MICROSCOPY 63
shifted up or down. Te shift in energy gives information about the phonon modes in the system.
Scanning samples in a micro-
Raman system, however, suffers from several problems. As a sample is scanned, even a very flat sample, it is hard to keep the distance of the lens to the
sample constant. Tus, as one goes from pixel to pixel under the lens of a Raman, a mixture of sample and air is sampled in the voxel (volumetric picture element) that is illuminated. Tis causes intensity variations in the Raman that are unrelated to the chemical composition of the sample and are artifactual. Tis is even more pronounced with rough samples and standard methods of auto-focus are simply not accurate enough for a whole host of problems that are being investigated today.
Te atomic force microscope, being a very high-resolution type of scanning probe microscope, has demonstrated resolution of fractions of a nanometer, making it one of the foremost tools for imaging, measuring and manipulating matter at the nano-scale. Te information is gathered by ‘feeling’ the surface with a mechanical probe. .
Fig. 2. Nanonics MultiView 4000 MultiProbe System for scanning probe microscopy permits full integration with optical techniques such as Raman using Negative- Stiffness vibration isolation.
Te AFM consists of a micro-
scale cantilever with a sharp tip (probe) at its end that is used to scan the specimen surface. Te cantilever is typically silicon or silicon nitride with a tip radius of curvature on the order of nanometers. When the tip is brought into proximity of a sample surface, forces between the tip and the sample lead to a deflection of the cantilever. Resultant characteristics, such as mechanical, electrostatic, magnetic, chemical and other forces are then measured by the AFM using, typically, a laser spot reflected from the top surface of the cantilever into an array of photodiodes.
Most systems employing AFM in concert with Raman perform separately, executing either an AFM scan or a Raman scan independently. Direct integration of Raman spectroscopy with AFM technique, however, has opened the door to significantly improved technique and sample analyses.
Megapixels in milliseconds
Our microscopes, our software and you. Together we’re like Red, Green and Blue.
Image recording in milliseconds with intuitive workfl ow-based software to guide you through your experiment. You don’t need to compromise on the time it takes or the results you’ve been looking for.
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leica-microsystems.com/rgb
For more information ✔ at
www.scientistlive.com/eurolab
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