The electron-phonon coupling of a series aromatic molecules is calculated on the same basis as for alkali-doped fullerites and graphite intercalation compounds. It shown to be inversely proportional number $\ensuremath{\pi}$ bonded atoms, effect curvature being less important. implication these results superconductivity corresponding molecular crystals discussed.

We present the results of picosecond ultrasonic experiments performed at different laser wavelengths in samples all grown on silicon (100) substrates. In blue range we report strong oscillations reflectivity curves. experimental and numerical that identify origin these a acousto-optic interaction substrate. Then propose to explain high amplitude by relation with direct interband transitions which fall same range. This explanation is supported two other evidences: First, sudden changes phase...

The attenuation of longitudinal acoustic phonons up to frequencies nearing $250\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}$ is measured in vitreous silica with a picosecond optical technique. By taking advantage interferences on the probe beam, difficulties encountered early pioneering experiments are alleviated. Sound damping at and room temperature consistent relaxation dominated by anharmonic interactions thermal bath, extending Brillouin scattering data. Our result variance claims recent...

We have studied the effect of wavelength change on picosecond acoustic pulses generated using a femtosecond laser. For first time, we show that pulse shape can be strongly influenced by laser wavelength. The results are in excellent agreement with calculation based thermoelastic model which connects them to significant changes piezo-optical constants. There similarities between present study and stress modulation spectroscopy, allows us ascribe observations interband transitions suggests...

We present a way of using picosecond ultrasonics to simultaneously get the thickness and elastic properties thin dielectric layers. This is based on use blue probe which shown improve detection acousto-optic oscillations in from sound velocity can be measured refractive index. At same wavelength strong response silicon used detect arrival acoustic pulse. apply this scheme various materials deposited substrates.

We fabricate e-beam lithographied two-dimensional lattices of nanometric metal cubes various sizes and lattice parameters. Using ultrafast laser acoustics, we time resolve two kinds vibrations in such crystals: individual cube lower frequencies strongly dependent on the parameter. From complementary experiments an analytical model, assign these modes to acoustic collective (i.e., phonons) artificial crystal. Their unprecedented detection takes advantage another periodicity effect acting...

Complete mechanical measurements are performed in submicron films using the picosecond ultrasonic technique. The Al layer deposited on top of sample acting as a transducer is replaced with nanostructured film. Using an usual setup we can excite and detect high-frequency longitudinal surface acoustic waves. From this deduce Young’s modulus Poisson’s ratio any isotropic thin Experimental results obtained for silica silicon very good agreement literature.

We study the elastic properties of two-dimensional phononic crystals made aluminum nanocube lattices. From experimental point view, collective modes resulting from coupling between cubes inside crystal are excited and time resolved using ultrafast acoustics. derive a general theoretical model modes. analytical expression we discuss influence numerous parameters on detected frequencies. then present results various samples which all exhibit an excellent agreement with model. The description...

We report picosecond acoustic measurements in silica-glass films grown by wet thermal oxidation on a $(111)$ silicon substrate. The longitudinal phonons are observed over the range from 150 to 300 GHz using an infrared pump and second harmonic blue probe. transducer is aluminum thin film deposited top. Multiple interference effects analyzed fully taken into account. They lead signal presenting rapid oscillations as function of sample thicknesses. latter determined separate interferometry....

The authors report on acoustic attenuation measurements in transparent thin films by picosecond ultrasonics. This ultrafast technique has already been proposed for such but usually is overestimated and a specific sample configuration needed. Here they present another way of using this which overcomes both difficulties. Experimental results obtained silica show very good agreement with literature. validates the protocol then applied to various other materials used microelectronics.

We explore from both the theoretical and experimental points of view influence laser wavelength on strain pulses detected in thin transparent layers using picosecond ultrasonic technique. From a analysis displacement detection involved such experiments, we predict amplitude sign changes signals as is tuned. Experimental results performed various samples at different wavelengths are found to be excellent agreement with description. Several applications based high sensitivity phenomenon...

