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91.
A new thin-film electro-optic switch employing two stable states of polarization is proposed and investigated. The design can be further employed to realize a TE-TM polarization converter by constructing a Mach-Zehnder type interferometer integrated optical switch. The limitations and design procedures for electro-optic devices are also discussed. 相似文献
92.
Pure 2,2'-Dibromo-9,9'-spirobifluorene was synthesized by a method that did not involve troublesome dibromination of 9,9'-spirobifluorene or Sandmeyer reaction of 2,2'-diamino-9,9'-spirobifluorene. A series of donor-acceptor orthogonally substituted 9,9'-spirobifluorene was subsequently prepared showing rich variation of fluorescence in solution and in solid state. [reaction: see text] 相似文献
93.
The quantized electronic structure in Pb films on Si(111) varies substantially as the film thickness increases. The changes in electronic energy cause the thermal stability of the films to oscillate with an approximate bilayer period. The phase of the oscillations can be controlled by interfacial engineering. Comparison of Pb films prepared on Si(111) terminated by In, Au, and Pb as interfactants reveals a phase reversal. For , films made of odd numbers of atomic layers (5, 7, and 9) are more stable than the even ones. This trend is reversed for the other two cases. 相似文献
94.
It is demonstrated that ultrahigh-resolution angular measurement can be achieved via surface-plasmon-resonance excitation in which the phase difference between p- and s-polarized reflected waves is monitored as a function of the incidence angle. Resolutions down to 1.9 x 10(-6) deg are obtained by performing the measurements at optimal incident wavelengths. This represents an order of magnitude improvement compared with previously reported values. 相似文献
95.
Atomically uniform Pb films are successfully prepared on Si(111), despite a large lattice mismatch. Angle-resolved photoemission measurements of the electronic structure show layer-resolved quantum well states which can be correlated with dramatic variations in thermal stability. The odd film thicknesses N = 5, 7, and 9 monolayers show sharp quantum well states. The even film thicknesses N = 6 and 8 do not, but are much more stable than the odd film thicknesses. This correlation is discussed in terms of a total energy calculation and Friedel-like oscillations in properties. 相似文献
96.
Wen-Shyan Hong Chen-Shiang Lee Michael Y Chiang 《Journal of organometallic chemistry》2004,689(2):277-285
The reaction of thiophene-2-carboxaldehyde thiosemicarbazone (2-C4H3SCHNNHC(S)NH2) (1) with diiron nonacarbonyl under mild conditions in anhydrous benzene yields three iron carbonyl organometallic clusters: (i) Fe2S2 square-base pyramidal cluster 2 ([Fe(CO)3]3(μ3-S)2), (ii) Fe2S2 square-base pyramidal metal carbene cluster 3 ([Fe(CO)3]2Fe(CO)2(μ3-S)2(C(NH2)NHNCH (2-C4H3S)), and (iii) double butterfly cluster 4 ([Fe(CO)3]3Fe(CO)2(μ4-S)(C,N; C(NH2)NHNCH(2-C4H3S) (μ2-S, N; SC(NH2)NNCH(2-C4H3S)), and an octahedral complex 5 (Fe(CO)2(S, N; SC(NH2)NNCH (2-C4H3S))2. These products were fully characterized spectrally. The molecular structures of 1, 3, 4, and 5 have been determined by single-crystal X-ray diffraction. 相似文献
97.
Chiang CM Lu D Huang JT Hwang CC Cho CC Fan LJ Yang YW 《Journal of the American Chemical Society》2004,126(39):12242-12243
Fluorine-substituted ethyl groups on Cu(111) were generated by thermal scission of the C-I bond in the adsorbed C2F5I. Temperature-programmed reaction spectrometry observed a novel pathway resulting in the evolution of C4F6 above 400 K. Among the various isomers, this product was identified as hexafluro-2-butyne. Although abstraction of two fluorine atoms from the starting Cu-CF2CF3 was required, Cu-CCF3 (trifluoroethylidyne) was favored over Cu-CF=CF2 (trifluorovinyl) as the intermediate because this ethyl-ethylidyne-butyne pathway was suppressed on a Cu(100) surface devoid of the key threefold hollow binding sites for ethylidyne. Once formed, perfluoroethylidyne readily coupled to afford a tightly surface-bound hexafluoro-2-butyne up to 400 K. Therefore, the C-F bonds adjacent to the metal were found to be more susceptible to the bond activation, leading the chemisorbed perfluoroethyl to eliminate two F atoms successively from the alpha-carbon. This preference for alpha-elimination rather than beta-elimination (the most favorable route in hydrocarbons) may be quite general for metal surface-mediated reactions involving fluorinated alkyl groups. 相似文献
98.
Alternating layer and island growth of Pb on Si by spontaneous quantum phase separation 总被引:2,自引:0,他引:2
Hong H Wei CM Chou MY Wu Z Basile L Chen H Holt M Chiang TC 《Physical review letters》2003,90(7):076104
Real-time in situ x-ray studies of continuous Pb deposition on Si(111)-(7x7) at 180 K reveal an unusual growth behavior. A wetting layer forms first to cover the entire surface. Then islands of a fairly uniform height of about five monolayers form on top of the wetting layer and grow to fill the surface. The growth then switches to a layer-by-layer mode upon further deposition. This behavior of alternating layer and island growth can be attributed to spontaneous quantum phase separation based on a first-principles calculation of the system energy. 相似文献
99.
100.
Propagation characteristics of a segmented cladding fiber 总被引:3,自引:0,他引:3
We propose a novel optical fiber design that consists of a uniform core and a segmented cladding formed by alternate regions of high and low refractive indices in the azimuthal direction. The structure is analyzed by use of the radial effective-index method, and the propagation characteristics of the structure are studied. The fiber has a highly dispersive cladding and shows characteristics similar to those of photonic-crystal fibers and holey fibers. The novel fiber offers the possibility of single-mode operation over a wide range of wavelengths with a large core diameter. 相似文献