We report the design of several symmetric star-shaped closed carbon cages using ball and stick models. Despite the presence of seven- and eight-membered rings, these hollow carbon sprockets—containing less than 500 carbon atoms—are predicted to be more energetically stable than C60. Also, we show that these sprockets can be connected to capped fullerene tubules to form a nanostructure similar to a mechanical gear and shaft. In addition, using molecular dynamics and a reactive hydrocarbon potential, we show that these gears can be turned against each other at high angular velocities without large deformations. These nanogears illustrate some of the possible complex small structures that can be formed by inserting 5-, 7-, and 8-membered rings in an otherwise graphitic network. These nanogears also show surprisingly robust mechanical properties.

The effects of C60 molecular orientation and rotation on the electronic structure of fcc C60 solid have been investigated by performing a band structure calculation with self-consistent mixed-basis all electron and full-potential approach within local density approximation. We present an angle-dependent density of states of HOMO and LUMO bands, which should be compared to the angle-resolved photoemission data.

C50 films, are deposited on Si(111) substrates using neutral cluster beams of fullerenes generated from a crucible with a special nozzle. X-ray diffraction (XRD) have been used to investigate the structural properties of C50 films, which indicate highly textural films as close-packed structure with strong (110) XRD assignment and 400Å for correlation length. Raman spectrum indicates the existence of stable C60 films. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) measurements are carried out to analyze the electronic properties of the films. The resistivity to contamination of C50 film deposited here is better than that deposited by MBE. Different kinds of oxygen contamination on the surfaces of C50 films and HDPG are detected by the results of O 1s XPS analyses.

The superconducting properties of several binary and ternary fullerene compounds are investigated by means of ac susceptibility technique. The susceptibility X = X'-iX” is observed as a function of temperature for different magnetic field amplitudes (0.01 G - 20 G). The samples are characterized by X-ray diffraction (XRD) analysis and the fcc-lattice constants a0 are determined. Furthermore the influence of the preparation procedure, especially the treatment of the C60 starting material on the superconducting properties is discussed.

Ytterbium doped C60 (YbxC60) has been synthesized through the use of a liquid ammonia intercalation route. This allows for precise control of the stoichiometric composition. Magnetization data were taken in fields up to 1 Tesla and temperatures between 5 and 300 K on samples with 1≤X≤5. We find the ytterbium introduces significant anisotropies into the system which give rise to long time magnetic relaxation effects that persist to high temperatures. We suggest the existence of an amorphous structure to explain the results.

We have produced bundles of nanotubes by vapor-phase condensation of carbon on highly-oriented pyrolytic graphite (HOPG). The bundles are found to have widths between 15 nm and 50 nm, and up to 200 nm long. They are composed of concentric tubules with 2-4 nm in diameter. Atomic resolution STM images reveal their graphitic surface structure.

Buckytubes are considered for high current density cold field emitter array electron sources. They may provide more stable, higher-brightness emission than existing cold field emitter arrays.

We have in-situ measured the density of states (DOS) around the top of valence band of pristine C60 films by means of total yield photoelectron spectroscopy. The top of valence band (TVB) of C60 was located at 5.00eV below the vacuum level. Considerable amplitude of gap states was observed up to 0.9eV above the TVB. Kelvin probe method revealed that the Fermi level of amorphous C60 film was located at 0.47eV above the TVB. The improvement of crystallinity in C60 films, which induced the increase in electrical conductivity as well, increased the DOS above the TVB. The electric conduction of C60 films cannot be explained with a simple picture for carrier conduction in semiconductors.

