## 4 Conclusions  
In this paper, the _Pinus sylvestris_ L. var. _mongholica Litv_ veneers were used as the substrate, and the copper film was deposited on the surface of the ultrasonic pretreated wood veneer by magnetron sputtering to prepare the \"environmentally friendly\" copper-coated wood-based composite materials. The metallization of wood veneers does not affect the crystalline region of wood, and the crystal structure of wood cellulose is not destroyed, but the intensity of characteristic peaks of crystal faces is reduced. Ultrasonic treatment aggravates the porous structure of wood, and a rough metal copper film interface is constructed on the surface of the wood by magnetron sputtering to change the surface wettability of the wood from hydrophilic to strongly hydrophobic. Under the sputtering condition of a substrate temperature of 200 \({}^{\circ}\)C, the copper film is uniform, densely arranged, and the surface water contact angle reaches 149.9\({}^{\circ}\), which has almost super-hydrophobic properties. It can be seen that ultrasonic treatment of wood aggravates the porous structure of wood and makes the surface of wood rougher. The magnetron sputtering method can be used to construct a rough metal film interface on the surface of the wood, so that the surface wettability of the wood undergoes a transformation from hydrophilic to strongly hydrophobic. The lotus leaf effect is realized on the wood surface. The ultrasonic treatment of wood combined with magnetron sputtering to prepare copper thin films can provide new ideas for wood modification. In future research, it can be combined with chemical methods to prepare more wood composites with strong practicality and excellent performance.  
Conceptualization, H.M. and J.L.; methodology, H.M.; software, J.L.; validation, H.M., J.L. and D.Q.; formal analysis, X.D.; investigation, Y.W.; resources, D.Q.; data curation, Y.T.; writing--original draft preparation, H.M.; writing--review and editing, J.L.; visualization, Y.W.; supervision, Y.W.; project administration, J.L.; funding acquisition, D.Q. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the Fundamental Research Funds for the Central Universities (2572020 BC07).  
The authors declare no conflict of interest.  
The data that support the findings of this study are available within the article. The numerical datasets and additional SEM images are available from the corresponding author upon reasonable request.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sputtering Time** & **Element** & **Percentage by Weight/\%** & **Atom Percentage/\%** \\ \hline \multirow{2}{*}{0 s} & C & 52.68 & 59.73 \\  & O & 47.32 & 40.27 \\ \hline \multirow{3}{*}{50 s} & C & 45.38 & 59.84 \\  & O & 35.85 & 35.49 \\  & Cu & 18.77 & 4.68 \\ \hline \multirow{3}{*}{150 s} & C & 24.77 & 49.43 \\  & O & 19.79 & 29.65 \\  & Cu & 55.44 & 20.92 \\ \hline \multirow{3}{*}{10 min} & C & 10.41 & 32.8 \\  & O & 7.83 & 18.51 \\  & Cu & 81.76 & 48.69 \\ \hline \multirow{3}{*}{15 min} & C & 8.05 & 28.03 \\  & O & 5.83 & 15.26 \\ \cline{1-1}  & Cu & 86.12 & 56.71 \\ \hline \multirow{3}{*}{15 min (200 \({}^{\circ}\)C)} & C & 9.21 & 30.95 \\ \cline{1-1}  & O & 6.03 & 15.21 \\ \cline{1-1}  & Cu & 84.76 & 53.83 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Weight percentage of surface elements before and after coating.