Complementary Ring Oscillators Research Articles

A flexible high potential printed battery for powering printed electronics

Mechanically flexible arrays of alkaline electrochemical cells fabricated using stencil printing onto fibrous substrates are shown to provide the necessary performance characteristics for driving ink-jet printed circuits. Due to the dimensions and material set currently required for reliable low-temperature print processing of electronic devices, a battery potential greater than that sourced by single cells is typically needed. The developed battery is a series interconnected array of 10 low resistance Zn-MnO2 alkaline cells, giving an open circuit potential of 14 V. This flexible battery is used to power an ink-jet printed 5-stage complementary ring oscillator based on organic semiconductors.

Contact properties of high-mobility, air-stable, low-voltage organic n-channel thin-film transistors based on a naphthalene tetracarboxylic diimide

Air-stable bottom-gate, top-contact n-channel organic transistors based on a naphthalene diimide exhibiting electron mobilities up to 0.8 cm2/Vs at low voltages were fabricated. Transistors with channel lengths of 1 μm show a transconductance of 60 mS/m, but are significantly limited by the contact resistance. Transmission line measurements in combination with contact resistance models were applied to investigate this influence. Both contact resistance and contact resistivity are proportional to the inverse gate overdrive voltage. Organic complementary ring oscillators were fabricated on a flexible plastic substrate showing record signal delays down to 17 μs at a supply voltage of 2.6 V.

Effect of gate electrode conductivity on operation frequency of inkjet-printed complementary polymer ring oscillators

We report the effect of the conductivity of the gate electrode on operation speeds in printed organic ring oscillators (RO). The highly conducting gate electrode leads to a superior oscillation frequency (as high as ~30kHz) for the printed ROs. Above the optimum thickness of the gate electrodes (~30nm), inkjet-printed p-type poly(3-hexylthiophene) (P3HT) and n-type poly([N,N-9-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,59-(2,29-bithiophene)) (P(NDI2OD-T2)) organic field-effect transistors showed reasonably high hole and electron mobilities of ~0.05cm2V−1s−1 and ~0.25cm2V−1s−1, respectively. Complementary inverters and ring oscillators based on these p- and n-type semiconductor transistors were constructed, where the inverters showed the inverting voltage, (Vinv) near the ideal switching points at 1/2 the drain voltage (VDD), high gain (~10), low static power consumptions, as well as high noise margin (~60% of 1/2VDD). Finally, printed P3HT complementary ring oscillators with a gate thickness over 30nm exhibited the highest oscillation frequency (~30kHz).

Low-voltage, high speed inkjet-printed flexible complementary polymer electronic circuits

We report the development of high-performance inkjet-printed organic field-effect transistors (OFETs) and complementary circuits using high-k polymer dielectric blends comprising poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) and poly(methyl methacrylate) (PMMA) for high-speed and low-voltage operation. Inkjet-printed p-type polymer semiconductors containing alkyl-substituted thienylenevinylene (TV) and dodecylthiophene (PC12TV12T) and n-type P(NDI2OD-T2) OFETs showed high field-effect mobilities of 0.1–0.4cm2V−1s−1 and low threshold voltages down to 5V. These OFET properties were modified by changing the blend ratio of P(VDF-TrFE) and PMMA. The optimum blend – a 7:3wt% mixture of P(VDF-TrFE) and PMMA – was successfully used to realize high-performance complementary inverters and ring oscillators (ROs). The complementary ROs operated at a supplied bias (VDD) of 5V and showed an oscillation frequency (fosc) as high as ∼80kHz at VDD=30V. Furthermore, the fosc of the complementary ROs was significantly affected by a variety of fundamental parameters such as the electron and hole mobilities, channel width and length, capacitance of the gate dielectrics, VDD, and the overlap capacitance in the circuit configuration.

Core‐Brominated Tetraazaperopyrenes as n‐Channel Semiconductors for Organic Complementary Circuits on Flexible Substrates

AbstractOrganic thin‐film transistors (TFTs) are prepared by vacuum deposition and solution shearing of 2,9‐bis(perfluoroalkyl)‐substituted tetraazaperopyrenes (TAPPs) with bromine substituents at the aromatic core. The TAPP derivatives are synthesized by reacting known unsubstituted TAPPs with bromine in fuming sulphuric acid, and their electrochemical properties are studied in detail by cyclic voltammetry and modelled with density functional theory (DFT) methods. Lowest unoccupied molecular orbital (LUMO) energies and electron affinities indicate that the core‐brominated TAPPs should exhibit n‐channel semiconducting properties. Current‐voltage characteristics of the TFTs established electron mobilities of up to μn = 0.032 cm2 V−1 s−1 for a derivative which was subsequently processed in the fabrication of a complementary ring oscillator on a flexible plastic substrate (PEN).

