The effect of substrate topography on the local electronic structure of WS2 nanotubes

We explore the possibility of controlling electronic properties along an in organic nanotube (INT) through the influence of nanometer-scale features in the underlying substrate. We examined single multi-walled WS2 INTs using s canning tunneling microscopy (STM) in high vacuum. As long as the INTs He f lat on MoS2 (0 0 0 1) or graphite (0 0 0 1) surfaces, they appear semimetal lic. However, when the INT is suspended above the surface due to crossing s teps or other nanotubes, a band gap opens up. We discuss this observation i n terms of either a potential drop under the INT, or a change in its electr onic properties due to its distortion when it lies flat on a surface. (C) 2 001 Elsevier Science B.V. All rights reserved.