Graphene wrinkles create semiconductor behaviour

Graphene might be the flattest material known to humanity, but it isn’t actually that flat. Like many things that are flat in theory it is prone to crinkling and wrinkling. This can be a problem, but it now also seems that it can be an opportunity. Researchers at RIKEN, the Japanese applied research organisation, have found that when graphene wrinkles, this changes the way that electrons pass through the material; moreover, they’ve used the tip of a scanning tunnelling electron microscope (STEM) to manipulate the structure of the material, which provides a physical method to alter its electrical conducting properties.

The team, led by Yousoo Kim, was trying to grow graphene on a substrate of single-crystal nickel using chemical vapour deposition with acetylene, but found that instead of generating graphene on the surface, they were making a nickel carbide. To avoid this, they tried cooling the nickel surface rapidly, which worked, but generated a graphene film with 5nm-wide microwrinkles in it.