Carrier type

Fig. 1. Logarithmic scale of the electrical conductivities of materials categorized by magnitude and carrier type, ie, ionic and electronic, conductors. The various categories and applications ate given. The wide conductivity range for the different valence/defect states of Ti oxide is highlighted. MHD is...

The device model describes transport in the organic device by the time-dependent continuity equation, with a drift-diffusion form for the current density, coupled to Poisson s equation. To be specific, consider single-carrier structures with holes as the dominant carrier type. In this case,... 

Kuroe, A., Muramatsu, S., Fusayasu, H., et al., "Predicted Outputs of High-Frequency Carrier-Type Magnetic Head for 100 Gb/in. Generation, /. Magn. Magn. Mater, Vol. 235, 2001, pp. 382-387. 

The highly dispersible calix[4]arene neutral carriers can also improve the durability for neutral-carrier-type ion sensors. Time-course changes in both sensitivity (slope for Na+ calibration graph) and selectivity (selectivity coefficient for Na" " with respect to K+) were followed in the Na -ISFETs based on ion-sensing membranes of silicone rubber-(l), plasticized PVC-(l), and plasticized PVC-(2) (Fig. 2). Deterioration proceeded quite quickly in the Na -ISFETs of plasticized PVC-(2) both the Na+ sensitivity and selectivity... 

Selectivity coefficients values for K - and Na -ISFETs with the optimized ion-sen-sing membranes encapsulating valinomycin and bis(12-crown-4) are summarized in Fig. 9. The selectivity coefficient for with respect to Na in the K -ISFET is 2 x 10 " and that for Na with respect to in the Na -ISFET is 3 x 10. The selectivity coefficient values are similar to those for the ISFETs and ion-selective electrodes with the previous membrane materials containing the same neutral carriers. The high sensitivity and selectivity for the neutral-carrier-type ISFETs based on sol-gel-derived membranes can last for at least 3 weeks. 

Appropriate fabrication of sol-gel-derived membranes encapsulating neutral carriers such as valinomycin can afford an excellent type of neutral-carrier-type ion-sensing membranes for ISFETs [27] as already mentioned. The simple encapsulation of neutral carriers in sol-gel-derived membranes, however, has a drawback the encapsulated neutral carriers are still apt to exude from the membranes into aqueous sample solutions, which thereby makes the resulting ion sensors less durable and more toxic. Incorporation of neutral carriers to sol-gel-derived membranes by covalent bonding is desirable. 

The sol-gel-derived membrane ISFETs based on bis(12-crown-4) and valinomycin were applied for Na+ and K+ assay in blood sera [27]. For reproducibility checking, the metalion assay was carried out ten times for each sample, using two different control sera. The ISFETs gave reliable data both in Na+ and K+ assay. The coefficient of variation ranges between 0.45 and 0.78%, thus indicating excellent reproducibility in the serum cation assay with the ISFETs of neutral-carrier-type sol-gel-derived membranes. The results for real blood sera for normal human for the cation assay showed relative errors within 2% for the Na assay and within 4% for the assay. 

The authors postulated that the conductivity is proportional to the number of carriers in the film and that the mobility of polarons is equal to that of bipolarons, hence the conductivity is independent of carrier type. Thus, the conductivity increases steadily as polarons, and then both polarons and bipolarons, are generated but should attain a steady value when polaron recombination to give half as many bipolarons becomes important. 

Thus, it appears that the transition represented by the anodic peak in the cyclic voltammogram of polypyrrole is due to a changeover in the dominant carrier type and is accompanied by a dramatic contraction of the film. The authors strongly suspected that this contraction was due to electro-striction associated with bipolaron formation. As a further test they also carried out experiments intended to test if proton expulsion from the film occurred on oxidation. They found that it did indeed occur but monotonically at alt potentials > -0.6 F, in agreement with the extremely elegant work of Tsai et at. (1987), and so could not be responsible for the relatively sudden contraction at potentials > —0.2 V. 

There appear to be two major ways by which ionophores aid ions to cross membrane barriers. Ionophores such as valinomycin and nonactin enclose the cation such that the outside of the complex is quite hydro-phobic (and thus lipid-soluble). The transport behaviour thus involves binding of the cation at the membrane surface by the antibiotic, followed by diffusion of the complexed cation across the membrane to the opposite surface where it is released. Such carrier type ionophores can be very efficient, with one molecule facilitating the passage of thousands of ions per second. A prerequisite for efficient transport by this type of ionophore is that both the kinetics of complex formation and dissociation be fast. 

Criteria 6 and 7 are important because in order to vary the kinetically relevant parameters such as the spatial distribution of charge carriers and the thermodynamic driving force, semiconductor electrodes with different majority carrier types, doping densities and band gaps must be used. 

In general, a two-layer device structure is more efficient than single-layer architectures. There are two key reasons for this. First, each layer can be separately optimized for the injection and transport of one carrier type. Second, exciton formation and radiative decay take place close to the HTL-ETL interface away from the quenching sites at the organic-metal contacts. 

Typical photocurrent transients are shown in Fig. 6 for electrons and in Fig. 7 for holes. The shape of these curves is representative for all transients observed in the study and is characteristic of dispersive transport [64-68]. The carrier mobility p was determined from the inflection point in the double logarithmic plots (cf. Fig. 6b and Fig. 7b) [74]. TOF measurements were performed as a function of carrier type, applied field, and film thickness (Fig. 8). As can be seen from Fig. 8, the drift mobility is independent of L, demonstrating that the photocurrents are not range-limited but indeed reflect the drift of the carrier sheet across the entire sample. Both the independence of the mobility from L, and the fact that the slopes of the tangents used to determine the mobility (Fig. 6 and Fig. 7) do not add to -2 as predicted by the Scher-Montroll theory, indicate that the Scher-Montroll picture of dispersive transients does not adequately describe the transport in amorphous EHO-OPPE [69]. The dispersive nature of the transient is due to the high degree of disorder in the sample and its impact on car-... 

It would seem that the carrier identification would be readily resolved by experiment. In fact, numerous experiments have found the carriers to be electrons in BaPb B Og (78)(79), the carrier concentration and Tc readily scaling with Bi content until a CDW decreases the carrier density. This interpretation is well supported by a magnetic susceptibility study (80). Even though the parent compound BaBiOg is a hole type semiconductor (81), the carrier type has been shown to be n or electronic in character (75) in Ba K BiOg. 

In carrier type guns ranging from 2 5/8 to 5 inches OD, the Jet Perforators are threaded on a strand of Primacord and loaded into the gun, a steel tube which is sealed at both ends. The gun serves to control the standoff distance and prevents the well fluid from interfering with the jet formation. For through-tubing completion a smaller version of the carrier-type perforator can be supplied... 

OXIDATION RESISTANCE OF ORANGE TERPENES vs. CARRIER TYPE... 

While the infeed solids content of the infeed material has an unquestionably greater influence on the retention of volatile flavors than does the type of carrier used, carrier type does influence flavor retention during spray drying (4, 16, 31, 3Z. ... 

Breech Mechanism. The assembly at the rear of a gun which receives the round of ammo, inserts it into the chamber, fires the round by detong the primer and extracts the empty case(Refs 1,4 5). Breech mechanisms may be divided into a)Carrier -type and b)Tray-type operating mechanisms(Ref... 

Bipolar Transistors. In bipolar devices, both electrons and holes participate in the conduction process, in contrast to MOSFETs, in which only one carrier type dominates. Bipolar technology has been used typically for high-speed-logic applications. 

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