Novel microscope to reveal nano truths

Washington, May 9 (IANS) Nature is full of objects that even powerful scanning electron microscopes (SEMs) cannot see. But a new microscope would reveal many more truths about such "invisible" objects.

In an effort to extract a little more truth from the world of nanomaterials and nanostructures, researchers at the National Institute of Standards and Technology have built the first low-energy focused ion beam (FIB) microscope that uses a lithium ion source.

The team's new approach opens up the possibility of creating a whole category of FIBs using any one of up to 20 different elements, greatly increasing the options for imaging, sculpting, or characterising materials.

"By analysing the energy with which the ions scatter, the microscope should be able to not only see that adjacent materials are chemically different, but also identify the elements that make them up," researchers said.

Although the new microscope's resolution is not yet as good as a SEM or a helium ion microscope (HIM), it can image nonconductive materials and can more clearly visualise the chemical composition on the surface of a sample than the higher-energy SEMs and FIBs.

The new instrument first cools a gas of neutral lithium atoms to a temperature of about 600 microkelvins - just a few millionths of a degree above absolute zero - using lasers and a magneto-optical trap (MOT) to hold the atoms.

Another laser ionises the atoms and then electric fields accelerate them, straightening out their flight and focusing the beam on a target.

The team has demonstrated how their microscope could help to solve a common problem in nanoimprint lithography, a process for stenciling patterns on silicon chips.