Structures of metal nanoparticles adsorbed on MgO(001). I. Ag and Au

Abstract

The structure of metal clusters supported on a MgO(001) substrate is investigated by a computational approach, with the aim to locate stable structural motifs and possible transition sizes between different epitaxies. Metal-metal interactions are modeled by a second-moment approximation tight-binding potential, while metal-oxide interactions are modeled by an analytic function fitted to first-principles calculations. Global optimization techniques are used to search for the most stable structural motifs at small sizes (N < or = 200), while at larger sizes different structural motifs are compared at geometric magic numbers for clusters up to several thousand atoms. Metals studied are Ag, Au, Pd, and Pt. They are grouped according to their mismatch to the oxide substrate (lattice constant of the metal versus oxygen-oxygen distance on the surface). Ag and Au, which have a smaller mismatch with MgO, are studied in Paper I, while Pd and Pt, with a larger mismatch, are investigated in Paper II. For Ag the cube-on-cube (001) epitaxy is favored in the whole size range studied, while for Au a transition from the (001) to the (111) epitaxy is located at N=1200. The reliability of the model is discussed in the light of the available experimental data.

Epitaxial Ag(001) grown on MgO(001) and TiN(001): Twinning, surface morphology, and electron surface scattering

“…5 Aspects that are of particular interest and that are examined preferentially with an epitaxial metal-ceramic interface are the metal layer growth mode, morphology, crystal quality, and strain relaxation as well as technologically important properties, including wetting/adhesion, electromigration, electron scattering, and oxygen and metal interdiffusion. [6][7][8][9][10] The Ag(001)/MgO(001) system has been widely studied with both theoretical [11][12][13][14][15][16] and experimental [17][18][19][20][21] methods as a prototypical metal-oxide system, which is particularly simple because of the absence of interfacial chemical reactions at moderate temperatures, a relatively small lattice parameter mismatch of 2.98% between fcc Ag and rock salt MgO, and the resulting four-fold symmetric cube-on-cube 19,22 epitaxy. In addition, Ag has gained interest as a candidate for future interconnect metallization, 23 due to its lower bulk resistivity than Cu, its similar electromigration resistance, and its potential to provide a solution to the dramatic resistivity increase associated with diffuse surface and grain boundary scattering in Cu interconnect wires with decreasing width.…”

Growth and morphology of metal particles on MgO/Mo(001): A comparative STM and diffraction study

“…The interfacial registry between Ag and the MgO support is readily deduced from the observed particle shapes and has been addressed in various papers before. 42 In this way, interfacial Ag atoms exclusively bind to lattice oxygen, which requires 3% expansion of the Ag bulk lattice only. The development of well-defined particle shapes can thus be understood despite the exceptionally low affinity of silver toward oxygen.…”

Effect of gold composition on the orientations of oxide nuclei during the early stage oxidation of Cu-Au alloys

“…Such a size dependent orientation has been observed in various epitaxial systems such as metal clusters (Ag, Au, Pd, and Pt) supported on MgO(100) 31 or Si (111) substrates. [32][33][34] However, such size dependent orientation is not observed for oxide islanding during the oxidation of Cu in our experiments.…”