Illustration for article titled Check Your Reflection in the Worlds Smoothest Mirror

Have you ever wanted to analyze your own blemishes at nanometer resolution? Send rays of helium atoms to smash into specimens of your choosing? Look at a biological sample under a microscope without having to stain it first? You're in luck, because teams of researchers from Spain and England are out to help you achieve those dreams. After this week's unveiling of the world's smoothest mirror, we are closer than ever to a microscope that can non-invasively examine materials at an atomic level.The quest for a new kind of microscope started when Bodil Holst and William Allison, two researchers at the Cavendish Laboratory in Cambridge, UK, began to focus beams of atomic helium using a mirror. In a 1997 Nature article, Holst and Allison describe the eventual goal of their experiment:

A helium atom microscope would be a unique non-destructive tool for reflection or transmission microscopy. It could be used to investigate fragile and insulating materials such as polymers and certain biological samples. Focusing mirrors also have the potential to increase spatial resolution and intensity in conventional helium-surface scattering instruments.


Holtz and Allison shot a helium beam into a super-smooth silicon crystal; that silicon mirror then reflected and focused the beam into a detector that measured the incident atoms. To get the best-quality eventual microscope, their aim was to focus their 2-millimeter helium beam through the mirror and into the smallest spot size possible. An ideal focusing would not only reflect helium atoms at the proper angle, but also preserve the intensity of the helium beam. These early efforts, however, were limited by the quality of their mirror. As smooth as the silicon was, it focused only 1% of the helium atoms to their satisfaction. Enter Rodolfo Miranda of the Autonomous University of Madrid, Spain. In research published last week in Advanced Materials, Miranda and his team revealed their success at creating the smoothest surface yet. Their optical reflective device — a silicon crystal covered with an extremely thin layer of lead — can focus 15% of those helium atoms. The key to this success is the lead coating. The metal film over the mirror focuses the helium atoms far more tightly, and also manages to better preserve the beam's intensity. Though most metals tend to cluster on the surface of silicon, it is possible to restrain this growth by keeping the metal coating ultra-thin. As Miranda discovered, certain tiny thicknesses of lead on silicon can exist in energetically favorable states, keeping the surface of the mirror atomically smooth. Using these smoother mirrors, Miranda expects to be focusing a 100-nanometer beam of helium by next summer, Nature News reports. Biologists, materials scientists, and other microscope enthusiasts? You should expect to be getting almost uncomfortably up-close and personal with your subjects. Image from Advanced Materials.

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