Ultrathin deposition of copper on room temperature SrTiO₃(100)

An SrTiO₃(110) surface was prepared and characterized under ultraclean conditions in ultrahigh vacuum. The methods used were Auger electron spectroscopy, electron energy loss spectroscopy, UV photoelectron spectroscopy and high resolution electron energy loss spectroscopy and low energy electron diffraction. Copper was gradually deposited at room temperature by electron beam evaporation upon a (1 × 1) SrTiO₃(110) surface, until several monolayers were reached. Although charging effects disturb the Auger measurements, it is possible to determine that the room temperature growth mode is of the Volmer-Weber type (islanding) and non-epitaxial. Five well-defined energy losses are attributed to interband transitions and plasmons in the range below 30 eV, while the UV photoelectron spectra showed three strong peaks characteristic of Cu 3d and O 2p bands, with copper appearing as an impurity in the band gap. It is suggested that the formation of islands is associated with TiO₂-terminated layers at the surface. The copper is weakly bound to the substrate and desorbs at 500°C.