User`s guide

Agilent 5500 SPM Components 2
Agilent 5500 SPM User’s Guide 35
Probes
The SPM techniques described in Chapter 1, “Introduction to the
Agilent 5500,” are accomplished using either a wire tip (for STM) or,
for AFM imaging, a tip at the free end of a cantilever (a “probe”). STM
tips are made by cutting or electrochemical etching Platinum-Iridium or
tungsten wire. AFM cantilevers are fabricated from silicon or silicon
nitride with an integrated sharp tip at the end.
The selection of probe and tip geometry, cantilever spring constant, and
cantilever resonance frequencies will vary depending on application,
type of sample surface, imaging environment, and type of image being
generated. Tip geometry may be tetrahedral, pyramidal or conical. Tip
sharpness, defined by radius of curvature and sidewall angles, greatly
affects the resolution available with the probe.
Common cantilever shapes are triangular (V-shaped) and rectangular
(beam-shaped). Cantilever spring constants vary from a fraction of N/m
(soft) to tens or hundreds of N/m (stiff). Cantilevers for any type of AC
Mode imaging (ACAFM, MAC, etc.) will have resonance frequencies
ranging from tens to hundreds of kilohertz.
Cantilevers for particular imaging modes may be coated with reflecting,
conductive or magnetic materials.