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Multiferroic materials capable of robust magnetoelectric coupling at room temperature are currently being explored for their possible multifunctional device applications. Highly (100)-oriented Pb(Fe0.5Ta0.5)x(Zr0.53Ti0.47)1−x (PZTFTx) thin films (x = 0.2 and 0.3) with a thickness of about 300 nm were grown on La0.67Sr0.33CoO3 (LSCO)-buffered MgO 100-oriented substrates via the pulsed laser deposition method. An analysis of their X-ray diffraction patterns suggests the stabilization of the orthorhombic phase in the thin films at room temperature. Dielectric spectroscopic measurements of the metal–insulator–metal (Pt/PZTFTx/LSCO) thin-film capacitors as a function of temperature revealed a diffuse ferroelectric-to-paraelectric phase transition around Tm ~520 and 560 K for the x = 0.2 and 0.3 thin films, respectively. Well-saturated electrical hysteresis loops with large remanent (Pr) and saturation (Ps) polarizations were observed in these capacitors, which indicates the establishment of intrinsic ferroelectric ordering in the thin films at room temperature. These thin films retained ferromagnetic/ferrimagnetic ordering up to 300 K and showed saturation magnetization values of 8.3 (x = 0.2) and 6.1 (x = 0.3) emu/cm3 at room temperature. The magnetoelectric coupling constants of 2040 mV/cmOe (x = 0.2) and 850 mV/cmOe (x = 0.3), respectively, were obtained at an in-plane bias field at room temperature. The present study demonstrates that PZTFTx thin films are multiferroic at room temperature with large magnetoelectric couplings, and these materials may be suitable for use in magnetic sensors and spintronic device applications. [ABSTRACT FROM AUTHOR]

The discovery of single-phase multiferroic materials and the understanding of intriguing physics of the coupling mechanisms between their spin and polarization are important for the next generation of multifunctional devices. In this work, we report dielectric, ferroelectric, and magnetization results of Pd-substituted room-temperature magnetoelectric multiferroic Pb(Zr0.20Ti0.80)0.7Pd0.3O3 (PZTPd) thin films. Highly c axis oriented PZTPd thin films were grown on {(LaAlO3)0.3(Sr2AlTaO6)0.7} substrates using the pulsed laser deposition technique. These films were phase pure and stabilized in a tetragonal phase. Atomic force microscopic studies indicated a homogeneous distribution of grains on the films' surface with a surface roughness (RQ) of ∼5.4 nm. A large dielectric constant of ∼1780 and a low loss tangent value of ∼0.52 were observed at 1 kHz measured at room temperature. Temperature dependent dielectric studies on Pt/PZTPd/La0.7Sr0.3MnO3 metal–insulator–metal heterostructure capacitors between 80 and 660 K indicated a diffused ferroelectric to paraelectric phase transition around 515 K. The polarization hysteresis loops observed at room temperature were attributed to its ferroelectric behavior. Saturated magnetization hysteresis loop with remanent magnetization of 1.54 emu/cm3 was obtained at room temperature. Ferromagnetic ordering in thin films was found to sustain in the entire temperature range from 5 to 395 K, as revealed from the constant behavior of the dM/dT curve with temperature. The mixed oxidation states of palladium (Pd2+/Pd4+) dispersed in the polar Pb(Zr0.20Ti0.80)O3 matrix were revealed from our high resolution x-ray photoelectron spectroscopic studies and is ascribed to the origin of ferromagnetic ordering in the film. These findings suggest that PZTPd thin films are multiferroic (ferroelectric–ferromagnetic) at room temperature. [ABSTRACT FROM AUTHOR]

Magnetoelectric (ME) composite thin films are promising candidates for novel applications in future nanoelectronics, spintronics, memory, and other multifunctional devices as they exhibit much higher ME coupling and transition temperatures (Tc) than well-known single phase multiferroics discovered to date. Among the three types of multiferroic composite nanostructures, (2–2) layered and (1–3) vertically aligned composite nanostructures exhibit comparatively smaller ME coupling due to different shortcomings that restrict their use in many applications. Here, we study the morphological, piezoresponse force microscopic (PFM), ferroelectric, magnetic, and magnetodielectric properties of 0–3 [magnetic nanoparticles (0) homogeneously distributed in ferroelectric matrices (3)] multiferroic composite thin films. The Pb(Fe0.5Nb0.5)O3 (PFN)–Ni0.65Zn0.35Fe2O4 (NZFO) particulate composite films were synthesized by pulsed laser deposition. These particulate composite thin films are completely c-axis oriented with very low surface roughness. We observed magnetic and ferroelectric Tc above room temperature (RT) for all composite thin films. The PFN–NZFO 0–3 composites exhibit large polarization, high saturated magnetization with low coercive field, and low dielectric loss along with magnetodielectric coupling at RT. These nanocomposites might be utilized in next generation nano/microelectronics and spintronic devices. [ABSTRACT FROM AUTHOR]

