We have explored the influence of deposition pressure and temperature on the growth of BiFeO 3 thin films by pulsed laser deposition onto (001)-oriented SrTiO 3 substrates. Singlephase BiFeO 3 films are obtained in a region close to 10 -2 mbar and 580°C. In non-optimal conditions, X-ray diffraction reveals the presence of Fe oxides or of Bi 2 O 3 . We address the influence of these parasitic phases on the magnetic and electrical properties of the films and show that films with Fe 2 O 3 systematically exhibit a ferromagnetic behaviour, while singlephase films have a low bulk-like magnetic moment. Conductive-tip atomic force microscopy mappings also indicate that Bi 2 O 3 conductive outgrowths create shortcuts through the BiFeO 3 films, thus preventing their practical use as ferroelectric elements in functional heterostructures.

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.

We compare the field emission characteristics of dense (10 9 nanofibers/cm 2 ), sparse (10 7 nanofibers/cm 2 ), and patterned arrays (10 6 nanofibers/cm 2 ) 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.

It has been claimed that graphene growth on copper by chemical vapor deposition is dominated by crystallization from the surface initially supersaturated with carbon adatoms, which implies that the growth is independent of hydrocarbon addition after the nucleation phase. Here, we present an alternative growth model based on our observations that oppose this claim. Our Gompertzian sigmoidal growth kinetics and secondary nucleation behavior support the postulate that the growth can be controlled by adsorption-desorption dynamics and the dispersive kinetic processes of catalytic dissociation and dehydrogenation of carbon precursors on copper.

This work reports enhanced thermoelectric properties of transparent thin films. The influence of the composition, thickness and deposition method has been studied, reaching a ZT > 0.1 at room temperature.