Surface plasmon resonance-coupled photoluminescence and resistive switching behavior of pulsed laser-deposited Ag:SiC nanocermet thin films

In this study, Ag:SiC nanocermets were prepared via rapid thermal annealing (RTA) of pulsed laser-deposited SiC/Ag/SiC trilayers grown on Si substrate. Atomic force microscope images show that silver nanoparticles (Ag NPs) are formed after RTA, and the size of NPs increases with increasing Ag deposition time (t Ag). Sharp dip observed in the reflectance spectra confirmed the existence of Ag surface plasmons (SPs). The infrared transmission spectra showed an intense and broad absorption band around 780–800 cm−1 that can be assigned to Si-C stretching vibration mode. Influence of t Ag on the spectral characteristics of SP-enhanced photoluminescence (PL) and electrical properties of silicon carbide (SiC) films has been investigated. The maximum PL enhancement by 5.5 times for Ag:SiC nanocermets is achieved when t Ag ≈ 50 s. This enhancement is due to the strong resonant coupling between SiC and the SP oscillations of the Ag NPs. Presence of Ag NPs in SiC also induces a forming-free resistive switching with switching ratio of 2 × 10−2. The analysis of I–V curves demonstrates that the trap-controlled space-charge-limited conduction with filamentary model is the governing mechanism for the resistive switching in nanocerment thin films.

Microstructure of highly oriented, hexagonal, boron nitride thin films grown on crystalline silicon by radio frequency plasma-assisted chemical vapor deposition

We present a high‐resolution electron microscopy study of the microstructure of boron nitride thin films grown on silicon (100) by radio‐frequency plasma‐assisted chemical vapor deposition using B2H6 (1% in H2) and NH3 gases. Well‐adhered boron nitride films grown on the grounded electrode show a highly oriented hexagonal structure with the c‐axis parallel to the substrate surface throughout the film, without any interfacial amorphous layer. We ascribed this textured growth to an etching effect of atomic hydrogen present in the gas discharge. In contrast, films grown on the powered electrode, with compressive stress induced by ion bombardment, show a multilayered structure as observed by other authors, composed of an amorphous layer, a hexagonal layer with the c‐axis parallel to the substrate surface and another layer oriented at random

Amphoteric nano-, micro-, and macrogels, membranes, and thin films

This review describes the state-of the-art of nano-, micro- and macrogels, membranes, micro- and nanocapsules, as well as multilayered thin films exhibiting amphoteric character. The synthetic strategies and physicochemical properties of amphoteric materials are outlined in light of the stimuli-responsive behavior and their potential application in nanotechnology, biotechnology and medicine.

Photoluminescent behavior of SrZrO(3)/SrTiO(3) multilayer thin films

A detailed investigation was made into the origin of photoluminescence in an alternate multilayer system of SrZrO(3) (SZO) and SrTiO(3) (STO) thin films. XRD and room-temperature PL studies revealed a high consistency with respect to improved crystallization at elevated temperatures. The photoluminescence behaviour of SZO/STO multilayered system consists in the superposition of independent photoluminescence emissions of both STO and SZO films. Based on the present results and on previous experimental and theoretical data, we propose that the origin of the photoluminescence emission results from structural disorder generated by the presence of distortions in the ideal constituent clusters of these materials. (c) 2009 Elsevier B.V. All rights reserved.

Photoluminescence of barium titanate and barium zirconate in multilayer disordered thin films at room temperature

The emission of wide band photoluminescence showed a synergic effect on barium zirconate and barium titanate thin films in alternate multilayer system at room temperature by 488 nm exiting wavelength. The thin films obtained by spin-coating were annealed at 350, 450, and 550 degrees C for 2 h. The X-ray patterns revealed the complete separation among the BaTiO3 and BaZrO3 phases in the adjacent films. Visible and intense photoluminescence was governed by BaZrO3 thin films in the multilayer system. Quantum mechanics calculations were used in order to simulate ordered and disordered thin films structures. The disordered models, which were built by using the displacement of formers and modifier networks, showed a different symmetry in each system, which is in accordance with experimental photoluminescence emission, thus allowing to establish a correlation among the structural and optical properties of these multilayered systems.

