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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.
Molecular-beam epitaxy takes place in high vacuum or ultra-high vacuum (10 −8 –10 −12 Torr).The most important aspect of an MBE process is the deposition rate (typically less than 3,000 nm per hour) that allows the films to grow epitaxially (in layers on top of the existing crystal).
Austenitic stainless steels are the most common choice for high vacuum and ultra-high vacuum systems. Not all alloys are suitable; e.g. the free-machining 303 steel contains sulfur, which tends to outgas. Alloys with good weldability under argon arc welding are usually chosen. 304 stainless steel is a common choice of a stainless steel.
Its construction and principle of operation is simple. It consists of a titanium filament through which a high current (typically around 40 A) is passed periodically. This current causes the filament to reach the sublimation temperature of titanium, and hence the surrounding chamber walls become coated with a thin film of clean titanium.
An oil diffusion pump is used to achieve higher vacuum (lower pressure) than is possible by use of positive displacement pumps alone. Although its use has been mainly associated within the high-vacuum range, down to 1 × 10 −9 mbar (1 × 10 −7 Pa), diffusion pumps today can produce pressures approaching 1 × 10 −10 mbar (1 × 10 −8 Pa) when properly used with modern fluids and accessories.
On the VUV ring, the endstations were usually UHV (ultra-high vacuum) chambers that were used to conduct experiments using methods such as XPS, UPS, LEEM, and NEXAFS. In some beamlines , there were other analytical tools used in conjunction with synchrotron radiation, such as a mass spectrometer , a high-power laser , or a gas chromatography ...
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