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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. Preparation and single molecule structure of electroactive polysilane end-grafted on a crystalline silicon surface

    NASA Astrophysics Data System (ADS)

    Furukawa, Kazuaki; Ebata, Keisuke

    2000-12-01

    Electrically active polysilanes of poly(methylphenylsilane) (PMPS) and poly[bis(p-n-butylphenyl)silane] (PBPS), which are, respectively, known as a good hole transporting material and a near-ultraviolet electroluminescent material, are end-grafted directly on a crystalline silicon surface. The single polysilane molecules are clearly distinguished one from the other on the surface by means of atomic force microscopy observations. End-grafted single molecules of PMPS are observed as dots while end-grafted PBPS appear as worms extending for more than 100 nm on the crystalline silicon surface.

  4. Thin single-crystalline silicon solar cells for space applications

    NASA Astrophysics Data System (ADS)

    Nijs, J.; Caymax, M.; Acke, P.; Roggen, J.; Lambrechts, M.; Gravesen, P.

    1986-11-01

    A technology to perform etching after the formation of the solar cell, using epitaxial deposition of the active layer of the cell combined with an etch stop technique is proposed. This can result in highly efficient silicon solar cells with thicknesses down to 10 microns.

  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. Dissolution chemistry and biocompatibility of single-crystalline silicon nanomembranes and associated materials for transient electronics.

    PubMed

    Hwang, Suk-Won; Park, Gayoung; Edwards, Chris; Corbin, Elise A; Kang, Seung-Kyun; Cheng, Huanyu; Song, Jun-Kyul; Kim, Jae-Hwan; Yu, Sooyoun; Ng, Joanne; Lee, Jung Eun; Kim, Jiyoung; Yee, Cassian; Bhaduri, Basanta; Su, Yewang; Omennetto, Fiorenzo G; Huang, Yonggang; Bashir, Rashid; Goddard, Lynford; Popescu, Gabriel; Lee, Kyung-Mi; Rogers, John A

    2014-06-24

    Single-crystalline silicon nanomembranes (Si NMs) represent a critically important class of material for high-performance forms of electronics that are capable of complete, controlled dissolution when immersed in water and/or biofluids, sometimes referred to as a type of "transient" electronics. The results reported here include the kinetics of hydrolysis of Si NMs in biofluids and various aqueous solutions through a range of relevant pH values, ionic concentrations and temperatures, and dependence on dopant types and concentrations. In vitro and in vivo investigations of Si NMs and other transient electronic materials demonstrate biocompatibility and bioresorption, thereby suggesting potential for envisioned applications in active, biodegradable electronic implants.

  7. 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

  8. Reduction in the thermal conductivity of single crystalline silicon by phononic crystal patterning.

    PubMed

    Hopkins, Patrick E; Reinke, Charles M; Su, Mehmet F; Olsson, Roy H; Shaner, Eric A; Leseman, Zayd C; Serrano, Justin R; Phinney, Leslie M; El-Kady, Ihab

    2011-01-12

    Phononic crystals (PnCs) are the acoustic wave equivalent of photonic crystals, where a periodic array of scattering inclusions located in a homogeneous host material causes certain frequencies to be completely reflected by the structure. In conjunction with creating a phononic band gap, anomalous dispersion accompanied by a large reduction in phonon group velocities can lead to a massive reduction in silicon thermal conductivity. We measured the cross plane thermal conductivity of a series of single crystalline silicon PnCs using time domain thermoreflectance. The measured values are over an order of magnitude lower than those obtained for bulk Si (from 148 W m(-1) K(-1) to as low as 6.8 W m(-1) K(-1)). The measured thermal conductivity is much smaller than that predicted by only accounting for boundary scattering at the interfaces of the PnC lattice, indicating that coherent phononic effects are causing an additional reduction to the cross plane thermal conductivity.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Formation of single crystalline tellurium supersaturated silicon pn junctions by ion implantation followed by pulsed laser melting

    NASA Astrophysics Data System (ADS)

    Xiyuan, Wang; Yongguang, Huang; Dewei, Liu; Xiaoning, Zhu; Xiao, Cui; Hongliang, Zhu

    2013-06-01

    Pn junctions based on single crystalline tellurium supersaturated silicon were formed by ion implantation followed by pulsed laser melting (PLM). P type silicon wafers were implanted with 245 keV 126Te+ to a dose of 2 × 1015 ions/cm2, after a PLM process (248 nm, laser fluence of 0.30 and 0.35 J/cm2, 1-5 pulses, duration 30 ns), an n+ type single crystalline tellurium supersaturated silicon layer with high carrier density (highest concentration 4.10 × 1019 cm-3, three orders of magnitude larger than the solid solution limit) was formed, it shows high broadband optical absorption from 400 to 2500 nm. Current—voltage measurements were performed on these diodes under dark and one standard sun (AM 1.5), and good rectification characteristics were observed. For present results, the samples with 4-5 pulses PLM are best.

  14. 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.

  15. 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⁾

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

    DOE PAGES

    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

  17. 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.

  18. Reflection-type single long-pulse solar simulator for high-efficiency crystalline silicon photovoltaic modules.

    PubMed

    Hu, Binxin; Li, Buyin; Zhao, Rixin; Yang, Tiechen

    2011-06-01

    Photovoltaic module measurements are predominantly taken by using pulsed solar simulators. However, significant errors can be generated when the existing simulators are applied to current high-efficiency crystalline silicon photovoltaic modules. This paper presents the design and implementation of a novel solar simulator featuring reflection-type light source and single long-pulse flash. The analysis and experimental study of the capacitance effect and the technical details of the simulator including reflection-type lamp house, xenon flash lamp power supply, and source-measure unit are introduced. The results show that the complete system achieves Class AAA performance in accordance with the international standard. The proposed simulator outperforms other similar products on the market and has been adopted by some well-known photovoltaic module manufacturers. The practical application demonstrates that this high-performance and cost-effective simulator is quite suitable for photovoltaic module production line.

  19. 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.

  20. Ellipsometric study of the polysilicon/thin oxide/single-crystalline silicon structure and its change upon annealing

    NASA Astrophysics Data System (ADS)

    Petrik, P.; Lohner, T.; Fried, M.; Gyulai, J.; Boell, U.; Berger, R.; Lehnert, W.

    2002-09-01

    Polysilicon/thin oxide/single-crystalline silicon structures used as emitters of bipolar transistors were measured using spectroscopic ellipsometry. The thin SiOx layer was deposited on the substrate in a rapid thermal processing chamber, then polysilicon was deposited, implanted with As, and annealed. During annealing the SiOx layer dissolves to islands retarding the diffusion of As, which results in a shallow p-n junction. The process--and as a consequence, the device performance--depends sensitively on the thickness of the oxide layer. We developed optical models to measure the thickness of the SiOx layer at each process step, i.e., after SiOx deposition, after polysilicon deposition, and after annealing. The structure, the surface quality, and the homogeneity of the polysilicon layers were obtained from the same optical model. The thickness of the initially 0.76-0.86 nm SiOx layer decreased to the detection limit of about 0.2 nm during annealing, together with a significant crystallization of the deposited amorphous Si resulting in a perfectly smooth surface with a native oxide layer. The uncertainty of the measurement of the SiOx layer after annealing was typically 0.2 nm even below the polysilicon layer of about 150 nm. Our results show that ellipsometry is a proper tool for the measurement of the thickness of the buried SiOx boundary layer, which can be applied as an in line or in situ measurement as well.

  1. 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.

  2. 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.

  3. Rotating Anisotropic Crystalline Silicon Nanoclusters in Graphene.

    PubMed

    Chen, Qu; Koh, Ai Leen; Robertson, Alex W; He, Kuang; Lee, Sungwoo; Yoon, Euijoon; Lee, Gun-Do; Sinclair, Robert; Warner, Jamie H

    2015-10-27

    The atomic structure and dynamics of silicon nanoclusters covalently bonded to graphene are studied using aberration-corrected transmission electron microscopy. We show that as the cluster size increases to 4-10 atoms, ordered crystalline cubic phases start to emerge. Anisotropic crystals are formed due to higher stability of the Si-C bond under electron beam irradiation compared to the Si-Si bond. Dynamics of the anisotropic crystalline Si nanoclusters reveal that they can rotate perpendicular to the graphene plane, with oscillations between the two geometric configurations driven by local volume constraints. These results provide important insights into the crystalline phases of clusters of inorganic dopants in graphene at the intermediate size range between isolated single atoms and larger bulk 2D forms.

  4. 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.

  5. 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%.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. High-speed thin-film transistors on single-crystalline, unstrained- and strained-silicon-based nanomembranes

    NASA Astrophysics Data System (ADS)

    Yuan, Hao-Chih

    This research focuses on developing high-performance single-crystal Si-based nanomembranes and high-frequency thin-film transistors (TFTs) using these nanomembranes on flexible plastic substrates. Unstrained Si or SiGe nanomembranes with thickness of several tens to a couple of hundred nanometers are derived from silicon-on-insulator (SOI) or silicon-germanium-on-insulator (SGOI) and are subsequently transferred and integrated with flexible plastic host substrates via a one-step dry printing technique. Biaxial tensile-strained Si membranes that utilize elastic strain-sharing between Si and additionally grown SiGe thin films are also successfully integrated with plastic host substrates and exhibit predicted strain status and negligible density of dislocations. Biaxial tensile strain enhances electron mobility and lowers Schottky contact resistance. As a result, flexible TFTs built on the strained Si-membranes demonstrate much higher electron effective mobility and higher drive current than the unstrained counterpart. The dependence of drive current and transconductance on uniaxial tensile strain introducing by mechanical bending is also discussed. A novel combined "hot-and-cold" TFT fabrication process is developed specifically for realizing a wide spectrum of micro-electronics that can exhibit RF performance and can be integrated on low-temperature plastic substrate. The "hot" process that consists of ion implant and high-temperature annealing for desired doping type, profile, and concentration is realized on the bulk SOI/SGOI substrates followed by the "cold" process that includes room-temperature silicon-monoxide (SiO) deposition as gate dielectric layer to ensure the process compatibility with low-temperature, low-cost plastics. With these developments flexible Si-membrane n-type RF TFTs for analog applications and complementary TFTs for digital applications are demonstrated for the first time. RF TFTs with 1.5-mum channel length have demonstrated record-high f

  11. Improved Josephson Qubits incorporating Crystalline Silicon Dielectrics

    NASA Astrophysics Data System (ADS)

    Gao, Yuanfeng; Maurer, Leon; Hover, David; Patel, Umeshkumar; McDermott, Robert

    2010-03-01

    Josephson junction phase quibts are a leading candidate for scalable quantum computing in the solid state. Their energy relaxation times are currently limited by microwave loss induced by a high density of two-level state (TLS) defects in the amorphous dielectric films of the circuit. It is expected that the integration of crystalline, defect-free dielectrics into the circuits will yield substantial improvements in qubit energy relaxation times. However, the epitaxial growth of a crystalline dielectric on a metal underlayer is a daunting challenge. Here we describe a novel approach in which the crystalline silicon nanomembrane of a Silicon-on-Insulator (SOI) wafer is used to form the junction shunt capacitor. The SOI wafer is thermocompression bonded to the device wafer. The handle and buried oxide layers of the SOI are then etched away, leaving the crystalline silicon layer for subsequent processing. We discuss device fabrication issues and present microwave transport data on lumped-element superconducting resonators incorporating the crystalline silicon.

  12. 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.

  13. Crystalline Silicon Dielectrics for Superconducting Qubit Circuits

    NASA Astrophysics Data System (ADS)

    Hover, David; Peng, Weina; Sendelbach, Steven; Eriksson, Mark; McDermott, Robert

    2009-03-01

    Superconducting qubit energy relaxation times are limited by microwave loss induced by a continuum of two-level state (TLS) defects in the dielectric materials of the circuit. State-of-the-art phase qubit circuits employ a micron-scale Josephson junction shunted by an external capacitor. In this case, the qubit T1 time is directly proportional to the quality factor (Q) of the capacitor dielectric. The amorphous capacitor dielectrics that have been used to date display intrinsic Q of order 10^3 to 10^4. Shunt capacitors with a Q of 10^6 are required to extend qubit T1 times well into the microsecond range. Crystalline dielectric materials are an attractive candidate for qubit capacitor dielectrics, due to the extremely low density of TLS defects. However, the robust integration of crystalline dielectrics with superconducting qubit circuits remains a challenge. Here we describe a novel approach to the realization of high-Q crystalline capacitor dielectrics for superconducting qubit circuits. The capacitor dielectric is a crystalline silicon nanomembrane. We discuss characterization of crystalline silicon capacitors with low-power microwave transport measurements at millikelvin temperatures. In addition, we report progress on integrating the crystalline capacitor process with Josephson qubit fabrication.

  14. 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.

  15. Mechanical Properties of Crystalline Silicon Carbide Nanowires.

    PubMed

    Zhang, Huan; Ding, Weiqiang; Aidun, Daryush K

    2015-02-01

    In this paper, the mechanical properties of crystalline silicon carbide nanowires, synthesized with a catalyst-free chemical vapor deposition method, were characterized with nanoscale tensile testing and mechanical resonance testing methods inside a scanning electron microscope. Tensile testing of individual silicon carbide nanowire was performed to determine the tensile properties of the material including the tensile strength, failure strain and Young's modulus. The silicon carbide nanowires were also excited to mechanical resonance in the scanning electron microscope vacuum chamber using mechanical excitation and electrical excitation methods, and the corresponding resonance frequencies were used to determine the Young's modulus of the material according to the simple beam theory. The Young's modulus values from tensile tests were in good agreement with the ones obtained from the mechanical resonance tests.

  16. 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.

  17. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    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%).

  19. 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

  20. 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

  1. 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.

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

    DOEpatents

    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.

  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. Stability of SiNX/SiNX double stack antireflection coating for single crystalline silicon solar cells.

    PubMed

    Lee, Youngseok; Gong, Daeyeong; Balaji, Nagarajan; Lee, Youn-Jung; Yi, Junsin

    2012-01-05

    Double stack antireflection coatings have significant advantages over single-layer antireflection coatings due to their broad-range coverage of the solar spectrum. A solar cell with 60-nm/20-nm SiNX:H double stack coatings has 17.8% efficiency, while that with a 80-nm SiNX:H single coating has 17.2% efficiency. The improvement of the efficiency is due to the effect of better passivation and better antireflection of the double stack antireflection coating. It is important that SiNX:H films have strong resistance against stress factors since they are used as antireflective coating for solar cells. However, the tolerance of SiNX:H films to external stresses has never been studied. In this paper, the stability of SiNX:H films prepared by a plasma-enhanced chemical vapor deposition system is studied. The stability tests are conducted using various forms of stress, such as prolonged thermal cycle, humidity, and UV exposure. The heat and damp test was conducted for 100 h, maintaining humidity at 85% and applying thermal cycles of rapidly changing temperatures from -20°C to 85°C over 5 h. UV exposure was conducted for 50 h using a 180-W UV lamp. This confirmed that the double stack antireflection coating is stable against external stress.

  5. Stability of SiNX/SiNX double stack antireflection coating for single crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Lee, Youngseok; Gong, Daeyeong; Balaji, Nagarajan; Lee, Youn-Jung; Yi, Junsin

    2012-01-01

    Double stack antireflection coatings have significant advantages over single-layer antireflection coatings due to their broad-range coverage of the solar spectrum. A solar cell with 60-nm/20-nm SiNX:H double stack coatings has 17.8% efficiency, while that with a 80-nm SiNX:H single coating has 17.2% efficiency. The improvement of the efficiency is due to the effect of better passivation and better antireflection of the double stack antireflection coating. It is important that SiNX:H films have strong resistance against stress factors since they are used as antireflective coating for solar cells. However, the tolerance of SiNX:H films to external stresses has never been studied. In this paper, the stability of SiNX:H films prepared by a plasma-enhanced chemical vapor deposition system is studied. The stability tests are conducted using various forms of stress, such as prolonged thermal cycle, humidity, and UV exposure. The heat and damp test was conducted for 100 h, maintaining humidity at 85% and applying thermal cycles of rapidly changing temperatures from -20°C to 85°C over 5 h. UV exposure was conducted for 50 h using a 180-W UV lamp. This confirmed that the double stack antireflection coating is stable against external stress.

  6. Stability of SiNX/SiNX double stack antireflection coating for single crystalline silicon solar cells

    PubMed Central

    2012-01-01

    Double stack antireflection coatings have significant advantages over single-layer antireflection coatings due to their broad-range coverage of the solar spectrum. A solar cell with 60-nm/20-nm SiNX:H double stack coatings has 17.8% efficiency, while that with a 80-nm SiNX:H single coating has 17.2% efficiency. The improvement of the efficiency is due to the effect of better passivation and better antireflection of the double stack antireflection coating. It is important that SiNX:H films have strong resistance against stress factors since they are used as antireflective coating for solar cells. However, the tolerance of SiNX:H films to external stresses has never been studied. In this paper, the stability of SiNX:H films prepared by a plasma-enhanced chemical vapor deposition system is studied. The stability tests are conducted using various forms of stress, such as prolonged thermal cycle, humidity, and UV exposure. The heat and damp test was conducted for 100 h, maintaining humidity at 85% and applying thermal cycles of rapidly changing temperatures from -20°C to 85°C over 5 h. UV exposure was conducted for 50 h using a 180-W UV lamp. This confirmed that the double stack antireflection coating is stable against external stress. PMID:22221389

  7. (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.

  8. 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.

  9. 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.

  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. 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.

  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. 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.

  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. Threshold for permanent refractive index change in crystalline silicon by femtosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Bachman, D.; Chen, Z.; Fedosejevs, R.; Tsui, Y. Y.; Van, V.

    2016-08-01

    An optical damage threshold for crystalline silicon from single femtosecond laser pulses was determined by detecting a permanent change in the refractive index of the material. This index change could be detected with unprecedented sensitivity by measuring the resonant wavelength shift of silicon integrated optics microring resonators irradiated with femtosecond laser pulses at 400 nm and 800 nm wavelengths. The threshold for permanent index change at 400 nm wavelength was determined to be 0.053 ± 0.007 J/cm2, which agrees with previously reported threshold values for femtosecond laser modification of crystalline silicon. However, the threshold for index change at 800 nm wavelength was found to be 0.044 ± 0.005 J/cm2, which is five times lower than the previously reported threshold values for visual change on the silicon surface. The discrepancy is attributed to possible modification of the crystallinity of silicon below the melting temperature that has not been detected before.

  16. Diffusion of silicon in crystalline germanium

    SciTech Connect

    Silvestri, H.H.; Bracht, H.; Hansen, J. Lundsgaard; Larsen, A.Nylandsted; Haller, E.E.

    2005-06-06

    We report the determination of the diffusion coefficient of Si in crystalline Ge over the temperature range of 550 to 900 C. A molecular beam epitaxy (MBE) grown buried Si layer in an epitaxial Ge layer on a crystalline Ge substrate was used as the source for the diffusion experiments. For samples annealed at temperatures above 700 C, a 50 nm thick SiO{sub 2} cap layer was deposited to prevent decomposition of the Ge surface. We found the temperature dependence of the diffusion coefficient to be described by a single activation energy (3.32 eV) and pre-factor (38 cm{sup 2}/s) over the entire temperature range studied. The diffusion of the isovalent Si in Ge is slower than Ge self-diffusion over the full temperature range and reveals an activation enthalpy which is higher than that of self-diffusion. This points to a reduced interaction potential between the Si atom and the native defect mediating the diffusion process. For Si, which is smaller in size than the Ge self-atom, a reduced interaction is expected for a Si-vacancy (Si-V{sub Ge}) pair. Therefore we conclude that Si diffuses in Ge via the vacancy mechanism.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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 108 and a high field-effect mobility of 609 cm2 V-1 s-1.

  3. 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}.

  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. Crystalline quality improvement in silicon films on sapphire using recrystallization from the silicon-sapphire interface

    SciTech Connect

    Alexandrov, P. A. Demakov, K. D.; Shemardov, S. G.; Kuznetsov, Yu. Yu.

    2010-10-15

    The use of the process of solid-phase recrystallization reduces to a great extent the number of defects in the silicon layer. An amorphous layer was formed by implantation of silicon ions. The crystalline quality of the SOS structures has been assessed by the method of high-resolution double-crystal X-ray diffraction. Silicon layers with a thickness d = 1000-2500 A and a high crystalline quality have been obtained after implantation of 150-keV silicon ions with subsequent high-temperature annealing.

  6. Diode laser processed crystalline silicon thin-film solar cells

    NASA Astrophysics Data System (ADS)

    Varlamov, S.; Eggleston, B.; Dore, J.; Evans, R.; Ong, D.; Kunz, O.; Huang, J.; Schubert, U.; Kim, K. H.; Egan, R.; Green, M.

    2013-03-01

    Line-focus diode laser is applied to advance crystalline silicon thin-film solar cell technology. Three new processes have been developed: 1) defect annealing/dopant activation; 2) dopant diffusion; 3) liquid phase crystallisation of thin films. The former two processes are applied to either create a solar cell device from pre-crystallised films or improve its performance while reducing the maximum temperature experienced by substrate. The later process is applied to amorphous silicon films to obtain high crystal and electronic quality material for thin-film solar cells with higher efficiency potential. Defect annealing/dopant activation and dopant diffusion in a few micron thick poly-Si films are achieved by scanning with line-focus 808 nm diode laser beam at 15-24 kW/cm2 laser power and 2~6 ms exposure. Temperature profile in the film during the treatment is independent from laser power and exposure but determined by beam shape. Solar cell open-circuit voltages of about 500 mV after such laser treatments is similar or even higher than voltages after standard rapid-thermal treatments while the highest temperature experienced by glass is 300C lower. Amorphous silicon films can be melted and subsequently liquid-phase crystallised by a single scan of line laser beam at about 20 kW/cm2 power and 10-15 ms exposure. Solar cells made of laser-crystallised material achieve 557 mV opencircuit voltage and 8.4% efficiency. Electronic quality of such cells is consistent with efficiencies exceeding 13% and it is currently limited by research-level simplified cell metallisation.

  7. 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...

  8. 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...

  9. 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.

  10. Single Crystal Silicon Instrument Mirrors

    NASA Technical Reports Server (NTRS)

    Bly, Vince

    2007-01-01

    The goals for the fabrication of single crystal silicon instrument mirrors include the following: 1) Develop a process for fabricating lightweight mirrors from single crystal silicon (SCS); 2) Modest lightweighting: 3X to 4X less than equivalent solid mirror; 3) High surface quality, better than lambda/40 RMS @ 633nm; 4) Significantly less expensive than current technology; and 5) Negligible distortion when cooled to cryogenic temperatures.

  11. 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.

  12. Inkjet technology for crystalline silicon photovoltaics.

    PubMed

    Stüwe, David; Mager, Dario; Biro, Daniel; Korvink, Jan G

    2015-01-27

    The world's ever increasing demand for energy necessitates technologies that generate electricity from inexhaustible and easily accessible energy sources. Silicon photovoltaics is a technology that can harvest the energy of sunlight. Its great characteristics have fueled research and development activities in this exciting field for many years now. One of the most important activities in the solar cell community is the investigation of alternative fabrication and structuring technologies, ideally serving both of the two main goals: device optimization and reduction of fabrication costs. Inkjet technology is practically evaluated along the whole process chain. Research activities cover many processes, such as surface texturing, emitter formation, or metallization. Furthermore, the inkjet technology itself is manifold as well. It can be used to apply inks that serve as a functional structure, present in the final device, as mask for subsequent structuring steps, or even serve as a reactant source to activate chemical etch reactions. This article reviews investigations of inkjet-printing in the field of silicon photovoltaics. The focus is on the different inkjet processes for individual fabrication steps of a solar cell. A technological overview and suggestions about where future work will be focused on are also provided. The great variety of the investigated processes highlights the ability of the inkjet technology to find its way into many other areas of functional printing and printed electronics.

  13. 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.

  14. 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.

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

    DOE PAGES

    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

  16. 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.

  17. 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.

  18. 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.

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

    SciTech Connect

    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. Crystalline-silicon reliability lessons for thin-film modules

    NASA Astrophysics Data System (ADS)

    Ross, R. G., Jr.

    1985-10-01

    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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. Crystalline silicon solar cells with high resistivity emitter

    NASA Astrophysics Data System (ADS)

    Panek, P.; Drabczyk, K.; Zięba, P.

    2009-06-01

    The paper presents a part of research targeted at the modification of crystalline silicon solar cell production using screen-printing technology. The proposed process is based on diffusion from POCl3 resulting in emitter with a sheet resistance on the level of 70 Ω/□ and then, shaped by high temperature passivation treatment. The study was focused on a shallow emitter of high resistivity and on its influence on output electrical parameters of a solar cell. Secondary ion mass spectrometry (SIMS) has been employed for appropriate distinguishing the total donor doped profile. The solar cell parameters were characterized by current-voltage characteristics and spectral response (SR) methods. Some aspects playing a role in suitable manufacturing process were discussed. The situation in a photovoltaic industry with emphasis on silicon supply and current prices of solar cells, modules and photovoltaic (PV) systems are described. The economic and quantitative estimation of the PV world market is shortly discussed.

  10. 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.

  11. 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.

  12. 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.

  13. TOPICAL REVIEW: New crystalline silicon ribbon materials for photovoltaics

    NASA Astrophysics Data System (ADS)

    Hahn, G.; Schönecker, A.