Complementary integrated circuits on plastic foil using inkjet printed n- and p-type organic semiconductors: Fabrication, characterization, and circuit analysis

Complementary thin-film transistor circuits composed of 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS–PEN) and a rylene carboxylic diimide derivative for p- and n-channel thin-film transistors (TFTs) were fabricated on flexible foils. The so-called staggered TFT configuration is used, meaning that the semiconductors layers are deposited last. The work-function of the injecting gold electrodes were modified using several self-assembled monolayers (SAMs). For optimized contacts the mobility of the n- and p-channel TFTs was 0.5cm2/Vs and 0.2cm2/Vs, respectively. Strongly degraded performance is obtained when the n-channel material was printed on contacts optimized for the p-channel TFT, and vice versa. This illustrates that for CMOS circuits we need careful work-function engineering to allow proper injection for both electrons and holes. We show for the first time that by using a bimolecular mixture for the SAM we can systematically vary the work function, and demonstrate how this affects the performance of discrete n-type and p-type transistors, as well as CMOS inverters and ring oscillators. Under optimal processing conditions we realized complementary 19-stage ring oscillators with 10μs stage delay operating at 20V.

Tetrachlorinated Tetraazaperopyrenes (TAPPs): Highly Fluorescent Dyes and Semiconductors for Air‐Stable Organic n‐Channel Transistors and Complementary Circuits

A range of 2,9-perfluoroalkyl-substituted tetraazaperopyrene (TAPP) derivatives (1-5) was synthesised by reacting 4,9-diamino-3,10-perylenequinone diimine (DPDI) with the corresponding carboxylic acid chloride or anhydride in the presence of a base. The reaction of compounds 1-4 with dichloroisocyanuric acid (DIC) in concentrated sulphuric acid resulted in the fourfold substitution of the tetraazaperopyrene core, yielding the 2,9-bisperfluoroalkyl-4,7,11,14-tetrachloro-1,3,8,10-tetraazaperopyrenes 6-9, respectively. The optical and electrochemical data demonstrate the drastic influence of the core substitution on the properties. All compounds are highly luminescent (fluorescence quantum yields of up to Φ=0.8). The LUMO energies of the tetrachlorinated TAPP derivatives (determined by cyclic voltammetry and computed by DFT calulations) were found to be below -4 eV. In the course of this work the performance of TAPP derivatives in organic thin-film transistors (TFTs) was investigated, and their n-channel characteristics with field-effect mobilities of up to 0.14 cm(2) V(-1) s(-1) and an on/off current ratio of >10(6) were confirmed. Long-term stabilities of 3-4 months under ambient conditions of the devices were established. Complementary inverters and ring oscillators with n-channel TFTs based on compound 8 and p-channel TFTs based on dinaphtho-[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) were fabricated on a glass substrate.

Complementary ring oscillator fabricated via direct laser-exposure and solution-processing of a single-layer organic film

A complementary ring oscillator is realized by exposing a solution-processed single-layer organic film to area-selective laser-light exposure and solution development. The pristine film comprises a blend of two organic semiconductors: p-type poly(3-hexylthiophene-2,5-diyl) (P3HT) and n-type [6,6]-phenyl C61 butyric acid methyl ester (PCBM). The exposure transforms PCBM into an insoluble form, and the subsequent development selectively removes the non-exposed PCBM while leaving exposed PCBM and P3HT intact. The 5-step ring oscillator exhibits a frequency of 10mHz, a power delay product of 2.0μJ, and an energy delay product of 22μJs. Opportunities for performance improvements of the scalable fabrication technique are highlighted in an accompanying analysis.

Polyelectrolyte‐Gated Organic Complementary Circuits Operating at Low Power and Voltage

Organic complementary inverters and ring oscillators based on polyelectrolyte-gated thin-film transistors are demonstrated. Detrimental electrochemical doping is suppressed by using polyanionic and polycationic gate insulators in the p- and n-channel transistors, respectively. The circuits operate at supply voltages between 0.2 V and 1.5 V, have a static power consumption of less than 2.5 nW per logic gate and show propagation delays down to 0.26 ms per stage.

Complementary Ring Oscillator Exclusively Prepared by Means of Gravure and Flexographic Printing

A complementary ring oscillator has been prepared using exclusively fast and continuous rotary printing methods, namely, gravure and flexographic printing, so that all layers were additively deposited and no additional patterning nor interconnecting step whatsoever was involved. This became possible due to the availability of a printable air-stable n-type organic semiconductor, i.e., a small molecule perylene derivative. Using the same dielectric for both types of transistors, the characteristics of the n-type transistors are reasonably similar to the ones of the p-type transistors, which are based on the previously used organic semiconductor 6,13-bis(triisopropylsilylethynyl) pentacene. The printed circuits are robust against variations of individual transistor parameters and significantly outperform comparable unipolar circuits in terms of all relevant properties. The superior performance can be attributed to complementary circuitry, the advantage of which is thereby demonstrated for the case of printed circuits.

