  A number of recent experiments have showed that surfactants can modify the
growth mode of an epitaxial film, suppressing islanding and promoting
layer-by-layer growth. Here I introduce a set of coupled equations to describe
the nonequilibrium roughening of an interface covered with a thin surfactant
layer. The surfactant may drive the system into a novel phase, in which the
surface roughness is negative, corresponding to a flat surface.
