scanning transmission electron microscopy

File:Stemschema1.JPG{{See also|Electron diffraction#History|Transmission electron microscopy#History|label 1=Electron diffraction|label 2=Transmission electron microscopy}}

The first STEM was built in 1938 by Baron Manfred von Ardenne,{{cite journal |last=von Ardenne |first=M |year=1938 |title=Das Elektronen-Rastermikroskop. Theoretische Grundlagen |journal=Z. Phys. |volume=109 |pages=553–572 |bibcode=1938ZPhy..109..553V |doi=10.1007/BF01341584 |issue=9–10 |s2cid=117900835}}{{cite journal |last=von Ardenne |first=M |year=1938 |title=Das Elektronen-Rastermikroskop. Praktische Ausführung |journal=Z. Tech. Phys. |volume=19 |pages=407–416}} working in Berlin for Siemens. However, at the time the results were inferior to those of transmission electron microscopy, and von Ardenne only spent two years working on the problem. The microscope was destroyed in an air raid in 1944, and von Ardenne did not return to his work after World War II.[http://www-g.eng.cam.ac.uk/125/achievements/mcmullan/mcm.htm D. McMullan, SEM 1928 – 1965]

The technique was not developed further until the 1970s, when Albert Crewe at the University of Chicago developed the field emission gun{{cite journal |last=Crewe |first=Albert V |author2=Isaacson, M. |author3=Johnson, D. |year=1969 |title=A Simple Scanning Electron Microscope |journal=Rev. Sci. Instrum. |volume=40 |pages=241–246 |doi=10.1063/1.1683910 |bibcode=1969RScI...40..241C |issue=2 |url=https://digital.library.unt.edu/ark:/67531/metadc1061663/ |type=Submitted manuscript}} and added a high-quality objective lens to create a modern STEM. He demonstrated the ability to image atoms using an annular dark field detector. Crewe and coworkers at the University of Chicago developed the cold field emission electron source and built a STEM able to visualize single heavy atoms on thin carbon substrates.{{cite journal |last=Crewe |first=Albert V |author2=Wall, J. |author3=Langmore, J. |year=1970 |title=Visibility of a single atom |journal=Science |volume=168 |pages=1338–1340 |doi=10.1126/science.168.3937.1338 |pmid=17731040 |issue=3937 |bibcode=1970Sci...168.1338C |s2cid=31952480}}

By the late 1980s and early 1990s, improvements in STEM technology allowed for samples to be imaged with better than 2 Å resolution, meaning that atomic structure could be imaged in some materials.{{cite journal |author1=Shin, D.H. |author2=Kirkland, E.J. |author3=Silcox, J. |title=Annular dark field electron microscope images with better than 2 Å resolution at 100 kV |journal=Appl. Phys. Lett. |year=1989 |volume=55 |issue=23 |pages=2456 |doi=10.1063/1.102297 |bibcode=1989ApPhL..55.2456S |citeseerx=10.1.1.466.7672}}

The addition of an aberration corrector to STEMs enables electron probes to be focused to sub-angstrom diameters, allowing images with sub-angstrom resolution to be acquired. This has made it possible to identify individual atomic columns with unprecedented clarity.

