Progress on hafnium oxide-based emerging ferroelectric materials and applications

Abstract

Since the discovery of ferroelectricity in Si-doped HfO₂ in 2011, HfO₂-based materials have attracted extensive interest from researchers. Their various advantages provide a broad research prospect in the field of ferroelectric materials and devices. Researchers have conducted effective studies on the origin of ferroelectricity, the wake-up effect, the fatigue effect, and the potential for device applications. These studies contribute to a better understanding of the properties and applications of HfO₂-based materials. This article provides a comprehensive review of the origin and influencing factors of ferroelectricity in HfO₂, advantages in material applications, and limitations in applications from multiple perspectives. It also introduces the currently mature methods for preparing HfO₂-based ferroelectric materials and cutting-edge applications in different device fields. Finally, the future development prospects of HfO₂-based materials are also discussed.

Keywords

hafnium oxide / ferroelectric materials / orthorhombic phase / synaptic behavior

References

[1] Mcadams H,Blake T.A 64-Mb embedded FRAM utilizing a 130-nm 5LM Cu/FSG logic process.IEEE J Solid State Circuits2004;39:667-77

[2] Xie L,Dong Z.Nonvolatile photoelectric memory induced by interfacial charge at a ferroelectric PZT-gated black phosphorus transistor.Adv Elect Mater2019;5:1900458

[3] Sulzbach MC,Long X.Unraveling ferroelectric polarization and ionic contributions to electroresistance in epitaxial Hf_0.5Zr_0.5O₂ tunnel junctions.Adv Elect Mater2020;6:1900852

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

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

[6] Guo J,Xu X.Rhombohedral R3 phase of Mn-doped Hf_0.5Zr_0.5O₂ epitaxial films with robust ferroelectricity.Adv Mater2024;36:e2406038

[7] Eom D,Lee W.Temperature-driven co-optimization of IGZO/HZO ferroelectric field-effect transistors for optoelectronic neuromorphic computing.Nano Energy2025;138:110837

[8] Yu Y,Xu Z.Structure-evolution-designed amorphous oxides for dielectric energy storage.Nat Commun2023;14:3031 PMCID:PMC10213053

[9] Zhao D,Liao X.Microstructural evolution and ferroelectricity in HfO₂ films.Microstructures2022;2:2022007

[10] Banerjee W,Kamba S.Hafnium Oxide (HfO₂) - A multifunctional oxide: a review on the prospect and challenges of hafnium oxide in resistive switching and ferroelectric memories.Small2022;18:e2107575

[11] Cao J,Zhu Y.An overview of ferroelectric hafnia and epitaxial growth.Rap Res Lett2021;15:2100025

[12] Breyer ET,Mikolajick T.Perspective on ferroelectric, hafnium oxide based transistors for digital beyond von-Neumann computing.Appl Phys Lett2021;118:050501

[13] Park MH,Mikolajick T,Hwang CS.Review and perspective on ferroelectric HfO₂-based thin films for memory applications.MRS Commun2018;8:795-808

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

[15] Ohtaka O,Kunisada T.Phase relations and volume changes of hafnia under high pressure and high temperature.J Am Ceram Soc2001;84:1369-73

[16] Park MH,Kim HJ.Ferroelectricity and antiferroelectricity of doped thin HfO₂-based films.Adv Mater2015;27:1811-31

[17] Howard CJ,Ohtaka O.Crystal structures of two orthorhombic Zirconias.J Am Ceram Soc1991;74:2321-3

[18] Arashi H.Pressure-induced phase transformation of HfO₂.J Am Ceram Soc1992;75:844-7

[19] Huan TD,Rossetti GA.Pathways towards ferroelectricity in hafnia.Phys Rev B2014;90:064111

[20] Materlik R,Kersch A.The origin of ferroelectricity in Hf_1-xZr_xO₂: a computational investigation and a surface energy model.J Appl Phys2015;117:134109

[21] Lee HJ,Lee K.Scale-free ferroelectricity induced by flat phonon bands in HfO₂.Science2020;369:1343-7

[22] Sang X,Schenk T,Lebeau JM.On the structural origins of ferroelectricity in HfO₂ thin films.Appl Phys Lett2015;106:162905

[23] Park MH,Mikolajick T,Hwang CS.Thermodynamic and kinetic origins of ferroelectricity in fluorite structure oxides.Adv Elect Mater2019;5:1800522

