Above the band gap structures in Ge nanoparticles: optical-absorption spectra

1996 ◽  
Vol 18 (7) ◽  
pp. 865-872 ◽  
Author(s):  
P. Tognini ◽  
L. C. Andreani ◽  
M. Geddo ◽  
A. Stella ◽  
P. Cheyssac ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Band Gap ◽  
Absorption Spectra ◽  
Optical Absorption Spectra

Optical Absorption of Doped and Undoped Bulk SiC

2000 ◽  
Vol 640 ◽  
Author(s):  
K. Miller ◽  
Q. Zhou ◽  
J. Chen ◽  
M. O. Manasreh ◽  
Z. C. Feng ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Optical Absorption ◽  
Band Gap ◽  
Absorption Spectra ◽  
Spectral Region ◽  
Sharp Peak ◽  
Band Edge ◽  
Optical Absorption Spectra ◽  
Bulk Silicon ◽  
Free Carriers

ABSTRACTOptical absorption spectra of undoped, n-type, and semi-insulating 6H and 4H bulk silicon carbide (SiC) were obtained in the spectral region of 200 – 3200 nm (6.20 – 0.3875 eV). Several features were observed in the absorption spectra collected for various samples. A sharp peak below the band gap was observed in 4H SiC. The intensity of this peak was observed to increase in samples that exhibit larger absorption due to free carriers, which leads us to conclude that the defect responsible for this peak is also the source of the free carriers in the materials. Additionally, a series of optical absorption peaks separated by approximately 21 meV were observed around 0.9185 eV (1350 nm). These peaks are zero phonon lines of intraband transitions in the VSi 3d shell. The optical absorption near the band edge was observed to be sample dependent. The variation of the band gap as a function of temperature is also observed to be sample dependent.

Optical Investigation of Bi2O3-B2O3 Glass System

2010 ◽  
Vol 93-94 ◽  
pp. 336-339 ◽  
Author(s):  
Kitipun Boonin ◽  
Jakrapong Kaewkhao ◽  
Pichet Limsuwan
Keyword(s):  
Optical Absorption ◽  
Band Gap ◽  
Absorption Spectra ◽  
Wavelength Range ◽  
Absorption Edge ◽  
Optical Band Gap ◽  
Fundamental Absorption Edge ◽  
Optical Investigation ◽  
Optical Absorption Spectra ◽  
Molar Volumes

Glasses with composition xBi2O3:(100-x)B2O3 with 30x70 (in mol%) have been prepared using the normal melt-quench technique and investigated their properties. The optical absorption spectra of the glasses have been measured in the wavelength range 400-700 nm. It has been found that, the fundamental absorption edge has been identified from the optical absorption spectra. The values of optical band gap were decreased and the molar volumes were increased, with the addition of Bi2O3, due to the formulation of non-bridging oxygen (NBOs).

Novel electronic and optical properties of ultrathin silicene/arsenene heterostructures and electric field effects

2017 ◽  
Vol 19 (16) ◽  
pp. 10644-10650 ◽  
Author(s):  
Huabing Shu ◽  
Yilong Tong ◽  
Jiyuan Guo
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Electric Field ◽  
Band Gap ◽  
Absorption Spectra ◽  
Optical Absorption Spectra ◽  
Electric Field Effects ◽  
Electronic And Optical Properties ◽  
Vertical Electric Field ◽  
Variable Band Gap

The variable band-gap of the Si/As heterostructure (left) and optical absorption spectra for AA-stacking under a vertical electric field (right).

Band-gap engineering in amorphous/microcrystalline ScxGa1-xN.

