Ferroelectricity is a very powerful, yet still complex and somewhat mysterious property that has been under investigation for over 70 years. However, the advances in theoretical models, synthesis and characterization have unlocked the potential to tailor ferroelectric materials for disruptive breakthroughs in energy, medicine and electronics. For instance, the recent discovery of ferroelectricity in binary oxides such as doped HfO2 and ZrO2 has escalated the interest for ferroelectric-based nanoelectronics as it holds the promise to overcome current limitations of perovskite-based materials integration. A variety of dopant materials are currently explored in combination with known binary oxide systems to achieve ferroelectric othorhombic phases that are showing a strong electrical polarization. However, the intimate nature of ferroelectricity in these materials remains elusive while local physical analysis is required to gain the theoretical and experimental understanding of these phenomena. This PhD project aims to study the properties of ferroelectricity in binary oxides combining different nm-resolved characterization techniques applied to various materials. Nanoscale electron diffraction methods will be combined with piezo-response force microscopy (PFM) to enable the analysis of crystal structure in thin-films, sensing and manipulating the ferroelectric domains while investigating the main materials' parameters affecting the ferroelectricity. The fundamentals questions that this project aims to tackle are:
- What determines the appearance of ferroelectricity/flexoelectricity in binary-oxides, which parameters are key to achieve a strong and stable electrical polarization. How do they compare with standard ferro/piezo systems like Barium Titanate (BTO) and lead zirconate titanate (PZT) grown on Si(001).
- Study the optimal growth conditions to obtain low- to a high-symmetry phases via substitutional doping. The role of crystal orientation, dead layer and grain boundaries will be investigated.
- How to probe individual ferroelectric domains, their formation and manipulation. Probing domain's size (how small can a single domain be scaled in binary oxide ferroelectrics), electrical and piezoelectric properties to be combined with structural and chemical analysis.
- Ferroelectric domain walls in binary-oxides. Can they be used, formed and manipulate to enable a domain wall nanoelectronics concept? Controlling their formation and studying their electrical and magnetic properties will be a task of the project as well.
- Developing the best method for analyzing their piezo-electric response and polarization, with PFM and band excitation PFM.
- The analysis of the materials will be complemented by the characterization of integrated devices based on Si:HfO2 (here used as a model system), such as FeFET and FeRAM.
To ensure a high impact outcome, we will provide close supervision by senior scientists, hands-on training in the lab, regular interaction with leading imec experts on ferroelectricity, and a wide variety of training possibilities at imec and KULeuven.
Required background: Physics, Materials science, Nanotechnology
Type of work: literature (10%), technology study (20%), experimental work (70%)
Supervisor: Wilfried Vandervorst
Daily advisor: Umberto Celano
The reference code for this position is 2020-021. Mention this reference code on your application form.
Chinese nationals who wish to apply for the CSC scholarship, should use the following code when applying for this topic: CSC2020-12.