Energy Band Model

Figure 5. Schematic of energy band model of the rutile form of TiOz (4)...

Hubbard J., and Jain K.P., (1968). Generalized spin susceptibility in the correlated narrow-energy-band model. J. Phys. C (Proc. Phys. Soc.), Ser. 2 1 1650-1657. 

Stukel, D. J., R. N. Euwema, T. C. Collins, F. Herman, and R. L. Kortum (1969). Self-consistent orthogonalized-plane-wave and empirically refined ortho-gonalized-plane-wave energy band models for cubic ZnS, ZnSe, CdS, and CdSe. Phys. Rev. 179, 740-51. 

To facilitate a self-contained description, we will start with well-established aspects related to the semiconductor energy band model and the electrostatics at semiconductor electrolyte interfaces in the dark . We shall then examine the processes of light absorption, electron-hole generation and charge separation at these interfaces. Finally, the steady-state and dynamic (i.e., transient or periodic) aspects of charge transfer will be considered. Nanocrystalline semiconductor films and size quantization are briefly discussed, as are issues related to electron transfer across chemically modified semiconductor electrolyte interfaces. 

Electron Energy Levels in Semiconductors and Energy Band Model... 

Fig. 9.16 Energy band model for particles embedded in a monograin membrane. (Compare with Fig. 9.1,5).

Fig. 11.7 Energy band model and photovoltage in terms of differences in the quasi-Fermi levels...

Energy Band Models Used to Depict Energy States of Solids Insulator Semi-Conductor... 

The ENERGY BAND MODEL has arisen to serve as an easy method of representing electron states in the solid. The Fermi level usually defines the top of the valence band, and is related to the 1st BriUouin Zone in the solid. We generally draw a band model as in 5.3.9.(next page) which... 

Note that quenching by electron transfer is a special case of quenching via a charge-transfer state as discussed above (Sect. 4.2.2) for Eu. There is also no principal difference between quenching by electron transfer and quenching via photoionization. However, the former has a localized character, the latter is used in energy band models where delocalization is more important. 

Iitg. 8,4. Energy band model showing the electronic transitions in a storage phosphor (a) generation of electrons and holes (b) electron and hole trapping (c) electron release due to stimulation (4) recombination. Solid circles are electrons, open circles are holes. Center I presents an electron trap, center 2 a hole trap... 

Fig. 12. Resistivity in the plane of layers, p, as a function of number of periods M in a-Si H/a-SiN H superlattice for diflFerent a-Si H layer spacing i The full curves were computed from Eq. (7) for the energy-band model given in Fig. 13. Experimental L, (A) = 1200 (V), 400 (O), 160 ( ), 80 (O), 40 (A). [From Tiedje and Abeles (1984).]...

The substances emitting luminescence are called phosphors. Some phosphors are basically semiconductors describable in terms of the energy band model. Professionals have examined the photoluminescence (PL) of different materials and developed many macro and microscopic luminescence-based devices used in different fields. 

Fig. 4 Schematic energy band model of the polycrystalline (1-type semiconductor, having grain boundary at the solid-electrolyte interface.

We have studied the resistance and thermopower behavior of the p -phase [9]. From the temperature-dependent resistance curve, one can see clearly a metal-semiconductor phase transition at about 140 K (Fig. 2), whereas on the temperature-dependent thermopower curve, only a very small (but distinct) kink appears at the same temperature (Fig. 3). To interpret these seemingly conflicting phenomena, a two-energy band model was used [9]. In this model, the conductivity is due to a combination of the two bands, and the thermopower is due to a competition of the two bands. From the room-temperature X-ray diffraction, which shows the iodine atoms arranged randomly, we speculate that, at room temperature, there should be an energy gap at the Fermi surface, but that the random arrangement of iodine atoms smears the gap. Thus, the crystal stays metallic at room temperature. 

The valence bond theory is useful in explaining the structure and the geometry of molecules, but it is not suitable to explain the properties of semiconductor materials. The energy-band model for electrons can be applied to all crystalline solids and allows identifying a conductor, an insulator or a semiconductor material. Indeed, the properties of a solid are determined by the difference of energy between the different bands and the distribution of the electrons contained within. 

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