Ecp Edsger Smits

Increasing the noise margin in organic circuits using dual gate field-effect transistors

Complex digital circuits reliably work when the noise margin of the logic gates is sufficiently high. For p-type only inverters, the noise margin is typically about 1 V. To increase the noise margin, we fabricated inverters with dual gate transistors. The top gate is advantageously used to independently tune the threshold voltage.

Ordered Semiconducting Self-Assembled Monolayers on Polymeric Surfaces Utilized in Organic Integrated Circuits

We report on a two-dimensional highly ordered self-assembled monolayer (SAM) directly grown on a bare polymer surface. Semiconducting SAMs are utilized in field-effect transistors and combined into integrated circuits as 4-bit code generators. The driving force to form highly ordered SAMs is packing of the liquid crystalline molecules caused by the interactions between the linear alkane moieties and the pi-pi stacking of the conjugated thiophene units. The fully functional circuits demonstrate long-range order over large areas, which can be regarded as the start of flexible monolayer electronics.

On the width of the recombination zone in ambipolar organic field effect transistors

The performance of organic light emitting field effect transistors is strongly influenced by the width of the recombination zone. We present an analytical model for the recombination profile. By assuming Langevin recombination, the recombination zone width W is found to be given byW=4.34dδ, with d and δ the gate dielectric and accumulation layer thicknesses, respectively. The model compares favorably to both numerical calculations and measured surface potential profiles of an actual ambipolar device.

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.

Balancing Hole and Electron Conduction in Ambipolar Split-Gate Thin-Film Transistors

Complementary organic electronics is a key enabling technology for the development of new applications including smart ubiquitous sensors, wearable electronics, and healthcare devices. High-performance, high-functionality and reliable complementary circuits require n- and p-type thin-film transistors with balanced characteristics. Recent advancements in ambipolar organic transistors in terms of semiconductor and device engineering demonstrate the great potential of this route but, unfortunately, the actual development of ambipolar organic complementary electronics is currently hampered by the uneven electron (n-type) and hole (p-type) conduction in ambipolar organic transistors. Here we show ambipolar organic thin-film transistors with balanced n-type and p-type operation. By manipulating air exposure and vacuum annealing conditions, we show that well-balanced electron and hole transport properties can be easily obtained. The method is used to control hole and electron conductions in split-gate transistors based on a solution-processed donor-acceptor semiconducting polymer. Complementary logic inverters with balanced charging and discharging characteristics are demonstrated. These findings may open up new opportunities for the rational design of complementary electronics based on ambipolar organic transistors.

Meta-stability effects in organic based transistors

The electrical stability of metal insulator semiconductor (MIS) capacitors and field effect transistor structures based in organic semiconductors were investigated. The device characteristics were studied using steady state measurements AC admittance measurements as well as techniques for addressing trap states. Temperature-dependent measurements show clear evidence that an electrical instability occurs above 200 K and is caused by an electronic trapping process. It is suggested that the trapping sites are created by a change in the organic conjugated chain, a process similar to a phase transition.