Scanning probe nanolithography of conducting metal oxides

The scanning tunneling microscope (STM) was used to form nanometer-size holes in thin conducting films of thallium (III) oxide. Hole formation was only observed when the process was performed in humid ambient conditions. The hole formation was attributed to localized electrochemical etching reactions beneath the STM tip. Etching reactions consistent with the observed hole formation are a direct electrochemical reduction of thallium (III) oxide to soluble Tl (I) at negative sample bias, and local reduction of pH at positive sample bias. The fastest etching was observed at negative sample bias. Holes as small as 10 nm or as large as 1 μm in diameter could be etched in the films.