A High-Temperature STM-Study of Iron Silicide Formation on High Index Silicon Surfaces
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A High-Temperature STM-Study of Iron Silicide Formation on High Index Silicon Surfaces
Martin Kneppe, Evgueni Kot, Volker Dorna, and Ulrich Köhler
Experimentalphysik IV, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
ABSTRACT
The nucleation and initial growth of iron silicide on Si(113), Si(5 5 12) and Si(114) is studied using high temperature STM. During MBE and gas source deposition (precursor Fe(CO)5 ) STM-"movies" at temperatures up to 600◦ C directly show the kinetics of silicide formation on the surface. A complete 2D-wetting layer is formed on all vicinal surfaces for temperatures below 510◦ C. A chain-like silicide structure with a mixture of dierent periodicities (4×n), with n ranging from 2-6, is found. Above one monolayer growth proceeds with anisotropic 3D-silicide-islands. The wetting layer was found to be only metastable at lower growth temperature. At temperatures above 510◦ C the 2D-silicide layer does not wet the substrate anymore. In the equilibrium growth mode, 3D-islands directly grow on the bare Si-substrate. The anisotropy of the 3D-islands is extremly temperature dependent resulting in an aspect ratio up to 50 at 600◦ C. Especially on Si(114) a one-dimensionally nanostructured silicide layer can be grown in this way. A lateral spreading of the 3Dislands forming an interconnected silicide layer is achieved on Si(113) by a stochiometric codeposition of Fe and Si. INTRODUCTION
Thin epitaxial lms are becoming more and more important in modern semiconductor technology due to the lateral and vertical decrease in structure size. Silicide layers are often unintentionally present as an interface layer in between a metal and the silicon substrate. Some silicides, as iron silicide, on the other hand, provide interesting physical properties which may be useful in semiconductor technology. A precise control of the layer morphology is an essential step towards possible applications. In the case of iron silicide on Si(111) three-dimensional pyramidal islands already form in the submonolayer range. The sidewalls of these islands are tilted about 30◦ towards the [001]-direction against the (111)-substrate. A number of stable silicon surfaces have been found in that direction [2] with Si(113) as one of the most stable of these faces. The atomic structure of this silicon face is explained by a model containing a subsurface self-interstitial [3] but there is still little knowledge about the growth behavior on this surface. Homo-epitaxial growth on Si(113) shows a strong anisotropy in the island shape [4, 5] which leads to nearly one-dimensional structures along [1¯10]. Another possible application of Si(113) is given by its self organized structuring due to faceting when the surface is annealed[1]. For most technological applications it is important to inhibit rough interfaces and provide wetting of the surface with the silicide. Because of the silicide surfaces found on Si(111) being nearly parallel to Si(113) a closer look at the P10.2.1
silicide growth on neighboring stable phases Si(114) and Si(5
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