Raman spectroscopy of undoped and doped single crystal C60

Abstract

Summary form only given. We present high resolution Raman spectra of undoped single crystals at low temperatures using laser exitations in the red and green spectral range. A splitting of the H/sub g/ modes in A/sub g/, E/sub g/ and F/sub g/ modes was found. A maximum of 8 splitted components could be observed. The doping of the single crystals with potassium was performed at temperatures slightly above room temperature and the doping process was studied by using in-situ Raman spectroscopy. Up to the penetration depth of the laser homogeneous single phases of K/sub 1/ C/sub 60/ and K/sub 3/C/sub 60/ could be obtained. The doped phases were identified by the position of the A/sub g/ pinch mode, which is very sensitive relative to the charge transfer. At cooling the high temperature phase K/sub 1/C/sub 60/ was observed to undergo a sharp transition into C/sub 60/ and K/sub 3/C/sub 60/ between 430 K and 410 K. In addition temperature dependent Raman measurements were performed on single phase K/sub 3/C/sub 60/. At liquid nitrogen temperature an unexpected strong splitting and selective line broadening of the H/sub g/ modes was observed.