Next Article in Journal
Dimensionless Analysis to Determine Elastoplastic Properties of Thin Films by Indentation
Next Article in Special Issue
Modeling of Ionizing Radiation Effects for Negative Capacitance Field-Effect Transistors
Previous Article in Journal
Water-Soluble Holographic Photopolymers for a Sustainable Future—A Review
Previous Article in Special Issue
Combined Raman Spectroscopy and Magneto-Transport Measurements in Disordered Graphene: Correlating Raman D Band and Weak Localization Features
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Coatings
Volume 12
Issue 11
10.3390/coatings12111766
coatings-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Improvement of Ferroelectricity in Ce-Doped Hf0.5Zr0.5O2 Thin Films

by
Yong-Guang Xiao
1,2,*,
Si-Wei Liu
1,2,
Li-Sha Yang
1,2,
Yong Jiang
1,2,
Ke Xiong
1,2,
Gang Li
1,2,
Jun Ouyang
1,2 and
Ming-Hua Tang
1,2
1
Key Laboratory of Key Film Materials & Application for Equipments (Hunan Province), School of Material Sciences and Engineering, Xiangtan University, Xiangtan 411105, China
2
Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Material Sciences and Engineering, Xiangtan University, Xiangtan 411105, China
*
Author to whom correspondence should be addressed.
Coatings 2022, 12(11), 1766; https://doi.org/10.3390/coatings12111766
Submission received: 14 October 2022 / Revised: 14 November 2022 / Accepted: 16 November 2022 / Published: 18 November 2022
(This article belongs to the Special Issue Advanced Ferroelectric Materials and Films: Properties and Applications for Post Moorish Era)
Browse Figures
Versions Notes

Abstract

:
At present, ion doping is a popular method typically used to regulate the ferroelectric properties of Hf0.5Zr0.5O2 films. In this work, Ce (cerium)–doped Hf0.5Zr0.5O2 (Ce: HZO) films on Pt/TiN/SiO2/Si substrates were prepared by the chemical solution deposition (CSD) method. The microstructure and ferroelectric properties of the Ce–doped HZO films were investigated in detail. The experimental results showed that the remanent polarization value of the films with cerium doping concentration of 7 mol% reached 17 μC/cm2, which is a significant improvement compared with the undoped Hf0.5Zr0.5O2 films. The reason for this may be the introduction of cerium ions, which can introduce a certain number of oxygen vacancies, thus stabilizing the formation of the orthogonal phase. Interestingly, the films were shown to be nearly fatigue free after 109 cycles of testing. These results demonstrate that cerium ion doping is an effective method for stabilizing the formation of the orthogonal phase of HZO films, and improving the ferroelectricity of HZO thin films.

1. Introduction

In the past, hafnium dioxide has typically been used as a high-k dielectric in state-of-the-art complementary metal–oxide–semiconductor devices [1,2]. However, since the discovery that hafnium oxide doped with silicon has ferroelectric properties [3], it has attracted great attention because of its chemical simplicity, good compatibility with CMOS processes, and excellent scalability [4,5]. In recent years, HfO2 thin films doped with elements such as Y [6], Al [7], Zr [8], Sr [9], etc., showing good ferroelectric properties, have been reported. At the same time, scholars have carried out a lot of exploratory work retarding the origins of ferroelectricity of hafnium oxide [10,11,12]. It is generally believed that the ferroelectricity originates from the metastable orthorhombic phase (o-phase: Pca21). However, the steady phase is the paraelectric monoclinic phase (m-phase: P21/c). To obtain the steady ferroelectric o phase under normal conditions, many methods have been developed to stabilize the ferroelectric o phase, such as through doping elements [13,14], using flexible substrates [15,16], optimizing the annealing process [17,18], implementing special electrode materials [19,20], selecting crystal orientation [21], etc.
Among the many hafnium-based ferroelectric thin films, HZO ferroelectric thin film is the most promising choice for the application of ferroelectric memory. A lot of optimization work has been carried out with respect to its ferroelectric properties. For instance, Maxim et al. [22] fabricated La: HZO films, and a high remanent polarization value (2Pr = 30 μC/cm2) and excellent durability with 4 × 1010 endurance cycle tests were obtained. Mohit et al. [23] prepared Y: HZO films, and the experimental results showed that the doping of yttrium helped to introduce oxygen vacancies, stabilizing the ferroelectric o phase, and improving the remanent polarization value. In addition, Yin et al. [24] also improved the ferroelectricity and durability through a small concentration of Sr doping. The results showed that Sr doping increased the grain size of HZO films, thereby reducing the grain boundaries between grains and reducing the leakage current. Compared with undoped HZO films, the microstructure and ferroelectric properties of the doped hafnium zirconium oxide thin films were significantly improved by ion regulation.
In a previous report [25], HZO films were successfully prepared by a solution method. However, the films exhibited a low remanent polarization of 8 μC/cm2 and a rough surface. Recently, Shiraishi et al. [10] and Künneth et al. [26] reported that Ce element is an excellent dopant that is helpful in regulating the microstructure and improving the ferroelectric properties of hafnium oxide thin films. In the present work, we report Ce doping in Hf0.5Zr0.5O2 films, and different Ce concentrations (0 mol%, 2 mol%, 5 mol%, 7 mol%, 9 mol%) HZO thin films are fabricated by chemical solution deposition method on Pt/Ti/SiO2/Si substrates. The effects of cerium content on the microstructure and ferroelectric properties of HZO films are systematically investigated. The results demonstrate that improvement of ferroelectric polarization can be realized in CeO2-HZO solid solution thin films.

