Effects of heat treatment and concentration on the luminescence properties of erbium-doped silica sol–gel films

• DOI: 10.1016/s0022-3093(01)00903-6
• Publication Date: 2002-10-14T16:04:50Z
• Authors: L.H Slooff; M.J.A de Dood; A van Blaaderen; A Polman
• Keywords: 02 engineering and technology; 0210 nano-technology

Abstract Erbium-doped sol–gel films with different Er concentrations were formed by spin-coating a solution of erbium-nitrate, tetra-ethoxy-silane (TEOS), ethanol, water and HCl on a Si substrate. Refractive index, film thickness and composition were measured as a function of Er concentration. The Er/Si ratio in the film is roughly proportional to the Er/Si ratio in solution, while the Si/O ratio varies with the Er concentration. The film thickness increases with increasing Er concentration, which is attributed to the increased viscosity of the spin-coat solution compared to pure SiO 2 . All films show a lower refractive index and atomic density than pure SiO 2 , which is ascribed to a slightly porous structure. After annealing at 750 °C in vacuum the films show clear room-temperature luminescence at 1.53 μm from Er 3+ . The luminescence lifetime is rather constant (10–12 ms) up to Er concentrations of 1.0 at.%. The luminescence lifetime reduces significantly if annealing is performed in air rather than in vacuum.