Cathodoluminescence spectra

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. 

Fig, 4.7. Steady-state cathodoluminescence spectra of scheelite samples... 

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... 

Figure 2. Cathodoluminescence spectra from synthetic Cr- and Mn-doped enstatite.

FIGURE 6 Cathodoluminescence spectra obtained in the defective area of the crystal which appeared yellow in an optical microscope (a) and in the transparent area of the crystal (b). Note changes in the intensities of the yellow luminescence peak (2.4 eV) and band to band luminescence (3.5 eV). 

Figure 1. Cathodoluminescence spectra of the ZnO and Alo.nGao.ssN layers measured at room temperature. I ,ax (ZnO) = 387 nm, FWHM (ZnO) = 21 nm.

The cathodoluminescence spectra of heavily B-doped (111) coalesced films on Pt(lll) had an edge emission band at 5.0 eV at room temperature [385, 435]. In Figure 13-20 [435], B-doped films were synthesized by MPCVD with B/C = 3300 ppm in the source gas. When the film thickness was 1.8 pm, there was an intense band A in the wavelength region of 400 to 600 nm in addition to a weak band at 248 nm (5.0 eV). When the film thickness was increased to 16 pm, band A entirely disappeared, and the CL spectrum consisted of the 248-nm band only. The major difference between the two films was that the 1.8-pm thick film consisted of (11 l)-oriented diamond grains, while the (111) faces were significantly... 

Figure 24. Cathodoluminescence spectra of Triassic conodonts (carbonate-fluorapatite) from Germany. 1 and 2 in the left-hand spectra refer to two points on the same fossil. Modified after Habermann et al. (2000).

Pressure treatment of p-BN polycrystals leads to a change both of broad-band parameters (A, B, C) and of the zero-phonon lines of the cathodoluminescence spectra and to a change in the appearance of RC centers. The centers PC-1 (2.84 eV), PC-2 (2.325 eV), and PC-3 (1.79 eV probably an interstitial center) have been detected in pressure-treated samples. The appearance of the A and B bands (between 1.85 and 3.25 eV) can be connected with electronic states in the band gap via boron and nitrogen vacancies, the appearance of the C band (1.55 to 1.85 eV) depends on the plastic deformation [29 to 31]. 

A particularly striking example of this is the visible light emission from some porous silicon and silicon nanoparticle structures originally ascribed to photoluminescence but later revealed to be blackbody thermal radiation by careful experimentation (Costa et al. 1998 Roura and Costa 2002). Some very spectrally broad cathodoluminescence spectra published are also likely to be primarily thermal radiation, as discussed in the handbook chapter Cathodoluminescence of Porous Silicon. ... 

To determine the band gap of the alloys, electron beam cathode luminescence measurements were made on pressed bars of the powder. The band gap value assigned to each semiconductor corresponded to the energy of the maximum in the cathodoluminescence spectrum. 

The short-wavelength limit of the continuous spectrum is clearly a quantum phenomenon. X-ray generation by electron bombardment in principle resembles cathodoluminescence, and both processes are inverse photoelectric effects. The short-wavelength limit, Xq, discovered by Duane and Hunt6 obeys the relationship... 

Figure 3.34. Electronic structure and dopant distributions in catalysts revealed by cathodoluminescence in electron microscopy unreacted Sb/Sn oxide catalyst with a band-gap of 1.9 eV is shown by the spectrum B. The reacted catalyst at A shows a band-gap of 2.6 eV, demonstrating a peak shift indicative of surface segregation of Sb. (After Boyes et al 1985.)...

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... 

To reiterate STEM is mainly practised because point-by-point analysis can be carried out. The information available is at least three-dimensional a two-dimensional image, which is a projection of the specimen, and for each picture element, one or more spectra either electron energy loss or X-ray emission, or any other spectrum such as optical cathodoluminescence. An important question is, given an incident probe of a certain size, do say, how large is the region from which the spectra originate ... 

E. 0. Hulburt. J. Formanek said that the chromium salts do not react with alkanna tincture. L. de Boisbaudran examined the fluorescence spectrum. According to T. Tanaka, chromium is the principal agent in the cathodoluminescence of corundum. No series spectrum has been observed with chromium, but the lines have been studied from this point of view by L. Janicki, A. Dufour, P. G. Nutting, H. N. Russell, S. Goudsmit, E. Kromer, M. Steenbeck, H. Deslandres,... 

The PL, CL (cathodoluminescence), TL and PSL spectra of Sm doped Y2Si05 and of Sm +- and Tb -codoped Y2Si05 was studied by Meiss et al. (1994a). Figure 34 shows TL spectra of Y2Si05 Sm (0.02) and those of phosphors codoped by 0.1 and 0.001 Tb in curves 1 to 3, respectively. The spectra were taken at 350 K after X-iriadiation. The spectrum in curve 1 is characteristic of Sm, and those with 0.1 Tb (curve 2) and with 0.001 Tb (curve 3) give mainly Tb emission. The PSL of the X-irradiated phosphor obtained by illumination in the 380 nm band gives two intense PSL bands, at 650 and... 

Cathodoluminescence is also observable from mar biological and geological materials which have natural properties as scintillators. In such cases the spectrum is more complex than that from a semiconductor, major spectral peaks usitally being identifiable with the... 

---