2. Experimental Procedure

The experimental process is presented in Figure 1. Hafnium acetylacetonate, zirconium acetylacetonate, acetylacetone, acetic acid and cerium nitrate were used to prepare precursor solutions. The concentration of the precursor solution was 0.1 mol/L, and the ambient humidity was kept between 10% and 30%. The weighed hafnium source, zirconium source (the mole ratio of hafnium source to hafnium source was 0.5∶0.5) and cerium source were poured into the sample bottle. Then, the acetic acid and acetylacetone with a volume ratio of 4:1 were added to the sample bottle. The obtained mixed solution was then heated and stirred in the water bath for 2 h with the temperature at 55–60 °C so as to facilitate the dissolution of cerium nitrate particles. After stirring, it was left for 72 h, then the precursor solution was filtered, before being packaged and stored in order to obtain the desired solution.
The substrate we used was Pt (111)/TiN/SiO2/Si (100), with a sheet resistance of 0.001–0.005 Ω/cm. The substrate was cleaned using the standard RCA process. Before preparing the films, the surface was wiped with ethanol to ensure that the substrate surface was clean. The prepared precursor was dropped in the center of the substrate, and rotated at 500 rpm for 15 s and 3000 rpm for 30 s, respectively, to obtain a layer of thin film, which was then dried at 180 °C for 3 min and 400 °C for 5 min. Then, the thin film was annealed in an N2 atmosphere by raising the temperature to 800 °C for 150 s, and then cooling to room temperature. Finally, a block electrode and a point electrode of Pt were plated on the thin film using an ion sputtering apparatus (GSL1100X–SPC–12, made by Hefei Jinke, Hefei, China), and the radius and the thickness of the point electrode were 100 µm and about 30 nm, respectively. It should be noted that the point electrode was prepared by means of a mask. When the ion sputtering instrument was powered on, the target splashed atoms in all directions under the action of voltage, and the atoms fell on the surface of the sample, which was covered with a mask to form the point electrodes. The phase of the films were analyzed using Grazing–angle incident X-ray diffraction (GIXRD, Neo–confucianism Ultima IV, Tokyo, Japanese). The chemical composition and valence state of the film surface species were obtained by X-ray photoelectron spectroscopy (XPS, Thermo Scientific K–Alpha, Waltham, MA, USA). The structure of the film was characterized by high-resolution transmission electron microscopy (HRTEM, FEI Talos F200X, Hillsboro, OR, USA). The ferroelectric and dielectric properties of the films were measured using a TF3000 Analyzer and a semiconductor analyzer (Agilent B1500A, Agilent Technologies, CA, America).

