SEM Cambridge S150 at Geological Institute, University Kiel, 1980

SEM opened sample chamber

The scanning electron microscope (SEM) is a type of electron microscope capable of producing high-resolution images of a sample surface. Due to the manner in which the image is created, SEM images have a characteristic three-dimensional appearance and are useful for judging the surface structure of the sample. The SEM was pioneered by Manfred von Ardenne in the 1930s ^{[1] [2]}. The instrument was further developed by Charles Oatley and first commercialized by Cambridge Instruments Image File history File linksMetadata Download high-resolution version (1346x878, 112 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Scanning electron microscope Metadata This file contains additional information, probably added from the digital camera or scanner used... Image File history File linksMetadata Download high-resolution version (1346x878, 112 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Scanning electron microscope Metadata This file contains additional information, probably added from the digital camera or scanner used... Image File history File linksMetadata SEM_chamber1. ... Image File history File linksMetadata SEM_chamber1. ... This article does not cite any references or sources. ... Manfred von Ardenne (January 20, 1907 - May 26, 1997) was a German inventor. ... Sir Charles Oatley (1904–1996), Professor of Electrical Engineering, University of Cambridge, 1960–1971, and developer of one of the first scanning electron microscopes. ...

Scanning process

Low-temperature SEM magnification series for a snow crystal.

An insect coated in gold, having been prepared for viewing with a scanning electron microscope.

In a typical SEM, electrons are thermionically emitted from a tungsten or lanthanum hexaboride (LaB₆) cathode and are accelerated towards an anode; alternatively, electrons can be emitted via field emission (FE). Tungsten is used because it has the highest melting point and lowest vapour pressure of all metals, thereby allowing it to be heated for electron emission. The electron beam, which typically has an energy ranging from a few hundred eV to 100 keV, is focused by one or two condenser lenses into a beam with a very fine focal spot sized 0.4 nm to 5 nm. The beam passes through pairs of scanning coils or pairs of deflector plates in the electron optical column, typically in the objective lens, which deflect the beam horizontally and vertically so that it scans in a raster fashion over a rectangular area of the sample surface. When the primary electron beam interacts with the sample, the electrons lose energy by repeated scattering and absorption within a teardrop-shaped volume of the specimen known as the interaction volume, which extends from less than 100 nm to around 5 µm into the surface. The size of the interaction volume depends on the electrons' landing energy, the atomic number of the specimen and the specimen's density. The energy exchange between the electron beam and the sample results in the emission of electrons and electromagnetic radiation, which can be detected to produce an image, as described below. Download high resolution version (900x3994, 1532 KB)Low temperature scanning electron microscope [1] magnification series, from 93x to 36,000x magnification series, of a snow crystal. ... Download high resolution version (900x3994, 1532 KB)Low temperature scanning electron microscope [1] magnification series, from 93x to 36,000x magnification series, of a snow crystal. ... Snow is a type of precipitation in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. ... Image File history File links Metadata Size of this preview: 496 × 600 pixelsFull resolution (1859 × 2248 pixel, file size: 698 KB, MIME type: image/jpeg) Photo credit: Peter Halasz. ... Image File history File links Metadata Size of this preview: 496 × 600 pixelsFull resolution (1859 × 2248 pixel, file size: 698 KB, MIME type: image/jpeg) Photo credit: Peter Halasz. ... Thermionic emission (archaically known as the Edison effect) is the flow of electrons from a metal or metal oxide surface, caused by thermal vibrational energy overcoming the electrostatic forces holding electrons to the surface. ... General Name, Symbol, Number tungsten, W, 74 Chemical series transition metals Group, Period, Block 6, 6, d Appearance grayish white, lustrous Standard atomic weight 183. ... Lanthanum hexaboride (LaB6, also called lanthanum boride and (incorrectly) LaB) is an inorganic chemical, a boride of lanthanum. ... Diagram of a copper cathode in a Daniells cell. ... Diagram of a zinc anode in a galvanic cell. ... Also known as Fowler-Nordheim tunneling, field emission is a form of quantum tunneling in which electrons pass through a barrier in the presence of a high electric field. ... The electronvolt (symbol eV) is a unit of energy. ... A lens. ... An objective lens is the lens in a microscope, telescope, camera or other optical instrument, that receives the first light rays from the object being observed. ... Suppose the smiley face in the top left corner is an RGB bitmap image. ...

