Interface structure of AlN/TiN/MgO(001) prepared by molecular beam epitaxy
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Interface structure of AlN/TiN/MgO(001) prepared by molecular beam epitaxy X.L. Ma,a) Y. Sugawara, and N. Shibata Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, 456 Nagoya, Japan
Y. Ikuhara Department of Materials Science, University of Tokyo, 113 Tokyo, Japan (Received 15 April 1999; accepted 29 September 1999)
Thin AlN films were grown by molecular beam epitaxy on MgO(001) substrate with a thin TiN buffer layer. The as-prepared AlN/TiN/MgO(001) interfaces have been characterized by cross-sectional high-resolution electron microscopy (HREM). It is found that the thin TiN buffer layer is epitaxially grown on the MgO(001) substrate and hexagonal AlN epitaxially on the as-received TiN(001). Based on the growth orientation relationship and HREM images, atomistic structure models for the AlN/TiN interface are proposed, image simulated, and compared with experimental images.
I. INTRODUCTION
Much attention has been paid to the film growth of AlN because of its attractive properties, such as high thermal conductivity, chemical inertness, electrical insulation, large energy gap of 6.2 eV, and high surface acoustic wave velocity.1–3 It is a potential candidate for applications in microelectronics ranging from optoelectronic and high-temperature devices to electronics packaging. Thin films of the hexagonal AlN have been epitaxially prepared on several substrates such as Si,4–11 SiC,12–17 sapphire,9,18,19 and GaAs.20 However, in most cases, the as-prepared films are polycrystalline. Details of the growth of these polycrystals on various substrates are not experimentally clarified yet, although the orientation relationship between two different crystals can be theoretically predicted.21 In our recent study of the AlN film grown on MgO(001) with a TiN buffer layer,22 we reported the orientation relationships between the asgrown films and MgO substrate. We also rationalized the experimental observation by theoretical calculations on the basis of three-dimensional lattice continuity. The growth of hexagonal AlN on the substrate was dominated by the orientation relationship (1210)AlN//(110)TiN// (110)MgO, and (0001)AlN//(001)TiN//(001)MgO, although another oriented growth with less frequency was also observed. a)
Address all correspondence to this author. Present address: Department of Materials Science, School of Engineering, University of Tokyo, 113 Tokyo, Japan. e-mail: [email protected] J. Mater. Res., Vol. 14, No. 12, Dec 1999
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Interfacial structure is of importance because of its potential influence on electronic properties. Interfacial structure contains two aspects from the viewpoint of crystallography: first, the orientation relationship between film and substrate; and second, the atomistic bonding between two materials across the interface. Previous work on AlN films grown on various substrates only focused on the orientation relationships between the epitaxial film and employed substrate. Few pape
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