Growth redox conditions and interface effects govern polarization switching speed, retention and reliability in epitaxial Hf_0.5Zr_0.5O₂ thin films

Abstract

Ferroelectric HfO₂-based thin films are promising for next-generation non-volatile memories. Achieving further understanding of how the interfaces and defects influence switching dynamics and reliability is essential for device optimization. Here, we investigate the polarization switching kinetics, breakdown strength, and retention of a series of epitaxial Hf_0.5Zr_0.5O₂ (HZO) of increasing thickness and grown using different oxidation conditions on substrates with different orientations. Time-dependent ferroelectric characterization shows that films in the intermediate thickness range (≈5-10 nm), which exhibit the largest remanent polarization (above 30 μC/cm²), show slower switching. In addition, polarity-dependent switching kinetics is observed in ultrathin films, which is attributed to built-in electric fields associated with asymmetry between interfaces. Reliability analysis shows that the breakdown electric field decreases with increasing thickness, reaching up to ~55 MV/cm,, while the retention remains stable in the optimal thickness range. These results demonstrate that the interplay between film thickness, interface symmetry, and oxidation conditions during growth governs the switching dynamics and reliability of epitaxial HZO films, providing guidelines for the design of high-performance ferroelectric devices.

Keywords

Ferroelectric hafnia / HfO₂ / ZrO₂ / pulsed laser deposition

References

[1] Böscke TS,Bräuhaus D,Böttger U.Ferroelectricity in hafnium oxide thin films.Appl Phys Lett2011;99:102903

[2] Shao M,Liu H.Challenges and recent advances in HfO₂-based ferroelectric films for non-volatile memory applications.Chip2024;3:100101

[3] Yang W,Li H.Ferroelectricity of hafnium oxide-based materials: Current status and future prospects from physical mechanisms to device applications.J Semicond2023;44:053101

[4] Schroeder U,Mikolajick T.The fundamentals and applications of ferroelectric HfO₂.Nat Rev Mater2022;7:653-69

[5] Materano M,Kersch A,Mikolajick T.Interplay between oxygen defects and dopants: effect on structure and performance of HfO₂-based ferroelectrics.Inorg Chem Front2021;8:2650-72

[6] Park MH,Yang K.Review of defect chemistry in fluorite-structure ferroelectrics for future electronic devices.J Mater Chem C2020;8:10526-50

[7] Lee J,Kwon JY.Role of oxygen vacancies in ferroelectric or resistive switching hafnium oxide.Nano Converg2023;10:55 PMCID:PMC10692067

[8] Lee Y,Kim SH,Park MH.Effect of stress on fluorite-structured ferroelectric thin films for semiconductor devices.Mater Sci Semicond Process2023;160:107411

[9] Materano M,Lomenzo PD.Influence of oxygen content on the structure and reliability of ferroelectric Hf_xZr_1-xO₂ layers.ACS Appl Electron Mater2020;2:3618-26

[10] Kumar G,Das A,De S.Insights into oxygen vacancy effects on ferroelectric behavior of hafnium oxide: a review.Physica Status Solidi2025;222:2500376

[11] Schroeder U,Müller J.Impact of different dopants on the switching properties of ferroelectric hafniumoxide.Jpn J Appl Phys2014;53:08LE02

[12] Schroeder U,Mittmann T,Mikolajick T.Recent progress for obtaining the ferroelectric phase in hafnium oxide based films: impact of oxygen and zirconium.Jpn J Appl Phys2019;58:SL0801

[13] Wei Y,Salverda M.A rhombohedral ferroelectric phase in epitaxially strained Hf_0.5Zr_0.5O₂ thin films.Nat Mater2018;17:1095-100

[14] Lyu J,Solanas R,Sánchez F.Robust ferroelectricity in epitaxial Hf_1/2Zr_1/2O₂ thin films.Appl Phys Lett2018;113:082902

[15] Estandía S,Chisholm MF,Sánchez F.Domain-matching epitaxy of ferroelectric Hf_0.5Zr_0.5O₂(111) on La_2/3Sr_1/3MnO₃(001).Cryst Growth Des2020;20:3801-6

[16] Schimpf J,Manna M.Interface effects in the phase determination of Hf_0.5Zr_0.5O₂ epitaxial thin films.APL Mater2025;13:011104

[17] Huang C,Zheng S,Liao M.Interface effects induced by aZrO₂ seed layer on the phase stability and orientation of HfO₂ ferroelectric thin films: a first-principles study.Phys Rev Appl2021;16:044048

[18] Shi S,Cao T.Interface-engineered ferroelectricity of epitaxial Hf_0.5Zr_0.5O₂ thin films.Nat Commun2023;14:1780 PMCID:PMC10063548

[19] Jiao P,Xi Z.Ferroelectric Hf_0.5Zr_0.5O₂ thin films deposited epitaxially on (110)-oriented SrTiO₃.Appl Phys Lett2021;119:252901

