Synthesis and photoresponse of rare earth doped phosphosilicates

Abstract

Phosphate ceramics doped with Sm³⁺ and Tb³⁺ ions were synthesized through sol-gel process. Thin films of Tb³⁺ doped phosphosilicates were fabricated by spin coating of the phosphosilicate sols on SiO_x/indium-tin-oxide/glass substrates. The gels synthesized by reaction of P₂O₅ with tetraethoxy silane (TEOS) were fired in air at a temperature range of 200°C - 900°C. The crystal structure was examined by x-ray diffractometry. Si₅O(PO₄)₆ was the only crystalline phase. The fluorescence spectra of Sm³⁺ as a function of firing temperature, composition and structure of the matrices were investigated. The intensity of Sm³⁺ emission increased with increasing firing temperatures and greater proportion of phosphorus. The photocurrent of the films at 355 nm laser excitation was observed. The photoresponse as a function of laser energy was linear and showed no sign of saturation. The films exhibited stable photoresponse under a high number of laser shots.