Acoustic microscopy techniques

Evans et al. (2005) recently reported significant improvements in the scanning acoustic microscopy technique as well as in the extension of ultrasonic reflectometry to the... 

The brief history, operation principle, and applications of the above-mentioned techniques are described in this chapter. There are several other measuring techniques, such as the fluorometry technique. Scanning Acoustic Microscopy, Laser Doppler Vibrometer, and Time-of-flight Secondary Ion Mass Spectroscopy, which are successfully applied in micro/nanotribology, are introduced in this chapter, too. 

Scanning acoustic microscopy (SAM) is a relatively new technique which broke through in the mid-seventies and was commercialized recently. The SAM uses sound to create visual images of variations in the mechanical properties of samples. The ability of acoustic waves to penetrate optically opaque materials makes it possible to provide surface or subsurface stmctural images nondestmctively, which might... 

The acoustic microscopy s primary application to date has been for failure analysis in the multibillion-dollar microelectronics industry. The technique is especially sensitive to variations in the elastic properties of semiconductor materials, such as air gaps. SAM enables nondestructive internal inspection of plastic integrated-circuit (IC) packages, and, more recently, it has provided a tool for characterizing packaging processes such as die attachment and encapsulation. Even as ICs continue to shrink, their die size becomes larger because of added functionality in fact, devices measuring as much as 1 cm across are now common. And as die sizes increase, cracks and delaminations become more likely at the various interfaces. 

Karnaukhov V.N, Yashin V.A. and Krivenko V.G. (1985). Microspectrofluorimeters. Proceedings of First Soviet -Germany International Symposum. Microscopy, Fluorimetry and Acoustic Microscopy. Moscow, p.160-164. Reigosa Roger, M.J. and Weiss, O. (2001). Fluorescence technique. In Handbook of Plant Ecophysiology Technique, (Ed., M.J. Reigosa Roger) Pp. 155-171. Kluwer Academic Publishers, Dordrecht. 

The line-focus-beam technique with its associated analysis has been more extensively used than any other method for quantitative acoustic microscopy. 

Faridian, F. and Somekh, M. G. (1986). Frequency modulation techniques in acoustic microscopy. IEEE 1986 Ultrasonics Symposium, pp. 769-73. IEEE, New York. [23,71]... 

Yue, G. Q., Nikoonahad, M and Ash, E. A. (1982). Subsurface acoustic microscopy using pulse compression techniques. IEEE 1982 Ultrasonics Symposium, pp. 935-8. IEEE, New York. [70]... 

Acoustic microscopy has a special place in this powerful armoury. It depends on the elastic response of the material to acoustic waves, and therefore provides information on local changes in elastic properties thus, for example, it is particularly sensitive to fine cracks (which might not be observable by other techniques). It has already been applied to a wide range of materials, including biological specimens, minerals, semiconductor devices, composites, ceramics, etc. As is the case for all other techniques, it is essential to have a clear understanding of the contrast mechanisms, so that the observations can be interpreted with confidence. This book provides potential users, such as materials scientists and biologists, with a comprehensive account of the basic techniques, of the contrast mechanisms, and of the way the techniques can be applied to obtain information on microstructure in different types of specimen. 

When the first edition was published in 1992, the resolution of the acoustic microscope techniques used at the time was controlled by the wavelength. In practice the frequency-dependent attenuation of the acoustic wave in the coupling fluid sets a lower limit to the wavelength, and therefore to the resolution, of about 1 pm for routine applications. Since then scanning probe techniques with nanometre scale resolution have been developed along the lines of the atomic force microscope. This has resulted in the development of the ultrasonic force microscopy techniques, in which the sample is excited by... 

There was, however, one topic which was not included in the first edition, which has undergone substantial development in the intervening years. It could have been foreseen in 1986 a paper was presented at the IEEE Ultrasonics Symposium entitled Ultrasonic pin scanning microscope a new approach to ultrasonic microscopy (Zieniuk and Latuszek 1986,1987). With the advent of atomic force microscopy, it proved possible to combine the nanometre-scale spatial resolution of scanning probe microscopy with the sensitivity to mechanical properties of acoustic microscopy. The technique became known as ultrasonic force microscopy, and has been joined by cognate techniques such as atomic force acoustic microscopy, scanning local-acceleration microscopy, and heterodyne force microscopy. 

Following the publication of the first edition of Acoustic microscopy, two volumes were published of Advances in acoustic microscopy (Briggs 1995 Briggs and Arnold 1996). In these some of the concepts and applications were further developed, and new topics were introduced. Those two volumes serve as supplements to the second edition the material in them has not been repeated, though in a few places reference has been made to chapters in them. The main addition in this second edition is the chapter on ultrasonic force microscopy and related techniques. We trust that Acoustic microscopy will continue to serve as a helpful resource for further generations of microscopists who wish to image and measure elastic properties at high resolution. 

The choice of the nondestructive technique used in the examination of the sample on hand also depends upon the complexity of the shape of the sample. The following order of the methods is in progressively increasing complexity of the shape of the sample to be examined acoustic microscopy, microwave method, eddy current, magnetic particle, X-ray radiography, ultrasonics, liquid penetrant and visual methods. 

Acoustic microscopy. Although this technique is mainly used in the medical field, various interesting analytical applications have been developed and analytical chemists are encouraged to contribute new ones by exploiting advances in instrumentation in this field. An aooustic microscope, which also constitutes an example of a half-laser instrument, is desoribed below. 

This chapter describes the results of an ongoing study we are conducting into the nanoscale mechanical properties, chemical composition and structure of healthy enamel, carious lesions and the acquired salivary pellicle layer. A variety of material characterization techniques are being used, including nanoindentation, scanning electron microscopy (SEM), electron microprobe analysis (EMPA), scanning acoustic microscopy, atomic force microscopy (AFM) and time-of-flight secondary ion mass spectroscopy (TOF SIMS). 

Several other techniques referred to as microscopy and based on several different phenomena can be found in the literature. These include acoustic microscopy based on the interactions of acoustic waves with materials [28] the projection microscopy which is still under development and gives a hologram image of the sample illuminated by a beam of low energy electrons [29]. For membrane applications a scarming electrochemical microscope has been developed based on the measurement of the local flux of electroactive ions across the membrane. The ability to detect 1 pm radius pores separated by 50-100 pm has been demonstrated with mica membranes [30]. 

QCM provides this kind of readout without the necessity to open the incubator door. As the cells are anchored directly onto the surface of the mechanical transducer, the device can be easily integrated into biotechnological reactors or other experimental setups. Alternative techniques like scanning force microscopy or scanning acoustic microscopy [43] are more powerful in the sense that they may provide a laterally resolved elasticity mapping however, due to the technical requirements of these devices, the cell cultures have to be manipulated and removed from their cell culture environment. 

Scanning laser acoustic microscopy (SLAM) - See Techniques for Materials Characterization, page 12-1. 

Acoustic waves are often used in microscopy techniques for failure analysis and reliability testing of modem devices. Although they have a quite large wavelength up to several centimeters, they can be well used for nanoscopic investigations by introduction of near-field conditions [1], e.g. with microprobes. These microprobes can be used either as an acoustic source [2,3] or as a detector [4,5] together with a comparably large acoustic transducer. 

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