scholarly journals Imaging ultra thin layers with helium ion microscopy: Utilizing the channeling contrast mechanism

2012 ◽  
Vol 3 ◽  
pp. 507-512 ◽  
Author(s):  
Gregor Hlawacek ◽  
Vasilisa Veligura ◽  
Stefan Lorbek ◽  
Tijs F Mocking ◽  
Antony George ◽  
...  
Keyword(s):  
High Performance ◽  
High Surface ◽  
Thin Layers ◽  
Light Elements ◽  
Ion Channeling ◽  
Surface Sensitivity ◽  
Helium Ion ◽  
Contrast Mechanism ◽  
Assembled Monolayers ◽  
Ion Microscopy

Background: Helium ion microscopy is a new high-performance alternative to classical scanning electron microscopy. It provides superior resolution and high surface sensitivity by using secondary electrons. Results: We report on a new contrast mechanism that extends the high surface sensitivity that is usually achieved in secondary electron images, to backscattered helium images. We demonstrate how thin organic and inorganic layers as well as self-assembled monolayers can be visualized on heavier element substrates by changes in the backscatter yield. Thin layers of light elements on heavy substrates should have a negligible direct influence on backscatter yields. However, using simple geometric calculations of the opaque crystal fraction, the contrast that is observed in the images can be interpreted in terms of changes in the channeling probability. Conclusion: The suppression of ion channeling into crystalline matter by adsorbed thin films provides a new contrast mechanism for HIM. This dechanneling contrast is particularly well suited for the visualization of ultrathin layers of light elements on heavier substrates. Our results also highlight the importance of proper vacuum conditions for channeling-based experimental methods.

scholarly journals Imaging of carbon nanomembranes with helium ion microscopy

2015 ◽  
Vol 6 ◽  
pp. 1712-1720 ◽  
Author(s):  
André Beyer ◽  
Henning Vieker ◽  
Robin Klett ◽  
Hanno Meyer zu Theenhausen ◽  
Polina Angelova ◽  
...  
Keyword(s):  
Self Assembly ◽  
High Surface ◽  
Charge Compensation ◽  
Depth Of Field ◽  
Free Standing ◽  
Transmission Electron ◽  
Helium Ion ◽  
Assembled Monolayers ◽  
Efficient Charge ◽  
Radiation Induced

Carbon nanomembranes (CNMs) prepared from aromatic self-assembled monolayers constitute a recently developed class of 2D materials. They are made by a combination of self-assembly, radiation-induced cross-linking and the detachment of the cross-linked SAM from its substrate. CNMs can be deposited on arbitrary substrates, including holey and perforated ones, as well as on metallic (transmission electron microscopy) grids. Therewith, freestanding membranes with a thickness of 1 nm and macroscopic lateral dimensions can be prepared. Although free-standing CNMs cannot be imaged by light microscopy, charged particle techniques can visualize them. However, CNMs are electrically insulating, which makes them sensitive to charging. We demonstrate that the helium ion microscope (HIM) is a good candidate for imaging freestanding CNMs due to its efficient charge compensation tool. Scanning with a beam of helium ions while recording the emitted secondary electrons generates the HIM images. The advantages of HIM are high resolution, high surface sensitivity and large depth of field. The effects of sample charging, imaging of multilayer CNMs as well as imaging artefacts are discussed.

scholarly journals Digging gold: keV He+ ion interaction with Au

2013 ◽  
Vol 4 ◽  
pp. 453-460 ◽  
Author(s):  
Vasilisa Veligura ◽  
Gregor Hlawacek ◽  
Robin P Berkelaar ◽  
Raoul van Gastel ◽  
Harold J W Zandvliet ◽  
...  
Keyword(s):  
Ion Beam ◽  
Normal Incidence ◽  
Sample Surface ◽  
Primary Energy ◽  
Periodic Surface ◽  
Helium Bubbles ◽  
Surface Sensitivity ◽  
Helium Ion ◽  
Helium Implantation ◽  
Ion Microscopy

