Kl. Akers et M. Moskovits, RAMAN-SPECTRA AND ELECTRICAL-RESISTIVITY MEASUREMENTS OF KXC60 (X=0,3AND 6) THIN-FILMS, Journal of electron spectroscopy and related phenomena, 64-5, 1993, pp. 871-876
We report the Raman spectroscopy and resistivity of C, films as a func
tion of exposure to potassium vapour. Thin films of C-60 are prepared
under UHV conditions using a resistively heated effusive beam source (
400 - 450 degrees C). Stepwise dosing of the C-60 film with potassium
results in the formation of mixtures of the three phases: C-60, K3C60
and K6C60. Subsequent addition of C-60 returns the film to a prior com
position. Our spectra indicate a granular solid film with spots of var
ying composition; No evidence is found of a K4C60, phase. As a functio
n of potassium dosing the resistivity decreases steadily to a minimum
value of 0.0092 ohm-cm, characteristic of K3C60, and then increases st
eadily to a final intermediate value which changed little with further
addition of potassium. We also report surface enhanced Raman spectros
copy (SERS) spectra of C-60 on rough silver films with and without exp
osure to potassium vapour. We do not observe a K3C60 phase on rough si
lver films; however there is a small red shift of the pentagonal pinch
mode upon exposure to potassium vapour in addition to a large red shi
ft induced by the rough silver film.