探花直播 of Cambridge - Deepak Venkateshvaran

鈥楩ruitcake鈥� structure observed in organic polymers

sc604 — Thu, 02 Jun 2022 08:35:03 +0000

探花直播field of organic electronics has benefited from the discovery of new semiconducting polymers with molecular backbones that are resilient to twists and bends, meaning they can transport charge even if they are flexed into different shapes.

It had been assumed that these materials resemble a plate of spaghetti at the molecular scale, without any long-range order. However, an international team of researchers found that for at least one such material, there are tiny pockets of order within. These ordered pockets, just a few ten-billionths of a metre across, are stiffer than the rest of the material, giving it a 鈥榝ruitcake鈥� structure with harder and softer regions.

探花直播work was led by the 探花直播 of Cambridge and Park Systems UK Limited, with KTH Stockholm in Sweden, the Universities of Namur and Mons in Belgium, and Wake Forest 探花直播 in the USA. Their results, reported in the journal Nature Communications, could be used in the development of next-generation microelectronic and bioelectronic devices.

Studying and understanding the mechanical properties of these materials at the nanoscale 鈥� a field known as nanomechanics 鈥� could help scientists fine-tune those properties and make the materials suitable for a wider range of applications.

鈥淲e know that the fabric of nature on the nanoscale isn鈥檛 uniform, but finding uniformity and order where we didn鈥檛 expect to see it was a surprise,鈥� said Dr Deepak Venkateshvaran from Cambridge鈥檚 Cavendish Laboratory, who led the research.

探花直播researchers used an imaging technique called higher eigen mode imaging to take nanoscale pictures of the regions of order within a semiconducting polymer called indacenodithiophene-co-benzothiadiazole (C16-IDTBT). These pictures showed clearly how individual polymer chains line up next to each other in some regions of the polymer film. These regions of order are between 10 and 20 nanometres across.

鈥� 探花直播sensitivity of these detection methods allowed us to map out the self-organisation of polymers down to the individual molecular strands,鈥� said co-author Dr Leszek Spalek, also from the Cavendish Laboratory. 鈥淗igher eigen mode imaging is a valuable method for characterising nanomechanical properties of materials, given the relatively easy sample preparation that is required.鈥�

Further measurements of the stiffness of the material on the nanoscale showed that the areas where the polymers self-organised into ordered regions were harder, while the disordered regions of the material were softer. 探花直播experiments were performed in ambient conditions as opposed to an ultra-high vacuum, which had been a requirement in earlier studies.

鈥淥rganic polymers are normally studied for their applications in large area, centimetre scale, flexible electronics,鈥� said Venkateshvaran. 鈥淣anomechanics can augment these studies by developing an understanding of their mechanical properties at ultra-small scales with unprecedented resolutions.

鈥淭ogether, the fundamental knowledge gained from both types of studies could inspire a new generation of soft microelectronic and bioelectronic devices. These futuristic devices will combine the benefits of centimetre scale flexibility, micrometre scale homogeneity, and nanometre scale electrically controlled mechanical motion of polymer chains with superior biocompatibility.鈥�

探花直播research was funded in part by the Royal Society.

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Reference:
Illia Dobryden et al. 鈥�Dynamic self-stabilization in the electronic and nanomechanical properties of an organic polymer semiconductor.鈥� Nature Communications (2022). DOI: 10.1038/s41467-022-30801-x

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Researchers have analysed the properties of an organic polymer with potential applications in flexible electronics and uncovered variations in hardness at the nanoscale, the first time such a fine structure has been observed in this type of material. 聽

Deepak Venkateshvaran

Polymer film with a region of parallel alignment of individual polymer chains

探花直播text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright 漏探花直播 of Cambridge and licensors/contributors as identified.聽 All rights reserved. We make our image and video content available in a number of ways 鈥� as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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A new spin on organic semiconductors

sc604 — Tue, 26 Mar 2019 00:00:59 +0000

探花直播international team from the UK, Germany and the Czech Republic has聽found that these materials could be used for 鈥榮pintronic鈥� applications, which could make cheap organic semiconductors competitive with silicon for future computing applications. 探花直播results are reported in the journal Nature Electronics.

