Oxygen-Induced Dissociation of Cu Islands Supported on TiO₂(110)

Abstract

Scanning tunneling microscopy studies of Cu islands grown on TiO 2 (110) demonstrate that these islands disappear from the STM images after exposure to oxygen gas (60-2000 Langmuir). Based on X-ray photoelectron spectroscopy experiments, the disappearance of the Cu islands cannot be explained by the loss of Cu from the surface or by a dramatic change in the electronic properties of the islands. The adsorption of oxygen appears to weaken the Cu-Cu bond, allowing two-dimensional (2D) islands to form on the surface at the expense of the existing three-dimensional (3D) islands. Thermodynamically, the conversion of 3D to 2D islands is favored by the lower surface free energy of the oxidized Cu compared to that of copper itself. This effect has also been observed for Ni islands, but the rate of island disappearance is slower even though Ni is more easily oxidized than Cu.

Interaction of nanostructured metal overlayers with oxide surfaces

“…On a defective surface, however, a Ag atom sitting on a neutral Mg vacancy, V 0 s , donates two valence electrons to the four O atoms surrounding the vacancy which forms strong ionic bonds between the Ag and O atoms [74]. As we will show below, defects on oxide surfaces, such as Al 2 O 3 (0001), MgO(100), SiO 2 , and TiO 2 (110), greatly affect metal adsorption and the atomic interaction energy.…”

“…For example, thin epitaxial Nb films on TiO 2 (110) have (110) interface formed at room temperature. A distorted interface between Nb and TiO 2 crystal is present [90].…”

“…(c) HRTEM image of a 0.5% Rh/Ce 0.8 Tb 0.2 O 2−x catalyst reduced at 1173 K showing the encapsulation of Rh particle by support [94]. (d) HRTEM image of Cr/TiO 2 (110) interface formed at 400 • C. The interface layer of Ti x Cr y O z is from the interdiffusion between Cr overlayers and TiO 2 substrate. been prepared by molecular beam epitaxy (MBE) at room temperature.…”

Preparation of atomically dispersed Cu species on a TiO2 (110) surface premodified with an organic compound

“…A well-defined single crystal oxide is used as a model substrate to investigate the metal-oxide interaction [1]. Cu on a rutile TiO 2 (110) surface is one of the most widely investigated surfaces [2][3][4][5][6][7][8][9][10] because supported Cu on oxides has important catalytic properties [11][12][13]. These studies have demonstrated that it is usually quite difficult to obtain fine clusters less than 1 nm in size by simple vacuum evaporation of Cu on the TiO 2 (110) [6,8].…”

Thermal behaviour of ultra-thin Co overlayers on rutile TiO2(100) surface

“…Due to lower surface energies of the Co oxides compared to pure Co metal the conversion of 3D Co island to 2D oxide structure is energetically favorable. The small size islands dissociate and disappear due to their conversion into 2D structures [28]. Surface morphological change from 3D island to 2D structure should enhance the XPS Co intensity.…”