ON THE ELECTRONIC TRANSPORT MECHANISM IN MAGNETRON-SPUTTERED POLYCRYSTALLINE ZnO THIN FILMS

Zinc oxide ( ZnO ) thin films were deposited onto glass substrates by d.c. magnetron sputtering. The structural analysis, by X-ray diffraction and atomic force microscopy, indicate that the studied films are polycrystalline and have a wurtzite (hexagonal) structure. The film crystallites are preferentially oriented with (002) planes parallel to the substrates. The mechanism of electronic transport is explained in terms of Seto's model elaborated for polycrystalline semiconducting films (crystallite boundary trapping theory). Some parameters of used model (impurity concentration, density and energy of the trapping states, etc.) have been calculated. The optical bandgap (Eg0 = 3.28–3.37 eV ) was determined from absorption spectra.

Relationship Between Fatigue Behavior and Nonlinear Dynamic Viscoelasticity for High-Density Polyethylenes with Different Aggregation States

Relationships between fatigue behavior and nonlinear dynamic viscoelastic properties for the annealed, isothermally crystallized, and oriented high-density polyethylenes (HDPEs) with different molecular aggregation states were intensively discussed. Nonlinear dynamic viscoelasticity under cyclic fatigue was estimated on the basis of nonlinear viscoelastic parameter (NVP) which was defined as the contribution of higher harmonics of Fourier expanded stress signal. Fatigue strength of specimens decreased with an increase in the magnitude of NVP. Thus, NVP can be used as an index of fatigue strength for polymeric solids. Also, higher-order structural changes of specimens by cyclic straining were investigated and it was concluded that the nonlinear dynamic viscoelasticity under cyclic fatigue became dominant with an increase in cyclic straining concentration at the amorphous and/or spherulite or crystallite boundary regions.