No abstract

No abstract

Polymeric thin films have been awakening continuous and growing interest for application in nanotechnology. For such applications, the assessment of their (nano)mechanical properties is a key issue, since they may dramatically vary between the bulk and the thin film state, even for the same polymer. Therefore, techniques are required for the in situ characterization of mechanical properties of thin films that must be nondestructive or only minimally destructive. Also, they must also be able to probe nanometer-thick ultrathin films and layers and capable of imaging the mechanical properties of the sample with nanometer lateral resolution, since, for instance, at these scales blends or copolymers are not uniform, their phases being separated. Atomic force microscopy (AFM) has been proposed as a tool for the development of a number of techniques that match such requirements. In this review, we describe the state of the art of the main AFM-based methods for qualitative and quantitative single-point measurements and imaging of mechanical properties of polymeric thin films, illustrating their specific merits and limitations.

No abstract

No abstract

The aim of this review is to highlight the recent advances and the main remaining challenges related to the issue of electron field emission (FE) from nanodiamonds. The roadmap for FE vacuum microelectronic devices envisages that nanodiamonds could become very important in a short time. The intrinsic properties of the nanodiamond materials indeed meet many of the requirements of cutting-edge technologies and further benefits can be obtained by tailored improvements of processing methodologies. The current strategies used to modulate the morphological and structural features of diamond to produce highly performing emitting systems are reported and discussed. The focus is on the current understanding of the FE process from nanodiamond-based materials and on the major concepts used to improve their performance. A short survey of non-conventional microsized cold cathodes based on nanodiamonds is also reported. IntroductionMiniaturized electron sources based on the field emission (FE) process, namely "cold-cathodes", are nowadays replacing the conventional thermoionic electron sources. FE-based devices are able to operate at high frequency and at high current densities, have no need of heating and are characterized by reduced weight and by instantaneous switching on. Moreover, Maria Letizia TerranovaProfessor of Chemistry at Tor Vergata University of Rome (Italy), Maria Letizia Terranova heads the Minima lab at the Department of Chemical Science and Technology. She has expertise on different scientific topics, including nuclear chemistry, laser-induced reactions in the gas-phase, ion-and laserinduced modifications in solids, electrochemical and vapour deposition processes. Her research activity is mainly focused on the synthesis, processing and functional testing of nanomaterials: carbon nanostructures (nanodiamonds, nanotubes, graphenes, onions), nanocomposites and hybrid organic/ inorganic structures. Materials and systems are produced for applications in micro/nano-electronics, optoelectronics, energetics, sensing, thermal management and bio-related nanotechnologies. She has co-authored 290 papers, 4 patents, and co-edited 4 books. Silvia OrlanducciIn 2004 Fowler-Nordheim and the experiments by Spindt and coworkers 3 paved the way for a number of subsequent researches on FE-based vacuum electronics. The good performance of such devices is based on the fact that, according to the Fowler-Nordheim law, the emitted current density J depends strongly on the local applied electric field E and that geometric factors typical of nanostructures (sharp edges, tips, peaks, nanoprotrusions) locally increase the concentration of electric field at the emitter sites. The ratio of the local field to the applied field, the so-called electric field enhancement factor β, 1 independently of the material, is a key factor influencing the field emission characteristics. In the last two decades the design, realization and application of a new generation of cold cathodes based on advanced nanomaterials have been the object of tremendous i...

We report a new class of nanostructured carbon materials, which couple nanosized diamond with single-walled carbon nanotubes. This exciting material is being produced in our laboratories in a modified CVD reactor by means of reactions between carbon nanopowders and atomic H. Field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, and reflection high-energy electron diffraction (RHEED) have been used to study samples grown for various deposition times. The information achieved by combined use of these characterization techniques has enabled the construction of a time-growth sequence for the two carbon nanophases and has enlightened the peculiar growth of such hybrid carbon systems. The tubular inner structures are found to be bundles of single-walled carbon nanotubes (SWNT) up to 15 μm long, and the outer deposits consist of well-shaped diamond crystallites with diameters in the 20−100 nm range. The one-step synthesis approach described here provides an experimental route to the production of ordered arrays of rigid nanotubes coated by diamond nanocrystallites.

No abstract