bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Study of Bismuth Induced Levels in CZT Using TEES/TSC
Authors: Soundararajan Raji , Jones Kelly A. , Swain Santosh , Lynn Kelvin 
Published: December 2009

AbstractConsidering the desirable effects of doping CdTe with heavy elements like Bi, we have grown a Cadmium Zinc Telluride (Zn=10%) ingot with Bi (doping levels ∼1014 to 1015 at/cm3) as the heavy element dopant for use as a room temperature radiation detector, using the Bridgman method. In-spite of a high bulk resitivity (∼1010?cm), and the ability to hold high electric field (>2000 V/cm), these lightly doped crystals had a poor spectral resolution for the Co-57 photo peaks and ??e measurements were so low that these measurement were not reliable. Thermo electric effect spectroscopy (TEES) and thermally stimulated current (TSC) experiments on samples C and F (single crystals close to the tip and the heel of the ingot respectively) have revealed various defect levels in the band gap. Among these defect levels, we have identified and characterized two Bi-related deep levels namely a deep donor level L5 (thermal ionization energy: 0.33[5] to 0.39[5] eV and trap cross-section: 7.1[5] × 10-17 to 2.54 [5] × 10-16 cm2), and a deep acceptor level L8 (thermal ionization energy of 0.82 [5] eV and trap cross-section of 2.59 [5] × 10-12 cm2). These levels were responsible for the observed high electrical resistivity (∼1010 ?*cm) in the CdZnTe samples. From a comparison to studies on Bi doped CdTe samples, level L8 was tentatively associated with the (0/-) transition of (BiCd- - OTe) complex, however is still under study. Since these defect levels also act as trapping centers for charge carriers, in spite of the semi-insulating behavior the samples are poor radiation detectors.
Quantifying the Flow of Exergy and Carbon through the Natural and Human Systems
Authors: Sassoon Richard E , Hermann Weston A , Hsiao I-Chun , Milkovic Ljuba , Simon Aaron J , Benson Sally M 
Published: December 2009

AbstractExergy is the useful portion of energy that allows us to do work and perform energy services. While energy is conserved, exergy is not; some exergy is destroyed whenever energy undergoes a conversion. We gather exergy from distinct, energy-carrying resources that are found in the natural world. These resources are converted into energy carriers that are convenient to use in our factories, vehicles, and buildings for heating, lighting and mechanical services. While there is no shortage of exergy resources, there are considerable environmental, economic, and other constraints associated with the manner and magnitude of their use. This article describes an approach to examining and presenting data on energy use at a global scale. It provides insights into the efficiencies and carbon emissions of many energy pathways, and can provide a basis for an examination of future energy options. In this study, we trace the flow of exergy and carbon through the natural and human systems, revealing the major destructions of exergy, the exergy efficiency of engineered energy processes, and the processes with the highest associated atmospheric carbon emissions. These data have been collected in a relational database available online at http://gcep.stanford.edu/research/exergy/data.html and are presented here in a set of exergy and carbon flow charts.
High-temperature Oxidation of Metallic Alloys for SOFC Interconnects: Stress and Morphological Developments during Oxide Scale Growth
Authors: Saillard Audric , Cherkaoui Mohammed , Capolungo Laurent , Busso Esteban P. 
Published: December 2009

AbstractThis work investigates the critical stress and morphological evolutions which occur during the high-temperature oxidation of metallic alloys for SOFC interconnects. Two mechanisms of stress generation are considered related to (1) the local volume change associated with the direct oxidation of the metal and to (2) a secondary oxidation process within grain boundaries. A specific formulation is developed to include the influence of the stress state at the metal-oxide interface on the local oxidation kinetics. The oxidation of a chromia-forming SOFC interconnect metallic alloy is simulated and stress and morphological evolutions are investigated.
Localized56Fe+ion implantation of TiO2using anodic porous alumina
Authors: Jensen Jens , Sanz Ruy , Jaafar Mirian , Hernández-Vélez Manuel , Asenjo Agustina , Hallen Anders , Vázquez Manuel 
Published: December 2009

