Photoelectron spectroscopy measurements of the electronic structure of carbon-60 and other carbon based material thin films.

摘要

Carbon is a flexible atom in the way of bonding and hence presents various unique physical, chemical and biological behaviors in the solid state. The synthesis of molecular carbon structures in the form of C₆₀ and other fullerenes has stimulated intense interest in spherical carbon structures. The C₆₀ fullerene received much attention from scientists in many fields of expertise. C₆₀ is the soccer-ball shaped molecule that constitutes the third elemental form of carbon, after graphite and diamond. In recent years there has been much interest in carbon nanotubes.; A detailed understanding of the thin film growth and characterization is crucial for the application of carbon based thin films. Diamond films were grown by plasma enhanced chemical vapor deposition (PECVD) and hot filament assisted chemical vapor deposition (HFCVD). C₆₀ based material thin films and carbon nanotube thin films were grown by laser vapor deposition and sublimation deposition. These films were characterized by ultra violet photoelectron spectroscopy (UPS), x-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD).; The UPS system has been built in University of Texas at Arlington. The valence band electronic structures of thin film were measured using UPS and compared with the theoretical calculation.; Diamond, C₆₀ and carbon nanotubes are carbon-based materials that have different crystal structures. It has been observed that different crystal structures of materials have different electronic valence band structures. We observed the crystallographic structures of carbon based thin films using XRD. We examined the surface valence band electronic structures of carbon based thin films in connection with its electronic transport properties using UPS and XPS. We have deposited C₆₀ and carbon nanotubes on silicon and copper substrates using a sublimation method. We have studied copper to C₆₀ and copper to carbon nanotube interface using UPS. The C₆₀ cage has been doped using laser vapor deposition of Lanthanium (La). The electronic valence band structures of C₆₀ have been studied as a function of La doping using UPS. UPS showed that the density of states near the Fermi edge is significantly affected by La doping. UPS also demonstrated that the La 5p orbitals strongly hybridize with the C₆₀ cage.