Field emission microscopy of carbon nanotube caps

We report field emission microscopy images from single walled carbon nanotu bes showing resolvable fine structure with five- and six-fold symmetry. We present evidence indicating that these images have atomic resolution and th at they depict the electronic structure of individual nanotube caps under h igh-field conditions. Fine structure is observed only after removal of surf ace adsorbates. Prior to adsorbate removal, these images show symmetrical l obed patterns and several other behaviors characteristic of chemisorbed res onant tunneling states. (C) 1999 American Institute of Physics. [S0021-8979 (99)05907-1].