It has been demonstrated that the Modulated Photo Current (MPC) technique is a very good tool to probe the density of states (DOS) in the band gap of semiconductors. In this technique two regimes have been underlined: the low frequency or recombination regime and the high frequency or trapping-and-release regime. It is the latter case that has been mainly used up to now. In this paper we concentrate on the recombination regime. Calculations are made for a single species of trapping states characterized by the respective capture coefficients of electrons and holes. From the general continuity equations, a very simple relation is found between the density of states around the pseudo Fermi level and the slope of the tangent of the phase shift as function of the angular frequency of the excitation. A simulation illustrates the validity of this relation by comparing the DOS reconstructed from both the high frequency and the low frequency regimes of the MPC technique with that introduced in the simulation. The approximations used to obtain this very simple relation are underlined. Finally, it is suggested that by combining the results of the MPC technique obtained in the low and high frequency regimes, good orders of magnitude of the capture coefficient of the majority carriers and of their mobility can be obtained.

Deposition of pure and Ge-doped silica as well as silicon oxynitride films has been studied in a recently developed matrix distributed electron cyclotron resonance (MDECR) reactor. Process parameters were optimized in order to obtain optical quality thin films at low substrate temperatures and high deposition rates without post-deposition treatment. The choice of injection system is shown to be of crucial importance for the deposition of high quality materials in low pressure PECVD. It has been found that injecting silane near the surface allows to obtain films with a low OH absorption independently of silane flow i.e. growth rate in a certain range of process parameters. On the contrary, in the case of uniform distribution of silane in the reactor volume the hydrogen content increases with silane flow, which affects the quality of films deposited at higher rates. With the optimized injection system, stress-free silica films with a low absorption have been deposited at the rates up to 70 nm/min at temperatures lower than 150 °C. Non-absorbing oxynitride films with a controllable refractive index ranging from 1.46 to 1.86 have been obtained from SiH4/O2/N2 mixtures. Ge-doped silica films with a Ge content of up to 4% has been deposited using a mixture GeH4 in H2 as a dopant. The properties of deposited films have been studied as a function of process parameters. The results show that the MDECR concept, that permits, in principle, unlimited scaling of substrate size, can be technology of choice for the deposition of optical thin films and functional coatings.

A superconducting metallic film bolometer in contact with thermal bath of temperature T0, is biased by a (i) constant current $I_{\mathrm{b} }$, or by (ii) the constant voltage $U_{\mathrm{b}}$. The absorption of the time-dependent power of a phonon beam W(t) elevates temperature of the film to $T(t)>T_{\mathrm{0}}$. The thermal contact of the bolometer with the environment is characterized by the thermal conductance G, and it depends on $[T^{n}(t)-T_{\mathrm{0}}^{n}]$ ($n=4{-}6$). For both above methods of bias, we derive ordinary nonautonomous nonlinear differential equations of the first order. These equations are numerically solved. The knowledge of W(t) allows one to calculate (i) $U_{\mathrm{b} }(t)$ or (ii) $I_{\mathrm{b}}(t)$. The inverse problem of calculation of W(t) from known (i) $U_{\mathrm{b}}(t)$ or (ii) $I_{\mathrm{b}}(t)$ is also solved. Using W(t) calculated in computer experiments, we obtained the bolometer signal, and compared it with results of real experiments performed on GaAs in which $I_{\mathrm{b}}$ is fixed, and U is measured. Comparison of calculated results with results obtained for the linearized model shows that the nonlinearity is essential for the correct description of metallic superconducting film bolometer response.

The misfit stress induced by a lattice mismatch is determined by a curvature analysis performed by Transmission Electron Microscopy on plan view samples. The different samples examined consist of Ga$_{1-x}$InxAs layers grown by molecular beam epitaxy on a (100) GaAs substrate, with a nominal mismatch of 0.7 and 1.4%. The layer thicknesses are lower than the critical thickness for plastic relaxation. The curvature radius as well as the substrate thickness are determined directly by bend contour analysis. For each sample, the measurement was performed on different areas corresponding to different substrate thicknesses. The experimental value of the in-plane component of the stress is deduced by applying the Stoney's formula over the whole range of substrate thickness. The accuracy of the method is better than 15%. Experimental values of the misfit stress are ten to fifty per cent lower than the theoretical value calculated for pseudomorphic layers. This discrepancy is discussed in terms of partial relaxation.

