Study of Erbium Thin Film Oxidation in the Electron Microscope

This paper describes the formation of suspect ErO single crystals during erbium evaporation onto NaCl in ultrahigh vacuum (10 −8 Torr); and a unique twinning phenomenon in these f.c.c. NaCl‐type crystals (a = 5.12 Å) is observed by electron microscopy. The oxidation of thin erbium foils (650 Å thickness) directly within the electron microscope by double condenser beam heating of selected areas and the sequential recrystallization and growth of the completely oxidized erbium (Er 2 O 3 ) are investigated. It is shown that the Er 2 O 3 films have a b.c.c. structural characteristic with the unit cell defined by a vacancy defect CaF 2 structure composition possessing the T 5 (I2 1 3) space group for a = 10.55 Å. Er oxidation in the electron microscope at a background pressure of roughly 10 −4 Torr appeared to be logarithmic, and presumably lattice diffusion controlled.