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In this article, an optical bio-chemical sensor based on D-shaped optical fiber is presented for ethanol detection application. The gold and graphene nanolayers are coated for inducing the SPR over an optical fiber flat surface. The molecularly imprinted polymer (MIP) thin film is also coated over the gold film to enhance the molecular interaction between the sensing fluid and the sensing surface. The ethanol concentration is detected with reference to the 0% concentration and increased to 90% in a sample solution. The shift in resonance wavelength detects the concentration of the ethanol in the fluid sample due to the change in RI. The result shows a very good agreement between the concentration of ethanol in fluid and the resonance wavelength (RW) shift. The maximum obtained average sensitivity is 2.5 nm/concentration (every 10%) or 714 nm/RIU with Au/MIP thin film and 1137 nm/RIU for graphene/Au/MIP thin film. Based on the result and optical properties of the proposed sensor, it might be used as a real-time alcohol detector. This sensor can protect foods and drinks from the imbalance of chemicals and preservatives. [ABSTRACT FROM AUTHOR]

Very recently, the discovery of ultra-tetragonal PbTiO3 thin films was reported [Zhang et al., Science, 361, 494 (2018)], in which the switchable out-of-plane polarization was seen to be almost twice that of any previously known ferroelectric. To understand more about this system and to explore features that might contribute to these remarkable functional properties, we have mapped the polarization microstructure on the nanoscale using piezoresponse force microscopy (PFM) (scan sizes less than 700 nm). Our study reveals an extremely fine-scale pattern, with individual domains typically 20–50 nm in size, all of which exhibit both out-of-plane and in-plane polarization components. In-plane vector PFM polarization maps show strongly charged quadrant-lattice domain arrays with fourfold domain wall junctions (vertices). The existence of fourfold vertices in ferroelectrics is rare but can be explained via the "Ashkin-Teller" model, in which very large interfacial lattice mismatch strains and local electric fields play a role. This ultra-tetragonal ferroelectric system was expected to contain straightforward c-axis out-of-plane 180° domains, but instead shows an extremely rich nanoscale domain tiling pattern; these unusual nanodomains may be important in facilitating the extremely high switchable polarization values previously reported. [ABSTRACT FROM AUTHOR]

The work reports on the interaction of the photo electrodes with the electrolytes and dyes since it is imperative to investigate the degradation behavior of the transparent conducting electrodes in terms of structural, optical and electrical properties along with the corrosion resistance behavior. Three electrodes, one indium tin oxide (ITO) and two aluminium doped zinc oxide (AZO), two dyes (Eosin Yellow and Ruthenium Red), and two electrolytes, potassium iodide (KI) and lithium iodide (LiI) were used in this investigation. Twelve solar cells were fabricated with the aforementioned combination of electrodes, dyes and electrolytes. Open circuit voltage (Voc) of the fabricated cells as a function of time (for 30 days) were recorded. Changes in the structure and elemental composition of the electrodes after interaction with the dye and electrolyte were analyzed using X-Ray Diffraction and EDX, respectively. Transparency and sheet resistance of the electrodes before and after interaction with electrolytes and dyes was observed. Corrosion behavior of the three electrodes was studied using an electrochemical analyzer with KI and LiI electrolytes. [ABSTRACT FROM AUTHOR]

The conductive characteristics of Bi0.9La0.1Fe0.96Mg0.04O3 (BLFM) thin film are investigated at various temperatures and a negative differential resistance (NDR) is observed in the thin film, where a leakage current peak occurs upon application of a downward electric field above 80 °C. The origin of the NDR behavior is shown to be related to the ionic defect of oxygen vacancies (VO••) present in the film. On the basis of analyzing the leakage mechanism and surface potential behavior, the NDR behavior can be understood by considering the competition between the polarized distribution and neutralization of VO••. [ABSTRACT FROM AUTHOR]

This article reports on the formation and electronic characteristics of conducting carbon nanowires produced by swift heavy ion irradiation of a fullerene thin film. This study shows that it is possible to create arrays of carbon nanowires, which are perfectly parallel to each other and perpendicular to the substrate. As-deposited fullerene films exhibit poor field emission characteristics with breakdown fields as high as 51 V/μm, whereas low dose ion irradiated fullerene film produces a threshold field as low as 9 V/μm. The present approach of making conducting carbon nanowires by ion irradiation for potential field emitters and large area applications is also discussed. [ABSTRACT FROM AUTHOR]

