Elastic Stiffness of Co Thin Films at High Temperatures Monitored by Picosecond Ultrasound

Arita

Yokoyama

et al. 2015

Jpn. J. Appl. Phys.

Self Cite

(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 ± 0.7 GPa 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.

Section: Introductionmentioning

confidence: 78%

Acoustic properties of co-doped AlN thin films at low temperatures studied by picosecond ultrasonics

Arita

Yokoyama

et al. 2015

Jpn. J. Appl. Phys.

Self Cite

“…35 We can then obtain the elastic constant C 11 ¼ qv 2 , where q is the mass density. We built two vacuum chambers for low-temperature 36 and high-temperature 37 measurements. The specimens were attached to heat exchangers, and both pump and probe lights were normally incident to them through a 20-times objective lens and a glass window.…”

mentioning

confidence: 99%

Elastic constant C11 of 12C diamond between 10 and 613 K

Applied Physics Letters

Arita

Ogi

et al. 2016

We measured the temperature dependence of the elastic constant C11 of a 12C diamond monocrystal using picosecond ultrasonics between 10 and 613 K. We found that C11 is almost temperature independent below room temperature; the temperature coefficient around 300 K is −6.6 MPa/K. Our results show a significantly higher Einstein temperature than reported values by ∼30%, indicating that diamond has a larger zero-point energy, which remains dominant around ambient temperature. We also calculated the temperature dependence of the elastic constants using ab-initio methods, resulting in good agreement with measurements. Our study shows that below-ambient-temperature measurements are not sufficient to extract the Debye temperature and the Grüneisen parameter of high-Debye-temperature materials.

“…C L of the pure a-W film is lower than the corresponding bulk value 51 by 5.4% similar to the usual metallic thin films (thin films often show 5-20% lower elastic constants than bulks due to defects). 49,[52][53][54] We find that C L of b-W is lower than that of the pure a-W film by 10%. Elastic constants of bulk b-W have not been reported since pure bulk b-W was not obtained.…”

mentioning

confidence: 66%

Elastic constants of beta tungsten thin films studied by picosecond ultrasonics and density functional theory

Applied Physics Letters

Lee

Ogi

et al. 2020

Tungsten thin films are used for various applications and sometimes exhibit an A15 structure (b-W). They have some superior properties in comparison to the bcc structure (a-W), such as a higher superconducting transition temperature and larger spin Hall angle. However, elastic constants of b-W are unclear, which restricts mechanical applications and reliable density-functional-theory calculations. In this study, we synthesized a-W, b-W, and mixed-phase W films and determined their elastic constants by picosecond ultrasonics. We also calculated the elastic constants based on density functional theory and reveal that b-W has a larger elastic anisotropy and smaller shear modulus. Our calculation further indicates a stable stacking faulted b-W, which leads to a monoclinic structure.