Off-axis electron holography of electrostatic potentials in unbiased and reverse biased focused ion beam milled semiconductor devices.

Off-axis electron holography in the transmission electron microscope (TEM) is used to measure two-dimensional electrostatic potentials in both unbiased and reverse biased silicon specimens that each contain a single p-n junction. All the specimens are prepared for examination in the TEM using focused ion beam (FIB) milling. The in situ electrical biasing experiments make use of a novel specimen geometry, which is based on a combination of cleaving and FIB milling. The design and construction of an electrical biasing holder are described, and the effects of TEM specimen preparation on the electrostatic potential in the specimen, as well as on fringing fields beyond the specimen surface, are assessed.