Revisiting the delta-phase of poly(vinylidene fluoride) for solution-processed ferroelectric thin films Li, Mengyuan; Wondergem, Harry J.; Spijkman, Mark-Jan; Asadi, Kamal; Katsouras, Ilias; Blom, Paul W. M.; de Leeuw, Dago M.

The first dual‐gate thin‐film transistor (DGTFT) was reported in 1981 with CdSe as the semiconductor. Other TFT technologies such as a‐Si:H and organic semiconductors have led to additional ways of making DGTFTs. DGTFTs contain a second gate dielectric with a second gate positioned opposite of the first gate. The main advantage is that the threshold voltage can be set as a function of the applied second gate bias. The shift depends on the ratio of the capacitances of the two gate dielectrics. Here we review the fast growing field of DGTFTs. We summarize the reported operational mechanisms, and the application in logic gates and integrated circuits. The second emerging application of DGTFTs is sensitivity enhancement of existing ion‐sensitive field‐effect transistors (ISFET). The reported sensing mechanism is discussed and an outlook is presented.

Buried electrodes and protection of the semiconductor with a thin passivation layer are used to yield dual‐gate organic transducers. The process technology is scaled up to 150‐mm wafers. The transducers are potentiometric sensors where the detection relies on measuring a shift in the threshold voltage caused by changes in the electrochemical potential at the second gate dielectric. Analytes can only be detected within the Debye screening length. The mechanism is assessed by pH measurements. The threshold voltage shift depends on pH as ΔVth = (Ctop/Cbottom) × 58 mV per pH unit, indicating that the sensitivity can be enhanced with respect to conventional ion‐sensitive field‐effect transistors (ISFETs) by adjusting the ratio of the top and bottom gate capacitances. Remaining challenges and opportunities are discussed.

The semiconductor of an organic field‐effect transistor is stripped with adhesive tape, yielding an exposed gate dielectric, accessible for various characterization techniques. By using scanning Kelvin probe microscopy we reveal that trapped charges after gate bias stress are located at the gate dielectric and not in the semiconductor. Charging of the gate dielectric is confirmed by the fact that the threshold voltage shift remains, when a pristine organic semiconductor is deposited on the exposed gate dielectric of a stressed and delaminated field‐effect transistor.

We have investigated the ferroelectric phase diagram of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA). The binary nonequilibrium temperature composition diagram was determined and melting of αand β-phase PVDF was identified. Ferroelectric β-PVDF:PMMA blend films were made by melting, ice quenching, and subsequent annealing above the glass transition temperature of PMMA, close to the melting temperature of PVDF. Addition of PMMA suppresses the crystallization of PVDF and, as a consequence, the roughness of blend films was found to decrease with increasing PMMA content. Using timedependent 2D numerical simulations based on a phase−field model, we qualitatively reproduced the effect of PMMA on the crystallization rate and the spherulite shape of PVDF. The remnant polarization scaled with the degree of crystallinity of PVDF. The thermal stability of the polarization is directly related to the Curie temperature. We show that, at high temperature, the commodity ferroelectric PVDF:PMMA blends outperform the commonly employed specialty copolymer poly(vinylidene fluoride−trifluoroethylene) (P(VDF−TrFE)).

Origin of the drain current bistability in polymer ferroelectric field-effect transistors Naber, R. C. G.; Massolt, J.; Spijkman, M.; Asadi, K.; Blom, P. W. M.; de Leeuw, D. M.

Beyond the Nernst-limit with dual-gate ZnO ion-sensitive field-effect transistors Spijkman, M.; Smits, E. C. P.; Cillessen, J. F. M.; Biscarini, F.; Blom, P. W. M.; de Leeuw, D. M.

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. a b s t r a c tOrganic ultra-thin film field effect transistors (FET) are operated as label-free sensors of deoxyribonucleic acid (DNA) adsorption. Linearized plasmid DNA molecules (4361 base pairs) are deposited from a solution on two monolayers thick pentacene FET. The amount of adsorbed DNA is measured by AFM and correlated to the concentration of the solution. Electrical characteristics on the dried DNA/pentacene FETs were studied as a function of DNA concentration in the solution. Shift of the pinch-off voltage across a wide range of DNA concentration, from very diluted to highly concentrated, is observed. It can be ascribed to additional positive charges in the semiconductor induced by DNA at a rate of one charge for every 200 base pairs. The sensitivity 74 ng/cm 2 , corresponding to 650 ng/ml, is limited by the distribution of FET parameters upon repeated cycles, and is subjected to substantial improvement upon standardization. Our work demonstrates the possibility to develop label-free transducers suitable to operate in regimes of high molecular entanglement.