Red Cathodoluminescence Research Articles

Analytical Color Fluorescence Electron Microscopy Observation of Laser Diodes

Laser diodes with the multilayer heterostructure have been observed in cathodoluminescence (CL) images using an analytical color fluorescence electron microscope. An AlGaInP/GaInP chip, which is commercially available as 670 nm red laser diode, emits red CL from a part of the p-AlGaInP layer just above the p-GaInP layer and between the n-GaAs blocking layers. A chip that has no blocking layers emits only very weak red CL, which indicates the strong relation of CL with laser emission. In images of a CdZnSe/ZnSe diode that emits 530 nm blue laser light at room temperature, a blue CL emission appears which is much stronger in the n-type region, in particular in the n-ZnSSe cladding layer, than in the p-type region

Two chondrule groups each with distinctive rims in Murchison recognized by cathodoluminescence

Abstract— Two groups of chondrules in the Murchison CM chondrite, which have previously been identified on the basis of FeO in the chondrule grains, are readily identified from cathodoluminescence (CL) and belong to those of the ordinary chondrite group A and B chondrules of Sears et al. (1992a). All chondrules are surrounded by fine‐grained rims containing forsterite with bright red CL, but on group A chondrules an outer thin rim grades into a much thicker rim, with a lower density of forsterite grains, which in turn grades into the central chondrule. Group B chondrules have only the thin outer rim with a high density of small forsterite grains. This is the first time an unequivocal correlation has been observed between chondrule rim thickness and the composition of the object on which the rim is located. We suggest that while all objects in the meteorite (group B chondrules, refractory inclusions, mineral and chondrule fragments, clasts) acquired a very thin rim during processing in a wet regolith, the thick rims on group A chondrules were formed by aqueous alteration of precursor metal‐ and sulfide‐rich rims which are a characteristic of group A chondrules in ordinary chondrites.

Dolomitization of the Devonian Swan Hills Formation, Rosevear Field, Alberta, Canada

ABSTRACTThe Swan Hills Formation (Middle‐Upper Devonian) of the Western Canada Basin is host to several NW‐SE‐trending gas fields developed in massive replacement dolostone. One of these, the Rosevear Field, contains two major dolostone trends along opposing margins of a marine channel that penetrates into a platform‐reef complex. Dolostones consist predominantly of branching and bulbous strdmatoporoid floatstones and rudstones with well‐developed moldic and vuggy porosity. Replacement dolomite is coarsely crystalline (100‐600 μm), inclusion‐rich, composed of euhedral through anhedral crystals and has a blotchy to homogeneous red cathodoluminescence. Geochemically, replacement dolomite is characterized by (i) nearly stoichiometric composition (50.1‐51.1 mol% CaCO3), (ii) negative δ18O values (mean=‐7.5‰, PDB) and (iii) variable 87Sr/86Sr ratios ranging from values similar to Late Devonian‐Early Mississippian seawater (∼0.7082) to radiogenic compositions comparable to saddle dolomite cements (>0.7100).Dolomitization began after widespread precipitation of early, equant calcite spar and after the onset of pressure solution, implying that replacement dolomite formed in a burial environment. Oxygen isotope data suggest that dolomite formed at 35‐75°C, temperatures reached during burial in Late Devonian through Jurassic time, at minimum depths of 450 m. The linear NW‐SE orientation of most dolomite fields in the Swan Hills Formation is suggestive of fault control on fluid circulation. Two models are proposed for fault‐controlled circulation of dolomitizing fluids at the Rosevear Field. In the first, compaction‐driven, updip fluid migration occurred in response to basin tilting commencing in the Late Palaeozoic. Deep basinal fluids migrating updip were focused into channel‐margin sediments along fault conduits. The second model calls upon fault‐controlled convective circulation of (i) warm Devonian‐Mississippian seawater or (ii) Middle Devonian residual evaporitic brines.The overlap in 87Sr/86Sr and δ18O compositions, and similar cathodoluminescence properties between replacement and saddle dolomites provide evidence for neomorphism of some replacement dolomite. Quantitative modelling of Sr and O isotopes and Sr abundances suggests partial equilibration of some replacement dolomite with hot radiogenic brines derived during deep burial of the Swan Hills Formation in the Late Cretaceous‐Palaeocene. Interaction of replacement dolomite with deep brines led to enrichment in 87Sr while leaving δ18O similar to pre‐neomorphism values.

