Acceptors concentration, effect

The decrease in free carriers (holes) after hydrogenation of p-type Si is also evidenced by the decrease in IR absorption at the longer wavelengths, where free-carrier absorption dominates, and by a decrease in the device capacitance of Schottky-barrier diodes, due to the increase in the depletion width (at a given reverse bias) as the effective acceptor concentration decreases. 

Figure 10.13. Dependence of energy transfer on concentration of Phenol Red, for the protonated (Roi = 28.3 A) and unprotonated form (R02 = 52.5 A). The inset shows the pH-dependent energy transfer using an acceptor concentration of 4 x 10 3 M (effect of diffusion is omitted).

Particular attention should be paid to the possibility of singlet interactions when aromatic hydrocarbons and other compounds which fluoresce are employed as sensitizers. Unambiguous evidence for this phenomenon can be obtained from the effect of acceptor on sensitizer fluorescence and it can be minimized by the use of low acceptor concentrations. Interestingly, not all aromatic hydrocarbons engage in the type of quenching158 that seems to involve charge transfer for example, triphenylene fluorescence is not affected by piperylene.160... 

The existence of these dielectrically different phases can also cause concentration gradients within the micelle so that effective concentrations of reagents substantially different from the bulk concentrations can be attained, Scheme 5. This concentration effect can be utilized to control bimolecular quenching events, especially when short-lived intermediates are involved. In an anionic micelle, for example, a neutral donor may dissolve in the hydrophobic core, while the electron deficient acceptor (either as a neutral molecule or as a cation) may associate with the surface head... 

Thus, we have to conclude that, without knowing the physical nature of the frequency dependence of the differential capacitance of a semiconductor electrode, the donor (or acceptor) concentration in the electrode cannot be reliably determined on the basis of the Schottky theory, irrespective of the Mott-Schottky plot presentation format. Therefore, the reported in literature acceptor concentrations in diamond, determined by the Schottky theory disregarding the frequency effect under discussion, must be taken as an approximation only. However, we believe that the o 2 vs. E plot (the more so, when the exponent a approaches 1), or the Ccaic 2 vs. E plot, are more convenient for a qualitative comparison of electrodes made of the same semiconductor material. 

Ion Scattering Spectroscopy mass, molar mass effective mass of electron concentration of ions or charge carriers concentration of acceptors concentration of donors coordination number of shell j complex refraction index photo ionization cross-section electric charge gas constant... 

Figure 3. Effects of annealing on mobility of bulk ZnO. The fits (not shown) give acceptor concentrations of = 1.8x10 cm for the unannealed sample, and 1.2x10 cm for the annealed sample.

Electrical measurements, mainly temperature-dependent Hall-effect measurements, have been critical in the elucidation of donors and acceptors in ZnO. The main background donors in state-of-the-art VP-grown ZnO have been shown to be H and Al, and the acceptor, Vzn. Other possible donors that must be investigated further are the defects Vo and Znj. Although Vzn seems to be the main electrically active acceptor, still N is evidently present at a much higher concentration. If this is true, then N must be passivated, and the likely passivator is H. Indeed, annealing experiments lead to a much higher acceptor concentration, presumable due to the... 

The effect of the acceptor concentration on the transfer/hydrolysis ratio is shown in Fig. 22, which has been drawn from the data of Arnaud. No... 

Effects of varying light intensity, wavelength, acceptor concentration, and of rotating the sample tube suggest that the tetrachlorophthaIic anhydride-catalyzed reaction is biphotonic. 

A good linear correlation was found between the integrated absorption of the strongest RT line centred at 347 meV and the neutral acceptor concentration obtained from Hall effect measurements of five natural lib diamonds [43]. This was later converted into a RT calibration factor of this band of 1 x 1014 cm-1, assumed to be valid for B concentrations up to a few 1018 cm-3. For larger B concentrations going up to 1 x 102°cm 3, a calibration factor of about one order of magnitude larger was obtained by correlation with SIMS measurements on CVD diamonds [64], These calibration factors are discussed in the review by Thonke [177],... 

Figure 1. Effect of donor particle concentration on the initial rate of lipid transfer. The computer-drawn curves are based on the kinetic model by Van den Besselaar et al. (1975) for protein-catalyzed phospholipid exchange. The kinetic constants are for, the transfer of phosphatidylcholine from liposomes containing 12 mol% phosphatidic acid to liposomes containing 2 mol% phosphatidic acid. The three curves represent three different acceptor concentrations indicated above the appropriate curves.

The role of exciplexes in self-sensitized photo-oxidations has been further investigated by Stevens and co-workers.273 - Photoperoxidation of 1,3-diphenyl-isobenzofuran in solution proceeds at a rate which is independent of acceptor concentration when this is very low, and this observation has been interpreted in terms of a re-encounter of x02 and ground-state acceptor molecules generated in the same triplet-triplet annihilation act. This interpretation accounts for the failure of tetramethylethylene to inhibit the reaction completely. Processes 1—3 in Scheme 8 account for the observations if re-encounter effects are included,... 

Table I. Effect of Acceptor Concentration on Product Yield for Photo-Oxygenation of 2-Methyl-2-pentene (A) in ferf-Butyl Alcohol...

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