AVS 50th International Symposium
    Surface Science Friday Sessions
       Session SS2-FrM

Paper SS2-FrM2
Temperature Dependence of the Noncommutative Valence Band Offset at @alpha@-Cr@sub 2@O@sub 3@/@alpha@-Fe@sub 2@O@sub 3@ Epitaxial Heterojunctions

Friday, November 7, 2003, 8:40 am, Room 328

Session: Oxide Surfaces and Interfaces
Presenter: J.R. Williams, Pacific Northwest National Laboratory
Authors: J.R. Williams, Pacific Northwest National Laboratory
S.A. Chambers, Pacific Northwest National Laboratory
Correspondent: Click to Email
The valence band discontinuity at @alpha@-Cr@sub 2@O@sub 3@/@alpha@-Fe@sub 2@O@sub 3@ interfaces in epitaxial heterojunctions grown on @alpha@-Al@sub 2@O@sub 3@ (0001) substrate has been measured as a function of deposition temperature. A prior study, conducted at a given temperature, showed a noncommutative band offset of -0.3 ± 0.1 and +0.7 ± 0.1 eV in this system when the top layer is Fe@sub 2@O@sub 3@ and Cr@sub 2@O@sub 3@ respectively. This was attributed to an interface dipole that presumably depends on the growth sequence. In this study deposition temperatures of 500°C to 850°C have been investigated, and preliminary results show that this noncommutative band offset is largely independent of deposition temperature. This is an unexpected result, as the interface dipole is expected to change with deposition temperature due to interfacial mixing. Specifically we find that the binding energy difference between the Cr 3p and Fe 3p shallow core levels remains at 11.85 ± 0.08 eV (12.36 ± 0.20 eV) for structures with Fe@sub 2@O@sub 3@ (Cr@sub 2@O@sub 3@) as the top layer, and that these values are independent of deposition temperature. RHEED analysis of these structures shows that in all cases the Fe@sub 2@O@sub 3@ layer is unstrained, while the Cr@sub 2@O@sub 3@ layer is strained to match the lattice parameter of Fe@sub 2@O@sub 3@. This work was supported by U.S. DOE BES Department of Chemical Sciences.