Transport measurements in intercalated graphite and fullerene compounds

Miscellaneous · Wed Jan 01 00:00:00 EST 1992

OSTI ID:6981488

Vittorio, S.L. di.

THe author has investigated the transport properties of fluorine-intercalated vapor-grown graphite fibers with concentrations spanning the range C[sub 2.9]F to C[sub 6.6]F, corresponding to stage I and stage II samples. The samples were characterized by X-ray diffraction, weight uptake measurements and X-ray Photo-electron Spectroscopy (XPS). Among all Graphite Intercalation Compounds (GIC), fluorine is unique in that intercalation introduces a large disorder into the very ordered pristine graphene planes. Intercalation with an acceptor compound increases the anisotropy of the conductivity. Therefore, dilute samples exhibit weak localization and carrier-carrier interaction effects typical of a two-dimensional disordered metal. As the fluorine concentration increases, the bonding between fluorine and carbons shifts from ionic to covalent, which reduces the carrier concentration, resulting in a metal-insulator transition and strong localization. Magnetotransport at low temperatures (0.5K-30K) has been used to investigate the effect of disorder on the electronic properties of both metallic and semiconducting two-dimensional solids. The disorder present in the fluorine GICs was characterized by Transmission Electron Microscopy (TEM) as well as Electronic Spin Resonance (ESR). The distribution of fluorine throughout the graphene layers is inhomogeneous, with the formation of both dilute and concentrated islands. The bonding between carbon and fluorine is predominantly ionic within the dilute islands, whereas the concentrated islands contain mostly localized electrons. Another feature is the waviness of the graphene planes, which increases with increasing fluorine concentration. The disorder is explained by a model of nucleation of a covalent fluorine phase within the ionic matrix at high fluorine concentration. The last chapter describes the intercalation of C[sub 60] with Rubidium, and an Electron Spin Resonance study of the various Rb[sub x]C[sub 60] samples prepared.

• Research Organization: Massachusetts Inst. of Tech., Cambridge, MA (United States)
• OSTI ID: 6981488
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CARBON FLUORIDES
ELECTRICAL PROPERTIES
FLUORINE
ATOM TRANSPORT
FULLERENES
GRAPHITE
CARBON FIBERS
CHEMICAL BONDS
CLATHRATES
ORDER-DISORDER TRANSFORMATIONS
RUBIDIUM
RUBIDIUM CARBIDES
ALKALI METAL COMPOUNDS
ALKALI METALS
CARBIDES
CARBON
CARBON COMPOUNDS
ELEMENTAL MINERALS
ELEMENTS
FIBERS
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
HALOGENS
METALS
MINERALS
NEUTRAL-PARTICLE TRANSPORT
NONMETALS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
RADIATION TRANSPORT
RUBIDIUM COMPOUNDS
360606* - Other Materials- Physical Properties- (1992-)
360602 - Other Materials- Structure & Phase Studies