scholarly journals Direct temperature dependence measurements of dark conductivity and two-beam coupling in LiNbO_3:Fe

2008 ◽  
Vol 16 (6) ◽  
pp. 3993 ◽  
Author(s):  
S. A. Basun ◽  
G. Cook ◽  
D. R. Evans
Keyword(s):  
Temperature Dependence ◽  
Dark Conductivity ◽  
Beam Coupling

Metastable Defect Kinetics in Hydrogen Passivated Polycrystalline Silicon

1994 ◽  
Vol 336 ◽  
Author(s):  
N. H. Nickel ◽  
R. A. Street ◽  
W. B. Jackson ◽  
N. M. Johnson
Keyword(s):  
Temperature Dependence ◽  
Polycrystalline Silicon ◽  
Direct Evidence ◽  
Slow Cool ◽  
Dark Conductivity ◽  
Active Hydrogen ◽  
Thermally Activated ◽  
Rate Dependent ◽  
Si Films ◽  
Metastable Defect

ABSTRACTThe temperature dependence of the dark conductivity, σD, of unhydrogenated and hydrogen passivated polycrystalline silicon (poly-Si) films was Measured. While σD of unhydrogenated poly-Si did not exhibit any influence of thermal treatment prior to the measurement, striking effects were observed in hydrogenated poly-Si films. Below 268 K a cooling-rate dependent metastable change of σD is observed. The dark conductivity increases by more than 8 orders of magnitude. This frozen-in state is metastable: Annealing and a slow cool restore the temperature dependence of the relaxed state. The time and temperature dependence of the relaxation reveal that this process is thermally activated with 0.74 eV. The lack of the quenching metastability in unhydrogenated poly-Si is direct evidence that the metastable changes in σD are due to the formation and dissociation of an electrically active hydrogen complex, in the grain-boundary regions.

Optical Limiting with Lithium Niobate

1999 ◽  
Vol 597 ◽  
Author(s):  
Gary Cook ◽  
David C. Jones ◽  
Craig J. Finnan ◽  
Lesley L. Taylor ◽  
Tony W. Vere ◽  
...  
Keyword(s):  
Lithium Niobate ◽  
Diffusion Theory ◽  
Photovoltaic Effect ◽  
Optical Gain ◽  
Optical Limiting ◽  
Dark Conductivity ◽  
Simple Diffusion ◽  
Beam Coupling ◽  
Coupling Equations ◽  
Focusing Lens

AbstractIron doped lithium niobate (Fe:LiNbO3) in a simple focal plane geometry has demonstrated efficient optical limiting through two-beam coupling. The performance is largely independent of the total Fe concentration and the oxidation state of the Fe ions, providing the linear optical transmission of uncoated crystals is between 30% and 60%. Fe has been found to be the best dopant for LiNbO3, giving the widest spectral coverage and the greatest optical limiting. Optical limiting in Fe:LiNbO3 has been shown to be very much greater than predicted by simple diffusion theory. The reason for this is a higher optical gain than expected. It is suggested that this may be due to an enhancement of the space-charge field arising from the photovoltaic effect. The standard two-beam coupling equations have been modified to include the effects of the dark conductivity. This has produced a theoretical intensity dependence on the ΔOD which closely follows the behaviour observed in the laboratory. A further modification to the theory has also shown that the focusing lens f-number greatly affects the optical limiting characteristics of Fe:LiNbO3. A lens f-number of approximately 20 gives the best results.

Temperature dependence of two-beam coupling and dark decay in photorefractive BaTiO3

1996 ◽  
Vol 28 (10) ◽  
pp. 1509-1520 ◽  
Author(s):  
J. Y. Chang ◽  
C. Y. Huang ◽  
R. H. Tsou ◽  
M. W. Chang ◽  
C. C. Sun
Keyword(s):  
Temperature Dependence ◽  
Beam Coupling ◽  
Dark Decay

Light-Induced Metastable Changes in a-SiSx:H

1995 ◽  
Vol 377 ◽  
Author(s):  
S. L. Wang ◽  
P. C. Taylor
Keyword(s):  
Activation Energy ◽  
Temperature Dependence ◽  
Annealing Temperature ◽  
Dark Conductivity ◽  
Sulfur Concentration ◽  
Thermally Activated ◽  
Dramatic Difference ◽  
The Creation ◽  
Sulfur Donor

ABSTRACTMetastable light-induced increases in the dark conductivities of a-SiSx:H alloys are explained as photo-activation of hydrogen-passivated sulfur donor sites. For a sulfur concentration (sulfur-to-silicon ratio) of 5.6 × 103 the excess dark conductivity as a function of illumination temperature is thermally activated with an activation energy of 0.72 eV. When the sulfur concentration is 3.3 × 102, the temperature dependence is very weak. This dramatic difference in the temperature dependence of the creation of increased dark conductivity is explained by a lowering of the annealing temperature for the metastable changes as the sulfur concentration increases. We discuss the influence of this new metastability on the possibility of obtaining more stable films.

