The growth of ultrathin films of copper on polycrystalline ZrO2

X-ray photoelectron spectroscopy (XPS/XAES) and work function measurements (WF) have been used to study the Cu/ZrO2 interface. Copper was deposited up to a thickness of 26 Å at room temperature (RT) and up to 8 Å at 673 K. At RT deposition it was found that, after the formation of just about 1 ML, copper starts to form three-dimensional clusters, exhibiting a Stranski–Krastanov growth process. At 673 K, 3D copper clusters begin to form from the very early stages of deposition, which reveals a stronger 3D character. The XPS results did not show any strong interaction between ZrO2 and Cu. Copper clusters exhibited core-level shifts due to both final and initial state effects. Work function measurements carried out during deposition at 673 K yielded additional information about the copper growth mode and the copper–zirconia interaction, which is consistent with the XPS results. Furthermore, the work function of clean ZrO2 was measured as 3.1±0.1 eV from the width of the ultraviolet photoelectron spectrum (UPS).