With the goal of expanding the capabilities of focused ion beam microscopy and milling systems, we have demonstrated nanoscale focusing of chromium ions produced in a magneto-optical trap ion source (MOTIS). Neutral chromium atoms are captured into a magneto-optical trap and cooled to 100 µK with laser light at 425 nm. The atoms are subsequently photoionized and accelerated to energies between 0.5 keV and 3 keV. The accelerated ion beam is scanned with a dipolar deflector and focused onto a sample by an einzel lens. Secondary electron images are collected and analyzed, and from these a beam diameter is inferred. The result is a focused probe with a one-standard-deviation radius as small as 205(10) nm. While this probe size is in the useful range for nanoscale applications, it is almost three times larger than is predicted by ray-tracing simulations. Possible explanations for this discrepancy are discussed.
Citation: Journal of Vacuum Science and Technology B
Pub Type: Journals
focused ion beams, chromium, MOTIS, nanotechnology