Effect of molecular orientation on electrical bistability of organic molecules in a monolayer

We study the effect of molecular orientation on electrical bistability of an organic molecule in a monolayer. The planer nickel phthalocyanine molecules could be oriented parallel or perpendicular to the electrode substrate in a monolayer. In this work, we report that On/Off ratio and hence the electrical bistability, transport gap, and density of states of the molecules depend on the orientation of the molecules. The transport gap of the molecules decreases upon conductance-switching. This leads to a decrease in barrier heights with electrodes and hence higher tunneling current for the high-conducting state. Multilevel conductance has been demonstrated in the monolayer of the molecules.

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► Electrical bistability in organic molecules: role of orientation of the molecules.
► Current–voltage characteristics with scanning tunneling microscope tip.
► Transport gap vis-à-vis electrical bistability.
► Multilevel conductance.