Thin films of CoPc of various thickness have been deposited onto glass substrates using thermal evaporation technique at room temperature. The dark electrical resistivity measurements were carried out at different temperature range (298–423 K). An estimation of mean free path ( $\ell_{0}$ ) of charge carriers in CoPc thin films and bulk resistivity, $\rho_{B}$ was attempted. Measurements of thermoelectric power confirm that CoPc thin films behave as p-type semiconductors. The ac conductivity (σ ac) has been investigated in the frequency range (102–106 Hz) and temperature range (298–407 K). σ ac is found to be proportional to ωs where s ≈ 0.879 which is frequency and temperature independence. The ac conductivity interpreted by the correlated barrier hopping (CBH) model with centers of intimate valence alternation pairs type with a maximum barrier height, W M ≈ 1.594 eV.

It is known that the structure dependence of the lifetimes of quasi-bound states in rectangular multi-barrier structures is significant but still ambiguous. In this paper, we report the elaborate dependence of the lifetimes of higher quasi-bound states in symmetrical double-barrier structures on structure parameters, such as well width, barrier width and composition mole fraction. Based on the energy uncertainty condition at quasi-bound states method, numerical calculations are carried out to investigate the structure dependence of the lifetimes of higher quasi-bound states. The calculation results show that the lifetimes of higher quasi-bound states vary with structure parameters as a simple and exact function, and that the lifetimes of higher quasi-bound states increase exponentially with structure parameters.

We report continuous wave and time resolved photoluminescence studies of self-assembled InP quantum dots grown by metalorganic chemical vapor deposition. The quantum dots are embedded into indirect band-gap In0.5Al0.5P layers or In0.5Al0.3Ga0.2P layers with a conduction band line-up close to the direct-to-indirect crossover. As revealed by photoluminescence spectra, efficient interdiffusion of species from the barrier layers produces (Al,In)P or (Al,Ga,In)P-dots. This interdiffusion creates potential barriers that are repulsive for electrons of X valleys around the QDs. Both samples show a fast exponential decay component with a time constant between 0.5 and 0.7 ns. In addition, the sample with indirect band gap matrix shows a slow non-exponential time-decay, which is still visible after more than 100 µs. The fast component is attributed to direct recombination of electron-hole pairs in the dots whilst the slow component, which follows a power law t −0.75 results from recombination of holes in the dots and electrons in metastable states around the dots.

A slab two-dimensional photonic crystal in diamond is being considered for quantum information processing. In view of the low refractive index of diamond, the question whether a high Q cavity is achievable has to be addressed. Here, various geometrical designs of single point defects and double heterostructures for the formation of high Q nanocavities in diamond are modeled. The highest value of vertical quality factor $Q_{v}\sim70\,000$ was achieved in double heterostructures. This result seems to be significant for further consideration of photonic crystals in diamond for quantum electrodynamics applications.


A theoretical model is presented for the study of the scattering and the localisation of spin-waves at an extended inhomogeneous structural and magnetic boundary separating ultrathin Heisenberg ferromagnetic films. The model system consists of two different magnetic materials A and B with different thickness of two and three atomic layers, on either side of a defect atomic step. The matching technique is used with nearest neighbour magnetic exchange to analyse both the localisation and the scattering spin dynamics. The localised spin states that manifest themselves as Rayleigh branches, and the local densities of spin states are calculated on this boundary. The coherent reflection and transmission scattering properties of spin-waves incident from the interior of the ultrathin films on the inhomogeneous boundary are also calculated. The numerical calculations are applied in particular to a system of three Fe ferromagnetic atomic layers and two Gd ferromagnetic atomic layers, across a defect atomic step. The results illustrate the occurrence of Fano resonances in the transmitted spectra due to the localised spin states on the inhomogeneous boundary. An interesting physical effect is observed for this magnetic and atomic step boundary, namely the frequency selective conductance of the spin-waves via Fano resonances, by an appropriate choice of the angle of spin-wave incidence on the boundary.

An analytical expression of the free energy consisting of the strain energy, surface energy and interfacial energy for the coherent island/substrate system, as well as the evolving relations of aspect ratio against volume of the island and misfit of the system, which provides a broad perspective on island behavior, is obtained, and used to study the equilibrium shapes of the systems. Under certain growth conditions in systems with a film/substrate lattice misfit, deposed material is known to aggregate into islandlike shapes with geometries having triangular shaped cross-sections. A two-dimensional model assuming liner elastic behavior is used to analyze an isolated triangular shaped island with elastic properties similar to those of the substrate assumed to be semi-infinite. The results show that in order to minimize the total free energy, a coherent island will adopt a particular height-to-width aspect ratio that is a function of only the island volume. The effect of a misfit dislocation on the equilibrium shape of an island is in passing examined. These can serve as a basis for interpretation of experiments.

