The hole transport properties of gallium antimonide with various degrees of tellurium compensation have been investigated in the temperature range of 4.2-300 K. For the undoped GaSb, the p-type conductivity arises from a doubly ionizable native defect V Ga Ga Sb. In the Te compensated samples, apart from the Te-donor level and the V Ga Ga Sb center, an acceptor level resulting from complexation of V Ga Ga Sb with Te Sb has been found. This acceptor level lies ϳ70 meV above the valence band edge. The concentration of this center depends on the melt composition and the level of Te present in the melt during growth of crystals. Most interestingly, at very low level of Te concentration, an additional triple native acceptor ͑V Ga Ga Sb V Ga ͒ has also been observed. With the increase in Te concentration, the mobility decreases and a shift in the mobility peak to higher temperature is observed. The low-temperature mobility is limited by ionized impurity scattering. At higher temperatures, the scattering mechanisms depend on Te concentration in the sample. In this regime, significant contributions from acoustic, nonpolar optical, and polar optical phonon scattering are observed for samples with low levels of Te. In contrast, the impurity scattering dominates even at room temperature for highly compensated crystals.

Polyaniline/ZnFe 2 O 4 nanocomposites were synthesized by a simple and inexpensive one-step in situ polymerization method in the presence of ZnFe 2 O 4 nanoparticles. The structural, morphological, and electrical properties of the samples were characterized by wide angle X-ray diffraction (WAXD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). WAXD and SEM revealed the formation of polyaniline/ZnFe 2 O 4 nanocomposites. Infrared spectroscopy indicated that there was some interaction between the ZnFe 2 O 4 nanoparticles and polyaniline. The dc electrical conductivity measurements were carried in the temperature range of 80 to 300 K. With increase in the doping concentration of ZnFe 2 O 4 , the conductivity of the nanocomposites found to be decreasing from 5.15 to 0.92 Scm À1 and the temperature dependent resistivity follows ln q(T) $ T À1/2 behavior. The nanocomposites (80 wt % of ZnFe 2 O 4 ) show a more negative magnetoresistance compared with that of pure polyaniline (PANI). These results suggest that the interaction between the polymer matrix PANI and zinc nanoparticles take place in these nanocomposites.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is an important opto-electronic material, and its room temperature electrical conductivity can be prominently enhanced by chemical treatment; it is technologically significant to investigate its temperature and magnetic field dependent charge transport characteristics. Here, we analyzed the low temperature charge transport properties of pristine and acid-treated PEDOT:PSS thin films by studying the variation in resistance as a function of temperature and magnetic field (T ∼ 300 to 4.2 K, H ∼ up to 5 T). The acid-treated sample exhibited much improved charge transport behavior at low T, with a resistivity ratio [ρ(4.2 K)/ρ(300 K)] of ∼5.7 × 102, which is three orders of magnitude smaller than that of the pristine sample. Nevertheless, both pristine and acid-treated samples followed hopping conduction, obeying R(T)∝expT−1/2andR(T)∝expT−1/3, respectively, in the low T regime. Furthermore, positive magnetoresistance of ∼16% (at 4.2 K and 5 T) was displayed by acid-treated samples that could be due to the wave function shrinkage phenomenon.

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