Carbon nanotubes were produced by catalytic decomposition of acetylene over a supported transition metal catalyst[3,4]. STM samples have been prepared[5] by ultrasonication of nanotube containing material purified from the catalyst.
In Fig. 1. the STM image and the
corresponding line cut are shown for a carbon
nanotube placed over other carbon nanotubes stacked in a regular
way, i. e. on a ''raft''.
Ratio of
measured half width, HW, to measured height, h, is
close to unity.
This means that an apparent broadening, (defined as B = 2 HW / h),
by a factor of 2.18 is present in the image.
Figure 1:
STM measurement on a carbon nanotube placed on other nanotubes:
a) constant current image of a ''raft'' of carbon nanotubes,
, 
;
b) line cut marked in the image is taken
through a tube well separated from other tubes.
HW/h ratio is close to unity.
In Fig. 2., we show an STM image acquired over a
nanotube on HOPG. Apparent broadening
from comparison of HW with h is B = 3.24.
If one
takes in account that the nanotube floats over the support at a
height of 
,then the corrected broadening BC is:
BC = 2.85 for nanotube over the raft, and BC = 4.29 for
nanotube over HOPG.
Figure 2:
STM measurement on a carbon nanotube placed on graphite:
a) constant current image of individual nanotubes (A and C)
and of a ''raft'' (B) composed of four nanotubes,
, 
;
b) line cut marked in the image is taken
through object A. HW/h ratio is 3.24.