Fabrication of a cobalt phthalocyanine free-standing film on an ionic liquid surface for memory device applications.

The fabrication of a metal phthalocyanine (MPc) film with good transferability and exploitation of its properties are very important for further application. In this study, a continuous free-standing film of CoPc was obtained on an ionic liquid (IL) surface via a physical vapor deposition (PVD) method. The as-obtained film has a β-phase structure and is constructed with one dimensional CoPc to form a network structure. The morphology of the film could be easily tuned by tunning the flow rate of the carrier gas. More importantly, the device based on these films shows obvious electrical switching and negative differential resistance (NDR) characteristics. The maximum ON/OFF current ratio of two distinctive conductivity states is ∼100 at a reading voltage of +30 V. The conductivity and conductive switching behavior of the NW constructed device are better than the device constructed with NRs. The NDR effect and electrical switching conduction mechanism can be explained by the charge trap elements of the Co II /Co I redox couples. The above results open up the possibility of CoPc as a memory medium for information storage and logic circuits applications.