Joe Amato at Colgate University

Joe Amato, Ph.D., at Colgate University, uses a Dimension 3100 (from Veeco Metrology Group) fitted with an nPoint N-XY100A nanopositioner. The AFM tip is used to locally oxidize niobium thin films. The resulting oxide dots are about 100nm in diameter and 6-12nm thick.

Each dot is a pinning site for superconducting vortices. In operation, the AFM tip is raised off the film surface and the film is moved via the nPoint x-y stage, which is controlled by National Instruments' LabVIEW™ software program and a DAQ card. The tip is returned to the surface and an oxide dot is formed by passing a current from the tip through the film. The tip is again raised and the stage moved to form a periodic array of oxide dots. The stage is easy to control and it has permitted a ten-times increase in translational speed over the original AFM scanner. An array of dots can be oxidized at a rate of about 2 per second; the speed limited only by the anodization time rather than the stage movement. The nPoint x-y stage gives the ability to make low distortion arrays, increases the speed, and improves the uniformity of the dots. The ultimate goal is to make arrays of 4000-8000 dots.