COBDEN GROUP

Lab: Phys/Astr B308
Tel: (206) 543 0435
Fax: (206) 616 2774

Research: Scanned probe microscopy

1. Tip-modulation scanned-gate microscopy

We (well, actually Neil Wilson) have invented a new mode of scanned-gate microscopy which eliminates the nonlocal background that limits the standard scanned-gate microscopy (SGM) technique (preprint).  In tmSGM we measure the change in gating signal as a biased tip is oscillated above the sample.

tm-SGM requires a slightly more complicated setup, but the improvement in resolution, noise and locality is dramatic.

2. Nanotube AFM tips

We mounted nanotubes on AFM tips to study electrical conduction through them with sliding mercury contacts (paper) and have used them for high-resolution electric-force microscopy (EFM) probes.


Left: TEM image of a nanotube mounted on an AFM tip.  Middle: mercury dipping.  Right: current through a dipped tube.

3. New patterning techniques

We (well, actually Shiho Iwanaga, with Bruce Darling in EE) have used a voltage-biased AFM tip to write visible patterns in V₂O₅ films. Local changes in the films' optical and conducting properties can be induced (paper).  We aim to be able to write conducting patterns in an insulating film, and to understand the mechanisms involved.

Left: optical image of coloured squares (5 microns on each side) written in a V₂O₅ film using a biased conducting AFM tip.  Right: scheme of the locations where voltages were applied. First, the area inside the soled rectangle was raster scanned with +6 V tip bias, turning it green.  Then the area surrounded by the broken line was scanned at -7 V bias, turning the central square back to yellow.