Showing papers on "Cathodoluminescence published in 1978"

Surface effects on the low‐energy cathodoluminescence of zinc oxide

Abstract: A rapid initial brightness slump and occasional subsequent recovery observed for the zinc‐doped zinc oxide phosphor undergoing cathodoluminescence is shown to depend on the surface work function. A quantitative model leads to an explanation of the dependence on surface potential in terms of field‐aided or retarded surface recombination. Evidence is given that temporarily recovered surfaces result from dynamic surface adsorption of barium.

Growth and properties of GaxAl1-xN compounds

Abstract: Thin films of alloys in the GaxAl1-xN system have been prepared by vapour phase deposition onto sapphire substrates. The absorption edge and highest cathodoluminescence peak energies vary smoothly through the range with some bowing.

Ion microprobe, electron microprobe and cathodoluminescence data for Allende inclusions with emphasis on plagioclase chemistry

Abstract: Three Type B inclusions from the Allende meteorite have been analyzed. A grain-to-grain characterization of mineral chemistry and isotopic content was made possible by the use of a range of techniques, including luminescence and scanning electron microscopy and electron and ion microprobe analysis. Cathodoluminescence was used in fine-grained, optically opaque regions to distinguish between sub-micrometer phases, such as garnet and Si-rich material, subsequently identified by electron probe and scanning electron microscope analyses. Four types of luminescence patterns, due to twinning, primary sector zoning, alteration of boundaries and fractures, and shock effects, were identified in Allende plagioclase. Luminescence color exhibited a strong correlation with Mg content and provided a guide for an electron probe quantitative map of Mg and Na distributions. Ion microprobe studies of individual grains revealed large excesses of Mg-26.

SEM cathodoluminescence studies of dislocation recombination in GaP

Abstract: Single dislocations in epitaxial layers of GaP have been investigated using high resolution scanning electron microscope (SEM) cathodoluminescence (CL) techniques. The minority carrier lifetime was measured from the CL decay time constant, and impurity concentrations were assessed from a detailed analysis of the CL spectra. The minority carrier lifetime reduction at single dislocations varied between 10 and 40% depending on doping and growth procedure, decreasing to zero at approximately one diffusion length from the dislocation. A model based on recombination at an internal cylindrical surface did not adequately fit the experimental results, and it was therefore assumed that recombination occurred at a Cottrell atmosphere of impurities or defects surrounding the dislocation. Evidence to support such behaviour was obtained from CL spectra, which showed aggregation of nitrogen and a centre, probably a vacancy-donor complex, at 1.72 eV around dislocations. The close similarity between bulk and dislocation temperature dependence of lifetime suggests that the bulk recombination centre may be aggregating around dislocations.

Photo‐ and cathodoluminescence of Cd0.3Hg0.7Te alloys

Abstract: Photo- and cathodoluminescence of n- and p-type Cd0.3Hg0.7Te alloys are investigated in the temperature range 17 to 77 K. The luminescence spectra are found to be independent of the method of excitation and to consists of two bands. The energy separation of the bands is in a good agreement with that from the literature and does not depend on the type of alloy conductivity. Narrowing of the cathodoluminescence bands which is typical for stimulated generation is achieved under a high level of electron beam excitation both in the intrinsic and the impurity spectrum bands. The recombination centres involved are assumed to be the native lattice defects. [Russian Text Ignored].

Dopant tracing of terrace growth in GaAs LPE layers

Abstract: Growth terraces on the surface of GaAs liquid phase epitaxial layers leave behind traces of increased doping concentration in the interior of the layer. These traces have been observed on (110) cleavage planes perpendicular to the (100) surface. Spatially resolved photoluminescence, cathodoluminescence, and photoetching have been applied to reveal the traces of the terraces. A fine structure on the photoetched cleavage plane indicates that the increase of thickness of the layer is caused in part by lateral growth of fine terraces traveling across the treads of the high terraces.

Fine structure in the cathodoluminescence spectrum from chromium-doped gallium arsenide

Abstract: It has been reported previously that chromium in gallium arsenide gives rise to two luminescence bands, one centred around 0.80 eV with a no-phonon line at 0.839 eV, the other centred around 0.56 eV. High-resolution cathodoluminescence measurements are reported which show that the line at 0.839 eV consists of nine components, and that there are three no-phonon components at approximately 0.574 eV associated with the lower energy band. Temperature dependence measurements show that there is no shift in the transition energies in the temperature range 4-25K and indicate that splitting occurs in both the initial and final states of the transitions.

Fine structure in the GR1 cathodoluminescence from natural semiconducting diamond

Abstract: Fine structure is observed on the GR1 zero-phonon lines in the cathodoluminescence spectra from lightly irradiated ( approximately 1021 2 MeV electrons m-2) natural semiconducting diamond. Temperature dependence measurements over the interval 4 to 77K indicate that the structure derives from the excited state of the centre. Four closely spaced lines are observed in the T to E transition and it is proposed that the spectrum is due to a combination of luminescence from perturbed and unperturbed GR1 centres. The perturbation is specific, rather than random, splitting the excited T state into three levels; the energy separations between the lowest and the two higher levels are 1.4 and 3.5 meV. Measurements on heavily irradiated samples suggest that the perturbation may be associated with the radiation damage itself-perhaps due to the mutual interaction between close separation GR1 centres.

Cathodoluminescence study of Zn doped Gan

Abstract: The luminescence properties of GaN doped with Zn are reported. As the Zn concentration increases four different emissions are found using cathodoluminescence : blue (2.85 eV), green (2.5 eV), yellow (2.2 eV) and sometimes red (1.9 eV). Through the analysis of the influence of temperature, injection and time dependence, the blue, green and yellow emissions are found to fit a pair transition model, with a strong phonon coupling. The recombination model is discussed in view of the observed variation of the emission intensities versus injection level.