3. Results

3.1. Microstructure Characterization of Ce: HZO Films

Figure 2a demonstrates the XRD pattern of Ce: HZO films, with all films being annealed at 800 °C. It can be observed that the films show phase transitions with increasing cerium doping concentrations. A relatively prominent diffraction peak can be seen at 2θ = 30.4°. This peak corresponds to the (111) plane of o/t phase; although it is difficult to identify the specific phase due to their similar lattice parameters, this peak can still provide information for the identification of the structural evolution in the phase transition process [27,28,29]. Figure 2b shows that when the doping concentration changes from 0 mol% to 7 mol%, the diffraction peak of the ferroelectric o phase gradually increases, and the ferroelectric o phase potentially becomes dominant. However, when the cerium doping concentration reaches 9 mol%, the diffraction peak of (111)t is enhanced compared with the case of 7 mol%, indicating an increase in the tetragonal phase. Meanwhile, the diffraction peak of (111)o becomes weak, indicating a decrease in the ferroelectric o phase. Theoretical studies have shown that the use of an appropriate ion doping concentration can reduce the relative free energy of the m phase and the metastable o phase of HfO2 and ZrO2, thus realizing the stable formation of o phase [30]. However, the diffraction peaks at 31.7° for (111)m and 35.2° for (020)m are very weak for all doping conecentrations, and change only slightly. For the doping concentration of 0 mol%, the (–111)m diffraction peak at 26.8° is more obvious, which is suppressed with increasing doping concentration.
The chemical states and bonding environments of Ce: HZO films can be directly understood through analysis using X-ray photoelectron spectroscopy. Figure 3a presents the high-resolution XPS spectrum of Hf 4f. The bimodal peak positions of Hf 4f for the 7 mol% sample are at 16.8 eV and 18.5 eV, respectively, which can be attributed to Hf 4f7/2 and Hf 4f5/2, respectively, corresponding to the +4 valence state of hafnium in HfO2 [31]. The binding energy at about 530 eV in Figure 3b is related to the lattice oxygen, indicating the formation of Hf-O bonds, Zr–O bonds and Ce–O bonds [27]. Meanwhile, the higher binding energy at about 532 eV corresponds to non-lattice oxygen. The presence of non-lattice oxygen can be attributed to the overlapping of the surface hydroxyl groups and oxygen vacancies, but it is difficult to distinguish their contributions [28,32]. With regard to oxygen vacancies, they may be introduced when Hf4+ is replaced by Ce3+, similar to what occurs in Y-HfO2 ferroelectric films [33]. Figure 3c shows the XPS spectra of Ce3+ and Ce4+. Figure 3d presents the XPS survey spectra of 7 mol% Ce-doped films without the impurity peak. It can be observed from Figure 3a,b that the bond energy of both Hf 4f and O1s increases with increasing doping concentration, which may be related to the increase in oxygen vacancy concentration in the thin film. In a study on La: HfO2 [34], it was reported that the films with pure oxygen vacancies on the surface were able to inhibit the formation of the m phase, while a large number of oxygen vacancies caused the ferroelectric properties of the films to disappear, and a moderate oxygen vacancy concentration contributed to the stabilization of the ferroelectric o phase.
Figure 4a reveals the cross-sectional transmission electron microscope (TEM) images of the 7 mol% Ce: HZO metal–ferroelectric–metal (MIM) structure. To improve the conductivity during the test, a gold layer was deposited on platinum. It can be seen that the thickness of the Ce: HZO film was 20 nm. An enlarged HRTEM image is shown in Figure 4b. The two selected regions are marked with a yellow frame and an orange frame, respectively. Fast Fourier transform (FFT) was performed to obtain the phase structure; the inter-plane distance of the yellow frame was about 2.94 Å and the orange frame was 2.54 Å [35,36], corresponding to the (111)o and (020)m planes, respectively. It can be seen that the proportion of o phase in the thin film was much more than that of the m phase. Combined with XRD and the electrical properties (described below), the stable formation of ferroelectric o phase can be confirmed.

