Nanomechanical properties of NbN films prepared by pulsed laser deposition using nanoindendation

Structural and mechanical properties of niobium nitride thin films deposited by pulsed laser deposition were investigated using X-ray diffraction, atomic force microscopy, and nanoindentation. Niobium nitride was deposited on Si(1 0 0) by pulsed laser deposition (PLD) of Nb in nitrogen background. A Nanoindenter XP equipped with a dynamic contact module (DCM II) head was used in conjunction with the continuous stiffness method (CSM) in depth and load control modes to measure the hardness and modulus of the NbN thin films. NbN film reveals simple cubic δ-NbN structure with the corresponding reflections of (1 1 1), (2 0 0), and (2 2 0) planes. Highly textured NbN film shows a strong (1 1 1) preferred orientation. The NbN thin films depict polycrystalline structure, with a wide range of grain sizes that range from 15 to 40 nm with an average surface roughness of 6 nm. The average modulus of the film is 420 ± 60 GPa, whereas for the substrate the average modulus is 180 GPa, which is considered higher than the average modulus for Si reported in the literature due to pile-up. The hardness of the film increases monotonically from an average of 12 GPa for deep indents (Si substrate) measured using XP CSM and load control (LC) modes to an average of 25 GPa measured using the DCM II head in CSM and LC modules. The average hardness of the Si substrate is 12 GPa.