Thin film ferroelectric composites and method of making

• US 5,846,893 A
• Filed: 12/08/1995
• Issued: 12/08/1998
• Est. Priority Date: 12/08/1995
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: The United States of America As Represented By The Secretary of Agriculture
• Inventors: Sengupta, Somnath, Sengupta, Louise
• Primary Examiner(s): JONES, DEBORAH D
• Application Number:
  US08/569,470
• Time in Patent Office: 1,096 Days
• Field of Search: 501/137, 501/108, 501/119, 501/121
• US Class Current: 501/137
• CPC Class Codes: C04B 35/465 based on alkaline earth metal titanates
• CPC Class Codes: C04B 35/62222 obtaining ceramic coatings coating of mortars, concrete, artificial or natural stone or ceramics C04B41/45; laminated ceramic products B32B18/00; coating metallic materials C23; coating of glass C03C17/00, applying ceramic coatings on silicon for semi-conductor purposes H01L
• CPC Class Codes: C23C 14/08 Oxides C23C14/10 takes precedence
• CPC Class Codes: C23C 14/28 by wave energy or particle radiation C23C14/32 - C23C14/48 take precedence
• CPC Class Codes: H01Q 3/44 varying the electric or magnetic characteristics of reflecting, refracting, or diffracting devices associated with the radiating element

Abstract

A thin film composite material comprises barium strontium titanate represented as Ba_1-x Sr_x TiO₃ wherein x is greater than 0.0 but less than or equal to 0.75 and a magnesia-based compound such as MgZrO₃, MgTiO₃, MgAl₂ O₄ and mixtures thereof. The thin film ferroelectric composite is made using pulsed laser deposition and exhibits high tunability, low loss and a low dielectric constant.

Claims

1. A thin film ferrolectric composite material comprising:

barium strontium titanate, said barium strontium titanate represented as Ba_1-x Sr_x TiO₃, wherein x is greater then 0.0 but less than or equal to 0.75; and

a magnesia-based compound;

wherein the weight ratio of said barium strontium titanate and said magnesia based compound ranges from approximately 99%-40% barium strontium titanate to approximately 1%-60% magnesia based compound in effective amounts to provide a composite having a low dielectric constant, low loss tangent and high tunability.

2. The thin film ferroelectric composite material of claim 1, wherein said barium strontium titanate is Ba_1-x Sr_x TiO₃, wherein x=0.35 to 0.40.

3. The thin film composite material of claim 1, wherein said magnesia based compound is selected from the group consisting of MgZrO₃, MgTiO₃, MgAl₂ O₄, mixtures thereof.

4. The thin film of claim 3, wherein said compound is MgTiO₃.

5. The thin film of claim 3, wherein said compound is MgZrO₃.

6. The thin film of claim 3, wherein said compound is MgAl₂ O₄.

7. A method of making a thin film ferrolectric composite material comprising the steps of:

a) providing at least one ceramic disc as an oblation target of a composition comprising barium strontium titanate, said barium strontium titanate represented as Ba_1-x Sr_x TiO₃, wherein x is greater than 0.0 but less than or equal to 0.75; and

a magnesia based compound, wherein the weight ratio of said barium strontium titanate and to said magnesia-based compounds ranges from 99-40% barium strontium titanate to approximately 1-60% magnesia based compounds (are present) in an effective amount to provide a composite having a low dielectric constant, low loss tangent and a high tunability

b) providing a substrate; and

c) depositing a thin film of said composition on said substrate using a pulsed laser.

8. The method of claim 7 wherein said magnesia based compound is selected from the group consisting of MgZrO₃, MgTiO₃, MgAl₂ O₄ and mixtures thereof.

9. The method of claim 8, wherein said compound is MgTiO₃.

10. The method of claim 8, wherein said compound is MgZrO₃.

11. The method of claim 8, wherein said compound is MgAl₂ O₄.

12. The method of claim 7 wherein said pulsed laser is a krypton fluoride excimer laser.

13. The method of claim 8 wherein said substrate is at a temperature of 450°

C. and a distance between the substrate and target is 50 mm.