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We propose a high sensitivity biosensor based on a GHz phononic crystal (PnC) waveguide, and demonstrate its operation by numerical simulations. The geometry consists of a micron-scale freestanding PnC silica waveguide plate with embedded Au nanopillars for bioparticle attachment, the PnC plate lying between two groups of periodic metal strips for GHz Lamb-wave acoustic generation and detection with ultrashort light pulses. By precise choice of the waveguide defect width, this biosensor is designed to work using a single, isolated waveguide mode. We study the influence of the waveguide defect width on the acoustic dispersion and transmission of this mode. Bioparticle attachment is simulated by investigation of the Au nanopillar mass loading, and is shown to shift the waveguide transmission peak to lower frequencies. We thereby demonstrate femtogram detection, showing that our approach provides a new methodology for label-free ultra-sensitive biosensing.

The hydrogen energy, which is environmentally friendly and does not emit carbon dioxide, has been attracting attention as an alternative fuel to the fossil fuel. In the shift to a hydrogen energy society, the highly sensitive hydrogen gas sensor has been required for the storage and management of hydrogen gas. In this study, we propose a film deposition method to induce the in-plane plastic deformation in the thin film and apply it to a hydrogen gas sensor, where the palladium film formed by this method is deposited on a thin quartz resonator. It is found that the sensor chip with the plastically deformed palladium film is about 1.5 times more sensitive than the conventional sensor chip and has high-speed response. The developed sensor is a novel device that can be used in an oxygen-free environment without any temperature compensation and constant heating.

We study the lattice thermal conductivity of isotope diamond superlattices consisting of 12C and 13C diamond layers at various superlattice periods. It is found that the thermal conductivity of a superlattice is significantly deduced from that of pure diamond because of the reduction of the phonon group velocity near the folded Brillouin zone. The results show that asymmetric superlattices with a different number of layers of 12C and 13C diamonds exhibit higher thermal conductivity than symmetric superlattices even with the same superlattice period, and we find that this can be explained by the trade-off between the effects of phonon specific heat and phonon group velocity. Furthermore, impurities and imperfect superlattice structures are also found to significantly reduce the thermal conductivity, suggesting that these effects can be exploited to control the thermal conductivity over a wide range.

This paper studies the structural design of the wireless-electrodeless quartz crystal microbalance (QCM) sensor, which has a rectangular AT-cut quartz oscillator installed in the microchannel fabricated by nanoimprint lithography. The quartz oscillator was supported by the micropillars in the microchannel, and by optimizing the micropillar arrangement, it was found that the structural damping could be significantly reduced by performing the finite elemental piezoelectric analysis. This behavior was then confirmed by the experiments using the evaluation chips. By supporting the four corners of the quartz oscillator with the micropillars, the structural damping could be reduced, achieving a high-quality factor (Q-factor) of about 24700. This high Q-factor was also realized in the experiments, and we investigated its application to a hydrogen-gas sensor. We succeeded in detecting hydrogen gas with an extremely low concentration of 10 ppm.

This is the Accepted Manuscript version of an article accepted for publication in Japanese Journal of Applied Physics. IOP Publishing Ltd are not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.35848/1347-4065/abea50., For visualizing propagation of an acoustic wave and evaluating the local sound velocity in micro/nano-meter structures, confocal picosecond ultrasonics is developed. In conventional picosecond ultrasonics, the measurement of local sound velocity was difficult, and macroscopic sound velocity and elastic properties were measured. However, in confocal picosecond ultrasonics, a confocal laser-scanning microscope is embedded in the optics of the picosecond ultrasonics, and the depth resolution is improved. Using the developed optics, we successfully observed propagation of an acoustic wave in thin film. In this paper, the optics we developed and the experimental results on silica film are reported.

