An electron microscope is a microscope that uses a beam of electrons as a source of illumination. They use electron optics that are analogous to the glass lenses of an optical light microscope. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light, electron microscopes have a higher resolution of about 0.1 nm, which compares to about 200 nm for light microscopes. Electron microscope may refer to:
A microscope is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisible to the eye unless aided by a microscope.
A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that contain information about the surface topography and composition of the sample. The electron beam is scanned in a raster scan pattern, and the position of the beam is combined with the intensity of the detected signal to produce an image. In the most common SEM mode, secondary electrons emitted by atoms excited by the electron beam are detected using a secondary electron detector. The number of secondary electrons that can be detected, and thus the signal intensity, depends, among other things, on specimen topography. Some SEMs can achieve resolutions better than 1 nanometer.
Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a grid. An image is formed from the interaction of the electrons with the sample as the beam is transmitted through the specimen. The image is then magnified and focused onto an imaging device, such as a fluorescent screen, a layer of photographic film, or a sensor such as a scintillator attached to a charge-coupled device.
Photoemission electron microscopy is a type of electron microscopy that utilizes local variations in electron emission to generate image contrast. The excitation is usually produced by ultraviolet light, synchrotron radiation or X-ray sources. PEEM measures the coefficient indirectly by collecting the emitted secondary electrons generated in the electron cascade that follows the creation of the primary core hole in the absorption process. PEEM is a surface sensitive technique because the emitted electrons originate from a shallow layer. In physics, this technique is referred to as PEEM, which goes together naturally with low-energy electron diffraction (LEED), and low-energy electron microscopy (LEEM). In biology, it is called photoelectron microscopy (PEM), which fits with photoelectron spectroscopy (PES), transmission electron microscopy (TEM), and scanning electron microscopy (SEM).
An X-ray microscope uses electromagnetic radiation in the X-ray band to produce magnified images of objects. Since X-rays penetrate most objects, there is no need to specially prepare them for X-ray microscopy observations.
Transmission Electron Aberration-Corrected Microscope (TEAM) is a collaborative research project between four US laboratories and two companies. The project's main activity is design and application of a transmission electron microscope (TEM) with a spatial resolution below 0.05 nanometers, which is roughly half the size of an atom of hydrogen.
A scanning transmission electron microscope (STEM) is a type of transmission electron microscope (TEM). Pronunciation is [stɛm] or [ɛsti:i:ɛm]. As with a conventional transmission electron microscope (CTEM), images are formed by electrons passing through a sufficiently thin specimen. However, unlike CTEM, in STEM the electron beam is focused to a fine spot which is then scanned over the sample in a raster illumination system constructed so that the sample is illuminated at each point with the beam parallel to the optical axis. The rastering of the beam across the sample makes STEM suitable for analytical techniques such as Z-contrast annular dark-field imaging, and spectroscopic mapping by energy dispersive X-ray (EDX) spectroscopy, or electron energy loss spectroscopy (EELS). These signals can be obtained simultaneously, allowing direct correlation of images and spectroscopic data.
Transmission electron cryomicroscopy (CryoTEM), commonly known as cryo-EM, is a form of cryogenic electron microscopy, more specifically a type of transmission electron microscopy (TEM) where the sample is studied at cryogenic temperatures. Cryo-EM is gaining popularity in structural biology.
Focused ion beam, also known as FIB, is a technique used particularly in the semiconductor industry, materials science and increasingly in the biological field for site-specific analysis, deposition, and ablation of materials. A FIB setup is a scientific instrument that resembles a scanning electron microscope (SEM). However, while the SEM uses a focused beam of electrons to image the sample in the chamber, a FIB setup uses a focused beam of ions instead. FIB can also be incorporated in a system with both electron and ion beam columns, allowing the same feature to be investigated using either of the beams. FIB should not be confused with using a beam of focused ions for direct write lithography. These are generally quite different systems where the material is modified by other mechanisms.
Electron-beam-induced deposition (EBID) is a process of decomposing gaseous molecules by an electron beam leading to deposition of non-volatile fragments onto a nearby substrate. The electron beam is usually provided by a scanning electron microscope, which results in high spatial accuracy and the possibility to produce free-standing, three-dimensional structures.
