摘要 :
We report the detection of [Ne Ⅱ] emission at 12.81 μm in four out of the six optically thick dust disks observed as part of the FEPS Spitzer Legacy program. In addition, we detect a H Ⅰ (7-6) emission line at 12.37 μm from th...
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We report the detection of [Ne Ⅱ] emission at 12.81 μm in four out of the six optically thick dust disks observed as part of the FEPS Spitzer Legacy program. In addition, we detect a H Ⅰ (7-6) emission line at 12.37 μm from the source RX J1852.3—3700. Detections of [Ne Ⅱ] lines are favored by low mid-infrared excess emission. Both stellar X-rays and extreme ultraviolet (EUV) photons can sufficiently ionize the disk surface to reproduce the observed line fluxes, suggesting that emission from Ne~+ originates in the hot disk atmosphere. On the other hand, the H Ⅰ (7-6) line is not associated with the gas in the disk surface, and magnetospheric accretion flows can account for at most ～30% of the observed flux. We conclude that accretion shock regions and/or the stellar corona could contribute to most of the H Ⅰ (7-6) emission. Finally, we discuss the observations necessary to identify whether stellar X-rays or EUV photons are the dominant ionization mechanism for Ne atoms. Because the observed [Ne Ⅱ] emission probes very small amounts of gas in the disk surface (～10~(-6) M_J) we suggest using this gas line to determine the presence or absence of gas in more evolved circumstellar disks.
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We investigate the interaction of hydrogen with the B2 TiFe (001) and (110) surfaces sing the full-potential linearized augmented plane wave (FLAPW) method. The changes in the electronic structures in the different B2 TiFe surface...
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We investigate the interaction of hydrogen with the B2 TiFe (001) and (110) surfaces sing the full-potential linearized augmented plane wave (FLAPW) method. The changes in the electronic structures in the different B2 TiFe surfaces in comparison with the bulk ground state are analyzed. Ferromagnetic order is found in the Fe-terminated (001) surface with the magnetic moment 2.27 μB, which quickly diminishes inside the film. The absorption of hydrogen onto the Fe/TiFe (001) surface results in a decrease in the magnetic moment.
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Polarized Raman scattering has been performed on CaC_6 superconductor. We identify two of the three Raman-active E_g phonon modes at 440 and 1508 cm~(-1) expected for the R3m space group of CaC_6. These first-order scattering mode...
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Polarized Raman scattering has been performed on CaC_6 superconductor. We identify two of the three Raman-active E_g phonon modes at 440 and 1508 cm~(-1) expected for the R3m space group of CaC_6. These first-order scattering modes appear along with the D and G bands around 1300 and 1600 cm~(-1) that are similar in origin to the corresponding bands in plain graphite. The intensities of the D and G bands in CaC_6 correlate with degree of disorder. The D band arises from the double resonant Raman-scattering process; its frequency shifts as a function of excitation energy with ～35 cm~(-1) /eV. The double resonant Raman scattering probes phonon excitations with finite wave vector q. We estimate the characteristic spacing of structural defects to be on the scale of about 100 A by comparing the intensity of the D band and the 1508 cm~(-1) E_g mode in CaC_6 to calibrated intensity ratio of analogous bands in disordered graphites. A sharp superconducting coherence peak at 24 cm~(-1) is observed below T_c.
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Time-integrated and femtosecond time-resolved photoluminescence spectroscopy has been used to study the dynamic emission polarization anisotropy for thin films of a conjugated polymer whose chains had been aligned through a nanoim...
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Time-integrated and femtosecond time-resolved photoluminescence spectroscopy has been used to study the dynamic emission polarization anisotropy for thin films of a conjugated polymer whose chains had been aligned through a nanoimprinting technique. The r
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Near-field scanning optical microscopy (NSOM) studies of self-assembled InAs quantum dot broad area laser diodes (QD-BALDs) with different active layer were performed. The high resolution ( < 100 nm) of NSOM provides a detailed mapping of the laser output from the active region. Representative near-field electroluminescence (EL) spectra taken the cross section of the QD-BALD structures below and above the lasing threshold are plotted. Moreover, spatially resolved near-field scanning images of the waveguide are obtained by collecting the EL as the tip is scanned across the surface. Such near-field measurements show a relationship between laser emission and different active layer structure....
