Secondary Electron Imaging of Monolayer Titania Nanosheets

Extremely thin monolayer titania nanosheets on silicon substrate appear as dark islands in scanning electron microscopy (SEM) images. To explain the origin of this dark contrast, we compared images with reference titania thin films, which show bright contrast. Carbon deposition only 1 nm thick reversed the contrast of this reference. This result suggests that a slight change of surface potential altered the efficiency of secondary electron emission. This high sensitivity of secondary electrons to surface potential is promising for improvement of thin-film observation by SEM. (C) 2009 The Japan Society of Applied Physics DOI: 10.1143/APEX.2.105504