  Pairs of atomic scale terraces on a single crystal metal surface can be made
to merge controllably under suitable conditions to yield steps of double height
and width. We study the effect of various physical parameters on the formation
of defects in a kinetic model of step doubling. We treat this manifestly non-
equilibrium problem by mapping the model onto a 1-D random sequential
adsorption problem and solving this analytically. We also do simulations to
check the validity of our treatment. We find that our treatment effectively
captures the dynamic evolution and the final state of the surface morphology.
We show that the number and nature of the defects formed is controlled by a
single dimensionless parameter $q$. For $q$ close to one we show that the
fraction of defects rises linearly with $\epsilon \equiv 1-q$ as $0.284 \times
\epsilon$. We also show that one can arrive at the final state faster and with
fewer defects by changing the parameter with time.