[24] Park MH,Kim HJ.Understanding the formation of the metastable ferroelectric phase in hafnia-zirconia solid solution thin films.Nanoscale2018;10:716-25

[25] Fan P,Yang Q.Origin of the intrinsic ferroelectricity of HfO₂ from ab initio molecular dynamics.J Phys Chem C2019;123:21743-50

[26] Wu Y,Jiang J.Unconventional polarization-switching mechanism in (Hf,Zr)O₂ ferroelectrics and its implications.Phys Rev Lett2023;131:226802

[27] Zhu T,Duan X,Liu S.Origin of interstitial doping induced coercive field reduction in ferroelectric hafnia.Phys Rev Lett2025;134:056802

[28] Peng R,Cheng X,Liao M.Revealing the role of spacer layer in domain dynamics of Hf_0.5Zr_0.5O₂ thin films for ferroelectrics.Adv Funct Mater2024;34:2403864

[29] Wang S,Liu Z.Unconventional ferroelectric-ferroelastic switching mediated by non-polar phase in fluorite oxides.Adv Mater2025;37:e2415131

[30] Li X,Gao A.Ferroelastically protected reversible orthorhombic to monoclinic-like phase transition in ZrO₂ nanocrystals.Nat Mater2024;23:1077-84

[31] Qi Y,Lau C.Stabilization of competing ferroelectric phases of HfO₂ under epitaxial strain.Phys Rev Lett2020;125:257603

[32] Wang Y,Guzman R.A stable rhombohedral phase in ferroelectric Hf(Zr)_1+xO₂ capacitor with ultralow coercive field.Science2023;381:558-63

[33] Lee K,Choi IH.Deterministic orientation control of ferroelectric HfO₂ thin film growth by a topotactic phase transition of an oxide electrode.ACS Nano2024;18:12707-15

[34] Wang S,Yang X.Unlocking the phase evolution of the hidden non-polar to ferroelectric transition in HfO₂-based bulk crystals.Nat Commun2025;16:3745 PMCID:PMC12012034

[35] Materano M,Mulaosmanovic H.Polarization switching in thin doped HfO₂ ferroelectric layers.Appl Phys Lett2020;117:262904

[36] Xu X,Qi Y.Kinetically stabilized ferroelectricity in bulk single-crystalline HfO₂:Y.Nat Mater2021;20:826-32

[37] Cheng H,Liu JM.Structure and stability of La- and hole-doped hafnia with/without epitaxial strain.J Phys Condens Matter2024;36:205401

[38] Zhang Y,Wang D.Enhanced ferroelectric properties and insulator-metal transition-induced shift of polarization-voltage hysteresis loop in VO_x-capped Hf_0.5Zr_0.5O₂ thin films.ACS Appl Mater Interfaces2020;12:40510-7

[39] Athle R,Irish A,Timm R.Effects of TiN top electrode texturing on ferroelectricity in Hf_1-xZr_xO₂.ACS Appl Mater Interfaces2021;13:11089-95 PMCID:PMC8027987

[40] Mimura T,Shimizu T.Formation of (111) orientation-controlled ferroelectric orthorhombic HfO₂ thin films from solid phase via annealing.Appl Phys Lett2016;109:052903

[41] Liu S.Effects of growth orientations and epitaxial strains on phase stability of HfO₂ thin films.Phys Rev Mater2019;3:054404

[42] Park JY,Yang K.Engineering strategies in emerging fluorite-structured ferroelectrics.ACS Appl Electron Mater2022;4:1369-80

[43] Islamov DR,Orlov OM,Krasnikov GY.Impact of oxygen vacancy on the ferroelectric properties of lanthanum-doped hafnium oxide.Appl Phys Lett2020;117:162901

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

[45] Kirbach S,Eßlinger S.Doping concentration dependent piezoelectric behavior of Si:HfO₂ thin-films.Appl Phy Lett2021;118:012904

[46] Müller J,Böscke TS.Ferroelectricity in yttrium-doped hafnium oxide.J Appl Phys2011;110:114113

[47] Starschich S,Schneller T,Böttger U.Chemical solution deposition of ferroelectric yttrium-doped hafnium oxide films on platinum electrodes.Appl Phy Lett2014;104:202903

