Small pencils

John Clark (
Sun, 13 Sep 1998 01:11:09 -0400

The American Institute of Physics Bulletin of Physics News Number 390 September 10, 1998 by Phillip F. Schewe and Ben Stein

NANOTUBE NANOLITHOGRAPHY. Carbon nanotubes have previously been used as tips in atomic force microscopes (AFM) for producing images. But now for the first time nanotube tips have been used as pencils for writing 10-nm-width structures on silicon substrates. Ordinary graphite pencils write by wearing themselves down, but this is not the case with nanotube pencils developed at Stanford by Hongjie Dai (, 650-725-4518) and his colleagues. The robustness of the nanotube tips permits a writing rate---0.5 mm/sec---five times faster than was possible with older AFM tips. The way the nanotube writes is for an electric field, issuing from the nanotube, to remove hydrogen atoms from a layer of hydrogen atop a silicon base. The exposed silicon surface oxidizes; thus the "writing" consists of narrow SiO2 tracks. The Stanford results should help the development of nanofabrication, since tip wear problems have been an obstacle to the use of probe microscopes in lithography and data storage at the nm size scale. (Dai, Franklin, and Han, Applied Physics Letters, 14 September 1998; figure at