AbstractWe present result following localized ion implantation of rutile titanium dioxide (TiO2) using anodic porous alumina as a mask. The implantation were performed with 100 keV56Fe+ions using a fluence of 1.3·1016ions/cm2. The surface modifications where studied by means of SEM, AFM/MFM and XRD. A well-defined hexagonal pattern of modified material in the near surface structure is observed. Local examination of the implanted areas revealed no clear magnetic signal. However, a variation in mechanical and electrostatic behavior between implanted and non-implanted zones is inferred from the variation in AFM signals.
Thermoelectric Generators of Sequentially Deposited Si/Si+Ge Nano-layered Superlattices
Authors: Smith Cydale , Pugh Marcus , Martin Hervie , Hill Rufus Durel , James Brittany , Budak Satilmis , Heidary K , Muntele Claudiu , Ila Daryush 
Published: December 2009

AbstractEffective thermoelectric materials have a low thermal conductivity and a high electrical conductivity. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2sσ/ KTC, σ is the electrical conductivity T/KTC, where S is the Seebeck coefficient, T is the absolute temperature and KTC is the thermal conductivity. In this study we have prepared the thermoelectric generator device of Si/Si+Ge multi-layer superlattice films using the ion beam assisted deposition (IBAD). To determine the stoichiometry of the elements of Si and Ge in the grown multilayer films and the thickness of the grown multi-layer films Rutherford Backscattering Spectrometry (RBS) and RUMP simulation software package were used. The 5 MeV Si ion bombardments were performed to make quantum clusters in the multi-layer superlattice thin films to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity.Keywords: Ion bombardment, thermoelectric properties, multi-nanolayers, Figure of merit.
Fabrication of Micro-Fluid-Channel Structures by Focused Ion Beam Techniques
Authors: Yanagisawa Junichi , Kobayashi Hiroaki , Koreyama Kakunen , Akasaka Yoichi 
Published: December 2009

AbstractOne of the new applications of focused Ga ion beam (Ga FIB) techniques to fabricate micro fluid channels on plate glass was demonstrated. After discussing features of the FIB etched patterns, narrow channel or Y-shaped channels were fabricated by FIB etching on a patterned plate glass which was prepared by photo-lithography and wet etching processes. Micro fluid devices were then constructed using polydimethylsiloxane (PDMS) sheet and silicone rubber tubes and the water (or ink) flow in the devices was observed under a microscope using a syringe pump. Although no discussion based on fluid mechanics has done at present, the present results indicate a possibility of applying FIB techniques to fabricate micro fluid devices which can be used in bio- and/or chemical-related fields.
Swift Heavy Ion Irradiation Induced Effects in Si/SiOx Multi-Layered Films and Nanostructures
Authors: Gerlach Jurgen W , Patzig C. , Assmann W. , Bergmaier A. , Höche Th. , Zajadacz J. , Fechner R. , Rauschenbach Bernd 
Published: December 2009

AbstractAmorphous Si/SiOx multi-layered films and nanostructures were deposited on Si substrates by the glancing angle deposition technique using Ar ion beam sputtering of a Si sputter target in an intermittent oxygen atmosphere at room temperature. The chemical composition of the samples was characterized by time-of-flight secondary ion mass spectrometry, as well as - for quantifying these first results - by elastic recoil detection analysis using a 200 MeV Au ion beam. The latter method was found to lead to a significant alteration of the sample morphology, resulting in the formation of complex nanometric structures within the layer stacks. In order to investigate these swift heavy ion irradiation induced effects in more detail, a series of experiments was conducted to determine the dominating influences. For this purpose, specific glancing angle deposited multilayered films and nanostructures were irradiated to constant ion fluence with the same 200 MeV Au ion beam at different incidence angles. Scanning electron microscopy of the stacks before and after swift Au ion irradiation revealed considerable changes in film morphology and density as a function of the ion incidence angle, such as an increased porosity of the silicon layers, accompanied by a layer swelling. In contrast, the SiOx layers did not show such effects, but exhibited clearly visible swift heavy ion tracks. The observed effects became stronger with decreasing ion incidence angle.
Localized Gallium Doping and Cryogenic Deep Reactive Ion etching in Fabrication of Silicon Nanostructures
Authors: Chekurov Nikolai , Grigoras Kestutis , Peltonen Antti , Franssila Sami , Tittonen Ilkka 
Published: December 2009