This is the Accepted Manuscript version of an article accepted for publication in Japanese Journal of Applied Physics. IOP Publishing Ltd are not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.35848/1347-4065/ab78e2., Sensitivity of a hydrogen-gas sensor based on lattice expansion of palladium highly depends on the surface morphology of palladium. We find that the sensitivity can be significantly improved by exposing the as-deposited palladium film to low-power plasma. The hydrogen-gas detection was performed by a wireless-electrodeless AT-cut quartz-crystal resonator with 125 MHz fundamental resonance frequency. It detects hydrogen gas through bending deformation of the resonator caused by the volume expansion of palladium. The surface morphology of palladium film before and after the plasma treatment were analyzed using atomic force microscopy. The plasma treated palladium film exhibits a rougher surface, finer grains, voids, and grain boundary extension. Such morphology and structure changes along with defects induced by the ion bombardment during the plasma treatment strongly contribute to increase in hydrogen absorption rate and then the sensor sensitivity. We further investigate the thickness dependence of the sensitivity, revealing an optimum palladium film thickness of 300 nm.

The anisotropic elastic constants of Co/Pt superlattice thin films were measured by resonant ultrasound spectroscopy and picosecond laser ultrasound. The experimental results were compared with the ab initio calculations for perfect superlattices. The calculated out-of-plane elastic constant C33 is consistent with the measured value within 4%. However, the measured in-plane elastic constant C11 is smaller than the calculated value by 15–20%.

Complete sets of elastic constants of rare-earth bismuth iron garnet (111) films containing Pb were determined by resonant-ultrasound spectroscopy. Resonant-ultrasound spectroscopy can be used to determine all independent elastic constants from one specimen by measuring the resonance frequencies of free vibrations. For accurate measurement of the resonance frequencies, we used a tripod transducer, and the vibration modes of each resonance frequency were identified by laser-Doppler interferometry. Rare-earth bismuth–iron garnet belongs to the space group Ia3d, and shows cubic symmetry. However, it was nearly elastically isotropic; 2C44/(C11 - C12) = 0.99. Their elastic constants were almost independent of the Pb content; C11 = 242.9 ±4.4 GPa, C12 = 99.1 ±2.0 GPa, and C44 = 71.1 ±0.8 GPa. The observed isotropic elasticity corresponds to that of the other garnet group crystals.

We have succeeded to electromagnetically excite and detect MHz-frequency-range ultrasound shear wave in polycrystalline Al under high pressures. The noncontact thickness-resonant electromagnetic acoustic resonance technique enables us to excite and detect polarized pure shear waves in an Al polycrystalline specimen in a pressurizing liquid through the Lorentz-force mechanism. Shear-mode resonance spectra have been successfully obtained up to 0.55 GPa at ambient temperature. Quasiharmonic analysis for the pressure dependence of shear modulus yields the zone-center shear-mode Gruneisen parameter γS to be 2.683, which agrees well with previously reported values calculated from the third-order elastic constants.

In this study, we investigate the behavior of the room-temperature recovery of elastic constants of Cu thin films by monitoring the mechanical resonance frequencies of the film/substrate specimen throughout the deposition process using resonant-ultrasound spectroscopy. The thin films were deposited on a (001) Si substrate located on a needle tripod transducer set in a vacuum chamber. The free-vibration resonance frequencies of the Cu/Si specimen were measured before, during, and after magnetron-sputtering deposition, yielding the evolution of the elastic constants of the Cu thin films. Recovery of the elastic constants of Cu thin films is completed in a much shorter time than that for bulk Cu; after the deposition, the elastic constants C11 and C66 increased by 1.0–2.4% and 2.2–5.3%, respectively, within 20 min. The recovery behaviors are well explained by the dislocation-damping theory. The recovery rate is larger than that of bulk Cu by a factor of 100, indicating much lower activation energies for point defect migration and dislocation sliding in the film.

Hirotsugu Ogi, Kazuma Motohisa, Kenichi Hatanaka, Toshinobu Ohmori, Masahiko Hirao and Masayoshi Nishiyama. High-frequency wireless and electrodeless quartz crystal microbalance developed as immunosensor. Japanese Journal of Applied Physics, 2007, 46(7S), 4693. https://doi.org/10.1143/JJAP.46.4693., A wireless and electrodeless high-frequency quartz crystal microbalance (QCM) was developed for monitoring biochemical reactions in real time without using any labeling procedures. An analytical vibrational calculation for a multilayered plate showed that the QCM sensitivity significantly deteriorates when metallic electrodes are present on the crystal surfaces, indicating the importance of an electrodeless QCM biosensor. The 30-μm-thick electrodeless QCM immunosensor was excited, and its mechanical vibration was detected contactlessly using an antenna located outside the QCM cells. The homebuilt QCM system was used to detect human immunoglobulin G (hIgG) using staphylococcal protein A (SPA) immobilized on the crystal surface and to demonstrate the higher sensitivity of the electrodeless QCM than that of the conventional QCM. The 30-μm-thick QCM, with a 54MHz fundamental frequency, successfully monitored the hlgG-SPA binding reaction for a hIgG concentration of 100pg/mL.

