Capsule-free fluid delivery and beam-induced electrodeposition in a scanning electron microscope

Abstract

Gold coated borosilicate nanocapillaries are used to locally deliver aqueous, electrolytic CuSO₄ solution into the low vacuum chamber of an environmental scanning electron microscope (ESEM). Capillary flow of the liquid is induced by bringing a nanocapillary into contact with a substrate. A microscopic droplet is stabilized by controlling the droplet evaporation rate with the substrate temperature and the pressure of H₂O vapor injected into the vacuum chamber. An electron beam is admitted to the droplet through a pressure limiting aperture. Electrochemical reduction of aqueous Cu²⁺ to solid, high purity, deposited Cu is achieved by biasing the nanocapillary and supplying current by the beam which acts as a virtual cathode and enables electrodeposition on both conductive and insulating substrates. Delivery of liquids into vacuum enables localized, capsule-free beam induced electrochemistry, opening new pathways for direct-write nano and micro-lithography via beam induced electrodeposition.