Aberration-corrected STEM was demonstrated with 1.9 Å resolution in 1997{{cite journal |author1=Batson, P.E. |author2=Domenincucci, A.G. |author3=Lemoine, E. |year=1997 |title=Atomic resolution electronic structure in device development |journal=Microsc. Microanal. |volume=3 |issue=S2 |pages=645 |doi=10.1017/S1431927600026064 |bibcode=1997MiMic...3S.645B|s2cid=250948492 }} and soon after in 2000 with roughly 1.36 Å resolution.{{cite journal |doi=10.1093/jmicro/50.3.177 |pmid=11469406 |title=Progress in aberration-corrected scanning transmission electron microscopy |journal=Microscopy |volume=50 |issue=3 |pages=177–185 |year=2001 |last1=Dellby |first1=N. |last2=Krivanek |first2=O. L.|author2-link=Ondrej Krivanek |last3=Nellist |first3=P. D.|author3-link=Peter Nellist |last4=Batson |first4=P. E. |last5=Lupini |first5=A. R. |doi-access=free}} Advanced aberration-corrected STEMs have since been developed with sub-50 pm resolution.{{cite journal |title=Detection of Single Atoms and Buried Defects in Three Dimensions by Aberration-Corrected Electron Microscope with 0.5-Å Information Limit |pmid=18793491 |journal=Microscopy and Microanalysis |year=2008 |volume=14 |issue=5 |pages=469–477 |doi=10.1017/S1431927608080902 |last1=Kisielowski |first1=C. |last2=Freitag |first2=B. |last3=Bischoff |first3=M. |last4=Van Lin |first4=H. |last5=Lazar |first5=S. |last6=Knippels |first6=G. |last7=Tiemeijer |first7=P. |last8=Van Der Stam |first8=M. |last9=von Harrach |first9=S. |last10=Stekelenburg |first10=M. |last11=Haider |first11=M. |last12=Uhlemann |first12=S. |last13=Müller |first13=H. |last14=Hartel |first14=P. |last15=Kabius |first15=B. |last16=Miller |first16=D. |last17=Petrov |first17=I. |last18=Olson |first18=E.A. |last19=Donchev |first19=T. |last20=Kenik |first20=E.A. |last21=Lupini |first21=A.R. |last22=Bentley |first22=J. |last23=Pennycook |first23=S.J. |last24=Anderson |first24=I.M. |last25=Minor |first25=A.M. |last26=Schmid |first26=A.K. |last27=Duden |first27=T. |last28=Radmilovic |first28=V. |last29=Ramasse |first29=Q.M. |last30=Watanabe |first30=M. |display-authors=29 |bibcode=2008MiMic..14..469K |s2cid=12689183 }}

Aberration-corrected STEM provides the added resolution and beam current critical to the implementation of atomic resolution chemical and elemental spectroscopic mapping.

File:Scanning transmission electron microscopy srtio3 compare adf abf.jpg{{More citations needed section|talk=y|date=September 2023}}{{Main|Annular dark-field imaging}}

In annular dark-field mode, images are formed by fore-scattered electrons incident on an annular detector, which lies outside of the path of the directly transmitted beam.

By using a high-angle ADF detector, it is possible to form atomic resolution images where the contrast of an atomic column is directly related to the atomic number (Z-contrast image).{{cite journal |author1=Pennycook, S.J. |author2=Jesson, D.E. |title=High-resolution Z-contrast imaging of crystals |journal=Ultramicroscopy |year=1991 |volume=37 |issue=1–4 |pages=14–38 |doi=10.1016/0304-3991(91)90004-P |url=https://zenodo.org/record/1258469 |type=Submitted manuscript}} Directly interpretable Z-contrast imaging makes STEM imaging with a high-angle detector an appealing technique in contrast to conventional high-resolution electron microscopy, in which phase-contrast effects mean that atomic resolution images must be compared to simulations to aid interpretation.

In STEM, bright-field detectors are located in the path of the transmitted electron beam. Axial bright-field detectors are located in the centre of the cone of illumination of the transmitted beam, and are often used to provide complementary images to those obtained by ADF imaging.{{cite journal |title=High-resolution imaging of silicon (111) using a 100 keV STEM |journal=Ultramicroscopy |year=1990 |volume=32 |issue=2 |pages=93–102 |doi=10.1016/0304-3991(90)90027-J |last1=Xu |first1=Peirong |last2=Kirkland |first2=Earl J. |last3=Silcox |first3=John |last4=Keyse |first4=Robert|doi-access=free }} Annular bright-field detectors, located within the cone of illumination of the transmitted beam, have been used to obtain atomic resolution images in which the atomic columns of light elements such as oxygen are visible.{{cite journal |title=Dynamics of annular bright field imaging in scanning transmission electron microscopy |journal=Ultramicroscopy |year=2010 |volume=32 |issue=7 |pages=903–923 |doi=10.1016/j.ultramic.2010.04.004 |pmid=20434265 |last1=Findlay |first1=S.D. |last2=Shibata |first2=N. |last3=Sawada |first3=H. |last4=Okunishi |first4=E. |last5=Kondo |first5=Y. |last6=Ikuhara |first6=Y.}}

File:Stem dpc schematic magnetic explanation.jpg

Differential phase contrast (DPC) is an imaging mode which relies on the beam being deflected by electromagnetic fields. In the classical case, the fast electrons in the electron beam is deflected by the Lorentz force, as shown schematically for a magnetic field in the figure to the left. The fast electron with charge −1 {{Var|e}} passing through an electric field E and a magnetic field B experiences a force F:

:$\backslash mathbf\{F\}\; =\; -e\backslash mathbf\{E\}\; -\; e\backslash mathbf\{v\}\; \backslash times\; \backslash mathbf\{B\}$

