High‐Throughput Exploration of Phase Evolution in (Pb1−XBaX)ZrO3 Thin Films

Antiferroelectric thin films hold significant potential for bringing novel physics phenomena and fascinating properties. Their applications are often intertwined with the antiferroelectric‐ferroelectric phase transition, which is contingent on the chemical compositions of the constituent material. Nevertheless, the prevailing trial‐and‐error‐based research methodology is ill‐suited for the exploration of the relationship between chemical compositions and the antiferroelectric‐ferroelectric phase transition. To address this challenge, a high‐throughput synthesis strategy for antiferroelectric thin films is presented, which is enabled by an advanced high‐throughput pulsed laser deposition technology. The effectiveness of this synthesis strategy using (Pb1−XBaX)ZrO3 and achieving precise control over the parameter X is showcased. This approach allows for the deposition of (Pb1−XBaX)ZrO3 thin films encompassing nine chemical compositions ranging from X = 0 to X = 0.08. Based on this high‐throughput method, the composition that corresponds to the phase transition of (Pb1−XBaX)ZrO3, falling within the range of X = 0.04 to X = 0.06 is pinpointed. Furthermore, a temperature‐dependent correlation between the phase transition and chemical composition is established. This work not only presents a practical routine for establishing a comprehensive map of material chemical composition in relation to the properties of antiferroelectric thin films but also offers a method for the high‐throughput exploration of complex oxide thin films.


Introduction
9][10] Wherein, the doping elements stand out as the most attractive route due to the antiferroelectricity that can be adjusted or maintained by controlling the elemental content conveniently.[17][18][19][20][21] Notably, the introduction of Ba 2+ dopants results in a significant reduction in the critical electric field, [17] leading to substantial reductions in device power consumption and device size.Nevertheless, limited studies have been conducted to establish a comprehensive relationship between the doping ratios and phase transition characteristics in antiferroelectric thin films.In the case of (Pb 1−X Ba X )ZrO 3 thin films, lots of studies have investigated the relationship between doping ratios and property performance, but the majority of these reports are based on individually prepared samples, [18,21] their method is not only laborintensive and time-consuming but also prone to experimental errors, which can introduce uncertainties in the relationship between material chemical compositions and properties.
[24] High-throughput synthesis, as an indispensable step, enables parallel experiments on a single parameter to be conducted with great efficiency. [25,26][29] More recent high-throughput synthesis methods that combine thin film deposition with masking technology have attracted considerable attention, and have successfully produced samples with concentration gradients in chemical compositions, leading to the fabrication of high-throughput thin films such as (Ba,Sr,Ce)(Mn,Ce)O 3 , Cu─Cr─Co and Mg X Zn 1−X O. [30][31][32][33] Nonetheless, there have been no reports on high-throughput methods to produce antiferroelectric thin films and subsequent exploration of their phase transition.This is primarily because antiferroelectric thin films typically demand stringent growth conditions, and their phase transition properties are extremely sensitive to their chemical compositions. [17]Consequently, challenges arise in both the preparation process and the associated data analysis.
