 300K to 900K. The Curie temperatures of the nanoring and nanotube samples were found to decrease with decreasing the mean wall thickness. The Curie temperatures of the hollow magnetite nanostructures follow a finite-size scaling relation with the scaling exponent ν = 1.04 ± 0.03. By comparison with those of the zero-dimensional Fe3O4 particles and two-dimensional Fe3O4 films, we show that the scaling relation for our hollow nanostructures is in better agreement with the quasi-two-dimensional finite-size scaling law.

  4. Exploring metamagnetism of single crystalline EuNiGe3 by neutron scattering

    NASA Astrophysics Data System (ADS)

    Fabrèges, X.; Gukasov, A.; Bonville, P.; Maurya, A.; Thamizhavel, A.; Dhar, S. K.

    2016-06-01

    We present here a neutron diffraction study, both in zero field and as a function of magnetic field, of the magnetic structure of the tetragonal intermetallic EuNiGe3 on a single crystalline sample. This material is known to undergo a cascade of transitions, first at 13.2 K towards an incommensurate modulated magnetic structure, then at 10.5 K to an antiferromagnetic structure. We show here that the low-temperature phase presents a spiral moment arrangement with wave vector k =(1/4 ,δ ,0 ) . For a magnetic field applied along the tetragonal c axis, the square root of the scattering intensity of the (1 0 1) reflection matches very well the complex metamagnetic behavior of the magnetization along c measured previously. For the magnetic field applied along the b axis, two magnetic transitions are observed below the transition to a fully polarized state.

  5. Carrier Transport Mechanism in Single Crystalline Organic Semiconductor Thin Film Elucidated by Visualized Carrier Motion.

    PubMed

    Matsubara, Kohei; Abe, Kentaro; Manaka, Takaaki; Iwamoto, Mitsumasa

    2016-04-01

    Time-resolved microscopic second harmonic generation (TRM-SHG) measurement was conducted to evaluate temperature dependence of the anisotropic carrier transport process in 6,13-Bis(triisopropylsilylethynyl) (TIPS) pentacene single crystalline domains for two orthogonal directions. Enhancement of the electric field induced SHG (EFI-SHG) signal at the electrode edge at low temperature suggests the presence of potential drop in the injection process. We directly evaluated temperature dependence of the carrier mobility by taking into account the potential drop, and concluded that the Marcus theory is appropriate to interpret the carrier transport in anisotropic TIPS pentacene thin film. TRM-SHG method is a facile and effective way to directly visualize transport process in anisotropic materials and to evaluate injection and transport processes simultaneously. PMID:27451638

  6. Orientation dependent size effects in single crystalline anisotropic nanoplates with regard to surface energy

    NASA Astrophysics Data System (ADS)

    Assadi, Abbas; Salehi, Manouchehr; Akhlaghi, Mehdi

    2015-07-01

    In this work, size dependent behavior of single crystalline normal and auxetic anisotropic nanoplates is discussed with consideration of material surface stresses via a generalized model. Bending of pressurized nanoplates and their fundamental resonant frequency are discussed for different crystallographic directions and anisotropy degrees. It is explained that the orientation effects are considerable when the nanoplates' edges are pinned but for clamped nanoplates, the anisotropy effect may be ignored. The size effects are the highest when the simply supported nanoplates are parallel to [110] direction but as the anisotropy gets higher, the size effects are reduced. The orientation effect is also discussed for possibility of self-instability occurrence in nanoplates. The results in simpler cases are compared with previous experiments for nanowires but with a correction factor. There are still some open questions for future studies.

  7. Four-fold symmetric anisotropic magnetoresistance of single-crystalline Ni(001) film

    SciTech Connect

    Xiao, X.; Li, J. X.; Ding, Z.; Wu, Y. Z.

