Characteristic electrical

The forward and reverse characteristics for a Schottky diode formed with an aluminium/polyacetylene Schottky junction and a gold ohntic contact (polyacetylene thickness 500 nm) is shown in figure 13. This device shows a particularly good characteristic with a high forward te reverse ratio which reaches a maximum of S x 1(P at a bias of 1.5 V, and is lintited at this value by the high bulk resistance of the undepleted polyacetylene layer. We note that this value is very much higher than values found previously for Schottky barriers formed with Shirakawa polyacetylene and other conjugated polymers [57-62,64]. 

The slope of log(J) versus V gives the ideality factor, n = 1.3 at low biases. This value, though larger than 1, is considerably smaller than found for other polymer Schottky barriers, and we consida that it is appropriate to analyse the data here with the models 

We have obtained some limited data for the J(V) characteristics as a function of temperature. In the range between room temperature and 240 K, Jq can be fitted to an activated temperature dependence, with an energy of activation of about 0.8 eV. However, the ideality factor also increases as the temperature falls, and we do not consider that the data can be used to resolve between the different prefactors in the thermionic emission and diffusion models (equations 16 and 14 respectively). However, we note that the activation energy within the diffusion model is equal to the sum of the barrier height and the activation energy for the mobility. From section 4.2 the latter is expected fo be in the range 

3 to 0.4 eV, and we consider that the 0.8 eV measured here may be consistent with the barrier height as previously determined. 

Junctions formed with indium and with chromium also showed reasonable Schottky barrier formation, though we find in general that the ideality factors for these devices were poorer than for the aluminium structures, with values of 2 found in both cases. There is some variation in the barrier height deduced from the value of Jq fitting to the diffusion model using the same parameters as used above we find lower values for )b, of 0.34 eV for chromium and 0.42 eV for indium. 

There are bulk and contact components to the dark current. The bulk current originates from charge generation through gap states. Electrons are excited from the valence band to empty gap states and from filled traps to the conduction band. These excitations generate electron-hole pairs which are separated and collected by the internal 

There is a larger thermal generation current when the voltage is first applied, because the equilibrium E. is above Ef Y  

The depletion charge in low defect density a-Si H is 7 x 10 C cm , AE is about 0.1 eV and the leakage current has a decay time constant of about 100 s. Thus the thermal generation current is estimated to be 

The low voltage data in Fig. 10.5 are explained by the thermal generation current. As formulated above, has no voltage dependence. However, the generation current is reduced when the bias voltage is too small to deplete the sensor, because not all the electron-hole pairs are collected. This is indicated by region A in Fig. 

The contact leakage current for an ideal Schottky barrier is the saturation current J, which depends on the barrier height according to Eq. (9.14). Examples of the forward J-V characteristics of some p-4-n sensors are shown in Fig. 10.6 and compared with a palladium Schottky barrier sensor. The ideality factor of the p-i-n devices is 

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Sulfur hexafluoride [2551-62-4] 6 molecular weight 146.07, is a colorless, odorless, tasteless gas. It is not flammable and not particularly reactive. Its high chemical stabiUty and excellent electrical characteristics have led to widespread use in various kinds of electrical and electronic equipment such as circuit breakers, capacitors, transformers, microwave components, etc (see Electronic materials). Other properties of the gas have led to limited usage in a variety of unique appHcations ranging from medical appHcations to space research. 

The glass-ceramic phase assemblage, ie, the types of crystals and the proportion of crystals to glass, is responsible for many of the physical and chemical properties, such as thermal and electrical characteristics, chemical durabiUty, elastic modulus, and hardness. In many cases these properties are additive for example, a phase assemblage comprising high and low expansion crystals has a bulk thermal expansion proportional to the amounts of each of these crystals. 

Electrical Properties. Erom a chemical standpoint, HDPE is a saturated aUphatic hydrocarbon and hence a good insulator. Its electrical characteristics are given in Table 1. Because polymer density and molecular weight affect electrical properties only slightly, HDPE is widely used for wire and cable insulation. 

Properties desired in cable insulation and flexible circuit substrate materials include mechanical flexibiUty, fatigue endurance, and resistance to chemicals, water absorption, and abrasion. Both thermoplasts and thermosets are used as cable-insulating materials. Thermoplastic materials possess excellent electrical characteristics and are available at relatively low cost. 

The electrical characteristics of ceramic materials vary gteady, since the atomic processes ate different for the various conduction modes. The transport of current may be because of the motion of electrons, electron holes, or ions. Electrical ceramics ate commonly used in special situations where reftactoriness or chemical resistance ate needed, or where other environmental effects ate severe (see Refractories). Thus it is also important to understand the effects of temperature, chemical additives, gas-phase equilibration, and interfacial reactions. 

