Perovskite oxide film and ferroelectric film using the same, ferroelectric device, and method for manufacturing perovskite oxide film
A perovskite oxide film is formed on a substrate, in which the perovskite oxide film has an average film thickness of not less than 5 μm and includes a perovskite oxide represented by a general formula (P) given below: (K 1-w-x ,A w ,B x )(Nb 1-y-z ,C y ,D z )O 3 (P), where: 0<w<1.0, 0≦x≦0.2, 0≦y<1.0, 0≦z≦0.2, 0<w+x<1.0, A is an A-site element having an ionic valence of 1 other than K, B is an A-site element, C is a B-site element having an ionic valence of 5 , D is a B-site element, each of A to D is one kind or a plurality of kinds of metal elements.
1. A perovskite oxide film formed on a substrate, wherein the film has an average film thickness of not less than 5 μm and includes a perovskite oxide represented by a general formula (P) given below:
(K 1-w-x ,A w ,B x )(Nb 1-y-z ,C y ,D z )O 3 (P),
where: 0<w<1.0, 0≦x≦0.2, 0≦y<1.0, 0≦z≦0.2, 0<w+x<1.0; A is an A-site element having an ionic valence of 1 other than K, B is an A-site element, C is a B-site element having an ionic valence of 5, and D is a B-site element; each of A to D is one kind or a plurality of kinds of metal elements; and although 1:3 is a standard ratio of the total number of moles of the A-site elements and of the total number of moles of the B-site elements to the number of moles of the oxygen atoms, the ratio may be deviated from 1:3 within a range in which a perovskite structure can be formed.
2. The perovskite oxide film of claim 1 , wherein the substrate has a lattice constant of 0.37 to 0.425 nm.
3. The perovskite oxide film of claim 1 , wherein the substrate includes, as a major component, a compound selected from the group consisting of strontium titanate, potassium tantalite, calcium fluoride, scandium perovskite oxide, nickel perovskite oxide, and yttria-stabilized zirconia.
4. The perovskite oxide film of claim 1 , wherein the substrate is a metal substrate.
5. The perovskite oxide film of claim 1 , wherein the substrate is a resin substrate.
6. The perovskite oxide film of claim 1 , wherein the element A is at least one kind of metal element selected from the group consisting of Li, Na, Rb, and Cs.
7. The perovskite oxide film of claim 1 , wherein the element B is at least one kind of metal element selected from the group consisting of Ca, Sr, Ba, Sn, Pb, Y, La, and Bi.
8. The perovskite oxide film of claim 1 , wherein the element C is at least one kind of metal element selected from the group consisting of V, Sb, and Ta.
9. The perovskite oxide film of claim 1 , wherein the element D is at least one kind of metal element selected from the group consisting of Ti, Mn, Cr, Fe, Co, Ni, Cu, and Zn.
10. The perovskite oxide film of claim 1 , wherein the film thickness is not less than 10 μm.
11. The perovskite oxide film of claim 10 , wherein the film thickness is not less than 50 μm.
12. The perovskite oxide film of claim 1 , wherein the film has a crystalline orientation.
13. The perovskite oxide film of claim 12 , wherein the film is an epitaxial film.
14. The perovskite oxide film of claim 1 , wherein the film is a ferroelectric film.
15. A ferroelectric device, comprising a substrate, the perovskite oxide film of claim 14 , and a pair of electrodes for applying an electric field to the perovskite oxide film.
16. The ferroelectric device of claim 15 , wherein the substrate has a lattice constant of 0.37 to 0.425 nm.
17. The ferroelectric device of claim 15 , wherein:
the pair of electrodes comprises a back contact electrode formed between the substrate and the perovskite oxide film and an upper electrode formed on the perovskite oxide film; and
the back contact electrode includes, as a major component, Pt, LaNiO 3 , a lanthanum layered perovskite compound, or SrRuO 3 .
18. The ferroelectric device of claim 15 , wherein the substrate is a metal substrate or a resin substrate and the ferroelectric device comprises a buffer layer between the substrate and the back contact electrode.
19. A perovskite oxide film forming method for forming the perovskite oxide film of claim 1 , wherein the film forming is performed by hydrothermal synthesis.
20. The perovskite oxide film forming method of claim 19 , wherein the film forming is performed at a film forming temperature of not greater than 300° C.