Preliminary electrical characterization of Langmuir-Blodgett films formed from the didodecyldimethylammonium salt of Pt(DMIT)2 is reported. The in-plane conductivity of the films was found to be strongly voltage dependent for lateral electric fields in excess of about 10 kV m-1. In the ohmic low-field region of the characteristic the film conductivity was approximately 3*10-6 S m-1. Under vacuum, film conductivity decreased so much that the contribution of the film to the total current flow could not be distinguished from the parallel contribution through the glass substrate. This suggests strongly that atmospheric moisture and/or oxygen are implicated in the conduction mechanism of the undoped film. Exposure to bromine vapour led to an increase of about six orders of magnitude in the in-plane conductivity. However, when the bromine was replaced by air the conductivity quickly decreased to about 0.08 S m-1. Cycling the film temperature between 284 and 300 K gave rise to an unusual observation; the current decreased by several orders of magnitude as the temperature increased. The authors believe this to be associated with changes in film structure. The higher film conductance observed after bromine oxidation was completely lost when films were placed in vacuum, suggesting complete removal of bromine from the samples. The transverse conductivity of undoped films was between two and four orders of magnitude smaller than the in-plane conductance and depended on the type of electrodes used, namely gold, ITO glass or aluminium. Transverse measurements on bromine-doped films were deemed impractical because vacuum evaporation of the counter-electrode would have caused loss of bromine from the films.
Authors: Sandeep Gupta, D.M. Taylor, Allan E. Underhill
DOI: https://doi.org/10.1088/0022-3727/26/10/028
Publish Year: 1993
