The present paper reports the measurements on space charge limited conduction in amorphous thin films of Ge20Se $_{80-x}$ Agx (x = 0, 10, 15, 20). I−V characteristics have been measured at various fixed temperatures. These characteristics show that, at low electric fields, an ohmic behaviour is observed. However, at high electric fields (E ~ 104 V/cm), the current becomes superohmic. At high fields (104 V/cm), current could be fitted to the theory of space charge limited conduction (SCLC) in case of uniform distribution of localized states in the mobility gap of these materials. Using the theory of SCLC for the uniform distribution of the traps, the density of localized states near Fermi level is calculated. It is observed that, on addition of Ag in Ge20Se80 alloy, density of localized states first increases till 10 at% of Ag and then decreases.

We have study the effect of Tin impurity and Swift heavy ion irradiation on the optical properties of the chalcogenide thin films. Thin films are prepared by thermal evaporation technique and irradiated by swift heavy ion beam of 60 MeV Si5+ ion with influence of 5 × 1012 ions/cm2. The SHI induced structural and optical changes in the thin films due to which optical band gap decrease. Reduction of the optical band gap is may be due to increase the defect states near to the band tails in the band gap on irradiation.

We present results concerning the carrier transfer between In(Ga)As quantum rings in a stacked multilayer structure, which is characterised by a bimodal size distribution. This transfer of carriers explains the observed temperature behaviour of diode lasers based on that kind of stacked layer structures. The inter-ring carrier transfer can be possible by phonon assisted tunnelling from the ground state of the small-ring family towards the big-ring family of the bimodal size distribution. This process is thermally activated in the range 40–80 K.

Hydrogen diffusion is monitored during plasma conditions corresponding to the growth of polymorphous and microcrystalline silicon thin films in the temperature range from 50 to 300 °C. Structural changes of the films were monitored in situ by Spectroscopic Ellipsometry measurements and interpreted with the Bruggemann Effective Medium Approximation along with the Tetrahedron Model. For both materials, diffusion of hydrogen leading to the formation of a hydrogen-rich subsurface layer during the first minute of exposure to the hydrogen plasma is observed. This initial phase was followed by a steady-sate regime during which the thickness of the subsurface layer stayed relatively constant and the total film thickness decreased as a function of time. This steady-state is explained as the result of the equilibrium between hydrogen diffusion and etching. The hydrogen diffusion coefficient and etching rate were calculated from these measurements and found to be higher in amorphous than in polymorphous silicon. This result is consistent with the growth dynamics of polymorphous silicon. It also provides information concerning the nucleation of micro-crystallites in amorphous silicon under very large atomic hydrogen flow conditions. Moreover, it also explains why polymorphous silicon films do not undergo the phase transition to microcrystalline, even if deposited under relatively similar large atomic hydrogen flow conditions.

Transient laser-induced anomalous photovoltaic effect hasbeen studied in La0.8Sr0.2MnO3 films grown on theSrTiO3 (001) substrates by laser molecular beam epitaxy. It isdemonstrated that the signal polarity is reversed when the films areirradiated through the substrate rather than at the air/filminterface. The microstructures in these films are clarified in termsof the oriented microdomains with their (101) plane parallel to thesubstrate surface, suggesting off-diagonal Seebeck effect plays animportant role for our observation. From the results, we obtain theanisotropy of the thermoelectric power $\Delta S=S_{ab}-S_{c}=0.3~\mu$ V/K, where S ab and S c are the ab-plane and c-axis Seebeck coefficients.

Reactively evaporated TiO2 thin films were deposited on the glass substrate by electron beam heating technique. In the first stage evaporation rates are varied keeping substrate temperature fixed at 200 °C and oxygen flow rate at 9.0 sccm for all the samples. The deposition rates were varied from 0.12–0.20 nm/s with a step of 0.02 to optimize the optical constants for the film in the wavelength band of 380–850 nm as a high index material for multilayer optical coatings and filters. The films prepared at higher deposition rates have shown low refractive index values and comparatively higher extinction coefficients for the given substrate temperature in the desired spectral range. The best optical constants were observed for the sample prepared at 0.12 nm/s (at λ = 550 nm: n: 2.39 and k: of the order of 10−9). However, the variation in refractive index for all the samples was found to be in the range of 2.39–2.21 at 550 nm. In the second stage, films were prepared at a fixed deposition rate of 0.12 nm/s at different substrate temperature (50 °C, 100 °C, 150 °C and 200 °C) to study the optical properties of the films as a function of substrate temperature in order to investigate the potential of TiO2 film application as medium index layer. It was observed that refractive index decreases with decreasing substrate temperature. However, it was not found true for absorption. Instead, at Ts = 50 °C extremely low absorption (of the order of 10−5) has been observed with refractive index of 1.83, which increased sharply for next higher substrate temperature. Variation in absorption characteristics is found with varying substrate temperatures. The result shows that TiO2 films can be used as high and medium index layer in optical coating by varying the deposition parameters during growth. Effectively, one can achieve performance of two materials with only one. This effect could be utilized to produce variable index layers and coatings. Two samples with best high and medium optical constant values, were further investigated using Atomic force microscopy (AFM), X-ray diffraction (XRD) and scanning electron microscopy (SEM) for surface and structure analysis. The results show that the particle size for the film is very small (10–20 nm), and the surface appears to be very compact, smooth and free of pinholes with roughness in angstrom range, extremely suitable for optical applications in single and multilayer structures.

