Synergetic contributions of chemical doping and epitaxial stress to polarization in ferroelectric HfO2 films

Song, Tingfeng; Tan, Huan; Robert, Anne-Claire; Estandía, Saúl; Gàzquez, Jaume; Sánchez, F.; Fina, Ignasi

doi:10.1016/j.apmt.2022.101621

Cited by 16 publications

(26 citation statements)

References 36 publications

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“…All samples show similar topography, as revealed by atomic force microscopy data reported in the indicated references, with smooth surfaces (root mean square <0.5 nm) showing terraces and steps. ,,,− Topography in the thickness set of samples has not been reported, but a similar or smoother surface can be expected. Scanning transmission electron microscopy in some representative samples of those reported here − shows grain sizes in the 5–10 nm range. The reference ≈140 nm PbZr 0.2 Ti 0.8 O 3 film on the SrRuO 3 bottom electrode on the SrTiO 3 (001) substrate with d 33 ≈ 37 pm V –1 was also grown for comparison.…”

Section: Methodssupporting

confidence: 62%

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Effects of Doping, Stress, and Thickness on the Piezoelectric Response and Its Relation with Polarization in Ferroelectric HfO₂

Tan,

Estandía,

Sánchez

et al. 2023

ACS Appl. Electron. Mater.

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The piezoelectric response in hafnia is of interest because it is a CMOScompatible material. It is known that polarization depends on the stabilization of the orthorhombic phase, which depends on several parameters, such as doping, stress, and thickness. Here, the piezoelectric response in epitaxial doped HfO 2 films characterized by piezoelectric force microscopy, is investigated considering this multifactorial dependence. The impact of different levels of La and Zr doping, variations of stress effects controlled by substrate selection, and thickness effects on piezoresponse is analyzed. It is found that the piezoelectric response is mainly correlated with the polarization, i.e., it is primarily determined by the amount of the orthorhombic phase. Interestingly, Zr doping of hafnia is observed to result in a larger piezoresponse than La doping for films showing similar polarization. The piezoresponse is found to be the greatest for the pure ZrO 2 film; however, the actual ferroelectric response is not observed by piezoelectric force microscopy, indicating an exception to the general tendency. It is concluded that in the case of samples showing larger amounts of the orthorhombic phase, extrinsic effects due to the tip radii effect can influence the evaluation of the amplitude of the piezoresponse.

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Section: Methodssupporting

confidence: 62%

“…PFM amplitude and phase images after prepoling the samples with the microscopy tip at ±8 V (indicated with symbols) for (a–f) Hf 0.98 La 0.02 O 2 and (g–l) Hf 0.5 Zr 0.5 O 2 sets of films on indicated substrates. Panels (a–f) reproduced from ref . Panels (g–l) reproduced from ref .…”

Section: Resultsmentioning

confidence: 99%

Effects of Doping, Stress, and Thickness on the Piezoelectric Response and Its Relation with Polarization in Ferroelectric HfO₂

Tan,

Estandía,

Sánchez

et al. 2023

ACS Appl. Electron. Mater.

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“…The θ–2θ scan using a point detector (see Supporting Information Figure S2) was used to determine a lattice spacing of ≈ 2.962 Å between HZO(111) planes. The 2θ–χ frame does not show the presence of any other spurious phase, although precedent transmission electron microscopy studies have identified traces of a minority monoclinic paraelectric phase. , Monoclinic, tetragonal, and cubic nonferroelectric phases of ZrO 2 and HfO 2 are the stable ones. , The ultimate reason for stabilization of the metastable ferroelectric orthorhombic phase is still under debate, and several origins such as doping, capping layers effect, stress effects, , and surface and/or interface energy contributions , have been proposed. YSZ(002), CeO 2 (002), and LNO (001) spots from the buffer layer are also visible.…”

Section: Resultsmentioning

confidence: 99%

“…36,37 Monoclinic, tetragonal, and cubic nonferroelectric phases of ZrO 2 and HfO 2 are the stable ones. 4,5 The ultimate reason for stabilization of the metastable ferroelectric orthorhombic phase is still under debate, and several origins such as doping, capping layers effect, 38 stress effects, 35,39 and surface and/or interface energy contributions 40,41 have been proposed. YSZ(002), CeO 2 (002), and LNO (001) spots from the buffer layer are also visible.…”

Section: ■ Resultsmentioning

confidence: 99%

Ferroelectric Electroresistance after a Breakdown in Epitaxial Hf_0.5Zr_0.5O₂Tunnel Junctions

Long

Tan

Sánchez

et al. 2023

ACS Appl. Electron. Mater.

