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A broadband antireflective nanostructure with Ag nanoparticles on SiO2 nanocolumns has been presented. Ag nanoparticles are located at the top of SiO2 nanocolumns which are deposited on Si substrates. SiO2 nanocolumns are fabricated by oblique angle deposition through electron beam evaporation, and Ag nanoparticles are fabricated by thermal evaporation. Experimental results show that the average reflection can reach 3.84% in the range of 400–700 nm and 5.75% in the range of 400–1100 nm, much lower than that of Ag islands on SiO2 thin films. The simulation shows that the broadband low reflection can be attributed to the localized surface plasmon resonance of Ag nanoparticles whose resonance wavelengths depends on the size of Ag nanoparticles. The different diameters of SiO2 nanocolumns determine the size distribution of Ag nanoparticles which resonate in a wide wavelength range and lead to a broadband low reflection. This provides a possible way to fabricate a broadband antireflection structure.

Field electron emission behavior of individual multiwalled carbon nanotubes (MWNTs), that are elements of a vertically aligned array grown on a Si wafer, were analyzed with a scanning anode field emission microscope. The electron emission of each MWNT followed the conventional Fowler–Nordheim field emission mechanism after their apexes were freed from the erratic adsorption species using a conditioning process at room temperature. The conditioning process led to stable emission currents and reduced their variations ΔI/I to less than 30% between different MWNTs of the array. This opens the possibility for using MWNTs in an array as independent electron sources for massively parallel microguns.

We compare the field emission characteristics of dense (109 nanofibers/cm2), sparse (107 nanofibers/cm2), and patterned arrays (106 nanofibers/cm2) of vertically aligned carbon nanofibers on silicon substrates. The carbon nanofibers were prepared using plasma-enhanced chemical vapor deposition of acetylene and ammonia gases in the presence of a nickel catalyst. We demonstrate how the density of carbon nanofibers can be varied by reducing the deposition yield through nickel interaction with a diffusion layer or by direct lithographic patterning of the nickel catalyst to precisely position each nanofiber. The patterned array of individual vertically aligned nanofibers had the most desirable field emission characteristics, highest apparent field enhancement factor, and emission site density.

In order to utilize the unique properties of carbon nanotubes in microelectronic devices, it is necessary to develop a technology which enables high yield, uniform, and preferential growth of perfectly aligned nanotubes. We demonstrate such a technology by using plasma-enhanced chemical-vapor deposition (PECVD) of carbon nanotubes. By patterning the nickel catalyst, we have deposited uniform arrays of nanotubes and single free-standing aligned nanotubes at precise locations. In the PECVD process, however, detrimental amorphous carbon (a-C) is also deposited over regions of the substrate surface where the catalyst is absent. Here, we show, using depth-resolved Auger electron spectroscopy, that by employing a suitable deposition (acetylene, C2H2) to etching (ammonia, NH3) gas ratio, it is possible to obtain nanotube growth without the presence of a-C on the substrate surface.

The microgun is a combination of a nanotip and a microlens which is composed of two planar micron-size bore electrodes and a coplanar four-pole deflector microfabricated on the same Si chip. The focusing and deflection characteristics of the microgun, working as an immersion lens at 100 V, have been studied both experimentally and by numerical simulations. Results show unique electron optics properties due mainly to the coherence of the electron beam emitted from the nanotip and to the noninteraction of the incident electrons with the different microelectrodes. The focus spot can reach nanometric dimensions with minimum aberrations and a deflection amplitude of ∼2.5 mrad/V.

Modifications of noise performances induced by hot-carrier degradation in polycrystalline silicon thin-film transistors, made by excimer laser crystallization, are presented. In particular, the normalized drain current spectral density of these devices shows an evident 1/f behavior, and as the device characteristics are degraded by prolonged bias stressing, the noise performances worsen. Hot-carrier degradation results in the formation of both interface states, that have been evaluated through the analysis of the sheet conductance, as well as of oxide traps near the insulator/semiconductor interface, as evidenced by the 1/f noise measurements. A strong correlation between interface state and oxide trap densities has been found, suggesting a common origin for the generation mechanism of the two types of defects.