AbstractWe present a novel fabrication method to create controlled 3-dimensional silicon nanostructures with the lateral dimensions that are less than 50 nm as a result of a rapid clean room compatible process. We also demonstrate periodic and nonperiodic lattices of nanopillars in predetermined positions with the minimum pitch of 100 nm. One of the uses of this process is to fabricate suspended silicon nanowhiskers.
Ion Implanted SiO2 Substrates for Nucleating Silicon Oxide Nanowire Growth
Authors: Johnson Jason L. , Choi Yongho , Ural Ant 
Published: December 2009

AbstractWe experimentally demonstrate a simple and efficient approach for silicon oxide nanowire growth by implanting Fe+ ions into thermally grown SiO2 layers on Si wafers and subsequently annealing in argon and hydrogen to nucleate silicon oxide nanowires. We study the effect of implantation dose and energy, growth temperature, and H2 gas flow on the SiOx nanowire growth. We find that sufficiently high implant dose, high growth temperature, and the presence of H2 gas flow are crucial parameters for silicon oxide nanowire growth. We also demonstrate the patterned growth of silicon oxide nanowires in localized areas by lithographic patterning and etching of the implanted SiO2 substrates before growth. This works opens up the possibility of growing silicon oxide nanowires directly from solid substrates, controlling the location of nanowires at the submicron scale, and integrating them into nonplanar three-dimensional nanoscale device structures.
Fabrication and Surface Modification of Porous Nano-Structured NiTi Orthopedic Scaffolds for Bone Implants
Authors: Wu Shuilin , Liu Xiangmei , Chu Paul K , Hu Tao , Yeung Kelvin Wai Kwok , Chung Jonathan C Y 
Published: December 2009

AbstractNear-equiatomic porous nickel-titanium shape memory alloys (NiTi SMAs) are becoming one of the most promising biomaterials in bone implants because of their unique advantages over currently used biomaterials. For example, they have good mechanical properties and lower Young�s modulus relative to dense NiTi, Ti, and Ti-based alloys. Porous NiTi SMAs are relatively easy to machine compared to porous ceramics such as hydroxyapatite and calcium phosphate that tend to exhibit brittle failure. The porous structure with interconnecting open pores can also allow tissue in-growth and favors bone osseointegration. In addition, porous NiTi alloys remain exhibiting good shape memory effect (SME) and superelasticity (SE) similar to dense NiTi alloys. To optimize porous NiTi SMAs in bone implant applications, the current research focuses on the fabrication methods and surface modification techniques in order to obtain adjustable bone-like structures with good mechanical properties, excellent superelasticity, as well as bioactive passivation on the entire exposed surface areas to block nickel ion leaching and enhance the surface biological activity. This invited paper describes progress in the fabrication of the porous materials and our recent work on surface nanorization of porous NiTi scaffolds in bone grafts applications.
Ion Implantation as Surface Treatment for Osseointegration of Musculoskeletal Implants: From the Lab to the Clinic
Authors: Braceras Iñigo , Alava Jose Iñaki , Muñoz Roberto , De Maeztu Miguel Angel 
Published: December 2009

AbstractA key process in a successful treatment of patients with a great variety of musculoskeletal implants requires a fast, reliable and consistent osseointegration. Among the parameters that affect this process, it is widely admitted that implant surface topography, surface energy and composition play an important role.Different surface modification techniques to improve osseointegration have been proposed and tested to date, but most focus on microscale features, and few control surface modifications at nanoscale. On the other hand, ion implantation modifies the outermost surface properties in relation to the nanotopography, chemical and physical characteristics at nanoscale. The meta-stable surface that results from the treatment, affects the adsorption of bio-molecules in the very first stages of the implant placement, and thus the signaling pathway that promotes the differentiation and apposition of osteoblast cells.This study aimed at assessing the performance, in terms of osseointegration levels and speed, of ion implanted titanium made implants. The study included several in vitro and in vivo tests. The latter, comprised different insertion periods and both experimental and commercial implants as comparative surfaces. The final stage of the study included clinical trials in human patients.In each and every case, bone integration improvement of tested materials/implants was achieved for the CO ion implanted samples. Furthermore, contact osteogenesis was observed in the ion implanted samples, unlike the Ti control samples, where only distance osteogenesis occurred, being this potentially one of the reasons for their faster healing and osseointegration process.Finally, the use of ion implantation as a surface modification tool that allows for evaluating the effects of nanotopography and composition changes independently is presented.
Nanoscale Surface Patterning of Silicon Using Local Swelling Induced by He Implantation through NSL-Masks
Authors: Fischer Frederic J.C. , Weinl Michael , Lindner Jöerg K N , Stritzker Bernd 
Published: December 2009

