Thickness dependence of the resistivity of Platinum group metal thin films

We report on the thin film resistivity of several platinum-group metals (Ru, Pd, Ir, Pt). Platinum-group thin films show comparable or lower resistivities than Cu for film thicknesses below about 5\,nm due to a weaker thickness dependence of the resistivity. Based on experimentally determined mean linear distances between grain boundaries as well as ab initio calculations of the electron mean free path, the data for Ru, Ir, and Cu were modeled within the semiclassical Mayadas--Shatzkes model [Phys. Rev. B 1, 1382 (1970)] to assess the combined contributions of surface and grain boundary scattering to the resistivity. For Ru, the modeling results indicated that surface scattering was strongly dependent on the surrounding material with nearly specular scattering at interfaces with SiO2 or air but with diffuse scattering at interfaces with TaN. The dependence of the thin film resistivity on the mean free path is also discussed within the Mayadas--Shatzkes model in consideration of the experimental findings.Comment: 28 pages, 9 figure

Global and local corrosion of welded joints of high-strength low-alloy automotive steel

Global and local corrosion techniques were used to study the corrosion behaviour of weld joints of a high strength low alloy steel (LNE500), typically employed in the automotive industry, in Brazil. The welded joints were prepared by gas metal arc welding (GMAW). Two welding transfer modes were used in order to obtain different heat inputs (HI): pulsed (PUL) and cold metal transfer (CMT). Local and global corrosion analysis techniques presented complementary information. While the local in-situ analysis (scanning vibrating electrode technique) revealed the weld metal (WM) as the region where corrosion started, conventional electrochemical techniques (Potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS)) revealed a higher corrosion rate in the coarse-grained heat affected zone (CGHAZ), which was preferentially corroded. A superior corrosion resistance of the weld metal obtained using CMT over the PUL transfer mode was revealed by EIS and PP. In addition, the results from CMT and PUL samples show that austenite grain size affects the propagation of the corrosion process. The results are discussed based on microstructural and compositional aspects of the different regions that characterize the welded joints