The Use of a Scanning Tunneling Microscope to Estimate Film Thickness and Conductivity of an Electrochemically Produced Poly-1 -Aminoanthracene Film

An electronically conductive poly-l-aminoanthracene (PAA) film was prepared electrochemically on Pt, Au, and C substrates by cycling the potential between -0.40 and +0.80 V in MeCN/TBAPF₆ solutions. Adding pyridine to the solution resulted in a marked increase in the growth rate of the polymer film, as indicated by a large increase of faradaic current. A new scanning tunneling microscopy (STM) approach is also presented to determine film thickness and film conductivity through measuring the tip current vs. tip displacement. In this approach, the tip excursion between its initial contact with the polymer film and its contact with the Pt substrate is a measure of film thickness. A comparison of the STM current-displacement behavior in the poly-l-aminoanthracene film to that of a polypyrrole film relates to film conductivity. The PAA film was about an order of magnitude less conductive than polypyrrole.