The surface potential of oxygen on iron, cobalt and manganese

Abstract

Listen

Translate article

Polycrystalline films of iron, cobalt and manganese were evaporated at pressures of less than 10 −9 Torr on to fused silica substrates. The effect of the absorption of oxygen was followed by measuring changes in the surface potentials of the films by a photoelectric technique. Exposure of the iron films to about 1 × 10 19 oxygen molecules m −2 caused a change in surface potential of about − 0.2 eV; on further exposure the surface potential of the adsorbed layer rose to a maximum of about − 0.1 eV at about 4 × 10 19 molecules m −2 and then decreased rapidly. Similar features were observed for cobalt and manganese. The changes in the surface potential may be explained as follows: the initial decrease is due to the chemisorption of oxygen. The subsequent increase in surface potential may be due to interchange between adatoms and metal atoms (iron), or to burial of the adatoms in voids in the lattice structure of the metal (cobalt and manganese). The final decrease is due to the formation of an oxide layer.