We studied the relationship between elastic constants and microstructure in sputtered vitreous SiO 2 thin films using pump-probe picosecond laser ultrasound. The delayed probe light pulse is diffracted by the acoustic wave excited by the pump light pulse, inducing Brillouin oscillations, seen as reflectivity change in the probe pulse, whose frequency can be used to extract the sound velocity and elastic moduli. Theoretical calculations were made to explain the asymmetric response of Brillouin oscillations and to predict the possible error limit of the determined elastic constants. The thin films containing defects exhibited lower elastic constant. A micromechanics modeling was developed to evaluate defect porosity and attenuation caused by scattering was able to predict the defect size. Elastic moduli of the defect-free specimens increased with increasing sputtering power, eventually exceeding the bulk value, and correlated with phonon frequencies, indicating that the decrease in the Si-O-Si bond angle of the tetrahedral structure increased the stiffness.

Hopping conduction and piezoelectricity in Fe-doped GaN studied by non-contacting resonant ultrasound spectroscopy

A quantitative theory is presented for the frequency dependence of the ultrasonic attenuation in the nearly one-dimensional antiferromagnet which has small, but not negligible, interchain couplings. At temperatures well above the Nee1 temperature T,,, the ultrasonic attenuation a is described by a scaling function, a = 03G(ot,), where t, indicates the characteristic time after which the three-dimensional diffusion takes over. The theory is compared with the frequency dependence of the ultrasonic attenuation in CsNiC1, (a onedimensional Heisenberg antiferromagnet) and the effect of the interchain coupling on the one-dimensional spin dynamics is discussed.

In this study, an elastic-stiffness evaluation in transparent or translucent thin films using Brillouin oscillations detected by picosecond ultrasound is conducted. An ultrahigh-frequency (>∼50 GHz) strain pulse is generated using femtosecond light pulse in specimens and observed to propagate in the film-thickness direction. The time-delayed probe light pulse enters the specimen, which is diffracted by a strain pulse, causing oscillations in the reflectivity change of the probe light pulse. The oscillation frequency gives the elastic modulus with ellipsometry for refractive index. The theoretical calculation predicts the accuracy of stiffness measurement. The methodology is applied to the study of amorphous silica, amorphous tantalum oxide, diamond thin films, and silicon wafers.

This study proposes a methodology for evaluating specific binding behavior between proteins using a resonance acoustic microbalance with a naked-embedded quartz (RAMNE-Q) biosensor. We simultaneously measured the frequency responses of fundamental (58 MHz) and third-order (174 MHz) modes during multi step injections of proteins and deduced the thickness and viscosity evolutions of the protein layer. The viscosity increases with the progress of the binding reaction in nonspecific binding, but it markedly decreases in specific-binding cases. Thus, the highfrequency RAMNE-Q biosensor can be a powerful tool for evaluating specificity between proteins without measuring dissipation.