Ivan Nausieda

Mixed-Signal Organic Integrated Circuits in a Fully Photolithographic Dual Threshold Voltage Technology

Analog & digital circuits implemented in a dual threshold voltage (VT) p-channel organic technology are presented. The dual VT organic technology is compatible with large-area and mechanically flexible substrates due to its low processing temperature (≤ 95°C) and scalable patterning techniques. We demonstrate the first analog & digital organic integrated circuits produced by a dual-gate metal process. The analog circuits are powered by a 5-V supply and include a differential amplifier and a two-stage uncompensated operational amplifier (op-amp). A dynamic comparator is measured to have an input offset voltage of 200 mV and latching time of 119 ms. Both the comparator and the op-amp dissipate 5 nW or less. Area-minimized digital logic is presented. Inverters powered by a 3-V supply were measured to have positive noise margins and consumed picowatts of power. An 11-stage ring oscillator, also powered by a 3-V supply, swings near rail to rail at 1.7 Hz. These results demonstrate dual threshold voltage process feasibility for large-area flexible mixed-signal organic integrated circuits.

Dual Threshold Voltage Organic Thin-Film Transistor Technology

A fully photolithographic dual threshold voltage (VT) organic thin-film transistor (OTFT) process suitable for flexible large-area integrated circuits is presented. The nearroom-temperature (<; 95 °C) process produces integrated dual VT pentacene-based p-channel transistors. The two VT s are enabled by using two gate metals of low (aluminum) and high (platinum) work function. The Al and Pt gate OTFTs exhibit nominally identical current-voltage transfer curves shifted by an amount ΔVT. The availability of a high-VT device enables area-efficient zero-Vos high-output-resistance current sources, enabling high-gain inverters. We present positive noise margin inverters and rail-to-rail ring oscillators powered by a 3-V supply-one of the lowest supply voltages reported for OTFT circuits. These results show that integrating nand p-channel organic devices is not mandatory to achieve functional area-efficient low-power organic integrated circuits.

An integrated organic circuit array for flexible large-area temperature sensing

Traditionally, several technologies have been used for temperature sensing, including integrated silicon ^#x0394;VBE and #x0394;Vt circuits, resistance temperature detectors, and thermocouples [1]. The organic thin-film transistor (OTFT) is a new technology suitable for temperature sensing because of two key advantages. First, OTFTs have the ability to be fabricated on flexible and large-area substrates [2]. This ability allows an OTFT temperature sensor to be used for applications such as electronic skin, biomedical thermal imaging, and structural temperature monitoring [2]. Second, the OTFTs semiconductor trap states make OTFTs highly responsive to temperature. This paper presents the first integrated OTFT temperature sensing circuit array. The array is compatible with flexible and large-area substrates, and its outputs are 22 times more responsive than the MOSFET implementation while dissipating 90nW of power per cell.

Dual threshold voltage integrated organic technology for ultralow-power circuits

For the first time, we demonstrate control of organic thinfilm transistors (OTFT) threshold voltage (VT) by modifying the gate work function. We present a near-room-temperature, fully lithographic process to fabricate integrated pentacene dual VT OTFTs suitable for large-area and flexible mixed signal circuits. Platinum and aluminum are used as the gate metals for the high VT (more depletion-like) and low VT (more enhancement-like) p-channel devices, respectively. The availability of a high VT device enables area-efficient zero-VGS current source loads. We demonstrate positive noise margin inverters which use pico Watts of power and a 3 V supply. Compared to a single VT implementation, the dual VT inverter occupies an area that is 30× smaller, and is 17× faster. These results show that p-channel only organic technologies can produce functional and low-power circuits without integrating a complementary device.

An Organic Imager for Flexible Large Area Electronics

An active-matrix organic imager suitable for large area flexible electronics is presented. The imager is fabricated using low-temperature (<95degC) processing, producing integrated organic transistors, organic photodetectors, and metal interconnects. Each pixel has a responsivity of 6 times 10-5 A/W and an on/off ratio of 880. The 4 times 4 array occupies 10.2mm2 and is powered by a 25V supply.

Molecular organic electronic circuits

Electronic energy disorder associated within amorphous and polycrystalline molecular organic thin film structures strongly affects the macroscopic observable behavior of organic field effect transistors (OFET) and poses practical challenges to implementing OFET circuits. It has been convenient to ignore the detailed physical processes associated with this disorder and model OFET behavior as equivalent to silicon FETs, but such simplifications limit our ability to develop integrated circuit technology as they fail to predict the true integrated OFET behavior. This talk will highlight the evolution of the organic electronic circuit technology and the challenges that lay ahead, emphasizing the need for physically accurate models of device behavior as the cornerstone of any future circuit advancements