Coherent and diffuse X-ray scattering in crystals modulated by a surface acoustic wave

Abstract

Equations describing the coherent and diffuse scattering in a crystal modulated by a surface acoustic wave (SAW) are derived using the dynamical X‐ray diffraction theory. The effect of depth attenuation of the Rayleigh surface wave amplitude on the crystal rocking curve profiles is investigated. Results of the numerical simulation of the dynamical diffraction in a mosaic crystal modulated by a SAW, taking into account a block size distribution, are presented. It is shown that the diffuse scattering is distributed in the reciprocal space not only in the vicinity of the main diffraction peak but also about the satellite diffraction peaks, and this distribution depends on the size fluctuations of the crystal defects. Theoretical reciprocal space maps and rocking curves are compared with the corresponding experimental results.

On the theory of X-ray acoustic resonance in the Bragg geometry

“…The procedure for deriving the equations describ ing X ray diffraction by a laterally modulated crystal in triple crystal diffractometry is described in detail in [14]. It was shown that if a plane X ray wave is incident on the crystal, the diffracted beam has a nonzero amplitude for the values of q x that are multiples of the wavenumber κ s of the lateral modulation (i.e., for val ues of = nκ, where n = 0, ±1, ±2, … are the numbers of diffraction orders).…”

“…Using the boundary conditions, we can write the solution for a Rayleigh surface wave in the form [14,16] (1)…”

“…An impor tant aspect of the theory being developed is that an ultrasonic perturbation is treated as a Rayleigh surface wave. In addition, the theory is constructed as applied to the method of high resolution triple axial (triple crystal) diffractometry, which makes it possible to ana lyze reciprocal space maps [14,15]. Such an approach makes it possible to perform quantitative analysis of the effect of acoustic fields on X ray diffraction in an …”

Effect of the ultrasonic frequency on the multiple X-ray scattering from a LiNbO3 crystal modulated by a surface acoustic wave

“…X ray diffraction, which is highly sensitive to lattice strain, is successfully used to study acoustic waves in near surface layers of crystals [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The specific features of SAW propagation in solids were monitored by X ray topography [3][4][5], grazing X ray diffraction [6,7], and double and triple crystal X ray diffraction [8][9][10][11][12][13][14][15][16][17]. Various effects accompanying X ray scattering in SAW modulated crystals were described in terms of the dynamical [11][12]18] and kinematical [10,13,19] diffraction theories.…”

Observation of sagittal X-ray diffraction by surface acoustic waves in Bragg geometry

“…Different materials, such as LiNbO 3 , have been used as a carrier of the SAWs in different crystallographic geometries (Roshchupkin et al, 1992(Roshchupkin et al, , 1998Tucoulou et al, 2001). Appropriate theoretical models have been developed for the explanation of diffraction properties, especially the dependence of the diffracted intensity on the amplitude of the high-frequency signal applied to the device for the SAWs' excitation (Punegov et al, 2010;Schelokov et al, 2004). The first example of such a device was reported by Tucoulou et al (1997), who demonstrated for the first time the feasibility of a fast diffraction chopper for synchrotron radiation single-bunch pulses.…”