The experimental research in ultrasound impact on iron–boron pair transformation in silicon n+-p-p+ structures has revealed the decrease in concentration of pairs dissociated by light, as well as in the time of pair associations. The FeB pair changes were monitored by measuring short circuit current kinetics. The ultrasound influence was investigated at different light intensities, temperatures, frequencies, and power of acoustic waves. The possible mechanisms underlying the revealed effects were analyzed.
We report the observations of nonstructural acousto-injection luminescence (NAIL) from metallized LiNbO3 wafers. The samples under study are the X-or Y-cut wafers with the silver paste electrodes on opposite surfaces. The thickness is 1 -2 mm and other linear dimensions are in the range of 2 to 25 mm. Experiments are done at room temperature in the MHz-frequency range. Mainly the fundamental shear ultrasound modes are excited in the samples. Experimentally are measured the spectra of NAIL, photo-luminescence spectra, acousto-electric properties, X-Ray diffraction under NAIL. The NAIL and other effects appear above certain threshold amplitude of the acoustical strain that is about 10 -5 . The involvement of the microstructural non-uniformities in the effects observed is experimentally identified by the photo-luminescence of point defects taken from different micro-regions of the samples. The data are explained in terms of the considerable acoustic stresses and piezoelectric fields that are capable injecting charge carriers from the metal contacts into a crystal.
First observation of the reorientation of ferroelectric domains in the lithium niobate single crystals induced by ultrasound is reported. This effect is detected from the samples, which are treated by megahertz frequency-range ultrasound with above certain threshold amplitude at room temperature. Acoustic strain amplitude causing the domain reorientation is of the order of E10−5. The effect is directly revealed by chemically etched crystal surfaces, and independently confirmed by the acoustically induced evolution of x-ray diffraction rocking curves and changes in acousto-electric properties of the lithium niobate crystals. The physical mechanism responsible for the interaction of the domains and ultrasound can be attributed to the mechanical stress and piezoelectric field produced by a piezo-active acoustic wave. A new effect of acousto-domain interaction in ferroelectric crystals might be taken into account for a wide variety of fundamental physical phenomena involving propagation of the acoustic waves in real crystals.
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