Detection of secondary electrons

The most common imaging mode monitors low energy (<50 eV) secondary electrons. Due to their low energy, these electrons originate within a few nanometers from the surface. The electrons are detected by an Everhart-Thornley detector which is a type of scintillator-photomultiplier device and the resulting signal is rendered into a two-dimensional intensity distribution that can be viewed and saved as a Digital image. This process relies on a raster-scanned primary beam. The brightness of the signal depends on the number of secondary electrons reaching the detector. If the beam enters the sample perpendicular to the surface, then the activated region is uniform about the axis of the beam and a certain number of electrons "escape" from within the sample. As the angle of incidence increases, the "escape" distance of one side of the beam will decrease, and more secondary electrons will be emitted. Thus steep surfaces and edges tend to be brighter than flat surfaces, which results in images with a well-defined, three-dimensional appearance. Using this technique, resolutions less than 1 nm are possible. The Everhart-Thornley Detector is a detector used in scanning electron microscopes (SEMs). ... A scintillator is a device or substance that absorbs high energy (ionizing) electromagnetic or charged particle radiation then, in response, fluoresces photons at a characteristic Stokes-shifted (longer) wavelength, releasing the previously absorbed energy. ... Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ... A digital image is a representation of a two-dimensional image as a finite set of digital values, called picture elements or pixels. ...

Detection of backscattered electrons

Backscattered electrons consist of high-energy electrons originating in the electron beam, that are reflected or back-scattered out of the specimen interaction volume. Backscattered electrons may be used to detect contrast between areas with different chemical compositions, especially when the average atomic number of the various regions is different, since the brightness of the BSE image tends to increase with the atomic number.

Backscattered electrons can also be used to form an electron backscatter diffraction (EBSD) image. This image can be used to determine the crystallographic structure of the specimen. Electron Backscatter Diffraction Image - Taken from National Institute of Standards and Technology Materials Reliability Division Electron backscatter diffraction (EBSD), also known as backscatter Kikuchi diffraction (BKD) is a microstructural-crystallographic technique used to elucidate the crystallographic texture or preferred orientation of any crystalline or polycrystalline materials. ...

There are fewer backscattered electrons emitted from a sample than secondary electrons. The number of backscattered electrons leaving the sample surface upward might be significantly lower than those that follow trajectories toward the sides. Additionally, in contrast with the case with secondary electrons, the collection efficiency of backscattered electrons cannot be significantly improved by a positive bias common on Everhart-Thornley detectors. This detector positioned on one side of the sample has low collection efficiency for backscattered electrons due to small acceptance angles. The use of a dedicated backscattered electron detector above the sample in a "doughnut" type arrangement, with the electron beam passing through the hole of the doughnut, greatly increases the solid angle of collection and allows for the detection of more backscattered electrons. The Everhart-Thornley Detector is a detector used in scanning electron microscopes (SEMs). ...

Beam-injection analysis of semiconductors

The nature of the SEM's probe, energetic electrons, makes it uniquely suited to examining the optical and electronic properties of semiconductor materials. The high-energy electrons from the SEM beam will inject charge carriers into the semiconductor. Thus, beam electrons lose energy by promoting electrons from the valence band into the conduction band, leaving behind holes. Charge carrier denotes in physics a free (mobile, unbound) particle carrying an electric charge. ... In solids, the valence band is the highest range of electron energies where electrons are normally present at zero temperature. ... In semiconductors and insulators, the conduction band is the range of electron energy, higher than that of the valence band, sufficient to make the electrons free to accelerate under the influence of an applied electric field and thus constitute an electric current. ... For the following two reasons the electron hole was introduced into calculations: If an electron is excited into higher state it leaves a hole in its old state. ...

In a direct bandgap material, recombination of these electron-hole pairs will result in cathodoluminescence; if the sample contains an internal electric field, such as is present at a p-n junction, the SEM beam injection of carriers will cause electron beam induced current (EBIC) to flow. In semiconductor physics, a direct bandgap means that the minimum of the conduction band lies directly above the maximum of the valence band in momentum space. ... Cathodoluminescence is an optical and electrical phenomenon whereby a beam of electrons is generated by an electron gun (e. ... A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ... Electron beam induced current (EBIC) is a semiconductor analysis technique performed in a scanning electron microscope (SEM) or scanning transmission electron microscope (STEM). ...

Cathodoluminescence and EBIC are referred to as "beam-injection" techniques, and are very powerful probes of the optoelectronic behavior of semiconductors, particularly for studying nanoscale features and defects.

