Precipitates in GaN epilayers grown on sapphire substrates

1998 ◽  
Vol 13 (8) ◽  
pp. 2100-2104 ◽  
Author(s):  
Junyong Kang ◽  
Tomoya Ogawa
Keyword(s):  
Grain Boundaries ◽  
Atomic Number ◽  
Luminescence Intensity ◽  
Energy Dispersive Spectrometry ◽  
Deep Levels ◽  
Energy Dispersive ◽  
Yellow Luminescence ◽  
X Ray ◽  
Sapphire Substrates ◽  
Atomic Number Contrast

Precipitates in GaN epilayers grown on sapphire substrates were investigated by atomic number contrast (ANC), wavelength-dispersive x-ray spectrometry (WDS), energy-dispersive spectrometry (EDS), and cathodoluminescence (CL) techniques. The results showed that the precipitates are mainly composed of gallium and oxygen elements and distribute more sparsely and inhomogeneously in directions in the sample grown on substrate nitridated for a longer period. Yellow luminescence intensity was imaged to be stronger in the precipitates. The results suggest that the precipitates are formed on dislocations and grain boundaries by substituting oxygen onto the nitrogen site, and result in the formations of deep levels nearby.

Impact of Energy-Dispersive Spectrometry in Materials Science Microanalysis

1998 ◽  
Vol 4 (6) ◽  
pp. 567-575 ◽  
Author(s):  
David B. Williams
Keyword(s):  
Grain Boundaries ◽  
Energy Dispersive Spectrometry ◽  
Equilibrium Phase ◽  
Boundary Segregation ◽  
Temper Embrittlement ◽  
Energy Dispersive ◽  
Small Scale ◽  
X Ray ◽  
Elemental Segregation

X-ray microanalysis of materials using energy-dispersive spectrometry (EDS) has made the greatest impact in studies of compositional changes at atomic-level interfaces. The small physical dimensions of the silicon detector make EDS the X-ray analyzer of choice for analytical transmission electron microscopy (AEM). X-ray analysis of thin foils in the AEM has contributed to our understanding of elemental segregation to interphase interfaces and grain boundaries, as well as other planar defects. Measurement of atomic diffusion on a small scale close to interphase interfaces has permitted determination of substitutional atomic diffusivities several orders of magnitude smaller than previously possible and has also led to the determination of low-temperature equilibrium phase diagrams through the measurement of local interface compositions. Elemental segregation to grain boundaries is responsible for such deleterious behavior as temper embrittlement, stress-corrosion cracking, and other forms of intergranular failure. On the other hand, segregation can bring about improvement in behavior: sintering aids in ceramics and de-embrittlement of intermetallics. EDS in the AEM has been responsible for quantitative analysis of all aspects of the segregation process and, more recently, in combination with electron energy-loss spectrometry (EELS) has given insight into why boundary segregation results in such significant macroscopic changes in properties.

Morphology of and Silicon Distribution within the Non-Glandular Trichomes of Soybean

1997 ◽  
Vol 3 (S2) ◽  
pp. 101-102
Author(s):  
R.N. Paul ◽  
C.D. Elmore ◽  
D. Gibson
Keyword(s):  
Energy Dispersive Spectrometry ◽  
Glandular Trichomes ◽  
Energy Dispersive ◽  
Fixed Tissue ◽  
Trifoliate Leaf ◽  
X Ray ◽  
Transmission Electron ◽  
Leaf Surfaces ◽  
Semithin Sections ◽  
Juvenile Plants

Three near isolines of soybean [Glycine max (L.) Merr.], glabrous, normal, and dense, were examined by light, scanning electron, and transmission electron microscopy, as well as by energy dispersive x-ray spectroscopy. This was done in order to determine the morphology and possible functions, in addition to conveying insect resistance, of their non-glandular trichomes.The uppermost fully expanded trifoliate leaf from greenhouse grown juvenile plants was chosen for examination. Fixed tissue was examined by LM, TEM and SEM as previously described. Some tissue was prepared for energy dispersive spectrometry by fixing in glutaraldehyde but omitting osmium. The tissue was then dehydrated, critical point dried, and coated with carbon. Si x-ray maps were made on the adaxial and abaxial leaf surfaces of all three biotypes.LMs of Spurr embedded toluidine blue stained semithin sections of normal (Fig. 1) and glabrous (Fig. 2) trichomes appear similar in structure.

