Large-area plastic nanogap electronics enabled by adhesion lithography

Semple, J. Edward; Georgiadou, Dimitra G.; Wyatt-Moon, Gwenhivir; Seitkhan, Akmaral; Yengel, Emre; Rossbauer, Stephan; Bottacchi, Francesca; McLachlan, Martyn A.; Bradley, Donal D. C.; Anthopoulos, Thomas D.

doi:10.1038/s41528-018-0031-3

Cited by 34 publications

(54 citation statements)

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“…Whether the WF is increased or reduced is highly dependent on the SAM character; namely the dipole moment and electron withdrawing/donating nature of the SAM tail, and the chemical nature of the anchoring head group . Therefore, we employed two types of thiol‐based SAMs, 4‐methylbenzenethiol (MBT) and pentafluorobenzenethiol (PFBT) (Figure a), to reduce and increase, respectively, the energetic mismatch between Au and P‐90. The WFs of the untreated and functionalized electrodes were measured using Kelvin Probe (KP), finding the energetic mismatch in the Au, Au:MBT, and Au:PFBT P‐90 OECTs to be 1.2, 0.5, and 1.6 eV, respectively (Figure b).…”

Section: A Summary Of the Dispersive And Polar Surface Energy Componementioning

confidence: 99%

On the Role of Contact Resistance and Electrode Modification in Organic Electrochemical Transistors

et al. 2019

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Contact resistance is renowned for its unfavorable impact on transistor performance. Despite its notoriety, the nature of contact resistance in organic electrochemical transistors (OECTs) remains unclear. Here, by investigating the role of contact resistance in n‐type OECTs, the first demonstration of source/drain‐electrode surface modification for achieving state‐of‐the‐art n‐type OECTs is reported. Specifically, thiol‐based self‐assembled monolayers (SAMs), 4‐methylbenzenethiol (MBT) and pentafluorobenzenethiol (PFBT), are used to investigate contact resistance in n‐type accumulation‐mode OECTs made from the hydrophilic copolymer P‐90, where the deliberate functionalization of the gold source/drain electrodes decreases and increases the energetic mismatch at the electrode/semiconductor interface, respectively. Although MBT treatment is found to increase the transconductance three‐fold, contact resistance is not found to be the dominant factor governing OECT performance. Additional morphology and surface energy investigations show that increased performance comes from SAM‐enhanced source/drain electrode surface energy, which improves wetting, semiconductor/metal interface quality, and semiconductor morphology at the electrode and channel. Overall, contact resistance in n‐type OECTs is investigated, whilst identifying source/drain electrode treatment as a useful device engineering strategy for achieving state of the art n‐type OECTs.

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Section: A Summary Of the Dispersive And Polar Surface Energy Componementioning

confidence: 99%

On the Role of Contact Resistance and Electrode Modification in Organic Electrochemical Transistors

et al. 2019

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“…demonstrated. Recently a proof-of-concept nanogap n-PLEDs based on four different solution-processed organic polymers, covering emission across the whole visible spectrum, has also been reported [17].…”

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“…Herein we report on a-Lith fabricated coplanar green-emitting n-PLEDs on both glass and plastic substrates and study their optoelectronic characteristics. The a-Lith process steps to obtain nanogap separated asymmetric metal contacts, comprising a gold (Au) anode and an aluminium (Al) cathode, have been reported elsewhere [9,17]. The scanning electron micrograph (recorded with a LEO Gemini 1525 field emission scanning electron microscope with the operating voltage at 5 kV) shown in figure 1(a) depicts a separation of ∼15 nm between the Au and Al electrodes.…”

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confidence: 99%

“…For instance, the current measured in the 1 cm width diode at 10 V (7.6 mA) is over an order of magnitude larger as compared to the 4 mm width device (0.14 mA) shown in figure 2(a). To give an estimate of the range of current densities obtained with our devices, we have used the geometrical area of various electrode widths and calculated current densities (the geometrical area calculation is mentioned above and also reported in our recent publication [17]) ranging from circa 5×10 5 to 2.5×10 6 mA cm −2 for the interdigitated 20 and 1 cm-long electrodes, respectively, shown in figure 3(a). These values are in accordance with other nanoscale OLED reports containing devices of similar active area, although based on a vertical architecture [24].…”

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Flexible nanogap polymer light-emitting diodes fabricated via adhesion lithography (a-Lith)