[48] Mimura T,Funakubo H.Ferroelectricity in YO_1.5-HfO₂ films around 1 μm in thickness.Appl Phys Lett2019;115:032901

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

[50] Müller J,Bräuhaus D.Ferroelectric Zr_0.5Hf_0.5O₂ thin films for nonvolatile memory applications.Appl Phys Lett2011;99:112901

[51] Müller J,Schröder U.Ferroelectricity in simple binary ZrO₂ and HfO₂.Nano Lett2012;12:4318-23

[52] Yan F,Chen Y,Liao M.Optimization of ferroelectricity and endurance of hafnium zirconium oxide thin films by controlling element inhomogeneity.J Adv Ceram2024;13:1023-31

[53] Ansari E,Hartmann E,Stolichnov I.Vanadium-doped hafnium oxide: a high-endurance ferroelectric thin film with demonstrated negative capacitance.Nano Lett2025;25:2702-8 PMCID:PMC11849039

[54] Zhou C,Feng Y.Enhanced polarization switching characteristics of HfO₂ ultrathin films via acceptor-donor co-doping.Nat Commun2024;15:2893 PMCID:PMC10991407

[55] Park MH,Kim YJ,Hwang CS.The effects of crystallographic orientation and strain of thin Hf_0.5Zr_0.5O₂ film on its ferroelectricity.Appl Phys Lett2014;104:1243-400

[56] Karbasian G,Yadav AK,Hu C.Stabilization of ferroelectric phase in tungsten capped Hf_0.8Zr_0.2O₂.Appl Phys Lett2017;111:022907

[57] Onaya T,Sawamoto N.Improvement in ferroelectricity of Hf_xZr_1-xO₂ thin films using ZrO₂ seed layer.Appl Phys Express2017;10:081501

[58] Weeks SL,Narasimhan VK,Chiang T.Engineering of Ferroelectric HfO₂-ZrO₂ nanolaminates.ACS Appl Mater Interfaces2017;9:13440-7

[59] Cao R,Zhao S.Effects of capping electrode on ferroelectric properties of Hf_0.5Zr_0.5O₂ thin films.IEEE Electron Device Lett2018;39:1207-10

[60] Chen L,Dai YW.Ultra-low power Hf_0.5Zr_0.5O₂ based ferroelectric tunnel junction synapses for hardware neural network applications.Nanoscale2018;10:15826-33

[61] Yoong HY,Zhao J.Epitaxial ferroelectric Hf_0.5Zr_0.5O₂ thin films and their implementations in memristors for brain-inspired computing.Adv Funct Mater2018;28:1806037

[62] Bouaziz J,Baboux N.Huge reduction of the wake-up effect in ferroelectric HZO thin films.ACS Appl Electron Mater2019;1:1740-5

[63] Estandía S,Gazquez J.Engineering ferroelectric Hf_0.5Zr_0.5O₂ thin films by epitaxial stress.ACS Appl Electron Mater2019;1:1449-57

[64] Goh Y,Park SK.Crystalline phase-controlled high-quality hafnia ferroelectric with RuO₂ electrode.IEEE Trans Electron Devices2020;67:3431-4

[65] Goh Y,Park SK.Oxygen vacancy control as a strategy to achieve highly reliable hafnia ferroelectrics using oxide electrode.Nanoscale2020;12:9024-31

[66] Goh Y,Lee Y,Jeon S.Ultra-thin Hf_0.5Zr_0.5O₂ thin-film-based ferroelectric tunnel junction via stress induced crystallization.Appl Phys Lett2020;117:242901

[67] Lyu J,Fina I.High polarization, endurance and retention in sub-5 nm Hf_0.5Zr_0.5O₂ films.Nanoscale2020;12:11280-7

[68] Zou Z,Wang D.Enhancement of ferroelectricity and homogeneity of orthorhombic phase in Hf_0.5Zr_0.5O₂ thin films.Nanotechnology2021;32:335704

[69] Kim H,Oh Y.A simple strategy to realize super stable ferroelectric capacitor via interface engineering.Adv Materials Inter2022;9:2102528

[70] Wang Y,Zhao J.A robust high-performance electronic synapse based on epitaxial ferroelectric Hf_0.5Zr_0.5O₂ films with uniform polarization and high Curie temperature.Appl Mater Today2022;29:101587

