Page 193 - Science at the nanoscale

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STM image (left) of C 60 molecular chains on self-assembled
Figure 8.22.
α-sexithiophene (6T) molecules on Ag(111). Right: Corresponding molec-
ular model (from author’s lab).
Tunnel
Z
Current
A
X
X
(a)
Z
A
Z
X
X
(b) 8.3. Scanning Probe Microscopy 183 ch08
Figure 8.23. Illustration of the (a) constant-height and (b) constant-
current modes of operation.
into a line plot or image reflecting the magnitude of the tunneling
current. In constant-current mode, the STM tip is rastered across
the XY plane with continuous adjustment of its Z-position such
that the tunneling current remains the same via a current feed-
back loop (Fig. 8.23(b)). In this case, the topographical contour of
the sample surface is generated by plotting the variation of the Z