Applied Surface Science, Vol.254, No.9, 2720-2724, 2008
Impact of O-2 exposure on surface crystallinity of clean and Ba terminated Ge(100) surfaces
In analogy with the case of Sr on Si [Y. Liang, S. Gan, M. Engelhard, Appl. Phys. Lett. 79 ( 2001) 3591], we studied surface crystallinity and oxidation behaviour of clean and Ba terminated Ge(1 0 0) surfaces as a function of oxygen pressure and temperature. The structural and chemical changes in the Ge surface layer were monitored by LEED, XPS and real-time RHEED. In contrast to the oxidation retarding effect, observed for 1/2 monolayer of Sr on Si, the presence of a Ba termination layer leads to a pronounced increase in Ge oxidation rate with respect to clean Ge. In fact, while the Ge(1 0 0) surface terminated with 1/2 ML Ba amorphizes for a pO(2) of 10(-2) Torr, LEED indicates that clean Ge forms a thin (4.5 angstrom), 1 x 1 ordered oxide upon aggressive O-2 exposure (150 Torr, 200 degrees C, 30 min). We briefly discuss the origins for the difference in behaviour between Ba on Ge and Sr on Si. (C) 2007 Elsevier B. V. All rights reserved.