Charged interface

Figure 1-3. In Ihis improved bilaycr device structure lor a polymer LED an extra ECHB layer has been inserted between the PPV and the cathode metal. The EC11B material enhances the How of electrons but resists oxidation. Electrons and holes then accumulate near the PPV/EC1113 layer interface. Charge recombination and photon generation occurs in the PPV layer and away from the cathode.

By comparing impedance results for polypyrrole in electrolyte-polymer-electrolyte and electrode-polymer-electrolyte systems, Des-louis et alm have shown that the charge-transfer resistance in the latter case can contain contributions from both interfaces. Charge-transfer resistances at the polymer/electrode interface were about five times higher than those at the polymer/solution interface. Thus the assignments made by Albery and Mount,203 and by Ren and Pickup145 are supported, with the caveat that only the primary source of the high-frequency semicircle was identified. Contributions from the polymer/solution interface, and possibly from the bulk, are probably responsible for the deviations from the theoretical expressions/45... 

Kruger J, Bach U, Plass R, Cevey L, PiccireUi M, Gratzel M (2001) High efficiency solid-state photovoltaic device due to inhibition of interface charge recombination. Appl Phys Lett 79 2085-2087... 

An anodic oxide grown in pure water at 10 pA cm-2 to thicknesses between 4 and 10 nm and subsequently annealed at 700 °C in N2 for 1 hour, showed an interface charge density (1011 eV 1 cnT2) and a dielectric breakdown field strength (11-14 MV cm-1) that are comparable with known values for thermal oxides [Ga2]. While the breakdown field strength of anodic oxides is comparable to thermal... 

Fig. 4-6. llie inner potential, 4, and the outer potential, tf, of two condensed phases A and B before and after their contact d4 )= inner (outer) potential difference between two contacting phases o = surface or interface charge dip = surface or interface dipole. 

Nanocrystalline semiconductor thin film photoanodes, commonly comprised of a three dimensional network of inter-connected nanoparticles, are an active area of photoelectrochemistiy research [78-82] demonstrating novel optical and electrical properties compared with that of a bulk, thick or thin film semiconductor [79,80]. In a thin film semiconductor electrode a space charge layer (depletion layer) forms at the semiconductor-electrolyte interface charge carrier separation occurs as a result of the internal electric... 

Interestingly, this forward current is not controlled by the interface charge-transfer kinetics but entirely by the diffusion and recombination of holes injected into the valence band. This was demonstrated by using differently doped Si electrodes having different diffusion lengths for holes. 

El Haskouri, J., M. Roca, S. Cabrera, J. Alamo, A. Beltran-Porter, D. Beltran-Porter, M. D. Marcos, and P. Amoros. 1999. Interface charge density matching as driving force for new mesostruc-tured oxovanadium phosphates with hexagonal structure, [CTA]xVG BI 0. Chem. Mater. 11 1446-1454. 

At this interface, charges are separated and form the double-layer capacitor, but because electrons can transfer freely between the two phases, the interfacial charge <2i is fixed at only one value by the equilibrium potential Eeq. 

A high barrier in the conduction band due to unfavorable band line-up or interface charge at the buffer/TCO junction may impede the majority carrier transport at this nn-junction. There are no indications for a significant barrier in standard cells but it has been made responsible for the poor performance of certain cells with alternative Cd-free buffer layers [9]. 

Fig. 9.3. Band diagrams of chalcopyrite/buffer/TCO heterojunctions illustrating the influence of buffer doping and interface charge...

McEvoy, A.J., Etman, M. and Memming, R. 1985. Interface charging and intercalation effects on d-band transition metal diselenide photoelectrodes. J. Electroanal. Chem., 190.225-241. 

Interest in the electronic properties of interfaces centers around a-Si H/Si3N4, because this combination is used in multilayers (Section 9.4) and field effect transistors (Section 10.1.2). The electronic structure of the interface is illustrated in Fig. 9.18. Apart from the band offset which confines carriers to the a-Si H layer, the distribution of localized interface states and the band bending are the main factors which govern the electronic properties of the interface. The large bulk defect density of the SijN also has an effect on the electronic properties near the interface. Band bending near the interface may result from the different work functions of the two materials or from an extrinsic source of interface charge - for example, interface states. 

The charge carrier transport model of the CoFe/MgO/CoFe nanostructure taking into account the Schottky barrier and interface charge was developed. TMR and 1-V characteristics were calculated on the basis of experimental data and modeled for different parameters of the nanostructure. Estimates of TMR are realized through the variation of height of the effective barrier for spin-up and spin-down electrons. Growth of TMR is 0.18, 0.40 and 0.55 when the energy difference between barriers is 0.02 eV, 0.05 eV and 0.10 eV, respectively. 

I-V characteristics and TMR for CoFe/MgO/Si nanostructure were modeled based on the charge carrier transport taking into account Schottky barrier and interface charge states. TMR can reach 5-25% in the range of external biases of... 

Abbreviations used p, density 0/Si, atomic ratio R, resistivity RF, refractive index BF, breakdown field DI, dielectric constant Ncd.n , effective interface charge density at flatband potential N, interface surface states density mobile ionic charge density r, ratio... 

FIGURE 3.29. Interface charge density and Vn, as a function of water content in ethylene glycol. After Mende and Hensel. ... 

S. Bengtsson and L. Engstrom, Interface charge control of directly bonded silicon structures, J. Appl. Phys. 66(3), 1231, 1989. 

ELECTROCHEMICAL INSTABILITY AT LIQUID/UQUID INTERFACES charge density in W. Similarly, for the diffuse part of the double layer in O,... 

Electrochemistry (electrodics) is concerned with chemical reactions that involve the transfer of electric charge across a solid/electrolyte interface. Charge-trcinsfer reactions are of two types one is electron transfer, the other is ion transfer together with neutralization of the ion at the surface of the solid. 

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