Extension of the asymptotically-correct approximation to Fowler-Guggenheim adsorption

The epitaxial growth of antimony on to atomically clean tungsten has been studied by reflection high energy electron diffraction, and an attempt made to evaluate the influence of the substrate symmetry by using the three crystal planes, (100), (110) and (112). The growth was found to be dependent on the deposition conditions. Evaporation in high background pressures (P > 1 × 10^?8 Torr) and using high evaporation rates $\text{(10}\text{monolayers}\text{min}\text{)}$ led initially to an amorphous layer on all three surfaces. This crystallised partially at thicknesses of about 150 Å leaving the close packed pseudocubic (111) plane parallel to the surface. Using ultra-high vacuum conditions (P < 5 × 10^?9 Torr during evaporation) and low evaporation rates (3 monolayers per minute) a series of submonolayer structures formed, different for each surface and depending strongly on the surface symmetry and lattice parameters. Continued evaporation led to the formation of three dimensional islands of antimony. For all three surfaces, the majority of these islands consisted of normal bulk antimony with its pseudocubic (100) plane parallel to the surface. However, a smaller amount of a hitherto unreported face centred cubic phase of antimony was also found on each surface. A comparison of the results obtained on the three surfaces in terms of the relative influence of the substrate and absorbate atomic interactions has been made.