共查询到20条相似文献,搜索用时 62 毫秒
1.
《Surface science》1993,296(1):L15-L20
Using scanning tunneling microscopy (STM), we have observed an antiphase domain boundary of single-atom width on a Si(111)-(7 × 7) surface. The extra row of adatoms forming the boundary lies on the unfaulted half of the 7 × 7 unit cell, in agreement with total energy calculations using the first-principles self-consistent pseudofunction method. The filled-state STM image shows a missing interior adatom on the unfaulted half, in agreement with calculations of the partial density of states of an adatom surrounded by three rest-atoms. 相似文献
2.
Scanning tunneling microscope-light emission (STM-LE) from the Si(1 1 1)-(7×7) surface has been measured using silver tips. For silver tips photon emission was enhanced by more than 100 times as compared with that for tungsten or platinum–iridium alloy tips. A broad spectrum with a single peak at ∼2.25 eV was observed. The spectrum obtained can be reproduced by a theory based on the macroscopic dielectric response of the tip-sample system, indicating that the observed emission arises from the localized plasmons on the silver tip excited by tunneling electrons. Spatial variations in the emission intensity at the atomic scale was observed even under low bias voltage (2 V) and low tunneling current (1 nA) conditions. 相似文献
3.
We have measured the coverage dependence of vibrational excitation spectra of C70 molecules adsorbed on a Si(1 1 1)-(7×7) surface using high-resolution electron-energy-loss spectroscopy. At the monolayer coverage, the intensity of the 57 meV peak increases, and those of the 83 and 178 meV peaks decrease. Taking into account the dipole selection rule, the change in intensity of the 57 meV peak indicates that the average angle between the long axes of C70 molecules and surface normal is about 40°. The decreases in intensities of the 83 and 178 meV peaks suggest that the rotational motion of molecules is quenched upon adsorption. We will discuss the Coriolis interaction between the accidentally degenerate A2″ and E1′ modes. 相似文献
4.
《Surface science》1990,227(3):L125-L129
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Geometric magnetic frustration in Ba(2)Sn(2)Ga(3)ZnCr(7)O(22): a two-dimensional spinel based Kagomé lattice 总被引:1,自引:0,他引:1
The properties of a two-dimensional geometrically frustrated magnetic material based on the Kagomé net, Ba(2)Sn(2)ZnGa(3)Cr(7)O(22), are reported. The Kagomé net is fully filled with magnetic ions. A Curie-Weiss theta theta(W) = -312 K is found with a spin glass transition at approximately 1.5 K, indicating strong geometrical magnetic frustration. This compound is the most two dimensional of a structural series with the geometrically frustrated materials ZnCr(2)O(4) and SrCr(8)Ga(4)O(19). The comparison of their properties tests the influence of different degrees of coupling between Kagomé layers on magnetic frustration within a single chemical and structural family. 相似文献
6.
《Surface science》1991,247(1):L221-L223
Using a scanning tunnelling microscope we have observed an interesting new fault on the Si(111)-7 × 7 surface, corresponding to an adatom registry shift of 1 bulk unit cell in the [1̄1̄2] direction. We propose a model to account for the structure along the fault. 相似文献
7.
《Nuclear Physics A》1988,487(2):420-432
8.
Z. Chvoj Z. Chromcová V. Cháb 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,76(3):453-461
In this article we investigate the complex 1D mesoscopic model of adatom diffusion and the evolution of an ordered phase on
the substrate surface. The analysis of the theoretical model is compared with the experimental results of the spreading of
Au
adatoms on Si(111)-(7×7) surface. The steady state solutions and their stability conditions are determined within the concept
of the traveling-wave solution. It is shown that the formation of the ordered
phase (5×2) and the difference in the diffusion of Au on (7×7) and on (5×2) structure results in a sharp edge of diffusion
front which corresponds to the coverage of a saturated
(5×2) phase. This edge moves linearly in time and α can be determined by experiment. The system of model equations enables
the damped waves solution or temporary evolution of two steps. 相似文献
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在核物理实验中,往往需要测知离子流的电量与离子流强度。比较简便的方法是用积分电路来测量电量,同时可指示离子流强度。本文所介绍的是一个实用的积分电路,其中包括直流放大,触发电路,计数电路及稳定电源等。离子流的强度由仪器上电流表指出,电量由机械记数器的数字来表示。 相似文献
11.
