scholarly journals AlGaN-Based Bragg Reflectors

1997 ◽  
Vol 2 ◽  
Author(s):  
O. Ambacher ◽  
M. Arzberger ◽  
D. Brunner ◽  
H. Angerer ◽  
F. Freudenberg ◽  
...  
Keyword(s):  
Refractive Index ◽  
Molecular Beam ◽  
Molar Fraction ◽  
Bragg Reflectors ◽  
Near Ultraviolet ◽  
Photothermal Deflection Spectroscopy ◽  
Interference Fringes ◽  
Measured Absorption ◽  
Ultraviolet Spectral Region ◽  
Photothermal Deflection

We have studied the dependence of the absorption edge and the refractive index of wurtzite AlxGa1−xN films on composition using transmission, ellipsometry and photothermal deflection spectroscopy. The Al molar fraction of the AlxGa1−xN films grown by plasma-induced molecular beam epitaxy was varied through the entire range of composition (0 ≤ x ≤ 1). We determined the absorption edges of AlxGa1−xN films and a bowing parameter of 1.3 ± 0.2 eV. The refractive index below the bandgap was deduced from the interference fringes, the dielectric function between 2.5 and 25 eV from ellipsometry measurements. The measured absorption coefficients and refractive indices were used to calculate the design and reflectivity of AlGaN-based Bragg reflectors working in the blue and near-ultraviolet spectral region.

An Investigation of Photo-Induced Degradation by Means of Photothermal Deflection Spectroscopy

1987 ◽  
Vol 95 ◽  
Author(s):  
M. S. Bennett ◽  
S. Wiedeman ◽  
J. L. Newton ◽  
K. Rajan
Keyword(s):  
Optical Absorption ◽  
Fermi Level ◽  
Single Peak ◽  
Defect States ◽  
Hydrogenated Silicon ◽  
Photothermal Deflection Spectroscopy ◽  
Amorphous Hydrogenated Silicon ◽  
Measured Absorption ◽  
Photothermal Deflection

AbstractAbsorption measurements of as deposited and photodegraded intrinsic amorphous hydrogenated silicon films were made using photothermal deflection spectroscopy (PDS). The films were light-soaked in situ using HeNe laser light to simulate AM1 illumination. An increase in subbandgap absorption occurred predominantly near energies of 1.2eV. A simple model was developed in which a density of states function is hypothesized and the resulting optical absorption at subgap energies is calculated. The measured absorption could be well matched in all cases by assuming a single peak of defect states at or slightly below the Fermi level. Further, the observed changes in optical absorption due to degradation could be modeled by increasing the density of the single peak of defect states and moving the Fermi level towards the valence band.

Photoluminescence and Photothermal Deflection Spectroscopy of InAs Quantum Dot Superlattices Grown on GaAs by Molecular Beam Epitaxy

1997 ◽  
Vol 36 (Part 2, No. 6B) ◽  
pp. L811-L814 ◽  
Author(s):  
Yuan-Tung Dai ◽  
Ying-Tsang Liu ◽  
Ray-Ming Lin ◽  
Ming-Chih Harris Liao ◽  
Yang-Fang Chen ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Quantum Dot ◽  
Molecular Beam ◽  
Photothermal Deflection Spectroscopy ◽  
Photothermal Deflection ◽  
Inas Quantum Dot

Optical Absorptions and EL2-Like Defects in Low Temperature Grown Molecular-Beam-Epitaxial GaAs

1995 ◽  
Vol 378 ◽  
Author(s):  
S. K. So ◽  
M. H. Chan ◽  
K. T. Chan
Keyword(s):  
Molecular Beam Epitaxy ◽  
Low Temperature ◽  
Absorption Spectra ◽  
Molecular Beam ◽  
Epitaxial Gaas ◽  
Molecular Beam Epitaxial ◽  
Photothermal Deflection Spectroscopy ◽  
Photothermal Deflection ◽  
Phase Spectra ◽  
Defect Densities

