Electrical Contacts to Carbon Nanotubes Down to 1nm in Diameter

TL;DR

This study investigates the electrical contact properties of rhodium and palladium to single-walled carbon nanotubes, revealing diameter-dependent behaviors and challenges in forming ohmic contacts for very small diameters.

Contribution

It provides the first detailed analysis of how contact quality varies with nanotube diameter, especially down to 1 nm, highlighting the limitations for metallic SWNTs.

Findings

Rhodium and Palladium form near-ohmic contacts for SWNTs > 1.6 nm.

Positive Schottky barriers exist for smaller semiconducting SWNTs.

Ohmic contacts are difficult for metallic SWNTs below 1.0 nm.

Abstract

Rhodium (Rh) is found similar to Palladium (Pd) in making near-ohmic electrical contacts to single-walled carbon nanotubes (SWNTs) with diameters d > ~ 1.6 nm. Non-negligible positive Schottky barriers (SBs) exist between Rh or Pd and semiconducting SWNTs (S-SWNTs) with d < ~ 1.6 nm. With Rh and Pd contacts, the characteristics of SWNT field-effect transistors (FETs) and SB heights at the contacts are largely predictable based on the SWNT diameters, without random variations among devices. Surprisingly, electrical contacts to metallic SWNTs (M-SWNTs) also appear to be diameter dependent especially for small SWNTs. Ohmic contacts are difficult for M-SWNTs with diameters < ~ 1.0 nm possibly due to tunnel barriers.