bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Surface Plasmon Resonance on the Photoluminescence from Si Quantum Dot Structures for Third Generation Solar Cell Applications
Authors: Pillai Supriya , Hohn Joel J. , Johnson Craig M. , Conibeer Gavin J. 
Published: November 2012

ABSTRACTLow dimensional structures like quantum dots (QDs) offers the the ability to tune the absorption properties of standard semiconductor materials. However, QDs are relatively weak light absorbers and hence may benefit significantly from coupling with plasmonic modes in nearby metal structures. In the case of a Si QD absorber layer for photovoltaic applications, enhanced absorption would lead to improved power conversion efficiency. Silver metal nanoparticles (MNPs) were deposited on Si QD structures using the self-assembly method of evaporation and annealing. Room temperature photoluminescence (PL) measurements were used to study the surface plasmon (SP) enhanced emission from the samples. The results were compared to conventional metal back reflectors. Enhanced surface plasmon coupled emission (SPCE) from Si QDs in the vicinity of silver metal nanoparticles (MNPs) is observed with a good correlation between the enhancement and the resonance excitation. Quenching was observed from the same emitter layers placed in close proximity to thin flat silver reflector layers, indicating the importance of the spacer layer between a metal layer and the quantum dots in optimising enhancement. The results have implications for the design of SP-enhanced QD solar cells.
Reduced Reflection in polycrystalline silicon thin films through ion implantation induced surface textures and deposition of silver nanostructures
Authors: Akhter Perveen , Kadakia Nirag , Malladi Girish , Huang Mengbing 
Published: November 2012

ABSTRACTThis work investigates a novel method to enhance light trapping within polycrystalline silicon (poly-Si) thin films for photovoltaic applications. The method combines the use of hydrogen ion implantation for creation of surface textures in poly-Si thin films and the deposition of silver nanostructures on the textured surface. Poly-Si thin films were prepared by solid phase crystallization of amorphous silicon (a-Si) layer deposited on a SiO2/Si substrate. The a-Si was annealed at various temperatures 600 -1050 °C for 48 hours to grow grains of different size in p-Si, as confirmed by x-ray diffraction (XRD) measurements. These samples were then implanted with 20-keV hydrogen ions to a dose of 1017/cm2, and some with an additional implant with 90-keV argon ions to a dose 5×1015 /cm2. Following implantation, these samples were annealed in an Ar ambient at different temperatures. Surface blistering effects were observed using an optical microscope. Optical specular reflection measurements in the spectral range 400-1100 nm indicated that the reflectance of the samples with higher blistering had decreased remarkably from 40% to 10%. Lastly, the poly-Si samples with various textures were deposited with silver thin film followed by annealing in nitrogen ambient for forming Ag nanostructures on textured poly-Si surfaces. Scanning Electron Microscope (SEM) was used to image the surface structures. The formation of Ag nanoparticles on the poly-Si surface, with textures created by implantation followed by low-temperature annealing (e.g., 400 °C), can significantly reduce light reflection as opposed to the case with Ag nanoparticles formed on an un-textured, poly-Si surface.
Ablation Free Dicing of 4H-SiC Wafers with Feed Rates up to 200 mm/s by Using Thermal Laser Separation
Authors: Lewke Dirk , Koitzsch Matthias , Schellenberger Martin , Pfitzner Lothar , Ryssel Heiner , Zühlke Hans-Ulrich 
Published: November 2012

ABSTRACTThis paper presents Thermal Laser Separation (TLS) as a novel dicing technology for silicon carbide (SiC) wafers. Results of this work will play an important role in improving the SiC dicing process regarding throughput and edge quality. TLS process parameters were developed for separating 4H-SiC wafers. Separated SiC dies were analyzed and compared with results produced with current state of the art blade dicing technology. For the first time, fully processed 100 mm 4H-SiC wafers with a thickness of 450 μm, including epi-layer and back side metal layers, could be separated with feed rates up to 200 mm/s. Besides the vastly improved dicing speed, the TLS separation process results in two important features of the separated SiC devices: First, edges are free of chipping and therefore of higher quality than the edges produced by blade dicing. Second, the TLS process is kerf free, which allows for reducing the necessary dicing street width and hence increasing the number of devices per wafer.
Oxygen Reduction Reaction Electrocatalytic Activity of SAD-Pt/GLAD-Cr Nanorods
Authors: Khudhayer Wisam J. , Kariuki Nancy , Myers Deborah J. , Shaikh Ali U. , Karabacak Tansel 
Published: November 2012

