The microscope uses a sharp tip as an ultra-small probe, which is brought gently into near contact with a material surface. A particular physical property, such as contact force, can be detected in the microscopic region below the tip. As the probe is scanned back and forth across the surface, images of this property can be captured by the microscope. The probe consists of a sharpened glass fiber, similar in size and shape to a small sewing needle but with a much finer tip that tapers down to a tiny, nearly flat area at the end. The SET is formed on this tiny area.
Electrical connections extend from the junctions up the side of the needle to the detectors.
They are Michael J. Yoo, now at Philips Laboratories, and Theodore A. Fulton, Harald F. Hess, Robert L. Willett, LaRue N. Dunkleberger, Robert J. Chichester, Loren N. Pfeiffer, and Kenneth W. West, all of Bell Labs. Hess noted that usually many electrical charges are sensed by the probe at once. But, we were able to detect individual electrons by using light to move a very small fraction of them to different locations. By comparing the 'before' and 'after' picture, we can see individual spots where a new electron has arrived or where an old one has disappeared. The location and the amount of dopants and how they release electrons is critical to device performance.