Structural role of fluorine in amorphous silica

Youngman, Randall E.; Sen, Sabyasachi

doi:10.1016/j.jnoncrysol.2004.08.255

Cited by 44 publications

(25 citation statements)

References 24 publications

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“…An understanding of these structure-property relationships is crucial especially considering the current widespread use of F-doped silicas in long-haul telecommunications and next-generation photolithographic processes. We are currently expanding our studies to include a detailed examination of the effect of fluorine content and fictive temperature on the speciation of fluorine in F-doped aSiO 2 [22].…”

Section: Resultsmentioning

confidence: 99%

The nature of fluorine in amorphous silica

Youngman¹,

Sen²

2004

Journal of Non-Crystalline Solids

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Section: Resultsmentioning

confidence: 99%

The nature of fluorine in amorphous silica

Youngman¹,

Sen²

2004

Journal of Non-Crystalline Solids

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“…Youngman et al 45), 46) performed a nuclear magnetic resonance (NMR) study on 19 F and 29 Si in silica glass. They clarified that F ions substitute the oxygen ion sites to form tetrahedral SiO 3 F units in silica glass.…”

Section: Mechanism Of F-doping Effectmentioning

confidence: 99%

Doping effects in amorphous oxides

Funabiki

Kamiya

Hosono

2012

J. Ceram. Soc. Japan

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Impurity doping of crystalline Si is one of the most striking techniques in semiconductor technology. A rigid and perfect crystalline lattice is prerequisite for effective doping. However, it has been reported to date that introducing a small amount of impurities drastically improves also the properties of amorphous materials. This paper reviews three pronounced doping effects on optical and electrical properties of amorphous oxides; i.e., (i) F-doping of silica glass to improve the vacuum-ultraviolet optical transmission and radiation toughness, (ii) codoping effects on solubility enhancement of rare earth ions in silica glass melt, and (iii) electron-carrier generation in transparent amorphous oxide semiconductors. It is emphasized that effectiveness of electron doping is determined by the magnitude of electron affinity and stabilization energy of a dopant. Importance of the local structure formed around a dopant ion and the location of conduction band minimum measured from the vacuum level is addressed to understand the doping effects in amorphous oxides.

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“…[4][5][6][7][8] The structural origin of this effect was analyzed in F-modified glasses from chemical vapor deposition ͑CVD͒ methods, identifying different roles of fluorine, mainly in the modification of the mean bond energy and the structural disorder of the amorphous matrix. 5,[9][10][11] In this scenario, fabrication of F-modified silica from sol-gel synthesis 12 should, in principle, be an interesting target because of the relatively lowcost and sustainable features of the process, and for the expected improvement in radiation hardness with respect to other types of silica. 13,14 However, only few studies on F-doped sol-gel silica have been reported regarding preforms for low-index optical fibers, 15 and no vuv data have been published on fluorinated silica from sol-gel synthesis.…”

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confidence: 99%

High-energy shift of the Urbach ultraviolet absorption from attenuated dynamical disorder in fluorine modified sol-gel silica

Палеари

Meinardi

Lauria

et al. 2007

Applied Physics Letters

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Fluorine modified amorphous silica has been synthetized via sol-gel route and studied through analysis of the temperature dependence of the Urbach absorption tail in the vacuum-ultraviolet region. The modified glass has a steep absorption edge above 8 eV, with the absorption coefficient ␣ ϰ exp͓E / E U ͑T͔͒ showing Urbach energy values E U ͑T͒ ranging between 50 and 66 meV. The comparison of E U ͑T͒ with pure silica data indicates a structural softening caused by the reduction of dynamical disorder, and suggests that the F-modified sol-gel synthesis is an appropriate route for achieving high energy shifts of the absorption edge. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2794429͔ Several technological areas are looking for new material compositions and synthetic routes for the production of optical materials with transmission window extending into the vacuum ultraviolet ͑vuv͒ region and with improved radiation hardness and thermal stability. 1,2 In specific applications such as photomasks for lithography at 157 nm and materials for vuv sources, silicalike structural features are unique in assuring low thermal expansion coefficient and good workability. 3 For these reasons, modifications of silica optical properties through specific synthesis or doping processes are currently being investigated to extend its operational window into the vuv. Fluorine modified silica-based materials are promising candidates for these applications, since the silica absorption edge shifts toward high energy after fluorine doping. [4][5][6][7][8] The structural origin of this effect was analyzed in F-modified glasses from chemical vapor deposition ͑CVD͒ methods, identifying different roles of fluorine, mainly in the modification of the mean bond energy and the structural disorder of the amorphous matrix. 5,[9][10][11] In this scenario, fabrication of F-modified silica from sol-gel synthesis 12 should, in principle, be an interesting target because of the relatively lowcost and sustainable features of the process, and for the expected improvement in radiation hardness with respect to other types of silica. 13,14 However, only few studies on F-doped sol-gel silica have been reported regarding preforms for low-index optical fibers, 15 and no vuv data have been published on fluorinated silica from sol-gel synthesis. In fact, sol-gel silica usually contains a large number of OH groups that are responsible for a broad absorption band at 8 eV, 16 which is strongly detrimental for vuv applications. In the present work, we disclose a method for the fabrication of optical grade bulk samples of F-doped dry silica by means of a modified sol-gel method. Our results show that the achievable reduction of dynamical disorder and -OH content opens the way to the utilization of sol-gel materials in vuv applications.Bulk samples, about 0.5 mm thick, of fluorine-modified silica were prepared by the sol-gel technique, cogelling tetraethoxysilane and trimethoxyfluorosilane, with concentration ratio 1:9. After gelation and drying, the xerogel samp...

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Structural role of fluorine in amorphous silica

Cited by 44 publications

References 24 publications

The nature of fluorine in amorphous silica

The nature of fluorine in amorphous silica

Doping effects in amorphous oxides

High-energy shift of the Urbach ultraviolet absorption from attenuated dynamical disorder in fluorine modified sol-gel silica

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