Ambient Pressure X-ray Photoelectron Spectroscopy Study of Room-Temperature Oxygen Adsorption on Cu(100) and Cu(111)

Bo-Hong Liu^1*, Maximilian Huber^1,2, Matthijs A. van Spronsen³, Miquel Salmeron³, Hendrik Bluhm^1,4

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, email:Liu.bh@nsrrc.org.tw

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)R45^o 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)R45^o 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