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The recent discovery of ferroelectricity in doped HfO2 has opened perspectives on the development of memristors based on ferroelectric switching, including ferroelectric tunnel junctions. In these devices, conductive channels are formed in a similar manner to junctions based on nonferroelectric oxides. The formation of the conductive channels does not preclude the presence of ferroelectric switching, but little is known about the device ferroelectric properties after conduction path formation or their impact on the electric modulation of the resistance state. Here, we show that ferroelectricity and related sizable electroresistance are observed in pristine 4.6 nm epitaxial Hf0.5Zr0.5O2 (HZO) tunnel junctions grown on Si. After a soft breakdown induced by the application of suitable voltage, the resistance decreases by about five orders of magnitude, but signatures of ferroelectricity and electroresistance are still observed. Impedance spectroscopy allows us to conclude that the effective ferroelectric device area after the breakdown is reduced, most likely by the formation of conducting paths at the edge.

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“…[10,11,12] One of the most promising strategies used to stabilize the orthorhombic (o-) phase and enhance the ferroelectric properties of HZO films was the use of tensile stress. [13,14,15] Different tensile stress levels can be obtained by the appropriate choice of the electrodes, since the difference in the thermal expansion coefficient (TEC) of HZO and the electrode is one of the important origins of tensile stress when the films are cooled down to room temperature.…”

Section: Introductionmentioning

confidence: 99%

Ferroelectric Orthorhombic ZrO₂ Thin Films Achieved Through Nanosecond Laser Annealing

et al. 2023

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A new approach for the stabilization of the ferroelectric orthorhombic ZrO2 films is demonstrated through nanosecond laser annealing (NLA) of as‐deposited Si/SiOx/W(14 nm)/ZrO2(8 nm)/W(22 nm), grown by ion beam sputtering at low temperatures. The NLA process optimization is guided by COMSOL multiphysics simulations. The films annealed under the optimized conditions reveal the presence of the orthorhombic phase, as confirmed by X‐ray diffraction, electron backscatter diffraction, and transmission electron microscopy. Macroscopic polarization‐electric field hysteresis loops show ferroelectric behavior, with saturation polarization of 12.8 µC cm−2, remnant polarization of 12.7 µC cm−2 and coercive field of 1.2 MV cm−1. The films exhibit a wake‐up effect that is attributed to the migration of point defects, such as oxygen vacancies, and/or a transition from nonferroelectric (monoclinic and tetragonal phase) to the ferroelectric orthorhombic phase. The capacitors demonstrate a stable polarization with an endurance of 6.0 × 105 cycles, demonstrating the potential of the NLA process for the fabrication of ferroelectric memory devices with high polarization, low coercive field, and high cycling stability.

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Synergetic contributions of chemical doping and epitaxial stress to polarization in ferroelectric HfO2 films

Cited by 16 publications

References 36 publications

Effects of Doping, Stress, and Thickness on the Piezoelectric Response and Its Relation with Polarization in Ferroelectric HfO₂

Effects of Doping, Stress, and Thickness on the Piezoelectric Response and Its Relation with Polarization in Ferroelectric HfO₂

Ferroelectric Electroresistance after a Breakdown in Epitaxial Hf_0.5Zr_0.5O₂Tunnel Junctions

Ferroelectric Orthorhombic ZrO₂ Thin Films Achieved Through Nanosecond Laser Annealing

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Synergetic contributions of chemical doping and epitaxial stress to polarization in ferroelectric HfO2 films

Cited by 16 publications

References 36 publications

Effects of Doping, Stress, and Thickness on the Piezoelectric Response and Its Relation with Polarization in Ferroelectric HfO2

Effects of Doping, Stress, and Thickness on the Piezoelectric Response and Its Relation with Polarization in Ferroelectric HfO2

Ferroelectric Electroresistance after a Breakdown in Epitaxial Hf0.5Zr0.5O2Tunnel Junctions

Ferroelectric Orthorhombic ZrO2 Thin Films Achieved Through Nanosecond Laser Annealing

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Product

Resources

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Effects of Doping, Stress, and Thickness on the Piezoelectric Response and Its Relation with Polarization in Ferroelectric HfO₂

Effects of Doping, Stress, and Thickness on the Piezoelectric Response and Its Relation with Polarization in Ferroelectric HfO₂

Ferroelectric Electroresistance after a Breakdown in Epitaxial Hf_0.5Zr_0.5O₂Tunnel Junctions

Ferroelectric Orthorhombic ZrO₂ Thin Films Achieved Through Nanosecond Laser Annealing