The authors would like to acknowledge Daniel Bufford, Samuel Briggs, Claire Chisolm, Anthony Monterrosa, Brittany Muntifering, Patrick Price, Daniel Buller, Barney Doyle, Jennifer Schuler, and Mackenzie Steckbeck for their technical and scientific input. Christopher M. Barr and Khalid Hattar were fully supported by Department of Energy Office of Science Basic Energy Science program. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology &#38; Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. DOE&#8217;s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed in the article do not necessarily represent the views of the U.S. DOE or the United States Government.

The authors have nothing to disclose.

The procedures described in this document are specific to the I3TEM facility at Sandia National Laboratories, however the general approach can be applied to other in situ ion irradiation TEM facilities. There is a facilities group called the Workshop On TEM With In situ Irradiation (WOTWISI), that holds biannual meetings to discuss ion accelerator electron microscopes. There are several facilities in Japan including at the Japan Atomic Energy Research Institute (JAERI)8, and the National Institute for Materials Science (NIMS)9. Another facility capable of in situ ion irradiation is the Microscope and Ion Accelerator for Materials Investigations (MIAMI) facility at the University of Huddersfield77. CSNSM-JANNUS Orsay facility78 equipped with a FEI Tecnai G2 20 TEM working at 200 kV and coupled with the IRMA ion implanter. IVEM-Tandem Facility at Argonne National Lab is a Nuclear Science User Facility10. These facilities integrate ion accelerators differently which results in unique angles of intersection of the ion beam and electron beam. Some of the Japanese facilities introduce the ion beam at 30-45&#176; from the electron beam, ANL and MAIMI similarly at 30&#176; JANNUS at an angle of 68&#176;, and I&#179;TEM and Wuhan university have ion beams normal to the electron beam.
Depending on the material and starting form of the sample a variety of techniques can be used to prepare a specimen for TEM. The specimen needs to be sufficiently thin (less than about 100 nm) to be imaged in a TEM. Several methods for specimen preparation can be found in the handbook of TEM sample prep methodologies37. Of greatest ease are nanoparticles which can readily be drop cast. Thin films deposited on soluble substrate are also quite easy to prepare (Figure 2). Bulk metallic material can be prepared by polishing thin followed by punching through with jet polish where the area around the hole is thin enough for TEM viewing. The focused ion beam (FIB) lift out method is a well-known method for preparing a variety of materials for TEM and has been described in depth previously39,79,80. One primary advantage of the technique is the ability to selectively examine sites such as grain and phase boundaries. Another advantage is the variety of possible sample geometries including: foils, nano tension, nanopillars, and atom probe needles for additional stress environments or correlative studies. The drawback for FIB prepared samples for in situ ion irradiation experiments is that damage induced by the FIB process convolutes damage accumulated during the experiment making it difficult to determine quantitative observations. Biological or polymer samples can be prepared via cryo-FIB or cryo-microtomy, however these processes are not detailed here.
When planning ion beam implantation or irradiation experiments it is necessary to consider a number of important parameters for the ions. Penetration depth, flux/fluence, and radiation damage are variables that are often controlled when investigating effects of radiation. These parameters are modeled using a variety of simulation techniques. Stopping Range of Ions in Materials, SRIM, is a Monte Carlo simulation written to calculate ion deposition profiles in materials exposed to energetic beams of ions21,81. An alternative to SRIM is the Robinson model82 which uses a variety of functions to model the various physics of high energy ion interaction in materials. Another alternative is a model developed for single event effects in aerospace applications which can be adapted for use in ion beam experiments83. SRIM uses the Kinchin-Pease84 equation to model the displacement of atoms by radiation. The software is easy to use, and a range of ions, target elements, and ion energies can be quickly calculated with a variety of useful outputs. However, the software is limited in choice of models to use and since it is a Monte Carlo program takes a large number of iterations, and proportionally longer time to run the larger the simulation. The Robinson model utilizes a modified version of the Kinchin-Pease equation84 that has a higher agreement with experimental results, however, it is more difficult to use. Because of its widespread adoption and ease of use, methods for using SRIM were applied here and have generally become the industrial standard.
One of the primary limitations when considering multibeam in situ TEM is the sample geometry. Because of the nature of TEM as a projection imaging technique and the linear ion beam, shadowing of the electron beam or ion beams can affect the experiment. Shadows from the electron beam and ion beam can be formed from the sample stage, mounts, and even other parts of the sample. To avoid shadowing of the sample by the stage, most stages have a tilt limitation between 25&#176; and 40&#176;. More consideration must also be taken to account for geometries where the sample may shadow itself or be shadowed by the TEM grid. For this reason, when mounting the specimen, take care to mount such that there is the lowest possibility of shadowing. For FIB mounting samples on post grids this means attaching to the end of the post at the furthest out and highest point.
