Barium strontium titanate containing multilayer structures on metal foils

• US 20040175585A1
• Filed: 03/05/2003
• Published: 09/09/2004
• Est. Priority Date: 03/05/2003
• Status: Abandoned Application

• Current Assignee: Energenius, Inc.
• Original Assignee: Energenius, Inc.
• Inventors: Zou, Qin, Xing, George, Hirmer, Gerhard
• Application Number:
  US10/382,307
• Publication Number:
  US 20040175585A1
• Time in Patent Office: Days
• US Class Current: 428/469
• CPC Class Codes: H01G 4/1227 based on alkaline earth titanates

Abstract

The invention relates to multilayered structures having a crystalline or partially crystalline barium strontium titanate (BST) dielectric thin film composites and a metallic foil substrate. A barrier layer may be interposed between the metallic foil substrate and dielectric thin film. In addition, the invention relates to a capacitor comprised of the multilayer structure containing such composites.

Claims

1. A multilayer composite comprising:

a metallic foil substrate;

a crystalline or partly crystalline barium strontium titanate dielectric thin film.

2. The multilayer composite of claim 1, further comprising a barrier layer interposed between the metallic foil substrate and the dielectric thin film.

3. The multilayer composite of claim 1, wherein the barium strontium titanate of the formula (Ba_xSr_1-x)Ti_yO_z, wherein 0≦

x≦

1.0, y is from about 0.50 to about 0.80 to about 1.30, and z is between from about 2.5 to about 3.5.

4. The multilayer composite of claim 3, wherein x is between from about 0.1 to about 0.9.

5. The multilayer composite of claim 4, wherein x is between from about 0.4 to about 0.75 and y is between from about 0.95 to about 1.05.

6. The multilayer composite of claim 1, wherein the dielectric thin film is composed of a single or multiple layers of barium strontium titanates with x composition gradation, or composition alternation, or same composition, as depicted in either FIGS. 1(a) and (b).

7. The multilayer composite of claim 1, wherein the multilayer composite has a thickness of from about 100 nm to about 1000 nm.

8. The multilayer composite of claim 1, wherein the barium strontium titanate has a perovskite structure.

9. The multilayer composite of claim 1, wherein the barium strontium titanate is principally of random orientation and is granular crystalline.

10. The multilayer composite of claim 1, wherein the metallic foil substrate is titanium, stainless steel, brass, nickel, copper, copper nickel or silver foil.

11. The multilayer composite of claim 1, wherein the metallic foil has a thickness less than 0.1 mm.

12. The multilayer composite of claim 10, wherein the metallic foil substrate is either a flat surface, texture surface or macroporous.

13. The multilayer structure of claim 2, wherein the barrier layer is interposed between the metallic foil substrate and the crystalline barium strontium titanate dielectric thin film as depicted in either FIG. 1(c), or 1(d).

14. The multilayer composite of claim 2, wherein the barrier layer comprises a metallic layer, a conductive oxide, a dielectric layer, or a ferroelectric layer.

15. The multilayer composite of claim 14, wherein the barrier layer has a thickness of from about 10 nm to about 2000 nm.

16. The multilayer composite of claim 14, wherein:

the metallic layer is selected from platinum, titanium or nickel;

the conductive oxide layer is selected from LaNiO₃, IrO₂, RuO₂, or La_0.5Sr_0.5CoO₃;

the dielectric layer is selected from TiO₂, Ta₂O₅, or MgO; and

the ferroelectric layer is selected from barium titanate, lead titanate, or strontium titanate.

17. The multilayer structure of claim 2, wherein the barium strontium titanate dielectric thin film and metallic foil substrate comprises a parallel interconnection of dielectrics and metallic foil.

18. The multilayer structure of claim 1, wherein the temperature at which the multilayer structure is formed is less than or equal to 650°

C.

19. A capacitor comprised of the multilayer structure of claim 1.

20. The capacitor of claim 19, wherein the capacitor exhibits a capacitance density of about 200 to about 300 nF/cm² at 10 kHz frequency, a dielectric loss less than 3% at 10 kHz frequency, a leakage current density less than about 10⁻

7 A/cm at a 5V operating voltage, and a breakdown field strength of from about 750 kV/cm to about 1.2 MV/cm at room temperature.