To render the efficiency of future research on antiferroelectric thin films, we have developed a high-throughput pulsed laser deposition (HT-PLD) technology for depositing antiferroelectric thin films.The HT-PLD technology is enabled by an HT-PLD system that is equipped with modules of rapidly switchable targets and fast-moving masks, which can divide the substrate into desirable local regions with precise control of the chemical compositions of films in each region.The use of HT-PLD technol-ogy not only allows precise control over the doping chemical composition but also ensures the uniform growth parameters of antiferroelectric thin films.As a result, we initially employed the HT-PLD technique to screen the deposit temperature for PbZrO 3 film.Subsequently, the fabrication of high-throughput (Pb 1−X Ba X )ZrO 3 antiferroelectric films with gradients in Ba 2+ concentrations is achieved.Furthermore, we conducted an indepth investigation into the evolution of atomic structure features and changes in the electrical properties of the films resulting from chemical composition doping.Our work presents a practical method for the high-throughput synthesis of antiferroelectric thin films, and the high-throughput strategy is significant for the formation of a comprehensive and high-quality database between the composition, structure, and properties of materials, as well as the establishment of an advanced system for the development of novel materials. [34]

Results and Discussion
To achieve high-quality PbZrO 3 thin films, as shown in Figure 1a-I, our first step was to identify the optimal deposition temperature, utilizing a high-throughput pulsed laser deposition system.The voltage-dependent polarization (P-V) loops and switching current (I-V) curves for PbZrO 3 thin films deposited under different temperate are shown in Supplementary Figure S1 (Supporting Information), where PbZrO 3 thin films deposited at 600 °C show more stable antiferroelectric phase, and we set 600 °C as the deposition temperature in following experiments.Subsequently, as shown in Figure 1a-II, we employed a movable mask system and rapidly switched between dual targets, PbZrO 3 and BaZrO 3 , to deposit specific regions with precise chemical composition content, resulting in (Pb 1−X Ba X )ZrO 3 thin film on SrTiO 3 (111) substrate.The right panel of Figure 1a-III showcases the actual photograph of the deposited films with significant color liner contrast, closely resembling the schematic drawing of high-throughput (Pb 1−X Ba X )ZrO 3 thin films in the left panel of Figure 1a-III, suggesting that we have obtained highthroughput gradient thin films.Noted that the dimensions of each chemical composition zone are ≈1.1 × 10 mm 2 , and to minimize the influence of elemental diffusion among different chemical composition regions, structural experiments and electric properties tests on high-throughput (Pb 1−X Ba X )ZrO 3 thin films were carried out on central region (≈0.5 × 10 mm 2 ) of each chemical composition regions.Additional details regarding the fabrication process for (Pb 1−X Ba X )ZrO 3 thin films can be found in the Experimental Section.To establish the correlation between the color liner contrast and chemical composition gradient, the X-ray photoelectron spectroscopy (XPS) spectra of the resulting high-throughput (Pb 1−X Ba X )ZrO 3 thin films are measured.Figure S2a (Supporting Information) presents the Ba, Zr, and Pb spectrum of the resulting high-throughput (Pb 0.94 Ba 0.06 )ZrO 3 thin film.Notably, locally magnified detail maps of Ba and Pb are shown in Figure 1b,c, revealing reflection peaks located at 795.3, 780, 142.9, and 138.1 eV, corresponding to Ba 3d 3/2 , Ba 3d 5/2, Pb 4f 5/2 , and Pb 4f 7/2 , [35,36] respectively.Furthermore, as shown in Figure S2b,c (Supporting Information), the intensity of the Ba 3d 3/2 and Ba 3d 5/2 peaks gradually increases with an increasing Ba doping level from X = 0 to X = 0.08.In contrast, the intensity of the Pb 4f 5/2 and Pb 4f 7/2 peaks gradually decreases, indicating the efficacy of this high-throughput method in fabricating (Pb 1−X Ba X )ZrO 3 thin films with gradient chemical compositions.
Noted that the diffraction peaks of Pb and Ba exhibit a progressive broadening and a shift toward higher energy bands with the increase in Ba content, which may be attributed to the fact that the doping of Ba induces the creation of cavities inside the thin film and results in defects such as O and Pb vacancies. [37,38]s shown in Figure 2a, the P-V loops of the high-throughput (Pb 1−X Ba X )ZrO 3 thin films were measured at room temperature.For X = 0, the antiferroelectric type P-V loop exhibits a characteristic double hysteresis loop with saturation and remanent polarization of ≈47.87 and 3.27 μC cm −2 , respectively.Besides, quadruple switching peaks were observed in the I-V curves of PbZrO 3 as shown in Figure S3 (Supporting Information), such quadruple switching peaks correspond to antiferroelectric-ferroelectric phase switching induced by external electric fields, which confirms the antiferroelectric phase of the obtained PbZrO 3 thin films.In the X range of 0 ≤ X ≤ 0.02, the P-V loops and I-V curves demonstrate an improvement in polarization intensity and current with increasing X, which reveals that the enhancement of antiferroelectric property is a result of doping a small amount of Ba 2+ .This is due to the fact that Ba 2+ doped into the PbZrO 3 thin film