Fabrication and Characterization of Zinc Oxide Nanorods on Electrohydrodynamic Jet Printed Silver Micropillars

The integration of three-dimensional (3D) nanostructures into optoelectronic devices offers significant potential for performance enhancement and expanded functionality. However, the advancement of 3D nanostructures has been constrained by the absence of effective fabrication techniques. This study introduces a two-step fabrication method for 3D nanostructures, combining the growth of zinc oxide (ZnO) nanorods (NRs) on silver (Ag) micropillars (MPs). The Ag MPs, which exhibit a controlled aspect ratio, were fabricated using drop-on-demand electro-hydrodynamic (DoD-EHD) printing, achieving a maximum height of 67 μm, a diameter of 2.60 μm, and an aspect ratio of ∼26. The number and spacing of the pillars can be precisely adjusted via software and motion control, underscoring the method’s versatility in the production of diverse 3D structures. Subsequently, high-density ZnO nanorods (NRs) were grown on the surface of Ag micropillars (MPs) using the hydrothermal method, resulting in NRs with an average length of 5 μm and a diameter of 0.80 μm. Characterization of the resulting 3D structures demonstrated the uniform morphology, high crystallinity, and superior optical properties. The identification of a double-band regime at 3.05 eV for Ag MPs and that at 3.40 eV for ZnO NRs confirmed the successful formation of out-of-plane 3D metal-semiconductor heterojunctions, highlighting their potential for application in advanced optoelectronic devices.