Cathodic Behavior and Redox Couples - Electrochemistry of Silicon and Its Oxide - page 250

deposition onto n -Si in a solution and copper deposition in a
solution at relative small overpotentials are found to follow the progressive nucleation
model whereas copper deposition at large overpotentials follows instantaneous nucle-
ation. The density of the nuclei, depending on many factors, increases rapidly

with increasing deposition overpotential. It is about for copper deposited at
-0.8V in a Figure 6.13 shows that the nucleus density
is determined by the deposition at whereas it is little affected by subsequent
deposition at -1.1 V. At time less than 0.9 s the deposition is dominated by nucleation
whereas it is by growth at a longer time. The rate of nucleation increases linearly on a
logarithmic scale with increasing cathodic overpotential.
During electroless deposition of copper in HF solution, the nucleation process
dominates initially for about 60 s to produce nanometer-sized nucleus deposits; then
growth of the copper grains takes over. 120 As soon as nuclei of metal deposits are
formed, the kinetics of deposition is changed as the metal nuclei act as catalytic sites
for further metal deposition. The rate of deposition increases with increasing HF con-
centration. 789 The silicon surface roughens as the deposition continues due to the
corrosion reactions.
Deposition of Pb in 5mM

1145

0mM solution at large over-
potentials occurs It follows a progressive nucleation
process at low overpotentials and is mainly initiated at the surface inhomogeneities.
The number of atoms in the critical nucleus is estimated to be very small, about 11.
The small Pb clusters are stable within a certain anodic potential range.
The morphology of nuclei can be characterized in terms of deposit size and
density. Figure 6.14 shows copper precipitate size distribution of n- and

and 1

831,967

via a 3D island growth.

p -Si materials

in 0.5% HF solution. 407 The density is higher on n- than on -type silicon whereas the

size is larger on p- Si than on n -Si indicating that the rate of nucleation is higher on

p