Low-energy electron diffraction ͑LEED͒ results have showed that Dy films grown on W͑100͒ at room temperature are highly disordered. By growing Dy on W͑100͒ at 470 K, an epitaxial relation was found for Dy/W͑100͒ in which Dy(0001)ʈW(100) and Dy͓112 0͔ʈW͓010͔. Annealing to 770 K improved significantly the quality of the LEED pattern. The Dy hexagonal lattice is slightly distorted along the ͓010͔ and ͓001͔ axes of the W͑100͒ substrate, resulting in a c(8ϫ2) commensurate unit cell. The lattice

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... ants of the Dy overlayer have been found to be extended by 0.7% ͑along W͓010͔͒ and by 1.5% relative to the Dy bulk lattice constant. Scanning tunneling microscopy ͑STM͒ studies of the annealed film showed that this annealing temperature for Dy/W͑100͒ will produce flat and well-ordered films of c(8ϫ2) structure. STM studies have shown that Dy also forms a (6ϫ2) structure in some regions of the surface.