ABSTRACTNanorod arrays of chromium (Cr) were grown on glassy carbon (GC) electrodes by a dc magnetron sputtering glancing angle deposition (GLAD) technique. The Cr nanorods were used as low-cost, high surface area, metallic supports for a conformal layer of Pt thin film catalyst, as a potential low-loading electrocatalyst for the oxygen reduction reaction (ORR) in polymer electrolyte membrane (PEM) fuel cells. A dc magnetron sputtering small angle deposition (SAD) technique was utilized for a conformal coating of Pt on Cr nanorods. The ORR activity of SAD-Pt/GLAD-Cr electrodes was investigated using cyclic voltammetry (CV) and rotating-disk electrode (RDE) techniques in a 0.1 M HClO4 solution at room temperature. A reference sample consisting of GLAD Cr nanorods coated with a Pt thin film deposited at normal incidence (θ = 0o) was prepared and compared with the SAD-Pt/GLAD-Cr nanorods. Compared to GLAD Cr nanorods coated with Pt thin film at θ = 0o, the SAD-Pt/GLAD-Cr nanorod electrode exhibited higher ECSA and area-specific and mass-specific ORR activity. These results indicate that the growth of catalyst layer on the base-metal nanorods by the SAD technique provides a more conformal and possibly a nanostructured coating, significantly enhancing the catalyst utilization.
Simulation of Grazing-Incidence Synchrotron X-ray Topographic Images of Threading c+a Dislocations in 4H-SiC
Authors: Wu Fangzhen , Byrappa Shayan , Wang Huanhuan , Chen Yi , Raghothamachar Balaji , Dudley Michael , Sanchez Edward K. , Chung Gil , Hansen Darren , Mueller Stephan G. , Loboda Mark J. 
Published: November 2012

ABSTRACTSynchrotron X-ray topography (SXRT) of various geometries has been successfully utilized to image c+a dislocations in 4H-SiC crystals. Although molten potassium hydroxide(KOH) can be used to reveal the location of such dislocations, it is not possible to determine their senses or their Burgers vector magnitude. A simple, non-destructive method has been proposed to determine the Burgers vector of these c+a dislocations called the ray tracing simulation, which has been successfully implemented previously in revealing the dislocation sense and magnitude of micropipes, closed-core threading screw dislocations (TSDs) and threading edge dislocations (TEDs) in 4H-SiC. In this paper, grazing incidence topography is performed using the monochromatic beam for the horizontally cut wafers to record pyramidal reflections of 11-28 type. Ray tracing simulation has been successfully implemented to correlate the simulated images with experimental images which are discussed in the paper.
Reduction of Triangular Defects on 100mm 4° off-axis 4H-SiC using a Chloride Based CVD process
Authors: Das Hrishikesh , Sunkari Swapna , Oldham Timothy , Rodgers Josh , Casady Janna 
Published: November 2012

ABSTRACTHomoepitaxial layers were grown with very low surface roughness on 4", 4˚ off-axis substrates, but a new kind of large obtuse angled triangular defect that spanned 1000-2000 μm was observed. Process changes resulted in reduction of the size and concentration of these triangular defects from 3.5cm-2 to 0.13cm-2. Both large and small triangular defects were found to have a similar core structure. No degradation in the epitaxial morphology or quality was seen due to the process change. JBS diodes fabricated on wafers with large triangular defects had much higher leakage when the triangular defects were present in the active area of the diodes.
A New Family of Light Emitting Si Nanoparticles
Authors: Shirahata Naoto 
Published: November 2012

ABSTRACTColor-tuning of UV luminescent silicon nanocrystals (Si NCs) was successfully achieved by precise size control of non-oxidized NCs. The alkoxy-capped Si NCs was synthesized via sodium biphenylide reduction of SiCl4 encapsulated with inverse micelles, and subsequent alkoxylation of surface Si-Cl bonds. Due to the high molecular packing density of alkoxy monolayers, outermost surface of the NCs was completely protected from oxidation even under ambient conditions. Interestingly, the optical absorption and emission spectra were blueshifted with reduction of non-oxidized NC size, and we found strong light emission in the UV range when the NCs were smaller than 2.5 nm. More than 20% of PL quantum efficiencies (QYs) were estimated from those UV luminescent NCs. Monodispersed NCs without oxide can provided narrow PL spectra with 35-40 nm of line-widths, while the presence of oxidized surface region of NCs led to the broad PL spectra. In addition, the redshift of PL spectra were observed from the partially-oxidized NCs which were formed due to the lower surface molecular coverage, suggesting the significant difference in optical transition of photogenerated carriers between the non-oxidized and the partially-oxidized NCs. This can be well-illustrated by comparing decay profiles of the carriers for each sample through the time-resolved PL spectroscopic observation.
Improved conductivity of ZnO thin films by exposure to an atmospheric hydrogen plasma
Authors: Illiberi A. , Kniknie B. , van Deelen J. , Steijvers H.L.A.H. , Habets D. , Simons P.J.P.M. , Janssen A.C. , Beckers E.H.A. 
Published: November 2012