Dielectric thin film capacitors, storing large charge density, are useful in electric energy storing devices. Highly oriented lead-free BaZr0.20Ti0.80O3 (BZT20) thin films were grown on a conducting bottom layer La0.7Sr0.3MnO3 deposited on a MgO (100) substrate under an oxygen atmosphere using a pulsed laser deposition technique. X-ray diffraction studies indicate that BZT20 films were stabilized in a (100) oriented tetragonal phase. Microstructural studies on thin films indicate a smooth film (a roughness of ∼1.25 nm) with a thickness of around 320 nm. The structural sensitive A1(TO2) Raman band exhibits a discontinuous change across the tetragonal-cubic phase transition temperature Tc ∼ 275 K. The appearance of the broad Raman band in the cubic (Pm−3m) phase at an elevated temperature suggests the activation of symmetry forbidden Raman active bands. The temperature dependent band frequency and integrated intensity of the structural sensitive A1(TO2) band show anomaly across Tc. Temperature dependent dielectric studies (100–650 K) carried out in a wide range of frequencies 102–106 Hz on a fabricated Pt/BZT20/LSMO metal-insulator-metal capacitor suggest a broad dispersive peak of around 290 K. The polarization relaxation follows the Vogel-Fulcher relation with an activation energy of Ea = 0.047 eV and a freezing temperature of Tf = 246 K. The slim polarization P-E loops with a remanent polarization of ∼89.6 μC/cm2 and an EC value of ∼0.29 MV/cm were observed, suggesting its local ferroelectric ordering in corroboration with Raman and dielectric findings. From the P-E loop analysis, a large energy storage density of 31.9 J/cm3 and an energy storage efficiency of 56% were obtained. Our experimental results revealed that the BZT20 thin film capacitors have potential for energy storage device applications. [ABSTRACT FROM AUTHOR]

Optical and structural properties of pulsed laser-deposited CdSSe thin films were grown using different temperatures on different substrates. The results of optical and structural investigation show that these films are suitable for optoelectronics applications. The energy band gap lies in the range that is suitable for the desired purpose. x-ray diffraction (XRD) analysis indicated preferential orientation in the (220) direction. The band gap energy of these films is in the range of 2.277 to 2.641 eV. [ABSTRACT FROM AUTHOR]

(Ba0.955Ca0.045)(Zr0.17Ti0.83)O3 [BCZT] epitaxial were grown on La0.67Sr0.33MnO3 (LSMO)‐coated (100)‐oriented MgO single crystal substrates by the pulsed laser deposition (PLD) technique. Herein, we report crystal structure, ferroelectric, piezoresponse force microscopy (PFM), and energy storage properties near the morphotropic phase boundary (MPB) composition of [Ba0.850Ca0.15Zr0.1Ti0.90O3] solid solution. Epitaxial growth of the films was confirmed using X‐ray diffraction (XRD) spectra. Room‐temperature Raman spectroscopy confirms perovskite phase of BCZT films. Room‐temperature polarization‐electric field (P‐E) loops confirm the ferroelectric nature of BCZT films. Ferroelectric hysteresis loops demonstrate high saturation polarization (Pmax ~ 97.96 μC/cm2) and remanant polarization (Pr ~ 70.1 μC/cm2) at an applied maximum electric field ~2.77 MV/cm. The optimized BCZT epitaxial thin films have shown moderate dielectric properties at different measured frequencies (10‐100 kHz). Nanoscale piezoresponse force microscopy (PFM) images demonstrate switchable ferroelectric polarization of these thin films above ±9 V of dc voltage applied. Energy storage properties measured from ferroelectric loops revealed a high discharge curve energy density ~27.5 J/cm3 at a maximum electric field of 2.77 MV/cm. Epitaxial‐grown BCZT films are suitable candidate materials for capacitor applications. [ABSTRACT FROM AUTHOR]

Bi5FeTi3O15 (BFTO) based Aurivillius rerroelectrlc thin films were rabrlcated on strontium ruthanate coated amorphous ffised silica substrates using pulsed laser deposition technique. Optical, rerroelectrlc, and piezoresponse properties or these thin films were investigated. The estimated refractive index (n) and extinction coefficient (k) for these films were in the range from 2.40 to 2.59 and 0.012 to 0.19, respectively. The bandgap or the BFTO thin layers was estimated to be 2.88 eV. Domain switching and hysteresis loops or BFTO films were studied utilizing piezoresponse force microscopy (PFM). The measured apparent polarization (Pr) and coercive field (Ec) for the samples were 20 µC/cm² and 250kV/cm, respectively. The amplitude and phase hysteresis curves obtained from PFM characterization reveal that these films can be switched below 5 V. These results suggest that BFTO in thin film form is a promising material for photo rerroelectrlc and optoelectronic devices applications. [ABSTRACT FROM AUTHOR]

