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Ultra-high vacuum (often spelled ultrahigh in American English, UHV) is the vacuum regime characterised by pressures lower than about 1 × 10 −6 pascals (1.0 × 10 −8 mbar; 7.5 × 10 −9 Torr). UHV conditions are created by pumping the gas out of a UHV chamber.
Materials for use in vacuum are materials that show very low rates of outgassing in vacuum and, where applicable, are tolerant to bake-out temperatures. The requirements grow increasingly stringent with the desired degree of vacuum to be achieved in the vacuum chamber. The materials can produce gas by several mechanisms.
UHV may refer to: Ultra-high vacuum, the vacuum regime characterised by pressures lower than about 10 −7 pascal; Ultra-high voltage, a classification of overhead power line with an operating voltage of higher than 800 kV; University of Houston–Victoria, a university in Victoria, Texas, US
Ion pumps are commonly used in ultra-high vacuum (UHV) systems, as they can attain ultimate pressures less than 10 −11 mbar. [1] In contrast to other common UHV pumps, such as turbomolecular pumps and diffusion pumps, ion pumps have no moving parts and use no oil. They are therefore clean, need little maintenance, and produce no vibrations.
In 1975, Bommel et al. then achieved to form monolayer graphite on the C-face as well as the Si-face of hexagonal SiC. The experiment was carried out under UHV with a temperature of 800 °C and hints for a graphene structure could be found in LEED patterns and the change in the carbon Auger peak from a carbide character to a graphite character.
ultra-high vacuum (UHV) Pressure can be achieved by elaborate materials (e.g. low-carbon stainless steel), metal sealings, special surface preparations and cleaning, bake-out and high vacuum pumps; molecular flow regime for gases below 1 × 10 −9 Pa: extreme-high vacuum (XHV)