Electronic transport in crystalline siloxene

For the planar silicon polymer siloxene the anisotropy of the dark conductivity is determined to be about 10(3), with a conductivity parallel 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 optical bandgap. A pronounced photoconductivity is found, which is several orders of magnitude larger than the dark conductivity. At low temperatures, the photoconductivity is thermally activated with an activation energy of 40 meV. The same energy is found for the Urbach-slope parameter in the subgap absorption of siloxene crystals determined with photothermal deflection spectroscopy. (C) 1997 Elsevier Science Ltd.