3.2. Electrical Properties of Ce: HZO Thin Films

Figure 5a shows the corresponding P-E hysteresis loop of Ce: Hf0.5Zr0.5O2 thin films with Ce doping concentrations ranging from 0 mol% to 9 mol%. The applied electric field was 2.5 MV/cm. It can be observed that the P-E hysteresis loop shows a small residual polarization at a doping concentration of 0 mol%. The reason for this can be seen in the XRD results presented in Figure 2. In the 0 mol% case, the diffraction peak of (111)o is not clear, indicating that the stable ferroelectric o phase has not been formed. Thus, the ferroelectricity will be very weak. With an increase in the Ce content to 5 mol%, the film shows a mixed phase consisting of o phase and m phase, and the ferroelectricity gradually appears, showing a residual polarization value of about 13 μC/cm2. Furthermore, when the Ce content reaches 7 mol%, the film exhibits pronounced ferroelectric properties, and the residual polarization value is nearly 17 μC/cm2, which is a remarkable improvement compared with the existing results listed in Table 1. However, with the increase in Ce content to 9 mol%, there is an obvious decrease in the remanent polarization, which can be seen clearly from Figure 5b. This phenomenon can also be understood from the GIXRD results presented in Figure 2. In Figure 2b, an increase in the tetragonal phase and a decrease in the ferroelectric o phase can be observed compared with the 7 mol% case, resulting in a decrease in residual polarization value. In Figure 5b, the values of the coercive field for films different Ce doping concentrations are also presented. In each case, the value of Ec of the Ce: Hf0.5Zr0.5O2 thin films is less than 1.2 MV/cm. The relatively low values of Ec may help to improve the endurance of the thin films.
Testing the relative dielectric constant versus electric field (Ɛr–E) curve is also an effective method for characterizing the ferroelectric and dielectric properties of thin films [28]. Figure 6a shows Ce: HZO thin films with different doping concentrations. The Ɛr–E curve is normal for ferroelectrics when the doping concentration is between 0 mol% and 7 mol%. When the doping concentration is 9 mol%, the Ɛr–E curve presents a double butterfly shape, showing antiferroelectricity characteristics. In previous studies, it has been found that the monoclinic phase of the hafnium oxide ferroelectric film showed a low relative dielectric constant, while the orthogonal phase and cubic phase had a high dielectric constant [13,22,37]. As shown in Figure 6b, with a doping concentration of 0 mol%, the lowest relative dielectric constant can be observed, which may be related to the dominant monoclinic phases in the film, and this phenomenon is consistent with the GIXRD diagram. The monoclinic phase decreases with increasing Ce content, while the high dielectric phase increases obviously, and the relative dielectric constant increases. With the increase in doping concentration, the hysteresis electric field of the film finally stays at about 0.2 MV/cm, which may be due to the change in film uniformity caused by different cerium doping concentrations [38]. These results indicate that the introduction of cerium can promote the uniformity of HZO films.
The polarization fatigue of the HfO2 ferroelectric layer is an important factor in determining the lifetime of non-volatile memory devices. Figure 7 shows the endurance properties of Ce: HZO thin films with three different concentrations—0 mol%, 5 mol%, and 7 mol%. The films were cycled with a bipolar square wave at a cycle field of 2.5 MV/cm and a frequency of 500 kHz. Compared with the initial state, there was a slight increase in the polarization before 106 switching cycles. This phenomenon can be attributed to the more uniform distribution of oxygen vacancies, which can reduce the domain wall pinning, and more and more domains are involved in the polarization reversal, leading to an increase in remanent polarization [39,40]. For the pure and 5 mol% concentration HZO thin films, after 108 cycling tests, obvious polarization fatigue was evident, which can be attributed to the cumulative Joule heating and charge trapping effects induced by the leakage current [24]. It is worth mentioning that the Ce: HZO thin films with 7 mol% concentration showed a stable endurance up to 109 bipolar switching cycles, which is better than the results previously reported [41,42,43]. These experimental results show that doping with cerium can greatly improve the durability of Hf0.5Zr0.5O2 films.
Table
Table 1. Properties of HfO2-based ferroelectric thin films fabricated by CSD.
Table 1. Properties of HfO2-based ferroelectric thin films fabricated by CSD.
DopantRemanent Polarization
(μC/cm2)		Coercive Field
(MV/cm)		Dopant Concentration (mol%)Substrate
(Bottom Electrode)		Film
Sm12(−1.1, +1.6)5.2Pt[11]
(Zr, Y)15(−1.4, +1.4)5Pt/Ti/SiO2/Si[23]
(Zr, Sr)14.6(−1.1, +1.1)0.5Pt/Ti/SiO2/Si[24]
Zr8(−0.8, +0.8)50Pt/TiO2/(100) Si[25]
Pr6.9(−1.2, +1.2)5Pt/TiO2/(100) Si[28]
Y14.2(+1.4, −1.8)2Si (100)[33]
La12.5(−1.1, +1.6)5.2Pt[34]
Y10(−1.6, +1.0)5Pt[39]
Ba12(−1.7, +1.5)7.5Pt/TiO2/SiO2[44]
Ca5(−0.9, +0.7)5.2Si (100)[44]
Mg3(−0.8, +0.8)7.5Pt/TiO2/SiO2[44]
(Zr, Ce)17(−1.2, +1.1)7Pt/Ti/SiO2/SiThis work

4. Conclusions

In summary, Ce: Hf0.5Zr0.5O2 thin films were successfully prepared by chemical solution deposition. The XPS results showed that appropriate Ce doping can introduce a certain amount of oxygen vacancies, which helps to form the ferroelectric o phase. In addition, Ce doping can improve the dielectric properties and uniformity of HZO films. In the Ce: Hf0.5Zr0.5O2 thin film with a doping concentration of 7 mol%, a stable ferroelectric o phase was formed, and the residual polarization value reached 17 μC/cm2. Meanwhile, after 109 bipolar switching cycles, the film showed good endurance, and only slight degradation of polarization. The results show that cerium doping can improve the ferroelectric properties and durability of Hf0.5Zr0.5O2 thin films.

