Atomic detail observation of adsorbed molecules and metal clusters on carbon nanotube electron emitters

Molecular images and dynamics of adsorbates on carbon nanotube (CNT) electron emitters revealed so far by field emission microscopy (FEM) are reviewed after a brief account of the field emission phenomena and the merit of CNTs as the field emitter. The species adsorbed on CNTs are inorganic and organic common gaseous molecules (H2, N2, O2, CO, CO2, CH4) and aluminum (Al) clusters. In the case of N2 and CO2 molecules, dumbbell-shaped images, reflecting their molecular shapes, have been observed. For the case of Al deposition on CNTs, FEM images revealing atomic detail of an Al cluster with the cubo-octahedron structure were observed. Discussion on the spatial resolution in FEM for CNTs suggests the probable observation of some atomic structures with a resolution of the order of 0.3 nm.