occupies A site and acts as donor dopant, and the small amount of Ba 2+ inhibits the mobility of oxygen vacancies, reduces domain wall pinning and decreases the Pbsite vacancies, which leads to increase of the polarization. [39]Note that a comprehensive explanation of the Ba 2+ content-dependent field-induced phase transition can be found in Table S1 (Supporting Information).The polarization intensity and the characteristic double hysteresis loop of the antiferroelectric material diminish as the value of X varies from 0.03 to 0.05, indicating a regime in which there is competition between the antiferroelectric and ferroelectric-like phases.Meanwhile, the quadruple switching peaks in the I-V curves are maintained, though the intensity of peaks also becomes weaker, which further confirms that the (Pb 1−X Ba X )ZrO 3 thin films with 0.03 ≤ X ≤ 0.05 are dominated by the antiferroelectric phase of the material.The ferroelectric-like hysteresis loops are obtained when X increases, When X is increased above 0.06, the ferroelectriclike hysteresis loops and I-V curves are obtained, suggesting that the phase of (Pb 1−X Ba X )ZrO 3 transitions from antiferroelectric to ferroelectric-like when X ≥ 0.06. [40]To validate the structural phase transition, specific chemical compositions from the high-throughput (Pb 1−X Ba X )ZrO 3 thin films with = X = 0.04, and X = 0.06 were selected for cross-sectional transmission electron microscopy (TEM) analysis.As shown in the left panel of Figure 2b, clear interfaces between the homogeneous (Pb 1−X Ba X )ZrO 3 , SrRuO 3 , and SrTiO 3 layers can be observed, and the thickness of the (Pb 1−X Ba X )ZrO 3 is estimated to be ≈25.5 ± 1 nm.Importantly, the (Pb 1−X Ba X )ZrO 3 thin films exhibit a single-layer structure without delamination, suggesting that the high-throughput method developed for the fabrication of (Pb 1−X Ba X )ZrO 3 structure leads to a solid-solution thin films.To further verify the solid-solution structure of the high-throughput (Pb 1−X Ba X )ZrO 3 thin films, selected area electron diffraction (SAED) images from specific chemical composition regions were undertaken.As shown in the right panel of Figure 2b, an ordered lattice structure in each of the three different regions indicates the single-phase nature of the high-throughput (Pb 1−X Ba X )ZrO 3 (X = 0.00, 0.04, 0.06) thin films.Interestingly, the SAED patterns from both X = 0.00 and X = 0.04 show an orthorhombic crystal structure with diffraction spots arranged in a rectangle, whereas the SAED patterns from X = 0.06 indicate a rhombohedral crystal structure with diffraction spots arranged in a rhombus, this indicates that the (Pb 1−X Ba X )ZrO 3 thin films undergo a structural phase transition phase when X increases from 0.04 to 0.06.The TEM and SAED analyses confirmed the solid-solution structure of the high-throughput (Pb 1−X Ba X )ZrO 3 thin films and indicated the possibility of the structural phase transition within the thin films.
To gain insight into the variations induced by increasing Ba concentration, we have created a schematic diagram illustrating the crystal structure evolution of PbZrO 3 thin film doped with Ba.In its ground state, PbZrO 3 takes a typical ABO 3 perovskite structure, and it crystallizes with an orthorhombic structure with a space group Pbam. [41]As shown in the right panel of Figure 3a, PbZrO 3 exhibits the Pham phase structure along the c-axis, accompanied by two adjacent sublattices with antiparallel polarization directions along the plane perpendicular.Figure 3b illustrates the structure of (Pb 1−X Ba X )ZrO 3 doped with Ba 2+ , where Ba 2+ ions partially replace Pb 2+ ions at the A-sites.This substitution induces lattice distortions due to the displacement of A-site ions and the tilting of oxygen octahedra. [17,21,42]Consequently, these lattice distortions give rise to new structure types, specifically a rhombohedral observed along the b-axis, termed the R3cH phase structure.The phase of (Pb 1−X Ba X )ZrO 3 can be predicted by considering the tolerance factor (t), defined as t = , where R A , R B , and R O are the average ionic radii of the A-site cations, B-site cations and oxygen anions, respectively.Since the radius of Ba 2+ (1.61 Å) is larger than that of Pb 2+ (1.49Å), the tolerance factor of (Pb 1−X Ba X )ZrO 3 can be gradually adjusted across a critical point by increasing the quantity of Ba 2+ ions in the thin films, which means that the increased Ba 2+ doping can decrease the stability of antiferroelectric phase.As can be concluded from the hysteresis loops of (Pb 1−X Ba X )ZrO 3 in Figure 2a the phase transition occurs ≈X = 0.06, while the corresponding t value can be evaluated as 0.9663.This value is slightly smaller than the theoretically estimated value, [42] such difference may arise from the compressive misfit constraint imposed by the SrTiO 3 substrate. [43,44]For X ≥ 0.06, corresponding to t ≥ 0.9663, stable ferroelectric-like hysteresis loops are observed.It can be concluded that the key impact for the field-induced phase transition is the value of X, where the antiferroelectric phase is to be stabilized when X < 0.06 (corresponding t < 0.9663) and the ferroelectric-like phase is to be stabilized when X > 0.06 (corresponding t > 0.9663). [45]These results indicate that the phase transition from antiferroelectric to a ferroelectriclike phase in (Pb 1−X Ba X )ZrO 3 thin films occurs within the X = 0.04 to X = 0.06.