This article presents a highly sensitive gold/Ti 3 C 2 T x coated photonic crystal fiber (PCF)-based surface plasmon resonance (SPR) sensor for cancer cells detection. The hybrid gold/Ti 3 C 2 T x layer is coated circularly over PCF for occurrence of SPR by coupled mode theory. The simulations and numerical analysis are done by the finite element method. The resonance wavelength shift is measured between normal and cancerous cell samples to estimate the wavelength sensitivity and resolution. In results, the maximum wavelength sensitivity for breast cancer MCF-7 cells is achieved as 10,714 nm/RIU in x-polarization mode and 13,071 nm/RIU in y-polarization mode with very low resolution of 10−6 RIU. The impact of the MXene (Ti 3 C 2 T x) thin film on sensitivity is also observed. In addition, the optimization of parametric variation is analyzed with machine learning technique with low mean squared error of 0.01525. <2% error is obtained in sensitivity analysis with multilayer perceptron regressor. Due to the advanced results and machine learning application, this sensor can be used as a fast, efficient and low-cost cancer disease detection device. [Display omitted] • A gold/Ti 3 C 2 T x coated PCF based SPR sensor is presented and numerically analyzed for detecting various cancer cells. • Vertical confinement path is used to transform the energy from core mode to SPR mode with external sensing approach. • The normal to cancerous cell is detected by measuring the corresponding resonance wavelength shift. • The Multilayer Perceptron regressor has been employed on ANN model for predicting the output of PCF-SPR sensor. [ABSTRACT FROM AUTHOR]

In this article, an Au/Ti 3 C 2 T x MXene hybrid layered D-shaped Photonic Crystal Fiber (DPCF) based Surface Plasmonic Resonance (SPR) biosensor is proposed. The D-shape of PCF is used to make the sensor practically more feasible. The MXene-Au hybrid thin films are placed over the DPCF to induce the surface plasmon polariton (SPP). The resonance wavelength shift occurs when analytes refractive index (RI) is changed. The numerical analysis has been performed by finite element analysis. The results have shown the wavelength sensitivity of 7000 nm/RIU and 13,000 nm/RIU for MXene layer thickness of 14 nm and 27 nm respectively. On comparing, it has been observed that the MXene/Au layered sensor has achieved 3.5 to 6.5 times higher wavelength-sensitivity compared to without MXene thin film. In addition, sensing parameters like resolution, amplitude sensitivity and figure of merit has also been investigated. The proposed sensor is used for sensing the analytes having RI range of 1.33–1.39. The range of RI covers most of the blood cells compositions, cancerous cells, protein and viruses. Therefore, this study can facilitate the use of MXene material with D-shaped PCF to detect the biochemical and chemical liquids. Photonic crystal fiber, MXene material, Gold, Surface plasmon resonance, Biomolecules. • A surface plasmon resonance sensor based on D-shape of PCF is proposed using Mxene/Au material thin film for the first time. • The sensing analytes having a refractive index (RI) range of 1.33–1.39 are used. The range of RI covers most of the bio analyte's RI like blood cells, cancerous cells, RNA/DNA, malaria-infected RBCs, protein and viruses. • The results show the wavelength sensitivity of 7000 nm/RIU and 13,000 nm/RIU for Mxene layer thickness 14 nm and 27 nm respectively. • On comparing, it has been observed that the Mxene/Au layered sensor has 3.5 to 6.5 times higher wavelength-sensitivity than without the Mxene thin layer. • The effect of the Mxene layer on other sensing parameters like resolution, amplitude sensitivity and figure of merit has also been investigated. [ABSTRACT FROM AUTHOR]

Fatigue failure in ferroelectrics has been intensively investigated in the past few decades. Most of the mechanisms discussed for ferroelectric fatigue have been built on the “hypothesis of variation in charged defects”, but these are rarely evidenced by experimental observation. Here, using a combination of complex impedance spectra techniques, piezoresponse force microscopy and first-principles theory, we examine the microscopic evolution and redistribution of charged defects during the electrical cycling in BiFeO 3 thin films. The dynamic formation and melting behaviors of oxygen vacancy ( V O ) order are identified during the fatigue process. It reveals that the isolated V O tends to self-order along grain boundaries to form a planar-aligned structure, which blocks the domain reversals. Upon further electrical cycling, migration of V O within vacancy clusters is accommodated with a lower energy barrier (∼0.2 eV) and facilitates the formation of a nearby-electrode layer incorporated with highly concentrated V O . The interplay between the macroscopic fatigue and microscopic evolution of charged defects clearly demonstrates the role of ordered V O clusters in the fatigue failure of BiFeO 3 thin films. [ABSTRACT FROM AUTHOR]

