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The change in the crystallization process of an organic semiconductor layer in the presence of a small amount of TiO2 nanoparticles from the Volmer–Weber mode to the Stranski–Krastanov mode is reported and explained.

Solution processable dielectric nanomaterials were prepared by the polymer-templated synthesis of hybrid nanoparticles containing TiO2. Well defined poly(styrene-co-acrylonitrile)-b-poly(acrylic acid)-poly(divinylbenzene) (PSAN-b-PAA-PDVB) star-shaped copolymers were prepared using activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) and then used as templates for the synthesis of nanoconfined TiO2. Unexpectedly, even very low inorganic loadings significantly modified the surface of the poly(methyl methacrylate), (PMMA), layers. Relatively thick (with a thickness of 0.6 μm, affordable for the inkjet printing method) PMMA layers comprising merely 0.4% wt. of the hybrid TiO2 nanoparticles were applied as gate dielectrics for organic field effect transistors (OFETs). Such a low content of hybrid nanoparticles, which essentially did not affect the dielectric properties of the PMMA layer, significantly improved the efficiency of the obtained OFETs, as compared with OFETs based on pure PMMA as gate dielectrics, e.g. charge carrier mobility has increased nearly 10-fold from ca. 0.06 to ca. 0.5 cm2 V−1 s−1. The improvement of OFET parameters may be explained by a significant decrease of roughness (root mean square roughness of the dielectric layer was reduced from 15.3 nm to 0.43 nm) and change of surface energy (from 32.4 to 45.5 mN m−1) of the gate dielectric layer induced by hybrid nanoparticles. OFETs with novel dielectric layers showed current–voltage characteristics with high drain currents and negligible hysteresis. The presented results showed that the physicochemical properties of the surface of the polymer layer may be easily modified by the addition of small amounts of new hybrid nanoparticles.

In this work, the multiferroic bismuth ferrite materials Bi0.9RE0.1FeO3 doped by rare-earth (RE = La, Eu, and Er) elements were obtained by the solution combustion synthesis. Structure, electrical, and magnetic properties of prepared samples were investigated by X-ray photoelectron spectroscopy, Mössbauer spectroscopy, electrical hysteresis measurement, broadband dielectric spectroscopy, and SQUID magnetometry. All obtained nanomaterials are characterized by spontaneous electrical polarization, which confirmed their ferroelectric properties. Investigation of magnetic properties at 300.0 K and 2.0 K showed that all investigated Bi0.9RE0.1FeO3 ferrites possess significantly higher magnetization in comparison to bismuth ferrites obtained by different methods. The highest saturation magnetisation of 5.161 emu/g at 300.0 K was observed for the BLaFO sample, while at 2.0 K it was 12.07 emu/g for the BErFO sample. Several possible reasons for these phenomena were proposed and discussed.

There is an urgent need for the development of elastic dielectric materials for flexible organic field effect transistors (OFETs). In this work, detailed analysis of the AC and DC electrical conductivity of a series of flexible poly(dimethylsiloxane) (PDMS) polymers crosslinked by metal-ligand coordination in comparison to neat PDMS was performed for the first time by means of broadband dielectric spectroscopy. The ligand was 2,2-bipyridine-4,4-dicarboxylic amide, and Ni2+, Mn2+, and Zn2+ were introduced for Cl−, Br−, and I− salts. Introduction of metal salt and creation of coordination bonds resulted in higher permittivity values increasing in an order: neat PDMS &lt, Ni2+ &lt, Mn2+ &lt, Zn2+, accompanied by conductivity values of the materials increasing in an order: neat PDMS &lt, Cl− &lt, I− &lt, Br−. Conductivity relaxation time plot as a function of temperature, showed Vogel-Fulcher–Tammann dependance for the Br− salts and Arrhenius type for the Cl− and I− salts. Performed study revealed that double-edged challenge can be obtained, i.e., dielectric materials with elevated value of dielectric permittivity without deterioration too much the non-conductive nature of the polymer. This opens up new perspectives for the production of flexible dielectrics suitable for gate insulators in OFETs. Among the synthesized organometallic materials, those with chlorides salts are the most promising for such applications.

Poly(dimethylosiloxane) (PDMS) cross-linked by metal-ligand coordination has a potential functionality for electronic devices applications. In this work, the molecular dynamics of bipyridine (bpy)&ndash, PDMS-MeCl2 (Me: Mn2+, Fe2+, Ni2+, and Zn2+) are investigated by means of broadband dielectric spectroscopy and supported by differential scanning calorimetry and density functional theory calculations. The study of molecular motions covered a broad range of temperatures and frequencies and was performed for the first time for metal-ligand cross-linked PDMS. It was found that the incorporation of bpy moieties into PDMS chain prevents its crystallization. The dielectric permittivity of studied organometallic systems was elevated and almost two times higher (&epsilon, &prime, ~4 at 1 MHz) than in neat PDMS. BpyPDMS-MeCl2 complexes exhibit slightly higher glass transition temperature and fragility as compared to a neat PDMS. Two segmental type relaxations (&alpha, and &alpha, ac) were observed in dielectric studies, and their origin was discussed in relation to the molecular structure of investigated complexes. The &alpha, ac relaxation was observed for the first time in amorphous metal-ligand complexes. It originates from the lower mobility of PDMS polymer chains, which are immobilized by metal-ligand coordination centers via bipyridine moieties.

