Hydrogen diffusion coefficient

Fig. 16. Hydrogen diffusion coefficient as a function of inverse temperature.

For completeness it should be mentioned that the passivation of gold, presumably via the same AuH complex, has also been studied in p-type silicon, where it is the donor rather than the acceptor level of gold that is active (Hansen et al., 1984). Though no profiles were reported in this work, apparent hydrogen diffusion coefficients inferred by these authors are of the same order as the Pearton (1985) points of Fig. 16 at temperatures 110°C and below. 

Fig. 14. Time dependence of the hydrogen diffusion coefficient for a p-type doped a-Si H sample annealed at 200°C (Street et al., 1987b).

The concentration profile studies find that the hydrogen diffusion coefficient in a-Si H is thermally activated, as shown in Fig. 17 (Street et al., 1987). Over the temperature range of 130 to 300°C, the diffusion data is described by the Arhennius expression... 

Fig. 19. Hydrogen diffusion coefficient, measured at 240°C, as a function of phosphine and diborane gas phase doping level, deduced from the data in Fig. 17. The dependence on dangling bond density is indicated on the top horizontal scale (Street el al., 1987b).

Fig. 22. Arhennius plot of the hydrogen diffusion coefficient for n-type a—Si=H (HT 4[PH3]/SiH4]), comparing the fast diffusing component in columnar material with data for a noncolumnar sample (labeled normal) (Street and Tsai, 1988).

Exposure of bulk GaAs Si wafers to a capacitively coupled rf deuterium plasma at different temperatures generates deuterium diffusion profiles as shown in Fig. 1. These profiles are close to a complementary error function (erfc) profile. At 240°C, the effective diffusion coefficient is 3 x 10 12 cm2/s. The temperature dependence of the hydrogen diffusion coefficient is given by (Jalil et al., 1990) ... 

Lastly, we studied the effect of 7-stress on the effective time to steady state and the corresponding magnitude of the peak hydrogen concentration. We found that a negative T -stress (which is the case for axial pipeline cracks) reduces both the effective time to steady state and the peak hydrogen concentration relative to the case in which the T -stress effect is omitted in a boundary layer formulation under small scale yielding conditions. This reduction is due to the associated decrease of the hydrostatic stress ahead of the crack tip. It should be noted that the presented effective non-dimensional time to steady state r is independent of the hydrogen diffusion coefficient D 9. Therefore, the actual time to steady state is inversely proportional to the diffusion coefficient (r l/ ). 

One possible general approach to calculate the conductivity in proton conductors is the phenomenological approach applying the formalism of nonequilibrium thermodynamics [13] (Section 5.7.6) to calculate the FIGURE 8.10 Hydrogen hydrogen diffusion coefficient in oxides [36],... 

Fig. 2.20. The temperature dependence of the hydrogen diffusion coefficient at different doping levels as indicated (Street, Tsai, Kakalios and Jackson 1987b), including data from Carlson and Magee (1978).

The hydrogen diffusion coefficients shown in Pig. 2.20 are thermally activated. 

Fig. 2.22. The power law decrease in the time dependence of the hydrogen diffusion coefficient of p-type a-Si H (Street et at. 1987b).

The hydrogen diffusion coefficient is not constant, but decreases with time (Street et al. 1987b). The data in Fig. 2.22 show a power law decrease in p-type a-Si H of the form r , with a 0.2 at the measurement temperature of 2(X) C. The time dependence is associated with a distribution of traps originating from the disorder. A similar effect is found in the trap-limited motion of electrons and holes and is analyzed in Section 3.2.1. The time dependence of is reflected in the kinetics of structural relaxation discussed in Section 6.3.1. 

Fig. 6.23. A test of Eq. (6.89) relating the relaxation time to the hydrogen diffusion coefficient. Many different manifestations of the equilibration process are included in the data (Jackson and Moyer 1988).

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