    2004-12-01

    The objective of this article is to review, in relation to photovoltaic applications, the current status of crystalline silicon ribbon technologies as an alternative to technologies based on wafers originating from ingots. Increased wafer demand, the foreseeable silicon feedstock shortage, and the need for a substantial module cost reduction are the main issues that must be faced in the booming photovoltaic market. Ribbon technologies make excellent use of silicon, as wafers are crystallized directly from the melt at the desired thickness and no kerf losses occur. Therefore, they offer a high potential for significantly reducing photovoltaic electricity costs as compared to technology based on wafers cut from ingots. However, the defect structure present in the ribbon silicon wafers can limit material quality and cell efficiency. We will review the most successful of the ribbon techniques already used in large scale production or currently in the pilot demonstration phase, with special emphasis on the defects incorporated during crystal growth. Because of the inhomogeneous distribution of defects, mapped characterization techniques have to be applied. Al and P gettering studies give an insight into the complex interaction of defects in the multicrystalline materials as the gettering efficiency is influenced by the state of the chemical bonding of the metal atoms. The most important technique for improvement of carrier lifetimes is hydrogenation, whose kinetics are strongly influenced by oxygen and carbon concentrations present in the material. The best cell efficiencies for laboratory-type (17%-18% cell area: 4 cm2) as well as industrial-type (15%-16% cell area: {\\ge } 80~{\\mathrm {cm^{2}}} ) ribbon silicon solar cells are in the same range as for standard wafers cut from ingots. A substantial cost reduction therefore seems achievable, although the most promising techniques need to be improved.

  14. 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.

  15. 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.

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  20. 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.

  1. Dry plasma processing for industrial crystalline silicon solar cell production

    NASA Astrophysics Data System (ADS)

    Hofmann, M.; Rentsch, J.; Preu, R.

    2010-10-01

    This paper gives an overview on the standard crystalline silicon solar cell manufacturing processes typically applied in industry. Main focus has been put on plasma processes which can replace existing, mainly wet chemical processes within the standard process flow. Finally, additional plasma processes are presented which are suited for higher-efficient solar cells, i.e. for the “passivated emitter and rear cell” concept (PERC) or the “heterojunction with intrinsic thin layer” approach (HIT). Plasma processes for the deposition of thin dielectric or semiconducting layers for surface passivation, emitter deposition or anti-reflective coating purposes are presented. Plasma etching processes for the removal of phosphorus silicate glass or parasitic emitters, for wafer cleaning and masked and mask-free surface texturisation are discussed.

  2. Performance Enhancement of Crystalline Silicon Solar Cells by Coating with Luminescent Silicon Nanostructures

    NASA Astrophysics Data System (ADS)

    Basu, Tuhin Shuvra; Ray, Mallar; Bandyopadhyay, Nil Ratan; Pramanick, Ashit Kumar; Hossain, Syed Minhaz

    2013-03-01

    In this work we report a technique that is potentially capable of increasing the efficiency of crystalline silicon solar cells, which dominate the present-day market of photovoltaic devices. The simple and cost-effective method involves coating the surface of a commercially procured silicon solar cell with luminescent silicon nanocrystals. Core/shell silicon/silicon-oxide nanostructures are fabricated by an inexpensive and reproducible technique, where coarse silicon powders are repeatedly milled, oxidized, and etched until their sizes are reduced so as to exhibit room-temperature photoluminescence under ultraviolet excitation. A thin coating of these nanostructures on a standard solar cell, obtained by a simple dip-coating method, increases the open-circuit voltage and short-circuit current, which consequently increases the maximum power delivered by ~16.3% and efficiency by almost ˜39%. We propose that the core/shell nanostructures act as luminescent convertors that convert higher-energy photons to lower-energy photons, thereby leading to less thermal relaxation loss of photoexcited carriers.

  3. A magnesium/amorphous silicon passivating contact for n-type crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Wan, Yimao; Samundsett, Chris; Yan, Di; Allen, Thomas; Peng, Jun; Cui, Jie; Zhang, Xinyu; Bullock, James; Cuevas, Andres

    2016-09-01

    Among the metals, magnesium has one of the lowest work functions, with a value of 3.7 eV. This makes it very suitable to form an electron-conductive cathode contact for silicon solar cells. We present here the experimental demonstration of an amorphous silicon/magnesium/aluminium (a-Si:H/Mg/Al) passivating contact for silicon solar cells. The conduction properties of a thermally evaporated Mg/Al contact structure on n-type crystalline silicon (c-Si) are investigated, achieving a low resistivity Ohmic contact to moderately doped n-type c-Si (˜5 × 1015 cm-3) of ˜0.31 Ω cm2 and ˜0.22 Ω cm2 for samples with and without an amorphous silicon passivating interlayer, respectively. Application of the passivating cathode to the whole rear surface of n-type front junction c-Si solar cells leads to a power conversion efficiency of 19% in a proof-of-concept device. The low thermal budget of the cathode formation, its dopant-less nature, and the simplicity of the device structure enabled by the Mg/Al contact open up possibilities in designing and fabricating low-cost silicon solar cells.

  4. 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

  5. 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.

  6. Dynamics of light-induced FeB pair dissociation in crystalline silicon

    SciTech Connect

    Geerligs, L.J.; Macdonald, Daniel

    2004-11-29

    The dynamics of light-induced dissociation of iron-boron (FeB) pairs in p-type crystalline silicon is investigated. The dissociation is observed to be a single-exponential process which is balanced with thermal repairing. The dissociation rate is proportional to the square of the carrier generation rate and the inverse square of the FeB concentration. This suggests that the dissociation process involves two recombination or electron capture events. A proportionality constant of 5x10{sup -15} s describes the dissociation rate well in the absence of other significant recombination channels. The dissociation rate decreases in the presence of other recombination channels. These results can be used for reliable detection of iron in silicon devices and materials, and for further elucidation of the electronically driven FeB dissociation reaction.

  7. 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.

  8. 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.

  9. 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...

  10. 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. Photovoltaic Technology Co., Ltd. Zhejiang Sunflower Light Energy Zhejiang Sunflower Light...

  11. 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.

  12. Degradation Analysis of Weathered Crystalline-Silicon PV Modules: Preprint

    SciTech Connect

    Osterwald, C. R.; Anderberg, A.; Rummel, S.; Ottoson, L.

    2002-05-01

    We present an analysis of the results of a solar weathering program that found a linear relationship between maximum power degradation and the total UV exposure dose for four different types of commercial crystalline Si modules. The average degradation rate for the four modules types was 0.71% per year. The analysis showed that losses of short-circuit current were responsible for the maximum power degradation. Judging by the appearance of the undegraded control modules, it is very doubtful that the short-circuit current losses were caused by encapsulation browning or obscuration. When we compared the quantum efficiency of a single cell in a degraded module to one from an unexposed control module, it appears that most of the degradation has occurred in the 800 - 1100 nm wave-length region, and not the short wavelength region.

  13. 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

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

    PubMed

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

    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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Magnetotransport of single crystalline NbAs

    DOE PAGES

    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

  20. 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.

  1. 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.

  2. Reactive ion etching (RIE) technique for application in crystalline silicon solar cells

    SciTech Connect

    Yoo, Jinsu

    2010-04-15

    Saw damage removal (SDR) and texturing by conventional wet chemical processes with alkali solution etch about 20 micron of silicon wafer on both sides, resulting in thin wafers with which solar cell processing is difficult. Reactive ion etching (RIE) for silicon surface texturing is very effective in reducing surface reflectance of thin crystalline silicon wafers by trapping the light of longer wavelength. High efficiency solar cells were fabricated during this study using optimized RIE. Saw damage removal (SDR) with acidic mixture followed by RIE-texturing showed the decrease in silicon loss by {proportional_to}67% and {proportional_to}70% compared to conventional SDR and texturing by alkaline solution. Also, the crystalline silicon solar cells fabricated by using RIE-texturing showed conversion efficiency as high as 16.7% and 16.1% compared with 16.2%, which was obtained in the case of the cell fabricated with SDR and texturing with NaOH solution. (author)

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. Aluminum gettering of crystalline silicon for improvement of minority carrier diffusion length and for studies of fundamental diffusion mechanisms

    NASA Astrophysics Data System (ADS)

    Joshi, Subhash Mukund

    Large-grained, multi crystalline silicon for solar cell applications is a very inhomogeneous material with localized regions of high dislocation density and large impurity and precipitate concentrations which limit solar cell efficiency by acting as carrier recombination sites. Due to slow dissolution of precipitates in multi crystalline silicon, these regions cannot be improved by conventional gettering treatments for removal of metal impurities which give good results for single crystal silicon. Extended, high-temperature aluminum gettering is shown to successfully improve the minority carrier diffusion lengths in these localized, poor quality regions and to homogenize the electrical properties of multicrystalline silicon wafers. Cold is a substitutional-interstitial impurity in silicon, whereby its diffusion creates non-equilibrium concentrations of the native point defects in silicon, self-interstitials and vacancies. The diffusion. of gold is therefore controlled by the relaxation of these non-equilibrium point defect concentrations by dislocations or surfaces. Deliberate gold contamination of single-crystal, dislocation-free silicon wafers has been performed followed by aluminum gettering of the gold in silicon. It is shown that the aluminum gettering process can successfully getter gold in silicon, and that the outdiffusion of gold from the silicon is controlled by the proximity to the wafer surfaces rather than by proximity to the aluminum gettering layer. The indiffusion of gold in silicon has been widely demonstrated by experiments and modeling to be dominated by the Kick-Out mechanism, whereby the indiffusion of gold causes supersaturation of self-interstitials, with a minimal contribution from the Frank-Turnbull mechanism, whereby the indiffusion of gold causes undersaturation of vacancies. Fitting of the above-mentioned experimental results on aluminum gettering of gold has been done to show that the opposite holds true for outdiffusion of gold, i

  8. Magnetism in single-crystalline CePtSn.

    SciTech Connect

    Bordallo, H. N.; Chang, S.; Lacerda, A. H.; Nakotte, H.; Takabatake, T.; Torikachvili, M. S.

    1999-08-04

    CePtSn exhibits two antiferromagnetic transitions at low temperatures. We report on magnetoresistance and in magnetization studies of single-crystalline CePtSn in magnetic fields up to 18 T. The data were taken to establish the magnetic phase diagrams for CePtSn in fields applied along the principal directions.

  9. Cavity polaritons in an organic single-crystalline rubrene microcavity

    NASA Astrophysics Data System (ADS)

    Tsuchimoto, Yuta; Nagai, Hikaru; Amano, Masamitsu; Bando, Kazuki; Kondo, Hisao

    2014-06-01

    We fabricated a single-crystalline rubrene microcavity using a simple solution technique and observed cavity polaritons in the microcavity at room temperature (RT). Large Rabi splitting energies were obtained from dispersion of the cavity polaritons. Furthermore, photoluminescence from the cavity polaritons was observed at RT. The findings will be of importance for the application of cavity polaritons.

  10. Single crystalline SiGe layers on Si by solid phase epitaxy

    NASA Astrophysics Data System (ADS)

    Lieten, R. R.; McCallum, J. C.; Johnson, B. C.

    2015-04-01

    We demonstrate a straightforward way to obtain single crystalline SiGe layers on silicon substrates. Amorphous SiGe layers, deposited by plasma enhanced chemical vapour deposition on Si, are transformed into single crystalline and smooth layers by solid phase epitaxy during annealing in a N2 atmosphere. The SiGe layers relax during the crystallization anneal and become slightly tensile strained during cooldown due to the thermal mismatch. The SiGe layers show excellent structural quality for compositions ranging from Ge- to Si-rich. The Ge content can be accurately estimated from the SiH4 to GeH4 flow ratio. Furthermore, the crystallization temperature decreases linearly with increasing Ge content from 725 °C for a-Si to 475 °C for a-Ge.

  11. Low temperature oxidation of crystalline silicon using excimer laser irradiation

    NASA Astrophysics Data System (ADS)

    Nayar, Vishal; Boyd, Ian W.; Goodall, F. N.; Arthur, G.

    In this paper we present a study of ultra-violet laser oxidation of silicon at low temperature (< 650° C), using both 249 and 193 nm radiation. Calculation of the surface temperature rise during the laser pulses suggests that non-thermal oxidation mechanisms are present. In addition to the growth of planar thin oxides over macroscopic areas, a new technique for selectivity oxidising silicon by direct image projection, i.e., direct growth lithography (DGL) is also preliminarily presented.

  12. Electrically Active Defects In Solar Cells Based On Amorphous Silicon/Crystalline Silicon Heterojunction After Irradiation By Heavy Xe Ions

    NASA Astrophysics Data System (ADS)

    Harmatha, Ladislav; Mikolášek, Miroslav; Stuchlíková, L'ubica; Kósa, Arpád; Žiška, Milan; Hrubčín, Ladislav; Skuratov, Vladimir A.

    2015-11-01

    The contribution is focused on the diagnostics of structures with a heterojunction between amorphous and crystalline silicon prepared by HIT (Heterojunction with an Intrinsic Thin layer) technology. The samples were irradiated by Xe ions with energy 167 MeV and doses from 5 × 108 cm-2 to 5 × 1010 cm-2. Radiation defects induced in the bulk of Si and at the hydrogenated amorphous silicon and crystalline silicon (a-Si:H/c-Si) interface were identified by Deep Level Transient Spectroscopy (DLTS). Radiation induced A-centre traps, boron vacancy traps and different types of divacancies with a high value of activation energy were observed. With an increased fluence of heavy ions the nature and density of the radiation induced defects was changed.

  13. 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.

  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.

  15. 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,...

  16. 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.

  17. 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.

  18. 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...

  19. 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...

  20. 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...

  1. 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.

  2. 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

  3. 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.

  4. 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).

  5. 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.

  6. 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.

  7. IR characterization of hydrogen in crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Stavola, M.; Kleekajai, S.; Wen, L.; Peng, C.; Yelundur, V.; Rohatgi, A.; Carnel, L.; Kalejs, J.

    2009-12-01

    Hydrogen is commonly introduced into silicon solar cells to reduce the deleterious effects of defects and to increase cell efficiency. A process that is widely used by industry to introduce hydrogen is by the post-deposition annealing of a hydrogen-rich SiN x layer that is used as an anti-reflection coating. A number of questions about this hydrogen introduction process and hydrogen's subsequent interactions with defects have proved difficult to address because of the low concentration of hydrogen that is introduced into the Si bulk. We have used the fundamental knowledge of hydrogenated defects that has been revealed by recent investigations of impurity-H complexes to develop strategies by which hydrogen in silicon can be detected by IR spectroscopy with high sensitivity. The introduction of hydrogen into Si by the post-deposition annealing of a SiN x coating has been investigated.

  8. Nanoimprinted diffraction gratings for crystalline silicon solar cells: implementation, characterization and simulation.

    PubMed

    Mellor, Alexander; Hauser, Hubert; Wellens, Christine; Benick, Jan; Eisenlohr, Johannes; Peters, Marius; Guttowski, Aron; Tobías, Ignacio; Martí, Antonio; Luque, Antonio; Bläsi, Benedikt

    2013-03-11

    Light trapping is becoming of increasing importance in crystalline silicon solar cells as thinner wafers are used to reduce costs. In this work, we report on light trapping by rear-side diffraction gratings produced by nano-imprint lithography using interference lithography as the mastering technology. Gratings fabricated on crystalline silicon wafers are shown to provide significant absorption enhancements. Through a combination of optical measurement and simulation, it is shown that the crossed grating provides better absorption enhancement than the linear grating, and that the parasitic reflector absorption is reduced by planarizing the rear reflector, leading to an increase in the useful absorption in the silicon. Finally, electro-optical simulations are performed of solar cells employing the fabricated grating structures to estimate efficiency enhancement potential.

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. Luminescence of rutile structured crystalline silicon dioxide (stishovite)

    NASA Astrophysics Data System (ADS)

    Trukhin, A. N.; Smits, K.; Chikvaidze, G.; Dyuzheva, T. I.; Lityagina, L. M.

    2014-07-01

    Luminescence spectrum of synthetic mono-crystalline stishovite comprises a slow blue band at ~400 nm (~3.1 eV) and a fast UV band at ~260 nm (~4.7 eV), as well as some bands in near-infrared range of spectra. The NIR luminescence of stishovite crystal, excited with lasers 532 nm, 248 nm and 193 nm as well as x-ray, possesses several sharp lines. A zero phonon line is situated at 787 nm (1.57 eV) and grows with cooling. An anti-Stokes line is located at 771 nm (1.68 eV). This line disappears with cooling. In a powder sample of stishovite created by shock waves generated by the impact of a 50-m-diameter meteorite in Arizona 50,000 years ago, the PL broad blue band is situated at 425 nm (2.9 eV), the UV band at ~260 nm (~4.7 eV), and the sharp lines, seen only under 193 nm laser, at 689 nm (1.789 eV), 694 nm (1.785 eV) and 706 nm (1.754 eV). We ascribe the fast UV luminescence to singlet-singlet transitions and the slow blue band to triplet-singlet transitions of the same intrinsic defect of stishovite in both types of samples. The blue band in stishovite crystal exhibits delayed luminescence of recombination nature, whereas the blue band of Arizona's powder sample does not exhibit such effect. This difference is explained by different surroundings of luminescence center in those samples. NIR luminescence of mono-crystalline stishovite is ascribed to carbon impurity penetrated in the sample from graphite heater. NIR luminescence of powder from Arizona has not yet found an explanation.

  16. Crystalline-amorphous core-shell silicon nanowires for high capacity and high current battery electrodes.

    PubMed

    Cui, Li-Feng; Ruffo, Riccardo; Chan, Candace K; Peng, Hailin; Cui, Yi

    2009-01-01

    Silicon is an attractive alloy-type anode material for lithium ion batteries because of its highest known capacity (4200 mAh/g). However silicon's large volume change upon lithium insertion and extraction, which causes pulverization and capacity fading, has limited its applications. Designing nanoscale hierarchical structures is a novel approach to address the issues associated with the large volume changes. In this letter, we introduce a core-shell design of silicon nanowires for highpower and long-life lithium battery electrodes. Silicon crystalline-amorphous core-shell nanowires were grown directly on stainless steel current collectors by a simple one-step synthesis. Amorphous Si shells instead of crystalline Si cores can be selected to be electrochemically active due to the difference of their lithiation potentials. Therefore, crystalline Si cores function as a stable mechanical support and an efficient electrical conducting pathway while amorphous shells store Li(+) ions. We demonstrate here that these core-shell nanowires have high charge storage capacity ( approximately 1000 mAh/g, 3 times of carbon) with approximately 90% capacity retention over 100 cycles. They also show excellent electrochemical performance at high rate charging and discharging (6.8 A/g, approximately 20 times of carbon at 1 h rate).

  17. 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.

  18. 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.

  19. 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.

  20. Organic-inorganic halide perovskite/crystalline silicon four-terminal tandem solar cells.

    PubMed

    Löper, Philipp; Moon, Soo-Jin; de Nicolas, Sílvia Martín; Niesen, Bjoern; Ledinsky, Martin; Nicolay, Sylvain; Bailat, Julien; Yum, Jun-Ho; De Wolf, Stefaan; Ballif, Christophe

    2015-01-21

    Tandem solar cells constructed from a crystalline silicon (c-Si) bottom cell and a low-cost top cell offer a promising way to ensure long-term price reductions of photovoltaic modules. We present a four-terminal tandem solar cell consisting of a methyl ammonium lead triiodide (CH3NH3PbI3) top cell and a c-Si heterojunction bottom cell. The CH3NH3PbI3 top cell exhibits broad-band transparency owing to its design free of metallic components and yields a transmittance of >55% in the near-infrared spectral region. This allows the generation of a short-circuit current density of 13.7 mA cm(-2) in the bottom cell. The four-terminal tandem solar cell yields an efficiency of 13.4% (top cell: 6.2%, bottom cell: 7.2%), which is a gain of 1.8%abs with respect to the reference single-junction CH3NH3PbI3 solar cell with metal back contact. We employ the four-terminal tandem solar cell for a detailed investigation of the optical losses and to derive guidelines for further efficiency improvements. Based on a power loss analysis, we estimate that tandem efficiencies of ∼28% are attainable using an optically optimized system based on current technology, whereas a fully optimized, ultimate device with matched current could yield up to 31.6%.

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

    PubMed

    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.

  2. Observation of vacancy in crystalline silicon using low-temperature ultrasonic measurements

    NASA Astrophysics Data System (ADS)

    Goto, Terutaka; Yamada-Kaneta, Hiroshi; Sato, Koji; Hikin, Masatoshi; Nemoto, Yuichi; Nakamura, Shintaro

    2007-12-01

    We have successfully observed isolated vacancies in crystalline silicon using low-temperature ultrasonic measurements. The floating zone (FZ) silicon exhibits softening in longitudinal elastic constants consisting of transverse C44 and (C11-C12)/2 in part with decreasing temperature below 20 K down to 20 mK. The applied magnetic fields of up to 16 T at the base temperature 20 mK show no effect on the low-temperature softening in non-doped FZ silicon, while the fields of up to 2 T suppress the low-temperature softening in boron-doped FZ silicon. This experiment suggests that isolated vacancies with non-magnetic charge state V0 in the non-doped FZ silicon and with magnetic charge state V+ in the boron-doped FZ silicon lead to the low-temperature softening. We have also observed the low-temperature softening in the Pv-region of non-doped Czochralski (CZ) silicon ingot, which indicates vacancy distribution. A coupling of electric quadrupoles of triplet state of vacancy orbital to the elastic strains of the sound waves is discussed for description of the low-temperature softening.

  3. 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.

  4. 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

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. Electrochemical immobilization of Cs in single-crystalline SYNROC

    NASA Astrophysics Data System (ADS)

    Abe, Hideki; Satoh, Akira; Nishida, Kenji; Abe, Eiji; Naka, Takashi; Imai, Motoharu; Kitazawa, Hideaki

    2006-05-01

    The development of a disposal technique for the radiotoxic 137Cs in nuclear wastes is one of the most urgent issues in nuclear fuel technology. An effective disposal method of 137Cs is to immobilize it in a synthetic rock (SYNROC) material: cesium titanate hollandite, 137Cs xTi 8O 16 ( I4/ m, a=10.2866(3) Å, c=2.9669(1) Å). Practical applications of 137Cs xTi 8O 16 have been restricted so far because the conventional synthetic method requires strong chemical reducers and reaction temperatures higher than 1250 °C. In this report, we present a milder preparation method of Cs xTi 8O 16 by electrolysis of a mixture of Cs 2MoO 4 and TiO 2 in ambient atmosphere at 900 °C. The Cs content in the resultant single-crystalline Cs 1.35Ti 8O 16 is competitive with the highest value in polycrystalline Cs 1.36±0.03Ti 8O 16 prepared by the conventional synthetic method. The electrochemical preparation of Cs 1.35Ti 8O 16 is a promising way to immobilize a high quantity of 137Cs ions in a stable form of single-crystalline SYNROC.

  11. Ultrasonic study of vacancy in single crystal silicon at low temperatures

    NASA Astrophysics Data System (ADS)

    Akatsu, M.; Goto, T.; Y-Kaneta, H.; Watanabe, H.; Nemoto, Y.; Mitsumoto, K.; Baba, S.; Nagai, Y.; Nakamura, S.

    2009-03-01

    We have performed ultrasonic measurements at low temperatures in order to investigate vacancy in single crystal silicon. The longitudinal elastic constants of non-doped and boron-doped silicon grown by a floating zone method exhibit appreciable softening with decreasing temperature down to 20 mK. The softening of boron-doped silicon is easily suppressed in applied magnetic field up to 2 T, while the softening of non-doped silicon is robust in fields even up to 16 T. The softening of elastic constants in high-purity crystalline silicon is certainly caused by the coupling of elastic strains of the ultrasonic waves to electric quadrupoles of the vacancy orbital.

  12. 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.'

  13. 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.

  14. 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.

  15. Microdefects and self-interstitial diffusion in crystalline silicon

    NASA Astrophysics Data System (ADS)

    Knowlton, William Barthelemy

    In this thesis, a study is presented of D-defects and self-interstitial diffusion in silicon using Li ion (Lisp+) drifting in an electric field and transmission electron microscopy (TEM). Obstruction of Lisp+ drifting has been found in wafers from certain but not all FZ p-type Si. Incomplete Lisp+ drifting always occurs in the central region of the wafers. This work established that interstitial oxygen is not responsible for hindering Lisp+ drifting. The Osb i concentration was measured ({˜}2× 10sp{15}\\ cmsp{-3}) by local vibrational mode Fourier transform infrared spectroscopy and did not vary radially across the wafer. TEM was performed on a samples from the partially Lisp+ drifted area and compared to regions without D-defects. Precipitates were found only in the region containing D-defects that had partially Lisp+ drifted. This result indicates D-defects are responsible for the precipitation that halts the Lisp+ drift process. The precipitates were characterized using selected area diffraction (SAD) and image contrast analysis. The results suggested that the precipitates may cause stacking faults and their identity may be lithium silicides such as Lisb{21}Sisb5\\ and\\ Lisb{13}Sisb4. TEM revealed a decreasing distribution of Li precipitates as a function of Lisp+ drift depth along the growth direction. A preliminary model is presented that simulates Lisp+ drifting. The objective of the model is to incorporate the Li precipitate density distribution and Lisp+ drift depth to extract the size and capture cross-section of the D-defects. Nitrogen (N) doping has been shown to eliminate D-defects as measured by conventional techniques. However, Lisp+ drifting has shown that D-defects are indeed still present. Lisp+ drifting is able to detect D-defects at concentrations lower than conventional techniques. Lisp+ 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Resonant wideband polarizer with single silicon layer

    NASA Astrophysics Data System (ADS)

    Lee, Kyu J.; Curzan, James; Shokooh-Saremi, Mehrdad; Magnusson, Robert

    2011-05-01

    We present the design, fabrication, and characterization of a guided-mode resonance polarizer operating in the telecommunication band. This polarizer consists of a single one-dimensional silicon grating layer and a glass substrate. The device is designed using inverse mathematical methods and fabricated by thin-film deposition, holographic-interference patterning, and etching. The fabricated polarizer has high transmittance for transverse-magnetic polarization and low transmittance for transverse-electric polarization over a ˜200 nm wavelength range. Its experimental extinction ratio is ˜670:1 at a central wavelength λc=1563 nm. Experimental and theoretical results are in good agreement.

  1. 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.

  2. Single-Event Effects in Silicon and Silicon Carbide Power Devices

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

    NASA Electronics Parts and Packaging program-funded activities over the past year on single-event effects in silicon and silicon carbide power devices are presented, with focus on SiC device failure signatures.

  3. 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

  4. 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.

  5. 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.

