On-Surface Synthesis of Chlorinated Narrow Graphene Nanoribbon Organometallic Hybrids.

Graphene nanoribbons (GNRs) and their derivatives attract growing attention due to their excellent electronic and magnetic properties as well as the fine-tuning of such properties that can be obtained by heteroatom substitution and/or edge morphology modification. Here, we introduce graphene nanoribbon derivatives-organometallic hybrids with gold atoms incorporated between the carbon skeleton and side Cl atoms. We show that narrow chlorinated 5-AGNROHs (armchair graphene nanoribbon organometallic hybrids) can be fabricated by on-surface polymerization with omission of the cyclodehydrogenation reaction by a proper choice of tailored molecular precursors.

Adsorption behavior of tin phthalocyanine onto the (110) face of rutile TiO.

The adsorption behavior of tin phthalocyanine (SnPc) molecules on rutile TiO(110) was studied by scanning tunneling microscopy (STM). Low-temperature STM measurements of single molecules reveal the coexistence of two conformations of molecules on the TiO surface. Density functional theory-based simulations (DFT) indicate that the difference originates from the position of the tin atom protruding from the molecule plane.

Nonacene Generated by On-Surface Dehydrogenation.

The on-surface synthesis of nonacene has been accomplished by dehydrogenation of an air-stable partially saturated precursor, which could be aromatized by using a combined scanning tunneling and atomic force microscope as well as by on-surface annealing. This transformation allowed the in-detail analysis of the electronic properties of nonacene molecules physisorbed on Au(111) by scanning tunneling spectroscopy measurements. The spatial mapping of molecular orbitals was corroborated by density functional theory calculations.

Ordering of Zn-centered porphyrin and phthalocyanine on TiO(011): STM studies.

Zn(II)phthalocyanine molecules (ZnPc) were thermally deposited on a rutile TiO(011) surface and on Zn(II)-tetraphenylporphyrin (ZnTPP) wetting layers at room temperature and after elevated temperature thermal processing. The molecular homo- and heterostructures were characterized by high-resolution scanning tunneling microscopy (STM) at room temperature and their geometrical arrangement and degree of ordering are compared with the previously studied copper phthalocyanine (CuPc) and ZnTPP heterostructures. It was found that the central metal atom may play some role in ordering and growth of phthalocyanine/ZnTPP heterostructures, causing differences in stability of upright standing ZnPc versus CuPc molecular chains at given thermal annealing conditions.

Scanning probe microscopy studies on the adsorption of selected molecular dyes on titania.

Titanium dioxide, or titania, sensitized with organic dyes is a very attractive platform for photovoltaic applications. In this context, the knowledge of properties of the titania-sensitizer junction is essential for designing efficient devices. Consequently, studies on the adsorption of organic dyes on titania surfaces and on the influence of the adsorption geometry on the energy level alignment between the substrate and an organic adsorbate are necessary.

The butterfly - a well-defined constant-current topography pattern on Si(001):H and Ge(001):H resulting from current-induced defect fluctuations.

Dangling bond (DB) arrays on Si(001):H and Ge(001):H surfaces can be patterned with atomic precision and they exhibit complex and rich physics making them interesting from both technological and fundamental perspectives. But their complex behavior often makes scanning tunneling microscopy (STM) images difficult to interpret and simulate. Recently it was shown that low-temperature imaging of unoccupied states of an unpassivated dimer on Ge(001):H results in a symmetric butterfly-like STM pattern, despite the fact that the equilibrium dimer configuration is expected to be a bistable, buckled geometry.

Ordered heteromolecular overlayers formed by metal phthalocyanines and porphyrins on rutile titanium dioxide surface studied at room temperature.