[20] Lyu X,Song T,Sánchez F.Cooperative effects of interface symmetry, redox conditions and low-thickness to improve polarization in ferroelectric Hf_0.5Zr_0.5O₂ films.ACS Appl Mater Interfaces2025;17:32596-603 PMCID:PMC12147076

[21] Song T,Estandía S.Improved polarization and endurance in ferroelectric Hf_0.5Zr_0.5O₂ films on SrTiO₃(110).Nanoscale2022;14:2337-43

[22] Yun Y,Li M.Intrinsic ferroelectricity in Y-doped HfO₂ thin films.Nat Mater2022;21:903-9

[23] Song T,Qian M,Sánchez F.Large enhancement of ferroelectric polarization in Hf_0.5Zr_0.5O₂ films by low plasma energy pulsed laser deposition.J Mater Chem C2022;10:1084-9

[24] Mittmann T,Lomenzo PD.Origin of ferroelectric phase in undoped HfO₂ films deposited by sputtering.Adv Mater Inter2019;6:1900042

[25] Mittmann T,Lomenzo PD.Stabilizing the ferroelectric phase in HfO₂-based films sputtered from ceramic targets under ambient oxygen.Nanoscale2021;13:912-21

[26] Lyu X,Quintana A,Sánchez F.Highly stable epitaxially crystallized ferroelectric Hf_0.5Zr_0.5O₂ films.ACS Appl Electron Mater2023;5:6142-8

[27] Buragohain P,Mimura T,Funakubo H.Effect of film microstructure on domain nucleation and intrinsic switching in ferroelectric Y:HfO₂ thin film capacitors.Adv Funct Mater2021;32:2108876

[28] Li Y,Li X.Unveiling the role of domain wall propagation in enhancing switching properties of ferroelectric Ga-doped HfO₂ thin films.Mater Today Chem2025;49:103091

[29] Ali F,Sánchez F.Fast switching and high polarization in ferroelectric Hf_0.5Zr_0.5O₂ films.Small Sci2026;6:e202500465 PMCID:PMC12910630

[30] Lee DH,Yang K.Domains and domain dynamics in fluorite-structured ferroelectrics.Appl Phys Rev2021;8:021312

[31] Kim J,Koo R.Hybrid ferroelectric-ionic memristive hardware for high scalability in-memory computing.Nat Commun2026;17:6687 PMCID:PMC13385777

[32] Fina I,Langenberg E.Nonferroelectric contributions to the hysteresis cycles in manganite thin films: A comparative study of measurement techniques.J Appl Phys2011;109:074105

[33] Song T,Magén C,Sánchez F.Improved polarization-retention-endurance in Hf_0.5Zr_0.5O₂ films by ZrO₂ capping via electrostatic effects.Adv Elect Mater2023;10:2300509

[34] Zhang Q,Zhu J.Direct observation of interface-dependent multidomain state in the BaTiO₃ tunnel barrier of a multiferroic tunnel junction memristor.ACS Appl Mater Interfaces2021;13:43641-7

[35] Estandía S,Mishra R,Sánchez F.Insights into the atomic structure of the interface of ferroelectric Hf_0.5Zr_0.5O₂ grown epitaxially on La_2/3Sr_1/3MnO₃.Phys Rev Mater2021;5:074410

[36] Chatterjee S,Gaidhane A,Chauhan YS.Ferroelectric FDSOI FET modeling for memory and logic applications.Solid State Electron2023;200:108554

[37] Tagantsev AK,Setter N,Tsukada M.Non-Kolmogorov-Avrami switching kinetics in ferroelectric thin films.Phys Rev B2002;66:214109

[38] Weibull W.A statistical distribution function of wide applicability.J Appl Mech1951;18:293-7

[39] Huang T,Chen C.Demonstration of robust breakdown reliability and enhanced endurance in gallium doped HfO₂ ferroelectric thin films.IEEE Electron Device Lett2023;44:1476-9

[40] Song T,Fina I.Impact of non-ferroelectric phases on switching dynamics in epitaxial ferroelectric Hf_0.5Zr_0.5O₂ films.APL Mater2022;10:031108

[41] Stathis JH.Percolation models for gate oxide breakdown.J Appl Phys1999;86:5757-66

[42] Wurfel P.Depolarization-field-induced instability in thin ferroelectric films-experiment and theory.Phys Rev B1973;8:5126-33

[43] Mehta RR,Jacobs JT.Depolarization fields in thin ferroelectric films.J Appl Phys1973;44:3379-85

[44] Kim DJ,Kim YS.Polarization relaxation induced by a depolarization field in ultrathin ferroelectric BaTiO₃ capacitors.Phys Rev Lett2005;95:237602

[45] Mehmood F,Lomenzo PD.Bulk depolarization fields as a major contributor to the ferroelectric reliability performance in lanthanum doped Hf_0.5Zr_0.5O₂ capacitors.Adv Mater Inter2019;6:1901180