Electromagnetic acoustic resonance (EMAR) is a contactless resonance method using an electromagnetic acoustic transducer (EMAT). In this study, EMAR was applied to detect the creep damage process in Cr–Mo–V steel, which is an important structural material for thermal energy plants. The material was exposed to temperatures up to 923 K at various stresses. Two types of EMAT were used: bulk-wave EMAT for plate samples and axial-shear-wave EMAT for cylindrical samples. We measured ultrasonic attenuation in the frequency range between 1 and 7 MHz as creep progressed. Attenuation coefficient exhibits a much larger sensitivity to damage accumulation than velocity. It shows a maximum peak at approximately 30% and a minimum peak at 50% of the creep life, independent of the applied stress and the type of EMAT used. EMAR has the potential for assessing damage progress and for predicting the creep life of metals.

Understating elastic properties of thin films is a matter of deep interest both in scientific and industrial fields. In this paper, we propose a combination of resonant-ultrasound spectroscopy coupled with the laser-Doppler interferometry and pump-probe photoacoustics for measuring anisotropic elastic constants of deposited thin films. Among the five independent elastic constants, the resonant-ultrasound spectroscopy is sensitive to the in-plane elastic constants, C11, C13, and C66, and pump-probe photoacoustics to the out-of-plane elastic constant, C33. We apply this to Cu thin films deposited on monocrystalline Si substrates by the magnetron-sputtering method. Cu thin films show elastic anisotropy, C33>C11. The cause of this elastic anisotropy is attributed to the textured structure and the columnar structure. These effects are estimated by X-ray diffraction measurements and micromechanics calculations.

We measured light scattering in a single crystal of ZrW2O8 (ZWO) in the frequency range between 0.1 and 1100 cm−1 and in the temperature range between 3.5 and 300 K. From the temperature dependence of the optical and acoustic phonon frequencies, we found that low-frequency phonon modes below 100 cm−1 have large relative temperature coefficients (total anharmonicity values). The longitudinal acoustic mode, whose Brillouin light scattering has not been reported thus far, was found to have the largest negative total anharmonicity in a wide temperature range, indicating the possibility that the acoustic modes, as well as the low-frequency optical modes that are associated with the motions of WO4 and ZrO6 polyhedra, should contribute to the negative thermal expansion of ZWO.

Hirotsugu Ogi, Toshinobu Omori, Kenichi Hatanaka, Masahiko Hirao and Masayoshi Nishiyama. Detection of glypiean-3 proteins for hepatocellular carcinoma marker using wireless-electrodeless quartz-crystal microbalance. Japanese Journal of Applied Physics, 2008, 47(5S), 4021. https://doi.org/10.1143/JJAP.47.4021., Pure shear-wave resonances were excited and detected in 18- and 30-μm-thick electrodeless AT-cut quartz plates in liquids using line antennas contactlessly, achieving high-frequency quartz-crystal microbalances (QCMs). Their fundamental resonance frequencies (85 and 54 MHz) were monitored to study interactions in real time between human glypican-3 and an anti-glypican-3 antibody: glypican-3 is a prospective protein marker for hepatocellular carcinoma. Their affinity was determined by the Langmuir kinetics. This study demonstrates the high ability of the wireless-electrodeless QCM for detection of the protein markers and development of drugs for disorders.