Abstract: Optical, magnetocapacitance and dielectric properties of different composite films of BiFeO3–poly(vinylidene-fluoride) (with concentration of BiFeO3; 70, 60, 50 and 40wt%) are reported here for first time. The grain size was observed to be ∼50nm by using atomic force microscopy. A peak in refractive index appears at ∼455nm, which is found to be shifting towards lower wavelengths, while simultaneously the value of the optical energy band gap is found to increase with an increase in the concentration of PVDF in the composite. It was observed that PVDF, which works as matrix, increases the magnetocapacitance. The magnetocapacitance (MC) of BFO60 (BiFeO3; 60wt%) was found higher than Nb doped BiFeO3, which may be useful for device applications. [Copyright &y& Elsevier]

Abstract: We report on the electronic charge transfer in cobalt doped fullerene thin films by means of near-edge x-ray-absorption fine structure (NEXAFS) spectroscopy measurement. Co-doped fullerene films were prepared by co-deposition technique and subjected to energetic ion irradiation (120MeV Au) for possibly alignment or interconnect of randomly distributed metal particles. Polarization dependent NEXAFS spectra revealed the alignment of Co and C atoms along the irradiated ionic path. The structural changes in Co-doped as-deposited and ion irradiated fullerene films were investigated by means of Raman spectroscopy measurements. Downshift of pentagonal pinch mode Ag(2) in Raman spectroscopy indicated the electronic charge transfer from Co atom to fullerene molecules, which is further confirmed by NEXAFS at C K-edge for Co-doped fullerene films. [Copyright &y& Elsevier]

Abstract: Nanocrystalline indium oxide-doped tin oxide thin film sensors have been synthesized using sol–gel dip-coating technique. The sensors were spin-coated with three different types of polymer namely polymethyl methacrylate (PMMA), poly-perfluorobutenyl vinyl ether (Cytop), fluoropolymer (Fluoropel). The room temperature sensor characteristics (response time, electrical response and recovery time) of the three sensors with different polymer coating were compared at hydrogen concentrations of 600, 1500, 6000 and 15,000ppm and at two different humidity levels of 14% and 65%. It was found that the polymer coating preserves the selective sensing property of indium oxide-doped tin oxide even at high humidity. The response kinetics of the sensors with different coatings has been compared. [Copyright &y& Elsevier]

The commonly-used nanoindentation experiments for measuring hardness of thin films may not give the accurate results when the thickness of the film is in the range of few hundred nanometers or less due to the unavoidable substrate effects. The available analysis methods usually work well when the indentation depth is less than one tenth of the total thickness of the film; otherwise, it is very difficult to determine the film-only properties without substrate effects. This work proposes an alternative analysis to measure the hardness of ultra-thin film from nanoindentation data. This method is tested for numbers of bulk materials and the results agreed well with literature reported values; the method is then applied to thin films. It is found that this analysis can give very accurate results for different kind of film-substrate systems such as soft-films on hard-substrate and hard-film on soft-substrate. As the proposed method is based on the measurement of hardness at each indentation step therefore, it is also capable to show at what indentation depth the substrate starts affecting the indentation-measured hardness values. [ABSTRACT FROM AUTHOR]

Abstract: Modifications of the C70 molecule (fullerene) under swift heavy ion irradiation are investigated. C70 thin films were irradiated with 120MeV Au ions at fluences from 1×1012 to 3×1013 ions/cm2. The energetic ion impacts lead to the destruction of the C70 molecule. To investigate the stability of C70 fullerene, the damage cross-section and radius of the damaged cylindrical zones are evaluated by fitting the evanescence of C70 vibration modes recorded by Raman spectroscopy. Conductivity measurements together with Raman and optical absorption studies revealed that an irradiation fluence of 3×1013 ions/cm2 results in complete amorphization of the carbon structure of the fullerene molecules. [Copyright &y& Elsevier]

Abstract: Three phase transitions (face centered to simple cubic, surface rearrangement from (2×2) to (1×1) and glass transition) in fullerene thin films and the effect of 150MeV Ti ion irradiation on these transitions have been studied, using temperature dependence of electrical resistivity measurements. The structural properties of the C60 thin films are studied by X-ray diffraction, atomic force microscopy and UV–vis spectroscopy. It is observed that defect creation by ion irradiation in the films lead to quenching and broadening of structural phase transitions but the transition temperatures did not show significant shifting under ion irradiation. [Copyright &y& Elsevier]