For experiments involving simultaneous irradiation by multiple ion species, there are limitations. Because the different ion species are being produced by different accelerators or sources the second beam must be bent by the magnet into the path of the first. This bending angle for the described instrumentation is about 20&#176;. There must be a high ratio of beam rigidity for the bending to result in colinear beams. Beam rigidity (B&#961;) is defined by total momentum divided by total charge, it can be calculated by:
<img alt="Equation" src="/files/ftp_upload/61293/61293eq4v2.png" />&#160; &#160; &#160;Equation (4)
Where p is momentum, q is charge, &#946; is particle bending velocity proportionality (&#946; = &#957;/c), m0 is the rest mass of the ion, c is the speed of light, and &#947; is the relativistic Lorentz factor:
<img alt="Equation" src="/files/ftp_upload/61293/61293eq5v3.png" />&#160; &#160; &#160;Equation (5)
This means that for multibeam experiments, it is best to use high energy heavy ions and low energy light ions such as Au and He respectively. If multiple beams are being produced by the same accelerator, they must have the same mass/energy ratio, for example 4He+ and 2D2+. Imaging conditions can also affect the ion beams. The objective lens magnetic field in high magnification imaging modes can be strong enough to bend the path of ions. Keep in mind the type of analysis that is desired when aligning the ion beams.
Contrast in TEM can arise from differences in thickness, phase, crystal order, and chemistry. Depending on the feature to be examined, there are several different types of contrast and imaging conditions that should be considered. Understanding the mechanisms behind diffraction contrast and phase contrast is useful. Understanding how to manipulate the electron microscope to achieve two-beam dynamical, bright-field kinematical, and weak-beam dark-field imaging conditions will also be useful. These are described in detail in Jenkins and Kirk, 200050.
To analyze dislocations, multiple diffraction patterns at different angles must be indexed to determine the reciprocal space lattice vector (g). Two beam imaging conditions can then be used to determine the Burgers vector of the dislocations (b). In weak beam dark-field, the dislocations can be imaged with higher resolution and contrast. This method is applied when there is a high density of dislocations or many partials. To calculate volumetric dislocation density, the thickness of the foil must be measured precisely in the area of interest. This can be done using a technique such as electron energy loss spectroscopy or convergent beam electron diffraction. For low angle grain boundaries, the dislocations in the boundary can be distinguished as a network under two beam dynamical conditions. For high angle grain boundaries, one grain is imaged in two beam dynamical conditions and the other in kinematical conditions. Twin boundaries can be characterized similarly. Fresnel imaging conditions are used to visualize gas filled bubbles and voids. Small cavities are more visible when the image is slightly out of focus and in kinematical diffraction conditions. Underfocused conditions are used to determine real diameter. Bubbles can also induce strain fields for which values can be estimated in the case of small bubbles. Automated Crystal Orientation Mapping (ACOM) is used to map several grains and their orientation similar to Electron Back Scatter Diffraction (EBSD) in the scanning electron microscope (SEM). It is best if crystals are through thickness to avoid interference from overlapping diffraction patterns.
It is possible to conduct experiments with other external stressors such as temperature and mechanical stress. The sample preparation and experimental considerations are much the same as for the multibeam experiments. Care needs to be taken in ensuring that the heating method and temperature range is appropriate for the material. Geometry must also be considered to avoid shadowing effects. The special holders for heating or mechanical testing will have specific geometric constraints and their specifications must be consulted14. Combinations of these stressors are also possible. In situ mechanical testing requires additional sample preparation to the appropriate geometry. There are specialized stages for experiments to test mechanical performance in various loading conditions such as: tension, compression, bend, fatigue, and creep. In situ heating can be performed both while irradiating and after irradiation for anneal studies. MEMS based, or conductive heating stages can be used to control temperatures up to 1000 &#176;C. Higher temperatures can be achieved using an in situ laser to heat samples to a few thousand degrees Celsius33. Samples can be subjected to different environments with in situ holders. This includes various gases, liquids, and even corrosive environments.
In summary, in situ multibeam TEM experiments have the capability to emulate extreme environments and observe the microstructure and material evolution in real time at the nanoscale. The insight into the fundamental mechanisms governing dynamic processes gained from these experiments can help inform predictive models that pave the way for design of next generation materials. It is important to prepare samples as described to insure the best chance for a successful experiment.

