Thin film multi-layered pyroelectric capacitor

• US 7,732,770 B2
• Filed: 06/09/2008
• Issued: 06/08/2010
• Est. Priority Date: 06/19/2007
• Status: Expired due to Fees

• Current Assignee: Board of Trustees of The University of Alabama (University of Alabama System)
• Original Assignee: Board of Trustees of The University of Alabama (University of Alabama System)
• Inventors: Han, Hui, Pandey, Raghvendra Kumar, Kotru, Sushma
• Primary Examiner(s): Porta; David P
• Assistant Examiner(s): BOOSALIS, FANI POLYZOS
• Application Number:
  US12/135,810
• Publication Number:
  US 20080315100A1
• Time in Patent Office: 729 Days
• Field of Search: 250/338.3, 250/342, 250/370.01, 250/338.4, 250/338.1
• US Class Current: 250/338.3
• CPC Class Codes: G01J 5/02 Constructional details
• CPC Class Codes: G01J 5/023 Particular leg structure or construction or shape; Nanotubes
• CPC Class Codes: G01J 5/024 Special manufacturing steps or sacrificial layers or layer structures
• CPC Class Codes: G01J 5/04 Casings
• CPC Class Codes: G01J 5/046 Materials; Selection of thermal materials
• CPC Class Codes: G01J 5/34 using capacitors, e.g. pyroelectric capacitors
• CPC Class Codes: H10N 15/10 Thermoelectric devices using thermal change of the dielectric constant, e.g. working above and below the Curie point

Abstract

Aspects described herein provide for the design and fabrication of a device with an enhanced pyroelectric response signal comprised of multi-capacitors that are connected in series. These capacitors are fabricated using multi-layers of materials such as lead zirconate titanate (PZT), Ba_xSr_1-xTiO₃ (barium strontium titanate) and Bi₄Ti₃O₁₂ (bismuth titanate) films that exhibit pyroelectric affect and belong to the class of polar materials. By controlling the poling direction of the multi-layer integrated structure, the pyroelectric voltage can be aligned in one direction, and as a result, the voltage output from the single element is the total contribution from each capacitor.

Claims

1. A pyroelectric device comprised of:

a plurality of layers of a polar dielectric material having a pyroelectric coefficient, p, wherein each layer exhibits pyroelectric properties;

a plurality of conductive electrodes, wherein each conductive electrode is substantially in contact with at least a portion of one surface of a respective at least one of said plurality of layers of polar dielectric material,

wherein said electrodes are electrically connected in a series configuration as to form a series of capacitors comprised of said plurality of layers of polar dielectric material and plurality of conductive electrodes.

2. The pyroelectric device of claim 1, wherein at least one layer of said polar dielectric material is comprised of lead zirconate titanate (PZT), Ba_xSr_1-xTiO₃ (barium strontium titanate), or Bi₄Ti₃O₁₂ (bismuth titanate) films.

3. The pyroelectric device of claim 1, wherein at least one of said electrodes are comprised of platinum, gold, iridium oxide, or other conductive oxides such as super-conducting 123 YBCO.

4. The pyroelectric device of claim 1, wherein at least one layer of said polar dielectric material is comprised of lead zirconate titanate (PZT) and at least one of said electrodes are comprised of platinum.

5. The pyroelectric device of claim 1, wherein the pyroelectric device is comprised of a platinum top electrode, a first layer of PZT, a first interim platinum electrode, a second layer of PZT, a second interim platinum electrode, a third layer of PZT, and a platinum bottom electrode resulting in three capacitors electrically connected in series.

6. The pyroelectric device of claim 1, wherein said pyroelectric device has an output response resulting from exposure to infra-red (IR) radiation.

7. The pyroelectric device of claim 6, wherein and said configuration provides IR detection capabilities with a greater output response than conventional single-element IR detectors.

8. The pyroelectric device of claim 7, wherein the output response is up to 103 percent greater than the output response of the single-element IR detection device.

9. The pyroelectric device of claim 6, wherein the output response is an output current.

10. The pyroelectric device of claim 9, wherein the output current is determined by the equation:

$I=A·<br><br>p·<br><br>\frac{d<br><br>T}{d<br><br>t},$

where p is the pyroelectric coefficient, T is temperature, t is time, and A is the area of the series of capacitors.

11. The pyroelectric device of claim 10, wherein the output response is the pyroelectric current, I, monitored as a pyroelectric voltage drop, V, across an external resistor.

12. The pyroelectric device of claim 1, wherein the plurality of layers of a polar dielectric material and the plurality of conductive electrodes are stacked vertically one on top of another.

13. The pyroelectric device of claim 1, wherein the plurality of layers of a polar dielectric material and the plurality of conductive electrodes are arranged horizontally or laterally such that they are electrically interconnected by leads that run from the top electrode of one top electrode-polar dielectric material-bottom electrode stack to the bottom electrode of an adjacent stack such that each stack forms a capacitor and the leads form a serial connection between the stacks.

14. The pyroelectric device of claim 1, wherein said pyroelectric device is used in a pyroelectric radiometer, a gas sensor, a non-contact temperature measurement device, a motion sensor, an alarm system, or a fire detector.

15. The pyroelectric device of claim 1, wherein the series of capacitors comprises two capacitors.

16. The pyroelectric device of claim 1, wherein the series of capacitors comprises three capacitors.

17. The pyroelectric device of claim 1, wherein at least one of the plurality of layers of a polar dielectric material having a pyroelectric coefficient, p is comprised of lead zirconate titanate (PZT) having p in the range of about 1×

10<sup>−

4</sup> C/m²·

K to about 4×

10<sup>−

4</sup> C/m²·

K.

18. The pyroelectric device of claim 17, wherein p is about 2×

10<sup>−

4</sup> C/m²·

K.

19. The pyroelectric device of claim 1, wherein at least one of the plurality of layers of a polar dielectric material having a pyroelectric coefficient, p, is comprised of Ba_xSr_1-xTiO₃ (barium strontium titanate) having p in the range of about 2×

10<sup>−

4</sup> C/m²·

K to about 4×

10<sup>−

4</sup> C/m²·

K.