page_title: Scanning helium ion microscope
hierarchical_section_title: Scanning helium ion microscope
caption_attribution_description: Comparison between imaging in FE-SEM and HIM imaging of organic matrix in secretory stage mouse enamel. The mineral phase of forming prisms has been removed by etching thus exposing the organic matrix. (A,B) FE-SEM images show the variable structure of the organic matrix, the spaces accommodating the forming prisms appear as a black hole, however, due to limited depth of field. Organic matrix forming the wall, as it were, of the prism spaces is smooth and similar to lace as indicated (marked as ##). Spherical structures of up to ~100 nm diameter are abundant between forming prisms (arrow heads) and rod like features of several hundred nanometer length and less than 100 nm diameter can be discerned (open arrows). (C,D): HIM images reveal with great depth of field the network-like organization of organics delimiting the prism space. The matrix between prisms appears smooth and no structural details can be clearly discerned.
context_page_description: A scanning helium ion microscope is an imaging technology based on a scanning helium ion beam. Similar to other focused ion beam techniques, it allows to combine milling and cutting of samples with their observation at sub-nanometer resolution.
  In terms of imaging, SHIM has several advantages over the traditional scanning electron microscope. Owing to the very high source brightness, and the short De Broglie wavelength of the helium ions, which is inversely proportional to their momentum, it is possible to obtain qualitative data not achievable with conventional microscopes which use photons or electrons as the emitting source. As the helium ion beam interacts with the sample, it does not suffer from a large excitation volume, and hence provides sharp images with a large depth of field on a wide range of materials. Compared to a SEM, the secondary electron yield is quite high, allowing for imaging with currents as low as 1 femtoamp. The detectors provide information-rich images which offer topographic, material, crystallographic, and electrical properties of the sample.
context_section_description: A scanning helium ion microscope (SHIM, HeIM or HIM) is an imaging technology based on a scanning helium ion beam. Similar to other focused ion beam techniques, it allows to combine milling and cutting of samples with their observation at sub-nanometer resolution.
  In terms of imaging, SHIM has several advantages over the traditional scanning electron microscope (SEM). Owing to the very high source brightness, and the short De Broglie wavelength of the helium ions, which is inversely proportional to their momentum, it is possible to obtain qualitative data not achievable with conventional microscopes which use photons or electrons as the emitting source. As the helium ion beam interacts with the sample, it does not suffer from a large excitation volume, and hence provides sharp images with a large depth of field on a wide range of materials. Compared to a SEM, the secondary electron yield is quite high, allowing for imaging with currents as low as 1 femtoamp. The detectors provide information-rich images which offer topographic, material, crystallographic, and electrical properties of the sample. In contrast to other ion beams, there is no discernible sample damage due to relatively light mass of the helium ion. The drawback is the cost.
  SHIMs have been commercially available since 2007, and a surface resolution of 0.24 nanometers has been demonstrated.
caption: Comparison of SEM (top) and SHIM (bottom) images of mouse enamel. SHIM images have a superior depth of field, showing internal structure in enamel tunnels, which appear as black spots in SEM images.[1]
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