INFLUENCE OF HIGH-TEMPERATURE HEAT TREATMENT ON SURFACE ORDER AND FACETING OF SOME MO, W, TA AND RE CRYSTAL SURFACES

Observations on (100), (111), (310) Mo, (100), (110) W, (110) Ta and (0001) Re have been made, using the LEED technique, after prolonged heat treatments at about 2000°C and after subsequent cleaning by the Ar+ ion bombardment and annealing technique. Even after high temperature heat treatment, bulk contaminant diffused to the surface at appreciably lower temperatures in some cases. When faceting caused by heat treatment occurred, it was accompanied by this diffusion of bulk contaminant to the surface. This and other observations indicate that the observed faceting was promoted by surface contamination and that, in its absence, faceting probably would not have occurred for any of the surfaces which were examined. © 1969.