Complementary-like Inverters Research Articles

Highly Flexible and High-Performance Complementary Inverters of Large-Area Transition Metal Dichalcogenide Monolayers.

Complementary inverters constructed from large-area monolayers of WSe2 and MoS2 achieve excellent logic swings and yield an extremely high gain, large total noise margin, low power consumption, and good switching speed. Moreover, the WSe2 complementary-like inverters built on plastic substrates exhibit high mechanical stability. The results provide a path toward large-area flexible electronics.

High mobility ambipolar organic field-effect transistors with a nonplanar heterojunction structure

Ambipolar organic field-effect transistors (OFETs) based on a bilayer structure of highly crystalline small molecules, n-type α,ω-diperfluorohexylquaterthiophene (DFH-4T) and p-type dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT), are investigated. By employing DFH-4T/DNTT as the bottom/top layers and appropriate high work function (WF) electrodes in a bottom-gate, top-contact configuration, the superior ambipolar characteristics with matched electron and hole mobilities of 1–1.1 cm2 V−1 s−1 are achieved. Intriguingly, this high-performance device exhibits a unique feature of an extremely rough, nonplanar heterojunction in the DFH-4T/DNTT combination and a large electron injection barrier from the high WF electrodes to DFH-4T, suggesting some underlying mechanisms for the effective charge transport and injection. The electrical and structural analyses reveal that the crystal packing of the bottom DFH-4T layer supports the growth of a high-quality DNTT crystal network for high-mobility hole transport upon the nonplanar heterojunction, and also enables the formation of an enlarged organic/metal contact surface for efficient electron injection from the high WF electrodes, as the key attributes leading to an overall excellent ambipolar behavior. The effect of intrinsic charge accumulation at the heterojunction interface on the ambipolar conduction is also discussed. Furthermore, a complementary-like inverter constructed with two DFH-4T/DNTT ambipolar OFETs is demonstrated, which shows a gain of 30.

Control of Ambipolar Transport in SnO Thin-Film Transistors by Back-Channel Surface Passivation for High Performance Complementary-like Inverters.

For ultrathin semiconductor channels, the surface and interface nature are vital and often dominate the bulk properties to govern the field-effect behaviors. High-performance thin-film transistors (TFTs) rely on the well-defined interface between the channel and gate dielectric, featuring negligible charge trap states and high-speed carrier transport with minimum carrier scattering characters. The passivation process on the back-channel surface of the bottom-gate TFTs is indispensable for suppressing the surface states and blocking the interactions between the semiconductor channel and the surrounding atmosphere. We report a dielectric layer for passivation of the back-channel surface of 20 nm thick tin monoxide (SnO) TFTs to achieve ambipolar operation and complementary metal oxide semiconductor (CMOS) like logic devices. This chemical passivation reduces the subgap states of the ultrathin channel, which offers an opportunity to facilitate the Fermi level shifting upward upon changing the polarity of the gate voltage. With the advent of n-type inversion along with the pristine p-type conduction, it is now possible to realize ambipolar operation using only one channel layer. The CMOS-like logic inverters based on ambipolar SnO TFTs were also demonstrated. Large inverter voltage gains (>100) in combination with wide noise margins are achieved due to high and balanced electron and hole mobilities. The passivation also improves the long-term stability of the devices. The ability to simultaneously achieve field-effect inversion, electrical stability, and logic function in those devices can open up possibilities for the conventional back-channel surface passivation in the CMOS-like electronics.

Ambipolar inverters with natural origin organic materials as gate dielectric and semiconducting layer.

Thin film electronics fabricated with non‐toxic and abundant materials are enabling for emerging bioelectronic technologies. Herein complementary‐like inverters comprising transistors using 6,6′‐dichloroindigo as the semiconductor and trimethylsilyl‐cellulose (TMSC) films on anodized aluminum as bilayer dielectric layer are demonstrated. The inverters operate both in the first and third quadrant, exhibiting a maximum static gain of 22 and a noise margin of 58% at a supply voltage of 14 V. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

Naphthodithiophenediimide (NDTI)-based triads for high-performance air-stable, solution-processed ambipolar organic field-effect transistors

We report new NDTI-based triad-type ambipolar molecular semiconductors for high-performance air-stable, solution-processed OFETs and complementary-like inverters.

