Photoinduced Reactions of Oxygen-Deficient Centers with Molecular Hydrogen in Silica Glasses

Radzig, V. A.; Баграташвили, В. Н.; Tsypina, S. I.; Chernov, P. V.; Рыбалтовский, А. О.

doi:10.1021/j100017a054

Cited by 53 publications

(58 citation statements)

References 13 publications

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“…[15], Radzig et al observed the photo-induced decay of H(I) center (=Si • -H). Their experimental observation is connected with the present result, since H(I) and H(II) both belong to an isoelectronic series of defects, localized respectively on a Si, Ge, Sn atom, which are known to have similar formation and spectroscopic properties [15][16][17].…”

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confidence: 99%

H(II) Centers in natural silica under repeated UV laser irradiations

Messina

Cannas

Boscaino

2005

Journal of Non-Crystalline Solids

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Abstract:We investigated the kinetics of H(II) centers (=Ge • -H) in natural silica under repeated 266nm UV irradiations performed by a Nd:YAG pulsed laser. UV photons temporarily destroy these paramagnetic defects, their reduction being complete within 250 pulses. After re-irradiation, H(II) centers grow again, and the observed recovery kinetics depends on the irradiation dose; multiple 2000 pulses re-irradiations induce the same post-irradiation kinetics of H(II) centers after each exposure cycle. The analysis of these effects allows us to achieve a deeper understanding of the dynamics of the centers during and after laser irradiation.

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confidence: 99%

H(II) Centers in natural silica under repeated UV laser irradiations

Messina

Cannas

Boscaino

2005

Journal of Non-Crystalline Solids

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“…To increase the photosensitivity of germanosilicate glass the ''chemical'' pathways of UV energy relaxation in GODC should be accelerated. [3][4][5] The mechanisms of GODC chemical phototransformation are very complicated, and they are far from being completely understood. Different parameters of glass such as concentration of Ge 5,6 and other dopants 7 and impregnated molecular species ͑like hydrogen 5,8 ͒, can be critical for these mechanisms.…”

Section: ͓S0003-6951͑00͒01437-6͔mentioning

confidence: 99%

“…1 and 2͒ could be explained by the photochemical inhomogeneity of GODC in a glass, when different groups of GODC have slightly different spectroscopic parameters and different photoreaction probabilities. 3,18,19 It is commonly believed that the chemical transformation of the triplet excited state of GODC is caused by a tunneling charge transfer to traps located in a neighboring coordination shell, 5 since no free electrons appear in this case. This effect has been treated as a transformation of triplet excited oxygen monovacancy from normal configuration to an anomalous one ͑''puckered'' states͒.…”

Section: ͓S0003-6951͑00͒01437-6͔mentioning

confidence: 99%

Effect of electric field on one-quantum photodecay of oxygen-deficient centers in germanosilicate fibers

Рыбалтовский

Zavorotny

Chernov

et al. 2000

Applied Physics Letters

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The effect of a strong electric field ͑up to 10 6 V/cm͒ on one-quantum UV photoexcitation and photodecomposition of germanium oxygen deficient centers ͑GODC͒ in twin-hole germanosilicate fibers with internal wire electrodes is reported. The fiber has been irradiated with the UV light of a deuterium lamp and triplet photoluminescence of GODC has been used to monitor the kinetics of its photodecay. Applying such an electric field did not affect the spectral characteristics of GODC but increased the rate of their one-quantum photodecomposition, while direct photoionization and charge separation did not take place. We have also shown that this effect is caused by the suppression of secondary photoinduced recombination processes of intermediates, rather than by acceleration of primary photodecomposition of GODC. © 2000 American Institute of Physics. ͓S0003-6951͑00͒01437-6͔The effect of UV photosensitivity of Ge-doped silica glass is widely used for effective photoinscription of fiber and planar microstructures.1 This effect is recognized to be associated with structural phototransformation of germanium oxygen-deficient centers ͑GODC͒ and local density alteration in a Ge-doped glass network. Exposure of GODC to UV light is produced mostly in 242 nm singlet absorption band (S 0 -S 1 electron transition͒ and also in weak triplet absorption 330 nm band (S 0 -T 1 electron transition͒.2 Singlet photoexcitation of GODC results in the appearance of two luminescence bands-singlet band centered at about 300 nm (S 1 -S 0 transition͒ and triplet band at about 400 nm (T 1 -S 0 transition͒. To increase the photosensitivity of germanosilicate glass the ''chemical'' pathways of UV energy relaxation in GODC should be accelerated.3-5 The mechanisms of GODC chemical phototransformation are very complicated, and they are far from being completely understood. Different parameters of glass such as concentration of Ge 5,6 and other dopants 7 and impregnated molecular species ͑like hydrogen 5,8 ͒, can be critical for these mechanisms. It should be noticed that the mechanism of charge ͑elec-tron or hole͒ displacement has always been considered as an initial step of GODC phototransformation. This is why one of the possible approaches to control GODC phototransformation calls for the application of a strong electric field. 9-11It is important that depending on UV light intensity, both one-quantum and two-quantum GODC photodecomposition may occur. 9,12 It was shown directly in Ref. 8, that UV photoexcitation of GODC with intense pulses of KrF laser ( ϭ248 nm, ⌽Ͼ10 Ϫ2 J/cm 2 ͒ in an electric field results in efficient two-quantum ionization of GODC and generation of photocurrent pulses. It has been observed in similar cases that the effects of a strong electric field on acceleration of both GODC decomposition 10 and formation of Bragg gratings 11 can be quite naturally attributed to the increase of displacement of charge carriers from ionized GODC and, as a result, to the suppression of recombination processes. The effects of a strong electric f...

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“…The stability of point defects generated in amorphous silicon dioxide (a-SiO 2 ) by laser or ionizing radiation is often conditioned by their reactivity with mobile species such as molecular hydrogen [1][2][3][4][5]. This is particularly true for paramagnetic defects like the E' center, consisting in un unpaired electron spin on a silicon atom (≡Si•), whose generation is one of the main causes of degradation of optical transparency of a-SiO 2 in the ultraviolet (UV), due to its optical absorption (OA) band peaked at 5.8eV [3,[6][7] .…”

Section: Introductionmentioning

confidence: 99%

Stability of E′ centers induced by 4.7eV laser radiation in SiO2

Messina

Cannas

2007

Journal of Non-Crystalline Solids

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The kinetics of E' centers (≡Si•) induced by 4.7eV pulsed laser irradiation in dry fused silica was investigated by in situ optical absorption spectroscopy. The stability of the defects, conditioned by reaction with mobile hydrogen of radiolytic origin, is discussed and compared to results of similar experiments performed on wet fused silica. A portion of E' and hydrogen are most likely generated by laser-induced breaking of Si-H precursors, while an additional fraction of the paramagnetic centers arise from another formation mechanism. Both typologies of E' participate to the reaction with H 2 leading to the post-irradiation decay of the defects. This annealing process is slowed down on decreasing temperature and is frozen at T=200K, consistently with the diffusion properties of H 2 in silica.

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Photoinduced Reactions of Oxygen-Deficient Centers with Molecular Hydrogen in Silica Glasses

Cited by 53 publications

References 13 publications

H(II) Centers in natural silica under repeated UV laser irradiations

H(II) Centers in natural silica under repeated UV laser irradiations

Effect of electric field on one-quantum photodecay of oxygen-deficient centers in germanosilicate fibers

Stability of E′ centers induced by 4.7eV laser radiation in SiO2

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