Method of producing vapours of controlled composition

摘要

In the continuous production of a vapour mixture of constant composition by the evaporation of a solution 5 of two or more components, the composition of the solution is maintained constant throughout the evaporation by the flow of a second solution 6, which is richer in the more volatile component(s), into the evaporator 1 from vessel 2 via line 3 and one-way ball valve 4. The ratio of the surface areas of liquid in evaporator 1 and vessel 2 is determined by a specified mathematical formula. The evaporator may be achieved by heating the solution 5, or by bubbling a carrier gas through it via tube 10. The vapour mixture generated in evaporator 1 may be used to produce a solid layer of material on substrate 12 in vessel 13, either by condensation or thermal decomposition. Example 1 relates to the production of the compound V3Si by the thermal decomposition of a vapour containing 3 mols. of VCl4 to 1 mol. of SiCl4 carried in hydrogen gas. Example 2 relates to the production of an epitaxial layer of silicon, containing 5 x 1017 atoms of phosphorus per cm.3, on a single crystal silicon substrate.