Chemistry Reference
In-Depth Information
Fig. 7.8 a and b Averaged
I-V curves (dashed red curve,
left scale) and d
2
I/dV
2
spectra
(solid blue curve, right scale)
measured over an OD and
OH, respectively. The inset
shows fractional occupation
of the high-current state for
an OD measured as a function
of bias voltage. The tip height
was fixed at V
s
= 24 mV and
I
t
= 5 nA during the
measurements. The I-
V curves are average of 300
and 200 scans for OD and
OH, respectively, to improve
the S/N ratio. The d
2
I/dV
2
spectra were measured using
a lock-in amplifier with an
rms modulation of 6 mV at
590 Hz
which gives a larger tip-molecule distance, the ratio between the high and low
current states is changed; the ratio becomes smaller (the high current state lives
longer). Although the quantitative description of this kind perturbation is still open
question, the same tendency is clearly observed in Co atom hopping on Cu(111),
where Co atom is also bounds to a double-well potential [
17
].
7.2.3 STM-IETS of a Hydroxyl Group on Cu(110)
The averaged I-V curves (red dashed lines) and the IET spectra (blue solid lines) for
an OD and OH are shown in Fig.
7.8
, which are measured with fixed the tip at the
one depression of the STM image (indicated by asterisk in the inset image of
Fig.
7.8
a). The gap conditions during the measurement and the modulation voltage
of the IETS are described in the caption. In order to exclude the influence of the
substrate and tip, both the IET spectra and I-V curves are displayed after subtraction
