Ferroelectric and Dielectric Properties of Hf_0.5Zr_0.5O₂ Thin Film Near Morphotropic Phase Boundary

Abstract

Since the discovery of ferroelectric (FE) properties in HfO 2 -based materials, [1] numerous advantages, such as simple structures, strong binding energy between oxygen and transition metal ions, large bandgap (%5.3-5.7 eV), and compatibility with current complementary metal-oxide semiconductor technologies, led to extensive research that focused on potential diverse applications, such as FE memory, ferroelectric field-effect transistors (Fe-FETs), pyroelectric sensors, and energy harvesters. Meanwhile, from the material survey of FEs, it is conventional that the structural phase transition induced by a compositional change plays a special role in obtaining excellent piezoelectric and dielectric properties. [2][3][4][5][6][7][8][9] The phase boundary known as morphotropic phase boundary (MPB) separates regions of different symmetries by varying their composition in FEs. [2][3][4][5][6][7][8][9] In fact, when different structural phases are almost degenerated near the MPB, rotations of polarization occur in response to external electric fields instead of a change in the magnitude of polarization. [5] Consequently, materials exhibit maximum piezoelectric and dielectric responses near the MPB, as several phases coexist, and there is nearly no energy barrier separating them. The MPB has garnered significant practical interest, because the variable that drives the transition (i.e., compositions) is inherent. Therefore, it provides an alternative approach to boost the dielectric constant ϵ r without degrading the bandgap. MPB ceramics are the basis of a wide range of piezoelectric and dielectric technologies, such as high-k materials, sensors, actuators, smart systems, ultrasound generation, and sensing and underwater acoustics. These applications motivated researchers to investigate the existence of MPB in the novel promising ceramic compounds, e.g., PbHfO 3 -PbTiO 3 -Pb(Mg 1/3 Nb 2/3 )O 3 , [10,11] lead-free BiFeO 3 -BaTiO 3 , [12,13] Pb(In 1/

A grease for domain walls motion in HfO2-based ferroelectrics

“…Although the experimental data agree with equation (1) [9,19,20], this equation is only valid when domain nucleation and growth are suppressible and Landau-Ginzburg-based uniform switching occurs during polarization switching of HfO 2 samples [13,14]. Several groups have shown that the switching kinetics of the HfO 2 based ferroelectrics result from the nucleation and growth of domains [21][22][23][24][25].…”

“…The formation of the monoclinic phase (m-phase) was nonexistent for all devices, and the o/t phase characteristic peaks were observable. The o (111) and t (011) peaks were at 2θ°-30.4°a nd 30.8°, respectively [19,20]. As the T A increased, a left shift of o/t Bragg peak from 2θ°to 30.5°occurred (see inset of figure 2(b)), revealing the formation of polar o-phase and reduction of t-phase [19,20], which was in line with polarization evolution due to the annealing condition presented in figure 2(a).…”

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

“…A novel approach based on the existence of morphotropic phase boundaries (MPB) was recently developed. [281,283,[292][293][294][295] This approach introduced a substantial improvement in the dielectric properties of HfO 2 -based thin films. In fact, the discovery of ferroelectricity and anti-ferroelectricity in HfO 2 -ZrO 2 (HZO) solid solution thin films [246][247][248][249][250][251][252][253][254][255][256][257][258][259][260][261][262] paved the way for enhancing dielectric properties through MPB, which will be discussed later in Section 8.…”

Field‐Induced Ferroelectric Phase Evolution During Polarization “Wake‐Up” in Hf0.5Zr0.5O2 Thin Film Capacitors

“…The ferroelectric O-phase is reported to have a lower dielectric constant than the antiferroelectric T-phase. [21,24] Measurements conducted far from the peaks in the C-V curve are less influenced by domain wall contributions [25] to the capacitance and provide a more reliable measure of the dielectric constant. In the present case, the majority O-phase ALD 250 °C sample has a lower dielectric constant than the majority T-phase ALD 200 °C sample for all cycling states, Figure 4a,b.…”