JPK instruments nanowizard afm - Cantilever Types for Imaging Modes

20
JPK Instruments NanoWizard
®
Handbook Version 2.2
Intermittent contact mode
For
intermittent contact mode AFM in air, stiffer cantilevers with resonance
frequencies above 100 kHz are re
quired (resonance frequencies between 200 and
300 kHz deliver the best results). Some intermittent contact mode cantilevers are
available with lower r
esonance frequencies, in the 100 kHz range. These can be
useful for AFM instruments from some other manufacturers that are not able to use
such high frequencies as the NanoWizard
®
AFM. The
disadvantage is that the
scanning speed must be lower to reach the same resolution.
• High force constant
• “hard cantilevers”
• High resonant frequency
• Shorter and thicker
m
k
π
s
2
1
Freq.Re =f.
It is possible to use softer cantilevers (such as the ones designed for contact mode),
but it is more difficult to establish a stable feed
back with them. The problem in air is
that the vibrating cantilever has to cope with a thin water layer which is always
present on a sample surface at in ambient conditions. The strong adhe
sion of the
water layers on the sample and tip can trap
the cantilever on the surface, making the
imaging unstable. If the humidity of the environment is reduced, this can improve the
situation, however.
For intermittent contact mode in liquid, softer cantilevers are often used, because
when the cantilever a
nd surface are immersed in liquid there is not this problem with
the surface water capillary layers. So for intermittent contact mode in liquid, often
“contact mode” cantilevers are actually used.
General points
Both silicon and silicon nitride cantilev
ers are available form many suppliers, but a
reflective back surface coating is recommended for superior feedback. The unique
chip holder of the NanoWizard
®
allows you to use tips from most manufacturers, and
probes are available from our website. The inst
rument was performance tested with
probes from NanoWorld
®
, NanoSensors
®
, Veeco
®
, Olympus
®
and Mikromasch
®
.
The examples of technical data given below are from the NanoWorld
®
cantilevers
CONT and NCH. The listing is just to give a comparison for typical values.
Technical data Typical value Range
Thickness
Mean Width
Length
Force Constant
Resonant Frequency
2 µm
50 µm
450 µm
0.2 N/m
13 kHz
1.5 - 2.5
45 – 55
445 – 455
0.07 - 0.4
9 - 17
Contact mode
Technical data Typical value Range
Thickness
Mean Width
Length
Force Constant
Resonant Frequency
4 µm
30 µm
125 µm
42 N/m
320 kHz
3.5 - 4.5
25 – 35
120 – 130
21 – 78
250 - 390
Intermittent contact mode
4.4 Tip modification
For many applications, the tip is modified chemically or physically to give particular