SCANNING FORCE MICROSCOPY STUDY OF PATTERNED MONOLAYERS OF ALKANETHIOLS ON GOLD - IMPORTANCE OF TIP-SAMPLE CONTACT AREA IN INTERPRETING FORCE MODULATION AND FRICTION FORCE MICROSCOPY IMAGES
G. Bar et al., SCANNING FORCE MICROSCOPY STUDY OF PATTERNED MONOLAYERS OF ALKANETHIOLS ON GOLD - IMPORTANCE OF TIP-SAMPLE CONTACT AREA IN INTERPRETING FORCE MODULATION AND FRICTION FORCE MICROSCOPY IMAGES, Langmuir, 13(3), 1997, pp. 373-377
Several patterned monolayers of alkanethiols CH3(CH2)(n-1)SH on a poly
crystalline Au substrate were prepared by using microcontact printing
and solution deposition methods, and their surfaces were examined by I
R spectroscopy, scanning force microscopy, lateral force microscopy (L
FM), and force modulation microscopy(FMM). Our work Shows that LFM and
FMM can detect differences in packing density of chemically identical
molecules which are too small to be detected by IR, ellipsometry, and
wetting measurements and suggests that the tip-sample contact area is
an important parameter governing the contrasts of LFM and FMM images.
Stiffness images obtained with FMM depend on changes in the Young's m
odulus of a sample surface as well as in the tip-sample contact area.
As a result, a surface region of small modulus can have a large stiffn
ess due to its large contact area.