Ly. Li et al., Quantitative measurements of frictional properties of n-alkanethiols on Au(111) by scanning force microscopy, J PHYS CH B, 103(39), 1999, pp. 8290-8295
We present a quantitative study of the frictional properties of self-assemb
led alkanethiol monolayers on Au-(111) as a function of chain length using
scanning force microscope, The lateral and normal forces are calibrated in
situ using a combination of the two-slope method proposed by Ogletree ct al
, and the added mass method proposed by Cleveland er nl. The comparative st
udy of the same system by another calibrated Si3N4 tip was carried out. The
friction coefficients for the same alkanethiol system, but with different
tips, differ by less than 15%, indicating the reliability of nanoscale fric
tional and normal force measurements using a scanning force microscope. An
in situ experimental force calibration for each cantilever is needed in old
er to perform absolute force measurements. Our results also show that frict
ional fords depend strongly on the number of carbon atoms in the alkane cha
in. The friction coefficient of alkanethiol decreases as the chain length i
ncreases and is lower than that of a bare Au(lll) surface.