scholarly journals Quantitative analysis by energy dispersive X-ray fluorescence by the transmission method applied to geological samples

1994 ◽  
Vol 51 (2) ◽  
pp. 197-206 ◽  
Author(s):  
S.M. Simabuco ◽  
V.F. Nascimento Filho
Keyword(s):  
Atomic Number ◽  
Energy Dispersive ◽  
X Rays ◽  
Geological Samples ◽  
Transmission Method ◽  
Absorption Effect ◽  
X Ray ◽  
Fundamental Parameters ◽  
Absorption Correction

Three certified samples of different matrices (Soil-5, SL-1/IAEA and SARM-4/SABS) were quantitatively analysed by energy dispersive X-ray fluorescence with radioisotopic excitation. The observed errors were about 10-20% for the majority of the elements and less than 10% for Fe and Zn in the Soil-5, Mn in SL-1, and Ti, Fe and Zn in SARM-4 samples. Annular radioactive sources of Fe-55 and Cd-109 were utilized for the excitation of elements while a Si(Li) semiconductor detector coupled to a multichannel emulation card inserted in a microcomputer was used for the detection of the characteristic X-rays. The fundamental parameters method was used for the determination of elemental sensitivities and the irradiator or transmission method for the correction of the absorption effect of characteristic X-rays of elements on the range of atomic number 22 to 42 (Ti to Mo) and excitation with Cd-109. For elements in the range of atomic number 13 to 23 (Al to V) the irradiator method cannot be applied since samples are not transparent for the incident and emergent X-rays. In order to perform the absorption correction for this range of atomic number excited with Fe-55 source, another method was developed based on the experimental value of the absorption coefficients, associated with absorption edges of the elements.

Quality Assurance of Energy Dispersive Spectrometry Systems

1998 ◽  
Vol 4 (S2) ◽  
pp. 214-215
Author(s):  
E. B. Steel ◽  
R. B. Marinenko
Keyword(s):  
Quality Control ◽  
Energy Dispersive Spectrometry ◽  
Standard Procedure ◽  
Energy Dispersive ◽  
X Ray ◽  
Standard Procedures ◽  
Reliability Sensitivity ◽  
Control Procedures ◽  
Analysis System ◽  
Quality Instruments

Monitoring the performance and capabilities of energy dispersive X-ray spectrometers (EDS) and related x-ray analysis electronics and software is important for maintaining and improving the reliability, sensitivity, and accuracy of the x-ray analysis system. There is growing demand for quality systems through laboratory accreditation, ISO 9000, ISO Guide 25 and related programs that require set quality control procedures for analytical instrumentation. In such cases it is frequently more useful to have one national/international standard. This approach is not only more efficient than having each analyst devise their own system, but the use of the same standard procedures among labs would allow direct intercomparison of results. This intercomparison can help labs and manufacturers determine what are normal versus abnormal results and lead to higher quality instruments and analyses.We are designing a standard procedure to maximize the efficiency of each quality control (QC) measurement so that we spend as little time monitoring the analysis system as is possible.

Electron probe x-ray microanalysis with energy-dispersive x-ray spectrometry: The basics of x-ray spectrum interpretation

1994 ◽  
Vol 52 ◽  
pp. 376-377
Author(s):  
Dale E. Newbury
Keyword(s):  
Atomic Number ◽  
Electron Probe ◽  
Energy Dispersive ◽  
X Ray ◽  
Linear Dimensions ◽  
Specimen Volume ◽  
Spectrum Interpretation ◽  
The Rich ◽  
Source Of Information ◽  
Basic Level

Electron probe x-ray microanalysis (EPMA) with energy dispersive x-ray spectrometry (EDS) provides the capability for detecting elements with atomic number ≥ 4 (beryllium) from an excited specimen volume with linear dimensions of micrometers and a mass in the picogram range. To maximize the utility of EPMA/EDS, the analyst needs to understand the rich source of information that is potentially available in the x-ray spectrum. At its most basic level, interpretation of the spectrum consists of recognizing and identifying the various components of the spectrum as recorded by the EDS system: characteristic peaks, artifacts, and continuum background. While a modern EDS system is capable of making this interpretation in an automatic fashion, the careful analyst will always check the computer’s interpretation, which of course demands that the analyst be at least as "smart" as the computer! A systematic examination of spectra from pure elements or simple compounds is a good way to develop the necessary working knowledge.