Abstract: Thermally evaporated ZnO thin films have been irradiated with 100MeV Au8+ ions at different fluence from 5×1011 ions/cm2 to 5×1013 ions/cm2. The optical and structural properties of the irradiated and pristine films were studied using Fourier transform infrared spectroscopy (FTIR), UV–visible absorption spectroscopy, photoluminescence (PL), atomic force microscopy (AFM) and XRD. FTIR results showed that for low fluence, the transmittance of the film decreased and increased again at higher fluence but Zn–O bond remains unaffected by irradiation. As revealed from the absorption spectra, absorption edge is not changed by the irradiation but the optical absorption is increased. The AFM study of the films implied that roughness decreased at low fluence values up to 5×1012 ions/cm2 and at higher fluences the roughness increased. [Copyright &y& Elsevier]

We report the x-ray magnetic circular dichroism (XMCD) studies on Fe doped fullerene thin film and bulk highly oriented pyrolytic graphite. The element-specific hysteresis curves were recorded by measuring the XMCD at the Fe L3 edge as a function of the applied field strength at different temperatures. These investigations suggest that Fe doped fullerene is ferromagnetic at room temperature, while Fe atoms are driven to a nonmagnetic/paramagnetic state with the interaction of graphite matrix. [ABSTRACT FROM AUTHOR]

Lead vanadate (PbVO3) is a multifunctional material which is both polar and magnetic. Its optical properties, important for linear and nonlinear optical spectroscopy of the material, are presented. Using spectroscopic ellipsometry, the refractive index and absorption versus wavelength of lead vanadate thin films at 295 K is reported. Using optical second harmonic generation, the nonlinear optical coefficients were determined to be d15/d31=0.20±0.02, d33/d31=316.0±4.4, and |d33|=10.40±0.35 pm/V at a fundamental wavelength of 800 nm. [ABSTRACT FROM AUTHOR]

We report the ordering of carbon nanostructures under energetic ion irradiation at low fluence (<5×1011 ions/cm2). Fullerene thin films and multiwalled carbon nanotube (MWCNT) films were irradiated with 200 MeV Au and 60 MeV Ni ions at different ion fluences, respectively. The changes in the irradiated films have been investigated by means of Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction, and Raman spectroscopy. FTIR and Raman spectroscopy show the improvement of vibration strength in low fluence irradiated fullerene and MWCNT films. X-ray diffraction analysis on low fluence irradiated fullerene films revealed the structural order along the (220) atomic planes. [ABSTRACT FROM AUTHOR]

The control of polarization rotation (PR) is a key issue of applying undoped zinc oxide (ZnO) as information storage devices. A systematic study of ZnO thin films by conducting piezoresponse force microscopy (PFM) technique on samples with different electrodes, film thicknesses, and deposition oxygen partial pressures, P O 2 allows disclosing the possible factors those affecting the PR behavior. The results clearly indicate that higher work function conductive material, such as Pt, is a promising candidature as the top electrode and bottom electrode to ensure the PR occur and maintain in ZnO films. From the effects of film thickness study, PR behavior can be observed in film downscaled to 15 nm. However, in order to avoid current leakage and maintain the rotated polarization state, thicker film with about 240 nm is preferred. In addition, in the film deposited with a low P O 2 (>5 × 10−6 Torr), more atomic point defects such as oxygen vacancy may lead the sample into a large leakage current and deteriorate the PR behavior. Hence, by this systematic study, it is proved that the PR behavior of undoped ZnO thin films can be optimized with proper deposition parameters. Image 1 • Possible factors affecting the PR behavior are studied comprehensively. • Pt is a promising electrode candidature for PR behavior comparing with Au and ITO. • Unambiguous PR behavior is found in film with a thickness reduced to 15 nm. • P O 2 below 5 × 10−6 Torr might hinder the PR behavior. [ABSTRACT FROM AUTHOR]

Reports on the optical characterization of positive electrode (e.g. MEH-PPV/Alq3) composite made by studying its absorption and photoluminescence spectra. Growing of the MEH-PPV films over glass substrate using spin cast technique; Conclusion that optical properties of MEH-PPV films is greatly improved by using a bilayer heterostructure with Alq3.

• Nickel sulphide nano-particles was successfully synthesized and incorporated in the thin film organic solar cell. • NiS is found to be an important dopant for improving photons harvesting in thin film polymer solar cell. • Local surface plasmon resonance of NiS in polymer blend matrix is responsible for high optical absorption. Nickel sulphide (NiS) nano-composite were synthesized and used as dopant in the hole transport layer of the thin film organic solar cell (TFOSC). The nano-particles are intended to assist in the charge transport processes at the interface between the active layer and the anode. Thin film solar cells were fabricated using photo-active layer composed of poly-3-hexylthiophene (P3HT) and (6-6) phenyl-C61-butyric acid methyl ester (PCBM) blend. The solar cells employed NiS doped PEDOT:PSS hole transport layer (HTL) which are investigated in terms of changes in optical and electrical properties of the films. The electrical properties of the newly fabricated solar cells showed significant improvement in photo-generated current as the result of reduced charge carrier recombination and enhanced charge transport processes at the interface. This in turn boost the power conversion efficiency (PCE) of the devices by 95% compared to the devices without NiS doped HTL. The observed PCE enhancement is attributable to the excitation of the localized surface plasmon resonance exhibited by the presence of NiS in hole transport layer. It is noted in the investigation that the performance of the solar cell is dependant on the concentration of NiS nano-particles in PEDOT:PSS layer. As consequence, the highest recorded PCE in this study was 6.03% at 0.1% NiS by weight, which is encouraging result for device fabrication in ambient laboratory condition. [ABSTRACT FROM AUTHOR]

