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The spin-dependent electronic transport properties of a zigzag zinc oxide (ZnO) nanoribbon are studied by using density functional theory with non-equilibrium Green’s functions. We calculate the spin-polarized band structure, projected density of states, Bloch states, and transmission spectrum of the ZnO nanoribbon. It is determined that all Bloch states are located at the edge of the ZnO nanoribbon. The spin-up transmission eigenchannels are contributed from Zn 4s orbital, whereas the spin-down transmission eigenchannels are contributed from Zn 4s and O 2p orbitals. By analyzing the current–voltage curves for the opposite spins of the ZnO nanoribbon device, negative differential resistance (NDR) and spin filter effect are observed. Moreover, by constructing the ZnO nanoribbon modified by the Zn-edge defect, the spin-up current is severely suppressed because of the destruction of the spin-up transmission eigenchannels. However, the spin-down current is preserved, thus resulting in the perfect spin filter effect. Our results indicate that the ZnO nanoribbon modulated by the edge defect is a practical design for a spin filter.

By constructing the iterative formula with a so-called convergence-control parameter, the generalized two-dimensional differential transform method is improved. With the enhanced technique, the nonlinear fractional Kolmogorov-Petrovskii-Piskunov equations are dealt analytically and approximate solutions are derived. The results show that the employed approach is a promising tool for solving many nonlinear fractional partial differential equations. The algorithm described in this work is expected to be employed to solve more problems in fractional calculus.

Atomic hydrogen plays an important role in the chemical vapour deposition of diamond and other functional materials. This paper reports the experimental determinations of atomic hydrogen density in dielectric barrier discharge hydrogen plasmas via optical emission spectrometry using Ar as an actinometer. At certain discharge conditions (ac 24 kHz, 28 kV of peak-to-peak voltage), the approximate hydrogen dissociation fractions calculated from the emission intensities with respect to electron temperatures obtained with the Langmuir probe, are decreased from 0.099 to 0.01 as the gas pressure increases from 2 to 4 Torr. The relative H atom mole fractions as a function of discharge parameters (spatial position and gas flow rate) have been investigated. It is shown that the discharge characteristics strongly depend on the spatial position but not on the gas flow rate. The influences of the above operating parameters on the emission intensities have been discussed.

Atomic hydrogen plays an important role in the chemical vapour deposition of functional materials, plasma etching and new approaches to the chemical synthesis of hydrogen-containing compounds. This work reports experimental determinations of atomic hydrogen in microwave discharge hydrogen plasmas formed from the TM01 microwave mode in an ASTeX-type reactor, via optical emission spectroscopy using Ar as an actinometer. The relative intensities of the H atom Balmer lines and Ar-750.4 nm emissions as functions of input power and gas pressure have been investigated. At an input microwave power density of 13.5 W cm−3, the approximate hydrogen dissociation fractions calculated from electron-impact excitation and quenching cross sections in the literature, decreased from ~0.08 to ~0.03 as the gas pressure was increased from 5 to 25 Torr. The influences of the above cross sections, and the electron and gas temperatures of the plasmas on the determination of the hydrogen dissociation fraction data have been discussed.

Hydrogen ions (H+, , ) from the near-ground-electrode region in dielectric barrier discharge plasmas were characterized using a molecular beam mass spectrometer under a hydrogen pressure of 1?80?Torr. The measured H+ current is more than one to a few orders of magnitude greater than the currents of and at a pressure of 1?15?Torr, with a peak-to-peak voltage of 50?kV and 35?kHz ac power source. At a gas pressure range of 15?80?Torr, only the H+ ionic signal is observed. The hydrogen ion currents rise with increasing discharge voltage and ac frequency but exhibit a maximum over the H2 pressure range studied. The H? ionic signal is also detected under certain discharge conditions within a hydrogen pressure of 1.5?35?Torr. The main physicochemical processes of interaction between hydrogen ions, neutrals and electrons in the alternative and temporary cathode sheath near the discharge electrode have been discussed. The dependence of the mean energy of H? ions on H2 pressure has also been obtained.

The hydroperoxyl radical (HO2) plays an important role in combustion systems, atmospheric chemistry and the removal of air pollutants by non-thermal plasmas. This work reports the determination of the hydroperoxyl radical in dielectric barrier discharge plasmas via near-infrared continuous wave cavity ring-down spectroscopy. HO2 radicals were observed in discharges of HCHO/O2/H2O/N2 mixtures around 6625.7 cm−1 in the first H–OO stretching overtone, (2, 0, 0)–(0, 0, 0), of its ground electronic state . At certain discharge conditions (ac frequency of 5 kHz, peak-to-peak voltage of 6.5 kV, 1900 ppm HCHO, 20% O2, 3.5% H2O in N2, Ptotal = 30 Torr), HO2 radical concentration was determined to be 1.0 × 1013 molecules cm−3. The temporary evolution of HO2 concentration was obtained using the 'time window' method. The effects of oxygen concentration, water concentration, the discharge voltage and discharge gas pressure on the concentration of HO2 radicals have been investigated. The detection limit of our setup for the HO2 radical is ~1 × 1011 molecules cm−3.