Scanning tunneling microscopy investigations of ruthenium- and osmium-modified Pt(100) and Pt(110) single crystal substrates

Ruthenium and osmium were deposited in sub-monolayer amounts on Pt(100) and Pt(110) single crystal surfaces via spontaneous deposition and explored using scanning tunneling microscopy (STM) and cyclic voltammetry. The results were compared to previously published Pt(111) data to yield a comprehensive discussion of all low-index platinum surfaces modified by ruthenium and osmium. Ex-situ STM was utilized to image the deposition characteristics of ruthenium and osmium islands on Pt(hkl). The spontaneous deposition procedure yielded a maximum coverage of 0.22 and 0.10 monolayer of ruthenium on Pt(100) and Pt(110), respectively. Homogeneous deposition of ruthenium on the Pt(hkl) surfaces was observed without preferential deposition on step edges or surface defect sites. In contrast to the results with Pt/Ru, the spontaneous deposition of osmium yields osmium clusters preferentially (though not exclusively) at surface defect sites and step edges. Osmium island deposition occurs at a greater rate than ruthenium on all low index surfaces, and follows the same affinity as Ru; that is, deposition on Pt(100) is greater than Pt(111) which is greater than Pt(110). It was also determined that both ruthenium and osmium deposit in mainly mono-layer high islands on all three crystal faces.