Monitoring of Longitudinal-Wave Velocity and Attenuation of SrTiO₃at Low Temperatures Using Picosecond Ultrasound Spectroscopy

Abstract

The effects of P b doping, oxygen doping (6 = 0.1,0.2,0.4 and 0.5) and high pressure (4, 8, 15 and 20GPa) on the electronic structure of Hg,,,Pb,,,Ba,Ca,Cu,O,+, have been examined by the recursion method. Our calculations show that Pb doping only decreases the hole concentration slightly and oxygen doping increases the hole concentration monotonically and significantly as 6 varies from 0 to 0.5, with each excess oxygen atom contributing about 1.7 holes to the CuO, layers. The optimal 6 is estimated to be around 0.4. The hole concentration increases initially with pressure but decreases as P > 8 GPa (i. e., dn/dP does change sign at N 8 GPa). The suppressed T,(P) by Pb substitution has to be described in the modified Neumeier's model.

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

“…We developed the optics for the picosecond ultrasound spectroscopy measurements at cryogenic temperature and its detail appears elsewhere, 6) and observed Brillouin oscillation, whose frequency f is well-approximately written by the Bragg's diffraction low: 7) f = 2nv 33 /λ, where n and v 33 are the refractive index and sound velocity of a specimen, and λ is the wavelength of probe light (400 nm). We measured n by ellipsometry method using an instrument V-VASE produced by J.…”

Temperature behavior of sound velocity of fluorine-doped vitreous silica thin films studied by picosecond ultrasonics

“…We constructed optics for normal-incident picosecond ultrasonics at cryogenic temperature measurements 35 and the multi-angle-incident picosecond ultrasonics to measure refractive index n and longitudinal-wave velocity v simultaneously at room temperature as shown in Fig. 1.…”

Elimination of bandwidth effect in attenuation measurement with picosecond ultrasonics

“…Therefore, it has also been used for the attenuation measurement. [11][12][13][14] However, when the attenuation coefficient is determined from the damping of the Brillouin oscillation, there is a concern. Brillouin oscillation is detected through the reflectivity change in the probe light reflected from a specimen in which acoustic phonons are propagating; the probe light is reflected at both the specimen surface and the acoustic pulse; the latter occurs by backward diffraction.…”