Magnetoelectric multiferroics, because of their coupled electric and magnetic ordering in a single phase, are eminent for applications in logic and nonvolatile memory devices. Recent advances in computational modeling, synthesis, and characterization techniques are spurring significant advances in the study of these materials. During last several years, our group at University of Puerto Rico has been involved in synthesizing novel single-phase room temperature multiferroic materials that included not only solid solutions of lead zirconate titanate with lead iron tungstate, lead iron niobate, and lead iron tantalate, but also recently discovered palladium substituted room temperature multiferroics, namely PbPd0.3Ti0.7O3 and Pb(Zr0.2Ti0.8)Pd0.3O3. In this review, we have reported thin films of the above materials that were synthesized using pulsed laser deposition technique on various substrates at Speclab, University of Puerto Rico. We describe in detail thin film fabrication, structural diffraction analyses (XRD, TEM), dielectric, ferroelectric, piezo-response force microscopy, and magnetization results on recently grown Pd-substituted lead titanate and lead zirconate titanate thin films in an elaborate manner. The films were phase pure and stabilized in c-axis oriented tetragonal phase (P4mm) with surface roughness RQ of 2–4 nm. Temperature-dependent dielectric studies on metal-dielectric-metal heterostructure capacitors indicate that ferroelectric to paraelectric phase transition is above 500 K. A proof of ferroelectricity was confirmed from strong domain switching responses using piezo-response force microscopy. These films showed ferromagnetic ordering below 395 K. The origin of magnetic ordering in these materials was attributed to the existence of Pd2+ and Pd4+ mixed oxidation states of palladium dispersed in the polar matrices. We conclude with the above findings that these multiferroics may have potential applications.in nonvolatile memory and other multifunctional devices. [ABSTRACT FROM AUTHOR]

SrBi[SUB2]Ta[SUB2]O[SUB9] thin films on various bottom electrodes/substrates such as Pt/TiO[SUB2]/SiO[SUB2]/Si (Pt) and LaNiO[SUB3]/Pt/TiO[SUB2]SiO[SUB2]/Si (LNO) were grown using the pulsed laser deposition technique. X-ray diffraction studies revealed that as-grown (at 500°C) films were crystallized in the layered structure after annealing at 800°C. Films grown on platinized silicon exhibited maximum value of remanent polarization (2P[SUBr]˜21.5μC/cm[SUP2]) with coercive field (E[SUBc]) of˜67 kV/cm. The dielectric constant and dissipation factor also decreased with the introduction of a 50 nm conducting LaNiO3 oxide electrode at the interface of Pt and SBT thin films, which might be contributed by the high resistive oxide electrode layers. The dc leakage characteristics of the films were studied at elevated temperatures and the data were fitted with the Schottky emission model. The barrier heights of the films grown on Pt and LNO substrates were estimated to be 1.27 and 1.12 eV with optical dielectric constants of 6.3 and 17, respectively. The reduction in barrier height was attributed to the lower work function of the LNO electrode. [ABSTRACT FROM AUTHOR]

Highly oriented 0.90[PbZr0.53Ti0.47]0.10[La0.80Sc0.20]O3-δ (PLZTS) thin films deposited on La0.67Sr0.33MnO3 (LSMO) coated MgO (100) substrates were grown by pulsed laser deposition technique. Temperature dependent dielectric measurements on metal-ferroelectric-metal Pt/PLZTS/LSMO thin film capacitors were carried out at several frequencies which exhibit high dielectric constants (450–580) with the diffuse peak around 400 K, and the diffusivity parameter γ was obtained as 1.96 for 100 kHz data. The slim polarization-electric field hysteresis loop was observed with less remanent polarization (∼7–10 μC/cm2) indicating its relaxor behavior. Temperature dependent Raman spectra measured between 80 and 550 K show softening of the symmetric E(LO2) band that disappeared at 300 K, corroborating the tetragonal-cubic phase transition. From the analysis of the measured hysteresis loops, the recovered energy density Ure ∼ 19 J/cm3 with the efficiency η ∼ 66% was estimated, suggesting its possible application in energy density capacitors. [ABSTRACT FROM AUTHOR]

We report structural, optical, temperature and frequency dependent dielectric, and energy storage properties of pulsed laser deposited (100) highly textured BaZrxTi1-xO3 (x=0.3, 0.4, and 0.5) relaxor ferroelectric thin films on La0.7Sr0.3MnO3/MgO substrates which make them potential lead-free capacitive energy storage materials for scalable electronic devices. A high dielectric constant of ~1400–3500 and a low dielectric loss of<0.025 were achieved at 10 kHz for all three compositions at ambient conditions. Ultrahigh stored and recoverable electrostatic energy densities as high as 214±1 and 156±1 J/cm3, respectively, were demonstrated at a sustained high electric field of ~3MV/cm with an efficiency of 72.8±0.6% in an optimum 30% Zr substituted BaTiO3 composition. [ABSTRACT FROM AUTHOR]

A highly sensitive hydrogen gas sensor has been developed utilizing 3% copper-doped zinc oxide thin films. These films were deposited using pulsed laser deposition technique on quartz substrates with predeposited interdigitated platinum electrodes. The deposited films were characterized by X-ray diffraction and atomic force microscopy. The hydrogen sensing properties of the sensor were studied at three operating temperatures, viz., 50 °C, 100 °C, and 150 °C. We observed that the sensor shows good performance even at a low operating temperature of 50 °C for a very small concentration of hydrogen (10 ppm). [ABSTRACT FROM PUBLISHER]

Temperature stability of voltage tunability and figure of merit (FOM) were investigated for the pulsed laser deposited Ba0.6Sr0.4TiO3(BST0.6) thin films on platinum coated silicon [Pt(111)/TiOx/SiOx/Si(100)] substrates. The structural and micro-structural properties of these films were analyzed using x-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. Metal-ferroelectric-metal (MFM) mono-dielectric layer stacks were fabricated using these films and their temperature and voltage dependent dielectric properties were quantified. The temperature dependence of dielectric properties were analysed using the modified Curie-Weiss law. The films showed a good dielectric tunability of about 40% at a bias field of 125 kV/cm. The determined figure of merits are found to be highly sensitive to the temperature changes. The observed ferroelectric-like behaviour in these films above the Curie point (Tc) has been attributed to the thermal expansion mismatch and the substrate induced misfit strain with the Pt/Si substrate. [ABSTRACT FROM PUBLISHER]

