Establishing Ohmic contacts for in situ current–voltage characteristic measurements on a carbon nanotube inside the scanning electron microscope

The authors contact individual multi-walled carbon nanotubes — on a substrate or freely suspended — with tungsten, gold and platinum tips carried by a four-MM3A nanoprobe system, then measure current–voltage characteristics inside the SEM. They develop reproducible recipes for genuine Ohmic contacts, either Joule-heating the junction or beam-cleaning contaminated tips, which lets intrinsic nanotube behaviour be told apart from contact artefacts. Measured tip–CNT–tip resistances ranged from 14 to 200 kΩ.