Noncontact Atomic Force Microscopy - Yale School of Engineering ...

Development of quartz force sensors for noncontact atomic force
microscopy/spectroscopy
Kenichirou Hori 1 , Toyoko Arai 1 and Masahiko Tomitori 2
(a) (b)
Amplitude[nm]
Flexural oscillation amplitude and phase
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Amplitude[nm]
Phase[degree]
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Frequency[Hz]
P.I-23
1 Graduate School of Natural science & Technology, Kanazawa University, Kanazawa, Ishikawa, Japan
2 School of Materials Science, Japan Advanced Institute of Science and Technology, Nomi, Ishikawa Japan
In order to extend the application of noncontact atomic force microscopy (nc-AFM),
force sensors have still held the key to supplement the functions of nc-AFM, in particular,
for force spectroscopy. For example, bias-voltage noncontact atomic force spectroscopy
(nc-AFS) [1] developed on the basis of nc-AFM, invokes probes suitable to electric
conductance measurements with high force sensitivity to characterize the relationship
between binding state and electronic state. One possibility is to use quartz, one of
piezoelectric materials with a high Q, e.g., successfully demonstrated by Giessibl [2], on
which a metal or a Si needle is attached as a probe. Though a Si probe seems suitable to
examine the relationship between electronic states and chemical bonding force for Si
samples from point contact to non-contact through pseudo-contact regime, a metallic
needle sounds as a good conductor tip. The tip material is also desired to be easily
exchangeable. Moreover, the reduction of cantilever oscillation amplitude takes
advantage for conductance measurement [3], which were also realized using quartz force
sensors. Here we report the development of a quartz force sensor using lithographic
techniques from a quartz wafer, which has electrodes suitable to simultaneous
conductance measurement with high sensitivity of force at a small oscillation amplitude
with feasibility of probe material change.
We fabricated a quartz sensor with gold-plated multi-electrodes, one of which is to
fix the potential of a probe for conductance measurement. Figure 1 shows a schematic of
the sensor and mechanical characteristics of a flexure mode in air near its resonance
frequency measured using a heterodyne optical interferometer. This sensor exhibits a
longitudinal mode as well,
analyzed them by a finite
element method. To avoid Q
degradation, bonding of Si tip
onto quartz without adhesive
agent is adopted.
[1] T. Arai and M. Tomitori: Phys.
Rev. B 73 (2006) 073307.
[2] F.J. Giessibl: Appl. Phys. Lett. 76
(2000) 1470.
[3] T. Arai and M. Tomitori: Jpn. J.
Appl. Phys. 39 (2000) 3753.
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Fig.1(a) Schematic of a fabricated sensor. (b) Resonance
curves of the flexural mode of the sensor without a probe.
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Phase[degree]