Zirconia-ormosil films doped with PbS quantum dots

Zirconia-ormosil (organically modified silicates) films doped with different concentrations of PbS quantum dots were synthesized by sol-gel processing. A sol containing 3-(trimethoxysilil)propylmethacrylate as matrix precursor was mixed with a PbS colloidal doping sol. The control of the particle size was obtained by using 3-mercaptopropyltrimethoxysilane as capping agent in the PbS colloidal sol. The micro structure of the films was investigated by Fourier transform infrared spectroscopy, Rutherford backscattering spectrometry, X-ray diffraction and high resolution transmission electron microscopy. Linear and non-linear optical properties were studied by absorption spectrophotometery and non-linear m-line technique. A curing temperature of 130°C allowed a good degree of densification without deterioration of the sulfide particles and the change in refractive index from the substrate was sufficient to support waveguide modes. The doping concentration affected the mean particle size, shifting the linear absorption to shorter wavelengths for films doped with a smaller amount of PbS. The non-linear refractive index n2 was measured at 1.064 μm. A negative and fully reversible non-linear effect was measured, with n2 values in the range 10-15-10-16 m2/W, depending on the concentration of PbS quantum dots. © 1999 Elsevier Science B.V. All rights reserved.