Multilayer transfer matrix characterization of complex materials with scanning acoustic microscopy (original) (raw)
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2008
Microscopic objects including living cells on a planar substrate are investigated in bio-medical applications of scanning acoustic microscopy. Beside of the observation of lateral structures, the determination of sample properties such as density, sound velocity, and attenuation is desired, from which elastic properties can be derived. This can be achieved with the aid of the acoustic phase and magnitude contrast represented in a polar plot. For homogeneous and sufficiently planar objects the contrast in magnitude and phase is a function of the properties of the substrate and the coupling fluid, which both can easily be determined, and of the mechanical properties of the sample under observation. For observation in reflection and variable thickness of the sample the signal will depend on the actual thickness. This signature of the object can be fitted based on a conventional ray model for the sound propagating in the coupling medium and the sample. The model includes also the refraction and reflection at all interfaces between transducer, lens material, coupling fluid, object, and substrate. The method is demonstrated for a chitosan film deposited on a glass substrate. The scheme presented here is capable to reach a resolution of about and even below 1% for relevant quantities in applications involving imaging at 1.2 GHz in aqueous coupling fluids.
Scanning Acoustic Microscopy: A Physicist’s Tool
Europhysics News Europhysics News(vol. 22, number 9):p. 167-170, 1991
-Principle of the scanning acoustic microscope (SAM ). The spherical interface between the sapphire rod and the coupling fluid (usually water) acts as a lens for pulsed ultrasonic waves travelling down the rod. Spherical ultrasonic waves strike the sam ple and are reflected back into the trans ducer for conversion into a useful signal.
Scanning acoustic microscopy for mapping the microstructure of soft materials
2009
Acoustics provides a powerful modality with which to 'see' the mechanical properties of a wide range of elastic materials. It is particularly adept at probing soft materials where excellent contrast and propagation distance can be achieved. We have constructed a scanning acoustic microscope capable of mapping the physical microstructure of such materials. We review the general principles of scanning acoustic microscopy and present new examples of its application in imaging biological matter, industrial materials and particulate systems.
SPIE Proceedings, 2015
Joining ceramics to metals is difficult because of residual stresses that can develop during the cooling process. Scanning acoustic microscopy (SAM) is a well-recognized tool to characterize the elastic properties of materials and can be applied to materials with elastic discontinuities such as the interface of a ceramic/metal joint. Acoustic information was obtained by applying the V (z) curve method, which measured the output signal of the transducer as a function of the position, z. The velocity of the surface acoustic waves, V saw , of the material was calculated from the V (z) curve. In this work, a simulation of the V (z) curve was updated. The pupil-function splitting method was combined with the angular-spectrum approach of V (z) theory in order to obtain the V (z) curve for the interface between different materials. The V saw value at the interface was calculated from the simulated V (z) curve. A series of experiments were performed to measure the V saw values at the interface of a Si 3 N 4 /Cu joint using the SAM. By comparing the measured values with the calculated values, the reliability of this simulation was verified. The simulation can be used to test the boundary conditions of bimaterial samples. iii Table of Contents List of Figures vi List of Tables viii List of Symbols ix iv 2.3.2.1 The Reflectance Function R(k x) and the Leaky-wave Form of R(k x
A Transfer Matrix Approach for Acoustic Analysis of a Multilayered Active Acoustic Coating
Journal of Sound and Vibration, 2001
A transfer matrix approach is presented to evaluate and analyze the acoustic characteristics of a multilayered active acoustic coating, which can be applied to actively reduce sound re#ection and/or transmission upon a given sound wave excitation. Expressions are derived to obtain the re#ection and transmission coe$cients, and to separate the incident sound pressure with re#ected sound pressure from two integrated piezoelectric sensor layers. Numerical results for re#ection and transmission coe$cients of three cases are presented to verify the approach and to depict its e!ectiveness in the "eld of study and simulation of a multilayered active acoustic coating with a backing plate.
