共查询到20条相似文献,搜索用时 15 毫秒
1.
《Applied Surface Science》1987,28(3):279-290
A Au(334) surface cleaned and annealed under ultra-high vacuum conditions was examined in air using a scanning tunneling microscope. The STM images reveal a smooth surface with a plateau structure. On top of the plateaus parallel rows of monatomic height steps can be observed. Annealing this surface in air to around 600 ° C results in segregation of impurities that form surface oxides. STM examination of this air annealed surface shows a structure where the plateaus have developed into large (111) facets. These facets are atomically smooth except for some steps near the edges. Au(111) films on mica, examined in air, were found to be atomically smooth over thousands of ångströms, with the surface having occasional monatomic height steps. Several transient effects encountered in STM imaging in air are discussed. 相似文献
2.
Shi-xuan Du Ye-liang Wang Qi Liu Hai-gang Zhang Hai-ming Guo Hong-jun Gao 《Frontiers of Physics in China》2010,5(4):380-386
The motion of single molecules on surfaces plays an important role in nanoscale engineering and bottom-up construction of
complex devices at single molecular scale. In this article, we review the recent progress on single molecular rotors self-assembled
on Au(111) surfaces. We focus on the motion of single phthalocyanine molecules on the reconstructed Au(111) surface based
on the most recent results obtained by scanning tunneling microscopy (STM). An ordered array of single molecular rotors with
large scale is self-assembled on Au(111) surface. Combined with first principle calculations, the mechanism of the surface-supported
molecular rotor is investigated. Based on these results, phthalocyanine molecules on Au (111) are a promising candidate system
for the development of adaptive molecular device structures. 相似文献
3.
The morphology of a Au(111) surface has been observed with the STM (scanning tunneling microscope) after ion bombardment with 2.5 keV Ne+ ions at about 400 K. Mostly triangular and hexagonal shaped vacancy islands are seen in the STM topographs. They are bounded by monatomic steps, oriented along the closed packed 110 directions. The general morphology confirms the conclusions inferred from TEAS (thermal energy atom scattering) measurements on ion bombarded Pt(111) surfaces. The observation of a propensity for the formation of {100} microfacetted 110 ledges is discussed. 相似文献
4.
F. Maroun S. Morin A. Lachenwitzer O. M. Magnussen R. J. Behm 《Surface science》2000,460(1-3):249-263
Based on time-dependent in situ scanning tunneling microscopy (STM) studies, we demonstrate that for Ni on Ag(111) and Ru on Au(111), electrochemical metal-on-metal deposition can result in pronounced substrate surface restructuring. For Ni/Ag(111), we observe that at low deposition flux and low coverage, Ni submonolayer islands at steps are partly embedded in the Ag terraces, whereas at higher deposition flux and higher coverage, substrate restructuring results in the formation of monolayer bays in the Ag terraces. We suggest that this restructuring process proceeds predominantly via step edge diffusion of Ag atoms. For Ru/Au(111), the formation of fjords and monolayer holes in the Au terraces is observed at low and high Ru coverage, respectively. The importance of the Au surface mobility for the restructuring process is demonstrated by comparing experiments in H2SO4 and HCl solutions, in which Au exhibits strongly different surface mobilities. For this system, restructuring involves Au diffusion along Au steps, Au atom detachment from the Au steps, and upward exchange diffusion. According to these observations and their comparison with similar findings for vacuum deposition, we conclude that this restructuring requires (i) a high substrate surface mobility and (ii) a stronger bonding of substrate atoms to deposit islands than to the substrate. 相似文献
5.
Using a low temperature, ultrahigh vacuum scanning tunneling microscope (STM), dI/dV differential conductance maps were recorded at the tunneling resonance energies for a single Cu phthalocyanine molecule adsorbed on an Au(111) surface. We demonstrated that, contrary to the common assumption, such maps are not representative of the molecular orbital spatial expansion, but rather result from their complex superposition captured by the STM tip apex with a superposition weight which generally does not correspond to the native weight used in the standard Slater determinant basis set. Changes in the molecule conformation on the Au(111) surface further obscure the identification between dI/dV conductance maps and the native molecular orbital electronic probability distribution in space. 相似文献
6.
7.