For a magnetic field, this can be expressed as the amount of beam deflection experienced by the electron, {{math|β{{sub|L}}}}:

:$\backslash beta\_L\; =\; -\backslash frac\{e\backslash lambda\}\{h\}\; \backslash int\; \backslash mathbf\{B\}\; \backslash times\; d\backslash mathbf\{l\}$

where $\backslash lambda$ is the wavelength of the electron, $h$ the Planck constant and $\backslash textstyle\backslash int\; \backslash mathbf\{B\}\; \backslash times\; d\backslash mathbf\{l\}$ is integrated magnetic induction along the trajectory of the electron. This last term reduces to $B\_S\; t$ when the electron beam is perpendicular to a sample of thickness $t$ with constant in-plane magnetic induction of magnitude $B\_S$. The beam deflection can then be imaged on a segmented or pixelated detector.{{cite journal |last1=Krajnak |first1=Matus |last2=McGrouther |first2=Damien |last3=Maneuski |first3=Dzmitry |last4=Shea |first4=Val O' |last5=McVitie |first5=Stephen |title=Pixelated detectors and improved efficiency for magnetic imaging in STEM differential phase contrast |journal=Ultramicroscopy |date=June 2016 |volume=165 |pages=42–50 |doi=10.1016/j.ultramic.2016.03.006 |pmid=27085170 |doi-access=free}} This can be used to image magnetic{{cite journal |last1=McVitie |first1=S. |last2=Hughes |first2=S. |last3=Fallon |first3=K. |last4=McFadzean |first4=S. |last5=McGrouther |first5=D. |last6=Krajnak |first6=M. |last7=Legrand |first7=W. |last8=Maccariello |first8=D. |last9=Collin |first9=S. |last10=Garcia |first10=K. |last11=Reyren |first11=N. |last12=Cros |first12=V. |last13=Fert |first13=A. |last14=Zeissler |first14=K. |last15=Marrows |first15=C. H. |title=A transmission electron microscope study of Néel skyrmion magnetic textures in multilayer thin film systems with large interfacial chiral interaction |journal=Scientific Reports |date=9 April 2018 |volume=8 |issue=1 |pages=5703 |doi=10.1038/s41598-018-23799-0 |pmid=29632330 |pmc=5890272 |bibcode=2018NatSR...8.5703M |arxiv=1711.05552}} and electric fields{{cite journal |last1=Haas |first1=Benedikt |last2=Rouvière |first2=Jean-Luc |last3=Boureau |first3=Victor |last4=Berthier |first4=Remy |last5=Cooper |first5=David |title=Direct comparison of off-axis holography and differential phase contrast for the mapping of electric fields in semiconductors by transmission electron microscopy. |journal=Ultramicroscopy |date=March 2019 |volume=198 |pages=58–72 |doi=10.1016/j.ultramic.2018.12.003 |pmid=30660032 |s2cid=58636157|doi-access=free }} in materials. While the beam deflection mechanism through the Lorentz force is the most intuitive way of understanding DPC, a quantum mechanical approach is necessary to understand the phase-shift generated by the electromagnetic fields through the Aharonov–Bohm effect.

File:Ferromagnetic domains in spiral pattern for Fe60Al40.jpg

Imaging most ferromagnetic materials require the current in the objective lens of the STEM to be reduced to almost zero. This is due to the sample residing inside the magnetic field of the objective lens, which can be several Tesla, which for most ferromagnetic materials would destroy any magnetic domain structure.{{cite journal |last1=Chapman |first1=J N |title=The investigation of magnetic domain structures in thin foils by electron microscopy |journal=Journal of Physics D: Applied Physics |date=14 April 1984 |volume=17 |issue=4 |pages=623–647 |doi=10.1088/0022-3727/17/4/003|s2cid=250805904 }} However, turning the objective lens almost off drastically increase the amount of aberrations in the STEM probe, leading to an increase in the probe size, and reduction in resolution. By using a probe aberration corrector it is possible to get a resolution of 1 nm.{{cite journal |last1=McVitie |first1=S. |last2=McGrouther |first2=D. |last3=McFadzean |first3=S. |last4=MacLaren |first4=D.A. |last5=O’Shea |first5=K.J. |last6=Benitez |first6=M.J. |title=Aberration corrected Lorentz scanning transmission electron microscopy |journal=Ultramicroscopy |date=May 2015 |volume=152 |pages=57–62 |doi=10.1016/j.ultramic.2015.01.003 |pmid=25677688 |url=http://eprints.gla.ac.uk/102200/2/102200.pdf}}