  6. Single-crystalline octahedral Au-Ag nanoframes.

    PubMed

    Hong, Xun; Wang, Dingsheng; Cai, Shuangfei; Rong, Hongpan; Li, Yadong

    2012-11-01

    We report the formation of single-crystalline octahedral Au-Ag nanoframes by a modified galvanic replacement reaction. Upon sequential addition of AgNO(3), CuCl, and HAuCl(4) to octadecylamine solution, truncated polyhedral silver nanoparticles formed first and then changed into octahedral Au-Ag nanoframes, without requiring a conventional Ag removal step with additional oxidation etchant. The nanoframes have 12 sides, and all of the eight {111} faces are empty. The side grows along the [110] direction, and the diameter is less than 10 nm. The selective gold deposition on the high-energy (110) surface, the diffusion, and the selective redeposition of Au and Ag atoms are the key reasons for the formation of octahedral nanoframes.

  7. Single crystalline Si substrate growth by lateral diffusion epitaxy

    NASA Astrophysics Data System (ADS)

    Li, Bo; Yu, Hao Ling; Shen, Huaxiang; Kitai, Adrian

    2013-03-01

    A novel crystal growth method named lateral diffusion epitaxy (LDE) as well as the necessary growth apparatus are described in detail. Single crystalline Si strips are grown on (1 1 1) Si substrates by LDE. The thickness of the LDE Si strips is around 100 μm, and the aspect ratio of width to thickness is around 2 which is an improvement compared with Si strips grown by conventional liquid phase epitaxy (LPE). The LDE Si strip can be peeled off from the substrate for further device processing since the 100 μm thickness provides reasonable mechanical strength. Due to the low cost of LDE technology it is potentially a good candidate for PV application if the LDE can achieve continuous growth and therefore grow Si strips in sizes for practical application.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Modelisation of boron diffusion from ultra-low-energy implantation in crystalline silicon

    NASA Astrophysics Data System (ADS)

    Ihaddadene-Le Coq, L.; Marcon, J.; Dush-Nicolini, A.; Masmoudi, K.; Ketata, K.

    2003-12-01

    We have investigated and modeled the boron diffusion in silicon following ultra-low-energy implantation (500 eV). It is well known that reducing implant energies is an effective way to eliminate transient enhanced diffusion due to the excess of interstitials from the implant. However, for sub-keV B implants diffusion remains enhanced. This enhancement is linked to the presence of a silicon boride layer located at the silicon surface which creates interstitials. This phenomenon is named "boron enhanced diffusion" (BED). The BED effect is of obvious interest since it counteracts the advantage obtained by reducing the ion implantation energy. For these reasons, we have investigated the diffusion of low-energy boron implanted in crystalline silicon and tested a complete simulation program, which takes into account the effect of boron precipitation and the effect of the silicon boride layer as a source of self-interstitials. Experimental results have been simulated and consistent parameters have been found to fit the data. BED effect has been studied. Model parameters extractions have been discussed.

  13. 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.

  14. 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.

  15. 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.

  16. 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).

  17. 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.

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

    PubMed

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

    2016-01-20

    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.

  19. 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

  20. 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

  1. 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.

  2. Band offsets at the crystalline / hydrogenated amorphous silicon interface from first-principles

    NASA Astrophysics Data System (ADS)

    Hazrati, Ebrahim; Jarolimek, Karol; de Wijs, Gilles A.; InstituteMolecules; Materials Team

    2015-03-01

    The heterojunction formed between crystalline silicon (c-Si) and hydrogenated amorphous silicon (a-Si:H) is a key component of a new type of high-efficiency silicon solar cell. Since a-Si:H has a larger band gap than c-Si, band offsets are formed at the interface. A band offset at the minority carrier band will mitigate recombination and lead to an increased efficiency. Experimental values of band offsets scatter in a broad range. However, a recent meta-analysis of the results (W. van Sark et al.pp. 405, Springer 2012) gives a larger valence offset (0.40 eV) than the conduction offset (0.15 eV). In light of the conflicting reports our goal is to calculate the band offsets at the c-Si/a-Si:H interface from first-principles. We have prepared several atomistic models of the interface. The crystalline part is terminated with (111) surfaces on both sides. The amorphous structure is generated by simulating an annealing process at 1100 K, with DFT molecular dynamics. Once the atomistic is ready it can be used to calculate the electronic structure of the interface. Our preliminary results show that the valence offset is larger than the conduction band offset.

  3. 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.

  4. Epitaxial Growth of Zinc Oxide on Single Crystalline Gold Plates

    NASA Astrophysics Data System (ADS)

    Greenberg, Kathryn; Joo, John; Baram, Mor; Clarke, David; Hu, Evelyn

    2012-02-01

    Although metal-oxide interfaces are the critical components of many electronic and optical devices, it is rare to find epitaxial metal-oxide structures. We demonstrate for the first time, a method for the low temperature, epitaxial growth of zinc oxide (ZnO) on single crystalline gold plates. The gold plates, up to 100μm in width, are grown from a gold-surfactant complex. Even with the large lattice mismatch between (111) gold and (0001) ZnO, we are able to form epitaxial zinc oxide at 90^oC on top of the single crystal gold plates. This epitaxial growth is confirmed using transmission electron microscopy, electron diffraction, and electron backscatterer diffraction. Micro-photoluminescence is also performed to investigate the optical properties of the epitaxial zinc oxide. We remove the grown ZnO membranes from the gold plates using a stamping and etching process. These membranes can potentially be used to fabricate high quality microdisks and photonic crystals. The metal-oxide interfaces that we have fabricated may have the ability to be used in a number of technologically important applications, including as better electrical contacts and for improved light extraction from planar LED structures.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

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

    DOE PAGES

    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

  14. 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/.

  15. 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.

  16. Mismatched front and back gratings for optimum light trapping in ultra-thin crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Hsu, Wei-Chun; Tong, Jonathan K.; Branham, Matthew S.; Huang, Yi; Yerci, Selçuk; Boriskina, Svetlana V.; Chen, Gang

    2016-10-01

    The implementation of a front and back grating in ultra-thin photovoltaic cells is a promising approach towards improving light trapping. A simple design rule was developed using the least common multiple (LCM) of the front and back grating periods. From this design rule, several optimal period combinations can be found, providing greater design flexibility for absorbers of indirect band gap materials. Using numerical simulations, the photo-generated current (Jph) for a 10-μm-thick crystalline silicon absorber was predicted to be as high as 38 mA/cm2, which is 11.74% higher than that of a single front grating (Jph=34 mA/cm2).

  17. Superconducting single crystalline YBa2Cu3O7- δ on SrTiO3 buffered Si (100)

    NASA Astrophysics Data System (ADS)

    Jahangir Moghadam, Mohammadreza; Ahmadi Majlan, Kamyar; Zhang, Hao; Shen, Xuan; Chrysler, Matthew; Conlin, Patrick; Hensley, Ricky; Su, Dong; Wei, John; Ngai, Joseph

    2015-03-01

    The growth of crystalline oxides on semiconductors enables new functionalities to be integrated with semiconducting technologies. Here, thin films of optimally-doped (001)-oriented YBa2Cu3O7- δ are epitaxially integrated on silicon (001) through growth on a SrTiO3 buffer. The former is grown using pulsed-laser deposition and the latter is grown on Si using oxide molecular beam epitaxy. The single crystal nature of the SrTiO3 buffer enables very high transition temperatures to be achieved. For a 30 nm thick SrTiO3 buffer, YBa2Cu3O7- δ films exhibiting a transition temperature of ~ 95 K, and a narrow transition width (<5 K) are achieved. The integration of single crystalline YBa2Cu3O7- δ on Si (001) paves the way for the potential exploration of cuprate materials in a variety of applications.

  18. 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.

  19. 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.

  20. 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

  1. 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

  2. Synthesis and magnetic properties of single-crystalline magnetite nanowires

    NASA Astrophysics Data System (ADS)

    Han, Qin; Liu, Zhenghui; Xu, Yingying; Zhang, Han

    2007-09-01

    By carefully controlling the reaction conditions, nanowires of Fe 3O 4 are directly acquired from nanowires of α-Fe 2O 3 in a reduced atmosphere at 410-430 °C. X-ray diffraction, Raman spectrum, and transmission electron microscopic analyses demonstrate that the product is single-crystalline Fe 3O 4. The nanowires have diameters of 40-90 nm and lengths of 10-20 μm, which are close to those of the pristine α-Fe 2O 3 nanowires. By studying different growth conditions, we find that hydrogen can push the conversion of the crystal structures, while temperature determines the chemical composition of the final products. The magnetic properties of as-prepared Fe 3O 4 nanowires are measured using a quantum design magnetic property measurement system. The nanowires show a ferrimagnetic behavior at room temperature and their magnetic properties are strongly influenced by surface and interface effects. The Verwey transition temperature ( TV=116 K) is found to be a little lower than that of bulk materials, which can be attributed to the small deviation from stoichiometry caused by the oxygen vacancies near the surfaces. Below 12 K, the nanowires show a spin-glass-like behavior owing to the disordered frozen magnetic state at the surfaces.

  3. 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.

  4. Formation of high conductive nano-crystalline silicon embedded in amorphous silicon-carbide films with large optical band gap

    NASA Astrophysics Data System (ADS)

    Ji, Yang; Shan, Dan; Qian, Mingqing; Xu, Jun; Li, Wei; Chen, Kunji

    2016-10-01

    High conductive phosphorus-doped nano-crystalline Si embedded in Silicon-Carbide (SiC) host matrix (nc-Si:SiC) films were obtained by thermally annealing doped amorphous Si-rich SiC materials. It was found that the room conductivity is increased significantly accompanying with the increase of doping concentrations as well as the enhanced crystallizations. The conductivity can be as high as 630 S/cm for samples with the optical band gap around 2.7 eV, while the carrier mobility is about 17.9 cm2/ V.s. Temperature-dependent conductivity and mobility measurements were performed which suggested that the carrier transport process is strongly affected by both the grain boundaries and the doping concentrations.

  5. 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.

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

    DOE PAGES

    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

  7. 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.

  8. 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.

  9. 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.

  10. On the origin of anisotropic lithiation in crystalline silicon over germanium: A first principles study

    NASA Astrophysics Data System (ADS)

    Chou, Chia-Yun; Hwang, Gyeong S.

    2014-12-01

    Silicon (Si) and germanium (Ge) are both recognized as a promising anode material for high-energy lithium-ion batteries. Si is abundant and best known for its superior gravimetric energy storage capacity, while Ge exhibits faster charge/discharge rates and better capacity retention. Recently, it was discovered that Si lithiation exhibits strong orientation dependence while Ge lithiation proceeds isotropically, although they have the same crystalline structure. To better understand the underlying reasons behind these distinctive differences, we examine and compare the lithiation behaviors at the Li4Si/c-Si(1 1 0) and Li4Ge/c-Ge(1 1 0) model systems using ab initio molecular dynamics simulations. In comparison to lithiated c-Si, where a sharp amorphous-crystalline interface remains and advances rather slowly, lithiated c-Ge tends to loose its crystallinity rapidly, resulting in a graded lithiation front of fast propagation speed. Analysis of the elastic responses and dynamics of the host Si and Ge lattices clearly demonstrate that from the beginning of the lithiation process, Ge lattice responds with more significant weakening as compared to the rigid Si lattice. Moreover, the more flexible Ge lattice is found to undergo facile atomic rearrangements during lithiation, overshadowing the original crystallographic characteristic. These unique properties of Ge thereby contribute synergistically to the rapid and isotropic lithiation.

  11. 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.

  12. 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.

  13. Advanced APCVD-processes for high-temperature grown crystalline silicon thin film solar cells.

    PubMed

    Driessen, Marion; Merkel, Benjamin; Reber, Stefan

    2011-09-01

    Crystalline silicon thin film (cSiTF) solar cells based on the epitaxial wafer-equivalent (EpiWE) concept combine advantages of wafer-based and thin film silicon solar cells. In this paper two processes beyond the standard process sequence for cSiTF cell fabrication are described. The first provides an alternative to wet chemical saw damage removal by chemical vapor etching (CVE) with hydrogen chloride in-situ prior to epitaxial deposition. This application decreases the number of process and handling steps. Solar cells fabricated with different etching processes achieved efficiencies up to 14.7%. 1300 degrees C etching temperature led to better cell results than 1200 degrees C. The second investigated process aims for an improvement of cell efficiency by implementation of a reflecting interlayer between substrate and active solar cell. Some characteristics of epitaxial lateral overgrowth (ELO) of a patterned silicon dioxide film in a lab-type reactor constructed at Fraunhofer ISE are described and first solar cell results are presented.

  14. 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.

  15. Role of MW-ECR hydrogen plasma on dopant deactivation and open-circuit voltage in crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Madi, D.; Prathap, P.; Slaoui, A.

    2015-01-01

    Plasma hydrogenation is an efficient method to passivate intergrain and intragrain defects of polycrystalline silicon (pc-Si) solar cells. The hydrogenation experiments were carried out in hydrogen plasma generated in an electron cyclotron resonance system controlling different operating parameters such as microwave power ( P MW), process time ( t H) and hydrogenation temperature ( T H) for a fixed hydrogen flux of 30 sccm. The hydrogenation of n+pp+ pc-Si solar cells resulted in an improvement in the open-circuit voltage. The improvement was correlated with the dopant deactivation due to the formation of boron-hydrogen bonding. This was demonstrated from the changes in the doping level after hydrogenation of n+p diode structures made using single crystalline silicon as a reference material. It was found that deactivation of boron was more pronounced at high microwave plasma power, in good agreement with the high open-circuit voltage values obtained on pc-Si mesa cells. On the other hand, the effect of longer hydrogenation time and higher temperature resulted in a decrease of boron deactivation, while an increase in V oc with a tendency of saturation at high T H was observed. Reasons for such behavior were thoroughly explained.

  16. Thin film silicon by a microwave plasma deposition technique: Growth and devices, and, interface effects in amorphous silicon/crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Jagannathan, Basanth

    Thin film silicon (Si) was deposited by a microwave plasma CVD technique, employing double dilution of silane, for the growth of low hydrogen content Si films with a controllable microstructure on amorphous substrates at low temperatures (<400sp°C). The double dilution was achieved by using a Ar (He) carrier for silane and its subsequent dilution by Hsb2. Structural and electrical properties of the films have been investigated over a wide growth space (temperature, power, pressure and dilution). Amorphous Si films deposited by silane diluted in He showed a compact nature and a hydrogen content of ˜8 at.% with a photo/dark conductivity ratio of 10sp4. Thin film transistors (W/L = 500/25) fabricated on these films, showed an on/off ratio of ˜10sp6 and a low threshold voltage of 2.92 volts. Microcrystalline Si films with a high crystalline content (˜80%) were also prepared by this technique. Such films showed a dark conductivity ˜10sp{-6} S/cm, with a conduction activation energy of 0.49 eV. Film growth and properties have been compared for deposition in Ar and He carrier systems and growth models have been proposed. Low temperature junction formation by undoped thin film silicon was examined through a thin film silicon/p-type crystalline silicon heterojunctions. The thin film silicon layers were deposited by rf glow discharge, dc magnetron sputtering and microwave plasma CVD. The hetero-interface was identified by current transport analysis and high frequency capacitance methods as the key parameter controlling the photovoltaic (PV) response. The effect of the interface on the device properties (PV, junction, and carrier transport) was examined with respect to modifications created by chemical treatment, type of plasma species, their energy and film microstructure interacting with the substrate. Thermally stimulated capacitance was used to determine the interfacial trap parameters. Plasma deposition of thin film silicon on chemically clean c-Si created electron

  17. Frictional Properties of Single Crystalline and Quasicrystalline Surfaces

    NASA Astrophysics Data System (ADS)

    Gellman, Andrew

    2000-03-01

    The use of ultra-high vacuum surface science methods has been aplied to the problem of studying friction between single srystalline and quasicrystalline metal surfaces. A experimental apparatus has been developed that combines the ability to perform surface preparation and analysis with the ability to make measurements of macroscopic friction forces between surfaces in sliding contact. This UHV chamber allows simultaneous preparation and characterization of two sample surfaces. These are usually single crystalline samples of the same metal and can be either perfectly clean or modified by adsorbed species such as atoms or molecules. Once prepared these two surfaces can be brought into contact under an applied normal load (Fn = 0.001 0.1 N) and sheared relative to one another at constant velocity (vs = 1 100 mm/s). Both normal and shear forces are measured simultaneously enabling one to determine a coefficient of friction. This unique apparatus has been used to study a number of problems in tribology. Adsorbed species on metal surfaces serve as a lubricants and prevent direct metal-metal contact. We have addressed the issue of surface coverage effects on interfacial friction. Surfaces have been prepared with adsorbed species ranging continuously in coverage from zero monolayers to many ( 100) monolayers. These experiments have been performed with pairs of both Ni(100) and Cu(111) surfaces. The interesting observation has been that adsorbed layers of atoms have little or no influence on friction coefficients between the two surfaces at coverages below one monolayer. Adsorbed molecules such as ethanol or trifluoroethanol are more interesting in this regard. They also have little influence on friction when adsorbed at coverages of < 1 monolayer, however, once the coverage exceeds 1 monolayer the coefficient of friction drops substantially. Friction reaches its limit at coverages of 5 10 monolayer. It is quite interesting to note that these metal single crystal surface

  18. 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.

  19. Fabricating a Microcomputer on a Single Silicon Wafer

    NASA Technical Reports Server (NTRS)

    Evanchuk, V. L.

    1983-01-01

    Concept for "microcomputer on a slice" reduces microcomputer costs by eliminating scribing, wiring, and packaging of individual circuit chips. Low-cost microcomputer on silicon slice contains redundant components. All components-central processing unit, input/output circuitry, read-only memory, and random-access memory (CPU, I/O, ROM, and RAM) on placed on single silicon wafer.

  20. 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.

  1. Investigation of modified p-n junctions in crystalline silicon on glass solar cells

    NASA Astrophysics Data System (ADS)

    Lausch, D.; Werner, M.; Naumann, V.; Schneider, J.; Hagendorf, C.

    2011-04-01

    In this paper various methods for studying p-n junctions in thin film solar cells are applied with the aim to localize and investigate defects on a microscopic scale. Different electron and ion beam characterization methods are introduced to determine the p-n junction position using two different examples from crystalline silicon on glass thin film technology. In a first example, planview and cross section electron beam induced current measurements revealed that oxygen rich columnar growth at textured substrates strongly disturbs the p-n junction. In a second example, diffusion from glass substrate is identified by ToF-SIMS to influence the electrical and structural characteristics of the thin Si layer resulting in a modified p-n junction. A model describing the formation of both defect structures is introduced.

  2. 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

  3. 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.

  4. 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.

  5. Quantum confinement of crystalline silicon nanotubes with nonuniform wall thickness: Implication to modulation doping

    NASA Astrophysics Data System (ADS)

    Yan, Binghai; Zhou, Gang; Zeng, Xiao Cheng; Wu, Jian; Gu, Bing-Lin; Duan, Wenhui

    2007-09-01

    First-principles calculations of crystalline silicon nanotubes (SiNTs) show that nonuniformity in wall thickness can cause sizable variation in the band gap as well as notable shift in the optical absorption spectrum. A unique quantum confinement behavior is observed: the electronic wave functions of the valence band maximum and conduction band minimum are due mainly to atoms located in the thicker side of the tube wall. This is advantageous to spatially separate the doping impurities from the conducting channel in doped SiNTs. Practically, the performance of the SiNT-based transistors may be substantially improved by selective p /n doping in the thinner side of the tube wall in the spirit of modulation doping.

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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).

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

    SciTech Connect

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

    2015-06-16

    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. In conclusion, 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.

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

    DOE PAGES

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

    2015-06-16

    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 pathsmore » and special configurations such as dumbbell complex, di-interstitial (IV-pair+2I) superdiffuser, tetrahedral vacancy complex, and more. In conclusion, 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.« less

  15. 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.

  16. Combined Effect of Mechanical Grooving and Stain-Etched Surface on Optical and Electrical Properties of Crystalline Silicon Substrates

    NASA Astrophysics Data System (ADS)

    Zarroug, Ahmed; Derbali, Lotfi; Ouertani, Rachid; Dimassi, Wissem; Ezzaouia, Hatem

    2014-05-01

    This paper investigates the combined effect of mechanical grooving and porous silicon (PS) on the front surface reflectance and the electronic properties of crystalline silicon substrates. Mechanical surface texturization leads to reduce the cell reflectance, enhance the light trapping and augment the carrier collection probability. PS was introduced as an efficient antireflective coating (ARC) onto the front surface of crystalline silicon solar cell. Micro-periodic V-shaped grooves were made by means of a micro-groove machining process prior to junction formation. Subsequently, wafers were subjected to an isotropic potassium hydroxide (KOH) etching so that the V-shape would be turned to a U-shape. We found that the successive treatment of silicon surfaces with stain-etching, grooving then alkaline etching enhances the absorption of the textured surface, and decreases the reflectance from 35% to 7% in the 300-1200 nm wavelength range. We obtained a significant increase in the overall light path that generates the building up of the light trapping inside the substrate. We found an improvement in the illuminated I-V characteristics and an increase in the minority carrier lifetime τeff. Such a simple method was adopted to effectively reinforce the overall device performance of crystalline silicon-based solar cells.

  17. High performance organic/20 μm crystalline-silicon heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    He, Jian; Gao, Pingqi; Sheng, Jiang; Yang, Xi; Zhou, Suqiong; Ying, Zhiqin; Ye, Jichun

    2015-06-01

    Si/organic hybrid solar cells have attracted considerable attention as a promise long-range photovoltaic technique with low process cost and high power conversion efficiency. However, the consumption of a whole bulk silicon wafer in this kind of cells is obviously not cost-effective. Here, we report a flexible poly (3, 4-ethylene-dioxythiophene):polystyrenesulfonate/crystalline silicon (c-Si) heterojunction solar cell with substrate thickness of sub-20 μm. The c-Si substrate has a nanopore surface texturing fabricated by a sample metal-assisted chemical etching process. In comparison to the non-textured thin c-Si cell, the nanopore-textured cell shows a 19.5% increase in JSC and a 40.2% increase in the efficiency. The inherent advantages of absorption improvement, p-n junction area increase, and carrier collection capability enhancement endow this nanopore-textured thin c-Si hybrid solar cell to approach an efficiency of 8.7%, as high as its bulk counterpart.

  18. Temperature dependence of the band-band absorption coefficient in crystalline silicon from photoluminescence

    NASA Astrophysics Data System (ADS)

    Nguyen, Hieu T.; Rougieux, Fiacre E.; Mitchell, Bernhard; Macdonald, Daniel

    2014-01-01

    The band-band absorption coefficient in crystalline silicon has been determined using spectral photoluminescence measurements across the wavelength range of 990-1300 nm, and a parameterization of the temperature dependence has been established to allow interpolation of accurate values of the absorption coefficient for any temperature between 170 and 363 K. Band-band absorption coefficient measurements across a temperature range of 78-363 K are found to match well with previous results from MacFarlane et al. [Phys. Rev. 111, 1245 (1958)], and are extended to significantly longer wavelengths. In addition, we report the band-band absorption coefficient across the temperature range from 270-350 K with 10 K intervals, a range in which most practical silicon based devices operate, and for which there are only sparse data available at present. Moreover, the absorption coefficient is shown to vary by up to 50% for every 10 K increment around room temperature. Furthermore, the likely origins of the differences among the absorption coefficient of several commonly referenced works by Green [Sol. Energy Mater. Sol. Cells 92, 1305 (2008)], Daub and Würfel [Phys. Rev. Lett. 74, 1020 (1995)], and MacFarlane et al. [Phys. Rev. 111, 1245 (1958)] are discussed.

  19. Wafer-scale synthesis of single-crystal zigzag silicon nanowire arrays with controlled turning angles.

    PubMed

    Chen, Huan; Wang, Hui; Zhang, Xiao-Hong; Lee, Chun-Sing; Lee, Shuit-Tong

    2010-03-10

    Silicon nanowires (SiNWs) having curved structures may have unique advantages in device fabrication. However, no methods are available to prepare curved SiNWs controllably. In this work, we report the preparation of three types of single-crystal SiNWs with various turning angles via metal-assisted chemical etching using (111)-oriented silicon wafers near room temperature. The zigzag SiNWs are single crystals and can be p- or n-doped using corresponding Si wafer as substrate. The controlled growth direction is attributed to the preferred movement of Ag nanoparticles along 001 and other directions in Si wafer. Our results demonstrate that metal-assisted chemical etching may be a viable approach to fabricate SiNWs with desired turning angles by utilizing the various crystalline directions in a Si wafer.

  20. 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

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. In situ spectroscopic ellipsometry studies of hydrogen ion bombardment of crystalline silicon

    SciTech Connect

    Hu, Y.Z.; Li, M.; Conrad, K.; Andres, J.W.; Irene, E.A.; Denker, M.; Ray, M.; McGuire, G.

    1992-05-01

    Hydrogen-bombardment induced damage in single crystal silicon as a function of the substrate temperature, ion energy, and ion dose was studied using in situ spectroscopic ellipsometry over the photon energy range 2.0-5.5 eV under high vacuum conditions. The incident hydrogen ion energies were 300 and 1000 eV, and the doses were 10{sup 15}-10{sup 18} ions/cm{sup 2}. In situ spectroscopic ellipsometry results showed that the damage layer thicknesses for the samples bombarded at elevated temperatures are smaller than for samples bombarded at room temperature and subsequently annealed at the same elevated temperature. The diffusion coefficient for hydrogen in silicon of 6 x 10{sup {minus}15} cm{sup {minus}2}/s was obtained from the in situ spectroscopic ellipsometry data. 40 refs., 11 figs., 1 tab.

  6. 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

  7. One-dimensional single-crystalline bismuth oxide micro/nanoribbons: morphology-controlled synthesis and luminescent properties.

