1. University of Michigan, Department of Chemical Engineering
Atomic Layer Deposition of Zirconium Oxide for Fuel Cell Applications UIC REU – Summer 2011 AMReL Lab, UIC Department of Bioengineering and Department of Chemical Engineering
Christine James
University of Michigan, Department of Chemical Engineering

2. Overview
Background
Atomic Layer Deposition
Data Collected
Future Work

3. Fuel Cell Advantages Provides clean energy Very efficient
Fossil fuel
2007
Provides clean energy
Hydrogen fuel cells
only emit water
Very efficient
Fuel Values
Hydrogen: kJ/g
Gasoline: 48 kJ/g
Coal: kJ/g
Santhanam et al., Introduction to Hydrogen Technology, 2009, Hoboken, NJ: J. Wiley.
Natural
Gas 23 %
Coal 23 %
Nuclear Power 8 %
Renewable Energy 6 %
Source: US Energy Information Agency
Petroleum 40 %
Environmentally friendly
Hydrogen is not the only fuel, there are also other carbohydrides and biofuels

4. Sections of the Fuel Cell
SOFC FUEL CELL
Cathode
Oxygen is reduced
Electrical Current
Fuel In
Air In
Electrolyte
Transports the oxygen ions
Excess Fuel and Water
Unused Gases Out
Anode
Hydrogen is oxidized
www1.eere.energy.gov

5. Solid Oxide Fuel Cells (SOFCs)
Current SOFCs are high temperature
Temperature: about 1000 °C
Intermediate Temperature Fuel Cells
Temperature: °C
Smaller scale applications
Allows use of alternate materials
Starts and stops faster
Reduces corrosion
Offers a wide range of possibilities
The reduced corrosion improves the durability

6. Problem with Reducing Temperature
High temperatures needed to transport O2- ions
Requirement can be as high as 1200° C
Low temperatures cause ionic resistance
Approach
Deposit electrolytes and analyze
Samples from atomic to bulk-like thickness
Method to be used:
Atomic Layer Deposition
Deposit oxide layers on silicon then platinum (Pt)

7. Atomic Layer Deposition (ALD)
H2O
Tri-methyl
aluminum
Al(CH3)3(g)
Methyl group
(CH3)3(g)
Hydroxyl (OH)
from surface
absorbed H2O
Reaction of
TMA with OH
Methane reaction product CH4

8. Chosen Precursor www.aloha.airliquide.com Precursors
Growth Temperature
Impurities
Metal Precursor
O source
Range (°C)
Preferred (°C)
Saturation verified
C [-at%]
H [-at%]
at 300 °C
ZyALD
Ozone
300
Yes
<1
N.R.
Niinistö, et al., Advanced Engineering Materials, 2009, 11, No.4, 223.

9. ALD System
ZyALD
There are 4 bubblers so that we can use 4 precursors and this is important when depositing all sections of the fuel cell
ZyALD

10. Pulse and Purge times required
Reactor Temperature: 300°C Bubbler Temperature: 50°C Bubbler Pressure: 10 torr Precursor: ZyALD Precursor Pulse Time: Precursor Purge Time: Oxidizer Pulse Time: Oxidizer Purge Time: Run for 40 cycles
20 s
10 s
Varied
1.5 s
Varied
1 s
17 s
Varied
6 s
Varied Zr

11. Temperature Window Reactor Temperature: Varied
Bubbler Pressure: 10 torr
Bubbler Temperature: 50°C
Precursor: ZyALD
Temperature
Window
Precursor Condensation
Precursor Decomposition

12. Comparison to Work from another group
Niinistö, et al., J. Mater. Chem. 18, 5243 (2008).

13. Thickness vs. Cycles Run
Reactor Temperature: 300°C
Bubbler Pressure: 10 torr
Bubbler Temperature: 50°C
Precursor: ZyALD
Slope: .87
R² =

14. Future Work Deposit the zirconium oxide on Platinum
Run electrochemical analysis
Electrolyte: Zirconium Oxide
Silicon Substrate
Platinum

15. Summary Goal is to lower operating temperature of the fuel cell
By decreasing electrolyte layer thickness
Atomic Layer Deposition (ALD) is being used
Have determined some necessary parameters:
Pulse and Purge times
Temperature Window for ALD
Have compared cycles and thickness
Proved linear relationship
Next Steps:
Deposit on Platinum
Run Electrochemical analysis

16. Acknowledgements National Science Foundation
EEC-NSF Grant #
Graduate Mentor: Runshen Xu
Professor Takoudis and Professor Jursich