Abstract:The optical absorptions and the defect densities of GaAs grown by low temperature molecular-beam-epitaxy at growth temperatures between 200-580 °C were evaluated by photothermal deflection spectroscopy. The shapes of the absorption spectra exhibit EL2-like characteristics. Defect densities were found to be in the range of 1018-1019 cm−3. The PDS phase spectra were shown to be useful to differentiate the absorptions of the epilayer from those of the bulk.

scholarly journals Complex refractive indices in the near-ultraviolet spectral region of biogenic secondary organic aerosol aged with ammonia

2014 ◽  
Vol 16 (22) ◽  
pp. 10629-10642 ◽  
Author(s):  
J. M. Flores ◽  
R. A. Washenfelder ◽  
G. Adler ◽  
H. J. Lee ◽  
L. Segev ◽  
...  
Keyword(s):  
Refractive Index ◽  
Spectral Region ◽  
Secondary Organic Aerosol ◽  
Complex Refractive Index ◽  
Organic Aerosol ◽  
Refractive Indices ◽  
Near Ultraviolet ◽  
Ultraviolet Spectral Region ◽  
P Distribution

Distribution of the number of N atoms and the change in the complex refractive index of unreacted and NH3-aged limonene SOA.

scholarly journals A broadband optical cavity spectrometer for measuring weak near-ultraviolet absorption spectra of gases

2011 ◽  
Vol 4 (3) ◽  
pp. 425-436 ◽  
Author(s):  
J. Chen ◽  
D. S. Venables
Keyword(s):  
Absorption Spectra ◽  
Cross Sections ◽  
Optical Cavity ◽  
Absorption Cross ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Near Ultraviolet ◽  
Low Concentrations ◽  
Measured Absorption ◽  
Atmospheric Observations

Abstract. Accurate absorption spectra of gases in the near–ultraviolet (300 to 400 nm) are essential in atmospheric observations and laboratory studies. This paper describes a novel incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) instrument for measuring very weak absorption spectra from 335 to 375 nm. The instrument performance was validated against the 3B1-X1A1 transition of SO2. The measured absorption varied linearly with SO2 column density and the resulting spectrum agrees well with published spectra. Using the instrument, we report new absorption cross-sections of O3, acetone, 2-butanone, and 2-pentanone in this spectral region, where literature data diverge considerably. In the absorption minimum between the Huggins and Chappuis bands, our absorption spectra fall at the lower range of reported ozone absorption cross-sections. The spectra of the ketones agree with prior spectra at moderate absorptions, but differ significantly at the limits of other instruments' sensitivity. The collision-induced absorption of the O4 dimer at 360.5 nm was also measured and found to have a maximum cross-section of ca. 4.0×10−46 cm5 molecule−2. We demonstrate the application of the instrument to quantifying low concentrations of the short-lived radical, BrO, in the presence of stronger absorptions from Br2 and O3.

scholarly journals Photothermal Deflection Spectroscopy Study of Nanocrystalline Si (nc-Si) Thin Films Deposited on Porous Aluminum with PECVD

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
S. Ktifa ◽  
M. Ghrib ◽  
F. Saadallah ◽  
H. Ezzaouia ◽  
N. Yacoubi
Keyword(s):  
Optical Properties ◽  
Energy Gap ◽  
Chemical Vapor ◽  
Nanocrystalline Silicon ◽  
Porous Aluminum ◽  
Force Microscopy ◽  
Photothermal Deflection Spectroscopy ◽  
Atomic Force ◽  
Photothermal Deflection ◽  
Morphology Characterization

We have studied the optical properties of nanocrystalline silicon (nc-Si) film deposited by plasma enhancement chemical vapor deposition (PECVD) on porous aluminum structure using, respectively, the Photothermal Deflection Spectroscopy (PDS) and Photoluminescence (PL). The aim of this work is to investigate the influence of anodisation current on the optical properties of the porous aluminum silicon layers (PASL). The morphology characterization studied by atomic force microscopy (AFM) technique has shown that the grain size of (nc-Si) increases with the anodisation current. However, a band gap shift of the energy gap was observed.

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