  Light induced current in two-dimensional (2D) layered materials emerges from
mechanisms such as photothermoelectric effect, photovoltaic effect or nonlocal
hot carrier transport. Semiconducting layered transition metal dichalcogenides
have been studied extensively in recent years as the generation of current by
light is a crucial process in optoelectronic and photovoltaic devices. However,
photocurrent generation is unexpected in metallic 2D layered materials unless a
photothermal mechanism is prevalent. Typically, high thermal conductivity and
low absorption of the visible spectrum prevent photothermal current generation
in metals. Here, we report photoresponse from two-terminal devices of
mechanically exfoliated metallic 3R-NbS$_2$ thin crystals using scanning
photocurrent microscopy (SPCM) both at zero and finite bias. SPCM measurements
reveal that the photocurrent predominantly emerges from metal/NbS$_2$ junctions
of the two-terminal device at zero bias. At finite biases, along with the
photocurrent generated at metal/NbS$_2$ junctions, now a negative photoresponse
from all over the NbS$_2$ crystal is evident. Among our results, we realized
that the observed photocurrent can be explained by the local heating caused by
the laser excitation. These findings show that NbS$_2$ is among a few metallic
materials in which photocurrent generation is possible.
