Ferroelectric Thin Film Capacitors Research Articles

Enhanced ferroelectric properties in BiAlO3 modified lead‐free Mn‐doped Bi0.5(Na0.8K0.2)0.5TiO3 thin films

AbstractMn‐doped (1‐x)Bi0.5(Na0.8K0.2)0.5TiO3‐xBiAlO3 (Mn:BNKT‐xBA) thin films were synthesized on lanthanum nickelate‐coated silicon substrates by sol‐gel method. The second phase issue of the film can be effectively addressed by optimizing the substrate, and the maximum polarization and breakdown strength can be increased by introducing the proper amount of Al3+, which is advantageous for the film for energy storage. The results have shown that the Mn:BNKT‐0.03BA film exhibits superior ferroelectric properties (with remanent polarization (Pr) of 23.72 µC/cm2, maximum polarization (Pmax) of 75.37 µC/cm2), which could be an excellent candidate for ferroelectric thin film capacitors.

Lead-free BaTiO3-based relaxor ferroelectric thin film rendering rapid discharge rate for pulsed power energy application

Ferroelectric thin film capacitors have large application potential in pulsed-power electronic and electrical systems due to their high-power density and rapid discharge capabilities. Although lead-based dielectrics are promising, the pursuit of eco-friendly, lead-free alternatives is gaining research attention. Here, the Bi and Li co-doped BaTiO3 thin film exhibiting relaxor ferroelectric properties was investigated for its energy storage properties. The fabricated polycrystalline Ba0.85(Bi0.5Li0.5)0.15TiO3 thin film by pulsed laser deposition revealed good breakdown strength (∼4 MV cm−1), a slim ferroelectric loop, and low leakage characteristics suitable for energy storage applications. The film exhibits a significant value of recoverable energy density (∼70 J cm−3) with better frequency and thermal stability. Notably, the better overall performance parameters of the film, including a sizable power density (261 MW cm−3) and a fast discharge rate (150 ns), along with good energy density and breakdown strength, make the material suitable for pulsed-power energy applications.

Composite Right/Left-Handed Leaky-Wave Antenna with Electrical Beam Scanning Using Thin-Film Ferroelectric Capacitors

This article presents a wide-angle-scanning leaky-wave antenna (LWA) based on a composite right/left-handed (CRLH) transmission line. In contrast to traditional semiconductor elements, thin-film ferroelectric capacitors were implemented in the CRLH unit cells to enable electric beam scanning. The proposed CRLH LWA has a single-layer design without metalized vias and is compatible with PCB and thin-film technologies. To fabricate the CRLH LWA prototype, dielectric material substrates and thin-film ferroelectric capacitors were manufactured, and their characteristics were investigated. Double-sided metalized fluoroplast-4 reinforced with fiberglass with a permittivity of 2.5 was used as a substrate for CRLH LWA prototyping. A solid solution of barium strontium titanate (BaxSr1−xTiO3) with a composition of x=0.3 was used as a ferroelectric material in electrically tunable capacitors. The characteristics of the manufactured ferroelectric thin-film capacitors were measured at a frequency of 1 GHz using the resonance method. The capacitors have a tunability of about two and a quality factor of about 50. The antenna prototype consists of ten units with a total length of 1.25 wavelengths at the operating frequency of close to 2.4 GHz. The experimental results demonstrate that the main beam can be shifted within the range of −40 to 16 degrees and has a gain of up to 3.2 dB. The simple design, low cost, and excellent wide-angle scanning make the proposed CRLH LWA viable in wireless communication systems.

