1,721,118 research outputs found
Anisotropic resistivity of (100)-oriented mesoporous silicon
No full textThe resistivity of (100) -oriented mesoporous silicon has been studied using two different electrode configurations. The authors observed that the electronic transport along the longitudinal direction (parallel to the sample surface) is strongly inhibited at room temperature but not along the perpendicular direction. They show that such electrical anisotropy can be removed by heating the material, reporting an increase of six orders of magnitude of the longitudinal conductivity when the temperature rises from 20 to 100 °C. These experimental findings are interpreted on the basis of the material morphology and nanostructuration, which determine the availability of percolative pathways for free charge carriers
Slow conductivity relaxation and simple aging in nanostructured mesoporous silicon at room temperature
No full textExperimental observations of peculiar time-dependent charge transport phenomena, such as slow conduc- tivity relaxation, nonergodicity, and simple aging, are reported here for mesoporous silicon at room tempera- ture. These effects are discussed on the basis of the strong disorder in the nanocrystalline silicon network constituting the material. Taking into account various independent results reported in literature, the authors suggest that the observed behavior may reflect nonequilibrium glassy dynamics due to Anderson localization and Coulomb interactions
Electrical Properties of Meso-Porous Silicon: From a Surface Effect to Coulomb Blockade and More
No full textSince the Volker Lehmann’s paper “Resistivity of Porous
Silicon: a surface effect” published in 1995, a great deal of
effort has been produced in understanding the basic
mechanisms ruling the electron transport in Si mesostructures
and how these phenomena are affected by external environment.
After more than 10 years, new experimental evidences and
physical insights have been obtained, like gas sensitivity,
chemisorptions phenomena, Coulomb blockade and glassy
dynamics at room temperature, but reading that former paper,
the feeling of an extraordinary comprehension and intuition of
the physical phenomena occurring in this fascinating material is
continuously accompanying the reader.
A review of these major results in studying electronic transport
in mesoporous silicon will be reported, starting from the still
valid intuitions of Volker Lehmann in his paper
Coulomb blockade sensors based on nanostructured mesoporous silicon
No full textMesoporous silicon (mesoPS) is a nanosponge where Si nanocrystals are interconnected forming a disordered 3D array. The electronic
characteristics of this material are particularly interesting, due to some intriguing effects, such as a huge increase of conductivity,
reversible insulator-to-metal transition and n- or p-type doping of the nanocrystals, exhibited in presence of donor or acceptor molecules
like NH3 and NO2. Here we report on the observation of a sharp conductance gap, which can be ascribed to Coulomb blockade
phenomena. Moreover, we show that the width of the gap can be tuned by NO2 molecules, so that the fabrication of highly sensitive
threshold sensors is possible. Our results suggest that electrochemical etching of heavily doped Si can be used as a simple self-assembly
technique for the production of Si nanocrystal arrays and for the fabrication of sensitive nanosensors
Anisotropic electrical response of mesoporous silicon to NO2
No full textThe I–V characteristics of Mesoporous Silicon (mesoPS) samples have been studied both in vacuum and in presence of NO2 traces. By the use of different electrode configurations, the longitudinal (parallel to the sample surface) and transverse (perpendicular to the sample surface) components of the electrical conduc- tance have been independently measured and compared. We show that the electrical response of mesoPS to NO2 is anisotropic, and that the best sensing performance is achieved by monitoring the longitudinal conductance variation
Electrical Properties of Mesoporous Silicon: From a Surface Effect to Coulomb Blockade
No full textSince the publication of the paper oV. Lehmann, F. Hofmann, F. Moeller, and U. Gruening, Thin Solid Films, 255, 2 (1995), a great deal of effort has been produced to understand the basic mechanisms ruling the electron transport in Si mesostructures and how these phenomena are affected by the external environment. After more than 10 years of studies on mesoporous silicon in interaction with gas molecules, the latest experimental evidences and physical insights have been revealed, such as gas sensitivity, chemisorption phenomena, coulomb blockade, and glassy dynamics at room temperature. But by reading that former paper, the feeling of an extraordinary comprehension and intuition of the physical mechanisms occurring in this fascinating material con- tinuously accompanied the reader. A review of these major results, starting from the first evidence of a strong interaction with nitrogen dioxide, to the in situ Fourier transform IR and electron paramagnetic resonance spectroscopy studies, and to the more recent electronic transport experiments on this material was reported, which follows Lehmann’s intuitions in his paper
Coulomb blockade tuned by NO2 molecules in nanostructured silicon
No full textWe have demonstrated that the electrochemical etching of heavily doped Si can be used as a simple self-assembly technique for the fabrication of Si nanocrystal arrays.
The obtained nanostructures exhibit CB behavior at RT, and are very sensitive to the presence of molecules with high electron affinities, such as NO2. Thus, exploiting the tunability of the quantum properties of our arrays, we have fabricated CB gas sensors operating at RT, whose sensing range is selected just by varying the bias voltage. These results could have important implications for the fabrication of quantum devices
based on Si nanocrystals
Colloidal Lithography
No full textThis chapter is a visual guide to the numerous approaches to nanolithography nanofabrication on large area based on supramolecular self-assembly. A short history of this recent scientific and technological field, an outline of the most-cited methods of self-assembly, and tables reporting different nanofabrication methods are reported. Indications on requirements, advantages, and drawbacks of the various approaches are also listed in the table. Thanks to the recently developed metal-assisted catalytic etching (MACE), the colloidal patterns can be easily propagated to silicon and other semiconductors opening a wide field of morphology, nanostructures, and applications
Fabrication of periodic arrays of metallic nanoparticles by block copolymer templates on HfO2 substrates
No full textThe optical response above the band gap of light emitting porous silicon as investigated by photoacoustic spectroscopy
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