The transmission electron microscope (TEM) is widely utilized for its ability to observe specimens at the nanoscale. Early in the development of electron microscopes, microscopists identified in situ TEM as a powerful tool that could be used to directly observe the role of crystal defects, kinetic measurements of reaction rates, and the fundamental mechanisms in dynamic processes1. By carefully controlling the environment and directly observing material evolution, insight into fundamental mechanisms can be gained. This knowledge informs predictive modeling for materials response2,3, which is critically important in applications where traditional materials reliability testing is prohibitively difficult; applications where materials are extremely remote, in incredibly hostile environments, in service for exceedingly long times, or a combination of these factors. Radiation environments are one such example where there are significant challenges to conducting experimental studies due to the hazards of radiation areas, handling of radioactive material, and long timelines required for effects.
Space and nuclear reactor settings are both examples of these extreme radiation environments. Materials for nuclear energy can be exposed to high energy neutrons, as well as a spectrum of high energy charged particles. Likewise, in space applications materials can be exposed to a variety of charged particles. Understanding and developing predictive modeling of the resulting material evolution from exposure to these complex and extreme environments requires insight into the fundamental mechanisms occurring at the nanoscale. In situ TEM is one tool for investigating these dynamic nanoscale mechanisms in real time4,5.
In situ ion irradiation experiments in the TEM began in 1961 with the serendipitous emission of O- ions from a contaminated tungsten electron gun filament6. Researchers at Harwell were the first to link a heavy ion accelerator to a TEM for direct observation of ion irradiation effects7. More recently several facilities have assembled microscopes with multiple attached ion accelerators to enable in situ multibeam ion irradiation experiments including at the Japan Atomic Energy Research Institute8, National Institute for Materials Science9, Argonne National Laboratory10, University of Huddersfield11, JANNUS Orsay12, Wuhan University13, Sandia National Laboratories14, and others15 including multiple facilities under development. Multibeam ion irradiation can be used to study the synergistic effects that occur due to simultaneous gas generation and displacement cascade damage in materials exposed to complex radiation environments. Elevated or cryogenic temperature TEM stages are often utilized with multibeam irradiation to more closely mimic specific environments, as temperature plays a significant role in defect evolution. Additionally, mechanical testing stages can be utilized to quantify the role of synergistic effects on mechanical property changes as a function of irradiation dose.
Ion irradiation has been used as an accelerated aging technique to simulate the atomic displacement cascade damage that occurs during neutron irradiation in a reactor environment, as the technique can provide many orders of magnitude faster damage rate while avoiding prolonged activation of the target material16. The I3TEM facility at Sandia National Laboratories harnesses two types of accelerators to make possible a wide range of ion species and energies. The high energy ion beam is produced by a 6 MV Tandem accelerator and low energy ions are produced by a 10 kV Colutron accelerator. Au ions up to 100 MeV have been produced in the Tandem, while the Colutron has successfully run gaseous species including H, Deuterium (D), He, N, and Xe14,17. A mixed D2 and He gas plasma can be utilized to perform triple ion irradiation with the heavy ion beam coming from the Tandem, and a mixed D2 + He beam coming from the Colutron.
Controlled production of ions allows for precise dosing of material to reach a target damage and implantation concentration. When simulating neutron irradiation with ion beam irradiation, the damage dose, in displacements per atom (dpa) can be computed. This value represents the average number of displacements of an atom from its original lattice site position, and is not the same as the total defect concentration. Calculating the total defect concentration requires more advanced simulation tools with the capability to account for recombination effects. The dpa can be calculated using ion irradiation damage models such as the Monte Carlo simulation software Stopping Range of Ions in Matter (SRIM)18. SRIM can output vacancy distribution, stopping powers, and ion ranges in a target based on the target composition, ion species, and ion energy. This provides information necessary for quantifying ion implantation, radiation damage, sputtering, ion transmission, as well as medical and biological applications.
When considering this tool for investigating the effects of irradiation it is important to design the experiment to take full advantage of the strengths of the technique. The utilization of in situ TEM irradiation creates an ideal scenario to quantify the dynamic evolution of defects created in radiation environments. While this technique provides insight into defect evolution including loop faulting/defaulting reactions and defect-grain boundary (GB) accommodation mechanisms, significant experimental limitations exist in comparing the defect quantification to bulk scale irradiations due to well-known thin-film effects including loss of point defect and defect clusters to the sample surface19,20.
This article provides novel considerations and procedures on preparation and mounting of samples for in situ multibeam TEM experiments. Also described are experimental design considerations including modeling and geometric considerations specific to the I&#179;TEM facility as well as protocol for beam alignment and beam characterization. A demonstration of the use of SRIM to calculate the energy required for a given depth of ion implantation, and the ion distribution and damage profile is provided. While the modeling methods21,22 and some sample preparation methods have been reported previously, the application of this information to experimental design is emphasized here. Representative results from in situ TEM experiments are presented and typical data analysis is also described.

