  Understanding the electronic transport properties of layered, van der Waals
transition metal halides (TMHs) and chalcogenides is a highly active research
topic today. Of particular interest is the evolution of those properties with
changing thickness as the 2D limit is approached. Here, we present the
electrical conductivity of exfoliated single crystals of the TMH, cluster
magnet, Nb3Cl8, over a wide range of thicknesses both with and without
hexagonal boron nitride (hBN) encapsulation. The conductivity is found to
increase by more than three orders of magnitude when the thickness is decreased
from 280 {\mu}m to 5 nm, at 300 K. At low temperatures and below ~50 nm, the
conductance becomes thickness independent, implying surface conduction is
dominating. Temperature dependent conductivity measurements indicate Nb3Cl8 is
an insulator, however the effective activation energy decreases from a bulk
value of 310 meV to 140 meV by 5nm. X-ray photoelectron spectroscopy (XPS)
shows mild surface oxidation in devices without hBN capping, however, no
significant difference in transport is observed when compared to the capped
devices, implying the thickness dependent transport behavior is intrinsic to
the material. A conduction mechanism comprised of a higher conductivity surface
channel in parallel with a lower conductivity interlayer channel is discussed.