Author Contributions

Writing—original draft preparation, Y.-G.X. and S.-W.L.; writing—review and editing, L.-S.Y., Y.J., K.X., G.L., J.O. and M.-H.T. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the cultivation projects of the National Major R & D Project (grant no. 92164108), the National Natural Science Foundation of China under Grant Nos. 51872250, and 11835008, the technology innovation leading plan (Science and technology tackling) project of Hunan Provincial new and high-tech industry under Grant No. 2020GK2052, the State Key Laboratory of Intense Pulsed Radiation Simulation and Effect (North west Institute of Nuclear Technology) under Grant No. SKLIPR1814, the Foundation of Innovation Center of Radiation Application (grant no. KFZC2020020901), and the Key Laboratory of Low Dimensional Materials & Application Technology of Ministry of Education (Xiangtan University) under Grant No. KF20180203.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

All data included in this study are available upon request by contact with the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Hu, Y.Q.; Wang, C.H.; Dong, H.; Wallace, R.M.; Cho, K.; Wang, W.H.; Wang, W.C. Origin of indium diffusion in high-k oxide HfO2. ACS Appl. Mater. Interfaces 2016, 8, 7595–7600. [Google Scholar] [CrossRef] [PubMed]
  2. Tirmali, P.M.; Khairnar, A.G.; Joshi, B.N.; Mahajanl, A.M. Structural and electrical characteristics of RF-sputtered HfO2 high-k based MOS capacitors. Solid-State Electron. 2011, 62, 44–47. [Google Scholar] [CrossRef]
  3. Böscke, T.S.; Müller, J.; Bräuhaus, D.; Schröder, U.; Böttger, U. Ferroelectricity in hafnium oxide thin films. Appl. Phys. Lett. 2011, 99, 102903. [Google Scholar] [CrossRef]
  4. Khan, A.I.; Keshavarzi, A.; Datta, S. The future of ferroelectric field-effect transistor technology. Nat. Electron. 2020, 3, 588–597. [Google Scholar] [CrossRef]
  5. Park, M.H.; Lee, Y.H.; Mikolajick, T.; Schroeder, U. Review and perspective on ferroelectric HfO2-based thin films for memory applications. MRS Commun. 2018, 8, 795–808. [Google Scholar] [CrossRef] [Green Version]
  6. Olsen, T.; Schröder, U.; Müller, S.; Krause, A.; Martin, D.; Singh, A.; Müller, J. Co-sputtering yttrium into hafnium oxide thin films to produce ferroelectric properties. Appl. Phys. Lett. 2012, 101, 082905. [Google Scholar] [CrossRef]
  7. Mueller, S.; Mueller, J.; Singh, A.; Riedel, S.; Sundqvist, J.; Schroeder, U.; Mikolajick, T. Incipient ferroelectricity in Al-doped HfO2 thin films. Adv. Funct. Mater. 2012, 22, 2412–2417. [Google Scholar] [CrossRef]
  8. Chouprik, A.; Chernikova, A.; Markeev, A.; Mikheev, V.; Negrov, D.; Spiridonov, M.; Zarubin, S.; Zenkevich, A. Electron transport across ultrathin ferroelectric Hf0.5Zr0.5O2 films on Si. Microelectron. Eng. 2017, 178, 250–253. [Google Scholar] [CrossRef]
  9. Wei, A.Q.; Chen, C.; Tang, L.; Zhou, K.C.; Zhang, D. Chemical solution deposition of ferroelectric Sr: HfO2 film from inorganic salt precursors. J. Alloys Compd. 2018, 731, 546–553. [Google Scholar] [CrossRef]
  10. Sourav, D.; Han, Q.B.; Bu, W.X.; Baig, M.A.; Sung, P.J.; Su, C.J.; Lee, Y.J.; Lu, D.D. Uniform crystal formation and electrical variability reduction in hafnium-oxide-based ferroelectric memory by thermal engineering. ACS Appl. Electron. Mater. 2021, 3, 619–628. [Google Scholar]
  11. Starschich, S.; Griesche, D.; Schneller, T.; Böttger, U. Chemical solution deposition of ferroelectric hafnium oxide for future lead free ferroelectric devices. ECS J. Solid State Sci. Technol. 2015, 4, P419. [Google Scholar] [CrossRef]