    PubMed

    Ling, B; Sun, X W; Zhao, J L; Shen, Y Q; Dong, Z L; Sun, L D; Li, S F; Zhang, S

    2010-12-01

    Based on a facile vapor-phase transport method without any catalyst and template, one-dimensional single-crystalline bismuth oxide (Bi2O3) micro/nanoribbons were fabricated on silicon substrates in large quantities and morphology-controlled fabrication of Bi2O3 was achieved from a single precursor. The widths of Bi2O3 ribbons varied from 0.2 to 20 microm depending on the deposition temperatures. The thickness was in the range of 0.1-2 microm and the length reached several hundred micrometers and even millimeter range. The detailed composition and structural analysis confirmed the single-crystalline nature of alpha-Bi2O3 micro/nanoribbons with monoclinic structure. The photoluminescence spectrum of a single Bi2O3 ribbon showed a broadband emission from 450 to 750 nm in the visible region, consisting two peaks located at 589 and 697 nm which were primarily originated from the impurity ions and crystal defects. A self-catalyzed vapor-solid model was proposed to account for the growth mechanism of Bi2O3 ribbons with different morphologies. PMID:21121334

  8. 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.

  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. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. Nature of the metastable boron-oxygen complex formation in crystalline silicon

    NASA Astrophysics Data System (ADS)

    Crandall, Richard S.

    2010-11-01

    Transient capacitance measurements reveal new physics of metastable defect formation in boron-doped oxygen-containing crystalline silicon solar cells. These measurements demonstrate that holes are deeply trapped during defect formation and removed during thermal annealing with activation energy of 1.3 eV. Previous theoretical models {Du et al., [Phys. Rev. Lett. 97, 256602 (2006)] and Adey et al., [Phys. Rev. Lett. 93, 055504 (2004)]} are supported by present findings that defect formation is a slow two-stage process with activation energies of 0.17 eV and 0.4 eV at high and low temperature, respectively. Repulsive hole capture by a positive oxygen-dimer determines the defect formation rate at low temperature {Du et al., [Phys. Rev. Lett. 97, 256602 (2006)]}. The high temperature process is governed by a structural conversion of the dimer {Du et al., [Phys. Rev. Lett. 97, 256602 (2006)] and Adey et al., [Phys. Rev. Lett. 93, 055504 (2004)]}. An abnormally low rate prefactor allows this low-enthalpy reaction to be observed at the higher temperature. This dimer conversion presents an excellent example of an "entropy barrier" that explains the low conversion rate. Disparate formation and annealing results published here and in other publications are related by the Meyer-Neldel rule with an isokinetic temperature of 410 K.

  18. 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.

  19. 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.

  20. 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.

  1. 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).

  2. 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.

  3. 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.

  4. 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

  5. High crystalline quality single crystal chemical vapour deposition diamond

    NASA Astrophysics Data System (ADS)

    Martineau, P. M.; Gaukroger, M. P.; Guy, K. B.; Lawson, S. C.; Twitchen, D. J.; Friel, I.; Hansen, J. O.; Summerton, G. C.; Addison, T. P. G.; Burns, R.

    2009-09-01

    Homoepitaxial chemical vapour deposition (CVD) on high pressure, high temperature (HPHT) synthetic diamond substrates allows the production of diamond material with controlled point defect content. In order to minimize the extended defect content, however, it is necessary to minimize the number of substrate extended defects that reach the initial growth surface and the nucleation of dislocations at the interface between the CVD layer and its substrate. X-ray topography has indicated that when type IIa HPHT synthetic substrates are used, the density of dislocations nucleating at the interface can be less than 400 cm-2. X-ray topography, photoluminescence imaging and birefringence microscopy of HPHT grown synthetic type IIa diamond clearly show that the extended defect content is growth sector dependent. lang111rang sectors contain the highest concentration of both stacking faults and dislocations but lang100rang sectors are relatively free of both. It has been shown that HPHT treatment of such material can significantly reduce the area of stacking faults and cause dislocations to move. This knowledge, coupled with an understanding of how growth sectors develop during HPHT synthesis, has been used to guide selection and processing of substrates suitable for CVD synthesis of material with high crystalline perfection and controlled point defect content.

  6. Shock compression of [001] single crystal silicon

    DOE PAGES

    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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Fabrication of surface plasmon resonators by nanoskiving single-crystalline gold microplates

    NASA Astrophysics Data System (ADS)

    Wiley, Benjamin J.; Lipomi, Darren J.; Bao, Jiming; Capasso, Federico; Whitesides, George M.

    2009-02-01

    This paper demonstrates the sectioning of chemically synthesized, single-crystalline microplates of gold with an ultramicrotome to produce single-crystalline nanowires. This method produces collinearly aligned nanostructures with small, regular changes in dimension with each consecutive cross-section. The diamond knife cuts cleanly through microplates 100 nm thick without bending the resulting nanowire, and cuts through the sharp edges of a crystal to generate nanoscale tips. This paper demonstrates that the smooth surface of the single-crystalline gold nanowires allows them to guide plasmons with lower loss than rough, polycrystalline nanowires, and that the sharp tips on the singlecrystalline nanowires serve as optical antenna that selectively couple light into the nanowire at the resonance frequency of the sharp tip.

  12. 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

  13. 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.

  14. 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.

  15. Electrical properties of grain boundaries and dislocations in crystalline silicon: Influence of impurity incorporation and hydrogenation

    NASA Astrophysics Data System (ADS)

    Park, Yongkook

    This thesis examines the electrical properties of grain boundaries (GBs) and dislocations in crystalline silicon. The influence of impurity incorporation and hydrogenation on the electrical properties of grain boundaries , as well as the electrical activity of impurity decorated dislocations and the retention of impurities at dislocations at high temperatures have been investigated. The electrical properties of Si GB were examined by C-V, J-V , and capacitance transient methods using aluminum/Si(100)/Si(001) junctions. First, the density of states and the carrier capture cross-sections of the clean GB were evaluated by C-V/J-V analyses. The density of GB states was determined as 4.0x1012 cm-2eV -1. It was found that the states close to the valance band edge have relatively smaller hole capture cross sections than those at higher energy position, and electron capture cross sections are at least two or three orders larger than the corresponding hole capture cross sections. Secondly, the influence of iron contamination and hydrogenation following iron contamination on the electrical properties of (110)/(001) Si GB was characterized by a capacitance transient technique. Compared with the clean sample, iron contamination increased both the density of states by at least three times and the zero-bias barrier height by 70 meV, while reducing by two orders of magnitude the electron/hole capture cross-section ratio. Hydrogenation following iron contamination led to the reduction of the density of Fe-decorated GB states, which was increased to over 2x1013 cm-2eV-1 after iron contamination, to ˜1x1013 cm-2 eV-1 after hydrogenation treatment. The increased zero-bias GB energy barrier due to iron contamination was reversed as well by hydrogen treatment. The density of GB states before and after hydrogenation was evaluated by J-V, C-V and capacitance transient methods using gold/direct-silicon-bonded (DSB) (110) thin silicon top layer/(100) silicon substrate junctions. The GB

  16. {116} faceted anatase single-crystalline nanosheet arrays: facile synthesis and enhanced electrochemical performances

    NASA Astrophysics Data System (ADS)

    Li, Feng; Li, Xiaoning; Peng, Ranran; Zhai, Xiaofang; Yang, Shangfeng; Fu, Zhengping; Lu, Yalin

    2014-10-01

    Single-crystalline anatase TiO2 nanosheet arrays were synthesized on a transparent conductive fluorine-doped tin oxide (FTO) substrate with a unique one-step alcohol-thermal process. The nanosheets were nearly vertically grown on the FTO substrate along their <11&cmb.macr;0> zone, and they were dominated by {116} facets. The as-fabricated {116} faceted single-crystalline anatase nanosheet arrays exhibit a much higher reduction capacity and a much better electrochemical reversibility than both {001} faceted anatase single-crystalline nanosheet arrays and P25 film. The results indicate a promising application potential for the new material in the photoelectrochemical field.Single-crystalline anatase TiO2 nanosheet arrays were synthesized on a transparent conductive fluorine-doped tin oxide (FTO) substrate with a unique one-step alcohol-thermal process. The nanosheets were nearly vertically grown on the FTO substrate along their <11&cmb.macr;0> zone, and they were dominated by {116} facets. The as-fabricated {116} faceted single-crystalline anatase nanosheet arrays exhibit a much higher reduction capacity and a much better electrochemical reversibility than both {001} faceted anatase single-crystalline nanosheet arrays and P25 film. The results indicate a promising application potential for the new material in the photoelectrochemical field. Electronic supplementary information (ESI) available: Photo of the large area STNA-116, FESEM images of STNA-001 and STNA-116 with a series of growth time, the enlarged XRD pattern, the simulated SAED pattern, the reflectance spectra, the cyclic voltammograms of P25 on the FTO substrate. See DOI: 10.1039/c4nr04248d

  17. 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.

  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. 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

  20. 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.

  1. Influence of hydrogen effusion from hydrogenated silicon nitride layers on the regeneration of boron-oxygen related defects in crystalline silicon

    SciTech Connect

    Wilking, S. Ebert, S.; Herguth, A.; Hahn, G.

    2013-11-21

    The degradation effect boron doped and oxygen-rich crystalline silicon materials suffer from under illumination can be neutralized in hydrogenated silicon by the application of a regeneration process consisting of a combination of slightly elevated temperature and carrier injection. In this paper, the influence of variations in short high temperature steps on the kinetics of the regeneration process is investigated. It is found that hotter and longer firing steps allowing an effective hydrogenation from a hydrogen-rich silicon nitride passivation layer result in an acceleration of the regeneration process. Additionally, a fast cool down from high temperature to around 550 °C seems to be crucial for a fast regeneration process. It is suggested that high cooling rates suppress hydrogen effusion from the silicon bulk in a temperature range where the hydrogenated passivation layer cannot release hydrogen in considerable amounts. Thus, the hydrogen content of the silicon bulk after the complete high temperature step can be increased resulting in a faster regeneration process. Hence, the data presented here back up the theory that the regeneration process might be a hydrogen passivation of boron-oxygen related defects.

  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. Optical cavity modes of a single crystalline zinc oxide microsphere.

    PubMed

    Moirangthem, Rakesh Singh; Cheng, Pi-Ju; Chien, Paul Ching-Hang; Ngo, Buu Trong Huynh; Chang, Shu-Wei; Tien, Chung-Hao; Chang, Yia-Chung

    2013-02-11

    A detailed study on the optical cavity modes of zinc oxide microspheres under the optical excitation is presented. The zinc oxide microspheres with diameters ranging from 1.5 to 3.0 µm are prepared using hydrothermal growth technique. The photoluminescence measurement of a single microsphere shows prominent resonances of whispering gallery modes at room temperature. The experimentally observed whispering gallery modes in the photoluminescence spectrum are compared with theoretical calculations using analytical and finite element methods in order to clarify resonance properties of these modes. The comparison between theoretical analysis and experiment suggests that the dielectric constant of the ZnO microsphere is somewhat different from that for bulk ZnO. The sharp resonances of whispering gallery modes in zinc oxide microspheres cover the entire visible window. They may be utilized in realizations of optical resonators, light emitting devices, and lasers for future chip integrations with micro/nano optoelectronic circuits, and developments of optical biosensors. PMID:23481759

  4. Healing of graphene on single crystalline Ni(111) films

    SciTech Connect

    Zeller, Patrick; Wintterlin, Joost; Speck, Florian; Ostler, Markus; Weinl, Michael; Schreck, Matthias; Seyller, Thomas

    2014-11-10

    The annealing of graphene layers grown on 150 nm thick single crystal Ni(111) films was investigated in situ by low energy electron microscopy and photoemission electron microscopy. After growth, by means of chemical vapor deposition of ethylene, the graphene layers consist of several domains showing different orientations with respect to the underlying Ni surface and also of small bilayer areas. It is shown that, in a controlled process, the rotated domains can be transformed into lattice-aligned graphene, and the bilayer areas can be selectively dissolved, so that exclusively the aligned monolayer graphene is obtained. The ordering mechanism involves transport of C atoms across the surface and solution in the bulk.

  5. 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.

  6. 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.

  7. 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

  8. Flexible single-crystal silicon nanomembrane photonic crystal cavity.

    PubMed

    Xu, Xiaochuan; Subbaraman, Harish; Chakravarty, Swapnajit; Hosseini, Amir; Covey, John; Yu, Yalin; Kwong, David; Zhang, Yang; Lai, Wei-Cheng; Zou, Yi; Lu, Nanshu; Chen, Ray T

    2014-12-23

    Flexible inorganic electronic devices promise numerous applications, especially in fields that could not be covered satisfactorily by conventional rigid devices. Benefits on a similar scale are also foreseeable for silicon photonic components. However, the difficulty in transferring intricate silicon photonic devices has deterred widespread development. In this paper, we demonstrate a flexible single-crystal silicon nanomembrane photonic crystal microcavity through a bonding and substrate removal approach. The transferred cavity shows a quality factor of 2.2×10(4) and could be bent to a curvature of 5 mm radius without deteriorating the performance compared to its counterparts on rigid substrates. A thorough characterization of the device reveals that the resonant wavelength is a linear function of the bending-induced strain. The device also shows a curvature-independent sensitivity to the ambient index variation.

  9. Slow crack growth in single-crystal silicon.

    PubMed

    Connally, J A; Brown, S B

    1992-06-12

    Time-dependent crack growth has been measured on a precracked, single-crystal silicon cantilever beam 75 micrometers long that was excited at resonance. Growth of the precrack changes the resonant frequency of the beam, which is correlated to crack length. The measured steady-state crack growth rate was as slow as 2.9 x 10(-13) meter per second, although the apparatus can measure crack growth rates as low as 10(-15) meter per second. It is postulated that static fatigue of the native surface silica layer is the mechanism for crack growth. These experiments demonstrate the possibility of rate-dependent failure of silicon devices and the applicability of linear elastic fracture mechanics to small-scale micromechanical devices. The results indicate that slow crack growth must therefore be considered when evaluating the reliability of thin-film silicon structures.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. Organic nanowire/crystalline silicon p-n heterojunctions for high-sensitivity, broadband photodetectors.

    PubMed

    Deng, Wei; Jie, Jiansheng; Shang, Qixun; Wang, Jincheng; Zhang, Xiujuan; Yao, Shenwen; Zhang, Qing; Zhang, Xiaohong

    2015-01-28

    Organic/inorganic hybrid devices are promising candidates for high-performance, low-cost optoelectronic devices, by virtue of their unique properties. Polycrystalline/amorphous organic films are widely used in hybrid devices, because defects in the films hamper the improvement of device performance. Here, we report the construction of 2,4-bis[4-(N,N-dimethylamino)phenyl]squaraine (SQ) nanowire (NW)/crystalline Si (c-Si) p-n heterojunctions. Thanks to the high crystal quality of the SQ NWs, the heterojunctions exhibit excellent diode characteristics in darkness. It is significant that the heterojunctions have been found to be capable of detecting broadband light with wavelengths spanning from ultraviolet (UV) light, to visible (Vis) light, to near-infrared (NIR) light, because of the complementary spectrum absorption of SQ NWs with Si. The junction is demonstrated to play a core role in enhancing the device performance, in terms of ultrahigh sensitivity, excellent stability, and fast response. The photovoltaic characteristics of the heterojunctions are further investigated, revealing a power conversion efficiency (PCE) of up to 1.17%. This result also proves the potential of the device as self-powered photodetectors operating at zero external bias voltage. This work presents an important advance in constructing single-crystal organic nanostructure/inorganic heterojunctions and will enable future exploration of their applications in broadband photodetectors and solar cells.

  17. High-Quality Single Crystalline Ge(111) Growth on Si(111) Substrates by Solid Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Sun, Bing; Chang, Hu-Dong; Lu, Li; Liu, Hong-Gang; Wu, De-Xin

    2012-03-01

    Heterogeneous integration of crystalline Ge layers on cleaned and H-terminated Si(111) substrates are demonstrated by employing a combination of e-beam evaporation and solid phase epitaxy techniques. High-quality single crystalline Ge(111) layers on Si(111) substrates with a smooth Ge surface and an abrupt interface between Ge and Si are obtained. An XRD rocking curve scan of the Ge(111) diffraction peak shows a FWHM of only 260 arcsec for a 50-nm-thick Ge layer annealed at 600°C with a ramp-up rate of 20°C/s and a holding time of 1 min. The AFM images exhibit that the rms surface roughness of all the crystalline Ge layers are less than 2.1 nm.

  18. Sharp and bright photoluminescence emission of single-crystalline diacetylene nanoparticles

    NASA Astrophysics Data System (ADS)

    Kim, Seokho; Kim, Hyeong Tae; Park, Dong Hyuk; Xianling, Piao; Cui, Chunzhi

    2016-08-01

    Amorphous nanoparticles (NPs) of diacetylene (DA) molecules were prepared by using a reprecipitation method. After crystallization through a solvent-vapor annealing process, the highly crystalline DA NPs show different structural and optical characteristics compared with the amorphous DA NPs. The single crystal structure of DA NPs was confirmed by using high-resolution transmission electron microscopy (HR-TEM) and wide angle X-ray scattering (WAXS). The luminescence color and the photoluminescence (PL) characteristics of the DA NPs were measured using color charge-coupled device (CCD) images and high-resolution laser confocal microscope (LCM). The crystalline DA NPs, emit bright green light compared with amorphous DA NPs and the main PL peak of the crystalline DA NPs exhibits relatively narrow, blue-shift phenomena due to enhanced interactions between the DA molecules in the nano-size crystal structure.

  19. Single-Crystalline SrRuO3 Nanomembranes: A Platform for Flexible Oxide Electronics.

    PubMed

    Paskiewicz, Deborah M; Sichel-Tissot, Rebecca; Karapetrova, Evguenia; Stan, Liliana; Fong, Dillon D

    2016-01-13

    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 × 10(7), 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.

  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. 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.

  2. 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.

  3. Preparation of high purity crystalline silicon by electro-catalytic reduction of sodium hexafluorosilicate with sodium below 180 °C.

    PubMed

    Chen, Yuan; Liu, Yang; Wang, Xin; Li, Kai; Chen, Pu

    2014-01-01

    The growing field of silicon solar cells requires a substantial reduction in the cost of semiconductor grade silicon, which has been mainly produced by the rod-based Siemens method. Because silicon can react with almost all of the elements and form a number of alloys at high temperatures, it is highly desired to obtain high purity crystalline silicon at relatively low temperatures through low cost process. Here we report a fast, complete and inexpensive reduction method for converting sodium hexafluorosilicate into silicon at a relatively low reaction temperature (∼ 200 °C). This temperature could be further decreased to less than 180 °C in combination with an electrochemical approach. The residue sodium fluoride is dissolved away by pure water and hydrochloric acid solution in later purifying processes below 15 °C. High purity silicon in particle form can be obtained. The relative simplicity of this method might lead to a low cost process in producing high purity silicon.

  4. 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

  5. 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

  6. Principle of direct van der Waals epitaxy of single-crystalline films on epitaxial graphene.

    PubMed

    Kim, Jeehwan; Bayram, Can; Park, Hongsik; Cheng, Cheng-Wei; Dimitrakopoulos, Christos; Ott, John A; Reuter, Kathleen B; Bedell, Stephen W; Sadana, Devendra K

    2014-09-11

    There are numerous studies on the growth of planar films on sp(2)-bonded two-dimensional (2D) layered materials. However, it has been challenging to grow single-crystalline films on 2D materials due to the extremely low surface energy. Recently, buffer-assisted growth of crystalline films on 2D layered materials has been introduced, but the crystalline quality is not comparable with the films grown on sp(3)-bonded three-dimensional materials. Here we demonstrate direct van der Waals epitaxy of high-quality single-crystalline GaN films on epitaxial graphene with low defectivity and surface roughness comparable with that grown on conventional SiC or sapphire substrates. The GaN film is released and transferred onto arbitrary substrates. The post-released graphene/SiC substrate is reused for multiple growth and transfer cycles of GaN films. We demonstrate fully functional blue light-emitting diodes (LEDs) by growing LED stacks on reused graphene/SiC substrates followed by transfer onto plastic tapes.

  7. Principle of direct van der Waals epitaxy of single-crystalline films on epitaxial graphene

    NASA Astrophysics Data System (ADS)

    Kim, Jeehwan; Bayram, Can; Park, Hongsik; Cheng, Cheng-Wei; Dimitrakopoulos, Christos; Ott, John A.; Reuter, Kathleen B.; Bedell, Stephen W.; Sadana, Devendra K.

    2014-09-01

    There are numerous studies on the growth of planar films on sp2-bonded two-dimensional (2D) layered materials. However, it has been challenging to grow single-crystalline films on 2D materials due to the extremely low surface energy. Recently, buffer-assisted growth of crystalline films on 2D layered materials has been introduced, but the crystalline quality is not comparable with the films grown on sp3-bonded three-dimensional materials. Here we demonstrate direct van der Waals epitaxy of high-quality single-crystalline GaN films on epitaxial graphene with low defectivity and surface roughness comparable with that grown on conventional SiC or sapphire substrates. The GaN film is released and transferred onto arbitrary substrates. The post-released graphene/SiC substrate is reused for multiple growth and transfer cycles of GaN films. We demonstrate fully functional blue light-emitting diodes (LEDs) by growing LED stacks on reused graphene/SiC substrates followed by transfer onto plastic tapes.

  8. 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

  9. Single crystal silicon capacitors with low microwave loss in the single photon regime

    NASA Astrophysics Data System (ADS)

    Weber, S. J.; Murch, K. W.; Slichter, D. H.; Vijay, R.; Siddiqi, I.

    2011-04-01

    We have fabricated superconducting microwave resonators in a lumped element geometry using single crystal silicon dielectric parallel plate capacitors with C >2 pF. Aluminum devices with resonant frequencies between 4.0 and 6.5 GHz exhibited an average internal quality factor Qi of 2×105 in the single photon excitation regime at T =20 mK. Attributing the observed loss solely to the capacitive element, our measurements place an upper bound on the loss tangent of the silicon dielectric layer of tan δi=5×10-6. This level of loss is an order of magnitude lower than is currently observed in structures incorporating amorphous dielectric materials, thus making single crystal silicon capacitors an attractive, robust route for realizing long-lived quantum circuits.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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%.

  15. A novel method for gas flow and impurity control in directional solidification of multi-crystalline silicon

    NASA Astrophysics Data System (ADS)

    Bellmann, M. P.; Lindholm, D.; M'Hamdi, M.

    2014-08-01

    In this paper the potential of a specially designed argon gas injector for controlling the gas flow and transport of impurities in directional solidification of multi-crystalline silicon is evaluated. The gas injector which consists of a valve allows one to control the flow direction independently in the vertical and horizontal directions. Based on a gas flow model derived from a semi-industrial crystallization furnace the impact of different gas injection combinations on the gas flow pattern and impurity transport is studied. Special focus is given to the SiO evacuation from the melt-free surface, the CO formation at graphite surfaces and the CO evacuation from the furnace interior. It is found that for gas flow pattern formed through horizontal rather than vertical gas injection, SiO and CO are evacuated most effectively from the furnace interior and the formation of CO is inhibited. Such a type of gas injector presents a versatile tool for controlling the flow and impurity transport in the gas phase and possibly improving the material properties of crystalline silicon.

  16. 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.

  17. 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.

  18. Fabrication and temperature dependence of the resistance of single-crystalline Bi nanowires

    NASA Astrophysics Data System (ADS)

    Wang, X. F.; Zhang, J.; Shi, H. Z.; Wang, Y. W.; Meng, G. W.; Peng, X. S.; Zhang, L. D.; Fang, J.

    2001-04-01

    Single-crystalline Bi nanowires with diameters ranging from 20 to 70 nm were prepared by electrodeposition using nanoporous aluminum oxide membranes rather than the more usual track-etched polycarbonate membranes. X-ray diffraction and selected area electron diffraction investigations revealed that the nanowires are essentially single crystalline and highly oriented. The temperature dependence of zero-field resistance of different diameter nanowires indicated that these Bi nanowires undergo a semimetal-semiconductor transition due to two-dimensional quantum confinement effects. The resistance maximum was observed at 50 K in zero magnetic field for 20 nm Bi nanowires, while the resistance minimum at 258 K for 50 nm Bi nanowires, due to the quantum size effect.

  19. 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

  20. Molecular beam epitaxy of single crystalline GaN nanowires on a flexible Ti foil

    NASA Astrophysics Data System (ADS)

    Calabrese, Gabriele; Corfdir, Pierre; Gao, Guanhui; Pfüller, Carsten; Trampert, Achim; Brandt, Oliver; Geelhaar, Lutz; Fernández-Garrido, Sergio

    2016-05-01

    We demonstrate the self-assembled growth of vertically aligned GaN nanowire ensembles on a flexible Ti foil by plasma-assisted molecular beam epitaxy. The analysis of single nanowires by transmission electron microscopy reveals that they are single crystalline. Low-temperature photoluminescence spectroscopy demonstrates that in comparison to standard GaN nanowires grown on Si, the nanowires prepared on the Ti foil exhibit an equivalent crystalline perfection, a higher density of basal-plane stacking faults, but a reduced density of inversion domain boundaries. The room-temperature photoluminescence spectrum of the nanowire ensemble is not influenced or degraded by the bending of the substrate. The present results pave the way for the fabrication of flexible optoelectronic devices based on GaN nanowires on metal foils.

  1. Integrated electro-optic devices of melt-processable single-crystalline organic films

    NASA Astrophysics Data System (ADS)

    Figi, Harry; Jazbinšek, Mojca; Hunziker, Christoph; Koechlin, Manuel; Günter, Peter

    2010-02-01

    Organic electro-optic (EO) materials are the materials of choice for high speed optical modulators with modulation frequencies greater than 100 GHz. This is due to the large EO effects observed and a low material dispersion of the dielectric constant resulting in a very small velocity mismatch between the optical and electrical waves. However, the implementation of organic materials into real devices has been hindered by several factors such as an insufficient long-term thermal and photochemical stability of the widely investigated poled polymers or the lack of available structuring techniques for the inherently superior organic EO crystalline materials. Here we report on the realization of integrated organic EO single-crystalline Mach-Zehnder modulators by a recently developed melt based channel growth technique. The main fabrication concept is to grow the organic EO singlecrystals from the melt directly in pre-structured and electroded waveguide channels, which were obtained by standard optical lithographic techniques and wafer bonding. By this method single crystal structure details with a size below 30 nm have been achieved and the growth of single-crystalline Mach-Zehnder modulators has been successfully demonstrated, where we have chosen DAT2 (2-(3-(2-(4-dimethylaminophenyl)vinyl)-5,5- dimethylcyclohex-2-enylidene)malononitrile) as EO material. The half-wave voltage × length product determined in the DAT2 based Mach-Zehnder modulators has been found to be 78 +/- 2 Vcm for TE-modes and 60 +/-1 Vcm for TM-modes at a wavelength of 1.55 μm. The accuracy and reproducibility of the process allowed also for the realization of the first EO single-crystalline microring resonator in an organic material.

