BZT-BCT materials, devices, and methods

Abstract

Illustrative embodiments of articles of manufacture comprising a first electrode layer including La0.67Sr0.33MnO3 (LSMO) and an insulating layer adjacent the first electrode layer, where the insulating layer includes 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-BCT), are disclosed. Illustrative embodiments of optoelectronic devices, capacitors, and non-volatile random access memories comprising the foregoing articles and methods of manufacturing the foregoing articles are also disclosed.

Description

Attorney Docket 71900-435019Client Docket 25-001-UPR- 1 - BZT-BCT MATERIALS, DEVICES, AND METHODSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U. S. Provisional Application No.63 / 746763, filed January 17, 2025, the disclosures of which are incorporated herein by reference.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under Grant No. OIA-1849243, awarded by the National Science Foundation. The government has certain rights in the invention.TECHNICAL FIELD

[0003] The present disclosure relates generally to 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 materials, to devices utilizing the same, and related methods.BACKGROUND

[0004] Ferroelectric materials have been applied to storage devices of non-volatile random-access memory (“NVRAM”). Ferroelectric films offer great potential for NVRAM devices, but experience limitations such as fatigue, electrical degradation (high leakage current), and aging effects, which in turn limit the lifetime of such devices. In particular, ferroelectric materials often lose their switchable polarization characteristics with a repeated number of polarization cycles. There is a need for high performance and environmentally friendly materials that are comparable in performance to lead-based materials, such as Pb(ZrTi)O3 (“PZT”).Attorney Docket 71900-435019Client Docket 25-001-UPR- 2 - SUMMARY OF THE INVENTION

[0005] Illustrative embodiments of the invention are described in the following enumerated clauses. Any combination of the following clauses is contemplated, along with any applicable combination with the embodiments described in the descriptions of the drawings.1. An article of manufacture comprising:a first electrode layer comprising La0.67Sr0.33MnO3 (“LSMO”); andan insulating layer adjacent the first electrode layer, wherein the insulating layer comprises 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (“BZT-BCT”).2. The article of clause 1, wherein the first electrode layer consists of LSMO. 3. The article of clause I or clause 2, wherein the insulating layer consists of BZT-BCT.4. The article of any preceding clause, wherein the insulating layer is an epitaxial layer grown on the first electrode layer.5. The article of any preceding clause, wherein the insulating layer has been formed using pulsed laser deposition.6. The article of any preceding clause, further comprising an MgO substrate, wherein the first electrode layer is positioned between the insulating layer and the MgO substrate.7. The article of clause 6, wherein the first electrode layer is adjacent the MgO substrate.8. The article of clause 6 or clause 7, wherein the MgO substrate is (lOO)-oriented.9. The article of any one of clauses 6-8, wherein the MgO substrate is a single-crystal substrate.10. The article of any preceding clause, wherein the BZT-BCT of the insulating layer has c-axis oriented crystallography.Attorney Docket 71900-435019Client Docket 25-001-UPR- 3 - 11. The article of any preceding clause, further comprising a second electrode layer, wherein the insulating layer is positioned between the first and second electrode layers.12. The article of clause 11, wherein the second electrode layers comprises gold. 13. The article of clause 12, wherein the second electrode layer consists of a plurality of gold dots.14. The article of any preceding clause, wherein the insulating layer has a remnant polarization greater than 60 μC / cm2.15. The article of any preceding clause, wherein the insulating layer exhibits less than 10% polarization degradation after 1012switching cycles.16. The article of any preceding clause, wherein the insulating layer exhibits no more than 3% polarization degradation after 1012switching cycles.17. The article of any preceding clause, wherein the article is lead-free.18. An optoelectronic device comprising the article of any one of clauses 1-17. 19. The optoelectronic device of clause 18, wherein the optoelectronic device is an ultraviolet photodetector.20. The optoelectronic device of clause 18 or clause 19, wherein the insulating layer has an optical bandgap of about 3.9 eV.21. A capacitor comprising the article of any one of clauses 1-17.22. The capacitor of clause 21, wherein the capacitor has exhibits leakage current less than 10’4A at applied voltages up to 70 V.23. A non-volatile random access memory comprising the capacitor of clause 21 or clause 22.Attorney Docket 71900-435019Client Docket 25-001-UPR- 4 - 24. A method of manufacture comprising:forming a first electrode layer comprising LSMO; andforming an insulating layer adjacent the first electrode layer, wherein the insulating layer comprises BZT-BCT.25. The method of clause 24, wherein the first electrode layer consists of LSMO. 26. The method of clause 24 or clause 25, wherein the insulating layer consists of BZT-BCT.27. The method of any one of clauses 24-26, wherein forming the insulating layer comprises epitaxially growing the insulating layer on the first electrode layer.28. The method of any one of clauses 24-27, wherein forming the insulating layer comprises forming the insulating layer using pulsed laser deposition.29. The method of clause 27 or clause 28, wherein a distance of about 5 mm is maintained between the first electrode layer and a plasma plume during the pulsed laser deposition.30. The method of any one of clauses 27-29, wherein the insulating layer is formed at a temperature of 730° C.31. The method of any one of clauses 27-30, further comprising annealing the insulating layer at 750° C for 1 hour in oxygen ambient.32. The method of any one of clauses 24-31, wherein forming the first electrode layer comprises coating an MgO substrate with LSMO.33. The method of clause 32, wherein the MgO substrate is (lOO)-oriented.34. The method of clause 32 or clause 33, wherein the MgO substrate is a singlecrystal substrate.35. The method of any one of clauses 24-34, further comprising forming a second electrode layer adjacent the insulating layer.Attorney Docket 71900-435019Client Docket 25-001-UPR- 5 - BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The concepts described herein are illustrated by way of example and not by way of limitation in the accompanying figures. For simplicity and clarity of illustration, elements illustrated in the figures are not necessarily drawn to scale. The detailed description particularly refers to the accompanying figures in which:

