The semi-closed nature of the hot-wall-epitaxy reactor provides a growth regime at high vapour pressures without loss of source material and offers the possibility to dope the epilayers or to form compounds during growth. The successful growth of C60 epilayers was further improved by a post-growth in-situ annealing process. In a series of experiments, the annealing time and temperature were varied between 10 and 60 minutes and 120°C and 220°C, respectively. The crystalline quality was analysed by high resolution X-ray diffraction and X-ray pole figure studies which showed an FWHM of the (111) reflex of 140 arcsec.
Additional single crystal BaxC60 epilayers have been grown on (100) surfaces of cleaved mica by hot-wall epitaxy. The Ba doping material and C60 were evaporated from independent sources at different Ba source temperatures to form BaxC60 with different x values. The growth rate was mainly controlled by changing the Ba source temperature in the range of 470°C to 750°C and varied between 0.22 A/s and 31 A/s. A special wiring in the growth chamber allowed an in-situ measurement of the electrical properties of the BaxC60 during and after growth without breaking the vacuum. The installation of a permanent magnet with a B field of 0.43 Tesla made it possible to obtain from Hall effect measurements the type and concentration of carriers in the BaxC60 epilayers as a function of the Ba content as well as the surprisingly high mobility of 6 x 103
cm2/Vs at a carrier concentration of n = 2 x 1018cm3.
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