ABSTRACTAluminum-doped zinc oxide (ZnOx:Al) films have been deposited on a moving glass substrate by a high throughput metalorganic chemical vapor deposition process at atmospheric pressure. Thin (< 250 nm) ZnOx:Al films have a poor crystalline quality, due to a small grain size and the presence of different crystallographic orientations. The crystalline quality improves with increasing film thickness (from 50 nm to 1000 nm), resulting in a lower value of resistivity (from 100 Ohm cm to 1·10-3 Ohm cm, respectively). We have investigated the variation in the films’ conductivity and transparency induced by a post-deposition exposure to a He/H2 atmospheric plasma. The resistivity of thin (< 250 nm) films is found to decreased sharply from 100 Ohm cm to about 4·10-3 Ohm cm by a short (∼ seconds) plasma exposure, while the resistivity of thicker films remains unaffected.
All Hot Wire CVD Organic/Inorganic Hybrid Barrier Layers for Thin Film Encapsulation
Authors: Spee Diederick A. , Schipper Merijn R. , van der Werf Karine H.M. , Rath Jatindra K. , Schropp Ruud E.I. 
Published: November 2012

ABSTRACTA water vapor barrier layer is presented that is deposited entirely at temperatures below ∼100oC. Our method, using hot wire chemical vapor deposition (HWCVD), is effective in reducing the issue of pinholes in single layers of silicon nitride (SiNx) made at such low substrate temperatures. We succeeded in depositing an all hot-wire simple three-layer structure consisting of two low-temperature SiNx layers with a polymer layer in between, exhibiting a water vapor transmission rate (WVTR) as low as 5*10-6 g/m2/day, determined at a temperature of 60°C and a relative humidity of 90%. This WVTR is low enough for organic and polymer devices. In a second experiment the robustness of the barrier layer is shown with respect to environmental dust.
Rare Earth Nanocomposites Based on Chitosan Platforms for Biological Applications
Authors: Yasmin Zannatul , Zhang Maogen , Gorski Waldemar , Maswadi Saher , Glickman Randolph , Nash Kelly L. 
Published: November 2012

ABSTRACTChitosan (CHIT), a natural biopolymer, has established its applicability in numerous studies including, tissue scaffolds, topical antimicrobial agents, glucose biosensors and drug delivery platforms. Among these applications, biosensors utilizing CHIT has been championed due its excellent film-forming ability, biocompatibility, good adhesion, non-toxicity, and susceptibility to chemical modification due to the presence of plentiful amino groups and hydroxyl groups. The challenge in development of many biosensing materials is that they should offer robust and tunable characteristics (fluorescence, magnetic, thermal, etc.) while remaining biocompatible. In this work, a facile method was developed to synthesize biocompatible hetero-nanoparticles which inherently display multifunctionality based on a few interchangeable components. As an example, we present a system composed of rare earth metal oxide (REMO) nanoparticles, Er doped Y2O3, with the attachment of gold nanostructures using CHIT. The resulting REMO@CHIT@Au0 hybrid nanoparticles are capable of displaying tunable optical properties due to the surface plasmon resonance of the gold nanoparticles useful to photoacoustic applications. An overview of the nanostructure components are given followed by morphological and spectroscopic analyses. The results of the characterizations are the focus of our future work towards the applicability of these systems to biological sensing, detection and contrast agents.
Raster Scanning Laser and UV Processing of nanocrystalline TiO2 Films for Sintering in Dye Solar Cells: Device Performance, Throughput and Embodied Energy
Authors: Mincuzzi Girolamo , Zardetto Valerio , Vesce Luigi , Schulz-Ruhtenberg Malte , Gillner Arnold , Reale Andrea , Di Carlo Aldo , Brown Thomas M. 
Published: November 2012

