The effects of space charge on contrast in images obtained using the environmental scanning electron microscope

We present experimental evidence for the existence of a space charge in the environmental scanning electron microscope. Space charge formation is attr ibuted to differences in the mobilities of negative and positive charge car riers in the imaging gas. A model is proposed for the behavior of space cha rge during image acquisition. The effects of space charge on images acquire d using the gaseous secondary electron detector, ion current, and backscatt ered electron signals are interpreted using the proposed model.