Polyethylene (PE) based composites with segregated carbon nanotubes (CNTs) network was successfully prepared by hot compressing of a mechanical mixture of PE and CNT powders. Through comparison with a composite comprising randomly distributed carbon nanotubes of the same concentration, we prove that namely the segregated CNT network is responsible for the excellent electrical properties, i.e., 10−1 S/m at 0.5–1% and 10 S/m at 6–12% of CNT. The investigation of the complex impedance in the frequency range 1 kHz–2 MHz shows that the sign of real part of the dielectric permittivity ε r ′ changes from positive to negative in electrically percolated composites indicating metal-like behavior of CNT segregated network. The obtained negative permittivity and AC conductivity behavior versus frequency for high CNT content (3–12%) are described by the Drude model. At the same time, in contrast to reflective metals, high electromagnetic shielding efficiency of fabricated PE composites in the frequency range 40–60 GHz, i.e., close to 100% at 1 mm thick sample, was due to absorption coursed by multiple reflection on every PE-CNT segregated network interface followed by electromagnetic radiation absorbed in each isolated PE granule surrounded by conductive CNT shells.

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The behaviour of localized states in Pd/nano-or mesoporous Si/p-Si heterojunctions is studied by the DLTS technique in a vacuum and different atmospheres: ambient air, Ar, N 2 , CO 2 , O 2 . The complex DLTS spectra of both signs related to electron and hole traps in porous Si are detected. The intensity of DLTS peaks and activation energy is shown to be dependent on the morphology of the porous layers and ambient atmosphere in which DLTS measurements were carried out. The shift of activation energy with increase of the applied reverse voltage is interpreted from the point of view of a spatially inhomogeneous distribution of localized states in a porous layer. The cyclic transformation of DLTS spectra is observed for consecutive measurements in a vacuum and ambient atmosphere. Oxygen adsorption (at partial pressure of a few mbar) results in strong passivation of deep traps in mesoporous Si.

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