OXIDATION OF CLEAN RUTHENIUM SURFACES .1. FIELD-ION MICROSCOPE STUDIES

The oxidation of ruthenium metal surfaces has been investigated in the field ion microscope. At low partial pressures of oxygen well ordered surface rearrangement of the metal occurs to an extent dependent upon temperature, oxygen pressure and surface coverage. Above 10-3 Torr, a crystalline oxide film is formed which is very closely related in structure to the underlying metal, since coincidence between the major poles of oxide and metal predominates. Between 600 K and 950 K the oxide is of fairly constant thickness (20-35 layers), irrespective of the period of oxidation and deepest over the closest packed metal surfaces. Protective behaviour by the oxide is attributed to close structural fit to the metal and the absence of high angle boundaries. Above 950 K, protection is less effective and oxide thickening occurs, associated with less precise nucleation on the metal and a more highly defective oxide layer. © 1979.