scholarly journals Optical fundamental band-gap energy of semiconductors by photoacoustic spectroscopy

1994 ◽  
Vol 04 (C7) ◽  
pp. C7-129-C7-132 ◽  
Author(s):  
J. Caetano de Souza ◽  
A Ferreira da Silva ◽  
H. Vargas
Keyword(s):  
Band Gap ◽  
Photoacoustic Spectroscopy ◽  
Band Gap Energy ◽  
Fundamental Band ◽  
Gap Energy

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.

Temperature Dependence Of The Fundamental Band Gap In Hexagonal GaN

1997 ◽  
Vol 482 ◽  
Author(s):  
H. Herr ◽  
V. Alex ◽  
J. Weber
Keyword(s):  
Temperature Dependence ◽  
Band Gap ◽  
Line Shape ◽  
Free Exciton ◽  
Band Gap Energy ◽  
Recombination Process ◽  
Photoluminescence Spectra ◽  
High Quality ◽  
Fundamental Band ◽  
Gap Energy

AbstractPhotoluminescence spectra of hexagonal GaN were measured in the temperature range T= 2 – 1200 K. We identify the Free Exciton (FX) as the dominant recombination process in our high quality samples for temperatures above 200 K. From the line shape fit of the FX we determine the excitonic band gap shift with temperature. An analysis according to the empirical Varshni equation gives Eg (T)-Eg(0 K) = (-α T2)/(T + β), with α = (7.3 ± 0.3)·10−4 eV/K and β = (594 ± 54) K. We have detected significant differences in the band gap energy at low and higher temperatures for GaN layers grown on different substrate materials. Heating GaN above 1200 K leads to irreversible changes in the near band gap photoluminescence spectra.

scholarly journals Pressure dependence of the fundamental band-gap energy of CdSe

2004 ◽  
Vol 84 (1) ◽  
pp. 67-69 ◽  
Author(s):  
W. Shan ◽  
W. Walukiewicz ◽  
J. W. Ager ◽  
K. M. Yu ◽  
J. Wu ◽  
...  
Keyword(s):  
Band Gap ◽  
Pressure Dependence ◽  
Band Gap Energy ◽  
Fundamental Band ◽  
Gap Energy

STUDY OF BAND GAP ENERGY AND THERMAL PROPERTIES OF PbI2 BY PHOTOACOUSTIC SPECTROSCOPY

2012 ◽  
Vol 26 (16) ◽  
pp. 1250098 ◽  
Author(s):  
DHARAMVIR SINGH AHLAWAT
Keyword(s):  
Thermal Properties ◽  
Single Crystal ◽  
Band Gap ◽  
Photoacoustic Spectroscopy ◽  
Characteristic Frequency ◽  
Band Gap Energy ◽  
Front Side ◽  
Experimental Conditions ◽  
Gap Energy ◽  
Amplitude Measurement

The present work determined the band gap energy of PbI 2 equal to 2.31 eV by amplitude measurement of the photoacoustic (PA) signal using the front side detection configuration. Furthermore, the thermal properties were obtained from the phase recording of the PA signal at the characteristic frequency 55 Hz of the single crystal (250 μm). These properties have also been compared with the earlier reported values under identical experimental conditions by amplitude recording of the PA signal on the same PA spectrometer.

scholarly journals Band gap energy determination by photoacoustic spectroscopy under continuous light excitation

2006 ◽  
Vol 89 (23) ◽  
pp. 231926 ◽  
Author(s):  
N. G. C. Astrath ◽  
F. Sato ◽  
F. Pedrochi ◽  
A. N. Medina ◽  
A. C. Bento ◽  
...  
Keyword(s):  
Band Gap ◽  
Photoacoustic Spectroscopy ◽  
Continuous Light ◽  
Band Gap Energy ◽  
Gap Energy ◽  
Light Excitation ◽  
Energy Determination

Temperature dependence of the fundamental band gap energy of Cd1−xCoxTe single crystals

1998 ◽  
Vol 109 (4) ◽  
pp. 235-237 ◽  
Author(s):  
Hyekyeong Kim ◽  
Gwangsoo Jeen ◽  
Seongtae Park ◽  
Young-Hun Hwang ◽  
Young-Ho Um ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Band Gap ◽  
Single Crystals ◽  
Band Gap Energy ◽  
Fundamental 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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