[0007] FIG. 1A is a simplified diagram of an illustrative embodiment of a capacitor formed from a BZT-BCT thin film on an Lao 67Sro3? Mn03 (“LS MO”) -coated (100) -oriented MgO substrate;

[0008] FIG. IB illustrates an initial polarization-field hysteresis loop of the capacitor of FIG. 1A;

[0009] FIG. 1C illustrates the polarization-field hysteresis loop of the capacitor of FIG.1A after 1012polarization cycles;

[0010] FIG. 2 illustrates ferroelectric polarization fatigue characteristics of the capacitor of FIG. 1A;

[0011] FIG. 3 illustrates transmittance spectra with a stable wide-bandgap (Eg~3.9 eV) of BZT-BCT ferroelectric thin films on LSMO-coated (lOO)-oriented MgO;

[0012] FIG. 4A illustrates current density versus electric field (J-E) characteristics of vertical electrodes formed from BZT-BCT ferroelectric thin films on LSMO-coated (100)-oriented MgO;

[0013] FIG. 4B illustrates current density versus electric field (J-E) characteristics of lateral electrodes formed from BZT-BCT ferroelectric thin films on LSMO-coated (100) -oriented MgO;

[0014] FIG. 4C illustrates leakage current density as a function of electric field for the BZT-BCT thin films;Attorney Docket 71900-435019Client Docket 25-001-UPR- 6 -

[0015] FIG. 5A illustrates transient current responses of vertical electrodes formed from BZT-BCT ferroelectric thin films on LSMO-coated (lOO)-oriented MgO to a xenon-arc lamp light source with laser powers of 12W, 14W, 16W at an applied bias voltage of 20 V;

[0016] FIG. 5B illustrates a transient current response of lateral electrodes formed from BZT-BCT ferroelectric thin films on LSMO-coated (lOO)-oriented MgO to a xenon-arc lamp light source with a laser power of 16W at an applied bias voltage of 20 V;

