上海龙凤后花园油压店

Graphene origami opens up new spintronics features

first_img The scientists, A. T. Costa, et al., from institutions in Brazil, Ireland, Singapore, and the US, have published their paper on graphene origami in a recent issue of EPL.”While bandgap opening and spin-polarized currents are two separate features contained in the wish list of every graphene researcher, we have identified a way that might tick both boxes at once,” coauthor Mauro Ferreira, Associate Professor at Trinity College Dublin, told Phys.org.Since the bandgap is an energy range where no electron states exist, opening a bandgap in graphene transforms it from a conducting material to a semiconducting material. Semiconducting graphene would be more useful, and could have particularly interesting applications for spintronics devices, which exploit the electron’s quantum mechanical property of spin in addition to its property of electric charge. One reason that graphene is a promising spintronics material is that, compared to other materials, it has an extremely small spin-orbit interaction (SOI). This means that its spin interacts very little with its orbital motion, and so spin dissipation is practically negligible in graphene. As a result, information stored in graphene’s spin can be retained for considerably longer times than in other materials. A small SOI also means that the information can travel over long distances with very little loss.Although a small SOI has many advantages, here the scientists wanted to increase the SOI in parts of graphene because doing so is necessary for opening a bandgap. Recent research has demonstrated that SOI is enhanced when graphene is mechanically bent. Here, the researchers theoretically showed that a 2D graphene sheet molded into periodic ridges and troughs has an enhanced SOI in the curved regions.Increasing the SOI is half of the process to inducing a bandgap; the other half is applying a magnetic field. As the researchers explain, the SOI and magnetic field complement each other in such a way that both quantities must be enhanced to induce a bandgap. The magnitude of the bandgap is ultimately determined by the smaller of these two quantities.One way that a magnetic field can be applied is by doping the graphene with magnetic atoms. Doping is also another way to enhance SOI, so the whole process could potentially be achieved by doping with the right adsorbants. This method has some advantages compared to previous attempts to open up a bandgap in graphene. So far, previous methods have failed to produce technologically relevant semiconducting graphene for several reasons, including that the bandgap size is too small and that disorder emerges into the system. The researchers here predict that the new method may overcome these difficulties and finally achieve useful semiconducting graphene.The second important effect of the new method—that it spin-polarizes the current—means that the electrons’ spins are aligned in the same direction. This feature is particularly important for engineering spintronics devices. In their current study, the researchers showed that the new process can be easily realized by depositing graphene sheets on a substrate with periodic trenches. In the future, they plan to perform measurements on the resulting graphene’s electrical properties. “While we have good experimental control on how the graphene sheets are folded, to measure the transport properties of such origami-like structures remains challenging,” Ferreira said. “The next step is to adapt some of the transport measurement techniques to deal with the structures in this new geometry.” Journal information: Europhysics Letters (EPL) © 2013 Phys.org. All rights reserved. (a) To grow graphene fin-like structures, the researchers draped a graphene sheet over a patterned stamp. Below, (b) a scanning electron micrograph and (c) an atomic force microscope image show a small portion of the folded graphene surface. Credit: A. T. Costa, et al. ©2013 EPL This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. More information: A. T. Costa, et al. “Origami-based spintronics in graphene.” EPL, 104 (2013) 47001. DOI: 10.1209/0295-5075/104/47001center_img Elucidation of spin state of conduction electrons in graphene (Phys.org) —Despite graphene’s many impressive properties, its lack of a bandgap limits its use in electronic applications. In a new study, scientists have theoretically shown that a bandgap can be opened in graphene by folding 2D graphene sheets origami-style and exposing them to a magnetic field. In addition to opening up a bandgap, this method also produces spin-polarized current in the graphene sheets, making them attractive for spintronics applications. Citation: Graphene origami opens up new spintronics features (2013, December 19) retrieved 18 August 2019 from https://phys.org/news/2013-12-graphene-origami-spintronics-features.html Explore furtherlast_img read more

first_imgJanuary 5, 2017 This story originally appeared on PCMag Attend this free webinar and learn how you can maximize efficiency while getting the most critical things done right. Register Now » Free Webinar | Sept 5: Tips and Tools for Making Progress Toward Important Goals The synchronized ballet of traffic light adjustments that turned Los Angeles into a parking lot, helping Mark Wahlberg and Charlize Theron escape with an armored truck full of cash in The Italian Job, is no longer the stuff of Hollywood legend.The tech behind it is already rolling on the installation trucks of companies like Silver Spring Networks, which is snapping up municipal contracts from Copenhagen to California, installing smart street lights and utility meters that beam data back to headquarters, enabling energy savings and reducing costs.The 15-year-old company is using a planned community under construction near Denver to demonstrate how a smart street light network can do everything from offering free Wi-Fi to alerting motorists when a parking space opens up. Theoretically, the lights could be the target of an Italian Job-style hack, too, but that’s not likely, according to Silver Spring CEO Mike Bell.”We take a common sense approach to security,” he said in an interview at CES on Wednesday. There are 25 million Silver Spring sensors all over the world, and their military-grade security standards offer a good starting point, although Bell acknowledged that the security practices of some municipalities and other partners are sometimes deficient.”From a public good perspective, our devices offer the minimum level of security you should have,” he said. In other words, it’s more likely that a breach would occur in the network of a utility company or local government than as a result of a lone hacker roaming the streets with a laptop.Those weak links, among many other reasons, is why “it’s always easier if you’re in first,” according to Bell. The company has seen success in Paris, where every street light uses its sensors, and New York City, where Con Edison is about to replace all of its customers’ existing gas and electricity meters with smart ones. But communities engineered from the ground up for secure connected devices, like the planned Pena Station near the Denver airport, will be a crucial proving ground.Pena’s street lights will have controllable smart LED lights, offer Wi-Fi access, sense temperature and air quality and use cameras for public safety and parking management. If a bulb is about to burn out, the city will automatically be notified, eliminating costly inspections. Assuming all goes well, the lights will expand across Denver via a partnership between Silver Spring and Panasonic. Part of what makes Silver Spring’s expansion easier than, say, the rollout of 5G is that its sensors communicate on unlicensed radio spectrum. That means no waiting for spectrum auctions, a nice benefit during tumultuous times for the Federal Communications Commission.As for Los Angeles, though, Silver Spring likely won’t be expanding there: the city already signed a contract for smart streetlights with Philips. 3 min readlast_img read more