Scanning helium ion microscope

A scanning helium ion microscope (SHIM, HeIM or HIM) is a high-resolution imaging instrument that uses a scanning helium ion beam to visualize at sub-nanometer resolution. It was developed in the mid-2000s for nanotechnology applications, and has been demonstrated to have a better surface resolution than scanning electron microscopes.

Scanning helium ion microscope (SHIM) was developed in the mid-2000s as a new microscopy technique for nanotechnology applications.² It uses a focused beam of helium ions to scan a specimen's surface instead of electrons used in a scanning electron microscope (SEM).³⁴ It utilizes a gas field ionization source (GFIS), which is used to produce a highly focused beam of helium ions.⁵

The very high source brightness, and the short De Broglie wavelength of the helium ions, enables extremely small probe sizes.⁴⁵ Similar to other focused ion beam techniques, it allows to combine milling and cutting of samples with their observation at sub-nanometer resolution.⁵⁶ A surface resolution of 0.24 nanometers has been demonstrated by Zeiss.⁷⁸

When the helium ions interact with a sample under visualization, it does not suffer from large excitation volume, and hence produces a much smaller interaction volume compared to electrons, leading to better surface sensitivity. These characteristics enable the SHIM to obtain qualitative data with a greater resolution that is not achievable with conventional microscopes which use photons or electrons as the emitting source.⁴ The small interaction volume results in high contrast images, with a large depth of field on a wide range of materials.² The microscope is also better at imaging insulating materials because it causes less charging on interaction with such materials compared to electron beams.⁴

The SHIMs were made commercially available by Zeiss in 2007, and the first microscope was shipped to the National Institute of Standards and Technology.⁹ However, it was discontinued by Zeiss in 2023.¹⁰