Substrate Temperature Dependence of the Optical and Electronic Properties of Glow Discharge Produced a-Ge:H

1989 ◽  
Vol 149 ◽  
Author(s):  
Yuan- Min Li ◽  
Warren A. Turner ◽  
Choochon Lee ◽  
William Paul
Keyword(s):  
Glow Discharge ◽  
Substrate Temperature ◽  
Temperature Dependence ◽  
Electronic Properties ◽  
Dark Conductivity ◽  
Index Of Refraction ◽  
Atmospheric Contamination ◽  
Optical And Electronic Properties ◽  
Substrate Temperatures ◽  
Post Deposition

ABSTRACTGlow discharge a-Ge:H films produced at substrate temperatures (Tδ) between 50°C and 350°C, with and without a top a-Si:H capping layer, have been studied. The uncapped samples produced at Tδ < 250°C suffer severe post-deposition atmospheric contamination, resulting in orders of magnitude of unstable increase in both the photoresponse and dark conductivity. The capped samples, which have very much reduced immediate post-deposition contamination, show only small increases in the efficiency-mobility-lifetime product (ŋμτ) with increasing Tδ. This contrasts with the results of earlier similar studies on uncapped samples, which showed a peak in either the photoconductivity1 or the ratio of photoconductivity to dark conductivity2 for 150°C < Tδ < 2000C. We have also observed a decrease in the bandgap, a narrowing of the band-tails, an increase in the index of refraction, and a reduction of hydrogen content of the films with increasing Tδ.

scholarly journals Neutron irradiation influence on mobility and compensation of dark conductivity in silicon

2016 ◽  
Vol 56 (2) ◽  
Author(s):  
Juozas Vidmantis Vaitkus ◽  
Algirdas Mekys ◽  
Vytautas Rumbauskas ◽  
Jurgis Storasta
Keyword(s):  
Temperature Dependence ◽  
Carrier Concentration ◽  
Neutron Irradiation ◽  
Cluster Model ◽  
Neutron Fluence ◽  
Dark Conductivity ◽  
Free Carrier ◽  
Free Carrier Concentration ◽  
Effective Generation ◽  
Cluster Environment

The electrical properties of the neutron irradiated Si were analysed by means of the Hall effect and magnetoresistance temperature dependence. It was demonstrated that the electron mobility decreased with increasing the neutron fluence in a wide fluence range, and the microinhomogeneities in samples caused differences between the mobility values from the measured Hall and magnetoresistance effects. Exploiting the magnetoresistance mobility temperature dependence, the free carrier concentration dependence on temperature was analysed. It was found that the neutron irradiation introduced deep levels in the upper part of the bandgap, but their contribution decreased with increasing the neutron fluence – that is explained by more effective generation of acceptor type levels in the middle or lower part of the bandgap. The activation energy of the free carrier concentration did not follow the homogeneous semiconductor model, so the dark conductivity origin, that is related to the modified cluster model and cluster environment, was proposed.

Thermoelectric properties of doped and undoped mixed phase hydrogenated amorphous/nanocrystalline silicon thin films

2010 ◽  
Vol 1245 ◽  
Author(s):  
James Kakalios ◽  
Yves Adjallah ◽  
Charlie Blackwell
Keyword(s):  
Thin Films ◽  
Seebeck Coefficient ◽  
Temperature Dependence ◽  
Nanocrystalline Silicon ◽  
Dark Conductivity ◽  
Mixed Phase ◽  
Positive Temperature ◽  
Silicon Thin Films ◽  
Similar Temperature Dependence ◽  
Hydrogenated Amorphous

AbstractThe Seebeck coefficient and dark conductivity for undoped, and n-type doped thin film hydrogenated amorphous silicon (a-Si:H), and mixed-phase films with silicon nanocrystalline inclusions (a/nc-Si:H) are reported. For both undoped a-Si:H and undoped a/nc-Si:H films, the dark conductivity is enhanced by the addition of silicon nanocrystals. The thermopower of the undoped a/nc-Si:H has a lower Seebeck coefficient, and similar temperature dependence, to that observed for undoped a-Si:H. In contrast, the addition of nanoparticles in doped a/nc-Si:H thin films leads to a negative Seebeck coefficient (consistent with n-type doping) with a positive temperature dependence, that is, the Seebeck coefficient becomes larger at higher temperatures. The temperature dependence of the thermopower of the doped a/nc-Si:H is similar to that observed in unhydrogenated a-Si grown by sputtering or following high-temperature annealing of a-Si:H, suggesting that charge transport may occur via hopping in these materials.

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