[71] Mehmood F,Vishnumurthy P.Reliability improvement from La₂O₃ interfaces in Hf_0.5Zr_0.5O₂-based ferroelectric capacitors.Adv Mater Inter2023;10:2202151

[72] Wang T,Chou C,Chen M.Impact of monolayer engineering on ferroelectricity of sub-5 nm Hf_0.5Zr_0.5O₂ thin films.Acta Mater2023;250:118848

[73] Cao Y,Yang Y.Structural engineering of H_0.5Z_0.5O₂-based ferroelectric tunneling junction for fast-speed and low-power artificial synapses.Adv Elect Mater2023;9:2201247

[74] Jia S,Yang Q.Developing HZO-based superlattices to enhance fatigue-resistance by charge injection suppression.Adv Funct Mater2025;35:2501470

[75] Hoffmann M,Schenk T.Stabilizing the ferroelectric phase in doped hafnium oxide.J Appl Phys2015;118:072006

[76] Kobayashi M.On device design for steep-slope negative-capacitance field-effect-transistor operating at sub-0.2V supply voltage with ferroelectric HfO₂ thin film.AIP Adv2016;6:025113

[77] Park MH,Lee G.A comprehensive study on the mechanism of ferroelectric phase formation in hafnia-zirconia nanolaminates and superlattices.Appl Phys Rev2019;6:041403

[78] Peng Y,Liu Y.HfO₂-ZrO₂ superlattice ferroelectric capacitor with improved endurance performance and higher fatigue recovery capability.IEEE Electron Device Lett2022;43:216-9

[79] Cheema SS,Wang LC.Ultrathin ferroic HfO₂-ZrO₂ superlattice gate stack for advanced transistors.Nature2022;604:65-71

[80] Bai N,Huang J.Designing wake-up free ferroelectric capacitors based on the HfO₂/ZrO₂ superlattice structure.Adv Elect Mater2023;9:2200737

[81] Gong Z,Peng Y,Yu X.Physical origin of the endurance improvement for HfO₂-ZrO₂ superlattice ferroelectric film.Appl Phys Lett2022;121:242901

[82] Kim S,Kim MJ,Jin HS.Method to achieve the morphotropic phase boundary in Hf_xZr_1-xO₂ by electric field cycling for DRAM cell capacitor applications.IEEE Electron Device Lett2021;42:517-20

[83] Das D,Gaddam V.Sub 5 Å-EOT Hf_xZr_1-xO₂ for next-generation DRAM capacitors using morphotropic phase boundary and high-pressure (200 atm) annealing with rapid cooling process.IEEE Trans Electron Devices2022;69:103-8

[84] Kashir A.A CMOS-compatible morphotropic phase boundary.Nanotechnology2021;32:445706

[85] Kashir A.Ferroelectric and dielectric properties of Hf_0.5Zr_0.5O₂ thin film near morphotropic phase boundary.Phys Status Solidi2021;218:2000819

[86] Oh S,Hwang H.Composition optimization of Hf_xZr_1-xO₂ thin films to achieve the morphotrophic phase boundary for high- k dielectrics.J Appl Phy2023;133:154102

[87] Gaddam V,Kim T,Kim C.Novel approach to high κ (~59) and low EOT (~3.8 Å) near the morphotrophic phase boundary with AFE/FE (ZrO₂/HZO) bilayer heterostructures and high-pressure annealing.ACS Appl Mater Interfaces2022;14:43463-73

[88] Lin Y,Chang S.Role of electrode-induced oxygen vacancies in regulating polarization wake-up in ferroelectric capacitors.Appl Sur Sci2020;528:147014

[89] Buragohain P,Schenk T.Nanoscopic studies of domain structure dynamics in ferroelectric La:HfO₂ capacitors.Appl Phys Lett2018;112:222901

[90] Mizutani K,Wakabayashi H,Chang EY.Cerium oxide capping on Y-doped HfO₂ films for ferroelectric phase stabilization with endurance improvement.Jpn J Appl Phys2022;61:021006

[91] Pešić M,Larcher L.Physical mechanisms behind the field-cycling behavior of HfO₂-based ferroelectric capacitors.Adv Funct Mater2016;26:4601-12

[92] Cheng Y,Ye KH.Reversible transition between the polar and antipolar phases and its implications for wake-up and fatigue in HfO₂-based ferroelectric thin film.Nat Commun2022;13:645 PMCID:PMC8814215