In general, the phase transition in antiferroelectric thin films is contingent upon both the temperature and constituent chemical compositions of the thin films. [17,46]To investigate the influence of chemical composition doping on the phase transition temperature of (Pb 1−X Ba X )ZrO 3 thin films, the P-V loops of high-throughput (Pb 1−X Ba X )ZrO 3 (X = 0, 0.02, 0.04, and 0.06) thin films were measured in the temperature range from 25 to 325 °C.As shown in Figure 4a, the PbZrO 3 thin film exhibits typical double hysteresis loops at room temperature.Furthermore, with the increase in temperature, the double hysteresis loop feature gradually diminishes, and the coercive voltage decreases until reaching 275 °C.At 300 °C, the P-E loop exhibits paraelectric behavior, suggesting the absence of antiferroelectricity upon heating. [47]Simultaneously, the remnant polarization begins to increase around this temperature, signifying a phase transition.Consequently, the PbZrO 3 thin film appears to undergo a transition from an antiferroelectric to a paraelectric state at 300-325 °C.Note that the Curie temperature (T c ) of bulk PbZrO 3 is reported to be 230 °C, [47] the difference in T c observed may be attributed to the presence of residual stress between the film and substrate.In the case of (Pb 1−X Ba X )ZrO 3 thin film with X = 0.02, as displayed in Figure 4b, a phase transition similar to that of X = 0 was observed, albeit with a transition temperature found to be approximately between 275 and 300 °C.This lower transition temperature can be attributed to the introduction of Ba 2+ , which affects the stability of the antiferroelectric phase. [48]When the doping content was further increased to X = 0.04, the antiferroelectricparaelectric phase transition occurred between 175 and 225 °C (in Figure 4c).In the (Pb 1−X Ba X )ZrO 3 thin films with X = 0.06, ferroelectric-like hysteresis loops are observed at room temperature (in Figure 4d).As the temperature exceeded 100 °C, the films exhibit hysteresis loops characteristic of the paraelectric phase.The correlation between T c and Ba 2+ doping content is plotted in Figure S4 (Supporting Information), whereas linear decreased T c along with increased Ba content may be a result of the phase structure transitions caused by the substitution of Pb 2+ by Ba 2+ .On the one hand, the addition of Ba generates local random stresses since the radius of Ba 2+ is larger than that of Pb 2+ , and it destabilizes the antiferroelectric order. [49,50]On the other hand, the substitution of Ba 2+ leads to the appearance of diffusive phase transition characteristics in (Pb 1−X Ba X )ZrO 3 thin films, and the degree of relaxation behavior is enhanced with the increase of Ba 2+ content. [17,51,52]

Conclusion
In summary, an HT-PLD system was employed to deposit (Pb 1−X Ba X )ZrO 3 thin films, which encompassed 9 distinct material chemical compositions spanning the X = 0 to X = 0.08 range.A detailed chemical analysis was conducted to confirm the successful development of a high-throughput method, enabling precise control of material composition in (Pb 1−X Ba X )ZrO 3 thin films.Significantly, through evaluations of electrical properties, we have identified the composition range within X = 0.04 to X = 0.06 as the phase transition region of (Pb 1−X Ba X )ZrO 3 .Further examinations affirmed the structural phase transition induced by Ba doping, as evidenced by microstructural analyses.Furthermore, we have established a correlative relationship between the phase transition and the constituent chemical compositions as a function of temperature.This work not only presents a practical method for the synthesis of high-throughput complex oxide thin films but also contributes to the creation of a valuable material database for future experimental investigations into antiferroelectric thin films.

