Properties of zirconia films dispersed with PbS nanoparticles
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PbS/ZrO2 optical films were prepared by the dip-coating method from a mixed sol containing two precursors, Zr(OC3H7)4 and Pb(CH3COO)2. The phase structure and size of PbS nanoparticles were characterized by x-ray diffraction and transmission electron microscopy, respectively. Optical absorption and fluorescence spectra were taken on the PbS/ZrO2 films. Larger blue shifts of band edge and weak fluorescence emission of PbS were observed. The third-order nonlinear properties of PbS/ZrO2 films were studied. The calculated values of nonlinear refractive indexes n2 varied between 10−8 and 10−9 cm2/W.
I. INTRODUCTION
Transparent optically functional films hold considerable promise for applications in the fields of communications and photoelectrons. These applications range from integrated optical devices (all optical swatches, modulators, amplifiers, etc.) to photocatalysis and sensors.1 It is easy to create optically functional materials by dispersing semiconductor nanoparticles into suitable matrix films (such as glass, ceramic, and polymer). These materials are suitable candidates for study of the linear and nonlinear optical properties of nanoparticles, including absorption, fluorescence, and the larger third-order optical nonlinearity. Reisfled2 and Beecroft et al.3 have given detailed reviews about these research works. PbS is superior to other semiconductors, mainly because the absorption band of PbS is at 3350 nm,4 which can be easily shifted to the telecommunication region by the quantum size effect. Larger optical nonlinearities can also be obtained in PbS nanoparticle-dispersed films.5 Studies on the films doped with PbS semiconductor nanoparticles, such as glasses6–8 or polymers9–11 have been reported. Guglielmi et al.12 reported PbS nanoparticle-dispersed SiO2 and SiO2/TiO2 films, so that the absorption edge of PbS particles could be shifted to 1100 nm. The similar results were also reported from other research.13,14 The most investigated matrix materials are SiO2, SiO2/ TiO2, and polymers. ZrO2 films have been paid more attention in recent years. The properties of ZrO2 films,
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Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 15, No. 11, Nov 2000
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such as high mechanical and thermal stability, and high refractive index15 are superior to other previously investigated matrix materials. It is easy to incorporate semiconductor nanoparticles into ZrO2 film and to perform their linear or nonlinear optical properties. The aim of the work reported in this paper was to synthesize ZrO2 films with minimized absorption edge at 1.3–1.5 m, through dispersing PbS nanoparticles, and to study their optical properties.
II. EXPERIMENTAL
Although many routes can be used to prepare semiconductor nanoparticles dispersed films, the sol-gel method is usually adopted, because of ease and low cost of preparation and high optical quality of films.16,17 In this work, the sol-gel technique combined with the dip-coating method was
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