Graphene-based tunnel junction

The tunneling current in a junction formed by graphene half-planes and bilayer graphene with two possible packing types and two possible orientations of the crystal lattice is calculated by the Green’s function technique in the framework of the tight-binding approximation. It is shown that the band structure of graphene oriented toward the junction by the armchair-type edges leads to a power-law dependence of the tunneling current on applied voltage being specific for each specific kind of graphene. The characteristic features of this dependence are determined by the change in the number of transport channels with the growth of the applied voltage. For all junctions under study with zigzag edges oriented toward each other, it is found that the tunneling current exhibits characteristic peaks related to the existence of the localized edge states. The effects induced by the gate voltage are also studied. For the structures with zigzag edges, it is shown that the effect of switching off/on takes place for the junctions. The junctions formed by the graphene armchair edges do not exhibit any pronounced switching phenomena and the growth of the bias voltage results in higher values of the conductivity.     

Surface Morphology,Microstructure, and Piezoelectric Response of Perovskite Islands in Lead Zirconate Titanate Thin Films

Physics of the Solid State - Features of the microstructure and piezoelectric response of perovskite islands in a pyrochlore phase matrix in lead zirconate titanate thin films prepeared by the...     

Two-Stage Conversion of Silicon to Nanostructured Carbon by the Method of Coordinated Atomic Substitution

Physics of the Solid State - A fundamentally new method of obtaining epitaxial layers of nanostructured carbon on silicon substrates has been considered. Epitaxial growth in the case of seemingly...     

Catalysis of the 〈b̄b〉 Condensate in the Composite Higgs Model

Increasing external pressure gives rise to s–d electron transfer in calcium that results in the localization of the charge density in the interstices of the crystal structure, i.e., the formation of an electride. The corresponding electronic states are partially filled and localized and, hence, electronic correlations could arise. We have carried out theoretical calculations for the high-pressure phases of Ca taking into account the Coulomb interactions between the electronic states centered on the interstitial site. The results of our calculations and proposed microscopic model showed that the structural phase transition under high pressure is due to an interplay of hybridization and correlation effects. Furthermore, it was found that the Coulomb repulsion can explain the experimentally observed anomalous increase in resistivity of the simple cubic phase of calcium under pressure.

     

Determining the phase composition of yttrium oxide nanopowders by means of luminescence

The possibility of developing a luminescence technique for phase composition analysis is demonstrated via the example of bi-phase yttria nanopowders doped with neodymium ions. The deviation from X-ray diffraction reference values is ±2%. It is found that the results depend on the inhomogeneity of the crystalline phase distribution within a sample’s bulk, rather than on the luminescence scattering by powder nanoparticles. A luminescence coefficient that determines the phase inhomogeneity in nanopowders is introduced.     

Epitaxial growth of cadmium telluride films on silicon with a buffer silicon carbide layer

An epitaxial 1–3-μm-thick cadmium telluride film has been grown on silicon with a buffer silicon carbide layer using the method of open thermal evaporation and condensation in vacuum for the first time. The optimum substrate temperature was 500°C at an evaporator temperature of 580°C, and the growth time was 4 s. In order to provide more qualitative growth of cadmium telluride, a high-quality ~100-nm-thick buffer silicon carbide layer was previously synthesized on the silicon surface using the method of topochemical substitution of atoms. The ellipsometric, Raman, X-ray diffraction, and electron-diffraction analyses showed a high structural perfection of the CdTe layer in the absence of a polycrystalline phase.