  2. Fast visible light photoelectric switch based on ultralong single crystalline V₂O₅ nanobelt.

    PubMed

    Lu, Jianing; Hu, Ming; Tian, Ye; Guo, Chuanfei; Wang, Chuang; Guo, Shengming; Liu, Qian

    2012-03-26

    A photoelectric switch with fast response to visible light (<200 μs), suitable photosensitivity and excellent repeatability is proposed based on the ultralong single crystalline V₂O₅ nanobelt, which are synthesized by chemical vapor deposition and its photoconductive mechanism can well be explained by small polaron hopping theory. Our results reveal that the switch has a great potential in next generation photodetectors and light-wave communications.

  3. Patterned Aqueous Growth of Single Crystalline Zinc Oxide for Photonic Applications

    NASA Astrophysics Data System (ADS)

    Pooley, Kathryn Jessica

    Typically a top-down approach is used in the fabrication of functional nanodevices beginning with the bulk material and imposing a two or three-dimensional structure on the material through a combination of lithography and etching. Pre-patterning of a substrate, resulting in the selective growth of a material, has potential for forming three-dimensional device structures in ways that can be more efficient and which can avoid process complexity and process induced damage. In this thesis, the low temperature (90°C) aqueous growth of complex, single crystalline zinc oxide (ZnO) three-dimensional devices through pre-patterned micron and nanometer sized molds is presented. This work focuses on the quality of the single crystalline ZnO material, the constrained growth of ZnO through various sizes and shapes of molds, and the fabrication of several device structures including pillars, rings, and photonic crystals. Due to their single crystalline nature and crystallographically smooth sidewalls, photonic devices created using this growth method have the potential to outperform traditionally fabricated structures in a range of optoelectronic applications. In addition, metal-oxide interfaces are the critical components of many electrical and optical devices, and it is rare to find epitaxial metal-oxide structures. In this work, the first demonstration of low temperature, epitaxial growth of ZnO on single crystalline gold plates is presented. The quality and structure of the ZnO on the gold plates is investigated using scanning electron microscopy, atomic force microscopy, and photoluminescence spectroscopy. The epitaxial growth is confirmed using electron backscatter diffraction and transmission electron microscopy. The metal-oxide interfaces fabricated have the potential to be used in a number of technologically important applications. Possible examples include creating high quality electrical contacts on high bandgap materials and improving light extraction from planar

  4. 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

  5. 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.

  6. 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.

  7. 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].

  8. 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.

  9. Formation of shallow boron emitters in crystalline silicon using flash lamp annealing: Role of excess silicon interstitials

    NASA Astrophysics Data System (ADS)

    Riise, Heine Nygard; Schumann, Thomas; Azarov, Alexander; Hübner, Renè; Skorupa, Wolfgang; Svensson, Bengt G.; Monakhov, Edouard

    2015-07-01

    Shallow, Boron (B)-doped p+ 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 × 1019 cm-3 and 3 × 1020 cm-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/cm2 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Stress effects on the initial lithiation of crystalline silicon nanowires: Reactive molecular dynamics simulations using ReaxFF

    DOE PAGES

    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

  15. 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.'

  16. 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

  17. Solution-grown organic single-crystalline donor-acceptor heterojunctions for photovoltaics.

    PubMed

    Li, Hanying; Fan, Congcheng; Fu, Weifei; Xin, Huolin L; Chen, Hongzheng

    2015-01-12

    Organic single crystals are ideal candidates for high-performance photovoltaics due to their high charge mobility and long exciton diffusion length; however, they have not been largely considered for photovoltaics due to the practical difficulty in making a heterojunction between donor and acceptor single crystals. Here, we demonstrate that extended single-crystalline heterojunctions with a consistent donor-top and acceptor-bottom structure throughout the substrate can be simply obtained from a mixed solution of C60 (acceptor) and 3,6-bis(5-(4-n-butylphenyl)thiophene-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione (donor). 46 photovoltaic devices were studied with the power conversion efficiency of (0.255±0.095)% under 1 sun, which is significantly higher than the previously reported value for a vapor-grown organic single-crystalline donor-acceptor heterojunction (0.007%). As such, this work opens a practical avenue for the study of organic photovoltaics based on single crystals.

  18. 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.

  19. 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.

  20. Amorphous/crystalline silicon interface passivation: Ambient-temperature dependence and implications for solar cell performance

    DOE PAGES

    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

  1. 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.

  2. RETRACTION: Electronic characteristics of n-type nanocrystalline/p-type crystalline silicon heterostructure

    NASA Astrophysics Data System (ADS)

    Wei, Wensheng; Wang, Tianmin; He, Yuliang

    2008-03-01

    It has come to the attention of IOP Publishing that this article should not have been submitted for publication owing to its substantial replication of an earlier paper (Wensheng Wei, Tianmin Wang and Yuliang He 2008 Investigation on high mobility nanocrystalline Si with crystalline Si heterostructure Superlattices and Microstructures 41 216-226). Consequently this paper has been retracted by IOP Publishing.

  3. Towards Room Temperature Silicon Memory Using Single Electron Effects.^*

    NASA Astrophysics Data System (ADS)

    Tiwari, Sandip

    1996-03-01

    In a semiconductor device, transport, where single electron effects prevail, is usually characterized by sub-μ A currents, large time-constants, and non-linearities that are not suitably harnessed by conventional methods of implementing logic. However, many of the attributes of single electron effects are quite appropriate for memories and we summarize one promising implementation involving low interface state density nano-crystals of silicon that are electrostatically coupled to a conducting channel whose conduction is modulated by a control gate.(S. Tiwari, et al., Digest of 52nd Annual Device Research Conference IVA-4 (1994))(S. Tiwari, et al., Digest of 53rd Annual Device Research Conference, 50 (1995))(S. Tiwari, et al., Digest of International Electron Devices Meeting (1995)) Single electron effects manifest themselves in the nano-crystals of silicon (5--7 nm in dimensions) where Coulombic energies of ≈ 60 meV are presently achieved, sufficient for 77 K demonstrations. Large threshold voltage shifts (> 0.2--0.25 V) are achieved by using large enough density of such nano-crystals where single/multiple electron storage occurs and appear as plateaus in threshold voltage - gate voltage characteristics. The charging of the nano-crystals occurs from an inversion layer and discharging occurs to a depletion region. Scaling of nano-crystals size is expected to shift this operational behavior to room temperature, and very low power behavior should be expected from scaled structures utilizing only a single nano-crystal. ^*Performed in collaboration with F. Rana, K. Chan, J. Welser, and H. Hanafi

  4. Direct growth of single-crystalline III–V semiconductors on amorphous substrates

    DOE PAGES

    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

  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. 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

  7. 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.

  8. 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.

  9. Silicon technologies for arrays of Single Photon Avalanche Diodes

    PubMed Central

    Ceccarelli, Francesco; Rech, Ivan; Ghioni, Massimo

    2016-01-01

    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/near-infrared 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. PMID:27761058

  10. 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.

  11. 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.

  12. 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).

  13. Modeling the growth of PECVD silicon nitride films for crystalline silicon solar cells using factorial design and response surface methodology

    SciTech Connect

    Nybergh, K.; Marjamaeki, T.; Skarp, E.

    1997-12-31

    Silicon nitride was grown on polished Si wafers by a parallel plate PECVD reactor. Reaction gases were NH{sub 3} and 3% SiH{sub 4} in Ar and the rf frequency was 13.56 MHz. The film thickness and refractive index were measured by an ellipsometer. The results were analyzed using response surface methodology. The results indicate that the silane-to-ammonia flow rate ratio is the dominating parameter when determining the refractive index and that the total gas flow rate and the chamber pressure dominate the growth rate, whereas rf power has a less strong impact on growth rate and no impact on refractive index. The previous results will be used when growing passivating antireflection coatings on three grain Si solar cells.

  14. Mitigating mechanical failure of crystalline silicon electrodes for lithium batteries by morphological design [Morphological design of silicon electrode with anisotropic interface reaction rate for lithium ion batteries

    DOE PAGES

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

    2015-06-08

    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 counteractmore » 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. In conclusion, 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.« less

  15. Mitigating mechanical failure of crystalline silicon electrodes for lithium batteries by morphological design [Morphological design of silicon electrode with anisotropic interface reaction rate for lithium ion batteries

    SciTech Connect

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

    2015-06-08

    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. In conclusion, 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.

  16. 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.

  17. 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.

  18. 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.

  19. Conically shaped single-crystalline diamond backing plates for a diamond anvil cell

    NASA Astrophysics Data System (ADS)

    Krauss, G.; Reifler, H.; Steurer, W.

    2005-10-01

    Based on computer-aided design (CAD) and finite-element calculations (FEM), single-crystalline diamond backing plates were tailored as a replacement of beryllium for high-pressure diamond anvil cells with a focus on in-house single-crystal experiments. Although the modified cell has an opening angle of 90°, a very homogeneous stress distribution all over the backing plate was realized to avoid failure. The conically shaped backing plates work well in the targeted pressure range up to Mg2Co3Sn10.15 up to 9.69 GPa. The influence of simultaneous diffraction phenomena in the diamonds (diamond dips) is illustrated by single-counter and area-detector measurements using standard laboratory equipment.

  20. 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.

  1. 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

  2. Preparation and oxidation resistance of single crystalline β-Zn4Sb3

    NASA Astrophysics Data System (ADS)

    Liu, Hong-xia; Deng, Shu-ping; Li, De-cong; Shen, Lan-xian; Cheng, Feng; Wang, Jin-song; Deng, Shu-kang

    2016-11-01

    This study prepared a Zn-rich single crystal β-Zn4Sb3 using a Sn flux method based on the stoichiometric ratios of Zn4.4Sb3Sn3. The oxidation resistance of the sample was determined by exploring the effects of heat treatment in air on electrical transport properties and thermal stability, which is of practical importance in the application of the material at high temperatures. Results showed that the prepared sample possessed high electrical transport properties, with a high power factor of 1.67×10-3 W m-1 K-2 at 563 K. The heat treatment in air weakened the electrical conductivity of the single crystalline β-Zn4Sb3, whereas the Seebeck coefficients were rarely independent of the annealing condition. Eventually, the power factor obtained after the first heating at 523 K for 4 h became comparable to that of the as-prepared sample, although it decreased after the second heating at 573 K for 5 h. Nevertheless, the single crystalline β-Zn4Sb3 still possessed a good thermal stability after the heat treatment process.

  3. Rare orbital glass state in single crystalline Y2Mo2O7

    NASA Astrophysics Data System (ADS)

    Silverstein, Harlyn; Zhou, Haidong; Hallas, Alannah; Gardner, Jason; Qiu, Yiming; Ehlers, Georg; Savici, Andrei; Yamani, Zahra; Gingras, Michel; Gaulin, Bruce; Fritsche, Katharina; Ross, Kate; Wiebe, Christopher

    2012-02-01

    Perhaps one of the most curious cases of frustrated pyrochlores, Y2Mo2O7 was first classified as a spin glass in 1986. Conventionally, spin glasses must exhibit some sort of chemical disorder although oxygen vacancies and Y-Mo site mixing is virtually absent in all studies to date. NMR and neutron PDF experiments show the presence of local disorder. While other studies have shown a lattice deformation occurring near Tg=22K, these distortions cannot be detected globally and may not be enough to explain the spin glass behavior. For 25 years, researchers have struggled to resolve spin glass theory with the data; the problem lies in that, until now, scientists have been unable to grow single crystal samples due to the oxidation of Mo^4+ to Mo^6+ at low temperatures. Here, we report the synthesis and characterization of the world's first single crystalline sample of Y2Mo2O7. Unlike powder samples, single crystalline Y2Mo2O7 heat capacity measurements show a T^2 dependence. Neutron scattering experiments show isotropic, broad, liquid-like collective modes and high-Q diffuse scattering characteristic of an orbital liquid to orbital glass transition at Tg.

  4. 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.

  5. 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.

  6. Relativistic tight-binding approximation method for materials immersed in a uniform magnetic field: Application to crystalline silicon

    NASA Astrophysics Data System (ADS)

    Higuchi, Katsuhiko; Hamal, Dipendra Bahadur; Higuchi, Masahiko

    2015-02-01

    We present a relativistic tight-binding (TB) approximation method that is applicable to actual crystalline materials immersed in a uniform magnetic field. The magnetic Bloch theorem is used to make the dimensions of the Hamiltonian matrix finite. In addition, by means of the perturbation theory, the magnetic hopping integral that appears in the Hamiltonian matrix is reasonably approximated as the relativistic hopping integral multiplied by the magnetic-field-dependent phase factor. In order to calculate the relativistic hopping integral, the relativistic version of the so-called Slater-Koster table is also given in an explicit form. We apply the present method to crystalline silicon immersed in a uniform magnetic field, and reveal its energy-band structure that is defined in the magnetic first Brillouin zone. It is found that the widths of energy-bands increase with increasing the magnetic field, which indicates the magnetic-field dependence of the appropriateness of the effective mass approximation. The recursive energy spectrum, which is the so-called butterfly diagram, can also be seen in the k -space plane perpendicular to the magnetic field.

  7. Low temperature surface passivation of crystalline silicon and its application to interdigitated back contact silicon heterojunction (ibc-shj) solar cell

    NASA Astrophysics Data System (ADS)

    Shu, Zhan

    With the absence of shading loss together with improved quality of surface passivation introduced by low temperature processed amorphous silicon crystalline silicon (a-Si:H/c-Si) heterojunction, the interdigitated back contact silicon heterojunction (IBC-SHJ) solar cell exhibits a potential for higher conversion efficiency and lower cost than a traditional front contact diffused junction solar cell. In such solar cells, the front surface passivation is of great importance to achieve both high open-circuit voltage (Voc) and short-circuit current (Jsc). Therefore, the motivation of this work is to develop a low temperature processed structure for the front surface passivation of IBC-SHJ solar cells, which must have an excellent and stable passivation quality as well as a good anti-reflection property. Four different thin film materials/structures were studied and evaluated for this purpose, namely: amorphous silicon nitride (a-SiNx:H), thick amorphous silicon film (a-Si:H), amorphous silicon/silicon nitride/silicon carbide (a-Si:H/a-SiN x:H/a-SiC:H) stack structure with an ultra-thin a-Si:H layer, and zinc sulfide (ZnS). It was demonstrated that the a-Si:H/a-SiNx:H/a-SiC:H stack surpasses other candidates due to both of its excellent surface passivation quality (SRV<5 cm/s) and lower absorption losses. The low recombination rate at the stack structure passivated c-Si surface is found to be resulted from (i) field effect passivation due to the positive fixed charge (Q fix~1x1011 cm-2 with 5 nm a-Si:H layer) in a-SiNx:H as measured from capacitance-voltage technique, and (ii) reduced defect state density (mid-gap Dit~4x1010 cm-2eV-1) at a-Si:H/c-Si interface provided by a 5 nm thick a-Si:H layer, as characterized by conductance-frequency measurements. Paralleled with the experimental studies, a computer program was developed in this work based on the extended Shockley-Read-Hall (SRH) model of surface recombination. With the help of this program, the experimental

  8. Wafer-size free-standing single-crystalline graphene device arrays

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    We report an approach of wafer-scale addressable single-crystalline graphene (SCG) arrays growth by using pre-patterned seeds to control the nucleation. The growth mechanism and superb properties of SCG were studied. Large array of free-standing SCG devices were realized. Characterization of SCG as nano switches shows excellent performance with life time (>22 000 times) two orders longer than that of other graphene nano switches reported so far. This work not only shows the possibility of producing wafer-scale high quality SCG device arrays but also explores the superb performance of SCG as nano devices.

  9. Structural and Optical Properties of Single Crystalline Bismuth Nanoparticles in Polymer

    NASA Astrophysics Data System (ADS)

    Kabir, Lutful; Mandal, Swapan K.

    We report here the structural and optical properties of Bi nanoparticles in polymer (polypyrrole) matrix. The nanoparticles are synthesized following a wet chemical route. The X-ray diffraction data clearly shows the growth of single crystalline Bi nanoparticles within the host polymer. The microstructure of the Bi nanoparticles obtained by transmission electron microscopy (TEM) reveals clearly the formation of spherical shaped nanoparticles of average size˜27 nm with a narrow size distribution. The optical absorption spectrum exhibits a distinct peak at 278 nm which is attributed to the surface plasmon band of Bi nanoparticles. The absorption spectrum is found to be described well following Mie theory.

  10. Multiple phase transitions in single-crystalline Na_{1-delta}FeAs.

    PubMed

    Chen, G F; Hu, W Z; Luo, J L; Wang, N L

    2009-06-01

    Specific heat, resistivity, susceptibility, and Hall coefficient measurements were performed on high-quality single-crystalline Na_{1-delta}FeAs. This compound is found to undergo three successive phase transitions at around 52, 41, and 23 K, which correspond to structural, magnetic, and superconducting transitions, respectively. The Hall effect result indicates the development of energy gap at low temperature due to the occurrence of spin-density-wave instability. Our results provide direct experimental evidence of the magnetic ordering in the nearly stoichiometric NaFeAs.

  11. 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.

  12. 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.

  13. Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe3O4 nanoparticle rings

    NASA Astrophysics Data System (ADS)

    Takeno, Yumu; Murakami, Yasukazu; Sato, Takeshi; Tanigaki, Toshiaki; Park, Hyun Soon; Shindo, Daisuke; Ferguson, R. Matthew; Krishnan, Kannan M.

    2014-11-01

    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.

  14. Magnetic anisotropy engineering: Single-crystalline Fe films on ion eroded ripple surfaces

    NASA Astrophysics Data System (ADS)

    Liedke, M. O.; Körner, M.; Lenz, K.; Grossmann, F.; Facsko, S.; Fassbender, J.

    2012-06-01

    We present a method to preselect the direction of an induced in-plane uniaxial magnetic anisotropy (UMA) in thin single-crystalline Fe films on MgO(001). Ion beam irradiation is used to modulate the MgO(001) surface with periodic ripples on the nanoscale. The ripple direction determines the orientation of the UMA, whereas the intrinsic cubic anisotropy of the Fe film is not affected. Thus, it is possible to superimpose an in-plane UMA with a precision of a few degrees—a level of control not reported so far that can be relevant for example in spintronics.

  15. Current-driven morphological evolution of single-layer epitaxial islands on crystalline substrates

    NASA Astrophysics Data System (ADS)

    Dasgupta, Dwaipayan; Sfyris, Georgios I.; Maroudas, Dimitrios

    2013-12-01

    We develop and validate a nonlinear model for the current-driven dynamics of single-layer epitaxial islands on crystalline substrates. Simulations based on the model show that the dependence of the stable steady island migration speed vm on the inverse of the island size is not linear for larger-than-critical island sizes. In this nonlinear regime, we report morphological transitions, Hopf bifurcations, and instabilities for various surface crystallographic orientations and island misfit strains. Proper rescaling of vm gives a universal linear relationship for its dependence on island size.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. Dislocation formation in seed crystals induced by feedstock indentation during growth of quasimono crystalline silicon ingots

    NASA Astrophysics Data System (ADS)

    Trempa, M.; Beier, M.; Reimann, C.; Roßhirth, K.; Friedrich, J.; Löbel, C.; Sylla, L.; Richter, T.

    2016-11-01

    In this work the dislocation formation in the seed crystal induced by feedstock indentation during the growth of quasimono (QM) silicon ingots for photovoltaic application was investigated. It could be shown by special laboratory indentation experiments that the formed dislocations propagate up to several millimeters deep into the volume of the seed crystal in dependence on the applied pressure of the feedstock particles on the surface of the seed crystal. Further, it was demonstrated that these dislocations if they were not back-melted during the seeding process grow further into the silicon ingot and drastically reduce its material quality. An estimation of the apparent pressure values in a G5 industrial crucible/feedstock setup reveals that the indentation phenomenon is a critical issue for the industrial production of QM silicon ingots. Therefore, some approaches to avoid/reduce the indentation events were tested with the result, that the most promising solution should be the usage of suitable feedstock particles as coverage of the seed.

  2. 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.

  3. One-dimensional model of the equiaxed grain formation in multi-crystalline silicon

    NASA Astrophysics Data System (ADS)

    Beaudhuin, M.; Duffar, T.; Lemiti, M.; Zaidat, K.

    2011-03-01

    During solidification of low purity silicon for photovoltaic (PV) cells, solute rejection at the growth interface leads to an increase of the carbon concentration in the liquid phase and then to the precipitation of silicon carbide (SiC). When the precipitate radius becomes higher than the silicon critical nucleus radius, SiC can act as a refining agent for the Si and Si equiaxed grains appear in the liquid. The grain structure of the ingot changes from columnar to small grains, also known as grits. We developed a one-dimensional analytical model of this series of phenomena, including C segregation, SiC nucleation and growth, Si nucleation on the SiC precipitates and subsequent growth of the Si equiaxed grains. The equations are implemented under Matlab software in order to predict the columnar to equiaxed transition (CET) during the directional solidification of PV Si. We carried out calculations of the position and thickness of the equiaxed areas and of the number and size of Si grits as a function of the main process parameters: thermal gradient and growth velocity. Recommendations in order to adapt the growth process parameters to the initial carbon content are given. It is expected that coupling this model to global 3D numerical simulation codes could help improving the yield of ingot solidification.

  4. Interplay between crystallinity profiles and the performance of microcrystalline thin-film silicon solar cells studied by in-situ Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Fink, T.; Muthmann, S.; Mück, A.; Gordijn, A.; Carius, R.; Meier, M.

    2015-12-01

    The intrinsic microcrystalline absorber layer growth in thin-film silicon solar-cells is investigated by in-situ Raman spectroscopy during plasma enhanced chemical vapor deposition. In-situ Raman spectroscopy enables a detailed study of the correlation between the process settings, the evolution of the Raman crystallinity in growth direction, and the photovoltaic parameters η (solar cell conversion efficiency), JSC (short circuit current density), FF (fill factor), and VOC (open circuit voltage). Raman spectra were taken every 7 nm of the absorber layer growth depending on the process settings. The Raman crystallinity of growing microcrystalline silicon was determined with an absolute error of approximately ±5% for total absorber layer thicknesses >50 nm. Due to this high accuracy, inherent drifts of the Raman crystallinity profiles are resolvable for almost the entire absorber layer deposition. For constant process settings and optimized solar cell device efficiency Raman crystallinity increases during the absorber layer growth. To compensate the inhomogeneous absorber layer growth process settings were adjusted. As a result, absorber layers with a constant Raman crystallinity profile — as observed in-situ — were deposited. Solar cells with those absorber layers show a strongly enhanced conversion efficiency by ˜0.5% absolute. However, the highest FF, VOC, and JSC were detected for solar cells with different Raman crystallinity profiles. In particular, fill factors of 74.5% were observed for solar cells with decreasing Raman crystallinity during the later absorber layer growth. In contrast, intrinsic layers with favorable JSC are obtained for constant and increasing Raman crystallinity profiles. Therefore, monitoring the evolution of the Raman crystallinity in-situ provides sufficient information for an optimization of the photovoltaic parameters with surpassing depth resolution.

  5. Ferromagnetism in Silicon Single Crystals with Positively Charged Vacancy Clusters

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Zhang, Xinghong; Yuan, Quan; Han, Jiecai; Zhou, Shengqiang; Song, Bo

    Defect-induced ferromagnetism provides an alternative for organic and semiconductor spintronics. Here, we investigated the magnetism in Silicon after neutron irradiation and try to correlate the observed magnetism to particular defects in Si. Commercially available p-type Si single crystal wafer is cut into pieces for performing neutron irradiations. The magnetic impurities are ruled out as they can not be detected by secondary ion mass spectroscopy. With positron annihilation lifetime spectroscopy, the positron trapping center corresponding to lifetime 375 ps is assigned to a kind of stable vacancy clusters of hexagonal rings (V6) and its concentration is enhanced by increasing neutron doses. After irradiation, the samples still show strong diamagnetism. The weak ferromagnetic signal in Si after irradiation enhances and then weakens with increasing irradiation doses. The saturation magnetization at room temperature is almost the same as that at 5 K. The X-ray magnetic circular dichroism further provides the direct evidence that Silicon is the origin of this ferromagnetism. Using first-principles calculations, it is found that positively charged V6 brings the spin polarization and the defects have coupling with each other. The work is financially supported by the Helmholtz Postdoc Programme (Initiative and Networking Fund, PD-146).

  6. X-ray scattering and diffraction from ion beam induced ripples in crystalline silicon

    SciTech Connect

    Biermanns, Andreas; Pietsch, Ullrich; Grenzer, Joerg; Hanisch, Antje; Facsko, Stefan; Carbone, Geradina; Metzger, Till Hartmut

    2008-08-15

    We report on periodic ripple formation on Si(001) surfaces after bombardment with Xe{sup +} ions with energies between 5 and 35 keV under incidence angles of 65 deg. and 70 deg. The sputter process leads to the formation of a rippled amorphous surface layer, followed by a rippled interface toward crystalline material. Using grazing-incidence small-angle scattering and diffraction, we show that the surface morphology is exactly reproduced at the interface. In addition, we observe that the crystal lattice close to the interface is anisotropically expanded. The lattice expansion parallel to the ripples is larger than those perpendicular to them.

  7. 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.

  8. Large-scale growth of millimeter-long single-crystalline ZnS nanobelts

    NASA Astrophysics Data System (ADS)

    Li, Jianye; Zhang, Qi; An, Lei; Qin, Luchang; Liu, Jie

    2008-11-01

    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.

