  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.
