Luminescence of Er-doped silicon oxide-zirconia thin films

Er-doped silicon oxide-zirconia thin film samples were prepared by rf co-sputtering. Chemical composition was determined by energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) showed that the films were amorphous. X-ray photoelectron spectroscopy (XPS) measurements showed that the matrix of the films consists of a ZrO₂ main body with pockets of silicon oxide, containing no Si nanoparticles (np) distributed within it. The samples were annealed to 700 °C. Er³⁺: ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2, ⁴F_9/2→⁴I_15/2, ⁴I_11/2→⁴I_15/2, and ⁴I_13/2→⁴I_15/2 emissions were observed. Excitation wavelength dependence and excitation photon flux dependence results for the ⁴I_13/2→⁴I_15/2 emission were explained as due to resonant energy transfer from defects in the matrix. ⁴I_11/2→⁴I_15/2 emission dependence on ⁴I_13/2→⁴I_15/2 emission showed that no energy transfer upconversion (ETU) processes were involved and that it was due only to branching from higher levels. ⁴I_13/2→⁴I_15/2 peak intensity decay was interpreted as corresponding to two different populations of Er³⁺ ions. Energy transfer from the defects to the Er ions is very efficient. We concluded that Er-doped silicon oxide-zirconia is a promising material for photonic applications, being excitable at low pumping powers and producing broad-band ⁴I_13/2→⁴I_15/2 emission.