O'Keefe, Ross, and Baronavski, using laser vaporization of graphite and time-of-flight mass spectrometric detection have observed enhanced abundances of C+N cluster ions not only for n=50 and 60 but also for N = 44. Stimulated by this experimental result we have carried out a search for unusually stable C44 fullerene isomers. In this search, all possible 87 fullerene isomers of C44 were first generated and then classified according to the number of bonds, p, shared by abutting pentagons. We found that for C44 the minimum value of p is 8 and that there are only two C44 fullerenes with this value of p. Self-consistent geometry optimized calculations at the AM1 level show that these two special C44 fullerene isomers—although differing from one another by only about 0.1 eV in total energy—are over 1.0 eV more stable than any of the other possible 85 fullerene isomers of C44. These self-consistent-field calculations not only single out these two C44 fullerenes for special attention, but also further confirm the instability of abutting pentagons for lower fullerenes (those fullerenes with less than 60 carbon atoms).

We report here on the structural properties of carbon nanotubes prepared by contact arc-discharge at low helium pressure of 100 torr. In contrast to the conventional arcdischarge, the contact discharge reduces the gap between the electrodes to a minimum value while still maintaining a plasma. The resulting carbonaceous deposit on the cathode surface, with the contact discharge operating under 100 torr helium atmosphere, contains the columnar structures with high density carbon nanotubes. These columnar structures are several millimeters in length, much longer than those generated under the conventional arc-discharge. These experimental results reveal that reducing the gap adds greater stability to the arc-discharge and establishes conditions that favor high-density nanotube growth under a low helium pressure.

The amphiphilic fullerene derivative (1-aza-18-crown-6)-hydrofullerene-60 (C60-1A18C6, 1) exhibits improved Langmuir and Langmuir-Blodgett (LB) film forming properties and the resulting LB films exhibit a nonlinear second order susceptibility, X(2)pp of 3.2 pm/V, the highest yet reported for a fullerene or fullerene derivative.

The X-band PLDMR of C70 films and C70 molecules isolated in a toluene/polystyrene glass matrix (C70:T/PS) is described. The PLDMR of C70:T/PS strikingly differs from that observed in C60:T/PS due to much longer triplet lifetimes. The PLDMR of C70 films indicates that the delocalized triplet is distorted by intermolecular interactions and shows a half-field resonance due to triplet-triplet fusion. In addition, a broader powder pattern and a narrow enhancing line at g=2.0029 are observed. The former is attributed to a localized triplet exciton of size similar to a 5- or 6-membered ring. The latter is believed to result from enhanced polaron recombination. The PLDMR of oxidized and photopolymerized films quenches the localized triplet and reveals the possibility of an even more delocalized exciton.

We present results from a detailed study of photoconductivity in thin C60 films. It is shown that the generation of mobile charge carriers involves molecular electronic transitions coupled to molecular vibrations. The vibrational bands broaden with temperature and shift at the fcc-to-scphase transition. For excitations with energy below ∼1.8 eV photoconduction appears to involve a tail of defect states whose distribution is somewhat dependent on sample preparation.

Ionic metal-fullerene adducts C60M ( M = Li+, Mg2+, Ca2+, Sr2+, Ba2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, A13+ Ag+, Ce3+ ) are synthesized by reaction of watersoluble C60Lin with metal salt. 13C NMR of C60Li in D20 gives a sharp peak at 171.44 ppm which is much higher than the chemical shift of C60 in benzene ( 142.98 ppm ). Elemental analysis suggests the state of C60 in the adducts is C605-. ESR spectra of the adducts show a strong narrow peak at 9=2.001. UV-Vis and IR spectra of those adducts are completely different from those of C60. Magnetic measurement indicates that C60Li, C60Ce are antiferromagnetism and C60Fe adducts is ferromagnetism in the range of 150–300 K. But C60Fe adduct becomes paramagnetism when temperature is lower than 150 K. Mossbauer spectroscopy indicates Fe3+ in C60Fe adduct is Fe3+ (I.S.=0.30 mm/s, Q.S.=0.67 mm/s). The experimental results strongly suggest that C605- is a stable single free radical polyanion of fullerene which is a weak acid radical and possesses the similar properties with general inorganic anion. This is the first report on the synthesis and properties of air-stable and water-soluble polyanion of fullerene( C605-). A method for preparing metal-fullerene adducts has been developed, and many unusual properties of the adducts are found.

