Nascent Metal Atom Condensation in Self-Assembled Monolayer Matrices: Coverage-Driven Morphology Transitions from Buried Adlayers to Electrically Active Metal Atom Nanofilaments to Overlayer Clusters during Aluminum Atom Deposition on Alkanethiolate/Gold Monolayers (original) (raw)
Related papers
2D/3D Metallic Nano-objects Self-Organized in an Organic Molecular Thin Film
ACS Omega
We present the fabrication and investigation of the properties of nanocomposite structures consisting of two-dimensional (2D) and three-dimensional (3D) metallic nano-objects selforganized on the surface and inside of organic molecular thin-film copper tetrafluorophthalocyanine (CuPcF 4). Metallic atoms, deposited under ultrahigh vacuum (UHV) conditions onto the organic ultrathin film, diffuse along the surface and self-assemble into a system of 2D metallic overlayers. At the same time, the majority of the metal atoms diffuse into the organic matrix and selforganize into 3D nanoparticles (NPs) in a well-defined manner. The evolution of the morphology and electronic properties of such structures as a function of nominal metal content is studied under UHV conditions using transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), and photoelectron spectroscopy (PES) techniques. Using HR-TEM, we have observed the periodicity of atomic planes of individual silver NPs. The steady formation of agglomerates from individual single nanocrystallites with intercrystallite boundaries is observed as well. PES reveals generally weak chemical interactions between silver and the organic matrix and n-doping of CuPcF 4 at the initial stages of silver deposition, which is associated with charge transfer from the 2D wetting layer on the basis of core-level spectra shift analysis.
Ordered Au Nanoparticle Array on Au(111) through Coverage Control of Precursor Metal–Organic Chains
The Journal of Physical Chemistry C, 2016
Metal−organic overlayer structures formed by 1,4phenylene-diisocyanide (PDI) and Au adatoms on Au(111) in UHV, their stability in air, and the tip-induced Au nanoparticle formation on PDI−Au(111) surfaces in air were investigated using scanning tunneling microscopy (STM) and vibrational spectroscopy. This study reveals that the distribution of Au nanoparticles created during tip-induced release of Au atoms from molecule-Au adatom complexes shows strong dependence on the PDI coverage. Ordered Au nanoparticle arrays form in the medium-coverage regime, while more disordered distributions are observed at low and saturation coverages. The different distributions of Au nanoparticles are a direct consequence of the coverage-dependent assembly of (PDI−Au) n chains, their different stability in air, and a templating effect of the Au(111) surface, which is most pronounced for medium coverage, where phases of densely packed (PDI−Au) n chains and disordered PDI−Au assemblies are confined, respectively, to the fcc and hcp regions of the (22 × √3) surface reconstruction of Au(111). The Au nanoparticles nucleate preferentially in the disordered or defective regions of the PDI−Au precursor overlayer, and their formation requires ambient air and high negative tip-bias, suggesting an electrochemical initiation of Au release from the molecule−Au adatom complexes.
Structural Evolution of Gas-Phase Coinage Metal Clusters in Thiolate Self-Assembled Monolayers on Au
The Journal of Physical Chemistry C, 2012
Metallization of organic surfaces is important especially for applications in molecular electronics. It can be realized by different means, one promising albeit less studied method being gas-phase deposition of metal clusters. Here, we report on the interactions of gas-phase Cu, Ag, and Au clusters with n-dodecanethiolate self-assembled monolayers (SAMs) on Au substrate. The morphology and composition of the deposited clusters and their impact on the interface structure of the SAM/Au substrate were investigated using scanning tunneling microscopy. The chemical and physical interactions between the clusters and thiolates were characterized using X-ray photoelectron spectroscopy. The Au clusters are found to penetrate through the monolayer as a whole and partially retain their spherical geometry, whereas atom-by-atom diffusion and/or defect-mediated penetration are proposed for the Cu and Ag clusters.
Journal of Physics: Condensed Matter, 2014
The realization of metal–molecule junctions for future electronic devices relies on our ability to assemble these heterogeneous objects at a molecular level and understand their structure and the behavior of the electronic states at the interface. Delocalized interface states near the metal Fermi level are a key ingredient for tailoring charge injection, and such a delocalization depends on a large number of chemical, structural and morphological parameters, all influencing the spatial extension of the electron wavefunctions. Our large-scale dynamical simulations, combined with experiments, show that a double-decker organometallic compound (ferrocene) can be deposited on a Cu(111) surface, providing an ideal system to investigate the adsorption, the interface states and localized spin states at a metal–organometallic interface. Adsorbed ferrocene is shown to have a peculiar pattern and realizes a 2D-like interface state strongly resembling Shockley's surface state of Cu. By a subsequent deposition of single metal atoms on the adsorbed ferrocene, we analyze the sensitivity of the interface state to local modifications of the interface potential. This provides an insight into adsorption, spin configuration and charge redistribution processes, showing how to tune the electron behavior at a metal–molecule interface.
The Journal of Physical Chemistry B, 2006
We report scanning tunneling microscopy observations on the formation of 2D Co-based coordination compounds on the reconstructed Au(111) surface. Preorganized arrays of Co bilayer islands are shown to be local reaction sites, which are consumed in the formation of Co-terephthalate aggregates and regular nanoporous grids. The latter exhibit a planar geometry stabilized by the smooth substrate. The nanogrids are based on a rectangular motif, which is understood as an intrinsic feature of a 2D cobaltous terephthalate sheet and dominates over the templating influence of the quasihexagonal substrate atomic lattice. The dynamics of the Co island dissolution and metallosupramolecular self-assembly could be monitored in situ. Complementary first-principles calculations were performed to analyze the underlying driving forces and to examine general trends in 2D metal-carboxylate formation. The findings indicate the wide applicability of coordination chemistry concepts at surfaces, which moreover can be spatially confined by using templated substrates, and its potential to synthesize arrangements unavailable in bulk materials.
Understanding Structure and Bonding of Multilayered Metal–Organic Nanostructures
The Journal of Physical Chemistry C, 2013
For organic and hybrid electronic devices, the physicochemical properties of the contained interfaces play a dominant role. To disentangle the various interactions occurring at such heterointerfaces, we here model a complex, yet prototypical, threecomponent system consisting of a Cu−phthalocyanine (CuPc) film on a 3,4,9,10-perylenetetracarboxylic-dianhydride (PTCDA) monolayer adsorbed on Ag(111). The two encountered interfaces are similar, as in both cases there would be no bonding without van der Waals interactions. Still, they are also distinctly different, as only at the Ag(111)− PTCDA interface do massive charge-rearrangements occur. Using recently developed theoretical tools, we show that it has become possible to provide atomistic insight into the physical and chemical processes in this comparatively complex nanostructure distinguishing between interactions involving local rearrangements of the charge density and longrange van der Waals attraction.
Chemistry of metal atoms reacting with alkanethiol self-assembled monolayers
Applied Surface Science, 2006
Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is utilized to investigate the behavior of vapor-deposited K, Au and Ti atoms on several alkanethiol self-assembled monolayers (SAM). The goals are to acquire information about chemical reactions between metal atoms and surface organic functional groups, penetration of metal atoms through the SAMs, growth modes of metal overlayers on top of the SAMs and damage of organic molecules. It is found that appearance of new characteristic peaks and disappearance of initial peaks may indicate chemical reactions or decomposition of organic molecules. The relationship between metal dose and intensity of surface organic functional group-related peaks provides information about penetration or cluster-formation of metal atoms. In addition, removing the metal overlayers by chemical etching and then characterizing samples again is a complementary approach that can reveal valuable information about the location of the metal atoms. #