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DS: Fachverband Dünne Schichten

DS 9: Thin Film Characterisation: Structure Analysis and Composition (XRD, TEM, XPS, SIMS, RBS, ...) II

DS 9.1: Talk

Monday, March 14, 2011, 12:00–12:15, GER 38

The interface of epitaxial bixbyite-structured rare-earth sesquioxides on Si(111) — •Michael Niehle, Tatsuro Watahiki, and Achim Trampert — Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin

Rare-earth oxides (RE₂O₃) are promising high-κ materials for replacement of SiO₂ as insulator in CMOS technology. They are required for further downscaling. Recently, the possibility to grow single domain RE₂O₃ in the cubic bixbyite structure on Si(111) with atomically smooth, chemically stable and crystalline interfaces has been demonstrated by molecular beam epitaxy. Understanding the interface’s microstructure is necessary to optimize growth conditions and to estimate applicability in future devices. Binary Gd₂O₃ or an adequate ternary alloy like (La,Lu)₂O₃ allow for a nearly lattice matched epitaxial growth. High-resolution transmission electron microscopy (HRTEM) is used to demonstrate that a coherently grown heterostructure is feasable. Two models for the atomic configuration at the interface are proposed and incorporated in a supercell which serves as input for HRTEM image simulation applying the multi-slice algorithm. Results of the simulation are confirmed by comparison to experimental HRTEM-images of (La_1−xLu_x)₂O₃ and (Gd_1−xLu_x)₂O₃ with x ≈ 0.5 and x ≈ 0, respectively. Competing crystal structures to the bixbyite phase are excluded.