Deposition and photoluminescence of sol-gel derived Tb³⁺:Zn₂SiO₄ films on SiO₂/Si

Tb³⁺ doped Zn₂SiO₄ films have been deposited on SiO₂ buffered Si wafers by sol-gel method. The structures of these films have been investigated with X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The results revealed that these films were composed of nanometer-size grains with a Willemite structure and had smooth surfaces. Photoluminescence measurements of the films showed a strong emission from ⁵D₄ to ⁷F₅ at 544 nm. The blue emission from ⁵D₃-⁷F_j was depressed because of cross-relaxation effect. The decay kinetics of the ⁵D₄-⁷F₅ green emission was studied and a best fitting was obtained by a double exponential function. The lifetime of the excited ⁵D₄ state is estimated to be 5.2 ms.