High resolution chemical imaging on the helium ion microscope

Auteurs

D. Dowsett, J. N. Audinot, F. Vollnhals, S. Eswara, and T. Wirtz

Référence

in 16th European Microscopy Congress 2016: Instrumentation and Methods: Spectromicroscopies and analytical microscopy (electrons and photons, experiment and theory), Lyon, France, August 28 - September 2, 2016, Wiley-VCH, 2016

Description

The ORION NanoFab helium ion microscope (HIM) has become an ideal tool for imaging and nano-patterning tool owing to its high lateral resolution. Helium ions lead to resolutions of 0.5 nm for SE based imaging, while structures with sub 20 nm feature sizes may be rapidly patterned using Ne. Despite these advantages, the analysis capability of the machine is currently limited. At beam energies of 35 kV helium ions do not lead to the emission of characteristic X-rays from a sample. While some compositional information can be obtained from back scattered helium, identifying elemental information is more difficult. Secondary Ion Mass Spectrometry (SIMS) is a powerful ion beam based technique for analyzing surfaces with high sensitivity and high mass resolution. SIMS is based on the generation and identification of characteristic secondary ions by irradiation with a primary ion beam (in this case helium or neon). The typical interaction volume for SIMS is around 10 nm in the lateral direction. As the probe size in the HIM is substantially smaller (both for He and Ne) the lateral resolution is limited only by fundamental considerations and not, as is currently the case on commercial SIMS instruments, the probe size. The prospect of adding SIMS to the HIM yields not just a powerful analytical capability, but opens the way for in-situ correlative imaging combining high resolution SE images with elemental maps from SIMS.

We have developed a prototype SIMS spectrometer specifically adapted to the HIM. Notably the instrument is capable of producing elemental SIMS maps with lateral resolution limited only by the fundamental interaction between the primary beam and the sample. All elements/isotopes and small clusters with masses up to 500 amu are detectable with a mass resolution M/ΔM greater than 400 and parallel detection of 4 mass channels.

In this presentation we will introduce the HIM-SIMS technique and present the latest application results in the field of materials science.

Lien

doi:10.1002/9783527808465.EMC2016.6559