bluuebunny/crossref_metadata_2025_split huggingface dataset:
Absorber Films of Antimony Chalcogenides via Chemical Deposition for Photovoltaic Application
Authors: Nair M. T. S. , Rodríguez-Lazcano Y. , Peña Y. , Messina S. , Campos J. , Nair P. K. 
Published: April 2011

ABSTRACTAntimony sulfide thin films (300 nm) have been deposited on glass substrates at 1–10°C from chemical bath. When heated these become crystalline and photoconductive with optical band gap (direct) of 1.7 eV. Thin films formed from chemical baths containing SbCl3 and sodium selenosulfate are of mixed phase Sb2O3/Sb2Se3, which when heated in the presence of Se-vapor converts to single phase Sb2Se3 film with optical band gap of 1.1 eV. Such films possess dark conductivity of 10-8 ohm-1cm-1 and show photosensitivity of two orders. Reaction of Sb2S3-CuS in nitrogen at 400°C produces crystalline, photoconductive p-type CuSbS2 with optical band gap (direct) of 1.5 eV. By controlling the deposition and heating condition, (i)Sb2S3-(p)CuSbS2 layer is formed, which is utilized in a photovoltaic structure, (n)CdS:In-(i)Sb2S3-(p)CuSbS2, with a Voc of 345 mV and Jsc 0.18 mA/cm2 under 1 kW m-2 tungsten halogen illumination. In the case of a structure, CdS:Cl-Sb2S3-Cu2-xSe, Voc of 350 mV and Jsc of 0.5 mA/cm2 are observed.
AgSbSe2 thin films for photovoltaic structures produced through reaction of chemically deposited selenium thin films with Ag and Sb2S3
Authors: Bindu K. , Nair M. T. S. , Nair P. K. 
Published: April 2011

ABSTRACTSelenium thin films (350 nm) deposited from a 0.01 M solution of Na2SeSO3 of pH 4.5 maintained at 10 °C for 13 h, have been used as a source of selenium vapour for reaction with vacuum deposited Ag thin film on chemically deposited Sb2S3+Ag layers. When a stack of Sb2S3+Ag is heated in contact with Se film, AgSbSe2 is formed through solid state reaction of Sb2S3 and Ag2Se. The latter is formed at 80°C through the reaction of Ag-film in Se-vapour. This thin film is photoconductive and p-type. The optical band gap is nearly 1 eV and dark conductivity, 10-3 Ω-1cm-1. This thin film has been incorporated to form a photovoltaic structure, SnO2:F-(n)CdS:In-(i)Sb2S3-(p)AgSbSe2-silver print. Voc> 400 mV and Jsc>12 mA/cm2 have been observed in this under an illumination intensity of 1 kWm-2.
Current Transport Study of Schottky and P-N Junction Solar Cells Using Metal-Induced Growth Poly-Si Thin Films
Authors: Ji Chunhai , Kim Joon-Dong , Anderson Wayne A. 
Published: April 2011

AbstractPoly-Si thin films deposited at low temperature by using the metal-induced growth (MIG) method have the advantage of less metal impurity contaminations and relative large grains with preferred crystal orientation of (220). In recent research, the Schottky solar diode made of MIG poly-Si shows Jsc of 12 mA/cm2 and Voc of 0.214V. In this paper, current transport mechanisms were studied by current-voltage-temperature (I-V-T) testing from 100 K to 400K. For the samples deposited by a one-step sputtering process, the large value of ideality factor (n) and abnormal increase of barrier height with the temperature implies that the current transport mechanism does not follow the pure thermionic-emission theory, which was proven to be thermionic-field emission due to the highly doped Si film. By using a two-step sputtering process, the ideality factor and Au-Schottky barrier height at room temperature were about 1.5 and 0.7 eV, which was improved from one-step sputtering. Hydrogenation by electron cyclotron resonance (ECR) plasma can further improve the Schottky diode ideality factor and barrier height. Although a low-level Phosphors-doped Si target was used for poly-Si thin film deposition, a thermionic-field emission mechanism was still found by plotting the activation energy (E0) versus the testing temperature range. Capacitance-voltage (C-V) analysis revealed an unexpected carrier density of 1017 cm−3 level, which is 1000 times higher than the doping density level in the Si film. “Oxygen thermal donor” effect was assumed due to high oxygen level (1020 cm−3) detected by SIMS and processing at ∼ 600 °C. Increasing of the total carrier density due to the oxygen donor may cause the transport mechanism change from pure thermionic emission to thermionic-field emission. Reducing oxygen in the Si film by filtering the sputtering gas to 50 ppb oxygen level was proven to be effective. C-V results gave ∼1016 cm−3 level of carrier density after using oxygen filtering. P-N junction solar cells were made by B-ion implantation into n-type Si film and dopant activation at 700 °C. I-V-T study showed similar curves for P-N junction as for Schottky junction devices. This implies that the current transport was dominated by the Si films instead of the junctions for both Schottky and P-N junction devices.
Metamorphic GaInP-GaInAs Layers for Photovoltaic Applications
Authors: Bett A. W. , Baur C. , Dimroth F. , Schöne J. 
Published: April 2011

