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ABSTRACT
Local atomic structure, chemistry and bonding at interface or grain boundary can often radically alter properties of materials. However, to catch such an impact on an atomistic level remains challenging. Although direct imaging using scanning transmission electron microscopy (STEM), the highest resolution so far [1], makes the atomic-scale characterization a reality, it is still not always straightforward especially in the case of interface, for which its own complications might cause incomplete imaging. Here we combine the advanced STEM image with additional first-principles calculations to address structure of a few technologically important interfacial systems and relate it to property on atomic level.
The interfacial systems involve functional SiC/Ti3SiC2 interface, A-site excess, nonstoichiometric oxides, La0.5Srn+1-0.5TinO3n+1, and grain boundaries in MgO. The SiC/Ti3SiC2 interface is important because it can facilitate the formation of Ohmic contact, which has been a long-standing issue limiting the device processing in SiC technology [2]. The formation of Ohmic contact is attributed to an epitaxial, coherent and atomically ordered interface, which can trap even atomic monolayer of carbon. The La0.5Srn+1-0.5TinO3n+1 oxides present an unexpected insulator-to-metal transition that is driven by an intrinsically insulating unit cell [3]. The transition is accompanied by electron localization due to the strain-induced lattice distortion, and is unusual as the majority of electrons in the conducting phase are confined forming a two dimensional electron gas. As for the MgO grain boundary, defect complexes are spontaneously clustered, affecting fundamentally intrinsic properties of MgO.
Key Words: Structure and property; interface; scanning electron microscopy; theoretical calculation
REFERENCES
1. Buban, J.P., K. Matsunaga, J. Chen, N. Shibata, W.Y. Ching, T. Yamamoto, and Y. Ikuhara. 2006. “Grain Boundary Strengthening in Alumina by Rare Earth Impurities,” Science, 311:212-215.
3. Wang, Z.C., M. Okude, M. Saito, S. Tsukimoto, A. Ohtomo, M. Tsukada, M. Kawasaki, and Y. Ikuhara. 2010. “Dimensionality-Driven Insulator-Metal Transition in A-Site Excess Non-stoichiometric Perovskites,” Nature Communications, 1:106-1-7.
Z.C. Wang*, M. Saito, S. Tsukimoto, Y. Ikuhara, WPI, Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
Y. Ikuhara, The University of Tokyo, Tokyo, Japan
*Email: zcwang@wpi-aimr.tohoku.ac.jp |
