Steplike Lineshape of Low Temperature Photoreflectance Spectra of InAlAs

1995 ◽  
Vol 406 ◽  
Author(s):  
Y. Baltagi ◽  
E. Bearzi ◽  
C. Bru-Chevallier ◽  
T. Benyattou ◽  
G. Guillot ◽  
...  
Keyword(s):  
Low Temperature ◽  
Band Gap ◽  
Photo Luminescence ◽  
Band Gap Energy ◽  
Carrier Localization ◽  
Gap Energy ◽  
Lattice Matched

AbstractWe have performed low temperature photoreflectance spectra on several MBE-InAlAs layers lattice matched to InP. Unusual lineshapes of PR spectra are observed at temperatures below 40K, characterized by a step at the InAlAs band gap energy. This step is shown to be related to a strong modification of the photo luminescence background of the photoreflectance spectra. This modification is attributed to an effect of carrier localization due to clustering effects in the InAlAs layers

PHOTOINDUCED PHENOMENA OF CHALCOGEN MICROCLUSTERS CONFINED IN THE ZEOLITE CAGES

1996 ◽  
Vol 03 (01) ◽  
pp. 711-715 ◽  
Author(s):  
K. MARUYAMA ◽  
T. TSUZUKI ◽  
M. YAO ◽  
H. ENDO
Keyword(s):  
Low Temperature ◽  
Band Gap ◽  
Photoacoustic Spectroscopy ◽  
Band Gap Energy ◽  
Dangling Bonds ◽  
Absorption Bands ◽  
Appreciable Change ◽  
Gap Energy ◽  
Zeolite 4A ◽  
Photoinduced Phenomena

Photoacoustic spectroscopy measurements have been carried out on the Se-ring microclusters confined in the cages of zeolite 4A. The shift of photoabsorption edge and the new absorption bands around 1.5 and 1.9 eV appeared by illumination of the light having the band-gap energy at low temperature. These phenomena may be associated with the distortion of Se ring and the formation of dangling bonds. Mixing of S or Te to the Se microclusters causes appreciable change in the photoinduced phenomena.

Estimation of Effective Band Gap Energy of CdxZn1-xS/ZnS Multiple Quantum Wells Lattice-Matched to GaP Substrates

2004 ◽  
Vol 43 (6A) ◽  
pp. 3491-3492
Author(s):  
Chikara Onodera ◽  
Tadayoshi Shoji ◽  
Yukio Hiratate ◽  
Tsunemasa Taguchi
Keyword(s):  
Quantum Wells ◽  
Band Gap ◽  
Band Gap Energy ◽  
Multiple Quantum Wells ◽  
Multiple Quantum ◽  
Gap Energy ◽  
Lattice Matched

Temperature dependence of the direct band gap energy and donor–acceptor transition energies in Be‐doped GaAsSb lattice matched to InP

1994 ◽  
Vol 65 (19) ◽  
pp. 2442-2444 ◽  
Author(s):  
K. G. Merkel ◽  
V. M. Bright ◽  
M. A. Marciniak ◽  
C. L. A. Cerny ◽  
M. O. Manasreh
Keyword(s):  
Temperature Dependence ◽  
Band Gap ◽  
Band Gap Energy ◽  
Transition Energies ◽  
Direct Band Gap ◽  
Gap Energy ◽  
Donor Acceptor ◽  
Direct Band ◽  
Lattice Matched

scholarly journals Synergistic Adsorption and Photocatalytic Activity under Visible Irradiation Using Ag-ZnO/GO Nanoparticles Derived at Low Temperature

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Viet Ha Tran Thi ◽  
The Ha Cao ◽  
Tri Nhut Pham ◽  
Tien Thanh Pham ◽  
Manh Cuong Le
Keyword(s):  
Photocatalytic Activity ◽  
Low Temperature ◽  
Visible Light ◽  
Band Gap ◽  
Surface Area ◽  
Irradiation Time ◽  
Removal Rate ◽  
Band Gap Energy ◽  
Gap Energy ◽  
Visible Irradiation

Ag-ZnO/graphene oxide (AG-ZnO/GO) nanocomposite was synthesized via facile aqueous solution reactions at low temperature in order to improve the photocatalytic activity for cationic dye removal under visible light irradiation. Analytical techniques were carried out in order to determine the abilities including structure, state of elements, morphology, and surface area of synthesized materials. Ag-ZnO/GO nanocomposite presented an extremely high removal rate of methylene blue (MB) not only under UV light (over 99% removal) but also under visible light (85% removal) during the same irradiation time. In this study, initial process parameters of catalyst dosage, MB concentration, and pH of the solution were also examined for MB removal efficiency effects. The proposed mechanisms for the increased removal of MB by Ag-ZnO/GO nanocomposite under visible irradiation include increased photocatalytic degradation, mainly due to increased charge transfer capacity by lowering band gap energy; minimized recombination of the excited electron-hole pairs of ZnO with the addition of Ag into the ZnO crystal lattice; and an increased adsorption capacity with the addition of GO with high surface area and semiconductor function with zero band gap energy.

