In-Situ Spectroscopy of Ion-Induced Photon Emission During Metal Nanoparticle Formation in Silica Glass with High-Flux Cu Implantation

1999 ◽  
Vol 569 ◽  
Author(s):  
Thi Thi Lay ◽  
H. Amekura ◽  
Y. Takeda ◽  
N. Kishimoto
Keyword(s):  
Current Density ◽  
Silica Glass ◽  
Substrate Surface ◽  
Broad Band ◽  
Photon Emission ◽  
Metal Nanoparticle ◽  
Ex Situ ◽  
Background Intensity ◽  
High Flux

ABSTRACTIon-induced photon emission from a silica glass irradiated with high-flux Cu ions was measured in a wavelength range from 450 nm to 800 nm, while nanoyarticles spontaneously formed in the silica glass. Current density was varied up to 100 µA/cm2 at a constant total dose of 3×106ions/cm2. The photon emission primarily arose from the vicinity of the substrate surface and consisted of sharp peaks due to neutral and singly-ionized species, Cu(I), Cu(II) and Si(II) ions, as well as a broad-band background. Intensity of Si(II) and Cu(I) increased with increasing current density. On the other hand, Cu(II) did not show a monotonic increase, decreasing around 100 µA/cm2. Measurements of in-situ EDX and ex-situ RBS were also conducted to study the relevant mechanisms. The ion-induced photon emission was attributed to recombination processes of sputtered ions and electrons in the plasma, induced by the high-flux Cu beam.

The Oxide/Nitride Interface: a study for gate dielectrics and field passivation

2003 ◽  
Vol 786 ◽  
Author(s):  
B.P. Gila ◽  
B. Luo ◽  
J. Kim ◽  
R. Mehandru ◽  
J.R. LaRoche ◽  
...  
Keyword(s):  
Gate Dielectrics ◽  
Substrate Surface ◽  
Surface Preparation ◽  
Dielectric Materials ◽  
Ex Situ ◽  
Dielectric Films ◽  
Interface Quality ◽  
Gas Source ◽  
Gas Source Mbe

ABSTRACTThe study of the effects of substrate surface preparation of GaN, both in-situ and ex-situ and the subsequent deposition of dielectric materials is necessary to create a viable GaN FET technology. Surface preparation techniques have been explored using RHEED, AES, SIMS and C-V measurements to produce films of low interface trap density, 1–2E11 eV−1cm−2. A similar study of the as-fabricated HEMT surface was carried out to create a cleaning procedure prior to dielectric passivation. Dielectric films of Sc2O3 and MgO were deposited via gas-source MBE. Post-deposition materials characterization included AES, TEM, XRR and XPS, as well as gate pulse and isolation current measurements for the passivated HEMT devices. From this study, the relationship between the interface structure and chemistry and the quality of the oxide/nitride electrical interface has been determined. The resulting process has led to the near elimination of the current collapse phenomenon. In addition, the resulting oxide/nitride interface quality has allowed for the first demonstration of inversion in GaN.

scholarly journals Analytical Investigation of Fuel Cells by Using In Situ and Ex Situ Diagnostic Methods

2010 ◽  
Vol 638-642 ◽  
pp. 1125-1130
Author(s):  
Günter Schiller ◽  
Erich Gülzow ◽  
Mathias Schulze ◽  
Norbert Wagner ◽  
K. Andreas Friedrich
Keyword(s):  
Fuel Cells ◽  
Current Density ◽  
Printed Circuit Boards ◽  
Analytical Investigation ◽  
Diagnostic Methods ◽  
Electrochemical Methods ◽  
Measuring System ◽  
Ex Situ ◽  
German Aerospace

The study of the behaviour of fuel cells by using various in-situ and ex-situ diagnostic methods is a main topic at the German Aerospace Center (DLR). The degradation of cell components of polymer electrolyte fuel cells (PEFC, DMFC) and of solid oxide fuel cells (SOFC) are of special interest. For this purpose physical and electrochemical methods are used individually as well as in combination. In addition to routinely applied electrochemical methods different methods for locally resolved current density measurements by means of segmented cell technology and integrated temperature sensors have been developed. The latest development with segmented bipolar plates based on printed circuit boards (PCB) is used both in single PEFC cells and stacks. Furthermore, a measuring system for segmented SOFC cells has been developed allowing for the spatially resolved characterisation of cells in terms of current density/voltage characteristics, impedance spectroscopy data, operating temperature and gas composition. The paper summarises the capabilities at DLR with respect to the analysis of fuel cells’ behaviour and gives examples of analytical studies to discuss the potentials and limitations of the diagnostic methodology that is applied.

