Electrochemical Liquid-Liquid-Solid Deposition of Crystalline Ge Nanowires as a Function of Ga Nanodroplet Size

Direct preparation of crystalline Ge nanowires from dissolved aqueous solutions of GeO2 via electrodeposition through an electrochemical liquid-liquid-solid (ec-LLS) process using a variety of Ga nano/microdroplets has been demonstrated. Templated silica films featuring regularly spaced openings with defined sizes were prepared on degenerately doped Si substrates by a modified natural lithography patterning process. These platforms were used to electrodeposit Ga droplet arrays with defined sizes and pitch. The Ga nano/microdroplets subsequently facilitated Ge nanowire ec-LLS in water as a function of droplet size. The amperometric responses recorded during ec-LLS depended on the Ga nanodroplet size. However, none of the recorded current-time profiles fit either Cottrell-type or standard nucleation models. Similarly, electron micrographs of the as-produced Ge nanowires showed a strong correlation between the base size of the Ge nanowires and the Ga droplet diameter. All nanowires featured a consistent taper, with a cone angle of approximately 10°. For the largest Ga droplets, no nanowires were observed under the employed ec-LLS conditions. Instead, a large isotropic Ge deposit covered with small Ge nanowires was observed. These cumulative results provide the first probe of the effects that liquid metal size(volume) have on electrodeposition by ec-LLS.