Cold emission of electrons from metals

The phenomenon of electron emission under the action of a strong external electric field on a metal has been known since the end of the 19th century. By the early 1920s this phenomenon had been comparatively well studied experimentally. The main features of cold emission have been theoretically explained by Fowler and Nordheim [31] on the basis of the ideas of electron tunneling. 

v is the velocity corresponding to the Fermi energy. One can see that cold emission has certain similarities with the ionization of atoms by the external electric field (see Sect. 2.1). 

In Table 1 is shown the cold electron emission current calculated by Bethe and Zommerfeld [32] with allowance for the image potential. One can see that in fields of several million volts per centimeter the electron current initially jumps but then swiftly reaches very high values. Experimentally, a 

The cold electron emission current (A cm 2) in strong electric fields (V cm ) [32] 1 is the work function 

At present, very high ultimate values of tunnel emission flow density can be obtained ( 10 ° A cm-2). The tunnel emission of electrons from metals is widely used in modern technology in developing various devices where high currents or intensive electron beams are required. 

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The exponential factor can be seen to have the same dependence on parameters as in the cases of atom ionization by the electric field and cold emission of electrons from metals. 

Concepts relating to the tunneling of particles through a potential barrier were introduced in pioneering works in physics immediately after the creation of quantum mechanics and were used to account for such phenomena as a-decay of atomic nuclei [1,2], cold emission of electrons from metals [3] and the ionization of atoms in strong electric fields [4],... 

The cold emission of electrons from a metal cathode at a hlgji negative voltage ( ). 

The X-ray spectra of tantalum have been investigated.1 The emission of electrons from tantalum when heated to high temperatures has received considerable investigation.2 Electron emission from the cold metal has been studied by Bother,3 and the arrangement of electron groups in the atom by Lessheim and Samuel.4 Tantalum is not radioactive.5... 

Certainly the most common property of surfaces used in the area of surface diffusion studies is the field-induced emission of electrons. The property of field emission under vacuum conditions was first observed as early as 1897 [242] and in 1923 Schottky [243] attempted to explain field-emission from cold metals theoretically. The most significant practical advance came in 1937 with the invention of the field-emission microscope by Muller [7]. 

Enhanced imaging of several dairy products has been demonstrated through the application of a relatively elaborate preparative technique in combination with a cold-field emission scanning electron microscope (FESEM) [86], The preparative methods include a metal-impregnation technique, termed tannin-ferrocyanide-osmium (TA-F-O, Figure 21), which was adapted from Hirano et al. [87]. 

Arcs with hot cathode spots. If the cathode is made from lower-melting-point metals like copper, iron, silver, or mercury, the high temperatme required for emission caimot be sustained permanently. Electric current flows in this case through hot spots that appear, move fast, and disappear on the cathode surface. Current density in the spots is extremely high (10" -10 A/cm ), which leads to intensive but local and short heating and evaporation of the cathode material while the rest of the cathode actually stays cold. The mechanism of electron emission from the hot spots is thermionic field emission. Cathode spots appear not only on the low-melting-point cathodes but also on refractory metals at low currents and low pressures. 

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