A new high-speed detector for electron microscopes uses every transmitted electron to measure electric and magnetic fields
Electron microscopes excel at imaging small structures —even individual atoms! — but they are nearly blind to the important electric and magnetic fields within these structures. For example, they cannot easily “see” the magnetic fields that record information in magnetic storage media. Scientists have long known that electric and magnetic fields create tiny shifts in electron microscopy images, but the shifts are too small to be measured with conventional electron detectors.
Researchers at Cornell University have developed a new type of imaging electron detector that is 100 times faster than conventional detectors and that can detect from 1 to 1,000,000 electrons per pixel — a 1000x improvement in dynamic range. As a result, scientists can now measure the tiny shifts on every electron that passes through a sample! The result is a rapid, accurate and quantitative map of electric and magnetic fields on the nanoscale. The technique is well-suited to imaging nanostructures, and is easier to interpret and less sensitive to noise and artifacts than previous electron microscope methods.