Oxford Instruments Cypher SPM, Руководство пользователя

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Cypher SPM
User Guide
Some cantilevers are photothermally sensitive and provide large amplitudes, such as 100 nm,
even with the lowest filter cube (0.01x). Using a 1.00x filter cube on such a sensitive cantilever could
cause overheating and permanent damage to the lever.
It is always best to start with a low gain filter cube when testing a new type of cantilever. If the
desired amplitude is not attained with the 0.01x filter cube, you can scale the filter cube up to attain
the desired amplitude. Once the correct filter cube is defined for a particular cantilever, all can-
tilevers with the same model number are expected to achieve similar amplitudes (within a factor of
~2), such that the filter cube test can be avoided in future experiments.
Importantly, blueDrive has the best performance when the lowest filter cube required to attain the
desired amplitude is used. For example, it is better to use the 0.30x filter cube to drive the can-
tilever with 2 mW of drive amplitude, rather than using the 1.00x filter cube with 2 mW of drive
amplitude. Both of these filter cubes allow a drive amplitude of 2 mW; however, the 0.30x filter
cube has only 3 mW of DC light power at the cantilever, compared to 10 mW of DC light power for
the 1.00x filter cube. This means that the same cantilever amplitude is attained in both scenarios,
but using the 1.00x filter cube leads to roughly 3 times more heating of the cantilever.
Filter cube gain
factor DC power @
cantilever Max (AC) drive
amplitude Min (AC) drive
amplitude
1.00x 10 mW 9 mW 1 mW
0.30x 3 mW 2.7 mW 0.3 mW
0.10x 1 mW 0.9 mW 0.1 mW
0.03x 0.3 mW 0.27 mW 0.03 mW
0.01x 0.1 mW 0.09 mW 0 mW
The Minimium (AC) drive amplitude, which is fixed in software, is there to remind the user to switch
the filter cube to a lower value when requiring lower cantilever amplitudes, rather than simply turn-
ing down the drive amplitude electronically in the Tune panel.
The following figure explains why it is better to change filter cubes rather than lower the drive amp-
litude in the Tune panel. The AC and DC power of the blue light are illustrated with respect to chan-
ging the amplitude on the Tune panel (left graph) versus changing the filter cube (right graph). The
latter is the preferred option because it lowers the amount of blue light shining on the cantilever.
Page 133 of 243 16 blueDrive photothermal excitation