Cathodoluminescence, CL

Cathodoluminescence (CL), i.e., the emission of light as the result of electron-beam bombardment, was first reported in the middle of the nineteenth century in experiments in evacuated glass tubes. The tubes were found to emit light when an electron beam (cathode ray) struck the glass, and subsequendy this phenomenon led to the discovery of the electron. Currendy, cathodoluminescence is widely used in cathode-ray tube-based (CRT) instruments (e.g., oscilloscopes, television and computer terminals) and in electron microscope fluorescent screens. With the developments of electron microscopy techniques (see the articles on SEM, STEM and TEM) in the last several decades, CL microscopy and spectroscopy have emerged as powerfirl tools for the microcharacterization of the electronic propenies of luminescent materials, attaining spatial resolutions on the order of 1 pm and less. Major applications of CL analysis techniques include  

1 Uniformity characterization of luminescent materials (e.g., mapping of defects and measurement of their densities, and impurity segregation studies) 

Obtaining information on a material s electronic band structure (related to the fundamental band gap) and analysis of luminescence centers Measurements of the dopant concentration and of the minority carrier diffusion length and lifetime 

Microcharacterization of semiconductor devices (e.g., degradation of optoelectronic devices) 

Analysis of stress distributions in epitaxial layers In-situ characterization of dislocation motion in semiconductors Depth-resolved studies of defects in ion-implanted samples and of interface states in heterojunctions. 

---

The incoming electron beam interacts with the sample to produce a number of signals that are subsequently detectable and useful for analysis. They are X-ray emission, which can be detected either by Energy Dispersive Spectroscopy, EDS, or by Wavelength Dispersive Spectroscopy, WDS visible or UV emission, which is known as Cathodoluminescence, CL and Auger Electron Emission, which is the basis of Auger Electron Spectroscopy discussed in Chapter 5. Finally, the incoming... 

Cathodoluminescence, CL, involves emission in the UV and visible region and as such is not element specific, since the valence/conduction band electrons are involved in the process. It is therefore sensitive to electronic structure effects and is sensitive to defects, dopants, etc., in electronic materials. Its major use is to map out such regions spatially, using a photomultiplier to detect all emitted light without... 

It is worth summarizing at this point the different excitation methods used for phosphors that will be referred to throughout this chapter. There are three types photoluminescence (PL) which is based on initial excitation by absorption of light, cathodoluminescence (CL) which is based on bombardment with a beam of electrons, as in a cathode ray tube (CRT) and electroluminescence (EL) which is based on application of an electric field (either a.c. or d.c.) across the phosphor. 

In the cathodoluminescence (CL) technique in the EM, the wavelength of light emitted by selective electron stimulation can be directly related to the local band-gap energy of the catalyst material, and the intensity of the signal to the... 

Wurtz-synthesized PMPS was selected as the material to be studied when subjected to cathodoluminescence (CL).98 The CL method of the study of PMPS is based on the measurement of CL intensity of emitted light after its passage through the specimen, as shown in Figure 20. For the PMPS degradation measurements, electron beam energy of 10k eV was used. The PL emission spectrum consists of two emission bands. The maximum of the... 

Cathodoluminescence (CL), or the emission of light upon electron irradiation, has long been recognized. Initially observations were... 

Other groups reported the solution synthesis of a cerium-doped inorganic phosphor library (73) to optimize their structure as luminescence down-converters in white Light Emitting Diodes (LEDs) and the use of cathodoluminescence (CL) (74) to identify... 

In this monograph, a number of notations, units, and abbreviations will be used, and they are summarized in Appendix A. It contains lists of notations for crystal orientations, process parameters for CVD, analytical techniques, CVD reactors, crystal growth, and carbon materials in addition to a description of standard diamond film characterizations, i.e. Raman spectroscopy and cathodoluminescence (CL). The readers are recommended to just quickly read through Appendix A at this point. 

Samples were impregnated with a high-temperature blue-dyed epoxy resin before thin-section preparation. Polished thin sections were examined with a petrographic microscope and by using a hot-cathodoluminescence (CL) microscope (Matter Ramseyer, 1985). Most of the samples were stained using Dickson s (1966) method, and point counted (300 points per sample). 

The cathodoluminescence (CL) response for 30 samples shows that calcite is for the most part homogeneous and unzoned. However, some concretions contain calcite cement that is zoned on the micrometre scale. CL of authigenic calcite ranges... 

Standard petrographical and mineralogical techniques, including optical and cathodoluminescence (CL) microscopy. X-ray diffraction (XRD) and electron microprobe analysis (EPMA), were used to characterize detrital and diagenetic minerals and textural relationships. Thin sections were half stained with K-Fe cyanide for rapid identification... 

The amount and quality of information in these studies varies greatly and only a few of the more recent papers applied a combination of several different methods to decipher the origin of saddle dolomite. We scanned published work for the following information on saddle dolomite occurrences optical mineralogy, cathodoluminescence (CL) characteristics, elemental composition, carbon, oxygen and strontium isotopic compositions, and fluid inclusion analysis. In the following sections we shall address these types of data in detail. 

---