Cathodoluminescence

Cathodoluminescence, the emission of light when atoms excited by high-energy electrons return to their ground state, is analogous to UV-induced fluorescence, and some materials such as zinc sulphide and some fluorescent dyes, exhibit both phenomena. Cathodoluminescence is most commonly experienced in everyday life as the light emission from the inner surface of the cathode ray tube in television sets and computer CRT monitors. In the SEM, CL detectors either collect all light emitted by the specimen, or can analyse the wavelengths emitted by the specimen and display a spectrum or an image of the cathodoluminescence in real colour. Cathodoluminescence is an optical and electrical phenomenon whereby a beam of electrons is generated by an electron gun (e. ...

X-ray microanalysis

X-rays, which are also produced by the interaction of electrons with the sample, may also be detected in an SEM equipped for energy-dispersive X-ray spectroscopy or wavelength dispersive X-ray spectroscopy. Energy dispersive X-ray spectroscopy (EDS or EDX) is an analytical tool predominantly used for chemical characterization. ... The Wavelength dispersive X-ray spectroscopy is a method used to determine the energy spectrum of an X-ray radiation. ...

Resolution of the SEM

The spatial resolution of the SEM depends on the size of the electron spot, which in turn depends on the magnetic electron-optical system which produces the scanning beam. The resolution is also limited by the size of the interaction volume, or the extent to which the material interacts with the electron beam. The spot size and the interaction volume both might be large compared to the distances between atoms, so the resolution of the SEM is not high enough to image individual atoms, as is possible in the transmission electron microscope (TEM). The SEM has compensating advantages, though, including the ability to image a comparatively large area of the specimen; the ability to image bulk materials (not just thin films or foils); and the variety of analytical modes available for measuring the composition and nature of the specimen. Depending on the instrument, the resolution can fall somewhere between less than 1 nm and 20 nm. In general, SEM images are easier to interpret than TEM images. Transmission electron microscopy (TEM) is an imaging technique whereby a beam of electrons is focused onto a specimen causing an enlarged version to appear on a fluorescent screen or layer of photographic film (see electron microscope), or can be detected by a CCD camera. ...

Environmental SEM

Conventional SEM requires samples to be imaged under vacuum, which means that samples that would produce a significant amount of vapour, e.g. biological samples, need to be either dried or cryogenically frozen. This means that processes involving transitions to or from liquids or gases, such as the drying of adhesives or melting of alloys, liquid transport, chemical reactions and solid-air-gas systems in general could not be observed.

The first commercial development of the Environmental SEM (ESEM) in the late 1980s ^{[3] [4]} allowed samples to be observed in low-pressure gaseous environments (e.g. 1-50 Torr) and high relative humidity (up to 100%). This was made possible by the development of a secondary-electron detector ^{[5] [6]} capable of operating in the presence of water vapour and by the use of pressure-limiting apertures with differential pumping in the path of the electron beam to separate the vacuum regions around the gun and lenses from the sample chamber. The torr (symbol: Torr) or millimeter of mercury (mmHg) is a non-SI unit of pressure. ... This article or section is not written in the formal tone expected of an encyclopedia article. ...

The first commercial ESEMs were produced by the ElectroScan Corporation in USA in 1988 ^[7]. ElectroScan were later taken over by Philips (now FEI Company) in 1996 ^[8]. FEI Company (NASDAQ: FEIC), founded in 1971, is a supplier of electron microscopy tools to researchers, developers and manufacturers working on the nanoscale. ...

ESEM is especially useful for non-metallic and biological materials because coating with carbon or gold is unnecessary. Plastics and Elastomers can now be routinely examined, as can biological samples. Coating is irreversible, and may reduce the value of the results obtained. Thus very small details on the surface of the sample may be concealed by the coating, let alone that coating is done under vacuum, which drastically alters hydrated specimens. The term plastics covers a range of synthetic or semi-synthetic organic condensation or polymerization products that can be molded or extruded into objects or films or fibers. ... The term elastomer is often used interchangeably with the term rubber, and is preferred when referring to vulcanisates. ...

See also

Wikibooks has more about this subject:

Nanowiki

• List of surface analysis methods
• TEM

Image File history File links Wikibooks-logo-en. ... List of surface analysis methods LIBS - Laser induced breakdown spectroscopy EBSD - Electron backscatter diffraction XRF - X-ray fluorescence analysis LOES - Laser optical emission spectroscopy LS - Light (Raman) scattering IRS - Infra Red spectroscopy SEIRA -Surface enhanced infrared absorption spectroscopy FTIR - Fourier transform infrared absorption spectroscopy; e. ... Transmission electron microscopy (TEM) is an imaging technique whereby a beam of electrons is focused onto a specimen causing an enlarged version to appear on a fluorescent screen or layer of photographic film (see electron microscope), or can be detected by a CCD camera. ...

