Change of TO and LO mode frequency of evaporated SiO2 films during aging in air
| Autor: | Josette Rivory, S. Fisson, G. Vuye, A. Brunet-Bruneau |
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| Rok vydání: | 2000 |
| Předmět: | |
| Zdroj: | Journal of Applied Physics. 87:7303-7309 |
| ISSN: | 1089-7550 0021-8979 |
| DOI: | 10.1063/1.372984 |
| Popis: | The microstructural modifications, induced by atmospheric water vapor, in the silica network of porous amorphous SiO2 films, evaporated by electron gun and capped by a nonporous TiO2 layer, have been investigated. We have taken advantage of infrared ellipsometric measurements to extract the infrared complex dielectric function of the SiO2 films in the 600–5000 cm−1 range, from which we deduce the actual values of the frequencies of the Si–O–Si stretching vibrational modes [transverse optic (TO) and longitudinal optic (LO)]. The TO and LO frequency shifts are studied experimentally and reproduced by simulation. Experimental data show the increase as a function of time in air of both TO and LO frequencies, and of the refractive index in the visible range. The film is modeled as a mixture of two constituents: a silica matrix, with variable density, and pores, into which water can penetrate. We show that the TO frequency is mainly sensitive to the silica matrix density, while the LO frequency gives informatio... |
| Databáze: | OpenAIRE |
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