International Journal of Modern Physics B

The Cd${}_x$Zn${}_{1-x}$O thin films have been deposited on glass and Si substrates at room-temperature with different Cd contents (x = 0, 2%, 4% and 6 wt.%) by pulsed laser deposition (PLD) technique. X-ray diffraction (XRD) analyses evidenced that the films possess polycrystalline and a hexagonal ZnO crystal structure for x = 0, 2% and 4% with a preferred orientation in the a-axis (101) direction, while films with a mixed hexagonal and cubic structure was revealed for x = 6 wt.%. Electrical measurement presented that the resistivity decreased with increased temperature and concentration of Cd. The deliberated activation energy was reduced was from 0.224 to 0.113 eV with increase doping concentration. Current–voltage (I–V) and capacitance–voltage (C–V) characteristics of the fabricated Cd${}_x$Zn${}_{1-x}$O/p-Si heterojunction varied with the applied bias and the Cd concentration. The results of the values of built-in potential (V${}_{\mathrm{\text{bi}}}$) and the ideality factor (n) increased with raising Cd concentration.

In this paper, a separated sliding mode strategy is proposed for the synchronization of network systems. To break the predicament caused by the inhomogeneity of nodes coupling in complex network, a colored network with different node systems and edges is given. According to the nonlinear subsystem of the colored complex networks, a separated sliding mode controller is designed, while for the linear subsystem, some appropriate system parameters are established to implement synchronization. Then, based on the Lyapunov stability theory, the performance of the sliding mode controller is appraised through the synchronization for the colored networks consisting of different-dimensional systems and nonidentical interactions. In the end, two simulation illustrations are employed to demonstrate the presented control method.

Graphene has been considered one of the most important materials for many applications due to its unique electronic structure, physical and chemical properties. Graphite flakes are the main source of graphene oxide which can be transformed to graphene after reduction. The effect of irradiation on graphene oxide has been rarely studied, only few studies dealing with the irradiation of graphene oxide with gamma radiation were reported. The effect of irradiation of graphene oxide with gamma ray doses (low linear energy transfer) has been previously studied. It was found that there are no changes in the crystalline structure of graphene oxide after irradiation. Graphene oxide was prepared by modified Hummer’s method. The scanning electron microscopy image of the obtained sample suggests the presence of both single and multilayer graphene oxide sheets. The structural measurements for the graphene oxide samples with high linear energy transfers were carried out after irradiations with different doses of alpha particle (9.30–479.90 Gy). The effect of irradiation on oxygen functional groups of graphene oxide was followed by Fourier transforms infra-red spectrometer. Moreover, the irradiation effect on the lamellar space of graphene oxide layers was measured by X-ray diffraction. It was found that the d-spacing of graphene oxide was decreased after alpha particles irradiation with different doses. The effect of irradiation on dielectric constant and conductivity of graphene oxide samples was measured in the frequency range (200 Hz–1.00 MHz). The dielectric measurements show less dependence on irradiation doses. The graphene oxide sample can be used as radiation dosimeter for $\alpha$-particles in the range of the low irradiation doses.

A detailed numerical study of low-loss silicon on insulator (SOI) waveguide bend is presented using the fully three-dimensional (3D) finite-difference time-domain (FDTD) method. The geometrical parameters are optimized to minimize the bending loss over a range of frequencies. Transmission results for the conventional single bend and photonic crystal assisted SOI waveguide bend are compared. Calculations are performed for the transmission values of TE-like modes where the electric field is strongly transverse to the direction of propagation. The best obtained transmission is over 95% for TE-like modes.

We investigate the low-energy excitations of a dilute atomic Bose gas confined in a anharmonic trap interacting with repulsive forces. The dispersion law of both surface and compression modes is derived and analyzed for large numbers of atoms in the trap, which show two branches of excitation and appear two critical values, where one of them indicates collective excitation which would be unstable dynamically, and the other one indicates the existing collective mode with lower frequency under anharmonic influence than that in harmonic trapping case. Our work reveals the key role played by the anharmonicity and interatomic forces which introduce a rich structure in the dynamic behavior of these new many-body systems.

An oscillatory differential method of local diagnostics of superconductors is applied to the analysis of the trapped magnetic flux and the effective demagnetization factor in YBCO samples. Regular steps over certain intervals of the external field are observed on the magnetic-field dependence of these parameters. It is demonstrated that, as the external field increases, crystallites in a sample are decomposed into sub- and nanocrystallites with a size much less than the penetration depth $\lambda$ of the magnetic field. The first critical thermodynamic magnetic fields of sub- and nanocrystallites are determined. These results allow one to reveal the interaction mechanism between magnetic and crystalline microstructures of superconductors and provide a deeper insight into the physical processes that occur in high-temperature superconductors (HTSCs) in a magnetic field.

