Processing of epitaxial LiMn 2 O 4 thin film on MgO(110) through metalorganic precursor
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Koichi Kikuta and Shin-ichi Hirano Graduate School of Engineering, Nagoyua University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan (Received 21 April 2000; accepted 6 September 2000)
Epitaxial LiMn2O4 was successfully synthesized by coating a [Li–Mn–O] metalorganic precursor solution onto MgO (110) substrates at temperatures as low as 350 °C. Cross-sectional transmission electron microscopy observation revealed that the orientation relationship between LiMn2O4 and MgO was (111)LiMn2O4//(111)MgO, (110)LiMn2O4//(110)MgO, and [112]LiMn2O4//[112]MgO, which resulted in the (111)LiMn2O4 planes growing perpendicular to the surface plane of MgO. The interface structure consisted of (111) layers of Mn atoms in the LiMn2O4 crystal aligned with the Mg atoms in the (111) planes of the MgO substrate when viewed along the [112] direction.
I. INTRODUCTION
In recent years, there has been considerable interest in high energy density rechargeable batteries for use in electronic devices. The increase in demand for lightweight portable equipment means that microbatteries must be developed as power sources. Intensive efforts have been directed at fabricating the cell components of these all-solid-state microbatteries, particularly by thin film techniques. LiMn2O4 spinel,1–10 the layered compound LiCoO211,12 and LiNiO213–15 have been extensively investigated for use as cathodic materials in lithium secondary batteries because they all possess the characteristic electrochemical property of intercalation and deintercalation of lithium ions into their crystal structure. In each case, it has been demonstrated that the lithium ions are reversibly inserted between the layered planes. To facilitate the intercalation process in microbatteries, it is beneficial to prepare a lithiated intercalation cathode film with the intercalated plane perpendicular to the surface of the substrate. Several lithium intercalation compounds have been fabricated in thin film form by techniques such as chemical vapor deposition, evaporation, and sputtering.16–23 These thin films all have an amorphous or random polycrystalline structure, since a microstructually controlled
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Present address: Japan Fine Ceramics Center, Research and Development Laboratory, 2-4-1 Mutsuno, Atsuta-ku, Nagoya, 4568587, Japan.
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J. Mater. Res., Vol. 15, No. 12, Dec 2000 Downloaded: 18 Mar 2015
thin film has not yet been prepared. Chemical processing via a solution route using metalorganic precursors is advantageous for preparing thin films with desired stoichiometry, controlled purity, and compositional homogeneity.24 If an appropriate precursor solution and substrate are chosen in terms of the lattice parameter and crystal structure of the desired compound, microstructually controlled or highly oriented thin films can be fabricated. In this study, we report on the preparation of lithium manganese oxide thin film using a metalorganic precursor solution. In this process, we focus on the fabrication of an epitaxial thin film with the (111) interc
