Spot-profile-analyzing LEED study of the epitaxial growth of Fe, Co, and Cu on Cu(100).

Abstract

The structure of epitaxial films of Fe, Co, and Cu grown at 80--300 K on Cu(100) has been investigated using a spot-profile-analyzing low-energy 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 thickness and deposition temperature. Rings of this type have been studied extensively by Henzler et al. and correlated with the mean separation between islands. Much can be inferred about the growth mechanism through a study of these Henzler rings. The rings contract radially with increasing deposition temperature or with increasing annealing temperature as thermally activated diffusion permits the formation of larger islands with greater distances between them. For all three systems studied here, the onset of thermal diffusion becomes apparent as the ring contracts radially for deposition temperatures above about 150 K. However, for deposition at 80 K, where thermally activated diffusion should be completely suppressed, rings are observed with a radius corresponding to a mean separation between islands on the order of ten atoms. Of the three elements, Fe gives the strongest rings and Cu the weakest. The value of the mean separation suggests that upon condensation these atoms do not come to rest at the immediate site of impact but instead experience some very transient type of mobility associated with the impact and accommodation process.