<table>
	<tbody>
		<tr>
			<td>Colutron Accelerator</td>
			<td>Colutron Research Corporation</td>
			<td>G-1</td>
			<td>10 kV ion accelerator</td>
		</tr>
		<tr>
			<td>Cu Omniprobe Lift-Out Grid with 4 posts</td>
			<td>Ted Pella</td>
			<td>DM71302</td>
			<td>Cu Omniprobe Lift-Out Grid with 4 posts</td>
		</tr>
		<tr>
			<td>Double Tilt Cryo TEM Stage</td>
			<td>Gatan</td>
			<td>DT636</td>
			<td>Cryogenically cooled double tilt TEM holder</td>
		</tr>
		<tr>
			<td>Double Tilt Heating TEM Stage</td>
			<td>Gatan</td>
			<td>DT652</td>
			<td>Resistive heater equipped double tilt TEM holder</td>
		</tr>
		<tr>
			<td>I3TEM</td>
			<td>JEOL</td>
			<td>JEM-2100</td>
			<td>Modified transmission electron microscope for in-situ ion irradiation</td>
		</tr>
		<tr>
			<td>Isopropanol</td>
			<td>Fisher Scientific</td>
			<td>A459-4</td>
			<td>70 % v/v isopropanol</td>
		</tr>
		<tr>
			<td>Mo Omniprobe Lift-Out Grid with 4 posts</td>
			<td>Ted Pella</td>
			<td>DM810113</td>
			<td>Mo Omniprobe Lift-Out Grid with 4 posts</td>
		</tr>
		<tr>
			<td>Petri Dish</td>
			<td>Fisher Scientific</td>
			<td>Corning 316060</td>
			<td>60 mm diamter 15 mm height petri dish</td>
		</tr>
		<tr>
			<td>Picoindenter TEM Stage</td>
			<td>Bruker Hysitron</td>
			<td>PI95</td>
			<td>Picoindenter TEM Stage</td>
		</tr>
		<tr>
			<td>Scios 2</td>
			<td>Thermofisher Scientfic</td>
			<td>SCIOS2</td>
			<td>Dual beam focused ion beam scaning electron microscope</td>
		</tr>
		<tr>
			<td>Tandem Accelerator</td>
			<td>High Voltage Engineering Corporation</td>
			<td></td>
			<td>6 MV Van de Graaff-Pelletron ion accelerator</td>
		</tr>
		<tr>
			<td>Tomography TEM holder</td>
			<td>Hummingbird</td>
			<td></td>
			<td>TEM holder for tomography measurements</td>
		</tr>
		<tr>
			<td>Tweezers</td>
			<td>PELCO</td>
			<td>5373-NM</td>
			<td>Reverse action self closing fine tip tweezer</td>
		</tr>
	</tbody>
</table>

