Longitudinal resistivity measurements on single
Mo6S9−xIx
(x = 4.5, 6 and 7) molecular nanowire bundles ranging in diameter from
d = 7 nm
to 1 µm
are performed to investigate the longitudinal transport properties of individual
bundles. Different contacting methods are used to study diverse nanocircuit
manufacturing technologies that can be used for interconnects based on
Mo6S9−xIx. The measurements show ubiquitously linear
I–V
characteristics with Pd, Au, Ag and Ti contact metals. The highest room-temperature conductivity achieved
is σ0∼10 S m−1
using Ag contacts. The critical current densities typically achieved are
Jc∼104 A cm−2. The observed metallic behaviour at room temperature is consistent with the band structure
calculated using density functional theory (DFT). At low temperatures, the conductivity is
found to decrease, following variable range hopping (VRH) behaviour of the form
σ = σ0exp−(T0/T)β reasonably well,
but the exponent β
changes upon annealing. From fits to the temperature dependence of the conductivity, a change from
β∼1/4 to
β∼1/2
is observed, which may be explained by a change in dimensionality from 3D-like
VRH to 1D-like VRH following the removal of intra-bundle interstitial iodine.
We demonstrate that photoisomerizable liquid-crystal elastomer soft films can be used as tunable holographic gratings. Optomechanical mechanism of imprinting one-dimensional grating structure into the soft matrix by two-beam uv laser interference can be clearly resolved from the time dependence of the reading beam diffraction patterns. We analyze the observed response in terms of cis-trans isomerization-controlled modulation of the grating profile. The grating period can be tuned reversibly by stretching or contraction of the specimen, either thermomechanically or by applying external stress. Temperature-induced modifications of the grating parameters in the vicinity of the nematic-paranematic phase transition are also examined.
Mo6S3I6 nanowire networks of interest are found to change their resistance in response to the presence of analyte vapors. The vapor sensing behavior is quantitatively described very well phenomenologically in terms of the concentration of adsorbed analyte molecules in the contact tunneling junctions, and an expression is derived for the dynamics and sensor resistance in terms of analyte vapor pressure. The time response of the sensor is observed to follow simple adsorption–desorption kinetics. The network sensor shows very clear selectivity, whereby the response is related to the dipole moment of the analyte. The response function favors rapid detection of small analyte concentrations.
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