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SSL Seminar Series 2001 No. 12
Combined talks (two speakers) on SiC (0001) reconstruction surfaces.
Time: July 18, 2001, 5:00-6:00pm
Venue: Physics Resource Room, S13, 02-16
Speaker I: Xie Xianning (Chem. Dept. NUS)
Title: The evolution of 3x3, 6x6, sqrt(3) x sqrt(3)R30° and
6sqrt(3)x6sqrt(3)R30° superstructures on 6H-SiC(0001) surfaces studied
by reflection high energy electron diffraction (RHEED)
Abstract
The studies of surfaces and interfacial structures on SiC have received
a lot of attention recently due to the distinctive electronic properties
of the various superstructures and their importance in the homoepitaxial
growth of SiC. RHEED has several advantages over LEED in qualitative
structural analysis. In particular, the grazing incidence angle and
long probing length of RHEED electron beam renders the technique especially
sensitive to surface asperities and topographical variation. In this
work, we present high quality RHEED patterns of 3x3, 6x6, sqrt(3)
x sqrt(3)R30° and 6sqrt(3) x 6sqrt(3)R30° superstructures obtained
on the Si-enriched SiC(0001) surfaces by careful annealing in vacuum.
A well-defined 6x6 superstructure was detected by RHEED for the first
time following annealing the 3x3 phase. All the superstructures were
further characterized by AES, UPS and EELS. Based on the twisted Si-adlayer
3x3 model, we proposed a structural model for the 6x6 metastable phase.
Speaker II: Ong Wei Jie (SSL, Phys. Dept.
NUS)
Title: Phase transition of SiC (0001) 3X3 to Si rich 6X6 surface
reconstruction
Abstract
There has been little observation of the phase transition mechanism
of SiC(0001) 3x3 to Si rich 6x6 reconstruction. Pseudomorphic 6X6
superstructures were first observed using RHEED by Dr KP Loh and Xie
XN. The diffraction technique is complemented by the STM to proposed
a possible structural model of the 6x6 reconstruction as well as the
mechanism preceding its formation. We have managed to capture STM
images of the 3x3 to 6x6 phase transition, which would allow us to
discuss the mechanics of the surface structural change in greater
detail. |
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