    2015-11-28

    Temperature, current-direction, and film-thickness dependent anisotropic magnetoresistance measurements were performed on single-crystalline face-centered-cubic nickel films. An additional four-fold symmetry was confirmed besides the typical two-fold term even at room temperature. The angular-dependent longitudinal resistivity resolves into a two-fold term, which varies as a function of current direction, and a four-fold term, which is isotropically independent of current direction. The experimental results are interpreted well using an expression based on the phenomenological model. Both the two- and four-fold terms vary inversely proportional to film thickness, indicating that interfacial scattering can significantly influence the spin-dependent transport properties.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  9. Weak antilocalization and conductance fluctuation in a single crystalline Bi nanowire

    SciTech Connect

    Kim, Jeongmin; Lee, Seunghyun; Kim, MinGin; Lee, Wooyoung E-mail: pk2015@columbia.edu; Brovman, Yuri M.; Kim, Philip E-mail: pk2015@columbia.edu

    2014-01-27

    We present the low temperature transport properties of an individual single-crystalline Bi nanowire grown by the on-film formation of nanowire method. The temperature dependent resistance and magnetoresistance of Bi nanowires were investigated. The phase coherence length was obtained from the fluctuation pattern of the magnetoresistance below 40 K using universal conductance fluctuation theory. The obtained temperature dependence of phase coherence length and the fluctuation amplitude indicates that the transport of electrons shows 2-dimensional characteristics originating from the surface states. The temperature dependence of the coherence length derived from the weak antilocalization effect using the Hikami–Larkin–Nagaoka model is consistent with that from the universal conductance fluctuations theory.

  10. Modulated surface nanostructures for enhanced light trapping and reduced surface reflection of crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Tayagaki, Takeshi; Hoshi, Yusuke; Hirai, Yuji; Matsuo, Yasutaka; Usami, Noritaka

    2016-05-01

    We demonstrated the fabrication of modulated surface nanostructures as a new surface texture design for thin wafer solar cells. Using a combination of conventional alkali etching and colloidal lithography, we fabricated surface textures with micrometer and nanometre scales on a Si substrate. These modulated surface nanostructures exhibit reduced surface reflection in a broad spectral range, compared with conventional micrometer textures. We investigated optical absorption using a rigorous coupled wave analysis simulation, which revealed a significant reduction in surface reflection over a broad spectral range and efficient light trapping (comparable to that of conventional micrometer-scale textures) for the modulated nanostructures. We found that the modulated surface nanostructures have a high potential of improving the performance of thin wafer crystalline Si solar cells.

  11. From amorphous to crystalline silicon nanoclusters: structural effects on exciton properties.

    PubMed

    Borrero-González, L J; Nunes, L A O; Guimarães, F E G; Wojcik, J; Mascher, P; Gennaro, A M; Tirado, M; Comedi, D

    2011-12-21

    Synchrotron x-ray absorption spectroscopy (XAS) and electron spin resonance (ESR) experiments were performed to determine, in combination with Raman spectroscopy and x-ray diffraction (XRD) data from previous reports, the structure and paramagnetic defect status of Si-nanoclusters (ncls) at various intermediate formation stages in Si-rich Si oxide films having different Si concentrations (y = 0.36-0.42 in Si(y)O(1-y)), fabricated by electron cyclotron resonance plasma-enhanced chemical vapor deposition and isochronally (2 h) annealed at various temperatures (T(a) = 900-1100 °C) under either Ar or (Ar + 5%H(2)) atmospheres. The corresponding emission properties were studied by stationary and time dependent photoluminescence (PL) spectroscopy in correlation with the structural and defect properties. To explain the experimental data, we propose crystallization by nucleation within already existing amorphous Si-ncls as the mechanism for the formation of the Si nanocrystals in the oxide matrix. The cluster-size dependent partial crystallization of Si-ncls at intermediate T(a) can be qualitatively understood in terms of a 'crystalline core-amorphous shell' Si-ncl model. The amorphous shell, which is invisible in most diffraction and electron microscopy experiments, is found to have an important impact on light emission. As the crystalline core grows at the expense of a thinning amorphous shell with increasing T(a), the PL undergoes a transition from a regime dominated by disorder-induced effects to a situation where quantum confinement of excitons prevails. PMID:22129528

