Yuri V. Gulyaev

Surface Acoustic Waves in Inhomogeneous Media

This monograph covers important problems caused by the interaction of different types of surface acoustic waves with surface inhomogeneities. The problem of surface acoustic wave interaction with periodic topographic gratings, widely used in filters and resonators, is given careful consideration. The most important results of surface wave scattering by local defects such as grooves, random roughness and elastic wedges are described. Different theoretical approaches and practical rules for solving the surface wave problems are also presented.

Acoustoelectronics: history, present state, and new ideas for a new era

The application of high-frequency acoustic devices to the enhancement of electronics saw an extraordinary growth in both Eastern and Western countries in the sixties and seventies. A major impetus for these developments was the tension existing between the Soviet Bloc countries in the east and the former Allied countries in the west. Government military spending on both sides provided funding to explore new acoustoelectronic concepts in universities, institutes, and major defense companies. The direct exchange of visits between scientists and engineers of the East and West was limited until the 1980s, when travel restrictions were lifted on both sides and authors that has previously only been names in the open literature became face-to-face contacts and enjoyed exchanges at conferences of mutual interest. This resulted in a new era of cooperative work between the East and West and a large number of device applications that are seen in electronic systems around the world today. This paper explores the major acoustoelectronic developments of the sixties and seventies from an eastern and western perspective.

Impedance Method in the Theory of Surface Waves in Inhomogeneous and Layered Media

This chapter deals with the impedance method for analysing surface waves in inhomogeneous piezoelectric structures. This analysis is based on the following arguments. We do not construct wave field solutions in the whole inhomogeneous structure by joining these fields on boundaries of irregularity, but consider only the fields on a certain convenient plane and describe the half-spaces (bordering this plane) by surface impedance matrices; the form of these matrices is defined not only by the medium character, but also by the properties of scattering inhomogeneities. This approach is quite natural because of the plane character of typical structures and allows us to split a complicated boundary-value problem of obtaining fields into two simpler independent problems: a problem of finding the surface impedances independent of fields and a problem of solving equations of motion on a plane with given impedances of adjusting half-spaces. And in this case a minimal number of variables is used for the description of both problems, and the problems themselves are posed in a compact form convenient for constructing both exact and approximate solutions by means of methods of perturbations.

Scattering of Surface Waves by Local Irregularities

Here the impedance approach to the analysis of wave propagation in inhomogeneous media presented in the previous chapter is used to investigate the scattering of these waves by a specific local boundary or bulk irregularities. The boundary irregularities of small height or depth in the form of groups of extended projections or hollows are the main functional elements of a large class of signal processing acoustoelectronic devices with reflecting gratings [4.1, 2]; band-pass or dispersion filters [4.3, 4], resonators [4.5], structural transducers [4.6, 7]. The boundary irregularities of finite dimensions are used as elements of two-periodic structures [4.8, 9], and the analysis of their scattering properties is also necessary for investigation of the surface wave propagation along rough surfaces [4.10-12]. The parameters of surface wave scattering by bulk inclusions in the acoustic lines material are used in seismology [4.13].

Interaction Between Electrode Structures and Surface Waves in Piezoelectrics

A system of thin electrodes on a piezoelectric surface is one of the main elements of all practical acoustoelectronic SAW signal processing devices [14.1-3]. Because the boundary value problem describing the interaction between SAW and electrode structures is extremely complicated and at the same time very important for practical applications, a great deal of literature has been occupied with this problem for different model assumptions and approximations. Here we list the main papers where the known calculation methods are given.

Mutual Transformation of Bulk and Surface Acoustic Waves by Periodic Irregularities

If the frequency becomes greater than the Bragg frequency, for a certain critical frequency \( {f_{sc}} = 2{f_0}{v_t}/({v_R}{v_t}) \)(vt is the shear bulk wave velocity), the surface acoustic waves begin to scatter into bulk waves by the surface irregularities (Fig. 8.la). First, a shear bulk wave scattered backwards appears, and if the frequency continues to grow, a longitudinal wave appears.For λ=l the scattered waves propagate along the normal to the surface (Fig. 8.lb). If the wavelength continues to decrease (Fig. 8.1c), some scattered waves appear.

Basic Types of Surface Acoustic Waves in Solids

At present there exist about ten thousand books and papers dealing with the subject of surface acoustic waves in solids first described by Rayleigh in 1885 [1.1], and it is impossible even to mention all of them. But it is hardly necessary to do this, since there exist a great number of reviews [1.2-5] and monographs [1.6-18] concerning both the properties of surface acoustic waves and their application in special signal processing devices. Therefore, in this review chapter we present only the basic properties of the Rayleigh waves, Gulyaev—Bleustein waves, and waves of certain other types that are very often referred to in original chapters of this monograph.

Standardization of Information Technologies in Fundamental Research in Russia

This article presents the history, current state, and directions of research and implementation of open information system technologies in the Russian Academy of Sciences. Since 1993 when work on the systematized application of open systems principles was initiated by the Russian Academy of Sciences, a number of important results could be achieved. The authors now define directions for the further development of open systems technology - formalization of available approaches, better integration with other IT technologies, and expansion of scope from nanotechnologies up to GRID-technologies.

P1L-3 Characteristics of LLSAW in Periodical Systems of Layered Electrodes

Resonant characteristics of longitudinal leaky surface acoustic waves (LLSAW) in infinite periodic interdigital transducers (IDT) with layered electrodes are calculated. An electrode is assumed to be consisted of two parts - under-layer of crystal material and top layer of aluminum. The simplest structure is a periodic array of grooves of rectangular shape etched in the substrate with aluminum (AL) electrodes positioned on tops between adjacent grooves. Such a structure on YZ-cut of-lithium niobate (YZ-LN) shows calculated quality factors of two times larger as compared to AL electrodes on smooth surface with dissipation in electrodes taken into account. As an additional combination the under-layer of titanium-dioxide (TiO2)-AL is considered. This combination shows quality factors approximately three times larger than the structure with AL electrodes on smooth surface

Waves in a Half-space with Account of Surface Effects

Up to this point we considered the surface acoustic waves propagating in one or another inhomogeneous medium and did not concern ourselves with either the methods for producing the solid surfaces or their influence on the surface wave properties. Meanwhile, even in the case when a free surface is formed by cutting along the cleavage planes, i.e., when the surface is perfect, there is always a near-surface imperfect layer with properties which differ from those of the bulk medium since the upper surface atoms are under different conditions than those in the bulk media [15.1-4]. In this case there is a stressed state within the layer, and the near-surface atoms are characterized by other constants of elastic interaction. The thickness of a disturbed near-surface layer usually has the order of interatomic distance in a crystal lattice, i.e., is equal to 2-5 A.