Scanning tunneling spectroscopy of fullerenes, diamondoids, and organometallic molecular nanostructures

Molecule-based carbon nanostructures display a great variety of geometries and electronic features, making them a promising basis for novel technological applications. Understanding their local electronic properties is of essential importance for future molecule-based device construction. This dissertation is aimed at understanding and manipulating the electronic properties of molecule-based carbon nanostructures.; The dissertation is divided into three main parts. The first part describes the technical aspects of a home-built low-temperature ultra-high vacuum (UHV) scanning tunneling microscope (STM), which was the main instrument used in our studies.; The second part discusses scanning tunneling spectroscopy (STS) studies for three different molecules that have great nanotechnological potential: C60 fullerenes, diamondoids, and organometallic magnetic molecules. Our studies of C60 behavior include observation of energy-resolved molecular orbitals, molecule-substrate interactions, and the Jahn-Teller effect. Our studies of new sp3 bonded diamondoid molecules are focused on the tetramantane molecule. We have characterized this molecule both with elastic and inelastic spectroscopy, and have performed single-molecule manipulation using the "sliding process" and voltage-pulses. The organometallic element focused on here is the titanocene chloride dimer. This molecule shares many characteristics of the fullerenes, such as conjugated carbon rings, but it has additional magnetic properties due to the incorporation of two spin-12 Ti atoms in an antiferromagnetic configuration. Ordered patterns for submonolayer coverages of this molecule on Au(111) were synthesized and will be discussed, including spectroscopic features. STS of the some disordered titanocene molecules shows sharp resonances near the Fermi energy that may be magnetic in origin.; The third part of this thesis is focused on the development of new techniques for investigating local magnetic and spin properties. The construction of a spin-polarized STM, capable of characterizing fluctuations in spin density at the Angstrom scale, will be discussed. Our progress in construction of a STM electron spin resonance (ESR) instrument will also be addressed.