Optoelectronic Tuning of Sputtered ZnO–Au–Ag (NPs) Films Through Gold Interlayer Design

Abstract

This study investigates the tunability of the optoelectronic properties of ZnO-Au-Ag nanoparticle (NP) heterostructures through accurate control of the intermediate gold layer thickness. Three different configurations were fabricated via RF magnetron sputtering, followed by post-deposition annealing at 300 μC to induce the formation of Ag nanoparticles while preserving the Au interlayer. The resulting ZnO-Au-Ag (NP) structures exhibited Au ultrathin layers with different thicknesses. Optical characterization revealed a bandgap modulation from 3.35 to 3.66 eV, demonstrating the strong influence of plasmonic coupling between the Au interlayer and Ag nanoparticles. The incorporation of the gold layer enhanced visible-light absorption while maintaining UV transparency, with absorption at 550 nm increasing from 48.2% to 51.8%, despite the higher metallic content. Electrical transport measurements indicated a significant increase in carrier concentration, from 4.04 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sup> cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> (reference) to 3.37 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sup> cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> for the 4 nm Au layer, confirming efficient carrier activation through localized surface plasmon resonance (LSPR). These findings highlight the potential of ZnO-Au-Ag (NP) heterostructures for the development of nextgeneration transparent conducting electrodes and plasmon-enhanced electronic devices. In addition, the electrical and optical properties can be tuned by increasing the thickness of different layers for power optoelectronic applications.