The mechanism of ballistic electron emission from nanocrystalline silicon diodes has been studied for nanocrystallized polysilicon (NPS) based devices. The electron emission characteristics of two devices with NPS layers prepared under different conditions are compared in relation to the nanostructural analyses by transmission electron microscope (TEM) and energy-dispersive x-ray microanalyzer (EDX). In the sample where a chainlike nanocrystalline silicon (nc-Si) structure is produced along columnar poly-Si grains, a sufficient electron emission current density of 3.0 mA/cm(2) was observed with a high emission efficiency (2.8%) and stability. The surface and interfacial oxidation of nc-Si particles is another important factor for efficient emission. The results indicate that control of interconnected nc-Si structures is a key issue for the efficient ballistic electron emission. (C) 2004 American Vacuum Society.