Cathodoluminescence emission

B. Cathodoluminescence Emission produced from irradiation of (5-particles... 

Figure 7.22 Cathodoluminescence emission spectra of Mn2+ doped plasma-sprayed hydroxyapatite coatings in the as-sprayed state (KT) and immersed in HBSS for 7 (7KT) and 28 (28KT) days (Gotze, 2000).

Mariano AN (1988) Some further geological applications of cathodoluminescence. In Cathodoluminescence of Geological Materials. Marshall D J (ed) Unwin Hyman, Boston Mariano AN (1989) Cathodoluminescence emission spectra of REE activators in minerals. Rev Mineral 21 339-348... 

Phosphors are commerdaUy available with cathodoluminescent emission over the entire visible band, including ultraviolet and near-infrared. Table 5.6 Ksts the important characteristics of the most common phosphors used in video display appKcations. Absolute phosphor efficiency is measured as the ratio of total absolute energy emitted to the total excitation energy applied. When evaluating or comparing picture... 

Donor and acceptor levels are the active centers in most phosphors, as in zinc sulfide [1314-98-3] ZnS, containing an activator such as Cu and various co-activators. Phosphors are coated onto the inside of fluorescent lamps to convert the intense ultraviolet and blue from the mercury emissions into lower energy light to provide a color balance closer to daylight as in Figure 11. Phosphors can also be stimulated directly by electricity as in the Destriau effect in electroluminescent panels and by an electron beam as in the cathodoluminescence used in television and cathode ray display tubes and in (usually blue) vacuum-fluorescence alphanumeric displays. 

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... 

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 ... 

Band gaps in semiconductors can be investigated by other optical methods, such as photoluminescence, cathodoluminescence, photoluminescence excitation spectroscopy, absorption, spectral ellipsometry, photocurrent spectroscopy, and resonant Raman spectroscopy. Photoluminescence and cathodoluminescence involve an emission process and hence can be used to evaluate only features near the fundamental band gap. The other methods are related to the absorption process or its derivative (resonant Raman scattering). Most of these methods require cryogenic temperatures. 

Emission of light due to an allowed electronic transition between excited and ground states having the same spin multiplicity, usually singlet. Lifetimes for such transitions are typically around 10 s. Originally it was believed that the onset of fluorescence was instantaneous (within 10 to lO-" s) with the onset of radiation but the discovery of delayed fluorescence (16), which arises from thermal excitation from the lowest triplet state to the first excited singlet state and has a lifetime comparable to that for phosphorescence, makes this an invalid criterion. Specialized terms such as photoluminescence, cathodoluminescence, anodoluminescence, radioluminescence, and Xray fluorescence sometimes are used to indicate the type of exciting radiation. 

Microscopic techniques, 70 428 Microscopists, role of, 76 467 Microscopy, 76 464-509, See also Atomic force microscopy (AFM) Electron microscopy Light microscopy Microscopes Scanning electron microscopy (SEM) Transmission electron microscopy (TEM) acronyms related to, 76 506-507 atomic force, 76 499-501 atom probe, 76 503 cathodoluminescence, 76 484 confocal, 76 483-484 electron, 76 487-495 in examining trace evidence, 72 99 field emission, 76 503 field ion, 76 503 fluorescence, 76 483 near-held scanning optical,... 

For comparison, steady-state cathodoluminescence spectra (Fig. 4.7) are presented from two scheelite samples with different rare-earth elements concentrations (Table 4.5). It is clearly seen that only broadband emissions are detected, while the narrow Unes of several rare-earth elements, mostly Sm + are extremely weak. 

The active participation of the So level is indirectly accredited by the simultaneous observation of UV and visible emission in cathodoluminescence... 

A possible candidate may be Tm ". For example, the doublets at 803 and 817 nm and at 796 and 813 nm are the strongest ones in cathodoluminescence spectra of fluorite and scheelite activated by Tm " (Blank et al. 2000). It is possible to suppose that the strong fines at 805 and 820 nm with a relatively short decay time of 60 ps in the titanite luminescence spectrum belong to Tm " ". They appear under 532 nm excitation and are evidently connected with the electron transition. Similar emission of Tm " was also detected in... 

The fluorescence properties of europium compounds offer another possibility for using them as a red component in colour television tubes. As all fluorescence compounds are not capable of producing laser action, they still stand a chance of being used as phosphors. Those phosphors which have a main emission peak between 6110 and 6140 A are the only ones suitable. The cathodoluminescence properties of several Eu3+ doped GdaOs and YVO4 proved to be highly efficient red emittors for colour... 

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... 

Complementary studies of neutral [20] and charged [16] intrinsic trapped centers, comparison of cathodoluminescence [21] and thermoluminescence data [12] with results of analysis of photoelectron scattering [13] and pump-probe experiments [14] allow us to extend the energy relaxation scheme (Fig.2d, dotted arrows) including electron-hole recombination channels. The formation of H-band emitting centers (R2+) occurs through the excitation of STH by an exciton. The bulk recombination of trapped holes with electrons populates the (R2 ) states with subsequent M-band emission [22], After surface recombination of STH with electrons the excited dimers escape from the surface of the crystal with subsequent IF-band emission. 

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

The emission of a range of photons from ultraviolet (UV) to infrared, referred to as cathodoluminescence, is mainly caused by recombination of electron-hole pairs in the sample. 

An efficiency of the cathodoluminescent light source depends directly from the efficiencies of its basic components an electron gun and luminescent covering. The diminishing of the power consumption and the increasing of the cathodoluminescent lamps efficiency are provided with application of field emission cathodes made of carbon fibers. 

The purpose of the current work is the development of the effective electron-optical system for the cathodoluminescent light source with the field emission cathode based on polyacrylonitrile (PAN) carbon fibers [1]. 

The electron-optical system of the cathodoluminescent lamp consists of electron gun and luminescent screen, which is covered by phosphor. It represents the triode construction. The base of this triode is the cathode-modulator unit (CMU) that consists of field emission cathode and extraction electrode (modulator). 

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