  Hexagonal boron nitride (h-BN) is a two dimensional (2D) layered insulator
with superior dielectric performance that offers excellent interaction with
other 2D materials (e.g. graphene, MoS2). Large-area h-BN can be readily grown
on metallic substrates via chemical vapor deposition (CVD), but the impact of
local inhomogeneities on the electrical properties of the h-BN and their effect
in electronic devices is unknown. Here it is shown that the electrical
properties of h-BN stacks grown on polycrystalline Pt vary a lot depending on
the crystalline orientation of the Pt grain, but within the same grain the
electrical properties of the h-BN are very homogeneous. The reason is that the
thickness of the CVD-grown h-BN stack is different on each Pt grain. Conductive
atomic force microscopy (CAFM) maps show that the tunneling current across the
h-BN stack fluctuates up to 3 orders of magnitude from one Pt grain to another.
However, probe station experiments reveal that the variability of electronic
devices fabricated within the same Pt grain is surprisingly small. As
cutting-edge electronic devices are ultra-scaled, and as the size of the
metallic substrate grains can easily exceed 100 {\mu}m (in diameter), CVD-grown
h-BN stacks may be useful to fabricate electronic devices with low variability.
