Adsorption of Large Organic Molecules on Clean and Hydroxylated Rutile TiO₂(110) Surfaces

Abstract

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.

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

“…Godlewski et al investigated Violet Lander molecules that belong to the family of large non-planar species that are specially designed to act as molecular wires supported with spacer groups to increase the altitude of the polyaromatic board above the surface [45,64]. The authors investigated the adsorption on the (110) and (011) surfaces and observed that the molecules adsorb as single entities and adapt their conformation to the geometrical structure of the surface.…”

Atomic‐ and molecular‐scale devices and systems for single‐molecule electronics

“…Increasing the distance between the active part and substrate should result in attenuated coupling between the device and the surface. Molecules with such spacer groups (often called legs) have already been examined on several substrates, for example, Lander molecules have been deposited on Cu 41, 42, TiO 2 43, 44, and InSb 45. Lander family molecules possess legs that are connected to the active board by σ bonds and are partially free to rotate.…”

“…It has also been observed that these molecules can be manipulated by the STM tip in the “walk‐like” manner with spacer groups acting as moving legs (see, e.g., Refs. 41–44) or may create hydrogen bonds between each other leading to formation of molecular wires 46.…”

“…The active board of Lander molecules is a π‐system that in principle could be utilized as a molecular wire. To some extent the effect of decoupling from the underlying substrate is demonstrated by the fact that in the STM image a Lander molecule appears as four lobes arranged in a rhomboidal or rectangular geometry 41–45. Such an appearance is ascribed to tunneling through the spacer legs 41.…”

“…Such an appearance is ascribed to tunneling through the spacer legs 41. There is only a single report on a successful attempt to image the active board, i.e., when the molecule is deposited on a TiO 2 (110) surface 43. Additionally, Moresco et al 42 report on formation of the contact between a molecular wire, i.e., the Lander molecule, and a metal electrode.…”