Dielectric imaging capability

Liquid toners are suspensions of toner particles in a fluid carrier. The carrier is typically a hydrocarbon. Dielectric, chemical, and mechanical properties of the Hquid must be compatible with the photoreceptor, the suspended toner particles, and the materials of the development equipment. Liquid toners are capable of producing higher resolution than dry toners because of the smaller (3—5 -lm) particle size achievable. Development of the latent image occurs as it passes through a bath of toner and the charged particles are attracted to the oppositely charged surface. 

The pyroelectric coefficient p, is a useful parameter with which to compare different materials. If the thin film acts as a dielectric in a capacitor and an external resistance is connected between the electrodes, a pyroelectric current, I, flows in the circuit this can be expressed as I = pA(dT/dt) where dT/dt is the rate of change of temperature, and A is the cross-sectional area of the device. In a thermal imager many considerations, other than a high value of p, must be borne in mind,when designing a pyroelectric detector capable of resolving a temperature difference in the scene temperature of O.IK. For example, the figure of merit for a thermal imaging device requires the pyroelectric materials to have low values of permittivity. 

Both AC and DC PDFs have been used to produce fuU-color, flat-panel large area dot-matrix devices. PDP systems operate in a memory mode. Memory operation is achieved through the use of a thick-fihn current-limiting series capacitor at each cell site. The internal cell memory capability eliminates the need for a refresh scan. The cell memory holds an image until it is erased. This eliminates flicker because each cell operates at a duty cycle of one. The series cell capacitor in an AC-PDP is fabricated using a thick-film screen-printed dielectric glass, as illustrated in Fig. 7.41. The gap separation between the two substrates is typically 4 mil. The surface of the thick-fihn dielectric is coated with a thin-film dielectric material such as magnesium oxide. 

In principle, surface potential microscopy is only usable on conductive substrates. However, the accumulation layer at the insulator-semiconductor interface can be viewed as a conductive layer, whereas the bulk of the semiconductor film is just part of the gap dielectric. In other words, KPFM is capable of imaging the actual potential in the conducting channel with a 100 nm lateral resolution [87-91]. A representative example of the potential profile across the conducting channel is shown in Fig. 9. 

---