ABSTRACTA crucial step in Dye Solar Cell (DSC) fabrication is the sintering of the TiO2 layer which needs to guarantee good electromechanical bonding between nanoparticles whilst maintaining sufficiently large porosity to yield performing devices. The standard procedure for TiO2 sintering requires firing in an oven at ∼ 500°C. An alternative procedure consists in utilizing laser scanning processing which has the advantageous potential of being noncontact, local, low cost, rapid, selective, automated and scalable. We analyzed and optimised a laser process for the sintering of the TiO2 layers in dye solar cells analyzing temperature profiles, throughput and the embodied energy. The development of electronic and photovoltaic devices on plastic substrates is of considerable interest due to the advantages they bring in terms of flexibility and easy processing for lightweight, low-cost large-area applications. An alternative sintering procedure compatible with flexible substrates and large area processing consists in utilizing a UV lamp. We subjected TiO2 pastes deposited on conductive transparent substrates to UV irradiation. Fully plastic devices fabricated through this method showed efficiencies of 4%.
In situ spectroscopic characterization of some LaNi1-xCoxO3 perovskite catalysts active for CH4 reforming reactions
Authors: Pereñiguez Rosa , Gonzalez-Delacruz Victor M. , Ternero Fatima , Holgado Juan P. , Caballero Alfonso 
Published: November 2012

ABSTRACTLanthana-supported Ni and Co catalysts were investigated by “operando” techniques (XAS and APPES) for methane reforming reactions. The samples were prepared by the “solid phase crystallization” method (spc), where the precursors La(Ni1-xCox)O3 contains homogeneously distributed metals (Ni, Co) in the crystal structure (perovskite), which, on further reduction, result in the formation of catalytic system Ni1-xCox/La2O3. The monometallic samples (NiLaO3, CoLaO3) have been compared with a bimetallic system of an intermediate composition Ni0.5Co0.5LaO3. This “operando” study has allowed us to obtain important conclusions about the bimetallic particles and the metal-support interactions. The data revealed the formation of bimetallic particles (NiCo); on these ones, the Ni avoids the Co oxidation during the reaction. However, this protection does not induce an improvement in the activity, which presents an intermediate behaviour between Ni/La2O3 and Co/La2O3. These bimetallic particles form a pseudo-alloy with the surface enriched in cobalt (under reduced conditions), resulting nearly in a core-shell structure (Ni@Co).
Hydrogen-Vacancy Effects in Pu-2 at. % Ga Alloys
Authors: Schwartz Daniel S. , Richmond Scott , Smith Alice I. , Costello Alison , Taylor Christopher D. 
Published: November 2012

ABSTRACTPlutonium and Pu-Ga alloys have been observed to have anomalous hydrogen solubility behavior, including a significant concentration dependence of hydrogen diffusivity in the dilute regime, a sharp drop off in the hydrogen solubility constant in the dilute regime, and a near complete absence of change in the Sieverts’ constant as the alloys are heated across phase transformation boundaries. We are investigating the possibility that a vacancy mechanism is responsible for this behavior. X-ray diffraction measurements show a 0.14% lattice contraction in Pu-2 at. % Ga alloys when they are charged with ~2 at. % hydrogen. The lattice re-expands when the hydrogen is removed. Density functional calculations show that increasing the number of hydrogen atoms associated with a vacant lattice site in Pu lowers the energy of the hydrogen-vacancy complex. These observations support the idea that vacancies are stabilized by hydrogen in the Pu lattice well beyond their thermal equilibrium concentration and could be responsible for the anomalous hydrogen response of Pu.
In-Situ Raman Spectroscopy Studies of Room-Temperature and Hydrothermal Reactions
Authors: McGrail Brendan T. , Jouffret Laurent J. , Villa Eric M. , Burns Peter C. 
Published: November 2012

ABSTRACTBy contracting with the Parr Instrument Company and Bruker Optical Systems, we have developed a system for continuous monitoring of hydrothermal and room temperature reactions by Raman spectroscopy. Using the uranyl peroxide cage cluster {[UO2(O2)(OH)]16[UO2(OM)2]4}24- (denoted {U20R}) and a coordination polymer made from uranyl ions and 4,4’-biphenyldicarboxylate as model systems, we demonstrate the spectroscopically observable changes associated with reaction progress and crystallization.
Carbon Effect on Thermal Ageing Simulations in Ferrite Steels
Authors: Nouchy Fabio , Claisse Antoine , Olsson Pär 
Published: November 2012