A semi-analytical version of single-angle ellipsometric inversion to determine the refractive index of non-absorbing films is re-examined to explore the possibility of speeding up and enhancing the reliability of its computational implementation by an a priori rejection of one of two potential solutions propagated from the one of the two roots of the quadratic equation arisen in the inversion process. The distribution of solution-determining parameters and root selection over the (refractive index)-thickness solution space depending on the measurement variables of wavelength and angle of incidence is surveyed and exhibits an interesting pattern, which can be harnessed depending on materials. Optimization depending on the measurement variables and potential application in spectroscopic and in situ ellipsometry is discussed. The feasibility of the method has been tested with samples of aluminium oxide and titanium oxide films on silicon substrates.

Results of experimental investigation of powerful microwave beams action on the metal-dielectric compositions are presented. Dielectric surfaces with introduced metallic grains as well as dielectric powder containing small admixtures of a metallic one have been explored as an objects of irradiation. At a relatively small microwave power ($P \le 1$ mW) all investigated targets were practically completely transparent for incident electromagnetic wave. At a relatively high power (microwave generators based on the gyratrons and powerful magnetrons) the irreversible changes in the electric and radiophysical properties of metal-dielectric composites exposed to microwave radiation whose intensity is below the threshold intensity for plasma production have been observed (sharp increase of conductivity and microwave absorption coefficient).

ESR, IR, optical absorption and photoluminescence spectra of Ho3+ doped tungsten phosphate glasses modified with three different modifier oxides viz., PbO, ZnO and CaO have been studied. The ESR spectral studies indicate tungsten ions are present in W5+ state in all the three glasses with the highest concentration in CaO modified glasses. From the measured intensities of various absorption bands of these glasses, the Judd-Ofelt (JO) parameters $\Omega_2$, $\Omega_4$ and $\Omega_6$ have been evaluated. The JO theory could successfully be applied to characterise the absorption and luminescence spectra of these glasses. From this theory various radiative properties like radiative transition probabilities, A, branching ratios, $\beta_r$, the radiative lifetimes, $\tau_R$, and the emission cross-sections, σE, for various emission levels of Ho3+ in these glasses have been determined and reported. An attempt has also been made to throw some light on the environment of Ho3+ ions in all the three glasses.

Absorption spectra, luminescence spectra and luminescence decay time are investigated for a borosilicate glass containing low 0.1 wt% Ce3+ and high 15 wt% Tb3+ concentrations, together with the time-resolved luminescence. A broad absorption band due to parity allowed f → d transition is observed for Ce3+. Sharp absorption bands are observed in 3100–1600 nm region which are due to the 7F6 → 7FJ (J = 0, 1, 2, 3, 4) transition of Tb3+, while much weak absorption bands due to the spin-forbidden 7F6 → 5DJ (J = 2, 3, 4), 5GJ (J = 3, 5, 6), 5LJ (J = 7, 8, 9, 10), 5HJ (J = 4, 5, 6), 5IJ (J = 7, 8) and 5FJ (J = 2, 4) transitions are observed in visible-UV region. By excitation with 266 nm laser line, two broad UV emission bands due to Ce3+ are observed at 360 and 390 nm besides the intense green emission bands due to the 5D4 → 7FJ (J = 6, 5, 4, 3) transition of Tb3+ and weak blue emission bands due to the 5D3 → 7FJ (J = 6, 5, 4, 3) transition. The decay time of the UV, blue and green emission is estimated to be 17 ns, 3.8 µs and 2.17 ms, respectively. The rise time of the green emission is about 4 µs after the Ce3+ emission and the Tb3+ blue emission. No rise time is observed for the latter emission.

