3.3 Growth morphologyFig. 3 shows S

3.3 Growth morphologyFig. 3 shows SEM cross-section images of Mo-N films on Si substrates. The film at 20% of nitrogen partial pressure has the denser morphology and presents a smoother surface than the others Fig. 3(a). A columnar structure with distinctive dense areas and rough surface were observed when the nitrogen partial pressure increases Fig. 3(b). The coating prepared at 2 ×10−3 mbar has a columnar microstructure Fig. 3(c). A tilt of about 10° is observed for coatings (c) and (d), probably due to the target inclination. This is consistent with the working pressure and the target inclination angle. This tilt is not seen for the other films, due to the fracture direction of the silicon substrate certainly orthogonal to the column tilt ones. The film observed in Fig. 3(d) has a dense columnar structure and less thickness than the other films, which is consistent with the decrease of the sputtering yield. The target surface was poisoned and the compound formation results in a decreased target erosion rate.