AVS 51st International Symposium
    Surface Science Wednesday Sessions
       Session SS1-WeM

Paper SS1-WeM9
Novel Stages of Growth of Metal Oxide Nanodots: Cu2O on SrTiO3(100)@footnote 1@

Wednesday, November 17, 2004, 11:00 am, Room 210B

Session: Metal Oxides and Clusters I: Formation and Structure
Presenter: I. Lyubinetsky, Pacific Northwest National Laboratory
Authors: I. Lyubinetsky, Pacific Northwest National Laboratory
A.A. El-Azab, Pacific Northwest National Laboratory
A.S. Lea, Pacific Northwest National Laboratory
S.T. Thevuthasan, Pacific Northwest National Laboratory
D.R. Baer, Pacific Northwest National Laboratory
Correspondent: Click to Email
Although similar to semiconductor nanostructures in some ways, oxide nanodots have been observed in greater structural variations. Here we report on a significant difference in the growth process which exhibits novel stages. Self-assembled formation of the crystalline cuprous oxide (Cu2O) nanodots on the SrTiO3(100) substrate has been carried out using oxygen plasma assisted MBE and evaluated by XPS, AES, XRD and AFM. Selective formation of the nanodots of single Cu2O-phase occurs only in a very narrow growth parameter window, in comparison with the bulk phase diagram. Formation of Cu2O nanoclusters (with the size range of 10-50 nm) may be described as progressing through several stages. Unlike lattice-mismatched heteroepitaxy in the majority of semiconductor systems, initial stages of the growth of oxide nanodots proceed without formation of the wetting layer. Already at sub-monolayer coverages, small, truncated square Cu2O dots start to form. At next, novel stage a continued deposition leads to increase of the dot density, not the size, and results in reaching a critical dot density, upon which larger nanoclusters start to grow. Resulting morphology consists of large islands on top of the closed-packed layer of the small nanodots. Using a kinetic model of film morphology development, we show that the larger island formation can be caused by small dot coalescence, driven by fluctuation of island-island separation at increased dot density. Under different surface conditions of the SrTiO3(100) substrate (high temperature annealed, perfect TiO2-terminated surface vs. original mixed-terminated surface) significant differences in the uniformity of the nanodot distribution have been observed. @FootnoteText@ @footnote 1@ This work was jointly supported by the Department of Energy (DOE), Basic Energy Sciences Division and the Laboratory Directed Research and Development at PNNL, which is operated by Battelle for the DOE.