Scanning Tunneling Microscopy and Spectroscopy of Carbon Nanotubes Interfaced With Silicon Surfaces

116 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.Single-walled carbon nanotubes (SWNTs) are high-aspect-ratio molecular wires that exhibit either metallic or semiconducting behavior depending upon their diameter and chiral angle. SWNTs support high-mobility electrical conduction, are chemically and mechanically robust, and can both emit and detect infrared light. These properties recommend SWNTs as the building blocks of a future molecular nanotechnology. In the near term, however, the integration of SWNTs with silicon-based complementary metal-oxide-semiconductor (CMOS) technology holds the greatest promise in terms of economic and manufacturing feasibility. In this thesis, the ultrahigh vacuum scanning tunneling microscope (UHV-STM) is used to examine SWNTs directly interfaced with the hydrogen-passivated Si(100) surface. An approach termed dry contact transfer (DCT) was developed for the UHV deposition of SWNTs with minimal disruption of the atomically flat Si(100)-2x1:H surface. Isolated, rather than bundled, SWNTs could be routinely located on the surface for atomically resolved imaging, tunneling current-voltage spectroscopy, lateral manipulation, and cutting with the room-temperature UHV-STM. The removal of hydrogen at the nanotube-silicon interface via UHV-STM electron-stimulated desorption resulted in structural and electronic modifications to the SWNT. The growing body of first-principles simulations of the SWNT/Si(100) system was drawn upon in the interpretation of such local perturbations. Weakly adsorbed SWNTs initially unstable in the presence of the rastered STM tip could be stabilized by depassivating the underlying H-Si(100) surface. Finally, feedback-controlled cutting of SWNTs with the UHV-STM was demonstrated as a precise and reproducible means of preparing one or more finite-sized SWNTs from an extended tube.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD