Low Temperature Scanning Tunneling Microscopy Studies of Surfaces and Molecules

Download or read book Low Temperature Scanning Tunneling Microscopy Studies of Surfaces and Molecules written by Lisa Marie Wesoloski and published by . This book was released on 2006 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanotechnology is described as an emerging science discipline that is expected to have a greater impact on life as we know it than any innovation since the industrial revolution. Superior, cheaper, stronger and more efficient products are predicted to change the way we live, use technology and conduct research. This dissertation focuses on a remarkable instrument, the low temperature scanning tunneling microscope (LT-STM), which is a powerful tool that has played a significant role in revolutionizing the fields of nanoscience and nanotechnology. The work in this dissertation is divided into three sections. First, the fundamental principles of nanoscience and the history of microscopy are introduced. The second part provides a thorough study of Bardeen's formula and its application in STM. The third part describes experimental investigations involving the physicochemical properties of matter at the nanoscale conducted by means of LT-STM. Studies begin with bare substrate surfaces and successively build in complexity as small molecules, solvents, nanoclusters and large organic molecules are examined on surfaces. Experiments show that carbon monoxide exhibits chemical contrast, while oxygen shows a lack thereof. Solvents are demonstrated to weaken surface bonds and induce surface atom mass transport and the tip is shown to assist the diffusion. Manganese nanoclusters are shown to generate a localized electronic state on graphite by either an electronic or magnetic perturbation. The aromatic molecule, decacyclene (DC) is shown to exhibit both bias-dependent and tip-dependent contrast reversal. In addition, intermolecular interactions are found to compete with the surface-to-molecule interactions as dimers are observed on the surface. Two geometric orientations of the dimers are proposed to explain dimer characteristics and their relation to substrate-dependent properties. Lastly, DC molecules are examined at coverages in excess of a monolayer and shown to form ordered domains of the boat-shape conformation. This dissertation emphasizes the local modifications of electronic structures upon physisorption and the interplay between surface-to-molecule and molecule-to-molecule interactions, which demonstrate the various complexities occurring at the nanoscale.