SEMICONDUCTIVITY AND GAS-SENSING PROPERTIES OF CROWN-ETHER-SUBSTITUTED LUTETIUM BISPHTHALOCYANINES

The conductivity of thin films of crown ether (15-crown-5, 18-crown-6) substituted lutetium bisphthalocyanines has been studied in the prese nce of various gases. Under vacuum the films show intrinsic semiconduc ting properties (sigma approximate to 10(-6) Omega(-1) cm(-1)). When e xposed to an oxidant (O-2, I-2, Br-2), the molecular semiconductors ar e progressively transformed into doped insulators (sigma approximate t o 10(-9) Omega(-1) cm(-1)). Exposure to wet nitrogen yields fully reve rsible conductivity changes: a two orders of magnitude difference in c onductivity is measured on oxidized films when the relative humidity v aries from 10% to 90%.