Ambient Pressure X-ray Photoelectron Spectroscopy Study of Room-Temperature Oxygen Adsorption on Cu(100) and Cu(111)
Bo-Hong Liu1*, Maximilian Huber1,2, Matthijs A. van Spronsen3, Miquel Salmeron3, Hendrik Bluhm1,4
1Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
2Department of Chemistry, Technical University of Munich, Garching, Baveria, Germany
3Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
4Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
* Presenter:Bo-Hong Liu,
We investigated the room-temperature chemisorption of oxygen on Cu(100) and Cu(111) using ambient-pressure X-ray photoelectron spectroscopy (APXPS). A shoulder-to-shoulder comparison between the oxygen gas titration on the two surfaces reveals that Cu(100) is the more active for oxygen dissociative chemisorption when the surfaces are clean. The (2√2x√2)R45o missing-row reconstruction appears in Cu(100)’s LEED image after about 104 Langmuir of oxygen exposure, whereas on Cu(111), no long-range ordering was observed throughout the whole experiment. A native oxide layer consisting of cuprous and cupric oxide shows up on Cu(111) at an oxygen exposure that is significantly lower than for Cu(100). This observation suggests that the (2√2x√2)R45o missing-row reconstruction may serve as a passivating layer for Cu(100) which slows down oxidation. It has been widely reported in the literature that the surface orientation and morphology influences copper oxidation, an observation that is supported in the current study also for the case of Cu(111).

Keywords: ambient pressure x-ray photoelectron spectroscopy, APXPS, copper oxidation, surface oxide