Positive electrodes distribution, generation

But even in a homogeneously doped material an etch stop layer can be generated by an inhomogeneous charge carrier distribution. If a positive bias is applied to the metal electrode of an MOS structure, an inversion layer is formed in the p-type semiconductor. The inversion layer passivates in alkaline solutions if it is kept at the PP using a second bias [Sm5], as shown in Fig. 4.16b. This method is used to reduce the thickness variations of SOI wafers [Og2]. Illuminated regions... 

Fig. 9.10. Deflection of a tube scanner. (A) Opposite and equal voltages are applied to the y electrodes of a tube scanner. The x, z electrodes are grounded. A positive stress (pressure) is generated in the upper quadrant, and a negative stress (tension) is generated in the lower quadrant. (B) At equilibrium, a distribution of stress and strain is established such that the total torque at each cross section is zero. This condition determines the deflection of the tube scanner in the y direction. (Reproduced from Chen, 1992, with permission.)...

The logarithmic response of ISEs can cause major accuracy problems. Very small uncertainties in the measured cell potential can thus cause large errors. (Recall that an uncertainty of 1 mV corresponds to a relative error of 4% in the concentration of a monovalent ion.) Since potential measurements are seldom better than 0.1 mV uncertainty, best measurements of monovalent ions are limited to about 0.4% relative concentration error. In many practical situations, the error is significantly larger. The main source of error in potentio-metric measurements is actually not the ISE, but rather changes in the reference electrode junction potential, namely, the potential difference generated between the reference electrolyte and sample solution. The junction potential is caused by an unequal distribution of anions and cations across the boundary between two dissimilar electrolyte solutions (which results in ion movement at different rates). When the two solutions differ only in the electrolyte concentration, such liquid junction potential is proportional to the difference in transference numbers of the positive and negative ions and to the log of the ratio of the ions on both sides of the junction ... 

The generation of photoexcited species at a particular position in the film structure has been shown in (6.19) and (6.20) to be proportional to the product of the modulus squared of the electric field, the refractive index, and the absorption coefficient. The optical electric field is strongly influenced by the mirror electrode. In order to illustrate the difference between single (ITO/polymer/Al) and bilayer (ITO/polymer/Ceo/Al) devices, hypothetical distributions of the optical field inside the device are indicated by the gray dashed line in Fig. 6.1. Simulation of a bilayer diode (Fig. 6.1b) clearly demonstrates that geometries may now be chosen to optimize the device, by moving the dissociation region from the node at the metal contact to the heterojunction. Since the exciton dissociation in bilayer devices occurs near the interface of the photoactive materials with distinct electroaffinity values, the boundary condition imposed by the mirror electrode can be used to maximize the optical electric field E 2 at this interface [17]. 

The dependence of S2/ >S i on the location of the electrode within the cavity may be rationalized as follows. When the electrode is at 1, B is generated by the electroreduction of A and then flows unperturbed out of the channel, so that a concentration profile of B within the charmel is established, and so that the concentration of B decreases in both X and z directions. However, when the electrode potential is stepped to 2. the concentration of B no longer varies mono-tonically with the x and z coordinates, but the precise distribution depends is determined by the electroreduction of B to C and the comproportionation reaction of A with C. In particular, at the downstream edge of the electrode, [B] rises rapidly with X and z, since B is no longer consumed electrochemically, but then passes through a maximum when C fully reacts. It is the position of this maximum within the EPR cavity that determines the ratio S2/S. ... 

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