Surface Characterisation and Modification by the Scanning Electrochemical Microscope (SECM)

Abstract

Methods of surface analysis and micromodification using the scanning electrochemical microscope (SECM) are described. An ultramicroelectrode (UME) is scanned in a liquid electrolyte a few microns above a sample's surface. The principles of SECM are explained. Local surface conductivity and reactivity can be imaged in the feedback and collector/generator mode. The same set‐up allows micromodification processes as well. The degree of doping of polyaniline deposited on a PETG film was increased locally. The generated structure formed an inter‐digital array consisting of doped and undoped polyaniline. Its local conductivity was successfully analysed in a second step. To fabricate a polymer microstructure the monomer 2,5‐bis(1‐methyl‐pyrrol‐2yl)‐thiophene was deposited by evaporation on an ITO substrate. Polymerisation was induced by the tip via an oxidation reaction. The remaining monomer was easily removed by organic solvents. A new method for the microdeposition of silver on a gold substrate is described. Silver cations were complexated in an aqueous solution of ammonia. Protons locally generated by the tip shifted the complexation equilibrium to create free silver cations. When the sample is held on an adequate potential they were deposited on the gold surface.

Advanced syntheses and microfabrications of conjugated polymers, C60-containing polymers and carbon nanotubes for optoelectronic applications

“…Polymerization of aniline in a microstructured fashion was achieved in spincast anilinium sulfate-containing Nafion onto a Pt electrode in a SECM unit [428], while electrochemically active polyaniline particles with a size ranging from 100 to 600 A Ê in diameter and 10 to 200 A Ê in height were prepared by using a Pt STM tip as an electrode for the electropolymerization of aniline [429]. Using the tip of a SECM as an electrode for region-specific oxidation of bromide into bromine, followed by the diffusion of the bromine into a conductive substrate covered with a thiophene derivative for a localized oxidative polymerization of thiophene monomers, a polythiophene line of width 20 "m has been successfully prepared [430]. The scanned probe technique has also been used for local deposition of C 60 molecules, as demonstrated by the region-specific position of C 60 along a one-atom-high step on a copper surface using a STM tip ( Fig.…”

Elektrochemische Rastermikroskopie zur direkten Abbildung von Reaktionsgeschwindigkeiten

“…[164] Nach Auflösung des AgCl verbleibt eine Silberlinie auf der Oberfläche, wobei das Substrat auch isolierend sein kann. [165] Schließlich lassen sich Polymerstrukturen bilden, wenn ein in der Arbeitslösung Abbildung 12. Möglichkeiten zur lokalen Oberflächenmodifikation.…”

Parallel Imaging and Template‐Free Patterning of Self‐Assembled Monolayers with Soft Linear Microelectrode Arrays

“…[1][2][3][4][5][6] The electrolytic generation of a reactive compound at the microelectrode (i.e. the SECM probe) allows the chemically well-defined transformation of various materials and layers that can be quantitatively controlled by adjusting the working distance, electrolysis current, and electrolysis time.…”

“…[5,7] Particular versatile are modifications relying on the use of probe-generated Br 2 that may form HOBr upon disproportionation in alkaline or neutral solution. Br 2 and HOBr act as oxidants and have been used for semiconductor etching, [1,8] polyaniline deposition, [3] and the deactivation of enzyme layers. [2] Other probe-generated reagents include metal ions for metal deposition, [9,10] catalytically active metal ions, [11] and aryl diazonium salts.…”