Exploring Ferroelectric Materials and RF Electronics: An Interview with Prof. Kevin Nadaud on Characterization, CMOS Integration, and Research Challenges

Tell us about your journey as a scientist up to now. What's your academic background?

I began my academic journey in electrical engineering, earning a master's degree in France, where I specialized in microwaves, high-frequency electronics, antennas, and communication devices. After completing my master’s from 2012 to 2015, I pursued a PhD at the University of Nantes, focusing on ferroelectric materials for microwave devices. Following my PhD, I spent a year as a post-doctoral researcher, working on microelectromechanical systems (MEMS) for radio frequency (RF) devices, which involved extensive cleanroom fabrication.

In 2016, I joined the University of Tours as an assistant professor. My research primarily centers on the electrical characterization of ferroelectric materials. Additionally, I'm involved in RF electronics, particularly using wide-bandgap materials like Gallium Nitride (GaN). My focus within ferroelectrics lies in the dynamics of ferroelectric domain walls, their characterization, and potential applications.

Prior to my PhD, my work was mainly centered around electronics and instrumentation. It was during my PhD that I was first introduced to material science, which sparked a lasting interest that I continue to pursue.

What do you view as the next big challenge(s) in this research field?

Ferroelectric materials hold significant potential across various fields due to their high and tunable dielectric permittivity as well as large piezoelectric coefficients. They are commonly used in applications such as sensors (including pressure, vibration sensors, and accelerometers), capacitors, and filters. However, a major challenge lies in their integration with conventional CMOS processes. Issues such as temperature sensitivity, differences in thermal expansion coefficients, and species diffusion create complexities.

Currently, ferroelectric materials must be manufactured through separate workflows and then incorporated as discrete components, similar to how printed circuit boards are assembled. This process involves additional fabrication steps and can potentially diminish performance. Achieving seamless integration with CMOS technology would allow us to combine the sensor components (using ferroelectrics) directly on the same chip as electronic components, such as power amplifiers and signal conditioning circuits.

Although alternatives such as hafnia or scandate-based materials exist, integrating materials like barium titanate or potassium sodium niobate with CMOS processes continues to be a significant challenge in this field.

How do Zurich Instruments' products support your research?

Zurich Instruments' products play a crucial role in my research, particularly in the electrical characterization of ferroelectric materials. This process often involves capacitance measurements, where a sine voltage is applied and the resulting current is measured. Due to the non-linearities in ferroelectrics, the current contains harmonics, which are invaluable for understanding domain wall dynamics.

Traditionally, the literature suggests using lock-in amplifiers for these measurements, but they typically demodulate only one harmonic at a time. The Zurich Instruments MFLI lock-in amplifier with the Multi-Demodulator option offers the advantage of simultaneous demodulation, saving time whilst ensuring that all harmonics are measured under consistent conditions.

Additionally, the hardware capability to integrate external signals from an arbitrary waveform generator is beneficial for performing transient capacitance measurements. The LabOne ecosystem, combined with the Python API, is incredibly valuable for automating measurements, streamlining the research process significantly.

What would you recommend to young researchers nowadays?

My first piece of advice would be, "Don't be afraid to change your research focus." This can be either by choice, such as wanting to explore something new or out of necessity, like seizing an unexpected opportunity. In any case, you will find ways to apply your existing skills or develop new ones. Embracing change can lead to personal growth and open up unforeseen pathways in your research career.