Measuring the Elastic Properties of Stressed Materials by Quantitative Acoustic Microscopy

Sklar, Z.; Mutti, P.; Stoodley, N. C.; Briggs, G. A. D.

doi:10.1007/978-1-4615-1873-0_6

Cited by 20 publications

(12 citation statements)

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“…The SAW velocity is inferred from oscillations in the microscope output that occur as the specimen is brought towards the lens from focus, a curve known as the VCz). A discussion of the analysis of the V(z) to obtain SAW velocities may be found elsewhere [8]. Measurements were made as a function of azimuthal angle, at a fixed frequency of 225 MHz, and are shown in figure 4. ,.-.., …”

Section: Methodsmentioning

confidence: 99%

“…It may be noted that the stress entered into equation (3) only needs to be specified using Hooke's law for a consistent level of approximation to be maintained [8]. By retaining terms up to cubic in the strain in the expansion (2), the effective elastic constants CijkI may be written as [7] :…”

Section: Lheory Acoustoelasticitymentioning

confidence: 99%

“…A number of techniques are available in the program to allow automatic tracking of a single dispersive SAW mode; this is particularly important when fitting calculated curves to experiment. The basic procedure follows that developed by Farnell & Adler [to] for an unstressed layer, and is described elsewhere [8]. Nalamwar & Epstein [11] have calculated velocities for a homogeneously stressed piezoelectric anisotropic layer, but their analysis is incorrect, since they did not maintain a consistent level of approximation for their effective elastic constants.…”

Section: Implementation For Sawsmentioning

confidence: 99%

“…The program developed here applies a non-linear least squares fit of theory to measurements of SAW angular or frequency dispersion made by any technique. The method is difficult to implement and is computationally expensive, but has the advantage of allowing a quantitative assessment of the errors in the fitted elastic constants [8]. A number of other methods, some of which are specific to acoustic microscopy, have been used to reduce the computational burden [15][16][17], and their merits are discussed elsewhere [8,17].…”

Section: Fittinand Proceduresmentioning

confidence: 99%

“…The inversion of the elastic constants of the layer is therefore very sensitive to the values used for the substrate. It is also known that the analysis procedure can introduce distortion into the shape of angular scans [8].…”

Section: Fittinand Proceduresmentioning

confidence: 99%

See 4 more Smart Citations

Elastic Constants of a Stressed Layer from Surface Acoustic Wave Measurements

Sklar

Mutti

Briggs

1995

Review of Progress in Quantitative Nondestructive Evaluation

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Parks Road Oxford OXl 3PH England INTRODUCTIONIt is well known that the propagation of both bulk and surface acoustic waves (SAWs) is affected by the presence of static stresses, a phenomenon known as the acoustoelastic effect. Ultrasonic measurements of velocity therefore depend on the stresses within the material, as well the elastic constants and the density. Although the effect of stress on the velocity is small, many ultrasonic methods are sufficiently accurate to detect the changes involved. When inverting such measurements to obtain elastic constants, it is desirable to take the effect of stress into account. Similarly, when using ultrasonic methods to measure stress, it is necessary to have accurate values for the elastic constants. In practice, the material parameters of the 'natural', unstressed state are often either completely unknown or not known with sufficient accuracy (as is usually the case for residual stresses), or else cannot be assumed to be equal to bulk values (as in the case of layered materials). This is a major distinction between situations involving residual as opposed to applied stress, since a reference state of some description is always available in the latter case.In this paper we show how to improve the estimation of the elastic constants of the natural state of a residually stressed layer from SAW measurements. To do this, we incorporate the stress into the forward calculation of the SAW velocity, so that fitting of the measured SAW dispersion then yields the elastic constants of the unstressed state. We then apply the procedure to GaAs wafers implanted with Si+ ions. BACKGROUND

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Section: Methodsmentioning

confidence: 99%

Section: Lheory Acoustoelasticitymentioning

confidence: 99%