Conductive Behavior and Morphology of Axially Modified Gallium Phthalocyanine Thin Films onto Indium Tin Oxide Substrates.

Semiconductor molecular films based on a gallium phthalocyanine chloride (GaPcCl) and a bidentateamine were prepared by using vacuum thermal evaporation and electrochemical techniquesin order to investigate the preferred conduction paths within the films. Scanning Electron Microscopy(SEM) and Atomic Force Microscopy (AFM) were employed to characterize the morphologyof the films. The conductivity measurements were performed with two different methods in orderto investigate preferential conduction directions. The film transverse conductivity was obtainedby using scanning tunneling spectroscopy (STS) and the in-plane film conductivity was measuredwith a four-point probe system. From spectroscopy measurements, the tunneling conductance(dI/dV) was also obtained. From these results, it was found that the conductive nature of the filmswas strongly influenced by the deposition technique which in turn defined the morphologicalcharacteristics of the film. The evaporated method showed better conductivity response and providedsemiconductor characteristics in the film transverse direction with an in-plane ohmic response.Finally, contact angle measurements were performed and showed hydrophobic characteristicsin all cases.