  Surfaces bombarded with low energy ion beams often display development of
self assembled patterns and quasi-periodic structures. Kinetic Monte Carlo
simulations have been performed to describe ion sputtered Tantalum surfaces. A
weak nonlinearity in the relaxation process has been introduced and the results
show that the Positive Schwoebel barrier, produced by the nonlinear
Hamiltonian, is necessary in describing ion bombarded Tantalum surfaces.
Furthermore, their scaling exponents suggest presence of a class other than
KPZ.
