28 ANALYTICAL AND LABORATORY EQUIPMENT
Fig. 2. Easy integration of the piezo scanner in a modular microscopy system from WITec, which makes it possible to combine a confocal Raman microscope with atomic force microscopy (AFM).
the measurement, a complete Raman spectrum is recorded for each pixel. Tese Raman spectra are like a specific fingerprint for each type of molecule, so that the chemical components of a sample can be identified for each pixel and their distribution in the sample can be displayed.
Te scanning stage used for the sample positioning is designed for working distances of 100 or 200µm in the axes of the
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scanning plane and 20µm in the direction of the Z axis. Position resolution is better than 2nm.
With the AFM method, a measuring tip is moved over the sample surface line by line in a defined grid. It measures the forces between a pointed measuring tip and the surface of the object. It gives information on the topography of the surface at a lateral resolution capacity of 10nm.
Since the distance between the measuring tip and the surface has to be kept constant, the position of the sample must be readjusted in the Z direction. Tis task is performed by the scanning stage. Te variation of the Z position together with the relevant X and Y coordinates for the spatial resolution then provides the high-precision topography information on the samples. Te AFM and Raman images are recorded in succession and then
superimposed and related to one another.
Precise positioning in all three axes and path accuracy during the scan are indispensable for achieving high-quality images.
For more information ✔ at
www.scientistlive.com/eurolab
Gernot Hamann is business development manager for microscopy at PI (Physik Instrumente), based in Karlsruhe, Germany.
www.pi.ws
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