Vapor deposition apparatus and method

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIG.
1, there is shown an inner evaporation crucible 1 surrounded by a second evaporation crucible 2.
The inner evaporation crucible 1 contains a charge 3 of a relatively low volatility constituent whilst second evaporation crucible 2 is charged with a much higher volatility constituent 4, such as magnesium.
The crucibles are centrally positioned under a collector 5 on which a deposit 6 is accumulated.
In use of the apparatus, the charge 3 in the inner evaporation crucible 1 is heated using an electron beam 7 focussed by magnet 8 to a temperature which causes a stream of vapour to rise towards collector 5.
Second evaporation crucible 2 is heated by radiant heaters (not shown) to generate an appreciable vapour pressure in the magnesium 4, such that streams of magnesium vapour are discharged towards the collector 5 through nozzles 9.
The nozzles 9 are angled towards the collector 5 so that the streams of magnesium vapour intersect the stream of vapour rising from the inner evaporation crucible 1.
This ensures that the combined vapour impinging on the collector 5 is an intimate mixture of constituents.
Each stream of magnesium vapour diverges after it leaves its respective nozzle 9 so the spacing between individual nozzles and their separation from the collector 5 is arranged such that a uniform population of magnesium atoms is delivered to the collector across a large proportion of its total surface area.
The separation between the inner evaporation crucible 1 and the collector 5 is also chosen to give uniform coverage over as much of the collector as possible.
FIGS.
2 and 3 show a preferred form of the apparatus in plan view and sectional view, respectively.
Here the inner evaporation crucible 10 is shown as a water-cooled copper crucible which is surrounded by an annular steel crucible 20.
Annular steel crucible 20 is covered with a steel lid 21 having eight nozzles 40 disposed around its inner circumference, which nozzles are convergently directed towards a collector (not shown) positioned above the inner crucible 10