Showing papers by "Marc Kastner published in 1980"
TL;DR: In this article, the authors reviewed the experimental evidence for defects and discussed two major areas of current controversy: the disparity between densities of defects measured by different means and various problems arising from recent photoluminescence experiments.
Abstract: The valence-alternation model for defects is briefly reviewed. The experimental evidence for defects is examined. Two major areas of current controversy are discussed: The disparity between densities of defects measured by different means and various problems arising from recent photoluminescence experiments.
43 citations
TL;DR: In this article, the photoluminescence (PL) originating from intrinsic defects in neutron-irradiated crystalline (x-) SiO 2 is observed and compared with that from amorphous (a)-SiO 2.
Abstract: Photoluminescence (PL) originating from intrinsic defects in neutron-irradiated crystalline (x-) SiO 2 is observed and compared with that from amorphous (a-) SiO 2 . The PL and photoluminescence excitation (PLE) spectra of x-SiO 2 are qualitatively similar to those of a-SiO 2 . This suggests that PL centers, similar to those found in amorphous systems, are present in ordered systems. In addition, the PL and PLE spectra a-SiO 2 and a-As 2 S 3 scale with energy band gap, suggesting that the radiative processes in a-SiO 2 and semiconducting chalcogenide glasses are alike. The similarity of the PL from x-SiO 2 to that from a-SiO 2 and the scaling of the PL from a-SiO 2 and a-As 2 S 3 with energy band gap strongly suggest that PL centers are unique bonding configurations which primarily depend on the chemistry of the system rather than on the degree of long range order.
28 citations
TL;DR: In this article, the authors measured the relaxation of photoinduced optical absorption (PA) and photocurrent following pulsed excitation in the range 295 K − 425 K. The decay of PA is well described by bimolecular recombination kinetics with a thermally activated rate coefficient b(T).
Abstract: Relaxation of photoinduced optical absorption (PA) and photocurrent (PC) following pulsed excitation is measured as a function of temperature in the range 295 K – 425 K. The decay of PA is well described by bimolecular recombination kinetics with a thermally activated rate coefficient b(T). The magnitude of b(T) yields a lower limit for the mobility of the PA excitation consistent with the hole drift mobility. In addition, first measurements of the time evolution of the PA spectrum are reported. The observed shift of the absorption band towards higher energy with increasing time is interpreted in terms of thermalization within a distribution of localized gap states.
16 citations
TL;DR: In this paper, a configurational-coordinate diagram is constructed which involves two important coordinates, the first coordinate determines the Stokes shift and linewidth of the photoluminescence.
Abstract: Recent experiments have provided a quantitative description of the non-radiative recombination process which competes with the intrinsic-defect photoluminescence in glasses like SiO2 and As2S3. Using these experimental observations, a configurational-coordinate diagram is constructed which involves two important coordinates. The first coordinate determines the Stokes shift and linewidth of the photoluminescence. The second coordinate can change with small activation energy and this change leads to complete relaxation of the excited states of valence-alternation pairs which are the photoluminescence centres. Since both partners of the pair have the same excited state when relaxation is complete, recombination must then be non-radiative. It is suggested that tunnelling between the two values for which this second coordinate minimises the energy may be the origin of the unusual low-temperature properties of glasses.
16 citations
TL;DR: In this article, the total light decay (TLD) and time-resolved spectra of the photoluminescence (PL) of a-As2S3 are reported, consistent with a model in which the PL centers are valence-alternation pairs which are bound at the glass transition temperature.
Abstract: The total light decay (TLD) and time-resolved spectra of the photoluminescence (PL) of a-As2S3 are reported. The time-resolved spectra disagree with those published by other workers. The current results are consistent with a model in which the PL centers are valence-alternation pairs which are bound at the glass transition temperature. The fit of the model to the data yields a value of ∼2.4 A for the decay length of the wavefunction for an electron and/or hole bound at the charged defect.
14 citations
TL;DR: In this article, the photoluminescence (PL) of x-SiO2 was observed and compared with that from amorphous (a-) SiO2.
Abstract: Photoluminescence (PL) originating from intrinsic defects in neutron-irradiated crystalline (x-)SiO2 is observed and compared with that from amorphous (a-)SiO2. The PL and photoluminescence excitation (PLE) spectra of x-SiO2 are qualitatively similar to those of a-SiO2. This suggests that PL centers, similar to those found in amorphous systems, are present in ordered systems. In addition, the PL and PLE spectra of a-SiO2 and a-As2S3 scale with energy band gap, suggesting that the radiative processes in a-SiO2 and semiconducting chalcogenide glasses are alike. The similarity of the PL from x-SiO2 to that from a-SiO2 and the scaling of the PL from a-SiO2 and a-As2S3 with energy band gap strongly suggest that PL centers are unique bonding configurations which primarily depend on the chemistry of the system rather than on the degree of long range order.
13 citations
01 Jan 1980
TL;DR: In this paper, the time decay of the 4.3 eV band is <10ns, but the 2.7 and 1.9 eV bands decay slower, in spite of the complexity of several PL bands.
Abstract: Photoluminescence (PL) time decay for annealed and neutron-irradiated amorphous (a-) SiO 2 is reported. PL bands at 4.3., 2.7 and 1.9 eV, excited by 7.8 eV radiation from a pulsed F 2 laser, are observed for both annealed and neutron-irradiated Suprasil W. The time decay of the 4.3 eV band is <10ns, but the 2.7 and 1.9 eV PL decay slower. In spite of the complexity of several PL bands, the time decays of the two low energy PL bands are simply composed of a couple of decay rates.
4 citations