Single-Walled Carbon Nanotubes as Shadow Masks for Nanogap Fabrication
  We describe a technique for fabricating nanometer-scale gaps in Pt wires on insulating substrates, using individual single-walled carbon nanotubes as shadow masks during metal deposition. More than 80% of the devices display current-voltage dependencies characteristic of direct electron tunneling. Fits to the current-voltage data yield gap widths in the 0.8-2.3 nm range for these devices, dimensions that are well suited for single-molecule transport measurements. 
E. P. De Poortere, L. M. Huang, M. Huang, S. J. Wind, S. O'Brien, J.   Hone, and H. L. Stormer