High resolution imaging of a multi-walled carbon nanotube with energy-filtered photoemission electron microscopy

Photoemission electron microscopy (PEEM) is a powerful and well established tool in surface science. In recent years, PEEM has been increasingly applied to new terrain, such as imaging of complex nano-objects and functional molecular materials, as well as time-resolved experiments. When applying PEEM to such new terrain, information on the mechanisms causing contrast in the PEEM image is particularly valuable. Here, we present a PEEM study on a complex nano-object - an individual multi-walled carbon nanotube (CNT) - to shed light on the origin of PEEM contrast. The presented PEEM images of the nanotube are of unsurpassed resolution and feature intensity variations along the nanotube. Complementary scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements on the same nanotube reveal topography as the dominant cause for the contrast observed along the nanotube. Energy-filtered PEEM measurements demonstrate that the contrast between nanotube and substrate mainly originates from their different electronic structures. The measurements further demonstrate that energy-filtered PEEM has the potential to image electronic structure variations of complex nano-objects and materials on nanometer length scales.