We present a detailed study of the structure and hydrogen bonding in silicon thin films ranging from amorphous to microcrystalline. We emphasize the results for hydrogenated polymorphous silicon films obtained under plasma conditions close to powder formation where silicon clusters and nanocrystals contribute to growth. Fourier Transform Infra-Red (FTIR) spectroscopy, Raman spectroscopy, X-Ray-Diffraction (XRD), and hydrogen evolution measurements are performed to characterize the hydrogen bonding and the structure of the films in their as-deposited state and after isochronal annealing at increasing temperature in the range of 300 to 600 °C. While Raman spectroscopy and XRD give an average information on the structure of the films, without clear evidence of the presence of crystallites in the polymorphous films, infrared spectroscopy and hydrogen evolution measurements which probe the local hydrogen related structure are shown to be perfectly adapted to characterize polymorphous silicon films. In particular, IR spectroscopy measurements, reveal the presence of a stretching band at 2030 cm−1, associated with a peak at 873 cm−1 in the bending region and a downward shift in the Si-H wagging mode from 640 cm−1 to 622 cm−1. We attribute the 2030 cm−1 mode to the presence of hydrogen bonded at the surface of the plasma produced silicon clusters and nanocrystals. This assignment is supported by hydrogen evolution measurements in which a sharp low-temperature hydrogen evolution peak appears at around 420 °C followed by up to five peaks at higher temperatures. This particular hydrogen bonding in polymorphous silicon films is also supported by isochronal annealing studies which show that the bands at 2030 cm−1 and 873 cm−1 vanish at annealing temperatures corresponding to the low temperature hydrogen evolution peak. Based on these results and their correlation with the hydrogen-related material structure, we propose a picture for the structure of polymorphous silicon films that accounts for the observed features.

A null collision Monte Carlo method is proposed to calculate the transport kinetics of charged particles in a non equilibrium background of atoms or molecules. The method is an implementation of the null collision Monte Carlo method of Skullerud, extended in order to include the translational distribution of neutrals, also in non uniform cases. As such, it delivers an exact solution of the linear Boltzmann equation. Two equivalent formulations of the method are proposed: an inductive one based on physical considerations, and a more formal one in which the method is deduced from the appropriate transport equation. As a test case, the method is applied to the thermal diffusion of H3+ ions diluted in H2 under an isobaric thermal gradient and with a transversal electric field.

Films are used in a wide range of electronic and mechanical technologies. An analytical solution is developed in this paper in order to investigate the effect of films on the thermal behavior at the vicinity of a static or moving rough interface. The roughness is modeled by multiple circular contacts which are assumed identical and regularly distributed over the interface according to a square net. The governing equations are solved by using the finite complex Fourier transform and the finite cosine Fourier transform. The developed solution is explicit and allows to calculate the three-dimensional steady-state temperature regardless of the velocity and the ratio of the real contact area to the apparent one. Thus, this solution can be also used for other applications such as the moving laser beam. The comparisons performed show a good agreement of our results with available models. We study the effects of: thermal properties of materials, the relative size of micro-contacts, the film thickness and the velocity, on the thermal behavior of the body.

When an almost single-mode IR laser beam is reflected from an IR window with a deposit of Rydberg Matter on the inner, vacuum face, the laser modes appear red-shifted; thus their maxima are observed at lower laser current. This effect is complementary to the previously reported blue-shifts of IR laser modes in transmission through Rydberg Matter. Both types of shifts are due to interaction between the laser modes, now proved by using only two isolated modes both in reflection and transmission. The general process is stimulated Raman scattering. Rydberg Matter is here formed from Rydberg states of K atoms and nitrogen molecules inside a vacuum chamber. A theoretical description is given that involves slow decay or increase in the energy of the photons interacting with the Rydberg Matter, depending on the temperature of this matter. This means that the two isolated modes studied may become almost resonant within certain frequency ranges. The energy increase (frequency blue-shifting) of photons passing hot Rydberg Matter has been reported previously. The description used explains both the red-shifted reflection and the blue-shifted transmission results.

