A watched nanopillar always bends…

UK researchers have solved a rather bendy nanotechnology problem by realising that observation itself, rather than an inherent property, can be at fault.

If a nanopillar were to bend in a forest, would it make any sound?

In a recent study, which was published in Nanotechnology, researchers at Bath University, have performed a number of experiments demonstrating that bending of nanopillars - a vital component of many nanotechnologies - arises not during their formation but during electron microscopy imaging of the grown pillars. 

Electron-beam induced deposition (EBID) is a nanofabrication technique capable of directly writing arbitrary 3D structures with a variety of materials. Lately, it has been recognised that EBID can be used to fabricate nanoscale free-standing structures for applications in scanning probe microscopy, field emission and for nanoscale electronics. However, a set of problems is often encountered in the deposition of closely spaced structures. In particular, when free-standing pillars are grown it is observed that a new growth process often causes bending of previously grown pillars.

The team at Bath University - Dan Burbridge and Dr Sergey Gordeev - have demonstrated that this is due to the effects of electron microscopy when imaging the grown pillars. They also found that this effect cannot be attributed to electrostatic interactions between the pillars during growth, as was previously thought. Instead they suggest a mechanism based on structural changes in the grown pillars caused by secondary electrons that are produced during the after-growth imaging.

EBID was discovered in the 1930s soon after fabrication of the first electron microscopes, and for a long time was treated as a nuisance as it caused contamination of samples during imaging. It is known to be a result of the decomposition of surface-adsorbed organic molecules that are usually present in the microscope's vacuum chamber.