 However, because the electron beam of an SEM or STEM is very small, it is scanned across the sample and variations in the induced EBIC are used to map the electronic activity of the sample.By using the signal from the picoammeter as the imaging signal, an EBIC image is formed on the screen of the SEM or STEM.When a semiconductor device is imaged in cross-section, the depletion region will show bright EBIC contrast.