Barbier A Mocuta C Kuhlenbeck H Peters KF Richter B Renaud G 《Physical review letters》2000,84(13):2897-2900
Using grazing-incidence x-ray diffraction, the p(2x2) surface structures of the single crystal NiO(111) and a 5 monolayer thick NiO(111) film on Au(111) were both shown to exhibit locally the theoretically predicted octopolar reconstruction, with some important differences. The single crystal exhibits a single Ni termination with double steps. The thin film exhibits both possible terminations (O and Ni) and single steps. These surfaces were found to be nonreactive with respect to hydroxylation. 相似文献
8.
Benjamin Fiedler Elena Rojo-Wiechel Johann Klassen Julia Simon Johannes Beck Moritz Sokolowski 《Surface science》2012,606(23-24):1855-1863
We report experiments by low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) on ordered structures of two sulfur-containing π-conjugated molecules on the Au(111)-surface, namely tetrabenzothianthrene (TBTA) and tetrathiotetracene (TTT). These molecules are candidates for donors in charge transfer salts. On Au(111) both molecules form long-range ordered structures that are commensurate to the top-most surface layer. For TBTA, the reconstruction of the Au(111) surface is maintained, whereas it is lifted by TTT. Both molecules lie flat on the surface. For TBTA, the structure indicates that the molecule is planarized upon adsorption. 相似文献
9.
T. Irawan D. Boecker F. Ghaleh C. Yin B. Von Issendorff H. Hövel 《Applied Physics A: Materials Science & Processing》2006,82(1):81-86
Gold and lead clusters were grown by the evaporation of metal atoms on rare gas layers on Au(111) and Pb(111). The growth was investigated with scanning tunneling microscopy (STM) and ultraviolet photoelectron spectroscopy (UPS). We studied the electronic coupling to the surface and charging effects in the photoemission process. For a rare gas film thickness of 60 ML we observed an electronic decoupling: the cluster spectra are no longer referenced to the Fermi edge, but to the vacuum energy of the substrate. For Pb clusters on a Au(111) substrate this leads to the remarkable result of a cluster-photoelectron signal above the Fermi energy defined by the ground level of the sample holder. PACS 33.60.Cv; 36.40.Mr; 68.37.Ef; 61.46.+w; 73.22.-f 相似文献
10.
The structure formation upon spinodal decomposition of a two-dimensional model system, a Au adatom gas on a Au(111) surface, was observed in situ by scanning tunneling microscopy (STM). A thermodynamically unstable state was prepared by applying microsecond voltage pulses to the STM tip in an electrochemical system, causing the random dissolution of Au atoms from the uppermost monolayer. Interconnected, labyrinthine island patterns were formed at Au coverages between 0.4 and 0.9 monolayer with dominating length scales lambda(m) of the order of a few nanometers. 相似文献
11.
Microscopic evidence for Au-adatom-induced self-assembly of alkanethiolate species on the Au(111) surface is presented. Based on STM measurements and density-functional theory calculations, a new model for the low-coverage self-assembled monolayer of alkanethiolate on the Au(111) surface is developed, which involves the adsorbate complexes incorporating Au adatoms. It is also concluded that the Au(111) herringbone reconstruction is lifted by the alkanethiolate self-assembly because the reconstructed surface layer provides reactive Au adatoms that drive self-assembly. 相似文献
12.
Observations of clean Si(111) and gold-deposited Si(111) surfaces have been performed using micro-probe reflection high-energy electron diffraction. It was found that many atomic steps on a Si(111) surface run in nearly the same direction, about 9° off the [1̄1̄2] direction. When gold was deposited on this surface at a substrate temperature of about 800°C, 5 × 1, diffuse √3 × √3R30°, sharp √3 × √3 R30° structures and Au clusters appeared on the surface with continuation of the deposition. During the deposition process, it was found that one kind of Si(111) 5 × 1 Au domain grew selectively along these atomic steps and nearly covered the entire surface. A phenomenon of gold clusters moving during the deposition was also observed. These clusters all moved in nearly the same direction so as to climb the atomic steps. 相似文献
13.
Molecular dynamics simulations with a classical many-body potential are used to study the high-temperature stability of stepped non-melting metal surfaces. We have studied in particular the Au(111) vicinal surfaces in the (M + 1,M− 1,M) family and the Au(100) vicinals in the (M,1,1) family. Some vicinal orientations close to the non-melting Au(111) surface become unstable close to the bulk melting temperature and facet into a mixture of crystalline (111) regions and localized surface-melted regions. On the contrary, we do not find high-temperature faceting for vicinals close to Au(100), also a non-melting surface. These (100) vicinal surfaces gradually disorder with disappearance of individual steps well below the bulk melting temperature. We have also studied the high-temperature stability of ledges formed by pairs of monatomic steps of opposite sign on the Au(111) surface. It is found that these ledges attract each other, so that several of them merge into one larger ledge, whose edge steps then act as a nucleation site for surface melting. 相似文献
14.
