Distribution of Pd clusters on ultrathin, epitaxial TiO_x films on Pt₃Ti(111)

Abstract

SummaryScanning tunnelling microscopy (STM) was used to investigate the nucleation and growth of palladium clusters on two different, ultrathin, epitaxial, titania films grown on a Pt3Ti(111) surface. The first oxide phase, z'-TiOx, is anisotropic and consists of parallel stripes separated by trenches. Defects (i.e., oxygen vacancies) in this structure are confined to these trenches and act as nucleation sites. Therefore, the Pd clusters are mostly arranged in unidirectional rows along the trenches, creating a template effect. The second phase, w'-TiOx, exhibits a hexagonal, long range, (7 × 7)R21.8°, Moiré-type superstructure with fewer and shallower defects, making the template effect less discernible.

Interaction of Gold with a Pinwheel TiO∼1.2 Film Formed on Rh(111) Facet: STM and DFT Studies

“…The height of the nanoparticles is ∼0.2 nm, the diameter of them changes in the range of 1.5 to 2 nm, the particle size distribution is very narrow, and the position of the particles exhibits a clear ordering (Figure e). These properties are characteristic for nanoparticles grown and templated on the top of TiO x -UTO film . Note that the surface concentration of the nanoparticles is ∼1.3 × 10 12 cm –2 which is only two to three times higher than the value received for Rh-free regions of TiO 2 (110) surface shown in Figure a.…”

“…These properties are characteristic for nanoparticles grown and templated on the top of TiO x -UTO film. 9 Note that the surface concentration of the nanoparticles is ∼1.3 × 10 12 cm −2 which is only two to three times higher than the value received for Rh-free regions of TiO 2 (110) surface shown in Figure 1a. The neighboring particles are in a distance of ∼1.6 nm very close to the unit cell vector of the wheel structure (Figure 4c,e).…”

“…Moreover, the huge interest for these films not only originates from fundamental aspects but also connects to the technological importance of the fabrication of different supported or self-supporting 2D materials like oxides, graphene, dichalcogenides, or polymers. ,,− Concerning the UTO films, they usually possess charge distribution balanced via strained atomic positions, which is also controlled by the substrate supporting them. The result is a periodic supercell (2 to 3 nm) structure making these films excellent candidates as templates. − This latter topic connects to the nanotechnology concept previously described using UTO films as nanotemplates for tailored growth of metal nanoparticles. Although, the controlled growth of the UTO films on different metal surfaces is not a new idea, nevertheless, it became possible only recently that the formation of an epitaxial oxide film can be followed on an atomic scale by scanning probe microscopy (SPM) techniques. ,, The results obtained in the past decade obviously led to a successful synthesis of the findings. − The most indicative parameter used for the characterization of UTO films is the oxidation state of the cation and the wetting ability of the oxide layer on different support metals.…”

TiOx/Pt3Ti(111) surface-directed formation of electronically responsive supramolecular assemblies of tungsten oxide clusters

“…In order to exclude possible tip–surface deconvolution effects (e.g., by a random W 3 O 9 pickup) it should be noted that neither soft pulsing procedures of the STM tip during the measurements nor a complete tip exchange had a significant influence on the observations. However, it is well known that the coincidence points of the w’-TiO x phase on the Pt 3 Ti alloy substrates exhibit unique electronic properties [ 21 , 23 ]. Thus, it is not surprising that the adsorption on such positions may result in extraordinary arrangements.…”

“…Both characteristics are implemented by atomically ordered titanium oxide ultrathin films grown on a bimetallic Pt 3 Ti(111) single crystal surface. More importantly, the use of this material has already proven successful in supporting the self-organization of Pd clusters [ 21 ].…”