Field-Directed Sputter Sharpening for Tailored Probe Materials and Atomic-Scale Lithography

Atomic force microscopy (AFM) is a powerful technique, but limited by the fact that probe tips made of silicon are fragile and quickly break or become blunt.  There is a need to develop AFM probe tips that are simultaneously very sharp and very hard. Here is shown a depiction of the field-directed sputter sharpening (FDSS) process, a new method to sharpen AFM probe tips. Incoming ions are deflected by the inhomogeneous electric field of a biased probe, resulting in reduced sputtering at the sharpest part of the probe. This increases the sharpness, which increases the local field inhomogeneity, ultimately leading to a self-limited sharpness. This is demonstrated for a tungsten STM tip in the middle images, showing before and after FDSS TEM images and a final tip radius of ~1 nm. The bottom images show before and after TEM images of a hafnium diboride-coated AFM probe. These FDSS processed probes are now being marketed by Tiptek, LLC, which is a startup company co-founded by CNEM participants Gregory Girolami and Joe Lyding and Advisory Board member Scott Lockledge.

Doc.: http://www.nature.com/ncomms/journal/v3/n7/full/ncomms1907.html

Schmucker, S., Kumar, N., Abelson, J., Daly, S., Girolamy , Bishof, . . . Lyding. (2012). Atomic force microscopy (AFM) is a powerful technique, but limited by the fact that probe tips made of silicon are fragile and quickly break or become blunt. Field-directed sputter sharpening for tailored probe materials and atomic-scale lithography. Nature Communications.