Self-organization of (001) cubic crystal surfaces

Self-organization on crystal surface is studied as a two dimensional spinodal decomposition in presence of a surface stress. The elastic Green function is calculated for a $(001)$ cubic crystal surface taking into account the crystal anisotropy. Numerical calculations show that the phase separation is driven by the interplay between domain boundary energy and long range elastic interactions. At late stage of the phase separation process, a steady state appears with different nanometric patterns according to the surface coverage and the crystal elastic constants

Imaging and manipulation of atoms by STM at room temperature

Since the realisation that scanned probe tips can interact with atoms at surfaces, much interest has focussed on the possibility of creating nano-structures with single atoms or molecules. The obstacles to manipulation of individual atoms at room or higher temperatures are of a fundamental nature. Atoms that are sufficiently well bound to a surface site to be stable at higher temperatures obviously require rather stronger interaction with the tip to be moved than do atoms physisorbed at a few K. The system is thus departing significantly from the idealised non-interacting STM, and entering the rather ill-charted terrain of tip-surface interactions. It is also necessary that the atoms being manipulated have a reasonably well defined parameter which controls the onset of movement, within the quite narrow band of current-voltage-separation configuration which is available in practice to STM. This may restrict the chemical species. We present room temperature STM investigations of three metal/halogen adsorption systems and show that bromine adsorbed on a Cu(100) surface meets the above requirements. We show that the Br adatoms may be reliably driven over the surface by the STM tip at room temperature. Controlled manipulation of a single Br adatom was also demonstrated. The manipulation mechanism was investigated and the atomic motion was found to be triggered at a threshold tunnelling current, but surprisingly appeared to be independent of the electric field between tip and surface. The role of the electric field in STM image formation was probed farther by quantitative experiments on a clean Ni(110) surface. It was demonstrated that for simple metals the effect of the electric field between tip and sample on STM image corrugations is negligible. (author)Available from British Library Document Supply Centre-DSC:D203956 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Scanning tunnelling microscopy study of palladium on stepped Cu(210) surfaces: chemical contrast and room-temperature tip-induced motion

10.1016/S0039-6028(99)00884-5Surface Science442155-64SUSC