33 research outputs found
Multi-component oxide nanosystems by Chemical Vapor Deposition and related routes: challenges and perspectives
No full textMulti-component oxide-based nanosystems are of primary technological importance for various applications of current interest, spanning from optoelectronics to catalysis, from chemical sensing to energy conversion and storage. Such a broad range of functional utilizations results from the joint features of nano-organized systems and the synergistic combination of constituent properties, which, in turn, can be tailored by means of flexible and scalable preparative strategies. An amenable synthetic option potentially meeting these standards is Chemical Vapor Deposition (CVD), either as such or in combination with other fabrication routes. To this regard, the present highlight provides an overview on the CVD-based growth and applicative potential of oxide-based nanocomposite systems. Special attention is devoted to three different categories, i.e. metal/oxide, oxide/oxide and carbon/oxide nanomaterials. For each of them, selected results on synthesis/applications of composite architectures with tailored morphology are presented, trying to address actual challenges and future trends in the field
1-D ZnO nano-assemblies by Plasma-CVD as chemical sensors for flammable and toxic gases
No full textIn this work, 1D ZnO nano-assemblies were prepared on Al2O3 substrates by plasma enhanced-chemical
vapor deposition (PE-CVD), and characterized in their morphology and chemical composition by field
emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDXS) and
X-ray photoelectron spectroscopy (XPS). For the first time, the sensing performances of PE-CVD ZnO
nanosystems were tested in the detection of toxic/combustible gases (CO, H2 and CH4), revealing very
good responses already at moderate working temperatures. In particular, carbon monoxide and hydrogen
detection was possible already at 100 °C, whereas methane sensing required a minimum temperature
of 200 °C. The performances of the present ZnO nanosystems, that make them attractive candidates
for technological applications, are presented and discussed in terms of their unique and controllable
morphological organization
Urchin-like ZnO nanorod arrays for gas sensing applications
No full textZnO nanorod assemblies were grown by plasma-enhanced chemical vapor deposition on polycrystalline Al2O3 at 200–300 °C, resulting in urchin-like 1-D ZnO NR arrays with a strong c-axis orientation. Their outstanding gas sensing responses and very low detection limits highlight the potential of the present systems in the production of high efficiency chemical sensors for a variety of applications
Investigation of niobium nitride and oxy-nitride films grown by MOCVD
No full textNiobium nitride (NbN) and niobium oxy-nitride (NbOxNy) thin films were grown by metalorganic chemical
vapor deposition (MOCVD) on Si(100) and Si(111) substrates using [Nb(NtBu)(NMe2){C(NiPr)2(NMe2)}2]
[NB; tBu=(CH3)3C; Me=CH3; iPr=(CH3)2CH] as a simultaneous Nb and N precursor. While NbN films were
synthesized under a pure N2 atmosphere, NbOxNy films were synthesized under N2–O2 flow (N2:O2=1–5) in
the temperature range 400–600 °C, as well as by NbN deposition followed by ex-situ thermal treatments under
flowing O2 at 400–600 °C. The samples were subjected to a multi-technique characterization in order to elucidate
the interplay between their structure, morphology and composition and the adopted processing parameters.
