Researchers at Harvard University in the US have developed a new, clean and simple technique, dubbed “ice lithography”, to fabricate nanodevices. The method, which relies on using a thin film of water ice as a resist for electron-beam lithography, does not contaminate or degrade samples, unlike many conventional nanofabrication processes.<\/p>\n
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“By using ice lithography, nanodevices, whose time-consuming fabrication usually requires several different instruments, can now be made more rapidly and easily in one cluster tool \u2013 a modified scanning electron microscope (SEM),” team member Anpan Han told nanotechweb.org<\/em>.<\/p>\n The researchers began by loading a sample made of carbon nanotubes into their SEM. Next, they cooled the sample down to 110\u00a0K and leaked water vapour into the SEM vacuum. The water condenses as a layer of amorphous ice on the cold sample.<\/p>\n Using the SEM’s electron beam, Han and colleagues then drew patterns on the sample. This step removes ice in those areas where electrical leads need to be added, thus forming a mask for metal electrodes contacting the nanotubes. Because ice is transparent, the researchers were able to see through it and make sure that the electrodes were precisely aligned with the nanotubes.<\/p>\n Ice layer protects<\/strong> Finally, the sample, which is still frozen, is removed and quickly dunked into a room-temperature alcohol solution. This removes the ice and Pd film from on top of the ice, leaving behind just the electrical leads connected to the nanotubes. Interconnections between the Pd and nanotubes exist at the points where ice had originally been removed by the electron beam and the resulting structure acts as a transistor.<\/p>\n “Our technique avoids using several different instruments and techniques like polymethylacrylate resist spinning, resist baking and unshielded e-beam exposure, to produce nanoscale structural components without contamination or damage,” said Han.<\/p>\n The team is now trying to improve the process by making 3D nanodevices and adding etching clusters during fabrication. “We also need to better understand the detailed mechanisms behind ice lithography, about which we know very little.”<\/p>\n The work was reported in Nano Letters<\/em>.<\/p>\n","protected":false},"excerpt":{"rendered":" Researchers at Harvard University in the US have developed a new, clean and simple technique, dubbed “ice lithography”, to fabricate […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[34],"tags":[],"class_list":["post-29302","post","type-post","status-publish","format-standard","hentry","category-technology-update"],"yoast_head":"\n
\nAnother advantage of the technique is that the nanotubes are “protected” by the ice layer and are only exposed to the electron beam in areas where the ice has been removed. The sample, with its nanopatterned ice resists, is then transferred to another chamber, where it is sputtered with palladium (Pd).<\/p>\n