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1. NANOELECTROMECHANICAL SYSTEMS 31
tunneling current constant. This is the called topography mode, and produces
an image of ( yxz , , I ≈ constant ).
t
STM tips are fabricated via chemical etching or mechanical grinding of
W, Pt-Ir, or pure Ir [41]. By using a magnetic probe tip the STM can be
made sensitive to the spin of the tunneling electrons. Besides the tip
sharpness and material properties, moving the tip with atomic scale
precision, to obtain atomic resolution image, necessitates the utilization of a
piezoelectric ceramic, whose extremely fine deformation is induced by an
applied voltage.
1.2.3.4.2 Atomic Force Microscopy
In AFM, Figure 1-29, a sharp tip is also brought very close to the sample
surface.
Figure 1-29. (a) Sketch of AFM system. (b) Probe detail. The sample may be held at ambient
conditions. (After [41].)
