Get documents about "Wireless Hydrogen Sensor Network
Document Sample
Wireless Hydrogen Sensor Networks
Using GaN-based Devices
Travis Anderson1, Hung-Ta Wang1, Byoung Sam Kang1,
Fan Ren1, Changzhi Li2, Zhen Ning Low2,
Jenshan Lin2, Stephen Pearton3
1 University of Florida, Chemical Engineering
2 University of Florida, Electrical and Computer Engineering
3 University of Florida, Materials Science and Engineering
University of Florida NHA Hydrogen Conference, March 21, 2007
NASA Funded Hydrogen Research at UF
• $10M funding over 4 years
• 27 Projects
• 60 Faculty members, post-docs, and graduate
students combined
UF NASA Funded Hydrogen Research Web Site:
http://www.mae.ufl.edu/NasaHydrogenResearch
University of Florida NHA Hydrogen Conference, March 21, 2007
NASA Funded Hydrogen Research at UF
Research Thrust Areas
• Fuel Cells (PEM and SOFC)
• Hydrogen Production, Storage, and Transport
• Nano Sensors - Hydrogen Leak Detection
Gas inlet
H2
Hydrogen-Selective Sensing
Gas outlet Single Crystal Nanowires at Room Temperature with
ZnO Nanorods
H2 Production PEM FC micro grids
& Cooling Plate
University of Florida NHA Hydrogen Conference, March 21, 2007
Motivation
Application fields:
• Fuel leak detection for
automobile, space shuttle,
and aircraft.
• Fire detection (CO, CO2).
• Emission, hydrocarbon,
and health monitor.
• Environmental control.
University of Florida NHA Hydrogen Conference, March 21, 2007
Group III Nitride
• Outstanding mechanical and
electronic properties
• Controllable wide range band
gap(3.4eV-6.2eV AlGaN)
• High thermal stability
• Chemical inertness
• AlGaN/GaN 2DEG for high
power and high frequency.
University of Florida NHA Hydrogen Conference, March 21, 2007
Device Fabrication
Ti/Al/Pt/Au
Pt
Ti/Au
SiNx
Al0.28Ga0.72N
GaN 2DEG
50 µm Sapphire
Optical microscopic image Device Cross-section
University of Florida NHA Hydrogen Conference, March 21, 2007
Sensing Mechanism
• H22H(chemisorption on Pt) H2
• Diffusion of H atom. Hs
H2(gas) 2Hs 2Hb 2Hi Hb
• Creation of a polarized layer
Pt Hi
at the interface AlGaN
• Decrease of barrier height. 2DEG
(Schottky diode); increase of GaN
channel cross-section. (FET)
University of Florida NHA Hydrogen Conference, March 21, 2007
Experimental Results
20
Nitorgen
Current (mA)
16
1% Hydrogen
12
8
4
0
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Biased Voltage (V)
qB eV ; ΔФ ~ -50 meV @ room T
JF A**T 2 exp exp 1 B
kT nkT
University of Florida NHA Hydrogen Conference, March 21, 2007
Practical Problem-False Alarm
Room temperature 50 °C
20
Nitrogen
16
Current (mA)
1% Hydrogen
12
8
4
0
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Biased Voltage (V)
1. Thermal effect to semiconductor and Schottky contact.
2. Voltage drift
University of Florida NHA Hydrogen Conference, March 21, 2007
Differential Diodes
Optical microscopic image
University of Florida NHA Hydrogen Conference, March 21, 2007
1% Hydrogen Test
University of Florida NHA Hydrogen Conference, March 21, 2007
Hardware Design
AC Wall Transformer Battery/Energy Harvest Internet
Cell Phone
Regulator Regulator
Battery Backup Control Microcontroller
Reference R0
1M 2M
Vout
Internet Server
ZigBee Wireless Network Server
Transceiver
1M 2M
Sensor R0 Monitor Monitor Monitor Monitor
Tx data Tx data Tx data Tx data
Power Up
Power Down
Warm up: 30 seconds 5s 1s 5s 1s 5s 1s 5s 1s
University of Florida NHA Hydrogen Conference, March 21, 2007
Wireless Sensor Module
Client can
deactivate alarm
University of Florida NHA Hydrogen Conference, March 21, 2007
Field Test
University of Florida NHA Hydrogen Conference, March 21, 2007
Conclusions
GaN-based sensors demonstrate rapid response (<1s) and
reversibility
Differential sensor devices eliminate sensitivity to
temperature and voltage drifts
TiB2 can be used in ohmic contacts to improve reliability
These sensors have been implemented in a wireless
detection circuit
Field testing is underway at Greenway Ford, Orlando, FL
We are seeking investors for a startup company
University of Florida NHA Hydrogen Conference, March 21, 2007
Acknowledgements
This work at UF is supported by:
1. NSF (CTS-0301178, monitored by Dr. M.
Burka and Dr. D. Senich)
2. NASA Kennedy Space Center Grant NAG
10-316 monitored by Mr. Daniel E. Fitch.
University of Florida NHA Hydrogen Conference, March 21, 2007
Hydrogen Sensing Test
Schematic illustration of gas sensor system
University of Florida NHA Hydrogen Conference, March 21, 2007
Room Temperature Test
University of Florida NHA Hydrogen Conference, March 21, 2007
50 °C Test
University of Florida NHA Hydrogen Conference, March 21, 2007
Comparison of Pd and Pt
[1]
[3]
[2]
Reference:
[1] W. Eberhardt, F. Greuter, E. W. Plummer, Phys. Rev. Lett. 46, 1085 (1981).
[2] http://www.rebresearch.com/H2sol2.htm
[3] http://www.rebresearch.com/H2perm2.htm
University of Florida NHA Hydrogen Conference, March 21, 2007
Gas Sensing Devices
Schottky diode [1] HEMT[2] Resistor[3]
[1] B. S. Kang, F. Ren, B. P. Gila, C. R. Abernathy and S. J. Pearton, Appl. Phys. Lett. 84 1123 (2004).
[2] B. S. Kang, R. Mehandru, S. Kim, F. Ren, R. C. Fitch, J. K. Gillespie, N. Moser, G. Jessen, T. Jenkins, R. Dettmer, D. Via, A. Crespo, B.
P. Gila, C. R. Abernathy and S. J. Pearton, Appl. Phys. Lett. 84 4635 (2004).
[3] H. T. Wang, B. S. Kang, F. Ren, L. C. Tien, P. W. Sadik, D. P. Norton, S. J. Pearton, Jenshan Lin, Appl. Phys. Lett. 86 243503 (2005).
University of Florida NHA Hydrogen Conference, March 21, 2007
