1,721,138 research outputs found
Gold nanotubes by template-directed synthesis
No full textGold nanotubes were prepared by radiofrequency-sputtering through a template-directed synthesis
in porous alumina substrates. The resulting composite material was subsequently treated in acidic
or alkaline aqueous solutions in order to selectively remove the membrane, thus resulting in the
obtainment of self-supporting Au nanotubules. The adopted strategy allows the preparation of both
composites and free-standing metal nanostructures with an aspect ratio tunable as a function of
the synthesis conditions and the membrane pore size
CVD Cu2O and CuO nanosystems characterized by XPS
No full textIn the present investigation, X-ray photoelectron and X-ray excited Auger electron spectroscopy
analyses of the principal core levels (O 1s, Cu 2p, and Cu LMM) of Cu2O and CuO nanosystems
are proposed. The samples were obtained by chemical vapor deposition starting from a novel
second-generation copper(II) precursor, Cu(hfa)2·TMEDA (hfa1,1,1,5,5,5-hexafluoro-
2,4-pentanedionate; TMEDA=N,N,N’,N’- tetramethylethylenediamine), under a dry O2
atmosphere. The obtained route led to pure, homogeneous and single-phase Cu(I) and Cu(II) oxide
nanosystems at temperatures of 300 and 500 °C, respectively, whose chemical nature could be
conveniently distinguished by analyzing the Cu 2p band shape and position, as well as by evaluating
the Auger parameters. The samples were characterized by O/Cu atomic ratios greater than the
expected stoichiometric values, due to marked interactions with the outer atmosphere attributed to
their high surface-to-volume ratio
Special Issue on 'CVD and Hydrogen'
No full textThis Special Issue has
tried to cover various key aspects in the
field of ‘CVD and hydrogen’, drawing
together both experimental and theoretical
viewpoints. The present research
activities are likely to fuel further
advances in hydrogen production, utilization,
and detection by using supported
films and nanomaterials with
specific features. In addition, it is hoped
that these articles will also pave the way
to further advanced applications of
CVD-related techniques in ‘CVD and
hydrogen’ fields, regarding, in particular,
low-temperature growth in plasmaassisted
routes, still scarcely present in
the depicted scenario
Au/SiO2 nanosystems by XPS
No full textAu/SiO2 nanocomposites were prepared by rf-sputtering of gold on amorphous silica substrates.
Deposition experiments were carried out in Ar plasmas at temperatures as low as 60 °C. Particular
attention was devoted to the combined influence of the applied rf power and total pressure on the
chemico-physical properties of the final nanosystems. In particular, low pressures (<0.2 mbar) and
high rf powers (>20 W) resulted in a higher sputtering yield, allowing the deposition of continuous
gold films on silica. Conversely, decreased sputtering yields (at higher pressures and lower powers)
enabled the preparation of discontinuous Au/SiO2 nanosystems. A thorough investigation of the
structure-properties relationships was attained by means of a multi-technique characterization. In
particular, laser reflection interferometry (LRI) was employed for an in situ monitoring of growth
processes, while glancing-incidence x-ray diffraction (GIXRD) and transmission electron
microscopy (TEM) provided valuable information on the system nanostructure. Moreover, x-ray
photoelectron spectroscopy (XPS), UV-Vis spectroscopy, and atomic force microscopy (AFM) were
used to investigate the chemical composition, optical properties, and surface morphology,
respectively. This study is dedicated to an XPS investigation of the principal core levels (Au, Si, O)
of Au/SiO2 nanosystems. In particular, detailed scans for the Au 4f, Si 2s, O 1s, and C 1s regions
and related data for a gold film on silica and a discontinuous Au/SiO2 specimen are presented and
discussed
Cerium(III) fluoride thin films by XPS
No full textNanocrystalline cerium fluoride thin films were synthesized by chemical vapor deposition (CVD)
using Ce(hfa)3*diglyme (hfa=1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; diglyme=bis
(2-metoxyethyl)ether) as precursor compound on Si(100) under N2+O2 atmosphere. The obtained
samples were analyzed by glancing-incidence x-ray diffraction (GIXRD), x-ray photoelectron
spectroscopy (XPS), and scanning electron microscopy (SEM), for a thorough characterization of
their microstructure, chemical composition, and morphology. This work is specifically dedicated to
the XPS characterization of a representative CeF3 thin film deposited at 350 °C. Besides the wide
scan spectrum, detailed spectra for the Ce 3d, F 1s, O 1s, and C 1s regions and related data are
presented and discussed. Both the F/Ce atomic ratio and Ce 3d peak shape and position point out
to the formation of CeF3 films, in agreement with the structural characterization. Moreover, carbon
