Phase transitions in ferroelectric silicon doped hafnium oxide

Abstract

We investigated phase transitions in ferroelectric silicon doped hafnium oxide (FE-Si:HfO2) by temperature dependent polarization and x-ray diffraction measurements. If heated under mechanical confinement, the orthorhombic ferroelectric phase reversibly transforms into a phase with antiferroelectric behavior. Without confinement, a transformation into a monoclinic/tetragonal phase mixture is observed during cooling. These results suggest the existence of a common higher symmetry parent phase to the orthorhombic and monoclinic phases, while transformation between these phases appears to be inhibited by an energy barrier

The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model

“…The antiferroelectric behavior observed in doped HfO2 1 and ZrO2 11 has been interpreted as a field induced phase transformation 19 . We examine the consistency of this statement with the Helmholtz free energy model containing a contribution for a polarized crystal in an electric field as described by Souza 69 .…”

“…Asymmetric stress effects have also been discussed as an explanation for the appearance of ferroelectric ZrO2 grains in cubic stabilized ZrO2 18 . Furthermore, stress effects in thin Hf0.5Zr0.5O2 films have been used as a possible explanation of how a cap electrode affects the ferroelectric phase by Müller 11,19 as well as film thickness causing film stress variation and appearance of a ferroelectric phase by Park 16 .…”

Ferroelectricity in Simple Binary Crystals

“…Thin films of HfO2 undergo a phase transition to a noncentrosymmetric orthorhombic structure, breaking the symmetry of inversion when the films are doped with Si, Y, Al, or Zr [18,19,[35][36][37][38]. The X-ray diffraction patterns of HfO2, Hf0.5Zr0.5O2 and ZrO2 thin films are shown in Figure 7 [38].…”

“…The Curie temperature (T c ) was estimated to be about 623 K [39,40]. [18,19,[35][36][37][38]. The X-ray diffraction patterns of HfO2, Hf0.5Zr0.5O2 and ZrO2 thin films are shown in Figure 7 [38].…”

“…Besides ZnO, Gedoped PbTe, a IV-VI narrow-gap semiconductor [16], and Zn-doped CdTe, a II-VI wide-gap semiconductor [17], have been investigated as materials of binary crystals accompanying ferroelectricity ( Figure 1). Moreover, recent works showed that thin films of HfO2-ZrO2 systems exhibit ferroelectricity [18,19]. Hafnia (HfO2) and Zirconia (ZrO2) have been well studied as high-k dielectric materials in CMOS (complementary metal-oxide semiconductor) technology.…”