scholarly journals Formation of Au-Silane Bonds

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Shira Yochelis ◽  
Eran Katzir ◽  
Yoav Kalcheim ◽  
Vitaly Gutkin ◽  
Oded Millo ◽  
...  
Keyword(s):  
Molecular Electronics ◽  
Self Assembly ◽  
Au Nanoparticles ◽  
Electrical Coupling ◽  
Gold Surface ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Fundamental Study ◽  
Covalent Bonds ◽  
Anchoring Groups

Many intriguing aspects of molecular electronics are attributed to organic-inorganic interactions, yet charge transfer through such junctions still requires fundamental study. Recently, there is a growing interest in anchoring groups, which considered dominating the charge transport. With this respect, we choose to investigate self-assembly of disilane molecules sandwiched between gold surface and gold nanoparticles. These assemblies are found to exhibit covalent bonds not only between the anchoring Si groups and the gold surfaces but also in plane crosslinks that increase the monolayer stability. Finally, using scanning tunneling spectroscopy we demonstrate that the disilane molecules provide strong electrical coupling between the Au nanoparticles and a superconductor substrate.

scholarly journals Au(100) as a Template for Pentacene Monolayer

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2393
Author(s):  
Artur Trembułowicz ◽  
Agata Sabik ◽  
Miłosz Grodzicki
Keyword(s):  
Self Assembly ◽  
Molecular Layer ◽  
High Vacuum ◽  
Gold Surface ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Height Difference ◽  
Characteristic Features ◽  
Reconstructed Surface

The surface of quasi-hexagonal reconstructed Au(100) is used as the template for monolayer pentacene (PEN) self-assembly. The system is characterized by means of scanning tunneling microscopy at room temperature and under an ultra-high vacuum. A new modulated pattern of molecules with long molecular axes (MA) arranged along hex stripes is found. The characteristic features of the hex reconstruction are preserved herein. The assembly with MA across the hex rows leads to an unmodulated structure, where the molecular layer does not recreate the buckled hex phase. The presence of the molecules partly lifts the reconstruction—i.e., the gold hex phase is transformed into a (1×1) phase. The arrangement of PEN on the gold (1×1) structure is the same as that of the surrounding molecular domain on the reconstructed surface. The apparent height difference between phases allows for the distinction of the state of the underlying gold surface.

scholarly journals Exploring the Adsorption Mechanism of Tetracene on Ag(110) by STM and Dispersion-Corrected DFT

Crystals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 13 ◽  
Author(s):  
Zhaofeng Liang ◽  
Qiwei Tian ◽  
Huan Zhang ◽  
Jinping Hu ◽  
Pimo He ◽  
...  
Keyword(s):  
Molecular Electronics ◽  
Self Assembly ◽  
Density Functional ◽  
Scanning Tunneling ◽  
Dispersion Force ◽  
Tunneling Microscopy ◽  
Functional Theory ◽  
Silver Substrate ◽  
The Difference ◽  
Low Dimensional

Self-assembled strategy has been proven to be a promising vista in constructing organized low-dimensional nanostructures with molecular precision and versatile functionalities on solid surfaces. Herein, we investigate by a combination of scanning tunneling microscopy (STM) and dispersion-corrected density functional theory (DFT), the adsorption of tetracene molecules on the silver substrate and the mechanism mediating the self-assembly on Ag(110). As expected, ordered domain is formed on Ag(110) after adsorption with adjacent molecules being imaged with alternating bright or dim pattern regularly. While such behavior has been assigned previously to the difference of molecular adsorption height, herein, it is possible to investigate essentially the mechanism leading to the periodic alternation of brightness and dimness for tetracene adsorbed on Ag(110) thanks to the consideration of Van der Waals (vdW) dispersion force. It is demonstrated that the adsorption height in fact is same for both bright and dim molecules, while the adsorption site and the corresponding interfacial charge transfer play an important role in the formation of such pattern. Our report reveals that vdW dispersion interaction is crucial to appropriately describe the adsorption of tetracene on the silver substrate, and the formation of delicate molecular architectures on metal surfaces might also offers a promising approach towards molecular electronics.