Recently, detectors have been developed for STEM that can record a complete convergent-beam electron diffraction pattern of all scattered and unscattered electrons at every pixel in a scan of the sample in a large four-dimensional dataset (a 2D diffraction pattern recorded at every 2D probe position).{{cite journal |title=High Dynamic Range Pixel Array Detector for Scanning Transmission Electron Microscopy |pmid=26750260 |arxiv=1511.03539 |journal=Microscopy and Microanalysis |year=2016 |volume=22 |issue=1 |pages=237–249 |doi=10.1017/S1431927615015664 |last1=Tate |first1=Mark W. |last2=Purohit |first2=Prafull |last3=Chamberlain |first3=Darol |last4=Nguyen |first4=Kayla X. |last5=Hovden |first5=Robert |last6=Chang |first6=Celesta S. |last7=Deb |first7=Pratiti |last8=Turgut |first8=Emrah |last9=Heron |first9=John T. |last10=Schlom |first10=Darrell G. |last11=Ralph |first11=Daniel C. |last12=Fuchs |first12=Gregory D. |last13=Shanks |first13=Katherine S. |last14=Philipp |first14=Hugh T. |last15=Muller |first15=David A. |last16=Gruner |first16=Sol M. |bibcode=2016MiMic..22..237T |s2cid=5984477}} Due to the four-dimensional nature of the datasets, the term "4D STEM" has become a common name for this technique.{{cite journal |last=Ophus |first=Colin |date=June 2019 |title=Four-Dimensional Scanning Transmission Electron Microscopy (4D-STEM): From Scanning Nanodiffraction to Ptychography and Beyond |journal=Microscopy and Microanalysis |language=en |volume=25 |issue=3 |pages=563–582 |doi=10.1017/S1431927619000497 |pmid=31084643 |bibcode=2019MiMic..25..563O |issn=1431-9276 |doi-access=free}}{{cite journal |url=https://analyticalscience.wiley.com/do/10.1002/was.00010003 |title=4D STEM with a direct electron detector |website=Wiley Analytical Science |language=en |access-date=2020-02-11}} The 4D datasets generated using the technique can be analyzed to reconstruct images equivalent to those of any conventional detector geometry, and can be used to map fields in the sample at high spatial resolution, including information about strain and electric fields.{{cite journal |title=Multimodal Acquisition of Properties and Structure with Transmission Electron Reciprocal-space (MAPSTER) Microscopy |journal=Microscopy and Microanalysis |year=2016 |volume=22(S3) |issue=S3 |pages=1412–1413 |doi=10.1017/S143192761600790X |last1=Ciston |first1=Jim |last2=Ophus |first2=Colin |last3=Ercius |first3=Peter |last4=Yang |first4=Hao |last5=Dos Reis |first5=Roberto |last6=Nelson |first6=Christopher T. |last7=Hsu |first7=Shang-Lin |last8=Gammer |first8=Christoph |last9=Özdöl |first9=Burak V. |last10=Deng |first10=Yu |last11=Minor |first11=Andrew |bibcode=2016MiMic..22S1412C |doi-access=free}} The technique can also be used to perform ptychography.

