OPTIMIZED EPITAXIAL-GROWTH OF FE ON AG(001)

We report on a comprehensive study of the growth of 5-nm-thick epitaxi al Fe(001) films on Ag(001) substrates which are deposited on Fe-preco vered GaAs(001) wafers. We characterize the films in situ by scanning tunneling microscopy, low-energy electron diffraction, X-ray photoelec tron spectroscopy, and depth profiling to obtain information about the geometrical and chemical surface structure. We find that the surface morphology is improved by either growing or postannealing the films at elevated temperatures. During deposition at and above room temperatur e, however, an atomic exchange process is activated that results in a thin Ag film (up to 1 ML) ''floating'' on top of the growing Fe film. We propose and confirm a growth procedure that yields clean, Ag-free s urfaces with a morphology superior to the other films. This optimized recipe consists of two steps: (i) low-temperature growth of the first 2 nm in order to form a diffusion barrier for the Ag substrate atoms, and (ii) high-temperature deposition of the final 3 nm to take advanta ge of the improved homoepitaxial growth quality of Fe at elevated temp eratures. The relevance of these results with respect to magnetic prop erties of multilayers is discussed.