Tunable emission from Eu:SiO_xN_y thin films prepared by integrated magnetron sputtering and plasma enhanced chemical vapor deposition

This paper reports tunable emission of trivalent (Eu³⁺) and divalent (Eu²⁺) europium (Eu) from SiO_xN_y films fabricated by integrated electron cyclotron plasma enhanced chemical vapor deposition and magnetron sputtering. The photoluminescence (PL) spectra of intense red emission from Eu³⁺ around 600 nm and blue (cyan) broadband emission from 400 to 750 nm of Eu²⁺ are observed under daylight conditions with the naked eye. The spectra reveal a strong dependency of the PL on the atomic concentration of the dopant and the silicon/nitrogen ratio. The atomic composition of the films is investigated by Rutherford backscattering spectrometry and elastic recoil detection analysis. Values of the refractive indices are obtained by variable angle spectroscopic ellipsometry. To confirm the presence of crystalline phases of europium silicate Eu_4.67(SiO₄)₃O [Eu₂(Si₂O₇)] and europium silicon oxynitride (EuSi₂N₂O₂) distributed in the amorphous host matrix of SiO_xN_y, high-resolution x-ray diffraction is used. The findings of this work are promising toward the realization of europium-doped Si-based materials for photonics and lighting technologies.