The Double Donor Issue of the EL2 Defect in GaAs.

1989 ◽  
Vol 163 ◽  
Author(s):  
M. O. Manasreh ◽  
G. J. Brown
Keyword(s):  
Absorption Spectrum ◽  
Fourier Transform ◽  
Complex Structure ◽  
Monochromatic Light ◽  
Thermal Recovery ◽  
Light Irradiation ◽  
Ir Absorption ◽  
Czochralski Technique ◽  
Induced Changes ◽  
Two Peaks

AbstractPhoto-induced changes in the infrared (IR) absorption spectrum of the EL2 defect in undoped and lightly alloyed unannealed GaAs materials grown by the liquid-encapsulated Czochralski technique were observed under a monochromatic light irradiation. These changes were attributed to the change of the charge states of EL2. The spectrum which is believed to be due to the charged EL2 exhibits a complex structure with two peaks at 1.07 and 1.32 eV and a shoulder at 0.94 eV. The EL2+/2+ → EL20/+ and EL20/+ → EL2+/2+ transitions were obtained by illuminating the sample with 0.7 ≤ hv ≤ 0.95 eV and 1.3 ≤ hv ≤1.5 eV, respectively. The transformation EL2+/2+ ↔ EL20/+ can be achieved in less than 10 sec and can be repeatedly switched back and forth between the two states. Fourier-transform photoconductivity (FTPC) measurements were performed on a large number of samples both semi-insulating and n-type. Two broad peaks were observed in the FTPC spectra with thresholds at 0.80 and 0.95 eV. The photoquenching and thermal recovery properties of these two peaks are identical to those of EL2. Both IR and FTPC results suggest strongly that EL2 is a double donor.

Characterization of Microcrystalline Transition from Amorphous Silicon as a Function of Hydrogen Dilution and Substrate Temperature of Hot-wire CVD

2002 ◽  
Vol 715 ◽  
Author(s):  
Keda Wang ◽  
Haoyue Zhang ◽  
Jian Zhang ◽  
Jessica M. Owens ◽  
Jennifer Weinberg-Wolf ◽  
...  
Keyword(s):  
Substrate Temperature ◽  
Sudden Change ◽  
Chemical Vapor ◽  
Threshold Value ◽  
Ir Absorption ◽  
Sudden Increase ◽  
Hot Wire ◽  
Hydrogen Dilution ◽  
Integral Absorption ◽  
Two Peaks

Abstracta-Si:H films were prepared by hot wire chemical vapor deposition. One group was deposited at a substrate temperature of Ts=250°C with varied hydrogen-dilution ratio, 0<R<10; the other group was deposited with fixed R=3 but a varied Ts from 150 to 550°C. IR, Raman and PL spectra were studied. The Raman results indicate that there is a threshold value for the microstructure transition from a- to μc-Si. The threshold is found to be R ≈ 2 at Ts = 250°C and Ts ≈ 200°C at R=3. The IR absorption of Si-H at 640 cm-1 was used to calculate the hydrogen content, CH. CH decreased monotonically when either R or Ts increased. The Si-H stretching mode contains two peaks at 2000 and 2090 cm-1. The ratio of the integral absorption peaks I2090/(I2090+I2090) showed a sudden increase at the threshold of microcrystallinity. At the same threshold, the PL features also indicate a sudden change from a- to μc-Si., i.e. the low energy PL band becomes dominant and the PL total intensity decreases. We attribute the above IR and PL changes to the contribution of microcrystallinity, especially the c-Si gain-boundaries.

The homogeneous Lorentzian IR absorption spectrum of (CF3)3CI at twice the threshold vibrational energy

1988 ◽  
Vol 146 (6) ◽  
pp. 599-604 ◽  
Author(s):  
V.N. Bagratashvili ◽  
S.I. Ionov ◽  
A.A. Stuchebrukhov ◽  
V.S. Letokhov ◽  
V.N. Lokhman ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Vibrational Energy ◽  
Ir Absorption

scholarly journals Absorption and Emission Spectra for C60 Anions

1994 ◽  
Vol 14 (1-3) ◽  
pp. 155-160 ◽  
Author(s):  
Tatsuhisa Kato
Keyword(s):  
Absorption Spectrum ◽  
Absorption Band ◽  
Theoretical Analysis ◽  
Room Temperature ◽  
Emission Spectra ◽  
Mirror Image ◽  
Ir Absorption ◽  
Near Ir ◽  
Laser Experiments ◽  
Ir Bands

