Optical Response of DyN

We report measurements of the optical response of polycrystalline DyN thin films. The frequency-dependent complex refractive index in the near IR-visible-near UV was determined by fitting reflection/transmission spectra. In conjunction with resistivity measurements, these identify DyN as a semiconductor with an optical energy gap of 1.2 eV. When doped with nitrogen vacancies it shows free carrier absorption and a blue-shifted gap associated with the Moss-Burstein effect. The refractive index of 2.0 ± 0.1 depends only weakly on energy. Far infrared reflectivity data show a polar phonon of frequency 280 cm−1 and a dielectric strength of Δe=20.