## 3 Results and Discussion
### Films' Composition and Chemical Bonding State
#### 3.3.3 XPS Analysis  
X-ray photoelectron spectroscopy was employed to understand the chemical bonding and composition of the near-surface layer of BC\({}_{\rm x}\)N\({}_{\rm y}\) films. Three samples of LPCVD films deposited at temperatures of 673, 873, and 973 K were analyzed. In the survey spectra of all the studied films, peaks of the elements such as B, C, N, and O were observed. The content of other elements in the films is below the detection limit of the XPS method. Table 2 presents the atomic ratios and the relative concentrations of elements in these films. With an increase in the synthesis temperature, the content of boron decreases, and the content of nitrogen and carbon increases. A similar trend in the change in the film composition was found by the EDX method. Information on the chemical structure of the BC\({}_{\rm x}\)N\({}_{\rm y}\) films was obtained from the analysis of the B1s, C1s, N1s, and O1s core-level spectra, which were fitted into components (Figure 8). The significant width and asymmetric shape of the recorded photoelectron lines indicate the non-uniform chemical environment of the atoms of boron, carbon, and nitrogen. These lines have a complex structure and are a superposition of four or more components with different contributions. The assignment of each component to certain types of bonds is taken from the literature. Figure 8a depicts the change of the binding energy of the B 1s level depending on the chemical environment. The B 1s peak is a superposition of at least four components. For all LPCVD samples, the main components at 188.0 eV and 189.0 eV correspond to \"boron-rich\" and \"carbon-rich\" boron carbides [3; 78]. By increasing the deposition temperature to 973 K, significant changes in their ratio were noticed. Simultaneously, the maximum of B 1 s peak shifts towards higher binding energies. Another component with an energy of 189.9 eV can be interpreted as a hybrid bond B-\(C_{\rm n}\)N\({}_{\rm 3-n}\)[79; 80]. The low-intensity component at 190.9 eV corresponds to B-N bonds in the h-BN compound [81]. Since the binding energies of B 1s in the B\({}_{2}\)O\({}_{3}\) compound are 192.0-193.7 eV [82], the component with an energy of 191.9 eV can be interpreted as hybrid bonds B-C(N)\({}_{\rm n}\)O\({}_{\rm 3-n}\). Table 3 lists the film composition and the binding energies for the B 1s line and the fraction of boron states in different chemical environments. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{\(\mathbf{T_{dep}}\) K} & \multirow{2}{*}{**[C]/[B]**} & \multirow{2}{*}{**[N]/[B]**} & \multirow{2}{*}{**[O]/[B]**} & \multicolumn{6}{c}{**Elemental Composition, at.\%**} \\ \cline{5-8}  & & & & **B** & **C** & **N** & **O** \\ \hline
673 & 0.44 & 0.07 & 0.20 & 59 & 26 & 4 & 12 \\
873 & 0.61 & 0.10 & 0.21 & 52 & 32 & 5 & 11 \\
973 & 0.77 & 0.13 & 0.25 & 46 & 36 & 6 & 12 \\ \hline \end{tabular}
\end{table} 
Table 2: Atomic ratios of elements and elemental composition of LPCVD BC\({}_{\rm x}\)N\({}_{\rm y}\) films from the XPS data. Figure 8b presents the C1s peaks with a complex fine structure. The main component peak, located at 284.8 eV, corresponded to the graphitic sp\({}^{2}\) C=C bonds. The intensity of this line increases with increasing deposition temperature. According to the Raman spectroscopy data for high-temperature films, it can be assumed that amorphous carbon is included in the structure of these films. It should be noted that surface carbon impurities, which are characterized by the presence of C-C and C-H bonds, have a close value of the binding energy. The components at lower binding energies are assigned to the formation of boron carbide bonds in the forms of B\({}_{4}\)C (282.5 eV) and BC\({}_{x}\) (283.3 eV) [79]. The spectra also exhibit weak peaks with binding energy near 286.3 eV, corresponding to the formation of C-N bonds in C-N\({}_{n}\)B\({}_{3-n}\) hybrid bonding [79].