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Impulsive Stimulated Thermal Scattering

Optical Imaging and Spectroscopy

  1. John A. Rogers1,
  2. Alex Maznev2,
  3. Keith A. Nelson3

Published Online: 18 MAY 2012

DOI: 10.1002/0471266965.com063.pub2

Characterization of Materials

Characterization of Materials

How to Cite

Rogers, J. A., Maznev, A. and Nelson, K. A. 2012. Impulsive Stimulated Thermal Scattering. Characterization of Materials. 1–17.

Author Information

  1. 1

    Bell Laboratories, Lucent Technologies, Murray Hill, NJ, USA

  2. 2

    Philips Analytical, Natick, MA, USA

  3. 3

    Massachusetts Institute of Technology, Cambridge, MA, USA

Publication History

  1. Published Online: 18 MAY 2012

Abstract

Impulsive stimulated thermal scattering (ISTS) is a purely optical, noncontact method for characterizing the acoustic behavior of surfaces, thin membranes, coatings, and multilayer assemblies, as well as bulk materials. The method has emerged as a useful tool for materials research in part because (1) it enables accurate, fast, and nondestructive measurement of important acoustic (direct) and elastic (derived) properties that can be difficult or impossible to evaluate in thin films using other techniques; (2) it can be applied to a wide range of materials that occur in microelectronics, biotechnology, optics, and other areas of technology; and (3) it does not require specialized test structures or impedance-matching fluids which are commonly needed for conventional mechanical and acoustic tests. Further, recent advances in experimental design have simplified the ISTS measurement dramatically, resulting in straightforward, low-cost setups, and even in the development of a commercial ISTS photoacoustic instrument that requires no user adjustments of lasers or optics. With this tool, automated single-point measurements, as well as scanning-mode acquisition of images of acoustic and other physical properties, are routine.

ISTS, which is based on transient grating (TG) methods, is a spectroscopic technique that measures the acoustic properties of thin films over a range of acoustic wavelengths. This article focuses only on ISTS measurement of acoustic motions in thin films. It begins with an overview of other related measurement techniques. It then describes the ISTS acoustic data and demonstrates how it can be used to determine (1) the stress and flexural rigidity in thin membranes; (2) the elastic constants of membranes and supported films; and (3) the thicknesses of single or multiple films in multilayer stacks.

Keywords:

  • impulsive stimulated thermal scattering (ISTS);
  • noncontact characterization;
  • photoacoustic analysis;
  • transient grating;
  • thin films;
  • phononic crystal;
  • acoustic dispersion