Contact AFM
Optimization of Scanning Parameters
Rev. D
Dimension 3100 Manual
127
Note:
The smaller end radius of etched silicon tips creates greater force between the
tip and sample. Therefore, etched silicon tips are not suggested for soft
samples.
8.3
Optimization of Scanning Parameters
Careful selection of scan parameters is important in the successful application of Contact Mode
AFM. In most cases, optimal parameter selection depends on the sample. It is beneficial to
experiment with a range of values within each parameter, however, please review discussions of the
scan parameters in the Realtime control panels in the
Command Reference Manual
before making
bold changes. The following section analyzes the effects of the most important parameters.
8.3.1 Data Type
Data type
is the first parameter set because the settings of other parameters depend on it. The
Data
type
parameter in the
Channel
control panels selects the type of data collected by the system.
Height
data corresponds to the change in piezo height needed to keep the cantilever deflection
constant.
Deflection
data comes from the differential signal off of the top and bottom photodiode
segments relative to the
Deflection Setpoint
.
The scan parameters required to collect accurate height data are different from the optimal
parameters for deflection data. To collect height data, the feedback gains must be high so that the tip
tracks the sample surface with minimal cantilever deflection. The position of the piezo during the
scan reflects the height of the sample. To collect accurate topographical data, set the
Data type
parameter to
Height
. Topographical
Deflection
data is only reasonable on very smooth, flat
samples. Topograhpical
Deflection
data is used infrequently and only for high resolution work.
CAUTION:
Large offsets are not recommended between engage and disengage
(2 volts) with etched silicon cantilevers in Contact Mode AFM
(450µm long only) because breakage is likely.
ATTENTION:
Il est recommandé de ne pas utiliser de forts décentrements
pendant l’engagement et le désengagement des céramiques piézo-
électriques (2 V) avec des pointes en silicium (longueur: 450µm)
sous peine de destruction de celles-ci.
VORSICHT:
Wir empfehlen, im Kontakt-Modus mit den geätzten
Siliziumspitzen (nur mit den 450µm langen) keine großen Offsets
zwischen engage und disengage-Zustand (2 Volt) zu haben, da
diese sonst leicht brechen könnten.
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