Cathodoluminescence Microscopy: A Valuable Technique for Studying Ceramic Materials

Over the past 10 to 20 years, cathodo-luminescence microscopy (CLM) has become an important, standard technique for studying many geological materials, but its application to ceramic material has not been fully realized. CLM has been found to be especially valuable in determining original porosity in carbonate rocks, a feature that was extremely important in determining the ability of petroleum and related fluids to migrate through the rocks and concentrate in the favorable structures where petroleum is found today. CLM constitutes one of the most significant techniques employed in the exploration for petroleum, but the results of those investigations remain largely unpublished in company files. A number of investigations have discussed the application of cathodoluminescence (CL) to studies of porosity in carbonates.Other applications of CLM to geology involve metals exploration. Halos of red CL feldspar in the rocks around carbon-atite deposits, which may contain rare earths, copper, and other metals, contrast with feldspar crystals with blue or blue-green CL that are distal from the ore deposits. Dolomite associated with lead-zinc ores may exhibit growth zoning by CL that can be used to trace the path of the ore fluids for distances of 100 miles or more. The detection of host rock limestone alteration in the Tri-State zinc-lead district, potassic and argillic alteration at the Henderson molybdenite mine, and ore guides in other metallic deposits by CL was discussed by Hagni.

Composite character of the red band emission in LEC GaP:S

Red cathodoluminescence (CL) from S doped LEC GaP has been investigated. Observations at different temperatures indicate that the emission has two components of wavelengths 732 and 705 nm, respectively. The results are discussed in terms of existing models involving donor-vacancy complexes.

Influence of vacancy defects on the luminescence of GaP studied by CL and positrons

Abstract Cathodoluminescence (CL) scanning electron microscopy and positron annihilation techniques have been used to investigate defects in electron irradiated LEC-GaP and its influence on CL emission. Defects produced by irradiation cause the quenching of green and red CL. The quenching is not related to Ga vacancies. P vacancies and other radiation defects contribute to the quenching of the green CL. Ga vacancies have been observed to anneal at 150 K.

Effect of thermal annealing on the cathodoluminescence of evaporated CdS films

Cathodoluminescence (CL) of evaporated undoped CdS films was investigated before and after thermal annealing in air and in vacuum at 300 °C for several hours. Pure CdS single crystals were studied for comparison. CL spectra were obtained at room temperature using the electron microprobe technique. The two well-known (green and red) CL bands of pure CdS were observed for all samples. Annealing of the films in air decreased the green luminescence while vacuum annealing led to its increase. The red luminescence increased under both annealing conditions. The results were explained in terms of radiative transitions attributed mainly to native defects and their complexes. The role of oxygen and residual impurities on the CL of thin films was discussed. A modulation of the CL spectra was obtained in thin films owing to optical interference.

Red cathodoluminescence from deformed MgO crystals

Red cathodoluminescence from deformed MgO crystals

Low-voltage red cathodoluminescence of ZnSe single crystals

Red cathodoluminescence from low-resistivity ZnSe:Cu, Al crystals has been observed under the excitation of low-energy electron beams below 50 V. Dependence of current and brightness on applied voltage as well as the emission spectrum are presented. The red emission of ZnSe tends to be subjected to degradation, while the blue and the green of ZnS previously observed do not.

Study of the Spectral Features of the Intensity and Kinetics of the Red Cathodoluminescence of Cinnabar

Among other emissions, the natural cinnabar presents, under cathodic excitation, a broad red band. Examining the spectral properties of the emitted intensity and of the radiative recombination probability between 4.2 and 300 K, an attempt is made to elucidate its mechanism of formation. The analysis of spectral modifications (shape, half-width, peak energy, intensity) according to the temperature leads to a diagram of transitions between at least two vibro-electronical states (one excited and one fundamental) of a same centre, the fundamental state being situated at about 300 meV above the valence band. The shape of the spectral distribution of life time is only compatible with the existence of a band at the origin of transitions and a model of centre is suggested possessing an excited band and submitted to an important vibrational coupling of the lattice. Entre autres emissions, le cinabre naturel, presente sous excitation cathodique, une large bande rouge. En examinant entre 4,2 et 300 K, les proprietes spectrales de l'intensite emise et de la probabilite de recombinaison radiative, nous avons tente d'elucider son mecanisme de formation. L'analyse des modifications spectrales (forme, largeur a mi-hauteur, position, intensite) en fonction de la temperature conduit a un schema de transitions entre au moins deux etats vibro electroniques (un excite et un fondamental) d'un měme centre, l'etat fondamental etant situe a environ 300 meV au-dessus de la bande de valence. La forme de la distribution spectrale de duree de vie etant seulement compatible avec l'existence d'une bande d'etats a l'origine des transitions, nous avons retenu un modele de centre possedant une bande d'etats excites, et soumis a un couplage vibrationnel important du reseau.