La 0.8 Sr 0.2 )MnO 3 -Yttria Stabilized Zirconia (LSM-YSZ) cathodes fired at various temperatures were studied using Focused Ion Beam -Scanning Electron Microscopy (FIB-SEM) three-dimensional (3D) tomography and Electrochemical Impedance Spectroscopy (EIS). The total cathode polarization resistance, measured at 800 • C in air, showed a minimum versus firing temperature, T f , at 1175 • C. The EIS showed two dominant responses that were fit well using a two (R-CPE) element equivalent circuit. The higher frequency (10 4 -10 5 Hz) response, attributed to YSZ grain boundary resistance within the LSM-YSZ composite, decreased with increasing T f and was explained by grain size increases estimated from the 3D structural data. The main EIS response, attributed to the oxygen reduction process, decreased in characteristic frequency from 500 to 1 Hz as T f increased, while its magnitude was minimized at 1175 • C. An electrochemical model quantitatively predicted the resistance minimum based primarily on a maximum in the density of electrochemically-active three-phase boundaries (TPBs), measured using 3D tomography. The active TPB density maximum resulted from two factors: substantial particle coarsening and densification at high T f that yielded a low TPB density, and low LSM-particle percolation at low T f that yielded a low fraction of active TPBs.

No abstract

Packaging applications in the semiconductor industry rely on electrodepositing metals into high aspect ratio (HAR) vias without the formation of any defects or voids. The process and economic efficiency of conventional methodologies are limited by the ability to achieve high deposition rates along with uniformity of the deposited metal layer. In this work, a contactless and scalable electrodeposition technique has been developed to deposit metallic nickel onto p-doped silicon wafers. The effect of various process variables such as deposition and etchant solution composition and concentration, solution temperature and stirring on nickel deposition rates have been investigated. The importance of backside silicon oxidation and subsequent oxide etching on the kinetics of nickel deposition on frontside silicon has been highlighted.