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This is the Accepted Manuscript version of an article accepted for publication in Japanese Journal of Applied Physics. IOP Publishing Ltd is 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/acb9a2., We examined the effects of the laser scan speed and power on the Sn fraction and crystallinity of GeSn wires of 1 μm width and 1 mm length fabricated by laser-induced local liquid phase crystallization on quartz substrates. The Sn fraction increased from 1% to 3.5% with an increasing scan speed from 5 to 100 μm s⁻¹, corresponding to a luminescence wavelength of 1770–2070 nm. This result can be interpreted as the scan speed dependence of the non-equilibrium degree during crystal growth. The increase in the laser power reduced the Sn fraction and caused a blue shift in the luminescence wavelength. We discuss these phenomena based on the growth kinetics of zone melting.

Cobalt is gaining strong attention as an alternative metal for very narrow interconnects of advanced LSIs. Cobalt interconnects are fabricated by a damascene process like in copper. Slurries for the chemical mechanical polishing contain both an oxidizer and a corrosion inhibitor, in addition to abrasives. To understand the chemistry of the cobalt surface exposed to slurries, we studied the development of a layer on cobalt surfaces in benzotriazole (BTA)–hydrogen peroxide (H2O2) aqueous solutions using in situ spectroscopic ellipsometry and a microfluidic optical cell specifically designed for this purpose. The layer growth mechanism is discussed in view of cobalt out-diffusion.

Spectroscopic ellipsometry is a powerful tool for the characterization of thin films/surfaces. To simultaneously extract optical constant and film thickness from ellipsometric parameters ψ and Δ, dispersion models of material’s refractive index and spectroscopic ellipsometry measurement have been often required. In this work, we propose an extraction method of optical parameters of thin films from the reflection and transmission ellipsometric parameters. This method necessitates neither spectroscopic information of ψ and Δ, nor dispersion models. Verification measurements were carried out with the single-point and imaging ellipsometers, respectively.

As an approach to integrate both single-point measurement ellipsometry and optical microscopy, imaging ellipsometry possesses the capability of measurement of distributions of optical constants and/or thickness of sample surfaces. Considering the exact distinguishment of neighboring surfaces from imaging ellipsometry measurement, in this note, we propose to use a new criterion for the lateral ellipsometry resolution: about 2.23 fold of the Abbe diffraction limit for a microscope. This criterion will be helpful for the estimation of the applicability of an imaging ellipsometer into the evaluation of micro-patterned surfaces.

To monitor the health of large-scale structures, a wireless measurement system, such as a bridge, is required. One of the methods of monitoring the health of large-scale structures involves the application of an impedance-loaded wireless surface acoustic wave (SAW) sensor. Additionally, a pressure-sensor-loaded SAW sensor can detect the vibration of a cantilever. In this study, a continuous wavelet transform (CWT) is adopted to analyze the sensor responses. The CWT results obtained were classified into two categories based on the attenuation at each frequency, which include the exponential or linear type. Furthermore, machine learning was applied to evaluate cantilever damage. The results indicate that a high accuracy evaluation of damage is feasible with the proposed method.

In the medical field, point-of-care testing (POCT) is garnering attention. An online inspection system can be realized by combining POCT and the Internet. Herein, we report the performances of a measurement system developed using online software for a shear horizontal surface acoustic wave (SH-SAW) sensor. The developed SH-SAW measurement system does not require a phase detection circuit. The developed system can be used when the system is connected to the Internet. This enables an online measurement system that can be used “by anyone, at anytime, and anywhere.” In this study, we used samples of glycerol and water mixtures and then measured the amplitude ratio and phase difference of the SH-SAW sensor. The validity of the developed system is confirmed by comparing the measured results with theoretical values.

Reduction of oxidized Rh catalysts under carbon monoxide (CO) exposure and reaction conditions were studied by using ambient-pressure x-ray photoelectron spectroscopy. First, Rh powders pressed into a pellet were deeply oxidized and the reduction process under 100 mTorr CO environment was monitored in situ at different temperatures. The oxidized Rh surfaces are composed of Rh2O3 and RhO2, the latter of which is more segregated near the surface. Both oxide species are reduced simultaneously to the metallic state; kinetic analyses indicate that the activation energy of the reduction of the Rh oxides is 1.68 eV, which is a little larger than those for Pd oxides, probably due to a stronger Rh–O interaction. Reduction of oxidized Rh nano-particles deposited on SiO2 under two reaction conditions (CO + O2 and CO + NO + O2) was observed with increasing temperature. It was found that the reduction temperature shifts to the higher temperature in the presence of NO, even though the S-factors are almost the same. The NO molecule more strongly prevents the reduction of oxidized Rh catalyst compared to O2.

Droplet manipulation is one of the important applications using surface acoustic waves (SAWs). It is necessary to determine the droplet position on a SAW device. When a short burst signal was applied, a reflected signal was observed. The mechanism of the reflected wave observed was investigated from the visualization of the acoustic streaming. The propagation path in the droplet was assumed from the observation results and compared with the experimental results. The results agree with the calculated results, when the water droplet volume is above 2.5 µl. Also, a transmitted signal is observed. The transmission depends on the longitudinal wave velocity of a liquid. The droplet position is determined from the measured results of the reflected and transmitted signals. Also, the results suggest that the longitudinal wave velocity is estimated from the reflection and transmission times, when the droplet position is known.

The development of sensors using surface acoustic wave (SAW) devices has been attracting attention. A shear horizontal SAW (SH-SAW) sensor can detect the properties and chemical reactions in liquids. To realize practical applications of the SAW sensor, it is necessary to discuss its properties. In this paper, SH-SAW sensors with a floating electrode unidirectional transducer (FEUDT) or an interdigital transducer (IDT) are compared and the insertion loss and phase characteristics are measured. Also, the phase shift between sample and reference liquids is evaluated. The results indicate that the SH-SAW sensor with the FEUDT is suitable for liquid measurements. The SH-SAW sensor with the FEUDT is then mounted in a newly developed SH-SAW sensing system. The system configuration is the same as that of a vector voltmeter measurement system. However, circuits have been developed that reduce its size. Using this system, several liquids are measured. The obtained results agree well with the theoretical values.