The continuing development of microelectronic devices has been accompanied by an increasing research drive in the development of portable or microfabricated power sources to power the devices. Processing compatible with that utilised in the microeletronics industry is being developed to integrate micropower sources with the devices to be powered. Solid state thin film versions of the micropower sources have been demonstrated by many groups and shown to require further devlopment to keep pace with the rapid progress in the field of micro and nanoelectronics. Recent developments in the field of micropower sources include attempts to 3D fabricate the electrochemical micropower sources to improve their capacity and current drain capabilities per unit footprint. This processing is complicated by the need to have uniform thin film deposition in 3D of all three components, anodes, electrolyte and cathodes for optimal device performance.

Our interest in electrochemical micropower is in the area of microbatteries and microfuel cells fabricated in 3D.

Figure 2.           Microfuel cell schematic.

In one project we have been investigating fuel cell catalyst electrodeposition incorporating carbon nanotubes (CNT) for improved catalyst performance. We have used AAO templates to structure the catalyst. The catalysts have been shown to have improved methanol oxidation characteristics and an improved CO tolerance to minimise inefficiencies in the oxidation reaction. In addition microscopy shows that in the catalyst composite the carbon nanotubes align with the platinum electrodeposit 

Figure 3. Anodic alumina templates and the resulting Pt/CNT composites formed in the templates. The bottom TEM images show the CNT aligned with the Pt host electrodeposit.

Projects

• Micro lithium ion advanced integrated rechargeable battery. (2005-2008) Enterprise Ireland, Technology Development.

• Napolyde: Nanostructured polymer deposition processes for mass production of innovative systems for energy production & control and for smart devices, EU FP6 (2005-2009)

• Microfabricated fuel cell in collaboration with Cork Institute of Technology. (2007-2010) Enterprise Ireland, Technology Development.

• Zero carbon emission microfuel cell design. (2008-2010) EPA

Recent publications

1. L.C.Nagle and J.F.Rohan, J. Power Sources, 185 (2008) 411-418. Aligned carbon nanotube composite deposition in platinum for fuel cell catalysts.

2. J.F.Rohan, D.P.Casey, B.Ahern, F.M.F.Rhen, S.Roy, D.Fleming and S.E.Lawrence, Electrochemistry Communications, 10 (2008) 1419-1422. Coaxial metal and magnetic alloy nanotubes in polycarbonate templates by electroless deposition.

3. L.Lewis, D.P.Casey, A.V.Jeyaseelan, J.F.Rohan and P.Maaskant, Applied Physics Letters, 92 (2008) 062113. Electroless nickel/gold ohmic contacts to p-type GaN.

4. C.Ó.Mathúna, T.O’Donnell, R.Martinez, J.F.Rohan and B.O’Flynn, Talanta, 75 (2008) 613-623. Energy Scavenging for Long-Term Deployable Mote Networks

5. W-M.Chen, P.McCloskey, J.F.Rohan, P.Byrne and P.J.McNally, IEEE Transactions on Components, Packaging and Manufacturing Technology, Part A, 30 1 (2007) 144-151, Preparation and temperature cycling reliability of electroless Ni under bump metallization.

6. L.C.Nagle, A.Loughlin and J.F.Rohan, Electrochemical Society Transactions, Vol 2, 6, (2007) 51-59. Electroless cobalt deposition from ammonia borane solutions.

7. L.C.Nagle and J.F.Rohan, Journal of the Electrochem. Society, 153 (11) C773-C776 (2006) Ammonia borane oxidation at gold microelectrodes in alkaline solutions,

8. J.F.Rohan, B.M.Ahern and L.C.Nagle, Electrochemical Society Transactions, Vol 1, Issue 31, 1-9 (2006) DMAB Oxidation for Electroless Deposition from Alkaline Solutions.

9. P.P.Maaskant, M.Akhter, N.Cordero, D.P.Casey, J.F.Rohan, B.J.Roycroft and B.Corbett, Physica Status Solidi (c) 2, No 7, 2907 - 2911 (2005) LED flip-chip assembly with electroplated AuSn alloy.

10. L.C.Nagle and J.F.Rohan, Electrochemical and Solid-State Letters, 8 (5) C77-C80 (2005) Investigation of dimethylamine borane oxidation at a gold microelectrode in base.

11. J.F.Rohan, P.A.Murphy and J.Barrett, Journal of the Electrochemical Society, 152, C32-C35 (2005) Zincate-free, electroless nickel deposition at aluminium bond pads

12. W.M.Chen, P.McCloskey, P.Byrne, P.Cheasty, G.Duffy, J.F.Rohan, J.Boardman, A.Mulcahy and S.C.O'Mathuna, Journal of Electronic Materials, 33 (2004) 900-907. Degradation of electroless Ni(P) under bump metallization (UBM) in Sn3.5Ag and Sn37Pb solders during high temperature storage.

13. J.F.Rohan and G.O’Riordan, Microelectronic Engineering, 65 (2003) 77-85. Characterisation of the electroless nickel deposit as a barrier layer / under bump metallurgy on IC metallisation.

14. J.F.Rohan, G.O’Riordan and J.Boardman, Applied Surface Science, 185 (2002) 289. Selective electroless nickel deposition on copper as a final barrier/bonding layer material for microelectronics applications.