Growth and luminescence study of Cr2+: ZnSe films deposited by radio-frequency magnetron co-sputtering

The Cr²⁺:ZnSe films were deposited on glass, Si or GaAs substrates at room temperature (RT) by radio-frequency magnetron sputtering of a SiO₂ target covered by ZnSe and Cr chips under argon pressure. The thickness of the films, determined by optical transmission measurements, is found in the range 3-45 mum. Raman spectroscopy and X-ray diffraction investigations reveal that the films are mainly constituted of pure cubic ZnSe, with a strong texture along the [111] direction. The photoluminescence (PL) properties of the films were investigated at different temperatures under direct excitation into the ⁵T₂rarr ⁵E intracenter absorption band of the Cr²⁺ ions (1750 nm) using a home made Tm³⁺:KY₃F laser (1850 nm). The PL spectra at 10K of a reference bulk crystal and a Cr²⁺:ZnSe film are measured. They exhibit a large emission band centred at 2200 nm, attributed to intrashell ⁵T₂rarr ⁵E transition of the Cr₂₊ ions.