Polymer-sorted semiconducting carbon nanotube networks for high-performance ambipolar field-effect transistors.

Efficient selection of semiconducting single-walled carbon nanotubes (SWNTs) from as-grown nanotube samples is crucial for their application as printable and flexible semiconductors in field-effect transistors (FETs). In this study, we use atactic poly(9-dodecyl-9-methyl-fluorene) (a-PF-1-12), a polyfluorene derivative with asymmetric side-chains, for the selective dispersion of semiconducting SWNTs with large diameters (>1 nm) from plasma torch-grown SWNTs. Lowering the molecular weight of the dispersing polymer leads to a significant improvement of selectivity. Combining dense semiconducting SWNT networks deposited from an enriched SWNT dispersion with a polymer/metal-oxide hybrid dielectric enables transistors with balanced ambipolar, contact resistance-corrected mobilities of up to 50 cm2·V–1·s–1, low ohmic contact resistance, steep subthreshold swings (0.12–0.14 V/dec) and high on/off ratios (106) even for short channel lengths (<10 μm). These FETs operate at low voltages (<3 V) and show almost no current hysteresis. The resulting ambipolar complementary-like inverters exhibit gains up to 61.

Hybrid Nanodielectrics for Low‐Voltage Organic Electronics

Nanoscale hybrid dielectrics composed of an ultra‐thin polymeric low‐κ bottom layer and an ultra‐thin high‐κ oxide top layer, with high dielectric strength and capacitances up to 0.25 μFcm−2, compatible with low‐voltage, low‐power, organic electronic circuits are demonstrated. An efficient and reliable fabrication process, with 100% yield achieved on lab‐scale arrays, is demonstrated by means of pulsed laser deposition (PLD) for the fast growth of the oxide layer. With this strategy, high capacitance top gate (TG), n‐type and p‐type organic field effect transistors (OFETs) with high mobility, low leakage currents, and low subthreshold slopes are realized and employed in complementary‐like inverters, exhibiting ideal switching for supply voltages as low as 2 V. Importantly, the hybrid double‐layer allows for a neat decoupling between the need for a high capacitance, guaranteed by the nanoscale thickness of the double layer, and for an optimized semiconductor–dielectric interface, a crucial point in enabling high mobility OFETs, thanks to the low‐κ polymeric dielectric layer in direct contact with the polymer semiconductor. It is shown that such decoupling can be achieved already with a polymer dielectric as thin as 10 nm when the top oxide is deposited by PLD. This paves the way for a very versatile implementation of the proposed approach for the scaling of the operating voltages of TG OFETs with very low level of dielectric leakage currents to the fabrication of low‐voltage organic electronics with drastically reduced power consumption.

Naphthalenediimide-Based Copolymers Incorporating Vinyl-Linkages for High-Performance Ambipolar Field-Effect Transistors and Complementary-Like Inverters under Air

We report the synthesis of two novel donor–acceptor copolymers poly{[N, N′-bis(alkyl)-1,4,5,8-naphthalene diimide-2,6-diyl-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-2-(2-(thiophen-2-yl)vinyl)thiophene]} (PNVTs) based on naphthalenediimide (NDI) acceptor and (E)-2-(2-(thiophen-2-yl)vinyl)thiophene donor. The incorporations of vinyl linkages into polymer backbones maintain the energy levels of the lowest unoccupied molecular orbits at −3.90 eV, therefore facilitating the electron injection. Moreover, the energy levels of the highest occupied molecular orbits increase from −5.82 to −5.61 eV, successfully decreasing the hole injection barrier. Atomic force microscopy measurements indicate that PNVTs thin films exhibit larger polycrystalline grains compared with that of poly{[N, N′-bis(2-octyldodecyl)-1,4,5,8-naphthalene diimide-2,6-diyl]-alt- 5,5′-(2,2′-bithiophene)} [P(NDI2OD-T2)], consistent with the stronger π–π stacking measured by grazing incidence X-ray scatting. To optimize devices performance, field-effect transistors (FETs) with three devices configurations have been investigated. The results indicate that the electron mobility of the vinyl-containing PNVTs exhibit about 3–5 times higher than that of P(NDI2OD-T2). Additionally, the vinyl-linkages in PNVTs remarkably enhance ambipolar transport of their top-gate FETs, obtaining high hole and electron mobilities of 0.30 and 1.57 cm2 V–1 s–1, respectively, which are among the highest values reported to date for the NDI-based polymers. Most importantly, ambipolar inverters have been realized in ambient, exhibiting a high gain of 155. These results provide important progresses in solution-processed ambipolar polymeric FETs and complementary-like inverters.

