Initial growth of Au on oxides

Abstract

The growth of Au clusters on TiO 2 .110/ − .1 × 1/ and −.1 × 2/ single-crystal surfaces and on ordered Al 2 O 3 films prepared on Re(0001) has been studied by low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), low-energy ion scattering spectroscopy (LEISS) and high-resolution electron energy-loss spectroscopy (HREELS). The results indicate that Au forms two-dimensional islands on the TiO 2 (110) surface at initial deposition of Au. On the alumina film, Au initially grows as three-dimensional clusters. The coverage of Au at which Au clusters change from non-metallic to metallic properties is found to be >0.3 monolayer equivalent (MLE) of Au deposition based on the energy shift of the surface plasmon measurements.

Surface chemistry of catalysis by gold

“…In a similar examination based upon the 5d band splitting, Lee et al had estimated that this transition should take place at a particle diameter of more than 1.9 nm, which corresponds to a hemispherical particle with over 100 atoms (325). Using HREELS, Guo et al estimated that this transition occurred for gold on TiO2 (110) at a coverage of 0.2 ML Au, which corresponds to particles of about 2 nm in diameter and 2 atomic layers high (242). For gold on a thin alumina film, the transition was not seen until a coverage of 0.3 ML of Au (242).…”

“…Using HREELS, Guo et al estimated that this transition occurred for gold on TiO2 (110) at a coverage of 0.2 ML Au, which corresponds to particles of about 2 nm in diameter and 2 atomic layers high (242). For gold on a thin alumina film, the transition was not seen until a coverage of 0.3 ML of Au (242). Whetten and co-workers found that discrete states in the optical absorption spectra began to emerge at diameters below 2 nm (~ 200 atoms) (326).…”

Angle resolved X-ray photoelectron spectroscopy study of Au deposited on Pt and Re surfaces

“…There is a growing evidence that chemical properties of gold clusters and thin films might become different from those of bulk gold surfaces [1,2]. Gold deposited on several metallic and non-metallic substrates has been extensively studied [1][2][3][4], but the modifications of its properties by size effects and by interaction with the supporting material are still far from being well understood. In this communication we report XPS measurements on Au/Pt and Au/Re systems in a gold coverage range from submonolayer amounts to several monolayers, and the core level and 5d-band shifts calculated using local density functional method within the initial state approximation.…”

The influence of electron confinement, quantum size effects, and film morphology on the dispersion and the damping of plasmonic modes in Ag and Au thin films

“…Gold nanosystems (thin films [124], quantum wires [125,126], and nanoparticles [127]) have attracted attention as a consequence of the discovery that Au is a selective catalyst for a variety of technologically relevant chemical reactions [128][129][130][131][132][133][134][135][136][137][138] and, moreover, that plasmonic excitations play an important role in heterogeneous catalysis [139][140][141][142]. Hence, understanding the nature of collective electronic excitations in gold films is important in order to tailor selective catalysts and to understand novel physical processes with potential technological applications [143,144].…”