We report here a comparative study of the in-plane strain states of standard GaN epilayer grown on sapphire (001) and flip-chip GaN epilayer bonded on Si (111) wafer by means of X-Ray diffraction (XRD), Raman spectroscopy, and photoluminescence (PL) spectroscopy. It is confirmed that the in-plane tensile strains can be largely reduced after the flip-chip process. The reduction of the biaxial strains determined by XRD, Raman, and PL analysis is found to be consistent.

A new method to evaluate the five parameters of illuminated solar cells is described. The method is based on nonlinear least squares approach. On calculating the lsqcurvefit-function with constraints, between the experimental current-voltage I(V) characteristic and a theoretical arbitrary characteristic based on Lambert W-function. The used model is implemented as a MATLAB® script which yields the I(V) characteristics of the LILT under test. The model has been validated against by applying it to experimental I(V) characteristics. Some parameters of the model have been measured directly whereas others have been evaluated by means of direct computation on the data sheet or by means of best-fit on the measured data. The results have been compared and an analysis of the errors is presented.

Based on the features of diode-pumped Yb3+:Y2SiO5 (Yb:YSO) lasers, a thermal model was established. According to the latest reports and measurements on thermal parameters, and further considering the heat transfer on side surface, thermal lensing effect of Yb:YSO was studied for the first time to our knowledge. Under the pump power of 17 W, the maximum temperature (488.4 °C) and the maximum distortion (1.24 μm) were obtained by solving Poisson equation using finite difference method. Moreover, thermal lens focal length was measured through a plane-plane cavity. All the results demonstrate that the theoretical result will be closer to the reality if we take the heat transfer on side surfaces into account.

The Fourier-transform infrared (FT-IR) spectra of magnesium phthalocyanine (MgPc) were investigated in the spectral range 500–4000 cm-1. The spectra allow characterization of vibration modes. A comparison of absorption spectra of powder, as-deposited and annealed films is presented. The dark electrical resistivity measurements were carried out at different temperatures in the range 308 to 423 K. Two activation energies Δ E 1 = 0.23 eV and Δ E 2 = 0.69 eV were obtained. The thermal activation energy Δ E 1 is associated with impurity conduction and Δ E 2 is associated with intrinsic conduction. The current density-voltage characteristics of MgPc at room temperature showed a linear ohmic conduction mechanism at low voltages. At higher voltages the space-charge-limited conduction (SCLC) accompanied as a single dominant level. The temperature dependence of current density allows the determination of some essential parameters such as the hole mobility (μ h ), the trapping factor Θ and the total trap concentration (N t ).

An experimental study on the pulsed laser ablation of copper by using Nd-YAG laser radiation of 1064 nm wavelength at a fluence of 13 J/cm2 is reported. A time-resolving plane Langmuir probe, placed at various angles with respect to the target surface normal, is used to record temporal variation of ion currents during the plasma expansion in vacuum. The measured angular distributions of integrated ion yields are strongly peaked in forward direction. The experimentally determined plume expansion coefficient Z inf/X inf = 2.1±0.2 is in good agreement with the previous studies. Time-of-flight measurements indicated that the energy of various ion components is highest along target surface normal and decreases with increase of the angle, however the effect of angle is more pronounced on the faster ions. The energy spread of the ions decreases approximately from ±670 eV to ±19 eV as the probe angle increases from 0° to 60°. The measured angular dependence of ion yield and most probable ion energy nicely follows the trends predicted by Anisimov's plume expansion model.

Thin-film transistors (TFT's) may have a low-quality back channel in addition to the high-quality main channel. The presence of the back channel can deteriorate TFT turn-off characteristics. We studied properties of the back channel in bottom-gate GaInZnO TFT's grown by rf sputtering. X-ray photoelectron spectroscopy (XPS) results confirmed existence of low-quality oxide in the back channel. We observed that 200 °C annealing increased binding energies of metals and oxygen on the surface. This energy increase can be explained as a result of tighter bonding between metals and oxygen. When the top surface of GaInZnO was removed by Ar etching, XPS did not show such energy increase after the annealing. XPS also showed that the top surface has significantly higher In concentration compared to the bulk.

