Oxidation Mechanism On One-Dimensional Pt-Induced Nanowires On Ge(001)

The oxidation mechanism on one-dimensional Pt-induced nanowires on Ge(001) (NWs/Ge(001)) was investigated on the atomic scale, by scanning tunneling microscopy and density functional theory calculations. It was found that, at 300 K, the dissociative chemisorption of oxygen forms a nonplanar pentagonal surface structure composed of two O atoms, two tilted Ge NW atoms, and one Pt side atom. Combined with the study of oxygen molecular adsorption at 77 K, the oxidation reaction pathway on the NWs/Ge(001) surface was successfully elucidated to undergo the transition from the physisorbed oxygen to the molecularly chemisorbed species, and finally to the dissociative product. Detailed analysis reveals that the stability of oxygen dissociative product is attributable to (1) the reduced repulsion between oxygen atoms through forming Pt-O bond; (2) the enhanced electronic coupling between O, Ge, and Pt atoms; and (3) the tilting geometry compensating for bond lengths difference between Ge-O and Pt-O bonds.