Controlled Mounting of Individual Multiwalled Carbon Nanotubes on Support Tips Niels de Jonge,* Yann Lamy, † and Monja Kaiser Philips Research Laboratories, Prof. Holstlaan 4, 5656 AA EindhoVen, The Netherlands Received September 18, 2003; Revised Manuscript Received October 16, 2003 ABSTRACT Individual multiwalled carbon nanotubes were mounted on tungsten support tips in a scanning electron microscope equipped with a nanomanipulator. It was possible to select the diameter of the nanotube to align the nanotube with respect to the tip axis and to tune the contact length of the nanotube and the support tip. We have also developed a way to control the length of the nanotube protruding from the support tip. Control over the nature of the nanotube cap was not obtained. A carbon nanotube mounted on a support tip can be applied as electron source in high-resolution electron beam instru- ments, 1 such as electron microscopes and electron beam lithography machines. Indeed, it was demonstrated that the carbon nanotube electron source has a stable emitted cur- rent, 2,3 a long lifetime, 4,5 a low energy spread, 3,6,7 and a high brightness. 1 A mounted nanotube can also serve as probe tip in scanning probe microscopes, such as an atomic force microscope and a scanning tunneling microscope, to enhance the spatial resolution of these instruments. 8 The high aspect ratio of the nanotube is an advantage for the imaging of rough surfaces or surfaces with deep pits. Chemically sensitive probes and magnetized probes were constructed from carbon nanotubes. 9-11 Of critical importance for these applications is that the carbon nanotube probe is not surrounded closely by other nanotubes, but that only one tube protrudes effectively from the support structure. First results have been obtained by mounting carbon nanotubes on a metal support tip with micromanipulators and an optical microscope. 8 This mount- ing technique was improved using nanomanipulators in a scanning electron microscope. 3,12,13 The main problem en- countered with these mounting techniques (and also with other techniques 14 ) is the difficulty to control the length of the nanotube protruding from the support tip. For application as electron source in an electron microscope, the tube length should measure 200-500 nm for a multiwalled nanotube with a typical diameter of 10 nm. This length is long enough to provide sufficient field enhancement and short enough to reduce vibrations of the tube. 15 Vibrations of the tube broaden the virtual source size with a radius of typically 2 nm and, as a consequence, reduce the brightness of the source. 1 It was found that the vibration amplitude of a 170 nm long nanotube was smaller than 0.2 nm, e.g., a high-resolution transmission electron microscope (TEM) image of its cap displayed details of 0.2 nm. For application in scanning probe * Corresponding author. E-mail: niels.de.jonge@philips.com. Fax: +31- 40-2742293. ² Present address: Ecole Supe ´rieure de Physique et de Chimie Indust- rielles de la ville de Paris, 10 Rue Vauquelin, 75005 Paris, France. VOLUME 3, NUMBER 12, DECEMBER 2003 © Copyright 2003 by the American Chemical Society 10.1021/nl034792h CCC: $25.00 © 2003 American Chemical Society Published on Web 10/28/2003