Chemical and physical properties of molecular nanostructures on surfaces investigated by means of scanning probe microscopy

Bc. Benjamin Jose MALLADA FAES

Doctoral thesis

Abstract:

This thesis encapsulates an extensive exploration of atomic-scale systems, employing scanning probe microscopy (SPM) techniques to investigate various facets of the field. Within this context, the field of SPM techniques has emerged as a powerful tool for unravelling atomic-scale phenomena, enabling precise imaging and manipulation of individual atoms and molecules. Of particular importance in this research is the utilization of ultra-high vacuum (UHV) metallic surfaces, which offer a pristine and controlled environment for studying atomic interactions. Moreover, the catalytic properties of metallic surfaces are of particular interest in this research. By investigating the interactions between adsorbates and the metal surface, valuable insights can be gained into heterogeneous catalysis, a vital process employed in numerous industrial applications. In addition, by operating at cryogenic temperatures at 4.5 K, the inherent thermal noise is significantly reduced, enhancing the precision and sensitivity of the experiments. One notable aspect explored in this thesis is the realm of on-surface synthesis, a field that enables atomic precision in the creation of new materials and nanostructures. By carefully controlling the adsorption and reactions of precursor molecules on the surface, it becomes possible to engineer tailored architectures with atomic precision. The atomic-level control attained through on-surface synthesis opens up exciting possibilities for designing novel materials with unique properties and functionalities. The characterization of these synthesized structures at the atomic scale is made possible through the application of scanning probe microscopy techniques, such as scanning tunnelling microscopy (STM), frequency-modulated atomic force microscopy (FM-AFM), and Kelvin probe force microscopy (KPFM). These techniques allow for real-space visualization and mapping of the surface properties, enabling researchers to explore the intricate details of atomic interactions and charge distributions. The thesis is divided into two sections: on-surface synthesis and charge distribution imaging. The on surface synthesis section investigates strain-driven chemical reactions, the on-surface synthesis of an iron porphyrin-based coordination polymer, and the incorporation of defects into anthracene-based polymers. The charge distribution imaging section uses KPFM to visualize charge distributions in single molecules and atoms, in particular the study of the charge spatial extension of single graphitic dopants boron and nitrogen dopants in graphene, the real-space observation of the -hole, an anisotropic charge distribution involved in the non-covalent -bond, in one single bromine atom and finally the observation of the influence of halogenated atoms in polyaromatic hydrocarbons in the creation of an electron depleted region within the molecule known as -hole. The thesis highlights the pivotal role of surfaces in on-surface synthesis and offers insights into catalytic properties, atomic control, and the absence of adsorption on surfaces under ultra-high vacuum (UHV) conditions.

Abstract:

This thesis encapsulates an extensive exploration of atomic-scale systems, employing scanning probe microscopy (SPM) techniques to investigate various facets of the field. Within this context, the field of SPM techniques has emerged as a powerful tool for unravelling atomic-scale phenomena, enabling precise imaging and manipulation of individual atoms and molecules. Of particular importance in this research is the utilization of ultra-high vacuum (UHV) metallic surfaces, which offer a pristine and controlled environment for studying atomic interactions. Moreover, the catalytic properties of metallic surfaces are of particular interest in this research. By investigating the interactions between adsorbates and the metal surface, valuable insights can be gained into heterogeneous catalysis, a vital process employed in numerous industrial applications. In addition, by operating at cryogenic temperatures at 4.5 K, the inherent thermal noise is significantly reduced, enhancing the precision and sensitivity of the experiments. One notable aspect explored in this thesis is the realm of on-surface synthesis, a field that enables atomic precision in the creation of new materials and nanostructures. By carefully controlling the adsorption and reactions of precursor molecules on the surface, it becomes possible to engineer tailored architectures with atomic precision. The atomic-level control attained through on-surface synthesis opens up exciting possibilities for designing novel materials with unique properties and functionalities. The characterization of these synthesized structures at the atomic scale is made possible through the application of scanning probe microscopy techniques, such as scanning tunnelling microscopy (STM), frequency-modulated atomic force microscopy (FM-AFM), and Kelvin probe force microscopy (KPFM). These techniques allow for real-space visualization and mapping of the surface properties, enabling researchers to explore the intricate details of atomic interactions and charge distributions. The thesis is divided into two sections: on-surface synthesis and charge distribution imaging. The on surface synthesis section investigates strain-driven chemical reactions, the on-surface synthesis of an iron porphyrin-based coordination polymer, and the incorporation of defects into anthracene-based polymers. The charge distribution imaging section uses KPFM to visualize charge distributions in single molecules and atoms, in particular the study of the charge spatial extension of single graphitic dopants boron and nitrogen dopants in graphene, the real-space observation of the -hole, an anisotropic charge distribution involved in the non-covalent -bond, in one single bromine atom and finally the observation of the influence of halogenated atoms in polyaromatic hydrocarbons in the creation of an electron depleted region within the molecule known as -hole. The thesis highlights the pivotal role of surfaces in on-surface synthesis and offers insights into catalytic properties, atomic control, and the absence of adsorption on surfaces under ultra-high vacuum (UHV) conditions.

Keywords

STM, AFM, KPFM, UHV, surfaces, on-surface synthesis, nanomaterials, carbon nanomaterials

Language used: English

Date on which the thesis was submitted / produced: 8. 6. 2023

Thesis defence

• Supervisor: doc. Ing. Pavel Jelínek, Ph.D.

Palacký University Olomouc

Faculty of Science

Doctoral programme / field:
Nanomaterial Chemistry / Nanomaterial Chemistry