Zitterbewegung, chirality, and minimal conductivity in graphene

It has been recently demonstrated experimentally that graphene, or single-layer carbon, is a gapless semiconductor with massless Dirac energy spectrum. A finite conductivity per channel of order of e²/h in the limit of zero temperature and zero charge carrier density is one of the striking features of this system. Here we analyze this peculiarity based on the Kubo and Landauer formulas. The appearance of a finite conductivity without scattering is shown to be a characteristic property of Dirac chiral fermions in two dimensions.     

A method based on a nonlinear generalized Heisenberg algebra to study the molecular vibrational spectrum

We propose a method, based on a generalized Heisenberg algebra (GHA), to reproduce the anharmonic spectrum of diatomic molecules. The theoretical spectrum generated by GHA allows us to fit the experimental data and to obtain the dissociation energy for the carbon monoxide molecule. Our outcomes are more accurate than the standard models used to study molecular vibrations, namely the Morse and the q-oscillator models and comparable to the perturbed Morse model proposed by Huffaker [CITE], for the first experimental levels. The dissociation energy obtained here is more accurate than all previous models.     

Thermostatistics of the multi-dimensional q-deformed fermionic Newton oscillators

The algebraic and representative properties of the multi-dimensional q-deformed fermionic Newton oscillator algebra are discussed. This algebra is covariant under the undeformed group U(n). The high- and low-temperature thermostatistical properties of a gas of the multi-dimensional q-deformed fermionic Newton oscillators are obtained.     

Production of CN(BΣ) state from dissociative excitation reaction of BrCN with microwave discharge flow of Ar

The mechanism of the dissociative excitation reaction of BrCN with the microwave discharge flow of Ar was investigated based on the CN(B²Σ⁺-X²Σ⁺) emission-spectroscopic and the electrostatic-probe measurements. By passing Ar and BrCN through P₂O₅, the contamination of H₂O molecules into the reaction region was reduced to ≈30%, being confirmed by monitoring the reduction of the OH(A²Σ⁺-X²Π) emission intensity. The variation of the CN(B²Σ⁺-X²Σ⁺) emission intensity on the pressure of Ar, P_Ar, of 0.1-0.3 Torr was compared with that of the density of electrons whose kinetic energy was lower than the ionization energy of BrCN, 11.9 eV. The dissociation of BrCN was found to proceed predominantly via the charge transfer from Ar⁺ followed by the BrCN⁺ − e⁻ recombination. When the contamination of H₂O molecules in the reaction region was not reduced, the dissociation via the energy transfer from metastable Ar atoms became significant. The present study shows that the contamination of H₂O molecules in the reaction system makes significant effect onto the gas-phase plasma process.     

The inhomogeneous invariance quantum supergroup of supersymmetry algebra

We consider an inhomogeneous quantum supergroup which leaves invariant a supersymmetric particle algebra. The quantum sub-supergroups of this inhomogeneous quantum supergroup are investigated.     

High‐temperature stability of Au/p‐type diamond Schottky diode

Rectification properties of Au Schottky diodes were investigated in high‐temperature operation. These diodes were fabricated on a p‐type diamond single crystal using the vacuum‐ultraviolet light/ozone treatment. The ideality factor n of the Schottky diodes decreased monotonically with increasing measurement temperature whereas the Schottky barrier height ?_b increased, and ?_b reached 2.6 eV at 550 K with n of 1.1. Through high temperature heating at 870 K, the mean value of ?_b at 300 K changed permanently from 2.2 eV to 1.1 eV. Decrease of ?_b might originate from a dissolution of oxygen termination at the Au/diamond interface. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hydrogen incorporation in ultrananocrystalline diamond/amorphous carbon films

The incorporation of hydrogen within ultrananocrystalline diamond/amorphous carbon composite films has been investigated by nuclear reaction analysis (NRA) and Fourier transform infrared spectroscopy (FTIR). The film bulk contains ca. 7.5–8% H (for a deposition temperature of 600 °C), while the H concentration in the surface region is considerably higher. FTIR measurements show that the hydrogen‐rich surface is formed right at the beginning of the deposition process and grows outward as the film thickness increases. It can thus be concluded that surface hydrogen species play an active role in the formation of ultrananocrystalline diamond/amorphous carbon films. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The influence of oxidation with nitric acid on the preparation and properties of active carbon enriched in nitrogen

The effect of oxidation by 20% nitric acid on the properties and performance of active carbons enriched with nitrogen by means of the reaction with urea in the presence of air has been studied. The study has been made on demineralised orthocoking coal and the carbonisates obtained from it at 600 or 700 °C, subjected to the processes of nitrogenation, oxidation and activation with KOH in different sequences. The amount of nitrogen introduced into the carbon with the aid of urea has been found to depend on the stage at which the process of nitrogenation was performed. The process of oxidation of the demineralised coal and the active carbon obtained from the former has been found to favour nitrogen introduction into the carbon structure. In the process of nitrogenation of the carbonisates the amount of nitrogen introduced has inversely depended on the temperature of carbonisation. The modifications of the processes permitted obtaining materials of different textural parameters, different acid-base character of the surface and different iodine sorption capacity.     

HPHT Synthesis of High-Quality Diamond Single Crystals with Micron Grain Size

High-quality diamond single crystals with micron grain size are synthesized with a new high-pressure and high-temperature （HPHT） synthesis technique in a cubic anvil high pressure apparatus. Morphology of the synthesized diamonds is observed by a scanning electron microscope （SEM）. The samples are characterized using laser Raman spectra. The results show that the new synthesis technique improves the nucleation of diamond greatly, and diamond single crystals with perfect morphology and micron grain size are successfully synthesized, with the average grain size of about 6μm. This work provides a new synthesis technique to implement industrialization of high-quality diamond single crystals with super-fine grain size, and paves the way for future development.     

On Room-Temperature Inversion of EPR Signals of P1 Centre in Synthetic Diamond

Room-temperature inversion of EPR absorption signals of P1 centre in synthetic diamond is studied by the transient nutation technique. Use of the bichromatic field, consisting of a transverse microwave field and longitudinal radio frequency field, allows to investigate the dynamics of P1 centres in the same field configuration as in cw EPR spectrometers. It is shown that the annealing decreases the P1 centre concentration and, respectively, increases the spin-spin relaxation time. As a result, the periodic inversion （nutation） of the P1 centre absorption signal is observed longer. It is assumed that the P1 centre signal inversion, which was previously observed by cw EPR, might be caused by the Bloch-Siegert effect in the bichromatic field.