Boron Nitride Crucible for Evaporating Aluminum from Electron Beam Source
Original Publication Date: 1978-Jan-01
Included in the Prior Art Database: 2005-Feb-20
A modified boron nitride cricibel 10 is employed to obtain high aluminum and/or aluminum alloy evaporation rates using an electron beam to heat the metal. Since the boron nitride is an insulating material, the crucible has a hole drilled through the bottom, and a pyrolytic graphite or a vitreous carbon plug 12 is inserted into the hole to make electrical contact to the copper hearth 16, as shown in the figure. The plug is used to prevent a charged electric field from being formed when the electrons bombard the metal in the crucible. This field, if formed, can redirect the electron beam to another area within the vacuum chamber.