[93] Mcmitchell SRC,Ronchi N.Elucidating possible crystallographic origins of wake-up mechanisms in ferroelectric hafnia.Appl Phys Lett2021;118:092902

[94] Rushchanskii KZ,Ležaić M.Ordering of Oxygen Vacancies and Related Ferroelectric Properties in HfO_{2-δ}.Phys Rev Lett2021;127:087602

[95] Miikkulainen V,Ritala M.Crystallinity of inorganic films grown by atomic layer deposition: overview and general trends.J Appl Phys2013;113:021301

[96] Cheema SS,Shanker N.Enhanced ferroelectricity in ultrathin films grown directly on silicon.Nature2020;580:478-82

[97] Yu T,Zhao J.Hf_0.5Zr_0.5O₂-based ferroelectric memristor with multilevel storage potential and artificial synaptic plasticity.Sci China Mater2021;64:727-38

[98] Liang Y,Wang Y.ZrO₂-HfO₂ superlattice ferroelectric capacitors with optimized annealing to achieve extremely high polarization stability.IEEE Electron Device Lett2022;43:1451-4

[99] Lee Y,Fields SS.Unexpectedly large remanent polarization of Hf_0.5Zr_0.5O₂ metal-ferroelectric-metal capacitor fabricated without breaking vacuum.Appl Phys Lett2021;118:012903

[100] Profijt HB,van de Sanden MCM.Plasma-assisted atomic layer deposition: basics, opportunities, and challenges.J Vac Sci Technol A2011;29:050801

[101] Van Bui H,Gupta A.Initial growth, refractive index, and crystallinity of thermal and plasma-enhanced atomic layer deposition AlN films.J Vac Sci Technol A2015;33:01A111

[102] Onaya T,Sawamoto N.Ferroelectricity of Hf_xZr_1-xO₂ thin films fabricated by 300 °C low temperature process with plasma-enhanced atomic layer deposition.Microelectron Eng2019;215:111013

[103] Ahn Y,Lim S.Effects of plasma power on ferroelectric properties of HfO₂-ZrO₂ nanolaminates produced by plasma enhanced atomic layer deposition.Surf Interfaces2023;37:102669

[104] Chesnokov YM,Rogozhin AE,Vasiliev AL.Microstructure and electrical properties of thin HfO₂ deposited by plasma-enhanced atomic layer deposition.J Mater Sci2018;53:7214-23

[105] Onaya T,Jung YC.Correlation between ferroelectricity and ferroelectric orthorhombic phase of Hf_xZr_1-xO₂ thin films using synchrotron X-ray analysis.APL Mater2021;9:031111

[106] Xiao W,Peng Y.Memory window and endurance improvement of Hf_0.5Zr_0.5O₂-based FeFETs with ZrO₂ seed layers characterized by fast voltage pulse measurements.Nanoscale Res Lett2019;14:254 PMCID:PMC6660534

[107] Chen H,Liu L.Significant improvement of ferroelectricity and reliability in Hf_0.5Zr_0.5O₂ films by inserting an ultrathin Al₂O₃ buffer layer.Appl Surf Sci2021;542:148737

[108] Ryu J,Kim S.Long-term and short-term plasticity of Ta₂O₅/HfO₂ memristor for hardware neuromorphic application.J Alloys Compd2021;850:156675

[109] Cho JW,Choi IH.Atomic layer deposition of epitaxial ferroelectric Hf_0.5Zr_0.5O₂ thin films.Adv Funct Mater2024;34:2314396

[110] Wang J,Zeng M.Excellent ferroelectric properties of Hf_0.5Zr_0.5O₂ thin films induced by Al₂O₃ dielectric layer.IEEE Electron Device Lett2019;40:1937-40

[111] Kashir A,Oh S.Large remnant polarization in a wake-up free Hf_0.5Zr_0.5O₂ ferroelectric film through bulk and interface engineering.ACS Appl Electron Mater2021;3:629-38

[112] Liu B,Zhang W.Excellent ferroelectric Hf_0.5Zr_0.5O₂ thin films with ultra-thin Al₂O₃ serving as capping layer.Appl Phys Lett2021;119:172902

