Regensburg 2004 – wissenschaftliches Programm

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O: Oberflächenphysik

O 39: Epitaxie und Wachstum III

O 39.7: Vortrag

Donnerstag, 11. März 2004, 17:15–17:30, H39

Epitaxial growth of thin Alumina on a Cr2 O3(0001) substrate — •Karifala Dumbuya1, Sven L. M Schroeder2, and Klaus Christmann11Freie Universität Berlin, Institut für Chemie, Takustrasse 3, 14195 Berlin, Germany — 2Molecular Materials Centre, Department of Chemical Engineering, UMIST, PO Box 88, Manchester, M60 1QD, UK

The growth of vapour-deposited Al and aluminium oxide on chromia Cr2 O3(0001) has been studied by auger electron spectroscopy (AES), low energy electron diffraction (LEED), ion scattering spectroscopy (LEIS), and x-ray photoelectron spectroscopy (XPS). If aluminium is deposited in the absence of oxygen, aluminium LVV auger signals are found in the 40-56 eV region, indicative of aluminium in the oxidised state (Metallic Al appears at 67 eV). This led us to conclude that the phenomenon of aluminothermy must have occured. Controlled evaporation of aluminium in an oxygen milieu, however, resulted in the growth of well ordered Al2 O3 films up to a thickness of 30 Å, whereby the epitactic growth could be monitored by LEED. These films were conducting enough to be subjected to electron spectroscopy. A gradual attenuation of the XP signals of Cr indicates layer-by-layer growth. A parallel and recently concluded investigation of the Cr2 O3/ Al2 O3 system using LEIS and XPS has corroborated our assumption that alumina grows on the Cr2 O3 substrate in an oriented manner. In addition, LEIS indicated that the uppermost Al2 O3 layers are Cr-free, and from XPS we deduced that Al actually exists in the Al3+ valence state.

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