ENERGY HARVESTING DEVICES AND METHODS OF FABRICATING THE SAME

• US 20130154439A1
• Filed: 09/07/2012
• Published: 06/20/2013
• Est. Priority Date: 12/16/2011
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: LEE, Sang Kyun, Yang, Yil Suk, Kim, Moonkeun
• Granted Patent: US 8,963,404 B2
• Time in Patent Office: Days
• US Class Current: 310/314
• CPC Class Codes: H02N 2/18 producing electrical output from mechanical input, e.g. generators for measurement devices G01
• CPC Class Codes: H02N 2/188 adapted for resonant operation
• CPC Class Codes: H10N 30/01 Manufacture or treatment
• CPC Class Codes: H10N 30/306 Cantilevers

Abstract

Energy harvesting devices are provided. The energy harvesting device includes a body, a proof mass spaced apart from the body, a cantilever extending from the body onto the proof mass, a first electrode layer on the cantilever opposite to the body, a first piezoelectric layer on the first electrode layer, a second electrode layer on the first piezoelectric layer, a second piezoelectric layer on the second electrode layer, a pair of third electrode layers on the second piezoelectric layer, and a magnetic layer between the second electrode layer and the second piezoelectric layer. Related methods are also provided.

Claims

1. An energy harvesting device, the device comprising:

a body;

a proof mass spaced apart from the body;

a cantilever extending from the body onto the proof mass;

a first electrode layer on the cantilever opposite to the body;

a first piezoelectric layer on the first electrode layer;

a second electrode layer on the first piezoelectric layer;

a second piezoelectric layer on the second electrode layer;

a pair of third electrode layers on the second piezoelectric layer; and

a magnetic layer between the second electrode layer and the second piezoelectric layer.

2. The device of claim 1, wherein the magnetic layer has a magnetic force for controlling a resonance frequency of the cantilever and the proof mass together with an external magnetic field applied to the proof mass.

3. The device of claim 2, wherein the magnetic layer includes a hard magnetic material and/or a soft magnetic material.

4. The device of claim 3, wherein the hard magnetic material includes at least one of carbon steel, strontium rubidium oxide, barium ferrite (Ba-ferrite), samarium cobalt 5 (SmCo5) and neodymium iron boride (Nd₂Fe₁₄B).

5. The device of claim 3, wherein the soft magnetic material includes at least one of ferrite, silicon steel and permalloy.

6. The device of claim 2, wherein the resonance frequency of the cantilever and the proof mass is controlled by intensity of the magnetic force of the magnetic layer.

7. The device of claim 1, wherein the body and the proof mass include a single crystalline silicon substrate or a silicon-on-insulator (SOI) substrate.

8. The device of claim 1, wherein the cantilever includes:

a first buffer layer between the body and the proof mass;

a shim plate on the first buffer layer opposite to the body and the proof mass;

a second buffer layer on the shim plate opposite to the first buffer layer.

9. The device of claim 8, wherein the shim plate includes a single crystalline silicon material, a polycrystalline silicon material or an amorphous silicon material.

10. The device of claim 8, wherein each of the first and second buffer layers includes a silicon oxide layer.

11. The device of claim 1, wherein each of the first and second piezoelectric layers includes at least one of a piezoelectric ceramic material, a piezoelectric semiconductor and a piezoelectric polymer material.

12. The device of claim 11, wherein each of the piezoelectric ceramic material, the piezoelectric semiconductor and the piezoelectric polymer material includes at least one of PZT, PVDF, PMN-PT, PZN-PT, PMN-PZT, ZnO and AlN.

13. The device of claim 1, wherein the first electrode layer, the first piezoelectric layer and the second electrode layer have a vertical harvesting mode of the cantilever and the proof mass.

14. The device of claim 1, wherein the pair of third electrode layers and the second piezoelectric layer have a horizontal harvesting mode of the cantilever and the proof mass.

15. The device of claim 14, wherein the pair of third electrode layers include a first inter-digital electrode and a second inter-digital electrode which are located at the same level and combined with each other.

16. The device of claim 1, wherein each of the first, second and third electrode layers includes at least one of a platinum layer and a titanium layer.

17. A method of fabricating an energy harvesting device, the method comprising:

providing a substrate;

forming a cantilever on the substrate;

forming a first electrode layer on the cantilever;

forming a first piezoelectric layer on the first electrode layer;

forming a second electrode layer on the first piezoelectric layer forming a magnetic layer on the second electrode layer;

forming a second piezoelectric layer on the magnetic layer;

forming a pair of third electrode layers separated from each other in a horizontal direction on the second piezoelectric layer; and

patterning the cantilever and removing a portion of the substrate to define a body and a proof mass separated from each other.

18. The method of claim 17, wherein forming the cantilever includes:

forming a first buffer layer on the substrate;

forming a shim plate on the first buffer layer; and

forming a second buffer layer on the shim plate.

19. The method of claim 17, wherein the magnetic layer is formed to include a hard magnetic material and/or a soft magnetic material using a sputtering process or a spin coating process.

20. The method of claim 17, wherein the cantilever is patterned using a dry etching process, and the substrate between the body and the proof mass is removed using a reactive ion etching (RIE) process or a chemical vapor etching process.