X-RAY-DIFFRACTION UNDER SURFACE-ACOUSTIC-WAVE EXCITATION

The influence of surface acoustic waves (SAW) on grazing incidence dif fraction (GID) and high resolution X-ray diffraction in Bragg-geometry (HRXD) was investigated on high-quality YZ-cut LiNbO3 single crystals , alpha(f)-resolved GID-profiles of the (00.6) and the (00.12) reflect ion 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 wer e measured and simulated by model calculations in the framework of dyn amical diffraction theory. The lattice displacements induced by the SA W were taken into account by varying the structure factors by an addit ional Debye-Waller factor. The model calculations agree well with expe rimental results and serve as an estimate for the amplitude of the lon gitudinal component of the SAW reaching 0.04 nm for the highest excita tion voltage. It is shown that under SAW excitation, the alpha(f)-prof ile of the weaker (00.12)-reflection can also be calculated using the distorted-wave-Born-approximation, which implies a kinematic descripti on of the scattering process. Under SAW-excitation, the integrated int ensity of HRXD profiles of the (30.0) Bragg-reflection increases up to 360% of its original value. This also shows the gain of diffracted in tensity caused by reduced extinction. (C) 1998 Elsevier Science B.V. A ll rights reserved.