We performed electric arc discharges in pure Si to generate luminous balls with lifetime in the order of seconds and several properties usually reported for natural ball lightning. This simple experiment does not rely on energy sources and excitation mechanisms that are improbable in the natural phenomenon and clearly demonstrates the role of vaporization and oxidation of Si, as proposed by the Abrahamson-Dinniss theory for ball-lightning formation.

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In this work we report on the formation of pure polyaniline fibres by the electrospinning method. The fibres present diameters ranging from hundreds of nanometres to a few micrometres and have lengths of hundreds of micrometres. The fibres were collected on SiO2/Si and Si wafer pieces in the form of isolated fibres. Morphological characterization by scanning electron microscopy shows smooth fibre surfaces and lack of failure effects such as necking and fibrillation. The current–voltage characteristics are linear and the conductivity values vary in the range usually observed for partially doped polyaniline.

In this work, alternative heterojunction devices to be used for gamma-radiation detection are presented. The high quality silicon/polyaniline heterostructures use polyaniline thin films as an active part of the device structure. Polyaniline thin films 40 nm thick were deposited onto silicon substrates (n-type, <100>, 1 ohm x cm) using the spin-coating technique from soluble polyaniline. The devices present excellent electrical characteristics, with a rectification ratio of 60,000 at +/- 1.0 V, reverse currents in the order of a few nA and ideality factor approximately 2. These electrical characteristics indicate great potential for their use in sensor applications. The heterojunction diode is very sensitive to gamma radiation in the dose range of 0-7000 Gy, presenting a linear response in the forward and reverse bias. The excellent electrical characteristics, together with the linear response with the dose strongly suggest the application of this device for spectrometry or dosimetry of low and high doses of gamma ray radiation.

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In this work, we address modal parameter fluctuations in statistical distributions describing charge-to-breakdown (QBD) and/or time-to-breakdown (tBD) during the dielectric breakdown regime of ultra-thin oxides, which are of high interest for the advancement of electronic technology. We reobtain a generalized Weibull distribution (q-Weibull), which properly describes (tBD) data when oxide thickness fluctuations are present, in order to improve reliability assessment of ultra-thin oxides by time-to-breakdown (tBD) extrapolation and area scaling. The incorporation of fluctuations allows a physical interpretation of the q-Weibull distribution in connection with the Tsallis statistics. In support to our results, we analyze tBD data of SiO2-based MOS devices obtained experimentally and theoretically through a percolation model, demonstrating an advantageous description of the dielectric breakdown by the q-Weibull distribution.

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We report a new method to form reproducible luminescent porous silicon layers in p-type and n-type substrates of low and high resisivity, with minimum apparatus and maximum simplicity. No equipment, formation of electrical contacts, illumination or addition of surfactants is needed. The porous silicon layer is formed by exposing the Si surface to the vapor generated by a dissolution reaction of a metal or Si in a HF/HNO 3 mixture. The PL spectra of the layers have peaks located from 1.85 eV to 2.1 eV. The currentvoltage characteristics of Al/PS/p-Si/Al devices formed on these layers are rectifying and follow an exponential dependence at low forward bias and a power law at high forward bias. ity. We have found that this technique yields uniform and reproducible PS layers with S-band (red, orange) photoluminescence (PL). We will present the method and a basic study of the morphology, electrical and photoluminescence properties of the formed layers.