ELECTRONIC TRANSPORT IN CRYSTALLINE SILOXENE

For the planar silicon polymer siloxene the anisotropy of the dark con ductivity is determined to be about 10(3), with a conductivity paralle l to the silicon planes of 10(-11) (Omega-cm)(-1) and perpendicular to the planes of 10(-14) (Omega-cm)(-1) at 250 degrees C. An activation energy of 1.25 eV is determined, which is approximately half of the op tical bandgap. A pronounced photoconductivity is found, which is sever al orders of magnitude larger than the dark conductivity. At low tempe ratures, the photoconductivity is thermally activated with an activati on energy of 40 meV. The same energy is found for the Urbach-slope par ameter in the subgap absorption of siloxene crystals determined with p hotothermal deflection spectroscopy. (C) 1997 Elsevier Science Ltd.