Particular attentionwas devoted to the presence of Nb–N and Nb–O–N phases and their distribution in the films,
as well as to surface oxidation phenomena. For the first time, niobium oxy-nitride coatings were obtained by CVD
starting from the above precursor compound, with growth rates up to 270 Å/min on Si(111) at 600 °C. The films
were characterized by a columnar-like/globular morphology when supported on Si(100)/Si(111) and revealed a
higher crystallinity on the latter substrate. Surface and in-depth compositional analyses evidenced a limited
carbon contamination and the Co-existence of niobiumnitride, NbON and Nb2O5. In particular, the presence of the
latter in the outermost sample layers was explained by oxidation phenomena occurring upon contact with the
outer atmosphere
MOCVD of niobium nitrides and oxy-nitrides using an all-nitrogen-coordinated precursor: thin-film deposition and mechanistic studies
No full textIn this study, niobium nitride and oxy-nitride thin films were
grown by metalorganic chemical vapor deposition (MOCVD) from the guanidinate based niobium compound
[Nb(NtBu)(NMe2){C(NiPr)2(NMe2)}2] that served either as a
single source precursor (SSP) for NbN or as a niobium and
nitrogen source for the growth of niobium oxy-nitride thin films in oxygen atmospheres. The decomposition of this SSP precursor was studied using NMR and mass spectrometry. From the mechanistic studies, it was evident that diisopropylcarbodiimide deinsertion
takes place at elevated temperatures. Pure niobium nitride films were obtained without any additional source of nitrogen during the MOCVD process, whereas in the presence of oxygen mixed phases of NbNx, NbOxNy and Nb2O5 were formed. The most relevant results are presented and discussed
1D ZnO nano-assemblies by Plasma-CVD as chemical sensors for flammable toxic and gases
No full textIn this work, 1D ZnO nano-assemblies were prepared on Al(2)O(3) substrates by plasma enhanced-chemical vapor deposition (PE-CVD), and characterized in their morphology and chemical composition by field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDXS) and X-ray photoelectron spectroscopy (XPS). For the first time, the sensing performances of PE-CVD ZnO nanosystems were tested in the detection of toxic/combustible gases (CO, H(2) and CH(4)), revealing very good responses already at moderate working temperatures. In particular, carbon monoxide and hydrogen detection was possible already at 100 degrees C. whereas methane sensing required a minimum temperature of 200 degrees C. The performances of the present ZnO nanosystems, that make them attractive candidates for technological applications, are presented and discussed in terms of their unique and controllable morphological organization. (C) 2010 Elsevier B.V. All rights reserved
Urchin-like ZnO nanorod arrays for gas sensing applications
No full textZnO nanorod assemblies were grown by plasma-enhanced chemical vapor deposition on polycrystalline Al(2)O(3) at 200-300 degrees C, resulting in urchin-like 1-D ZnO NR arrays with a strong c-axis orientation. Their outstanding gas sensing responses and very low detection limits highlight the potential of the present systems in the production of high efficiency chemical sensors for a variety of applications
Co3O4/ZnO Nanocomposites: From Plasma Synthesis to Gas Sensing Applications
No full textHerein, we describe the design, fabrication and
gas sensing tests of p-Co3O4/n-ZnO nanocomposites.
Specifically, arrays of oriented ZnO nanoparticles were
grown on alumina substrates by plasma enhanced−chemical
vapor deposition (PECVD) and used as templates for the
subsequent PECVD of Co3O4 nanograins. Structural,
morphological and compositional analyses evidenced the
successful formation of pure and high-area nanocomposites
with a tailored overdispersion of Co3O4 particles on ZnO and
an intimate contact between the two oxides. Preliminary
functional tests for the detection of flammable/toxic analytes (CH3COCH3, CH3CH2OH, NO2) indicated promising sensing
responses and the possibility of discriminating between reducing and oxidizing species as a function of the operating temperature
Plasma Processing of Nanomaterials: Emerging Technologies for Sensing and Energy Applications
No full textPlasma processing represents an attractive and versatile option for the fabrication of lowdimensional
nanomaterials, whose chemical and physical properties can be conveniently tailored
for the development of advanced technologies. In particular, Plasma Enhanced-Chemical Vapor
Deposition (PE-CVD) is an appealing route to multi-functional oxide nanoarchitectures under relatively
mild conditions, owing to the unique features and activation mechanisms of non-equilibrium
plasmas. In this context, the potential of plasma-assisted fabrication in advanced nanosystem development
is discussed. After a brief introduction on the basic categories of plasma approaches, the
perspectives of application to CVD processes are commented, reporting on the growth and characterization
of Co3O4 nanomaterials as a case study. Besides examining the interrelations between
the material properties and the synthesis conditions, special focus is given to their emerging applications
as catalysts for photo-assisted hydrogen production and solid state gas sensors
