SURFACE PREPARATION OF FES2 VIA ELECTROCHEMICAL ETCHING AND INTERFACE FORMATION WITH METALS

The effect of passing cathodic currents at potentials of hydrogen evolution through differently pretreated n-type pyrite (FeS2) electrodes is studied by XPS. It is shown that hydrogen evolution results in an etching of the crystal via dissolution of FeS2. Surfaces that are destroyed through sputtering or polishing are restored through this etching procedure. (100) and (111) surfaces behave similar to each other. When depositing gold onto the electrochemically etched surface in ultrahigh vacuum no change of the band bending of the clean surface (650 meV) is observed. An abrupt interface with FeS-like defects in the pyrite is formed. Deposition of platinum yields a ternary Pt-Fe-S interlayer between pyrite and metallic Pt. The band bending is reduced by 200 meV during contact formation. Concerning the chemical composition and the electronic structure the etched surfaces behave nearly identical to clean (100) cleavage planes of pyrite.