[0017] FIG. 6A illustrates a phase piezo-response force microscopy (“PFM”) image showing local ferroelectric switching after +12V poling of a capacitor formed from a BZT-BCT thin film on LSMO-coated (lOO)-oriented MgO;

[0018] FIG. 6B illustrates an amplitude PFM image showing local ferroelectric switching after +12V poling of the capacitor of FIG. 6A;

[0019] FIG. 7A illustrates electric field dependence of the dielectric constant of a capacitor formed from a BZT-BCT thin film on LSMO-coated (lOO)-oriented MgO;

[0020] FIG. 7B illustrates electric field dependence of dielectric loss of the capacitor of FIG. 7A;

[0021] FIG. 8 illustrates x-ray diffraction spectra for a capacitor formed from a BZT-BCT thin film on LSMO-coated (lOO)-oriented MgO; and

[0022] FIG. 9 illustrates Raman spectra for a capacitor formed from a BZT-BCT thin film on LSMO-coated (lOO)-oriented MgO.DETAILED DESCRIPTION OF THE DRAWINGS

[0023] While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will be described herein in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular formsAttorney Docket 71900-435019Client Docket 25-001-UPR- 7 -disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives consistent with the present disclosure and the appended claims.

[0024] References in the specification to “one embodiment,” “an embodiment,” “an illustrative embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may or may not necessarily include that particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. Additionally, it should be appreciated that items included in a list in the form of “at least one of A, B, and C” can mean (A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C). Similarly, items listed in the form of “at least one of A, B, or C” can mean (A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C).

[0025] In the drawings, some structural or method features may be shown in specific arrangements and / or orderings. However, it should be appreciated that such specific arrangements and / or orderings may not be required. Rather, in some embodiments, such features may be arranged in a different manner and / or order than shown in the illustrative figures. Additionally, the inclusion of a structural or method feature in a particular figure is not meant to imply that such feature is required in all embodiments and, in some embodiments, may not be included or may be combined with other features.

[0026] The present disclosure provides for successful growth of epitaxial ferroelectric films via pulsed laser deposition of 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (“BZT-BCT”) as capacitor materials on La0.67Sr0.33MnO3 (“LSMO”)-coated (100) -oriented MgO single crystal substrates to achieve stable and high ferroelectric switchability performance. BZT-BCT is a lead-free, pseudo binary solid solution including a phase boundary between rhombohedralAttorney Docket 71900-435019Client Docket 25-001-UPR- 8 - Ba(Zro 2Tio g)03 (“BZT”) and tetragonal (Bao " Cao?)TiO3 (“BCT”) components and having a high piezoelectric coefficient (e.g., d33 of 620 pC / N). The present disclosure utilizes perovskite-based LSMO as bottom electrode materials for better ferroelectric and fatigue-free capacitors with low leakage current behavior.

[0027] As further discussed below, the presently disclosed BZT-BCT films with c-axis oriented crystallography on LSMO-coated MgO substrate have shown a large remnant polarization (Pr) of 60 μC / cm2using pulsed laser deposition (PLD) techniques. The hysteresis loop was well saturated at a maximum voltage of ±70 V; a 2Pr~ value of ~54 μC / cm2and an Ec value close to 60 kV / cm were obtained. These hysteresis loop values are well within the requirements for NVRAM device applications. The fatigue tests on the films were performed using a 35 V square wave AC signal at a frequency of 1 MHz. FIG. 1C shows the results of the fatigue study performed over 1012cycles. Energy bandgap studies in the UV-visible region of the solar spectrum have shown a wide energy bandgap (Eg) of ~3.9 eV. The present disclosure allows for the efficient non-destructive ferroelectric capacitors, which sustain fatigue-free ferroelectric switching behavior over more than 1012switching cycles without fading ferroelectric properties, even at 70 V. The presently disclosed films exhibited only a 3% loss in polarization after 1012cycles.