The environmental scanning electron microscope (ESEM) is a scanning electron microscope (SEM) that allows for the option of collecting electron micrographs of specimens that are wet, uncoated, or both by allowing for a gaseous environment in the specimen chamber. Although there were earlier successes at viewing wet specimens in internal chambers in modified SEMs, the ESEM with its specialized electron detectors and its differential pumping systems, to allow for the transfer of the electron beam from the high vacuum in the gun area to the high pressure attainable in its specimen chamber, make it a complete and unique instrument designed for the purpose of imaging specimens in their natural state. The instrument was designed originally by Gerasimos Danilatos while working at the University of New South Wales.
Alex K. Zettl is an American experimental physicist, educator, and inventor.
Scanning confocal electron microscopy (SCEM) is an electron microscopy technique analogous to scanning confocal optical microscopy (SCOM). In this technique, the studied sample is illuminated by a focussed electron beam, as in other scanning microscopy techniques, such as scanning transmission electron microscopy or scanning electron microscopy. However, in SCEM, the collection optics is arranged symmetrically to the illumination optics to gather only the electrons that pass the beam focus. This results in superior depth resolution of the imaging. The technique is relatively new and is being actively developed.
Low-voltage electron microscope (LVEM) is an electron microscope which operates at accelerating voltages of a few kiloelectronvolts or less. Traditional electron microscopes use accelerating voltages in the range of 10-1000 keV.
Serial block-face scanning electron microscopy is a method to generate high resolution three-dimensional images from small samples. The technique was developed for brain tissue, but it is widely applicable for any biological samples. A serial block-face scanning electron microscope consists of an ultramicrotome mounted inside the vacuum chamber of a scanning electron microscope. Samples are prepared by methods similar to that in transmission electron microscopy (TEM), typically by fixing the sample with aldehyde, staining with heavy metals such as osmium and uranium then embedding in an epoxy resin. The surface of the block of resin-embedded sample is imaged by detection of back-scattered electrons. Following imaging the ultramicrotome is used to cut a thin section from the face of the block. After the section is cut, the sample block is raised back to the focal plane and imaged again. This sequence of sample imaging, section cutting and block raising can acquire many thousands of images in perfect alignment in an automated fashion. Practical serial block-face scanning electron microscopy was invented in 2004 by Winfried Denk at the Max-Planck-Institute in Heidelberg and is commercially available from Gatan Inc., Thermo Fisher Scientific (VolumeScope) and ConnectomX.
MEMS for in situ mechanical characterization refers to microelectromechanical systems (MEMS) used to measure the mechanical properties of nanoscale specimens such as nanowires, nanorods, whiskers, nanotubes and thin films. They distinguish themselves from other methods of nanomechanical testing because the sensing and actuation mechanisms are embedded and/or co-fabricated in the microsystem, providing—in the majority of cases—greater sensitivity and precision.
Scanning transmission X-ray microscopy (STXM) is a type of X-ray microscopy in which a zone plate focuses an X-ray beam onto a small spot, a sample is scanned in the focal plane of the zone plate and the transmitted X-ray intensity is recorded as a function of the sample position. A stroboscopic scheme is used where the excitation is the pump and the synchrotron X-ray flashes are the probe. X-ray microscopes work by exposing a film or charged coupled device detector to detect X-rays that pass through the specimen. The image formed is of a thin section of specimen. Newer X-ray microscopes use X-ray absorption spectroscopy to heterogeneous materials at high spatial resolution. The essence of the technique is a combination of spectromicroscopy, imaging with spectral sensitivity, and microspectroscopy, recording spectra from very small spots.
Liquid-phase electron microscopy refers to a class of methods for imaging specimens in liquid with nanometer spatial resolution using electron microscopy. LP-EM overcomes the key limitation of electron microscopy: since the electron optics requires a high vacuum, the sample must be stable in a vacuum environment. Many types of specimens relevant to biology, materials science, chemistry, geology, and physics, however, change their properties when placed in a vacuum.
Cryogenic electron microscopy (cryo-EM) is a cryomicroscopy technique applied on samples cooled to cryogenic temperatures. For biological specimens, the structure is preserved by embedding in an environment of vitreous ice. An aqueous sample solution is applied to a grid-mesh and plunge-frozen in liquid ethane or a mixture of liquid ethane and propane. While development of the technique began in the 1970s, recent advances in detector technology and software algorithms have allowed for the determination of biomolecular structures at near-atomic resolution. This has attracted wide attention to the approach as an alternative to X-ray crystallography or NMR spectroscopy for macromolecular structure determination without the need for crystallization.
