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

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.

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Nano-structuring, surface and bulk modification with a focused helium ion beam

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.3.67 ◽

2012 ◽

Vol 3 ◽

pp. 579-585 ◽

Cited By ~ 22

Author(s):

Daniel Fox ◽

Yanhui Chen ◽

Colm C Faulkner ◽

Hongzhou Zhang

Keyword(s):

Ion Irradiation ◽

Ion Beam ◽

High Dose ◽

Modification Process ◽

Dose Irradiation ◽

Probe Size ◽

Helium Ion ◽

High Incidence ◽

High Level ◽

Irradiation Process

We investigate the ability of a focused helium ion beam to selectively modify and mill materials. The sub nanometer probe size of the helium ion microscope used provides lateral control not previously available for helium ion irradiation experiments. At high incidence angles the helium ions were found to remove surface material from a silicon lamella leaving the subsurface structure intact for further analysis. Surface roughness and contaminants were both reduced by the irradiation process. Fabrication is also realized with a high level of patterning acuity. Implantation of helium beneath the surface of the sample is visualized in cross section allowing direct observation of the extended effects of high dose irradiation. The effect of the irradiation on the crystal structure of the material is presented. Applications of the sample modification process are presented and further prospects discussed.

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Effect of localized helium ion irradiation on the performance of synthetic monolayer MoS2 field-effect transistors

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.11.117 ◽

2020 ◽

Vol 11 ◽

pp. 1329-1335

Author(s):

Jakub Jadwiszczak ◽

Pierce Maguire ◽

Conor P Cullen ◽

Georg S Duesberg ◽

Hongzhou Zhang

Keyword(s):

Field Effect ◽

Carrier Mobility ◽

Field Effect Transistors ◽

Ion Irradiation ◽

Ion Beam ◽

Electrical Conductance ◽

Charge Carrier Mobility ◽

Electrical Performance ◽

Transistor Channel ◽

Helium Ion

Helium ion irradiation is a known method of tuning the electrical conductivity and charge carrier mobility of novel two-dimensional semiconductors. Here, we report a systematic study of the electrical performance of chemically synthesized monolayer molybdenum disulfide (MoS2) field-effect transistors irradiated with a focused helium ion beam as a function of increasing areal irradiation coverage. We determine an optimal coverage range of approx. 10%, which allows for the improvement of both the carrier mobility in the transistor channel and the electrical conductance of the MoS2, due to doping with ion beam-created sulfur vacancies. Larger areal irradiations introduce a higher concentration of scattering centers, hampering the electrical performance of the device. In addition, we find that irradiating the electrode–channel interface has a deleterious impact on charge transport when contrasted with irradiations confined only to the transistor channel.

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Fabrication of carbon nanomembranes by helium ion beam lithography

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.5.20 ◽

2014 ◽

Vol 5 ◽

pp. 188-194 ◽

Cited By ~ 19

Author(s):

Xianghui Zhang ◽

Henning Vieker ◽

André Beyer ◽

Armin Gölzhäuser

Keyword(s):

Ion Irradiation ◽

Ion Beam ◽

Electron Attachment ◽

Threshold Value ◽

Exposure Dose ◽

Ex Situ ◽

Cross Linking ◽

Universal Method ◽

Helium Ion ◽

The Cross

The irradiation-induced cross-linking of aromatic self-assembled monolayers (SAMs) is a universal method for the fabrication of ultrathin carbon nanomembranes (CNMs). Here we demonstrate the cross-linking of aromatic SAMs due to exposure to helium ions. The distinction of cross-linked from non-cross-linked regions in the SAM was facilitated by transferring the irradiated SAM to a new substrate, which allowed for an ex situ observation of the cross-linking process by helium ion microscopy (HIM). In this way, three growth regimes of cross-linked areas were identified: formation of nuclei, one-dimensional (1D) and two-dimensional (2D) growth. The evaluation of the corresponding HIM images revealed the dose-dependent coverage, i.e., the relative monolayer area, whose density of cross-links surpassed a certain threshold value, as a function of the exposure dose. A complete cross-linking of aromatic SAMs by He+ ion irradiation requires an exposure dose of about 850 µC/cm2, which is roughly 60 times smaller than the corresponding electron irradiation dose. Most likely, this is due to the energy distribution of secondary electrons shifted to lower energies, which results in a more efficient dissociative electron attachment (DEA) process.

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Modelling of Optical Damage in Nanorippled ZnO Produced by Ion Irradiation

Crystals ◽

10.3390/cryst9090453 ◽

2019 ◽

Vol 9 (9) ◽

pp. 453

Author(s):

Redondo-Cubero ◽

Vázquez ◽

Jalabert ◽

Lorenz ◽

Sedrine

Keyword(s):

Ion Irradiation ◽

Ion Beam ◽

Ion Scattering ◽

Force Microscopy ◽

Enhanced Absorption ◽

High Fluences ◽

Atomic Force ◽

Ripple Patterns ◽

Medium Energy Ion Scattering ◽

Induced Changes

Here, we report on the production of nanoripples on the surface of ZnO bulk substrates by ion beam erosion with 20 keV Ar+ ions at an oblique incidence (60°). The ripple patterns, analyzed by atomic force microscopy, follow a power law dependence for both the roughness and the wavelength. At high fluences these ripples show coarsening and asymmetric shapes, which become independent of the beam direction and evidence additional mechanisms for the pattern development. The shallow damaged layer is not fully amorphized by this process, as confirmed by medium energy ion scattering. A detailed study of the damage-induced changes on the optical properties was carried out by means of spectroscopic ellipsometry. Using a 3-layer model based on Tauc-Lorenz and critical point parameter band oscillators, the optical constants of the damaged layer were determined. The results showed a progressive reduction in the refractive index and enhanced absorption below the bandgap with the fluence.

