SPOT-PROFILE-ANALYZING LEED STUDY OF THE EPITAXIAL-GROWTH OF FE, CO, AND CU ON CU(100)

The structure of epitaxial films of Fe, Co, and Cu grown at 80-300 K o n Cu(100) has been investigated using a spot-profile-analyzing low-ene rgy electron-diffraction (LEED) instrument. In all three systems rings appear around the substrate LEED spots, although the rings differ in intensity and in diameter depending upon the variables of film thickne ss and deposition temperature. Rings of this type have been studied ex tensively by Henzler et al. and correlated with the mean separation be tween islands. Much can be inferred about the growth mechanism through a study of these Henzler rings. The rings contract radially with incr easing deposition temperature or with increasing annealing temperature as thermally activated diffusion permits the formation of larger isla nds with greater distances between them. For all three systems studied here, the onset of thermal diffusion becomes apparent as the ring con tracts radially for deposition temperatures above about 150 K. However , for deposition at 80 K, where thermally activated diffusion should b e completely suppressed, rings are observed with a radius correspondin g to a mean separation between islands on the order of ten atoms. Of t he three elements, Fe gives the strongest rings and Cu the weakest. Th e value of the mean separation suggests that upon condensation these a toms do not come to rest at the immediate site of impact but instead e xperience some very transient type of mobility associated with the imp act and accommodation process.