Elastic and anelastic properties of polycryatalline α-Mn at low temperature have been studied using electromagnetic acoustic resonance (EMAR) and resonance ultrasound spectroscopy coupled with a laser Doppler interferometer (RUS/Laser). α-Mn showed low Poisson's ratio both in the paramagnetic state at 290 K and in the anti-ferromagnetic state at 4 K. The acoustic Debye temperature was 479 K, showing good consistency with the previous work. Around the magnetic transition temperature (TN=98 K), remarkable changes in Poisson's ratio and internal friction are identified, indicating strong magnetic acoustic interaction at the transition temperature.

Optical properties of Si are important and widely studied. However, temperature dependence of the refractive index for visible light at low temperatures has not been measured. In this study, we measured the complex refractive index of Si at 400 nm between 10 and 300 K by picosecond ultrasound spectroscopy. The measured refractive index at room temperature agrees well with reported values, confirming the accuracy of our measurement, and we found that the refractive index at 10 K is smaller than reported values.

Tomohiro Shagawa, Hiroomi Torii, Fumihito Kato, Hirotsugu Ogi and Masahiko Hirao. Viscoelasticity evolution in protein layers during binding reactions evaluated using high-frequency wireless and electrodeless quartz crystal microbalance biosensor without dissipation. Japanese Journal of Applied Physics, 2015, 54(9), 096601. https://doi.org/10.7567/JJAP.54.096601., In this study, we demonstrate the effectiveness of a resonance acoustic microbalance with a naked embedded quartz (RAMNE-Q) biosensor for evaluating viscoelastic property changes in thin protein layers during protein deposition reactions without dissipation measurement. Quartz crystal microbalance (QCM) biosensors have conventionally been adopted for the viscoelasticity evaluation of adsorbed protein layers by measuring dissipation as well as resonance frequency. However, dissipation, or the vibrational energy loss, is easily affected by many factors and is rarely measured with sufficiently high accuracy. To evaluate viscoelasticity only from a reliable frequency response, one needs to perform an ultrahighfrequency measurement, which is here achieved using the RAMNE-Q biosensor. Simultaneous frequency measurement is performed for fundamental and overtone modes up to 406MHz of a 58MHz RAMNE-Q biosensor during various binding reactions, and evolutions of viscosity, shear modulus, and thickness of adsorbed protein layers are inversely evaluated. A marked difference is observed in the viscosity evolution between specific and nonspecific binding reactions. Furthermore, the reversed frequency response appears, which indicates the modification of the protein structure into a rigid structure.

Nagakubo A., Arita M., Yokoyama T., et al. "Acoustic properties of co-doped AlN thin films at low temperatures studied by picosecond ultrasonics", Japanese Journal of Applied Physics, 54(7), 07HD01 (2015) https://doi.org/10.7567/JJAP.54.07HD01., (Mg0.5Zr0.5)xAl1-xN and (Mg0.5Hf0.5)xAl1-xN thin films are AlN-base piezoelectric materials, and their piezoelectric coefficients are higher than those of pure AlN, being promising materials for acoustic devices. However, their acoustic properties remain unknown because of measurement difficulty for deposited thin films. In this study, we measure their longitudinal-wave elastic constants C33 and their temperature coefficients using picosecond ultrasound spectroscopy for 0 < x < 0.13; we obtain C33 = 398.2 ± 0.7GPa for pure AlN, and it largely decreases by doping Mg, Zr, and Hf, leading to a minimum values of 316.8 ± 1.6 GPa for (Mg0.5Zr0.5)0.126Al0.874N.

We have successfully developed the total-internal-reflection-fluorescence microscopy combined with a quartz-crystal microbalance (TIRFM-QCM) biosensor, and monitored the nucleation–fibrillation phenomenon of amyloid β1-40 peptide on the naked quartz surface. The cross-β-sheet structures were visualized with the TIRFM using the thioflavin-T (Th-T) label, and other unlabeled aggregates were detected through the frequency change of the 58-MHz wireless-electrodeless QCM throughout the aggregation reaction. The QCM response indicates significant adsorption of the peptides on the quartz surface at the early stage, which is followed by fibrillation. The non-cross-β-sheet oligomers are first formed, and nuclei appear in the oligomer region, from which fibrils originate and elongate. The two-color TIRFM observation was performed after the aggregation reaction with the Nile-red label as well as the ThT label for identifying nucleation from non-β-sheet regions. An aggregation model is proposed.

