Bidimensional intercalation of Ge between SiC(0001) and a heteroepitaxial graphite top layer
- LPSE, UMR CNRS-7014, Faculte des Sciences, 4, rue des Freres Lumiere, 68093 Mulhouse Cedex (France)
- Materials Testing and Research (EMPA), Feuerwerkerstrasse 39, 3602 Thun (Switzerland)
- LSGM, Departement de Physique, Faculte des Sciences et Techniques, BP 416, Tanger (Morocco)
High temperature annealing of 4H- or 6H-SiC(0001) crystals is well known to desorb Si from the surface and to generate a C-rich (6{radical}3x6{radical}3)R30 deg. (6{radical}3) reconstruction explained as a graphite monolayer in heteroepitaxial registry with the substrate. Ge deposition at room temperature and in the monolayer range on this graphitized reconstruction results in Ge islands. Using a number of surface techniques, we follow subsequent Ge morphology evolutions as a function of isochronal post-annealing treatments at increasing temperatures. In a particular temperature window Ge reacts with the substrate by diffusion under the graphite planes and wets the Si-terminated SiC surface. In spite of this bidimensional insertion of a Ge layer, the epitaxial relationship between the SiC substrate and the graphite is maintained as shown by very clear graphite-(1x1) LEED or RHEED patterns. They denote extended and well-ordered graphite planes at the surface of a graphite/Ge/SiC heterostructure. XPS analyses reveal a complete passivation of the intercalated Ge layer against oxidation by the overlying graphite sheets. Moreover, drastic spectroscopic changes on the bulk-SiC Si 2p and C 1s core levels are observed, depending on whether graphite(6{radical}3)/SiC or graphite(1x1)/Ge/SiC terminations are analyzed. In the latter case, the observed core level splitting of the bulk components is interpreted by a significant upward band bending ({approx}1.2 eV) of the n-doped SiC, making this second interface to act as a Schottky barrier. Above 1300 deg. C, a delayed Ge desorption takes place that allows the graphite sheets to re-form in their initial 6{radical}3 form, i.e., without Ge and with flatter bands.
- OSTI ID:
- 20719532
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 72, Issue 11; Other Information: DOI: 10.1103/PhysRevB.72.115319; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANNEALING
CRYSTAL GROWTH
CRYSTALS
DEPOSITION
DESORPTION
DIFFUSION
DOPED MATERIALS
ELECTRON DIFFRACTION
EPITAXY
EV RANGE
GERMANIUM
GRAPHITE
INTERFACES
LAYERS
MORPHOLOGY
OXIDATION
PASSIVATION
REFLECTION
SEMICONDUCTOR MATERIALS
SILICON CARBIDES
SUBSTRATES
SURFACES
TEMPERATURE DEPENDENCE
X-RAY PHOTOELECTRON SPECTROSCOPY