Vacancies in Homoepitaxially-Grown Ag and Cu films
- PDF / 116,737 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 99 Downloads / 157 Views
Vacancies in Homoepitaxially-Grown Ag and Cu films Cristian E. Botez, William C. Elliott, Paul F. Miceli and Peter W. Stephens1 Department of Physics and Astronomy, University of Missouri-Columbia, Columbia, MO 65211, U.S.A. 1 Department of Physics, State University of New York, Stony Brook, NY 11794, U.S.A. ABSTRACT X-ray scattering experiments on the homoepitaxial growth of Ag(001) Ag(111) and Cu(001) show that high vacancy concentrations can be achieved during low temperature deposition. It is observed that the vacancies, which can attain concentrations on the order of 2%, extend throughout the thickness of the deposited film. Moreover, vacancies are found to have a profound effect on the evolving morphology of certain surfaces, which is discussed in terms of prior studies of kinetic roughening in these systems.
INTRODUCTION The recent extensive interest in kinetic roughening during epitaxial growth, whereby the surface roughness increases with the coverage, centers on the underlying microscopic kinetic mechanisms that control the growth behavior, such as the impingement rate, diffusion across terraces, diffusion about step edges, and diffusion over step edges (the Ehrlich-Schwoebel barrier). These have been incorporated, in one form or another, into a number of theoretical and simulation studies [1] that have successfully explained certain features of experimental results. Experiments for noble metal surfaces, where the surface diffusion is high, have been performed largely at low temperatures [2]. Little attention has been directed toward the possibility of vacancy formation in these systems. Yet, the presence of vacancies is quite likely to affect the surface kinetics and the ensuing growth behavior. Recent work on Ag(001) [3] and Cu(001) [4] have suggested that the presence of vacancies impact the evolving surface roughness during growth, although, a detailed understanding is not yet at hand. Here, we demonstrate that vacancies form and incorporate into the growing film during the low-temperature homoepitaxial growth of Cu(001), Ag(001) and Ag(111). The experiments utilize x-ray scattering methods, which have the ability to simultaneously observe the surface morphology as well as subsurface defects.
EXPERIMENTAL PROCEDURE The experiments were carried out on the SUNY X3B2 beamline at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory. The samples were initially prepared by mechanical polishing to achieve miscuts of ~0.1° and were subsequently annealed at T=700°C in an ultrahigh vacuum chamber (base pressure 10-10 Torr) in order to remove the damage from polishing. Repeated cycles of Ar+ sputtering and high T annealing, performed in situ, allowed us O2.7.1
to obtain starting surfaces with large, flat terraces having a lateral size L > 5000Å and a rms roughness σ < 0.5 Å. As we have demonstrated elsewhere [5], such high-quality starting surfaces are important in kinetic roughening studies in order to avoid transient effects. Once a smooth, clean surface was achieved, metal atoms eva
Data Loading...
