Fabrication of crack-free blanket nanoporous gold thin films by galvanostatic dealloying

A galvanostatic dealloying method, wherein the material removal rate is directly controlled, is proposed for fabrication of constrained crack-free nanoporous gold (NPG) films. Uniform, three-dimensional, crack-free, blanket NPG films are fabricated by this method from both low and high Au concentration precursor alloys up to 1300 nm thickness, which cannot be obtained by other methods. Ag dissolution rate proved to be critical in maintaining the film stress below the threshold value at which cracks develop. The findings contribute to understanding the formation mechanisms of NPG films.

► Robust fabrication method for crack-free nanoporous gold films adhered to silicon substrates, over areas of many millimeter squares.
► High quality nanoporous gold films, with 3-dimensional porosity, 30 nm ligament width, low residual silver content (1.5–2 at.% Ag), and with thickness up to 1300 nm.
► Qualitative experimental evidence of the effect of dealloying current and film stress on surface evolution in nanoporous materials.