In-Situ and Ex-Situ Investigation of Lateral Current Density Variations in a PEM Fuel Cell With Serpentine Flow Field

2009 ◽  
Author(s):  
Andrew Higier ◽  
Hongtan Liu
Keyword(s):  
Fuel Cell ◽  
Flow Field ◽  
Contact Resistance ◽  
Current Density ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Operating Conditions ◽  
Ex Situ ◽  
Serpentine Flow Field

One of the most common types of flow field designs used in proton exchange membrane (PEM) fuel cell is the serpentine flow field. It is used for its simplicity of design, its effectiveness in distributing reactants and its water removal capabilities. The knowledge about where current density is higher, under the land or the channel, is critical for flow field design and optimization. Yet, no direct measurement data are available for serpentine flow fields. In this study a fuel cell with a single channel serpentine flow field is used to separately measure the current density under the land and channel on the cathode. In this manner, a systematic study is conducted under a wide variety of conditions and a series of comparisons are made between land and channel current density. Results show that under most operating conditions, current density is higher under the land than that under the channel. However, at low voltage, a rapid drop off in current density occurs under the land due to concentration losses. In order to investigate the cause of the variations of current density under the land and channel and series of ex-situ and in-situ experiments were conducted. In the ex-situ portion of the study, the contact resistance between the gas diffusion electrode (GDE) and the graphite flow plate were measured using an ex-situ impedance spectroscopy technique. The values of the contact resistance under the channel were found to be larger than that under the land. This implies that the contact resistance under the land and channel vary greatly, likely due to variations in compression under different section of the flow field. These variations in turn cause current density variations under the land and channel.

scholarly journals Optimisation and Scale-up of the Synthesis of Gold Nanoparticle-Wool Fibre Composites

2021 ◽  
Author(s):  
◽  
Thomas Wade Nilsson
Keyword(s):  
Gold Nanoparticles ◽  
Gold Nanoparticle ◽  
Laboratory Scale ◽  
Metal Nanoparticle ◽  
Ex Situ ◽  
Wool Fibre ◽  
Reaction Conditions ◽  
Gold Colloids ◽  
Fibre Composites

<p>Gold nanoparticles are known for their remarkable optical properties; they exhibit localised surface plasmon resonance bands in the visible region of the electromagnetic spectrum. This has led to their use as luxury dyes for the colouring of wool fibres. Gold is associated with wealth and desire, and as such, gold nanoparticle-wool fibre composites may be fabricated into high-quality garments, apparel, textiles and carpets for international markets.  Novel proprietary approaches for the laboratory-scale synthesis of gold nanoparticle-wool fibre composites have previously been developed by Professor James Johnston and Dr Kerstin Lucas. The innovative nanotechnology utilises the affinity of gold for sulfur-containing cystine residues in wool fibres, to attract and bind the gold nanoparticles. One approach involves the absorption of gold ions by wool fibres and the nucleation of gold nanoparticles in-situ. In an alternative method, gold nanoparticle colloids are synthesised ex-situ, and are then used to colour wool fibres.  The reaction conditions of the in-situ and ex-situ approaches were optimised with respect to cost-effectiveness and scalability. The gold content of the in-situ composites was minimised, and the range of possible colours widened, via the use of heat and external reducing agents. In the ex-situ process, the formation and stability of the gold nanoparticle colloids was studied, and the reaction conditions of the synthesis were optimised. The rate of uptake of gold nanoparticles to wool was controlled by manipulating the pH, concentration, volume, and wool to liquor ratio of the gold colloids, and by introducing auxiliary agents into the dyeing reactions. A range of chemical treatments and alternative stabilising agents were investigated to improve the washfastness properties of ex-situ gold nanoparticle-wool fibre composites.  There are numerous size-controllable syntheses of gold nanoparticle colloids at the laboratory-scale. However, when the process is scaled-up, gold nanoparticle synthesis is no longer trivial. A barrel reactor with a high velocity mixer was utilised to achieve uniform mixing and heating in the synthesis of gold nanoparticle colloids of up to 90 L in volume. The ratios of gold to stabilising agents in the colloidal gold syntheses were optimised to result in more stable and reproducible gold colloids for subsequent dyeing reactions.  The uniform colouring of small quantities of wool is easily achieved in the laboratory, but preventing colour variation across a kilogram of wool is a significant challenge. Initial kilogram-scale dyeing reactions in static tank reactors resulted in unevenly coloured gold nanoparticle-wool fibre composites. To overcome this, conventional hank dyeing equipment was used to colour felted merino yarn, in collaboration with the wool dyeing industry. Modified hank dyeing procedures were recreated in the laboratory, and composites with remarkable colour uniformity were produced. Industrial package dyeing reactors were then used to colour fine merino yarn with gold nanoparticle colloids. The uptake of gold nanoparticles was controlled by manipulating the owrates, ow direction and amounts of auxiliary agents that were employed in the dyeing reactions.  Based upon the success of the industrial dyeing reactions, novel dyeing reactors were developed for the colouring of hanks of wool fibres and yarns in the laboratory. These reactors utilised rapid dye circulation and pressure to produce gold nanoparticle-wool fibre composites with remarkable colour uniformity. The composites were used to fabricate luxury apparel and carpets for international trade expositions.  The pathway from synthesis in the laboratory to pilot-scale production of gold nanoparticle-wool fibre composites is presented. The PhD research was an integral step in the successful commercialisation of this innovative nanotechnology, and will assist in scaling-up the synthesis of metal nanoparticle colloids and nanocomposites in the future.</p>