[0028] As suggested in the simplified diagram of FIG. 1 A, photo-response measurements were carried out on an Au / BZT-BCT / LSMO / MgO sample (both in vertical and lateral configurations of electrodes) using a Keithley high resistance electrometer (6517B) with a Xenon arc lamp as the light source with an intensity of 100 mW / cm2at a maximum applied voltage of ± 20V (after completion of ferroelectric measurements). The measured photovoltaic (J-V) characteristics under both dark and light illumination conditions of ferroelectric BZT-BCT films in the metal / ferroelectric interface have shown the coupled phenomena of the bulk polarization and the interfacial Schottky barrier effect. The J-V curves with non-linearity in the low voltageAttorney Docket 71900-435019Client Docket 25-001-UPR- 9 -region (±10 V) are attributed to the interfacial Schottky behavior, and the linear feature in the high voltage region till ±20 V is ascribed to the dominant bulk polarization effect. Such I-V curve behavior in these films is attributed to depletion of the semiconductor-metal interface in the ferroelectric capacitors with sufficiently larger Schottky barrier height (Φ). When UV light is illuminated on to the BZT-BCT ferroelectric film, it will induce non-equilibrium photocarriers to conduction band through the interband transition.10029] FIG. IB illustrates initial ferroelectric (P-E) polarization hysteresis characteristics of BZT-BCT films on LSMO-coated (lOO)-oriented MgO substrate annealed at 750° C. The P-E properties of the films were measured with metal-insulator-metal configuration with gold (Au) top electrodes and LSMO as bottom electrodes at applied voltages of 30 to 70V at 4000 Hz using the standardized Multiferroic ferroelectric tester (Radiant Technologies). The top electrodes were deposited by DC magnetron sputtering using a DC power source (Advance Energy, model 60 MDX 500) using a shadow mask with a gold dot of 200 pm diameter and 200 nm thickness. The BZT-BCT films have shown a maximum remnant polarization of 64 μC / cm2. The hysteresis loops were well saturated at a maximum applied voltage (70V i.e., 2000kV / cm): a 2Pr~ value of 104 μC / cm2and a coercive field (Ec) value close to 557 kV / cm were obtained. These characteristic values are well within the requirements for NVRAM devices. As shown in FIG.1C, the BZT-BCT films have shown well saturated ferroelectric hysteresis loops even after >1012ferroelectric switching cycles with a maximum remnant polarization of 69.36 μC / cm2and with a 2Pr~ value of 124 μC / cm2and an coercive field (Ec) value close to 661 kV / cm. A perfect symmetrical polarization both before and after fatigue test measurements can be obtained from symmetrical electrode-ferroelectric BZT-BCT interface and homogeneous grains. It is believed that growth quality of the bottom electrode and ferroelectric layer is the reason for the excellent fatigue -free nature at higher applied electric field. The remnant polarization of the presentlyAttorney Docket 71900-435019Client Docket 25-001-UPR- 10 -disclosed thin films is higher than previously reported values for BZT-BCT materials both in thin films and bulk samples.

[0030] FIG. 2 represents fatigue test results of BZT-BCT thin films performed by applying bipolar pulses at 500 kHz with an amplitude of 35V @972 kV / cm. Switching polarization (±P*) and non-Switchable polarization (±PA) in BZT-BCT thin films after >1012ferroelectric switching cycles have shown stable polarization values. The films do not show any significant fatigue even after >1012switching cycles, and there is an increase in polarization even after >1012cycles. Fatigue measurements were made at an electric field greater than the coercive electric field or threshold electric field (Ec) required for an NVRAM cell. Considerably higher switchable polarizations were maintained after repetitive electrical cycling. The inset of FIG. 2 also represents the hysteresis properties of the films before and after fatigue cycling studies. The increase in switchable polarization was attributed to the light illumination. Ferroelectric hysteresis behavior was confirmed after measuring the polarization properties of the films after fatigue test. The presently disclosed BZT-BCT-based non-volatile ferroelectric random-access memory (“NV-FE-RAM”) devices are suitable for memory applications (read / erase / write operations) after a large number of switchable polarization cycles. The excellent ferroelectric hysteresis properties of the BZT-BCT films before and after fatigue cycling were similar to those shown in FIG. 2.

