116 research outputs found
Congenital bronchial atresia presenting as a cavitary lesion on chest radiography: a case report
This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens
Molecule-Electrode Interface Energetics in Molecular Junction: a Transition Voltage Spectroscopy Study
We assess the performances of the transition voltage spectroscopy (TVS)
method to determine the energies of the molecular orbitals involved in the
electronic transport though molecular junctions. A large number of various
molecular junctions made with alkyl chains but with different chemical
structure of the electrode-molecule interfaces are studied. In the case of
molecular junctions with clean, unoxidized electrode-molecule interfaces, i.e.
alkylthiols and alkenes directly grafted on Au and hydrogenated Si,
respectively, we measure transition voltages in the range 0.9 - 1.4 V. We
conclude that the TVS method allows estimating the onset of the tail of the
LUMO density of states, at energy located 1.0 - 1.2 eV above the electrode
Fermi energy. For oxidized interfaces (e.g. the same monolayer measured with Hg
or eGaIn drops, or monolayers formed on a slightly oxidized silicon substrate),
lower transition voltages (0.1 - 0.6 V) are systematically measured. These
values are explained by the presence of oxide-related density of states at
energies lower than the HOMO-LUMO of the molecules. As such, the TVS method is
a useful technique to assess the quality of the molecule-electrode interfaces
in molecular junctions.Comment: Accepted for publication in J. Phys. Chem C. One pdf file including
manuscript, figures and supporting informatio
High on-off conductance switching ratio in optically-driven self-assembled conjugated molecular systems
A new azobenzene-thiophene molecular switch is designed, synthesized and used
to form self-assembled monolayers (SAM) on gold. An "on/off" conductance ratio
up to 7x1E3 (with an average value of 1.5x1E3) is reported. The "on"
conductance state is clearly identified to the cis isomer of the azobenzene
moiety. The high "on/off" ratio is explained in terms of photo-induced,
configuration-related, changes in the electrode-molecule interface energetics
(changes in the energy position of the molecular orbitals with respect to the
Fermi energy of electrodes) in addition to changes in the tunnel barrier length
(length of the molecules). First principles DFT calculations demonstrate a
better delocalization of the frontier orbitals, as well as a stronger
electronic coupling between the azobenzene moiety and the electrode for the cis
configuration over the trans one. Measured photoionization cross-sections for
the molecules in the SAM are close to the known values for azobenzene
derivatives in solution.Comment: 1 file with main text, figure and suppementary informatio
σ-π molecular dielectric multilayers for low-voltage organic thin-film transistors
Very thin (2.3-5.5 nm) self-assembled organic dielectric multilayers have been integrated into organic thin-film transistor structures to achieve sub-1-V operating characteristics. These new dielectrics are fabricated by means of layer-by-layer solution phase deposition of molecular silicon precursors, resulting in smooth, nanostructurally well defined, strongly adherent, thermally stable, virtually pinhole-free, organosiloxane thin films having exceptionally large electrical capacitances (up to ≈2,500 nF·cm(-2)), excellent insulating properties (leakage current densities as low as 10(-9) A·cm(-2)), and single-layer dielectric constant (k)of ≈16. These 3D self-assembled multilayers enable organic thin-film transistor function at very low source-drain, gate, and threshold voltages (<1 V) and are compatible with a broad variety of vapor- or solution-deposited p- and n-channel organic semiconductors
- …