[en] The photoacoustic technique in the gas-cell/microphone configuration has been applied to determine optical and thermal parameters in ion-implanted silicon and gallium arsenide layers, as a function of the ion implantation dose. The results are in good agreement with those reported in the literature, thus demonstrating that the technique is suitable for determining, in a nondestructive way, thermal and optical parameters in thin layers as well as in bulk material, even at wavelengths for which the material is optically opaque. (author)

[en] Short communication

[en] Short communication

[en] Short communication

[en] Short communication

[en] The general theory of photoacoustic signals is adapted to the detection of liquid crystals' thermal parameters. The thermal-diffusion length to optical-absorption length ratio is given as a simple function of the phase, while the sample to gas effusivity ratio is given as a simple function of phase and normalized amplitude. A method allowing the determination of each thermal parameter separately is presented. Since it does not require strong thermal gradients in the sample, it is particularly well suited to the study of pretransitional effects in liquid crystals

[en] We report on calorimetric measurements carried out in an upgraded photopyroelectric setup enabling the determination of the frequency dependence of the specific heat and of the latent heat exchanged over first order transitions as well as the simultaneously determined nematic correlation length obtained from light scattering measurements. It has been applied to the study of the Nematic-Isotropic transition of 8CB liquid crystal confined in a silica nanoparticle network, where the specific heat shows a double peak structure.

[en] Germanium <100>, <110>, and <111> single crystals implanted with 46 keV Te ions with doses between 10₁₂ and 10₁₅ ions cm^-₂ have been analyzed by TEM of surface replicas, RHEED, and MeV He⁺ channelling. The combination of these types of measurements reveals the effect of crystalline orientation on heavy ion damage in a germanium lattice. The degree of disorder in the bulk, resulting from low dose implantation is lowest at <110> and <111> channelling and highest at <100> channelling. (author)

[en] The photoacoustic-technique application to the simultaneous characterization of the thermal diffusivity, specific-heat capacity and thermal conductivity of a liquid crystal at a phase transition is presented for the first time. The first two parameters show a critical decrease and increase, respectively, while the third one does not exhibit any critical behaviour

[en] A detailed study of the implantation-induced damage in Si on sapphire, carried out by optical-absorption measurements extending from energies above the band gap down to energies far into the subgap region of Si, is presented. The changes induced in the optical band gap, band-edge slopes, and in the subgap features of the spectra are carefully described. The various stages of formation and quenching of divacancies were monitored as a function of implantation conditions and annealing cycles through their 1.8-μm absorption band. It is shown that the divacancies strongly affect the population of band-tail states and the annealing studies revealed that the progressive quenching of the divacancy band is followed by the appearance of another absorption band, characteristic of some intrinsic secondary defect, whose annealing behavior is similar to the one observed for the five-vacancy electron-paramagnetic-resonance spectrum. The study of the structural relaxation process in implanted a-Si gave indications that the process is indeed associated with annihilation of defects as well as average strain reduction in the material, in agreement with earlier indications. Finally, some common features, such as band-edge inverse-logarithmic slope values and subgap features, are found in annealed implanted crystalline and a-Si