Our basic simulator, which is a much more interactive complement to the transmission electron microscope (TEM) training tools at Microscopy Australia, includes a ten "bowtie-crystal" icosahedral twin, a covalent solid, a metallic solid, an oxide/metal interface, and what else? More specialized versions, with e.g. interesting biomolecules (sans hydrogen) from the Protein DataBase, with unlayered graphene specimens for our work on solidifying "carbon rain"[3], and with thin film sulfides on amorphous SiO2, may be found:
(i) here for kinesin neck alpha-helices, rhodopsin, and DNA polymerase,
(ii) here for Pt-nanotube-ssDNA, hemoglobin iron labeled with gold, transmembrane proteins, and beta sheets,
(iii) here for unlayered graphene composite with sheets, and faceted or relaxed pentacones,
(iv) here for some sulfide/oxide composites, and
(v) here for a 23,760-atom quasi-crystal approximant, and some de Tomas "annealed" carbons.
Can you identify what the various specimens are in particular? Also, if you might like to think about extending this to the on-line exploration of procedurally generated structures (like those in MineCraft), let us know!
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This is a tutorial on use of our on-line TEM simulator. Astigmatism and focus correction are done on a 10 "bowtie" crystal isoahedral twin specimen as a first target, Later, more tilting and darkfield imaging is done on an interface between gold and TiO2 hemispheres.
The thumbnail shows brightfield and darkfield images of a transmembrane protein passing through a bilayer membrane, seen edge on, using atom positions from https://www.rcsb.org/structure/2MLR in the protein database.
The simulator illustrates both deBroglie phase contrast of the sort used in traditional high resolution TEMs with subspecimen imaging lenses, which takes place across the multi-nanometer transverse coherence width of single electrons, as well as amplitude contrast of the sort commonly used in scanning transmission electron microscopes.
This is a note about a set of on-line transmission electron microsope (TEM) simulators for exploring a wide variety of specimens on the atomic scale. The thumbnail shows an Au/ZnO2 bi-crystal tilted so that the phase-interface is side-on.
The left-half of the figure provides a strong-phase-object approximation deBroglie phase-contrast image of atom columns in projection down that orientation (top-left), and diffraction pattern of the crystal (top-right), a power-spectrum of the phase-contrast image (bottom-right), and the complex-color digital-darkfield image (obtained from the image Fourier transform) of periodicities selected by an aperture (white circle) in the power spectrum.
The right-half of the figure in effect reverses the path of electrons through the electron-optic system, which by reciprocity allows us to record (with comparable resolution) an incoherently-illuminated high-angle annular darkfield image of the same specimen.
For more on application of these tools, see for example our youtube playlist on nanoscience adventures.
Real-time recording of electron diffraction under tilt, of a zirconium diboride crystal with graphite inclusions in a 300 kV transmission electron microscope. The image is of a fluorescent screen being exposed directly to 300 keV electrons. Historically, this was seen with dark adapted eyes, allowing for more contrast sensitivity than available on a computer screen.
You can see diffraction spots blink in and out as reciprocal lattice spots intersect the Ewald sphere, and on the zirconium diboride crystals you can also see Kikuchi lines sweep by like roads that mark your location in crystal orientation space on that Ewald sphere.
Real-time recording of a grain boundary in zirconium diboride under tilt with brightfield illumination, in a 300 kV transmission electron microscope. Zirconium diBoride is an ultrahigh temperature material that was being examined for possible use in hypersonic aircraft. The image is of a fluorescent screen being exposed directly to 300 keV electrons.
The dark lines that move across the field of view as the specimen is tilted are "bend contour" lines, each associated with a specific set of lattice planes being tilted in to Bragg condition to send a diffracted beam outside the brightfield objective aperture.
Just over a minute, this Kinect "space animation" says a few words about the topic discussed here, and on the youtube playlist at https://www.youtube.com/playlist?list=PLKuVo2NtpOZzCJD1Fq4hJ4h9aonO3qq13
This 19 second Kinect animation only asks a few questions. However the thumbnail is 300 keV electron diffraction pattern of a TiMn quasicrystal approximant down a 5-fold direction, showing Leonard daVinci's golden ratio modulation rings associated with the underlying icosahedral building blocks!
This silent animation used Adobe Atmosphere to travel from the electron gun LaB6 emitter and anode, through the condenser aperture, then to a silicon shard specimen on a holey carbon film supported by a 3mm copper TEM gird. After looking around there for a while, you then drop down through the objective aperture, and eventually land on the fluorescent viewing screen looking up at the microscope operator.
The thumbnail shows the specimen on its support grid, along with an electron with longitudinal and transverse coherence widths multiple nanometers in size, in effect due to "uncertainty principle broadening". The stripes on the electron are meant to represent deBroglie phase stripes, which are not drawn to scale.
This is a slideshow about the strange world of electrons hard at work in a modern day transmission electron microscope. It covers the ways in which these electrons are fast, lonely, fat, long and focussed, The source was in part published in Microscopy Today, and available on an earlier webpage here.
The thumbnail itself illustrates some digital darkfield analysis work on an electron phase contrast image of tungsten carbide. An interactive Claymation storybook on this same topic is at https://gemini.google.com/share/3ee17f5a1b77 . More on the quantum mechanics of electron images is at https://youtu.be/N_K7yxQzq7o .
The slideshow here discusses how uncertainty principle broadening of electrons in a TEM makes possible electron phase contrast imaging of atomic columns (often called "high resolution TEM") by causing individual electrons to self-interfere across their own breadth! The mechanism itself is easily quantified e.g. in a Modern Physics course using the same piece-wise constant potential analysis that is used to quantify quantum tunneling.