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71.
72.
The region between epitaxial graphene and the SiC substrate has been investigated. 4H-SiC (0 0 0 1) samples were annealed in a high temperature molecular beam epitaxy system at temperatures between 1100 and 1700 °C. The interfacial layers between the pristine SiC and the graphene layers were studied by X-ray photoelectron spectroscopy. Graphene was found to grow on the SiC surface at temperatures above 1200 °C. Below this temperature, however, sp3 bonded carbon layers were formed with a constant atomic Si concentration. C1s and Si2p core level spectra of the graphene samples suggest that the interface layer we observe has a high carbon concentration and its thickness increases during the graphitization process. A significant concentration of Si atoms is trapped in the interface layer and their concentration also increases during graphitization. 相似文献
73.
Shallow acceptor levels in 4H- and 6H-SiC 总被引:2,自引:0,他引:2
S. R. Smith A. O. Evwaraye W. C. Mitchel M. A. Capano 《Journal of Electronic Materials》1999,28(3):190-195
Shallow impurities are the principal means of affecting the electrical properties of semiconductors in order to induce desired
characteristics. They can be used to isolate a region by introducing carriers of opposite charge, or they can be used to enhance
the number of carriers of a particular type. Thermal admittance spectroscopy has been used to determine the activation energies
of the principal p-type dopants, Al and B, in 4H and 6H-SiC, and temperature dependent Hall effect measurements were used
to study the shallow B acceptors in 6H-SiC. The accept or species B and Al occupy inequivalent lattice sites in the Si sublattice,
and would be expected to exhibit distinct energy levels for each site in analogy to the well known donor energy levels of
N. Activation energies for B in 6H-SiC were found to be Eh=Ev+0.27 eV, Ek1=Ev+0.31 eV, and Ek2=Ev+0.38 eV. Al acceptors in 4H-SiC were found to exhibit two energy levels at Eh=Ev+0.212 eV and Ek=Ev+0.266 eV. 相似文献