  12. Vertical Single-Crystalline Organic Nanowires on Graphene: Solution-Phase Epitaxy and Optical Microcavities.

    PubMed

    Zheng, Jian-Yao; Xu, Hongjun; Wang, Jing Jing; Winters, Sinéad; Motta, Carlo; Karademir, Ertuğrul; Zhu, Weigang; Varrla, Eswaraiah; Duesberg, Georg S; Sanvito, Stefano; Hu, Wenping; Donegan, John F

    2016-08-10

    Vertically aligned nanowires (NWs) of single crystal semiconductors have attracted a great deal of interest in the past few years. They have strong potential to be used in device structures with high density and with intriguing optoelectronic properties. However, fabricating such nanowire structures using organic semiconducting materials remains technically challenging. Here we report a simple procedure for the synthesis of crystalline 9,10-bis(phenylethynyl) anthracene (BPEA) NWs on a graphene surface utilizing a solution-phase van der Waals (vdW) epitaxial strategy. The wires are found to grow preferentially in a vertical direction on the surface of graphene. Structural characterization and first-principles ab initio simulations were performed to investigate the epitaxial growth and the molecular orientation of the BPEA molecules on graphene was studied, revealing the role of interactions at the graphene-BPEA interface in determining the molecular orientation. These free-standing NWs showed not only efficient optical waveguiding with low loss along the NW but also confinement of light between the two end facets of the NW forming a microcavity Fabry-Pérot resonator. From an analysis of the optical dispersion within such NW microcavities, we observed strong slowing of the waveguided light with a group velocity reduced to one-tenth the speed of light. Applications of the vertical single-crystalline organic NWs grown on graphene will benefit from a combination of the unique electronic properties and flexibility of graphene and the tunable optical and electronic properties of organic NWs. Therefore, these vertical organic NW arrays on graphene offer the potential for realizing future on-chip light sources. PMID:27438189

  13. Rational Concept for Designing Vapor-Liquid-Solid Growth of Single Crystalline Metal Oxide Nanowires.

    PubMed

    Klamchuen, Annop; Suzuki, Masaru; Nagashima, Kazuki; Yoshida, Hideto; Kanai, Masaki; Zhuge, Fuwei; He, Yong; Meng, Gang; Kai, Shoichi; Takeda, Seiji; Kawai, Tomoji; Yanagida, Takeshi

    2015-10-14

    Metal oxide nanowires hold great promise for various device applications due to their unique and robust physical properties in air and/or water and also due to their abundance on Earth. Vapor-liquid-solid (VLS) growth of metal oxide nanowires offers the high controllability of their diameters and spatial positions. In addition, VLS growth has applicability to axial and/or radial heterostructures, which are not attainable by other nanowire growth methods. However, material species available for the VLS growth of metal oxide nanowires are substantially limited even though the variety of material species, which has fascinating physical properties, is the most interesting feature of metal oxides. Here we demonstrate a rational design for the VLS growth of various metal oxide nanowires, based on the "material flux window". This material flux window describes the concept of VLS nanowire growth within a limited material flux range, where nucleation preferentially occurs only at a liquid-solid interface. Although the material flux was previously thought to affect primarily the growth rate, we experimentally and theoretically demonstrate that the material flux is the important experimental variable for the VLS growth of metal oxide nanowires. On the basis of the material flux window concept, we discover novel metal oxide nanowires, composed of MnO, CaO, Sm2O3, NiO, and Eu2O3, which were previously impossible to form via the VLS route. The newly grown NiO nanowires exhibited stable memristive properties superior to conventional polycrystalline devices due to the single crystallinity. Thus, this VLS design route offers a useful guideline for the discovery of single crystalline nanowires that are composed of functional metal oxide materials. PMID:26372675

