2D Ni Nanoclusters on Ultrathin MgO/Ag(100)

Ni nanoclusters up to 30 Å in diameter are grown by Ni deposition on ultrathin MgO/Ag(100) films at different temperatures and characterized by combining lowtemperature scanning tunneling microscopy with photoemission and vibrational spectroscopies. At 200 K, both small NixOy aggregates and 2D Ni nanoparticles of average size close to 12 Å form. The latter have a metallic nature and efficiently catalyze CO dissociation at 200 K. When Ni is deposited at 300 K, only larger 3D Ni clusters are observed.