Thin lead sulfide films were grown on single crystal GaAs(100) substrates by chemical deposition using Pb(NO3)2 and CS(NH2)2 with excess of NaOH in aqueous solution at a range of deposition temperatures 0–50 °C. The microstructure and morphology evolution were studied as a function of the deposition conditions, resulting in a wide range of microstructures. Ultrahigh resolution scanning electron microscopy and atomic force microscopy indicated a systematic change in particle shape and surface morphology as a function of deposition temperature and deposition time. X-ray diffraction of 200–500 nm thick films indicated a dominant $\langle 110\rangle$ texture throughout the deposition temperature range. At deposition temperatures above 40 °C, single crystal films were obtained. Cross-sectional transmission electron microscopy analyses showed a unique (011)PbS||(100)GaAs and [100]PbS||[011]GaAs orientation relationship.

Tl2Ba2CaCu2Oy (Tl-2212) thin films were fabricated on (001) LaAlO3 substrates by a two-step technique in a semi-closed aluminate crucible and a sealed steel container, respectively. First, the amorphous precursor films were deposited by the pulsed laser deposition (PLD) method, and then they were thalliated in different containers. Almost pure phase Tl-2212 thin films can be prepared in both of the containers. However, the as-annealed films show obvious differences in superconducting properties and microstructure.

GaN nanorods have been successfully synthesized on Si(111) substrates by magnetron sputtering through ammoniating the Ga2O3/ZnO films at 950 °C in a quartz tube. The GaN nanorods have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emission transmission electron microscope (FETEM), Fourier transform infrared (FTIR) system and fluorescence spectrophotometer. The results show that the nanorods are pure hexagonal GaN wurtzite structure with lengths of about several micrometers and diameters ranging from 100 nm to 750 nm, and the growth direction of GaN nanorods is perpendicular to (101) plane. The photoluminescence (PL) spectrum indicates that the good emission property for the nanorods. Finally, the growth mechanism is also briefly discussed.

We report energy transfer from polyfluorene containing binaphthyl, P(BiNDO-FO3), to the europium complex, Eu(dnm)3phen. The P(BiNDO-FO3) has an electroluminescence (EL) peak at 422 nm where as pure polyfluorene (PF) has an EL peak at 438 nm. We have doped both polymers and report energy transfer in P(BiNDO-FO3), which is not present in PF. This is due to overlap of the absorption spectrum in the Eu(dnm)3phen with the emission spectrum of the P(BiNDO-FO3) while there is no overlap with the emission spectrum of PF.

The optical constants of azo dye (Methyl Red (MR)) and azo dye doped polymer (ADP) (Polymethylmethacrylate (PMMA)) MR/PMMA have been investigated using Variable Angle Spectroscopic Ellipsometry (VASE). Pure MR was modeled using Lorentz formula with three oscillators. A Bruggmann effective medium approximation layer was employed with three constituents (MR, PMMA and void) to represent the thin film of MR/PMMA. The optical constants of MR/PMMA were determined at various MR concentrations. The results reveal that the optical constants of the blend system are a linear interpolation of the two constituents. Average optical constants were determined using multiple sample analysis.

Highly stable single axial mode operation is obtained in a pulsed injection seeded oscillator with an adjustable pulse length from 20 ns to more than 50 ns, at a constant output energy. The adjustment principle is described experimentally and analysed theoretically. The peak to peak time jitter added to a slow time drift is of the order of 1 nanosecond for a 20 nanoseconds pulse length.

A new halosulphate phosphor NaMgSO4F:Ce3+ and Na3SO4F:Ce3+ was synthesized by wet chemical method. The PL emission spectra of phosphors show strong Ce3+ emission due to the $5d\to 4f$ transition of Ce3+ ions. Ce3+ emission in new halosulphates NaMgSO4F and Na3SO4F lattice may be useful for a scintillation application. XRD and photoluminescence (PL) characterization of phosphors has been reported in this paper.

Foils of Polymethyl methacrylate (PMMA) 2 mm thick were studied by measuring the total Secondary Electron Emission yield $\sigma $ (SEE yield) in a dedicated Scanning Electron Microscope especially equipped to study the fundamental aspects of the charge transport and trapping in insulating materials. The intrinsic SEE yield $\sigma _{0}$ , (yield of the uncharged material) and the charging kinetics were studied under low current density $J=10^{+5 }$ pA/cm2. The curve of the primary beam energy variation of $\sigma _{0}$ exhibits a maximum intrinsic yield $\sigma _{\rm 0max}= 2.2$ at 370 ± 20 eV and two crossover energies $E_{I}=84$ ± 20 eV and $E_{II }=1465$ ± 20 eV for which $\sigma _{0} = 1$ . For $\sigma _{0}>$ 1 PMMA is positively charged and negatively for $\sigma _{0}<$ 1. As electron injection is proceeding under the low current density used, the SEE yield varies from $\sigma _{0}$ to the steady value $\sigma _{st}=1$ . This value that expresses the equality between the average number of emitted and injected electrons, characterizes the steady charge regime called “Self-Regulated Regime”. The evolution of $\sigma $ during the injection process is due to the internal field that blocks or enhances the secondary electron emission, according to the positive or negative nature of the trapped charges. A current density effect, characterized by a steady SEE yield slightly higher than unity, $\sigma _{st }=1.03$ , instead of one, is observed at high energy (for example 4000 eV) for a strong current density $J>10^{+6 }$ pA/cm2. It is interpreted by a field ionisation (Poole-Frenkel type) that enhances the secondary electron emission.

