Determination of the Valence Band Offset in GaAs/(Ga,Al)As Superlattices by Hot Electron Excitation Spectroscopy

1993 ◽  
Vol 300 ◽  
Author(s):  
H. Weinert ◽  
A. Zukauskas ◽  
V. Latinis ◽  
V. Stepankevicius
Keyword(s):  
Electron Excitation ◽  
High Energy ◽  
Relaxation Processes ◽  
Hot Electron ◽  
X Ray Diffraction ◽  
Excitation Energies ◽  
Pl Spectra ◽  
Lower Excitation ◽  
Diffraction Barrier

ABSTRACTA GaAs/Ga1−xA1xAs-superlattice was investigated using quasi-cw PL measurements at T=2 K. The relevant sample parameters were determined by X-ray diffraction: barrier thickness - 5 nm, qw-thickness - 5 nm, x = 0.41. A series of PL-spectra at medium, but constant excitation intensity for different excitation energy (from 1.64 eV to 2.1 eV) was measured. From the high-energy slope of the PL-spectra the electron-temperature Te was determined. A clearly structured dependence of Te on hvexc (excitation energy) was found. We assumed the pronounced structures of the Te - hvexc - hvexc - “spectrum” to be the onset-energies of new, for lower excitation energies not possible relaxation processes. Calculating the excess energy for each kind of carriers (heavy and light holes and electrons) separately, we found δEv=( 0.18 ± 0.05) ∆Eg for the investigated sample. Using this new experimental method one also is able to obtain the energies of higher electronic states (for example Γ → L -transitions) of GaAs/(Ga,Al)Assuperlattices.

X-ray diffraction cell for studying solid–gas reactions under gas pressures to 100 bar

2006 ◽  
Vol 39 (6) ◽  
pp. 850-855 ◽  
Author(s):  
E. MacA. Gray ◽  
D. J. Cookson ◽  
T. P. Blach
Keyword(s):  
Phase Transformation ◽  
Heat Flow ◽  
Real Time ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Time Determination ◽  
Gas Reactions ◽  
Gas Pressures

A pressure cell designed for high-energy X-ray diffraction in transmission mode is described. The cell is intended for use at temperatures up to 573 K with samples that are large enough to permit the real-time determination of the amount of absorbed gas by measuring the gas pressure. The design is driven by the need to ensure that the sample temperature is constant and uniform, despite the heat flow accompanying the reaction between the gas and the sample. The use of the cell is illustrated by its application to elucidating the hydriding phase transformation in the LaNi5–H2system.

Experimental determination of residual stress in silicon nitride diffusion bonds obtained by high-energy X-ray diffraction

2004 ◽  
Vol 148 (1) ◽  
pp. 60-63 ◽  
Author(s):  
M. Vila ◽  
M.L. Martínez ◽  
C. Prieto ◽  
P. Miranzo ◽  
M.I. Osendi ◽  
...  
Keyword(s):  
Residual Stress ◽  
Silicon Nitride ◽  
Experimental Determination ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffusion Bonds

Oxford HEXameter: Laboratory High Energy X-Ray Diffractometer for Bulk Residual Stress Analysis

2006 ◽  
Vol 524-525 ◽  
pp. 743-748 ◽  
Author(s):  
Alexander M. Korsunsky ◽  
Shu Yan Zhang ◽  
Daniele Dini ◽  
Willem J.J. Vorster ◽  
Jian Liu
Keyword(s):  
Accurate Determination ◽  
High Energy ◽  
Energy Dispersive ◽  
Detector Response ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
New Instrument ◽  
Synchrotron Beamlines

