A method for calibrating the line-focus-beam acoustic microscopy system

Abstract

Absolute accuracy of the line-focus-beam (LFB) acoustic microscopy system is investigated for measurements of the leaky surface acoustic wave (LSAW) velocity and attenuation, and a method of system calibration is proposed. In order to discuss the accuracy, it is necessary to introduce a standard specimen whose bulk acoustic properties, (e.g., the independent elastic constants and density) are measured with high accuracy. Single crystal substrates of gadolinium gallium garnet (GGG) are taken as standard specimens. The LSAW propagation characteristics are measured and compared with the calculated results using the measured bulk acoustic properties. Calibration is demonstrated for the system using two LFB acoustic lens devices with a cylindrical concave surface of 1-mm radius in the frequency range 100 to 300 MHz.

Quantitative Nondestructive Evaluation Techniques for Investigation of Very Thin Coatings

“…In contrary, when acoustical parameters of the coating and substrate are very close, the accuracy is poor. The absolute accuracy of leaky SAW velocity measurement in the range 100-300 MHz of about 0.02% is reported [3], the precision being significantly better (around 0.005%). To apply the method, the calibration dispersion curve has to be determined experimentally to take into account actual properties of the coating, which can be different from those of the bulk material.…”

Development of an improved calibration method for the LFB ultrasonic material characterization system

“…In actual measurements, the values of ∆z and α 0 depend on the system (mainly the LFB ultrasonic device) and ultrasonic frequency so that measured values of V LSAW and α LSAW obtained from (1) and (2) are different from the actual material values [13], [14]. We thus conduct the following system calibration according to the method proposed in the literature [13].…”

“…2 schematically illustrates the calibration method for the LFB-UMC system. First, the acoustical physical constants of standard specimens (elastic constants c E , piezoelectric constants e, dielectric constants ε S , and density ρ) must be accurately determined in advance [13], [15], [21]- [23]. Using the acoustical physical constants, we conducted calculations to obtain the theoretical values of the LSAW propagation characteristics according to the analytical procedure described in the literature [24].…”

“…This system also has evaluated lithium niobate (LiNbO 3 ) and LiTaO 3 single crystals and wafers used for SAW devices and optoelectronic devices in order to resolve various scientific and industrial problems [3]- [12]. However, measured results of LSAW propagation characteristics depend on the characteristics of the systems used (mainly ultrasonic devices), and usually deviate from the true propagation characteristics [13], [14]. Therefore, we have devised a system calibration method using standard specimens whose acoustical physical constants have been accurately determined [13].…”

“…However, measured results of LSAW propagation characteristics depend on the characteristics of the systems used (mainly ultrasonic devices), and usually deviate from the true propagation characteristics [13], [14]. Therefore, we have devised a system calibration method using standard specimens whose acoustical physical constants have been accurately determined [13]. We generally have adopted standard specimens such as isotropic materials of synthetic silica glass and nonpiezoelectric cubic crystals of gadolinium gallium garnet (GGG), silicon (Si), and Germanium (Ge) that can cover a wider material velocity range from 2600 to 5100 m/s.…”