Highly transparent, conducting, highly oriented, and almost single phase ZnO films have been deposited by simple e-beam evaporation method, and the deposition parameters were optimized. The films were prepared by (a) evaporation of ZnO at different substrate temperatures and (b) evaporation of ZnO at room temperature and subsequent annealing of the films in oxygen ambient at different temperatures. The characterizations of the film were performed by optical absorption spectroscopy (UV-visible), Fourier transform infrared spectroscopy, resistivity measurement, transmission electron microscopy (TEM), photoluminescence, and x-ray diffraction measurement. Absorption spectra revealed that the films were highly transparent and the band gap of the pre- and postannealed films was in good agreement with the reported values. The band gap of the films increases on increasing the substrate temperature as well as annealing temperature, whereas the resistivity of the film decreases with substrate temperature and increases with annealing temperature. Fourier transform infrared spectroscopy of ZnO films confirms the presence of Zn–O bonding. X-ray diffraction, electron diffraction, and TEM images with high resolution and Raman spectra of the films showed the formation of crystalline ZnO having wurtzite structure. [ABSTRACT FROM AUTHOR]

The photoactive film morphology of ternary molecules blend bulk heterojunction organic solar cell was investigated using various solvent additives. Two donor polymers namely poly(3-hexylthiophene) (P3HT) and thieno[3,4-b]thiophene/benzodithiophene (PTB7) at (1:1) stoichiometric ratio were employed together with (PCBM) fullerene molecule in the preparation of the solar cells. The photoactive films were treated with either uni- or binary solvent additives to improve film morphology and the miscibility of the molecules in the medium. The significant improvement on the performances of the devices were recorded using binary solvent additives (∼1% vol.) with power conversion efficiency improvement as high as 4.1% compared to 2.9% measured from the films treated with single additive solvent. The correlation between solar cell performance and film morphology have been discussed in terms of optical, electrical and surface morphology of the active layers of solution processed organic solar cells. [ABSTRACT FROM AUTHOR]

This paper reports a single step reactive extrusion process for fabrication of thermally stable, polylactic acid grafted cellulose nanocrystal(PLA- g -CNC) nanocomposite films using dicumyl peroxide as crosslinking agent. PLA- g -CNC nanocomposites were recycled without significant breakage in the molecular structure of PLA. The grafted PLA chains shields the sulfate and hydroxyl groups of CNCs, thereby enhancing the compatibilization with PLA matrix and preventing thermal degradation during extrusion. NMR and FTIR spectroscopy studies showed that amorphous PLA chains grafted on CNC surface through C–C bonds formation. Presence of such chemical crosslinks led to efficient transfer of modulus of CNCs to PLA matrix, thereby improving the tensile strength and young's modulus by∼40% and∼490%,respectively. Recycling of PLA- g -CNC doesn't alter the molecular weight, thermal, crystallization and mechanical properties of the nanocomposites significantly. Therefore, the current study provides a novel approach for fabricating CNC-reinforced-PLA nanocomposites which can be easily recycled and reused for multiple cycles. [ABSTRACT FROM AUTHOR]

Epitaxial tetragonal 425 and 611 nm thick Pb(Zr0.45Ti0.55)O3 (PZT) films are deposited by pulsed laser deposition on SrRuO3-coated (100) SrTiO3 24° tilt angle bicrystal substrates to create a single PZT grain boundary with a well-defined orientation. On either side of the bicrystal boundary, the films show square hysteresis loops and have dielectric permittivities of 456 and 576, with loss tangents of 0.010 and 0.015, respectively. Using piezoresponse force microscopy (PFM), a decrease in the nonlinear piezoelectric response is observed in the vicinity (720-820 nm) of the grain boundary. This region represents the width over which the extrinsic contributions to the piezoelectric response (e.g., those associated with the domain density/configuration and/or the domain wall mobility) are influenced by the presence of the grain boundary. Transmission electron microscope (TEM) images collected near and far from the grain boundary indicate a strong preference for (101)/( [ABSTRACT FROM AUTHOR]

