Semiconductors induced shifts

The remarkable insensitivity ofback-ET rates to pH-induced shifts in the conduction-band edge raises the question of why cb responds to pH in the first place. Experimentally, conduction-band edges for metal oxide semiconductor electrodes, including Sn02 electrodes, are observed to shift in the negative direction... 

A first test of this model was performed with pressure experiments on InP Yb3+. Here the Yb3+ ion introduces an electron trap to the semiconductor host. The pressure-induced shift of the 2F5/2 -> 2Ft/2 intra 4f shell transitions amounts to 0.96 meV/GPa up to 4 GPa (Stapor et al., 1991), while the bandgap energy of InP increases by 85 meV/GPa (Trommer et al., 1980). 

Cerdeira F, Buchenauer CJ, Poliak FH, Cardona M (1972) Stress-induced shifts of first-order Raman frequencies of diamond- and zinc-blende-type semiconductors. Phys Rev B 5 580-593... 

Zaban and co-workers reported the use of chemical redox titrations to measure the potential of sensitizers bound to Ti02 [136], An unexpected result from these studies is that redox couples that are not pH sensitive in fluid solution become pH dependent when bound to the semiconductor surface. The magnitude of the pH-induced shift varied from 21 to 53 mV per pH unit depending on the physical location of the sensitizer. Sensitizers inside the semiconductor double layer track the 59 mV pH shift of the semiconductor. When sensitzers were outside the double layer, their potential was almost independent of the semiconductor. This finding has important implications for the determination of interfacial energetics for dye sensitization and interfacial electron transfer studies [136]. 

There are a number of mechanisms that can produce frequency shifts in the NMR spectra of optically pumped semiconductors, including the hyperfine interaction, nuclear dipolar fields, and indirect / couplings. Using optically pumped Fe-doped InP, Sauer et a/. have explored how to experimentally distinguish these shift mechanisms from one another. The /-coupling-induced shift requires only a local population indium nuclei desirable by a Zeeman spin temperature. As has been shown by the authors, the observed by them shift of 700 Hz could be reproduced with /pin = + 224 Hz at an indium spin temperature of 11 mK, corresponding to 5% local polarization. 

Vasilopoulou M, Douvas A, Geotgiadou D et al (2014) Large work function shift of ra-ganic semiconductors inducing enhanced interfacial electron transfer in organic optoelectronics enabled by porphyrin aggregated nanostructures. Nano Res 7(5) 679-693... 

In this case, we have introduced more hydrogen than those incorporated in the previously referred paper [66], Therefore, more electrons were introduced during the H2 incorporation into the perovskite. Consequently, we can conclude that the studied material at 1023-1273 K behaves as a small band gap semiconductor, because of the increase of electrons with temperature in the conduction band, due to the shifting to the conduction band of the Fermi level and the hydrogen-induced level. Then, there will be a sufficient number of electrons in the conduction band to screen the proton and allow it to have a high coordination number, and be interstitially located in the tetrahedral and octahedral sites. 

The band bending eVbb at n-type semiconductors is expected to decrease EB and additional changes of are related to changes of the electron affinity x (fig 1). As the band bending can possible be reserved by illumination a light induced opposite shift of the spectrum equivalent to a photopotential (Uph) is expected. The relation between the electrochemical energy scale Ered/ox vs NHE and the absolute energy scale E vs vacuum level is made by the relation ... 

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