  12. Tromm, T.C.U.; Zhang, J.; Schubert, J.; Luysberg, M.; Zander, W.; Han, Q.; Meuffels, P.; Meertens, D.; Glass, S.; Bernardy, P.; et al. Ferroelectricity in Lu doped HfO2 layers. Appl. Phys. Lett. 2017, 111, 142904. [Google Scholar] [CrossRef] [Green Version]
  13. Mehmood, F.; Mikolajick, T.; Schroeder, U. Lanthanum doping induced structural changes and their implications on ferroelectric properties of Hf1-xZrxO2 thin film. Appl. Phys. Lett. 2020, 117, 092902. [Google Scholar] [CrossRef]
  14. Schroeder, U.; Yurchuk, E.; Müller, J.; Martin, D.; Schenk, T.; Polakowski, P. Impact of different dopants on the switching properties of ferroelectric hafniumoxide. Jpn. J. Appl. Phys. 2014, 53, 08LE02. [Google Scholar] [CrossRef]
  15. Shimizu, T.; Yokouchi, T.; Shiraishi, T.; Oikawa, T. Study on the effect of heat treatment conditions on metalorganic-chemical-vapor-deposited ferroelectric Hf0.5Zr0.5O2 thin film on Ir electrode. Jpn. J. Appl. Phys. 2014, 53, 09PA04. [Google Scholar] [CrossRef]
  16. Liu, B.W.; Zhang, Y.R.; Zhang, L.J.; Yuan, Q.T.; Zhang, W.; Li, Y.B. Excellent HZO ferroelectric thin films on flexible PET substrate. J. Alloys Compd. 2022, 919, 165872. [Google Scholar] [CrossRef]
  17. Lederer, M.; Bagul, P.; Lehninger, D.; Mertens, K.; Reck, A.; Olivo, R. Influence of annealing temperature on the structural and electrical properties of Si-doped ferroelectric hafnium oxide. ACS Appl. Electron. Mater. 2021, 3, 4115–4120. [Google Scholar] [CrossRef]
  18. Ali, T.; Olivo, R.; Kerdilès, S.; Lehninger, D.; Lederer, M.; Sourav, D.; Royet, A.-S.; Sünbül, A.; Prabhu, A.; Kühnel, K.; et al. Study of nanosecond laser annealing on silicon doped hafnium oxide film crystallization and capacitor reliability. In Proceedings of the 2022 IEEE International Memory Workshop (IMW), Dresden, Germany, 15–18 May 2022; pp. 1–4. [Google Scholar]
  19. Wang, D.; Zhang, Y.; Wang, J.L.; Luo, C.L.; Li, M.; Shuai, W.T.; Tao, R.Q.; Fan, Z.; Chen, D.Y.; Zeng, M. Enhanced ferroelectric polarization with less wake-up effect and improved endurance of Hf0.5Zr0.5O2 thin films by implementing W electrode. J. Mater. Sci. Technol. 2022, 104, 1–7. [Google Scholar] [CrossRef]
  20. Payne, A.; Hsain, H.A.; Lee, Y.; Strnad, A.N.; Jones, L.J.; Hanrahan, B. Thermal stability of antiferroelectric-like Al: HfO2 thin films with TiN or Pt electrodes. Appl. Phys. Lett. 2022, 120, 232901. [Google Scholar] [CrossRef]
  21. Katayama, K.; Shimizu, T.; Sakata, O.; Shiraishi, T.; Nakamura, S.; Kiguchi, T.; Akama, A.; Konno, J.T.; Uchida, H.; Funakubo, H. Orientation control and domain structure analysis of {100}-oriented epitaxial ferroelectric orthorhombic HfO2-based thin films. J. Appl. Phys. 2016, 119, 134101. [Google Scholar] [CrossRef]
  22. Kozodaev, M.G.; Chernikova, A.G.; Korostylev, E.V.; Park, M.H.; Khakimov, R.R.; Hwang, C.S.; Markeev, A.M. Mitigating wakeup effect and improving endurance of ferroelectric HfO2-ZrO2 thin films by careful La-doping. J. Appl. Phys. 2019, 125, 034101. [Google Scholar] [CrossRef]
  23. Mohit, T.M.; Haga, K.I.; Eisuke, T. Impact of annealing environment on electrical properties of yttrium-doped hafnium zirconium dioxide thin films prepared by the solution process. Jpn. J. Appl. Phys. 2020, 59, SPPB03. [Google Scholar] [CrossRef]
  24. Yin, L.; Gong, S.Q.; Li, X.Y.; Lu, B.B.; Peng, Q.X.; Zheng, S.Z.; Liao, M.; Zhou, Y.C. Improvement of ferroelectricity and endurance in Sr doped Hf0.5Zr0.5O2 films. J. Alloys Compd. 2022, 914, 165301. [Google Scholar] [CrossRef]
  25. Shuhei, N.; Hiroshi, F.; Hiroshi, U. Crystallization behavior and ferroelectric property of HfO2-ZrO2 films fabricated by chemical solution deposition. Jpn. J. Appl. Phys. 2018, 57, 11UF06. [Google Scholar]
