Eugenio Cantatore

Plastic transistors in active-matrix displays

The main advantages of using soluble semiconductive polymers in microelectronic devices are ease of processing and mechanical flexibility. Here we describe an active-matrix display with 64 × 64 pixels, each driven by a thin-film transistor with a solution-processed polymer semiconductor. In a significant step towards low-cost flexible displays, this polymer-dispersed liquid-crystal arrangement gives a reflective, low-power display with paper-like contrast, which can handle 256 grey levels while being refreshed at video speed.

A 13.56-MHz RFID System Based on Organic Transponders

RFID tags based on organic transistors are described, discussing in detail the IC blocks used to build the logic and the radio. Tags energized and read out at 13.56 MHz, de facto standard frequency for item-level identification, have been tested and enabled for the first time multiple-object identification, using different 6-bit codes. A complete 64-bit transponder, the most complex organic RFID tag reported to date, operates at 125 kHz and employs 1938 transistors

Bias stress in organic thin-film transistors and logic gates

Threshold voltage instabilities of all-organic thin-film transistors are investigated as a function of stress time and stress bias. The dominant effect is a positive threshold shift for negative gate bias stress which is explained by mobile ions drifting in the insulator when a gate field is applied. Trapping of charge carriers at the semiconductor–insulator interface plays only a minor role. Furthermore, we investigate the stress behavior of a basic logic element, an inverter. In comparison to a single transistor, we observe improved stability which arises from partial compensation of the parametric shifts during operation.

Organic complementary-like inverters employing methanofullerene-based ambipolar field-effect transistors

We demonstrate a complementary-like inverter comprised of two identical ambipolar field-effect transistors based on the solution processable methanofullerene [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The transistors are capable of operating in both the p- and n-channel regimes depending upon the bias conditions. However, in the p-channel regime transistor operation is severely contact limited. We attribute this to the presence of a large injection barrier for holes at the Au∕PCBM interface. Despite this barrier the inverter operates in both the first and third quadrant of the voltage output versus voltage input plot exhibiting a maximum gain in the order of 20. Since the inverter represents the basic building block of most logic circuits we anticipate that other complementary-like circuits can be realized by this approach.

Solution processible organic transistors and circuits based on a C-70 methanofullerene

We demonstrate ambipolar charge transport in organic field-effect transistors based on the solution processible methanofullerene [6,6]-phenyl-C71-butyric acid methyl ester ([70]PCBM). The electron mobility measured in the linear and saturated regimes is approximately equal and of the order of 1×10−3cm2∕Vs. In the linear regime, mobility is thermally activated with a strong gate bias dependence. The p-channel hole mobility is lower with a maximum value of 2×10−5cm2∕Vs. The n- and p-channel operations are characterized by a low (∼∣3∣V) and a high (∼∣50∣V) switch-on voltage, respectively, with the on-off current ratio on the order of 104 for both channels. Although the present findings are qualitatively similar to those reported previously for C60-methanofullerene-based transistors, [70]PCBM devices are more stable and easier to reproduce. By making use of this property we are able to demonstrate functional unipolar and complementarylike logic circuits with promising operating characteristics.

Ambient Intelligence Visions and Achievements: Linking Abstract Ideas to Real-World Concepts

The ambient intelligence vision is abstract and as such not useful for funding decisions, research project definition, and business plan development. This is in particular the case for the electronic design community. The European Commission intends for the EU to achieve world leadership in Information Societies technologies within ten years. To that end, it has incorporated the ambient intelligence vision in its Sixth Framework. Microelectronics and nano- and optical devices are seen as key technologies. Interesting chip-level challenges are found in, amongst others, explicit modeling of mobility and self-management, and novel computing substrates, based on electronic textiles or organic electronics.

Energy scavenging and power management in networks of autonomous microsensors

Networks of autonomous microsensors promise to revolutionize the way people interact with electronics, enabling ambient intelligence. In this paper we investigate different energy scavenging options in real applications to find out which devices are more suitable to power a microsensor having a volume of only 100mm^3. Photovoltaic cells are the most promising power generators when a power level of [emailxa0protected] is required. If the power consumption can be reduced to about [emailxa0protected], MEMS-based vibration-driven scavengers and thermoelectric generators can also be used. The paper presents as well a power management architecture that enables the use of a scavenger as power source, and discusses some consequences of the limited available volume on power electronics.

Polymer-based transistors used as pixel switches in active-matrix displays

— n nA 2-in. active-matrix display was demonstrated, containing 4096 solution-processed polymer-based transistors. By using the polymer-dispersed liquid-crystal display (LCD) effect, this results in a reflective, low-power display with paper-like contrast. The influence of the transistor parameters on the display performance is analyzed by use of a model for charging and discharging of the pixel capacitors. Good agreement was obtained between the model and the experimental data. Scaling behavior allows estimation of the performance required for transistors in a quarter-VGA display. These requirements are met by solution-processed pentacene transistors.

Circuit yield of organic integrated electronics

Research on organic electronics is focussed on materials and on the performance of discrete devices. Reliability and circuit yield is largely unexplored. Yield, based on measurements on digital organic circuits up to 1000 transistors, is described. The causes of yield loss are analyzed and design solutions to improve the yield are discussed.

Polymeric integrated circuits: fabrication and first characterisation

A technology to fabricate polymeric integrated circuits on 150-mm foils is presented. The technology is demonstrated with functional code generators. The integration level is about 700 transistors. The yield of the circuits has been measured as function of the complexity and has been correlated with intrinsic noise margin of the logic gates.