{"65044":{"#nid":"65044","#data":{"type":"news","title":"Technique Produces Graphene Nanoribbons with Metallic Properties","body":[{"value":"\u003Cp\u003EA new \u0022templated growth\u0022 technique for fabricating nanoribbons of epitaxial graphene has produced structures just 15 to 40 nanometers wide that conduct current with almost no resistance.  These structures could address the challenge of connecting graphene devices made with conventional architectures -- and set the stage for a new generation of devices that take advantage of the quantum properties of electrons.\u003C\/p\u003E\n\u003Cp\u003E\u0022We can now make very narrow, conductive nanoribbons that have quantum ballistic properties,\u0022 said Walt de Heer, a professor in the School of Physics at the Georgia Institute of Technology.  \u0022These narrow ribbons become almost like a perfect metal.  Electrons can move through them without scattering, just like they do in carbon nanotubes.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EDe Heer discussed recent results of this graphene growth process March 21st at the American Physical Society\u2019s March 2011 Meeting in Dallas.  The research was sponsored by the National Science Foundation-supported Materials Research Science and Engineering Center (MRSEC).\n\u003C\/p\u003E\n\u003Cp\u003EFirst reported Oct. 3 in the advance online edition of the journal \u003Cem\u003ENature Nanotechnology\u003C\/em\u003E, the new fabrication technique allows production of epitaxial graphene structures with smooth edges.  Earlier fabrication techniques that used electron beams to cut graphene sheets produced nanoribbon structures with rough edges that scattered electrons, causing interference.  The resulting nanoribbons had properties more like insulators than conductors.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022In our templated growth approach, we have essentially eliminated the edges that take away from the desirable properties of graphene,\u0022 de Heer explained.  \u0022The edges of the epitaxial graphene merge into the silicon carbide, producing properties that are really quite interesting.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EThe templated growth technique begins with etching patterns into the silicon carbide surfaces on which epitaxial graphene is grown.  The patterns serve as templates directing the growth of graphene structures, allowing the formation of nanoribbons and other structures of specific widths and shapes without the use of cutting techniques that produce the rough edges.\n\u003C\/p\u003E\n\u003Cp\u003EIn creating these graphene nanostructures, de Heer and his research team first use conventional microelectronics techniques to etch tiny \u0022steps\u0022  -- or contours -- into a silicon carbide wafer whose surface has been made extremely flat.  They then heat the contoured wafer to approximately 1,500 degrees Celsius, which initiates melting that polishes any rough edges left by the etching process.\n\u003C\/p\u003E\n\u003Cp\u003EEstablished techniques are then used for growing graphene from silicon carbide by driving the silicon atoms from the surface.  Instead of producing a consistent layer of graphene across the entire surface of the wafer, however, the researchers limit the heating time so that graphene grows only on portions of the contours.\n\u003C\/p\u003E\n\u003Cp\u003EThe width of the resulting nanoribbons is proportional to the depth of the contours, providing a mechanism for precisely controlling the nanoribbon structures.  To form complex structures, multiple etching steps can be carried out to create complex templates.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022This technique allows us to avoid the complicated e-beam lithography steps that people have been using to create structures in epitaxial graphene,\u0022 de Heer noted.  \u0022We are seeing very good properties that show these structures can be used for real electronic applications.\u0022 \n\u003C\/p\u003E\n\u003Cp\u003ESince publication of the \u003Cem\u003ENature Nanotechnology\u003C\/em\u003E paper, de Heer\u0027s team has been refining its technique.  \u0022We have taken this to an extreme -- the cleanest and narrowest ribbons we can make,\u0022 he said.  \u0022We expect to be able to do everything we need with the size ribbons that we are able to make right now, though we probably could reduce the width to 10 nanometers or less.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EWhile the Georgia Tech team is continuing to develop high-frequency transistors -- perhaps even at the terahertz range -- its primary effort now focuses on developing quantum devices, de Heer said.  Such devices were envisioned in the patents Georgia Tech holds on various epitaxial graphene processes.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022This means that the way we will be doing graphene electronics will be different,\u0022 he explained.  \u0022We will not be following the model of using standard field-effect transistors (FETs), but will pursue devices that use ballistic conductors and quantum interference. We are headed straight into using the electron wave effects in graphene.