Thin films of InSb with different thickness (t = 5, 10 and 15 kÅ) were deposited on to glass substrate by flash evaporation technique. The structural and electrical properties were investigated and the effect of films thickness on films properties was discussed. XRD analysis of the films as a function of film thickness revealed that crystallinity improves with film thickness. Temperature dependence of the Hall parameters were studied in a wide range, 20 < T < 300 K. The temperature variation of the Hall coefficient and conductivity shows an activated nature with negative temperature coefficient confirming that the prepared films of InSb are semiconducting in nature with n-type conductivity. Size effect was observed as the defect density is much smaller for thicker films and as a result electrical conductivity of the films increases with increasing film thickness with the increase of the charge carriers through the film. An increase in mobility with sample thickness has been observed. The mobility variations with temperature revealed a transition from lattice to impurity scattering in the observed temperature range.

CuIn1- x Alx S2 (CIAS) thin films with different compositions were deposited by the evaporation of the powder of CuIn1- x Alx S2 on to glass substrates heated at 200 °C. The different thin films were obtained with increasing the content aluminium in the powder. Structural, morphological and optical properties of the films were studied in function of the Al content. Polycrystalline CIAS thin films orientated preferentially along the (112) plane were obtained. Then the crystallites have a similar shape as that of all as-deposited films. The incorporation of aluminium atoms moves the main absorption on the left with varied band gap between 1.5 eV and 1.90 eV.

We present a study of purification of single-walled carbon nanotubes (SWCNTs) using different oxidation temperatures and chemical treatments. We have developed a simple two annealing-steps procedure resulting in high nanotube purity with minimal sample loss. The process involves annealing the SWCNTs at 300 °C for 2 h with subsequent reflux in 6 M HCl at 130 °C, followed by further annealing at 350 °C for 1 h with reflux in 6 M HCl at 130 °C. The process results in effective removal of carbon impurities and metal particles which are associated with SWCNTs production. The process is less time consuming (complete in 4.5 h) than conventional acid purification methods which require over 5 h, and less destructive than conventional methods with a yield of 26%. SWCNT purity was assessed using Raman spectroscopy, thermogravimetry and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy.

Chromium doped gamma ferrite nanopowders (16.91 nm to 25.61 nm) of the composition (Fe2- x Crx O3 for x = 0.00, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10) were successfully synthesized by a modified solution combustion method using citric acid as fuel at a temperature as low as 150 °C. The so prepared samples were examined by powder XRD for phase identification and crystallite size determination. The dimensions of particle size as calculated from XRD are in good agreement with those evaluated by transmission electron microscope (TEM). Fourier Transform Infrared (FTIR) analysis was carried out to identify the various chemical bonds present in the system. Magnetic examinations were performed in terms of magnetic susceptibility and hysteresis plots. A decrease in the blocking temperature with the increase of dopant concentration was observed which is explained on the basis of Néel's relaxation theory. A simple model has been suggested to explain the behaviour of hysteresis trends as the function of dopant concentration.

The focusing property of electromagnetic wave is investigated by a flat slab made of octagonal photonic quasicrystal. We obtain polarization-independent focusing by use of the all-dielectric photonic quasicrystal. The influence of geometrical factors of photonic quasicrystal on the focusing property for TM and TE polarizations is explored in detail. The results show that two orthogonal polarizations have a common focus point only under certain proper condition. Our results may be a useful guidance for the fabrication of lens devices capable of polarization-independent focusing by photonic quasicrystal.

A novel method for ionic collisions is presented based on a theoretical analysis of the long-standing wire fragmentation problem. Based on a Maxwellian approach of the transient electrodynamic forces we deduce a theoretical formula of the effective tensile force. A number of conducted experiments with low energy capacitor bank discharges are also reported with positive results. The new results show the possibility of building solid state ion colliders below the fragmentation threshold using high power electrical pulses with very low energy.