sample preparation and experimental design for in situ multi-beam transmission electron microscopy irradiation experiments

There is a need to understand materials exposed to overlapping extreme environments such as high temperature, radiation, or mechanical stress. When these stressors are combined there may be synergistic effects that enable unique microstructural evolution mechanisms to activate. Understanding of these mechanisms is necessary for the input and refinement of predictive models and critical for engineering of next generation materials. The basic physics and underlying mechanisms require advanced tools to be investigated. The in situ ion irradiation transmission electron microscope (I&#179;TEM) is designed to explore these principles.
To quantitatively probe the complex dynamic interactions in materials, careful preparation of samples and consideration of experimental design is required. Particular handling or preparation of samples can easily introduce damage or features that obfuscate the measurements. There is no one correct way to prepare a sample; however, many mistakes can be made. The most common errors and things to consider are highlighted within. The I&#179;TEM has many adjustable variables and a large potential experimental space, therefore it is best to design experiments with a specific scientific question or questions in mind.
Experiments have been performed on large number of sample geometries, material classes, and with many irradiation conditions. The following are a subset of examples that demonstrate unique in situ capabilities utilizing the I3TEM. Au nanoparticles prepared by drop casting have been used to investigate the effects of single ion strikes. Au thin films have been used in studies on the effects of multibeam irradiation on microstructure evolution. Zr films have been exposed to irradiation and mechanical tension to examine creep. Ag nanopillars were subjected to simultaneous high temperature, mechanical compression, and ion irradiation to study irradiation induced creep as well. These results impact fields including: structural materials, nuclear energy, energy storage, catalysis, and microelectronics in space environments.

