The dynamic roughening of a growing crystalline facet is reexamined by including nonlinear effects. A new and unusual fixed point controls the crossover between rough and faceted growth. Unlike linear treatments, the dynamics is no longer diffusive, and an anomalous decrease in mobility is predicted. Implications of these results for recent numerical simulations of growth and experiments on He films are discussed.

• Received 17 August 1990

DOI:https://doi.org/10.1103/PhysRevLett.66.441