FORMATION AND ELECTRICAL CHARACTERIZATION OF LANGMUIR-BLODGETT-FILMS OF METAL (DMIT)(2) CHARGE-TRANSFER SALTS

The pressure-area isotherms of mono- and divalent octadecylpyridinium M(dmit)2 charge transfer salts (M = Au, Pd or Pt) are presented and th e behaviour contrasted with previously reported results for tetraalkyl ammonium M(dmit)2 salts. The current voltage characteristics of Y-type Langmuir-Blodgett films of both salts showed similar behaviour upon d oping with bromine or iodine vapour. Immediately upon doping the condu ctivity of the films increased by many orders of magnitude but within a few hours this enhanced conductivity had decreased to an almost stab le value which was still several orders of magnitude greater than in t he undoped film. Interestingly, in this state the current-voltage char acteristic showed a clear square-law behaviour. Within a day or two, h owever, the contribution of this process to the overall conductivity d ecreased to reveal a stable ohmic behaviour from which the film conduc tivity was estimated to be 0.06 S m-1.