Self-poled ultra-thin ferroelectric PbZr0.52Ti0.48O3 (PZT) (5 and 7 nm) films have been grown by pulsed laser deposition technique on ferromagnetic La0.67Sr0.33MnO3 (LSMO) (30 nm) to check the effect of polar capping on magnetization for ferroelectric tunnel junction devices. PZT/LSMO heterostructures with thick polar PZT (7 nm) capping show nearly 100% enhancement in magnetization compared with thin polar PZT (5 nm) films, probably due to excess hole transfer from the ferroelectric to the ferromagnetic layers. Core-level x-ray photoelectron spectroscopy studies revealed the presence of larger Mn 3s exchange splitting and higher Mn3+/Mn4+ ion ratio in the LSMO with 7 nm polar capping. [ABSTRACT FROM AUTHOR]

We report the photovoltaic properties of doped ferroelectric [Bi0.9La0.1][Fe0.97Ti0.02Zr0.01]O3 (BLFTZO) thin films. Polycrystalline BLFTZO films were fabricated on Pt/TiO2/SiO2/Si substrates by pulsed laser deposition technique. Al-doped ZnO transparent top electrodes complete the ZnO:Al/BLFTZO/Pt metal-ferroelectric-metal capacitor structures. BLFTZO showed switchable photoresponse in both polarities. The open circuit voltage (VOC) and short circuit current (JSC) were found to be ~0.022 V and ~650 μA/cm², respectively after positive poling, whereas significant difference in VOC ~ 0.018V and JSC ~ 700 μA/cm² was observed after negative poling. The observed switchable photocurrent and photovoltage responses are explained on the basis of polarization flipping in BLFTZO due to the applied poling field. [ABSTRACT FROM AUTHOR]

We report the switchable photovoltaic effects in graphene/BiFeO3/Pt heterostructures. Pure phase polycrystalline BiFeO3 films were deposited on Pt/TiO2/SiO2/Si substrates by pulse laser deposition. A bilayer graphene was transferred onto the BiFeO3 film which serves as transparent conducting electrodes. The heterostructures showed switchable photovoltaic effect depending on ferroelectric polarization directions indicating depolarization field induced separation of photogenerated carriers. The open circuit voltage (VOC) and short circuit current density (JSC) were measured to be ~ 110 mV, ~92 μA/cm² in positive polarity and similar values were obtained when the polarity was reversed. The JSC and VOC also showed rapid response (< 100 ms) as a function of light exposure time. [ABSTRACT FROM AUTHOR]

The unipolar resistive switching characteristics of the amorphous LaLuO3thin films deposited by pulsed laser deposition have been studied. Reliable and repeatable nonvolatile switching of the resistance of LaLuO3films was obtained between two well defined states of low and high resistance with nearly constant resistance ratio ∼107and non-overlapping switching voltages in the range of 0.66-0.83 V and 1.9-2.7 V respectively. The temperature dependent measurement revealed metallic and semiconducting behavior in low and high resistance states respectively. The switching between low and high resistance states was attributed to the change in the separation between oxygen vacancies in light of the correlated barrier hopping theory. The current conduction mechanism of the device in high-resistance state followed the Poole's law, whereas the conduction in low-resistance state was found to be dominated by percolation. The resistance of low and high resistance states of the film showed no obvious degradation for up to ∼104seconds indicating good retention. The achieved characteristics of the resistive switching in LaLuO3thin films seem to be promising for futuristic nonvolatile memory applications. [ABSTRACT FROM AUTHOR]

We report a remarkable photovoltaic effect in pulsed laser deposited multiferroic aurivillius phase Bi5FeTi3O15 (BFTO) thin films sandwiched between ZnO:Al transparent conductive oxide top electrode and SrRuO3 bottom electrode fabricated on amorphous fused silica substrates. The structural and micro structural properties of these films were analysed by X-ray diffraction and atomic force microscopy techniques. The films were showing a photo sensitive ferroelectric behaviour with a notable apparent polarization in the range of 10-15 μC/cm². These films also exhibited a switchable photoresponse and this parameter was observed to be sensitive to polarisation field and the polarization direction. The device shows a large ON/OFF photo current ratio with an open circuit voltage of 0.14 V. The photo response at zero bias of this BFTO based heterostructures showed rapid increase to a saturation value of 6 μA at zero bias. [ABSTRACT FROM AUTHOR]

We report photovoltaic (PV) effect in multiferroic Bi0.9Sm0.1Fe0.95Co0.05O3 (BSFCO) thin films. Transition metal modified polycrystalline BiFeO3 (BFO) thin films have been deposited on Pt/TiO2/SiO2/Si substrate successfully through pulsed laser deposition (PLD). PV response is observed under illumination both in sandwich and lateral electrode configurations. The open-circuit voltage (Voc) and the short-circuit current density (Jsc) of the films in sandwich electrode configuration under illumination are measured to be 0.9 V and −0.051 µA cm−2. Additionally, we report piezoresponse for BSFCO films, which confirms ferroelectric piezoelectric behaviour. [ABSTRACT FROM AUTHOR]

