Nitridation effect on sapphire surface polaritons

Surface polaritons have been used to study the nitridation of sapphire substrates. The samples of nitridized sapphire were prepared by gas source molecular beam epitaxy with ammonia, and the nitridation process was controlled by reflection high energy electron diffraction. The external reflectivity infrared spectra at near normal incidence are not sensitive to the nitridation. On the other hand, the high-frequency minimum in the attenuated total reflection spectra splits near 700 cm− 1 due to the presence of aluminum nitride on the substrate surface, demonstrating high sensitivity of the surface polariton technique to the state of the surface.