Lithographic Applications of Redox Probe Microscopy

Abstract

The molecular-scale lithographic applications of a technique which we have developed and termed redox probe microscopy, RPM, in which an AFM tip is modified with redox-active materials, are presented. In this technique, the interactions between the tip and an adsorbate or between the tip and a surface are modulated by means of the electrode potential, allowing for the generation of desired surface structures and patterns. Two cases are presented: (a) the use of an RPM tip to deliberately manipulate and position objects (“microtweezers”) and (b) the utilization of an RPM tip to “pattern” a pH-sensitive block copolymer using what we term the “pH-stylus”. In the first case, the AFM tip is modified with a film of poly(vinylferrocene) and the adhesive interactions of the modified tip with sulfonated chromatography beads are deliberately controlled to be either strong or weak depending on the redox state of the ferrocene centers, allowing for the deliberate positioning of the beads to generate a pattern. In the pH-stylus, an RPM tip is modified with a hydroquinone self-assembling monolayer which upon oxidation releases protons. By a scan of such a modified tip over a pH-sensitive block copolymer and control of the electrode potential, the polymer film can be exposed to generate patterns.

Nanolithography and Nanochemistry: Probe‐Related Patterning Techniques and Chemical Modification for Nanometer‐Sized Devices

“…Ober et al [129] introduced a technique called redox probe microscopy (RPM), in which an AFM tip was modified with redox-active materials. When a potential was applied, the tipsurface interaction could be switched.…”

In Situ Observation of the Surface Processes Involved in Dissolution from the Cleavage Surface of Calcite in Aqueous Solution Using Combined Scanning Electrochemical–Atomic Force Microscopy (SECM‐AFM)

“…This simple analysis indicates that this methodology can be used to “dose” a target surface with a defined amount of reagent (protons). This method complements a recent study in which an gold AFM tip and cantilever covered with a monolayer of thio‐hydroquinone were used to produce protons 29…”

Application of scanning probe microscopy to the characterization and fabrication of hybrid nanomaterials

“…Maynor et al (2002) fabricated nanowires of conductive poly(thiophene) on a silicon substrate by in situ oxidative polymerization of the 3,4-ethylenedioxythiophene monomer using E-DPN. Agarwal et al (2003a) Diaz et al (2001) introduced an alternate approach to electrochemical nanolithography in which an AFM probe coated with a redox active material is electrochemically activated for lithography. These authors demonstrate the use of an AFM tip modified with a hydroquinone terminated monolayer, which releases hydrogen upon oxidation to the quinone, to perform local modifications of a pH-sensitive block copolymer on a silicon substrate.…”