Novel method for studying large-scale coalescence

We report upon the postdeposition dc resistance increase in discontinuous films of aluminum, copper, and silver on glass at a pressure of 2×10-5 Torr. The repeated deposition technique was employed to reduce the resistance of the films to a fixed initial value after the resistance had increased to a predetermined upper value. This process was continued until the film resistance remained steady with time, i.e., the film attained a stable configuration. Mobility coalescence was assumed to be responsible for the postdeposition resistance increase. Depending on the functional dependence of the film resistance on time, an agglomeration rate was defined and this parameter was studied for the different deposition cycles. For all the films studied, a steep fall in the agglomeration rate was observed to occur beyond a particular deposition cycle number after which it stabilizes. Large-scale coalescence (LSC) resulting in a network film structure is taken to be responsible for the fall in the agglomeration rate. Secondary nucleation and the coalescence of the sec- ondary nuclei with the network structure gives rise to small resistance changes after the LSC phenomenon is complete.