Molecular heterostructures are formed from meso-tetraphenyl porphyrins-Zn(II) (ZnTPP) and Cu(II)-phthalocyanines (CuPc) on the rutile TiO2(011) surface. We demonstrate that ZnTPP molecules form a quasi-ordered wetting layer with flat-lying molecules, which provides the support for growth of islands comprised of upright CuPc molecules. The incorporation of the ZnTPP layer and the growth of heterostructures increase the stability of the system and allow for room temperature scanning tunneling microscopy (STM) measurements, which is contrasted with unstable STM probing of only CuPc species on TiO2.

Characterization of individual molecular adsorption geometries by atomic force microscopy: Cu-TCPP on rutile TiO2 (110).

Functionalized materials consisting of inorganic substrates with organic adsorbates play an increasing role in emerging technologies like molecular electronics or hybrid photovoltaics. For such applications, the adsorption geometry of the molecules under operating conditions, e.g.

Energy loss triggered by atomic-scale lateral force.

We perform bimodal atomic force microscopy measurements on a Br-doped NaCl (001) surface to investigate the mechanisms behind frequency shift and energy dissipation contrasts. The peculiar pattern of the dissipated energy in the torsional channel, related to frictional processes, is increased at the positions of Br impurities, otherwise indistinguishable from Cl ions in the other measured channels. Our simulations reveal how the energy dissipates by the rearrangement of the tip apex and how the process is ultimately governed by lateral forces.

Interplay of the tip-sample junction stability and image contrast reversal on a Cu(111) surface revealed by the 3D force field.

Non-contact atomic force microscopy is used to measure the 3D force field on a dense-packed Cu(111) surface. An unexpected image contrast reversal is observed as the tip is moved towards the surface, with atoms appearing first as bright spots, whereas hollow and bridge sites turn bright at smaller tip-sample distances. Computer modeling is used to elucidate the nature of the image contrast.

Organic molecules reconstruct nanostructures on ionic surfaces.

Modification and functionalization of the atomic-scale structure of insulating surfaces is fundamental to catalysis, self-assembly, and single-molecule technologies. Specially designed syn-5,10,15-tris(4-cyanophenylmethyl)truxene molecules can reshape features on an ionic KBr (001) surface. Atomic force microscopy images demonstrate that both KBr monolayer islands and pits can reshape from rectangular to round structures, a process which is directly facilitated by molecular adsorption.

Functionalized truxenes: adsorption and diffusion of single molecules on the KBr(001) surface.

In this work, we have studied the adsorption and diffusion of large functionalized organic molecules on an insulating ionic surface at room temperature using a noncontact atomic force microscope (NC-AFM) and theoretical modeling. Custom designed syn-5,10,15-tris(4-cyanophenylmethyl)truxene molecules are adsorbed onto the nanoscale structured KBr(001) surface at low coverages and imaged with atomic and molecular resolution with the NC-AFM. The molecules are observed rapidly diffusing along the perfect monolayer step edges and immobilized at monolayer kink sites.

Systematic achievement of improved atomic-scale contrast via bimodal dynamic force microscopy.

Judiciously matched experiments, calculations, and theory demonstrate that a higher sensitivity to short-range interactions and, consequently, improved resolution on the atomic scale can be achieved by bimodal noncontact dynamic force microscopy. The combination of sub-Angström tip oscillation at the second flexural resonance of a commercially available silicon cantilever with the commonly used large amplitude oscillation at the fundamental resonance frequency enables this performance improvement while avoiding potentially damaging jump-to-contact instabilities.

Internal architecture and adsorption sites of Violet Lander molecules assembled on native and KBr-passivated InSb(001) surfaces.

The adsorption of individual Violet Lander molecules self-assembled on the c(8x2) reconstructed InSb(001) surface in its native form and on the surface passivated with one to three monolayers of KBr is investigated by means of low-temperature scanning tunneling microscopy (STM). Preferred adsorption sites of the molecules are found on flat terraces as well as at atomic step edges. For molecules immobilized on flat terraces, several different conformations are identified from STM images acquired with submolecular resolution and are explained by the rotation of the 3,5-di-tert-butylphenyl groups around sigma bonds, which allows adjustment of the molecular geometry to the anisotropic substrate structure.