AER/Inorganic Seminar – Kami Christensen

About the event

Speaker: Kami Christensen

Group: Dr. Kevin Kittilstved

Title: Dopant Stabilization of Hafnia Polymorphs for Thin Film Applications

Abstract: Polymorphism is a characteristic of many oxide materials that can be utilized for a multitude of applications. Material doping is commonly used to tune a materials properties (i.e. bandgap) and to make select polymorphs more energetically favorable. Recently, there has been considerable interest in yttrium-doped hafnia (Y:HfO2) for its ferroelectric properties to be used in electronic components. New sub-stoichiometric semiconducting polymorphs have been stabilized and studied utilizing pulsed LASER deposition (PLD) and molecular beam epitaxy (MBE). Foundational work into predicting stabilization of the orthorhombic phase based on doping conditions was done using density functional theory (DFT). A recent study has shown that there may be switchable polarization which contrasts standard thin film behavior, where polarization is directional.

Sources:

Kaiser et al., “Defect-Stabilized Substoichiometric Polymorphs of Hafnium Oxide with Semiconducting Properties.” ACS Appl. Mater. Interfaces 2022, 14 (1), 1290–1303.

Nand et al., “Different Polymorphs of Y Doped HfO2 Epitaxial Thin Films: Insights into Structural, Electronic and Optical Properties.” J. Alloys Compd. 2022, 928, 167099

Pavoni et al., “The Effect of Y Doping on Monoclinic, Orthorhombic, and Cubic Polymorphs of HfO₂: A First Principles Study.” Nanomaterials 2022, 12 (23), 4324.

Xu et al., “Kinetically Stabilized Ferroelectricity in Bulk Single-Crystalline HfO₂:Y.” Nat. Mater.2021, 20 (6), 826–832