Recording the intramolecular deformation of a 4-legs molecule during its STM manipulation on a Cu(211) surface (original) (raw)
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Selective internal manipulation of a single molecule by scanning tunneling microscopy
We have studied the adsorption of the polyaromatic molecule 1,4Љ-paratriphenyldimethylacetone, which we have nicknamed Trima. The originality of this linear molecule is that it was designed and synthesized to have two functionalities. First, chemisorb itself to the surface by its two ends rather like a bridge. Second, the central part of the molecule could then be rotated by injecting electrons with the tip of the scanning tunneling microscope ͑STM͒. The length of the molecule corresponds exactly to the spacing between five dimers in a row on the Si͑100͒-2 ϫ 1 surface. We found that the molecule adsorbs as expected on the clean silicon surface by using complementary STM and synchrotron radiation studies. Manipulation of individual molecules with the STM tip showed selective internal modifications that were highly voltage dependent. These manipulations were found to be compatible with an electronic excitation of the -* transition of the molecule.
Conformations and controlled manipulation of a long molecular wire on Cu(111)
Surface Science, 2005
Low temperature scanning tunnelling microscopy is employed to investigate in detail the conformations of single Violet Lander molecules (C 108 H 104 ) on Cu(1 1 1). The molecule consists of a long polyaromatic molecular board supported by four spacer legs. Several conformations, corresponding to different positions of the legs, are observed and characterised, showing that a much larger variety of conformations is possible compared with the other molecules of the Lander family. This is due to the longer central board and the consequently larger distance between the legs. Moreover, tip-induced conformational changes and molecular displacement are achieved in manipulation experiments.
Single Molecules, 2000
With the scanning tunneling microscope (STM) it became possible to perform controlled manipulations down to the scale of small molecules and single atoms, leading to the fascinating aspect of creating manmade structures on atomic scale. Here we present a short review of our work in the last five years on atomic scale manipulation investigations. Upon soft lateral manipulation of adsorbed species, in which only tip/particle forces are used, three different manipulation modes (pushing, pulling, sliding) can be discerned. We show that also manipulation of highly coordinated native substrate atoms is possible and demonstrate the application of these techniques as local analytic and synthetic chemistry tools with important consequences on surface structure research. Vertical manipulation of Xe and CO is presented, leading to improved imaging and even chemical contrast with deliberately functionalized tips. For the transfer of CO it is shown that beside tip voltage current effects play also an important role. This is also the case for the dissociation of molecules. With CO transferred deliberately to the tip we have also succeeded to perform vibrational spectroscopy on single molecules. Furthermore, first experiments aiming for the transfer of all manipulation modes to thin insulating films are described.
Controlled manipulation of a single molecular wire along a copper atomic nanostructure
Different stable conformations of a molecular wire along a short copper nanostructure are studied by means of low temperature scanning tunneling microscopy ͑STM͒ and controlled manipulations, with the aim of investigating the electronic contact of a single molecule to a metallic pad. The molecular wire is the so-called Lander molecule, a conjugated wire group supported by four legs. Independent of its position along the copper nanostructure, the central molecular wire is always in electronic interaction with the atomic wire underneath. This effect becomes visible in the STM images depending on the orientation of the legs. By STM manipulation, the molecular wire can be precisely positioned in an electronic contact conformation at the end of the atomic wire.
Study and Manipulation of Single Functionalized Molecules by Low Temperature STM
Journal of Scanning Probe Microscopy, 2007
Two types of functionalized molecules, wheels and switches, are studied with a low temperature scanning tunneling microscope. Lateral manipulation of wheel-dimer molecules is performed on a Cu(110) surface. If suitable parameters are chosen, not only a hopping, but also a rolling motion of the molecular wheels can be induced if the surface corrugation in the direction of motion is sufficient. The experimental observations clearly reflect the different mechanisms of hopping and rolling. While mostly only one wheel rolls, in some cases the rolling of both wheels is observed. The isomerization of single azobenzene derivatives on Au(111) is induced by applying a bias voltage between tip and sample. The process turns out to be perfectly reversible as the molecules, adsorbed in highly ordered islands, precisely restore their initial appearance after two subsequent switching events from trans to cis and back to trans. A detailed investigation of the driving process, studying the dependence of the threshold voltage on the tip-sample distance, reveals different mechanisms.
