JEOL JSPM-5200 Instructions Manual page 221

５ MEASUREMENT OPERATION
■ Drift Compensation
Sample thermal drift, no matter how small, poses a problem in continuous measurement
at the atomic level under ultra high vacuum, as this is a procedure which requires a
highly stable field of view. The Drift Control window is used to correct such drift as
occurs in the measurement image due to therm
correction is done by shifting the center point of the scanning area in the same direction
and through exactly the same distance as the drift, at the end of the scan. To implement
drift compensation, therefore, it is necessary to carry out preparatory steps (to obtain the
drift speed and direction).
In drift compensation, the amount of drift per unit of time is calculated from the distance
between a certain point observed when you scan the field of view first and the same point
observed when you scan it second. Each time the measurement ends, the field of view is
shifted automatically by the inverse amount of drift corresponding to the elapsed time.
The procedure for drift compensation is as follows.
1.
Click on the Advanced button in the Advanced tab window before starting
measurement. And select the Scan tab in the Advanced Control window that
appears.
Drift compensation uses the parameters in the Drift Control box in the Scan tab
window.
2.
Observe the first image an
Select a feature (a place such as a bright point or a hole that may indicate a defect)
in the image.
3.
Click on Set Drift Point to specify the first reference point.
The mouse cursor changes to the + mark; so specify the part of the measurement
image that you selected in advance.
4.
Observe the second image and grab it.
Confirm that the acquired image includes the selected feature.
5.
Click
Just as you selected the first feature point, specify the same feature in the second
image
calculated from the elapsed time and from the distance between the points in the
first and second images.
6.
Select Enable Correction.
Drift compensation begins.
You can specify the point up to three im
specify a third point, observe a third image and specify the point in it.
5-158
on Set Drift Point to specify th
(it has drifted to a different position). The drift speed and direction are
al or, sometimes, other causes. Drift
d grab it.
e second reference point.
ages for drift calculation. When you want to
TMPM5200-2