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Electroless Nickel Deposition: an Alternative for Graphene Contacting Sinziana Mirela Popescu, Anders J. Barlow, Sami Ramadan, Srinivas Ganti, Biswajit Ghosh, and John Hedley ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b08290 • Publication Date (Web): 21 Oct 2016 Downloaded from http://pubs.acs.org on October 24, 2016
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ACS Applied Materials & Interfaces
Electroless Nickel Deposition: an Alternative for Graphene Contacting Sinziana M. Popescu†*, Anders J. Barlow§, Sami Ramadan¥, Srinivas Ganti¥, Biswajit Ghosh‡, John Hedley† †
School of Mechanical and Systems Engineering, Newcastle University, NE1 7RU, United Kingdom §
National EPSRC XPS Users' Service (NEXUS), Newcastle University, NE1 7RU, United Kingdom ¥
School of Electrical and Electronics Engineering, Newcastle University, NE1 7RU, United Kingdom
‡
School of Energy Studies, Jadavpur University, Kolkata 700 032, India
*Corresponding author email address:
[email protected] ABSTRACT: We report the first investigation into the potential of electroless nickel deposition to form ohmic contacts on single layer graphene. Aiming to minimize the contact resistance on graphene, a statistical model was used to improve metal purity, surface roughness and coverage of the deposited film by controlling the nickel bath parameters (pH and temperature). The metalized graphene layers were patterned using photolithography and contacts deposited at temperatures as low as 60°C. The contact resistance was 215 ± 23 Ω over a contact area of 200 µm x 200 µm, which improved upon rapid annealing to 107 ± 9 Ω. This method shows promise towards low-cost and large-scale graphene integration into functional devices such as flexible sensors and printed electronics.
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KEYWORDS: contacting graphene, electroless nickel, contact resistance, transmission line method, interface characterization INTRODUCTION Novel nanomaterials such as graphene pose a challenge for available ohmic contact deposition techniques, as the associated contact resistance represents a major drawback in high-performance electronics applications 1. Different methods have been employed in order to reduce and control contact resistance on graphene, such as improved surface cleanliness 2, controlled introduction of graphene edges
3,4
and high purity controlled metal deposition 5. Contact arrangement and
interface engineering have also been attempted for graphene-metal interface improvement
6,7
.
Contact resistances on graphene have previously been reported in the range 294 Ω·µm 8 – 12 kΩ·µm
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using conventional (thermal and e-beam) evaporation techniques. The reproducibility
of contacting methods onto various types of graphene is acknowledged as a major challenge 9,10. The electroless nickel plating method provides opportunities over conventional evaporation approaches, the foremost being the processing time (in the order of a few minutes), cost and accessibility as it does not require the clean room infrastructure normally associated with evaporation techniques. It can be achieved at low temperatures (T
