INSTABILITIES IN THE GROWTH OF COMPACT ELECTRODEPOSITS

We have investigated the morphological instabilities in electrochemica l compact growth. The experimental system consisted in 0.5 M aqueous s olutions of CuSO4 in a quasi-2D strip geometry. The deposits were made at low constant current densities ranging between 20 and 100 mA cm(-2 ). We monitored the morphology of the growing interface and the electr ical parameters of the system. We find two different growth regimes: a t short times the interfaces show roughness scaling with a roughness e xponent, alpha = 0.78 +/- 0.05; at longer times an instability develop s which causes an increase in the growth speed and the external applie d voltage. Some characteristic time and length scales of this latter i nstability compare well with theoretical results in directional solidi fication models.