References

1. ^ von Ardenne, Manfred (1938). "Das Elektronen-Rastermikroskop. Theoretishce Grundlagen" (in German). Zeitschrift fur Physik 108: 553-572. 
2. ^ von Ardenne, Manfred (1938). "Das Elektronen-Rastermikroskop. Praktische Ausfurung" (in German). Z. Techn. Phys. 108: 407-416. 
3. ^ Danilatos, G,D (1988). "Foundations of environmental scanning electron microscopy". Advances in Electronics and Electron Physics 71: 109-250. 
4. ^ US4,823,006 (PDF version) (1989-4-18) Gerasimos D Danilatos, George C Lewis Integrated electron optical/differential pumping/imaging signal detection system for an environmental scanning electron microscope 
5. ^ Danilatos, G,D (1990). "Theory of the Gaseous Detector Device in the ESEM". Advances in Electronics and Electron Physics 78: 1-102. 
6. ^ US4,785,182 (PDF version) (1988-11-15) James F Mancuso, William B Maxwell, Gerasimos D Danilatos Secondary Electron Detector for Use in a Gaseous Atmosphere 
7. ^ History of Electron Microscopy, 1980s
8. ^ History of Electron Microscopy 1990s

Year 1988 (MCMLXXXVIII) was a leap year starting on Friday (link displays 1988 Gregorian calendar). ... is the 319th day of the year (320th in leap years) in the Gregorian calendar. ...

External links

General

• Notes on the SEM Notes covering all aspects of the SEM

History

• Microscopy History links from the University of Alabama Department of Biological Sciences
• The Early History and Development of SEM from Cambridge University Engineering Department
• Milestones in the History of Electron Microscopy from the Swiss Federal Institute of Zürich
• Environmental Scanning Electron Microscope (ESEM) history

Images

• Tescan Image Gallery Some great SEM images of various specimens, as well as analytical results
• Dennis Kunkel Microscopy, Inc. Large collection of SEM images - mostly false colour
• Jeol SEM Images Twelve SEM images of various specimens
• SEM Lab at the Smithsonian National Museum of Natural History; includes a gallery of images
• Rippel Electron Microscope Facility Many dozens of (mostly biological) SEM images from Dartmouth College.

Gallery of SEM images

The following are examples of images taken using a scanning electron microscope.

