## 2 Materials and Methods  
Fully sintered YSZ polycrystalline doped with 3 mol% Y\({}_{2}\)O\({}_{3}\) (Tosoh Corp., Tokyo, Japan) was used as the workpiece. Samples of rectangular plates with a thickness of 3 mm were prepared. The sample surface was sintered at 1500 \({}^{\circ}\)C and thermally etched at 1350 \({}^{\circ}\)C without polishing. The average grain size was 600 nm, and surface roughness was 309 \(\pm\) 18 nm Ra. The entire workpiece was cleaned with acetone and ethanol before the experiment. The Yb:KGW femtosecond pulsed laser (PHAROS-08-600-PP, Light Conversion, UAB, Vilnius, Lithuania) was used in this study. The laser parameters are summarized in Table 1. The laser wavelength was 1028 nm and the repetition frequency was 100 kHz. The laser spot diameter was 16 \(\upmu\)m at the focal point. The laser beam had a Gaussian energy distribution, and laser beam scanning was controlled by a galvanometer scanner system in the X and Y directions. The beam was focused onto the workpiece placed on an adjustable \(z\)-axis stage through an f0 lens. The schematics of the experimental process are shown in Figure 2. Firstly, a laser was irradiated on the entire sample surface to generate nanopores by using laser parameters summarized in Table 1 (a). Then, nano-silver dispersion liquid (Japan Ion Corp., Tokyo, Japan) was dropped onto the surface. The workpiece was dried in a vacuum desicator for 24 h to completely remove moisture from the surface to avoid hydrothermal degradation caused by contact between zirconia and water molecules [32]. To embed silver nanoparticles in the nanopores and remove excessive deposits simultaneously, the laser beam was scanned again on the workpiece. To investigate the nanoparticle embedding characteristics, the laser beam was scanned for various laser fluences, scanning speeds, and pulse widths summarized in Table 1 (b). To remove the excess dried film of the dispersion attached to the outside of the pore without processing the original YSZ surface, the laser fluence was set extremely smaller than the ablation threshold of zirconia to selectively remove only the target material from the surface. For the comparison, the Nd:YVO\({}_{4}\) nanosecond pulsed laser (Super Pulse 532-30, Inugu Laser Co., Ltd., Zhengzhou, China) and electric furnace (High-performance muffle furnace HPM-1N, AS One Corp., Osaka, Japan) were used to remove the excess dried film. The nanosecond pulsed laser was irradiated with various laser parameters summarized in Table 1 (c). Since the beam diameter was different from the femtosecond pulsed laser, the scanning speed was adjusted so that the pulse overlap rate was the same. On the other hand, the workpiece was heated in an electric furnace at 450 \({}^{\circ}\)C for 30 min in air. All experiments in this study were performed under atmospheric conditions. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Parameters**} & **(a)** & **(b)** & **(c)** \\  & **Nanopore Generation** & **Fixation of Nanoparticles** & **Fixation of Nanoparticles** \\ \hline Laser medium & Yb:KGW & Yb:KGW & Nd:YVO\({}_{4}\) \\ Wavelength: \(\lambda\) [nm] & 1028 & 1028 & 532 \\ Spot size [\(\upmu\)m] & 16 & 16 & 85 \\ Pulse width & 256 fs & 256 fs, 10 ps & 26 ns \\ Repetition frequency: \(f\) [kHz] & 100 & 100 & 100 \\ Scanning speed: \(v\) [mm/s] & 1000 & 10–500 & 53\(\sim\)1593 \\ Laser power: \(E\) [mW] & 450 & 60–140 & 1.7 \(\times\) 10\({}^{3}\)–4.0 \(\times\) 10\({}^{3}\) \\ Laser fluence: \(F\) [J/cm\({}^{2}\)] & 2.2 & 0.3\(\sim\)0.7 & 0.3–0.7 \\ Number of scans: \(N\) & 1 & 1 & 1 \\ Atmosphere & Air & Air & Air \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Experimental conditions. To observe silver nanoparticles in nano-silver dispersion, a field-emission transmission electron microscopy (FE-TEM, Tecnai G2, FEI Co., Hillsboro, OR, USA) was used. The nano-silver dispersion was dropped onto a glass plate and completely dried in a desiccator by removing the water.