At the University of Illinois at Urbana-Champaign we have examined SWNTs directly interfaced with the technologically important Si(100) surface, using an ultrahigh-vacuum scanning tunnelling microscope (UHV-STM). We are seeking to develop an atomistic understanding of how SWNTs behave when interfaced with silicon, and we are achieving this through a combination of atomically resolved imaging, tunnelling current-voltage spectroscopy, lateral manipulation and cutting with the room-temperature UHV-STM.
Our principal finding in the current work is that depending upon the type of impurities (dopants) intentionally incorporated into the silicon substrate, we can tune the electronic band alignments between a semiconducting SWNT and the underlying Si(100) surface that is terminated by a single atomic layer of hydrogen. Our results have implications for future electronic devices that may rely upon charge transport across a SWNT/Si(100) interface.
Future work will focus upon how UHV-STM modifications to the hybrid nanotube-silicon system, such as structural defects incorporated into the SWNT or charged Si “dangling bonds” positioned in close proximity to the tube, can be used to engineer a desired local electronic or mechanical response.