Large thermal hysteresis of ferroelectric transition in HfO2-based ferroelectric films

Abstract

The transition between the dielectric tetragonal and ferroelectric orthorhombic phases in 7%Y doped HfO2 and Hf0.5Zr0.5O2 films with various orientations and film thicknesses was investigated by high-temperature x-ray diffraction. All films demonstrate a different phase transition temperature on heating and cooling with thermal hysteresis with a gap of ΔT. This result clearly shows that the phase transition of the ferroelectric HfO2-based film is first order. The ΔT value of 40–210 °C in HfO2-based films is larger than that of other ferroelectric materials but similar to that of martensitic materials with large lattice deformation. This implies that the ferroelectric phase transition of HfO2-based films involves large lattice deformation. Moreover, we show that ΔT is changed by the size and composition effects. Our results are a step toward elucidating the mechanism of phase transition in ferroelectric HfO2-based films.

Hafnium Oxide (HfO2) – A Multifunctional Oxide: A Review on the Prospect and Challenges of Hafnium Oxide in Resistive Switching and Ferroelectric Memories

“…The absence of the ferroelectric soft mode can also be a consequence of the first‐order character of the phase transition (thermal hysteresis of T C up to 210 K was observed). [ 320 ] First‐principles calculations [ 249 ] confirm that high‐temperature cubic Fm $$\bar{3}$$ m structure (stable above 2870 K) can transform into nonpolar tetragonal P4 2 / nmc phase because of the instability of $$X_2^,$$ symmetry phonon, which involves antiparallel x displacement of neighboring oxygen atoms in the yz plane. Four phonons of $$\Delta _{15}^z$$, $$X_5^y$$, $$Y_5^z$$, and $$Z_5^y\;$$ symmetry should play the role in the phase transformation from t to o structure.…”

Microstructural evolution and ferroelectricity in HfO2 films

“…We will discuss how the polar Pca2 1 phase is stabilized by these growth parameters. In addition, the ferroelectricity in HfO 2 films has a strong electric field [118][119][120][121] and temperature dependence [18,122,123] , which has a strong correlation with the phase transformation under external stimuli [25,122] . While previous reviews [51,82] focused mainly on the FE properties, we will summarize the microstructure-property relations.…”

“…Encouraged by the significant potential of energy storage and transfer applications, further fundamental knowledge behind this temperature-induced FE property evolution was explored, especially with its structural mechanism. Park et al [122] investigated remanent polarization-microstructure relation from 80 to 400 K. Figure 11A gives an intensity contour map of grazing incidence X-ray diffraction (GIXRD) patterns of Si-doped HfO…”

“…Although HfO 2 FEs show significant potential for resolving critical difficulties that deter the [122] . GIXRD: Grazing incidence X-ray diffraction commercialization of FE memories, they also suffer from remarkable instability issues induced by electric fields, namely, wake-up and fatigue [25,33,118,141] .…”

“…Figure 11. (A) An intensity contour map of GIXRD patterns of Si-doped HfO 2 films from 110 to 410 K. GIXRD patterns of Si-doped HfO 2 films measured at (B) 410, (C) 350, (D) 275, (E) 200, (F) 125 and (G) 110 K. P-E curves of Si-doped HfO 2 films measured at (H) 400, (I) 350, (J) 275, (K) 200, (L) 125 and (M) 80 K[122] . GIXRD: Grazing incidence X-ray diffraction…”