Physical and Chemical Investigations of Selected Buckminsterfullerene-Based Materials

Studies of materials based on the molecule C _{60} have been performed in three complementary areas; namely, the reaction and passivation of aluminum with C_{60}, nanometer-scale materials engineering utilizing C _{60}, and the critical magnetic fields of superconducting rm K_3C _{60}. The majority of the C _{60} powder used in the investigations was produced in-house. Steps of the process for generating C_{60} from graphitic carbon are given. Fullerene-containing soot was generated in a modified plasma-arc reactor. Fullerenes were separated from soot using Soxhlet extraction. Lastly, C _{60} was separated from the other fullerenes using liquid chromatography. Experiments on the reaction of C_ {60} with aluminum were done on aluminum foils in ultra-high vacuum using Auger spectroscopy, temperature -programmed desorption, photoluminescence, and soft x-ray photoelectron spectroscopy. Strong bonding between C _{60} and aluminum is reported. Results show that when multilayer C_{60} is evaporated onto clean aluminum, all molecules except the monolayer in contact with the aluminum desorb when the sample is heated to 578 K. Photoelectron spectroscopy measurements indicate that electrons transfer from C _{60} to the aluminum at the interface. Additionally, the data may reveal that C_{60} molecules diffuse intact into the aluminum bulk when heating to the aluminum surface melting temperature occurs. The ease of preparing monolayer C_ {60} coverage on a surface by multilayer C_{60} evaporation followed by sublimation of all molecules but those in direct surface contact was examined for the preparation of multilayer and binding structures. The viability of the technique was not definitive. However, Fe/C_{60 }/Fe trilayers may show antiferromagnetic coupling and hence giant magnetoresistance at room temperature. Further, the use of C_{60} to bond metals to semiconductors is related. To resolve superconducting properties, an examination of rm K_3C_{60} was initiated. Most of the known superconducting fullerides are highly air sensitive making measurements complex. In order to overcome difficulties, a new method for synthesizing the samples was pioneered. Details of the synthesis and magnetic measurements are given. Critical fields and superconducting parameters derived from them are listed. Critical current trends are inferred from hysteresis data using the Bean model. Differences from the results of other researchers are addressed. Comparisons with electronic and phononic coupling theories are examined along with implications for the mechanism of superconductivity in this class of materials.