460 research outputs found
Tunnel current in self-assembled monolayers of 3-mercaptopropyltrimethoxysilane
The current density-voltage (J-V) characteristics of self assembled
monolayers of 3-mercaptopropyltrimethoxysilane (MPTMS) chemisorbed on the
native oxide surface of p+-doped Si demonstrate the excellent tunnel dielectric
behavior of organic monolayers down to 3 carbon atoms. The J-V characteristics
of MPTMS SAMs on Si are found to be asymmetric, and the direction of
rectification has been found to depend upon the applied voltage range. At
voltages < 2.45V, the reverse bias current was found to be higher than forward
bias current; while at higher voltages this trend was reversed. This result is
in agreement with Simmons theory. The tunnel barrier heights for this short
chain (2.56 and 2.14 eV respectively at Au and Si interfaces) are in good
agreement with the ones for longer chains (>10 carbon atoms) if the chain is
chemisorbed at the electrodes. These results extend all previous experiments on
such molecular tunnel dielectrics down to 3 carbon atoms. This suggests that
these molecular monolayers, having good tunnel behavior (up to 2.5 eV) over a
large bias range, can be used as gate dielectric well below the limits of
Si-based dielectrics.Comment: Small, in pres
Interface Dipole : Effects on Threshold Voltage and Mobility for both Amorphous and Poly-crystalline Organic Field Effect Transistors
We report a detailed comparison on the role of a self-assembled monolayer
(SAM) of dipolar molecules on the threshold voltage and charge carrier mobility
of organic field-effect transistor (OFET) made of both amorphous and
polycrystalline organic semiconductors. We show that the same relationship
between the threshold voltage and the dipole-induced charges in the SAM holds
when both types of devices are fabricated on strictly identical base
substrates. Charge carrier mobilities, almost constant for amorphous OFET, are
not affected by the dipole in the SAMs, while for polycrystalline OFET
(pentacene) the large variation of charge carrier mobilities is related to
change in the organic film structure (mostly grain size).Comment: Full paper and supporting informatio
Negative Differential Resistance, Memory and Reconfigurable Logic Functions based on Monolayer Devices derived from Gold Nanoparticles Functionalized with Electro-polymerizable Thiophene-EDOT Units
We report on hybrid memristive devices made of a network of gold
nanoparticles (10 nm diameter) functionalized by tailored
3,4(ethylenedioxy)thiophene (TEDOT) molecules, deposited between two planar
electrodes with nanometer and micrometer gaps (100 nm to 10 um apart), and
electropolymerized in situ to form a monolayer film of conjugated polymer with
embedded gold nanoparticles (AuNPs). Electrical properties of these films
exhibit two interesting behaviors: (i) a NDR (negative differential resistance)
behavior with a peak/valley ratio up to 17, and (ii) a memory behavior with an
ON/OFF current ratio of about 1E3 to 1E4. A careful study of the switching
dynamics and programming voltage window is conducted demonstrating a
non-volatile memory. The data retention of the ON and OFF states is stable
(tested up to 24h), well controlled by the voltage and preserved when repeating
the switching cycles (800 in this study). We demonstrate reconfigurable Boolean
functions in multiterminal connected NP molecule devices.Comment: Full manuscript, figures and supporting information, J. Phys. Chem.
C, on line, asap (2017
Physical Study by Surface Characterizations of Sarin Sensor on the Basis of Chemically Functionalized Silicon Nanoribbon Field Effect Transistor
Surface characterizations of an organophosphorus (OP) gas detector based on
chemically functionalized silicon nanoribbon field-effect transistor (SiNR-FET)
were performed by Kelvin Probe Force Microscopy (KPFM) and ToF-SIMS, and
correlated with changes in the current-voltage characteristics of the devices.
KPFM measurements on FETs allow (i) to investigate the contact potential
difference (CPD) distribution of the polarized device as function of the gate
voltage and the exposure to OP traces and, (ii) to analyze the CPD hysteresis
associated to the presence of mobile ions on the surface. The CPD measured by
KPFM on the silicon nanoribbon was corrected due to side capacitance effects in
order to determine the real quantitative surface potential. Comparison with
macroscopic Kelvin probe (KP) experiments on larger surfaces was carried out.
These two approaches were quantitatively consistent. An important increase of
the CPD values (between + 399 mV and + 302 mV) was observed after the OP sensor
grafting, corresponding to a decrease of the work function, and a weaker
variation after exposure to OP (between - 14 mV and - 61 mV) was measured.
Molecular imaging by ToF-SIMS revealed OP presence after SiNR-FET exposure. The
OP molecules were essentially localized on the Si-NR confirming effectiveness
and selectivity of the OP sensor. A prototype was exposed to Sarin vapors and
succeeded in the detection of low vapor concentrations (40 ppm).Comment: Paper and supporting information, J. Phys. Chem. C, 201
Metal/organic/metal bistable memory devices
We report a bistable organic memory made of a single organic layer embedded
between two electrodes, we compare to the organic/metal nanoparticle/organic
tri-layers device [L.P. Ma, J. Liu, and Y. Yang, Appl. Phys. Lett. 80, 2997
(2002)]. We demonstrate that the two devices exhibit similar
temperature-dependent behaviors, a thermally-activated behavior in their low
conductive state (off-state) and a slightly "metallic" behavior in their high
conductive state (on-state). This feature emphasizes a similar origin for the
memory effect. Owing to their similar behavior, the one layer memory is
advantageous in terms of fabrication cost and simplicity
A Silicon Nanowire Ion-Sensitive Field-Effect-Transistor with elementary charge sensitivity
We investigate the mechanisms responsible for the low-frequency noise in
liquid-gated nano-scale silicon nanowire field-effect transistors (SiNW-FETs)
and show that the charge-noise level is lower than elementary charge. Our
measurements also show that ionic strength of the surrounding electrolyte has a
minimal effect on the overall noise. Dielectric polarization noise seems to be
at the origin of the 1/f noise in our devices. The estimated spectral density
of charge noise Sq = 1.6x10-2 e/sqr(Hz) at 10 Hz opens the door to metrological
studies with these SiNW-FETs for the electrical detection of a small number of
molecules.Comment: One file including paper (with 3 figures) and supplementary
information (with 5 figures). Submitte
Water Electrolysis and Energy Harvesting with 0D Ion-Sensitive Field-Effect Transistors
The relationship of the gas bubble size to the size distribution critically
influences the effectiveness of electrochemical processes. Several optical and
acoustical techniques have been used to characterize the size and emission
frequency of bubbles. Here, we used zero-dimensional (0D) ion-sensitive
field-effect transistors (ISFETs) buried under a microbath to detect the
emission of individual bubbles electrically and to generate statistics on the
bubble emission time. The bubble size was evaluated via a simple model of the
electrolytic current. We suggest that energy lost during water electrolysis
could be used to generate electric pulses at an optimal efficiency with an
array of 0D ISFETs.Comment: One pdf file including paper and supporting informations. Nano
Letters, published on line (2013
Oligothiophene-derivatized azobenzene as immobilized photoswitchable conjugated systems
Immobilization of an azobenzene-bithiophene compound on a gold surface leads to self-assembled monolayers with photoswitchable electrical properties
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