[0031] FIG. 3 illustrates transmittance spectra with a stable wi de-bandgap (approximately Eg~3.9 eV) of BZT-BCT ferroelectric thin films (fabricated using pulsed-laser deposition technique on a LSMO-coated MgO substrate in the UV region). Specifically, the bandgap energies (Eg) were determined using the Tauc plot, [(αE)2vs. Eg], The observed wide-bandgap is less than that of pure MgO substrate (~6 eV, also graphed in FIG. 3 for comparison). The presently disclosed multilayer configuration comprises stratified BZT-BCT and LSMO layers grown on MgO (lOO)-oriented substrates by sequential deposition of semi-metallic LSMO andAttorney Docket 71900-435019Client Docket 25-001-UPR- 11 -ferroelectric BZT-BCT layers. BZT-BCT film has a transparency around ~50-52% with an absorption edge shifted from 272 nm to 300 nm. The obtained wide -bandgap (Eg~3.9 eV) falls in the UV-visible region of the solar spectrum. These wide -bandgap, ferroelectric nanostructure films can be efficiently used in UV detectors.

[0032] FIG. 4A shows the current density-electric field (J-E) characteristic of vertical electrodes formed from the presently disclosed BZT-BCT films on LSMO-coated MgO substrates tested in dark and light illumination, while FIG. 4B shows the same for a lateral electrode configuration. The photo-response measurements were carried out on the Au / BZT-BCT / LSMO / MgO sample using a 100 mW / cm2intensity xenon-arc lamp light source, as described above with reference to FIG. 1A. As can be seen in FIGS. 4A and 4B, both the dark and light-induced current is low which indicates high resistivity of the films at room temperature, meaning the BZT-BCT ferroelectric thin films are good insulators. The magnitude of photocurrent for vertical and lateral electrode excitations was found to be invariant compared to that of dark condition. From the data reflected in FIGS. 4A and 4B, it was inferred that the vertical electrode configuration showed a maximum Voc of -2.87 V (Dark) / -1.44 V (Photo) and a short-circuit current density (Jsc) of ~ 4.97041E-7 mA / cm2(Dark) / 8.03742E-7 mA / cm2(Photo), while the lateral electrode configuration showed a maximum Voc of -4.52 V (Dark) / -2.48 V (Photo) and a short-circuit current density (Jsc) of ~ 6.36585E-7 mA / cm2(Dark) / 1.07862E-6 mA / cm2(Photo).

[0033] FIG. 4C illustrates leakage current density as a function of electrical field for the presently disclosed BZT-BCT films. Low leakage current density (~10“9A / cm2) was observed at low electric field for the film, and as the electric field increased, there was an increase in the current density (~10-4A / cm2at 70V was observed). The leakage current behavior of the presently disclosed thin films was measured prior to the ferroelectric measurements using a Keithley 4200 system with a voltage increment of 0.5 V and a delay time of 10 s. FIG. 4C shows current (I) asAttorney Docket 71900-435019Client Docket 25-001-UPR- 12 -a function of bias voltage (V) by ramping the voltage from -70 to 70 V with a double voltage sweep in the sequence of 0 V — > +70 V — > 0 V — > -70 V 0 V, with the compliance current (Icc) of 0.01 A, over 300 cycles.

