X-Ray Correlation Photoacoustics for Depth Resolved Analysis of Layered Materials

Abstract

Correlation photoacoustic measurements were conducted on layered materials with an X-ray beam of synchrotron radiation and a conventional X-ray tube used for excitations. Impulse response signals of layered materials, including laminated samples of aluminum and lead foils and those of polymer and lead foils, were measured by a cross-correlation technique. For the laminated samples of aluminum and lead foils excited with the synchrotron radiation, peaks with different delay times were observed as separate ones where the first and the second peaks were assigned to the signals from the surface and a lower layer, respectively. The interval between the first and the second peaks was proportional to the thickness of the surface layer, and the intensity of the second peak was dependent on the optical property of the surface layer. For laminated samples of polymer and lead foils, an additional signal from the intermediate lead layer was observed besides those from the surface layer and the deep lead layer. They were also examined by ordinary photoacoustic measurements with visible light excitation; the results were found to be consistent with the results from X-ray measurements.