Ferroelectric and piezoelectric properties of Hf1-xZrxO2 and pure ZrO2 films

Starschich, S.; Schenk, Tony; Schroeder, Uwe; Boettger, Ulrich

doi:10.1063/1.4983031

Cited by 151 publications

(124 citation statements)

References 44 publications

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“…The 100, 200, and 500 nm-thick films exhibit almost the same d 33 in both pristine and cycle state. The absolute values are about 30% smaller than for the 1 μm-thick film, which again might be due to the slightly better average orientation of the thickest film.The order of magnitude of the effective d 33 as well as the observation of the decrease in displacement is in agreement with the earlier results ranging from 1 to 10 pm V À1 [1,17,42,43] (Starschich et al [17] quantified 10 pm V À1 for a unipolar measurement, whereas their Figure 2 suggests 20 pm V À1 for the pristine and 5 pm V À1 for the fatigued case of a bipolar large-signal measurement). Nonetheless, this behavior requires further studies, and CSD films do not endure as many switching cycles as their ALD or PVD counterparts (10 5 -10 11 depending on the frequency Figure 1. a) GIXRD patterns (log scale) of the 45 nm-thick La:HfO 2 thin films compared with the reference patterns from powder diffraction files (m, o, and c indicate the monoclinic, orthorhombic, and cubic phase, respectively); b) corresponding characteristics of polarization P versus electric field E; c) remanent polarization P r and relative permittivity ε r for different La contents.…”

supporting

confidence: 91%

“…The result is a dominant monoclinic bulk-phase and diminished FE behavior. In contrast, Park et al [48] showed that the 390 nm-thick solution-deposited ZrO 2 films in the report of Starschich et al [17] exhibit a fine-grained microstructure with grain radii in the range of 10 nm. It was proposed that this is the reason why the diminishment of the FE properties with increasing film thickness was only very minor.…”

mentioning

confidence: 93%

“…It should be pointed out that similar features can be found in refs. [17,30], even if less prominent or less visible due to a linear intensity axis. At the moment, we can only speculate that the microstructure discussed in Section 3 may play a role.…”

mentioning

confidence: 98%

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Toward Thick Piezoelectric HfO₂‐Based Films

Schenk

Godard

Mahjoub

et al. 2019

Physica Rapid Research Ltrs

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For HfO2‐based films, which are mainly prepared by atomic layer deposition, the desired ferroelectric (FE) properties typically vanish while extending the thickness beyond a limit of about 50 nm. Herein, the successful fabrication of a 1 μm‐thick piezoelectric La:HfO2 film is demonstrated using chemical solution deposition, paving the way toward sensor and actuator applications. After identifying the optimal La content, the film thickness is increased from 45 nm to 1 μm. Polarization and strain measurements evidence the persistence of the FE properties at all thicknesses and even a slight improvement due to a better orientation of the polar axis at higher thicknesses. Scanning electron microscopy and X‐ray reflectivity reveal a fine‐grained microstructure and a density of only 80% of the theoretical value, which seems to be a common issue of solution‐deposited HfO2‐based films, based on the performed literature survey. Using tilt‐angle‐dependent X‐ray diffraction scans, homogeneous nucleation is found to be the likely root cause of the observed microstructure. It is suggested that this microstructure issue is key for the optimization of cycling stability of solution‐based films to exploit the full potential of the HfO2 for cost‐efficient, thick piezoelectric films.

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confidence: 91%

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confidence: 93%

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Toward Thick Piezoelectric HfO₂‐Based Films

Schenk

Godard

Mahjoub

et al. 2019

Physica Rapid Research Ltrs

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“…The observations are compared to the system (Hf,Zr)O 2 , which has a much wider concentration window to achieve a stable ferroelectric phase. Combining these observations with the effects of grain size [3,13] and oxygen vacancies [52] on phase stability as well as the occurrence of internal bias fields, it can be concluded that the Si:HfO 2 system is a rather fragile system. This is mainly due to the role of Si as a very efficient stabilizer of the tetragonal phase which partially closes the window for a stable FE phase opened by factors such as O vacancies and surface energy.…”