Diffraction of penetrating radiation such as neutrons or high energy X-rays provides a powerful non-destructive method for the evaluation of residual stresses in engineering components. In particular, strain scanning using synchrotron energy-dispersive X-ray diffraction has been shown to offer a fast and highly spatially resolving measurement technique. Synchrotron beamlines provide best available instruments in terms of flux and low beam divergence, and hence spatial and measurement resolution and data collection rate. However, despite the rapidly growing number of facilities becoming available in Europe and across the world, access to synchrotron beamlines for routine industrial and research use remains regulated, comparatively slow and expensive. A laboratory high energy X-ray diffractometer for bulk residual strain evaluation (HEXameter) has been developed and built at Oxford University. It uses a twin-detector setup first proposed by one of the authors in the energy dispersive X-ray diffraction mode and allows simultaneous determination of macroscopic and microscopic strains in two mutually orthogonal directions that lie approximately within the plane normal to the incident beam. A careful procedure for detector response calibration is used in order to facilitate accurate determination of lattice parameters by pattern refinement. The results of HEXameter measurements are compared with synchrotron X-ray data for several samples e.g. made from a titanium alloy and a particulate composite with an aluminium alloy matrix. Experimental results are found to be consistent with synchrotron measurements and strain resolution close to 2×10-4 is routinely achieved by the new instrument.

Refinements in phase fraction determination of textured alloys from transmission diffraction data

2021 ◽  
Vol 54 (5) ◽  
pp. 1480-1489
Author(s):  
Adam Creuziger ◽  
Thien Phan ◽  
Darren Pagan
Keyword(s):  
Synthetic Data ◽  
High Energy ◽  
Phase Fraction ◽  
X Ray Diffraction ◽  
Complete Coverage ◽  
Order Of Magnitude ◽  
Fraction Measurement ◽  
Sample Texture ◽  
Fraction Determination

The use of high-energy synchrotron X-ray diffraction sources has become increasingly common for high-quality phase fraction measurements and microstructural evolution experiments. While the high flux, large volume illuminated and large number of diffraction vectors should reduce common sources of uncertainty and bias, the distribution of the diffraction vectors may still cause bias in the phase fraction measurement. This hypothesis of bias was investigated with example experimental data and synthetic data. The authors found that there may be bias depending on the sample texture, the distribution of diffraction vectors and the hkl planes used in the phase fraction measurement, even for nearly complete coverage of a pole figure. The authors developed a series of geometry-based correction values that reduced the measurement bias due to sampling scheme and texture in the phase fraction measurement by an order of magnitude. The efficacy of these corrections was demonstrated with application to both experimental and synthetic data.

A new approach to the determination of atomic-architecture of amorphous zeolite precursors by high-energy X-ray diffraction technique

2006 ◽  
Vol 8 (2) ◽  
pp. 224-227 ◽  
Author(s):  
Toru Wakihara ◽  
Shinji Kohara ◽  
Gopinathan Sankar ◽  
Seijiro Saito ◽  
Manuel Sanchez-Sanchez ◽  
...  
Keyword(s):  
High Energy ◽  
X Ray Diffraction ◽  
New Approach ◽  
X Ray ◽  
Zeolite Precursors

scholarly journals PL Spectra and Hot Charge Carrier Phenomena in an Undoped GaAs/AlGaAs Tunnel-Coupled Quantum Well

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Kanothai Jarusirirangsi ◽  
Paphavee van Dommelen ◽  
Chalongrat Daengngam
Keyword(s):  
Experimental Study ◽  
Quantum Well ◽  
Quantum Confinement ◽  
High Energy ◽  
Hot Electrons ◽  
Hot Electron ◽  
Energy Rate ◽  
Pl Spectra ◽  
Coupled Quantum Well ◽  
Undoped Gaas

In this research, we experimentally investigated the photoluminescence (PL) spectra of an undoped GaAs/Al0.36Ga0.64As Tunnel-Coupled Quantum Well (TCQW) at 300 K and 77 K. At 300 K, PL spectra were broadened at various laser intensities due to the characteristic quantum-confinement electron levels in the active region of the TCQW during pumping excitation. At 77 K, at selected excitation intensities, the high-energy tails in the PL spectra of the studied structure corresponded with hot electron temperatures as functions of the energy of emitted photons. The average scattering energy rate of hot electrons in the system was also studied at a lattice temperature of 77 K. The average scattering energy rate of hot electrons obtained from this experimental study was in agreement with the calculated theoretical value.