SEM picture of a bend in a seven-lobed polyester fiber. Note dotted line equals 20 micrometers. Download high resolution version (960x720, 80 KB)Scanning electron microscope image of a bend in a high surface area polyester fiber with a seven-lobed cross section. ... SEM picture of a bend in a high surface area polyester fiber with a seven-lobed cross section Polyester is a category of polymers, or, more specifically condensation polymers, which contain the ester functional group in their main chain. ... Fiber or fibre[1] is a class o f materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread. ...	An SEM image of various types of pollen. Download high resolution version (1228x935, 215 KB)Source and public domain notice at [1] Pollen from a variety of common plants: sunflower (Helianthus annuus), morning glory Ipomea purpurea, hollyhock (Sildalcea malviflora), lily (Lilium auratum), primrose (Oenothera fruticosa) and castor bean (Ricinus communis). ... Sem may refer to: Sem or Shem; (Hebrew) One of the sons of Noah in the Bible. ... SEM image of pollen grains from a variety of common plants: sunflower (Helianthus annuus), morning glory (Ipomoea purpurea), prairie hollyhock (Sidalcea malviflora), oriental lily (Lilium auratum), evening primrose (Oenothera fruticosa), and castor bean (Ricinus communis). ...	SEM Picture of a Diatom at magnification of 5000X. Download high resolution version (1024x768, 363 KB)SEM photo of Diatoms with 5000 X magnification File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Orders Centrales Pennales Diatoms (Greek: (dia) = through + (temnein) = to cut, i. ...	False coloured SEM image of soybean cyst nematode and egg. Image File history File links Download high resolution version (900x600, 193 KB)Low-temperature scanning electron micrograph of soybean cyst nematode and its egg. ... Binomial name Heterodera glycines Ichinohe, 1952 The soybean cyst nematode (SCN), Heterodera glycines, plant-parasitic nematode that is a devastating pest of the soybean (Glycine max) worldwide. ...
SEM image of an ant head. A photo of an ant head taken with a Scanning Electron Microscope [1] File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Subfamilies Aenictogitoninae Agroecomyrmecinae Amblyoponinae (incl. ...	SEM image of asbestos fibers. Image File history File links Download high resolution version (1024x1024, 421 KB) Anthophyllite asbestos, Scanning electron microscope picture from [1] File links The following pages link to this file: Asbestos Scanning electron microscope ... For other uses, see Asbestos (disambiguation). ...	Compound eye of Antarctic krill Euphausia superba. Download high resolution version (1574x1505, 252 KB)Antarctic krill Euphausia superba (Photo by Gerd Alberti and Uwe Kils) GFDL goto large resolution File links The following pages link to this file: Scanning electron microscope Antarctic krill User talk:Jimbo Wales Eye Compound eye Image:Krilleyekils. ... Compound eye of a dragonfly Compound eye of Antarctic krill as imaged by an electron microscope A compound eye is a visual organ found in certain arthropods such as insects and crustaceans. ... Binomial name Euphausia superba Dana, 1850 The Antarctic krill (Euphausia superba ) is a species of krill found in the Antarctic waters of the Southern Ocean. ...	Ommatidia of Antarctic krill eye. Image File history File links Download high resolution version (1158x1123, 220 KB)ommatidia of eye of Antarctic krill Photo by Uwe Kils) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The compound eye of insects is composed of hundreds of unit eyes called ommatidia. ... Binomial name Euphausia superba Dana, 1850 The Antarctic krill (Euphausia superba ) is a species of krill found in the Antarctic waters of the Southern Ocean. ...
SEM image of a discharged nematocyst. Image File history File links Nematocyst-discharged. ... Cnidocytes are prey-capture and defensive cells found on animals of the phylum Cnidaria. ...	SEM image of the upper body of a Drosophila. Image File history File links SEMFF.jpg‎ Summary Drosophila melanogaster upper body, photo taken by a Scanning Electron Microscope. ... Type species Drosophila funebris (Fabricius, 1787) Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called fruit flies, or more appropriately vinegar flies, wine flies, pomace flies, grape flies, and picked fruit-flies, a reference to the characteristic of many species to linger...	SEM images of the compound eye of a Drosophila. Image File history File links FFEYE2. ... Type species Drosophila funebris (Fabricius, 1787) Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called fruit flies, or more appropriately vinegar flies, wine flies, pomace flies, grape flies, and picked fruit-flies, a reference to the characteristic of many species to linger...	SEM image of the grasshopper's spiracle valve. Image File history File links Spiraclevalves. ... Families Superfamily: Tridactyloidea Cylindrachaetidae Ripipterygidae Tridactylidae Superfamily: Tetrigoidea Tetrigidae Superfamily: Eumastacoidea Chorotypidae Episactidae Eumastacidae Euschmidtiidae Mastacideidae Morabidae Proscopiidae Thericleidae Superfamily: Pneumoroidea Pneumoridae Superfamily: Pyrgomorphoidea Pyrgomorphidae Superfamily: Acridoidea Acrididae Catantopidae Charilaidae Dericorythidae Lathiceridae Lentulidae Lithidiidae Ommexechidae Pamphagidae Pyrgacrididae Romaleidae Tristiridae Superfamily: Tanaoceroidea Tanaoceridae Superfamily: Trigonopterygoidea Trigonopterygidae Xyronotidae Grasshoppers are herbivorous insects...
SEM image of normal circulating human blood. Image File history File links Download high-resolution version (1800x2239, 1365 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system Scanning electron microscope White blood cell Platelet Neutrophil granulocyte Lymphocyte Monocyte ... A scanning electron microscope image of normal circulating human blood. ...	SEM image of a hederelloid from the Devonian of Michigan (largest tube diameter is 0.75 mm). Image File history File links Metadata No higher resolution available. ... Hederellids are extinct colonial animals with calcitic tubular branching exoskeletons. ... Artists illustration of a Devonian scene. ...	Backscattered Electron image of an Antimony rich region in a fragment of ancient glass. Image File history File links No higher resolution available. ... General Name, Symbol, Number antimony, Sb, 51 Chemical series metalloids Group, Period, Block 15, 5, p Appearance silvery lustrous grey Standard atomic weight 121. ...	SEM image of the corrosion layer on the surface of an ancient glass fragment, note the laminar structure of the corrosion layer. Image File history File links No higher resolution available. ...