A systematic study was carried out in order to characterise a DC pulsed discharge used for the treatment of polystyrene thin films. The energy which is injected into plasma can be modulated while exploiting the discharge time (τ), the afterglow duration time (tag) and the treatment duration time (tt). The variations of the macroscopic properties of surface were monitored by measurement of the contact angle and we correlated these results of wettability with the way in which energy is distributed. The experimental results showed that the surface treatment was better (the largest wettability) for the smallest values of τ (2 µs) and largest times of tag (0.1 s). A sensitivity of the treatment to the distribution of energy was highlighted, and it is through this study that we will put forth assumptions on the species responsible for the treatment.

Fully microcrystalline silicon, μc-Si, thin films (<100 nm) have been deposited at low temperature (60 °C) on Corning glass and plastic flexible polyimide substrates by plasma enhanced chemical vapor deposition (PECVD) using SiF4-H2-He. The effect of deposition temperature on the structure, i.e., crystallinity and density, of μc-Si films is investigated by spectroscopic ellipsometry in the 1.5−5.5 eV energy range. Modeling of spectroscopic ellipsometry data is used for highlighting crystallinity of the substrate/film interface, i.e., the absence of any amorphous incubation layer. It is found that film crystallinity does not depend on film thickness, and it increases with the decrease of deposition temperature. The temperature dependence is explained on the basis of a like-Arrhenius kinetic analysis of the etching process by atomic fluorine and hydrogen of both μc-Si and a-Si phases.

Near-field optical signals are imaged in the vicinity of nano-holes using two different near-field optical microscopes. The experimental results are compared with electromagnetic field calculations based on a modal approximation. It turns out that an optical fibre detects the Poynting vector whereas the apertureless tip is sensitive to the field amplitude.

A realistic near-field calculation on metallic hole samples in illumination transmission conditions predicts certain light confinements around the holes. The purpose of this paper is to explain theoretically how an A-SNOM (Apertureless Scanning Near-field Optical Microscope) is able to detect the light confinement around the holes, and how it is possible, by defining a criterion of separation between two holes in near-field, to analyse the resolution as a function of the experimental parameters. The modulation of the probe height in A-SNOM is used for both distance control and separation of the near-field from the background scattered light. A realistic model of lock-in detection is used to calculate the images of test samples. Constant height mode images are presented at different amplitudes of probe modulation and average heights of the tip. We also discuss the detection at different demodulation harmonics.

Performances and advantages of different high-resolution microscopy techniques are compared. These include Soft X-ray Contact Microscopy (SXCM), Atomic Force Microscopy (AFM), Focused Ion Beam (FIB) and Transmission Electron Microscopy (TEM). It is shown that they allow complementary approaches to imaging of biological objects. These techniques have been used to image the same type of cells (Saccharomyces cerevisiae) thus providing a common benchmark. In particular it is shown that the novel FIB technique allows easy target cell selection, fast operation, high resolution, 3D imaging and sample manipulation during imaging.

In this paper a steady laminar 2D Poiseuille flow between two plates with chemical reactions on the upper wall is considered. This is a typical configuration in flow chambers (like the BIACORE one), which are used for the determination of the rate constants of reversible reactions between biological macromolecules. As the chamber thickness is small compared to its length, simplifications are possible, so, some asymptotic limits of mass conservation equation coupled with the wall chemistry are presented. We obtain a system with a large Péclet number. The small effects of the flow on the chemical reaction, which depend on the combination of the Damköhler and Péclet numbers, are highlighted. The results of these equations are favorably cross compared with the asymptotic (Lévêque) solution or with the simplified solutions (integral methods) found in the literature. The final result is that, due to the fact that the exchange coefficient is shown to be nearly constant, the simplified integral method is derived in a more rigorous way and its area of use is improved.

On the basis of experimental measurements of the electric field (which varies from 5 to 60 V/cm) and the N-atom relative density variation (one order of magnitude), mechanisms of ionization and dissociation in direct current glow discharges are discussed for pressures ranging from 0.5 to 5.0 torr and current between 1 and 50 mA. It is shown that: (i) at low pressure (E/N > 40 Td) ionization is governed by electronic impact and Penning reactions; (ii) at high pressure (E/N < 40 Td) the ionization is mainly governed by Penning reactions.