Surface/Low-Temperature Physics
Prof. Joe Amato is using a new technique for modifying surfaces of metallic thin films with an atomic force microscope (AFM). By passing electric current from a conducting AFM tip to the film, a small spot on the film will be oxidized. The spot diameter is less than 100 nm (0.1µm), and the spacing between spots can be as small as 200nm. A square array of 16 oxidized spots on a niobium thin film is shown below. Note the scale of the figure: the diameter of a human hair is about 100 µm. Niobium is a superconducting element, and the anodized spots are used to control the motion of superconducting vortices.
Initial anodization of patterns of the surfaces yielded the picture below.
More recently the patterning has become much more sophisticated and precise. The figure below shows square arrays of vortex pinning sites, which were formed on a thin film of MoGe. The pinning sites are oxidized regions of the film 150 nm in diameter, spaced 400 nm apart.
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This is a view of anodization spots on the surface of a 4-um wide thin film. A more detailed view of this pattern is shown below.
Measurements of the magnetoresistance of this films are new. Results are forthcoming.
This research has been supported by Research Corporation and a Senior Leave Grant from Colgate University.
Recent results on making anodization spots on surfaces:
Recent publications:
"Periodic Pinning Arrays Produced by Atomic Force Microscopy", J.C. Amato, T.S. Bramfeld, J.J. Bonifacio, Bull. Am. Phys. Soc. 44 (1) 1286 (1999).
"AFM Production of Periodic Pinning Arrays on Superconducting Thin Films", J.C. Amato, Jason Stewart, Patrick Heaney, CUR 2000 Conference at College of Wooster, OH (June 22, 2000).
"AFM Production of Periodic Pinning Arrays on Superconducting Thin Films", J.C. Amato, Jason Stewart, Patrick Heaney, Bull. Am. Phys. Soc. 46(1) 435 (2001).
[Background image was created by scanning the patterning of a surface via light interference. This work was done by Jessica Frank '01]
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