Reproducible Low Contact Resistance in Rubrene Single-Crystal   Field-Effect Transistors with Nickel Source and Drain Electrodes
  We have investigated the contact resistance of rubrene single-crystal field-effect transistors (FETs) with Nickel electrodes by performing scaling experiments on devices with channel length ranging from 200 nm up to 300 $\mu$m. We find that the contact resistance can be as low as 100 $\Omega$cm with narrowly spread fluctuations. For comparison, we have also performed scaling experiments on similar Gold-contacted devices, and found that the reproducibility of FETs with Nickel electrodes is largely superior. These results indicate that Nickel is a very promising electrode material for the reproducible fabrication of low resistance contacts in organic FETs. 
Iulian N. Hulea, Saverio Russo, Anna Molinari, and Alberto F. Morpurgo