2001 ◽  
Vol 693 ◽  
Author(s):  
M. E. Little ◽  
M. E. Kordesch
Keyword(s):  
Optical Absorption ◽  
Band Gap ◽  
Absorption Spectra ◽  
Optical Band Gap ◽  
Optical Absorption Spectra ◽  
X Ray Diffraction ◽  
Band Gap Engineering ◽  
X Ray ◽  
Bilayer Films ◽  
Quartz Substrates

AbstractReactive sputtering was used to grow thin films of ScxGa1-xN with scandium concentrations of 20%-70% on quartz substrates at temperatures of 300-675 K. X-ray diffraction (XRD) of the films showed either weak or no structure, suggesting the films are amorphous or microcrystalline. Optical absorption spectra were taken of each sample and the optical band gap was determined. The band gap varied linearly with increasing Ga concentration between 2.0 and 3.5 eV. Ellipsometry was used to confirm the band gap measurements and provide optical constants in the range 250-1200 nm. ScN and GaN have different crystal structures (rocksalt and wurzite, respectively), and thus may form a heterogeneous mixture as opposed to an alloy. Since the XRD data were inconclusive, bilayers of ScN/GaN were grown and optical absorption spectra taken. A fundamental difference in the spectra between the bilayer films and alloy films was seen, suggesting the films are alloys, not herterogeneous mixtures.

Optical Properties of Colloidal CdSe/ZnS core/shell Nanocrystals Embedded in a UV Curable Resin

2006 ◽  
Vol 959 ◽  
Author(s):  
Abhishek Joshi ◽  
Edwin Davis ◽  
Kaushik Narsingi ◽  
Omar Manasreh ◽  
B. D. Weaver
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Band Gap ◽  
Absorption Spectra ◽  
Energy Band ◽  
Core Shell ◽  
Optical Absorption Spectra ◽  
Energy Band Gap ◽  
Uv Curable ◽  
Uv Curable Resin

ABSTRACTOptical absorption and photoluminescence techniques were used to investigate the band gap of colloidal CdSe/ZnS core/shell nanocrystals matrixed in a UV curable resin. The band gap was measured for several nanocrystals with size ranging between 1.9 and 4.0 nm. The band gap (Eg) was determined from the first exciton peaks observed in the optical absorption spectra. Both Debye and Einstein temperatures were estimated from fitting the energy band gap vs. temperature using two different empirical expressions.

A Study of Electron Paramagnetic Resonance and Optical Absorption Spectra of VO2+ Ions in Alkali Barium Phosphate Glasses

2003 ◽  
Vol 17 (16) ◽  
pp. 3033-3047 ◽  
Author(s):  
V. Ramesh Kumar ◽  
R. P. S. Chakradhar ◽  
A. Murali ◽  
N. O. Gopal ◽  
J. Lakshmana Rao
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Optical Absorption ◽  
Band Gap ◽  
Absorption Spectra ◽  
Optical Band Gap ◽  
Phosphate Glasses ◽  
Epr Spectra ◽  
Optical Absorption Spectra ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

The electron paramagnetic resonance and optical absorption spectra of VO 2+ ions in different alkali barium phosphate glasses have been studied and the results have been analysed using C4v symmetry. The EPR spectrum shows eight hyperfine lines characteristic of VO 2+ ions. From the observed EPR spectra, the spin-Hamiltonian parameters, Fermi contact interaction parameter k, dipolar hyperfine coupling parameter P have been evaluated. The EPR spectra exhibit a marked concentration dependence. The EPR spectra were also recorded at different temperatures. The number of spins participating in resonance is found to be increasing with decreasing temperature. The paramagnetic susceptibility χ is calculated from the EPR data. As the temperature decreases, χ increases in accordance with Curie's law. The optical absorption spectrum exhibits two bands corresponding to the transitions 2B2g → 2B1g and 2B2g → 2Eg , characteristic of VO 2+ ions in octahedral symmetry with tetragonal distortion. From the ultraviolet edges of these optical absorption spectra, the optical band gap energies (Eopt) of the glass samples have been calculated. The optical band gap energy varies with alkali content. By correlating EPR and optical absorption data, the molecular orbital coefficients have been evaluated. The theoretical values of optical basicity of the glasses have also been evaluated.

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