Charge-compensated co-doping stabilizes robust hafnium oxide ferroelectricity
JOURNAL OF MATERIALS CHEMISTRY C(2024)
Abstract
Doping with various cations is considered to be a key method for inducing ferroelectricity in HfO2. However, previous studies often neglected the role of carriers introduced by heterovalent dopants. Here, using first-principles calculations, we show that carriers profoundly affect the stability of polar phases and advocate that carriers should be considered as a fundamental framework for understanding the origin of ferroelectricity in doped HfO2. Although doping with p-type elements that introduce holes can stabilize the polar phase, it is not sufficient to make them the ground state phase. However, when they are co-doped with an n-type V element, they not only stabilize the polar phase to the ground state, but also achieve charge neutrality through electron compensation. This is due to the formation of deep energy levels (electron-hole recombination centers) by V doping, similar to oxygen vacancies. Unlike oxygen vacancy compensation, which favors the formation of tetragonal phases, co-doping is more favorable for the formation of polar phases and the absence of structural defects. Our results contribute to the understanding of the origin of HfO2 ferroelectricity and provide a potential method for the preparation of HfO2-based films with excellent ferroelectric properties. Compensated co-doping not only achieves charge neutrality but is also highly favorable for the formation of polar phases and the absence of structural defects.
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