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.

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.

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.

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.

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.