The present invention relates to a technology to form a (001) oriented oxide thin film on a non-oriented substrate. More specifically, the present invention relates to a method of manufacturing a (001) oriented Dion-Jacobson perovskite-type oxide thin film and various perovskite-type oxide thin films oriented in a (001) direction thereon and expected to show high performance, and to a variety of perovskite-type (001) oriented multilayer films highly oriented and expected to show high performance, which are prepared by the manufacturing method.
In recent years, due to densely integrated electronic devices as well as the development of the Internet driven information society, advances in electronic materials used in the materials for a display and electronics has been an urgent issue.
Presently, there are an extremely large number of materials having a crystal lattice called a perovskite type, among the oxides used for electronic materials. Perovskite-type oxide ABO3 has a crystal structure in which the A ions (A is mainly an alkali metal, an alkaline earth metal, a rare earth element) occupy the space in the lattice formed by corner-sharing of the B ions octahedrally coordinated by oxygen (B is mainly a transition metal element) as shown in FIG. 1. Depending on the valence number and the size of the A ion, the number of the d electrons of the B ion is controlled and the distorted crystal structure may change. These various control parameters are responsible for manifestation of physical properties such as conductivity, dielectricity, emission characteristics and magnetism, which are useful for applications. Therefore, perovskite-type oxides have been extensively studied until now.
In actual applications, these oxide materials are often used in the form of a thin film. Usually, the higher the crystallinity, the better the various physical properties become. This also applies to perovskite-type oxides. An epitaxial thin film manufactured using a single crystal substrate may often show the best properties (Patent Literature 1). However, when applied as oxide materials, a single crystal substrate is rarely used, but non-oriented polycrystalline ceramics, a glass and a polycrystalline metal substrate are usually used. Therefore, in order to improve the properties of oxide thin film materials, the improvement of crystallinity, especially technologies for orientating crystal grains have been developed (Patent Literatures 2 and 3). However, because many of conventional orientation technologies mainly uses vapor phase methods such as sputtering and the ion beam assisted method, film-forming environments have limitations such as precise control of film-forming atmosphere, and there have been problems in handling of large-area thin film materials, product throughput and the like. To date, as a method of producing a certain type of metal oxide films, a method of manufacturing a metal oxide and a metal oxide thin film by excimer laser (Excimer Laser Assisted Metal Organic Deposition), which is highly on-demand film-forming technique, is known (Patent Literature 4). The method comprises the steps of: dissolving a metal organic acid salt or an organometallic compound MmRn (provided that M=a group 4b element of Si, Ge, Sn, Pb, a group 6a element of Cr, Mo, W, a group 7a element of Mn, Tc, Re; R=an alkyl group such as CH3, C2H5, C3H7, C4H9, or a carboxyl group such as CH3COO−, C2H5COO−, C3H7COO−, C4H9COO−, or a carbonyl group such as CO; wherein m, n are integers) in a soluble solvent; alternatively if a liquid, using it as is; dispersively applying the solution on the substrate; and then irradiating the substrate with the excimer laser in air.
The document describes a method of manufacturing a metal oxide product, comprising the steps of: forming a metal oxide on a substrate by dissolving a metal organic compound in a solvent to form a solution; applying the solution to the substrate; then drying the substrate; and irradiating the substrate with a laser beam of a wavelength of 400 nm or less, for example, excimer laser selected from ArF, KrF, XeCl, XeF, F2. The document also describes that the irradiation with a laser beam having a wavelength of 400 nm or less is performed in multiple steps where at the first step of the irradiation, the beam is weak enough not to result in complete decomposition of the metal organic compound and the subsequent irradiation is strong enough to allow the compound to be converted into an oxide. Further, it is also known that the metal organic compound is a compound of two or more components comprising different metals; and the resulting metal oxide is a composite metal oxide comprising different metals; and the metal in the metal organic salt is selected from the group consisting of iron, indium, tin, zirconium, cobalt, iron, nickel and lead.
For a perovskite-type oxide, known is a method of manufacturing a composite oxide thin film, comprising the steps of: applying a precursor coating solution containing raw materials of respective oxides of La, Mn and Ca, Sr or Ba on a surface of a coating target to obtain a film; then crystallizing the thin film formed on the coating target to form a composite oxide film (which does not show superconductivity) represented by the composition formula (La1−xMx) MnO3−δ (M: Ca, Sr, Ba, 0.09≦x≦0.50), wherein after applying the precursor coating solution on the surface of the coating target to obtain the film, the thin film formed on the surface of the coating target is irradiated with light having a wavelength of 360 nm or less to crystallize the thin film (Patent Literature 5). The document describes that as a light source for irradiating the thin film formed on the surface of the coating target, ArF excimer laser, KrF excimer laser, XeCl excimer laser, XeF excimer laser, third harmonic generation of YAG laser, or fourth harmonic generation of YAG laser is used, and the precursor coating solution to be applied on the surface of the coating target is adjusted by mixing an alkanolamine coordination compound of La, a carboxylate of Mn, and a metal or alkoxide of M in a primary alcohol having 1 to 4 carbon atoms to allow a reaction. For a perovskite-type oxide thin film which is a phosphor, in addition to a simple perovskite structure of the ABO3 type, the document also describes a method of manufacturing a thin film of a perovskite-related structure called the Dion-Jacobson phase represented by the composition formula A(Bn−1MnO3n+1) (wherein n is a natural number of 2 or greater; A is an alkali metal ion; B comprises a trivalent rare earth ion, Bi, a bivalent alkaline earth metal ion or a monovalent alkali metal ion; and M comprises Nb and Ta; wherein Ti may be solid soluted), or the Ruddlesden-Popper phase represented by the composition formula A2 (Bn−1MnO3n+1) (Patent Literature 6).    Patent Literature 1: Japanese Patent Laid-Open No. 2009-70926    Patent Literature 2: Japanese Patent Laid-Open No. 2004-530046    Patent Literature 3: Japanese Patent Laid-Open No. S63-236793    Patent Literature 4: Japanese Patent Laid-Open No. 2001-31417    Patent Literature 5: Japanese Patent Laid-Open No. 2000-256862    Patent Literature 6: Japanese Patent Laid-Open No. 2008-75073
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