A systematic study of the noise performances of polycrystalline silicon (polysilicon) thin-film transistors (TFTs) made by excimer laser crystallization is presented. The drain current spectral density of these devices shows an evident 1/f behavior and the origin of the noise was attributed to carrier number fluctuations. The flat-band voltage spectral density was found to be strongly correlated with the field-effect mobility, suggesting that the microscopic mechanism causing the carrier number fluctuations involves the localized states present at the grain boundaries. The noise level in the devices with the best electrical characteristics is comparable with that observed in c-Si metal–oxide–semiconductor field effect transistors, a major improvement if compared to polysilicon TFTs made by solid-phase crystallization.

Conformal growth is a confined epitaxial lateral overgrowth technique previously used to achieve low dislocation density GaAs films on Si. Conformal growth was used here to obtain high quality InP films on silicon, starting from GaAs seeds. Detailed characterization of the InP films (chemical etching of dislocations, photoluminescence at 300 K, cross‐section transmission electron microscopy) proved the high defect filtering power of this technique. Dislocations initially present in the GaAs seeds and dislocations generated at the InP/GaAs interface were blocked and did not propagate through the growing films. Dislocations densities below 5×105 cm−2 have been obtained in submicrometer‐thick conformal InP films on Si.

A systematic study of the noise performances of polycrystalline silicon thin film transistors is presented. The drain current spectral density of these devices shows an evident 1/ f behavior and scales, when operating in the linear regime, with the square of the mean value of the drain current. The origin of the noise can be ascribed to carrier number fluctuations related to the dynamic trapping and detrapping of the oxide traps.

By using selective epitaxy, submicron‐thick (100) GaAs films can be conformally grown between two sandwiching dielectric layers. The defect structure of such GaAs films is investigated using chemical etching and transmission electron microscopy. The conformally grown films exhibit specular surfaces and appear virtually free from defects. A qualitative model for defect trapping is presented which suggests that the dislocations are blocked on the capping dielectric layer when they should thread laterally.

A vertically aligned carbon nanotube mesh emitter array has been fabricated and tested, giving a current density of up to 1.5 A/cm2, and a threshold field of 1.5 V/μm for a current density 1 mA/cm2. Low temperature carbon nanotube growth is used to fabricate the carbon nanotube mesh emitter arrays significantly reducing the cost of the fabrication of large area electron emitters. This system exhibits ultralong lifetime.

International audience; A versatile chemical vapor deposition (CVD) based method for the fabrication and electrical measurement of individual carbon nanotube junctions was developed. ferritin or Fe particles were grafted on multiwalled carbon nanotubes (MWNTs) and used as catalysts for the subsequent growth of secondary MWNT by CVD. Junctions were then individually connected. The conductivities of the MWNTs and of the junction were measured. Statistical data show that the conductance of the MWNT-MWNT junction is similar to that of MWNT. This result paves the way for the use of carbon nanotubes as electrical interconnects in electronic applications.

Electronic transport properties of silicon nanowires grown by chemical vapor deposition, embedded in an insulating alumina nanoporous membrane are studied. Transport measurements were performed from 300to4.2K, which revealed a scaling law of the conductance as a function of the temperature and the dc bias voltage, which the authors interpreted as a Coulomb blockade manifestation. Magnetoconductive measurements at low temperature revealed a positive magnetoconductance which can be well fitted by quasi-one-dimensional (quasi-1D) weak localization theory. These results seem to indicate that electron-electron interactions and quasi-1D effect predominate on the electronic transport properties of these systems.

A novel technique of shaped crystal growth from the vapor is presented, which we call conformal vapor phase epitaxy. Using selective epitaxy as a main ingredient, we have obtained a conformal Si single‐crystal growth between two SiO2 films. Since vertical growth is physically impeded by a SiO2 cap, lateral to vertical growth ratios (overgrowth ratios) can be controlled at will. Using a standard chemical vapor deposition reactor, submicron thick (100)Si layers have been laterally grown with a totally controlled overgrowth ratio >20.