Charge Injection Engineering of Ambipolar Field-Effect Transistors for High-Performance Organic Complementary Circuits

Ambipolar π-conjugated polymers may provide inexpensive large-area manufacturing of complementary integrated circuits (CICs) without requiring micro-patterning of the individual p- and n-channel semiconductors. However, current-generation ambipolar semiconductor-based CICs suffer from higher static power consumption, low operation frequencies, and degraded noise margins compared to complementary logics based on unipolar p- and n-channel organic field-effect transistors (OFETs). Here, we demonstrate a simple methodology to control charge injection and transport in ambipolar OFETs via engineering of the electrical contacts. Solution-processed caesium (Cs) salts, as electron-injection and hole-blocking layers at the interface between semiconductors and charge injection electrodes, significantly decrease the gold (Au) work function (∼4.1 eV) compared to that of a pristine Au electrode (∼4.7 eV). By controlling the electrode surface chemistry, excellent p-channel (hole mobility ∼0.1-0.6 cm(2)/(Vs)) and n-channel (electron mobility ∼0.1-0.3 cm(2)/(Vs)) OFET characteristics with the same semiconductor are demonstrated. Most importantly, in these OFETs the counterpart charge carrier currents are highly suppressed for depletion mode operation (I(off) < 70 nA when I(on) > 0.1-0.2 mA). Thus, high-performance, truly complementary inverters (high gain >50 and high noise margin >75% of ideal value) and ring oscillators (oscillation frequency ∼12 kHz) based on a solution-processed ambipolar polymer are demonstrated.

Organic complementary inverter and ring oscillator on a flexible substrate

A complementary inverter was fabricated using pentacene and N-N′-dioctyl-3,4,9,10-perylene tetracarboxylic diimide-C8 (PTCDI-C8) for p- and n-type transistors on a poly(ether sulfone) substrate, respectively. The mobilities of the p- and n-type transistors were 0.056 and 0.013 cm2/V s, respectively. The inverter, which was composed of p- and n-type transistors, showed a gain of 48.6 when V DD=−40 V and at the maximum noise margin of V DD/2. A ring oscillator was also fabricated by cascading five inverters. The five-stage ring oscillator showed the maximum output frequency of 10 kHz when V DD=−170 V.

Complementary Organic Circuits Using Evaporated $ \hbox{F}_{16}\hbox{CuPc}$ and Inkjet Printing of PQT

Organic complementary inverters and ring oscillators are fabricated using a unique combination of inkjet printing and evaporation of organic semiconductors. p-Type poly (3, 3'''-didodecylquaterthiophene) (PQT) is inkjet printed, after which n-type copper hexadecafluorophthalocyanine (F16CuPc) is evaporated and patterned by shadow masking. A solution-processable bilayer gate dielectric with superior gate leakage characteristics and a simplified process stack is implemented. The inverters show a high noise margin, good gain characteristics, and a switching point close to Vdd/2. A five-stage ring oscillator is also demonstrated.

High speeds complementary integrated circuits fabricated with all‐printed polymeric semiconductors

AbstractInkjet‐printed high speed polymeric complementary circuits are fabricated using an n‐type ([poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐dithiophene)} [P(NDI2OD‐T2), Polyera ActivInk N2200] and two p‐type polymers [poly(3‐hexylthiophene) (P3HT) and a dithiophene‐based polymer (Polyera ActivInk P2100)]. The top‐gate/bottom‐contact (TG/BC) organic field‐effect transistors (OFETs) exhibit well‐balanced and very‐high hole and electron mobilities (μFET) of 0.2–0.5 cm2/Vs, which were enabled by optimization of the inkjet‐printed active features, small contact resistance both of electron and hole injections, and effective control over gate dielectrics and its orthogonal solvent effect (selection of poly(methyl methacrylate) and 2‐ethoxyethanol). Our first demonstrated inkjet‐printed polymeric complementary devices have been integrated to high‐performance complementary inverters (gain &gt;30) and ring oscillators (oscillation frequency ∼50 kHz). We believe that the operating frequency of printable organic circuits can be further improved more than 10 MHz by fine‐tuning of the device architecture and optimization of the p‐ and n‐channel semiconductor processing. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010

An Optimal Design Method for Complementary Metal Oxide Semiconductor Even-Stage Ring Oscillators Containing Latches