ABSTRACTGaxIn1−xAs and GayIn1−yP layers were grown lattice mismatched to GaAs and Ge by low-pressure metal organic vapor phase epitaxy (LP-MOPVE). These materials are very promising for further increasing the efficiency of monolithic triple-junction solar cells. Different buffer layer structures were realized. Transmission electron microscopy and x-ray diffraction analysis were used to characterize the quality of the crystal. Both linear and step-graded buffers in GaxIn1−xAs were successfully used under an active solar cell structure. GayIn1−yP as buffer material showed a worse performance. Excellent solar cell performance was achieved for lattice mismatched single-, dual- and triple-junction solar cells.
Effects of Grain Boundaries in Amorphous/Multicrystalline Silicon Heterojunction Photovoltaic Cells
Authors: Farrokh Baroughi M. , Sivoththaman S. 
Published: April 2011

ABSTRACTSpectral response and dark current-voltage characteristics of heterojunctions are used to investigate grain boundary degradation in photovoltaic properties of a-Si/mc-Si heterojunction solar cells. Measured spectral response inside the grain and on the grain boundary shows small but consistent QE degradation due to minority carrier recombination at the grain boundaries. No consistent difference is observed in dark current-voltage characteristics because of large diode area and periphery leakage current in the employed heterojunction diodes. Comparing measurement results and results from device modeling using the simulation software Medici, a recombination velocity of 4900 cm/sec is found at the grain boundaries of employed multicrystalline silicon wafer. The modeling and experimental results can also be used to define an effective grain area that serves as a measure of grain boundary recombination and the influence of grain size.
Characterization of the Local Titanium Environment in Doped Sodium Aluminum Hydride using X-ray Absorption Spectroscopy
Authors: Graetz J. , Ignatov A.Yu. , Tyson T.A. , Reilly J.J. , Johnson J. 
Published: April 2011

ABSTRACTTi K -edge x-ray absorption spectroscopy was used to explore the local titanium environment and valence in 2–4 mol% Ti-doped sodium alanate. An estimate of the oxidation state of the dopant, based upon known standards, revealed a zero-valent titanium atom. An analysis of the near-edge and extended fine structures indicates that the Ti does not enter substitutional or interstitial sites in the NaAlH4 lattice. Rather, the Ti is located on/near the surface and is coordinated by 10.2±1 aluminum atoms with an interatomic distance of 2.82±0.01 Å, similar to that of TiAl3. The Fourier transformed EXAFS spectra reveal a lack of long-range order around the Ti dopant indicating that the Ti forms nano-clusters of TiAl3. The similarity of the spectra in the hydrided and dehydrided samples suggests that the local Ti environment is nearly invariant during hydrogen cycling.
Noncovalent Functionalization of Single Walled Carbon Nanotubes Using Alternate Layer-By-Layer Polyelectrolyte Adsorption for Nanocomposite Fuel Cell Electrodes
Authors: Dhullipudi R. B. , Dobbins T. A. , Adiddela S.R. , Zheng Z. , Gunasekaran R. A. , Lvov Y. M. , Tittsworth R. 
Published: April 2011

ABSTRACTElectrodes which are resistant to chemical poisoning by CO, S, and other fuel impurities are needed to replace Pt in proton exchange membrane (PEM) fuel cells. We have designed composite electrodes comprised of single walled carbon nanotubes (CNTs) within a conducting polymer matrix. A method for solubilizing single-walled carbon nanotubes (CNTs) in aqueous media using polyelectrolyte layer-by-layer (LbL) nanoassembly of polystyrene sulfonate (PSS) and polyallylamine (PAH) at the CNT surface is elucidated. Once soluble, the CNTs were assembled onto planar substrates using alternate LbL nanoassembly to form nanocomposite films. These films will later be tested for their potential as alternative anodes in proton exchange membrane fuel cells.
Magnesium-Hydride Slurry Technology for Hydrogen Storage
Authors: Krishnan A. , Lu X. G. , Pal U. B. , McClaine A. W. 
Published: April 2011