Thermal effects in scanning acoustic microscopy for fine resolution applications
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 1994
Abssh.ucl-A novel scanning acoustic microscopy technique for achieving high resolution acoustic images by employing thermal effects and image subtraction has been studied and demonstrated. Experiments were performed on a perspex block patterned with a machined grid on the reverse surface, and on a buried channel in similar material. It was found that using the image subtraction technique, short periods of sample heating can lead to a stronger pattern selectivity, because of the strong temperature dependency of the elastic parameters of the polymer. In previous SAM techniques improvement in signal has been achieved through the use of special liquids as acoustic coupling media between the acoustic lens and the sample. The reported technique retains water as the coupling medium and the acoustic impedance matching is performed by varying the elastic parameters of the sample itself through direct heating. The temperature increase in the sample decreases the velocity of propagation of acoustic waves in the solid, and brings the acoustic impedance close to that of water. A theoretical model, including expressions for the acoustic aberrations, depth dependence and acoustic impedance matching has been derived. Examples of the results obtained are presented.
IEEE Transactions on Sonics and Ultrasonics, 1985
Abslmcf-A methodology for complete characterization of thin-and thick-film materials deposited on a substrate using widehand reflection acoustic microscopy is presented. A wideband reflection acoustic microscope that covers the frequency range of 50 to 175 MHz was constructed to carry out the experimental verification. The amplitude of the reflection coefficient of the film-substrate composite was measured versus the acoustic frequency to identify the resonant frequency of the specimen at which the film thickness is equal to one quarter of the acoustic wavelength. Then both the amplitude and the phase of the reflection coefficient at the resonant frequency were measured. Using the three measured quantities, thickness, acoustic velocity, and mass density of the film material are simultaneously determined without any prior knowledge. Two types of film materials, namely Pyrex glass film sputtered on a sapphire substrate and positive photoresist coated on a Pyrex glass substrate have been characterized using the methodology. The three measured acoustic parameters, film thickness, acoustic velocity, and mass density, agree well with the published values. For the frequency range of the microscope utilized the corresponding range of measurable film thickness is 30 pm to 5 pm for most inorganic materials, and 10 pm to 2 pm for most organic materials. For the case in which the film thickness is less than one quarter of the acoustic wavelength at the highest operation frequency of the microscope, the resonant frequency cannot be identified. However. one or two of the three acoustic parameters can still be determined by measuring the amplitude and the phase of the reflection coefficient at a fixed acoustic frequency. This capability has been demonstrated using a gold fdm deposited on fused quartz and an aluminum film evaporated on X-cut LiNbOj substrate. Three additional transducer/lens sets with staggered center frequencies are also being assembled to cover the entire frequency range from 175 MHz t o 1000 MHz so that the measurable range of the film thickness can be extended to the submicron region. Consequently, it is concluded that this characterization methodology should he highly useful For nondestructive study of thin-and thick-film materials in microelectronics.
Scanning Acoustic Microscopy: SAM
In book: Mechanical SpectroscopyEdition: Materials Science Forum, vol. 366-368Chapter: 9.4Publisher: Trans Tech Publications, Switzerland , 2001
Scanning acoustic microscopy is currently being used routinely for both imaging materials for qualitative examination as well as for measuring elastic properties in localized areas. This paper details the principles of this technique, the origin of the acoustic contrast, and its applications.
Characterization of heterogeneous matrix composites using scanning acoustic microscopy
Journal of Materials Science, 1993
Acoustic microscopy was used to examine the morphology of multi-phase matrices and composites. The acoustic microscopy imaging could easily resolve the rubber domains dispersed within a thermosetting or thermoplastic continuous phase. However, because the thermoplastic and thermosetting phase domains had comparable elastic moduli, the resolution between them was not always clear. Rayleigh wave distortion of imaging remained as one of the serious limitations that needed to be overcome in order for this technique to be widely utilized in heterogeneous/anisotropic media. In its present form, the acoustic imaging technique can be used to augment other existing analytical tools in order to generate more detailed morphological information that is useful in understanding structure-property relationships for multi-phase toughened matrices used in advanced composites.