Areas for Improvement in XRF Analysis of Low Atomic Number Elements

1992 ◽  
Vol 36 ◽  
pp. 73-80
Author(s):  
Bruno A.R. Vrebos ◽  
Gjalt T.J. Kuipéres
Keyword(s):  
Lower Limit ◽  
Atomic Number ◽  
Energy Dispersive Spectrometry ◽  
Limit Of Detection ◽  
Heavy Elements ◽  
Fluorescence Spectrometry ◽  
Accurate Analysis ◽  
X Ray ◽  
Made In

Accurate analysis of the light elements has been, from the early applications of X-ray fluorescence spectrometry a struggle compared to the determination of heavy elements in the same matrices. In contrast, there has been virtually no upper limit to the atomic number of the element that could be determined. The lower limit, however, has been continuously adjusted downward through the years. Clearly, the sensitivity as well as the lower limit of detection for the heavy elements have also been improved, but the effect is Jess striking than the advances made in the region of tight element performance. This paper deals specifically with wavelength dispersive sequential x-ray fluorescence spectrometry, although some of the observations made are equally applicable to energy dispersive spectrometry.

Measurement of Trace Constituents by Electron-Excited X-Ray Microanalysis with Energy-Dispersive Spectrometry

2016 ◽  
Vol 22 (3) ◽  
pp. 520-535 ◽  
Author(s):  
Dale E. Newbury ◽  
Nicholas W. M. Ritchie
Keyword(s):  
Mass Fraction ◽  
Energy Dispersive Spectrometry ◽  
Energy Dispersive ◽  
Matrix Correction ◽  
Silicon Drift Detector ◽  
High Count ◽  
X Ray ◽  
Trace Elemental ◽  
Trace Constituents ◽  
Minor Concentration

AbstractElectron-excited X-ray microanalysis performed with scanning electron microscopy and energy-dispersive spectrometry (EDS) has been used to measure trace elemental constituents of complex multielement materials, where “trace” refers to constituents present at concentrations below 0.01 (mass fraction). High count spectra measured with silicon drift detector EDS were quantified using the standards/matrix correction protocol embedded in the NIST DTSA-II software engine. Robust quantitative analytical results for trace constituents were obtained from concentrations as low as 0.000500 (mass fraction), even in the presence of significant peak interferences from minor (concentration 0.01≤C≤0.1) and major (C>0.1) constituents. Limits of detection as low as 0.000200 were achieved in the absence of peak interference.

scholarly journals Analysis of Elemental Segregation in a Microalloyed Cast Steel

2013 ◽  
Vol 652-654 ◽  
pp. 2465-2468 ◽  
Author(s):  
Jing Wei Zhao ◽  
Zheng Yi Jiang ◽  
Dong Bin Wei
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Cast Steel ◽  
Central Zone ◽  
Energy Dispersive ◽  
Surface Zone ◽  
Quantitative Investigation ◽  
X Ray ◽  
Elemental Segregation

Quantitative investigation is made on the elemental segregation in different zones of a heavy microalloyed cast steel by energy dispersive X-ray spectroscopy. It is demonstrated that C shows serious segregation tendency than that of Mn and Si, and the degree of C segregation in the surface zone is higher than that in the central zone. C enrichment is generally observed at both dendrite arm and grain boundaries, and more C segregation at dendrite arm boundary in contrast to that at grain boundary is found in this steel. The distribution of C concentration shows a decreased trend from root to tip along the dendrite arm boundary. The C concentration at trigeminal boundary intersection shows higher level than that at other position of the grain boundaries.

Energy-Dispersive Spectrometry from Then until Now: A Chronology of Innovation

1998 ◽  
Vol 4 (6) ◽  
pp. 559-566 ◽  
Author(s):  
John J. Friel ◽  
Richard B. Mott
Keyword(s):  
Digital Imaging ◽  
Energy Dispersive Spectrometry ◽  
Energy Dispersive ◽  
X Ray ◽  
Microbeam Analysis ◽  
Analysis Society ◽  
Microbeam Analysis Society

As part of the Microbeam Analysis Society (MAS) symposium marking 30 years of energy-dispersive spectrometry (EDS), this article reviews many innovations in the field over those years. Innovations that added a capability previously not available to the microanalyst are chosen for further description. Included are innovations in both X-ray microanalysis and digital imaging using the EDS analyzer.

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