Guard rings

Fig. 4.1. As shown on the left, the configuration of conducting plates on the flat faces of piezoelectric disks produces one-dimensional strain and electric field conditions with a guard-ring arrangement. On the right, the typical electrostatic conditions are shown. The axis through the thickness of the disk is chosen as the x axis.

To operate the ion TOF spectrometer in the velocity mode, we adapted a single-stage TOF spectrometer as shown in Fig. 3, which consisted of a repeller, an extractor (and guard rings, not shown) and a free-drift tube. After laser ionization, ions are extracted towards the MCP detector. For an ion with an initial kinetic energy Do, the total flight time t can be written as... 

Figure 6.12 Cross-sectional view of the 4H-SiC power BJT fabrication, (a) Starting epilayer structure. (b) Dry etching of emitter and base epilayers. (c) p implantation for guard rings and contacts to p-base. (d) Formation of ohmic contacts, (e) Over layer metal deposition, (f) Double metal process.

Electrical Measurements. Dielectric and I-V characteristics were determined on simple guard ring-dot MIS structures consisting of A1 - polyimide - degenerate silicon of resistivity 0 -. 02 ficm. 

Figure 1.5 (a and b) Typical electrode configurations used for the measurements of thermally stimulated currents. The sample surface ceU (a) may be augmented by additional contacts (b)-(d) to monitor potential distribution along the sample. The sandwich cell (e)-(h) is ideally suited for the use of guard rings of either rectangular or circular shapes. 

The technique of pellet preparation and the guard-ring electrode cell were described previously (8). The density of the pellets is 61% of the real zeolite density. No structural damage is observed with x-ray diffraction after pellets are made. 

Fig. 6. Conductivity methods, a) guard ring techniques, b) potential probe technique...

Thus, it is concluded that as far as possible experiments should be made on single crystal samples using guard ring techniques under conditions where the ambient atmosphere may be rigorously controlled. In the case of polymers single crystal samples of any size are virtually impossible to obtain. 

In any discussion of photoconductivity the importance of the ambient atmosphere and surface must be considered. Not only is the magnitude of the photocurrent dependent on the state of the surface but the provision of guard rings may completely alter the spectral response of the photocurrent. This, it has been suggested, is because the mobility of charge carriers is greater over the surface than through the bulk (35). 

Figure 13-1. Electrode systems, (a) Showing fringing effect and surface conduction in volume resistivity measurement (b) showing volume conduction in surface resistivity measurement (c) electrodes, guard ring and circuit for volume resistivity measurement (d) electrodes, guard plate and circuit for surface resistivity measurement. (G = glavanometer or other current measuring device.)...

A native oxide layer on an n-type mercury cadmium telluride substrate 11 is used in combination with ZnS to provide first level insulation 12. The ZnS is deposited by thermal evaporation and an opaque field plate is provided for signal channel definition. Second level insulation of ZnS is deposited. This layer is thicker than the first level, and is provided with a stepped or sloped geometry under the first level gates. Input and output diodes are provided with MIS guard rings to increase breakdown voltages. 

Provided that morphology does not change. The dependences on component potential and doping have to be discussed analogously. 5 An alternative technique uses guard rings.289... 

Fig. 5.22 Schematic diagram of a guard ring and circuit for measurements of high resistivity.

It is now necessary to describe the determination of conductivity in ionic solids. The circuit shown in Figure 8.9 is only a schematic representation. This type of measurement in high-impedance samples of ionic solids causes experimental problems that are avoided with the help of the so-called guard ring circuit, which prevents leakage currents affecting the measurement [16]. Besides, these circuits use an amplifier to deal with the high resistance of the sample. 

Fig. 2. Perspective cross sectional view of the temperature controlled drift cell after Kemper and Bowers design [22] (a) cooling line, (b) cell body, (c) buffer gas inlet, (d) cell end cap, (e) drift guard ring, (f) ion entrance hole, (g) ion focusing lens, (h) ceramic ring, (i) ion exit hole, (j) ceramic rod holding guard rings, (k) ceramic rods holding cell assembly...

The high resolution drift tube is fabricated from a six-inch diameter steel tube divided into three sections separated by ceramic breaks. The field in the interior is maintained by copper beryllium drift guard rings, connected to each other by a resistor chain. In Jarrold s apparatus [36] the ion exit hole has a diameter of 0.13 mm. The drift tube temperature is controlled by jackets around each section and by a recirculator with non-conducting temperature regulated fluorocarbon fluids. 

Fig. 5.5 A 3-terminal specimen holder (a) diagram of shielded electrode system with guard ring, (b) equivalent electrical circuit of the cell.

Berget applied the so-called guard-ring principle. 

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