scholarly journals Fabrication of carbon nanomembranes by helium ion beam lithography

2014 ◽  
Vol 5 ◽  
pp. 188-194 ◽  
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.

scholarly journals Bound (“Glassy”) Rubber as a Free Radical Cross-linked Rubber Layer on a Carbon Black

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1992 ◽  
Author(s):  
Alexey Kondyurin ◽  
Anastasia Eliseeva ◽  
Alexander Svistkov
Keyword(s):  
Free Radical ◽  
Carbon Black ◽  
Ion Beam ◽  
Cross Linking ◽  
Carbon Filler ◽  
Free Radical Reactions ◽  
Rubber Layer ◽  
Ion Beam Implantation ◽  
Cross Links ◽  
The Cross

A model of rubber with a cross-linked rubber layer on a carbon black filler has been proposed. The cross-links are the result of free radical reactions generated by carbon atoms with unpaired electrons at the edge of graphitic sheets in a carbon black filler. The experimental study of the cross-linking reactions in polyisoprene was done on a flat carbonized surface after ion beam implantation. The cross-linking process in the polyisoprene macromolecules between two particles was simulated. The model with a cross-linked rubber layer on a carbon filler as a “glassy layer” explains the mechanical properties of the rubber materials.

scholarly journals Ion beam profiling from the interaction with a freestanding 2D layer

2017 ◽  
Vol 8 ◽  
pp. 682-687 ◽  
Author(s):  
Ivan Shorubalko ◽  
Kyoungjun Choi ◽  
Michael Stiefel ◽  
Hyung Gyu Park
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Beam Current ◽  
Exposure Dose ◽  
Ion Beams ◽  
Gaussian Profile ◽  
Helium Ion ◽  
Spread Function ◽  
Sputtering Yields ◽  
Pattern Resolution

Recent years have seen a great potential of the focused ion beam (FIB) technology for the nanometer-scale patterning of a freestanding two-dimensional (2D) layer. Experimentally determined sputtering yields of the perforation process can be quantitatively explained using the binary collision theory. The main peculiarity of the interaction between the ion beams and the suspended 2D material lies in the absence of collision cascades, featured by no interaction volume. Thus, the patterning resolution is directly set by the beam diameters. Here, we demonstrate pattern resolution beyond the beam size and precise profiling of the focused ion beams. We find out that FIB exposure time of individual pixels can influence the resultant pore diameter. In return, the pore dimension as a function of the exposure dose brings out the ion beam profiles. Using this method of determining an ion-beam point spread function, we verify a Gaussian profile of focused gallium ion beams. Graphene sputtering yield is extracted from the normalization of the measured Gaussian profiles, given a total beam current. Interestingly, profiling of unbeknown helium ion beams in this way results in asymmetry of the profile. Even triangular beam shapes are observed at certain helium FIB conditions, possibly attributable to the trimer nature of the beam source. Our method of profiling ion beams with 2D-layer perforation provides more information on ion beam profiles than the conventional sharp-edge scan method does.

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

2019 ◽  
Vol 10 ◽  
pp. 1648-1657
Author(s):  
Michael Mousley ◽  
Santhana Eswara ◽  
Olivier De Castro ◽  
Olivier Bouton ◽  
Nico Klingner ◽  
...  
Keyword(s):  
Ion Irradiation ◽  
Ion Beam ◽  
Far Field ◽  
Ion Scattering ◽  
Full Field ◽  
Helium Ion ◽  
Powder Samples ◽  
Convergent Beam ◽  
Surface Diffraction ◽  
Possible Cause

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.

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

2012 ◽  
Vol 3 ◽  
pp. 579-585 ◽  
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.

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

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.

scholarly journals Amplified cross-linking efficiency of self-assembled monolayers through targeted dissociative electron attachment for the production of carbon nanomembranes

2017 ◽  
Vol 8 ◽  
pp. 2562-2571 ◽  
Author(s):  
Sascha Koch ◽  
Christopher D Kaiser ◽  
Paul Penner ◽  
Michael Barclay ◽  
Lena Frommeyer ◽  
...  
Keyword(s):  
Cross Section ◽  
Current Density ◽  
Electron Attachment ◽  
The Other ◽  
Self Assembled Monolayers ◽  
Cross Linking ◽  
Dissociative Electron Attachment ◽  
Electron Dose ◽  
Assembled Monolayers ◽  
The Cross

