24
The sample holder is now moved towards the tip with the help of the piezo
motor, until the tunneling current entered under ‘SetPoint’ is detected. Now
the distance between sample and tip is controlled by the feedback loop. If
the approach was successful, the LED on the scan head changes from or-
ange to green and the message box ‘Approach done’ appears.
- Click the ‘OK’-button.
Now the set tunneling current is flowing between tip and sample.
When the LED changes to red instead of green, the sample has ‘crashed’
into the tip, and the tip has to be cut again. (See chapter Problems and
Solutions).
Start measurement
When the tunneling current defined by ‘SetPoint’ is flowing between tip
and sample (LED green) you can start measuring:
- Click
in the ‘Scan Panel’ to maximize the range of the scan.
- Start measuring by clicking
in the ‘Scan Panel’.
If the preparation of tip and sample, and the approach were successful,
images of the measurement will show a line in the ‘LineView’ (figure start-
ing picture, left) and a plane in the ‘TopView’. Watch the displays for a while
until the ‘TopView’-image has been drawn about three times.
A ‘nervous’ line in the ‘LineView’ indicates a bad tunneling contact (figure
starting picture, right). Usually this is caused by the tip being too blunt or
instable. This means that you should stop measuring and cut a new tip:
- Click
and follow the instructions of the chapter Problems and Solu-
tions.
F
IRST
M
EASUREMENTS
S
TART
MEASUREMENT
Summary of Contents for easyScan E-STM
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