STM-based quantum transport through molecular wires

The further miniaturization of electronic devices is a strong driving force in science. In the last few decades, devices based on organic materials have been studied. One goal is to create applications performed nowadays by silicon-based CMOS technology with organic materials. In these studies the interest is placed upon diverse properties of the organic molecules, such as their electronic, geometric, thermal, optical, and electroluminescence characteristics. One of the main problems of these studies is the lack of geometrical control of the systems during the measurements. As the physical properties critically depend on the exact geometry, contradictory results are found in literature. To overcome this lack of control, this work introduces a new method which enables transport studies on single molecules with highly controlled junction geometries. The concept of this method, which is based on scanning probe techniques, will be presented as well as its realization. The method will be applied to molecule-metal junctions with molecules of dierent lengths which are contacted by dierent metal electrodes. It will be shown that highly reproducible experiments can be performed. Furthermore, the physical interpretation of the measurements will be discussed. It will be demonstrated that the profound knowledge of the geometry in these junctions helps to achieve a better understanding of the transport properties.