CURRENT–VOLTAGE PROPERTIES OF SELF-ASSEMBLY MONOLAYERS ON AU(111) SUBSTRATE USING SCANNING TUNNELING MICROSCOPY

2006 ◽  
Vol 05 (06) ◽  
pp. 907-911
Author(s):  
NAM-SUK LEE ◽  
HOON-KYU SHIN ◽  
YOUNG-SOO KWON
Keyword(s):  
Thin Film ◽  
Electrical Properties ◽  
Scanning Tunneling Microscopy ◽  
Self Assembly ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Organic Thin Film ◽  
Tunneling Microscopy ◽  
Current Voltage ◽  
Self Assembled

This study observes the morphology of self-assembled organic thin film that is formed at room temperature using a Scanning Tunneling Microscopy (STM) and examines its electrical properties using a Scanning Tunneling Spectroscopy (STS). The specimen used in this experiment that has a functional group for both sides and will be controlled to make self-assembled onto the Au (111) substrate. After the dilution of the specimen by 1 mM/ml and self-assembled onto the Au (111) substrate. Using a STM, the images of organic thin film can be observed. In addition, the electrical properties of organic thin film can also be examined by the junction structure of STM–organic thin film– Au (111) substrate by using a STM tip. As a result, we measured current–voltage (I–V) curve using STS, I–V curve also clearly shows several current peaks between the negative bias region (-1.42 V) and the positive bias region (1.30 V), respectively.

Scanning Tunneling Microscopy Imaging and Spectroscopy of a Single Viologen Molecule

2008 ◽  
Vol 8 (9) ◽  
pp. 4621-4625
Author(s):  
Nam-Suk Lee ◽  
Chang-Heon Yang ◽  
Won-Suk Choi ◽  
Young-Soo Kwon
Keyword(s):  
Self Assembly ◽  
Current Mode ◽  
Scanning Tunneling Spectroscopy ◽  
Constant Current ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Microscopy Imaging ◽  
Current Voltage ◽  
Imaging And Spectroscopy ◽  
Stm Images

A low-temperature ultrahigh-vacuum scanning tunneling microscope (UHV-STM) was used to image viologen (N-methyl-N′-di (8-mercaptooctyl)-4,4′-bipyridinium; HSC8VC8SH) molecules and to perform local spectroscopic measurements on these molecules. Self-assembly of viologen molecules was conducted on Au (111), which had been thermally deposited onto freshly cleaved, heated mica. Here, we demonstrate a novel SAM matrix appropriate for the isolation of viologen molecules composed of octanethiol (C8) in which HSC8VC8SH was inserted at defects in the molecular lattice. The isolated single molecules of viologen inserted in the SAM matrix were observed as protrusions in STM topography using a constant current mode. STM images at 298 K showed protrusions with a topographic height of about 2.71 nm (HSC8VC8SH) with viologen molecules that self-assembled on the substrate. The current–voltage (I–V) characteristics were measured while the electrical properties of the formed monolayer were scanned using scanning tunneling spectroscopy (STS). We found the high peak current-like rectification at +1.14 V (HSC8VC8SH). The rectification ratios, RR = J (at +2.5 V)/J (at −2.5 V), are in the range of 4.47.

Preparation, Characterization, and Electrical Properties of a Self-Assembled meso-Pyridyl Porphyrin Monolayer on Gold Surfaces

2005 ◽  
Vol 58 (11) ◽  
pp. 810 ◽  
Author(s):  
Amarchand Sathyapalan ◽  
Anup Lohani ◽  
Sangita Santra ◽  
Saurabh Goyal ◽  
M. Ravikanth ◽  
...  
Keyword(s):  
Soret Band ◽  
Gold Surface ◽  
Scanning Tunneling Spectroscopy ◽  
Uv Absorption ◽  
Self Assembled Monolayers ◽  
Scanning Tunneling ◽  
Force Microscopy ◽  
Gold Substrates ◽  
Assembled Monolayers ◽  
Self Assembled

A meso-pyridyl porphyrin, 5-(4-(2-(4-(S-acetylthiomethyl)phenyl)ethynyl)phenyl)-10,15,20-tris(4-pyridyl) porphyrin was synthesized by coupling of 5-{4-ethynyl}phenyl-10,15,20-tris(4-pyridyl) porphyrin with 4-(S-acetylthiomethyl)-4-iodobenzene under mild palladium coupling conditions. The meso-pyridyl porphyrin was used for the preparation of self assembled monolayers on gold substrates. The gold substrates were made by the thermal evaporation of gold on oxidized Si(100) surfaces. The self-assembled monolayers (SAMs) were characterized using ground state UV absorption and X-ray photoelectron spectroscopic (XPS) techniques and also by scanning probe microscopy (SPM) techniques. The UV-absorption spectra of the porphyrin monolayer exhibited a 10 nm red shift in the Soret band compared to the porphyrin in CHCl3 solution. This indicates that the porphyrin molecules are aligned on the gold substrate in a side-by-side orientation. The typical shifts in the binding energy by XPS revealed that the chemisorption of the thiolate species of the porphyrin to the surface occurs through a strong sulfur–gold bonding mechanism. Basic hexagonal (√3×√3) R 30° well ordered self-assembled monolayers of meso-pyridyl porphyrin was observed by molecular-resolution atomic force microscopy (AFM). Room temperature current–voltage (I–V) spectra by scanning tunneling spectroscopy (STS) at varying set point current were collected to study the electronic transport properties of the monolayers on the gold surface.