{{Main|Electron energy loss spectroscopy}}

As the electron beam passes through the sample, some electrons in the beam lose energy via inelastic scattering interactions with electrons in the sample. In electron energy loss spectroscopy (EELS), the energy lost by the electrons in the beam is measured using an electron spectrometer, allowing features such as plasmons, and elemental ionization edges to be identified. Energy resolution in EELS is sufficient to allow the fine structure of ionization edges to be observed, which means that EELS can be used for chemical mapping, as well as elemental mapping.{{cite book |editor=Egerton, R.F. |title=Electron Energy-Loss Spectroscopy in the Electron Microscope |publisher=Springer |isbn=978-1-4419-9582-7 |year=2011}} In STEM, EELS can be used to spectroscopically map a sample at atomic resolution.{{cite journal |title=Visualizing the interfacial evolution from charge compensation to metallic screening across the manganite metal–insulator transition |journal=Nature Communications |year=2014 |volume=5 |pages=3464 |doi=10.1038/ncomms4464 |pmid=24632721 |last1=Mundy |first1=Julia A. |last2=Hikita |first2=Yasuyuki |last3=Hidaka |first3=Takeaki |last4=Yajima |first4=Takeaki |last5=Higuchi |first5=Takuya |last6=Hwang |first6=Harold Y. |last7=Muller |first7=David A. |last8=Kourkoutis |first8=Lena F. |bibcode=2014NatCo...5.3464M |doi-access=free}} Recently developed monochromators can achieve an energy resolution of ~10 meV in EELS, allowing vibrational spectra to be acquired in STEM.{{cite journal |title=Vibrational spectroscopy in the electron microscope |journal=Nature |year=2016 |volume=514 |issue=7521 |pages=209–212 |doi=10.1038/nature13870 |pmid=25297434 |last1=Krivanek |first1=Ondrej L.|author1-link=Ondrej Krivanek |last2=Lovejoy |first2=Tracy C. |last3=Dellby |first3=Niklas |last4=Aoki |first4=Toshihiro |last5=Carpenter |first5=R. W. |last6=Rez |first6=Peter |last7=Soignard |first7=Emmanuel |last8=Zhu |first8=Jiangtao |last9=Batson |first9=Philip E. |last10=Lagos |first10=Maureen J. |last11=Egerton |first11=Ray F. |last12=Crozier |first12=Peter A. |bibcode=2014Natur.514..209K |s2cid=4467249}}

{{Main|Energy-dispersive X-ray spectroscopy}}

In energy-dispersive X-ray spectroscopy (EDX) or (EDXS), which is also referred to in literature as X-ray energy dispersive spectroscopy (EDS) or (XEDS), an X-ray spectrometer is used to detect the characteristic X-rays that are emitted by atoms in the sample as they are ionized by electron in the beam. In STEM, EDX is typically used for compositional analysis and elemental mapping of samples.{{cite journal |author1=Friel, J.J. |author2=Lyman, C.E. |title=Tutorial Review: X-ray Mapping in Electron-Beam Instruments |journal=Microscopy and Microanalysis |year=2006 |volume=12 |issue=1 |pages=2–25 |doi=10.1017/S1431927606060211 |pmid=17481338 |bibcode=2006MiMic..12....2F |citeseerx=10.1.1.548.9845 |s2cid=135786852}} Typical X-ray detectors for electron microscopes cover only a small solid angle, which makes X-ray detection relatively inefficient since X-rays are emitted from the sample in every direction. However, detectors covering large solid angles have been recently developed,{{cite journal |doi=10.1017/S1551929509000224 |title=Innovative Instrumentation for Analysis of Nanoparticles: The π Steradian Detector |journal=Microsc. Today |volume=17 |issue=4 |year=2009 |pages=56–59 |last1=Zaluzec |first1=Nestor J. |s2cid=137645643 |doi-access=free }} and atomic resolution X-ray mapping has even been achieved.{{cite journal |title=Quantitative atomic resolution elemental mapping via absolute-scale energy dispersive X-ray spectroscopy |journal=Ultramicroscopy |volume=168 |issue=4 |year=2016 |pages=7–16 |doi=10.1016/j.ultramic.2016.05.008 |pmid=27258645 |last1=Chen |first1=Z. |last2=Weyland |first2=M. |last3=Sang |first3=X. |last4=Xu |first4=W. |last5=Dycus |first5=J.H. |last6=Lebeau |first6=J.M. |last7=d'Alfonso |first7=A.J. |last8=Allen |first8=L.J. |last9=Findlay |first9=S.D. |doi-access=free}}

{{Main|Convergent-beam electron diffraction}}

Convergent-beam electron diffraction (CBED) is a STEM technique that provides information about crystal structure at a specific point in a sample. In CBED, the width of the area a diffraction pattern is acquired from is equal to the size of the probe used, which can be smaller than 1 Å in an aberration-corrected STEM (see above). CBED differs from conventional electron diffraction in that CBED patterns consist of diffraction disks, rather than spots. The width of CBED disks is determined by the convergence angle of the electron beam. Other features, such as Kikuchi lines are often visible in CBED patterns. CBED can be used to determine the point and space groups of a specimen.{{cite book |editor1=Reimer, L. |editor2=Kohl, R. |title=Transmission Electron Microscopy Physics of Image Formation |publisher=Springer |isbn=978-0-387-40093-8 |year=2008}}