Coherent phonon scattering and transmission via a three-terminal junction in low-dimensional structures is investigated. The model system consists of two-dimensional crystalline wave-guides, constructed of double atomic chains that are joined together by a nanostructured T-shaped junction. The matching method theoretical approach is used to study the dynamics of the system. A calculation is presented for the coherent reflection and transmission scattering probabilities of the system phonons, as elements of a Landauer type scattering matrix. The scattering and transmission spectra via the T-shaped junction are analyzed as a function of the incident frequency per propagating mode of the perfect wave-guides. Our results show that the junction is an effective phonon splitter and suggest that its characteristics may be controlled by varying its nanometric parameters. Asymmetric Fano-like resonances are observed in the spectra which result from the coherent coupling between the localized modes of the T-shaped junction and the propagating modes of the wave-guides.

Basing on finite-difference time-domain method and partial band gap effect of photonic crystal, we obtain collimated light beams from point optical source and two-dimensional photonic crystal structure. The diffusive light with some special frequencies can be collimated and propagate along a special direction within photonic crystal structure. Our study presents a new method to make light collimator.

Interconnected microstructural ZnO:Al thin films with low doping concentration (Al/Zn ≤1%) were deposited on (0001) sapphire substrates by the sol-gel technique. The effects of low doping concentration on the structural, optical and electrical properties of the films were investigated. Scanning electron microscope (SEM), X-ray diffraction (XRD), photoluminescence (PL), and four-point probe method were used to characterize the structural, optical and electrical properties. We found that with increasing the dopant concentration the interconnected thread becomes thinner, the (002) diffraction peak and the near band edge (NBE) emission are enhanced while the deep level emission (DLE) and the resistivity are decreased.

Room temperature Mössbauer, X-ray and IR spectral studies were carried out for the spinel system Mn0.5Zn0.5Alx Fe $_{2-x}$ O4, $0 \le x \le1$ , prepared using the usual ceramic technique. X-ray patterns confirm that all samples have single phase cubic spinel structure. The Mössbauer spectra of the samples show a six-line magnetic pattern and a central paramagnetic phase. They are assigned to two magnetic subpatterns and two quadrupole doublets due to Fe3+ ions at the tetrahedral A-sites and octahedral B-sites. The effect of increasing the Al3+ content x on the hyperfine interaction parameters is studied and discussed. The lattice constant, oxygen positional parameter, mean ionic radius of the A- and B-sites, bond lengths, edges and interionic distance are affected by the additional process x. They are determined and discussed as functions of x. The IR spectra shows six absorption bands in the range 222–1033 cm−1. The bands are attributed to the corresponding metal-oxygen complexes in the A- and B-sites. The hyperfine interaction parameters, the IR band positions and intensities reveal their dependence on the Fe3+−O2− bond length and the interionic distance at A- and B-sites. The variation of the quadrupole doublet splitting for the B-site and the oxygen parameter reveal the increasing trigonal distortion of the B-site oxygen coordination. The IR absorption at 222 cm−1, the velocity of the infrared waves when passed through the samples and the jump rate of the lattice vacancies were found to decrease.

The correlated photons source is obtained from the parametric down conversion of photons generated in a non linear crystal. When associated with a system of coincidences counting, this source allows one to measure the detection efficiencies of detectors working at photon counting levels, without the need for reference sources or detectors. At the Institut National de Métrologie (France), this method was implemented with the aim of realising a new standard detector for the absolute measurement of very weak radiations. The relative standard uncertainty of the detection efficiency measurements is 1.1%.

This study was undertaken to investigate whether low frequency magnetic fields can affect the characteristic of cancer cells. To achieve this, HL-60 cells were exposed to 20 mT, 50 Hz sinusoidal magnetic field and the cell viability, cell cycle phase distribution, DNA ladder and apoptotic morphology between control and exposed cells were examined. The results demonstrated that magnetic field had pronounced inhibition effects on cell growth, and small but significant changes in cell cycle phase can be observed. Internucleosomal DNA fragmentation and morphological changes after exposure indicate that the magnetic field induces apoptosis in HL-60 cells. The results also indicate that the growth-inhibitory property of MF on HL-60 cell growth was mainly due to the induction of apoptosis.