Heteroepitaxial growth of Ag on Si(111)-(7X7) surface at various conditions was experimentally studied by scanning tunneling microscopy. A growth model based on experiments was used for kinetic Monte Carlo (KMC) simulations. The simulations of nucleation and island growth at low coverage and fitting experimental data provided basic growth parameters. Further growth—formation of a discontinuous transition film (wetting layer)—was implemented into the basic model. The suggested growth mechanism was successfully tested using the KMC simulations. The choice of experiments, the role of minimizing processes and parameters in the model, and efficiency of the used approach is demonstrated and discussed. 相似文献
12.
本文基于有相互作用的结构件的概念,对Si(111)7×7结构模型的稳定性进行研究。利用紧束缚法,计算了各种结构件的形成能及其相互作用能。由这些结构件可灵活地构成各种大单胞的表面结构并对其进行总能计算,而避免了大工作量的计算。对Si(111)5×5和7×7DAS模型,我们得到其表面能分别为-0.467eV和-0.477eV,与Qian和Chadi的结果很接近。并指出,Harrison提出的7×7吸附原子模型和Binnig等人提出的7×7吸附原子-空位模型都是不稳定的。 相似文献
13.
《中国物理快报》2020,(2)
We investigate the adsorption of organic molecular semiconductor perylene on(7 × 7) reconstructed Si(111)surface by ultraviolet photoemission spectroscopy.It is observed that seven features that derive from the organic material are located at 0.71,2.24,4.0,5.9,7.46,8.65 and 9.95 eV in binding energy.The theoretical calculation results reveal the most stable adsorption geometry of organic molecule perylene on Si(111)(7 × 7) substrates is at the beginning of deposition. 相似文献
14.
《高压物理学报》1993,(4)
理论研究和数值模拟高加载率条件!:LY12铝合金损伤断裂现象的研究·············································…… .....................................·..·..·.……~·一“…王泽平黄风雷丁傲侠教铝、铜、铅压力熔化曲线的研究·············································……郑伟涛张瑞林Thomas一Fermi模峨的相对论修正·············································,····… 相似文献
15.
Makarewicz R 《The Journal of the Acoustical Society of America》2011,129(2):579-581
Measurements show that practically all noise of wind turbine noise is produced by turbine blades, sometimes a few tens of meters long, despite that the model of a point source located at the hub height is commonly used. The plane of rotating blades is the critical location of the receiver because the distances to the blades are the shortest. It is shown that such location requires certain condition to be met. The model is valid far away from the wind turbine as well. 相似文献
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《Surface science》1988,197(3):L269-L272
A two-dimensional Hubbard Hamiltonian is introduced in order to analyse the many-body effects associated with a dangling bond Si(111) 7×7 surface state located at the Fermi energy. Our results indicate that many-body effects can offer an explanation of recently reported experimental data. 相似文献
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In this paper, we calculate the branching ratios and the direct CP-violating asymmetries for decays B0 →a00(980)π0, a0+(980)π-, a0-(980)π and B- →a00(980)π-, a0-(980)π0 by employing the perturbative QCD (pQCD) factorization approach at the leading order. We found that (a) the pQCD predictions for the branching ratios are around (0.4 - 2.8) × 10-6, consistent with currently available experimental upper limits; (b) the CP asymmetries of B0→ao(980)π0 and B-→a0-(980)π0 decays can be large, about (70-80)% for α = 100°. 相似文献