The determination of the negative ion yield of 2′-chloro-1,1′-biphenyl (2-Cl-BP), 2′-bromo-1,1′-biphenyl (2-Br-BP) and 2′-iodo-1,1′-biphenyl (2-I-BP) upon dissociative electron attachment (DEA) at an electron energy of 0 eV revealed cross section values that were more than ten times higher for iodide loss from 2-I-BP than for the other halogenides from the respective biphenyls (BPs). Comparison with dissociative ionization mass spectra shows that the ratio of the efficiency of electron impact ionization induced fragmentation of 2-I-BP, 2-Br-BP, and 2-Cl-BP amounts to approximately 1:0.7:0.6. Inspired by these results, self-assembled monolayers (SAMs) of the respective biphenyl-4-thiols, 2-Cl-BPT, 2-Br-BPT, 2-I-BPT as well as BPT, were grown on a Au(111) substrate and exposed to 50 eV electrons. The effect of electron irradiation was investigated by X-ray photoelectron spectroscopy (XPS), to determine whether the high relative DEA cross section for iodide loss from 2-I-BPT as compared to 2-Br-BP and 2-Cl-BP is reflected in the cross-linking efficiency of SAMs made from these materials. Such sensitization could reduce the electron dose needed for the cross-linking process and may thus lead to a significantly faster conversion of the respective SAMs into carbon nanomembranes (CNMs) without the need for an increased current density. XPS data support the notation that DEA sensitization may be used to achieve more efficient electron-induced cross-linking of SAMs, revealing more than ten times faster cross-linking of 2-I-BPT SAMs compared to those made from the other halogenated biphenyls or from native BPT at the same current density. Furthermore, the transfer of a freestanding membrane onto a TEM grid and the subsequent investigation by helium ion microscopy (HIM) verified the existence of a mechanically stable CNM created from 2-I-BPT after exposure to an electron dose as low as 1.8 mC/cm2. In contrast, SAMs made from BPT, 2-Cl-BPT and 2-Br-BPT did not form stable CNMs after a significantly higher electron dose of 9 mC/cm2.

Point-Defect Migration in Crystalline Si: Impurity Content, Surface and Stress Effects

1998 ◽  
Vol 532 ◽  
Author(s):  
S. Coffa ◽  
S. Libertino ◽  
A. La Magna ◽  
V. Privitera ◽  
G. Mannino ◽  
...  
Keyword(s):  
Point Defect ◽  
Leakage Current ◽  
Room Temperature ◽  
Ion Irradiation ◽  
Deep Level ◽  
Ion Beam ◽  
Impurity Content ◽  
Ex Situ ◽  
Defect Migration

ABSTRACTThe results of several recent experiments aimed at assessing the room temperature migration properties of interstitials (D) and vacancies (V) in ion implanted crystalline Si are reviewed. We show that combining the results of ex-situ techniques (deep level transient spectroscopy and spreading resistance profilometry) and in-situ leakage current measurements new and interesting information can be achieved. It has been found that at room temperature I and V, generated by an ion beam, undergo fast long range migration (with diffusivities higher than 10−1 cm2/sec) which is interrupted by trapping at impurities (C, O) or dopant atoms and by recombination at surface. Analysis of two-dimensional migration of point defects injected through a photolithographically defined mask shows that a strong I recombination (characterized by a coefficient of 30 μm−1) occurs at the sample surface. Moreover, we have found that the strain field induced by an oxide or a nitride mask significantly affects defect migration and produces a strong anisotropy of the defect diffusivity tensor. Finally, using in-situ leakage current measuremens, performed both during and just after ion irradiation, the time scale of point defect evolution at room temperature has been determined and defect diffusivities evaluated. The implications of these results on our current understanding of defect and diffusion phenomena in Si are discussed.

In situ Transmission Electron Microscopy Investigation of Radiation Effects

2005 ◽  
Vol 20 (7) ◽  
pp. 1654-1683 ◽  
Author(s):  
R.C. Birtcher ◽  
M.A. Kirk ◽  
K. Furuya ◽  
G.R. Lumpkin ◽  
M-O. Ruault
Keyword(s):  
Radiation Effects ◽  
Ion Irradiation ◽  
Ion Beam ◽  
Ex Situ ◽  
In Situ Observation ◽  
Dislocation Loops ◽  
Transmission Electron ◽  
Microscopy Investigation ◽  
Ion Impact

In situ observation is of great value in the study of radiation damage utilizing electron or ion irradiation. We summarize the facilities and give examples of work found around the world. In situ observations of irradiation behavior have fallen into two broad classes. One class consists of long-term irradiation, with observations of microstructural evolution as a function of the radiation dose in which the advantage of in situ observation has been the maintenance of specimen position, orientation, and temperature. A second class has involved the recording of individual damage events in situations in which subsequent evolution would render the correct interpretation of ex situ observations impossible. In this review, examples of the first class of observation include ion-beam amorphization, damage accumulation, plastic flow, implant precipitation, precipitate evolution under irradiation, and damage recovery by thermal annealing. Examples of the second class of observation include single isolated ion impacts that produce defects in the form of dislocation loops, amorphous zones, or surface craters, and single ion impact-sputtering events. Experiments in both classes of observations attempt to reveal the kinetics underlying damage production, accumulation, and evolution.

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

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.

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

2003 ◽  
Vol 777 ◽  
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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