Atsushi Maehara, Nobutomo Nakamura, Hirotsugu Ogi and Masahiko Hirao. Elimination of bandwidth effect in attenuation measurement with picosecond ultrasonics. Japanese Journal of Applied Physics, 53, 8, 086602. https://doi.org/10.7567/JJAP.53.086602., We study the broadening effect of probing pulse light on the apparent attenuation of the Brillouin oscillation measured with picosecond ultrasonics. We observe experimentally that the attenuation of the Brillouin oscillation is sensitive to the bandwidth, and the apparent attenuation coefficient increases as the bandwidth increases, being far from the intrinsic attenuation coefficient. Theoretical calculation is performed to reconstruct the observed oscillations, and it is confirmed that there are several factors affecting the apparent attenuation in addition to the bandwidth. We finally propose equations that deduce the contribution of the broadening to the apparent attenuation of the Brillouin oscillation.

We found that the second through-thickness vibration mode of a gold/silicon-nitride composite thin film is selectively excited by picosecond ultrasound with high efficiency by controlling the thickness ratio. Its mechanical vibration frequency exceeds 50 GHz, making it promising for mass detectors with ultrahigh sensitivity. We developed a theoretical model based on the strain-energy ratio between gold and silicon-nitride layers and successfully explained the enhancement of the second vibration mode. A sensor chip was applied to detect immobilized proteins through the change in resonance frequency.

The group velocity of each higher torsional mode in a pipe depends on the wall thickness and it will convert to a lower mode when the thickness is smaller than a critical value, the so-called cut-off thickness. The fundamental torsional mode, T(0,1), and the first higher mode, T(0,2), are generated in pipes by an electromagnetic acoustic transducer (EMAT) and their mode conversion behaviors are investigated by changing the shape of a defect on the pipe. It is confirmed that the conversion behavior is sensitive to the shape of thickness transition and the total reflection of the T(0,2) mode occurs in a pipe with a tapered defect. On the basis of the mode conversion, defects with a cross-sectional loss larger than 35% are detectable.

We systematically study the relationship between the ultrasonically induced aggregation behavior of amyloid β1–40 peptide and acoustic pressures to clarify the dominant mechanism of the aggregation. With ultrasonic irradiation, the thioflavin-T (ThT) level of the Aβ solution rises after a lag time, takes a maximum at ∼5 h, and remains unchanged or decreases. Thus, we monitor the ThT level at 5 h to evaluate the progress of the β-sheet structure and investigate its correlation with the acoustic pressures of fundamental and harmonics waves. The second-harmonics-wave amplitude shows the highest correlation with the ThT level, indicating the dominant contribution of cavitation bubbles to the fibrillation phenomenon. The influence of solution pH and Ar gas are investigated to identify the aggregation mechanism. As a result, local condensation of the peptide due to the high affinity of hydrophobic residues to the bubble-solution interface causes a highly supersaturated solution, leading to precipitation of β-sheet-rich nuclei.

A picosecond ultrasound system for measuring the elastic stiffness of thin films at high temperatures is developed, and the elastic stiffness of Co films is measured up to 771 K during heating and cooling processes. The elastic stiffness of an as-deposited film is smaller than that of bulk Co. However, during heating, stiffening due to crystallization is observed, and in the cooling process, the elastic stiffness follows the temperature dependence of bulk Co. These results indicate that the as-deposited film is softer than the bulk and that once stiffening has occurred upon annealing, the Co thin film shows a similar elastic property to the bulk. The temperature dependence of acoustic attenuation is also discussed.

