No abstract

Inelastic helium atom scattering has been used to measure the phonons on a stepped metallic crystalline surface, Ni(977). When the scattering plane is oriented parallel to the step edges and perpendicular to the terraces, two branches of step-induced phonons are observed. These branches are identified as transversely polarized, step-localized modes that propagate along the step edge. Analysis reveals significant anisotropy in the force field near the step edge, with all forces near the step edge being substantially smaller than in the bulk. Such measurements provide valuable information on metallic bonding and interface stability near extended surface defects.

Inelastic helium atom scattering has been used to measure the surface and step localized phonons on a stepped metallic surface, Ni͑977͒. These time-of-flight measurements were carried out both perpendicular and parallel to the step direction. Surface phonon dispersion data collected across the steps show backfolding of the surface Rayleigh mode, and, most importantly, dramatic softening as compared to the forces present at the smooth Ni͑111͒ surface. This softening suggests significant relaxation perpendicular to the step edge. Single-phonon scattering data collected along the step direction reveals the presence of two new step-edge localized modes, as well as the Rayleigh mode for this direction of the crystal. The Rayleigh mode here does not exhibit the notable softening that was found for the other direction. Novel in-and out-of-phase scattering measurements, with respect to the terraces, lead us to assign the new step induced modes as the two transversely polarized vibrations which propagate along the direction of the step edge. An analytic one-dimensional lattice model is proposed which well represents the dispersion data for these two step modes; its use allows us to determine the effective local force field in the two transverse directions with respect to the step edge. The findings reported herein shed new light on such topics as interface stability, crystal growth, and charge redistribution in the vicinity of well-characterized extended surface defects.

We have observed that the reconstruction dynamics for stepped Ni(9 7 7) are influenced by the oxygen dissolution history of the crystal. Using a complementary approach incorporating both real-and reciprocal-space techniques, it is found that the upper end of the thermal range over which this stepped metal surface transforms from single to double steps increases with selvedge or sub-surface oxygen concentration. These results enhance our understanding of how adsorbate dissolution, and hence oxygen exposure history, modify energetic pathways for metallic oxidation.

Microfluidics-based biochips for biochemical analysis are receiving much attention nowadays. These composite microsystems, also known as lab-on-a-chip or bio-MEMS, offer a number of advantages over conventional laboratory procedures. They automate highly repetitive laboratory tasks by replacing cumbersome equipment with miniaturized and integrated systems, and they enable the handling of small amounts, e.g., micro- and nano-liters, of fluids. Thus they are able to provide ultra-sensitive detection at significantly lower costs per assay than traditional methods, and in a significantly smaller amount of laboratory space. Advances in microfluidics technology offer exciting possibilities in the realm of enzymatic analysis (e.g., glucose and lactate assays), DNA analysis (e.g., PCR and nucleic acid sequence analysis), proteomic analysis involving proteins and peptides, immuno-assays, and toxicity monitoring. Biochips can be used to detect molecules and/or sequence nucleic acid molecules with aid of an array of electrochemical detector cells containing one or more electrodes per cell where each cell being electrically isolated at a wafer level. For many applications it is beneficial to form a non-planar working electrode using a metal which will corrode during CMP steps. We’ve developed a novel Ag and Cu integration process which a) solves problems of metal corrosion over 3D topography during CMP step and b) prevents metal surface contamination with CMP residual slurry and polishing byproducts not usually removable by brush or megasonic cleaning. Electrochemical studies show corrosion behavior of thick Ag layers in different CMP slurries used in this process. SEM images of cross-sectioned metal lined electrochemical cells (vias) clearly demonstrate advantages of new process (right) without traces of corrosion vs conventional CMP process (left). This process can be used also for polishing of other metals and dielectrics over topography where aggressive cleaning post-CMP steps are not desirable. Figure 1