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Institute
Electronic properties of the 2x1 3C-SiC surface reconstruction studied with resonant photoemission
(2006)
We have studied the 2x1 reconstructed surface of the 3C-SiC polytype by means of photoemission spectroscopy. The reconstruction was characterized through Si2p and C1s core level and angle-integrated valence band spectroscopy, and confirmed by the observation of a two-domain 2x1 LEED pattern. The electronic properties of this surface were investigated by collecting valence band spectra at photon energies near the Si2p and C1s absorption edges. The results show a strong dependence of the photoemission intensity on the excitation energy with characteristic resonances for certain valence band features. With a detailed study of the resonances we are able to assign the electronic origin of the resonating states and the nature of the electronic transition near the absorption edges.
We report about organic and inorganic MIS stacks for new possibilities for high frequency and high power applications as well as for non volatile memory cell. The organic stack contains a ferroelectric polymer as the
functional layer. Poly[vinylidene fluoride trifluoroethylene] (P[VDF/TrFE]) is spin
coated from a solution onto oxidised silicon substrates. We report on the polarisation induced flatband voltage shifts. For the inorganic stack our attempt is to combine higk-k dielectrics
with high band gap semiconductors (SiC). Praseodymium oxide layers are
prepared by electron beam evaporation from Pr6O11
powder and in situ
controlling of interface and volume composition (XPS). Praseodymium silicate layers were prepared either by metal evaporation onto a thin ox-
ide on top of the semiconductor and following annealing steps or by a
wet chemical process out of aqueous Pr(NO3)3 solutions. Using spectro-scopic characterisation we investigate the stability of the various inter-faces within the stacks as well as the reactivity of the metal electrodes on thin Pr2O3. We report the results of electrical characterisation consisting of permittivity values, leakage current and density of interface states.
In ultra thin layers of high-K materials the value of the band gap can be
derived not explicitly although it is a key quantity in the electric behavior.
We use ELS with a monochromatized (50 meV - 150 meV) electron gun and primary energies between 20 eV and 30 eV. Starting with the native
SiO2/Si(001) layers we find that loss function of the substrate dominates
for using primary energies beyond 50 eV. In contrast at energies below 50 eV the loss intensity can be used to derived the band gap with an
accuracy of ±200 meV. We compare thin (<3 nm) films of HfOx, Pr2O3,Al2O3 and Si-Oxynitrides and discuss the band gap values as well as the scattered intensity observed within the gap.