Copper wetting of α-Al2O3(0001): theory and experiment

Mechanism of Cu Deposition on theα−Al2O3(0001) Surface

“…Recently we reported [14] a detailed theoretical study on the interaction of Cu atoms on a relaxed, clean, Al-terminated, -Al 2 O 3 (0001) surface also based on GGA-DFT calculations. At 1=3 ML (the smallest one can reach using a 1 1 cell), our calculations suggested that Cu atoms appear to reduce the surface, more specifically outermost Al atoms, with formation of Cu(I) ions, while increasing the coverage led to a buckled adlayer with the Cu atoms forming zigzag chains, and coexistence of Cu(I) and Cu(0) species, in agreement with the interpretation of XPS data [11]. Although this analysis provided a first understanding of the metal-support interface, some key questions concerning the growth mechanism at the earlier stages of Cu deposition still remain open.…”

“…The description corresponds therefore to a metal cluster likely partially oxidized, in which all atoms approximately have the same oxidation state. This description clearly disagrees with the Auger spectra [11], although agreeing with the formation of 3D clusters of Cu(0) observed when, for instance, a film is used [4].…”

“…Actually, -Al 2 O 3 (0001) surfaces are always hydroxylated [18], and those used in Ref. [11] had an estimated OH coverage of 0.47 ML. To consider the presence of H 2 O we start by adding one molecule per cell and compute the adsorption energy for both molecular and dissociative processes.…”

“…The temperature influence on the Cu deposition on partially hydroxylated -Al 2 O 3 (0001) surfaces was examined by Kelber et al [11]. The XPS data showed an initial layer-by-layer growth with formation of Cu(I) at < 0:35 ML, while at a higher , both Cu(I) and metallic Cu(0) were detected.…”

“…The interaction energy of Cu atoms with -Al 2 O 3 (0001) has been theoretically analyzed from local-density approximation density functional theory (DFT) calculations using models of clean and hydroxylated surfaces [11,12]. At Cu coverage of 1 ML, Lodziana et al reported generalized gradient approximation (GGA)-DFT interaction energies of 0.91 and 0.87-2.55 eV for clean and hydroxylated surfaces [13].…”