The thermal stability of thin copper films deposited on TiO2(110) studied by scanning tunneling microscopy

The morphology of Cu thin films is strongly dependent on the temperature of the substrate during and after deposition. Films grown at temperatures between 300 degrees C and 400 degrees C form clusters distributed in close packed domains and isolated clusters across the surface. Increased substrate temperatures result in cluster shape evolution indicative of mass flow and sintering. Deposition of Cu at substrate temperatures higher than 500 degrees C results in a completely different morphology of the film and the suppression of cluster formation. Annealing these Cu films. to temperatures of 700 degrees C allows the system to relax into an equilibrium state characterized by large facets in the film and large areas of exposed surface. These observations are discussed in terms of basic thermodynamic data for bulk Cu oxidation and surface tensions for this system.