scholarly journals Adsorption and self-assembly of porphyrins on ultrathin CoO films on Ir(100)

2020 ◽  
Vol 11 ◽  
pp. 1516-1524
Author(s):  
Feifei Xiang ◽  
Tobias Schmitt ◽  
Marco Raschmann ◽  
M Alexander Schneider
Keyword(s):  
Cobalt Oxide ◽  
Self Assembly ◽  
Density Functional ◽  
Oxide Films ◽  
Scanning Tunneling ◽  
Functional Surface ◽  
Tunneling Microscopy ◽  
Surface Anchoring ◽  
Self Assembled ◽  
Anchoring Groups

Porphyrins represent a versatile class of molecules, the adsorption behavior of which on solid surfaces is of fundamental interest due to a variety of potential applications. We investigate here the molecule–molecule and molecule–substrate interaction of Co-5,15-diphenylporphyrin (Co-DPP) and 2H-tetrakis(p-cyanophenyl)porphyrin (2H-TCNP) on one bilayer (1BL) and two bilayer (2BL) thick cobalt oxide films on Ir(100) by scanning tunneling microscopy (STM) and density functional theory (DFT). The two substrates differ greatly with respect to their structural and potential-energy landscape corrugation with immediate consequences for adsorption and self-assembly of the molecules studied. On both films, an effective electronic decoupling from the metal substrate is achieved. However, on the 1BL film, Co-DPP molecules are sufficiently mobile at 300 K and coalesce to self-assembled molecular islands when cooled to 80 K despite their rather weak intermolecular interaction. In contrast, on the 2BL film, due to the rather flat potential landscape, molecular rotation is thermally activated, which effectively prevents self-assembly. The situation is different for 2H-TCNPP, which, due to the additional functional anchoring groups, does not self-assemble on the 1BL film but forms self-assembled compact islands on the 2BL film. The findings demonstrate the guiding effect of the cobalt oxide films of different thickness and the effect of functional surface anchoring.

TWO-DIMENSIONAL SELF-ASSEMBLY OF SUPRAMOLECULAR STRUCTURES

2000 ◽  
Vol 07 (05n06) ◽  
pp. 661-666 ◽  
Author(s):  
MATTHIAS BÖHRINGER ◽  
WOLF-DIETER SCHNEIDER ◽  
RICHARD BERNDT
Keyword(s):  
Self Assembly ◽  
Electrostatic Interactions ◽  
Gold Surface ◽  
Two Dimensions ◽  
Molecular Structures ◽  
The Self ◽  
Scanning Tunneling ◽  
Two Dimensional ◽  
Tunneling Microscopy ◽  
Chiral Phase

We briefly review recent low temperature scanning tunneling microscopy (STM) investigations performed in our laboratory1–5 on the self-assembly of the dipolar organic molecule 1-nitronaphthalene (NN) adsorbed on the reconstructed Au(111) surface. NN becomes chiral upon planar adsorption on the gold surface. We observe several coverage-driven structural transformations which are associated with simultaneous changes in the enantiomeric composition of the self-assembled molecular structures. At low coverages almost exclusively decamers with an 8:2 ratio of the enantiomers are formed. In a medium coverage range enantiopure one-dimensional molecular double chains prevail on the surface. Subsequently, molecules with opposite handedness are admixed until at monolayer coverage racemic one- and two-dimensional structures coexist. Modeling shows that hydrogen bonding causes the observed self-assembly. A subtle interplay between the electrostatic interactions among the molecules and their interaction with the reconstructed metal surface is the origin of the observed coverage-driven chiral phase transition in two dimensions.

scholarly journals Extended iron phthalocyanine islands self-assembled on a Ge(001):H surface

2021 ◽  
Vol 12 ◽  
pp. 232-241
Author(s):  
Rafal Zuzak ◽  
Marek Szymonski ◽  
Szymon Godlewski
Keyword(s):  
Detailed Analysis ◽  
Self Assembly ◽  
Surface Defects ◽  
Scanning Tunneling Spectroscopy ◽  
Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Iron Phthalocyanine ◽  
Germanium Surface ◽  
Self Assembled

Self-assembly of iron(II) phthalocyanine (FePc) molecules on a Ge(001):H surface results in monolayer islands extending over hundreds of nanometers and comprising upright-oriented entities. Scanning tunneling spectroscopy reveals a transport gap of 2.70 eV in agreement with other reports regarding isolated FePc molecules. Detailed analysis of single FePc molecules trapped at surface defects indicates that the molecules stay intact upon adsorption and can be manipulated away from surface defects onto a perfectly hydrogenated surface. This allows for their isolation from the germanium surface.

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