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Some crucial aspects of the functionalisation of carbon nanotubes by nitric acid vapors are investigated, namely selectivity of the process and thermal stability in air of the functionalised materials. Results obtained by varying duration (0.5–5.0 h) of the conventional treatment with vapors at azeotropic HNO3concentration are compared with those obtained, for fixed duration (2.0 h), by using sub-azeotropic HNO3+H2O+Mg(NO3)2solution to generate acid vapors with acid concentration in the range 25–93 wt%, as recently proposed by us. A thorough picture is drawn based on evidences of high-resolution transmission electron microscopy, micro Raman spectroscopy, thermo-gravimetry, derivative thermo-gravimetry, and temperature-programmed desorption systematic analyses. [ABSTRACT FROM AUTHOR]

Due to its exceptional physical properties, synthetic diamond is an ideal material for the realization of UV and X-ray detectors to be used for the characterization of laser-generated plasmas. Diamond detectors are able to operate at high temperatures and in the presence of high fluxes of ionizing radiation, where traditional silicon-based detectors usually fail. In this paper, we report on Raman and electro-optical characterization of a structure consisting of intrinsic diamond/boron-doped diamond homoepitaxially grown by chemical vapor deposition onto a commercial high pressure high temperature Ib-type diamond substrate using a 1% CH4/H2 gas mixture. A metal-insulator-semiconductor (MIS) diode was obtained by thermally evaporating an aluminum contact on the growth surface of the intrinsic layer. The detection capability of this device operating in transverse configuration was measured in the deep UV spectral range. The device sensitivity has been estimated at different biasing voltages and at two wavelengths having different penetration depths into the material. The device was also tested at zero biasing voltage (photovoltaic mode operation), showing quite a good photoresponse. These results suggest that MIS structures based on high-quality homoepitaxial diamonds may be successfully utilized for photodetection even at zero bias. [ABSTRACT FROM AUTHOR]

Silicon carbide and silicon carbon nitride thin films were grown by pulsed laser ablation of SiC targets in vacuum or in the presence of a controlled N2 atmosphere. The influence of the substrate temperature and of the N2 partial pressure on the optical and structural properties of the samples were investigated by means of Fourier transform infrared (FTIR), Raman, X-ray photoelectron and ellipsometric spectroscopies. Samples deposited in vacuum showed a nearly 1:1 stoichiometry, thus preserving the target composition. In vacuum, by increasing the substrate temperature, a better crystalline quality of the films was observed from both FTIR and Raman spectroscopy. A nitrogen content up to about 20.8% was achieved performing the deposition process in the presence of an N2 atmosphere of 54 Pa. A widening of the optical band gap as a function of the nitrogen content was observed, together with a progressive decrease in the absorption coefficient and in the index of refraction values. [ABSTRACT FROM AUTHOR]