Electron drift mobility

The mobility of electrons in insulating, nonpolar liquids exhibits a wide variability reflecting the intricate details of the electron/neutral interaction in the condensed phase. Data have been reported for almost 100 liquids and a good compilation of the data has appeared (Freeman, 1987). Later developments were covered in a review (Holroyd and Schmidt, 1989). A detailed description of all the mobilities which have been measured would exceed the capacity of this book. Consequently, we have to limit our discussion to a few selected examples. The physical parameters which were most varied in the published works are the temperature and the electric field strength. Much less work has been done on mixtures. 

We will first discuss the simple atomic and molecular liquids then results on liquid hydrocarbons will be presented and the section will close with a discussion of the electron mobility in mixtures. 

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For many nonpolar liquids, the electron drift mobility is less than 10 cm /Vs, too low to be accounted for in terms of a scattering mechanism. In these liquids, electrons are trapped as discussed in Sec. 4. Considerable evidence now supports the idea of a two-state model in which equilibrium exists between the trapped and quasi-free states ... 

A survey is given of the theoretical and experimental studies of electron-ion recombination in condensed matter as classified into geminate and bulk recombination processes. Because the recombination processes are closely related with the magnitudes of the electron drift mobility, which is largely dependent on molecular media of condensed matter, each recombination process is discussed by further classifying it to the recombination in low- and high-mobility media. 

Electroded TOF experiments have already been described previously [29]. They were carried out under small-signal conditions to determine hole and electron drift mobility. Carriers were generated by illuminating the sample through the... 

Figure 5.9 Hole and electron drift mobility lifetime product /xt and residual potential versus Te content in a-Scj- Te films. The /xt product was xerographically measured by Abkowitz and Markovics [14].

Fig. 28. Electric field dependence of the solvated electron drift mobility in liquid ethane at various temperatures (K). After Doldissen et al. [348].

Electroluminescence in anthracene as a result of the injection of holes by a field-enhanced tunnelling through a surface barrier when a gold electrode is employed has been investigated (Sworakowski et al., 1974), and recombination has also been reported following injection from carbon fibre electrodes (Williams et al., 1972). In all cases, because of the difference in hole and electron drift mobilities, maximum light emission occurs near the positive electrode. 

The electric field dependence of the hole mobility in a series of PVK TNF films of varying composition is shown in Fig. 5(b)17. The carrier drift mobilities are extremely low and strongly dependent on the electric field. Similar electric field dependence was observed for electron drift mobilities. The mobilities obey the empirical relation... 

TNF it is dominated by electrons. Figure 6 shows the variation of the hole and electron drift mobility with the TNF PVK molar ratio. This plot provides provides valuable information on the nature of the transport in these materials17. The figure reveals that the hole transport is associated with uncomplexed carbazole, electron... 

Fig. 6. Variation of hole and electron drift mobility with TNF PVK molar ratio17)...

FIGURE 1 Calculated electron drift mobilities at 300 K in GalnN and AlInN as a function of composition, in the limit of negligible ionised impurity scattering, after [8],... 

A.R. Tameev, Z. He, G.H.W. Milburn, A.A. Kozlov, A.V. Vannikov, A. Puchala, D. Rasala, Electron drift mobility in polystyrene doped with bispyrazolopyridine derivatives, Appl. Phys. Lett. 81 (2002) 969-971. 

Fig. 5.19. Temperature dependence of the electron drift mobility of compensated a-Si H. Data for a range of applied fields from 3 x 10 to 5 X 10 V cm" are shown (Marshall el al. 1984).

Mobility Scales with Average Inter site Hopping Distance, Gill identified an exponential dependence of electron drift mobility on average TNF intersite hopping distance and noted an associated decrease in hole drift mobility (35). Gilfs subsidiary observation that TNF addition also decreased hole mobility precisely because complexed carbazole is removed as a hole transport site provided evidence for the key role of the discrete carbazole groups in hole transport. 

Figure 7, Activation energies (e) of hole and electron drift mobilities versus applied field in a 0.2 1 TNF-PVK film. (Reproduced with permission from reference 35. Copyright 1972 American Institute of Physics, Inc.)...

Figure 6.18 Results from junction-recovery measurements on Sn02/Ti02/Au diodes. The electron drift mobility and the mobility-lifetime product are determined for various injection conditions and forward bias. The electron mobility is found to increase with increasing injection level, while the mobility-lifetime product remains approximately constant. These findings can be consistently explained in a transport model based on trap filling and a transport-limited recombination mechanism. An alternative explanation can, however, also be based on a tunnelling transport model (Konenkamp, 2000a).

O. H. Leblanc, Hole and Electron Drift Mobilities in Anthracene, J. Chem. Phys. 33(2), 626-626(1960). 

Laser Raman spectroscopy has been used as a tool to elucidate the molecular structure of crystals, liquids, and amorphous alloys in the As-S-Se-Te system. Characteristic monomer and polymer structures have been identified, and their relative abundances have been estimated as a function of temperature and atomic composition. These spectroscopic estimates are supported by calculations based on the equilibrium polymerization theories of Tobolsky and Eisenberg (1,2) and of Tobolsky and Owen (3). Correlations between the molecular structure of the amorphous alloys and physicochemical properties such as the electron drift mobility and the glass transition temperature are presented. 

Figure 12 demonstrates a relationship between molecular structure as represented by the Seg ring concentration and a physical property, the electron drift mobility. The linear correlation confirms an earlier sup-... 

This characteristic of the material can cause complications in the vicinity of blocking contacts where the conductivity type can be inverted due to band-bending effects. Thus the carrier lifetime is likely to be anomalous near blocking contacts, an effect that is particularly significant in low-quality material and in the samples in which the depletion region is a large fraction of the total thickness. This effect may be responsible for some of the difficulties that have been reported with electron drift mobility measurements on thin (s l- zm) samples (Datta and Silver, 1981). 

In my opinion, the simplest explanation of the transient phtotcurrents, namely, that they represent charges drifting from one side of the sample, is also the correct one. This conclusion is supported by Street (1982) and Kirby and Paul (1982), in addition to Spear and Steemers (1983a,b), who have investigated the question in some detail. In the remainder of this chapter we shall assume that the conventional interpretation of the electron time-of-flight experiment is the correct one and that the electron drift mobility is on the order of 1 cm V sec at room temperature. 

Fig. 7. Field dependence of the electron drift mobility. The solid line is a fit to the data with a = 0.56 in Eq. (5).

Fig. 9. Temperature dependence of the electron drift mobility for a 3.8-/im-thick sample measuredwithanappliedfieldof 10 Vcm (solid circles) and 2 X 10 V cm (open circles). The lines are fits to the data, as discussed in the text. [After Tiedje et at. (1981a).]...

The effect of hydrogen content on electron transport has been studied by Tiedje et al. (1981b) in reactively sputtered material. A series of sputtered films prepared with different H contents, varying from 10 to 20%, exhibited no systematic trend in the electron drift mobility with H content, as is illustrated in Fig. 13. The conclusion drawn from this experiment was that... 

Fig. 13. Electron drift mobility at room temperature as a function of the partial pressure of H2 in the sputtering plasma for a series of sputtered a-Si H films. The atomic percent hydrogen in the films shown in the figure increased monotonically with partial pressure from 14 to 19.5%. [From Tiedje et al. (1981b).]...

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