The surface coordination chemistry of cuprate high-temperature superconductors

The goals of the research described in this dissertation were: (1) to explore the surface coordination chemistry of cuprate high-temperature superconductors (HTSCs); (2) to develop chemical methodology for directly tailoring the surface and interfacial properties of cuprate HTSCs.;This thesis documents the first survey of the surface coordination chemistry of a cuprate HTSC, YBa2Cu3O7-delta. Functional groups that can chemically bind to YBa2Cu3O 7-delta have been determined using cyclic voltammetry in conjunction with a series of redox-active ferrocenyl containing adsorbate molecules. Primary alkylamines have emerged as the optimum adsorbates for HTSCs, forming stable and robust monolayer films with no apparent damage to the bulk properties of the underlying superconductors. The interactions between alkylamine adsorbates and YBa2Cu3O7-delta have been shown to involve Cu(II)-NR3 coordination chemistry. The influence of organic monolayers on the properties of YBa2Cu3O 7-delta has been examined using cyclic voltammetry, X-ray powder diffraction, atomic force microscopy, and resistivity vs. temperature measurements. The presence of H2O in the soaking solution adversely affects the adsorption process due to a competing corrosion reaction. However, stable monolayers form on HTSC substrates under rigorously dry conditions. Significantly, monolayer modified HTSCs are substantially more stable to corrosion environmental reagents.;The formation kinetics of redox-active alkylamine monolayers on ceramic YBa2Cu3O7-delta are proposed to involve two major processes: a fast adsorption process and a relatively slow pore diffusion process. Surface-solution adsorbate exchange is very dynamic and reversible, which appears to occur via an associative pathway. Monolayers on c-axis-oriented thin films have been shown to be more densely-packed and stable than those on ceramic substrates. Notably, the surface alkylamine "ligands" display traits of Cu(II)-based coordination chemistry.;Finally this works shows that the surface and interfacial properties of YBa2Cu3O7-delta can be tailored at the molecular level using this monolayer-based surface modification methodology. The wettability, corrosion resistance, and adhesive properties of the HTSC surfaces can be controlled through choice of adsorbate. Importantly, the first artificial superconductor/insulator/metal tunnel junction has been prepared by this novel surface modification methodology, opening a new avenue for preparing monolayer-based HTSC devices and hybrid structures.