contamination is merely limited to the outermost sample layers
Nanostructured cadmium sulphide thin films by XPS
No full textNanostructured cadmium sulfide thin films were deposited on SiO2 by a cold-wall low-pressure
CVD reaction system starting from the single-source precursor Cd(O-iPrXan)2 [O-iPrXan = S2COCH(CH3)2]. Deposition experiments were carried out in an inert nitrogen atmosphere in
optimized pressure/gas flow conditions. The obtained films were analyzed by x-ray diffraction
(XRD), x-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) for a detailed
determination of their microstructure, chemical composition, and surface morphology, while UV-Vis
measurements were carried out in order to investigate their optical properties. Irrespective of the
preparative conditions, all the films displayed the typical absorption spectrum of CdS, with an
energy gap value Eg = 2.5 eV. AFM analyses showed that flat, uniform, and crack-free layers were
obtained under all the adopted synthetic conditions. This result is of interest in view of potential
applications in optoelectronic devices like solar cells, where a smooth and regular morphology is
required. In this work, XPS analyses of a representative CdS thin film deposited at 400 °C are
presented. Besides the wide scan spectrum, charge corrected binding energies for the Cd 3d5/2, Cd
3d3/2, Cd MNN, S 2p3/2, S 2p1/2, O ls, and C 1s surface photoelectron signals are reported and
discussed
A soft Plasma Enhanced-Chemical Vapor Deposition process for the tailored synthesis of SiO2 films
No full textThe availability of soft synthetic processes for the preparation of SiO2 films with tailored features plays a key role for several technological
applications, from optics to electronics, from surface modifications to barrier coatings. In such context, this work presents the development and
optimization of a Plasma Enhanced-Chemical Vapor Deposition route towards high-purity SiO2 films at near room temperature. Depositions were
performed from Ar and Ar–O2 plasmas using tetramethoxysilane as precursor, devoting particular attention to the interplay between film properties and
process parameters (RF- (Radio Frequency-) power, total pressure,O2/(Ar+O2) ratio and precursor vaporization temperature). Real-time information on
the growth process was gained by Laser Reflection Interferometry, while the chemical composition and bonding structure of the obtained layers were
analyzed by Fourier Transform Infrared Spectroscopy and X-ray Photoelectron Spectroscopy. Scanning Electron and Atomic Force Microscopies were
adopted to analyze the surface and cross-sectional filmmorphology. The systemstructural and optical properties were investigated by means of Glancing
Incidence X-Ray Diffraction and UV–Vis spectroscopy. Finally, nanoindentation measurements were performed to investigate film hardness. Under
optimized conditions, very pure silica films, characterized by a remarkable optical transparency and favorable mechanical properties, were obtained even
at RF-power values as low as 5 W and in the absence of O2 in the plasma
Synthesis of gold nanotubes by sputtering of gold into porous materials
No full textHollow 1-D gold nanostructures with controlled morphology could be readily obtained by RFsputtering
of gold into porous matrices (polycarbonate, polyester), used as scaffolds at low temperatures.
Post-synthesis membrane etching by oxygen plasmas or in solution enabled the preparation
of free-standing Au nanotubes maintaining the original morphology, that are attractive elements in
device structures, such as biosensors for DNA chips or nanoelectrode ensembles. The present
results appear extremely promising for the scale-up of different kinds of 1-D materials
Toward the Innovative Synthesis of Columnar CeO2 Nanostructures
No full textWe report on the preparation of supported columnar CeO2 nanostructures by a simple catalyst-free chemical vapor
deposition process at temperatures as low as 623 K. A suitable choice of experimental parameters enables us to control the structural and morphological features of the resulting ceria nanosystems
Structure and Optical Properties of Silica-Supported Ag-Au Nanoparticles
No full textBimetallic Ag-Au nanoparticles are synthesized by sequential deposition of Au and Ag on amorphous silica by Radio Frequency (RF)-sputtering under mild conditions. Specimens are thoroughly characterized by a multi-technique approach, aimed at investigating the system properties as a function of the Ag/Au content, as well as the evolution induced by ex-situ annealing under inert (N2) or reducing (4% H2/N2) atmospheres. The obtained results demonstrate the possibility to obtain Ag-Au alloyed nanoparticles with controllable size, shape, structure and dispersion under mild conditions, so that the optical properties can be finely tuned as a function of the synthesis and thermal treatment conditions
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