Conduction band, bottom

Fig. 24. Energy diagram of the boron-doped diamond/aqueous redox electrolyte solution interface (a) at the flat-band potential (b) at the equilibrium potential of Fe(CN)63, 4 system. Ec is the energy of conduction band bottom, Ev is the energy of valence band top, F is the Fermi level, Eft, is the flat-band potential. Shown are the electrochemical potential levels of the Fe(CN)63, 4 and quinone/hydroquinone (Q/H2Q) systems in solution. The electrode potential axis E is related to the standard hydrogen electrode (SHE). Reprinted from [110]. Copyright (1997), with permission from Elsevier Science.

For this newly considered superlattice, the unusual feature lies in the fact that the valence-band in one host semiconductor GaSbAs (barriers) is actually located very close to the conduction-band bottom in the other host semiconductor InGaAs, thus a strong interaction exists between these bands despite the fact that each individual compound has a relatively wide bandgap. Hence the description of quantum transport processes within this heterostructure is a multi-band problem. In studies presented here, multi-band... 

Let us recall in this connection that the thermodynamic work function is equal to w = x P Ec. Here x is the electron affinity of the semiconductor, and the position of F relative to the conduction-band bottom, Ec, in the semiconductor bulk is given by the following relations ... 

Thus, from the analysis of XANES and USXES data and SEM and AFM-images it follows that porous silicon is a multi-phase system containing nanocrystals of silicon covered with amorphous and oxide phases. Under laser excitation of visible photoluminescence electrons can transfer from conduction band bottom of the oxide phases to the valence band of silicon resulting in a broad luminescence band in the range of 1.8 - 2.4 eV. 

Comparison of the energy gap —1.9eV for Ino.5Gao.5P determined as the difference between the valence band top and the bottom of the conduction band with the energy of the photoluminescence peak demonstrates rather good accordance [2]. For InP quantum dots one can observe a decrease in conduction band bottom energy by the value 0.2 eV that results in reducing of the band gap in these nanostructures. 

Different points Negative potential of conduction band bottom (<0 V vs. RHE) H2-evolution capability on the surface (with co-catalyst) n-Type scanichigh mobility of e to back contact... 

The valence band potential of TaON can also be shifted negatively, due to hybridization of the 0-2p and N-2p orbitals. As a result, TaON powders show good photocatalytic activity for not only O2 evolution but also H2 evolution [25, 26]. The potential of the conduction band bottom is probably close to the potential of H /H2. Therefore, TaON is a promising semiconductor for photoelectrodes with the application of small external bias, although its photoelectrochemical performance is still poor [15]. 

Some controversy exists in the literature about the positions of the lowest conduction band minima. One result shows the lowest minimum at F and the minimum of the d states at X3, below some s states but above F1. Other results claim the symmetry point of the conduction band bottom is at X3 instead of Fi, whereas according to other authors F1 and X3 are nearly degenerate. 

Table 10.12. Dependence of the F-center energy-level position with respect to the conduction-band bottom of unrelaxed SrTiOs crystal with periodically distributed oxygen vacancies (e), its dispersion (6e) and distance between the nearest F centers (dp-p) as a function of the superceR size used in LCAO B3PW calculations 732 with 2x2x2 k-mesh ...

Tables 10.13a and b demonstrate the effect of the cychc-cluster increase for both HF and DFT-PWGGA methods, respectively. The main calculated properties are the total energy Etot (per primitive unit cell), one-electron band-edge energies of the valence-band top and conduction-band bottom e and Sc, MuUiken effective atomic charges q and full atomic valencies V. As is seen, the result convergence, as the supercell size increases, is quite different for the HF and DFT. We explain the much slower DFT convergence by a more covalent calculated electron-charge distribution, as compared to the HF case. For both methods, the convergence of local properties of the electronic structure is faster than that for the total and one-electron energies.

Analysis of the difference electron-density plots, calculated for the band and the 80-atom cyclic-cluster calculations confirms that the latter well reproduces the electron-density distribution in a perfect crystal. Lastly, the total and projected density of states for a perfect crystal show that the upper valence band consists of O 2p atomic orbitals with admixture of Ti 3d orbitals, whereas the Sr states contribute mainly to the energies close to the conduction-band bottom, in agreement with previous studies. 

---