Profiling Composition Variations in Composition-Modulated GaP/InP Short-Period Superlattices Using Resonance Raman Scattering

1999 ◽  
Vol 583 ◽  
Author(s):  
H. M. Cheong ◽  
Yong Zhang ◽  
A. G. Norman ◽  
J. D. Perkins ◽  
A. Mascarenhas ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Band Gap ◽  
Resonance Raman ◽  
Band Gap Energy ◽  
Resonance Raman Scattering ◽  
Rich Region ◽  
Gap Energy ◽  
Composition Modulation ◽  
Short Period ◽  
Short Period Superlattices

AbstractWe use resonance Raman scattering (RRS) and electroreflection (ER) measurements to profile the the composition and strain variations in laterally composition-modulated (CM) GaP/InP short-period superlattices (SPS's). The ER spectra of a GaP2.2/InP2.0 SPS give the fundamental band-gap energy at 1.69±0.05eV, which is about 210 meV lower than the band gap energy of a GaInP random alloy with the same overall composition. The RRS measurements reveal strong dependences of the phonon spectrum on the polarization and the excitation energy. In RRS spectra measured with the polarization of both excitation and scattered photons along the composition modulation direction, the GaP-like longitudinal optical (LO) phonon redshifts by 4.0±0.5 cm−1 near the resonance with the fundamental energy gap. On the other hand, when the polarizations are orthogonal to the composition modulation, the LO phonons redshift as much as 16 cm−1 at low excitation energies. A comparison of the experimental data with a model calculation gives the average In composition in the In-rich region as 0.70±0.02, and the average Ga composition in the Ga-rich region as 0.68±0.02. Our result also indicates that there are small volumes (less than 1% volume fraction) with very high In mole fraction.

Resonance Raman scattering studies of composition-modulated GaP/InP short-period superlattices

1999 ◽  
Vol 60 (7) ◽  
pp. 4883-4888 ◽  
Author(s):  
Hyeonsik M. Cheong ◽  
Yong Zhang ◽  
A. G. Norman ◽  
J. D. Perkins ◽  
A. Mascarenhas ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Resonance Raman ◽  
Resonance Raman Scattering ◽  
Short Period ◽  
Short Period Superlattices

Origin of short period oscillation near GaAs band-gap energy in photoreflectance

1997 ◽  
Vol 102 (4) ◽  
pp. 283-286
Author(s):  
Insun Hwang ◽  
Jae-Eun Kim ◽  
Hae Yong Park ◽  
C.D. Lee ◽  
Sam Kyu Noh
Keyword(s):  
Band Gap ◽  
Band Gap Energy ◽  
Gap Energy ◽  
Short Period ◽  
Period Oscillation

Resonance Raman Scattering in Short Period GaAs-AlAs Superlattices

1989 ◽  
pp. 157-164
Author(s):  
J. Menéndez ◽  
A. Pinczuk ◽  
J. P. Valladares ◽  
L. N. Pfeiffer ◽  
K. W. West ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Resonance Raman ◽  
Resonance Raman Scattering ◽  
Short Period

Band-GaP Energy and Physical Properties of InN Grown by RF-Molecular Beam Epitaxy

2003 ◽  
Vol 798 ◽  
Author(s):  
Yasushi Nanishi ◽  
Yoshiki Saito ◽  
Tomohiro Yamaguchi ◽  
Fumie Matsuda ◽  
Tsutomu Araki ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Band Gap ◽  
Hexagonal Wurtzite Structure ◽  
Band Gap Energy ◽  
High Quality ◽  
Precise Control ◽  
Gap Energy ◽  
Optimum Growth Temperature ◽  
Si Substrates ◽  
Aln Buffer

ABSTRACTThis paper describes studies on high-quality InN growth on sapphire by RF-MBE. Critical procedures to obtain high-quality InN films were investigated and (1) nitridation process of sapphire substrates prior to growth, (2) precise control of V/III ratio and (3) selection of optimum growth temperature were found to be essential. Detailed structural characterizations by XRD, TEM, Raman scattering and EXAFS indicate that InN films obtained in this study have ideal hexagonal wurtzite structure. FWHMs of ω-2Θ mode XRD and E2(high)-phonon-mode of Raman scattering are as small as 28.9 arcsec and 3.2 cm-1, respectively. True band gap energy of InN is also discussed based on optical characterization results obtained from well-characterized hexagonal InN grown in this study. PbS, instead of InGaAs, was used as a detector for PL study in order to solve the problem coming from the cut-off wavelength of InGaAs detector. Based on these systematic studies on structural and optical property characterizations using high-quality InN, true band-gap energy of InN is suggested to be less than 0.67 eV and approximately 0.65 eV at room temperature. Single-crystalline InN films are also successfully grown on Si substrates by a brief nitridation of the Si substrates. Significant improvement of InN crystal quality on Si substrates by the insertion of an AlN buffer layer is also demonstrated.

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.

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