## 3 Results
The peak at 286.6 eV is attributed to a C=N bond and to the formation of a carbide respectively [13]. The XPS spectra for the N-UNCD film in the N1s region (Figure 3b) shows a relatively weak but clear signal correlated with a single peak at 400 eV, confirming the presence of nitrogen in the N-UNCD films [7]. Figure 4 shows the Raman spectra of N-UNCD films grown at: (a) 3000 W, (b) 4000 W, and (c) 4500 W. The spectra exhibit the characteristic bands of N-UNCD reported in the literature, which are the G band at 1550 cm\({}^{-1}\) attributed to sp2 carbon bonds, and the D band at 1350 cm\({}^{-1}\) attributed to disorder-induced sp2 carbon bonds in grain boundaries. The D band at 1350 cm\({}^{-1}\) encapsulate the 1332 cm\({}^{-1}\) peak, which is the finger-print of diamond. In addition, the bands at 1450 cm\({}^{-1}\) and 1130 cm\({}^{-1}\) correspond to C=C and C-H bonds in transpoliacetilene (TPA) molecules, respectively, reported in [15; 16]. The intensity of the TPA peaks (1130 and 1450 cm\({}^{-1}\)), in the Raman spectra of the N-UNCD films, decreased as the total pressure and microwave power increased during film growth. This indicates that the grain boundary chemistry of the N-UNCD films presents more sp2 bonded carbon atoms and less TPA bonds with an increase in the total pressure and microwave power. This could be due to a higher incorporation of N atoms, as the total pressure and microwave power increases, since C-N bonds compete with TPA bonds in the grain boundaries as N atoms are getting incorporated. Figure 4d shows the substrate temperature vs. film grown pressure. The decrease in the intensities of the TPA bands, previously discussed, is correlated with an increase in the substrate temperature, obtaining a maximum substrate temperature for the film grown at 100 mbar and 4500 W, which is also the N-UNCD film with the lowest TPA bands intensities. These results are consistent with publications in the literature, which also show lower TPA Raman signals as the substrate temperature increases during the growth of UNCD and N-UNCD films [17; 18]. Figure 3: N 1s and C 1s XPS peaks from N-UNCD films grown at (**a**) 80, 90, and 100 mbar, at 4500 W; (**b**) N 1s XPS peak from N-UNCD film grown at 100 mbar; and (**c**) C 1s XPS peak from N-UNCD film grown at 100 mbar. Figure 5 shows the electrical measurements for N-UNCD film grown at 4000 and 4500 W with plasma pressure in the range 70-100 mbar. The electrical conductivity of the N-UNCD films increases (electrical resistivity decreases) as the microwave power and total plasma pressure increases during the films' growth, obtaining a maximum electrical conductivity (minimum electrical resistivity) for the N-UNCD film grown with a total pressure of 100 mbar and microwave power of 4500 W. This increase in electrical conductivity is correlated with a decrease in the Raman intensities of the TPA bands and an increase in the substrate temperature discussed previously, indicating that N atoms incorporation in the N-UNCD films' grain boundaries increases with the substrate temperature. Therefore, the effect of increasing the total pressure and microwave power of the plasma during the growth of N-UNCD films results in an increase of the substrate temperature in order to enhance, at the same time, the incorporation of N atoms in the grain boundaries of the N-UNCD films. Figure 4: Raman spectra of N-UNCD films grown at: (**a**) 3000 W (70–100 mbar); (**b**) 4000 W (70–100 mbar); (**c**) 4500 W (70–100 mbar); (**d**) Graph of the substrate temperature vs. film grown pressure. The rest of the samples were excessively resistive to be measured. The results shown in Figure 5 are consistent with data published in the literature, as it has been reported by other authors that a high substrate temperature (>800 \({}^{\circ}\)C) is required for more efficient incorporation of N atoms in N-UNCD films [5; 16; 18].