Title:Structure prediction and new stabilisation mechanisms in ferroelectric materials

Speaker:Bastien Francesco Grosso,University of Birmingham (UK)

Time:2024-10-16 15：00pm  

Venue:C302,New Science Building

Abstract:We use a combination of first-principles calculations, phenomenological modelling, high-throughput calculations, and machine learning techniques to identify new structures and functionalities in ferroelectric materials. Complex oxides are known for their many different functionalities, including ferroelectricity, which is relevant for technological applications such as non-volatile memory. The substantial intrinsic functionalities can be modified by growing the materials as thin films in superlattices or heterostructures. For instance, the change in the lattice constants caused by epitaxial strain imposed by the substrate can induce ferroelectricity in otherwise paraelectric strontium titanate or enhance the polarisation in bismuth ferrite. In heterostructures of polar and non-polar materials, the polar discontinuity at the interface results in an accumulation of surface charges, creating an electric field known as the depolarising field. This opposite field can cause the formation of domains in the polar material and cancel the ferroelectric properties. These effects highlight the strong structure-property relationship in such materials and the need for accurate predictions of stable polymorphs of existing materials and potential new ferroelectric candidates. In this talk, we will first consider one of the most studied ferroelectric materials, bismuth ferrite, as a toy model and explore the space of possible structural distortions using a combination of phonon modes and machine learning techniques. We will show how this method can uncover several previously unidentified low-energy phases. In the second part, we will discuss the importance of electrostatic engineering in unveiling hidden metastable phases with surprising intrinsic properties and show how our predictions were confirmed experimentally. In the last part, we will present our efforts to identify new ferroelectric materials. We will present a workflow we developed to identify new potential quaternary materials with ferroelectric properties. Finally, we will conclude by presenting our latest effort on identifying oxygen-free functional materials for better integration into microelectronic devices.

Bio:Dr Bastien Francesco Grosso is a Marie Sklodowska-Curie Research Fellow at the School of Chemistry, University of Birmingham (UK). He graduated in Physics (BSc and MSc) from Ecole Polytechnique Fédérale de Lausanne (EPFL, Switzerland). He wrote his MSc Thesis under the supervision of Prof. Eugene Mele and holds a PhD in Materials Theory from ETH Zurich (Switzerland) under the supervision of Prof. Nicola Spaldin. After completing his PhD, he moved to the UK. He worked as a postdoctoral researcher at the University College London (UCL) under the supervision of Prof. David Scanlon, before being awarded a Marie Curie individual fellowship in 2023. His research interests are functional materials and controlling their properties under external stimuli. He is also interested in materials discovery and identifying new stable materials using high-throughput calculations and machine learning techniques.