It can get activated by scattered neutrons, leading to γ-ray induced scintillation light that can be mistaken for neutron/Helium-3 capture events.
Nevertheless, some metal is required to produce the electric field required for the experiment. We use ion implantation to embed a thin (~200 nm) copper/germanium layer into an acrylic substrate. A silicon dioxide coating (similar to a scratch resistant coating on eyeglass lenses) underneath the metal layer improves robustness to solvents and thermal cycling.
Oak Ridge National Laboratory is managed by UT-Battelle LLC for the US Department of Energy