Interface atom mobility and charge transfer effects on CuO and Cu 2 O formation on Cu 3 Pd(111) and Cu 3 Pt(111)

We bombarded $$\mbox{$\text{Cu}_{3}\text{Pd}(111)$}$$ and $$\mbox{$\text{Cu}_{3}\text{Pt}(111)$}$$ with a 2.3 eV hyperthermal oxygen molecular beam (HOMB) source, and characterized the corresponding (oxide) surfaces with synchrotron-radiation X-ray photoemission spectroscopy (SR-XPS). At $$300\,\text{K}$$ , CuO forms on both $$\mbox{$\text{Cu}_{3}\text{Pd}(111)$}$$ and $$\mbox{$\text{Cu}_{3}\text{Pt}(111)$}$$ . When we increase the surface temperature to $$500\,\text{K}$$ , $$\mbox{$\text{Cu}_{2}\text{O}$}$$ also forms on $$\mbox{$\text{Cu}_{3}\text{Pd}(111)$}$$ , but not on $$\mbox{$\text{Cu}_{3}\text{Pt}(111)$}$$ . For comparison, $$\mbox{$\text{Cu}_{2}\text{O}$}$$ forms even at $$300\,\text{K}$$ on Cu(111). On $$\mbox{$\text{Cu}_{3}\text{Au}(111)$}$$ , $$\mbox{$\text{Cu}_{2}\text{O}$}$$ forms only after $$500\,\text{K}$$ , and no oxides can be found at $$300\,\text{K}$$ . We ascribe this difference in Cu oxide formation to the mobility of the interfacial species (Cu/Pd/Pt) and charge transfer between the surface Cu oxides and subsurface species (Cu/Pd/Pt).