Helium ion microscopy (HIM) was used to investigate the interaction of a focused He+ ion beam with energies of several tens of kiloelectronvolts with metals. HIM is usually applied for the visualization of materials with extreme surface sensitivity and resolution. However, the use of high ion fluences can lead to significant sample modifications. We have characterized the changes caused by a focused He+ ion beam at normal incidence to the Au{111} surface as a function of ion fluence and energy. Under the influence of the beam a periodic surface nanopattern develops. The periodicity of the pattern shows a power-law dependence on the ion fluence. Simultaneously, helium implantation occurs. Depending on the fluence and primary energy, porous nanostructures or large blisters form on the sample surface. The growth of the helium bubbles responsible for this effect is discussed.

scholarly journals Channeling in helium ion microscopy: Mapping of crystal orientation

2012 ◽  
Vol 3 ◽  
pp. 501-506 ◽  
Author(s):  
Vasilisa Veligura ◽  
Gregor Hlawacek ◽  
Raoul van Gastel ◽  
Harold J W Zandvliet ◽  
Bene Poelsema
Keyword(s):  
Secondary Electron ◽  
Geometric Model ◽  
Particle Beam ◽  
Surface Layers ◽  
Charged Particle Beam ◽  
Surface Information ◽  
Surface Sensitivity ◽  
Helium Ion ◽  
Ion Microscopy ◽  
Unique Surface

Background: The unique surface sensitivity and the high resolution that can be achieved with helium ion microscopy make it a competitive technique for modern materials characterization. As in other techniques that make use of a charged particle beam, channeling through the crystal structure of the bulk of the material can occur. Results: Here, we demonstrate how this bulk phenomenon affects secondary electron images that predominantly contain surface information. In addition, we will show how it can be used to obtain crystallographic information. We will discuss the origin of channeling contrast in secondary electron images, illustrate this with experiments, and develop a simple geometric model to predict channeling maxima. Conclusion: Channeling plays an important role in helium ion microscopy and has to be taken into account when trying to achieve maximum image quality in backscattered helium images as well as secondary electron images. Secondary electron images can be used to extract crystallographic information from bulk samples as well as from thin surface layers, in a straightforward manner.

scholarly journals Scanning transmission helium ion microscopy on carbon nanomembranes

2021 ◽  
Vol 12 ◽  
pp. 222-231
Author(s):  
Daniel Emmrich ◽  
Annalena Wolff ◽  
Nikolaus Meyerbröker ◽  
Jörg K N Lindner ◽  
André Beyer ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Dark Field ◽  
Acceptance Angle ◽  
Carbon Membranes ◽  
Thin Carbon ◽  
Helium Ion ◽  
Scanning Transmission ◽  
Contrast Mechanism ◽  
Ion Microscopy ◽  
And Performance

A dark-field scanning transmission ion microscopy detector was designed for the helium ion microscope. The detection principle is based on a secondary electron conversion holder with an exchangeable aperture strip allowing its acceptance angle to be tuned from 3 to 98 mrad. The contrast mechanism and performance were investigated using freestanding nanometer-thin carbon membranes. The results demonstrate that the detector can be optimized either for most efficient signal collection or for maximum image contrast. The designed setup allows for the imaging of thin low-density materials that otherwise provide little signal or contrast and for a clear end-point detection in the fabrication of nanopores. In addition, the detector is able to determine the thickness of membranes with sub-nanometer precision by quantitatively evaluating the image signal and comparing the results with Monte Carlo simulations. The thickness determined by the dark-field transmission detector is compared to X-ray photoelectron spectroscopy and energy-filtered transmission electron microscopy measurements.

scholarly journals Imaging of SARS-CoV-2 infected Vero E6 Cells by Helium Ion Microscopy

2020 ◽  
Author(s):  
Natalie Frese ◽  
Patrick Schmerer ◽  
Martin Wortmann ◽  
Matthias Schürmann ◽  
Matthias König ◽  
...  
Keyword(s):  
Biological Samples ◽  
High Surface ◽  
Three Dimensional ◽  
Charge Compensation ◽  
Microbial Interactions ◽  
Depth Of Field ◽  
Virus Particles ◽  
Helium Ion ◽  
Morphological Detail ◽  
Ion Microscopy

