Al Nanocluster Research Articles

Al nanocluster growth on Si(111) and Si(100) surfaces

The structure of Al films on Si in the submonolayer range has been extensively studied, but at coverages above one monolayer (ML), the structural behaviour is not elucidated as yet. The growth of nanoclusters out of Al films with 4 ML thickness, deposited on Si(111) and Si(100) surfaces by molecular beam epitaxy was studied with reflection high-energy electron diffraction, spot profile analysis low-energy electron diffraction and scanning force microscopy. Size distributions and temperature-dependent order–disorder phenomena of the clusters were measured. The Al cluster formation and structural organisation may be of relevance for practical applications such as the study of single electron tunneling and catalytic effects.

Parallel molecular dynamics simulations for the oxidation of an aluminium nanocluster

The oxidation of an Al nanocluster with radius 100 Å placed in oxygen gas at room temperature is investigated by performing molecular dynamics simulations on parallel computers. The simulations take into account the effects of dynamic charge transfer between Al and O on the basis of electronegativity-equalization principles. We thereby find that molten surface oxides are saturated to depths of 28-33 Å; this saturation is accompanied by depletion of oxygen near the cluster in the environment. Upon quenching the cluster further in oxygen gas, amorphous surface oxides with depths are formed. The microscopic structures of the amorphous oxides are characterized.

Oxidation Dynamics of Nanophase Aluminum Clusters: A Molecular Dynamics Study

ABSTRACTOxidation of an aluminum nanocluster (252,158 atoms) of radius 100Å placed in gaseous oxygen (530,727 atoms) is investigated by performing molecular-dynamics simulations on parallel computers. The simulation takes into account the effect of charge transfer between Al and 0 based on the electronegativity equalization principles. We find that the oxidation starts at the surface of the cluster and the oxide layer grows to a thickness of ∼28Å. Evolutions of local temperature and densities of Al and 0 are investigated. The surface oxide melts because of the high temperature resulting from the release of energy associated with Al-O bondings. Amorphous surface-oxides are obtained by quenching the cluster. Vibrational density-of-states for the surface oxide is analyzed through comparisons with those for crystalline Al, Al nanocluster, and α-Al2O3