ABSTRACTTwo major causes of hardening and subsequent embrittlement in ferrite steels are the spinodal decomposition of the binary Fe-Cr solid solution and the carbide formation due to the presence of carbon as foreign interstitial atoms. In the present work, simulations of the microstructure evolution due to thermal ageing are performed by means of a kinetic Monte Carlo code and using a state-of-the-art interatomic potential based on density functional theory (DFT) predictions and experimental data. The main issues concern the possibility to perform thermal ageing simulations in an acceptable computational time frame and to reproduce a realistic behavior of carbon kinetics and carbide formation. The simulations on the binary system show the microstructural evolution during thermal ageing and allowed to find an exponential trend related to the acceleration as a function of temperature. With the insertion of carbon in the model, the chromium precipitation tends to accelerate. The carbon clustering, analyzed separately, is faster with higher C concentrations and in lattices with segregated chromium.
Surface analytical study of uranium exposed to low pressures of hydrogen at ∼ 80°C
Authors: Harker Robert M. , Chohollo Afiya H. 
Published: November 2012

ABSTRACTIdentical samples of uranium coupons were prepared and each exposed to hydrogen for different times (where this time is significantly less than a classically understood ‘induction time’). Samples were prepared from rolled depleted uranium stock: as-received oxide was removed on all surfaces and two faces (~12x12 mm) were polished to a sub-micron standard. Samples were individually taken through a Vacuum Thermal Pre-Treatment cycle from room temperature to 200°C to the reaction temperature (80°C) over 40 hours and subsequently exposed to 10 mbar O2 for 24 hours. After O2 was removed, the samples were exposed to hydrogen for pre-determined times of up to 48 minutes. Examination of the samples by Scanning Electron Microscopy (SEM) has, as expected, identified small features protruding from the surface believed to have been caused by sub-surface precipitation of UH3. In general these features are circular and isolated from each other, have a diameter of less than 3μm and appear as either ‘flat-topped’ or ‘domed’ morphology. In addition, longer time exposure samples show a predominance of ‘area attack’ where coalesced sub-surface precipitation appears to be confined to particular metal grains. X-Ray Diffraction (XRD) data show an increase in the quantity of UH3 with time.
Pre-eminence of the Indirect Channel in the Resonant Inverse Photoelectron Spectroscopy of Cerium Oxide
Authors: Tobin J. G. , Yu S.-W. , Chung B.W. , Waddill G.D. 
Published: November 2012

ABSTRACTA strong resonance in the inverse photoelectron spectroscopy (IPES) of cerium oxide was reported recently. Here, it is shown that dominance of the indirect channel of the resonant inverse photoelectron spectroscopy (RIPES) is so complete that the photon energy dependence can be explained in terms of emission associated with a single photon energy.
The High-Temperature Phonon Anomalies of α-uranium.
Authors: Riseborough Peter S. 
Published: November 2012

ABSTRACTThere is a growing body of evidence that a number of mixed-valent and heavy-fermion materials show renormalized hybridization gaps either at the Fermi-energy or close to the Fermi-energy. In the former case, a heavy-fermion semiconducting state occurs and in the later case, the system remains metallic at low temperatures. The magnitudes of the hy-bridization gaps are observed to decrease with increasing temperature. The existence of a low-energy electronic energy scale creates a possibility that the Born-Oppenheimer ap-proximation may fail and that there may be a resonant coupling between the phonons and the electronic excitations. Here we argue that such a mechanism may be the cause of the phonon anomalies observed in neutron scattering experiments on the high-temperature phase of alpha-uranium.
An electron microscopy study on the Zr oxides formed during the transition to breakaway oxidation
Authors: Park Dong Jun , Choi Byoung Kwon , Park Jeong Yong 
Published: November 2012

ABSTRACTIn order to characterize the microstructure of oxide layers formed on Zircaloy-4 tubes during the breakaway transition, oxidation tests in a flowing steam environment were performed at 1000°C with a different oxidation time. It was found that breakaway oxidation occurred after the oxidation time of 3000s, and zirconium dioxide layers existed in two mixed crystallographic forms of the tetragonal and monoclinic phase in all samples. The zirconium oxide layers showed enhanced crystallinity, increase in grain size, and fine pores at the grain boundary after breakaway oxidation. We found that the initiation of breakaway-oxidation instability originated from these microstructural changes.