Electrochemical Liquid–Liquid–Solid Crystal Growth of Germanium Microwires on Hard and Soft Conductive Substrates at Low Temperature in Aqueous Solution

Highly ordered crystalline Ge microwire arrays with individual diameters larger than 1 μm have been grown in aqueous solutions at ambient pressure and below the boiling point of water through an electrochemical liquid–liquid–solid (ec-LLS) crystal growth process. A pertinent feature of this work is the use of a liquid metal patterning strategy which combines the utility of photolithography with the simplicity of doctor blading to produce macroscopic (>1 cm 2 ) arrays of liquid metal microelectrodes. Optical and electron micrographs showed the compatibility of the liquid metal patterning process and subsequent ec-LLS microwire growth with a wide assortment of different conductive substrates, including silicon, indium tin oxide, copper foil, titanium foil, stainless steel, and poly[(3,4-ethylenedioxy)thiophene]/poly(styrenesulfonate). Furthermore, a simple chemical bath lift-off procedure was developed to fully remove the Ge microwire arrays embedded in SU-8 photoresist without perturbing the order or quality of the material, resulting in a free-standing composite membrane. Data from energy-dispersive spectroscopy, Auger nanoprobe spectroscopic mapping, and four-terminal single microwire electrical measurements indicated that the specific liquid metal used for ec-LLS impacts the morphology and electrical properties of the resultant Ge microwires.