Loss mechanisms junctions

Semiconductor-electrolyte interface, photo generation and loss mechanism, 458 Semiconductor-oxide junctions, 472 Semiconductor-solution interface, and the space charge region, 484 Sensitivity, of electrodes, under photo irradiation, 491 Silicon, n-type... 

Although SC appears as loosely separated layers in micrographs (Figure 5), this appearance is false. It results from loss of intercellular cement during preparation for sectioning (2). However, such views do show some of the interdigitations that cooperate with desmosomes to lock cells together (44). The intercellular cement probably fills all space between these mechanical junctions in SC (32). 

Based on their observations Ho and Harker constructed a theory attributing the low and intermediate temperature loss mechanism to localised doping of the primary and secondary crystalline phases to create isolated microscopic regions of finite electrical conductivity localised within the grains and along individual grain Junctions and grain boundaries. A distribution of electrical conductivity values was shown to explain the observed frequency dependence between sapphire and alumina. 

Mechanisms 1 and 2 are included in the model that is used here for comparison with experimental data. Interface recombination and dark current effects are not included however, the experimental data have been adjusted to exclude the effects of dark current. To include the additional bulk and depletion layer recombination losses, the diffusion equation for minority carriers is solved using boundary conditions relevant to the S-E junction (i.e., the photocurrent is linearly related to the concentration of minority carriers at the interface). Using this boundary condition and assuming quasi-equilibrium conditions (flat quasi-Fermi levels) ( 4 ) in the depletion region, the following current-voltage relationship is obtained. 

Another interesting and different type of catalysis is involved in the catalyzed reconstruction of an indium oxide overlayer on indium. This study was alluded to earlier in the discussion of acetate ion species formed on indium oxide by chemisorption from several torr of acetic acid gas. At low partial pressures of acetic acid (<< 0.1 torr) the reversible adsorption of acetic acid catalyzes the reconstruction of a thin ( 10-15A), porous indium oxide overlayer to a defect-free (no pin holes) film as judged by pinhole sensitive tunnel junction measurements. Some clues as to the mechanism were obtained from IR plus Auger and electron loss spectroscopy as well as ellipsometry measurements. The overall process is shown in Fig. 8. This is an example where processes in the substrate themselves can be usefully catalyzed. 

The final type of chemical toxicity that will be presented are the vesicants, chemicals that cause blisters on the skin. There are two classes of blisters that implicate different mechanisms of vesication. Intraepidermal blisters are usually formed due to the loss of intercellular attachment caused by cytotoxicity or cell death. The second class occurs within the epidermal-dermal junction (EDJ) due to chemical-induced defects in the basement membrane components. The classic chemical associated with EDJ blisters is the chemical warfare agent sulfur mustard (bis-2-chloroethyl sulfide HD). HD is a bifunctional alkylating agent that is highly reactive with many biological macromolecules, especially those containing nucleophilic groups such as DNA and proteins. 

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