Experimental Section
The Fabrication of (Pb 1−X Ba X )ZrO 3 Thin Films: The (Pb 1−X Ba X )ZrO 3 thin films were deposited on SrTiO 3 (111) substrate by using dual targets of PbZrO 3 and BaZrO 3 in a high-throughput pulsed laser deposition (RP-HT-102, purchased from Arrayed Materials(China) Co., Ltd. ).The SrRuO 3 bottom electrode layer was first deposited on the SrTiO 3 (111) substrate at 600 °C an oxygen atmosphere of 80 mTorr.The temperature and oxygen pressure were respectively set as 600 °C and 100 mTorr for the deposition of high-throughput (Pb 1−X Ba X )ZrO 3 thin films.During highthroughput (Pb 1−X Ba X )ZrO 3 thin film deposition, the SrTiO 3 (111) substrate was divided into nine regions by using the rapid moving of multimasks, and the total number of pulsed laser shots was set to 36 000, wherein the variations of chemical compositions from X = 0 to X = 0.08 (Pb 1−X Ba X )ZrO 3 films in nine regions were controlled by varying the number of laser pulses shots from PbZrO 3 and BaZrO 3 targets.The laser pulses of PbZrO 3 and BaZrO 3 targets corresponding to (Pb 1−X Ba X )ZrO 3 thin films with chemical compositions ranging from X = 0 to X = 0.08 were 36 000/0, 35 640/360 35 280/720, 34 920/1080, 34 560/1440, 34 200/1800, 33 840/2160, 33 480/2520 and 33 120/2880, respectively.For the measurement of electric properties, Au electrodes with diameters of 100 μm were deposited by sputtering through a shadow mask.Note that the laser energy and repetition rate were set as 350 mJ and 9.9 Hz during SrRuO 3 and (Pb 1−X Ba X )ZrO 3 thin film deposition.
Structure and Electrical Properties Characterizations: The chemical valence state of the (Pb 1−X Ba X )ZrO 3 thin films was characterized via XPS(Escalab Xi + ).The low-resolution cross-sectional TEM images and SAED pattern were acquired on JEM-2100.The P-V hysteresis loops and I-V curves were measured using a Radiant Technology Precision Premium II texter (Radiant Technologies, Inc.) at a frequency of 10 KHz.For the temperature-dependent text, samples were tested by Radiant Technology Precision Premium II Tester and a semiconductor parameter analyzer (Agilent Technologies, B1500A).

Figure 1 .
Figure 1.High-throughput deposition of (Pb 1−X Ba X )ZrO 3 thin films.a) High-throughput thin films preparation process: I) High-throughput parameter screening; II) High-throughput (Pb 1−x Ba x )ZrO 3 thin film deposition; III) The schematic drawing of the designed high-throughput (Pb 1−X Ba X )ZrO 3 thin films (left) and the actual photograph of the deposited high-throughput (Pb 1−X Ba X )ZrO 3 thin films (right).b,c) The X-ray photoelectron spectroscopy (XPS) spectra of the Ba3d and Pb4f regions from high-throughput (Pb 1−X Ba X )ZrO 3 thin films.

Figure 2 .
Figure 2. The electrical properties and structure of high-throughput (Pb 1−X Ba X )ZrO 3 thin films.a) P-V loops of high-throughput (Pb 1−X Ba X )ZrO 3 thin films.b) The cross-sectional transmission electron microscopy (TEM) images of selected specific chemical compositions from the high-throughput (Pb 1−X Ba X )ZrO 3 thin films, including X = 0.00, X = 0.04, and X = 0.06.The corresponding selected area electron diffraction (SAED) for each chemical composition is shown in the right panel.

Figure 3 .
Figure 3. Schematic diagram of crystal structure evolution of PbZrO 3 thin film doped with Ba. a) Lattice structures of PbZrO 3 (left panel) and(b) (Pb 1−X Ba X )ZrO 3 (right panel) thin films.