  9. Highly efficient electrochemical responses on single crystalline ruthenium-vanadium mixed metal oxide nanowires.

    PubMed

    Chun, Sung Hee; Choi, Hyun-A; Kang, Minkyung; Koh, Moonjee; Lee, Nam-Suk; Lee, Sang Cheol; Lee, Minyung; Lee, Youngmi; Lee, Chongmok; Kim, Myung Hwa

    2013-09-11

    Highly efficient single crystalline ruthenium-vanadium mixed metal oxide (Ru1-xVxO2, 0≤x≤1) nanowires were prepared on a SiO2 substrate and a commercial Au microelectrode for the first time through a vapor-phase transport process by adjusting the mixing ratios of RuO2 and VO2 precursors. Single crystalline Ru1-xVxO2 nanowires show homogeneous solid-solution characteristics as well as the distinct feature of having remarkably narrow dimensional distributions. The electrochemical observations of a Ru1-xVxO2 (x=0.28 and 0.66)-decorated Au microelectrode using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrate favorable charge-transfer kinetics of [Fe(CN)6]3-/4- and Ru(NH3)6(3+/2+) couples compared to that of a bare Au microelectrode. The catalytic activity of Ru1-xVxO2 for oxygen and H2O2 reduction at neutral pH increases as the fraction of vanadium increases within our experimental conditions, which might be useful in the area of biofuel cells and biosensors.

  10. 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.

  11. Single-crystalline CuGeO{sub 3} nanorods: Synthesis, characterization and properties

    SciTech Connect

    Wang, Fangfang; Xing, Yan; Su, Zhongmin; Song, Shuyan

    2013-07-15

    Graphical abstract: - Highlights: • Single crystalline CuGeO{sub 3} nanorods were prepared via a hydrothermal route. • The material exhibits greatly enhanced activity in photocatalytic degradation of dyes. • The magnetic susceptibility measurements indicate spin-Peierls transition properties. • CuGeO{sub 3} nanorods may be of potential application in future integrated optical devices. - Abstract: Single crystalline CuGeO{sub 3} nanorods with a diameter of 20–35 nm and a length up to 1 μm have been prepared via a facile hydrothermal route with the assistance of ethylenediamine. Some influencing factors such as the reaction time, reaction temperature, the volume of ethylenediamine were revealed to play crucial roles in the formation of the CuGeO{sub 3} nanorods. A possible growth mechanism was proposed based on the experimental results. Significantly, this is the first time that CuGeO{sub 3} was used as a photocatalyst for organic pollutant degradation under UV light irradiation. The reaction constant (k) of CuGeO{sub 3} nanorods was five times that of the sample prepared by solid-state reaction under UV light irradiation. Additionally, the optical and magnetic properties of CuGeO{sub 3} nanorods were systematically studied.

  12. 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.

  13. 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.

  14. Electronic structure and magnetic and transport properties of single-crystalline UN

    NASA Astrophysics Data System (ADS)

    Samsel-Czekała, M.; Talik, E.; de v. Du Plessis, P.; Troć, R.; Misiorek, H.; Sułkowski, C.

    2007-10-01

    The electronic structure (both valence band and 4f core level spectra) of the cubic monocompound UN in the paramagnetic state was studied by x-ray photoelectron spectroscopy. The experimental results are compared with the results of calculations employing full-potential local-orbital minimum-basis full relativistic method with the spin-orbit coupling included implicitly. The molar susceptibility of a single crystal of antiferromagnetic UN (TN=51K) is reported along three main crystallographic directions between 1.9 and 300K . The observed magnetic characteristics are in agreement with previous studies. The observed small anisotropy in the ordered region is discussed. Results of electronic structure, magnetoresistivity, thermoelectric power, and thermal conductivity as studied on single-crystalline specimens are given and discussed from the viewpoint of dual and spin-density-wave-like character of the 5f electrons.

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. Growing Single Crystals From Low-Purity Silicon

    NASA Technical Reports Server (NTRS)

    Schmid, F.

    1984-01-01

    Heat exchanger method continuously moves impurities to outside of growth interface. Silicon heated in crucible to above melting point, and melted silicon then solidified by extracting heat from bottom of crucible by means of heat exchanger.

  20. Growth of single crystalline TaON on yttria-stabilized zirconia (YSZ)

    SciTech Connect

    Tao, Junguang Chai, J.W.; Wong, L.M.; Zhang, Z.; Pan, J.S.; Wang, S.J.

    2013-08-15

    Owing to its high stability in aqueous solution and high quantum efficiency, tantalum based oxyntride (TaON) has attracted increasing attentions for application as visible light photocatalyst. However, despite the recent progress in photocatalytic studies, its bulk charge transport mechanisms are yet to be discovered because of the lack of single crystal sample. In this paper, high quality single crystalline TaON(100) thin film was prepared on cubic YSZ(100) surface by reactive RF magnetron sputtering to avail the understandings of charge transport mechanism so as to improve the device efficiency. The stoichiometry, crystal phase and structure were examined in situ by x-ray photoelectron spectroscopy (XPS) and ex situ by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The TaON film crystallizes in monoclinic β-phase with its [010]/[001] directions aligned to those of the substrate. The small band gap of 2.5 eV as well as the high structure perfection suggests better performance for visible light water splitting. The method can be used to prepare other surface orientations to elucidate fundamental surface structure dependent photoactivities. - Graphical abstract: Structure of single crystalline β-TaON and its diffraction pole figure. Highlights: • High quality single crystal TaON(100) thin film were grown on YSZ(100) surface. • β-phase monoclinic TaON film is formed. • Its [010]/[001] directions are aligned to those of the substrate. • The small band gap and structure perfection suggest visible light photo-activity.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. Record high efficiency single-walled carbon nanotube/silicon p-n junction solar cells.

    PubMed

    Jung, Yeonwoong; Li, Xiaokai; Rajan, Nitin K; Taylor, André D; Reed, Mark A

    2013-01-01

    Carrier transport characteristics in high-efficiency single-walled carbon nanotubes (SWNTs)/silicon (Si) hybrid solar cells are presented. The solar cells were fabricated by depositing intrinsic p-type SWNT thin-films on n-type Si wafers without involving any high-temperature process for p-n junction formation. The optimized cells showed a device ideality factor close to unity and a record-high power-conversion-efficiency of >11%. By investigating the dark forward current density characteristics with varying temperature, we have identified that the temperature-dependent current rectification originates from the thermally activated band-to-band transition of carriers in Si, and the role of the SWNT thin films is to establish a built-in potential for carrier separation/collection. We have also established that the dominant carrier transport mechanism is diffusion, with minimal interface recombination. This is further supported by the observation of a long minority carrier lifetime of ~34 μs, determined by the transient recovery method. This study suggests that these hybrid solar cells operate in the same manner as single crystalline p-n homojunction Si solar cells.

  6. 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

  7. 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.

  8. 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.

  9. Growth and mechanisms of enamel-like hierarchical nanostructures on single crystalline hydroxyapatite micro-ribbons.

    PubMed

    Ma, Guobin; Liu, Xiang Yang; Wang, Mu

    2011-06-01

    In vitro growth of enamel-like microstructured hydroxyapatite (HAP) crystals is highly expected for developing novel biomaterials/scaffolds. It is also essential for a clearer understanding of in vivo biomineralization process. In this paper, hierarchical HAP structures are controllably fabricated by growth of nanocrystals on single crystalline micro-ribbon substrates in vitro at biophysical conditions. HAP crystals grown on the substrate change from disordered aggregations of nano-flakes to well-oriented nano-needles, branched bundles of nano-needles, and finally highly porous aggregates, with increase of F- concentrations. The flexibility of the size, morphology, and microstructure control highlights a method to produce hierarchical HAP structures for potential applications in dental restoration or bone implant. We demonstrate that the mutual effects of F- on the crystallinity of HAP and on the supersaturation of the solutions control the morphology and assembly properties of the products. Moreover, the products excellently mimic real tooth enamel structures formed with different F- intakes. The work represents an appropriate simplified model system for an in-depth understanding of the microscopic mechanisms of the effects of F- on enamel growth, and the relationship of enamel microstructures and dental diseases.

  10. Single layer of silicon quantum dots in silicon oxide matrix: Investigation of forming gas hydrogenation on photoluminescence properties and study of the composition of silicon rich oxide layers

    NASA Astrophysics Data System (ADS)

    Aliberti, P.; Shrestha, S. K.; Li, Ruoyu; Green, M. A.; Conibeer, G. J.

    2011-07-01

    Structures consisting of a single layer of silicon quantum dots in a SiO 2 matrix show interesting optoelectronic properties and potential use as energy selective filters, which are a crucial component for the realization of the hot carrier solar cell. In this work single layer silicon quantum dots in SiO 2 have been realized using a magnetron sputtering technique. Quantum dots are formed by annealing of a silicon rich oxide layer deposited between a thermally grown SiO 2 layer and a sputtered SiO 2 layer. The effects of a forming gas post-hydrogenation process on the photoluminescence of the single layer of quantum dots have been investigated in order to understand the photoluminescence mechanism. It was found that for sputtered silicon quantum dots in SiO 2 matrix the photoemission mechanisms are primarily due to quantum confinement and does not strongly rely on matrix defects. In addition, physical and optical properties of several thick silicon rich oxide layers, with different chemical compositions, have been investigated in order to optimize the stoichiometry of silicon rich oxide in the single layers.

  11. Random Si nanopillars for broadband antireflection in crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Choi, Junhee; Lee, Taek Sung; Jeong, Doo Seok; Lee, Wook Seong; Kim, Won Mok; Lee, Kyeong-Seok; Kim, Donghwan; Kim, Inho

    2016-09-01

    We demonstrate the fabrication of shallow Si nanopillar structures at a submicron scale which provides broadband antireflection for crystalline Si (c-Si) solar cells in the wavelength range of 350 nm-1100 nm. The Si random nanopillars were made by reactive ion etch (RIE) processing with thermally dewetted Sn metals as an etch mask. The diameters and coverages of the Si nanopillars were adjusted in a wide range of the nanoscale to microscale by varying the nominal thickness of the Sn metals and subsequent annealing temperatures. The height of the nanopillars was controlled by the RIE process time. The optimal size of the nanopillars, which are 340 nm in diameter and 150 nm in height, leads to the lowest average reflectance of 3.6%. We showed that the power conversion efficiency of the c-Si solar cells could be enhanced with the incorporation of optimally designed Si random nanopillars from 13.3% to 14.0%. The fabrication scheme of the Si nanostructures we propose in this study would be a cost-effective and promising light trapping technique for efficient c-Si solar cells.

  12. Ion beam injected point defects in crystalline silicon: Migration, interaction, and trapping phenomena

    SciTech Connect

    Priolo, F.; Libertino, S. |; Privitera, V.; Coffa, S.

    1997-11-01

    The recent work on the room temperature migration and trapping phenomena of ion beam generated point defects in crystalline Si is reviewed. It is shown that a small fraction ({approximately}10{sup {minus}6}) of the defects generated at the surface by a shallow implant is injected into the bulk. These defects undergo a long range trap-limited diffusion and interact with both impurities, dopants and preexisting defects along their path. In particular, these interactions result in dopant deactivation and/or partial annihilation of pre-existing vacancy-type defect markers. It is found that in highly pure, epitaxial Si layers, these effects extend to several microns from the surface, demonstrating a long range migration of point defects at room temperature. By a detailed analysis of the experimental evidences the authors have identified the Si self-interstitials as the major responsible for the observed phenomena. This allowed them to give a lower limit of 6 {times} 10{sup {minus}11} cm{sup 2}/s for the room temperature diffusion coefficient of the Si self-interstitials. Room temperature trap-limited migration of vacancies is also detected as a broadening in the divacancy profile of as implanted samples. In this case the room temperature diffusion coefficient of vacancies has been found to be {ge}3 {times} 10{sup {minus}12} cm{sup 2}/s. These data are presented and their implications discussed.

  13. Verification of models for the simulation of boron implantation into crystalline silicon

    SciTech Connect

    Hobler, G.; Simionescu, A.; Jahnel, F.; von Criegern, R.; Tian, C.; Stingeder, G.

    1996-01-01

    A comprehensive study of 20 keV B implantations into crystalline Si is presented. B has been implanted with doses between 10{sup 13} and 10{sup 16} cm{sup {minus}2} along the three channeling directions [110], [100], and [211] and parallel to (111) planes. In addition, implantations into (100)- and (110)-Si have been performed with tilt angles of 7{degree} and 38{degree}, respectively. The doping profiles have been measured with secondary ion mass spectroscopy. The experimental results are analyzed by Monte Carlo simulations using different models of lattice damage, thermal vibrations, and interatomic potentials. It is found that both the random interstitial and the split {l_angle}110{r_angle} interstitial model are adequate to describe the experimental dopant profiles, but not the tetrahedral interstitial model. Debye temperatures of 450 and 490 K both yield good results, but not 645 K. Finally, using the specific B{endash}Si Ziegler{endash}Biersack{endash}Littmark (ZBL) potential or the universal ZBL potential makes little difference in most cases, but the specific B{endash}Si clearly has to be preferred to obtain accurate [110] channeling profiles. {copyright} {ital 1996 American Vacuum Society}

  14. Morphology and local conductance of single crystalline Bi2Te3 thin films on mica.

    PubMed

    Rapacz, R; Balin, K; Wojtyniak, M; Szade, J

    2015-10-14

    The relation between surface morphology and local conductance was studied for single crystalline thin films of Bi2Te3 grown on mica. Atomic force microscopy and electron diffraction revealed the hexagonal order of the surface with quintuple layer steps and spiral islands. Furthermore, the experiments using contact mode AFM with conducting tip performed at room temperature revealed the high conductance of the surface, which was locally reduced due to changes in the local electronic structure at the defects (e.g. edges of the terraces). Contact current-voltage characteristics tested over the surface showed a linear behavior in every point, with the resistance significantly lower than the resistance of reference metallic samples (gold, platinum). We show that local conductivity AFM is a good technique to exploit the peculiar surface properties of topological insulators.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Electromigration and potentiometry measurements of single-crystalline Ag nanowires under UHV conditions.

    PubMed

    Kaspers, M R; Bernhart, A M; Meyer Zu Heringdorf, F-J; Dumpich, G; Möller, R

    2009-07-01

    We report on in situ electromigration and potentiometry measurements on single-crystalline Ag nanowires under ultra-high vacuum (UHV) conditions, using a four-probe scanning tunnelling microscope (STM). The Ag nanowires are grown in place by self-organization on a 4° vicinal Si(001) surface. Two of the four available STM tips are used to contact the nanowire. The positioning of the tips is controlled by a scanning electron microscope (SEM). Potentiometry measurements on an Ag nanowire were carried out using a third tip to determine the resistance per length. During electromigration measurements current densities of up to 1 × 10(8) A cm(-2) could be achieved. We use artificially created notches in the wire to initiate electromigration and to control the location of the electromigration process. At the position of the notch, electromigration sets in and is observed quasi-continuously by the SEM.

  2. Luminescent properties of Al2O3:Ce single crystalline films under synchrotron radiation excitation

    NASA Astrophysics Data System (ADS)

    Zorenko, Yu.; Zorenko, T.; Gorbenko, V.; Savchyn, V.; Voznyak, T.; Fabisiak, K.; Zhusupkalieva, G.; Fedorov, A.

    2016-09-01

    The paper is dedicated to study the luminescent and scintillation properties of the Al2O3:Ce single crystalline films (SCF) grown by LPE method onto saphire substrates from PbO based flux. The structural quality of SCF samples was investigated by XRD method. For characterization of luminescent properties of Al2O3:Ce SCFs the cathodoluminescence spectra, scintillation light yield (LY) and decay kinetics under excitation by α-particles of Pu239 source were used. We have found that the scintillation LY of Al2O3:Ce SCF samples is relatively large and can reach up to 50% of the value realized in the reference YAG:Ce SCF. Using the synchrotron radiation excitation in the 3.7-25 eV range at 10 K we have also determined the basic parameters of the Ce3+ luminescence in Al2O3 host.

  3. 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

  4. Electrode engineering for improving resistive switching performance in single crystalline CeO2 thin films

    NASA Astrophysics Data System (ADS)

    Liao, Zhaoliang; Gao, Peng; Meng, Yang; Fu, Wangyang; Bai, Xuedong; Zhao, Hongwu; Chen, Dongmin

    2012-06-01

    We have studied the electrode effect on the resistive switching behavior in the single crystalline films of CeO2 grown on Nb-SrTiO3. The fabricated devices with the top electrode made of non-reactive metals (Ag, Au, Pt) show bipolar resistive switching but are volatile. In contrast, the devices with top electrodes made of reactive metals (Al, Ta, Ti) present different bipolar resistive switching direction and are non-volatile, with Ta one having the best in OFF/ON switching ratio. The devices with these kinds of electrodes also exhibit remarkably different rectification behavior because of the difference of electrode/CeO2 interface formation. These results demonstrate that it is possible to improve the performance of resistive switching by electrode engineering.

  5. 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.

  6. Molten salt synthesis of single-crystalline K2Ti6O13 annular nanostructures.

    PubMed

    Zhang, Xianke; Tang, Shaolong; Yu, Jiangying; Zhai, Lin; Shi, Yangguang; Deng, Yu; Du, Youwei

    2010-08-01

    Single-crystalline K2Ti6O13 ring-like structures have been synthesized via a simple molten salt method without any templates and surfactants. The annular structures have several different types, such as nanoring, wheel-like and diskette-like ring. Each type of rings was characterized individually by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). These annular structures are formed by the loop-by-loop self-coiling of K2Ti6O13 nanobelts in the ring plane. The driving force of self-coiling is suggested to minimize the local electrostatic energy introduced by spontaneous polarization.

  7. Measuring the mobility of single crystalline wires and its dependence on temperature and carrier density.

    PubMed

    Amorim, Cleber A; Berengue, Olivia M; Kamimura, Hanay; Leite, Edson R; Chiquito, Adenilson J

    2011-05-25

    Kinetic transport parameters are fundamental for the development of electronic nanodevices. We present new results for the temperature dependence of mobility and carrier density in single crystalline In(2)O(3) samples and the method of extraction of these parameters which can be extended to similar systems. The data were obtained using a conventional Hall geometry and were quantitatively described by the semiconductor transport theory characterizing the electron transport as being controlled by the variable range hopping mechanism. A comprehensive analysis is provided showing the contribution of ionized impurities (low temperatures) and acoustic phonon (high temperatures) scattering mechanisms to the electron mobility. The approach presented here avoids common errors in kinetic parameter extraction from field effect data, serving as a versatile platform for direct investigation of any nanoscale electronic materials.

  8. 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.

  9. 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.

  10. Preparation of High Purity Crystalline Silicon by Electro-Catalytic Reduction of Sodium Hexafluorosilicate with Sodium below 180°C

    PubMed Central

    Chen, Yuan; Liu, Yang; Wang, Xin; Li, Kai; Chen, Pu

    2014-01-01

    The growing field of silicon solar cells requires a substantial reduction in the cost of semiconductor grade silicon, which has been mainly produced by the rod-based Siemens method. Because silicon can react with almost all of the elements and form a number of alloys at high temperatures, it is highly desired to obtain high purity crystalline silicon at relatively low temperatures through low cost process. Here we report a fast, complete and inexpensive reduction method for converting sodium hexafluorosilicate into silicon at a relatively low reaction temperature (∼200°C). This temperature could be further decreased to less than 180°C in combination with an electrochemical approach. The residue sodium fluoride is dissolved away by pure water and hydrochloric acid solution in later purifying processes below 15°C. High purity silicon in particle form can be obtained. The relative simplicity of this method might lead to a low cost process in producing high purity silicon. PMID:25153509

  11. Diameter-dependent thermoelectric figure of merit in single-crystalline Bi nanowires

    NASA Astrophysics Data System (ADS)

    Kim, Jeongmin; Lee, Seunghyun; Brovman, Yuri M.; Kim, Philip; Lee, Wooyoung

    2015-03-01

    The diameter-dependent thermoelectric properties of individual single-crystalline Bi nanowires grown by the on-film formation of nanowires method have been investigated. The electrical resistivity, Seebeck coefficient, and thermal conductivity were measured as functions of the nanowire diameter using an individual nanowire device. The thermoelectric figure of merit (ZT) calculated from the measured thermoelectric properties shows an increase from the bulk value to a maximum value of 0.28 at 109 nm-diameter, followed by a decrease upon further decreasing the diameter. This non-monotonic diameter dependence of ZT in Bi nanowires reveals simultaneous positive and negative contributions to the thermoelectric efficiency, driven by the change in intrinsic properties, which originates from the diameter-dependent classical and quantum size effects.The diameter-dependent thermoelectric properties of individual single-crystalline Bi nanowires grown by the on-film formation of nanowires method have been investigated. The electrical resistivity, Seebeck coefficient, and thermal conductivity were measured as functions of the nanowire diameter using an individual nanowire device. The thermoelectric figure of merit (ZT) calculated from the measured thermoelectric properties shows an increase from the bulk value to a maximum value of 0.28 at 109 nm-diameter, followed by a decrease upon further decreasing the diameter. This non-monotonic diameter dependence of ZT in Bi nanowires reveals simultaneous positive and negative contributions to the thermoelectric efficiency, driven by the change in intrinsic properties, which originates from the diameter-dependent classical and quantum size effects. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06412g

  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. Thermal oxidation of polycrystalline and single crystalline aluminum nitride wafers (Prop 2003-054)

    SciTech Connect

    Speakman, Scott A; Gu, Z; Edgar, J H; Blom, Douglas Allen; Perrin, J; Chaudhuri, J

    2006-10-01

    Two types of aluminum nitride (AlN) samples were oxidized in flowing oxygen between 900 C and 1150 C for up to 6 h - highly (0001) textured polycrystalline AlN wafers and low defect density AlN single crystals. The N-face consistently oxidized at a faster rate than the Al-face. At 900 C and 1000 C after 6 h, the oxide was 15% thicker on the N-face than on the Al-face of polycrystalline AlN. At 1100 C and 1150 C, the oxide was only 5% thicker on the N-face, as the rate-limiting step changed from kinetically-controlled to diffusion-controlled with the oxide thickness. A linear parabolic model was established for the thermal oxidation of polycrystalline AlN on both the Al- and N-face. Transmission electron microscopy (TEM) confirmed the formation of a thicker crystalline oxide film on the N-face than on the Al-face, and established the crystallographic relationship between the oxide film and substrate. The oxidation of high-quality AlN single crystals resulted in a more uniform colored oxide layer compared to polycrystalline AlN. The aluminum oxide layer was crystalline with a rough AlN/oxide interface. The orientation relationship between AlN and Al{sub 2}O{sub 3} was (0001) AlN//(10{bar 1}0) Al{sub 2}O{sub 3} and (1{bar 1}00) AlN//(01{bar 1}2) Al{sub 2}O{sub 3}.

  14. Effective interface state effects in hydrogenated amorphous-crystalline silicon heterostructures using ultraviolet laser photocarrier radiometry

    NASA Astrophysics Data System (ADS)

    Melnikov, A.; Mandelis, A.; Halliop, B.; Kherani, N. P.

    2013-12-01

    Ultraviolet photocarrier radiometry (UV-PCR) was used for the characterization of thin-film (nanolayer) intrinsic hydrogenated amorphous silicon (i-a-Si:H) on c-Si. The small absorption depth (approximately 10 nm at 355 nm laser excitation) leads to strong influence of the nanolayer parameters on the propagation and recombination of the photocarrier density wave (CDW) within the layer and the substrate. A theoretical PCR model including the presence of effective interface carrier traps was developed and used to evaluate the transport parameters of the substrate c-Si as well as those of the i-a-Si:H nanolayer. Unlike conventional optoelectronic characterization methods such as photoconductance, photovoltage, and photoluminescence, UV-PCR can be applied to more complete quantitative characterization of a-Si:H/c-Si heterojunction solar cells, including transport properties and defect structures. The quantitative results elucidate the strong effect of a front-surface passivating nanolayer on the transport properties of the entire structure as the result of effective a-Si:H/c-Si interface trap neutralization through occupation. A further dramatic improvement of those properties with the addition of a back-surface passivating nanolayer is observed and interpreted as the result of the interaction of the increased excess bulk CDW with, and more complete occupation and neutralization of, effective front interface traps.

  15. Effective interface state effects in hydrogenated amorphous-crystalline silicon heterostructures using ultraviolet laser photocarrier radiometry

    SciTech Connect

    Melnikov, A.; Mandelis, A.; Halliop, B.; Kherani, N. P.

    2013-12-28

    Ultraviolet photocarrier radiometry (UV-PCR) was used for the characterization of thin-film (nanolayer) intrinsic hydrogenated amorphous silicon (i-a-Si:H) on c-Si. The small absorption depth (approximately 10 nm at 355 nm laser excitation) leads to strong influence of the nanolayer parameters on the propagation and recombination of the photocarrier density wave (CDW) within the layer and the substrate. A theoretical PCR model including the presence of effective interface carrier traps was developed and used to evaluate the transport parameters of the substrate c-Si as well as those of the i-a-Si:H nanolayer. Unlike conventional optoelectronic characterization methods such as photoconductance, photovoltage, and photoluminescence, UV-PCR can be applied to more complete quantitative characterization of a-Si:H/c-Si heterojunction solar cells, including transport properties and defect structures. The quantitative results elucidate the strong effect of a front-surface passivating nanolayer on the transport properties of the entire structure as the result of effective a-Si:H/c-Si interface trap neutralization through occupation. A further dramatic improvement of those properties with the addition of a back-surface passivating nanolayer is observed and interpreted as the result of the interaction of the increased excess bulk CDW with, and more complete occupation and neutralization of, effective front interface traps.

  16. 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.

  17. Testing and Analysis for Lifetime Prediction of Crystalline Silicon PV Modules Undergoing Degradation by System Voltage Stress: Preprint

    SciTech Connect

    Hacke, P.; Smith, R.; Terwiliger, K.; Glick, S.; Jordan, D.; Johnston, S.; Kempe, M.; Kurtz, S.