This paper presents results of theoretical and experimental investigation of the welding arc in Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding (GMAW) processes. A theoretical model consisting in simultaneous resolution of the set of conservation equations for mass, momentum, energy and current, Ohm's law and Maxwell equation is used to predict temperatures and current density distribution in argon welding arcs. A current density profile had to be assumed over the surface of the cathode as a boundary condition in order to make the theoretical calculations possible. In stationary GTAW process, this assumption leads to fair agreement with experimental results reported in literature with maximum arc temperatures of ~21 000 K. In contrast to the GTAW process, in GMAW process, the electrode is consumable and non-thermionic, and a realistic boundary condition of the current density is lacking. For establishing this crucial boundary condition which is the current density in the anode melting electrode, an original method is setup to enable the current density to be determined experimentally. High-speed camera (3000 images/s) is used to get geometrical dimensions of the welding wire used as anode. The total area of the melting anode covered by the arc plasma being determined, the current density at the anode surface can be calculated. For a 330 A arc, the current density at the melting anode surface is found to be of 5 × 107 A m-2 for a 1.2 mm diameter welding electrode.

The aims of this work were to measure the entrance and exit dose for patient treated for head and neck tumors. The target absorbed dose was determined from the exit and entrance dose measurement.Twenty patients were evaluated. The results were compared to the calculated values and the midline dose was determinate and compared with the prescribed dose. 80 entrance doses and 80 exit doses measurements were performed. The average difference from expected values was 1.93% for entrance dose (SD 1.92%) and –0.34% for exit dose (SD 4.1%). The target absorbed dose differed from prescribed dose values by 2.94% (1.97%) for the results using the Noël method and 3.34% (SD: 2.29%) with the Rizzotti method.The total uncertainty budget in the measurement of the absorbed entrance and exit dose with diode, including diode reading, correction factors and diode calibration coefficient, is determined as 3.02% (1 s).Simple in vivo dose measurements are an additional safeguard against major setup errors and calculation or transcription errors that were missed during pre-treatment chart check.

Within the framework of the dielectric-continuum model, the equations of motion forp-polarization field in wurtzite quantum well are solved for the propagating optical phonon modes. The polarization eigenvector and the dispersion relation are derived by using the determinate method. The dispersion relation and phonon modes properties of the propagating optical phonons are investigated for GaN/AlN single QW. The numerical results show that the propagating phonons have a quantization character by a quantum number n that define its order. The propagating optical phonons are more dispersive for decreasing n, and the bands formed by the dispersion curves are narrower for higher order modes. The wave vector and width of quantum well have more important effect on phonon energy, with the increase of wave vector or width of quantum well, the energy of propagating optical phonon modes decrease in TO domain (between A 1 (TO) and E 1 (TO) frequency of GaN), and increase in LO domain (between GaN A 1 (LO) and E 1 (LO) frequency of GaN). The strain effects of QW structures have clear influence on the dispersion behavior of propagating optical phonons. The frequency of the propagating optical phonon modes is increased due to the strains of the QW structure.

The contact angle (Θ) of molten Sn and Sn-Ag alloys (0.5, 1.5, 3.5, 6 wt.% Ag)on Cu substrates have been studied by using sessile drop method at various temperatures (230, 250, 275 and 300 °C). Experimental results showed that additions of Ag to Sn resulted in a continuous decreasein the Θ up to 3.5 wt.% above which the Θ value was increased. Increasing alloy temperature also decreased the Θ proportionally. Experimental results revealed that a correlation between the Θ,alloy composition and the alloy temperature exists which yielded an empirical model to predict the Θ at a givenAg content and temperature for a given Sn-Ag alloy. The empirical model predicts the Θ reasonably well with the present work and the other published works.