Heteroepitaxial spherical electroless Au-plated Pt-based nanogap electrodes of radius 5 nm and gap separation 0.7 nm

Heteroepitaxial growth is demonstrated by electroless Au plating (ELGP) on polycrystalline Pt surface and initial ultrafine-linewidth Pt nanogap electrodes, confirmed by scanning transmission electron microscope cross-sectional images, atomic-resolution scanning electron microscope images, and energy-dispersive X-ray spectroscopy elemental maps. The gap between a pair of spherical multidomain heteroepitaxial Au on Pt electrodes of radius 5 nm is controlled to a value as small as 0.7 nm by the self-termination mechanism of ELGP without short circuit. The heteroepitaxial spherical Au/Pt nanogap electrodes are found to be robust against annealing at temperatures up to 573 K.