The α to β phase transformation of PVDF through the stretching process at different temperatures was investigated. The optimum stretching conditions were studied and characterised by infrared spectroscopy and differential scanning calorimetry. The maximum β−phase content was achieved at 80°C and a stretch ratio of 5. Accompanying the phase transformation, a orientation of the polymer chains and a packing of the crystalline structure is observed. The stretch ratio does not significantly affect the degree of crystallinity.

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Ferromagnetic (Ga,Mn)As nanowires grown by Mn-assisted molecular beam epitaxy

We have observed low frequency current oscillations in a semi-insulating GaAs sample grown by low temperature molecular beam epitaxy. For this, an experimental setup proper to measure high impedance samples with small external noise was developed. Spontaneous oscillations in the current were observed for some bias conditions. Although measurements were carried out from room temperature down to liquid helium, the dynamical analysis was carried out around 200 K where the signal to noise ratio was fairly favorable. To increase the data quality we have also used a noise reduction algorithm suitably developed for nonlinear systems. We observed attractors having low embedding dimension, limit cycle bifurcations, and chaotic behavior characteristic of nonlinear dynamical processes in route to chaos. Attractor reconstruction, Poincare sections, Lyapunov exponents, and correlation dimension were also analyzed.

Resonant x-ray scattering from self-assembled In P ∕ Ga As ( 001 ) islands: Understanding the chemical structure of quaternary quantum dots Appl. Phys. Lett. 92, 021903 (2008); 10.1063/1.2820756 Strain study of self-assembled InAs quantum dots by ion channeling technique

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The electronic transport properties of several Mg-doped GaAs nanowires are investigated. It is shown that Mg can be successfully used as a nontoxic and noncarcinogenic p-type dopant in GaAs nanowires. The doping levels, expanding over two orders of magnitude, and free holes mobility in the NW were obtained by the analysis of field effect transistors transfer curves. The study of the temperature dependence of the electrical resistivity of the nanowires shows that electronic transport changes from conduction of free holes, above room temperature, to variable hopping conduction at lower temperatures. Both, Mott and Efros-Shklovskii variable range hopping mechanism were clearly identified in the nanowires.

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