d.c. Dark Hall Mobility Measurements on Anthracene

Abstract

HALL voltage measurements of mobility against temperature are normally used in the studies of conduction processes in semiconductors, but they have serious limitations for high resistivity materials. It has been found that mobility measurements down to 10⁻⁶ m²/Vs are possible provided the resistivity is less than 10³ Ω;m (ref. 1). Previously, Mitchell and Putley² constructed apparatus for measurements on specimens up to 10⁸ Ωm, having mobilities of the order of 10⁻² m²/Vs. Dobrovol-skii and Gritsenko³ have shown that for cuprous oxide specimens of resistivity greater than 10² Ωm, it is not possible to separate surface and bulk effects using Hall voltage measurements. For organic semiconductors with aromatic ring structures the bulk resistivity is of the order of 10¹² Ωm and surface effects coupled with space charge effects make Hall voltage measurements impracticable.