PbZr0.53Ti0.47O3/CoFe2O4 multilayer nanostructures were grown on La0.5Sr0.5CoO3 coated MgO and Pt/TiO2/SiO2/Si substrates by pulsed laser deposition. Ferroelectric polarization decreased slowly in reducing the temperature from 300 to 200 K, with complete collapse of polarization at 100 K, but there was complete recovery of the polarization during heating. At the same time, the temperature dependent remanent magnetization of the multilayer nanostructures showed slow enhancement in the magnitude till 200 K with three-fold increase at 100 K compared to room temperature. Thus the enhancement in remanent magnetization and the decrease in polarization on lowering the temperature suggest that dynamic the magnetoelectric coupling existed in the multilayer systems. [ABSTRACT FROM AUTHOR]

The magnetic properties of BiFeO3(BFO) - CoFe2O4(CFO) heterostructure thin films, grown on (100), (110) and (111) SrTiO3 (STO) substrates by employing pulsed laser deposition (PLD) method, have been studied. The XRD patterns of BFO-CFO multilayer thin films compared with the pure CFO and BFO thin films grown using under identical conditions evidenced that all peaks present correspond to CFO and BFO structure in two separate phases. Micro-Raman spectra analysis also reveals the presence of BFO and CFO in two separate phases in the heterostructures thin films. The anomalous enhancement in magnetization has been observed for BFO-CFO multilayer thin films, relative to pure BFO thin films in all three different orientations. The saturation magnetization for (100), (111) and (110) oriented BFO-CFO thin films are 44, 62 and 80 emu/cc suggesting that (110) is most preferable direction to achieve the magneto electric (ME) coupling effect. [ABSTRACT FROM AUTHOR]

Development of lead-free BaTiO3/NiFe2O4/BaTiO3 (BTO/NFO/BTO) trilayer structure thin films is significant for the realization of eco-friendly and implantable microelectromechanical systems (MEMS)-based devices. In the present work, we report BTO/NFO/BTO trilayer structure as a representative ferroelectric/ferromagnetic/ferroelectric (FE/FM/FE) system deposited on Pt(111)/TiO2/SiO2/Si using Pulsed Laser Deposition (PLD) technique. We report the ferroelectric, magnetic, and ME properties of BTO/NFO/BTO trilayer nanoscale heterostructure having dimensions 140/80/140 nm, at room temperature. High room temperature dielectric constant ~2145 at 100 Hz with low dielectric loss ~0.05 at 1 MHz is observed. Further, the deposited (BTO/NFO/BTO) tri-layered thin films showed magnetoelectric, multiferroic behavior with remanent polarization of 8.63 μCcm−2 at about 0.25 MV/cm and a reasonably high saturation magnetization of ~16 emu/cm3 at ~10 kOe is witnessed at room temperature. Tri-layered films have shown interesting magnetoelectric (ME) coupling coefficient (αE) ~54.5 mV/cm Oe at room temperature. [ABSTRACT FROM AUTHOR]

PbSc0.5Nb(1 -x)/2Tax/2O3(PSNT for x = 0.3, PST for x = 1) nanoceramics and thin films were prepared by high energy ball mill with solid state reaction technique and pulse laser deposition (PLD) respectively. A comparative study of the microstructure, dielectric properties, and polarization of PSNT and PST thin films and nano ceramics were carried out over a wide range of temperature (100 K-600 K) and frequency (100 Hz to 1 MHz). High Resolution Transmission Electron Microscopy (HRTEM) image of PSNT and PST thin films indicate the presence of small polar nano regions (PNRs) and long range ordered regions in crystal lattice plane respectively. PST nanoceramics (PST-N) showed normal ferroelectric behavior where as its thin film form (PST-F) illustrated relaxor behavior. PSNT nanoceramics (PSNT-N) and its films (PSNT-F) demonstrated weak frequency dispersion and strong frequency dispersion in dielectric spectra respectively. A shift in dielectric maximum temperature (Tm) towards lower temperature side i.e. 65 K and 85 K were observed for PSNT-F and PST-F compare to their nanoceramices indicates greater role of substrate-electrode-interface strain on dielectric properties. Well behaved hysteresis at room temperature for PSNT-F point toward strong competition between short range order and long range order. A weak slim hesteresis for PST-F were observed at room temperature suggesting the existence of polar nano regions far above dielectric maximum temperature. [ABSTRACT FROM AUTHOR]

Bi-layered ferroelectric thin films of (Sr 0.8 Ba 0.2 )Bi 2 Ta 2 O 9 were grown on Pt/TiO 2 /SiO 2 /Si substrates using the pulsed laser deposition technique. The effect of oxygen pressure and annealing temperature on the structural and electrical properties were studied. The XRD results revealed that the films grown at lower oxygen pressure (100-200 mTorr) and annealed at higher temperature (>800 °C) have the evidence of secondary phase. Whereas, films grown at higher pressure (300 mTorr) and annealed at higher temperature ∼850 °C does not show any secondary phases. Increase in the intensity of optical phonon modes with annealing temperature is attributed to larger grain size at higher annealing temperatures. The films annealed at 800 °C show enhanced ferroelectric properties with remanent polarization (2P r ) of 23.5 μC/cm 2 and coercive field of ∼31 kV/cm. The Films annealed at higher temperature (800°C) have relatively higher dielectric constant with lower dissipation factor (∼0.02). Increased tangential loss with the annealing temperature (> 800 °C) is attributed to the interdiffusion of Bi in to Pt electrode. [ABSTRACT FROM AUTHOR]