[0034] FIGS. 5 A and 5B show transient current responses to light from a xenon-arc lamp light source. Specifically, the time-dependent current density (J) was measured under light ON and OFF conditions for vertical electrodes (at laser powers of 12W, 14W, and 16W in FIG. 5 A) and for lateral electrodes (at a laser power of 16W in FIG. 5). The transient cunent responses were measured at a bias voltage of 20V at a regular interval of 50 s. The cunent density shows a spike-like structure during light ON and OFF, which is ascribed to the pyroelectric nature of the fenoelectric materials under light illumination. A sharp rise in the cunent density with increased power was observed from the transient current response (see FIG. 5A). An abrupt rise in the cunent density (45.54 pA / cm2) was also observed under lateral electrode configuration at an applied power of 16W (see FIG. 5B). However, when the laser beam light illumination was OFF, photocurrent dropped rapidly and attained an initial value under dark condition. Overall, a small variation in the magnitude of the photocunent was witnessed over time. When the light illumination was switched ON, the cunent gradually increased to a maximum value with a spikelike structure, while the current-density decayed with time when the light was OFF. The positive photo-response current was observed during the light ON and OFF states respectively.

[0035] An abrupt increase in photocunent density under light illumination is attributed to the generation of photo-induced charge carriers, during the excitation of valence electrons from valence band to the conduction band along with the other trapped charged carriers at the impurity levels in the forbidden energy band gap. It is believed that induced thermal variation may be the reason for the sudden rise and fall with steady state condition of photocurrent during each cycle of illumination of light. This phenomena occurs in ferroelectrics is due to small decrease in resistance with raise in temperature during the light illumination and generates pyro-electricAttorney Docket 71900-435019Client Docket 25-001-UPR- 13 -current in ferroelectrics because of change in magnitude of ferroelectric polarization. Hence, the observed higher value of steady state photocurrent density in ferroelectric films during repeated light illumination cycles is attributed to ferroelectric photovoltaic effect in the presently disclosed BZT-BCT films.

[0036] FIGS. 6A and 6B illustrate local ferroelectric switching in out-of-plane piezoresponse force microscopy (“PFM”) phase and amplitude images, at room temperature after poling with +12 and -12 V after >1012ferroelectric switching cycles. BZT-BCT / LSMO / MgO films have displayed a relatively smooth surface with a roughness of approximately 4 nm. Upon reversing the electric field, clearly switchable domains patterns were recorded. Stable switchable bipolar patterns were written by an electrically-biased tip on the surface of film. Both phase and amplitude PFM images clearly demonstrate well-defined domain walls with clear boundary separation with opposite dark and bright contrasts in oppositely poled regions. The phase PFM image (FIG. 6A) shows the downward and upward polarization states with clear bright and dark regions with a nearly 180° phase change contrast. Here, the darker region corresponds to upward ferroelectric polarization and the brighter region represents downward ferroelectric polarization. The sharp dark and bright contrasts with opposite polarization switching confirm high quality atomically smooth surface with good ferroelectric properties.

[0037] FIGS. 7A and 7B illustrate typical capacitance-voltage (C-V) nonlinear dielectric properties for the presently disclosed BZT-BCT films on LSMO-coated (100) -oriented MgO single crystal substrates measured at different frequencies (1 kHz, 10 kHz) by superimposing an AC signal of 100 mV amplitude across the sample by sweeping DC bias (from the -40 V to +40 V voltage and back) on the film. The dielectric properties of the BZT-BCT films were measured in terms of the dielectric constant (E) (see FIG. 7A) and dissipation factor [loss factor (Tan §)] (see FIG. 7B). The applied AC electric field is less than the coercive field of the BZT-BCT films, so that the ferroelectric polarization state is not altered. This also minimizes the domain wallAttorney Docket 71900-435019Client Docket 25-001-UPR- 14 -contribution and allows the comparison of dielectric property values of thin films with the bulk materials. The bias-voltage dependent dielectric properties with more pronounced butterfly loops demonstrate the ferroelectric properties of the film and are attributed to the electric field that modulates the polarization sate of the film along the ferroelectric P-E hysteresis loop. The observed nonlinear hysteresis curves with the two dielectric maxima in C-V curves during electric field sweeping (forward and backward bias) is credited to polarization reversal and indicates that the BZT-BCT film is in a polar state. Well-shaped C-V curves were obtained for films annealed at 750 °C. It is believed that higher annealing temperature with good crystalline quality contributes to the dielectric properties of the BZT-BCT films. The dielectric constant dropped abruptly to a small value [e~ 1116 to 1045 for forward bias and e~980 to 917 backward bias] as the frequency was increased (1 kHz to 10 kHz) at zero voltage. At around the same frequency, the dissipation factor showed a very low dielectric dissipation factor (Tan 5 -0.17194, 0.19892 for forward bias 1 kHz and 0.03795 & 0.04562 for backward bias 10 kHz). The observation of C-V curves and hysteresis loops suggest ferroelectric behavior and tetragonal structure of the BZT-BCT films.