Among the various low pressure techniques being developed for the synthesis of diamond films and bulk diamond slabs the combustion flame synthesis process has some distinct advantages. In this approach the combustion reaction between acetylene and oxygen is utilized to generate the requisite energy to activate excess acetylene in the gas mix leading to the deposition of diamond films on a temperature controlled substrate brought into contact with the flame. Other diamond synthesis approaches, such as microwave enhanced and the filament assisted chemical vapor deposition processes, and the various arc jet techniques utilize mixtures of hydrogen and methane as the process gases. Oxygen and oxidizing specie ( such as OH radicals) in the flame ambient may be much more effective than atomic hydrogen in promoting the growth of diamond over the growth of graphite and other non- diamond forms of carbon. In addition this technique enables the growth of diamond at high rates and is relatively easily scaled for large area synthesis. In this paper a discussion of this technique is presented drawing upon recent research by the authors as well as published work to present a general discussion of the issues involved in the development of this technique of low pressure diamond synthesis.

The nucleation of independent diamond crystals can occur through graphitic, sp2, intermediates. Evidence from several sources indicates that diamond growth may take place through sp2 surface layers. Steady state analysis of simple reaction networks leads to expressions for the diamond growth rates, the concentration of sp2 impurities in the diamond, and for the nucleation rate of new crystals.

By control of deposition conditions, the morphologies of vapor-deposited polycrystalline diamond films may be varied deliberately from clean multi-micron crystallites to nanocrystalline ‘cauliflower’ nodules. Most attempts to connect diamond film ‘quality’ to growth conditions focus on competitive growth of non-diamond phases. In contrast, we propose that twinning is potentially the dominant factor. We develop a geometric parameterization of growth conditions to define conditions under which a common type of twin - the < 111> penetration twin - can outgrow and potentially bury the parent face on which it originated. We then show how the full range of CVD diamond crystal and film morphologies might be explained entirely in terms of penetration twins. This explanation does not entail reference to the actual mechanism of diamond growth. The geometric parameterization also suggests a ‘reactor map’ which serves as a powerful tool in process development and control.

This research investigates the growth of diamond thin films using an enclosed oxyacetylene torch. Using statistical experimental design, we have systematically explored the parameter space to construct maps of nucleation density, film quality, and growth rate as functions of growth conditions. The deposition process is divided into nucleation enhancement and growth, and each step is optimized separately. In the study of the nucleation enhancement, we vary R = O2/C2H2, substrate-flame distance (z), and pretreatment time and determine the nucleation density and nucleation uniformity using electron microscopy. For the growth study, the variables are R, z, and substrate temperature, and we employ two different Raman scattering measurements to assess film quality. In one case, we determine a quality ratio β = diamond peak/(diamond peak + nondiamond peak); the second indicator is the luminescence determined from the baseline of the spectrum. In the growth study, the best film quality is comparable to the best films grown in an atmospheric flame in which R is cycled. We also find that the growth rate is a factor of 10 less than in the atmospheric flame.

Three methods recently proposed for enhancing the nucleation density of thin film diamond on non-diamond surfaces during microwave plasma assisted chemical vapor deposition are investigated. The results of a series of nucleation and growth studies utilizing a dc biasing technique, carbon cluster (C70) thin film overlayers, and thin film metal (Fe) overlayers for diamond nucleation enhancement are presented. The influence of the substrate and plasma processing parameters under which the above nucleation enhancement effects occur has been determined for the three respective techniques.

In the present study, the new system used C3F8 and H2 as source gases. Filament-assisted chemical vapor deposition was utilized. Continuous diamond films were grown on the Si and Mo substrates without any surface pretreatment. The results of scanning electron microscopy, Raman spectroscopy, X-ray diffraction, and atomic force microscopy measurements indicate that the films deposited on the Mo substrates are of high quality. Homoepitaxial diamond films were grown on the high pressure synthetic single crystal diamond substrates. The results show that in our experimental conditions epitaxial films were easily grown on the (111) synthetic diamond substrates and sometimes epitaxial filmse also grown on the (100) synthetic diamond substrates.