Epitaxial growth of Ag films on Ge(001)

Abstract

The deposition of thin films of Ag on clean Ge(001) substrates has been investigated using low energy electron diffraction, Auger electron spectroscopy, and scanning electron microscopy. Ag was deposited from an effusion source onto Ge at both 325 and 600 K substrate temperatures. Deposition on high temperature substrates resulted in the formation of Ag islands with no apparent crystalline order, whereas films deposited at temperatures near 325 K onto clean Ge(001) 2×1 surfaces were oriented. The deposition of the equivalent of one Ag(001) monolayer on the Ge surfaces resulted in a Ge(001) 1×1-like LEED pattern. As deposition was continued (up to 500 monolayers), a pattern evolved which is consistent with two (011) 1×1 Ag domains oriented at 90° to one another. This behavior is interpreted in terms of a predominantly Stranski–Krastanov growth mechanism for the initial deposition of Ag onto near room temperature Ge(001) substrates. Annealing of a sample with a thin, ordered film revealed the original Ge(001) 2×1 LEED pattern, which demonstrated that the chemical interaction between Ge and Ag is very weak.