1,721,462 research outputs found
High throughput fabrication of nanoscale optoelectronic devices on large area flexible substrates using adhesion lithography
No full textNanoscale optoelectronic devices based on coplanar nanogap electrodes, when compared with traditional vertical devices, exhibit attractive characteristics, such as high density of integration, high sensitivity, fast response and multifunctionality. Moreover, their low-cost high-throughput fabrication on flexible disposable substrates opens up several new applications in sectors ranging from telecommunications and consumer electronics to healthcare - to name a few. However, their commercial exploitation has been hitherto impeded by technological bottlenecks, owing to the incompatibility of currently available fabrication techniques, eg. e-beam lithography, with industrial upscaling. Adhesion lithography is a nanopatterning technique that allows the facile high yield fabrication of coplanar metal electrodes separated by a sub-15 nm gap on large area substrates of any type, including plastic. These electrodes, when combined with solution-processed and/or low-dimensional nanostructured materials deposited at low, plastic-compatible, temperatures give rise to nanoscale optoelectronic devices with intriguing properties. It will be shown that both nanoscale light-emitting and light-sensing devices can be fabricated upon using light-emitting polymers along with self-assembling surface modifiers, and lead halide perovskites and functionalised colloidal PbS quantum dots, respectively. Emphasis will be given in recent advances in flexible nanoscale photodetectors fabricated with nanogap coplanar electrodes, operating in DUV up to NIR part of the spectrum. These devices exhibit high responsivity, sensitivity and fast response speed (hundreds of nanoseconds) owing to the extreme downscaling of key device dimensions. These results demonstrate that adhesion lithography combined with advanced materials concepts constitutes a new fabrication paradigm enabling a plethora of advanced applications within the field of flexible electronics
Adhesion lithography for fabrication of printed radio-frequency diodes
No full textRadio-frequency (RF) diodes are quintessential elements of passive RF identification tags that are used on livestock, luxury objects, and healthcare products. They are also used in near-field communication applications that enable wireless data transfer between devices. An RF diode—when matched to a suitable antenna—picks up the alternating current (AC) signal that is emitted from an RF source and transforms it to a DC signal. The DC signal can then be used to decode the information stored in the tagged object, or to simply power another electronic or optoelectronic device (e.g., a sensor, battery, or LED). The high demand for RF-harvesting devices, however, can only fully be met if their fabrication costs are substantially reduced. To realize this reduction in cost, novel printing technologies that permit manufacturing on large substrates are required. With these technologies it should be possible to ascertain that an increased diode performance (in terms of a small voltage drop, minimum leakage current, and a large gamut of operating frequencies) is attained
Zinc oxide solution-processed Schottky diodes operating at 5G frequencies
No full text5G networks are currently being deployed around the world, introducing a new era in machine-to-machine communications and reinforcing the Internet of Things. The 5G radiofrequency bands range from sub-1 GHz to 70 GHz, while the 6th generation (6G) is expected to cover bands at hundreds of GHz. There is a need for devices with high frequency performance and scalable manufacturing using inexpensive techniques and materials. Herein we present ZnO-based Schottky diodes, processed from solution on wafer scale with high yield. Coplanar nanogap electrodes are fabricated using a high-throughput low-cost technique, named adhesion lithography. The diodes’ cutoff frequency exceeds 100 GHz
Radio frequency diodes and circuits fabricated via adhesion lithography
No full textThe commercial interest in Radio Frequency Identification (RFID) tags keeps growing, as new application sectors, spanning from healthcare to electronic article surveillance (EAS) and personal identification, are constantly emerging for these types of electronic devices. The increasing demand for the so-called “smart labels” necessitates their high throughput manufacturing, and indeed on thin flexible substrates, that will reduce the cost and render them competitive to the currently widely employed barcodes. Adhesion Lithography (a-Lith) is a novel patterning technique that allows the facile high yield fabrication of co-planar large aspect ratio (<100,000) metal electrodes separated by a sub-20 nm gap on large area substrates of any type. Deposition of high mobility semiconductors from their solution at low, compatible with plastic substrates, temperatures and application of specific processing protocols can dramatically improve the performance of the fabricated Schottky diodes. It will be shown that in this manner both organic and inorganic high speed diodes and rectifiers can be obtained, operating at frequencies much higher than the 13.56 MHz benchmark, currently employed in passive RFID tags and near filed communications (NFC). This showcases the universality of this method towards fabricating high speed p- and n-type diodes, irrespective of the substrate, simply based on the extreme downscaling of key device dimensions obtained in these nanoscale structures. The potential for scaling up this technique at low cost, combined with the significant performance optimisation and improved functionality that can be attained through intelligent material selection, render a-Lith unique within the field of plastic electronics
Solution-processable n-type organic semiconductors for electronics and energy harvesting systems
Full text linkOrganic semiconductors provide a wealth of interesting properties like tailor made
electrical characteristics, cost effective large area fabrication and mechanical flexibility
which can be difficult to achieve with crystalline inorganic semiconductors. However,
their advance into applications such as logic circuits is hindered by the limited availability
of high performance air-stable n-type materials, which limits organics to unipolar circuits.
This thesis explores three different routes to improve the performance of n-type organic
semiconductors. Firstly a novel air-stable small molecule with mobilities of up to
0.6 cm2/Vs in TFTs is presented. We blend the small molecule with a polymer to
improve the thin film smoothness and homogeneity. In combination with an established
p-type small molecule:polymer blend semiconductor we demonstrate an air-stable, solution
processed, complementary inverter with gains above 5. Secondly we use doping to enhance
the properties of Fullerene semiconductors. The efficiency of the doping process is found
to depend strongly on the Fullerene derivative used as matrix material, but where
it is effective, we see an increase in charge carrier mobility by the filling of shallow
trap states and enhanced bias stress stability. Thirdly we investigate a new patterning
process called adhesion lithography for metal electrodes, which is compatible with high
throughput fabrication. We use the process to manufacture asymmetric electrodes
with a distance below 15 nm. Taking advantage of the short distance and the small
parasitic capacitance of the structure we fabricate Schottky diodes based on Fullerenes
with operating frequencies exceeding 20 MHz. These diodes can be used in wireless
communication or energy harvesting systems. The findings may help to develop new
materials and processes for the next generation of organic semiconductors.Open Acces
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Flexible nanogap polymer light-emitting diodes fabricated via adhesion lithography (a-Lith)
Full text linkWe 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 106. 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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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