X-Ray diffraction under surface acoustic wave excitation

Abstract

The influence of surface acoustic waves (SAW) on grazing incidence diffraction (GID) and high resolution X-ray diffraction in Bragg-geometry (HRXD) was investigated on high-quality YZ-cut LiNbO 3 single crystals. α f-resolved GID-profiles of the (00.6) and the (00.12) reflection as a function of the SAW excitation voltages show both substantial increase of the diffracted intensity (up to 100%) and a simultaneous sharpening of the profiles. Profiles for different incident angles were measured and simulated by model calculations in the framework of dynamical diffraction theory. The lattice displacements induced by the SAW were taken into account by varying the structure factors by an additional Debye–Waller factor. The model calculations agree well with experimental results and serve as an estimate for the amplitude of the longitudinal component of the SAW reaching 0.04 nm for the highest excitation voltage. It is shown that under SAW excitation, the α f-profile of the weaker (00.12)-reflection can also be calculated using the distorted-wave-Born-approximation, which implies a kinematic description of the scattering process. Under SAW-excitation, the integrated intensity of HRXD profiles of the (30.0) Bragg-reflection increases up to 360% of its original value. This also shows the gain of diffracted intensity caused by reduced extinction.