Metallic contamination was key to the discovery of semiconductor nanowires, but today it stands in the way of their adoption by the semiconductor industry. This is because many of the metallic catalysts required for nanowire growth are not compatible with standard CMOS (complementary metal oxide semiconductor) fabrication processes. Nanowire synthesis with those metals which are CMOS compatible, such as aluminium and copper, necessitate temperatures higher than 450 C, which is the maximum temperature allowed in CMOS processing. Here, we demonstrate that the synthesis temperature of silicon nanowires using copper based catalysts is limited by catalyst preparation. We show that the appropriate catalyst can be produced by chemical means at temperatures as low as 400 C. This is achieved by oxidizing the catalyst precursor, contradicting the accepted wisdom that oxygen prevents metal-catalyzed nanowire growth. By simultaneously solving material compatibility and temperature issues, this catalyst synthesis could represent an important step towards real-world applications of semiconductor nanowires.Comment: Supplementary video can be downloaded on Nature Nanotechnology websit

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The presence of gold on the sidewall of a tapered, single silicon nanowire is directly quantified from core-level nanospectra using energy-filtered photoelectron emission microscopy. The uniform island-type partial coverage of gold determined as 0.42+/-0.06 (approximately 1.8 ML) is in quantitative agreement with the diameter reduction of the gold catalyst observed by scanning electron microscopy and is confirmed by a splitting of the photothresholds collected from the sidewall, from which characteristic local work functions are extracted using a model of the full secondary electron distributions.

A theoretical analysis based on a perturbation method is used to elucidate the results of attenuated total reflection (ATR) measurements performed on silicon oxide layers of different thicknesses on silicon substrates. This analysis shows that the absorbance ATR spectrum in p polarization is the image of the layer energy loss function, under specific conditions. It is pointed out that the enhanced sensitivity of ATR is controlled by the air gap thickness, the optical properties of the media involved, and the probing light polarization. An exact ATR spectrum simulation using a matrix formalism showed that straightforward interpretation in terms of the layer dielectric function is limited to a very narrow layer thickness range. The ATR spectrum fitting process is considered for layers out of this range and evaluated for the interpretation of experimental silicon oxide layer spectra.

To fabricate and qualify nanodevices, characterization tools must be developed to provide a large panel of information over spatial scales spanning from the millimeter down to the nanometer. Synchrotron x-ray-based tomography techniques are getting increasing interest since they can provide fully three-dimensional (3D) images of morphology, elemental distribution, and crystallinity of a sample. Here we show that by combining suitable scanning schemes together with high brilliance x-ray nanobeams, such multispectral 3D volumes can be obtained during a single analysis in a very efficient and nondestructive way. We also show that, unlike other techniques, hard x-ray nanotomography allows reconstructing the elemental distribution over a wide range of atomic number and offers truly depth resolution capabilities. The sensitivity, 3D resolution, and complementarity of our approach make hard x-ray nanotomography an essential characterization tool for a large panel of scientific domains.

For a better understanding of the physical and electronic properties of emissive carbon films, one of the best ways is to compare the results obtained with several surface and structural analysis techniques. In this article, different types of carbon film depositions for developing large flat panel displays by field emission displays are analysed and the results are correlated with their emissivity. Pulse laser ablation films, hightemperature plasma-enhanced chemical vapour deposition (PECVD) films and low-temperature PECVD films are characterized by XPS, Raman spectroscopy, X-ray diffraction (XRD), specular X-ray reflectivity, transmission electron microscopy (TEM) and elastic recoil detection analysis (ERDA). The analyses lead us to conclude that the sp 2 /sp 3 ratio is not a crucial parameter for carbon film emissivity. Crystalline structure seems more important. The presence of graphite grains is essential for good and uniform emission. Combination of XPS, TEM, XRD, Raman spectroscopy and ERDA is necessary for the study of carbon film emission.

The presence of an ultrathin oxide layer at the high-k/SiO2 interface may result in an interfacial dipole related to the specific high-k dielectric used for the gate stacks. 1 nm HfO2/x nmAl2O3/SiO2/Si stacks with different x values (x=0, 0.4, 0.8, 1.2) have been prepared by atomic layer deposition. Using photoelectron spectroscopy, an Al-related interfacial dipole in the HfO2/Al2O3/SiO2 gate stack has been identified. X-ray photoelectron spectroscopy analysis shows that the dipole is correlated with the formation of an interfacial Al-silicate. The dipole is located at the Al-silicate interface between Al2O3 and SiO2, and its strength increases with the increase in Al2O3 thickness because of Al silicate growth. Such Al-related interfacial dipole should have potential applications in future positive metal-oxide-semiconductor devices.

Extending the detection limit of dopants for focused ion beam prepared semiconductor specimens examined by off-axis electron holography