[113] Wang C,Wang C.Evolution of pronounced ferroelectricity in Hf_0.5Zr_0.5O₂ thin films scaled down to 3 nm.J Mater Chem C2021;9:12759-67

[114] Kim S,Jeon YR,Ku B.Engineering synaptic characteristics of TaO_x/HfO₂ bi-layered resistive switching device.Nanotechnology2018;29:415204

[115] Shiraishi T,Yokouchi T.Impact of mechanical stress on ferroelectricity in (Hf_0.5Zr_0.5)O₂ thin films.Appl Phys Lett2016;108:262904

[116] Sulzbach MC,Gàzquez J,Fina I.Blocking of conducting channels widens window for ferroelectric resistive switching in interface-engineered Hf_0.5Zr_0.5O₂ tunnel devices.Adv Funct Mater2020;30:2002638

[117] 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

[118] Estandía S,Varela M.Critical effect of the bottom electrode on the ferroelectricity of epitaxial Hf_0.5Zr_0.5O₂ thin films.J Mater Chem C2021;9:3486-92

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

[120] Lyu J,Solanas R,Sánchez F.Growth window of ferroelectric epitaxial Hf_0.5Zr_0.5O₂ thin films.ACS Appl Electron Mater2019;1:220-8

[121] Long X,Estandía S.Enhanced electroresistance endurance of capped Hf_{0. 5}Zr_{0. 5}O₂ ultrathin epitaxial tunnel barriers.APL Mater2022;10:031114

[122] Mittermeier B,Horoschenkoff A.CMOS compatible Hf_0.5Zr_0.5O₂ ferroelectric tunnel junctions for neuromorphic devices.Adv Intell Syst2019;1:1900034

[123] Chen X,Tian Z,Zhu Y.A two-terminal binary HfO₂ resistance switching random access memory for an artificial synaptic device.J Mater Chem C2023;11:622-9

[124] Chen X,Tian Z,Su L.Study of resistive switching behavior in HfO₂ nanocrystals synthesized via a low temperature hydrothermal method.Nanotechnology2024;35:125203

[125] Jeong DS.Nonvolatile memory materials for neuromorphic intelligent machines.Adv Mater2018;30:e1704729

[126] Chanthbouala A,Cherifi RO.A ferroelectric memristor.Nat Mater2012;11:860-4

[127] Bégon-Lours L,Popoff Y.Ferroelectric, analog resistive switching in back-end-of-line compatible TiN/HfZrO₄/TiO_x junctions.Rap Res Lett2021;15:2000524

[128] Prasad B,Kalitsov A,Terris B.Large tunnel electroresistance with ultrathin Hf_0.5Zr_0.5O₂ ferroelectric tunnel barriers.Adv Elect Mater2021;7:2001074

[129] Du X,Wang H,Yin Y.High-speed switching and giant electroresistance in an epitaxial Hf_0.5Zr_0.5O₂-based ferroelectric tunnel junction memristor.ACS Appl Mater Interfaces2022;14:1355-61

[130] Yang Y.Probing memristive switching in nanoionic devices.Nat Electron2018;1:274-87

[131] Chand U,Huang C,Lin C.Investigation of thermal stability and reliability of HfO₂ based resistive random access memory devices with cross-bar structure.J Appl Phys2015;117:184105

[132] Murdoch BJ,Ganesan R,Bilek MMM.Memristor and selector devices fabricated from HfO_2-xN_x.Appl Phys Lett2016;108:143504

[133] Zhu Z,Gao C,Yan X.A Cu/HZO/GeS/Pt memristor for neuroinspired computing.Rap Res Lett2021;15:2100072

[134] Matveyev Y,Markeev A.Resistive switching and synaptic properties of fully atomic layer deposition grown TiN/HfO₂/TiN devices.J Appl Phys2015;117:044901

[135] Niu G,Auf der Maur M.Geometric conductive filament confinement by nanotips for resistive switching of HfO₂-RRAM devices with high performance.Sci Rep2016;6:25757 PMCID:PMC4867633

[136] Chandrasekaran S,Saminathan R,Tseng TY.Improving linearity by introducing Al in HfO₂ as a memristor synapse device.Nanotechnology2019;30:445205

[137] Zhu J,Yang Y.A comprehensive review on emerging artificial neuromorphic devices.Appl Phys Rev2020;7:011312

[138] Zeng T,Hu K.Approaching the ideal linearity in epitaxial crystalline-type memristor by controlling filament growth.Adv Mater2024;36:e2401021

[139] Covi E,Serb A,Fanciulli M.HfO₂-based memristors for neuromorphic applications. In 2016 IEEE International Symposium on Circuits and Systems (ISCAS); 2016.

