Field ion microscopic observations of the formation of molybdenum films epitaxially related to tungsten substrates

The field ion microscope was used to study the structure of molybdenum vapor-deposited on tungsten tips. Films prepared in the range 370 to 850 K were of duplex character having defective layer superimposed upon an epitaxial layer. When condensed at 77 K the molybdenum was microcrystalline in general, although parts of the deposit near the substrate were structurally similar to it. All films became entirely epitaxial when subsequently heated, with the low temperature films passing through intermediate structures similar to those possessed by the others as-formed. The transformation was associated with the outward progression of an epitaxial layer from the molybdenum-tungsten interface. (Auth.)