Surge arresters Electrical characteristics of a ZnO surge arrester Basic insulation level (BIL) ... 

The electrical characteristic of a buried pipeline corresponds to that of an extended ground with a longitudinal resistance (see Section 24.4.2). The longitudinal resistance, / , related to the length I is described by Eq. (24-70) and is termed the resistance per unit length (resistance load), R. ... 

In 1930 BASF, then part of IG Farhen, installed a plant for producing 100 tonnes of polystyrene per annum and in 1933 the first injection moulded articles were produced. In the US semi-plant-scale work at the Dow Chemical Company showed promise of commercial success in 1934. As a consequence there became available shortly before World War II a material of particular interest because of its good electrical insulation characteristics hut otherwise considerably inferior to the polystyrene available today. Because of these excellent electrical characteristics prices were paid of the order of several dollars per pound for these polymers. 

The electrical insulation properties of the acetal resins may be described as good but not particularly outstanding. There are available alternative materials which are better insulators and are also less expensive. There are, however, applications where impact toughness and rigidity are required in addition to good electrical insulation characteristics, and in these instances acetal resins would be considered. Table 19.3 lists some of the more important electrical characteristics of Delrin acetal resin. Data for the trioxane-based copolymer resin (e.g. Celcon) are virtually identical. 

D. Performance characteristics. (Usually includes following electrical characteristics efficiency, power-factor, locked rotor KVA, fullload speed, temperature rise and starting, break-down, and full-load torques.) Be sure to advise whether special test certification is to be furnished this always extends delivery time and increases cost. 

Figure 2-75. Lumped element models of transmission line electrical characteristics.

Constant-speed motors are usually suited for a speed range of less than 3 to 1 by field control, but mechanical and electrical characteristics govern maximum safe speeds. With constant voltage on the armature, as the field is weakened the speed increases and the motor develops constant horsepower. 

Electrical characteristics of surface films formed electrochemically can be analysed using frequency response analysis (FRA) (sometimes called electrochemical impedance spectroscopy, or This technique is... 

The electrical characteristics of the cell and electrode will comprise both capacitative and resistive components, but for simplicity the former may be neglected and the system can be represented by resistances in series (Fig. 19.36 > and c). The resistance simulates the effective series resistance of the auxiliary electrode A.E. and cell solution, whilst the potential developed across by the flow of current between the working electrode W.E. and A.E. simulates the controlled potential W.E. with respect to R.E. 

The photoinduced absorption and the electrical characteristics of the conjugated LPPP show that the optoelectrical properties are strongly dependent on charge carrier traps in the bandgap. From aromatic molecular crystals it is known that impurities and structural imperfections form localized states [34]. LPPP forms homogeneous and dense films with a mean interchain distance of about 20 A and ncgligi-... 

Figure 16-39. Electrical characteristics of the 1TO/OPV5/AI devices U-OPV5 (A), Oocl-OPV5 (O). and Ooct-OPV5-CN" ( ). The arrows indicate the onset of light emission.

Figure 16-41. Electrical characteristics lor single-layer ITO/Oocl-OI V.VAI devices with an as-deposited (O) or annealed (I20"C, 5 min 0) active layer. Inset luminance as a function of cell current for both thin-filin morphologies.

In this section the electronic structure of metal/polymcr/metal devices is considered. This is the essential starting point to describe the operating characteristics of LEDs. The first section describes internal photoemission measurements of metal/ polymer Schottky energy barriers in device structures. The second section presents measurements of built-in potentials which occur in device structures employing metals with different Schottky energy barriers. The Schottky energy barriers and the diode built-in potential largely determine the electrical characteristics of polymer LEDs. 

Recently, Mailiaras et al. [ 1511 have shown that for the analysis of the current-voltage characteristics of single layer OLEDs, it is of fundamental importance to properly account for the built-in potential. The electrical characteristics of MEH-... 

Electrical measurements on devices with different layer thickness have shown that the diode current depends on the applied field rather than the drive voltage. This is similar to what has been observed with our alternating PPV copolymers [68]. It indicates that field-driven injection determines the electrical characteristics. From Figure 16-39 it is evident that U-OPV5 has the lowest onset for both current and emission. By means of Fowler-Nordhcini analysis of the /-V -charac-teristics and optical absorption measurements, wc estimated the injection barrier for holes and the HOMO-LUMO gap, respectively [119]. The results of... 

Model Electrical characteristics (at room temperature) Dimensions (mm) Weight... 

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