Cathodoluminescence applied to immunofluorescence: Present state and improved technical prospects by prism spectrometer light selection

Abstract: For studies on cathodoluminescence, we equipped a scanning electron microscope with a prism spectrometer and sensitive photomultiplier. The apparatus is described and our initial results are presented on the analyse of cathodoluminescence.

Boron- and Fluorine-Ion-Implantation into ZnSe Single Crystals

Abstract: The photoelectric properties of boron- and fluorine-ion-implanted ZnSe have been investigated by means of photoconductivity and cathodoluminescence measurements. The photoconductivity spectra have shown the existence of shallow levels 0.12 and 0.10 eV originating from boron and fluorine impurities, respectively. The quenching effect on a copper green photoconduction band has been found in the fluorine-ion-implanted ZnSe. It is suggested that the quenching behaviour arises from the Coulombic interaction between the copper acceptors and the fluorine donors. The cathodoluminescence spectra have shown the formation of the self-activated luminescence (SAL) bands and the marked decrease of the copper green emission bands by the boron- and fluorine-ion-implantations.

Suggested Standards for the Reporting of Cathodoluminescence Results: METHOD PAPER

Abstract: The cathodoluminescence technique has become an important tool in sedimentary petrology. Its usefulness will be enhanced if important experimental details are included in publications based in part on cathodoluminescence observation. This is especially important when the absence of luminescence is reported since this may be a function of instrumental design or performance. Suggestions for standard reporting of parameters and observational data are presented.

Suggested standards for the reporting of cathodoluminescence results

Abstract: The cathodoluminescence technique has become an important tool in sedimentary petrology. Its usefulness will be enhanced if important experimental details are included in publications based in part on cathodoluminescence observation. This is especially important when the absence of luminescence is reported since this may be a function of instrumental design or performance. Suggestions for standard reporting of parameters and observational data are presented.

Cathodoluminescence around Dislocations in an LEC-GaP Crystal

Abstract: The relationship between crystal defects and luminescent properties of a liquid encapsulated Czochralski (LEC) GaP crystal has been investigated by the cathodoluminescence (CL) method together with the etching, X-ray and photoluminescence methods. The CL analyses with a high spatial resolution have been made around dislocations revealed by etching. The CL spectra outside and inside a dislocation consist of two main bands of the G-band (560 nm) and the R-band (710 nm). Monochromatic CL images of the two bands show a complemental contrast around dislocations; the G-band intensity decreases at dislocation grooves and D-pits, while the R-band intensity increases at the same regions. The monochromatic CL intensity profile across a dislocation has also been studied. A simple explanation of the recombination process around a dislocation has been made by considering the dislocation to be a sink of defects.

Gallium nitride emitting devices preparation and properties

Abstract: GaN:Zn//Al2O3 electroluminescent devices have been obtained with a wide range of emitted colours (blue, green, yellow and red) ; theses devices have high potential since external quantum efficiencies greater than 1 % and power efficiencies of about 10−3 have been reported. On the other hand, from the literature it seems that each colour is obtained randomly, since apparently the same method of preparation is used. We show that the properties of GaN:Zn (conductivity type, cathodoluminescence (peaks and efficiency)) can not be related uniquely to the partial pressure of zinc during the growth, but it is also necessary to take into account the partial pressure of HCl and the thickness of the π layer in order to obtain a satisfactory representation of these properties. From this knowledge, one can deduce the different parameters for growing layers for devices and control their properties. The device fabrication consists of the deposition of a Zn doped thin layer, which is nearly insulating but with p tendency (π layer), onto a Zn doped n type layer. It is demonstrated that the characteristics of the devices (I(V) curves, electroluminescent peaks and efficiencies are related to the characteristics of the π layer and on the transition from n to π. Blue LEDS with characteristics very similar to p-n junction characteristics have been obtained.

Comparison of the methods of cathodoluminescence, electronprobe microanalysis, and calcium staining, applied to human aorta with isthmus stenosis

Abstract: Electron probe x-ray microanalysis is a useful method for studying pathologic and age-related calcification mechanisms in the aorta and in muscular arteries by means of elemental analysis in microareas. In the present investigation, this method was correlated with the histochemical alizarin-S-calcium staining and with cathodoluminescence analysis in the scanning electron microscope. Portions of the proximal region of a human aorta with isthmus stenosis was shock-frozen and sectioned in a cryostat. Serial sections were investigated by calcium staining, electron probe, and cathodoluminescence microanalysis. Using quantitative electron probe microanalysis of calcium and phosphorus, it was shown that the principal regions of calcium phosphate mineralization could be located using either alizarin-S staining or cathodoluminescence analysis. The advantage of the cathodoluminescence analysis is its higher lateral resolution compared with that of light microscopy, and the fact that no special staining is required. In addition, it was possible to obtain scanning images, thus providing additional information about the topology of the tissue surface, which is necessary to decide whether or not the section is suitable for microanalysis. Quantitative microanalysis is a valuable tool for basic research on calcified arteries. The results of the combined analysis in the proximal and distal regions as well as in the stenosis will be published in a later paper.

Cathodoluminescence of Al/x/Ga/1-x/As grown by liquid-phase epitaxy

Abstract: Small-area contrast fluctuations observed in cathodoluminescence-mode SEM images of thin Al(x)Ga(1-x)As layers grown by liquid-phase epitaxy on GaAs:Cr substrates are attributed to local variations in alloy composition. Quantitative estimates of the composition excursions are obtained from the variations in CL intensity by calibration against compositions known from electron-probe microanalysis. In a typical sample, the CL variations are shown to correspond to peak-to-peak fluctuations of about 1 at. % of Al and occur over irregular regions generally in the range 6-20 microns in diameter.