    2012-07-01

    Acceleration factors are calculated for crystalline silicon PV modules under system voltage stress by comparing the module power during degradation outdoors to that in accelerated testing at three temperatures and 85% relative humidity. A lognormal analysis is applied to the accelerated lifetime test data considering failure at 80% of the initial module power. Activation energy of 0.73 eV for the rate of failure is determined, and the probability of module failure at an arbitrary temperature is predicted. To obtain statistical data for multiple modules over the course of degradation in-situ of the test chamber, dark I-V measurements are obtained and transformed using superposition, which is found well suited for rapid and quantitative evaluation of potential-induced degradation. It is determined that shunt resistance measurements alone do not represent the extent of power degradation. This is explained with a two-diode model analysis that shows an increasing second diode recombination current and ideality factor as the degradation in module power progresses. Failure modes of the modules stressed outdoors are examined and compared to those stressed in accelerated tests.

  18. Relationship between cross-linking conditions of ethylene vinyl acetate and potential induced degradation for crystalline silicon photovoltaic modules

    NASA Astrophysics Data System (ADS)

    Jonai, Sachiko; Hara, Kohjiro; Tsutsui, Yuji; Nakahama, Hidenari; Masuda, Atsushi

    2015-08-01

    In this study, we investigated the relationship in crystalline silicon (c-Si) photovoltaic (PV) modules between the cross-linking level of copolymer of ethylene and vinyl acetate (EVA) as the encapsulant and the degree of degradation due to potential induced degradation (PID) phenomenon. We used three methods for the determination of cross-linking level of EVA: xylene method, which is one of the solvent extraction methods (SEM), curing degree by differential scanning calorimetry (DSC), and viscoelastic properties by dynamic mechanical analysis (DMA). The results indicate that degradation of PV modules by PID test depends on the cross-linking level of EVA. The PV modules encapsulated by EVA with higher cross-linking level show lower degradation degree due to PID phenomenon. Also we showed that EVA with higher cross-linking level tended to be higher volume resistivity. This tendency is similar to that for electrical resistance value during the PID test. The PID test was also done by changing thickness of EVA between front cover glass and c-Si with the same cross-linking level. The PV modules encapsulated by thicker EVA between front cover glass and c-Si cell show lower degradation by PID. From these results, the PV modules encapsulated by EVA with higher cross-linking level, higher volume resistivity and increased thickness would be tolerant of PID phenomenon.

  19. Optimized absorption of solar radiations in nano-structured thin films of crystalline silicon via a genetic algorithm

    NASA Astrophysics Data System (ADS)

    Mayer, Alexandre; Muller, Jérôme; Herman, Aline; Deparis, Olivier

    2015-08-01

    We developed a genetic algorithm to achieve optimal absorption of solar radiation in nano-structured thin films of crystalline silicon (c-Si) for applications in photovoltaics. The device includes on the front side a periodic array of inverted pyramids, with conformal passivation layer (a-Si:H or AlOx) and anti-reflection coating (SiNx). The device also includes on the back side a passivation layer (a-Si:H) and a flat reflector (ITO and Ag). The geometrical parameters of the inverted pyramids as well as the thickness of the different layers must be adjusted in order to maximize the absorption of solar radiations in the c-Si. The genetic algorithm enables the determination of optimal solutions that lead to high performances by evaluating only a reduced number of parameter combinations. The results achieved by the genetic algorithm for a 40μm thick c-Si lead to short-circuit currents of 37 mA/cm2 when a-Si:H is used for the front-side passivation and 39.1 mA/cm2 when transparent AlOx is used instead.

  20. Cat-doping: Novel method for phosphorus and boron shallow doping in crystalline silicon at 80 °C

    SciTech Connect

    Matsumura, Hideki; Hayakawa, Taro; Ohta, Tatsunori; Nakashima, Yuki; Miyamoto, Motoharu; Thi, Trinh Cham; Koyama, Koichi; Ohdaira, Keisuke

    2014-09-21

    Phosphorus (P) or boron (B) atoms can be doped at temperatures as low as 80 to 350 °C, when crystalline silicon (c-Si) is exposed only for a few minutes to species generated by catalytic cracking reaction of phosphine (PH₃) or diborane (B₂H₆) with heated tungsten (W) catalyzer. This paper is to investigate systematically this novel doping method, “Cat-doping”, in detail. The electrical properties of P or B doped layers are studied by the Van der Pauw method based on the Hall effects measurement. The profiles of P or B atoms in c-Si are observed by secondary ion mass spectrometry mainly from back side of samples to eliminate knock-on effects. It is confirmed that the surface of p-type c-Si is converted to n-type by P Cat-doping at 80 °C, and similarly, that of n-type c-Si is to p-type by B Cat-doping. The doping depth is as shallow as 5 nm or less and the electrically activated doping concentration is 10¹⁸ to 10¹⁹cm⁻³ for both P and B doping. It is also found that the surface potential of c-Si is controlled by the shallow Cat-doping and that the surface recombination velocity of minority carriers in c-Si can be enormously lowered by this potential control.

  1. Behavior of the potential-induced degradation of photovoltaic modules fabricated using flat mono-crystalline silicon cells with different surface orientations

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Seira; Masuda, Atsushi; Ohdaira, Keisuke

    2016-04-01

    This paper deals with the dependence of the potential-induced degradation (PID) of flat, p-type mono-crystalline silicon solar cell modules on the surface orientation of solar cells. The investigated modules were fabricated from p-type mono-crystalline silicon cells with a (100) or (111) surface orientation using a module laminator. PID tests were performed by applying a voltage of -1000 V to shorted module interconnector ribbons with respect to an Al plate placed on the cover glass of the modules at 85 °C. A decrease in the parallel resistance of the (100)-oriented cell modules is more significant than that of the (111)-oriented cell modules. Hence, the performance of the (100)-oriented-cell modules drastically deteriorates, compared with that of the (111)-oriented-cell modules. This implies that (111)-oriented cells offer a higher PID resistance.

  2. Heterojunction solar cell fabricated by spin-coating of a CNT/PEDOT:PSS heteroemitter on top of a crystalline silicon absorber

    NASA Astrophysics Data System (ADS)

    Neitzert, Heinz-Christoph; Schwertheim, Stefan; Meusinger, Katrin; Leinhos, Marcel; Fahrner, Wolfgang R.

    2009-05-01

    Crystalline silicon / organic thin film heterojunction based solar cells have been realized using spin-coating deposition. Devices with different organic films, all based on PEDOT:PSS, which in some cases have been mixed with double-walled or multi-walled carbon nanotubes, have been compared. Highest conversion efficiencies have been obtained either with a highly conductive PEDOT:PSS emitter withut nanotubes or with a nanocomposite emitter consisting of low conductive PEDOT:PSS emitter mixed with multi-walled carbon nanotubes. Using the nanocomposite emitter, rather high values for the solar cell shunt resistances have been obtained without any etching procedure in order to improve the lateral current confinement. A comparison with a Schottky diode, realized as reference device by the evaporation of the top metal contact directly on top of the crystalline silicon substrate, showed that the heterodiode characteristics was not dominated by leakage current paths and short circuits through the organic layer.

  3. Fabrication of high-aspect-ratio nanotips integrated with single-crystal silicon cantilevers

    NASA Astrophysics Data System (ADS)

    Chen, Henry J. H.; Hung, C. S.

    2007-09-01

    This work presents a novel fabrication technique for an atomic force microscope (AFM) nanotip. The high-aspect-ratio silicon nanotip on a single-crystal silicon cantilever was manufactured using inductive coupling plasma (ICP) anisotropic etching and XeF2 isotropic silicon etching processes. The cantilever shape was defined and the high-aspect-ratio silicon nanotip structure was fabricated by ICP anisotropic deep silicon etching (~50-80 µm deep). Nanotip sharpening and single-crystal Si cantilever undercutting were achieved simultaneously via two-step XeF2 isotropic silicon etching. The final structures were observed by a scanning electron microscope (SEM) and the diameter of the nanotip was about ~30 nm. This process is simple, easy to use, CMOS post-process-compatible and suitable for the future IC integrated AFM nanotip applications.

  4. Crystallinity, Surface Morphology, and Photoelectrochemical Effects in Conical InP and InN Nanowires Grown on Silicon.

    PubMed

    Parameshwaran, Vijay; Xu, Xiaoqing; Clemens, Bruce

    2016-08-24

    The growth conditions of two types of indium-based III-V nanowires, InP and InN, are tailored such that instead of yielding conventional wire-type morphologies, single-crystal conical structures are formed with an enlarged diameter either near the base or near the tip. By using indium droplets as a growth catalyst, combined with an excess indium supply during growth, "ice cream cone" type structures are formed with a nanowire "cone" and an indium-based "ice cream" droplet on top for both InP and InN. Surface polycrystallinity and annihilation of the catalyst tip of the conical InP nanowires are observed when the indium supply is turned off during the growth process. This growth design technique is extended to create single-crystal InN nanowires with the same morphology. Conical InN nanowires with an enlarged base are obtained through the use of an excess combined Au-In growth catalyst. Electrochemical studies of the InP nanowires on silicon demonstrate a reduction photocurrent as a proof of photovolatic behavior and provide insight as to how the observed surface polycrystallinity and the resulting interface affect these device-level properties. Additionally, a photovoltage is induced in both types of conical InN nanowires on silicon, which is not replicated in epitaxial InN thin films. PMID:27455379

  5. Hydrogen diffusion in silicon from plasma-enhanced chemical vapor deposited silicon nitride film at high temperature

    NASA Astrophysics Data System (ADS)

    Sheoran, Manav; Kim, Dong Seop; Rohatgi, Ajeet; Dekkers, H. F. W.; Beaucarne, G.; Young, Matthew; Asher, Sally

    2008-04-01

    The stable hydrogen isotope deuterium (D), which is released during the annealing of deuterated silicon nitride films, diffuses through the crystalline silicon and is captured by a thin, amorphous layer of silicon sputtered on the rear surface. We report on the measurement of the concentration of "penetrated" D by secondary ion mass spectrometry to monitor the flux of D diffusing through single-crystalline silicon wafers. The penetrated D content in the trapping layer increases with the annealing time. However, the flux of D injected into the silicon from the silicon nitride layer decreases as annealing time increases.

  6. Microwave synthesis of single-crystalline perovskite BiFeO{sub 3} nanocubes for photoelectrode and photocatalytic applications

    SciTech Connect

    Joshi, Upendra A.; Jang, Jum Suk; Borse, Pramod H.; Lee, Jae Sung

    2008-06-16

    A simple microwave synthesis procedure has been developed for the single-crystalline perovskite nanocubes composed of bismuth ferrite (BiFeO{sub 3}). Typical nanocubes had sizes ranging from 50 to 200 nm. The single-crystalline nature of nanocubes was confirmed by high resolution transmission electron microscopy and selected area electron diffraction pattern. X-ray diffraction pattern showed the rhombohedral phase with R3c space group. The material showed photoinduced water oxidation activity in both photoelectrochemical and photocatalytic modes. It could become a useful material for photoelectrode and photocatalytic applications.

  7. Magnetic property and microstructure of single crystalline Nd2Fe14B ultrafine particles ball milled from HDDR powders

    NASA Astrophysics Data System (ADS)

    Li, W. F.; Hu, X. C.; Cui, B. Z.; Yang, J. B.; Han, J. Z.; Hadjipanayis, G. C.

    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.

  8. Fabrication of large-area ultra-thin single crystal silicon membranes

    SciTech Connect

    Dang, Z. Y.; Motapothula, M.; Ow, Y. S.; Venkatesan, T.; Breese, M. B. H.; Rana, M. A.; Osman, A.

    2011-11-28

    Perfectly, crystalline, 55 nm thick silicon membranes have been fabricated over several square millimeters and used to observe transmission ion channeling patterns showing the early evolution of the axially channeled beam angular distribution for small tilts away from the [011] axis. The reduced multiple scattering through such thin layers allows fine angular structure produced by the highly non-equilibrium transverse momentum distribution of the channeled beam during its initial propagation in the crystal to be resolved. The membrane crystallinity and flatness were measured by using proton channeling measurements and the surface roughness of 0.4 nm using atomic force microscopy.

  9. High mobility single crystalline ScN and single-orientation epitaxial YN on sapphire via magnetron sputtering

    SciTech Connect

    Gregoire, John M.; Kirby, Steven D.; Scopelianos, George E.; Dover, R. Bruce van; Lee, Felix H.

    2008-10-01

    The mechanical, chemical, and electronic properties of the lanthanoid nitrides give this class of materials many potential applications. While ScN research activity has sharply increased recently, investigations of growth methods for optimizing structural and, more importantly, electronic properties are still needed. YN has received some theoretical but very little experimental attention. We present results of x-ray diffraction and atomic force microscopy analyses of film structure as well as Hall effect measurements of electronic properties for sputter-deposited ScN and YN. Films are deposited at select values of sputter gas stoichiometry, gas pressure, and substrate temperature, and optimal values are suggested. Additionally, the role of deposition geometry is investigated. Grown under optimal conditions, ScN films are single crystalline and YN films are singly oriented with both nitrides exhibiting the same epitaxial relation to {alpha}-Al{sub 2}O{sub 3}(1102) substrates. Our films also exhibit the highest documented electron mobility for the respective materials, despite their high carrier concentration.

  10. Dendritic growth and crystalline quality of nickel-base single grains

    NASA Astrophysics Data System (ADS)

    Siredey, Nathalie; Boufoussi, M'Bareck; Denis, Sabine; Lacaze, Jacques

    1993-05-01

    It is a usual observation that subgrains exist in nickel-base single grain components solidified by the lost wax process. The associated misorientations are generally small, but they can eventually lead to casting defects in the case of highly complex mold shapes. This work presents an attempt to relate the formation of subgrain boundaries with the development of the dendritic solidification microstructure. Experimental investigations have been undertaken on cast components made of AM1 nickel-base superalloy designed for high temperature turbine blades. Single grains were obtained by means of a grain selector at the bottom of each part. Metallographic observations have been made to characterize the dendritic array, together with gamma diffraction to measure the crystalline quality of the material and X-ray topography for mapping of misorientations on a dendritic scale. Small misorientations between dendrite stems have been found at the upper end of the selector which lead to the formation of subgrains. Moreover, during the growth process, the total mosaicity of the material increases, firstly as a consequence of an increase in the misorientations between subgrains, and secondly because of a decrease of the internal quality of each subgrain. It is proposed that misorientations are due to thermomechanical stresses which build up during λ' precipitation at temperatures slightly below the solidus temperature of the alloy.

  11. High-Operation-Temperature Plasmonic Nanolasers on Single-Crystalline Aluminum.

    PubMed

    Chou, Yu-Hsun; Wu, Yen-Mo; Hong, Kuo-Bin; Chou, Bo-Tsun; Shih, Jheng-Hong; Chung, Yi-Cheng; Chen, Peng-Yu; Lin, Tzy-Rong; Lin, Chien-Chung; Lin, Sheng-Di; Lu, Tien-Chang

    2016-05-11

    The recent development of plasmonics has overcome the optical diffraction limit and fostered the development of several important components including nanolasers, low-operation-power modulators, and high-speed detectors. In particular, the advent of surface-plasmon-polariton (SPP) nanolasers has enabled the development of coherent emitters approaching the nanoscale. SPP nanolasers widely adopted metal-insulator-semiconductor structures because the presence of an insulator can prevent large metal loss. However, the insulator is not necessary if permittivity combination of laser structures is properly designed. Here, we experimentally demonstrate a SPP nanolaser with a ZnO nanowire on the as-grown single-crystalline aluminum. The average lasing threshold of this simple structure is 20 MW/cm(2), which is four-times lower than that of structures with additional insulator layers. Furthermore, single-mode laser operation can be sustained at temperatures up to 353 K. Our study represents a major step toward the practical realization of SPP nanolasers. PMID:27089144

  12. Investigating the chemical mist deposition technique for poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) on textured crystalline-silicon for organic/crystalline-silicon heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Hossain, Jaker; Ohki, Tatsuya; Ichikawa, Koki; Fujiyama, Kazuhiko; Ueno, Keiji; Fujii, Yasuhiko; Hanajiri, Tatsuro; Shirai, Hajime

    2016-03-01

    Chemical mist deposition (CMD) of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was investigated in terms of cavitation frequency f, solvent, flow rate of nitrogen, substrate temperature Ts, and substrate dc bias Vs as variables for efficient PEDOT:PSS/crystalline silicon (c-Si) heterojunction solar cells. The high-speed-camera and differential mobility analysis characterizations revealed that the average size and flux of PEDOT:PSS mist depend on f, type of solvent, and Vs. Film deposition occurred when positive Vs was applied to the c-Si substrate at Ts of 30-40 °C, whereas no deposition of films occurred with negative Vs, implying that the film is deposited mainly from negatively charged mist. The uniform deposition of PEDOT:PSS films occurred on textured c-Si(100) substrates by adjusting Ts and Vs. The adhesion of CMD PEDOT:PSS film to c-Si was greatly enhanced by applying substrate dc bias Vs compared with that of spin-coated film. The CMD PEDOT:PSS/c-Si heterojunction solar cell devices on textured c-Si(100) in 2 × 2 cm2 exhibited a power conversion efficiency η of 11.0% with better uniformity of the solar cell parameters. Furthermore, η was increased to 12.5% by adding an AR coating layer of molybdenum oxide MoOx formed by CMD. These findings suggest that CMD with negatively charged mist has great potential for the uniform deposition of organic and inorganic materials on textured c-Si substrates by suitably adjusting Ts and Vs.

  13. Thin-thick coexistence behavior of 8CB liquid crystalline films on silicon.

    PubMed

    Garcia, R; Subashi, E; Fukuto, M

    2008-05-16

    The wetting behavior of thin films of 4-n-octyl-4'-cyanobiphenyl (8CB) on Si is investigated via optical and x-ray reflectivity measurement. An experimental phase diagram is obtained showing a broad thick-thin coexistence region spanning the bulk isotropic-to-nematic (T(IN)) and the nematic-to-smectic-A (T(NA)) temperatures. For Si surfaces with coverages between 47 and 72 +/- 3 nm, reentrant wetting behavior is observed twice as we increase the temperature, with separate coexistence behaviors near T(IN) and T(NA). For coverages less than 47 nm, however, the two coexistence behaviors merge into a single coexistence region. The observed thin-thick coexistence near the second-order NA transition is not anticipated by any previous theory or experiment. Nevertheless, the behavior of the thin and thick phases within the coexistence regions is consistent with this being an equilibrium phenomenon.

  14. Integrated freestanding single-crystal silicon nanowires: conductivity and surface treatment.

    PubMed

    Lee, Chung-Hoon; Ritz, Clark S; Huang, Minghuang; Ziwisky, Michael W; Blise, Robert J; Lagally, Max G

    2011-02-01

    Integrated freestanding single-crystal silicon nanowires with typical dimension of 100 nm × 100 nm × 5 µm are fabricated by conventional 1:1 optical lithography and wet chemical silicon etching. The fabrication procedure can lead to wafer-scale integration of silicon nanowires in arrays. The measured electrical transport characteristics of the silicon nanowires covered with/without SiO(2) support a model of Fermi level pinning near the conduction band. The I-V curves of the nanowires reveal a current carrier polarity reversal depending on Si-SiO(2) and Si-H bonds on the nanowire surfaces.

  15. Recovery Act : Near-Single-Crystalline Photovoltaic Thin Films on Polycrystalline, Flexible Substrates

    SciTech Connect

    Venkat Selvamanickam; Alex Freundlich

    2010-11-29

    III-V photovoltaics have exhibited efficiencies above 40%, but have found only a limited use because of the high cost of single crystal substrates. At the other end of the spectrum, polycrystalline and amorphous thin film solar cells offer the advantage of low-cost fabrication, but have not yielded high efficiencies. Our program is based on single-crystalline-like thin film photovoltaics on polycrystalline substrates using biaxially-textured templates made by Ion Beam-Assisted Deposition (IBAD). MgO templates made by IBAD on flexible metal substrate have been successfully used for epitaxial growth of germanium films. In spite of a 4.5% lattice mismatch, heteroepitaxial growth of Ge was achieved on CeO2 that was grown on IBAD MgO template. Room temperature optical bandgap of the Ge films was identified at 0.67 eV indicating minimal residual strain. Refraction index and extinction coefficient values of the Ge films were found to match well with that measured from a reference Ge single crystal. GaAs has been successfully grown epitaxially on Ge on metal substrate by molecular beam epitaxy. RHEED patterns indicate self annihilation of antiphase boundaries and the growth of a single domain GaAs. The GaAs is found to exhibit strong photoluminescence signal and, an existence of a relatively narrow (FWHM~20 meV) band-edge excitons measured in this film indicates a good optoelectronic quality of deposited GaAs. While excellent epitaxial growth has been achieved in GaAs on flexible metal substrates, the defect density of the films as measured by High Resolution X-ray Diffraction and etch pit experiments showed a high value of 5 * 10^8 per cm^2. Cross sectional transmission electron microscopy of the multilayer architecture showed concentration of threading dislocations near the germanium-ceria interface. The defect density was found decrease as the Ge films were made thicker. The defects appear to originate from the MgO layer presumably because of large lattice mismatches

  16. Wafer-Scale Integration of Inverted Nanopyramid Arrays for Advanced Light Trapping in Crystalline Silicon Thin Film Solar Cells.

    PubMed

    Zhou, Suqiong; Yang, Zhenhai; Gao, Pingqi; Li, Xiaofeng; Yang, Xi; Wang, Dan; He, Jian; Ying, Zhiqin; Ye, Jichun

    2016-12-01

    Crystalline silicon thin film (c-Si TF) solar cells with an active layer thickness of a few micrometers may provide a viable pathway for further sustainable development of photovoltaic technology, because of its potentials in cost reduction and high efficiency. However, the performance of such cells is largely constrained by the deteriorated light absorption of the ultrathin photoactive material. Here, we report an efficient light-trapping strategy in c-Si TFs (~20 μm in thickness) that utilizes two-dimensional (2D) arrays of inverted nanopyramid (INP) as surface texturing. Three types of INP arrays with typical periodicities of 300, 670, and 1400 nm, either on front, rear, or both surfaces of the c-Si TFs, are fabricated by scalable colloidal lithography and anisotropic wet etch technique. With the extra aid of antireflection coating, the sufficient optical absorption of 20-μm-thick c-Si with a double-sided 1400-nm INP arrays yields a photocurrent density of 39.86 mA/cm(2), which is about 76 % higher than the flat counterpart (22.63 mA/cm(2)) and is only 3 % lower than the value of Lambertian limit (41.10 mA/cm(2)). The novel surface texturing scheme with 2D INP arrays has the advantages of excellent antireflection and light-trapping capabilities, an inherent low parasitic surface area, a negligible surface damage, and a good compatibility for subsequent process steps, making it a good alternative for high-performance c-Si TF solar cells. PMID:27071681

  17. Wafer-Scale Integration of Inverted Nanopyramid Arrays for Advanced Light Trapping in Crystalline Silicon Thin Film Solar Cells.

    PubMed

    Zhou, Suqiong; Yang, Zhenhai; Gao, Pingqi; Li, Xiaofeng; Yang, Xi; Wang, Dan; He, Jian; Ying, Zhiqin; Ye, Jichun

    2016-12-01

    Crystalline silicon thin film (c-Si TF) solar cells with an active layer thickness of a few micrometers may provide a viable pathway for further sustainable development of photovoltaic technology, because of its potentials in cost reduction and high efficiency. However, the performance of such cells is largely constrained by the deteriorated light absorption of the ultrathin photoactive material. Here, we report an efficient light-trapping strategy in c-Si TFs (~20 μm in thickness) that utilizes two-dimensional (2D) arrays of inverted nanopyramid (INP) as surface texturing. Three types of INP arrays with typical periodicities of 300, 670, and 1400 nm, either on front, rear, or both surfaces of the c-Si TFs, are fabricated by scalable colloidal lithography and anisotropic wet etch technique. With the extra aid of antireflection coating, the sufficient optical absorption of 20-μm-thick c-Si with a double-sided 1400-nm INP arrays yields a photocurrent density of 39.86 mA/cm(2), which is about 76 % higher than the flat counterpart (22.63 mA/cm(2)) and is only 3 % lower than the value of Lambertian limit (41.10 mA/cm(2)). The novel surface texturing scheme with 2D INP arrays has the advantages of excellent antireflection and light-trapping capabilities, an inherent low parasitic surface area, a negligible surface damage, and a good compatibility for subsequent process steps, making it a good alternative for high-performance c-Si TF solar cells.

  18. Environmental Qualification of a Single-Crystal Silicon Mirror for Spaceflight Use

    NASA Technical Reports Server (NTRS)

    Hagopian, John; Chambers, John; Rohrback. Scott; Bly, Vincent; Morell, Armando; Budinoff, Jason

    2013-01-01

    This innovation is the environmental qualification of a single-crystal silicon mirror for spaceflight use. The single-crystal silicon mirror technology is a previous innovation, but until now, a mirror of this type has not been qualified for spaceflight use. The qualification steps included mounting, gravity change measurements, vibration testing, vibration- induced change measurements, thermal cycling, and testing at the cold operational temperature of 225 K. Typical mirrors used for cold applications for spaceflight instruments include aluminum, beryllium, glasses, and glass-like ceramics. These materials show less than ideal behavior after cooldown. Single-crystal silicon has been demonstrated to have the smallest change due to temperature change, but has not been spaceflight-qualified for use. The advantage of using a silicon substrate is with temperature stability, since it is formed from a stress-free single crystal. This has been shown in previous testing. Mounting and environmental qualification have not been shown until this testing.

