Formation of One-Dimensional C60 Rows on TiO2(110)-1 × 2-cross-link Structure and Their Local Polymerization

Adsorption and Self-Assembly of Large Polycyclic Molecules on the Surfaces of TiO2 Single Crystals

Titanium dioxide is one of the most frequently studied metal oxides, and its (110) rutile surface serves as a prototypical model for the surface science of such materials. Recent studies have also shown that the (011) surface is relatively easy for preparation in ultra-high vacuum (UHV) and that both the (110) and (011) surfaces could be precisely characterized using scanning tunneling microscopy (STM). The supramolecular self-assembly of organic molecules on the surfaces of titanium dioxide plays an important role in nanofabrication, and it can control the formation and properties of nanostructures, leading to wide range of applications covering the fields of catalysis, coatings and fabrication of sensors and extends to the optoelectronic industry and medical usage. Although the majority of experiments and theoretical calculations are focused on the adsorption of relatively small organic species, in recent years, there has been increasing interest in the properties of larger molecules that have several aromatic rings in which functional units could also be observed. The purpose of this review is to summarize the achievements in the study of single polycyclic molecules and thin layers adsorbed onto the surfaces of single crystalline titanium dioxide over the past decade.

Modelling components of future molecular devices

We discuss challenges involved in modelling different components of molecular devices and give several examples that demonstrate how computer modelling evolved over the last few years to become a comprehensive tool for designing molecules, predicting their adsorption and diffusion at surfaces, simulating atomic force microscopy imaging and manipulation of atoms and molecules at insulating surfaces and studying electron conduction in prototype molecular devices. We describe some of the computational techniques used for modelling adsorption, diffusion, imaging and manipulation of organic molecules at surfaces and challenges pertaining to these studies, give several examples of applications and discuss further prospects for theoretical modelling of complex organic molecules at surfaces.

Adsorption of large organic molecules on clean and hydroxylated rutile TiO2(110) surfaces

Behavior of large organic molecules equipped with spacer groups (Violet Landers, VL) on the TiO(2)(110)-(1x1) surfaces is investigated by means of high-resolution scanning tunneling microscopy (STM). Two distinct adsorption geometries are observed. We demonstrate that the molecule adsorption morphology can be alternated by well-controlled STM tip-induced manipulation. It is used to probe the mobility of molecules and reveals locking in one of the analyzed adsorption sites, thus allow to enhance or reduce the mobility along the [001] direction. Field induced hydrogen desorption is used to perform lateral STM manipulation on a hydroxyl-free surface, which provides insight into the influence of surface hydroxyl groups on the molecule behavior. The ability to image with submolecular resolution both the central board and the spacer groups of the VL molecule is demonstrated.

Growth of ordered C60 islands on TiO2(110)

Non-contact atomic force microscopy is used to study C(60) molecules deposited on the rutile TiO(2)(110) surface in situ at room temperature. At submonolayer coverages, molecules adsorb preferentially at substrate step edges. Upon increasing coverage, ordered islands grow from the decorated step edges onto the lower terraces. Simultaneous imaging of bridging oxygen rows of the substrate and the C(60) island structure reveals that the C(60) molecules arrange themselves in a centered rectangular superstructure, with the molecules lying centered in the troughs formed by the bridging oxygen rows. Although the TiO(2)(110) surface exhibits a high density of surface defects, the observed C(60) islands are of high order. This indicates that the C(60) intermolecular interaction dominates over the molecule-substrate interactions that may cause structural perturbations on a defective surface. Slightly protruding C(60) strands on the islands are attributed to anti-phase boundaries due to stacking faults resulting from two islands growing together.