Laser-Reflectance Interferometry Measurements of Diamond-Film Growth

MRS Bulletin ◽  
1995 ◽  
Vol 20 (5) ◽  
pp. 29-31 ◽  
Author(s):  
Christopher D. Zuiker ◽  
Dieter M. Gruen ◽  
Alan R. Krauss
Keyword(s):  
Film Thickness ◽  
Film Growth ◽  
Substrate Surface ◽  
Diamond Films ◽  
Thin Film Deposition ◽  
Film Deposition ◽  
Index Of Refraction ◽  
Ex Situ ◽  
Laser Reflectance

The remarkable properties of diamond, including its hardness, chemical inertness, high thermal conductivity, low coefficient of friction, optical transparency, and semiconducting properties, have led to considerable research in the area of diamond thin-film deposition. Diamond films have been characterized ex situ by a large number of diagnostic techniques including Raman spectroscopy, x-ray diffraction, SEM, and TEM. In situ diagnostics, which can provide information in real time as the film is growing, are less common.Laser-reflectance interferometry (LRI) has been used to monitor the growth of diamond films in situ. The technique involves measuring the intensity of a laser beam reflected from the substrate surface on which the film is growing. The reflected beam is the sum of beams reflected by the gas-diamond interface and the diamond-silicon interface. Oscillations in the reflectivity are observed as the film grows because of interference between the reflected beams. Each oscillation indicates an increase in film thickness of λ/2n, where λ is the laser wavelength and n is the index of refraction of the film. If the index of refraction of the film is known, the thickness and growth rate can be determined in situ. For LRI measurements with 632.8-nm-wavelength HeNe lasers, the index of refraction of diamond films has been found to be within 10% of the bulk diamond value of 2.4. Each oscillation therefore indicates an increase in film thickness of 0.13 μm.The reflectivity measured by LRI is also affected by scattering because of surface roughness.

Enhanced critical current density in undoped MgB2 prepared by in situ/ex situ combination technique

2015 ◽  
Vol 218 ◽  
pp. 31-34 ◽  
Author(s):  
M. Shahabuddin Shah ◽  
M. Shahabuddin ◽  
Jafar M. Parakkandy ◽  
Salem Qaid ◽  
Nasser S. Alzayed
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Ex Situ ◽  
Combination Technique

A study of ruthenium ultrathin film nucleation on pretreated SiO2 and Hf–silicate dielectric surfaces

2007 ◽  
Vol 22 (8) ◽  
pp. 2254-2264 ◽  
Author(s):  
Filippos Papadatos ◽  
Steven Consiglio ◽  
Spyridon Skordas ◽  
Eric T. Eisenbraun ◽  
Alain E. Kaloyeros
Keyword(s):  
Grain Size ◽  
Rutherford Backscattering Spectrometry ◽  
Substrate Surface ◽  
Compressive Strain ◽  
Chemical Vapor ◽  
Nucleation And Growth ◽  
Ex Situ ◽  
Organic Chemical ◽  
Nucleation Density