In situ ion irradiation TEM experiments have been conducted on several material systems and with several different methods of specimen preparation 14,32,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70, 71,72,73,74,75. Below are a few selected systems that demonstrate this variety. Sample preparation methods include nanoparticle drop-casting, thin-film float off, cross-sectional FIB liftout on half-moon grid, push-to-pull foils, and nanopillars.
Highlighted here is an experiment on the effects of single ion strikes on Au nanoparticles (NPs)60. The number density of particles in the irradiation window was controlled by taking advantage of the capillary forces that pull NPs along as a droplet dries. By dropping off center, the droplet pulls NPs towards the edge of the disc as it dries. The active mechanisms for damage can be highlighted by taking the difference before and after an event (Figure 5). The measurements reveal several mechanisms for damage induced by single self-ion irradiation including creation of surface craters, sputtering, filament formation, and particle fragmentation where the types of damage depend on ion energy. Filament formation is seen at lower ion energies, whereas cratering, sputtering, and particle fragmentation are observed at high ion energies. These different energy regimes can be used to investigate the effects of the electronic and nuclear stopping powers.
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/61293/61293fig5v2.jpg" /> 
Figure 5: Effects of single 46 keV ions in NPs of decreasing size.&#160;Note that the magnification is similar for all micrographs. Each pair of micrographs is separated by 1 frame, about 0.25 s here. (a&#8211;c) A single ion strike in a 60 nm NP created a surface crater, marked by the white arrow. Panel (c) shows the difference image highlights the change between (a) and (b); features present only in (a) are dark and newly formed features present only in (b) appear light. (d&#8211;f) A single ion creating a crater in a 20 nm NP. Panel (f) shows the difference image of (d) and (e).&#160;This figure has been modified with permission from Cambridge University Press60. <a href="https://www.jove.com/files/ftp_upload/61293/61293fig5v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Nanocrystalline thin films of Au were prepared for in situ multibeam TEM experiments. The samples were deposited by pulsed laser deposition onto NaCl substrates then floated off in deionized water onto Mo TEM grids. The samples were annealed in a vacuum furnace at 300 &#176;C for 12 h to relax the as-deposited metastable nanocrystalline structure resulting in polycrystalline gold with ultrafine grain size.
In this study, 2.8 MeV Au4+ ions are used to simulate neutron irradiation. The energy is chosen based on SRIM modeling to result in peak damage within the film thickness (Figure 6a). Simultaneous 10 keV He+ simulates the production of &#945;-particles from neutron-radiation induced nuclear reactions. The He ion energy is chosen such that the ions are implanted within the foil thickness rather than passing through (Figure 6b).
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/61293/61293fig6v2.jpg" /> 
Figure 6: SRIM modeling.&#160;SRIM calculated (a) displacement and (b) concentration profiles as a function of depth for Au irradiated with various ion species. The total dpa profile (D + He + Au) is indicated by purple stars in (a). Lines of fit are a guides to the eye. This figure has been modified with permission from MDPI17. <a href="https://www.jove.com/files/ftp_upload/61293/61293fig6v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The material was then irradiated by Au ions and damage was observed with respect to fluence. The microstructure developed defects induced by the high energy ions (Figure 7). With increasing time of exposure and thus fluence, the damage increased linearly. At high doses the concentration of damage sites is too high to reliably quantify.
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/61293/61293fig7v2.jpg" /> 
Figure 7: TEM images showing damage spots.&#160;TEM images from in situ 2.8 MeV Au4+ irradiation into a Au foil using dose rates of 9.69 &#215; 1010 (a&#8211;c) and 9.38 &#215; 108 ions/cm2&#183;s (e&#8211;g), at fluences of 4.85 &#215; 108, 1.45 &#215; 1012 and 3.39 &#215; 1012 ions/cm2. (d,h) show linear increases in number of damage spots with time. All TEM images were taken at the same magnification. This figure has been modified with permission from MDPI17. <a href="https://www.jove.com/files/ftp_upload/61293/61293fig7v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
To explore the effects of multiple beams interacting with the material at the same time, double and triple ion beam irradiation is then performed on Au (Figure 8). Cavity nucleation, growth, and evolution are measured.
<img alt="Figure 8" class="xfigimg" src="/files/ftp_upload/61293/61293fig8v2.jpg" /> 