{{More citations needed section|talk=y|date=September 2023}}

Electron microscopy has accelerated research in materials science by quantifying properties and features from nanometer-resolution imaging with STEM, which is crucial in observing and confirming factors, such as thin film deposition, crystal growth, surface structure formation, and dislocation movement. Until recently, most papers have inferred the properties and behaviors of material systems based on these images without being able to establish rigorous rules for what exactly is observed. The techniques that have emerged as a result of interest in quantitative scanning transmission electron microscopy (QSTEM) closes this gap by allowing researchers to identify and quantify structural features that are only visible using high-resolution imaging in a STEM. Widely available image processing techniques are applied to high-angle annular dark field (HAADF) images of atomic columns to precisely locate their positions and the material's lattice constant(s). This ideology has been successfully used to quantify structural properties, such as strain and bond angle, at interfaces and defect complexes. QSTEM allows researchers to now compare the experimental data to theoretical simulations both qualitatively and quantitatively. Recent studies published have shown that QSTEM can measure structural properties, such as interatomic distances, lattice distortions from point defects, and locations of defects within an atomic column, with high accuracy. QSTEM can also be applied to selected area diffraction patterns and convergent beam diffraction patterns to quantify the degree and types of symmetry present in a specimen. Since any materials research requires structure-property relationship studies, this technique is applicable to countless fields. A notable study is the mapping of atomic column intensities and interatomic bond angles in a mott-insulator system.{{cite journal |title=Response of the Lattice across the Filling-Controlled Mott Metal-Insulator Transition of a Rare Earth Titanate |journal=Physical Review Letters |year=2017 |volume=119 |issue=18 |page=186803 |doi=10.1103/PhysRevLett.119.186803 |pmid=29219551 |last1=Kim |first1=Honggyu |last2=Marshall |first2=Patrick B. |last3=Ahadi |first3=Kaveh |last4=Mates |first4=Thomas E. |last5=Mikheev |first5=Evgeny |last6=Stemmer |first6=Susanne |bibcode=2017PhRvL.119r6803K |arxiv=1710.01425 |s2cid=206301792}} This was the first study to show that the transition from the insulating to conducting state was due to a slight global decrease in distortion, which was concluded by mapping the interatomic bond angles as a function of the dopant concentration. This effect is not visible by the human eye in a standard atomic-scale image enabled by HAADF imaging, thus this important finding was only made possible due to the application of QSTEM.

QSTEM analysis can be achieved using commonplace software and programming languages, such as MatLab or Python, with the help of toolboxes and plug-ins that serve to expedite the process. This is analysis that can be performed virtually anywhere. Consequently, the largest roadblock is acquiring a high-resolution, aberration-corrected scanning transmission electron microscope that can provide the images necessary to provide accurate quantification of structural properties at the atomic level. Most university research groups, for example, require permission to use such high-end electron microscopes at national lab facilities, which requires excessive time commitment. Universal challenges mainly involve becoming accustomed to the programming language desired and writing software that can tackle the very specific problems for a given material system. For example, one can imagine how a different analysis technique, and thus a separate image processing algorithm, is necessary for studying ideal cubic versus complex monoclinic structures.

Specialized sample holders or modifications to the microscope can allow a number of additional techniques to be performed in STEM. Some examples are described below.

{{Main|Electron tomography}}

STEM tomography allows the complete three-dimensional internal and external structure of a specimen to be reconstructed from a tilt-series of 2D projection images of the specimen acquired at incremental tilts.{{cite journal |title=Nanomaterial datasets to advance tomography in scanning transmission electron microscopy |journal=Scientific Data |year=2016 |volume=3 |issue=160041 |page=160041 |doi=10.1038/sdata.2016.41 |pmid=27272459 |pmc=4896123 |last1=Levin |first1=Barnaby D.A. |last2=Padgett |first2=Elliot |last3=Chen |first3=Chien-Chun |last4=Scott |first4=M.C. |last5=Xu |first5=Rui |last6=Theis |first6=Wolfgang |last7=Jiang |first7=Yi |last8=Yang |first8=Yongsoo |last9=Ophus |first9=Colin |last10=Zhang |first10=Haitao |last11=Ha |first11=Don-Hyung |last12=Wang |first12=Deli |last13=Yu |first13=Yingchao |last14=Abruña |first14=Hector D. |last15=Robinson |first15=Richard D. |last16=Ercius |first16=Peter |last17=Kourkoutis |first17=Lena F. |last18=Miao |first18=Jianwei |last19=Muller |first19=David A. |last20=Hovden |first20=Robert |bibcode=2016NatSD...360041L |arxiv=1606.02938}} High angle ADF STEM is a particularly useful imaging mode for electron tomography because the intensity of high angle ADF-STEM images varies only with the projected mass-thickness of the sample, and the atomic number of atoms in the sample. This yields highly interpretable three dimensional reconstructions.{{cite journal |doi=10.1016/S0304-3991(03)00105-0 |title=3D electron microscopy in the physical sciences: The development of Z-contrast and EFTEM tomography |journal=Ultramicroscopy |volume=96 |issue=3–4 |pages=413–431 |year=2003 |last1=Midgley |first1=P. A. |authorlink=Paul Midgley |last2=Weyland |first2=M. |pmid=12871805}}

