A DOUBLE-TEMPERATURE-GRADIENT TECHNIQUE FOR THE GROWTH OF SINGLE-CRYSTAL FULLERITES FROM THE VAPOR-PHASE

Fullerite single crystals were prepared by a sublimation-condensation method in a closed evacuated glass tube situated in a double-temperature-gradient furnace. Crystals of various size and up to 9 mg weight with well expressed smooth and shiny faces were obtained. X-ray analysis, interfacial angle measurements and observed morphological habits of selected crystals of C60 confirm the theoretically predicted and experimentally well established fcc structure at room temperature with two types of morphological faces, namely {111} and {100}. A strong tendency to twinning was observed. In the case of C70 crystals, a pure fcc structure was observed. Information on growth kinetics and on instability versus exposure to air and light were obtained from surface studies. Characteristic changes in a thin surface layer were observed when crystals were exposed to air and light. A new phase of C60 stabilized by oxygen was characterized.