Formation of epitaxial oxide nanodots on oxide substrate: Cu 2O on SrTiO 3(1 0 0)

Abstract

X-ray photoelectron spectroscopy analysis during the oxygen plasma assisted molecular beam epitaxy, combined with atomic force microscopy and scanning Auger microscopy have been used to evaluate the mechanism of single-phase Cu 2O nanodot formation on the SrTiO 3(1 0 0) surface. Formation of pure crystalline Cu 2O nanodots occurs rather in a narrow growth parameter window, outside which a coexistence of the multiple phases has been observed. Cuprous oxide nanodots on the SrTiO 3(1 0 0) substrate follow a growth mechanism which differs significantly from the growth modes observed for the majority of semiconductor quantum dots. Growth starts without wetting layer formation with appearance of well-ordered truncated square-based nanodots at submonolayer coverages. At the initial stages of growth, the nanodot size is only weakly changes with coverage and exponentially scales with temperature. After reaching a critical, temperature dependent dot density (∼10 13 cm −2 for 760 K growth temperature), growth of mid-sized nanoclusters starts through coalescence, which is eventually followed by large dome-shaped cluster formation at higher coverages. The coexistence of the different types of the clusters at high coverages results in a multimodal distribution of sizes and shapes.