[140] Jiang H,Lin P.Sub-10 nm Ta channel responsible for superior performance of a HfO₂ memristor.Sci Rep2016;6:28525 PMCID:PMC4917839

[141] Liu C,Cao Y,Wang P.Optimization of oxygen vacancy concentration in HfO₂/HfO_x bilayer-structured ultrathin memristors by atomic layer deposition and their biological synaptic behavior.J Mater Chem C2020;8:12478-84

[142] Ryu JH.Artificial synaptic characteristics of TiO₂/HfO₂ memristor with self-rectifying switching for brain-inspired computing.Chaos Solitons Fractals2020;140:110236

[143] Ismail M,Mahata C,Kim S.Demonstration of synaptic and resistive switching characteristics in W/TiO₂/HfO₂/TaN memristor crossbar array for bioinspired neuromorphic computing.J Mater Sci Technol2021;96:94-102

[144] Wang TY,He ZY.Atomic layer deposited Hf_0.5Zr_0.5O₂-based flexible memristor with short/long-term synaptic plasticity.Nanoscale Res Lett2019;14:102 PMCID:PMC6420527

[145] Margolin I,Mikheev V,Negrov D.Flexible HfO₂-based ferroelectric memristor.Appl Phys Lett2022;121:102901

[146] Matveyev Y,Negrov D.Polarization-dependent electric potential distribution across nanoscale ferroelectric Hf_0.5Zr_0.5O₂ in functional memory capacitors.Nanoscale2019;11:19814-22

[147] Fan Z,Wang J.Ferroelectric HfO₂-based materials for next-generation ferroelectric memories.J Adv Dielect2016;06:1630003

[148] Xiao Z,Cao J,Chen J.Controlling resistance switching performances of Hf_0.5Zr_0.5O₂ films by substrate stress and potential in neuromorphic computing.Adv Intell Syst2022;4:2100244

[149] Zhu Z,Huang X.Improving the synaptic behavior with polar orthorhombic phase in Hf_0.5Zr_0.5O₂ film.ACS Appl Electron Mater2023;5:4682-9

[150] Zhao Z.Ferroelectric memristor based on Hf_0.5Zr_0.5O₂ thin film combining memristive and neuromorphic functionalities.Rap Res Lett2020;14:2000224

[151] Huang W,Zhang Y.HfO₂-based ferroelectric field-effect-transistor with large memory window and good synaptic behavior.ECS J Solid State Sci Technol2021;10:065012

[152] Tsai SH,Wang X.Stress-memorized HZO for high-performance ferroelectric field-effect memtransistor.ACS Appl Electron Mater2022;4:1642-50

[153] Halter M,Bragaglia V.Back-end, CMOS-compatible ferroelectric field-effect transistor for synaptic weights.ACS Appl Mater Interfaces2020;12:17725-32

[154] Liang T,Zhao Y.High-performance artificial synapse developed by HZO on (110) NSTO.ACS Appl Nano Mater2024;7:19006-13

[155] Siannas N,Tsipas P.Electronic synapses enabled by an epitaxial SrTiO_3-δ/Hf_0.5Z_r0.5O₂ ferroelectric field-effect memristor integrated on silicon.Adv Funct Mater2024;34:2311767

[156] Nie F,Wang J.An adaptive solid-state synapse with Bi-directional relaxation for multimodal recognition and spatio-temporal learning.Adv Mater2025;37:e2412006

[157] Shen Z,Wang Q.Full-vdW heterosynaptic memtransistor with the ferroelectric inserted functional layer and its neuromorphic applications.Adv Funct Mater2025;35:2412832

[158] Hu Y,Liu N.Artificial optoelectronic synapses based on light-controllable ferroelectric semiconductor memristor.Adv Opt Mater2024;12:2302887

[159] Roy S,Jena AK.Analog-digital hybridity of resistive switching in ion-irradiated BiFeO₃ memristor for synergistic neuromorphic functionality and artificial learning.Adv Mater Technol2025;10:2400557