Size dependence of lifetime and absorption cross section of Si nanocrystals embedded in SiO2

2003 ◽  
Vol 82 (10) ◽  
pp. 1595-1597 ◽  
Author(s):  
C. Garcia ◽  
B. Garrido ◽  
P. Pellegrino ◽  
R. Ferre ◽  
J. A. Moreno ◽  
...  
Keyword(s):  
Cross Section ◽  
Absorption Cross Section ◽  
Size Dependence ◽  
Absorption Cross ◽  
Si Nanocrystals

Determination of absorption cross-section of Si nanocrystals by two independent methods based on either absorption or luminescence

2016 ◽  
Vol 108 (2) ◽  
pp. 023102 ◽  
Author(s):  
J. Valenta ◽  
M. Greben ◽  
Z. Remeš ◽  
S. Gutsch ◽  
D. Hiller ◽  
...  
Keyword(s):  
Cross Section ◽  
Absorption Cross Section ◽  
Absorption Cross ◽  
Si Nanocrystals

scholarly journals Changes of the absorption cross section of Si nanocrystals with temperature and distance

2017 ◽  
Vol 8 ◽  
pp. 2315-2323 ◽  
Author(s):  
Michael Greben ◽  
Petro Khoroshyy ◽  
Sebastian Gutsch ◽  
Daniel Hiller ◽  
Margit Zacharias ◽  
...  
Keyword(s):  
Cross Section ◽  
Absorption Cross Section ◽  
Occupation Number ◽  
Single Layer ◽  
Absorption Cross ◽  
Barrier Thickness ◽  
Experimental Conditions ◽  
Si Nanocrystals ◽  
Exponential Decrease ◽  
Optimum Separation

The absorption cross section (ACS) of silicon nanocrystals (Si NCs) in single-layer and multilayer structures with variable thickness of oxide barriers is determined via a photoluminescence (PL) modulation technique that is based on the analysis of excitation intensity-dependent PL kinetics under modulated pumping. We clearly demonstrate that roughly doubling the barrier thickness (from ca. 1 to 2.2 nm) induces a decrease of the ACS by a factor of 1.5. An optimum separation barrier thickness of ca. 1.6 nm is calculated to maximize the PL intensity yield. This large variation of ACS values with barrier thickness is attributed to a modulation of either defect population states or of the efficiency of energy transfer between confined NC layers. An exponential decrease of the ACS with decreasing temperature down to 120 K can be explained by smaller occupation number of phonons and expansion of the band gap of Si NCs at low temperatures. This study clearly shows that the ACS of Si NCs cannot be considered as independent on experimental conditions and sample parameters.

scholarly journals Photoelectric absorption cross section of silicon near the bandgap from room temperature to sub-Kelvin temperature

AIP Advances ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 025120
Author(s):  
C. Stanford ◽  
M. J. Wilson ◽  
B. Cabrera ◽  
M. Diamond ◽  
N. A. Kurinsky ◽  
...  
Keyword(s):  
Cross Section ◽  
Absorption Cross Section ◽  
Room Temperature ◽  
Absorption Cross ◽  
Photoelectric Absorption

scholarly journals Ultraviolet Absorption Cross-Sections of Ammonia at Elevated Temperatures for Nonintrusive Quantitative Detection in Combustion Environments

2021 ◽  
pp. 000370282199044
Author(s):  
Wubin Weng ◽  
Shen Li ◽  
Marcus Aldén ◽  
Zhongshan Li
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Absorption Cross Section ◽  
Elevated Temperatures ◽  
Uv Absorption ◽  
Energy Utilization ◽  
Quantitative Detection ◽  
Absorption Cross ◽  
Hot Gas

Ammonia (NH3) is regarded as an important nitrogen oxides (NOx) precursor and also as an effective reductant for NOx removal in energy utilization through combustion, and it has recently become an attractive non-carbon alternative fuel. To have a better understanding of thermochemical properties of NH3, accurate in situ detection of NH3 in high temperature environments is desirable. Ultraviolet (UV) absorption spectroscopy is a feasible technique. To achieve quantitative measurements, spectrally resolved UV absorption cross-sections of NH3 in hot gas environments at different temperatures from 295 K to 590 K were experimentally measured for the first time. Based on the experimental results, vibrational constants of NH3 were determined and used for the calculation of the absorption cross-section of NH3 at high temperatures above 590 K using the PGOPHER software. The investigated UV spectra covered the range of wavelengths from 190 nm to 230 nm, where spectral structures of the [Formula: see text] transition of NH3 in the umbrella bending mode, v2, were recognized. The absorption cross-section was found to decrease at higher temperatures. For example, the absorption cross-section peak of the (6, 0) vibrational band of NH3 decreases from ∼2 × 10−17 to ∼0.5 × 10−17 cm2/molecule with the increase of temperature from 295 K to 1570 K. Using the obtained absorption cross-section, in situ nonintrusive quantification of NH3 in different hot gas environments was achieved with a detection limit varying from below 10 parts per million (ppm) to around 200 ppm as temperature increased from 295 K to 1570 K. The quantitative measurement was applied to an experimental investigation of NH3 combustion process. The concentrations of NH3 and nitric oxide (NO) in the post flame zone of NH3–methane (CH4)–air premixed flames at different equivalence ratios were measured.

Sign in / Sign up

Export Citation Format

Share Document