The growth of aluminum on a rhenium (101̄0) surface

Abstract

Al thin films were deposited at 873 K on a Re(101̄0) surface and examined by means of low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), thermal desorption spectroscopy (TDS), and work function (ΔΦ) measurements. In the submonolayer range (0< Θ Al<0.6), we find two Al LEED structures, a p(3 × 1) at Θ Al ≈ 0.3, and a p(2 × 1) at Θ Al ≈ 0.5. In the same coverage range, a single TD state denoted as β 3 appears having a desorption energy of 440 kJ/mol. Close to Θ Al ≈ 1 another (2 × 1) LEED phase and a second TD state ( β 2) develop which exhibits a desorption energy of ∼ 375 kJ/mol. This (2 × 1) phase is then replaced up to Θ Al ≈ 2 by a clear c(2 × 2) phase, followed by a p(2 × 2) and another c(2 × 2) structure at still higher Al coverages. In this multilayer range, the TD spectra are dominated by a single desorption state denoted as β 1 which reflects a fractional-order kinetics and yields an activation energy of ∼ 345 kJ/mol. The deposition of Al reduces the Re work function by ∼ 1.2 eV. A plot of the Re versus Al Auger intensity reveals a clear break at Θ Al ≈ 1 and a less pronounced break around Θ Al ≈ 2, while for higher Al coverages the Re AES intensity decays unspecifically, which suggests deviations from a plain layer-by-layer growth. Up to ∼ 8 deposited monolayers the structure of the Al film is determined by the crystallography of the Re(101̄0) surface and by relaxation processes to overcome the misfit.