scholarly journals Chemical state mapping of simulant Chernobyl lava-like fuel containing material using micro-focused synchrotron X-ray spectroscopy

2021 ◽  
Vol 28 (6) ◽  
Author(s):  
Hao Ding ◽  
Malin C. Dixon Wilkins ◽  
Lucy M. Mottram ◽  
Lewis R. Blackburn ◽  
Daniel Grolimund ◽  
...  
Keyword(s):  
Oxidation State ◽  
Fuel Cycle ◽  
Chemical State ◽  
X Ray Diffraction ◽  
Excitation Energies ◽  
Essential Information ◽  
X Ray ◽  
Redox Active ◽  
X Ray Absorption

Uranium speciation and redox behaviour is of critical importance in the nuclear fuel cycle. X-ray absorption near-edge spectroscopy (XANES) is commonly used to probe the oxidation state and speciation of uranium, and other elements, at the macroscopic and microscopic scale, within nuclear materials. Two-dimensional (2D) speciation maps, derived from microfocus X-ray fluorescence and XANES data, provide essential information on the spatial variation and gradients of the oxidation state of redox active elements such as uranium. In the present work, we elaborate and evaluate approaches to the construction of 2D speciation maps, in an effort to maximize sensitivity to the U oxidation state at the U L 3-edge, applied to a suite of synthetic Chernobyl lava specimens. Our analysis shows that calibration of speciation maps can be improved by determination of the normalized X-ray absorption at excitation energies selected to maximize oxidation state contrast. The maps are calibrated to the normalized absorption of U L 3 XANES spectra of relevant reference compounds, modelled using a combination of arctangent and pseudo-Voigt functions (to represent the photoelectric absorption and multiple-scattering contributions). We validate this approach by microfocus X-ray diffraction and XANES analysis of points of interest, which afford average U oxidation states in excellent agreement with those estimated from the chemical state maps. This simple and easy-to-implement approach is general and transferrable, and will assist in the future analysis of real lava-like fuel-containing materials to understand their environmental degradation, which is a source of radioactive dust production within the Chernobyl shelter.

Quantitative determination of fragmentation kinetics and thermodynamics of colloidal silver nanowires by in situ high-energy synchrotron X-ray diffraction

Nanoscale ◽  
2014 ◽  
Vol 6 (1) ◽  
pp. 365-370 ◽  
Author(s):  
Zheng Li ◽  
John S. Okasinski ◽  
Jonathan D. Almer ◽  
Yang Ren ◽  
Xiaobing Zuo ◽  
...  
Keyword(s):  
Quantitative Determination ◽  
Silver Nanowires ◽  
High Energy ◽  
Colloidal Silver ◽  
X Ray Diffraction ◽  
Kinetics And Thermodynamics ◽  
X Ray

Solid-phase reactions in Ir/(111)Si systems studied by means of x-ray emission spectroscopy

1998 ◽  
Vol 13 (7) ◽  
pp. 1950-1955 ◽  
Author(s):  
E. Z. Kurmaev ◽  
V. R. Galakhov ◽  
S. N. Shamin ◽  
T. Rodríguez ◽  
A. Almendra ◽  
...  
Keyword(s):  
Emission Spectroscopy ◽  
Annealing Temperature ◽  
Solid Phase ◽  
Electron Excitation ◽  
High Energy ◽  
Excitation Energies ◽  
X Ray ◽  
Electron Beam Excitation ◽  
Solid Phase Reactions ◽  
Beam Excitation

High energy resolved x-ray emission spectroscopy with variable electron beam excitation is applied for study of solid-phase reactions in the Ir/(111)Si system as a function of annealing temperature. The formation of Ir silicides as a function of depth is studied by measurements of Si L2,3 x-ray emission valence spectra at different electron excitation energies (3–10 keV), and the results are compared with those of Rutherford backscattering.

Sign in / Sign up

Export Citation Format

Share Document