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Si(0 0 1) surface optical anisotropies induced by π-conjugated overlayers and oxidation
W.G. Schmidt,A. Hermann,F. Fuchs,F. Bechstedt 한국물리학회 2006 Current Applied Physics Vol.6 No.3
A density functional (DFT–GGA) study on the modification of the Si(001) surface optical response upon adsorption of 9,10-phenanthrenequinone and oxidation is presented. In the first case it is found that intramolecular p–p* transitions as well as adsorption-modified Si bulk states contribute to the optical signal. The molecular contributions differ strongly from the respective signals of gas-phase molecules, indicating the need for a cautious interpretation of experimental data. The calculations for oxidized Si structures show that local Si lattice deformations accompanying the oxidation of Si bulk bonds directly at the silicon–silicon oxide interface give rise to pronounced optical anisotropies that explain the experimental findings very well. In contrast, calculations for translationally invariant oxide structures fail to reproduce the experiment. This indicates the oxidation to occur layer-by-layer and strong disorder of the silicon oxide layers immediately above the interface.
Si(0 0 1) c(4 × 2)?p(2 × 2) surface phase transitions induced by electric fields and doping
W.G. Schmidt,K. Seino 한국물리학회 2006 Current Applied Physics Vol.6 No.3
Density functional calculations on the relative stability ofc(4· 2) andp(2· 2) reconstructed Si(001) surfaces exposed to external elec-tric elds and charge injection are presented. Electric elds parallel to the [001] direction or electrons inserted into surface states arefound to favor thep(2· 2) over thec(4· 2) reconstruction. This explains recent experimental ndings for Si and Ge(001).
Cho, W. B.,Yim, J. H.,Choi, S. Y.,Lee, S.,Schmidt, A.,Steinmeyer, G.,Griebner, U.,Petrov, V.,Yeom, D.-I.,Kim, K.,Rotermund, F. WILEY-VCH Verlag 2010 Advanced Functional Materials Vol.20 No.12
<P>Single-walled carbon-nanotube absorbers are experimentally demonstrated for laser mode-locking. A saturable absorber device is used to mode-lock three different bulk solid-state lasers in a 500 nm-wide wavelength interval. The devices exhibit a low saturation fluence of <10 mu J cm(-2), low scattering losses, and an exceptionally rapid relaxation, with time constants reaching <100 fs. The latter two properties are explained by a decreased curling tendency and increased tube-to-tube interactions of the nanotubes, respectively. These properties are the result of an optimized manufacturing procedure in combination with the use of a starting material with a higher microscopic order. The decreased scattering enables universal use of these devices in bulk solid-state lasers, which tend to be highly sensitive against non-saturable device losses as caused by scattering. The favorable saturable absorption properties are experimentally verified by mode-locking the three lasers, which all exhibit near transform-limited performance with about 100 fs pulse duration. The complete and unconditional absence of Q-switching side bands verifies the small saturation fluence of these devices.</P>
Microphotoluminescence spectroscopy of single CdTe/ZnTe quantum dots grown on Si(001) substrates
Lee, H S,Rastelli, A,Benyoucef, M,Ding, F,Kim, T W,Park, H L,Schmidt, O G IOP Pub 2009 Nanotechnology Vol.20 No.7
<P>We have studied the emission properties of single CdTe/ZnTe quantum dots (QDs) grown on Si(001) substrates by using molecular beam epitaxy and atomic layer epitaxy. The good quality of the QDs is attested by the resolution-limited emission, negligible background and absence of measurable spectral jitter or blinking. Power-dependent, polarization-dependent, and temperature-dependent microphotoluminescence spectroscopy measurements were performed to identify the exciton, the biexciton, and two oppositely charged excitons in the emission spectra of single QDs.</P>
High-precision photometry by telescope defocusing - VII. The ultrashort period planet WASP-103
Southworth, J.,Mancini, L.,Ciceri, S.,Budaj, J.,Dominik, M.,Figuera Jaimes, R.,Haugbolle, T.,Jorgensen, U. G.,Popovas, A.,Rabus, M.,Rahvar, S.,von Essen, C.,Schmidt, R. W.,Wertz, O.,Alsubai, K. A.,Boz Oxford University Press 2015 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.447 No.1
Stability of the Broad-line Region Geometry and Dynamics in Arp 151 Over Seven Years
Pancoast, A.,Barth, A. J.,Horne, K.,Treu, T.,Brewer, B. J.,Bennert, V. N.,Canalizo, G.,Gates, E. L.,Li, W.,Malkan, M. A.,Sand, D.,Schmidt, T.,Valenti, S.,Woo, J.-H.,Clubb, K. I.,Cooper, M. C.,Crawford American Astronomical Society 2018 The Astrophysical journal Vol.856 No.2
<P>The Seyfert 1 galaxy Arp 151 was monitored as part of three reverberation mapping campaigns spanning 2008-2015. We present modeling of these velocity-resolved reverberation mapping data sets using a geometric and dynamical model for the broad-line region (BLR). By modeling each of the three data sets independently, we infer the evolution of the BLR structure in Arp 151 over a total of 7 yr and constrain the systematic uncertainties in nonvarying parameters such as the black hole mass. We find that the BLR geometry of a thick disk viewed close to face-on is stable over this time, although the size of the BLR grows by a factor of similar to 2. The dynamics of the BLR are dominated by inflow, and the inferred black hole mass is consistent for the three data sets, despite the increase in BLR size. Combining the inference for the three data sets yields a black hole mass and statistical uncertainty of log(10)(M-BH/M-circle dot) = 6.82(-0.09)(+0.09) with a standard deviation in individual measurements of 0.13 dex.</P>
Mancini, L.,Giacobbe, P.,Littlefair, S. P.,Southworth, J.,Bozza, V.,Damasso, M.,Dominik, M.,Hundertmark, M.,Jørgensen, U. G.,Juncher, D.,Popovas, A.,Rabus, M.,Rahvar, S.,Schmidt, R. W.,Skottfelt, J.,S EDP Sciences 2015 Astronomy and astrophysics Vol.584 No.-
<P>Context. Photometric monitoring of the variability of brown dwarfs can provide useful information about the structure of clouds in their cold atmospheres.The brown-dwarf binary system Luhman16AB is an interesting target for such a study, because its components stand at the L/T transition and show high levels of variability. Luhman16AB is also the third closest system to the solar system, which allows precise astrometric investigations with ground-based facilities. Aims. The aim of the work is to estimate the rotation period and study the astrometric motion of both components. Methods. We have monitored Luhman16AB over a period of two years with the lucky-imaging camera mounted on the Danish 1.54m telescope at La Silla, through a special i + z long-pass filter, which allowed us to clearly resolve the two brown dwarfs into single objects. An intense monitoring of the target was also performed over 16 nights, in which we observed a peak-to-peak variability of 0.20±0.02mag and 0.34±0.02mag for Luhman16A and 16B, respectively. Results. We used the 16-night time-series data to estimate the rotation period of the two components. We found that Luhman16B rotates with a period of 5.1 ±0.1h, in very good agreement with previous measurements. For Luhman16A, we report that it rotates more slowly than its companion, and even though we were not able to get a robust determination, our data indicate a rotation period of roughly 8h. This implies that the rotation axes of the two components are well aligned and suggests a scenario in which the two objects underwent the same accretion process. The 2-year complete data set was used to study the astrometric motion of Luhman16AB. We predict a motion of the system that is not consistent with a previous estimate based on two months of monitoring, but cannot confirm or refute the presence of additional planetary-mass bodies in the system.</P>