The recent discovery of ferroelectricity in binary oxides such as doped HfO2 and ZrO2 has renewed 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.
- 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.
- Individual ferroelectric domains analysis, 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. The control their formation and the study their electrical and magnetic properties will be a task of the project.
- The analysis of the materials will be complemented by the characterization of integrated devices based on Al:HfO2 (here used as a model system), such as FeFET and FeRAM.
Required background: physics, engineering
Type of work: 70% experimental
Supervisor: Wilfried Vandervorst
Daily advisor: Umberto Celano
The reference code for this PhD position is STS1712-50. Mention this reference code on your application form.