The material is typically brought into vapor phase on a horizontal plane substrate. If the material of the substrate is different from that of the film in production, we refer to it as epitaxy. This can be used for:
- - a molecular cluster in a high vacuum (10-9 to 10-8Pa). This technique is used for semi-conductors;
- - a heated gas jet. For example, to make a diamond film, the gas is a hydrocarbon (CH4) heated either by an incandescent filament or a plasma torch. The substrate can be silica;
- - the sandwich method. The raw material “source” is planar and placed at a distance in the order of a millimeter from the substrate, which is also planar. This method is used for silicon carbide (which sublimes easily, as we have seen).
Crystals in the order of a millimeter
The solvent can be a metallic oxide with low melting point and be water soluble. We proceed in the normal way with one of the following two methods:
- - slow cooling;
- - solvent vaporization.
Batch crystallization theory applies to this method.