Cu microcrystals in sol-gel derived glasses
- PDF / 608,299 Bytes
- 5 Pages / 576 x 792 pts Page_size
- 63 Downloads / 196 Views
Arao Nakamura Nagoya University, Chikusa Nagoya, 464 Japan (Received 20 December 1994; accepted 8 June 1995)
Cu2+-containing SiC>2 and AI2O3 • 9SiO2 glasses were prepared by the sol-gel method and heated under reducing conditions to precipitate small-sized Cu and Cu 2 O crystals. Cu2+ ions incorporated in SiO2 glass were reduced by heating in N 2 to precipitate Cu 2 O and in H2 to precipitate Cu microcrystals with diameters of about 5 to 15 nm. Microcrystalline Cu-precipitated glass showed an optical absorption band at 560 nm and its third-order nonlinear susceptibility was 1.25 X 10"10 esu, which originated from the enhancement by the surface plasmon resonance of Cu particles. In contrast, Cu2+ ions incorporated in AI2O3 • 9SiC>2 glass remained unchanged after heating in the reducing gas atmospheres.
I. INTRODUCTION Small-sized metal and semiconductor-doped glasses are now popular objects to study the quantum confinement effect of electron-hole carriers and excitons in particles. In particles with diameters less than a critical size, the carriers and excitons are confined in the deep three-dimensional potential of the glass matrix, which is expected to give rise to large, resonant third-order nonlinearity.1 Small particles can be developed within transparent glasses by heat treatment for crystallization or reduction of metal ions.2^1 Although the size of the microcrystals can be controlled during heat treatment, the conventional melting method has some disadvantages. One disadvantage is the difference in final composition of the crystal because of the high volatility of crystal constituent ions during glass melting and heat treatment. For example, for preparation of copper-doped glasses,5 which are interesting because of the possibility of high third-order nonlinearity (^ 3 ), Cu2+ ion-containing glasses are reduced to form microcrystalline particles. Cuprous (Cu+) and cupric (Cu2+) ions also exist, in addition to metallic copper, which give different optical characteristics. The proportion of copper present in each of these possible states is determined by the glass composition and preparation conditions, such as melting temperature and furnace atmosphere, which should be strictly controlled. Rf sputtering,6 ion implantation,7 and sol-gel methods8'9 also have been applied to the preparation of copperdoped glasses. We have been conducting a study of the preparation of glasses doped with small-sized semiconductor crystals by the sol-gel process.10-11 The sol-gel method is an extension of the other conventional methods because 2648
J. Mater. Res., Vol. 10, No. 10, Oct 1995
http://journals.cambridge.org
Downloaded: 02 Dec 2014
it enables microcrystal-doped films to be obtained by chemical reaction without melting or vaporizing the raw materials. Our previous studies have reported on silica glasses doped with semiconducting metals, chalcogenides, and halides. Glasses containing metal ions were prepared from an alkoxy-derived solution, then allowed to react with reducing gases such as H2S and H2, forming fine cry
Data Loading...