ABSTRACTMagnesium hydride particles are suspended in an oil-based medium with dispersants to create a slurry that has great potential for hydrogen production and storage. Hydrogen is generated whenever needed by mixing the magnesium hydride slurry with water in a mixer. The byproduct is benign magnesium hydroxide (milk of magnesia). The primary purpose of the slurry is to moderate the reaction, allow thermal management and make it pumpable so it can be transported and metered like liquids so that the existing transportation infrastructure can be used. Thus, the magnesium hydride slurry lends itself well for automotive applications in conjunction with fuel cells. For such large-volume automotive applications, the success and economic viability of employing magnesium hydride slurry to transport and store hydrogen will depend on developing an effective recycling system for the magnesium hydroxide by-products. This paper discusses the feasibility of employing the Solid-Oxide-Oxygen-Ion-Conducting-Membrane (SOM) process for converting the by-product magnesium hydroxide to magnesium and regenerating the magnesium hydride slurry. The SOM process, in principle, utilizes a tubular yttria-stabilized-zirconia-based solid-oxide-fuel-cell as an anode in the temperature range 1100 – 1300 °C. The magnesium hydroxide is dissolved in a molten ionic flux and with the application of an electrical potential between an inert cathode in the flux and the anode, the oxygen ions are pumped out of the flux through the zirconia membrane and are oxidized at the anode. Magnesium vapor evolves at the cathode and is condensed in a separate chamber (condenser). By performing in-situ reforming of gaseous hydrocarbons within the tubular zirconia anode one can minimize the electrical power required for the electrolysis and generate the required hydrogen needed to convert the magnesium vapors in the condenser back to magnesium hydride.
Atomically Resolved STM Images of CVD Grown Carbon Nanotubes
Authors: Chiang Daniel , Lei Philip Zifeng , Dong Lifeng , Jiao Jun 
Published: April 2011

ABSTRACTAtomically resolved images of single-wall carbon nanotubes (CNT) grown in a chemical vapor deposition (CVD) chamber were obtained with the scanning tunneling microscope (STM) under ambient conditions. We found that the average diametersdof the CVD-grown CNTs appear to fall into a bimodal distribution of 1.0 and 0.6 nm, and the chiral angle Ø was observed to be close to zero degree. The summation of the lattice indices(n+m)was determined to be 14 and 9 ford=1.0nm andd=0.6nm, respectively. The most possible lattice index pairs(n, m)with a chiral angle close to zero degree are(7, 7)and(5, 4), which indicates that the larger nanotubes are metallic and the smaller nanotubes are semi-conductive.
A Scanning Tunneling Microscopy Study: Si/SiO2 Interface Roughness Induced by Chemical Etching
Authors: Yu Jixin , Liu Lequn , Lyding Joseph W. 
Published: April 2011

ABSTRACTThe Si/SiO2 interface roughness has received tremendous interest due to its relation to channel mobility degradation and dielectric reliability. We have used ultra-high vacuum scanning tunneling microscopy to directly examine the Si/SiO2 interface and study the roughening effect caused by chemical etching. The rms-roughness extracted quantitatively from the STM topography was found to be doubled from 0.111nm to 0.232nm by the normal NH4OH/H2O2 treatment, and further increased to 0.285nm for additional etching steps. It was also found that there were no regular single steps on the SiO2/Si(100) interface.
Optical near-field enhancement around lithographic metallic nanostructures using an azo-dye polymer: direct observation and realization of sub-wavelength complex structures
Authors: Hubert Christophe , Rumyantseva Anna , Lérondel Gilles , Grand Johan , Kostcheev Sergeï , Billot Laurent , Vial Alexandre , Bachelot Renaud , Royer Pascal , Chang Gilbert , Gray Stephen K. , Wiederrecht Gary P. , Schatz George C. 
Published: April 2011

ABSTRACTWe report on the direct observation of optical near-field enhancement around metallic nanoparticles. We used an easy to set up approach which consists in irradiating a photosensitive azo-dye polymer film spin-coated on metallic nanostructures. Photoinduced topographical modifications of the polymer film surface are characterized after irradiation by atomic force microscopy (AFM). Comparisons between AFM images and numerical simulations show that these photo-induced topography agrees with the near-field intensity distribution around the nano-structures. The possibility of generating complex structures is demonstrated.
The Features of Investigations and Observations of Nanoamorphous Metals and Nanocrystalline Oxides on Electron Microscope
Authors: Malkhasyan R. , Karakhanyan R. , Nazaryan M. , Khachatryan A. , Markosyan A. 
Published: April 2011

