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Structural investigations of hydrogenated epitaxial graphene grown on SiC(0001) are presented. It is shown that hydrogen plays a dual role. In addition to contributing to the well-known removal of the buffer layer, it goes between the graphene planes, resulting in an increase of the interlayer spacing to 3.6 Å–3.8 Å. It is explained by the intercalation of molecular hydrogen between carbon planes, which is followed by H2 dissociation, resulting in negatively charged hydrogen atoms trapped between the graphene layers, with some addition of covalent bonding to carbon atoms. Negatively charged hydrogen may be responsible for p-doping observed in hydrogenated multilayer graphene.

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Efficient control of intercalation of epitaxial graphene by specific elements is a way to change properties of the graphene. Results of several experimental techniques, such as X-ray photoelectron spectroscopy, micro-Raman mapping, reflectivity, attenuated total reflection, X-ray diffraction, and X-ray reflectometry, gave a new insight into the intercalation of oxygen in the epitaxial graphene grown on 4H-SiC(0001). These results confirmed that oxygen intercalation decouples the graphene buffer layer from the 4H-SiC surface and converts it into the graphene layer. However, in contrast to the hydrogen intercalation, oxygen does not intercalate between carbon planes (in the case of few layer graphene) and the interlayer spacing stays constant at the level of 3.35–3.32 Å. Moreover, X-ray reflectometry showed the presence of an oxide layer having the thickness of about 0.8 Å underneath the graphene layers. Apart from the formation of the nonuniform thin oxide layer, generation of defects in graphene caused by oxygen was also evidenced. Last but not least, water islands underneath defected graphene regions in both intercalated and non-intercalated samples were most probably revealed. These water islands are formed in the case of all the samples stored under ambient laboratory conditions. Water islands can be removed from underneath the few layer graphene stacks by relevant thermal treatment or by UV illumination.

The results of optical investigation of hydrogenated epitaxial bilayer graphene are presented. A softening and an increase of the intensity of the in-plane anti-symmetric phonon mode are observed at 0.2 eV. It is suggested that they both originate from coupling of the optically active phonon mode to virtual electronic transitions, which is related to the band structure of bilayer graphene and leads to the "charged phonon" effect. In addition, it is noted that optically active phonon peaks have pronounced Fano shapelines. It is argued that the Fano shapeline is attributed to the interaction of the phonon mode with a continuum of electronic transitions in valence bands of hydrogenated bilayer graphene.

Abstract-Absorption spectra in THz range of commonly used

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New possibilities are presented for the characterization of AIIIBV mixed superlattice compounds by the complementary use of synchrotron diffraction topography and rocking curves. In particular, using a synchrotron white beam and the section diffraction pattern of a 5 µm slit taken at a 10 cm film‐to‐crystal distance, it was possible to reproduce a set of stripes corresponding to interference fringes. These are analogous to the interference maxima revealed in high‐resolution rocking curves, but are created by the changes in orientation of the planes inclined to the surface which are induced by unrelaxed strain. The section diffraction topographic method enabled examination of the sample homogeneity along the narrow intersecting beam. This was important in the case of the present sample containing a twin lamella in the InP substrate wafer. Both the section and projection Bragg case topographic methods enabled the crystallographic identification of the twin lamella. Another characteristic feature indicated in the section topography was the bending of the stripes corresponding to the superlattice peaks close to the boundaries of the twin lamella. The most probable interpretation of this phenomenon is an increase in the thickness of the deposited layers close to the lamella, together with possible changes in the chemical composition, leading to a decrease in the mean lattice parameter in the superlattice.