Figure 8: In situ TEM images showing cavity growth.&#160;In situ TEM images showing cavity growth as a function of time due to (a&#8211;d) double ion irradiation with 5 keV D + 1.7 MeV Au and cavity formation and collapse as a function of time due to (e&#8211;h) triple ion irradiation with 10 keV He, 5 keV D and 2.8 MeV Au. Dashed circles highlight the cavity of interest in each image. This figure has been modified with permission from MDPI17. <a href="https://www.jove.com/files/ftp_upload/61293/61293fig8v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
To explore irradiation induced creep in Zr, a microelectromechanical system (MEMS) device was fabricated by sputter depositing Zr thin films on silicon-on insulator wafers followed by photolithographic patterning and subsequent deep reactive ion etching. Figure 9 shows the free standing Zr specimen and the Si push-to-pull test frame which enables in situ tensile testing. 1.4 MeV Zr ions were used to irradiate the specimen under load to determine irradiation creep response in Zr. By conducting the experiment in a TEM, dynamic mechanisms at the nanoscale can be observed. Measurements reveal a texture change as well as a lengthening of the specimen. Volumetric swelling was not expected due to the thin foil specimen geometry, room temperature conditions, and low levels of irradiation damage. This is confirmed by the lack of observed bubble and cavity formation.
<img alt="Figure 9" class="xfigimg" src="/files/ftp_upload/61293/61293fig9v2.jpg" /> 
Figure 9: In situ mechanical testing.&#160;(a) SEM image of the push-to-pull device with Zr tensile sample location highlighted. (b) Low-magnification TEM image of the device from (a). (c) Higher-magnification bright-field TEM image of the nanocrystalline Zr microstructure in the test region. This figure has been modified with permission from Springer Nature75. <a href="https://www.jove.com/files/ftp_upload/61293/61293fig9v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Additional mechanical stressor states can be applied simultaneously during in situ ion irradiation TEM experiments. Figure 10 shows work on high temperature irradiation induced creep of Ag nanopillars67. This utilizes a picoindentor to apply a controlled stress to a TEM specimen. Pillars were prepared from 1 &#956;m thick Ag film grown on Si by FIB milling. The pillars were irradiated with 3 MeV Ag&#179;+ ions. The specimens were heated with a 1064 nm laser beam coincident with both the ion beam and electron beam. The results of this study show that combined irradiation and temperature result in orders of magnitude faster creep rate than room temperature irradiation and high temperature thermal creep.
<img alt="Figure 10" class="xfigimg" src="/files/ftp_upload/61293/61293fig10v2.jpg" /> 
Figure 10: Radiation-induced creep.&#160;Radiation-induced creep rate versus pillar diameter at 75 and 125 MPa loading stresses (left), selected frames from video recording of in situ TEM radiation induced creep in Ag nanopillar irradiated by 3 MeV Ag ions (right). This figure has been modified with permission from Elsevier67. <a href="https://www.jove.com/files/ftp_upload/61293/61293fig10v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Considerations for the preparation of nanopillars for shallow ion irradiation has been described in depth by Hosemann et al.76. One of the key factors to consider is the shape of the nanopillar. At this small scale any deviation from ideal geometry can have a large impact on the mechanical performance. A rectangular prism tip is much better than a cylindrical tip due to tapering of the tip in annular milled geometry.
These representative results demonstrate a range of material systems, preparation methods, and complex environments that are possible with in situ ion irradiation TEM. In each case careful sample preparation and planning of experimental parameters are critical to extract meaningful data. Further detail on these considerations is discussed below.

Watch this Scientific Journal Video about Sample Preparation and Experimental Design for In Situ Multi-Beam Transmission Electron Microscopy Irradiation Experiments at JoVE.com

Sample Preparation and Experimental Design for In Situ Multi-Beam Transmission Electron Microscopy Irradiation Experiments

Sample preparation techniques are outlined with specific considerations for in situ ion irradiation TEM experiments. Ion species, energy, and fluence are discussed with methods for how to select and compute them. Finally, procedures for conducting an experiment are described and accompanied by the representative results.

There is a need to understand materials exposed to overlapping extreme environments such as high temperature, radiation, or mechanical stress. When these ...

Sample Preparation and Experimental Design for In Situ Multi-Beam Transmission Electron Microscopy Irradiation Experiments

Abstract