Hirotsugu Ogi, Tetsuya Kawamoto, Yohei Nakamichi and Masahiko Hirao. Picosecond ultrasound spectroscopy with a stable fiber laser for ultrahigh-frequency-oscillator applications: From nanomechanics to biosensors. Japanese Journal of Applied Physics, 2012, 51(7S), 07GA08. https://doi.org/10.1143/JJAP.51.07GA08., We developed a stable picosecond-ultrasound-spectroscopy system with a fiber-laser light source. A linearly polarized light pulse with 532nm wavelength is split into pump and probe light pulses using a polarized beam splitter (PBS). The ultrahigh-frequency acoustic waves excited by the pump light pulse are successfully detected using the delayed probe light pulse with a signal-to-noise ratio higher than that of the traditional titanium-sapphire pulse laser. The wavelength used allows deep inspection of silicon because of less light absorption. The developed system is also applied to a biosensor with an ultrathin Pt film resonator, which shows significantly improved stability at 100 GHz. The amount of frequency change caused by the adsorption of target molecules is of the order of 10⁻², which is much higher than that detected with conventional oscillator biosensors by a factor of 10⁴.

We measured the longitudinal-wave velocity and its attenuation in SrTiO3 between 20 and 300 K using picosecond ultrasound spectroscopy. From the temperature dependence of the velocity and attenuation, we monitored the cubic–tetragonal phase transition of SrTiO3 near 100 K, whereas no more transitions were indicated below 100 K. From the measured attenuation coefficients, we estimate the relaxation time τ. Because of the ultrahigh frequency measurements, the product ωτ is larger than unity, where the traditional theory for phonon–phonon interaction fails to explain the relaxation time. We then derived the relationship between the relaxation time and attenuation for ωτ>1.

We propose a new method for wall-thinning inspection based on mode conversion of shear horizontal (SH) guided waves, which is represented as group velocity change. Group velocities of higher modes of SH guided wave propagating in a plate-like wave guide depend on the thickness and frequency due to dispersive characteristic. There exists a cut-off thickness for each higher mode, below which the associated mode cannot propagate and mode conversion to lower ones is expected, leading to discontinuous velocity change. Here, the fundamental SH0 and first asymmetric SH1 modes are generated by the periodic-permanent-magnet electromagnetic acoustic transducer (PPM-EMAT) and propagated in aluminum plates containing thinning regions. A broad-range piezoelectric pinducer is used to detect the propagating wave in order to explore the mode conversions phenomena. We directly observed that the generated SH1 mode converts to SH0 mode in thinning region and converts back to SH1 mode when the thickness returns to original.

We present a high-frequency electrodeless quartz crystal microbalance (QCM) chip with a bare quartz resonator encapsulated in a silicon microchannel, which is fabricated by micromachining technology. This QCM chip packages an AT-cut quartz plate 2.5 mm long, 1.7 mm wide, and 9.6 µm thick, which is supported by micropillars without fixed parts. There is no issue about destruction during assembly because handling the fragile quartz resonator becomes unnecessary. The quartz resonator is electrodeless and not fixed; therefore, there are no losses due to electrodes and contacting wires. As a result, a high quality factor (Q-factor) and a high signal-to-noise ratio (SNR) can be obtained. The Q-factor is about 800–2800 at 170 MHz in the flow of the carrier solution. In addition, it is possible to reuse the device, because the quartz surfaces can adsorb receptor proteins nonspecifically, which can be removed by a washing procedure with a strong acid solution flowed in the microchannel. The high-frequency quartz resonator (170 MHz) encapsulated in the microchannel can reduce the influence of the viscosity contribution to the frequency shift, achieving highly sensitive and quantitative analysis. The QCM chip is excited and detects the shear vibrations of the quartz resonator by the line antennas without contact. Consequently, both sides of the quartz resonator can be used as the detection area in a solution. We succeeded in detecting the human immunoglobulin G (hIgG) at a concentration of 6 µg/ml via the staphylococcal protein A (SPA) immobilized nonspecifically on the developed QCM chip in real time without any labeling.

Staphylococcus aureus protein A (SPA) shows high nonspecific binding affinity on a naked quartz surface, and it can be used as the receptor protein for detecting immunoglobulin G (IgG), the most important immunoglobulin. The immunosensor ability, however, significantly depends on the immobilization procedure. In this work, the effect of the nonspecific immobilization procedure on the sensor sensitivity is studied using a home-built electrodeless quartz-crystal microbalance (QCM) biosensor. The pure-shear vibration of a 9.7-µm-thick AT-cut quartz plate is excited and detected in liquids by the line antenna located outside the flow channel. SPA molecules are immobilized on the quartz surfaces, and human IgG is injected to monitor the binding reaction between SPA and IgG. This study reveals that a long (nearly 24 h) immersion procedure is required for immobilizing SPA to achieve the tight biding with the quartz surfaces.