  14. Modification of crystalline silicon and diamond surfaces for the attachment of DNA

    NASA Astrophysics Data System (ADS)

    Strother, Todd Cory

    2001-07-01

    Hydrogen-terminated Si(111) surfaces are first modified by attachment of oligodeoxynucleotides, and characterized with respect to DNA surface density, chemical stability, and DNA hybridization binding specificity. Surface functionalization employs the reaction of o-unsaturated alkyl esters with the Si(111) surface using UV irradiation. Cleavage of the ester using potassium tert-butoxide yields a carboxyl-modified surface, which serves as a substrate for the attachment of DNA by means of an electrostatically adsorbed layer of polylysine and attachment of thiol modified DNA using a heterobifunctional cross-linker. The resultant DNA-modified surfaces are shown to exhibit excellent specificity and chemical stability under the conditions of DNA hybridization. The second approach is a more direct method of attaching oligonucleotides to silicon. UV light mediates the reaction of t-butyloxycarbonyl (t-BOC) protected o-unsaturated aminoalkane (10-aminodec-1-ene) with hydrogenterminated silicon (001). Removal of the t-BOC protecting group yields an aminodecane-modified silicon surface. The resultant amino groups can be coupled to thiol-modified oligodeoxyribonucleotides using a heterobifunctional crosslinker, permitting the preparation of DNA arrays. Two methods for controlling the surface density of oligodeoxyribonucleotides were explored: in the first, binary mixtures of 10-aminodec-1 ene and dodecene were utilized in the initial UV-mediated coupling reaction; a linear relationship was found between the mole fraction of aminodecene and the density of DNA hybridization sites. In the second, only a portion of the t-BOC protecting groups was removed from the surface by limiting the time allowed for the deprotection reaction. The final surface explored uses a UV-mediated reaction of alkenes to hydrogenterminated diamond. Polycrystalline diamond thin films are hydrogen terminated using a hydrogen plasma and are subjected to UV light in the presence of 1-alkenes. A

  15. Macroscopic Quantum Tunneling in a Bi2Sr2CaCu2O8+δ Single Crystalline Whisker

    NASA Astrophysics Data System (ADS)

    Kubo, Yuimaru; Takahide, Yamaguchi; Ueda, Shinya; Takano, Yoshihiko; Ootuka, Youiti

    2010-06-01

    Macroscopic quantum tunneling (MQT) has been observed in an intrinsic Josephson junction (IJJ) stack of a Bi2Sr2CaCu2O8+δ (BSCCO) single crystalline whisker with high precision using a home made setup. The cross-over temperature between thermal activation and MQT was about 260 mK, and the Josephson plasma frequency was estimated to be 86 GHz. Both the thermal escape theory and the MQT theory are consistent with the experiments. These facts strongly suggest that single crystalline BSCCO whiskers are high enough quality to be used as intrinsic Josephson quantum devices such as intrinsic Josephson phase qubits. This is the first demonstration of MQT in BSCCO single crystalline whiskers.

  16. Eighth workshop on crystalline silicon solar cell materials and processes: Extended abstracts and papers

    SciTech Connect

    1998-08-01

    The theme of this workshop is Supporting the Transition to World Class Manufacturing. This workshop provides a forum for an informal exchange of information between researchers in the photovoltaic and non-photovoltaic fields on various aspects of impurities and defects in silicon, their dynamics during device processing, and their application in defect engineering. This interaction helps establish a knowledge base that can be used for improving device fabrication processes to enhance solar-cell performance and reduce cell costs. It also provides an excellent opportunity for researchers from industry and universities to recognize mutual needs for future joint research. The workshop format features invited review presentations, panel discussions, and two poster sessions. The poster sessions create an opportunity for both university and industrial researchers to present their latest results and provide a natural forum for extended discussions and technical exchanges.

  17. Limiting factors for the application of crystalline upgraded metallurgical grade silicon

    SciTech Connect

    Schlosser, V.