  26. Künneth, C.; Materlik, R.; Falkowski, M.; Kersch, A. Impact of Four-Valent Doping on the Crystallographic Phase Formation for Ferroelectric HfO2 from First-Principles: Implications for Ferroelectric Memory and Energy-Related Applications. ACS Appl. Nano Mater. 2018, 1, 254–264. [Google Scholar] [CrossRef] [Green Version]
  27. Zheng, S.Z.; Zhao, Z.D.; Liu, Z.T.; Zeng, B.J.; Yin, L.; Peng, Q.X.; Liao, M.; Zhou, Y.C. Improvement of remanent polarization of CeO2-HfO2 solid solution thin films on Si substrates by chemical solution deposition. Appl. Phys. Lett. 2020, 117, 212904. [Google Scholar] [CrossRef]
  28. Liu, H.; Zheng, S.Z.; Chen, Q.; Zeng, B.J.; Jiang, J.; Peng, Q.X.; Liao, M.; Zhou, Y.C. Structural and ferroelectric properties of Pr doped HfO2 thin films fabricated by chemical solution method. J. Mater. Sci. Mater. Electron. 2019, 30, 5771–5779. [Google Scholar] [CrossRef]
  29. Shibayama, S.; Nagano, J.; Asaka, K.; Sakashita, M.; Nakatsuka, O. Impact of Wet Annealing on Ferroelectric Phase Formation and Phase Transition of HfO2-ZrO2 System. ACS Appl. Electron. Mater. 2021, 3, 2203–2211. [Google Scholar] [CrossRef]
  30. Falkowski, M.; Kersch, A. Optimizing the piezoelectric strain in ZrO2 and HfO2-Based incipient ferroelectrics for thin-film applications: An ab initio dopant screening study. ACS Appl. Mater. Interfaces 2020, 12, 32915–32924. [Google Scholar] [CrossRef]
  31. Avis, C.; Kim, Y.G.; Jang, J. Solution processed hafnium oxide as a gate insulator for low-voltage oxide thin-film transistors. J. Mater. Chem. 2012, 22, 17415–17420. [Google Scholar] [CrossRef]
  32. Pan, T.M.; Lu, C.H. Switching behavior in rare-earth films fabricated in full room temperature. IEEE Trans. Electron Devices 2012, 59, 956–961. [Google Scholar] [CrossRef]
  33. Wang, X.X.; Zhou, D.Y.; Li, S.D.; Liu, X.H.; Zhao, P.; Sun, N.; Ali, F.; Wang, J.J. Ferroelectric yttrium doped hafnium oxide films from all-inorganic aqueous precursor solution. Ceram. Int. 2018, 44, 13867–13872. [Google Scholar] [CrossRef]
  34. Islamov, D.R.; Zalyalov, T.M.; Orlov, O.M.; Gritsenko, V.A.; Krasnikov, G.Y. Impact of oxygen vacancy on the ferroelectric properties of lanthanum-doped hafnium oxide. Appl. Phys. Lett. 2020, 117, 162901. [Google Scholar] [CrossRef]
  35. Hsain, H.A.; Lee, Y.H.; Parsons, G. Compositional dependence of crystallization temperatures and phase evolution in hafnia-zirconia (Hf1-XZrX) O2 thin films. Appl. Phys. Lett. 2020, 116, 192901. [Google Scholar] [CrossRef]
  36. Xiao, W.W.; Liu, C.; Peng, Y.; Zheng, S.Z.; Zhang, C.F.; Liao, M.; Zhou, Y.C. Performance improvement of Hf0.5 Zr0.5O2-based ferroelectric-field-effect transistors with ZrO2 seed layers. IEEE Electron Device Lett. 2019, 40, 714–717. [Google Scholar] [CrossRef]
  37. Hoffmann, M.; Schroeder, U.; Schenk, T.; Shimizu, T.; Funakubo, H.; Sakata, O.; Pohl, D.; Drescher, M.; Adelmann, C.; Materlik, R.; et al. Stabilizing the ferroelectric phase in doped hafnium oxide. J. Appl. Phys. 2015, 118, 072006. [Google Scholar] [CrossRef]
  38. Zhao, Y.P.; Wang, G.C.; Lu, T.M.; Palasantzas, G.; De Hosson, J.T.M. Surface-roughness effect on capacitance and leakage current of an insulating film. Phys. Rev. B 1999, 60, 9157. [Google Scholar] [CrossRef] [Green Version]
  39. Fields, S.S.; Smith, S.W.; Ryan, P.J.; Jaszewski, I.A.; Alejandro, S.B.; Esteves, G.; Steve, L. Phase-exchange-driven wake-up and fatigue in ferroelectric hafnium zirconium oxide films. ACS Appl. Mater. Interfaces 2020, 12, 26577–26585. [Google Scholar] [CrossRef]
  40. Starschich, S.S.; Menzel, S.; Böttger, U. Evidence for oxygen vacancies movement during wake-up in ferroelectric hafnium oxide. Appl. Phys. Lett. 2016, 108, 032903. [Google Scholar] [CrossRef] [Green Version]
