In this work, we propose acoustic characterization as a new method to probe wetting states on a superhydrophobic surface. The analysis of the multiple reflections of a longitudinal acoustic wave from solid-liquid and solid-vapor interfaces enables to distinguish between the two well known Cassie-Baxter and Wenzel wetting configurations. The phenomenon is investigated experimentally on silicon micro-pillars superhydrophobic surfaces and numerically using a finite difference time domain method. Numerical calculations of reflection coefficients show a good agreement with experimental measurements, and the method appears as a promising alternative to optical measurement methods.

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Bulk materials have been synthesized by the Bridgman technique using the elements Cu, Ga, In, Se. Bulk samples have been characterized by EDS (Energy Dispersive Spectrometer), hot point, X‐ray diffraction, photoluminescence and spectroscopic ellipsometry (SE). The samples used were well crystallized and lended strong support to the achievement of a good stoechiometry. Energy levels above the gap in the band scheme were determined by measuring the dielectric function at ambient temperature for energies lying between 1.5 and 5.5 eV. Many transitions were observed above the gap for different samples of CuIn1–xGaxSe2 (0 ≤ x ≤ 1) alloy. Spectroscopic ellipsometry gave evidence for the interpretation of the choice of gap values which were compatible with that obtained from solar spectrum [1]. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

This work presents a theoretical calculation of the I-V characteristics of an n-p junction. The total current across the n-p junction is presented as the superposition of currents due to each region of the junction. It results in ideality factor values between 1 and 2. Threshold voltage values, related to the low and high level injection in each region, are introduced. The theoretical model is used to describe the experimental emitter-base I-V characteristics of a bipolar transistor. The effects of the electrical ageing are taken into account as a creation of a defect layer in the base, near the junction. A maximum error of 6% between the theoretical model and experiment is obtained.

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