Localized adsorption of organic additives during copper electrodeposition

The confocal laser scanning microscope (CLSM) was used in situ during electrochemical experiments to track localized fluorescence patterns of adsorbed organic agents and correlate such adsorption with the changes in surface morphology accompanying electrolysis. In solutions of 5 {dollar}mu{dollar}M DiOC{dollar}sb6{dollar}(3)/0.01 M {dollar}rm Hsb2SOsb4{dollar} with and without 0.05 M CuSO{dollar}sb4{dollar}, confocal imaging revealed that DiOC{dollar}sb6{dollar}(3) adsorbed to polycrystalline Au and inhibited cathodic processes occurring there. In the absence of dissolved Cu, DiOC{dollar}sb6{dollar}(3) adsorption on Au remained unaltered by changes in cathodic potential up to {dollar}-{dollar}750 mV (SSE). During Cu electrodeposition at {dollar}-{dollar}550 mV and at {dollar}-{dollar}650 mV (SSE), adsorbed DiOC{dollar}sb6{dollar}(3) restricted nucleation of Cu to a small number of active sites, where Cu grew hemispherically, and DiOC{dollar}sb6{dollar}(3) adsorption was maintained across regions where nucleation had not occurred. Instantaneous nucleation was approached under such conditions. When DiOC{dollar}sb6{dollar}(3) was present, copper growth proceeded according to the Volmer-Weber mechanism at {dollar}-{dollar}650 mV (SSE). Results from secondary ion mass spectrometry indicated that DiOC{dollar}sb6{dollar}(3), or a derivative of it, was incorporated into the deposit during Cu electrodeposition. When the Cu deposits were dissolved electrochemically at 0 mV (SSE), surfaces of Cu, not Au, became covered with previously incorporated DiOC{dollar}sb6{dollar}(3), which impeded the electrodissolution process. DiI did not exhibit an appreciable electrochemical or morphological effect on Cu electrodeposition. At 5 {dollar}mu{dollar}M, DiI was adsorbed at recesses of the deposit profile when Cu electrodeposition occurred at {dollar}-{dollar}390 mV (SSE).