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Due to their ability to interact with their environment, the interest in microcantilever sensors in biological or chemical applications is increasing. Moreover measurement of the sensor bending induced by molecular adsorption is improved by electrochemical actuation of the cantilever. This is why modelling the electro-elastic coupling is a key issue. Different methods are used to measure the bending induced by this electrochemical actuation. Among them, multiple wavelengths imaging microscopy provides full-field measurements. The local surface electrical charge density and the deformation field are obtained by decoupling wavelength-dependent and –independent contributions to the collected intensity. Based on a modelling of the electro-elastic coupling and on these full-field measurements, an identification method of the coupling parameters of the system is proposed herein.

In this paper we present an experimental and theoretical study of the thermoreflectance response as a function of the probe wavelength for layered microelectronics structures. The investigated sample consists of a polycrystalline silicon conducting track grown on a SiO2-coated Si substrate. Thermoreflectance measurements were carried out in the wavelength range from 450 to 750 nm with the track biased in modulated regime. An oscillating pattern is observed in the spectral region where the upper layer is transparent. Such oscillations are due to the interference resulting from the multiple reflections at the interfaces. Using a thermo-optical model, we show that the optical constants (n and k) of the materials, which are wavelength dependent, as well as their temperature derivatives (dn/dT and dk/dT), strongly influence the thermoreflectance signal. The optical thicknesses of the layers, mainly determined by the real part of the refractive indices, define the period of oscillation. On the other hand, the imaginary part of the refractive indices establishes the cutoff wavelength of the oscillations. Below this cutoff wavelength, the probe light does not penetrate the material and the upper-surface reflectance dominates the signal. [ABSTRACT FROM AUTHOR]

Examines the direct measurement of the polarization-dependent absorption and saturation in a single quantum well. Techniques used in characterizing semiconductor materials; Polarization-dependent absorption edge measurements; Theoretical model of absorption features and comparison with experiment.

Surface temperature measurements were performed with a scanning thermal microscope mounted with a thermoresistive wire probe of micrometric size. A CMOS device was designed with arrays of resistive lines 0.35 μm in width. The array periods are 0.8 μ m and 10 μm to study the spatial resolution of the SThM. Integrated Circuits (ICs) with passivation layers of micrometric and nanometric thicknesses were tested. To enhance signal-to-noise ratio, the resistive lines were heated with an ac current. The passivation layer of nanometric thickness allows us to distinguish the lines when the array period is 10 μm. The results raise the difficulties of the SThM measurement due to the design and the topography of ICs on one hand and the size of the thermal probe on the other hand. [ABSTRACT FROM AUTHOR]

Thermoreflectance microscopy can deliver thermal images with high spatial resolutions by measuring the variations of the reflection coefficient with temperature. It is therefore a unique tool to measure the temperature mapping of integrated circuits with submicronic features. However, integrated circuits are usually protected by a dielectric encapsulation layer which is transparent to visible light. The optical interference which occurs in these layers strongly modifies the reflectivity and can even forbid thermoreflectance measurements at some wavelengths. For each series of circuits, it is therefore necessary to determine the illumination wavelengths for which thermoreflectance will deliver optimal signals. A sequential wavelength scan can deliver this information but it is time consuming and therefore subject to drifts. We have developed a CCD camera-based thermoreflectance microscope coupled to a grating which disperses white light directly onto the CCD. This instrument gives the complete spectra of the reflection coefficient and its temperature dependence, R(λ) and dR/dT(λ), on one or several materials with only one acquisition. The optimal wavelength for thermoreflectance measurements can therefore be measured within minutes on any sample. A model taking into account multiple reflections and the thermal expansion of the encapsulation layer has been developed to explain the spectra R(λ) and dR/dT(λ) measured on encapsulated circuits. It can be used to predict qualitatively the optimal working wavelength. [ABSTRACT FROM AUTHOR]

We report a fast imaging method based on full field heterodyne interferometry for the purpose of frequency resolved temperature imaging. An integrated circuit is supplied with a modulated current resulting into a temperature modulation. The frequency content for this modulation is detected using an object beam and a reference beam, frequency-shifted to create a beating of the interference pattern. We obtain frequency domain spectra of the temperature with excellent precision. [ABSTRACT FROM AUTHOR]

In integrated circuits, most of the heating is produced in the active layers below the surface, making thermal measurements extremely difficult. The authors demonstrate that near infrared thermoreflectance can provide thermal imaging inside the circuit, through its silicon substrate. The use of an InGaAs camera with a noncoherent illumination in the 1.1–1.7 μm band allows fast thermal imaging with a diffraction-limited resolution of 1.7 μm. A silicon solid immersion lens was then used to further improve the resolution to 440 nm, corresponding to an effective numerical aperture of 2.36. [ABSTRACT FROM AUTHOR]

Using thermoreflectance microscopy with a camera, we have designed a system which delivers submicronic images of the alternative temperature variations in integrated circuits working in a modulated regime. A careful choice of the illumination wavelength permits us to highlight the heating in chosen parts of the sample and to optimize the thermoreflectance signal. We measure and explain the modifications of the photothermal response which are induced by the presence of a passivation layer. A calibration conducted on various materials with a thermocouple gives access to the absolute alternative temperature variations in integrated circuits working at frequencies between 0.1 Hz (quasipermanent regime) and 5 MHz. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Investigates magnetization-induced second-harmonic generation with surface plasmon excitation in an ultrathin Au/Co/Au multiplayer structure. Changes in the second-harmony intensity caused by the resonant coupling of surface plasmons with the fundamental light.

A comparative analysis of the Crustacean faunas found in Ypresian bioconstructions cropping out in the Eastern Lessini Mountains is carried out. The fossiliferous sites are: Contrada Gecchelina at Monte di Malo, San Pietro Mussolino, Vestenanova, and the Bolca area (Vicenza; Verona – NE Italy). The high value of the Shannon-Weaver biodiversity index calculated for these buildups confirms the hypothesis of the existence during the Early Eocene of a large lagoon characterized by shallow water and patch reefs. Juvenile specimens of Gecchelicarcinus lorigae and Alponella paleogenica are described.