Scanning tunneling microscopy studies of Pd–Sn catalyzed electroless Cu deposited on pyrolytic graphite

Abstract

Pyrolytic graphite (PG) has been found to be a suitable substrate for adsorption of a Pd–Sn catalyst commonly used as an initiator for deposition of electroless Cu on printed circuit boards. Adsorption on the basal (0001) plane is minimal and results in a highly ordered array of subnanometer catalytic clusters influenced by the substrate order. Significant adsorption, however, takes place at defects, boundaries, and edge planes, resulting in large clusters and patterns that follow the nanometer scale topography of the PG surface. Subjecting a seeded substrate to electroless Cu deposition for 30 sec results in a copper layer, which may be detected by both scanning tunneling microscopy (STM) and square wave voltammetry. STM indicates that the initial copper deposit, which also assumes order on a subnanometer scale, plates uniformly over the seed, resulting in large clusters that accumulate at significant seed adsorption sites.