[0038] FIG. 8 shows high-resolution X-ray diffraction (HR-XRD) patterns for BZT-BCT ferroelectric films on LSMO-coated (100) -oriented MgO single crystal substrates, before and after ferroelectric switching cycles. High quality films were successfully grown at an annealing temperature of 700°- 750°C by pulsed laser deposition technique. The 29-0 measurement confirms epitaxial growth of highly crystalline ferroelectric BZT-BCT films on LSMO-coated MgO substrate corresponding to

[0001] reflection plane. These single-phase peaks are highly oriented along the c-axis of the MgO substrate. XRD patterns also confirm the structural stability of ferroelectric films after repeated number polarization switching cycles. Hence, crystalline quality is highly maintained after fatigue measurements. The particle size analysis of BZT-BCT films was estimated using the Debye Scherer formula [D= (K*Z) / (P*cos(0))] on (002) plane. TheAttorney Docket 71900-435019Client Docket 25-001-UPR- 15 -size of the grown particles was 50-60 nm. As shown in FIG. 8, the structure of the BZT-BCT films matches well with JCPDs No. 05-0626 as a tetragonal perovskite structure at room temperature.

[0039] FIG. 9 shows Raman spectra for epitaxial BZT-BCT films, both before and after >1012ferroelectric switching cycles. Raman modes are assigned to perovskite tetragonal phase. Room temperature Raman active modes of BZT-BCT in tetragonal perovskite phase are: Ei(TO) at 75-77 cm-1, anti-symmetric modes Ai(TOi) and A1(TO2) were at around ~ 112-114 cm-1, -176-180 cm-1respectively. These asymmetric modes are credited Ti-0 phonon vibrations. The E(TO) / B1mode at 290-294 cm-1is a signature tetragonal mode and is attributed to asymmetric Ti-0 phonon vibration. Intense AI(TO3) / BI mode was observed at -513-519 cm-1. A broad Ai(LO) / E(LO) mode unique to the tetragonal phase and endorsed to the polar [ZrO6] and [TiO6] clusters in the crystal lattice was observed at around 724-726 cm-1. In addition to these prominent modes, an asymmetry breathing mode (Aig) was also present at around 818-824 cm-1and attributed to presence of dissimilar ions at the center of the octahedral in the crystalline lattice. This behavior is due to the chemical nature of the perovskite materials and is not related to structural distortion. The tetragonal structure of the fatigue-free films is not at all disturbed and confirms the molecular vibrational atomic structure stability and phase of BZT-BCT films.

[0040] While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such an illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.

[0041] There are a plurality of advantages of the present disclosure arising from the various features of the apparatus, system, and method described herein. It will be noted that alternative embodiments of the apparatus, system, and method of the present disclosure may notAttorney Docket 71900-435019Client Docket 25-001-UPR- 16 -include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of the apparatus, system, and method that incorporate one or more of the features of the present invention and fall within the spirit and scope of the present disclosure.

