Getter
A getter is a chemically reactive material, which serves to maintain a vacuum as long as possible. Move to the surface of a getter gas molecules with the atoms of the getter material is a direct chemical bond, or the gas molecules are retained by sorption. In this way, the gas molecules "captured".
In the getter pumps ( ion pump ) vacuum technology usually titanium ( titanium sublimation pump ) is used. Platinum is also suitable.
Applications
Electron tubes
We used this principle especially to bind residual gases in vacuum tubes (including CRTs ) or vacuum pumps. For functional ability of electron tubes, it is necessary that in its interior the best possible vacuum (high vacuum) prevails. Controls, using getter, bind the remaining gas molecules per se after the evacuation. To activate the getter material is heated, and the resulting reactive vapors bind the remaining gases by adsorption or chemical bonding. In addition, the downcast at the free surfaces Vapours may later bind incoming residual gas until its adsorption capacity is exhausted.
In electron tubes barium, aluminum or magnesium alloys, are often used. Bringing the getter in the form of a plate mounted on a pill or a ring together with the electrode system in the tube, and this heated inductively after pumping and melting of the glass bulb so as to evaporate the getter.
Semiconductor manufacturing
In the semiconductor manufacturing is still the so-called Defektgetterung known. This exploits that impurities in crystals preferably attach to fault zones of the crystal structure. The back side of a wafer is provided with specific crystal defects ( rough), so that during a subsequent heat treatment to diffuse impurities to these impurities. Another way to produce getter, a targeted insertion of foreign substances (for example, boron, phosphorus, argon) from the back. The front side used for the production of the circuit structures of the wafer is thus more pure.
Food production
For steam lines to the pharmaceutical and food industry vacuum insulation with barium Tubegettern is often used for reasons of hygiene. Barium getter are, due to their low equilibrium pressure for hydrogen also for vacuum insulation at higher temperatures (eg pipe systems in the petrochemical and chemical industries ).
Getter system of an electron beam
Tubegetter with barium
Zr -Fe getter in the outer bulb of a sodium vapor lamp