Diffraction of polar molecules at nanomasks with low charge density

The wave nature of matter is a cornerstone of modern physics and has been demonstrated for a wide range of fundamental and composite particles. While diffraction at nanomechanical masks is usually regarded to be independent of internal atomic or molecular states, the particles' polarizabilities and dipole moments lead to dispersive interactions with the grating surface. In prior experiments, such forces largely prevented coherent diffraction of polar molecules as they induce dephasing of the matter wave in the presence of randomly distributed charges inside the grating. Here, we show that surface milling using neon ions facilitates the fabrication of lowly charged nanomasks in gold-capped silicon nitride membranes. This allows us to observe diffraction of polar molecules with over four times larger electric dipole moment than in previous experiments, opening a path towards distinction of structural conformers in matter-wave experiments.