Helium ion microscopy (HIM) offers the opportunity to obtain direct views of biological samples such as cellular structures, virus particles, and microbial interactions. Imaging with the HIM combines sub-nanometer resolution, large depth of field, and high surface sensitivity. Due to its charge compensation capability, the HIM can image insulating biological samples without additional conductive coatings. Here, we present an exploratory HIM study of SARS-CoV-2 infected Vero E6 cells, in which several areas of interactions between cells and virus particles, as well as among virus particles, were imaged. The HIM pictures show the three-dimensional appearance of SARS-CoV-2 and the surface of Vero E6 cells at a multiplicity of infection of approximately 1 with great morphological detail. The absence of a conductive coating allows a distinction between virus particles bound to the cell membrane and virus particles lying on top of the membrane. After prolonged imaging, it was found that ion-induced deposition of hydrocarbons from the vacuum renders the sample sufficiently conductive to allow imaging even without charge compensation. The presented images demonstrate the potential of the HIM in bioimaging, especially for the imaging of interactions between viruses and their host organisms.

Electrospun Composite Nanofiber Transparent Conductor Layer for Solar Cells

2011 ◽  
Vol 1323 ◽  
Author(s):  
Justin Ritchie ◽  
Joël Mertens ◽  
Heejae Yang ◽  
Peyman Servati ◽  
Frank K. Ko
Keyword(s):  
Sheet Resistance ◽  
High Performance ◽  
Optical Transmission ◽  
Volume Fraction ◽  
Fibrous Composite ◽  
High Surface ◽  
High Surface Area ◽  
Thin Layers ◽  
Transparent Conductor ◽  
High Optical Transmission

ABSTRACTDeveloping a durable and scalable transparent conductor (TC) as an electrode with high optical transmission and low sheet resistance is a significant opportunity for enabling next generation solar cell devices. High performance fibrous composite materials based on a carrier polymer with embedded functional nanostructures have the potential to serve as a TC with high surface area that can be deposited by the novel and scalable process of electrospinning. This work presents the development of a fibrous TC, where polyacrylonitrile (PAN) is used as a carrier polymer for multi-walled carbon nanotubes (MWCNT) to create electroactive nanofibers 200-500nm in diameter. Once carbonized, thin layers of this material have a low sheet resistance and high optical transmission. It is shown that in a two stage carbonization process, the second stage temperature of above 700C is the primary factor in establishing a highly conductive material and single layers of nanofibers are typically destabilized at high temperatures. A high performance TC has been developed through optimizing carbonization rates and temperatures to allow for single nanofiber layers fabricated by electrospinning MWCNT/PAN solutions onto quartz. These TCs have been optimized for concentrations of MWCNTs less than 20% volume fraction with well above 90% transmissivity and sheet resistances of between .5-1kohm/square. The required MWCNT loading is well below that for TCs based on random networks of MWCNTs.

Contrast Mechanisms and Image Formation in Helium Ion Microscopy

2009 ◽  
Vol 15 (2) ◽  
pp. 147-153 ◽  
Author(s):  
David C. Bell
Keyword(s):  
Imaging System ◽  
Ion Source ◽  
Ion Imaging ◽  
Small Surface ◽  
Surface Sensitivity ◽  
Helium Ion ◽  
Contrast Mechanisms ◽  
Ion Microscopy ◽  
Imaging Instrument ◽  
Enhanced Surface

AbstractThe helium ion microscope is a unique imaging instrument. Based on an atomic level imaging system using the principle of field ion microscopy, the helium ion source has been shown to be incredibly stable and reliable, itself a remarkable engineering feat. Here we show that the image contrast is fundamentally different to other microscopes such as the scanning electron microscope (SEM), although showing many operational similarities due to the physical ion interaction mechanisms with the sample. Secondary electron images show enhanced surface contrast due the small surface interaction volume as well as elemental contrast differences, such as for nanowires imaged on a substrate. We present images of nanowires and nanoparticles for comparison with SEM imaging. Applications of Rutherford backscattered ion imaging as a unique and novel imaging mechanism are described. The advantages of the contrast mechanisms offered by this instrument for imaging nanomaterials are clearly apparent due to the high resolution and surface sensitivity afforded in the images. Future developments of the helium ion microscope should yield yet further improvements in imaging and provide a platform for continued advances in microscope science and nanoscale research.

scholarly journals Imaging of SARS-CoV-2 infected Vero E6 cells by helium ion microscopy