Cryogenic electron microscopy in STEM (Cryo-STEM) allows specimens to be held in the microscope at liquid nitrogen or liquid helium temperatures. This is useful for imaging specimens that would be volatile in high vacuum at room temperature. Cryo-STEM has been used to study vitrified biological samples,{{cite journal |title=Cryo-scanning transmission electron tomography of vitrified cells |journal=Nature Methods |year=2014 |volume=11 |issue=4 |pages=423–428 |doi=10.1038/nmeth.2842 |pmid=24531421 |last1=Wolf |first1=Sharon Grayer |last2=Houben |first2=Lothar |last3=Elbaum |first3=Michael |s2cid=5336785}} vitrified solid-liquid interfaces in material specimens,{{cite journal |title=Site-Specific Preparation of Intact Solid–Liquid Interfaces by Label-Free In Situ Localization and Cryo-Focused Ion Beam Lift-Out |journal=Microscopy and Microanalysis |year=2016 |volume=22 |issue=6 |pages=1338–1349 |doi=10.1017/S1431927616011892 |pmid=27869059 |last1=Zachman |first1=Michael J. |last2=Asenath-Smith |first2=Emily |last3=Estroff |first3=Lara A. |last4=Kourkoutis |first4=Lena F. |bibcode=2016MiMic..22.1338Z |s2cid=25314940|doi-access=free }} and specimens containing elemental sulfur, which is prone to sublimation in electron microscopes at room temperature.{{cite journal |title=Characterization of Sulfur and Nanostructured Sulfur Battery Cathodes in Electron Microscopy Without Sublimation Artifacts |journal=Microscopy and Microanalysis |year=2017 |volume=23 |issue=1 |pages=155–162 |doi=10.1017/S1431927617000058 |pmid=28228169 |last1=Levin |first1=Barnaby D.A. |last2=Zachman |first2=Michael J. |last3=Werner |first3=Jörg G. |last4=Sahore |first4=Ritu |last5=Nguyen |first5=Kayla X. |last6=Han |first6=Yimo |last7=Xie |first7=Baoquan |last8=Ma |first8=Lin |last9=Archer |first9=Lynden A. |last10=Giannelis |first10=Emmanuel P. |last11=Wiesner |first11=Ulrich |last12=Kourkoutis |first12=Lena F. |last13=Muller |first13=David A. |bibcode=2017MiMic..23..155L |s2cid=6801783 |url=https://zenodo.org/record/889883}}

In order to study the reactions of particles in gaseous environments, a STEM may be modified with a differentially pumped sample chamber to allow gas flow around the sample, whilst a specialized holder is used to control the reaction temperature.{{cite journal |title=ESTEM imaging of single atoms under controlled temperature and gas environment conditions in catalyst reaction studies |journal=Annalen der Physik |year=2013 |volume=525 |issue=6 |pages=423–429 |doi=10.1002/andp.201300068 |last1=Boyes |first1=Edward D. |last2=Ward |first2=Michael R. |last3=Lari |first3=Leonardo |last4=Gai |first4=Pratibha L. |bibcode=2013AnP...525..423B |s2cid=119973907}} Alternatively a holder mounted with an enclosed gas flow cell may be used.{{cite journal |title=Complex structural dynamics of nanocatalysts revealed in Operando conditions by correlated imaging and spectroscopy probes |journal=Nature Communications |year=2015 |volume=6 |page=7583 |doi=10.1038/ncomms8583 |pmid=26119246 |pmc=4491830 |last1=Li |first1=Y. |last2=Zakharov |first2=D. |last3=Zhao |first3=S. |last4=Tappero |first4=R. |last5=Jung |first5=U. |last6=Elsen |first6=A. |last7=Baumann |first7=Ph. |last8=Nuzzo |first8=R.G. |last9=Stach |first9=E.A. |last10=Frenkel |first10=A.I. |bibcode=2015NatCo...6.7583L}}

