The Piezo Force Module

For Electromechanical Measurements

Electromechanical coupling is one of the fundamental mechanisms underlying the functionality of many materials. These include inorganic, macro-molecular materials and many biological systems. The new Piezo Force Module from Asylum Research enables very high sensitivity, high bias, and crosstalk-free measurements on piezoelectrics (including biological systems in fluid), ferroelectrics and multiferroics. These capabilities are exclusively available on the MFP-3D™ AFM.

Piezoresponse Force Microscopy
In the last decade, piezoresponse force microscopy (PFM) has emerged as the preeminent tool for nanoscale imaging, spectroscopy, and manipulation of ferroelectric materials. More recently, these same
techniques are finding applications for a wider range of materials including soft polymer and biological materials. In response to these advances, Asylum Research has recently developed the new Piezo Force Module which combines new patent-pending measurement techniques and a unique high voltage capability that significantly expands the range and sensitivity of measurements.

Resonant-Enhanced Imaging Modes
Many measurement techniques have made use of cantilever resonances dating back to the invention of the AFM. Because of topographic crosstalk, this has precluded use in PFM. However, two new patent-pending measurement modes developed by researchers
at Asylum Research and their collaborators nearly eliminate crosstalk issues. These modes utilize cantilever resonances which inherently allow higher senstitivity measurements:

• Dual AC Resonance Tracking (DART)
• Band excitation (optional)

These modes avoid the limitations of conventional sinusoidal cantilever excitation while using resonance enhancement to provide new information on local response and energy dissipation which cannot
be obtained by standard AFM scanning modes. The large frequency range (1kHz - 2MHz) of the MFP-3D allows imaging both at the static condition, and effective use of several cantilever resonances and use of the inertial stiffening of the cantilever.

High Voltage Characterizes Even the Weakest Piezoelectric Materials
The MFP-3D Piezo Force Module accessory enables high voltage PFM measurements and advanced imaging modes for characterizing
piezoelectric materials. With the Piezo Force Module, a programmable bias of up to +220 volts is applied to the AFM tip using a proprietary high voltage amplifier, cantilever and sample holder. The amplitude of the response measures the local electromechanical activity of the surface while the phase yields information on the polarization direction. High probing voltages can characterize even the weakest piezoelectric sample and insure that you have the ability to switch even high-coercivity materials.

Spectroscopy Modes for Polarization Applications
Polarization dynamics can also be studied with these spectroscopy modes:

• Single-point hysteresis loop measurements (point and click)
• Switching Spectroscopy Mapping

These modes provide local measure of such parameters as coercive and nucleation biases, imprint, remanent response, and work of switching (area within the hysteresis loop), for correlation with local microstructure. Combined with the high-voltage module, these allow local polarization switching to be probed even in high-coercivity
materials such as electro-optical single crystals.

Additional Information

1. S. Jesse, S. Kalinin, R. Proksch, A.P. Baddorf, B.J. Rodriguez, "The band excitation method in scanning probe microscopy for rapid mapping of energy dissipation on the nanoscale." Nanotechnology 18, 435503 (2007).

2. B.J. Rodriguez, C. Callahan, S. Kalinin, R. Proksch, "Dual-frequency resonance-tracking atomic
force microscopy." Nanotechnology 18, 475504 (2007).

3. S. Kalinin, B.J. Rodriguez, S. Jesse, K. Seal, R. Proksch, S. Hohlbauch, I. Revenko, G. Thompson, A. Vertegel. "Towards local electromechanical probing of cellular and biomolecular systems in a liquid environment." Nanotechnology 18, 424020 (2007) .

4. See the R&D magazine Oct. ’07 article titled “A Biased View of the Nanoworld: Electromechanical Imaging by SPM.”

5. See the January 2008 Microscopy Today article "Nanoelectromechanics of Inorganic and Biological Systems: From Structural Imaging to Local Functionalities".

Specifications

Model PFM
The Piezo Force Module comes with the following items:
• HVA220 High Voltage Amplifier
• HV cantilever holder
• HV sample holder
• 70 Electri-lever probes
• Periodically Poled Lithium Niobate (PPLN) sample

Hardware
• HVA220 High Voltage Amplifier
- +220V at 75ma output to the tip
- 30V/microsecond slew rate
• Safe loading, HV sample holder
• HV cantilever holder

Software
Imaging
• Single frequency PFM
• Bit mapped voltage (ferroelectric lithography)
• Dual AC Resonance Tracking (DART)
• Band excitation (optional)

Spectroscopy
• Single point hysteresis loop measurements (point and click)
• Switching Spectroscopy Mapping

Specifications subject to change.

Download Piezo Force Module PDF

Rendered topography of a LiNbO₃ sample with the PFM signal painted on top.  Image was taken after switching spectroscopy mapping. Inset shows the hysteresis loops measured at an individual point, 4µm scan.

Topography of a red blood cell with the piezo response signal painted on top, 2µm scan. Image courtesy of B. Rodriguez and S. Kalinin, ORNL.

HVA220 High Voltage Amplifier

HV Sample Holder on the scanner

HV Sample Holder under the head

PFM Cantilever Holder