We report a strategy for preparing barium titanate precursor, being the composite of titanate nanosheets (TN) with barium ions (Ba-TN), which subjected to step sintering allows obtaining TiO2 rich barium titanate ceramics of stoichiometry BaTi4O9 or Ba2Ti9O20. These compounds are important in modern electronics due to their required dielectric properties and grains’ size that can be preserved in nanometric range. The morphology studies, structural characterization, and dielectric investigations were performed simultaneously in each step of Ba-TN calcinations in order to properly characterize type of obtained ceramic, its grains’ morphology, and dielectric properties. The Ba-TN precursor can be sintered at given temperatures, so that its dielectric permittivity can be tuned between 25 and 42 with controlled temperature coefficients that change from negative 32 ppm/°C for Ba-TN sintered at 900°C up to positive 37 ppm/°C after calcination at 1300°C. XRD analysis and Raman investigations performed for the Ba-TN in the temperature range of 900÷1250°C showed that below 1100°C we obtained as a main phase BaTi4O9, whereas the higher calcinations temperature transformed Ba-TN into Ba2Ti9O20. Taking into account trend of device miniaturization and nanoscopic size requirements, temperatures of 900°C and 1100°C seem to be an optimal condition for Ba-TN precursor calcinations that guarantee the satisfactory value of dielectric permittivity (ε=26 and 32) and ceramic grains with a mean size of ~180 nm and ~550 nm, respectively.

Effects of the elevated temperature on the structure evolution of the ZnO nanorod array (ZNA) and their hybrid nanocomposite with layered (tetramethyl)ammonium titanate (LTMAT) prepared by the liquid phase deposition were investigated. The vertically oriented ZnO nanorods were deposited on a quartz plate by a chemical bath deposition method and then they were penetrated by the LTMAT using the dip-coating method from the water solution. As a result of such an experimental procedure, an assembly composed of the ZNA with LTMAT was obtained and called hybrid nanocomposite. Since the LTMAT converts to TiO2 upon subsequent sintering at 350 °C, it can be regarded as TiO2 precursor for the thermal treatment experiments. The experiments with ZNA and their hybrid nanocomposite at the elevated temperature revealed coalescence of the deposited ZnO nanorods and crystallization of zinc titanate with Zn2TiO4 stoichiometry.

In this study, nanocrystalline (18–28 nm) perovskite-like bismuth ferrite rare earth-doped powders (Bi0.9RE0.1FeO3, where RE = La (BLaFO), Eu (BEuFO), and Er (BErFO)) were obtained by microwave-assisted modification of solution combustion synthesis (SCS). The influence of high load La3+, Eu3+, and Er3+ doping on structural, optical, and electrical properties of BiFeO3 was investigated. It was found that rare earth doping along with fast phase formation and quenching significantly distorts the crystal cells of the obtained materials, which results in the formation of mixed rhombohedral- (R3c-) orthorhombic (Pbnm) crystal structures with decreased lengths of Bi-O and Fe-O bonds along with a decreasing radius size of doping ions. This promotes reduction of the optical band gap energy and suppression of ionic polarization at high frequencies and results in enhanced dielectric permittivity of the materials at 1 MHz.

In this work we report a reproducible and efficient method of surface modification of titania nanoparticles (rutile) via reversible-deactivation radical polymerization. Herein, we graft poly(di(ethylene glycol) methyl ether methacrylate) from the surface of TiO 2 in an amount of 21 wt% within the reaction time of 3 h 15 min. The amount of grafted polymer was assessed by Thermogravimetric Analysis and it is one of the highest reported till now for this ceramic nanoparticles by atom transfer radical polymerization. The properties of inorganic-organic, i.e. core–shell material, as well as of pristine TiO 2 and neat polymer were examined by Infrared and Dielectric Spectroscopies. The shape of the nanoparticles and the thickness of the polymer coating shell were investigated by means of High Resolution Transmission Electron Microscopy. The obtained nanocomposite exhibits dielectric permittivity ϵ ′ = 18 and loss tangent around 1 × 10 −2 at 20 °C. The described method allows controlling a length and chemical structure of the grafted polymer from ceramic core, thus to tailor a physical properties of nanoparticles and of nanocomposites.