Scanning tunneling microscopy of singlemolecule magnets and hybrid-molecular magnets: two approaches to molecular spintronics

Molecular spintronics attempts both to improve the properties of current electronic devices and develop completely new devices by combining the advantages of molecular electronics and spintronics into one research eld. Investigating and evaluating the properties of molecular magnets and to eventually employ them in devices is a major goal of molecular spintronics. Two dierent kinds of molecular magnets are promising candidates for device development: Single-molecule magnets (SMMs) and hybrid-molecular magnets. Both are ideal building blocks for spintronic devices, such as spin-transistors and spin-valves. However the fabrication of devices requires the deposition on surfaces. Due to the interaction between molecules and surfaces being highly complex, only a fundamental understanding of these phenomena will eventually lead to the succesful application of molecular magnets in devices. To improve the understanding of the molecule-surface interaction both approaches have been investigated experimentally in this dissertation. Since surfaces are prone to contamination, these experiments were conducted in ultra-high vacuum. To gain more insight in such systems and to understand the adsorption phenomena, their structural, electronic and magnetic properties were studied on a microscopic scale with scanning tunneling microscopy (STM) and spectroscopy (STS). The interaction between SMMs and surfaces was exemplarily studied by depositing fNi4g on Au(111). fNi4g is a recently synthesized SMM where a cubane fNi II 4 (3Cl)4g core is responsible for the magnetic properties [1]. The magnetic core is protected by organic ligands exhibiting a thioether surface functionalization. Since thioether functionalized ligands had been widely neglected in earlier experiments, the deposition of fNi4g on Au(111) from solution and the resulting adsorption phenomena were studied by XPS and STM. Both methods revealed strong evidence for a ligand detachment during adsorption. The magnetic core however might be still structurally intact as indicated by XPS. Attempts to desorb the detached ligands and to subsequently image the magnetic core with STM by in-situ post-annealing were unsuccessful. Instead the post-annealing lead to the decomposition of the magnetic core and to a most likely sulfur induced reconstruction of the Au(111) surface. As a results of this study new strategies have been proposed to avoid the ligand detachment in future experiments. ...