Reporting their results in the journal Nanotechnology, researchers in the US (K A Brown, K J Satzinger and R M Westervelt) have proposed and demonstrated a method for performing KPFM with enhanced spatial resolution and improved resistance to topographical artifacts. The technique involves the use of coaxial AFM probes that are electrically shielded everywhere apart from at the very tip. The nanoscale electrode resembles the end of a coaxial cable.

Important feature

In the set-up, the spatial resolution of the probe is determined entirely by the size of the electrodes at the tip. This allows the users to tailor the technique and potentially offers a route to ultra-high resolution. Topographical artifacts are avoided because the tip-sample interaction changes very little with respect to the tip-sample separation.

Factor of five improvement

To demonstrate their method, the scientists created coaxial AFM probes with 50 nm thick insulating layers and calibrated the probes to measure the true work function despite the presence of the shell electrode. The configuration showed a factor of five improvement in spatial resolution over an unshielded probe.

Not only does this technique offer a way to improve the resolution and fidelity of KPFM measurements, but coaxial probes may improve any AFM measurement in which electrostatic interactions are important.

The group reported its work in the journal Nanotechnology.