This study explored the effects of substrate surface pretreatments on the nucleation and growth of metal–organic chemical vapor deposited ruthenium. In situ plasma (dry), featuring O2, Ar, and H2/Ar chemistries, and ex situ (wet) treatments, consisting of a standard RCA bath, were examined in the nucleation and growth of up to 50-nm-thick metallic Ru films on SiO2 and Hf–silicate surfaces. The resulting surface morphology, grain size, and roughness of the metallic films were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM), while Rutherford backscattering spectrometry (RBS) was used for compositional measurements. It was determined that an in situ plasma treatment using a H2/Ar yielded metallic Ru films with the highest nucleation density, smallest grain size, and lowest resistivity. Film buckling was also observed for the Ru films deposited on H2/Ar pretreated surfaces. The behavior was attributed to the presence of compressive strain. The films deposited on RCA-cleaned and Ar plasma treated surfaces exhibited very similar physical and electrical characteristics to the films grown on untreated substrates. Alternatively, the use of O2 plasma surface treatment adversely affected Ru nucleation on the SiO2 surface. Relevant mechanisms for Ru nucleation and growth on SiO2 and Hf–silicate nontreated surfaces are discussed in the context of the various predeposition dry and wet treatments.

MgB2 Composite Superconductors Made by Ex Situ and In Situ Process

2006 ◽  
Vol 47 ◽  
pp. 131-136 ◽  
Author(s):  
Pavol Kováč ◽  
I. Hušek ◽  
T. Melišek
Keyword(s):  
Current Density ◽  
Transport Current ◽  
Ex Situ ◽  
Boron Diffusion ◽  
Critical Temperatures ◽  
Mgb2 Wires ◽  
Composite Superconductors ◽  
Current Densities ◽  
Composite Wires

Generally, two basic routes called as in-situ and ex-situ process are used for composite MgB2 wires now. Mentioned processes have been used for making of single-core composite wires. The applied heat treatment parameters influence the microstructure of MgB2 phase, critical temperature and critical current density, but it has also decisive effect on the MgB2/metal reaction. It was found that the transport current densities are much more sensitive to the used sheath material than critical temperatures. The main factors limiting the transport current density are cracks introduced by deformation and porosity caused by the boron diffusion in ex-situ and in-situ wires, respectively.

scholarly journals Towards studying hierarchical assembly in real time: a Milky Way progenitor galaxy at z = 2.36 under the microscope

2020 ◽  
Vol 493 (4) ◽  
pp. 5653-5661 ◽  
Author(s):  
Tom O Zick ◽  
Daniel R Weisz ◽  
Bruno Ribeiro ◽  
Mariska T Kriek ◽  
Benjamin D Johnson ◽  
...  
Keyword(s):  
Near Infrared ◽  
Milky Way ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Star Clusters ◽  
Star Formation History ◽  
Ex Situ ◽  
Spectral Energy ◽  
Space Telescope

ABSTRACT We use Hubble Space Telescope (HST) imaging and near-infrared spectroscopy from Keck/Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE) to study the substructure around the progenitor of a Milky Way-mass galaxy in the Hubble Frontier Fields (HFF). Specifically, we study an $r_\mathrm{ e} = 40^{+70}_{-30}$ pc, $M_{\star } \sim 10^{8.2} \, \mathrm{M}_{\odot }$ rest-frame ultraviolet luminous ‘clump’ at a projected distance of ∼100 pc from a M⋆ ∼ 109.8 M⊙ galaxy at z = 2.36 with a magnification μ = 5.21. We measure the star formation history of the clump and galaxy by jointly modelling the broad-band spectral energy distribution from HST photometry and Hα from MOSFIRE spectroscopy. Given our inferred properties (e.g. mass, metallicity, dust) of the clump and galaxy, we explore scenarios in which the clump formed in situ (e.g. a star-forming complex) or ex situ (e.g. a dwarf galaxy being accreted). If it formed in situ, we conclude that the clump is likely a single entity as opposed to a aggregation of smaller star clusters, making it one of the most dense star clusters catalogued. If it formed ex situ, then we are witnessing an accretion event with a 1:40 stellar mass ratio. However, our data alone are not informative enough to distinguish between in situ and ex situ scenarios to a high level of significance. We posit that the addition of high-fidelity metallicity information, such as [O iii] 4363 Å, which can be detected at modest signal-to-noise ratio with only a few hours of James Webb Space Telescope(JWST)/Near-Infrared Spectrograph (NIRSpec) time, may be a powerful discriminant. We suggest that studying larger samples of moderately lensed substructures across cosmic time can provide unique insight into the hierarchical formation of galaxies like the Milky Way.

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