Effective band gap

Yin, W.-J. Chen, S. Yang,). Gong, X.qG. Yan Y. Wei, S.qH., Effective band gap narrowing of anatase Ti02 by strain along a soft crystal direction, Appl. Phys. Lett. 2010,96 221901-3. 

The most essential fact received in the present work that is that at increase in pressure from above 20 GPa conductivity of the sample instead of the further increase on the contrary starts to fall, that formally corresponds to increase in size of effective band-gap energy EG. It can be connected with phase transformations occurring in system and it is in agreement the data of X-Ray research. 

As the treated ITO samples show comparably high effective band gaps, we draw a conclusion as the following. A combination of Burstein-Moss-Shift and contributions of scattering [11] causes the increased Eg. It is not only a reason of Burstein-Moss-Shifl like Bender et al mentioned [13]. Eg = Eg q + AEg = Eg o + "R (37t nJ + fiZ, Where Eg... 

The oxygen vacancies formed at elevated temperatures and low oxygen partial pressure are assumed to be doubly ionized. The thermally activated charge disproportionation reaction given by Eq. (10.51) reflects the localized nature of electronic species and may be treated as equivalent to the generation of electrons and electron holes by ionization across a pseudo band gap cf. Eq. (10.27)). The associated free enthalpy of reaction may be taken equal to the effective band gap energy. 

Abstract. Copper phthalocyanine (CuPc)-fullerene (C60) photovoltaic cells are produced by organic vapour phase deposition reaching efficiencies of 3%. The electronic transport properties of the devices are investigated as a function of the CuPc C60 absorber blend layer composition and its preparation temperature. The analysis of the transport properties of the devices employs the one-diode model. It is shown that the dominant recombination process takes place at the donor-acceptor interfaces of the CuPc and C60 absorber domains. The activation energy of recombination is related to the effective band gap of the blend layer. 

For bulk semiconductors at room temperature, the mechanism for the resonant nonlinearity can be described by the band-filling model [82,87]. This is shown schematically in Figure 16b for a direct gap semiconductor such as CdS. Absorption of photons across the band gap, g, generates electrons and holes which fill up the conduction and valence band, respectively, due to the Pauli exclusion principle. If one takes a snap shot of the absorption spectrum before the electrons and holes can relax, one finds that the effective band gap, , increases (Figure 166), since transitions to the filled states are forbidden. The bleaching efficiency per photon absorbed can be derived as... 

Spectral response measurements of the photocurrent obtained from photoelectrodes made from this material show an effective band gap of 1.45—1.50 eV, in agreement with that expected from this composition.4... 

Spectral response of the CsSe, measured as for CdSe0. 6sTeo. 35 in Section A, shows an effective band gap of 1.75 eV. 

In this condition, and using the reduced mass of the electron-hole pair /t, one has the effective band gap energy, (keeping in mind that the energy of the lowest excited state E is the shift of g, i.e., the bandgap energy) ... 

The study on Au/TiO2(110) model catalyst performed by Goodman et al. [10] is the first study to lead to the proposal of a reaction mechanism on gold particles only . According to these authors when gold metal particles are small enough and bi-dimensional (Section 15.4.1), they lose their metallic properties due to the quantum size effect (band gap of 0.2-0.6eV), and become an active catalyst (Fig. 15.6). The role of the support would be to stabilise the small gold particles. 

Using the value of xo. the temperature dependence of the energy gap, Aeff(T), was determined from the experimental values using this expression (Fig. 9.20). It shows qualitatively the same temperature dependence as was found from the temperature dependence of the specific electrical conductivity (cf Fig. 9.16a). In particular, it exhibits the effective band gap above the Peierls transition, which is caused by the fluctuations of the one-dimensional CDW conductor and has the result that even above the Peierls transition, no genuine metallic conductivity is present. 

Broadening of the effective band gap of nanoporous layer playing role of a wide-band optical window and formation of PS layer with a variable band gap which can result in increase of photocurrent... 

Thus an effective band gap E - E exists (Fig. 2) which, for n-hexane, would be rather more than 6 eV. 

Table 1 shows the effective band gap as a function of crystallite size for CdS crystallites. The experimentally observed spectra (Fig. 9) are tlwn tte sum of widely differing spectra corresponding to various sizes, Le. inhomc neously... 

Takk L C fculated absoiption thresholds ( effective band gaps ) for CdS spherical crystallites d the indicated diameters. The shift is to higher energy than the bulk band gap. For cakxilations the CdS bairf gap has been taken to 2.S3 eV. Cafculations are from the elementary model, which overestimates the shifts for the smaller diameters [7]... 

Materials Bulk Band Gap Egb in eV Crystalline size in A Effective Band gap E b in eV Bohr radius aein A... 

Microstmcturing Glasses by Laser Processing Table 8.2. Effective band gap for various glasses [261]... 

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