Monolayer dual gate transistors with a single charge transport layer

A dual gate transistor was fabricated using a self-assembled monolayer as the semiconductor. We show the possibility of processing a dielectric on top of the self-assembled monolayer without deteriorating the device performance. The two gates of the transistor accumulate charges in the monomolecular transport layer and artifacts caused by the semiconductor thickness are negated. We investigate the electrical transport in a dual gate self-assembled monolayer field-effect transistor and present a detailed analysis of the importance of the contact geometry in monolayer field-effect transistors.

Beyond the Nernst-limit with dual-gate ZnO ion-sensitive field-effect transistors

The sensitivity of conventional ion-sensitive field-effect transistors (ISFETs) is limited to 59 mV/pH, which is the maximum detectable change in electrochemical potential according to the Nernst equation. Here we demonstrate a transducer based on a ZnO dual-gate field-effect transistor that breaches this boundary. To enhance the response to the pH of the electrolyte, a self-assembled monolayer has been used as a top gate dielectric. The sensitivity scales linearly with the ratio between the top and bottom gate capacitances. The sensitivity of our ZnO ISFET of 22 mV/pH is enhanced by more than two orders of magnitude up to 2.25 V/pH

Charge transport in dual-gate organic field-effect transistors

The charge carrier distribution in dual-gate field-effect transistors is investigated as a function of semiconductor thickness. A good agreement with 2-dimensional numerically calculated transfer curves is obtained. For semiconductor thicknesses larger than the accumulation width, two spatially separated channels are formed. The cross-over from accumulation into depletion of the two channels in combination with a carrier density dependent mobility causes a shoulder in the transfer characteristics. A semiconducting monolayer has only a single channel. The charge carrier density, and consequently the mobility, are virtually constant and change monotonically with applied gate biases, leading to transfer curves without a shoulder.

Formation of inversion layers in organic field-effect transistors

An inversion current in unipolar organic field-effect transistors is not observed, which can be due to trapping of electrons or to negligible electron injection. Here, we distinguish between both cases by studying the depletion current of unipolar p-type transistors based on a deliberately doped organic semiconductor. For each doping level, the current can be completely pinched off, which unambiguously shows that no inversion layer is formed. Numerical calculations show that for electron injection barriers >1 eV, the transistor is thermodynamically not in equilibrium, such that a steady state is not reached in the time frame of the experiment.

Controlling the on/off current ratio of ferroelectric field-effect transistors

The on/off current ratio in organic ferroelectric field-effect transistors (FeFETs) is largely determined by the position of the threshold voltage, the value of which can show large device-to-device variations. Here we show that by employing a dual-gate layout for the FeFET, we can gain full control over the on/off ratio. In the resulting dual-gate FeFET the ferroelectric gate provides the memory functionality and the second, non-ferroelectric, control gate is advantageously used to set the threshold voltage. The on/off ratio can thus be maximized at the readout bias. The operation is explained by the quantitative analysis of charge transport in a dual-gate FeFET

Origin of the drain current bistability in polymer ferroelectric field-effect transistors

The authors present measurements that elucidate the mechanism behind the observed drain current bistability in ferroelectric field-effect transistors based on the ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene) as the gate dielectric. Capacitance-voltage measurements on metal-insulator-semiconductor diodes demonstrate that the bistability originates from switching between two states in which the ferroelectric gate dielectric is either polarized or depolarized. Pulsed charge displacement measurements on these diodes enable a direct measurement of the accumulated charge in the polarized state of 40±3 mC/m2.

Beyond the Nernst-limit with dual-gate ZnO ion-sensitive field-effect transistors

The sensitivity of conventional ion-sensitive field-effect transistors (ISFETs) is limited to 59 mV/pH, which is the maximum detectable change in electrochemical potential according to the Nernst equation. Here we demonstrate a transducer based on a ZnO dual-gate field-effect transistor that breaches this boundary. To enhance the response to the pH of the electrolyte, a self-assembled monolayer has been used as a top gate dielectric. The sensitivity scales linearly with the ratio between the top and bottom gate capacitances. The sensitivity of our ZnO ISFET of 22 mV/pH is enhanced by more than two orders of magnitude up to 2.25 V/pH