New application note "Enhancing Piezoresponse Force Microscopy with Dual-Frequency-Resonance-Tracking: A Practical Guide”

Nanosurf just released a new application note, "Enhancing Piezoresponse Force Microscopy with Dual-Frequency-Resonance-Tracking: A Practical Guide”.

In the app note we dive deep into the fascinating world of piezoelectric materials. Leveraged in a broad spectrum of applications, including biomedical devices, advanced electronics, energy production and storage, and MEMS, these materials possess the ability to generate an internal electric field when subjected to mechanical stress, and conversely, to demonstrate mechanical strain when an electric field is applied. These unique properties form the cornerstone of various devices operating on piezoelectric effects.

The application note summarizes how traditional PFM techniques work. While efficient, these standard techniques often yield a relatively weak signal, requiring the application of high AC excitation voltage which can potentially influence the local polarization and inadvertently switch its direction.

Dual-Frequency-Resonance-Tracking (DFRT) was introduced to circumvent these challenges. This method enhances the signal strength by applying AC excitation at the contact resonance (CR) frequency, thereby amplifying the piezoelectric response. A detailed walkthrough of the DFRT setup and its operation shows how the technique optimizes the excitation frequencies and maintains them at a constant level. This translates into a high-fidelity PFM imaging process, minimal crosstalk with the surface topography, and alleviates the need for manual retuning of resonant frequency under changing conditions.

The application note illustrates the advantages using examples of DFRT-PFM measurements on a thin film of BaTiO3, the first polycrystalline ceramic material discovered to exhibit ferroelectricity. Detailed figures illustrate the sample topography, followed by a comprehensive depiction of the DFRT-PFM imaging process. It also shows ferroelectric switching using a box-in-box pattern, and arbitrary-pattern PFM lithography.

An important section of the note discusses the considerations for applying the voltage, bringing out the different outcomes when the excitation signal is applied to the sample or the probe. It underscores the importance of conducting PFM measurements in both ways to discern potential artifacts.

Topography of the BaTiO3 sample.

With a mix of theoretical insights and practical applications, this guide serves as an invaluable resource for researchers working with piezoelectric materials, aiming to streamline their work by leveraging the power of DFRT PFM. 

Download the full application note PDF today to learn more about DFRT PFM.