CVD graphene sheets electrochemically decorated with “core-shell” Co/CoO nanoparticles

The paper reports on the first successful fabrication of Co-graphene composites by electrochemical deposition of Co nanoparticles (NPs) on the sheets of twisted graphene. Characterization of the surface morphology and element mapping of twisted graphene decorated with Co NPs by transmission and scanning electron microscopy in combination with the energy-dispersive X-ray spectroscopy reveals the formation of isolated quasi-spherical oxidized Co NPs with the mean diameter h di _ 220 nm and core-shell structure. X-ray photoelectron spectroscopy indicates that the core of deposited NPs consists of metal Co while the shell is CoO. Composite Co-graphene samples containing core-shell NPs reveal an exchange bias field up to 160 Oe at 4 K as detected by vibrating sample magnetometry after the field cooling procedure

Study of p-Fe₃O₄/n-(GaAs,Si) Heterostructures: Fabrication and Physical Properties

We report preparation and investigation of p -n heterostructures based on Fe₃O₄ thin films grown on semiconductor Si and GaAs substrates. Fe₃O₄ films with thickness ranging from 60 to 300 nm were grown at 350÷450°C using dc magnetron sputtering technique. The measurement of X-ray diffraction and reflection high energy electron diffraction revealed polycrystalline microstructure of thin Fe₃O₄ films deposited on both Si and GaAs substrate. Investigation of surface composition by X-ray photoelectron spectroscopy showed that Fe 2p peak consists of three main peaks, namely, metallic iron Fe(0), Fe(II), and Fe(III). Transport measurements of Fe₃O₄/n-(Si, GaAs) heterostructures demonstrated nonlinear current-voltage (I -V) dependences in the temperature range from 300 K to 78 K

XPS study of graphene grown by atmospheric pressure CVD from n-decane precursor with nitrogenasa carrier gas

We present X-ray photoelectron spectroscopy study (XPS) of graphene films grown on copper foil by atmospheric pressure CVD with n-decane as a precursor, a mixture of nitrogen and hydrogen as a carrier gas, under different hydrogen flow rates. The XPS study revealed the characteristics of incorporated nitrogen, which was found to have a binding energy around 402 eV, the atomic concentration of incorporated nitrogen is higher for the sample synthesized with higher hydrogen flow rate

Degree of phase transformations in the conditions of polythermal synthesis of SrBaFeMoO6–δ

The sequence of phase transformations during the crystallization of SrBaFeMoO6 –δ by the solid-phase technique from a stoichiometric mixture of simple oxides SrCO3 þ BaCO3 þ 0.5Fe2O3 þ MoO3 was studied. It has been established that the synthesis of barium – strontium ferromolybdate proceeds through a series of sequential - parallel stages. It was found that to minimize the effect of intermediate reaction products, it is necessary to use combined synthesis modes. As a result of using combined synthesis modes for annealing for 20 h and T ¼ 1443 K in vacuum of 10 5 Torr at the pressure of residual oxygen gas 10 8 Pa, it was possible to obtain a single-phase barium – strontium ferromolybdate compound with superstructural ordering of iron and molybdenum cations

Nitrogen-doped twisted graphene grown on copper by atmospheric pressure CVD from decane precursor

We present Raman studies of graphene films grown on copper foil by atmospheric pressure CVD with n-decane as a precursor, a mixture of nitrogen and hydrogen as the carrier gas, under different hydrogen flow rates. A novel approach for the processing of the Raman spectroscopy data was employed. It was found that in particular cases, the various parameters of the Raman spectra can be assigned to fractions of the films with different thicknesses. In particular, such quantities as the full width at half maximum of the 2D peak and the position of the 2D graphene band were successfully applied for the elaborated approach. Both the G- and 2D-band positions of single layer fractions were blue-shifted, which could be associated with the nitrogen doping of studied films. The XPS study revealed the characteristics of incorporated nitrogen, which was found to have a binding energy around 402 eV. Moreover, based on the statistical analysis of spectral parameters and the observation of a G-resonance, the twisted nature of the double-layer fraction of graphene grown with a lower hydrogen feeding rate was demonstrated. The impact of the varied hydrogen flow rate on the structural properties of graphene and the nitrogen concentration is also discussed

Nitrogen doped twisted graphene

We review the properties of twisted graphene synthesized by atmospheric pressure chemical vapor deposition

Superconducting critical temperature and softening of the phonon spectrum in ultrathin nb- and nbn/graphene hybrids

Superconductivity is studied in hybrids consisting of ultrathin superconducting film/few layer graphene. Two different superconductors are used for this purpose, Nb and NbN. An increase in the superconducting critical temperature Tc is observed when graphene is put into contact with Nb. The largest increase is obtained for the thinnest Nb layer, which has a Tc 8% larger with respect to the single Nb film. In the case of NbN the effect is not as pronounced. Experimental data are discussed by considering the possible modification of the phonon spectrum in the superconductor due to the presence of the graphene. Within an elementary one-dimensional model based on elastic coupling between nearest-neighbor atoms, we demonstrate that the phonon spectrum in the superconductor is modified at low energies with the subsequent enhancement of the effective electron–phonon coupling constant. While the strong oscillating nature of the electron–phonon interaction, α2(ω), in NbN could lead to the insensitivity of Tc on the low-energy phonons generated by the graphene, the almost constant behavior of α2(ω) in Nb favors the increase of the superconducting critical temperature

Nitrogen-doped twisted graphene grown on copper by atmospheric pressure CVD from a decane precursor

We present Raman studies of graphene films grown on copper foil by atmospheric pressure CVD with n-decane as a precursor, a mixture of nitrogen and hydrogen as the carrier gas, under different hydrogen flow rates. A novel approach for the processing of the Raman spectroscopy data was employed. It was found that in particular cases, the various parameters of the Raman spectra can be assigned to fractions of the films with different thicknesses. In particular, such quantities as the full width at half maximum of the 2D peak and the position of the 2D graphene band were successfully applied for the elaborated approach. Both the G- and 2D-band positions of single layer fractions were blue-shifted, which could be associated with the nitrogen doping of studied films. The XPS study revealed the characteristics of incorporated nitrogen, which was found to have a binding energy around 402 eV. Moreover, based on the statistical analysis of spectral parameters and the observation of a G-resonance, the twisted nature of the double-layer fraction of graphene grown with a lower hydrogen feeding rate was demonstrated. The impact of the varied hydrogen flow rate on the structural properties of graphene and the nitrogen concentration is also discussed

Superconducting Critical Temperature and Softening of the Phonon Spectrum in Ultrathin Nb and NbN/graphene hybrids

Superconductivity is studied in hybrids consisting of ultrathin superconducting film/few layer graphene. Two different superconductors are used for this purpose, Nb and NbN. An increase in the superconducting critical temperature Tc is observed when graphene is put into contact with Nb. The largest increase is obtained for the thinnest Nb layer, which has a Tc 8% larger with respect to the single Nb film. In the case of NbN the effect is not as pronounced. Experimental data are discussed by considering the possible modification of the phonon spectrum in the superconductor due to the presence of the graphene. Within an elementary one-dimensional model based on elastic coupling between nearest-neighbor atoms, we demonstrate that the phonon spectrum in the superconductor is modified at low energies with the subsequent enhancement of the effective electron–phonon coupling constant. While the strong oscillating nature of the electron–phonon interaction, α2(ω), in NbN could lead to the insensitivity of Tc on the low-energy phonons generated by the graphene, the almost constant behavior of α2(ω) in Nb favors the increase of the superconducting critical temperature