Credit: © 2008 Nature

Extreme ultraviolet (EUV) radiation has applications in areas as diverse as imaging, spectroscopy and etching, but until recently the equipment needed to generate this radiation was both large and expensive. Seungchul Kim and co-workers1 at KAIST in South Korea have developed a new technique involving gold nanostructures that could eventually produce EUV radiation from devices the size of a laptop.

EUV is produced when a high-intensity laser is focused onto a gas, and the main experimental challenge is to reach the required intensity. Kim and co-workers do this by exploiting the field enhancement that takes places in the gap between two metallic nanostructures which, in this case, are two nanoscale gold triangles arranged in a bow-tie geometry.

The KAIST team arranged the gold nanostructures on a sapphire plate immersed in a jet of argon gas. Shining a laser beam on the nanostructures causes oscillations of electron density, known as plasmons, that produce free electrons on one tip and positive charges on the other. This, in turn, produces a plasmon-enhanced field that knocks electrons out of the argon atoms. The electrons and argon ions then recombine to release EUV radiation at wavelengths as short as 47 nm.