## 3 Results and Discussion
### Xps  
XPS analysis is conducted to evaluate the surface chemical composition of TMS plasma modified rayon flock synthetic leather. The surface stoichiometry was analyzed by studying the content of elements of carbon (C), oxygen (O), and silicon (S). Figure 10 shows the wide scan of the untreated and plasma modified, XPS results. The intensity of oxygen sharply decreased after TMS plasma treatment. The spectra features, along with binding energies and full width at half maximum (FWHM) of the treated samples, are reported in Table 4. The carbon and oxygen signals are composed of various peaks indicating the presence of different chemical surroundings of carbon and oxygen atoms. Table 5 shows the peak positions of the C1s features of plasma-modified samples. Deconvolution study reveals that the C1s peak was assigned to be C-H, C-O, O-C-O and C=O bonds (Figure 11). It is clear that the C-O, O-C-O, and C=O bonds' intensity decreased after TMS plasma treatment. The O-containing groups are dropped after TMS plasma treatment. On the contrary, the intensity of C-H bonds increases. \(H\)-containing groups, which are generated from TMS during plasma treatment, increase.  
Figure 10: Surface elementary composition of (**a**) untreated and (**b**) TMS plasma-modified rayon flock synthetic leather (treatment parameters: amount of TMS = 0.2 mL; flow rate of helium = 12.5 LPM; discharge power = 50 W; jet distance = 10 mm; treatment time = 30 s).  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Peak** & **Position (eV)** & **FWHM** \\ \hline C1s & 284.08–292.15 & 1.01–1.67 \\ O1s & 531.50–538.30 & 1.00–2.03 \\ Si\({}_{2}\)P & 102.05–107.39 & 1.88 \\ \hline \hline \end{tabular}
\end{table}
Table 4: XPS features of plasma-modified rayon flock synthetic leather.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Peak** & **Feature** & **Peak Position (eV)** \\ \hline C1 & C–H, C–C & 285.0 \\ C2 & C–O & 286.9 \\ C3 & C=O & 288.0 \\ C4 & O–C–O & 288.7 \\ \hline \hline \end{tabular}
\end{table}
Table 5: XPS position of C1s features of plasma-modified rayon flock synthetic leather.  
The XPS results confirm the FTIR-ATR results: Si-containing groups increased after plasma treatment. With the FTIR-ATR and TMS results, the nubs and burrs observed on the surface of plasma-modified samples are proved to be silicon compounds deposited by plasma treatment.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Sample** & **C** & **O** & **Si** & **N** & **O/C** & **Si/O** \\ \hline Untreated & 61.17 & 32.02 & 5.54 & 1.27 & 0.52 & 0.17 \\
0 mL TMS (treated with He plasma only) & 62.32 & 32.52 & 3.89 & 1.27 & 0.52 & 0.12 \\
0.1 mL TMS & 64.37 & 29.45 & 6.18 & N/A & 0.46 & 0.21 \\
0.15 mL TMS & 66.29 & 27.19 & 6.52 & N/A & 0.41 & 0.24 \\
0.2 mL TMS & 66.44 & 26.08 & 7.48 & N/A & 0.39 & 0.29 \\
0.25 mL TMS & 67.01 & 26.18 & 6.81 & N/A & 0.39 & 0.26 \\ \hline \end{tabular}
\end{table}
Table 6: Atomic percentage and ratio of rayon flock synthetic leather surface.  
Figure 11: XPS deconvoluted C1s peak in (**a**) untreated sample and (**b**) plasma-modified rayon flock synthetic leather (treatment parameters: amount of TMS = 0.2 mL; flow rate of helium = 12.5 LPM; discharge power = 50 W; jet distance = 10 mm; treatment time = 30 s).  
TMS plasma treatment successfully enhances the surface hydrophobicity of rayon flock synthetic leather. The improvement of surface hydrophobicity is attributed to the deposition of organosilicon by plasma treatment [26; 27; 28].