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A hybrid gate dielectric material for flexible OTFT is developed by using core–shell nanoparticles (SiO2@PSRXL) where the core and the shell consist of silica nanoparticles and polysiloxane resin, respectively. Since polysiloxane resin contains both thermal- and photo-crosslinkable functional groups, densely-crosslinked thin gate dielectric films can be easily prepared on various substrates by conventional solution casting followed by dual crosslinking. SiO2@PSRXL films exhibit high thermal stability (weight loss at 300 °C is smaller than 3 wt%). The dielectric films made of SiO2@PSRXL show an exceptionally low leakage current and no breakdown voltage up to 4.3 MV cm−1, which are comparable to those of silica dielectrics prepared by CVD. OTFT devices based on dibenzothiopheno[6,5-b:6′,5′-f]thieno[3,2-b]thiophene (DTBTT) as a semiconductor and SiO2@PSRXL as a gate dielectric exhibit good hole mobility (2.5 cm2 V−1 s−1) and Ion/Ioff ratio (106).

In this work, graphene field effect transistors (FETs) were fabricated on a trench structure made by carbonized poly(methylmethacrylate) to modify the graphene surface. The trench-structured devices showed different characteristics depending on the channel orientation and the pitch size of the trenches as well as channel area in the FETs. Periodic corrugations and barriers of suspended graphene on the trench structure were measured by atomic force microscopy and electrostatic force microscopy. Regular barriers of 160 mV were observed for the trench structure with graphene. To confirm the transfer mechanism in the FETs depending on the channel orientation, the ratio of experimental mobility (3.6-3.74) was extracted from the current-voltage characteristics using equivalent circuit simulation. It is shown that the number of barriers increases as the pitch size decreases because the number of corrugations increases from different trench pitches. The noise for the 140 nm pitch trench is 1 order of magnitude higher than that for the 200 nm pitch trench.

An experimental study of the low temperature magnetoresistance (MR) in a FeCl 3 -doped copolymer in which ethylenedioxythiophene and phenylene are alternatively linked by vinylene units is reported. The temperature dependence of conductivity followed characteristics of Coulomb gap variable range hopping (VRH) at low temperatures. The MR showed a crossover from negative to positive values. The crossover was explained by competition of negative and positive contributions which originated from quantum interference and shrinkage of wave function, respectively.

We present results of non-linear magneto resistance (MR) of polyacetylene nanofibers in high magnetic field up to H = 30 T at low temperature T = 1.5 K. The MR was proven to be of the spin origin; it reaches 16% at highest H . Unexpectedly, the MR was suppressed by increasing electric field E , vanishing at E ≳ 5 × 10 4 V/cm. It is understood that the doping induced spinless charged soliton pairs, which are initially confined to a certain distance because of the interchain phase correlations, and are deconfined in high electric fields, resulting in a vanishing magneto resistance (VMR). The role of the specific, degenerate ground state of the polyacetylene is confirmed by parallel studies of the different magneto resistances of polyaniline nanofibers which contrarily is not affected by the electric field.

Highly conducting nanofibrous composite of well-oriented single-walled carbon nanotubes (SWNTs) in polyaniline (PANI) and polyethylene oxide (PEO) have been fabricated using electrospinning. The room temperature electrical conductivity show nearly four order enhancement with highest (11.9 wt%) loading of SWNT in the PANI–PEO blend. The temperature dependent conductivities are measured in the range of 30–300 K and the results are analyzed by the fluctuation assisted tunneling model.

We report here our investigation on the grain-growth mechanism of diphenyl-dibenzothiopheno[6,5-b:6′,5′-f]thieno[3,2-b]thiophene (DPh-DBTTT), which was recently published as a high-performance organic semiconductor. Atomic force microscopy revealed that unconventional needle-like structures grew on the surface of DPh-DBTTT thin films, and these structures became more dominant as the film thickness increased and the deposited film's surface temperature decreased. In combination with the crystal structure simulations, the grazing-incidence wide-angle x-ray scattering data indicated that the DPh-DBTTT molecules preferred an edge-on orientation near the interface between the substrate and DPh-DBTTT thin film, while the needle-like structures consisted of a face-on arrangement of the molecules. We suggest that this structural change originates from the large step-edge energy barrier of the DPh-DBTTT molecules. Our findings would be highly valuable to the design of new high-performance organic semiconducting ma...