2021 ◽  
Vol 12 ◽  
pp. 172-179
Author(s):  
Natalie Frese ◽  
Patrick Schmerer ◽  
Martin Wortmann ◽  
Matthias Schürmann ◽  
Matthias König ◽  
...  
Keyword(s):  
Biological Samples ◽  
High Surface ◽  
Three Dimensional ◽  
Charge Compensation ◽  
Microbial Interactions ◽  
Depth Of Field ◽  
Virus Particles ◽  
Helium Ion ◽  
Morphological Detail ◽  
Ion Microscopy

Helium ion microscopy (HIM) offers the opportunity to obtain direct views of biological samples such as cellular structures, virus particles, and microbial interactions. Imaging with the HIM combines sub-nanometer resolution, large depth of field, and high surface sensitivity. Due to its charge compensation capability, the HIM can image insulating biological samples without additional conductive coatings. Here, we present an exploratory HIM study of SARS-CoV-2 infected Vero E6 cells, in which several areas of interaction between cells and virus particles, as well as among virus particles, were imaged. The HIM pictures show the three-dimensional appearance of SARS-CoV-2 and the surface of Vero E6 cells at a multiplicity of infection of approximately 1 with great morphological detail. The absence of a conductive coating allows for a distinction between virus particles bound to the cell membrane and virus particles lying on top of the membrane. After prolonged imaging, it was found that ion-induced deposition of hydrocarbons from the vacuum renders the sample sufficiently conductive to allow for imaging even without charge compensation. The presented images demonstrate the potential of the HIM in bioimaging, especially for the imaging of interactions between viruses and their host organisms.

First H+ Charge-Exchange Images in the Stim.

1976 ◽  
Vol 34 ◽  
pp. 504-505
Author(s):  
Wm. H. Escovitz ◽  
T. R. Fox ◽  
R. Levi-Setti
Keyword(s):  
Charge Exchange ◽  
Neutral Component ◽  
Channel Electron Multiplier ◽  
Electron Multiplier ◽  
Neutral Particles ◽  
Charged Beam ◽  
Scanning Transmission ◽  
Contrast Mechanism ◽  
Ion Microscopy ◽  
Beam Component

Charge exchange, the neutralization of ions by electron capture as the ions traverse matter, is a well-known phenomenon of atomic physics which is relevant to ion microscopy. In conventional transmission ion microscopes, the neutral component of the beam after it emerges from the specimen cannot be focused. The scanning transmission ion microscope (STIM) enables the detection of this signal to make images. Experiments with a low-resolution 55 kV STIM indicate that the charge-exchange signal provides a new contrast mechanism to detect extremely small amounts of matter. In an early version of charge-exchange detection (fig. 1), a permanent magnet installed between the specimen and the detector (a channel electron multiplier) sweeps the charged beam component away from the detector and allows only the neutrals to reach it. When the magnet is removed, both charged and neutral particles reach the detector.

Scanning ion microscopy images

1987 ◽  
Vol 45 ◽  
pp. 180-181
Author(s):  
R. Levi-Setti ◽  
J.M. Chabala ◽  
Y.L. Wang
Keyword(s):  
Metal Ion ◽  
Secondary Emission ◽  
Scanning Method ◽  
Ion Channeling ◽  
Secondary Ions ◽  
High Resolution Images ◽  
Ion Microscopy ◽  
Z Contrast ◽  
Focused Beams ◽  
Microscopy Images

Finely focused beams extracted from liquid metal ion sources (LMIS) provide a wealth of secondary signals which can be exploited to create high resolution images by the scanning method. The images of scanning ion microscopy (SIM) encompass a variety of contrast mechanisms which we classify into two broad categories: a) Emission contrast and b) Analytical contrast.Emission contrast refers to those mechanisms inherent to the emission of secondaries by solids under ion bombardment. The contrast-carrying signals consist of ion-induced secondary electrons (ISE) and secondary ions (ISI). Both signals exhibit i) topographic emission contrast due to the existence of differential geometric emission and collection effects, ii) crystallographic emission contrast, due to primary ion channeling phenomena and differential oxidation of crystalline surfaces, iii) chemical emission or Z-contrast, related to the dependence of the secondary emission yields on the Z and surface chemical state of the target.

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