Bulk strains in Si induced by thickness mode ultrasonic waves and analysed with x-ray Bragg diffraction

Abstract

In-depth thickness mode ultrasonic deformations were monitored by hard (22 keV) x-ray diffraction in Bragg geometry on a Si (1 1 1) crystal. The ultrasonic thickness mode standing wave was applied with a PZT transducer coupled to the Si crystal. Measurements were taken on the time-integrated mode and also at different phases of the ultrasonic excitation in stroboscopic mode. In-depth (2 mm) x-ray stroboscopic measurements on Si showed dynamical strains that were enough to set the crystal out of the diffraction condition. This opens new possibilities for applications such as a stroboscopic gradient x-ray monochromator made out of Si at back-diffraction geometry and stress–strain curve determination of crystals.

Intrinsic spatial resolution limit of the analyzer-based X-ray phase contrast imaging technique

“…Dynamical diffraction effects always play a hole when working with perfect and nearly perfect single crystals (strained due to stress crystals). Within the dynamical condition, the penetration of X-rays respect to the surface normal during diffraction (extinction depth) in perfect single crystals does not have a constant value [1][2][3][4][5][6]. The value changes for different angular positions on the crystal diffraction condition.…”

“…The value changes for different angular positions on the crystal diffraction condition. For higher X-ray energies this value can change from few micrometers to tens of millimeters for each different crystal angular position in the small angular range of the diffraction condition [5]. Such an effect can be minimized for nearly perfect single crystals, since the strain due to stress, strongly affects the extinction [3,7].…”