Electrical stray field energy

When a ferroelectric single crystal is cooled below the phase transition temperature the electrical stray field energy caused by the non-compensated polarization charges is reduced by the formation of ferroelectric domains, see Figure 1.19. The configuration of the domains follows a head-to-tail condition in order to avoid discontinuities in the polarization at the domain boundary, VP = a. The built-up of domain walls, elastical stress fields as well as free charge carriers counteract the process of domain formation. In addition, an influence of vacancies, dislocations and dopants exists. 

Figure 1.19 Reduction of electrical stray field energy by domain formation...

The number of tracks for interconnections is limited by the width of the interconnecting cable. A higher number of electrodes and interconnections is achieved when multi-layer strands are fabricated. We have developed double layer strands with sandwiched insulation layers of about 5 pm in thickness. Multiple metallization layers are used when concentric bipolar electrodes are fabricated. Bipolar concentric electrodes minimize the electrical stray field when applying current pulses. In this way, energy consumption for stimulation is reduced. 

The best imbedding liquid was found to be castor oil for measurements in water. Castor oil has an acoustic impedance close to that of water (so that the percentage of incident sound energy reflected at the interface is small) and a rather high absorbtion coefficient. The probe is placed in such way that the direction of propagation of the sound wave is perpendicular to the thermocouple wires. The response of the probe follows the pattern described above (see Figure 7). According to the authors, this type of probe is extremely useful because (i) it is small in size, (ii) it has a low input electrical impedance, and (iii) it is not sensitive to stray radio frequency fields. 

It often proves useful to measure the kinetic energies (KEs) of the resulting photoelectrons also. Such measurements also require use of a molecular beam so that their KEs (which are usually measured by TOP methods in a spectrometer designed to minimize stray electric and magnetic fields) can be recorded under collision-free conditions they provide the basis for a number of variants of photoelectron spectroscopy discussed below. 

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