{"66351":{"#nid":"66351","#data":{"type":"news","title":"Flower-Like Defects May Help Graphene Respond to Stress","body":[{"value":"\u003Cp\u003EBeyond its ability to conduct electrons almost without resistance, the nanomaterial graphene also has amazing mechanical properties, including high strength that could one day make it useful in lightweight, robust structures.  But this material is not without flaws -- including a family of flower-like defects that could detract from its electronic and mechanical properties. \u003C\/p\u003E\n\u003Cp\u003EIn a paper published in the journal \u003Cem\u003EPhysical Review B\u003C\/em\u003E, researchers at the Georgia Institute of Technology and the National Institute of Standards and Technology (NIST) have described a family of seven potential defect structures that may appear in sheets of graphene and imaged examples of the lowest-energy defect in the family. \n\u003C\/p\u003E\n\u003Cp\u003EThe defects may arise to help relieve mechanical stress in graphene\u0027s carbon-atom honeycomb structure by allowing atoms to spread out and occupy slightly more space.  Such stress may arise during the growth of graphene or by stretching the graphene sheet.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022For an engineer interested in the mechanical properties of graphene to create atom-thick membranes, for instance, it would be very important to understand these kinds of properties, which could give rise to plastic deformation of the material,\u0022 said Phillip First, one of the paper\u0027s co-authors and a professor in the Georgia Tech School of Physics.  \u0022For instance, it may be that these defects are just one part of the kinetic pathway to failure for a strained sheet of graphene.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EFor electronic applications, the defects could deflect electrons and cause backscattering that would increase the resistance of the material -- like a rock in a stream slows the flow of water.\u003Cbr \/\u003E\nHowever, First says improved growth techniques developed since the defect study began may eliminate that concern.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022With the growth techniques that have now been developed using silicon carbide, we typically do not see these defects,\u0022 he noted.  \u0022The defects occur on material that we know to be of a lower quality because of the growth conditions or substrate preparation.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EDefects can appear due to the movement of carbon atoms at high temperatures, explained NIST Fellow Joseph Stroscio.  Rearrangements of graphene that require the least amount of energy involve switching from the standard six-member carbon rings to structures containing either five or seven atoms.  The NIST researchers have discovered that stringing five- and seven-member rings together in closed loops creates a new type of defect or grain boundary loop in the honeycomb lattice.\n\u003C\/p\u003E\n\u003Cp\u003EAccording to NIST researcher Eric Cockayne, the fabrication process plays a big role in creating the defects.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022As the graphene forms under high heat, sections of the lattice can come loose and rotate,\u0022 he said.  \u0022As the graphene cools, these rotated sections link back up with the lattice, but in an irregular way.  It\u0027s almost as if patches of the graphene were cut out with scissors, turned clockwise, and made to fit back into the same place.  Only it really doesn\u0027t fit, which is why we get these flowers.\u0022\n\u003C\/p\u003E\n\u003Cp\u003ESo far, only the flower defect, which is composed of six pairs of five- and seven-atom rings, has been observed.  Modeling of graphene\u0027s atomic structure by the NIST team suggests there might be a veritable bouquet of flower-like configurations.  These configurations -- seven in all -- would each possess its own unique mechanical and electrical properties, Cockayne said.\n\u003C\/p\u003E\n\u003Cp\u003EFirst hopes the team can continue studying the defects, both to learn whether their formation can be controlled and to clarify the role of defects in the material\u0027s mechanical properties.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022Graphene is strong and light, so the mechanical properties are of great interest,\u0022 he noted.  \u0022Understanding just how it rips apart is an interesting question that has important implications.  But even with these defects, graphene is still spectacularly strong.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EGeorgia Tech contributions to this work were funded by the Semiconductor Research Corporation (NRI-INDEX) and by the National Science Foundation through the Georgia Tech Materials Research Science and Engineering Center (MRSEC) under grants DMR-0804908 and DMR-0820382.\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cem\u003EMark Esser of NIST also contributed to this article.\u003C\/em\u003E\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\nGeorgia Institute of Technology\u003Cbr \/\u003E\n75 Fifth Street, N.W., Suite 314\u003Cbr \/\u003E\nAtlanta, Georgia  30308  USA\n\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003E\n\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contacts\u003C\/strong\u003E: John Toon (404-894-6986)(\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E) or Abby Robinson (404-385-3364)(\u003Ca href=\u0022mailto:abby@innovate.gatech.edu\u0022\u003Eabby@innovate.gatech.edu\u003C\/a\u003E).\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\n\u003C\/p\u003E\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EIn a new study, researchers at the Georgia Institute of Technology and the National Institute of Standards and Technology (NIST) have described a family of seven potential defect structures that may appear in sheets of graphene.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Researchers describe family of defects in graphene."}],"uid":"27303","created_gmt":"2011-06-01 00:00:00","changed_gmt":"2016-10-08 03:08:49","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2011-06-01T00:00:00-04:00","iso_date":"2011-06-01T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"66352":{"id":"66352","type":"image","title":"Graphene defect structures","body":null,"created":"1449176931","gmt_created":"2015-12-03 21:08:51","changed":"1475894589","gmt_changed":"2016-10-08 02:43:09"}},"media_ids":["66352"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"149","name":"Nanotechnology and Nanoscience"},{"id":"135","name":"Research"},{"id":"150","name":"Physics and Physical Sciences"}],"keywords":[{"id":"2504","name":"conductance"},{"id":"531","name":"defect"},{"id":"429","name":"graphene"},{"id":"9115","name":"MRSEC"},{"id":"13305","name":"Phillip First"},{"id":"960","name":"physics"},{"id":"167229","name":"stress"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003E\u003Cstrong\u003EJohn Toon\u003C\/strong\u003E\u003Cbr \/\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\u003Ca href=\u0022http:\/\/www.gatech.edu\/contact\/index.html?id=jt7\u0022\u003EContact John Toon\u003C\/a\u003E\u003Cbr \/\u003E\u003Cstrong\u003E404-894-6986\u003C\/strong\u003E\u003C\/p\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}