The position-dependent oxygen vacancy dynamics induced by a biased scanning probe microscopy tip in Samarium doped ceria thin films grown on MgO (100) substrates is investigated. The granularity of the samples gives rise to spatially dependent local electrochemical activity, as explored by electrochemical strain microscopy. The kinetics of the oxygen vacancy relaxation process is investigated separately for grain boundaries and grains. Higher oxygen vacancy concentration variation and slower diffusion are observed in the grain boundary regions as compared to the grains. [ABSTRACT FROM AUTHOR]

In this work a numerical study has been carried out to gain physical insight into the phenomena of opposed flow flame spread over an array of thin solid fuel sheets in a microgravity environment. The two-dimensional (2D) simulations show that the flame spread rates for the multiple-fuel configuration are higher than those for the flame spreading over a single fuel sheet. This is due to reduced radiation losses from the flame and increased heat feedback to the solid fuel. The flame spread rate exhibits a non-monotonic variation with decrease in the interspace distance between the fuel sheets. Higher radiation heat feedback primarily as gas/flame radiation was found to be responsible for the increase in the flame spread rate with the reduction of the interspace distance. It was noted that as the interspace distance between the fuel sheets was reduced below a certain value, no steady solution could be obtained. However, at very small interspace distances, steady state spread rates were obtained. Here, due to oxygen starvation the flame spread rate decreased and eventually at some interspace distance the flame extinguished. With fuel emittance (equal to absorptance) reduced to ‘0’ the flame spread rate was nearly independent of the interspace distance, except at very small distances where the flame spread rate dropped due to oxygen starvation. A flame extinction plot with the extinction oxygen level was constructed for the multiple-fuel configuration at various interspace distances. The default fuel with an emittance of 0.92 was found to be more flammable in the multiple-fuel configuration than in a single fuel sheet configuration. For a fuel emittance equal to zero, the extinction oxygen limit decreases for both the single and the multiple fuel sheet configurations. However, the two flammability curves cross over at a certain fuel separation distance. The multiple-fuel configurations become less flammable compared to the single fuel sheet configuration below a certain separation distance. [ABSTRACT FROM PUBLISHER]

Abstract: Thin films with ZnO nanocrystals in silica were synthesized by rf reactive magnetron co-sputter deposition and post-annealing. The films were deposited from a ZnO/Si composite target in an rf oxygen plasma. The deposited films were annealed in air/vacuum at high temperatures to grow ZnO nanocrystals. The deposited and annealed films were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), uv–vis spectroscopy (UV–VIS) and photoluminescence (PL) measurements. FT-IR results of the films show the vibrational features of Si–O–Si and Zn–O bonds. UV–VIS spectra of the deposited film shows the band edge of ZnO. The XRD results of the films annealed at 750°C and 1000°C indicate the growth of ZnO nanocrystals with average crystallite sizes between 7nm and 26nm. PL measurements of the deposited film show a broad visible luminescence peak which can be due to ZnO. These results suggest the growth of ZnO nanocrystals in silica matrix. [Copyright &y& Elsevier]

This work reports on direct crystallization of PbZr 0.53 Ti 0.47 O 3 (PZT) thin films on glass and polymeric substrates, using pulsed thermal processing (PTP). Specifically, xenon flash lamps deliver pulses of high intensity, short duration, broadband light to the surface of a chemical solution deposited thin film, resulting in the crystallization of the film. Structural analysis by X-ray diffraction (XRD) and transmission electron microscopy show the existence of perovskite structure in nano-sized grains (≤5 nm). Local functional analysis by band excitation piezoelectric spectroscopy and electrostatic force microscopy confirm the presence of a ferroelectric phase and retention of voltage-written polarization for multiple days. Based on structural and functional analyses, strategies are discussed for optimization of pulse voltage and duration for the realization of crystalline ferroelectric thin films. For ∼200 nm-thick PZT films on glass substrates, 500 μs-long pulses were required for crystallization, starting with 100 pulses at 350 V, 10 or 25 pulses at 400 V and in general lower number of pulses at higher voltages (resulting in higher radiant energy). Overall power densities of >6.4 kW/cm2 were needed for appearance of peaks corresponding to the perovskite phase in the XRD. Films on glass processed at 350–400 V had a higher degree of 111-oriented perovskite grains. Higher applied radiant energy (through increased pulse voltage or count) resulted in more random and/or partially 001-oriented films. For ∼1 μm-thick PZT films on polymeric substrates, 10 to 25 250 μs-long pulses at voltages ranging between 200 to 250 V, corresponding to power densities of ∼2.8 kW/cm2, were optimal for maximized perovskite phase crystallization, while avoiding substrate damage. [ABSTRACT FROM AUTHOR]

