Thermo-controllable self-assembled structures of single-layer 4,4'-diamino-p-terphenyl molecules on Au(110)

Here we report the thermo-controllable self-assembled structures of single-layer 4, 4'-diamino-p-terphenyl(DAT)molecules on Au(110), which are investigated by scanning tunneling microscopy(STM) combined with density functional theory(DFT) based calculations. With the deposition of monolayer DAT molecules on Au(110) and subsequent annealing at 100℃, all DAT molecules adsorb on a(1×5) reconstructed surface with a ladder-like structure. After annealing the sample at about 200℃, STM images show three distinct domains, including DAT molecules on a(1×3) reconstructed surface, dehydrogenated molecules with two hydrogen atoms detached from one amino group(–2H-DAT) on a(1×5)reconstructed surface and dehydrogenated molecules with four hydrogen atoms detached from two amino groups(–4HDAT) on a(1×3) reconstructed surface through N–Au bonds. Furthermore, after annealing the sample to 350℃, STM image shows only one self-assembled structure with –4H-DAT molecules on a(1×3) reconstructed surface. Relative STM simulations of different self-assembled structures show excellent agreements with the experimental STM images at different annealing temperatures. Further DFT calculations on the dehydrogenation process of DAT molecule prove that the dehydrogenation barrier on a(1×5) reconstructed surface is lower than that on(1×3) one, which demonstrate the experimental results that the formation temperature of a(1×3) reconstructed surface is higher than that of a(1×5) one.     

Streuung spinpolarisierter Elektronen an Au(110)

Using the the spin modulated polarized electron gun based on photoemission from positive affinity GaAs the intensityI(E, , ) and asymmetry (E, , ) are measured in LEED from Au(110). The asymmetry is compared with the polarizationS(E, , ) which N. Müller obtained with a Mott detector after scattering an unpolarized electron beam from the same crystal. There is excellent agreement for the (00) beams, if the scattering plane is a mirror symmetry plane of the crystal (=0°, =90°). From the differences for the (00) and (11) beams at =35° and the (01/2) beam at =90° conditions for possible models for the reconstructed Au(110)–(1×2) surface may be derived.

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Die vorliegende Arbeit ist ein Auszug aus [1]

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Neue Addresse ab 1. Oktober 1980: B. Reihl, IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598, USA     

Chemisorption of CO on Cu(100), Ag(110) and Au(110)

The adsorption of CO on Cu, Ag and Au is studied using core and valence photoemission, X-ray absorption and autoionization of core excited states. The purpose is to investigate the nature of the adsorption bond starting out from the well-established chemisorption system CO/Cu(100)-c(2 × 2), and from the results we suggest that CO forms chemisorbed phases also on Ag(110) and Au(110). The photoemission spectra show strong shake-up satellites both for the valence levels and the core levels. The separation to the satellite appearing closest to the main line is observed to follow the position of the substrate d-band relative to the Fermi level. The CO adsorption strength for the noble metals is deduced to decrease in the order Cu-Au-Ag. This is based on the widths of the XA resonances, which are related to the adsorbate-substrate interaction strength of the core excited states, and the relative shake-up intensities, which are expected to increase with a decreasing adsorption strength in the ground state. The same trends regarding the shake-up intensities are observed both for the valence and core levels.     

Interplay between external strain and oxygen vacancies on a rutile TiO2(110) Surface

Comprehensive first-principle calculations on strained rutile TiO2(110) indicate that the formation energy of different types of oxygen vacancies depends on the external strain. For the unstrained state, the energetically favorable oxygen vacancy (EFOV) appears on the bridging site of the first layer; when 3% tensile strain along [11[over ]0] is applied, EFOV moves to the in-plane site, while 2% compressive strain along either [001] or [11[over ]0] shifts EFOV to the subbridging site. We therefore suggest that the distribution of oxygen vacancies can be engineered by external strain, which may help to improve the applications of a TiO2 surface where oxygen vacancy plays an important role.     

Imaging covalent bonding between two NO molecules on Cu(110)

Using a scanning tunneling microscope, we found metastable upright NO on Cu(110) with the 2π* molecular resonance at the Fermi level. Upon heating above 40 K, it converts to a bent structure with the loss of molecular resonance. By manipulating the distance between two upright NO, we controlled the overlap between 2π* orbitals and observed its splitting below and above the Fermi level, thus visualizing the covalent interaction between them.     

