Abstract. Nanocomposites with polypropylene/clay/wood flour were prepared by melt compounding. Thermal, mechanical and morphological properties were characterized. The addition of clay, compatibilizer and wood flour considerably improved the thermal stability (i.e., decomposition and melting temperatures) of the hybrids. The tensile modulus and strength of most hybrids were highly increased with the increased loading of clay, MAPP and wood flour, compared to the hybrids without wood flour. The wide angle X-ray diffraction (WAXD) patterns showed the increased d-spacing of clay layers, indicating enhanced compatibility between PP and clay with the addition of maleated polypropylene (MAPP). The transmission electron microscopy (TEM) photomicrographs illustrated the intercalated and partially exfoliated structures of the hybrids with clay, MAPP and wood flour.
The influence and the states of hydrogen in polycrystalline ZnO thin films were investigated by preparing films with different amounts of oxygen vacancies at various hydrogen potentials. The most notable effect of hydrogen addition was passivation of grain boundaries. The majority of hydrogen incorporation in polycrystalline ZnO films was attributed to hydrogen interstitials, and a substantially smaller number of multicentre bonds at oxygen vacancies were formed even at high hydrogen potentials. The major source of free carriers in polycrystalline ZnO films deposited without intentional hydrogen addition was oxygen vacancies with 2+ charge state with large atomic relaxation.
The optical properties of impurity doped ZnO thin films were analyzed by taking into account the nonparabolicity in the conduction-band and the optically determined carrier concentration and mobility were correlated with those measured by Hall measurement. The Drude parameters obtained by applying a simple Drude model combined with the Lorentz oscillator model for the optical transmittance and reflectance spectrum were analyzed by using the carrier density dependent bare band effective mass determined by the first-order nonparabolicity approximation. The squared plasma energy multiplied by the carrier density dependent effective mass yielded fairly linear relationship with respect to the carrier concentration in wide carrier density range of 1019 − 1021 cm−3, verifying the applicability of the nonparabolicity parameter for various types of impurity doped ZnO thin films. The correlation between the optical and Hall analyses was examined by taking the ratios of optical to Hall measurements for carrier density, mobility, and resistivity by introducing a parameter, Rdl, which represents the ratio of the resistances to electron transport from the inside of the lattice and from the crystallographic defects. For both the carrier concentration and mobility, the ratios of optical to Hall measurements were shown to exhibit a monotonically decreasing function of Rdl, indicating that the parameter Rdl could be used as a yardstick in correlating the optically determined carrier density and mobility with those measured by Hall analysis.
We have investigated lateral conduction mid-infrared photodetectors using the photoionization of holes in the valence band of self-assembled Ge/Si quantum dots. A mid-infrared photocurrent signal was observed in the photon energy range of 140–400 meV resulting from an intersubband transition in the valence band of self-assembled Ge quantum dots and subsequent lateral transport of photoexcited carriers in the SiGe conduction channel. The peak responsivity was 134 mA W−1 at a photon energy of 240 meV at T = 10 K. Furthermore, the band structure of the Ge QD system was estimated using electrical and optical measurements.
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