Critical effect of the bottom electrode on the ferroelectricity of epitaxial Hf_0.5Zr_0.5O₂thin films

Abstract

Epitaxial orthorhombic Hf0.5Zr0.5O2 (HZO) films on La0.67Sr0.33MnO3 (LSMO) electrodes show robust ferroelectricity, with high polarization, endurance and retention. However, no similar results have been achieved using other perovskite electrodes so...

Insights into the atomic structure of the interface of ferroelectric Hf0.5Zr0.5O2 grown epitaxially on La<

“…S1, Supplemental Material [37]), with ferroelectric switching peaks at ∼3-4 V and remanent polarization of ∼ 12 μC/cm 2 . Further macroscopic ferroelectric characterization of this film has been reported elsewhere [22,23]. Herein, we focus on the interface between the ferroelectric o-HZO and the LSMO buffer layer, although the interface between the paraelectric monoclinic phase of HZO and the LSMO buffer was also studied in detail, revealing small differences with the orthorhombic phase (see Figs.…”

“…As reported elsewhere [22], o-HZO (111)-oriented crystallites coexist with nonferroelectric monoclinic (001)-oriented crystallites in the studied film, both phases being epitaxial to LSMO. Among different bottom electrodes, only LSMO stabilizes the o-HZO phase, while other perovskite electrodes, such as LaNiO 3 or SrRuO 3 , only yield monoclinic HZO (m-HZO) [23]. The ferroelectric character of the studied film is revealed by an I-V curve and the corresponding integrated P-V loop (see Fig.…”

“…Ferroelectric HfO 2 thin films with different dopants have been grown epitaxially on various substrates such as the fluorite yttria-stabilized zirconia (YSZ) [14][15][16], Si [17], pyrochlore oxides [18], or perovskites like SrTiO 3 (STO) [19,20], LaAlO 3 [21], or GdScO 3 [22]. On the perovskite substrates, a strained La 2/3 Sr 1/3 MnO 3 (LSMO) buffer layer or a similar manganite buffer is generally essential to stabilize the metastable ferroelectric phase [19][20][21]23], with Nb-doped STO being the only perovskite substrate reported to permit the stabilization of the orthorhombic phase without the use of manganite buffers [24], as far as we know.…”

Improved polarization and endurance in ferroelectric Hf0.5Zr0.5O2 films on SrTiO3(110)

“…10,14 Furthermore, the orthorhombic phase grows epitaxially on LSMO and other La-doped manganites, but not on other popular oxide electrodes such as SrRuO3, LaNiO3 or La:BaSnO3. 19 These facts limit the possibilities of controlling the microstructure and the ferroelectric properties of epitaxial HfO2 films. Aiming to open new ways of control, we have investigated the growth of Hf0.5Zr0.5O2 (HZO) films on STO(110) substrates buffered with LSMO electrodes.…”

Microstructural evolution and ferroelectricity in HfO2 films

“…The macroscopic performance of FE materials is dominated by their microstructures [71][72][73] , which can be altered by dopants [20,74,75] , film thickness [50,[76][77][78] , thermal expansion and epitaxial strain [67,68,79,80] . In addition, mechanical, electrical, electromechanical and thermoelectric properties are crucial factors for the device applications of FE HfO 2 materials.…”