Giordano L Pacchioni G Goniakowski J Nilius N Rienks ED Freund HJ 《Physical review letters》2008,101(2):026102
We present a combined experimental (STM/scanning tunneling spectroscopy) and theoretical (density functional theory) study on the deposition of Au and Pd metal atoms on FeO/Pt(111) ultrathin films. We show that while the Pd atoms are only slightly oxidized, the Au atoms form positive ions upon deposition, at variance to a charge transfer into the Au atoms as observed for MgO/Ag(100). The modulation of the adsorption properties within the surface Moiré cell and the charging induce the formation a self-assembled array of gold adatoms on FeO/Pt(111), whereas Pd atoms are randomly distributed. 相似文献
15.
Using scanning tunneling microscopy/spectroscopy (STM/STS), angle resolved photoemission spectroscopy (ARPES) and first-principles density functional theory (DFT), we study the structural and the electronic properties of the Si(111)5 × 2-Au surface decorated with Pb adatoms. The STM topography data reveal that Pb adatoms form a similar superstructure to that observed in the case of Si adatoms on a bare Si(111)5 × 2-Au surface. The DFT calculations show that preferential adsorption sites of Pb atoms are located near the double Au chain. Bias dependent STM topography and spectroscopy together with the DFT calculations allow us to distinguish Pb from Si adatoms. Both the Si and Pb adatoms modify the electronic properties in the same way, which confirms the electronic origin of the stabilization of the surface. 相似文献
16.
Three different methods are used to manipulate and control
phthalocyanine based single molecular rotors on Au (111)
surface: (1) changing the molecular structure to alter the
rotation potential; (2) using the tunnelling current of the scanning
tunnelling microscope (STM) to change the thermal equilibrium of the
molecular rotor; (3) artificial manipulation of the molecular rotor
to switch the rotation on or off by an STM tip. Furthermore, a
molecular `gear wheel' is successfully achieved with two
neighbouring molecules. 相似文献
17.
Tip-enhanced Raman spectroscopy (TERS) is based on the optical excitation of localized surface plasmons in the tip-substrate cavity, which provides a large but local field enhancement near the tip apex. We report on TERS with smooth single crystalline surfaces as substrates. The adsorbates were CN- ions at Au(111) and malachite green isothiocyanate (MGITC) molecules at Au(111) and Pt(110) using either Au or Ir tips. The data analysis yields Raman enhancements of about 4 x 10(5) for CN- and up to 10(6) for MGITC at Au(111) with a Au tip, probing an area of less than 100 nm radius. 相似文献
18.
用扫描隧道显微镜在Cu(111)-Au和Pt(111)-Ag表面上对局域功函数进行了测量.在扫描的同时通过测量隧道电流对针尖样品间距离变化的响应,可以在得到扫描隧道显微镜(STM)图的同时得到功函数图.用这种方法,成功地观察到Au,Ag覆盖层与Cu,Pt衬底间的功函数的差别.结果表明:Au覆盖层的功函数介于Cu(111)和Au(111)的功函数之间,这与其它方法的结果一致.在Pt(111)-Ag表面观察到了局域功函数随覆盖层厚度的变化.本工作表明:扫描隧道显微镜在研究功函数与表面结构的关系方面是十分有用的;用测量局域功函数的方法还可以区分表面不同种的物质
关键词: 相似文献
19.
R. D. Fedorovich V. B. Nechytaylo L. V. Viduta A. A. Marchenko A. G. Naumovets 《光谱学快报》2013,46(6):372-377
Fourier transform infrared (FTIR) spectroscopy and scanning tunneling microscopy (STM) were used to study the molecular organization and morphology of vacuum-deposited tetracene layers. FTIR and optical measurements confirm that tetracene molecules are not dissociated during vacuum thermal deposition. With STM imaging, a highly ordered, closely packed, lamella-like structure of tetracene monolayer film on the Au(111) surface was observed. Electroluminescence from the nanocomposite consisting of Au nanoparticles and tetracene film is concentrated within submicron luminescent centers and occurs at voltages of 4–5 V in a superlinear section of conduction current–voltage curves. The results can be useful for the design of planar light-emitting devices. 相似文献