Fabry–Perot Antenna Based on an Electrically Tunable Slot Antenna and a Two-Layer Frequency-Selective Surface

Introduction. One of the directions in Fabry–Perot antenna design consists in increasing its operation frequency range. In the present work, we set out to develop a Fabry–Perot antenna with a smooth gain pattern across a wide frequency range. To that end, a tunable slot antenna based on a thin-film ferroelectric varactor was used. The major development criterion was a high uniformity of the gain pattern, not exceeding 1 dB in the given frequency band. Aim. To develop a Fabry–Perot antenna for the 4.9–5.5 GHz frequency range with a high gain uniformity within the operating frequency band.Materials and methods. The antenna under development was based on thin-film ferroelectric capacitors as tunable elements. Fluoroplastic plates metallized on both sides were used as a dielectric material for manufacturing a frequency selected surface and a slot antenna. The parameters of ferroelectric elements were measured using a resonance technique, while the parameters of the dielectric material were determined using the Nicholson–Ross–Weir method.Results. The developed antenna has an operating frequency band of 4.9–5.5 GHz. Samples of ferroelectric capacitors and foiled dielectric material were manufactured and experimentally investigated. A tunable slot antenna was fabricated, and its characteristics were measured. The simulation results show that the gain value of the developed Fabry–Perot antenna is not less than 10 dB in the operation frequency range. Variations in the gain value within the operating frequency band do not exceed 0.7 dB.Conclusion. A Fabry–Perot antenna based on an electrically tunable slot antenna and a two-layer frequency-selective surface was developed. The operating frequency band of the developed device ranges within 4.9–5.5 GHz, which corresponds to the frequency band of Wi-Fi networks. Optimization of the antenna design parameters made it possible to achieve higher gain values under their minor variations in the operation frequency band.

Influence of metal electrodes on the irradiation resistance of HZO ferroelectric thin film capacitors and mechanism analysis

In application scenarios such as astronautics, high-altitude aircraft, medical radiography, high-energy physics, and nuclear power plants, the irradiation resistance of electronic components is one of the basic requirements for their reliability. HfO2-based ferroelectric films have the advantages of high CMOS process compatibility, good miniaturizability, low operating voltage, and excellent irradiation resistance, which are the core materials for the new generation of irradiation resistance ferroelectric memories. In this paper, two kinds of metal-electrode ferroelectric capacitors, W/Hf0.5Zr0.5O2/W (WW) and Pt/Hf0.5Zr0.5O2/Pt (PP), have been prepared, and three gradient γ-irradiation experiments have been carried out on the two kinds of ferroelectric capacitors. The effect of metal electrodes on the irradiation resistance of Hf0.5Zr0.5O2 ferroelectric thin films was carefully investigated by comparing and analyzing the statistical laws of polarization change and rectangularity change before and after irradiation of a large number of devices. The experimental results show that the WW devices have better irradiation resistance than PP devices, and we further explain the irradiation resistance mechanism by first-principle calculations and finite element analysis to verify the credibility of the experimental results. Finally, we conducted a comparative test of the fatigue and wake-up characteristics of the WW devices before and after irradiation, and the results show that the prepared W/Hf0.5Zr0.5O2/W devices can withstand very high total γ-dose radiation, reaching up to 13.86 Mrad(Si), and they are very suitable for the application of irradiation resistant electronics.

BaTiO3-Based Ferroelectric Thin Film Capacitor on Silicon for Ultra-High Energy Storage Performance at Low Electric Field Strength

In the case of dielectric energy storage devices, excessive pursuit of giant electric fields means greater exposure to high temperatures and insulation damage risk. Ferroelectric thin film devices offer opportunities for energy storage needs under finite electric fields due to their intrinsically large polarization and the advantage of small size. Herein, we designed the capacitor’s dielectric layer by doping barium titanate Ba <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(1-x)</sub> Ce <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BCTO). The addition of highly charged ions Ce <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> induce cell shrinkage thus further optimizing the ferroelectric polarization. Accordingly, the capacitor with Au/BCTO/Au structure integrated directly on silicon substrate showed excellent energy storage performance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W_rec</i> ≈ 92.6 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> and η ≈ 86.5%) under only 1961 kV/cm. In addition, we significantly increased the electrical breakdown strength from 1726 kV/cm to 3426 kV/cm by adjusting the Ba <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.95</sub> Ce <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.05</sub> TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> film thickness, thus achieving ultra-high energy storage density (107.9 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ). The results expand the application prospects of silicon-based ferroelectric capacitors for energy storage at low electric field strength.

Mechanism of the Wake-Up and the Split-Up in AlOx/Hf0.5Zr0.5Ox Film.

