CHEMICAL ORDERING DURING SURFACE GROWTH

We study the effects of phase separation on the growth of thin solid f ilms by molecular beam epitaxy. We propose a continuum theory that tak es into account the fluctuations of the free surface and the phase sep aration and explain how bulk lamellar patterns develop from a competit ion between the surface phase separation and the constant burial of su rface domains by the incoming beam. The dependence of the wavelength o n the deposition rate is in excellent agreement with previous Monte Ca rlo results. We demonstrated that the free surface is modulated, with a period that is half the bulk modulation wavelength.