| Metal oxidation was investigated in ultra-high vacuum (UHV) environment using surface analytical techniques. Temperature programmed desorption (TPD) was employed to obtain macroscopic reaction kinetics, while low energy electron diffraction (LEED) monitored changes in surface periodic structure. Atomic-scale mechanisms were studied using Scanning Tunneling Microscopy (STM). Two oxidation reactions were involved: copper (Cu) etching by halogens and palladium (Pd) oxidation. Copper etching proceeds through two stages: formation of Cu halide and removal of the etch product above a certain temperature by sublimation. TPD experiments over a wide temperature range revealed that Cu halogenation follows a precursor mechanism. In order to compensate for the low vapor pressure of Cu halides, additional chemicals were introduced into the etching system, forming highly volatile compounds, and showing the possibility of etching Cu at or below room temperature.; As opposed to the two-stage Cu etching process, the oxidation of Pd was found to proceed through multi stages involving four and at least five distinct surface states on Pd(111) and Pd(100), respectively. The reactivity of surface oxygen phases on Pd(100) was studied by introducing CO; the surface reaction could be characterized by the refilling mechanisms. In comparing these two oxidation reactions, the Cu halogenation rate decreases with temperature, but the Pd oxidation rate increases with temperature up to the point where bulk PdO starts to decompose. |
