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Regions of single-layer- and bilayer graphene on the surface of thermally processed 4H-SiC substrates are studied using Kelvin probe force microscopy and Raman spectroscopy. We establish experimentally the key parameters of the adopted graphene growth technique which enables the fraction of bilayer graphene to be reduced to a minimum, while samples with a fraction of single-layer graphene as high as 95% are obtained.

The structural and electronic characteristics of epitaxial graphene films grown by thermal decomposition of the Si face of a semi-insulating 4H-SiC substrate in an argon environment have been studied by a large set of analytical techniques. It is shown that the results of a complex study make it possible to optimize the growth parameters and develop a reliable technology for the growth of high-quality single-layer graphene films. The charge-carrier concentration in the graphene layer was within 7 × 1011–1 × 1012 cm–2, and the maximum mobility of electrons at room temperature approached 6000 cm2/(V s).

The electrical properties of GaAs nanowires grown on a 6H-SiC (0001) substrate covered with graphene single layers and bilayers are studied. The nanowires are grown by molecular-beam epitaxy, with gold as a catalyst. The electrical properties are studied by measuring and analyzing the current–voltage characteristics of single nanowires vertically grown on a substrate. Numerical simulation of the experimental current–voltage curves revealed the presence of a ~0.6-V-high Schottky barrier between the nanowires and graphene. The appearance of the barrier is due to the formation of excess arsenic at the nanowire/graphene interface.

This work was devoted to the study of stable and unstable optical modes in segment shaped resonators. The size of the studied resonators was much larger than the wavelength of the emitted light, that allowed to use the approaches of geometric optics. It was observed, that with an increase in the δ/R deviation parameter (where δ is the deviation from the center of the half-disk) only a small number of stable spatial modes remain. The possibility of the existence of “sealed” (non-radiating modes) and “open” modes (radiating modes) in resonators of this type was also shown.

Piezoresistance effect of the InxGa1 –xAs nanowires was studied by scanning probe microscopy. The effect was investigated by measuring of the I–V curves with simultaneous bending of the nanowire by the probe. A modulation of the conductivity of In0.85Ga0.15As NWs induced by a mechanical stress exceeding three orders of magnitude was observed. For the explanation a model based on the surface states is presented. Such an observation opens new ways for the design of electromechanical switches with record parameters.

The structural, chemical, and electronic properties of epitaxial graphene films grown by thermal decomposition of the Si-face of a semi-insulating 6H-SiC substrate in an argon environment are studied by Raman spectroscopy, atomic-force microscopy, the low-energy electron diffraction method, X-ray photoelectron spectroscopy, angle-resolved photoemission spectroscopy and X-ray absorption spectroscopy at the carbon K edge. It is shown that the results of a systematic integrated study make it possible to optimize the growth parameters and develop a reliable technology for the growth of high-quality single-layer graphene films with a small fraction of bilayer graphene inclusions.

AbstractThe properties of the hybrid energy sources “piezoelectric nanogenerator-solar cell” based on GaAs nanowires with the wurtzite crystal structure were investigated. Measurements were performed by the bending of the nanowire by the probe of the atomic force microscope with simultaneous recording of short circuit current in dark and illuminated conditions. We show that a piezoelectric current pulse of ~10 pA arises in the “nanowire-probe” circuit during the deformation of nanowire by the AFM probe. Under laser illumination, the value of the pulse increases by two orders of magnitude as a result of the piezophototronic effect. Deformation of the nanowire boosts the photocurrent by 40% up to 0.5 nA.