We report on the thermoelectric power S(T), electrical resistivity and thermal conductivity measurements on the antiferromagnetic CeCoAl₄ compound and on the nonmagnetic reference compound, LaCoAl₄. The Néel temperature of CeCoAl₄ is T${}_N$ = 13.5 K and a metamagnetic-like transition occurs in the magnetic field of about 7.5 T. We show that the magnetic contribution to the thermoelectric power, S${}_f$(T), exhibits a large peak due to the crystal electric field (CEF) at about 240 K and a small anomaly around the ordering temperature. Surprisingly, the CEF related S${}_f$(T) peak is close to the upper CEF excitation energy ${\mathrm{\Delta }}_2$ = 202 K, in contrast to the usual case of the peak position being located at a fraction of the observed CEF energy level. The applicability of different theoretical and phenomenological models describing the temperature dependence of the Seebeck effect S${}_f$(T) has been tested and finally a calculation is proposed, which incorporates a full CEF levels scheme.

Systematic ab initio calculations reveal that the electronic and magnetic properties are modified by superlattices of zigzag and armchair Boron nitride nanosheet (BNNS). Superlattices are constructed by partially hydrogenated B and N atoms of BNNS. The results show that only no more than half N atoms hydrogenated superlattices are antiferromagnetic. The electronic properties of zigzag BN nanosheet superlattices depend on the degree of hydrogenation of N atoms sensitively. As a result, changing the degree of hydrogenation of N atoms results in the transition from semiconductor to metal.

In this paper, we investigate the stochastic transitions in a bistable Schlögl chemical reaction subjected to a nonextensive statistical noise (NESN) and a Gaussian white noise. The NESN is a correlated noise, and able to describe heavy-tailed noise distributions with certain deviation degree relative to Gaussian colored noise. With a unified-colored noise approximation method, the theoretical results of the steady state probability density function (PDF) and mean first passage time (MFPT) are obtained to demonstrate the influences of NESN. The validity of theoretical results has been confirmed by numerical simulations of the PDFs. Besides, stochastic P-bifurcation is discovered based on the changing of PDFs. The results show that the NESN will keep the conversion rate of substrate and the generation rate of products in the low state. Finally, from the MFPT, we find that the intensity and deviation degree of NESN, and Gaussian noise intensity can decrease the switching time between two states.

The structural and electronic properties of mono-vacancy (MV) defect in graphene-based Möbius strip (GMS) are studied in the framework of density functional theory (DFT) combined with the molecular dynamics (MD) simulations. Two kinds of MV defects are observed: the 59-type MV (a configuration with one pentagon and one nonagon ring) located at the curved areas of Möbius strip, and the 5566-type MV (a configuration with two pentagon and two hexagon rings) with one sp³ hybridized carbon appeared in the twisted areas. The 5566-type MV defect is the most stable configuration at 0 K, while the DFT-MD calculations show that it is unstable at room-temperature and will transform into a 59-type MV. Additionally, the melting behavior of GMSs is investigated through empirical potential MD simulations, and we find that their melting temperatures are about 2750 K, which is lower than that of carbon nanotubes and graphene.

A third-order nonlinear optical crystal of lithium hydrogen maleate dihydrate (LHMD) is grown by the process of slow evaporation at room-temperature. The LHMD crystal system is orthorhombic and is a member of P space group. Using FTIR spectral investigation, the presence of main functional groups in LHMD crystal is identified. The optical behavior of the crystal is determined by UV-Visible spectroscopy. The bandgap energy of the LHMD crystal is calculated to be 3.4 eV. By Vickers microhardness measurements, the mechanical behavior has been assessed. The melting point of LHMD is determined by TG-DTA analysis. The defects present in the LHMD crystal are studied by dielectric loss and dielectric constant. SHG studies are performed for the LHMD crystal by Kurtz and Perry method. The third-order nonlinear characteristics of the LHMD crystal are analyzed by Z-scan technique. The laser damage threshold (LDT) study is carried out to verify the suitability of the crystal for laser applications.

The transport of an underdamped particle driven by an external force in a periodic asymmetric potential with color noises is investigated. The corresponding mathematical model is established. By the method of the numerical simulation, we present the movement of the steady current of underdamped particles. Different parameters have different influences on current transport, such as increasing or decreasing. It is shown that the cooperations among the external force and the noises parameter lead to the phenomena: when the external force is not zero, the large external force may cause the large current value or the absolute value of the current. The current value is due to the effect of the cooperations of external force and noise parameter.