Elastic constant of dielectric nano-thin films using three-layer resonance studied by picosecond ultrasonics

Abstract

Elastic constants and sound velocities of nm order thin films are essential for designing acoustic filters. However, it is difficult to measure them for dielectric thin films. In this study, we use a three-layer structure where a dielectric nano-thin film is sandwiched between thicker metallic films to measure the longitudinal elastic constant of the dielectric film. We propose an efficiency function to estimate the optimal thicknesses of the components. We use Pt/NiO/Pt three-layer films for confirming our proposed method. The determined elastic constant of NiO deposited at room temperature is smaller than the bulk value by ∼40%. However, it approaches the bulk value as the deposition temperature increases. We also reveal that the uncertainty of the elastic constant of the Pt film insignificantly affects the accuracy of the determined elastic constant of NiO in this structure.

The angular dependence of magnetization dynamics induced by a GHz range strain pulse

“…Details are shown in our previous studies. [19][20][21][22][23] We detected the strain pulse from the reflectivity change of the probe light using a balanced detector 1 (BD-1). On the other hand, the magnetization dynamics is detected from the intensity difference between S and P polarization components of the reflected probe light using a balanced detector 2 (BD-2).…”

The angular dependence of magnetization dynamics induced by a GHz range strain pulse

“…Details are shown in our previous studies. [19][20][21][22][23] We detected the strain pulse from the reflectivity change of the probe light using a balanced detector 1 (BD-1). On the other hand, the magnetization dynamics is detected from the intensity difference between S and P polarization components of the reflected probe light using a balanced detector 2 (BD-2).…”

Two-photon photoacoustic spectroscopy of liquid solutions under degenerate and non-degenerate laser excitation

“…Photoacoustic spectroscopy (PAS), one type of photothermal spectroscopy, is one of the most sensitive optical methods for measuring photoabsorption and allows the observation of non-fluorescent molecules. Photoacoustic (PA) waves, including laser ultrasonics 16,17) and picosecond ultrasonics, 18) are generated by thermal expansion-induced pressure change caused by non-radiative relaxation of photo-absorbed molecules and are detected with a microphone or piezoelectric transducer. PAS has been used to measure solid and gas samples.…”