It might sound like a prop from a 1950s sci-fi flick, but researchers from the Military University in Munich, Germany, have built a new kind of microscope that creates images using antimatter. Specifically, the microscope uses anti-electrons, or positrons, to take pictures of defects in materials. This so-called scanning positron microscope (SPM), which is more sensitive than any current technology, may soon be used to study everything from corrosion to semiconductors.
Positrons and electrons share the same mass, but all their other properties, including charge, are completely opposite. When a positron and an electron collide they annihilate each other in a brilliant flash of light.
The SPM gets its positrons from the natural decay of a radioactive sodium isotope. The positrons pass through a series of electric fields that compress them into a short pulse and focus them into a two-micron dot on the surface of a material. Once inside, their charge pulls the positrons to so-called vacancies, defects where a positively charged nucleus is missing. The missing nucleus also means that there are fewer electrons in the region, and so the positron can avoid annihilation for a prolonged period of time. By measuring the time interval between the pulse and the flashes of light from annihilations, the researchers were able to gauge the number of vacancies in a given spot of the material.
The first results, which appear in the August 6 issue of Physical Review Letters, show that the SPM detects vacancies better than either an electron beam microscope or an optical microscope. Werner Triftshuser, the leader of the team, says that SPMs may soon be used to image vacancies in superconductors and thin films with unprecedented accuracy. "There is no other method which is as sensitive as a positron for detecting defects," he says.