Modification of optical properties of PC-PBT/Cr2O3 and PC-PBT/CdS nanocomposites by gamma irradiation

2020 ◽  
Vol 92 (2) ◽  
pp. 20402
Author(s):  
Kaoutar Benthami ◽  
Mai ME. Barakat ◽  
Samir A. Nouh
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Band Gap ◽  
Color Difference ◽  
Band Gap Energy ◽  
Polybutylene Terephthalate ◽  
Γ Irradiation ◽  
Gap Energy ◽  
Vis Spectroscopy ◽  
Oxygen Atoms

Nanocomposite (NCP) films of polycarbonate-polybutylene terephthalate (PC-PBT) blend as a host material to Cr2O3 and CdS nanoparticles (NPs) were fabricated by both thermolysis and casting techniques. Samples from the PC-PBT/Cr2O3 and PC-PBT/CdS NCPs were irradiated using different doses (20–110 kGy) of γ radiation. The induced modifications in the optical properties of the γ irradiated NCPs have been studied as a function of γ dose using UV Vis spectroscopy and CIE color difference method. Optical dielectric loss and Tauc's model were used to estimate the optical band gaps of the NCP films and to identify the types of electronic transition. The value of optical band gap energy of PC-PBT/Cr2O3 NCP was reduced from 3.23 to 3.06 upon γ irradiation up to 110 kGy, while it decreased from 4.26 to 4.14 eV for PC-PBT/CdS NCP, indicating the growth of disordered phase in both NCPs. This was accompanied by a rise in the refractive index for both the PC-PBT/Cr2O3 and PC-PBT/CdS NCP films, leading to an enhancement in their isotropic nature. The Cr2O3 NPs were found to be more effective in changing the band gap energy and refractive index due to the presence of excess oxygen atoms that help with the oxygen atoms of the carbonyl group in increasing the chance of covalent bonds formation between the NPs and the PC-PBT blend. Moreover, the color intensity, ΔE has been computed; results show that both the two synthesized NCPs have a response to color alteration by γ irradiation, but the PC-PBT/Cr2O3 has a more response since the values of ΔE achieved a significant color difference >5 which is an acceptable match in commercial reproduction on printing presses. According to the resulting enhancement in the optical characteristics of the developed NCPs, they can be a suitable candidate as activate materials in optoelectronic devices, or shielding sheets for solar cells.

Stability Investigation in the Optical Properties of Thermally Evaporated Ge5Se95-x Znx Thin Films

2015 ◽  
Vol 7 (3) ◽  
pp. 1923-1930
Author(s):  
Austine Amukayia Mulama ◽  
Julius Mwakondo Mwabora ◽  
Andrew Odhiambo Oduor ◽  
Cosmas Mulwa Muiva ◽  
Boniface Muthoka ◽  
...  
Keyword(s):  
Thin Films ◽  
Band Gap ◽  
Optical Band Gap ◽  
Thermal Evaporation ◽  
Optical Transition ◽  
Bulk Material ◽  
Band Gap Energy ◽  
Optical Absorbance ◽  
Gap Energy ◽  
Constituent Elements

 Selenium-based chalcogenides are useful in telecommunication devices like infrared optics and threshold switching devices. The investigated system of Ge5Se95-xZnx (0.0 ≤ x ≤ 4 at.%) has been prepared from high purity constituent elements. Thin films from the bulk material were deposited by vacuum thermal evaporation. Optical absorbance measurements have been performed on the as-deposited thin films using transmission spectra. The allowed optical transition was found to be indirect and the corresponding band gap energy determined. The variation of optical band gap energy with the average coordination number has also been investigated based on the chemical bonding between the constituents and the rigidity behaviour of the system’s network.

scholarly journals Polymer Thermal Treatment Production of Cerium Doped Willemite Nanoparticles: An Analysis of Structure, Energy Band Gap and Luminescence Properties

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1118
Author(s):  
Ibrahim Mustapha Alibe ◽  
Khamirul Amin Matori ◽  
Mohd Hafiz Mohd Zaid ◽  
Salisu Nasir ◽  
Ali Mustapha Alibe ◽  
...  
Keyword(s):  
Solid State ◽  
Thermal Treatment ◽  
Band Gap ◽  
Optical Band Gap ◽  
Dopant Concentration ◽  
Blue Emission ◽  
Green Emission ◽  
Band Gap Energy ◽  
Solid State Lighting ◽  
Gap Energy

The contemporary market needs for enhanced solid–state lighting devices has led to an increased demand for the production of willemite based phosphors using low-cost techniques. In this study, Ce3+ doped willemite nanoparticles were fabricated using polymer thermal treatment method. The special effects of the calcination temperatures and the dopant concentration on the structural and optical properties of the material were thoroughly studied. The XRD analysis of the samples treated at 900 °C revealed the development and or materialization of the willemite phase. The increase in the dopant concentration causes an expansion of the lattice owing to the replacement of larger Ce3+ ions for smaller Zn2+ ions. Based on the FESEM and TEM micrographs, the nanoparticles size increases with the increase in the cerium ions. The mean particles sizes were estimated to be 23.61 nm at 1 mol% to 34.02 nm at 5 mol% of the cerium dopant. The optical band gap energy of the doped samples formed at 900 °C decreased precisely by 0.21 eV (i.e., 5.21 to 5.00 eV). The PL analysis of the doped samples exhibits a strong emission at 400 nm which is ascribed to the transition of an electron from localized Ce2f state to the valence band of O2p. The energy level of the Ce3+ ions affects the willemite crystal lattice, thus causing a decrease in the intensity of the green emission at 530 nm and the blue emission at 485 nm. The wide optical band gap energy of the willemite produced is expected to pave the way for exciting innovations in solid–state lighting applications.

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