Metal bead crystals for easy heating by direct current.

The preparation of metal bead crystals with two wires attached to the crystal is described. These crystals allow for a very easy and efficient method to heat metal single crystals by direct current heating through the connecting wires of the bead crystal. This heating of the bead crystal is sufficient to clean metal surfaces such as the surfaces of Pt and Au as confirmed by Auger spectroscopy and scanning tunneling microscopy (STM). There is no need for any ion sputtering which is conventionally used to clean metal single crystal surfaces. The bead crystals with two leads fabricated from a wide range metals and metal alloys such as Cu, Mo, Ru, Rh, Pd, Ag, Ta, W, Re, Ir, Pt, Au, PtPd, PtRh, AuAg, and PtIr can be used as general purpose metal substrates for surface science studies and other applications. Additionally, these bead crystals can be used to reshape STM tips by indentation of the tip into the soft metal in order to recover atomic resolution imaging on hard substrates.

Superior regularity in erosion patterns by planar subsurface channeling.

The onset of pattern formation through exposure of Pt(111) with 5 keV Ar(+) ions at grazing incidence has been studied at 550 K by scanning tunneling microscopy and is supplemented by molecular-dynamics simulations of single ion impacts. A consistent description of pattern formation in terms of atomic scale mechanisms is given. Most surprisingly, pattern formation depends crucially on the angle of incidence of the ions. As soon as this angle allows subsurface channeling of the ions, pattern regularity and alignment with respect to the ion beam greatly improves. These effects are traced back to the positionally aligned formation of vacancy islands through the damage created by the ions at dechanneling locations.

New growth mode through decorated twin boundaries.

Scanning tunneling microscopy and low energy electron diffraction were used to investigate the growth of partly twinned Ir thin films on Ir(111). A transition from the expected layer-by-layer to a defect dominated growth mode with a fixed lateral length scale and increasing roughness is observed. During growth, the majority of the film is stably transformed to twinned stacking. This transition is initiated by the energetic avoidance of the formation of intrinsic stacking faults compared to two independent twin faults. The atomistic details of the defect kinetics are outlined.

Stacking-fault nucleation on Ir(111).

Variable temperature scanning tunneling microscopy experiments reveal that in Ir(111) homoepitaxy islands nucleate and grow both in the regular fcc stacking and in the faulted hcp stacking. Analysis of this effect in dependence on deposition temperature leads to an atomistic model of stacking-fault formation: The large, metastable stacking-fault islands grow by sufficiently fast addition of adatoms to small mobile adatom clusters which occupy in thermal equilibrium the hcp sites with a significant probability. Using parameters derived independently by field ion microscopy, the model accurately describes the results for Ir(111) and is expected to be valid also for other surfaces.