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The vapour deposition of antimony on silver {1 1 1} under ultra-high vacuum conditions has been studied by means of reflection high-energy electron diffraction (RHEED) and Auger electron spectroscopy (AES). At room temperature, no evidence for sub monolayer structures was obtained and a deposit of an apparent thickness equivalent to six monolayers was necessary before any diffraction features typical of the overlayer could be detected. With increasing film thickness, the formation of islands with random rotational orientation was detected with Sb (1 0 0) normal to the substrate surface. Annealing of the deposit at 573 K led to the formation of the intermetallic compound Ag3Sb in epitaxial relation to the substrate. Lattice parameters for pseudo-cubic antimony (a --0.613 nm) and hexagonal Ag3Sb (a = 0.295 nm and c = 0.482 nm) were obtained. I ntroductionIn spite of the contemporary importance of thin films of certain elements in the fabrication of electronic devices and numerous experimental observations, there still seems to be no more than a modest number of systematic studies directed towards the obtaining of precise structural information about their nucleation, growth, and orientation. As an example, we may cite antimony. Following G6rlich's discovery [1] of the alkali metal-antimony photocathode, the electronic applications of the Group V semi-metals has stimulated a considerable number of studies involving antimony. As a natural progression from early work of a more descriptive nature, to qualitative studies on the crystallization of the element on glass, the present trend towards studies ofvapour and electro-chemical growth on single crystal substrates under precisely defined conditions is clearly appropriate.A study of vapour deposition on the {1 00}, {110} and {211 } crystal faces of tungsten [2][3][4] has shown that antimony can form a series of submonolayer-coverage structures, ordered in relation to the symmetry of the substrate surface. In this system, the miscibility of the components and their tendency to form compounds are both very small and, on annealing the deposits, thermal desorption of antimony reverses the growth process to regenerate the substrate surface. One may assume that the degree of adsorbate-adsorbate interaction is comparable with that of adsorbatesubstrate interaction, both influencing the formation and orientation of the observed overlayer structures. In contrast, an early investigation of the deposition of antimony on a silver {111} [5] suggested a rather weak adsorbate-substrate interaction at room temperature. Diffraction data indicated that the antimony overlayer grows in a way similar to that on a non-crystalline substrate such as glass: an initial amorphous structure is succeeded by gradual crystallization of islands as a function of increased temperature and/or thickness of the deposit. These islands have random rotational orientation about a fibre axis corresponding to the pseudo-cubic (100) direction of antimony perpendicular to the substrate surface.In view of the poor...

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