Oxford Instruments Cypher SPM, Руководство пользователя

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Cypher SPM
User Guide
Current Offset
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There are often small, persistent current offsets associated with the AFM electronics that
must be subtracted. Zero the Current Offset by pressing the Zero button in the AR Do IV
Panel.
Applying Voltage
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Like the current, there are also often small, persistent voltage offsets between the AFM and
the sample. These will need to be zeroed as well, however this is done manually with a volt-
meter. It is best to measure the voltage between the “PogoOut” bias wire coming from the
cantilever holdersample puck and the cantilever holder clip. Enter the opposite value meas-
ured in to the S. Voltage Offset parameter. A typically offset is between 10-100mV.
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Sample bias for ORCA experiments can be set with the Sample Voltage parameter on the
DoIV panel.
When you first engage on the sample, you should start with a light contact force or low Setpoint,
but may find that you will have to slowly increase the force. This will reduce the tip-sample contact
resistance until the dominant resistance is the spreading resistance from the tip, rather than the
contact resistance. Typical deflections for conductive AC240 based cantilevers, or other similar can-
tilevers with spring constants around 2.5 N/m are 0.2-0.3 V. For cantilevers with spring constants of
20-40 N/m, deflections of less than 0.1-0.15 V are typical. For contact mode based probes with less
than 0.1 N/m, deflections should be 1 V or above.
Once you begin the image in Contact mode, begin raising the Sample Voltage until you see a cur-
rent response from your sample. You may need to, once again, readjust the Deflection at this
point.
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