Nanoscale gap fabrication and integration of carbon nanotubes by micromachining

This paper presents new techniques for fabricating nanoscale gaps based on microlithography and the assembly of a carbon nanotube (CNT) across a gap. A sharp nanoscale gap was fabricated by the controlled over-etching of an Al thin film. The etching process was monitored by measured resistance, and a nanoscale gap (similar to20 mn) was fabricated. A rounded gap was also created by using a lift-off process on a bridge pattern with a metal layer. The smallest gap created by this method was 150 nm. An ac electric field was used to deposit single-walled carbon nanotubes (SWCNTs) dispersed in a liquid across the prepared gaps. A highly oriented assembly was obtained for the deposition across this round gap. It was also demonstrated that a single multi-walled carbon nanotube (MWCNT) could be directionally deposited across a microscale gap when guided by a biased ac electric field. Compared with chemical vapor deposition (CVD) methods, suggested assembly procedure can be performed at a room temperature, thus providing more process freedom. Various configurations for device application and fundamental experiments can be conceived using the proposed method. (C) 2003 Elsevier Science B.V. All rights reserved.