Bright field and dark field transmission electron microscope (TEM) images of selected HSS-TiN films are shown in Fig. 4. Selected area diffraction patterns of each film are inset. The major d-spacings can be indexed to BCC Fe and FCC TiN, in agreement with the XRD. The bright field image of the film deposited at − 25 V (Fig. 4(a)) shows a largely disordered microstructure. The diffraction pattern (inset in Fig. 4(b)) contains rings that can be indexed to BCC Fe, consistent with the XRD analysis and shows that the film has nanocrystalline microstructure with no evidence of preferred orientation. The dark field image of this film (Fig. 4(b)) reveals nano-scale crystals embedded throughout. The bright field image of the film deposited with a substrate bias of − 300 V (Fig. 4(c)) shows a coarse microstructure. The diffraction pattern (inset in Fig. 4(d)) indicates preferred orientation of the {110} Fe and {200} TiN planes perpendicular to the direction of film growth and nano-crystallites with this orientation are embedded throughout the film (Fig. 4(d)).