Section: Wwwadvelectronicmatdementioning

confidence: 94%

Si Doped Hafnium Oxide—A “Fragile” Ferroelectric System

Richter

Schenk

Park

et al. 2017

Adv Elect Materials

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a wealth of different elements from the periodic table [7][8][9] have since exhibited ferroelectric properties. In their original publication, Böscke et al. [10] used ≈10 nm thick films of Si:HfO 2 and found the electrical behavior to evolve from paraelectric (PE) to ferroelectric (FE) and antiferroelectriclike to paraelectric again with a continuous increase in the Si dopant concentration. A similar electric evolution has also been shown for aluminum doping [11] and for (Hf,Zr)O 2 . [6,12] For the latter, an advanced understanding of the phase stabilization could be established, assisted in part by the very wide concentration window over which the changes occur. Ab initio calculations [13] interrogated the impact of surface energy in this system, revealing a phase transition from monoclinic pure HfO 2 to orthorhombic Hf 0.5 Zr 0.5 O 2 to tetragonal pure ZrO 2 for 10 nm film thickness, which aligns well the experimental observations. Moreover, inclusion of an electric field effect explained the antiferroelectriclike polarization hysteresis of pure ZrO 2 as the result of a fieldinduced phase transition from a nonpolar tetragonal to a polar orthorhombic phase. [6,13,14] Thus, instead of the term antiferroelectricity, field-induced ferroelectricity (FFE) is becoming a more precise and commonly used way to describe this behavior. While Si:HfO 2 and Al:HfO 2 have quickly been used in applications such as ferroelectric field effect transistors in 28 nm technology [15,16] and 3D capacitors, [17] basic material studies of doped ferroelectric HfO 2 have lagged those of the (Hf,Zr) O 2 system. By exploring a wide Si concentration range in fine steps, this work aims to gain insight into the phase transformations that occur in a doped HfO 2 system. Results and Discussion Impact of Annealing ConditionsAs a first step, planar capacitor stacks (Figure 1) with ≈36 nm thick HfO 2 films are deposited using a 22:1 HfO 2 :SiO 2 cycle ratio. As shown later, this results in a Si content that is slightly higher than the one that has produced the highest remanent polarization P r values in this study (Figure 7). As visible in Figure 2, the P r (measured under an electric field of 4 MV cm −1 and 10 kHz) increases for anneals at higher temperatures.Silicon doped hafnium oxide was the material used in the original report of ferroelectricity in hafnia in 2011. Since then, it has been subject of many further publications including the demonstration of the world's first ferroelectric field-effect transistor in the state-of-the-art 28 nm technology. Though many studies are conducted with a strong focus on application in memory devices, a comprehensive study on structural stability in these films remains to be seen. In this work, a film thickness of about 36 nm, instead of the 10 nm used in most previous studies, is utilized to carefully probe how the concentration range impacts the evolution of phases, the dopant distribution, the field cycling effects, and their interplay in the macroscopic ferroelectric response of the films. Si:HfO 2 appear...

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“…However, it does not necessarily imply that direct measurement is impossible. With the chemical solution deposition, fluorite‐structured ferroelectric oxide films with thickness up to 390 nm were fabricated . Therefore, direct measurement of Δ T or Δ S of doped HfO 2 or (Hf,Zr)O 2 thin films should be possible in the near future.…”

Section: Theoretical and Experimentally Observed δS Values And Appliementioning

confidence: 99%

Broad Phase Transition of Fluorite‐Structured Ferroelectrics for Large Electrocaloric Effect

Park

Mikolajick

Schroeder

et al. 2019

Physica Rapid Research Ltrs

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Field‐induced ferroelectricity in (doped) hafnia and zirconia has attracted increasing interest in energy‐related applications, including energy harvesting and solid‐state cooling. It shows a larger isothermal entropy change in a much wider temperature range compared with those of other promising candidates. The field‐induced phase transition occurs in an extremely wide temperature range, which contributes to the giant electrocaloric effect. This article examines the possible origins of a large isothermal entropy change, which can be related to the extremely broad phase transitions in fluorite‐structured ferroelectrics. While the materials possess a high entropy change associated with the polar–nonpolar phase transition, which can contribute to the high energy performance, the higher breakdown field compared with perovskites practically determines the available temperature range.

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Ferroelectric and piezoelectric properties of Hf1-xZrxO2 and pure ZrO2 films

Cited by 151 publications

References 44 publications

Toward Thick Piezoelectric HfO₂‐Based Films

Toward Thick Piezoelectric HfO₂‐Based Films

Si Doped Hafnium Oxide—A “Fragile” Ferroelectric System

Broad Phase Transition of Fluorite‐Structured Ferroelectrics for Large Electrocaloric Effect

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Ferroelectric and piezoelectric properties of Hf1-xZrxO2 and pure ZrO2 films

Cited by 151 publications

References 44 publications

Toward Thick Piezoelectric HfO2‐Based Films

Toward Thick Piezoelectric HfO2‐Based Films

Si Doped Hafnium Oxide—A “Fragile” Ferroelectric System

Broad Phase Transition of Fluorite‐Structured Ferroelectrics for Large Electrocaloric Effect

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Product

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Toward Thick Piezoelectric HfO₂‐Based Films

Toward Thick Piezoelectric HfO₂‐Based Films