Carbon nanotube modification using BaF2 vapor in ultra-high vacuum environment

Carbon nanotubes have attracted significant attention in the scientific community due to their unique properties and potential applications. One of the most promising applications is a carbon-nanotube transistor. The motivation of this work is to find ways to connect carbon nanotubes directly to silicon using Ba as a chemical link. We studied chemical interactions between carbon nanotubes and BaF2 vapors using x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Surfaces of silicon wafers were chemically modified to allow the epitaxial growth of BaF2 using molecular beam epitaxy (MBE). Samples containing 2D single crystal islands of BaF2 were covered with carbon nanotubes with an average coverage of 10 nanotubes per um(2). The samples were transferred to an outgasing station inside the MBE system and heated to 900degreesC for two hours in a pressure of 10(-9) mbar. XPS C1s data before and after heat show a major change in the nature of the carbon nanotube electronic states. In addition XPS shows formation of a Ba-C "carbide like" bond and no presence of fluorine. AFM images of the same region taken before and after heat exposure show remarkable changes in the surface morphology of the carbon-nanotube wall.