Dielectric layers are widely used in ferroelectric applications such as memory and negative capacitance devices. The wake-up and the split-up phenomena in the ferroelectric hafnia are well-known challenges in early-stage device reliability. We found that the phenomena even occur in the bilayer, which is composed of the hafnia and the dielectrics. The phenomena are known to be affected mainly by oxygen vacancies of hafnia. Dielectric layers, which are often metal oxides, are also prone to be affected by oxygen vacancies. To study the effect of the dielectric layer on the wake-up and the split-up phenomena, we fabricated ferroelectric thin-film capacitors with dielectric layers of various thicknesses and measured their field-cycling behaviors. We found that the movement of oxygen vacancies in the dielectric layer was predominantly affected by the polarization state of the ferroelectric layer. In addition, the mechanism of the field-cycling behavior in the bilayer is similar to that in ferroelectric thin films. Our results can be applied in ferroelectric applications that use dielectric layers.

Polarization switching dynamics simulation by using the practical distribution of ferroelectric properties

We investigated the internal bias field and coercive field in a typical ferroelectric thin-film capacitor and simulated polarization switching dynamics using Euler's method. The simulation results agreed well with the experimental results and reflected the well-known polarization domain switching model in which the polarization switching occurs on the order of nucleation, growth, and coalescence. The fit parameters (damping parameters affecting the polarization change rate) also followed a certain distribution. When the expected value was used instead of full distribution, the simulation results did not agree well with corresponding experimental results. The simulation results suggested no domain structure in the polarization switching dynamics, indicating that the polarization domain structure was affected by the distribution of the fit parameters. Our results demonstrate the possibility of simulation using realistic distribution of ferroelectric properties.

Enhanced energy storage properties in relaxor Pb(Mg1/3Nb2/3)O3-PbTiO3 thin-film capacitors by incorporating buffer layers

Recently, relaxor ferroelectric thin-film capacitors have attracted considerable attention for energy storage applications since their slim-type polarization–electric field hysteresis loops can yield large recoverable energy density (Wrec) and high efficiency (η). In this work, we study the effects of buffer layers on energy storage properties of 0.93Pb(Mg1/3Nb2/3)O3-0.07PbTiO3 (PMN-PT) thin-film capacitors with a 5 nm-thick SrTiO3 (STO) and LaAlO3 (LAO) films. The energy storage properties of Pt/PMN-PT/SrRuO3 (SRO) capacitors are found to be significantly changed by incorporating the STO or LAO buffer layer at the top Pt/PMN-PT interface, while inserting the buffer layer at bottom PMN-PT/SRO interface shows negligible effects on the electrical properties. Specifically, with the STO buffering, the breakdown field is dramatically increased in the Pt/STO/PMN-PT/SRO capacitor due to the existence of an internal field in the STO, which prevents the growth of electrical trees from the bottom SRO to the top Pt electrode, and a large Wrec of ∼48.91 J/cm3, more than three times of that of the PMN-PT capacitor, is achieved. However, buffered by the LAO, the Pt/LAO/PMN-PT/SRO capacitor exhibits a reduced relaxor character, which may be ascribed to a pinning effect of nanodomains associated with the charged LAO/PMN-PT interface. As a result, both Wrec and η are significantly lowered, compared to the non-buffered PMN-PT capacitor. These results provide physical insights into the modulation of relaxor and dielectric behaviors by designing the characteristics of buffer layers, demonstrating a way for enhancing energy storage properties in thin-film capacitors.

Interface engineering to optimize polarization and electric breakdown strength of Ba2Bi3.97Pr0.03Ti5O18/BiFeO3 ferroelectric thin-film for high-performance capacitors

