Biomedical subjects

Carlo Carraro

Publications and source records attributed to Carlo Carraro.

7 recordsLinked to original sources

PubMed2006

Resolving radial composition gradients in polarized confocal raman spectra of individual 3C-SiC nanowires.

Silicon carbide nanowires are being actively pursued as components for nanoelectromechanical sensors, nanocatalytic elements, and nano-optical circuits able to operate in harsh environment, high temperature, and high power applications. The effect of geometric confinement and polarization anisotropy in confocal Raman spectroscopy has been employed to detect axial and radial composition information in individual nanowires. Polarization anisotropy causes a significant increase in signal from the surface layer (relative to bulk), and combined with the increased surface-to-volume ratio at the nanoscale, it allows for the direct characterization of bulk and surface defects.

Journal Article↗

PubMed2006

Thermal behavior of perfluoroalkylsiloxane monolayers on the oxidized Si(100) surface.

The thermal stability of perfluoralkylsiloxane monolayers in a vacuum is investigated via X-ray photoelectron spectroscopy (XPS) for temperatures up to 600 degrees C. 1H,1H,2H,2H,-perfluorodecyltrichlorosilane (FDTS) monolayers are deposited on oxidized Si(100) surfaces from the vapor phase with various degrees of surface coverage. Significant monolayer desorption is observed to occur at temperatures below 300 degrees C regardless of the initial monolayer coverage. The desorption mechanism follows first-order kinetics and is independent of the initial coverage. Removal of FDTS is found to occur by the loss of the entire molecular chain, as evidenced by the fact that the CF(3)/CF(2) peak area ratios remain unaffected by the annealing process although CF(n)()/Si peak ratio declines with annealing. This is in sharp contrast to the behavior observed for octadecyltrichlorosilane monolayer for which elevated temperature leads to C-C bond breakage and successive shortening of the alkyl chain. It is also shown that the binding energy and the shape of the F 1s line are good indicators of the degree of disorder in the chain, as well as a measure of the interaction of the chain with the silicon surface.

Journal Article↗

PubMed2005

Selective growth of Si nanowire arrays via galvanic displacement processes in water-in-oil microemulsions.

Galvanic displacement processes are employed in water-in-oil microemulsions to deposit gold nanoclusters selectively on Si surfaces and sidewalls. The gold clusters then serve as catalysts to achieve selective growth of vertically and laterally aligned Si nanowire arrays by chemical vapor deposition via the vapor-liquid-solid growth mechanism. The size of the gold clusters is shown to have a good correlation with the microemulsion parameters, which in turn controls the size of the synthesized nanowires.

Journal Article↗

PubMed2004

Chemical and thermal stability of alkanethiol and sulfur passivated InP(100).

InP(100) surfaces treated with Na2Sx9H20 and CnH(2n+1)SH are examined by contact angle measurement, X-ray photoelectron spectroscopy, and atomic force microscopy to determine the chemical and thermal behavior of these passivated surfaces. The surfaces coated by octadecanethiol (n = 18) self-assembled monolayers (SAMs) are found to be more stable toward oxidation than the S-passivated surface. The chemical stability of octadecanethiol SAMs in various environments is examined. The thiol monolayer is found to be stable in 0.1 M HCl but degrades in 0.1 M NaOH, boiling chloroform, and water. The behavior of these surfaces at elevated temperatures under a vacuum is also investigated. The octadecanethiol-coated InP(100) is stable up to 473 K, above which the films begin to degrade. Unlike other substrates on which the entire molecule including the sulfur headgroup desorbs together, on InP, the sulfur headgroup remains on the surface even after annealing to 673 K. These observations suggest that the desorption occurs by S-C bond cleavage as well as In-S bond cleavage. The sulfur of S-passivated InP is found to be more thermally stable than that of the octadecanethiol monolayer, perhaps due to their different bonding geometries and hence energies.

Journal Article↗

PubMed2004

Surface chemistry and tribology of MEMS.

The microscopic length scale and high surface-to-volume ratio, characteristic of microelectro-mechanical systems (MEMS), dictate that surface properties are of paramount importance. This review deals with the effects of surface chemical treatments on tribological properties (adhesion, friction, and wear) of MEMS devices. After a brief review of materials and processes that are utilized in MEMS technology, the relevant tribological and chemical issues are discussed. Various MEMS microinstruments are discussed, which are commonly employed to perform adhesion, friction, and wear measurements. The effects of different surface treatments on the reported tribological properties are discussed.

Biocompatible Materials↗

PubMed2003

Continuous freezing in an infinite-range one-dimensional model.

The partition function of the classical one-dimensional hard rod fluid with a residual long range interaction can be evaluated exactly, with the aid of an auxiliary field, in the limit where the range of the potential goes to infinity. If the Fourier spectrum of the residual interaction lacks components at finite wave vector, the infinite range limit recovers the celebrated result of the Kac-Uhlenbeck-Hemmer model of condensation. Otherwise, it predicts a continuous second-order freezing transition.

Journal Article↗

PubMed2002

Existence and nature of a freezing transition inside three-dimensional arrays of narrow channels.

The density functional for matter confined inside a three-dimensional array of narrow channels is constructed. It is shown that the effect of long range interactions amounts to a three-dimensional quadratic perturbation on an array of one-dimensional hard rods. Hence, it follows that the recently proposed freezing transition of atoms confined in nanotube arrays is continuous. This conclusion is validated beyond mean field theory by Monte Carlo simulations in the NPT ensemble.

Journal Article↗