We analyzed the (0001) surface structures of hematite and chromia bulk single crystals by low energy electron diffraction (LEED). The hematite crystal was annealed in an O(2) atmosphere, p(O(2))≈3 × 10(-8) mbar, for several hours. The chromia crystal was sputtered with Ar(+) ions, E = 1 keV, and afterward heated up to 900 °C for 5 min under ultra-high-vacuum (UHV) conditions. I(V)-curve data sets of 12 symmetrically independent diffraction spots were measured at room temperature in the energy range E = 150-500 eV. Charging effects hindered measurements at lower energies. Our analysis of the hematite single crystal surface indicates that it is terminated by a single iron layer which is occupied at ≈50%. Relaxation effects along the c-axis are quite large and involve several iron double layers. For the chromia surface the results indicate that termination with a single Cr seems not to hold. Most probably the surface is terminated by two partially occupied Cr sites or chromyl groups. Relaxations in deeper layers are small in contrast to α-Fe(2)O(3)(0001).

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The change of structure of tetrahedral amorphous carbon (ta-C) films after nitrogen incorporation, particularly at a high concentration, was studied by near edge x-ray absorption fine structure (NEXAFS) spectroscopy and it was found to be very close to pyridine. The π* peak at the N K (nitrogen K) edge was decomposed into three components corresponding to different resonances. From a detailed analysis of N K edge by NEXAFS spectroscopy it was revealed that as the nitrogen concentration in the films increases, the σ*/π* intensity ratio decreases, indicating that there is an increase of the amount of C=N relative to the C–N bonds. By thermal annealing at different temperatures, up to 800 °C, the nitrogen concentration in the films is reduced. Intensity as well as the position of the π* peak at the C K edge changed with annealing temperature. At the same time, a decrease of the intensity of the π* peak at the N K edge and a very interesting change of the relative intensities of the three split components of this π* peak have been observed. The possible changes of structure of nitrogenated carbon films by annealing and thermal stability of the films have been thoroughly emphasized.