Scanning tunneling microscopy studies of fluorinated graphene films and field-directed sputter sharpening
Graphene fluoride is a two-dimensional fluorocarbon, and the wide-gap analogue of graphene. Among chemical derivatives of graphene, graphene fluoride is unique in its ease of synthesis and stability, as well as the extensive study of its bulk form, graphite fluoride. Only in the last few years, however, has graphene fluoride been isolated experimentally, and our understanding of its atomic and electronic structure, stability, reduction, and use as a platform for lithographic patterning is still limited. In this dissertation, an ultra-high vacuum scanning tunneling microscope (UHV-STM) is employed for the characterization of exfoliated double-sided graphene fluoride (ds-GF) and of single-sided graphene fluoride (ss-GF) on Cu foil. We explore the structure and stability of each material and, in particular, identify ss-GF as a stable, well-ordered, wide-gap semiconductor. This dissertation offers the first atomic-resolution study of this novel material, and the first UHV-STM measurement of its electronic structure. Furthermore, we develop the novel field-directed sputter sharpening (FDSS) technique for producing sharp metal probes with 1 – 5 nm radii of curvature, a prerequisite for high-resolution scanning tunneling microscopy (STM) imaging and nanolithography. We show that FDSS offers significant improvements in lithographic patterning, and is applicable to a range of materials, including the hard metallic-ceramic hafnium diboride (HfB2). Finally, we explore the use of HfB2-coated W wires for STM imaging and spectroscopy.
graphene, graphene fluoride, chemically modified graphene, scanning tunneling microscopy, scanning tunneling spectroscopy, hafnium diboride, sputter erosion sharpening, field-directed sputter sharpening
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign