Resistive Switching of Tetraaniline Films: From Ultrathin Monolayers to Robust Polymeric Blends

Oligomers of aniline and their derivatives have electrical and chemical properties that parallel those of polyaniline, while having the advantage of being available as homogeneous, chemically pure materials. Despite this advantage, little experimental data is available on the electrical transport properties of thin films of oligoanilines compared to polyaniline. Here, we investigate three types of ultrathin films (<50 nm thick) containing the emeraldine form of tetraaniline (TANI): self-assembled monolayers of the dithiocarbamate (DTC) derivative, spin-coated films of TANI, and spin-coated films of TANI/polymer blends. The electrical characteristics of these films, ranging in thickness from ∼1.4 nm (TANI-DTC monolayers), to ∼14 nm (neat TANI), to ∼40 nm (TANI/polymer blends), are obtained in junctions using Au and Hg-drop electrodes. High conductance on/off ratios between the emeraldine salt (on-state) and emeraldine base (off-state) are observed in all four systems (∼103–105 at V = +0.5 V), as demonstrated by exposing the as-prepared films to HCl vapor. Both the high electrical response toward acid doping and the mechanical robustness in TANI/polymer blends point toward oligoanilines as promising substitutes for polyaniline in next-generation molecular thin film devices.