Stark effect and photoconductivity of fullerene С70 measured on samples with a submicron electrode grating and sandwich geometry

The electroabsorption (Stark effect) and photoconductivity of polycrystalline fullerene C 70 in thinfilm samples with radically different geometries (sample 1 with interdigital Cr electrodes and sandwichlike sample 2 with SnO 2 and Al electrodes) have been investigated. It is noteworthy that sample 1 is a submicron grating with 0.88-µm gaps between electrodes. When measuring electroabsorption and photoconductivity, the external voltage does not exceed 4 V. It was assumed that the small gap size may significantly affect the polycrystalline film morphology and surface effects and, as a consequence, the electroabsorption and charge carrier mobility. However, the results of the Stark effect measurements on samples with different geometries differ by only 25%, whereas the spectral photoconductivity values differ by factors of 1–2.5. The increase in photoconductivity may be related to the decrease in the carrier mobility in the sandwich sample or the increase in the number of carriers under the influence of atmospheric oxygen in the surface layer of C 70 sample with interdigital electrodes.