Impact of Four-Valent Doping on the Crystallographic Phase Formation for Ferroelectric HfO${}_2$ from First-Principles: Implications for Ferroelectric Memory and Energy-Related Applications

Abstract

The ferroelectric properties of nanoscale silicon doped HfO${}_2$ promise a multitude of applications ranging from ferroelectric memory to energy-related applications. The reason for the unexpected behavior has not been clearly proven and presumably include contributions from size effects and doping effects. Silicon incorporation in HfO${}_2$ is investigated computationally by first-principles using different density functional theory (DFT) methods. Formation energies of interstitial and substitutional silicon in HfO${}_2$ paired with and without an oxygen vacancy prove the substitutional defect as the most likely. Within the investigated concentration window up to 12.5 formula unit %, silicon doping alone is not sufficient to stabilize the polar and orthorhombic crystal phase (p-o-phase), which has been identified as the source of the ferroelectricity in HfO${}_2$. On the other hand, silicon incorporation is one of the strongest promoters of the p-o-phase and the tetragonal phase (t-phase) within the group of investigated dopants, confirming the experimental ferroelectric window. Besides silicon, the favoring effects on the energy of other four-valent dopants, C, Ge, Ti, Sn, Zr and Ce, are examined, revealing Ce as a very promising candidate. The evolution of the volume changes with increasing doping concentration of these four-valent dopants shows an inverse trend for Ce in comparison to silicon. To complement this study, the geometrical incorporation of the dopants in the host HfO${}_2$ lattice was analyzed.

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Cited by in corpus (5)

• Progress in Computational Understanding of Ferroelectric Mechanisms in HfO${}_2$
• Disentangling stress and strain effects in ferroelectric HfO2
• First-principles study of oxygen vacancy defects in orthorhombic Hf${}_{0.5}$Zr${}_{0.5}$O${}_2$/SiO${}_2$/Si gate stack
• Interlayer-engineered local epitaxial templating induced enhancement in polarization (2P${}_r$ > 70$\mu$C/cm${}^2$) in Hf${}_{0.5}$Zr${}_{0.5}$O${}_2$ thin films
• Finite temperature effects on the structural stability of Si-doped HfO${}_2$ using first-principles calculations