５
MEASUREMENT OPERATION
TMPM5200-2
5-155
a.
•
He
•
So
us
This system executes capacitance compensation in such a way that when the
is 0 nA. Therefore, specify the Low and High
Specify the voltage at which to measure I-V.
re, assume that the I-V measurement range is to be from –1.0 V to +1.0 V.
, Enter –1.000 in Low Voltage/V and 1.000 in the High Voltage/V input box
ing the keyboard.
input voltage is 0 V, the current
Voltages so that they encompass 0 V.
b.
Click on the
button in the Source selection box on the SPS Parameters
window, and then select Linear current from the pull-down menu.
c.
Click on the
button in the Preamp Gain selection box on the SPS
hanges to “ ”.
g direction of the bias voltage for I-V
measurement. If Auto is selected, scanning is performed from a voltage near the
voltage specified for Bias/V on the SPM Parameters window.
Suppose that Bias/V is set to 1.0 V, and Low Voltage/V to –1.0 V and High Volt-
age/V to 1.0 V.
If Auto is selected, the scanning will be performed from +1.0 V to –1.0 V.
If Up is selected, the scanning will be performed from –1.0 V to +1.0 V regardless
of the value specified for Bias/V.
If Down is selected, the scanning will be performed from +1.0 V to –1.0 V regard-
less of the value specified for Bias/V.
e.
Click on the
Parameters window, and then select 1.00 V/nA from the pull-down menu.
This value determines the preamplifier gain for I-V measurement. If the measured
current gets saturated, decrease the gain.
d.
Select Auto by clicking on the radio button for Ramp Direction; then the
button c
Ramp Direction determines the scannin
button in the No to Average selection box and select 1 from
the pull-down menu.
This specifies the number of I-V measurements for data averaging. Increase the
number particularly when data is noisy or when a current to measure is very
small.
f.
Click on the
button in the SPS Mode selection box and select I—V from
the pull-down menu.
The I–V measurement is set to the specified SPS mode.
4.
Observe an STM image by performing the operations.
Since a CITS image is scanned in a range of 128
×
128 pixels, specify 128
×
128
for STM observation, too, and confirm that you can obtain a quality image.
5.
Click on the
button in the Acquisition selection box on the Scan frame in
the SPM Parameters window and then select SPS Mapping from the
pull-down menu.
6.
Click on the Repeat button in the SPM Parameters window.
The acquired CITS images will be displayed on the Display Window.
CITS images are displayed on one screen with divided frames. During scanning,
the imaging on each divided frame progresses simultaneously in real time.
Watch the progressing images on the screen, and if you are satisfied with the
quality of the images, grab the images before the present frame scan is com-
pleted. Otherwise, the next frame scan starts automatically without storing the
data when the present scan finishes.