Bias-induced oxygen ion dynamics underpins a broad spectrum of electroresistive and memristive phenomena in oxide materials. Although widely studied by device-level and local voltage-current spectroscopies, the relationship between electroresistive phenomena, local electrochemical behaviors, and microstructures remains elusive. Here, the interplay between history-dependent electronic transport and electrochemical phenomena in a NiO single crystalline thin film with a number of well-defined defect types is explored on the nanometer scale using an atomic force microscopy-based technique. A variety of electrochemically-active regions were observed and spatially resolved relationship between the electronic and electrochemical phenomena was revealed. The regions with pronounced electroresistive activity were further correlated with defects identified by scanning transmission electron microscopy. Using fully coupled mechanical-electrochemical modeling, we illustrate that the spatial distribution of strain plays an important role in electrochemical and electroresistive phenomena. These studies illustrate an approach for simultaneous mapping of the electronic and ionic transport on a single defective structure level such as dislocations or interfaces, and pave the way for creating libraries of defect-specific electrochemical responses. [ABSTRACT FROM AUTHOR]

S. Trolier‐McKinstry and co‐workers investigate the interaction between domain walls and a single grain boundary by comparing measurements of the local piezoelectric nonlinearity to domain structure. The two electron micrographs show the domain structure of the film, while the colored image is a map of the piezoelectric nonlinear response across a single grain boundary in a ferroelectric film. A minimum in the nonlinearity observed at the grain boundary is correlated to a change in the domain structure. [ABSTRACT FROM AUTHOR]

Functional properties of ferroelectric materials depend both on the residual domain states and on the mobility of domain walls in response to the applied electric and stress fields. This paper reviews the use of multidimensional scanning probe microscopy to assess these factors in the time- and voltage domains, with an emphasis on the manner in which domain walls respond collectively to stimuli. It is found that in many PbZr1-xTixO3-based capacitors, domain wall motion is correlated over length scales that exceed the domain and grain sizes by orders of magnitude, suggesting emergent collective electromechanical behavior. The role of mechanical boundary conditions and field history on the domain wall contributions and the stability of the ferroelectric domain state are discussed. [ABSTRACT FROM AUTHOR]

• Novel third-generation Ovonic memory materials have been synthesized. • Observed the significant electrical switching in thin-film samples. • Correlation between thermal stability and threshold switching voltage has been found. • Meyer-Neldel rule is observed in both d.c. conduction and resistive switching. The objective of the present research is to investigate the consequences of the incorporation of a small amount of Cd on the electrical switching behavior at high electric field 104 V/cm in Se 78-x Te 20 Sn 2 Cd x (x = 0, 2, 4, and 6) thin films. The thermal evaporation method has been utilized for thin-film deposition on a highly polished pyrographite substrate. The current-voltage (I-V) characteristics for the thin films of the examined samples exhibit a resistive switching of memory-type. The effect of ambient temperature and Cadmium content on the switching characteristics and voltage has been studied. The exponential decay in the observed average value of the switching voltage (V th) is found with the rise in temperature and Cd addition as well. An endeavor had been done to study the observed compositional dependence in terms of the thermal-induced glass transition temperature (T g), thermal stability, chemical bond approach, and lone-pair electrons (LP). On metal addition (Cd), the threshold voltage, glass transition temperature, and lone-pair electrons decrease while the chemical order network increases by the increase of the Cd-Se homopolar bonds. The switching phenomenon in amorphous Se 78-x Te 20 Sn 2 Cd x (0 ≤ x ≤ 6) thin films is elucidated according to an electro-thermal model based on the Joule-heating effect. [Display omitted] [ABSTRACT FROM AUTHOR]

Strain engineering, which employs biaxial misfit strain to deform the crystal structure, is a powerful tool to tune the physical behavior of epitaxial thin films. Here we show that a 10-nm-thick BiFeCO3 film is uniaxially strained by (HO)-oriented LaAlO3 substrate, which exhibits a monoclinic lattice with a giant c/a ∼ 1.24 and a unique stripe ferroelectric domain configuration, as revealed by high resolution synchrotron x-ray diffraction and piezoelectric force microscopy. A strain-phase diagram for BiFeCO3 under uniaxial strain condition is predicted by first-principles calculations, suggesting that monoclinic Pm phase with a large polarization of ∼130 μC/cm2 is the lowest-in-energy phase when strained by (HO)-oriented LaAlCO3 substrate. Our results provide a potential route to tune physical behavior of epitaxial ferroelectric thin films by uniaxial strain in (110) orientation, instead of widely investigated biaxial strain in (001) orientation. [ABSTRACT FROM AUTHOR]