Electrostatic capacitors based on dielectrics are ubiquitous components for applications in modern electronics and electric power systems. However, the relatively low energy density of electrostatic capacitors, which is one or two orders of magnitude lower than that of the batteries, has greatly hindered the implementation of its in energy storage devices. Here, we propose a strategy to overcome the tradeoff between high polarizability and breakdown electric field, and attain great enhancement energy storage density in the lead-free (Ba2Bi3.97Pr0.03Ti5O18/BiFeO3)N (BBPT/BFO)N multilayer ferroelectric thin films with different BFO layers through interface engineering. The interface engineering could be utilized to concurrently modify both polarization and local electric field strength caused by the synergistic effect of multiple polar structures and electric field amplifying effect. Accordingly, the discharged energy density of the optimized (BBPT/BFO)1 ferroelectric thin-film capacitors as high as ∼ 79.3 J/cm3 with discharged efficiency exceeding ∼ 75 % are achieved. Combined with its fatigue-free, favorable temperature and frequency stabilities, the multilayer ferroelectric thin films of BBPT/BFO could be a promising dielectric material for practical energy storage applications.

Electrically Controlled Reversible Polarization Fatigue–Recovery in Ferroelectric Thin Film Capacitors

Electrically Controlled Reversible Polarization Fatigue–Recovery in Ferroelectric Thin Film Capacitors

Strain Engineering of Energy Storage Performance in Relaxor Ferroelectric Thin Film Capacitors

AbstractDielectric energy storage capacitors are receiving a great deal of attention owing to their high energy density and fast charging–discharging speed. The current energy storage density of dielectrics is relatively low and cannot meet the requirements of miniaturization of pulsed power equipment. Therefore, increasing the energy storage density of dielectrics has become a research hotspot. Herein, using phase‐field simulations to design polymorphic nanodomains, the strain engineering of energy storage performance of binary and ternary solid solution relaxor ferroelectric films is investigated. The results show that the energy storage performance of the ternary film is better than that of the binary film due to the polymorphic nanodomains. In addition, as the film in‐plane strain is modified from −2% to 2%, the energy density is improved by 80%, and the efficiency also increases from 52% to 77%. This work proves the remarkable energy storage performance of polymorphic films and provides a theoretical basis to optimize the energy‐storage performance of ferroelectric thin‐film capacitors by adjusting the misfit strain.

Wake-up effect in Hf0.4Zr0.6O2 ferroelectric thin-film capacitors under a cycling electric field

We examined the wake-up effect in a TiN/Hf0.4Zr0.6O2/TiN structure. The increased polarization was affected by the cumulative duration of a switched electric field and the single application time of the field during each switching cycle. The space-charge-limited current was stable, indicating that the trap density did not change during the wake-up. The effective charge density in the space-charge region was extracted from capacitance–voltage curves, which demonstrated an increase in free charges at the interface. Based on changing characteristics in these properties, the wake-up effect can be attributed to the redistribution of oxygen vacancies under the electric field.

Flexible Lead-Free Ba0.5Sr0.5TiO3/0.4BiFeO3-0.6SrTiO3 Dielectric Film Capacitor with High Energy Storage Performance.

Ferroelectric thin film capacitors have triggered great interest in pulsed power systems because of their high-power density and ultrafast charge–discharge speed, but less attention has been paid to the realization of flexible capacitors for wearable electronics and power systems. In this work, a flexible Ba0.5Sr0.5TiO3/0.4BiFeO3-0.6SrTiO3 thin film capacitor is synthesized on mica substrate. It possesses an energy storage density of Wrec ~ 62 J cm−3, combined with an efficiency of η ~ 74% due to the moderate breakdown strength (3000 kV cm−1) and the strong relaxor behavior. The energy storage performances for the film capacitor are also very stable over a broad temperature range (−50–200 °C) and frequency range (500 Hz–20 kHz). Moreover, the Wrec and η are stabilized after 108 fatigue cycles. Additionally, the superior energy storage capability can be well maintained under a small bending radius (r = 2 mm), or after 104 mechanical bending cycles. These results reveal that the Ba0.5Sr0.5TiO3/0.4BiFeO3-0.6SrTiO3 film capacitors in this work have great potential for use in flexible microenergy storage systems.

