Carbon nanotubes can act as electron sources with very rigid structures, making them particularly interesting for use as point electron sources in high-resolution electron-beam instruments. Promising results have been reported with respect to some important requirements for such applications: a stable emitted current and a long lifetime. Two parameters of an electron source affect the resolution of these instruments: the energy spread of the emitted electrons and a parameter called the reduced brightness, which depends on the angular current density and the virtual source size. Several authors have measured a low energy spread associated with electron emission. Here we measure the reduced brightness, and find a value that is more than a factor of ten larger than provided by state-of-the-art electron sources in electron microscopes. In addition, we show that an individual multi-walled carbon nanotube emits most current into a single narrow beam. On the basis of these results, we expect that carbon nanotube electron sources will lead to a significant improvement in the performance of high-resolution electron-beam instruments.

Individual multiwalled carbon nanotubes were mounted on tungsten support tips in a scanning electron microscope equipped with a nanomanipulator. It was possible to select the diameter of the nanotube to align the nanotube with respect to the tip axis and to tune the contact length of the nanotube and the support tip. We have also developed a way to control the length of the nanotube protruding from the support tip. Control over the nature of the nanotube cap was not obtained.

A continuous SF 6 /O 2 plasma process at room temperature has been used to etch tapered through-silicon vias using a DRIE-ICP tool. These features (10-100 μm in diameter) are aimed for applications in 3D integration and MEMS packaging. The effects of various process parameters such as O 2 flow rate, platen bias, pressure and substrate temperature on the via profile (depth, slope angle and aspect ratio) development are investigated. The etching mechanism was also studied and x-ray photoelectron spectroscopy (XPS) analysis reveals a SiO x passivation layer of the order of ∼2 nm on the via sidewall and a substantial temperature dependence. Both tapering and anisotropy of etching depend on this passivation layer formation. Finally, suitable tapered vias with an aspect ratio of ∼5 and a slope angle of ∼83• are obtained by properly balancing the etching regimes. In this condition, a maximum etch rate of 7 μm min −1 is achieved.

Articles you may be interested inCurrent instabilities in rare-earth oxides-HfO 2 gate stacks grown on germanium based metal-oxidesemiconductor devices due to Maxwell-Wagner instabilities and dielectrics relaxation J. Vac. Sci. Technol. B 29, 01AB06 (2011); 10.1116/1.3532946 Direct tunneling stress-induced leakage current in ultrathin Hf O 2 ∕ Si O 2 gate dielectric stacksThe Maxwell-Wagner effect, the enhanced charge migration to the interface of a stack of two dielectrics with different conductances, is shown to cause asymmetric leakage current and electrical breakdown behavior for different electrode polarities. For this purpose, metal-insulator-silicon capacitors were fabricated consisting of bilayered silicon dioxide-lanthanum zirconate dielectric stacks. Maxwell-Wagner instability and Debye polarization can be distinguished upon comparing electron injection from both sides of the stack. The Maxwell-Wagner charges have relaxation times that are nearly five orders of magnitude larger than the Debye polarization, suggesting the long-lasting influence of these trapped charges in nanolaminated dielectric systems.

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CoFe exchanged-coupled multilayers are studied versus the thickness of the ferromagnetic (F) layer (eF) and the thickness of the antiferromagnetic (AF) layer (eAF). The F layer consists in Co90Fe10, Co50Fe50, and Co35Fe65, respectively. The AF layer is Ni50Mn50. Very high saturation magnetization (4πMs) are reported with 18.5, 23, and 24kG, respectively, combined with excellent soft rotational behaviors. The AF–F–AF multilayers cumulate top and bottom interfacial exchange coupling and show very high effective energy densities (Jex) of 1.01, 0.81, and 0.98ergcm−2, respectively. Jex increases with eAF up to a maximum for eAF⩾500Å. This leads to a strong bias field (Hex) with a classical 1∕eF dependence, which translates into a large uniaxial anisotropy (Hk) at 90° from the pinning direction. Typically, for eF=150Å, Hk is 741, 650, and 642Oe, respectively. However, this translation is rather complex and eF and 1∕eAF dependences of the ratio Hk∕Hex suggest a contribution of an intrinsic CoFe anisotropy. For all CoFe, it is shown that a ferromagnetic resonance frequency (fFMR) of 10GHz is achievable. Co35Fe65 mulilayers exhibit the highest eF×μ′ product, μ′ being very close to the theoretical ultimate permeability. Finally, the soft rotational behavior is shown unchanged over an angular range of ±30° from the pinning direction which is very unusual.

Index Terms-Radio-frequency (RF) characterisation, RF modeling, Si interposer, three-dimensional interconnects, through silicon via, through-wafer interconnect, TSV, vias.

International audienceA 60 GHz cavity-backed antenna array integrated on high-resistivity silicon is demonstrated. The antenna design makes use of Through-Silicon-Vias (TSV), silicon micromachining, and wafer-to-wafer bonding to meet the bandwidth and radiation gain requirements for short-range multi-Gbps communications. The fabrication process is presented. Simulated and experimental results show that the antenna element covers easily the 57–66 GHz standard band with good impedance matching and more than 5 dBi of gain. Several fixed-beam four-element antenna arrays demonstrate the capabilities for beam-steering across a range up to ±60°