Claims

Attorney Docket 71900-435019Client Docket 25-001-UPR- 17 - WHAT IS CLAIMED IS:

1. An article of manufacture comprising:a first electrode layer comprising La0.67Sr0.33MnO3(LSMO); and an insulating layer adjacent the first electrode layer, wherein the insulating layer comprises 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3(BZT-BCT).

2. The article of claim 1, wherein the first electrode layer consists of LSMO.

3. The article of claim 1 or claim 2, wherein the insulating layer consists of BZT-BCT.

4. The article of any preceding claim, wherein the insulating layer is an epitaxial layer grown on the first electrode layer.

5. The article of any preceding claim, wherein the insulating layer has been formed using pulsed laser deposition.

6. The article of any preceding claim, further comprising an MgO substrate, wherein the first electrode layer is positioned between the insulating layer and the MgO substrate.

7. The article of claim 6, wherein the first electrode layer is adjacent the MgO substrate.

8. The article of claim 6 or claim 7, wherein the MgO substrate is (100) -oriented.

9. The article of any one of claims 6-8, wherein the MgO substrate is a single-crystal substrate.

10. The article of any preceding claim, wherein the BZT-BCT of the insulating layer has c-axis oriented crystallography.

11. The article of any preceding claim, further comprising a second electrode layer, wherein the insulating layer is positioned between the first and second electrode layers.

12. The article of claim 11, wherein the second electrode layers comprises gold.Attorney Docket 71900-435019Client Docket 25-001-UPR- 18 -13. The article of claim 12, wherein the second electrode layer consists of a plurality of gold dots.

14. The article of any preceding claim, wherein the insulating layer has a remnant polarization greater than 60 μC / cm2.

15. The article of any preceding claim, wherein the insulating layer exhibits less than 10% polarization degradation after 1012switching cycles.

16. The article of any preceding claim, wherein the insulating layer exhibits no more than 3% polarization degradation after 1012switching cycles.

17. The article of any preceding claim, wherein the article is lead-free.

18. An optoelectronic device comprising the article of any one of claims 1-17.

19. The optoelectronic device of claim 18, wherein the optoelectronic device is an ultraviolet photodetector.

20. The optoelectronic device of claim 18 or claim 19, wherein the insulating layer has an optical bandgap of about 3.9 eV.

21. A capacitor comprising the article of any one of claims 1-17.

22. The capacitor of claim 21, wherein the capacitor has exhibits leakage current less than 10’4A at applied voltages up to 70 V.

23. A non-volatile random access memory comprising the capacitor of claim 21 or claim 22.

24. A method of manufacture comprising:forming a first electrode layer comprising La0.67Sr0.33MnO3(LSMO); and forming an insulating layer adjacent the first electrode layer, wherein the insulating layer comprises 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3(BZT-BCT).

25. The method of claim 24, wherein the first electrode layer consists of LSMO.Attorney Docket 71900-435019Client Docket 25-001-UPR- 19 - 26. The method of claim 24 or claim 25, wherein the insulating layer consists of BZT-BCT.

27. The method of any one of claims 24-26, wherein forming the insulating layer comprises epitaxially growing the insulating layer on the first electrode layer.

28. The method of any one of claims 24-27, wherein forming the insulating layer comprises forming the insulating layer using pulsed laser deposition.

29. The method of claim 27 or claim 28, wherein a distance of about 5 mm is maintained between the first electrode layer and a plasma plume during the pulsed laser deposition.

30. The method of any one of claims 27-29, wherein the insulating layer is formed at a temperature of 730° C.

31. The method of any one of claims 27-30, further comprising annealing the insulating layer at 750° C for 1 hour in oxygen ambient.

32. The method of any one of claims 24-31, wherein forming the first electrode layer comprises coating an MgO substrate with LSMO.

33. The method of claim 32, wherein the MgO substrate is (lOO)-oriented.

34. The method of claim 32 or claim 33, wherein the MgO substrate is a single-crystal substrate.

35. The method of any one of claims 24-34, further comprising forming a second electrode layer adjacent the insulating layer.

Images