Phenyl-substituted heteroacene, diphenyl-dibenzothiopheno[6,5-b:6′,5′-f]thieno[3,2-b]thiophene (DPh-DBTTT), is introduced as a thermally durable high-performance organic semiconductor. The DPh-DBTTT single crystals exhibit hole mobility up to 31.9 cm2 V−1 s−1, and the vacuum-deposited DPh-DBTTT thin-film transistors show a maximum mobility of 6.32 cm2 V−1 s−1. X-ray crystallographic analysis reveals that the small tilting angle between the phenyl substituent and the DBTTT core reduces the reorganization energy dramatically. The structure–property relationships are thoroughly investigated using atomic force microscopy, transmission electron microscopy, and grazing incidence X-ray diffraction analyses, in addition to charge-transport studies. The vacuum-deposited DPh-DBTTT thin-film transistors show superior thermal durability compared to the core DBTTT, which is highly valuable for device processability.

International audience; Polymer nanofibers are one-dimensional organic hydrocarbon systems containing conducting polymers where the non-linear local excitations such as solitons, polarons and bipolarons formed by the electron-phonon interaction were predicted. Magnetoconductance (MC) can simultaneously probe both the spin and charge of these mobile species and identify the effects of electron-electron interactions on these nonlinear excitations. Here we report our observations of a qualitatively different MC in polyacetylene (PA) and in polyaniline (PANI) and polythiophene (PT) nanofibers. In PA the MC is essentially zero, but it is present in PANI and PT. The universal scaling behavior and the zero (finite) MC in PA (PANI and PT) nanofibers provide evidence of Coulomb interactions between spinless charged solitons (interacting polarons which carry both spin and charge).

Reduced graphene oxide nanoribbon fibers were fabricated by using an electrophoretic self-assembly method without the use of any polymer or surfactant. We report electrical and field emission properties of the fibers as a function of reduction degree. In particular, the thermally annealed fiber showed superior field emission performance with a low potential for field emission (0.7 V µm(-1)) and a giant field emission current density (400 A cm(-2)). Moreover, the fiber maintains a high current level of 300 A cm(-2) corresponding to 1 mA during long-term operation.

Nonlinear local excitations like solitons, polarons, and bipolarons are known to be responsible for physical properties of conducting polymers. Recent experiments on nano-fibers in high electric and magnetic fields provide a further insight by demonstrating an effect of vanishing magnetoconductance (MC) in the polyacetylene (PA)—in contrast to other polymers. Here we present new experimental data and describe the theoretical model based on notion of solitons—dimerization kinks which can carry either the spin or the charge; they are allowed only in the PA with its degenerate ground state. The solitons experience a confinement force due to the interchange coupling which is erased by the electric field and disappears above critical field strength. The unbinding by tunneling allows for the transport of individual solitons, which sweeps off the spins residing at electronic intragap states associated with polarons, hence the vanishing MC.

Smart fabrics have attracted considerable attention due to their potential applications. The essential features of smart fabrics include wearability, weaveability, and stretchability, as well as their sensing/response capability, which is frequently based on electrical measurement. Thus, the electromechanical behavior of these fabrics is considered the most important material property. Here, we report the negative piezoresistance of single-walled carbon nanotube coated cotton yarn (SWNT-CY). The gauge factor (the ratio of the normalized change in piezoresistance to the change in strain) of SWNT-CY is measured to be − 24. It is noteworthy that the factor is negative and an order of magnitude higher than that for conventional metal strain gauges. The negative piezoresistance is due to mechanical contact between fabric fibers, which leads to better electrical paths of SWNT networks. The conduction behavior can be modeled as fluctuation-induced tunneling (FIT) through the contact barriers between conducting regions. The effective barrier strength of strained SWNT-CY is measured to be ~ 30% lower than that of unstrained SWNT-CY. This characteristic may offer new design opportunities for wearable electronics and has significant implications for sensor applications.