Surface electron states produced by a Rayleigh wave
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C PROPERTIES OF SOLIDS
Surface Electron States Produced by a Rayleigh Wave S. I. Khankinaa, V. M. Yakovenkoa, *, and I. V. Yakovenkob a
Institute of Radiophysics and Electronics, National Academy of Sciences of Ukraine, pr. Lenina 14, Kharkov, 61085 Ukraine b Molniya Research and Design Institute, Ministry of Education and Science of Ukraine, Kharkov, 61013 Ukraine *e-mail: [email protected] Received May 29, 2006
Abstract—The electronic properties of a semiconductor bounded by an uneven surface representing an infinitely high potential barrier are investigated. The surface irregularities are produced by a Rayleigh acoustic wave. It is shown that, on the boundary of a semiconductor, surface electron states (waves) may arise whose dispersion laws are obtained under the conditions when conduction electrons are located either in or outside the field of the acoustic wave. Existence domains of surface electron states are found that are distinguished by their physical properties. These domains are separated by a band gap whose width is determined by the height of irregularities. PACS numbers: 73.20.-r, 73.21.-b DOI: 10.1134/S1063776107030132
1. INTRODUCTION The investigation of the physical properties of the surface of a solid has always received a great deal of attention because the surface is an interesting and attractive object for science and technology. The study of electronic processes that occur on the surface of semiconductors, in particular, the excitation mechanisms of surface electron states attracts interest in modern micro and nanoelectronics. The possibility of existence of surface electron states in bounded crystals was first demonstrated as early as 1932 by Tamm [1]. Later, in 1939, the conditions under which these states arise were investigated in detail by Shockly [2]. These results were generalized by Lifshits and Pekar [3] in 1955 for nonpolar oscillations in a lattice. In the survey [3], these authors showed that there is a close analogy between the theory of surface electron states and the theory of surface vibrations of atoms in a crystalline lattice. In the one-dimensional case, one of the branches of the energy spectrum turns into the Rayleigh wave branch, while the other represent surface optical branches. In 1965, Kliwer and Fucks revealed a similarity between surface electron states and surface plasma oscillations [4]. In 1975, Agranovich, Antonyuk, and Mal’shukov investigated the processes of localization of electron–hole pairs (excitons) associated with bending vibrations of the surface [5]. The authors of [5] (see also [6]) showed that, in quasi-one-dimensional and quasi-two-dimensional semiconductors, the Coulomb attraction between electrons and holes located in different planes or threads leads to the deformation of the latter. As a result, an exciton is self-localized as a whole in the region of the deformation produced. This phenom-
enon may lead to the instability of the ground state of the semiconductor. A comprehensive survey of works devoted to the theoretical and experimental
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