  41. Song, T.F.; Tan, H.; Estandía, S.; Gàzquez, J.; Gich, M. Improved polarization and endurance in ferroelectric Hf0.5Zr0.5O2 films on SrTiO3 (110). Nanoscale 2022, 14, 2337–2343. [Google Scholar] [CrossRef]
  42. Kim, S.J.; Mohan, J.; Summerfelt, S.R.; Kim, J. Ferroelectric Hf0.5Zr0.5O2 thin films: A review of recent advances. JOM 2019, 71, 246–255. [Google Scholar] [CrossRef]
  43. Lyu, J.; Song, T.F.; Fina, I.; Sánchez, F. High polarization, endurance and retention in sub-5 nm Hf0.5Zr0.5 O2 films. Nanoscale 2020, 12, 11280–11287. [Google Scholar] [CrossRef] [PubMed]
  44. Starschich, S.; Boettger, U. An extensive study of the influence of dopants on the ferroelectric properties of HfO2. J. Mater. Chem. C 2017, 5, 333–338. [Google Scholar] [CrossRef]
Coatings 12 01766 g001 550
Figure 1. Schematic diagram of the experimental process.
Figure 1. Schematic diagram of the experimental process.
Coatings 12 01766 g001
Coatings 12 01766 g002 550
Figure 2. (a) GIXRD of different doping concentrations films; (b) zoomed-in view of the main peak from 28° to 32°.
Figure 2. (a) GIXRD of different doping concentrations films; (b) zoomed-in view of the main peak from 28° to 32°.
Coatings 12 01766 g002
Coatings 12 01766 g003 550
Figure 3. (a) High–resolution XPS spectra of Hf 4f and (b) O 1s core level with different Ce concentrations; (c) Ce 3d and (d) XPS survey spectra of 7 mol% Ce–doped films.
Figure 3. (a) High–resolution XPS spectra of Hf 4f and (b) O 1s core level with different Ce concentrations; (c) Ce 3d and (d) XPS survey spectra of 7 mol% Ce–doped films.
Coatings 12 01766 g003
Coatings 12 01766 g004 550
Figure 4. (a) TEM images of the Pt/Ce: HZO/Pt metal–ferroelectric–metal (MIM) structure; (b) cross-sectional HRTEM image of the 7 mol% Ce doping HZO films.
Figure 4. (a) TEM images of the Pt/Ce: HZO/Pt metal–ferroelectric–metal (MIM) structure; (b) cross-sectional HRTEM image of the 7 mol% Ce doping HZO films.
Coatings 12 01766 g004
Coatings 12 01766 g005 550
Figure 5. (a) P–E curves and (b) Pr for Ce: HZO thin films with different Ce concentrations.
Figure 5. (a) P–E curves and (b) Pr for Ce: HZO thin films with different Ce concentrations.
Coatings 12 01766 g005
Coatings 12 01766 g006 550
Figure 6. (a) Ɛr–E curves and (b) hysteresis electric field of Ce: HZO thin films with different Ce concentrations.
Figure 6. (a) Ɛr–E curves and (b) hysteresis electric field of Ce: HZO thin films with different Ce concentrations.
Coatings 12 01766 g006
Coatings 12 01766 g007 550
Figure 7. Endurance properties of thin films (0, 5, 7 mol%) at a cycling field of 2.5 MV/cm and a frequency of 500 kHz.
Figure 7. Endurance properties of thin films (0, 5, 7 mol%) at a cycling field of 2.5 MV/cm and a frequency of 500 kHz.
Coatings 12 01766 g007
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Xiao, Y.-G.; Liu, S.-W.; Yang, L.-S.; Jiang, Y.; Xiong, K.; Li, G.; Ouyang, J.; Tang, M.-H. Improvement of Ferroelectricity in Ce-Doped Hf0.5Zr0.5O2 Thin Films. Coatings 2022, 12, 1766. https://doi.org/10.3390/coatings12111766

AMA Style

Xiao Y-G, Liu S-W, Yang L-S, Jiang Y, Xiong K, Li G, Ouyang J, Tang M-H. Improvement of Ferroelectricity in Ce-Doped Hf0.5Zr0.5O2 Thin Films. Coatings. 2022; 12(11):1766. https://doi.org/10.3390/coatings12111766

Chicago/Turabian Style

Xiao, Yong-Guang, Si-Wei Liu, Li-Sha Yang, Yong Jiang, Ke Xiong, Gang Li, Jun Ouyang, and Ming-Hua Tang. 2022. "Improvement of Ferroelectricity in Ce-Doped Hf0.5Zr0.5O2 Thin Films" Coatings 12, no. 11: 1766. https://doi.org/10.3390/coatings12111766

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop