Fabrication and properties of solution processed all polymer thin‐film ferroelectric device

A ferroelectric device, making use of a flexible plastic, polyethylenterephtalate (PET), as a substrate was fabricated by all solution processes. PET was globally coated by a conducting polymer, poly(3,4‐ethylenedioxythiophene) poly(styrenesulfonate) acid (PEDOT/PSSH), which is used as bottom electrode. The ferroelectric copolymer, poly(vinylidenefluoride–trifluoroethylene) (PVDF–TrFE), thin film was deposited by spin‐coating process from solution. The top electrode, polyaniline, was coated by solution process as well. The ferroelectric properties were measured on this all solution processed all polymer ferroelectric thin‐film devices. A square and symmetric hysteresis loop was observed with high‐polarization level at 15‐V drive voltage on a all polymer device with 700 Å (PVDF–TrFE) film. The relatively inexpensive conducting polyaniline electrode is functional well and therefore is a good candidate as electrode material for ferroelectric polymer thin‐film device. The remnant polarization P_r was 8.5 μC/cm² before the fatigue. The ferroelectric degradation starts after 1 × 10³ times of switching and decreases to 4.9 μC/cm² after 1 × 10⁵ times of switching. The pulse polarization test shows switching take places as fast as a few micro seconds to reach 90% of the saturated polarization. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Bipolar resistive switching behavior and conduction mechanisms of composite nanostructured TiO2/ZrO2 thin film

In this work, TiO₂/ZrO₂ bilayer thin film was prepared on fluorine doped tin oxide (FTO)/glass substrates by using a simple and low-cost chemical solution deposition method. Reproducible bipolar resistive switching (RS) characteristics in Au/TiO₂/ZrO₂/FTO/glass devices are reported in this work. TiO₂/ZrO₂ bilayer thin films prepared in this work shows reversible bipolar resistive switching and unidirectional conduction performances under applying voltage and these special performances of TiO₂/ZrO₂ bilayer thin films was first reported. Obvious resistive switching performance can be observed after setting a compliance current, the ratio of high/low resistance reached about 100 at a read voltage of +0.1V and −0.1V and the RS properties showed no obvious degradation after 100 successive cycles tests. The resistive switching characteristics of Au/TiO₂/ZrO₂/FTO/glass device can be explained by electron trapping/detrapping related with the vacancy oxygen defects in TiO₂/ZrO₂ bilayer thin film layer. According to slope fitting, the main conduction mechanisms of the sample are Ohmic and Space charge limited current mechanism.     

Lateral Conduction Switching in Sputtered Ni‐rich NiO Thin Films for Write‐Once‐Read‐Many‐Times Memory Applications

Magnetron sputtering has been used to deposit Ni‐rich nickel oxide thin films. Based on the switching of lateral current conduction in the nickel oxide thin film between two in‐plane electrodes, a planar write‐once‐read‐many‐times memory device has been demonstrated. The switching from a low‐conductance state (i.e., the OFF state) to a high‐conductance state (i.e., the ON state) is induced by a writing voltage, and it is irreversible due to the formation of tilted conductive filaments that are hard to be dissolved by the Joule heating effect. For 80 devices under test, the writing voltage is in a narrow range of 2.0?3.5 V and the ON/OFF resistance ratio is larger than 10⁵ at the reading voltage of 0.3 V. An excellent reading endurance (10⁶ readings) for both ON and OFF states is demonstrated. The device is promising in low‐power applications as it can operate at ultra‐low voltages (e.g., the reading voltage can be below 100 mV).     

Crystallographic Orientation Dependence on Electrical Properties of (Bi,Na)TiO3‐based Thin Films

Orientation‐engineered (La, Ce) cosubstituted 0.94(Bi_0.5Na_0.5)TiO₃–0.06BaTiO₃ thin films were epitaxially deposited on CaRuO₃ buffered (LaAlO₃)_0.3(Sr₂AlTaO₆)_0.35 single‐crystal substrates by pulsed laser deposition. The ferroelectric, piezoelectric, dielectric, and leakage current characteristics of the thin films were significantly affected by the crystallographic orientation. We found that the (001)‐oriented film exhibited the best ferroelectric properties with remnant polarization P_r = 29.5 μC/cm² and coercive field E_c = 7.4 kV/mm, whereas the (111)‐oriented film demonstrated the largest piezoelectric response and dielectric permittivity. The bipolar resistive switching behavior, which is predominantly attributed to a combined effect of ferroelectric switching and formation/rupture of conductive filaments, was observed. The conduction mechanisms were determined to be ohmic conduction and Poole–Frenkel emission at high‐ and low‐resistance states, respectively, in all the films.     

The structure and electrochemical properties of poly(3,4‐propylenedioxythiophene)/SnO2 nanocomposites synthesized by mechanochemical route

In this study, the poly(3,4‐propylenedioxythiophene)/SnO₂ nanocomposites (PProDOT/SnO₂) with different contents of SnO₂ were successfully prepared by using hand grinding and ball milling methods, respectively. The effects of the synthesis methods and SnO₂ on the structure and electrochemical properties of the nanocomposites were deeply discussed. The results showed the structure of composites were highly affected by the increasing amount of nano‐SnO₂ particles in reaction medium of hand grinding method than ball milling method. And, the PProDOT/SnO₂ nanocomposites from ball milling method displayed similar absorption spectra, and ball milling method promoted the uniform distribution of nano‐SnO₂ particles in PProDOT matrix. However, PProDOT/SnO₂ nanocomposites from hand grinding method displayed the higher specific surface area and stronger synergetic effects between PProDOT and SnO₂ than that of PProDOT/SnO₂ nanocomposites from ball milling method. As a result, the PProDOT/SnO₂ nanocomposites from hand grinding method showed higher electrochemical activity than PProDOT/SnO₂ nanocomposites from ball milling method. Moreover, the specific capacitance and cycle stability of PProDOT/SnO₂ nanocomposites from both methods were higher than respective pure PProDOT. Among all the nanocomposites, PProDOT/15wt%SnO₂ nanocomposite from hand grinding method possessed the highest specific capacitance (259 F g⁻¹) with the best cycle performance (capacitance retention of 82% after 1,000 cycles). POLYM. COMPOS., 37:2884–2896, 2016. © 2015 Society of Plastics Engineers     

Impact of oxygen partial pressure on resistive switching characteristics of PLD deposited ZnFe2O4 thin films for RRAM devices

In this paper we show resistive switching characteristics of ZnFe₂O₄ thin films grown by pulsed laser deposition at various oxygen partial pressures. We discuss how the microstructure, surface roughness, oxidation condition, and resistive switching properties of ZnFe₂O₄ thin films are influenced by the oxygen partial pressure prevalent in the chamber during the deposition process. The films were deposited at oxygen partial pressure (pO₂) of 0.0013, 0.013, 0.13 and 1.3 mbar. The ZnFe₂O₄ thin film deposited at the lowest pO₂ (0.0013 mbar) did not display a resistive switching characteristic. The ZnFe₂O₄ device deposited at 0.13 mbar yielded the best results. These devices have a low SET variance and a large memory window (more than 2 orders of magnitude) due to an optimum amount of oxygen vacancies/ions contained in the ZnFe₂O₄ film, which is helpful for better resistive switching, than devices deposited at other oxygen pressures. We also find that the migration of oxygen vacancies is linked to the resistive switching process.     

Tricolor electrochromism of PEDOT film electrodeposited in mixed solution of boron trifluoride diethyl etherate and tetrahydrofuran: Hypsochromic effect

PEDOT [poly (3,4‐ethyldioxythiophene)] films have been electrochemically prepared in mixed solution of boron trifluoride diethyl etherate and tetrahydrofuran (BFEE‐THF). The film shows tricolor electrochromism which is claret red at ?0.8 V, light grey at 0.2 V, and sea blue at 1.0 V. The film retains 74% of the original electroactivity and unperturbed electrochromic behaviors after 3000 cycles indicating potential applications on EC devices. Spectroelectrochemistry indicates that the π‐π* transition absorption peak (λ_max) in the neutral state is located at 512 nm and the calculated energy gap (E_g) is 1.76 eV by the onset wavelength. Compared to the electropolymerization of PEDOT films in conventional solvent, tricolor electrochromism can be ascribed both to the low onset oxidation potential and polymerization rate in BFEE‐THF, which may result in a low conjugation length of PEDOT. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of the grain size of nanoparticle dye‐coated titanium dioxide on the short‐circuit current density and open‐circuit voltage of an indium tin oxide/titanium dioxide/poly(acrylonitrile)–propylene carbonate–lithium perchlorate/graphite solar cell

A dye‐sensitized indium tin oxide (ITO)/titanium dioxide (TiO₂)/polyacrylonitrile (PAN)–propylene carbonate (PC)–lithium perchlorate (LiClO₄)/graphite solar cell was fabricated, and its performance was tested in the dark and under the illumination of a 100 mW/cm² light. Three TiO₂ samples were used in the device, namely, uncoated TiO₂, a TiO₂ film coated with methyl red dye, and a TiO₂ film coated with coumarin dye. The films were deposited onto an ITO‐covered glass substrate by a controlled hydrolysis technique assisted with a spin‐coating technique. The films were characterized by scanning electron microscopy to determine their average grain size. The smallest grain size (48 nm) was obtained for the uncoated film. An electrolyte of PAN–LiClO₄ with PC plasticizer was prepared by a solution‐casting technique. A graphite electrode was prepared on a glass slide by an electron‐beam evaporation technique. The device showed rectification properties in the dark and showed a photovoltaic effect under illumination. The device with the uncoated TiO₂ film showed the highest short‐circuit current density (2.0 μA/cm²) and an open‐circuit voltage of 0.64 V because it possessed the smallest grain size. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

New Magneto‐Optical Film of Ce,Ga:GIG with High Performance

Ce³⁺‐doped Gd₃Fe₅O₁₂ (Ce:GIG) film has a good application prospect in the field of integrated optical device. In this article, Ce:GIG and Ce,Ga:GIG films were deposited onto the quartz glass substrate by using radio‐frequency magnetron sputtering technology. The crystal phase, surface morphology, magnetization, and magnetic circular dichroism properties of films were characterized by using the X‐ray powder diffraction, atomic force microscopy, vibrating sample magnetometer, and circular dichroism spectrometer. The results show that as‐prepared Ce,Ga:GIG films has a good quality and show an excellent magneto‐optical performance, and the doping of Ga³⁺ ion and the annealing process have significant effect on the magnetism and magneto‐optical performances. It is expected that Ce,Ga:GIG film with a moderate Ga³⁺‐doping content is a better candidate than Ce:GIG and Ce:YIG films for the next generation of integrated optical isolator and other magneto‐optical equipment.     

Structural,optical, and electrical characterization of the poly[9,9‐dioctylfluorenyl‐2,7‐diyl]‐co‐1,4‐benzo‐(2,1,3)‐thiadiazole thin film fabricated by electrostatic spray technique

The article presents the efficient fabrication of the Poly[9,9‐dioctylfluorenyl‐2,7‐diyl]‐co‐1,4‐benzo‐(2,1,3)‐thiadiazole (F8BT) thin film using the electrostatic spray technique. Electrostatic atomization of the in‐house developed F8BT polymer ink was achieved at considerable low voltage. The structural and optical characterizations of the fabricated F8BT thin film were thoroughly investigated. Furthermore, the organic diode structure with electrostatic spray deposited F8BT thin film was fabricated and its performance was analyzed by performing current voltage measurement. The current–voltage characteristic curve of the organic diode showed nonlinear diode like behavior, thereby confirming the proper interference established between organic diode adjacent layers. The space charged limited current mechanism has been found to be dominant in the fabricated organic device with carrier mobility value of 5.65 e^?4 cm²V^?1s^?1. POLYM. ENG. SCI., 54:675–681, 2014. © 2013 Society of Plastics Engineers     

Preparation and photocurrent generation of an electrostatically self‐assembled film of hemicyanine and poly(4‐styrenesulfonic acid‐co‐maleic acid)

In this article, we report on electrostatically self‐assembled thin films prepared by the alternative immersion of quartz‐coated and indium tin oxide coated glass substrates in aqueous solutions of a copolymer of poly(4‐styrenesulfonic acid‐co‐maleic acid) (PSSMA) and a hemicyanine of (E)?1,1′‐(propane‐1,3‐diyl)bis{4‐[4‐(dimethylamino)styryl]pyridinium} bromide (H³Br₂). The films were studied by means of ultraviolet–visible absorption and X‐ray photoelectron spectroscopies, scanning electron microscopy, and photoelectrochemical measurements. When irradiated with white light, the PSSMA/H³ monolayer film gave a stable cathodic photocurrent. The effects of the applied bias voltages, layer numbers of the (PSSMA/H³)_n films (where n stands for the number of bilayer films on both sides of the substrates), light intensities, pH value, and electron acceptor on the photocurrent generation of the (PSSMA/H³)_n film were examined. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39871.     

Electric field-induced phase transition and energy storage performance of highly-textured PbZrO3 antiferroelectric films with a deposition temperature dependence

Thin PbZrO₃ (PZO) antiferroelectric films with (001)-preferred orientation were deposited on SrRuO₃/Ca₂Nb₃O₁₀-nanosheet/Si substrates using pulsed laser deposition. Variation of the deposition temperature was found to play a key role in the control of the microstructure and strongly influence the energy storage performance of the thin film. The critical phase switching field, where the aligned antiferroelectric (AFE) domains start to transform into the ferroelectric (FE) state, decreased with increasing temperature. On the other hand, the content of the FE phase in the AFE PZO thin films increased with increasing deposition temperature. A large recoverable energy-storage density of 16.8?J/cm³ and high energy-storage efficiency of 69.2% under an electric field of 1000?kV/cm were achieved in the films deposited at 525?°C. This performance was due to the high forward switching field and backward switching field values and the low difference between these two fields. Moreover, the PZO thin films showed great charge-discharge cycling life with fatigue-free performance up to 10¹⁰ cycles and good thermal stability from room temperature to 100?°C.     

Thermal,optical, and electrical characterization of thin film coated RTV 655 bilayer system

Adhesion of thin films to hydrophobic elastomeric substrates is of particular interest in the area of flexible electronics and nano‐sensor technology. Here, nanometer‐thick Au films were deposited directly onto hydrophobic RTV 655 substrates by means of sputtering, thermal evaporation, and electroless techniques without an adhesion‐promoting layer. The bilayer system was exposed to repeat thermal cycling and changes to the surface morphology of the thin film were monitored electrically and optically. Buckle formation in the as‐deposited film was attributed to stress in the film and substrate stiffness rather than thermal coefficient mismatch between films. The Au‐RTV 655 interface was water tight and maintained a strong adhesion despite repeated thermal cycles. Sputtered and thermally evaporated carbon‐coated RTV 655 substrates were also studied in parallel for comparison. Periodic arrays of buckles formed in pre‐strained RTV 655 samples showed reproducibility in their optical properties demonstrating good adhesion between the two layers without an interfacial layer. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41396.     

Hybrid polyaniline–TiO2 nanocomposite Langmuir–Blodgett thin films: Self‐assembly and their characterization

Polyaniline (PANi)–titanium dioxide (TiO₂) nanocomposite materials were prepared by chemical polymerization of aniline doped with TiO₂ nanoparticles. Surface pressure–area (π‐A) isotherms of these nanocomposites show phase transformations in the monolayer during compression process. Multiple isotherms indicate that the monolayer of the nanocomposite material can retain its configuration during compression‐expansion cycles. Langmuir–Blodgett thin films of PANi–TiO₂ nanocomposite were deposited on the quartz and indium tin oxide coated conducting glass substrates. Fourier transfer infrared spectroscopy and UV–visible spectroscopy study indicates the presence of TiO₂ in PANi, whereas X‐ray Diffraction study confirmed the anatase phase of TiO₂ and particle size (～nm) of PANi–TiO₂. The morphology of Langmuir–Blodgett films of these nanocomposites was also characterized by atomic force microscopy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41386.     

Co‐doped ZnO thin films grown by pulsed electron beam ablation as model nano‐catalysts in fischer‐tropsch synthesis

A single‐step deposition of cobalt‐doped zinc oxide (Co‐ZnO) thin film nano‐composites on three different crystalline substrates, viz., Al₂O₃ (c‐sapphire), silicon (100) (Si), and SiO₂ (quartz) is reported, using pulsed electron beam ablation (PEBA). The results indicate that the type of substrate has no effect on Co‐ZnO films stoichiometry, morphology, microstructure, and film thickness. The findings show the presence of hexagonal close‐packed metallic Co whose content increases in the films deposited on Al₂O₃ and Si substrates relatively to SiO₂ substrate. The potential of the films as model nano‐catalysts has been evaluated in the context of the Fischer‐Tropsch (FT) process. Fuel fractions, which have been observed in FT liquid products, are rich in diesel and waxes. Specifically, Co‐ZnO/Al₂O₃ nano‐catalyst shows a selectivity of ～4%, 31%, and 65% towards gasoline, diesel, and waxes, respectively, while Co‐ZnO/SiO₂ nano‐catalyst shows a selectivity of ～12%, 51%, and 37%, for gasoline, diesel, and waxes, respectively. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3332–3340, 2018     

Structural Evolution of B–C Thin Films Deposited from SPSed‐Target and Dual‐Target

Boron carbide thin films have been synthesized via pulsed laser deposition process using Spark Plasma Sintered (SPSed) and dual‐targets, respectively. Two kinds of structural evolutions have been found by investigation of bonding environments in as‐deposited thin films via X‐ray photoelectron spectroscopy study. With decreasing of B/C ratio, films deposited from SPSed‐target show the transformation of B₁₁C‐CBB → B₁₁C‐CBC. In contrast, the films deposited from dual‐target present the B₁₁C‐CBB → B₁₀C₂‐CBB structural change.     

Resistive switching behavior in Lu2O3 thin film for advanced flexible memory applications

In this article, the resistive switching (RS) behaviors in Lu₂O₃ thin film for advanced flexible nonvolatile memory applications are investigated. Amorphous Lu₂O₃ thin films with a thickness of 20 nm were deposited at room temperature by radio-frequency magnetron sputtering on flexible polyethylene terephthalate substrate. The structural and morphological changes of the Lu₂O₃ thin film were characterized by x-ray diffraction, atomic force microscopy, and x-ray photoelectron spectroscopy analyses. The Ru/Lu₂O₃/ITO flexible memory device shows promising RS behavior with low-voltage operation and small distribution of switching parameters. The dominant switching current conduction mechanism in the Lu₂O₃ thin film was determined as bulk-controlled space-charge-limited-current with activation energy of traps of 0.33 eV. The oxygen vacancies assisted filament conduction model was described for RS behavior in Lu₂O₃ thin film. The memory reliability characteristics of switching endurance, data retention, good flexibility, and mechanical endurance show promising applications in future advanced memory.     

Facile growth of 1‐D nanowire‐based WO3 thin films with enhanced photoelectrochemical performance

A flame reactor embedded with a constant tungsten wire feeding system to prepare one‐dimensional (1‐D) nanostructured tungsten oxide thin film for photoelectrochemical (PEC) water splitting was developed. Photoactive vertically‐aligned nanowire‐based WO₃ thin films could be obtained with a controlled thickness via a flame vapor deposition process followed by air‐annealing. The PEC performances of WO₃ photoelectrodes for different thin film thicknesses were examined. The optimum thickness of WO₃ thin film was found to be about 7.2 μm for PEC water splitting based on incident photon‐to‐current efficiency plots and I–V curves. The WO₃ prepared with optimum thickness showed better PEC performance than those of recently reported nanostructured WO₃ photoanodes. © 2015 American Institute of Chemical Engineers AIChE J, 62: 421–428, 2016     

Effect of surface charges on the polarization of BaTiO3 thin films investigated by UHV‐SPM

Nanostructured BaTiO₃ polar thin films are increasingly critical to the function of future multilayer ceramic capacitors and related oxide‐based electronic devices. The effect of surface charges on BaTiO₃ polarization behavior is therefore investigated by ultra‐high vacuum scanning probe microscopy (UHV‐SPM) for 3 distinct morphologies—epitaxial, polycrystalline, and nanocrystalline films. Regardless of the film morphology, Kelvin probe force microscopy reveals that BaTiO₃ thin film surfaces exhibit positive charging after contact scanning by various noble AFM probes due to the work function difference between tip and specimen. According to piezoresponse force microscopy, these positive charges uniformly stabilize downward polarized domains. However, the hysteresis and concomitant surface charging behavior are strongly sensitive to microstructure and defects. In particular, the stability and switching behavior are influenced by bulk and interfacial defect distributions and hence correlated to film deposition methods and grain size. Such morphology dependent properties for BaTiO₃ films are revealed only through UHV measurements where screening charges from the ambient can be minimized, demonstrating the importance of UHV‐SPM for understanding ferroelectric thin films and nanostructures.     

Large Piezoelectricity and Ferroelectricity in Mn‐Doped (Bi0.5Na0.5)TiO3‐BaTiO3 Thin Film Prepared by Pulsed Laser Deposition

Mn‐doped (Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃ (MnBNBT) thin films were prepared on SrRuO₃ (SRO)‐coated (001) SrTiO₃ (STO) single crystal substrates by pulsed laser deposition under different processing conditions. Structural characterization (i.e., XRD and TEM) confirms the epitaxial growth of STO/SRO/MnBNBT heterostructures. Through the judicious control of deposition temperature, the defect level within the films can be finely tuned. The MnBNBT thin film deposited at the optimized temperature exhibits superior ferroelectric and piezoelectric responses with remanent polarization P_r of 33.0 μC/cm² and piezoelectric coefficient d₃₃ of 120.0 ± 20 pm/V.