60 research outputs found
Commutators on
The main result is that the commutators on are the operators not of
the form with and compact. We generalize
Apostol's technique (1972, Rev. Roum. Math. Appl. 17, 1513 - 1534) to obtain
this result and use this generalization to obtain partial results about the
commutators on spaces \X which can be represented as \displaystyle \X\simeq
(\bigoplus_{i=0}^{\infty} \X)_{p} for some or . In
particular, it is shown that every compact operator on is a commutator. A
characterization of the commutators on
is given. We also show
that strictly singular operators on are commutators.Comment: 17 pages. Submitted to the Journal of Functional Analysi
Microcrystalline silicon thin film transistors obtained by Hot-Wire CVD
Polysilicon thin film transistors (TFT) are of great interest in the field of large area microelectronics, especially because of their application as active elements in flat panel displays. Different deposition techniques are in tough competition with the objective to obtain device-quality polysilicon thin films at low temperature. In this paper we present the preliminary results obtained with the fabrication of TFT deposited by hot-wire chemical vapor deposition (HWCVD). Some results concerned with the structural characterization of the material and electrical performance of the device are presented
Thin Film Transistors obtained by Hot-Wire CVD
Hydrogenated microcrystalline silicon films obtained at low temperature (150-280°C) by hot wire chemical vapour deposition at two different process pressures were measured by Raman spectroscopy, X-ray diffraction (XRD) spectroscopy and photothermal deflection spectroscopy (PDS). A crystalline fraction >90% with a subgap optical absortion 10 cm -1 at 0.8 eV were obtained in films deposited at growth rates >0.8 nm/s. These films were incorporated in n-channel thin film transistors and their electrical properties were measured. The saturation mobility was 0.72 ± 0.05 cm 2/ V s and the threshold voltage around 0.2 eV. The dependence of their conductance activation energies on gate voltages were related to the properties of the material
Facile Synthesis of Amine-Functionalized Eu3+-Doped La(OH)3 Nanophosphors for Bioimaging
Here, we report a straightforward synthesis process to produce colloidal Eu3+-activated nanophosphors (NPs) for use as bioimaging probes. In this procedure, poly(ethylene glycol) serves as a high-boiling point solvent allowing for nanoscale particle formation as well as a convenient medium for solvent exchange and subsequent surface modification. The La(OH)3:Eu3+ NPs produced by this process were ~3.5 nm in diameter as determined by transmission electron microscopy. The NP surface was coated with aminopropyltriethoxysilane to provide chemical functionality for attachment of biological ligands, improve chemical stability and prevent surface quenching of luminescent centers. Photoluminescence spectroscopy of the NPs displayed emission peaks at 597 and 615 nm (λex = 280 nm). The red emission, due to 5D0 → 7F1 and 5D0 → 7F2 transitions, was linear with concentration as observed by imaging with a conventional bioimaging system. To demonstrate the feasibility of these NPs to serve as optical probes in biological applications, an in vitro experiment was performed with HeLa cells. NP emission was observed in the cells by fluorescence microscopy. In addition, the NPs displayed no cytotoxicity over the course of a 48-h MTT cell viability assay. These results suggest that La(OH)3:Eu3+ NPs possess the potential to serve as a luminescent bioimaging probe
Analysis of bias stress on thin-film transistors obtained by Hot-Wire Chemical Vapour Deposition
The stability under gate bias stress of unpassivated thin film transistors was studied by measuring the transfer and output characteristics at different temperatures. The active layer of these devices consisted of in nanocrystalline silicon deposited at 125 °C by Hot-Wire Chemical Vapour Deposition. The dependence of the subthreshold activation energy on gate bias for different gate bias stresses is quite different from the one reported for hydrogenated amorphous silicon. This behaviour has been related to trapped charge in the active layer of the thin film transistor
Nanoencapsulation of luminescent 3-hydroxypicolinate lanthanide complexes
We have synthesized luminescent nanoparticles comprising a core of lanthanide complexes and shells of
amorphous silica using reverse micelles as nanoreactors. 3-Hydroxypicolinate complexes of Eu(III), Tb(III),
and the corresponding heteronuclear complexes have been investigated as the photoactive cores. The size of
the silica particles is within the nanometer scale, which, together with the ability for surface biofunctionalization,
opens up perspectives for their use in bioapplications. Optical studies of the as-prepared nanoparticles reveal
that the luminescence properties of the 3-hydroxypicolinate complexes in the matrices are markedly different
from their original features
Analysis of bias stress on thin-film transistors obtained by Hot-Wire Chemical Vapour Deposition
The stability under gate bias stress of unpassivated thin film transistors was studied by measuring the transfer and output characteristics at different temperatures. The active layer of these devices consisted of in nanocrystalline silicon deposited at 125°C by Hot-Wire Chemical Vapour Deposition. The dependence of the subthreshold activation energy on gate bias for different gate bias stresses is quite different from the one reported for hydrogenated amorphous silicon. This behaviour has been related to trapped charge in the active layer of the thin film transistor.Peer ReviewedPostprint (published version
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