Ba0.5Sr0.5TiO3 (BST-0.5) thin films (600 nm) were deposited on single crystal MgO, SrTiO3 (STO), and LaAlO3 (LAO) substrates by pulsed laser deposition at an oxygen partial pressure of 80 mTorr and temperature of 720 °C. X-ray diffraction and in situ reflection high-energy electron diffraction routinely ascertained the epitaxial quality of the (100)-oriented nanocrystalline films. The broadband microwave (1–40 GHz) dielectric properties were measured using coplanar waveguide transmission line test structures. The out-of-plane relative permittivity (ε ⏊ /) exhibited strong substrate-dependent dielectric (relaxation) dispersions with their attendant peaks in loss tangent (tanδ), with the former dropping sharply from tens of thousands to ~1000 by 10 GHz. Although homogeneous in-plane strain (ϵ ǁ) , enhances ε ⏊ / with ε M g O B S T − 0.5 ⏊ / > ε S T O B S T − 0.5 ⏊ / > ε L A O B S T − 0.5 ⏊ /   at lower frequencies, two crossover points at 8.6 GHz and 18 GHz eventually change the trend to: ε S T O B S T − 0.5 ⏊ / > ε L A O B S T − 0.5 ⏊ / > ε M g O B S T − 0.5 ⏊ / . The dispersions are qualitatively interpreted using (a) theoretically calculated (T)− (ϵ ǁ) phase diagram for single crystal and single domain BST-0.5 film, (b) theoretically predicted ϵ ǁ -dependent, ε ⏊ / anomaly that does not account for frequency dependence, and (c) literature reports on intrinsic and extrinsic microstructural effects, including defects-induced inhomogeneous strain and strain gradients. From the Vendik and Zubko model, the defect parameter metric, ξ s , was estimated to be 0.51 at 40 GHz for BST-0.5 film on STO. [ABSTRACT FROM AUTHOR]

Cadmium selenide (CdSe) thin films were deposited on indium tin oxide (ITO) coated glass substrates using pulsed laser deposition (PLD) technique under different growth temperatures. Samples were investigated for their structural, morphological, and optical properties through X-ray diffraction (XRD), atomic force microscopy (AFM), and UV-Vis-NIR spectroscopy. AFM analysis revealed that the surface roughness of the as-grown CdSe thin films increased with the increase in deposition temperature. The optical constants and film thickness were obtained from spectroscopic ellipsometry analysis and are discussed in detail. The optical band gap of the as-grown CdSe thin films, calculated from the Tauc plot analysis, matched with the ellipsometry measurements, with a band gap of ~1.71 eV for a growth temperature range of 150 °C to 400 °C. The CdSe thin films were found to have a refractive index of ~3.0 and extinction coefficient of ~1.0, making it a suitable candidate for photovoltaics. [ABSTRACT FROM AUTHOR]

We have studied the leakage current conduction mechanism of pulsed-laser-deposited SrBi[sub 2]Nb[sub 2]O[sub 9] (SBN) thin films on platinized silicon substrates. The time-dependent dc leakage current densities of SBN thin films do not follow Curie-von Schweidler power law. Instead the contribution of conduction current is predominantly electronic. At lower fields, the leakage current follows the ohmic behavior, and it increases exponentially for higher fields. The leakage current density of the SBN thin films was studied at elevated temperatures, and the data were fitted with the Schottky emission model. The effective Richardson's constant was calculated to be about 8.7 × 10[sup -6] A/cm² K². The Schottky barrier height of the SBN thin films was estimated to be 1.37 eV. [ABSTRACT FROM AUTHOR]