This paper describes a design method for complementary metal oxide semiconductor (CMOS) ring oscillators composed of even-stage inverters. First, we propose a quantitative method to evaluate oscillation stability for an even-stage ring oscillator with a CMOS latch. The method uses static noise margin analysis to evaluate the static random access memory (SRAM) cell's data storage stability, by observing the similarity between the oscillator and SRAM cell circuitry. Next, the method is extended to oscillators with multiple latches. Finally, by analyzing oscillation stability using this method, we find that the range of stable oscillation conditions can be drastically widened by adding multiple single-channel latch circuits, and also by an appropriate design of their polarities and insertion positions. We also clarify through Monte Carlo simulations, that the optimized oscillator circuit is robust under process, voltage and temperature fluctuations and device characteristic variations.

Organic/inorganic hybrid complementary circuits based on pentacene and amorphous indium gallium zinc oxide transistors

Complementary inverters composed of pentacene for the p-channel thin-film transistors (TFTs) and amorphous indium gallium zinc oxide for the n-channel TFTs have been fabricated on glass substrates. The p- and n-channel TFTs have field-effect mobilities of 0.6 and 17.1 cm2/V s, respectively, and inverters yield a high gain of ∼56. Complementary five-stage ring oscillator exhibits a good dynamic operation with an output frequency of 200 Hz at 10 V. Since both channel layers are stable in air and can be formed by room temperature deposition process, the hybrid circuits are applicable to flexible electronic devices.

Low-voltage-operating organic complementary circuits based on pentacene and C 60 transistors

Low-voltage-operating organic complementary inverters and ring oscillators were fabricated using high field effect mobility pentacene and C 60 thin-film transistors (TFTs). The mobilities of pentacene and C 60 TFTs were 0.44 and 0.61 cm 2/V s, respectively. The complementary inverters composed of these TFTs operated in the voltage range of 2-10 V with large gain values up to 65. The inverter yields 5-stage ring oscillators with a high oscillation frequency of 80 Hz at 10 V.

Stretchable and Foldable Silicon Integrated Circuits

We have developed a simple approach to high-performance, stretchable, and foldable integrated circuits. The systems integrate inorganic electronic materials, including aligned arrays of nanoribbons of single crystalline silicon, with ultrathin plastic and elastomeric substrates. The designs combine multilayer neutral mechanical plane layouts and "wavy" structural configurations in silicon complementary logic gates, ring oscillators, and differential amplifiers. We performed three-dimensional analytical and computational modeling of the mechanics and the electronic behaviors of these integrated circuits. Collectively, the results represent routes to devices, such as personal health monitors and other biomedical devices, that require extreme mechanical deformations during installation/use and electronic properties approaching those of conventional systems built on brittle semiconductor wafers.

Complementary Logic Gates and Ring Oscillators on Plastic Substrates by Use of Printed Ribbons of Single-Crystalline Silicon

CMOS inverters and three-stage ring oscillators were formed on flexible plastic substrates by transfer printing of p-type and n-type single crystalline ribbons of silicon. The gain and the sum of high and low noise margins of the inverters were as high as ~150 and 4.5 V at supply voltages of 5 V, respectively. The frequencies of the ring oscillators reached 2.6 MHz at supply voltages of 10 V. These results, as obtained with devices that have relatively large critical dimensions (i.e., channel lengths in the several micrometer range), taken together with good mechanical bendability, suggest promise for the use of this type of technology for flexible electronic systems.

Ultralow-power organic complementary circuits

The prospect of using low-temperature processable organic semiconductors to implement transistors, circuits, displays and sensors on arbitrary substrates, such as glass or plastics, offers enormous potential for a wide range of electronic products. Of particular interest are portable devices that can be powered by small batteries or by near-field radio-frequency coupling. The main problem with existing approaches is the large power consumption of conventional organic circuits, which makes battery-powered applications problematic, if not impossible. Here we demonstrate an organic circuit with very low power consumption that uses a self-assembled monolayer gate dielectric and two different air-stable molecular semiconductors (pentacene and hexadecafluorocopperphthalocyanine, F16CuPc). The monolayer dielectric is grown on patterned metal gates at room temperature and is optimized to provide a large gate capacitance and low gate leakage currents. By combining low-voltage p-channel and n-channel organic thin-film transistors in a complementary circuit design, the static currents are reduced to below 100 pA per logic gate. We have fabricated complementary inverters, NAND gates, and ring oscillators that operate with supply voltages between 1.5 and 3 V and have a static power consumption of less than 1 nW per logic gate. These organic circuits are thus well suited for battery-powered systems such as portable display devices and large-surface sensor networks as well as for radio-frequency identification tags with extended operating range.