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Near-field scanning optical microscopy (NSOM) studies of self-assembled InAs quantum dot broad area laser diodes (QD-BALDs) with different active layer were performed. The high resolution ( < 100 nm) of NSOM provides a detailed mapping of the laser output from the active region. Representative near-field electroluminescence (EL) spectra taken the cross section of the QD-BALD structures below and above the lasing threshold are plotted. Moreover, spatially resolved near-field scanning images of the waveguide are obtained by collecting the EL as the tip is scanned across the surface. Such near-field measurements show a relationship between laser emission and different active layer structure.
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We compared the superluminescent diodes (SLDs) of two types in order to see the effect of embedding another quantum dots (QDs) layer. The insertion of another QDs layer showed a new possibility for a wider spectrum. In addition, t...
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We compared the superluminescent diodes (SLDs) of two types in order to see the effect of embedding another quantum dots (QDs) layer. The insertion of another QDs layer showed a new possibility for a wider spectrum. In addition, through comparing two kinds of SLD structures, the peak positions of the ground state and excited state were observed to be af-
fected differently by band-filling, thermal effect, and the overlap of tails of excited state (ES) gain, according to the wafer structure, and the effect of the cap layer is superior to the carrier non-uniformity. We also revealed the temperature sensitivity of carriers in QDs through measuring characteristic temperature.
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Terahertz reflectance spectra of the Ca-intercalated graphite CaC_6 reveal a superconducting gap below 11 K. The gap signature lacks a sharp onset to full reflectivity at 2Δ_0 but rather shows a distribution of gap values consist...
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Terahertz reflectance spectra of the Ca-intercalated graphite CaC_6 reveal a superconducting gap below 11 K. The gap signature lacks a sharp onset to full reflectivity at 2Δ_0 but rather shows a distribution of gap values consistent with an anisotropic gap. The experimental data were successfully fitted to the gap distribution obtained from density-functional calculations of Sanna et al. [Phys. Rev. B 75, 020511(R) (2007)]. The temperature dependence of the superconducting gap is characteristic for a BCS type superconductor.
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We report on the unusual behaviors of the optical properties for self-assembled InAs/GaAs quantum dots (QDs) by using photoluminescence (PL) spectroscopy. Distinctive double-emission QD peaks are observed in the PL spectra of the ...
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We report on the unusual behaviors of the optical properties for self-assembled InAs/GaAs quantum dots (QDs) by using photoluminescence (PL) spectroscopy. Distinctive double-emission QD peaks are observed in the PL spectra of the samples grown on high growth-temperature condition. From the excitation power-dependent and temperature-dependent PL measurements, these double-emission peaks are associated with the ground-state transitions from InAs QDs with two different size branches. In addition, the variation in the bimodal size distribution of the QD ensembles with different InAs coverage is demonstrated.
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In this study, Pt/IZO (In_xZn_(1-x)O_y) Schottky diodes were fabricated and the degradation phenomenon was investigated. The Pt/IZO Schottky diodes showed a rectifying ratio of 10~5, however, the electrical properties were degrade...
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In this study, Pt/IZO (In_xZn_(1-x)O_y) Schottky diodes were fabricated and the degradation phenomenon was investigated. The Pt/IZO Schottky diodes showed a rectifying ratio of 10~5, however, the electrical properties were degraded with aging. An increase in defect and carrier concentrations was observed from capacitance-voltage analysis and photoluminescence in the aged Pt/IZO Schottky diode. The degradation of the rectifying properties of the aged diodes originates possibly from the electron tunneling due to the increased defect concentrations.
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Atomic force microscopy (AFM) measurements were carried out to investigate the structural properties of CdTe/ZnTe quantum rings (QRs), and photoluminescence (PL) measurements were performed to determine the electron activation ene...
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Atomic force microscopy (AFM) measurements were carried out to investigate the structural properties of CdTe/ZnTe quantum rings (QRs), and photoluminescence (PL) measurements were performed to determine the electron activation energy. The AFM images showed that uniform CdTe QRs were formed on ZnTe buffer layers. While the excitonic peak corresponding to the transition from the ground electronic subband to the ground heavy-hole band (E_1-HH_1) in the CdTe/ZnTe QRs was shifted to higher energy in comparison with that in CdTe/ZnTe quantum wires and quantum wells, it was shifted to lower energy in comparison with that in CdTe/ZnTe quantum dots. The activation energy of the electrons confined in the CdTe QRs, as obtained from the temperature-dependent PL spectra, was higher than those in CdTe quantum wires and quantum wells and smaller than that in CdTe quantum dots. The present results can help improve understanding of the formation and optical properties of the CdTe QRs grown on ZnTe buffer layers.
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