鈥楽pin鈥� is the term for the intrinsic angular momentum of electrons, which is referred to as up or down. Using the up/down states of electrons instead of the 0 and 1 in conventional computer logic could transform the way in which computers process information.

Instead of moving packets of charge around, a device built on spintronics would transmit information using the relative spin of a series of electrons, known as a pure spin current. By eliminating the movement of charge, any such device would need less power and be less prone to overheating 鈥� removing some of the most significant obstacles to further improving computer efficiency. Spintronics could therefore give us faster, energy-efficient computers, capable of performing more complex operations than at present.

Since organic semiconductors, widely used in applications such as OLEDs, are cheaper and easier to produce than silicon, it had been thought that spintronic devices based on organic semiconductors could power a future computer revolution. But so far, it hasn鈥檛 worked out that way.

鈥淭o actually transfer information through spin, the electron鈥檚 spin needs to travel reasonable distances and live for a long enough time before the information encoded on it is randomised,鈥� said Dr Shu-Jen Wang, a recent PhD graduate of the 探花直播 of Cambridge鈥檚 Cavendish Laboratory, and the paper鈥檚 co-first author.

鈥淥rganic semiconductors have not been realistic candidates for spintronics so far because it was impossible to move spins around a polymer circuit far enough without losing the original information,鈥� said co-first author Dr Deepak Venkateshvaran, also from the Cavendish Laboratory. 鈥淎s a result, the field of organic spintronics has been pretty quiet for the past decade.鈥�

探花直播internal structure of organic semiconductors tends to be highly disordered, like a plate of spaghetti. As such, packets of charge don鈥檛 move nearly as fast as they do in semiconductors like silicon or gallium arsenide, both of which have a highly ordered crystalline structure. Most experiments on studying spin in organic semiconductors have found that electron spins and their charges move together, and since the charges move more slowly, the spin information doesn鈥檛 go far: typically only a few tens of nanometres.

Now, the Cambridge-led team say they have found the conditions that could enable electron spins to travel far enough for a working organic spintronic device.

探花直播researchers artificially increased the number of electrons in the materials and were able to inject a pure spin current into them using a technique called spin pumping. Highly conductive organic semiconductors, the researchers found, are governed by a new mechanism for spin transport that transforms them into excellent conductors of spin.

This mechanism essentially decouples the spin information from the charge, so that the spins are transported quickly over distances of up to a micrometre: far enough for a lab-based spintronic device.

鈥淥rganic semiconductors that have both long spin transport lengths and long spin lifetimes are promising candidates for applications in future spin-based, low energy computing, control and communications devices, a field that has been largely dominated by inorganic semiconductors to date,鈥� said Venkateshvaran, who is also a Fellow of Selwyn College.

As a next step, the researchers intend to investigate the role that chemical composition plays in an organic semiconductor鈥檚 ability to efficiently transport spin information within prototype devices.

探花直播research was coordinated by Professor Henning Sirringhaus at the Cavendish Laboratory and funded through a European Research Council (ERC) Synergy Grant jointly held by the 探花直播 of Cambridge, Imperial College London, 探花直播 of Mainz, Czech Academy of Sciences and Hitachi Cambridge Laboratory.

Reference:
Shu-Jen Wang, Deepak Venkateshvaran et al. 鈥�Long spin diffusion lengths in doped conjugated polymers due to enhanced exchange coupling.鈥� Nature Electronics (2019). DOI: 10.1038/s41928-019-0222-5

Researchers have found that certain organic semiconducting materials can transport spin faster than they conduct charge, a phenomenon which could eventually power faster, more energy-efficient computers.聽

Organic semiconductors have not been realistic candidates for spintronics so far because it was impossible to move spins far enough without losing the original information

Deepak Venkateshvaran

Deepak Venkateshvaran and Nanda Venugopal

Hand sketch of an organic lateral spin pumping device

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