Shape memory effect associated with martensitic transformations is of the rapidly developing field in nanotechnologies, where industrial use of systems established on that effect provide greater flexibility on the nano-devices fabrication of various kind. And therefore it addresses questions to the phase transition phenomena at low-scale and 1 arXiv:2002.07132v1 [cond-mat.mtrl-sci] 4 Feb 2020 its limitations and control. In this report, we studied the crystal structure of tapered plates of Ti 2 NiCu alloy and the temperature T c at which the martensitic transition occurs. We demonstrated that T c has a strongly descending character as a function of the plate thickness h. The critical thickness value at which the transition completely suppressed is 20 nm. Moreover, the obtained results for T c (h) curves indicate the hysteretic nature of the transition. These findings open the pathway for size limits indication and regimes modulation where the alloy-based nano-mechanical devices can be tuned to operate more efficiently.
Evanescent acoustic waves are characterized by purely imaginary or complex wavenumbers. Earlier, in 2019 by using a three dimensional (3D) finite element method (FEM) the possibility of the excitation and registration of such waves in the piezoelectric plates was theoretically shown. In this paper the set of the acoustically isolated interdigital transducers (IDTs) with the different spatial periods for excitation and registration of the evanescent acoustic wave in Y-cut X-propagation direction of lithium niobate (LiNbO3) plate was specifically calculated and produced. As a result, the possibility to excite and register the evanescent acoustic wave in the piezoelectric plates was experimentally proved for the first time. The evanescent nature of the registered wave has been established. The theoretical results turned out to be in a good agreement with the experimental ones. The influence of an infinitely thin layer with arbitrary conductivity placed on a plate surface was also investigated. It has been shown that the frequency region of an evanescent acoustic wave existence is very sensitive to the changes of the electrical boundary conditions. The results obtained may be used for the development of the method of the analysis of thin films electric properties based on the study of evanescent waves.
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