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High resolution may not be attainable when imaging real-time processes
such as molecular diffusion, crystallization, and wetting. This
depends on the characteristic process rates in relation to the scanning
rate and the distance between the scan sampling points. Moreover,
sharp probes needed for high resolution imaging require special
care in use, which leads to further reduction of the scanning speed.
10-nm resolution offered by General Purpose tips may be a compromise
in this case.
General Purpose probes are uncoated silicon tips that can be usually
used in Contact, Non-contact or Tapping mode for imaging topography
and mapping mechanical properties without significant limitations.
General Purpose probes for measuring electric and magnetic properties
are not available yet as these applications require tips with special
coatings, which increase the radius and decrease the resolution.
General Purpose probes having tips with a radius of about 10-nm
provide good-quality images for a broad variety of samples. The
best resolution is achieved when scanning spherical particles that
are hard and exhibit weak attraction to the tip. Note that the resolution
of AFM images larger than 1µm by 1µm may be more determined
by the density of sampling points ratio than the General Purpose
tip radius.
General recommendations apply to the cantilever choice. Contact
mode needs probes with small spring constant below 1N/m, Non-contact
mode requires high-frequency probes, while cantilevers with intermediate
spring constant and
resonant frequency are optimal for most of samples in Tapping mode.
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