G.I. Rusu

On the electronic transport properties of polycrystalline ZnSe films

Abstract Zinc selenide (ZnSe) thin films were deposited onto glass substrates by the quasi-closed volume technique under vacuum. The film structure was studied by X-ray diffraction (XRD) technique, scanning electron microscopy and atomic force microscopy (AFM). The investigations showed that the films are polycrystalline and have a cubic (zinc blende) structure. The films with stable structure can be obtained if they, after deposition, were submitted to a heat treatment. The mechanism of electrical conduction is discussed in terms of Seto’s model for polycrystalline semiconducting films. The values of optical energy gap have been determined from the absorption spectra.

The influence of heat treatment on the optical properties of titanium oxide thin films

Titanium oxide thin films were deposited by a DC sputtering technique onto unheated quartz substrates. X-ray diffraction (XRD) studies revealed an amorphous structure of the films. After heat treatment in air at different annealing temperatures (673, 873 and 1173 K) for a certain time (12, 2 and 3 h), the film structure becomes polycrystalline with mixed anatase and rutile phases. The morphology and the weight percentage of the phases strongly depend on the annealing conditions. With the increase of heat-treatment temperature till 1173 K, the weight percentage of rutile phase increases, being of 75%. As a consequence of changes in the structure and morphology of the studied films, the optical properties (refractive index, extinction coefficient, optical energy gap) change too.

Temperature dependence of the electrical conductivity and Seebeck coefficient of new poly(ester-syloxane)urethane elastomers in thin films

Abstract The temperature dependences of the electrical conductivity and the Seebeck coefficient for some new poly(ester-syloxane)urethane elastomers are studied. The measurements have been performed using thin films deposited from solution. It is found that the investigated polymers have semiconducting properties. Values of some semiconducting parameters of these films (activation energy of electrical conduction, charge carrier concentration, ratio of carrier mobilities) have been calculated. The correlations between some of these parameters and the molecular structure of the respective polymers are discussed.

On the electrical properties of some modified polysulfones in thin films

Abstract The temperature dependence of the electrical conductivity and the Seebeck coefficient for some chelate-modified polysulfones (PSF-Cs) derived from chloro-terminated polysulfones and bis (2,4-dihydroxybenzaldehyde) Cu2+ were studied. The measurements were performed using the thin films deposited from solution. The investigated polymers have semiconducting properties. The correlations between these properties and the molecular structure of the respective polymers are discussed.

High-field electrical conduction in thin-film sandwich structures of the metal/organic semiconductor/metal type

Abstract The investigated organic compounds are derivatives of the asparagic acid. Thin films of respective compounds were deposited from dimethylformamide solutions. The temperature dependences of the electrical conductivity and Seebeck coefficient are investigated. All compounds have semiconducting properties. The values of some characteristic parameters (activation energy, ratio of carrier mobilities, etc.) have been determined. Using sandwich cells of the type Al/organic compound/Al, the static current–voltage (J–U) characteristics have been studied. For lower values of intensity of electric field E ( E ≅6×102–2×103 V cm−1), J–U characteristics are ohmic. At higher values of E , the current density J increases faster than linear. For E ≅103–104 V cm−1, the obtained experimental data are in good agreement with the Richardson–Schottky law. At fields E >105 V cm−1, the experimental points deviate more and more from Schottky characteristics in direction of larger values of J. For explanation of these behaviours, the electron transitions through and over the potential barrier at metal-organic film interface are taken into account.

Studies on the electronic transport properties of some organic semiconductors in thin films

Abstract The investigated compounds are some derivatives of orthotolidin-N,N′-bis (4-aminobenzene-2-sulphonic) acid. The temperature dependences of the electrical conductivity and Seebeck coefficient are studied on the thin films deposited from dimethylformamide solution onto glass substrates. It is known that the investigated compounds have typical semiconducting properties. The values of some important parameters of the films (thermal activation energy of electrical conduction, concentrations and mobilities of charge carriers) have been determined. The correlations between some of these parameters and molecular structure of the respective compounds are discussed.

Anionic Nylon 6/Zinc Composite Materials: Evaluation of Thermal and Mechanical Behavior

This study deals with the experimentally investigated effect of zinc (Zn) particles on the thermal and mechanical properties of nylon 6/zinc composite materials. Nylon 6 and nylon 6 containing 6.0, 8.0, 12.0, 15.0, 20.0, and 25.0 wt.% of unmodified zinc particles, metal-polymer composite materials, were prepared by in situ anionic polymerization of є-caprolactam (CL) in the presence of metallic fillers using rotational molding technique. The characteristics, namely melting temperature, degree of crystallinity (first and second heating scan) and crystallization temperature, crystalline structure, thermal stability, and mechanical properties (flexural modulus, flexural strength, and notched Izod impact strength), of the nylon 6/zinc composites were determined for each sample. Different DSC, ATG, wide-angle X-ray diffraction, and mechanical measurements were performed. The results related to nylon 6 composites were compared with those obtained for pure nylon 6.

Coordination Polymers. 9. Chelate Polymers Derived from Bisphenolic Complexes and Propylenediamine

Abstract Chelate polymers derived from bis(2,4-dihydroxybenzaldehyde)propyl-enediimine M and bis(2,4-dihydroxyacetophenone)propylenediimine M (M = Fe2+, Co2+, Ni2+, Cu2+, Zn2+) with aromatic acid chlorides were prepared by interfacial polycondensation. Also, chelate polysiloxanes were obtained from the same monomers and α,ω-dichloropolydimethyl-siloxane. The spectral, thermal, magnetic, and electrical properties of the polychelates were studied.

Nylon 6/TiO2 Composites by in situ Anionic Ring-Opening Polymerization of ϵ-Caprolactam: Synthesis, Characterization, and Properties

Two series of nylon 6/TiO2 composites were obtained via anionic ring opening polymerization of ϵ-caprolactam in the presence of untreated and surface-treated TiO2 with 3-aminopropyltriethoxysilane (APTEOS) as coupling agent by the rotational molding technique. The polymerization process was carried out using a system initiator/activator based on sodium dicaprolactamato-bis(2-methoxyethoxo)aluminate and N,N′-[methylene-di(4,4′-phenylene)bis-carbamoyl]bis-ϵ-caprolactam. All tests were performed at the initial polymerization temperature of 160° ± 2°C. The influence of both untreated and treated TiO2 particle concentration on the degree of conversion (DC), intrinsic viscosity [η], weight-average molecular weight , and water absorption of pure nylon 6 and its composite materials was investigated in the range of 0.0 to 8.0 wt.% TiO2. The thermal behavior and crystalline structures of pure nylon 6 and its composites have been studied in correlation with filler concentration by differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), and room temperature wide-angle X-ray diffraction (WAXD). The mechanical characteristics, including tensile and flexural properties, elongation at break, and notched Izod impact strength, of nylon 6 and its composites as a function of TiO2 filler content were investigated for all samples. Experimental results revealed that the unmodified and surface-modified TiO2 as fillers had distinct influence on the degree of conversion, weight-average molecular weight, crystallization behavior, thermal stability, mechanical properties, and water absorption of nylon 6 matrix.

On the electrical properties of some new stable disubstituted ylides in thin films

The synthesis of six new 3-(4-halogenophenyl)-pyridaziniu-(4-chloroanilido)-(4-R-benzoyl)-metylides is described and the temperature dependence of the electrical conductivity and Seebeck coefficient for respective compounds is investigated. The measurements have been performed using thin films deposited from solution. The studied compounds have semiconducting properties. Some correlations between these properties and the chemical structures of the compounds are established. The values of some characteristic parameters of investigated compounds have been determined.