Remarkable Enhancement of Hole Transport in Top‐Gated N‐Type Polymer Field‐Effect Transistors by a High‐k Dielectric for Ambipolar Electronic Circuits

A remarkable enhancement of p-channel properties is achieved in initially n-channel dominant ambipolar P(NDI2OD-T2) organic field-effect transistors (OFETs) by the use of the fluorinated high-k dielectric P(VDF-TrFE). An almost two orders of magnitude increase in hole mobility (~0.11 cm(2) V(-1) s(-1) ) originates from a strong interface modification at the semiconductor/dielectric interface, which provides high-performance complementary-like inverters and ring oscillator circuits.

Complementary-like inverters based on an ambipolar solution-processed molecular bis(naphthalene diimide)-dithienopyrrole derivative

We report on high-mobility top-gate organic field-effect transistors (OFETs) and complementary-like inverters fabricated with a solution-processed molecular bis(naphthalene diimide)-dithienopyrrole derivative as the channel semiconductor and a CYTOP/Al2O3 bilayer as the gate dielectric. The OFETs showed ambipolar behavior with average electron and hole mobility values of 1.2 and 0.01cm2V−1s−1, respectively. Complementary-like inverters fabricated with two ambipolar OFETs showed hysteresis-free voltage transfer characteristics with negligible variations of switching threshold voltages and yielded very high DC gain values of more than 90V/V (up to 122V/V) at a supply voltage of 25V.

35.5L: Late‐News Paper: An Ambipolar Oxide TFT

AbstractWe fabricated transparent oxide semiconductor‐based ambipolar TFTs on SiO2/c‐Si with a maximum process temperature of 250 °C. Saturation mobilities of ∼0.81 cm2(Vs)−1 for p‐channel and ∼5×10−4 cm2(Vs)−1 for n‐channel operations were obtained at RT. We demonstrated a complementary‐like inverter comprised of two SnO‐based ambipolar TFTs. The inverter operated with a maximum voltage gain of ∼2.5. This is the first demonstration of an oxide‐based complementary‐like inverter using a single channel material, which allows simple fabrication of complementary logic circuits based on oxide TFTs. In addition, the device operates stably in air, is optically transparent and can be fabricated at 250 °C. Therefore, the essence of our findings can further be extended to flexible substrates. We expect that optimization of processing and more appropriate selection of source/drain electrode materials will improve the n‐channel mobilities, and pave the way for oxide‐based complementary circuit technology.

Low Operating Bias and Matched Input−Output Characteristics in Graphene Logic Inverters

We developed a simple and novel method to fabricate complementary-like logic inverters based on ambipolar graphene field-effect transistors (FETs). We found that the top gate stacks (with both the metal and oxide layers) can be simply prepared with only one-step deposition process and show high capacitive efficiency. By employing such a top gate as the operating terminal, the operating bias can be lowered within 2 V. In addition, the complementary p- and n-type FET pairs can be also simply fulfilled through potential superposition effect from the drain bias. The inverters can be operated, with up to 4-7 voltage gains, in both the first and third quadrants due to the ambipolarity of graphene FETs. For the first time, a match between the input and output voltages is achieved in graphene logic devices, indicating the potential in direct cascading of multiple devices for future nanoelectronic applications.

