The absence of simple examples of superconductivity adjoining itinerant-electron ferromagnetism in the phase diagram has for many years cast doubt on the validity of conventional models of magnetically mediated superconductivity. On closer examination, however, very few systems have been studied in the extreme conditions of purity, proximity to the ferromagnetic state and very low temperatures required to test the theory definitively. Here we report the observation of superconductivity on the border of ferromagnetism in a pure system, UGe2, which is known to be qualitatively similar to the classic d-electron ferromagnets. The superconductivity that we observe below 1 K, in a limited pressure range on the border of ferromagnetism, seems to arise from the same electrons that produce band magnetism. In this case, superconductivity is most naturally understood in terms of magnetic as opposed to lattice interactions, and by a spin-triplet rather than the spin-singlet pairing normally associated with nearly antiferromagnetic metals.

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High purity samples of the paramagnetic 4f-electron metal CeNi 2 Ge 2 exhibit a non-Fermi-liquid form of the resistivity ρ ∼ T x with x < 1.5 and decreasing towards 1 with increasing sample purity. Measurements of ρ versus T as a function of magnetic field and pressure show that this strange metallic phase is connected to the proximity of an antiferromagnetic quantum critical point as in the isoelectronic relative CePd 2 Si 2 near 2.8 GPa. The anomalous power-law dependence is surprisingly stable over extended ranges in temperature and pressure and challenges current theory of magnetic quantum phase transitions.

The visualization of the space–charge region in nanowire pn junctions (see image) is presented by far‐field optical microscopy. This general approach is a powerful tool for estimates of the carrier distributions and device capacitances. For the case of an n‐CdS/p+‐Si heterojunction we show that the carrier depletion widths in nanowires deviate from the traditional square‐root dependence purely due to electrostatic effects.

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We study the breakdown behavior of thin, abrupt silicon pin-diodes, using a low-power optical technique which can directly measure the avalanche multiplication factors even in the presence of large tunneling currents. Our measurements agree with a simple model for nonlocal avalanche generation, and we use this model to extend the breakdown predictions to a broad class of doped diodes similar to those found in the base-collector region of bipolar devices. Based on this analysis, we make quantitative estimates for the BV CEO breakdown of modern Si and SiGe high-speed bipolar transistors.

We demonstrate highly reproducible silicon nanowire diodes fabricated with a fully VLSI compatible etching technology, with diameters down to 30 nm. A contact technology based on recrystallized polysilicon enables specific contact resistances as low as rho approximately 10-7 Omega cm2. Our devices show a strongly diameter-dependent breakdown voltage at reverse bias, which we explain in terms of the influence of the surrounding dielectric. We suggest that this technology is suitable for incorporating nanowire-based functionalities into future integrated circuits.