(Invited) Ferroelectric Hafnium Oxide for Non-Volatile Memory Applications: From Single Capacitors to Memory Arrays

This year marks the 10th anniversary of the public announcement of the discovery of ferroelectricity in HfO2-based thin films. Tremendous strides have been made in both the physical understanding and the technological use of ferroelectric HfO2. These unique fluorite-structured ferroelectrics have outstanding potential for commercial applications due to their scalability, CMOS-compatibility, and facile manufacturability. Such advantages make ferroelectric HfO2 particularly attractive for nonvolatile memories technologies such as ferroelectric random access memory (FRAM) and ferroelectric field effect transistors. Due to the wide variety of conditions in which ferroelectricity can emerge in HfO2 thin films, there has been a vast effort by the international scientific community to enhance and optimize the ferroelectric properties using a wide variety of approaches. Advancements in thin film ferroelectric capacitor and memory array technologies are therefore progressing rapidly.The structural properties of HfO2 are a major focal point for technology development because the competition between several crystalline phases in HfO2 thin films can have a major impact on device performance. For thin film memory capacitors, stabilizing the polar orthorhombic phase and eliminating secondary paraelectric phases is paramount in achieving robust polycrystalline HfO2 ferroelectrics. Doping and the presence of a capping electrode during crystallization have been extensively demonstrated to influence the emergence and stability of the ferroelectric orthorhombic phase. Greater attention has been placed recently on the thin film growth conditions in atomic layer deposition and physical vapor deposition, especially with regard to the oxidation conditions that have been shown to have a substantial impact on the device performance of ferroelectric HfO2 and Hf0.5Zr0.5O2 capacitors. Composition, film growth, and the crystallization processes are critical aspects for thin film ferroelectric capacitor development and the latest developments will be comprehensively reviewed in the context of how the material properties relate to nonvolatile memory performance.Developments in thin film HfO2 ferroelectric capacitors are now coming to fruition with the emergence of ferroelectric random access memory arrays and demonstrators. Thin film ferroelectric HfO2 based capacitors are successfully being demonstrated in back-end-of-line (BEOL) processes at the 130nm CMOS technology. The performance of these early demonstrator memory arrays show very promising long term data retention, large memory windows with good statistical distributions, and projections for area scaling to nanoscale dimensions. The transition from large-scale micron-sized laboratory devices to smaller scale integrated capacitors has proven to be a major step forward in endurance cycling with >1011 cycles being reported in memory arrays. The most recent integration of thin film ferroelectric HfO2 capacitors into FRAM memory arrays and what future developments are expected for HfO2 ferroelectric random access memories will be presented. Figure 1

Local epitaxial-like templating effects and grain size distribution in atomic layer deposited Hf0.5Zr0.5O2 thin film ferroelectric capacitors

The microstructure in fluorite-structure oxide-based ferroelectric thin films, especially when on standard semiconductor manufacturing platforms, is poly-/nano-crystalline, which controls the functionality, performance, and reliability of the device technologies based on them. Understanding the relationships between microstructure, process, and performance for this class of materials has remained challenging. Here, a systematic approach is presented for analyzing and visualizing grains, their size distributions, and interlayer templating effects in ferroelectric thin film systems by utilizing an advanced microscopy technique, namely nanobeam electron diffraction, coupled with dark-field transmission electron microscopy and atomic resolution scanning transmission electron microscopy. A 10 nm TiN/10 nm Hf0.5Zr0.5O2 (HZO)/10 nm TiN ferroelectric heterostructure is probed. A geometric mean of the grain size in HZO of 26.8 nm ranging from 5 to 95 nm with top and bottom TiN layers having a much smaller grain size of approximately 6.8 nm ranging from 3 to 17 nm is observed. Furthermore, there is evidence of templating effects between HZO and TiN grain and domain boundaries showing [111] and [001] growth directions locally for HZO and TiN, respectively.

Monitoring Electrical Biasing of Pb(Zr0.2Ti0.8)O3 Ferroelectric Thin Films In Situ by DPC-STEM Imaging.

