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

Paper SS1-WeM10
Surface Stability of Epitaxial SrRuO@sub 3@ Films

Wednesday, November 17, 2004, 11:20 am, Room 210B

Session: Metal Oxides and Clusters I: Formation and Structure
Presenter: A.P. Baddorf, Oak Ridge National Laboratory
Authors: A.P. Baddorf, Oak Ridge National Laboratory
J. Shin, The University of Tennessee
S.V. Kalinin, Oak Ridge National Laboratory
R.G. Moore, The University of Tennessee
H.N. Lee, Oak Ridge National Laboratory
H.M. Christen, Oak Ridge National Laboratory
E.W. Plummer, The University of Tennessee
Correspondent: Click to Email
Strontium ruthenium oxide, SrRuO@sub 3@, may play an important role in oxide electronic devices because of its metallic nature and lattice constant compatible with many transition metal oxide perovskites. Use in device fabrication requires excellent surface and interface stability without reduction or loss of volatile oxides. Thin films of SrRuO@sub 3@ appear to be quite stable, retaining their crystalline nature, as observed with electron diffraction, even after exposure to atmosphere. Surprisingly, this stability disappears after annealing in vacuum to only 200@degree@C. We have studied the surface stability of epitaxial SrRuO@sub 3@ films using a combination of electron spectroscopies, diffraction, and scanning probe microscopy. Epitaxial SrRuO@sub 3@ thin films were grown by pulsed laser deposition using a stoichiometric target on (001) SrTiO@sub 3@ substrates. Atomic force microscopy images taken in air confirm the high quality of the films, showing uniformly spaced terraces with single steps on the film surface, which closely imitate those of the SrTiO@sub 3@ substrate. After reinsertion into vacuum, a (1x1) Low Energy Electron Diffraction (LEED) pattern has been observed at room temperature, revealing an excellent chemical stability in air. The LEED pattern disappears after a brief anneal in vacuum at 200@degree@C, indicating surface disordering. Films were annealed in high vacuum in steps of 100@degree@C up to 800@degree@C and studied after cooling by LEED, x-ray photoelectron spectroscopy, scanning tunneling microscopy and thermal desorption spectroscopy. Loss of SrO from the surface leads to surface pitting and then balling of metallic Ru at temperatures below 400@degree@C. Vibrational spectroscopy relates this monolayer decomposition to submonolayer concentrations of surface hydrocarbons. Stabilities are compared with in-situ films in a new chamber combining high pressure growth with surface characterization.