More About Cantilevers; General Points; Handling Information - JPK instruments nanowizard afm Handbook

4. More about cantilevers

4.1 General points

The terminology concerning cantilevers can be confusing. The large piece of silicon is
called the "chip", and is a support for handling with tweezers and for gripping with the
cantilever holder spring. The "cantilever" itself is generally in the range of 100 µm
long. The "tip" is the projection that is used for imaging, and is usually placed at the
very end of the cantilever. Often, however, the term "cantilever" is used when the
"chip" or "tip" is actually meant.
Normally the tip attached to the cantilever cannot be seen without a good microscope.
Depending on the material and application, the tips can be shaped like an Egyptian
pyramid, or longer and cone shaped. The cantilever itself is usually either rectangular
or triangular in shape, such as the examples shown below.
Many types of cantilevers and tips are available for different applications. Most are
microfabricated from silicon or silicon nitride, and batch fabrication of probes gives
reasonably consistent physical properties. AFM cantilevers generally have a metallic
coating on the back side to increase the reflectivity. Aluminium is a common choice
because of its high reflectivity, but gold is often better for cantilevers that will be used
in liquid, because it is so chemically inert.
magnetic sensitivity, or to modify the actual tip region to produce particular chemical
interactions with the sample.

4.2 Handling information

Cantilevers are expendable items and have to be replaced regularly. The lifetime of
AFM cantilevers strongly depends on the way they are handled. The price of a single
cantilever starts in the range of 15 EUR (Summer 2003) up to hundreds of Euros for
special application cantilevers.
Cantilevers are usually delivered in plastic packages called "gel packs" of up to 50
pieces. The chips are held on a soft and adhesive polymer layer. Movement and
damage during delivery and storage is prevented, but they easily can be released
from the adhesive layer with a pair of tweezers. Larger amounts of cantilevers are
often delivered as a whole wafer in nitrogen-filled plastic containers. In this case no
18
Other coatings can be used to give
JPK Instruments NanoWizard
®
Handbook Version 2.2
chip
cantileve
View from above
tip
cantilever
Magnified view from the side