Atomic force microscopy (AFM) was applied to the precise thickness mea
surements of thin lamellae about 10 nm thick of polyethylene single cr
ystals which were grown from dilute solutions and precipitated on clea
ved mica. The obtained values agree well with the thickness determined
by small angle X-ray scattering. Moreover, AFM observation allowed de
termination of the thickness difference of several angstroms in the di
fferent growth sectors of small crystals about several mum wide. From
the measurements, it was concluded that the free energy of the fold su
rface in the {110} growth sector was 30% larger than the values in the
{100} sector. The larger surface free energy in the {110} sector mean
s higher fold energy in the growth sector.