Focused-ion-beam Assisted Growth, Patterning, and Narrowing the Size Distributions of ZnO Nanowires for Variable Optical Properties and Enhanced Nonmechanical Energy Conversion

Despite extensive research and much progress, it remains critical and challenging to precisely grow nanowires structurally and dimensionally uniform. Here, we present a focused-ion-beam (FIB) assisted approach to controlling the ZnO nanowire growth with uniform diameters, height, and high crystalline quality. Vertical-alignment is also achieved on nonepitaxial substrates without the assistance of ZnO seeding layers (e.g., silicon and c-plane sapphire substrates). The programmable ability of FIB opens up new opportunities of creating complex patterns in our approach. A new alloy catalyst Au–Ga is developed for ZnO growth, with achievable narrow nanowire size distributions. Comparison studies of growth behavior in the temperature range 880–940 °C for Au and Au–Ga catalysts reveal different growth kinetics and rate-controlling mechanisms that are consistent with the vertical-alignment and drastically improved nanowire uniformity for FIB-assisted nanowire growth. Nanogenerators built with the improved nanowire platform exhibit a 2.5-fold increase in thermal energy conversion, demonstrating the promise of our approach for advanced functional devices.