Bismuth-layered ferroelectric thin films of Sr[sub 1-x]A[sub x]Bi[sub 2]Ta[sub 2]O[sub 9], with composition x=0 and 0.2, were fabricated by using the pulsed-laser deposition technique. Structural characterization of the films by x-ray diffraction and atomic force microscopy, revealed that the films are polycrystalline in nature with average grain size of 180 nm. The films displayed spherical grains with a surface roughness of 12 nm. The ferroelectric measurements of Sr[sub 0.8]Ba[sub 0.2]Bi[sub 2]Ta[sub 2]O[sub 9], SrBi[sub 2]Ta[sub 2]O[sub 9], and Sr[sub 0.8]Ca[sub 0.2]Bi[sub 2]Ta[sub 2]O[sub 9] showed saturated hysteretic behavior with remanent polarization (2P[sub r]) of 23.5, 17.9, 14 μC/cm[sup 2] and coercive field (E[sub c]) of 31.06, 74.2, 86.3 kV/cm for a maximum applied electric field of 360 kV/cm. Films exhibited minimal (<=17%) degradation of polarization for up to 10[sup 10] switching cycles. It was observed that the coercive field decreased with increase in the ionic size of partially substituted cations. The leakage current density of films were found to be of the order of ∼10[sup -8] A/cm[sup 2] for up to a breakdown field of about 75 kV/cm. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Thin films of CaBi[sub 2]Ta[sub 2]O[sub 9] (CBT) were deposited on Pt/TiO[sub 2]/SiO[sub 2]/Si substrates using the pulsed laser deposition technique at temperatures ranging from 500 to 700 °C. The presence of (115) and (00[UNDRLINE]10[/UNDRLINE]) orientations confirm the phase formation at the lower temperature (500 °C). Microstructure evolution of CBT films with oxygen pressure of 100-200 mTorr at a substrate temperature of 650 °C shows that the films deposited at lower pressure have a relatively smaller grain size and less surface roughness. The films grown at 650 °C exhibited a maximum polarization of (2P[sub m]) 17 μC/cm[sup 2], remanent polarization of (2P[sub r]) 8 μC/cm[sup 2] and coercive field of (E[sub c]) 128 kV/cm, with fatigue endurance up to 10[sup 10] switching cycles. The higher dielectric constant (∼115 at 100 kHz) with a relatively lower dissipation factor (0.02) at higher growth temperature (700 °C) was explained by the increased grain size. The higher leakage current density (∼10[sup -7] A/cm[sup 2]) at higher deposition temperature is attributed to the interfacial diffusion of the film and the substrate. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: We here report the structural and optical studies of Zn1−x−y Be x Mg y O (0≤ x ≤0.15; 0≤ y ≤0.20) powders and thin films. From the Rietveld refinement of the powder X-ray diffraction (XRD) patterns it was revealed that the value of ‘a’ lattice parameter remains almost unchanged whereas ‘c’ parameter reduces with Be and Mg co-doping in ZnO. The Zn-O bond length also decreases in co-doped samples. Raman studies of the pure ZnO powder showed all the characteristic peaks of the wurtzite hexagonal structure and with (Be, Mg) co-doping new modes appeared which can be attributed to arise as a result of substitution. The XRD of the films prepared from the powders using pulsed laser deposition (PLD) technique exhibited the preferential orientation and with increase in co-doping the (0002) peak also shifts to higher 2θ values suggesting the incorporation of Be/Mg at the Zn-site. From the UV–visible optical transmittance measurement it was noticed that the band gap of the pristine ZnO film is 3.3eV which enhanced up to 4.51eV for Zn0.7Be0.1Mg0.2O film which lies in the solar blind region and is very useful in the realization of deep UV detectors. [ABSTRACT FROM AUTHOR]

MgxZn1−xO (MZO) thin films were deposited from MZO targets as well as sequential deposition of ZnO/MgO multilayers on c-plane Al2O3 substrates using pulsed laser deposition. The total thickness of the films used in this study was ∼300 nm. For multilayer deposition, the thickness of each single ZnO layer was varied in the range of 0.75–2.5 nm followed with the MgO layer thickness of 1 nm. The structural transition from the hexagonal to the cubic phase was observed with the increase in Mg concentration at/above 40% from the single targets. Similar structural change was also observed with the decrease in thickness of single ZnO layer from 2.5 to 0.75 nm in multilayer deposition. The bandgap was increased with increase of Mg contents from 3.3 to 6.2 eV as well as with the change of ZnO sublayer thickness. In both cases it has not been possible to fabricate single-phase stable MZO alloys with a bandgap between 4 and 6 eV. [Copyright &y& Elsevier]

Highly oriented Pb(Zr 0.53 Ti 0.47) 0.90 Sc 0.10 O 3 (PZTS) thin films were deposited on La 0.67 Sr 0.33 MnO 3 (LSMO) buffer layer coated on MgO (100) substrates by following two subsequent laser ablation processes in oxygen atmosphere employing pulse laser deposition technique. The PZTS films were found to grow in tetragonal phase with orientation along (100) plane as inferred from x-ray diffractometry analysis. The structural sensitive symmetric E (LO 2) Raman band softened at elevated temperature along with its intensity continuously decreased until it disappeared in the cubic phase above 350 K. The existence of broad Raman bands at high temperature (>350 K) is attributed to the symmetry forbidden Raman scattering in relaxor cubic phase due to symmetry breaking in nano length scale. The temperature dependent dielectric measurements were performed on metal-ferroelectric-metal capacitors in the frequencies range of 102–106 Hz was observed to be diffused over a wide range of temperature 300–650 K and exhibits high dielectric constant ~5700 at room temperature. An excellent high energy storage density (U re) ~54 J/cm3 with efficiency ~70% was estimated at applied voltage 1.82 MV/cm. High DC breakdown strength, larger dielectric constant and high restored energy density values of our PZTS thin films indicate its usage in high energy storage applications. • T-dependent dielectric studies on Pt/PZTS/LSMO capacitor suggest its relaxor behavior • Excellent high energy storage density ~54 J/cm3 with efficiency ~70% was achieved • The structurally sensitive E (LO 2) Raman band soften at elevated temperature and vanishes in the cubic phase above 350 K [ABSTRACT FROM AUTHOR]