ABSTRACTThe present paper discusses two different active influences of an electron beam on a nanosize sample.The first observed influence is the formation of nanoparticle agglomerates due to the beam charge. This can be likened to the formation of fine sand and it enables the determination of grain magnitude of the given nanomaterial. This also enables to get a clear picture of the sample, which is latent at first due to the coating of nanoparticles and their agglomerates. For example, removal of nanopowder coatings has enabled for the first time to find self - assembling systems in a shape of double chain spatial helixes from inorganic particles (as DNA).The second type of influence is related to transformations, which distort the sample. Transformation of amorphous particles of metal into a crystalline state by means of local heating is the one of most importance.Growth of thread-shaped hollow and solid nanowhiskers from nanoparticles and their further disintegration to a great number of small crystals under influence of electron beam in the chamber of electron microscope was observed. Therefore it can be confirmed that it is necessary to use an electron microscope with special precautionary measures, when working with nanoamorphous metals.
Stress relaxation and medium-range order in diamond-like amorphous carbon films
Authors: Chen Xidong , Sullivan John , Friedmann Tom , Miller Dean 
Published: April 2011

ABSTRACTIn this paper, we have studied the relationship between medium-range order structures in and stress relaxation in amorphous diamond-like carbon films with fluctuation microscopy. Our preliminary results show strong correlation between stress relaxation and medium-range order. Our previous results showed that annealing films that had been through stress relaxation procedures caused great increase of medium-ranger order. In this paper, we have found that the increase of medium-range order in films that have been annealed before going through stress relaxation through removal of substrates is less pronounced than that of films that have been annealed after removal of substrates. We will discuss interpretations and implications of these results.
Structure and Dynamics of Water Adsorbed in Carbon Nanotubes: A Joint Neutron-Scattering and Molecular-Dynamics Study
Authors: de Souza Nicolas R. , Kolesnikov Alexander I. , Loong Chun-Keung , Moravsky Alexander P. , Loutfy Raouf O. , Burnham Christian J. 
Published: April 2011

ABSTRACTThe advent of nanocarbons, from single- and multiple-walled nanotubes to nanohorns, avails model studies of confined molecules on the nanoscale. Water encapsulated inside the quasi-one-dimensional channels of these materials is expected to exhibit anomalous behavior due to the unique geometry of nanotubes and the weak interaction between the water molecules and the carbon atoms. We have employed neutron small-to-wide angle diffraction, quasielastic and inelastic scattering in conjunction with molecular-dynamics simulations to characterize the structures and dynamics of water adsorbed in open-ended single- and double-walled nanotubes over a wide range of spatial and temporal scales. We find that a square-ice sheet wrapped next to the inner nanotube wall and a water chain in the interior are the key structural elements of nanotube-confined water/ice. This configuration results in a hydrogen-bond connectivity that markedly differs from that in bulk water. This significantly softened hydrogen-bond network manifests in strong energy shifts of the observed and simulated inter- and intra-molecular vibrations. The very large mean-square displacement of hydrogen atoms observed experimentally and the strong anharmonicity inferred from simulations explain the fluid-like behavior at temperatures far below the freezing point of normal water.
X-ray scattering: a wonderful tool to probe lattice strains in materials with small dimensions
Authors: Thomas Olivier , Loubens Audrey , Gergaud Patrice 
Published: April 2011

ABSTRACTX-ray diffraction was recognized from the early days as highly sensitive to atomic displacements. Indeed structural crystallography has been very successful in locating with great precision the position of atoms within an individual unit cell. In disordered systems it is the average structure and fluctuations about it that may be determined. In the field of mechanics diffraction may thus be used to evaluate elastic displacement fields. In this short overview we give examples from recent work where x-ray diffraction has been used to investigate average strains in lines, films or multilayers. In small objects the proximity of surfaces or interfaces may create very inhomogeneous displacement fields. X-ray scattering is again one of the best methods to determine such distributions. The need to characterize displacement fields in nanostructures together with the advent of third generation synchrotron radiation sources has generated new and powerful methods (anomalous diffraction, coherent diffraction, microdiffraction, …). We review some of the recent and promising results in the field of strain measurements in small dimensions via X-ray diffraction.
Single-state electronic structure measurements using time-resolved x-ray laser induced photoelectron spectroscopy
Authors: Nelson A. J. , Dunn J. , van Buuren T. , Hunter J. 
Published: April 2011

