SURFACE COORDINATION CHEMISTRY OF YBA2CU3O7-DELTA

The surface coordination chemistry of the cuprate superconductor, YBa2 Cu3O7-delta has been extensively surveyed using cyclic voltammetry in conjunction with a series of redox-active ferrocenyl containing adsorb ate molecules. Evidence supporting the adsorption of molecules with pr imary alkylamine, secondary alkylamine, tertiary alkylamine, arylamine , thiol, disulfide, and selenol functionalities is reported. Cyclic vo ltammetry, atomic force microscopy, scanning electron microscopy, X-ra y powder diffraction and resistivity vs temperature measurements were utilized to evaluate the influence of the modification conditions on t he bulk and surface properties of the high-T-c superconductor. The spo ntaneous adsorption of redox-active alkylamines, arylamines, and thiol s onto the surfaces of cuprate materials has been shown to produce sta ble and robust monolayer films with no apparent damage to the bulk pro perties of the underlying superconduetors. Of the molecules studied th us far, primary alkylamines have been determined to be the optimum ads orbates based upon surface coverage values and monolayer durability. T ertiary alkylamines form monolayers on YBa2Cu3O7-delta with an electro chemical persistence comparable to primary alkylamine monolayers, sugg esting that hydrogen binding with the surface is not necessary for ads orption. We propose that amines act as Lewis bases and bind to Lewis a cidic Cu surface site(s) in YBa2Cu3O7-delta to form stable coordinatio n bond(s).