| Abstrakt: |
The paper discusses results of drift mobility experiments in orthorhombic S, anthracene, trigonal and vitreous Se carried out under hydrostatic pressure pof up to 6 kbar. Some details of the experimental method are given. In the S crystals, where electrons propagate by an intermolecular hopping mechanism, the experiments show a remarkably large pressure dependence for the electron drift mobility (μe∋ exp (αp)). It is concluded, on the basis of small polaron theory, that this is caused by the increase in overlap energy between hopping states on neighbouring molecules. In narrow band materials, a less pronounced pressure dependence of μ would be expected, which is borne out by Kepler's results for anthracene. In trigonal Se, (μh c ≈ 26 cm2sec−1V−1) we found that μhwas substantially independent of pup to 5 kbar. The same applies to μeand μhin vitreous Se specimens and the implications of this result on the conduction mechanism are briefly discussed. It is also suggested that the pronounced pressure dependence of the steady dark- and photoconductivity in this material is primarily due to the effect of pressure on the injecting properties of the contacts. |
