STM Studies of Titantium DIOXIDE(100) Surface Reconstructions and Platinum Ultrathin Films on Hopg

Scanning Tunneling Microscopy (STM) has revolutionized surface science since its inception in 1982. The ability to spacially resolve both atomic and electronic structure have placed the STM in a well respected position on the forefront of surface research in very little time. This thesis represents research with the goal of adding STM techniques to the surface science laboratories in this department. The technique of STM is reviewed and utilized for the study of several surfaces in air and Ultrahigh Vacuum (UHV). Other surface techniques are utilized in conjunction with STM for studies in UHV. Preliminary studies involving calibration and testing of STMs are reported on graphite, Si(111) surface reconstructions, and diffraction gratings. Feasability studies are performed on several systems to find suitable systems for catalytic studies. The TiO_2(100) surface is examined with STM. Results confirm the 1 x 3 surface reconstruction spacing by imaging rows of Ti atoms. Individual atoms were unresolved. The studies also verify the existence of the two higher-order reconstructions: the 1 x 5 and the 1 x 7. The existence of these higher-order features had been the subject of recent debate. Spectroscopic results reveal the semiconductor band gap, but results on the existence of surface states were inconclusive. Finally, the structures of evaporated ultra-thin films of Pt on graphite are examined. The adsorbates form both two- and three-dimensional clusters. The two-dimensional islands display several structures including order with markedly small Pt-Pt interatomic distances. Spectroscopic measurements demonstrate the ability to distinguish Pt from graphite islands. The STM is shown to be an indispensible tool for the study of local atomic structure in surface science.