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991.
Photodesorption and photofragmentation of disilane adsorbed on a hydrogen terminated Si(100) surface
The photochemical mechanisms leading to the desorption and fragmentation of Si2H6 adsorbed on a hydrogen terminated Si(100) surface have been explored by recording the time-of-flight distributions of products escaping from the surface and by using electron energy loss spectroscopy to probe possible electronic excitations. Photodesorption of intact Si2H6 involves hot electrons that lose energy and move to the conduction band edge before initiating desorption. When the wavelength of the incident light is 193 nm, Si2H6 fragments give mostly Si, SiH2, H2 and SiH4, but this pathway is quenched at longer wavelengths. This is consistent with direct excitation, but we also show that a negative ion resonance is accessible to substrate electrons that have been excited by 193 nm light. 相似文献
992.
Hirofumi Maekawa 《Tetrahedron letters》2004,45(20):3869-3872
Mg-promoted reduction of a mixture of aromatic ketones (or imines) and aliphatic carbonyl compounds in N,N-dimethylformamide (DMF) brought about unique mixed pinacol type of cross coupling to give unsymmetrical vicinal diols (or amino alcohols) or α-hydroxyketones in good to moderate yields. The reaction may be initiated by electron transfer from magnesium metal to an aromatic carbonyl compound possessing a less negative reduction potential. The difference of reduction potential between aromatic ketones (or imines) and aliphatic carbonyl compounds was found to be one of the important key factors in this selective cross coupling. 相似文献
993.
In the present work, the formation of compounds associated to the diffusion of reducing elements (Mg, Al and W) to the Ni cap surface of oxide cathode has been studied by a new method. This method used two cathodes, one of them is coated and the other is uncoated, to be in an attach-contact mounted in a dummy tube. Different analytical techniques were used for this study: scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) and I/V electrical measurements. After oxide cathode plus decomposited and activated, Al and Mg doping elements take place during heating to 810 °C (Ni-Br) under a rich controlled Ba/SrO atmosphere through an acceleration life test.It is shown that the chemical transport occurs mainly by a grain boundary mechanism with significant pile-up of Mg compounds. Al and W show a superficial concentrations and distribution.The dc electrical characteristic shows very strong rectifying behaviour through the M-S junction due to the I/V curves, particularly after 144 h acceleration life time. The characteristics are found to be reversible and reproducible, and viewed a rectification ratio (r) of 100. The calculated ideality factor shows a value of n = 9.6, which is evidenced to the tunnelling conduction.The theoretical calculation shows that the interface thickness grows to (∼6 μm) after accelerated the cathode to 1896 h. 相似文献
994.
T. Kümmell A. Sauerwald A. Somers A. Lffler J.P. Reithmaier A. Forchel G. Bacher 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):108
Self-organized InAs and InGaAs quantum dashes have been investigated by chemically sensitive scanning transmission electron microscopy and photoluminescence spectroscopy. The quantum dashes exhibit a triangular cross section. Using electron energy loss spectroscopy, we show that no intermixing between quantum dashes and embedding barrier occurs during growth. By adjusting the nominal thickness of the InAs layer, the emission wavelength of the InAs quantum dashes can be tuned between 1.37 and 1.9 μm in a straightforward way. 相似文献
995.
α-Chlorocyclopentenones can readily be transformed into a variety of α-substituted cyclopentenones via their dimethyltrimethylene acetals. 相似文献
996.
G. S. Kliros 《Il Nuovo Cimento D》1991,13(1):99-104
Summary In a previous paper, Kliroset al. presented a model calculation of the Hall conductivity as a function of the Landau level broadening Γ for finite temperatures.
In this paper, the effect of Landau-level broadening on the structure of the Hall conductivity is investigated. The experimental
data regarding the Si-MOSFET and GaAs-heterostructure experiments are reproduced including a functional dependence of Γ on
the magnetic field. The influence of the effectiveg-factor is considered as well. 相似文献
997.
998.
建立了电子回旋共振(ECR)微波放电等离子体中离子输运过程的蒙特卡罗模型,考虑了离子与中性原子的电荷交换碰撞和弹性碰撞,以及精确依赖于离子能量的电荷交换和动量转移截面,模拟了源于氩气ECR微波放电的氩离子向衬底输运的过程,得到与实验报道相符的模拟结果。 相似文献
999.
Naoyuki Takahashi Arei Niwa Takato Nakamura 《Journal of Physics and Chemistry of Solids》2004,65(7):1259-1263
Indium nitride prepared under atmospheric pressure using a halide chemical vapor deposition method has been examined by means of a variety of analytical techniques. Scanning electron microscopic observations showed that the crystals deposited onto a Si(100) substrate have hexagonal pillar structure. Based on the X-ray diffraction and X-ray pole-figure analyses, it was deduced that each InN pillar crystal grows with a different rotation angle around the 〈001〉 axis. Transmission electron diffraction showed that they are of single-like form. This was also confirmed by the selected area electron diffraction image as well. 相似文献
1000.
Matthias Lehmann Jérôme Cornil Jean-Luc Brédas Simon Goddard Yves Geerts 《Tetrahedron》2004,60(14):3283-3291
Hexaazatriisothianaphthenes substituted with six alkylsulfanyl chains (propyl and dodecylsulfanyl) have been synthesised and their thermotropic, photophysical and oxidation-reduction properties characterised. Their synthesis has been motivated by the results of quantum-chemical calculations that point to efficient transport properties for these new electron-deficient mesogens since electron transport is predicted to be only slightly affected by rotational degrees of freedom in the discotic mesophase. 相似文献