Nanoscale morphology of electrolessly deposited silver metal

Electroless deposition of silver was studied to determine how chemical and physical parameters affect the morphology of the deposited metal. The study was conducted using variations of a silver deposition bath originally described by Danscher. The standard bath produced reflective and electrically conductive metal films comprised of agglomerates of small spheroidal nanoparticles. Removing gum arabic from the bath increased the deposition rate and changed the shape of the agglomerates but did not significantly change the size of the constituent nanoparticles. Replacing the citrate buffer with a dicarboxylate or monocarboxylate, which is less able to chelate Ag⁺, produced surfaces comprised of larger, more faceted metal particles. The longevity of the bath varied with the choice of carboxylate. A new formulation buffered with maleate exhibited the highest stability, depositing silver for several hours without unwanted spontaneous formation of silver metal in solution. Optical measurements of electrolessly deposited films revealed absorptions associated with silver nanoparticles. Electrical measurements showed that the as-deposited films were five orders of magnitude less conductive than bulk silver, but low-temperature annealing increased the conductivity by four orders of magnitude.