End-bonded contacts for carbon nanotube transistors with low, size-independent resistance

Making better small contacts Semiconducting single-walled carbon nanotubes have potential size and conductivity advantages over silicon for making smaller transistors. However, as metal electrical contacts decrease in size, the associated resistance increases to impractical values. Cao et al. reacted molybdenum films with semiconducting carbon nanotubes to create a carbide contact. The resistance of these contacts remained low even for 10-nm-scale contacts. Science, this issue p. 68 A covalent contact formed by the reaction of molybdenum and semiconducting carbon nanotubes has no Schottky barrier. Moving beyond the limits of silicon transistors requires both a high-performance channel and high-quality electrical contacts. Carbon nanotubes provide high-performance channels below 10 nanometers, but as with silicon, the increase in contact resistance with decreasing size becomes a major performance roadblock. We report a single-walled carbon nanotube (SWNT) transistor technology with an end-bonded contact scheme that leads to size-independent contact resistance to overcome the scaling limits of conventional side-bonded or planar contact schemes. A high-performance SWNT transistor was fabricated with a sub–10-nanometer contact length, showing a device resistance below 36 kilohms and on-current above 15 microampere per tube. The p-type end-bonded contact, formed through the reaction of molybdenum with the SWNT to form carbide, also exhibited no Schottky barrier. This strategy promises high-performance SWNT transistors, enabling future ultimately scaled device technologies.