Stationary beam full-field transmission helium ion microscopy using sub-50 keV He⁺: Projected images and intensity patterns

Abstract

A dedicated transmission helium ion microscope (THIM) for sub-50 keV helium has been constructed to investigate ion scattering processes and contrast mechanisms, aiding the development of new imaging and analysis modalities. Unlike a commercial helium ion microscope (HIM), the in-house built instrument allows full flexibility in experimental configuration. Here, we report projection imaging and intensity patterns obtained from powder and bulk crystalline samples using stationary broad-beam as well as convergent-beam illumination conditions in THIM. The He+ ions formed unexpected spot patterns in the far field for MgO, BN and NaCl powder samples, but not for Au-coated MgO. The origin of the spot patterns in these samples was investigated. Surface diffraction of ions was excluded as a possible cause because the recorded scattering angles do not correspond to the predicted Bragg angles. Complementary secondary electron (SE) imaging in the HIM revealed that these samples charge significantly under He+ ion irradiation. The spot patterns obtained in the THIM experiments are explained as artefacts related to sample charging. The results presented here indicate that factors other than channeling, blocking and surface diffraction of ions have an impact on the final intensity distribution in the far field. Hence, the different processes contributing to the final intensities will need to be understood in order to decouple and study the relevant ion-beam scattering and deflection phenomena.

Structural and chemical evolution of Au-silica core–shell nanoparticles during 20 keV helium ion irradiation: a comparison between experiment and simulation

“…Once the sample had dried, the grid was transferred between the TEM and the THIM instrument for TEM imaging and He + exposure respectively. For the He + ion beam irradiation a THIM instrument was used (details of which have been previously described 14 ). Briefly, this THIM comprises of a duoplasmatron ion source operated at 20 keV with helium gas, 2 Einzel lenses, 3 sets of X, Y deflector plates and a microchannel plate coupled to a phosphor screen detector placed behind the sample.…”

“…At LIST, a transmission HIM (THIM) prototype instrument has been developed which is capable of recording the transmitted helium ion signal from keV ions in both stationary-beam as well as scanning mode 14 .There is still much work to be done in assessing the capabilities of such THIM systems using sub 50 keV ions, and, in particular, the sample damage by the incident ions. In this paper we investigate the behaviour of Au-silica core–shell nanoparticles under He + irradiation in our THIM prototype.…”

“…At LIST, a transmission HIM (THIM) prototype instrument has been developed which is capable of recording the transmitted helium ion signal from keV ions in both stationary-beam as well as scanning mode 14 .There…”

Bio-imaging with the helium-ion microscope: A review

“…This section would be incomplete without mentioning two interesting new developments. Firstly, Mouseley et al have developed a full-field THIM, which is not based on a Zeiss Orion instrument, and which holds promise to conduct exciting THIM experiments also on biological samples [58]. Secondly, within the npSCOPE H2020 project an "instrument [is being developed] that couples the extraordinarily high resolution of the […] helium-ion microscope with sensors for composition (a mass spectrometer) and 3D visualization (transmitted ion detector) in order to more fully characterise individual nanoparticles and their interaction with their environment (tissue, cells, etc.)…”

Transmission ion microscopy and time-of-flight spectroscopy

“…Rossendorf, dresden, Germany, 3 Helmholtz-Zentrum Dresden-Rossendorf, United States, 4 Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Sachsen, Germany, 5 Luxembourg Institute of Science and Technology (LIST), Belvaux, Luxembourg A Transmission Ion Microscope (TIM), the Galileo prototype, has been built at the Luxembourg Institute of Science and Technology (LIST) [1]. This is part of a new interest in the imaging properties of transmitted helium ions [2] [3] [4].…”