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Electron and ion irradiation-induced dissolution of mechanical twins in the intermetalic U3Si: An in situ HVEM study

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100155232 ◽

1989 ◽

Vol 47 ◽

pp. 652-653

Author(s):

Charles W. Allen ◽

Robert C. Birtcher

Keyword(s):

Elevated Temperatures ◽

Ion Irradiation ◽

Ion Beam ◽

National Laboratory ◽

Argonne National Laboratory ◽

Heavy Ion ◽

High Energy ◽

Mechanical Twinning ◽

In Situ Experiments

The uranium silicides, including U3Si, are under study as candidate low enrichment nuclear fuels. Ion beam simulations of the in-reactor behavior of such materials are performed because a similar damage structure can be produced in hours by energetic heavy ions which requires years in actual reactor tests. This contribution treats one aspect of the microstructural behavior of U3Si under high energy electron irradiation and low dose energetic heavy ion irradiation and is based on in situ experiments, performed at the HVEM-Tandem User Facility at Argonne National Laboratory. This Facility interfaces a 2 MV Tandem ion accelerator and a 0.6 MV ion implanter to a 1.2 MeV AEI high voltage electron microscope, which allows a wide variety of in situ ion beam experiments to be performed with simultaneous irradiation and electron microscopy or diffraction.At elevated temperatures, U3Si exhibits the ordered AuCu3 structure. On cooling below 1058 K, the intermetallic transforms, evidently martensitically, to a body-centered tetragonal structure (alternatively, the structure may be described as face-centered tetragonal, which would be fcc except for a 1 pet tetragonal distortion). Mechanical twinning accompanies the transformation; however, diferences between electron diffraction patterns from twinned and non-twinned martensite plates could not be distinguished.

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Magnetization dynamics of irradiation-fabricated perpendicularly magnetized dots inside a softer magnetic matrix

MRS Proceedings ◽

10.1557/proc-777-t6.4 ◽

2003 ◽

Vol 777 ◽

Cited By ~ 2

Author(s):

T. Devolder ◽

M. Belmeguenai ◽

C. Chappert ◽

H. Bernas ◽

Y. Suzuki

Keyword(s):

Domain Wall ◽

Magnetic Anisotropy ◽

Magnetization Reversal ◽

Ion Irradiation ◽

Magnetic Nanostructures ◽

Magnetic Storage ◽

Exchange Field ◽

Static Magnetization ◽

Specific Domain ◽

Helium Ion

AbstractGlobal Helium ion irradiation can tune the magnetic properties of thin films, notably their magneto-crystalline anisotropy. Helium ion irradiation through nanofabricated masks can been used to produce sub-micron planar magnetic nanostructures of various types. Among these, perpendicularly magnetized dots in a matrix of weaker magnetic anisotropy are of special interest because their quasi-static magnetization reversal is nucleation-free and proceeds by a very specific domain wall injection from the magnetically “soft” matrix, which acts as a domain wall reservoir for the “hard” dot. This guarantees a remarkably weak coercivity dispersion. This new type of irradiation-fabricated magnetic device can also be designed to achieve high magnetic switching speeds, typically below 100 ps at a moderate applied field cost. The speed is obtained through the use of a very high effective magnetic field, and high resulting precession frequencies. During magnetization reversal, the effective field incorporates a significant exchange field, storing energy in the form of a domain wall surrounding a high magnetic anisotropy nanostructure's region of interest. The exchange field accelerates the reversal and lowers the cost in reversal field. Promising applications to magnetic storage are anticipated.

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Large-Scale Focused Helium Ion Beam Lithography

IEEE Transactions on Applied Superconductivity ◽

10.1109/tasc.2021.3057324 ◽

2021 ◽

Vol 31 (5) ◽

pp. 1-4

Author(s):

Jay C. LeFebvre ◽

Shane A. Cybart

Keyword(s):

Large Scale ◽

Ion Beam ◽

Ion Beam Lithography ◽

Helium Ion

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Comparison of short-range order in irradiated dysprosium titanates

npj Materials Degradation ◽

10.1038/s41529-021-00165-6 ◽

2021 ◽

Vol 5 (1) ◽

Author(s):

Roman Sherrod ◽

Eric C. O’Quinn ◽

Igor M. Gussev ◽

Cale Overstreet ◽

Joerg Neuefeind ◽

...

Keyword(s):

Long Range ◽

Short Range ◽

Structural Model ◽

Ion Irradiation ◽

Function Analysis ◽

Ion Beam ◽

Structural Response ◽

Heavy Ion ◽

Range Order ◽

Radiation Resistant

AbstractThe structural response of Dy2TiO5 oxide under swift heavy ion irradiation (2.2 GeV Au ions) was studied over a range of structural length scales utilizing neutron total scattering experiments. Refinement of diffraction data confirms that the long-range orthorhombic structure is susceptible to ion beam-induced amorphization with limited crystalline fraction remaining after irradiation to 8 × 1012 ions/cm2. In contrast, the local atomic arrangement, examined through pair distribution function analysis, shows only subtle changes after irradiation and is still described best by the original orthorhombic structural model. A comparison to Dy2Ti2O7 pyrochlore oxide under the same irradiation conditions reveals a different behavior: while the dysprosium titanate pyrochlore is more radiation resistant over the long-range with smaller degree of amorphization as compared to Dy2TiO5, the former involves more local atomic rearrangements, best described by a pyrochlore-to-weberite-type transformation. These results highlight the importance of short-range and medium-range order analysis for a comprehensive description of radiation behavior.

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