Dimension Icon SPM Scanner

The preamp board contains a preamplifier circuit for both photodetector signals, a laser diode power supply circuit that regulates the output of the laser, and a sensor preamplifier. The head is connected to a 48-pin male connector cable plugged into the socket on the front right of the Dimension Icon microscope.

A kinematic tilt stage positions the laser beam on the cantilever. The tilt stage consists of the laser diode, collimator, focusing lens, base plate, and the X and Y laser diode adjustment knobs. The X laser diode adjustment knob moves the beam parallel to the major axis of the cantilever substrate. The Y laser diode adjustment knob moves the beam perpendicular to the major axis of the cantilever substrate. See Align the Laser for more information on using the alignment knobs.

The four elements of the quad photodetector combine to provide different information depending on the operating mode. In all modes the four elements combine to form the SUM signalThe sum of all four photodetector quadrants (A+B+C+D); indicates how much laser power is reaching the detector. Reflective cantilevers have a higher SUM signal than non-reflective cantilevers. The first step of aligning the laser is to ensure that there is sufficient SUM signal measured from the detector.. The amplified differential signal between the two top elements and the two bottom elements provides a measure of the deflection of the cantilever. This differential signal is used in Contact AFM and TappingMode AFM. Similarly, the amplified differential signal between the sum of the two left photodiodes and the sum of the two right photodiodes provides a measure of the torsion in the cantilever, used in Lateral Force Mode and Torsional Resonance Mode Microscopy.

An adjustable mirror positions the reflected laser spot relative to the four photodetector elements using a kinematic mount and the photodetector mirror adjustment knobs. The photodetector mirror adjustment knobs assist the user in adjusting the position of the mirror to maximize the SUM signalThe sum of all four photodetector quadrants (A+B+C+D); indicates how much laser power is reaching the detector. Reflective cantilevers have a higher SUM signal than non-reflective cantilevers. The first step of aligning the laser is to ensure that there is sufficient SUM signal measured from the detector. and set the deflection signals.

The beamsplitter diverts some of the laser light directed towards the photodetector toward the Laser Spot Detector Screen. This screen provides a visual indication of the condition of the reflected spot and its position relative to the photodetector.

The electrodes used on the scanner piezo tube in the Dimension Icon scanner are oriented as shown when viewing the Dimension Icon microscope from the front:

The end of the scanner allows easy removal of the imaging probe assembly. This permits loading the tip on a separate fixture, called the probe holder (see Dimension Scanner Probe Holders for details).

See Piezoelectric Scanners for more information about the scanner and how it works.