Journal of Physics: Conference Series, 2005
Initially invented to image surfaces down to atomic scale, the scanning tunneling microscope (STM) has been further developed in the last few years to an operative tool, with which atoms and molecules can be manipulated at low substrate temperatures at will with atomic precision in different manners by using solely the tip-adparticle forces. In this way various artificial structures on naoscale have been created and in situ characterized with the STM. Such structures as well as single molecules can be investigated by scanning tunnelling spectroscopy (STS) both with respect to their local electronic and even vibrational properties. Modifications of single molecules can be induced by using the tunnelling electron current: Rotations, diffusional jumps, vibrational excitations, desorption, dissociation and even association can be induced in individual molecules, often in a rather precise way by tuning the voltage into the energy levels of specific vibrations or electronic levels. These possibilities give rise to startling new opportunities for physical and chemical experiments on the single atom and single molecule level. Here a brief overview on results obtained with these new techniques is given.
Manipulation of Atoms and Molecules with the Low-Temperature Scanning Tunneling Microscope
Japanese Journal of Applied Physics, 2001
The controlled manipulation with a scanning tunneling microscope (STM) down to the scale of small molecules and single atoms allows the buildup of molecular and atomic nanostructures. In the case of the lateral manipulation of adsorbed species, in which only tip/particle forces are used, three different manipulation modes (pushing, pulling, sliding) can be discerned. Vertical manipulation of Xe and CO is demonstrated, leading to the formation of functionalized tips, which can be used for improved imaging and even to perform vibrational spectroscopy on single molecules. Furthermore, we describe how we have reproduced a full chemical reaction with single molecules, whereby all basic steps, namely, preparation of the reactants, diffusion and association, are induced with the STM tip.
Conformation Manipulation and Motion of a Double Paddle Molecule on an Au(111) Surface
ACS Nano
The molecular conformation of a bisbinaphthyldurene (BBD) molecule is manipulated using a lowtemperature ultrahigh-vacuum scanning tunneling microscope (LT-UHV STM) on an Au(111) surface. BBD has two binaphthyl groups at both ends connected to a central durene leading to anti/syn/flat conformers. In solution, dynamic nuclear magnetic resonance indicated the fast interexchange between the anti and syn conformers as confirmed by density functional theory calculations. After deposition in a submonolayer on an Au(111) surface, only the syn conformers were observed forming small islands of self-assembled syn dimers. The syn dimers can be separated into syn monomers by STM molecular manipulations. A flat conformer can also be prepared by using a peculiar mechanical unfolding of a syn monomer by STM manipulations. The experimental STM dI/dV and theoretical elastic scattering quantum chemistry maps of the low-lying tunneling resonances confirmed the flat conformer BBD molecule STM production. The key BBD electronic states for a step-by-step STM inelastic excitation lateral motion on the Au(111) are presented requiring no mechanical interactions between the STM tip apex and the BBD. On the BBD molecular board, selected STM tip apex positions for this inelastic tunneling excitation enable the flat BBD to move controllably on Au(111) by a step of 0.29 nm per bias voltage ramp.
STM manipulation of molecular moulds on metal surfaces
Nano Research, 2009
Molecular Landers are a class of compounds containing an aromatic board as well as bulky side groups which upon adsorption of the molecule on a surface may lift the molecular board away from the substrate. Different molecular Landers have extensively been studied as model systems for nanomachines and the formation of molecular wires, as well as for their function as “molecular moulds”, i.e., acting as templates by accommodating metal atoms underneath their aromatic board. Here, we investigate the adsorption of a novel Lander molecule 1,4-bis(4-(2,4-diaminotriazine)phenyl)-2,3,5,6-tetrakis(4-tert-butylphenyl)benzene (DAT, C64H68N10) on Cu(110) and Au(111) surfaces under ultrahigh vacuum (UHV) conditions. By means of scanning tunneling microscopy (STM) imaging and manipulation, we characterize the morphology and binding geometries of DAT molecules at terraces and step edges. On the Cu(110) surface, various contact configurations of individual DAT Landers were formed at the step edges in a controlled manner, steered by STM manipulation, including lateral translation, rotation, and pushing molecules to an upper terrace. The diffusion barrier of single DAT molecules on Au(111) is considerably smaller than on Cu(110). The DAT Lander is specially designed with diamino-triazine side groups making it suitable for future studies of molecular self-assembly by hydrogen-bonding interactions. The results presented here are an important guide to the choice of substrate for future studies using this compound.
Interaction of a long molecular wire with a nanostructured surface: Violet Landers on Cu(211)
Chemical Physics Letters, 2006
Violet Lander molecules (long molecular wires with legs) are deposited on the nanostructured Cu(2 1 1) surface at 325 K and 177 K and investigated by low temperature scanning tunnelling microscopy. Selective population of (3 1 1) steps and local surface restructuring are observed for molecules adsorbed with their axis parallel to intrinsic steps. Thanks to the good matching between molecular dimensions and surface corrugation, molecules oriented perpendicularly to the steps assume conformations which allow tunnelling also through the molecular wire. The molecular wire terminations are hence self-contacted to the Cu(2 1 1) surface native (1 1 1) and (3 1 1) step edges.