\u0022\n\u003C\/p\u003E\n\u003Cp\u003ETaking advantage of the wave properties will allow electrons to be manipulated with techniques similar to those used by optical engineers.  For instance, switching may be carried out using interference effects -- separating beams of electrons and then recombining them in opposite phases to extinguish the signals.\n\u003C\/p\u003E\n\u003Cp\u003EQuantum devices would be smaller than conventional transistors and operate at lower power.  Because of its ability to transport electrons with virtually no resistance, epitaxial graphene may be the ideal material for such devices, de Heer said.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022Using the quantum properties of electrons rather than the standard charged-particle properties means opening up new ways of looking at electronics,\u0022 he predicted.  \u0022This is probably the way that electronics will evolve, and it appears that graphene is the ideal material for making this transition.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EDe Heer\u0027s research team hopes to demonstrate a rudimentary switch operating on the quantum interference principle within a year.  \n\u003C\/p\u003E\n\u003Cp\u003EEpitaxial graphene may be the basis for a new generation of high-performance devices that will take advantage of the material\u0027s unique properties in applications where higher costs can be justified.  Silicon, today\u0027s electronic material of choice, will continue to be used in applications where high-performance is not required, de Heer said.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022This is an important step in the process,\u0022 he added.  \u0022There are going to be a lot of surprises as we move into these quantum devices and find out how they work.  We have good reason to believe that this can be the basis for a new generation of transistors based on quantum interference.\u0022\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\n\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","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EA new \u0022templated growth\u0022 technique for fabricating nanoribbons of epitaxial graphene has produced structures just 15 to 40 nanometers wide that conduct current with almost no resistance.  These structures could address the challenge of connecting graphene devices.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Researchers have made graphene nanoribbons with metallic properties."}],"uid":"27303","created_gmt":"2011-03-21 00:00:00","changed_gmt":"2016-10-08 03:08:26","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2011-03-21T00:00:00-04:00","iso_date":"2011-03-21T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"65045":{"id":"65045","type":"image","title":"Growing epitaxial graphene","body":null,"created":"1449176783","gmt_created":"2015-12-03 21:06:23","changed":"1475894574","gmt_changed":"2016-10-08 02:42:54","alt":"Growing epitaxial graphene","file":{"fid":"192147","name":"tis35461.jpg","image_path":"\/sites\/default\/files\/images\/tis35461_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/tis35461_0.jpg","mime":"image\/jpeg","size":1731501,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/tis35461_0.jpg?itok=Q2grkYwo"}},"65046":{"id":"65046","type":"image","title":"Prof. Walt de Heer","body":null,"created":"1449176783","gmt_created":"2015-12-03 21:06:23","changed":"1475894574","gmt_changed":"2016-10-08 02:42:54","alt":"Prof. Walt de Heer","file":{"fid":"192148","name":"toh35777.jpg","image_path":"\/sites\/default\/files\/images\/toh35777_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/toh35777_0.jpg","mime":"image\/jpeg","size":1603740,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/toh35777_0.jpg?itok=GCENVzgL"}},"65047":{"id":"65047","type":"image","title":"Growing expitaxial graphene","body":null,"created":"1449176783","gmt_created":"2015-12-03 21:06:23","changed":"1475894574","gmt_changed":"2016-10-08 02:42:54","alt":"Growing expitaxial graphene","file":{"fid":"192149","name":"tfu35461.jpg","image_path":"\/sites\/default\/files\/images\/tfu35461_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/tfu35461_0.jpg","mime":"image\/jpeg","size":65166,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/tfu35461_0.jpg?itok=4hcNTgqa"}}},"media_ids":["65045","65046","65047"],"related_links":[{"url":"http:\/\/www.physics.gatech.edu\/","title":"Georgia Tech School of Physics"},{"url":"http:\/\/www.mrsec.gatech.edu\/","title":"Materials Research Science and Engineering Center"},{"url":"https:\/\/www.physics.gatech.edu\/user\/walter-de-heer","title":"Walt de Heer"}],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"141","name":"Chemistry and Chemical Engineering"},{"id":"145","name":"Engineering"},{"id":"149","name":"Nanotechnology and Nanoscience"},{"id":"135","name":"Research"},{"id":"150","name":"Physics and Physical Sciences"}],"keywords":[{"id":"10890","name":"conductor"},{"id":"9116","name":"epitaxial graphene"},{"id":"429","name":"graphene"},{"id":"12423","name":"nanoribbons"},{"id":"4827","name":"resistance"},{"id":"12422","name":"Walt de Heer"}],"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":""}}}