COLUMNAR GROWTH IN OBLIQUE-INCIDENCE BALLISTIC DEPOSITION - FACETING, NOISE-REDUCTION, AND MEAN-FIELD THEORY

Several aspects of the columnar structure encountered in vapor deposition at oblique particle incidence are studied through a combination of theoretical analysis and computer simulations. First, a general macroscopic theory of columnar growth is presented that yields, among other results, an expression for the columnar growth angle. We then focus on the role of noise in columnar growth, using two simple square-lattice ballistic deposition models-finite-density deposition and noise-reduced deposition-in which the amount of fluctuations in the growth process can be tuned by varying a control parameter. In both models faceting of the column tips stabilizes the columnar morphology. In the finite-density model, we find a faceting transition related to directed percolation. Some characteristics of columnar growth are retrieved within a mean-field approximation. Simulations carried out on d-dimensional hypercubic lattices up to d = 6 indicate that the deposit density converges to its mean-field value in the limit d --> infinity.