The influences of mismatch of ultrasonic propagation velocities on photoacoustic imaging are studied. The concentration-adjustable glycerin is used as an ultrasonic couplant to match the ultrasonic velocities in different media in order to eliminate the acoustic refraction, reduce the acoustic reflection, and rectify the acoustic path difference. Two biological phantoms are tested by using water and glycerin as ultrasonic couplant, respectively. The spatial resolution of reconstructed image by experimental evaluation also is estimated to be 0.12 mm. The experimental results demonstrate that the high-quality photoacoustic imaging can be obtained by matching the ultrasonic propagation velocities in different media. The contrast of reconstructed image is significantly improved and the image artifacts are obviously reduced after matching ultrasonic velocity. It has potential to promote photoacoustic imaging as a clinical diagnosis technique.

The ferroelectric and piezoelectric properties of Ag doped xPb(Mg1/3Nb2/3)O3-(1 − x) Pb(Zr0.532Ti0.468)O3 ceramics, for Ag = 0.5, 1 and 1.5 mole%, synthesized by the columbite precursor method were investigated. The experimental results indicate that stoichiometry plays a significant role in the solubility of Ag and it affects the physical properties. The factors influencing microstructural development of Ag doped PMN-PZT are the Ag and PMN concentrations and Ag diffusion during the sintering process as can be observed from the scanning electron micrograph. Grain growth is considerably enhanced up to 4.05 μm in 1 mole% Ag doped 0.7PMN-0.3PZT, while the apparent density continuously increased up to 7.89 gm/cm3 in 1 mole% Ag doped 0.8PMN-0.2PZT, respectively. It was observed that 1 mole% Ag doped 0.7PMN-0.3PZT attained maximum values for the dielectric permittivity (ε RT = 3864) at room temperature and the dielectric permittivity at the Curie temperature (ε Tc = 26826), respectively. The ferroelectric properties exhibited optimum values of P r = 36.82 μC/cm2 and P s = 45.29 μC/cm2 in 1 mole% Ag doped 0.7PMN-0.3PZT, respectively while the E c showed a decreasing trend throughout the series. The piezoelectric properties (d 33 = 297 pC/N and k p = 0.377) were enhanced in 1 mole% Ag doped 0.4PMN-0.6PZT and 0.7PMN-0.3PZT, respectively.

A universal solution method for the radiation transport equation in plane parallel geometry in the case of Lorentzian line shape is presented. As an example the plasma of an rf discharge in argon is considered. Spatial profiles and line densities of the four lowest excited argon atoms calculated by means of self-consistent models including and neglecting the radiation transport equationare compared with experimental data. It is found that the correct treatment of the radiation transport in gas discharge modelling significantly improves the agreement with measured densities and spatial profiles of the excited atoms.

This paper proposes concrete enhancement of pyrolysis spray disposal performance. Solution to heat equation in particular cases of uniform and non-uniform fluid deposit is yielded as a guide to geometrical and temporal parameters control. Implemented models take into account simultaneously deposited material and targeted device thermal and geometrical properties. Theoretical temperature time-response features are compared to experiment in order to enhance deposition and solidification processes.

Structural properties of liquid and amorphous Al2O3.2SiO2 (denoted as AS2) have been studied in a model containing 3025 particles under periodic boundary conditions with the Born-Mayer type pair potentials. Models have been obtained by cooling from the melt via molecular dynamics (MD) simulation. Structural properties of an amorphous model obtained at the temperature of 350 K have been analyzed in details through the partial radial distribution functions (PRDF), coordination number distribution, bond-angle distributions and interatomic distances. Calculations show that calculated data agree well with the experimental ones and with those obtained previously in other simulation works. The evolution of structure upon cooling from the melt was observed and discussed. We found a clear evidence of the existence of triclusters in the system. Diffusion constant of particles has been calculated and discussed. Calculations presented that the temperature dependence of diffusion constant D of components in the system shows an Arrhenius law at temperatures ranged from 2450 K to 4200 K and it shows a power law, $D\propto (T-T_C )^\gamma$ , at higher temperatures.