共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
4.
5.
原子尺度表面吸附Au原子的物理化学性质对研究纳米器件的制备以及表面催化等起着非常重要的作用.利用调频开尔文探针力显微镜研究了室温下Au在Si(111)-(7×7)表面吸附的电荷分布的特性.首先,利用自制超高真空开尔文探针力显微镜成功得到了原子尺度Au在Si(111)-(7×7)不同吸附位的表面形貌与局域接触电势差(LCPD);其次,通过原子间力谱与电势差分析了Au/Si(111)-(7×7)特定原子位置的原子特性,实现了原子识别;并通过结合差分电荷密度计算解释了Au/Si(111)-(7×7)表面间电荷转移与Au的吸附特性.结果显示,Au原子吸附有单原子和团簇形式.其中,Au团簇以6个原子为一组呈六边形结构吸附于Si(111)-(7×7)的层错半单胞内的3个中心原子位;单个Au原子吸附于非层错半单胞的中心顶戴原子位;同时通过电势差测量得知单个Au原子和Au团簇失去电子呈正电特性.表面差分电荷密度结果显示金在吸附过程中发生电荷转移,失去部分电荷,使得吸附原子位置上的功函数局部减少.在短程力、局域接触势能差和差分电荷密度发生变化的距离范围内,获得了理论和实验之间的合理一致性. 相似文献
6.
《Surface science》1990,227(3):L125-L129
7.
8.
I. Ošťádal P. Sobotík J. Mysliveček T. Jarolímek 《Czechoslovak Journal of Physics》1999,49(11):1613-1619
Initial stages of Ag on Si(111)−(7 × 7) surface nucleation were studied at submonolayer coverage. Samples were prepared by
thermal evaporation of Ag from tungsten wire under UHV conditions (p<2.5 × 10−8 Pa). Various deposition rates (0.002–0.1 ML s−1) were used to prepare Ag island films with coverages (0.002–2) ML (1 ML ≈ 7.58 × 1014 atoms cm−2) at room temperature. We observed preferential growth on faulted half unit cells (F cells). At constant coverage both the
island density and ratio of occupied F and U (unfaulted) cells are independent of the deposition rate, which is an evidence
for dominant influence of substrate structure. The preference of nucleation in the F cells against U cells decreases with
the coverage until the ratio is 1:1 for 1 ML Ag film. We have observed that presence of an Ag island in any type of the half
unit cell (F or U) considerably reduces nucleation probability in neighbouring cells. This results in forming of structural
patterns observed among randomly grown Ag-islands which is a new feature found for Ag/Si(111)−(7 × 7) system.
Presented at the VIII-th Symposium on Surface Physics, Třešt’ Castle, Czech Republic, June 28 – July 2, 1999.
This work was supported by the Grant Agency of Charles University — projects GAUK 34/97 and 147/99, by the Grant Agency of
Czech Republic — project GAČR 202/97/1109 and by the Ministry of Education grant VS 97116. 相似文献
9.
10.
为了较清楚地阐明扫描隧道显微镜针尖在样品表面原子操纵中的具体作用,根据第一性原理的离散变分理论计算,采用“团簇模型”研究了在无外加电场下,W针尖与样品Al(111)表面Al原子的相互作用.结果表明:随着W针尖与样品表面接近到一定程度(针尖与样品表面的距离S≤10a.u.(0.53nm))时,由于针尖原子与样品表面原子的相互作用,使位于针尖正下方的表面Al原子在脱离表面时感受到一稳定的势阱,即在无外场的情况下,当W针尖与样品Al(111)表面接近到一定程度时,由于针尖的吸引作用,将使针尖正下方的Al原子自动离开样品表面而移向W针尖,实现Al(111)表面单个Al原子的操纵.
关键词: 相似文献
11.
12.
《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
13.
14.
《Surface science》1995,341(3):L1085-L1090
Scanning tunneling microscopy was used to study the morphological evolution of Si(111)-7 × 7 exposed to molecular bromine. Etching at 900 K results in the removal of adatoms and conversion from the 7 × 7 surface to a 1 × 1 Br-terminated structure. Removal is dominated by bilayer step retreat with edge profiles that reflect etching anisotropies. Unique structures attributed to regrowth of Si released during step etching were consistent with six-membered Si rings terminated with Br. The distribution of such rings near the steps reflects the local bonding and etching anisotropies for the steps. Theoretical analyses of these rings terminated with Cl determine bond lengths, bond angles, and charge transfer within the ring. 相似文献
15.
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
16.
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
17.
18.
19.
《Surface science》1996,367(2):L47-L53
Scanning tunneling microscopy (STM) is used to study surface diffusion of a special type of point defects at Si(111)-7 × 7 surfaces. These defects survive even after annealing up to 1250°C. They appear darker than Si adatoms at the tunneling biases ranging from −3 to +3 V, but they are not true vacancies. We found that these vacancy-like defects (hereafter, we refer to them as pseudo-vacancies) are not caused by adsorption of major contaminants in the vacuum chamber, nor by dopants. We also observed migration of pseudo-vacancies between nearest neighboring Si adatom sites at temperatures above 500°C. Most of the jumps are within a half of the 7 × 7 unit cell. Thousands of STM images were recorded from 520 to 610°C and the activation energies and frequency factors were determined. Varying the tunneling current produces almost no effect on the diffusion, but varying the scanning speed produces a small effect. 相似文献