Increased data storage densities are required for the next generation of nonvolatile random access memories and data storage devices based on ferroelectric materials. Yet, with intensified miniaturization, these devices face a loss of their ferroelectric properties. Therefore, a full microscopic understanding of the impact of the nanoscale defects on the ferroelectric switching dynamics is crucial. However, collecting real-time data at the atomic and nanoscale remains very challenging. In this work, we explore the ferroelectric response of a Pb(Zr0.2Ti0.8)O3 thin film ferroelectric capacitor to electrical biasing in situ in the transmission electron microscope. Using a combination of high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and differential phase contrast (DPC)-STEM imaging we unveil the structural and polarization state of the ferroelectric thin film, integrated into a capacitor architecture, before and during biasing. Thus, we can correlate real-time changes in the DPC signal with the presence of misfit dislocations and ferroelastic domains. A reduction in the domain wall velocity of 24% is measured in defective regions of the film when compared to predominantly defect-free regions.

Modifying energy storage performances of new lead-free system ferroelectric capacitors through interfacial stress

Ferroelectric energy storing is one of the most potential research hotspots in functional materials. To seek for better performance, current strategies are mostly relied on structure designing and multi-element (more than 5) doping. Till now, energy storage density (ESD) for ferroelectric thin film capacitors have reached to over 100 J/cm3, which seems to be a bottleneck, and the corresponding material structure and chemical composition are also becoming complex. Thus, exploiting simple and single-layered candidates will probably re-develop this field. For epitaxial thin films, interfacial stress from substrates will assist. Hence, a new system of Sm doped BaZr0.2Ti0.8O3 (BaZr0.2Ti0.8O3-2%Sm2O3, abbr. BZTS) thin films were epitaxially grown on STO substrates and a better ESD of 40.42 J/cm3 with η of 85.03% was obtained in 200-nm film. The effects of interfacial stress between films and substrates on the ferroelectric performance of BZTS thin films have been systematically discussed. The interfacial pressure stress offered by substrates enhanced the thermal stability and Sm doping facilitated the ferroelectric behavior. Finally, this new BZTS system thin films shown rather a better ferroelectric reliability in both temperature and frequency than the only-BZT system, making it a proper candidate to be composited with other materials in next-generation functional materials.

Evaluation of energy storage performance of ferroelectric materials by equivalent circuit model

Dielectric capacitors with large energy storage density, low hysteresis loss, low temperature dependence and high temperature adaptability show great advantages in high temperature applications of electronic devices. In this work, a large energy storage density (W ~ 28.776 J/cm3) and ultra-high efficiency (η ~ 87.36%) have been simultaneously achieved in the CuX(Ba0.88Ca0.12)1-X(Zr0.12Ti0.88)O3 (X = 0.1) lead-free relaxor ferroelectric thin film capacitors deposited on Pt(111)/TiOX/SiO2/Si(100) substrates by using a sol-gel method. The results show that the dielectric permittivity and dielectric loss change a little in the temperature range of 30–400 °C. The reason of low dielectric loss and temperature insensitivity is revealed by means of Raman spectrum fitting and equivalent circuit model (the I-E curve of ferroelectric materials is regarded as an equivalent circuit of equivalent capacitance (C), equivalent resistance (R) and polarization charge (Ip(t)) in parallel, given by the equation I(t)=V(t)/R+KC+Ip(t)). The results prove that the stability of slope (K) is positively correlated with the stability of energy storage performance of ferroelectric materials, which provides the basis for the evaluation of energy storage performance of ferroelectric materials.

Nonlinear domain wall velocity in ferroelectric Si-doped HfO2 thin film capacitors

We investigate the nonlinear response of the domain wall velocity (v) to an external electric field (Eext) in ferroelectric Si-doped HfO2 thin film capacitors using piezoresponse force microscopy (PFM) and switching current measurements. We verified the reliability of the PFM images of ferroelectric domain switching by comparing the switched volume fraction in the PFM images with the time-dependent normalized switched polarization from the switching current data. Using consecutive time-dependent PFM images, we measured the velocity of the pure lateral domain wall motion at various Eext. The Eext-dependent v values closely follow the nonlinear dynamic response of elastic objects in a disordered medium. The thermally activated creep and flow regimes were observed based on the magnitude of Eext. With a dynamic exponent of μ = 1, our thin film was found to have random-field defects, which is consistent with the Lorentzian distribution of characteristic switching time that was indicated in the switching current data.