Exhibition ends 11.19 at the Museo de Ciencias of the Universidad de Navarra and 11.30 at the Librería Científica of CSIC in Madrid. 

Online accessible at:

The surface of a Ru(0001) crystal is shown. The black and white stripes correspond to atomically flat ruthenium terraces separated by steps of the height of a single atom, 0.21 nanometers!. The three black regions close to the edge of the image are graphene “islands” of a height of 0.33 nanometers.

The image (20 nanometers) is recorded using a low-energy electron microscope (we have two such instruments available in Spain). Its working scheme is similar to that of a transmission electron microscope, but the use of electrons with energies of a few electron-volts (here 41.5 eV) provides an exquisite surface sensitivity. In addition, these electrons have the right wavelength to be diffracted by the atoms in the sample if they are arranged in an ordered structure: a crystal. The image is a dark-field one, since it employes a diffracted beam. For this reason, terraces separated by monoatomic steps show an alternating black-white contrast. The quantum effect of diffraction allows this extraordinary contrast.

PHOTOGRAPHIC EQUIPMENT: low-energy electron microscope ELMITEC LEEM III.

AUTHORS: José Emilio Prieto, Juan de la Figuera, Guiomar Delgado