Complex metallic surface phases in the Al/Cu(111) system: An experimental and computational study

Abstract

To cite this version: T. Duguet, Emilie Gaudry, Th. Deniozou, J. Ledieu, M.-C. de Weerd, et al.. Complex metallic surface phases in the Al/Cu(111) system: An experimental and computational study. Physical Review B:The growth of complex intermetallics as surface alloys is investigated by annealing Al thin films deposited on Cu͑111͒ substrate in ultrahigh vacuum. Already at room temperature, the large lattice mismatch between Al and Cu results in interfacial intermixing. Upon annealing, various phases are formed by diffusion depending on the thickness of the Al films and the annealing temperature. The surface structures are characterized by scanning tunneling microscopy, low-energy electron diffraction, and x-ray photoelectron spectroscopy. Three different superlattice phases are identified as well as the complex Hume-Rothery ␥-Al 4 Cu 9 phase. The epitaxial relationships between the surface phases and the Cu͑111͒ substrate are determined. We further investigate the electronic structure of the ␥ phase by density functional calculations. Experimental valence bands are compared to calculated density of states and simulated STM images are used to identify possible bulk planes appearing as surface termination.

Surfaces of Al-based complex metallic alloys: atomic structure, thin film growth and reactivity

“…Annealing a 20 ML thick film leads to the formation of five domains of γ -AlCu exposing the (110) surface. The latter phase had been previously reported when annealing a thick Cu film adsorbed on the fivefold i -AlPdMn surface to 623 K [89] and by annealing Al thin films deposited on a Cu(111) surface [90]. Complementary to these studies, the adsorption of Cu atoms has been carried out on the AlCo(100) surface for different coverages and temperature regimes [85].…”

Nanodomains due to Phason Defects at a Quasicrystal Surface

“…As presented elsewhere, these regions are identified as TM-rich on the basis of their atomic-scale structure, and their bias dependence in STM imaging. The presence of TM atoms at the surface, as opposed to Al atoms, leads to a stronger bias dependence [15]. This point will be key to much of the following interpretation.…”

“…Previous consideration of nanodomains on clean TMrich terraces, led to the conclusion that they could be phason-related [15]. The possible surface terminations in the bulk model should be considered as surfaces of thick blocks of atoms, separated by distances following a Fibonacci sequence.…”

“…All of these heights can be categorized as small (S) and large (L), and combinations thereof. For this system, S and L have been determined experimentally to be 0.47 and 0:77 AE 0:05 nm, respectively [15]. Then the step sequence above the nanodomain is L-ðLSLÞ-S-L-LS, which is a portion of a Fibonacci sequence.…”

“…The surface investigated with STM using the WSxM software [16], exhibits two main types of terraces which are Al-rich and transition-metal (TM)-rich [15]. The TMrich terraces often include nanodomains of the Al-rich structure, whereas the Al-rich terraces almost never exhibit defects of the TM-rich structure.…”