Photoluminescent behavior of SrZrO3/SrTiO3 multilayer thin films

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Epitaxially grown LiNbO3 thin films by polymeric precursor method

LiNbO3 thin films were grown on (0001) sapphire substrates by a chemical route, using the polymeric precursor method. The overall process consists of preparing a coating solution from the Pechini process, based on metallic citrate polymerization, the precursor films, deposited by dip coating, are then heat treated to eliminate the organic material and to synthesize the phase. In this work, we studied the influence of the heat treatment on the structural and optical properties of single-layered films. Two routes were also investigated to increase the film thickness: increasing the viscosity of the coating solution and/or increasing the number of successively deposited layers. The x-ray diffraction theta -2 theta scans revealed the c-axis orientation of the single- and multilayered films and showed that efficient crystallization can be obtained at temperatures as low as 400 degreesC, the phi-scan diffraction evidenced the epitaxial growth with two in-plane variants, A microstructural study revealed that the films were crack free, homogeneous, and relatively dense. Finally, the investigation of the optical properties (optical transmittance and refractive index) confirmed the good quality of the films. These results indicate that the polymeric precursor method is a promising process to develop lithium niobate waveguides.

The influence of crystallization route on the properties of lanthanum-doped Bi4Ti3O12 thin films prepared from polymeric precursors

Pure and lanthanum-doped Bi4Ti3O12 thin films were deposited on Pt/Ti/SiO2/Si substrate using a polymeric precursor solution. The spin-coated films were specular and crack-free and crystalline after annealing at 700 degreesC for 2 h. Crystallinity and morphological evaluation were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Multilayered films obtained using the intermediate-crystalline layer route present a dense microstructure with spherical grains. Films obtained using the intermediate-amorphous layer, present elongated grains around 250 nm in size. The dielectric and ferroelectric properties of the lanthanum-doped Bi4Ti3O12 films are strongly affected by the crystallization route. The hysteresis loops are fully saturated with a remnant polarization and drive voltage of the films, heat-treated by the intermediate-crystalline (P-r = 20.2 muC/cm(2) and V = 1.35 V) and for the film heat-treated by amorphous route (P-r = 22.4 muC/cm(2) and V = 2.99 V). (C) 2004 Elsevier B.V. All rights reserved.

Dielectric properties and microstructure of SrTiO3/BaTiO3 multilayer thin films prepared by a chemical route

Multilayer thin films with perovskite structures were produced by the polymeric precursor method. SrTiO3/BaTiO3 (STO/BTO) multilayers were deposited on Pt(111)/Ti/SiO2/Si(100) substrates by the spin-coating technique and heated in air at 700 degreesC. The microstructure and crystalline phase of the multilayered thin films were examined by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), resolution-high transmission electron microscopy (HRTEM), atomic force microscopy (AFM) and X-ray diffraction. The SrTiO3/BaTiO3 multilayer thin films consisted of grainy structures with an approximate grain size of 60 nm. The multilayered thin films showed a very clear interface between the components. The SrTiO3/BaTiO3 multilayer thin films revealed dielectric constants of approximately 527 and loss tangents of 0.03 at 100 kHz. The dielectric constant calculated for this multilayer film system is the value of the sum of each individual component of the film, i.e. The total value of the sum of each SrTiO3 (STO) and BaTiO3 (BTO) layer. The multilayer SrTiO3/BaTiO3 obtained by the polymeric precursor method, also showed a ferroelectric behavior with a remanent polarization of 2.5 muC/cm(2) and a coercive field of 30 kV/cm. The multilayer films displayed good fatigue characteristics under bipolar stressing after application of 10(10) switching cycles. (C) 2001 Published by Elsevier B.V. B.V. All rights reserved.

The influence of crystallization route on the SrBi2Nb2O9 thin films

Polycrystalline SrBi2Nb2O9-layered ferroelectric thin films were synthesized on Pt/Ti/SiO2/Si substrate using the polymeric precursors solution. The dip-coated films were specular and crack-free and crystallized during firing at 700 °C. Single-, double-, and triple-layered films were obtained by several dips in the deposition solution, and the influence of crystallization between each dip was studied. Microstructure and morphological evaluation were followed by grazing incident x-ray diffraction (GIXRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Multilayered films obtained using the intermediate-crystallized layer route present a dense microstructure with spherical grains, with a preferential orientation in the 〈215〉 direction; films obtained using the intermediate-amorphous layer route are polycrystalline and present elongated grains around 250 nm in size.

