Polythiophene precursor electrochemical nanolithography: highly local thermal and morphological characterization

We describe the formation of nanopatterns on an electroactive polythiophene precursor (polyterthiophene methylmethacrylate, P3T) film using a current-sensing atomic force microscopy (CS-AFM) technique. Patterning parameters such as applied bias voltages, sweep duration, and scan rate were adapted for the nanolithographic electrochemical patterning process. The formation of nanopatterns on the film was mainly attributed to the electrochemical cross-linking and oxidation process of the terthiophene units. This is related to the electron transport process under an applied electric field and mass transfer due to Joule heating generated in a localized area from the tip. To further highlight the role of Joule heating, thermal AFM lithography of various blend film compositions (P3T:PMMA) was made using the heated tip AFM (HT-AFM) method. The thermal effects on local morphology were then studied not only as a function of sequential increase in local temperature, but also by nano-scale direct thermal-writing.