  Graphene has been extensively studied for a variety of electronic and
optoelectronic applications. The reported contact resistance between metal and
graphene, or rather its specific contact resistance (R{_C}), ranges from a few
tens of {\Omega} {\mu}m up to a few k{\Omega} {\mu}m. Manufacturable solutions
for defining ohmic contacts to graphene remain a subject of research. Here, we
report a scalable method based on laser irradiation of graphene to reduce the
R{_C} in nickel-contacted devices. A laser with a wavelength of {\lambda} = 532
nm is used to induce defects at the contact regions, which are monitored
\textit{in-situ} using micro-Raman spectroscopy. Physical damage is observed
using \textit{ex-situ} atomic force and scanning electron microscopy. The
transfer line method (TLM) is used to extract R{_C} from back-gated graphene
devices with and without laser treatment under ambient and vacuum conditions. A
significant reduction in R{_C} is observed in devices where the contacts are
laser irradiated, which scales with the laser power. The lowest R{_C} of about
250 {\Omega} {\mu}m is obtained for the devices irradiated with a laser power
of 20 mW, compared to 900 {\Omega} {\mu}m for the untreated devices. The
reduction is attributed to an increase in defect density, which leads to the
formation of crystallite edges and in-plane dangling bonds that enhance the
injection of charge carriers from the metal into the graphene. Our work
suggests laser irradiation as a scalable technology for R{_C} reduction in
graphene and potentially other two-dimensional materials.