  19. Silane-catalysed fast growth of large single-crystalline graphene on hexagonal boron nitride

    PubMed Central

    Tang, Shujie; Wang, Haomin; Wang, Hui Shan; Sun, Qiujuan; Zhang, Xiuyun; Cong, Chunxiao; Xie, Hong; Liu, Xiaoyu; Zhou, Xiaohao; Huang, Fuqiang; Chen, Xiaoshuang; Yu, Ting; Ding, Feng; Xie, Xiaoming; Jiang, Mianheng

    2015-01-01

    The direct growth of high-quality, large single-crystalline domains of graphene on a dielectric substrate is of vital importance for applications in electronics and optoelectronics. Traditionally, graphene domains grown on dielectrics are typically only ~1 μm with a growth rate of ~1 nm min−1 or less, the main reason is the lack of a catalyst. Here we show that silane, serving as a gaseous catalyst, is able to boost the graphene growth rate to ~1 μm min−1, thereby promoting graphene domains up to 20 μm in size to be synthesized via chemical vapour deposition (CVD) on hexagonal boron nitride (h-BN). Hall measurements show that the mobility of the sample reaches 20,000 cm2 V−1 s−1 at room temperature, which is among the best for CVD-grown graphene. Combining the advantages of both catalytic CVD and the ultra-flat dielectric substrate, gaseous catalyst-assisted CVD paves the way for synthesizing high-quality graphene for device applications while avoiding the transfer process. PMID:25757864

  20. Nb-doped single crystalline MoS{sub 2} field effect transistor

    SciTech Connect

    Das, Saptarshi E-mail: das@anl.gov; Demarteau, Marcellinus; Roelofs, Andreas

    2015-04-27

    We report on the demonstration of a p-type, single crystalline, few layer MoS{sub 2} field effect transistor (FET) using Niobium (Nb) as the dopant. The doping concentration was extracted and determined to be ∼3 × 10{sup 19}/cm{sup 3}. We also report on bilayer Nb-doped MoS{sub 2} FETs with ambipolar conduction. We found that the current ON-OFF ratio of the Nb-doped MoS{sub 2} FETs changes significantly as a function of the flake thickness. We attribute this experimental observation to bulk-type electrostatic effect in ultra-thin MoS{sub 2} crystals. We provide detailed analytical modeling in support of our claims. Finally, we show that in the presence of heavy doping, even ultra-thin 2D-semiconductors cannot be fully depleted and may behave as a 3D material when used in transistor geometry. Our findings provide important insights into the doping constraints of 2D materials, in general.

  1. Facile fabrication of electrolyte-gated single-crystalline cuprous oxide nanowire field-effect transistors.

    PubMed

    Stoesser, Anna; von Seggern, Falk; Purohit, Suneeti; Nasr, Babak; Kruk, Robert; Dehm, Simone; Di Wang; Hahn, Horst; Dasgupta, Subho

    2016-10-14

    Oxide semiconductors are considered to be one of the forefront candidates for the new generation, high-performance electronics. However, one of the major limitations for oxide electronics is the scarcity of an equally good hole-conducting semiconductor, which can provide identical performance for the p-type metal oxide semiconductor field-effect transistors as compared to their electron conducting counterparts. In this quest, here we present a bulk synthesis method for single crystalline cuprous oxide (Cu2O) nanowires, their chemical and morphological characterization and suitability as active channel material in electrolyte-gated, low-power, field-effect transistors (FETs) for portable and flexible logic circuits. The bulk synthesis method used in the present study includes two steps: namely hydrothermal synthesis of the nanowires and the removal of the surface organic contaminants. The surface treated nanowires are then dispersed on a receiver substrate where the passive electrodes are structured, followed by printing of a composite solid polymer electrolyte (CSPE), chosen as the gate insulator. The characteristic electrical properties of individual nanowire FETs are found to be quite interesting including accumulation-mode operation and field-effect mobility of 0.15 cm(2) V(-1) s(-1). PMID:27609560

  2. Facile fabrication of electrolyte-gated single-crystalline cuprous oxide nanowire field-effect transistors

    NASA Astrophysics Data System (ADS)

    Stoesser, Anna; von Seggern, Falk; Purohit, Suneeti; Nasr, Babak; Kruk, Robert; Dehm, Simone; Wang, Di; Hahn, Horst; Dasgupta, Subho

    2016-10-01

    Oxide semiconductors are considered to be one of the forefront candidates for the new generation, high-performance electronics. However, one of the major limitations for oxide electronics is the scarcity of an equally good hole-conducting semiconductor, which can provide identical performance for the p-type metal oxide semiconductor field-effect transistors as compared to their electron conducting counterparts. In this quest, here we present a bulk synthesis method for single crystalline cuprous oxide (Cu2O) nanowires, their chemical and morphological characterization and suitability as active channel material in electrolyte-gated, low-power, field-effect transistors (FETs) for portable and flexible logic circuits. The bulk synthesis method used in the present study includes two steps: namely hydrothermal synthesis of the nanowires and the removal of the surface organic contaminants. The surface treated nanowires are then dispersed on a receiver substrate where the passive electrodes are structured, followed by printing of a composite solid polymer electrolyte (CSPE), chosen as the gate insulator. The characteristic electrical properties of individual nanowire FETs are found to be quite interesting including accumulation-mode operation and field-effect mobility of 0.15 cm2 V-1 s-1.

  3. Synthesis of single-crystalline Zn metal nanowires utilizing cold-wall physical vapor deposition.

    PubMed

    Kast, Michael; Schroeder, Philipp; Hyun, Youn J; Pongratz, Peter; Bruückl, Hubert

    2007-08-01

    Zinc metal nanowires (NWs) of two different morphologies have been synthesized in a cold-wall physical vapor deposition (CWPVD) chamber at high vacuum conditions and growth temperatures of 150 degrees C. Substrates initially seeded by gold or platinum crystals show NWs of wool-like and/or unidirectional morphologies. Transmission electron microscopy (TEM) studies revealed that the rodlike NWs consist of single-crystalline Zn covered with a thin native oxide. NWs of wool-like morphology are suppressed using platinum as the seed metal. NW growth proceeds via vapor-solid (VS) kinetics without any catalyst particles on the wire tips. The highest observed growth rates exceed the Zn deposition rate by factors up to 860, indicating the dominant role of surface diffusion of Zn adatoms, also along the NWs. The surface diffusion length of Zn adatoms on the NW side facet is determined to be 39 mum. Direct impingement of precursor atoms on the NW tip is not significant for the growth process.

  4. Enhanced piezoelectric properties of vertically aligned single-crystalline NKN nano-rod arrays.

    PubMed

    Kang, Min-Gyu; Oh, Seung-Min; Jung, Woo-Suk; Moon, Hi Gyu; Baek, Seung-Hyub; Nahm, Sahn; Yoon, Seok-Jin; Kang, Chong-Yun

    2015-05-08

    Piezoelectric materials capable of converting between mechanical and electrical energy have a great range of potential applications in micro- and nano-scale smart devices; however, their performance tends to be greatly degraded when reduced to a thin film due to the large clamping force by the substrate and surrounding materials. Herein, we report an effective method for synthesizing isolated piezoelectric nano-materials as means to relax the clamping force and recover original piezoelectric properties of the materials. Using this, environmentally friendly single-crystalline NaxK1-xNbO3 (NKN) piezoelectric nano-rod arrays were successfully synthesized by conventional pulsed-laser deposition and demonstrated to have a remarkably enhanced piezoelectric performance. The shape of the nano-structure was also found to be easily manipulated by varying the energy conditions of the physical vapor. We anticipate that this work will provide a way to produce piezoelectric micro- and nano-devices suitable for practical application, and in doing so, open a new path for the development of complex metal-oxide nano-structures.

  5. Enzyme-modified field effect transistors based on surface-conductive single-crystalline diamond.

    PubMed

    Härtl, Andreas; Baur, Barbara; Stutzmann, Martin; Garrido, Jose A

    2008-09-01

    Enzyme-modified field effect transistors (ENFETs) were realized using surface-conductive single-crystalline diamond films. The enzymes penicillinase and acetylcholinesterase were immobilized onto the active area of diamond-based electrolytic solution gated FETs, using different organic linker molecules and cross-linking chemistries. The active area of the devices was patterned to generate enzyme-modified regions next to surface-conductive regions. Penicillinase was chosen as a robust model system, but the main focus of the present paper is on acetylcholinesterase, an enzyme essential for many neuronal signal transduction processes. All the different ENFETs show a clear and specific response to the corresponding substrate, penicillin and acetylcholine. The device response is based on the pH sensitivity of the surface-conductive active area and is enabled by the local pH change induced during the enzymatic reaction. The devices demonstrate promising stability and characteristic variations of the enzymatic activity with measurement conditions. Furthermore, the results from the ENFET measurements were compared with the results of spectrophotometric experiments, carried out with enzymes immobilized on diamond substrates and also with free enzymes in solution. This allows an analysis of the enzyme kinetics, as well as qualitative comparison of the different functionalization methods employed in this study.

  6. Nanometre-thick single-crystalline nanosheets grown at the water–air interface

    PubMed Central

    Wang, Fei; Seo, Jung-Hun; Luo, Guangfu; Starr, Matthew B.; Li, Zhaodong; Geng, Dalong; Yin, Xin; Wang, Shaoyang; Fraser, Douglas G.; Morgan, Dane; Ma, Zhenqiang; Wang, Xudong

    2016-01-01

    To date, the preparation of free-standing 2D nanomaterials has been largely limited to the exfoliation of van der Waals solids. The lack of a robust mechanism for the bottom-up synthesis of 2D nanomaterials from non-layered materials has become an obstacle to further explore the physical properties and advanced applications of 2D nanomaterials. Here we demonstrate that surfactant monolayers can serve as soft templates guiding the nucleation and growth of 2D nanomaterials in large area beyond the limitation of van der Waals solids. One- to 2-nm-thick, single-crystalline free-standing ZnO nanosheets with sizes up to tens of micrometres are synthesized at the water–air interface. In this process, the packing density of surfactant monolayers adapts to the sub-phase metal ions and guides the epitaxial growth of nanosheets. It is thus named adaptive ionic layer epitaxy (AILE). The electronic properties of ZnO nanosheets and AILE of other materials are also investigated. PMID:26786708

  7. Facile fabrication of electrolyte-gated single-crystalline cuprous oxide nanowire field-effect transistors.

    PubMed

    Stoesser, Anna; von Seggern, Falk; Purohit, Suneeti; Nasr, Babak; Kruk, Robert; Dehm, Simone; Di Wang; Hahn, Horst; Dasgupta, Subho

    2016-10-14

    Oxide semiconductors are considered to be one of the forefront candidates for the new generation, high-performance electronics. However, one of the major limitations for oxide electronics is the scarcity of an equally good hole-conducting semiconductor, which can provide identical performance for the p-type metal oxide semiconductor field-effect transistors as compared to their electron conducting counterparts. In this quest, here we present a bulk synthesis method for single crystalline cuprous oxide (Cu2O) nanowires, their chemical and morphological characterization and suitability as active channel material in electrolyte-gated, low-power, field-effect transistors (FETs) for portable and flexible logic circuits. The bulk synthesis method used in the present study includes two steps: namely hydrothermal synthesis of the nanowires and the removal of the surface organic contaminants. The surface treated nanowires are then dispersed on a receiver substrate where the passive electrodes are structured, followed by printing of a composite solid polymer electrolyte (CSPE), chosen as the gate insulator. The characteristic electrical properties of individual nanowire FETs are found to be quite interesting including accumulation-mode operation and field-effect mobility of 0.15 cm(2) V(-1) s(-1).

  8. Crystalline Bis-urea Nanochannel Architectures Tailored for Single-File Diffusion Studies.

    PubMed

    Bowers, Clifford R; Dvoyashkin, Muslim; Salpage, Sahan R; Akel, Christopher; Bhase, Hrishi; Geer, Michael F; Shimizu, Linda S

    2015-06-23

    Urea is a versatile building block that can be modified to self-assemble into a multitude of structures. One-dimensional nanochannels with zigzag architecture and cross-sectional dimensions of only ∼3.7 Å × 4.8 Å are formed by the columnar assembly of phenyl ether bis-urea macrocycles. Nanochannels formed by phenylethynylene bis-urea macrocycles have a round cross-section with a diameter of ∼9.0 Å. This work compares the Xe atom packing and diffusion inside the crystalline channels of these two bis-ureas using hyperpolarized Xe-129 NMR. The elliptical channel structure of the phenyl ether bis-urea macrocycle produces a Xe-129 powder pattern line shape characteristic of an asymmetric chemical shift tensor with shifts extending to well over 300 ppm with respect to the bulk gas, reflecting extreme confinement of the Xe atom. The wider channels formed by phenylethynylene bis-urea, in contrast, present an isotropic dynamically average electronic environment. Completely different diffusion dynamics are revealed in the two bis-ureas using hyperpolarized spin-tracer exchange NMR. Thus, a simple replacement of phenyl ether with phenylethynylene as the rigid linker unit results in a transition from single-file to Fickian diffusion dynamics. Self-assembled bis-urea macrocycles are found to be highly suitable materials for fundamental molecular transport studies on micrometer length scales.

  9. Silane-catalysed fast growth of large single-crystalline graphene on hexagonal boron nitride.

    PubMed

    Tang, Shujie; Wang, Haomin; Wang, Hui Shan; Sun, Qiujuan; Zhang, Xiuyun; Cong, Chunxiao; Xie, Hong; Liu, Xiaoyu; Zhou, Xiaohao; Huang, Fuqiang; Chen, Xiaoshuang; Yu, Ting; Ding, Feng; Xie, Xiaoming; Jiang, Mianheng

    2015-03-11

    The direct growth of high-quality, large single-crystalline domains of graphene on a dielectric substrate is of vital importance for applications in electronics and optoelectronics. Traditionally, graphene domains grown on dielectrics are typically only ~1 μm with a growth rate of ~1 nm min(-1) or less, the main reason is the lack of a catalyst. Here we show that silane, serving as a gaseous catalyst, is able to boost the graphene growth rate to ~1 μm min(-1), thereby promoting graphene domains up to 20 μm in size to be synthesized via chemical vapour deposition (CVD) on hexagonal boron nitride (h-BN). Hall measurements show that the mobility of the sample reaches 20,000 cm(2) V(-1) s(-1) at room temperature, which is among the best for CVD-grown graphene. Combining the advantages of both catalytic CVD and the ultra-flat dielectric substrate, gaseous catalyst-assisted CVD paves the way for synthesizing high-quality graphene for device applications while avoiding the transfer process.

  10. Enhanced piezoelectric properties of vertically aligned single-crystalline NKN nano-rod arrays

    PubMed Central

    Kang, Min-Gyu; Oh, Seung-Min; Jung, Woo-Suk; Gyu Moon, Hi; Baek, Seung-Hyub; Nahm, Sahn; Yoon, Seok-Jin; Kang, Chong-Yun

    2015-01-01

    Piezoelectric materials capable of converting between mechanical and electrical energy have a great range of potential applications in micro- and nano-scale smart devices; however, their performance tends to be greatly degraded when reduced to a thin film due to the large clamping force by the substrate and surrounding materials. Herein, we report an effective method for synthesizing isolated piezoelectric nano-materials as means to relax the clamping force and recover original piezoelectric properties of the materials. Using this, environmentally friendly single-crystalline NaxK1-xNbO3 (NKN) piezoelectric nano-rod arrays were successfully synthesized by conventional pulsed-laser deposition and demonstrated to have a remarkably enhanced piezoelectric performance. The shape of the nano-structure was also found to be easily manipulated by varying the energy conditions of the physical vapor. We anticipate that this work will provide a way to produce piezoelectric micro- and nano-devices suitable for practical application, and in doing so, open a new path for the development of complex metal-oxide nano-structures. PMID:25955763

  11. Temperature dependent van der Pauw-Hall measurements on sodium doped single crystalline cadmium telluride

    SciTech Connect

    Ahmad, Faisal R.

    2015-03-21

    In this report, results of the temperature dependent electrical conductivity measurements conducted on single crystalline cadmium telluride (CdTe), containing sodium (Na) impurities are presented and discussed. The electrical conductivity measurements were conducted using an apparatus that allowed the implementation of a standard van der Pauw-Hall effect technique through which the electrical resistivity, concentration of majority carriers, as well as the carrier mobility were determined for temperatures ranging between 24 K and 350 K. Over this temperature range, the electrical resistivity was observed to change by 7 orders of magnitude. Hall measurements showed that the hole concentration at 300 K was ∼3 × 10{sup 15 }cm{sup –3} and the hole mobility at the same temperature was ∼80 cm{sup 2}/V s. Measuring the concentration of holes as a function of the sample temperature enabled the estimation of the acceptor energy level with respect to the valence band maximum to be ∼60 meV. The same data also revealed the potential presence of a compensating donor level. Furthermore, the hole mobility was also analyzed over the entire temperature range and the data revealed that above 100 K, the carrier mobility was dominated by the scattering of holes from lattice vibrations.

  12. Fabrications and application of single crystalline GaN for high-performance deep UV photodetectors

    NASA Astrophysics Data System (ADS)

    Velazquez, R.; Aldalbahi, A.; Rivera, M.; Feng, P.

    2016-08-01

    High-quality single crystalline Gallium Nitride (GaN) semiconductor has been synthesized using molecule beam epitaxy (MBE) technique for development of high-performance deep ultraviolet (UV) photodetectors. Thickness of the films was estimated by using surface profile meter and scanning electron microscope. Electronic states and elemental composition of the films were obtained using Raman scattering spectroscopy. The orientation, crystal structure and phase purity of the films were examined using a Siemens x-ray diffractometer radiation. The surface microstructure was studied using high resolution scanning electron microscopy (SEM). Two types of metal pairs: Al-Al, Al-Cu or Cu-Cu were used for interdigital electrodes on GaN film in order to examine the Schottky properties of the GaN based photodetector. The characterizations of the fabricated prototype include the stability, responsivity, response and recovery times. Typical time dependent photoresponsivity by switching different UV light source on and off five times for each 240 seconds at a bias of 2V, respectively, have been obtained. The detector appears to be highly sensitive to various UV wavelengths of light with very stable baseline and repeatability. The obtained photoresponsivity was up to 354 mA/W at the bias 2V. Higher photoresponsivity could be obtained if higher bias was applied but it would unavoidably result in a higher dark current. Thermal effect on the fabricated GaN based prototype was discussed.

  13. Single-crystalline, wormlike hematite photoanodes for efficient solar water splitting

    PubMed Central

    Kim, Jae Young; Magesh, Ganesan; Youn, Duck Hyun; Jang, Ji-Wook; Kubota, Jun; Domen, Kazunari; Lee, Jae Sung

    2013-01-01

    A hematite photoanode showing a stable, record-breaking performance of 4.32 mA/cm2 photoelectrochemical water oxidation current at 1.23 V vs. RHE under simulated 1-sun (100 mW/cm2) irradiation is reported. This photocurrent corresponds to ca. 34% of the maximum theoretical limit expected for hematite with a band gap of 2.1 V. The photoanode produced stoichiometric hydrogen and oxygen gases in amounts close to the expected values from the photocurrent. The hematitle has a unique single-crystalline “wormlike” morphology produced by in-situ two-step annealing at 550°C and 800°C of β-FeOOH nanorods grown directly on a transparent conducting oxide glass via an all-solution method. In addition, it is modified by platinum doping to improve the charge transfer characteristics of hematite and an oxygen-evolving co-catalyst on the surface. PMID:24045290

  14. Cavity Polaritons in a Single-Crystalline Organic Microcavity Prepared at Room Temperature Using a Simple Solution Technique

    NASA Astrophysics Data System (ADS)

    Bando, Kazuki; Nagai, Hikaru; Amano, Masamitsu; Kanezashi, Keigo; Kumeta, Shohei; Kondo, Hisao

    2013-11-01

    We have developed a novel method of fabricating high-quality crystalline organic microcavities using a simple solution technique. Anthracene single crystals were grown from solution at room temperature in a gap of ˜200 nm between two joined distributed Bragg reflectors. The method is easier to perform than the conventional melting technique and the crystals have no strain caused by thermal expansion. Clear cavity polariton modes and giant Rabi splitting energies were observed as well as those in the microcavities prepared using the melting technique. The method can be applied to the fabrication of various crystalline organic microcavities.

  15. Current-direction dependence of the transport properties in single-crystalline face-centered-cubic cobalt films

    SciTech Connect

    Xiao, X.; Liang, J. H.; Chen, B. L.; Li, J. X.; Ding, Z.; Wu, Y. Z.; Ma, D. H.

    2015-07-28

    Face-centered-cubic cobalt films are epitaxially grown on insulating LaAlO{sub 3}(001) substrates by molecular beam epitaxy. Transport measurements are conducted in different current directions relative to the crystal axes. We find that the temperature dependent anisotropic magnetoresistance ratio strongly depends on the current direction. However, the anomalous Hall effect shows isotropic behavior independent of the current direction. Our results demonstrate the interplay between the current direction and the crystalline lattice in single-crystalline ferromagnetic films. A phenomenological analysis is presented to interpret the experimental data.

  16. High-quality single crystalline NiO with twin phases grown on sapphire substrate by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Uchida, Kazuo; Yoshida, Ken-ichi; Zhang, Dongyuan; Koizumi, Atsushi; Nozaki, Shinji

    2012-12-01

    High-quality single crystalline twin phase NiO grown on sapphire substrates by metalorganic vapor phase epitaxy is reported. X-ray rocking curve analysis of NiO films grown at different temperatures indicates a minimum full width at half maximum of the cubic (111) diffraction peak of 0.107° for NiO film grown at as low as 550 °C. Detailed microstructural analysis by Φ scan X-ray diffraction and transmission electron microscopy reveal that the NiO film consists of large single crystalline domains with two different crystallographic orientations which are rotated relative to each other along the [111] axis by 60°. These single crystal domains are divided by the twin phase boundaries.

  17. Optoelectronic transport properties in amorphous/crystalline silicon solar cell heterojunctions measured by frequency-domain photocarrier radiometry: Multi-parameter measurement reliability and precision studies

    SciTech Connect

    Zhang, Y.; Melnikov, A.; Mandelis, A.; Halliop, B.; Kherani, N. P.; Zhu, R.

    2015-03-15

    A theoretical one-dimensional two-layer linear photocarrier radiometry (PCR) model including the presence of effective interface carrier traps was used to evaluate the transport parameters of p-type hydrogenated amorphous silicon (a-Si:H) and n-type crystalline silicon (c-Si) passivated by an intrinsic hydrogenated amorphous silicon (i-layer) nanolayer. Several crystalline Si heterojunction structures were examined to investigate the influence of the i-layer thickness and the doping concentration of the a-Si:H layer. The experimental data of a series of heterojunction structures with intrinsic thin layers were fitted to PCR theory to gain insight into the transport properties of these devices. The quantitative multi-parameter results were studied with regard to measurement reliability (uniqueness) and precision using two independent computational best-fit programs. The considerable influence on the transport properties of the entire structure of two key parameters that can limit the performance of amorphous thin film solar cells, namely, the doping concentration of the a-Si:H layer and the i-layer thickness was demonstrated. It was shown that PCR can be applied to the non-destructive characterization of a-Si:H/c-Si heterojunction solar cells yielding reliable measurements of the key parameters.

  18. Optoelectronic transport properties in amorphous/crystalline silicon solar cell heterojunctions measured by frequency-domain photocarrier radiometry: multi-parameter measurement reliability and precision studies.

    PubMed

    Zhang, Y; Melnikov, A; Mandelis, A; Halliop, B; Kherani, N P; Zhu, R

    2015-03-01

    A theoretical one-dimensional two-layer linear photocarrier radiometry (PCR) model including the presence of effective interface carrier traps was used to evaluate the transport parameters of p-type hydrogenated amorphous silicon (a-Si:H) and n-type crystalline silicon (c-Si) passivated by an intrinsic hydrogenated amorphous silicon (i-layer) nanolayer. Several crystalline Si heterojunction structures were examined to investigate the influence of the i-layer thickness and the doping concentration of the a-Si:H layer. The experimental data of a series of heterojunction structures with intrinsic thin layers were fitted to PCR theory to gain insight into the transport properties of these devices. The quantitative multi-parameter results were studied with regard to measurement reliability (uniqueness) and precision using two independent computational best-fit programs. The considerable influence on the transport properties of the entire structure of two key parameters that can limit the performance of amorphous thin film solar cells, namely, the doping concentration of the a-Si:H layer and the i-layer thickness was demonstrated. It was shown that PCR can be applied to the non-destructive characterization of a-Si:H/c-Si heterojunction solar cells yielding reliable measurements of the key parameters. PMID:25832239

  19. Wear particles of single-crystal silicon carbide in vacuum

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1980-01-01

    Sliding friction experiments, conducted in vacuum with silicon carbide /000/ surface in contact with iron based binary alloys are described. Multiangular and spherical wear particles of silicon carbide are observed as a result of multipass sliding. The multiangular particles are produced by primary and secondary cracking of cleavage planes /000/, /10(-1)0/, and /11(-2)0/ under the Hertzian stress field or local inelastic deformation zone. The spherical particles may be produced by two mechanisms: (1) a penny shaped fracture along the circular stress trajectories under the local inelastic deformation zone, and (2) attrition of wear particles.

  20. Thin Single Crystal Silicon Solar Cells on Ceramic Substrates: November 2009 - November 2010

    SciTech Connect

    Kumar, A.; Ravi, K. V.

    2011-06-01

    In this program we have been developing a technology for fabricating thin (< 50 micrometres) single crystal silicon wafers on foreign substrates. We reverse the conventional approach of depositing or forming silicon on foreign substrates by depositing or forming thick (200 to 400 micrometres) ceramic materials on high quality single crystal silicon films ~ 50 micrometres thick. Our key innovation is the fabrication of thin, refractory, and self-adhering 'handling layers or substrates' on thin epitaxial silicon films in-situ, from powder precursors obtained from low cost raw materials. This 'handling layer' has sufficient strength for device and module processing and fabrication. Successful production of full sized (125 mm X 125 mm) silicon on ceramic wafers with 50 micrometre thick single crystal silicon has been achieved and device process flow developed for solar cell fabrication. Impurity transfer from the ceramic to the silicon during the elevated temperature consolidation process has resulted in very low minority carrier lifetimes and resulting low cell efficiencies. Detailed analysis of minority carrier lifetime, metals analysis and device characterization have been done. A full sized solar cell efficiency of 8% has been demonstrated.