    1984-05-01

    Differently processed upgraded metallurgical grade silicon (UMG-Si) has been used to produce planar diffused solar cells. The results obtained from these cells were used to evaluate the limiting factors governing the conversion efficiency in UMG-Si-cells. The present state of practical cell processing was taken into account for the discussion of the potential of new technologies. For conventionally processed cells on UMG-Si having a planar junction, it appears that a conversion efficiency of about 13 percent under AM1.5 conditions (incident light intensity = 1 kWm/sup -2/, T = 27/sup 0/C) cannot be exceeded. Experimentally a conversion efficiency of 10.5 percent was obtained.

  18. On the capability of deep level transient spectroscopy for characterizing multi-crystalline silicon

    SciTech Connect

    Mchedlidze, T.; Nacke, M.; Hieckmann, E.; Weber, J.

    2014-01-07

    The suitability of the deep level transient spectroscopy (DLTS) technique in exploring locations with high and degraded carrier lifetimes containing grain-boundaries (GBs) in multicrystalline silicon (mc-Si) wafers was studied. The types and locations of GBs were determined in mc-Si samples by electron backscatter diffraction. Mesa-type Schottky diodes were prepared at (along) GBs and at reference, GB-free locations. Detected DLTS signals varied strongly along the same GB. Experiments with dislocation networks, model structures for GBs, showed that GB-related traps may be explored only using special arrangement of a GB and the diode contacts. Iron-related carrier traps were detected in locations with degraded carrier lifetimes. Densities of the traps for near-GB and for GB free locations were compared to the lifetime measurement results.

  19. Influence of hydrogen on the regeneration of boron-oxygen related defects in crystalline silicon

    NASA Astrophysics Data System (ADS)

    Wilking, S.; Herguth, A.; Hahn, G.

    2013-05-01

    When exposed to light, boron doped monocrystalline Czochralski grown silicon suffers from degradation of the minority carrier lifetime due to the formation of recombination active boron-oxygen related defects. The so called regeneration procedure is able to convert these recombination active defects into a new less recombination active state characterized by a higher minority charge carrier lifetime and stability under illumination. However, the exact working principle on microscopic scale is still unknown even though some influencing factors were identified. The role of hydrogen in the regeneration process is investigated in this work. We find that the characteristic regeneration time constant is subject to variation depending on the process parameters of a Plasma Enhanced Chemical Vapor Deposition a-SiNx:H deposition, namely the applied gas flows, as well as on the thermal history of the sample prior to applying the regeneration procedure. The positive effect of a short high temperature (800-900 °C) step leads to the idea that the presence of atomic hydrogen in the silicon bulk is crucial for the regeneration effect to occur. The different regeneration behavior of samples with variable thickness of a hydrogen diffusion barrier, namely an Al2O3 layer capped by SiNx:H, supports those results. Finally, the importance of hydrogen for regeneration is directly shown on samples having different hydrogen bulk concentrations due to direct hydrogenation in a Microwave Induced Remote Hydrogen Plasma reactor. A new model to explain the effect of the regeneration of boron-oxygen related defect centers based on the possible role of atomic hydrogen is presented.

  20. Magnetic property and microstructure of single crystalline Nd2Fe14B ultrafine particles ball milled from HDDR powders

    SciTech Connect

    Li, WF; Hu, XC; Cui, BZ; Yang, JB; Han, JZ; Hadjipanayis, GC

    2013-08-01

    In this work we report the microstructure and magnetic property of single crystalline Nd2Fe14B ultrafine particles ball milled from HDDR Nd-Fe-B alloys. The average size of the particles is 283 nm, and TEM observation reveals that these particles are single crystalline. The coercivity of these particles is 6.0 kOe, which is much higher than that of the particles ball milled from sintered and hot pressed Nd-Fe-B magnets. Micromagnetic analysis shows that the coercivity degradation is caused by surface damage during ball milling. (C) 2013 Elsevier B.V. All rights reserved.