Resist-free fabricated carbon nanotube field-effect transistors with high-quality atomic-layer-deposited platinum contacts

Carbon nanotubes are considered as alternative channel material for future transistors, but several challenges exist for reliable fabrication of these devices. In this work, carbon nanotube field-effect transistors (CNTFETs) were fabricated by patterning of Pt contacts using a combination of electron beam induced deposition and area-selective atomic layer deposition (ALD). This bottom-up technique eliminates compatibility issues caused by the use of resist films and lift-off steps. Electrical characterization of a set of 33 CNTFETs reveals that using this direct-write ALD process for Pt patterning yields improved contacts as compared to evaporated Pt, most likely due to improved wettability of the contacts on the carbon nanotube. Moreover, these CNTFETs can be characterized as unipolar p-type transistors with a very low off-state current.