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1.
Anisotropic evolution of the step edges on the compressive-strained In0.2Ga0.8As/GaAs(001) surface has been investigated by scanning tunneling microscopy (STM). The experiments suggest that step edges are indeed sinuous and protrude somewhere a little way along the [110] direction, which is different from the classical waviness predicted by the theoretical model. We consider that the monatomic step edges undergo a morphological instability induced by the anisotropic diffusion of adatoms on the terrace during annealing, and we improve a kinetic model of step edge based on the classical Burton Cabrer-Frank (BCF) model in order to determine the normal velocity of step enlargement. The results show that the normal velocity is proportional to the arc length of the peninsula, which is consistent with the first result of our kinetic model. Additionally, a significant phenomenon is an excess elongation along the [110] direction at the top of the peninsula with a higher aspect ratio, which is attributed to the restriction of diffusion lengths. 相似文献
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The coverage and temperature-dependent nucleation behaviors of the Gd@C82 metallofullerenes on Cu(111) have been studied by low-temperature scanning tunneling microscopy (LT-STM) in detail. Upon molecular deposition at low temperature, Gd@C82 molecules preferentially decorate the steps and nucleate into single layer islands with increasing coverage. Further annealing treatment leads some of the Gd@C82 molecules to assemble into bright and dim patches, which are correlated to the adsorption induced substrate reconstruction. Upon sufficient thermal activation, Gd@C82 molecules sink into the Cu(111) surface one-copper-layer-deep, forming hexagonal close-packed molecular islands with intra-molecular details observed as striped patterns. By considering the commensurability between the Gd@C82 nearest-neighbor distance and the lattice of the underlying Cu(111), we clearly identified two kinds of in-plane molecular arrangements as (19(1/2)×19(1/2))R23.4°and (19(1/2)×19(1/2))R36.6°with respect to Cu(111). Within the assembled Gd@C82 molecular, island molecules with dim-bright contrast are spatially distributed, which may be modulated by the preexisted species on Cu(111). 相似文献
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Two Ge-induced incommensurate phases, γ and β, on Si(111) are observed and studied by {/it in situ} scanning tunneling microscopy. The γ phase consists of aligned triangular domains whose stacking sequence is faulted with respect to the Si(111)-1×1 surface. The β phase consists of two kinds of triangular domains whose stacking sequences are faulted and unfaulted with respect to the Si(111)-1×1 surface, respectively. In the β phase, two types of domain walls, zigzag'' and face-to-face'', form to release the strain. The triangular domains all exhibit a quasi-1×1 hexagonal close-packed structure. By studying the structural evolution from magic clusters to incommensurate structures, the structure models for γ and β phases are proposed. 相似文献
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《中国物理快报》2002,19(3):409-412
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Large-area self-assembly of rubrene has been fabricated on Au(111) surface and studied by scanning tunnelling microscopy. The rubrene monolayer on A u(111) surface is characterized by well-ordered row-like structures similar to the a-b plane of rubrene single crystal. However, the directions of the neighboured molecular rows are opposite to each other. In a two-layer film of rubrene on Au(111) surface, the arrangements of the top molecular rows are determined by the underneath rows, suggesting an orthorhombic crystal structure with a = 1.26 nm, b = 4.36 nm, c = 0.17nm for multilayer ofrubrene on Au(111). 相似文献
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Transformation behaviors,structural and magnetic characteristics of Ni-Mn-Ga films on MgO (001) 下载免费PDF全文
Ferromagnetic Ni-Mn-Ga films were fabricated by depositing on MgO (001) substrates at temperatures from 673 K to 923 K. Microstructure, crystal structure, martensitic transformation behavior, and magnetic properties of the films were studied. With increasing deposition temperature, the surface morphology of the films transforms from granular to continu- ous. The martensitic transformation temperature is not dependent on deposition temperature; while transformation behavior is affected substantially by deposition temperature. X-ray analysis reveals that the film deposited at 873 K has a 7M marten- site phase, and its magnetization curve provides a typical step-increase, indicating the occurrence of magnetically induced reorientation (MIR). In situ magnetic domain structure observation on the film deposited at 873 K reflects that the marten- sitic transformation could be divided into two periods: nucleation and growth, in the form of stripe domains. The MIR occurs at the temperature at which martensitic transformation starts, and the switching field increases with the decrease of temperature due to damped thermal activation. The magnetically induced martensitic transformation is related to the difference of magnetization between martensite and austenite. A shift of martensite temperature of dT/dH = 0.43 K/T is observed, consistent with the theoretical value, 0.41 K/T. 相似文献
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In order to predict the actual quantity of non-bulk GaAs layers after long-time homoepitaxy on GaAs (001) by theo- retical calculation, a half-terrace diffusion model based on thermodynamics is used to calculate the ripening time of GaAs layers to form a fiat morphology in annealing. To verify the accuracy of the calculation, real space scanning tunneling microscopy images of GaAs surface after different annealing times are obtained and the roughness of the GaAs surface is measured. The results suggest that the half terrace model is an accurate method with a relative error of about 4.1%. 相似文献
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During epitaxial growth of MnAs on GaAs(001) by molecular-beam epitaxy (MBE) the surface exhibits various reconstructions depending on the growth conditions. These reconstructions have been studied during growth by reflection high-energy electron diffraction (RHEED) and reflectance difference spectroscopy (RDS). A feature sensitive to the surface structure was identified in the RD spectra. After growth, the (1×2) and (1×1) reconstructions were cooled down to room temperature and imaged in ultrahigh vacuum with a conventional scanning tunneling microscope (STM). Atomic-scale images of these surfaces are presented. 相似文献
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用扫描隧道显微镜(STM)研究了室温下天冬氨酸在Cu(001)表面的吸附行为.实验发现,在较 低的覆盖度下,天冬氨酸分子在Cu(001)表面存在两种吸附状态.从STM数据估算出两种吸附 状态下天冬氨酸分子在Cu(001)表面的扩散激活能分别为079±001eV,088±005eV. 随着覆盖度的提高,天冬氨酸分子最终在Cu(001)表面形成一均匀衬度的吸附层,但并不形 成有序吸附结构,也不能使台阶发生小面化.天冬氨酸分子的这些吸附特点是迄今研究过的 所有氨基酸在Cu(001)表面吸附时不具有的.
