Selective growth of stacking fault free <100> nanowires on a polycrystalline substrate for energy conversion application.

Cubic semiconductor nanowires grown along <100> directions have been reported to be promising for optoelectronics and energy conversion applications, owing to their pure zinc-blende structure without any stacking fault. But, till date, only limited success has been achieved in growing <100> oriented nanowires. Here we report the selective growth of stacking fault free <100> nanowires on a commercial transparent conductive polycrystalline fluorine-doped SnO (FTO) glass substrate via a simple and cost-effective chemical vapor deposition (CVD) method. By means of crystallographic analysis and density functional theory calculation, we prove that the orientation relationship between the Au catalyst and the FTO substrate play a vital role in inducing the selective growth of <100> nanowires, which opens a new pathway for controlling the growth directions of nanowires via the elaborate selection of the catalyst and substrate couples during the vapor-solid-liquid (VLS) growth process. The ZnSe nanowires grown on the FTO substrate are further applied as a photoanode in photoelectrochemical (PEC) water splitting. It exhibits a higher photocurrent than the ZnSe nanowires without preferential orientations on a Sn-doped InO3 (ITO) glass substrate, which we believe to be correlated with the smooth transport of charge carriers in ZnSe <100> nanowires with pure zinc-blende structures, in distinct contrast with the severe electron scattering happened at the stacking faults in ZnSe nanowires on the ITO substrate, as well as the efficient charge transfer across the intensively interacting nanowire-substrate interfaces.