Plasma etched Ag nanospheres for large increases of ZnO fluorescence emission: A combined theoretical-experimental study

Ag nanoparticles are prepared on p-type silicon substrates by magnetron sputtering, and then Ag nanospheres are constructed using appropriate plasma etching conditions. By comparing and analyzing the AFM and SEM morphologies, the experimental parameters are optimized continuously to achieve Ag nanospheres with uniform size distribution. Finally, ZnO films are deposited on the upper layer to form Ag/ZnO composite films. Compared with Ag/ZnO with unetched Ag nanoparticles, its fluorescence emission is enhanced 140 times by adjusting the optimum coupling distance of Ag nanospheres. In this work, based on the experimental results, the coupling effect of Ag nanospheres and ZnO films is theoretically simulated using COMSOL Multiphysics. According to the plasmon electromagnetic coupling theory, the dielectric function relationship is deduced. At the same time, the relationship between the electric field distribution, scattering cross section, skin depth and fluorescence emission is analyzed, which also confirm theoretically that the plasma resonance of Ag nanospheres enhance the fluorescence emission of ZnO. It provides reliable theoretical and experimental parameters for improving the light response and fluorescence emission efficiency of optical devices.