Investigation of titanium nitride coating by broadband laser ultrasonic spectroscopy

We present a laser ultrasonic method to investigate a titanium nitride (TiN) coating specimen. The technique is based on the principle of surface acoustic wave (SAW) dispersion during acoustic propagation on a half-space with the presence of a thin layer. Due to the high efficiency of laser line-source excitation, we have been able to generate and detect a SAW with an excellent signal-to-noise ratio in a wide frequency band. An inverse fitting algorithm was employed to extract simultaneously the thickness and the elastic parameters of the TiN coating from the experimental SAW velocity dispersion curve.