Nanoparticles and biological cells have been studied in liquid environments using liquid-phase electron microscopy{{cite journal |last1=de Jonge |first1=N. |last2=Ross |first2=F.M. |date=2011 |title=Electron microscopy of specimens in liquid |url=https://www.researchgate.net/publication/51735636 |journal=Nature Nanotechnology |volume=6 |issue=8 |pages=695–704 |doi=10.1038/nmat944 |pmid=12872162 |bibcode=2003NatMa...2..532W |s2cid=21379512}} in STEM, accomplished by mounting a microfluidic enclosure in the specimen holder.{{cite journal |last1=de Jonge |first1=N. |last2=Peckys |first2=D.B. |last3=Kremers |first3=G.J. |last4=Piston |first4=D.W. |date=2009 |title=Electron microscopy of whole cells in liquid with nanometer resolution |journal=Proceedings of the National Academy of Sciences of the USA |volume=106 |issue=7 |pages=2159–2164 |doi=10.1073/pnas.0809567106 |pmid=19164524 |bibcode=2009PNAS..106.2159J |pmc=2650183 |doi-access=free}}{{cite journal |title=Quantitative Description of Crystal Nucleation and Growth from in Situ Liquid Scanning Transmission Electron Microscopy |journal=ACS Nano |year=2015 |volume=9 |issue=12 |pages=11784–11791 |doi=10.1021/acsnano.5b03720 |pmid=26509714 |last1=Ievlev |first1=Anton V. |last2=Jesse |first2=Stephen |last3=Cochell |first3=Thomas J. |last4=Unocic |first4=Raymond R. |last5=Protopopescu |first5=Vladimir A. |last6=Kalinin |first6=Sergei V.}}{{cite journal |title=Direct-write liquid phase transformations with a scanning transmission electron microscope |journal=Nanoscale |year=2016 |volume=8 |issue=34 |pages=15581–15588 |doi=10.1039/C6NR04994J |pmid=27510435 |last1=Unocic |first1=Raymond R. |last2=Lupini |first2=Andrew R. |last3=Borisevich |first3=Albina Y. |last4=Cullen |first4=David A. |last5=Kalinin |first5=Sergei V. |last6=Jesse |first6=Stephen |osti=1333640}}

A low-voltage electron microscope (LVEM) is an electron microscope that is designed to operate at relatively low electron accelerating voltages of between 0.5 and 30 kV. Some LVEMs can function as an SEM, a TEM, and a STEM in a single compact instrument. Using a low beam voltage increases image contrast which is especially important for biological specimens. This increase in contrast significantly reduces, or even eliminates the need to stain biological samples. Resolutions of a few nm are possible in TEM, SEM and STEM modes. The low energy of the electron beam means that permanent magnets can be used as lenses and thus a miniature column that does not require cooling can be used.{{cite journal |last=Nebesářová |first=Jana |author2=Vancová, Marie |year=2007 |url=https://www.cambridge.org/core/journals/microscopy-and-microanalysis/article/div-classtitlehow-to-observe-small-biological-objects-in-low-voltage-electron-microscopediv/9A089B9CA06B9F5D18A2CD12EA4B2A24 |title=How to Observe Small Biological Objects in Low-Voltage Electron Microscope |journal=Microscopy and Microanalysis |volume=13 |issue=S03 |pages=248–249 |doi=10.1017/S143192760708124X |bibcode=2007MiMic..13S.248N |s2cid=138891812|url-access=subscription }}{{cite journal |last=Drummy |first=Lawrence, F. |author2=Yang, Junyan |author3=Martin, David C. |year=2004 |title=Low-voltage electron microscopy of polymer and organic molecular thin films |journal=Ultramicroscopy |volume=99 |pages=247–256 |doi=10.1016/j.ultramic.2004.01.011 |pmid=15149719 |issue=4}}

• Electron diffraction
• Energy filtered transmission electron microscopy (EFTEM)
• High-resolution transmission electron microscopy (HRTEM)
• Scanning confocal electron microscopy (SCEM)
• Scanning electron microscope (SEM)
• Transmission electron microscopy (TEM)
• 4D scanning transmission electron microscopy (4D STEM)

{{Reflist|30em}}

{{Electron microscopy}}

Category:Electron beam

Category:Electron microscopy techniques

Category:German inventions of the Nazi period