A phenomenological approach is developed to identify the physical parameters causing dc-voltage-induced tunability of aluminum nitride (AlN) acoustic resonators, widely used for RF filters. The typical resonance frequency these resonators varies from 2.038 GHz at -200 V 2.062 +200 V. This indicates, based on measurements versus dc bias and model used, that AlN stiffness variation prominent effect because both antiresonance experience a similar variation, respectively, 24 MHz 19 400...

We report on the strong laser wavelength effects in shape of acoustical pulses generated and detected thin metallic films using ultrashort optical pulses. The experiments have been performed aluminum copper. In both cases, we observed a sign change part signals vicinity well-known interband transition. identify origin phenomenon detection mechanism. These results let us demonstrate role picosecond ultrasonics may play study electronic structure films.

We present a method for refractive indices and longitudinal sound velocity measurements from picosecond ultrasonic experiments made at different probe incidence angles. For transparent or semitransparent materials such as dielectrics semiconductors, can lead to oscillations in the reflectivity curves whose frequency depends on indices, angle. From these data we establish simple calculation of verify it GaAs sample. show fluorinated silica glass aluminum nitride practical applications this...

The tremendous development of tactile interface in many customers' applications, such as smartphone, leads industrials to study "haptic interfaces" which allow the user interact with its environment by sense touch. This paper reports on a unique solution based Pb(Zr <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.52</inf> , Ti xmlns:xlink="http://www.w3.org/1999/xlink">0.48</inf> )O xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> (PZT)...

Nowadays, the haptic effect is used and developed for many applications—particularly in automotive industry, where mechanical feedback induced by a system enables user to receive information while their attention kept on road driving. This article presents development of vibrotactile button based printed piezoelectric polymer actuation. Firstly, characterization electro-active as actuator model able predict electromechanical behavior this device are summarized. Then, design circular...

We present experimental results obtained in two-color pump-probe experiments performed semiconductor self-assembled quantum dot (QD) layers. The sample reflectivities several acoustic contributions, among which are strong phonon wave packets. A comparison between one- and a fine analysis of the echo shape attest that high magnitude pulse emerges from each single QD layer. This conclusion is supported by numerical modeling perfectly reproduces our signals only if we introduce generation...

We present experimental results demonstrating that the generation of terahertz acoustic waves using femtosecond laser pulses is possible in quantum dots (QDs). Very short and strong are emitted from a buried QD layer detected at sample surface. By tuning wavelength we can detect, room temperature, frequencies above 1 THz photoelastic mechanism. A theoretical model supports such capability shows around an interband transition bandwidth detection be greatly improved. These suggest...

This work describes the assessment of acoustic properties sputtered tantalum oxide films intended for use as high-impedance reflectors solidly mounted resonators operating in gigahertz frequency range. The are grown by sputtering a metallic target under different oxygen and argon gas mixtures, total pressures, pulsed dc powers, substrate biases. structural assessed through infrared absorption spectroscopy X-ray diffraction measurements. Their impedance is deriving mass density from...

We demonstrate the ability to construct wide-area spatial mappings of buried interfaces in thin film stacks a non-destructive manner using two color picosecond acoustics. Along with extraction layer thicknesses and sound velocities from acoustic signals, morphological information presented is powerful demonstration phonon imaging as metrological tool. For series heterogeneous (polymer, metal, semiconductor) that have been treated chemical procedure known alter properties, reveal changes...

We present picosecond ultrasonic characterizations on e-beam evaporated Ir thin films and AlN deposited by pulsed DC reactive sputtering Ir. Picosecond ultrasonics is an optical technique which uses ultrashort laser pulses to generate detect very short acoustic pulses. first investigate the properties of measuring samples various thicknesses deposition parameters. It permits extract longitudinal sound velocity, impedance losses in electrode. Second, we focus films. measure thickness velocity...

Thin-film sol-gel Pb(Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.52</sub> , Ti xmlns:xlink="http://www.w3.org/1999/xlink">0.48</sub> )O xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (PZT) can be used in many actuator applications thanks to its high piezoelectric coefficients. The accurate knowledge of mechanical properties such as Young's modulus (E) and Poisson ratio (v) or stiffness matrix is a key point for predictive design,...