关键词:
表面吸附
扫描隧道显微镜
氨基酸 相似文献
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Scanning tunnelling microscopy is utilized to investigate the local bias voltage tunnelling dependent transformation between (2×1) and c(4×2) structures on Ge(001) surfaces, which is reversibly observed at room temperature and a critical bias voltage of -0.80 V. Similar transformation is also found on an epitaxial Ce islands but at a slightly different critical bias voltage of -1.00V. It is found that the interaction between the topmost atoms on the STM tip and the atoms of the dimers, and the pinning effect induced by Sb atoms, the nacancies or the epitaxial clusters, can drive the structural transformation at the critical bias voltage. 相似文献
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利用Si(001)向[110]方向偏4°角的斜切表面作为衬底,成功地制备了分布均匀的单畴的单原子In链阵列.扫描隧道显微镜分析表明,沉积的In原子优先吸附在台面上沿着台阶内边缘的位置,并在两个Si的二聚体链之间形成稳定的In二聚体.In二聚体组成直的单原子链,其生长机理与Car提出的“表面聚合反应”相一致.另外,衬底具有非常窄的台面和双原子层台阶边的特殊结构是形成单畴的单原子链的关键.
关键词:
铟单原子链
硅邻近面
扫描隧道显微镜 相似文献
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Shibin Li Jiang Wu Zhiming Wang Zhenhua Li Yuanjie Su Zhiming Wu Yadong Jiang Gregory J. Salamo 《固体物理学:研究快报》2012,6(1):25-27
When a GaAs(001) substrate is heated up to 650 °C in a scanning electron microscope (SEM) vacuum chamber with vacuum range from 10–4 Torr to 10–5 Torr, real‐time SEM observation reveals microscale pits on GaAs substrate surface. The annealing process of GaAs substrate in vacuum causes excess evaporation of arsenic and accumulation of gallium as liquid droplets on the surface. As the function of electrochemical drills, the gallium droplets etch away GaAs beneath the surface to make microscale holes on GaAs substrate. With small amount of oxygen in the chamber acting as etching catalyst, gallium droplets etch GaAs much faster than in ultra‐high vacuum (UHV) MBE chamber. This process provides an easy technique to fabricate microscale pits on GaAs(001) surface.
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Barbara Pieczyrak Leszek Jurczyszyn Barbara Stankiewicz 《Czechoslovak Journal of Physics》2006,56(1):85-92
We present theoretical study of structural and electronic properties of SiC(001)-p(2 × 1)-Si-terminated surface and the formation
of its STM images. Ab initio calculations independently performed with the use of plane-wave and local-orbital basis have shown that the structure of
this surface is built up by long symmetric silicon dimers, which agrees with the results of previous ab initio studies done by other authors. STM simulations show that the variation of the tunneling current along substrate surface very
well reproduces the localization properties of occupied and unoccupied surface states (π, π*). We have found that the tensile
stress applied along dimers axis causes the buckling of surface dimers and transfer of the charge between dimers atoms. This
result suggests that the buckling of silicon surface dimers observed in LEED measurements might be caused by external stress.
Presented at the X-th Symposium on Suface Physics, Prague, Czech Republic, July 11–15, 2005. 相似文献
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We study the concentration of adatoms on GaAs(001) during annealing under MBE conditions. By rapidly cooling the sample from typical growth temperatures and typical As overpressures, the thermal concentration of adatoms can be frozen into small islands on the terraces. The area of the resulting islands is measured with STM far from terrace steps, giving an estimate of the concentration of adatoms during equilibrium. We find that a surprisingly large concentration of adatoms is present for typical growth temperatures, e.g. 0.18 monolayer at 600°C. Possible consequences for current growth models are discussed. 相似文献
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Gd islands were grown on W(1 1 0) surface by evaporating Gd on the substrate at room temperature and subsequent annealing. STM images reveal in many cases islands which have a deep hole inside them. The appearance of the hole is associated with the application of an AC field. No such holes appear when the sample is heated by a DC current. We show that this can be explained by the combined affect of the AC field and the barrier to diffusion introduced by steps that can create a nucleus for further growth of an island which includes a hole in the middle. This may be generalized to a technique of tailoring the size, shape and distances of islands by, for example, two orthogonal AC fields with a phase delay of 90° between them. 相似文献
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We report on temperature-programmed growth of graphene islands on Ru(0001) at annealing temperatures of 700°C,800°C,and 900°C.The sizes of the islands each show a nonlinear increase with the annealing temperature.In 700°C and 800°C annealings,the islands have nearly the same sizes and their ascending edges are embedded in the upper steps of the ruthenium substrate,which is in accordance with the etching growth mode.In 900°C annealing,the islands are much larger and of lower quality,which represents the early stage of Smoluchowski ripening.A longer time annealing at 900°C brings the islands to final equilibrium with an ordered moir’e pattern.Our work provides new details about graphene early growth stages that could facilitate the better control of such a growth to obtain graphene with ideal size and high quality. 相似文献