SPM Principles

AFM Oxidation Lithography

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AFM Anodic Oxidation Lithography is a kind of the AFM Voltage Lithography. With the help of the Voltage Lithography not only geometrical properties of the surface but also the local electrophysical properties of the sample surface can be changed. For example, by application of voltage to conductive cantilever the electrochemical processes on the surface can be stimulated under the probe tip and metalic layer can be oxidased.
Particularly tip-induced oxidation of the surface of hyperfine titanium film on the silicon substrate under normal conditions is demonstrated on the animated picture [1]. In air or other humid atmosphere the probe and the surface of the sample are covered by thin film of absorbed water. When the tip approaches sufficiently close to the surface, these absorbed layers come in contact and water bridge is produced because of capillary effect. With application of a corresponding electric field the electrochemical reaction in water-surface border, in water and in the probe will be initiated through that bridge. If the surface is positively charged and the tip negatively, then the tip and the surface will interact electrochemically as anode and cathode correspondingly. Oxide will grow on the point right under the tip.

For complex pictures Raster Lithography can be execute by using PCX-file [2]. Difference between minimum and maximum tone voltage will be applied proportionally to brightness and, correspondingly, anode oxide will grow to a different height forming different contrast of topographical image.

References

 

1. Nanotechnology 12, 273 (2001). 
2. "1st euspen topical conference on fabrication and metrology in nanotechnology". -Copenhagen, 2000. V.1, р.222-228.