Early-stage evolution of nanoscale oxides on Ni(111) and Ni-Cr(111) surfaces

The early stages of oxidation on Ni(111) and Ni-18 wt%Cr(111) surfaces were studied with scanning tunneling microscopy/spectroscopy. After exposure to oxygen at 500 degrees C, chemisorbed p(2 x2)O adlayers appear on Ni(111) without oxide formation. On the Ni-Cr(111) surface 2D NiO(100) layers rapidly accumulate on the terraces. These coexist with Cr-rich clusters, which coalesce as oxidation progresses. Larger oxide nodules with 3D-island morphology are identified as chromia and are found embedded in the NiO(100). Spectroscopy reveals electronic heterogeneity, highlighting the chemical variation between each oxide species. A schematic is constructed that highlights the associated Ni- and Cr- reaction pathways on Ni-Cr(111) alloy surfaces.

Automated summary

The early stages of oxidation on Ni(111) and Ni-18 wt%Cr(111) surfaces were studied using scanning tunneling microscopy/spectroscopy. Chemisorbed p(2 x2)O adlayers appear on Ni(111) while 2D NiO(100) layers rapidly accumulate on the Ni-Cr(111) surface along with Cr-rich clusters.