Absorption spectra are detected for C60− and C602− produced electrolytically in solution at room temperature. Theoretical analysis of the spectrum of C60− by CNDO/S calculations gives an interpretation of the characteristic near-IR bands, the weak visible bands, and the strong bands in the UV region. The emission spectrum of C60− is a mirror image of the near-IR absorption band, and the detection of the emission reconfirms our original assignment of the absorption spectrum. The nature of the spectrum of C602− is characterized by a similar orbital picture to that of C60−. Further laser experiments of significance are proposed.

scholarly journals SOLVOTHERMAL SYNTHESIS OF BI2WO6 AND ITS PHOTOCATALYTIC ACTIVITY UNDER VISIBLE LIGHT IRRADIATION

2018 ◽  
Vol 54 (4B) ◽  
pp. 42
Author(s):  
Trinh Duy Nguyen
Keyword(s):  
Absorption Spectrum ◽  
Photocatalytic Activity ◽  
Visible Light ◽  
Visible Light Irradiation ◽  
Solvothermal Synthesis ◽  
Solvothermal Method ◽  
Visible Region ◽  
High Photocatalytic Activity ◽  
Light Irradiation ◽  
Different Temperatures

Flower-like Bi2WO6 were successfully synthesized using the solvothermal method at different temperatures and characterized by XRD, FE-SEM, and DRS. We also investigated the photocatalytic activity of Bi2WO6 for the decomposition of rhodamine B under visible light irradiation. From XRD and SEM results, the reaction temperature has significant effects on the morphologies of the samples. From DRS results, Bi2WO6 samples displayed the absorption spectrum up to the visible region and then they showed the high photocatalytic activity under visible light irradiation, as a comparison with TiO2-P25.

IR absorption spectrum of hydrogen xanthane

1970 ◽  
Vol 13 (11) ◽  
pp. 1445-1449 ◽  
Author(s):  
R. S. Lebedev ◽  
A. V. Korshunov ◽  
R. P. Chumakova ◽  
V. E. Volkov
Keyword(s):  
Absorption Spectrum ◽  
Ir Absorption

scholarly journals The mid-IR absorption spectrum of gas-phase clusters of the nucleobases guanine and cytosine

2004 ◽  
Vol 6 (10) ◽  
pp. 2810-2815 ◽  
Author(s):  
Joost M. Bakker ◽  
Isabelle Compagnon ◽  
Gerard Meijer ◽  
Gert von Helden ◽  
Martin Kabeláč ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Gas Phase ◽  
Ir Absorption ◽  
Gas Phase Clusters

Effect of pH, temperature, amount of litter and storage density on ammonia emissions from stable manure

1996 ◽  
Vol 127 (4) ◽  
pp. 501-509 ◽  
Author(s):  
T. Dewes
Keyword(s):  
Laboratory Tests ◽  
Ammonia Emission ◽  
Ammonia Emissions ◽  
Ph Values ◽  
Degrading Bacteria ◽  
Proteolytic Bacteria ◽  
Stable Manure ◽  
Induced Changes ◽  
Two Peaks ◽  
And Storage

SUMMARYIn laboratory tests using stable manure consisting of wheat straw and slurry, ammonia emission was found to have two peaks corresponding to the population dynamics of proteolytic bacteria and amino acid-degrading bacteria respectively. Cumulative ammonia emissions over 14 days were 0·8–23·2% of the initial total nitrogen (Nt) and were both abiotically and biotically induced. Changes in pH had the most significant effect on the abiotically induced ammonia emissions. After 14 days of decomposition, at pH values of 6·0 and 7·5, abiotically induced emissions remained close to the limit of detectability, whereas at pH 9·0 as much as 9·8% of the initial Nt was lost. An increase in storage pressure from 0 to 400 and 800 kp/m2 generally decreased the biotic emissions to 9·6, 2·8 and 2·3%; while increasing the amounts of litter (2·5, 5·0 and 15·0 kg straw/LAU per day) led to a decline not only in the biotic (17·1, 12·8, 3·5%) but also in the abiotic emissions (6·1, 5·5, 1·6%). Varying the temperature (20, 30 and 40 °C) resulted in biotically induced emissions of 7·9, 11·7 and 11·6%, respectively, and abiotically induced emissions of 1·1, 1·4 and 2·2% of the initial Nt. At temperatures of 30 and 40 °C, the amount of microbially digested sources of carbon available was obviously sufficient to permit almost total reincorporation of NH4+ from 4 days onwards.

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