AbstractA novel technique to form periodically nanostructured Si surface morphologies based on nanosphere lithography (NSL) and He ion implantation induced swelling is studied in detail. It is shown that by implantation of keV He ions through the nanometric openings of NSL masks regular arrays of hillocks and rings can be created on silicon surfaces. The shape and size of these surface features can be easily controlled by adjusting the ion dose and energy as well as the mask size. Feature heights of more than 100 nm can be obtained, while feature distances are typically 1.15 or 2 (hillock or ring) nanosphere radii, which are chosen to be between 100 and 500 nm in this study. Atomic force and scanning electron microscopy measurements of the surface morphology are supplemented by cross-sectional transmission electron microscopy, revealing the inner structure of hillocks to consist of a central cavity surrounded by a hierarchical arrangement of smaller voids. The surface morphologies developed here have the potential to be useful for fixing and separating nano-objects on a silicon surface.
Ion Beam Synthesis of Ge Nanocrystals Embedded in SiO2 Matrix
Authors: N Srinivasa Rao , Pathak Anand , D Kabiraj , Khan S A , Panigrahi B K , Nair K G M , Avasthi D K 
Published: December 2009

AbstractHigh fluences of low energy Ge+ ions were implanted into Si matrix. We have also deposited Ge and SiO2 composite films by using the Atom beam sputtering (ABS). The as implanted/as-deposited films were irradiated by Swift Heavy Ions (SHI) with various energies and fluences. These pristine and irradiated samples were subsequently characterized by XRD and Raman to understand the crystallization behavior. Raman studies of the films indicate the formation of Ge crystallites as a result of SHI irradiation. Glancing angle X-ray diffraction results also confirm the presence of Ge crystallites in the irradiated samples. Moreover, the crystalline nature of Ge improves with an increase in fluence. Rutherford back scattering was used to quantify the concentration of Ge in SiO2 matrix and the film thickness. These detailed results have been discussed and compared with the ones available in literature. The basic mechanism for crystallization induced by SHI in these films will be presented.
Fabrication and Characterization of Thermoelectric Generators From SiO2/SiO2+Au Nano-layered Superlattices
Authors: Pugh Marcus , Hill Rufus Durel , James Brittany , Martin Hervie , Smith Cydale , Budak S. , Heidary Kaveh , Muntele Claudiu , Ila Daryush 
Published: December 2009

AbstractThe efficiency of the thermoelectric devices is limited by the properties of n- and p-type semiconductors. Effective thermoelectric materials have a low thermal conductivity and a high electrical conductivity. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2σT/K, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature and K is the thermal conductivity. In this study we prepared the thermoelectric generator device of SiO2/SiO2+Au multi-layer super-lattice films using the ion beam assisted deposition (IBAD). In order to determine the stoichiometry of the elements of SiO2 and Au in the grown multilayer films and the thickness of the grown multi-layer films Rutherford Backscattering Spectrometry (RBS) and RUMP simulation software package was used. The 5 MeV Si ion bombardments was performed to make quantum clusters in the multi-layer super-lattice thin films to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity. To characterize the thermoelectric generator devices before and after Si ion bombardments we measured the cross-plane Seebeck coefficient, the cross-plane electrical conductivity, and the cross-plane thermal conductivity for different fluences.
Study of Silicon Carbide Ceramics
Authors: Abunaemeh Malek Amir , Ojo Ibidapo , Seif Mohamed , Muntele Claudiu , Ila Daryush 
Published: December 2009

AbstractThe TRISO fuel that is intended to be used for the generation IV nuclear reactor design consists of a fuel kernel of Uranium Oxide (UOx) coated in several layers of materials with different functions. One consideration for some of these layers is Silicon Carbide (SiC) [1]. The design, manufacture and fabrication of SiC are done at the Center for Irradiation of Materials (CIM). This light weight material can maintain dimensional and chemical stability in adverse environments and very high temperatures. The characterization of the elemental makeup of the SiC material used is done using X-ray photoelectron spectroscopy (XPS). Nano-indentation is used to determine the hardness, stiffness and Young's Modulus of the material. Raman Spectroscopy is used to characterize the chemical bonding for different sample preparation temperatures.
Band Gap Engineering of Nano Scale AlGaN Epitaxial Layers by Swift Heavy Ion Irradiation
Authors: N SATHISH , G Devaraju , N Srinivasa Rao , Pathak Anand , Turos Andrzej , Khan S A , Avasthi D K , Trave E , Mazzoldi P 
Published: December 2009