The nonlinear response of a ferroic to an applied field has been studied through the phenomenological Rayleigh Law for over a hundred years. Yet, despite this, the fundamental physical mechanisms at the nanoscale that lead to macroscopic Rayleigh behavior have remained largely elusive, and experimental evidence at small length scales is limited. Here, it is shown using a combination of scanning probe techniques and phase field modeling, that nanoscale piezoelectric response in prototypical Pb(Zr,Ti)O3 films appears to follow a distinctly non-Rayleigh regime. Through statistical analysis, it is found that an averaging of local responses can lead directly to Rayleigh-like behavior of the strain on a macroscale. Phase-field modeling confirms the twist of the ferroelastic interface is key in enhancing piezoelectric response. The studies shed light on the nanoscale origins of nonlinear behavior in disordered ferroics. [ABSTRACT FROM AUTHOR]

Abstract: It was found that Langmuir–Blodgett (LB) deposition process led to the direct formation of ferroelectric β phase in poly(vinylidene fluoride) (PVDF) homopolymer ultra-thin films, in which the molecular chains were parallel to the substrates and the dipoles were aligned perpendicular to the substrates. Theoretical analysis and experimental results further showed that the mechanism of forming the β phase and the dipole orientation were attributed to the hydrogen bonds formed between the PVDF molecules and water through the LB deposition. A large local effective piezoelectric coefficient (d zz) of −49.4 pm/V was observed in the self-polarized PVDF LB film. [Copyright &y& Elsevier]

Nonlinear optics is an essential component of modern laser systems and optoelectronic devices. It has also emerged as an important tool in probing the electronic, vibrational, magnetic, and crystallographic structure of materials ranging from oxides and metals, to polymers and biological samples. This review focuses on the specific technique of optical second harmonic generation ( SHG), and its application in probing ferroelectric complex oxide crystals and thin films. As the dominant SHG interaction mechanism exists only in materials that lack inversion symmetry, SHG is a sensitive probe of broken inversion symmetry, and thus also of bulk polar phenomena in materials. By performing in-situ SHG polarimetry experiments in different experimental conditions such as sample orientation, applied electric field, and temperature, one can probe ferroelectric hysteresis loops and phase transitions. Careful modeling of the polarimetry data allows for the determination of the point group symmetry of the crystal. In epitaxial thin films with a two-dimensional arrangement of well-defined domain orientations, one can extract information about intrinsic material properties such as nonlinear coefficients, as well as microstructural information such as the local statistics of the different domain variants being probed. This review presents several detailed examples of ferroelectric systems where such measurements and modeling are performed. The use of SHG microscopic imaging is discussed, and its ability to reveal domain structures and phases not normally visible with linear optics is illustrated. [ABSTRACT FROM AUTHOR]

An in situ x-ray diffraction (XRD) setup is designed and installed in the materials science beam line of the Pelletron accelerator at the Inter-University Accelerator Centre for in situ studies of phase change in swift heavy ion irradiated materials. A high vacuum chamber with suitable windows for incident and diffracted X-rays is integrated with the goniometer and the beamline. Indigenously made liquid nitrogen (LN2) temperature sample cooling unit is installed. The snapshots of growth of particles with fluence of 90 MeV Ni ions were recorded using in situ XRD experiment, illustrating the potential of this in situ facility. A thin film of C60 was used to test the sample cooling unit. It shows that the phase of the C60 film transforms from a cubic lattice (at room temperature) to a fcc lattice at around T=255 K. [ABSTRACT FROM AUTHOR]

Thin films terminated with oligo(ethylene glycol) (OEG) could be photochemically grafted onto ultrathin silicon carbide layers that were generated on silicon substrates viacarbonization with acetylene at 820 °C. The OEG coating reduced the non-specific adsorption of fibrinogen on the substrates by 99.5% and remained resistant after storage in PBS for 4 weeks at 37 °C. [ABSTRACT FROM AUTHOR]

The capacitance dispersion in La and Mg co-substituted BiFeO3 thin film has been studied at different stages of polarization switching. A negative capacitance (NC) behavior is observed in the sample that is fatigued above 109 switching cycles. The origin of the NC is investigated through analyzing relaxation processes and charge transport kinetics by admittance spectroscopy. An activation energy of ∼0.6 eV and a zero field mobility μ0=5.33±0.02×10-13m2/Vs are thus obtained. A physical mechanism is proposed to explain this behavior. It involves a redistribution of oxygen vacancies, which are trapped at the film/electrode interface during the fatigue process. [ABSTRACT FROM AUTHOR]