THE EFFECT OF 3 ORGANIC ADDITIVES ON THE STRUCTURE AND GROWTH OF ELECTRODEPOSITED COPPER - AN IN-SITU SCANNING PROBE MICROSCOPY STUDY

The growth morphology of copper crystallites and the influence of tris -aminophenyl and benzothiazolium (BT) derivatives, have been studied i n-situ using scanning probe microscopy (SPM). We have examined the ver y initial stages of deposition, following copper nucleation at defects in the substrate, up until the formation of relatively thick copper l ayers. The substrates onto which bulk copper was deposited were Au(111 ) precovered with UPD copper. Additive BT-B was the most effective at surpressing the perpendicular growth of the copper crystallites and fa voured instead their lateral spreading. 2-(4-Dimethylaminophenyl)-6-me thylbenzothiazole (BT-A) and crystal violet only showed effective surp ression of the crystallites vertical growth for low deposition rates f rom very dilute Cu2+ solutions. In the case of the quasi-2D growth, la yer deposition occurred via a ''birth-and-spread'' mechanism, with def ects in the underlying layer providing favourable nucleation sites for the next one. A pronounced substrate effect was seen in the case of c opper deposition under effective additive influence. In this case the first quasi-two-dimensional copper layer reached a thickness equivalen t to between 4-7 monolayers, while subsequent 2-D layers were typicall y one monolayer high. Models for the copper electrocrystallization, in the absence and presence of additives, are proposed. The importance o f 2-D nucleation in determining the crystallites external shape is dis cussed.