Layer-by-layer grown scalable redox-active ruthenium-based molecular multilayer thin films for electrochemical applications and beyond

Here we report the first study on the electrochemical energy storage application of a surface-immobilized ruthenium complex multilayer thin film with anion storage capability. We employed a novel dinuclear ruthenium complex with tetrapodal anchoring groups to build well-ordered redox-active multilayer coatings on an indium tin oxide (ITO) surface using a layer-by-layer self-assembly process. Cyclic voltammetry (CV), UV-Visible (UV-Vis) and Raman spectroscopy showed a linear increase of peak current, absorbance and Raman intensities, respectively with the number of layers. These results indicate the formation of well-ordered multilayers of the ruthenium complex on ITO, which is further supported by the X-ray photoelectron spectroscopy analysis. The thickness of the layers can be controlled with nanometer precision. In particular, the thickest layer studied (65 molecular layers and approx. 120 nm thick) demonstrated fast electrochemical oxidation/reduction, indicating a very low attenuation of the charge transfer within the multilayer. In situ-UV-Vis and resonance Raman spectroscopy results demonstrated the reversible electrochromic/redox behavior of the ruthenium complex multilayered films on ITO with respect to the electrode potential, which is an ideal prerequisite for e.g. smart electrochemical energy storage applications. Galvanostatic charge–discharge experiments demonstrated a pseudocapacitor behavior of the multilayer film with a good specific capacitance of 92.2 F g−1 at a current density of 10 μA cm−2 and an excellent cycling stability. As demonstrated in our prototypical experiments, the fine control of physicochemical properties at nanometer scale, relatively good stability of layers under ambient conditions makes the multilayer coatings of this type an excellent material for e.g. electrochemical energy storage, as interlayers in inverted bulk heterojunction solar cell applications and as functional components in molecular electronics applications.

Nanostructured thin films obtained by electrodeposition over a colloidal crystal template: applications in electrochemical devices

Colloidal particles have been used to template the electrosynthesis of several materials, such as semiconductors, metals and alloys. The method allows good control over the thickness of the resulting material by choosing the appropriate charge applied to the system, and it is able to produce high density deposited materials without shrinkage. These materials are a true model of the template structure and, due to the high surface areas obtained, are very promising for use in electrochemical applications. In the present work, the assembly of monodisperse polystyrene templates was conduced over gold, platinum and glassy carbon substrates in order to show the electrodeposition of an oxide, a conducting polymer and a hybrid inorganic-organic material with applications in the supercapacitor and sensor fields. The performances of the resulting nanostructured films have been compared with the analogue bulk material and the results achieved are depicted in this paper.

Structure of disordered gold-polymer thin films using small angle x-ray scattering

We have investigated the structure of disordered gold-polymer thin films using small angle x-ray scattering and compared the results with the predictions of a theoretical model based on two approaches-a structure form factor approach and the generalized Porod law. The films are formed of polymer-embedded gold nanoclusters and were fabricated by very low energy gold ion implantation into polymethylmethacrylate (PMMA). The composite films span (with dose variation) the transition from electrically insulating to electrically conducting regimes, a range of interest fundamentally and technologically. We find excellent agreement with theory and show that the PMMA-Au films have monodispersive or polydispersive characteristics depending on the implanted ion dose. (C) 2010 American Institute of Physics. [doi:10.1063/1.3493241]

Depth-dependent local structures in thin films unraveled by grazing-incidence X-ray absorption spectroscopy

A method of using X-ray absorption spectroscopy together with resolved grazing-incidence geometry for depth profiling of atomic, electronic or chemical local structures in thin films is presented. The quantitative deconvolution of thickness-dependent spectral features is performed by fully considering both scattering and absorption formalisms. Surface oxidation and local structural depth profiles in nanometric FePt films are determined, exemplifying the application of the method.