Nitridation of Nb surface by nanosecond and femtosecond laser pulses

Abstract Niobium nitride samples were prepared by laser nitridation in a reactive nitrogen gas environment at room temperature using a Q-switched Nd:YAG nanosecond laser and a Ti:sapphire femtosecond laser. The effects of laser fluence on the formed phase, surface morphology, and electronic properties of the NbN x were investigated. The samples were prepared at different nanosecond laser fluences up to 5.0 ± 0.8 J/cm 2 at fixed nitrogen pressure of ∼2.7 × 10 4 Pa formed NbN x with mainly the cubic δ-NbN phase. Femtosecond laser nitrided samples were prepared using laser fluences up to 1.3 ± 0.3 mJ/cm 2 at ∼4.0 × 10 4  Pa nitrogen pressure. Laser induced ripple patterns oriented parallel to the beam polarization were formed with spacing that increases with the laser fluence. To achieve a laser-nitrided surface with desired crystal orientation the laser fulence is an important parameter that needs to be properly adjusted.