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RISS 인기검색어
- 검색키워드
- 저자 : Khaled A. Elsayed (검색결과 2 건)
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Khaled M. Elsabawy,Elsayed E. Kandyel,Morsy M.A. Sekkina 한국물리학회 2009 Current Applied Physics Vol.9 No.1
Although BPSCCO superconducting regime has very low stability under high oxygen pressures as reported in the literature, we managed to synthesize relatively pure 2212-BPSCCO and their Nb-doped samples having general formula Bi1-xNbxPbSr2CaCu2O8, where x = 0.1, 0.2, 0.4 and 0.6 mole, respectively, at moderate oxygen pressure (~30 bar). The superconducting measurements proved that the best recorded Tc ~ 69 K was for the undoped 2212-BPSCCO, while the lowest Tc ~ 58 K was recorded for the maximum doped sample x = 0.6 mole indicating that superconductive transition temperatures Tcs decrease regularly with increasing Nb-dopant concentration from x = 0.1 to 0.6, respectively. The lattice parameter c exhibited a slight length compression as Nb-dopant ratio increases from 0.1 to 0.6 mole, respectively. From SE-microscopic analysis, the average grain size was estimated and found in between 0.44 and 1.6 lm which is considered relatively high to that reported in the literature. The measured Jc’s values were found to be enhanced remarkably as Nb-dopant concentration increases. Although BPSCCO superconducting regime has very low stability under high oxygen pressures as reported in the literature, we managed to synthesize relatively pure 2212-BPSCCO and their Nb-doped samples having general formula Bi1-xNbxPbSr2CaCu2O8, where x = 0.1, 0.2, 0.4 and 0.6 mole, respectively, at moderate oxygen pressure (~30 bar). The superconducting measurements proved that the best recorded Tc ~ 69 K was for the undoped 2212-BPSCCO, while the lowest Tc ~ 58 K was recorded for the maximum doped sample x = 0.6 mole indicating that superconductive transition temperatures Tcs decrease regularly with increasing Nb-dopant concentration from x = 0.1 to 0.6, respectively. The lattice parameter c exhibited a slight length compression as Nb-dopant ratio increases from 0.1 to 0.6 mole, respectively. From SE-microscopic analysis, the average grain size was estimated and found in between 0.44 and 1.6 lm which is considered relatively high to that reported in the literature. The measured Jc’s values were found to be enhanced remarkably as Nb-dopant concentration increases.
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Band offsets and optical conduction in the CdSe/GaSe interface
T.S. Kayed,A.F. Qasrawi,Khaled A. Elsayed 한국물리학회 2016 Current Applied Physics Vol.16 No.7
In this work, the design and characterization of CdSe/GaSe heterojunction is considered. The CdSe/GaSe thin film interface was prepared by the physical vapor deposition technique. Systematic structural and optical analysis were performed to explore the crystalline nature, the optical band gaps, the conduction and valence band offsets, the dielectric spectra, and the frequency dependent optical conductivity at terahertz frequencies. The X-ray diffraction analysis revealed a polycrystalline interface that is mostly dominated by the hexagonal CdSe oriented in the (002) direction. It was also found that the CdSe/GaSe interface exhibits conduction and valence band offsets of 1.35 and 1.23/1.14 eV, respectively. The dielectric spectra displayed two dielectric resonance peaks at 530 and 445 THz. Moreover, the computational fittings of the optical conductivity of the interface revealed a free carrier scattering time of 0.41 (fs) for a free carrier density of 7.0 1018 (cm3). The field effect mobility for the CdSe/GaSe interface was found to be 5.22 (cm2/Vs). The remarkable features of this device having large band offsets and qualitative optical conduction dominated by a scattering time in the order of femtoseconds in addition to the dielectric property nominate the device to be used in optoelectronic technology.
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