Anisotropy in growth-front roughening

We consider a linear anisotropic growth equation that includes two anisotropic physical processes, evaporation/condensation and surface diffusion, to describe the roughening of the growth fronts generated by noises. By solving this equation analytically, we show that there are two different types of growth-front anisotropy: correlation length anisotropy and scaling anisotropy. A scaling anisotropy can generate different values of roughness exponent in different surface directions. It is shown that a competition of the two growth processes can lead to a rotation of the direction of anisotropy. We also consider the effect of growth-front roughening due to the anisotropy in surface diffusion barrier (Schwoebel barrier) to show that the surface can form ripple structures over time. These results are used to explain recent experimental results on growth-front anisotropy.