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Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P314
Angle-scanned photoelectron diffraction applied to study the SiO2/4H-
SiC(0001)-interface
Mark Schürmann 1 , Stefan Dreiner 1 , Ulf Berges 1 , Carsten Westphal 1
1 Universität Dortmund, Experimentelle Physik 1, Otto-Hahn-Straße 4, 44227 Dort-
mund
Photoelectron diffraction is a surface sensitive technique which combines the chemical
sensitivity of XPS with the possibility to conduct structure determinations. In this
work angle-scanned photoelectron diffraction was applied to investigate the interface
between ultrathin SiO2 films and 4H-SiC(0001). SiC is a semiconductor material with
a large bandgap, which is, due to it’s properties, an attractive material for the application
in semiconductor devices designed for operation at high temperatures, with
high currents and high frequencies. The thermal oxidation of SiC surfaces leads to
amorphous SiO2 films at the surface. The interface of these films to the SiC substrate
is assumed to be an important source of defect states, which represent an obstacle for
the application of SiC in MOS devices.
At the U41-PGM beamline at BESSY 2 (Berlin), synchrotron radiation with high flux
and sufficient spectral resolution was available. Thus it was possible to separate three
components in the Si 2p XPS spectra corresponding to Si emitters in the SiC bulk, the
SiO2, and at the interface. Further, the O 1s signal from the silicon oxide layer and the
C 1s signal from the SiC substrate were measured. Therefore experimental diffraction
patterns are available which contain structural information about depths of the sample.
For each of them a comparison with simulation calculations is presented, which
provides information about the local atomic structure around the respective emitter.
A model was found, in which the interface structure is very similar to ordered silicate
layers on SiC as described by Bernhardt and coworkers [1]. Structural differences to
ordered silicate layers were primarily found within the near-interface region of the oxide
film. The size of locally ordered regions near the interface in the oxide film could be
determined.
[1] J. Bernhardt et al., Appl. Phys. Lett. 74, 1084 (1999)