Role of Au(+) in supporting and activating Au(7) on TiO(2)(110)

The adhesion properties and catalytic activity of rutile TiO(2)(110)-supported Au(7) nanoclusters in different oxidation states are investigated by means of density functional theory. The calculations cover both surface science conditions of reduced TiO(2) and real catalyst conditions of oxidized (alkaline) TiO(2) supports. Large adhesion energies of Au(7) are found only when modeling real catalysts where the cluster becomes cationic with Au(+) ions in Au-O or Au-OH bonds. The full catalytic cycle for oxidation of CO by O(2) over Au(7) on alkaline TiO(2)(110) is calculated and found to involve only small activation barriers. In the presence of the CO reductant, the Au(+) sites are capable of cycling between bonding of atomic and molecular oxygen. We confirm our findings by comparison of calculated and experimental infrared stretch frequency data for adsorbed CO.     

Interface properties and electronic structures of aromatic molecules with anhydride and thio-functional groups on Ag(111) and Au(111) substrates

First-principles calculations for several aromatic molecules with anhydride and thio groups on Ag(111) and Au(111)reveal that the self-assembly structures and the interface properties are mainly determined by the functional groups of aromatic molecules. Detailed investigations of the electronic structures show that the electrons in molecular backbone are redistributed and charge transfer occurs through the bond between the metal and the functional groups after these molecules have been deposited on a metal substrate. The interaction between Ag(111)(or Au(111)) and aromatic molecules with anhydride functional groups strengthens the π bonds in the molecular backbone, while that between Ag(111)(or Au(111))and aromatic molecules with sulfur weakens the π bonds. However, the intrinsic electronic structures of the molecules are mostly conserved. The large-sized aromatic backbone has less influence on the nature of electronic structures than the small-sized one, either at the interface or at the molecules. These results are useful to build the good metal–molecule contact in molecule-based devices.     

Relaxation and electronic states of Au(100), (110) and (111) surfaces

Using a first-principles method based on density functional theory, we investigate the surface relaxation and electronic states of Au(100), (110) and (111) surfaces. The calculated results show that the relaxations of the (100) and (110) surfaces of the metal are inward relaxations. However, the Au(111) surface shows an ‘anomalous’ outward relaxation, although several previous theoretical studies have predicted inward relaxations that are contrary to the experimental measurements. Electronic densities of states and the respective charge density distribution along the Z-axis of the relaxed surfaces are analyzed, and the origin of inward and outward relaxation is discussed in detail.     

Multilayer distortion in the reconstructed (110) surface of Au

A new LEED intensity analysis of the reconstructed Au(110)-(1×2) surface results in a modification of the missing row model with considerable distortions which are at least three layers deep. The top layer spacing is contracted by about 20%, the second layer exhibits a lateral pairing displacement of 0.07 Å and the third layer is buckled by 0.24 Å. Distortions in deeper layers seem to be probable but have not been considered in this analysis. The inter-atomic distances in the distorted surface region show both an expansion and a contraction compared to the bulk value and range from 5% contraction to about 4% expansion.     

(111) facets as the origin of reconstructed Au(110) surfaces

The Au(110) surface has been investigated by scanning tunneling microscopy. The reconstructed surface consists of long ribbons of narrow (111) facets along the [1$\text{1}$0] direction with maximum three free rows. Two-row facets give rise to the 1 × 2 reconstruction of the missing-row type, while three-row facets account for the 1 × 3 reconstruction. Disorder arises from locally random sequences of the two facets.     

Interplay between ordered growth and intermixing of Pt on patterned Au surfaces

We have investigated the growth of submonolayer coverage of platinum on two gold surfaces (Au(1 1 1) and Au(7 8 8)), at temperatures ranging from 110 K to 300 K. The Scanning Tunneling Microscope images reveal a competition between the ordered growth of nanodots and a random intermixing between Pt and Au. The Pt deposition on the Au(1 1 1) surface at room temperature shows an ordered growth limited by the insertion of Pt atoms into the surface layer and the subsequent modifications of the herringbone surface pattern. In contrast, for Pt on the Au(7 8 8) stepped surface, perfect ordered growth is observed over a wide temperature range.     

Calculation of electron-spin polarization in photoemission from Au(110)

We have calculated the spin polarization of electrons photoemitted by circularly polarized light from Au(110). Results for the spin polarization of the angular resolved photoyield are given for clean and contaminated surfaces for photon energies ?Ω up to 10 eV. In addition we calculated the spectrum for energy resolved photoelectrons for $\text{?Ω = 8.5 eV}$. Our calculations demonstrate that from an analysis of the spin polarization of energy resolved photoelectrons detailed information on the electronic structure of solids follows.