AbstractEpitaxial AlGaN/GaN layers grown by MBE on SiC substrates were irradiated with 150 MeV Ag ions at a fluence of 5×1012 ions/cm2. AlGaN/GaN MQWs were grown on Sapphire substrate by MOCVD and irradiated with 200 MeV Au8+ ions at a fluence of 5×1011 ions/cm2 . These samples were used to study the effects of SHI on optical properties of AlGaN/GaN based nano structures. RBS/Channelling strain measurements were carried out at off normal axis of irradiated and unirradiated samples. In as grown samples, AlGaN layer is partially relaxed with a small compressive strain. After irradiation this compressive strain increases by 0.22% in AlGaN layer. Incident ion energy dependence of dechannelling parameter shows E1/2 dependence, which corresponds to the dislocations. Defect densities were calculated from the E1/2 graph. As a result of irradiation defect density increased on both GaN and AlGaN layer. Optical properties of AlGaN/GaN MQWs before and after irradiation have been analyzed using PL. This study shows that SHI increase the confinement effects in the MQWs and intensity of the active layer of the MQWs luminescence is increased by one order. This may be due to the induced strain in GaN and AlGaN layers. Some unwanted yellow luminescence has also been introduced by the SHI possibly due the point defects or defect luminescence from the induced dislocations in GaN bulk epitaxial layers. In this study, we present some new results concerning high energy irradiation on AlGaN/GaN heterostructures and MQWs characterized by RBS/Channelling and PL.
Importance of Internal Ion Beam Parameters on the Self-organized Pattern Formation with Low-energy Broad Beam Ion Sources
Authors: Cornejo Marina I , Ziberi Bashkim , Tartz Michael , Neumann Horst , Frost Frank , Rauschenbach Bernd 
Published: December 2009

AbstractThe low energy ion beam erosion of solid surfaces is a simple bottom-up approach for the generation of nanostructures. For certain sputtering conditions caused by self-organization processes well ordered nanostructures on the surface like one-dimensional ripples or regular arrays of dots can be formed [1]. Using broad beam sources, the low energy ion beam erosion can be a cost-efficient method to produce large-area nanostructured surfaces in a one-step process.The processes involved have been studied in the last decades and the pattern formation is attributed to the competition of curvature dependant sputtering and various relaxation mechanisms. It is also well known that the ion beam incidence angle (the angle between the sample surface normal and the axis of the beam source) is one critical parameter that determines the surface topography. However, inherent to all broad beam sources, the ion beam exhibits a certain divergence, i.e. the ion trajectories are not parallel to each other. This generates a spread of the local incidence angle with respect to the geometrically defined beam incidence angle.Recent studies showed that the divergence angle and angular distribution of the ions, here called internal beam parameters, also affect the surface topography [2].The angular distribution can be controlled by the total voltage applied on the geometrical defined ion optical system of the broad beam ion source. For the given multi-aperture two-grid ion optical system the total voltage is the sum of the voltages applied to the first (screen) and second (accelerator) grid. This total voltage, together with the geometrical characteristics of the used grid systems, including the shape of the plasma sheath boundary at the screen grid, define the overall ion-optical parameters of the source, i. e. the divergence angle and angular distribution of the ions within the beam.In this contribution a first approach of the effect of the internal beam parameters on the surface topography is presented. It was analyzed the effect on the topography on Si surfaces of some experimental parameters that affect the internal beam parameters by changing the ion-optical parameters and the shape of the plasma sheath boundary. Explicitly, the influence of the discharge voltage, the operation time and the distance between the screen and accelerator grid is shown.[1]	B. Ziberi, M. Cornejo, F. Frost, B. Rauschenbach, J. Phys.: Condens. Matter (submitted).[2]	B. Ziberi, F. Frost, M. Tartz, H. Neumann, B. Rauschenbach, Appl. Phys. Lett. 92, 063102 (2008)