A nonlinear acoustic measurement is studied for creep damage evaluation. An electromagnetic acoustic transducer (EMAT) magnetostrictively couples to a surface-shear-wave resonance along the circumference of a cylindrical specimen during the creep of Cr–Mo–V steels. The excitation of the EMAT at half of the resonance frequency caused a standing wave to contain only the second-harmonic component, which was received by the same EMAT for determining the second-harmonic amplitude. This measured surface-wave nonlinearity showed a peak at 30% and a minimum at 50% of the total life. We interpreted these phenomena in terms of dislocation mobility and restructuring, with support from scanning electron microscope (SEM) and transmission electron microscope (TEM) observations. This noncontact resonance-EMAT measurement can monitor the evolution of surface-shear-wave nonlinearity throughout creep life and has a potential to assess damage advance and predict the creep life of metals.

A homebuilt wireless–electrodeless high frequency quartz crystal microbalance is adopted for long-time monitoring of the aggregation behavior of amyloid β1–42 peptide in a flow-cell system. The monomer amyloid peptides are immobilized on both surfaces of the crystal, and an amyloid-β solution is injected. The monotonic frequency decrease indicates aggregation on the crystal, which yields aggregation rate. Aggregation is observed even at a peptide concentration as low as 550 nM.

The Co/Pt superlattice shows perpendicular magnetic anisotropy, which makes the magnetization direction of the Co layer perpendicular to the film surface when the Co layer is less than about 20 Å thick. One possible cause of perpendicular magnetic anisotropy is large elastic strain at the interfaces between the Co and Pt layers. The elastic strain also changes the macroscopic elastic constants of the Co/Pt superlattice through lattice anharmonicity. In this study, we determined the anisotropic elastic constants of Co/Pt superlattice thin films using resonance ultrasound spectroscopy coupled with the laser/Doppler-interferometry method and studied the relationship between elastic and magnetic properties. We clearly observe a correlation between them, which is interpreted in terms of lattice anharmonicity.

Nobutomo Nakamura, Hirotsugu Ogi and Masahiko Hirao. Resonance ultrasound spectroscopy for measuring elastic constants of thin films. Japanese Journal of Applied Physics, 2004, 43(5S), 3115. https://doi.org/10.1143/JJAP.43.3115., We show an advanced technique for measuring elastic constants C ij of thin films deposited on substrates. Thin films often show anisotropy between the in-plane and out-of-plane directions because of their columnar structure, residual stress, texture, and incohesive bond. Then, thin films show macroscopically transverse isotropy and have five independent C ij. All the film Cij affect free-vibration resonance frequencies of the film/substrate layered specimen. Therefore, measuring the resonance frequencies permits us to determine the thin-film Cij with the other known parameters. In order to yield reliable Cij of thin films, we have to measure the resonance frequencies with sufficient accuracy and identify vibration modes of the measured resonance frequencies. We overcome these problems by developing a tripod and using a laser-Doppler interferometer, respectively. We applied the present technique to a copper thin film. Measured Cij are smaller than those of bulk and show elastic anisotropy. We attribute these features to the incohesive bond regions.

Hirotsugu Ogi, Kayo Wada and Masahiko Hirao. Energy trap for axial-shear-wave resonance in a stepped cylindrical rod: Theory and measurement. Japanese Journal of Applied Physics, 2004, 43(5S), 3024. https://doi.org/10.1143/JJAP.43.3024., The methodology to trap the vibrational energy of an axially polarized surface-shear wave (axial-shear wave) in a stepped cylindrical rod is presented. The central part of the rod where the resonance vibration was trapped had a slightly larger diameter. The magnetostriction effect of steel enabled us to generate and detect the resonance with noncontacting. An approximated analysis was used to derived a resonance equation and displacement distribution of trapped axial-shear-wave modes. The displacement was measured along the axial direction and it exponentially decreased with the distance from the center. This trend agreed with the theoretical calculation.