Chemical properties of two-dimensional oxide systems: Adsorption of (WO3)3 clusters on CuWO4

A two-dimensional ternary oxide layer, Cu-tungstate (CuWO4) on Cu(110), has been tested as a substrate for the adsorption of (WO3)3 cluster molecules from the gas phase. Scanning tunneling microscopy/spectroscopy and X-ray photoelectron spectroscopy have been used to characterize the adsorbed species, while density functional theory has scanned the energy landscape for stable adsorption modes. The (WO3)3 clusters adsorb in preferential adsorption sites at low temperature (85 K) as stable, only slightly perturbed units, as established both experimentally and theoretically. The preferred sites are the Cu surface rows in the [100] substrate direction, which feature elastic flexibility as a result of ultrasoft phonon modes and are a characteristic of this two-dimensional ternary oxide structure.