1. 2 August 2007 Jon Brame Fabrication and Testing of a Strain-Based Carbon Nanotube Magnetometer Structure Jon A. Brame, Johnathan Goodsell, Stephanie A. Getty¹, Y. Zheng¹ And David A. Allred Brigham Young University ¹NASA GSFC Code 541 Began as an NASA ESMD Student-Faculty Program

2. 2 August 2007 Jon Brame Overview 1.Project Motivation and Goal 2.Fabrication Process 3.Outcomes

3. 2 August 2007 Jon Brame CNT Properties Change in Conductivity with Strain –Tombler, et al (Nature, 2000) –Single tube

4. 2 August 2007 Jon Brame CNT Properties Change in Conductivity with Strain –Tombler, et al (Nature, 2000) –Single tube

5. 2 August 2007 Jon Brame Motivation Space Magnetometry –Spacecraft Orientation –Magnetic Field Studies Planetary Exploration –Astronaut/Rover Orientation –Planetary Geology

6. 2 August 2007 Jon Brame Device Operation

7. 2 August 2007 Jon Brame Gold Si02 Si Needle

8. 2 August 2007 Jon Brame Prototype

9. 2 August 2007 Jon Brame Process: Catalyst Indirect Iron Catalyst Deposition Vacuum Chamber for Thin Film Deposition

10. 2 August 2007 Jon Brame Process: SWCNT Growth Chemical Vapor Deposition (CVD) SWCNT Growth CVD Growth Furnace Diagram of CVD Growth Process SEM Image of SWCNT Mat

11. 2 August 2007 Jon Brame Process – Electrical Contact Gold Contact Pads –Detector Development Lab (DDL) –E-Beam Lithography –Deposition: Chrome(100Å)- Gold(1000Å) –Lift-off

12. 2 August 2007 Jon Brame Process – Iron Needle Iron Needle –Device Alignment –E-Beam Lithography pattern –Deposition: Chrome-Iron- Chrome –Lift-off Diagram of SWCNT network, contact pads and iron needle

13. 2 August 2007 Jon Brame Process – Trench Lithography (manual) Etching –Buffered Oxide Etch –KOH Diagram of completed device Au SWCNTs Remnant needle Trench

14. 2 August 2007 Jon Brame Results Completed Magnetometer Prototype Successfully etched trench with SWCNT spanning gap between gold electrodes

15. 2 August 2007 Jon Brame Results Magnetic Field Measurement Testing

16. 2 August 2007 Jon Brame Micrograph of Test Structure

17. 2 August 2007 Jon Brame

18. 2 August 2007 Jon Brame Gold pad SWCNT mat Iron needle Trench alignment mark “Rolled-up” SWCNT mat

19. 2 August 2007 Jon Brame ab c Device resistance decreases as magnetic field is increased, At some point contact with one of the pads becomes intermittent leading to the noisy signal during time period c 500 seconds into the experiment the field is ramped down (b) Experimental Results Note: Behavior during a & b are the opposite of what was expected to happen.

20. 2 August 2007 Jon Brame CONCLUSIONS 1.A fabrication process for magnetometer test structures has been demonstrated. 2.An array of prototype magnetometer test structures has been successfully fabricated. 3.The test structures consist of a high aspect-ratio iron needle suspended above a trench by a mat of SWCNT. Gold pads electrically contact the SWCNT mat. This fabrication process is now available and being used in various field sensing applications. 4.Initial magnetic testing indicates that there is some correlation between magnetic field and measured resistance in the device. 5.Further device fabrication and testing is necessary to establish the extent of this relationship.

21. 2 August 2007 Jon Brame The design for the next iteration of gold-pad geometry features three separate sets of pads (labeled a, b & c) to contact specific sections of nanotubes. In this figure the black Xs represents the nanotube mat and the horizontal line is the needle. Dividing the pads into three sets makes it possible to uses the outer set of pads (labeled a & c) to measure the strain across the outer portions of the nanotubes.

22. 2 August 2007 Jon Brame Acknowledgements Bryan Hicks, Rachel Bis, Melissa Harrison Branch 541: Dewey Dove, D. Stewart Bruno Munoz, Carl Taylor, Len Wang, D. Rowland BYU: Prof. Richard Vanfleet, Dr. Jeffrey Farrer, Prof. Robert Davis, David Hutchinson Other: Lynda Goodsell, Bill Heaps Division 540; Dick Fahey; Joshua Halpern; ESMD; Rocky Mountain Space Grant Consortium

23. 2 August 2007 Jon Brame We gratefully acknowledge financial support from NASA GSFC Director’s Discretionary Fund, the NASA Internal Research and Development Fund, the Rocky Mountain Space Grant Consortium, and the Student/Faculty Internship Program for the summers of 2006 and 2007 which provided support for J. A. Brame, J. E. Goodsell, & D. D. Allred

24. 2 August 2007 Jon Brame Outcome: BYU Collaboration