Ferroelectric recording medium and ferroelectric storage apparatus
A ferroelectric recording medium includes an electrode layer, a ferroelectric recording layer, and a protection layer formed in this order on a substrate, wherein the ferroelectric recording layer includes a ferroelectric layer, and a lattice constant of a material constituting the ferroelectric layer and a lattice constant of a material constituting the electrode layer or the substrate are lattice-matched within a range of ±10%.
1. A ferroelectric recording medium including an electrode layer, a ferroelectric recording layer, and a protection layer formed in this order on a substrate,
wherein the ferroelectric recording layer includes a ferroelectric layer and a paraelectric layer, the paraelectric layer being disposed between the ferroelectric layer and the electrode layer,
the paraelectric layer includes one or more paraelectrics selected from the group comprising oxide, nitride, carbide, boride, and silicide,
a lattice constant of a material constituting the ferroelectric layer and a lattice constant of a material constituting the electrode layer or the substrate are lattice-matched within a range of ±10%, and
a lattice constant of a paraelectric constituting the paraelectric layer and a lattice constant of a ferroelectric constituting the ferroelectric layer are lattice-matched within a range of ±10%.
2. The ferroelectric recording medium according to claim 1 , wherein the ferroelectric layer is a single-crystal film.
3. The ferroelectric recording medium according to claim 1 , wherein the ferroelectric layer has an amorphous structure with short-range order,
a distance of the short-range order is equal to or less than 2 nm, and
a lattice constant of the amorphous structure and the lattice constant of the material constituting the substrate are lattice-matched within a range of ±10%.
4. The ferroelectric recording medium according to claim 1 , wherein the substrate includes silicon, and
the ferroelectric layer includes hafnium oxide.
5. The ferroelectric recording medium according to claim 4 , wherein the ferroelectric layer includes a mixture including hafnium oxide and one or more additives selected from the group comprising silicon, aluminum, gadolinium, yttrium, lanthanum, and strontium, or a mixed crystal Hf x Zr 1-x O 2 , where x is 0.3 to 0.6, including hafnium oxide and zirconium dioxide.
6. The ferroelectric recording medium according to claim 5 , wherein a content of the one or more additives is 1 atom % to 20 atom %.
7. The ferroelectric recording medium according to claim 1 , wherein a film thickness of the paraelectric layer is 1 nm to 100 nm.
8. The ferroelectric recording medium according to claim 1 , wherein a film thickness of the paraelectric layer is 1 nm to 30 nm,
a film thickness of the ferroelectric layer is 1 nm to 30 nm,
the film thickness of the paraelectric layer is equal to or less than the film thickness of the ferroelectric layer, and
a difference between the film thickness of the paraelectric layer and the film thickness of the ferroelectric layer is equal to or less than 10 nm.
9. A ferroelectric storage apparatus comprising:
the ferroelectric recording medium of claim 1 ;
a conductive probe configured to write information to and read information from the ferroelectric recording medium;
a probe slider configured to cause the conductive probe to travel by floating above a surface of the ferroelectric recording medium;
a ferroelectric recording medium driving unit configured to rotate the ferroelectric recording medium; and
a recording-and-reproduction signal processing unit configured to process a write signal and a read signal of information transmitted to and received from the conductive probe.