ABSTRACTWe demonstrate single-shot x-ray laser induced time-of-flight photoelectron spectroscopy on semiconductor and metal surfaces with picosecond time resolution. The LLNL COMET compact tabletop x-ray laser source provides the necessary high photon flux (>1012/pulse), monochromaticity, picosecond pulse duration, and coherence for probing ultrafast changes in the chemical and electronic structure of these materials. Static valence band and shallow core-level photoemission spectra are presented for ambient temperature Ge(100) and polycrystalline Cu foils. Surface contamination was removed by UV ozone cleaning prior to analysis. In addition, the ultrafast nature of this technique lends itself to true single-state measurements of shocked and heated materials. Time-resolved electron time-of-flight photoemission results for ultra-thin Cu will be presented.
In situX-ray Reflectivity Study of Oxidation Kinetics in Iron and Stainless steel
Authors: Kim D. H. , Kim S. S. , Lee H. H. , Jang H. W. , Kim J. W. , Tang M. , Liang K. S. , Sinha S. K. , Noh D. Y. 
Published: April 2011

ABSTRACTIn situspecular x-ray reflectivity was applied to study the growth kinetics of passive oxide films on iron and stainless steel substrates in pH 8.4 borate buffer solution. Under electrical potential from 0 to 800 mV, the growth rate of oxide films decreases exponentially in thickness following the direct logarithmic growth law predicted in the point defect model. The electric field in the oxide on iron is independent of the applied potentials consistent with the point defect model. In stainless steel, however, the electric field depends strongly on the applied potential indicating that the oxide properties change as the applied potential varies.
Fluctuation X-ray Microscopy for Measuring Medium-Range Order
Authors: Fan Lixin , McNulty Ian , Paterson David , Treacy Michael M.J. , Murray Gibson J. 
Published: April 2011

ABSTRACTMany x-ray techniques exist to probe long- and short-range order in matter, in real space by imaging and in reciprocal space by diffraction and scattering. However, measuring mediumrange order (MRO) in disordered materials is a long-standing problem. Based on fluctuation electron microscopy, which was applied successfully to the understanding of MRO in amorphous materials, we have developed fluctuation x-ray microscopy (FXM). This novel approach offers quantitative insight into medium-range correlations in materials at nanometer and larger length scales. It examines spatially resolved fluctuations in the intensity of a series of x-ray speckle patterns. The speckle variance depends on higher order correlations that are more sensitive to MRO. Systematically measuring the speckle variance as function of the momentum transfer and x-ray illumination size produces a fluctuation map that contains information about the degree of MRO and the correlation length. This approach can be used for the exploration of MRO and subtle spatial structural changes in a wide range of disordered materials from soft condensed matter to nanowire arrays, semiconductor quantum dot arrays and magnetic materials. It will also help us to understand the mechanisms of order-disorder transitions and may lead to control of ordering, which is important in developing ordered structures tailored for particular applications. A theory for FXM and preliminary experimental results from polystyrene latex spheres are discussed in this paper.
2D and 3D X-Ray Structural Microscopy Using Submicron-Resolution Laue Microdiffraction
Authors: Budai John D. , Yang Wenge , Larson Bennett C. , Tischler Jonathan Z. , Liu Wenjun , Ice Gene E. 
Published: April 2011

ABSTRACTWe have developed a scanning, polychromatic x-ray microscopy technique with submicron spatial resolution at the Advanced Photon Source. In this technique, white undulator radiation is focused to submicron diameter using elliptical mirrors. Laue diffraction patterns scattered from the sample are collected with an area detector and then analyzed to obtain the local crystal structure, lattice orientation, and strain tensor. These new microdiffraction capabilities have enabled both 2D and 3D structural studies of materials on mesoscopic length-scales of tenths-to-hundreds of microns. For thin samples such as deposited films, 2D structural maps are obtained by step-scanning the area of interest. For example, 2D x-ray microscopy has been applied in studies of the epitaxial growth of oxide films. For bulk samples, a 3D differential-aperture x-ray microscopy technique has been developed that yields the full diffraction information from each submicron volume element. The capabilities of 3D x-ray microscopy are demonstrated here with measurements of grain orientations and grain boundary motion in polycrystalline aluminum during 3D thermal grain growth. X-ray microscopy provides the needed, direct link between the experimentally measured 3D microstructural evolution and the results of theory and modeling of materials processes on mesoscopic length scales.