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A field emission gun (FEG) is a type of electron gun in which a sharply pointed Müller-type[clarification needed] emitter[1]: 87–128 is held at several kilovolts negative potential relative to a nearby electrode, so that there is sufficient potential gradient at the emitter surface to cause field electron emission. Emitters are either of cold-cathode type, usually made of single crystal tungsten sharpened to a tip radius of about 100 nm, or of the Schottky type,[1]: 1–28 in which thermionic emission is enhanced by barrier lowering in the presence of a high electric field. Schottky emitters are made by coating a tungsten tip with a layer of zirconium oxide (ZrO2) decreasing the work function of the tip by approximately 2.7 eV.[2]
In electron microscopes, a field emission gun is used to produce an electron beam that is smaller in diameter, more coherent and with up to three orders of magnitude greater current density or brightness than can be achieved with conventional thermionic emitters such as tungsten or lanthanum hexaboride (LaB 6)-tipped filaments. The result in both scanning and transmission electron microscopy is significantly improved signal-to-noise ratio and spatial resolution, and greatly increased emitter life and reliability compared with thermionic devices.
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A fieldemissiongun (FEG) is a type of electron gun in which a sharply pointed Müller-type[clarification needed] emitter: 87–128 is held at several kilovolts...
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of an emission source or cathode, which may be a tungsten filament, a lanthanum hexaboride (LaB6) single crystal or a fieldemissiongun. The gun is connected...
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1970s, when Albert Crewe at the University of Chicago developed the fieldemissiongun and added a high-quality objective lens to create a modern STEM. He...
needed] Low-voltage SEM is typically conducted in an instrument with a fieldemissionguns (FEG) which is capable of producing high primary electron brightness...
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anti-inflammatory peptide, and feG, its D-isomeric form Fieldemissiongun, a type of electron gun Ferroelectric generator This disambiguation page lists...
a magnetic field is called cyclotron emission. For particles in the mildly relativistic range (≈85% of the speed of light), the emission is termed gyro-synchrotron...
introduced in 1939 by Kossel and Möllenstedt. The development of the FieldEmissionGun (FEG) in the 1970s, the Scanning Transmission Electron Microscopy...
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By knowing the amount of infrared energy emitted by the object and its emissivity, the object's temperature can often be determined within a certain range...
either through heating (thermionic emission) or in an electric field that is sufficient to cause field electron emission. Once initiated, a vacuum arc can...
Gun laws in the United States regulate the sale, possession, and use of firearms and ammunition. State laws (and the laws of the District of Columbia...
pointed) tip. This bias voltage creates a repulsive electrostatic field that suppresses emission of electrons from most areas of the cathode. The emitter tip...
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