Surface Phases of Metals on Silicon as Material for Surface Engineering
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Surface Phases of Metals on Silicon as Material for Surface Engineering
Alexander A. Saranin, Sergey V. Rizhkov, Dmitriy A. Tsukanov, Victor G. Lifshits Institute of Automation and Control Processes, FEB RAS, Vladivostok, Russia Andrey V. Zotov Vladivostok State University, Vladivostok, Russia Kenjiro Oura Department of Electronic Engineering, Osaka University, Suita, Osaka 565, Japan Shuji Hasegawa Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan ABSTRACT To study structural and transport properties of the surface phases on silicon, a number of adsorbate/silicon systems on Si(100) and Si(111) surfaces has been investigated using scanning tunneling microscopy (STM), reflection-high-energy-electron diffraction (RHEED) and in-situ electrical resistance measurements. Results of investigations of formation and electrical properties of Si-Al, Si-Na, Si-Ag and Si-In surface structure are presented. INTRODUCTION The processes on the surface (like those in the bulk) are also directed to the establishment the thermodynamic equilibrium state of the system. So, all processes at the surface come to surface phases’ formation. One can consider Si surface phases as an extremely thin layer in the thermodynamic equilibrium state with crystalline substrate (with the layer thickness of the order of monoatomic layer) with composition, structure, and properties definitely differ from those of the corresponding planes of bulk substrate and bulk adsorbate, as well as bulk adsorbate compound, if available. In other words, the surface phase on Si is a specific 2D-substrate with its own characteristics [1, 2]. A number of Si-Me surface phases formation has been found to involve a substantial redistribution in Si substarte's top layer (i.e. surface Si mass transport) because Si-Me surface phases consist from adsorbate atoms and Si atoms [for example, see 3, 4]. This phenomenon influences a surface morphology decreasing electrical conductivity of substrate [5]. Using this phenomenon, reversibly, the surface morphology can be controlled by adding small amount of Si atoms prior to making the Si-Me phase. For example, if one provides additional amount of Si, which is exactly necessary for the surface phase formation, the substrate Si atoms do not need to be incorporated, resulting in the step-terrace configuration kept unchanged at the surface phase formation. Results of in situ surface resistance measurements for a number of Si-Me surface structures depending on surface phases' composition and surface morphology are presented in this paper. EXPERIMENTAL Experiments were carried out in separate UHV chambers with base pressure of less than 2 x 10-10 Torr, one of which was for in-situ electrical resistance measurements at low temperatures combined with RHEED, and the other was for STM with RHEED. The substrates used were P-doped Si(100) (35-40 Ohm⋅cm) and Si(111) (50 Ohm⋅cm) wafers. An atomically clean Si(100)2x1 and Si(111)7x7 surfaces P5.28.1
were prepared in situ by direct heating up to 1250°C. Aluminu
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