Magnetoelectric multiferroic Properties of BTO/CFO/BTO thin films grown on Pt/TiO 2 /SiO 2 /Si. [Display omitted] • Multiferroic thin films were successfully grown using PLD. • Improved magnetoelectric properties for BTO-CFO-BTO. • Interesting multiferroic and magnetoelectric properties. A magnetoelectric multiferroic bi-phase system with robust ferroelectric and ferro/ferri-magnetism response at room temperature would be ideally suitable for microelectronics, memory devices, and for spintronic applications. BaTiO 3 /CoFe 2 O 4 /BaTiO 3 (BTO/CFO/BTO) heterostructured films were pulsed laser deposition grown on Pt(1 1 1)/TiO 2 /SiO 2 /Si substrates. High quality polycrystalline films were grown by thermal annealing at 750 °C, at an oxygen partial pressure of 100 mTorr for 1 h. Crystal quality and phase formation information was monitored using X-ray diffraction (XRD). XRD confirm the growth of polycrystalline heterostructures and the coexistence of both perovskite BTO and spinel CFO phases in heterostructures. In order to obtain robust magnetoelectric coupling, we studied the tri-layer structure as a representative ferroelectric/ferrimagnetic/ferroelectric system. We report the ferroelectric, leakage current behavior, ferrimagnetic, and frequency dependent ME properties of the films. Ferroelectric BTO and ferrimagnetic inverse spinel CFO nature is also confirmed using the piezoresponse force microscopy and magnetic force microscopy measurements. These nanostructures exhibit high saturation polarization (Ps ∼ 99.86 µC/cm2), saturation magnetization (Ms ∼ 51.48 emu/cm3), and a strong ME coupling coefficient of ∼ 274 mV/cm-Oe with a bias magnetic field of + 90 Oe, anda frequency of 1 kHz revealing them as prospective candidates for multifunctional applications. [ABSTRACT FROM AUTHOR]

High quality (1 0 0) oriented thin films of (Y 0.9 Bi 0.1 )(Fe 0.5 Cr 0.5 )O 3 [YBFCO] were deposited on (1 0 0) LAO substrates with conducting LNO buffer layer as bottom electrode. YBFCO thin film was found to demonstrate interesting room temperature multiferroic properties where the origin of weak ferroelectricity could be mainly attributed to disordered transition metal ions of unlike spins, and magnetic behavior was ascribed to uncompensated weak ferromagnetism arises due to magnetic cluster state in disordered system. Dielectric anomaly near magnetization reversal temperature ( T irr ) revealed magnetodielectric effect in YBFCO film. In addition, leakage current behavior of the film was explained by trap-controlled space-charge-limited current conduction (SCLC) mechanism. [ABSTRACT FROM AUTHOR]

Rare-earth (Sm) and transition metal (Co) modified polycrystalline BiFeO3 (BFO) thin films have been deposited on Pt/TiO2/SiO2/Si substrate successfully through pulsed laser deposition (PLD) technique. Piezoelectric, leakage current and temperature dependent dielectric and magnetic behaviour were investigated for the films. Typical "butterfly-shaped" loop were observed in BSFCO films with an effective piezoelectric constant (d33) ~94 pm/V at 0.6 MV/cm. High dielectric constant ~900 and low dielectric loss ~0.25 were observed at room temperature. M-H loops have shown relatively high saturation magnetization ~35 emu/cm³ at a maximum field of H ~20 kOe. Enhanced magnetoelectric coupling response is observed under applied magnetic field. The multiferroic, piezoelectric, leakage current behaviours were explored. Such studies should be helpful in designing multiferroic materials based on BSFCO films. [ABSTRACT FROM AUTHOR]

Abstract: Monoclinic Bi2Zn2/3Nb4/3O7 (m-BZN) thin films were deposited by pulsed laser deposition on fused silica substrates at different oxygen pressures. Microwave dielectric and Raman scattering studies were systematically carried out on films that had been annealed at 600 °C after deposition. The dielectric constant of films changes in the range 56–71 due to varying the oxygen pressure during deposition. X-ray diffraction measurements indicate that the BZN thin films deposited at the oxygen pressure of 10 Pa have the best crystalline quality. Atomic force microscopy results show that the surface roughness of the m-BZN film increases with the increase of oxygen pressure. The anomalous change in two higher-frequency Ag modes appearing at 774 and with varying oxygen pressure also suggests a nonequivalent change in the oxygen octahedra around the Nb and Zn and is closely related to the microwave dielectric properties of the thin films. [Copyright &y& Elsevier]

In this study, we have improved the remanent polarization of SrBi2Ta2O9 (SBT) and SrBi2Nb2O9 (SBN) thin films using Ca substitution at Sr-site. SBT and SBN thin films with different concentrations of Ca were deposited on Pt/TiO2/SiO2/Si substrates using pulsed-laser-deposition technique. The lattice parameters was found to be decreased with Ca incorporation and was attributed to the smaller ionic radii of Ca than for Sr. The modification in lattice vibrational frequencies with the incorporation of Ca in SBT and SBN films was investigated using micro-Raman spectroscopy. The grain size was increased with the increase in the Ca concentrations in SBT and SBN thin films. The SBT thin films with 20% Ca contents exhibited remnant polarization of ∼23.8 μC/cm2 with a coercive field of ∼175 kV/cm. The remanent polarization was found to be ∼35.5 μC/cm2 for SBN thin films with 10% Ca incorporation. The dielectric constant of SBT and SBN films was found to be decrease with Ca concentrations and observed to be independent of grain size. [Copyright &y& Elsevier]