Improving the Uniform Distribution of Nano-Ag in Al-Doped ZnO Film to Enhance Its Application in Soft Touch Sensing Electrodes

Oxygen plasma etching has been performed to roughen the surface structure of an Al-doped ZnO (AZO) seed layer. The distribution of Ag nanoparticles was optimized to improve the characteristics of a film and facilitate its application as a touch sensing electrode. First, an intermittent procedure was performed to optimize the quality of the AZO seed layer. After the optimal parameters were obtained according to the figure-of-merit, the surface of the seed layer was roughened, and the depth of surface roughening was affected by adjusting the etching power of the oxygen plasma, and the surface roughness uniformity was affected by adjusting the etching time. Finally, by changing the etching oxygen flow rate, the width of the rough structure was further affected. The above three steps can optimize the surface roughness structure and effectively improve the uniform distribution of Ag nano-particles. To improve the sensitivity (SE) and stability (ST) of the film, the density of nano-Ag particles was modulated. The characteristics of film carriers were measured with a Hall effect analyzer. The surface morphology of the seed layer and the crystallinity change of the film were examined using electron microscopy, x-ray diffraction, ultraviolet–visible spectroscopy, and atomic force microscopy. The results revealed that a favorable film quality was achieved by performing three intermittent procedures. When the AZO seed layer surface was etched with a power of 50 W for 5 min, a 50-sccm etching oxygen flow and a 90-W nano-Ag deposition power were applied for 20 s, the density and distribution of the nano-Ag particles was favorable, and the SE and ST of the film were optimal. Under these conditions, the film’s resistance was 3.21 × 10⁻³ Ω-cm, its SE was 45.04%–52.48%, and its ST error was within 7.44%.