et al. 2018

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We report the development of coplanar green colour organic light-emitting diodes (OLEDs) based on asymmetric nanogap electrodes fabricated on different substrates including glass and plastic. Using adhesion lithography (a-Lith) we pattern Al and Au layers acting as the cathode and anode electrodes, respectively, separated by an inter-electrode distance of <15 nm with an aspect ratio of up to 10 6 . Spin-coating the organic light-emitting polymer poly(9,9-dioctylfluorene-alt-bithiophene) (F8T2) on top of the asymmetric Al-Au nanogap electrodes results in green light-emitting nanogap OLEDs with promising operating characteristics. We show that the scaling of the OLED's width from 4 to 200 mm can substantially improve the light output of the device without any adverse effects on the manufacturing yield. Furthermore, it is found that the light-emitting properties in the nanogap area differ from the bulk organic film, an effect attributed to confinement of the conjugated polymer chains in the nanogap channel. These results render a-Lith particularly attractive for low cost facile fabrication of nanoscale light-emitting sources and arrays on different substrates of arbitrary size.Nanometer-sized polymer light-emitting diodes (n-PLEDs) have been proposed as light sources in subwavelength scanning near-field optical microscopes as well as in nanoscale photo-patterning to create simultaneously a large number of identical patterns [1,2]. Their unique advantages are colour tunability, versatility in geometrical pattern selection and ease of manufacturing of nanostructured arrays using low cost solution processing on substrates of arbitrary size and shape [3]. From an operational standpoint, miniaturised light-emitting diodes are advantageous to larger area ones, as higher current densities can be sustained thanks to efficient dissipation of Joule heating [4,5]. Indeed a suppression of organic light-emitting diodes (OLEDs) rolloff characteristics has been observed upon narrowing the current injection/transport area down to 50 nm [6]. These developments led to demonstration of low threshold amplified spontaneous emission in light-emitting polymer films [7], which could pave the way to the realisation of electrically pumped organic lasers [8]. Further progress has, however, been hindered by manufacturing challenges, as shadow masking and conventional photolithography cannot produce nanometer-sized electrode feature between different metals, and e-beam lithography is not suitable for upscale while it is often limited to a single electrode material. We have recently introduced adhesion lithography (a-Lith) technique as a viable alternative for the scalable sub-15 nm patterning of asymmetric, i.e. of different work function, coplanar metal electrodes on large area flexible substrates [9]. The asymmetric nature of the electrodes, which is difficult to obtain with other common nanopatterning techniques, allows for a range of electronic nanogap devices to be created via simply depositing a single layer of active material on top of d...

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“…The method—referred to as adhesion lithography or “a‐lith”—has the advantage of involving only a few simple processing steps that can be carried out at room temperature under ambient conditions, using inexpensive equipment. Adhesion lithography provides a rapid route to highly aligned, electrically isolated, asymmetric electrodes separated on the nanometer length scale, and has been successfully applied to a broad range of nanogap devices, including light‐emitting diodes, optical sensors, high frequency (>20 MHz) Schottky diodes, field effect transistors, and memristors …”

Section: Introductionmentioning

confidence: 99%

Spontaneous Formation of Nanogap Electrodes by Self‐Peeling Adhesion Lithography

Luo

Hoff

deMello

2019

Adv Materials Inter

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others are limited to the patterning of a single metal, and consequently cannot be applied to the fabrication of asymmetric nanoscale devices such as rectifiers and ambipolar devices that require the use of closely spaced dissimilar metal electrodes.Beesley et al. recently reported an alternative method for fabricating arrays of high aspect-ratio asymmetric nanogap electrodes, which exploits the ability of selected self-assembled monolayers (SAMs) to attach conformally to a prepatterned metal layer and thereby weaken adhesion to a subsequently deposited metal film. [24] The method-referred to as adhesion lithography or "a-lith"-has the advantage of involving only a few simple processing steps that can be carried out at room temperature under ambient conditions, using inexpensive equipment. Adhesion lithography provides a rapid route to highly aligned, electrically isolated, asymmetric electrodes separated on the nanometer length scale, and has been successfully applied to a broad range of nanogap devices, including light-emitting diodes, [25] optical sensors, [26] high frequency (>20 MHz) Schottky diodes, [27,28] field effect transistors, [29,30] and memristors. [30,31] The main processing steps in the usual a-lith procedure are summarized in Figure 1. A thin (≈50 nm) metal film (M1) is deposited on a substrate, and selectively patterned to expose the underlying substrate in regions where a second metal will subsequently be deposited (Figure 1a). An alkyl-containing metallophilic SAM is conformally attached to all exposed surfaces of M1, with the alkyl chains facing outwards from the metal surface ( Figure 1b). Next, a second metal film (M2) is uniformly deposited over the full area of the substrate (Figure 1c). Owing to the presence of the SAM, the adhesion of M2 to M1 is much weaker than its adhesion to the substrate. In consequence, if an adhesive tape or film is applied uniformly to the surface of M2 (Figure 1d) and then pulled away (Figure 1e-(i)), M2 will detach from the regions above M1 and remain only in those areas where M2 is in direct contact with the substrate. Hence, at the end of the procedure the two metals will sit in a complementary arrangement, side-by-side on the substrate, separated in the limiting case by just the length of the SAM-a few nanometers or less. The SAM may subsequently be removed by UV/ozone or oxygen plasma treatment, leaving an unfilled gap between the two electrodes (Figure 1f).In practice, the reported electrode spacings achieved with adhesion lithography have been substantially higher than the SAM length, typically lying in the 15-100 nm size range, depending on how the peeling step is carried out. (Factors such Adhesion lithography ("a-lith") is a simple method for forming nanoscale gaps between dissimilar metals. In its usual form, a metal is patterned on a substrate, and conformally coated with an alkyl-functionalized self-assembled monolayer, rendering it nonadhesive to other metals; a second metal is then deposited uniformly over the full area of the substrate; finall...

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Large-area plastic nanogap electronics enabled by adhesion lithography

Cited by 34 publications

References 63 publications

On the Role of Contact Resistance and Electrode Modification in Organic Electrochemical Transistors

On the Role of Contact Resistance and Electrode Modification in Organic Electrochemical Transistors

Flexible nanogap polymer light-emitting diodes fabricated via adhesion lithography (a-Lith)

Spontaneous Formation of Nanogap Electrodes by Self‐Peeling Adhesion Lithography

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