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991.
992.
Diamond-like carbon (DLC) films were deposited on Si(1 0 0) substrates using plasma deposition technique. The deposited films were irradiated using 2 MeV N+ ions at fluences of 1×1014, 1×1015 and 5×1015 ions/cm2. Samples have been characterized by using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). Analysis of Raman spectra shows a gradual shift of both D and G band peaks towards higher frequencies along with an increase of the intensity ratio, I(D)/I(G), with increasing ion fluence in irradiation. These results are consistent with an increase of sp2 bonding. XPS results also show a monotonic increase of sp2/sp3 hybridization ratio with increasing ion fluence. Plan view TEM images show the formation of clusters in the irradiated DLC films. HRTEM micrographs from the samples irradiated at a fluence of 5×1015 ions/cm2 show the lattice image with an average interplanar spacing of 0.34 nm, revealing that the clusters are graphite clusters. The crystallographic planes in these clusters are somewhat distorted compared to the perfect graphite structure. 相似文献
993.
Taizo Kawauchi Katsuyuki Fukutani Shunji Kishimoto Yoshitaka Yoda 《Applied Surface Science》2009,256(4):962-964
Measurements of the internal-conversion electron emission due to the inelastic nuclear resonant excitation are reported. S0169433209006977-si1.gif"> thin films of 20 and 1.3 nm thickness were deposited on Si(1 1 1), and the internal-conversion electrons were measured as a function of the photon energy. From the inelastic part of the spectra, the phonon density of states was obtained. Whereas the phonon density of states of 20-nm thick film resembles that of bulk S0169433209006977-si2.gif">-Fe, the 1.3-nm thick film revealed an obvious softening of the acoustic mode. 相似文献
994.
Ayako Imai Kenji Mawatari Nobuo Ueno Kazuyuki Sakamoto 《Applied Surface Science》2009,256(4):1156-1159
The thickness-dependent electronic structures of Dy silicide films grown on a Si(1 1 1) surface have been investigated by angle-resolved photoelectron spectroscopy. Two (1×1) periodic bands, both of them cross the Fermi level, have been observed in the silicide films formed by Dy coverages of 1.0 monolayer and below, and more than five (S0169433209007570-si2.gif">) periodic bands have been observed in thicker films. Taking the (S0169433209007570-si3.gif">) periodic structure of Dy atoms in the submonolayer silicide film into account, the periodicity of the two metallic bands indicate that they mainly originate from the orbitals of Si atoms, which form a (1×1) structure. Of the (S0169433209007570-si5.gif">) periodic bands observed in thick films, four of them are well explained by the folding of the (1×1) bands into a (S0169433209007570-si7.gif">) periodicity. Regarding the other band, the three (S0169433209007570-si8.gif">) periodic bands would originate from the electronic states related to the inner Si layers that form a (S0169433209007570-si9.gif">) structure, and the one observed in the 3.0 ML film only might originate from the electron located at the interface between bulk Si and the Dy silicide film. 相似文献
995.
We consider the covariant quantization of generalized abelian gauge theories on a closed and compact n-dimensional manifold whose space of gauge invariant fields is the abelian group of Cheeger–Simons differential characters. The space of gauge fields is shown to be a non-trivial bundle over the orbits of the subgroup of smooth Cheeger–Simons differential characters. Furthermore each orbit itself has the structure of a bundle over a multi-dimensional torus. As a consequence there is a topological obstruction to the existence of a global gauge fixing condition. A functional integral measure is proposed on the space of gauge fields which takes this problem into account and provides a regularization of the gauge degrees of freedom. For the generalized p-form Maxwell theory closed expressions for all physical observables are obtained. The Green’s functions are shown to be affected by the non-trivial bundle structure. Finally the vacuum expectation values of circle-valued homomorphisms, including the Wilson operator for singular p-cycles of the manifold, are computed and selection rules are derived. 相似文献
996.
C.A.C. Passos M.T.D. Orlando J.L. Passamai Jr. E.V.L. de Mello 《Physica B: Condensed Matter》2009,404(19):3123-3126
A model to describe the critical current density behavior of high-Tc polycrystalline superconductors is proposed for all magnetic field values. The main features of the model are as follows: the transport critical current density is controlled by the weak-link network at grain boundaries. The size distribution of weak links is well represented by a Gamma-type distribution. Finally, the tunneling critical current between grains follows a Fraunhofer diffraction pattern or a modified pattern if the applied magnetic field is lower or higher than the first critical field Hc1. 相似文献
997.
以硝酸铋、硫代乙酰胺和氨三乙酸等为原料,利用水热法在180℃下反应12h得到Bi2S3纳米带.X射线粉末衍射结果表明产物对应于正交晶相的Bi2 S3(JCPDS:17-320),晶胞参数为a=1.110 6 nm,1,b=1.099 3 nm,c=O.389 2 nm,与文献报道值(a=1.114 9nm ,b=1.1304 nm,c=O.3981 nm)基本一致;通过透射电镜观察其形貌为均匀的带状,宽约100 nm;高分辨透射电镜照片显示晶体沿y轴优先生长;通过对x射线光电子能谱分析得到Bi和S的原子个数比例约为2:3,与目标产物Bi2 S3的计量比一致;测试显示Bi2S3纳米带的拉曼吸收峰出现在195 cm-1处,与块体Bi2s3(236 cm-1)相比,其吸收峰红移了41 cm-1,体现了纳米材料的表面效应.紫外-可见吸收光谱研究发现Bi2S3纳米带在450nm左右有吸收,计算得到Eg约为1.58 eV(块体Bi2S3的巨为1.3 eV),在光电领域有潜在的应用价值. 相似文献
998.
A.Martínez Torres 《中国物理C(英文版)》2009,33(12)
We have studied the ππN system and coupled channels by using of the Faddeev equations and two N~* and one △ states, all of them with J~P = 1/2~+, have been found in the formalism as dynamically generated states. In addition, signatures for a new N* resonance with J~P = 1/2~+ are found around an energy of 1920 MeV in the three-body center of mass system. 相似文献
999.
1000.