Ambipolar organic transistors and near-infrared phototransistors based on a solution-processable squarilium dye

Implementation of organic transistors in low-end, large-volume microelectronics depends, greatly, on the level of performance that can be achieved, but also on the compatibility of the technology with low-cost processing methodologies. Here we examine the suitability of a family of solution-processable zwitterionic molecules, so-called squarilium dyes, for the fabrication of organic ambipolar transistors and their application in (opto)electronic circuits. Ambipolar organic semiconductors and transistors are interesting because they could deliver performance characteristics (i.e. noise margins and signal gain) similar to that of complementary logic, but with the fabrication simplicity associated with unipolar logic (i.e. single semiconductor material and single type of metal electrodes). By designing squarilium dyes with appropriate electrochemical characteristics we demonstrate single-layer organic transistors that exhibit ambipolar charge transport with balanced electron and hole mobilities. By integrating a number of these ambipolar transistors we are also able to demonstrate complementary-like voltage inverters with wide noise margin and high signal gain. Another interesting feature of the squarilium dyes studied here is their strong absorption in the near-infrared (NIR) region of the electromagnetic spectrum. By exploring this interesting property we are able to demonstrate NIR light-sensing ambipolar organic transistors with promising operating characteristics.

Air Stable Ambipolar Organic Field-Effect Transistors and Complementary-Like Inverters Prepared with Surface-Modified Gate Dielectrics

Air stable ambipolar organic field-effect transistors containing p/n heterojunctions are achieved by passivating the electron trapping sites on the SiO 2 surface. The morphology of the heterojunctions is controlled by the film thicknesses of p- and n-channel semiconductors, thereby affecting the device air stability and the electrical characteristics. Further, air stable complementary-like inverters, which are able to work both in the first and the third quadrants with a high gain up to 30, are also demonstrated.

Realization of ambipolar pentacene thin film transistors through dual interfacial engineering

Ambipolar conduction of a pentacene-based field-effect transistor can be attributed to dual interface engineering, which occurs at the dielectric∕semiconductor interface and electrode∕semiconductor interface. While the former was realized by utilizing a hydroxyl-free gate dielectric, the latter was made feasible by the use of appropriate metal source and drain electrodes. The field-effect hole and electron mobilities of 0.026 and 0.0023cm2∕Vs, respectively, were extracted from the transfer characteristics of pentacene organic field-effect transistors utilizing polymethyl methacrylate as the trap-reduction interfacial modified layer and Al as the source and drain (S∕D) electrodes. We demonstrated a complementarylike inverter by using two identical ambipolar transistors and it can be operated both in the first and third quadrants with a high output voltage gain of around 10.

Organic inverter circuits employing ambipolar pentacene field-effect transistors

Ambipolar transport has been observed in pentacene films grown on polyvinyl alcohol gate dielectric with hole and electron mobilities of 0.3 and 0.04cm2∕Vs, respectively. A simple device structure with Au as source-drain electrode can be used to operate a transistor in both p-channel and n-channel modes without employing low work function metal electrodes for ambipolar charge injection. Using ambipolar pentacene field-effect transistors, we construct a complementarylike inverter with voltage inversion gain of ∼10. These inverters are able to operate both in first and third quadrants of the voltage output to voltage input characteristics which is a unique feature of employing ambipolar transistors.

Ambipolar Field‐Effect Transistors Based on Solution‐Processable Blends of Thieno[2,3‐b]thiophene Terthiophene Polymer and Methanofullerenes

Thin-film field-effect transistors showing n- and p-type conduction under different bias conditions are produced from solution-processable ambipolar blends of thieno[2,3-b]thiophene terthiophene polymer and phenyl C61 butyric acid methyl ester (see Figure). Balanced charge transport in this blend is achieved by treating the insulator interface with alkyl-chain silanes. Complementary-like inverters have been fabricated on a single substrate, showing a maximum gain of 65.

Integrated Complementary-Like Circuits Based on Organic Ambipolar Transistors

AbstractWe report on an approach towards integrated complementary-like circuits based on organic ambipolar transistors. In particular, we show that ambipolar transport can be achieved within a single transistor channel using gold electrodes and a solution processable polymer-small molecule blend as the electroactive material. To demonstrate the suitability of these devices for practical utilisation in logic circuits we realise complementary-like voltage inverters comprised entirely of ambipolar transistors. Moreover, by integrating several such inverters we are able to demonstrate more complex circuits such as ring oscillators.

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.